Discharge electrode, method for manufacturing discharge electrode, and method for manufacturing electronic device

Abstract

A discharge electrode according to one aspect of the present disclosure is used in a gas laser device for exciting a fluorine-containing laser gas by discharging, the discharge electrode being provided with: a cathode having an elongated cathode discharge surface; and an anode having an elongated anode discharge surface, the anode being disposed in a posture in which the anode discharge surface faces the cathode discharge surface, a plurality of recesses being formed in an initial state on the cathode discharge surface, and a plurality of recesses being not formed in an initial state on the anode discharge surface.

Description

Technical Field

[0001] The present disclosure relates to a discharge electrode, a method for manufacturing the discharge electrode, and a method for manufacturing an electronic device. Background Art

[0002] In recent years, in semiconductor exposure devices, as semiconductor integrated circuits become smaller and more highly integrated, there is a demand for higher resolution. Therefore, the wavelength of light emitted from the exposure light source is being shortened. For example, as a gas laser device for exposure, a KrF excimer laser device that outputs a laser with a wavelength of about 248nm and an ArF excimer laser device that outputs a laser with a wavelength of about 193nm are used.

[0003] The spectral line width of the natural oscillation light of the KrF excimer laser device and the ArF excimer laser device is as wide as 350pm to 400pm. Therefore, if the projection lens is made of a material that allows ultraviolet rays such as KrF and ArF lasers to pass through, chromatic aberration may sometimes occur. As a result, the resolution may be reduced. Therefore, it is necessary to narrow the spectral line width of the laser output from the gas laser device to a level where chromatic aberration can be ignored. Therefore, in order to narrow the spectral line width, a narrowing module (Line Narrowing Module: LNM) including narrowing elements (etalon, grating, etc.) is sometimes provided in the laser resonator of the gas laser device. Hereinafter, a gas laser device with a narrowed spectral line width is referred to as a narrowed gas laser device.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2004-179599

[0007] Patent Document 2: Japanese Patent Application Publication No. 2004-146579 Summary of the invention

[0008] A discharge electrode according to one aspect of the present disclosure is used in a gas laser device, which excites a laser gas containing fluorine by discharge, wherein the discharge electrode comprises: a cathode having an elongated cathode discharge surface; and an anode having an elongated anode discharge surface, the anode being arranged with the anode discharge surface facing the cathode discharge surface, a plurality of depressions being formed on the cathode discharge surface in an initial state, and a plurality of depressions not being formed on the anode discharge surface in an initial state.

[0009] A discharge electrode according to one aspect of the present disclosure is used in a gas laser device, which excites a laser gas containing fluorine by discharge, wherein the discharge electrode comprises: a cathode having an elongated cathode discharge surface; and an anode having an elongated anode discharge surface, wherein the anode is arranged with the anode discharge surface facing the cathode discharge surface, and the cathode discharge surface has a plurality of depressions formed thereon in an initial state, and further, a coating is formed on the depressions.

[0010] A method for manufacturing a discharge electrode according to one aspect of the present disclosure is provided. The discharge electrode is used in a gas laser device that excites a laser gas containing fluorine by discharge. The discharge electrode comprises: a cathode having an elongated cathode discharge surface; and an anode having an elongated anode discharge surface, the anode being arranged with the anode discharge surface facing the cathode discharge surface. The method for manufacturing the discharge electrode comprises the following steps: a first step of forming a plurality of depressions on the cathode discharge surface; and a second step of forming a coating on the inner peripheral surface of the depressions.

[0011] A method for manufacturing an electronic device according to one aspect of the present disclosure includes the following steps: generating laser light using a gas laser device; outputting the laser light to an exposure device; and exposing the laser light to a photosensitive substrate in the exposure device to manufacture the electronic device, wherein the gas laser device uses a discharge electrode to excite a laser gas containing fluorine by discharge, and the discharge electrode comprises: a cathode having an elongated cathode discharge surface; and an anode having an elongated anode discharge surface, the anode being arranged with the anode discharge surface facing the cathode discharge surface, a plurality of depressions being formed on the cathode discharge surface in an initial state, and a plurality of depressions not being formed on the anode discharge surface in an initial state.

[0012] A method for manufacturing an electronic device according to one aspect of the present disclosure includes the following steps: generating laser light using a gas laser device; outputting the laser light to an exposure device; and exposing the laser light to a photosensitive substrate in the exposure device to manufacture the electronic device. The gas laser device uses a discharge electrode to excite a laser gas containing fluorine by discharge. The discharge electrode comprises: a cathode having an elongated cathode discharge surface; and an anode having an elongated anode discharge surface. The anode is arranged in a posture in which the anode discharge surface is opposite to the cathode discharge surface. The cathode discharge surface has a plurality of depressions formed on it in an initial state, and further, a coating is formed on the depressions. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings, merely as examples.

[0014] Figure 1 It is a side view schematically showing the structure of a gas laser device according to a comparative example.

[0015] Figure 2It is a cross-sectional view schematically showing the structure of a gas laser device according to a comparative example.

[0016] Figure 3 It is a schematic diagram of a discharge electrode of a comparative example.

[0017] Figure 4 This is a graph showing the change over time in the fluorine consumption of the laser gas.

[0018] Figure 5 This is a schematic diagram of the discharge electrode according to the first embodiment.

[0019] Figure 6 It is a diagram showing a depression on the cathode discharge surface of the discharge electrode according to the first embodiment.

[0020] Figure 7 It is a cross-sectional view of the cathode discharge surface.

[0021] Figure 8 This is a schematic diagram of the manufacturing process of a gas laser device.

[0022] Fig. 9 It is a diagram showing the step of forming the depressions on the cathode discharge surface.

[0023] Fig.10 It is a diagram showing the temporal change of the state of the cathode discharge surface.

[0024] Fig.11 It is a diagram showing the overall surface shape of the cathode discharge surface and the anode discharge surface.

[0025] Fig.12 It is a figure which shows the coating of the depression of the cathode discharge surface.

[0026] Fig.13 It is a figure which shows the order of a coating process.

[0027] Fig.14 This is a diagram showing an example of a discharge electrode according to the second embodiment.

[0028] Fig.15 This is a diagram showing another example of the discharge electrode according to the second embodiment.

[0029] Fig.16 This is a diagram schematically showing a configuration example of an exposure apparatus. DETAILED DESCRIPTION

[0030] <Content>

[0031] 1. Comparative Example

[0032] 1.1 Structure

[0033] 1.2 Action

[0034] 1.3 Topics

[0035] 2. First Implementation

[0036] 2.1 Structure and Action

[0037] 2.2 Manufacturing method of discharge electrode

[0038] 2.3 Function and effect

[0039] 2.4 Modification of the First Embodiment

[0040] 2.4.1 Modification 1 (Surface shape of cathode discharge surface)

[0041] 2.4.1.1 Relationship between the surface shape of the cathode discharge surface and the amount of cathode consumption 2.4.1.2 Relationship between the surface shape of the cathode discharge surface and the surface shape of the anode discharge surface 2.4.2 Modification 2 (depressed coating)

[0042] 2.4.2.1 Structure, function and effect of coating

[0043] 2.4.2.2 Coating formation method

[0044] 3. Second Implementation

[0045] 3.1 Structure

[0046] 3.2 Manufacturing method of discharge electrode

[0047] 3.3 Function and effect

[0048] 4. Other Modifications

[0049] 5. Method for manufacturing electronic devices

[0050] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The embodiments described below represent several examples of the present disclosure and do not limit the content of the present disclosure. In addition, the structures and actions described in the embodiments may not all be necessary as the structures and actions of the present disclosure. In addition, the same reference numerals are marked on the same components, and repeated descriptions are omitted.

[0051] 1. Comparative Example

[0052] First, comparative examples of the present disclosure are described. The comparative examples of the present disclosure are methods that the applicant recognizes are only known to the applicant, and are not publicly known examples recognized by the applicant himself.

[0053] 1.1 Structure

[0054] use Figure 1 as well as Figure 2 The structure of a gas laser device 2 according to a comparative example is schematically shown. Figure 1The structure of the gas laser device 2 is schematically shown. Figure 2 Observed from the Z direction Figure 1 2 is a cross-sectional view of a gas laser device 2. The gas laser device 2 is a discharge-excitation type gas laser device that excites laser gas by discharge, and is, for example, an excimer laser device.

[0055] exist Figure 1 In FIG. 1 , the traveling direction of the pulse laser light PL outputted from the gas laser device 2 is defined as the Z direction. The discharge direction described later is defined as the Y direction. In addition, the direction orthogonal to the Z direction and the Y direction is defined as the X direction.

[0056] The gas laser device 2 includes a laser chamber 10 , a charger 11 , a pulse power module (PPM) 12 , a pulse energy measurement unit 13 , a control unit 14 , a pressure sensor 17 , and a laser resonator. The laser resonator is composed of a narrowband module 15 and an output coupler (OC) 16 .

[0057] The laser chamber 10 is, for example, a metal container formed of aluminum metal with nickel plating applied on the surface. Figure 1 and Figure 2 As shown, a discharge electrode 20, a ground plate 21, wiring 22, a fan 23, a heat exchanger 24, a preionization discharge section 19, an electrical insulation guide 32, and a metal damper 33 are provided in the laser chamber 10. The preionization discharge section 19 includes a preionization outer electrode 19a, a dielectric tube 19b, and a preionization inner electrode 19c.

[0058] Laser gas as a laser medium is sealed in the laser chamber 10. The laser gas contains, for example, argon, krypton, xenon, etc. as a rare gas, neon, helium, etc. as a buffer gas, and fluorine as a halogen gas.

[0059] Furthermore, an opening is formed in the laser chamber 10. An electrical insulating plate 26 is provided to block the opening. A plurality of feedthroughs 25 are embedded in the electrical insulating plate 26. The PPM 12 is disposed on the electrical insulating plate 26. The laser chamber 10 is grounded.

[0060] The discharge electrode 20 is composed of a pair of electrodes, namely, a cathode 27 and an anode 28. The cathode 27 has a discharge surface 27A on one side, and the anode 28 has a discharge surface 28A on one side. The cathode 27 and the anode 28 are arranged in the laser chamber 10 so that the discharge surfaces 27A and the discharge surfaces 28A face each other. The space between the discharge surface 27A of the cathode 27 and the discharge surface 28A of the anode 28 is referred to as a discharge space 30. The surface of the cathode 27 opposite to the discharge surface 27A is supported by an electrical insulating plate 26. The surface of the anode 28 opposite to the discharge surface 28A is supported by a grounding plate 21. In this specification, in order to distinguish the discharge surface 27A of the cathode 27 from the discharge surface 28A of the anode 28, the discharge surface 27A is referred to as a cathode discharge surface 27A, and the discharge surface 28A is referred to as an anode discharge surface 28A.

[0061] The feed-through 25 is connected to the cathode 27. In addition, the feed-through 25 is connected to the PPM 12.

[0062] The ground plate 21 is connected to the laser chamber 10 via the wiring 22. The laser chamber 10 is grounded. The ground plate 21 is grounded via the wiring 22. The end portion of the ground plate 21 in the Z direction is fixed to the laser chamber 10.

[0063] The fan 23 is a cross-flow fan for circulating the laser gas in the laser chamber 10, and is disposed on the side opposite to the discharge space 30 with respect to the ground plate 21. The laser chamber 10 is connected to a motor 23a for rotationally driving the fan 23.

[0064] The laser gas blown out from the fan 23 flows into the discharge space 30. The flow direction of the laser gas flowing into the discharge space 30 is substantially parallel to the X direction. The laser gas flowing out of the discharge space 30 can be sucked into the fan 23 via the heat exchanger 24. The heat exchanger 24 performs heat exchange between the refrigerant supplied to the inside of the heat exchanger 24 and the laser gas.

[0065] The electric insulating guide 32 is arranged on the surface of the electric insulating plate 26 on the discharge space 30 side in a manner sandwiching the cathode 27. The electric insulating guide 32 is formed in a shape that guides the flow of the laser gas so that the laser gas from the fan 23 flows efficiently between the cathode 27 and the anode 28. The electric insulating guide 32 and the electric insulating plate 26 are formed of ceramics such as alumina (Al2O3) that has low reactivity with fluorine gas.

[0066] The metal damper 33 is disposed on the surface of the ground plate 21 on the discharge space 30 side so as to sandwich the anode 28. The metal damper 33 is formed of, for example, porous nickel metal having low reactivity with fluorine gas.

[0067] The laser chamber 10 is provided with a laser gas supply device and a laser gas exhaust device (not shown). The laser gas supply device includes a valve and a flow control valve, and is connected to a gas cylinder containing laser gas. The laser gas exhaust device includes a valve and an exhaust pump.

[0068] Windows 10a and 10b for emitting light generated in the laser chamber 10 to the outside are provided at the ends of the laser chamber 10. The laser chamber 10 is arranged so that the optical path of the optical resonator passes through the discharge space 30 and the windows 10a and 10b.

[0069] The narrowband module 15 includes a prism 15a and a grating 15b. The prism 15a widens the beam width of the light emitted from the laser chamber 10 through the window 10a and transmits the light toward the grating 15b.

[0070] The grating 15b is configured in a Littrow configuration in which the incident angle and the diffraction angle are the same. The grating 15b is a wavelength selection element that selectively extracts light near a specific wavelength according to the diffraction angle. The spectral line width of the light returned from the grating 15b to the laser chamber 10 via the prism 15a is narrowed.

[0071] The output coupling mirror 16 transmits a part of the light emitted from the laser chamber 10 through the window 10b, and reflects the other part to return to the laser chamber 10. The surface of the output coupling mirror 16 is coated with a partial reflection film.

[0072] Light emitted from the laser chamber 10 reciprocates between the narrowband module 15 and the output coupling mirror 16, and is amplified each time it passes through the discharge space 30. A portion of the amplified light is output as pulse laser light PL via the output coupling mirror 16. The pulse laser light PL is an example of "laser" in the technology disclosed herein.

[0073] The pulse energy measurement unit 13 is disposed on the optical path of the pulse laser light PL outputted via the output coupling mirror 16. The pulse energy measurement unit 13 includes a beam splitter 13a, a focusing optical system 13b, and a light sensor 13c.

[0074] The beam splitter 13a transmits the pulsed laser PL with high transmittance, and reflects a part of the pulsed laser PL toward the focusing optical system 13b. The focusing optical system 13b focuses the light reflected by the beam splitter 13a on the light receiving surface of the optical sensor 13c. The optical sensor 13c measures the pulse energy of the light focused on the light receiving surface, and outputs the measured value to the control unit 14.

[0075] The pressure sensor 17 detects the gas pressure in the laser chamber 10 and outputs the detected value to the control unit 14. The control unit 14 determines the gas pressure of the laser gas in the laser chamber 10 based on the detected value of the gas pressure and the charging voltage of the charger 11.

[0076] The charger 11 is a high voltage power source that supplies a charging voltage to a charging capacitor included in the PPM 12. The PPM 12 includes a solid switch SW controlled by the control unit 14. When the solid switch SW changes from off to on, the PPM 12 generates a high voltage pulse based on the electric energy retained in the charging capacitor and applies it to the discharge electrode 20.

[0077] The control unit 14 is a processor that sends and receives various signals to and from the exposure device control unit 110 provided in the exposure device 100. For example, the target pulse energy of the pulse laser PL output to the exposure device 100 and signals related to the target oscillation timing are sent from the exposure device control unit 110 to the control unit 14.

[0078] The control unit 14 centrally controls the operation of each component of the gas laser device 2 based on various signals sent from the exposure device control unit 110 , the measured value of the pulse energy, the detected value of the gas pressure, and the like.

[0079] Figure 3 2 shows the structure of the discharge electrode 20. Figure 3 In the figure, the pre-ionization discharge unit 19, the electrical insulation guide 32, the metal damper 33, etc. are omitted.

[0080] The cathode 27 and the anode 28 are substantially rectangular parallelepiped shapes with the Z direction as the length direction. The cathode discharge surface 27A and the anode discharge surface 28A are also elongated shapes with the Z direction as the length direction. The cathode discharge surface 27A and the anode discharge surface 28A each have an X direction orthogonal to the length direction as the width direction, and are opposed in the Y direction. As an example, the cathode 27 and the anode 28 are formed of metal such as copper.

[0081] The surface shape of the cathode discharge surface 27A is a plane or a curved surface. When the cathode discharge surface 27A is a curved surface, the curved surface is a curved surface that is convex toward the opposite anode discharge surface 28A. The cross-sectional shape of the cathode discharge surface 27A in the width direction, that is, the cross-sectional shape on the XY plane, is a straight line when the cathode discharge surface 27A is a plane, and is an ellipse or other curved line when the cathode discharge surface 27A is a curved surface. The cathode discharge surface 27A is formed by a smooth surface without bumps in the initial state. Here, the initial state refers to the state of the stage before the laser chamber 10 is assembled using the discharge electrode 20 and other components in the device manufacturing process of the gas laser device 2. The details of the stage before assembly will be described later.

[0082] The anode discharge surface 28A is also the same as the cathode discharge surface 27A. That is, the surface shape of the anode discharge surface 28A is a plane or a curved surface convex toward the cathode discharge surface 27A, and the cross-sectional shape is also composed of a straight line or an ellipse or other curved line. In addition, the anode discharge surface 28A is also formed by a smooth surface without concavities and convexities in the initial state.

[0083] 1.2 Action

[0084] The control unit 14 controls the laser gas supply device to supply the laser gas into the laser chamber 10, and drives the motor 23a to rotate the fan 23. Thus, the laser gas in the laser chamber 10 circulates.

[0085] The control unit 14 receives a signal related to the target pulse energy Et and the target oscillation timing transmitted from the exposure device control unit 110 .

[0086] The control unit 14 sets a charging voltage Vhv corresponding to the target pulse energy Et for the charger 11. The control unit 14 stores the value of the charging voltage Vhv set for the charger 11. The control unit 14 operates the solid-state switch SW of the PPM 12 in synchronization with the target oscillation timing.

[0087] When the solid switch SW of the PPM 12 changes from off to on, a voltage is applied between the preionization inner electrode 19c and the preionization outer electrode 19a of the preionization discharge section 19 and between the cathode 27 and the anode 28. As a result, corona discharge is generated in the preionization discharge section 19, generating UV (Ultraviolet) light. The laser gas in the discharge space 30 is irradiated with UV light, so that the laser gas is preionized.

[0088] Thereafter, when the voltage between the cathode 27 and the anode 28 reaches the insulation breakdown voltage, a main discharge is generated in the discharge space 30. If the discharge direction of the main discharge is set as the direction of electron flow, the discharge direction is from the cathode 27 to the anode 28. When the main discharge is generated, the laser gas in the discharge space 30 is excited to emit light. The main discharge is an arc discharge, hereinafter referred to as discharge.

[0089] The metal damper 33 prevents the acoustic wave generated by the discharge from being reflected and returning to the discharge space 30. In addition, by circulating the laser gas in the laser chamber 10, the discharge product generated in the discharge space 30 moves to the downstream side.

[0090] The light emitted from the laser gas is reflected by the narrowband module 15 and the output coupling mirror 16 and reciprocates in the laser resonator, thereby performing laser oscillation. The light narrowbanded by the narrowband module 15 is output from the output coupling mirror 16 as pulsed laser light PL.

[0091] A part of the pulse laser light PL outputted from the output coupling mirror 16 enters the pulse energy measuring unit 13. The pulse energy measuring unit 13 measures the pulse energy E of the incident pulse laser light PL and outputs the measured value to the control unit 14.

[0092] The control unit 14 stores the measured value of the pulse energy E measured by the pulse energy measuring unit 13. The control unit 14 calculates the difference ΔE between the measured value of the pulse energy E and the target pulse energy Et. The control unit 14 performs feedback control on the charging voltage Vhv based on the difference ΔE so that the measured value of the pulse energy E becomes the target pulse energy Et.

[0093] When the charging voltage Vhv is higher than the maximum value of the allowable range, the control unit 14 controls the laser gas supply device to supply laser gas to the laser chamber 10 until the pressure reaches a predetermined value. When the charging voltage Vhv is lower than the minimum value of the allowable range, the control unit 14 controls the laser gas exhaust device to exhaust the laser gas from the laser chamber 10 until the pressure reaches a predetermined value.

[0094] 1.3 Topics

[0095] One of the factors that determines the durability of the laser chamber 10 is the consumption of the cathode 27. The cause of the consumption of the cathode 27 is presumed to be as follows. When the discharge starts, the ionized particles in the laser gas collide with the cathode discharge surface 27A, and copper, which is the material of the cathode 27, is ejected from the cathode discharge surface 27A. It is believed that due to such a phenomenon such as sputtering on the cathode discharge surface 27A, the cathode discharge surface 27A is physically cut, and the cathode 27 is consumed.

[0096] Figure 4 is the fluorine content in the laser gas immediately after the laser chamber 10 starts to operate. Figure 4 A graph showing the time-dependent changes in the consumption of (represented by F2 in FIG. 1 ). Figure 4 The horizontal axis is the working time of the laser chamber 10, and the vertical axis is the fluorine consumption. Figure 4 As shown in the middle dotted rectangle, the fluorine consumption is relatively large in the initial stage of operation including just after the operation starts. Then, as time passes, the fluorine consumption decreases, and soon enters a stable period with low fluorine consumption. It is estimated that there is a positive correlation between the fluorine consumption and the consumption of the cathode 27. This is because the copper ejected from the cathode discharge surface 27A during discharge is dusted and combined with the fluorine in the laser gas. This is because the fluorine in the laser gas is consumed by combining with such dusted copper.

[0097] A large amount of fluorine consumed in the laser gas means a large amount of copper dust generated, that is, a large amount of cathode discharge surface 27A is cut, and cathode 27 is consumed rapidly. Figure 4 When estimating the temporal change of the fluorine consumption shown in FIG. 1 , it is considered that the consumption of the cathode 27 is large at the initial stage of the operation, but gradually decreases as the operation time passes and stabilizes at a state smaller than that at the initial stage of the operation.

[0098] In order to extend the life of the laser chamber 10 , it is required to reduce the consumption of the cathode 27 at the initial stage of operation.

[0099] 2. First Implementation

[0100] 2.1 Structure and Action

[0101] The discharge electrode 20 of the first embodiment of the present disclosure is also used in the gas laser device 2 in the same manner as the discharge electrode 20 of the comparative example. The gas laser device 2 using the discharge electrode 20 of the first embodiment has the same structure as the gas laser device 2 of the comparative example except that the structure of the discharge electrode 20 is different, and operates in the same manner.

[0102] Figure 5 and Figure 6 The structure of the discharge electrode 20 of the first embodiment is schematically shown. Figure 6 In the figure, reference numeral AR1 indicates a part of the discharge surface 27A. Reference numeral AR2 indicates a part of the discharge surface 28A. As shown in the enlarged view of region AR1, the discharge electrode 20 of this embodiment has a plurality of depressions 29 formed on the cathode discharge surface 27A in the initial state (see Figure 6 Here, the plurality of depressions 29 refers to a density of 100 / mm 2 The hatching of the cathode discharge surface 27A indicates a region where the depressions 29 are formed. In the present embodiment, a plurality of depressions 29 are formed over the entire region of the cathode discharge surface 27A.

[0103] On the other hand, as shown in the enlarged view of the region AR2, the anode discharge surface 28A has no depressions 29 in the initial state. More specifically, the anode discharge surface 28A is a smooth surface having no depressions 29 and a surface roughness Ra of less than 25.

[0104] like Figure 6 As shown, in this embodiment, the planar shape of the recess 29 is circular. Figure 7 An enlarged view showing a cross section in the width direction of the cathode discharge surface 27A. In the present embodiment, the diameter DM of the recess 29 is 20 μm to 100 μm, and the depth DP of the recess 29 is 5 μm to 30 μm. In addition, the inner circumferential surface 29a of the recess 29 is a curved surface. Preferably, the shape of the inner circumferential surface 29a is a spherical surface. In addition, the plurality of recesses 29 are regularly arranged. In the present embodiment, the arrangement of the plurality of recesses 29 is a square arrangement in which the longitudinal and lateral intervals PT of adjacent recesses 29 are equally spaced.

[0105] The width of the cathode discharge surface 27A is about several mm. The number of the depressions 29 per unit area on the cathode discharge surface 27A is 100 / mm. 2 More than, preferably 1000 pieces / mm 2 More than 3000 pieces / mm 2Furthermore, it is preferable that the depressions 29 are formed at a uniform density over the entire area of ​​the cathode discharge surface 27A.

[0106] The cathode discharge surface 27A is a smooth surface before the recesses 29 are formed, so the periphery of the recesses 29 becomes a convex portion 31 that is relatively higher than the recesses 29 by forming a plurality of recesses 29. In this way, the cathode discharge surface 27A is formed with fine concavities and convexities consisting of a plurality of recesses 29 and the convex portions 31 around the recesses 29.

[0107] Figure 8 The following is an overview of the manufacturing process of the gas laser device 2. Figure 8 As shown, the device manufacturing process includes a component manufacturing process of manufacturing components such as the discharge electrode 20 and a device assembling process of assembling the manufactured components. In the component manufacturing process, the depression 29 is formed on the cathode discharge surface 27A. On the other hand, the depression 29 is not formed on the anode discharge surface 28A.

[0108] In the device assembly process, the components such as the discharge electrode 20 manufactured in the component manufacturing process are supplied, and the laser chamber 10 is assembled using the supplied components such as the discharge electrode 20. The stage before assembly refers to the stage after the discharge electrode 20 is manufactured in the component manufacturing process and before the laser chamber 10 is assembled in the device assembly process. The state of the discharge electrode 20 at this stage is the "initial state" of the technology disclosed in the present invention. That is, in the initial state, the discharge electrode 20 of the first embodiment has a plurality of recesses 29 formed on the cathode discharge surface 27A, and no plurality of recesses 29 are formed on the anode discharge surface 28A.

[0109] 2.2 Manufacturing method of discharge electrode

[0110] Fig. 9 2 shows a depression forming process for forming depressions 29 on the cathode discharge surface 27A. In the present embodiment, as an example, the depression forming process is performed by etching as follows. First, in step S10, a photoresist is uniformly applied to the cathode discharge surface 27A of the cathode 27. A mask pattern having the shape, size, and interval of a plurality of depressions 29 is transferred to the applied photoresist by exposure to form a mask 51. Thus, a mask 51 having a plurality of holes 51a corresponding to the shape, size, and interval of the plurality of depressions 29 is formed.

[0111] In the etching of step S20, the etching liquid 52 is blown to the cathode discharge surface 27A on which the mask 51 is formed, and only the portion corresponding to the plurality of holes 51a of the mask 51 is etched in the cathode discharge surface 27A. As a result, a plurality of recesses 29 corresponding to the arrangement pattern of the holes 51a of the mask 51 are formed in the cathode discharge surface 27A. After the etching of step S20 is completed, the mask 51 is removed from the cathode discharge surface 27A in step S30. Through such a recess forming process, a plurality of recesses 29 are formed in the cathode discharge surface 27A.

[0112] 2.3 Function and effect

[0113] Fig.10 In addition to expressing Figure 4 In addition to the graph showing the temporal change of fluorine consumption shown in FIG. 1 , the temporal change of the cathode discharge surface 27A which is smooth in the initial state as in the comparative example is also shown. Fig.10 In FIG. 1 , region AR3 represents a part of the smooth cathode discharge surface 27A of the comparative example, and the enlarged view of region AR3 represents the state when the gas laser device 2 is actually operated. The enlarged view on the left side of region AR3 represents the state at the beginning of the operation when the fluorine consumption is high, and the enlarged view on the right side of region AR3 represents the state in the stable period when the fluorine consumption is reduced.

[0114] like Fig.10 As shown in FIG. 1 , even if the cathode discharge surface 27A is a smooth surface at the beginning of the operation, when the consumption of the cathode 27 due to discharge progresses and reaches the stable period, it becomes a state where fine concavities and convexities consisting of the concavities 56 and the convexities 57 around them are formed. As described above, in the stable period, the consumption of the cathode 27 is also less than that at the beginning of the operation. If these results are examined, it is considered that the state of the cathode discharge surface 27A is also related to the amount of consumption of the cathode 27. When the cathode discharge surface 27A has fine concavities and convexities caused by the concavities 29, the consumption of the cathode 27 is also reduced. In principle, it is presumed that the discharge is dispersed in the cathode discharge surface 27A due to the fine concavities and convexities, and the consumption of the cathode 27 is reduced.

[0115] As described above, in the discharge electrode 20 of the first embodiment, a plurality of depressions 29 are formed on the cathode discharge surface 27A in the initial state. Therefore, the state of the cathode discharge surface 27A is close to the state of the stable period in which the consumption of the cathode 27 is small (see Fig.10 As a result, cathode discharge surface 27A enters a stable period in which the consumption of cathode 27 is small from the initial stage of operation, so the consumption of cathode 27 at the initial stage of operation is reduced. In addition, since the consumption of cathode 27 is reduced, the amount of copper and the like combined with fluorine in the laser gas is also reduced, so it is also expected that the consumption of fluorine in the laser gas will be reduced.

[0116] On the other hand, the polarity of the anode discharge surface 28A is different from that of the cathode discharge surface 27A, so it is believed that consumption caused by a phenomenon such as sputtering will not occur. In the anode discharge surface 28A, ionized fluorine in the laser gas is attracted due to the polarity. As a result, fluorine enters the anode discharge surface 28A, and the anode discharge surface 28A is directly fluorinated. Therefore, for the anode discharge surface 28A, the depression 29 for the purpose of reducing the consumption of the anode 28 is not required. In addition, in the case where the depression 29 is formed on the anode discharge surface 28A, the surface area of ​​the anode discharge surface 28A increases, and the fluorinated area may also increase. When the fluorination of the anode discharge surface 28A progresses, the life is also reduced. Therefore, by not forming the depression 29 on the anode discharge surface 28A, the reduction in the life of the anode discharge surface 28A can be suppressed. It is further preferred that the anode discharge surface 28A does not have a depression 29, and is preferably a smooth surface with a surface roughness Ra of less than 25 as in the present embodiment. Thus, compared with the case where the surface roughness Ra is 25 or more, the surface area of ​​the anode discharge surface 28A is further reduced, and thus a reduction in the life can be further suppressed.

[0117] Furthermore, the depressions 29 of the cathode discharge surface 27A have a diameter DM in the range of 20 μm to 100 μm, a depth DP in the range of 5 μm to 30 μm, and a number of 1000 / mm. 2 Above, preferably 3000 pieces / mm 2 The above number per unit area is close to the state of stable period (refer to Fig.10 Thus, the state of the cathode discharge surface 27A can be made closer to the state of the stable period, so it is expected that the consumption of the cathode 27 at the initial stage of operation can be further reduced.

[0118] Furthermore, by regularly arranging the recesses 29, it is possible to suppress the concentration of the electric field. When the electric field is concentrated, arc discharge may occur. By suppressing the concentration of the electric field, the generation of arc discharge can be suppressed, and the stability of the discharge is improved. Furthermore, by forming the recesses 29 in the entire area of ​​the cathode discharge surface 27A, the concentration of the electric field can be further suppressed. Thus, the stability of the discharge is further improved. In addition, by suppressing the concentration of the electric field, it is also possible to expect the effect of reducing the local variation of the cathode consumption in the cathode discharge surface 27A.

[0119] Furthermore, by making the inner peripheral surface 29a of the recess 29 into a curved surface shape, the concentration of the electric field can be further suppressed compared with a shape with corners such as a triangular cross-sectional shape, and thus the stability of the discharge is further improved.

[0120] In addition, as a method for forming the recess 29, Fig. 9The formation method based on etching shown in the figure can also be a method other than etching. For example, the depression 29 can also be formed by methods such as sandblasting, laser processing, and electric discharge processing. However, if the depression 29 is formed by sandblasting, the inner peripheral surface 29a of the depression 29 does not have a curved surface shape, and sometimes it is easy to form an angle on the inner peripheral surface 29a. If the inner peripheral surface 29a has an angle, it also becomes a cause of unstable discharge. Therefore, as a method for forming the depression 29, etching is preferred.

[0121] 2.4 Modification of the First Embodiment

[0122] 2.4.1 Modification 1 (Surface shape of cathode discharge surface)

[0123] Fig.11 The example shown is an example in which the overall surface shape of the cathode discharge surface 27A is set to be a curved surface that is convex toward the anode discharge surface 28A in the width direction orthogonal to the length direction. In addition, in this embodiment, the cross-sectional shape of the cathode discharge surface 27A in the width direction is an ellipse with a ratio of a short radius to a long radius, that is, an aspect ratio of 1 / 5 or less. That is, Fig.11 As shown, when the short radius of the ellipse of the cathode discharge surface 27A is SRk and the long radius is LRk, the overall surface shape of the cathode discharge surface 27A satisfies the condition of SRk / LRk≤1 / 5. As an example, SRk / LRk is about 1 / 8.

[0124] It should be noted that the overall surface shape refers to the outer shape when the cross-sectional shape is macroscopically observed without considering fine concavities and convexities such as the concavities 29. When microscopically observed, the cathode discharge surface 27A of the modification example 1 also has fine concavities and convexities caused by the concavities 29, but Fig.11 The fine unevenness is omitted in the illustration.

[0125] 2.4.1.1 Relationship between the surface shape of the cathode discharge surface and the cathode consumption

[0126] Even if the overall surface shape of the cathode discharge surface 27A is a convex surface with a large curvature at the beginning of operation, it becomes a convex surface with a small curvature and approaches a plane during the stable period when the consumption of the cathode 27 is small. In principle, when the cathode discharge surface 27A is set as a convex surface with a small curvature, it is presumed that the discharge is easily concentrated on the convex portion, and the consumption of the convex portion progresses and approaches a plane. Therefore, it is believed that by making the overall shape of the cathode discharge surface 27A close to a plane from the beginning of operation, the consumption of the cathode 27 at the beginning of operation can be reduced. Fig.11 As shown in FIG. 1 , by making the overall surface shape of the cathode discharge surface 27A a convex surface with a small curvature, the consumption of the cathode 27 in the initial stage of the operation can be reduced.

[0127] In addition, the cathode discharge surface 27A may be a flat surface instead of a curved surface. In this way, the consumption of the cathode 27 at the beginning of operation can also be reduced. However, when the cathode discharge surface 27A is a flat surface, corners are easily formed at both ends in the width direction, so discharge concentration may occur in these parts. Therefore, if Fig.11 As shown in FIG. 1 , the cathode discharge surface 27A is preferably a convex curved surface with a small curvature.

[0128] 2.4.1.2 Relationship between the surface shape of the cathode discharge surface and the surface shape of the anode discharge surface

[0129] In addition, if Fig.11 As shown in FIG. 1 , the overall surface shape of the anode discharge surface 28A is also similar to that of the cathode discharge surface 27A, and is preferably a curved surface convex toward the cathode discharge surface 27A in the width direction, and the cross-sectional shape is an ellipse. Furthermore, it is preferred that the aspect ratio of the ellipse in the anode discharge surface 28A is greater than the aspect ratio of the ellipse in the cathode discharge surface 27A. That is, Fig.11 As shown, when the short radius of the ellipse of the anode discharge surface 28A is SRa and the long radius is LRa, it is preferable to satisfy the condition of SRa / LRa>SRk / LRk. The reason is as follows.

[0130] In the cathode discharge surface 27A and the anode discharge surface 28A, if the surface shapes of both are close to a plane, corners are likely to be generated at both ends in the width direction. Therefore, it is considered that the discharge is likely to be concentrated at the corners, and the discharge is likely to become unstable. If the discharge becomes unstable, there is a possibility that the beam profile of the pulsed laser PL becomes uneven, or the consumption of the discharge electrode 20 increases. As described above, from the viewpoint of reducing the consumption of the cathode 27, it is preferable to make the cathode discharge surface 27A close to a plane. For the anode discharge surface 28A used in combination with such a cathode discharge surface 27A close to a plane, from the viewpoint of ensuring the stability of the discharge, it is preferably set to a convex curved surface with a curvature larger than that of the cathode discharge surface 27A. For example, when the aspect ratio (SRk / LRk) of the ellipse of the cathode discharge surface 27A is less than 1 / 5, the aspect ratio (SRa / LRa) of the ellipse of the anode discharge surface 28A is about 2 / 3.

[0131] 2.4.2 Modification 2 (depressed coating)

[0132] 2.4.2.1 Structure, function and effect of coating

[0133] like Fig.12As shown in the modification example, a coating 36 may be formed on the recess 29. The material of the coating 36 is a high-resistance material having a greater resistance than the material of the cathode 27, an insulating material, and a material having a low reactivity with fluorine. As such a material, for example, fluorides such as copper fluoride (CuF2) and nickel fluoride (NiF2) are preferred. In addition, ceramics such as aluminum oxide (Al2O3) and zirconium oxide (ZrO2) having a low reactivity with fluorine may also be used. In the cathode discharge surface 27A, in order to ensure a discharge area, the coating 36 is formed only on the inner peripheral surface 29a of the recess 29, and is not formed on the convex portion 31 around the recess 29.

[0134] In the cathode discharge surface 27A, the resistance of the coating 36 is greater than the resistance of the convex portion 31, so the discharge in the recess 29 is suppressed, and the discharge is performed in the convex portion 31. Since the discharge in the recess 29 is suppressed, the consumption of the cathode 27 can be further reduced. In addition, when the discharge is performed in the recess 29, the discharge sometimes becomes uneven. By forming the coating 36 in the recess 29, the discharge generation site is limited to the convex portion 31, and it can also be expected that the stability of the discharge is improved.

[0135] 2.4.2.2 Coating formation method

[0136] As an example, through Fig.13 The coating process shown forms a coating 36. Fig.13 The coating process shown is an example of using fluoride as the material of the coating layer 36. Fig.13 As shown, the coating process includes step S100 of fluoriding the entire surface of cathode discharge surface 27A and step S200 of removing coating 36 of protrusion 31 as unnecessary portion by grinding.

[0137] 3. Second Implementation

[0138] 3.1 Structure

[0139] Next, Fig.14 and Fig.15 The discharge electrode 20 of the second embodiment shown in FIG. 2 is the same as the discharge electrode 20 of the first embodiment in that the cathode discharge surface 27A has the recesses 29. In the second embodiment, the size and number of the recesses 29, the shape of the inner circumferential surface 29a of the recesses 29, the overall surface shape of the cathode discharge surface 27A, etc. are also the same as those of the first embodiment.

[0140] The first difference between the discharge electrode 20 of the first embodiment and the discharge electrode 20 of the second embodiment is that, in the discharge electrode 20 of the first embodiment, the coating 36 formed on the recess 29 is an optional structure, whereas, in the discharge electrode 20 of the second embodiment, the coating 36 is an essential structure.

[0141] The second difference is that, while the discharge electrode 20 of the first embodiment requires that the recess 29 is not formed on the anode discharge surface 28A, the discharge electrode 20 of the second embodiment may or may not have the recess 29 formed on the anode discharge surface 28A. Fig.14 The example shown is an example in which the depression 29 is not formed on the anode discharge surface 28A. Fig.15 The example shown is an example in which the depressions 29 are formed on the anode discharge surface 28A. Of course, the depressions 29 having a size and number different from those of the depressions 29 may be formed on the anode discharge surface 28A. In addition, in the second embodiment, the surface roughness Ra of the anode discharge surface 28A may be 25 or more. That is, in the discharge electrode 20 of the second embodiment, the anode discharge surface 28A may be in any form.

[0142] 3.2 Manufacturing method of discharge electrode

[0143] The method for manufacturing the discharge electrode 20 of the second embodiment is similar to that shown in the example Fig. 9 and Fig.13 The method for manufacturing the discharge electrode 20 of the first embodiment and its modified example is the same.

[0144] 3.3 Function and effect

[0145] In the discharge electrode 20 of the second embodiment, the effects of the plurality of depressions 29 and the coating 36 formed on the cathode discharge surface 27A are similar to those of the first embodiment. Fig.12 The effects described in the illustrated modification are the same.

[0146] 4. Other Modifications

[0147] The gas laser device 2 using the discharge electrode 20 of the first and second embodiments is a narrowband laser device, but is not limited thereto and may be a gas laser device that outputs natural oscillation light. For example, a high reflection mirror may be provided instead of the narrowband module 15 .

[0148] In the first and second embodiments, the gas laser device 2 is an excimer laser device, but it may be an F2 molecular laser device using a laser gas containing fluorine gas and a buffer gas instead. That is, the gas laser device 2 of the present disclosure may be a gas laser device that excites the laser gas containing fluorine by discharge.

[0149] 5. Method for manufacturing electronic devices

[0150] Fig.16 The following is a schematic diagram of a configuration example of an exposure device 100. The exposure device 100 includes an illumination optical system 104 and a projection optical system 106. The illumination optical system 104 illuminates a mask pattern of a mask (not shown) arranged on the mask stage RT using, for example, pulsed laser light PL incident from a gas laser device 2. The projection optical system 106 projects the pulsed laser light PL transmitted through the mask in a reduced size and forms an image on a workpiece (not shown) arranged on a workpiece stage WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with a photoresist.

[0151] The exposure device 100 causes the mask stage RT and the work stage WT to move in parallel synchronously, thereby exposing the workpiece to the pulsed laser PL reflecting the mask pattern. After the mask pattern is transferred to the semiconductor wafer through the above exposure process, a semiconductor device can be manufactured through multiple processes. A semiconductor device is an example of an "electronic device" in the present disclosure.

[0152] Fig.16 The gas laser device 2 shown uses the discharge electrode 20 of the first embodiment or the second embodiment.

[0153] Furthermore, the gas laser device 2 is not limited to the manufacture of electronic devices, but can also be used for laser processing such as hole drilling.

[0154] The above description is intended to be illustrative rather than limiting, and therefore, it is obvious to those skilled in the art that modifications may be made to the various embodiments of the present disclosure without departing from the scope of the appended claims.

[0155] The terms used in this specification and the appended claims should be interpreted as "non-limiting" terms. For example, the terms "including" or "comprising" should be interpreted as "not limited to the parts recorded as including". The term "having" should be interpreted as "not limited to the parts recorded as having". In addition, the phrase "one" recorded in this specification and the appended claims should be interpreted as "at least one" or "one or more". In addition, the terms "at least one of A, B and C" should be interpreted as "A", "B", "C", "A+B", "A+C", "B+C" or "A+B+C", and should also be interpreted to include their combinations with contents other than "A", "B" and "C".

Claims

1. A discharge electrode used in a gas laser device that excites a laser gas containing fluorine by discharge, wherein: The discharge electrode comprises: a cathode having a cathode discharge surface of an elongated shape; and an anode having an elongated anode discharge surface, wherein the anode discharge surface is arranged in a posture where the anode discharge surface faces the cathode discharge surface, A plurality of depressions are formed on the cathode discharge surface in an initial state, and a plurality of depressions are not formed on the anode discharge surface in an initial state.

2. The discharge electrode according to claim 1, wherein: The diameter of the depression is 20 μm to 100 μm, and the depth is 5 μm to 30 μm.

3. The discharge electrode according to claim 1, wherein: The number of the depressions is 1000 / mm 2 above.

4. The discharge electrode according to claim 3, wherein: The number of the depressions is 3000 / mm 2 above.

5. The discharge electrode according to claim 1, wherein The depressions are regularly arranged.

6. The discharge electrode according to claim 1, wherein The recess is formed over the entire area of ​​the cathode discharge surface.

7. The discharge electrode according to claim 1, wherein: The inner peripheral surface of the recess is a curved surface.

8. The discharge electrode according to claim 1, wherein The anode discharge surface is a smooth surface with a surface roughness Ra less than 25.

9. The discharge electrode according to claim 1, wherein: The cathode discharge surface has an overall surface shape that is a curved surface that is convex toward the anode discharge surface in a width direction orthogonal to the length direction, and a cross-sectional shape in the width direction is an ellipse with a ratio of a short radius to a long radius, i.e., an aspect ratio, of 1 / 5 or less.

10. The discharge electrode according to claim 9, wherein: The overall surface shape of the anode discharge surface is a curved surface convex toward the cathode discharge surface in the width direction, and the cross-sectional shape in the width direction is an ellipse, In the anode discharge surface, the aspect ratio of the ellipse is greater than the aspect ratio of the ellipse of the cathode discharge surface.

11. The discharge electrode according to claim 1, wherein The cathode discharge surface has a plane surface.

12. The discharge electrode according to claim 1, wherein A coating layer is formed in the depression.

13. The discharge electrode according to claim 12, wherein: The coating is fluoride.

14. A discharge electrode used in a gas laser device that excites laser gas containing fluorine by discharge, wherein: The discharge electrode comprises: a cathode having a cathode discharge surface of an elongated shape; and an anode having an elongated anode discharge surface, wherein the anode discharge surface is arranged in a posture where the anode discharge surface faces the cathode discharge surface, On the cathode discharge surface, a plurality of depressions are formed in an initial state. Furthermore, a coating is formed on the depression.

15. The discharge electrode according to claim 14, wherein: The coating is fluoride.

16. The discharge electrode according to claim 14, wherein The diameter of the depression is 20 μm to 100 μm, and the depth is 5 μm to 30 μm.

17. The discharge electrode according to claim 14, wherein: The number of the depressions is 1000 / mm 2 above.

18. The discharge electrode according to claim 14, wherein The number of the depressions is 3000 / mm 2 above.

19. The discharge electrode according to claim 14, wherein: The depressions are regularly arranged.

20. The discharge electrode according to claim 14, wherein: The recess is formed over the entire area of ​​the cathode discharge surface.

21. The discharge electrode according to claim 14, wherein The concave surface of the depression is a curved surface.

22. The discharge electrode according to claim 14, wherein: The cathode discharge surface has an overall surface shape that is a curved surface that is convex toward the anode discharge surface in a width direction orthogonal to the length direction, and a cross-sectional shape in the width direction is an ellipse with a ratio of a short radius to a long radius, i.e., an aspect ratio, of 1 / 5 or less.

23. The discharge electrode according to claim 14, wherein: The cathode discharge surface has a plane surface.

24. A method for manufacturing a discharge electrode, the discharge electrode being used in a gas laser device, the gas laser device exciting a laser gas containing fluorine by discharge, the discharge electrode comprising: a cathode having an elongated cathode discharge surface; and an anode having an elongated anode discharge surface, the anode being arranged in a posture where the anode discharge surface faces the cathode discharge surface, wherein: The manufacturing method of the discharge electrode comprises the following steps: A first step of forming a plurality of depressions on the cathode discharge surface; and The second step is to form a coating on the inner peripheral surface of the recess.

25. The method for manufacturing a discharge electrode according to claim 24, wherein: In the first process, the recess is formed by etching.

26. A method for manufacturing an electronic device, wherein: The manufacturing method of the electronic device comprises the following steps: Using a gas laser device to generate laser light; outputting the laser light to an exposure device; and exposing the photosensitive substrate to the laser in the exposure device to manufacture an electronic device, The gas laser device uses a discharge electrode to excite a laser gas containing fluorine by discharge. The discharge electrode comprises: a cathode having a cathode discharge surface of an elongated shape; and an anode having an elongated anode discharge surface, wherein the anode discharge surface is arranged in a posture where the anode discharge surface faces the cathode discharge surface, A plurality of depressions are formed on the cathode discharge surface in an initial state, and a plurality of depressions are not formed on the anode discharge surface in an initial state.

27. A method for manufacturing an electronic device, wherein: The manufacturing method of the electronic device comprises the following steps: Using a gas laser device to generate laser light; outputting the laser light to an exposure device; and exposing the photosensitive substrate to the laser in the exposure device to manufacture an electronic device, The gas laser device uses a discharge electrode to excite a laser gas containing fluorine by discharge. The discharge electrode comprises: a cathode having a cathode discharge surface of an elongated shape; and an anode having an elongated anode discharge surface, wherein the anode discharge surface is arranged in a posture where the anode discharge surface faces the cathode discharge surface, The cathode discharge surface is formed with a plurality of depressions in an initial state. Furthermore, a coating is formed on the depression.

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