JPH10270352A - Aligner for manufacturing integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aligner device which is not deteriorated in its characteristic, such as the durability, light transmissivity, etc., even when the device emits ArF excimer laser and can be manufactured at a low cost by constituting its optical system by combining of a synthetic quarts glass optical body having specific physical properties with a fluorite optical body. SOLUTION: The optical system of the aligner is constituted by combining a synthetic quarts glass optical body with a flourite optical body. The optical body (wafer-side optical body) on the side where the density ε (mJ/cm<2> ) of light energy transmitted through the optical bodies is relatively large is constituted of single-crystal fluorite and the optical body (light-source side optical body) on the side where the density ε (mJ/cm<2> ) of light energy transmitted through the optical bodies is relatively small is constituted of synthetic quartz glass having a hydrogen molecule concentration of 1×10<17> to 5×10<18> molecules/cm<3> which is nearly equal to the doped concentration of the glass under a normal pressure so that the optical system may have high transmissivity as a whole. A more preferable optical system is constituted of a plurality of kinds of synthetic quarts glass optical bodies and a single-crystal fluorite optical body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a 64M to 256M
In particular, an integrated circuit manufacturing exposure apparatus is used to illuminate an integrated circuit pattern with a narrow band short-wavelength ultraviolet laser beam and print the integrated circuit pattern on a wafer using an optical system made of quartz glass material. The present invention relates to an exposure apparatus for manufacturing an integrated circuit.

[0002]

2. Description of the Related Art Conventionally, an optical lithography technique for transferring a pattern on a mask onto a wafer using light is superior in cost in comparison with other techniques using an electron beam or a Χ-ray, so that an integrated circuit is used. Is widely used as an exposure apparatus for manufacturing a semiconductor device. Conventionally, an exposure apparatus utilizing such photolithography technology has a light source of a wavelength of 3 from a high-pressure mercury lamp.
An exposure apparatus has been developed to form a pattern having a line width of 0.5 to 0.4 μm using an i-line of 65 nm. Such an exposure apparatus corresponds to an integrated circuit of 16 Mbit-DRAM or less. On the other hand, the next-generation 64 Mbit to 256 Mbit has an imaging performance of 0.25 to 0.35 μm,
The G bit requires a resolution of 0.13 to 0.20 μm, but the resolution of 0.35 μm exceeds the wavelength of the i-line, and KrF light is used as a light source. Further, in the region below 0.20 μm, Ar instead of KrF light
rF light, particularly an ArF excimer laser, is used.

However, there are various problems in the optical lithography technique using an ArF excimer laser, one of which is a problem of an optical material for forming a lens, a mirror and a prism constituting a projection optical system. That is, ArF 19
Optical materials having a good transmittance at a wavelength of 3 nm are substantially limited to quartz glass, particularly high-purity synthetic quartz glass.
F light causes damage to quartz glass at least 10 times greater than KrF light.

[0004] The resistance of quartz glass to irradiation with excimer laser is described in Japanese Patent Application No. Hei.
No. 5226, it depends on the concentration of hydrogen contained. For this reason, in a conventional exposure apparatus using a KrF excimer laser as a light source, if the concentration of hydrogen contained in the quartz glass constituting the optical system is 5 × 10 ¹⁶ molecules / cm ³ or more, sufficient durability can be secured. It is described in the art. However, since the influence of the ArF laser beam on the quartz glass is greater than that of KrF as described above, the degree of damage (change in transmittance and change in refractive index) caused by the ArF laser beam on the synthetic quartz glass is limited. Examination shows that the required hydrogen molecule concentration is Kr
In some cases, it has been found that the concentration of hydrogen molecules is required to be 100 to 1000 times or more higher than that of the F laser light, specifically, a hydrogen molecule concentration of 5 × 10 ¹⁸ molecules / cm ³ or more is required.

[0005] There are two methods for incorporating hydrogen molecules into synthetic quartz glass. First, when the atmosphere during production is adjusted to include hydrogen molecules in synthetic quartz glass at normal pressure, the concentration of hydrogen molecules that can be contained is the highest. Up to about 5 × 10 ¹⁸ molecules / cm ³ . As another method, even when doping hydrogen molecules into quartz glass by pressurized heat treatment in a hydrogen atmosphere, the upper limit of 10 atm / atmosphere which is not subject to the high-pressure gas control method.
The upper limit of the concentration of hydrogen molecules introduced in the hydrogen treatment of cm ² is also 5 × 10 ¹⁸ molecules / cm ³ .

For this reason, 5 × 10 ¹⁸ molecules /
If it is intended to contain hydrogen molecules of cm ³ or more, 1
It is necessary to perform the heat treatment at a high pressure hydrogen pressure much higher than 0 atm, for example, 100 atm or more and at a temperature of 1000 ° C or more. (Japanese Unexamined Patent Publication No. 4-164833 and others)

[0007]

However, heat treatment at a high-pressure hydrogen pressure of 100 atm or more and a temperature of 1000 ° C. or more induces new defects in quartz glass. Although it is preferable to carry out in the range (JP-A-6-166528), when a large amount of hydrogen molecules of 5 × 10 ¹⁸ molecules / cm ³ or more is introduced into the quartz glass optical body by hydrogen heat treatment in this temperature range, the In addition to the drawback that the diffusion rate is not so high, the processing of a large optical body takes a very long time.In addition, performing heat treatment in a high-pressure atmosphere reduces the homogeneity of the refractive index of the quartz glass optical body and causes distortion. Is also introduced. Therefore, even when the high-pressure heat treatment is performed, a heat treatment for re-adjustment is necessary. Therefore, a refractive index sufficient to contain 5 × 10 ¹⁸ molecules / cm ³ or more of hydrogen molecules and constitute an optical system of the exposure apparatus is required. Quartz glass having optical characteristics such as homogeneity and low distortion is extremely complicated industrially and very expensive after a long time treatment.

Further, even if quartz glass containing hydrogen molecules of 5 × 10 ¹⁸ molecules / cm ³ or more and having optical characteristics such as uniform refractive index and low distortion can be provided, the ArF excimer laser beam will not emit KrF. Since the damage to the quartz glass is about ten times greater than that of the above, it is inevitable that the damage causes a volume contraction (change) that causes a change in the refractive index of the quartz glass over time.

According to the present invention, even when an exposure apparatus is constructed using a short-wavelength ultraviolet laser beam having a narrow band, in particular, an ArF excimer laser, the optical system can be manufactured without deteriorating the quality such as durability and light transmittance. An object of the present invention is to provide an exposure apparatus which can be easily manufactured at low cost as a whole.

[0010]

The present invention focuses on the following points. As described above, in order to improve the durability of the ArF excimer laser exposure apparatus, 5 × 10 ¹⁸ molecules /
Including hydrogen molecules of cm ³ or more is industrially extremely complicated, requires a long-term treatment, is difficult to produce, and is very expensive. Therefore, the gist of the present invention is that the optical system is configured by a combination of synthetic quartz glass and fluorite.

A technique in which a synthetic quartz glass and fluorite are combined with an optical system used in such a projection exposure apparatus is also disclosed in JP-A-8-78319 (first prior art). Are completely different and different inventions.

That is, in the first prior art, the optical system is composed of a diffraction optical element having a positive power, a quartz lens having a negative power, and a fluorite lens having a positive power. Such a technique employs the above-described structure to correct chromatic aberration. In this conventional technique, different dispersion variances are obtained by using a combination of the power diffraction optical element and a quartz lens or a fluorite lens which is a refractive lens. Chromatic aberration is corrected by using an optical element having the following characteristics.In particular, by combining these, an optical system having an imaging characteristic with a small secondary spectrum of chromatic aberration is realized, and thereby the radius of curvature of the lens can be increased. Large in optical design
Not only does there be room for improvement in specifications such as A and large field, but also the eccentricity tolerance becomes loose in manufacturing, and the manufacturability is improved. Therefore, in the prior art, a quartz lens having a negative power and a fluorite lens having a positive power are combined due to design and manufacturing problems.
An object of the present invention is to prevent deterioration due to laser irradiation due to high-power laser irradiation as in the present invention. Therefore, the present invention and the prior art have different configurations due to the difference in the above objects.

That is, in order to improve the laser resistance of the present invention, according to the first aspect of the present invention, the optical system includes a combination of an optical body made of synthetic quartz glass and fluorite, and the light transmitted through the optical body. An optical body located at a position where the energy density ε (mJ / cm ² ) is relatively large (hereinafter referred to as a wafer-side optical body) may be made of single crystal fluorite and may be damaged when irradiated with an ArF excimer laser. And the optical body at a position where the light energy density ε (mJ / cm ² ) passing through the optical body is relatively small (hereinafter referred to as the light source side optical body) is 1 × which is doped at normal pressure. 10 ¹⁷
It is made of synthetic quartz glass having a hydrogen molecule concentration of not less than molecules / cm ^{3 and not} more than 5 × 10 ¹⁸ molecules / cm ³ , and the emphasis is placed on the homogeneity of the refractive index, thereby achieving a high transmittance of the entire optical system. Characterized in that, more preferably, the optical system is composed of a plurality of types of synthetic silica glass optical body and a single crystal fluorite optical body, among the optical body, the single crystal fluorite optical body has a uniform refractive index Δn is 3 × 10 ⁻⁶ / cm or less and the birefringence is 2 nm / cm or less, and a plurality of kinds of synthetic silica glass optical bodies are 5 × 10 ¹⁷ molecules / cm ³ or more and 5 × 10 ¹⁸ molecules / c.
a quartz glass optical body having a hydrogen molecule concentration of not more than m ³ , a refractive index homogeneity Δn of not more than 2 × 10 ⁻⁶ and a birefringence of not more than 1 nm / cm, and 1 × 10 ¹⁷ molecules / cm ³ More than 5
It has a hydrogen molecule concentration of × 10 ¹⁸ molecules / cm ³ or less, a refractive index homogeneity Δn of 2 × 10 ⁻⁶ or less, and a birefringence of 1 n.
It is good to be composed of a combination of quartz glass optical bodies of m / cm or less.

That is, in the present invention, in a high energy level region of a laser, instead of using a quartz glass optical body, a fluorite, particularly a single crystal fluorite, which is resistant to a change in transmittance by a laser is used, and an optical element which does not cause any compaction is used. Even if a fluorite is used, it is extremely difficult to achieve optical characteristics such as uniformity of refractive index and low birefringence for fluorite having a large diameter used for lithography. Therefore, in the low energy level region of the laser, by using synthetic quartz glass that can contain hydrogen at normal pressure and has high homogeneity, the transmittance resistance and high homogeneity of the entire optical system can be maintained.

That is, as for the relationship between the fluorite and the synthetic quartz glass, the specified values of the refractive index distribution (.DELTA.n) and the homogeneity of the birefringence nm / cm are set to the specified values of the synthetic quartz glass as described above. It is better to set the light source side optical body to be more favorable than the uniformity of the wafer side optical body from the specified value. More specifically, as set forth in claim 4, the wafer-side optical body is a single-crystal phosphor having a refractive power homogeneity Δn of 3 × 10 ⁻⁶ / cm or less and a birefringence of 2 nm / cm or less. It is preferable that the light source side optical body is formed of a synthetic quartz glass material having a refractive index homogeneity Δn of 2 × 10 ⁻⁶ / 1 cm or less and a birefringence of 1 nm / cm or less.

Excimer laser light generally has a wide oscillation wavelength, and ordinary laser light is used. The oscillation wavelength width of a monochromatic lens system made of only quartz is 1.5 p.
If not less than m, chromatic aberration will occur. Accordingly, the present invention provides the short wavelength ultraviolet laser light with an oscillation wavelength width of 1.5 pm.
(FWHM: full width at half maximum) is a second feature that the laser device is constituted by an ArF excimer laser having a width of not more than (FWHM: full width at half maximum). The fluorite used as the optical body has a thickness of 1 c at 193 nm after irradiating 1 × 10 ⁶ pulses with a laser energy density per pulse of 50 mJ / cm ² as described in claim 2.
The internal transmittance per m is acceptable up to about 98%.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. It's just FIG.
Is a schematic configuration diagram of a lithography exposure apparatus using an ArF excimer laser applied to the present invention (the basic configuration is No. 182 · O
plus E, Special Feature: State-of-the-art lithography technology 1) Photo-resolution technology in optical lithography), where 1 is an ArF excimer laser light source and 2 is a deformation for forming a pattern image without interference of diffraction light on the wafer surface The illuminating means has, for example, a quadrupole illumination or an annular illumination light source shape in which a central portion is a light shielding surface. 3 is ArF irradiated from the light source
A condenser lens for guiding the excimer laser light to the reticle, 4 is a mask (reticle), 5 is a projection optical system, for example, a narrow band of light by combining a lens group having a positive refractive power and a lens group having a negative refractive power. A pupil plane is formed in the optical system while improving the resolution to improve the resolving power. Numeral 6 denotes a wafer placed on a wafer stage 7, and a mask pattern formed on the reticle 4 is image-formed on the wafer 6 via the projection optical system.

In this apparatus, the ArF excimer laser light source is provided with a wavelength selecting element such as a prism, a diffraction grating, an etalon, or the like in a laser cavity, as is well known, to obtain a 1.0 to 1.5 pm spectrum. A narrow band excimer laser having a width can be obtained. (Optical and Qu
antum Electronics Vol.25 (1993) pp.293-310)

The projection optical system 5 includes a condensing lens group 5b disposed closest to the wafer surface and a lens group 5 disposed near the pupil plane for forming a pattern light on the wafer surface.
Although a exists, a secondary light source, which is an image of the light source, is formed on the pupil plane. Therefore, when a light source image appears discretely on the pupil plane, energy concentrates on the image, which causes damage to the optical system together with the wafer side. On the other hand, on the reticle side, the energy density becomes smaller by the square of the imaging magnification as compared with the wafer side.

The present embodiment focuses on this point, that is, specifically, the size of the pupil plane of the ArF excimer laser is from φ30 to φ50 mm according to the reference.
It is reasonable to determine the energy density on the basis of several times this area. For example, if the reticle sensitivity is set to 20 to 50 mJ and this is exposed by laser irradiation of 20 to 30 pulses, the energy density per pulse on the pupil surface is 0.6 to 1.7 mJ / cm ² , and more precisely, the exposure surface and the pupil The energy densities of the wafer-side lens groups arranged closest to the wafer surface are about 75 to 90% of 0, even if it is assumed that the wafer surface is slightly larger. .4
It is estimated to be about 1.5 mJ / cm ² . It is also assumed that the pupil plane is slightly lower.

On the other hand, in order to improve the resolving power, the projection optical system is constructed by combining a lens group having a positive refractive power and a lens group having a negative refractive power (for example, the above prior art and Japanese Patent Laid-Open No. In this case, it is necessary to eliminate aberrations in each lens group as much as possible. In such a case, it is better to set the actual reduction or enlargement magnification of each lens group to some extent. And the energy density of the next lens unit from the wafer side or the position closest to the pupil plane is about １ ／ of 0.4 to 1.5 mJ / cm ² , specifically 0.1 to 0.4 mJ / cm ^2. It is estimated to be about. Most other lens groups (including the light source side lens) have an energy density ε ≦ 0.1 m per pulse.
J / cm ² . Therefore, one of the wafer side lens groups
Energy density per pulse ε ≦ 0.1 mJ / cm
^In the lens group of No. ² , the resolution of the entire optical system can be improved by placing importance on optical homogeneity rather than durability.

In this embodiment, ε: ≦ 0.
In the case of synthetic quartz glass constituting the light source side optical body of 1 mJ / cm ² , the hydrogen molecule concentration C _{H2 is set} to 1 × 10 ¹⁷ ≦ C _H2 ≦ 5.
Although it is set as low as × 10 ¹⁸ molecules / cm ³ , the refractive index distribution (Δn) is ≦ 1 × 10 ⁻⁶ and the birefringence is ≦ 1.00 nm /.
cm, which is the wavelength of ArF laser
The transmittance at 93 nm is set gently to 99.5% or more.

In the lens group near the pupil plane and the wafer side closest to the wafer, durability is emphasized in the lens group in which the energy density per pulse is 0.4 ≦ ε (mJ / cm ² ). Thereby, the durability of the entire optical system can be improved. Therefore, in the present embodiment, a lens made of single crystal fluorite is used in the case of an optical body with ε: 0.4 ≦ ε, the refractive index distribution (Δn) is ≦ 3 × 10 ⁻⁶ ,
The amount of birefringence is set gently at ≦ 2.0 nm / cm to facilitate the manufacture, but the light transmittance is maintained at 99.8% or more at 193 nm, which is the wavelength of the ArF laser. I have.

Further, the optical body such as a lens having the received light energy located at the next stage such as a high-density lens has a middle point between the ^two and is located in the range of ε: 0.1 ≦ ε ≦ 0.4 mJ / cm ^2. In the case of an optical body, the hydrogen molecule concentration C _{H2 is set} to 5 × 10 ¹⁷
≦ C _H2 ≦ 5 × 10 ¹⁸ molecules / cm ³ and the refractive index distribution (Δ
n) is ≦ 2 × 10 ⁻⁶ , the birefringence is ≦ 1.0 nm / cm,
The transmittance at 193 nm, which is the wavelength of the ArF laser, is set slightly gently to 99.5% or more to facilitate the manufacture. And preferably 0.4 ≦ ε ≦ 1.5 mJ / c
The sum of the optical path lengths of the optical body of m ² is 25% or less of the optical path length of the entire optical system, and 0.1 ≦ ε ≦ 0.4 (mJ / c
m ² ) By combining and arranging the optical systems so that the total optical path length of the optical body of the optical system is 25% or less of the entire optical path length of the optical system, the optical system can be maintained while maintaining the durability, as shown in Examples described later. High transmittance can be achieved as a whole.

Now, when considering the lens material constituting the projection optical system, it is necessary to determine the diameter of the lens or the like and the degree of deterioration is severe. According to the above-mentioned reference, the ArF excimer laser is used. Of the pupil plane is about φ30 to φ50 mm, and it is reasonable to determine the pupil plane on the basis of several times this area. That is, at the position close to the pupil plane or the wafer plane, 0.4 ≦ ε (m
J / cm ² ), more specifically 0.4 ≦ ε ≦ 1.5 (m
Considering that the maximum diameter of the pupil plane is φ50 mm when the use area is 80%, the lens diameter for receiving an ArF excimer laser having an energy density of J / cm ² ) is about φ80 mm at maximum, and therefore, ε: 0.4
The lens diameter of the optical body of ≦ ε ≦ 1.5 mJ / cm ² is approximately 80
It is estimated to be less than or equal to φ. Further, by the same calculation,
ε: In the case of a lens with 0.1 ≦ ε ≦ 0.4 mJ / cm ² , the magnification is about 2 to 3 times the pupil plane, and the lens diameter corresponds to a lens having a diameter of about 80 to 100 mm. I do.

When the lens diameter is larger than this (100 mm), the energy density ε is naturally as low as 0.1 mJ / cm ² . Also in this case, the total optical path length of the optical body such as a lens having a diameter of φ80 mm or less is 25% or less of the entire optical system, and the total optical path length of the optical body such as a lens having a diameter of φ80 mm to φ100 mm is the optical path length of the optical system. It is better to set it to 25% or less of the whole.

The present invention is applicable not only to the projection optical system exposure apparatus shown in FIG. 1 but also to a reflection optical system exposure apparatus. That is, FIG. 2 is a schematic diagram showing a configuration of a lens and the like of a reflection optical system exposure apparatus using a prism type beam splitter in order to achieve high resolution (the basic configuration is No. 182 · O plus E,
The feature is briefly described in “Special Feature: Cutting Edge of Lithography Technology 1) Optical Resolution Technology in Optical Lithography”. In order to briefly explain the configuration, light passing through a beam splitter 13 from a light source 11 through a first lens group 12 is converted into a second lens. Through group 14,
After that, the light is turned by the mirror 15 and then the third lens group 1
6, the reticle 17 is scanned with the condensed light, and then returns to the beam splitter 13 again via the third lens group 16, the mirror 15, and the second lens group 14, and this time the splitter 13 Then, the image is formed by the fourth lens group 19 and the integrated circuit pattern is printed on the wafer 18.

Also in this apparatus, the ArF excimer laser light source is provided with a wavelength selecting element such as a prism, a diffraction grating, an etalon, or the like in a laser resonator, as is well known, so that the ArF excimer laser light source is 1.0 to 1.5 pm. A narrow band excimer laser having a spectrum width can be obtained. The fourth lens group 19 closest to the wafer after the deflection to the splitter 13
Is the energy density per pulse 0.4 ≦ ε ≦ 1.5
To receive the strongest light energy of mJ / cm ^2, a single crystal fluorite lens is used, and the refractive index distribution (Δn) is ≦ 3 × 1.
0 ⁻⁶ , the birefringence is gently set to ≦ 2.0 nm / cm to facilitate the production, but the light transmittance is not higher than that of ArF.
The transmittance at 193 nm, which is the wavelength of the laser, is 99.
It is maintained at 8% or more.

In this apparatus, the third reticle 17 side
For the lens group 16, 1
Energy density per pulse 0.1 ≦ ε ≦ 0.4mJ
/ Cm ^2, the hydrogen molecule concentration C _H2 molecule / cm ^{3 is set} to 5 × 10 ¹⁷ ≦ C _H2 ≦ 5 × 10 ¹⁸
The refractive index distribution (Δn) may be set to ≦ 2 × 10 ⁻⁶ , the birefringence may be set to gently as ≦ 1.0 nm / cm, and other lenses, mirrors, and prism type beam splitters may be used. In particular, since the optical body near the light source side receives only the energy of energy density ε ≦ 0.1 mJ / cm ² per pulse, the hydrogen molecule concentration C _H2 molecule / cm ³ of the lens group and the like is 1 × 10 ^{Although 17} ≦ C _H2 ≦ 5 × 10 ¹⁸ , high quality is maintained with a refractive index distribution (Δn) of ≦ 1 × 10 ⁻⁶ and a birefringence of ≦ 1 nm / cm.

The relationship between the lens diameters is the same as that described above, and the sum of the optical path lengths of the fourth lens group 19 whose lens aperture is set to φ80 mm or less is 25% or less of the optical path length of the entire optical system. Also, in the present embodiment, the durability can be improved by arranging the optical systems in such a manner that the total optical path length of the optical body of the third lens group 16 is set to 25% or less of the entire optical path length of the optical system. Transmittance 99.8% / cm as an average value of the entire optical system while maintaining the light transmittance
It is estimated that can be achieved.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the exposure apparatus shown in FIGS. 1 and 2, it takes a very long time to confirm the long-term stability of optical characteristics under actual operating conditions. Only a quartz glass optical body for manufacturing was taken out, and a simulation experiment in which actual operation was accelerated was performed.

In general, the rate of progress of damage in laser irradiation of quartz glass increases in proportion to the square of the energy density (fluence) of the irradiated excimer laser.
Vol. 23, No. 10, "Quartz Glass for Excimer Laser", by Akira Fujinoki, hereinafter referred to as Reference 1. This was used as a reference for acceleration experiments.

First, the optical material used will be described.
A quartz glass ingot was prepared by a so-called DQ method in which silicon tetrachloride was deposited on a rotating substrate while being hydrolyzed by an oxyhydrogen flame. The obtained quartz glass ingot contains 800 to 1000 ppm of OH groups and contains 5 × hydrogen molecules.
It contained 10 ¹⁸ molecules / cm ² . This quartz glass ingot was homogenized by the method described in JP-A-7-267662, and was heated and gradually cooled at 1150 ° C. for 40 hours for strain relief annealing. While the optical properties of the resulting homogeneous optical quartz glass material was measured in three directions in the absence of striae and Δn was measured refractive index distribution in the interferometer (Zygo MarkIV) is 1 × 10 ^-6 And an extremely good value.
Also, the amount of birefringence was measured with a crossed Nicols strain gauge,
The amount of birefringence was 1 nm / cm or less.

This quartz glass material for optics is described in the literature (New Gl
ass VoL6 No, 2 (1989) 191-196 “Quartz glass for stepper”), because it satisfies the optical properties required for the quartz glass member used in the excimer laser stepper, A semiconductor exposure apparatus using ArF as a light source can be manufactured by configuring an optical component using the semiconductor device. On the other hand, when the concentration of hydrogen molecules contained in the quartz glass material for optics was measured by a laser Raman method, it was 5 × 10 ¹⁷ molecules / cm ² . (Sample number A)

The content of hydrogen molecules was measured using a Raman spectrophotometer, which was measured using a Raman spectrophotometer NR1100 manufactured by JASCO Corporation with an excitation wavelength of 488 nm.
This was carried out by a host counting method using H-MATSU R943-02 manufactured by Hamamatsu Photonics with an output of r laser light of 700 mW. The content of this hydrogen molecule is determined by Raman scattering spectrum at 800 cm ^-1 observed at this time.
The area intensity ratio between the iO ₂ scattering band and the scattering band observed at 4135-40 cm ⁻¹ of hydrogen was calculated by converting it to concentration. The conversion constant is 4135 cm ^-1 / 800 c in the literature.
m ^-1 × 1.22 × 10 ²¹ (Zhurnal Pri-Kladnoi Spektr
oskopii, Vol. 46, No. 6, PP987-991, June, 1987) was used.

The optical quartz glass material is φ60 m
A sample of mxt20mm is cut out and 100
After performing the oxidation treatment at 0 ° C. × 20 hours, a hydrogen doping treatment was performed at 600 ° C. × 1000 hours in a hydrogen gas pressurized (8 atm) atmosphere in an atmosphere furnace. When the refractive index distribution of the sample after the treatment was measured, Δn was 2 × 10 ⁻⁶ , the amount of birefringence was 2 nm / cm, and the concentration of contained hydrogen molecules was 4 × 10 ¹⁸ molecules / cm ² . (Sample number B)

On the other hand, among the high-purity optical fluorites of φ60 × t20, UV grade products (eg, Applied Koken CaF2 / UV grade, Optron CaF2 / UV grade, etc.) were prepared, and the laser characteristics were evaluated. . Evaluation is 1.0 to 1.5
The energy density per pulse is 50 mJ / cm ² using a narrow band ArF excimer laser having a pm spectrum width.
The change was performed by changing the transmittance due to irradiation of 10 ⁶ shots at p, 300 Hz.

Even with the same UV grade, a small absorption at 200 nm, 320 nm and 380 n by laser irradiation
It was found that some of the m showed large absorption and some did not. As shown in FIG. 3, in the sample C, the transmittance after excimer laser irradiation was 99.000 at 193 nm.
Although a good value of 0% was shown, in sample D shown in FIG. 4, very large absorption bands were developed at 250 nm and 370 nm, and the transmittance at 193 nm was 95.
3%. The refractive index homogeneity Δn of each of the samples C and D is 2 × 10 ⁻⁶ or less, and the birefringence is 2 nm / cm.
It was below. Further, the transmittance at 193 nm before the laser irradiation was a good value of 99.8%.

Next, an experiment was performed to predict the life of the optical system when an exposure apparatus was constructed using the optical bodies of Samples A to D. Life expectancy experiments were performed on samples AD.
ArF excimer laser with energy density of 50 mJ / c
Irradiation of 1 × 10 ⁶ shots at 300 Hz with m ² p (acceleration test) was performed to measure changes in optical characteristics as changes in transmittance and changes in refractive index at 193 nm. This When εmJ / cm ² light energy density of the laser transmitted through the optical body in the actual operation as shown in Document 1, corresponding to the acceleration test ^twice (100 / ε). Table 1 shows the results. The assumed energy density in the table indicates the energy density when the optical body is actually used to estimate the transmittance change, and the estimated values of the transmittance change and the refractive index change are the estimated values. This is a predicted value of a change in transmittance and a change in refractive index when a 5 × 10 ¹⁰ shot laser is irradiated at an energy density.

[0040]

[Table 1]

From the experimental results, the following table shows the results of a study on combinations that can maintain a high transmittance over a long period of time and maintain the stability of the refractive index when a reduction optical system is constructed by combining these optical bodies. It is shown in FIG.

[0042]

[Table 2]

[0043] As will be understood from this Table 2, the energy density (mJ / cm ²⁾ small to correspond to (0.1 ≧ epsilon), medium (0.1 ≦ ε ≦ 0.4, large (0. 4 ≦ ε),
With the configuration of [A + B + C], the average transmittance of the entire optical system is 98.6% / cm, and the change in average refractive index is 1.3.
× 10 ⁻⁶ / 1 cm, which satisfies the target standard value.

Also in the case of the configuration of [A + A + C], the total transmittance is 97.1% and the average refractive index change is 2.2.
Although slightly exceeding the target reference value of × 10 ⁻⁶ / 1 cm, it almost satisfied the reference value. In particular, in an actual imaging optical system, the energy density of the laser transmitted through each lens differs depending on the design of the optical system.
A + C] may be able to withstand practical use. still,
According to this experiment, in order to suppress the decrease in transmittance due to laser irradiation to a level that does not cause any problem, the optical path length of the optical member where the laser energy density per pulse is 0.1 mJ / cm ² or less is set as follows: At least 5 of the total optical path length
It turned out that it was necessary to be 0% or more.

For calculation, it was assumed that the optical path length at each energy density was about 2 (50%): 1 (25%): 1 (25%) for the above energy densities: small: medium: large.

According to this simulation experiment, an exposure apparatus comprising an optical system composed of a synthetic silica glass optical body and a fluorite optical body as defined in the claims has a sufficient optical characteristic stability over a long period of time even in actual operation. Is expected to be realized.

[0047]

As described above, according to the present invention, even when an ArF excimer laser exposure apparatus is configured using an optical system made of quartz glass containing hydrogen, durability and quality are not deteriorated. The entire optical system can be easily manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is an exposure apparatus for manufacturing an integrated circuit using a projection optical system to which the present invention is applied.

FIG. 2 is an exposure apparatus for manufacturing an integrated circuit using a reflection optical system to which the present invention is applied.

FIG. 3 is a graph showing an absorption band of a sample C, which is an example of the present invention, obtained by irradiating fluorite with laser.

FIG. 4 is a graph showing the absorption band of fluorite of a sample D as a comparative example of the present invention by laser irradiation.

[Description of Signs] 1 ArF excimer laser light source 2 Deformation illumination means 3 Condenser lens 4 Mask (reticle) 5 Projection optical system 6 Wafer 11 Light source 12 First lens group (synthetic silica glass optical body) 13 Beam splitter 14 Second lens group (Synthetic silica glass optical body) 15 Mirror 16 Third lens group (Synthetic silica glass optical body) 17 Reticle 19 Fourth lens group (Fluorite optical body) 18 Wafer

Claims (5)

[Claims] An exposure apparatus for manufacturing an integrated circuit by illuminating an integrated circuit pattern with a short-wavelength ultraviolet laser beam having a narrow band and printing the integrated circuit pattern on a wafer by a projection optical system or a reflection optical system. In the above, the optical system is constituted by a combination of an optical body made of synthetic quartz glass and an optical body made of fluorite, and a light energy density which is arranged closest to a wafer exposure surface and / or a pupil surface and transmits through the optical body. ε (mJ / cm
² ) At least one optical body at a position where the relative increase is relatively large is made of single crystal fluorite, and is disposed at a position away from the wafer exposure surface and / or the pupil surface and has a light energy density ε (mJ) transmitted through the optical body. / Cm
² ) At least one optical body at a position where the relative value is relatively small is 1 × 10 ¹⁷ molecules / cm ³ or more and 5 × 10 ¹⁸ molecules / cm.
Each of them is made of synthetic quartz glass having a hydrogen molecule concentration of ³ or less, and the short-wavelength ultraviolet laser light has an oscillation wavelength width of 1.5 pm.
(FWHM: full width at half maximum) An exposure apparatus for manufacturing integrated circuits, comprising an ArF excimer laser having a width of not more than (FWHM). 2. The method according to claim 1, wherein the fluorite used as the optical body has a laser energy density per pulse of 50 mJ / cm ^2.
Thickness at 193 nm after 1 × 10 ⁶ pulse irradiation with
2. The exposure apparatus according to claim 1, wherein the internal transmittance per cm is 98% or more. 3. An exposure apparatus for manufacturing a semiconductor circuit according to claim 1, wherein the specified value of the synthetic quartz glass optical body is set as the specified value of the homogeneity of the refractive index distribution (Δn) and the birefringence (nm / cm). An exposure apparatus for manufacturing an integrated circuit, wherein the exposure apparatus is set to a value better than the specified value of the fluorite optical body. 4. The fluorite optical body has a refractive index homogeneity Δn.
Is not more than 3 × 10 ⁻⁶ / cm and the birefringence is 2 nm / c.
m or less, and the synthetic quartz glass optical body has a refractive index homogeneity Δn of 2
2. The integrated circuit manufacturing exposure apparatus according to claim 1, wherein the exposure apparatus is made of a synthetic quartz glass material having a birefringence of 1 × 10 ⁻⁶ / cm or less and a birefringence of 1 nm / cm or less. 5. An optical system constituting the projection optical system is composed of a plurality of kinds of synthetic silica glass optical bodies and a single crystal fluorite optical body, wherein the single crystal fluorite optical body has a refractive index. Has a homogeneity Δn of 3 × 10 ⁻⁶ / 1 cm or less and a birefringence of 2 nm
/ Cm or less, and a plurality of types of synthetic quartz glass optical bodies,
It has a hydrogen molecule concentration of 5 × 10 ¹⁷ molecules / cm ³ or more and 5 × 10 ¹⁸ molecules / cm ³ or less, and has a refractive index homogeneity Δn of 2 × 1
0 and the quartz glass optical body ^-6 or less and the birefringence amount is less than 1nm / cm, 1 × 10 ¹⁷ molecules / cm ³ to 5 × 10
^It has a hydrogen molecule concentration of ¹⁸ molecules / cm ³ or less, a refractive index homogeneity Δn of 2 × 10 ⁻⁶ or less, and a birefringence of 1 nm / c.
2. The exposure apparatus according to claim 1, wherein the exposure apparatus is composed of a combination of quartz glass optical bodies having a diameter of m or less.