JP2649357B2 - Excimer laser wavelength controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength control device for a narrow-band oscillation excimer laser, and more particularly to a wavelength control device for an excimer laser used as a light source for a reduction projection exposure apparatus.

[Conventional technology]

Attention has been paid to the use of excimer lasers as light sources for reduction projection exposure apparatuses for manufacturing semiconductor devices. This is because the excimer laser has a short wavelength (KrF laser has a wavelength of about 248.4 nm), which may extend the limit of light exposure to 0.5 μm or less. This is because many excellent advantages such as a deeper focal depth, a smaller numerical aperture (NA) of the lens, a larger exposure area, and a larger power can be expected as compared with the line.

However, there is a problem to be solved when using an excimer laser as a light source of a reduction projection exposure apparatus.
There are two major problems.

One is that the wavelength of the excimer laser is as short as 248.35 nm, and the material that transmits this wavelength is quartz, CaF ₂ and MgF _2.
That is, only quartz can be used as a lens material in terms of uniformity and processing accuracy. This makes it impossible to design a reduction projection lens with chromatic aberration correction. Therefore, to the extent that this chromatic aberration is negligible
It is necessary to narrow the band of the excimer laser.

Another problem is how to prevent speckle patterns generated with the narrow band of the excimer laser and how to reduce the power accompanying the narrow band.

As a technique for narrowing the band of an excimer laser, there is a technique called an injection lock method. In this injection lock system, a wavelength selecting element (etalon, diffraction grating, prism, etc.) is arranged in a cavity of an oscillator stage, a spatial mode is restricted by a pinhole, and a single mode oscillation is performed. Synchronize injection. For this reason, the output light has high coherence,
When this is used as a light source for a reduction exposure apparatus,
A pattern occurs. It is considered that the generation of the speckle pattern depends on the number of spatial transverse modes included in the laser beam. That is, if the number of spatial transverse modes contained in the laser beam is small, a speckle pattern is likely to occur, and if the number of spatial modes is large, the speckle pattern
It is known that patterns hardly occur. The above-described injection lock method is essentially a technique for narrowing the bandwidth by remarkably reducing the number of spatial transverse modes. Since the occurrence of a speckle pattern becomes a serious problem, it cannot be used in a reduced projection exposure apparatus.

Another promising technique for narrowing the band of an excimer laser is an etalon that is a wavelength selection element.
As a conventional technique using this etalon, AT & T Bell Labs has proposed a technique in which an etalon is arranged between a front mirror of an excimer laser and a laser chamber to narrow the band of the excimer laser. However, this method has the problems that the spectral line width cannot be made very narrow, the power loss due to etalon insertion is large, and the number of spatial transverse modes cannot be made too large.

Therefore, the inventors have a large effective diameter (about several tens mmφ) between the rear mirror of the excimer laser and the laser chamber.
The etalon configuration is adopted.
Narrow band excimer laser light with an output of about 50 mJ per pulse is obtained by performing a uniform narrowing with a spectrum width of about 0.003 nm or less at full width at half maximum in a range of × 10 mm ² . In other words, by employing a configuration in which an etalon is arranged between the rear mirror of the excimer laser and the laser chamber, the reduction in the bandwidth of the laser, the securing of the number of spatial transverse modes, and a reduction in power loss due to insertion of the etalon reduce the size of the reduced projection exposure apparatus. It solved the essential problem required for a light source.

However, the configuration in which the etalon is arranged between the rear mirror of the excimer laser and the laser chamber has excellent advantages in narrowing the band, securing the number of spatial transverse modes, and reducing power loss, but the power transmitted through the etalon is low. Since the etalon becomes extremely large, a physical change such as a temperature change occurs in the etalon, which causes a problem that the center wavelength of the oscillation output laser light fluctuates, multi-wavelength oscillation occurs, and the power is remarkably reduced. This tendency is particularly noticeable when two or more etalons having different free spectral ranges are used for narrowing the band.

[Problems to be solved by the invention]

When a configuration in which an etalon having a large effective diameter is arranged between the rear mirror and the laser chamber in this manner is employed as a light source of a reduction projection exposure apparatus in terms of narrowing the band, securing the number of spatial transverse modes, and reducing power loss. When recruiting,
Although a favorable advantage is generated, a new problem such as a fluctuation of the oscillation center wavelength and a fluctuation of the power arises, which is remarkable when two or more etalons having different free spectral ranges are arranged between the rear mirror and the laser chamber. became.

The present invention relates to an excimer laser having a configuration in which two or more etalons having different free spectral ranges are arranged between a rear mirror and a laser chamber. In the excimer laser, the center wavelength of output laser light is fixed with high accuracy to reduce fluctuations in laser power. It is another object of the present invention to provide an excimer laser wavelength control device capable of obtaining a stable output.

[Means for solving the problem]

According to the present invention, the wavelength selection characteristics of two or more etalons having different free spectral ranges disposed between the rear mirror and the laser chamber are feedback-controlled by detecting the center wavelength of the output laser light and the power of the center wavelength. I do.

In the present invention, the center wavelength and the power are stabilized by executing the following two controls simultaneously or alternately.

1) Center wavelength control: at least the transmission wavelength of the etalon having the minimum free spectral range is shifted, and the output center wavelength is controlled to a desired wavelength.

2) Superposition control: Shifting the transmission center wavelengths of the other etalons except for the etalon having the minimum free spectral range, controls the transmission center wavelengths of all the etalons so that they overlap, thereby obtaining the maximum power. .

Here, the control of the transmission center wavelength of the etalon can be achieved by controlling the temperature and angle of the etalon, the refractive index of the gas in the etalon gap (that is, the gas pressure), and the etalon gap interval.

That is, according to the present invention, at least two etalons are arranged between the laser chamber of the excimer laser and the rear mirror, and the wavelength of the output laser light is controlled by controlling the wavelength selection characteristics of these etalons. In the wavelength control device, a wavelength detecting means for detecting the wavelength of the output laser light, a power detecting means for detecting the power of the center wavelength of the output laser light, and a wavelength detected by the wavelength detecting means for matching a desired specific wavelength. A first control unit for controlling at least a wavelength selection characteristic of an etalon having a minimum free spectral range among the etalons; and a control unit for excluding an etalon having a minimum free spectral range so that the detection power by the center wavelength power detection unit is maximized. And second control means for controlling the selected wavelength characteristic of the etalon. Ete is achieved.

According to the invention, at least two etalons are arranged between the laser chamber of the excimer laser and the rear mirror, and the wavelength selection characteristics of these etalons are controlled to control the wavelength of the output laser light. In the wavelength control device, first power detection means for detecting the output power of the laser, second power detection means for detecting the power of a predetermined wavelength component of the output laser light, and the output of the second power detection means And a wavelength selection characteristic of at least a minimum etalon of a free spectral range among the etalons so that the power standardized by the standardization means is maximized. First control means for controlling, and the free spectral range so that the second power is maximized. It constituted comprising a second control means for controlling the wavelength selection characteristic of the other of the etalon, except the smallest etalon.

[Action]

According to the present invention, the center wavelength of the output laser light is fixed at a desired wavelength by the first control means for controlling the center wavelength, and the power of the center wavelength is maximized by the second control means for performing the overlay control. Is controlled as follows.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention. An excimer laser 10 to be controlled has a rear mirror 1, a laser chamber 2, and a front mirror 3, and two etalons 4 having different free spectral ranges between the rear mirror 1 and the laser chamber 2, respectively.
It is constructed by inserting 5.

Part of the laser light output from the excimer laser 10 is extracted as sample light via the beam splitter 11,
The light is inputted to an oscillation center wavelength and center wavelength power detector 14 via a lens 12 and an optical fiber 13.

The oscillation center wavelength and center wavelength power detector 14 detects the oscillation center wavelength λ of the excimer laser 10 and the power Pλ of the center wavelength included in the sample light. As the oscillation center wavelength and center wavelength power detector 14, the one shown in FIG. 3 can be used.

Oscillation center wavelength and center wavelength power detector shown in FIG.
14 comprises a diffraction grating type spectroscope 140 comprising concave mirrors 143, 145 and a diffraction grating 144, and an optical position sensor 146. The sample light inputted through the optical fiber 13 is
And is input from the entrance slit 142 of the spectroscope 140. The light input from the entrance slit 142 is a concave mirror 143
Are reflected and become parallel light, and are irradiated on the diffraction grating 144.
The diffraction grating 144 is fixed at a predetermined angle and reflects at a diffraction angle corresponding to the wavelength of the incident light. The light is guided to the diffraction grating concave mirror 145, and the reflected light from the concave mirror 145 is reflected by the optical position sensor 14.
Guided to 6 and imaged. That is, the diffraction image of the incident slit 142 corresponding to the wavelength of the incident light is formed on the light receiving surface of the optical position sensor 146, and the center wavelength λ of the sample light can be detected from the position of the diffraction image of the incident slit 142. it can. The center wavelength power Pλ can be detected from the light intensity of the diffraction image of the entrance slit 142.

Note that a photodiode array, a PSD (position sensitive device), or the like can be used as the optical position sensor 146. Here, the optical position sensor 14
When using a photodiode array as 6, the center wavelength is detected by the position of the light receiving channel with the maximum light intensity,
The center wavelength power is detected from the light intensity of the channel corresponding to the center wavelength or the sum of the light intensity of the channels near the center wavelength. When a PSD is used as the light position sensor 146, the size of the light receiving surface of the PSD is set to a size that does not receive the side peak as shown in FIG. From the center wavelength power.

The center wavelength λ and the center wavelength power Pλ of the sample light detected by the oscillation center wavelength and center wavelength power detector 14 are input to the wavelength controller 15.

The wavelength controller 15 is connected to the etalon 4 via the driver 16.
And 5 are selected so that the center wavelength of the sample light, that is, the output light of the excimer laser 10, coincides with a predetermined desired wavelength, and the center wavelength power is maximized. I do. Here, the control of the wavelength selection characteristics of the etalons 4 and 5 by the driver 16 is performed by controlling the temperatures of the etalons 4 and 5, controlling the angles of the etalons 4 and 5, and controlling the pressure in the air gaps of the etalons 4 and 5. , And control of the gap intervals of the etalons 4 and 5 and the like. For example, when the control of each angle of the etalons 4 and 5 is adopted, an angle adjusting mechanism as shown in FIG. 29 can be used.

In FIG. 29, the etalon 4 is mounted on an etalon mounting plate 42 by an etalon holder 41, and the etalon mounting plate 42 is mounted on one end of a substrate 44 by a hinge 43. The substrate 44 has a tapped hole 45 formed at the other end, and a screw 51 having one end abutting on the etalon mounting plate 42 and the other end directly connected to the pulse motor 46 is inserted into the tapped hole 45. Is mounted on a pulse motor mounting plate 48 so as to be movable in the traveling direction of a screw 51 by a linear guide 47. A screw 47 and an etalon mounting plate 42 are provided between the etalon mounting plate 42 and the board 44.
A spring 49 is provided for maintaining contact with the spring. In such a configuration, if the pulse motor 48 is controlled by the driver 16, the angle of the etalon 4 with respect to the optical axis can be controlled with high accuracy. In FIG. 29, a rod 50 is for fixing the angle adjusting mechanism to the excimer laser main body.

Before describing the details of the control by the wavelength controller 15, the principle of this control will be described with reference to FIG.

FIG. 2 is a graph showing the wavelength selection characteristics of two etalons 4 and 5 having different free spectral ranges used in this embodiment. The etalon ΔE ₁ (for example, etalon 4) having a small free spectral range is used. ) Is indicated by a solid line, and the wavelength selection characteristic of etalon ΔE ₂ (for example, etalon 5) having a large free spectral range is indicated by a dotted line. For the excimer laser 10 shown in FIG. 1, the oscillation occurs at a wavelength region where the wavelength selection characteristics are overlapped in the wavelength selection characteristics and the etalon #e ₂ etalon #e _1, the output laser having a wavelength corresponding to the overlapping portion Light is obtained. As is clear from FIG. 2, the maximum output laser light power is obtained in the case of FIG. 2A where the transmission center wavelengths of the etalon ΔE ₁ and the etalon ΔE ₂ coincide with each other.
Transmission center wavelength of the E ₁ and etalon #e ₂ second view (b), the second
It can be understood that when the laser beam shifts as shown in FIG. 3C, the output laser light power decreases, and the side peaks increase exponentially instead, resulting in multi-wavelength oscillation. Considering the case where the transmission center wavelength of the etalon ♯E _{1 having} a small free spectral range is fixed and the transmission center wavelength of the etalon ♯E _{2 having} a large free spectral range is shifted, in this case, the oscillation center wavelength of the excimer laser is obtained. It has been found by experiment that there is almost no change.

Thus, in the wavelength controller 15 of this embodiment, first, a difference Δλ (= λ−λ ₀ ) between the oscillation center wavelength λ detected by the oscillation center wavelength and the center wavelength power detector 14 and a preset wavelength λ ₀ is determined. Calculate and fix the oscillation center wavelength to the desired setting wavelength by shifting the transmission center wavelength of etalon ♯E ₁ or etalon ♯E ₁ and ♯E ₂ having a small free spectral range, and then ♯E having a large free spectral range By shifting the transmission center wavelength of ( _{2) in} the direction in which the output laser light power increases, the etalon
The transmission center wavelengths of E ₁ and ΔE ₂ are controlled to overlap.

FIG. 5 shows a specific control example of the wavelength controller 15. First, in step 151, the oscillation center wavelength and the center wavelength power are read. Here, a predetermined number of sampling laser pulses oscillated, by averaging and calculates the oscillation center wavelength λ and the center wavelength power P _2. The reason why such a process is performed is that, since the excimer laser is a pulse gas laser, the output laser light power varies from pulse to pulse.

Next, the center wavelength λ detected in step 152 and a preset desired wavelength λ are set. Is calculated (Δλ = λ−λ ₀ ).

Subsequently, in step 153, the difference ΔPλ between the currently sampled (read) center wavelength power Pλ and the previously sampled center wavelength power Pλ−1 is calculated (ΔPλ = Pλ−Pλ−1). Thereafter, the process proceeds to the center wavelength control subroutine 200.

The contents of the center wavelength control subroutine 200 are shown in FIG. That is, in the central wavelength control subroutine 200 performs a control to shift by a value Δλ calculating the transmission wavelength of the free spectral range of small etalon #e ₁ in step 152 (step 201). Incidentally, in the central wavelength control subroutine 200, as well as free spectral range smaller etalon #e _1, it may be configured to shift the transmission wavelength with regard free spectral range greater etalon #e _2. FIG. 7 shows the contents of the center wavelength control subroutine 200 in this case. In FIG. 7, control is performed to shift the transmission wavelengths of both etalons ♯E ₁ and ♯E ₂ by a value Δλ (step
202).

When the center wavelength control subroutine 200 ends, the process proceeds to the etalon superposition control subroutine 300. The contents of the etalon superposition control subroutine 300 are shown in FIG. First, in step 301, it is determined whether the value ΔPλ calculated in step 153 is positive (ΔPλ> 0). If ΔPλ> 0, step 30
Branched into two, the previous control determines whether to shift a large transmission wavelength of the etalon #e ₁ of free spectral range on the short wavelength side (at the time of sampling) is performed. If it is determined that the shift to the short wavelength side in this determination branches to step 303, it is shifted by the short wavelength side more predetermined small wavelength transmission wavelength of the etalon #e _2. Step 30
Is determined to have shifted the transmission wavelength of the last etalon #e ₂ to the long wavelength side in 2 the process proceeds to step 304, it shifts the transmission wavelength of the etalon #e ₂ only the longer wavelength side by a predetermined small wavelength.

If it is determined in step 301 that ΔPλ ≦ 0, the process proceeds to step 305. Step 305 In the previous control determines whether to shift the transmission wavelength of the etalon #e ₂ (during sampling) on the shorter wavelength side is performed. Here, if it is determined to have shifted to the short wavelength side branches to step 306, it shifts the transmission wavelength of the etalon #e ₂ by a predetermined small wavelength to the long wavelength side. The shift in step 305, when it is determined that the shift transmission wavelength of the previous etalon #e ₂ to the long wavelength side, the process proceeds to step 307, the transmission wavelength of the etalon #e ₂ by a predetermined small wavelength on the short wavelength side Let it.

Thus, the etalon overlay control subroutine 30
In 0, it determines the transmission wavelength shift direction of the etalon #e ₂ to increase the output laser light power based on the shift direction of the code and the previous transmission wavelength values DerutaPiramuda, transmission of the etalon #e ₂ on this determination the direction Shift the wavelength.

FIG. 9 shows the relationship between the transmission wavelength spectrum of etalon ΔE ₂ and the actual laser oscillation spectrum under the relationship between the superposition of etalons ΔE ₁ and ΔE ₂ . In FIG. 9, the dotted line shows the transmission spectrum of etalon ΔE ₂ , and the solid line shows the actual laser oscillation spectrum. In FIG. 9, λE ₁ indicates the transmission center wavelength of the etalon ΔE ₁ and λE ₂ indicates the transmission center wavelength of the etalon ΔE ₂ .
Ninth output power max conditions in maximum picture from the ninth diagram transmission center wavelength RamudaE ₂ apparent as etalon #e ₁ in the transmission center wavelength RamudaE ₁ and etalon #e ₂ was wrapped completely (b)
It can be seen that the maximum output laser light power cannot be obtained in the state of FIG. 9A or 9C where Pλ is obtained and the superposition is insufficient.

FIG. 10 shows an etalon superposition control subroutine 300.
In this example, control is performed when the number of etalons inserted between the rear mirror of the excimer laser and the laser chamber is three or more, that is, a plurality of etalons to be subjected to etalon superposition control are provided. Etalon ♯
E ₂ , ♯E ₃ ... ♯En show the control when En. This first
The control in FIG. 0 is basically the same as that shown in FIG. However, in FIG. 10, a plurality of etalons ♯E ₂ , ♯E
Steps 308 and 309 are added to the flow shown in FIG. 8 in order to control ₃ ... That is, in step 308, it is determined whether or not the superposition of the currently controlled etalon ♯Ek has been completed. If it is determined that the process has been completed, the process branches to step 309, and in the next superposition control of the etalon, the superposition control of the etalon エ Ek + 1 is performed instead of the etalon ♯Ek. This control is continued until k = n. In addition,
In the embodiment shown in FIG. 10, the etalons ♯E _{2 to} ♯En are configured to be sequentially controlled, but the order of the control is arbitrary. If the superposition control is executed for all the etalons of the etalons ♯E _{2 to} ♯En, the maximum output laser light power can be obtained.

FIG. 11 shows a modification in which the oscillation center wavelength and center wavelength power detector 14 is configured using a monitor etalon. In this modified example, a monitor etalon 147 is used instead of the diffraction grating type spectroscope 140 shown in FIG.

As shown in FIG. 11, a position sensor 146 is provided at a position where interference fringes generated by the monitor etalon 147 can be detected. Using the fact that the interference fringes move when the center wavelength changes, the center wavelength can be detected.

As the optical position sensor 146, a photodiode array or a PSD may be used.

In the case of a photodiode array, the detection of the center wavelength power can be detected from the light intensity of the channel of the center wavelength or the sum of the light intensity of the channels near the center wavelength.

Also, in the case of SPD, it can be detected from the output of the PSD by installing it so that the interference fringe of the side peak does not enter the light receiving surface of the PSD.

When a photodiode array is used, it may be installed so that a light receiving surface and a plurality of interference fringes are formed. Further, as a design of the monitor etalon 147, when the difference between the peak wavelength of the side peak and the center wavelength is Δλside, the free spectral range of the monitor etalon and the FSRmoniter are Δλsidc ≠ n · FSRmoniter (n = 1, 2, 3,...). ). In this way, it is possible to prevent interference fringes due to a spectrum including the center wavelength from overlapping with interference fringes due to side peaks.

FIG. 12 shows another embodiment of the present invention.
This embodiment uses an excimer laser without directly detecting the oscillation wavelength.
The oscillation wavelength 10 is controlled to a desired wavelength. Compared with the embodiment shown in FIG. 1, the oscillation center wavelength and center wavelength power detector 14 detects monitor power and monitor power for detecting predetermined wavelength component power. And a predetermined wavelength component power detector 17
Accordingly, the configuration of the wavelength controller 18 is slightly different from that of the wavelength controller 15 shown in FIG.

The monitor power and predetermined wavelength component power detector 17 detects the light intensity of the sample light input via the optical fiber 13 as the monitor power, and detects the predetermined wavelength component power of the sample light as the predetermined wavelength component power. Things. This monitor power and predetermined wavelength component power detector
As FIG. 17, the one shown in FIG. 13 can be used.

A monitor power and predetermined wavelength component power detector 17 shown in FIG. 13 includes a diffraction grating type spectroscope 170 including concave mirrors 173 and 175 and a diffraction grating 174, and a first detector for detecting monitor component power.
And a second light intensity detector 177 for detecting a predetermined wavelength component power.

The sample light input through the optical fiber 13 is a lens
The light is condensed at 171, passes through a beam splitter 178,
The light enters from the zero entrance slit 172. This entrance slit
The light incident from 172 is reflected by the concave mirror 173 and the diffraction grating
Irradiated at 174. The diffraction grating 174 is fixed at a predetermined angle, and the incident light is diffracted according to its wavelength.
The diffracted light is guided to the concave mirror 175, and the reflected light from the concave mirror 175 forms a diffraction image on the exit slit 176, and is guided to a second light intensity detector 177 for detecting the intensity of the light transmitted through the exit slit 176. I will

A part of the light condensed by the lens 171 is reflected by the half mirror 178 and guided to the first light intensity detector 179.

That is, in the monitor power and predetermined wavelength component power detector 17, only the desired set wavelength component set by the angle of the diffraction grating 174 is used as the second light intensity detector.
Guided to 177. Therefore, the second light intensity detector 177
As a result, the light intensity of a desired set wavelength component is detected as a predetermined wavelength component power Pλ. In addition, since the sample light input through the optical fiber 13 is directly input to the first light intensity detector 179, the light intensity of the input sample light is detected as the monitor power PL. Note that a photomultiplier, a photodiode, or the like can be used as the first light intensity detector 179 and the second light intensity detector 177.

The monitor power PL and the predetermined wavelength component power Pλ of the sample light detected by the monitor power and the predetermined wavelength component power detector 17 are input to the wavelength controller 18.

The wavelength controller 18 controls the wavelength selection characteristics (transmission center wavelength) of the etalons 4 and 5 via the driver 16 based on the input monitor power PL and predetermined wavelength component power Pλ.

FIG. 14 shows a specific control example of the wavelength controller 18. First, in step 181, the monitor power PL and the predetermined wavelength component power input from the monitor power and the predetermined wavelength component power detector 17 are read. Here, the laser pulse oscillated is sampled for a predetermined number in the same manner as in step 151 in FIG. 5, and is averaged to calculate a predetermined wavelength component power Pλ.

Next, in step 182, the predetermined wavelength component power Pλ read and calculated in step 181 is used as the monitor power.
By dividing by PL, a predetermined wavelength component power Pλ is normalized (= Pλ / PL).

Subsequently, in step 183, the predetermined wavelength component power and the predetermined wavelength component power Pλ standardized in step 182, the normalized value P-1 of the previously sampled predetermined wavelength component power, and the predetermined wavelength component power Pλ-1
Are calculated as Δ and Δλ, respectively (Δ =
− ₋₁ , ΔPλ = Pλ−Pλ ₋₁ ).

Next, in step 184, it is determined whether or not to perform center wavelength control. This determination is made based on whether the center wavelength control was performed last time or the etalon superposition control was performed. That is, if the etalon superposition control was performed last time, it is determined that the center wavelength control is to be performed. If the center wavelength control was performed last time, it is determined that the center wavelength control is not to be performed. This is because, as will be apparent from the description below, in this embodiment, the central wavelength control and the etalon superposition control are configured to be executed alternately.

If it is determined in step 184 that the center wavelength control is to be performed, the center wavelength control branches to a subroutine.

If it is determined in step 184 that central wavelength control is not to be performed, the process proceeds to step 185, where it is determined whether to perform etalon superposition control. The determination in step 185 is also performed based on whether the center wavelength control was performed last time or the etalon superposition control was performed, and when the center wavelength control was performed last time, it is determined that the etalon superposition control is performed,
When the etalon superposition control is performed last time, it is determined that the etalon superposition control is not performed. If it is determined in step 185 that the etalon overlapping control is to be performed, the process branches to an etalon overlapping subroutine 500.

The contents of the center wavelength control subroutine 400 are shown in FIG. First, in step 401, it is determined whether the value Δ calculated in step 183 is positive (Δ> 0). If Δ> 0, the flow branches to step 402 to determine whether or not the transmission wavelength of the etalon ΔE _{1 having} a small free spectral range has been shifted to the shorter wavelength side during the previous control (during sampling). If it is determined that the shift to the short wavelength side in this determination branches to step 403, shifting to the more short wavelength side of the transmission wavelength of the etalon #e _1. If it is determined in step 402 that the transmission wavelength of the etalon ΔE _{1 was} previously shifted to the longer wavelength side, the process shifts to step 404 to shift the transmission wavelength of the etalon ΔE ₁ to the longer wavelength side.

If it is determined in step 401 that Δ ≦ 0, the process proceeds to step 405. Step 405 In the previous control determines whether to shift the transmission wavelength of the etalon #e ₁ (during sampling) on the shorter wavelength side is performed. If it is determined to have shifted to the short wavelength side branches to step 406, it shifts the transmission wavelength of the etalon #e ₁ to the long wavelength side. Further, in step 405, when it is determined that the shift transmission wavelength of the previous etalon #e ₁ to the long wavelength side shifts to step 404, shifts the transmission wavelength of the etalon #e ₁ on the short wavelength side.

As described above, the etalon さ せ る that increases the output power of the laser based on the sign of Δ and the previous shift direction of the transmission wavelength.
Determining the transmission wavelength shift direction of E _1, shifts the transmission wavelength of the etalon #e ₁ on this determination the direction. Although only the transmission wavelength of ΔE ₁ is shifted here, the transmission wavelengths of ΔE ₁ and ΔE ₂ may be simultaneously shifted by the same amount.

Upon completion of the above control, the flow shifts to step 408 to determine whether or not the center wavelength control has been completed. If it is determined that the center wavelength control has been completed, the process branches to step 409, and the next control executes a process of setting the overlap control.

The contents of the etalon superposition subroutine 500 are shown in FIG. First, in step 501, step 181
It is determined whether or not the difference ΔPλ between the calculated predetermined wavelength component power Pλ and the previously sampled predetermined wavelength component power Pλ−1 is positive (ΔPλ> 0). If ΔPλ> 0, the flow branches to step 502 to determine whether or not the transmission wavelength of the etalon ΔE _{2 having} a large free spectral range has been shifted to the shorter wavelength side during the previous control (at the time of sampling). If it is determined that the shift to the short wavelength side in this determination branches to step 503, shifting to the more short wavelength side of the transmission wavelength of the etalon #e _2. Further, when it is determined that the shift transmission wavelength of the previous etalon #e ₂ to the long wavelength side shifts to step 504 in step 502, to shift the transmission wavelength of the etalon #e ₂ to the long wavelength side.

If it is determined in step 501 that ΔP ≦ 0, the process proceeds to step 505. Step 505 In the previous control determines whether to shift the transmission wavelength of the etalon #e ₂ (during sampling) on the shorter wavelength side is performed. If it is determined to have shifted to the short wavelength side branches to step 506, it shifts the transmission wavelength of the etalon #e ₂ to the long wavelength side. Further, in step 505, when it is determined that the shift transmission wavelength of the previous etalon #e ₂ to the long wavelength side shifts to step 507, shifts the transmission wavelength of the etalon #e ₂ to the short wavelength side.

Thus to determine the transmission wavelength shift direction of the etalon #e ₂ to increase the output power of the laser based on the sign of ΔPλ the shift direction of the previous transmission wavelength, shifts the transmission wavelength of the etalon #e ₂ on this determination the direction Let it.

Upon completion of the above control, the flow shifts to step 508 to determine whether or not the overlay control has been completed. Here, when it is determined that the superposition control has been completed, the process branches to step 509, and the next control executes a process of setting to perform the center wavelength control. Further, when three or more etalons are arranged in the laser resonator, the superposition control of the etalons may be performed sequentially as shown in FIG.

FIG. 17 shows a modification in which the monitor power and the predetermined wavelength component power detector 17 are configured using a monitor etalon.

As shown in FIG. 17, a slit 181 is placed at a position where the interference fringe created by the monitor etalon 180 can be detected,
The second light intensity detector 177 is installed immediately after the slit 181.

Further, the intensity of the sample light scattered by the monitor etalon 180 is measured by the second light intensity detector 179.

With such a configuration, the monitor power and the predetermined wavelength component power can be detected in the same manner as that shown in FIG.

FIG. 18 shows another example of the configuration of the monitor power and the predetermined wavelength component power detector 17. In this configuration example, light absorption by gas atoms and molecules is used. The gas filled cell 182 is filled with a gas exhibiting light absorption at a desired set center wavelength. The sample light is beam splitter 18
3. The light enters the gas filled cell 182 through the window 184 and is guided to the second light intensity detector 177 through the window 185. In addition, a part of the sample light is
The light is reflected by 3 and guided to the first light intensity detector 179.

Here, when the wavelength of the sample light does not match the characteristic absorption wavelength of the gas sealed in the gas sealing cell 182, the light transmitted through the gas sealing cell 182 does not attenuate much, but when matched, greatly attenuates. By measuring the amount of attenuated light with the second light intensity detector 177, it is possible to detect a predetermined wavelength component power. In addition, the first light intensity detector 179
Monitor power is detected.

FIG. 19 shows still another configuration example of the monitor power and predetermined wavelength component power detector 17. In this configuration example, predetermined wavelength component power is detected using fluorescence (laser-induced saturation fluorescence, hereinafter referred to as LIF) generated by light absorption by gas atoms and molecules. As shown in FIG. 19, the LIF cell 186 is filled with a gas that generates fluorescence by absorbing light having a desired set center wavelength. The fluorescence generated in the LIF cell 186 is extracted through the window 187 and detected by the second light intensity detector 177.

When the wavelength of the sample light input through the beam splitter 183 and the window 184 matches the characteristic absorption wavelength of the gas sealed in the LIF cell 186, the atoms and molecules of the gas absorb the laser light and generate fluorescence ( If they do not match, no fluorescence is generated).

By measuring the intensity of the fluorescence with the light intensity detecting element A, the power of a predetermined wavelength component can be detected. The monitor power is detected by the first light intensity detector 179.

The gas enclosed in the LIF cell 186 has a wavelength of about 248.35 ± 0.2 nm
In the case of a KrF narrow-band oscillation excimer laser that can be tuned (oscillation wavelength selection) with SO, O ₂ , N ₂ O, OCS, C ₆ H ₆ , H ₂ CO,
CH ₃ Br, CH ₃ I, CF ₃ I, CH ₃ -C (= 0) -CH ₃ , N C-C CH
Etc. can be used. In addition, the wavelength is 351 nm, 337 nm,
When using other excimer lasers such as 308 nm, 222 nm, 193 nm and 157 nm, a substance having a characteristic absorption wavelength at that wavelength may be selected.

FIG. 20 shows a further configuration example of the monitor power and predetermined wavelength component power detector 17. In this configuration example, a hollow cathode lamp is used. As shown in FIG. 20, the hollow cathode lamp 188 has an anode 189 and a cathode 190 inside, and is filled with a gas having a characteristic absorption wavelength at a desired set center wavelength. When the wavelength of the sample light entering the hollow cathode lamp through the beam splitter 183 and the window 184 does not match the characteristic absorption wavelength of the sealed gas, the gas atoms and molecules in the lamp 188 are photoionized. do not do. Therefore, DC current 191,
The discharge current flowing through the resistor R, the anode 189, and the cathode 190 does not change.

However, the wavelength of the sample light is
When the characteristic absorption wavelengths of the gas atoms and molecules enclosed in the tube 8 coincide with the characteristic absorption wavelengths, the gas atoms and molecules in the lamp 188 are photoionized, and the discharge current amount changes. The center wavelength power can be detected by detecting the amount of change via the capacitor C. The monitor power is detected by the first light intensity detector 179 (LOG method).

The hollow cathode lamp 188 has a wavelength of about 2
Kr tunable (selectable oscillation wavelength) at 48.35 ± 0.2nm
In the case of an F narrow band oscillation excimer laser, an Hg or Fe-based hollow cathode lamp can be used. As described above, when wavelength control is performed using characteristic absorption lines of atoms or molecules, the oscillation wavelength can be fixed at a desired absolute wavelength with high accuracy and for a long period of time. Becomes

FIG. 21 shows still another embodiment of the present invention. In this embodiment, the oscillation using a center wavelength and center wavelength power detector 14a using a diffraction grating type spectroscope that detects a large change in the center wavelength and the center wavelength power and the monitor etalon that detects a minute change in the center wavelength are used. A central wavelength detector 14b is provided. In general, a monitor etalon can have a very high resolution, and is optimal for detecting minute changes in the center wavelength. However, in order to increase the resolution of the monitor etalon, its free spectral range must be reduced. That is, the resolution R of the monitor etalon is (Where n is the refractive index of the medium between the mirror surfaces of the etalon, d is the mirror interval of the etalon, t is the finesse of the etalon, and λ is the wavelength). The free spectral range FSR Is represented by Therefore, when the resolution R of the monitor etalon is expressed by using the free spectral range FSR, Becomes Here, the finesse of the etalon cannot be increased more than a certain degree, so that the free spectral range FSR must be reduced in order to increase the resolution. However, when the detected wavelength shifts by the same wavelength as the free spectral range FSR, the monitor etalon produces almost the same interference fringe as the wavelength before the shift. Therefore, it is impossible for a high-resolution monitor etalon to detect a large change in the center wavelength. In particular, in the case of a pulse laser such as an excimer laser, when the wavelength changes for each pulse, it may not be possible to detect in which direction the wavelength has shifted. Therefore, in this embodiment, an oscillation center wavelength detector 14b using a high-resolution monitor etalon is provided to control the wavelength with high accuracy, and an oscillation using a diffraction grating type spectrometer is used to detect a large change in the center wavelength. A center wavelength and center wavelength detector 14a is provided.

As the oscillation center wavelength and center wavelength power detector 14a using the diffraction grating type spectroscope, the same one as shown in FIG. 3 can be used. The obtained center wavelength λg and center wavelength power Pλ are input to the wavelength controller 15a.

Oscillation center wavelength detector 14b using monitor etalon
As shown in FIG. 11, a high-precision center wavelength λe detected by the oscillation center wavelength detector 14b is also input to the wavelength controller 15a.

The wavelength controller 15a controls the wavelength selection characteristics of the etalons 4 and 5 based on the input values λg, λe, and Pλ.

FIG. 22 shows a specific control example of the wavelength controller 15a. First, in step 154, the center wavelength and the center wavelength power input from the oscillation center wavelength and center wavelength power detector 14a using the diffraction grating type spectrometer were read and input from the oscillation center wavelength detector 14b using the monitor etalon. Read the center wavelength with high accuracy. Here, for the same reason as in step 151 of FIG. 5, a predetermined number of oscillated laser pulses are sampled and averaged to calculate the center wavelength λg, center wavelength power Pλ, and center wavelength λe.

Next, the process proceeds to step 155, where the λ calculated in step 154 is used.
g, the difference between the set wavelength λ ₀ and λe Δλg, Δλe, namely Δλg
= Λg−λ ₀ , Δλe = λe−λ ₀ is calculated.

Then, the process proceeds to step 156, where the absolute value of the amount of change of the center wavelength detected by the center wavelength power detector 14a and the center wavelength of oscillation using the diffraction grating spectroscope with respect to the set wavelength |
Is Δλg | larger than 1/2 of the free spectral range FSR of the monitor etalon of the oscillation center wavelength detector 14b (| Δλg
g |> FSR / 2). Where | Δλg |
If it is determined that> FSR / 2, the flow branches to step 157 to execute a process of setting the change amount Δλ of the center wavelength to the set wavelength as Δλ = Δλg. If it is determined that | Δλg | ≦ FSR / 2, the flow shifts to step 158 to execute processing for setting the variation Δλ of the center wavelength to the set wavelength as Δλ = Δλe.

 The subsequent steps are the same as those shown in FIG.

As described above, in this embodiment, the oscillation center wavelength and center wavelength power detector 14a using the diffraction grating type spectroscope and the oscillation center wavelength detector 14b using the monitor etalon are provided, and the oscillation center wavelength and the center wavelength power are detected. Value of the change amount of the center wavelength detected by the detector 14a with respect to the set wavelength | Δ
λg | is larger than 1/2 of the free spectral range FSR of the monitor etalon of the oscillation center wavelength detector 14b (| Δλg |
> FSR / 2) The change wavelength Δλg with respect to the oscillation center wavelength and the center wavelength detected by the center wavelength power detector 14a or the set wavelength of the set center wavelength detected by the oscillation center wavelength detector 14b based on the determination of whether or not FSR / 2) The change amount Δλe with respect to is switched and selected.

In this embodiment, a monitor etalon having a free spectral range larger than the free spectral range of the monitor etalon used in 14b is used instead of the one using a diffraction grating type spectroscope as the oscillation center wavelength and center wavelength power detector 14a. The same configuration can be obtained by using the used one. Although the center wavelength power Pλ is detected by the oscillation center wavelength and center wavelength power detector 14a, this may be detected by using the oscillation center wavelength detector 14b using a monitor etalon.

FIG. 23 shows still another embodiment of the present invention.
In this embodiment, an oscillation center wavelength and center wavelength power detector using a diffraction grating type spectroscope as shown in FIG.
It is configured using a predetermined wavelength component power detector 17a using a monitor etalon 14c and a monitor etalon as shown in FIG.

FIG. 24 shows a wavelength controller 15b in this embodiment.
3 shows a specific control example. First, step 15
8, the center wavelength λg input from the center wavelength and center wavelength power detector 14c using the diffraction grating spectroscope.
In the predetermined wavelength component power detector 17a using the monitor etalon while reading the center wavelength power and
Read the center wavelength power. Here, for the same reason as in step 151 in FIG. 5, a predetermined number of oscillated laser pulses are sampled and averaged to calculate the center wavelength power P and the predetermined wavelength component power Pmλ.

Next, the process proceeds to step 159. In this step, a predetermined wavelength component power detector 17a using a monitor etalon is used.
Whether or not the predetermined wavelength component power Pmλ is detected,
That is, it is determined whether or not Pmλ = 0. Where Pmλ =
If it is determined to be 0, the process branches to step 160 to execute a process of setting the center wavelength λ to λ = λg, and further calculates a difference Δλ from the set wavelength λ ₀ (Δλ = λg−λe). The process proceeds to the wavelength control subroutine 200. This center wavelength control subroutine 200 is the same as the center wavelength control subroutine 200 shown in FIG.

If it is determined in step 159 that Pmλ ≠ 0, the process proceeds to step 162, where the predetermined wavelength component power P
By dividing mλ by the central wavelength power P, a value Pλ obtained by normalizing a predetermined wavelength component power Pmλ is calculated (P
λ = Pmλ / P).

Then, the process proceeds to step 163, in which the value Pλ standardized in step 162 and the value Pλ
−1 is calculated (ΔPλ = Pλ−Pλ−
1).

Thereafter, the process proceeds to the center wavelength control subroutine 400.
This center wavelength control subroutine 400 is the same as the center wavelength control subroutine 400 shown in FIG.

When the center wavelength control subroutine 200 or 400 is completed, the process proceeds to the etalon superposition control subroutine 300. This etalon overlay control subroutine 300 is the etalon overlay control subroutine 300 shown in FIG.
Is the same as

Note that in this embodiment, instead of using the diffraction grating type spectroscope as the oscillation center wavelength and center wavelength power detector 14c, a fine is used for a predetermined wavelength component power detector 17a that detects a change in wavelength. The same configuration can be obtained by using a monitor etalon using a monitor etalon having a larger free spectral range than the free spectral range of the monitor etalon.

Instead of the monitor etalon, a wavelength detector using characteristic absorption lines of atoms or molecules as shown in FIGS. 18 to 20 may be used as the predetermined wavelength component power detector 17a for detecting a minute wavelength change. . The control method in this case may be the same as in FIG. When such a wavelength detector is used, the oscillation wavelength can be fixed at a desired absolute wavelength with high accuracy and for a long period of time.

FIG. 25 shows still another embodiment of the present invention.
In this embodiment, the monitor power using a diffraction grating type spectroscope as shown in FIG. 13 and the monitor power using a predetermined wavelength component power detector 17b and a high resolution monitor etalon as shown in FIG. And a predetermined wavelength component power detector 17c.

FIG. 26 shows a wavelength controller 18a in this embodiment.
3 shows a specific control example. First, step 16
In 4, the monitor power input from the detector 17b using the diffraction grating type spectroscope and the predetermined wavelength component power are read, and the monitor power using the monitor etalon and the monitor power input from the predetermined wavelength component power detector 17c and Read the center wavelength power. Here, the fifth
A predetermined number of laser pulses oscillated for the same reason as in step 151 in FIG.
Predetermined wavelength component detector 17b using PL, diffraction grating type spectrometer
The predetermined wavelength component power Pg by the monitor and the predetermined center wavelength power P by the predetermined wavelength component detector 17c by the monitor etalon
e is calculated.

Next, the process proceeds to step 165, where the center wavelength powers Pe and P
Execute the normalization processing of g (e = Pe / Pg, g = Pg / PL).

Subsequently, the process proceeds to step 166, where the difference Δe, between the standard value e, g and the standard value e−1, g−1 at the time of the previous reading,
Processing for calculating Δg (Δe = ee−1, Δg
= Gg-1) Execute.

Subsequently, the flow shifts to step 167, where it is determined whether or not e> 0. Here, if e> 0, step
The process branches to 168 to execute the process of setting Δλ = Δe. Thereafter, the center wavelength control subroutine 400a and the etalon superposition subroutine 300 are executed. Here, the center wavelength control subroutine 400a is the same as the center wavelength control subroutine 400 shown in FIG. 14, and the etalon superposition subroutine 300 is the same as the etalon superposition subroutine 300 shown in FIG.

If it is determined in step 167 that Pe> 0 is not satisfied, the process proceeds to step 169, and processing for setting ΔPλ = ΔPg is executed. Thereafter, if it is determined in step 184 that the center wavelength is to be controlled, the process branches to a center wavelength control subroutine 400,
If it is determined in step 185 that the etalon overlapping control is to be performed, the process branches to an etalon overlapping subroutine 500. The center wavelength control subroutine 400 and the etalon superposition subroutine 500 are the same as those shown in FIG.

FIG. 27 shows still another embodiment of the present invention.
In this embodiment, a monitor power and center wavelength power detector 17d using a diffraction grating type molecular optical device as shown in FIG. 13 and an oscillation center wavelength using a high resolution monitor etalon as shown in FIG. It is configured using the detector 14d.

FIG. 28 shows a wavelength controller 18b in this embodiment.
3 shows a specific control example. First, step 17
At 0, the monitor power using the diffraction grating type spectrometer and the monitor power and the predetermined wavelength component power input from the predetermined wavelength component power detector 17d are read, and the center wavelength input from the oscillation center wavelength 14d using the monitor etalon is read. Read. Here, step 151 in FIG.
For the same reason as described above, a predetermined number of oscillated laser pulses are sampled, averaged, and the monitor power PL and the predetermined wavelength component power Pg by the monitor power and the predetermined wavelength component power detector 17d, and the oscillation center wavelength detector The center wavelength λe is calculated by 14d.

Next, the processing shifts to step 171 to normalize the predetermined wavelength component power Pg by the diffraction grating spectroscope (g = Pg / P
L) and monitor etalon oscillation center wavelength detector 14d
In the detected difference of the central wavelength λe the set wavelength λ ₀ Δλe
(Δλe = λe−λ ₀ ) and a predetermined wavelength component power Pg
Then, a difference ΔPg (ΔPg = Pg−Pg−1) between the wavelength and the previously sampled predetermined wavelength component power Pg−1 is calculated.

Subsequently, the absolute value of the difference between the center wavelength λe and the set wavelength λ ₀ |
ΔΔe | is larger than 1/2 of the free spectral range FSR of the monitor etalon of the oscillation center wavelength detector 14d (| Δλ
e |> FSR / 2) is determined. Where | Δλe |> F
If it is determined to be SR / 2, the center wavelength control subroutine
200, the etalon superposition subroutine 300 is executed.
Here, the center wavelength control subroutine 200 and the etalon superposition subroutine 300 are the same as those shown in FIG.

If it is determined in step 172 that | Δλe |> FSR / 2 is not satisfied, the process proceeds to step 173 to calculate a difference Δg between the value g normalized in step 171 and the value g−1 normalized in the previous reading. Processing (Δg = gg−1) is performed.

Subsequently, in step 174, a process of setting ΔPλ = ΔPg is executed, and the process proceeds to the center wavelength control subroutine 400. This center wavelength control subroutine 400 is the same as that shown in FIG.

In the embodiment shown in FIGS. 21 to 28, a detector using a monitor etalon is used as a detector for detecting a minute change near the center wavelength, and a large change is obtained using a diffraction grating type spectroscope or Although the configuration using a monitor etalon having a free spectral range larger than the free spectral range of the monitor etalon has been described, FIG. 18, FIG. 19 as a detector for detecting a minute change near the center wavelength, The same configuration can be obtained by using one utilizing absorption lines of atoms or molecules as shown in FIG.

〔The invention's effect〕

As described above, according to the present invention, in an excimer laser in which at least two etalons are arranged between a rear mirror and a laser chamber, output wavelength control is performed by combining center wavelength control and superposition control. In addition, a stable center wavelength can be obtained and power fluctuation can be made very small. Therefore, when an excimer laser to which the present invention is applied is used as a light source of a reduction projection exposure apparatus, a stable focus position,
Magnification and high resolution can be obtained, and the exposure time can be kept constant and the exposure amount can be easily controlled.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a wavelength control device for an excimer laser according to the present invention, FIG. 2 is a graph showing the principle of wavelength control according to the present invention, and FIG. 3 is a diagram of the embodiment shown in FIG. FIG. 4 is a diagram showing details of an oscillation center wavelength and a center wavelength power detector. FIG. 4 is a graph for explaining an operation when the PSD is used as an optical position detector of the detector shown in FIG. 3, and FIGS. FIG. 9 is a flow chart for explaining the operation of the embodiment shown in FIG. 11, FIG. 10 is a flow chart showing a modified example of the etalon superposition subroutine shown in FIG.
FIG. 13 is a diagram showing a modification of the oscillation center wavelength and center wavelength power detector shown in FIG. 3, FIG. 12 is a block diagram showing another embodiment of the present invention, and FIG. 13 is a diagram shown in FIG. FIG. 4 is a diagram showing details of a monitor power and a predetermined wavelength component power detector,
14 to 16 are flow charts for explaining the operation of the embodiment shown in FIG. 12, and FIGS. 17 to 20 are examples of changes in the monitor power and the predetermined wavelength component power detector shown in FIG. FIG. 21, FIG. 21 is a block diagram showing another embodiment of the present invention, FIG. 22 is a flowchart for explaining the operation of the embodiment shown in FIG. 21, and FIG. 23 is another embodiment of the present invention. 24 is a flowchart showing the operation of the embodiment shown in FIG. 23, FIG. 25 is a block diagram showing another embodiment of the present invention, and FIG. 26 is an embodiment shown in FIG. 27 is a block diagram showing another embodiment of the present invention, FIG. 28 is a flowchart showing the operation of the embodiment shown in FIG. 27, and FIG. 29 is one of the angle adjusting mechanisms.
It is a mechanism diagram showing an example. DESCRIPTION OF SYMBOLS 1 ... Rear mirror, 2 ... Laser chamber, 3 ... Front mirror, 4,5 ... Etalon, 10 ... Excimer laser, 11 ... Beam splitter, 14 ... Oscillation wavelength and center wavelength power detector, 15, 18 ... wavelength controller, 16 ...
... Driver, 17 ... Monitor power and predetermined wavelength power detector.

Claims (28)

(57) [Claims] An excimer laser wavelength control apparatus for arranging at least two etalons between a laser chamber of an excimer laser and a rear mirror, and controlling the wavelength of output laser light by controlling the wavelength selection characteristics of these etalons, respectively. A wavelength detecting means for detecting a wavelength of the output laser light; a power detecting means for detecting a power of a center wavelength of the output laser light; and a power detecting means for detecting the wavelength of the output laser light. First control means for controlling at least the wavelength selection characteristic of the etalon having the minimum free spectral range; and other etalons excluding the etalon having the minimum free spectral range so that the power detected by the power detection means having the center wavelength is maximized. Second controlling the wavelength selection characteristics of
A wavelength control device for an excimer laser, comprising: 2. The method according to claim 1, wherein the control of the wavelength selection characteristic of the etalon is performed by changing at least one selected from the temperature, angle, pressure of the gap, and gap interval of the etalon. A wavelength controller for an excimer laser as described in the above. 3. The etalon disposed between the laser chamber and the rear mirror comprises a first etalon having a small free spectral range and a second etalon having a large free spectral range. The wavelength control of an excimer laser according to claim 1, wherein at least the wavelength selection characteristic of the first etalon is controlled, and the second control means controls the wavelength selection characteristic of the second etalon. apparatus. 4. An etalon disposed between the laser chamber and the rear mirror comprises three or more etalons, and the first control means comprises at least a minimum of a free spectral range among the three or more etalons. 2. The excimer laser according to claim 1, wherein the wavelength selection characteristics of the etalon are controlled, and the second control means sequentially controls the wavelength selection characteristics of the other etalons except the etalon having the minimum free spectral range. Wavelength control device. 5. A first control means for calculating a difference between a wavelength detected by the wavelength detection means and a specific wavelength, and a transmission center wavelength of the etalon is shifted by the value calculated by the calculation means. The wavelength control device for an excimer laser according to claim 1, further comprising: means. 6. A second control means for calculating a difference between the output of the power detection means sampled last time and the output of the power detection means sampled this time, a sign of a value calculated by the calculation means, Claims comprising: means for determining a wavelength shift direction for increasing power based on the wavelength shift direction at the time of sampling; and means for shifting the transmission center wavelength of the etalon in the wavelength shift direction determined by the determination means. An excimer laser wavelength controller according to item (1). 7. A diffraction grating type spectroscope in which a rotation angle of a diffraction grating is fixed at a desired angle, and an optical position sensor for detecting a position of a diffraction image of an entrance slit of the diffraction grating type spectrometer. The wavelength control device for an excimer laser according to claim 1, further comprising: 8. The power detecting means includes: a diffraction grating type spectroscope in which the rotation angle of the diffraction grating is fixed to a desired angle; and a light detection device for detecting a light intensity of a diffraction image of an entrance slit of the diffraction grating type spectrometer. 2. A wavelength control device for an excimer laser according to claim 1, further comprising: 9. The apparatus according to claim 1, wherein said wavelength detecting means includes a monitor etalon and an optical position sensor for detecting a position of an interference fringe formed by said monitor etalon.
10. A wavelength control device for an excimer laser according to claim 7. 10. The power detecting means according to claim 1, wherein said power detecting means comprises a monitor etalon and light detecting means for detecting the light intensity of interference fringes formed by said monitor etalon.
10. A wavelength control device for an excimer laser according to claim 7. 11. An excimer laser wavelength control device for arranging at least two etalons between a laser chamber of an excimer laser and a rear mirror, and controlling the wavelength of output laser light by controlling the wavelength selection characteristics of these etalons, respectively. A first power detecting means for detecting the output power of the laser; and a second power detecting means for detecting the power of a predetermined wavelength component of the output laser light.
A power detecting means, a term qualifying means for normalizing an output of the second power detecting means by an output of the first power detecting means, and a power standardizing means for maximizing the power standardized by the normalizing means. A first method for controlling the wavelength selection characteristics of at least the etalon having the minimum free spectral range among the etalons
And second control means for controlling the wavelength selection characteristics of other etalons other than the etalon having the smallest free spectral range so that the second power for detecting the predetermined wavelength component power is maximized. Excimer laser wavelength controller equipped. 12. A first control means for calculating a difference between the output of the standardization means sampled last time and the output of the normalization means sampled this time, a sign of a value calculated by the calculation means, Claims comprising: means for determining a wavelength shift direction for increasing power based on the wavelength shift direction at the time of sampling; and means for shifting the transmission center wavelength of the etalon in the wavelength shift direction determined by the determination means. The wavelength control device for an excimer laser according to item (11). 13. A second control means for calculating a difference between a second power sampled last time and a second power sampled this time, a sign of a value calculated by the calculation means, A means for judging a wavelength shift direction in which power is increased based on the wavelength shift direction, and means for shifting a transmission center wavelength of the etalon in the wavelength shift direction judged by the judgment means. An excimer laser wavelength controller according to the item 11). 14. The excimer laser according to claim 11, wherein said first power detecting means comprises a light detecting element for detecting the light intensity of the laser light inputted to said second power detecting means. Wavelength control device. 15. A second power detecting means, comprising: an output slit provided in a diffraction grating type spectroscope in which a rotation angle of the diffraction grating is fixed at a desired angle; and a light detecting means for detecting an intensity of light transmitted through the slit. The wavelength control device for an excimer laser according to claim 11, further comprising an element. 16. The second power detecting means is provided with a slit for detecting a light intensity of a monitor etalon and an interference fringe formed by the monitor etalon, and detects a light intensity of light transmitted through the slit. The wavelength control device for an excimer laser according to claim 11, further comprising: a light detecting unit that performs the operation. 17. The second power detecting means comprises a cell filled with a gas absorbing light of a specific wavelength, and a light detecting element for detecting the intensity of light transmitted through the cell. The wavelength control device for an excimer laser according to item (11). 18. The second power detecting means includes a cell filled with a gas that emits fluorescence by absorbing light of a specific wavelength, and a detection element for detecting the fluorescence generated from the cell. The wavelength control device for an excimer laser according to item (11). 19. A second power detecting means, comprising: a cell in which a gas absorbing light of a desired wavelength and an electrode to which a predetermined voltage is applied are enclosed; and a current detecting means for detecting a change in current flowing through the electrode. The wavelength control device for an excimer laser according to claim 11, further comprising: 20. An excimer laser wavelength control apparatus for arranging at least two etalons between a laser chamber of an excimer laser and a rear mirror, and controlling the wavelength of output laser light by controlling the wavelength selection characteristics of these etalons, respectively. A first wavelength detecting means using a high-resolution monitor etalon for detecting a minute change in the center wavelength of the output laser light; and a lower resolution than the monitor etalon for detecting a large change in the center wavelength of the output laser light. A second wavelength detection unit, wherein an absolute value of a difference between a detection wavelength and a set wavelength by the second wavelength detection unit is larger than a half of a free spectral range of a monitor etalon of the first wavelength detection unit. Selects the detection wavelength of the second wavelength detection means, and selects the detection wavelength of the first wavelength detection means if the detection wavelength is smaller. And-option unit, the selected wavelength by the selection means to control at least the free wavelength selection characteristics of the spectral range minimum of the etalon of the etalon in order to match the desired specific wavelengths 1
Control means for controlling the wavelength selection characteristics of other etalons other than the etalon having the minimum free spectral range so that the power detected by the power detection means for the center wavelength is maximized.
A wavelength control device for an excimer laser, comprising: 21. An excimer laser wavelength controller according to claim 20, wherein said second wavelength detecting means comprises a diffraction grating type spectroscope. 22. The apparatus according to claim 20, wherein said second wavelength detecting means uses a monitor etalon having a free spectral range larger than the free spectral range of the monitor etalon of said first wavelength detecting means. Excimer laser wavelength control device. 23. A wavelength of an excimer laser for arranging at least two etalons between a laser chamber of a laser of an excimer laser and a rear mirror, and controlling a wavelength of an output laser beam by controlling wavelength selection characteristics of these etalons, respectively. In the control device, first power detection means for detecting the power of the center wavelength of the output laser light, and second power detection means using a high-resolution monitor etalon for detecting the power of a predetermined wavelength component of the output laser light Means for normalizing the output of the second power detection means with the output of the first power detection means; and wavelength detection having a lower resolution than the monitor etalon for detecting a large change in the center wavelength of the output laser light. Means, when the first power is not detected, so that a detection wavelength of the wavelength detection means coincides with a desired specific wavelength. First control means for controlling at least the wavelength selection characteristic of the etalon having the minimum free spectral range among the etalons, and when the first power is detected, the power standardized by the normalization means has a maximum power. Preferably, the power detected by the second control means for controlling at least the wavelength selection characteristic of the etalon having the minimum free spectral range of the etalon and the first power detection means for detecting the power of the center wavelength of the output laser light is maximized. A wavelength control device for an excimer laser, comprising: third control means for controlling the wavelength selection characteristics of other etalons other than the minimum etalon in the free spectral range as much as possible. 24. The second power detecting means comprises a cell filled with a gas absorbing light of a specific wavelength, and a light detecting element for detecting the intensity of light transmitted through the cell. The wavelength control device for an excimer laser according to item (23). 25. The second power detecting means comprises a cell filled with a gas that emits fluorescence by absorbing light of a specific wavelength, and a detection element for detecting the fluorescence generated from the cell. The wavelength control device of an excimer laser according to item (23). 26. A second power detecting means, comprising: a cell in which a gas absorbing a light of a desired wavelength and an electrode to which a predetermined voltage is applied are enclosed; and a current detecting means for detecting a change in a current flowing through the electrode. The wavelength control device for an excimer laser according to claim 23, comprising: 27. An excimer laser wavelength control apparatus for arranging at least two etalons between a laser chamber of an excimer laser and a rear mirror, and controlling the wavelength of output laser light by controlling the wavelength selection characteristics of these etalons, respectively. A first power detecting means for detecting the output power of the laser; a second power detecting means using a high-resolution monitor etalon for detecting the power of a predetermined wavelength component of the output laser light; Third to detect power of predetermined wavelength component
Power detection means, first normalization means for normalizing the output of the second power detection means with the output of the first power detection means, and the output of the third power detection means to the first Second normalizing means for normalizing based on the output of the power detecting means, and when the output of the first normalizing means is detected, the power standardized by the first normalizing means is the maximum. It is preferable to control at least the wavelength selection characteristics of the etalon having the minimum free spectral range of the etalon, and the wavelengths of other etalons excluding the etalon having the minimum free spectral range so that the detection power of the second power detection means is maximized. A first control unit for controlling the selection characteristic; and when the output of the first normalization unit is not detected, the output is standardized by the second normalization unit. An excimer laser wavelength control device comprising: a second control means for controlling at least the wavelength selection characteristic of the etalon having the minimum free spectral range among the etalons so that the power is maximized. 28. An excimer laser wavelength control apparatus for arranging at least two etalons between a laser chamber of an excimer laser and a rear mirror, and controlling the wavelength of output laser light by controlling the wavelength selection characteristics of these etalons, respectively. A wavelength detecting means using a high-resolution monitor etalon for detecting a center wavelength of the output laser light; a first power detecting means for detecting an output power of the laser; and a power of a predetermined wavelength component of the output laser light. Second to detect
A power detecting means, a normalizing means for normalizing an output of the second power detecting means by an output of the first power detecting means, and an absolute value of a difference between a wavelength detected by the wavelength detecting means and a set wavelength. If the wavelength is smaller than one-half of the free spectral range of the monitor etalon of the etalon, at least the minimum of the free spectral range of the etalon is adjusted so that the detection wavelength of the standardizing means matches a desired set wavelength. Controlling the wavelength selection characteristics of the etalon other than the etalon having the minimum free spectral range so that the power detected by the second power detection means is maximized. Control means, the absolute value of the difference between the set wavelength and the wavelength detected by the wavelength detection means, the monitor etalon of the wavelength detection means If it is larger than one-half of the free spectral range, control the wavelength selection characteristic of at least the etalon of the minimum free spectral range among the etalons so that the power standardized by the normalizing means is maximized. A wavelength control device for an excimer laser, comprising: