JP2006019365A - Ultraviolet laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prolong the exchanging cycle of a band-narrowed module by extending the service life of a band-narrowed element or a line selecting element contained in the band-narrowed module. <P>SOLUTION: The band-narrowed module is constituted of one or more prisms, a grating, and an enclosure which contains the band-narrowed elements and can be displaced and fixed freely in the facing direction of electrodes. The enclosure is provided with an opening through which light comes in and out of the enclosure and the lengths of the opening, prisms, and grating in the facing direction of the electrodes are made longer than the length of a beam profile in the facing direction of the electrodes by two or more times. Consequently, two or more light incident areas are formed in the facing direction of the electrodes on the diffracting surfaces of the prisms and grating. Each light incident area on the diffracting surface of the grating is checked for spectrum in combination with the light incident area of the corresponding prism, and the curvature of the area is adjusted in advance so that the area may obtain the optimum spectral characteristics. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultraviolet laser device used as a light source of a semiconductor exposure apparatus, and particularly to prolonging the service life of a narrowband element or line select element provided in the ultraviolet laser apparatus.

  As a light source of the semiconductor exposure apparatus, an ultraviolet laser apparatus such as a narrow band excimer laser apparatus, a line select fluorine molecular laser apparatus, or a narrow band fluorine laser apparatus is used. A lens optical system using calcium fluoride or quartz as a material is provided inside the semiconductor exposure apparatus. When this lens optical system is used for ultraviolet light, aberration becomes a problem. Therefore, it is necessary to reduce the problem of this aberration by narrowing the oscillation spectrum width of the ultraviolet laser used as the light source.

First, a narrow band excimer laser device will be described.
The narrow-band excimer laser device narrows a laser beam using a narrow-band device, such as a KrF excimer laser that oscillates in a wavelength band of about 248 nm or an ArF excimer laser that oscillates in a band of about 193 nm. A laser device. When the band is not narrowed, the oscillation spectrum width is about 300 pm, but by narrowing the band, the oscillation spectrum width can be narrowed to 1 pm or less, and further to 0.5 pm or less.

FIG. 8 is a plan view showing the configuration of the narrow-band excimer laser device.
The laser chamber 1 is metallic, and a laser gas serving as a laser medium is sealed inside. The laser gas is mainly composed of a gas such as a halogen gas, a buffer gas, or a rare gas. Fluorine gas (F2) is used as the halogen gas, and neon gas (Ne) is used as the buffer gas. In the case of a KrF excimer laser, krypton (Kr) is used as a rare gas, and in the case of an ArF excimer laser, argon (Ar) is used as a rare gas. A pair of discharge electrodes 3 facing each other is provided inside the laser chamber 1, and a high voltage pulse power source is provided outside. In FIG. 8, the pair of discharge electrodes 3 are arranged to face each other in the direction perpendicular to the drawing, and the high voltage pulse power source is not shown.

  CaF 2 windows 4 and 5 are provided on both sides (left and right in the drawing) of the laser chamber 1. On the optical axis on the window 4 side, a grating 26 having one or more (one in FIG. 8) prisms 25 and a diffraction surface 26a formed with a plurality of grooves parallel to each other is provided. Since the prism 25 has a function of expanding light emitted from the laser chamber 1 in a specific direction, it is also called a beam expander. The grating 26 has a function of reflecting light incident on the diffraction surface 26a in a direction corresponding to the wavelength. In other words, the grating 26 reflects light having a wavelength within a specific narrow band in a specific direction. According to such a configuration, only the light having a wavelength within a specific narrow band of the light emitted from the laser chamber 1 returns to the laser chamber 1 side again, and the prism 25 and the grating 26 are referred to as a narrow band element. A monitor box 8 incorporating a front mirror 7 is provided on the optical axis on the window 5 side. The prism 25, the grating 26, and the front mirror 7 constitute an optical resonator.

  Usually, the band narrowing elements such as the prism 25 and the grating 26 are included in the housing 20. This unit is referred to as a narrowband module 2. In the narrow-band module 2, the inside of the casing is purged with dry clean nitrogen gas or rare gas in order to discharge dust that causes damage to each optical element and oxygen that is a source of ozone generation out of the casing. The

  In addition, as a practical narrow band narrowing element, many are composed of a combination of a prism and a grating, but there are cases in which a combination of a prism and an etalon, a combination of an etalon and a grating, or the like is examined.

  Here, the operation of the narrow-band excimer laser device will be described with reference to FIG. When a current is supplied to the pair of discharge electrodes 3 from a high voltage pulse power source (not shown) and the voltage between the discharge electrodes 3 exceeds the breakdown voltage, a discharge occurs between the discharge electrodes 3 in the laser chamber 1. The laser gas is excited by this discharge, and light is generated when the state further shifts to the ground state. The light transmitted through the window 4 enters the prism 25. In the prism 25, the width of light is expanded in a predetermined direction. The light emitted from the prism 25 enters the diffraction surface 26 a of the grating 26. Of the light incident on the diffraction surface 26 a, only light having a wavelength within a specific narrow band is reflected to the laser chamber 1 side via the prism 25. The light that has returned to the laser chamber 1 passes through the window 5, enters the front mirror 7, and is reflected toward the laser chamber 1 side. Thus, the light reciprocates between the grating 26 and the front mirror 7 a plurality of times through the laser chamber 1. Meanwhile, the energy of the light having a wavelength in the specific narrow band is amplified, and when the energy reaches a certain level, the laser light is emitted from the front mirror 7.

In the following, the prior art related to the narrowband module will be additionally described.
As disclosed in Patent Document 1 below, when the angle formed by the prism and the optical axis is changed, the angle formed by the diffraction surface of the grating and the optical axis changes, and as a result, the wavelength of the laser light emitted from the front mirror changes. To do. Even if the angle of the grating itself is changed, the angle formed by the diffraction surface of the grating and the optical axis changes, so that the same result can be obtained. In addition, the configuration is such that the light emitted from the prism is reflected by the high reflection mirror and incident on the grating. Even if the angle formed by the high reflection mirror and the optical axis is changed, the angle formed by the diffraction surface of the grating and the optical axis is not changed. Because it varies, similar results are obtained.

  Even when the narrowband module is mounted on an excimer laser, the oscillation spectrum differs for each laser device, and variations in the oscillation center wavelength and spectrum width appear. The cause is individual differences in the prism and the grating itself. Yet another cause is that the distortion of the wavefront of the light incident on the prism differs for each laser device. It is estimated that the variation in the wavefront of light is caused by the variation in the discharge characteristics.

  Patent Document 2 below discloses a technique applied when a plurality of prisms are combined. When a band-narrowing module is configured by combining a plurality of prisms, spectral variations occur due to variations in the characteristics of the prisms themselves. Therefore, it is usually impossible to use the prisms that have been purchased in combination. The technique of Patent Document 2 measures the light transmission characteristics of a plurality of prisms individually in advance and predicts the light transmission characteristics when any three or four prisms are combined based on the individual measurement results. Among the results, a combination of prisms capable of obtaining a characteristic close to a desired light transmission characteristic is provided in the narrowband module. The band-narrowing module thus configured is mounted on the laser device.

  When laser oscillation is actually performed with a laser device equipped with a narrow band module and the spectrum of the output laser beam is checked, there may be a problem that a desired spectrum width cannot be obtained. Patent Document 3 below discloses a technique for obtaining a desired spectral width by finely adjusting the curvature of the diffraction surface of the grating.

  However, in order to check the spectrum of the output laser light as in the technique of Patent Document 3, a large-resolution spectroscope with high resolution is required. Since it is practically impossible to bring a large spectrometer into a semiconductor factory where a laser device is installed, it is not possible to perform a spectrum check at a semiconductor manufacturing factory. Therefore, it is necessary to check the spectrum by bringing the narrow-band module into the laser manufacturing factory.

  Checking operations at the laser manufacturing plant are necessary so that the checking light is incident on the narrowband module, the spectral characteristics of the light reflected from the module are measured, and the spectrum has a desired spectral width, etc. According to the procedure, the fine adjustment of the curvature of the diffraction surface of the grating is performed.

  Next, the line select fluorine molecular laser device will be described. Unlike the excimer laser device described above, the fluorine molecular laser device originally has a narrow band with an oscillation spectrum width of 1 pm or less. However, a plurality of oscillation spectra appear mainly with center wavelengths of about 157.5 nm and 157.6 nm. Therefore, the above-mentioned aberration is also a problem. In order to alleviate this problem, it is necessary to selectively oscillate any one of a plurality of oscillation spectra and suppress other oscillation spectra. A fluorine molecular laser device that realizes this is called a line select fluorine molecular laser device. The oscillation spectrum is selected using an optical element such as a prism or an etalon. These are called line select elements. In the fluorine molecular laser device, since the oscillation spectrum with the center wavelength of 157.6 nm has the maximum light energy, the oscillation spectrum is normally selectively oscillated to suppress other oscillation spectra.

  The narrow-band fluorine molecular laser device refers to a laser device that further reduces the aberration problem by further narrowing the spectrum width that selectively oscillates in the above-described line select fluorine molecular laser device. In order to narrow the spectrum width, a prism, an etalon, and a grating are used.

  By the way, the various ultraviolet laser devices described above output light having a wavelength of about 248 nm in the deep ultraviolet region and about 193 nm or about 157 nm in the vacuum ultraviolet region. It is known that when ultraviolet light having a large photon energy passes through various optical elements or is incident on and reflected from the surface, the light energy itself causes deterioration of the coating on the surface of the various optical elements. . As optical elements that deteriorate due to ultraviolet light, there are a window and various mirrors in addition to a band narrowing element and a line select element. If the laser oscillation can no longer satisfy the desired specifications due to the deterioration of these optical elements, the optical elements need to be replaced.

  At the time of exchanging the optical element of the excimer laser apparatus or the fluorine molecular laser apparatus, the laser oscillation is stopped, the optical element is removed from the laser apparatus, and a replacement operation for attaching a new optical element is performed. Semiconductor exposure processing is performed in a clean room of a semiconductor factory. However, if the above-described replacement operation is performed in a clean room, the cleanliness in the clean room may be reduced.

The following Patent Document 4 and Non-Patent Document 1 disclose a technique capable of maintaining the cleanliness in the clean room with respect to the window replacement work among the optical element replacement work.
In the technique of Patent Document 4, a rotatable window holder is provided in the laser chamber, and a large window is held by this window holder. At this time, a portion other than the central portion of the window is disposed on the optical axis to be a light transmitting portion. When the light transmission portion of the window deteriorates and the light transmittance decreases with the progress of laser oscillation, the window holder is rotated. Then, the light transmission part of the window located on the optical axis moves, and the other part is located on the optical axis.

  As another form, the laser chamber is provided with a rotatable window holder, and a plurality of windows are held by the window holder. At this time, only one of the windows is arranged on the optical axis. When the window deteriorates and the light transmittance decreases with the progress of laser oscillation, the window holder is rotated. Then, the window located on the optical axis moves, and the other windows are located on the optical axis.

  According to these two modes, since a large-scale part replacement operation is not necessary, the cleanliness in the clean room is maintained, and the window replacement operation is shortened.

In the technique of Non-Patent Document 1, a window holder that is slidable in a direction orthogonal to the light emission direction is provided. When replacing the window, the window is mounted on the window holder, and the window holder is slid to place the window on the optical axis. According to this configuration, an effect equivalent to that of Patent Document 4 can be obtained.
Japanese Patent No. 2631554 JP-A-11-214803 JP 2000-208848 A Japanese Utility Model Publication No. 1-65162 Lambda Physik catalog

  Of the optical elements used in the ultraviolet laser apparatus, the grating is severely deteriorated. On the other hand, when the minimum prism is provided in the vicinity of the laser chamber, the prism may be deteriorated due to the transmission of high-energy light. Therefore, the grating and prism also need to be replaced.

  Patent Document 4 describes that the technique may be applied to optical elements other than windows. However, there is a problem in diverting this technology to a narrow band element such as a grating or a prism or a line select element.

  The spectral characteristics of the laser device are affected by the combination of prism and grating. In order to obtain a desired spectral characteristic, it is necessary to select an appropriate prism and adjust the curvature of the diffraction surface of the grating corresponding to the prism. In reality, the spectrum of the band-narrowing module is checked at the laser manufacturing factory at the shipping stage of the laser device, the appropriate prism is selected, and the curvature of the grating for the selected prism is finely adjusted. The combination with the curvature of the grating is optimized.

  Here, it is assumed that Patent Document 4 is applied to a grating. In this case, the grating is displaced instead of the window. Then, the relative positional relationship between the grating and the prism changes. The characteristics of the grating vary (distribution) even within the same diffraction plane. For this reason, the relationship between the optimized prism and the grating is broken due to the displacement of the grating, and the spectral characteristics may be changed. For this reason, the technique of Patent Document 4 cannot be simply applied to the grating.

  Therefore, conventionally, it has been considered that a means of replacing parts is appropriate for the deterioration of the grating and the prism. However, if these optical elements are exchanged individually, a spectrum check of the band-narrowing module is required each time the optical elements are exchanged. As described above, the spectrum check must be performed at the laser manufacturing plant. This is a very cumbersome task. Therefore, in practice, a new spectrum-checked narrowband module is stored in the laser manufacturing factory, and workers go to the semiconductor factory as needed to replace the old narrowband module with a new narrowband module. Is done.

  Replacing the conventional narrowband module requires labor. Furthermore, if an expensive optical element such as a grating or a prism is replaced, the cost increases. These problems are reduced if the exchange period of the narrowband module is long.

  The present invention has been made in view of such a situation, and it is an object of the present invention to extend the service life of a narrowband element or a line select element included in a narrowband module and lengthen the replacement period of the narrowband module. It is what.

The first invention is
A laser chamber having a pair of opposed discharge electrodes therein and a laser medium;
An optical resonator including one or more prisms and a grating having a diffractive surface formed with a plurality of grooves parallel to each other, and
A laser beam is emitted from the laser chamber in a direction perpendicular to the electrode facing direction, the laser beam is enlarged by the prism, is incident on the diffraction surface of the grating, and is a predetermined wavelength band among the laser beams reflected by the diffraction surface. In the ultraviolet laser apparatus in which only the laser beam is returned to the laser chamber through the prism,
The prism is included so that the electrode facing direction and the light expansion direction of the prism are orthogonal to each other, the grating is included so that the electrode facing direction and the groove direction of the grating are parallel, and laser light enters and exits. A housing having an opening and being displaceable in the electrode facing direction with respect to the laser chamber and being fixed at a predetermined position;
The length of the opening, the prism and the grating in the electrode facing direction is at least twice as long as the length of the beam profile in the electrode facing direction, and two or more light incident areas located on the diffraction surface of the grating It is characterized in that each curvature is adjusted.

  In the first invention, a band narrowing module is constituted by one or more prisms, a grating, and a casing that includes these band narrowing elements and that can be displaced and fixed in the direction of electrode facing. The housing is provided with an opening through which laser light enters and exits, and the length of the opening, the prism and the grating in the electrode facing direction is at least twice as long as the length of the laser light beam profile in the electrode facing direction. . Then, two or more light incident areas are formed in the direction of electrode facing on the diffraction surfaces of the prism and the grating. Each light incident area of the diffraction surface of the grating is subjected to a spectrum check in combination with the light incident area of the corresponding prism, and the curvature is adjusted in advance so that optimum spectral characteristics can be obtained.

  Regarding the usage of the first invention, assuming that the electrode facing direction is the vertical direction, and that the vertical length of each band-narrowing element is approximately twice the beam profile to form two light incident regions. explain. For example, first, the case is placed in the upper position to perform laser oscillation. The laser light is incident on a light incident area below the prism or grating. Then, the lower side of each narrow-band element deteriorates. When the desired spectral characteristics cannot be obtained, the case is placed in the lower position and laser oscillation is performed. The laser light is incident on the light incident area on the upper side of the prism or grating. When the desired spectral characteristics cannot be obtained, a new band narrowing module is replaced.

The second invention is the first invention,
A housing driving means for driving the housing in the electrode facing direction is provided.

  In the second invention, the housing is driven in the electrode facing direction by the motor (housing driving means).

The third invention is
A laser chamber having a pair of opposed discharge electrodes therein and a laser medium;
An optical resonator including one or more prisms and a grating having a diffractive surface formed with a plurality of grooves parallel to each other, and
A laser beam is emitted from the laser chamber in a direction perpendicular to the electrode facing direction, the laser beam is enlarged by the prism, is incident on the diffraction surface of the grating, and is a predetermined wavelength band among the laser beams reflected by the diffraction surface. In the ultraviolet laser apparatus in which only the laser beam is returned to the laser chamber through the prism,
The prism is included so that the electrode facing direction and the light expansion direction of the prism are orthogonal to each other, the grating is included so that the electrode facing direction and the groove direction of the grating are parallel, and laser light enters and exits. A housing having an opening;
The length of the grating in the electrode facing direction is at least twice as long as the length of the beam profile in the electrode facing direction, and two or more light incident areas located on the diffraction surface of the grating are each adjusted in curvature. Further, the grating itself is displaceable in the electrode facing direction in the casing and can be fixed at a predetermined position.

  In the third invention, a band-narrowing module is constituted by one or more prisms, a grating that can be freely displaced and fixed in the electrode facing direction, and a housing that contains these band-narrowing elements. The housing is provided with an opening through which laser light enters and exits. The length of the grating in the electrode facing direction is at least twice as long as the length of the laser beam beam profile in the electrode facing direction. Then, two or more light incident regions are formed on the diffraction surface of the grating in the electrode facing direction. Each light incident area of the diffraction surface of the grating is subjected to a spectrum check in combination with the light incident area of the prism, and the curvature is adjusted in advance so as to obtain optimum spectral characteristics.

  The usage of the third invention will be described on the assumption that the electrode facing direction is the up-down direction and the length of the grating in the up-down direction is about twice the beam profile to form two light incident regions. For example, the laser is first oscillated by placing the grating in the upper position. The laser light is incident on the light incident area below the grating. Then, the lower side of the grating deteriorates. If the desired spectral characteristics cannot be obtained, the grating is placed at the lower position and laser oscillation is performed. The laser light is incident on the light incident area on the upper side of the grating. When the desired spectral characteristics cannot be obtained, a new band narrowing module is replaced.

The fourth invention is the third invention,
Grating driving means for driving the grating in the electrode facing direction is provided.

  In the fourth invention, the grating is driven in the electrode facing direction by the motor (housing driving means).

5th invention is 1st, 3rd invention,
The grating is composed of a plurality of grating groups overlapping in the electrode facing direction.

  In the fifth invention, a plurality of gratings are stacked in the electrode facing direction, and a long grating group is formed in the electrode facing direction. Each of the plurality of gratings has a light incident region, and the curvature is individually adjusted. This grating group can obtain the same effect as a single grating that is long in the electrode facing direction.

  According to the present invention, since the band narrowing element or the line select element is provided with two or more light incident areas whose curvatures are individually adjusted, even if one light incident area deteriorates, other light incident areas are not affected. Available. In this way, since the service life of one narrow band element can be extended, the replacement period of the narrow band module is doubled or more. Therefore, it is possible to reduce the cost required for the replacement work of the narrowband module, and to reduce the labor of the worker who performs the replacement work of the narrowband module.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In each embodiment of the present specification, the ultraviolet laser is a narrow band excimer laser device using a prism and a grating as a narrow band element.

  FIG. 1 is a front view showing a configuration of a narrow-band excimer laser device. FIG. 2 is a diagram showing the band narrowing module fixed at the upper fixed position. FIG. 3 is a diagram showing the band narrowing module fixed at the lower fixed position. 2 (a) and 3 (a) show a cross section viewed from the front, and FIGS. 2 (b) and 3 (b) show AA shown in FIGS. 2 (a) and 3 (a). A cross section in the plane is shown. FIG. 1 shows the arrangement of a pair of discharge electrodes 3 provided in the laser chamber.

  As shown in FIG. 1, the laser chamber 1 is placed on the pedestal 6, and the front mounting plate 40 and the rear mounting plate 30 are fixed upright in the vertical direction. The monitor box 8 is fixed to the front mounting plate 40. The band narrowing module 2 is fixed to the rear mounting plate 30. In the present embodiment, the vertical direction and the electrode facing direction of the pair of discharge electrodes 3 in the laser chamber 1 are parallel to each other. Therefore, in the following, this electrode facing direction is referred to as the vertical direction.

  As shown in FIGS. 2A and 2B and FIGS. 3A and 3B, the rear mounting plate 30 has a light passage port 31 therethrough and a screw thread from the narrowband module 2 side. A plurality of female screw portions that can be freely combined are provided. The light passage port 31 is located on the optical axis of the laser light L emitted from the laser chamber 1. Two fixing positions of the band narrowing module 2 are provided on the rear mounting plate 30 in the vertical direction. The distance at which the two fixed positions are separated is at least twice as long as the length of the beam profile of the laser beam L in the vertical direction (hereinafter simply referred to as “the length of the beam profile”). Each fixing position is determined by a female screw portion. Four upper female screw portions 32U are threaded at the upper fixed position, and four lower female screw portions 32L are threaded at the lower fixed position. The relative positional relationship between the upper female screw portion 32U and the relative positional relationship between the lower female screw portion 32L and each other are the same.

  The band-narrowing module 2 includes a prism 25 fixed to a pedestal 27, a grating 26 fixed to the pedestal 28, and a housing 20 containing these. The housing | casing 20 is a substantially six-sided box shape which has three sets of surfaces which mutually oppose. One of them is fixed in close contact with the rear mounting plate 30. Therefore, the plate forming this one surface is referred to as a mounting surface side plate 21. The mounting surface side plate 21 is longer in the vertical direction than the facing surface. This vertically long part is referred to as edge 23. Two holes 24 are provided in the upper and lower edges 23, respectively. Therefore, the mounting surface side plate 21 is provided with four holes 24. The relative positional relationship of the holes 24 with respect to each other is the same as the relative positional relationship between the upper female screw portion 32U and the lower female screw portion 32L provided in the rear mounting plate 30. The mounting surface side plate 21 is provided with a light passage port 22 therethrough. The length of the light passage opening 22 in the vertical direction (hereinafter simply referred to as “the length of the light passage opening 22”) is longer than the length of the beam profile of the laser light L by at least twice.

  FIG. 4 is a perspective view showing an example of the arrangement of prisms and gratings. FIG. 4 shows a state in which the two upper and lower laser beams L are incident on the prism 25 and the grating 26. However, these two laser beams L are shown for explanation, and actual laser oscillation is performed. Then, only one of the upper and lower laser beams L enters the prism 25 and the grating 26.

  The prism 25 is arranged so that its light expansion direction and the vertical direction are orthogonal to each other. The angle in the horizontal plane perpendicular to the vertical direction is adjusted so as to obtain a desired spectral characteristic. The grating 26 is provided with a large number of grooves parallel to each other on the diffraction surface 26a, and is arranged on the optical axis of the laser light emitted from the prism 25 so that the groove direction and the vertical direction are parallel to each other. The prism 25 and the grating 26 are fixed at the same height position. The lengths of the prism 25 and the grating 26 in the vertical direction (hereinafter simply referred to as “the length of the prism 25 and the grating 26”) HP and HG are two or more times longer than the length HL of the beam profile of the laser beam L. For this reason, two incident areas (light incident areas) A1 and A2 of the laser beam L are formed on the prism 25 in the upper and lower directions. Similarly, an incident area (light incident area) B1 of the laser beam L is formed on the diffraction surface 26a of the grating 26. , B2 are formed two above and below.

  Although omitted in FIGS. 2 to 4, the grating 26 is provided with a mechanism for adjusting the curvature.

  FIG. 5 is a diagram showing a grating curvature adjustment mechanism. FIG. 5A shows a state where the grating is pressed, and FIG. 5B shows a state where the grating is pulled.

  The curvature adjusting mechanism 50 includes a support member 51 that supports both side surfaces of the grating 26, a gripping member 52 that grips the upper and lower central portions of the grating 26, and a central portion of the grating 26 that is pushed or pulled via the gripping member 52. It consists of a spring 53 and a pushing member 54 that move in the direction.

  As shown in FIG. 5A, when the pushing member 54 is moved in the pushing direction, the central portion of the grating 26 is pushed, and the diffractive surface 26a is formed into a convex surface. As shown in FIG. 5B, when the pushing member 54 is moved in the pulling direction, the central portion of the grating 26 is pulled, and the diffractive surface 26a is formed into a concave surface. When the pressing member 54 is fixed, the curvature of the grating 26 is maintained. The curvature adjustment mechanism 50 enables high-precision adjustment in nanometer units. The curvature of the diffractive surface 26a is adjusted in advance for each light incident region using the curvature adjusting mechanism 50. This curvature adjustment will be described later.

  A plurality of prisms may be provided in the housing 20, and a total reflection mirror may be provided between the prism 25 and the grating 26. In such a case, the vertical lengths of the plurality of prisms and total reflection mirrors need to be longer than the length of the beam profile of the laser light L by at least twice.

Here, the curvature adjustment of the grating 26 will be described.
When the band narrowing module 2 is configured, spectrum check is performed by combining a desired prism 25 and a grating 26.

  First, the band narrowing module 2 is arranged so that the check light is incident on the lower light incident area of the prism 25 and the lower light incident area of the grating 26. Then, the check light is emitted into the narrowband module 2 and the spectral characteristics of the light returning from the narrowband module 2 are measured. The curvature of the diffraction surface 26a of the grating 26 is adjusted as necessary so that the spectrum has a desired spectral width or the like. In this way, the spectral characteristics obtained by the combination of the lower side of the prism 25 and the lower side of the grating 26 are brought into an optimum state.

  Subsequently, the band narrowing module 2 is arranged so that the check light is incident on the light incident area on the upper side of the prism 25 and the light incident area on the upper side of the grating 26. Then, the check light is emitted into the narrowband module 2 and the spectral characteristics of the light returning from the narrowband module 2 are measured. The curvature of the diffraction surface 26a of the grating 26 is adjusted as necessary so that the spectrum has a desired spectral width or the like. By doing so, the spectral characteristics obtained by the combination of the upper side of the prism 25 and the upper side of the grating 26 are brought into an optimum state.

  When the spectral characteristics obtained by the upper combination of the narrowband elements 25 and 26 are optimized, the spectral characteristics obtained by the lower combination of the narrowband elements 25 and 26 are also optimal. Most preferred. However, since an actual optical element has a variation (distribution) in characteristics even with one part name, this is not necessarily the case. In such a case, both the spectral characteristics obtained by the upper combination of the narrowband elements 25 and 26 and the spectral characteristics obtained by the lower combination of the narrowband elements 25 and 26 are obtained by the narrowband module. It is sufficient to find an adjustment point that falls within the specification range of 2.

  The above spectrum check is performed at the laser manufacturing factory prior to shipment of the narrowband module 2. In addition, the order of the check in the combination above the narrow band narrowing elements 25 and 26 and the check in the combination below the narrow band narrowing elements 25 and 26 may be reversed.

  Next, the fixing operation of the band narrowing module 2 and the changing operation of the fixing position will be described.

  The band narrowing module 2 is fixed to the rear mounting plate 30. For example, as shown in FIGS. 2A and 2B, the band narrowing module 2 is fixed at the upper fixed position. When the band narrowing module 2 is fixed to the upper fixed position of the rear mounting plate 30, the positions of the four holes 24 and the four upper female screw portions 32U are aligned, the male screw 18 is inserted into the hole 24, and the upper female Screwed onto the screw portion 32U. When the four male screws 18 are screwed into the upper female screw portions 32 </ b> U, the band narrowing module 2 is fixed to the rear mounting plate 30.

  When laser oscillation is performed, the laser light L passes through the lower part of the light passage opening 22 of the housing 20, passes through the lower part of the prism 25, and enters the lower part of the grating 26. When laser oscillation is repeated in this state, the band-narrowing element, particularly the lower portion of the grating 26, is significantly deteriorated. When parameters such as the spectrum width do not satisfy the specification due to the deterioration of the band narrowing element, the fixed position of the band narrowing module 2 is changed.

  In this case, as shown in FIGS. 3A and 3B, the band-narrowing module 2 is fixed at the lower fixed position. When the narrow band module 2 is fixed at the lower fixed position of the rear mounting plate 30, first, the male screw 18 screwed into each upper female thread portion 32U is removed, and the narrow band module 2 is translated downward. To do. Then, the positions of the four holes 24 and the four lower female screw portions 32L are aligned, the male screw 18 is inserted into the hole 24, and further screwed into the lower female screw portion 32L. When the four male screws 18 are screwed into the lower female screw portions 32 </ b> L, the band narrowing module 2 is fixed to the rear mounting plate 30.

  When laser oscillation is performed, the laser light L passes through the upper part of the light passage port 22 of the housing 20, passes through the upper part of the prism 25, and enters the upper part of the grating 26. If laser oscillation is repeated in this state, the band-narrowing element, particularly the upper portion of the grating 26, is significantly deteriorated. When parameters such as the spectrum width do not satisfy the specifications due to the deterioration of the narrow band element, the narrow band module 2 itself is replaced.

  A positioning pin that contacts the housing 20 to position the band-narrowing module 2 may be provided so as to be freely inserted into and removed from the rear mounting plate 30. In this case, the rear mounting plate 30 is perforated with an upper positioning hole and a lower positioning hole. When the narrow band module 2 is fixed to the upper fixing position, the positioning pin is inserted into the upper positioning hole, and the edge 23 of the housing 20 is brought into contact with the positioning pin. When the band narrowing module 2 is fixed at the lower fixing position, the positioning pin is inserted into the lower positioning hole, and the edge 23 of the housing 20 is brought into contact with the positioning pin.

  In the above, an example has been described in which the band narrowing module 2 is fixed to the lower fixed position after being attached to the upper fixed position, but the order of the upper and lower fixed positions may be reversed.

  Note that the end portions of the band-narrowing elements such as the prism 25 and the grating 26 may have a processing distortion or a poor surface coating state. For this reason, it is preferable that the end portion of the band narrowing element is not included in the light incident region. For this reason, it is preferable to make the lengths of the prism and grating longer than the length of the beam profile of the laser beam L by + α or more.

  In the present embodiment, an example in which two fixed positions are provided is shown, but it is not necessary to determine the number thereof. When N fixed positions are provided, the lengths of the light passage opening 22, the prism 25, and the grating 26 of the housing 20 are made longer than the length of the beam profile of the laser light L by N times or more, and the rear mounting plate 30. N sets of female screw portions may be provided.

  In the present embodiment, the lengths of the prism 25 and the grating 26 are longer than the length of the beam profile of the laser beam L. However, a narrow band module may be configured by preparing a plurality of prisms and gratings whose length in the vertical direction is substantially equal to the length of the beam profile of the laser beam L and stacking these in the vertical direction. In this case, curvature adjustment may be performed for each grating in combination with a corresponding prism.

  According to the present embodiment, since the band narrowing element or the line select element is provided with two or more light incident areas whose curvatures are individually adjusted, even if one light incident area deteriorates, another light incident area Can be used. That is, the service life of one narrow band narrowing element can be extended. Therefore, the exchange period of the narrowband module is more than doubled. Therefore, it is possible to reduce the cost required for the replacement work of the narrowband module, and to reduce the labor of the worker who performs the replacement work of the narrowband module.

  As described above, the adjustment of the narrow-band module must be performed at the laser manufacturing factory. For this reason, for example, when a laser apparatus is shipped from a laser manufacturing factory in one country to countries around the world, an operator must bring the adjusted narrow-band module to the site and perform an exchange operation. Such work requires time and cost. According to the present invention, since the replacement work itself is ½ or less, time and cost burden can be greatly reduced.

  In the first embodiment, the fixed position of the band narrowing module 2 is determined by setting the screw position. On the other hand, in the second embodiment, the band narrowing module 2 is driven by the motor in the vertical direction, and the fixed position of the band narrowing module 2 is determined by setting the stop position of the motor. Only the points different from the first embodiment will be described below.

  FIG. 6 is a diagram showing a narrow-band module that can be displaced in the vertical direction. 6 (a) shows a cross section viewed from the front, FIG. 6 (b) shows a cross section along the plane AA shown in FIG. 6 (a), and FIG. 6 (c) shows a plan view. Has been.

  Two linear guides 60 are provided between the rear mounting plate 30 and the mounting surface side plate 21 of the housing 20. The linear guide 60 is fixed to the rear mounting plate 30 and the mounting surface side plate 21 with its longitudinal direction parallel to the vertical direction.

  A motor 61 is fixed to the rear mounting plate 30. The rotation shaft of the motor 61 is connected to the housing 20 via a ball screw 62. The ball screw 62 includes a rotating part 62 a including a screw and a linearly moving part 62 b including a nut. The rotating part 62 a is connected to the rotation shaft of the motor 61, and the linearly moving part 62 b is connected to the housing 20.

  When the rotating shaft of the motor 61 rotates, the rotating part 62a rotates. In response to this rotational movement, the linear motion part 62b linearly moves in the vertical direction. The band-narrowing module 2 operates in the vertical direction along with the vertical movement of the linear motion part 62b. The band narrowing module 2 is guided in the vertical direction by the linear guide 60.

  As shown in FIG. 6B, the rear mounting plate 30 is provided with an upper limit switch 65 and a lower limit switch 66. The upper limit switch 65 and the lower limit switch 66 detect the upper surface position of the mounting surface side plate 21 of the housing 20. When the upper limit switch 65 detects that the upper surface of the mounting surface side plate 21 has reached the set upper limit position, the upper limit switch 65 outputs a motor stop signal to a controller (not shown). Upon receiving this signal, the controller stops the operation of the motor 61. When the lower limit switch 66 detects that the upper surface of the mounting surface side plate 21 has reached the set lower limit position, the lower limit switch 66 outputs a motor stop signal to a controller (not shown). Upon receiving this signal, the controller stops the operation of the motor 61.

  The fixed position of the band narrowing module 2 is determined by the upper limit position set by the upper limit switch 65 and the lower limit position set by the lower limit switch 66. The length of separation between the upper limit position and the lower limit position is twice or more longer than the length of the beam profile of the laser beam L.

  The work for changing the fixing position of the band-narrowing module 2 does not require the screw attachment and removal work performed in the first embodiment, and is performed only by operating and stopping the motor 61.

  In the present embodiment, an example in which two fixed positions are provided is shown, but it is not necessary to determine the number thereof. If N fixed positions are required, the lengths of the light passage port 22, the prism 25, and the grating 26 of the housing 20 may be longer than the length of the beam profile of the laser beam L by at least N times. N Mitt switches may be provided.

  According to this embodiment, the same effect as that of the first embodiment can be obtained. Further, the use of a motor or limit switch makes it easier to change the fixed position of the narrowband module.

  In the first and second embodiments, the fixed position of the band narrowing module 2 is changed. In the third embodiment, the fixed position of the grating is changed. Below, it demonstrates centering on a different point from 1st, 2nd embodiment.

FIG. 7 is a diagram showing a narrow-band module including a grating that can be displaced in the vertical direction. FIG. 7 shows a cross section viewed from the front.
The band-narrowing module 72 includes a prism 75 fixed to the pedestal 77, a grating 76 fixed to the pedestal 78, and a housing 70 containing these. The length of the grating 76 in the electrode facing direction is at least twice as long as the length of the beam profile in the electrode facing direction. The housing 70 is detachably fixed at a predetermined position on the rear mounting plate 80.

  A motor 91 is provided outside the housing 70. The rotating shaft of the motor 91 is connected to a base 78 of the grating 76 via a ball screw 92. The ball screw 92 includes a rotating part 92a including a screw and a linearly moving part 92b including a nut. The rotating part 92a is connected to a rotation shaft of the motor 91, and the linearly moving part 92b is connected to a pedestal 78. Since the rotating portion 92 a of the ball screw 92 is inserted into the housing 70, the grating 76 inside the housing 70 can be displaced up and down by a motor 91 outside the housing 70.

  Although not shown in FIG. 7, a limit sensor that detects an upper limit position and a lower limit position of any of the grating 76, the pedestal 78, and the rotating portion 92 a of the ball screw 92 is provided in the housing 70.

Here, the curvature adjustment of the grating 76 will be described.
When the narrow-band module 72 is configured, spectrum check is performed by combining a desired prism 75 and a grating 76.

  First, the band narrowing module 72 is arranged so that the check light enters the light incident area of the prism 75 and the light incident area below the grating 76. Then, the check light is emitted into the narrowband module 72, and the spectral characteristics of the light returning from the narrowband module 72 are measured. The curvature of the diffraction surface of the grating 76 is adjusted as necessary so that the spectrum has a desired spectral width or the like. By doing so, the spectral characteristics obtained by the combination of the prism 75 and the lower side of the grating 76 are optimized.

  Subsequently, the band narrowing module 72 is arranged so that the check light is incident on the light incident area of the prism 75 and the light incident area on the upper side of the grating 76. Then, the check light is emitted into the narrowband module 72, and the spectral characteristics of the light returning from the narrowband module 72 are measured. The curvature of the diffraction surface of the grating 76 is adjusted as necessary so that the spectrum has a desired spectral width or the like. By doing so, the spectral characteristics obtained by the upper combination of the prism 75 and the grating 76 are optimized.

  When the spectral characteristic obtained by the upper combination of the prism 75 and the grating 76 is set to the optimum state, the spectral characteristic obtained by the lower combination of the prism 75 and the grating 76 is most preferably in the optimum state. However, since an actual optical element has a variation (distribution) in characteristics even with one part name, this is not necessarily the case. In such a case, both the spectral characteristics obtained by the upper combination of the prism 75 and the grating 76 and the spectral characteristics obtained by the lower combination of the prism 75 and the grating 76 fall within the specification range of the narrowband module 72. What is necessary is just to find such an adjustment point.

  The above spectrum check is performed at the laser manufacturing factory prior to shipment of the narrowband module 72. Further, the order of the check in the upper combination of the prism 75 and the grating 76 and the check in the lower combination of the prism 75 and the grating 76 may be reversed.

  In the present embodiment, an example in which two fixed positions are provided is shown, but it is not necessary to determine the number thereof. When N fixed positions are required, the length of the grating 76 may be longer than the length of the beam profile of the laser light L by N times or more, and only N mitt switches may be provided.

  According to this embodiment, the same effect as that of the first embodiment can be obtained. Further, the use of a motor or limit switch makes it easier to change the fixed position of the narrowband module.

FIG. 1 is a front view showing a configuration of a narrow-band excimer laser device. FIG. 2 is a diagram showing the band narrowing module fixed at the upper fixed position. FIG. 3 is a diagram showing the band narrowing module fixed at the lower fixed position. FIG. 4 is a perspective view showing an example of the arrangement of prisms and gratings. FIG. 5 is a diagram showing a grating curvature adjustment mechanism. FIG. 6 is a diagram showing a narrow-band module that can be displaced in the vertical direction. FIG. 7 is a diagram showing a narrow-band module including a grating that can be displaced in the vertical direction. FIG. 8 is a plan view showing the configuration of the narrow-band excimer laser device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser chamber 2, 72 ... Narrow-band module 3 ... Discharge electrode 18 ... Male screw 20, 70 ... Case 22 ... Light passage port 24 ... Hole 25, 75 ... Prism 26, 76 ... Grating 30, 80 ... Back mounting Plate 32U ... Upper female screw portion 32L ... Lower female screw portion 61, 91 ... Motor 62, 92 ... Ball screw 62a, 92a ... Turning portion 62b, 92b ... Linear motion portion 65 ... Upper limit switch 66 ... Lower limit switch

Claims (5)

A laser chamber having a pair of opposed discharge electrodes therein and a laser medium;
An optical resonator including one or more prisms and a grating having a diffractive surface formed with a plurality of grooves parallel to each other, and
A laser beam is emitted from the laser chamber in a direction perpendicular to the electrode facing direction, the laser beam is enlarged by the prism, is incident on the diffraction surface of the grating, and is a predetermined wavelength band among the laser beams reflected by the diffraction surface. In the ultraviolet laser apparatus in which only the laser beam is returned to the laser chamber through the prism,
The prism is included so that the electrode facing direction and the light expansion direction of the prism are orthogonal to each other, the grating is included so that the electrode facing direction and the groove direction of the grating are parallel, and laser light enters and exits. A housing having an opening and being displaceable in the electrode facing direction with respect to the laser chamber and being fixed at a predetermined position;
The length of the opening, the prism and the grating in the electrode facing direction is at least twice as long as the length of the beam profile in the electrode facing direction, and two or more light incident areas located on the diffraction surface of the grating An ultraviolet laser device characterized in that each curvature is adjusted. The ultraviolet laser device according to claim 1, further comprising housing driving means for driving the housing in the electrode facing direction. A laser chamber having a pair of opposed discharge electrodes therein and a laser medium;
An optical resonator including one or more prisms and a grating having a diffractive surface formed with a plurality of grooves parallel to each other, and
A laser beam is emitted from the laser chamber in a direction perpendicular to the electrode facing direction, the laser beam is enlarged by the prism, is incident on the diffraction surface of the grating, and is a predetermined wavelength band among the laser beams reflected by the diffraction surface. In the ultraviolet laser apparatus in which only the laser beam is returned to the laser chamber through the prism,
The prism is included so that the electrode facing direction and the light expansion direction of the prism are orthogonal to each other, the grating is included so that the electrode facing direction and the groove direction of the grating are parallel, and laser light enters and exits. A housing having an opening;
The length of the grating in the electrode facing direction is at least twice as long as the length of the beam profile in the electrode facing direction, and two or more light incident areas located on the diffraction surface of the grating are each adjusted in curvature. The ultraviolet laser device characterized in that the grating itself is displaceable in the electrode-facing direction within the casing and can be fixed at a predetermined position. The ultraviolet laser device according to claim 3, further comprising a grating driving unit that drives the grating in the electrode facing direction. The ultraviolet laser device according to claim 1, wherein the grating is composed of a plurality of grating groups overlapping in the electrode facing direction.

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