JP2008270149A - Extreme ultraviolet light source device and extreme ultraviolet light generating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extreme ultraviolet light source device in which the position of a discharge channel can be demarcated and the density of high-temperature plasma material in a discharge channel can be established as appropriate, and a long pulse of irradiation can be realized. <P>SOLUTION: A first energy beam 23 is irradiated to a high-temperature plasma material to evaporate it. When the evaporated material reaches a discharge region, pulse power is applied between the electrodes 11, 12 and a second energy beam 24 is irradiated. Thereby, plasma is heated and excited to carry out EUV irradiation. The irradiated EUV is condensed by an EUV condenser mirror 2 and extracted. Since the first and the second laser beams 23, 24 are irradiated, spatial density distribution of the high-temperature plasma material can be established in a prescribed distribution and the position of the discharge channel can be can be demarcated. Further, since the material gas of which ion density is nearly equal to the ion density under extreme ultraviolet irradiation condition is supplied to the discharge passage, long pulse of EUV irradiation becomes possible. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an extreme ultraviolet light source device and an extreme ultraviolet light generation method for generating extreme ultraviolet light from plasma generated by discharge, and in particular, an energy beam is applied to a high temperature plasma raw material for generating extreme ultraviolet light supplied in the vicinity of a discharge electrode. The present invention relates to an extreme ultraviolet light source device and an extreme ultraviolet light generation method for generating extreme ultraviolet light from plasma generated by discharge from vaporized high-temperature plasma raw material after irradiation.

With the miniaturization and high integration of semiconductor integrated circuits, improvement in resolving power is demanded in the projection exposure apparatus for production. In order to meet the demand, the exposure light source has been shortened, and as a next-generation semiconductor exposure light source following the excimer laser device, extreme ultraviolet light (hereinafter referred to as EUV (hereinafter referred to as EUV)) having a wavelength of 13 to 14 nm, particularly 13.5 nm. Extreme ultraviolet light source devices (hereinafter also referred to as EUV light source devices) have been developed.
Several methods for generating EUV light in an EUV light source apparatus are known. One of them is a method for generating high-temperature plasma by heating and exciting EUV radiation species and extracting EUV light emitted from the plasma. is there.

EUV light source devices employing such a method are classified into LPP (Laser Produced Plasma) type EUV light source devices and DPP (Discharge Produced Plasma) type EUV light source devices, depending on the high temperature plasma generation method. They are broadly divided (for example, see Non-Patent Document 1).
The LPP EUV light source device uses EUV radiation from high-temperature plasma generated by irradiating a target such as a solid, liquid, or gas with a pulse laser. On the other hand, the DPP EUV light source device uses EUV radiation from high-temperature plasma generated by current driving.
In both types of EUV light source devices described above, Xe (xenon) ions of around 10 valence are currently known as radioactive species that emit EUV light with a wavelength of 13.5 nm, that is, as a high-temperature plasma raw material for EUV generation. Li (lithium) ions and Sn (tin) ions have attracted attention as high-temperature plasma raw materials for obtaining stronger radiation intensity. For example, Sn has a conversion efficiency that is a ratio of the EUV light emission intensity with a wavelength of 13.5 nm to the input energy for generating high-temperature plasma several times larger than Xe.

In recent years, as a method for generating high-temperature plasma, a method (hereinafter also referred to as a hybrid method) in which a high-temperature plasma raw material is combined with laser beam irradiation and heating with a large current based on discharge has been proposed.
An EUV light source apparatus adopting a hybrid method is described in, for example, Patent Document 1. The outline will be described below.
The hybrid method in the EUV light source device described in Patent Document 1 is performed according to the following procedure. FIG. 4C of Patent Document 1 is an explanatory diagram of an EUV light source apparatus adopting a hybrid system.

In the figure, the grounded outer electrode forms a discharge vessel. An insulator is installed inside the outer electrode, and an inner electrode on the high voltage side is installed inside the insulator. As the high-temperature plasma raw material, for example, xenon (Xe) gas or a mixed gas of xenon (Xe) and helium (He) is used. Such a high-temperature plasma source gas is supplied into the discharge vessel from a gas path provided in the inner electrode. In the discharge vessel, an RF play-on coil for pre-ionizing the high temperature plasma source gas, a focusing lens for focusing the laser beam, and the like are arranged.
The generation of EUV radiation is performed as follows.
First, the source gas, which is a high-temperature plasma source introduced into the discharge vessel, is preionized by supplying pulsed power to the RF play-on coil. Next, the laser beam that has passed through the condensing lens is condensed in a predetermined region in the discharge vessel. Since the high temperature plasma source gas is preionized, it is decomposed near the laser focus.
Next, pulse power is applied between the outer electrode and the inner electrode, and a discharge is generated. Due to the pinch effect caused by the discharge, the high temperature plasma raw material is heated and excited to generate high temperature plasma, and EUV radiation is generated from this high temperature plasma.

Here, in the vicinity of the laser focal point, the conductivity is reduced by electron emission. Therefore, the position of the discharge channel in the discharge region (the space where the discharge between the electrodes occurs) is defined at the position where the laser focus is set. That is, the plasma pinch position is defined by the laser beam. Therefore, the positional stability of the generation point of EUV radiation is improved.
When the EUV light source device is used as an exposure light source, it is required to improve the pointing stability of the light emitting point. The hybrid EUV light source device described in Patent Document 1 can be said to be an example that meets the above requirements.

  In recent years, high-temperature plasma raw material for EUV generation (hereinafter also referred to as high-temperature plasma raw material) is generated by combining vaporization by laser beam irradiation and heating by a large current based on discharge to generate high-temperature plasma. Methods for generating EUV radiation from plasma have been proposed (see, for example, Patent Document 3, Patent Document 4, Patent Document 5, etc.). Hereinafter, this method is referred to as a LAGDPP (Laser Assisted Gas Discharge Produced Plasma) method.

  In each of the above-described EUV light source devices, Xe (xenon) ions of about 10 valence are currently known as a radiation species that emits EUV light having a wavelength of 13.5 nm, that is, a high-temperature plasma raw material. Li (lithium) ions and Sn (tin) ions have attracted attention as high-temperature plasma raw materials for obtaining strength. For example, Sn has a conversion efficiency that is a ratio of the EUV light emission intensity at a wavelength of 13.5 nm to the input energy for generating high temperature plasma several times larger than Xe.

Next, the mechanism leading to EUV radiation based on the above-described methods will be briefly described with reference to FIG.
FIG. 38 is a diagram showing what state change path the high-temperature plasma raw material (which is described as a fuel solid in FIG. 38 as an example) reaches a condition that satisfies the EUV radiation condition.
In the figure, the vertical axis represents ion density (cm ⁻³ ), and the horizontal axis represents electron temperature (eV). The figure shows that when the vertical axis is advanced downward, the high temperature plasma raw material expands and the ion density decreases, and when it progresses upward, it is compressed and the ion density increases. Further, when proceeding to the right along the horizontal axis, the high-temperature plasma raw material is heated and the electron temperature rises.

In the LPP method, for example, a solid or liquid target of a high-temperature plasma raw material such as Sn or Li (shown as a fuel solid in the upper left of FIG. 38. In the solid state, the ion density of a metal such as Sn or Li is about 10 ²² cm ⁻³ . And the electron temperature is 1 eV or less). The high-temperature plasma raw material irradiated with the laser beam is heated and vaporized at a stroke until the electron temperature exceeds 300 eV, for example, and high-temperature plasma is generated. The generated high-temperature plasma expands, and eventually the ion density in the high-temperature plasma becomes about 10 ¹⁷ to 10 ²⁰ cm ⁻³ and the electron temperature becomes about ²⁰ to ³⁰ eV. EUV is radiated from the high temperature plasma that has reached such a state. (Route 1 in FIG. 38)
That is, in the LPP method, the plasma generated by being heated by the laser beam expands, so that the plasma is subjected to the EUV radiation conditions (that is, the ion density of 10 ¹⁷ to 10 ²⁰ cm ⁻³ and the electron temperature of 20). ~ 30 eV).

On the other hand, in the DPP method, for example, the inside of a discharge vessel in which electrodes are arranged is used as a gaseous high-temperature plasma raw material atmosphere, and discharge is generated between the electrodes in the atmosphere to generate initial plasma.
For example, Sn, which is a high temperature plasma raw material, is supplied into the discharge vessel in a gas state of stannane (SnH ₄ ), and initial plasma is formed by discharge. The ion density in the initial plasma is, for example, about 10 ¹⁶ cm ⁻³ , the electron temperature is, for example, about 1 eV or less, and the above EUV radiation conditions (that is, the ion density of 10 ¹⁷ to 10 ²⁰ cm ⁻³ , electrons (Temperature is 20-30 eV) not satisfied (initial state of pinch in FIG. 38).
Here, the above-mentioned initial plasma is contracted in the radial direction of the discharge flow path by the action of the self-magnetic field of the direct current flowing between the electrodes by the discharge. As a result, the density of the initial plasma increases and the plasma temperature also rises rapidly. Such an action is hereinafter referred to as a pinch effect. Due to heating by the pinch effect, the ion density of the plasma that has become high temperature reaches 10 ¹⁷ to 10 ²⁰ cm ⁻³ and the electron temperature reaches about ²⁰ to ³⁰ eV, and EUV is emitted from this high temperature plasma. (Route 2 in FIG. 38)
That is, in the DPP method, the generated plasma is compressed, so that the plasma satisfies the above EUV radiation conditions (that is, ion density of 10 ¹⁷ to 10 ²⁰ cm ⁻³ and electron temperature of ^{20 to} 30 eV). To do.

In the LAGDPP method, a target (high temperature plasma raw material) such as solid or liquid is irradiated with a laser beam to vaporize the raw material to generate a gaseous high temperature plasma raw material atmosphere (initial plasma). Similar to the DPP method, the ion density in the initial plasma is, for example, about 10 ¹⁶ cm ⁻³ , the electron temperature is, for example, about 1 eV or less, and the above EUV radiation conditions (that is, the ion density is 10 ¹⁷ to 10 ²⁰ cm). ⁻³ , the electron temperature is not 20-30 eV) (initial state of the pinch in FIG. 38). Thereafter, due to compression and heating by driving the discharge current, the ion density of the plasma that has become high reaches 10 ¹⁷ to 10 ²⁰ cm ⁻³ and the electron temperature reaches about ²⁰ to ³⁰ eV, and EUV is emitted from this high temperature plasma.
Examples of LAGDPP are described in Patent Document 3, Patent Document 4, and Patent Document 5. Both of them describe vaporizing a high-temperature plasma raw material by laser irradiation to generate a “cold plasma”, generating a high-temperature plasma using a pinch effect by a discharge current, and emitting EUV from the high-temperature plasma. . That is, according to the conventional example, the heating by the discharge current driving in the LAGDPP method uses the pinch effect as in the DPP method. That is, in FIG. 38, high-temperature plasma that satisfies the EUV radiation conditions is formed via path 3 → path 2.

In the case of the LPP method, the high temperature plasma generated by irradiating the high temperature plasma raw material with a laser beam expands and cools within a short time. Therefore, the high-temperature plasma that has reached the EUV radiation condition is cooled within a short time (for example, 10 ns) and does not satisfy the EUV radiation condition, and the EUV radiation from the plasma stops.
On the other hand, in the case of the DPP method or the LAGDPP method, as described above, a pulsed discharge current flows between the discharge electrodes, and the initial plasma of the high temperature plasma raw material is compressed and heated by the pinch effect and reaches EUV radiation conditions.
However, the high-temperature plasma shrunk in the radial direction of the discharge channel rapidly expands in the direction of the discharge channel within a short time as the discharge current rapidly decreases, and the pinch effect disappears, and the density is lowered and cooled. The As a result, the plasma in the discharge region does not satisfy the EUV radiation condition, and the EUV radiation from the plasma stops.

In addition, the discharge between electrodes is started from the vacuum arc discharge by the laser trigger in a comparatively wide area | region, and transfers to gas discharge (a pinch discharge is also included) with high temperature plasma raw material supply. Thereafter, a discharge column (plasma column) is formed. In this specification, the “discharge region” is defined as a space including all the discharge phenomena.
In the above discharge region, when the discharge increases as the discharge column (plasma column) grows and the internal current density shifts to gas discharge, the discharge drive current flows predominantly in the discharge column. A spatial region having a high current density is defined as a “discharge channel”. Here, since the discharge channel is a region where the discharge drive current flows dominantly, this discharge channel is also referred to as a discharge path or a discharge current path.

Next, the long pulse conversion of EUV radiation will be described.
As described above, EUV radiation is generated in a pulse shape within a short time. Therefore, the energy conversion efficiency is extremely small. When an EUV light source device is used as a semiconductor exposure light source, the EUV light source device is required to operate with both high efficiency and high output as much as possible. If high-efficiency EUV generation conditions can be maintained for a long time, a high-efficiency and high-power EUV light source becomes possible. As a result, the emission pulse width is expected to be longer.
Patent Documents 6 and 7 disclose a method of making EUV radiation into a long pulse in a DPP EUV generator. Hereinafter, based on Patent Documents 6 and 7, a conventional long pulse method will be described with reference to FIGS. 39 and 40. FIG.
39 and 40 are diagrams showing the relationship of (a) plasma current I, (b) plasma radius column r, and (c) EUV radiation output with respect to the elapsed time from the start of discharge. The horizontal axis represents time, and the vertical axis represents plasma current I, plasma column radius r, and EUV radiation output. The long pulses of EUV radiation in Patent Documents 6 and 7 are realized by separately controlling the plasma heating and compression process and the high temperature and high pressure state maintaining process in the DPP type EUV generator.

In the conventional DPP method, as shown in FIG. 39, the waveform of the plasma current I flowing inside a uniform plasma column formed between a pair of electrodes increases with the passage of time after the start of discharge and passes a peak. The waveform decreases. Hereinafter, in order to facilitate understanding, the waveform of the current I is a sine waveform.
As the plasma current I increases, plasma heating and compression occur. In other words, the radius r of the generated plasma column gradually decreases due to the pinch effect as the plasma current I flows, and becomes the minimum when the value of the plasma current I starts to decrease beyond the peak.
Near the peak of the waveform of the plasma current I, the plasma temperature and ion density are within a predetermined range (for example, as shown in FIG. 38, the electron temperature is 5 to 200 eV, and the ion density is about 10 ¹⁷ to 10 ²⁰ cm ⁻³ ). During the period A that reaches, EUV radiation is generated.
However, after the peak of the waveform of the plasma current I passes, the current value decreases with time, so the pinch effect is weakened, the plasma expands, and the plasma temperature decreases. The expanding plasma has a large kinetic energy and quickly leaves the discharge region.
As a result, EUV radiation is terminated. The duration of EUV radiation is, for example, only about 10 ns.

On the other hand, the methods described in Patent Documents 6 and 7 are configured such that the waveform of the plasma current I flowing between the pair of electrodes is as shown in FIG. That is, the waveform of the plasma current I increases with the passage of time after the start of discharge, and further increases with the passage of time in the vicinity of the peak (for example, the vicinity of the time when the plasma is pinched and EUV radiation starts). Is.
As shown in FIG. 40, the waveform of the plasma current I is configured to include a heating current waveform portion (M) followed by a confined current waveform portion (N). The heating current waveform portion (M) is equivalent to the waveform of the plasma current I shown in FIG. In FIG. 40, for easy understanding, the heating current waveform portion (M) is shown as a sine waveform.

Within the period of the heating current waveform portion (M), plasma heating and compression occur as the plasma current I increases. That is, the radius r of the generated plasma is gradually reduced by the pinch effect as the plasma current I flows, and becomes minimum when the value of the plasma current I starts to decrease beyond the peak. In the vicinity of the peak of the waveform of the plasma current I, the plasma temperature and the ion density are within a predetermined range (for example, as shown in FIG. 38, the electron temperature is 5 to 200 eV and the ion density is about 10 ¹⁷ to 10 ²⁰ cm ⁻³ ). And EUV radiation is generated.
After EUV radiation is generated, the waveform of the plasma current I shifts to the confined current waveform portion (N).
As described above, the plasma compressed by the pinch effect tends to expand with a large kinetic energy. Here, when the intensity of the plasma current I is increased to strengthen the action of the self-magnetic field, the plasma to be expanded can be maintained in a compressed state.

When the pressure of the plasma in the pinch state is P _pp , the density of the plasma is n _pp , the Boltzmann coefficient is k, and the temperature of the plasma is T _pp , the pressure P _pp of the plasma in the pinch state is n _pp kT Proportional to _pp .
P _pp ∝n _pp kT _pp (101)
On the other hand, the compression pressure P _B by the self-magnetic field B of the plasma current I is made, the _zero magnetic permeability in a vacuum mu, when the plasma radius is r,
P _B = μ ₀ I ² / 2πr (102)
It becomes. here,
P _B ≧ P _pp (103)
If this condition is satisfied, the plasma is maintained in a pinch state. Here, since the plasma in the pinch state is a high-temperature plasma having a large plasma density n _pp and plasma temperature T _pp, it is necessary to increase the plasma current I in order to satisfy the equation (103).

That is, by increasing the plasma current I after the plasma is pinched and then maintaining the current value constant, the pinch effect is maintained and the plasma temperature and ion density are within a predetermined range (plasma radius). Is small).
Theoretically, EUV radiation continues while the plasma temperature and ion density are maintained within predetermined ranges (period B in FIG. 40). That is, EUV radiation can be made into a long pulse.
FIG. 40 shows an example in which the time point when the plasma is pinched and the plasma radius is minimized is the transition point from the heating current waveform portion (M) to the confined current waveform portion (N).

  Actually, even if the plasma current I has a confined current waveform portion (N) that maintains a current value peak exceeding the peak of the heating current waveform portion (M), the plasma column due to the growth of fluid instability It is difficult to maintain the high temperature plasma in a compressed state for a long time due to the collapse of the plasma. For this reason, the confined current waveform portion (N) eventually decreases with time, the pinch effect is weakened, the plasma expands, and the plasma temperature decreases. As a result, EUV radiation is terminated. In the example of Patent Document 6, it is described that the EUV output maintenance time (maintenance time of high-temperature plasma) can be long-pulsed to about 30 ns.

FIG. 41 is a configuration example of a DPP-type EUV light source device for realizing the long pulse method of EUV radiation described in Patent Documents 6 and 7.
A high temperature plasma raw material is introduced from the raw material supply / exhaust unit 16 into the chamber 1 which is a discharge vessel. The high temperature plasma raw material is a raw material for forming a radioactive species that emits EUV radiation having a wavelength of 13.5 nm in the high temperature plasma generation unit 10 in the chamber 1, and is, for example, xenon (Xe) or Sn vapor. The introduced high-temperature plasma raw material flows through the chamber 1 and reaches the gas outlet 17.
The raw material supply / exhaust unit 16 has exhaust means (not shown) such as a vacuum pump, and the exhaust means is connected to a gas exhaust port 17 of the chamber.
That is, the high temperature plasma raw material that has reached the gas exhaust port 17 is exhausted by the exhaust means provided in the raw material exhaust / supply unit 16.

In the chamber 1, a ring-shaped first main discharge electrode (cathode) 11 and a second main discharge electrode (anode) 12 are disposed via an insulating material 1 f. The chamber 1 includes a first container 1d on the first main discharge electrode side made of a conductive material and a second container 1e on the second main discharge electrode side made of the same conductive material. The first container 1d and the second container 1e are separated and insulated by the insulating material 1f.
The second container 1d and the second main discharge electrode 12 of the chamber 1 are grounded, and the first container 1d and the first main discharge electrode 11 are supplied with approximately -5 kV to -20 kV from the pulse power generator 5. Is applied. As a result, a discharge is generated in the high temperature plasma generator 10 between the ring-shaped first and second main discharge electrodes 11 and 12, and high temperature plasma is generated by the pinch effect as described above. EUV radiation with a wavelength of 13.5 nm is generated. The generated EUV radiation is reflected by the EUV collector mirror 2 provided on the second main discharge electrode 12 side, and is emitted from the EUV light extraction unit 7 to an irradiation unit (not shown).

Incidentally, the plasma current (discharge current) waveform shown in FIG. 40A is obtained as follows, for example. Another current that is not another sine waveform is superimposed on a current having a sine waveform. That is, the confined current waveform portion (N) is formed by superimposing a current having a pattern different from that of the heating current waveform portion (M) on the current having the heating current waveform portion (M).
In order to obtain such a current waveform, the high voltage pulse generation unit 5 is configured in parallel with, for example, discharge circuit units having independent switching elements SW1 and SW2 as shown in FIG.

The pulse power generation unit 5 shown in FIG. 41 includes a discharge circuit unit A1 composed of a series circuit of a capacitor C1 and a switch SW1, and a discharge circuit unit A2 composed of a series circuit of a capacitor C2 and a switch SW2. The electrode 11 and the second main discharge electrode 12) are connected in parallel. Here, the high voltage power supply CH is for charging the capacitors C1 and C2. The coil L1 represents an inductance component obtained by combining the parasitic inductance of the capacitor C1 and the inductance of the circuit loop formed by the capacitor C1, the switch SW1, and the load. Similarly, the coil L2 represents an inductance component obtained by combining the parasitic inductance of the capacitor C2 and the inductance of the circuit loop formed by the capacitor C2, the switch SW2, and the load. The diodes D ₁ and D ₂ are for regulating the current direction so that the electrical energy stored in the capacitors C 1 and C ₂ is transferred only to the load.

The high voltage pulse generator shown in FIG. 41 operates as follows. The first high-voltage power source CH, charges the capacitor C1, C2 of the discharge circuit via a respective diode D _1, D _2. Next, the first switch SW1 of the discharge circuit unit 1 is turned on, and the electric energy stored in the first capacitor C1 is applied between the first main discharge electrode 11 and the second main discharge electrode 12 for discharging. To start. At this time, the current flowing between the first discharge electrode 11 and the second discharge electrode 12 is used for plasma pinch. That is, high temperature plasma is generated by Joule heating due to the pinch effect. This current corresponds to the heating current waveform portion (M) in the waveform of FIG.

Next, when emission of EUV light having a wavelength of 13.5 nm starts due to the pinch effect of the plasma, the second switch SW2 of the discharge circuit unit A2 is turned on, and the electric energy stored in the second capacitor C2 is changed to the first When applied between the main discharge electrode 11 and the second main discharge electrode 2b, the current from the second capacitor C2 is added to the current flowing between the first discharge electrode 11 and the second discharge electrode 2b. This current is used as a current for maintaining the pinch state of the high-temperature high-density plasma. In the waveform of FIG. 40A, it corresponds to the confined current waveform portion (N).
The control of the first switch SW1 and the second switch SW2 and the control of the raw material supply / exhaust unit 16 are performed by the main controller 26. The main controller 26 controls the control elements based on the operation command signal from the control unit 27 of the exposure machine.

“Current Status and Future Prospect of EUV Light Source for Lithography” J. Plasma Fusion Res. Vol. 79. No. 3, P219-260, March 2003 Special table 2005-522839 JP 2004-214656 A JP-T-2007-515741 Special table 2007-505460 gazette International Publication No. 2005/101924 Pamphlet International Publication No. 2006/120942 Pamphlet JP 2007-123138 A JP-T-2002-504746

However, the configuration of the apparatus as disclosed in Patent Document 1 has the following problems. According to the EUV light source device, the position of the discharge channel is defined by the irradiation of the laser beam. However, in order to realize efficient generation of EUV radiation, it is necessary to set the high-temperature plasma raw material (gas) distribution in the discharge channel to a predetermined spatial density distribution.
That is, even if the position of the discharge channel is defined, EUV light having a wavelength of 13.5 nm is generated from the plasma generated by the discharge if, for example, the density distribution of the high-temperature plasma raw material (gas) in the discharge channel is not a predetermined spatial density distribution. do not do.
In the EUV light source device of Patent Document 1, the source gas is supplied into the discharge vessel from a gas path provided in the inner electrode. However, since it is impossible to actively control the spatial density distribution of the high temperature plasma raw material (gas) in the discharge channel, the spatial density distribution of the high temperature plasma raw material (gas) suitable for EUV radiation is not necessarily in the discharge channel. It cannot be obtained.

  On the other hand, in the above-described conventional EUV radiation long pulse method, the EUV radiation long pulse method disclosed in Patent Documents 6 and 7 is used in a DPP type EUV generator in a plasma heating and compression process and a high temperature and high pressure state. This is realized by controlling the maintenance process separately. That is, in order to maintain the pinch state of the plasma, as shown in FIG. 40A, the value of the plasma current I after the plasma reaches the pinch state is higher than that of the conventional DPP method. It is necessary to supply energy to the discharge space so as to be larger than the value of the plasma current I before reaching.

  After the end of EUV radiation, the energy supplied to the discharge space is converted into heat. In a DPP type EUV generator that employs a conventional long pulse method, a larger discharge current flows than a general DPP method that does not employ a long pulse technology in order to maintain the pinch state of plasma. For this reason, in such an EUV generation apparatus, heat input to the electrode is increased as compared with the conventional DPP type EUV generation apparatus. For this reason, a part of the electrode is melted, evaporated, or sputtered by heat load to form debris, and the debris easily damages the EUV collector mirror.

Further, in order to maintain the plasma pinch state, it is necessary to change the waveform of the plasma current I as shown in FIG. Here, the time during which the plasma is pinched to a high temperature state by the heating current waveform portion (M) of the waveform of the plasma current I shown in FIG. 40A is about 10 ns, and in order to maintain the pinch state In this period, it is necessary to flow the plasma current I so that the confined current waveform portion (N) having the waveform of the plasma current I is generated.
In other words, the allowable error of the time for supplying the current for generating the confined current waveform portion (N) of the current waveform must be about 10 ns or less, and high-precision control is required for synchronizing the operation timings of the switches SW1 and SW2. Is required.

The present invention has been made in view of the above circumstances, and a first problem of the present invention is that the position of the discharge channel can be defined and the density of the high-temperature plasma raw material (gas) in the discharge channel is determined. An object of the present invention is to provide an EUV light source apparatus and an EUV generation method that can be set as appropriate.
Further, the second problem of the present invention is that the first problem can be achieved, and that the EUV radiation is long without applying a large heat load to the electrode as in the prior art and without requiring high-precision control. An object of the present invention is to provide an extreme ultraviolet light generation method and an extreme ultraviolet light source device capable of realizing pulsing.

The EUV light source device of the present invention irradiates a first energy beam to a radiation species that emits EUV light having a wavelength of 13.5 nm, that is, solid or liquid Sn or Li that is a raw material for high-temperature plasma. Vaporize. The vaporized high temperature plasma raw material spreads at a predetermined speed around the normal direction of the surface of the high temperature plasma raw material on which the energy beam is incident.
Therefore, the high-temperature plasma raw material that is vaporized by the first energy beam irradiation and spreads at a predetermined speed is the discharge region and the position of the raw material, the irradiation direction of the first laser beam to the raw material, the irradiation energy of the first energy, etc. Is appropriately set to be supplied to the discharge region.
As the energy beam, a laser beam, an ion beam, an electron beam, or the like can be employed.

Here, by appropriately setting the intensity (energy) of the first energy beam and the irradiation direction, the spatial density distribution of the vaporized high temperature plasma raw material in the discharge region can be set to a predetermined distribution.
On the other hand, by irradiating the predetermined position of the discharge region with the second energy beam, the discharge starts and the position of the discharge channel can be defined as the irradiation position of the second energy beam. For example, when the second energy beam is a laser beam, the position of the discharge channel is defined at a position where the laser focus is set by condensing the laser beam (starting laser beam) at a predetermined position in the discharge region. It becomes possible to do. Therefore, the positional stability of the generation point of EUV radiation is improved.
Further, as described above, since the discharge starts when the second energy beam is irradiated to a predetermined position in the discharge region, the discharge start timing is controlled by controlling the irradiation timing of the second energy beam. It becomes possible to control.

Here, by appropriately setting the irradiation timing of the first energy beam and the irradiation timing of the second energy beam, at least one of the vaporized raw materials whose spatial density distribution is a predetermined distribution in the discharge channel where the position is defined. With the part reaching the discharge channel, it is possible to generate a discharge so that the magnitude of the discharge current is equal to or greater than the lower limit of the discharge current value required to obtain EUV radiation of a predetermined intensity It becomes.
As a result, efficient EUV radiation can be realized.

Hereinafter, (1) irradiation timing of the first energy beam (raw material energy beam) and second energy beam (starting energy beam), (2) electrode position, raw material supply position, and raw material energy beam irradiation position. The mutual relationship, (3) the energy of the energy beam for raw materials will be described. Hereinafter, a laser beam is taken as an example of the energy beam. (1) Timing Hereinafter, the EUV generation method in the present invention will be described with reference to a timing chart.
1 and 2 are timing charts for explaining the EUV generation method in the present invention. FIG. 1 shows a case where the first laser beam is irradiated faster than the second laser beam, and FIG. A case where the first laser beam is irradiated later than the second laser beam is shown.
First, as shown in FIGS. 1 and 2, a trigger signal is input (time Td) to a switching means (for example, IGBT) of a pulse power supply means that applies pulse power between a pair of electrodes, and the switching means is turned on. (See FIGS. 1 and 2A).

After Δtd, the interelectrode voltage reaches the threshold value Vp (see FIG. 5B). This threshold value Vp is a voltage value when the value of the discharge current that flows when discharge occurs is equal to or greater than the threshold value Ip (the description of the threshold value Ip will be described later). That is, when discharge occurs below the threshold value Vp, the peak value of the discharge current does not reach the threshold value Ip.
If no discharge occurs as it is, the voltage between the electrodes reaches the maximum voltage and is maintained. (Dashed line in Fig. 2 (b))
At a time T2 (T2 = Td + Δtd) after the time when the interelectrode voltage reaches the threshold value Vp, the second laser beam (starting laser beam) is irradiated onto the discharge region (see FIG. 3C). Note that the second laser beam may be applied to one of the pair of electrodes. Hereinafter, the discharge region includes the electrode surface.

Discharge is started by irradiation with the second laser beam (starting laser beam), and after Δti, the magnitude of the discharge current reaches the above-described threshold value Ip (see FIG. 4D). This threshold value Ip is a lower limit of the discharge current value necessary for obtaining EUV radiation having a predetermined intensity. A period during which the discharge current value is equal to or greater than the threshold value Ip is denoted by Δtp.
During the Δtp period after this time (T2 + Δti), the vaporized raw material is vaporized by the first laser beam (raw material laser beam), and the vaporized raw material has a predetermined spatial density distribution among the high-temperature plasma raw materials spreading at a predetermined speed. The raw material is irradiated with the first laser beam so that at least a part reaches the discharge region.
When the time from when the first laser beam is irradiated to the raw material to when at least a part of the vaporized raw material having a predetermined spatial density distribution reaches the discharge region is denoted by Δtg, (T2 + Δti−Δtg) ˜ ( The raw material laser beam is irradiated at a time point (T1) during the period of (T2 + Δti + Δtp−Δtg) (see FIG. 5E). Thereby, EUV light is radiated (see (f) in the figure).
Here, FIG. 1 shows an example in which the rise of the discharge current is quick and the second laser beam (starting laser beam) is irradiated after the first laser beam (raw material laser beam) is irradiated.
On the other hand, FIG. 2 shows an example in which the rise of the discharge current is slow and the first laser beam is irradiated after the second laser beam irradiation.

(2) Interrelationship between electrode position, raw material supply position, and raw material laser beam irradiation position As described above, in the EUV light source device of the present invention, high-temperature plasma vaporized by the first laser beam (raw material laser beam). The raw material is allowed to reach the discharge area. An example of the positional relationship is shown below.
As an example, the case where the supply of the high-temperature plasma raw material serving as the target of the first laser beam is dropped in the form of droplets will be described. Note that the method of supplying the high-temperature plasma raw material is not limited to this. For example, as shown later, a wire-shaped high temperature plasma raw material may be supplied.

FIGS. 3A and 3B are schematic configuration diagrams for explaining the positional relationship. FIG. 3A is a top view and FIG. 3B is a front view. That is, FIG. 3B is a view of FIG. 3A viewed from the direction of the arrow. In the figure, 11 is an electrode (anode), 12 is an electrode (cathode), 2 is an extreme ultraviolet light collector mirror (hereinafter also referred to as EUV collector mirror), 20 is a raw material supply means, 21 is a raw material, and 23 is a first material. 1 laser beam (laser beam for raw material).
The first laser beam 23 is applied to the dropped high temperature plasma raw material 21. The irradiation position is a position where the dropped high temperature plasma raw material 21 has reached the vicinity of the discharge region.
In the example shown in FIG. 3, a pair of plate-like electrodes 11 and 12 are arranged at a predetermined interval. The discharge region is located in the space between the pair of electrodes 11 and 12. The high temperature plasma raw material 21 is a space between the pair of electrodes 11 and 12 and the extreme ultraviolet light collector mirror 2 by the raw material supply means 20 and is supplied in the gravity direction to the vicinity of the discharge region.

When the high temperature plasma raw material 21 reaches the vicinity of the discharge region, the first laser beam 23 is irradiated to the high temperature plasma raw material 21. The high temperature plasma raw material vaporized by irradiation with the first laser beam 23 spreads around the normal direction of the surface of the high temperature plasma raw material on which the first laser beam 23 is incident.
Therefore, when the first laser beam 23 is irradiated to the side of the surface of the high-temperature plasma raw material 21 supplied by the raw material supply means 20 that faces the discharge region, the vaporized high-temperature plasma raw material 21 ′ becomes the direction of the discharge region. To spread.
Here, the EUV collector mirror 2 described above often constitutes an oblique incident optical system that sets the condensing direction so that the optical axis is in one direction. In order to construct such an oblique incidence optical system, generally, an EUV collector mirror having a structure in which a plurality of thin concave mirrors are arranged with high precision in a nested manner is used. In the EUV collector mirror having such a structure, the plurality of thin concave mirrors described above are supported by a support column that substantially coincides with the optical axis and a support that extends radially from the support column.

In FIG. 3, the first laser beam 23 is introduced from the optical axis direction defined by the condenser mirror 2 to irradiate the high temperature plasma raw material 21. Therefore, if there is a shift in the synchronization between the irradiation position of the first laser beam 23 and the high temperature plasma raw material position 21, the first laser beam 23 is irradiated to the EUV collector mirror 2, and in some cases, the EUV There is also a possibility of damaging the condenser mirror 2.
As described above, when it is necessary to prevent the first laser beam 23 from reaching the EUV collector mirror 2 when the first laser beam 23 is erroneously irradiated, as shown in FIGS. The traveling direction of the first laser beam 23 may be adjusted so as not to reach the EUV collector mirror 2.

By the way, the high temperature plasma raw material vaporized by the irradiation of the first laser beam 23 as described above spreads around the normal direction of the surface of the high temperature plasma raw material on which the first laser beam 23 is incident. Therefore, when the first laser beam 23 is irradiated to the side of the surface of the high temperature plasma raw material 21 facing the discharge region, the vaporized high temperature plasma raw material 21 ′ spreads in the direction of the discharge region.
Here, of the vaporized high temperature plasma raw material 21 ′ supplied to the discharge region by the irradiation of the first laser beam 23, a part of the high temperature plasma raw material 21 ′ that has not contributed to the high temperature plasma formation by the discharge, or the decomposition as a result of the plasma formation. A part of the generated atomic gas cluster comes into contact with the low temperature portion in the EUV light source device as debris and is deposited.

For example, when the high-temperature plasma raw material is Sn, a part of the metal cluster such as Sn or Snx of atomic gas that does not contribute to the formation of the high-temperature plasma or atomic gas decomposed as a result of the plasma formation is used as debris as an EUV light source. A tin mirror is made in contact with the low temperature part in the device.
Here, as shown in FIG. 4B, when the high temperature plasma raw material 21 is supplied by the raw material supply means to the space side where the EUV collector mirror 2 of the pair of electrodes 11 and 12 does not face, the first laser is supplied. The beam 23 is irradiated to the high temperature plasma raw material 21 from the EUV collector mirror 2 side so that the vaporized high temperature plasma raw material 21 ′ is supplied to the discharge region.
In this case, the high temperature plasma raw material vaporized by the irradiation with the first laser beam 23 spreads in the direction of the discharge region and the EUV collector mirror 2. That is, debris is emitted to the EUV collector mirror 2 by irradiation of the high temperature plasma raw material 21 with the first laser beam 23 and discharge generated between the electrodes 11 and 12. When debris accumulates on the EUV collector mirror 2, the reflectance of the EUV collector mirror 2 with respect to 13.5 nm is lowered, and the device performance of the EUV light source device is deteriorated.
Therefore, as shown in FIGS. 3 and 4A, the high temperature plasma raw material is supplied to the space between the pair of electrodes 11 and 12 and the EUV collector mirror 2 and in the vicinity of the discharge region. It is preferable to do.

When the high temperature plasma raw material 21 supplied in this way is irradiated with the first laser beam 23 on the side of the high temperature plasma raw material surface facing the discharge region as described above, the vaporized high temperature plasma raw material 21 ′ is Although it spreads in the direction of the discharge region, it does not spread in the direction of the EUV collector mirror 2.
That is, as described above, by supplying the high temperature plasma raw material 21 and setting the irradiation position of the first laser beam 23, it is possible to suppress debris from traveling to the EUV collector mirror 2. .

Here, a case is considered in which a pair of electrodes separated by a predetermined distance are columnar as shown in FIG. Here, FIG. 5A is a top view and FIG. 5B is a front view. That is, FIG. 5B is a diagram when FIG. 5A is viewed from the direction of the arrow.
In this case, the high-temperature plasma raw material 21 is a space on a plane perpendicular to the optical axis and is supplied to the vicinity of the discharge region, and the first laser beam 23 is heated from the direction perpendicular to the optical axis. Even if the plasma raw material 21 is irradiated, the vaporized high temperature plasma raw material 21 ′ does not spread in the direction of the EUV collector mirror 2. Therefore, the debris generated by the irradiation of the first laser beam 23 to the high temperature plasma raw material 21 and the discharge generated between the electrodes 11 ′ and 12 ′ hardly proceeds with respect to the EUV collector mirror 2.
Of course, even when a pair of electrodes separated by a predetermined distance is columnar, as shown in FIG. 3 and FIG. You may supply with respect to the space between optical mirrors and the discharge region vicinity.

(3) Regarding the energy of the raw material laser beam The time Δtg from when the first laser beam (raw material laser beam) 23 is irradiated to the raw material until at least a part of the vaporized raw material reaches the discharge region is the discharge region. And the raw material irradiated with the first laser beam 23 and the speed at which the vaporized raw material spreads.
Here, the distance between the discharge region and the raw material 21 irradiated with the first laser beam is such that the position of the discharge region and the raw material 21 and the first laser beam 23 on the raw material 21 when the first laser beam 23 is irradiated. Depends on the direction of irradiation.
On the other hand, as described above, the high-temperature plasma raw material 21 ′ vaporized by the irradiation with the first laser beam 23 has a predetermined velocity centered on the normal direction of the surface of the high-temperature plasma raw material on which the first laser beam 23 is incident. Spread with. The predetermined speed depends on the irradiation energy of the first laser beam 23 applied to the raw material 21.

After all, the time Δtg from the time when the raw material is irradiated with the first laser beam 23 until at least a part of the vaporized raw material having a predetermined spatial density distribution reaches the discharge region is the position of the discharge region and the raw material 21. Depending on the irradiation direction of the first laser beam 23 to the raw material 21 and the irradiation energy of the first laser beam 23, the predetermined time is set by appropriately setting these parameters.
Note that, by appropriately setting these parameters, the spatial density distribution of the vaporized high temperature plasma raw material can be set to a predetermined distribution.

When the above-mentioned first laser beam (raw material laser beam) 23 is irradiated to vaporize the raw material, the above-mentioned long pulse can be realized by appropriately selecting the irradiation condition and discharge current of the first laser beam. Become.
That is, in order to maintain the compressed state of the plasma due to the pinch effect, the EUV radiation conditions (that is, the ion density of 10 ¹⁷ to 10 ²⁰ cm ⁻³ and the electron temperature of 20 to 20 are applied without flowing a large current to the discharge region. A high temperature plasma satisfying about 30 eV) is maintained, and a long pulse of EUV radiation is realized.

The high temperature plasma generation in the DPP method of the present invention will be described with reference to FIG. Note that the vertical and horizontal axes in FIG. 6 are the same as those in FIG.
An energy beam is irradiated to a solid or liquid high-temperature plasma raw material (shown as an example of a fuel solid in FIG. 6) disposed outside the discharge region. For example, a laser beam is used as the energy beam. Hereinafter, a laser beam will be described as an example.
The solid or liquid high-temperature plasma raw material irradiated with the laser beam is heated and vaporized, and reaches a discharge channel formed in advance in the discharge region. Here, the vaporized high temperature plasma raw material is a laser beam so as to be a low temperature plasma gas having an ion density of about 10 ¹⁷ to 10 ²⁰ cm ⁻³ and an electron temperature of about 1 eV or less when reaching the discharge region. The irradiation energy is appropriately set. That is, by irradiating a high-temperature plasma raw material with a laser beam, a low-temperature plasma gas in which the ion density in the plasma satisfies the EUV radiation conditions but the electron temperature is low is formed. (Route (I) in FIG. 6)

  The low temperature plasma is supplied to a discharge channel formed in advance in a discharge region between the electrodes, and the low temperature plasma is heated by a discharge current. Here, regarding the ion density of the low temperature plasma gas, since the EUV radiation conditions are already satisfied, the compression effect by the pinch effect as in the conventional DPP method may be small. That is, the current flowing between the electrodes mainly contributes only to the heating of the low temperature plasma. The electron temperature of the plasma reaches 20 to 30 eV by heating, and EUV is radiated from the high-temperature plasma that has become the EUV radiation condition (path (II) in FIG. 6).

Here, it is possible to realize a long pulse of EUV radiation by continuously supplying the above-described low-temperature plasma gas to a discharge channel previously formed between the electrodes. Hereinafter, the long pulse method will be described with reference to FIGS.
7 shows a multi-pinch method, and FIG. 8 shows a non-pinch method.

FIG. 7 is a diagram for explaining plasma current, low-temperature plasma radius, and EUV radiation in the case of the multi-pinch method.
Electric power is supplied between the electrodes, and at time t = t ₀ (by applying a trigger), vacuum discharge starts and current starts to flow, and a discharge channel (discharge current path) is formed (FIG. 7A). . At a time point tp when the current I reaches a threshold value Ip described later, the cross-sectional size of the discharge channel is thin due to the influence of the current self-magnetic field.
On the other hand, at the time point tp described above, a high-temperature plasma raw material irradiated with a laser beam (ie, a low-temperature plasma gas having an ion density corresponding to EUV radiation conditions and a low electron temperature) is selected as a thin discharge channel flowing in the discharge region. To reach the target.
Here, the current threshold Ip is defined as P _B , which is the compression pressure of the current due to the self-magnetic field, and the plasma pressure P _p .
P _B >> P _p (104)
Is set to be That is, the current value is set such that the low temperature plasma gas can be sufficiently compressed by the self magnetic field.
The threshold Ip can heat the electron temperature of the low-temperature plasma gas (the ion density in the plasma is about 10 ¹⁷ to 10 ²⁰ cm ⁻³ and the electron temperature is about 1 eV or less) to ^{20 to} 30 eV or more. It is also a current value having a large energy.

As described above, the low-temperature plasma selectively supplied to the thin discharge channel is generated by irradiating a solid or liquid high-temperature plasma raw material with a laser beam. The irradiation condition of the laser beam is appropriately set based on the distance from the high temperature plasma raw material arranged outside the discharge area to the discharge area. The irradiation energy is an energy that vaporizes the solid or liquid high-temperature plasma raw material but does not increase the electron temperature so much (* As shown in FIG. 6, the electron temperature slightly increases due to laser irradiation) For example, it is in the range of 10 ⁵ W / cm ² to 10 ¹⁶ W / cm ² .
By irradiating such a laser beam onto a solid or liquid high-temperature plasma raw material, a high-temperature plasma raw material (low-temperature plasma gas) having an ion density corresponding to EUV radiation conditions and a low electron temperature is continuously applied for about 10 μs. Can be supplied between the electrodes.
Generally, the discharge duration in the conventional DPP method and LAGDPP method is about 2 μs. That is, compared with the conventional discharge duration, the supply of the low-temperature plasma gas can be regarded as a steady continuous supply.

Conditions such as laser beam irradiation conditions and arrangement of the high-temperature plasma raw material are appropriately adjusted so that the low-temperature plasma gas selectively reaches the thin discharge channel. By such adjustment, a vaporized high temperature plasma raw material (low temperature plasma gas) flow with good directivity is configured, and the flow is set to be concentrated in the vicinity of a narrow discharge channel. By comprising in this way, a low-temperature plasma gas is selectively continuously supplied with respect to a thin discharge channel.
If a solid or liquid high-temperature plasma material is disposed in the discharge region, the energy generated by the discharge directly acts on the high-temperature plasma material, and the conditions for vaporizing the high-temperature plasma material change every moment. For this reason, a low-temperature plasma gas having an ion density corresponding to EUV radiation conditions and a low electron temperature cannot be selectively continuously supplied to a thin discharge channel.

The low-temperature plasma gas supplied to the narrow discharge channel is heated by a pinch effect by a current having a value equal to or higher than the threshold value Ip or a confinement effect by a self-magnetic field, and becomes high-temperature plasma, and EUV is emitted from this high-temperature plasma.
Here, since EUV radiation is realized through the path (II) in FIG. 6, the compression action by the pinch effect is small, and the ratio of the confinement effect by the self magnetic field and the heating process by Joule heating increases. That is, EUV radiation can be performed even when a relatively small current is applied to the discharge region instead of a large current as in the conventional DPP method and the LAGDPP method. Further, energy can be efficiently input (that is, heated) to the plasma without performing a high-speed and short pulse discharge current as in the prior art. Therefore, the discharge current pulse can be set longer than the conventional one.

The compressed high-temperature plasma is pushed out along the plasma density gradient in the discharge channel axial direction immediately after the maximum compression, and is separated mainly in the axial direction of the discharge channel. At the same time, the discharge channel expands in the radial direction, and as a result, the plasma density and the electron temperature inside the discharge channel rapidly decrease. Conventionally, EUV radiation has ended at this point.
However, as described above, since a steady flow of the low-temperature plasma gas exists around the discharge channel, the low-temperature plasma gas is supplied to the space where the plasma density in the discharge channel is reduced without time difference. Therefore, before the diameter of the discharge channel increases so much, the discharge channel becomes narrower again due to the pinch effect or the confinement effect by the self magnetic field, the low-temperature plasma gas is heated, and EUV radiation continues by the mechanism described above. ((B) and (c) of FIG. 7)

Such repetition of the pinch effect or the confinement effect due to the self magnetic field lasts as long as the discharge current continues.
As described above, in the present invention, since it is not necessary to shorten the current at high speed, it is possible to set the discharge current pulse longer than in the conventional case. That is, since the repetition of the confinement effect by the pinch effect or the self magnetic field can be maintained for a long period of time, it is possible to realize a long pulse of EUV radiation. Hereinafter, this method using the continuous pinch effect will be referred to as a multi-pinch method.

  In the conventional DPP method using the pinch effect, a high temperature plasma source gas having a low ion density is supplied to the discharge region. (Initial state of the pinch in FIG. 6). The low density gas is uniformly filled in the entire discharge vessel (discharge region). The discharge channel due to the initial plasma generated by the discharge in the low-density gas atmosphere is as thick as the diameter of the discharge vessel in the initial state. A current pulse is required. Further, in order to increase the energy input efficiency to the plasma by discharge, the discharge current must be shortened at high speed. Therefore, EUV radiation ends with a single pinch effect, and the pulse width of EUV radiation is about 200 ns at most. (Route 2 in FIG. 38)

Further, in the conventional DPP method, the low-density gas (high-temperature plasma raw material) in the discharge vessel enters the region where the first pinch is finished and the plasma density in the discharge channel is lowered. It becomes thicker and returns to the diameter of the discharge channel in the initial state in the first pinch effect. Therefore, if a multi-pinch is to be implemented, a large current is required as in the first pinch. Actually, as described above, since the discharge current is a high-speed short pulse, it is impossible to perform the second pinch in the remaining time after the end of the first pinch.
Also in the LAGDPP system, the pinch effect is used, and EUV radiation is generated via the path 2 via the path 3 of FIG. That is, a low-density high-temperature plasma source gas is supplied to the discharge region by laser irradiation of the high-temperature plasma source.
Hereinafter, as in the case of the DPP method, an initial plasma is generated by discharge in a low-density gas atmosphere, and a high-power current pulse is required to make the initial plasma a high-temperature plasma by the pinch effect, and a high discharge current is required. It is necessary to shorten the pulse. Thus, EUV radiation ends with a single pinch effect.

In addition, as disclosed in Patent Document 5, in the LAGDPP method, discharge is generated after discharge of the high-temperature plasma source gas by laser beam irradiation, so the ratio of the high-temperature plasma source gas that leaves the discharge region without being heated is high. Grows and is not efficient.
That is, in the conventional DPP method and LAGDPP method, in order to realize a long pulse of EUV radiation, as in Patent Document 6 or Patent Document 7, the plasma heating and compression process and the compression maintaining process are controlled separately. However, it is necessary to adopt a method of supplying energy to the discharge space so that the plasma current value after the plasma reaches the pinch state is larger than the plasma current value before the plasma reaches the pinch state. I don't get it.

By the way, when the compression pressure by the current self-magnetic field is P _B and the plasma pressure P _p ,
P _B ≧ P _p (105)
Even when the current value is set such that the low-temperature plasma gas is weakly compressed by the self-magnetic field and maintained at such a level that the low-temperature plasma gas expands and the ion density does not decrease. Long pulse of radiation can be realized.
The threshold value Ip2 can heat the electron temperature of the low-temperature plasma gas (the ion density in the plasma is about 10 ¹⁷ to 10 ²⁰ cm ⁻³ and the electron temperature is about 1 eV or less) to ^{20 to} 30 eV or more. It is also a current value having a large energy.

FIG. 8 is a diagram for explaining the plasma current, the low temperature plasma radius, and the EUV radiation in the case of the non-pinch method. Hereinafter, the non-pinch method will be described with reference to FIG.
Electric power is supplied between the electrodes, and discharge starts and current starts flowing at time t = t ₀ (FIG. 8A). At the time point tp when the current I reaches the threshold value Ip2, the cross-sectional size of the discharge channel is reduced by the influence of the current self-magnetic field. When the current threshold value Ip when the multi-pinch effect is used and the threshold value Ip2 are compared, Ip> Ip2, so that the cross-sectional size of the discharge channel is larger than when the multi-pinch effect is used.
On the other hand, at the time point tp described above, as in the case of using the multi-pinch effect, a low-temperature plasma gas having an ion density corresponding to EUV radiation conditions and a low electron temperature selectively reaches a narrow discharge channel flowing in the discharge region. Like that. As described above, the low temperature plasma gas is configured to be selectively supplied continuously to the thin discharge channel.

The low-temperature plasma gas supplied to the narrow discharge channel is heated in a state where the low-temperature plasma gas is maintained at such a level that the low-temperature plasma gas expands and the ion density does not decrease by being compressed with a current having a threshold value Ip2 or more. It becomes high temperature plasma, and EUV is radiated from this high temperature plasma. That is, since the ion density of the low-temperature plasma gas satisfies the EUV radiation conditions from the beginning, EUV radiation is realized by heating while maintaining the ion concentration (path (II) in FIG. 6).
Therefore, EUV radiation can be performed even when a relatively small current is passed through the discharge region instead of a large current as in the conventional DPP method and LAGDPP method. Further, energy can be efficiently input (that is, heated) to the plasma without performing a high-speed and short pulse discharge current as in the prior art. Therefore, the discharge current pulse can be set longer than the conventional one.

Here, since a steady flow of the low temperature plasma gas exists around the discharge channel, the low temperature plasma gas having a predetermined ion density is constantly supplied to the discharge channel. Therefore, while the discharge current continues, heating of the low temperature plasma gas is maintained in the discharge channel, and EUV radiation continues. ((B) and (c) of FIG. 8)
Even in this case, it is not necessary to shorten the current at high speed, so that the discharge current pulse can be set longer than in the prior art. That is, since continuous heating of the low temperature plasma gas and generation of the high temperature plasma can be maintained for a long period of time, it is possible to realize a long pulse of EUV radiation.
In this method, the current threshold Ip2 is set to such a current value that the low temperature plasma gas is weakly compressed by the self-magnetic field (maintained so that the low temperature plasma gas expands and the ion density does not decrease). It is heated without apparently shrinking, and becomes high-temperature plasma. Therefore, this method is hereinafter referred to as a non-pinch method.

Here, whether the multi-pinch method or the non-pinch method is determined by the thickness of the discharge channel if the drive current value is the same, and the shape of the discharge electrode, the beam diameter of the laser beam to be irradiated, etc. are selected. If the discharge channel is made thinner, the multi-pinch method is used, and if the discharge channel is made thicker, the non-pinch method is used.
In the non-pinch method, since the diameter of the discharge channel is larger than that of the multi-pinch method, the size of the high-temperature plasma is also larger than that of the multi-pinch method. That is, since the size of the EUV radiation source is larger than that of the multi-pinch method, when the present invention is applied to an EUV light source apparatus for exposure, the size of the EUV radiation source is reduced by adopting the multi-pinch method rather than the non-pinch method. This is preferable because it can be made smaller.

  When the EUV light is extracted by the multi-pinch method, the peak power input in one pinch is smaller than in the case where the same EUV output is extracted with a single pinch with the same energy conversion efficiency. Therefore, it becomes possible to suppress the peak power input to the electrode, and the generation of debris due to sputtering of the electrode can be reduced. In addition, the number of ions contributing to EUV emission in one pinch is small. Accordingly, the light source size can be reduced, which is advantageous in designing the exposure optical system.

As described above, in the present invention, a long pulse of EUV radiation is realized as follows.
(I) A narrow discharge channel is generated in advance in the discharge region.
(Ii) Outside a discharge region, a solid or liquid high temperature plasma raw material is irradiated with an energy beam and vaporized, and a low temperature plasma gas having an ion density corresponding to EUV radiation conditions and a low electron temperature (fuel vapor: ion in FIG. 6) A density of about 10 ¹⁷ to 10 ²⁰ cm ⁻³ and an electron temperature of about 1 eV or less).
(Iii) When the value of the discharge current reaches a predetermined threshold (Ip or Ip2), the low temperature plasma is selectively cooled to a low temperature so that the low temperature plasma gas reaches the thin discharge channel. Supply a steady flow of plasma gas. As a result, the discharge acts on the low temperature plasma, the electron temperature rises, passes through the path II in FIG. 6, forms high temperature plasma that satisfies the EUV radiation conditions, and generates EUV radiation.
(Iv) Here, since the low temperature plasma gas is supplied to the discharge channel formed in advance, the discharge current pulse does not have to be a large current, a high speed, and a short pulse, and the current pulse has a longer rise time than the conventional current pulse. It can be a pulse. EUV radiation continues as long as a somewhat narrow discharge channel persists. Therefore, the discharge circuit is configured such that the discharge current pulse is longer than that of the conventional DPP method and LAGDPP method, and the discharge current pulse is made longer, thereby making the duration of the narrow discharge channel longer than the conventional one. As a result, a long pulse of EUV radiation is realized.
(V) When the multi-pinch method is used and the current threshold is set to be Ip, the diameter of the thin discharge channel pulsates within the time when the discharge current pulse continues, but it is relatively thin. In this state, pinching of the low temperature plasma is repeatedly performed, and EUV radiation is generated.
When the current threshold is set to be Ip2 as a non-pinch method, the diameter of the thin discharge channel is relatively larger than that of the multi-pinch method within the time when the discharge current pulse continues. While maintaining a very thin state, the heating of the low temperature plasma is continued, the temperature and density of the plasma necessary for EUV radiation are maintained, and EUV radiation is generated.
In the non-pinch method, as described above, since the diameter of the discharge channel is larger than that of the multi-pinch method, the size of the high temperature plasma is also larger than that of the multi-pinch method.

Based on the above, in the present invention, the above-described problem is solved as follows.
(1) Raw material supply means for supplying a liquid or solid raw material, first energy beam irradiation means for irradiating the raw material with a first energy beam to vaporize the raw material, and discharging the vaporized raw material by discharge Generated in a discharge region of a discharge by a pair of electrodes separated by a predetermined distance, pulse power supply means for supplying pulse power to the electrodes, and a pair of electrodes for generating heat plasma by heating excitation in the container In an extreme ultraviolet light source device having condensing optical means for condensing extreme ultraviolet light emitted from the high-temperature plasma and an extreme ultraviolet light extraction unit for extracting the condensed extreme ultraviolet light, electric power is applied. By irradiating a second energy beam between the formed electrodes, a discharge is started in the discharge region and a second path that defines a discharge path at a predetermined position in the discharge region. Energy provided beam irradiation means.
The first energy beam irradiating means irradiates a first energy beam to a material supplied into a space excluding the discharge region, where the vaporized material can reach the discharge region. .
(2) Raw material supply means for supplying a liquid or solid raw material, first energy beam irradiation means for irradiating the raw material with a first energy beam to vaporize the raw material, and discharging the vaporized raw material by discharge A pair of electrodes separated by a predetermined distance for generating heat plasma by heating and exciting in the container, pulse power supply means for supplying pulse power of 1 μs or more to the electrodes, and a discharge region of discharge by the pair of electrodes In an extreme ultraviolet light source device having condensing optical means for condensing extreme ultraviolet light radiated from the high temperature plasma generated inside, and an extreme ultraviolet light extraction unit for extracting the collected extreme ultraviolet light, By irradiating the second energy beam between the electrodes to which power is applied, discharge is started in the discharge region, and a discharge path is defined at a predetermined position in the discharge region. Providing a second energy beam irradiation means that.
The first energy beam irradiating means irradiates a source material disposed in a space outside the discharge path, where the vaporized source material can reach the discharge path, with the first energy beam, and the electrode After a discharge path is defined between them, a source gas having an ion density substantially equal to the ion density under extreme ultraviolet light emission conditions is supplied to the discharge path.
(3) In the above (1) and (2), the first energy beam irradiating means and the second energy beam irradiating means are configured such that at least a part of the vaporized material having a predetermined spatial density distribution reaches the discharge region. Each operation timing is set so that the discharge current of the discharge generated in the discharge region is equal to or greater than a predetermined threshold.
(4) In the above (1), (2) and (3), the raw material supply by the raw material supply means is performed by dropping the raw material into a droplet shape in the direction of gravity.
(5) In the above (1), (2), and (3), the raw material supply by the raw material supply means is performed by continuously moving the linear raw material using the raw material as a linear raw material.
(6) In the above (1), (2) and (3), the raw material supply means includes a raw material supply disk, and the raw material supply by the raw material supply means supplies the liquid raw material to the raw material supply disk as the raw material. The raw material supply disk supplied with the liquid raw material is rotated to move the liquid raw material supply unit of the raw material supply disk to the irradiation position of the energy beam.
(7) In the above (1), (2), and (3), the raw material supply means includes a capillary, and the raw material supply by the raw material supply means uses the raw material as a liquid raw material and the liquid raw material through the capillary as an energy beam. It is performed by supplying to the irradiation position.
(8) In the above (1), (2), and (3), a tubular nozzle is provided at the energy beam irradiation position of the raw material, and at least a part of the raw material vaporized by the energy beam irradiation is ejected from the tubular nozzle.
(9) In the above (8), a narrowed portion is provided in a part of the inside of the tubular nozzle.
(10) In the above (1), (2), (3), (4), (5), (6), (7), and (8), the discharge region is substantially parallel to the discharge direction generated between the pair of electrodes. Magnetic field applying means for applying a magnetic field is further provided.
(11) In the above (1), (2), (3), (4), (5), (6), (7), (8), (9), and (10), the pair of electrodes are disk-shaped electrodes, It is rotationally driven so that the discharge generation position changes.
(12) In the above (11), the pair of disc-shaped electrodes are arranged such that the edge portions of the peripheral portions of both electrodes face each other with a predetermined distance apart.
(13) In the above (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), and (12), a laser beam is used as the energy beam.
(14) A liquid or solid raw material for radiating extreme ultraviolet light supplied into a container including a pair of electrodes therein is irradiated with a first energy beam to vaporize the vaporized raw material. In an extreme ultraviolet light generation method for generating extreme ultraviolet light by generating heat by exciting with an electrode discharge to generate high-temperature plasma, the first energy beam is in a space excluding the discharge region and is vaporized. Irradiating the raw material supplied in the space where the raw material can reach the discharge region, and starting the discharge in the discharge region of the discharge by the pair of electrodes by the second energy beam irradiated to the discharge region; and A discharge path is defined at a predetermined position in the discharge region.
(15) A liquid or solid raw material for radiating extreme ultraviolet light supplied into a container including a pair of electrodes therein is irradiated with a first energy beam to vaporize, and the pair of vaporized raw materials is used. In the extreme ultraviolet light generation method of generating extreme ultraviolet light by generating heat by exciting by discharge with an electrode, the first energy beam is a space excluding the discharge region and is vaporized. The raw material is irradiated to the raw material supplied in a space where the raw material can reach the discharge region, and the discharge is started in the discharge region of the discharge by the pair of electrodes by the second energy beam irradiated to the discharge region, and A discharge path is defined at a predetermined position in the discharge region, and after the discharge path is defined between the electrodes, an ion density is extremely purple in the discharge path by the first energy beam. Supplying a substantially equal raw material gas to the ion density in the light emitting condition, the discharge, the raw material gas is heated to extreme ultraviolet radiation satisfying temperature, to continuously generate more extreme ultraviolet light 200 ns.
(16) In the above (15), the discharge current of the discharge generated in the discharge region is greater than or equal to a predetermined threshold at a timing when at least a part of the vaporized material having a predetermined spatial density distribution reaches the discharge region. As described above, the irradiation timings of the first energy beam and the second energy beam are respectively set.
(17) In the above (16), the time data of the discharge start timing and the time data of the timing at which the discharge current reaches a predetermined threshold value are acquired, and the first energy beam and the second energy beam are obtained based on both time data. Correct the irradiation timing.
(18) In the above (16) and (17), prior to the irradiation of the first energy beam and the second energy beam for which the irradiation timing is set, the first energy beam is irradiated to the raw material at least once.

In the present invention, the following effects can be obtained.
(1) By appropriately setting the intensity and irradiation direction of the first energy beam, the spatial density distribution of the vaporized high-temperature plasma raw material in the discharge region can be set to a predetermined distribution.
In addition, by irradiating a predetermined position in the discharge region with the second energy beam, the position of the discharge channel can be defined, and the position stability of the generation point of EUV radiation can be improved. Furthermore, the discharge start timing can be controlled by controlling the irradiation timing of the second energy beam.
(2) Upon irradiation with the first energy beam, at least a part of the vaporized material having a predetermined spatial density distribution reaches the discharge region, and the discharge current of the discharge generated in the discharge region is a predetermined threshold value. By setting the irradiation timings of the first energy beam and the second energy beam so that the second energy beam is irradiated at the timing described above, efficient EUV radiation can be performed.
(3) By providing a magnetic field application means for applying a magnetic field substantially parallel to the discharge direction generated between the pair of electrodes with respect to the discharge region, the size of the high-temperature plasma that emits EUV can be reduced, It is possible to increase the EUV radiation time.
(4) The pair of electrodes are disk-like electrodes and are rotationally driven so that the discharge generation position on the electrode surface changes, thereby reducing the wear speed of the electrodes and extending the life of the electrodes.
(5) The time data of the discharge start timing and the time data of the timing at which the discharge current reaches a predetermined threshold are acquired, and the irradiation timings of the first energy beam and the second energy beam are corrected based on both time data. By this, it is possible to reliably realize efficient EUV radiation.
(6) Prior to the irradiation of the first energy beam and the second energy beam for which the irradiation timing is set, the first energy beam is irradiated to the raw material at least once to generate discharge between the discharge electrodes. Therefore, it is possible to reliably generate a discharge at a desired timing.
(7) A narrow discharge channel is previously generated in the discharge region, and a steady flow of a low-temperature plasma gas having an ion density corresponding to EUV radiation conditions and a low electron temperature is selectively applied to the thin discharge channel from outside the discharge region. Since the EUV radiation is generated by supplying a discharge to the low temperature plasma gas, the discharge current does not need to be a large current as in the conventional DPP method and the LAGDPP method, and a relatively small current is supplied to the discharge region. EUV radiation is possible even if it is flowed.
Further, it is possible to efficiently input energy to the plasma without reducing the discharge current at a high speed and with a short pulse as in the prior art. Therefore, the discharge current pulse can be set longer than the conventional one.
In addition, the discharge circuit is configured so that the discharge current pulse is longer than that of the conventional DPP method and LAGDPP method, and the discharge current pulse is made longer, thereby making the duration of the narrow discharge channel longer than the conventional one. As a result, a long pulse of EUV radiation is realized.
For example, when the duration of the discharge channel is at least 1 μs or longer, the duration of the discharge channel can be reliably made longer than 200 ns. That is, if the duration of the discharge channel is set to 1 μs or more, the duration of EUV radiation can be reliably made longer than the duration of conventional EUV radiation (200 ns).

(8) In the long pulse, the discharge current does not need to be a large current as in the conventional DPP method and the LAGDPP method, and it is not necessary to perform a high-speed and short pulse of the discharge current. Therefore, it is possible to reduce the thermal load applied to the electrodes as compared with the conventional case, and it is possible to suppress the generation of debris.
(9) Unlike the conventional long pulse technology, it is not necessary to control the plasma current waveform so as to maintain the pinch state of the high temperature plasma, and therefore it is not necessary to flow a large current in the discharge space. Further, since it is not necessary to change the waveform of the plasma current in order to maintain the pinch effect, high-precision synchronous control and current control are not required.
(10) By irradiating the discharge path (discharge channel) with the energy beam for fixing the discharge path and fixing the discharge path with the energy beam, the position stability of the generation point of EUV radiation can be improved.

1. Embodiments FIG. 9 and FIG. 10 show the configuration (cross-sectional view) of an extreme ultraviolet (EUV) light source device according to an embodiment of the present invention. FIG. 9 is a front view of the EUV light source apparatus of this embodiment, and EUV radiation is extracted from the left side of the figure. FIG. 10 is a top view of the EUV light source apparatus of the present embodiment.
The EUV light source device shown in FIGS. 9 and 10 has a chamber 1 that is a discharge vessel. The chamber 1 is roughly divided into two spaces via a partition wall 1c having an opening. A discharge part is arranged in one space. The discharge unit is a heating excitation unit that heats and excites a high-temperature plasma raw material containing EUV radiation species. The discharge part is composed of a pair of electrodes 11, 12 and the like.

In the other space, EUV light emitted from high-temperature plasma generated by heating and exciting the high-temperature plasma raw material is collected, and irradiation optics of an exposure apparatus not shown from the EUV extraction section 7 provided in the chamber 1 is used. An EUV collector mirror 2 that leads to the system, and a debris trap for suppressing debris generated as a result of plasma generation by discharge from moving to the EUV light collector are disposed. In the present embodiment, as shown in FIGS. 9 and 10, the debris trap includes a gas curtain 13 b and a foil trap 3.
Hereinafter, the space in which the discharge unit is disposed is referred to as a discharge space 1a, and the space in which the EUV collector mirror is disposed is referred to as a condensing space 1b.

A vacuum exhaust device 4 is connected to the discharge space 1a, and a vacuum exhaust device 5 is connected to the condensing space 1b. The foil trap 3 is held in the light collection space 1b of the chamber 1 by, for example, a foil trap holding partition wall 3a. That is, in the example shown in FIGS. 9 and 10, the condensing space 1b is further divided into two spaces by the foil trap holding partition 3a.
In FIGS. 9 and 10, the discharge part is shown to be larger than the EUV condensing part, but this is for ease of understanding, and the actual magnitude relationship is as shown in FIGS. is not. Actually, the EUV collector is larger than the discharge part. That is, the condensing space 1b is larger than the discharge space 1a.

Hereinafter, each part and operation | movement of the EUV light source device of a present Example are demonstrated.
(1) Discharge part A discharge part consists of the 1st discharge electrode 11 which is a metal disk-shaped member, and the 2nd discharge electrode 12 which is also a metal disk-shaped member. The first and second discharge electrodes 11 and 12 are made of, for example, a refractory metal such as tungsten, molybdenum, or tantalum, and are disposed to face each other with a predetermined distance therebetween. Here, one of the two electrodes 11 and 12 is a ground side electrode, and the other is a high voltage side electrode.
Although the surfaces of both electrodes 11 and 12 may be arranged on the same plane, as shown in FIG. 10, the edge portion of the peripheral portion where the electric field concentrates when applying electric power has a predetermined distance so that electric discharge is likely to occur. It is preferable to arrange them so as to face each other with a distance therebetween. That is, it is preferable to arrange each electrode so that a virtual plane including each electrode surface intersects. The predetermined distance is the distance at the shortest distance between the edge portions of the peripheral portions of both electrodes.

As will be described later, when pulse power is applied to both the electrodes 11 and 12 from the pulse power supply means, discharge occurs at the edge portion of the peripheral edge. In general, a large amount of discharge is generated in the portion where the distance between the edge portions of the peripheral portions of the electrodes 11 and 12 is the shortest.
Consider a case where the surfaces of both electrodes 11 and 12 are arranged on the same plane. In this case, the predetermined distance is the distance at the shortest distance between the side surfaces of each electrode. In this case, the occurrence position of the discharge is on a virtual contact line formed when the side surface of the disk-shaped electrode and a virtual plane perpendicular to the side surface are brought into contact with each other. The discharge can occur at an arbitrary position on the virtual contact line of each electrode. Therefore, when both electrode surfaces are arranged on the same plane, the discharge position may not be stable.
On the other hand, as shown in FIG. 10, when the edge portions of the peripheral portions of the electrodes 11 and 12 are arranged so as to face each other with a predetermined distance therebetween, the distance between the edge portions of the peripheral portions of the electrodes 11 and 12 as described above. Since most discharge occurs in the shortest part, the discharge position is stabilized. Hereinafter, a space in which a discharge between both electrodes is generated is referred to as a discharge region.

As described above, when the edge portions of the peripheral portions of the electrodes 11 and 12 are arranged so as to face each other with a predetermined distance, when viewed from above as shown in FIG. 10, the first and second discharge electrodes The two electrodes are arranged in a radial pattern around a position where an imaginary plane including the surface of the two intersects. In FIG. 10, the part with the longest distance between the edge portions of the peripheral portions of both electrodes arranged radially is on the opposite side to the EUV collector mirror described later when the intersection position of the virtual plane is the center. It is installed to be located.
Here, the portion with the longest distance between the edge portions of the peripheral portions of the electrodes 11 and 12 arranged radially is located on the same side as the EUV collector mirror 2 with the intersection position of the virtual plane as the center. It is also possible to install it. However, in this case, the distance between the discharge region and the EUV collector mirror 2 becomes long, and the EUV collector efficiency is lowered accordingly, which is not practical.

The hybrid EUV light source apparatus of this embodiment uses EUV radiation from high-temperature plasma generated by current driving by discharge of a high-temperature plasma raw material vaporized by irradiation with a first laser beam (raw material laser beam). It is. The heating excitation means for the high temperature plasma raw material is a large current due to the discharge generated between the pair of electrodes 11 and 12. Therefore, the electrodes 11 and 12 are subjected to a large thermal load accompanying the discharge. Further, since high temperature plasma is generated in the vicinity of the discharge electrode, the electrodes 11 and 12 are also subjected to a thermal load from this plasma. Such a thermal load gradually wears the electrode and generates metal debris.
When the EUV light source device is used as a light source device of an exposure apparatus, the EUV radiation emitted from the high-temperature plasma is collected by the EUV collector mirror 2 and the collected EUV radiation is emitted to the exposure apparatus side. The metal debris damages the EUV collector mirror 2 and degrades the EUV light reflectance in the EUV collector mirror 2.
In addition, the electrodes 11 and 12 gradually wear out, so that the electrode shape changes. Thereby, the discharge generated between the pair of electrodes 11 and 12 becomes gradually unstable, and as a result, the generation of EUV light also becomes unstable.

When the above-described hybrid EUV light source device is used as a light source for a mass production type semiconductor exposure apparatus, it is necessary to suppress the above-described electrode wear and to make the electrode life as long as possible.
In order to meet such a demand, the EUV light source device shown in FIGS. 9 and 10 is configured such that the first electrode 11 and the second electrode 12 have a disk shape and rotate at least during discharge. is doing. That is, by rotating the first and second electrodes 11 and 12, the position where pulse discharge occurs in both electrodes changes for each pulse. Therefore, the thermal load received by the first and second electrodes 11 and 12 is reduced, the wear speed of the electrodes 11 and 12 is reduced, and the life of the electrodes can be extended. Hereinafter, the first electrode 11 is also referred to as a first rotating electrode, and the second electrode 12 is also referred to as a second rotating electrode.

  Specifically, a rotation shaft 22e of the first motor 22a and a rotation shaft 22f of the second motor 22b are respectively provided at substantially central portions of the first rotation electrode 11 and the second rotation electrode 12 on the disk. It is attached. When the first motor 22a and the second motor 22b rotate the rotary shafts 22e and 22f, respectively, the first rotary electrode 11 and the second rotary electrode 12 rotate. The direction of rotation is not particularly restricted. Here, the rotating shafts 22e and 22f are introduced into the chamber 1 through, for example, mechanical seals 22c and 22d. The mechanical seals 22c and 22d allow the rotation shaft to rotate while maintaining a reduced-pressure atmosphere in the chamber 1.

As shown in FIG. 9, the first rotating electrode 11 is arranged so that a part of the first rotating electrode 11 is immersed in a conductive first container 11 b that houses a conductive power supply molten metal 11 a. Similarly, the 2nd rotating electrode 12 is arrange | positioned so that the one part may be immersed in the electroconductive 2nd container 12b which accommodates the electroconductive molten metal 12a for electric power feeding.
The first container 11b and the second container 12b are connected to a power generator 8 which is a pulse power supply means via insulating power introduction sections 11c and 12c capable of maintaining a reduced pressure atmosphere in the chamber 1. . As described above, the first and second containers 11b and 12b and the molten metal for power supply 11a and 12a are conductive, and part of the first rotating electrode 11 and part of the second rotating electrode 12 are electrically conductive. Is immersed in the molten metal for power supply 11a, 12a, the first rotating electrode 11 is applied by applying pulse power from the pulse power generator 8 between the first container 11b and the second container 12b. A pulse power is applied between the second rotating electrode 12 and the second rotating electrode 12.
In addition, as the molten metal 11a, 12a for feeding, a metal that does not affect EUV radiation during discharge is employed. In addition, the molten metal 11a, 12a for power supply also functions as a cooling means for the discharge part of each rotary electrode 11, 12. Although not shown, the first container 11b and the second container 12b are provided with temperature adjusting means for maintaining the molten metal in a molten state.

(2) Discharge starting mechanism In the EUV light source device of the present embodiment, the second laser source 24a that irradiates a predetermined point in the discharge region with the second laser beam (starting laser beam) 24 and the second laser. A second laser control unit 24b for controlling the operation of the source 24b is provided.
As described above, since the edge portions of the peripheral portions of the rotary electrodes 11 and 12 are arranged so as to face each other with a predetermined distance, the distance between the edge portions of the peripheral portions of the electrodes 11 and 12 is the shortest portion. Many discharges occur. Therefore, the discharge position is stabilized. However, if the edge portion is deformed due to wear or the like due to discharge, the stability of the discharge position decreases.
Here, when the starting laser beam 24 is focused at a predetermined position in the discharge region, the conductivity is reduced by electron emission in the vicinity of the laser focus. Therefore, the position of the discharge channel is defined at the position where the laser focus is set. Therefore, the positional stability of the generation point of EUV radiation is improved.

Examples of the second laser source 24a that emits the second laser beam (starting laser beam) 24 include a carbon dioxide laser source, a solid-state laser source such as a YAG laser, a YVO ₄ laser, and a YLF laser, an ArF laser, and a KrF. An excimer laser source such as a laser or a XeCl laser can be employed.
In this embodiment, the laser beam is irradiated as an energy beam irradiated to a predetermined point in the discharge region. However, instead of the laser beam, an ion beam or an electron beam may be irradiated to the high temperature plasma raw material.

FIG. 11 shows an example of condensing the second laser beam (starting laser beam) 24. FIG. 11A shows an example in which the second laser beam 24 is focused on a predetermined point in the discharge region. For example, a convex lens 24d is used as the condensing optical system 24c. Dielectric breakdown between the electrodes is induced by concentrating the second laser beam 24 in a dot shape at a predetermined point in the discharge region in the vicinity of the electrodes. Here, in the vicinity of the laser focal point (condensing point), the conductivity is reduced by electron emission. Therefore, the position of the discharge channel is defined at the position where the laser condensing point is set.
That is, by fixing the dielectric breakdown occurrence point by laser irradiation, the position of the discharge channel is fixed to a local region of the discharge region. Therefore, the positional stability of the generation point of EUV radiation is improved. In particular, it is possible to reduce the generation point of EUV radiation by performing point focusing.

FIG. 11B shows an example in which the second laser beam 24 is focused on a predetermined point in the discharge region. As the condensing optical system 24b, for example, two cylindrical lenses 24e and 24f are used. As is well known, the cylindrical lens has a function of focusing or diffusing light only in one axial direction. Each of the two cylindrical lenses 24e and 24f shown in FIG. 11B has a function of focusing the second laser beam 24 in a uniaxial direction. The two cylindrical lenses are arranged so that the axial directions for converging the starting laser beam 24 are orthogonal to each other.
Dielectric breakdown between the electrodes is induced by focusing the second laser beam 24 linearly on a predetermined point in the discharge region in the vicinity of the electrodes. As with point focusing, the position of the discharge channel is defined on the laser focus.
That is, by fixing the line condensing position of the second laser beam 24 by laser irradiation, the position of the discharge channel is fixed to a local region of the discharge region. Therefore, the positional stability of the generation point of EUV radiation is improved.

(3) Pulse power generator The pulse power generator 8 which is a pulse power supply means includes a first container 11b and a second container 12b which are loads via a magnetic pulse compression circuit unit comprising a capacitor and a magnetic switch. That is, pulse power having a short pulse width is applied between the first rotating electrode 11 and the second rotating electrode 12.
9 and 10 show examples of the configuration of the pulse power generator.
The pulse power generator shown in FIGS. 9 and 10 has a two-stage magnetic pulse compression circuit using two magnetic switches SR2 and SR3 each composed of a saturable reactor. The capacitor C1, the first magnetic switch SR2, the capacitor C2, and the second magnetic switch SR3 constitute a two-stage magnetic pulse compression circuit.
The magnetic switch SR1 is for reducing switching loss in the solid state switch SW which is a semiconductor switching element such as IGBT and is also called magnetic assist. The solid-state switch SW is the switching means described above, and is also referred to as switching means below.

The configuration and operation of the circuit will be described below with reference to FIGS. First, the charging voltage of the charger CH is adjusted to a predetermined value Vin, and the main capacitor C0 is charged by the charger CH. At this time, the solid state switch SW such as IGBT is turned off.
When the charging of the main capacitor C0 is completed and the solid switch SW is turned on, the voltage applied to both ends of the solid switch SW is mainly applied to both ends of the magnetic switch SR1.
When the time integration value of the charging voltage V0 of the main capacitor C0 applied to both ends of the magnetic switch SR1 reaches a limit value determined by the characteristics of the magnetic switch SR1, the magnetic switch SR1 is saturated and the magnetic switch enters, and the main capacitor C0, the magnetic switch A current flows in the loop of SR1, the primary side of the step-up transformer Tr1, and the solid switch SW. At the same time, a current flows through the secondary side of the step-up transformer Tr1 and the loop of the capacitor C1, and the charge stored in the main capacitor C0 is transferred and charged to the capacitor C1.

Thereafter, when the time integral value of the voltage V1 in the capacitor C1 reaches a limit value determined by the characteristics of the magnetic switch SR2, the magnetic switch SR2 is saturated and the magnetic switch is turned on, and enters the loop of the capacitor C1, the magnetic switch SR2, and the capacitor C2. A current flows, and the charge stored in the capacitor C1 is transferred to charge the capacitor C2.
After this, when the time integration value of the voltage V2 in the capacitor C2 reaches a limit value determined by the characteristics of the magnetic switch SR3, the magnetic switch SR3 is saturated and the magnetic switch is turned on, and the first container and the second container, A high voltage pulse is applied between the first rotating electrode and the second rotating electrode.
Here, the pulse width of the current pulse flowing through each stage is set by setting the inductance of the capacity transfer type circuit of each stage composed of the magnetic switches SR2 and SR3 and the capacitors C1 and C2 to be smaller as it goes to the subsequent stage. A pulse compression operation is performed so that the pulses gradually become narrower, and it becomes possible to realize a strong short pulse discharge between the first rotating electrode and the second rotating electrode, and the input energy to the plasma also increases.

(4) Raw material supply and raw material vaporization mechanism The high temperature plasma raw material 21 for emitting extreme ultraviolet light is discharged from the raw material supply unit 20 provided in the chamber 1 in a liquid or solid state in the discharge region (of the first rotating electrode 11). A space between the edge portion of the peripheral edge portion and the edge portion of the peripheral edge portion of the second rotary electrode 12 is supplied in the vicinity of a space where discharge occurs. Specifically, the high temperature plasma raw material 21 is supplied to a space excluding the discharge region, where the vaporized high temperature plasma raw material can reach the discharge region.
The raw material supply unit 20 is provided, for example, on the upper wall of the chamber 1, and the high temperature plasma raw material 21 is supplied (dropped) in the form of droplets in the space near the discharge region.
The high-temperature plasma raw material supplied in the form of droplets is dropped and irradiated by a first laser beam (raw material laser beam) 23 emitted from the first laser source 23a when reaching the space near the discharge region. Being vaporized.

Examples of the first laser source 23a that emits the first laser beam 23 include a carbon dioxide gas laser source, a solid-state laser source such as a YAG laser, a YVO ₄ laser, and a YLF laser, an ArF laser, a KrF laser, and an XeCl laser. An excimer laser source or the like can be employed. In this embodiment, the laser beam is irradiated as an energy beam irradiated to the high temperature plasma raw material 21. However, instead of the laser beam, an ion beam or an electron beam may be irradiated to the high temperature plasma raw material.
As described above, the high temperature plasma raw material vaporized by the irradiation of the first laser beam 23 spreads around the normal direction of the surface of the high temperature plasma raw material on which the first laser beam 23 is incident. Therefore, it is necessary to irradiate the first laser beam 23 on the side of the surface of the high-temperature plasma material facing the discharge region so that the vaporized high-temperature plasma material spreads in the direction of the discharge region.

Here, a part of the high-temperature plasma raw material after vaporization supplied to the discharge region by the irradiation of the first laser beam 23 that did not contribute to the high-temperature plasma formation by the discharge, or decomposed as a result of the plasma formation. A part of the cluster of atomic gas comes into contact with the low temperature part in the EUV light source device as debris, and is deposited.
Therefore, it is preferable to supply the high temperature plasma raw material 21 and irradiate the high temperature plasma raw material 21 with the first laser beam 23 so that the vaporized high temperature plasma raw material does not spread in the direction of the EUV collector mirror.
Specifically, the high temperature plasma raw material 21 is a space between the pair of electrodes 11 and 12 and the EUV collector mirror 2 and is a space excluding the discharge region, and the vaporized high temperature plasma raw material is the discharge region. The raw material supply unit 20 is adjusted so as to be supplied to a space that can reach the position. Furthermore, the first laser beam 23 irradiates the raw material supplied to this space to the side of the high temperature plasma raw material surface facing the discharge region so that the vaporized high temperature plasma raw material spreads in the direction of the discharge region. As a result, the first laser source 23 is adjusted.
By adjusting as described above, it is possible to suppress debris from proceeding to the EUV collector mirror 2.

As described above, the high temperature plasma raw material vaporized by the irradiation of the first laser beam 23 spreads around the normal direction of the surface of the high temperature plasma raw material on which the first laser beam 23 is incident. Specifically, the density of the high-temperature plasma raw material that is vaporized and scattered by the irradiation of the first laser beam 23 becomes the highest in the normal direction, and decreases as the angle increases from the normal direction.
Based on the above, the supply position of the high temperature plasma raw material 21 to the discharge region and the irradiation conditions such as the irradiation energy of the first laser beam 23 are such that the spatial density distribution of the vaporized high temperature plasma raw material supplied to the discharge region is In the discharge region, the temperature is appropriately set so that the high temperature plasma raw material has a condition such that EUV radiation is efficiently extracted after being heated and excited.
A raw material recovery means 25 for recovering the high temperature plasma raw material that has not been vaporized may be provided below the space to which the high temperature plasma raw material is supplied.

(5) EUV light condensing unit The EUV light emitted from the discharge unit is collected by an oblique incidence type EUV condensing mirror 2 provided in the EUV light condensing unit, and EUV light extraction provided in the chamber 1 The light is guided from the unit 7 to the irradiation optical system of the exposure apparatus (not shown).
The oblique incidence type EUV collector mirror 2 generally has a structure in which a plurality of thin concave mirrors are arranged in a nested manner with high accuracy. The shape of the reflecting surface of each concave mirror is, for example, a spheroidal shape, a rotating paraboloid shape, or a Walter shape, and each concave mirror is a rotating body shape. Here, the Walter shape is a concave shape in which the light incident surface is composed of a rotation hyperboloid and a rotation ellipsoid, or a rotation hyperboloid and a rotation paraboloid in order from the light incidence side.
The base material of each concave mirror described above is, for example, nickel (Ni) or the like. Since EUV light having a very short wavelength is reflected, the reflecting surface of the concave mirror is configured as a very good smooth surface. The reflective material applied to the smooth surface is, for example, a metal film such as ruthenium (Ru), molybdenum (Mo), and rhodium (Rh). Such a metal film is densely coated on the reflecting surface of each concave mirror.
By configuring in this way, the EUV collector mirror can reflect and condense EUV light with an oblique incident angle of 0 ° to 25 ° satisfactorily.

(6) Debris trap In order to prevent damage to the EUV collector mirror 2 between the discharge unit and the EUV light collector, the first and second rotating electrodes 11, which are in contact with the high-temperature plasma generated after discharge, 12 captures the debris such as metal powder generated by sputtering the peripheral edge of the high-temperature plasma, or the debris caused by the EUV radiation species such as Sn or Li in the high-temperature plasma raw material, and allows only EUV light to pass through. A debris trap is installed.
As described above, in the EUV light source apparatus of the present embodiment shown in FIGS. 9 and 7, the debris trap is composed of the gas curtain 13 b and the foil trap 3.

The gas curtain 13b is constituted by a gas supplied from the gas supply unit 13 into the chamber 1 through the nozzle 13a.
FIG. 9 shows the gas curtain mechanism. The nozzle 13a has a rectangular parallelepiped shape, and the opening from which the gas is discharged has an elongated rectangular shape. When gas is supplied from the gas supply unit 13 to the nozzle 13a, sheet-like gas is released from the opening of the nozzle 13a, and a gas curtain 13b is formed. The gas curtain 13 b changes the traveling direction of the debris and suppresses the debris from reaching the EUV collector mirror 2. Here, the gas used for the gas curtain 13b is preferably a gas having a high transmittance with respect to EUV light. For example, a rare gas such as helium (He) or argon (Ar), hydrogen (H ₂ ), or the like is used. .
Further, a foil trap 3 is provided between the gas curtain 13 b and the EUV collector mirror 2. The foil trap 3 is described as “foil trap” in Patent Document 8, for example. The foil trap 3 is composed of a plurality of plates installed in the radial direction of the high temperature plasma generation region and a ring-shaped support that supports the plates so as not to block EUV light emitted from the high temperature plasma. Yes.

When such a foil trap 3 is provided between the gas curtain 13b and the EUV collector mirror 2, the pressure between the high temperature plasma and the foil trap 3 increases. As the pressure increases, the gas density of the gas curtain present in the field increases and collisions between gas atoms and debris increase. Debris reduces kinetic energy by repeated collisions. Therefore, energy when debris collides with the EUV collector mirror 2 is reduced, and damage to the EUV collector mirror 2 can be reduced.
In addition, the gas supply unit 14 may be connected to the light collection space 1b side of the chamber 1 to introduce a buffer gas unrelated to the emission of EUV light. The buffer gas supplied from the gas supply unit 14 passes through the foil trap 3 from the EUV collector mirror 2 side, and exhausts from the vacuum exhaust device 4 through the space between the foil trap holding partition wall 3a and the partition wall 1c. Is done. By generating such a gas flow, it is possible to prevent debris that could not be captured by the foil trap 3 from flowing into the EUV collector mirror 2 and reduce damage to the EUV collector mirror 2 due to debris.

Here, in addition to the buffer gas, a halogen gas such as chlorine (Cl ₂ ) or a hydrogen radical may be supplied from the gas supply unit 14 to the light collection space. These gases function as cleaning gases that react with the debris deposited on the EUV collector mirror 2 without being removed by the debris trap and remove the debris. Therefore, it is possible to suppress a decrease in function such as a decrease in reflectance of the EUV collector mirror due to debris deposition.

(7) Bulkhead The pressure in the discharge space 1a is set so that a discharge for heating and exciting the high-temperature plasma raw material vaporized by the laser beam irradiation for the raw material is generated satisfactorily and needs to be maintained in a vacuum atmosphere below to some extent. .
On the other hand, in the condensing space 1b, since it is necessary to reduce the kinetic energy of the debris by the debris trap, it is necessary to maintain a predetermined pressure at the debris trap portion.
9 and 10, a predetermined gas is flowed from the gas curtain, a predetermined pressure is maintained by the foil trap 3, and the kinetic energy of the debris is reduced. Therefore, it is necessary to maintain the condensing space in a reduced pressure atmosphere having a pressure of about several hundred Pa as a result.
Here, in the EUV light source device of the present invention, a partition wall 1c that partitions the inside of the chamber 1 into a discharge space and a condensing space is provided. The partition 1c is provided with an opening for spatially connecting both spaces. Since the opening functions as a pressure resistance, when the discharge space is exhausted by the vacuum exhaust device 4 and the condensing space is exhausted by the vacuum exhaust device 5, the gas flow rate from the gas curtain 13b, the size of the opening, the exhaust of each vacuum exhaust device. By appropriately considering the capability and the like, it is possible to maintain the discharge space 1a at several Pa and the light collection space 1b at appropriate pressures.

(8) Raw Material Monitor The raw material monitor 20a monitors the position of the raw material dropped from the raw material supply unit 20 in the form of droplets. For example, as shown in FIG. 9, the time when the raw material dropped from the raw material supply unit 20 reaches a position P1 in the vicinity of the raw material monitor 20a is monitored. As will be described later, based on the monitoring result, the time from when the raw material reaches the position P1 until it reaches the position P2 where the first laser beam (raw material laser beam) 23 is irradiated is obtained. The monitoring is performed using, for example, a known laser measurement method. The raw material detection signal is transmitted from the raw material supply monitor 20a to the control unit 26. Since the raw material 21 is dropped in the form of droplets as described above, the raw material detection signal becomes an intermittent pulse signal.

(9) Operation of Extreme Ultraviolet Light (EUV) Light Source Device When used as an exposure light source, the EUV light source device of the present embodiment operates as follows, for example. 13 and 14 are flowcharts showing the operation of this embodiment, and FIG. 15 is a time chart. The operation of this embodiment will be described below with reference to FIGS.
The control unit 26 of the EUV light source device stores time data Δtd, Δti, and Δtg shown in FIGS.
That is, Δtd is from when the trigger signal is input to the switching means of the pulse power supply means (pulse power generator 8) (time Td) until the switching means is turned on and the interelectrode voltage reaches the threshold value Vp. It's time. Δti is the time until the magnitude of the current flowing between the electrodes reaches the threshold value Ip after the start of discharge. Δtg is the time from when the raw material is irradiated with the first laser beam until at least a part of the vaporized raw material having a predetermined spatial density distribution reaches the discharge region.

In general, when the voltage V applied to the discharge electrodes 11 and 12 is large, the rise of the voltage waveform between the discharge electrodes becomes faster. Therefore, the above-described Δtd depends on the voltage V applied to the discharge electrodes 11 and 12. The control unit 26 of the EUV light source device stores the relationship between the voltage V and time Δtd obtained in advance through experiments or the like as a table.
Further, the control unit 26 of the EUV light source apparatus is a position where the raw material 21 is irradiated with the first laser beam (raw material laser beam) 23 when the raw material reaches a predetermined position (for example, P1 in FIG. 12). The time Δtm until reaching (for example, P2 in FIG. 12) is stored.
Further, the control unit 26 inputs the main trigger signal to the switching means of the pulse power supply means from the time when the main trigger signal is output to the correction means α, β and the switching means of the pulse power supply means. The delay time d1 until the time when becomes on is stored. The correction times α and β will be described later.

First, a standby command from the control unit of the EUV light source device is transmitted to the vacuum exhaust device 5, the vacuum exhaust device 4, the gas supply unit 13, the gas supply unit 14, the first motor 22a, and the second motor 22b ( Step S101 in FIG. 13 and S201 in FIG. 15).
The vacuum exhaust device 5, the vacuum exhaust device 4, the gas supply unit 13, and the gas supply unit 14 that have received the standby command start operation. That is, the evacuation device 4 operates and the discharge space becomes a vacuum atmosphere. On the other hand, the vacuum evacuation device 5 operates, the gas supply unit 13 operates to form the gas curtain 13b, and the gas supply unit 14 operates to supply the buffer gas and the cleaning gas into the condensing space 1b. As a result, the condensing space 1b reaches a predetermined pressure. Further, the first motor 22a and the second motor 22b operate, and the first rotating electrode 11 and the second rotating electrode 12 rotate. Hereinafter, the above-described operation states are collectively referred to as a standby state (step S102 in FIG. 13 and S202 in FIG. 15).

After such a standby state, the control unit 26 of the EUV light source device transmits an operation start command signal to the raw material supply unit 20 and the raw material monitor 20a (step S103 in FIG. 13 and S203 in FIG. 15).
The raw material supply unit 20 that has received the operation start command signal starts dropping the liquid or solid high-temperature plasma raw material (for example, liquid tin) for EUV radiation into a droplet. On the other hand, the material monitor 20a that has received the operation start command signal starts a monitoring operation, and transmits a material detection signal to the control unit 26 of the EUV light source device when the material reaches a position P1 described later (step S104 in FIG. 13). , S204 in FIG.
At this time, since the dropped raw material 21 is not irradiated with the first laser beam (raw material laser beam) 23, it is recovered by the raw material recovery means 25 as it is.
The control unit 26 of the EUV light source apparatus transmits a standby completion signal to the control unit 27 of the exposure apparatus (step S105 in FIG. 13 and S205 in FIG. 15).

The control unit 26 of the EUV light source apparatus receives a light emission command from the control unit 27 of the exposure apparatus that has received the standby completion signal. When the exposure apparatus controls the intensity of EUV radiation, the emission command includes intensity data of EUV radiation. (Step S106 in FIG. 13 and S206 in FIG. 15).
The control unit 26 of the EUV light source device transmits a charge control signal to the charger CH of the pulse power generator 8. The charge control signal includes, for example, a discharge start timing data signal. As described above, when EUV radiation intensity data is included in the light emission command from the control unit 27 of the exposure apparatus, a charging voltage data signal for the main capacitor C0 is also included in the charging control signal.
For example, the relationship between the EUV radiation intensity and the charging voltage to the main capacitor C0 is obtained in advance by experiments or the like, and a table storing the correlation between the two is created. The control unit 26 of the EUV light source apparatus stores this table, and calls the charging voltage data of the main capacitor C0 from the table based on the EUV radiation intensity data included in the light emission command received from the control unit 27 of the exposure apparatus. . Based on the called charging voltage data, the control unit 26 of the EUV light source device transmits a charging control signal including a charging voltage data signal for the main capacitor C0 to the charger CH of the pulse power generator (step S107 in FIG. 13). , S207 in FIG.
The charger CH charges the main capacitor C0 as described above. (Step S108 in FIG. 13).

The control unit 26 of the EUV light source device determines whether or not the first EUV light is generated (referred to as the first pulse) after the operation is started (step S109 in FIG. 13). Go to S110. If it is not the first pulse, the process goes to step S116.
In step S110, the control unit 26 of the EUV light source apparatus outputs the main trigger signal to the switching unit of the pulse power supply unit, and the first laser control unit 23b that controls the operation of the first laser source 23a. The transmission timing of one trigger signal and the transmission timing of the second trigger signal to the second laser control unit 24b that controls the operation of the second laser source 24a are calculated.
In the case of the first pulse, the count values of the voltage counter and current counter, which will be described later, cannot be used, and feedback correction, which will be described later, cannot be performed. Therefore, the previously stored time data Δtd, Δti, Δtg, Δtm, d1, α, β Based on this, the timing is determined.

As shown in FIGS. 1 and 2, in practice, the first trigger signal is input to the switching means of the pulse power supply means (pulse power generator 8) with reference to the time Td when the main trigger signal is input and the switching means is turned on. It is desirable to set the times T1 and T2 during which the second laser beam 24 and the second laser beam 24 are irradiated.
In this embodiment, from the time Td ′ at which the main trigger signal is output to the switching means of the pulse power supply means to the time Td at which the main trigger signal is input to the switching means of the pulse power supply means and the switching means is turned on. The delay time d1 is obtained in advance. Then, the time Td ′ at which the main trigger signal is output to the switching means of the pulse power supply means is corrected by the delay time d1 to obtain the time Td when the switching means is turned on.

On the other hand, a delay time d2 from the time T1 ′ at which the first trigger signal is sent until the first laser beam (raw material laser beam) 23 is irradiated, and the second time from the time T2 ′ at which the second trigger signal is sent. Since the delay time d3 until the laser beam (starting laser beam) 24 is irradiated is so small as to be negligible on the order of ns, it is not considered here.
When the first laser source 23a and the second laser source 24a are, for example, a Q switch type YAG laser device or the like, the first time point Td ′ when the main trigger signal is output to the switching means of the pulse power supply means is used as a reference. Transmission timing T1 ′ of the first trigger signal to the first laser control unit 23b that controls the operation of the laser source 23a, and the second trigger to the second laser control unit 24b that controls the operation of the second laser source 24a. By setting the signal transmission timing T2 ′, the irradiation time of the first laser beam 23 and the second laser beam 24 with reference to the time Td when the main trigger signal is input to the switching means of the pulse power supply means. Setting of T1 and T2 is realized.

When the time point at which the main trigger signal is transmitted is used as a reference (time Td ′), the timing T1 ′ for sending the first trigger signal to the first laser control unit 23b and the second for controlling the operation of the second laser source 24a. The timing T2 ′ for sending the second trigger signal to the laser controller 24b is obtained as follows.
As is clear from FIGS. 1 and 2, the timing T2 at which the second laser beam 23 is irradiated is based on the time Td when the switching means of the pulse power supply means is turned on, as a reference.
T2 ≧ Td + Δt (1)
It becomes.
Therefore, the transmission timing T2 ′ of the second trigger signal to the second laser control unit that controls the operation of the second laser source when the time Td ′ at which the main trigger signal is transmitted is used as a reference is T2 ′ + d3 ≧ ( Td ′ + d1) + Δtd (2)
It becomes. Here, since the delay time d3 is negligibly small, the transmission timing T2 ′ of the second trigger signal is T2 ′ ≧ Td ′ + d1 + Δtd (3)
It becomes.
Here, the time point at which the second laser beam is irradiated may be delayed somewhat from Δtd so that the second laser beam is irradiated when the voltage between the electrodes surely exceeds the threshold value Vp. . When this delay time is defined as a correction time α and equation (3) is transformed,
T2 ′ ≧ Td ′ + d1 + Δtd + α (4)
It becomes.
In this example,
T2 ′ = Td ′ + d1 + Δtd + α (5)
And Of course, the setting of T2 ′ is not limited to the expression (5), and it is sufficient to satisfy the expression (4). For example, T2 ′ = Td ′ + d1 + Δtd may be set.

On the other hand, from FIG. 1 and FIG. 2, the timing T1 at which the first laser beam 23 is irradiated and the timing T2 at which the second laser beam 24 is irradiated have the following relationship.
T2 + Δti ≦ T1 + Δtg ≦ T2 + Δti + Δtp (6)
In this embodiment, when the discharge current surely exceeds the threshold value Ip, the time point at which the first laser beam 23 is irradiated is delayed somewhat from Δti so that the first laser beam 23 is irradiated. When this delay time is defined as the correction time β and the relationship between the timings T1 and T2 is set,
T2 + Δti + β = T1 + Δtg (7)
It becomes.
Here, the correction time β is
0 ≦ β ≦ Δtp (8)
It becomes.
Of course, the setting of the relationship between the timings T1 and T2 is not limited to the expression (7), and the expression (6) may be satisfied. For example, T2 + Δti = T1 + Δtg or T2 + Δti + Δtp = T1 + Δtg may be used.

When the equation (7) is transformed into the relationship between the transmission timing T1 ′ of the first trigger signal and the transmission timing T2 ′ of the second trigger signal,
(T2 ′ + d3) + Δti + β = (T1 ′ + d2) + Δtg (9)
It becomes. Here, since the delay times d2 and d3 are negligibly small, the equation (9) is
T2 ′ + Δti + β = T1 ′ + Δtg
T1 ′ = T2 ′ + Δti + β−Δtg (10)
It becomes.
Substituting equation (5) into equation (10),
T1 ′ = (Td ′ + d1 + Δtd + α) + Δti + β−Δtg
= Td ′ + d1 + (Δtd + Δti−Δtg) + (α + β) (11)
It becomes.

As described above, the transmission timing T1 ′ of the first trigger signal and the transmission timing T2 ′ of the second trigger signal with respect to the time point Td ′ at which the main trigger signal is transmitted are expressed by the following equation (11): It is represented by the formula (5).
Here, the EUV light source device in the present embodiment is supplied by dropping the raw material into droplets. Therefore, the time when the dropped material reaches the irradiation position P2 of the first laser beam in FIG. 12, the time Td ′ when the main trigger signal is transmitted, the transmission timing T1 ′ of the first trigger signal, The timing T2 ′ for sending the second trigger signal needs to be synchronized.

Assuming that the time when the raw material reaches position P1 in FIG. 12 is Tm and the raw material reaches irradiation position P2 after Δtm from Tm, the time when the raw material reaches irradiation position P2 is Tm + Δtm.
That is, when the time Tm is used as a reference,
T1 = Tm + Δtm (12)
Must be established.
When the expression (12) is transformed into the expression of the first trigger signal transmission timing T1 ′,
(T1 ′ + d2) = Tm + Δtm (13)
It becomes. Here, the delay time d2 is so small that it can be ignored.
T1 ′ = Tm + Δtm (14)
It becomes.

Therefore, when the time Tm is used as a reference, the time Td ′ at which the main trigger signal is transmitted, the timing T1 ′ at which the first trigger signal is sent to the first laser control unit, and the second time for controlling the operation of the second laser source. The transmission timing T2 ′ of the second trigger signal to the laser control unit is obtained as follows.
Td ′ = Tm + (Δtm−Δtd−Δti + Δtg) −d1− (α + β) (15)
T1 ′ = Tm + Δtm (14)
T2 ′ = Tm + (Δtm + Δtg−Δti) −β (16)

Here, Δtm is obtained from FIG. 12 as follows.
As shown in FIG. 12, the position of the material discharge unit of the material supply unit 20 is P0, the position where the material monitor 20a monitors the material is P1, the irradiation position of the first laser beam 23 is P2, and the distance between P0 and P1. Is L, and the distance between P0 and P2 is Lp.
The time when the raw material 21 is located at P0 is the origin, and as described above, the time when the raw material 21 reaches P1 is Tm, and the time when the raw material 21 reaches the irradiation position P2 is Tm + Δtm.
If the material falling speed at position P0 is 0 and the gravitational acceleration is G,
L = (1/2) GTm ² (17)
Lp = (1/2) G (Tm + Δtm) ² (18)
It becomes. (18) From the equation (19), Δtm is obtained as in the equation (19).
Δtm = (2Lp / G) ^1/2 − (2L / G) ^1/2 (19)

That is, in step S110 of FIG. 13, the control unit 26 of the EUV light source apparatus uses the equations (15), (14), (16) based on the time data Δtd, Δti, Δtg, Δtm, d1, α, β stored in advance. ) (19), the timing Td ′ for transmitting the main trigger signal when the time Tm is set as a reference, the timing T1 ′ for sending the first trigger signal to the first laser control unit 23b, and the second laser source 24a The transmission timing T2 ′ of the second trigger signal to the second laser control unit 24b that controls the operation is obtained (S208 in FIG. 15).
Here, the time data Δtd is called from a table that stores the correspondence between the voltage V and the time Δtd. The data of the voltage V applied to the discharge electrode stores, for example, the correlation between the EUV radiation intensity and the charge voltage to the main capacitor C0 when the charge control signal is transmitted to the charger CH of the pulse power generator in step S107. The charging voltage data of the main capacitor C0 called from the table is used as it is.

  The control unit 26 of the EUV light source device uses the time point when the raw material detection signal from the raw material monitor 20a is first detected as the reference time from the time when the charger charging stabilization time tst, which is the time until the charging of the main capacitor C0 is stabilized, has passed. Tm is set (step S111 in FIG. 13 and S204 and S207 in FIG. 15). The setting of the reference time Tm is not necessarily limited to the time when the raw material detection signal is first detected after the charger charging stabilization time tst has elapsed. For example, the time point when the raw material detection signal is detected a predetermined number of times after the time tst has elapsed may be set as the reference time point Tm.

  The control unit 26 of the EUV light source device uses the reference time point Tm set in step S111 as a reference, and obtains the main trigger signal based on the time point Tm, which is obtained by the equations (15), (14), (16), and (19). The transmission timing Td ′, the transmission timing T1 ′ of the first trigger signal to the first laser control unit 23b, and the second trigger signal to the second laser control unit 24b that controls the operation of the second laser source 24a. At the delivery timing T2 ′, the main trigger signal, the first trigger signal, and the second trigger signal are respectively switched to the switching means of the pulse power supply means (pulse power generator 8), the first laser control unit 23b, and the second laser. It transmits to the control part 24b (step S112 of FIG. 13, S209, S213, S217 of FIG. 15).

The control unit 26 of the EUV light source device operates a voltage counter (not shown) that measures until the voltage between the electrodes reaches the threshold value Vp at the start of output of the main trigger signal. In addition, a current counter (not shown) that measures until the discharge current reaches the threshold value Ip at the start of output of the second trigger signal is operated (step S113 in FIG. 14 and S212 and S216 in FIG. 15).
The voltage counter and the current counter are cleared to 0 when a light emission command signal is input from the controller 27 of the exposure machine. The voltage counter is for feedback control in order to make the time until the interelectrode voltage reaches the threshold value Vp after the output of the main trigger signal. On the other hand, the current counter is for feedback control in order to keep the time until the discharge current reaches the threshold value Ip after the output of the second trigger signal.
That is, the timing Td ′ for transmitting the main trigger signal with respect to the time point Tm, the timing T1 ′ for sending the first trigger signal to the first laser controller, and the second for controlling the operation of the second laser source. The second trigger signal transmission timing T2 ′ to the laser control unit of the first is determined based on the equations (15), (14), (16), and (19) as described above, as described above. However, after the second time, as will be described later, the above formulas (15), (14), (16), and (19) are determined based on the values corrected based on the count values of the voltage counter and the current counter.

The control unit 26 of the EUV light source device detects the timing when the voltage between the electrodes reaches the threshold value Vp by a voltage monitor (not shown in FIGS. 9 and 7), and stops the voltage counter. Further, the timing at which the discharge current reaches the threshold value Ip is detected by a current monitor (not shown), and the current counter is stopped (step S114 in FIG. 14 and S212 and S216 in FIG. 15).
In step S112 in FIG. 13, when the main trigger signal is sent at the timing Td ′ based on the equation (15) and the main trigger signal is input to the switching means of the pulse power supply means, when the delay time d1 has elapsed, the switching means ( For example, IGBT) is turned on (S209 and S210 in FIG. 15).
When the switching means is turned on, the voltage between the first rotating electrode 11 and the second rotating electrode 12 rises, and the voltage between the electrodes reaches the threshold value Vp after time Δtd. As described above, the threshold value Vp is a voltage value when the value of the discharge current that flows when discharge occurs is equal to or greater than the threshold value Ip (S210 and S211 in FIG. 15).

As described above, in step S112, the second trigger signal is sent to the second laser control unit 24b at the timing T2 ′ based on the equation (16). As a result, the second laser beam (starting laser beam) 24 is irradiated to the discharge region at a time T2 after the time when the interelectrode voltage reaches the threshold value Vp (Td + Δtd) (S213 and S214 in FIG. 15).
The second laser beam 24 is irradiated to the discharge region, and discharge starts in the discharge region. After Δti after the start of discharge, the magnitude of the discharge current reaches the threshold value Ip (S214 and S215 in FIG. 15). This threshold value Ip is a lower limit of the discharge current value necessary for obtaining EUV radiation having a predetermined intensity. A period during which the discharge current value is equal to or greater than the threshold value Ip is denoted by Δtp.
Further, as described above, in step S112, the first trigger signal is sent to the first laser control unit 23b at the timing T1 ′ based on the equation (14). As a result, the first laser beam (raw material laser beam) 23 is irradiated at time T1 during the period of (T2 + Δti−Δtg) to (T2 + Δti + Δtp−Δtg) (S215, S217, and S218 in FIG. 15).

That is, as a result of the control unit 26 of the EUV light source apparatus transmitting each trigger signal in step S112, the position of the discharge channel is defined at a predetermined position. Further, in the discharge channel where the position is defined, EUV radiation having a predetermined magnitude of discharge current is obtained in a state where at least a part of the vaporized material having a predetermined spatial density distribution reaches the discharge channel. For this reason, the discharge occurs so as to be equal to or higher than the lower limit of the discharge current value necessary for this.
Discharge is generated between the edge portions of the peripheral edge portions of the first rotating electrode 11 and the second rotating electrode 12, and plasma is formed. When the plasma is heated and excited by a pulsed large current flowing through the plasma, EUV radiation having a wavelength of 13.5 nm is generated from the high temperature plasma (step S115 in FIG. 14 and S219 in FIG. 15).

The predetermined spatial density distribution is set so that EUV radiation is generated as efficiently as possible. Specifically, a suitable spatial density distribution as described above is the supply position of the high temperature plasma raw material to the discharge region, the irradiation direction of the first laser beam 23 to the high temperature plasma raw material, the irradiation energy of the first laser beam 23, and the like. Is set as appropriate.
Further, since the position of the discharge channel is defined at a predetermined position by the irradiation of the second laser beam 24, the position stability of the position where the plasma is generated is improved.
That is, as a result of the control unit 26 of the EUV light source device transmitting each trigger signal, efficient generation of EUV radiation and stabilization of the EUV radiation generation position are realized.
The EUV radiation radiated from the plasma passes through an opening provided in the partition wall 1 c and the foil trap 3, and is collected by the oblique incidence type EUV collector mirror 2 disposed in the collection space 1 b and provided in the chamber 1. The EUV light extraction unit 7 is guided to an irradiation optical system of an exposure apparatus (not shown).

When the first EUV radiation is finished as described above, the process then returns to step S106 in FIG. 13 to wait for a light emission command from the exposure apparatus.
After receiving the light emission command, the process proceeds to step S109 through steps S107 and S108 described above. Since the next EUV radiation is not the first pulse, the process goes from step S109 to step S116. In step S116, the control unit 26 of the EUV light source device outputs the value of the voltage counter, which is the time until the voltage between the electrodes reaches the threshold value Vp after starting the output of the main trigger signal measured in step S114, and the second trigger signal. The first trigger signal transmission timing T1 ′ to the first laser controller 23b and the second laser source 24a based on the value of the current counter, which is the time until the discharge current reaches the threshold value Ip after the start of the output of The feedback calculation of the transmission timing T2 ′ of the second trigger signal to the second laser control unit 24b that controls the operation is performed by the following equation.

tvcal = (d1 + Δtd) −tvc (20)
tical = Δti−tic (21)
Here, tvcal is a correction value for the time from when the output of the main trigger signal starts until the interelectrode voltage reaches the threshold value Vp, and tvc is the time measured by the voltage counter. Further, tical is a correction value for the time until the discharge current reaches the threshold value Ip after the output of the second trigger signal starts, and tic is the time measured by the current counter. (Step S116 in FIG. 13 and S208 in FIG. 15).

As apparent from the equation (20), tvcal is the time Td when the main trigger signal is input to the switching means of the pulse power supply means and the switching means is turned on from the time Td ′ when the main trigger signal is output. And a correction value of the sum total of the delay time d1 until the voltage between the electrodes reaches the threshold value Vp from the time Td when the switching means is turned on.
As described above, a semiconductor switching element such as an IGBT capable of flowing a large current is often used for the solid state switch SW which is a switching means of the pulse power supply means. Such semiconductor switching elements such as IGBTs vary to some extent when the gate signal (corresponding to the main trigger signal in this embodiment) is input and actually turned on. That is, the equation (20) takes into account correction of variations in switching elements.

The control unit 26 of the EUV light source apparatus considers the correction value obtained in step S116, the timing Td ′ for transmitting the main trigger signal when the time Tm is used as a reference, and the first to the first laser control unit 23b. The trigger signal transmission timing T1 ′ and the second trigger signal transmission timing T2 ′ to the second laser control unit 24b for controlling the operation of the second laser source 24a are determined by the following equations (step S117 in FIG. 13). S208 in FIG.
Td ′ = Tm + (Δtm−Δtd−Δti + Δtg) −d1− (α + β) − (tvcal + tical) (22)
T1 ′ = Tm + Δtm (14)
T2 ′ = Tm + (Δtm + Δtg−Δti) −β-tical (23)
Δtm = (2Lp / G) ^1/2 − (2L / G) ^1/2 (19)

The control unit 26 of the EUV light source apparatus is based on the time when the material detection signal from the material monitor or 20a is first detected from the time when the charger charging stabilization time tst which is the time until the charging of the main capacitor C0 is stabilized. Time Tm is set (step S118 in FIG. 13 and S204 and S207 in FIG. 15).
The setting of the reference time Tm is not limited to the time when the raw material detection signal is first detected after the charger charging stabilization time tst has elapsed. For example, the time point when the raw material detection signal is detected a predetermined number of times after the time tst has elapsed may be set as the reference time point Tm.
Next, the control unit 26 of the EUV light source apparatus uses the reference time point Tm set in step S118 as a reference, and the main time when the reference point is the time point Tm obtained by the equations (22), (14), (23), and (19). Timing Td ′ for transmitting the trigger signal, timing T1 ′ for sending the first trigger signal to the first laser controller 23b, and second for the second laser controller 24b for controlling the operation of the second laser source 24a. At the trigger signal transmission timing T2 ′, the main trigger signal, the first trigger signal, and the second trigger signal are respectively sent to the switching means of the pulse power supply means, the first laser control unit 23b, and the second laser control unit 24b. It transmits (step S119 in FIG. 13, S209, S214, S217 in FIG. 15).

Next, the process proceeds to step S113 in FIG. 14, and the control unit 26 of the EUV light source apparatus operates a voltage counter that measures until the voltage between the electrodes reaches the threshold value Vp at the start of output of the main trigger signal. Further, the current counter that measures the time until the discharge current reaches the threshold value Ip when the output of the second trigger signal starts is operated (S212 and S216 in FIG. 15). As described above, the voltage counter and the current counter are cleared to 0 when a light emission command signal is input from the controller of the exposure machine.
The control unit 26 of the EUV light source device detects the timing when the voltage between the electrodes reaches the threshold value Vp by a voltage monitor (not shown in FIGS. 9 and 10), and stops the voltage counter. Further, the timing at which the discharge current reaches the threshold value Ip is detected by a current monitor (not shown), and the current counter is stopped (step S114 in FIG. 14 and S212 and S216 in FIG. 15).

In step S112, when the main trigger signal is sent at the timing Td ′ based on the equation (22) and the main trigger signal is input to the switching means of the pulse power supply means, the switching means is turned on after the delay time d1 has elapsed. (S209, S210 in FIG. 14).
When the switching means is turned on, the voltage between the first rotating electrode 11 and the second rotating electrode 12 rises, and the voltage between the electrodes reaches the threshold value Vp after time Δtd (S210 and S211 in FIG. 15).
As described above, in step S112, the second trigger signal is sent to the second laser control unit 24b at the timing T2 ′ based on the equation (23). As a result, the second laser beam (starting laser beam) 24 is irradiated to the discharge region at a time T2 after the time when the interelectrode voltage reaches the threshold value Vp (Td + Δtd) (S213 and S214 in FIG. 15).
The second laser beam 24 is irradiated to the discharge region, and discharge starts in the discharge region. After Δti after the start of discharge, the magnitude of the discharge current reaches the threshold value Ip (S214 and S215 in FIG. 15).

As described above, in step S112, the first trigger signal is sent to the first laser control unit 23b at the timing T1 ′ based on the equation (14). As a result, the first laser beam (raw material laser beam) is irradiated at time T1 during the period of (T2 + Δti−Δtg) to (T2 + Δti + Δtp−Δtg) (S215, S217, and S218 in FIG. 15).
That is, as a result of the control unit 26 of the EUV light source device transmitting each trigger signal in step S119, the position of the discharge channel is defined at a predetermined position. In addition, EUV radiation having a predetermined magnitude of discharge current is obtained in a state where at least a part of the vaporized material having a predetermined spatial density distribution reaches the discharge channel in the discharge channel where the position is defined. For this reason, discharge occurs so that the discharge current value is not less than the lower limit.

Discharge is generated between the edge portions of the peripheral edge portions of the first rotating electrode 11 and the second rotating electrode 12, and plasma is formed. When the plasma is heated and excited by a pulsed large current flowing through the plasma, EUV radiation having a wavelength of 13.5 nm is generated from the high temperature plasma (step S115 in FIG. 14 and S219 in FIG. 15).
The predetermined spatial density distribution is set so that EUV radiation is generated as efficiently as possible.
Further, since the position of the discharge channel is defined at a predetermined position, the position stability of the position where the plasma is generated is improved.
That is, as a result of the transmission of each trigger signal from the control unit of the EUV light source device in step S119, efficient generation of EUV radiation and stabilization of the generation position of EUV radiation are realized.

The EUV radiation radiated from the plasma passes through the opening provided in the partition wall 1 c and the foil trap 3 and is collected by the oblique incidence type EUV collector mirror 2 disposed in the collection space, and is provided in the chamber 1. Further, the light is guided from the EUV light extraction unit 7 to an irradiation optical system of an exposure apparatus (not shown).
Hereinafter, as long as the exposure process continues, the processes between step S106 to step S115 are repeated. When the exposure process ends, the process ends after step S115.
By operating as described above, the spatial density distribution of the vaporized high temperature plasma raw material supplied to the discharge region by the irradiation of the first laser beam 23 is set so that EUV radiation is generated as efficiently as possible. Note that, as a result of the irradiation with the first laser beam 23, the supply position of the material to the discharge region, the irradiation direction of the first laser beam 23 to the material, the first The irradiation energy of one laser beam 23 is appropriately set in advance.
On the other hand, by condensing the second laser beam 24 at a predetermined position in the discharge region, the discharge is started and the position of the discharge channel is defined at the position where the laser focus is set. Therefore, the positional stability of the generation point of EUV radiation is improved.

Here, since the irradiation timing of the first laser beam 23 and the irradiation timing of the second laser beam 24 are set as described above, the spatial density distribution is a predetermined distribution in the discharge channel where the position is defined. Discharge so that the magnitude of the discharge current is equal to or greater than the lower limit of the discharge current value necessary for obtaining EUV radiation of a predetermined intensity in a state where at least a part of the vaporized raw material reaches the discharge channel. Will occur.
As a result, efficient EUV radiation can be realized.
In particular, in this embodiment, the time until the interelectrode voltage reaches the threshold value Vp after the output of the main trigger signal and the time until the discharge current reaches the threshold value Ip after the output of the second trigger signal are constant. Feedback control is performed so that Therefore, for example, even if the operation of a semiconductor switching element such as an IGBT used as a solid-state switch SW that is a switching means of a pulse power supply means varies, it is possible to reliably realize efficient EUV radiation. Become.
As shown in FIG. 10, a magnet 6 may be provided near the discharge region where plasma is generated, and a magnetic field may be applied to the plasma.

  As described above, in the EUV light source device of the present invention, the high-temperature plasma raw material is supplied to the space near the discharge region of the discharge space in the vacuum atmosphere, and the supplied high-temperature plasma raw material is irradiated with the laser beam. And the vaporized high temperature plasma raw material is supplied to the discharge region. Next, at the time when the vaporized gas is supplied to the discharge region, a discharge is generated to generate plasma that emits EUV radiation. The plasma generated in this manner is considered to diffuse and disappear due to the particle density gradient of the high-temperature plasma raw material after vaporization in the discharge region. That is, it is considered that the plasma size increases because the plasma diffuses.

Here, consider the case where a uniform magnetic field is applied substantially parallel to the discharge direction generated between the first and second rotating electrodes.
Charged particles in a uniform magnetic field are subjected to Lorentz force. Since the Lorentz force works in a direction perpendicular to the magnetic field, the charged particles move in a uniform circular motion on a plane perpendicular to the magnetic field. On the other hand, in the direction parallel to the magnetic field, the charged particles do not receive an external force, and thus move at a constant velocity with the initial velocity. Therefore, the motion of the charged particles is a combined motion of the above, and therefore, a spiral motion with a constant pitch is performed along the magnetic field (in the magnetic field direction).
Therefore, when applying a uniform magnetic field substantially parallel to the discharge direction generated between the first and second rotating electrodes 11 and 12, the turning radius of the charged particles that spirally move around the lines of magnetic force is sufficiently small. When a magnetic field is applied, it is estimated that the amount of plasma diffusion described above can be reduced. That is, it is considered that the plasma size can be reduced as compared with the case where no magnetic field is applied. Moreover, since it is considered that the plasma lifetime can be maintained for a longer time than when it diffuses and disappears spontaneously, when a magnetic field is applied as described above, EUV is emitted longer than when no magnetic field is applied. It will be possible to make it.

That is, when the magnetic field is applied as described above, the size of the high-temperature plasma that emits EUV (that is, the size of the EUV light source) can be reduced, and the EUV emission time can be extended. Therefore, the EUV light source device of the present invention is more preferable as an exposure light source by applying a magnetic field.
In addition, when the turning radius of the charged particles described above is sufficiently smaller than the shortest distance from the plasma generation position to the EUV collector mirror 2, the debris that are fast ions among the debris caused by the high temperature plasma raw material is the turning radius. It does not reach the condenser mirror with a spiral motion. That is, it is estimated that the amount of debris that is ions can be reduced by applying a magnetic field.

2. 9 and FIG. 10 In the EUV light source device of the present invention, the high-temperature plasma raw material for emitting extreme ultraviolet light is supplied in the vicinity of the discharge region in a liquid or solid state. In the EUV light source apparatus shown in Example 1, the raw material is supplied in the form of droplets.
Of course, the supply mechanism of the high temperature plasma raw material is not limited to the configuration shown in the above embodiment. Hereinafter, other examples of the high-temperature plasma raw material supply unit will be described.

(1) First Modification FIGS. 16 and 17 are views for explaining a first modification of the embodiment. Specifically, FIG. 16 is a front view of the EUV light source apparatus of the present invention, and EUV radiation is extracted from the left side of the figure. That is, FIG. 16 shows the EUV light source device of the embodiment shown in FIG. 9 with the raw material supply unit replaced. In order to facilitate understanding, FIG. 16 shows the arrangement and configuration of the raw material supply unit with emphasis, and a part of the EUV light source device is omitted. The omitted parts are the same as those in FIG.
On the other hand, FIG. 17 is a top view of the EUV light source apparatus of this embodiment, and a part of the EUV light source apparatus is omitted as in FIG.

In the modification shown in FIGS. 16 and 17, the linear raw material 31 is used as the high temperature plasma raw material. Specifically, it is a metal wire containing an extreme ultraviolet light emitting species, and includes, for example, Sn (tin).
The raw material supply unit 30 in the first modification has a function of supplying the linear raw material 31 to a predetermined space. The raw material supply unit 30 includes a reel 30a, a reel 30e, a positioning unit 30b, a positioning unit 30c, a linear raw material 31, and a drive mechanism 30d. The drive mechanism 30d is driven and controlled by a control unit (not shown in FIGS. 16 and 17).

The linear raw material 31 is wound around the reel 30a and the reel 30e. The reel 30 a is an upstream reel that feeds the linear raw material 31. On the other hand, the reel 30e is a downstream reel that winds the linear raw material 31 delivered from the reel 30a. The linear raw material 31 is delivered from the reel 30a when the reel 30e is rotationally driven by the drive mechanism 30d.
The linear raw material 31 delivered from the reel 30a is vaporized when irradiated with the first laser beam (raw material laser beam) 23 emitted from the first laser source 23a. As described above, the direction in which the vaporized high temperature plasma raw material spreads depends on the incident position of the first laser beam 23 on the raw material 31.
Therefore, the linear raw material 31 is positioned by the positioning means 30b and the positioning means 30c so that the incident position of the first laser beam 23 on the linear raw material 31 faces the discharge region. This positioned position is a position where the raw material vaporized by irradiating the linear raw material 31 with the first laser beam 23 can reach the discharge region.

Then, when the linear raw material 31 is supplied and the linear raw material 31 is irradiated with the first laser beam 23, the first high-temperature plasma raw material (liquid raw material) after vaporization spreads in the direction of the discharge region. The optical axis of the first laser beam 23 emitted from the laser source 23a and the energy of the first laser beam 23 are adjusted.
Here, the distance between the discharge region and the linear raw material 31 is set so that the vaporized high temperature plasma raw material that spreads in the direction of the discharge region by laser beam irradiation reaches the discharge region with a predetermined spatial density distribution.
As shown in FIGS. 16 and 17, the linear raw material 31 is preferably supplied to the space between the pair of electrodes 11 and 12 and the EUV collector mirror 2.
When the first laser beam 23 is applied to the linear raw material 31 supplied in this manner to the side facing the discharge region on the surface of the linear raw material as described above, the vaporized linear raw material becomes the discharge region. However, it does not spread in the direction of the EUV collector mirror 2.
That is, by setting the supply position of the linear raw material 31 to the discharge region and the irradiation position of the first laser beam 23 as described above, it is possible to suppress the debris from proceeding to the EUV collector mirror 2. Is possible.

(2) Second Modification FIGS. 18, 19, and 20 are diagrams for explaining a second modification of the above-described embodiment. Specifically, FIG. 18 is a front view of the EUV light source apparatus of this embodiment, and EUV radiation is extracted from the left side of the figure. That is, FIG. 18 shows the EUV light source apparatus of the embodiment shown in FIG. 9 with the raw material supply unit 20 replaced.
In order to facilitate understanding, FIG. 18 shows the arrangement and configuration of the raw material supply unit with emphasis, and a part of the EUV light source device is omitted. The omitted parts are the same as those in FIG.
On the other hand, FIG. 19 is a top view of the EUV light source device of the present invention, FIG. 20 is a side view of the EUV light source device of the present invention, and a part of the EUV light source device is omitted as in FIG. Note that FIG. 19 shows a case where power is supplied to the electrodes 11 and 12 via the slider. For example, pulse power is supplied to the electrode 12 from the power introduction unit 12c as shown in FIG. This is done via the mover 12d.

In the second modification shown in FIGS. 18, 19, and 20, a liquid material is used as the high-temperature plasma material. Specifically, it is a liquid raw material containing an extreme ultraviolet light radiation species, and includes, for example, Sn (tin).
The raw material supply unit 40 in the second modification has a function of supplying a liquid raw material to a predetermined space. The raw material supply unit 40 includes a liquid raw material supply means 40a, a raw material supply disk 40b, and a third motor 40c. The liquid source supply unit 40a and the third motor drive mechanism (not shown) are driven and controlled by a control unit (not shown) in FIGS.

A groove is provided in the side surface of the raw material supply disk 40b. First, the liquid material is supplied into the groove by the liquid material supply means 40a. Next, the raw material supply disk 40b is rotated in one direction by the third motor 40c. The liquid raw material supplied to the groove moves with the rotation of the groove.
The liquid raw material supplied to the groove is vaporized when irradiated with the first laser beam (raw material laser beam) 23 emitted from the first laser source 23a. As described above, the direction in which the vaporized high temperature plasma raw material spreads depends on the incident position of the first laser beam 23 on the raw material. Therefore, the material supply disc 40b is arranged with respect to the discharge region so that the incident position of the first laser beam 23 on the liquid material supplied to the groove part faces the discharge region.
Specifically, the raw material supply disk 40b is arranged so that the side surface provided with the groove faces the discharge region. The position where the material supply disc 40b is disposed is a position where the material vaporized by irradiating the liquid material supplied to the groove with the first laser beam 23 can reach the discharge region.

Then, when the liquid source is supplied and the first laser beam 23 is irradiated to the groove facing the discharge region, the first plasma beam 23 (liquid source) after vaporization spreads in the direction of the discharge region. The optical axis of the first laser beam 23 emitted from the laser source 23a and the energy of the first laser beam 23 are adjusted.
The distance between the discharge region and the material supply disk 40b is set so that the high-temperature plasma raw material after vaporization spreading in the direction of the discharge region by irradiation with the first laser beam 23 reaches the discharge region with a predetermined spatial density distribution. Is done.

Here, since the liquid raw material supplied to the groove portion moves with the rotation of the groove portion, the liquid raw material is continuously supplied into the groove portion by the liquid raw material supply means 40a, thereby irradiating the predetermined first laser beam 23. It is possible to supply continuously to the position.
As shown in FIGS. 18, 19, and 20, in the configuration of the second modified example, the liquid material supplied to the groove is a space on a plane perpendicular to the optical axis, and discharge The first laser beam 23 moves with respect to the vicinity of the region, and is irradiated to the liquid material supplied to the groove portion from a direction perpendicular to the optical axis. Therefore, the vaporized high temperature plasma raw material (liquid raw material) does not spread in the direction of the EUV collector mirror 2. Therefore, the debris generated by the irradiation of the first laser beam 23 to the high temperature plasma raw material and the discharge generated between the electrodes hardly proceeds with respect to the EUV collector mirror 2.

(3) Third Modification FIGS. 21 and 22 are diagrams for explaining a third modification of the embodiment. Specifically, FIG. 21 is a top view of the EUV light source apparatus of this embodiment, and EUV radiation is extracted from the left side of the figure. On the other hand, FIG. 22 is a side view of the EUV light source apparatus of the present invention.
FIGS. 21 and 22 show the EUV light source apparatus of the embodiment shown in FIG. 9 with the raw material supply unit 20 and electrodes replaced. In order to facilitate understanding, FIG. 21 shows an emphasis on the arrangement and configuration of the raw material supply unit, and a part of the EUV light source device is omitted. The omitted parts are the same as those in FIG.
In the third modification shown in FIGS. 21 and 22, a liquid material is used as the high temperature plasma material. Specifically, it is a liquid raw material containing an extreme ultraviolet light radiation species, and includes, for example, Sn (tin).
The raw material supply unit 50 in the third modification has a function of supplying a liquid raw material to a predetermined space. The raw material supply unit 50 includes a liquid raw material bath 50a, a capillary 50b, a heater 50c, a liquid raw material bus control unit 50d, and a heater power source 50e. The liquid source bus control unit 50d and the heater power supply 50e are driven and controlled by a control unit not shown in FIGS.

The liquid source bath 50a accommodates a liquid source containing an extreme ultraviolet light radiation species. The liquid raw material bath 50a is provided with a capillary 50b which is a very thin tube. The capillary 50b penetrates through the liquid source container of the liquid source bath 50a. In the raw material supply unit 50 in the third modified example, the liquid raw material accommodated in the liquid raw material bath 50a is transported through the capillary 50b and guided to the tip of the capillary 50b by capillary action.
For example, Sn (tin) is used as the liquid source containing the extreme ultraviolet light radiation species contained in the liquid source bath 50a. The temperature of the liquid source bath is controlled by the liquid source bus control unit 50d so that Sn maintains a liquid state. The capillary 50b is heated by the heater 50c in order to avoid solidification of the liquid material in the tube. Power supply to the heater 50c is performed by a heater power source 50e.

When the liquid material that has reached the tip of the capillary 50b is irradiated with the first laser beam (raw material laser beam) 23 emitted from the first laser source 23a, the liquid material is vaporized. As described above, the direction in which the vaporized high temperature plasma raw material spreads depends on the incident position of the first laser beam 23 on the raw material.
Therefore, the tip of the capillary 50b is arranged so that the incident position of the first laser beam 23 on the liquid material reaching the tip of the capillary 50b faces the discharge region. Note that the position where the tip of the capillary 50b is disposed is a position where the raw material vaporized by irradiating the liquid material supplied to the tip of the capillary 50b with the first laser beam 23 can reach the discharge region.

Then, when the liquid source is supplied to the tip of the capillary 50b and the tip of the capillary is irradiated with the first laser beam 23, the first gas plasma (liquid source) after vaporization is expanded in the direction of the discharge region. The optical axis of the laser beam emitted from the laser source 23a and the power of the first laser beam 23 are adjusted.
Here, the distance between the discharge region and the tip of the capillary 50b is set so that the vaporized high-temperature plasma raw material spreading in the direction of the discharge region by laser beam irradiation reaches the discharge region with a predetermined spatial density distribution.
Further, since the liquid source supplied to the tip of the capillary 50b moves from the liquid source bath 50a by capillary action, it can be continuously supplied to the irradiation position of the predetermined source laser beam 23.

In the third modification shown in FIGS. 21 and 22, the first electrode 11 ′ and the second electrode 12 ′, which are columnar electrodes, are employed. The first electrode 11 ′ and the second electrode 12 ′ are spaced apart by a predetermined distance, and both are connected to the pulse power generator 8. Of course, it is also possible to employ a rotating electrode as the electrode.
As shown in FIGS. 21 and 22, in the configuration of the third modification, the tip of the capillary 50b to which the liquid material is supplied is located in a space on a plane perpendicular to the optical axis, and the first The laser beam 23 is applied to the liquid material supplied to the tip of the capillary 50b disposed at the above position. Therefore, the vaporized high temperature plasma raw material (liquid raw material) does not spread in the direction of the EUV collector mirror 2. Therefore, the debris generated by the irradiation of the raw material laser beam to the high temperature plasma raw material and the discharge generated between the electrodes hardly proceeds with respect to the EUV collector mirror 2.

(4) Vaporized raw material discharge nozzle As described above, in the present invention, the high temperature plasma raw material is irradiated with the first energy beam (raw material energy beam) 23 and vaporized. The vaporized high temperature plasma raw material spreads at a predetermined speed. By appropriately setting the supply position of the raw material to the discharge region, the irradiation direction of the first energy beam 23 to the raw material, the irradiation energy of the first energy beam 23, etc., the vaporized high temperature plasma raw material is supplied into the discharge region. Is done. Further, the above setting makes it possible to set the spatial density distribution of the vaporized high temperature plasma raw material in the discharge region to a predetermined distribution.
At this time, it is preferable that the high temperature plasma raw material that spreads in the direction of the discharge region by irradiation with the first energy beam reaches the discharge region as much as possible. When there are many high temperature plasma raw materials which reach | attained except the discharge area | region, the taking-out efficiency of EUV radiation from the supplied high temperature plasma raw materials falls, and it is unpreferable. Further, a part of the high temperature plasma raw material that has reached the outside of the discharge region may come into contact with the low temperature portion in the EUV light source device as debris and be deposited.

Therefore, as shown in FIG. 23, a raw material ejection tubular nozzle may be attached to the irradiation position of the first energy beam 23 of the high temperature plasma raw material.
FIG. 23 is a conceptual diagram when a tubular nozzle is used.
As shown in FIG. 23A, the first energy beam 23 passes through the through hole of the tubular nozzle 60a. When the high temperature plasma raw material 21 is irradiated with the first energy beam 23 that has passed through the tubular nozzle 60a, the raw material is vaporized. As shown in FIG. 23B, the vaporized raw material 21 ′ passes through the tubular nozzle 60a and is ejected from the tubular nozzle 60a.
The injection angle of the vaporized raw material 21 ′ ejected from the tubular nozzle 60a is limited by the tubular nozzle 60a. For this reason, it is possible to supply a vaporized material having good directivity and high density to the discharge region.

The shape of the tubular nozzle is not limited to the straight tube shape as shown in FIG. For example, as in the conceptual diagram shown in FIG. 24, a nozzle shape for high-speed injection in which a narrow portion is provided in a part of the inside of the nozzle may be used.
As shown in FIG. 24A, the first energy beam 23 passes through the through hole of the high-speed injection nozzle 60b. When the high temperature plasma raw material 21 is irradiated with the first energy beam 23 that has passed through the high-speed injection nozzle 60b, the raw material is vaporized. Here, since the narrowed portion 62 is provided inside the high-speed jet nozzle 60b, the space between the narrowed portion 62 and the portion irradiated with the first energy beam 23 of the high temperature plasma raw material 21 (FIG. 24). The pressure rises suddenly in the pressure riser 63) of (b) due to the vaporized raw material. And as shown in FIG.24 (b), the vaporization raw material is accelerated from the opening part of the constriction part 62, and is injected as a high-speed gas flow with good directivity.
Here, the injection direction of the high-speed gas flow depends on the direction of the high-speed injection nozzle 60b. That is, the traveling direction of the vaporized raw material 21 ′ does not depend on the incident direction of the first energy beam 23 to the high temperature plasma raw material 21.

Note that since the opening of the constricted portion 62 has a small cross-sectional area, it is considered that the high temperature plasma raw material 21 is solidified and the opening is blocked when the first energy beam 23 is not irradiated to the high temperature plasma raw material 21 for a long time. It is done. Therefore, as shown in FIG. 24C, the high-speed injection nozzle 60b may be heated by a heater 64 or the like so that the high-temperature plasma raw material 21 does not solidify inside the high-speed injection nozzle 60b.
The tubular nozzle 60a and the high-speed injection nozzle 60b shown in FIGS. 23 and 24 can be applied to the above-described embodiments and modifications. However, it is more effective that the tubular nozzle 60a and the high-speed jet nozzle 60b are as close to the high-temperature plasma raw material 21 as possible.
In particular, since the high-speed injection nozzle 60b needs to form the pressure riser 63, the narrow portion 62 and the portion where the first energy beam 23 of the high-temperature plasma raw material 21 is irradiated inside the high-speed injection nozzle 60b. It is desirable to configure the space between the two as an airtight space as much as possible. For example, as shown in FIG. 25, it is preferable to use a raw material supply unit 60 in which a raw material container 60c for storing the high-temperature plasma raw material 21 and a high-speed injection nozzle 60b are integrated.

The rectifying mechanism is not limited to the above example. For example, in the solid high-temperature plasma raw material 21, a recess 61a may be formed in advance at a position where the laser beam 23 is irradiated as shown in FIG.
When the laser beam 23 is applied to the recess 61a of the high temperature plasma raw material 21, the high temperature plasma raw material 21 is vaporized and a low temperature plasma gas 21 'is generated. Here, the injection angle of the low-temperature plasma gas 21 ′ ejected from the recess 61a is limited by the wall-shaped nozzle of the recess 8a. Therefore, a low-temperature plasma gas flow with good directivity can be selectively and continuously supplied to the discharge channel.

(5) Operation of the EUV light source device in the modified example of the embodiment In the various modified examples described above, the high temperature plasma raw material is continuously supplied to the irradiation position of the first laser beam (raw material laser beam) 23. . Therefore, the operation example of the EUV light source apparatus in these modified examples is somewhat different from the operation example of the EUV light source apparatus in the above embodiment. Hereinafter, the operation of the EUV light source apparatus will be described using the first modification as an example.
27 and 28 are flowcharts showing the operation of this embodiment, and FIG. 29 is a time chart. The operation of this embodiment will be described below with reference to FIGS. Since there is no significant difference in operation between the present modification and the above-described embodiment, the same parts as those described with reference to FIGS. 13 to 15 will be described briefly.

As described above, the control unit 26 of the EUV light source device stores the time data Δtd, Δti, and Δtg. As described above, Δtd is the time from when the trigger signal is input to the switching means of the pulse power supply means (time Td) until the switching means is turned on and the interelectrode voltage reaches the threshold value Vp, Δti Is the time from the start of discharge until the magnitude of the current flowing between the electrodes reaches the threshold value Ip. Δtg is the time at which a part of the vaporized raw material enters the discharge region from the time when the first laser beam is irradiated on the raw material. It is the time to reach.
Further, the relationship between the voltage V and the time Δtd obtained in advance through experiments or the like is stored as a table, and the correction time α, β and the time point when the main trigger signal is output to the switching means of the pulse power supply means. The delay time d1 until the time when the switching means is turned on is stored.

First, a standby command is transmitted from the control unit 26 of the EUV light source device (step S301 in FIG. 27, S401 in FIG. 29), and as described above, the vacuum exhaust devices 4 and 5 and the gas supply unit 13 that have received the standby command. , 14 etc. start operation. Thereby, the discharge space 1a becomes a vacuum atmosphere. Further, buffer gas and cleaning gas are supplied into the condensing space 1b, and the condensing space 1b reaches a predetermined pressure. Further, the first motor 22a and the second motor 22b operate, and the first rotating electrode 11 and the second rotating electrode 12 rotate. Further, when the reel 30e is rotationally driven by the drive mechanism 30d, the reel 30e is sent out from the reel 30a and enters a standby state (step S302 in FIG. 27, S402 in FIG. 29).
The control unit 26 of the EUV light source apparatus transmits a standby completion signal to the control unit 27 of the exposure apparatus (step S305 in FIG. 27 and S405 in FIG. 29).
The control unit 26 of the EUV light source apparatus receives a light emission command from the control unit 27 of the exposure apparatus (step S306 in FIG. 27 and S406 in FIG. 29).

After realizing the standby state, the control unit 26 of the EUV light source device transmits a charge control signal to the charger CH of the pulse power generator 8. The charge control signal includes, for example, a discharge start timing data signal, and the charge voltage data signal for the main capacitor C0 is also included in the charge control signal. As described above, the control unit 26 of the EUV light source device refers to the table storing the relationship between the EUV radiation intensity and the charging voltage to the main capacitor C0, obtains charging voltage data of the main capacitor C0, and supplies it to the main capacitor C0. The charging control signal including the charging voltage data signal is transmitted to the charger CH of the pulse power generator (step S307 in FIG. 27, S407 in FIG. 29).
The charger CH charges the main capacitor C0 as described above (step S308 in FIG. 27).
Next, the control unit 26 of the EUV light source apparatus determines whether or not it is the first EUV light generation (referred to as an initial pulse) after the start of operation (step S309 in FIG. 27). Go to step S310.
If it is not the first pulse, the process goes to step S316.

In step S310, the control unit 26 of the EUV light source apparatus transmits the first trigger signal transmission timing to the first laser control unit 23b that controls the operation of the first laser source 23a, and the operation of the second laser source 24a. The transmission timing of the second trigger signal to the second laser control unit 24b to be controlled is calculated.
In the case of the first pulse, since the feedback correction cannot be performed as described above, the timing is determined based on the time data Δtd, Δti, Δtg, d1, α, β stored in advance.
That is, as described above, the operation of the first laser source 23a is controlled based on the equations (11) and (5) with reference to the time point Td ′ when the main trigger signal is output to the switching means of the pulse power supply means. The timing T1 ′ for sending the first trigger signal to the first laser controller 23b and the timing T2 ′ for sending the second trigger signal to the second laser controller 24b for controlling the operation of the second laser source 24a are obtained. (S408 in FIG. 29).
Thereby, it is possible to set the times T1 and T2 when the first laser beam and the second laser beam are irradiated with reference to the time Td when the main trigger signal is input to the switching means of the pulse power supply means.

Next, the control unit 26 of the EUV light source device transmits a main trigger signal to the switching means of the pulse power supply means after the charger charging stabilization time tst, which is the time until the charging of the main capacitor C0 is stabilized. The timing at that time is Td ′ (step S311 in FIG. 27, S409 in FIG. 29).
The control unit 26 of the EUV light source apparatus uses the time Td ′ at which the main trigger signal is transmitted as a reference, and calculates the first trigger signal to the first laser control unit 23b, which is obtained in step S310 according to equations (5) and (11). At the transmission timing T1 ′ and the transmission timing T2 ′ of the second trigger signal to the second laser control unit 24b, the first trigger signal and the second trigger signal are sent to the first laser control unit 23b and the second laser, respectively. It transmits to the control part 24b (step S312 of FIG. 27, S413, S417 of FIG. 29).

In addition, as described above, the control unit 26 of the EUV light source device measures the voltage counter that measures until the voltage between the electrodes reaches the threshold value Vp when the output of the main trigger signal starts, and the discharge current when the output of the second trigger signal starts. The current counter that measures until the threshold value Ip is reached is operated (step S313 in FIG. 28, S410 and S412 in FIG. 29).
As described above, in the voltage counter and the current counter, the time until the interelectrode voltage reaches the threshold value Vp after the output of the main trigger signal, and the discharge current reaches the threshold value Ip after the output of the second trigger signal. This is for feedback control in order to keep the time until the operation is constant. That is, the first trigger signal transmission timing T1 ′ and the second trigger signal transmission timing T2 ′ are determined based on the equations (5) and (11) as described above for the first time (initial pulse). However, after the second time, the above formulas (5) and (11) are determined based on values corrected based on the count values of the voltage counter and current counter.

The control unit 26 of the EUV light source device detects the timing when the voltage between the electrodes reaches the threshold value Vp by a voltage monitor (not shown), stops the voltage counter, and the discharge current reaches the threshold value Ip by a current monitor (not shown). The current counter is detected, and the current counter is stopped (step S314 in FIG. 28, S412 and S416 in FIG. 29).
Here, when the main trigger signal is transmitted at the timing Td ′ in step S311, the switching means (for example, IGBT) after the delay time d1 has elapsed since the main trigger signal was input to the switching means of the pulse power supply means. Is turned on (S409, S410 in FIG. 29).
When the switching means is turned on, the voltage between the first rotating electrode 11 and the second rotating electrode 12 rises, and the voltage between the electrodes reaches the threshold value Vp after time Δtd. As described above, the threshold value Vp is a voltage value when the value of the discharge current that flows when discharge occurs is equal to or greater than the threshold value Ip (S410 and S411 in FIG. 29).

As described above, in step S312, the second trigger signal is sent to the second laser control unit 24b at the timing T2 ′ based on the equation (5). As a result, the second laser beam (starting laser beam) 24 is irradiated on the discharge region at time T2 after the time when the interelectrode voltage reaches the threshold value Vp (Td + Δtd) (S413 and S414 in FIG. 29).
The second laser beam 24 is irradiated to the discharge region, and discharge starts in the discharge region. After Δti after the start of discharge, the magnitude of the discharge current reaches the above-described threshold value Ip (S414 and S415 in FIG. 29). This threshold value Ip is a lower limit of the discharge current value necessary for obtaining EUV radiation having a predetermined intensity.

As described above, in step S312, the first trigger signal is sent to the first laser control unit 23b at the timing T1 ′ based on the equation (11). As a result, the first laser beam (raw material laser beam) 23 is irradiated at time T1 during the period of (T2 + Δti−Δtg) to (T2 + Δti + Δtp−Δtg) (S415, S417, and S418 in FIG. 29). That is, the control unit 26 of the EUV light source device transmits the main trigger signal in step S311, and transmits the first trigger signal and the second trigger signal in step S312, and as a result, the position of the discharge channel is defined at a predetermined position. . Further, in the discharge channel where the position is defined, EUV radiation having a predetermined intensity of discharge current is generated in a state where at least a part of the vaporized material having a predetermined spatial density distribution reaches the discharge channel. Discharge occurs so as to be equal to or greater than the lower limit of the discharge current value necessary for obtaining.
As a result, plasma is formed, and when the plasma is heated and excited by a pulsed large current flowing through the plasma, the EUV radiation having a wavelength of 13.5 nm is generated from the high temperature plasma (steps S315 in FIG. 28, FIG. 29). S419).
As described above, the EUV radiation emitted from the plasma passes through the opening provided in the partition wall 1c, the foil trap 3, and is collected by the oblique incidence type EUV collector mirror 2 disposed in the collection space 1b. The light is guided from an EUV light extraction unit 7 provided in the chamber 1 to an irradiation optical system of an exposure apparatus (not shown).

  As described above, when the first EUV radiation is completed, the process returns to step S306 and waits for a light emission command from the exposure apparatus. After receiving the light emission command, the process proceeds to step S309 through steps S307 and S308 described above. Since the next EUV radiation is not the first pulse, the process goes from step S109 to step S316. In step S316, the control unit 26 of the EUV light source device sends the first trigger signal T1 ′ to the first laser control unit based on the value of the voltage counter and the value of the current counter, and the second laser. The feedback calculation of the transmission timing T2 ′ of the second trigger signal to the second laser control unit for controlling the operation of the source is performed from the equations (20) and (21) (step S316 in FIG. 27, S408 in FIG. 29).

The control unit 26 of the EUV light source apparatus considers the correction value obtained in step S316 and uses the time Td ′ at which the main trigger signal is transmitted as a reference for the first trigger signal to the first laser control unit 23b. The transmission timing T1 ′ and the transmission timing T2 ′ of the second trigger signal to the second laser control unit 24b for controlling the operation of the second laser source 24a are determined by the following equations (step S317 in FIG. 27, FIG. 29). S408).
T2 ′ = Td ′ + d1 + Δtd + α + tvcal (24)
T1 ′ = Td ′ + d1 + (Δtd + Δti−Δtg) + (α + β) + (tvcal + tical) (25)

The control unit 26 of the EUV light source device transmits a main trigger signal after the time point when the charger charging stabilization time tst, which is the time until the charging of the main capacitor C0 is stabilized, has elapsed. The timing at that time is Td ′ (step S318 in FIG. 27, S409 in FIG. 29).
Then, the first laser control unit 23b based on the time Td ′ obtained by the equations (24) and (25) with the time Td ′ transmitted to the switching means of the pulse power supply means as a reference. The first trigger signal and the second trigger signal are sent at the timing T1 ′ for sending the first trigger signal to the second trigger signal T2 ′ for sending the second trigger signal to the second laser control unit 24b for controlling the operation of the second laser source 24a. The trigger signals are transmitted to the first laser control unit 23b and the second laser control unit 24b, respectively (step S319 in FIG. 27, S413 and S417 in FIG. 29).

Next, the process proceeds to step S313 in FIG. 28. As described above, the voltage counter that measures the time until the voltage between the electrodes reaches the threshold value Vp at the start of the output of the main trigger signal is operated, and the output of the second trigger signal is performed. A current counter that starts and measures the discharge current reaching the threshold value Ip is operated (S410 and S412 in FIG. 29).
Then, the timing at which the interelectrode voltage reaches the threshold value Vp is detected by a voltage monitor (not shown), and the voltage counter is stopped. Further, the timing at which the discharge current reaches the threshold value Ip is detected by a current monitor (not shown), and the current counter is stopped (step S314 in FIG. 28, S412 and S416 in FIG. 29).

Here, in step S311, when the main trigger signal is transmitted at timing Td ', the switching means is turned on as described above (S409, S410 in FIG. 29), and the voltage between the electrodes reaches the threshold value Vp after time Δtd. (S410, S411 in FIG. 29).
In step S312, the second trigger signal is sent to the second laser control unit 24b at the timing T2 ′ based on the equation (5), and at the time T2 after the time (Td + Δtd) when the interelectrode voltage reaches the threshold value Vp, The second laser beam (starting laser beam) 24 is irradiated to the discharge region (S413 and S414 in FIG. 29).
The second laser beam is applied to the discharge region, and discharge starts in the discharge region. After the start of the discharge, after Δti, the magnitude of the discharge current reaches the threshold value Ip (S414 and S415 in FIG. 29).

As described above, in step S312, the first trigger signal is sent to the first laser control unit 23b at the timing T1 ′ based on the expression (11). As a result, the first laser beam (raw material laser beam) 23 is irradiated at time T1 during the period of (T2 + Δti−Δtg) to (T2 + Δti + Δtp−Δtg) (S415, S417, and S418 in FIG. 29).
Thereby, as a result of the control unit of the EUV light source device transmitting each trigger signal in steps S318 and S319, the position of the discharge channel is defined at a predetermined position.
Further, in the discharge channel where the position is defined, EUV radiation having a predetermined intensity of discharge current is generated in a state where at least a part of the vaporized material having a predetermined spatial density distribution reaches the discharge channel. Discharge occurs so as to be equal to or greater than the lower limit of the discharge current value necessary for obtaining.

Discharge is generated between the edge portions of the peripheral edge portions of the first rotating electrode 11 and the second rotating electrode 12, and plasma is formed. When the plasma is heated and excited by a pulsed large current flowing through the plasma, EUV radiation having a wavelength of 13.5 nm is generated from the high temperature plasma (step S315 in FIG. 28, S419 in FIG. 29).
The EUV radiation radiated from the plasma passes through an opening provided in the partition wall 1 c and the foil trap 3, and is collected by the oblique incidence type EUV collector mirror 2 disposed in the collection space 1 b and provided in the chamber 1. The EUV light extraction unit 7 is guided to an irradiation optical system of an exposure apparatus (not shown).
Hereinafter, as long as the exposure process continues, the processes between Steps S306 to S315 are repeated. When the exposure process ends, the process ends after step S315.

By operating as described above, as described above, the spatial density distribution of the vaporized material supplied to the discharge region by the irradiation of the first laser beam 23 is such that EUV radiation is generated as efficiently as possible. Is set. Further, by focusing the second laser beam 24 at a predetermined position in the discharge region, the position of the discharge channel is demarcated at the position where the laser focus is set. Therefore, the positional stability of the generation point of EUV radiation is improved.
Since the irradiation timing of the first laser beam 23 and the irradiation timing of the second laser beam 24 are set as described above, at least a part of the vaporized material having a predetermined spatial density distribution is supplied to the discharge channel. In the reached state, discharge occurs when the magnitude of the discharge current is equal to or greater than the lower limit of the discharge current value necessary to obtain EUV radiation of a predetermined intensity. As a result, efficient EUV radiation can be realized.
Further, as described above, the time until the interelectrode voltage reaches the threshold value Vp after the output of the main trigger signal and the time until the discharge current reaches the threshold value Ip after the output of the second trigger signal are constant. Therefore, even if the operation of the semiconductor switching element used as the solid state switch SW which is the switching means of the pulse power supply means varies, it is possible to surely realize efficient EUV radiation. Is possible.

(6) Adjusted irradiation Adjusted irradiation of the first energy beam 23 may be performed so that a discharge is easily generated between the discharge electrodes. Hereinafter, measures for improving the startability of such discharge will be briefly described.
As an example, the procedure for carrying out the adjustment irradiation in the EUV light source apparatus shown in the embodiments of FIGS. 9 and 10 will be described. FIG. 30 shows a timing chart when the adjustment irradiation is performed.
As described above, in the EUV light source device shown in the embodiment, the first laser beam (raw material laser beam) 23 for supplying the raw material and the second energy beam (starting laser beam) 24 for starting the discharge are used. By appropriately setting the irradiation timing, the discharge current of the discharge generated in the discharge region is greater than or equal to a predetermined threshold at the timing when at least a part of the vaporized high temperature plasma raw material having a predetermined spatial density distribution reaches the discharge region. Set to be.
In this procedure, prior to irradiating the first laser beam (raw material laser beam) 23 whose irradiation timing with the second laser beam 24 is appropriately set, the first laser beam 23 is subjected to high-temperature plasma. The raw material is irradiated at least once.

In the example shown in FIG. 30, the first laser beam 23 is irradiated three times before the first laser beam 23 whose irradiation timing with the second laser beam 24 is appropriately set. Such laser beam irradiation is referred to as adjustment irradiation.
When the adjustment irradiation is performed, the vaporized high temperature plasma raw material reaches the discharge region. The first laser beam (raw material laser beam) 23 to be adjusted and irradiated has no correlation with the second laser beam 24 for starting the discharge, and the second laser beam 24 is not irradiated. A part of the vaporized high temperature plasma raw material that has reached adheres to the first discharge electrode 11 and the second discharge electrode 12.
In such a state, when the second energy beam 23 is irradiated to a predetermined position in the discharge region, the high-temperature plasma attached to the first discharge electrode 11 and the second discharge electrode 12 located in the vicinity of the discharge region. A part of the raw material is vaporized. Since the vaporized material contributes to the discharge, the discharge is easily generated reliably between the discharge electrodes. That is, the discharge startability is improved.
In order to vaporize part of the high temperature plasma raw material attached to the discharge electrodes 11 and 12, at least part of the second energy beam 24 is partially irradiated with the high temperature plasma raw material attached to the discharge electrodes 11 and 12. It is necessary to

3. Long Pulse Next, the long pulse of EUV radiation in the present invention will be described.
In the following, (1) a basic configuration example of an EUV light source apparatus that implements the EUV generation method of the present invention, (2) an EUV generation procedure of the present invention, (3) irradiation timing of an energy beam (laser beam), (4) raw material supply System, (5) rectification mechanism, (6) electrode position, high temperature plasma raw material supply position, mutual relationship of energy beam (laser beam) irradiation position, (7) energy of energy beam for raw material vaporization, (8) specific configuration An example will be described. Hereinafter, a laser beam will be described as an example of the energy beam, but the energy beam may be an electron beam or the like.

(1) Basic configuration example of an EUV light source apparatus that implements the EUV generation method of the present invention First, a basic configuration example will be described. FIG. 31 shows a basic configuration example of a long pulse EUV light source apparatus according to the present invention.
In the figure, a first electrode 11 and a second electrode 12 are installed inside a chamber 1 which is a discharge vessel. For example, the first electrode 11 is a cathode, the second electrode 12 is an anode, and the second electrode 12 is grounded. That is, a negative high voltage is applied between both electrodes.
A pulse power supply means 15 is connected to both electrodes. The pulse power supply means 15 employs, for example, a PFN (Pulse Forming Network) circuit system in order to flow a current having a long pulse width between both electrodes.

In addition, the high-temperature plasma raw material 8 is disposed outside the discharge region, although it is in the vicinity of the pair of electrodes described above. For example, a metal such as tin (Sn) or lithium (Li) is used as the high temperature plasma raw material 21. These may be solid or liquid. FIG. 31 schematically shows an example in which the high temperature plasma raw material 21 is a solid metal.
A laser source 23a is used to generate low temperature plasma (vaporized high temperature plasma raw material). The laser beam 23 emitted from the laser source 23 a is guided into the chamber 1 and is irradiated to the solid or liquid high-temperature plasma raw material 21. The irradiation energy of the laser is such an energy that vaporizes the solid or liquid high-temperature plasma raw material but does not increase the electron temperature so much, for example, in the range of 10 ⁸ W / cm ² to 10 ¹⁹ W / cm ² .
When the high temperature plasma raw material 21 is irradiated with a laser beam, at least a part of the high temperature plasma raw material 21 is vaporized and ejected as a low temperature plasma gas 21 ′. By appropriately setting the conditions of the laser beam to be irradiated, for example, continuously vaporized high temperature plasma raw material (low temperature plasma gas 21 ′) is ejected from the solid high temperature plasma raw material 21 for a period of about 10 μs.

As described above, the low temperature plasma gas is selected with respect to the discharge channel formed in advance between the electrodes in the state where the ion density in the plasma is about 10 ¹⁷ to 10 ²⁰ cm ^-3 and the electron temperature is about 1 eV or less. It is configured to supply automatically.
The discharge channel is narrowed by the self-magnetic field of the discharge current. In general, a material vapor ejected from a solid material or a liquid material by laser beam irradiation proceeds while expanding in a three-dimensional direction. Therefore, the low temperature plasma gas ejected from the high temperature plasma raw material 21 is rectified into a steady flow with good directivity by a rectification mechanism (not shown). An example of the rectifying mechanism will be described later.

(2) EUV Generation Procedure of the Present Invention The EUV generation method in the present invention will be described using the timing chart shown in FIG. As an example, a multi-pinch method is taken as an example.
First, a trigger signal is input (time point Td) to the switching means (for example, IGBT) of the pulse power supply means 15 that applies pulse power between the pair of electrodes 11 and 12 ((a) in FIG. 32). It becomes an on state.
Along with this, the voltage between the electrodes increases ((b) of FIG. 32). Then, discharge is generated at time T1 (= Td + Δtd) when the voltage reaches a certain threshold value Vp ((c) in FIG. 32). The discharge is generated by the operation of the discharge starting means (not shown in FIG. 31). This threshold value Vp is a voltage value when the value of the discharge current that flows when discharge occurs is equal to or greater than the threshold value Ip (or Ip2 or more in the case of the non-pinch method). That is, when discharge occurs below the threshold value Vp, the peak value of the discharge current does not reach the threshold value Ip or Ip2.

A discharge current starts to flow between the electrodes from time T1, and a discharge channel is formed. Then, when Δti has elapsed (T1 + Δti), the value of the discharge current reaches the threshold value Ip. This threshold value Ip, as described above, P _B the compression pressure by the self-magnetic field of the current, when the pressure P _p of the plasma, is set so that _{P B} »P _p (the (104) below). That is, the current value is such that the low temperature plasma gas can be sufficiently compressed by the self magnetic field.
The threshold Ip can heat the electron temperature of the low-temperature plasma gas (the ion density in the plasma is about 10 ¹⁷ to 10 ²⁰ cm ⁻³ and the electron temperature is about 1 eV or less) to ^{20 to} 30 eV or more. It is also a current value having a large energy.
Further, at the time (T1 + Δti), the diameter of the discharge channel flowing through the discharge region is sufficiently thin.

After this time (T1 + Δti), the laser beam is outside the discharge region so that at least a part of the low-temperature plasma gas having an ion density corresponding to the EUV radiation condition and a low electron temperature selectively reaches the thin discharge channel. The arranged high-temperature plasma raw material is irradiated (FIG. 32 (d)). When the time from when the laser beam is irradiated to the high temperature plasma raw material until at least part of the low temperature plasma gas reaches the discharge channel is Δtg, the laser beam is at the time (T1 + Δti−Δtg) or the time T2 after that. Irradiated to high temperature plasma raw material. FIG. 32 shows a case where time point T2 = T1 + Δti−Δtg.
After a time τ _heat from the time (T1 + Δti = T2 + Δtg), a discharge acts on the low-temperature plasma gas, the electron temperature reaches 20-30 eV and becomes high-temperature plasma, and EUV radiation from the high-temperature plasma is started ((FIG. 32 ( e)).

Since the thin discharge channel is continuously supplied with a low-temperature plasma gas having an ion density corresponding to the EUV radiation condition and a low electron temperature, the pinch effect or the confinement effect by the self magnetic field is repeatedly performed. Therefore, the diameter of the thin discharge channel becomes narrower, wider, or shows a pulsating behavior, but is kept relatively thin. That is, pinching of the low temperature plasma is repeatedly performed, and EUV radiation continues.
EUV radiation generated in the discharge region is reflected by the EUV collector mirror 2 and emitted from the EUV light extraction unit 7 to an irradiation unit (not shown).

Here, in the conventional DPP method and the LAGDPP method using the pinch effect, the time for which EUV radiation is maintained is, for example, 200 ns or less. Therefore, the time for which the discharge channel having a current value of Ip continues is small. From the time point (T1 + Δti = T2 + Δtg) when a part of the low temperature plasma gas reaches (200 ns + τ _heat ), the pulse power supply means 15 and the pair of electrodes (the first electrode 11 and the second electrode 12) are continued. By setting such a discharge circuit, it is possible to realize a long pulse of EUV radiation as compared with the DPP method and the LAGDPP method using the conventional pinch effect.

In the DPP method and the LAGDPP method using the conventional pinch effect, the duration of the discharge channel is 1 μs or less at the longest, and the time during which EUV radiation continues by pinching the initial plasma (period A in FIG. 10) is long. Both were less than 200ns.
As a result of verification by the inventors' experiments, in the present invention, when the duration of the discharge channel is at least 1 μs or longer, the duration of the discharge channel having a current value of Ip or more or Ip2 or more is surely longer than 200 ns. It turns out that you can. That is, when the duration of the discharge channel is set to 1 μs or more, the duration of EUV radiation can be reliably made longer than the duration of conventional EUV radiation (200 ns).
Even in the case of the non-pinch method, if the threshold value is set to be Ip2, a long pulse of EUV radiation can be realized by the same mechanism as described above, and detailed description thereof will be omitted.

  In the present invention, unlike the long pulse method of EUV radiation in Patent Documents 6 and 7, which controls the plasma current waveform so as to maintain the pinch state of the plasma, it is not necessary to flow a large current through the discharge space. Further, since it is not necessary to change the waveform of the plasma current I as shown in FIG. 40A in order to maintain the pinch effect, the discharge current (plasma current) waveform in this method has no inflection point.

(3) Energy Beam (Laser Beam) Irradiation Timing In the EUV generation procedure described above, at least a part of the low temperature plasma gas reaches the thin discharge channel after the time when the value of the discharge current reaches the threshold value Ip. The timing at which the laser beam is irradiated onto the high temperature plasma raw material is set.
Here, when at least a part of the low temperature plasma gas reaches the discharge channel before the time when the value of the discharge current after the discharge reaches the threshold value Ip (case A), or before the occurrence of the discharge, Consider a case (case B) where at least a part has reached a region where a discharge channel is generated after discharge.
In cases A and B, the low-temperature plasma is not sufficiently heated until the value of the discharge current reaches the threshold value Ip. As a result, the proportion of low-temperature plasma that does not contribute to EUV emission increases. Radiation efficiency will decrease.

In case A and case B, a low temperature plasma material that is selectively supplied as a steady flow into a region where a discharge channel is generated after discharge until the value of the discharge current reaches the threshold value Ip. The plasma gas expands and the density decreases. Therefore, the density of the high-temperature plasma raw material in the discharge region approaches the initial pinch condition in FIG. In such a state, since the diameter of the discharge channel is large, a large current is required as the discharge current in order to make the discharge channel narrow and to produce high-temperature plasma.
In particular, in the case B, since the low temperature plasma gas is supplied before the discharge, the discharge channel is formed by the gas discharge of the high temperature plasma source gas which has expanded and the density has been reduced, and the diameter of the discharge channel is thicker than the case A. Become. Therefore, in order to make the discharge channel narrow and to make the initial plasma into a high temperature plasma by the pinch effect, a current pulse of a high speed and a short pulse with a certain amount of power is required as in the DPP method (close to the path 2 in FIG. 38). Become).

In the present invention, as described above, since the discharge circuit is formed so as to increase the duration of the discharge channel, it is difficult to realize the current pulse required in case B.
Therefore, at least after the discharge has started (case A), preferably, as shown in FIG. 32, at least a part of the low temperature plasma gas reaches the thin discharge channel after the time when the value of the discharge current reaches the threshold value Ip. As described above, it is important to set the timing at which the laser beam is irradiated onto the high temperature plasma raw material.

(4) Raw Material Supply System As described above, the present invention irradiates a high-temperature plasma raw material with an energy beam such as a laser beam, and has a low-temperature plasma gas (within the plasma) having an ion density corresponding to EUV radiation conditions and a low electron temperature. The ion density is about 10 ¹⁷ to 10 ²⁰ cm ⁻³ and the electron temperature is about 1 eV or less), and the low-temperature plasma is supplied to the discharge region. FIG. 31 schematically shows an example in which the high-temperature plasma raw material is a solid metal. However, as described above, the high-temperature plasma material may be in a liquid state.
As a configuration example of a raw material supply system that supplies a low-temperature plasma gas to a discharge region using a solid high-temperature plasma raw material, for example, as schematically shown in FIG. 31, a solid metal (for example, , Sn) and configured to irradiate a laser beam.
As another example, a high-temperature plasma raw material formed into a wire shape is supplied to a space where a low-temperature plasma gas generated when a laser beam is irradiated can reach a predetermined region using two sets of reels. The high-temperature plasma raw material is irradiated with a laser beam.

On the other hand, as a configuration example of a raw material supply system for supplying a low temperature plasma gas to a discharge channel using a liquid high temperature plasma raw material, for example, a liquid high temperature plasma raw material is formed in a droplet shape and irradiated with a laser beam. When the droplet-shaped high-temperature plasma material reaches the space, a laser beam is applied to the droplet-shaped high-temperature plasma material. Configure to irradiate.
As an example of using a solid high-temperature plasma raw material, as described in Patent Document 6, the electrode itself is composed of a solid high-temperature plasma raw material (for example, Li), and the electrode is irradiated with a laser beam. It is also conceivable to generate a low temperature plasma gas and supply the low temperature plasma gas to the discharge channel.

Moreover, as an example using a liquid high temperature plasma raw material, the structure as described in patent document 4 can be considered. That is, the electrode has a rotating electrode structure, and a liquid high-temperature plasma raw material that is a heated molten metal is contained in a container. And it arrange | positions so that a part (peripheral part) of a rotating electrode may be immersed in the said container which accommodates a liquid high temperature plasma raw material. Then, by rotating the electrode, the liquid high-temperature plasma raw material attached to the peripheral surface of the electrode is transported to the discharge region. By irradiating the transported liquid high temperature plasma raw material with a laser beam, a low temperature plasma gas is generated, and the low temperature plasma is supplied to the discharge channel.
However, this configuration places the high temperature plasma raw material in the discharge region, and the generation of the low temperature plasma gas and the supply to the discharge channel based on such a method are not preferable for the following reasons.
In the case of the configuration described in Patent Documents 4 and 6, the discharge is started by the plasma (or neutral vapor) generated when the laser beam is applied to the electrode surface. Therefore, the supply of the low temperature plasma gas is performed prior to the discharge, and as described above, the ratio of the low temperature plasma that does not contribute to the EUV light emission increases, and the EUV radiation efficiency decreases.

Further, since the low temperature plasma gas is supplied before the discharge, the discharge channel is formed by the high temperature plasma raw material gas discharge which has expanded and the density has been reduced, and the diameter of the discharge channel is increased. Therefore, in order to form a high temperature plasma by narrowing the discharge channel, a certain amount of high power current is required.
In addition to supplying the low temperature plasma gas to the discharge channel, the electrode itself (or the liquid high temperature adhering to the electrode) is generated by the temperature rise of the electrode due to the drive current accompanying the progress of the discharge in addition to the supply by laser beam irradiation. There is also a supply due to evaporation of the plasma raw material.
Therefore, the parameters of the low temperature plasma gas change every moment depending on the discharge current, and the output of EUV radiation varies. Further, the position of the high temperature plasma varies due to the variation of the discharge channel during discharge, and the size of the high temperature plasma apparently increases.
The above-mentioned problems occur because the high-temperature plasma raw material and the electrode are integrated, and the supply of the low-temperature plasma gas depends on both the laser beam irradiation and the discharge current (plasma current).

  Therefore, in the present invention, the high temperature plasma raw material and the electrode are separate from each other, and the supply of the low temperature plasma gas depends only on the laser beam irradiation and is independent of the discharge current. That is, as in the configuration example shown in FIG. 31 and the other configuration examples described above (wire shape, droplet shape), the supply control of the low temperature plasma gas and the control of the drive current flowing between the electrodes are independent from each other. The raw material supply system is configured.

(5) Rectification mechanism As described above, the low-temperature plasma gas is configured to be selectively supplied to the discharge channel narrowed by the self-magnetic field of the discharge current after the discharge is generated between the electrodes. In general, a material vapor ejected from a solid material or a liquid material by irradiation with a laser beam proceeds while expanding in a three-dimensional direction. Therefore, when a low temperature plasma gas is ejected by irradiating a solid or liquid high temperature plasma raw material with a laser beam, the flow of the ejected low temperature plasma gas is rectified to form a flow with good directivity. It is set so that it is continuously supplied in a concentrated manner near the narrow discharge channel.
As the rectifying mechanism for rectifying the flow of the jetted low temperature plasma gas, the one shown in FIGS. 23 to 25 can be used. Moreover, you may comprise as FIG.

(6) Interrelationship between electrode position, high temperature plasma raw material position, and energy beam (laser beam) irradiation position As described above, in the present invention, the low temperature plasma gas is caused to reach the discharge channel by the laser beam. The positional relationship is as shown in FIG. 4, for example.
That is, a pair of plate-like electrodes 11 and 12 are arranged at a predetermined interval. The discharge channel is generated in a discharge region located in a space between the pair of electrodes 11 and 12.
The low-temperature plasma gas 21 ′ generated by the irradiation of the laser beam 23 onto the high-temperature plasma raw material 21 spreads in the direction in which the laser beam is incident. Therefore, by irradiating the surface facing the discharge region of the high temperature plasma raw material 21 with the laser beam 23, the low temperature plasma gas 21 ′ is supplied to the discharge channel generated in the discharge region.

As described above, a part of the low temperature plasma gas supplied to the discharge channel by the laser beam irradiation that did not contribute to the high temperature plasma formation, or a cluster of atomic gases that are decomposed and generated as a result of the high temperature plasma formation. A part contacts and deposits in the low temperature part in an EUV light source device as a debris.
Here, as shown in FIG. 4B, when the high temperature plasma raw material 21 is supplied to the space side where the EUV collector mirror 2 does not face the pair of electrodes 11 and 12, as described above, the laser beam 23 The low-temperature plasma gas 21 ′ generated by the irradiation is spread in the direction of the discharge channel and the EUV collector mirror 2, and debris is emitted to the EUV collector mirror 2. Therefore, as shown in FIG. 4A, the high temperature plasma raw material 21 is disposed in a space between the pair of electrodes 11 and 12 and the EUV collector mirror 2 and in the vicinity of the discharge region. Is preferred.
When the laser beam 23 is irradiated to the high temperature plasma raw material 21 arranged in this way on the side of the high temperature plasma raw material surface facing the discharge region as described above, the low temperature plasma gas 21 'spreads in the direction of the discharge region. However, it does not spread in the direction of the EUV collector mirror 2.

  As shown in FIG. 5, the high temperature plasma raw material 21 is a space on a plane perpendicular to the optical axis and is disposed near the discharge region, and the laser beam 23 is perpendicular to the optical axis. Even if the high temperature plasma raw material 21 is irradiated from the direction, the low temperature plasma gas 21 ′ does not spread in the direction of the EUV collector mirror 2. Therefore, the debris generated by the irradiation of the laser beam to the high temperature plasma raw material 21 and the discharge generated between the electrodes 11 and 12 hardly progresses with respect to the EUV collector mirror 2.

(7) Energy of energy beam for raw material vaporization As described above, the time Δtg from the time when the laser beam is irradiated to the high temperature plasma raw material until at least a part of the low temperature plasma gas reaches the discharge channel is equal to the discharge channel and the high temperature. The predetermined time is set by appropriately setting these parameters depending on the position of the plasma raw material, the irradiation direction of the laser beam onto the high temperature plasma raw material, and the irradiation energy of the laser beam.

As described above, the EUV generation method with a long pulse according to the present embodiment generates a thin discharge channel in the discharge region in advance, and ions corresponding to the EUV radiation condition from the outside of the discharge region to the thin discharge channel. A steady flow of a low-temperature plasma gas having a low density and a low electron temperature (the ion density is about 10 ¹⁷ to 10 ²⁰ cm ⁻³ and the electron temperature is about 1 eV or less) is selectively supplied.
Here, the supply timing of the low-temperature plasma gas is the low-temperature plasma gas (the ion density is about 10 ¹⁷ to 10 ²⁰ cm ⁻³ , the electron temperature after the time when the value of the discharge current reaches a predetermined threshold value (Ip or Ip2). Is set to reach a thin discharge channel. As a result, a discharge acts on the low temperature plasma gas, and a high temperature plasma that satisfies the EUV radiation condition is formed through the path II in FIG. 9 to generate EUV radiation.

Here, the low temperature plasma gas is supplied to the discharge channel, and EUV radiation is realized through the path (II) in FIG. 6, so that the discharge current is a large current as in the conventional DPP method or LAGDPP method. The EUV radiation is possible even when a relatively small current is supplied to the discharge region. Further, it is possible to efficiently input energy to the plasma without reducing the discharge current at a high speed and with a short pulse as in the prior art. Therefore, the discharge current pulse can be set longer than the conventional one.
EUV radiation continues as long as a somewhat narrow discharge channel lasts. Therefore, the discharge circuit is configured such that the discharge current pulse is longer than that of the conventional DPP method and LAGDPP method, and the discharge current pulse is made longer, thereby making the duration of the narrow discharge channel longer than the conventional one. As a result, a long pulse of EUV radiation is realized.

In the multi-pinch method, the threshold value Ip is set so that P _B >> P _p as shown in the above equation (104) when the compression pressure due to the current self-magnetic field is P _B and the plasma pressure P _p. The
That is, the threshold value Ip is a current value that can sufficiently compress the low temperature plasma gas by the self magnetic field. The threshold value Ip is also a current value having energy capable of heating the electron temperature of the low temperature plasma gas to 20 to 30 eV or more. Here, when the value of the discharge current becomes Ip, the diameter of the discharge channel flowing through the discharge region is sufficiently thin.

The continuous supply of the low temperature plasma gas to the narrow discharge channel repeatedly performs the pinch effect or the confinement effect by the self magnetic field. At this time, the diameter of the thin discharge channel becomes narrower or wider, or shows a pulsating behavior, but is kept relatively thin.
Such repetition of the pinch effect of the low-temperature plasma gas or the confinement effect due to the self-magnetic field lasts for the duration of the discharge current.
As described above, in the present invention, the discharge current pulse can be set longer than the conventional one, and the confinement effect by continuous pinch or self magnetic field can be maintained for a long time. Long pulse can be realized (multi-pinch method).

In the non-pinch method, the threshold value Ip2 is set so that P _B ≧ P _p as shown in the equation (105). That is, the threshold value Ip2 is a current value that weakly compresses the low temperature plasma gas by the self magnetic field (maintained to such an extent that the low temperature plasma gas expands and the ion density does not decrease). The threshold value Ip2 is also a current value having energy capable of heating the electron temperature of the low temperature plasma gas to 20 to 30 eV or more. Here, when the value of the discharge current becomes Ip2, the diameter of the discharge channel flowing through the discharge region is narrowed.

By continuously supplying the low temperature plasma gas to the narrow discharge channel, the low temperature plasma gas is heated to a high temperature plasma in a state where it is expanded and maintained so that the ion density does not decrease, and EUV is emitted from this high temperature plasma. The
While maintaining the ion concentration of such a low temperature plasma gas, the heating is continued for the duration of the discharge current. As described above, in the present invention, the discharge current pulse can be set longer than the conventional one, and the temperature and density of the plasma necessary for EUV radiation are maintained for a long time by continuing the heating of the low temperature plasma. Therefore, a long pulse of EUV radiation can be realized (non-pinch method).
In the non-pinch method, since the diameter of the discharge channel is larger than that of the multi-pinch method, the size of the high-temperature plasma is also larger than that of the multi-pinch method.

As a result of verification by the inventors' experiments, in the present invention, when the duration of the discharge channel is at least 1 μs or longer, the duration of the discharge channel having a current value of Ip or more or Ip2 or more is surely longer than 200 ns. It turns out that you can. That is, when the duration of the discharge channel is set to 1 μs or more, the duration of EUV radiation can be reliably made longer than the duration of conventional EUV radiation (200 ns).
As described above, the discharge current does not need to be a large current as in the conventional DPP method and the LAGDPP method, and it is not necessary to shorten the discharge current at high speed. Therefore, it is possible to reduce the thermal load applied to the electrodes as compared with the conventional case, and it is possible to suppress the generation of debris.
Further, in the present invention, unlike the conventional long pulse technology, it is not necessary to control the plasma current waveform so as to maintain the pinch state of the high temperature plasma, and therefore it is not necessary to flow a large current through the discharge space. Further, since it is not necessary to change the waveform of the plasma current in order to maintain the pinch effect, high-precision current control is not required. That is, the discharge current (plasma current) waveform in this method has no inflection point.

Further, it is preferable to configure the raw material supply system so that the supply control of the low temperature plasma gas and the control of the drive current flowing between the electrodes are independent from each other.
With this configuration, the supply of low-temperature plasma is not affected by the discharge current (plasma current), so that the stability of EUV radiation is improved.
Furthermore, it is desirable to arrange (or supply) the high temperature plasma raw material in the space between the pair of electrodes and the EUV collector mirror and irradiate the laser beam on the side of the high temperature plasma raw material surface facing the discharge region. .
By doing so, the low temperature plasma gas spreads in the direction of the discharge region, but does not spread in the direction of the EUV collector mirror. Therefore, it is possible to suppress debris from proceeding to the EUV collector mirror.

Next, a specific configuration example of the EUV light source apparatus having a long pulse will be described.
As described above, according to the EUV radiation method of the present embodiment, the pulse width of EUV radiation is set by constantly supplying a low-temperature plasma gas to a predetermined narrow discharge channel and setting the discharge current pulse width longer than before. Long pulse.
Therefore, the vacuum arc discharge gradually shifts to gas discharge from the time when the low temperature plasma gas arrives. That is, finally, a thin discharge channel of gas discharge is established, and low temperature gas plasma is selectively supplied to the discharge channel of thin gas discharge.
Here, the formation position of the discharge channel of the gas discharge is not necessarily the same as the position where the discharge channel of the vacuum arc is formed. As the transition from vacuum arc discharge to gas discharge occurs, the position of the gas discharge channel may vary.

That is, although the discharge channel of the gas discharge is formed in the vicinity of the discharge channel position of the vacuum arc discharge, the stability of the position of the gas discharge channel is not necessarily highly accurate.
When an EUV light source is used as an exposure light source, high stability of the EUV radiation source is required. That is, there is a need for higher accuracy in the position stability of the discharge channel in gas discharge.

FIG. 33 is a diagram showing a state of starting discharge between electrodes in this embodiment. In this embodiment, starting discharge between electrodes is performed when at least a part of the low-temperature plasma gas arrives.
As shown in FIG. 33, a part of the low-temperature plasma gas generated by irradiating the high-temperature plasma raw material with the first laser beam reaches the discharge region, and the discharge region is filled with the low-temperature plasma gas having a low concentration to some extent. At this point, the second laser beam is focused at a predetermined position in the discharge region to start discharge. As described above, since the discharge region is filled with the low-temperature plasma gas having a low concentration, the discharge at this time is a gas discharge.
Here, in the vicinity of the focal point of the second laser beam, the conductivity is increased by electron emission. Therefore, the position of the discharge channel of the gas discharge is defined at the position where the laser focus is set. That is, the position of the gas discharge is defined by the second laser beam.
Thus, in the EUV radiation system shown in the present embodiment, since the position of the discharge channel itself of the gas discharge is defined, it is possible to achieve high accuracy of the positional stability of the discharge channel in the gas discharge.

(8) Embodiment of EUV light source device having a long pulse in the present invention FIGS. 34 and 35 show an embodiment of an EUV light source device adopting the extreme ultraviolet light (EUV) generation method of the present invention.
FIG. 34 is a block diagram of the EUV light source device, and EUV radiation is extracted from the right side of the figure. FIG. 35 is a configuration example of the power supply means in FIG.
The EUV light source device shown in FIG. 34 has a chamber 1 that is a discharge vessel. In the chamber 1, the discharge space 1 a for generating high-temperature plasma by inputting power to the above-described low-temperature plasma gas, and the EUV light provided in the chamber 1 by condensing EUV light emitted from the high-temperature plasma are collected. It has an EUV light condensing space 1b that leads from the extraction unit 7 to an irradiation optical system of an exposure apparatus (not shown). The chamber 1 is connected to an exhaust device 5, and the inside of the chamber 1 is brought into a reduced pressure atmosphere by the exhaust device.

Hereinafter, the configuration of each unit will be described.
(A) Discharge part The discharge part 1a is formed so that the first discharge electrode 11 that is a metal disk-like member and the second discharge electrode 12 that is also a metal disk-like member sandwich the insulating material 110. Arranged structure. The center of the first discharge electrode 11 and the center of the second discharge electrode 12 are arranged substantially coaxially, and the first discharge electrode 11 and the second discharge electrode 12 are separated by the thickness of the insulating material 110. It is fixed at the position. Here, the diameter of the second discharge electrode 12 is larger than the diameter of the first discharge electrode 11. In addition, since the 1st discharge electrode 11 and the 2nd discharge electrode 12 rotate, it may be called a rotation electrode below.

A rotating shaft (rotating shaft) 22e of a motor 22a is attached to the second discharge electrode 12. Here, the rotary shaft 22e is attached to the approximate center of the second discharge electrode 12 so that the center of the first discharge electrode 11 and the center of the second discharge electrode 12 are positioned substantially coaxially with the rotary shaft 22e. It is done.
The rotating shaft 22e is introduced into the chamber 1 through, for example, a mechanical seal 22c. The mechanical seal 22c allows the rotation of the rotary shaft 22e while maintaining a reduced pressure atmosphere in the chamber 1.
Below the second discharge electrode 12, a first slider 22g and a second slider 22h made of, for example, a carbon brush are provided. The second slider 22h is electrically connected to the second discharge electrode 12. On the other hand, the first slider 22 g is electrically connected to the first discharge electrode 11 through a through hole 22 i that penetrates the second discharge electrode 12.
In addition, it is comprised so that a dielectric breakdown may not generate | occur | produce between the 1st slider 22g electrically connected with the 1st discharge electrode 11, and the 2nd discharge electrode 12 by the insulation mechanism which abbreviate | omitted illustration. ing.

The first slider 22g and the second slider 22h are electrical contacts that maintain electrical connection while sliding, and are connected to the pulse power supply means 15. The pulse power supply means 15 supplies power between the first discharge electrode 11 and the second discharge electrode 12 via the first slider 22d and the second slider 22e.
That is, even if the motor 22a is operated and the first discharge electrode 11 and the second discharge electrode 12 are rotating, the first discharge electrode 11 and the second discharge electrode 12 are not connected to each other. Electric power is applied from the pulse power supply means 15 via the slider 22g and the second slider 22h.

As shown in FIG. 31, the pulse power supply means 15 includes a PFN circuit section, and, for example, a pulse having a relatively long pulse width is provided between the first discharge electrode 11 and the second discharge electrode 12 that are loads. Apply power. The wiring from the power supply means 15 to the first slider 22g and the second slider 22h is made through an insulating current introduction terminal (not shown). The current introduction terminal is attached to the chamber 1 and enables electrical connection from the power supply means to the first slider and the second slider while maintaining a reduced-pressure atmosphere in the chamber 1.
Peripheral portions of the first discharge electrode 11 and the second discharge electrode 12 that are metal disk-shaped members are formed in an edge shape. As will be described later, when power is applied from the power supply means 15 to the first discharge electrode 11 and the second discharge electrode 12, a discharge is generated between the edge-shaped portions of both electrodes. When discharge occurs, both electrodes reach a high temperature. Therefore, the first discharge electrode 11 and the second discharge electrode 12 are made of a refractory metal such as tungsten, molybdenum, or tantalum. The insulating material 20c is made of, for example, silicon nitride, aluminum nitride, diamond, or the like.
When generating a discharge to generate EUV radiation, the first and second discharge electrodes 11, 12 are rotated. Thereby, the position where discharge occurs in both electrodes changes for each pulse. Therefore, the thermal load received by the first and second discharge electrodes 11 and 12 is reduced, the wear speed of the discharge electrode is reduced, and the life of the discharge electrode can be extended.

(B) Power Supply Unit FIG. 35 shows a configuration example of an equivalent circuit of the power supply unit 15. The equivalent circuit of the power supply means 15 shown in FIG. 35 is composed of a charger CH1, a solid state switch SW, a PFN circuit portion having an LC distributed constant circuit configuration in which a set of a capacitor C and a coil L is cascaded in n stages, and a switch SW1. Is done. An example of the operation of the power supply means is as follows. First, the set charging voltage of the charger CH1 is adjusted to a predetermined value Vin. When the solid switch SW is turned on, n capacitors C constituting the PFN circuit unit are charged, and when the switch SW1 is turned on, a voltage is applied between the first main discharge electrode and the second main discharge electrode. Applied.
Thereafter, when a discharge occurs between the electrodes, a current flows between the electrodes. Here, since the circuit loops formed by the capacitors C and the loads have different inductances, the periods of the currents flowing through the circuit loops are different from each other. Since the current flowing between the electrodes is a superposition of the current flowing through each circuit loop, a current pulse having a long pulse width flows between the electrodes as a result.

(C) Low temperature plasma gas supply means In FIG. 34, the means for supplying the low temperature plasma gas includes a high temperature plasma raw material 21, a laser source 23a for irradiating the high temperature plasma raw material 21 with a laser beam 23, and a high temperature plasma irradiated with the laser beam. It is comprised from the nozzle 60b for high-speed injection which is a rectification | straightening means which rectifies | straightens the low-temperature plasma gas injected from the raw material 21 to a steady flow with good directivity.
The high-temperature plasma raw material 21 is a space on a plane substantially perpendicular to the optical axis of the EUV collector mirror 2 described later, and is close to the discharge region between the first discharge electrode 11 and the second discharge electrode 12. Placed in. The arrangement of the high-speed nozzle 60b is set so that the low-temperature plasma gas ejected from the nozzle is selectively supplied to a region where a narrow discharge channel is generated in the discharge region.
By arranging the high temperature plasma raw material 21 and the high-speed jet nozzle 60b in this way, the low temperature plasma gas supplied to the discharge channel does not spread in the direction of the EUV collector mirror 2. Therefore, the debris generated by the irradiation of the laser beam 23 onto the high temperature plasma raw material 21 and the discharge generated between the electrodes hardly proceeds with respect to the EUV collector mirror 2.

  The high-speed jet nozzle 60b is a cylindrical member having a narrowed portion provided therein as shown in FIG. When the high-temperature plasma raw material 21 is irradiated with the laser beam 23 that has passed through the nozzle for high-speed injection, the high-temperature plasma raw material 21 is vaporized to generate a low-temperature plasma gas. Here, since the constricted portion is provided inside the high-speed injection nozzle 60b, the pressure between the constricted portion and the portion irradiated with the laser beam of the high temperature plasma raw material is rapidly increased by the low temperature plasma gas. To rise. Then, the low-temperature plasma gas is accelerated from the opening portion of the constricted portion and is injected as a high-speed gas flow with good directivity. Here, the injection direction of the high-speed gas flow depends on the direction of the high-speed injection nozzle. That is, the traveling direction of the vaporized material does not depend on the incident direction of the laser beam to the high temperature plasma material.

The laser beam 23 emitted from the laser source 23a is incident on the high temperature plasma raw material 21 through the half mirror 23e, the condensing means 23c, and the incident window 23d provided in the chamber 1.
Further, the wavelength of the second laser beam 24 emitted from the second laser source 24a is set to a wavelength region that transmits the half mirror 23e, and the second laser beam 24 transmits the half mirror 23e. The light is condensed at a predetermined position in the discharge space through the light condensing means 23 c and the incident window 23 d provided in the chamber 1.
The first laser beam 23 whose wavelength is set to the reflection wavelength of the half mirror is reflected from the half mirror 23e disposed at an inclination of about 45 degrees. Then, the incident direction to the half mirror 23e of the second laser beam 24 whose wavelength is set to the transmission wavelength of the half mirror 23e is set to be substantially the same as the reflection direction of the first laser beam 23. It is possible to provide one incident window portion 23d.
As the first laser source 23 a that emits the first laser beam 23 and the second laser source 24 a that emits the second laser beam, for example, a Q-switched ND ⁺ -YAG laser device is used. One of the wavelength of the first laser beam 23 and the wavelength of the second laser beam 24 is wavelength-converted by, for example, a wavelength conversion element.

As described above, a part of the low temperature plasma gas generated by irradiating the high temperature plasma raw material 21 with the first laser beam 23 reaches the discharge region, and the discharge region is filled with the low temperature plasma gas having a low concentration to some extent. At this point, the second laser beam 24 is focused on a predetermined position in the discharge region to start discharge.
Therefore, it is necessary to irradiate the high temperature plasma material 21 with the first laser beam 23 prior to the discharge, and a high voltage is applied from the power supply means 15 between the first discharge electrode 11 and the second discharge electrode 12. When the high temperature plasma material 21 is irradiated with the first laser beam 23 in such a state, discharge may be generated by the trigger of the first laser beam 23. Therefore, it is necessary to apply a high voltage between the first discharge electrode and the second discharge electrode after the first laser beam is emitted from the first laser source.

(D) EUV radiation condensing unit The EUV radiation emitted from the discharge space 1a is condensed by an oblique incidence type EUV condensing mirror 2 provided in the EUV radiation condensing space 1b, and EUV provided in the chamber 1 The light extraction unit 7 guides the irradiation optical system of an exposure apparatus (not shown).
The EUV collector mirror 2 includes, for example, a plurality of spheroids having different diameters or rotating paraboloid-shaped mirrors. These mirrors are arranged on the same axis so as to overlap the rotation center axis so that the focal positions substantially coincide with each other. For example, on the reflecting surface side of the base material having a smooth surface made of nickel (Ni) or the like, ruthenium ( By densely coating a metal film such as Ru), molybdenum (Mo), and rhodium (Rh), EUV light having an oblique incident angle of 0 ° to 25 ° can be favorably reflected.
In FIG. 34, the discharge space 1a is shown as being larger than the EUV light collection space 1b, but this is for ease of understanding, and the actual magnitude relationship is not as shown in FIG. Actually, the EUV light collection space 1b is larger than the discharge space 1a.

(E) Debris trap In order to prevent damage to the EUV collector mirror 2 between the discharge space 1a and the EUV light collection space 1b, the first and second discharge electrodes 11 and 12 in contact with the high-temperature plasma are provided. A debris trap for capturing debris such as metal powder generated by sputtering of the peripheral portion with high-temperature plasma, debris caused by Sn or Li as a radioactive species, and allowing only EUV light to pass therethrough is installed.
In the EUV light source device shown in FIG. 34, a foil trap 3 is employed as a debris trap. The foil trap 3 is described as “foil trap” in Patent Document 8, for example. The foil trap is composed of a plurality of plates installed in the radial direction of the high temperature plasma generation region and a ring-shaped support that supports the plates so as not to block EUV radiated from the high temperature plasma. The foil trap 3 is provided between the discharge space 1 a and the EUV collector mirror 2. Since the pressure inside the foil trap 3 is higher than that of the surrounding atmosphere, the debris passing through the foil trap decreases the kinetic energy due to the influence of the pressure. Therefore, energy when debris collides with the EUV collector mirror is reduced, and damage to the EUV collector mirror can be reduced.

Hereinafter, the operation of the EUV light source apparatus will be described with reference to FIGS. As an example, a multi-pinch method is taken as an example.
The control unit 26 of the EUV light source device stores time data Δtd, Δtg, Δts, γ, δ.
Δtd is the time from when the trigger signal is input to SW1 which is the switching means of the power supply means 15 (time Td) until the switching means is turned on and the interelectrode voltage reaches the threshold value Vp. Δtg is a time from when the high temperature plasma raw material is irradiated with the first laser beam until at least a part of the low temperature plasma gas reaches the discharge region. Δts is a time during which the density of the low-temperature plasma gas in the discharge region is within a range in which the gas discharge by the laser trigger can be started with reference to the time when at least a part of the low-temperature plasma gas reaches the discharge region.
On the other hand, γ and δ are correction times, and details will be described later.

In general, when the voltage V applied to the discharge electrodes 11 and 12 is large, the rise of the voltage waveform between the discharge electrodes 11 and 12 becomes faster. Therefore, the above-described Δtd depends on the voltage V applied to the discharge electrodes 11 and 12. The control unit 26 of the EUV light source device stores the relationship between the voltage V and time Δtd obtained in advance through experiments or the like as a table.
Further, the control unit 26 stores a delay time d1 from the time when the main trigger signal is output to the switch SW1 which is the switching means of the pulse power supply means 15 to the time when the switching means is turned on.

First, a standby command from the control unit 26 of the EUV light source device is transmitted to the exhaust device 5 and the motor 22a (step S501 in FIG. 36, S601 in FIG. 37).
The exhaust device 5 that has received the standby command starts its operation. That is, the exhaust device 5 operates and the inside of the chamber 1 is in a reduced pressure atmosphere. Further, the motor 22a operates to rotate the first rotation (discharge) electrode 11 and the second rotation (discharge) electrode 12. Hereinafter, the above-described operation states are collectively referred to as a standby state (step S502 in FIG. 36 and S602 in FIG. 37).
The control unit 26 of the EUV light source apparatus transmits a standby completion signal to the control unit 27 of the exposure apparatus (step S503 in FIG. 36 and S603 in FIG. 37).
The control unit 26 of the EUV light source apparatus receives a light emission command from the control unit 27 of the exposure apparatus that has received the standby completion signal. When the exposure apparatus controls the intensity of EUV radiation, the emission command includes intensity data of EUV radiation. (Step S504 in FIG. 36, S604 in FIG. 37).

The control unit 26 of the EUV light source device transmits a charge control signal to the charger CH <b> 1 of the power supply unit 15. The charge control signal includes, for example, a discharge start timing data signal. As described above, when EUV emission intensity data is included in the light emission command from the control unit 27 of the exposure apparatus, the charging voltage data signal of each capacitor C of the PFN circuit unit of the power supply means 15 is also included in the charge control signal. It is.
For example, the relationship between the EUV radiation intensity and the charging voltage to each capacitor C is obtained in advance by experiments or the like, and a table storing the correlation between the two is created. The control unit 26 of the EUV light source device stores this table, and charges each capacitor C of the PFN circuit unit from the table based on the EUV radiation intensity data included in the light emission command received from the control unit 27 of the exposure apparatus. Recall voltage data. Then, based on the called charging voltage data, the control unit 26 of the EUV light source device transmits a charging control signal including a charging voltage data signal for each capacitor C to the charger CH1 of the power supply means (step S505 in FIG. 36). S605 in FIG. 37).
The charger CH1 charges each capacitor C as described above. (Step S506 in FIG. 36).

  The control unit 26 of the EUV light source apparatus calculates the timing of outputting the main trigger signal to the switch SW1 of the power supply unit 15 with reference to the timing of outputting the first trigger signal to the first laser source 23a. The timing is determined based on time data d1 stored in advance. Further, the control unit 26 of the EUV light source apparatus calculates the timing for outputting the second trigger signal to the second laser source 24a with reference to the timing for outputting the first trigger signal to the first laser source 23a. The timing is determined based on the time data d1, Δtg, Δts, Δtd stored in advance (step S507 in FIG. 36, S606 in FIG. 37).

In practice, a switch that is a switching means of the power supply means 15 is based on the time TL1 at which the first trigger signal is output to the first laser source 23a and the first laser beam is emitted from the first laser source 23a. It is desirable to set the time Td when the SW1 is turned on and the time TL2 when the second laser beam is emitted from the second laser source.
In this embodiment, from the time Td ′ at which the main trigger signal is output to the switching means of the power supply means 15 to the time Td at which the main trigger signal is input to the switching means of the pulse power supply means 15 and the switching means is turned on. The delay time d1 is determined in advance. Then, the time Td ′ at which the main trigger signal is output to the switching means of the power supply means 15 is corrected by the delay time d1 to obtain the time Td when the switching means is turned on.

On the other hand, when the first laser source 23a is a Q-switched Nd ⁺ -YAG laser, the delay time d2 from the time TL1 ′ at which the first trigger signal is transmitted to the time when the first laser beam is emitted is ns order. It is so small that it can be ignored. Further, the delay time d3 from the time TL1 ′ at which the second trigger signal is transmitted to the time when the first laser beam 23 is irradiated is ns when the first laser source 23a is a Q-switched Nd ⁺ -YAG laser. Since it is so small that it can be ignored, it is not considered here. That is, it is considered that time TL1 ′ = TL1 and time TL2 ′ = TL2.

  That is, the timing Td ′ at which the main trigger signal is output to the switch SW1 of the power supply means 15 on the basis of the time TL1 ′ at which the first trigger signal is output to the first laser source 23a, and the second trigger signal to the second laser source 24a. By setting the time point TL2 ′ to output the switch SW1, the switch SW1 that is the switching means of the power supply means 15 with reference to the time point TL1 at which the first laser beam is emitted from the first laser source 23a is substantially turned on. The setting of the time Td at which the second laser beam is emitted from the second laser source 24a is realized.

When the time TL1 ′ at which the first trigger signal is transmitted is used as a reference, the timing Td ′ at which the main trigger signal is output to the switch SW1 of the power supply unit 15 is obtained as follows.
In this embodiment, a part of the low temperature plasma gas generated by irradiating the high temperature plasma raw material 21 with the first laser beam 23 reaches the discharge region, and the discharge region is filled with the low temperature plasma gas having a low concentration to some extent. At this point, the second laser beam 24 is focused on a predetermined position in the discharge region to start discharge.
Therefore, it is necessary to irradiate the high temperature plasma material 21 with the first laser beam 23 prior to the discharge. Here, when the high temperature plasma material 21 is irradiated with the first laser beam 23 in a state where a high voltage is applied from the power supply means between the first discharge electrode 11 and the second discharge electrode 12 which are loads. Since the first laser beam 23 passes through the vicinity of the discharge region, a discharge may occur due to the trigger of the first laser beam 23. That is, when a part of the first laser beam 23 is irradiated to the discharge electrodes 11 and 12, thermoelectrons are emitted from the irradiated discharge electrodes and the discharge is started.
Therefore, it is necessary to apply a high voltage between the first discharge electrode 11 and the second discharge electrode 12 after the first laser beam 23 is emitted from the first laser source 23a.

That is, the time Td when the switch SW1 which is the switching means of the power supply means 15 is turned on is based on the time TL1 when the first laser beam 23 is emitted from the first laser source 23a, and Td ≧ TL1. 30).
Therefore, the main trigger signal transmission timing Td ′ to the switch SW1 of the power supply means when the time point TL1 ′ for transmitting the first trigger signal is used as a reference is
Td ′ + d1 ≧ TL1 ′ + d2 (31)
It becomes. Here, since the delay time d2 is negligibly small, the main trigger signal transmission timing Td ′ is Td ′ + d1 ≧ TL1 ′ (32)
It becomes.

In this embodiment, the time Td at which the main trigger signal is transmitted and the switch SW1 is turned on is set so that the voltage is applied after the first trigger signal is transmitted and the first laser beam 23 is reliably emitted. It is assumed that the laser beam 23 is set to be somewhat delayed from the time point TL1 at which the laser beam 23 is emitted. The delay time at this time is defined as the correction time γ, and the equation (32) is transformed. Td ′ + d1 = TL1 ′ + γ (33)
It becomes. That is, when the time TL1 ′ at which the first trigger signal is transmitted is used as a reference, the timing Td ′ at which the main trigger signal is output to the switch SW1 of the power supply means is Td ′ = TL1 ′ + γ−d1 (34)
It becomes.

When the main trigger signal is transmitted and the switch SW1 is turned on, the voltage between the electrodes rises. Here, the discharge needs to be generated after time T1 (= Td + Δtd) when the voltage between the electrodes reaches a certain threshold value Vp. As described above, the threshold value Vp is a voltage value when the value of the discharge current that flows when the discharge occurs is equal to or greater than the threshold value Ip or Ip2.
That is, when discharge occurs below the threshold value Vp, the peak value of the discharge current does not reach the threshold value Ip or Ip2.
In this embodiment, the second laser beam is focused at a predetermined position in the discharge region to start discharge. Therefore, the second laser beam emission timing TL2 needs to be set after time T1 when the interelectrode voltage reaches the threshold value Vp.
That is,
TL2 ≧ Td + Δtd (35)
It becomes.
Therefore, the relationship between the timing TL2 ′ for sending the second trigger signal and the timing Td ′ for sending the main trigger signal is:
TL2 ′ ≧ Td ′ + d1 + Δtd (36)
It becomes.

On the other hand, in this embodiment, a part of the low temperature plasma gas generated by irradiating the high temperature plasma raw material 21 with the first laser beam 23 reaches the discharge region, and the discharge region is filled with the low temperature plasma gas having a low concentration to some extent. At this point, the second laser beam 24 is focused at a predetermined position in the discharge region to start discharge. As described above, the steady flow of the low-temperature plasma gas is generated from the high-temperature plasma raw material 21 by the irradiation of the first laser beam 23.
Immediately after the beginning of the steady flow of the low-temperature plasma gas in the discharge region (at the time when at least a part of the low-temperature plasma gas reaches the discharge region), the density of the low-temperature plasma gas occupying the discharge region is small, and the second laser Gas discharge plasma is generated by a laser trigger by irradiation of the beam 24.
However, as the steady flow continues, the density of the low-temperature plasma gas occupying the discharge region increases with time and reaches a predetermined value (for example, ion density of 10 ¹⁷ cm ³ to 10 ²⁰ cm ³ ). To do. In this case, even when the second laser beam 24 is used as a trigger, gas discharge is unlikely to occur, and no discharge occurs, or spark discharge due to a voltage increase occurs. That is, the start of discharge by the second laser beam 24 cannot be controlled, and the position of the discharge channel cannot be defined.

Therefore, the irradiation with the second laser beam 24 needs to be performed in a time zone in which the density of the low-temperature plasma gas occupying the discharge region is somewhat small.
With reference to the time when at least a part of the low temperature plasma gas reaches the discharge region, the time during which the density of the low temperature plasma gas in the discharge region is within a range in which gas discharge by the laser trigger can be started is Δts, and the first laser beam When the time from when the high temperature plasma raw material is irradiated to when at least a part of the low temperature plasma gas reaches the discharge region is denoted by Δtg, the emission timing TL2 of the second laser beam 24 satisfies the following equation: There is a need.
TL1 + Δtg ≦ TL2 ≦ TL1 + Δtg + Δts (37)
Therefore, the relationship between the timing TL2 ′ for sending the second trigger signal and the timing TL1 ′ for sending the first trigger signal is:
TL1 ′ + Δtg ≦ TL2 ′ ≦ TL1 ′ + Δtg + Δts (38)
It becomes.

That is, the timing TL2 ′ for sending the second trigger signal needs to be set so as to satisfy the following expression.
TL2 ′ ≧ Td ′ + d1 + Δtd (36)
TL1 ′ + Δtg ≦ TL2 ′ ≦ TL1 ′ + Δtg + Δts (38)
Here, for ease of understanding,
TL2 ′ = Td ′ + d1 + Δtd (39)
And
Expression (39) becomes as follows by substituting Expression (34).
TL2 ′ = TL1 ′ + γ + Δtd (40)

The timing TL2 ′ for sending the second trigger signal coincides with the time point after the correction time ε has elapsed (0 <ε <Δts) from the time point TL1 ′ + Δtg when at least part of the low temperature plasma gas reaches the discharge region. It will be set as follows.
That is,
TL2 ′ = TL1 ′ + γ + Δtd (40)
TL2 ′ = TL1 ′ + Δtg + ε (0 <ε <Δts) (41)
The relationship between the correction time ε and the correction time γ is
ε = γ + Δtd−Δtg (42)
It becomes.

That is, in this embodiment, the second trigger signal transmission timing TL2 ′ is set as follows.
TL2 ′ = TL1 ′ + Δtg + ε (0 <ε <Δts, ε = γ + Δtd−Δtg) (43)
By setting the transmission timing TL2 ′ of the second trigger signal as shown in Expression (43), the second laser beam reaches the voltage Vp between the electrodes, and the density of the low-temperature plasma gas in the discharge region is laser. Irradiation is performed within a time range in which gas discharge by a trigger can be started.

The control unit 26 of the EUV light source apparatus sets a time point TL1 ′ after the time point when the charger charging stabilization time tst, which is a time until the charging of each capacitor C is stabilized, and at the time point TL1 ′, the first laser A first trigger signal is transmitted to the source 23a (step S508 in FIG. 36, S605 and S607 in FIG. 37).
The control unit 26 of the EUV light source apparatus transmits the main trigger signal to the switch SW1 of the power supply unit 15 at the timing Td ′ that is set in step S607 and transmits the main trigger signal when the time TL1 ′ is used as a reference. Further, the second trigger signal is transmitted to the second laser source 24a at the timing TL2 ′ at which the second trigger signal is transmitted with the time point TL1 ′ as a reference. (Step S509 in FIG. 36, S610 and S613 in FIG. 37).
In step S608, the first laser beam 24 is irradiated onto the high temperature plasma raw material 21 almost simultaneously with the transmission of the first trigger signal (S607 and S608 in FIG. 36).

When the high temperature plasma raw material is irradiated with the first laser beam, a steady flow of the low temperature plasma gas is generated from the high temperature plasma raw material, and at least a part of the low temperature plasma gas reaches the discharge region after time Δtg (see FIG. 37). S609).
As described above, in step 609, the main trigger signal is sent to the switch SW1 of the power supply means 15 at the timing Td ′ based on the equation (34). As a result, the switch SW1 is turned on after time d1, the voltage between the first rotating electrode 11 and the second rotating electrode 12 rises, and the voltage between the electrodes reaches the threshold value Vp after time Δtd. As described above, the threshold value Vp is a voltage value when the value of the discharge current that flows when discharge occurs is equal to or greater than the threshold value Ip (S610, S611l, and S612 in FIG. 37).

On the other hand, as described above, in step S609, the second trigger signal is sent to the second laser source 24a at the timing TL2 ′ based on the equation (43).
As a result, the second laser beam 24 falls within the discharge region within a time range in which the voltage between the electrodes reaches Vp and the density of the low temperature plasma gas in the discharge region is in a state where gas discharge can be started by the laser trigger. The light is condensed at a predetermined position.
As a result, gas discharge is generated in the discharge region. As described above, in the vicinity of the focal point of the second laser beam 24, the conductivity is increased by electron emission. Therefore, the position of the discharge channel of the gas discharge is defined at the position where the laser focus is set. That is, the position of the gas discharge is defined by the second laser beam (S613 and S614 in FIG. 37).
When Δti has elapsed after the start of discharge, the magnitude of the discharge current reaches the above-described threshold value Ip (S615 in FIG. 37).

At time T1 + τ _heat (> T1 + Δti), the electron temperature of the low temperature plasma gas reaches 20 to 30 eV and becomes high temperature plasma, and EUV radiation from the high temperature plasma is started. (Step S510 in FIG. 36, S616 in FIG. 37).
Since the supply of the low temperature plasma gas to the discharge region starts before the start of the discharge and the thin discharge channel of the gas discharge is formed, the low temperature plasma gas is continuously supplied to the thin discharge channel of the gas discharge. The pinch effect or the confinement effect by the self magnetic field is repeatedly performed. Therefore, the diameter of the thin discharge channel becomes narrower, wider, or shows a pulsating behavior, but is kept relatively thin. That is, pinching of the low temperature plasma is repeatedly performed, and EUV radiation continues.

Here, in the conventional DPP method and the LAGDPP method using the pinch effect, the time for which EUV radiation is maintained is, for example, 200 ns or less, so that the time for which a discharge channel having a current value of Ip or more continues is thin discharge A discharge circuit comprising the pulse power supply means 15 and a pair of electrodes (the first electrode 11 and the second electrode 12) so that the supply of the low-temperature plasma gas to the channel continues for (200 ns + τ _heat ) or more from the discharge start time T1. By setting this, it is possible to realize a long pulse of EUV radiation as compared with the conventional DPP method and the LAGDPP method using the pinch effect.
The EUV radiation radiated from the high temperature plasma passes through the foil trap 3 and is collected by the oblique incidence type EUV collector mirror 2 disposed in the collection space, and from the EUV light extraction unit 7 provided in the chamber 1. The light is guided to an irradiation optical system of an exposure apparatus (not shown).

In the EUV generation method of the present embodiment, a long pulse of EUV radiation can be realized by the multi-pinch method and the non-pinch method, as in the EUV generation method of the first embodiment.
In addition, the thermal load applied to the electrodes can be reduced as compared with the conventional case, and the generation of debris can be suppressed. Furthermore, unlike the conventional long pulse technique, it is not necessary to flow a large current through the discharge space and to change the waveform of the discharge current in order to maintain the pinch effect. That is, highly accurate current control is not required.
In particular, in this embodiment, a part of the low-temperature plasma gas generated by irradiating the high-temperature plasma raw material with the first laser beam reaches the discharge region, and the discharge region is filled with the low-temperature plasma gas having a low concentration to some extent. At this point, the second laser beam is focused at a predetermined position in the discharge region, and gas discharge is started instead of vacuum arc discharge.

Here, in the vicinity of the focal point of the second laser beam, the conductivity is increased by electron emission. Therefore, the position of the discharge channel of the gas discharge is defined at the position where the laser focus is set. That is, the position of the gas discharge is defined by the second laser beam.
Thus, in the EUV radiation system shown in the present embodiment, since the position of the discharge channel itself of the gas discharge is defined, it is possible to achieve high accuracy of the positional stability of the discharge channel in the gas discharge.
The pulse width of the second laser beam that defines the discharge channel position of the gas discharge is desirably a short pulse to some extent. When the pulse width of the second laser beam is a short pulse, the peak power of the second laser beam is increased. That is, ion drift in the region where the second laser beam is focused is reduced, and the degree of ionization is increased. Therefore, the diameter of the discharge channel becomes smaller and the boundary of the discharge channel becomes clear. That is, the diameter of the high-temperature plasma serving as the EUV radiation source is reduced, and it is possible to provide an EUV light source device suitable as an exposure light source. For example, the pulse width is preferably 1 ns or less.

It is a timing chart (1) explaining EUV generation in the present invention. It is a timing chart (2) explaining EUV generation in the present invention. It is the schematic (1) for demonstrating the mutual relationship of an electrode, a raw material supply position, and the irradiation position of the laser beam for raw materials. It is the schematic (2) for demonstrating the mutual relationship of an electrode, a raw material supply position, and the irradiation position of the laser beam for raw materials. It is the schematic (3) for demonstrating the mutual relationship of an electrode, a raw material supply position, and the irradiation position of the laser beam for raw materials. It is a figure explaining the path | route until a high temperature plasma raw material reaches the conditions which satisfy | fill the conditions of EUV radiation in this invention. It is a figure explaining the long pulse (multi-pinch system) method of this invention. It is a figure explaining the long pulse-ized (non-pinch system) method of this invention. It is a figure which shows the cross-sectional structure (front view) of the EUV light source device of the Example of this invention. It is a figure which shows the cross-sectional structure (top view) of the EUV light source device of the Example of this invention. It is a figure which shows the condensing example of the 2nd laser beam (starting laser beam). It is a figure explaining the monitoring of the position of the raw material dripped from a raw material supply unit. It is a flowchart (1) which shows operation | movement of the Example shown in FIG. 9, FIG. It is a flowchart (2) which shows operation | movement of the Example shown in FIG. 9, FIG. It is a time chart which shows operation | movement of the Example shown in FIG. 9, FIG. It is a figure which shows the 1st modification (front view) of the EUV light source device of the Example shown in FIG. 9, FIG. It is a figure which shows the 1st modification (top view) of the EUV light source device of the Example shown in FIG. 9, FIG. It is a figure which shows the 2nd modification (front view) of the EUV light source device of the Example shown in FIG. 9, FIG. It is a figure which shows the 2nd modification (top view) of the EUV light source device of the Example shown in FIG. 9, FIG. It is a figure which shows the 2nd modification (side view) of the EUV light source device of the Example shown in FIG. 9, FIG. It is a figure which shows the 3rd modification (top view) of the EUV light source device of the Example shown in FIG. 9, FIG. It is a figure which shows the 3rd modification (side view) of the EUV light source device of the Example shown in FIG. 9, FIG. It is a conceptual diagram at the time of attaching the tubular nozzle for raw material ejection to the irradiation position of the 1st energy beam. It is a figure which shows the case where the nozzle for raw material ejection is provided in the irradiation position of the 1st energy beam, and the constriction part is provided in a part inside nozzle. It is a figure which shows the case where the raw material accommodating part which accommodates a high temperature plasma raw material, and the nozzle for high-speed injection are comprised integrally. It is a figure which shows the case where a recessed part is formed in the position where the beam of a high temperature plasma raw material is irradiated. It is a flowchart (1) which shows operation | movement of the 1st modification of the EUV light source device of the Example shown in FIG. 9, FIG. It is a flowchart (2) which shows operation | movement of the 1st modification of the EUV light source device of the Example shown in FIG. 9, FIG. It is a time chart which shows operation | movement of the 1st modification of the EUV light source device of the Example shown in FIG. 9, FIG. It is a figure explaining adjustment irradiation. It is a figure which shows the basic structural example of the EUV light source device made into the long pulse based on this invention. It is a time chart for demonstrating operation | movement of the EUV light source device shown in FIG. It is a figure explaining operation | movement of the EUV light source device of the Example of this invention made into the long pulse. It is a figure which shows the structural example of the Example of the EUV light source device made into the long pulse. It is a figure which shows the structural example of the equivalent circuit of an electric power supply means. It is a flowchart which shows the operation | movement of the Example shown in FIG. It is a time chart which shows the operation | movement of the Example shown in FIG. It is a figure explaining the path | route until a high temperature plasma raw material reaches the conditions which satisfy the conditions of EUV radiation. It is a figure which shows the relationship between the plasma electric current I, the radius r of a plasma column, and EUV radiation output in the conventional DPP type EUV generator. It is a figure which shows the relationship between the plasma electric current I at the time of making a long pulse in the conventional DPP type EUV generator, the radius r of a plasma column, and EUV radiation output. It is a figure which shows the structural example of the conventional DPP system EUV light source device for implement | achieving the long pulse-izing method of EUV radiation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chamber 1a Discharge space 1b Condensing space 1c Bulkhead 2 EUV condensing mirror 3 Foil trap 4,5 Vacuum exhaust device 6 Magnet 7 EUV extraction part 8 Pulse power generator 11, 12 Discharge electrode 11a, 12a Molten metal 11b for electric power feeding, 12b Container 11c, 12c Power introduction part 13, 14 Gas supply unit 13a Nozzle 13b Gas curtain 15 Pulse power supply means 20 Raw material supply unit 20a Raw material monitor 21 Raw material 22a, 22b Motor 22c, 22d Mechanical seal 22e, 22f Rotating shaft 23 For raw material Laser beam (first laser beam)
23a 1st laser source 23b 1st laser control part 24 Laser beam for starting (2nd laser beam)
24a 2nd laser source 24b 2nd laser control part 25 Raw material collection | recovery means 26 Control part 27 Exposure machine (control part)
30 Raw material supply unit 31 Linear raw material 40 Raw material supply unit 40a Liquid raw material supply means 40b Raw material supply disk 40c Motor 50 Raw material supply unit 50a Liquid raw material bath 50b Capillary 50c Heater 50d Liquid raw material bus control unit 50e Heater power supply 60a Tubular nozzle 60b Nozzle for high speed injection 62 Narrow part 63 Pressure rise part 64 Heater

Claims (18)

A container and raw material supply means for supplying a liquid or solid raw material for emitting extreme ultraviolet light in the container;
A first energy beam irradiating means for irradiating the raw material with the first energy beam to vaporize the raw material; and a predetermined energy source for heating and exciting the vaporized raw material in the vessel by discharge to generate high-temperature plasma. A pair of electrodes separated by a distance; and pulse power supply means for supplying pulse power to the electrodes;
Condensing optical means for condensing the extreme ultraviolet light emitted from the high-temperature plasma generated in the discharge region of the discharge by the pair of electrodes, and an extreme ultraviolet light extraction unit for extracting the collected extreme ultraviolet light In an extreme ultraviolet light source device having
The extreme ultraviolet light source device further starts a discharge in the discharge region by irradiating a second energy beam between electrodes to which power is applied, and discharges a discharge path to a predetermined position in the discharge region. A second energy beam irradiation means for defining
The first energy beam irradiating means irradiates a first energy beam to a material supplied into a space excluding the discharge region, where the vaporized material can reach the discharge region. An extreme ultraviolet light source device. A container and raw material supply means for supplying a liquid or solid raw material for emitting extreme ultraviolet light in the container;
A first energy beam irradiating means for irradiating the raw material with the first energy beam to vaporize the raw material; and a predetermined energy source for heating and exciting the vaporized raw material in the container by discharge to generate high-temperature plasma. A pair of electrodes separated by a distance; and a pulse power supply means for supplying a pulse power of 1 μs or more to the electrodes;
Condensing optical means for condensing the extreme ultraviolet light emitted from the high-temperature plasma generated in the discharge region of the discharge by the pair of electrodes, and an extreme ultraviolet light extraction unit for extracting the collected extreme ultraviolet light In an extreme ultraviolet light source device having
The extreme ultraviolet light source device further starts a discharge in the discharge region by irradiating a second energy beam between electrodes to which power is applied, and discharges a discharge path to a predetermined position in the discharge region. A second energy beam irradiation means for defining
The first energy beam irradiating means irradiates a source material disposed in a space outside the discharge path, in which the vaporized source material can reach the discharge path, with the first energy beam, and the electrode An extreme ultraviolet light source device characterized in that, after a discharge path is defined in between, a source gas having an ion density substantially equal to the ion density under extreme ultraviolet light emission conditions is supplied to the discharge path. The first energy beam irradiating means and the second energy beam irradiating means are configured to detect a discharge generated in the discharge region at a timing when at least a part of the vaporized material having a predetermined spatial density distribution reaches the discharge region. The extreme ultraviolet light source device according to claim 1, wherein each operation timing is set so that the discharge current is equal to or greater than a predetermined threshold value. 4. The extreme ultraviolet light source device according to claim 1, wherein the raw material supply by the raw material supply means is performed by dropping the raw material into a droplet shape in the direction of gravity. The extreme ultraviolet ray according to claim 1, 2, or 3, wherein the raw material supply by the raw material supply means is performed by continuously moving the linear raw material using the raw material as a linear raw material. Light source device. The raw material supply means includes a raw material supply disk,
The raw material supply by the raw material supply means is performed by supplying the raw material as a liquid raw material, supplying the liquid raw material to the raw material supply disk, rotating the raw material supply disk supplied with the liquid raw material, and supplying the liquid raw material of the raw material supply disk. The extreme ultraviolet light source device according to claim 1, wherein the supply unit is moved to an irradiation position of the energy beam. The raw material supply means includes a capillary,
The raw material supply by the raw material supply means is performed by using the raw material as a liquid raw material and supplying the liquid raw material to an irradiation position of an energy beam through the capillary. 4. The extreme ultraviolet light source device according to 3. A tubular nozzle is provided at the energy beam irradiation position of the raw material,
4. The extreme ultraviolet light source device according to claim 1, wherein at least a part of the raw material vaporized by irradiation with an energy beam is ejected from the tubular nozzle. 9. The extreme ultraviolet light source device according to claim 8, wherein a narrowed portion is provided in a part of the inside of the tubular nozzle. 7. A magnetic field applying means for applying a magnetic field substantially parallel to a discharge direction generated between the pair of electrodes to the discharge region is further provided. , 7, 8 or the extreme ultraviolet light source device according to claim 9. The pair of electrodes are disk-shaped electrodes, and are rotationally driven so as to change a discharge generation position on the electrode surface. , 9 or the extreme ultraviolet light source device according to claim 10. The extreme ultraviolet light source device according to claim 11, wherein the pair of electrodes having a disc shape are arranged such that edge portions of peripheral edges of both electrodes face each other with a predetermined distance therebetween. . 13. The extreme ultraviolet light source device according to claim 1, wherein the energy beam is a laser beam. A liquid or solid raw material for radiating extreme ultraviolet light supplied into a container including a pair of electrodes therein is irradiated with a first energy beam to vaporize the vaporized raw material by the pair of electrodes. In the extreme ultraviolet light generation method of generating extreme ultraviolet light by generating high temperature plasma by heat excitation by discharge,
The first energy beam is applied to a material supplied in a space excluding the discharge region, in which the vaporized material can reach the discharge region,
An extreme in which discharge is started in the discharge region of the discharge by the pair of electrodes by the second energy beam irradiated to the discharge region, and a discharge path is defined at a predetermined position in the discharge region. Ultraviolet light generation method. A liquid or solid raw material for radiating extreme ultraviolet light supplied into a container including a pair of electrodes therein is irradiated with a first energy beam to vaporize the vaporized raw material by the pair of electrodes. In the extreme ultraviolet light generation method of generating extreme ultraviolet light by generating high temperature plasma by heat excitation by discharge,
The first energy beam is applied to a material supplied in a space excluding the discharge region, in which the vaporized material can reach the discharge region,
A discharge is started in the discharge region of the discharge by the pair of electrodes by the second energy beam irradiated to the discharge region, and a discharge path is defined at a predetermined position of the discharge region,
After the discharge path is defined between the electrodes, the first energy beam supplies the discharge path with a source gas whose ion density is substantially equal to the ion density in the extreme ultraviolet radiation condition.
An extreme ultraviolet light generation method, characterized in that the raw material gas is heated to a temperature satisfying the extreme ultraviolet light radiation condition by discharge to continuously generate extreme ultraviolet light of 200 ns or more. The first energy beam and the first energy beam so that the discharge current of the discharge generated in the discharge region is greater than or equal to a predetermined threshold at the timing when at least a part of the vaporized material having a spatial density distribution of the predetermined distribution reaches the discharge region. 16. The method for generating extreme ultraviolet light according to claim 14, wherein the irradiation timing of the second energy beam is set. The time data of the discharge start timing and the time data of the timing when the discharge current reaches a predetermined threshold value are acquired, and the irradiation timing of the first energy beam and the second energy beam is corrected based on both time data. The method for generating extreme ultraviolet light according to claim 16. 15. The first energy beam is irradiated to the raw material at least once prior to the irradiation of the first energy beam and the second energy beam whose irradiation timing is set as described above. The extreme ultraviolet light generation method according to claim 15, 16 or 17.

Images