JP3905111B2 - Laser apparatus and wavelength detection method - Google Patents

Description

  The present invention generally relates to laser devices, and more particularly, to a laser device capable of controlling the wavelength of output laser light. Furthermore, it is related with the wavelength detection method of detecting a wavelength using such a laser apparatus.

  An excimer laser is used as a light source of a reduction projection exposure apparatus (hereinafter referred to as a stepper) for manufacturing a semiconductor device. Only synthetic quartz and fluorite (calcium fluoride) can be used as a lens material that can sufficiently transmit excimer laser light and obtain uniformity and processing accuracy. Therefore, it is difficult to design a reduction projection lens with chromatic aberration correction. Therefore, when using a laser beam with a short wavelength as a light source for a stepper, it is necessary to narrow the laser beam to such an extent that chromatic aberration can be ignored. In addition, the wavelength of the narrowed output laser beam is highly accurate. It is necessary to control stabilization.

Stabilization of the oscillation wavelength of a narrow band excimer laser has been performed by making a part of the laser output light enter a spectroscope and measuring using an etalon or a grating. Patent Document 1 below discloses an excimer laser device that uses an etalon and a grating to stabilize the oscillation wavelength. FIG. 18 shows the configuration of such an apparatus.
In FIG. 18 , in the laser chamber 100, an electrode (not shown) for discharging and exciting a sealed laser gas, a fan (not shown) for circulating the laser gas, and the like are provided. A window 101 and a front mirror 103 are disposed on the front side of the laser chamber 100, and a window 102 and a narrow band narrowing unit 130 are disposed on the rear side. The band narrowing unit 130 functions as a rear mirror and narrows the band of the output laser light. For example, a prism or the like is disposed. The narrow-band laser beam is output through the front mirror 103, and a part of the laser beam is extracted by the partial reflection mirror 104. The extracted laser light is guided to the monitor etalon 430 and the grating type spectrometer 440 together with the reference light generated from the reference light source 105. Data representing the wavelengths detected by the monitor etalon 430 and the grating-type spectroscope 440 is output to the wavelength controller 108, and based on this data, the wavelength selection element disposed in the narrowband unit 130 via the driver 109. The selected wavelength is controlled.

FIG. 19 shows a specific example of the monitor etalon 430. In FIG. 19 , a part of the laser light divided by the partial reflection mirror 104 (FIG. 18 ) is made uniform by the diffusion plate 431, passes through the partial reflection mirror 432, and the reference light generated from the reference light source 105 is These are reflected by the partial reflection mirror 432 and emitted toward the etalon 435. The laser light and the reference light transmitted through the etalon 435 pass through the achromatic lens 434 and form interference fringes 437 and 438, respectively. Here, by detecting the positions of the interference fringes 437 by the laser light and the interference fringes 438 by the reference light by the sensor 436, the relative wavelength of the laser light with respect to the reference light is detected, and a known reference having a stable wavelength is detected. The absolute wavelength of the laser beam can be obtained from the wavelength of light (for example, output light of a mercury isotope lamp). In this way, if the laser wavelength is calculated from the difference between the interference fringe position 438 of the reference light and the interference fringe position 437 of the laser light, the fluctuation of the spectral characteristics of the spectrometer that varies depending on the temperature or the like can be canceled out. it can.

FIG. 20 shows a specific example of the grating type spectrometer 440. In FIG. 20 , the reference light and a part of the divided laser light enter the incident optical system 451 through the same optical path, are totally reflected by the mirror 443, are guided to the concave mirror 442, and are guided by the concave mirror 442 at the position of the entrance slit 444. The light is condensed and passes through the entrance slit 444. The light that has passed through the incident slit 444 is converted into parallel light by the concave mirror 445 and is incident on the grating 446. The light reflected and diffracted by the grating 446 has a different diffraction angle depending on the wavelength. This diffracted light is reflected by the concave mirror 447 and forms an image on the focal plane 452 as an incident slit image of the diffracted light. The incident slit images 448 and 449 of the respective diffracted lights with respect to the respective wavelengths are formed on the focal plane, and the positions of the incident slit images 448 and 449 change when the wavelength changes. Therefore, the relative position of the laser light relative to the reference light is detected by detecting the positions of the incident slit image 448 of the diffracted light of the reference light and the positions of the incident slit image 449 of the laser light by the optical position sensor 450, respectively. The absolute wavelength of the laser beam can be detected.

Referring to FIG. 18 again, this laser apparatus includes a monitor etalon 430 that divides a narrow wavelength range using an etalon with high resolution and a grating-type spectrometer 440 that uses a grating to divide a wide wavelength range with low resolution. is doing. When the difference Δλ between the target oscillation wavelength λ _T of the laser and the actual oscillation wavelength λ _L of the laser is large, the laser wavelength is measured using the grating-type spectroscope 440, and the target is controlled by controlling the wavelength selection element of the laser. When approaching the oscillation wavelength and when the difference becomes sufficiently small, the monitor etalon 430 is used to detect the laser oscillation wavelength with high accuracy and to control the laser oscillation wavelength closer to the target oscillation wavelength. That is, the monitor etalon and the grating-type spectrometer are selectively used depending on whether the difference between the laser oscillation wavelength and the target oscillation wavelength is large or small.

Here, when the gap of the etalon is d, the refractive index of the space of the etalon gap is n, and the angle at which the light of wavelength λ is incident on the etalon (tilt angle from the vertical incident optical axis) is θ, the following equation (1) holds. Sometimes light passes through the etalon with maximum intensity and is focused at a position corresponding to the wavelength λ.
m · λ = 2 · n · d · cos θ (1)
In the formula (1), m is an integer called an order. Here, if the wavelength when θ = 0 is λ ₀ , the equation (2) is established.
m · λ ₀ = 2 · n · d (2)
Equation (3) is obtained from Equation (1) and Equation (2).
m (λ ₀ −λ) = 2 nd (1−cos θ) = 4 nd · sin ² (θ / 2) (3)
Since sin θ≈θ when θ≈0, equation (4) is obtained as an approximate expression.
m (λ ₀ −λ) = n · d · θ ² (4)
Assuming that the focal length of the condenser lens is f and the radius of interference fringes is r (m), r (m) = f · tan θ≈fθ, and therefore equation (5) is obtained.
λ = λ ₀ − (n · d / (f ² · m)) · (r (m)) ² (5)
Here, the output light wavelength of the light source serving as the wavelength reference is λ _S , the wavelength of the laser light is λ _L , the interference fringe radii are r (m _S ), r (m _L ), and the respective orders are m _S , m _If it is set to _L , (6) Formula and (7) Formula will be obtained.
λ _S = λ ₀ − (n · d / (f ² · m _S )) · (r (m _S )) ² (6)
λ _L = λ ₀ − (n · d / (f ² · m _L )) · (r (m _L )) ² (7)
Equation (8) is obtained from Equation (6) and Equation (7).
λ _L = λ _S − (n · d / f ² ) ((r (m _L )) ² / m _L − (r (m _S )) ² / m _S )
(8)
In Equation (8), λ _S , n, d, and f are known values, and the interference fringe radii r (m _S ) and r (m _L ) are actually measured values in the corresponding orders m _S and m _L. The wavelength λ _{L of the} laser light can be calculated.

  By the way, in the equation (8), the refractive index n is constant. However, when the number of gas molecules in the etalon gap changes, the value of the refractive index n varies. In general, the refractive index of a substance varies with wavelength. Therefore, the optical length n · d of the etalon gap is not constant. Therefore, a calculation formula that takes into account the change in refractive index with wavelength is obtained below. Since the focal length f of the lens varies depending on the wavelength due to aberration, the lens is assumed to be achromatic.

Assuming that the laser wavelength is λ _L , the reference light wavelength is λ _S , and the refractive indices at these wavelengths are n _L and n _S , respectively, Equation (6) and Equation (7) are Equation (6 ′) and Equation (7), respectively. ').
λ _S = λ ₀ − (n _S · d / (f ² · m _S )) · (r (m _S )) ² (6 ′)
λ _L = λ ₀ − (n _L · d / (f ² · m _L )) · (r (m _L )) ² (7 ′)
The expression (8 ′) is obtained from the expressions (6 ′) and (7 ′).
λ _L = λ _S − (d / f ² ) [(n _L · (r (m _L )) ² / m _L )
+ (N _S · (r (m _S )) ² / m _S )] (8 ′)
If the equation (8 ′) is used, the wavelength of the laser beam can be calculated more accurately.

Japanese Patent No. 2631553

  However, since the etalon material expands and contracts due to heat, the etalon gap d is not essentially constant. Since a technique has been developed to keep the etalon gap d substantially constant using Zerodur (registered trademark), the etalon gap d is constant in the equation (8 ′), but in reality the fluctuation of the etalon gap d is ignored. I know I can't.

  That is, the etalon is coated with a multilayer reflective film so that laser light of each wavelength can be reflected with high reflectivity. Since these reflective films are hygroscopic, they are affected by the humidity in the atmosphere in which the etalon is stored or installed. When the amount of water contained in the reflective film of etalon varies, the film thickness of the reflective film changes or the optical characteristics change, and the etalon gap d in the equation (8 ′) changes with time.

For example, by using a first wavelength detector that splits a wide wavelength range with a low resolution using an etalon and a second wavelength detector that splits a narrow wavelength range with a high resolution using an etalon, the laser oscillation wavelength When the control is performed so as to be close to the target oscillation wavelength, if the laser wavelength λ _L is calculated based on (8 ′), only a numerical value that does not take into account the fluctuation of the etalon gap d can be obtained. Therefore, even if control is performed such that the wavelength error Δλ = λ _T −λ _L is reduced using the numerical value λ _L , control that actually decreases the wavelength error Δλ is not necessarily performed.

When a wavelength detector including a grating is used as the first wavelength detector as in the laser device shown in FIG. 18 , problems such as etalon do not occur, but after control by the first wavelength detector. When the control is shifted to the control by the second wavelength detector, the same problem occurs.

  On the other hand, when the etalon is not used and the grating is mounted on the first and second wavelength detectors, the amount of light is small. Since it is necessary to integrate the detection results, the wavelength cannot be accurately controlled for each pulse. Therefore, it is necessary to employ an etalon in order to control the wavelength for each pulse.

The etalon gap d in the equation (8 ′) fluctuates under the influence of ambient humidity after manufacturing the etalon, during storage, and after being mounted on the laser, so the fluctuation value of the etalon gap d is corrected by calculation. It is extremely difficult to do. Although it is theoretically possible to manage the etalon so that the humidity during storage and use is constant, storage and transportation become complicated, and the wavelength monitoring of the laser beam becomes complicated, increasing costs. It also leads to.
For this reason, there has been a demand for the development of a laser apparatus including a wavelength measuring means that does not affect the wavelength measurement even when the characteristics change due to aging of the etalon.

  The present invention has been made to solve the above-mentioned problems, and provides a laser apparatus capable of performing accurate wavelength control without affecting wavelength measurement even if characteristic fluctuations due to changes in etalon over time occur. With the goal. Furthermore, an object of this invention is to provide the method of detecting and controlling a wavelength using such a laser apparatus.

In order to solve the above problem, a laser apparatus according to a first aspect of the present invention includes a laser oscillator, a first reference light source, and a grating-type spectrometer, and a wavelength of reference light output from the first reference light source. The first wavelength detecting means for detecting the wavelength of the laser light output from the laser oscillator, the second reference light source and the etalon-type spectrometer, and the reference light output from the second reference light source. A second wavelength detecting means for detecting the wavelength of the laser light output from the laser oscillator based on the wavelength; a laser light wavelength detection value obtained by oscillating the laser oscillator and obtained by the first wavelength detecting means; The difference between the laser beam wavelength detection value obtained by the second wavelength detection means is calculated and stored, and the laser wavelength detection value obtained by the second wavelength detection means when the laser oscillator is subsequently oscillated is recorded. By adding the further stored difference to the difference between the laser light target wavelength, the laser light wavelength detection value obtained by the second wavelength detection means caused by thickness variation of the reflection film is coated on the etalon spectrometer And a control means for correcting the error .

A laser apparatus according to a second aspect of the present invention includes a laser oscillator, a first reference light source, and a grating-type spectroscope, and is based on the wavelength of reference light output from the first reference light source. A first wavelength detecting means for detecting the wavelength of the laser light outputted from the oscillator; a second wavelength detecting means for detecting the wavelength of the laser light outputted from the laser oscillator; The wavelength of the laser light output from the laser oscillator is calculated based on the reference light obtained by the wavelength detection means and the detection result of the laser light, and the position of the interference fringes when the laser light is input to the etalon spectrometer is calculated. stored as reference consisting interference fringe position, the difference between the subsequent a second interference fringe position and the reference of the resulting laser beam by the wavelength detecting means when the laser oscillator oscillated fringe position By calculating the difference between the laser light oscillation wavelength value and the laser light target wavelength, the laser light obtained by the second wavelength detecting means caused by the change in the thickness of the reflective film coated on the etalon spectroscope Control means for correcting an error in the detected wavelength value.

The wavelength detection method according to the first aspect of the present invention uses the first wavelength detection unit including the first reference light source and the grating-type spectroscope, and uses the wavelength of the reference light output from the first reference light source. The step (a) of detecting the wavelength of the laser beam outputted from the laser oscillator by oscillating the laser oscillator, and the second wavelength detecting means including the second reference light source and the etalon-type spectrometer, (B) detecting the wavelength of the reference light output from the reference light source of No. 2 and the wavelength of the laser light output from the laser oscillator, and the laser light wavelength detection value obtained in step (a) and step (b) The laser light wavelength detection value obtained by the second wavelength detecting means and the laser light target wavelength when the difference between the laser light wavelength detection value obtained in the above is calculated and stored, and then the laser oscillator is oscillated. By adding the difference stored relative difference, corrects the error of the laser beam wavelength detection value obtained by the second wavelength detection means caused by thickness variation of the reflection film is coated on the etalon spectrometer comprising a step (c) to.

The wavelength detection method according to the second aspect of the present invention uses the first wavelength detection means including the first reference light source and the grating-type spectroscope, and the reference light output from the first reference light source. The step (a) of detecting the wavelength of the laser beam output from the laser oscillator based on the wavelength, and the position of the interference fringe when the laser beam is input to the second wavelength detecting means including the etalon-type spectrometer a step (b ') for storing as a reference becomes interference fringe position, then the interference fringe position where the interference fringe position and the reference of the resulting laser beam by the second wavelength detecting means when the laser oscillator oscillated By calculating the difference between the laser light oscillation wavelength value obtained from the difference and the laser light target wavelength, it is obtained by the second wavelength detecting means caused by the change in the thickness of the reflective film coated on the etalon-type spectrometer. And (c) correcting the error of the detected laser light wavelength.

  According to the present invention, it is possible to provide a laser apparatus capable of performing accurate wavelength control without affecting wavelength detection even when characteristic fluctuations due to aging of etalon occur. Furthermore, it is possible to provide a method for detecting and controlling the wavelength using such a laser device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same reference number is attached | subjected about the same component and these description is abbreviate | omitted.

FIG. 1 shows a configuration of a laser apparatus according to the first embodiment of the present invention. In FIG. 1, the laser apparatus includes a laser resonator that generates laser light. The laser chamber 1 of the laser resonator is filled with a mixed gas containing a gas such as Ar, F ₂ , and He as a laser medium at several atmospheric pressures. In the laser chamber 1, a pair of discharge electrodes (not shown) are arranged facing each other in a direction perpendicular to the paper surface, and a high voltage power source (not shown) such as a pulse power module is interposed between the electrodes. A pulsed high voltage is applied. When a laser medium is supplied into the laser chamber 1 and a high voltage is applied between the electrodes to cause a discharge, light is generated from the laser medium.

  On the rear side and front side walls of the laser chamber 1, windows 2 and 3 are respectively arranged so as to make a predetermined Brewster angle with the optical axis passing through the laser chamber 1. On the rear side of the laser chamber 1, a band narrowing unit 30 that functions as a rear mirror and narrows the output laser beam is disposed.

  The laser beam narrowed by the wavelength narrowing unit 30 enters the laser chamber 1 from the window 2, and the amplified laser beam passes through the window 3 from the laser chamber 1 and is output to the outside of the laser resonator. Is done. The laser device according to the present embodiment includes a second wavelength detection unit 50 in front of the first wavelength detection unit 60. The laser beam emitted from the window 3 is emitted toward the second wavelength detection means 50.

  The laser light incident on the second wavelength detection means 50 is transmitted in the first direction (right side in the figure) and the second direction (lower side in the figure) by the beam splitter 4 arranged in the second wavelength detection means 50. And divided. The laser beam that has passed through the beam splitter 4 in the first direction is divided by the beam splitter 5 into the first direction (right side in the figure) and the third direction (lower side in the figure). The laser beam that has passed in the direction of is emitted in the direction of the first wavelength detection means 60. The laser light incident on the first wavelength detection means 60 is transmitted in the first direction (right side in the figure) and the fourth direction (lower side in the figure) by the beam splitter 6 disposed in the second wavelength detection means. The laser light that has been split into two and passed through the beam splitter 6 in the first direction enters the exposure device as output light of the laser device.

  On the other hand, the laser beam reflected in the second direction by the beam splitter 4 passes through the partial reflection mirror 7 installed below the beam splitter 4 and enters the coarse etalon spectroscope 12. The laser light reflected in the third direction by the beam splitter 5 passes through the partial reflection mirror 8 disposed below the beam splitter 5 and enters the fine etalon-type spectrometer 13. Further, a part of the second reference light generated from the second reference light source 10 is reflected by the partial reflection mirror 7 and enters the coarse etalon spectroscope 12, and the remaining reference light passes through the partial reflection mirror 7. It passes through and is reflected by the partial reflection mirror 8 and enters the fine etalon spectroscope 13.

  The laser light reflected in the fourth direction by the beam splitter 6 passes through the partial reflection mirror 9 disposed below the beam splitter 6 and enters the grating type spectrometer 14. Further, the first reference light generated from the first reference light source 11 is reflected by the partial reflection mirror 9 and enters the grating type spectrometer 14.

  The result detected by the grating-type spectrometer 14 arranged in the first wavelength detection means 60 and the coarse etalon-type spectrometer 12 and the fine etalon-type spectrometer 13 arranged in the second wavelength detection means 50 are used. The detected result is output to the wavelength controller 15, and the wavelength selection element disposed in the narrowband unit 30 is controlled via the driver 16.

Hereinafter, the principle of a method for detecting and controlling the wavelength using the laser apparatus shown in FIG. 1 will be described.
After the laser light oscillation starts, first, the reference light generated from the first reference light source 11 and the laser light generated from the laser oscillator are spectrally separated using the first wavelength detecting means 60, and the reference light and the laser light are obtained. The wavelength λ _{L of the} laser beam is calculated from the difference in the position of focusing on the line sensor. However, since the grating-type spectroscope 14 has a large light loss, the wavelength is detected by the integrated value of a plurality of pulsed laser beams.

Here, since the grating is used, there is no influence of the reflection film characteristic fluctuation that occurs when the etalon is used, and an accurate value (absolute wavelength) of the wavelength λ _L of the laser beam can be obtained. In the case where the wavelength lambda _L of the laser beam is out largely from the target oscillation wavelength lambda _T by controlling the disposed narrowed portion wavelength selecting element, a target oscillation wavelength a wavelength lambda _L of the laser beam close to λ _T. When the difference between the wavelength λ _{L of the} laser beam and the target oscillation wavelength λ _T is reduced, interference formed on the line sensor when light having the wavelength λ _T is incident on the etalon disposed in the second wavelength detecting means. The fringes and the interference fringes formed on the line sensor when light of wavelength λ _L is incident are adjacent to each other with the same order. Therefore, if the two interference fringes are matched by controlling the wavelength selection element, the wavelength λ _{L of the} laser light can be reliably brought close to the target oscillation wavelength λ _T.

In other words, stores the position Ps of the interference fringes formed on the line sensor when a laser light was irradiated to the second wavelength detector as the wavelength lambda _S. A position on the line sensor corresponding to the target oscillation wavelength λ _T of the laser beam (hereinafter referred to as “position PT”) is obtained with reference to the position Ps of the interference fringe, and the wavelength selection element is controlled to thereby control the laser beam. What is necessary is just to make it the interference fringe to form approach the said position PT . In addition, since the position Ps is a value reflecting various changes in the characteristics of the etalon, even if the etalon characteristics change, errors in the control for bringing the wavelength λ _{L of the} laser light closer to the target oscillation wavelength λ _T are reduced. . Also, since an etalon is used, it is possible to feed back so as to control the wavelength by detecting the wavelength for each pulse oscillation of the laser.

  If the laser apparatus shown in FIG. 1 is used, the wavelength of the laser light can be calibrated while outputting the laser light to the exposure apparatus.

  FIG. 2 shows a configuration of a specific example of the first wavelength detecting means. In FIG. 2, a beam splitter 71 that divides the generated laser light and a total reflection mirror 72 are arranged, and a partial reflection mirror 73 is arranged above the total reflection mirror 72 and reflected by the total reflection mirror 72. The laser light passes through the partial reflection mirror 73 and is guided toward the grating type spectrometer 69. Further, the first reference light generated from the Pt lamp as the first reference light source 74 passes through the interference filter 75, the lens 75 ′, and the shutter 76, enters the partial reflection mirror 73, is reflected, and is reflected to the first. The light is emitted toward the wavelength detecting means. The lens 75 ′ collects the light from the reference light source 74 and efficiently enters the spectroscope 69. The grating-type spectroscope 69 is entirely covered with a casing so that the temperature of the entire interior can be adjusted, and a slit 67 is disposed at the entrance to the grating-type spectroscope. The laser light and the first reference light that have passed through the slit 67 are totally reflected by three total reflection mirrors, that is, the mirror 66, the mirror 65, and the mirror 64, and then become parallel light by the lens 63 and enter the grating 62. Next, the laser light and the first reference light dispersed by the grating 62 pass through the lens 63, are reflected by the mirror 64, the mirror 65, and the mirror 66 and then enter the CCD 68. The beam splitter 71 is disposed on a moving stage (not shown), and is disposed at a position indicated by a solid line when the optical path of the laser light is closed, and is indicated by a broken line when the optical path of the laser light is opened. Arranged at the indicated position.

Here, it will be described below that an interference filter 75 can be used by using a mirror provided with a dielectric multilayer film.
The Pt lamp generates not only ultraviolet light but also visible light. Further, regarding the diffracted light from the grating spectrometer, if the product of the diffraction order and the wavelength is the same even at different wavelengths, the diffraction angles are the same. For example, if the diffraction order m1 at the wavelength λ1 and the diffraction order m2 at the wavelength λ2 satisfy the relationship m1 × λ1 = m2 × λ2, the spectra of λ1 and λ2 are diffracted at the same position and cannot be identified. . Therefore, it is necessary to take out only the emission line near 193 nm of the Pt lamp. For this purpose, an interference filter having a wavelength bandpass characteristic may be used. However, the transmittance is very small. For example, the transmittance of a filter that transmits only a region with a half width of ± 20 nm in a region of 193 nm is 15%. . For this reason, the detected spectrum intensity is reduced, the S / N ratio is lowered, and the wavelength detection accuracy is deteriorated.

  In order to improve this, it is possible to use a dielectric multilayer mirror having a high light reflectance near the wavelength of 193 nm as the mirror 64 and the mirror 65 in FIG. 2 without using an interference filter. For example, when a mirror having spectral reflectance characteristics as shown in FIG. 3A is used for the mirror 64 and the mirror 65, the light is reflected by the multilayer mirror a total of four times after entering the grating spectrometer. become. For this reason, the spectral reflectance characteristic is as shown in FIG. 3B, and the reflectance at a wavelength of 193 nm is 90% or more, and is nearly 0% at other wavelengths. Therefore, as a result, a filter function having a half width of ± 7 nm and a transmittance of 90% or more is realized, and the performance is much superior to that of the interference filter.

  The grating-type spectroscope 69 is preferably a sealed structure. With such a configuration, the detected waveform of the spectrum can be made less susceptible to the disturbance due to the gas flow in the grating spectrometer, the refractive index variation, and the refractive index distribution. In addition, by keeping the entire sealed casing at a constant temperature, it is possible to prevent changes in spectroscope performance due to thermal expansion of mechanical parts and casing due to changes in outside air temperature, and to perform stable wavelength measurement. It can be carried out.

  Next, a method for detecting and controlling the wavelength using the laser apparatus according to the first embodiment of the present invention will be described. 4 to 8 are flowcharts showing an example of a method for detecting and controlling the wavelength. Wavelength detection in the present embodiment will be specifically described by taking an example in which an ArF excimer laser and a Ne-encapsulated Pt (platinum) lamp are used as a first reference light source. The target oscillation center wavelength of the narrow-band ArF excimer laser for semiconductor exposure is about 193.368 nm ± 0.1 nm. On the other hand, the Ne-encapsulated Pt lamp has a plurality of oscillation lines in the vicinity of a wavelength of 193 nm. Here, a Pt wavelength Pt1 = 193.43690 nm and a Ne wavelength Pt2 = 193.34545 nm are used as reference wavelengths.

In FIG. 4, first, it is determined whether it is after gas exchange or after a predetermined time (T ₁ ) has elapsed since the start of the operation of the laser apparatus. In the case of either after gas exchange or after a predetermined time has elapsed, a wavelength detection subroutine (FIG. 5 and FIG. 6) by the first wavelength detection means (grating type spectrometer + first reference light source). ). That is, every time the gas is exchanged and every time a predetermined time elapses, the first wavelength detection means using the grating spectrometer determines whether there is a large deviation from the target oscillation wavelength. The predetermined time (T ₁ ) is, for example, 1 week to 1 month. When the above case does not apply, the routine proceeds to a wavelength detection subroutine (FIG. 7) by the second wavelength detection means (course & fine etalon + second reference light source).

The wavelength detection subroutine by the first wavelength detection means will be described below.
Flow charts of the wavelength detection subroutine by the first wavelength detection means including the grating spectrometer are shown in FIGS. As shown in FIG. 5, when the wavelength detection subroutine by the first wavelength detection means is started, first, in step S21, current is supplied to the heater to heat the first wavelength detection means, and temperature control is started. To do. Thereby, when the wavelength detection is started, the first wavelength detecting means is heated so as to be within a predetermined temperature range. The reason for doing so is that a heat source such as a laser chamber exists in the vicinity of the first wavelength detecting means, and in order to prevent the first wavelength detecting means from being heated and causing the spectral characteristics to fluctuate in advance. This is because it is necessary to raise the temperature of the wavelength detection means itself.

  In step S22, it is determined whether or not the first wavelength detection means is within a predetermined temperature range. If the first wavelength detection means is not within the predetermined temperature range, the temperature of the first wavelength detection means is within the predetermined temperature range. After waiting until it stabilizes, the process proceeds to step S23. If the first wavelength detection means falls within the predetermined temperature range, the shutter of the first reference light source (Pt lamp) is closed in step S23.

  Next, in step S24, it is determined whether or not the first reference light source has reached the end of life from the total of the past light emission times, and if it has reached the end of life, an error signal is issued to output the first reference light source. Replace the lamp. If the first reference light source has not reached the end of its life, the first reference light source is turned on in step S25. In step S26, it is determined whether a predetermined time has elapsed from when the first reference light source is turned on until the light emission is stabilized. If the predetermined time has not been reached, step S26 is repeated. If a predetermined time has elapsed since the power of the first reference light source is turned on, the output of the CCD line sensor is detected with the shutter kept closed in step S27. This is for measuring background noise and removing the noise from the optical signal detected in a later step. Next, in step S28, the shutter of the first reference light source is opened, and in step S29, the spectrum of the reference light (Pt, Ne) output from the first reference light source is measured, and the spectral data of the reference light is stored. .

  The reference light passes through the slit, is reflected by each mirror, is collimated by a lens having a focal length of 820 mm, and is diffracted by a grating (number of groove lines: 94 / mm, blaze angle: 80 degrees). The diffracted light follows the reverse optical path, is again reflected by each mirror, and enters the CCD line sensor (sensor pixel size: 24 microns). The CCD line sensor is, for example, a light receiving element in which 1024 channel CCD elements are arranged, and each channel corresponds to the wavelength of the dispersed light. Therefore, the Pt wavelength Pt1 = 193.43690 nm and the Ne wavelength Pt2 = 193. A CCD element corresponding to each of 00345 nm detects strong light intensity. Since the light emission intensity of the Pt lamp is small, light reception by the line sensor is performed for a certain period of time, and the spectrum is measured by integrating and averaging the light reception intensity.

Thereafter, as shown in FIG. 6, the shutter of the first reference light source is closed (step S30), the power of the first reference light source is turned off (step S31), and the time during which the first reference light source is turned on is determined. Store it and add it to the past lighting time (step S32). In step S33, in order to sample the laser beam, the beam splitter is moved to the solid line position using the moving stage to close the optical path of the laser beam. Next, in step S34, the excimer laser oscillation is started, the laser beam is made incident into the wavelength detecting means, and the spectrum of the laser beam is measured using a grating type spectrometer (step S35). Thereafter, the moving stage is used to move to the beam splitter broken line position to open the optical path of the laser light (step S36). Using the spectral data of the reference light (Pt, Ne), the absolute wavelength λ _A of the laser light is calculated (step S37). FIG. 8 shows how to obtain the absolute wavelength of the laser beam.

  As shown in FIG. 8, in step S51, first, background measurement data is subtracted from the spectral data of the reference light and the laser light to remove noise components. That is, if the background measurement data is represented by BG (x), the spectrum measurement data of the Pt lamp is represented by Pt ′ (x), and the spectrum measurement data of the excimer laser is represented by Ex ′ (x), the spectrum of the Pt lamp is represented by Pt (x). = Pt ′ (x) −BG (x), and the spectrum of the laser beam is obtained by Ex (x) = Ex ′ (x) −BG (x). Here, x represents the channel numbers 1 to 1024 of the CCD element.

Next, in step S52, a peak position (a position where the received light intensity is maximum) is detected within the detection range of Pt (wavelength Pt1), and it is determined whether or not the peak position is within the range of 193.43690 nm ± Δλ _Pt ( Step S53). Here, Δλ _Pt represents an allowable range of error of the peak position, and is set to about 5 pm, for example. If the detected peak position of Pt is outside the above range, an error signal is generated assuming that the spectrometer is not operating normally or that the lamp is abnormal. If the peak position is within the predetermined range, in step S54, the peak position X1 is calculated by quadratic function interpolation calculation. Next, the peak position (the position where the received light intensity is maximum) is searched within the detection range of Ne (wavelength Pt2), and it is determined whether or not the peak position is within the range of 193.00345 nm ± Δλ _Ne . Here, Δλ _Ne represents an allowable range of the peak position error, and is set to about 5 pm, for example. If the detected Ne peak position is outside the above range, an error signal is generated on the assumption that the spectrometer is not operating normally or the lamp is abnormal. If the peak position is within the above range, in step S57, the peak position X2 is calculated by quadratic function interpolation calculation. In order to calculate the peak position more accurately in step S54 and step S57, interpolation data such as quadratic function interpolation calculation, cubic function interpolation calculation, etc. is appropriately selected using data in the vicinity of the peak position. Preferably it is done.

Next, the peak position is calculated in the same procedure for the laser wavelength Ex. In step S58, the peak position of the laser beam is detected, and in step S59, it is determined whether the peak position is within a predetermined range. If the detected peak position is within the predetermined range, in step S60, for example, the peak position _XEx is calculated using a quadratic function interpolation calculation.

In step S61, the actual oscillation wavelength (absolute wavelength) λ of the laser is calculated from the calculated peak positions (X1, X2, X _Ex ) using the following equations (1) to (4). _Ex (= λ _A ) is obtained.

Here, β0 is the emission angle of the grating spectrometer when the diffracted light returns to the center position (coordinate origin) of the CCD, and β1 and β2 are the wavelengths when the wavelengths of the reference light generated from the reference light source are λ1 and λ2, respectively. exit angle of the grating spectrometer, the beta _Ex is the emission angle of the grating spectrometer in the case of excimer laser. Further, X1, X2 are the positions where the wavelength λ1 of the reference light, each of the spectra of λ2 is focused on the CCD, the distance from the CCD center _{position, X Ex} the position spectrum of the excimer laser is focused on the CCD , From the CCD center position, f represents the focal length of the lens.

More specifically with reference to FIG. 9, the reference light (wavelength λ1) is emitted by the grating at an emission angle β1, and forms an image at a position X1 from the CCD center position. Similarly, the reference light (wavelength λ2) is emitted by the grating at the emission angle β2 and forms an image at a distance of X2 from the CCD center position, and the excimer laser light is emitted by the grating at the emission angle _βEx , and the CCD center position. from forms an image at a distance of _{X Ex.} FIG. 10 shows the relationship between the position of the reference light and excimer laser light of the Pt lamp imaged on the CCD and the sensor output.

Referring to FIG. 6 again, in step S38, interference fringes between the coarse etalon and the fine etalon are detected using the second reference light source. In general, a coarse etalon-type spectrometer is used for coarse measurement, and a fine etalon-type spectrometer is used for fine measurement. In step S39, the interference fringes by the excimer laser are detected. In step S40, the wavelength λ _{E of the} excimer laser is calculated from the interference fringes by the second reference light source and the excimer laser. Then, in step S41, the equation Δλ _A = λ _E calculating a [Delta] [lambda] _a using 1-? _a.

The wavelength detection subroutine by the second wavelength detection means will be described below.
As shown in FIG. 7, when the wavelength detection subroutine by the second wavelength detection means is started, the second reference light source is turned on in step S11, and it is determined in step S12 whether the light emission of the reference light source is stable. If it is not stable, step S11 is repeated until it is stabilized. When the emission of the reference light source is stabilized, the coarse etalon interference fringe or the fine etalon interference fringe is detected by the second reference light (step S13). Next, the excimer laser is oscillated (step S14), and if not oscillated, steps S13 to S14 are repeated until oscillating. After the oscillation, interference fringes due to the excimer laser are detected in step S15. Next, in step S16, by using the interference fringes by the second reference light and laser light, to calculate the wavelength lambda _E of the laser beam. In step S17, Δλ = λ _T −λ _E is calculated, and in step S18, the target oscillation wavelength of the wavelength controller is shifted by (Δλ + Δλ _A ). Thereafter, the operations in steps S14 to S18 are repeated.

  Here, the case where the combination of the oscillation line 193.00345 nm and 193.4369 nm of the Pt lamp is used is described. The wavelength may be detected using a combination of 74245 nm and 193.4369 nm. In addition to the Pt lamp, emission lines of 193.759 nm and 193.00345 nm of an As lamp may be used.

  In the above operation, the position of the interference fringes formed on the line sensor by the second wavelength detecting means is measured at the same time as the time for splitting the laser beam by the first wavelength detecting means, and the position is determined as the first time. If calibration is performed with the absolute wavelength value obtained by the wavelength detection means, even if the characteristics of the etalon change due to various factors, it can be recalibrated to the correct absolute wavelength. The change in the characteristics of the etalon is a phenomenon that changes very slowly with time, and a level that adversely affects the wavelength control of the laser light takes several months or more. Therefore, before reaching such a level, for example, every few weeks to every month, recalibration using the second wavelength detection means may be performed.

  In the present invention, the spectrum of the laser beam and the spectrum of the reference light source can be measured simultaneously. In the wavelength detection and control method according to the first embodiment, first, the spectrum of the Pt lamp, which is the first reference light source, is measured, and then the spectrum of the excimer lamp laser light is measured. This is because when the spectrum and the spectrum of the laser beam are measured, the measurement cannot be performed when the wavelength of the laser beam matches the emission line of the Pt lamp. However, if the wavelength region of the laser beam that can be measured is limited to only the portion other than the emission line of the Pt lamp, the spectrum of the Pt lamp and the spectrum of the excimer laser beam can be measured simultaneously. According to this method, it is possible to avoid the influence of fluctuations in spectroscope performance due to a shift in measurement time for measuring the spectrum of the Pt lamp and the spectrum of the laser beam.

Hereinafter, a second embodiment of the present invention will be described in which the first wavelength detection means simultaneously detects the wavelength by the grating and measures the wavelength of the first reference light. FIG. 11 is a flowchart for explaining a wavelength detection method according to the second embodiment of the present invention.
When starting the wavelength detection by the first wavelength detecting means, in step S120, a current is supplied to the heater to heat the first wavelength detecting means, and temperature control is started. In step S121, it is determined whether the first wavelength detecting means is within a predetermined temperature range. If the first wavelength detecting means is not within the predetermined temperature range, the process waits until the first wavelength detecting means is stabilized within the predetermined temperature range, and then the step. The process proceeds to S122. If the first wavelength detection means is within the predetermined temperature range, the shutter of the first reference light source is closed at step 122.

  Next, in step S123, it is determined whether the first reference light source has reached the end of life from the total of the past light emission times. If the life has not been reached, the second reference light source is turned on (step S124). . In step S125, it is determined whether a predetermined time has elapsed from when the first reference light source is turned on until the light emission is stabilized. If the predetermined time is not reached, step S125 is repeated until the predetermined time is exceeded. If the predetermined time is exceeded, the background is measured (step S126). In step S127, the shutter of the first reference light source is opened, the beam splitter is moved, and the optical path is closed (step S128).

  In step S129, it is determined whether the target oscillation wavelength of the excimer laser beam is within the wavelength measurement range. If it is not within the measurement range, for example, as shown in FIG. 13B, the excimer laser oscillation wavelength is measured. Move within the range (step S130). For example, when it is within the measurement range as shown in FIG. 13A, the excimer laser is oscillated in step S131, and in step S132, the first reference light source and the excimer laser beam are used by using a grating type spectrometer. And simultaneously measure the spectrum. Thereafter, the shutter of the first reference light source is closed (step S133), and the power of the first reference light source is turned off (step S134). In step S135, the lighting time of the first reference light source is added, and the beam splitter is moved to open the optical path (step S136).

In step S137, the absolute wavelength λ _A of the laser beam is obtained, and in step S138, interference fringes of coarse etalon and fine etalon by the second reference light source are detected. Next, in step S139, interference fringes due to excimer laser light are detected. In step S140, interference fringes by the second reference light and the excimer laser light are obtained, and the oscillation wavelength λ _E of the excimer laser is obtained by calculation. Then, determine the Δλ _A from the equation Δλ _A = λ _E -λ _A.

Next, a laser device according to a third embodiment of the present invention will be described.
FIG. 14 shows the configuration of a laser apparatus according to the third embodiment of the present invention. In FIG. 14 , the laser beam narrowed by the wavelength narrowing unit 31 enters the laser chamber 1 from the window 2, and the amplified laser light passes through the window 3 from the laser chamber 1 to form a laser resonator. Is output outside of. The laser beam emitted from the window 3 is emitted toward the second wavelength detection means 51.

  The laser light emitted from the window 3 is divided into a first direction (right side in the figure) and a second direction (lower side in the figure) by a beam splitter 71 arranged in the second wavelength detection means 51. . The laser beam that has passed through the beam splitter 71 in the first direction is divided by the beam splitter 6 into a first direction (right side in the figure) and a third direction (lower side in the figure). The laser light that has passed in the direction of is incident on the exposure device as output light of the laser device. Here, the second wavelength detecting means 51 includes only a fine etalon type spectrometer, and does not include a coarse etalon type spectrometer. Accordingly, the laser light reflected in the second direction by the beam splitter 71 is incident on the fine etalon spectrometer 72 disposed below the beam splitter 71. The laser beam reflected in the third direction by the beam splitter 6 passes through the partial reflection mirror 9 disposed below the beam splitter 6 and is combined with the first reference light reflected by the partial reflection mirror 9. The light enters the grating type spectrometer 14.

Hereinafter, a method for performing wavelength detection and control using the laser apparatus shown in FIG. 14 will be described. However, the grating-type spectrometer 14 has the same configuration as that shown in FIG. 1, and the fine etalon-type spectrometer 72 has a 2 pm etalon with an FSR smaller than the usual 10 pm and a focal length. A 300 mm lens was used, and a CCD sensor having a pixel size of 25 microns and a number of pixels of 512 ch was used. According to the present embodiment, a value smaller than the etalon FSR used in the laser apparatus shown in FIG. 1 can be used, so that it is possible to perform wavelength detection with high resolution. is there.

FIGS. 15 to 17 show flowcharts of the wavelength detection method according to the third embodiment of the present invention. Here, wavelength detection is performed using a fine etalon type spectrometer every pulse, and wavelength detection is performed using a grating type spectrometer every several pulses (N).
As shown in FIG. 15 , first, in step S91, the counter is reset. Next, a wavelength measurement subroutine (FIG. 16 ) by the fine etalon type spectrometer is started (step S92). As shown in FIG. 16, in step S101, detects the interference fringes by the excimer laser, determine the amount of movement of the wavelength position by comparing the position X _A of the position and the previous fringes current interference fringes, from which The current wavelength λ _N is calculated (step S102). Next, in step S103, a target oscillation wavelength λ _T as a target is obtained, and a difference Δλ = λ _T −λ _N from the target oscillation wavelength is calculated. Next, the control wavelength of the wavelength controller is changed by Δλ.

Referring to FIG. 15 again, in step S93, the interference fringe position Xi is stored. In step S94, exposure of the grating type spectroscope is started and the count is incremented by one (step S95). Next, it is determined whether or not the count number Cnt has exceeded the predetermined count number N (step S96). If the predetermined count number has not been exceeded, the process returns to step S92, and the operations from step S92 to S96 are repeated. When the count number exceeds the predetermined count number, exposure of the grating-type spectrometer is stopped (step S97), and the average position X from the interference fringe position Xi (i = 0,..., N−1) is stopped. _A is calculated. Incidentally, in this time, the wavelength corresponding to the position X _A is unknown.

Next, in step S99, a wavelength measurement subroutine by the grating type spectroscope and the first reference light source is started. As shown in FIG. 17 , in step S111, the spectral portion of the excimer laser light and the spectral portion of the reference light output from the first reference light source are cut out from the exposed spectral waveform. Next, in step S112, the absolute wavelength λ _A of the laser beam is calculated, and in step S113, a difference Δλ = λ _T −λ _A from the target oscillation wavelength λ _T is calculated. In step S114, the control wavelength of the wavelength controller is changed by Δλ.
Referring again to Figure 15, at step S100, the absolute wavelength lambda _A calculated in step S112, the wavelength corresponding to the position _{X A} of the interference fringes. This makes it possible to control the wavelength of the laser light for each pulse while using the absolute wavelength of the reference light measured by the grating spectrometer as a reference.

However, using a laser apparatus shown in FIG. 1 or FIG. 14, it is also possible first wavelength detecting means determines whether or not functioning properly. That is, measurement is performed by using three known light emission lines as the wavelength of the first reference light source (Pt lamp), assuming that two of these are the reference wavelengths and the other is the wavelength of the excimer laser light. . If the measured wavelength is the same as the wavelength of the Pt lamp, it can be determined that the first wavelength detecting means is functioning normally.

It is a figure which shows the structure of the laser apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the structure of the wavelength detection means containing the grating used for the laser apparatus of this invention. (A) is a figure which shows the relationship between the spectral reflectance and wavelength of the mirror which formed the dielectric multilayer film, (b) is the spectral reflectance and wavelength at the time of reflecting 4 times by the mirror which formed the dielectric multilayer film. It is a figure which shows the relationship. It is a flowchart which shows the wavelength detection method which concerns on the 1st Embodiment of this invention. 5 is a flowchart illustrating a wavelength detection method (first half) by a first wavelength detection unit in the wavelength detection method according to the first embodiment of the present invention. 5 is a flowchart illustrating a wavelength detection method (second half) by a first wavelength detection unit in the wavelength detection method according to the first embodiment of the present invention. 5 is a flowchart illustrating a wavelength detection method by a second wavelength detection unit in the wavelength detection method according to the first embodiment of the present invention. It is a flowchart which shows the method of calculating | requiring an absolute wavelength in the wavelength detection method which concerns on the 1st Embodiment of this invention. It is a figure which shows the image of the laser beam and reference light which were diffracted by this and imaged on the CCD sensor. It is a figure which shows the relationship between the position of the reference light imaged on the CCD sensor, and a laser beam. It is a flowchart which shows the wavelength detection method (first half) which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows the wavelength detection method (latter half) which concerns on the 2nd Embodiment of this invention. (A) is a figure which shows the case where the spectrum of an excimer laser beam exists in a measurement range when implementing a wavelength detection method, (b) is a figure which shows the case where it does not exist in a measurement range. It is a figure which shows the structure of the laser apparatus which concerns on the 3rd Embodiment of this invention. It is a flowchart which shows the wavelength detection method which concerns on the 3rd Embodiment of this invention. It is a flowchart which shows the wavelength detection method by the 2nd wavelength detection means in the wavelength detection method which concerns on the 3rd Embodiment of this invention. It is a flowchart which shows the wavelength detection method by the 1st wavelength detection means in the wavelength detection method which concerns on the 3rd Embodiment of this invention. It is a figure which shows the structure of the conventional laser apparatus. It is a figure which shows the specific example of the monitor etalon used for a laser apparatus. It is a figure which shows the specific example of the grating type | mold spectrometer used for a laser apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,100 Laser chamber 2, 3, 101, 102 Window 4, 5, 6, 71 Beam splitter 7, 8, 9, 73, 104, 432 Partial reflection mirror 10 2nd reference light source 11 1st reference light source 12 Course Etalon type spectrometer 13 Fine etalon type spectrometer 14, 69, 440 Grating type spectrometer 15 Wavelength controller 16 Driver 30, 31, 130 Narrow band part 50, 51 Second wavelength detection means 60, 61 First wavelength detection Means 62, 446 Grating 63 Lens 64 to 66, 72, 73
67 Slit 68 CCD sensor 71 Moving stage 74 First reference light source 75 Interference filter (193 nm filter)
76 Shutter 103 Front mirror 105 Reference light source 108 Wavelength controller 109 Driver 244, 245 Concave mirror 246, 443 Mirror 62, 446 Grating 430 Monitor etalon 431 Diffuser plate 442, 445, 447 Concave mirror 444 Incident slit 448, 449 Incident slit image 450 Optical position Sensor 451 Incident optical system 452 Focal plane

Claims (18)

A laser oscillator;
A first wavelength detector that includes a first reference light source and a grating-type spectrometer, and detects the wavelength of the laser light output from the laser oscillator based on the wavelength of the reference light output from the first reference light source; Means,
A second wavelength detector that includes a second reference light source and an etalon-type spectrometer and detects the wavelength of the laser light output from the laser oscillator based on the wavelength of the reference light output from the second reference light source; Means,
Oscillating the laser oscillator to calculate and store the difference between the laser light wavelength detection value obtained by the first wavelength detection means and the laser light wavelength detection value obtained by the second wavelength detection means; By adding the stored difference to the difference between the laser light wavelength detection value obtained by the second wavelength detecting means and the laser light target wavelength when the laser oscillator is oscillated to the etalon type spectroscope Control means for correcting an error in the wavelength detection value of the laser beam obtained by the second wavelength detection means caused by a change in the film thickness of the reflective film coated thereon;
A laser apparatus comprising: A laser oscillator;
A first wavelength detector that includes a first reference light source and a grating-type spectrometer, and detects the wavelength of the laser light output from the laser oscillator based on the wavelength of the reference light output from the first reference light source; Means,
A second wavelength detecting means that includes an etalon-type spectrometer and detects the wavelength of the laser beam output from the laser oscillator;
The wavelength of the laser beam output from the laser oscillator is calculated based on the detection result of the reference beam and the laser beam obtained by the first wavelength detector, and the laser beam is input to the etalon-type spectrometer. The position of the interference fringe is stored as a reference interference fringe position, and when the laser oscillator is subsequently oscillated, the interference fringe position of the laser light obtained by the second wavelength detection means and the reference interference By calculating the difference between the value of the laser light oscillation wavelength obtained from the difference from the fringe position and the laser light target wavelength, the second result caused by the change in the thickness of the reflective film coated on the etalon-type spectrometer is obtained. Control means for correcting an error in the laser light wavelength detection value obtained by the wavelength detection means;
A laser apparatus comprising: The second wavelength detecting means generated when the control means changes the film thickness of the reflective film coated on the etalon-type spectrometer due to the influence of humidity in the atmosphere where the etalon-type spectrometer is installed. The laser apparatus according to claim 1, wherein an error in the detected value of the laser light wavelength obtained by the correction is corrected. The laser oscillator includes a narrowing means for narrowing a laser beam output from the laser oscillator,
Said control means controls said narrowing means to approach the wavelength of the laser beam output from the laser oscillator to the target wavelength, the laser device according to any one of claims 1-3.   The first wavelength detection means includes a mirror using an interference filter or a dielectric multilayer film having a wavelength bandpass characteristic in order to filter the first reference light output from the first reference light source. The laser apparatus of any one of Claims 1-4.   The laser apparatus according to claim 1, wherein the second wavelength detection unit includes a plurality of etalon spectrometers that perform detection with different accuracy.   The laser device according to any one of claims 1 to 6, wherein the grating-type spectrometer is disposed in a sealed housing having a temperature control means.   The first or second reference light source is one selected from the group consisting of a Pt lamp, a Ne-enclosed Pt lamp, and an As lamp, and is a known output from the first or second reference light source. The laser device according to claim 1, wherein two emission lines are used as a reference wavelength.   Two of the three known light emission lines output from the first reference light source are used in place of the reference light output from the first reference light source, and the known output from the first reference light source is used. Whether the first wavelength detecting means is functioning normally by measuring the wavelength by using the other of the three emission lines instead of the laser beam output from the laser oscillator. The laser device according to claim 1, wherein self-diagnosis is performed. Using the first wavelength detection means including the first reference light source and the grating type spectrometer, the wavelength of the reference light output from the first reference light source and the laser oscillator are oscillated to output from the laser oscillator. Detecting the wavelength of the laser beam to be detected;
Using the second wavelength detection means including a second reference light source and an etalon-type spectrometer, the wavelength of the reference light output from the second reference light source and the wavelength of the laser light output from the laser oscillator Detecting step (b);
The difference between the laser light wavelength detection value obtained in step (a) and the laser light wavelength detection value obtained in step (b) is calculated and stored, and then the second laser oscillator is oscillated when the laser oscillator is oscillated. By adding the stored difference to the difference between the laser light wavelength detection value obtained by the wavelength detection means and the laser light target wavelength, the change in the thickness of the reflective film coated on the etalon-type spectrometer A step (c) of correcting an error in the laser light wavelength detection value obtained by the second wavelength detection means that occurs;
A wavelength detection method comprising: The wavelength of the laser light output from the laser oscillator based on the wavelength of the reference light output from the first reference light source using the first wavelength detection means including the first reference light source and the grating type spectrometer. Detecting step (a);
Storing the position of the interference fringes when the laser light is input to the second wavelength detection means including the etalon-type spectrometer as a reference interference fringe position (b ′);
Thereafter, when the laser oscillator is oscillated, the value of the laser light oscillation wavelength obtained from the difference between the interference fringe position of the laser light obtained by the second wavelength detecting means and the reference interference fringe position and the laser light target A step of correcting an error in a laser light wavelength detection value obtained by the second wavelength detection means caused by a change in the film thickness of the reflective film coated on the etalon spectroscope by calculating a difference from the wavelength. (C),
A wavelength detection method comprising: Step (c) is the second wavelength detection that occurs when the film thickness of the reflective film coated on the etalon spectrometer changes due to the influence of humidity in the atmosphere in which the etalon spectrometer is installed. The wavelength detection method according to claim 10 or 11, which is a step of correcting an error in a laser beam wavelength detection value obtained by the means. The step ( a ) uses the first wavelength detection means to detect two known light emission lines output from the first reference light source and the wavelength of the laser light output from the laser oscillator. includes Rukoto the absolute wavelength of laser light by,
Step (c) performs wavelength control of the laser beam so that the wavelength of the laser beam output from the laser oscillator approaches the target wavelength based on the detection result obtained by using the second wavelength detector. The wavelength detection method of Claim 10 including this. Based on the detection result in step (a), the method further comprises a step of performing rough adjustment so that the wavelength of the laser light output from the laser oscillator approaches a target wavelength,
Step (c) comprises performing a further close as to fine-tune the wavelength of the laser beam outputted from the laser oscillator to the target wavelength, claim 1:10 3 any one wavelength detection method according to.   The wavelength detection method according to claim 10, wherein step (b) includes performing detection with different accuracy using second wavelength detection means including a plurality of etalon-type spectrometers.   The wavelength detection method according to any one of claims 10 to 15, further comprising a step of adjusting the grating spectrometer to a predetermined temperature before step (a).   The step (a) includes simultaneously detecting the wavelength of the reference light output from the first reference light source and the wavelength of the laser light output from the laser oscillator. 4. A method for detecting the wavelength of laser light according to item.   Two of the three known light emission lines output from the first reference light source are used in place of the reference light output from the first reference light source, and the known output from the first reference light source is used. Whether the first wavelength detecting means is functioning normally by measuring the wavelength by using the other of the three emission lines instead of the laser beam output from the laser oscillator. The wavelength detection method according to claim 10, further comprising a step of self-diagnosis.

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