JP2000256019A - Quartz glass and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide quartz glass which is used as a lens material for the image formation optical system of ultraviolet laser for excimer laser lithography or the like, and to provide a method for producing the same. SOLUTION: In quartz glass synthesized by the direct method using raw materials comprising organosilicon compounds, the quartz glass having an internal absorption coefficient of <=0.001 cm-1 in the wavelength region of >=190 nm is obtained by suppressing the concentration of formyl radicals formed in the inside of the quartz glass by X-ray irradiation to be not more than 2×1014 radical/cm3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quartz glass used as a lens material of an image forming optical system of an ultraviolet laser such as an excimer laser lithography and a method of manufacturing the same.

[0002]

2. Description of the Related Art A reduction projection exposure apparatus (or an optical lithography apparatus) is mainly used for transferring an integrated circuit pattern such as an IC or LSI. A projection optical system used in this apparatus is required to have a large exposure area and a higher resolution over the entire exposure area with the increase in integration of integrated circuits. To improve the resolution of the projection optical system, shorten the exposure wavelength or increase the numerical aperture (NA) of the projection optical system.
May be increased.

[0003] Exposure wavelengths are g-line (436 nm) to i-line (365 nm), as well as KrF (248 nm) and ArF (19 nm).
3nm) Excimer lasers are being shortened.
In general, optical glass used as an illumination optical system of a reduction projection exposure apparatus or a lens member of a projection optical system using a light source having a wavelength longer than the i-line has a sharp decrease in light transmittance in a wavelength region shorter than the i-line. In particular, in the wavelength region of 250 nm or less, almost no optical glass transmits light.
Therefore, only quartz glass and calcium fluoride crystal can be used as a material of a lens constituting an optical system of a reduction projection exposure apparatus using an excimer laser as a light source. These two materials are indispensable materials for performing chromatic aberration correction in an imaging optical system of an excimer laser. In the imaging optical system of the excimer laser, particularly in the projection optical system, the internal absorption loss coefficient of the lens material is 0.001 cm ^-1 (= thickness 1c).
An extremely low-loss material with a light absorption of 0.1% or less per m) is required. Quartz glass that achieves such a low absorption loss has conventionally been produced by a gas phase synthesis method called a direct method. In this production method, oxygen gas and hydrogen gas are mixed and burned in a burner made of quartz glass, and high purity silicon tetrachloride gas is diluted with a carrier gas (usually oxygen gas) as a raw material gas from the center of the burner. The raw material gas is ejected and reacted (hydrolysis reaction) with water generated by the combustion of the surrounding oxygen gas and hydrogen gas to generate fine silica glass particles, and the fine silica glass particles are located below the burner and are rotated. And a method of depositing on a target made of an opaque quartz glass plate that is oscillating and pulling down, and simultaneously fusing and vitrifying by the combustion heat of the oxygen gas and hydrogen gas to obtain a quartz glass ingot.

In recent years, for the purpose of improving the durability of quartz glass manufactured by the direct method with respect to irradiation with excimer laser light and reducing hydrochloric acid discharged from the manufacturing apparatus, the quartz glass is substantially free of chlorine. Attempts have been made to produce quartz glass from organosilicon compounds. As the organosilicon compound, as an alkoxysilane, tetraethoxysilane (chemical formula: Si (OC ₂ H ₅ ))
_4, abbreviations: TEOS), tetramethoxysilane (chemical formula: Si (OCH _{3) 4,} abbreviation: TMOS), methyltrimethoxysilane _{(Formula: CH 3 Si (OCH 3)} 3, abbreviations:
MTMS), siloxanes such as octamethylcyclotetrasiloxane (chemical formula: (SiO (CH ₃ ) ₂ ) ₄ , abbreviation: OMCTS), hexamethyldisiloxane (chemical formula: (CH ₃ ) ₃ SiOSi (CH ₃ ) ₃ , abbreviation : HMD
S), tetramethylcyclotetrasiloxane (chemical formula:
(SiCH ₃ OH) ₄ , abbreviation: TMCTS), dodecamethylcyclohexasiloxane (chemical formula: (Si (CH ₃ ))
₂ O) ₆ (abbreviation: TMCTS) and the like are mainly used.

[0005]

However, quartz glass synthesized by a direct method using an organosilicon compound as a raw material gas has a problem that the internal absorption coefficient becomes 0.001 cm ^-1 or more in a wavelength region of about 210 nm or less. There was a point. That is, the wavelength of the ArF excimer laser is 1
0.001 cm internal absorption coefficient even at 93.4 nm
^-1 or more, and could not meet the specifications of the ArF excimer laser stepper as an optical member of the projection lens.
Therefore, there has been a demand for a quartz glass synthesized by a direct method using an organosilicon compound as a raw material gas and having a low loss of an internal absorption coefficient of 0.001 cm ^-1 or less in a wavelength region of 190 nm or more.

[0006] Accordingly, the present invention provides an organosilicon compound as a raw material.
In quartz glass synthesized by a direct method as a gas, 1
0.001 internal absorption coefficient in the wavelength region of 90 nm or more
cm ^-1Excellent light transmission characteristics with extremely low loss of
It is an object to provide a quartz glass having the same.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have studied the method of producing residual gas in quartz glass synthesized by a direct method using a raw material gas comprising an organosilicon compound. We focused on carbon concentration. As a result of diligent research, the concentration of formyl radicals generated inside quartz glass when irradiated with X-rays was 2 × 10 2 in quartz glass synthesized by a direct method using a raw material gas composed of an organosilicon compound. It has been found that by setting the number to ¹⁴ / cm ³ or less, it is possible to provide quartz glass having an internal absorption coefficient of 0.001 cm ⁻¹ or less in a wavelength region of 190 nm or more. The formyl radical
It is represented by the following equation.

[0008]

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Therefore, the quartz glass of the present invention is a quartz glass synthesized by a direct method using a raw material gas comprising an organosilicon compound, as described in claim 1,
The method is characterized in that the concentration of formyl radicals generated inside when irradiated with X-rays is 2 × 10 ¹⁴ / cm ³ or less. At this time, the X-ray used for the irradiation has a voltage of 50 kV,
It is preferable that the X-rays are emitted from a rhodium tube to which a current of 2 mA is applied.

Further, the quartz glass of the present invention contains substantially no chlorine in the quartz glass obtained since the raw material gas at the time of synthesis is an organosilicon compound, and its concentration is 0.1%.
ppm or less. Furthermore, the quartz glass of the present invention has an OH group concentration of 800 ppm or more and 130 ppm or more.
0 ppm or less, and the hydrogen molecule concentration is 1 × 10 ¹⁶ / cm ³ or more and 4 × 10 ¹⁸ / cm ³ or less.

The quartz glass of the present invention can be produced under the following conditions during the production by the direct method. That is, according to the present invention, as described in claim 9, a first tube for discharging a source gas and a carrier gas of an organosilicon compound, which is disposed at a central portion, and a periphery of the first tube. Concentrically arranged on the first
A second tube for ejecting hydrogen gas, a third tube arranged concentrically around the second tube and ejecting the first oxygen gas, and a third tube for ejecting the first oxygen gas. A fourth tube concentrically disposed therearound for ejecting a second hydrogen gas, and a second oxygen gas disposed between the outer periphery of the third tube and the inside of the fourth tube; A plurality of fifth tubes for ejecting gas, a third tube disposed concentrically around the fourth tube and a third tube;
A sixth pipe for ejecting hydrogen gas, and a plurality of first pipes arranged between the outer circumference of the fourth pipe and the inner circumference of the sixth pipe for ejecting the third oxygen gas. In a method for producing a synthetic quartz glass for ultraviolet light by a direct method using a burner provided with a seven pipe, a ratio of an ejection flow rate of oxygen gas 1 to an ejection flow rate of hydrogen gas 1 is 0.7 to 2.0. And oxygen gas 2
The ratio of the ejection flow rate of hydrogen to the ejection flow rate of hydrogen gas 2 is 0.5
By setting the ratio of the ejection flow rate of the oxygen gas 3 to the ejection flow rate of the hydrogen gas 3 to 0.2 to 0.5, the formyl generated inside when X-rays are irradiated A quartz glass having a radical concentration of 2 × 10 ¹⁴ / cm ³ or less and having an internal absorption coefficient of 0.001 cm ^-1 or less in a wavelength region of 190 nm or more can be provided.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Under the conventional conditions for producing quartz glass by the direct method, in order to increase the concentration of hydrogen molecules, the supply flow ratio of oxygen gas and hydrogen gas is set to an excess hydrogen condition, that is, the oxygen gas flow rate / The hydrogen gas flow rate was set to 0.5 or less. This is because, in the prior art in which quartz glass was synthesized using silicon tetrachloride as a raw material gas, the reaction process of producing quartz glass from the silicon tetrachloride raw material was governed by a hydrolysis reaction in an oxygen-hydrogen flame. No problems occurred. However, when synthetic quartz glass is produced by a direct method using an organosilicon compound as a raw material gas, the reaction process leading to quartz glass is not a hydrolysis reaction but an oxidation reaction. Therefore, if the flow rates of oxygen gas and hydrogen gas are set in the same manner as in the case of the silicon tetrachloride raw material, oxygen required for the oxidation reaction is absolutely insufficient. This causes a very serious problem in the production of quartz glass using the organosilicon compound raw material gas. That is, the raw material gas of the organosilicon compound is in an incompletely combusted state, and a large amount of a carbon compound remains in the obtained quartz glass. The present inventors have found that the carbon compound remaining in the quartz glass is a cause of generating a large amount of formyl radical when irradiated with X-rays.

[0013] The large amount of carbon compound means that the carbon compound is contained in a large amount as compared with the conventional quartz glass produced using silicon tetrachloride as a raw material. The present inventors expected that is 1 ppm or less. Therefore, it has been difficult to quantify the carbon concentration in quartz glass by combustion / infrared spectroscopy or charged particle activation analysis, which is usually used as a method for analyzing carbon content. Of course, it was difficult to detect and quantify even ICP-AES (inductively coupled plasma emission spectroscopy) and ICP-MS (inductively coupled plasma mass spectrometry). In fact, these conventional analytical methods could not obtain an effective numerical value as the carbon content in quartz glass. Finally, the present inventors determined the concentration of formyl radical generated by X-ray irradiation using an electron spin resonance analyzer (El
ectron Spin Resonance Spectrometer (abbreviation: ESR)
Although the method of detecting and quantifying by using the method cannot determine only the total carbon concentration, it has been found that it is a very effective means for obtaining knowledge of the carbon concentration in quartz glass.

Although the mechanism of the formation of formyl radical by X-ray irradiation is not clear,

[0015]

Embedded image

It is considered that the reaction is caused by a reaction inside the quartz glass. At this time, the precursor (precursor) of the formyl radical is CO, which is one of the carbon compounds remaining during the synthesis. The following reaction is considered as a supply source of H ⁰ in this reaction.

[0017]

Embedded image

[0018]

Embedded image

At this time, the above reaction was caused by X-ray irradiation, but not by ArF.KrF excimer laser light irradiation. That is, no formyl radical was generated by irradiation with ArF.KrF excimer laser light. Next, a method for reducing a carbon compound in quartz glass synthesized by a direct method using a raw material gas composed of an organosilicon compound will be described.

FIG. 2 is a schematic view of a quartz glass manufacturing apparatus by a direct method. FIG. 3 shows an example of the structure of the gas outlet at the tip of the burner. The burner is provided at a central portion, and is provided with a first tube for ejecting a source gas and a carrier gas of an organosilicon compound, and is disposed concentrically around the first tube and has a hydrogen gas 1 (first gas). A second pipe for ejecting hydrogen gas), and an oxygen gas 1 (first oxygen gas) which is arranged concentrically around the second pipe and
A third tube for ejecting hydrogen gas, a fourth tube arranged concentrically around the third tube and ejecting hydrogen gas 2 (second hydrogen gas), A plurality of fifth tubes disposed between the outer periphery of the tube and the inside of the fourth tube for ejecting oxygen gas 2 (second oxygen gas), and concentric circles around the fourth tube A sixth pipe for ejecting hydrogen gas 3 (third hydrogen gas), disposed between the outer circumference of the fourth pipe and the inner circumference of the sixth pipe; Gas 3
And a plurality of seventh tubes for ejecting (third oxygen gas). The present inventors have used the above burner,
Quartz glass was produced under various synthesis conditions, and the formyl radical concentration generated by X-ray irradiation in the produced quartz glass and the synthesis conditions were investigated in detail.

As a result, the ratio of the flow rate of the oxygen gas 1 to the flow rate of the hydrogen gas 1 is set to 0.7 to 2.0, and the ratio of the flow rate of the oxygen gas 2 to the flow rate of the hydrogen gas 2 is set. X-rays are synthesized by synthesizing quartz glass by setting the ratio between the ejection flow rate of the oxygen gas 3 and the ejection flow rate of the hydrogen gas 3 to 0.2 or more and 0.5 or less. It was found that the concentration of formyl radicals generated inside the quartz glass when irradiated with γ was not more than 2 × 10 ¹⁴ / cm ³ .

Further, the formyl radical concentration and 1
When the correlation with the 93.4 nm absorption coefficient was examined, FIG.
A very good correlation like 1 was obtained. Sand
In the prior art, the formyl radical concentration is
2 × 10¹⁴Pieces / cm^ThreeCannot be less than
Has an absorption coefficient of 0.001 cm at a wavelength of 193.4 nm. ^-1
Although the following quartz glass could not be obtained, the method of the present invention
From the formyl radical concentration of 2 × 10¹⁴Pieces / cm^ThreeLess than
Below, resulting in an absorption coefficient at a wavelength of 193.4 nm.
0.001cm^-1Very low loss quartz glass
You've got to get

The power notation in Table 2 is represented by "E". For example, “1.7E + 14” becomes “1.7 × 10 ¹⁴ ”
Represents that. As described above, according to the present invention, in a quartz glass synthesized by a direct method using a raw material gas composed of an organosilicon compound, the concentration of formyl radical generated inside the quartz glass when irradiated with X-rays is 2 × 1
With 0 ¹⁴ / cm ³ or less, it is possible to make the internal absorption coefficient in the above wavelength region 190nm to 0.001 cm ^-1 or less.

[0024]

【Example】

[0025]

[Table 1]

The quartz glass ingots of the examples and comparative examples were produced by using a synthetic quartz glass manufacturing apparatus by a direct method shown in FIG. Oxygen gas and hydrogen gas are spouted from the spout 6 at the tip of the quartz glass burner 7, mixed and burned, and high purity (purity of 99.99% or more,
The metal impurity Fe concentration is 10 ppb or less, and the Ni and Cr concentrations are 2 ppb or less. ) Is diluted with a carrier gas (nitrogen gas: flow rate 3.5 slm), and the raw material flow rate is spouted from the central pipe 21 at the burner tip at a set flow rate shown in Table 1, and oxidized in a combustion flame. The reaction generates quartz glass fine particles (soot), which are rotated at a speed of 7 rotations per minute, oscillated at a moving distance of 80 mm, at a cycle of 90 seconds, and lowered at a descent speed shown in Table 1. Φ
The synthetic quartz glass ingot IG was synthesized by being deposited on the upper part of a 200 mm quartz glass target 5 and simultaneously melted by the heat of the flame. Under the conditions shown in Table 1, an ingot having a diameter of 150 to 250 mm and a length of 300 to 600 mm was obtained.

FIG. 3 shows the configuration of the gas outlet at the tip of the burner. The burner is disposed at the center and is provided with a first pipe 21 having an inner diameter of 4.0 mm for ejecting a source gas and a carrier gas of an organosilicon compound, and is disposed concentrically around the first pipe. A second tube 22 for ejecting hydrogen gas 1, a third tube 23 arranged concentrically around the second tube and ejecting oxygen gas 1, A fourth tube 24 concentrically disposed around the periphery of the fourth tube 24 for ejecting hydrogen gas 2, and disposed between the outer periphery of the third tube and the inside of the fourth tube and ejecting oxygen gas 2; A plurality of fifth pipes 25, a sixth pipe 26 disposed concentrically around the fourth pipe and ejecting the hydrogen gas 3, an outer periphery of the fourth pipe and the A plurality of seventh pipes 27 disposed between the inner circumference of the sixth pipe and ejecting the oxygen gas 3. Is Na. Dimension of each pipe (m
m) is as follows.

[0028] Using the synthetic quartz glass manufacturing apparatus and the burner as described above, quartz glass ingots of Examples and Comparative Examples were produced.

Working Examples and Comparative Examples
Raw material type, flow rate, ingot descent speed, hydrogen during production
Flow rate of gas 1-3, flow rate of oxygen gas 1-3, oxygen gas 1
Ratio of the flow rate of hydrogen gas to the flow rate of hydrogen gas 1 (= oxygen gas
1 flow rate / 1 flow rate of hydrogen gas), jet flow rate of oxygen gas 2 and water
Ratio to the flow rate of raw gas 2 (= flow rate of oxygen gas 2 / hydrogen gas 2)
2 flow rate), the flow rate of oxygen gas 3 and the flow rate of hydrogen gas 3
Each ratio with the flow rate (= 3 flow rates of oxygen gas / 3 flow rates of hydrogen gas)
Table 1 shows the setting conditions. Organic silicon compound raw material gas
As siloxanes, hexamethyldisiloxa
(Chemical formula: (CH_Three)_ThreeSiOSi (CH_Three)_Three, Abbreviation: H
MDS), octamethylcyclotetrasiloxane (chemical
Formula: (Si (CH_Three)_TwoO)_Four, Abbreviation: OMCTS)
Methyltrimethoxysilane as alkoxysilanes
Orchid (chemical formula: CH_ThreeSi (OCH_Three) _Three, Abbreviation: MTM
S) was used. As shown in Table 1, the gas flow rate of the embodiment
Is the difference between the jet flow rate of oxygen gas 1 and the jet flow rate of hydrogen gas 1.
The ratio is 0.7 or more and 2.0 or less, and the ejection flow rate of oxygen gas 2 and water
Both the ratio to the flow rate of the raw gas 2 to be injected is 0.5 or more and 1.0 or less
Below, the flow rate of the oxygen gas 3 and the flow rate of the hydrogen gas 3
The ratio is set to satisfy the condition of 0.2 or more and 0.5 or less.
Was. The gas flow rate of the comparative example is the same as the flow rate condition of the example.
Were set under conditions that did not satisfy

Next, the method of measuring the concentration of each component and the absorption coefficient will be described below. A sample having a shape with a diameter of 60 mm and a thickness of 10 mm was cut out from the center of the ingot in the radial direction, 100 mm from the uppermost surface (ingot head), one by one for each ingot. These test pieces were used as test pieces for transmittance evaluation. The parallelism of each of the two opposing surfaces is within 10 seconds, the flatness of each surface is within three Newton rings, and the surface roughness of each surface is r.
Precision polishing was performed so that ms = 10 angstroms or less, and finally polishing was performed so that the thickness of the test piece was 10 ± 0.1 mm. Further, a finish polishing process using high-purity SiO ₂ powder was performed so that no abrasive remained on the surface. The wavelength of the test piece thus obtained is 190 to 40.
The internal loss coefficient in the region of 0 nm is calculated as disclosed in Japanese Patent Application No. 5-2112.
17 and a spectrophotometer adjusted by the method of Japanese Patent Application No. 10-9846. The internal absorption coefficient was calculated by subtracting the internal scattering coefficient from the internal loss coefficient. A
The internal loss coefficient of the synthetic quartz glass at the oscillation wavelength of the rF excimer laser of 193.4 nm is 0.0015 c.
m ^−1, and 19 of each test piece shown in Table 1.
The 3.4 nm absorption coefficient is a value obtained by subtracting the internal scattering loss value from the internal loss coefficient.

A test specimen having a shape of 10.times.2.7.times.2.3 mm for determining formyl radical was cut out from the vicinity of the transmittance test specimen of each ingot. All surfaces were finished with fine grinding. These test pieces were irradiated with X-rays under the following conditions. X-ray irradiator: X-ray fluorescence analyzer (Rigaku Denki: RIX)
3000) X-ray tube: Rhodium (Rh) tube Tube voltage: 50 kV Tube current: 2 mA X-ray irradiation time: 22 seconds The X-ray irradiation dose (dose) applied to the sample under these conditions is about 0. .01 Mrad (Megarad). Within 1 minute after the X-ray irradiation, the test piece was placed in a dewar containing liquid nitrogen, and the test piece was cooled to a temperature of liquid nitrogen (77 K). Then, ESR (electron spin resonance) measurement was performed under the following conditions. The formyl radical concentration was determined. Apparatus: Electron spin resonance apparatus (JEOL: JES-RE)
2X) Sample temperature: 77K Microwave frequency: 9.2 GHz Microwave power: 1 mW Standard sample: Copper sulfate pentahydrate Next, the OH group concentration was determined by using the test piece for transmittance evaluation as it was, Quantified by measuring the absorption at .38 μm. The measurement of the hydrogen molecule concentration was performed by a laser Raman spectrophotometer. An argon ion laser (output: 400 mW) having a wavelength of 488 nm is incident on the test piece, and 800 cm ^-1 of the Raman scattered light emitted in the direction perpendicular to the incident light direction (peak caused by vibration of the basic structure of quartz glass: reference light) ) And 4135 cm ⁻¹ (peak due to vibration of hydrogen molecules) were measured, and the intensity ratio was determined.

Next, a 10 mm × 10 mm × 5 mm Cl, Na, K analysis sample was cut out from a portion adjacent to each transmittance evaluation test piece. Quantification of these impurity concentrations was performed by activation analysis using thermal neutron irradiation. Also,
From locations adjacent to those samples, alkaline earth metals,
Samples for elemental analysis of transition metals and Al were cut out.
Quantification of each element was performed by inductively coupled plasma emission spectroscopy. Table 1 shows the values of the Na concentration. The Na concentration in each of the examples was 0.002 ppm or less, and 193.4.
It was confirmed that there was no effect on the absorption loss in nm. Further, the Cl concentration was lower than the lower limit of detection (0.
1 ppm) or less, and chlorine-free, which is a feature of synthetic quartz glass produced using an organosilicon compound as a raw material gas, has been achieved. Furthermore, the K concentration was below the lower limit of detection (50 ppb) in all the test pieces. Also, alkaline earth metals Mg, Ca, transition metals Sc, Ti, V, C
r, Mn, Fe, Co, Ni, Cu, Zn, and Al
Of each element in Examples and Comparative Examples was 20
ppb or less.

As described above, test pieces for analysis were cut out from the produced synthetic quartz glass ingot and analyzed. Table 2 shows the OH group concentration, hydrogen molecule concentration, sodium (Na) concentration, formyl radical concentration, wavelength 1
The absorption coefficient at 93.4 nm is shown. In Table 2, the notation of the power is "E". For example, "1.7E + 1
“4” represents “1.7 × 10 ¹⁴ ”.

[0034]

[Table 2]

As shown in Table 2, the ratio of the jet flow rate of oxygen gas 1 to the jet flow rate of hydrogen gas 1 is 0.7 or more and 2.0 or less, the jet flow rate of oxygen gas 2 and the jet flow rate of hydrogen gas 2 And the gas flow rate so as to satisfy the condition that the ratio of the jet flow rate of the oxygen gas 3 to the jet flow rate of the hydrogen gas 3 is 0.2 to 0.5. The synthetic quartz glass of Examples 1 to 6 which were set and synthesized were quartz glass synthesized by a direct method using a raw material gas composed of an organosilicon compound. The concentration of formyl radical generated is 2 × 10 ¹⁴
Pieces / cm ³ or less. Thereby, Ar
The absorption coefficient at 193.4 nm which is the wavelength of the F excimer laser achieved 0.001 cm ^-1 or less. Formyl radical concentration of Examples and Comparative Examples in Table 1, 193.4 nm
FIG. 1 shows a graph of the absorption coefficient data.

According to the present invention, in a quartz glass synthesized by a direct method using a raw material gas composed of an organosilicon compound, the concentration of formyl radical generated in the quartz glass when irradiated with X-rays is 2 × 10 ¹⁴ By making the number per piece / cm ³ or less, it has become possible to provide a quartz glass having an extremely low loss of an internal absorption coefficient of 0.001 cm ⁻¹ or less in a wavelength region of 190 nm or more.

Synthetic silica glass optics having features of the present invention
Of the members, the maximum diameter is 250 mm and the thickness is 70 mm.
The maximum refractive index difference in the irradiation region of the xima laser is Δn ≦ 2 ×
10 ^-6And the maximum birefringence is 2 nm / cm or less.
And alkaline earth metal M
g, Ca, Al, transition metal Sc, Ti, V, Cr, M
n, Fe, Co, Ni, Cu, Zn
20 ppb or less each, Na concentration of alkali metal is 2 pp
b and K impurity concentration is 50 ppb or less
ArF excimer laser stepper projection lens
Was produced. And the resolution of the obtained projection optical system is
Achieved 0.19μm in line and space,
Obtaining good imaging performance as a Shima laser stepper
did it.

[0038]

According to the present invention, in a quartz glass synthesized by a direct method using an organosilicon compound as a raw material gas, 1
0.001 internal absorption coefficient in the wavelength region of 90 nm or more
It has become possible to provide quartz glass having an extremely low loss of not more than cm ^-1 and excellent light transmission characteristics.

[Brief description of the drawings]

FIG. 1 is a diagram showing a correlation between a formyl radical concentration and a 193.4 nm absorption coefficient.

FIG. 2 is a diagram showing a configuration of a synthetic quartz glass manufacturing apparatus.

FIG. 3 shows a structure of a gas ejection portion at a tip of a burner.

[Explanation of symbols]

 1: Synthetic quartz glass manufacturing apparatus 4: Refractory 5: Target 6: Gas outlet 7: Burner IG: Synthetic quartz glass ingot 21: First tube 22: Second tube 23: Third tube 24: Fourth Tube 25: Fifth Tube 26: Sixth Tube 27: Seventh Tube

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C03C 4/00 C03C 4/00 (72) Inventor Hiroki Jimbo 3-2-3 Marunouchi, Chiyoda-ku, Tokyo 4G014 AH16 4G062 AA04 BB02 DA08 DB01 DB02 DC01 DD01 DE01 DE02 DF01 EA01 EA10 EB01 EB02 EC01 EC02 ED01 ED02 EE01 EE02 EF01 EG01 FA01 FA10 FB01 FF01 FG01 F01 FG01 F01 FF01 GB01 GC01 GD01 GE01 HH01 HH03 HH04 HH05 HH07 HH08 HH09 HH10 HH12 HH13 HH15 HH17 HH18 JJ01 JJ03 JJ06 JJ07 KK01 KK03 KK05 KK07 KK10 MM02 NN01

Claims (9)

[Claims] 1. A quartz glass synthesized by a direct method using a raw material gas comprising an organosilicon compound, wherein the formyl radical generated when irradiated with X-rays has a concentration of 2%.
× 10 ¹⁴ pieces / cm ³ or less. 2. The X-ray according to claim 1, wherein the X-ray has a voltage of 50 kV,
The quartz according to claim 1, wherein the X-rays are emitted from a rhodium tube to which a current of 2 mA is applied, and the irradiation dose (dose) is 0.01 Mrad (megarad) or more and 1 Mrad (megarad) or less. Glass. 3. Chlorine in the quartz glass according to claim 1.
Concentration is 0.1 ppm or less, OH group concentration is 800 ppm or less
1300ppm or less, hydrogen molecule concentration is 1 × 10¹⁶Pieces/
cm ^Three4 × 10 or more¹⁸Pieces / cm^ThreeIt is characterized by the following
Quartz glass. 4. The quartz glass according to claim 1, wherein an internal absorption coefficient in a wavelength region of 190 nm or more is 0.001 cm ^-1 or less. 5. The quartz glass according to claim 1, wherein the organosilicon compound is an alkoxysilane. 6. The quartz glass according to claim 1, wherein the organosilicon compound is a siloxane. 7. The quartz glass according to claim 5, wherein the alkoxysilane is tetraethoxysilane, tetramethoxysilane, or methyltrimethoxysilane. 8. The quartz glass according to claim 6, wherein the siloxane is hexamethyldisiloxane, octamethylcyclotetrasiloxane, dodecamethylcyclohexasiloxane, or tetramethylcyclotetrasiloxane. 9. A first tube disposed at a central portion for ejecting a raw material gas and a carrier gas of an organosilicon compound, and a first hydrogen gas disposed concentrically around the first tube. A second tube for ejecting oxygen gas, a third tube arranged concentrically around the second tube and ejecting the first oxygen gas, and a concentric circle around the third tube. A fourth tube arranged in a shape and ejecting a second hydrogen gas;
A plurality of fifth tubes arranged between the outer periphery of the third tube and the inside of the fourth tube for ejecting a second oxygen gas, and concentrically around the fourth tube; A sixth pipe for ejecting a third hydrogen gas, and a third oxygen gas arranged between the outer circumference of the fourth pipe and the inner circumference of the sixth pipe. A plurality of seventh tubes for producing a synthetic quartz glass for ultraviolet by a direct method using a burner provided with a plurality of seventh tubes, wherein the flow rate of the first oxygen gas and the flow rate of the first hydrogen gas are different. The ratio is 0.7 or more and 2.0 or less, and the second
The ratio of the jet flow rate of the oxygen gas to the jet flow rate of the second hydrogen gas is set to be 0.5 to 1.0, and the ratio of the jet flow rate of the third oxygen gas to the jet flow rate of the third hydrogen gas. 2. The method for producing quartz glass according to claim 1, wherein is set to 0.2 or more and 0.5 or less.