WO2006035748A1

WO2006035748A1 - Euv generator

Info

Publication number: WO2006035748A1
Application number: PCT/JP2005/017703
Authority: WO
Inventors: Gohta Niimi; Toshio Yokota
Original assignee: Ushio Denki Kabushiki Kaisha
Priority date: 2004-09-29
Filing date: 2005-09-27
Publication date: 2006-04-06
Also published as: KR20070058385A; JPWO2006035748A1; TW200613706A

Abstract

An EUV generator for generating EUV light by generating plasma discharge between a first electrode (1) and a second electrode (2) provided in a chamber (30), wherein an electron beam generator is used as a stand-by ionizing unit (5) to emit an electron beam into the chamber (30) via an electron beam transmitting membrane (5b). The chamber (30) is divided into a first container (30a) and a second container (30b) by an insulation material (3), the electron beam transmitting membrane (5b) is at the same potential as the first electrode (1) in the chamber (30) and the first container (30b), the second container (30b) and the second electrode are at the ground potential, a minus high voltage is applied to the first electrode (1) from a discharge voltage application circuit (50), and a minus high voltage is applied to the cathode of the stand-by ionizing unit (5) from a stand-by ionizing power supply (110).

Description

Specification

EUV generator

Technical field

[0001] The present invention relates to an EUV generating device for generating extreme ultraviolet (EUV) based on gas discharge.

Background art

[0002] Due to the miniaturization of semiconductor integrated circuits, the exposure technology (lithography) is shorter! Wavelength light is needed. Currently, a light source device that emits light with a wavelength of 11 to 14 nm, called extreme ultraviolet (EUV), is being developed.

There are several known methods for generating the EUV. One of them is a method of generating a high-temperature and high-density plasma and taking out the EUV from the plasma cover (for example, see Non-Patent Document 1).

Figure 4 shows the schematic configuration of the EUV generator using the above plasma.

A gas (for example, xenon Xe) that causes discharge is introduced into the chamber 30 which 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 generator 31 in the chamber 30 is adjusted to lPa to 20Pa.

[0003] Inside chamber 30 is a ring-shaped first main discharge electrode (force sword) 1 and a second main discharge electrode

An (anode) 2 is disposed 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, which are made of a conductive material, and the first container 30a and the second container 30b. The container 30b 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 the discharge voltage application circuit 100 is connected to the second container 30a and the electrode 1. Therefore, a discharge voltage of about 5 kV to 20 kV is applied, and a high-temperature and high-density plasma discharge is generated in the high-temperature and high-density plasma generation section 31 between the ring-shaped electrodes 1 and 2, and EUV light is emitted from the plasma chamber. Radiated.

The emitted EUV light is reflected by the EUV collector mirror 4 provided on the electrode 2 side, The light is emitted to an irradiator (not shown) through the data generator 6.

The discharge voltage application circuit 100 applies a discharge voltage to the electrodes 1 and 2 and supplies a preliminary ionization pulse to the preliminary ionization 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 pulsed voltage is supplied from the power supply 101 to the transformer TR1 via the capacitor CO. The voltage generated on the next side is supplied to electrodes 1 and 2 via a magnetic pulse compression circuit comprising capacitor Cl, saturable rear tuttle L1, capacitor C2, and saturable rear tuttle L2. Thereby, as described above, a discharge voltage of −20 kV is applied, and energy of about lOjZshot 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.

[0005] Conventionally, high-temperature and high-density plasma for generating EUV has been generated and maintained in a capillary (capillary) with a diameter of about Φ5-6mm, so the diameters of electrodes 1 and 2 are accordingly adjusted accordingly. (The discharge method using the capillary is described in P247 of Non-Patent Document 1 above).

However, as mentioned above, tens of kW of power is input to the electrode, so if the electrode diameter remains the same as the current Φ5 to 6πιπι, the electrode and the insulating material generate intense heat and can withstand practical use. A long life cannot be maintained.

In order to suppress the heat generation of the electrode and extend its life, the diameter of the electrode must be expanded to about 10 mm and the capillaries must be thickened. However, the initial gas force suitable for generating EUV from the high-temperature and high-density plasma generator 31 Under the low pressure of lPa to 20Pa as described above, stable discharge is less likely to occur when the electrode spacing is widened, and The output becomes unstable.

Pre-ionization is required to generate a stable discharge under conditions where discharge is difficult to occur. For this reason, a preionization unit 40 is provided as shown in FIG. When a high voltage is applied to the preliminary ionization unit 40 from the discharge voltage application circuit 100 via the transformer TR2, as shown in FIG. 4, a slip discharge is generated and the ionization of the working gas is promoted. An example in which a preionization unit is combined with an EUV generator is disclosed in Patent Document 1, for example. In the device described in Patent Document 1, the preionization unit 5 is provided in the chamber 1 of the EUV generator.

Patent Document 1: Japanese Patent Application Laid-Open No. 2003-218025

Non-Patent Document 1: Eiki Hotta “5. Current Status of Discharge-Generated Plasma Light Source 5.1 Discharge-Generated Plasma Light Source Research” J. Plasma Fusion Res. Vol. 79. No. 3, Ρ245-251, March 2003

Disclosure of the invention

Problems to be solved by the invention

However, the EUV generator equipped with the preliminary ionization unit 40 shown in FIG. 4 has the following problems.

(0 As described above, the high-temperature and high-density plasma generating unit 31 in the chamber has a low pressure of lPa to 20Pa, and the preliminary ionization is not effective with the method using ultraviolet rays. For this reason, conventionally, as shown in FIG. 4, a preliminary ionization unit 40 is provided in the chamber 30 as shown in FIG.

For this reason, there is a risk of contamination of the chamber 30 by materials scattered from the preionization unit during discharge of the preionization unit, and contamination of the preionization unit by materials generated from the electrodes during 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 to solve the above-mentioned problems of the prior art. Contamination of the EUV generator with a substance scattered from the preliminary ionization unit, and a spare with a substance that also scatters the EUV generator as much as possible. It is an object to provide an EUV apparatus equipped with a preliminary ionization unit that can prevent contamination of the ionization unit, can be easily replaced and maintained, and can efficiently perform preliminary ionization. And

Means for solving the problem

In the present invention, the above problems are solved as follows.

(1) A chamber provided with a gas inlet and an exhaust port, and provided on the gas inlet side. A ring-shaped first electrode to which the discharge voltage is applied, a grounded ring-shaped second electrode provided on the exhaust port side with an insulating material interposed between the first electrode and the second electrode, Using an EUV generator equipped with a mirror provided on the electrode side of the electrode, an electron beam generator is used as a preliminary ionization unit, which transmits electron beams but does not allow contaminants to pass through./ Through the chamber.

(2) The gas inlet side and the exhaust port side of the chamber 1 are electrically isolated by the insulating material, and an opening is provided in the gas inlet side chamber 1, and the opening is provided through the transmission window. A preionization unit for emitting an electron beam is provided in the chamber.

The transmission window, the gas introduction side chamber 1 and the first electrode are connected so as to be electrically at the same potential, and a high voltage is applied between the first electrode and the second electrode. To connect a first power source and apply 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 second power supply.

The invention's effect

In the present invention, the following effects can be obtained.

(1) Since the electron beam generator is used as the preionization unit, the electron beam can be used with high efficiency for preionization at low pressure.

(2) Between the first and second electrodes of the EUV generator and the preionization unit, there is a transmission window that transmits electron beams but does not transmit contaminants. The influence of!

(3) Since an opening is provided in the chamber, an electron beam generator is attached to the opening as a preionization unit, and the opening force chamber is irradiated with an electron beam through the transmission window. Therefore, it is possible to easily replace the transmission window, replace the preionization unit, and perform maintenance and inspection.

(4) The gas inlet side and the exhaust port side of the chamber 1 are electrically insulated by the insulating material, and an opening is provided in the chamber 1 on the gas inlet side. The pre-ionization unit that radiates the electron beam is provided on the top, and the transmission window, the gas introduction side chamber, and the first electrode are connected to have the same potential. Can be prevented from occurring, and damage to the transmission window can be prevented. In addition, 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 preliminary ionization unit, Alternatively, since the second power source for applying a high voltage is connected between the second electrode and the preionization unit, an electron beam can be effectively irradiated from the preionization unit into the chamber. Is possible.

Brief Description of Drawings

FIG. 1 is a diagram showing a configuration of an EUV apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an electron beam generator and a connection with a power supply circuit.

FIG. 3 is a view showing a modification of the embodiment of the present invention.

FIG. 4 is a diagram showing a configuration example of a conventional EUV apparatus having a preliminary ionization unit.

Explanation of symbols

1, 2 Main discharge electrode

3 Insulation material

4 EUV collector mirror

6 Huinoleta

5 Pre-ionization unit

10 Gas inlet

11 Gas exhaust port

30 chambers

30a first container

30b second container

31 High-temperature and high-density plasma generator

50 Discharge voltage application circuit

110 Standby ionization power supply

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows a configuration of an EUV generator equipped with a preionization unit according to an embodiment of the present invention. A ring-shaped main discharge electrode 1 and a main discharge electrode 2 are arranged through an insulating material 3 in a chamber 30 which 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 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 high-temperature and high-density plasma generating unit 31 in the chamber 30 is exhausted. The pressure is adjusted to lPa ~ 20Pa.

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 CO and a switch SW1 charged to the discharge voltage, and a parallel circuit force of a resistor R and a rear tuttle L connected in parallel to the series circuit. Note that a parallel circuit including only the resistor R may be used without using the rear tuttle L. Note that a circuit for charging the capacitor CO to a discharge voltage may be a circuit similar to the discharge voltage application circuit 100 shown in FIG. .

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 vessel 30a are grounded via the resistor R and the rear tuttle L, It becomes a potential. In addition, when using only the resistance R without using the rear tuttle L, the value is close to the installation potential. When the switch SW1 is closed, a negative high voltage charged in the capacitor CO 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 connected. A pulsed discharge voltage of several tens of kV is applied to. 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 cover.

The emitted EUV light is reflected and collected by an EUV collector mirror 4 provided on the main discharge electrode 2 side, and is emitted to an irradiation unit (not shown) through a filter 6.

As described above, 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 the conductive material, so that the main discharge electrode 1 and the first container 30 are used. 30a is the same potential In addition, the main discharge electrode 2 and the second container 30b are at 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.

[0013] An opening 31 is provided on the first electrode 1 side of the chamber 30 and an electron beam is generated as the preliminary ionization unit 5 so that an electron beam can be irradiated into the chamber 30 from the opening 31. A line generator is provided.

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 is provided with a filament heater 5c, which is an electron beam source, and a force sword 5d in an insulating container 5a made of an insulating member such as glass, and the filament heater 5c. The lead wire from the force sword 5d is led out to the outside through the introduction pins 5e, 5f and 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 hermetically sealed, and the inside is kept in a vacuum. The electron beam permeable film 5b is conductive.

[0014] A current is supplied from the filament power transformer 111 of the power supply 120 to the filament heater 5c through the introduction pins 5e and 5f to heat the filament heater, and the force sword 5d from the booster circuit 112 through the introduction pin 5g. In addition, by applying a negative high voltage of −30 kV to −60 kV and setting the electron beam transmission window 5b to the ground potential, the electron beam transmission film 5b is passed through the electron beam transmission film 5b as shown by the dotted arrow in FIG. An electron beam is emitted.

As the material of the electron beam permeable film 5b, silicon Si is used. In addition, silicon nitride (SiN), aluminum (A1), titanium (Ti), beryllium (Be), or the like can be used.

The inside of the preionization unit 5 is usually set to a low pressure such as 1 X 10 " ⁴ Pa (l X 10" ⁶ Torr), so that the electrons emitted from the filament heater 5c are not absorbed! . Therefore, insulation between the electron beam permeable film 5b and the force sword 5d can be secured.

[0015] If the electron beam generator is used as a preionization unit, even if the pressure in the chamber 30 without a preionization unit by slip discharge in the chamber as in the conventional example is low, it is effective. Preionization can be performed.

In paragraph 0033 of Patent Document 1, the preliminary ionization pulse generator 6 is used for sliding. Electricity is generated, and sliding discharge is described as generating high-speed charged particles (fast electrons) in addition to radiation from infrared radiation to X-ray radiation, which promotes ionization of working gas. It is thought that radiation generated mainly from ultraviolet radiation to X-ray radiation contributes little to the preionization of the high-speed charged particles.

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 light is provided has a ground potential to prevent discharge from occurring between the EUV collector mirror 4 and the like. Therefore, a high voltage HV1 of several tens of kV is applied to the main discharge electrode 1 and the container 30a of the chamber 30.

For this reason, even if the electron beam generator shown in Fig. 2 is used as a preliminary ionization unit of an EUV device, and this electron beam generator is used as a preliminary ionization unit and is directly attached to the chamber 30 of the EUV generator, Since the potential of the container 30a on the side of the main discharge electrode 1 of the chamber 30 is a negative high voltage HV1, the electron beam transmission film 5b of the electron beam generator cannot be set to the ground potential as shown in FIG.

[0017] It should be noted that the electron beam permeable membrane 5b is set to the ground potential and the electron beam generator can be attached to the container 30a of the chamber 30 through an insulating material. In this state, the main discharge electrode 1 and the container 30a are negatively charged. When a high voltage is applied, a discharge may occur between the main discharge electrode 1 or the container 30a and the electron beam transmissive film 5b. In particular, when 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. If 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 at the ground potential is decelerated, and the electron beam is effectively irradiated into the chamber 30. Not.

Therefore, in the present 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 to generate an electron beam. The negative high voltage—higher voltage than HV1—HV2 (I HV1 I <I HV2 |) was applied to the force sword 5d of the device (preliminary ionization unit 5) from the booster circuit 112 of the preliminary ionization power supply 110 . The configuration of the standby ionization power source 110 is the same as that shown in FIG. A filament power transformer 111 for supplying a current to the irament heater 5c and a booster circuit 112 for applying a negative high voltage to the force sword are provided.

As a result, it is possible to prevent discharge between the electron beam permeable membrane 5b, the main discharge electrode 1 and the container 30a, and effectively, from the electron beam generator (preliminary ionization unit 5), the chamber 30 can be irradiated with an electron beam.

The electron beam permeable membrane 5b of the electron beam generator is a force cathode that is normally used at a ground potential as described in FIG. 2 and Japanese Patent Application Laid-Open No. 10-512092. Since it is possible to apply up to approximately 60 kV to 5d, there is no problem even if the voltage applied to the force sword 5d is made larger than the negative high voltage applied to the main discharge electrode 1 to the negative side. Can be generated.

[0019] The EUV apparatus shown in Fig. 1 operates as follows.

Xenon is introduced from the gas inlet 10 and exhausted from the exhaust 11 by a vacuum pump. Xenon gas flows through the chamber 30 from the main discharge electrode 1 side to 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 force sword 5d of the preionization unit 5 (electron beam generator), and the electron beam passes through the electron beam transmission film 5b and is irradiated into the chamber 30. The 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 , Grounded through resistor R and rear tuttle L, and at ground potential.

When the switch SW1 is closed, a negative high voltage charged in the capacitor CO 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 are applied. Between the two, a negative high voltage HV1, for example, 20 kV, which is a discharge voltage, is applied. Since the electron beam permeable membrane 5b of the preionization unit 5 is attached to the container 30a of the chamber 30, it has the same potential as the container 30a and the main discharge electrode 1.

[0020] When the xenon force in the chamber 30 is pre-ionized by the electron beam irradiated from the pre-ionization 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 and EUV light is emitted. The emitted EUV light is collected by the EUV collector mirror 4 and emitted to the irradiation section through 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 permeable membrane 5b becomes small, and the electron beam into the chamber 30 is reduced. Although the irradiation dose is small, preionization is caused by electrons at the moment of the rise of the main discharge. When a negative high voltage is applied to the main discharge electrode 1, the electron irradiation amount is somewhat Even if it is less, there will be no problem.

According to this embodiment, since the discharge space in the chamber 30 and the preionization unit 5 are separated from each other by the electron beam permeable film 5b, for example, a substance scattered from the main discharge electrodes 1 and 2 by sputtering is It does not enter the preionization unit 5 and the preionization unit is not contaminated. Conversely, contamination in the chamber due to the preionization unit 5 can be prevented, so that the life of the apparatus can be extended.

In addition, since the preliminary ionization unit 5 is attached to the outside of the chamber 30, the replacement and maintenance of the preliminary ionization unit 5 can be easily performed.

FIG. 3 shows a modification of the above 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 1 and the negative side of the discharge voltage application circuit 100 are connected, and the other configurations are the same as those in FIG.

With the above configuration, the output voltage of the standby ionization power supply 110 can be made lower than in the case of FIG. 1. For example, in the case of HVl = −20 kV and one HV2 = −60 kV in FIG. With the configuration shown in Fig. 3, HV1 = -20 kV and one HV2 = -40 kV.

In the above embodiment, the force preionization unit described for the case where the preionization unit 5 is attached to the outside of the chamber 1 30 may be incorporated in the chamber 1. This configuration makes it difficult to replace and maintain the preionization unit compared to the case of Fig. 1. As shown in Fig. 1, an electron beam is irradiated into the chamber through the electron beam permeable membrane. With this configuration, it is possible to prevent the contamination of the preionization unit and the contamination in the chamber as in the embodiment of FIG. In the above-described embodiment, the case where the electron beam generator described in JP-T-10-512092 is used has been described. However, an electron beam generator having another configuration may be used.

Claims

The scope of the claims

[1] a chamber having a gas inlet and an exhaust port;

A ring-shaped first electrode to which a discharge voltage is provided in the chamber and provided on the gas inlet side;

A grounded ring-shaped second electrode provided on the exhaust port side via an insulating material with respect to the first electrode;

In the EUV generator provided with the condensing mirror provided on the second electrode side, a preliminary ionization unit that emits an electron beam through a transmission window is provided in the chamber on the first electrode side. Has been

EUV generator characterized by that.

[2] In the chamber 1, the gas inlet side and the exhaust side are electrically insulated by the insulating material,

An opening is provided in the chamber on the gas introduction side, and a preionization unit that radiates an electron beam into the chamber through the transmission window is provided in the opening.

The first window for applying a high voltage between the first electrode and the second electrode is connected so that the transmission window and the gas introduction side chamber 1 and the first electrode are electrically at the same potential. For 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. The second power supply is connected

The EUV generator according to claim 1, wherein: