JP2007279084A - Wavelength conversion optical system, laser light source, exposure device, inspection object inspecting device, and processing device for polymer crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength conversion optical system having small variation of output light in its projection direction. <P>SOLUTION: An eighth harmonic emitted by an eighth-harmonic generating optical element 12 is partially separated by a half-mirror 17 and made incident on a monitor device 18. The monitor device 18 has imaging elements such as a two-dimensional CCD, calculates the projection direction of the eighth harmonic from the position where the light is incident on those imaging elements, and sends it to a projection light direction controller 19. The projection light direction controller 19 sends a command to a lens position controller 20 so that the eighth harmonic is projected in the predetermined direction, and then the attitude of a lens L is changed to control the incident direction of a fundamental wave incident on the eighth-harmonic generating optical element 12 through a dichroic mirror 13, a dichroic mirror 10, and a seventh-harmonic generating optical element 11. Consequently, the projection direction of the eighth harmonic is controlled to the predetermined direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wavelength conversion optical system, a laser light source, an exposure apparatus, a test object inspection apparatus, and a polymer crystal processing apparatus.

  In recent years, laser light has been used for various applications, for example, cutting and processing metal, used as a light source of a photolithography apparatus in a semiconductor manufacturing apparatus, used in various measuring apparatuses, surgery, ophthalmology. It is used for surgery and treatment equipment such as dentistry.

  However, the ArF excimer laser oscillation apparatus is configured by sealing argon gas, fluorine gas, neon gas, or the like in a chamber, and it is necessary to seal these gases. Furthermore, it is necessary to fill and collect each gas, and there is a problem that the apparatus tends to be large and complicated. In addition, the ArF excimer laser oscillation apparatus also has a problem that it is necessary to periodically exchange internal gas or perform overhaul in order to maintain predetermined laser light generation performance.

  Therefore, it is preferable to use a solid-state laser as the laser light source instead of such an excimer laser. However, the wavelength of the laser light emitted from the solid-state laser is from the visible region to the infrared region. For example, the wavelength is too long to be used in an inspection apparatus, so that high resolution cannot be obtained. Therefore, a method has been developed in which long-wavelength light emitted from such a solid-state laser is converted into short-wavelength ultraviolet light (for example, eighth harmonic wave) by using a wavelength conversion optical element made of a nonlinear optical crystal. For example, it describes in Unexamined-Japanese-Patent No. 2001-353176 (patent document 1).

This is because the near-infrared light (fundamental wave) emitted from the solid-state laser is optically amplified, and the second and third harmonics of the fundamental wave are generated by the wavelength conversion optical system using the wavelength conversion optical element. To generate 5th harmonic from 2nd harmonic and 3rd harmonic, 7th harmonic from 5th harmonic and 2nd harmonic, and finally generate 8th harmonic from 7th harmonic and fundamental wave It is.
JP 2001-353176 A

In such a wavelength conversion optical element used for wavelength conversion, there is an optical path variation or change called pointing variation. This is because
(1) Thermal characteristics fluctuation of wavelength conversion optical element (wavelength conversion crystal)
(2) Processing error of wavelength conversion optical element (wavelength conversion crystal) (difference due to individual differences of elements that occur during element replacement)
(3) Changes in the optical axis due to atmospheric fluctuations
(4) Changes in the optical axis associated with optical adjustment, which are unavoidable problems under normal conditions. If a pointing variation occurs in the wavelength conversion optical element in the middle of wavelength conversion, the incident angle to the next incident wavelength conversion optical element changes, so that a change in wavelength conversion efficiency occurs, and further a pointing variation occurs. Further, if the direction of the light emitted from the final stage wavelength conversion optical element, which is the output of the wavelength conversion optical system, changes or fluctuates, there may be inconveniences in the optical system using the output.

  The present invention has been made in view of such circumstances. A wavelength conversion optical system in which a change in the output direction of output light is small, a laser light source using the same, an exposure apparatus using the laser light source, and a test object are disclosed. It is an object to provide an object inspection device and a polymer crystal processing device.

  The first means for solving the above-mentioned problem is that the wavelength conversion optical element is used, and the outgoing light having a frequency that is the sum of the frequencies of these two lights from the two incident lights incident on the wavelength conversion optical element. A wavelength conversion optical system that generates a monitor device that monitors the direction of the emitted light, at least one of the incident light, an incident direction changing device that changes an incident direction to the wavelength conversion optical element, and A wavelength conversion optical system comprising: an outgoing light direction control device that operates the incident direction changing device so that an outgoing direction of the outgoing light monitored by a monitor device is constant.

  A second means for solving the above-mentioned problem is the first means, and a first wavelength conversion optical system that forms a fifth harmonic wave from the first fundamental wave through at least one wavelength conversion optical element. A second harmonic wave forming optical element that forms a second harmonic wave from the second fundamental wave, and a third fundamental wave and the second harmonic wave emitted from the second harmonic wave forming optical element in the same optical path. 1 optical member, the third fundamental wave, the second harmonic wave emitted from the second harmonic wave forming optical element, and the fifth harmonic wave emitted from the first wavelength conversion optical system are combined in the same optical path. A second optical member; a seventh harmonic wave forming optical element that forms a seventh harmonic wave from the second harmonic wave and the fifth harmonic wave; the third fundamental wave emitted from the seventh harmonic wave forming optical element; A wavelength conversion optical system comprising: an eighth harmonic wave forming optical element that forms an eighth harmonic wave from the seventh harmonic wave A.

  Third means for solving the problem is the second means, wherein the monitor device monitors the emission direction of the eighth harmonic wave from the eighth harmonic wave forming optical element, The incident direction changing device changes the incident direction of the third fundamental wave to the eighth harmonic wave forming optical element.

  A fourth means for solving the above-described problems is that at least one laser light source that oscillates the first fundamental wave, the second fundamental wave, and the third fundamental wave, and amplifies the three fundamental waves, respectively. A plurality of optical fiber amplifiers, a plurality of delay devices for controlling the timing at which at least two of the three fundamental waves are incident on each of the optical fiber amplifiers, and a wavelength that is the first means or the third means A laser light source having a conversion optical system.

  A fifth means for solving the above-mentioned problems is a laser light source as the fourth means, a mask support part for holding a photomask provided with a predetermined exposure pattern, and an object for holding an exposure object. A holding unit, an illumination optical system that irradiates the photomask held by the mask support unit with ultraviolet light emitted from the laser light source, and the photomask that has passed through the illumination optical system. An exposure apparatus comprising: a projection optical system configured to irradiate an exposure object held by the object holding unit with irradiation light.

  A sixth means for solving the above-mentioned problems includes a laser light source as the fourth means, a support part for holding the test object, a detector for detecting light from the test object, and the laser. A test object inspection apparatus comprising: an illumination optical system that irradiates the test object with ultraviolet light emitted from a light source; and an optical system that guides light from the test object to the detector. .

  A seventh means for solving the above-described problem is a polymer crystal processing apparatus for processing a polymer crystal, the laser light source being the fourth means, and the laser light emitted from the laser light source. And an optical system that guides the polymer crystal as a workpiece and focuses the polymer crystal on a processing place of the polymer crystal, and a mechanism that changes a relative position between the optical system and the polymer crystal. This is a processing apparatus for polymer crystals.

  According to the present invention, a wavelength conversion optical system with a small change in the emission direction of output light, a laser light source using the same, an exposure device using the laser light source, a test object inspection device, and a polymer crystal A processing apparatus can be provided.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. Before that, FIG. 1 shows the principle of a method for controlling the emission direction of output light constant in the wavelength conversion optical system of the present invention. It explains using.

When light having a wavelength λ3 corresponding to the sum of these frequencies is generated from light having wavelengths λ1 and λ2, the phase matching condition in the wavelength conversion optical element is that the wave number vectors of the respective lights are K1, K2, and K3. and when,
K1 + K2 = K3
It becomes. This relationship is shown in FIG.

Here, it is assumed that the traveling direction of the generated light changes as shown in FIG. 1B and the wave vector K3 changes to K3 ′. At this time, consider a method of changing the wave number vector K2 ′ of the light of λ2 to K2 ″ and returning the wave number vector K3 ′ to the wave number vector K3.
K2 "= K3-K3 '+ K2'
If the direction is established, it can be adjusted. Changing the wave vector K2 ′ to K2 ″ can be realized by changing the incident direction of the incident light having the wavelength λ2.

  FIG. 2 is a diagram showing an outline of the wavelength conversion optical system and the optical system of the laser apparatus according to the embodiment of the present invention. In FIG. 2, a collimator lens and a condensing lens are indicated by an ellipse, and the description thereof is omitted. Further, P-polarized light is indicated by an arrow, S-polarized light is indicated by a dot with a circle, a fundamental wave is indicated by ω, and an n-fold wave is indicated by nω.

  In this embodiment, a fundamental wave (wavelength 1547 nm) emitted from one DFB laser (not shown) is divided into three and amplified by the first EDFA 1, the second EDFA 2, and the third EDFA 14, respectively. However, the fundamental waves emitted from the three DFB lasers may be amplified by EDFAs.

  As shown in FIG. 2, the P-polarized fundamental wave amplified by the first EDFA 1 is incident on the first second harmonic wave forming optical element (PPLN crystal) 3, and the first second harmonic wave forming optical element 3. , A double wave of P-polarized light is generated along with the fundamental wave. The fundamental wave and the second harmonic wave are incident on the third harmonic wave forming optical element (LBO crystal) 4. From the third harmonic wave forming optical element 4, a third harmonic wave of S-polarized light is generated together with the fundamental wave and the second harmonic wave. Note that the second harmonic wave forming optical element 3 is not limited to a PPLN crystal, and a PPKTP crystal, a PPSLT crystal, an LBO crystal, or the like can also be used.

  By passing these lights through the two-wavelength wave plate 5, only the second harmonic wave is converted into S-polarized light. As the two-wavelength wave plate, for example, a wave plate made of a uniaxial crystal flat plate cut parallel to the optical axis of the crystal is used. For light of one wavelength (double wave), the polarization is rotated, and for the light of the other wavelength, the thickness of the wavelength plate (crystal) is adjusted to that of one wavelength so that the polarization does not rotate. The light is cut to be an integral multiple of λ / 2, and the light of the other wavelength is cut to be an integral multiple of λ. Then, the second and third harmonic waves, both of which are S-polarized light, are incident on the fifth harmonic wave forming optical element (LBO crystal) 6. From the fifth harmonic wave forming optical element 6, the fifth harmonic wave of P-polarized light is generated together with the second and third harmonic waves. The fundamental wave of P-polarized light passes through the fifth harmonic wave forming optical element 6 as it is.

  The fifth harmonic wave generated from the fifth harmonic wave forming optical element 6 has an elliptical cross section because of a walk-off, and as it is, the light collecting property is poor and cannot be used for the next wavelength conversion. Therefore, this elliptical cross-sectional shape is shaped into a circular shape by the cylindrical lenses 7 and 8. As the fifth harmonic wave forming optical element 6, a BBO crystal or a CBO crystal can also be used.

  On the other hand, the P-polarized fundamental wave delayed by the first delay device 15 and amplified by the second EDFA 2 is incident on the second double wave forming optical element (PPLN crystal) 9 and the second double wave. From the wave forming optical element 9, a double wave of P-polarized light is generated together with the fundamental wave. Note that PPKTP crystal, PPSLT crystal, LBO crystal or the like may be used instead of the PPLN crystal. It is preferable that the conversion efficiency from the fundamental wave to the double wave is as high as possible and the durability is excellent.

  Further, the S-polarized fundamental wave delayed by the second delay device 16 and amplified by the third EDFA 14 is combined by the dichroic mirror 13 with the above-mentioned P-polarized double wave. In this example, the dichroic mirror 13 transmits the fundamental wave and reflects the second harmonic wave. The synthesized fundamental wave of S-polarized light and the second harmonic wave of P-polarized light are synthesized by the dichroic mirror 10 with the above-mentioned fifth harmonic wave of P-polarized light. In this example, the dichroic mirror 10 transmits the fundamental wave and the second harmonic wave and reflects the fifth harmonic wave. For this light synthesis, a bulk type optical element can be used. For example, a color separation / synthesis mirror (dichroic mirror), a reflection type and a transmission type diffractive optical element can be used.

  The combined fundamental wave of S-polarized light, second harmonic wave of P-polarized light, and fifth harmonic wave of P-polarized light are incident on the seventh harmonic wave forming optical element (CLBO crystal) 11, and the seventh harmonic wave forming optical element 11 A 7th harmonic wave of S-polarized light is generated. These lights are incident on an eighth harmonic wave forming optical element (CLBO crystal) 12 where the S-polarized fundamental wave and the S-polarized seventh harmonic wave are combined to generate a P-polarized eighth harmonic wave. If it is desired to separate only the 8th harmonic wave from the light of other wavelengths emitted from the 8th harmonic wave forming optical element 12, these may be separated by using a dichroic mirror, a polarization beam splitter, and a prism.

  A part of the eighth harmonic wave emitted from the eighth harmonic wave forming optical element 12 is separated by the half mirror 17 and enters the monitor device 18. The monitor device 18 has a position detection element such as a two-dimensional CCD, calculates the emission direction of the eighth harmonic wave from the position where the light is incident on these image pickup devices, and sends it to the emission light direction control device 19. The outgoing light direction control device 19 sends a command to the lens position control device 20 so that the emission direction of the eighth harmonic wave becomes a predetermined direction, changes the posture of the lens L, and the dichroic mirror 13 and the dichroic mirror 10. The incident direction of the fundamental wave incident on the eighth harmonic wave forming optical element 12 through the seventh harmonic wave forming optical element 11 is controlled. Thereby, based on the principle demonstrated using FIG. 1, it controls so that the emission direction of an 8th harmonic turns into a predetermined direction. Although not shown, a fundamental wave folding mirror may be disposed between the lens L and the dichroic mirror 13. In this case, by changing the attitude of this mirror, 8 The incident direction of the fundamental wave incident on the double wave forming optical element 12 may be controlled.

  In the above description, the wavelength conversion in the eighth harmonic wave forming optical element 12 has been described as an example. However, in the optical system shown in FIG. 2, by changing the incident direction of the second harmonic wave or the fifth harmonic wave, 7 It is also possible to control the emission direction of the seventh harmonic wave in the harmonic wave forming optical element 11.

  Next, an exposure apparatus 100 that is configured by using the laser apparatus 21 according to the embodiment of the present invention and that is used in a photolithography process that is one of semiconductor manufacturing processes will be described with reference to FIG. To do. The exposure apparatus used in the photolithography process is, in principle, the same as photolithography, and a device pattern precisely drawn on a photomask (reticle) is applied to a semiconductor wafer or glass substrate coated with a photoresist. Optically project and transfer onto

  In this exposure apparatus 100, the above-described laser device 21, illumination optical system 102, mask support table 103 that supports a photomask (reticle) 110, projection optical system 104, and semiconductor wafer 115 that is an exposure object are placed. The mounting table 105 to hold | maintain and the drive device 106 which moves the mounting table 105 horizontally are comprised.

  In this exposure apparatus 100, the laser beam output from the laser apparatus 21 described above is input to an illumination optical system 102 including a plurality of lenses, and passes through the photomask 110 that is supported by the mask support base 103. Irradiate the entire surface. The light irradiated in this way and passed through the photomask 110 has an image of a device pattern drawn on the photomask 110, and this light was placed on the mounting table 105 via the projection optical system 104. A predetermined position of the semiconductor wafer 115 is irradiated.

  At this time, the image of the device pattern of the photomask 110 is reduced on the semiconductor wafer 115 by the projection optical system 104 and imaged and exposed. According to the exposure apparatus as described above, it is possible to obtain an exposure apparatus that is small and has good maintainability and operability by making use of the characteristics of an ultraviolet light source that is small and light and has a high degree of freedom in arrangement.

  Next, a mask defect inspection apparatus configured using the laser apparatus 21 according to the present invention described above will be described below with reference to FIG. The mask defect inspection apparatus optically projects a device pattern precisely drawn on a photomask onto a TDI sensor (Time Delay and Integration), compares the sensor image with a predetermined reference image, and determines the pattern from the difference. Extract defects. The mask defect inspection apparatus 120 includes the laser device 21 described above, an illumination optical system 112, a mask support base 113 that supports the photomask 110, a drive device 116 that horizontally moves the mask support base, a projection optical system 114, And a TDI sensor 125.

  In this mask defect inspection apparatus 120, the laser beam output from the laser apparatus 21 described above is input to an illumination optical system 112 composed of a plurality of lenses, and is passed through the photo supported on the mask support 113. A predetermined area of the mask 110 is irradiated. The light thus irradiated and passed through the photomask 110 has an image of a device pattern drawn on the photomask 110, and this light is coupled to a predetermined position of the TDI sensor 125 via the projection optical system 114. Imaged.

  The horizontal movement speed of the mask support 113 and the transfer clock of the TDI 125 are synchronized. The test object is not limited to a mask, but is also used for inspection of a wafer, a liquid crystal panel, and the like. When the object to be inspected is a wafer, the reflected light from the wafer is detected to inspect the wafer for defects.

  FIG. 5 is a schematic diagram of a polymer crystal processing apparatus constructed using the laser apparatus 21 of the present invention. The ultraviolet short pulse laser beam 139 emitted from the laser device 21 is applied to the polymer crystal 138 placed in the sample container 136 via the shutter 132, the intensity adjusting element 133, the irradiation position control mechanism 134, and the condensing optical system 135. Focused irradiation. The sample container 136 is mounted on the stage 137 and can move in the three-dimensional direction of the x-axis, y-axis, and z-axis in the xyz orthogonal coordinate system with the optical axis direction as the z-axis, It can rotate around the z-axis. The processing of the polymer crystal is performed by the laser beam focused on the surface of the polymer crystal 138.

  By the way, when processing a workpiece which is a polymer crystal, it is necessary to confirm where the laser beam is irradiated on the workpiece. However, since laser light is usually not visible light and cannot be visually observed, it is preferably used in combination with an optical microscope.

  An example is shown in FIG. In the optical system shown in (a), the laser light from the ultraviolet short pulse laser system 141 (corresponding to reference numerals 21 and 132 to 134 in FIG. 7) is condensed at a predetermined point via the condensing optical system 135. . The stage 137 has a function as described with reference to FIG. 8, and a sample container 136 containing a polymer crystal 138 is placed on the stage 137. Visible light from the illumination light source 142 is reflected by the reflected light 143, and the sample container 136 is Koehler illuminated. The polymer crystal 138 is viewed by the eye 146 through the objective lens 144 and the eyepiece 145 of the optical microscope. A cross-shaped mark is formed at the optical axis position of the optical microscope so that the optical axis position can be visually observed.

  The focus position of the optical microscope (the in-focus position, that is, the object surface that is in focus when viewed) is fixed. The laser light condensed by the condensing optical system 135 is condensed at the optical axis position of the optical microscope and at the focal position of the optical microscope. Therefore, when a workpiece is placed on the stage 137 and the image is observed with an optical microscope, the laser beam from the laser system 141 is focused at a position that is in focus and at the center of the cross mark. It has come to be. The relative positional relationship among the laser system 141, the condensing optical system 135, and the optical microscope unit is fixed, and only the stage 137 is movable relative to these fixed systems.

  Therefore, by processing while moving the stage 137 so that the place to be processed is the optical axis position of the optical microscope and the in-focus position, the processing of the desired place and the processing of the desired shape are performed. be able to. If it is desired to perform processing automatically, an automatic focus adjustment device is attached to the optical microscope and the stage 137 is driven by the command, and a predetermined portion of the stage 137 is placed on the optical axis of the optical microscope. In this way, the stage 137 may be driven. Alternatively, the stage 137 may be driven two-dimensionally or three-dimensionally by a servo mechanism after the reference position is first adjusted.

  The laser device of the present invention can also be used for a laser treatment device, but the technique described in Patent Document 1 can be used as it is only with a different laser device, and therefore the description thereof is omitted.

It is a figure for demonstrating the principle of the method of controlling the emission direction of output light uniformly in the wavelength conversion optical system of this invention. It is a figure which shows the outline | summary of the wavelength conversion optical system which is embodiment of this invention, and the optical system of a laser apparatus. It is a figure which shows the outline | summary of the exposure apparatus using the laser apparatus which is embodiment of this invention. It is a figure which shows the outline | summary of the mask defect inspection apparatus using the laser apparatus which is embodiment of this invention. It is a figure which shows the outline | summary of the processing apparatus of the polymer crystal using the laser apparatus which is embodiment of this invention. It is a figure which shows the example which uses the processing apparatus of the polymer crystal using the laser apparatus which is embodiment of this invention in combination with an optical microscope.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st EDFA, 2 ... 2nd EDFA, 3 ... 1st 2nd wave generation optical element, 4 ... 3rd wave formation optical element, 5 ... 2 wavelength plate, 6 ... 5th wave formation optical element , 7 ... Cylindrical lens, 8 ... Cylindrical lens, 9 ... Second second harmonic forming optical element, 10 ... Dichroic mirror, 11 ... 7th harmonic forming optical element, 12 ... 8th harmonic forming optical element, 13 ... Dichroic mirror , 14 ... third EDAF amplifier, 15 ... first delay device, 16 ... second delay device, 17 ... half mirror, 18 ... monitor device, 19 ... outgoing light direction control device, 20 ... lens position control device

Claims (7)

  A wavelength conversion optical system that uses a wavelength conversion optical element to generate, from two incident light incident on the wavelength conversion optical element, an output light having a frequency that is the sum of the frequencies of the two lights, and outputs the light A monitoring device that monitors the direction of light, an incident direction changing device that changes an incident direction to the wavelength conversion optical element of at least one of the incident lights, and an emission direction of the emitted light monitored by the monitor device. A wavelength conversion optical system comprising: an outgoing light direction control device that operates the incident direction changing device so as to be constant.   The wavelength conversion optical system according to claim 1, wherein the first wavelength conversion optical system forms a fifth harmonic wave from the first fundamental wave through at least one wavelength conversion optical element, and the second fundamental wave. A second optical wave forming optical element that forms a second harmonic wave, a first optical member that combines a third fundamental wave and the second harmonic wave emitted from the second harmonic wave forming optical element in the same optical path; A second optical member that synthesizes the fundamental wave of 3 and the second harmonic wave emitted from the second harmonic wave forming optical element and the fifth harmonic wave emitted from the first wavelength conversion optical system in the same optical path; A seventh harmonic wave forming optical element that forms a seventh harmonic wave from the second harmonic wave and the fifth harmonic wave, and an eighth harmonic wave from the third fundamental wave and the seventh harmonic wave emitted from the seventh harmonic wave forming optical element. A wavelength conversion optical system, comprising:   3. The wavelength conversion optical system according to claim 2, wherein the monitor device monitors an emission direction of the eighth harmonic wave from the eighth harmonic wave forming optical element, and the incident direction changing device is the eighth magnification device. A wavelength conversion optical system characterized by changing the direction of incidence of the third fundamental wave on a wave forming optical element.   At least one laser light source that oscillates the first fundamental wave, the second fundamental wave, and the third fundamental wave, a plurality of optical fiber amplifiers that respectively amplify the three fundamental waves, and the three fundamental waves A laser light source comprising: a plurality of delay devices that respectively control the timing at which at least two fundamental waves of the light beams enter the optical fiber amplifiers; and the wavelength conversion optical system according to claim 2.   The laser light source according to claim 4, a mask support part for holding a photomask provided with a predetermined exposure pattern, an object holding part for holding an exposure object, and ultraviolet light emitted from the laser light source. An illumination optical system for irradiating the photomask held on the mask support part, and an exposure target held on the object holding part for irradiating the photomask via the illumination optical system and passing therethrough An exposure apparatus having a projection optical system for irradiating an object.   The laser light source according to claim 4, a support unit for holding the test object, a detector for detecting light from the test object, and irradiating the test object with ultraviolet light emitted from the laser light source. A test object inspection apparatus, comprising: an illumination optical system to be operated; and an optical system for guiding light from the test object to the detector.   A polymer crystal processing apparatus for processing a polymer crystal, wherein the laser light source according to claim 4 and laser light emitted from the laser light source are guided to a polymer crystal as a workpiece, An apparatus for processing a polymer crystal, comprising: an optical system that focuses light on a processing position of the molecular crystal; and a mechanism that changes a relative position between the optical system and the polymer crystal.

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