Extreme ultraviolet light generating apparatus and method for manufacturing electronic devices

Abstract

To provide an extreme ultraviolet light generator that suppresses reliability from decreasing.SOLUTION: An extreme ultraviolet light generator 100 includes: a first light source that emits first excitation light; a laser oscillator 135 that includes an active medium and emits laser beam by irradiating the active medium with the first excitation light to laser oscillate; a measuring device 400 that measures the pulse energy and pulse time width of the laser beam; a temperature controller 137 that adjusts the temperature of a cooling medium that cools the first light source; and a processor 121, the processor controls a temperature controller that adjusts the temperature of the cooling medium so that the pulse energy measured by the measuring device falls within a target range of the pulse energy, and a current value of the current supplied to the first light source is adjusted so that the pulse time width measured by the measuring device falls within a target range of the pulse time width.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to an extreme ultraviolet light generating apparatus and a method for manufacturing an electronic device. [Background technology]

[0002] In recent years, with the miniaturization of semiconductor processes, the miniaturization of transfer patterns in optical lithography for semiconductor processes has progressed rapidly. In the next generation, fine processing of 10 nm or less will be required. For this reason, there is a demand for the development of semiconductor exposure equipment that combines a device for generating extreme ultraviolet (EUV) light with a wavelength of approximately 13 nm and a reduced projection reflective optical system.

[0003] As an EUV light generation device, development of a Laser Produced Plasma (LPP) type device that uses plasma generated by irradiating a target material with laser light is progressing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2017 / 0280545 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-51897 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-289066 [Patent Document 4] Summary of the specification of U.S. Patent Application Publication No. 2008 / 0143989

[0005] An extreme ultraviolet light generation apparatus according to one aspect of the present disclosure is an extreme ultraviolet light generation apparatus that generates extreme ultraviolet light by irradiating a droplet target with laser light, and includes: a first light source that emits first excitation light; a laser oscillator that includes an active medium and irradiates the active medium with the first excitation light to cause laser oscillation and emit laser light; a measuring instrument that measures the pulse energy and pulse time width of the laser light; a temperature regulator that adjusts the temperature of a cooling medium that cools the first light source; and a processor, wherein the processor controls the temperature regulator to adjust the temperature of the cooling medium so that the pulse energy measured by the measuring instrument falls within a target range for the pulse energy, and may also adjust a current value of a current supplied to the first light source so that the pulse time width measured by the measuring instrument falls within a target range for the pulse time width.

[0006] Furthermore, a method for manufacturing an electronic device according to one aspect of the present disclosure includes an extreme ultraviolet light generation apparatus that generates extreme ultraviolet light by irradiating a droplet target with laser light, the method including: a first light source that emits first excitation light; a laser oscillator that includes an active medium and that emits laser light by irradiating the active medium with the first excitation light; a measuring instrument that measures the pulse energy and pulse time width of the laser light; a temperature regulator that adjusts the temperature of a cooling medium that cools the first light source; and a processor, wherein the processor controls the temperature regulator to adjust the temperature of the cooling medium so that the pulse energy measured by the measuring instrument falls within a target range for the pulse energy, and adjusts a current value of a current supplied to the first light source so that the pulse time width measured by the measuring instrument falls within a target range for the pulse time width. The method may also include outputting the extreme ultraviolet light generated by the extreme ultraviolet light generation apparatus to an exposure apparatus, and exposing a photosensitive substrate in the exposure apparatus to the extreme ultraviolet light to manufacture an electronic device.

[0007] In addition, a manufacturing method for an electronic device according to another aspect of the present disclosure may include an extreme ultraviolet light generation apparatus that generates extreme ultraviolet light by irradiating a droplet target with laser light, the method including: a first light source that emits first excitation light; a laser oscillator that includes an active medium, the laser oscillator including the first excitation light irradiating the active medium to cause laser oscillation and emit the laser light; a measuring instrument that measures pulse energy and pulse time width of the laser light; a temperature regulator that adjusts the temperature of a cooling medium that cools the first light source; and a processor, wherein the processor controls the temperature regulator to adjust the temperature of the cooling medium so that the pulse energy measured by the measuring instrument falls within a target range of the pulse energy, and adjusts a current value of a current supplied to the first light source so that the pulse time width measured by the measuring instrument falls within a target range of the pulse time width. [Brief explanation of the drawings]

[0008] 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 schematic diagram showing an example of the overall configuration of an electronic device manufacturing apparatus. [Figure 2] FIG. 2 is a schematic diagram showing an example of the schematic configuration of an inspection device connected to an EUV light generation system. [Figure 3] FIG. 3 is a schematic diagram showing an example of the overall configuration of an extreme ultraviolet light generation apparatus of a comparative example. [Figure 4] FIG. 4 is a schematic diagram showing an example of the general configuration of a main pulse laser device. [Figure 5] FIG. 5 is a schematic diagram showing an example of the schematic configuration of a laser oscillator. [Figure 6] FIG. 6 is a schematic diagram illustrating a schematic configuration example of a part of the extreme ultraviolet light generation apparatus according to the first embodiment. [Figure 7] FIG. 7 is a control flowchart of the processor according to the first embodiment. [Figure 8] FIG. 8 is a schematic diagram illustrating a schematic configuration example of a part of an extreme ultraviolet light generation apparatus according to the second embodiment. [Figure 9] FIG. 9 is a schematic diagram illustrating a schematic configuration example of a part of an extreme ultraviolet light generation apparatus according to the third embodiment. [Figure 10] FIG. 10 is a view of the amplifier of the third embodiment as viewed from the X direction. [Figure 11] FIG. 11 is a view of the amplifier of the third embodiment as viewed from the Y direction. [Figure 12] FIG. 12 is a control flowchart of the processor according to the third embodiment. Embodiment

[0009] 1. Overview 2. Description of electronic device manufacturing equipment 3. Description of the extreme ultraviolet light generation device as a comparative example 3.1 Configuration 3.2 Operation 3.3 Challenges 4. Description of the extreme ultraviolet light generation device according to the first embodiment 4.1 Configuration 4.2 Operation 4.3 Actions and Effects 5. Description of the extreme ultraviolet light generation device according to the second embodiment 5.1 Configuration 5.2 Operation 5.3 Actions and Effects 6. Description of the extreme ultraviolet light generation device according to the third embodiment 6.1 Configuration 6.2 Operation 6.3 Actions and Effects

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below are examples of the present disclosure and are not intended to limit the scope of the present disclosure. Furthermore, not all of the configurations and operations described in each embodiment are necessarily essential to the configurations and operations of the present disclosure. Identical components are designated by the same reference numerals, and redundant descriptions will be omitted.

[0011] 1. Overview An embodiment of the present disclosure relates to an extreme ultraviolet light generation apparatus that generates light with a wavelength called extreme ultraviolet (EUV), and an electronic device manufacturing apparatus. Note that hereinafter, extreme ultraviolet light may also be referred to as EUV light.

[0012] 2. Description of electronic device manufacturing equipment FIG. 1 is a schematic diagram showing an example of the overall configuration of an electronic device manufacturing apparatus. The electronic device manufacturing apparatus shown in FIG. 1 includes an EUV light generation system 100 and an exposure apparatus 200. The exposure apparatus 200 includes a mask irradiation unit 210 including multiple mirrors 211 and 212, which are reflective optical systems, and a workpiece irradiation unit 220 including multiple mirrors 221 and 222, which are reflective optical systems separate from the reflective optical system of the mask irradiation unit 210. The mask irradiation unit 210 illuminates a mask pattern on a mask table MT via the mirrors 211 and 212 with EUV light 101 incident from the EUV light generation system 100. The workpiece irradiation unit 220 forms an image of the EUV light 101 reflected by the mask table MT onto a workpiece (not shown) placed on a workpiece table WT via the mirrors 221 and 222. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist. Exposure apparatus 200 synchronously translates mask table MT and workpiece table WT to expose the workpiece to EUV light 101 that reflects the mask pattern. By using the exposure process described above, a device pattern can be transferred onto a semiconductor wafer, thereby manufacturing a semiconductor device.

[0013] FIG. 2 is a schematic diagram showing an example of the overall configuration of an inspection system 300 connected to the EUV light generation system 100. The inspection system 300 includes an illumination optical system 310 including multiple mirrors 311, 313, and 315, which are reflective optical systems, and a detection optical system 320 including multiple mirrors 321 and 323, which are reflective optical systems separate from the reflective optical system of the illumination optical system 310, and a detector 325. The illumination optical system 310 reflects EUV light 101 incident from the EUV light generation system 100 by the mirrors 311, 313, and 315, and irradiates a mask 333 placed on a mask stage 331. The mask 333 includes a mask blank before a pattern is formed. The detection optical system 320 reflects the EUV light 101, which reflects the pattern from the mask 333, by the mirrors 321 and 323, and forms an image on the light receiving surface of the detector 325. The detector 325 receives the EUV light 101 and acquires an image of the mask 333. The detector 325 is, for example, a TDI (Time Delay Integration) camera. The image of the mask 333 acquired through the above-described process is used to inspect the mask 333 for defects, and the inspection results are used to select a mask suitable for manufacturing an electronic device. Then, the pattern formed on the selected mask is exposed and transferred onto a photosensitive substrate using the exposure apparatus 200, thereby manufacturing an electronic device.

[0014] 3. Description of the extreme ultraviolet light generation device as a comparative example 3.1 Configuration A comparative example of an EUV light generation system 100 will be described. Note that the comparative example of the present disclosure refers to a configuration that the applicant recognizes as being known only by the applicant, and is not a publicly known example that the applicant acknowledges. In the following, the EUV light generation system 100 that emits EUV light 101 toward an exposure system 200 as an external device, as shown in FIG. 1, will be used for the description. Note that the same functions and effects can be obtained with an EUV light generation system 100 that emits EUV light 101 toward an inspection system 300 as an external device, as shown in FIG. 2.

[0015] 3 is a schematic diagram showing an example of the overall configuration of the EUV light generation system 100 of this embodiment. As shown in Fig. 3, the EUV light generation system 100 mainly includes a chamber apparatus 10, a main pulse laser beam irradiation system MPS including a main pulse laser apparatus 130, a pre-pulse laser beam irradiation system PPS including a pre-pulse laser apparatus 140, and a control system 120.

[0016] The chamber apparatus 10 is a sealable container. The chamber apparatus 10 includes an inner wall 10b that encloses an internal space of a low-pressure atmosphere. The chamber apparatus 10 also includes a sub-chamber 15. A target supply unit 40 is attached to the sub-chamber 15 so as to penetrate the wall of the sub-chamber 15. The target supply unit 40 includes a tank 41, a nozzle 42, and a pressure regulator 43, and supplies a droplet target DL to the internal space of the chamber apparatus 10. The droplet target DL may also be referred to simply as a droplet or a target.

[0017] The tank 41 stores a target material that will become the droplet targets DL. The target material contains tin. The interior of the tank 41 is in communication with a pressure regulator 43 that adjusts the pressure inside the tank 41. A heater 44 and a temperature sensor 45 are attached to the tank 41. The heater 44 heats the tank 41 with current supplied from a heater power supply 46. This heating melts the target material in the tank 41. The temperature sensor 45 measures the temperature of the target material in the tank 41 via the tank 41. The pressure regulator 43, the temperature sensor 45, and the heater power supply 46 are electrically connected to a processor 121 included in the control system 120.

[0018] The nozzle 42 is attached to the tank 41 and discharges the target material. A piezoelectric element 47 is attached to the nozzle 42. The piezoelectric element 47 is electrically connected to a piezoelectric power supply 48 and is driven by a voltage applied from the piezoelectric power supply 48. The piezoelectric power supply 48 is electrically connected to the processor 121. By operation of the piezoelectric element 47, the target material discharged from the nozzle 42 is turned into a droplet target DL.

[0019] The chamber apparatus 10 is a box attached to an inner wall 10b of the chamber apparatus 10, and includes a target collection unit 14 that communicates with the internal space of the chamber apparatus 10 via an opening 10a provided in the inner wall 10b of the chamber apparatus 10. The opening 10a is provided directly below the nozzle 42, and the target collection unit 14 is a drain tank that collects unwanted droplet targets DL that pass through the opening 10a and reach the target collection unit 14.

[0020] At least one through-hole is provided in the inner wall 10b of the chamber device 10. This through-hole is covered by a window 12, through which pulsed laser beams emitted from the main pulse laser device 130 and the pre-pulse laser device 140 pass.

[0021] A laser focusing optical system 13 is also disposed within the interior space of the chamber apparatus 10. The laser focusing optical system 13 includes a laser focusing mirror 13A and a high-reflection mirror 13B. The laser focusing mirror 13A reflects and focuses the laser light passing through the window 12. The high-reflection mirror 13B reflects the light focused by the laser focusing mirror 13A. The positions of the laser focusing mirror 13A and the high-reflection mirror 13B are adjusted by a laser beam manipulator 13C so that the focusing position of the laser light within the interior space of the chamber apparatus 10 is a position specified by the processor 121. The focusing position is adjusted to be directly below the nozzle 42. When the laser light irradiates the target material at the focusing position, plasma is generated by the irradiation, and EUV light 101 is emitted from the plasma. The region where the plasma is generated is sometimes referred to as a plasma generation region AR.

[0022] An EUV light collector mirror 75 including, for example, a spheroid-shaped reflecting surface 75a is disposed in the interior space of the chamber apparatus 10. The reflecting surface 75a reflects EUV light 101 emitted from the plasma in the plasma generation region AR. The reflecting surface 75a has a first focal point and a second focal point. The reflecting surface 75a may be disposed, for example, so that the first focal point is located in the plasma generation region AR and the second focal point is located at an intermediate focus point IF. In FIG. 3 , a line passing through the first and second focal points is indicated as a focal line L0. In the following description, the direction in which the focal line L0 extends may be referred to as the Z direction, the ejection direction of the droplet target DL and perpendicular to the Z direction as the X direction, and the direction perpendicular to the Z and X directions as the Y direction.

[0023] The EUV light generation system 100 also includes a connection part 19 that connects the internal space of the chamber apparatus 10 with the internal space of the exposure system 200. A wall having an aperture formed therein is disposed inside the connection part 19. This wall is preferably disposed so that the aperture is located at the second focal point. The connection part 19 is an exit port for the EUV light 101 in the EUV light generation system 100, and the EUV light 101 is emitted from the connection part 19 and enters the exposure system 200.

[0024] The EUV light generation system 100 also includes a pressure sensor 26 and a target sensor 27. The pressure sensor 26 and the target sensor 27 are attached to the chamber apparatus 10 and electrically connected to the processor 121. The pressure sensor 26 measures the pressure in the internal space of the chamber apparatus 10 and outputs a signal related to the pressure to the processor 121. The target sensor 27 includes, for example, an imaging function and detects the presence, trajectory, position, flow velocity, etc. of the droplet target DL ejected from the nozzle hole of the nozzle 42 in response to instructions from the processor 121. The target sensor 27 may be disposed inside the chamber apparatus 10 or may be disposed outside the chamber apparatus 10 and detect the droplet target DL through a window (not shown) provided in the wall of the chamber apparatus 10. The target sensor 27 includes a light-receiving optical system (not shown) and an imaging unit (not shown), such as a charge-coupled device (CCD) or a photodiode. The light-receiving optical system forms an image of the trajectory of the droplet target DL and its surroundings on the light-receiving surface of the imaging unit to improve the detection accuracy of the droplet target DL. The imaging unit detects the trajectory of the droplet target DL and changes in the light passing around it as the droplet target DL passes through a light collection area of ​​a light source unit (not shown) that is arranged to improve contrast within the field of view of the target sensor 27. The imaging unit converts the detected changes in light into an electrical signal that serves as image data for the droplet target DL and outputs this electrical signal to the processor 121.

[0025] The main pulse laser device 130 is, for example, a YAG laser device or a CO2 laser device, includes a master oscillator that performs burst operation, and emits main pulse laser light MPL. Note that burst operation is an operation in which continuous main pulse laser light MPL is emitted at a predetermined repetition rate during burst on, and emission of the main pulse laser light MPL is suppressed during burst off.

[0026] The pre-pulse laser device 140 emits a pre-pulse laser beam PPL having linearly polarized light polarized in a predetermined direction. In the example of FIG. 3 , the wavelength of the pre-pulse laser beam PPL is different from the wavelength of the main pulse laser beam MPL. Therefore, for example, if the main pulse laser device 130 is a YAG laser device, the pre-pulse laser device 140 is, for example, a CO laser device. Note that the pre-pulse laser beam PPL and the main pulse laser beam MPL may have the same wavelength. In this case, the main pulse laser device 130 and the pre-pulse laser device 140 are, for example, both YAG laser devices or both CO laser devices. The pre-pulse laser device 140 is configured to emit the pre-pulse laser beam PPL at a timing different from the timing at which the main pulse laser beam MPL is emitted from the main pulse laser device 130. This control is performed by a control system 120, which will be described later.

[0027] The propagation directions of the main pulsed laser beam MPL and the pre-pulse laser beam PPL are adjusted by a laser beam delivery optical system having a plurality of mirrors. The laser beam delivery optical system that adjusts the propagation direction of the main pulsed laser beam MPL includes mirrors 31 and 32. The laser beam delivery optical system that adjusts the propagation direction of the pre-pulse laser beam PPL includes a mirror 33 and a beam combiner 34. The beam combiner 34 is disposed at a position where the optical path of the pre-pulse laser beam PPL intersects with the optical path of the main pulsed laser beam MPL. In this example, the beam combiner 34 disposed in this manner is a dichroic mirror that reflects the pre-pulse laser beam PPL and transmits the main pulsed laser beam MPL, thereby causing the optical path of the main pulsed laser beam MPL and the optical path of the pre-pulse laser beam PPL to roughly overlap each other. The orientation of at least one of the mirrors 31, 32, and 33 and the beam combiner 34 is adjusted by an actuator (not shown). This adjustment allows the main pulse laser beam MPL and the pre-pulse laser beam PPL to be appropriately propagated from the window 12 into the internal space of the chamber apparatus 10. Note that if the pre-pulse laser beam PPL and the main pulse laser beam MPL have the same wavelength but have polarization directions that differ by 90°, the beam combiner 34 may be a polarizer.

[0028] The main pulse laser beam irradiation system MPS is a system that irradiates a target material with a main pulse laser beam MPL. Therefore, in this example, the main pulse laser beam irradiation system MPS includes, in addition to the main pulse laser device 130, mirrors 31 and 32, a beam combiner 34, and a laser focusing optical system 13. Furthermore, the pre-pulse laser beam irradiation system PPS is a system that irradiates a target material with a pre-pulse laser beam PPL. Therefore, in this example, the pre-pulse laser beam irradiation system PPS includes, in addition to the pre-pulse laser device 140, a mirror 33, the beam combiner 34, and a laser focusing optical system 13.

[0029] The processor 121 of the control system 120 of the present disclosure is a processing device including a storage device storing a control program and a CPU (Central Processing Unit) that executes the control program. The processor 121 is specially configured or programmed to execute various processes described herein and controls the entire EUV light generation apparatus 100. The processor 121 receives inputs such as a signal related to the pressure in the internal space of the chamber apparatus 10 measured by the pressure sensor 26, a signal related to image data of the droplet target DL captured by the target sensor 27, and a burst signal instructing a burst operation from the exposure apparatus 200. The processor 121 processes the various signals and may control, for example, the timing at which the droplet target DL is discharged and the discharge direction of the droplet target DL. The processor 121 may also control the emission timing of the main pulse laser device 130 and the pre-pulse laser device 140, the propagation direction and focus position of the main pulse laser beam MPL and the pre-pulse laser beam PPL, and the like. The various controls described above are merely examples, and other controls may be added as necessary, as described below.

[0030] The processor 121 in this example is electrically connected to the main pulse laser device 130 and the pre-pulse laser device 140 via a delay circuit 122 of the control system 120. The delay circuit 122 slightly changes the trigger signals of the main pulse laser device 130 and the pre-pulse laser device 140 output from the processor 121. Specifically, the delay circuit 122 generates a delay in the trigger signals input to the main pulse laser device 130 and the pre-pulse laser device 140 so that the irradiation timing of the main pulse laser device 130 is delayed relative to the irradiation timing of the pre-pulse laser device 140.

[0031] The chamber apparatus 10 is provided with a central gas supply unit 81 that supplies an etching gas to the internal space of the chamber apparatus 10. As described above, since the target material contains tin, the etching gas is, for example, a hydrogen-containing gas in which the hydrogen gas concentration is considered to be 100%. Alternatively, the etching gas may be a balance gas in which the hydrogen gas concentration is, for example, approximately 3%. The balance gas may include nitrogen (N2) gas or argon (Ar) gas. Incidentally, when the target material constituting the droplet target DL is irradiated with the main pulse laser beam MPL in the plasma generation region AR and converted into plasma, tin microparticles and charged tin particles are generated. The tin constituting these microparticles and charged particles reacts with hydrogen contained in the etching gas supplied to the internal space of the chamber apparatus 10. When tin reacts with hydrogen, it becomes stannane (SnH4), a gas at room temperature.

[0032] The center-side gas supply unit 81 has a frustum-shaped side surface and passes through a through-hole 75c formed in the center of the EUV light collector mirror 75. The center-side gas supply unit 81 is sometimes called a cone. The center-side gas supply unit 81 also includes a center-side gas supply port 81a, which is a nozzle. The center-side gas supply port 81a is located on the focal line L0 of the reflecting surface 75a. The focal line L0 is aligned with the central axis of the reflecting surface 75a. The center-side gas supply port 81a supplies an etching gas from the center of the reflecting surface 75a toward the plasma generation region AR. The etching gas is preferably supplied from the center-side gas supply port 81a along the focal line L0, in a direction away from the center of the reflecting surface 75a. The center-side gas supply port 81a is connected to a gas supply device (not shown), which is a tank, via a piping (not shown) of the center-side gas supply unit 81, and the etching gas is supplied from the gas supply device. The operation of the gas supply device is controlled by the processor 121. A supply gas flow rate regulator (not shown), which is a valve, may be disposed in the piping (not shown).

[0033] The center-side gas supply port 81a is a gas supply port that supplies an etching gas into the internal space of the chamber apparatus 10, and also serves as an emission port through which the pre-pulse laser beam PPL and the main pulse laser beam MPL are emitted into the internal space of the chamber apparatus 10. The pre-pulse laser beam PPL and the main pulse laser beam MPL pass through the window 12 and the center-side gas supply port 81a and proceed toward the internal space of the chamber apparatus 10.

[0034] An exhaust port 10E is provided on the inner wall 10b of the chamber apparatus 10. Since the exposure device 200 is disposed on the focal line L0, the exhaust port 10E is provided on the inner wall 10b on the side of the focal line L0. The direction along the central axis of the exhaust port 10E is, for example, perpendicular to the focal line L0. Furthermore, when viewed from a direction perpendicular to the focal line L0, the exhaust port 10E is provided on the opposite side of the reflecting surface 75a with respect to the plasma generation region AR. The exhaust port 10E exhausts gas from the internal space of the chamber apparatus 10. The exhaust port 10E is connected to an exhaust pipe 10P, which is connected to an exhaust pump 60.

[0035] When the target material is converted into plasma in the plasma generation region AR as described above, residual gas is generated in the internal space of the chamber apparatus 10 as exhaust gas. The residual gas contains tin particles and charged particles generated by the conversion of the target material into plasma, stannane formed when these particles react with the etching gas, and unreacted etching gas. Note that some of the charged particles are neutralized in the internal space of the chamber apparatus 10, and these neutralized charged particles are also included in the residual gas. The residual gas is sucked into the exhaust pump 60 via the exhaust port 10E and the exhaust pipe 10P.

[0036] 4 is a schematic diagram showing an example of the general configuration of the main pulse laser device 130. The main pulse laser device 130 includes a first laser light source 131, a first lens 133, a laser oscillator 135, and a temperature regulator 137.

[0037] An example of the first laser light source 131 is a laser diode bar. In a laser diode bar, multiple laser diodes are arranged in a horizontal row on the same substrate. Each laser diode emits a first excitation light toward a laser oscillator 135 through a first lens 133. The wavelength of the first excitation light is, for example, approximately 808 nm. In FIG. 4, each first excitation light is collectively indicated by a single dashed arrow. The first laser light source 131 is connected to the processor 121 via a delay circuit 122 and is controlled by the processor 121. Note that the delay circuit 122 is not shown in FIG. 4.

[0038] The first lens 133 is a cylindrical convex lens provided between the first laser light source 131 and the laser oscillator 135. The convex surface of the first lens 133 faces the laser oscillator 135, and the first lens 133 focuses the first excitation light from the first laser light source 131 onto a laser crystal 135a (described later) of the laser oscillator 135. In FIG. 4 and FIG. 5 (described later), the focusing of the first excitation light is omitted from the illustration.

[0039] 5 is a schematic diagram showing an example of the schematic configuration of the laser oscillator 135. The laser oscillator 135 includes a laser crystal 135a, a resonator mirror 135b, and a Pockels cell 135c.

[0040] An active medium is added to the laser crystal 135a. Examples of the active medium include Nd:YAG, Nd:YVO4, and Yb:YAG. The active medium is excited by the first excitation light from the first laser light source 131 and emits light.

[0041] Resonator mirror 135b consists of a pair of mirrors, with laser crystal 135a and Pockels cell 135c disposed between the pair of mirrors. One mirror is disposed between first lens 133 and laser crystal 135a, and Pockels cell 135c is disposed between laser crystal 135a and the other mirror. One mirror is a dichroic mirror that transmits the first excitation light from first laser light source 131 and reflects at least a portion of the light from laser crystal 135a toward laser crystal 135a. The other mirror is a polarizing mirror that reflects, toward laser crystal 135a, light from laser crystal 135a whose polarization direction has not been changed by Pockels cell 135c, and transmits, toward mirror 31 (not shown in FIG. 5), light whose polarization direction has been changed by Pockels cell 135c. In FIG. 5, the light traveling from laser crystal 135a toward resonator mirror 135b is indicated by a dashed arrow, and for ease of viewing, this arrow is shifted from the arrow indicating the first excitation light.

[0042] The Pockels cell 135c includes an electro-optic crystal 135f and a pair of electrodes 135g sandwiching the electro-optic crystal 135f. When a voltage is applied between the pair of electrodes 135g from a power supply (not shown), the Pockels cell 135c rotates the polarization direction of light passing through the electro-optic crystal 135f by 90 degrees. Furthermore, when no voltage is applied between the pair of electrodes 135g, the Pockels cell 135c does not rotate the polarization direction of light passing through the electro-optic crystal 135f. The pair of electrodes 135g are connected to the processor 121 via a delay circuit 122, and the timing of voltage application is appropriately controlled by the processor 121. Note that the delay circuit 122 is not shown in FIG. 5.

[0043] The first excitation light from the first laser light source 131 is focused onto the laser crystal 135a by the first lens 133, exciting the active medium of the laser crystal 135a. This causes the laser crystal 135a to emit spontaneously emitted light, a portion of which travels to one of the resonator mirrors 135b, and another portion of which passes through the Pockels cell 135c and travels to the other mirror. When no voltage is applied between the electrodes 135g of the Pockels cell 135c, the light travels back and forth between the resonator mirrors 135b. In this way, the laser crystal 135a and the resonator mirrors 135b form a Fabry-Perot resonator. The light is amplified by passing through the laser crystal 135a as it travels back and forth between the resonator mirrors 135b. When a voltage is applied between the pair of electrodes 135g of the Pockels cell 135c, the polarization direction of the amplified light is changed when it passes through the electro-optic crystal 135f. In the Pockels cell 135c, the timing of voltage application is controlled by the processor 121. As a result, the light whose polarization direction has been changed passes through the other mirror of the resonator mirror 135b as the main pulse laser beam MPL and travels toward the mirror 31. Note that although the traveling directions of the first excitation beam and the main pulse laser beam MPL are different in each of FIGS. 4 and 5, they are shown differently for ease of viewing. In particular, FIG. 4 merely shows the traveling directions of the first excitation beam and the main pulse laser beam MPL in a simplified manner and does not show the actual traveling paths of each.

[0044] Returning to Fig. 4, the temperature regulator 137 will be described. The temperature regulator 137 is a chiller that adjusts the temperature of a cooling medium that cools the first laser light source 131 and the laser oscillator 135, and cools the first laser light source 131 and the laser oscillator 135 with the cooling medium. In Fig. 5, the temperature regulator 137 is not shown. The cooling medium may be, for example, a liquid. In the comparative example, the temperature of the cooling medium is set to a predetermined temperature.

[0045] A portion of a pipe 137a is connected to the temperature regulator 137 and the first laser light source 131 so that a cooling medium circulates between the temperature regulator 137 and the first laser light source 131. In Fig. 4, the flow of the cooling medium in the pipe 137a is indicated by solid arrows. The first laser light source 131 is connected to the pipe 137a. Specifically, the above-mentioned substrate on which the multiple laser diodes of the first laser light source 131 are arranged is disposed on the pipe 137a. The cooling medium cools the first laser light source 131 through the pipe 137a and the substrate.

[0046] Furthermore, another portion of the pipe 137a branches off from a portion of the pipe 137a where the cooling medium travels from the temperature regulator 137 to the first laser light source 131. This branched pipe 137a extends to the laser oscillator 135, connects to the laser oscillator 135, and merges with a portion of the pipe 137a where the cooling medium returns from the first laser light source 131 to the temperature regulator 137. In this way, another portion of the pipe 137a is connected to the temperature regulator 137 and the laser oscillator 135 so that the cooling medium circulates between them. At the connection between the pipe 137a and the laser oscillator 135, a substrate (not shown) on which the laser crystal 135a is disposed is disposed in the pipe 137a. The cooling medium cools the laser crystal 135a through the pipe 137a and the substrate.

[0047] As described above, the first laser light source 131 and the laser oscillator 135 are cooled by the same cooling medium. After cooling, the cooling medium returns to the temperature regulator 137 through the pipe 137a, and after the temperature is adjusted again by the temperature regulator 137, it flows to the first laser light source 131 and the laser oscillator 135 as described above, cooling them. Note that the position of the pipe 137a and the direction of circulation of the cooling medium are not particularly limited.

[0048] 3.2 Operation Next, the operation of the EUV light generation system 100 of the comparative example will be described.

[0049] In the EUV light generation system 100, the atmosphere in the internal space of the chamber apparatus 10 is exhausted, for example, when the system is newly installed or during maintenance. At this time, the internal space of the chamber apparatus 10 may be repeatedly purged and exhausted to exhaust atmospheric components. An inert gas such as nitrogen or argon is preferably used as the purge gas. When the pressure in the internal space of the chamber apparatus 10 subsequently drops below a predetermined pressure, the processor 121 starts introducing an etching gas from the gas supply device into the internal space of the chamber apparatus 10 via the central gas supply unit 81. At this time, the processor 121 may control a supply gas flow rate regulator and an exhaust pump 60 (not shown) to maintain the pressure in the internal space of the chamber apparatus 10 at the predetermined pressure. The processor 121 then waits until a predetermined time has elapsed since the start of the introduction of the etching gas.

[0050] In addition, the processor 121 causes the exhaust pump 60 to exhaust the gas in the internal space of the chamber apparatus 10 through the exhaust port 10E, and maintains the pressure in the internal space of the chamber apparatus 10 at an approximately constant level based on a signal related to the pressure in the internal space of the chamber apparatus 10 measured by the pressure sensor 26.

[0051] The processor 121 also supplies current from the heater power supply 46 to the heater 44 to heat and maintain the target material in the tank 41 at a predetermined temperature equal to or higher than the melting point, thereby raising the temperature of the heater 44. Based on the output of the temperature sensor 45, the processor 121 adjusts the value of the current supplied from the heater power supply 46 to the heater 44 to control the temperature of the target material to the predetermined temperature. When the target material is tin, the predetermined temperature is equal to or higher than the melting point of tin, approximately 231°C, for example, between 240°C and 290°C. This completes preparations for discharging the droplet target DL.

[0052] Once preparation is complete, the processor 121 controls the pressure regulator 43 to supply inert gas from a gas supply source (not shown) into the tank 41 and adjust the pressure within the tank 41 so that the molten target material is discharged from the nozzle hole of the nozzle 42 at a predetermined flow rate. Under this pressure, the target material is discharged from the nozzle hole into the chamber apparatus 10. The target material discharged from the nozzle hole may take the form of a jet. At this time, the processor 121 applies a voltage of a predetermined waveform from the piezoelectric power supply 48 to the piezoelectric element 47 to generate the droplet target DL. The predetermined waveform may be, for example, a sine wave, a square wave, or a sawtooth wave. The vibration of the piezoelectric element 47 can propagate through the nozzle 42 to the target material being discharged from the nozzle hole of the nozzle 42. The target material is divided by this vibration at a predetermined period, becoming the droplet target DL. The diameter of the droplet target DL is approximately 20 μm or less.

[0053] When the droplet target DL is discharged, the target sensor 27 detects the timing at which the droplet target DL passes a predetermined position in the internal space of the chamber apparatus 10. The processor 121 controls the timing at which the pre-pulse laser beam PPL is emitted from the pre-pulse laser device 140 based on a signal from the target sensor 27 so that the droplet target DL is irradiated with the pre-pulse laser beam PPL, and outputs a trigger signal. The trigger signal from the processor 121 is input to the pre-pulse laser device 140 and the main pulse laser device 130 via a delay circuit 122. However, the delay circuit 122 inputs the trigger signal to the pre-pulse laser device 140 before inputting it to the main pulse laser device 130. When the trigger signal is input, the pre-pulse laser device 140 emits the pre-pulse laser beam PPL. The main pulse laser beam MPL is not emitted at the timing at which the pre-pulse laser beam PPL is emitted.

[0054] The pre-pulse laser light PPL is a picosecond pulse laser light having a temporal pulse width of, for example, 10 ps or more and 100 ps or less, or a nanosecond pulse laser light having a pulse width of, for example, 10 ns or more and 300 ns or less. The pulse width refers to the interval between the times when the intensity of the laser light is half of its maximum value, before and after the intensity reaches its maximum value. The picosecond pulse laser light and the nanosecond pulse laser light have roughly the same energy per pulse. Therefore, the picosecond pulse laser light has a higher energy density than the nanosecond pulse laser light. The fluence of the pre-pulse laser light PPL is, for example, 0.1 J / cm. 2 More than 100J / cm 2 Preferably, the fluence is 1 J / cm for picosecond pulsed laser light. 2 More than 20J / cm 2 or less than 1 J / cm for nanosecond pulsed laser light. 2 More than 3J / cm 2The pre-pulse laser beam PPL emitted from the pre-pulse laser device 140 and having linear polarization is reflected by the mirror 33 and the beam combiner 34 and irradiated onto the droplet target DL via the laser focusing optical system 13. At this time, the processor 121 controls the laser beam manipulator 13C of the laser focusing optical system 13 so that the pre-pulse laser beam PPL is focused near the plasma generation region AR. The droplet target DL irradiated with the pre-pulse laser beam PPL is diffused by laser ablation due to the energy of the laser beam, becoming a diffused target. Therefore, the pre-pulse laser beam irradiation system PPS is a system that irradiates the droplet target DL with the pre-pulse laser beam PPL to generate a diffused target.

[0055] The diffused target is a target in which the droplet target DL has been diffused, and therefore has a larger diameter and a lower density of the target material than the droplet target DL.

[0056] When a trigger signal is input to the main pulse laser device 130 with a delay from when a trigger signal is input to the pre-pulse laser device 140, the main pulse laser device 130 emits the main pulse laser beam MPL. Specifically, the processor 121 causes the first laser light source 131 to emit a first excitation beam. When the first excitation beam is incident on the laser oscillator 135, the laser oscillator 135 oscillates and emits the main pulse laser beam MPL via the Pockels cell 135c. At this time, a cooling medium flows through the piping 137a to cool the first laser light source 131 and the laser oscillator 135. The time difference between the timing at which the pre-pulse laser beam PPL is emitted and the timing at which the main pulse laser beam MPL is emitted is, for example, 50 ns or more and 500 ns or less in the case of a picosecond pulse laser beam, and 50 ns or more and 150 ns or less in the case of a nanosecond pulse laser beam. The processor 121 and the delay circuit 122 control the timing at which the main pulse laser beam MPL is emitted from the main pulse laser device 130 so that the diffused target is irradiated with the main pulse laser beam MPL, and output a light emission trigger signal.

[0057] The main pulse laser beam MPL has a pulse width of, for example, 1 ns or more and 50 ns or less, more preferably 15 ns or more and 20 ns or less. The main pulse laser beam MPL emitted from the main pulse laser device 130 is reflected by mirrors 31 and 32, transmitted through the beam combiner 34, and irradiated onto the diffused target in the plasma generation region AR via the laser focusing optical system 13. At this time, the processor 121 controls the laser beam manipulator 13C of the laser focusing optical system 13 so that the main pulse laser beam MPL is focused onto the plasma generation region AR. The diffused target irradiated with the main pulse laser beam MPL becomes plasma due to the energy of the laser beam, and light including EUV light is emitted from this plasma. Therefore, the main pulse laser beam irradiation system MPS is a system that generates EUV light by irradiating a diffused target with the main pulse laser beam MPL.

[0058] When the main pulse laser beam MPL is irradiated onto a diffused target in which the density of the target material has been reduced, more of the target material is converted into plasma, enabling the efficient emission of EUV light, compared to when the main pulse laser beam MPL is directly irradiated onto a droplet target DL.

[0059] Of the light including EUV light generated in the plasma generation region AR, EUV light 101 is collected at an intermediate focus point IF by the EUV light collector mirror 75 and then enters the exposure device 200 from the connection part 19 .

[0060] When the target material is converted into plasma, tin particles are generated as described above. These particles diffuse into the internal space of the chamber apparatus 10. The particles diffusing into the internal space of the chamber apparatus 10 react with the hydrogen-containing etching gas supplied from the center-side gas supply unit 81 to become stannane. Most of the stannane produced by the reaction with the etching gas flows into the exhaust port 10E along with the unreacted etching gas. At least a portion of the unreacted charged particles, particles, and etching gas also flow into the exhaust port 10E. The unreacted etching gas, particles, charged particles, stannane, etc. that flow into the exhaust port 10E flow as residual gas from the exhaust pipe 10P into the exhaust pump 60, where they are subjected to predetermined exhaust processing, such as detoxification.

[0061] 3.3 Challenges The optimal temperature for cooling the first laser light source 131 varies depending on factors such as deterioration of the first laser light source 131. Therefore, if the deterioration occurs while the temperature of the cooling medium remains set to a predetermined temperature, the temperature of the cooling medium may deviate from the optimal temperature, making it more difficult to cool the first laser light source 131 than expected. This may change the wavelength of the first excitation light emitted from the first laser light source 131, and the change in wavelength may reduce the electron inversion efficiency in the laser crystal 135a of the laser oscillator 135. This may reduce the pulse energy of the main pulse laser beam MPL and cause it to fall outside the target pulse energy range. In this case, the exposure apparatus 200 temporarily stops the EUV light generation apparatus 100. The processor 121 then causes the laser oscillator 135 to oscillate with the first excitation light, causing the main pulse laser beam MPL to emit, and reacquires the optimal temperature for cooling the cooling medium so that the pulse energy of the main pulse laser beam MPL falls within the target range. Finally, the administrator of the EUV light generation system 100 resets the temperature of the cooling medium to the optimal temperature in the temperature controller 137. However, at this optimal temperature, although the pulse energy falls within the target pulse energy range, the pulse time width of the main pulse laser beam MPL may extend and fall outside the target pulse time width range. Therefore, even if the first laser light source 131 is cooled with a cooling medium at an optimal temperature for the pulse energy, the pulse time width of the main pulse laser beam MPL may fall outside the target pulse time width range. If the pulse energy or pulse time width does not fall within the respective target ranges, the plasma generation efficiency may decrease. This may result in the EUV light 101 not being emitted that satisfies the performance required by the exposure tool 200 or the inspection tool 300, raising concerns that the reliability of the EUV light generation system 100 may be reduced.

[0062] Therefore, in the following embodiment, an EUV light generation system 100 that can suppress a decrease in reliability will be exemplified.

[0063] 4. Description of the extreme ultraviolet light generation device according to the first embodiment Next, a description will be given of the configuration of the EUV light generation system 100 of embodiment 1. Note that the same components as those described above are denoted by the same reference numerals, and redundant description will be omitted unless otherwise specified.

[0064] 4.1 Configuration 6 is a schematic diagram showing an example of the overall configuration of a portion of the EUV light generation system 100 of this embodiment. The EUV light generation system 100 of this embodiment differs from the EUV light generation system 100 of the comparative example in that the EUV light generation system 100 further includes a measuring instrument 400 and a processor 121 controls a temperature controller 137.

[0065] The measuring instrument 400 is disposed downstream of the laser oscillator 135 with respect to the traveling direction of the main pulse laser beam MPL emitted from the laser oscillator 135. The measuring instrument 400 includes a first beam splitter 401, a first condenser lens 403, an integrating sphere 405, a first photodiode 407, and an integrating circuit 409.

[0066] The first beam splitter 401 is disposed on the optical path of the main pulse laser beam MPL from the laser oscillator 135 to the plasma generation region AR, and is preferably disposed on the optical path between the laser oscillator 135 and the mirror 31. The first beam splitter 401 transmits a portion of the main pulse laser beam MPL emitted from the laser oscillator 135 and reflects another portion of the main pulse laser beam MPL toward a first collecting lens 403. The first collecting lens 403 collects the main pulse laser beam MPL reflected by the first beam splitter 401 onto a portion of the inner wall of an integrating sphere 405. The integrating sphere 405 diffuses and reflects the main pulse laser beam MPL, which has been collected onto a portion of the inner wall by the first collecting lens 403, multiple times on the inner wall of the integrating sphere 405 to homogenize the intensity and output the homogenized beam to a first photodiode 407. The first photodiode 407 receives the main pulse laser beam MPL from the integrating sphere 405, and upon receiving the main pulse laser beam MPL, outputs a signal corresponding to the light intensity of the main pulse laser beam MPL to the integrating circuit 409. Furthermore, the first photodiode 407 does not output a signal unless it receives the main pulse laser beam MPL. The integrating circuit 409 integrates the signal from the first photodiode 407 to measure the pulse energy of the main pulse laser beam MPL. The integrating circuit 409 is connected to the processor 121, and outputs a signal related to the measured pulse energy of the main pulse laser beam MPL to the processor 121.

[0067] Additionally, measuring instrument 400 further includes a second beam splitter 421 , a second condenser lens 423 , a second photodiode 427 , and a detection circuit 429 .

[0068] The second beam splitter 421 is disposed on the optical path of the main pulse laser beam MPL from the laser oscillator 135 to the plasma generation region AR, and is preferably disposed between the laser oscillator 135 and the mirror 31. The second beam splitter 421 of this embodiment is provided between the first beam splitter 401 and the mirror 31 with respect to the traveling direction of the main pulse laser beam MPL emitted from the laser oscillator 135. The second beam splitter 421 transmits a portion of the main pulse laser beam MPL that has transmitted through the first beam splitter 401 toward the mirror 31, and reflects another portion of the main pulse laser beam MPL toward a second collecting lens 423. The second collecting lens 423 collects the main pulse laser beam MPL reflected by the second beam splitter 421 onto a second photodiode 427. The second photodiode 427 receives the main pulse laser beam MPL focused by the second focusing lens 423, and outputs a signal to the detection circuit 429 when it receives the main pulse laser beam MPL, but does not output a signal when it does not receive the main pulse laser beam MPL. The detection circuit 429 detects rising and falling signals from the signals from the photodiode, and measures the pulse time width of the main pulse laser beam MPL from this detection. The detection circuit 429 is connected to the processor 121, and outputs a signal related to the measured pulse time width of the main pulse laser beam MPL to the processor 121.

[0069] The processor 121 of this embodiment is connected to a temperature regulator 137 and controls the temperature of the cooling medium in the temperature regulator 137. This control will be described later. The cooling medium of this embodiment is, for example, a liquid such as water. The liquid may be other than water, and the cooling medium may be a gas such as water vapor.

[0070] 4.2 Operation Next, the operation of the processor 121 in this embodiment will be described.

[0071] FIG. 7 is a diagram showing a control flowchart of the processor 121 of this embodiment. The control flowchart of this embodiment includes steps SP11 to SP14. In the start state shown in FIG. 7 , a portion of the main pulse laser beam MPL is reflected by each of the beam splitters 401 and 421, and the pulse energy and pulse time width of the main pulse laser beam MPL are measured by the measuring instrument 400, which is different from the comparative example. Hereinafter, the pulse energy of the main pulse laser beam MPL and the pulse time width of the main pulse laser beam MPL may be simply referred to as the pulse energy and the pulse time width. Signals relating to the pulse energy and the pulse time width, respectively, are input from the measuring instrument 400 to the processor 121. Note that in the start state, as in the comparative example, a cooling medium flows through the piping 137a to cool the first laser light source 131 and the laser oscillator 135. Furthermore, the pre-pulse laser beam PPL and the main pulse laser beam MPL advance to the plasma generation region AR, where EUV light 101 is generated, and the EUV light 101 enters the exposure device 200.

[0072] (Step SP11) In this step, if the pulse energy measured by the measuring instrument 400 is not within the target range of the pulse energy, the processor 121 advances the control flow to step SP12. On the other hand, if the measured pulse energy is within the target range, the processor 121 advances the control flow to step SP13.

[0073] (Step SP12) In this step, the processor 121 controls the temperature regulator 137, which adjusts the temperature of the cooling medium so that the pulse energy measured by the measuring instrument 400 falls within the target range of the pulse energy. Specifically, when the pulse energy measured by the measuring instrument 400 is smaller than the target range of the pulse energy, the processor 121 controls the temperature regulator 137 to lower the temperature of the cooling medium.

[0074] The cooling medium whose temperature has been reduced in this step flows through the pipe 137a and proceeds to the first laser light source 131 and the laser oscillator 135, cooling them. After cooling them, the cooling medium flows through the pipe 137a and returns to the temperature regulator 137, where its temperature is adjusted again. When the temperature of the cooling medium decreases, the cooling medium becomes more effective in cooling the first laser light source 131, and the change in the wavelength of the first excitation light emitted from the first laser light source 131 is suppressed by the cooling. This suppresses a decrease in the electron inversion efficiency in the laser crystal 135a of the laser oscillator 135, and the pulse energy falls within the target range. Note that fluctuations in pulse energy are often due to deterioration of the first laser light source 131, etc., so it is unlikely that the pulse energy will exceed the target value. If the pulse energy is greater than the target value, the processor 121 controls the temperature regulator 137 to increase the temperature of the cooling medium. After controlling temperature regulator 137 that adjusts the temperature of the cooling medium, processor 121 returns the control flow to step SP11. Then, when the pulse energy falls within the target range of pulse energy in step SP11, processor 121 advances the control flow to step SP13.

[0075] (Step SP13) In this step, if the pulse time width measured by the measuring instrument 400 falls within the target range for the pulse time width, the processor 121 returns the control flow to step SP11. If the measured pulse time width does not fall within the target range, the processor 121 advances the control flow to step SP14.

[0076] (Step SP14) In this step, the processor 121 adjusts the current value of the current supplied to the first laser light source 131 so that the pulse time width measured by the measuring instrument 400 falls within the target range of the pulse time width. Specifically, the processor 121 decreases the current value when the pulse time width measured by the measuring instrument 400 is smaller than the target range of the pulse time width, and increases the current value when the pulse time width is larger than the target range of the pulse time width. This is because a smaller current value increases the pulse time width, and an larger current value decreases the pulse time width.

[0077] After adjusting the current value, processor 121 returns the control flow to step SP13. If the pulse time width falls within the target range for the pulse time width in step SP13, processor 121 returns the control flow to step SP11. Because the pulse energy has already fallen within the target range for the pulse energy in steps SP11 and SP12, when the pulse time width falls within the target range for the pulse time width in steps SP13 and SP14, the pulse energy and pulse time width fall within their respective target ranges.

[0078] 4.3 Actions and Effects In the EUV light generation system 100 of this embodiment, the processor 121 controls the temperature regulator 137, which adjusts the temperature of the cooling medium so that the pulse energy measured by the measuring instrument 400 in step SP12 falls within the target range of the pulse energy, and also adjusts the current value of the current supplied to the first laser light source 131 so that the pulse time width measured by the measuring instrument 400 in step SP14 falls within the target range of the pulse time width.

[0079] In the EUV light generation system 100, the processor 121 controls the temperature regulator 137, which adjusts the temperature of the cooling medium so that the pulse energy measured by the measuring instrument 400 falls within a target range for the pulse energy. By adjusting the temperature in this manner, even if the first laser light source 131 deteriorates and the optimal temperature for cooling the cooling medium changes, deviation between the temperature of the cooling medium and the optimal temperature can be suppressed. Suppressing the deviation can facilitate cooling of the first laser light source 131, and can suppress changes in the wavelength of the first excitation light emitted from the first laser light source 131 due to cooling. This allows the pulse energy to fall within the target range. However, when the processor 121 controls the temperature regulator 137, which adjusts the temperature of the cooling medium based on the pulse energy as described above, the temperature of the cooling medium may not be optimal for the pulse time width. However, in this EUV light generation system 100, the processor 121 controls the temperature regulator 137, which adjusts the temperature of the cooling medium, and then adjusts the current value of the current supplied to the first laser light source 131 so that the pulse time width measured by the measuring instrument 400 falls within the target range for the pulse time width. When the pulse energy and pulse time width fall within their respective target ranges as described above, a decrease in plasma generation efficiency can be suppressed. This makes it possible to emit EUV light 101 that satisfies the performance required by the exposure tool 200 and the inspection tool 300, and suppresses a decrease in the reliability of the EUV light generation system 100. Furthermore, according to the EUV light generation system 100 of this embodiment, the pulse energy and pulse time width can be kept within their respective target ranges without shutting down the EUV light generation system 100.

[0080] Furthermore, in the EUV light generation system 100 of this embodiment, after adjusting the current value in step SP14, the processor 121 returns the flow from step SP13 to steps SP11 and SP12, and again controls the temperature regulator 137 that adjusts the temperature of the cooling medium.

[0081] With this configuration, the adjustment of the current value causes the pulse time width to fall within the target range for the pulse time width, but this adjustment can prevent the pulse energy from again departing from the target range for the pulse energy, compared to when the temperature adjuster 137 is not controlled again. Therefore, with this configuration, the pulse energy and the pulse time width can fall within their respective target ranges. Note that the processor 121 may end the control flow if the pulse time width falls within the target range for the pulse time width in step SP13 or if the processor 121 has adjusted the current value of the current supplied to the first laser light source 131 in step SP14.

[0082] Furthermore, in the EUV light generation system 100 of this embodiment, the laser oscillator 135 is further cooled. With this configuration, changes in the wavelength of the first excitation light in the laser oscillator 135 can be suppressed more effectively than when the laser oscillator 135 is not cooled, and deviation of the pulse energy from the target range can be further suppressed. Note that although the cooling medium cools the laser oscillator 135, the piping 137a does not necessarily have to extend to the laser oscillator 135, and the cooling medium does not necessarily have to cool the laser oscillator 135.

[0083] The first beam splitter 401 and the second beam splitter 421 may be arranged in reverse positions, and the order of their arrangement is not particularly limited.

[0084] 5. Description of the extreme ultraviolet light generation device according to the second embodiment Next, a description will be given of the configuration of an EUV light generation system 100 according to embodiment 2. Note that the same components as those described above are denoted by the same reference numerals, and redundant description will be omitted unless otherwise specified.

[0085] 5.1 Configuration 8 is a schematic diagram showing an example of the schematic configuration of a portion of an EUV light generation system 100 according to this embodiment. The EUV light generation system 100 according to this embodiment differs from the EUV light generation system 100 according to the first embodiment in that the main pulse laser unit 130 further includes a second laser light source 161, a second lens 163a, a dichroic mirror 163b, and an amplifier 165, and that the piping 137a extends to the second laser light source 161 and the amplifier 165, and the cooling medium further cools them.

[0086] The second laser light source 161 may be, for example, a laser diode bar, similar to the first laser light source 131. In the following description, the excitation light emitted by the second laser light source 161 will be referred to as the second excitation light. In FIG. 8, the second excitation light of each of the multiple laser diodes in the laser diode bar is collectively indicated by a single dashed arrow. The second laser light source 161 is controlled by the processor 121 via the delay circuit 122. The wavelength of the second excitation light is, for example, approximately 808 nm.

[0087] The second lens 163a is a cylindrical convex lens provided between the second laser light source 161 and the dichroic mirror 163b. The convex surface of the second lens 163a faces the dichroic mirror 163b, and the second lens 163a focuses the second excitation light from the second laser light source 161 onto the dichroic mirror 163b. The dichroic mirror 163b transmits the main pulse laser light MPL from the laser oscillator 135 and reflects the second excitation light from the second laser light source 161. Then, each of the main pulse laser light MPL and the second excitation light proceeds to the amplifier 165.

[0088] The amplifier 165 of this embodiment includes a laser crystal 165a. The laser crystal 165a is a columnar member and is held inside by a cylindrical holder 165d. The laser crystal 165a is doped with the same active medium as the active medium of the laser crystal 135a. The active medium is excited by the second excitation light from the second laser light source 161. In this state, when the main pulse laser beam MPL from the laser oscillator 135 is incident on the laser crystal 165a, the main pulse laser beam MPL is amplified by stimulated emission. In this way, the amplifier 165 amplifies the main pulse laser beam MPL emitted from the laser oscillator 135 by the second excitation light. The amplified main pulse laser beam MPL proceeds to the first beam splitter 401.

[0089] A portion of the piping 137a in this embodiment extends from the first laser light source 131 to the temperature regulator 137 via the second laser light source 161 so that the cooling medium circulates among the temperature regulator 137, the first laser light source 131, and the second laser light source 161. A substrate on which a plurality of laser diodes in the second laser light source 161 are arranged is disposed in the piping 137a, and the cooling medium cools the second laser light source 161 through the piping 137a and the substrate.

[0090] Another part of the pipe 137a extends from the laser oscillator 135 to the amplifier 165, connects to the amplifier 165, and merges with a part of the pipe 137a where the cooling medium returns from the second laser light source 161 to the temperature regulator 137. In this way, another part of the pipe 137a is connected to the temperature regulator 137, the laser oscillator 135, and the amplifier 165 so that the cooling medium circulates through each of them. At the connection between the pipe 137a and the amplifier 165, a holder 165d is arranged in the pipe 137a. The cooling medium cools the laser crystal 165a through the pipe 137a and the holder 165d.

[0091] A portion of the cooling medium flowing from the temperature regulator 137 passes through the first laser light source 131 and flows to the second laser light source 161 to cool them. Another portion of the cooling medium passes through the laser oscillator 135 and flows to the amplifier 165 to cool them. After cooling, the cooling medium returns to the temperature regulator 137 through the pipe 137a, and after its temperature is adjusted again by the temperature regulator 137, it flows to each of the components as described above and cools them. The position of the pipe 137a and the direction of circulation of the cooling medium are not particularly limited.

[0092] The measuring instrument 400 of this embodiment is disposed downstream of the amplifier 165 with respect to the traveling direction of the main pulse laser beam MPL emitted from the laser oscillator 135, and measures the pulse energy and pulse time width of the main pulse laser beam MPL emitted from the amplifier 165.

[0093] 5.2 Operation Next, the operation of the processor 121 in this embodiment will be described. The control flowchart of this embodiment is the same as the control flowchart of the first embodiment shown in FIG. 7. However, in the operation of this embodiment, part of the starting state differs from the starting state of the first embodiment. Specifically, in the starting state of this embodiment, the main pulse laser beam MPL from the laser oscillator 135 is amplified by the amplifier 165. Parts of the amplified main pulse laser beam MPL are reflected by each of the beam splitters 401 and 421, and the pulse energy and pulse time width are measured by the measuring instrument 400. In addition, a cooling medium flows through the pipe 137a to cool the first laser light source 131, the laser oscillator 135, the second laser light source 161, and the amplifier 165. The starting state other than the above is the same as the starting state of the first embodiment.

[0094] Furthermore, the pulse energy in step SP11 of this embodiment is the pulse energy of the main pulse laser beam MPL output from the amplifier 165 and measured by the measuring instrument 400. Furthermore, in step SP12 of this embodiment, the processor 121 controls the temperature regulator 137, which adjusts the temperature of the cooling medium so that the pulse energy amplified by the amplifier 165 and measured by the measuring instrument 400 falls within a target range of the pulse energy. The cooling medium flows through the piping 137a and proceeds to the first laser light source 131, the laser oscillator 135, the second laser light source 161, and the amplifier 165 to cool them. After cooling them, the cooling medium flows through the piping 137a and returns to the temperature regulator 137, where its temperature is adjusted again. The pulse time width in step SP13 is the pulse time width of the main pulse laser beam MPL output from the amplifier 165 and measured by the measuring instrument 400.

[0095] 5.3 Actions and Effects The cooling medium of the present embodiment further cools the second laser light source 161. With this configuration, a change in the wavelength of the second excitation light can be suppressed compared to when the second laser light source 161 is not cooled. As a result, the pulse energy of the main pulse laser light MPL amplified in the amplifier 165 by the second excitation light whose change in wavelength is suppressed can fall within a target range. Note that although the cooling medium cools the second laser light source 161, the piping 137a does not necessarily extend to the second laser light source 161, and the cooling medium does not necessarily cool the second laser light source 161.

[0096] Furthermore, the measuring instrument 400 of this embodiment measures the pulse energy and pulse time width of the main pulse laser beam MPL emitted from the amplifier 165. With this configuration, compared to a case in which the measuring instrument 400 is provided between the laser oscillator 135 and the amplifier 165 and measures the pulse energy and pulse time width of the main pulse laser beam MPL before it enters the amplifier 165, it is easier to keep the pulse energy and pulse time width of the main pulse laser beam MPL within their respective target ranges when irradiating the droplet target DL. Therefore, a decrease in plasma generation efficiency can be suppressed, and EUV light 101 that satisfies the performance required by the exposure apparatus 200 and the inspection apparatus 300 can be emitted. Note that the measuring instrument 400 may also be provided between the laser oscillator 135 and the amplifier 165 and measure the pulse energy and pulse time width of the main pulse laser beam MPL after it is emitted from the laser oscillator 135 and before it is amplified by the amplifier 165.

[0097] Furthermore, in the measuring instrument 400 of this embodiment, the cooling medium further cools the amplifier 165. With this configuration, changes in the wavelengths of the second excitation light and the main pulse laser light MPL in the amplifier 165 can be suppressed more effectively than when the amplifier 165 is not cooled, and the pulse energy can fall within a target range. Note that, although the cooling medium cools the amplifier 165 in this embodiment, the piping 137a does not need to extend to the amplifier 165, and the cooling medium does not necessarily need to cool the amplifier 165.

[0098] In this embodiment, the cooling medium does not have to cool the laser oscillator 135 as in the first embodiment.

[0099] 6. Description of the extreme ultraviolet light generation device according to the third embodiment Next, a description will be given of the configuration of an EUV light generation system 100 according to embodiment 3. Note that the same components as those described above are denoted by the same reference numerals, and redundant description will be omitted unless otherwise specified.

[0100] 6.1 Configuration 9 is a schematic diagram showing an example of the schematic configuration of a portion of the EUV light generation system 100 of this embodiment. The EUV light generation system 100 of this embodiment further includes a monitor 500. The monitor 500 will be described later.

[0101] FIG. 10 is a view of the amplifier 165 of this embodiment as viewed from the X direction. FIG. 11 is a view of the amplifier 165 of this embodiment as viewed from the Y direction. This embodiment differs from embodiment 2 in that the amplifier 165 is a slab-type amplifier. As shown in FIGS. 10 and 11, the amplifier 165 of this embodiment includes a second lens 163a, a laser crystal 165a, and a resonator mirror 165b. The second lens 163a of this embodiment is provided between the second laser light source 161 and the laser crystal 165a. The laser crystal 165a of this embodiment is a flat member and is sandwiched between a pair of substrates 165f. The main surface of the laser crystal 165a is located in the XZ plane. The resonator mirror 165b consists of a pair of concave mirrors. Hereinafter, the pair of concave mirrors, one concave mirror of the pair of concave mirrors, and the other concave mirror of the pair of concave mirrors may be simply referred to as the pair of mirrors, one mirror, and the other mirror. Laser crystal 165a is disposed between the pair of mirrors, and each concave surface of resonator mirror 165b faces laser crystal 165a. One mirror of resonator mirror 165b is provided between second lens 163a and laser crystal 165a, and the other mirror of resonator mirror 165b is provided between laser crystal 165a and first beam splitter 401. Second excitation light from second laser light source 161 is focused on laser crystal 165a by second lens 163a. ​​At this time, the second excitation light passes through one mirror of resonator mirror 165b. Laser crystal 165a absorbs the second excitation light and is excited. The laser oscillator 135 of this embodiment is disposed to the side of the other one of the resonator mirrors 165b and on the opposite side of the second laser light source 161 with respect to the other mirror, and the main pulse laser light MPL from the laser oscillator 135 passes beside the other mirror and enters the laser crystal 165a. When the main pulse laser light MPL passes through the excited laser crystal 165a, it is amplified by stimulated emission. The main pulse laser light MPL then travels in a zigzag pattern between the resonator mirrors 165b and is further amplified as it passes through the laser crystal 165a as it travels. The amplified main pulse laser light MPL passes beside the other one of the resonator mirrors 165b and travels toward the first beam splitter 401.9 and 10, the propagation directions of the second excitation light and the main pulse laser light MPL from the laser oscillator 135 and the amplifier 165 are different, but are shown differently for ease of viewing. In particular, Fig. 9 merely shows the propagation directions of the second excitation light and the main pulse laser light MPL from the laser oscillator 135 and the amplifier 165 in a simplified manner, and does not show the actual propagation paths of each.

[0102] When the amplifier 165 is a slab-type amplifier, if the thermal lens conditions in the laser crystal 165a change, the divergence angle of the main pulse laser beam MPL emitted from the amplifier 165 may deviate from the expected value. This may cause the spot shape of the main pulse laser beam MPL when irradiating the droplet target DL to deform from the desired shape to an unintended shape. For example, the desired shape is a circle, and the unintended shape is an ellipse. Therefore, in this embodiment, the divergence angle is monitored by the monitor 500, and the divergence angle is adjusted by adjusting the current value of the current of the second laser light source 161, thereby maintaining the spot shape at the desired shape.

[0103] As shown in FIG. 9, the monitor 500 includes a third beam splitter 501, a third condenser lens 503, a camera 505, and a measurement circuit 509.

[0104] The third beam splitter 501 is disposed on the optical path of the main pulse laser beam MPL from the other of the resonator mirrors 165b of the amplifier 165 to the plasma generation region AR, and is preferably disposed between the other mirror and the mirror 31. The third beam splitter 501 of this embodiment is provided between the second beam splitter 421 and the mirror 31 with respect to the traveling direction of the main pulse laser beam MPL emitted from the laser oscillator 135. The third beam splitter 501 transmits a portion of the main pulse laser beam MPL that has passed through the second beam splitter 421 toward the plasma generation region AR, and reflects another portion of the main pulse laser beam MPL toward a third collecting lens 503. The third collecting lens 503 collects the main pulse laser beam MPL reflected by the third beam splitter 501 on a detection surface of a camera 505. The camera 505 acquires image data of the main pulse laser beam MPL focused on the detection surface by the third focusing lens 503, and outputs a signal related to the image data to a measurement circuit 509. The measurement circuit 509 measures the divergence angle of the main pulse laser beam MPL emitted from the amplifier 165 based on the image data and the distance from the other of the resonator mirrors 165b of the amplifier 165 to the detection surface. The measurement circuit 509 is connected to the processor 121, and outputs a signal related to the measured divergence angle of the main pulse laser beam MPL to the processor 121.

[0105] 6.2 Operation Next, the operation of the processor 121 in this embodiment will be described.

[0106] 12 is a diagram showing a control flowchart of the processor 121 of the present embodiment. The control flowchart of the present embodiment further includes step SP15 and step SP16. The start state shown in FIG. 12 differs from that of the second embodiment in that a part of the main pulse laser beam MPL outputted from the amplifier 165 is reflected by the third beam splitter 501, the divergence angle of the main pulse laser beam MPL is measured by the monitor 500, and a signal related to the divergence angle is input to the processor 121.

[0107] In step SP13, if the pulse time width measured by measuring instrument 400 is not within the target range for the pulse time width, processor 121 advances the control flow to step SP14. If the measured pulse time width is within the target range, processor 121 advances the control flow to step SP15.

[0108] (Step SP15) In this step, if the divergence angle measured by the monitor 500 falls within the target range of the divergence angle, the processor 121 returns the control flow to step SP11. If the measured divergence angle does not fall within the target range, the processor 121 advances the control flow to step SP16.

[0109] (Step SP16) In this step, the processor 121 adjusts the current value of the current supplied to the second laser light source 161 so that the divergence angle measured by the monitor 500 falls within the target range of the divergence angle. In step SP12, the temperature of the cooling medium is adjusted. At this time, the cooling medium also cools the second laser light source 161. If the second laser light source 161 is also cooled to this temperature, the divergence angle of the main pulse laser beam MPL may not fall within the target range. For this reason, in this step, the processor 121 adjusts the current value to keep the divergence angle within the target range of the divergence angle. This prevents the spot shape of the main pulse laser beam MPL from changing from the target shape to an unintended shape when irradiating the droplet target DL.

[0110] After adjusting the current value, the processor 121 returns the control flow to step SP15.

[0111] 6.3 Actions and Effects The amplifier 165 of this embodiment is a slab-type amplifier 165. The processor 121 also adjusts the current value of the current supplied to the second laser light source 161 so that the divergence angle of the main pulse laser beam MPL measured by the monitor 500 falls within a target range of the divergence angle of the main pulse laser beam MPL.

[0112] This configuration can prevent the spot shape of the main pulse laser beam MPL from changing from a desired shape to an unintended shape when irradiating the droplet target DL, thereby preventing a portion of the main pulse laser beam MPL from not irradiating the diffused target and causing a loss of the main pulse laser beam MPL, and thus preventing a decrease in plasma generation efficiency.

[0113] In this embodiment, the processor 121 may end the control flow after adjusting the current value of the current supplied to the second laser light source 161 in step SP16.

[0114] In this embodiment, the order in which the first beam splitter 401, the second beam splitter 421, and the third beam splitter 501 are arranged is not particularly limited.

[0115] The above description is intended to be illustrative rather than limiting. Thus, it will be apparent to one skilled in the art that modifications can be made to the disclosed embodiments without departing from the scope of the claims. It will also be apparent to one skilled in the art that the disclosed embodiments can be used in combination. Terms used throughout this specification and claims should be construed as "open ended" unless expressly stated otherwise. For example, words such as "comprise," "have," "comprise," and "equip" should be construed as meaning "without excluding the presence of elements other than those listed." In addition, the modifier "a" should be construed as meaning "at least one" or "one or more." In addition, the term "at least one of A, B, and C" should be construed as "A," "B," "C," "A+B," "A+C," "B+C," or "A+B+C," and should also be construed as including combinations other than "A," "B," and "C."

Claims

1. An extreme ultraviolet light generation device that generates extreme ultraviolet light by irradiating a droplet target with laser light, a first light source that emits first excitation light; a laser oscillator including an active medium, the laser oscillator oscillating by irradiating the active medium with the first excitation light to emit the laser light; a measuring instrument for measuring the pulse energy and pulse time width of the laser light; a temperature regulator that regulates the temperature of a cooling medium that cools the first light source; a processor; Equipped with The processor controls the temperature regulator to adjust the temperature of the cooling medium so that the pulse energy measured by the measuring instrument falls within a target range of the pulse energy, and adjusts the current value of the current supplied to the first light source so that the pulse time width measured by the measuring instrument falls within a target range of the pulse time width. Extreme ultraviolet light generator.

2. 2. The extreme ultraviolet light generating apparatus according to claim 1, The processor controls the temperature regulator to lower the temperature of the cooling medium when the pulse energy measured by the measuring instrument is less than a target range of the pulse energy.

3. 2. The extreme ultraviolet light generating apparatus according to claim 1, The processor decreases the current value when the pulse time width measured by the measuring instrument is smaller than the target range of the pulse time width, and increases the current value when the pulse time width is larger than the target range of the pulse time width.

4. 2. The extreme ultraviolet light generating apparatus according to claim 1, The processor controls the temperature regulator to adjust the temperature of the cooling medium, and then adjusts the current value.

5. The extreme ultraviolet light generating apparatus according to claim 4, After adjusting the current value, the processor again controls the temperature regulator to adjust the temperature of the cooling medium.

6. 2. The extreme ultraviolet light generating apparatus according to claim 1, The cooling medium further cools the laser oscillator.

7. 2. The extreme ultraviolet light generating apparatus according to claim 1, a second light source that emits second excitation light; an amplifier that amplifies the laser light emitted from the laser oscillator by the second excitation light; Furthermore, The cooling medium further cools the second light source.

8. The extreme ultraviolet light generating apparatus according to claim 7, The measuring instrument measures the pulse energy and pulse time width of the laser light emitted from the amplifier.

9. The extreme ultraviolet light generating apparatus according to claim 7, The amplifier is a slab type amplifier.

10. The extreme ultraviolet light generating apparatus according to claim 9, a monitor that measures the divergence angle of the laser light emitted from the amplifier, The processor adjusts the current value of the current supplied to the second light source so that the divergence angle of the laser light measured by the monitor falls within a target range of the divergence angle of the laser light.

11. The extreme ultraviolet light generating apparatus according to claim 7, The cooling medium further cools the amplifier.

12. 2. The extreme ultraviolet light generating apparatus according to claim 1, The cooling medium is water.

13. An extreme ultraviolet light generation device that generates extreme ultraviolet light by irradiating a droplet target with laser light, a first light source that emits first excitation light; a laser oscillator including an active medium, the laser oscillator oscillating by irradiating the active medium with the first excitation light to emit the laser light; a measuring instrument for measuring the pulse energy and pulse time width of the laser light; a temperature regulator that regulates the temperature of a cooling medium that cools the first light source; a processor; Equipped with the processor controls the temperature regulator to adjust the temperature of the cooling medium so that the pulse energy measured by the measuring instrument falls within a target range of the pulse energy, and adjusts a current value of a current supplied to the first light source so that the pulse time width measured by the measuring instrument falls within a target range of the pulse time width; and outputs the extreme ultraviolet light generated by an extreme ultraviolet light generation device to an exposure apparatus; exposing a photosensitive substrate to the extreme ultraviolet light in the exposure apparatus to manufacture an electronic device; A method for manufacturing an electronic device, comprising:

14. An extreme ultraviolet light generation device that generates extreme ultraviolet light by irradiating a droplet target with laser light, a first light source that emits first excitation light; a laser oscillator including an active medium, the laser oscillator oscillating by irradiating the active medium with the first excitation light to emit the laser light; a measuring instrument for measuring the pulse energy and pulse time width of the laser light; a temperature regulator that regulates the temperature of a cooling medium that cools the first light source; a processor; Equipped with the processor controls the temperature regulator to adjust the temperature of the cooling medium so that the pulse energy measured by the measuring instrument falls within a target range of the pulse energy, and adjusts a current value of a current supplied to the first light source so that the pulse time width measured by the measuring instrument falls within a target range of the pulse time width; and irradiates a mask with the extreme ultraviolet light generated by an extreme ultraviolet light generation device to inspect the mask for defects; selecting a mask using the results of said test; The pattern formed on the selected mask is transferred onto a photosensitive substrate by exposure. A method for manufacturing an electronic device, comprising:

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