JPH03245583A - Narrow band oscillation excimer laser - Google Patents

Abstract

PURPOSE:To obtain laser rays of required wavelength from the beginning of a first pulse by a method wherein a means which enables a reference light to pass, a means which detects a transmitted light, and a means which controls the variable elements of the transmitted light are provided to the center of an etalon. CONSTITUTION:A wavelength selection element etalon 15 is placed between a window 11 of a laser chamber 10 and a rear mirror 13, and light is projected onto the center of the element etalon 15 from a reference light source 16 making a prescribed angle with a laser optical axis OA. The light source 16 generates light rays which make the transmitted light maximal in intensity when the transmitted laser rays of the etalon are long as prescribed in wavelength. The wavelength of a reference light is determined basing on the required wavelength of the output laser ray and the angle which laser rays make with the optical axis OA. The etalon transmitted reference light is detected by a sensor 17, the detection output is added to a CPU 18, and the etalon 15 is controlled by a driver 19 to vary the etalon transmitted light in wavelength so as to make the detection output of the sensor 17 maximal. Concretely, one out of the angle of the etalon with an optical axis, a pressure inside an air gap, and a gap between mirror faces is controlled. By this constitution, the etalon transmitted laser ray is controlled to be always constant in wavelength, so that laser rays stable in wavelength can be obtained including a first pulse at the beginning of oscillation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a narrowband oscillation excimer laser, and particularly to one suitable for use as a light source for a reduction projection exposure apparatus.

[Conventional technology]

The use of excimer lasers as light sources for reduction projection exposure apparatuses for manufacturing semiconductor devices is attracting attention.

This is because the wavelength of the excimer laser is short (the wavelength of the KrF laser is approximately 248.4rv), so the limit of optical exposure can be reduced to 0.
．． 5 μm or less, the depth of focus is deeper than the G-line and I-line of conventional mercury lamps for the same resolution, and the numerical aperture (NA) of the lens is small, making it possible to reduce the exposure area. This is because many excellent advantages can be expected, such as the ability to increase the size of the engine and the ability to obtain large amounts of power.

However, the wavelength of excimer laser is 248°35n
Im is short, so materials that transmit this wavelength are quartz and Ca.
There are only F2, MgF2, etc., and in reality, only quartz can be used as a lens material in terms of uniformity and processing precision, so it is difficult to design a reduction projection lens that corrects chromatic aberration. It is necessary to narrow the band of the excimer laser to the extent that

One technique for narrowing the band of excimer lasers is to use an etalon, which is a wavelength selection element.

FIG. 8 shows a conventional example of a narrow band oscillation excimer laser constructed using an etalon.

This narrowband oscillation excimer laser has a narrowband unit 2 disposed on the rear side of the laser chamber 1 to narrow the band. The band narrowing unit 2 includes an etalon and a rear mirror. Laser chamber 1
A part of the laser light outputted from the laser beam is guided through a beam splitter 3 to a wavelength detection device 4, where the wavelength of the output laser light is detected. The detected wavelength of the wavelength detection device 4 is applied to a central processing control unit (CPU) 5, and the CPU 5 feedback-controls the selected wavelength of the etalon of the band narrowing unit 2 based on this detected wavelength to obtain a desired band narrowing wavelength. It has gained.

By the way, an excimer laser is a pulsed laser,
Moreover, the oscillation must be performed in burst mode, or the oscillation must be stopped for a certain period of time when exchanging reticles and wafers. However, in the method of feedback controlling the wavelength after detecting the output wavelength of the laser as shown in FIG. The wavelength was significantly different from the one set.

[Problem that the invention seeks to solve]

Conventional narrow-band oscillation excimer lasers that feedback control the oscillation wavelength have a problem with the wavelength stability of one pulse-throttle when oscillation is resumed. This point had to be improved when used as a light source.

Therefore, the purpose of the present invention is to provide a narrowband oscillation excimer laser with excellent wavelength stability, and in particular, even when oscillation is stopped for a certain period of time and then oscillation is restarted, a laser beam of a desired wavelength can be generated from one pulse]. The objective is to provide a narrow band oscillation excimer laser that can emit light by 1%.

[Means for solving problems]

According to the present invention, in a narrow band oscillation excimer laser in which an etalon is disposed in a resonator, there is provided a means for transmitting a reference light into the center of the etalon, and a means for transmitting a reference light through the center of the etalon. and a control means for controlling a transmission wavelength variable element of the etalon in response to the detection output of the detection means.

[Function] A reference light is transmitted through the center of an etalon placed in a resonator, the wavelength selection characteristics of the etalon are directly detected from this transmitted reference light, and based on this detection output, the transmission wavelength variable element of the etalon, e.g. At least one of the angle of the etalon with respect to the optical axis, the pressure in the air gap, and the mirror spacing is controlled. As a result, the transmission wavelength of the etalon is always controlled even when oscillation is stopped, and even if oscillation is restarted after oscillation has stopped for a certain period of time, laser light of the desired wavelength can be obtained from the first pulse. .

〔Example〕

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

FIG. 1 shows an embodiment of a narrow band oscillation excimer laser according to the present invention. In this embodiment, an optical resonator is configured by a mirror 13 and a front mirror 14, which are arranged sandwiching a laser chamber 10 having windows 11 and 12, and a wavelength An etalon 15, which is a selection element, is arranged. A reference light source 16 projects reference light near the center of the etalon 15 at a predetermined angle with respect to the optical axis OA of the laser. Here, the reference light source 16 is one that generates light of a wavelength such that the light intensity of the transmitted light of the reference light becomes maximum when the transmitted wavelength of the laser light of the etalon 15 reaches a desired wavelength. The wavelength of this reference light is the desired wavelength of the output laser light and the optical axis O of the laser.
It can be determined if the angle of the λ quasi-light with respect to A is known.

The reference light transmitted through the etalon is received by the optical sensor 17.

As this optical sensor 17, a light intensity sensor such as a photodiode is used. The detection output of the optical sensor 17 is applied to a central processing control unit (CPU) 18. The CPU 18 controls the transmission wavelength of the etalon 15 via the etalon driver 19 so that the detection output of the optical sensor 17 is maximized.

Specifically, the control of the transmission wavelength of the etalon 15 by the etalon driver 19 includes the transmission wavelength variable element of the etalon 15,
For example, this is done by controlling at least one of the angle of the etalon 15 with respect to the optical axis, the pressure within the air gap, and the distance between mirror surfaces.

With this configuration, the transmission wavelength of the etalon 15 is always controlled to be constant regardless of whether the laser is oscillating or not, so the wavelength remains stable even during the first pulse at the start of laser oscillation. output laser light can be obtained.

FIG. 2 shows another embodiment of the invention.

In this embodiment, the reference light transmitted through the etalon 15 is condensed by the lens 20 to generate interference fringes, and the transmission wavelength of the etalon 15 is controlled based on the interference fringes. . Reference light source 1
The reference light projected from 6 at a predetermined angle with respect to the optical axis OA of the laser passes through the etalon 15 and is focused by the lens 20 to generate interference fringes. This interference fringe is detected by the optical sensor 21. Here, as the optical sensor 21, a one-dimensional or two-dimensional optical position sensor that can detect the position and intensity of interference fringes, such as a photodiode array or PSD, can be used. Optical sensor 21
The detected output is applied to a central processing control unit (CPU) 22. The CPU 22 controls the transmission wavelength of the etalon 15 via the etalon driver 23 based on the detection output of the optical sensor 21. In this case, the CPU 22 controls the transmission wavelength variable element of the etalon 15 so that the optical sensor 21 can detect interference fringes at a desired position.

In this example, a slit and a light intensity sensor for detecting the intensity of light passing through the slit are arranged at desired positions where interference fringes occur, and the etalon is set so that the output of this light intensity sensor is maximized. 15 transmission wavelengths may be controlled.

Further, when the amount of light from the reference light source 16 is small, a convex lens may be disposed between the base coating light source 16 and the etalon 15.

FIG. 3 shows still another embodiment of the invention. In this embodiment, a polarizing element that selectively transmits only P-polarized light is placed inside the laser beam resonator, and the etalon is equipped with a polarizing element that selectively transmits only P-polarized light.
This allows only polarized light to pass through, thereby making it possible to align the optical axis of the laser beam with the optical axis of the reference light. In FIG. 3, a P-polarized light total reflection S-polarized light transmission mirror 31 is arranged on the optical axis of the laser chamber 10 at an angle of 45 degrees with this optical axis. A polarizing element 30 that transmits only P-polarized light is arranged between the windows 11 of 10 and 10.

Further, an etalon 15 is arranged on the optical axis of the reflected light of the P-polarized light total reflection S-polarized light transmission mirror 31,
A P-polarized light total reflection S-polarized light transmission mirror 32 is arranged at an angle of @, and a rear mirror 13 is arranged on the optical axis of the reflected light of the P-polarized light total reflection S-polarized light transmission mirror 32. Furthermore, the etalon 1
A reference light source 16 is disposed on the opposite side to the side where No. 5 is disposed, and a position where it receives the transmitted light of the P-polarized light total reflection S-polarized light transmission mirror 32,
That is, the lens 33 and the optical sensor 34 are arranged on the optical axis of the reflected light of the P-polarized light total reflection and S-polarized light transmission mirror 31.

The detection output of the optical sensor 34 is detected by the central processing control unit (CPU).
Added to 35. Based on the detection output of the optical sensor 34, the CPU 35 sends the optical sensor 3 via the etalon driver 36.
4 detects the interference fringes at the desired position.
control the transmission wavelength variable element.

In this configuration, this laser oscillator is connected to the rear mirror 1.
3 and the front mirror 14, the P-polarized light oscillates.

In addition, the reference light projected from the reference light source is P-polarized total reflection S
Only the S-polarized light is selected by the polarization transmission mirror 31, passes through the etalon 15, the P-polarization total reflection S-polarization transmission mirror 32, and is received by the optical sensor 34. Here, the optical axis of the laser beam and the optical axis of the reference light match between the P-polarized light total reflection S-polarized light transmission mirror 3] and the P-polarized light total reflection S-polarized light transmission mirror 32, but the laser light here is P-polarized light. Since the reference light is S-polarized light, there is no interference between the two.

According to this embodiment, the optical axis of the laser beam and the optical axis of the reference light can be made to coincide, and the transmission wavelength of the etalon 15 can be controlled with high precision.

In the above embodiment, a polarizing element 30 that transmits only P-polarized light was used, but this was replaced with one that transmitted only S-polarized light, and the S-polarized light transmitting mirror 3 was used to completely reflect P-polarized light.
1 and 32 may be replaced with S-polarized total reflection PB light transmission mirrors, respectively.

FIG. 4 shows still another embodiment of the invention. In this embodiment, two etalons are used, different reference lights are transmitted through each etalon, and the transmission wavelengths of the two etalons are thereby controlled separately. In this embodiment, a P-polarized light total reflection S-polarized light transmission mirror 31 is arranged on the optical axis of the laser chamber 10 at an angle of 45'' with this optical axis. A polarizing element 30 that transmits only P-polarized light between it and the window 11 of the chamber 10
is placed. In addition, P-polarized light total reflection S-polarized light transmission mirror 3
A first etalon 15 is arranged on the optical axis of the first reflected light,
Furthermore, a P-polarized light total reflection S-polarized light transmission mirror 41 is arranged at an angle of 45@ with respect to this forward axis, and a second etalon 42 is arranged on the optical axis of the reflected light of this P-polarized light total reflection S-polarized light transmission mirror 41. Furthermore, a P-polarized light total reflection S-polarized light transmission mirror 43 is arranged at an angle of 45 degrees with the optical axis of the reflected light of the P-polarized light total reflection S-polarized light transmission mirror 41. A rear mirror 13 is arranged on the optical axis.

Further, a first reference light source 16 is disposed on the optical axis of the reflected light from the P-polarized total reflection S-polarized light transmission mirror 31 on the opposite side to the side on which the first etalon 15 is arranged, and the P-polarized total reflection S-polarized light transmission mirror 41 The position where the transmitted light is received, that is, the total reflection of P-polarized light S
A lens 33 and a first optical sensor 34 are arranged on the optical axis of the reflected light from the polarized light transmitting mirror 31.

Further, a second reference light source 40 is arranged on the optical axis of the reflected light from the P-polarized total reflection S-polarized light transmission mirror 41 on the opposite side to the side where the second etalon 42 is disposed. The position where the transmitted light is received, that is, the total reflection of P-polarized light S
A lens 44 and a second optical sensor 45 are arranged on the optical axis of the light reflected by the polarized light transmitting mirror 41.

The detection outputs of optical sensors 34 and 45 are applied to a central processing control unit (CPU) 46. The CPU 46 is the optical sensor 3
Etalon driver 4 based on the detection outputs of 4 and 45.
The first etalon 15 is arranged such that the optical sensors 34 and 45 detect interference fringes at desired positions via the optical sensors 7 and 48, respectively.
and the transmission wavelength variable element of the second etalon 42, respectively.

According to such a configuration, the optical axes of the first and second reference lights can be aligned with the optical axes of the laser beams, so the wavelength can be controlled with high precision, and
Since the transmission wavelengths of the two etalons can be controlled so as to match, there is no need to control the overlapping of the transmission wavelengths of the two etalons, which was conventionally necessary.

In this embodiment as well, the polarizing element 30 is replaced with one that transmits only S-polarized light, and the S-polarized light-transmitting mirrors 31, 41 and 43 are replaced with P-polarized light-transmitting mirrors that totally reflect S-polarized light. Good too.

FIG. 5 shows still another embodiment of the invention. In this embodiment, a prism that selectively transmits only P-polarized light and has a beam expansion function is arranged in an optical resonant type. In this embodiment as well, two etalons are used; a reference light is projected onto one etalon, and the transmitted wavelength is controlled based on the transmitted light, while the other etalon is feedback-controlled by the output laser light. In FIG. 5, a prism 50 disposed in an optical resonant type has a coating 50a on one surface that selectively transmits only P-polarized light. The first etalon 15 is arranged on the optical axis of the refracted light of the prism 50, and furthermore, at an angle of 45° with this optical axis, the P-polarized light is totally reflected S.
A polarized light transmitting mirror 41 is arranged, and this P polarized light is totally reflected S4.
- A second etalon 42 is arranged on the optical axis of the reflected light from the light transmitting mirror 41, and furthermore, at an angle of 45 degrees with the optical axis of the reflected light of the S polarized light transmitting mirror 41, the P polarized light is totally reflected. An S-polarized light transmitting mirror 43 is disposed, and a rear mirror 13 is disposed on the optical axis of the reflected light of the P-polarized light totally reflected S-polarized light transmitting mirror 43.

In addition, a second reference light source 40 and an interference filter 55 are arranged on the optical axis of the reflected light from the S-polarized light transmitting mirror 43 for total reflection of P-polarized light, on the opposite side to the side on which the second etalon 42 is disposed. A lens 44 and an optical sensor 45 are arranged at a position where the transmitted light of the reference light of the polarized light transmitting mirror 41 is received, that is, on the optical axis of the reflected light of the P polarized light total reflection S polarized light transmitting mirror 43 .

A part of the laser beam output from the front mirror 14 is
The output laser beam is separated by a beam splitter 52 and guided to a wavelength detector 53, where the wavelength of the output laser beam is detected. The detection wavelength of the wavelength detection device 53 is determined by the central processing unit 1; control device (CPU) 54.
Based on this detected wavelength, the CPU 54 controls the transmission wavelength of the first etalon to match the desired wavelength via the etalon driver 47.

Furthermore, the detection output of the optical sensor 45 is output from the central processing control unit (C
PU) added to 51. Based on the detection output of the optical sensor 45, the CPU 51 uses the etalon driver 48 to
so that the optical sensor 45 detects interference fringes at a desired position.
The transmission wavelength variable element of the second etalon 42 is controlled.

In the embodiments described above, the first etalon 15 used has a transmission wavelength width narrower than that of the second etalon 42. Therefore, the oscillation wavelength of the laser device of this embodiment is determined by the transmission wavelength of the first etalon 15. Therefore, in the above embodiment, the second etalon 42 is controlled based on the output of the optical sensor 45 that detects the transmitted reference light, and the first etalon 15 is controlled by sampling the actual output laser light. There is. In this case, the etalon 15 in node 1 and the second etalon 42 are controlled by separate control systems, and there is no need to control the overlapping of the transmission wavelengths of the first etalon 15 and the second etalon 42. Therefore, it is possible to speed up wavelength control and r41 force control.

In addition, in this embodiment, since a prism having a beam expansion function is used, the energy density of the laser beam passing through the first and second etalons 15.42 is lowered, so that the energy density of the laser beam passing through the first and second etalons 15.42 is lowered. can extend the lifespan of

Furthermore, in the above configuration, a low-pressure mercury lamp can be used as the reference light source, and a filter that selectively transmits only the 7 nm oscillation line 25B of the mercury lamp can be used as the interference filter 55. In this case, since the wavelength of the reference light is very close to the wavelength of 248.4 nm of the KrF excimer laser, the coating of the reflective film of the etalon may be left as is.

FIG. 6 shows still another embodiment of the invention. In this embodiment, the first talon 15 is arranged on the optical axis of the laser chamber 10, and the P-polarized light total reflection S-polarized light transmission mirror 60 is placed at an angle of 45@ with this optical axis.
and S-polarized light total reflection P-polarized light transmission mirror 61 are arranged in parallel, and a second
etalon 42 is arranged. Also, on the optical axis of the two transmitted lights of this second etalon 42, at an angle of 45 degrees with these optical axes, there is a P-polarized light total reflection S-polarized light transmission mirror 62 and an S-polarized light total reflection P (a light transmission mirror 63). are arranged in parallel, P
Polarized light total reflection S polarized light transmission mirror 62 and S polarized light total reflection P
The rear mirror 13 is placed on the optical axis of the reflected light from the polarized light transmitting mirror 63.
is placed.

Further, a reference light source 40 and an interference filter 55 are arranged on the optical axis of the reflected light from the P-polarized total reflection 'S-polarized light transmission mirror 60 and the S-polarized total reflection P-polarized light transmission mirror 61 on the opposite side to the side where the etalon 42 is arranged. Positions that receive the transmitted light of the P-polarized light total reflection S-polarized light transmission mirror 62 and the S-polarized light total reflection P-polarized light transmission mirror 63, that is, the reflected light of the P-polarized light total reflection S-polarized light transmission mirror 60 and the S-polarized light total reflection P-polarized light transmission mirror 61 A lens 44 and a photosensor 45 are arranged on the optical axis of.

A part of the laser beam output from the front mirror 14 is
The output laser beam is separated by a beam splitter 52, guided to a wavelength detector 53, and the wavelength of the output laser beam is detected. The detected wavelength of the wavelength detection device 53 is applied to a central processing control unit (CPU) 54, and based on this detected wavelength, the CPU 54 adjusts the transmission wavelength of the first etalon 15 to match the desired wavelength via the etalon driver 47. Control.

In addition, the detection output of the optical sensor 45 is output from the central processing control unit (C
PU) added to 51. Based on the detection output of the optical sensor 45, the CPU 51 uses the etalon driver 48 to
so that the optical sensor 45 detects interference fringes at a desired position.
The transmission wavelength variable element of the second etalon 42 is controlled.

According to the above embodiment, since both the P-polarized light and the S-polarized light are amplified within the optical resonator, more efficient oscillation is possible.

In the above embodiment, the first etalon 15, which determines the oscillation wavelength of this laser device, is controlled using an external wavelength detector 53. It is also possible to perform the same control as the second etalon 42 by bending the optical path again using a reflective P-polarized light transmitting mirror.

FIG. 7 shows still another embodiment of the invention. This embodiment is configured using one etalon and one grating.

In this embodiment, the selection wavelength width by the grating is wider than the transmission wavelength width of the etalon, and since the selection wavelength hardly changes, the grating is not controlled. Only controls the etalon.

In FIG. 7, a prism 50 arranged in an optical resonant type
A coating 50a that selectively transmits only P-polarized light is provided on one surface of the lens. A P-polarized light total reflection S-polarized light transmission mirror 41 is arranged on the optical axis of the refracted light of the prism 50 at an angle of 45'' with the front axis. An etalon 42 is arranged, and furthermore, a P-polarized light-total-reflection S-polarized-light transmission mirror 43 is arranged at an angle of 45 degrees with the optical axis of the reflected light of this P-polarized light total reflection Si light transmission mirror 41, and a P-polarized light-total reflection S-polarized light transmission mirror 43 is arranged. A grating 70 is arranged on the optical axis of the reflected light from the mirror 43.

Further, on the optical axis of the reflected light of the P-polarized light total reflection S-polarized light transmission mirror 43, a second reference light source 40 and an interference filter 55 are arranged on the opposite side of the etalon 42, and the P-polarized light total reflection S-polarized light transmission A lens 44 and an optical sensor 45 are arranged at a position where the transmitted light of the reference light of the mirror 41 is received, that is, on the optical axis of the reflected light of the P-polarized light total reflection and S-polarized light transmission mirror 43 .

Furthermore, the detection output of the optical sensor 45 is output from the central processing control unit (C
PU) added to 51. Based on the detection output of the optical sensor 45, the CPU 51 controls the transmission wavelength variable element of the etalon 42 so that the optical sensor 45 detects interference fringes at desired positions via the etalon driver 48.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of this invention, FIG. 2 is an explanatory diagram showing another embodiment of this invention, and FIG. 3 is an explanatory diagram showing one embodiment of the present invention.
Explanatory diagram showing another embodiment of this invention using polarized light, No. 4
Figure 2 is an explanatory diagram showing an embodiment other than this invention using this etalon, Figure 5 is an explanatory diagram showing another embodiment of the invention using a prism, and Figure 6 is an explanatory diagram showing another embodiment of the invention using this etalon. FIG. 7 is an explanatory diagram showing another embodiment of the invention that amplifies both lights, FIG. 7 is an explanatory diagram showing another embodiment of the invention using a grating, and FIG. 8 is an explanatory diagram showing a conventional example. 1.10...Laser chamber, 11.12...Window, 13...Rear mirror 14...Front mirror 15.42...Etalon, 16.40...Reference light source, 17.21.34 .45...light sensor, 18.2
2.35.46.51.54...CPU, 19.23
．． 36.47.48...Etalon driver, 2o13
3.44... Lens, 30... Polarizing element, 31.3
2.41.43.60.62-P polarized light total reflection S polarized light transmission mirror 50... Prism, 61.63... S polarized light total reflection P polarized light transmission mirror Figure 3

Claims (8)

[Claims] (1) In a narrowband oscillation excimer laser in which an etalon is arranged in a resonator, means for transmitting a reference light into the center of the etalon, a detection means for detecting the reference light transmitted through the etalon, and a detection means for detecting the reference light transmitted through the etalon. A narrow band oscillation excimer laser comprising: control means for controlling a transmission wavelength variable element of the etalon in accordance with a detection output. (2) The narrowband oscillation excimer laser according to claim 1, wherein the control means controls at least one of the angle of the etalon with respect to the optical axis, the pressure within the air gap, and the spacing between mirror surfaces. (3) The detection means detects the light intensity of the reference light transmitted through the etalon, and the control means controls the transmission wavelength variable element of the etalon so that the detected light intensity of the detection means is maximized. The narrowband oscillation excimer laser according to claim 1, wherein the narrowband oscillation excimer laser controls: (4) The detection means detects interference fringes of the reference light transmitted through the etalon, and the control means controls the transmission wavelength variable element of the etalon in accordance with the position of the interference fringes detected by the detection means. The narrowband oscillation excimer laser according to claim 1, wherein the narrowband oscillation excimer laser controls: (5) In a narrowband oscillation excimer laser in which an etalon is arranged in a resonator, polarizing means is arranged in the resonator and selectively transmits P-polarized light (or S-polarized light), and arranged on both sides of the etalon, two mirrors that selectively reflect P-polarized light (or S-polarized light), selectively transmit S-polarized light (or P-polarized light), and respectively bend optical axes in the resonator; means for transmitting the reference light to the center of the etalon by projecting the reference light along an optical axis between the two mirrors; a detection means for detecting the reference light transmitted through the etalon and the two mirrors; A narrow band oscillation excimer laser comprising: control means for controlling a transmission wavelength variable element of the etalon in response to a detection output of the detection means. (6) In a narrowband oscillation excimer laser in which a plurality of etalons are arranged in a resonator, means for transmitting a reference light to the center of one of the plurality of etalons, and a means for transmitting a reference light transmitted through the etalon. a first detection means for detecting; a first control means for controlling a transmission wavelength variable element of the one etalon in response to a detection output of the first detection means; and a laser beam output from the resonator. a second detection means for detecting the wavelength of the second detection means; and a second control means for controlling the transmission wavelength variable element of another etalon among the plurality of etalons in response to the detection output of the second detection means. Equipped with narrow band oscillation excimer laser. (7) In a narrowband oscillation excimer laser in which a plurality of etalons are arranged in a resonator, polarizing means is arranged in the resonator and selectively transmits P-polarized light (or S-polarized light); are arranged on both sides of one etalon in the P-polarized light (or S-polarized light), and
two mirrors that selectively transmit polarized light (or P-polarized light) and bend the optical axis in the resonator; and a reference light is projected along the optical axis between the two mirrors. means for transmitting the reference light through the center of one etalon; first detection means for detecting the reference light transmitted through the one etalon and the two mirrors; and a detection output of the first detection means. a first control means for controlling the transmission wavelength variable element of the etalon in accordance with the above; a second detection means for detecting the wavelength of the laser beam output from the resonator; and a detection means for the second detection means. A narrow band oscillation excimer laser comprising: second control means for controlling a transmission wavelength variable element of another of the plurality of etalons in accordance with the output. (8) In a narrowband oscillation excimer laser in which an etalon is disposed in a resonator, a laser beam disposed on one side of the etalon, selectively reflecting P-polarized light and selectively transmitting S-polarized light, a first mirror that bends the optical axis; arranged in parallel with the first mirror, selectively reflects S-polarized light and selectively transmits P-polarized light, and bends the optical axis in the resonator; a second mirror bent at the same angle as the mirror; and a second mirror disposed on the other side of the etalon to face the first mirror, selectively reflecting P-polarized light and selectively transmitting S-polarized light; The third part bends the optical axis in the resonator.
a mirror disposed in parallel with the third mirror and facing the second mirror, selectively reflecting the S-polarized light and selectively transmitting the P-polarized light, and aligning the optical axis in the resonator. The third
a fourth mirror that is bent at the same angle as the mirror; and a fourth mirror that is bent at the same angle as the mirror of the etalon; means for transmitting the reference light through the first and second mirrors, the etalon and the third mirror;
and a narrowband oscillation excimer laser, comprising: a detection means for detecting reference light transmitted through a fourth mirror; and a control means for controlling a transmission wavelength variable element of the etalon in response to a detection output of the detection means.