JP4893730B2 - Extreme ultraviolet light source device - Google Patents

Abstract

The invention relates to an extreme ultraviolet light source device, comprising a pair of discharge electrodes (2a, 2b, 52a, 52b) arranged spaced apart from each other; a pulsed power supply means (3, 53) supplying pulsed power to said discharge electrodes (2a, 2b); a raw material supply means (7) adapted for supplying raw material (M) for generating extreme ultraviolet radiation onto said discharge electrodes (2a, 2b, 52a, 52b); an energy beam emitting means (10, 60) adapted for radiating an energy beam (LB2) to the raw material (M) on said discharge electrodes (2a, 2b, 52a, 52b) to gasify said raw material (M); a means (11, 61, 85, 95, 105) for forming a depression (MA) in the raw material (M) supplied onto said discharge electrodes (2a, 2b, 52a, 52b); and a controller (6, 56). Said controller (6, 56) is adapted to control the depression forming means (11, 61, 85, 95, 105) such that it forms a depression (MA) in the raw material (M) supplied onto the discharge electrodes (2a, 2b, 52a, 52b) before the voltage between the electrodes (2a, 2b, 52a, 52b) increases by means of the supply of pulsed power to the discharge electrodes (2a, 2b, 52a, 52b) by said pulsed power supply means (3, 53), and before the energy beam (LB2) is radiated to the raw material (M) on the electrodes (2a, 2b, 52a, 52b) by said energy beam emitting means (10, 60). The invention also relates to a process for generating EUV radiation.

Description

  The present invention relates to an extreme ultraviolet light source device (hereinafter also simply referred to as EUV light source device) that emits extreme ultraviolet light (hereinafter also simply referred to as EUV light). In particular, the present invention relates to an extreme ultraviolet light source device that is expected as an exposure light source for next-generation semiconductor integrated circuits.

As miniaturization and higher integration of the semiconductor integrated image path progress, an exposure apparatus for manufacturing thereof is required to improve resolution. In order to improve the resolution, it is common to use an exposure light source that emits light of a short wavelength. An excimer laser device is used as an exposure light source that emits light having a short wavelength, but an extreme ultraviolet light source device that emits extreme ultraviolet light having a wavelength of 13.5 nm as an alternative light source for next-generation exposure. Development is underway.
As one method for generating extreme ultraviolet light, there is a method in which a high-density and high-temperature plasma is generated by heating and exciting a discharge gas including an extreme ultraviolet light radiation source, and the extreme ultraviolet light emitted from the plasma is taken out.
Extreme ultraviolet light source devices that employ such a method are roughly classified into an LPP (Laser Produced Plasma) method and a DPP (Discharge Produced Plasma) method, depending on the method of generating high-density and high-temperature plasma.

The LPP type extreme ultraviolet light source device emits laser light to a target made of raw materials including extreme ultraviolet light radiation, generates high-density high-temperature plasma by laser ablation, and emits extreme ultraviolet light emitted therefrom. It is what you use.
The DPP type extreme ultraviolet light source device generates a high-density high-temperature plasma by discharge by applying a high voltage between electrodes supplied with a discharge gas including an extreme ultraviolet light source, and is emitted from there. It uses ultraviolet light. Such a DPP type extreme ultraviolet light source device is advantageous in that the light source device can be made smaller and the power consumption of the light source system is smaller than that of the LPP type extreme ultraviolet light source device. Therefore, practical application is expected.

Xe (xenon) ions having about 10 valences are known as materials for generating the above-described high-density high-temperature plasma, but Li (lithium) ions, Sn ( Tin) ions are attracting attention.
For example, Sn is large because the extreme ultraviolet light conversion efficiency given by the ratio between the electric input necessary for generating high-density and high-temperature plasma and the radiation intensity of extreme ultraviolet light having a wavelength of 13.5 nm is several times larger than Xe. It is expected as a radiation source to obtain output extreme ultraviolet light. For example, as shown in Patent Document 1, development of an extreme ultraviolet light source device using, for example, SnH ₄ (stannane) gas as an extreme ultraviolet light radiation source has been advanced.
In recent years, in the above DPP method, solid or liquid Sn or Li supplied to the electrode surface where discharge occurs is vaporized by irradiating with an energy beam such as a laser beam, and then high temperature plasma is generated by discharge. A generation method is disclosed in Non-Patent Document 1.

FIG. 13 is a diagram for simply explaining the EUV light source device shown in Non-Patent Document 1. In FIG.
The EUV light source device includes a discharge unit 1a that accommodates a pair of disc-shaped discharge electrodes 2a and 2b, an EUV condensing unit 1b that accommodates a foil trap 4 and a condensing reflector 5, and a gas exhaust unit 1c. The chamber 1 is provided.
A pair of disc-shaped discharge electrodes 2a and 2b are arranged in the discharge part 1a.
The pair of disk-like electrodes 2a and 2b are arranged vertically on the paper surface of the drawing with the insulating material 2c interposed therebetween.
A rotating shaft 2e of a motor 2d is attached to the discharge electrode 2b located below the paper surface. The discharge electrodes 2a and 2b are connected to the pulse power supply unit 3 through the sliders 2g and 2b.
A groove 21b is provided in the periphery of the discharge electrode 2b, and a solid material M (Li or Sn) for generating high-temperature plasma is disposed in the groove. The raw material M is supplied from the raw material supply means 7 to the groove portion 21b.

In the EUV light source device described above, the incident window 1e is supplied from the energy beam irradiator 10 including the energy beam source 11 and the energy beam source control unit 12 to the high temperature plasma raw material disposed in the groove 21b of the discharge electrode 2b. An energy beam such as a laser beam is irradiated through the gas, and a solid material is vaporized between the discharge electrodes 2a and 2b.
In this state, pulse power is supplied from the pulse power supply unit 3 between the discharge electrodes 2a and 2b, discharge occurs between the edge portion of the discharge electrode 2a and the edge portion of the discharge electrode 2b, and EUV light is emitted. Is done.
The emitted EUV light enters the EUV collector 1b through the foil trap 4, is collected by the condenser reflector 5 at the condensing point P of the EUV light source device, and is emitted from the EUV light extraction unit 1d.
JP 2004-279246 A “Current Status and Future Prospects of Research on EUV Light Sources for Lithography” J. Plasma Fusion Res. March 2003, Vol. 79. No. 3, P219-260

The above-mentioned EUV light source device has a problem in practical use that it is impossible to obtain an output of extreme ultraviolet light sufficient to form a pattern with a desired line width on a semiconductor substrate. ing.
The reason why the output of extreme ultraviolet light cannot be obtained sufficiently is not clear, but is expected as follows, for example.
In the conventional EUV light source device, the raw material vaporized by irradiation with the energy beam is freely expanded. When the raw material expands freely, the density of the gas generated by the vaporization of the raw material is low and the spatial distribution is wide, so that the plasma generated between the pair of electrodes tends to increase.
If the spatial spread of the plasma generated between the electrodes is large, the current density flowing through the plasma is reduced, preventing the plasma from reaching a high temperature state, ionization is inhibited, and the plasma ion density is also reduced. . Furthermore, the self-absorption by the plasma is increased by increasing the spatial spread.
As described above, when the vaporized raw material freely expands and a plasma having a large spatial spread is generated, the output of the extreme ultraviolet light emitted from the plasma can be a factor.

As described above, the conventional EUV light source device has a problem that a sufficient extreme ultraviolet light output cannot be obtained.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an EUV light source device that can ensure a practically sufficient output of extreme ultraviolet light.

Extreme ultraviolet radiation that irradiates the raw material on the electrode with energy beam, vaporizes the raw material, generates high-density and high-temperature plasma by discharge by applying high voltage between the electrodes, and emits extreme ultraviolet light emitted from it In the light source device, in the present invention, before the material is irradiated with the energy beam and vaporized, a recess is formed in the energy beam irradiation surface of the material on the electrode.
By irradiating the recess with the energy beam, when the raw material is vaporized, the free expansion of the raw material is regulated by the inner wall surface of the concave and the directivity is increased. Therefore, the density of the gas generated by vaporizing the raw material becomes high and the spatial distribution is narrow, so that the spatial spread of the plasma generated between the pair of discharge electrodes is smaller than that of the conventional EUV light source device. Can be.
Thus, by reducing the spatial spread of the plasma, the density of the current flowing through the plasma can be increased, the plasma can be easily brought to a high temperature state, and the plasma ion density is increased. At the same time, by suppressing the spread of the plasma, self-absorption by the plasma is reduced. For this reason, the output of EUV light can be made high compared with the conventional EUV light source device.
The recess is formed by, for example, irradiating the material on the electrode with an energy beam independently of the energy beam before irradiating the energy beam for vaporizing the material, or using a rod-shaped member as the material. It can be formed by contacting.
Based on the above, in the present invention, the above-described problems are solved as follows.
(1) A pair of discharge electrodes arranged apart from each other, pulse power supply means for supplying pulse power to the discharge electrodes, and material supply for supplying raw materials for emitting extreme ultraviolet light onto the discharge electrodes An extreme ultraviolet ray comprising means, an energy beam irradiation means for irradiating the raw material on the electrode with an energy beam to vaporize the raw material, a means for forming a recess in the raw material supplied on the discharge electrode, and a controller. In the light source device, the raw material supply means includes a container filled with the raw material melt, and the discharge electrodes pass through the raw material melt filled in the container while rotating, and the control Before the voltage between the electrodes rises by supplying the pulse power to the discharge electrode by the pulse power supply means, and the energy on the material on the electrode by the energy beam irradiation means. Before irradiating the Bimu, by means of forming the recess, provided on the discharge electrode raw material to form a recess, when the energy beam is irradiated material is vaporized, the inner wall surface of the recess By restricting the free expansion of the raw material, directivity is imparted.
(2) In the above (1), the energy beam irradiating means for vaporizing the raw material also serves as the energy beam irradiating means for forming the recess, and the recess is formed on the surface of the raw material by irradiating the energy beam. Form.

In the present invention, the following effects can be obtained.
(1) Before the voltage between the electrodes rises and before the material on the electrode is irradiated with the energy beam by the energy beam irradiation means to vaporize the material, a recess is formed in the material on the electrode. On the other hand, since the energy beam is irradiated, the spatial spread of the plasma generated between the pair of discharge electrodes can be made smaller than that of the conventional EUV light source device. For this reason, it is expected that the output of EUV light can be made higher than that of a conventional EUV light source device.
(2) Since a recess is formed in the raw material on the electrode and the raw material is vaporized by irradiating the recess with the energy beam, the raw material is disposed outside the electrode, and the raw material is irradiated with the energy beam. Compared with the case where the vaporized raw material reaches the electrode, the spread of the vaporized raw material can be reduced. For this reason, compared with the case where a raw material is arrange | positioned out of an electrode, the output of EUV light can be made high.
(3) The apparatus configuration can be simplified by combining the energy beam irradiation means for vaporizing the raw material and the energy beam irradiation means for forming the recess.

FIG. 1 is a diagram showing a schematic configuration of an EUV light source apparatus which is a premise of the present invention.
The EUV light source device is partitioned into a discharge unit 1a that houses a discharge electrode and an EUV light collection unit 1b that houses a foil trap 4 and a condenser reflector 5, and emits EUV light toward an exposure device. A chamber 1 having an EUV extraction part 1d is provided.
The chamber 1 is provided with a gas exhaust unit 1c for exhausting the discharge unit 1a and the EUV condensing unit 1b to make the chamber 1 in a vacuum state.
The pair of disc-shaped discharge electrodes 2a and 2b are arranged to face each other with the insulating member 2c interposed therebetween, and the centers of the electrodes are arranged coaxially.
A rotating shaft 2e of a motor 2d is attached to the discharge electrode 2b below the vertical direction. In the rotating shaft 2e, the center of the discharge electrode 2a and the center of the discharge electrode 2b are located on the same axis as the rotating shaft 2e. The rotating shaft 2e is introduced into the chamber 1 through a mechanical seal 2f.
The mechanical seal 2f allows rotation of the rotating shaft 2e while maintaining a reduced pressure atmosphere in the chamber 1.

Sliders 2g and 2h made of, for example, a carbon brush or the like are provided below the discharge electrode 2b.
The slider 2g is electrically connected to the discharge electrode 2a through a through hole provided in the discharge electrode 2b. The slider 2h is electrically connected to the discharge electrode 2b.
The pulse power supply unit 3 supplies pulse power to the discharge electrodes 2a and 2b via the sliders 2g and 2h, respectively.
The peripheral portions of the disc-shaped discharge electrodes 2a and 2b are formed in an edge shape.
In the discharge electrode 2b, an annular groove 21b is formed in the vicinity of the end of a plane orthogonal to the rotation axis 2e, and in the vicinity of the discharge electrode 2b, a raw material supply means 7 for supplying a raw material M for generating high temperature plasma. Is provided.
A liquid or solid raw material M for generating high temperature plasma supplied from the raw material supply means 7 is arranged inside the groove 21b. The raw material M is, for example, tin (Sn) or lithium (Li).
The diameter of the discharge electrode 2a in the upper vertical direction is smaller than the diameter of the discharge electrode 2b in the lower vertical direction. Thereby, it is easy to irradiate the raw material M from above with the energy beam.

The pulse power supply unit 3 supplies power between the discharge electrodes 2a and 2b. As a result, discharge occurs between the edge portions of both electrodes.
Since the discharge electrodes 2a and 2b are made of a refractory metal such as tungsten, molybdenum, or tantalum, the peripheral portions of the discharge electrodes 2a and 2b are not melted even when the temperature becomes high due to discharge. The insulating member 2c is made of silicon nitride, aluminum nitride, diamond or the like, and insulation between the discharge electrodes 2a and 2b is ensured.
The chamber 1 is provided with an energy beam radiator 10 for irradiating the raw material M with an energy beam such as a laser beam to vaporize the raw material M.
The energy beam irradiator 10 includes an energy beam source 101 that irradiates the material M with the energy beam LB2, and an energy beam source controller 102 that controls the operation of the energy beam source 101. The energy beam LB2 irradiated from the energy beam source 101 is condensed by the condenser lens 103, passes through the window portion 1e, and is irradiated to the raw material M.

In addition, the chamber 1 is provided with a recess-forming energy one-beam irradiator 11 that irradiates the energy beam LB1 independently of the energy beam irradiator 10 in order to form a recess in the surface of the raw material M.
The recess forming energy beam irradiator 11 includes an energy beam source 111 that irradiates the material M with the energy beam LB1 and an energy beam source controller 112 that controls the operation of the energy beam source 111. The energy beam LB1 irradiated from the energy beam source 111 is condensed by the condenser lens 113, passes through the window 1f, and is irradiated onto the raw material M.
The irradiation of the energy beam LB1 by the recess forming energy beam irradiator 11 is performed prior to the irradiation of the energy beam LB2 by the energy beam radiator 10, and the energy beam LB2 is applied to the recess formed by the energy beam LB1. Irradiated. Since the discharge electrodes 2a and 2b are rotated in the direction of the arrow in the figure, the irradiation position of the energy beam LB1 is in front of the irradiation position of the energy beam LB2 by the energy beam radiator 10, and the formed recess is It is transferred to the irradiation position of the energy beam LB2 by the rotation of the discharge electrodes 2a and 2b.
Since the rotation speed of the discharge electrodes 2a and 2b is slow with respect to the time from the irradiation of the energy beam LB1 to the irradiation of the energy beam LB2, actually, the irradiation position of the energy beam LB1 and the irradiation position of the energy beam LB2 are It does n’t change much. In FIG. 1, the irradiation position of the energy beam LB1 and the irradiation position of the energy beam LB2 are exaggerated and separated.

  As the energy beam sources 101 and 111, for example, a carbon dioxide laser source, a solid-state laser source such as a YAG laser, or an excimer laser source such as an ArF laser or a KrF laser can be used. Further, as the energy beam sources 101 and 111, ion beams and electron beams can be used instead of laser sources. In the following description, it is assumed that the energy beam is a laser beam.

The pulse power supply unit 3 as pulse power supply means applies pulse power having a short pulse width between the discharge electrode 2a and the discharge electrode 2b via a magnetic pulse compression circuit unit including a capacitor and a magnetic switch.
FIG. 1 shows a configuration example of a pulse power generator. The pulse power generator shown in FIG. 1 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 configuration and operation of the circuit will be described below with reference to FIG. First, the charging voltage of the charger CH is adjusted to a predetermined value, 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 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 through 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 to be charged in 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.
Thereafter, when the time integral 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 between the discharge electrode 2a and the discharge electrode 2b. A high voltage pulse is applied.
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 discharge with a short pulse between the discharge electrode 2a and the discharge electrode 2b, and the input power to the plasma also increases.

The foil trap 4 is fixed to the EUV collector 1b of the chamber 1 by a partition wall 4a. The foil trap 4 suppresses scattering of debris generated mainly from the material constituting the discharge electrode and the raw material M for generating high-temperature plasma toward the condensing reflecting mirror 5.
The foil trap 4 is formed with a plurality of narrow spaces partitioned by a plurality of thin plates extending radially.
The condensing reflecting mirror 5 arranged in the EUV condensing part 1b has a light reflecting surface 5a for reflecting EUV light having a wavelength of 13.5 mm radiated from high temperature plasma.
The condensing reflecting mirror 5 is composed of a plurality of light reflecting surfaces 5a arranged in a nested manner without contacting each other.
Each light reflecting surface 5a is formed by densely coating a metal such as Ru (ruthenium), Mo (molybdenum), Rh (rhodium) on the reflecting surface of a base material having a smooth surface made of Ni (nickel) or the like, It is formed so as to satisfactorily reflect extreme ultraviolet light having an incident angle of 0 to 25 °.
Each light reflecting surface 5a is configured to collect EUV light radiated from the high temperature plasma at a condensing point P.

The control unit 6 relates to the irradiation timing of the laser beam emitted from the energy beam irradiators 10 and 11 and the supply timing of the pulse power from the pulse power supply unit 3 to the discharge electrodes 2a and 2b as follows. The beam irradiators 10 and 11 and the pulse power supply unit 3 are controlled.
That is, before the voltage between the electrodes rises by supplying pulse power to the discharge electrodes 2a and 2b, and before the energy beam is irradiated onto the material on the electrode by the energy beam irradiator 10, energy beam irradiation is performed. A laser beam is irradiated from the machine 11 to form a recess in the raw material supplied on the discharge electrode.

FIG. 2 is a partial explanatory view of the extreme ultraviolet light source device of FIG. FIG. 3 is a time chart showing the irradiation timing of the energy beam (laser beam), the supply timing of pulse power, and the generation of EUV light, (a) is the irradiation timing of the first laser beam LB1, (b). Is the timing at which the switch SW is turned on, (c) is the voltage of the capacitor C2, (d) is the irradiation timing of the second laser beam LB2, (e) is the discharge current flowing between the electrodes, (f) is the EUV light Radiation timing.
The extreme ultraviolet light source device of FIG. 1 is characterized in that a recess is formed on the surface of the raw material by irradiation with a laser beam. Specifically, the following steps 1 to 3 are executed by the control unit 6.
<Procedure 1>
At time T1, the control unit 6 sends a signal to the energy beam source control unit 112, and as shown in FIG. 2A, the first laser beam LB1 is supplied from the energy beam source 111 onto the discharge electrode 2b. Irradiate the surface of the raw material M (FIG. 3A). As shown in FIG. 2B, the surface of the raw material M is irradiated with the first laser beam to form a recess MA.

<Procedure 2>
As shown in FIG. 3, the control unit 6 turns on the switch SW (IGBT) at time T2 (FIG. 3B). Time T2 is after a predetermined time has elapsed from time T1.
When the switch SW is turned on, the voltage between the discharge electrodes 2a and 2b rises after a delay time based on the magnetic switches SR1 to SR3, and after a time Δtd, the voltage of the capacitor C2 reaches the threshold value Vp (FIG. 3C). ).
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. The threshold value Ip is a lower limit value of a discharge current value required for producing a high temperature plasma that emits a desired EUV light intensity.

<Procedure 3>
Assuming that the time from when the switch SW is turned ON to when the voltage of the capacitor C2 rises is Δtd, the control unit 6 performs time T3 after the time when the voltage of the capacitor C2 reaches the threshold value Vp as shown in FIG. At (T3 ≧ T2 + Δtd), a signal is sent to the energy beam source control unit 102 to cause the energy beam source 101 to irradiate the second laser beam. 2C, the second laser beam LB2 is irradiated to the recess MA formed on the surface of the raw material M in the procedure 1, and the raw material M is vaporized (FIG. 3D). ).
The raw material vaporized in the procedure 3 spreads in a three-dimensional direction centering on the normal direction of the surface of the raw material M, and reaches the discharge electrode 2a facing the discharge electrode 2b provided with the raw material M. Assuming that the time from the irradiation of the second laser beam to the time when the vaporized raw material reaches the discharge electrode 2a is Δti, at the time T4 (T3 + Δti), between the edge portions of the peripheral edges of the discharge electrodes 2a and 2b. The discharge starts. Thereby, plasma is generated between the discharge electrodes 2a and 2b, and the plasma is heated by the discharge current flowing between the discharge electrodes 2a and 2b (FIG. 3E).
When the plasma is heated by the pulsed discharge current to a high temperature, EUV light having a wavelength of 13.5 nm is emitted from the high temperature plasma (FIG. 3 (f)).
In the above, after the switch SW (IGBT) is turned ON in the procedure 2, the second laser beam is emitted from the energy beam source 101 in the procedure 3. For example, the delay of the pulse power supply unit 3 is small. Therefore, when Δtd is small and the distance between the electrodes is large, the time Δti until the vaporized material reaches the discharge electrode 2a is large, and when Δtd <Δti, the order of the above steps 2 and 3 is changed. It may be reversed.

The EUV light source device shown in FIG. 1 can improve the intensity of EUV light because the source is vaporized by irradiating the second laser beam to the recess formed on the surface of the source M.
Moreover, the raw material supplied onto the discharge electrode by the means for forming the recess before the voltage between the electrodes rises and before the energy beam irradiation means irradiates the raw material on the electrode with the energy beam. Therefore, there is no possibility that the discharge starts between the discharge electrodes 2a and 2b due to the material vaporized when the recess is formed.
In other words, after the pulse power is supplied to the discharge electrodes 2a and 2b, when the raw material is irradiated with the first laser beam in order to form the recess, the discharge electrode 2a and the discharge electrode 2a are formed by the raw material M vaporized when the recess is formed. Discharge may start between 2b, and discharge cannot be started at an appropriate timing. In order not to cause such a problem, it is important to execute as described above.

In the EUV light source device shown in FIGS. 1 and 2 , an energy beam irradiator for forming a recess MA on the surface of the raw material M, and an energy beam in the concave MA formed in the raw material M are used. And an energy beam irradiator for vaporizing the raw material for vaporizing the raw material M.
However, the use of two or more energy beam irradiation machine necessarily be independent is not essential, for example, may perform step 1 and step 3 above using only the energy beam irradiation device 10.
FIG. 4 shows a configuration example of an extreme ultraviolet light source device including one energy beam irradiator.
4 has the same configuration as that shown in FIG. 1 except that only the energy beam irradiator 10 is provided and the energy beam irradiator 11 is omitted. The operation is the same as that shown in FIG.
In FIG. 4, in the procedure 1, the surface of the raw material M is irradiated with the first laser beam from the energy beam irradiator 10 to form a recess, and the procedure 2 is performed as described above, followed by the procedure 3. Thus, at the time T3 after the time when the voltage of the capacitor C2 reaches the threshold value Vp, the source M is vaporized by irradiating the second laser beam from the energy beam source 10 to the recess formed on the surface of the material M. .
The vaporized raw material reaches the discharge electrode 2a opposite to the discharge electrode 2b, discharge is started between the peripheral edge portions of the discharge electrodes 2a and 2b, plasma is generated, and EUV light is generated.

FIG. 5 is a top view showing a schematic configuration of the EUV light source apparatus according to the embodiment of the present invention, and FIG. 6 is a front view showing a schematic configuration of the EUV light source apparatus according to the embodiment of the present invention.
The EUV light source apparatus shown in the figure has a chamber 51 that is a discharge vessel. The chamber 51 is partitioned by a partition wall 54a into a discharge space 51a in which a pair of discharge electrodes 52a and 52b is accommodated, and an EUV condensing space 51b in which the condensing reflector 55 is accommodated, and EUV light is directed toward the exposure apparatus. EUV extraction part 51d for emitting. The chamber 51 is provided with a gas exhaust unit 51c for evacuating the chamber 51.
In the discharge space 51a, a pair of discharge electrodes 52a and 52b that rotate independently from each other are disposed apart from each other. The discharge electrodes 52a and 52b are heating excitation means for heating and exciting the raw material M.
In the EUV condensing space 51b, a condensing reflecting mirror 55 for condensing EUV light emitted from high-temperature plasma formed between a pair of discharge electrodes is disposed.

The discharge electrodes 52a and 52b are made of, for example, a refractory metal such as molybdenum, tungsten, or tantalum, and are disposed to face each other while being separated from each other. One of the discharge electrodes 52a and 52b is a ground side electrode, and the other is a high voltage side electrode.
The discharge electrodes 52a and 52b are preferably arranged such that virtual planes including the surfaces of the discharge electrodes intersect each other. If the discharge electrodes 52a and 52b are arranged in this way, a large amount of discharge is generated in the portion (discharge region) where the distance between the edge portions of the peripheral portions of the electrodes 52a and 52b is the shortest, so that the discharge position is stabilized.
In addition, it is preferable that the discharge electrodes 52a and 52b are disposed so as to gradually approach the condenser reflector 55. When arranged in this manner, the distance between the discharge region between the pair of discharge electrodes 52a and 52b and the condensing reflection mirror 55 is reduced, so that extreme ultraviolet light can be efficiently collected.

The discharge electrodes 52 a and 52 b of the EUV light source device shown in FIGS. 5 and 6 have a disk shape and are controlled by the control unit 56 to rotate independently of each other. By rotating the discharge electrodes 52a and 52b at the time of discharge, the position of the high-temperature plasma generated between both electrodes changes for each pulse, so that the thermal load received by the discharge electrodes 52a and 52b is reduced. Therefore, the service life of the discharge electrodes 52a and 52b can be extended.
As for discharge electrode 52a, 52b, the rotating shaft 52e of the motor 52d is attached to each approximate center part. Each rotating shaft 52e is introduced into the chamber 51 through a mechanical seal 52f. The mechanical seal 52f allows rotation of the rotating shaft 52e while maintaining a reduced pressure atmosphere in the chamber 51.

The foil trap 54 and the condenser reflector 55 shown in FIGS. 5 and 6 have the same configurations as the foil trap 4 and the condenser reflector 5 of the EUV light source device shown in FIG. 1 , respectively. The foil trap 54 is fixed to the EUV collector 51b of the chamber 51 by a partition wall 54a. The condensing reflecting mirror 55 is composed of a plurality of light reflecting surfaces 55a arranged in a nested manner without contacting each other.
The EUV light source device shown in FIGS. 5 and 6 includes containers 57a and 57b filled with a melt of the raw material M. The raw material M is composed of a melt of a conductive material, for example, a melt of tin. Discharge electrodes 52a and 52b are arranged so as to pass through the melt of raw material M filled in containers 57a and 57b, respectively. That is, the discharge electrodes 52a and 52b rotate during discharge and are immersed in the raw material M filled in the containers 57a and 57b, respectively, so that the raw material M is applied to the surfaces thereof. In addition, although illustration is abbreviate | omitted, the containers 57a and 57b are provided with the temperature control means for maintaining the raw material M in the molten state.

  Further, the containers 57 a and 57 b are electrically connected to the pulse power supply unit 53. The containers 57a and 57b are electrically connected to the pulse power supply unit 53 through the power introduction units 58a and 58b. The power introduction units 58a and 58b have insulation and maintain a reduced pressure atmosphere in the chamber 51. The pulse power supply unit 53 applies pulse power to the discharge electrodes 52a and 52b through the melt of the raw material M filled in the containers 57a and 57b, respectively.

The EUV light source apparatus of FIGS. 5 and 6 includes an energy beam irradiator 60 that irradiates a laser beam to a raw material M that generates high-temperature plasma and a predetermined point in a discharge region. The energy beam irradiator 60 includes an energy beam source 601 and an energy beam source control unit 602 that controls the operation of the energy beam source 601.
The laser beam emitted from the energy beam source 601 is condensed by the condenser lens 603, passes through the window portion 51e, and is irradiated to the peripheral portion of the discharge electrode 52a. The raw material M is vaporized between the discharge electrodes 52a and 52b by the laser beam.
The chamber 51 is provided with a recess forming energy beam irradiator 61 that irradiates an energy beam independently of the energy beam irradiator 60 in order to form a recess in the surface of the raw material M.
The recess forming energy beam irradiator 61 includes an energy beam source 611 that irradiates the material M with an energy beam, and an energy beam source controller 612 that controls the operation of the energy beam source 611. The laser beam emitted from the energy beam source 611 is condensed by the condenser lens 613, passes through the window 51 f, and is irradiated onto the raw material M.

The energy beam sources 601 and 611 that emit laser beams are, for example, carbon dioxide laser sources, solid laser sources such as YAG lasers, and excimer laser sources such as ArF lasers and KrF lasers. In addition, as the energy beam sources 601 and 611, an ion beam or an electron beam can be used instead of a laser source.
The pulse power supply unit 53 has a two-stage magnetic pulse compression circuit using two magnetic switches SR2 and SR3 made of a saturable reactor, as in the extreme ultraviolet light source device of FIG. 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 control unit 56 relates to the laser beam irradiation timing from the energy beam irradiators 60 and 61 and the pulse power supply timing from the pulse power supply unit 53 to the discharge electrodes 52a and 52b. Are executed in the following order, the energy beam irradiators 60 and 61 and the pulse power supply unit 53 are controlled.
That is, as described above, the laser beam is irradiated from the energy beam irradiator 61 before the voltage between the electrodes rises and before the energy beam irradiator 60 irradiates the material on the electrode with the energy beam. A recess is formed in the raw material supplied on the discharge electrode.

FIG. 7 is a partial explanatory view of the EUV light source device of FIGS. 5 and 6. The above-described procedures 1 to 3 will be specifically described with reference to FIG.
The raw material M adheres to the peripheral part of the discharge electrode 52a when the discharge electrode 52a passes through the melt of the raw material M filled in the container 57a. The raw material M adhering to the peripheral portion of the discharge electrode 52a is in a solid state.
<Procedure 1>
As shown in FIG. 7, the first laser beam emitted from the energy beam source 611 is applied to the energy beam irradiation surface of the raw material M attached to the peripheral edge of the discharge electrode 52a. A recess MA is formed on the energy beam irradiated surface of the raw material M irradiated with the first laser beam.
<Procedure 2>
As shown in (b) of the time chart of FIG. 3, the switch SW of the pulse power supply unit 3 is turned on.
<Procedure 3>
As shown in (c) and (d) of the time chart of FIG. 3 described above, after the voltage of the capacitor C2 exceeds the threshold value Vp, the second laser beam emitted from the energy beam source 601 is changed into the recess MA of the raw material M. Irradiate.
The raw material vaporized in step 3 reaches the discharge electrode 52b facing the discharge electrode 52a as described above, and discharge starts between the peripheral edge portions of the discharge electrodes 52a and 52b, and the plasma is heated to a high temperature. From this high temperature plasma, EUV light having a wavelength of 13.5 nm is emitted.

As shown in FIG. 7, the area of the raw material M reached by the second laser beam irradiated from the energy beam source 601 is from the area of the raw material M reached by the first laser beam irradiated from the energy beam source 611. is seperated. This is because the recess MA formed in the raw material M attached to the peripheral edge of the discharge electrode 52a moves in the circumferential direction as the discharge electrode 52a rotates in the circumferential direction at a predetermined speed. This is because the laser beam emitted from the source 611 is applied to the recess MA formed in the raw material M applied to the discharge electrode 52a.
In addition, since the rotational speed of the discharge electrodes 52a and 52b is slow with respect to the time from the irradiation of the first laser beam to the irradiation of the second laser beam, in practice, the irradiation position of the first laser beam The irradiation position of the second laser beam does not change greatly. In FIG. 7, the irradiation positions of the first and second laser beams LB1 and LB2 are exaggerated and separated.

The extreme ultraviolet light source device shown in FIGS. 5 to 7 is a recess forming energy beam irradiator that irradiates an energy beam independently of the energy beam irradiator 60 in order to form the recess MA on the surface of the raw material M. 61 is provided.
However, as described above, the extreme ultraviolet light source device of the present invention does not necessarily include two energy beam irradiators. For example, the procedure for forming the recess MA on the surface of the raw material M (the above procedure 1) and the procedure for irradiating the recess MA with the energy beam (the above procedure 3) are executed only by the energy beam irradiator 60. You may do it.

FIG. 8 is a partial explanatory view for sharpening another example of the recess forming means according to the EUV light source device of FIGS. 5 and 6.
In the EUV light source device shown in FIG. 8, the discharge electrode 52a is rotationally driven, passes through the melt of the raw material M filled in the container 57a, and the raw material M adheres to the peripheral edge of the discharge electrode 52a in a solid state.
The recess forming means 85 is made of a metal rod-like member fixed by a predetermined means, and has a pointed head 86 with a sharp tip formed in contact with the raw material M attached to the peripheral edge of the discharge electrode 52a. ing. The recess forming means 85 is controlled by the control unit 56 shown in FIG. 5 so as to advance and retreat in a direction orthogonal to the tangential direction of the discharge electrode 52a. In other words, the recess forming means 85 is configured such that the pointed head 86 comes into contact with the raw material M attached to the peripheral portion of the discharge electrode 52a, and the pointed portion 86 retracts from the raw material M attached to the peripheral portion of the discharge electrode 52a. The operation is repeated alternately.

In the EUV light source device of FIG. 8, the above-described procedures 1 to 3 are executed by the control unit 56 provided in the extreme ultraviolet light source device of FIGS.
<Procedure 1>
The controller 56 drives the recess forming means 85 to bring the pointed head 86 closer to the rotating discharge electrode 52a, and makes the pointed head 86 contact the surface of the raw material M attached to the peripheral edge of the discharge electrode 52a. Let On the surface of the raw material M, a plurality of hole-shaped recesses MA that are separated from each other in the circumferential direction of the discharge electrode 52a are formed.
<Procedure 2>
As shown in (b) of the time chart of FIG. 3, the switch SW of the pulse power supply unit 3 is turned on.
<Procedure 3>
The control unit 56 sends a signal to the energy beam source control unit 602 after the voltage of the capacitor C2 exceeds the threshold value Vp as shown in (c) and (d) of the time chart of FIG. Driven to irradiate the recess MA of the raw material M with the second laser beam. The raw material vaporized in step 3 reaches the discharge electrode 52b facing the discharge electrode 52a as described above, and discharge starts between the peripheral edge portions of the discharge electrodes 52a and 52b, and the plasma is heated to a high temperature. From this high temperature plasma, EUV light having a wavelength of 13.5 nm is emitted.

FIG. 9 is a partial explanatory view for explaining another example of the recess forming means according to the EUV light source device of FIGS. 5 and 6.
In the EUV light source device of FIG. 9, the discharge electrode 52a is rotationally driven by the control unit 56, passes through the melt of the raw material M filled in the container 57a, and the raw material M is in a solid state at the periphery of the discharge electrode 52a. Adhere to.
As shown in FIG. 9, the recess forming means 95 is made of a metal rod-like member fixed by a predetermined means, and has a pointed head 96 that abuts on the raw material M adhering to the peripheral edge of the discharge electrode 52a. Have.

In the EUV light source apparatus of FIG. 9, the above-described procedures 1 to 3 are executed by the control unit 56 provided in the extreme ultraviolet light source apparatus of FIGS.
<Procedure 1>
The control unit 56 drives the recess forming means 95 to bring the pointed head 96 close to the rotating discharge electrode 52a and bring the pointed head 96 into contact with the raw material M adhering to the peripheral edge of the discharge electrode 52a. A groove-like recess MA extending in the circumferential direction of the discharge electrode 52a is formed on the surface of the raw material M.
<Procedure 2>
As shown in (b) of the time chart of FIG. 3, the switch SW of the pulse power supply unit 3 is turned on.
<Procedure 3>
The control unit 56 sends a signal to the energy beam source control unit 602 after the voltage of the capacitor C2 exceeds the threshold value Vp as shown in (c) and (d) of the time chart of FIG. Driven to irradiate the recess MA of the raw material M with the second laser beam. The raw material vaporized in step 3 reaches the discharge electrode 52b facing the discharge electrode 52a as described above, and discharge starts between the peripheral edge portions of the discharge electrodes 52a and 52b, and the plasma is heated to a high temperature. From this high temperature plasma, EUV light having a wavelength of 13.5 nm is emitted.

FIG. 10 is a partial explanatory view for explaining another example of the recess forming means according to the EUV light source device of FIGS. 5 and 6. In addition, FIG.10 (b) shows sectional drawing of the discharge electrode 52a.
The EUV light source device of FIG. 10 has a groove 521a formed over the entire circumference of the peripheral edge of the discharge electrode 52a, and has a pointed portion 106 that abuts on the material M adhering along the groove 521a of the discharge electrode 52a. A recess forming means 105 is provided. The recess forming means 105 is made immovable with respect to the discharge electrode 52a rotating in the circumferential direction.
In the EUV light source device of FIG. 10, the above-described procedures 1 to 3 are executed by the control unit 56 provided in the extreme ultraviolet light source device of FIGS.
<Procedure 1>
The controller 56 drives the recess forming means 105 to bring the pointed head 106 closer to the rotating discharge electrode 52a, and makes the pointed head 106 contact the raw material M adhering along the groove 521a of the discharge electrode 52a. Let On the surface of the raw material M, a strip-shaped recess MA extending in the circumferential direction of the discharge electrode 52a is formed.

<Procedure 2>
As shown in (b) of the time chart of FIG. 3, the switch SW of the pulse power supply unit 3 is turned on.
<Procedure 3>
The control unit 56 drives the energy beam source 601 by sending a signal to the energy beam source control unit 602 after the voltage of the capacitor C2 exceeds the threshold value Vp according to (c) and (d) of the time chart of FIG. Then, the second laser beam is irradiated to the recess MA of the raw material M.
The raw material vaporized in step 3 reaches the discharge electrode 52b facing the discharge electrode 52a as described above, and discharge starts between the peripheral edge portions of the discharge electrodes 52a and 52b, and the plasma is heated to a high temperature. From this high temperature plasma, EUV light having a wavelength of 13.5 nm is emitted.
Also in the second embodiment, as described above, for example, the Δtd is small because the delay of the pulse power supply unit 3 is small, and the vaporized material is applied to the discharge electrode 2a because the interelectrode distance is large. When the time to reach Δti is large and Δtd <Δti, the order of the procedure 2 and the procedure 3 may be reversed.

Oite The EUV light source equipment of the present invention described above, the raw material are recesses formed in the energy beam irradiation surface of the energy beam to the depression is irradiated, compared with the conventional EUV light source device The output of EUV light can be increased. The reason is considered as follows. Hereinafter, a description will be given with reference to FIGS. 11 and 12.
FIG. 11 shows the difference in the generation state of the initial discharge plasma between the case where the recess is not formed on the energy beam irradiation surface of the raw material (FIG. 11A) and the case where the recess is formed (FIG. 11B). It is a figure explaining.
As shown in FIG. 11A, in the case where no recess is formed on the surface of the raw material that is irradiated with the energy beam, when the raw material M is irradiated with the laser beam, the initial discharge plasma spreads and the generated plasma Density decreases. For this reason, even if the plasma is heated by discharge, the amount of plasma that contributes to the generation of EUV light is reduced, and it is considered that only weak EUV light can be obtained.

On the other hand, as shown in FIG. 11B, when a recess is formed on the energy beam irradiation surface of the raw material, when the energy beam is irradiated and the raw material is vaporized, free expansion of the raw material occurs. Since it is regulated by the inner wall surface of the recess, lateral spread is reduced and directivity is increased. Therefore, the density of the gas generated by vaporizing the raw material becomes high and the spatial distribution is narrow, so that the spatial spread of the plasma generated between the pair of discharge electrodes is smaller than that of the conventional EUV light source device. Can be.
In this way, by reducing the spatial spread of the plasma generated between the discharge electrodes, the density of the current flowing in the plasma can be increased, so that the plasma can be easily brought to a high temperature state and ionization is prevented. As a result, the ion density of the plasma is increased. Furthermore, by suppressing the spread of plasma, self-absorption by plasma is reduced. Therefore, the output of EUV light can be made higher than that of a conventional EUV light source device.
Moreover, FIG. 12 is a figure which shows the visible light image of the laser ablation plasma in the case where there is no recess and when there is a recess.
When there is no recess, the plasma spreads spatially as shown in FIG. 9A. However, by providing the recess, the spread of the plasma can be reduced as shown in FIG. The density of the current flowing through the plasma can be increased.

It is a figure which shows schematic structure of the EUV light source device used as the premise of this invention. It is a partial explanatory view of the extreme ultraviolet light source device of FIG. It is the time chart which showed the irradiation timing of energy beam, the supply timing of pulse electric power, and generation | occurrence | production of EUV light. It is a figure which shows the structural example of the EUV light source device provided with one energy beam irradiation machine. It is a figure (top view) which shows schematic structure of the EUV light source device of embodiment of this invention. It is a figure (front view) which shows schematic structure of the EUV light source device of embodiment of this invention. FIG. 7 is a partial explanatory diagram of the EUV light source device of FIGS. 5 and 6. FIG. 7 is a diagram (1) illustrating another example of the recess forming means according to the EUV light source device of FIGS. 5 and 6. FIG. 7 is a diagram (2) illustrating another example of the recess forming means according to the EUV light source device of FIGS. 5 and 6. FIG. 7 is a diagram (3) illustrating another example of the recess forming means according to the EUV light source device of FIGS. 5 and 6. It is a figure explaining the difference in the production | generation state of an initial discharge plasma in the case where a recessed part is not formed, and the case where a recessed part is formed. It is a figure which shows the visible light image of the laser ablation plasma in the case where there is no recess and when there is a recess. It is a figure for demonstrating a EUV light source device simply.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,51 Chamber 1a Discharge part 1b EUV condensing part 1c, 51c Gas exhaust unit 1d, 51d EUV extraction part 2a, 2b, 52a, 52b Discharge electrode 2c Insulating member 2d, 52d Motor 2e, 52e Rotating shaft 2f, 52f Mechanical seal 2g, 2h Slider 21b Groove 3, 53 Pulse power supply 4, 54 Foil trap 5, 55 Condensing reflector 51a Discharge space 51b Condensing space 57a, 57b Containers 58a, 58b Power introducing unit 6, 56 Control unit 60 61 Energy beam irradiation machine 7 Raw material supply means 85, 95, 105 Recess formation means 10, 11 Energy beam irradiation machine 101, 111 Energy beam source 601, 611 Energy beam source 102, 112 Energy beam source controller 602, 612 Energy Beam source controller SR2, SR3 Magnetic switch C1, C2 Capacitor SR1 Magnetic switch (magnetic assist)
CH charger C0 Main capacitor SW Solid switch Tr1 Step-up transformer M Raw material

Claims (2)

A pair of discharge electrodes spaced apart from each other;
Pulse power supply means for supplying pulse power to the discharge electrode;
Raw material supply means for supplying a raw material for emitting extreme ultraviolet light onto the discharge electrode;
Energy beam irradiation means for irradiating the raw material on the electrode with an energy beam to vaporize the raw material;
Means for forming a recess in the raw material supplied on the discharge electrode;
An extreme ultraviolet light source device comprising a control unit,
The raw material supply means comprises a container filled with a melt of the raw material,
Each discharge electrode passes through the raw material melt filled in the container while rotating,
The control unit irradiates the source material on the electrode with the energy beam before the voltage between the electrodes rises by supplying the pulse power to the discharge electrode by the pulse power supply unit and with the energy beam irradiation unit. Prior to forming a recess in the raw material supplied onto the discharge electrode by means of forming the recess, and when the raw material is vaporized by irradiation with the energy beam, the inner wall of the recess An extreme ultraviolet light source device characterized by restricting free expansion and imparting directivity . The means for forming the recess is for irradiating an energy beam to form a recess on the surface of the raw material, and the energy beam irradiation means for vaporizing the raw material is an energy beam for forming the recess. 2. The extreme ultraviolet light source device according to claim 1, which also serves as an irradiation means.

Images