JP2001044550A - Laser device for radiation of ultra-narrow bandwidth - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser device for radiation of a ultra-narrow bandwidth that oscillates with only one line without using an etalon, and in which the width of the wave in the line can be ultra-narrowed to about 0.2 pm. SOLUTION: A wedge plate 15 has a wedge, wherein an angle αformed with an incidence surface 15a and an exit surface 15b is about 4.4 deg.. Furthermore the wedge plate 15 is formed of a calcium fluoride board with the incidence surface 15a and the exit surface 15b that are both uncoated. A laser beam L1 is refracted at an angle of about 37.1 deg. with respect to perpendiculars of the incidence surface 15a at entering the wedge plate 15. Sine the wedge angle αis about 4.4 deg., the laser beam hits the exit surface 15b at an angle of about 32.7 deg. in the wedge plate 15. Thus an angle θ3 of the light exiting from the exit surface 15b is about 57 deg. that is a Brewster angle (arcsin (1.55865*sin 32.7)).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a narrow band laser device for narrowing an oscillation laser beam from a laser chamber and supplying it to an exposure device as an exposure light source, and particularly to a fluorine laser or a laser having a shorter wavelength than this laser. The present invention relates to an ultra-narrow band laser device for narrowing a band of a laser beam.

[0002]

2. Description of the Related Art There are various types of performance required for an exposure apparatus for lithography, such as resolution, alignment accuracy, processing capability, and apparatus reliability. Among them, the resolution R directly leading to the miniaturization of the pattern is R = k · λ /
NA (k: constant, λ: exposure wavelength, NA: numerical aperture of the projection lens). Therefore, in order to obtain good resolution, the shorter the exposure wavelength λ, the more advantageous.

Therefore, in a conventional exposure apparatus, the i-line (wavelength: 365 nm) of a mercury lamp and the wavelength of 248 nm
Krypton fluorine (KrF) excimer laser is used as a light source for an exposure machine. These are called an i-line exposure machine and a KrF exposure machine, respectively. As the projection optical system used in the i-line exposure machine and the KrF exposure machine, a reduction projection lens combining a large number of lenses made of quartz glass is used. Widely used.

As a next-generation exposure apparatus for performing fine processing, argon fluorine (ArF) having a wavelength of 193 nm is used.
An exposure machine using an excimer laser as an exposure light source has begun to be used, and is called an ArF exposure machine. In the ArF exposure apparatus, the ArF exposure device narrows the wavelength band to about 0.6 pm.
An F excimer laser is used, and an achromatic lens made of two kinds of materials is used in the reduction projection optical system.

[0005] Etalons and mode selectors are known as band-narrowing elements for narrowing the wavelength width of an ArF excimer laser to about 0.6 pm.

The mode selector is also called an interferometer-type wavelength selection element, and is a technique in which a part of a laser resonator is constituted by an optical system equivalent to that of an interferometer. Two mirrors provided with a total reflection film are used. And one beam splitter provided with a partial reflection film.

For such an interferometer type wavelength selecting element, for example, “PROCEEDINGOF THE IEEE”
E, VOL. 60, NO. 4, APRIL 1972,
pp. 422-441 ".

In the next-generation lithography exposure apparatus of the above-mentioned ArF exposure apparatus, the light source has a wavelength of about 157 n.
A fluorine exposure machine using a fluorine laser of m is under study.

In this fluorine laser, there are two oscillation lines (also called oscillation lines) having different wavelengths and light intensities.
The wavelengths are 157.5233 nm and 157.629, respectively.
9 nm, and the wavelength width of each oscillation line is 1-2 pm
It is said to be about.

To use the fluorine laser for exposure,
In general, it is advantageous to select and use only one line of a wavelength (157.6299 nm) having a high intensity (hereinafter, referred to as one line). ~ 2 were used.

Regarding the two lines of the fluorine laser, for example, “CAN.J.PHYS.VOL.63,
1985, pp. 217-218 ".

Regarding one line of a fluorine laser, for example, “SPIE, 24th International
onal Symposium on Microlio
thography, February. 1999. The experimental results are reported in

[0013]

However, in the case of a fluorine exposure apparatus, it becomes difficult to apply a refraction-type reduction projection optical system using only a lens, which has been generally used in conventional exposure apparatuses (that is, up to an ArF exposure apparatus).

The reason is that at a wavelength of 157 nm, the transmittance of quartz glass becomes extremely low, and only a very limited material such as calcium fluoride can be used.

Therefore, when a reduction projection lens is formed by using a monochromatic lens made of only calcium fluoride,
It is said that narrowing the band is insufficient even if the fluorine laser is made into one line, and it is necessary to narrow the band to one-tenth of the wavelength width (about 0.2 pm) for one line. ing.

As described above, it was difficult to narrow the band to 0.2 pm or less for one line of the fluorine laser.
It is considered necessary to apply a catadioptric reduction projection optical system (also called a catadioptric type), which is said to be usable in a wavelength width 10 times wider than a total refractive optical system using only a lens, as the reduction projection optical system. Had been.

Conventionally, in a fluorine laser, it has been difficult to further narrow the band of laser light which has been made into one line by using, for example, an etalon (hereinafter, referred to as ultra-narrow band) for the following reasons. .

Generally, an etalon requires a partial reflection film. However, at a wavelength of 157 nm in a fluorine laser, it was difficult to form a partially reflective film having high light resistance.

That is, in the vacuum ultraviolet region having a wavelength of 157 nm, the absorption rate of many optical materials is high. Therefore, the temperature rise due to the absorption of laser light by these optical materials easily causes damage to the partial reflection film.

In the case of a fluorine laser, the pulse width is 5 to 5.
Since it is 10 ns, which is as short as about half of that of the excimer laser, the peak power of the pulsed laser light is increased, so that the coating material is easily damaged.

Therefore, an object of the present invention is to provide an ultra-narrow band laser device which oscillates with only one oscillation line without using an etalon and can narrow the wavelength width of the oscillation line to about 0.2 pm. To provide.

[0022]

In order to solve the above-mentioned problems, a first invention of the present invention comprises a laser chamber for oscillating a laser beam of a fluorine laser or a laser having a shorter wavelength than the laser. An ultra-narrow band laser device that narrows a band of a laser beam from a laser chamber and supplies it as an exposure light source to an exposure device, comprising: an interferometer type wavelength selection element having a beam splitting surface; The device is characterized in that an incident angle of laser light oscillated from the laser chamber on the beam splitting surface is larger than a Brewster angle.

According to a second aspect, in the first aspect,
The interferometer-type wavelength selection element is configured by two reflectors having a function of a total reflection surface and a predetermined wedge plate having a function of the beam splitting surface and not being subjected to a coating process. Features.

According to a third aspect, in the first aspect,
The interferometer-type wavelength selection element includes one reflector having a function of a total reflection surface, and a predetermined wedge plate having a function of a total reflection surface and a beam splitting surface and not being subjected to a coating process. It is characterized by being.

According to a fourth aspect of the present invention, in the second or third aspect, the predetermined wedge plate splits the laser beam oscillated from the laser chamber at an incident angle larger than the Brewster angle. When incident on the surface, the optical axis of the laser beam emitted from the emission surface located on the side opposite to the beam splitting surface and the angle formed by the perpendicular to the emission surface should be the Brewster angle. It is characterized by being formed of an element.

According to a fifth aspect of the present invention, in the second aspect or the third aspect, the laser beam emitted from the interferometer-type wavelength selection element is transmitted and has the same function as the predetermined wedge plate. A second wedge plate that has not been treated, wherein the edge of the second wedge plate is
The second wedge plate is arranged such that the second wedge plate is located on the side opposite to the edge position of the predetermined wedge plate with reference to the optical axis of the laser beam from the interferometer type wavelength selection element. It is characterized by.

Next, the first and second inventions and the fourth and fifth inventions will be described with reference to FIGS.

As shown in FIG. 1, the interferometer type wavelength selecting element 12 includes a wedge plate 15 as a beam splitter having a partially reflecting surface (beam splitting surface) for splitting a laser beam.
And two mirrors 14a, 1a and 1b, which are arranged so that the laser light reflected on the partial reflection surface of the wedge plate 15 resonates.
4b.

The wedge plate 15 has a wedge having an angle (wedge angle) α formed by an incident surface 15a having a function of a partial reflection surface (that is, a surface for Fresnel reflection) and an emission surface 15b of about 4.4 degrees. I have.

The wedge plate 15 is made of uncoated calcium fluoride (CaF 2) on both the front surface and the back surface (ie, the entrance surface 15a and the exit surface 15b).
It is formed of a substrate.

Further, as shown in FIG.
Has the same configuration and function as the wedge plate 15, but the edge position is arranged in the opposite direction to the wedge plate 15 with respect to the optical axis of the laser beam.

Incidentally, the laser beam L1 is applied to the wedge plate 15
The light is refracted when it enters the interior, and the refraction angle is about 37.1 degrees (referred to as θ2) with respect to the perpendicular to the incident surface 15a (see FIG. 2).

Further, since the wedge angle α of the wedge plate 15 is about 4.4 degrees, the angle at which the laser light strikes the emission surface 15b in the wedge plate 15 is about 32.7 degrees (that is, 47.1-.). 4.4 = 32.7).

Therefore, the angle between the optical axis of the light emitted from the light exit surface 15b and the perpendicular to the light exit surface 15b (hereinafter, referred to as the angle).
Angle θ3 of about 57 degrees (that is, arcs
in (1.55865 * sin32.7) = 57) (see FIG. 2). That is, the angle θ3 of the emission angle becomes substantially the Brewster angle θB.

Then, the laser beam L2 is applied to the wedge plate 17
, The traveling direction of the laser beam L3 becomes parallel to the traveling direction of the laser beam L1.

As described above, according to the first, second, and fourth aspects of the present invention, oscillation is performed by only one oscillation line without using an etalon, and the oscillation line has a wavelength width of about 0.5 mm.
The band can be narrowed to about 2 pm.

Further, since the incident angle is set to be larger than the Brewster angle, the reflectivity on the beam splitting surface is increased, and it is possible to dispose a reflecting material that totally reflects.

Further, since the reflectance on the beam splitting surface is increased, it is not necessary to apply a partial reflection film on the beam splitting surface.

Further, since a wedge plate is used,
The angle of the outgoing light on the outgoing surface opposite to the beam splitting surface (that is, the incident surface) can be adjusted to a Brewster angle of about 57 degrees, so that it is not necessary to apply an anti-reflection coating to the outgoing surface of the wedge plate.

That is, in a wedge plate having a function as a beam splitting surface, damage to the wedge plate can be suppressed (reduced) without applying a partial reflection film and a non-reflection coating. Further, according to the fifth aspect of the present invention, it is possible to oscillate with only one oscillation line without using an etalon, and to narrow the wavelength width of the oscillation line to about 0.2 pm.

Further, since the interferometer type wavelength selecting element has two wedge plates arranged so that the positions of the edges are opposite to the optical axis of the laser light,
Since the directions of refraction of the laser light in these two wedge plates are opposite, the traveling direction of the laser light incident on the interferometer-type wavelength selection element and the traveling direction of the laser light emitted from the interferometer-type wavelength selection element are different. Can be parallel.

Next, the third invention will be described with reference to FIG.

As shown in FIG. 5, the interferometer type wavelength selecting element 20 is a wavelength selecting element having two reflecting surfaces 21a and 21b and one partial reflecting surface 22a. Wedge plate 23 having the same reflection surface 22a
Is formed.

The wedge plate 23 is used for the laser chamber 1
3 (see FIG. 1) with the Brewster angle θ
When the light is incident on the partial reflection surface 22a of the wedge plate 23 at an incident angle θ1 larger than B (about 57 degrees) (for example, 70 degrees), the exit surface (Brew) located on the opposite side to the partial reflection surface 22a The optical component is formed and arranged such that the angle (the emission angle) between the optical axis of the laser light emitted from the (star surface) 22b and the perpendicular to the emission surface becomes the Brewster angle θB.

The wedge plate 23 has uncoated calcium fluoride (CaF 2) on both the front and back surfaces (ie, the partial reflection surface 22 a and the emission surface 22 b).
2) It is formed of a substrate.

According to the third aspect of the invention, it is possible to oscillate with only one oscillation line without using an etalon, and to narrow the wavelength width of the oscillation line to about 0.2 pm.

In the interferometer type wavelength selecting element,
The optical distance between one reflector having the function of a total reflection surface and the total reflection surface of the wedge plate is shortened (for example, about 10
mm).

According to a sixth aspect, in the second aspect,
The interferometer-type wavelength selector is a Michelson-type interferometer-type wavelength selector.

Next, the sixth invention will be described with reference to FIG.

The interferometer type wavelength selecting element 30 is a type utilizing a Michelson interferometer, and has two reflecting surfaces and one partially reflecting surface. That is, the interferometer-type wavelength selecting element 30 includes two mirrors 34 a and 34 b and a wedge plate 35. The laser light transmitted through the dispersing prism 33b is applied to the uncoated wedge plate 35.
The light is incident at an angle of about 85 degrees.

As described above, according to the sixth aspect of the invention, oscillation can be performed with only one oscillation line without using an etalon, and the wavelength width of the oscillation line can be narrowed to about 0.2 pm.

Further, since the incident angle is set to be larger than the Brewster angle, the reflectivity on the beam splitting surface is increased, and it is possible to dispose a reflecting material that totally reflects.

Further, since a wedge plate is used,
The angle of the outgoing light on the outgoing surface opposite to the beam splitting surface (that is, the incident surface) can be adjusted to a Brewster angle of about 57 degrees, so that it is not necessary to apply an anti-reflection coating to the outgoing surface of the wedge plate.

According to a seventh aspect, in the second aspect,
The interferometer-type wavelength selection element is a Michelson-type interferometer-type wavelength selection element, and the predetermined wedge plate is formed of a dispersion prism.

Next, the seventh invention will be described with reference to FIG.

A Michelson interferometer type interferometer type wavelength selecting element 50 is formed by one dispersion prism 33b used as a wedge plate and two mirrors 34a and 34b. That is, of the dispersion prisms 33a and 33b used to make the fluorine laser into one line, the dispersion prism 33a in the dispersion prism 33b is used.
The beam is split on the side surface (corresponding to the beam splitting surface).

Also, the laser beam from the dispersion prism 33a is incident at a large incident angle of about 85 degrees so that the reflectance on the surface (corresponding to the beam splitting surface) is about 50%. , A dispersion prism 33b.

As described above, according to the seventh aspect of the invention, oscillation can be performed with only one oscillation line without using an etalon, and the wavelength width of the oscillation line can be narrowed to about 0.2 pm.

Further, since the incident light is made incident at an angle of incidence (for example, about 85 degrees) larger than the Brewster angle (about 57 degrees), although the surface reflection of the dispersing prism increases, Since the laser beam due to the reflection is used in the interferometer type wavelength selecting element, the surface reflection does not cause a loss.

That is, it is used to further narrow the band of the laser light that has been made into one line, and the laser light due to the surface reflection of the dispersing prism can be used effectively.

In an eighth aspect based on the sixth or seventh aspect, the interferometer-type wavelength selection element is provided between the reflecting surface for reflecting the laser beam transmitted through the predetermined wedge plate and the wedge plate. A second wedge plate, which has the same function as the predetermined wedge plate and is not subjected to a coating process, is further provided, and the second wedge plate and the predetermined wedge plate are separated from the predetermined wedge plate. The two edges are arranged so as to be located on opposite sides with respect to the optical axis of the laser light.

Next, the eighth invention will be described with reference to FIG.

This interferometer type wavelength selecting element 40 is also a type utilizing a Michelson interferometer, and has two mirrors 41.
a, 41b and two wedge plates 42, 43.

The wedge plate 42 has a wedge angle α of about 18 degrees, like the wedge plate 35 in the interferometer type wavelength selection element 30. The wedge plate 42 is arranged so that the incident angle of the laser beam L41 is larger than the Brewster angle.

On the other hand, the second wedge plate 43 is positioned between the wedge plate 42 and the mirror 41 so that, for example, the position of the edge of the second wedge plate 43 is opposite to that of the wedge plate 42 with respect to the laser beam L42. Are located.

As described above, according to the eighth aspect,
Oscillation can be achieved with only one oscillation line without using an etalon, and the wavelength width of the oscillation line can be narrowed to about 0.2 pm.

Further, since the interferometer type wavelength selection element has two wedge plates arranged so that the positions of the edges are opposite to the optical axis of the laser light,
Since the directions of refraction of the laser beam in these two wedge plates are opposite, even if a temperature change occurs in these two wedge plates, the direction of refraction of the laser beam becomes constant, and thus the interferometer type wavelength selection element Can be stabilized.

Further, in a ninth aspect based on the first aspect, the interferometer-type wavelength selection element has one reflecting material having a function of a total reflection surface, and a function of the beam splitting surface and the partial reflection surface. A wedge plate that has not been subjected to a coating process, and the wedge plate is configured such that, when the laser light oscillated from the laser chamber is incident on the beam splitting surface at an incident angle greater than the Brewster angle, The laser light transmitted through its own wedge plate is formed so as to be emitted perpendicular to the partial reflection surface.

Next, the ninth invention will be described with reference to FIG.

The interferometer-type wavelength selecting element 70 is composed of a wedge plate 71 and a mirror 71.
The first partial reflection surfaces 71a and 71b are both formed of an uncoated calcium fluoride (CaF2) substrate.

When the incident light enters the partial reflection surface 71a at an angle of about 70 degrees, which is larger than the Brewster angle, the wedge plate 71
It is formed and arranged so that transmitted light passing through the inside is emitted perpendicular to the partial reflection surface 71b.

Further, the partial reflection surface 71b of the wedge plate 71
Has the function of a partially reflecting surface, but functions as an output mirror.

As described above, according to the ninth aspect,
Oscillation can be achieved with only one oscillation line without using an etalon, and the wavelength width of the oscillation line can be narrowed to about 0.2 pm.

[0074]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an ultra-narrow band fluorine laser device 10.
FIG. 3 is a configuration diagram illustrating a configuration of a zero.

As shown in the figure, in the ultra-narrow band fluorine laser apparatus 100, a resonator is constituted by a total reflection mirror 11 and an interferometer type wavelength selecting element 12, and a laser is provided between the resonators. A chamber 13 is provided.

The interferometer type wavelength selection element 12 includes a wedge plate 15 as a beam splitter having a partial reflection surface (that is, a beam division surface) for splitting a laser beam, and a laser beam reflected by the partial reflection surface of the wedge plate 15. And two mirrors 14a and 14b arranged so as to resonate.

The wedge plate 15 has an angle (wedge angle) α between an incident surface 15a having a function of a partially reflecting surface (that is, a surface for Fresnel reflection) and an exit surface 15b located on the opposite side to the incident surface. It has a wedge of about 4.4 degrees.

The wedge plate 15 is made of uncoated calcium fluoride (CaF 2) on both the front surface and the back surface (ie, the entrance surface 15a and the exit surface 15b).
It is formed of a substrate.

Further, the wedge plate 15 is arranged so that the laser beam L1 from the laser chamber 13 is incident on the incident surface 15a of the wedge plate 15 at an incident angle larger than the Brewster angle θB (about 57 degrees). Have been.

FIG. 2 shows an enlarged view of such an interferometer type wavelength selecting element 12. FIG. 2 shows a piezo element 16 and a wedge plate 17 arranged on a mirror 14a, in addition to the interferometer type wavelength selection element 12.

The piezo element 16 slightly moves the mirror 14a back and forth according to the movement control of a control device (not shown). When the mirror 14a moves back and forth, the distance (optical distance) between the mirror 14a and the mirror 14b changes with this movement, so that the wavelength selected by the interferometer-type selection element 12 changes. By controlling the piezo element 16 to adjust the optical distance in this way, the wavelength is stabilized.

Here, the optical distance between the mirror 14a and the mirror 14b is set to be about 20 mm.

The reason is that a fluorine laser (157 nm)
In the case where the interval between wavelengths at which the reflectance becomes maximum (hereinafter, referred to as FSR) becomes 0.5 pm or less, about 1 p
Even if the center of the selected wavelength is centered on the center of the line of the original wavelength width of m, the selected wavelengths on both sides will also fall within the wavelength width of 1 pm.
Oscillation occurs as a thin line of a book.

Therefore, in order to prevent this, it is necessary to make the FSR larger than 0.5 pm. Therefore, the distance (optical distance) between the two reflecting surfaces of the interferometer type wavelength selecting element 12 is required.
Must be less than about 24 mm (the grounds for which will be described later), and in this embodiment, the optical distance is set to about 20 mm.

The wedge plate 17 has the same structure and function as the wedge plate 15, but its edge position is arranged in the direction opposite to the case of the wedge plate 15 with respect to the optical axis of the laser beam L2. Have been. That is, the edge of the wedge plate 15 is located on the side of the mirror 14b, whereas the edge of the wedge 17 is located on the side of the mirror 14a. Further, the wedge plate 17 is arranged so that the incident angle of the laser beam L2 becomes the Brewster angle θB (about 57 degrees).

Although the wedge plate 17 will be described in detail later, the laser light L
2 is used to make the optical axis 2 parallel to the optical axis of the laser beam L1.

Incidentally, the ultra-narrow band fluorine laser device 1
The laser light generated at 00 is a P-wave,
Since the wedge plate 15 is arranged so that the incident angle θ1 to the wedge plate 15 is about 70 degrees, the wedge plate 15
Is about 5%, as can be seen from the graph shown in FIG. In addition, the reflectance of the interferometer-type wavelength selection element 12 as a whole is a curve having a high reflectance at a specific wavelength, as shown in FIG. In FIG. 4, the FSR is about 0.6 pm.

Here, the FSR, which is the interval between the wavelengths at which the reflectivity is maximized, is expressed by Equation 1.

FSR = λ ＾ 2 / 2d (1) where λ is a wavelength, d is an optical distance between two reflection surfaces where laser light resonates, and ＾ is a power exponent.

In this embodiment, since the optical distance between the mirror 14a and the mirror 14b is set to about 20 mm, λ = 157.6299 nm and d = 20 mm are substituted into the above equation (1). Is calculated, FSR ≒
0.6 pm. This is consistent with the fact that the reflectance is high at about every 0.6 pm, as can be seen from FIG.

Here, in order to prevent one line from oscillating as three thin lines, the FSR should be 0.5 p
The reason why the optical distance d needs to be larger than m and the optical distance d must be smaller than 24 mm for that purpose will be described.

By modifying the above equation (1), the optical distance d is represented by the following equation (2).

D = λ ＾ 2 / (2 · FSR) (2) where λ = 157.6299 nm, FSR = 0.5 p
By substituting m into Equation 2 above and calculating Equation 2,
d ≒ 24 mm. Since the optical distance d is inversely proportional to the FSR, the optical distance d must be less than 24 mm in order to make the FSR larger than 0.5 pm.

By the way, it is known that the gain of the fluorine laser is much higher than that of the excimer laser.
Therefore, in this embodiment, laser oscillation occurs when the reflectance of the output mirror (the entire interferometer-type wavelength selection element 12) is about 1% or more. On the other hand, when the reflectance is about 1% or less, laser oscillation is suppressed.

In the region where the laser oscillation oscillates at a reflectance of about 1% or more, as shown in FIG.
m) is about 0.15 pm, which is 1/4 of the wavelength width of m). Therefore, one line of the original wavelength width (about 1 pm) is narrowed to about 1/6.

In the interferometer type wavelength selecting element 12 which functions as an output mirror, the laser beam L1 is applied to the wedge plate 1
5, the light is refracted at an angle of about 37.1 degrees (referred to as .theta.2) with respect to a perpendicular to the incident surface 15a (see FIG. 2).

Since the wedge angle α of the wedge plate 15 is about 4.4 degrees, the angle at which the laser light strikes the emission surface 15b in the wedge plate 15 is about 32.7 degrees (that is, 37.1 degrees). 4.4 = 32.7).

Therefore, the angle between the optical axis of the light emitted from the light exit surface 15b and the perpendicular to the light exit surface 15b (hereinafter, referred to as the angle).
Angle θ3 of about 57 degrees (that is, arcs
in (1.55865 * sin32.7) = 57) (see FIG. 2). That is, the angle θ3 of the emission angle becomes substantially the Brewster angle θB.

As described above, when the laser beam L2 is emitted from the emission surface 15b at an emission angle of the Brewster angle θB, almost no reflection occurs on the emission surface 15b.

It is better that the optical axis of the laser beam L2 and the optical axis of the laser beam L1 are parallel, but actually, these two optical axes are not parallel.

Therefore, when the laser beam L2 is transmitted through the wedge plate 17, the wedge plate 17 whose edge position is arranged in the opposite direction to that of the wedge plate 15 has a refraction characteristic that is different from that of the wedge plate 15. As a result, the laser light L3 emitted from the wedge plate 17 becomes parallel to the optical axis of the laser light L1.

The operation of the ultra-narrow band fluorine laser device 100 having the following configuration will be described with reference to FIGS.

When the laser light L1 emitted from the laser chamber 13 enters the wedge plate 15, a part of the laser light is reflected on the incident surface 15a of the wedge plate 15, and the other laser light passes through the wedge plate 15. The transmitted laser light is emitted as a laser light L2 in a direction in which the emission angle has the Brewster angle θB.

On the other hand, the incident surface 15 of the wedge plate 15
The laser light reflected on a is reflected on the mirror 14b and transmitted through the wedge plate 15, and then reflected on the mirror 14a. The laser beam reflected by the mirror 14a is transmitted to the wedge plate 15
The laser beam L2 is reflected on the emission surface 15b of the laser beam and emitted as a laser beam L2, and transmits through the wedge plate 15.

The laser light transmitted through the wedge plate 15 is reflected by the mirror 14b, further reflected by the incident surface 15a of the wedge plate 15, and then proceeds into the laser chamber 13.

Then, the laser light L2 emitted from the wedge plate 15 at the Brewster angle θB further passes through the wedge plate 17, and
A laser beam L3 parallel to the optical axis of the laser beam L1 is emitted. The emitted laser light L3 has a wavelength width of about 0.2.
The band is narrowed to about pm.

In the above embodiment, the narrowing of the band width of the fluorine laser has been described. However, the present invention is not limited to this. For example, a laser having a shorter wavelength than the fluorine laser, for example, a rare gas molecule having a wavelength of 126 nm. Laser = Argon dimer (Ar2) It can also be applied to a case where the band of a laser is narrowed.

In this case, the same interferometer type wavelength selecting element 1
When employing No. 2, it is necessary to change the distance (optical distance d = 20 mm) between the mirrors 14a and 14b.

That is, λ = 126 nm, FSR = 0.
By substituting 5 pm into Equation 2 and calculating Equation 2, d ≒ 16 mm. Therefore, if the optical distance d is 1
What is necessary is just to set to less than 6 mm.

As described above, according to the present embodiment, the following operation and effect can be obtained.

(A) An uncoated wedge plate is used as a beam splitter used in an interferometer type wavelength selection element, and the wedge plate is arranged so that the incident angle is larger than the Brewster angle. Since the optimum reflectance for oscillating the fluorine laser at a specific selective wavelength can be obtained, it is not necessary to apply a partial reflection film to the partially reflecting surface of the wedge plate.

(B) Further, the emission angle is Brewster angle θB
The laser beam L2 is emitted from the emission surface 15b at an angle (approximately 57 degrees), so that almost no reflection occurs on the emission surface 15b, so that it is not necessary to apply an anti-reflection coating on the emission surface of the wedge plate. .

In other words, since it is not necessary to apply the partial reflection film and the non-reflection coating to the wedge plate, it is possible to suppress the damage to the wedge plate. Therefore, the life of the wedge plate and the life of the interferometer type wavelength selection element can be extended.

(C) Further, the edge position is the wedge plate 1
Wedge plate 17 arranged in the opposite direction to the case of 5
The laser light L2 is transmitted through the
Can be returned parallel to the optical axis of the laser beam L1.
(D) Further, oscillation is performed by only one oscillation line without using an etalon, and the oscillation line has a wavelength width of about 0.2 pm.
Bandwidth can be narrowed to the extent.

[Second Embodiment] FIG. 5 is a configuration diagram showing a configuration of an interferometer type wavelength selection element 20 according to another embodiment of the interferometer type wavelength selection element 12 shown in FIG. .

As shown in the figure, the interferometer type wavelength selecting element 20 is a wavelength selecting element having two reflecting surfaces 21a and 21b and one partial reflecting surface (beam splitting surface) 22a. The reflection surface 21a and the partial reflection surface 22a are formed on the same wedge plate 23.

[0118] The wedge plate 23 is
3 (see FIG. 1) with the Brewster angle θ
When the light is incident on the partial reflection surface 22a of the wedge plate 23 at an incident angle θ1 larger than B (about 57 degrees) (for example, 70 degrees), the exit surface (Brew) located on the opposite side to the partial reflection surface 22a The optical component is formed and arranged such that the angle (the emission angle) between the optical axis of the laser light emitted from the (star surface) 22b and the perpendicular to the emission surface becomes the Brewster angle θB.

The wedge plate 23 has uncoated calcium fluoride (CaF 2) on both the front and back surfaces (ie, the partial reflection surface 2a and the emission surface 22b).
2) It is formed of a substrate.

The laser beam incident on the interferometer-type wavelength selecting element 20 having such a configuration resonates between the reflecting surfaces 21a and 21b.

Although not shown in FIG. 5, similarly to the interferometer-type wavelength selection element 12, a piezo element is disposed on the surface opposite to the reflection surface 21b, and the movement control of a control device (not shown) is performed. Therefore, it is slightly moved back and forth.

Incidentally, in the interferometer type wavelength selecting element 20, compared with the optical distance between the mirror 14a and the mirror 14b in the interferometer type wavelength selecting element 12 (see FIG. 2), the reflection surface 21a It has a feature that it is easy to shorten the optical distance between itself and the reflection surface 21b.

The reason is that, as shown in FIG. 5, the wedge plate 23 is formed with one reflection surface 21a and a partial reflection surface 22a, and the wedge plate 23 has an incident angle of about 70 degrees. Since the laser light L1 is inclined, the laser light L1 can be made incident on the partial reflection surface 22a in the vicinity of the reflection surface 21a, and the laser light reflected on the partial reflection surface 22a is reflected by the reflection surfaces 22a and 22b. This is because resonance can occur between the two.

Here, in particular, if one line of the fluorine laser is further narrowed, it is necessary to make the distance (optical distance) between the two reflecting surfaces in the interferometer type wavelength selecting element 20 20 mm or less as described above. is there.

That is, as described in the first embodiment, the FSR of the fluorine laser (157 nm) is not more than 0.1.
At 5 pm or less, one line becomes three thin lines and oscillates. Therefore, the FSR needs to be larger than 0.5 pm. Therefore, the two reflection surfaces of the interferometer type wavelength selection element 20 The spacing (optical distance) must be less than about 24 mm.

It is desirable to set the optical distance to about 12 mm. Because λ = 157.6299
Substituting nm and d = 12 mm into Equation 1 above,
Is calculated, the FSR becomes about 1 pm, so that it is easy to narrow the bandwidth of one line.

The interferometer type wavelength selecting element 20 having the following configuration
Will be described with reference to FIG.

First, when the laser beam L1 is incident on the partially reflecting surface 22a of the wedge plate 23, the laser beam L1 is reflected by the partially reflecting surface 22a and transmits through the wedge plate 23. The transmitted laser light is emitted from the emission surface (Brewster surface) 22b as laser light L2 with an emission angle = Brewster angle θB.

On the other hand, the laser light reflected on the partial reflection surface 22a is reflected on the reflection surface 21b of the mirror 24, passes through the wedge plate 23, and is reflected on the reflection surface 21a. The laser light reflected by the reflection surface 21a transmits through the wedge plate 23 and is reflected by the partial reflection surface 22a to be emitted from the emission surface 22b.
Proceed to.

The laser beam that has traveled to the emission surface 22b has a Brewster angle θB from the emission surface 22b.
It is emitted as 2. The emitted laser light L2 is
The wavelength width is narrowed to about 0.2 pm.

On the other hand, the laser beam reflected by the reflecting surface 21a and transmitted through the wedge plate 23 is reflected by the reflecting surface 21b of the mirror 24.
After that, the light is further reflected on the partial reflection surface 22a, and then proceeds to the inside of the laser chamber 13.

In the above embodiment, the laser light L
On the second side, a wedge plate having the same configuration and function as the wedge plate 23 is disposed, and the wedge plate is positioned such that the position of the edge with respect to the optical axis of the laser beam L2 is the wedge plate 2.
3 may be arranged in the opposite direction. Thereby, the laser beam L2 can be made parallel to the laser beam L1.

In the above-described embodiment, the narrow band of the fluorine laser is described. However, the present invention is not limited to this, and a laser having a shorter wavelength than the fluorine laser, for example, an Ar2 laser having a wavelength of 126 nm is used. It can also be applied to narrowing the bandwidth.

As described above, according to the second embodiment, the operation and effect of the above-described first embodiment can be expected, and of course, the reflection surface 21a and the By forming the reflection surface 22a, it becomes easy to shorten the optical interval between the two reflection surfaces in the interferometer-type wavelength selection element 40.

[Third Embodiment] FIG. 6 is a configuration diagram showing the configuration of an ultra-narrow band fluorine laser device 200.

As shown in the figure, in the ultra-narrow band fluorine laser apparatus 200, a resonator is constituted by the output mirror 31 and the interferometer type wavelength selecting element 30. That is, the interferometer-type wavelength selection element 30 functions as a total reflection mirror. In this resonator, there are provided a laser chamber 32 and two dispersing prisms 33 for making the fluorine laser into one line.
a and 33b are arranged.

The interferometer type wavelength selecting element 30 is a type utilizing a Michelson interferometer, and has two reflecting surfaces and one partial reflecting surface. That is, the interferometer-type wavelength selecting element 30 includes two mirrors 34 a and 34 b and a wedge plate 35.

The features of this embodiment include the optical distance from the partial reflection surface (incident surface) 35a of the wedge plate 35 to the mirror 34a and the optical distance from the exit surface (Brewster surface) 35b of the wedge plate 35 to the mirror 34b. Since the FSR that is the period of the selected wavelength is determined by the difference from the distance, it is easy to make the FSR larger than 0.5 pm.

In this embodiment, the laser beam transmitted through the dispersion prism 33b is incident on the uncoated wedge plate 35 at an angle of about 85 degrees. As described above, when the incident angle is 85 degrees, the reflectance on the wedge plate 35 is about 50%, as can be seen from the reflectance graph shown in FIG.

In the reflectance characteristic of the Michelson interferometer-type interferometer type wavelength selecting element 30 as a whole, when the partial reflectance is 50%, reflection and transmission appear alternately as shown in FIG. The wavelength selection characteristics are the best.

The wedge angle α of the wedge plate 35 is
It is about 18 degrees. As a result, the laser beam incident on the wedge plate 35 at an incident angle of 85 degrees exits the wedge plate 35 at a Brewster angle θB of about 57 degrees, so that the emission surface 35b of the wedge plate 35 No return loss occurs.

The operation of the ultra-narrow band fluorine laser device 200 having the following configuration will be described with reference to FIG.

When the laser light oscillated from the laser chamber 32 passes through the dispersion prisms 33a and 33b, the laser light is converted into one iran.

When this one-lined laser beam enters the incident surface 35a of the wedge plate 35, it passes through the wedge plate 35 and is reflected by the incident surface 35a. The laser light reflected on the incident surface 35a is reflected on the mirror 34a, and again reflected on the incident surface 35a.
3b and 33a.

On the other hand, the laser beam transmitted through the wedge plate 35 is emitted from the emission surface 35b at a Brewster angle θB, and is totally reflected by the mirror 34b.
5. Transmit through the dispersing prisms 33b and 33a.

The laser beam transmitted through the dispersing prism 33a passes through the laser chamber 32 and is output from the output mirror 31.
Is emitted from. The emitted laser light is narrowed to a wavelength width of about 0.2 pm. In the above-described embodiment, the narrow band of the fluorine laser has been described. However, the present invention is not limited to this, and a laser having a shorter wavelength than the fluorine laser, for example, having a wavelength of 126 n
It can be applied to the case where the band width of the Ar2 laser of m is reduced.

As described above, according to the third embodiment, the operation and effect of the above-described first embodiment can be expected.

When the interferometer type wavelength selection element is a Michelson interferometer type, about 85
If the laser beam is set to be incident at an angle of degrees, the coating of the wedge plate 35 on the side of the incident surface 35a for the partial reflection becomes unnecessary. Furthermore, the wedge angle should be about 1
By setting the angle to 8 degrees, the emission surface 35b of the wedge plate 35
Reflection loss can be eliminated.

[Fourth Embodiment] FIG. 8 is a configuration diagram showing the configuration of an interferometer-type wavelength selection element 40 as an alternative to the above-described interferometer-type wavelength selection element 30.

This interferometer-type wavelength selecting element 40 is also of a type utilizing a Michelson interferometer, and has two mirrors 41.
a, 41b, wedge plate 42 and second wedge plate 43
It is composed of The two wedge plates 42 and 43 are both formed of calcium fluoride (CaF2).

The wedge plate 42 has a wedge angle α of about 18 degrees, similarly to the wedge plate 35 in the interferometer type wavelength selection element 30. Further, the wedge plate 42 is arranged such that the incident angle of the laser beam L41 is incident at an angle larger than the Brewster angle θB.

On the other hand, the second wedge plate 43 has a shape similar to the shape of the wedge plate 42 (of course, it may have the same shape), and has the same function as the wedge plate 42.

Further, the arrangement angle of the wedge plate 43 is such that not only the edge position of the wedge plate 43 with respect to the laser beam L42 is opposite to the edge position of the wedge plate 42, but also the center axis of the wedge plate 43 (in FIG. Part shown by the dotted line)
The Brewster angle is about 57 degrees with respect to the laser beam L42. For this reason, the reflection loss on the incident surface and the exit surface of the laser beam on the wedge plate 43 is as small as about 0.1%.

The mirror 41b is arranged so that the laser beam L43 emitted from the wedge plate 43 is incident at an incident angle of 90 degrees (vertical).

Next, the function of the second wedge plate 43 in the interferometer type wavelength selecting element 40 will be described.

In the wedge plate 42, the refraction angle at the wedge plate 42 slightly changes due to a temperature rise caused by the passage of the laser beam L41 from the dispersion prism 33b (see FIG. 6).

This is because the refractive index of calcium fluoride (CaF2), which is the material of the wedge plate 42, has temperature dependence. Therefore, the traveling direction of the laser beam L42 is slightly shifted with the temperature change of the wedge plate 42. Similarly, with the temperature change of the wedge plate 43, the laser light L43
Is slightly shifted.

In this embodiment, however, the wedge plate 43 is used.
Similarly, the temperature of the wedge plate 43 also rises, but since the position of the wedge plate 43 is opposite to that of the wedge plate 42 with respect to the laser beam L42 as shown in FIG.
The direction of refraction of the laser beam at the wedge plate 43 is opposite to that of the wedge plate 42.

That is, the relationship that the refraction directions of the transmitted light and the emitted light are refracted in the direction of the elevation angle or the depression angle on the wedge plate 42 with respect to the optical axis of the laser light before refraction is as follows.
In the wedge plate 43, on the contrary, it means that the light is refracted in the direction of the depression angle or the elevation angle.

Therefore, since the traveling direction of the laser beam L43 is almost constant irrespective of the change in temperature, the angle of incidence on the mirror 41b is always vertical, and the selected wavelength as the interferometer type wavelength selecting element 40 is selected. Will almost not shift.

The interferometer type wavelength selecting element 40 having the following configuration
Will be described with reference to FIG.

First, when the laser beam L41 transmitted through the dispersion prism 33b (see FIG. 6) is incident on the partially reflecting surface (incident surface) 42a of the wedge plate 42, a part of the laser beam is
After being reflected by the partial reflection surface 42a, reflected by the mirror 41a, and further reflected by the partial reflection surface 42a, the light proceeds to the dispersion prism 33b.

On the other hand, the other laser light in the laser light L41 incident on the partial reflection surface 42a is
After passing through the mirrors 41 and 43, the light is totally reflected by the mirror 41b and again passes through the two wedge plates 43 and 42, and then proceeds to the dispersion prism 33b.

The laser beam thus advanced to the dispersion prism 33 passes through the dispersion prism 33a and the laser chamber 32, and is emitted from the output mirror 31. The emitted laser light is narrowed to a wavelength width of about 0.2 pm.

In the above-described embodiment, the narrow band of the fluorine laser has been described. However, the present invention is not limited to this, and a laser having a shorter wavelength than the fluorine laser, for example, an Ar2 laser having a wavelength of 126 nm is used. It can also be applied to narrowing the bandwidth.

As described above, according to the fourth embodiment, the positional relationship between the wedge plate 42 and the wedge plate 43 is
Since the laser light L42 is arranged so that the edges thereof are located on opposite sides, the wedge plate 4
Irrespective of the change in the refraction direction due to the temperature rise due to 2, 43, the traveling direction of the laser beam L43 is almost constant and the angle of incidence on the mirror 41b is always vertical. The selected wavelength does not shift. That is, a stable selected wavelength can be obtained.

Further, since the second wedge plate 43 is arranged such that the central axis (line indicated by a dotted line) has a Brewster angle of about 57 degrees with respect to the laser beam L42, the wedge plate 43 is provided. The reflection loss (approximately 0.1%) of the laser beam on the incidence surface and the emission surface of the plate 43 can be suppressed.

[Fifth Embodiment] FIG. 9 is a configuration diagram showing the configuration of an ultra-narrow band fluorine laser device 300.

The ultra-narrow band fluorine laser device 3 shown in FIG.
Reference numeral 00 denotes a configuration in which the wedge plate 35 is removed from the configuration shown in FIG. 6 and the arrangement of the two mirrors 34a and 34b is changed. Note that parts that perform the same functions as the components shown in FIG. 6 are denoted by the same reference numerals.

In the example of FIG. 9, one dispersion prism 33b used as a wedge plate and two mirrors 34a,
4b, a Michelson interferometer type interferometer type wavelength selecting element 50 is formed.

That is, of the dispersion prisms 33a and 33b used to convert the fluorine laser into one line, the beam is divided on the surface of the dispersion prism 33b on the dispersion prism 33a side (corresponding to a beam division surface). I have to. In addition, the dispersion prism 33a is set so that the laser beam from the dispersion prism 33a is incident at a large incident angle of about 85 degrees so that the reflectance is about 50% on that surface (corresponding to a beam splitting surface). 33b are arranged.

The feature of this embodiment is that the beam splitting surface required for the interferometer type wavelength selecting element 50 is
In order to further narrow the band of the laser light of one line, in addition to the optical components of the dispersion prisms 33a, 33b and the mirror 34b necessary for making one line of the fluorine laser, the surface is replaced by the surface of 3b. The optical components necessary to configure the interferometer-type wavelength selection element include mirror 34a
You only need to add them.

The operation of the ultra-narrow band fluorine laser device 300 having the following configuration will be described with reference to FIG.

The laser light oscillated from the laser chamber 32 passes through the dispersion prism 33a,
, Part of the laser light is reflected by the dispersion prism 33b, and the other laser light is transmitted by the dispersion prism 33b.

The laser beam reflected by the dispersion prism 33b is reflected by the mirror 34a, and is again reflected by the dispersion prism 33b.
After being reflected by b, the light passes through the dispersion prism 33a.

On the other hand, the laser beam transmitted through the dispersion prism 33b is reflected by the mirror 34b, and then transmitted through the two dispersion prisms 33b and 33a.

The laser beam transmitted through the dispersing prism 33a passes through the laser chamber 32 and is output from the output mirror 31.
Is emitted from. The emitted laser light is narrowed to a wavelength width of about 0.2 pm.

In the above-described embodiment, the narrow band of the fluorine laser has been described. However, the present invention is not limited to this, and a laser having a shorter wavelength than the fluorine laser, for example, an Ar2 laser having a wavelength of 126 nm may be used. It can also be applied to narrowing the bandwidth.

As described above, according to the fifth embodiment, the dispersion prism 33b functioning as a beam splitting surface
Since the laser beam is incident on the surface on the side of the dispersion prism 33a at a large incident angle of about 85 degrees in order to make the reflectivity about 50%, the effect of dispersion by the dispersion prism 33b is increased.

That is, the dispersing prism is used to unify the two lines of the fluorine laser into one. Generally, in the dispersing prism, when the incident angle of the laser beam increases, the difference in the refraction angle due to the difference in wavelength increases. Become.

In general, when a dispersing prism is used for a laser resonator, the incident angle of the laser beam is often set to about 57 degrees, which is the Brewster angle θB, so that the loss of the laser beam due to this is reduced. .

On the other hand, in the present embodiment, the incident light is made incident at an angle much larger than about 57 degrees (about 85 degrees), so that the surface reflection of the dispersing prism increases. However, since the laser beam due to the surface reflection is used in the interferometer type wavelength selection element, the surface reflection does not cause a loss.

That is, it is used to further narrow the band of the laser light made into one line, and the laser light due to the surface reflection of the dispersing prism is effectively used.

[Sixth Embodiment] FIG. 10 is a configuration diagram showing a configuration of an ultra-narrow band fluorine laser device 400.

Ultra-narrow band fluorine laser device 4 shown in FIG.
Reference numeral 00 denotes a configuration in which a mirror 61 is added to the configuration shown in FIG. Note that parts that perform the same functions as the components shown in FIG. 9 are denoted by the same reference numerals.

The ultra-narrow band fluorine laser device 400 uses a Michelson interferometer type interferometer type wavelength selecting element 60 like the ultra-narrow band fluorine laser device 300 shown in FIG. A dispersion prism is used for the beam splitting surface.

However, in the interferometer type wavelength selecting element 60 of this embodiment, the interferometer type wavelength selecting element is doubled. The two dispersing prisms 33a and 33b are both formed such that the edge angle α is 72 degrees.

That is, the ultra-narrow band fluorine laser 400
, Two dispersing prisms 3 for making one line
Each of 3a and 33b functions as a beam splitting surface of the interferometer type wavelength selecting element 60. That is, the dispersion prism 3
3b and two mirrors 34a and 34b constitute a first Michelson interferometer, and a dispersion prism 33a
And the mirror 61 constitute a second Michelson interferometer.

The two dispersing prisms 33a and 33b
In the same manner as in the fifth embodiment, in order to set the reflectance on the surface corresponding to each partial reflection surface to about 50%,
The laser beam is incident at a large incident angle of about 85 degrees.

The interferometer-type wavelength selecting element 60 in the ultra-narrow band fluorine laser device 400 having the following configuration is composed of a two-stage Michelson interferometer, but the basic operation is as follows. Since it is the same as the selection element 50, the description is omitted here.

In the above-described embodiment, the narrowing of the band width of the fluorine laser has been described. However, the present invention is not limited to this, and a laser having a shorter wavelength than the fluorine laser, for example, an Ar2 laser having a wavelength of 126 nm is used. It can also be applied to narrowing the bandwidth.

As described above, according to the sixth embodiment, each of the two dispersing prisms used to make one line has the function of an interferometer-type wavelength selection element, thereby narrowing the width. The effect of banding can be increased.

[Seventh Embodiment] FIG. 11 is a configuration diagram showing a configuration of an ultra-narrow band fluorine laser device 500.

The ultra-narrow band fluorine laser device 5 shown in FIG.
Reference numeral 00 denotes mirrors 34a, 3a in the configuration shown in FIG.
4b and the output mirror 31, the interferometer type wavelength selecting element 70 is added in place of the output mirror 31, and the mirror 34
The configuration is such that a total reflection mirror 73 is added instead of a. Note that parts that perform the same functions as the components shown in FIG. 6 are denoted by the same reference numerals.

In the ultra-narrow band fluorine laser apparatus 500, a resonator is constituted by the total reflection mirror 73 and the interferometer type wavelength selection element. In this resonator, a laser chamber 32 and two dispersing prisms 33a and 33b for converting a fluorine laser into one line are arranged. The interferometer-type wavelength selection element 70 also has a function as an output mirror.

The interferometer type wavelength selecting element 70 is composed of a wedge plate 71 and a mirror 72.
The first partial reflection surfaces 71a and 71b are both formed of an uncoated CaF2 substrate.

When the incident light enters the partial reflection surface 71a at an angle of about 70 degrees larger than the Brewster angle θB, the wedge plate 71
1 is formed and arranged so as to be emitted perpendicularly (90 degrees) to the partial reflection surface 71b.

Further, the partial reflection surface 71b of the wedge plate 71
Has the function of a partially reflecting surface, but functions as an output mirror.

Since the angle of incidence on the wedge plate 71 is about 70 degrees as described above, the reflectance on the wedge plate 71 is about 5 degrees, as can be seen from the graph shown in FIG.
%. Therefore, as shown in FIG. 12, transmission and reflection alternately appear in the reflectance of the interferometer-type wavelength selection element 70 as a whole, and the wavelength selection characteristic is the best.

The operation of the ultra-narrow band fluorine laser device 500 having the following configuration will be described with reference to FIG.

The laser light emitted from the laser chamber 32 passes through the dispersion prisms 33a and 33b, is reflected by the total reflection mirror 73, passes through the dispersion prisms 33b and 33a, further passes through the laser chamber 32, and The light enters the meter-type wavelength selection element 70.

When this laser beam is incident on the partially reflecting surface 71a of the wedge plate 71, a part of the laser beam is transmitted through the wedge plate 71, while the other laser beam is reflected by the partially reflecting surface 71a. Then, the light is further reflected by the mirror 72 and returns to the partial reflection surface 71a. The laser light returned in this way is reflected on the partial reflection surface 71a, and proceeds into the laser chamber 32 again.

A part of the laser light transmitted through the wedge plate 71 is reflected by the partial reflection surface 71b, returns to the original position, further transmits through the partial reflection surface 71a, and proceeds to the laser chamber 32.
On the other hand, other laser light is emitted perpendicular to the partial reflection surface 71b (output mirror). The emitted laser light is narrowed to a wavelength width of about 0.2 pm.

In the above-described embodiment, the narrow band of the fluorine laser has been described. However, the present invention is not limited to this, and a laser having a shorter wavelength than the fluorine laser, for example, an Ar2 laser having a wavelength of 126 nm may be used. It can also be applied to narrowing the bandwidth.

As described above, according to the seventh embodiment, the same operation and effect as those of the first embodiment can be expected.

[Eighth Embodiment] FIG. 13 is a configuration diagram showing the configuration of a fluorine exposure machine 700 using an ultra-narrow band fluorine laser device.

The fluorine exposure apparatus 700 is roughly divided into the ultra-narrow band fluorine laser apparatus 100 shown in FIG.

The exposure apparatus main body 600 is arranged on a grating 81 in a clean room. Are located.

The laser beam L20 of only a strong line (oscillation line) having a wavelength width of about 0.2 pm and extracted from the ultra-narrow band fluorine laser apparatus 100 is reflected by the mirror 83a and travels upward, and the aperture in the grating 81 is opened. After passing through the section 84, the process proceeds into the exposure apparatus main body 600.

[0210] The laser beam L20 is stopped down by the lens 85,
Further, the laser light travels through a glass rod 86 made of calcium fluoride and repeats total reflection inside the glass rod 86, thereby emitting a laser beam L21 having a uniform beam intensity distribution.

The laser beam L21 is reflected by the mirror 83b, passes through the beam shaper 87 to expand the beam cross section, and is further reflected by the mirror 83c to irradiate the reticle 89 through the condenser lens 88.

The laser beam L22 emitted from the reticle 89
Passes through the reduction projection lens 90 and hits the wafer 91. That is, the pattern in the reticle 89 is transferred onto the wafer 91 by the reduction projection lens 90, so that the pattern is exposed on the reticle 89. In addition,
The wafer 91 is mounted on a stage 92.

In the fluorine exposure machine 700 of this embodiment,
As the reduction projection optical system, a reduction projection lens 90 is used, and the reduction projection lens 90 is configured by a monochromatic lens made of calcium fluoride.

As described above, the reduction projection optical system using only the lens can be used because the wavelength width of the laser beam L20 extracted from the ultra-narrow band fluorine laser apparatus 100 is about 0.2 pm, This is because the chromatic aberration in the reduction projection lens 90 can be ignored because it is as narrow as about 1/5 of the fluorine laser.

Therefore, the configuration of the exposure machine main body 600 is as follows.
It becomes equivalent to that of the conventional KrF exposure machine. The major difference is that the material of the lens is simply changed from quartz to calcium fluoride, so the design of the reduction projection lens is the same as the conventional one, and the design cost is greatly reduced. Can be.

As described above, according to the eighth embodiment, in the fluorine exposure apparatus, the price of the fluorine laser device (ultra-narrow band fluorine laser device) increases significantly, and the efficiency of the laser increases. The all-refractive reduction projection optical system can be used without deterioration.

That is, as the reduction projection optical system, the conventional K
The design can be similar to that of the rF exposure machine. In other words, a simulation tool similar to the conventional one can be used, and a reduced projection optical system can be designed in a short time, and labor costs can be significantly reduced. A fluorine exposure machine can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of an ultra-narrow band fluorine laser device 100 according to a first embodiment.

FIG. 2 is a configuration diagram showing an enlarged configuration of an interferometer-type wavelength selection element 12 of the ultra-narrow band fluorine laser apparatus 100.

FIG. 3 is a graph showing the reflectance characteristics of uncoated CaF2.

FIG. 4 is a graph showing the reflectance characteristics of the interferometer type wavelength selection element 12.

FIG. 5 is a configuration diagram showing a configuration of an interferometer-type wavelength selection element 20 according to a second embodiment.

FIG. 6 is a configuration diagram showing a configuration of an ultra-narrow band fluorine laser device 200 according to a third embodiment.

FIG. 7 is a graph showing the reflectance characteristics of the interferometer-type wavelength selection element 30.

FIG. 8 is a configuration diagram showing a configuration of an interferometer-type wavelength selection element 40 according to a fourth embodiment.

FIG. 9 is a configuration diagram showing a configuration of an ultra-narrow band fluorine laser device 300 according to a fifth embodiment.

FIG. 10 is a configuration diagram showing a configuration of an ultra-narrow band fluorine laser device 400 according to a sixth embodiment.

FIG. 11 is a configuration diagram showing a configuration of an ultra-narrow band fluorine laser device 500 according to a seventh embodiment.

FIG. 12 is a graph showing a reflectance characteristic of the interferometer-type wavelength selection element 70;

FIG. 13 is a configuration diagram showing a configuration of a fluorine exposure apparatus 700 according to an eighth embodiment.

[Explanation of symbols]

11,73 Total reflection mirror 12,20,30,40,50,60,70 Interferometer type wavelength selection element 14a, 14b, 24,34a, 34b, 41a, 41
b, 61, 72 Mirrors 15, 23, 35, 42, 4
3, 71 Wedge plate 33a, 33b Dispersion prism 100, 200, 300, 400, 500 Ultra-narrow band fluorine laser device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuaki Iwata 1200 Manda, Hiratsuka-shi, Kanagawa Prefecture Inside Komatsu Seisakusho Laboratories (72) Inventor Shinji Nagai 1200 Manda, Hiratsuka-shi, Kanagawa Prefecture Komatsu Seisakusho F Terms (reference) 5F071 AA04 HH05 JJ08 5F072 AA04 HH05 JJ08 JJ13 RR05 YY09

Claims (9)

[Claims] A laser chamber for oscillating laser light of a fluorine laser or a laser having a shorter wavelength than the laser, and narrowing a band of the laser light from the laser chamber;
An ultra-narrow band laser device for supplying an exposure light source to an exposure device, comprising: an interferometer-type wavelength selector having a beam splitting surface, wherein the interferometer-type wavelength selector is a laser beam oscillated from the laser chamber. An ultra-narrow band laser device, wherein the angle of incidence on the beam splitting surface is larger than the Brewster angle. 2. The interferometer-type wavelength selecting element comprises two reflectors having a function of a total reflection surface and a predetermined wedge plate having a function of the beam splitting surface and not subjected to a coating process. 2. The ultra-narrow band laser device according to claim 1, wherein: 3. An interferometer type wavelength selecting element comprising: one reflecting material having a function of a total reflection surface; and a predetermined wedge plate having a function of a total reflection surface and a beam splitting surface and not being subjected to a coating process. 2. The ultra-narrow band laser device according to claim 1, comprising: 4. The predetermined wedge plate, when the laser beam oscillated from the laser chamber is incident on the beam splitting surface at an incident angle larger than the Brewster angle, 3. The optical element according to claim 2, wherein an angle between an optical axis of the laser light emitted from the emission surface located on the opposite side and a perpendicular to the emission surface is a Brewster angle. Or the ultra-narrow band laser device according to 3. 5. A second wedge plate through which laser light emitted from the interferometer type wavelength selection element is transmitted and which has the same function as the predetermined wedge plate and is not subjected to a coating process, The second wedge plate is configured such that an edge of the second wedge plate is located on a side opposite to a position of an edge of the predetermined wedge plate with reference to an optical axis of laser light from the interferometer type wavelength selection element. 4. The ultra-narrow band laser device according to claim 2, wherein two wedge plates are arranged. 6. The ultra-narrow band laser device according to claim 2, wherein said interferometer type wavelength selector is a Michelson type interferometer type wavelength selector. 7. The interferometer-type wavelength selector according to claim 2, wherein the interferometer-type wavelength selector is a Michelson-type interferometer-type wavelength selector, and the predetermined wedge plate is formed of a dispersion prism. Ultra narrow band laser device. 8. The interferometer type wavelength selecting element has the same function as the predetermined wedge plate between the wedge plate and a reflection surface for reflecting the laser beam transmitted through the predetermined wedge plate. A second wedge plate that has not been subjected to a coating process is further provided, and the second wedge plate and the predetermined wedge plate are based on an optical axis of laser light from the predetermined wedge plate. The ultra-narrow band laser device according to claim 6, wherein the edges are arranged so as to be located on opposite sides. 9. The interferometer-type wavelength selection element comprises: one reflector having a function of a total reflection surface; and a wedge plate having a function of the beam splitting surface and a partial reflection surface and not being coated. When the laser light oscillated from the laser chamber is incident on the beam splitting surface at an angle of incidence greater than the Brewster angle, the laser light transmitted through its own wedge plate is 2. The ultra-narrow band laser device according to claim 1, wherein the laser device is formed so as to be emitted perpendicular to the partial reflection surface.