Gas laser device and manufacturing method for electronic device

Abstract

To provide a gas laser device capable of burst output without extraction, and a manufacturing method for an electronic device.SOLUTION: A gas laser device for discharging and exciting laser gas passing through a discharge space between a first discharge electrode and a second discharge electrode, includes: a plate that supports the first discharge electrode; a guide member that is disposed on the plate and guides the laser gas to the discharge space; a dielectric pipe that is disposed between the guide member and the first discharge electrode apart from the plate and the first discharge electrode; a first path including the guide member, to which a part of the laser gas flows as a branch; a second path including the dielectric pipe and the plate, to which a part of the branch flowing out of the first path flows; and a third path including the dielectric pipe and the first discharge electrode and guiding the branch flowing out of the second path toward an upstream side of the laser gas relative to the discharge space.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present disclosure relates to gas laser apparatus and methods for manufacturing electronic devices. [Background technology]

[0002] In recent years, semiconductor exposure devices have been required to improve their resolution in response to the miniaturization and high integration of semiconductor integrated circuits. To this end, the wavelength of light emitted from exposure light sources has been shortened. For example, KrF excimer laser devices, which output laser light with a wavelength of approximately 248 nm, and ArF excimer laser devices, which output laser light with a wavelength of approximately 193 nm, are used as gas laser devices for exposure.

[0003] The spectral linewidth of the spontaneously oscillating light from KrF excimer laser devices and ArF excimer laser devices is as wide as 350 to 400 pm. Therefore, if a projection lens is constructed using a material that transmits ultraviolet light, such as KrF and ArF laser light, chromatic aberration may occur. As a result, resolution may decrease. Therefore, it is necessary to narrow the spectral linewidth of the laser light output from the gas laser device to a level where chromatic aberration is negligible. Therefore, a line narrowing module (LNM) containing a line narrowing element (e.g., an etalon or grating) may be installed inside the laser resonator of the gas laser device to narrow the spectral linewidth. Hereinafter, a gas laser device with a narrowed spectral linewidth is referred to as a line narrowing gas laser device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 2714357 [Patent Document 2] Summary of the specification of U.S. Patent No. 6,529,538

[0005] A gas laser device according to one aspect of the present disclosure is a gas laser device that discharges and excites laser gas passing through a discharge space between a first discharge electrode and a second discharge electrode, and includes: a plate that supports the first discharge electrode; a guide member that is arranged on the plate and that guides the laser gas to the discharge space; a dielectric pipe that is arranged between the guide member and the first discharge electrode and spaced apart from both the plate and the first discharge electrode; a first path that includes the guide member and into which a portion of the laser gas flows as a diverted flow; a second path that includes the dielectric pipe and the plate and into which the diverted flow flowing out of the first path flows; and a third path that includes the dielectric pipe and the first discharge electrode and that guides the diverted flow flowing out of the second path upstream of the laser gas from the discharge space.

[0006] A method for manufacturing an electronic device according to one aspect of the present disclosure includes a gas laser apparatus that discharges and excites laser gas passing through a discharge space between a first discharge electrode and a second discharge electrode, the gas laser apparatus comprising: a plate supporting the first discharge electrode; a guide member arranged on the plate for guiding the laser gas to the discharge space; a dielectric pipe arranged between the guide member and the first discharge electrode and spaced apart from the plate and the first discharge electrode; a first path including the guide member and into which a portion of the laser gas flows as a diverted flow; a second path including the dielectric pipe and the plate and through which the diverted flow flowing out of the first path flows; and a third path including the dielectric pipe and the first discharge electrode and which guides the diverted flow flowing out of the second path to a laser gas upstream of the discharge space, generating laser light using the gas laser apparatus; outputting the laser light to an exposure apparatus; and exposing a photosensitive substrate in the exposure apparatus to the laser light to manufacture an electronic device. [Brief explanation of the drawings]

[0007] Some embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 is a side view schematically showing the configuration of a gas laser device according to a comparative example. [Figure 2] FIG. 2 is a cross-sectional view schematically showing the configuration of a gas laser device according to a comparative example. [Figure 3] FIG. 3 is a cross-sectional view showing in detail the configuration in the vicinity of the main electrode in the laser chamber. [Figure 4] FIG. 4 is a diagram showing an example of an ideal flow velocity distribution of the laser gas passing through the discharge space. [Figure 5] FIG. 5 is a timing chart showing the operation of the gas laser device. [Figure 6] FIG. 6 is a diagram showing an example of the simulation results of the laser gas flow. [Figure 7] FIG. 7 is a diagram showing an example of the flow velocity distribution of the laser gas passing through the discharge space when leakage occurs. [Figure 8] FIG. 8 is a cross-sectional view showing in detail the configuration near the main electrode in the laser chamber according to the first embodiment. [Figure 9] FIG. 9 is an enlarged view of the vicinity of the dielectric pipe. [Figure 10] FIG. 10 is a plan view of a portion including the anode electrode and the dielectric pipe as seen from the discharge space. [Figure 11] FIG. 11 is a diagram showing an example of a simulation result of the flow of laser gas in the first embodiment. [Figure 12] FIG. 12 is a diagram showing an example of the flow velocity distribution of the laser gas passing through the discharge space in the first embodiment. [Figure 13] FIG. 13 is a timing chart showing the operation of the gas laser device according to the first embodiment. [Figure 14] FIG. 14 is a diagram showing in detail the configuration near the main electrode in the laser chamber according to the second embodiment. [Figure 15] FIG. 15 is a plan view of a portion including the anode electrode and the dielectric pipe as seen from the discharge space. [Figure 16] FIG. 16 is a diagram showing an example of a simulation result of the flow of laser gas in the second embodiment. [Figure 17] FIG. 17 is a diagram schematically showing an example of the configuration of an exposure apparatus. Embodiment

[0008] <Contents> 1. Comparative Example 1.1 Configuration 1.2 Operation 1.3 Challenges 2. First embodiment 2.1 Configuration 2.2 Operation 2.3 Effects 3. Second embodiment 3.1 Configuration 3.2 Operation 3.3 Effects 4. Manufacturing method of electronic devices

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit the content of the present disclosure. Furthermore, not all of the configurations and operations described in the embodiments are necessarily essential as the configurations and operations of the present disclosure. Note that the same components are given the same reference symbols, and redundant explanations will be omitted.

[0010] 1. Comparative Example First, a comparative example of the present disclosure will be described. The comparative example of the present disclosure is a form that the applicant recognizes as being known only by the applicant, and is not a publicly known example that the applicant acknowledges.

[0011] 1.1 Configuration The configuration of a gas laser device 2 according to a comparative example will be described using Figures 1 and 2. Figure 1 shows a schematic configuration of the gas laser device 2. Figure 2 is a cross-sectional view of the gas laser device 2 shown in Figure 1 as seen from the Z direction. The gas laser device 2 is a discharge excitation type gas laser device that discharges and excites laser gas, such as an excimer laser device.

[0012] 1, the traveling direction of pulsed laser light PL output from gas laser device 2 is defined as the Z direction. The discharge direction, which will be described later, is defined as the Y direction. The direction perpendicular to the Z direction and the Y direction is defined as the X direction. The pulsed laser light PL is an example of the "laser light" according to the technology of the present disclosure.

[0013] 1, 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 processor 14, a pressure sensor 17, and a laser resonator. The laser resonator is composed of a line narrowing module 15 and an output coupling mirror 16.

[0014] The laser chamber 10 is a metal container made of, for example, aluminum metal with a nickel-plated surface. As shown in Figures 1 and 2, the interior of the laser chamber 10 is provided with a main electrode 20, a ground plate 21, wiring 22, a fan 23, a heat exchanger 24, an insulating guide 28, a conductive guide 29, and a preionization electrode 30. The preionization electrode 30 includes an outer preionization electrode 31, a dielectric pipe 32, and an inner preionization electrode 33.

[0015] A laser gas containing fluorine is sealed as a laser medium inside the laser chamber 10. The laser gas contains, for example, rare gases such as argon, krypton, and xenon, buffer gases such as neon and helium, and halogen gases such as fluorine and chlorine.

[0016] An opening is formed in the laser chamber 10. An electrical insulating plate 26 with a feedthrough 25 embedded therein is attached to the laser chamber 10 via an O-ring (not shown) so as to close the opening. The PPM 12 is placed on the electrical insulating plate 26. The laser chamber 10 is grounded.

[0017] The PPM 12 includes a charging capacitor (not shown) and is connected to the main electrode 20 via a feedthrough 25. The PPM 12 includes a switch SW for discharging the main electrode 20. The charger 11 is connected to the charging capacitor of the PPM 12. Hereinafter, the discharge occurring at the main electrode 20 will be referred to as the main discharge.

[0018] The main electrode 20 comprises a cathode electrode 20a and an anode electrode 20b. The cathode electrode 20a and the anode electrode 20b are arranged in the laser chamber 10 so that their discharge surfaces face each other. The space between the discharge surface of the cathode electrode 20a and the discharge surface of the anode electrode 20b is called a discharge space 27. The surface of the cathode electrode 20a opposite the discharge surface is supported by an electrically insulating plate 26 and connected to a feedthrough 25. The surface of the anode electrode 20b opposite the discharge surface is supported by a ground plate 21. The anode electrode 20b is an example of a "first discharge electrode" according to the technology of the present disclosure. The cathode electrode 20a is an example of a "second discharge electrode" according to the technology of the present disclosure. The ground plate 21 is an example of a "plate" according to the technology of the present disclosure.

[0019] The ground plate 21 is connected to the laser chamber 10 via wiring 22. The laser chamber 10 is connected to the ground. Therefore, the ground plate 21 is connected to the ground via wiring 22. An end of the ground plate 21 in the Z direction is fixed to the laser chamber 10.

[0020] Fan 23 is a cross-flow fan for circulating laser gas within laser chamber 10, and is disposed on the opposite side of ground plate 21 from discharge space 27. A motor 23a that rotates fan 23 is connected to laser chamber 10.

[0021] The laser gas blown out from fan 23 flows into discharge space 27. The flow direction of the laser gas flowing into discharge space 27 is approximately parallel to the X direction. The laser gas flowing out from discharge space 27 is sucked into fan 23 via heat exchanger 24. Heat exchanger 24 changes the temperature of the laser gas by exchanging heat between the laser gas and a refrigerant supplied inside heat exchanger 24.

[0022] Insulating guide 28 is disposed on the surface of electrical insulating plate 26 facing discharge space 27, sandwiching cathode electrode 20a therebetween. Insulating guide 28 is formed in a shape that guides the flow of laser gas so that the laser gas from fan 23 flows efficiently between cathode electrode 20a and anode electrode 20b. Insulating guide 28 and electrical insulating plate 26 are formed of ceramic such as alumina (Al2O3), which has low reactivity with fluorine gas.

[0023] Conductive guide 29 is disposed on the surface of ground plate 21 facing discharge space 27, sandwiching anode electrode 20b therebetween. Similar to insulating guide 28, conductive guide 29 is formed in a shape that guides the flow of laser gas so that the laser gas from fan 23 flows efficiently between cathode electrode 20a and anode electrode 20b. Conductive guide 29 is formed, for example, from porous nickel metal that has low reactivity with fluorine gas.

[0024] Laser gas supply device 18a and laser gas exhaust device 18b are connected to laser chamber 10. Laser gas supply device 18a includes a valve and a flow control valve, and is connected to a gas cylinder containing laser gas. Laser gas exhaust device 18b includes a valve and an exhaust pump.

[0025] Windows 10a and 10b are provided at the ends of the laser chamber 10 to emit light generated within the laser chamber 10 to the outside. The laser chamber 10 is arranged so that the optical path of the optical resonator passes through the discharge space 27 and the windows 10a and 10b.

[0026] The line narrowing module 15 includes a prism 15a and a grating 15b. The prism 15a expands the beam width of the light emitted from the laser chamber 10 through the window 10a and transmits the expanded beam toward the grating 15b.

[0027] Grating 15b is arranged in a Littrow configuration, where the angle of incidence and the angle of diffraction are the same. Grating 15b is a wavelength selection element that selectively extracts light near a specific wavelength depending on the diffraction angle. The spectral width of the light returning from grating 15b to laser chamber 10 via prism 15a is narrowed.

[0028] The output coupling mirror 16 transmits a portion of the light emitted from the laser chamber 10 via the window 10b and reflects the other portion back into the laser chamber 10. The surface of the output coupling mirror 16 is coated with a partially reflective film.

[0029] The light emitted from the laser chamber 10 travels back and forth between the line narrowing module 15 and the output coupling mirror 16, and is amplified each time it passes through the discharge space 27. A portion of the amplified light is output as pulsed laser light PL via the output coupling mirror 16.

[0030] The pulse energy measuring unit 13 is disposed in the optical path of the pulsed laser light PL output via the output coupling mirror 16. The pulse energy measuring unit 13 includes a beam splitter 13a, a focusing optical system 13b, and an optical sensor 13c.

[0031] The beam splitter 13a transmits the pulsed laser light PL with high transmittance and reflects a portion of the pulsed laser light 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 measurement value to the processor 14.

[0032] The pressure sensor 17 detects the gas pressure inside the laser chamber 10 and outputs the detected value to the processor 14. The processor 14 determines the gas pressure of the laser gas inside the laser chamber 10 based on the detected gas pressure value and the charging voltage of the charger 11.

[0033] The charger 11 is a high-voltage power supply that supplies a charging voltage to a charging capacitor included in the PPM 12. The switch SW of the PPM 12 is controlled by the processor 14. When the switch SW changes from off to on, the PPM 12 generates a high-voltage pulse from the electrical energy stored in the charging capacitor and applies it to the main electrode 20.

[0034] The processor 14 is a processing device that transmits and receives various signals to and from an exposure apparatus controller 110 provided in the exposure apparatus 100. For example, the processor 14 receives from the exposure apparatus controller 110 a target pulse energy of the pulsed laser light PL output to the exposure apparatus 100, an oscillation trigger signal, and the like.

[0035] The processor 14 comprehensively controls the operation of each component of the gas laser device 2 based on various signals sent from the exposure apparatus controller 110, measured values ​​of pulse energy, detected values ​​of gas pressure, and the like.

[0036] The processor 14 functions as a controller for the gas laser device 2. For example, the processor 14 is a processing device including a storage device in which a control program is stored and a CPU (Central Processing Unit) that executes the control program. The processor 14 is specially configured or programmed to execute various processes included in the present disclosure. The storage device is a non-transitory computer-readable storage medium, and includes, for example, a memory that is a primary storage device and a storage that is an auxiliary storage device. The storage device may be a semiconductor memory, a hard disk drive (HDD) device, a solid-state drive (SSD) device, or a combination of two or more of these.

[0037] 3 shows in detail the configuration near the main electrode 20 inside the laser chamber 10. In the following explanation, the upstream side refers to the side from which the laser gas flows into the discharge space 27, relative to the discharge space 27. The downstream side refers to the side from which the laser gas flows out of the discharge space 27, relative to the discharge space 27.

[0038] The preionization outer electrode 31 is disposed between the anode electrode 20b and the dielectric pipe 32, and is held in contact with the side surface of a metal holding member 34. The holding member 34 is fixed to the upstream side surface of the anode electrode 20b. The preionization inner electrode 33 is disposed inside the dielectric pipe 32, and the preionization outer electrode 31 is in contact with the outside of the dielectric pipe 32.

[0039] The insulating guide 28 is disposed so as to cover the upstream and downstream side surfaces of the cathode electrode 20a. The surface of the insulating guide 28 is inclined so that the surface approaches the electrical insulating plate 26 as it becomes farther away from the cathode electrode 20a.

[0040] The conductive guide 29 includes a first guide member 29a, a second guide member 29b, and a third guide member 29c. The first guide member 29a and the third guide member 29c are arranged upstream of the anode electrode 20b. The second guide member 29b is arranged downstream of the anode electrode 20b. The first guide member 29a is an example of a "guide member" according to the technology of the present disclosure.

[0041] First guide member 29a is disposed on ground plate 21 so as to guide laser gas into discharge space 27. Dielectric pipe 32 is disposed between first guide member 29a and anode electrode 20b, spaced apart from ground plate 21 and anode electrode 20b. Second guide member 29b is disposed on ground plate 21 downstream of anode electrode 20b so as to cover the downstream side surface of anode electrode 20b.

[0042] The third guide member 29c is disposed between the dielectric pipe 32 and the anode electrode 20b so as to cover the upstream side surface of the anode electrode 20b and to guide the laser gas to the discharge space 27. The third guide member 29c is located close to the dielectric pipe 32.

[0043] The surface of the conductive guide 29 is generally inclined so that the further away from the anode electrode 20b it is, the closer it is to the ground plate 21.

[0044] The upstream and downstream side surfaces of the cathode electrode 20a near its discharge surface are not covered with the insulating guide 28, and protrude from the surface of the insulating guide 28 toward the anode electrode 20b. As a result, the discharge surface of the cathode electrode 20a is spaced apart from the surface of the insulating guide 28.

[0045] The upstream and downstream side surfaces of the anode electrode 20b near its discharge surface are not covered with the conductive guide 29, and protrude from the surface of the conductive guide 29 toward the cathode electrode 20a. As a result, the discharge surface of the anode electrode 20b is spaced apart from the surface of the conductive guide 29.

[0046] 1.2 Operation Next, the operation of gas laser apparatus 2 according to the comparative example will be described. First, processor 14 controls laser gas supply device 18a to supply laser gas into laser chamber 10, and drives motor 23a to rotate fan 23. This causes the laser gas filled in laser chamber 10 to circulate as shown by the arrows in FIG.

[0047] The processor 14 receives a target pulse energy and an oscillation trigger signal from the exposure apparatus controller 110. The oscillation trigger signal is a signal that instructs the gas laser apparatus 2 to output one pulse of pulsed laser light PL.

[0048] The processor 14 sets a charging voltage according to the target pulse energy in the charger 11. The processor 14 operates the switch SW of the PPM 12 in synchronization with the oscillation trigger signal.

[0049] When the switch SW of the PPM 12 is turned from off to on, a voltage is applied between the preionization inner electrode 33 and the preionization outer electrode 31 of the preionization electrode 30, and between the cathode electrode 20a and the anode electrode 20b. This causes a corona discharge at the preionization electrode 30, generating UV (Ultraviolet) light. The laser gas in the discharge space 27 is irradiated with the UV light, thereby preionizing the laser gas.

[0050] Thereafter, when the voltage between the cathode electrode 20a and the anode electrode 20b reaches the breakdown voltage, a main discharge occurs in the discharge space 27. If the discharge direction of the main discharge is the direction in which electrons flow, then the discharge direction is from the cathode electrode 20a to the anode electrode 20b. When the main discharge occurs, the laser gas in the discharge space 27 is excited and emits light.

[0051] Laser oscillation occurs when light emitted from the laser gas is reflected by the line narrowing module 15 and the output coupling mirror 16 and travels back and forth within the laser resonator. The light narrowed in line by the line narrowing module 15 is output from the output coupling mirror 16 as pulsed laser light PL.

[0052] A portion of the pulsed laser light PL output from the output coupling mirror 16 is incident on the pulse energy measuring unit 13. The pulse energy measuring unit 13 measures the pulse energy of the incident pulsed laser light PL and outputs the measurement value to the processor 14.

[0053] The processor 14 calculates the difference ΔE between the measured pulse energy and the target pulse energy, and based on the difference ΔE, the processor 14 feedback-controls the charging voltage so that the measured pulse energy becomes the target pulse energy.

[0054] When the charging voltage becomes higher than the maximum value of the allowable range, processor 14 controls laser gas supply device 18a to supply laser gas into laser chamber 10 until the predetermined pressure is reached. When the charging voltage becomes lower than the minimum value of the allowable range, processor 14 controls laser gas exhaust device 18b to exhaust laser gas from laser chamber 10 until the predetermined pressure is reached.

[0055] Fig. 4 shows an example of an ideal flow velocity distribution of laser gas passing through discharge space 27. In Fig. 4, P1 indicates the position of the discharge surface of cathode electrode 20a in the Y direction, and P2 indicates the position of the discharge surface of anode electrode 20b in the Y direction. P3 indicates the center position of discharge space 27 in the Y direction. The solid line indicates the flow velocity distribution of the laser gas, and the dashed line indicates the average flow velocity calculated from the flow velocity distribution of the laser gas. The same applies to Figs. 7 and 12, which will be described later.

[0056] The main discharge generates discharge products in the discharge space 27. Because the discharge products are conductive, if the discharge products remain in the discharge space 27, arc discharge due to the discharge products may occur. However, the laser gas is rectified by the surfaces of the insulating guide 28 and the conductive guide 29, and ideally passes through the discharge space 27 with a flow velocity distribution as shown in FIG. 4. The laser gas moves the discharge products generated in the discharge space 27 downstream and removes them, thereby suppressing the occurrence of arc discharge due to the discharge products.

[0057] 1.3 Challenges 5 is a timing chart showing the operation of gas laser apparatus 2. When a semiconductor wafer is exposed using exposure apparatus 100, exposure is performed by outputting pulsed laser light PL from gas laser apparatus 2 at a predetermined repetition rate, a so-called "burst output." However, for example, exposure using pulsed laser light PL is paused during periods when exposure apparatus 100 moves the semiconductor wafer, replaces the semiconductor wafer, or replaces the mask. That is, during exposure using gas laser apparatus 2, burst output periods TB during which burst output is performed and burst pause periods TR during which burst output is paused are repeatedly executed.

[0058] If the above-mentioned arc discharge occurs during the burst output period TB, the laser gas is not sufficiently excited during the arc discharge, resulting in a so-called "dropout" where pulsed laser light PL is not output. In the gas laser device 2 according to the comparative example, it is believed that dropout is suppressed if the discharge products in the discharge space 27 are removed by the flow of laser gas as described above. However, the applicant has confirmed that dropout may occur during the burst output period TB even in the gas laser device 2 according to the comparative example, as shown in FIG. 5.

[0059] Therefore, the present applicant conducted a simulation of the laser gas flow to deduce the cause of the leak. Figure 6 shows an example of the results of the simulation of the laser gas flow. The laser gas flow includes a "main flow," which is a laminar flow that proceeds at high speed in the X direction along the surfaces of the insulating guide 28 and the conductive guide 29 without separating from the discharge surfaces of the cathode electrode 20a and the anode electrode 20b. A laminar flow is a state in which a fluid flows regularly in a fixed direction. In Figure 6, M1 to M5 represent multiple components contained in the main flow. The same applies to Figures 11 and 16, which will be described later.

[0060] In addition to the main flow, the flow of laser gas includes "stagnation" that occurs downstream of the cathode electrode 20a and the anode electrode 20b. The stagnation is turbulence that occurs when the laser gas separates from the discharge surfaces of the cathode electrode 20a and the anode electrode 20b, and laser gas that is separated from the main flow by this turbulence. The stagnation is laser gas that travels at a low speed in the X direction along the surfaces of the insulating guide 28 and the conductive guide 29, and stagnates between the main flow and these surfaces. It is presumed that the distribution of this stagnation is the cause of the occurrence of the leak.

[0061] The stagnation accumulates while flowing in the opposite direction to the mainstream flow, causing part of the mainstream flow to transition into stagnation after passing through the discharge space 27. For this reason, it is presumed that the stagnation applies flow resistance to the mainstream flow, causing a decrease in flow velocity. Hereinafter, the stagnation that occurs in the cathode-side space between the surface of the insulating guide 28 and the mainstream flow will be referred to as "cathode-side stagnation." Furthermore, the stagnation that occurs in the anode-side space between the surface of the conductive guide 29 and the mainstream flow will be referred to as "anode-side stagnation."

[0062] It is presumed that the laser gas that has passed through discharge space 27 flows biased toward second guide member 29b while being subjected to a force in the -Y direction due to the suction effect caused by the rotation of fan 23. For this reason, it is presumed that the stagnation on the cathode side and the stagnation on the anode side become asymmetric.

[0063] Specifically, cathode-side stagnation generated on the discharge surface of the cathode electrode 20a is continuously sent into the cathode-side space. The cathode-side stagnation expands while absorbing part of the mainstream. As a result, mainstream component M1 does not reattach to the insulating guide 28, but instead encounters significant flow resistance from the cathode-side stagnation and proceeds while slowing down. Furthermore, it is presumed that the slowdown of mainstream component M1 leads to a chain reaction of slowdowns of mainstream components M2 to M4. Reattachment refers to the phenomenon in which a fluid flowing along a wall surface separates from the wall surface and then flows again as a laminar flow along the wall surface.

[0064] Anode-side stagnation generated at the anode electrode 20b is also sent one after another into the anode-side space, but because the laser gas flows while being subjected to a force in the -Y direction, the generated anode-side stagnation quickly reattaches, preventing it from growing larger. By preventing the anode-side stagnation from growing larger, mainstream component M5 reattaches to the conductive guide 29, reducing flow path resistance. This increases the flow velocity of mainstream component M5, and it is presumed that, overall, the mainstream that has passed through the discharge space 27 flows with a bias toward the conductive guide 29.

[0065] 7 shows an example of the flow velocity distribution of the laser gas passing through discharge space 27 when leakage occurs. When leakage occurs, the flow velocity decreases near position P1 on the discharge surface of cathode electrode 20a, and this causes a decrease in the average flow velocity. This reduces the removal rate of the discharge products, which is thought to cause arc discharge, resulting in leakage.

[0066] In order to increase the removal rate of the discharge products, it is conceivable to increase the flow rate of the laser gas by increasing the rotation speed of the fan 23. However, increasing the rotation speed of the fan 23 causes various problems, such as increased power consumption, difficulty in controlling the fan 23, non-uniform flow rate due to increased vibration of the fan 23, and damage to the fan 23.

[0067] It is also possible to reduce the rotation speed of the fan 23 to prevent the cathode-side stagnation from becoming thicker, but reducing the rotation speed of the fan 23 would reduce the speed at which discharge products are removed, and in this case, burst output operation at a high repetition frequency would not be possible.

[0068] Therefore, an object of the present disclosure is to provide a gas laser device that enables burst output without any dropouts, and a method for manufacturing an electronic device.

[0069] 2. First embodiment 2.1 Configuration The gas laser device 2 according to the first embodiment of the present disclosure has the same configuration as the gas laser device 2 according to the comparative example, except that the configuration inside the laser chamber 10 is different.

[0070] 8 shows in detail the configuration near the main electrode 20 in the laser chamber 10 according to the first embodiment. This embodiment differs from the comparative example only in that the third guide member 29c shown in FIG. 6 is not provided. That is, in this embodiment, the conductive guide 29 includes a first guide member 29a and a second guide member 29b. As a result, in this embodiment, a branch flow path 40 is formed around the dielectric pipe 32, through which a branch flow branched from the main flow of laser gas flows.

[0071] The branch flow path 40 includes a first path 41, a second path 42, and a third path 43. The first path 41 includes a first guide member 29a, and a portion of the main laser gas flows into the first path 41 as a branch flow. The second path 42 includes a dielectric pipe 32 and a ground plate 21, and the branch flow flowing out from the first path 41 flows through the second path 42. The third path 43 includes a dielectric pipe 32 and an anode electrode 20b, and guides the branch flowing out from the second path 42 to the upstream side of the discharge space 27. In this embodiment, the first path 41 includes a first guide member 29a and a dielectric pipe 32.

[0072] Specifically, the first path 41 is a gap between the dielectric pipe 32 and the first guide member 29a. The second path 42 is a gap between the dielectric pipe 32 and the ground plate 21. The third path 43 is a gap between the dielectric pipe 32 and the anode electrode 20b. Note that the holding member 34 and a part of the preionization outer electrode 31 are present within the third path 43.

[0073] The first path 41 has an inlet 41a at its end, through which a portion of the main flow of laser gas flows in. The third path 43 has an outlet 43a at its end, through which the branched flow flows toward the main flow. The branched flow that flows in from the inlet 41a flows through the branched flow path 40 via the first path 41, the second path 42, and the third path 43 in that order, before flowing out from the outlet 43a and rejoining the main flow upstream of the discharge space 27.

[0074] FIG. 9 is an enlarged view near the dielectric pipe 32. The surface of the first guide member 29a is a plane parallel to the Z direction and non-parallel to the X and Y directions. E1 is a virtual plane extending from the surface of the first guide member 29a toward the discharge space 27. E2 is a virtual plane parallel to the virtual plane E1 and in contact with the surface of the dielectric pipe 32. F is the outer diameter of the dielectric pipe 32.

[0075] In order to allow a part of the main flow of the laser gas to flow into the shunt passage 40, it is preferable that a part of the dielectric pipe 32 protrudes toward the main flow side from the virtual plane E1. The protrusion amount dtop of the dielectric pipe 32 is defined by the distance between the virtual plane E1 and the virtual plane E2. It is preferable that the protrusion amount dtop and the outer diameter F satisfy the relationship of 0 < dtop ≦ 0.5F.

[0076] FIG. 10 is a plan view of a portion including the anode electrode 20b and the dielectric pipe 32 seen from the discharge space 27. The discharge surface of the anode electrode 20b is a rectangle extending in the Z direction. The first guide member 29a, the second guide member 29b, the dielectric pipe 32, and the pre-ionization outer electrode 31 are arranged along the longitudinal direction of the discharge surface of the anode electrode 20b.

[0077] The dielectric pipe 32 extends in the Z direction, and both ends are held by a pair of holding members 35. The pair of holding members 35 are arranged on the ground plate 21 and form both end faces in the Z direction of the shunt passage 40. The inlet 41a and the outlet 43a are each a rectangle extending in the Z direction.

[0078] The preionization outer electrode 31 includes a contact portion 31a, a fixed portion 31b, and multiple connection portions 31c. The contact portion 31a extends in the Z direction and is in contact with the dielectric pipe 32. The fixed portion 31b extends in the Z direction and is held by a holding member 34. Each of the multiple connection portions 31c extends in the X direction and is connected between the contact portion 31a and the fixed portion 31b. The multiple connection portions 31c are arranged at equal intervals in the Z direction. The preionization outer electrode 31 has a ladder shape as a whole, and the spaces between two adjacent connection portions 31c each form an outlet 43a through which a branch of the laser gas passes.

[0079] If the minimum width of the inlet 41a in the direction perpendicular to the direction of the diverted current is defined as din and the minimum width of the outlet 43a in the direction perpendicular to the direction of the diverted current is defined as dout, then it is preferable that the relationship dout≧din be satisfied. Furthermore, if the distance between the discharge surface of the cathode electrode 20a and the discharge surface of the anode electrode 20b is defined as D, it is preferable that the relationship 0.1D≦din≦0.5D be satisfied. In this embodiment, the minimum width din is the length of the inlet 41a in the X direction, and the minimum width dout is the length of the outlet 43a in the X direction.

[0080] 2.2 Operation The operation of the gas laser device 2 according to this embodiment is the same as that of the comparative example, except for the difference in the effect due to the formation of the shunt flow path 40.

[0081] Fig. 11 shows an example of the results of a simulation of the flow of laser gas in the first embodiment. As shown in Fig. 11, in this embodiment, a portion of the main flow component M5 separates and flows from the inlet 41a into the branch channel 40. The branch flow travels through the branch channel 40 along the surface of the dielectric pipe 32, and reaches the outlet 43a. The mechanism by which the branch flow is generated and travels through the branch channel 40 is presumed to be due to the Coanda effect.

[0082] Stagnation having a flow component opposite to the direction of the diverted flow occurs in the shunt flow path 40 on the side surface of the first guide member 29a, the surface of the ground plate 21, the side surface of the holding member 34, and the side surface of the anode electrode 20b. Hereinafter, the stagnation occurring in the shunt flow path 40 will be referred to as "diverted flow stagnation."

[0083] The branched current that has reached the outlet 43a passes through the space of the ladder-shaped preionization outer electrode 31 and flows out toward the upstream insulating guide 28, i.e., in the +Y direction. The flowing branched current merges with the mainstream component M5 upstream of the discharge space 27. In this way, the branched current has enough kinetic energy to overcome the branched current stagnation and merge with the mainstream component M5.

[0084] After the divided flows join, mainstream component M5 enters discharge space 27 in a state biased toward cathode electrode 20a compared to the comparative example shown in Fig. 6. At this time, mainstream components M1 to M4 are also influenced by mainstream component M5 in a chain reaction, and enter discharge space 27 in a state biased toward cathode electrode 20a. Therefore, the mainstream as a whole enters discharge space 27 in a state biased toward cathode electrode 20a compared to the comparative example.

[0085] To summarise the above, according to this embodiment, the following first to fourth effects can be obtained.

[0086] As a first effect, a branch flow having kinetic energy capable of changing the position of the main flow is generated. The branch flow generated by the Coanda effect travels in the branch flow path 40 along the surface of the dielectric pipe 32, and therefore flows out of the branch flow path 40 without losing much of its kinetic energy. This first effect occurs at all positions in the Z direction of the branch flow path 40. As a result, a branch flow with little variation in kinetic energy flows out of the outlet 43a in the Z direction.

[0087] As a second effect, a diverted current flows out from the outlet 43a in the +Y direction. Because the dielectric pipe 32 is located upstream of the discharge space 27, the diverted current generated by the Coanda effect separates from the dielectric pipe 32 and flows out from the outlet 43a in the +Y direction. In addition, because the dielectric pipe 32 extends in the Z direction, the diverted current flows out in the +Y direction from all positions in the Z direction of the outlet 43a.

[0088] As a third effect, the entire main stream is displaced toward the cathode electrode 20a. Since the branch stream traveling in the +Y direction joins the main stream entering the discharge space 27 in the +X direction, the entire main stream enters the discharge space 27 in a state where it has been displaced toward the cathode electrode 20a.

[0089] The fourth effect is improved symmetry between the cathode-side stagnation and the anode-side stagnation. Entering the discharge space 27 with the entire mainstream displaced toward the cathode electrode 20a promotes reattachment of the mainstream component M1 in the cathode-side space, suppressing the growth of the cathode-side stagnation. Meanwhile, reattachment of the mainstream component M5 in the anode-side space is delayed, causing the anode-side stagnation to grow. This improves the symmetry between the cathode-side stagnation and the anode-side stagnation.

[0090] Fig. 12 shows an example of the flow velocity distribution of the laser gas passing through discharge space 27 in the first embodiment. Fig. 12 shows the flow velocity distribution and average flow velocity in this embodiment, as well as the ideal flow velocity distribution and average flow velocity. According to Fig. 12, in this embodiment, a drop in flow velocity occurs near discharge surface position P2 of anode electrode 20b, but the flow velocity approaches the ideal value as it approaches discharge surface position P1 of cathode electrode 20a.

[0091] 2.3 Effects According to this embodiment, the symmetry between the cathode-side stagnation and the anode-side stagnation is improved, and the flow velocity distribution of the laser gas passing through the discharge space 27 approaches an ideal flow velocity distribution, thereby improving the insufficient removal of discharge products. As a result, arc discharge is suppressed, and a continuous burst output is possible as shown in FIG.

[0092] 3. Second embodiment 3.1 Configuration A gas laser device 2 according to the second embodiment of the present disclosure has the same configuration as the gas laser device 2 according to the first embodiment, except that the configuration inside the laser chamber 10 is different.

[0093] 14 shows in detail the configuration near the main electrode 20 in the laser chamber 10 according to the second embodiment. This embodiment differs from the first embodiment only in the configuration of the conductive guide 29. In this embodiment, a first guide member 29a of the conductive guide 29 is disposed close to the dielectric pipe 32. In addition, a through hole 50 is formed in the first guide member 29a, extending from the upstream end toward the anode electrode 20b along the X direction.

[0094] In this embodiment, the first path 41 of the shunt flow path 40 is formed by a through hole 50. An inlet 41a into which the shunt flow flows is an opening on the upstream side of the through hole 50. The second path 42 is a gap between the dielectric pipe 32 and the ground plate 21, as in the first embodiment. The third path 43 is a gap between the dielectric pipe 32 and the anode electrode 20b, as in the first embodiment. Note that the holding member 34 and a part of the preionization outer electrode 31 are present within the third path 43.

[0095] 15 is a plan view of a portion including the anode electrode 20b and the dielectric pipe 32, viewed from the discharge space 27. The through-hole 50 extends in the Z direction. In this embodiment, the pair of holding members 35 extend from the dielectric pipe 32 to the first guide member 29a. As a result, the pair of holding members 35 form both end faces of the first path 41 in the Z direction.

[0096] In this embodiment as well, it is preferable to satisfy the relationships dout≧din and 0.1D≦din≦0.5D. In this embodiment, the branch flow flows into the inlet 41a in the X direction, so the minimum width din is the length in the Y direction.

[0097] 3.2 Operation The operation of the gas laser device 2 according to this embodiment is the same as that of the first embodiment, except for the difference in the configuration of the shunt channel 40.

[0098] Fig. 16 shows an example of the results of a simulation of the flow of laser gas in the second embodiment. As shown in Fig. 16, even when through-hole 50 is used as first path 41, the same branching as in the first embodiment occurs, and therefore the same effect as in the first embodiment can be obtained.

[0099] 3.3 Effects According to this embodiment, as in the first embodiment, the symmetry between the cathode-side stagnation and the anode-side stagnation is improved, and the flow velocity distribution of the laser gas passing through the discharge space 27 approaches an ideal flow velocity distribution, thereby improving the insufficient removal of discharge products. As a result, arc discharge is suppressed, and a burst output without any dropouts is possible.

[0100] 4. Manufacturing method of electronic devices 17 shows a schematic configuration example of exposure apparatus 100. Exposure apparatus 100 includes an illumination optical system 104 and a projection optical system 106. Illumination optical system 104 illuminates a reticle pattern of a reticle (not shown) placed on a reticle stage RT with pulsed laser light PL incident thereon, for example, from a gas laser device 2. Projection optical system 106 reduces and projects the pulsed laser light PL that has passed through the reticle, forming an image on a workpiece (not shown) placed on a workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist.

[0101] Exposure apparatus 100 exposes a workpiece to pulsed laser light PL reflecting a reticle pattern by synchronously translating a reticle stage RT and a workpiece table WT. After transferring the reticle pattern to a semiconductor wafer through the exposure process described above, a semiconductor device can be manufactured through multiple processes. A semiconductor device is an example of an "electronic device" in this disclosure.

[0102] The gas laser device 2 is not limited to use in the manufacture of electronic devices, but can also be used for laser processing such as drilling.

[0103] The above description is intended to be illustrative rather than limiting. Thus, it will be apparent to those skilled in the art that modifications may be made to the embodiments of the present disclosure without departing from the scope of the appended claims.

[0104] Terms used throughout this specification and the appended claims should be interpreted as "open ended" terms. For example, the terms "include" or "including" should be interpreted as "not limited to what is stated as including." The term "having" should be interpreted as "not limited to what is stated as having." Additionally, the modifier "a" used in this specification and the appended claims should be interpreted as "at least one" or "one or more." Additionally, the term "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 as including combinations other than "A," "B," and "C."

Claims

1. A gas laser device that discharge-excites laser gas passing through a discharge space between a first discharge electrode and a second discharge electrode, a plate supporting the first discharge electrode; a guide member disposed on the plate for guiding the laser gas to the discharge space; a dielectric pipe disposed between the guide member and the first discharge electrode and spaced apart from the plate and the first discharge electrode; a first path including the guide member, into which a portion of the laser gas flows as a branched flow; a second path including the dielectric pipe and the plate, through which the branched flow flowing out of the first path flows; a third path including the dielectric pipe and the first discharge electrode, which guides the branched flow flowing out from the second path to an upstream side of the laser gas relative to the discharge space; A gas laser device comprising:

2. 2. The gas laser device according to claim 1, the guide member is disposed at a distance from the dielectric pipe, The first path includes the guide member and the dielectric pipe.

3. 3. The gas laser device according to claim 2, A portion of the dielectric pipe protrudes from an imaginary plane formed by extending the surface of the guide member toward the discharge space.

4. 4. The gas laser device according to claim 3, When the protrusion amount of the dielectric pipe is dtop and the outer diameter of the dielectric pipe is F, the relationship 0<dtop≦0.5F is satisfied.

5. 2. The gas laser device according to claim 1, The guide member has a through hole formed therein. The first path is formed by the through hole.

6. 2. The gas laser device according to claim 1, When the minimum width at the inlet of the first path in a direction perpendicular to the direction in which the diverted flow flows is defined as din, and the minimum width at the outlet of the third path in a direction perpendicular to the direction in which the diverted flow flows is defined as dout, the relationship dout≧din is satisfied.

7. 7. The gas laser device according to claim 6, When the distance between the discharge surface of the first discharge electrode and the discharge surface of the second discharge electrode is D, the relationship 0.1D≦din≦0.5D is satisfied.

8. 2. The gas laser device according to claim 1, The first discharge electrode is an anode electrode, and the second discharge electrode is a cathode electrode.

9. 9. The gas laser device according to claim 8, A ladder-shaped preionization outer electrode is provided between the first discharge electrode and the dielectric pipe.

10. 10. The gas laser device according to claim 9, A preionization inner electrode is provided inside the dielectric pipe.

11. 11. The gas laser device of claim 10, the plate is a ground plate; The guide member is electrically conductive.

12. 12. The gas laser device of claim 11, a conductive guide including the guide member as a first guide member; The conductive guide includes a second guide member disposed on the plate downstream of the first discharge electrode so as to cover a side surface of the first discharge electrode.

13. 13. The gas laser device of claim 12, The first discharge electrode protrudes from the surface of the conductive guide toward the second discharge electrode.

14. 14. The gas laser apparatus of claim 13, The second discharge electrode is provided with insulating guides arranged to cover the upstream and downstream side surfaces of the second discharge electrode.

15. 15. The gas laser apparatus of claim 14, The second discharge electrode protrudes from the surface of the insulating guide toward the first discharge electrode.

16. A method for manufacturing an electronic device, comprising: A gas laser device that discharge-excites laser gas passing through a discharge space between a first discharge electrode and a second discharge electrode, a plate supporting the first discharge electrode; a guide member disposed on the plate for guiding the laser gas to the discharge space; a dielectric pipe disposed between the guide member and the first discharge electrode and spaced apart from the plate and the first discharge electrode; a first path including the guide member, into which a portion of the laser gas flows as a branched flow; a second path including the dielectric pipe and the plate, through which the branched flow flowing out of the first path flows; a third path including the dielectric pipe and the first discharge electrode, which guides the branched flow flowing out from the second path to an upstream side of the laser gas relative to the discharge space; generating laser light by a gas laser device comprising: outputting the laser light to an exposure device; exposing a photosensitive substrate to the laser light in the exposure apparatus to manufacture an electronic device; A method for manufacturing electronic devices.

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