JP2000290028A - Production of synthetic quartz glass for ultraviolet ray and member obtained by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain glass having both of high transmissivity and high resistance to ultraviolet rays in the vacuum ultraviolet region by concentrically arranging plural pipes of hydrogen ejecting pipes and oxygen ejecting pipes around the pipe for ejecting an organic silicon compound being a raw material and specifying the ratio of the amount of gaseous oxygen to the amount of gaseous hydrogen. SOLUTION: A burner is constituted by concentrically arranging second pipes for ejecting gaseous hydrogen and third pipes for ejecting gaseous oxygen around a first pipe for ejecting an organic silicon compound being a raw material, further providing fourth pipes for ejecting gaseous hydrogen, providing fifth plural pipes for ejecting gaseous oxygen between the third and the fourth pipes, furthermore providing sixth pipes for ejecting gaseous hydrogen around the fourth pipes and providing seventh pipes for ejecting gaseous oxygen between the fourth and sixth pipes. The ratio (b/a) of the amount of gaseous oxygen (b) ejected from the third pipe to the amount of gaseous hydrogen (a) ejected from the second pipe is set to be not more than 0.5. The ratio (d/c) of the amount of gaseous oxygen (d) ejected from the fifth pipe to the amount of gaseous hydrogen (c) ejected from the fourth pipe is set to be not less than 0.55.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing quartz glass, and more particularly to a method for producing a synthetic quartz glass for an optical member used in an ultraviolet laser in general, and a quartz glass produced thereby. is there.

[0002]

2. Description of the Related Art Conventionally, in an optical lithography technique for exposing and transferring a fine pattern of an integrated circuit onto a wafer such as silicon, an exposure apparatus called a stepper is used. The light source of this stepper has been changed from g-line (436 nm) to i-line (365n) with the recent high integration of LSI.
m), KrF (248 nm) and ArF (193 nm).
nm) Excimer lasers are being shortened in wavelength.

In general, synthetic quartz glass is used as an optical material used as an illumination system of a stepper or a projection lens, since high transmittance and ultraviolet resistance in a wavelength region shorter than i-line are required. However, even in the case of quartz glass, absorption is caused by various factors in the vacuum ultraviolet region. In the case of a high-precision optical system such as a stepper, even if such absorption is very small, there is a problem in that optical performance is degraded due to heat generated by absorption and fluorescence.

[0004]

SUMMARY OF THE INVENTION The present inventors have found that the above-mentioned conventional quartz glass has the following problems. Particularly, it is difficult to achieve sufficient characteristics with respect to the transmittance to vacuum ultraviolet rays and the resistance to ultraviolet rays. I found that it was not reached.
That is, in the photolithography technology in the vacuum ultraviolet region, the energy is higher than that of the i-line or the KrF excimer laser, so that the burden on the material such as the lens is extremely large. For this reason, the life of the lens and the optical system using the conventional synthetic quartz glass was short, and the performance of the optical system was significantly reduced.

[0005] The durability of ArF excimer laser, which is a kind of vacuum ultraviolet ray, is greatly influenced by chlorine contained in quartz glass. When light in the ultraviolet region acts on quartz glass, 5.8 eV called an E 'center is obtained.
And the transmittance in the ultraviolet region is significantly reduced. Chlorine present in the member must also be reduced as much as possible because it can be a precursor of the 5.8 eV absorption band. Conventionally, silicon tetrachloride, which has been used for the synthesis of quartz glass, contains about 30 to 150 ppm of chlorine in the obtained quartz glass member. Sex is inferior. Therefore, synthesis of quartz glass using an organosilicon compound has recently been performed. However, in these conventional technologies,
No consideration is given to the carbon remaining in the glass contained in the organosilicon compound.

Further, since the organosilicon compound undergoes an oxidation reaction simultaneously with the hydrolysis reaction in the flame used during the synthesis, the atmosphere during the synthesis must be an oxygen-excess atmosphere. However, in the synthesis in such an atmosphere, a phenomenon is seen in which the concentration of contained hydrogen molecules, which is a factor necessary for improving the durability to ultraviolet light, decreases. Accordingly, an object of the present invention is to obtain a synthetic quartz glass having both high transmittance in the vacuum ultraviolet region and high ultraviolet resistance, which can be used for a high-precision optical system such as optical lithography in the vacuum ultraviolet region. .

[0007]

Accordingly, the present invention relates to a method for obtaining quartz glass having a high transmittance in a vacuum ultraviolet region and an ultraviolet resistance when an organosilicon compound is used as a raw material. , Earnestly studied. As a result, reducing the amount of formyl radicals (the amount generated when X-rays are irradiated at 0.1 kW for 22 sec) derived from carbon impurities contained in the component obtained by synthesis improves the vacuum ultraviolet transmittance. Was found to be a necessary condition. In order to reduce the amount of formyl radicals, it is effective to make the ratio of oxyhydrogen gas ejected from the burner more oxygen-rich, but when the synthesis is performed under these synthesis conditions, the oxidizing atmosphere becomes stronger. In addition, since there is a great possibility that the concentration of hydrogen molecules imparting UV durability is reduced, it is necessary to perform a heat treatment in a hydrogen atmosphere on the quartz glass obtained in order to compensate for the decrease. However, the hydrogen atmosphere heat treatment may be contaminated by secondary factors such as mixing of impurities. Also, a decrease in the concentration of hydrogen molecules leads to an increase in the concentration of hydroxyl groups having an inverse correlation, which has a less favorable effect on the increase in the refractive index and the generation of distortion caused by excimer laser irradiation. For this reason, only the synthesis has a low hydroxyl group concentration,
In addition, it has been desired to develop a method for synthesizing quartz glass having a small amount of formyl radicals generated by X-ray irradiation and a high hydrogen molecule concentration. As a result of investigating these facts in detail, in the burner structure used in the present invention, the factor controlling the hydroxyl group concentration is the ratio of the oxyhydrogen gas in the second tube and the third tube, and the formed formyl radical It was concluded that the factors governing the amount were the oxyhydrogen gas ratio of the second and third tubes and the oxyhydrogen gas ratio of the fourth and fifth tubes. That is, the second tube and the organic silicon compound as a raw material is less SiO ₂ particles oxidation and hydrolysis OH group concentration produced by oxyhydrogen gas flowing out from the third tube, and further a fourth tube and a fifth The fine particles are oxidized by the oxyhydrogen gas flowing out of the tube and completely burned. In order to perform this efficiently, the ratio (b / a) of the amount of hydrogen gas (a) ejected from the second tube to the amount of oxygen gas (b) ejected from the third tube is 0.50.
Below, it was found that the ratio (d / c) of the amount of hydrogen gas (c) ejected from the fourth tube to the amount of oxygen gas (d) ejected from the fifth tube (d / c) was required to be 0.55 or more. .

Therefore, in the present invention, among the oxyhydrogen flames used for synthesizing the organosilicon compound as a raw material,
The ratio (b / a) of the amount of hydrogen gas (a) ejected from the second tube to the amount of oxygen gas (b) ejected from the third tube is 0.50 or less, and the hydrogen gas ejected from the fourth tube The ratio (d / c) of the amount (c) to the amount (d) of oxygen gas ejected from the fifth pipe is 0.55 or more. By doing so, the hydroxyl group concentration, which greatly affects the amount of increase in the refractive index, is suppressed to the optimum value, the amount of formyl radicals, which affects the transmittance, is reduced, and the absorption induced by excimer laser irradiation is further reduced. Can be contained in an amount capable of reducing the hydrogen molecule concentration.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as an organosilicon compound used as a raw material, a compound having a boiling point of 170 ° C. or lower, for example, hexamethyldisiloxane, methyltrimethoxysilane, tetramethoxysilane, octamethylcyclotetrasiloxane, etc. No. As described above, the amount of formyl radical derived from carbon contained in the obtained quartz glass affects the transmittance in the vacuum ultraviolet region. In order to reduce the total amount, in the present invention, the synthesis is performed in an oxidizing flame.

The burner used in the present invention is provided with a first pipe arranged at the center and for ejecting a raw material, and a second pipe arranged concentrically around the first pipe and ejecting hydrogen gas. A second tube, a third tube arranged concentrically around the second tube and for ejecting oxygen gas, and a concentrically arranged around the third tube and ejecting hydrogen gas And a plurality of fifth tubes arranged between the outer periphery of the third tube and the inner periphery of the fourth tube for ejecting oxygen gas; A sixth pipe arranged concentrically around the pipe and ejecting hydrogen gas, and disposed between the outer circumference of the fourth pipe and the inner circumference of the sixth pipe, and And a plurality of seventh tubes for spouting. This burner is made of quartz glass, and it is possible to independently control the flow rate and flow rate of the gas ejected from each tube. Such control is performed using, for example, a mass flow controller.

An organosilicon compound is introduced into the first tube. When the organic silicon compound itself is a liquid, the raw material is vaporized by a vaporizer and then sent to a mass flow controller together with a carrier gas. As a carrier gas, an inert gas such as nitrogen or helium is used.
Examples of the present invention will be described below.

Examples and Comparative Examples A high-purity quartz glass ingot was prepared by burning oxygen gas and hydrogen gas at the flow rates and flow rates shown in Table 1 with a quartz glass burner as shown in the figure, and starting from the center. The synthesis was carried out by a method called a so-called oxyhydrogen flame hydrolysis method, which was diluted with a carrier gas and jetted out. During synthesis,
The target made of an opaque quartz glass plate on which the glass was laminated was rotated and rocked at a constant cycle, and simultaneously lowered, thereby keeping the position of the upper part of the ingot constant from the burner at all times.

[0013]

[Table 1]

Thus, a plurality of ingots were synthesized. From this ingot, cut out a test piece,
A measurement sample was obtained by polishing. Table 2 shows the results of this measurement.

[0015]

[Table 2]

[0016]

As described above, the burner structure used for the synthesis of quartz glass is disposed at the center and the first tube for ejecting the raw material composed of the organosilicon compound is provided around the first tube. A second tube arranged concentrically and for ejecting hydrogen gas; a third tube arranged concentrically around the second tube and ejecting oxygen gas; A fourth tube arranged concentrically around the tube and for ejecting hydrogen gas, and disposed between the outer periphery of the third tube and the inner periphery of the fourth tube and ejecting oxygen gas; A plurality of fifth tubes, a sixth tube arranged concentrically around the fourth tube and for ejecting hydrogen gas, an outer periphery of the fourth tube and the sixth tube. A plurality of seventh tubes disposed between the inner periphery of the tubes and for ejecting oxygen gas, and a second tube. The ratio (b / a) of the amount of hydrogen gas ejected from the pipe (a) to the quantity of oxygen gas ejected from the third pipe (b) is 0.50 or less, and the quantity of hydrogen gas ejected from the fourth pipe (c) By setting the ratio (d / c) of the oxygen gas amount (d) ejected from the fifth pipe to 0.55 or more, the transmittance in the vacuum ultraviolet region is high, and chlorine containing high ultraviolet durability is not contained. Quartz glass was obtained.

Continued on the front page F term (reference) 4G014 AH15 AH16 4G062 AA04 BB02 CC07 MM02 NN16 5H309 CC20 DD08 EE04 FF01 GG02 JJ06

Claims (13)

[Claims] 1. An organic silicon compound is jetted from a burner,
Glass particles are obtained by hydrolysis or oxidation reaction in a flame containing oxygen and hydrogen, and the glass particles are deposited on a heat-resistant target opposed to a burner, and simultaneously fused to be substantially free of chlorine. A method for producing a synthetic quartz glass for vacuum ultraviolet rays for obtaining glass, wherein the burner is disposed at a central portion and a first tube for ejecting a raw material made of an organosilicon compound, and around the first tube. A second tube arranged concentrically and for ejecting hydrogen gas; a third tube arranged concentrically around the second tube and ejecting oxygen gas; A fourth tube arranged concentrically around the tube and for ejecting hydrogen gas, and disposed between the outer periphery of the third tube and the inner periphery of the fourth tube and ejecting oxygen gas; A plurality of fifth tubes and the fourth tube A sixth pipe arranged concentrically around and for ejecting hydrogen gas; and a sixth pipe arranged between the outer periphery of the fourth tube and the inner periphery of the sixth tube for ejecting oxygen gas. A burner comprising a plurality of seventh tubes;
The ratio (b / a) of the amount of hydrogen gas (a) ejected from the second tube to the amount of oxygen gas (b) ejected from the third tube is 0.50 or less, and the hydrogen gas ejected from the fourth tube A method for producing a synthetic quartz glass for ultraviolet light, wherein a ratio (d / c) of the amount (c) to the amount (d) of oxygen gas ejected from the fifth tube is 0.55 or more. 2. The method for producing quartz glass according to claim 1, wherein the organosilicon compound is a compound contained in alkoxysilanes or siloxanes containing no chlorine in the molecule. A method for producing synthetic quartz glass for ultraviolet light. 3. The synthetic quartz for ultraviolet light according to claim 1, wherein the ratio of the total amount of oxygen gas to the total amount of hydrogen gas is a flame of 0.53 or more. Glass manufacturing method. 4. The method for producing quartz glass according to claim 1, wherein the amount of oxygen gas (e) obtained by subtracting the amount of combustion of the organosilicon compound ejected from the first tube from the total amount of oxygen gas and the total amount of hydrogen A method for producing a synthetic quartz glass for ultraviolet light, wherein a ratio (e / f) to a gas amount (f) is 0.48 or more. 5. A synthetic quartz glass optical member produced by the production method according to claim 1, wherein the concentration of hydrogen molecules contained in the optical member is 2 × 10 ¹⁷ atoms / cm ³ or more. , Synthetic quartz glass members. 6. A synthetic quartz glass optical member manufactured by the manufacturing method according to claim 1, wherein a concentration of a hydroxyl group contained in the optical member is 1100 ppm or less. 7. A synthetic quartz glass optical member manufactured by the manufacturing method according to claim 1, wherein the amount of carbon contained in the optical member is 10 ppm or less. 8. A synthetic quartz glass optical member manufactured by the manufacturing method according to claim 1, wherein the optical member has X
0.1 kW, the amount of formyl radicals generated when irradiated for 22 sec is 2 × 10 ¹⁴ / cm ³ or less,
Synthetic quartz glass member. 9. A synthetic quartz glass optical member manufactured by the manufacturing method according to claim 1, wherein Ar of the optical member is
A synthetic quartz glass member having an initial internal transmittance of 99.5% or more at an F excimer laser wavelength. 10. A synthetic quartz glass optical member synthesized by the manufacturing method according to claim 1, wherein the sodium concentration of the optical member is 20 ppb or less. 11. A synthetic quartz glass optical member synthesized by the manufacturing method according to claim 1, wherein the optical member is
A synthetic quartz glass member characterized in that the amount of absorption induced by irradiating an ArF excimer laser with 400 mJ / cm 2 · p, 1 × 10 6 pulses is 0.2 / cm or less. 12. A synthetic quartz glass optical member synthesized by the manufacturing method according to claim 1, wherein said optical member is
A synthetic quartz glass member characterized in that the amount of increase in the refractive index when irradiating an ArF excimer laser with 400 mJ / cm ² · p, 1 × 10 ⁶ pulses is 1.5 × 10 ⁻⁶ or less. 13. A synthetic quartz glass optical member synthesized by the manufacturing method according to claim 1, wherein the optical member is
A synthetic quartz glass member having a maximum strain of 2.5 nm / cm or less when irradiated with an ArF excimer laser at 400 mJ / cm ² · p, 1 × 10 ⁶ pulses.