JP2014032277A - Ultraviolet laser device, exposure device including the same, and inspection device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide new means that can output deep ultraviolet laser light having a wavelength of less than 200 nm.SOLUTION: A ultraviolet laser device comprises: a laser light output part 1 that outputs infrared laser light La in a band having a wavelength of 1800 to 2000 nm; a first wavelength conversion optical system 30a that sequentially performs a wavelength conversion of the infrared laser light output from the laser light output part and outputs first ultraviolet laser light Lv; and a second wavelength conversion optical system 30b to which infrared laser light La and the first ultraviolet laser light Lvare incident. The second wavelength conversion optical system 30b is configured to include a wavelength conversion optical element 35 that generates second ultraviolet laser light Lvby a sum frequency generation of the first ultraviolet laser light Lvand the infrared laser light, and a wavelength conversion optical element 36 that generates deep ultraviolet laser light Lo by a sum frequency generation of the second ultraviolet laser light Lvand the infrared laser light.

Description

  The present invention includes a laser light output unit that outputs laser light having an infrared wavelength, and a wavelength conversion optical system that converts the wavelength of the infrared laser light output from the laser light output unit into laser light having an ultraviolet wavelength. Relates to an ultraviolet laser device that outputs deep ultraviolet laser light having a wavelength of 200 nm or less.

  As systems that use deep ultraviolet laser light having a wavelength of 200 nm or less, for example, exposure apparatuses, inspection apparatuses, treatment apparatuses, and the like are known. Various configurations have been proposed as an ultraviolet laser device suitable for such a system. For example, seed light having an infrared wavelength emitted from a laser light source is amplified by an erbium (Er) -doped fiber amplifier (EDFA), and the wavelength of the amplified infrared laser light is sequentially converted by a plurality of wavelength conversion optical elements. In addition, an ultraviolet laser device that outputs deep ultraviolet laser light having a wavelength of 200 nm or less is known (see, for example, Patent Document 1 and Patent Document 2). With such a configuration, a small, all-solid-state ultraviolet laser device that is easy to handle and is realized.

JP 2004-86193 A JP 2010-93210 A

  However, the proposed ultraviolet laser device has advantages and disadvantages. An object of this invention is to provide the ultraviolet laser apparatus of a novel structure which can output the deep ultraviolet laser beam whose wavelength is 200 nm or less. It is another object of the present invention to provide an exposure apparatus, an inspection apparatus, and the like provided with a newly configured ultraviolet laser apparatus.

  In order to solve the above problems, a first aspect illustrating the present invention is an ultraviolet laser device. This ultraviolet laser device has a laser beam output unit that outputs infrared laser light having a wavelength in a band of 1800 to 2000 nm, and the infrared laser beam output from the laser beam output unit is sequentially wavelength-converted by a plurality of wavelength conversion optical elements. A first wavelength conversion optical system that generates a first ultraviolet laser beam, which is the eighth harmonic of the infrared laser beam, and an infrared laser beam output from the laser beam output unit and the first wavelength conversion optical system; And a second wavelength conversion optical system on which the generated first ultraviolet laser light is incident. The second wavelength conversion optical system is a first wavelength conversion optical element that generates the second ultraviolet laser light by generating the sum frequency of the first ultraviolet laser light and the infrared laser light (for example, the wavelength conversion optical element 35 in the embodiment). ) And the second wavelength conversion optical element that generates deep ultraviolet laser light having a wavelength of 200 nm or less by generating the sum frequency of the second ultraviolet laser light and the infrared laser light (for example, the wavelength conversion optical element 36 in the embodiment). And is configured.

  The phase matching in the first wavelength conversion optical element may be type II phase matching in which infrared laser light is ordinary light, first ultraviolet laser light is abnormal light, and second ultraviolet laser light is generated as ordinary light. it can. Alternatively, the phase matching in the first wavelength conversion optical element is a type II phase matching in which infrared laser light is abnormal light, first ultraviolet laser light is ordinary light, and second ultraviolet laser light is generated as abnormal light. Can do.

  The phase matching in the second wavelength conversion optical element may be type I phase matching in which infrared laser light and second ultraviolet laser light are ordinary light and deep ultraviolet laser light is generated as extraordinary light. Alternatively, the phase matching in the second wavelength conversion optical element may be type I phase matching in which infrared laser light and second ultraviolet laser light are abnormal light and deep ultraviolet laser light is generated as ordinary light.

  The first wavelength conversion optical element may be an LBO crystal, and the second wavelength conversion optical element may be a CLBO crystal. Further, the laser beam output unit can be configured to include a thulium-doped fiber amplifier.

  The infrared laser beam output from the laser beam output unit can be configured to pass through the first wavelength conversion optical system and enter the second wavelength conversion optical system.

  In addition, the infrared laser light output from the laser light output unit may be branched in the middle of the optical path and incident on the second wavelength conversion optical system.

  Alternatively, the laser beam output unit includes a first laser beam output unit that outputs a first infrared laser beam having a wavelength in a band of 1800 to 2000 nm and a second infrared beam having a wavelength of 1800 to 2000 nm. A second laser beam output unit that outputs a laser beam, the first infrared laser beam output from the first laser beam output unit is incident on the first wavelength conversion optical system, and the second laser beam output unit The second infrared laser beam output from the laser beam can be made incident on the second wavelength conversion optical system.

  A second aspect illustrating the present invention is an exposure apparatus. The exposure apparatus includes: the ultraviolet laser apparatus according to any one of the above; a mask support unit that holds a photomask on which a predetermined exposure pattern is formed; an exposure object support unit that holds an exposure object; and an ultraviolet laser. An illumination optical system that irradiates the photomask held by the mask support with the deep ultraviolet laser light output from the apparatus, and a projection that projects the light transmitted through the photomask onto the exposure target held by the exposure target support And an optical system.

  A third aspect illustrating the present invention is an inspection apparatus. This inspection apparatus includes the ultraviolet laser device according to any one of the above, a test object support unit that holds a test object, and a deep ultraviolet laser beam output from the ultraviolet laser device that is held by the test object support unit. And an illumination optical system for irradiating the test object and a detector for detecting light from the test object.

  According to the ultraviolet laser device of the first aspect, it is possible to provide an ultraviolet laser device having a novel configuration capable of outputting deep ultraviolet laser light having a wavelength of 200 nm or less.

  According to the exposure apparatus of the second aspect, it is possible to provide an exposure apparatus provided with a newly configured ultraviolet laser apparatus. According to the inspection apparatus for the third aspect, a newly configured ultraviolet laser apparatus is provided. An inspection device can be provided.

It is a block diagram of an ultraviolet laser device shown as an embodiment of the present invention. It is a schematic block diagram of the ultraviolet laser apparatus of a 1st structure form. It is a schematic block diagram of the ultraviolet laser apparatus of a 2nd structure form. It is a schematic block diagram of the ultraviolet laser apparatus of a 3rd structure form. It is a schematic block diagram of the ultraviolet laser apparatus of a 4th structure form. It is a schematic block diagram of the exposure apparatus illustrated as an aspect of this invention. It is a schematic block diagram of the test | inspection apparatus illustrated as an aspect of this invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. A block diagram of an ultraviolet laser device LS (LS1 to LS4) shown as an embodiment of the present invention is shown in FIG. The ultraviolet laser device LS includes a laser beam output unit 1 that outputs infrared laser beam La (La ₁ , La ₂ ) having a wavelength band of 1800 to 2000 nm, and an infrared laser beam La output from the laser beam output unit 1. Is converted to a deep ultraviolet laser beam Lo, and is provided with a wavelength conversion unit 3 that outputs the laser beam, a laser beam output unit 1, a control unit 8 that controls the operation of the wavelength conversion unit 3, and the like. The specific wavelength of the infrared laser light La (La ₁ , La ₂ ) can be set according to the wavelength of the deep ultraviolet laser light Lo output from the ultraviolet laser device LS, the configuration of the wavelength conversion unit 3, and the like.

The wavelength conversion unit 3 is provided with a wavelength conversion optical system 30 including a plurality of wavelength conversion optical elements, a condensing lens, a mirror, and the like. The wavelength conversion optical system 30 includes a first wavelength conversion optical system 30 a on which the infrared laser light La (La ₁ ) output from the laser light output unit 1 is incident, and an infrared laser light output from the laser light output unit 1. La (La ₂ ) and a second wavelength conversion optical system 30b on which the output light of the first wavelength conversion optical system 30a is incident.

The first wavelength conversion optical system 30a is provided with three wavelength conversion optical elements 31, 32, and 33. The infrared laser beam La (La ₁ ) output from the laser beam output unit 1 is sequentially wavelength-converted in the process of passing through these wavelength conversion optical elements 31, 32, 33, and the infrared laser beam La (La ₁ ). The first ultraviolet laser light Lv ₁ that is the eighth harmonic of the _first is generated.

Two wavelength conversion optical elements 35 and 36 are provided in the second wavelength conversion optical system 30b. The wavelength conversion optical element 35 generates a sum frequency of the first ultraviolet laser light Lv ₁ output from the first wavelength conversion optical system 30 a and the infrared laser light La (La ₂ ) output from the laser light output unit 1. As a result, the second ultraviolet laser light Lv ₂ is generated. The wavelength conversion optical element 36 has a wavelength of 200 nm by generating a sum frequency of the second ultraviolet laser light Lv ₂ generated by the wavelength conversion optical element 35 and the infrared laser light La (La ₂ ) transmitted through the wavelength conversion optical element 35. The following deep ultraviolet laser light Lo is generated and output from the ultraviolet laser device LS. In the ultraviolet laser device LS configured as described above, deep ultraviolet laser light can be output with a simple configuration in which superposition is performed only once.

  Hereinafter, a specific configuration of the ultraviolet laser device LS will be described with reference to FIG. 2 showing an outline of the ultraviolet laser device LS1 of the first configuration form. In each figure, what is indicated by an ellipse on the optical path is a collimator lens or a condensing lens, and the description thereof is omitted.

In the ultraviolet laser device LS1, the laser beam output unit 1 includes a first laser beam output unit 1a that outputs a _first infrared laser beam La ₁ in a wavelength band of 1800 to 2000 nm, and a wavelength of 1800 to 2000 nm. And a second laser beam output unit 1b for outputting the _second infrared laser beam La2 in the band. The wavelengths of the first infrared laser light La ₁ and the second infrared laser light La ₂ are set according to the wavelength of the deep ultraviolet laser light Lo output from the ultraviolet laser device LS, the configuration of the wavelength conversion unit 3, and the like. can do.

The configuration illustrated in FIG. 2 includes the wavelength of the _first infrared laser beam La ₁ output from the first laser beam output unit 1a and the second infrared laser beam La output from the second laser beam output unit 1b. _The case where the wavelengths of ₂ are both 1934 nm is shown.

  The first laser light output unit 1a includes a first laser light source 11 that emits seed light having a wavelength of 1934 nm, and a first fiber amplifier 21 that amplifies the seed light output from the first laser light source 11. The Similarly, the second laser light output unit 1b includes a second laser light source 12 that emits seed light having a wavelength of 1934 nm, and a second fiber amplifier 22 that amplifies the seed light output from the second laser light source 12. Configured. In each figure, description of the excitation light source in the fiber amplifier is omitted.

  As the first laser light source 11 and the second laser light source 12, a DFB (Distributed Feedback) semiconductor laser having an oscillation wavelength of about 1934 nm can be preferably used. The DFB semiconductor laser can adjust and set the oscillation wavelength within a predetermined range by controlling the temperature with a temperature controller using a Peltier element or the like, and can generate seed light having a narrow wavelength after the setting. it can. Further, the DFB semiconductor laser can be CW oscillated or pulsed at an arbitrary intensity by controlling the waveform of the excitation current.

  An external modulator such as an EOM (Electro Optic Modulator) is provided between the output port of the DFB semiconductor laser and the fiber amplifier, and the output light of the DFB semiconductor laser that has been CW oscillation or pulse oscillation is cut out by the external modulator. The seed light having a required pulse waveform may be output to the fiber amplifier.

As the first fiber amplifier 21 and the second fiber amplifier 22, a thulium-doped fiber amplifier (TDFA) in which thulium (Tm) is doped in the core of the amplification optical fiber can be preferably used. The thulium-doped fiber amplifier has a gain in the band of 1700 to 2100 nm in wavelength. Therefore, seed light having a wavelength of 1800 to 2000 nm can be efficiently amplified. In addition, the thulium-doped fiber amplifier can be stably operated up to a higher output region as compared with the erbium-doped fiber amplifier (EDFA), and the high-power first and second infrared laser beams. La ₁ and La ₂ can be obtained.

The first infrared laser beam La ₁ having a wavelength of 1934 nm emitted from the first laser light source 11 and amplified by the first fiber amplifier 21 is output from the first laser beam output unit 1 a and is output from the first wavelength conversion unit 3. The light enters the wavelength conversion optical system 30a. The second infrared laser beam La ₂ having a wavelength of 1934 nm emitted from the second laser light source 12 and amplified by the second fiber amplifier 22 is output from the second laser beam output unit 1b and is transmitted through the mirror 42 to the wavelength conversion unit. 3 is incident on the dichroic mirror 41.

  The first laser light output unit 1a is composed of the first laser light source 11 and the first fiber amplifier 21, and the second laser light output unit 1b is composed of the second laser light source 12 and the second fiber amplifier 22. Although the form has been exemplified, at least one of the laser light output units is configured by using a fiber laser (Tm fiber laser) in which a resonator such as an FBG (Fiber Bragg Grating) is incorporated at the input / output end of the fiber amplifier. May be.

The first wavelength conversion optical system 30a on which the first infrared laser light La ₁ output from the first laser light output unit 1a is incidentally includes three wavelength conversion optical elements 31, 32, and 33 as main components. In the first wavelength conversion optical system 30a, the incident first infrared laser light La ₁ is sequentially wavelength-converted in the process of passing through the wavelength conversion optical elements 31, 32, 33, and the first infrared laser light La _{1 is obtained.} The first ultraviolet laser light Lv ₁ that is the eighth harmonic of the _first is generated.

The wavelength conversion optical element 31 is a nonlinear optical crystal that generates the second harmonic of the first infrared laser light La ₁ by second harmonic generation (SHG). The first infrared laser light La ₁ having a wavelength of 1934 nm incident on the wavelength conversion optical element 31 is wavelength-converted in the process of passing through the wavelength conversion optical element 31 and has a wavelength of 967 nm (hereinafter referred to as 967 nm light). Occurs. As the wavelength conversion optical element 31, a PPLN (Periodically Poled LiNbO ₃ ) crystal can be suitably used. By using a PPLN crystal as the wavelength conversion optical element 31, 967 nm light with high efficiency and high beam quality can be generated.

The wavelength conversion optical element 31 may be a quasi phase matching (QPM) crystal such as a PPLT (Periodically Poled LiTaO ₃ ) crystal or PPKTP (Periodically Poled KTiOPO ₄ ). Also, LBO (LiB ₃ O ₅ ) crystals can be used. The 967 nm light generated by the wavelength conversion optical element 31 enters the wavelength conversion optical element 32.

The wavelength conversion optical element 32 is a nonlinear optical crystal that generates a second harmonic of 967 nm light by second harmonic generation (SHG). The 967 nm light incident on the wavelength conversion optical element 32 is wavelength-converted in the process of passing through the wavelength conversion optical element 32, and laser light having a wavelength of 483.5 nm, which is the fourth harmonic of the _first infrared laser light La1. (Hereinafter referred to as 484 nm light) occurs. An LBO crystal can be suitably used as the wavelength conversion optical element 32. At this time, the walk-off angle is as small as 8 mrad, and 484 nm light with relatively good beam quality can be obtained. As the wavelength conversion optical element 32, a PPLT crystal can also be used. The 484 nm light generated by the wavelength conversion optical element 32 enters the wavelength conversion optical element 33.

The wavelength conversion optical element 33 is a nonlinear optical crystal that generates the second harmonic of 484 nm light by second harmonic generation (SHG). The 484 nm light (the fourth harmonic of the first infrared laser light) incident on the wavelength conversion optical element 33 is wavelength-converted in the process of passing through the wavelength conversion optical element 33, and the first infrared laser light La ₁ A first ultraviolet laser beam Lv ₁ having a wavelength of 241.8 nm, which is the eighth harmonic, is generated. As the wavelength conversion optical element 33, a CLBO (CsLiB ₆ O ₁₀ ) crystal can be suitably used. At this time, since the walk-off angle is as small as 14 mrad and the effective nonlinear optical constant d _eff is as high as d _eff = 0.91 pm / V, the first ultraviolet laser light Lv ₁ can be generated with high efficiency. As the wavelength conversion optical element 33, a BBO (β-BaB ₂ O ₄ ) crystal can also be used.

Since the first ultraviolet laser beam Lv ₁ emitted from the CLBO crystal has an elliptical beam cross section due to the walk-off, the beam cross section is shaped into a circular shape by two cylindrical lenses, and the first dichroic mirror 41 Incident on one surface. On the other hand, the second infrared laser beam La ₂ output from the second laser beam output unit 1 b is incident on the second surface of the dichroic mirror 41.

The dichroic mirror 41 is configured to have wavelength selectivity that reflects light in the wavelength band of the first ultraviolet laser light Lv ₁ and transmits light in the wavelength band of the _second infrared laser light La ₂ . The reflection wavelength of the dichroic mirror 41 is arbitrary as long as it is shorter than the wavelength of the second infrared laser light La ₂ and within the wavelength band including the wavelength of the first ultraviolet laser light Lv ₁ , for example, 350 nm to 400 nm. It can be set to a degree or less. By setting in this way, the first ultraviolet laser light Lv ₁ included in the light emitted from the first wavelength conversion optical system 30a and light of other wavelength components (first infrared laser light, 967 nm light, 484 nm light) can be separated using the dichroic mirror 41. Thereby, it is possible to prevent the laser light having an unnecessary wavelength from entering the second wavelength conversion optical system 30b and the emission from the second wavelength conversion optical system 30b.

Therefore, the first ultraviolet laser light Lv ₁ having a wavelength of 241.8 nm incident on the first surface of the dichroic mirror 41 is reflected by the dichroic mirror 41 and enters the wavelength conversion optical element 35 of the second wavelength conversion optical system 30b. Further, the second infrared laser light La ₂ having a wavelength of 1934 nm incident on the second surface of the dichroic mirror 41 is transmitted through the dichroic mirror 41 and superimposed coaxially with the first ultraviolet laser light Lv ₁ , thereby converting the second wavelength. The light enters the wavelength conversion optical element 35 of the optical system 30b. The first ultraviolet laser beam Lv ₁ and the second infrared laser beam La ₂ are set so that the planes of polarization when entering the wavelength conversion optical element 35 are orthogonal to each other. For example, the second infrared laser light La ₂ is incident on the wavelength conversion optical element 35 with the polarization plane being s-polarized light whose vertical plane is perpendicular to the paper surface, and the first ultraviolet laser light Lv ₁ is p-polarized light whose polarization plane is parallel to the paper surface. Set.

The wavelength conversion optical element 35 is a nonlinear optical crystal that generates a sum frequency of the first ultraviolet laser light Lv ₁ and the second infrared laser light La ₂ by sum frequency generation (SFG). Further, the wavelength conversion optical element 35 makes the second infrared laser light La ₂ incident as ordinary light, the first ultraviolet laser light Lv ₁ incident as abnormal light, and generates the second ultraviolet laser light Lv ₂ as ordinary light. It is. As such a wavelength conversion optical element 35, an LBO crystal is used in this configuration example. As the wavelength conversion optical element 35, a CLBO crystal, a BBO crystal, or a CBO (CsB ₃ O ₅ ) crystal can also be used. The case where these crystals are used will be described later.

The wavelength conversion optical element (LBO crystal) 35 has a crystal temperature of about 300 degrees K, the second infrared laser light La ₂ is ordinary light (o), and the first ultraviolet laser light Lv ₁ is abnormal light (e). Incident and phase matched by type II phase matching. In the wavelength conversion optical element 35, the first and second infrared laser beams are generated by generating the sum frequency of the second infrared laser beam La ₂ having a wavelength of 1934 nm and the first ultraviolet laser beam Lv ₁ having a wavelength of 241.8 nm. The second harmonic laser light Lv ₂ having a wavelength of 214.9 nm is generated.

At this time, the first ultraviolet laser light Lv ₁ incident as extraordinary light (e) causes a walk-off due to birefringence, but the walk-off angle is as small as about 8 mrad, which is excellent with the second infrared laser light La _2. Overlay is ensured. The beam shape of the second ultraviolet laser light generated in the wavelength conversion optical element 35 is also kept relatively good. Further, the effective nonlinear optical constant of the LBO crystal in this wavelength conversion is relatively high at d _eff = 0.77 pm / V. For this reason, the second ultraviolet laser light is efficiently generated in the wavelength conversion optical element 35, and the second ultraviolet laser light Lv ₂ with good beam quality is output from the wavelength conversion optical element 35.

Furthermore, the second ultraviolet laser light Lv ₂ generated in the wavelength conversion optical element 35 and the second infrared laser light La ₂ transmitted through the wavelength conversion optical element 35 are both ordinary light (o). For this reason, the second infrared laser beam La ₂ and the second ultraviolet laser beam Lv ₂ do not deviate greatly from the position of the center of gravity of the beam, and the wavelength is maintained in a state where the spatial superposition is well maintained. The light is emitted from the conversion optical element 35.

Thus, the next-stage wavelength conversion optical element can be provided without providing an optical element for beam shaping or overlay adjustment between the wavelength conversion optical element 35 and the wavelength conversion optical element 36 whose wavelength band is already in the ultraviolet region. The wavelength can be efficiently converted at 36. The second infrared laser light La ₂ and the second ultraviolet laser light Lv ₂ emitted from the wavelength conversion optical element 35 are incident on the wavelength conversion optical element 36.

The wavelength conversion optical element 36 is a nonlinear optical crystal that generates a sum frequency of the second ultraviolet laser light Lv ₂ and the second infrared laser light La ₂ by sum frequency generation (SFG). Further, the wavelength converting optical element 36 makes the second infrared laser light La ₂ and the second ultraviolet laser light Lv ₂ incident as ordinary light (o) and generates the deep ultraviolet laser light Lo as abnormal light (e). It is an optical crystal. As such a wavelength conversion optical element 36, a CLBO crystal is used in this configuration example. As the wavelength conversion optical element 36, an LBO crystal, a BBO crystal, or a CBO crystal can also be used. The case where these crystals are used will be described later.

The wavelength conversion optical element (CLBO crystal) 36 has a crystal temperature of about 420 degrees K, and the second infrared laser beam La ₂ and the second ultraviolet laser beam Lv ₂ are incident as ordinary light (o), and the type I phase Phase matching is performed by matching. In the wavelength conversion optical element 36, the first and second infrared laser beams are generated by generating a sum frequency of the second infrared laser beam La ₂ having a wavelength of 1934 nm and the second ultraviolet laser beam Lv ₂ having a wavelength of 214.9 nm. The deep ultraviolet laser light Lo having a wavelength of 193.4 nm is generated.

Here, the second infrared laser beam La ₂ and the second ultraviolet laser beam Lv ₂ emitted from the preceding wavelength conversion optical element 35 are in the same polarization state (for example, s-polarized light), and the phase in the wavelength conversion optical element 36. The matching is a type I phase matching in which the polarization direction of incident light is parallel. Therefore, it is not necessary to provide a wavelength plate or the like for adjusting the polarization direction between the wavelength conversion optical element 35 and the wavelength conversion optical element 36 whose wavelength band is in the deep ultraviolet region. Further, the effective nonlinear optical constant of the CLBO crystal in this wavelength conversion is as high as d _eff = 0.93 pm / V, and the deep ultraviolet laser light Lo is generated with high efficiency.

  The deep ultraviolet laser light Lo having a wavelength of 193.4 nm generated by the wavelength conversion optical element 36 is emitted from the second wavelength conversion optical system 30b and output from the ultraviolet laser device LS1.

  Thus, in the ultraviolet laser device LS1, the phase matching in the first wavelength conversion optical element 35 in the second wavelength conversion optical system 30b is such that the second infrared laser light is ordinary light, and the first ultraviolet laser light is abnormal light. And the type II phase matching for generating the second ultraviolet laser light as ordinary light, and the phase matching in the second wavelength conversion optical element 36 in the second wavelength conversion optical system 30b is the second infrared laser light and the second This is type I phase matching in which ultraviolet laser light is used as ordinary light and deep ultraviolet laser light is generated as extraordinary light. Therefore, there is no need to provide an optical element such as a beam shaping optical system or a wavelength plate between the wavelength conversion optical element 35 and the wavelength conversion optical element 36 in which the wavelength band is in the deep ultraviolet region, and the wavelength is simple. An ultraviolet laser device that outputs deep ultraviolet laser light of 200 nm or less can be provided.

  The wavelength 1934 nm of the first and second infrared laser beams is a wavelength that can be easily amplified in a thulium-doped fiber amplifier (TDFA). The thulium-doped fiber amplifier is an erbium-doped fiber amplifier. Compared with (EDFA) etc., it is a fiber amplifier that can operate stably up to a higher output region. Therefore, by using TDFA as the first and second fiber amplifiers 21 and 22, high-power infrared laser light can be supplied to the wavelength converter 3 and high-power deep ultraviolet laser light can be obtained.

Further, the first infrared laser light La ₁ output from the first fiber amplifier 21 enters the first wavelength conversion optical system 30 a and the second infrared laser light La ₂ output from the second fiber amplifier 22. Can be supplied to each of the first wavelength conversion optical system 30a and the second wavelength conversion optical system 30b. An output and highly efficient ultraviolet laser apparatus can be provided.

  In the above embodiment, the case where the wavelength of the first and second infrared laser beams is 1934 nm has been described, but the wavelength can be appropriately selected within the range of 1800 to 2000 nm. Moreover, although the case where the wavelength of the 1st infrared laser beam and the wavelength of the 2nd infrared laser beam were made the same was demonstrated, both can also be made into a different wavelength.

In the case where the short-pulse deep ultraviolet laser light Lo is output from the ultraviolet laser device LS1, the first and second ultraviolet laser lights and the second infrared laser light are timed in the wavelength conversion optical elements 35 and 36. To overlap each other. Specifically, the pulse light (seed light) generated by the first laser light source 11 becomes the first ultraviolet laser light Lv ₁ and enters the wavelength conversion optical element 35, and the pulse generated by the second laser light source 12. The generation timing of these pulse lights is adjusted or set so that the light (seed light) becomes the second infrared laser beam La ₂ and enters the wavelength conversion optical element 35 at the same timing, or these 2 The optical path length of one path may be adjusted and set.

(Second configuration form)
Next, the ultraviolet laser device LS2 of the second configuration form will be described with reference to FIG. The ultraviolet laser device LS2 of this configuration mode is the same as the ultraviolet laser device LS1 of the first configuration mode described above, except that the configuration of the laser light output unit 1 is different. That is, in the ultraviolet laser device LS2 of this configuration, the first laser beam output unit 1a and the second laser beam output unit 1b described above are integrated, and one infrared laser beam generated in the laser beam output unit 1 is integrated. La is divided into two, and each infrared laser beam is configured to enter the first wavelength conversion optical system 30a and the second wavelength conversion optical system 30b. The wavelength conversion optical elements 31, 32 and 33 constituting the first wavelength conversion optical system 30a, the wavelength conversion optical elements 35 and 36 constituting the second wavelength conversion optical system 30b, etc. are described with reference to FIG. The configuration is the same as that of the ultraviolet laser device LS1. Therefore, the same parts in FIG. 3 are denoted by the same reference numerals, and a duplicate description is omitted. In the following, description will be made centering on parts different in configuration from the ultraviolet laser device LS1. In FIG. 3, the description of the lens and the like is omitted, and the optical path of the laser beam is mainly shown.

  In the ultraviolet laser device LS2, the laser beam output unit 1 generates and outputs a single infrared laser beam La having a wavelength in a band of 1800 to 2000 nm. Although the wavelength of the infrared laser light La can be set as appropriate, the present configuration example shows a case where the wavelength is set to 1934 nm as in the laser light output unit described above.

  The laser light output unit 1 includes a laser light source 13 that emits seed light having a wavelength of 1934 nm, and a fiber amplifier 23 that amplifies the seed light output from the laser light source 13. As the laser light source 13, a DFB semiconductor laser having an oscillation wavelength of about 1934 nm can be suitably used. Also, an external modulator such as an EOM is provided between the output port of the DFB semiconductor laser and the fiber amplifier, and the output light of the DFB semiconductor laser that has been CW-oscillated or pulse-oscillated is cut out by the external modulator to obtain the required pulse waveform. The seed light may be output to the fiber amplifier.

  As the fiber amplifier 23, a thulium-doped fiber amplifier (TDFA) can be preferably used. By using a thulium-doped fiber amplifier, high-power infrared laser light La can be obtained relatively easily.

The infrared laser light La having a wavelength of 1934 nm emitted from the laser light source 13 and amplified by the fiber amplifier 23 is divided into two at an appropriate ratio by the beam splitter 43. One infrared laser beam (first infrared laser beam) La ₁ is incident on the first wavelength conversion optical system 30a, and the other infrared laser beam (second infrared laser beam) La ₂ is the first one. The light enters the two-wavelength conversion optical system 30b.

The beam splitter 43 may be provided in either the laser beam output unit 1 or the wavelength conversion unit 3. That is, the beam splitter 43 is provided in the laser beam output unit 1 so that the first and second infrared laser beams La ₁ and La ₂ enter the wavelength conversion unit 3, or the beam splitter 43 is wavelength-converted. It may be configured to be provided in the unit 3 so that a single infrared laser beam La is incident on the wavelength conversion unit.

First first wavelength converting optical system 30a to infrared laser light La ₁ is incident, and a second second wavelength conversion optical system 30b that infrared laser light La ₂ is incident, in the ultraviolet laser device LS1 already described This is the same as the first wavelength conversion optical system 30a and the second wavelength conversion optical system 30b.

That is, the first wavelength converting optical system 30a is provided with three wavelength conversion optical element 31, 32 and 33, the first infrared laser beam La ₁ incident on the first wavelength converting optical system 30a wavelength conversion sequentially wavelength conversion in the process of passing through the optical element 31, 32 and 33, the first ultraviolet laser beam Lv ₁ wavelength 241.8nm is eighth harmonic of the infrared laser beam La is generated.

The first ultraviolet laser light Lv ₁ generated by the first wavelength conversion optical system 30 a is incident on the first surface of the dichroic mirror 46 via the mirror 45. On the other hand, the second infrared laser light La ₂ branched by the beam splitter 43 is incident on the second surface of the dichroic mirror 46 via the mirror 44.

The dichroic mirror 46 is configured to have a wavelength selectivity that reflects light in the wavelength band of the first ultraviolet laser light Lv ₁ and transmits light in the wavelength band of the infrared laser light La. The reflection wavelength of the dichroic mirror 46 is shorter than the wavelength of the infrared laser light La and is arbitrary within a wavelength band including the wavelength of the first ultraviolet laser light Lv ₁ , but can be set to, for example, about 350 nm to 400 nm or less. With this setting, the first ultraviolet laser light Lv ₁ included in the light emitted from the first wavelength conversion optical system 30a and light of other wavelength components (first infrared laser light, 967 nm light, 484 nm). Light) can be separated using a dichroic mirror 46. Thereby, it is possible to prevent the laser light having an unnecessary wavelength from entering the second wavelength conversion optical system 30b and the emission from the second wavelength conversion optical system 30b.

The first ultraviolet laser light Lv ₁ having a wavelength of 241.8 nm incident on the first surface of the dichroic mirror 46 is reflected by the dichroic mirror 46 and enters the wavelength conversion optical element 35 of the second wavelength conversion optical system 30b. The second infrared laser light La ₂ having a wavelength of 1934 nm that is incident on the second surface of the dichroic mirror 46 is transmitted through the dichroic mirror 46 and superimposed coaxially with the first ultraviolet laser light Lv ₁ , thereby converting the second wavelength. The light enters the wavelength conversion optical element 35 of the optical system 30b.

The first ultraviolet laser beam Lv ₁ and the second infrared laser beam La ₂ are set so that the planes of polarization when entering the wavelength conversion optical element 35 are orthogonal to each other. For example, the second infrared laser light La ₂ is incident on the wavelength conversion optical element 35 with s-polarized light whose polarization plane is orthogonal to the paper surface, and the first ultraviolet laser light Lv ₁ is p-polarized light whose polarization surface is parallel to the paper surface. Set. In the present configuration, the first infrared laser beam La ₁ and the second infrared laser beam La ₂ are based on a common infrared laser beam La. In the first wavelength converting optical system 30a of the crystal structure shown as a typical example, a first polarization direction of the infrared laser beam La ₁ incident, a first polarization direction of the ultraviolet laser beam Lv ₁ for emitting the The same (for example, p-polarized light).

Therefore, as a specific means for setting the polarization directions of the first ultraviolet laser beam Lv ₁ and the second infrared laser beam La ₂ incident on the wavelength conversion optical element 35 to be orthogonal to each other, the beam is split by a beam splitter 43. For example, a configuration in which a wavelength plate (λ / 2 plate) is disposed on one of the optical paths, for example, on the optical path toward the second wavelength conversion optical system 30b, and the polarization plane of the _second infrared laser light La ₂ is rotated by 90 degrees is exemplified. The Alternatively, using a polarizing beam splitter (PBS) as a beam splitter 43, for example an infrared laser beam La polarization plane is inclined at an angle 45 degrees is incident, a first infrared laser light La ₁ and s-polarized light of p-polarized light A configuration in which the laser beam is divided into the _second infrared laser beam La ₂ is exemplified. With such a configuration, the first ultraviolet laser beam Lv ₁ and the second infrared laser beam La ₂ can be made incident on the wavelength conversion optical element 35 with the polarization planes orthogonal to each other.

  The subsequent configuration of the second wavelength conversion optical system 30b, the wavelength conversion process in the second wavelength conversion optical system 30b, and the like are the same as those of the ultraviolet laser device LS1 having the first configuration described above. Therefore, only the gist is briefly summarized below.

The wavelength conversion optical element 35 makes the second infrared laser light La ₂ incident as ordinary light, the first ultraviolet laser light Lv ₁ incident as abnormal light, and generates the second ultraviolet laser light, which is sum frequency light, as ordinary light. LBO crystals are preferably used. In the wavelength conversion optical element 35, the ninth harmonic of the infrared laser light La is generated by the sum frequency generation of the second infrared laser light La ₂ having a wavelength of 1934 nm and the first ultraviolet laser light Lv ₁ having a wavelength of 241.8 nm. The second ultraviolet laser light Lv ₂ having a wavelength of 214.9 nm is generated.

At this time, the walk-off angle of the first ultraviolet laser light Lv ₁ that is incident as the abnormal light (e) is as extremely small as about 8 mrad, and a good overlay with the _second infrared laser light La ₂ is ensured. The beam shape of the second ultraviolet laser light Lv ₂ generated by the wavelength conversion optical element 35 is also kept relatively good. Further, the effective nonlinear optical constant of the LBO crystal in this wavelength conversion is relatively high. For this reason, the second ultraviolet laser light is efficiently generated in the wavelength conversion optical element 35, and the second ultraviolet laser light Lv ₂ with good beam quality is output from the wavelength conversion optical element 35.

Furthermore, since the second ultraviolet laser light Lv ₂ generated in the wavelength conversion optical element 35 and the second infrared laser light La ₂ transmitted through the wavelength conversion optical element 35 are both ordinary light, the positions of the center of gravity of both beams Is not greatly deviated, and the light is emitted from the wavelength conversion optical element 35 in a state where the spatial superposition is kept good.

Thus, the next-stage wavelength conversion optical element is provided without providing an optical element for beam shaping or overlay adjustment between the wavelength conversion optical element 35 and the wavelength conversion optical element 36 whose wavelength band is in the deep ultraviolet region. The wavelength can be efficiently converted at 36. The second infrared laser light La ₂ and the second ultraviolet laser light Lv ₂ emitted from the wavelength conversion optical element 35 are incident on the wavelength conversion optical element 36.

The wavelength conversion optical element 36 is a nonlinear optical crystal that causes the second infrared laser light La ₂ and the second ultraviolet laser light Lv ₂ to be incident as ordinary light, and generates the deep ultraviolet laser light Lo, which is sum frequency light, as abnormal light. Yes, a CLBO crystal is preferably used. In the wavelength conversion optical element 36, the 10th harmonic of the infrared laser light La is generated by the sum frequency generation of the second infrared laser light La ₂ having a wavelength of 1934 nm and the second ultraviolet laser light Lv ₂ having a wavelength of 214.9 nm. The deep ultraviolet laser light Lo having a wavelength of 193.4 nm is generated.

Here, the second infrared laser beam La ₂ and the second ultraviolet laser beam Lv ₂ emitted from the preceding wavelength conversion optical element 35 are in the same polarization state (for example, s-polarized light), and the phase in the wavelength conversion optical element 36. The matching is a type I phase matching in which the polarization direction of incident light is parallel. Therefore, it is not necessary to provide a wavelength plate or the like for adjusting the polarization direction between the wavelength conversion optical element 35 and the wavelength conversion optical element 36 whose wavelength band is in the deep ultraviolet region. Further, the effective nonlinear optical constant of the CLBO crystal in this wavelength conversion is high, and deep ultraviolet laser light is generated with high efficiency. The deep ultraviolet laser light Lo having a wavelength of 193.4 nm generated by the wavelength conversion optical element 36 is emitted from the second wavelength conversion optical system 30b and output from the ultraviolet laser device LS1.

  As described above, the phase matching in the wavelength conversion optical element 35 is type II phase matching in which the second infrared laser light is ordinary light, the first ultraviolet laser light is abnormal light, and the second ultraviolet laser light is generated as ordinary light. The phase matching in the wavelength conversion optical element 36 is type I phase matching in which the second infrared laser light and the second ultraviolet laser light are ordinary light and the deep ultraviolet laser light is generated as extraordinary light. Therefore, there is no need to provide an optical element such as a beam shaping optical system or a wavelength plate between the wavelength conversion optical element 35 and the wavelength conversion optical element 36 in which the wavelength band is in the deep ultraviolet region, and the wavelength is simple. An ultraviolet laser device that outputs deep ultraviolet laser light of 200 nm or less can be provided.

  Further, the ultraviolet laser device LS2 of this configuration form divides the infrared laser light La output from the fiber amplifier 23 into two and enters the first wavelength conversion optical system 30a and the second wavelength conversion optical system 30b. It has a configuration to let you. As a result, the configuration of the laser light output unit 1, and thus the overall configuration of the ultraviolet laser device, can be simplified, and an ultraviolet laser device that outputs deep ultraviolet laser light of 200 nm or less can be provided at low cost.

(Third configuration form)
Next, an ultraviolet laser device LS3 having a third configuration will be described with reference to FIG. The ultraviolet laser device LS3 of this configuration mode is different from the ultraviolet laser device LS2 of the second configuration mode except for the branching position of the infrared laser light incident on the second wavelength conversion optical system 30b. This is the same as the laser device LS2. That is, in the ultraviolet laser device LS3 of this configuration, the infrared laser beam is branched from the middle of the optical path of the first wavelength conversion optical system 30a and is incident on the second wavelength conversion optical system 30b. The laser light output unit 1, the wavelength conversion optical elements 31, 32, and 33 that constitute the first wavelength conversion optical system 30a, the wavelength conversion optical elements 35 and 36 that constitute the second wavelength conversion optical system 30b, and the like are described above. This is the same as the two-configuration ultraviolet laser device LS2. Therefore, the same parts in FIG. 4 are denoted by the same reference numerals and redundant description is omitted, and a brief description will be given focusing on the parts different from the ultraviolet laser device LS2. In FIG. 4, as in FIG. 3, the description of the lens and the like is omitted, and the optical path of the laser beam is mainly shown.

  Infrared laser light La having a wavelength of 1934 nm emitted from the laser light source 13 in the laser light output unit 1 and amplified by the fiber amplifier 23 enters the wavelength conversion optical element 31 of the first wavelength conversion optical system 30a.

  A dichroic mirror is provided on the optical path of the first wavelength conversion optical system 30a to branch the infrared laser light La ′ that has passed through the wavelength conversion optical element 31 without being wavelength converted. FIG. 4 illustrates a configuration in which a dichroic mirror 47 is provided between the wavelength conversion optical element 31 and the wavelength conversion optical element 32. The dichroic mirror 47 has a wavelength selectivity that reflects light in the wavelength band of the infrared laser light La and transmits light in the wavelength band of 967 nm light.

Therefore, the 967 nm light generated by the wavelength conversion optical element 31 passes through the dichroic mirror 47 and enters the wavelength conversion optical element 32. Then, the wavelength conversion is sequentially performed in the process of passing through the wavelength conversion optical elements 32 and 33, and the first ultraviolet laser light Lv ₁ having a wavelength of 241.8 nm is generated. The first ultraviolet laser light Lv ₁ generated by the wavelength conversion optical element 33 is incident on the first surface of the dichroic mirror 46 via the mirror 45. On the other hand, the infrared laser beam La ′ that has passed through the wavelength conversion optical element 31 without being wavelength-converted is reflected by the dichroic mirror 47 and enters the second surface of the dichroic mirror 46 via the mirror 44.

As described above, the dichroic mirror 46 has a wavelength selectivity that reflects light in the wavelength band of the first ultraviolet laser light Lv ₁ and transmits light in the wavelength band of the infrared laser light La. . Therefore, the first ultraviolet laser light Lv ₁ incident on the first surface of the dichroic mirror 46 is reflected by the dichroic mirror 46 and enters the wavelength conversion optical element 35 of the second wavelength conversion optical system 30b. The infrared laser beam La ′ incident on the second surface of the dichroic mirror 46 is transmitted through the dichroic mirror 46 and superimposed on the first ultraviolet laser beam Lv _{1 so} as to be converted by the second wavelength conversion optical system 30b. The light enters the optical element 35.

The first ultraviolet laser beam Lv ₁ and the infrared laser beam La ′ are set so that the planes of polarization when entering the wavelength conversion optical element 35 are orthogonal to each other. For example, the infrared laser light La ′ is set to be incident on the wavelength conversion optical element 35 with s-polarized light whose polarization plane is orthogonal to the paper surface, and the first ultraviolet laser light Lv ₁ is p-polarized light whose polarization surface is parallel to the paper surface. For example, a wavelength plate 48 is disposed on one of the optical paths branched by the dichroic mirror 47, for example, the optical path toward the second wavelength conversion optical system 30b, and the polarization plane of the infrared laser light La ′ is rotated by 90 degrees.

  The subsequent configuration of the second wavelength conversion optical system 30b, the wavelength conversion process in the second wavelength conversion optical system 30b, and the like are the same as those of the ultraviolet laser devices LS1 and LS2 of the first and second configuration modes described above.

  Therefore, in the ultraviolet laser device LS3, it is not necessary to provide an optical element such as a beam shaping optical system or a wavelength plate between the wavelength conversion optical element 35 and the wavelength conversion optical element 36 whose wavelength band is in the deep ultraviolet region. An ultraviolet laser apparatus that outputs a deep ultraviolet laser beam having a simple configuration and a wavelength of 200 nm or less can be provided. In addition, the ultraviolet laser device LS3 of this configuration form the infrared laser light La output from the fiber amplifier 23 is branched in the middle of the optical path of the first wavelength conversion optical system 30a and is incident on the second wavelength conversion optical system 30b. It has a configuration to let you. As a result, the configuration of the laser light output unit 1, and thus the overall configuration of the ultraviolet laser device, can be simplified, and an ultraviolet laser device that outputs deep ultraviolet laser light of 200 nm or less can be provided at low cost.

(Fourth configuration form)
Next, an ultraviolet laser device LS4 having a fourth configuration will be described with reference to FIG. The ultraviolet laser device LS4 of the present configuration form is basically the same as the other configurations except that the infrared laser beam transmitted through the first wavelength conversion optical system 30a is incident on the second wavelength conversion optical system 30b. This is the same as the laser devices LS1 to LS3 in the third configuration form. That is, in the ultraviolet laser device LS4 of the present configuration, the infrared laser light incident on the second wavelength conversion optical system 30b is generated at a different laser light output unit or output from the laser light output unit. The light that has passed through the first wavelength conversion optical system 30a is used without branching the light along the optical path. The laser light output unit 1, the wavelength conversion optical elements 31, 32, 33 that constitute the first wavelength conversion optical system 30a, the wavelength conversion optical elements 35, 36 that constitute the second wavelength conversion optical system 30b, etc. These can be configured in the same manner as the ultraviolet laser devices LS2 and LS3 in the second and third configuration modes described above. Therefore, the same reference numerals are given to the same parts in FIG. 5 to omit redundant description, and the main points of the present configuration will be briefly described. In addition, like FIG.3, FIG.4, description of a lens etc. is abbreviate | omitted and it shows mainly the optical path of a laser beam.

Infrared laser light La having a wavelength of 1934 nm emitted from the laser light source 13 in the laser light output unit 1 and amplified by the fiber amplifier 23 enters the first wavelength conversion optical system 30a. The first wavelength conversion optical system 30a is provided with three length conversion optical elements 31, 32, and 33 in series. The wavelength conversion optical element 31 is a nonlinear optical crystal that generates the second harmonic (967 nm light) of the infrared laser light La, and a PPLN crystal, a PPLT crystal, or an LBO crystal is preferably used. The wavelength conversion optical element 32 is a non-linear optical crystal that generates the second harmonic (484 nm light) of 967 nm light, and a PPLT crystal or LBO crystal is preferably used. The wavelength conversion optical element 33 is a nonlinear optical crystal that generates the second harmonic (first ultraviolet laser light Lv ₁ ) of 484 nm light, and a CLBO crystal is preferably used.

In this configuration mode, a configuration using a PPLT crystal as the wavelength conversion optical element 32 is illustrated. When a PPLT crystal is used as the wavelength conversion optical element 32, no walk-off occurs in the generated 484 nm light. Therefore, excellent beam superposition can be realized in the second wavelength conversion optical system 30b. The first ultraviolet laser light Lv ₁ generated by the wavelength conversion optical element 33 and the infrared laser light La ′ transmitted through the wavelength conversion optical elements 31, 32, 33 are incident on the second wavelength conversion optical system 30b. At this time, the first ultraviolet laser light Lv ₁ and the infrared laser light La ′ incident on the wavelength conversion optical element 35 are set so that their polarization planes are orthogonal to each other.

Two wavelength conversion optical elements 35 and 36 are provided in the second wavelength conversion optical system 30b. The wavelength conversion optical element 35 is a nonlinear optical crystal that generates a sum frequency of the first ultraviolet laser light Lv ₁ and the infrared laser light La ′ by sum frequency generation (SFG). On the other hand, the wavelength conversion optical element 35 in the present configuration is nonlinear to cause the infrared laser light La ′ to be incident as extraordinary light, the first ultraviolet laser light Lv ₁ as ordinary light, and the second ultraviolet laser light Lv ₂ to be generated as extraordinary light. It is an optical crystal. Examples of such a wavelength conversion optical element 35 include a CLBO crystal, a CBO crystal, and a BBO crystal. Here, a configuration using a CBO crystal as the wavelength conversion optical element 35 is illustrated.

When a CBO crystal is used as the wavelength conversion optical element 35, the walk-off angle of the infrared laser light La ′ is 10 mrad, and the walk-off angle of the second ultraviolet laser light Lv ₂ is 18 mrad (the difference between the two is 8 mrad). Since it is small, the beam shape is also kept relatively good and the effective nonlinear optical constant is as high as 1.29 pm / V, so that the second ultraviolet laser light Lv ₂ can be generated efficiently. The second ultraviolet laser light Lv ₂ generated by the wavelength conversion optical element 35 and the infrared laser light infrared laser light La ′ transmitted through the wavelength conversion optical element 35 are incident on the wavelength conversion optical element 36.

The wavelength conversion optical element 36 is a nonlinear optical crystal that generates a sum frequency of the second ultraviolet laser light Lv ₂ and the second infrared laser light La ₂ by sum frequency generation (SFG). The wavelength conversion optical element 36 is a non-linear optical crystal that makes the infrared laser light La ′ and the second ultraviolet laser light Lv ₂ incident as ordinary light (o) and generates the deep ultraviolet laser light Lo as abnormal light (e). is there. Examples of such a wavelength conversion optical element 36 include a CLBO crystal, an LBO crystal, and a BBO crystal. Here, a configuration using an LBO crystal is illustrated. When an LBO crystal is used as the wavelength conversion optical element 36, the effective nonlinear optical constant is lower than that of the CLBO crystal, but the walk-off angle of the generated deep ultraviolet laser light Lo is about half that of the CLBO crystal. The deep ultraviolet laser light Lo having a good beam shape can be generated.

As another configuration of the wavelength conversion optical element 36 that generates the sum frequency of the second ultraviolet laser beam Lv ₂ and the second infrared laser beam La ₂ , an infrared laser beam La ′ and a second ultraviolet laser beam Lv ₂ are used. There exists a form which injects with extraordinary light (e) and generates deep ultraviolet laser light Lo as ordinary light (o). As such a wavelength conversion optical element 36, a CBO crystal is exemplified. When a CBO crystal is used as the wavelength conversion optical element 36, the walk-off angle of the infrared laser light La ′ is 17 mrad and the walk-off angle of the second ultraviolet laser light Lv ₂ is approximately 39 mrad. Is as high as 1.79 pm / V, the deep ultraviolet laser light Lo can be generated relatively efficiently.

  In the ultraviolet laser device LS4 described above, infrared laser light generated by a single laser light output unit is used and transmitted through wavelength conversion optical elements arranged in series without providing a branching optical path or the like, and a depth of 200 nm or less. Ultraviolet laser light can be output. In addition, since the walk-off angle of the beam generated in each wavelength conversion optical element is approximately 20 mrad or less, it is possible to omit the lens disposed between the wavelength conversion optical elements. Now, assuming that the crystal length of the wavelength conversion optical element is L, the beam diameter of the incident laser beam is D, and the walk-off angle is ρ, if Lρ <D, superposition can be realized without a lens. For example, when the crystal length L = 5 mm, the walk-off angle ρ = 10 mrad, and the beam diameter D = 300 μm, Lρ = 50 μm, and a relatively good overlay can be realized.

  Furthermore, all the lenses between the wavelength conversion optical elements can be omitted by appropriately setting the condensing spot diameter (and spot position) of the infrared laser light La output from the laser light output unit 1. . For example, if the infrared laser beam La output from the laser beam output unit 1 is focused so that the focused spot diameter (diameter) is D = 300 μm, then the confocal length (the beam diameter is approximately constant). The possible length range is about 73 mm. If each crystal length of the wavelength conversion optical elements 31, 32, 33, 35, and 36 is 5 mm, the length when these five wavelength conversion optical elements are arranged in series is 25 mm, and a space is provided between them. Even so, it can be placed within the confocal length.

  Therefore, according to the ultraviolet laser device LS4 having such a configuration, it is possible to provide an ultraviolet laser device that outputs a deep ultraviolet laser beam having a wavelength of 200 nm or less with a very simple configuration.

  In the examples of the first to fourth configuration modes described above, the wavelength of the infrared laser light output from the laser light output unit 1 is 1934 nm, and the wavelength of the deep ultraviolet laser light output from the wavelength conversion unit 3 is 193. A specific configuration is illustrated for the case of .4 nm. However, the present invention is not limited to such a specific example, the wavelength of the infrared laser light, the wavelength of the deep ultraviolet laser light, the configuration of the first wavelength conversion optical system 30a, the second wavelength conversion optical system 30b, etc. It can be changed as appropriate.

  The ultraviolet laser devices LS (LS1 to LS4) as described above are small and light and easy to handle. Optical processing devices such as exposure devices and stereolithography devices, inspection devices such as photomasks and wafers, microscopes, The present invention can be suitably applied to systems such as observation devices such as telescopes, measuring devices such as length measuring devices and shape measuring devices, and phototherapy devices.

  Next, as a first application example of a system including the ultraviolet laser device LS (LS1 to LS4), FIG. 6 shows a schematic configuration of an exposure apparatus used in a photolithography process such as semiconductor manufacturing or liquid crystal panel manufacturing. Will be described with reference to FIG. The exposure apparatus 100 is in principle the same as photolithography, and a device pattern precisely drawn on a quartz glass photomask 113 is applied to an exposure object 115 such as a semiconductor wafer or glass substrate coated with a photoresist. Optically project and transfer.

  The exposure apparatus 100 includes an ultraviolet laser apparatus LS, an illumination optical system 102, a mask support base 103 that holds a photomask 113, a projection optical system 104, and an exposure object support table 105 that holds an exposure object 115. And a drive mechanism 106 that moves the exposure object support table 105 in a horizontal plane. The illumination optical system 102 includes a plurality of lens groups, and irradiates the photomask 113 held on the mask support 103 with the deep ultraviolet laser light output from the ultraviolet laser device LS. The projection optical system 104 is also composed of a plurality of lens groups, and projects the light transmitted through the photomask 113 onto the exposure object 115 on the exposure object support table.

  In the exposure apparatus 100 having such a configuration, the deep ultraviolet laser light output from the ultraviolet laser apparatus LS is input to the illumination optical system 102, and the deep ultraviolet laser light adjusted to a predetermined light flux is held on the mask support 103. The photomask 113 is irradiated. The light that has passed through the photomask 113 has an image of a device pattern drawn on the photomask 113, and this light of the exposure object 115 held on the exposure object support table 105 via the projection optical system 104. A predetermined position is irradiated. As a result, the image of the device pattern on the photomask 113 is image-exposed at a predetermined magnification on the exposure object 115 such as a semiconductor wafer or a liquid crystal panel.

  Such an exposure apparatus 100 includes an ultraviolet laser apparatus LS that can output a high-output deep ultraviolet laser light Lo with a simple configuration. Therefore, an exposure apparatus having a simple configuration can be provided.

  Next, as a second application example of the system including the ultraviolet laser device LS (LS1 to LS4), an overview of an inspection device used in an inspection process of a photomask, a liquid crystal panel, a wafer, or the like (test object). The configuration will be described with reference to FIG. An inspection apparatus 200 illustrated in FIG. 7 is suitably used for inspecting a fine device pattern drawn on a light-transmitting object 213 such as a photomask.

  The inspection device 200 detects light from the ultraviolet laser device LS, the illumination optical system 202, the test object support table 203 that holds the test object 213, the projection optical system 204, and the test object 213. A TDI (Time Delay Integration) sensor 215 and a drive mechanism 206 that moves the object support base 203 in a horizontal plane are configured. The illumination optical system 202 includes a plurality of lens groups, and adjusts the deep ultraviolet laser light output from the ultraviolet laser device LS to a predetermined light flux and irradiates the object 213 held on the object support table 203. The projection optical system 204 is also composed of a plurality of lens groups, and projects the light transmitted through the test object 213 onto the TDI sensor 215.

  In the inspection apparatus 200 having such a configuration, the deep ultraviolet laser light output from the ultraviolet laser apparatus LS is input to the illumination optical system 202, and the deep ultraviolet laser light adjusted to a predetermined luminous flux is applied to the test object support base 203. The object 213 such as a photomask held is irradiated. The light from the object 213 (transmitted light in this configuration example) has an image of a device pattern drawn on the object 213, and this light is transmitted to the TDI sensor 215 via the projection optical system 204. Projected and imaged. At this time, the horizontal movement speed of the test object support table 203 by the drive mechanism 206 and the transfer clock of the TDI sensor 215 are controlled in synchronization.

  Therefore, an image of the device pattern of the test object 213 is detected by the TDI sensor 215, and by comparing the detection image of the test object 213 detected in this way with a predetermined reference image set in advance, The defect of the fine pattern drawn on the test object is extracted. In the case where the test object 213 does not have optical transparency like a wafer or the like, the reflected light from the test object is incident on the projection optical system 204 and guided to the TDI sensor 215 in the same manner. can do.

  Such an inspection apparatus 200 includes an ultraviolet laser apparatus LS that can output a high-output deep ultraviolet laser light Lo with a simple configuration. Therefore, an inspection device having a simple configuration can be provided.

LS Ultraviolet laser device LS1 Ultraviolet laser device LS2 in the first configuration form Ultraviolet laser device LS3 in the second configuration form Ultraviolet laser device LS4 in the third configuration form Ultraviolet laser device La, La ′ in the fourth configuration form Infrared laser light La ₁ First infrared laser beam La ₂ Second infrared laser beam Lv ₁ First ultraviolet laser beam Lv ₂ Second ultraviolet laser beam Lo Deep ultraviolet laser beam 1 Laser beam output unit 1 a First laser beam output unit 1 b Second Laser light output unit 11 First laser light source 12 Second laser light source 13 Laser light source 21 First fiber amplifier 22 Second fiber amplifier 23 Fiber amplifier 3 Wavelength conversion unit 30 Wavelength conversion optical system 30a First wavelength conversion optical system 30b Second wavelength Conversion optical system 31, 32, 33, 35, 36 Wavelength conversion optical element 41 Dichroic mirror 43 Beam splitter 46 Dichroic mirror -47 Dichroic mirror 100 Exposure apparatus 102 Illumination optical system 103 Mask support base 104 Projection optical system 105 Exposure object support table 113 Photomask 115 Exposure object 200 Inspection apparatus 202 Illumination optical system 203 Test object support stage 204 Projection optical system 213 DUT 215 TDI sensor

Claims (13)

A laser beam output unit that outputs infrared laser beam having a wavelength in a band of 1800 to 2000 nm;
A first wavelength that sequentially converts the wavelength of the infrared laser beam output from the laser beam output unit by a plurality of wavelength conversion optical elements to generate a first ultraviolet laser beam that is an eighth harmonic of the infrared laser beam. A conversion optical system;
A second wavelength conversion optical system on which the infrared laser light output from the laser light output unit and the first ultraviolet laser light generated by the first wavelength conversion optical system are incident;
The second wavelength conversion optical system includes:
A first wavelength conversion optical element that generates a second ultraviolet laser beam by generating a sum frequency of the first ultraviolet laser beam and the infrared laser beam;
An ultraviolet laser apparatus comprising: a second wavelength conversion optical element that generates deep ultraviolet laser light having a wavelength of 200 nm or less by generating a sum frequency of the second ultraviolet laser light and the infrared laser light. The phase matching in the first wavelength conversion optical element is type II phase matching in which the infrared laser light is ordinary light, the first ultraviolet laser light is abnormal light, and the second ultraviolet laser light is generated as ordinary light. The ultraviolet laser device according to claim 1. The phase matching in the first wavelength conversion optical element is type II phase matching in which the infrared laser light is abnormal light, the first ultraviolet laser light is ordinary light, and the second ultraviolet laser light is generated as abnormal light. The ultraviolet laser device according to claim 1. The phase matching in the second wavelength conversion optical element is type I phase matching in which the infrared laser light and the second ultraviolet laser light are ordinary light and the deep ultraviolet laser light is generated as extraordinary light. The ultraviolet laser device according to any one of claims 1 to 3. The phase matching in the second wavelength conversion optical element is type I phase matching in which the infrared laser light and the second ultraviolet laser light are abnormal light and the deep ultraviolet laser light is generated as ordinary light. The ultraviolet laser device according to any one of claims 1 to 3. The ultraviolet laser device according to claim 1, wherein the first wavelength conversion optical element is an LBO crystal. The ultraviolet laser device according to claim 1, wherein the second wavelength conversion optical element is a CLBO crystal. The ultraviolet laser apparatus according to claim 1, wherein the laser light output unit includes a thulium-doped fiber amplifier. 9. The infrared laser light output from the laser light output unit passes through the first wavelength conversion optical system and enters the second wavelength conversion optical system. The ultraviolet laser device according to item. The said infrared laser beam output from the said laser beam output part is branched in the middle of an optical path, and injects into the said 2nd wavelength conversion optical system, It is any one of Claims 1-8 characterized by the above-mentioned. Ultraviolet laser device. The laser beam output unit is
A first laser beam output unit that outputs the first infrared laser beam having a wavelength in a band of 1800 to 2000 nm;
A second laser beam output unit that outputs the second infrared laser beam having a wavelength in a band of 1800 to 2000 nm,
The first infrared laser beam output from the first laser beam output unit is incident on the first wavelength conversion optical system, and the second infrared laser beam output from the second laser beam output unit. Is incident on the second wavelength conversion optical system. 9. The ultraviolet laser device according to claim 1, wherein The ultraviolet laser device according to any one of claims 1 to 11,
A mask support for holding a photomask on which a predetermined exposure pattern is formed;
An exposure object support for holding the exposure object;
An illumination optical system for irradiating the photomask held by the mask support with the deep ultraviolet laser light output from the ultraviolet laser device;
An exposure apparatus comprising: a projection optical system that projects light transmitted through the photomask onto an exposure target held by an exposure target support. The ultraviolet laser device according to any one of claims 1 to 11,
An object support for holding the object;
An illumination optical system for irradiating the test object held by the test object support portion with the deep ultraviolet laser light output from the ultraviolet laser device;
An inspection apparatus comprising: a detector that detects light from the test object.

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