Gas laser apparatus and method for manufacturing electronic devices

Abstract

A laser device according to one aspect of the present disclosure includes: a power supply; a main capacitor; a solid-state switch; a step-up transformer; a first magnetic pulse compression circuit that has a first transfer capacitor and a first magnetic switch and that is connected to a secondary side of the step-up transformer; a second magnetic pulse compression circuit that has a second transfer capacitor and a second magnetic switch and that is connected downstream of the first magnetic pulse compression circuit; a peaking capacitor that is connected downstream of the second magnetic pulse compression circuit; a pair of discharge electrodes formed of a cathode electrode and an anode electrode; a regenerative transformer that transfers, to the main capacitor, electric charge generated by the pair of discharge electrodes after a main discharge; and a reset circuit that resets the first magnetic switch and the second magnetic switch. A potential (Ec) of the cathode electrode in a period from 0.5 μs to 20 μs after the main discharge starts is in a range from -200V to 200V.

Description

[Technical Field]

[0001] This disclosure relates to a gas laser apparatus and a method for manufacturing electronic devices. [Background technology]

[0002] In recent years, semiconductor lithography equipment has been required to improve resolution as semiconductor integrated circuits become smaller and more integrated. Therefore, efforts are being made to shorten the wavelength of light emitted from lithography light sources. For example, gas laser equipment used for lithography includes KrF excimer laser equipment that outputs laser light with a wavelength of approximately 248 nm, and ArF excimer laser equipment that outputs laser light with a wavelength of approximately 193 nm.

[0003] The spectral linewidth of the spontaneously emitted light from KrF and ArF excimer laser systems is broad, ranging from 350 to 400 pm. Therefore, when 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 a gas laser system until chromatic aberration is negligible. For this reason, gas laser systems may be equipped with a Line Narrowing Module (LNM) containing narrowing elements (such as etalons or gratings) within the laser resonator to narrow the spectral linewidth. In the following, a gas laser system with a narrowed spectral linewidth will be referred to as a narrow-band gas laser system. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 4702889 [Patent Document 2] Summary of U.S. Patent No. 7295591

[0005] A gas laser apparatus according to one aspect of this disclosure includes a power supply, a main capacitor connected in parallel to the power supply, a solid switch, a step-up transformer whose primary side is connected in parallel to the main capacitor via the solid switch, a first transfer capacitor to which the charge of the main capacitor is transferred, a first magnetic pulse compression circuit connected to the secondary side of the step-up transformer and having a first magnetic switch, a second transfer capacitor to which the charge of the first transfer capacitor is transferred, a second magnetic pulse compression circuit connected downstream of the first magnetic pulse compression circuit and having a second magnetic switch, and a second magnetic pulse compression circuit connected downstream of the second magnetic pulse compression circuit. The system comprises a peaking capacitor onto which the charge of the transfer capacitor is transferred, a pair of discharge electrodes consisting of a cathode electrode and an anode electrode connected in parallel to the peaking capacitor, a regenerative transformer whose primary side is connected in parallel to the main capacitor and whose secondary side is connected in parallel to the first transfer capacitor, which transfers the charge generated by the pair of discharge electrodes to the main capacitor after the main discharge, and a reset circuit for resetting the first magnetic switch and the second magnetic switch, wherein the potential of the cathode electrode is within the range of -200V to 200V during a period of 0.5μs to 20μs from the start of the main discharge.

[0006] A method for manufacturing an electronic device relating to one aspect of the present disclosure is a method for manufacturing an electronic device comprising: a power supply; a main capacitor connected in parallel to the power supply; a solid switch; a step-up transformer whose primary side is connected in parallel to the main capacitor via the solid switch; a first transfer capacitor to which the charge of the main capacitor is transferred; a first magnetic pulse compression circuit having a first magnetic switch and connected to the secondary side of the step-up transformer; a second transfer capacitor to which the charge of the first transfer capacitor is transferred; a second magnetic pulse compression circuit having a second magnetic switch and connected downstream of the first magnetic pulse compression circuit; and a peaking capacitor connected downstream of the second magnetic pulse compression circuit to which the charge of the second transfer capacitor is transferred. The gas laser apparatus comprises a pair of discharge electrodes consisting of a cathode electrode and an anode electrode, connected in parallel to a peaking capacitor; a regenerative transformer whose primary side is connected in parallel to a main capacitor and whose secondary side is connected in parallel to a first transfer capacitor, which transfers the charge generated by the pair of discharge electrodes to the main capacitor after the main discharge; and a reset circuit for resetting a first magnetic switch and a second magnetic switch, wherein the potential of the cathode electrode during a period of 0.5 μs to 20 μs from the start of the main discharge is within the range of -200 V to 200 V; the laser beam is generated by the gas laser apparatus, the laser beam is output to an exposure apparatus, and the laser beam is exposed to a photosensitive substrate in the exposure apparatus in order to manufacture an electronic device. [Brief explanation of the drawing]

[0007] Some embodiments of this disclosure are described below, merely as examples, with reference to the accompanying drawings. [Figure 1] Figure 1 is a schematic side view showing the configuration of a gas laser apparatus according to a comparative example. [Figure 2] Figure 2 is a schematic cross-sectional view showing the configuration of a gas laser apparatus according to a comparative example. [Figure 3] Figure 3 is a circuit diagram showing the configuration of a pulse power module related to a comparative example. [Figure 4] Figure 4 shows the configuration of a saturable reactor that makes up a typical magnetic switch. [Figure 5]FIG. 5 is a graph showing the magnetization curve of the core of the saturable reactor. [Figure 6] FIG. 6 is a graph showing an example of the voltage change of each capacitor during the magnetic pulse compression operation and the regeneration operation. [Figure 7] FIG. 7 is a graph showing an example of the potential change of the cathode electrode after the main discharge in the gas laser device according to the comparative example. [Figure 8] FIG. 8 is a graph showing the calculation result of the relationship between the capacitance of the first transfer capacitor and the residual voltage of the first transfer capacitor. [Figure 9] FIG. 9 is a graph showing an example of the voltage change of the first transfer capacitor with respect to the elapsed time since the start of the main discharge. [Figure 10] FIG. 10 is a graph showing an example of the potential change of the cathode electrode after the main discharge in the gas laser device according to the embodiment. [Figure 11] FIG. 11 is a diagram schematically showing a configuration example of the exposure apparatus. Embodiment <00​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ 3. Method for manufacturing electronic devices

[0009] The embodiments of this disclosure will be described in detail below with reference to the drawings. The embodiments described below are examples of the disclosure and are not intended to limit the scope of this disclosure. Furthermore, not all configurations and operations described in the embodiments are necessarily essential to the configurations and operations of this disclosure. The same reference numerals are used for identical components, and redundant descriptions are omitted.

[0010] 1. Comparative Example First, the comparative examples of this disclosure will be described. The comparative examples of this disclosure are forms that the applicant recognizes as being known only to the applicant, and are not prior art that the applicant acknowledges.

[0011] 1.1 Overview of the Gas Laser System 1.1.1 Configuration Figures 1 and 2 schematically illustrate the configuration of the gas laser apparatus 2 according to the comparative example. Figure 1 schematically shows the configuration of the gas laser apparatus 2. Figure 2 is a cross-sectional view of the gas laser apparatus 2 shown in Figure 1, viewed from the Z direction. The gas laser apparatus 2 is a discharge-excited gas laser apparatus, for example, an excimer laser apparatus.

[0012] In Figure 1, the direction of propagation of the pulsed laser beam PL output from the gas laser device 2 is defined as the Z direction. The discharge direction, described later, is defined as the Y direction. The direction perpendicular to both the Z and Y directions is defined as the X direction.

[0013] In Figure 1, the gas laser apparatus 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. The charger 11 is an example of a "power supply" related to the technology of this disclosure.

[0014] The laser chamber 10 is a metal container formed of, for example, aluminum metal with nickel plating on its surface. Inside the laser chamber 10 are a pair of discharge electrodes 20, a ground plate 21, wiring 22, a fan 23, a heat exchanger 24, and a pre-ionization discharge section 19. As shown in Figure 2, the pre-ionization discharge section 19 includes a pre-ionization outer electrode 19a, a dielectric pipe 19b, and a pre-ionization inner electrode 19c.

[0015] The laser chamber 10 is filled with laser gas, which serves as the laser medium. The laser gas includes, for example, rare gases such as argon, krypton, and xenon, buffer gases such as neon and helium, and halogen gases such as chlorine and fluorine.

[0016] Furthermore, an opening is formed in the laser chamber 10. An electrical insulating plate 26 is provided via an O-ring 18, which acts as a sealing member, to close this opening. Multiple feedthroughs 25 are embedded in the electrical insulating plate 26. Multiple peaking capacitors 27 and a holder 28 that holds them are arranged on the electrical insulating plate 26. The PPM 12 is placed on this holder 28. The laser chamber 10 and the holder 28 are grounded.

[0017] The pair of discharge electrodes 20 consists of a cathode electrode 20a and an anode electrode 20b. The cathode electrode 20a and the anode electrode 20b are positioned opposite each other within 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 the discharge space. The side of the cathode electrode 20a opposite to the discharge surface is supported by an electrical insulating plate 26. The side of the anode electrode 20b opposite to the discharge surface is supported by a ground plate 21.

[0018] The feedthrough 25 is connected to the cathode electrode 20a. Also, as shown in Figure 2, the feedthrough 25 is connected to the peaking capacitor 27 held in the holder 28 via a connector 29. The connector 29 is a component for connecting the peaking capacitor 27 to other components.

[0019] The wall 28a forming the internal space of the holder 28 is made of a metallic material such as aluminum. Inside the holder 28 are a plurality of peaking capacitors 27, a connection part 29, and the high-voltage terminal 12b of the PPM 12. The peaking capacitors 27 are capacitors that supply the electrical energy received and stored from the PPM 12 to a pair of discharge electrodes 20. The peaking capacitors 27 are, for example, ceramic capacitors whose dielectric material is strontium titanate.

[0020] The peaking capacitors 27 are arranged in a matrix, with two in the X direction and multiple in the Z direction. Multiple peaking capacitors 27 are connected in parallel via a connection part 29. In each peaking capacitor 27, one electrode 27a is connected to the high-voltage terminal 12b and the feedthrough 25 via the connection part 29, and the other electrode 27b is connected to the wall 28a of the holder 28 via the connection part 29.

[0021] The connection section 29 includes a connection plate 29a and connection terminals 29b and 29c. The connection plate 29a is made of a conductive plate with a U-shaped cross-section and is connected to the high-voltage terminal 12b and the feedthrough 25.

[0022] The ground plate 21 is connected to the laser chamber 10 via wiring 22. The laser chamber 10 is grounded. The ground plate 21 is grounded via wiring 22. The Z-direction end of the ground plate 21 is fixed to the laser chamber 10.

[0023] Fan 23 is a cross-flow fan for circulating laser gas within the laser chamber 10 and is positioned on the opposite side of the discharge space from the ground plate 21. A motor 23a is connected to the laser chamber 10 to rotate fan 23.

[0024] The laser gas blown out from fan 23 flows into the discharge space. The direction of the laser gas flowing into the discharge space is approximately parallel to the X direction. The laser gas flowing out of the discharge space can be drawn back into fan 23 via heat exchanger 24. Heat exchanger 24 performs heat exchange between the refrigerant supplied inside heat exchanger 24 and the laser gas.

[0025] The ends of the laser chamber 10 are provided with windows 10a and 10b for emitting 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 and the windows 10a and 10b.

[0026] 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 it to the grating 15b.

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

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

[0029] Light emitted from the laser chamber 10 travels back and forth between the narrowband module 15 and the output coupling mirror 16, and is amplified each time it passes through the discharge space. A portion of the amplified light is output as pulsed laser light PL via the output coupling mirror 16. Pulsed laser light PL is an example of "laser light" related to the technology of this disclosure.

[0030] The pulse energy measurement unit 13 is positioned in the optical path of the pulsed laser light PL output via the output coupling mirror 16. The pulse energy measurement 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 onto the light-receiving surface of the light sensor 13c. The light sensor 13c measures the pulse energy of the light focused onto the light-receiving surface and outputs the measured value to the control unit 14.

[0032] The pressure sensor 17 detects the gas pressure inside 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 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 constant charging voltage to the main capacitor C0, which will be described later, included in the PPM 12. The PPM 12 includes a solid switch SW controlled by the control unit 14. The solid switch SW is a semiconductor switching element composed of an insulated gate bipolar transistor (IGBT). When the solid switch SW is switched from OFF to ON, the PPM 12 generates a high-voltage pulse from the electrical energy held in the main capacitor C0 and applies it to the pair of discharge electrodes 20.

[0034] The control unit 14 is a processor that sends and receives various signals to and from the exposure apparatus control unit 110, which is located in the exposure apparatus 100. For example, signals related to the target pulse energy and target oscillation timing of the pulsed laser light PL output to the exposure apparatus 100 are transmitted to the control unit 14 from the exposure apparatus control unit 110.

[0035] The control unit 14 comprehensively controls the operation of each component of the gas laser apparatus 2 based on various signals transmitted from the exposure apparatus control unit 110, measured pulse energy values, detected gas pressure values, etc.

[0036] 1.1.2 Operation The control unit 14 controls a laser gas supply unit (not shown) to ensure that laser gas is supplied into the laser chamber 10.

[0037] The control unit 14 drives the motor 23a to rotate the fan 23. This causes the laser gas inside the laser chamber 10 to circulate.

[0038] The control unit 14 receives signals related to the target pulse energy Et and target oscillation timing transmitted from the exposure apparatus control unit 110.

[0039] The control unit 14 sets the charging voltage Vhv in the charger 11 according to the target pulse energy Et. The control unit 14 stores the value of the charging voltage Vhv set in the charger 11. The control unit 14 operates the solid switch SW of the PPM 12 in synchronization with the target oscillation timing.

[0040] When the solid switch SW of the PPM12 is switched from OFF to ON, a voltage can be applied between the pre-ionization inner electrode 19c and the pre-ionization outer electrode 19a of the pre-ionization discharge section 19. This causes a corona discharge to occur in the pre-ionization discharge section 19, generating UV (Ultraviolet) light. The laser gas in the discharge space is irradiated with UV light, causing the laser gas to be pre-ionized. Then, a voltage is applied to the pair of discharge electrodes 20.

[0041] Subsequently, a main discharge occurs in the discharge space. If the direction of the main discharge is defined as the direction in which electrons flow, then the discharge direction is from the cathode electrode 20a towards the anode electrode 20b. When the main discharge occurs, the laser gas in the discharge space is excited and emits light.

[0042] Light emitted from the laser gas is reflected by the narrowband module 15 and the output coupling mirror 16, and travels back and forth within the laser resonator, causing laser oscillation. The narrowbanded light from the narrowband module 15 is output as pulsed laser light PL from the output coupling mirror 16.

[0043] A portion of the pulsed laser light PL output from the output coupling mirror 16 is incident on the pulse energy measurement unit 13. The pulse energy measurement unit 13 measures the pulse energy E of the incident pulsed laser light PL and outputs the measured value to the control unit 14.

[0044] The control unit 14 stores the measured value of pulse energy E measured by the pulse energy measurement unit 13. The control unit 14 calculates the difference ΔE between the measured value of pulse energy E and the target pulse energy Et. Based on the difference ΔE, the control unit 14 feedback-controls the charging voltage Vhv so that the measured value of pulse energy E becomes the target pulse energy Et.

[0045] 1.2 Pulse Power Module 1.2.1 Configuration Figure 3 schematically shows the configuration of the PPM12 in the comparative example. The PPM12 includes a power supply circuit 30 as a high-voltage generator and a reset circuit 31. In Figure 3, the multiple peaking capacitors 27 connected in parallel as described above are represented as a single peaking capacitor Cp.

[0046] The power supply circuit 30 is connected between the charger 11 and the peaking capacitor Cp. The power supply circuit 30 includes a main capacitor C0, a solid switch SW, a step-up transformer TC1, a first magnetic pulse compression circuit MPC1, a second magnetic pulse compression circuit MPC2, and a regenerative transformer TC2. The solid switch SW is controlled by the control unit 14 described above.

[0047] The main capacitor C0 is connected in parallel to the charger 11. The step-up transformer TC1 has its primary side connected in parallel to the main capacitor C0 via a solid switch SW. Specifically, the step-up transformer TC1 includes a primary winding TC11 and a secondary winding TC12. The primary winding TC11 is connected in parallel to the main capacitor C0 via a solid switch SW and a magnetic switch SR0.

[0048] The first magnetic pulse compression circuit MPC1 is connected in parallel to the secondary side of the step-up transformer TC1. Specifically, the first magnetic pulse compression circuit MPC1 includes a first transfer capacitor C1 and a first magnetic switch SR1. The first transfer capacitor C1 is connected in parallel to the secondary winding TC12 of the step-up transformer TC1, and the charge from the main capacitor C0, which is charged by the charger 11, is transferred to it.

[0049] The second magnetic pulse compression circuit MPC2 is connected downstream of the first magnetic pulse compression circuit MPC1. Specifically, the second magnetic pulse compression circuit MPC2 includes a second transfer capacitor C2 and a second magnetic switch SR2. The second transfer capacitor C2 is connected in parallel to the first transfer capacitor C1 via the first magnetic switch SR1, and the charge of the first transfer capacitor C1 is transferred to the second transfer capacitor C2.

[0050] A peaking capacitor Cp is connected in parallel to the second transfer capacitor C2 via a second magnetic switch SR2. Charge from the second transfer capacitor C2 is transferred to the peaking capacitor Cp. A pair of discharge electrodes 20 are connected in parallel to the peaking capacitor Cp.

[0051] After the main discharge occurs between the pair of discharge electrodes 20, charge can move in the reverse direction and then in the forward direction between the peaking capacitor Cp and the main capacitor C0, which can adversely affect the main discharge. Therefore, the regenerative transformer TC2 and diodes D1 and D2 constitute a regenerative circuit that stores the charge transferred from the peaking capacitor Cp to the main capacitor C0 after the main discharge in the main capacitor C0, and regenerates it as part of the next charging energy.

[0052] The regenerative transformer TC2 includes a primary winding TC21 and a secondary winding TC22. The primary winding TC21 is connected in parallel to the main capacitor C0 via diode D1. The secondary winding TC22 is connected in parallel to the first transfer capacitor C1 via diode D2.

[0053] In Figure 3, the dots shown on the step-up transformer TC1 and the regenerative transformer TC2 represent the winding polarity. In the step-up transformer TC1, the primary winding TC11 and the secondary winding TC12 have opposite polarities. Therefore, the step-up transformer TC1 transfers the voltage charged to the main capacitor C0 to the first transfer capacitor C1 with reverse polarity, i.e., in reverse phase. In the regenerative transformer TC2, the primary winding TC21 and the secondary winding TC22 have the same polarity. Therefore, the regenerative transformer TC2 transfers the voltage charged to the first transfer capacitor C1 to the main capacitor C0 without changing polarity, i.e., in phase.

[0054] The reset circuit 31 includes a reset power supply 32, a reset winding LR0 for the magnetic switch, a reset winding LR1 for the first magnetic switch, a reset winding LR2 for the second magnetic switch, a reset winding TC1R for the boost transformer, and a reset winding TC2R for the regenerative transformer. The reset windings LR0, LR1, LR2, TC1R, and TC2R are connected in series and connected to the reset power supply 32. The reset power supply 32 is a constant current source.

[0055] The reset winding LR0 for the magnetic switch is wound around the core of the magnetic switch SR0 and resets the operating point of the core when energized. The reset winding LR1 for the first magnetic switch is wound around the core of the first magnetic switch SR1 and resets the operating point of the core when energized. The reset winding LR2 for the second magnetic switch is wound around the core of the second magnetic switch SR2 and resets the operating point of the core when energized. The reset winding TC1R for the boost transformer is wound around the core of the boost transformer TC1 and resets the operating point of the core when energized. The reset winding TC2R for the regenerative transformer is wound around the core of the regenerative transformer TC2 and resets the operating point of the core when energized.

[0056] The reset circuit 31 is magnetically coupled to the magnetic switches SR0, SR1, and SR2 included in the power supply circuit 30. The magnetic switches SR0, SR1, and SR2 are composed of saturable reactors. Magnetic switch SR0 reduces switching losses that occur in solid switches SW.

[0057] The first magnetic pulse compression circuit MPC1 and the second magnetic pulse compression circuit MPC2 are designed so that each element sequentially narrows the pulse width of the current pulse in order to generate a large discharge at the pair of discharge electrodes 20. The first magnetic pulse compression circuit MPC1 compresses the pulse width of the current pulse during charge transfer from the first transfer capacitor C1 to the second transfer capacitor C2. The second magnetic pulse compression circuit MPC2 compresses the pulse width of the current pulse during charge transfer from the second transfer capacitor C2 to the peaking capacitor Cp.

[0058] 1.2.2 Magnetic Switches Next, the detailed configuration and operation of the magnetic switches SR0, SR1, and SR2 included in the power supply circuit 30 will be described. Figure 4 shows the configuration of a saturable reactor that constitutes a typical magnetic switch. Figure 5 shows the magnetization curve of the core of the saturable reactor. As shown in Figure 4, the core CR is wound with a main winding SR and a reset winding LR. The reset winding LR is connected to the reset circuit 31.

[0059] When the operating point of core CR is at point "0" in Figure 5, a DC current flows through the reset winding LR, causing the operating point of core CR to move to P5. When an excitation current flows through the main winding SR, the magnetic field strength H increases. As a result, the operating point of core CR moves from P5, through P4, towards P1.

[0060] When the operating point of core CR reaches P1, the magnetic flux density B within core CR becomes greater than or equal to the saturation magnetic flux density, and the saturable reactor saturates. At this time, the inductance of the saturable reactor decreases rapidly, and the main winding SR becomes conductive. The operating point of core CR is at a point where the magnetic field strength H is much greater than P1 when the saturable reactor is saturated, but it moves from P1 to P2 as the current flowing through the main winding SR decreases. At this time, the inductance of the saturable reactor increases rapidly, so the current flowing through the main winding SR decreases rapidly. When the current in the main winding SR becomes 0, the operating point of core CR stops at P2, and magnetic flux remains in core CR.

[0061] When excitation current flows again to the main winding SR while the operating point of core CR is at P2, the operating point of core CR moves from P2 towards P1. The change in magnetic flux density B at this time is smaller than the change when it moves from P5 through P4 towards P1. Therefore, the inductance of the saturable reactor does not become sufficiently large when it is not saturated, and magnetic pulse compression operation can hardly be performed. In order to perform magnetic pulse compression operation, a magnetic reset is necessary to return the operating point of core CR from P2 to P5 via P3. Therefore, a DC current in the opposite direction to that of the main winding SR flows as a reset current through the reset winding LR. The operating point of core CR is returned to P5 after the current in the main winding SR becomes 0.

[0062] 1.2.3 Operation The operation of the PPM12 in the comparative example will be explained using Figure 6. First, with the solid switch SW turned OFF by the control unit 14, the main capacitor C0 is charged by the charger 11. Here, the voltage Vc0 of the charged main capacitor C0 is positive.

[0063] When the control unit 14 switches the solid switch SW from OFF to ON, the voltage Vc0 across the main capacitor C0 is applied to the magnetic switch SR0. When the time integral of the voltage Vc0 across the main capacitor C0 reaches a limit value determined by the characteristics of the magnetic switch SR0, the magnetic switch SR0 saturates and its inductance decreases. Time t1 in Figure 6 indicates the timing at which the inductance of the magnetic switch SR0 decreases.

[0064] After time t1, current flows through the loop of the main capacitor C0, magnetic switch SR0, the primary winding TC11 of the step-up transformer TC1, and the solid switch SW. Simultaneously, current also flows through the loop of the secondary winding TC12 of the step-up transformer TC1 and the first transfer capacitor C1. As a result, the charge stored in the main capacitor C0 is transferred to the first transfer capacitor C1, and the first transfer capacitor C1 is charged to the negative side.

[0065] When the time integral of the voltage Vc1 across the first transfer capacitor C1 reaches a limit value determined by the characteristics of the first magnetic switch SR1, the first magnetic switch SR1 saturates and its inductance decreases. Time t2 in Figure 6 indicates the timing at which the inductance of the first magnetic switch SR1 decreases.

[0066] After time t2, current flows through the loop of the first transfer capacitor C1, the second transfer capacitor C2, and the first magnetic switch SR1. As a result, the charge stored in the first transfer capacitor C1 is transferred to the second transfer capacitor C2, and the second transfer capacitor C2 is charged to the negative side.

[0067] When the time integral of the voltage Vc2 across the second transfer capacitor C2 reaches a limit determined by the characteristics of the second magnetic switch SR2, the second magnetic switch SR2 saturates and its inductance drops sharply. Time t3 in Figure 6 indicates the timing at which the inductance of the second magnetic switch SR2 decreases.

[0068] After time t3, current flows through the loop of the second transfer capacitor C2, the peaking capacitor Cp, and the second magnetic switch SR2. As a result, the charge stored in the second transfer capacitor C2 is transferred to the peaking capacitor Cp, and the peaking capacitor Cp is charged to the negative side.

[0069] When the voltage Vcp across the peaking capacitor Cp reaches the breakdown voltage, the laser gas between the pair of discharge electrodes 20 undergoes dielectric breakdown, initiating the main discharge. This main discharge excites the laser medium, generating light.

[0070] After the main discharge, a reverse voltage is applied to the peaking capacitor Cp due to residual charge from the main discharge, etc. In other words, the peaking capacitor Cp is charged to the positive side. Time t4 in Figure 6 indicates the timing when the peaking capacitor Cp is charged to the positive side.

[0071] After time t4, charge is transferred from the peaking capacitor Cp to the second transfer capacitor C2, and then from the second transfer capacitor C2 to the first transfer capacitor C1. Similar to the peaking capacitor Cp, the second transfer capacitor C2 and the first transfer capacitor C1 are subjected to a voltage with the opposite polarity to the charging voltage during magnetic pulse compression operation. That is, the second transfer capacitor C2 and the first transfer capacitor C1 are charged to the positive side. Time t5 in Figure 6 shows the timing when the second transfer capacitor C2 is charged to the positive side. Time t6 in Figure 6 shows the timing when the first transfer capacitor C1 is charged to the positive side.

[0072] During regenerative operation, the solid switch SW is OFF, so charge transfer from the first transfer capacitor C1 to the main capacitor C0 is performed via the regenerative transformer TC2. As a result, the main capacitor C0 is charged to the same polarity as the voltage charged by the charger 11, i.e., the positive side. At this time, the solid switch SW is OFF, and the diodes D1 and D2 are connected in reverse polarity, so charge is accumulated in the main capacitor C0 until the solid switch SW is switched ON by the control unit 14.

[0073] When the regenerative operation is complete, the voltages Vc1, Vc2, and Vcp are almost zero. However, since current continues to flow through the reset circuit 31 even after the main capacitor C0 has been charged by the regenerative operation, the voltages Vc1, Vc2, and Vcp change. Voltages Vcp and Vc2 decrease over time and rise simultaneously at the timing when the core of the second magnetic switch SR2 is reset. On the other hand, voltage Vc1 rises over time and then decreases.

[0074] Then, the voltages Vc1, Vc2, and Vcp all rise in sync with the timing when the core of the first magnetic switch SR1 is reset, and then fall when the core of the boost transformer TC1 is reset, eventually converging to 0.

[0075] When the repetition frequency of the pulsed laser light PL is approximately 4 kHz or less, the pulse interval is approximately 250 μs or more, so the voltages Vc1, Vc2, and Vcp converge to 0 between the occurrence of the main discharge and the next magnetic pulse compression operation.

[0076] However, if the repetition frequency of the pulsed laser light PL is approximately 6 kHz or higher, the pulse interval is approximately 166 μs or less, so the next magnetic pulse compression operation starts before the voltages Vc1, Vc2, and Vcp converge to zero. This is because the voltages Vc1, Vc2, and Vcp have high peak values ​​on the positive side and require time to converge to zero. If charging starts due to the magnetic pulse compression operation while a voltage is present in the peaking capacitor Cp, it may adversely affect the main discharge.

[0077] 1.2.4 Adjusting the pulse power module In order to suppress the adverse effects on the main discharge, it is preferable to reduce the peak value of the voltage Vcp generated due to the reset current after the main discharge. In the comparative example, an upper limit value VL is set at the elapsed time T from the main discharge, and PPM12 is adjusted so that the voltage Vcp becomes equal to or lower than the upper limit value VL. For example, for the period of 1 μs ≤ T < 20 μs, VL = 0 V; for the period of 20 μs ≤ T < 30 μs, VL = 300 V; and for the period of 30 μs ≤ T, VL = 500 V.

[0078] Specifically, in the comparative example, in order to suppress the voltage Vcp of the peaking capacitor Cp to be equal to or lower than the upper limit value VL, PPM12 is adjusted in advance so as to satisfy the first adjustment condition and the second adjustment condition. The first adjustment condition is a condition for making the voltage Vc1 negative after the regeneration operation is completed. The second adjustment condition is a condition for suppressing the rising speed of the voltage Vcp after the regeneration operation is completed.

[0079] The parameters related to the first adjustment condition and the second adjustment condition are defined as follows. C C0 : Capacitance of the main capacitor C0 C C1 : Capacitance of the first transfer capacitor C1 C C2 : Capacitance of the second transfer capacitor C2 C Cp : Capacitance of the peaking capacitor Cp N TC11 : Number of turns of the primary winding TC11 of the step-up transformer TC1 N TC12 : Number of turns of the secondary winding TC1₂ of the step-up transformer TC1 N TC21 : Number of turns of the primary winding TC21 of the flyback transformer TC2 N TC22 : Number of turns of the secondary winding TC22 of the flyback transformer TC2 I TC1R : Reset current flowing through the reset winding TC1R of the step-up transformer I TC2R : Reset current flowing through the reset winding TC2R of the flyback transformer

[0080] The first adjustment condition is defined by the following equations (1) and (2).

[0081]

number

number

[0082] The second adjustment condition is defined by equations (3) and (4) below. Here, K is a constant representing a predetermined voltage rise rate.

[0083]

number

number

[0084] Also, capacity C C1 ,C C2 ,C Cp The relationship shown in equation (5) below is satisfied.

number

[0085] 1.3 Challenges The applicant confirmed that when the gas laser apparatus 2, a comparative example in which PPM12 was adjusted as described above, was discharged, a negative kickback waveform occurred between the pair of discharge electrodes 20 after the main discharge, and the arc discharge intensity increased. When the arc discharge intensity increases, the amount of wear on the pair of discharge electrodes 20 increases, shortening their lifespan. In addition, the energy stability of the laser output also decreases.

[0086] Furthermore, the Applicant has confirmed that the intensity of arc discharge increases when CM1200hc-66X (hereinafter referred to as "66X") or 5SNA_1000N330300 (hereinafter referred to as "ABB") is used rather than when CM1200HC-66H (hereinafter referred to as "66H") is used as the solid-state switch SW. 66H and 66X are IGBT modules manufactured by Mitsubishi Electric Corporation, and ABB is an IGBT module manufactured by ABB Ltd.

[0087] As shown in FIG. 7, the increase in the intensity of arc discharge is considered to be caused by the occurrence of the first peak PK1, the second peak PK2, and the third peak PK3 in the potential Ec of the cathode electrode 20a after the main discharge. When the elapsed time from the main discharge is T, the first peak PK1 and the second peak PK2 occur during the period of 0.5 μs < T < 5 μs. The third peak PK3 occurs during the period of 5 μs < T < 20 μs. The first peak PK1 and the second peak PK2 are negative potentials of about -1.5 kV. The third peak PK3 is a negative potential of about -400 V.

[0088] 1.3.1 The First Peak The first peak PK1 is caused by the voltage remaining in the first transfer capacitor C1 after the magnetic pulse compression operation. Specifically, when the voltage is transferred from the first transfer capacitor C1 to the second transfer capacitor C2 for the main discharge, the voltage remains in the first transfer capacitor C1. The reason for the voltage remaining in the first transfer capacitor C1 is that the transfer efficiency is not 100% due to the loss of the first magnetic switch SR1, and C as in the above formula (5) C1 =C C2 is set. The residual voltage of the first transfer capacitor C1 migrates to the pair of discharge electrodes 20 through the first transfer capacitor C1, the second transfer capacitor C2, and the peaking capacitor Cp after the main discharge, thereby generating the first peak PK1.

[0089] 1.3.2 The Second Peak The second peak PK2 occurs because the first transfer capacitor C1 is charged due to the solid switch SW not being completely turned OFF during regenerative operation, resulting in an unregenerative voltage. The unregenerative voltage refers to the voltage that remains in the first transfer capacitor C1 during regenerative operation without being transferred to the main capacitor C0. Specifically, it is preferable that the solid switch SW is completely OFF at time t5 as shown in Figure 6, but due to the turn-off time of the solid switch SW, the solid switch SW is not completely OFF at time t5, resulting in an unregenerative voltage.

[0090] Compared to the 66H, the 66X and ABB have shorter turn-on times but longer turn-off times. Therefore, using the 66X or ABB as the solid switch SW increases the unregenerated voltage of the first transfer capacitor C1.

[0091] 1.3.3 Third Peak The third peak PK3 is caused by the current generated in the first magnetic pulse compression circuit MPC1 and the second magnetic pulse compression circuit MPC2 by the reset current used to reset the first magnetic switch SR1 and the second magnetic switch SR2. In other words, the third peak PK3 is caused by the energy injection from the reset circuit 31 to the pair of discharge electrodes 20.

[0092] In Figure 3, Ir represents the reset current flowing through the reset circuit 31 when the first magnetic switch SR1 and the second magnetic switch SR2 are reset. Isr1 represents the current generated in the first magnetic pulse compression circuit MPC1 during reset. Isr2 represents the current generated in the second magnetic pulse compression circuit MPC2 during reset. Currents Isr1 and Isr2 are the currents required to return the first magnetic switch SR1 and the second magnetic switch SR2 to their initial state.

[0093] 2. Embodiments 2.1 Configuration and Operation The gas laser apparatus 2 according to the embodiment of this disclosure has the same configuration as the gas laser apparatus 2 according to the comparative example, except that the adjustment conditions for PPM 12 are different. Furthermore, the operation of the gas laser apparatus 2 according to this embodiment is the same as the operation of the gas laser apparatus 2 according to the comparative example.

[0094] 2.2 Adjusting the pulse power module In this embodiment, the first peak PK1, second peak PK2, and third peak PK3 that occur in the potential Ec of the cathode electrode 20a after the main discharge are suppressed by changing the adjustment conditions of PPM12 in the comparative example. The following describes only the differences from the comparative example.

[0095] 2.2.1 First Peak In this embodiment, in order to suppress the residual voltage of the first transfer capacitor C1, which is the cause of the first peak PK1, capacitance C C1 ,C C2 ,C Cp Adjust it so that it satisfies the relationship in equation (6) below. That is, instead of equation (5) above, use equation (6) below to find the capacity C C1 ,C C2 ,C Cp Adjust the following. Here, suppressing residual voltage means bringing the residual voltage closer to zero.

[0096]

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[0097] Figure 8 shows the capacitance C of the first transfer capacitor C1. C1 The calculation results showing the relationship with the residual voltage of the first transfer capacitor C1 are shown below. Specifically, Figure 8 shows the capacitance C of the second transfer capacitor C2. C2 Using the parameter, the capacitance C C1 The results of varying the capacitance from 5nF to 10nF are shown.

[0098] The capacity C is set such that the above equation (6) is satisfied and the charger 11 is at maximum output, and the below equation (7) is satisfied. C1 We confirmed that adjusting this suppressed the first peak PK1.

[0099]

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[0100] Here, Vrd represents the residual voltage of the first transfer capacitor C1.

[0101] 2.2.2 Second Peak In this embodiment, in order to suppress the unregenerated voltage, which is the cause of the second peak PK2, the turns ratio of the primary winding TC21 and the secondary winding TC22 of the regenerative transformer TC2 is adjusted to satisfy equation (8) below, instead of equation (2) above. Here, suppressing the unregenerated voltage means bringing the unregenerated voltage closer to 0.

[0102]

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[0103] This alters the voltage relationship between the primary and secondary sides of the regenerative transformer TC2, making it more difficult for the first transfer capacitor C1 to charge during regenerative operation.

[0104] Figure 9 shows an example of the change in the voltage Vc1 of the first transfer capacitor C1 with respect to the elapsed time T since the start of main discharge. Figure 9 shows the change in voltage Vc1 when 66H and 66X are used as the solid switch SW. Compared to 66H, 66X has a longer turn-off time and there is a period during regenerative operation when it is not completely OFF, so it generates a larger unregenerated voltage than 66H.

[0105] By adjusting the regenerative transformer TC2 to satisfy equation (8) above, the unregenerated voltage is suppressed. For example, when using 66X as the solid switch SW, adjusting the regenerative transformer TC2 to satisfy equation (8) above will suppress the unregenerated voltage more than when using 66H as the solid switch SW and equation (8) above is not satisfied.

[0106] Therefore, by adjusting the regenerative transformer TC2 to satisfy equation (8) above, the second peak PK2 is suppressed.

[0107] 2.2.3 Third Peak In this embodiment, in order to suppress the energy injection from the reset circuit 31 to the pair of discharge electrodes 20, which is the cause of the third peak PK3, the reset current Ir flowing through the reset circuit 31 is set to 3A or more. Furthermore, the current Isr1 generated in the first magnetic pulse compression circuit MPC1 during reset and the current Isr2 generated in the second magnetic pulse compression circuit MPC2 during reset are made to satisfy the following equation (9).

[0108]

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[0109] The relationship in equation (9) above can be satisfied by adjusting the ratio of the number of windings of the first magnetic switch SR1 to the number of windings of the second magnetic switch SR2.

[0110] By satisfying the relationship in equation (9) above, the reset force of the second magnetic switch SR2 becomes higher than that of the first magnetic switch SR1. Furthermore, by setting the reset current Ir to 3A or more, the reset force of the second magnetic switch SR2 is increased. As a result, energy injection from the reset circuit 31 to the pair of discharge electrodes 20 is suppressed, and the third peak PK3 is suppressed.

[0111] 2.3 Effects By adjusting PPM12 as described above, the first peak PK1, the second peak PK2, and the third peak PK3 are suppressed. As a result, as shown in Figure 10, the potential Ec of the cathode electrode 20a during the period from 0.5 μs to 20 μs after the start of the main discharge is within the range of -200 V to 200 V. For example, the start of the main discharge is identified as the point at which a breakdown occurs between the pair of discharge electrodes 20 due to the voltage transferred from the main capacitor C0 to the peaking capacitor Cp via magnetic pulse compression operation.

[0112] By suppressing the negative kickback waveform in this way, arc discharge is suppressed, extending the lifespan of the pair of discharge electrodes 20. Furthermore, this improves the energy stability of the laser output.

[0113] 3. Method for manufacturing electronic devices Figure 11 schematically shows an example configuration of the exposure apparatus 100. The exposure apparatus 100 includes an illumination optical system 104 and a projection optical system 106. The illumination optical system 104 illuminates the reticle pattern of a reticle (not shown) placed on the reticle stage RT with pulsed laser light Lp incident from, for example, a gas laser device 2. The projection optical system 106 reduces and projects the pulsed laser light Lp that has passed through the reticle onto a workpiece (not shown) placed on the workpiece table WT, forming an image. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist.

[0114] The exposure apparatus 100 exposes the workpiece with pulsed laser light Lp that reflects the reticle pattern by synchronously moving the reticle stage RT and the workpiece table WT in parallel. After transferring the reticle pattern to the semiconductor wafer through the exposure process described above, a semiconductor device can be manufactured by going through several processes. The semiconductor device is an example of an "electronic device" in this disclosure.

[0115] The above description is intended to be illustrative and not restrictive. It will therefore be apparent to those skilled in the art that modifications can be made to each embodiment of this disclosure without departing from the scope of the attached claims.

[0116] Terms used throughout this specification and the accompanying claims should be interpreted as “non-limiting.” For example, the terms “includes” or “contains” should be interpreted as “not limited to what is described as included.” The term “has” should be interpreted as “not limited to what is described as having.” Furthermore, the modifying phrase “one” as used throughout this specification and the accompanying claims should be interpreted as “at least one” or “one or more.”

Claims

1. Power supply and A main capacitor connected in parallel to the aforementioned power supply, Solid switches and A step-up transformer whose primary side is connected in parallel to the main capacitor via the solid switch, A first transfer capacitor onto which the charge of the main capacitor is transferred, and a first magnetic pulse compression circuit having a first magnetic switch and connected to the secondary side of the step-up transformer, A second transfer capacitor onto which the charge of the first transfer capacitor is transferred, and a second magnetic pulse compression circuit having a second magnetic switch and connected downstream of the first magnetic pulse compression circuit, A peaking capacitor connected downstream of the second magnetic pulse compression circuit, onto which the charge of the second transfer capacitor is transferred, A pair of discharge electrodes, consisting of a cathode electrode and an anode electrode, connected in parallel to the peaking capacitor, A regenerative transformer is connected in parallel to the main capacitor on its primary side and in parallel to the first transfer capacitor on its secondary side, and after the main discharge, the charge generated by the pair of discharge electrodes is transferred to the main capacitor. A reset circuit for resetting the first magnetic switch and the second magnetic switch, Equipped with, When the pulse interval of the pulsed laser light generated by repeatedly generating a main discharge is 166 μs or less, the potential of the cathode electrode during a period of 1 μs to 20 μs from the start of the main discharge is within the range of -200 V to 200 V, and is a potential that remains above zero potential after changing from negative potential to positive potential. Gas laser device.

2. A gas laser apparatus according to claim 1, The capacitance of the first transfer capacitor is C. Ｃ１ The capacitance of the second transfer capacitor is C Ｃ２ The capacitance of the peaking capacitor is C Ｃｐ In that case, C Ｃｐ <C Ｃ１ <C Ｃ２ It satisfies the relationship.

3. A gas laser apparatus according to claim 2, 5nF < C Ｃ１ <The relationship 10nF is satisfied.

4. A gas laser apparatus according to claim 3, When Vrd is the residual voltage of the first transfer capacitor remaining after charge has been transferred from the first transfer capacitor to the second transfer capacitor, the relationship -1.5kV < Vrd < 0V is satisfied.

5. A gas laser apparatus according to claim 1, Let the capacitance of the main capacitor be C Ｃ０ and the capacitance of the first transfer capacitor be C Ｃ１ Let the number of turns of the primary winding of the regeneration transformer be N ＴＣ２１ and the number of turns of the secondary winding of the regeneration transformer be N ＴＣ２２ When this is the case, N ＴＣ２２ / N ＴＣ２１ > (C Ｃ０ / C Ｃ１ ) ０．５ satisfies the relationship.

6. A gas laser apparatus according to claim 5, The number of turns of the primary winding of the aforementioned step-up transformer is N ＴＣ１１ The number of turns of the secondary winding of the step-up transformer is N ＴＣ１２ In that case, N ＴＣ１２ / N ＴＣ１１ > (C Ｃ０ / C Ｃ１ ) ０．５ It satisfies the relationship.

7. A gas laser apparatus according to claim 1, When Isr1 is the current generated in the first magnetic pulse compression circuit during reset, and Isr2 is the current generated in the second magnetic pulse compression circuit during reset, the relationship Isr2 > 2.5 × Isr1 is satisfied.

8. A gas laser apparatus according to claim 7, The reset current flowing through the reset circuit during a reset is 3A or more.

9. A gas laser apparatus according to claim 1, The capacitance of the main capacitor is C. Ｃ０ The capacitance of the first transfer capacitor is C Ｃ１ The capacitance of the second transfer capacitor is C Ｃ２ The capacitance of the peaking capacitor is C Ｃｐ The number of turns of the primary winding of the regenerative transformer is N ＴＣ２１ The number of turns of the secondary winding of the regenerative transformer is N ＴＣ２２ When the current generated in the first magnetic pulse compression circuit during reset is denoted as Isr1, and the current generated in the second magnetic pulse compression circuit during reset is denoted as Isr2, C Ｃｐ <C Ｃ１ <C Ｃ２ , N ＴＣ２２ / N ＴＣ２１ > (C Ｃ０ / C Ｃ１ ) ０．５ The relationship is satisfied, and Isr2 > 2.5 × Isr1.

10. A gas laser apparatus according to claim 1, A solid-state switch is an insulated-gate bipolar transistor.

11. A gas laser apparatus according to claim 1, The step-up transformer has a primary winding and a secondary winding with opposite polarity, while the regenerative transformer has a primary winding and a secondary winding with the same polarity.

12. A method for manufacturing electronic devices, Power supply and A main capacitor connected in parallel to the aforementioned power supply, Solid switches and A step-up transformer whose primary side is connected in parallel to the main capacitor via the solid switch, A first transfer capacitor onto which the charge of the main capacitor is transferred, and a first magnetic pulse compression circuit having a first magnetic switch and connected to the secondary side of the step-up transformer, A second transfer capacitor onto which the charge of the first transfer capacitor is transferred, and a second magnetic pulse compression circuit having a second magnetic switch and connected downstream of the first magnetic pulse compression circuit, A peaking capacitor connected downstream of the second magnetic pulse compression circuit, onto which the charge of the second transfer capacitor is transferred, A pair of discharge electrodes, consisting of a cathode electrode and an anode electrode, connected in parallel to the peaking capacitor, A regenerative transformer is connected in parallel to the main capacitor on its primary side and in parallel to the first transfer capacitor on its secondary side, and after the main discharge, the charge generated by the pair of discharge electrodes is transferred to the main capacitor. A reset circuit for resetting the first magnetic switch and the second magnetic switch, Equipped with, When the pulse interval of the pulsed laser light generated by repeatedly generating a main discharge is 166 μs or less, the potential of the cathode electrode during a period of 1 μs to 20 μs from the start of the main discharge is within the range of -200 V to 200 V, and is a potential that remains above zero potential after changing from negative potential to positive potential. A gas laser device generates laser light, The laser light is output to the exposure apparatus, To manufacture an electronic device, the process involves exposing a photosensitive substrate to laser light within the exposure apparatus. A method for manufacturing electronic devices.

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