JPH1152443A - Laser beam generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To approximate a wavelength to 248 nm, to obtain high output, to eliminate toxicity and to enhance resolution performance by obtaining an output laser beam of a specific wavelength from two laser beams. SOLUTION: A first laser beam source 1 consisting of respectively Q switch solid-state lasers is an Nd:YAG solid-state laser which generates the first laser beam of a wavelength λ1 (=946 nm). A second laser beam source 2 is an Nd: YLF solid-state laser which generates the second laser beam of a wavelength λ2 (=1047 nm). The first and second laser beams are made the same in the respective optical axes by using a dichroic mirror 3. The first and second laser beams are made incident on a sum frequency generator(SFG) 4, by which the laser beams are converted to the laser beam of a wavelength λ3 =λ1.λ2/(λ+λ2)}. The wavelength λ3 turns to about 497 nm. This laser beam is subjected to wavelength conversion to an output laser beam λ4 of λ4[=λ3/2=λ1.λ2/ 2(λ1+λ2)} in wavelength. This wavelength λ4 turns to about 248.5 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser light generator suitable for use as an exposure light source, a processing device, and the like of a step type projection exposure apparatus (stepper) used for fine processing of a semiconductor wafer in a semiconductor manufacturing apparatus. About.

[0002]

2. Description of the Related Art There is a strong demand for a laser light source used for such an exposure light source or a processing apparatus to have a shorter wavelength and a higher output. Conventionally, this light source for exposure has a wavelength of 2
A 48 nm krypton fluoride (KrF) gas laser was used.

On the other hand, Nd: YAG (Nd ³⁺ : Y ₃ Al ₅ O ₁₂ , N
eodym: Yttrium Alminium Garnet) solid-state laser or Nd: Y
LF (Nd ³⁺ : LiYF ₄ , Neodym: Yttrium Lithium Floride)
2. Description of the Related Art A laser light generator that obtains a fourth harmonic from laser light from a solid-state laser by nonlinear wavelength conversion is widely used. That is, the wavelength from the solid-state laser is 1064 nm.
The wavelength of the fourth harmonic of the laser light is 266 nm.

[0004]

The KrF gas laser has a considerably short wavelength and a high output, so that it is suitable for an exposure light source of a step type projection exposure apparatus, but has the following disadvantages. ing. That is, the KrF gas laser has the drawback that the KrF gas is toxic, the life of the gas itself is short, and the life of components of the light source is short.

In addition, Nd: YAG solid-state lasers and Nd: YL
Laser light from F solid-state laser is converted by nonlinear wavelength conversion.
The laser light generating device for obtaining the fourth harmonic has the features that a semiconductor laser can be used as an excitation light source of a solid-state laser, high reliability and low maintenance cost. Disadvantages. That is, a laser light source used in an exposure apparatus and a processing apparatus in a semiconductor manufacturing apparatus requires a precise design in order to enhance resolution performance, and a refractive index dispersion of a glass material used, such as synthetic quartz. 20 nm from the wavelength dependence of the refractive index)
At different wavelengths, desired resolution performance cannot be obtained, and thus such laser light generators have not been adopted as light sources or processing devices for exposure devices in semiconductor manufacturing equipment, despite the superiority of solid-state lasers.

[0006] In view of the above, the present invention has a wavelength of 248.
It is an object of the present invention to propose a laser light generating device which is close to nm, has a high output, has no toxicity, has a long service life, and has high resolution performance.

[0007]

A laser light generator according to the present invention comprises: a first laser light source comprising a solid-state laser for generating a first laser light having a wavelength of λ1 (= 946 nm);
A second laser light source including a solid-state laser that generates a second laser beam having a wavelength of λ2 (= 1047 nm), and a wavelength of λ1 · λ2 / ｛2 (λ1 + λ) from the first and second laser beams.
2) a non-linear wavelength converting means for obtaining the output laser light of｝.

According to the present invention, the wavelength is λ1 (= 9).
The first laser light from a first laser light source, which is a solid-state laser that generates a first laser light of 46 nm), and the solid-state laser that generates a second laser light having a wavelength of λ2 (= 1047 nm). The wavelength of the second laser light from the second laser light source is converted by the nonlinear wavelength conversion means, so that the wavelength is λ1 / λ2 / {2 (λ1 + λ2)}.
(≒ 248.5 nm) output laser light is obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A laser light generator according to the present invention comprises a first laser light source comprising a solid-state laser for generating a first laser light having a wavelength of λ1 (= 946 nm), and a laser light having a wavelength of λ2 (= 1047 nm). A second laser light source composed of a solid-state laser that generates the second laser light, and a wavelength λ1 · λ2 / {2 (λ1 + λ2)} from the first and second laser lights.
And a non-linear wavelength converting means for obtaining the output laser light.

In this case, the first laser light source is Nd: Y
AG solid-state laser, and the second laser light source is Nd: Y
LF solid-state laser.

The nonlinear wavelength converting means includes a sum frequency generator for obtaining a laser beam having a wavelength of λ1 / λ2 / (λ1 + λ2) from the first and second laser beams, and a wavelength of λ1 / λ2 from the sum frequency generator. And a second harmonic generator for obtaining a laser beam having a wavelength of λ1 / λ2 / {2 (λ1 + λ2)} from a laser beam of / (λ1 + λ2).

The nonlinear wavelength converting means includes first and second harmonic generators for obtaining laser beams having wavelengths of λ1 / 2 and λ2 / 2 from the first and second laser beams, and the first and second harmonic generators. It is also possible to use a sum frequency generator that obtains a laser beam having a wavelength of λ1 / λ2 / {2 (λ1 + λ2)} from a laser beam having a wavelength of λ1 / 2 and λ2 / 2 from a wave generator.

The first and second laser light sources are each composed of a Q-switched solid-state laser that oscillates at the same repetition frequency.

A driving device including a pulse generator for generating a pulse signal of a predetermined frequency and delay means for obtaining first and second trigger pulse signals having a predetermined time difference from the pulse signal from the pulse generator; : A first component constituting a YAG solid-state laser (Q-switched solid-state laser) and a first component constituting an Nd: YLF solid-state laser (Q-switched solid-state laser), respectively.
The first and second trigger pulse signals are supplied to the light control elements of the second and second resonators, respectively, so that the optical resonance operation is performed for each trigger pulse period.

The delay means is constituted by a variable delay means, and is capable of adjusting a predetermined time difference so that the intensity of the output laser light is maximized.

The nonlinear wavelength converting means comprises two or three nonlinear wavelength converters, and at least one of the nonlinear wavelength converters comprises β-barium borate, lithium borate, or cesium lithium borate. Consists of

[Embodiment] An embodiment of a laser beam generator according to the present invention will be described below in detail with reference to FIGS. First, the embodiment of FIG. 1A will be described. Each Q
First and second laser light sources 1 and 2 comprising a switched solid-state laser are provided. The first laser light source 1 is, specifically,
This is an Nd: YAG solid-state laser that generates a first laser beam having a wavelength of λ1 (= 946 nm). Second laser light source 2
Specifically, the second wavelength of λ2 (= 1047 nm)
Nd: YLF solid-state laser that generates the laser light of

The Nd: YAG solid-state laser has a wavelength of 10
It is a low-cost and highly reliable laser light source because it has strong oscillation at 64 nm, is often used in industrial applications, and can be excited by a semiconductor laser. In recent years, by increasing the brightness of a semiconductor laser, which is a light source for excitation, it has become possible to increase the excitation density in a laser medium, and the wavelength becomes 9
It has become possible to oscillate at 46 nm.

The wavelength of the Nd: YAG solid-state laser is 946 n
The oscillation of m is an oscillation called a pseudo-three level, and the wavelength is 10
Although the oscillation efficiency is lower than the oscillation at 64 nm, high-efficiency oscillation that is sufficiently practical can be achieved by cooling the laser medium or the like. The oscillation of 946 nm can be realized by selecting reflectors having different characteristics as a pair of reflectors constituting a resonator in the solid-state laser.

The Nd: YLF solid-state laser is a Nd: YAG
Like solid-state lasers, they are often used in industrial applications.
Since it can be excited by a semiconductor laser, it is an inexpensive and highly reliable laser light source having a wavelength of 1053 nm.
In addition to the oscillation at, oscillation with a wavelength of 1047 nm is also possible.

The first and second laser beams from the first and second laser light sources 1 and 2 are made to have the same optical axis by using a dichroic mirror 3. FIG.
In the case of A, the second laser beam is emitted from the dichroic mirror 3
The first laser beam is incident and reflected at an angle of 45 degrees with respect to one surface of the dichroic mirror 3, and the first laser beam is incident and reflected at an angle of 45 degrees with respect to the other surface of the dichroic mirror 3, so that the respective optical axes are the same. But it is also possible to do the opposite. Incidentally, a wavelength dispersion prism can be used instead of the dichroic mirror 3. In FIG. 1A,
Although the optical path of the first laser light emitted from the first laser light source 1 is deflected by 90 degrees in the middle, the deflection is performed by a not-shown total reflection mirror.

The first and second laser beams having wavelengths λ1 and λ2 from the first and second laser light sources 1 and 2, respectively, are:
After each optical axis is the same, sum frequency generation (SF
G: Sum frequency generation), and the wavelength is λ3 ｛= λ1 / λ2 / (λ1 + λ).
2) It is converted into the laser light of ①. This wavelength λ3 is about 497
nm.

The materials of the sum frequency generator 4 include lithium borate (LiB ₃ O ₅ ) (LBO), potassium titanate phosphate (KTiOPO ₄ ) (KTP), and β-barium borate (β-
BaB ₂ O ₄ ) (BBO) and the like are possible.

The laser light having a wavelength of λ3 from the sum frequency generator 4 is converted by the second harmonic generator 5 into a laser beam having a wavelength of λ4 [= λ
3/2 = λ1 · λ2 / {2 (λ1 + λ2)}]. This wavelength λ4 is about 248.
5 nm.

The material of the second harmonic generator 5 is as follows.
β-barium borate (β-BaB ₂ O ₄ ) (BBO), cesium lithium borate (CsLiB ₆ O ₁₀ ) (CLBO) and the like are possible.

Next, the embodiment of FIG. 1B will be described.
In FIG. 1B, parts corresponding to those in FIG. In the embodiment of FIG. 1A, the wavelengths of the first and second laser light sources 1 and 2 are respectively λ1,
The first and second laser beams of λ2 are converted by the sum frequency generator 4 into laser beams of wavelength λ3 ｛= λ1 / λ2 / (λ1 + λ2) ２, and the laser beam of wavelength λ3 is converted to the second harmonic. The wavelength is λ4 [= λ1 · λ2 /
{2 (λ1 + λ2)}].
Obviously, the positions of the sum frequency generator and the second harmonic generator may be interchanged.

That is, in the embodiment of FIG. 1B, the first and second
The first and second laser beams having wavelengths of λ1 and λ2 from the laser light sources 1 and 2 are respectively separated by second harmonic generators 5A and 5B into λ1 / 2.
(= 473 nm) and λ2 / 2 (= 523.5 nm). And the wavelengths are respectively λ1 / 2,
After the laser light of λ2 / 2 is made to have the same optical axis by the dichroic mirror 3, the wavelength is λ4 [= λ1 · λ2 / ｛2 (λ
1 + λ2)｝]. The wavelength λ4 of this output laser light is 248.5 nm, and FIG.
The wavelength is the same as the wavelength of the output laser light in the case of A.

Next, first and second laser light sources 1, 2 each comprising a solid-state laser in the embodiment of FIGS.
An example of a specific configuration and an example of a driving device thereof will be described. First
And second laser light sources 1 and 2 are laser resonators 9A and 9B including a pair of opposing reflecting mirrors (concave mirrors) 10A and 10B and 11A and 11B, and lasers disposed in the laser resonators 9A and 9B. Excitation light sources (semiconductor lasers and other lasers are possible) 7A, 7B for exciting the media 6A, 6B and the laser media 6A, 6B, respectively.
And light collectors 8A and 8B and light control elements 12A and 12B.

Next, a driving device for the first and second laser light sources 1 and 2 will be described. For example, 3 kHz to 10 k
A pulse signal from the pulse generator 13 for generating a pulse signal having a constant frequency of about
τB (τA ≠ τB) delay device (variable delay device) 14A, 1
The trigger pulse signal is supplied to the optical control elements 14A and 14B after being delayed by being supplied to the optical control elements 4A and 14B.

Then, only during the pulse period in which the trigger pulse signal is supplied to each of the light control elements 12A and 12B, the first
And the second laser beam passes through each light control element 12A, 12B, and the laser beam from the laser medium 6A, 6B repeatedly travels between the pair of reflecting mirrors 10A, 10B and 11A, 11B in forward and reverse directions. During the other periods, the light control elements 12A and 12B prevent the first and second laser beams from traveling.

The first and second laser beams reciprocate between the opposing reflecting mirrors 10A, 10B and 11A, 11B constituting the laser resonators 9A, 9B of the first and second laser light sources 1, 2, respectively. When the laser beam advances and has a large power, the first and second laser beams are emitted from the reflecting mirrors 10A and 10B or 11A and 11B to the outside.

Then, the first and second laser light sources 1 and 2
The time difference between the first and second laser beams is adjusted by adjusting the delay amount of the delay device 14A and / or 14B so that the power of the first and second laser beams becomes maximum. ing.

The pulse laser used for high-efficiency, high-power non-linear conversion has a Q that is triggered by an external signal.
This is a laser light source called a Q-switched laser that obtains a pulse laser beam having a short time width, that is, a high peak value by a switch.

The power of the laser light output from the sum frequency generator 4 shown in FIGS. 1A and 1B is expressed as a function of the product of the instantaneous values of the powers of the two laser lights input to the sum frequency generator 4. If the two laser lights input to the sum frequency generator 4 are pulsed laser lights, the respective pulse periods need to overlap, and if not, the two laser lights are mutually Without this, the product of the instantaneous values of the powers of the two laser beams becomes zero.

In order for the two pulse laser beams input to the sum frequency generator 4 to overlap in time, it is necessary that their repetition frequencies be completely the same, and as shown in FIG. The pulse signal from the pulse generator 13 is delayed by separate delay units 14A and 14B to generate respective trigger pulse signals, which are transmitted to the light control elements 12A and 12B of the first and second laser light sources 1 and 2. I am trying to supply.

However, the rising timing of the Q switch pulse differs depending on the laser light source. Therefore, even if the two Q switch laser light sources are triggered by the same trigger pulse signal, the pulse laser light of the same timing is generated. Is not limited, the first and second
Laser light sources, ie, two Q-switch laser light sources 1,
2 to change the relative timing of the trigger pulse signal supplied thereto so that the respective pulsed laser beams are synchronized, that is, while observing the timing of the pulsed laser beam with a measuring instrument, or generating the second harmonic. Vessel 5 (FIG. 1A)
) Or one of the delay units 14A and 14B or both of the delay amounts τA and τB so that the power of the pulsed laser light output from the sum frequency generator 4 (the case of FIG. 1B) is maximized. Variable.

[0037]

According to the first aspect of the present invention, the wavelength is λ1 (=
946 nm) of a first laser light source composed of a solid-state laser that generates a first laser beam, and a wavelength of λ2 (= 1047 n).
m) a second laser light source composed of a solid-state laser for generating a second laser light, and a non-linear light source for obtaining an output laser light having a wavelength of λ1 / λ2 / {2 (λ1 + λ2)} from the first and second laser lights. Wavelength conversion means, the wavelength is 248n
m, high output, no toxicity, long life, and a high resolution laser light generator can be obtained.

The first non-linear wavelength converting means of the present invention has a wavelength of λ1 / λ2 /
A sum frequency generator for obtaining (λ1 + λ2) laser light, and the wavelength from the sum frequency generator is λ1 · λ2 / (λ1 + λ2)
From the laser light having a wavelength of λ1 / λ2 / ｛2 (λ1 + λ
2) a second harmonic generator for obtaining the laser light of｝, or a wavelength of λ1 from the first and second laser lights.
/ 2, λ2 / 2, the first and second harmonic generators for obtaining laser light, and the wavelengths of the first and second harmonic generators are λ
From the laser light of 1/2 and λ2 / 2, the wavelength is λ1 / λ2 /
And a sum frequency generator that obtains {2 (λ1 + λ2)} laser light.

In the laser light generating apparatus according to the first aspect of the present invention, the first and second laser light sources are each composed of a Q-switch solid-state laser that oscillates at the same repetition frequency, and generates a pulse signal of a predetermined frequency. And a driving device having delay means for obtaining first and second trigger pulse signals having a predetermined time difference from a pulse signal from the pulse generator, respectively, to constitute an Nd: YAG solid-state laser and an Nd: YLF solid-state laser, respectively. Since the first and second trigger pulse signals are supplied to the respective light control elements of the first and second resonators to perform the optical resonance operation in each of the trigger pulse periods,
The conversion efficiency of the sum frequency generator constituting the nonlinear wavelength conversion means can be increased, and the time difference between the first and second trigger pulse signals is adjusted by the delay means, so that the intensity of the output laser light is maximized. Can be adjusted so that

[Brief description of the drawings]

FIG. 1A is a block diagram showing one embodiment of the present invention. B is a block diagram showing another embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration example of a laser light source in the embodiment of FIGS. 1A and 1B and an example of a driving device thereof.

[Explanation of symbols]

1 First laser light source, 2 Second laser light source, 3 Dichroic mirror, 4 Sum frequency generator, 5, 5A, 5
B second harmonic generator, 6A, 6B laser medium, 7
A, 7B Excitation light source, 8A, 8B Condenser, 9A, 9B
Resonator, 10A, 10B Reflector, 11A, 11B
Reflector.

Claims (11)

[Claims] 1. A first laser light source comprising a solid-state laser for generating a first laser light having a wavelength of λ1 (= 946 nm), and a solid-state laser for generating a second laser light having a wavelength of λ2 (= 1047 nm) A second laser light source comprising: and a wavelength λ1 / λ2 / from the first and second laser lights.
A non-linear wavelength converter for obtaining {2 (λ1 + λ2)} output laser light. 2. The laser light generating device according to claim 1, wherein the first laser light source is a Nd: YAG solid-state laser, and the second laser light source is a Nd: YLF solid-state laser. Characteristic laser light generator. 3. The laser light generating device according to claim 1, wherein said nonlinear wavelength converting means has a wavelength of λ1 / λ2 / from the first and second laser lights.
A sum frequency generator that obtains (λ1 + λ2) laser light, and a wavelength from the sum frequency generator is λ1 · λ2 / (λ1 + λ)
From the laser light of 2), the wavelength is λ1 / λ2 / ｛2 (λ1 +
λ2) A second harmonic generator for obtaining a laser beam of｝. 4. The laser light generating device according to claim 1, wherein said nonlinear wavelength converting means has a wavelength of λ1 / 2, λ2 from said first and second laser lights.
First and second harmonic generators for obtaining a laser beam of ２/2, and wavelengths from the first and second harmonic generators are λ1 / 2, λ
From the 2/2 laser beam, the wavelength is λ1 / λ2 / ｛2 (λ1
And a sum frequency generator for obtaining a laser beam of + λ2)｝. 5. The laser light generator according to claim 1, wherein the first and second laser light sources are each a Q-switch solid-state laser that oscillates at the same repetition frequency. apparatus. 6. The laser light generator according to claim 5, wherein a pulse generator for generating a pulse signal of a predetermined frequency, and first and second trigger pulses having a predetermined time difference from the pulse signal from the pulse generator. A driving device having a delay means for obtaining a signal is provided, and the first and second optical control elements of the first and second resonators constituting the Nd: YAG solid-state laser and the Nd: YLF solid-state laser, respectively, are provided with the first and second optical control elements, respectively. A laser light generating device, wherein a second trigger pulse signal is supplied to perform an optical resonance operation for each trigger pulse period. 7. The laser light generating apparatus according to claim 6, wherein said delay means is constituted by a variable delay means, and said predetermined time difference can be adjusted so that the intensity of said output laser light is maximized. A laser light generator characterized by the following. 8. The laser light generating device according to claim 1, wherein said nonlinear wavelength converting means comprises two or three nonlinear wavelength converters, and at least one of said nonlinear wavelength converters is provided.
The non-linear wavelength converters are made of β-barium borate. 9. The laser light generating device according to claim 1, wherein said nonlinear wavelength converting means comprises two or three nonlinear wavelength converters, and at least one of them.
The non-linear wavelength converter is made of lithium borate. 10. The laser light generating device according to claim 1, wherein said nonlinear wavelength converting means comprises two or three nonlinear wavelength converters, and at least one of said nonlinear wavelength converters.
The non-linear wavelength converter is made of cesium lithium borate. 11. The laser light generator according to claim 3, wherein the sum frequency generator is made of an optical crystal of potassium titanate phosphate.