JPWO2006035748A1 - EUV generator - Google Patents

Abstract

The first electrode 1 and the second electrode 2 are provided in the chamber 30, and an electron beam is generated as a preionization unit 5 in an EUV generator that generates EUV light by generating plasma discharge between the two electrodes. Using an apparatus, an electron beam is emitted into the chamber 30 through the electron beam permeable film 5b. The chamber 30 is divided into a first container 30a and a second container 30b by an insulating material 3, and the electron beam permeable film 5b is at the same potential as the first electrode 1 and the container 30b of the chamber 30, The second container 30b and the second electrode are grounded, a negative high voltage is applied to the first electrode 1 from the discharge voltage application circuit 50, and a negative high voltage is applied from the preliminary ionization power source 110 to the cathode of the preliminary ionization unit 5. Apply voltage.

Description

  The present invention relates to an EUV generator for generating extreme ultraviolet rays (EUV) based on gas discharge.

In order to miniaturize a semiconductor integrated circuit, light having a shorter wavelength is required in the exposure technique (lithography). Currently, a light source device that emits light having a wavelength of 11 to 14 nm, called extreme ultraviolet (EUV), has been developed.
Several methods for generating the EUV are known, and one of them is a method for generating a high-temperature and high-density plasma and extracting the EUV from the plasma (see, for example, Non-Patent Document 1).
FIG. 4 shows a schematic configuration of an EUV generator using the above plasma.
A gas (for example, xenon Xe) that causes discharge is introduced into the chamber 30 that is a discharge vessel from the gas inlet 10. The introduced gas flows through the chamber 30 and is exhausted from the exhaust port 11 to which a vacuum pump (not shown) is attached. The pressure of the high-temperature and high-density plasma generating unit 31 in the chamber 30 is adjusted to 1 Pa to 20 Pa.

In the chamber 30, a ring-shaped first main discharge electrode (cathode) 1 and a second main discharge electrode (anode) 2 are arranged via an insulating material 3. The chamber 30 is composed of a first container 30a on the first main discharge electrode 1 side and a second container 30b on the main discharge electrode 2 side made of a conductive material. The first container 30a and the second container 30 b is separated and insulated by the insulating material 3.
The second container 30b and the discharge electrode 2 of the chamber 30 are grounded, and a discharge voltage of about −5 kV to −20 kV is applied to the second container 30a and the electrode 1 from the discharge voltage application circuit 100, and the ring 30 The high-temperature and high-density plasma generator 31 between the two electrodes 1 and 2 generates a high-temperature and high-density plasma discharge, and EUV light is emitted from the plasma.
The emitted EUV light is reflected by the EUV collector mirror 4 provided on the electrode 2 side, and is emitted to an irradiation unit (not shown) through the filter 6.

The discharge voltage application circuit 100 applies a discharge voltage to the electrodes 1 and 2 and supplies a preionization pulse to the preionization unit 40.
The discharge voltage application circuit 100 is basically the same as a normal discharge circuit. When the switch SW1 is opened and closed, a pulse voltage is supplied from the power source 101 to the transformer TR1 via the capacitor C0. A voltage generated on the next side is supplied to the electrodes 1 and 2 through a magnetic pulse compression circuit including a capacitor C1, a saturable reactor L1 and a capacitor C2, and a saturable reactor L2. Thereby, as described above, a discharge voltage of −20 kV is applied, and energy of about 10 J / shot is applied to the electrodes 1 and 2 at a frequency of several kHz. Therefore, energy of several tens of kW is input to the discharge electrodes 1 and 2. A transformer TR2 is connected in series to the secondary side of the transformer TR1 of the discharge voltage application circuit 100, and a preliminary ionization pulse is supplied from the transformer TR2 to the preliminary ionization unit 40.

Conventionally, high-temperature and high-density plasma for generating EUV has been generated and maintained in a narrow tube (capillary) having a diameter of about Φ5 to 6 mm. The discharge method used is described in P247 of Non-Patent Document 1).
However, as described above, since several tens of kW of electric power is input to the electrode, if the diameter of the electrode remains the current Φ5 to 6 mm, the electrode and the insulating material generate intense heat, and the electrode is long enough to withstand practical use. Can't keep life.
In order to suppress the heat generation of the electrode and extend the life, the diameter of the electrode must be increased to about 10 mm and the capillary must be thickened. However, when the initial gas suitable for generating EUV from the high-temperature and high-density plasma generating unit 31 is as low as 1 Pa to 20 Pa as described above, stable discharge is less likely to occur when the electrode interval is widened. The output becomes unstable.
Preionization is necessary to generate a stable discharge under conditions where the discharge is difficult to occur. For this reason, as shown in FIG. 4, a preionization unit 40 is provided. By applying a high voltage to the preliminary ionization unit 40 via the transformer TR2 from the discharge voltage application circuit 100, as shown in FIG. 4, a slip discharge is generated and the ionization of the working gas is promoted.
An example in which a preliminary ionization unit is combined with an EUV generator is disclosed in Patent Document 1, for example. In the thing of patent document 1, the preionization unit 5 is provided in the chamber of EUV generator.
JP 2003-218025 A Eiki Hotta, “5. Current status of discharge generated plasma light source-5.1 discharge generated plasma light source” J. Plasma Fusion Res. Vol. 79. No.3, P245-251, March 2003

However, the EUV generator having the preliminary ionization unit 40 shown in FIG. 4 has the following problems.
(i) As described above, the high-temperature and high-density plasma generating unit 31 in the chamber has a low pressure of 1 Pa to 20 Pa, and pre-ionization is less effective in the method using ultraviolet rays, and the pre-ionization unit using slip discharge or the like. Is required. For this reason, conventionally, as shown in FIG. 4, the preliminary ionization unit 40 is provided in the chamber 30.
For this reason, there is a concern that the chamber 30 is contaminated by the material scattered from the preliminary ionization unit during the discharge of the preliminary ionization unit, and the preliminary ionization unit is contaminated by the material generated from the electrode during the main discharge.
(ii) Since the preionization unit is provided in the chamber 30, the preionization unit cannot be easily removed, and the preionization unit cannot be easily replaced or inspected.
The present invention has been made in order to solve the above-mentioned problems of the prior art, and the contamination of the EUV generator due to the material scattered from the preliminary ionization unit, and the preliminary ionization unit due to the material scattered from the electrode of the EUV generator. It is an object of the present invention to provide an EUV apparatus equipped with a preionization unit that can prevent precontamination, can be easily replaced and maintained, and can efficiently perform preionization. .

In the present invention, the above problem is solved as follows.
(1) A chamber provided with a gas introduction port and an exhaust port, a ring-shaped first electrode provided with a discharge voltage provided on the gas introduction port side, and insulated from the first electrode In an EUV generator comprising a grounded ring-shaped second electrode provided on the exhaust port side through a material and a mirror provided on the second electrode side, an electron beam generator is used as a preliminary ionization unit. Used, the electron beam is radiated into the chamber through a transmission window that transmits the electron beam but does not transmit the contaminant.
(2) The gas inlet side and the exhaust side of the chamber are electrically insulated by the insulating material, and an opening is provided in the gas inlet side chamber. The opening is opened in the chamber through the transmission window. Is provided with a preionization unit that emits an electron beam.
Then, the transmission window, the gas introduction side chamber, and the first electrode are electrically connected to have the same potential, and a high voltage is applied between the first electrode and the second electrode. A second power source for connecting a first power source and applying a high voltage between the first electrode and the electron beam radiation source of the preionization unit or between the second electrode and the preionization unit. Connect the power supply.

In the present invention, the following effects can be obtained.
(1) Since an electron beam generator is used as the preionization unit, an efficient electron beam can be used for preionization at a low pressure.
(2) Since a transmission window that transmits electron beams but does not transmit contaminants is provided between the first and second electrodes of the EUV generator and the preionization unit, there is no influence of mutual contamination. .
(3) Since an opening is provided in the chamber, an electron beam generator is attached to the opening as a preionization unit, and the electron beam is irradiated from the opening into the chamber through the transmission window. Replacement of the transmission window, replacement of the preionization unit, and maintenance can be easily performed.
(4) The gas inlet side and the exhaust port side of the chamber are electrically insulated by the insulating material, and an opening is provided in the gas inlet side chamber, and an electron beam is introduced into the chamber through a transmission window in the opening. Since the pre-ionization unit that radiates is provided and the transmission window, the gas introduction side chamber, and the first electrode are connected to have the same electric potential, a discharge is generated between the discharge electrode and the transmission window. Can be prevented, and the breakage of the transmission window can be prevented.
Further, a first power source for applying a high voltage is connected between the first electrode and the second electrode, and between the first electrode and the electron beam radiation source of the preionization unit, or Since the second power source for applying a high voltage is connected between the second electrode and the preliminary ionization unit, the electron beam can be effectively irradiated into the chamber from the preliminary ionization unit.

It is a figure which shows the structure of the EUV apparatus of the Example of this invention. It is a figure which shows the connection of the structure of an electron beam generator, and a power supply circuit. It is a figure which shows the modification of the Example of this invention. It is a figure which shows the structural example of the conventional EUV apparatus which has a preliminary ionization unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Main discharge electrode 3 Insulation material 4 EUV condensing mirror 6 Filter 5 Preionization unit 10 Gas inlet 11 Gas exhaust 30 Chamber 30a 1st container 30b 2nd container 31 High temperature high density plasma generation part 50 Discharge voltage Application circuit 110 Pre-ionization power supply

FIG. 1 shows the configuration of an EUV generator equipped with a preliminary ionization unit according to an embodiment of the present invention.
A ring-shaped main discharge electrode 1 and a main discharge electrode 2 are disposed through an insulating material 3 in a chamber 30 that is a discharge vessel. The chamber 30 is composed of a first container 30a on the main discharge electrode 1 side and a second container 30b on the main discharge electrode 2 side made of a conductive material, and the first container 30a and the second container 30b are formed as described above. It is separated and insulated by the insulating material 3.
A gas inlet 10 is provided in the chamber 30, and a gas (for example, xenon Xe) that causes discharge is introduced from the gas inlet 10. The introduced gas flows through the chamber 30 and is exhausted from the exhaust port 11 to which a vacuum pump (not shown) is attached. As described above, the pressure of the high-temperature and high-density plasma generator 31 in the chamber 30 is It is adjusted to 1 Pa to 20 Pa.
The second container 30b and the main discharge electrode 2 are grounded, and a discharge voltage application circuit 50 is connected between the second container 30a, the main discharge electrode 1, and the second container 30b.
The discharge voltage application circuit 50 includes a series circuit of a capacitor C0 and a switch SW1 charged to the discharge voltage, and a parallel circuit of a resistor R and a reactor L connected in parallel to the series circuit. Note that a parallel circuit including only the resistor R without using the reactor L may be used. The circuit for charging the capacitor C0 to the discharge voltage is not shown in the figure, but a circuit similar to the discharge voltage application circuit 100 shown in FIG. 4 can be used.

When no discharge voltage is applied to the main discharge electrodes 1 and 2, the switch SW1 is open, and the first main discharge electrode 1 and the first container 30a are grounded via the resistor R and the reactor L, and grounded. It becomes a potential. In addition, when the reactor L is not used without using the reactor L, the value is close to the installation potential. When the switch SW1 is closed, a negative high voltage charged in the capacitor C0 is applied to the main discharge electrode 1 and the first container 30a, and between the first main discharge electrode 1 and the second main discharge electrode 2. Is applied with a pulsed discharge voltage of −several tens of kV. As a result, high-temperature and high-density plasma discharge is generated between the ring-shaped electrodes 1 and 2, and EUV light is emitted from the plasma.
The emitted EUV light is reflected and collected by the EUV collector mirror 4 provided on the main discharge electrode 2 side, and is emitted to an irradiation unit (not shown) through the filter 6.
As described above, since the chamber 30 is divided into the first container 30a and the second container 30b by the insulating material 3 and these containers 30a and 30b are used as conductive materials, the main discharge electrode 1 and the first container 30a are the same. In addition, the main discharge electrode 2 and the second container 30b become the ground potential. Therefore, no discharge occurs between the container 30a and the main discharge electrode 1 and between the container 30b and the main discharge electrode 2.

An opening 31 is provided on the first electrode 1 side of the chamber 30, and an electron beam generator for generating an electron beam is provided as the preliminary ionization unit 5 so that an electron beam can be irradiated into the chamber 30 from the opening 31. It is done.
As such an electron beam generator, for example, an electron beam generator described in JP-T-10-512092 can be used.
FIG. 2 shows a configuration example of the electron beam generator.
As shown in FIG. 2, the electron beam generator includes a filament heater 5c and a cathode 5d, which are electron beam sources, in an insulating container 5a made of an insulating member such as glass. From the filament heater 5c and the cathode 5d, Are led out to the outside through the introduction pins 5e, 5f, 5g. A power source 120 is connected to the introduction pins 5e, 5f, and 5g.
The insulating container 5a is provided with an electron beam permeable film 5b that transmits an electron beam, the insulating container 5a is sealed, and the inside is kept in a vacuum. The electron beam permeable film 5b is conductive.

A current is supplied from the filament power transformer 111 of the power source 120 to the filament heater 5c via the introduction pins 5e and 5f to heat the filament heater, and from −30 kV to the cathode 5d from the booster circuit 112 via the introduction pin 5g. By applying a negative high voltage of −60 kV and setting the electron beam transmission window 5b to the ground potential, an electron beam is emitted through the electron beam transmission film 5b as shown by the dotted arrow in FIG. The
Silicon Si is used as the material of the electron beam transmissive film 5b, but silicon nitride (SiN), aluminum (Al), titanium (Ti), beryllium (Be), or the like can be used.
The inside of the preliminary ionization unit 5 is usually set to a low pressure of, for example, 1 × 10 ⁻⁴ Pa (1 × 10 ⁻⁶ Torr) or less so that electrons emitted from the filament heater 5c are not absorbed. Therefore, insulation between the electron beam permeable film 5b and the cathode 5d can be secured.

If the electron beam generator is used as a preionization unit, preionization is effectively performed even if the pressure in the chamber 30 is low without providing a preionization unit by sliding discharge in the chamber as in the conventional example. be able to.
In paragraph 0033 of Patent Document 1, a sliding discharge is generated by the preliminary ionization pulse generator 6, and the sliding discharge is caused by high-speed charged particles (fast electrons) in addition to radiation from infrared radiation to X-ray radiation. Although it is described that it promotes ionization of working gas, it is mainly radiation from ultraviolet radiation to X-ray radiation that is generated by sliding discharge, and the contribution of the above high-speed charged particles to preionization is low it is conceivable that.

By the way, when the electron beam generator shown in FIG. 2 is used as a preliminary ionization unit of an EUV apparatus, the following problems occur.
In FIG. 1, the main discharge electrode 2 on the side where the EUV collector mirror 4 for taking out the light is provided has a ground potential in order to prevent discharge from occurring between the EUV collector mirror 4 and the like. The high voltage -HV1 of -several tens of kV is applied to the discharge electrode 1 and the container 30a of the chamber 30.
For this reason, the electron beam generator shown in FIG. 2 is used as the preliminary ionization unit of the EUV apparatus, and the electron beam generator is used as the preliminary ionization unit and is directly attached to the chamber 30 of the EUV generator. Since the potential of the container 30a on the main discharge electrode 1 side becomes a negative high voltage -HV1, the electron beam transmitting film 5b of the electron beam generator cannot be grounded as shown in FIG.

  It is conceivable that the electron beam transmission film 5b is set to the ground potential and the electron beam generator is attached to the container 30a of the chamber 30 through an insulating material. In this state, a negative high voltage is applied to the main discharge electrode 1 and the container 30a. Is applied, a discharge may occur between the main discharge electrode 1 or the container 30a and the electron beam permeable film 5b. In particular, if a discharge occurs between the main discharge electrode 1 and the electron beam permeable film 5b, the electron beam permeable film 5b may be damaged, causing troubles in the apparatus. Further, when the main discharge electrode 1 and the container 30a have a negative high voltage, the electron beam transmitted through the electron beam transmission film 5b set to the ground potential is decelerated, and the electron beam is not effectively irradiated into the chamber 30. .

Therefore, in this embodiment, as shown in FIG. 1, the main discharge electrode 1 and the container 30a on the main discharge electrode 1 side and the electron beam transmission film 5b of the electron beam generator are set to the same potential, and the electron beam generator (preliminary) A voltage −HV2 (| HV1 | <| HV2 |) higher than the negative high voltage −HV1 was applied to the cathode 5d of the ionization unit 5) from the booster circuit 112 of the preliminary ionization power source 110. The configuration of the preionization power supply 110 is the same as that shown in FIG. 2, and includes a filament power transformer 111 that supplies current to the filament heater 5c and a booster circuit 112 that applies a negative high voltage to the cathode. ing.
As a result, discharge can be prevented from occurring between the electron beam permeable membrane 5b, the main discharge electrode 1 and the container 30a, and the inside of the chamber 30 can be effectively prevented from the electron beam generator (preliminary ionization unit 5). Can be irradiated with an electron beam.
The electron beam transmission film 5b of the electron beam generator is normally used at a ground potential as described in FIG. 2 and Japanese Patent Publication No. 10-512092, but the cathode 5d. Therefore, even if the voltage applied to the cathode 5d is made larger than the negative high voltage applied to the main discharge electrode 1, the electron beam can be generated without any problem. Can be made.

The EUV apparatus shown in FIG. 1 operates as follows.
Xenon is introduced from the gas inlet 10 and exhausted from the exhaust port 11 by a vacuum pump. Xenon gas flows in the chamber 30 from the main discharge electrode 1 side toward the main discharge electrode 2 side. The inside of the chamber 30 is depressurized by differential evacuation and set to a predetermined pressure.
A negative high voltage −HV2, for example, −60 kV, is applied to the cathode 5d of the preliminary ionization unit 5 (electron beam generator), and the electron beam passes through the electron beam transmission film 5b and is irradiated into the chamber 30. As described above, when no discharge voltage is applied to the main discharge electrodes 1 and 2, the switch SW1 of the discharge voltage application circuit 50 is open, and the first main discharge electrode 1 and the first container 30a are It is grounded via a resistor R and a reactor L and is at a ground potential.
When the switch SW1 is closed, a negative high voltage charged in the capacitor C0 is applied to the main discharge electrode 1 and the first container 30a, and the first main discharge electrode 1 and the second main discharge electrode 2 are applied. A negative high voltage −HV1, for example −20 kV, which is a discharge voltage, is applied between them. Since the electron beam permeable membrane 5 b of the preliminary ionization unit 5 is attached to the container 30 a of the chamber 30, it has the same potential as the container 30 a and the main discharge electrode 1.

When the xenon in the chamber 30 is preionized by the electron beam irradiated from the preionization unit 5 and a pulsed negative high voltage is applied to the main discharge electrode 1 and the main discharge electrode 2, plasma discharge occurs between them. And EUV light is emitted.
The emitted EUV light is collected by the EUV collector mirror 4 and emitted to the irradiation unit via the filter 6.
When a negative high voltage is applied to the main discharge electrode 1, the potential difference between the cathode 5d of the preionization unit 5 and the electron beam transmission film 5b becomes small, and the irradiation amount of the electron beam into the chamber 30 becomes Although it becomes smaller, the pre-ionization is caused by electrons at the moment of rising of the main discharge. When a negative high voltage is applied to the main discharge electrode 1, there is a problem even if the electron irradiation amount is somewhat reduced. Does not occur.
According to the present embodiment, since the discharge space in the chamber 30 and the preionization unit 5 are separated by the electron beam permeable film 5b, for example, a substance scattered by sputtering from the main discharge electrodes 1 and 2 is preliminarily stored. It does not enter the ionization unit 5 and the preliminary ionization unit is not contaminated. On the contrary, since the contamination in the chamber by the preliminary ionization unit 5 can be prevented, the life of the apparatus can be extended.
Moreover, since the preliminary ionization unit 5 is attached to the outside of the chamber 30, the replacement and maintenance inspection of the preliminary ionization unit 5 can be easily performed.

FIG. 3 shows a modification of the above-described embodiment. In this embodiment, the preliminary ionization power source 110 is a power source that is electrically isolated from the discharge voltage application circuit 100, and the positive side of the preliminary ionization power source 110 is connected to the discharge side. The negative side of the voltage application circuit 100 is connected, and other configurations are the same as those in FIG.
With the above configuration, the output voltage of the preliminary ionization power supply 110 can be made lower than that in the case of FIG. 1. For example, in the case of −HV1 = −20 kV and −HV2 = −60 kV in FIG. With the configuration of 3, it is possible to set −HV1 = −20 kV and −HV2 = −40 kV.

In the above embodiment, the case where the preliminary ionization unit 5 is attached to the outside of the chamber 30 has been described. However, the preliminary ionization unit may be incorporated in the chamber. With this configuration, replacement of the preionization unit, maintenance, and inspection are more difficult than in the case of FIG. 1, but as shown in FIG. 1, an electron beam is irradiated into the chamber through the electron beam transmission film. By configuring, as in the embodiment of FIG. 1, it is possible to prevent contamination of the preionization unit and contamination in the chamber.
Moreover, although the case where the electron beam generator described in the Japanese translation of PCT publication No. 10-512092 was used was demonstrated in the said Example, the electron beam generator of another structure can also be used.

Claims (2)

A chamber provided with a gas inlet and an exhaust port;
A ring-shaped first electrode to which a discharge voltage provided on the gas inlet side is applied in the chamber;
A grounded ring-shaped second electrode provided on the exhaust port side through an insulating material with respect to the first electrode;
In an EUV generation device comprising a condenser mirror provided on the second electrode side,
An EUV generator according to claim 1, wherein a preionization unit that emits an electron beam through a transmission window is provided in the chamber on the first electrode side. In the chamber, the gas inlet side and the exhaust port side are electrically insulated by the insulating material,
The gas introduction side chamber is provided with an opening, and the opening is provided with a preionization unit that emits an electron beam into the chamber through a transmission window,
The transmission window, the gas introduction side chamber, and the first electrode are electrically connected to have the same potential, and a first voltage for applying a high voltage between the first electrode and the second electrode is provided. A second power source for applying a high voltage between the first electrode and the electron source of the preionization unit or between the second electrode and the preionization unit is connected to a power source The EUV generator according to claim 1, wherein:

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