JP2000086257A - Production of quartz glass fly eye lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure necessary transmittance to KrF excimer laser and ArF excimer laser by cooling a quartz glass fly eye lens hotformed at the softening temperature to room temperature, heating the lens to a specified temperature and holding it in an atmosphere of hydrogen having a specified pressure for a specified time. SOLUTION: A quartz glass fly eye lens hot-formed at the softening temperature is cooled to room temperature, heated to 300-800 deg.C and held in an atmosphere of hydrogen having >=9.8×104 Pa pressure for >=24 hr. The solubility of hydrogen molecules at the temp. and pressure is 1×1018-3×1018 molecules/cm3 and hydrogen molecules are sufficiently diffused by holding this state for <=24 hr. Since the lens is heated to a high temperature of 1,350 deg.C the number of hydrogen molecules decrease to 5×1016 and the transmittance lowers to the level of 80%. It is necessary to ensure >=95% transmittance. The number of hydrogen molecules in the quartz glass reduced to 1/100-1/200 in the hot forming process can be returned to 1×1018 molecules/cm3 as the value before the hot forming and the lowering of the transmittance due to a change in physical properties is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method of manufacturing a quartz glass fly-eye lens.

[0002]

2. Description of the Related Art In recent years, the wavelength used in semiconductor exposure apparatuses has been shortened from i-ray (365 nm) to KrF excimer laser (248 nm) or ArF excimer laser (193 nm) in order to increase resolution. Optical glass can be used up to the wavelength of the i-line, but in the case of KrF excimer laser or ArF excimer laser, the optical material is quartz glass due to the problem of light transmittance. In this apparatus, a quartz fly-eye lens is used for converting light having non-uniform illuminance from a light source into light having uniform illuminance.

Conventionally, this type of manufacturing method of a quartz fly-eye lens has been performed by grinding a rectangular rod-shaped element 31 as shown in FIG.
The fly-eye lens 32 having a plurality of optically functional surfaces has been manufactured by polishing and then bonding and bundling the individual elements. This is because the softening temperature of quartz glass is 1300 ° C. or higher, and the forming temperature range is extremely higher than that of optical glass of 800 ° C. or lower. Because it was difficult.

[0004]

The physical properties required of such a quartz glass fly-eye lens are that the transmittance to a KrF excimer laser or an ArF excimer laser is 9%.
5% or more is secured. Generally, when a quartz glass is irradiated with a KrF excimer laser or an ArF excimer laser, the transmittance of the quartz glass rapidly decreases due to a change in physical properties inside the quartz glass, and becomes about 80%. In order to avoid such a sharp decrease in transmittance, a certain amount or more of hydrogen molecules having a function of suppressing a change in physical properties are secured inside the quartz glass. Its value is generally 1 × 10 ¹⁸ or more. When the quartz glass retaining the hydrogen molecules is heated to a temperature of 1300 ° C. or higher and pressed, the number of hydrogen molecules in the glass becomes 1/100 to 1 /
As a result, the transmittance was not able to be secured for a KrF excimer laser or an ArF excimer laser.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a quartz glass fly-eye lens which has a required transmittance for a KrF excimer laser or an ArF excimer laser and which is physically stable by heat molding. .

[0006]

The inventors of the present invention have conducted intensive studies, and as a result, after cooling a quartz glass fly-eye lens heated and formed at a softening temperature to room temperature, the temperature was reduced to 300 to 300.degree.
It was manufactured by a method of heating to 800 ° C. and maintaining the pressure in a hydrogen atmosphere of 9.8 × 10 ⁴ Pa or more for 24 hours or more. The solubility of hydrogen molecules at this temperature and pressure is 1 to
The density is 3 × 10 ¹⁸ / cm ³ , and by maintaining this state for 24 hours or more, hydrogen molecules can be sufficiently diffused.

The reason why the temperature is set to 300 ° C. or higher is that if the temperature is lower than 300 ° C., the solubility of hydrogen molecules is low and the diffusion coefficient becomes unrealistic. This is because if the temperature is higher, impurities other than hydrogen molecules (for example, carbon) are diffused and the transmittance is deteriorated. The reason why the pressure of the hydrogen atmosphere is set to 9.8 × 10 ⁴ Pa or higher is that the above-mentioned solubility cannot be secured at a pressure lower than 9.8 × 10 ⁴ Pa. In addition, the reason why the hydrogen molecule is held for 24 hours or more is that if the time is shorter than that, the hydrogen molecules are not sufficiently diffused.

[0008] By doing so, the amount of hydrogen molecules inside the quartz glass, which has been reduced to 1/100 to 1/200 in the heat forming process, can be returned to the level before the heat forming, and the permeation due to the change in physical properties can be achieved. The reduction in the rate was able to be suppressed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. First, a square 30mm × 30 as shown in FIG.
Quartz glass material 1 polished on both sides to a thickness of 20 mm and a thickness of 20 mm
Prepare The transmittance of the quartz glass material 1 is 95%,
The hydrogen molecular weight is 1 × 10 ¹⁸ , and as an initial value, it has sufficient physical property values with respect to a KrF excimer laser or an ArF excimer laser.

The quartz glass material 1 is divided into 25 sections of 6 mm × 6 mm as shown in FIG. 5, and each of the upper and lower ceramic molds 21 and 22 having a plurality of finished surfaces 23 each of which is concavely polished to R8 mm. Place in the middle. The quartz glass material 1, the upper mold 21 and the lower mold 22 are set in a molding apparatus (not shown), and are molded by heating at a softening temperature of 1350 ° C., and after cooling, are taken out at room temperature. Make lens 2.

The quartz fly-eye lens 2 has 1350
Because of heating at a high temperature of 5 ° C., the amount of hydrogen molecules was 5 × 10 ¹⁶
It has a transmittance of the order of 80% and cannot withstand irradiation by a KrF excimer laser or an ArF excimer laser. A quartz fly-eye lens formed by heating and having an initial amount of hydrogen molecules of 1/100 to 1/200 is placed in a vacuum / gas atmosphere furnace as shown in FIG. Open and evacuate. When the degree of vacuum becomes 1.33 Pa or less, the valve 16 is closed, the valve 18 is opened, and hydrogen gas is introduced and replaced. The pressure of the hydrogen gas is 9.8 × 10 ⁴ Pa or more. After confirming the pressure, heat treatment is performed according to a heating schedule as shown in FIG. The temperature is raised to 300 ° C. in one hour, and then maintained for at least 24 hours and cooled. At room temperature after cooling, hydrogen gas is safely exhausted from the valve 17, air is introduced, and the quartz glass fly-eye lens is taken out. When the physical properties of the quartz glass fly-eye lens after the treatment process in the above hydrogen atmosphere were measured again, the transmittance was 95% and the hydrogen molecular weight was returned to 1 × 10 ¹⁸ , and the KrF excimer laser and the ArF excimer were used. Sufficient properties were obtained for the laser.

[0013]

As described above, according to the present invention, first, when quartz glass is heated and formed, a KrF excimer laser or A
Although it was at a level where physical properties could not be used for rF excimer laser, problems in physical properties could be solved by treating in a hydrogen atmosphere after heat molding, and a method of manufacturing a quartz glass fly-eye lens by heat molding was developed. It was established. For this reason, the upper and lower molds having a plurality of finishing surfaces as shown in FIG. 5 can be machined with very high precision, and the functional surfaces of the individual elements transferred using the upper and lower molds are also manufactured with very high precision. As a result, it was possible to stably supply elements with extremely high precision as compared with the fly-eye lens manufactured by the conventional method as shown in FIG. In addition, the manufacturing method by heat molding can shorten the number of manufacturing steps and achieve cost reduction as compared with the conventional processing method.

[Brief description of the drawings]

FIG. 1 is a material diagram of a manufacturing method according to an embodiment.

FIG. 2 is a quartz glass fly-eye lens manufactured according to the embodiment.

FIG. 3 is a diagram of a heat treatment apparatus used in the embodiment.

FIG. 4 is a heating schedule diagram of the embodiment.

FIG. 5 is a diagram showing a molding structure according to the embodiment;

FIG. 6 is a diagram of an element manufactured by bonding according to a conventional method.

[Explanation of Signs of Main Parts]

DESCRIPTION OF SYMBOLS 1 ... Quartz glass material 2 ... Quartz glass fly-eye lens manufactured by heat molding 11 ... Vacuum / gas atmosphere furnace chamber 12 ... Heater 13 ... Heat insulation plate 14 ... Placement table 15 ... Rotary pump 16 ... Valve 17 ... Valve 18 ... Valve 19 ... Hydrogen supply equipment 20 ... Quartz glass fly-eye lens 21 ... Upper mold 22 ... Lower mold 23 ... Finished surface 31 ... One lens manufactured by conventional method 32 ... Fly-eye lens manufactured by conventional method

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Jun Takano 3-2-3 Marunouchi, Chiyoda-ku, Tokyo F-term in Nikon Corporation (reference) 4G014 AH00

Claims (1)

[Claims] After cooling a quartz glass fly-eye lens heated and formed at a softening temperature to room temperature, the temperature is raised to 300-80.
A method for producing a quartz glass fly-eye lens, characterized in that the quartz glass fly-eye lens is heated to 0 ° C. and kept in a hydrogen atmosphere at a pressure of 9.8 × 10 ⁴ Pa or more for 24 hours or more.