JPH1022215A - Aligner for manufacturing integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To configure an aligner at a low cost for the entire optical system so as to be easily manufactured without deteriorating the durability and quality, even in the case of using the optical system comprising a hydrogen-doped quartz glass to configure an ArF excimer laser aligner. SOLUTION: At least a lens being a component of an optical system 5 comprises an optical member made of a hydrogen-doped synthetic quartz glass, the lens comprises a plurality of kinds of the aforementioned members with different hydrogen molecular concentration, the lens, a mirror and a prism or the like being components of a optical system 5 comprises an optical member made of the quartz glass, and the optical system 5 is made up of a combination of a 1st optical system group whose hydrogen molecular concentration CH2 molecules/cm<3> is selected to be 1×10<17> <=CH2 <=5×10<18> and a 2nd optical system group whose hydrogen molecular concentration CH2 molecules/cm<3> is selected to be 5×10<18> <=CH2 <=5×10<19> , and the total of the optical path length of the 2nd optical system is selected to be 20% of the entire optical path length of the optical system or below, preferably 15% or below so as to attain a high permeability for the entire optical system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus for manufacturing an integrated circuit in the range of 64M to 256M, and more particularly to an optical system made of quartz glass which illuminates a pattern of an integrated circuit with laser light from an ArF excimer laser. To print an integrated circuit pattern on a wafer to manufacture 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 36 emitted 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 5 nm.
It corresponds to an integrated circuit below the bit-DRAM. On the other hand, for next generation 64Mbit ~ 256Mbit, 0.25 ~
An imaging performance of 0.35 μm, and 0.13-0.
Although a resolution of 20 μm is required, a resolution of 0.35 μm is lower than the wavelength of the i-line, and KrF light is used as a light source. And in the region below 0.20 μm, Kr
ArF light, particularly an ArF excimer laser, is used instead of F light.

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 that constitute a projection optical system. That is, 19 of ArF
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 damages quartz glass more than KrF light
10 times larger.

Now, the resistance of quartz glass to irradiation with excimer laser is described in Japanese Patent Application No. 1-11 filed by the present applicant.
45226 depending 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 ArF laser light on quartz glass is greater than that of KrF as described above, the degree of damage (change in transmittance and change in refractive index) caused to synthetic quartz glass by ArF laser light is limited. Examination shows that the required hydrogen molecule concentration is Kr
In some cases, it has been found that a concentration of hydrogen molecules that is 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] The concentration of hydrogen molecules contained in the quartz glass constituting the optical system is a number determined by the conditions for synthesizing the raw material and / or the conditions of the subsequent heat treatment step (including hydrogen dope). The hydrogen molecule concentration is uniquely determined if the range due to process variation is ignored.
Therefore, a synthetic quartz glass member used for an optical system such as a mirror and a lens constituting an exposure apparatus is composed of only one kind of synthetic quartz glass from the viewpoint of hydrogen concentration. There are two methods of including hydrogen molecules in synthetic quartz glass. First, when adjusting the atmosphere during manufacture and including hydrogen molecules in synthetic quartz glass at normal pressure, the concentration of hydrogen molecules that can be included is up to 5 × It is up to about 10 ¹⁸ molecules / cm ³ . As another method, even when hydrogen molecules are doped into quartz glass by pressurized heat treatment in a hydrogen atmosphere, hydrogen molecules introduced in hydrogen treatment at an upper limit of 10 atm / cm ² which are not subject to the high-pressure gas control method. The concentration is still 5
× 10 ¹⁸ molecules / cm ³ is the upper limit.

For this reason, 5 × 10 ¹⁸ molecules / c are contained in quartz glass.
When it is intended to include hydrogen molecules of m ³ or more, 10
It is necessary to perform the heat treatment at a high hydrogen pressure which is much higher than the atmospheric pressure. For example, Japanese Patent Application Laid-Open No. 4-16 filed by the present applicant
No. 4833 discloses a technique capable of doping about 5 × 10 ¹⁸ (molecules / cm ³ ) of hydrogen molecules by remelting and heating at a temperature of 1750 ° C. in a high-pressure atmosphere of argon gas 100%. I have.

[0007]

However, the re-melting heat treatment at a temperature of 1750 ° C. is preferably performed at a heat treatment temperature in the range of 200 to 800 ° C. in order to induce new defects in quartz glass. Japanese Patent Application Laid-Open No. Hei 6-166528).
When introducing a large amount of hydrogen molecules of ¹⁸ molecules / cm ³ or more,
Since the diffusion rate of hydrogen molecules is not very high, the processing of large optical members takes a very long time.In addition, heat treatment in a high-pressure atmosphere reduces the homogeneity of the refractive index of the quartz glass optical members. Also, there is a problem that distortion is introduced. Therefore, even when the high-pressure heat treatment is performed, heat treatment for re-adjustment is necessary, and therefore, contains a hydrogen molecule of 5 × 10 ¹⁸ molecules / cm ³ or more and has a refractive index sufficient to constitute an optical system of the exposure apparatus. Quartz glass having optical properties such as homogeneity and low distortion is industrially extremely complicated and extremely expensive after a long time treatment.

According to the present invention, even when an ArF excimer laser exposure apparatus is constructed using an optical system made of hydrogen-doped quartz glass, the optical system as a whole can be manufactured without deteriorating the quality such as durability and light transmittance. It is an object of the present invention to provide an exposure apparatus which can be easily manufactured at low cost.

[0009]

The present invention focuses on the following points. First, as described above, in order to improve the durability of an ArF excimer laser exposure apparatus, containing hydrogen molecules of 5 × 10 ¹⁸ molecules / cm ³ or more is industrially extremely complicated and requires a long time treatment. It is difficult to manufacture and very expensive. On the other hand, Reference 2 (New Gl
According to ass VoL6 No, 2 (1989) 191-196, "About quartz glass for steppers", written by Kazuo Ushida), 99.0% (lowest level)% is required as a transmittance for exposure equipment required for stepper projection lenses.
/ Cm or more, refractive index distribution (Δn) ≦ 1 × 10 ⁻⁶ , birefringence n
m / cm ≦ 1.00, but as described above, when high-concentration hydrogen doping of 5 × 10 ¹⁸ molecules / cm ³ is performed by pressure treatment, quartz glass having a uniform refractive index as described above Cannot be obtained. On the other hand, if quartz glass is manufactured with emphasis on the refractive index, it is not possible to obtain a high-concentration hydrogen-doped glass, and damage may occur when irradiated with ArF excimer laser.

Accordingly, the present invention manufactures an integrated circuit by illuminating a pattern of the integrated circuit with laser light from an ArF excimer laser, and projecting and printing the pattern of the integrated circuit on a wafer by an optical system made of a quartz glass material. In the exposure apparatus, the lenses, mirrors, prisms, etc. constituting the optical system are composed of synthetic quartz glass optical members, and one pulse of excimer laser light transmitted through the optical members in the group of optical members. Energy density ε
(MJ / cm ² ), a plurality of optical members having different hydrogen molecule concentrations are effectively combined to achieve a transmittance of ≧ 99.0% / cm as a whole optical system. .

More specifically, in the invention according to claim 2, the optical system is provided with a hydrogen molecule concentration C _H2 molecule / cm.
³ is 1 × 10 ¹⁷ ≦ C _H2 ≦ 5 × 10 ¹⁸ , and the hydrogen molecule concentration C _H2 molecule / cm ^{3 of} the optical member group is 5 × 10 ¹⁸ ≦ C _H2.
The second optical system group of ≦ 5 × 10 ¹⁹ is combined, and the total optical path length of the second optical system group is set to 20% or less, preferably 15% or less of the optical path length of the entire optical system. And More preferably, as in the invention according to claim 3, the optical system has a hydrogen molecule concentration C _H2 molecule / cm ³ of 1 × 10 ¹⁷ ≦ C _H2 ≦ 5.
× 10 ¹⁸ first optical system group and hydrogen molecule concentration C _H2 molecule / c
a second optical system group in which m ³ is 5 × 10 ¹⁷ ≦ C _H2 ≦ 5 × 10 ¹⁸ , and a hydrogen molecule concentration C _H2 molecule / cm ³ is 5 × 10 ¹⁸ ≦ C _H2 ≦ 5 × 10 ¹⁹
And the sum of the optical path lengths of the second optical system group is 20% or less, preferably 15%, of the optical path length of the entire optical system.
% Or less, and the sum of the optical path lengths of the third optical system group is set to 20% or less, preferably 15% or less of the optical path length of the entire optical system.

According to the fourth and fifth aspects of the present invention, the homogeneity (.DELTA.n) of the refractive index and the birefringence amount are low, but the hydrogen concentration is high, whereas the hydrogen concentration is low. The refractive index homogeneity (Δn) and the amount of birefringence achieve the required resolution characteristics by effectively combining high-quality quartz glass optical members, and at the same time achieve high transmittance as a whole optical system. is there. That is, the invention according to claim 4 illuminates an integrated circuit pattern with a laser beam from an ArF excimer laser, and projects and prints the integrated circuit pattern on a wafer by an optical system composed of a quartz glass optical member. In the exposure apparatus for manufacturing, the quartz glass optical member group has an energy density ε (mJ / cm) per pulse of ArF excimer laser light transmitted through the optical member.
^{The following} three types are classified according to ₂ ), and the combinations of the properties of hydrogen molecule concentration (C _H2 ), refractive index homogeneity (Δn), and birefringence amount contained in each optical member group are shown in the table below. As shown, the transmittance of the entire optical system is ≥99.0
% / Cm. ε mJ / cm ² Hydrogen molecule concentration C _H2 molecule / cm ³ Refractive index distribution (Δn) Birefringence nm / cm 1) ≦ 0.2 1 × 10 ¹⁷ ≦ C _H2 ≦ 5 × 10 ¹⁸ ≦ 1 × 10 ⁻⁶ ≦ 1.00 2) 0.2 ≦ ε ≦ 0.6 5 × 10 ¹⁷ ≦ _{CH 2} ≦ 5 × 10 ¹⁸ ≦ 3 × 10 ⁻⁶ ≦ 3.0 3) 0.6 ≦ ε ≦ 1.5 5 × 10 ¹⁸ ≦ _{CH 2} ≦ 5 × 10 ¹⁹ ≦ 5 × 10 ^-6 ≤5.0

According to a fifth aspect of the present invention, the object of the present invention is achieved more smoothly by combining an optical path length and the like with the fourth aspect of the present invention. The total is 20% or less of the optical path length of the entire optical system, preferably 15%
Hereinafter, the optical systems are combined and arranged so that the total of the optical path lengths of the optical members in the above 2) is 20% or less, preferably 15% or less of the entire optical path length of the optical system.

[0014]

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.
FIG. 1 is a schematic configuration diagram of a lithography exposure apparatus using an ArF excimer laser applied to the present invention. 1 is an ArF excimer laser light source, and 2 is a deformation for forming a pattern image on a wafer surface without interference of diffraction light. 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 a condenser lens for guiding the excimer laser light emitted from the light source to the reticle, 4 is a mask (reticle), 5 is a projection optical system,
For example, by combining a lens group having a positive refractive power and a lens group having a negative refractive power to narrow the band of light, a pupil plane is formed in the optical system to improve the resolution. Reference numeral 6 denotes a wafer mounted on a wafer stage 7 and the reticle 4
Is formed on the wafer 6 via the projection optical system.

In such an apparatus, the projection optical system includes a condenser lens group 5a arranged closest to the wafer surface and a lens group 5b arranged near the pupil plane in order to form pattern light on the wafer surface. Exists, but a secondary light source which is an image of the light source is formed on the pupil plane. Therefore, when a light source image discretely appears on the pupil plane, energy concentrates on the light source 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.

This embodiment focuses on such a point, that is, specifically, the size of the pupil plane of the ArF excimer laser is about φ30 to φ50 mm according to the reference document. It is reasonable to determine the energy density on the basis of double. For example, if the resist 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 plane is 0.7 to 1.7 mJ / cm ² , and more precisely, the energy density on the exposure plane and the pupil plane is The densities are different, and even if it is assumed that the wafer surface is slightly larger, the energy density of the lens group disposed closest to the wafer surface is about 80 to 90% of 0.6 to 1.5 mJ / cm. It is estimated to be about ² . It is also assumed that the pupil plane is slightly lower.

On the other hand, in order to narrow the band of light and improve the resolving power, the projection optical system is constituted by combining a lens group having a positive refractive power and a lens group having a negative refractive power (for example, 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 nearest position of the wafer (or pupil plane) is about １ ／ of 0.6 to 1.5 mJ / cm ² , specifically 0.2
It is estimated to be about 0.6 mJ / cm ² . Most other lens groups, especially the lens on the light source side farther than the pupil plane and the lens group, have an energy density per pulse of ε ≦ 0.2 m.
J / cm ² . Therefore, in a lens group in which the energy density per pulse is ε ≦ 0.2 mJ / cm ² ,
By prioritizing light transmittance over durability, the transmittance of the entire optical system can be improved. Therefore, in the present embodiment, in the case of an optical member located on the light source side of ε: ≦ 0.2 mJ / cm ² , in other words, in the case of a member far from the wafer or the pupil plane, the hydrogen molecule concentration C _{H2 is set} to 1 × 10 ¹⁷ ≦ C _H2 ≦ 5 × 10 ¹⁸ molecules / cm ³ , but the refractive index distribution (Δn) is ≦ 1 × 1
0 ^-6, the birefringence is maintained at ≦ 1.00 nm / cm and high quality.

Further, the energy density per pulse, especially, in the side lens group near the pupil plane or the wafer, is particularly equal to 0.1.
In the lens group satisfying 6 ≦ ε ≦ 1.5, the durability of the entire optical system can be improved by placing importance on the durability. Therefore, in the present embodiment, particularly, in the case of an optical system of ε: 0.6 ≦ ε ≦ 1.5 mJ / cm ² that receives high light energy, the hydrogen molecule concentration C _{H2 is set} to 5 × 10 ¹⁸ ≦ C _H2 ≦ 5 × 10 ¹⁹ molecules /
cm ³ , the refractive index distribution (Δn) is ≦ 5 × 1
0 ^-6, the birefringence amount is set slowly and ≦ 5.0 nm / cm, facilitated manufacturing. Further, the optical member such as a lens whose received light energy is located at the next stage of the high-density lens has a middle point between the ^two . In the case of an optical system of ε: 0.2 ≦ ε ≦ 0.6 mJ / cm ² , the hydrogen molecule concentration C _H2 Is set to 5 × 10 ¹⁷ ≦ C _H2 ≦ 5 × 10 ¹⁸ molecules / cm ³ , the refractive index distribution (Δn) is ≦ 3 × 10 ^-6 , and the birefringence is ≦ 3.0 nm / cm. Is facilitated. The sum of the optical path lengths of the optical members satisfying 0.6 ≦ ε ≦ 1.5 mJ / cm ² is 20% or less, preferably 15% or less of the optical path length of the entire optical system.
The sum of the optical path lengths of the optical members ² is 20 of the total optical path length of the optical system.
% Or less, preferably 15% or less, it is possible to achieve high transmittance as a whole of the optical system while maintaining durability, as shown in Examples described later.

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 lens configuration of a reflection optical system exposure apparatus using a prism type beam splitter in order to achieve a high resolution.
The light from the light source 11 that has passed through the beam splitter 13 via the first lens group 12 passes through the second lens group 14, is then deflected by the mirror 15, and then condensed by the third lens group 16. After the reticle 17 is scanned with the condensed light, the beam returns to the beam splitter 13 again via the third lens group 16, the mirror 15, and the second lens group 14, and is turned to the splitter 13 this time. An integrated circuit pattern is printed on the wafer 18 after being imaged in the group 19.

According to such an apparatus, the fourth lens group 19 after being turned to the splitter 13 receives the strongest light energy with an energy density per pulse of 0.6 ≦ ε ≦ 1.5 mJ / cm ² , so that the hydrogen molecule concentration C _H2 molecule / Cm ³ is 5 × 10 ¹⁸ ≦
Even if the setting is set to be high as C _H2 ≦ 5 × 10 ¹⁹ , the refractive index distribution (Δ
n) may be set to ≦ 5 × 10 ⁻⁶ , and the birefringence may be set to a gradual value of ≦ 5.0 nm / cm. In the present apparatus, the light is condensed and scanned by the third lens group 16 on the reticle 17 side. Since it is estimated that an energy density per pulse of 0.2 ≦ ε ≦ 0.6 mJ / cm ² is received, the hydrogen molecule concentration C _H2 molecule / cm ^{3 is set} to 5 × 10 ¹⁷ ≦ C _H2 ≦ 5 × 10 ¹⁸ and refracted. The rate distribution (Δn) is ≦ 3 × 10 ⁻⁶ , and the birefringence is ≦ 3.0 nm / cm
Since other lenses, mirrors, and prism type beam splitters receive only energy with an energy density of ε ≦ 0.2 mJ / cm ² per pulse, hydrogen in the lens group and the like is not required. The molecular concentration C _H2 molecule / cm ³ is set to 1 × 10 ¹⁷ ≦ C _H2 ≦ 5 × 10 ¹⁸ , but the refractive index distribution (Δn) is ≦ 1 × 10 ⁻⁶ and the birefringence is ≦ 1.
Maintain a high quality of 00 nm / cm.

The total optical path length of the fourth lens group 19 is 20% or less, preferably 15% or less of the optical path length of the entire optical system, and the total optical path length of the optical members of the third lens group 16 is optical. By combining and arranging the optical systems so as to be 20% or less, preferably 15% or less of the entire optical path length of the system, it is possible to achieve high transmittance as a whole of the optical system while maintaining durability in the present embodiment. Is estimated to be possible.

[0022]

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 member to be manufactured was taken out, and a simulation experiment in which actual operation was accelerated was performed.

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

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 contained 800 to 1000 ppm of OH groups and contained 5 × 10 ¹⁸ molecules / cm ^{2 of} hydrogen molecules. 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. The optical properties of the obtained homogeneous quartz glass material for optics were measured, but there were no striae in three directions.
When the refractive index distribution was measured with an interferometer (Zygo Mark IV), Δn showed an extremely good value of 1 × 10 ⁻⁶ . The amount of birefringence was measured using a crossed Nicols strain gauge, and the amount of birefringence was 1 nm / cm or less.

This quartz glass material for optics is disclosed in Reference 2 (New
Glass VoL6 No, 2 (1989) 191-196 "Quartz glass for steppers" by Kazuo Ushida), which satisfies the optical characteristics required for quartz glass members used in excimer laser steppers. By configuring an optical component using a glass material, a semiconductor exposure apparatus using ArF as a light source can be manufactured. 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 No. A) The content of hydrogen molecules was measured using a Raman spectrophotometer, which is a Raman spectrophotometer NR manufactured by JASCO Corporation.
Using a 1100, an Ar laser beam with an excitation wavelength of 488 nm and an output of 700 mW, Homamatsu Photonics R943
Performed by the host counting method using -02.
The hydrogen molecule content is obtained by converting the area intensity ratio between the SiO ₂ scattering band observed at 800 cm ⁻¹ and the hydrogen scattering band observed at 4135-40 cm ⁻¹ in the Raman scattering spectrum at this time into a concentration. I asked. Conversion constants are based on literature values
4135cm ^-1 / 800cm ^-1 × 1.22 × 10 ²¹ (Zhurnal Pri-Kl
adnoi Spektroskopii, Vol. 46, No. 6, PP987-991, June, 1
987) was used.

The optical quartz glass material is φ60 mm
Xt20mm sample is cut out at 1000 ℃
After performing the oxidation treatment for a period of time, hydrogen doping treatment was performed in an autoclave in a high-pressure (50 atm) atmosphere of hydrogen gas at 600 ° C. for 1000 hours. When the refractive index distribution of the sample after the treatment was measured, Δn was 4 × 10 ⁻⁶ and the birefringence was 5 nm / c.
m, the contained hydrogen molecule concentration was 2 × 10 ¹⁹ molecules / cm ² . (Sample number D)

Further, from the quartz glass material for optics, φ60 mm
Xt20mm sample is cut out at 1000 ℃
After performing the oxidation treatment for a period of time, hydrogen doping treatment was performed in an atmosphere furnace under a pressurized hydrogen gas atmosphere (9 atm) at 600 ° C. for 1000 hours. When the refractive index distribution of the sample after the treatment was measured, Δn was 3 × 10 ⁻⁶ , the amount of birefringence was 3 nm / cm, and the concentration of contained hydrogen molecules was 5 × 10 ¹⁸ molecules / cm ² . (Sample number B)

Again from the quartz glass material for optics, φ60 mm
Xt20mm sample is cut out at 1000 ℃
After performing the oxidation treatment for a period of time, hydrogen doping treatment was performed at 600 ° C. for 1000 hours in a hydrogen gas pressurized (3 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 2 × 10 ¹⁸ molecules / cm ² . (Sample number C)

Here, except for the samples A and C, only one kind of quartz glass is not sufficient in homogeneity to constitute an exposure apparatus using an ArF excimer laser as a light source. Although the amount was found to be too large, the optical members represented by the samples A, B, C, and D were converted into the optical path length as the projection optical system of the apparatus of FIG.
When the homogeneity of the refractive index of the entire optical system was calculated assuming that the lens system was configured at 1: 1, Δn per 1 cm of the optical path was 2 × 10 ⁻⁶ and the average value of birefringence was 2 nm / cm. It was found that sufficient optical characteristics were obtained to constitute the above.

The transmittance of the four samples to ultraviolet light having a wavelength of 193 nm was measured using an ultraviolet spectrophotometer.
The internal transmittance per m showed a good value of 99.8%. Again, it has sufficient transmittance to constitute an excimer laser stepper.

The four samples thus obtained were irradiated with an ArF excimer laser to examine changes in optical characteristics. The irradiation condition is that the energy density per pulse is 10 mJ / cm
^{2. The} irradiation frequency was 300 Hz. This is, as shown in Document 1, when the light energy density of a laser transmitted through an optical member in an actual operation is εmJ / cm ² , (100
/ Epsilon) corresponds to an accelerated test ^twice. Table 1 shows the results of excimer laser irradiation of each sample. The number of irradiation was 2.5 × 10 ⁷ shots, showing a change in the transmittance at 193 nm and a change in the refractive index due to this irradiation.

[0032]

[Table 1]

For sample D, the amount of change in the refractive index was too small to perform an accurate measurement. From these results, it was found that the change in the refractive index of the optical member due to the irradiation of the ArF laser was the most important parameter as a parameter for determining the stability of the exposure apparatus. Since sufficient measurement accuracy was not obtained for sample D,
Using the results of Samples A to C, the relationship between the hydrogen concentration and the rate of increase in the refractive index was obtained and extrapolated to calculate.

Here, from the conditions of the acceleration simulation experiment, the acceleration rate with respect to the case where the energy density of the ArF excimer laser beam transmitted through the quartz glass optical member is εmJ / cm ^{2 in} the actual operation of the exposure apparatus is (100)
/ Epsilon) it is considered to be ^twice the energy density of the ArF excimer laser light is expected refractive index of 1 × 10 ¹⁰ shots after in the case of 0.6 mJ / cm ² (3 years at 100Hz of continuous irradiation) The change is as shown in the table below for each sample.

[0035]

[Table 2] Sample number Estimated value of change in refractive index after irradiation Judgment A 4.04 × 10 ^-7 usable B 1.60 × 10 ^-7 usable C 8.68 × 10 ^-8 usable D 3.42 × 10 ^-8 usable

Since sufficient measurement accuracy was not obtained for sample D, the relationship between the hydrogen concentration and the rate of increase in the refractive index was obtained using the results of samples A to C, and the relationship was extrapolated and calculated.

Next, when the energy density of the ArF excimer laser beam is 0.6 mJ / cm ² , the expected change in the refractive index after 1 × 10 ¹⁰ shots (3 years with continuous irradiation at 100 Hz) is shown in the following table for each sample. become that way.

[0038]

[Table 3] Sample No. Expected value of change in refractive index after irradiation Judgment A 3.63 × 10 ^-6 cannot be used B 1.14 × 10 ^-6 can be used C 7.81 × 10 ^-7 can be used D 3.08 × 10 ^-7 can be used

Next, when the energy density of the ArF excimer laser beam is 1.0 mJ / cm ² , the expected change in the refractive index after 1 × 10 ¹⁰ shots (3 years with continuous irradiation at 100 Hz) is shown in the following table for each sample. become that way.

[0040]

[Table 4] Sample No. Expected value of refractive index change after irradiation Judgment A 1.01 × 10 ^-5 Not available B 4.00 × 10 ^-6 Not available C 2.17 × 10 ^-6 Not available D 8.56 × 10 ^-7 Available

According to this simulation experiment, an exposure apparatus comprising an optical system composed of a plurality of types of synthetic quartz glass optical members defined in the claims achieves sufficient optical characteristic stability over a long period of time even in actual operation. It is expected to be possible.

[0042]

As described above, according to the present invention, ArF is formed by using an optical system made of hydrogen-doped quartz glass.
Even when configuring an excimer laser exposure device,
The optical system as a whole can be easily manufactured at low cost without deteriorating durability and quality.

[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.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 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 12 13 Beam splitter 14 Second lens group 15 Mirror 16 Third lens group 17 Reticle 19th 4 lens groups 18 wafers

Claims (5)

[Claims] An exposure for manufacturing an integrated circuit by illuminating an integrated circuit pattern with laser light from an ArF excimer laser, projecting the integrated circuit pattern onto a wafer by an optical system made of quartz glass material, and printing. In the apparatus, a lens, a mirror, a prism, and the like constituting the optical system are configured by an optical member made of synthetic quartz glass, and an energy density per one pulse of excimer laser light transmitted through the optical member in the optical member group. An exposure apparatus for manufacturing an integrated circuit, wherein a plurality of optical members having different hydrogen molecule concentrations are effectively combined in accordance with ε (mJ / cm ₂ ). 2. The method according to claim 1, wherein the optical system has a hydrogen molecule concentration C _H2 molecule /
a first optical system group whose cm ³ is 1 × 10 ¹⁷ ≦ C _H2 ≦ 5 × 10 ¹⁸ ,
The hydrogen molecule concentration C _H2 molecule / cm ^{3 of the} optical member group is 5 × 10 ¹⁸ ≦
The second optical system group of C _H2 ≦ 5 × 10 ¹⁹ is combined, and the total optical path length of the second optical system group is set to 20% or less, preferably 15% or less of the optical path length of the entire optical system. The exposure apparatus for manufacturing a semiconductor according to claim 1, wherein: 3. The optical system according to claim 1, wherein a hydrogen molecule concentration C _H2 molecule /
a first optical system group whose cm ³ is 1 × 10 ¹⁷ ≦ C _H2 ≦ 5 × 10 ¹⁸ ,
The hydrogen molecule concentration C _H2 molecule / cm ³ is 5 × 10 ¹⁷ ≦ C _H2 ≦ 5 × 10
^{The 18} second optical system group and the hydrogen molecule concentration C _H2 molecule / cm ³ are 5
The third optical system group of × 10 ¹⁸ ≦ C _H2 ≦ 5 × 10 ¹⁹ is combined, and the sum of the optical path lengths of the second optical system group is the total optical path length of the optical system.
The total optical path length of the third optical system group is set to 20% or less, preferably 15% or less, and the total of the optical path lengths of the third optical system group is set to 20% or less, preferably 15% or less. Item 1
The exposure apparatus for manufacturing a semiconductor according to the above. 4. An integrated circuit is manufactured by illuminating a pattern of an integrated circuit with laser light from an ArF excimer laser, projecting the pattern of the integrated circuit onto a wafer by an optical system including a quartz glass optical member, and printing the pattern. In the exposure apparatus, the quartz glass optical member group may include Ar that transmits through the optical member.
According to the energy density ε (mJ / cm ² ) per pulse of the F excimer laser light, it is classified into the following three types, and the homogeneity of the hydrogen molecule concentration (C _H2 ) and the refractive index contained in each optical member group. An exposure apparatus for manufacturing an integrated circuit, wherein a combination of properties of the property (Δn) and the amount of birefringence is set as shown in the following table, and the transmittance of the entire optical system is ≧ 99.0% / cm. . ε mJ / cm ² Hydrogen molecule concentration C _H2 molecule / cm ³ Refractive index distribution (Δn) Birefringence nm / cm 1) ≦ 0.2 1 × 10 ¹⁷ ≦ C _H2 ≦ 5 × 10 ¹⁸ ≦ 1 × 10 ⁻⁶ ≦ 1.00 2) 0.2 ≦ ε ≦ 0.6 5 × 10 ¹⁷ ≦ _{CH 2} ≦ 5 × 10 ¹⁸ ≦ 3 × 10 ⁻⁶ ≦ 3.0 3) 0.6 ≦ ε ≦ 1.5 5 × 10 ¹⁸ ≦ _{CH 2} ≦ 5 × 10 ¹⁹ ≦ 5 × 10 ^-6 ≤5.0 5. The optical system according to claim 1, wherein the total optical path length of the optical member is 20% or less, preferably 15% or less of the optical path length of the entire optical system. 5. The exposure apparatus according to claim 4, wherein the optical systems are combined and arranged so as to be 20% or less, preferably 15% or less, of the entire optical path length.