Extreme ultraviolet light generation method, extreme ultraviolet light generation device, and method for manufacturing electronic device

Abstract

To provide an EUV light generation method that can spare a plurality of main pulse laser devices.SOLUTION: An extreme ultraviolet light generation method comprises a target supply step of ejecting a droplet target DL into a chamber (SP1), a pre-pulse laser beam irradiation step of irradiating the droplet target DL with pre-pulse laser beam PPL to generate a diffusion target DT (SP2), and a main pulse laser beam irradiation step of irradiating the diffusion target with main pulse laser beam MPL to generate extreme ultraviolet light (SP3), wherein the main pulse laser beam includes first main pulse laser beam and second main pulse laser beam, and in the main pulse laser beam irradiation step (SP3), the diffusion target may be irradiated with the first main pulse laser beam MPL1 having higher energy density at a central portion than at an outer peripheral portion and the second main pulse laser beam MPL2 having higher energy density at the outer peripheral portion than at the central portion.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a method for generating extreme ultraviolet light, an apparatus for generating extreme ultraviolet light, 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] Japanese Patent Application Laid-Open No. 2003-270551 [Patent Document 2] U.S. Patent No. 9,113,540 [Patent Document 3] Summary of the specification of U.S. Patent No. 10,131,017

[0005] An extreme ultraviolet light generation method according to one aspect of the present disclosure includes a target supply step of discharging a droplet target into a chamber, a pre-pulse laser light irradiation step of irradiating the droplet target with a pre-pulse laser beam to generate a diffused target, and a main pulse laser light irradiation step of irradiating the diffused target with a main pulse laser beam to generate extreme ultraviolet light, wherein the main pulse laser beam includes a first main pulse laser beam and a second main pulse laser beam, and in the main pulse laser light irradiation step, the diffused target may be irradiated with the first main pulse laser beam, the energy density of which is higher in a central portion than in a peripheral portion, and the second main pulse laser beam, the energy density of which is higher in an outer peripheral portion than in a central portion.

[0006] Furthermore, an extreme ultraviolet light generation apparatus according to an aspect of the present disclosure includes a target supply unit that outputs a droplet target into a chamber, a pre-pulse laser beam irradiation system that irradiates the droplet target with a pre-pulse laser beam to generate a diffused target, and a main pulse laser beam irradiation system that irradiates the diffused target with a main pulse laser beam to generate extreme ultraviolet light, wherein the main pulse laser beam includes a first main pulse laser beam and a second main pulse laser beam, and the main pulse laser beam irradiation system may irradiate the diffused target with the first main pulse laser beam, the central portion of which has a higher energy density than the peripheral portion, and the second main pulse laser beam, the peripheral portion of which has a higher energy density than the central portion.

[0007] Furthermore, a method for manufacturing an electronic device according to an aspect of the present disclosure may include a target supply step of outputting a droplet target into a chamber, a pre-pulse laser light irradiation step of irradiating the droplet target with a pre-pulse laser light to generate a diffused target, and a main pulse laser light irradiation step of irradiating the diffused target with a main pulse laser light to generate extreme ultraviolet light, wherein the main pulse laser light includes a first main pulse laser beam and a second main pulse laser beam, and the main pulse laser light irradiation step may include outputting extreme ultraviolet light generated by an extreme ultraviolet light generation method in which the diffused target is irradiated with the first main pulse laser beam, the central portion of which has a higher energy density than the peripheral portion, and the second main pulse laser beam, the peripheral portion of which has a higher energy density than the central portion, to an exposure apparatus, and exposing a photosensitive substrate to the extreme ultraviolet light using the exposure apparatus to manufacture the electronic device.

[0008] Furthermore, a method for manufacturing an electronic device according to another aspect of the present disclosure may include: a target supply step of outputting a droplet target into a chamber; a pre-pulse laser light irradiation step of irradiating the droplet target with a pre-pulse laser beam to generate a diffused target; and a main pulse laser light irradiation step of irradiating the diffused target with a main pulse laser beam to generate extreme ultraviolet light, wherein the main pulse laser beam includes a first main pulse laser beam and a second main pulse laser beam; and the main pulse laser light irradiation step may include irradiating a mask with extreme ultraviolet light generated by an extreme ultraviolet light generation method in which the diffused target is irradiated with the first main pulse laser beam, the central portion of which has a higher energy density than the peripheral portion, and the second main pulse laser beam, the peripheral portion of which has a higher energy density than the central portion, to inspect the mask for defects, selecting a mask using the inspection results, and exposing and transferring a pattern formed on the selected mask onto a photosensitive substrate. [Brief explanation of the drawings]

[0009] 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 overall schematic configuration of an electronic device manufacturing apparatus different from the electronic device manufacturing apparatus shown in FIG. [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 flowchart showing the operation of the extreme ultraviolet light generation apparatus. [Figure 5] FIG. 5 is a diagram showing the state of a diffused target irradiated with picosecond pulsed laser light as pre-pulse laser light. [Figure 6] FIG. 6 is a diagram showing the state of a diffused target irradiated with nanosecond pulsed laser light as pre-pulse laser light. [Figure 7] FIG. 7 is a schematic diagram illustrating an example of the overall configuration of the extreme ultraviolet light generation apparatus according to the first embodiment. [Figure 8] FIG. 8 is a schematic diagram showing an example of a beam adjusting optical system. [Figure 9] FIG. 9 is a diagram showing the distribution of the energy density of the first main pulse laser beam irradiated onto the diffused target. [Figure 10] FIG. 10 is a diagram showing the distribution of the energy density of the second main pulse laser beam irradiated onto the diffused target. [Figure 11] FIG. 11 is a diagram showing the timing and intensity at which each laser beam is irradiated onto a target material. [Figure 12] FIG. 12 is a schematic diagram illustrating an example of the overall configuration of an extreme ultraviolet light generation apparatus according to the second embodiment. Embodiment

[0010] 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

[0011] 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.

[0012] 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.

[0013] 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.

[0014] FIG. 2 is a schematic diagram illustrating an example of the overall configuration of an electronic device manufacturing apparatus different from the electronic device manufacturing apparatus illustrated in FIG. 1. The electronic device manufacturing apparatus illustrated in FIG. 2 includes an EUV light generation apparatus 100 and an inspection apparatus 300. The inspection apparatus 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 the EUV light 101 incident from the EUV light generation apparatus 100 by the mirrors 311, 313, and 315, and irradiates the 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 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.

[0015] 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.

[0016] 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 main pulse laser beam irradiation system MPS including a main pulse laser device 130, a pre-pulse laser beam irradiation system PPS including a pre-pulse laser device 140, a chamber device 10, and a control system 120 including a processor 121.

[0017] 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 device 40 is attached to the sub-chamber 15 so as to penetrate the wall of the sub-chamber 15. The target supply device 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 as a droplet or a target for short.

[0018] 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 the processor 121.

[0019] 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.

[0020] The chamber apparatus 10 includes a target collection unit 14. The target collection unit 14 is a box attached to an inner wall 10b of the chamber apparatus 10, and is in communication 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.

[0021] 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.

[0022] 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.

[0023] An EUV light collector mirror 75 including, for example, a spheroid-shaped reflecting surface 75a is disposed in the internal 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. For example, the reflecting surface 75a may be disposed so that its first focal point is located in the plasma generation region AR and its second focal point is located at an intermediate focal point IF. In FIG. 3, a line passing through the first focal point and the second focal point is indicated as a focal line L0.

[0024] 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.

[0025] 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 indicating this 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. When the droplet target DL passes through a light collection area of ​​a light source (not shown) that is arranged to improve contrast within the field of view of the target sensor 27, the imaging unit detects the trajectory of the droplet target DL and changes in the light passing around it. The imaging unit converts the detected changes in light into an electrical signal that serves as image data for the droplet target DL. The imaging unit outputs this electrical signal to the processor 121.

[0026] 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.

[0027] The pre-pulse laser device 140 emits a pre-pulse laser beam PPL. In the example of FIG. 3, the wavelength of the pre-pulse laser beam PPL may be 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. 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.

[0028] The propagation directions of the main pulse 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 pulse 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 dichroic mirror 34. The dichroic mirror 34 reflects the pre-pulse laser beam PPL and transmits the main pulse laser beam MPL, thereby causing the optical paths of the main pulse laser beam MPL and the pre-pulse laser beam PPL to roughly overlap each other. The orientation of at least one of these mirrors 31-34 is adjusted by an actuator (not shown), and this adjustment allows the main pulse laser beam MPL and the pre-pulse laser beam PPL to propagate appropriately from the window 12 into the internal space of the chamber apparatus 10.

[0029] 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 dichroic mirror 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, a dichroic mirror 34, and a laser focusing optical system 13.

[0030] 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 output, the output direction of the droplet target DL, etc. 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 directions of the main pulse laser beam MPL and the pre-pulse laser beam PPL, and the focusing positions of the main pulse laser beam MPL and the pre-pulse laser beam PPL. The various controls described above are merely examples, and other controls may be added as needed, as described below.

[0031] 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. 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.

[0032] 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.

[0033] The center-side gas supply unit 81 has a side surface shaped like a truncated cone 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 a focal line L0 that passes through the first and second focal points of the reflecting surface 75a. The focal line L0 is aligned with the central axis direction 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).

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 3.2 Operation Next, the operation of the EUV light generation system 100 of the comparative example will be described. Fig. 4 is a flowchart showing the operation of the EUV light generation system 100. As shown in Fig. 4, the EUV light generation method of this example includes a target supply step SP1, a pre-pulse laser beam irradiation step SP2, and a main pulse laser beam irradiation step SP3.

[0038] Before the target supply step SP1, the EUV light generation system 100 is prepared for operation. 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. To exhaust atmospheric components, the internal space of the chamber apparatus 10 may be repeatedly purged and exhausted. 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.

[0039] The processor 121 also controls the exhaust pump 60 to exhaust gas from 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 indicating the pressure in the internal space of the chamber apparatus 10 measured by the pressure sensor 26.

[0040] 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, 231.93°C, for example, between 240°C and 290°C. This completes preparations for discharging the droplet target DL.

[0041] (Target supply step SP1) This step discharges droplet targets DL into the chamber apparatus 10. In this step, the processor 121 controls the pressure regulator 43 to supply an inert gas from a gas supply source (not shown) into the tank 41 and adjust the pressure in 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 of the nozzle 42. The target material discharged from the nozzle hole may take the form of a jet. To generate the droplet targets DL, the processor 121 applies a voltage of a predetermined waveform from the piezoelectric power supply 48 to the piezoelectric element 47. The piezoelectric power supply 48 applies the voltage so that the waveform of the voltage value is, for example, sinusoidal, rectangular, or sawtooth. 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 droplet targets DL. The diameter of the droplet target DL is generally 20 μm or less.

[0042] (Pre-pulse laser light irradiation step SP2) This step is a step of generating a diffused target by irradiating the droplet target DL with the pre-pulse laser beam PPL. When the droplet target DL is discharged, the target sensor 27 detects the timing of the droplet target DL passing through a predetermined position in the internal space of the chamber apparatus 10. The processor 121 controls the timing of emission of the pre-pulse laser beam PPL 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 output 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 when the pre-pulse laser beam PPL is emitted.

[0043] The pre-pulse laser beam (PPL) has a Gaussian energy density profile and a temporal pulse width τ PPL The pre-pulse laser beam is, for example, a picosecond pulsed laser beam with a pulse width of 10 ps or more and 100 ps or less, or a nanosecond pulsed laser beam with a pulse width of 10 ns or more and 300 ns or less. The pulse width is the interval between the times when the intensity of the laser beam is at half of its maximum value before and after the intensity reaches its maximum value. The picosecond pulsed laser beam and the nanosecond pulsed laser beam have roughly the same energy per pulse. Therefore, the picosecond pulsed laser beam has a higher energy density than the nanosecond pulsed laser beam. The fluence of the pre-pulse laser beam 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 is reflected by the mirror 33 and the dichroic mirror 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.

[0044] The diffused target is a target obtained by diffusing the droplet target DL, and therefore has a larger diameter and a lower density of the target material than the droplet target DL. As described above, the diameter of the droplet target DL is approximately 20 μm or less, while the diameter of the diffused target is approximately 70 μm. FIG. 5 illustrates a diffused target irradiated with picosecond pulsed laser light as the pre-pulse laser light PPL, and FIG. 6 illustrates a diffused target irradiated with nanosecond pulsed laser light as the pre-pulse laser light PPL. As shown in FIGS. 5 and 6 , the density of the target material is higher in the outer peripheral portion DTo than in the central portion DTc of each diffused target DT. However, the diffused target DT generated by irradiation with picosecond pulsed laser light is generated by irradiating a high-energy laser light for a shorter period of time, and therefore has a larger difference in the density of the target material between the central portion DTc and the outer peripheral portion DTo.

[0045] (Main pulse laser light irradiation step SP3) In this step, the diffused target DT is irradiated with the main pulse laser beam MPL to generate EUV light. 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. The time difference between when the pre-pulse laser beam PPL is emitted and when 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 DT is irradiated with the main pulse laser beam MPL, and output a light emission trigger signal.

[0046] The main pulse laser beam MPL has a Gaussian energy density profile and a pulse width of, for example, 1 ns to 50 ns, more preferably 15 ns to 20 ns. The main pulse laser beam MPL emitted from the main pulse laser device 130 is reflected by mirrors 31 and 32, transmitted through the dichroic mirror 34, and irradiated onto the diffused target DT 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 on the plasma generation region AR. The diffused target DT 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 the diffused target DT with the main pulse laser beam MPL.

[0047] By irradiating the main pulse laser beam MPL onto the diffused target DT, in which the density of the target material has been reduced in this manner, 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 irradiated directly onto the droplet target DL.

[0048] Of the light containing EUV light generated in the plasma generation region AR, EUV light 101 is collected at an intermediate focus IF by the EUV light collector mirror 75 and then enters the exposure device 200 from the connection part 19 .

[0049] 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 etching gas containing hydrogen supplied from the central gas supply unit 81 to become stannane. Most of the stannane obtained by the reaction with the etching gas flows into the exhaust port 10E along with the flow of unreacted etching gas. At least a portion of the unreacted charged particles, particles, and etching gas also flow into the exhaust port 10E.

[0050] The unreacted etching gas, fine particles, charged particles, stannane, etc. that have flowed into the exhaust port 10E flow as residual gases from the exhaust pipe 10P into the exhaust pump 60, where they are subjected to a predetermined exhaust process such as being made harmless.

[0051] 3.3 Challenges When a diffused target DT is irradiated with a main pulse laser beam MPL having a Gaussian energy density profile, as in the EUV light generation system 100 of the comparative example, the target material is highly likely to be converted into plasma at a central portion DTc of the diffused target DT. However, in the EUV light generation system 100 of the comparative example, the laser beam irradiated onto the outer peripheral portion DTo of the diffused target DT has a lower energy density than the laser beam irradiated onto the central portion DTc. Therefore, the target material is less likely to be converted into plasma at the outer peripheral portion DTo, where the density of the target material is high. Unreacted target material that is not converted into plasma is exhausted from the exhaust pipe 10P or becomes debris and adheres to the inner wall 10b of the chamber apparatus 10 or the reflecting surface 75a of the EUV light collector mirror 75. Thus, unreacted target material does not contribute to the generation of EUV light. For this reason, there is a demand for more efficient generation of EUV light.

[0052] Therefore, in the following embodiments, an EUV light generation method and an EUV light generation apparatus capable of efficiently generating EUV light are exemplified.

[0053] 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.

[0054] 4.1 Configuration 7 is a schematic diagram showing an example of the overall configuration of an EUV light generation system 100 of this embodiment. As shown in Fig. 7, in the EUV light generation system 100 of this embodiment, the configuration of the main pulse laser irradiation system MPS is different from the configuration of the main pulse laser irradiation system MPS of the comparative example. The main pulse laser irradiation system MPS of this embodiment differs from the main pulse laser irradiation system MPS of the comparative example in that it includes a first main pulse laser device 131, a second main pulse laser device 132, a beam adjusting optical system 50, a mirror 35, and a polarizer 36.

[0055] The first and second main pulse laser devices 131, 132 are electrically connected to the processor 121 via a delay circuit 122. The first main pulse laser device 131 emits a first main pulse laser beam MPL1 with a Gaussian distribution in which the energy density is higher in the center than in the periphery, and the second main pulse laser device 132 emits a second main pulse laser beam MPL2 with a similar energy density distribution. That is, the main pulse laser beam of this embodiment includes the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2. Note that in this embodiment, the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 are laser beams with the same wavelength but with polarization directions that differ by 90 degrees from each other. The first main pulse laser device 131 and the second main pulse laser device 132 are, for example, both YAG laser devices or both CO laser devices.

[0056] The polarizer 36 is provided at a position where the first main pulse laser beam MPL1 is incident. The polarization direction of the first main pulse laser beam MPL1 that is highly transmitted through the polarizer 36 matches the polarization direction of the first main pulse laser beam MPL1. Therefore, the first main pulse laser beam MPL1 is transmitted through the polarizer 36.

[0057] The beam adjusting optical system 50 is provided at a position where the second main pulse laser beam MPL2 is incident. The beam adjusting optical system 50 is an optical system that converts a laser beam having a higher energy density in the center than in the outer periphery into a laser beam having a higher energy density in the outer periphery than in the center, for example, converting a laser beam having a Gaussian energy density in the vertical cross section into a laser beam having a circular energy density in the vertical cross section. Therefore, the second main pulse laser beam MPL2 incident on the beam adjusting optical system 50 is converted into a laser beam having a circular energy density.

[0058] FIG. 8 is a schematic diagram showing an example of the beam adjusting optical system 50. The beam adjusting optical system 50 of this example includes a pair of axicon lenses 51 and 52 and a condenser lens 53. Each of the axicon lenses 51 and 52 is a conical lens. The axicon lens 51 and the axicon lens 52 are arranged so that their vertices face each other with a predetermined distance between them and their rotational symmetry axes coincide with the optical axis of the second main pulse laser beam MPL2. The axicon lens 51 is also arranged so that the second main pulse laser beam MPL2 is incident on the center of the bottom surface of one axicon lens 51 along the rotational symmetry axis. Therefore, the second main pulse laser beam MPL2 also propagates along the rotational symmetry axis of the other axicon lens 52. The condenser lens 53 is arranged so that the surface onto which the second main pulse laser beam MPL2 is incident faces the bottom surface of the other axicon lens 52.

[0059] When the second main pulse laser beam MPL2 having a Gaussian energy density distribution is incident on the bottom surface of the axicon lens 51, the laser beam is converted into a laser having a higher energy density at the periphery than at the center, and is emitted from the bottom surface of the axicon lens 52. In this example, the second main pulse laser beam MPL2 having an annular shape is emitted from the axicon lens 52.

[0060] The collecting lens 53 collects the second main pulse laser beam MPL2 emitted from the bottom surface of the axicon lens 52. The annular second main pulse laser beam MPL2 has a Gaussian energy density distribution at the focal point due to condensation of the annulus, but has an annular energy density distribution near the focal point. In this example, the curvature and the like of the collecting lens 53 are determined so that the second main pulse laser beam MPL2 is collected with an annular energy density distribution in the plasma generation region AR. Note that a collecting mirror may be used instead of the collecting lens 53. Furthermore, in this example, the beam adjusting optical system 50 has been described using the example of FIG. 8 , but the beam adjusting optical system 50 of this embodiment is not limited to the example of FIG. 8 as long as it is an optical system that converts a laser beam having a higher energy density in the center than in the periphery into a laser beam having a higher energy density in the periphery than in the center.

[0061] The mirror 35 reflects the second main pulse laser beam MPL2 emitted from the beam adjusting optical system 50 toward the polarizer 36. As described above, the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 have polarization directions that differ by 90 degrees from each other, and therefore the polarization direction of the first main pulse laser beam MPL1 passing through the polarizer 36 differs from that of the second main pulse laser beam MPL2. For this reason, the polarizer 36 reflects the second main pulse laser beam MPL2. The polarizer 36 is positioned at an angle such that the optical path of the first main pulse laser beam MPL1 passing through the polarizer 36 and the optical path of the second main pulse laser beam MPL2 reflected by the polarizer 36 generally coincide with each other. The first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 emitted from the polarizer 36 are reflected by the mirror 31, propagate through the same optical path as the main pulse laser beam MPL in Comparative Example 1, and are collected in the plasma generation region AR, where they are irradiated onto the diffused target DT. However, in this embodiment, the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 are irradiated onto the diffused target DT at different times, as will be described later.

[0062] 9 is a diagram showing the distribution of energy density of the first main pulse laser beam MPL1 irradiated onto the diffused target DT. As described above, the first main pulse laser beam MPL1 does not pass through the beam adjusting optical system 50, and therefore the first main pulse laser beam MPL1 irradiated onto the diffused target DT is a Gaussian laser beam with a higher energy density in the center than in the outer periphery. In FIG. 9, the diameter of the first main pulse laser beam MPL1 is indicated by D1. The diameter is the distance from the cross section of the laser beam where the intensity of the laser beam is 1 / e of the peak intensity. 2 The diameter D1 is preferably equal to or larger than the diameter of the diffused target DT in a direction perpendicular to the optical axis of the first main pulse laser beam MPL1, and is preferably 20 μm or more and 100 μm or less.

[0063] FIG. 10 is a diagram showing the distribution of the energy density of the second main pulse laser beam MPL2 irradiated on the diffusion target DT. As described above, since the second main pulse laser beam MPL2 passes through the beam adjustment optical system 50, the second main pulse laser beam MPL2 irradiated on the diffusion target DT is an annular laser beam having a higher energy density in the outer peripheral portion than in the central portion. In FIG. 10, the inner diameter of the second main pulse laser beam MPL2 is indicated by D2, and the outer diameter is indicated by D3. The inner diameter D2 and the outer diameter D3 are the diameters at which the intensity of the laser beam becomes 1 / e 2 of the peak intensity in the cross section of the laser beam, respectively. The outer diameter D3 is preferably not less than the diameter of the diffusion target DT in the direction perpendicular to the optical axis of the second main pulse laser beam MPL2, and is preferably not less than 20 μm and not more than 100 μm.

[0064] Also, it is preferable that D2≦D1. By making the diameter D1 of the first main pulse laser beam MPL1 not less than the inner diameter D2 of the second main pulse laser beam MPL2, it is possible to suppress the occurrence of a gap between the outer periphery of the first main pulse laser beam MPL1 irradiated on the diffusion target DT and the inner periphery of the second main pulse laser beam MPL2, and it is possible to suppress the diffusion target DT that does not become plasma. In particular, it is preferable that D1 = D2. In this case, it is possible to suppress the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 from being irradiated at the same position of the diffusion target DT, and the laser beam can be efficiently absorbed by the diffusion target DT. Also, it is preferable that D1≦D3. However, D2 < D3, and the outer diameter D3 of the second main pulse laser beam MPL2 is not less than the diameter D1 of the first main pulse laser beam MPL1. Although the number of diffusion targets DT that do not become plasma may increase compared with the above, D1 < D2 may be satisfied, or D3 < D1 may be satisfied.

[0065] Furthermore, the fluence of the second main pulse laser beam MPL2 is preferably higher than the fluence of the first main pulse laser beam MPL1. As described above, whether the droplet target DL is irradiated with a picosecond pulse laser beam or a nanosecond pulse laser beam as the pre-pulse laser beam PPL, the density of the target material is higher in the outer peripheral portion DTo than in the central portion DTc of the diffused target DT. Therefore, when the fluences satisfy the above relationship, a laser beam with higher energy can be irradiated onto the portion of the diffused target DT where the density of the target material is high, and the laser beam can be efficiently absorbed by the diffused target DT, thereby more effectively converting the diffused target DT into plasma. The fluence of the first main pulse laser beam MPL1 is the value obtained by dividing the energy of the first main pulse laser beam MPL1 by the area of ​​a circle with diameter D1, and the fluence of the second main pulse laser beam MPL2 is the value obtained by dividing the energy of the second main pulse laser beam MPL2 by the difference between the area of ​​diameter D3 and the area of ​​diameter D2. The fluence of the first main pulse laser beam MPL1 may be equal to or greater than the fluence of the second main pulse laser beam MPL2.

[0066] 4.2 Operation Next, the operation of the EUV light generation system 100 of this embodiment will be described. The flowchart showing the operation of the EUV light generation system 100 of this embodiment is similar to the flowchart showing the operation of the EUV light generation system 100 of the comparative example shown in FIG. 4. However, in this embodiment, the main pulse laser beam irradiation step SP3 is different. Since the target supply step SP1 and the pre-pulse laser beam irradiation step SP2 of this embodiment are similar to those of the comparative example, the main pulse laser beam irradiation step SP3 will be described.

[0067] (Main pulse laser light irradiation step SP3) This step in the present embodiment is a step of irradiating the diffused target DT with the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2. In the present embodiment, after the pre-pulse laser beam PPL is emitted from the pre-pulse laser device 140, the first main pulse laser beam MPL1 is first emitted from the first main pulse laser device 131. The first main pulse laser beam MPL1 passes through the polarizer 36, is reflected by the mirrors 31 and 32, passes through the dichroic mirror 34, passes through the laser focusing optical system 13, reaches the plasma generation region AR, and is irradiated onto the diffused target DT.

[0068] 11 is a diagram showing the timing and intensity at which each laser beam is irradiated onto a target material. As shown in FIG. 11 , after the pre-pulse laser beam PPL is emitted from the pre-pulse laser device 140, the target material is irradiated with the first main pulse laser beam MPL1. The interval between the timing at which the droplet target DL is irradiated with the pre-pulse laser beam PPL and the timing at which the diffused target DT is irradiated with the first main pulse laser beam MPL1 is, for example, 50 ns to 500 ns in the case of a picosecond pulse laser beam, and 50 ns to 150 ns in the case of a nanosecond pulse laser beam, as described above. Therefore, the processor 121 and the delay circuit 122 input a light emission trigger signal to the first main pulse laser device 131 so that the diffused target DT is irradiated with the first main pulse laser beam MPL1 at such a time interval.

[0069] When the diffused target DT is irradiated with the first main pulse laser beam MPL1, the central portion DTc of the diffused target DT is mainly converted into plasma, and EUV light is emitted from the diffused target DT. As a result, the density of the target material is further reduced in the central portion DTc of the diffused target DT irradiated with the first main pulse laser beam MPL1. Furthermore, because the first main pulse laser beam MPL1 is also irradiated to the periphery of the outer peripheral portion DTo of the diffused target DT, the density of the target material is also reduced near the inner periphery of the outer peripheral portion DTo of the diffused target DT. However, because the energy density of the first main pulse laser beam MPL1 at the central portion is higher than that at the outer peripheral portion, the central portion DTc of the diffused target DT is converted into plasma more than the periphery of the outer peripheral portion DTo.

[0070] Following the emission of the first main pulse laser beam MPL1 from the first main pulse laser device 131, the second main pulse laser device 132 emits the second main pulse laser beam MPL2. The second main pulse laser beam MPL2 is converted by the beam adjusting optical system 50 from a state in which the energy density is higher in the center than in the periphery to a state in which the energy density is higher in the periphery than in the center. The second main pulse laser beam MPL2 emitted from the beam adjusting optical system 50 is reflected by the mirror 35 and the polarizer 36, and then propagates along the same optical path as the first main pulse laser beam MPL1. The second main pulse laser beam MPL2 then reaches the plasma generation region AR, and is irradiated onto the diffused target DT that was irradiated with the first main pulse laser beam MPL1.

[0071] The interval between the time when the diffused target DT is irradiated with the first main pulse laser beam MPL1 and the time when the diffused target DT is irradiated with the second main pulse laser beam MPL2 is preferably 1 ns or more and 10 ns or less. Therefore, the interval between the time when the diffused target DT is irradiated with the first main pulse laser beam MPL1 and the time when the diffused target DT is irradiated with the second main pulse laser beam MPL2 is shorter than the interval between the time when the droplet target DL is irradiated with the pre-pulse laser beam PPL and the time when the diffused target DT is irradiated with the first main pulse laser beam MPL1. In this manner, so that the diffused target DT is irradiated with the second main pulse laser beam MPL2, the processor 121 and the delay circuit 122 input a trigger signal to the second main pulse laser device 132 with a delay from the time when the trigger signal is input to the first main pulse laser device 131.

[0072] By irradiating the diffused target DT with the second main pulse laser beam MPL2, the outer periphery DTo of the diffused target DT is mainly turned into plasma, and EUV light is emitted from the diffused target DT. In this way, by irradiating the diffused target DT with the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2, the diffused target DT can be turned into plasma as a whole.

[0073] 4.3 Actions and Effects In the EUV light generation system 100 and the EUV light generation method of this embodiment, a diffused target DT is irradiated with a first main pulse laser beam MPL1 having a higher energy density in the center than in the outer periphery, and a second main pulse laser beam MPL2 having a higher energy density in the outer periphery than in the center. As described above, the diffused target DT has a higher target material density in the outer periphery DTo than in the center DTc. Therefore, the first main pulse laser beam MPL1 can mainly convert the target material in the lower-density center DTc into plasma, and the second main pulse laser beam MPL2 can mainly convert the target material in the higher-density outer periphery DTo into plasma. Therefore, the EUV light generation system 100 and the EUV light generation method of this embodiment can reduce unreacted target material that is not converted into plasma, thereby generating EUV light more efficiently.

[0074] The second main pulse laser beam MPL2 is not limited to a circular laser beam as long as the energy density of the outer periphery is higher than that of the center. For example, the energy density of the outer periphery is higher than that of the center, and the intensity of the laser beam in the center is 1 / e of the peak intensity. 2 It may be more than that.

[0075] Furthermore, in the EUV light generation system 100 and the EUV light generation method of this embodiment, the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 are irradiated onto the diffused target DT at different timings. Therefore, when there is a region where the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 overlap, it is possible to prevent the energy density in that region from becoming unnecessarily high. However, in the present invention, the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 may be irradiated onto the diffused target DT simultaneously.

[0076] In the EUV light generation system 100 and the EUV light generation method of this embodiment, the diffused target DT is irradiated with the first main pulse laser beam MPL1 and then the second main pulse laser beam MPL2. In this manner, the first main pulse laser beam MPL1 can mainly convert the target material in the low-density central portion DTc into plasma, and can also convert the target material around the high-density region in the outer periphery DTo of the diffused target DT into plasma. Therefore, the second main pulse laser beam MPL2 can efficiently irradiate the target material in the high-density outer periphery DTo, and can more efficiently convert the outer periphery DTo of the diffused target DT into plasma. However, in the present invention, the diffused target DT may be irradiated with the second main pulse laser beam MPL2 and then the first main pulse laser beam MPL1 in this order.

[0077] In the EUV light generation system 100 and the EUV light generation method of this embodiment, the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 are laser beams with the same wavelength. Therefore, the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 can be set to wavelengths that are easily absorbed by the diffused target DT. However, in the present invention, the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 may be laser beams with different wavelengths. In this case, it is preferable that the first main pulse laser beam MPL1, which is irradiated mainly onto a portion of the diffused target DT where the target material has a low density, is a CO laser beam, and the second main pulse laser beam MPL2, which is irradiated mainly onto a portion of the diffused target DT where the target material has a high density, is a YAG laser beam. In this case, a dichroic mirror that transmits the first main pulse laser beam MPL1 and reflects the second main pulse laser beam MPL2 may be used instead of the polarizer 36. If a dichroic mirror is used, the polarization directions of the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 may be the same or different.

[0078] 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.

[0079] 5.1 Configuration 12 is a schematic diagram showing an example of the overall configuration of an EUV light generation system 100 of this embodiment. As shown in FIG. 12, in the EUV light generation system 100 of this embodiment, the configuration of the main pulse laser irradiation system MPS is different from the configuration of the main pulse laser irradiation system MPS of the comparative example. In the first embodiment, the main pulse laser irradiation system MPS includes first and second main pulse laser devices 131 and 132, but in this embodiment, the main pulse laser irradiation system MPS includes a main pulse laser device 130, as in the comparative example. Furthermore, the main pulse laser irradiation system MPS of this embodiment differs from the main pulse laser irradiation system MPS of the first embodiment in that it further includes a beam splitter 37, a λ / 2 wave plate 38, and a mirror 39.

[0080] A main pulse laser beam MPL is emitted from the main pulse laser device 130. This main pulse laser beam MPL has a Gaussian energy density distribution. In this embodiment, the polarization direction of the main pulse laser beam MPL emitted by the main pulse laser device 130 and the polarization direction of high transmittance of the polarizer 36 differ by 90° from each other.

[0081] The beam splitter 37 is provided at a position where the main pulse laser beam MPL emitted from the main pulse laser device 130 is incident. The beam splitter 37 transmits a part of the main pulse laser beam MPL to form a first main pulse laser beam MPL1, and reflects another part of the main pulse laser beam MPL to form a second main pulse laser beam MPL2.

[0082] The λ / 2 wave plate 38 is provided at a position where the first main pulse laser beam MPL1 is incident after passing through the beam splitter 37. Therefore, the polarization direction of the first main pulse laser beam MPL1 is changed by 90° as it passes through the λ / 2 wave plate 38. Therefore, the polarization direction of the first main pulse laser beam MPL1 after passing through the λ / 2 wave plate 38 matches the polarization direction of the first main pulse laser beam MPL1 passing through the polarizer 36.

[0083] The mirror 39 is provided at a position where the second main pulse laser beam MPL2 reflected by the beam splitter 37 is incident. The mirror 39 reflects the second main pulse laser beam MPL2 toward the beam adjusting optical system 50. Therefore, similar to the first embodiment, the second main pulse laser beam MPL2 is converted into a laser beam having a higher energy density in the outer periphery than in the center, and is reflected by the mirror 35 and the polarizer 36.

[0084] In the main pulse laser beam irradiation system MPS of this embodiment, the optical path of the second main pulse laser beam MPL2 is configured to be longer than the optical path of the first main pulse laser beam MPL1. Therefore, in this embodiment, the beam splitter 37, mirror 39, λ / 2 wave plate 38, beam adjusting optical system 50, mirror 35, and polarizer 36 configure an optical delay circuit that delays the second main pulse laser beam MPL2 by a predetermined time relative to the first main pulse laser beam MPL1. The optical path difference between the second main pulse laser beam MPL2 and the first main pulse laser beam MPL1 is, for example, 0.3 m or more and 3 m or less. With this optical path difference, the second main pulse laser beam MPL2 enters the plasma generation region AR with a time difference of 1 ns or more and 10 ns or less relative to the first main pulse laser beam MPL1.

[0085] 5.2 Operation Next, the operation of the EUV light generation system 100 in this embodiment will be described. As in the first embodiment, the flowchart showing the operation of the EUV light generation system 100 in this embodiment is the same as the flowchart showing the operation of the EUV light generation system 100 in the comparative example shown in FIG. 4. However, the main pulse laser beam irradiation step SP3 differs from those in the comparative example and the first embodiment. In this embodiment, the target supply step SP1 and the pre-pulse laser beam irradiation step SP2 are also the same as those in the comparative example, and therefore the main pulse laser beam irradiation step SP3 will be described.

[0086] (Main pulse laser light irradiation step SP3) Similar to the first embodiment, this step in the present embodiment is a step of irradiating the diffused target DT with the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2. In the present embodiment, after the pre-pulse laser beam PPL is emitted from the pre-pulse laser device 140, the main pulse laser beam MPL is emitted from the main pulse laser device 130. The main pulse laser beam MPL is incident on the beam splitter 37, and a portion of the main pulse laser beam MPL passes through the beam splitter 37 as the first main pulse laser beam MPL1. The first main pulse laser beam MPL1 that has passed through the beam splitter 37 passes through the λ / 2 wave plate 38 and the polarizer 36, and reaches the plasma generation region AR, similar to the first main pulse laser beam MPL1 in the first embodiment, and is irradiated onto the diffused target DT. The energy density distribution and fluence of the first main pulse laser beam MPL1 in the present embodiment are similar to those in the first embodiment. Therefore, the diffused target DT irradiated with the first main pulse laser beam MPL1 is turned into plasma in the same manner as in the first embodiment.

[0087] The timing at which the first main pulse laser beam MPL1 is irradiated onto the diffused target DT is the same as that in embodiment 1. Therefore, the processor 121 and the delay circuit 122 input a light emission trigger signal to the main pulse laser device 130 so that the diffused target DT is irradiated with the first main pulse laser beam MPL1 at such time intervals.

[0088] Furthermore, another portion of the main pulse laser beam MPL emitted from the main pulse laser device 130 is reflected by the beam splitter 37 as the second main pulse laser beam MPL2. The second main pulse laser beam MPL2 reflected by the beam splitter 37 is reflected by the mirror 39 and converted into a laser beam having a higher energy density in the outer periphery than in the center by the beam adjusting optical system 50. The second main pulse laser beam MPL2, whose energy density distribution has been converted, is reflected by the mirror 35 and the polarizer 36 and reaches the plasma generation region AR, similar to the second main pulse laser beam MPL2 in the first embodiment, and is irradiated onto the diffused target DT. At this time, the time difference between the timing at which the first main pulse laser beam MPL1 irradiates the diffused target DT and the timing at which the second main pulse laser beam MPL2 irradiates the diffused target DT is 1 ns or more and 10 ns or less. The energy density distribution and fluence of the second main pulse laser beam MPL2 in this embodiment are similar to those in the first embodiment. Therefore, the diffused target DT irradiated with the second main pulse laser beam MPL2 is converted into plasma in the same manner as in the first embodiment.

[0089] The timing at which the diffused target DT is irradiated with the second main pulse laser beam MPL2 is the same as that in embodiment 1. Therefore, the optical path difference between the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 is set in the optical delay circuit so that the diffused target DT is irradiated with the second main pulse laser beam MPL2 in this manner.

[0090] 5.3 Actions and Effects In the EUV light generation apparatus 100 and EUV light generation method of this embodiment, a Gaussian laser beam emitted from a single main pulse laser apparatus 130 is split into two laser beams, one of which is converted into a first main pulse laser beam MPL1, and the other split laser beam is converted into a second main pulse laser beam MPL2, and the other laser beam is delayed.

[0091] According to the EUV light generation system 100 and the EUV light generation method, it is not necessary to use multiple main pulse laser devices, which can reduce costs.

[0092] In the EUV light generation system 100 and the EUV light generation method of this embodiment, the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 have the same wavelength, and therefore the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 can be set to wavelengths that are easily absorbed by the diffused target DT.

[0093] In the EUV light generation system 100 of this embodiment, the λ / 2 wave plate 38 is disposed in the optical path through which the first main pulse laser beam MPL1 propagates but the second main pulse laser beam MPL2 does not. However, the λ / 2 wave plate 38 may be disposed in the optical path through which the second main pulse laser beam MPL2 propagates but the first main pulse laser beam MPL1 does not. In this case, the polarizer 36 is disposed so that its polarization direction coincides with the polarization direction of the main pulse laser beam MPL emitted from the main pulse laser device 130.

[0094] In the EUV light generation system 100 and EUV light generation method of this embodiment, the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 are irradiated onto the diffused target DT at different timings. However, in the present invention, the first main pulse laser beam MPL1 and the second main pulse laser beam MPL2 may be irradiated onto the diffused target DT simultaneously. In this case, it is sufficient that the optical path length of the propagation of the first main pulse laser beam MPL1 and the optical path length of the propagation of the second main pulse laser beam MPL2 are the same.

[0095] In the EUV light generation system 100 and EUV light generation method of this embodiment, the diffused target DT is irradiated with the first main pulse laser beam MPL1 and then the second main pulse laser beam MPL2 in this order. However, in the present invention, the diffused target DT may be irradiated with the second main pulse laser beam MPL2 and then the first main pulse laser beam MPL1 in this order. In this case, to achieve this timing, an optical delay circuit may be provided in the optical path through which the first main pulse laser beam MPL1 propagates but the second main pulse laser beam MPL2 does not.

[0096] 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. a target supply step of discharging a droplet target containing a target material into a chamber; a pre-pulse laser beam irradiation step of irradiating the droplet target with a pre-pulse laser beam to generate a diffused target including a portion where the density of the target material is relatively low and a portion where the density of the target material is relatively high; a main pulse laser light irradiation step of irradiating the diffused target with a main pulse laser light to generate extreme ultraviolet light; Equipped with the main pulse laser beam includes a first main pulse laser beam and a second main pulse laser beam, In the main pulse laser beam irradiation step, the first main pulse laser beam, which has a higher energy density in the central portion than in the peripheral portion, is irradiated onto a portion of the diffused target where the density of the target material is relatively low, and the second main pulse laser beam, which has a higher energy density in the peripheral portion than in the central portion, is irradiated onto a portion of the diffused target where the density of the target material is relatively high. Extreme ultraviolet light generation method.

2. The extreme ultraviolet light generating method according to claim 1, the density of the target material at the center of the diffusion target is lower than the density of the target material at the outer periphery of the diffusion target; In the main pulse laser beam irradiation step, the first main pulse laser beam is irradiated onto a central portion of the diffused target, and the second main pulse laser beam is irradiated onto an outer periphery of the diffused target.

3. 2. The method for generating extreme ultraviolet light according to claim 1, The first main pulse laser beam and the second main pulse laser beam are irradiated onto the diffused target at different timings.

4. 4. The method for generating extreme ultraviolet light according to claim 3, The diffused target is irradiated with the first main pulse laser beam and then the second main pulse laser beam in this order.

5. 4. The method for generating extreme ultraviolet light according to claim 3, The time difference between the timing at which the first main pulse laser beam is irradiated onto the diffused target and the timing at which the second main pulse laser beam is irradiated onto the diffused target is 1 ns or more and 10 ns or less.

6. 4. The method for generating extreme ultraviolet light according to claim 3, The first main pulse laser beam and the second main pulse laser beam are laser beams having the same wavelength.

7. 7. The method for generating extreme ultraviolet light according to claim 6, Gaussian laser light emitted from a single laser device is split into two laser lights, one of which is the first main pulse laser light, and the other split laser light is converted into the second main pulse laser light, and either one of the laser lights or the other laser light is delayed.

8. 2. The method for generating extreme ultraviolet light according to claim 1, The fluence of the second main pulse laser beam is higher than the fluence of the first main pulse laser beam.

9. 2. The method for generating extreme ultraviolet light according to claim 1, the second main pulse laser beam is an annular laser beam, The outer diameter of the first main pulse laser beam is equal to or greater than the inner diameter of the second main pulse laser beam.

10. 2. The method for generating extreme ultraviolet light according to claim 1, The wavelength of the first main pulse laser beam and the wavelength of the second main pulse laser beam are different from each other.

11. 11. The method for generating extreme ultraviolet light according to claim 10, The first main pulse laser beam is CO ２ The second main pulse laser beam is a YAG laser beam.

12. a target supply unit that outputs a droplet target containing a target material into the chamber; a pre-pulse laser beam irradiation system that irradiates the droplet target with a pre-pulse laser beam to generate a diffused target including a portion where the density of the target material is relatively low and a portion where the density of the target material is relatively high; a main pulse laser light irradiation system that irradiates the diffused target with a main pulse laser light to generate extreme ultraviolet light; Equipped with the main pulse laser beam includes a first main pulse laser beam and a second main pulse laser beam, The main pulse laser beam irradiation system irradiates a portion of the diffused target where the density of the target material is relatively low with the first main pulse laser beam, the energy density of which is higher in the central portion than in the peripheral portion, and irradiates a portion of the diffused target where the density of the target material is relatively high with the second main pulse laser beam, the energy density of which is higher in the peripheral portion than in the central portion. Extreme ultraviolet light generator.

13. The extreme ultraviolet light generating apparatus according to claim 12, The main pulse laser beam irradiation system irradiates the diffused target with the first main pulse laser beam and the second main pulse laser beam at different timings.

14. The extreme ultraviolet light generating apparatus according to claim 13, The main pulse laser beam irradiation system irradiates the diffused target with the first main pulse laser beam and then the second main pulse laser beam in this order.

15. The extreme ultraviolet light generating apparatus according to claim 13, The time difference between the timing at which the first main pulse laser beam and the second main pulse laser beam are irradiated onto the diffused target is 1 ns or more and 10 ns or less.

16. The extreme ultraviolet light generating apparatus according to claim 13, The first main pulse laser beam and the second main pulse laser beam are laser beams having the same wavelength.

17. The extreme ultraviolet light generating apparatus according to claim 16, The main pulse laser beam irradiation system includes a laser device, a beam splitter that splits a Gaussian laser beam emitted from the laser device into two laser beams and sets one of the laser beams as the first main pulse laser beam, a beam adjusting optical system that converts the other laser beam split by the beam splitter into the second main pulse laser beam, and a delay circuit that delays the one laser beam or the other laser beam.

18. The extreme ultraviolet light generating apparatus according to claim 12, The fluence of the second main pulse laser beam is higher than the fluence of the first main pulse laser beam.

19. The extreme ultraviolet light generating apparatus according to claim 12, the second main pulse laser beam is an annular laser beam, The outer diameter of the first main pulse laser beam is equal to or greater than the inner diameter of the second main pulse laser beam.

20. a target supply step of outputting a droplet target containing a target material into a chamber; a pre-pulse laser beam irradiation step of irradiating the droplet target with a pre-pulse laser beam to generate a diffused target including a portion where the density of the target material is relatively low and a portion where the density of the target material is relatively high; a main pulse laser light irradiation step of irradiating the diffused target with a main pulse laser light to generate extreme ultraviolet light; Equipped with the main pulse laser beam includes a first main pulse laser beam and a second main pulse laser beam, In the main pulse laser beam irradiation step, the first main pulse laser beam, which has a higher energy density in the central portion than in the peripheral portion, is irradiated onto a portion of the diffused target where the density of the target material is relatively low, and the second main pulse laser beam, which has a higher energy density in the peripheral portion than in the central portion, is irradiated onto a portion of the diffused target where the density of the target material is relatively high. outputting the extreme ultraviolet light generated by the extreme ultraviolet light generation method to an exposure device; exposing a photosensitive substrate to the extreme ultraviolet light by the exposure apparatus to manufacture an electronic device. A method for manufacturing an electronic device, comprising:

21. a target supply step of outputting a droplet target containing a target material into a chamber; a pre-pulse laser beam irradiation step of irradiating the droplet target with a pre-pulse laser beam to generate a diffused target including a portion where the density of the target material is relatively low and a portion where the density of the target material is relatively high; a main pulse laser light irradiation step of irradiating the diffused target with a main pulse laser light to generate extreme ultraviolet light; Equipped with the main pulse laser beam includes a first main pulse laser beam and a second main pulse laser beam, In the main pulse laser beam irradiation step, the first main pulse laser beam, which has a higher energy density in the central portion than in the peripheral portion, is irradiated onto a portion of the diffused target where the density of the target material is relatively low, and the second main pulse laser beam, which has a higher energy density in the peripheral portion than in the central portion, is irradiated onto a portion of the diffused target where the density of the target material is relatively high. irradiating a mask with the extreme ultraviolet light generated by the extreme ultraviolet light generating method to inspect the mask for defects; selecting a mask using the results of said testing; exposing and transferring the pattern formed on the selected mask onto a photosensitive substrate; A method for manufacturing an electronic device, comprising:

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