WO1991001579A1 - Narrow-band oscillation excimer laser and wavelength detector - Google Patents

Abstract

A narrow-band oscillation excimer laser that can be suitably used as a source of light of a reduced projection exposing device for producing semiconductor devices, and a wavelength detector. In this laser, the direction along the lines of the grating is brought nearly into agreement with the direction of beam expansion by a prism expander, and a polarizer element is disposed in an optical resonator to selectively generate linearly polarized waves nearly in parallel with the direction of beam expansion. Further, a rear-side or a front-side window in a laser chamber is so arranged that a Brewster's angle is nearly obtained with respect to an ooptical axis of the laser within a plane defined by the direction of beam expansion and the optical axis. Moreover, on one surface of the prism constituting the prism beam expander is formed a reflection-preventing film that selectively prevents the reflection of only the polarized component which is nearly in parallel with the direction of beam expansion. The device for detecting the wavelength of the narrow-band oscillation excimer laser permits reference light emitted from a reference source and light to be detected to fall on an etalon, introduces light through an etalon to an optical system for converging the light to form an image on the detecting surface of a light detector, and determines the wavelength of the laser beam from the interference fringe detected by the light detector.

Description

 Excise Laser and Wavelength Detector Technology

 The present invention relates to a narrow-band oscillation excimer laser and a wavelength detector, and is particularly suitable for use as a light source for a reduction projection exposure apparatus for manufacturing semiconductor devices. . Background technology

 Attention has been paid to excimer lasers as light sources for reduction projection exposure apparatuses (hereinafter referred to as steppers) for manufacturing semiconductor devices. Because the wavelength of the excimer laser is short (KrF wavelength is about 248.4 nm), it is possible to extend the limit of light exposure to 0.5 m or less. If the resolution is the same as that of the mercury lamp, the depth of focus and the number of apertures (NA) of the lens will be deeper than the conventional mercury lamp g-line and i-line. It is possible to expect many excellent advantages, such as a small exposure area, a large exposure area, and a large power. .

 At this point, an excimer laser used as a light source for a stepper is required to have a narrow band with a line width of 3 pm or less, and a large force is required. Output power is required.

The technique of excimer laser narrowing is the power that has been conventionally called the locking lock method. This According to the above-mentioned absorption-pick-up method, a wavelength selection element (etalon, diffraction grating, prism, etc.) is arranged in a capaci- ty at the stage of an oscillation, and the pixel is picked up. The space mode is restricted by the hall, and this laser

 According to the method of selecting the operation mode to oscillate the light and to inject the light by a wide width step, a relatively large output power can be obtained, but a relatively large output pulse can be obtained. However, it was difficult to achieve 100% of the mouth sucking efficiency due to the presence of a bottle. ¾ The disadvantage was that the purity of the skull deteriorated. However, the output light of this type of base has a coherence property of 问 <, and the base that uses it as a light source for reduced exposure generates a super-saturated light. It is thought that the generation of the stickiness pattern depends on the number of spatial modes included in the laser light. In other words, it is easy to generate a speckle pattern in which the number of spatial transverse modes covered by the laser light is small, and conversely, the spatial mode is reduced.

.

It is known that as the number increases, it becomes more difficult to generate a sticky note return. The above-mentioned Ingen 3 no-mouth method is essentially a technique for narrowing the bandwidth by significantly reducing the number of spatial modes, and Reduced projection exposure cannot be used because the generation of a speckle pattern is a major problem.o

Another promising technique for narrowing the bandwidth of an excimer is to use a gap-gap etalon, which is a wavelength selective element. Conventional technology using a gap etalon is a technology developed by AT & T Bell Laboratories. An air gap etalon is placed between the front mirror and the laser chamber of the laser to reduce the bandwidth of the laser. Some technologies have been proposed to achieve this. This method does not make the spectrum line width much narrower, and has a large power loss due to air gap etalon insertion. The problem is that it is difficult to increase the number of horizontal space modes. Also, the air gap outlet has a problem in durability.

 Therefore, a grating with comparatively excellent durability is adopted as a wavelength selection element, and the wavelength of the laser light is narrowed. For excimer lasers that use this grating as a wavelength-selective element, for which a Shima laser has been proposed, Position the pinhole in the resonator to reduce the angle of the beam in the resonator, or launch the beam into the grating. The laser light is expanded by a beam expander. The power of this beam extruder is that of using a prism beam extruder constructed using prism. " is there .

 At this point, the narrow-band oscillation excimer laser used for the stebber narrows the line width to 3 pm or less, as described above, and increases the bandwidth. Output is required.

However, if a pinhole is arranged inside the resonator with a large amount of force, the output will be very small. Space required to prevent the occurrence of The number of modes is also reduced and cannot be adopted.

 Also, when using the prism beam expander, the enlargement ratio of the prism beam expander is reduced to reduce the line width. Need to be identified.

 If you increase the enlargement rate of the prism beam exon, you can configure the prism beam extruder. The angle of incidence of the laser beam on the prism must be increased, and the number of prisms needs to be increased, resulting in a large loss. However, there is a problem that a large output cannot be obtained.

 In addition, when the narrow laser excimer laser is used as the light source of the stebber, it is necessary to narrow the output laser light of the excimer laser. Therefore, it is necessary to stably control the wavelength of the narrowed output laser light with high accuracy.

 Conventionally, a monaural etalon power has been used to measure the wavelength line width of output light from a narrow-band oscillation excimer laser or to detect the wavelength. Yes. The monitor etalon is constructed using an air gap with a partial reflection mirror arranged opposite to it with a predetermined gap. The transmission wavelength of the air gap is expressed as follows.

 m λ = 2 nd ♦ cos Θ

Where m is an integer, d is the distance between the partial reflection mirrors of the etalon, n is the refractive index between the partial reflection mirrors, and S is the normal to the eta-ron and the incident light. It is the angle formed by the optical axis.

According to this equation, if n, d, and m are constant, the wavelength changes. It can be understood that when it changes, it changes. The monitor etalon uses this property to detect the wavelength of the light to be detected, and in the above-mentioned monitor etalon, If the pressure in the gap and the ambient temperature change, the angle 0 described above will change even if the wave length is constant. Therefore, when using a monitor etalon, wavelength detection is performed by controlling the pressure and the ambient temperature in the air gap to a constant value.

 However, it is difficult to control the pressure and ambient temperature in the air gap with high accuracy, and therefore, the absolute wavelength is detected with sufficient accuracy. I can't do that.

 Then, a reference light whose wavelength is known in advance is input to the monitor etalon together with the light to be detected, and the relative value of the detected light with respect to this reference light is input. There has been proposed a device for detecting the absolute wavelength of the detected light by detecting the wavelength.

 In such devices, the transmitted light from the monitor etalon should be directly incident on the detection surface of a photodetector such as a CCD image sensor. ing .

 Since this device is designed so that the output of the monitor etalon is directly incident on the photodetector, the detected light and the reference light can be sufficiently separated. A large amount of light cannot enter the photodetector, causing inconveniences such as no interference fringes on the photodetector.

The purpose of the present invention is to provide an excimer laser using a brilliance beam extruder and a grating as a narrowing element. -A narrow-band oscillation excimer laser that does not increase loss even if the enlargement rate of the prism beam expander is increased. It must be provided.

 Another object of the present invention is to allow the reference light and the light to be detected to enter the photodetector with sufficient amounts of light, respectively, An object of the present invention is to provide a narrow-band oscillation excimer laser wavelength detector capable of detecting each interference fringe with high accuracy. Opening of the light

 In order to achieve the above object, in the narrow-band oscillation excimer laser of the present invention, the drawing direction of the grating and the bliss beam are provided. When the beam expansion direction of the spreader is almost the same as that of the prism beam, the linearly polarized wave almost parallel to the beam expansion direction of the prism beam expander. And selective oscillation means for selectively oscillating is provided. The selective oscillating means can be constituted by a light emitting element arranged in the optical resonator.

 Further, the selective oscillating means is substantially in the direction of the beam expansion direction of the prism pad and in the plane of the laser optical axis with respect to the laser optical axis. It can be configured to include the front or rear window of the laser chamber arranged so as to form a star angle. O

The selective oscillating means is the prism beam exciter. Of the polarization component almost parallel to the beam expansion direction of the The prism beam exciton, which selectively prevents reflection of light. It can be constructed by including an anti-reflection film coated on one side of the prism that constitutes the solder

 Like this, prism beam exno. By selectively oscillating a linearly polarized wave that is almost parallel to the beam expansion direction of the beam, the angle of incidence on the prism increases and the prism increases. The loss can be reduced even if the number of increases. This is because a linearly polarized wave parallel to the beam expansion direction of the beam expander has a large transmittance even if the prism incident angle is large. It is. In addition, a large output can be obtained even with a narrower spectral line width.

 Also, the wavelength detector of the narrow-band oscillation excimer laser according to the present invention, the reference light generated from the reference light source and the light to be detected are incident on the etalon. An illuminating means, an etalon, a light condensing means for condensing light transmitted through the etalon, and a light condensing means disposed on a rear focal plane of the light condensing means. And light detecting means for detecting interference fringes of the light condensed.

The reference light or the detection light transmitted through the aperture is collected by the light collecting means, and then the light detection light is disposed on the focal plane of the light collecting means. It is imaged on the detection surface of the means. Brief explanation of drawings 1 (a) and 1 (b) are a plan view and a side view showing one embodiment of a narrow-band oscillation excimer laser according to the present invention.

 2 (a) and 2 (b) are a plan view and a side view showing another embodiment of the narrow-band oscillation excimer laser of the present invention.

 3 (a) and 3 (b) are a plan view and a side view showing still another embodiment of the narrow-band oscillation excimer laser according to the present invention.

 FIG. 4 is a diagram showing an embodiment of a wavelength detecting device of the narrow-band oscillation excimer laser according to the present invention.

 FIG. 5 is a diagram showing another embodiment of the wavelength detecting device of the narrow-band oscillation excimer laser of the present invention using a converging mirror. FIG. 6 is a merging type optical fiber. FIG. 9 is a diagram showing another embodiment of the wavelength detection device of the gobo region oscillation excimer laser of the present invention using the present invention;

 FIG. 7 is a diagram showing another embodiment of the wavelength detector of the narrow-band oscillation excimer laser of the present invention using a lamp as the reference light.

 FIG. 8 is a diagram showing another embodiment of the wavelength detector of the narrow-band oscillation excimer laser according to the present invention using a lamp and an optical fiber.

 FIG. 9 is a diagram showing another embodiment of the wavelength detector of the narrow-band oscillation excimer laser of the present invention in which the shutter and the fin are introduced.

 FIG. 10 is a flow chart showing the main routine of wavelength detection j in the configuration of FIG.

Fig. 11 shows an example of a reference light detection subroutine. Roach

 FIG. 12 is a flowchart showing an example of a detected light detection subroutine. BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

 FIGS. 1 (a) and 1 (b) show an embodiment of the narrow-band oscillation excimer laser according to the present invention, and FIG. 1 (a) is a plan view thereof, and FIG. Figure (b) shows the side view. The narrow-band oscillation excimer laser of this embodiment has a front mirror 11 and a grating 6 having the functions of a rear mirror and a wavelength selection element. Between the laser chamber 3, the polarizing element 4 and the beam expander (prism beam expander). The rhythms 5a, 5b are arranged. In this case, an optical resonator is configured between the front mirror 1 and the grating 6.

 The laser channel <3 is not shown because the laser gas containing KrF etc. is filled in such a way that it can be circulated, and the laser gas is excited. Discharge electrodes are placed. Further, windows 2a and 2b are arranged at both ends of the laser chamber 3 at predetermined angles.

The grating 6 selects light of a specific wavelength by using light diffraction, and has a large number of grooves arranged in a certain direction. In this specification, this number of grooves and The direction at right angles is called the drawing direction. Grating

6 is to select light of a specific wavelength by changing the angle of the grating 6 with respect to the incident light in the plane including this drawing direction. can do . That is, the grating 6 transmits only a specific diffracted light corresponding to the angle of the grating with respect to the incident light in a predetermined direction (in this case, the incident light). In this direction), thereby performing a selection operation for light of a specific wavelength.

 The prism 5a, 5b force, the resulting prism beam, the beam, the beam expansion direction force and the drawing direction of the grating 6 It is arranged so that it almost matches. The grating 6 is illuminated by the laser beam expanded by the prism beam expander.

The polarizing element 4 selectively selects only the polarized waves that are almost parallel to the prism 5a, 5b force, and the beam expansion direction of the resulting prism beam expander. Through. The polarizing element 4 includes, for example, a polarizing prism, a blue light dispersion prism, and a glass prism using a birefringent material (crystal, calcite, etc.). scan board co Do Let 's you transmitting a predetermined polarization component in the blanking re-menu was or whether you place at is te angle glass la scan the substrate (quartz, C a F ₂ or M g F 2 was) -It can be composed of things with tents.

According to such a configuration, the apparatus shown in FIGS. 1 (a) and 1 (b) is a prism beam exhaust comprising prisms 5a and 5b. Linear deviation almost parallel to the beam expansion direction of the spanner It is selectively oscillated by light waves. Here, a linearly polarized wave parallel to the beam expansion direction of the prism beam expander has a large transmittance even if the angle of incidence on the prism is large. Therefore, even if the enlargement rate of the beam expander is increased to reduce the line width of the spectrum, the loss does not increase so much. . In other words, it is possible to construct a narrow loss oscillation laser with low loss.

 FIGS. 2 (a) and 2 (b) show another embodiment of the present invention. FIG. 2 (b) is a plan view thereof, and FIG. 2 (b) is a side view thereof. It is. In this embodiment, a specific linearly polarized wave is selected by the rear window 2b of the laser chamber 3. . In this embodiment, the rear side window 2b of the laser channel 3 has a prism 5a, 5b force, and a prism beam. In the direction of the beam expansion direction of the mu-expander and in the plane of the laser optical axis, the laser light axis should be almost zero at the laser beam optical axis. In the configuration shown in Fig. 2, only the window 2b on the rear side is set to the plunger angle in the configuration shown in Fig. 2. Both the window 2b and the front window ゥ 2a may be arranged at a predetermined price at the evening angle, or the front window may be provided. Only window 2a may be placed at the blue evening angle.

FIGS. 3 (a) and 3 (b) show another embodiment in addition to the present invention. Here, FIG. 3 (a) is a plan view, and FIG. 3 (b) is a side view of the side view. The prisms 5a and 5b that make up the prism beam expander have polarization components parallel to the expansion direction of the prism beam expander. It is constituted by coating an antireflection film for selectively preventing reflection of only light. In FIG. 3 (b), portions 5c and 5b indicated by dotted lines indicate the coating portion.

 In this case, the coating should be performed on at least one light-transmitting surface of at least one prism. In this case, even if the angle of incidence on the prism becomes large, it is possible to maintain a transmittance of 99% or more.

 FIG. 4 shows an embodiment of a gouge band oscillation excimer laser wavelength detecting apparatus according to the present invention. In this embodiment, the output light La of the narrow-band oscillation excimer laser 1 用 is used as the detection light, and the He-Ne laser is used as the reference light source 20. Lasers such as lasers or Ar lasers are used. The wavelength of the reference laser and the wavelength of the excimer laser light generated from the reference light source 2 ° are different.

 A part of the laser light La output from the narrow-band oscillation excimer laser 10 is sampled by the beam splitter 30. This sampling light is applied to the beam splitter 40. The reference light Lb output from the reference light source 20 is applied to the other surface of the beam splitter 40.

The beam splitter 40 transmits a part of the sampling light La output from the beam splitter 30 and outputs the beam splitter. Further, a part of the reference light Lb output from the reference light source 20 is reflected, and thereby, the sampling light and the reference light are formed. The trapping light of the sampling light and the reference light synthesized by the beam splitter 40 forms the beam by the concave lens 50. After being spread, it is irradiated onto etalon 60.

 The etalon 60 is composed of two transparent plates 60 a and 60 b, the inner surfaces of which are partially reflected mirrors, and which is provided for the etalon 60. The transmitted wave length is different depending on the angle of the incident light. That is, the etalon 60 is provided with a two-wavelength reflective film to reflect both the reference light La and the excimer laser light La having different wavelengths. O

 The light transmitted through the etalon 6 ◦ is incident on the focusing lens 70. This condenser lens 70 is, for example, an achromatic lens with chromatic aberration correction, and passes through the achromatic condenser lens 70. The chromatic aberration is corrected.

The light detector 80 is disposed at the focal point of the converging lens 70, so that the light passing through the converging lens 70 is converted to an optical position detector. The first interference fringe corresponding to the wavelength of the reference light and the second interference fringe corresponding to the wavelength of the test light are formed on the detection surface of the light detector 8◦. Form interference fringes. The photodetector 80 detects the first and second interference fringes, and based on the detection, determines the relative wavelength of the detected light with respect to the wavelength of the reference light. Detects the wavelength and detects the wavelength of the known reference light. Detects the absolute wavelength of the detected light based on the calculated relative wavelength

 In addition, it is configured using a one-dimensional or two-dimensional image sensor, a diode array, or a PSD (POSIT ION SENSITIVE DETECTOR) as the photodetector 8 °. can do .

 In this way, after expanding the beam with the concave lens 5 °, the beam is incident on the etalon 60 and the transmitted light of the etalon 60 is condensed. The image is formed on the photodetector 80 by the lens 70, so that a sufficient amount of light is incident on the photodetector 80 、 and both light Are formed satisfactorily.

 FIG. 5 shows another embodiment of the narrow-band oscillation excimer laser wavelength detecting apparatus according to the present invention. In the following, in the other drawings including this FIG. 5, parts having the same functions are denoted by the same reference numerals for convenience of explanation.o

In the embodiment shown in FIG. 5, instead of the achromatic condensing lens 70, a condensing mirror 90 such as a concave mirror or an off-axis parabolic mirror is used. To use. In other words, the reference beam Lb and the excimer laser beam La are transmitted through the concave lens 50 to expand the beam, and are incident on the etalon 60. The transmitted light from the lamp 60 is reflected by the condensing mirror 90, and the reflected light is reflected on the detection surface of the photodetector 80 arranged at the focal position of the condensing mirror 90. Make it incident. Collection Since the optical mirror 90 is a reflecting surface, there is no chromatic aberration at all, and this causes both interference fringes of the excimer laser light La and the reference laser light Lb to be reduced. It is possible to form an image on the photodetector 80 located at the same position, that is, at the focal position of the mirror 90 o

 Also in the embodiment shown in FIG. 5, the concave lens 50 and the condensing mirror 90 allow the interference fringes with a sufficient light amount as in the previous embodiment. Can be detected with high accuracy.

 FIG. 6 shows another embodiment in addition to the narrow-band oscillation excimer laser wavelength detector of the present invention.

 In the embodiment shown in FIG. 6, the excimer laser light La and the reference laser light Lb are synthesized by the merged optical fiber 4a. This is what we did. That is, the excimer laser sampled at the beam splitter 30 is a condensing lens 11 and an optical fiber. After passing through the optical fiber 13 and the optical fiber 13, the optical multiplexer:! 4, and the reference laser beam Lb generated from the reference light source 20 is a condensing lens 15, an optical fiber sleeve 16, and an optical fiber. The light is incident on the optical trap 14 through the bar 17. The optical multiplexer 14 multiplexes the two lights La and Lb, and the multiplexed light is incident on the optical fiber 18. Then, the light power spread through the sleeve 19 is incident on the monitor etalon 60. The light transmitted through the monitor etalon 60 is formed on an optical detector 80 through an achromatic condensing lens 70.

In the embodiment shown in FIG. 6, the position of the interference fringe is It does not depend on the position of the converging type optical fiber 10 and is determined only by the positional relationship between the etalon 60, the focusing lens 70, and the light detector 80. Thus, there is an advantage that the adjustment work of the optical system is made easier by taking advantage of the advantages of the previous embodiment.

 In the embodiment shown in FIG. 6, chromatic aberration correction is performed by using the achromatic condensing lens 70, but this lens 70 is replaced. The concave mirror shown in Fig. 5 or the parabolic mirror 90 can be used instead.

 Fig. 7 shows another example of the narrow-band oscillation excimer laser wavelength detector of the present invention in which the lamp 20a, which is a surface light source, is used as the reference light source. An example is shown. The lamp 20a is, for example, a mercury lamp that generates reference light having a wavelength of 253.7 nm. That is, the excimer laser light La sampled by the beam splitter 30 is formed by the concave lens 21. After the beam is spread, it is incident on the beam splitter 40, and the beam splitter 40 emits the reference light L from the mercury lamp 20 at the beam splitter 40. After being formed with c, the etalon 60 is irradiated. The light transmitted through the etalon 60 is imaged on the photodetector 80 via the achromatic condensing lens 70.

Also in the embodiment shown in FIG. 7, the chromatic aberration correction is performed by using the achromatic condensing lens 70, but this lens 70 Instead of using the concave mirror or the outer parabolic mirror 90 shown in Fig. 5 above, It is also good.

 FIG. 8 also shows another embodiment of the narrow-band oscillation excimer laser wavelength detecting apparatus of the present invention in which a mercury lamp 2a is used as a reference light source. In this embodiment, the excimer laser light La is guided to the beam splitter 40 by using the optical fiber 23. are doing . In other words, the excimer laser light sampled by the beam splitter 3 ◦ is shifted by the focusing lens 11 to the slave 2. The light is incident on the optical fiber 2, passes through the optical fiber 23, and is emitted through the sleeve 24. The light expanded by passing through the sleeve 24 is incident on the beam splitter 4 ° where the mercury lamp 2 ° is output. After being synthesized with the reference light Lc from the above, the etalon 60 is irradiated. The light transmitted through the aperture 60 is imaged on the photodetector 80 via the achromatic condensing lens 70.

 In the embodiment shown in FIG. 8, instead of the achromatic condensing lens 70, the concave mirror or the off-axis parabolic shown in FIG. 5 is used instead. You can use a surface mirror 9 ◦.

 FIG. 9 shows another embodiment of the narrow-band oscillation excimer laser wavelength detecting apparatus according to the present invention. In this embodiment, FIG. In this embodiment, the achromatic condensing lens 70 is replaced with a condensing mirror 90 such as a concave mirror, an off-axis parabolic mirror, etc. It is designed to add notes 41 and shots 42 and 43.

That is, the mercury lamp 20a power and the reference light Lc First, a filter 41 for selecting and outputting only a predetermined wavelength is provided between the shutter 42 and the beam splitter 40, and the filter 41 is provided for the filter 41. Thus, only the reference light having a predetermined wavelength is incident on the beam splitter 4 °. For example, when used as a wavelength detector for a KrF narrow-band excimer laser (wavelength: 248.4 nm), use water as the lamp 20a. Use a silver lamp and use an interference filter with a wavelength of 253.7 nm close to the wavelength of the excimer laser as the filter 16. do it . In addition, the shutters 42 and 43 are provided to separately detect the reference light and the test light (excimer laser light). When detecting the reference light, open shutter 42 and close shutter 43. On the other hand, when detecting the light to be detected, the shutter 43 is opened and the shutter 42 is closed.

 In this example, it is assumed that the file 41 is arranged between the beam split 40 and the beam 42. However, the fins 41 may be inserted between the lamps 20a and 42. Further, when the wavelength of the reference light and the wavelength of the light to be detected are close to each other and the light to be detected passes through the filter 41, the filter 41 is used for beam scanning. It may be arranged at an appropriate position in the optical path from the splitter 40 to the optical detector 80.

Next, the detection operation of the reference light and the light to be detected in the embodiment shown in FIG. 9 will be described with reference to the flowcharts shown in FIGS. 1 to 12. It is explained. Fig. 1 shows the main routine for wavelength detection. First, the reference light detection subroutine is executed.

(Step 100). In this reference light detection subroutine, as shown in FIG. 11, the shutter 43 on the detected light side is closed and the shutter on the reference light side is closed. By opening the window 42, only the reference light Lc is incident on the photodetector 80 via the etalon 60 (step 20). 0, 210). Then, the radius Rs of the interference fringe of the reference light formed on the photodetector 80 is detected, and the radius Rs is stored (step 220).

 When the reference light detection subroutine is completed, the timer value T of the timer is cleared to zero (step 110), and then the timer value T is reset. Check whether it is longer than a predetermined set time K (for example, several minutes) (Step 120). If it is T <K, the detected light detection subroutine is executed (step 140). In this detected light detection subroutine, as shown in FIG. 12, the shutter 42 on the reference light side is closed, and the shutter on the detected light side is closed. By opening the evening 43, only the detected light La is incident on the photodetector 80 via the aperture 60 (step 30). 0, 310). Then, the radius Re of the interference fringe of the detected light formed on the photodetector 80 is detected (step 320).

When this detected light detection subroutine is completed, the radius Re obtained by the routine and the reference light subroutine are used. The absolute wavelength of the light to be detected is detected by comparing the obtained and stored radius R s (step 150). Thereafter, the processing of steps 140 and 150 is repeated until T> K.

 Then, in step 120, when 〉> Κ, the reference light detection subroutine shown in FIG. 11 was executed again, and the value obtained by the routine was obtained. The stored data R s is updated with the radius R s of the interference fringe of the reference light. Thereafter, the timer value T is cleared to zero, and then the detected light detection subroutine is executed again.

 All of the above processing is performed automatically.

 In other words, in such wavelength detection processing, if the wavelengths of the reference light and the light to be detected are close to each other, it is difficult to detect both interference fringes simultaneously. The two are detected separately by the shutters 42 and 43, and the reference light is relatively stable, so the preset comparison is made. The interference fringes are detected at a predetermined long period K, and the light to be detected is always detected when the reference light is not detected. That is, in this case, the detection cycle of the reference light is set to be sufficiently longer than the detection cycle of the light to be detected.

 In this embodiment, the radius of the interference fringe is detected, but the diameter or position of the interference fringe is detected to obtain the absolute wavelength of the light to be detected. You can do it.

At this point, in the embodiment shown in FIGS. 4 to 9 described above. If the reference light and the amount of light to be detected are small and it is difficult to detect the interference fringe, place a collimator lens in front of Etalon 60. Alternatively, the amount of light may be increased by making parallel light incident on the etalon.

 Further, in the embodiment shown in FIGS. 4 to 9, the beam splitter 4 ◦ receives the detection light on the transmission side and the reference light on the reflection side. Although they are arranged so that they are implemented, these relationships may be reversed. Also, this beam splitter 4 ◦ uses a partial reflection mirror when the wavelengths of the reference light and the detection light are close to each other, and uses a dichroic mirror when the wavelength difference is large. It is recommended that you use each of the Ic mirrors.

 Further, in the above-described embodiment, the configuration is made by using the air outlet, but instead of the air outlet, the solid ethanol is used instead of the air outlet. The same configuration can be achieved by using a component.

 However, in the above embodiment, the chromatic aberration of the focusing lens 70 is corrected, or the reference light and the light are covered by using the focusing mirror 90. The force to match the imaging position of the detection light <The focusing lens 70 or the photodetector 80 is configured to be movable in the optical axis direction. Accordingly, the difference in the imaging position may be absorbed.

Further, in the embodiments shown in FIGS. 4, 6, 7, and 8, when the wavelengths of the reference light and the light to be detected are close to each other, the light without chromatic aberration correction is collected. The lens may be inserted between etalon 60 and photodetector 80. Further, in the embodiment shown in FIG. 5, FIG. 5, or FIG. 7, the laser beam La is expanded by the concave lens 50 or 21 to form the The force that makes it incident on 0; ', a convex lens is used in place of this concave lens, and after the light is condensed by the convex lens, the spread is increased. Such light may be incident on the aperture 60. In addition, a diffusing plate (for example, slip glass) may be used in place of the concave lens 50. Industrial applications

 As described above, according to the narrow-band oscillation excimer laser of the present invention, the drawing direction of the grating and the bristle beam extruder And the beam expansion direction of the beam is almost the same, and a linearly polarized wave that is almost parallel to the beam expansion direction of the prism beam expander is selectively emitted. By providing the selective oscillation means for oscillating, the loss in the prism beam expander can be almost eliminated. This makes it possible to narrow the spectral line width and obtain a large output.

Further, according to the wavelength detector of the narrow-band oscillation excimer laser of the present invention, a simple condensing means can be provided behind the etalon. The configuration allows a sufficient amount of light to be incident on the photodetector, thereby ensuring that interference fringes are formed on the photodetector. Thus, the absolute wavelength of the detected light can be detected with high accuracy. In particular, an achromatic lens or a focusing mirror is used as a focusing means. This makes it possible to detect the absolute wavelength with high accuracy without making the optical system movable even if the reference light and the detection light have different wavelengths. .

 The wavelength detector of the narrow-band oscillation excimer laser and the narrow-band oscillation excimer laser according to the present invention is used as a light source of a reduction projection exposure apparatus for manufacturing semiconductor devices. It is suitable for adoption.

Claims

Range of request  1. A narrow-band oscillation excimer laser using a prism beam expander and a grating as a band-narrowing element.  The drawing direction of the grating and the beam expanding direction of the prism beam are substantially matched with each other.  A narrow-band oscillation excimer provided with a selective oscillating means for selectively oscillating a linearly polarized wave almost parallel to the beam expanding direction of the prism beam extruder. Laser. 2. The narrow oscillation oscillator according to claim 1, wherein said selective oscillating means is a polarizing element disposed in an optical resonator. 3. The selective oscillating means is arranged so that the beam is not substantially shifted from the laser beam axis in the plane of the beam expansion direction of the prism beam expander and the laser beam axis. BLUES Claims that include the window on the rear or front side of the laser chamber, arranged at the evening angle 2. The narrow-band oscillation excimer laser according to item 1. 4. The selective oscillating means is coated on at least one side of the prisms constituting the prism beam expander. Zum Beam Ex. Dutch 2. The narrow-band oscillation excimer laser according to claim 1, further comprising an anti-reflection film for selectively preventing only a polarization component substantially parallel to the expansion direction. The. 5. Incident means for injecting the reference light generated from the reference light source and the laser light to be detected output from the narrow-band oscillation excimer laser power into the output port;  A light condensing means for condensing the light transmitted through the aperture; and an interference fringe disposed on a rear focal plane of the light condensing means and condensed by the light condensing means. Light detection means for detecting  A wavelength detector for a narrow-band oscillation excimer laser, wherein the wavelength of the light to be detected is detected based on the detection output of the light detection means. 6. The wavelength detector of a narrow-band oscillation excimer laser according to claim 5, wherein the reference light source is a reference laser light source that generates laser light. 7. The incident means is:  A beam splitter for synthesizing a reference laser beam generated from the reference laser light source and the laser beam to be detected, the beam splitter and the beam splitter; A concave lens interposed between the etalon and The narrow-band oscillation exciter according to claim 6 comprising: Ma Laser wavelength detector. 8. The incident means is:  A beam splitter for synthesizing the reference laser light generated from the reference laser light source and the laser light to be detected, the beam splitter and the emitter. A diffusion plate interposed between the lamp and  7. The wavelength detecting device for a narrow-band oscillation excimer laser according to claim 6, comprising: 9. The incidence means is:  The laser light to be detected is introduced from the first input end, the reference laser light is guided from the second input end, and these combined lights are radiated to the outlet. 7. The wavelength detecting device for a narrow-band oscillation excimer laser according to claim 6, further comprising a converging type optical fiber means. 10. The wavelength detecting device according to claim 5, wherein the reference light source is a lamp. 1 1. The incidence means A concave lens into which the laser light to be detected is incident; a reference light generated from the lamp, which is disposed after the concave lens; and an output of the concave lens. A beam split that creates light and The wavelength detecting device for a gouge band oscillation excimer laser according to claim 1, comprising: 1 2. The lighting means  An optical fiber for introducing the laser light to be detected, an optical fiber sleeve provided at an end of the optical fiber,  Beam splitter for combining the output light of the optical fiber sleeve with the reference light, and entering the combined light into the etalon;  10. The wavelength detection device for a narrow-band oscillation excimer laser according to claim 10, comprising: 13. A finolator for selectively outputting only light having a predetermined wavelength out of the light generated from the lamp and the laser light to be detected is connected to the lamp and the lamp. 12. The wavelength detecting device for a narrow-band oscillation excimer laser according to claim 10, wherein said wavelength detecting device is disposed in any one of the optical paths between the light detecting means and the light detecting means. 1 4. The incidence means  First shutter means for blocking reference light generated from the reference light source; 6. The narrow-band oscillation excimer laser wavelength detector according to claim 5, further comprising second shutter means for blocking the light to be detected. 15. The wavelength detecting device for a narrow-band oscillation excimer laser according to claim 5, wherein the condensing means is an achromatic lens on which chromatic aberration correction has been performed. 16. The condensing mirror according to claim 5, wherein said condensing means is a condensing mirror for reflecting light transmitted through said etalon and for inputting said reflected light to said light detecting means. Detector for narrow-band oscillation excimer laser. 17. The narrow band oscillation excimer laser according to claim 16, wherein said converging mirror is a concave mirror. 18. The wavelength detection of a narrow-band oscillation excimer laser according to claim 16, wherein the converging mirror is an off-axis parabolic mirror. 19. The etalon is irradiated with the reference light and the light to be detected generated from the reference light source, and is formed by the light transmitted through the etalon. Wavelength detection for detecting the wavelength of the light to be detected by detecting the first interference fringe corresponding to the reference light and the second interference fringe corresponding to the light to be detected by the light detecting means. Device The first interference pattern and the second interference pattern In addition to the detection at another time, the narrow-band oscillation excimer laser in which the detection period of the second interference fringe is made longer than the detection period of the second interference fringe -Wavelength control device.