JPH0733259B2 - Ultraviolet-resistant synthetic quartz glass and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention does not cause solarization even when irradiated with high energy such as synthetic quartz glass for ultraviolet light resistance, especially excimer laser, and therefore it is a lens for ultraviolet lingography. ，
TECHNICAL FIELD The present invention relates to a synthetic quartz glass for UV resistance, which is useful as a material for excimer laser windows and mirrors, and a method for producing the same.

[Conventional technology and problems to be solved] Synthetic quartz glass is made into silica powder by hydrolyzing and pyrolyzing silicon compounds such as silicon tetrachloride in oxyhydrogen flame, and then it is made into vitrified glass. It is well known that it is made by the method, and synthetic quartz glass obtained by such a method has good ultraviolet transparency, so it is suitable for lenses, cell materials, photomasks, etc. in the ultraviolet region. It is used.

On the other hand, with regard to the use of this kind of ultraviolet transmission, recently, the use of a short wavelength such as an excimer laser has been performed,
According to this, especially when used for lithography, it is expected that the line width can be made smaller, so that the degree of integration of the target semiconductor wafer can be further increased. Since the synthetic quartz glass obtained has structural defects, it suffers from the problem that its ultraviolet transmission characteristics are significantly deteriorated due to solarization when it is irradiated with high energy such as an excimer laser. Has been.

[Means and Actions for Solving the Problem] The present invention relates to a quartz glass for ultraviolet rays which can solve such disadvantages and a method for producing the same, which is synthetic quartz produced by a flame hydrolysis method. In glass, the OH group content is in the range of 1 to 1,000 ppm, the dissolved amount of hydrogen gas is 0.1 ml / 100 g or less, synthetic quartz glass for ultraviolet light resistance and synthesis produced by flame hydrolysis method Quartz glass in helium gas 50
The gist is a method for producing a synthetic quartz glass for ultraviolet ray resistance, which is characterized by heating at 0 ° C. or higher and degassing.

That is, the present inventors have conducted various studies to develop a synthetic quartz glass for ultraviolet light resistance that does not cause solarization even when irradiated with high energy rays such as excimer laser, and as a result, silicon tetrachloride, etc. Synthetic quartz glass made by sintering silica obtained by treating a silicon compound by the flame hydrolysis method causes solarization when irradiated with an excimer laser, but this is the synthetic quartz obtained in this way. It was found that it is related to the content of OH groups contained in glass and the dissolved amount of hydrogen gas, and therefore the OH group content is set in the range of 1 to 1,000 ppm and the dissolved amount of hydrogen gas is 0.1 ml / 100 g. It was confirmed that such solarization can be prevented by the following, and the present invention was completed by conducting research on a method for producing such synthetic quartz glass. Let

The present invention will be described in more detail below.

The synthetic quartz glass which does not cause solarization found by the present inventors may be made by treating a silicon compound such as silicon tetrachloride by a known oxyhydrogen flame hydrolysis method. , This product has an OH group content of 1 to 1,000p
pm, and the dissolved amount of hydrogen gas is required to be 0.1 ml / 100 g or less.

This means that when the OH group content is below 1 ppm,
There is a peak of absorption of ultraviolet rays of 260 nm, and when it is 1,000 ppm or more, the absorption of ultraviolet rays near 170 nm increases and solarization occurs, and the dissolved amount of hydrogen gas is 0.1 ml / 100 g or more. And the absorption of 180-220 nm ultraviolet rays increases and causes solarization, but this OH
The group content is 1 to 1,000 ppm, and the dissolved amount of hydrogen gas is 0.1 ml /
If it is 100 g or less, the above-mentioned ultraviolet absorption disappears, so solarization does not occur even if irradiated with high-energy ultraviolet light with a short wavelength such as an excimer laser, and thus the ultraviolet transmittance does not decrease. It is based on the results of experiments by the inventors.

In addition, such synthetic quartz glass reacts with a silicon compound such as silicon tetrachloride in an oxyhydrogen flame and hydrolyzes it into silica fine powder, which is then converted into a refractory material such as quartz rods and silicon carbide rods. Sintered after being deposited on a flexible carrier,
It can be obtained by subsequent vitrification, but synthetic quartz glass made by such a method is usually OH.
Since the group content is in the range of 1 to 1,000 ppm, OH
As far as the group content is concerned, it may be left as it is. Depending on the manufacturing conditions, the OH group content may exceed 1,000 ppm, so at this time, the silica fine powder deposited on the carrier should be mixed with chlorine gas or SOCl at a temperature below the sintering temperature before sintering. _When treated in the presence of ₂ gases, the OH group content is 1-1,0
It is recommended to set it to 00ppm.

However, since the synthetic quartz glass produced by this known oxyhydrogen flame hydrolysis method hydrolyzes a silicon compound in an oxyhydrogen flame, the dissolved amount of hydrogen gas is usually 1 to 20.
Since it is said to be ml / 100 g, it is necessary that this be 0.1 ml / 100 g or less, but the synthetic quartz glass obtained by this method according to the present invention in helium gas is used. It was confirmed that the hydrogen gas was degassed when heated at a temperature of 500 ° C. or higher, for example, for 10 hours or longer, and the dissolved amount of this hydrogen gas could be easily set to 0.1 ml / 100 g or less. This provides an advantage that a synthetic quartz glass that does not cause solarization even when irradiated with a laser or the like can be easily obtained.

[Examples] Next, examples of the present invention will be described.

Example Hydrogen gas was supplied to the outermost side of a burner having a triple-tube structure, and oxygen gas was supplied to the inner side thereof at 4 l / min and 2 l / min, respectively, and ignited to form an oxyhydrogen flame, and silicon tetrachloride was formed from the center thereof. Was fed at a rate of 500 ml / min in a gaseous state, and flame hydrolysis thereof produced finely divided silica, which was axially deposited and collected on a quartz glass starting material.

Then, this porous silica body was calcined in a helium gas atmosphere at 1,400 ° C. for 1 hour to form a transparent vitreous silica glass, and then in a helium gas, 800
When heat-treated at ℃ for 24 hours, the OH group content and gas dissolved amount of this product were examined. As a result, the OH group content was 200 ppm and the hydrogen gas dissolved amount was 0.08 ml / 100 g.

Next, this quartz glass was irradiated with a laser under argon gas, and the increase in the absorption coefficient at 260 nm was measured, which was only 1/10 of that of the quartz glass produced by the conventional method. When used as a mask substrate for lithography, no solarization occurred at all.

Claims (2)

[Claims] 1. A synthetic quartz glass produced by the flame hydrolysis method, characterized in that the OH group content is in the range of 1 to 1,000 ppm and the hydrogen gas dissolved amount is 0.1 ml / 100 g or less. Synthetic quartz glass for ultraviolet rays. 2. The synthetic quartz glass for ultraviolet light resistance according to claim 1, wherein the synthetic quartz glass produced by the flame hydrolysis method is heated in helium gas at 500 ° C. or higher to degas. Method.