Laser system and method for manufacturing electronic device

Abstract

A laser system is provided with: a pump laser device that outputs pump laser light of a first wavelength; a signal laser device that outputs signal laser light of a second wavelength longer than the first wavelength; and an amplification system that includes a plurality of optical parametric crystals that output amplified light of a second wavelength, the amplification system being arranged such that the waist positions of first amplified light of the second wavelength, which is output from the first optical parametric crystal and is incident on the second optical parametric crystal, and the pumping laser light incident on the second optical parametric crystal, coincide with each other. The amplification system has a first beam diameter adjustment optical system in which the ratio of the beam waist diameter of the pump laser light in the second parametric crystal to the beam waist diameter of the first amplified light is set so that the ratio of the beam waist diameter of the pump laser light in the second parametric crystal to the beam waist diameter of the second amplified light is equal to or greater than the first beam diameter. The ratio of the beam waist diameter of the pump laser to the beam waist diameter of the signal laser in the first parametric crystal is greater than that of the first parametric crystal.

Description

Technical Field

[0001] The present disclosure relates to laser systems and methods of manufacturing electronic devices. Background Art

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

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

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: U.S. Patent No. 6208458

[0007] Patent Document 2: Japanese Patent Application Publication No. 2001-27771

[0008] Patent Document 3: Japanese Patent Application Publication No. 2010-66381 Summary of the invention

[0009] A laser system according to one aspect of the present disclosure comprises: a pump laser device that outputs a pump laser of a first wavelength; a signal laser device that outputs a signal laser of a second wavelength longer than the first wavelength; and an amplification system comprising a plurality of optical parametric crystals that transmit the pump laser and the signal laser to output amplified light of a second wavelength, the plurality of optical parametric crystals comprising a first optical parametric crystal and a second optical parametric crystal arranged in series with the first optical parametric crystal, the amplification system being arranged such that a signal outputted from the first optical parametric crystal and incident on the second optical parametric crystal The beam waist positions of the first amplified light of the second wavelength of the crystal and the pump laser incident on the second optical parametric crystal are consistent with each other, and the first amplified light and the pump laser are coaxially incident on the second optical parametric crystal, and the amplification system has the following first beam diameter adjustment optical system: the ratio of the beam waist diameter of the pump laser in the second optical parametric crystal to the beam waist diameter of the first amplified light in the second optical parametric crystal is set to be larger than the ratio of the beam waist diameter of the pump laser in the first optical parametric crystal to the beam waist diameter of the signal laser in the first optical parametric crystal.

[0010] A method for manufacturing an electronic device according to another aspect of the present disclosure includes the following steps: generating a laser beam having a second wavelength by a laser system, performing wavelength conversion on the laser beam having the second wavelength to generate an ultraviolet laser beam, outputting the ultraviolet laser beam to an exposure device, and exposing the ultraviolet laser beam on a photosensitive substrate in the exposure device to manufacture the electronic device, wherein the laser system includes: a pump laser device that outputs a pump laser beam having a first wavelength; a signal laser device that outputs a signal laser beam having a second wavelength longer than the first wavelength; and an amplification system that includes a plurality of optical parametric crystals that output amplified light having a second wavelength by transmitting the pump laser beam and the signal laser beam, wherein the plurality of optical parametric crystals include a first optical parametric crystal; a second optical parametric crystal that transmits the pump laser beam and the signal laser beam to the photosensitive substrate; and a second optical parametric crystal that transmits the pump laser beam and the signal laser beam to the photosensitive substrate. The invention relates to a body and a second optical parametric crystal arranged in series with the first optical parametric crystal, the amplification system is arranged so that the waist positions of the first amplified light of the second wavelength output from the first optical parametric crystal and incident on the second optical parametric crystal and the pump laser incident on the second optical parametric crystal are consistent with each other, and the first amplified light and the pump laser are coaxially incident on the second optical parametric crystal, and the amplification system has the following first beam diameter adjustment optical system: the ratio of the beam waist diameter of the pump laser in the second optical parametric crystal to the beam waist diameter of the first amplified light in the second optical parametric crystal is set to be larger than the ratio of the beam waist diameter of the pump laser in the first optical parametric crystal to the beam waist diameter of the signal laser in the first optical parametric crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Hereinafter, several embodiments of the present disclosure will be described as simple examples with reference to the accompanying drawings.

[0012] Figure 1 The structure of an exemplary solid-state laser system is schematically shown.

[0013] Figure 2 The structure of the amplifier system in the solid-state laser system is schematically shown.

[0014] Figure 3 An example configuration of a beam diameter adjustment optical system is schematically shown.

[0015] Figure 4 FIG. 1 is an explanatory diagram schematically showing the propagation of laser light inside each optical parametric crystal and in the vicinity of an incident / exit portion in an amplifier system of a laser system according to a comparative example.

[0016] Figure 5 This is an explanatory diagram schematically showing the propagation of laser light inside each optical parametric crystal and in the vicinity of the incident and emitted light portion in the amplification system of the laser system according to the first embodiment.

[0017] Figure 6 The configuration of an amplifier system applied to the laser system of the second embodiment is schematically shown.

[0018] Figure 7 Modification 1 of the beam diameter adjustment optical system is schematically shown.

[0019] Figure 8 Modification 2 of the beam diameter adjustment optical system is schematically shown.

[0020] Fig. 9 The structure of the exposure device is schematically shown. DETAILED DESCRIPTION

[0021] -Table of contents-

[0022] 1. Description of solid-state laser system

[0023] 1.1 Structure

[0024] 1.2 Action

[0025] 1.3 Description of the amplification system

[0026] 1.3.1 Structure

[0027] 1.3.2 Action

[0028] 2.Topic

[0029] 3. Implementation Method 1

[0030] 3.1 Structure

[0031] 3.2 Actions

[0032] 3.3 Basis of the beam waist diameter ratio condition

[0033] 3.3.1 Calculation of divergence angle ratio

[0034] 3.3.2 Calculation of pump laser utilization efficiency

[0035] 3.4 Effects

[0036] 4. Implementation Method 2

[0037] 4.1 Structure

[0038] 4.2 Actions

[0039] 4.3 Effects

[0040] 5. Modification 1 of the beam diameter adjustment optical system

[0041] 5.1 Structure

[0042] 5.2 Actions

[0043] 5.3 Effects

[0044] 5.4 Control Example

[0045] 6. Modification 2 of the beam diameter adjustment optical system

[0046] 7. About laser systems using excimer amplifiers

[0047] 8. About the manufacturing method of electronic devices

[0048] 9. Others

[0049] Below, the embodiments of the present disclosure are described in detail with reference to the accompanying drawings. The embodiments described below show several examples of the present disclosure and do not limit the content of the present disclosure. In addition, the structures and actions described in each embodiment are not necessarily all necessary for the structures and actions of the present disclosure. In addition, the same reference numerals are marked on the same structural elements and repeated descriptions are omitted.

[0050] 1. Description of solid-state laser system

[0051] 1.1 Structure

[0052] Figure 1 The structure of an exemplary solid-state laser system 10 is schematically shown.

[0053] The solid-state laser system 10 includes a laser system 100, a wavelength conversion system 50, and a solid-state laser control unit 60. The laser system 100 includes a signal laser device 20, an amplifier system 30, and a pump laser device 40. The solid-state laser system 10 outputs a pulse laser with a wavelength of about 1553 nm and a pulse laser with a wavelength of about 257.6 nm from the laser system 100, and inputs the two pulse lasers into the wavelength conversion system 50 for wavelength conversion, thereby outputting a pulse laser with a wavelength of about 193.4 nm.

[0054] The signal laser device 20 includes a semiconductor laser 21 and a solid-state amplifier 22. The semiconductor laser 21 performs CW (Continuous Wave) oscillation in a single longitudinal mode at a wavelength of approximately 1553 nm.

[0055] The solid-state amplifier 22 includes a semiconductor optical amplifier (Semiconductor Optical Amplifier: SOA) that amplifies the CW oscillation laser light output from the semiconductor laser 21 .

[0056] The pump laser device 40 includes a semiconductor laser 42, a solid-state amplifier 43, an LBO crystal 45 and a CLBO crystal 46 as nonlinear optical crystals, and a dichroic mirror DM1. "LBO" is represented by the chemical formula LiB3O5. "CLBO" is represented by the chemical formula CsLiB6O 10 express.

[0057] The semiconductor laser 42 performs CW oscillation in a single longitudinal mode at a wavelength of about 1030 nm. The solid-state amplifier 43 is an amplifier including an SOA, a Yb fiber amplifier, and a Yb:YAG crystal.

[0058] The combination of two nonlinear optical crystals, the LBO crystal 45 and the CLBO crystal 46, converts the wavelength of light of approximately 1030 nm into fourth harmonic light (wavelength of approximately 257.6 nm).

[0059] The dichroic mirror DM1 is arranged on the optical path between the LBO crystal 45 and the CLBO crystal 46, and transmits the pulse laser with a wavelength of about 515nm with high transmittance, and highly reflects the pulse laser with a wavelength of about 1030nm. The pulse laser with a wavelength of about 1030nm highly reflected by the dichroic mirror DM1 is incident on the amplification system 30 as pump laser.

[0060] The amplification system 30 includes an optical parametric amplifier (OPA). The OPA is an amplifier including a PPLN crystal (periodically poled lithium niobate) or a PPKTP crystal (periodically poled KTP). The OPA amplifies the signal laser pulses by inputting pump laser and signal laser.

[0061] The wavelength conversion system 50 includes a dichroic mirror DM2, two CLBO crystals, namely, a CLBO crystal 52 and a CLBO crystal 53, and two rotating tables, namely, a rotating table 54 and a rotating table 55, which change the incident angles of the CLBO crystals 52 and 53. The CLBO crystals 52 and 53 are respectively arranged on the rotating tables 54 and 55 including piezoelectric elements (not shown), and are configured to be able to change the incident angles of each crystal at high speed.

[0062] The dichroic mirror DM2 is constructed to highly reflect the pulsed laser with a wavelength of approximately 1533 nm output from the amplifier system 30 and to transmit the pulsed laser with a wavelength of approximately 257.6 nm output from the CLBO crystal 46 of the pump laser device 40 with high transmittance, and is configured so that the two pulsed lasers are coaxially incident on the CLBO crystal 52.

[0063] The CLBO crystal 52 and the CLBO crystal 53 are arranged in series, and generate a secondary sum frequency to output a pulse laser having a wavelength of about 193.4 nm.

[0064] The solid-state laser control unit 60 is connected to the signal laser device 20, the pump laser device 40 and the wavelength conversion system 50, and includes a processor not shown in the figure. The processor is a processing device configured to include a CPU (Central Processing Unit) and a memory not shown in the figure. The processor may also include a GPU (Graphics Processing Unit). The processor is specially configured or programmed to perform various processes included in the present disclosure.

[0065] 1.2 Action

[0066] The solid laser control unit 60 controls the current value of the semiconductor laser 42 of the pump laser device 40 to make it perform CW oscillation and output CW laser light with a wavelength of about 1030 nm. Furthermore, the solid laser control unit 60 pulses the CW laser light using the SOA of the solid amplifier 43, and performs pulse amplification through the Yb fiber amplifier and Yb:YAG crystal amplifier including the solid amplifier 43.

[0067] The LBO crystal 45 converts the pulse laser light with a wavelength of about 1030 nm into the second harmonic light with a wavelength of about 515 nm. The second harmonic light with a wavelength of about 515 nm passes through the dichroic mirror DM1 with high transmittance, and is further converted into pulse laser light by the CLBO crystal 46. The pulse laser light is ultraviolet light with a wavelength of about 257.6 nm.

[0068] Here, the dichroic mirror DM1 highly reflects the pulse laser light having a wavelength of about 1030 nm that has not been wavelength-converted by the LBO crystal 45 , and causes the pulse laser light to enter the OPA as the pump laser light of the amplifier system 30 .

[0069] In addition, the solid laser control unit 60 controls the current value of the semiconductor laser 21 of the signal laser device 20 to output a CW laser with a wavelength of about 1553nm. Furthermore, the solid laser control unit 60 amplifies the signal laser device 20 through the solid amplifier 22, and outputs a CW laser with a wavelength of about 1553nm.

[0070] The OPA of the amplification system 30 receives pulsed laser light with a wavelength of about 1030 nm reflected by the dichroic mirror DM1 as pump laser light, and receives CW laser light with a wavelength of about 1553 nm output from the signal laser device 20 as signal laser light, thereby outputting amplified pulsed laser light with a wavelength of about 1553 nm.

[0071] The two pulse lasers, the pulse laser with a wavelength of about 1553 nm output from the amplification system 30 and the pulse laser with a wavelength of about 257.6 nm output from the pump laser device 40, are input to the wavelength conversion system 50. The pulse laser with a wavelength of about 1553 nm reflected by the dichroic mirror DM2 and the pulse laser with a wavelength of about 257.6 nm transmitted through the dichroic mirror DM2 are coaxially incident on the CLBO crystal 52. Then, after the sum frequency is generated by the CLBO crystal 52 and the wavelength is converted to a wavelength of about 220.9 nm, the pulse laser with a wavelength of about 193.4 nm is output by the sum frequency with the pulse laser with a wavelength of about 1553 nm in the CLBO crystal 53.

[0072] The incident angle of each light incident on the CLBO crystal 52 and the CLBO crystal 53 can be adjusted by the solid-state laser control unit 60, and the wavelength conversion efficiency can be compensated.

[0073] 1.3 Description of the amplification system

[0074] 1.3.1 Structure

[0075] Figure 2 The configuration of the amplification system 30 is schematically shown. The amplification system 30 includes a plurality of PPLN crystals 301 and 302, beam diameter adjustment optical systems 311 to 314, dichroic mirrors DM3 to DM6, attenuators 330 and 332, a beam splitter BS1, and optical path forming mirrors MR1 ​​to MR3.

[0076] The beam diameter adjustment optical systems 311 and 312 are configured so that the beam waist diameters of the signal laser and the pump laser incident on the PPLN crystal 301 are approximately the same in the crystal. The beam diameter adjustment optical system 311 is arranged on the optical path of the signal laser, and the beam diameter adjustment optical system 312 is arranged on the optical path of the pump laser.

[0077] The beam diameter adjustment optical systems 313 and 314 are configured so that the beam waist diameters of the signal laser and the pump laser incident on the PPLN crystal 302 are approximately the same in the crystal. The beam diameter adjustment optical system 313 is arranged on the optical path of the signal laser between the PPLN crystal 301 and the PPLN crystal 302, and the beam diameter adjustment optical system 314 is arranged on the optical path of the pump laser.

[0078] The beam diameter adjustment optical systems 311 to 314 may be configured to maintain the distance between the lenses of the opposing lens pairs (see Figure 3 ) The beam waist position and beam waist diameter of each of the signal laser light and the pump laser light can be adjusted by the beam diameter adjustment optical systems 311 to 314 .

[0079] The beam splitter BS1 is arranged on the optical path of the pump laser to split the pump laser from the pump laser device 40 and make the pump laser incident on the beam diameter adjustment optical systems 312 and 314. The mirror MR1 is arranged to reflect the pump laser reflected by the beam splitter BS1 and guide it to the beam diameter adjustment optical system 314.

[0080] The dichroic mirrors DM3 and DM5 are dichroic mirrors for combining the signal laser and the pump laser so that the two lasers are incident on the PPLN crystals 301 and 302 coaxially. The dichroic mirrors DM3 and DM5, for example, highly reflect light with a wavelength of about 1553 nm and transmit light with a wavelength of about 1030 nm with high transmittance. The dichroic mirror DM3 is arranged on the optical path between the beam diameter adjustment optical systems 311 and 312 and the PPLN crystal 301. The dichroic mirror DM5 is arranged on the optical path between the beam diameter adjustment optical systems 313 and 314 and the PPLN crystal 302. The reflector MR2 is arranged so that the signal laser emitted from the beam diameter adjustment optical system 311 is incident on the dichroic mirror DM3.

[0081] The dichroic mirrors DM4 and DM6 are dichroic mirrors for separating the pump laser light and the idler light from the output light of the PPLN crystals 301 and 302. The dichroic mirrors DM4 and DM6, for example, highly reflect the signal laser light having a wavelength of about 1553 nm, and transmit the pump laser light having a wavelength of about 1030 nm and the idler light having a wavelength of about 3070 nm with high transmittance.

[0082] Attenuators 330 and 332 absorb the pump laser light and idler light separated by dichroic mirrors DM4 and DM6. A plurality of reflection mirrors MR1 ​​to MR3 are arranged to constitute the optical path of the OPA.

[0083] Figure 3 The following is a configuration example 1 of the beam diameter adjustment optical system 311. The beam diameter adjustment optical system 311 includes lenses 321 and 322. The lenses 321 and 322 are held by lens holders 323 and 324, respectively, and are arranged to face each other on a base plate 326. The other beam diameter adjustment optical systems 312 to 314 may have the same configuration.

[0084] 1.3.2 Action

[0085] Figure 4 The diagram schematically shows the propagation of the signal laser light, the pump laser light, and the amplified light inside the PPLN crystals 301 and 302 and near the incident and emitted parts in the cross section including the optical axis of the signal laser light of the amplifier system 30 of the laser system 100 of the comparative example. The comparative example disclosed in the present invention is a method that the applicant recognizes that only the applicant knows, and is not a known example acknowledged by the applicant himself.

[0086] Figure 4 The cross-sectional profiles SP1 and SP2 attached to the left figure F4A and the right figure F4B respectively schematically show the cross-sectional intensity distribution of the signal laser, the pump laser and the amplified light at the beam waist position in the crystal. The horizontal direction of each cross-sectional profile SP1 and SP2 represents the radial direction of the beam waist, and the vertical direction represents the normalized intensity.

[0087] exist Figure 4 In FIG. 1 , the signal laser, pump laser, and amplified light related to each PPLN crystal 301 , 302 are represented as “signal input,” “pump,” and “signal output,” respectively.

[0088] The signal laser and pump laser incident on the amplifier system 30 are incident on the PPLN crystal 301 via the beam diameter adjustment optical systems 311 and 312, respectively. At this time, the beam waist positions of the signal laser and pump laser incident on the PPLN crystal 301 are consistent with each other, and the beam waist diameters of the two coaxially incident lasers inside the PPLN crystal 301 are set to be the same for the pump laser and the signal laser (refer to Figure 4 The signal laser and the pump laser are incident on the PPLN crystal 301, thereby generating optical parametric amplification in the PPLN crystal 301, generating amplified light of about 1553 nm, the same wavelength as the signal laser, and idler light of a wavelength corresponding to the difference frequency of the signal laser and the pump laser (about 3070 nm).

[0089] The pump laser light and idler light output from the PPLN crystal 301 are absorbed by the attenuator 330 via the dichroic mirror DM4.

[0090] Light with a wavelength of about 1553 nm including amplified light output from the PPLN crystal 301 and signal laser light enters the PPLN crystal 302 via the dichroic mirror DM4, the beam diameter adjustment optical system 313, and the dichroic mirror DM5. The laser light with a wavelength of about 1553 nm output from the PPLN crystal 301 becomes the signal laser light input to the PPLN crystal 302.

[0091] The pump laser beam branched by the beam splitter BS1 enters the PPLN crystal 302 via the reflector MR1, the beam diameter adjustment optical system 314, and the dichroic mirror DM5. At this time, the beam waist diameter inside the PPLN crystal 302 is set so that the pump laser beam and the signal laser beam become the same (see Figure 4 F4B on the right). Optical parametric amplification occurs in the PPLN crystal 302, generating amplified light of about 1553 nm, the same wavelength as the signal laser, and idler light of a wavelength (about 3070 nm) corresponding to the difference frequency between the signal laser and the pump laser.

[0092] The pump laser and idler light output from the PPLN crystal 302 are absorbed by the attenuator 332 via the dichroic mirror DM6. The amplified light and signal laser output from the PPLN crystal 302 are used in the wavelength conversion system 50 (see Figure 1 )'s CLBO crystal 52 generates the sum frequency.

[0093] 1.3.3 Function / Effect

[0094] The beam waist diameter inside each of the PPLN crystals 301 and 302 is adjusted so that it becomes the same in the pump laser and the signal laser. This is because, in order to expand the region where phase matching is efficiently achieved at the beam waist position where the beam is regarded as a plane wave, the beam waists of the same diameter are set near the center of the crystal. As a result, the mode matching of the signal laser and the pump laser is improved, and stronger amplified light is obtained.

[0095] 2.Topic

[0096] The output light of the PPLN crystals 301 and 302 includes the transmitted light of the input signal laser (transmitted signal laser) in addition to the amplified light and the idler light. As described above, in order to efficiently generate the amplified light, in the amplifier system 30 of the comparative example, the internal beam waist diameter of the PPLN crystals 301 and 302 is set to be the same in the pump laser and the signal laser.

[0097] The power density of the amplified light is proportional to the product of the power densities of the input signal laser and the pump laser. Therefore, the amplified light has a smaller beam diameter at the beam waist than the input signal laser and has a larger divergence angle. On the other hand, the input signal laser also directly exits from the PPLN crystals 301 and 302, so the PPLN crystals 301 and 302 respectively output light of the same wavelength and two divergence angles.

[0098] The input signal laser and the amplified light of the same wavelength and different divergence angles propagate differently. That is, two beams of the same wavelength, the same degree of power and different divergence angles propagate coaxially. Sometimes, the smaller the difference in power between the input signal laser and the amplified light, the more problematic it becomes. That is, sometimes the following issues arise.

[0099] [Issue] In the optical system of the post-OPA, two lights of the same wavelength with different convergence positions coexist. In applications that require precise convergence and imaging, a complex optical system may be required. In particular, in applications such as multi-stage amplification where the latter stage approaches saturation amplification, it is difficult to adjust the beam propagation of the latter stage.

[0100] 3. Implementation Method 1

[0101] 3.1 Structure

[0102] The structure of the laser system 100 of the first embodiment can be Figure 1 to Figure 3 The structures shown are the same. Figure 5 The propagation of the signal laser light, the pump laser light, and the amplified light inside the PPLN crystals 301 and 302 and in the vicinity of the incident and emitted light parts of the amplification system 30 of the laser system 100 according to the first embodiment is schematically shown. Figure 5 The cross-sectional profiles SP1 and SP2B attached to the left figure F5A and the right figure F5B respectively schematically show the cross-sectional intensity distribution of the signal laser, the pump laser and the amplified light at the beam waist position in the crystal. The horizontal direction of each cross-sectional profile SP1 and SP2B represents the radial direction of the beam waist, and the vertical direction represents the normalized intensity.

[0103] In the laser system 100 of the first embodiment, the Figure 3 The beam propagation described in Figure 5 That is, Figure 5 As shown in the left figure F5A of FIG. 1 , the beam diameter adjustment optical systems 311 and 312 are set so that the beam waists of the pump laser and the signal laser are obtained at the center of the PPLN crystal 301. At this time, the beam waist diameters of the pump laser and the signal laser become the same. This is similar to Figure 4 The same as the comparative example illustrated in the left figure F4A.

[0104] That is, the beam diameter adjustment optical systems 311 and 312 are set so that the beam waist positions of the pump laser and the signal laser incident on the PPLN crystal 301 are consistent, and the beam waist diameters of the two are the same diameter at the center of the PPLN crystal 301. In addition, the description of "center" related to the crystal is not limited to the strict center point, and includes the meaning of the vicinity of the center roughly regarded as the center. The description of "consistent" is not limited to the case of strict consistency, and includes the concept of consistency within an allowable range that can be substantially regarded as consistent. In addition, the description of the beam waist diameter as "the same diameter" is not limited to the case of the strictly same (equal) diameter, and includes the concept of the same diameter within an allowable range that can be substantially regarded as the same diameter.

[0105] Furthermore, in the laser system 100 of the first embodiment, as Figure 5 As shown in the right figure F5B, the beam diameter adjustment optical systems 313 and 314 are adjusted so that the beam waists of the pump laser and the signal laser are obtained at the center of the PPLN crystal 302.

[0106] At this time, the beam waist positions of the pump laser and the signal laser (amplified light of the PPLN crystal 301) incident on the PPLN crystal 302 are aligned at the center of the PPLN crystal 302, and the ratio of the beam waist diameter of the pump laser in the PPLN crystal 302 to the beam waist diameter of the signal laser is greater than the ratio (1 times) of the beam waist diameter of the pump laser in the PPLN crystal 301 to the beam waist diameter of the signal laser. Therefore, the beam diameter adjustment optical systems 313 and 314 are set so that the beam waist diameter of the pump laser in the PPLN crystal 302 is in the range of 1.5 to 2.6 times the beam waist diameter of the signal laser. The conditions for the ratio of the beam waist diameter of the pump laser to the beam waist diameter of the signal laser specified here are set based on the conditions that the divergence angle ratio of the transmitted signal laser and the amplified light is 0.8 times or more and 1.2 times or less, and the utilization efficiency of the pump laser is 25% or more. The basis for the preferred range related to the ratio of the beam waist diameter will be described later.

[0107] 3.2 Action

[0108] Optical parametric amplification occurs in the first (primary) PPLN crystal 301 of the amplifier system 30 in which the PPLN crystal 301 and the PPLN crystal 302 are arranged in series, and amplified light of the same wavelength as the signal laser is generated. The beam is regarded as a plane wave, and in order to expand the area where phase matching is efficiently achieved, the beam diameter adjustment optical systems 311 and 312 are adjusted so that the beam waist of the same diameter is obtained near the crystal center of the PPLN crystal 301. At this time, amplified light with a larger divergence angle than the signal laser is generated in the PPLN crystal 301, but in most cases, the signal laser after passing through the PPLN crystal 301 has a very weak power compared to the amplified light. This is because, in most cases, the primary stage of the amplification stage in the multi-stage amplification becomes a setting that emphasizes the amplification gain.

[0109] The beam diameter adjustment optical system 313 is set for the propagation of the amplified light output from the PPLN crystal 301. Therefore, the transmitted signal laser light having a divergence angle different from that of the amplified light is attenuated due to vignetting and diffusion. As a result, the light amount of the transmitted signal laser light incident on the second-stage PPLN crystal 302 is relatively reduced to a negligible level.

[0110] On the other hand, the amplified light outputted from the PPLN crystal 301 is incident as the signal laser of the PPLN crystal 302, and is further amplified by optical parametric amplification. At this time, an amplified light having the same wavelength as the input signal laser of the PPLN crystal 302 is further generated, but it is adjusted so that the beam waist diameter of the pump laser becomes 1.5 to 2.6 times that of the signal laser in the PPLN crystal 302, so that the amplified light outputted from the PPLN crystal 302 has the same degree of divergence angle as the signal laser after passing through the PPLN crystal 302. Here, the power of the signal laser after passing through the PPLN crystal 302 becomes a value that cannot be ignored relative to the corresponding amplified light. This is because, in most cases, the number of amplification stages in the multi-stage amplification is set using the saturation region of the amplification curve. However, according to the structure of the first embodiment, the signal laser passing through the PPLN crystal 302 and the amplified light of the PPLN crystal 302 can have the same degree of divergence angle.

[0111] That is, the ratio of the beam waist diameter of the pump laser in the first-stage PPLN crystal 301 to the beam waist diameter of the signal laser is about 1, whereas the ratio of the beam waist diameter of the pump laser in the second-stage PPLN crystal 302 to the beam waist diameter of the signal laser (amplified light from the PPLN crystal 301) is larger and is set to a range of 1.5 to 2.6 times. As a result, the transmitted signal laser (amplified light from the PPLN crystal 301) output from the PPLN crystal 302 and the amplified light of the PPLN crystal 302 propagate at the same divergence angle. Other actions and Figure 1The operation of the solid-state laser system 10 is the same.

[0112] The PPLN crystal 301 is an example of the “first optical parametric crystal” in the present disclosure, and the PPLN crystal 302 is an example of the “second optical parametric crystal” in the present disclosure. The beam diameter adjustment optical system 313 and the beam diameter adjustment optical system 314 are examples of the “first beam diameter adjustment optical system” in the present disclosure. The beam diameter adjustment optical system 311 and the beam diameter adjustment optical system 312 are examples of the “second beam diameter adjustment optical system” in the present disclosure. The beam diameter adjustment optical system 313 is an example of the “third beam diameter adjustment optical system” in the present disclosure, and the beam diameter adjustment optical system 314 is an example of the “fourth beam diameter adjustment optical system” in the present disclosure. The beam diameter adjustment optical system 311 is an example of the “fifth beam diameter adjustment optical system” in the present disclosure, and the beam diameter adjustment optical system 312 is an example of the “sixth beam diameter adjustment optical system” in the present disclosure.

[0113] A wavelength of about 1030 nm is an example of the “first wavelength” in the present disclosure, and a wavelength of about 1553 nm is an example of the “second wavelength” in the present disclosure. Semiconductor laser 42 is an example of the “first semiconductor laser” in the present disclosure, and the CW laser output from semiconductor laser 42 is an example of the “first CW laser” in the present disclosure. Semiconductor laser 21 is an example of the “second semiconductor laser” in the present disclosure, and the CW laser output from semiconductor laser 21 is an example of the “second CW laser” in the present disclosure. Solid-state amplifier 43 is an example of the “first solid-state amplifier” in the present disclosure, and solid-state amplifier 22 is an example of the “second solid-state amplifier” in the present disclosure. The amplified light output from PPLN crystal 301 is an example of the “first amplified light” in the present disclosure, and the amplified light output from PPLN crystal 302 is an example of the “second amplified light” in the present disclosure. Solid-state laser system 10 and laser system 100 are each an example of a “laser system” in the present disclosure.

[0114] 3.3 Basis of the beam waist diameter ratio condition

[0115] 3.3.1 Calculation of divergence angle ratio

[0116] Here, the basis for the condition that the beam waist diameter of the pump laser light is preferably 1.5 to 2.6 times the beam waist diameter of the signal laser light will be described.

[0117] Assume that the beam intensities of the input signal laser, pump laser, and amplified light of the PPLN crystal are I s ,I p ,I a , assuming that each light has 1 / e 2 Radius w s 、wp 、w a Gaussian beam. Assuming that the beam intensity of the amplified light is I a The beam intensity I of the input signal laser s and the pump laser beam intensity I p When the product is proportional to the intensity distribution of the amplified light beam I a (x, y) is expressed as shown in the following formula (1).

[0118] [Mathematical formula 1]

[0119]

[0120] According to formula (1), it can be expressed as shown in the following formula (2).

[0121] [Mathematical formula 2]

[0122]

[0123] The divergence angle θ of the Gaussian beam can be expressed as θ=λ / πw using the wavelength λ and the beam waist diameter w. Therefore, the divergence angle θ of the amplified light is a The divergence angle θ of the signal laser s The ratio is expressed as follows:

[0124] [Mathematical formula 3]

[0125]

[0126] As the allowable divergence angle ratio, the calculation becomes θ a / θ s When the condition is ≤1.2, equation (4) is obtained based on equation (3).

[0127] [Formula 4]

[0128]

[0129] Formula (4) shows the conditions for making the divergence angle ratio a beam waist diameter ratio of 1.2 or less, and specifies the lower limit of the beam waist diameter ratio (wp / ws), which is the ratio of the beam waist diameter of the pump laser to the beam waist diameter of the signal laser. On the other hand, according to formula (3), the divergence angle ratio always takes a value greater than 1, and therefore the condition that the divergence angle ratio is greater than 0.8 is always satisfied.

[0130] 3.3.2 Calculation of pump laser utilization efficiency

[0131] The upper limit of the preferred beam waist diameter ratio is determined from the viewpoint of pump laser utilization efficiency. Here, the pump laser utilization efficiency E is defined as shown in the following equation (5).

[0132] [Mathematical formula 5]

[0133]

[0134] Among them, A in formula (5) is determined as, in w s =w p When E=1.

[0135] The numerator and denominator of formula (5) are calculated as in formula (6) and formula (7), respectively.

[0136] [Mathematical formula 6]

[0137]

[0138] [Formula 7]

[0139]

[0140] Therefore, according to equations (6) and (7), equation (5) is expressed as follows: equation (8).

[0141] [Mathematical formula 8]

[0142]

[0143] Assuming that the pump laser utilization efficiency E is 25% or more as the allowable range, when the condition of E≥0.25 is calculated in equation (8), equation (9) is obtained.

[0144] [Mathematical formula 9]

[0145]

[0146] Formula (9) shows the conditions for the beam waist diameter ratio for making the pump laser utilization efficiency E 25% or more, and defines the ratio of the beam waist diameter of the pump laser to the beam waist diameter of the signal laser, i.e., the beam waist diameter ratio (w p / w s ) is the upper limit value. According to equations (4) and (9), the preferred beam waist diameter ratio (w p / w s ) is set to a range of greater than 1.5 and less than 2.6.

[0147] 3.4 Effects

[0148] According to Embodiment 1, the divergence angles of the signal laser and the amplified light after passing through the PPLN crystal 302 are similar, and the beam diameter adjustment in the subsequent optical system becomes easy. On the other hand, in the PPLN crystal 301, the mode matching of the signal laser and the pump laser becomes better, and a stronger amplified light is obtained. Therefore, efficient multi-stage amplification becomes easy.

[0149] 4. Implementation Method 2

[0150] 4.1 Structure

[0151] use Figure 2 The amplifier system 30 described above performs optical parametric amplification in two stages by means of two PPLN crystals 301 and 302. However, it may be configured to perform optical parametric amplification in three or more stages. When performing optical parametric amplification in three or more stages, the beam waist diameters of the pump laser and the signal laser are set to be the same only in the primary (first stage) PPLN crystal 301, and the beam waist diameter of the pump laser is set to 1.5 to 2.6 times the beam waist diameter of the signal laser in the second stage PPLN crystal 302 and all subsequent PPLN crystals.

[0152] Alternatively, among the plurality of PPLN crystals arranged in series, the beam waist diameters of the signal laser and the pump laser may be increased together at the later stage PPLN crystals. This may be applied when a larger PPLN crystal is arranged at the later stage.

[0153] When in the latter stage of multi-stage amplification, the power of the signal laser and the amplified light increases, and the energy density at the beam waist tends to become high. Therefore, it is preferred to select a PPLN crystal with a larger cross-sectional area in the latter stage, and increase the beam waist diameters of the signal laser and the pump laser together so that the energy density does not exceed the damage threshold of the PPLN crystal. That is, with respect to the PPLN crystal configured in the latter stage, the cross-sectional area of ​​the PPLN crystal in the plane perpendicular to the optical axis of the signal laser and the pump laser at the beam waist is made larger than that of the PPLN crystal in the previous stage. Along with this, in the latter stage, the beam waist diameters of the signal laser and the pump laser in the PPLN crystal are increased together. Among them, the beam waist diameter of the pump laser in each PPLN crystal is set to 1.5 to 2.6 times the beam waist diameter of the signal laser.

[0154] Figure 6 The structure of the amplifier system 32 used in the laser system 100 of the second embodiment is schematically shown. Figure 2 The amplification system 30 described in the application Figure 6 The amplification system 32 is shown. Figure 6 The amplification system 32 shown is for Figure 2 The differences of the amplification system 30 shown are described below.

[0155] The amplifier system 32 is configured by configuring three PPLN crystals 301, 302, and 303 in series to perform three-stage optical parametric amplification. Figure 2 The beam diameter adjustment optical system 315, the dichroic mirror DM7, the PPLN crystal 303, the dichroic mirror DM8 and the attenuator 334 are added to the rear stage of the PPLN crystal 302. In addition, the amplification system 32 replaces Figure 2 The optical system 310 has a beam splitter BS2 in addition to the reflection mirror MR1, and further has a reflection mirror MR4 for guiding the pump laser light branched by the beam splitter BS2 to the PPLN crystal 303 and a beam diameter adjustment optical system 316.

[0156] 4.2 Action

[0157] The operation up to the second stage of the amplifier stage is the same as that of Embodiment 1. The amplified light having a wavelength of about 1553 nm output from the PPLN crystal 302 and the transmitted signal laser light become the signal laser light incident on the third-stage PPLN crystal 303. The amplified light of the PPLN crystal 302 and the transmitted signal laser light after passing through the PPLN crystal 302 are reflected by the dichroic mirror DM6, and are incident on the PPLN crystal 303 via the beam diameter adjustment optical system 315 and the dichroic mirror DM7.

[0158] In addition, the pump laser after passing through the beam splitter BS2 is incident on the PPLN crystal 303 coaxially with the signal laser via the reflector MR4, the beam diameter adjustment optical system 316 and the dichroic mirror DM7. As a result, the signal laser is further amplified by optical parametric amplification in the PPLN crystal 303. At this time, amplified light of the same wavelength as the signal laser of the PPLN crystal 303 is further generated, but the beam diameter adjustment optical systems 315 and 316 are adjusted so that the beam waist diameter of the pump laser becomes 1.5 to 2.6 times that of the signal laser in the PPLN crystal 303, so that the amplified light output from the PPLN crystal 303 has a divergence angle of the same degree as that of the signal laser after passing through the PPLN crystal 303 (the amplified light from the PPLN crystal 302).

[0159] The idler light output from the PPLN crystal 303 passes through the dichroic mirror DM8 and is absorbed by the attenuator 334. The amplified light output from the PPLN crystal 303 and the transmitted signal laser light are reflected by the dichroic mirror DM8 and output from the amplification system 32 via the reflection mirror MR5. The operation of the wavelength conversion system 50 thereafter is the same as that of the first embodiment.

[0160] In addition, Figure 6 An example of performing three-stage optical parametric amplification is described in the figure, but a structure of performing four or more stages of amplification may also be adopted.

[0161] 4.3 Effects

[0162] According to the second embodiment, it is possible to suppress the damage of the PPLN crystal, increase the number of OPA stages, and obtain a higher power laser with a wavelength of about 1553 nm.

[0163] 5. Modification 1 of the beam diameter adjustment optical system

[0164] 5.1 Structure

[0165] Figure 7 Modification 1 of the beam diameter adjustment optical system is schematically shown. Figure 3 The beam diameter adjustment optical system 311 of the lens pair described in the above is applied Figure 7 The structure of the beam diameter adjustment optical system 310 can be applied to Figure 2 and Figure 6 The beam diameter is adjusted by one or more of the optical systems 311 to 316 shown. Figure 7 structure, for Figure 3 The differences are explained.

[0166] The beam diameter adjustment optical system 310 is provided with a variable beam expander 350 with variable magnification between the opposing lens pair (lens 321 and lens 322). The variable beam expander 350 has lenses 351, 352, 353, lens holders 361, 362, 363, and single-axis stages 364, 365 that can move parallel to the optical axis. The single-axis stages 364, 365 may also be linear stages, each having a driver 366, 367. The single-axis stages 364, 365 are configured to be driven via the drivers 366, 367 according to instructions from the solid-state laser control unit 60 to adjust the inter-lens distance of the lenses 351, 352, 353. The single-axis stages 364, 365 are each an example of a "lens moving mechanism" in the present disclosure.

[0167] The lens 351 is held by a lens holder 361 and is disposed on the base plate 326. The lens 351 may be a concave lens. The lens 352 and the lens 353 are held by lens holders 362 and 363, respectively, and are fixed to single-axis stages 364 and 365. The single-axis stages 364 and 365 are disposed on the base plate 326. The lens 352 and the lens 353 may be convex lenses, respectively.

[0168] In addition, Figure 7 , the variable beam expander 350 using three lenses 351, 352, and 353 is illustrated; however, the variable beam expander 350 may be configured to include more than three lenses.

[0169] 5.2 Action

[0170] The solid-state laser control unit 60 sends commands to the drivers 366 and 367 to move the uniaxial stages 364 and 365 parallel to the optical axis, thereby controlling the positions of the lenses 352 and 353. This allows the beam expansion factor to be adjusted while maintaining the collimation of the beam.

[0171] 5.3 Effects

[0172] Figure 7 The beam diameter adjustment optical system 310 shown constitutes a zoom system, and therefore, it is easy to adjust the beam waist diameter without changing the beam waist position.

[0173] 5.4 Control Example

[0174] The output from the beam diameter monitor, which is a beam diameter monitor such as a beam analyzer (not shown) that monitors the beam diameters of the pump laser and the signal laser in each optical path for performing multi-stage optical parametric amplification, may be input to the solid-state laser control unit 60, thereby controlling the positions of the single-axis stages 364 and 365. For example, the single-axis stages 364 and 365 may be controlled so that the beam waist diameters of the pump laser and the signal laser in the PPLN crystal 301 are approximately the same, and the single-axis stages 364 and 365 may be controlled so that the beam waist diameter of the pump laser in the PPLN crystal 302 is 1.5 to 2.6 times the beam waist diameter of the signal laser in the PPLN crystal 302.

[0175] According to such a configuration, the beam diameter adjustment optical system 310 can be controlled, and therefore, even if there is a fluctuation in the system due to a heat load or the like, an appropriate beam waist diameter can always be maintained in each crystal.

[0176] 6. Modification 2 of the beam diameter adjustment optical system

[0177] Figure 8 Modification 2 of the beam diameter adjustment optical system is schematically shown. Figure 3 The beam diameter adjustment optical system 311 using the lens pair described in Figure 8 The beam diameter adjustment optical system 340 is shown. The beam diameter adjustment optical system 340 can be applied to Figure 2 and Figure 6 One or more of the beam diameter adjustment optical systems 311 to 316 shown. The beam diameter adjustment optical system 340 is composed of a reflection mirror optical system including a plurality of concave mirrors 371 and 372 instead of a lens pair. According to the beam diameter adjustment optical system 340, the thermal lens effect caused by the absorption of laser light by the lens can be suppressed.

[0178] 7. About laser systems using excimer amplifiers

[0179] The solid-state laser system 10 including the laser system 100 described in each of the first embodiment and the second embodiment may be used in combination with an excimer amplifier (not shown).

[0180] That is, the laser system 100 may be configured such that pulsed laser light of ultraviolet light output from the solid-state laser system 10 is input as seed light of the excimer amplifier, and the excimer amplifier outputs amplified pulsed laser light.

[0181] The excimer amplifier may be, for example, a multi-pass amplifier that amplifies pulsed laser light by passing through a discharge space in a cavity sealed with excimer laser gas multiple times (eg, three times), or an amplifier having an optical resonator such as a Fabry-Perot resonator or a ring resonator.

[0182] 8. About the manufacturing method of electronic devices

[0183] Fig. 9 An example of the structure of the exposure device 800 is schematically shown. The exposure device 800 includes an illumination optical system 806 and a projection optical system 808. The laser system 110 is a laser system including the solid laser system 10 described in Embodiments 1 and 2. The laser system 110 may also be a structure obtained by combining the solid laser system 10 and an excimer amplifier. Ultraviolet laser light is generated using the laser system 110 and output to the exposure device 800. The illumination optical system 806 illuminates the mask pattern of the mask (not shown) arranged on the mask stage RT by the laser light incident from the laser system 110. The projection optical system 808 performs reduced projection of the laser light after passing through the mask so that it is imaged on the workpiece (not shown) arranged on the workpiece stage WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with a photoresist.

[0184] The exposure device 800 causes the mask stage RT and the work stage WT to move in parallel in opposite directions synchronously, thereby exposing the workpiece to a laser beam reflecting the mask pattern. After the mask pattern is transferred to the semiconductor wafer through the above exposure process, a semiconductor device can be manufactured through multiple processes. A semiconductor device is an example of an "electronic device" in the present disclosure.

[0185] 9. Others

[0186] The above description is not limiting but merely illustrative. Therefore, it is clear to those skilled in the art that changes can be made to the embodiments of the present disclosure without departing from the claims. In addition, it is also clear to those skilled in the art that the embodiments of the present disclosure can be used in combination.

[0187] Unless explicitly stated otherwise, the terms used in this specification and claims as a whole should be interpreted as "non-limiting" terms. For example, terms such as "including", "having", "having", and "having" should be interpreted as "excluding the existence of structural elements other than the structural elements to be recorded". In addition, the modifier "one" should be interpreted as meaning "at least one" or "one or more". In addition, terms such as "at least one of A, B, and C" should be interpreted as "A", "B", "C", "A+B", "A+C", "B+C", or "A+B+C". Furthermore, it should be interpreted as also including combinations of them and parts other than "A", "B", and "C".

Claims

1. A laser system comprising: A pump laser device that outputs a pump laser of a first wavelength; a signal laser device that outputs a signal laser having a second wavelength longer than the first wavelength; and an amplification system including a plurality of optical parametric crystals, the plurality of optical parametric crystals transmitting the pump laser and the signal laser to output amplified light of the second wavelength, The plurality of optical parametric crystals include a first optical parametric crystal and a second optical parametric crystal arranged in series with the first optical parametric crystal. The amplification system is configured such that the first amplified light of the second wavelength output from the first optical parametric crystal and incident on the second optical parametric crystal and the pump laser incident on the second optical parametric crystal have respective beam waist positions that coincide with each other, and the first amplified light and the pump laser incident on the second optical parametric crystal are coaxially incident on the second optical parametric crystal. The amplification system has a first beam diameter adjustment optical system as follows: the ratio of the beam waist diameter of the pump laser in the second optical parametric crystal to the beam waist diameter of the first amplified light in the second optical parametric crystal is set to be larger than the ratio of the beam waist diameter of the pump laser in the first optical parametric crystal to the beam waist diameter of the signal laser in the first optical parametric crystal.

2. The laser system according to claim 1, wherein: The amplification system is configured such that the beam waist positions of the signal laser incident on the first optical parametric crystal and the pump laser incident on the first optical parametric crystal are consistent with each other, and the signal laser and the pump laser are incident on the first optical parametric crystal coaxially. The amplification system further includes a second beam diameter adjustment optical system in which a beam waist diameter of the signal laser light in the first optical parametric crystal and a beam waist diameter of the pump laser light in the first optical parametric crystal are set to the same diameter.

3. The laser system according to claim 1, wherein: A ratio of a beam waist diameter of the pump laser light in the second optical parametric crystal to a beam waist diameter of the first amplified light in the second optical parametric crystal is in a range of 1.5 to 2.6 times.

4. The laser system according to claim 1, wherein: The first beam diameter adjustment optical system comprises: a third beam diameter adjustment optical system, which is disposed on an optical path between the first optical parametric crystal and the second optical parametric crystal and adjusts a beam waist diameter of the first amplified light; and The fourth beam diameter adjustment optical system is disposed on an optical path of the pump laser light and adjusts a beam waist diameter of the pump laser light incident on the second optical parametric crystal.

5. The laser system of claim 1, wherein: The divergence angle of the second amplified light of the second wavelength output from the second optical parametric crystal is greater than or equal to 0.8 times and less than or equal to 1.2 times the divergence angle of the first amplified light output from the second optical parametric crystal after passing through the second optical parametric crystal.

6. The laser system of claim 2, wherein: The second beam diameter adjustment optical system comprises: a fifth beam diameter adjustment optical system, which is disposed on an optical path of the signal laser light incident on the first optical parametric crystal and adjusts a beam waist diameter of the signal laser light; and The sixth beam diameter adjustment optical system is disposed on an optical path of the pump laser light and adjusts a beam waist diameter of the pump laser light incident on the first optical parametric crystal.

7. The laser system of claim 2, wherein: The beam waist positions of the signal laser light incident on the first optical parametric crystal and the pump laser light incident on the first optical parametric crystal are set so that the beam waists are located at the center of the first optical parametric crystal. The beam waist positions of the first amplified light of the second wavelength incident on the second optical parametric crystal and the pump laser light incident on the second optical parametric crystal are set so as to obtain the respective beam waists at the center of the second optical parametric crystal.

8. The laser system of claim 1, wherein: The amplification system includes three or more optical parametric crystals including the first optical parametric crystal and the second optical parametric crystal, which are arranged in series. The amplification system is configured to perform multi-stage optical parametric amplification of three or more stages using the plurality of optical parametric crystals, and in the multi-stage optical parametric amplification, the first optical parametric crystal is used as the first stage of the amplification stages.

9. The laser system of claim 8, wherein: A ratio of a beam waist diameter of the pump laser light to a beam waist diameter of the amplified light of the second wavelength in each optical parametric crystal disposed at a subsequent stage of the first optical parametric crystal is in a range of 1.5 to 2.6 times.

10. The laser system of claim 1, wherein: The multiple optical parametric crystals are configured in series, and the beam waist diameters of the pump lasers respectively incident on the multiple optical parametric crystals for multi-stage optical parametric amplification are set so that the beam waist diameter of the pump laser incident on the optical parametric crystal configured at a relatively later stage in the series configuration becomes larger.

11. The laser system of claim 10, wherein: In the serial arrangement of the plurality of optical parametric crystals, an optical parametric crystal arranged at a relatively later stage has a larger crystal cross-sectional area perpendicular to the optical axis of the pump laser than an optical parametric crystal arranged at a relatively earlier stage.

12. The laser system of claim 1, wherein: The first beam diameter adjustment optical system has a structure in which a variable beam expander with variable magnification is arranged between a pair of opposing lenses. The variable beam expander includes three or more lenses and a lens moving mechanism for changing the distance between the three or more lenses.

13. The laser system of claim 2, wherein: The second beam diameter adjustment optical system has a structure in which a variable beam expander with variable magnification is arranged between the opposing lens pairs. The variable beam expander includes three or more lenses and a lens moving mechanism for changing the distance between the three or more lenses.

14. The laser system of claim 1, wherein: The first beam diameter adjustment optical system is composed of a reflecting mirror optical system including a plurality of concave mirrors.

15. The laser system of claim 2, wherein: The second beam diameter adjustment optical system is composed of a reflecting mirror optical system including a plurality of concave mirrors.

16. The laser system of claim 1, wherein: The laser system further includes a wavelength conversion system that receives the amplified light of the second wavelength output from the amplification system and ultraviolet light and outputs a sum frequency light thereof.

17. The laser system of claim 16, wherein: The laser system further includes a nonlinear optical crystal that receives the pump laser light having the first wavelength and converts the wavelength of the pump laser light into the ultraviolet light as the higher harmonic light.

18. The laser system of claim 16, wherein: The wavelength conversion system comprises a plurality of nonlinear optical crystals arranged in series, A plurality of sum frequencies are generated by the plurality of nonlinear optical crystals.

19. The laser system of claim 1, wherein: The pump laser device comprises: a first semiconductor laser that outputs a first CW laser beam having the first wavelength; and a first solid-state amplifier for pulsing and amplifying the first CW laser light, The pulse laser light of the first wavelength outputted from the first solid-state amplifier is used as the pump laser light. The signal laser device comprises: a second semiconductor laser that outputs a second CW laser beam having the second wavelength; and a second solid-state amplifier for amplifying the second CW laser light, The CW laser light of the second wavelength output from the second solid-state amplifier is used as the signal laser light.

20. A method for manufacturing an electronic device, comprising the following steps: The laser system generates a second wavelength of laser light. The laser light of the second wavelength is wavelength-converted to generate ultraviolet laser light, The ultraviolet laser is output to an exposure device, exposing the ultraviolet laser light on a photosensitive substrate in the exposure device to manufacture an electronic device, The laser system has: A pump laser device that outputs a pump laser of a first wavelength; a signal laser device that outputs a signal laser having the second wavelength longer than the first wavelength; and an amplification system including a plurality of optical parametric crystals, the plurality of optical parametric crystals transmitting the pump laser light and the signal laser light to output amplified light of the second wavelength, The plurality of optical parametric crystals include a first optical parametric crystal and a second optical parametric crystal arranged in series with the first optical parametric crystal. The amplification system is configured such that the first amplified light of the second wavelength output from the first optical parametric crystal and incident on the second optical parametric crystal and the pump laser incident on the second optical parametric crystal have respective beam waist positions that coincide with each other, and the first amplified light and the pump laser incident on the second optical parametric crystal are coaxially incident on the second optical parametric crystal. The amplification system has a first beam diameter adjustment optical system as follows: the ratio of the beam waist diameter of the pump laser in the second optical parametric crystal to the beam waist diameter of the first amplified light in the second optical parametric crystal is set to be larger than the ratio of the beam waist diameter of the pump laser in the first optical parametric crystal to the beam waist diameter of the signal laser in the first optical parametric crystal.

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