JP2011063457A - Synthetic quartz glass and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a synthetic quartz glass which can eliminate defects due to the fluorescence emission of an optical material used for a stepper exposure device used for the exposure and the transfer of a fine pattern of an exposure device, a laser processing device, an optical cleaning device, an integrated circuit or the like to reduce intensity of fluorescence emission, and which has excellent transmission performance. <P>SOLUTION: The synthetic quartz glass before hydrogen impregnation processing has the suppressed defect corresponding to the fluorescence peak in 280 nm band and the suppressed defect corresponding to the fluorescence peak in 390 nm band, and after the hydrogen impregnation processing, has the suppressed defect corresponding to the fluorescence peak in 280 nm band, the suppressed defect corresponding to the fluorescence peak in 390 nm band and the suppressed defect corresponding to the fluorescence peak in 650 nm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a synthetic quartz glass for a UV optical system and a method for producing the synthetic quartz glass.

  For example, in various apparatuses such as an exposure apparatus, a laser processing apparatus, and a light cleaning apparatus, a large amount of optical system members are used for an illumination system and a projection system. In particular, an optical member used in an exposure apparatus called a stepper used to expose and transfer a fine pattern of an integrated circuit or the like includes a KrF (248 nm) excimer laser from an i-line (365 nm) or the like of a stepper light source. Shortening the wavelength to an ArF (193 nm) excimer laser or the like is underway. For this reason, a high-purity synthetic quartz glass that is excellent in transmission characteristics in the ultraviolet region is used as the material of this optical system member.

  By the way, when intense light such as the above-mentioned excimer laser light passes through the optical system member, fluorescent light emission may occur. Since this fluorescence emission is an event excited by light absorption, the presence of this fluorescence causes light absorption in the optical system member, and the transmittance of the optical system member is reduced by this light absorption. Is shown. That is, it can be seen from this fluorescence emission that there is a defect in the optical system member.

  In order to suppress the fluorescence emission as described above, a method is known in which synthetic quartz glass is heat-treated in a hydrogen atmosphere and the synthetic quartz glass is impregnated with hydrogen (for example, see Patent Document 1).

Japanese Patent No. 2660531

  By the way, when the present inventors investigated the wavelength region where the fluorescence emission intensity is high in the synthetic stone glass, it was found that the fluorescence emission intensity was extremely high in the wavelength regions of 280 nm, 390 nm and 650 nm. That is, if the intensity of the fluorescence emission in the wavelength ranges of 280 nm, 390 nm, and 650 nm can be reduced, quartz glass having more excellent transmission performance can be obtained, and an optical member without defects can be manufactured.

  However, when the presence or absence of fluorescence emission when excimer laser light was transmitted through the hydrogen-treated synthetic quartz glass was investigated, the intensity of fluorescence emission in the wavelength range of 650 nm was reduced, but in the wavelength range of 280 nm and 390 nm. It was confirmed that the intensity of the fluorescence emission was not reduced. That is, the synthetic quartz glass treated with hydrogen as in Patent Document 1 is one in which only the fluorescence emission in one wavelength region of the wavelength region where the intensity of the fluorescence emission is extremely high is suppressed, and the other wavelength region There is a possibility that fluorescence emission will occur.

  An object of the present invention is to deal with such a problem. That is, it is an object of the present invention to provide a synthetic quartz glass with few defects and better transmission performance. Furthermore, it is an object of the present invention to provide a method for producing synthetic quartz glass that can improve the transmission performance of synthetic quartz glass.

  In order to achieve the above object, a synthetic quartz glass according to the present invention has at least the following configuration.

  That is, the synthetic quartz glass before the hydrogen impregnation treatment has suppressed defects corresponding to the fluorescence peak in the 280 nm band and defects corresponding to the fluorescence peak in the 390 nm band, and corresponds to the fluorescence peak in the 280 nm band by the hydrogen impregnation treatment. And a defect corresponding to a fluorescence peak in the 390 nm band and a defect corresponding to a fluorescence peak in the 650 nm band are suppressed.

The synthetic quartz glass before hydrogen impregnation treatment has a spectral irradiance of 5 pW / cm ³ / nm for the fluorescence peaks in the 280 nm band and 390 nm band when irradiated with a KrF excimer laser at 20 mJ / Pulse / cm ² and 100 Hz for 30 minutes. It is as follows.

Synthetic quartz glass before hydrogen impregnation treatment has a spectral irradiance of 5 pW / cm ³ / nm for fluorescence peaks in the 280 nm band and 390 nm band when irradiated with ArF excimer laser at 5 mJ / Pulse / cm ² and 100 Hz for 30 minutes. It is as follows.

The synthetic quartz glass after the hydrogen impregnation treatment has a hydrogen content of 3 × 10 ¹⁷ molecules / cm ³ or more.

  In order to achieve the above object, a method for producing quartz glass according to the present invention comprises at least the following steps.

  That is, the method includes a step of generating a quartz glass fine particle deposit by a vapor phase synthesis method, and a sintering step of sintering the quartz glass fine particle while increasing the temperature. In the sintering step, the quartz glass Is a production method characterized in that the time of exposure to an atmosphere of 1100 ° C. to 1350 ° C. is 180 minutes or less.

  In the sintering step, the pressure when the quartz glass is exposed to an atmosphere of 1100 ° C. to 1350 ° C. is 1 Pa or more.

  The synthetic quartz glass obtained by the manufacturing method includes a hydrogen impregnation treatment step in a hydrogen atmosphere at 500 ° C. or lower.

  The synthetic quartz glass of the present embodiment is a material used for the UV optical system. For example, it is used for the UV optical system of various apparatuses such as an exposure apparatus, a laser processing apparatus, and an optical cleaning apparatus, and has excellent ultraviolet transmission characteristics. High purity synthetic quartz glass.

  Examples of the UV optical system here include a KrF excimer laser (248 nm), an ArF excimer laser (193 nm), an F2 excimer laser (157 nm), a YAG-FHG laser (266 nm), a Xe2 excimer lamp (172 nm), and an ArF excimer lamp. This is an optical system that uses a laser or a lamp that emits light with a wavelength of 300 nm or less, mainly (193 nm) or the like as a light source.

Synthetic quartz glass having the above-described performance is manufactured from a glass fine particle deposit using a VAD (vapor phase axis) method in which glass fine particles using SiCl ₄ are hydrolyzed in a flame. For example, A.I. A glass fine particle deposition step (VAD method, etc.); Sintering step of glass fine particle deposit, D. forming a glass fine particle sintered body into a disk shape; It is manufactured by a manufacturing method including a step of impregnating a molded synthetic quartz glass with hydrogen.

  In addition, the above-described synthetic quartz glass has suppressed defects corresponding to the fluorescence peak in the 280 nm band and defects corresponding to the fluorescence peak in the 390 nm band before the hydrogen impregnation treatment. The defect corresponding to the peak is suppressed.

  According to the synthetic quartz glass having such a configuration, there are defects corresponding to a fluorescence peak in the 280 nm band, a defect corresponding to a fluorescence peak in the 390 nm band, and a defect corresponding to a fluorescence peak in the 650 nm band, where the intensity of fluorescence emission is extremely high. Be suppressed. Therefore, it is possible to manufacture an optical system member having better transmission performance and having no defects.

Further, the above-described synthetic quartz glass has the performance before hydrogen impregnation treatment, for example, the spectrum of fluorescence peaks in the 280 nm band and the 390 nm band when a KrF excimer laser is irradiated for 30 minutes at 20 mJ / Pulse / cm ² and 100 Hz. The irradiance is preferably 5 pW / cm ³ / nm or less, or the spectral irradiance of fluorescence peaks in the 280 nm band and the 390 nm band when irradiated with ArF excimer laser at 5 mJ / Pulse / cm ² and 100 Hz for 30 minutes. Is preferably 5 pW / cm ³ / nm or less.

The synthetic quartz glass preferably has a hydrogen content of 3 × 10 ¹⁷ molecules / cm ³ or more after the hydrogen impregnation treatment.

  The synthetic quartz glass before the hydrogen impregnation treatment here means a glass fine particle sintered body obtained in the above-mentioned step B and a glass body after molding obtained in the step C, and any of these synthetic quartz glasses can be synthesized. Hydrogen impregnation treatment can also be performed on quartz glass.

  Next, a preferred method for producing the above-described synthetic quartz glass will be described.

A: Glass particulate deposit manufacturing process A VAD (vapor phase axis) method or the like is used to hydrolyze SiCl ₄ in a flame to produce a glass particulate deposit. That is, the glass fine particle raw material is supplied to a flame injection means such as a burner, glass fine particles are generated in the flame ejected by the flame injection means, and the generated glass fine particles are deposited on the starting rod to deposit the glass fine particles. Manufacture the body.

B: Glass particulate deposit body sintering step Transparent glass particulate sintering is performed by inserting the glass particulate deposit body obtained in step A into a sintering furnace and sintering while increasing the temperature in the sintering furnace. Get the body. In this step, after the glass fine particle deposit is inserted, the incinerator is heated to gradually increase the temperature, and is heated for a predetermined time in an atmosphere having a maximum temperature of about 1550 ° C. for sintering treatment. At this time, it is preferable that the time of exposure to the atmosphere of 1100 ° C. to 1350 ° C. within the temperature at which the glass particulate deposit rises is 180 minutes or less, and the time of exposure to the atmosphere of 1100 ° C. to 1350 ° C. The pressure is preferably 1 Pa or more.

  The time for which the glass particulate deposit is exposed to the atmosphere of 1100 ° C. to 1350 ° C. may be any number of minutes as long as it is 180 minutes or less. Moreover, the upper limit of the pressure at the time of exposing to 1100 degreeC-1350 degreeC atmosphere is about 500 Pa.

  By this step B, defects corresponding to the fluorescence peak in the 280 nm band and defects corresponding to the fluorescence peak in the 390 nm band are suppressed.

  It is considered that the defect corresponding to the fluorescence peak in the 280 nm band described above is caused by the oxygen deficiency defect. This oxygen deficiency defect increases because the amount of oxygen released increases as the time of exposure to a high-temperature atmosphere in the glass fine particle deposited state before sintering proceeds increases. Further, the oxygen deficiency defect increases because the amount of oxygen released increases as the pressure when exposed to a high temperature atmosphere is lower (the degree of vacuum is higher). Therefore, by limiting the exposure time to a high temperature atmosphere in the glass fine particle deposit state to 180 minutes or less and limiting the pressure to 1 Pa, it corresponds to a defect corresponding to a fluorescence peak in the 280 nm band and a fluorescence peak in the 390 nm band. Defects can be suppressed.

C: Step of forming glass fine particle sintered body into disk shape The glass fine particle sintered body obtained in step B is ground and cut to produce a disk-shaped synthetic quartz glass.

D: Hydrogen impregnation treatment step The synthetic quartz glass obtained in step C is impregnated with hydrogen to obtain synthetic quartz glass. In this step, it is preferable to perform a hydrogen impregnation treatment in a hydrogen atmosphere at 500 ° C. or lower. You may perform the hydrogen impregnation process of this process in the state of the glass fine particle sintered compact obtained at the process B. FIG.

If the hydrogen content after the hydrogen impregnation treatment is 3 × 10 ¹⁷ molecules / cm ³ or more, the 650 nm fluorescent defect can be almost completely removed. The temperature in the hydrogen atmosphere for obtaining this amount of impregnated synthetic quartz glass is a temperature below the melting point of the quartz glass material, in addition to being able to explode hydrogen, simplifying the production facility, and A temperature that allows efficient penetration into quartz glass is preferred. The specific temperature is 500 ° C. or lower and the lower limit is about 150 ° C.

  By this step D, defects corresponding to the fluorescence peak in the 650 nm band are suppressed.

  According to the manufacturing method described above, a defect corresponding to a fluorescence peak in the 280 nm band with extremely high fluorescence emission intensity, a defect corresponding to a fluorescence peak in the 390 nm band, and a defect corresponding to a fluorescence peak in the 650 nm band are suppressed. Quartz glass can be produced. Therefore, it is possible to manufacture a synthetic quartz glass that has an excellent transmission performance and can manufacture an optical member with few defects.

  Hereinafter, the present invention will be specifically described with reference to examples. In this example, synthetic quartz glass before hydrogen impregnation (step C) formed using a glass fine particle sintered body (step B) produced under the following sintering conditions 1 to 3, and hydrogen impregnation for this synthetic quartz glass The synthetic quartz glass after hydrogen impregnation performed under the following hydrogen impregnation treatment conditions (step D) was used as an example, and the glass fine particle sintered body (step B) produced as the following sintering condition 4 was molded. Synthetic quartz glass before hydrogen impregnation (step C) and synthetic quartz glass after hydrogen impregnation (step D) obtained by performing hydrogen impregnation treatment on the synthetic quartz glass under the following conditions are used as comparative examples. Moreover, synthetic quartz glass was manufactured with the manufacturing method of the process A-the process D except that the sintering conditions of the process B differed in each example. In addition, a present Example does not limit the scope of the present invention.

<Sintering conditions>
Sintering condition 1 (Example 1): The time for exposure to the atmosphere of 1100 ° C. to 1350 ° C. in step B is 150 minutes, and the pressure when exposed to the atmosphere of 1100 ° C. to 1350 ° C. is sintered at 10 Pa.
Sintering condition 2 (Example 2): The time of exposure to the atmosphere of 1100 ° C. to 1350 ° C. in Step B is 180 minutes, and the pressure when exposed to the atmosphere of 1100 ° C. to 1350 ° C. is sintered at 10 Pa.
Sintering condition 3 (Example 3): The exposure time in the atmosphere of 1100 ° C. to 1350 ° C. in step B is 150 minutes, and the pressure when exposed to the atmosphere of 1100 ° C. to 1350 ° C. is sintered at 1 Pa.
Sintering condition 4 (comparative example): The time when exposed to the atmosphere of 1100 ° C. to 1350 ° C. in step B is 600 minutes, and the pressure when exposed to the atmosphere of 1100 ° C. to 1350 ° C. is sintered at 5 Pa.
In this example, the thickness of the synthetic quartz glass before impregnation with hydrogen produced in Step C is 10 mm.

<Hydrogen impregnation treatment conditions>
In both the examples and comparative examples, the synthetic quartz glass before hydrogen impregnation produced in step C is subjected to hydrogen impregnation at a hydrogen atmosphere temperature of 300 ° C., a hydrogen atmosphere pressure of 7 Pa, and a treatment time of 240 minutes.

<Comparison method>
Comparative method 1: KrF excimer laser light is irradiated on the synthetic quartz glass of the example before hydrogen impregnation and the comparative example, and fluorescence emission in the 280 nm band, 390 nm band, and 650 nm band is confirmed (see Table 1).
Comparative method 2: KrF excimer laser light is irradiated on the synthetic silica glass of the examples and comparative examples after hydrogen impregnation, and fluorescence emission in the 280 nm band, 390 nm band, and 650 nm band is confirmed. Further, the transmittance of the synthetic quartz glass of this example and the comparative example and the presence or absence of deterioration with time were examined (see Table 2).

The irradiation conditions of the KrF excimer laser light are 20 mJ / Pulse / cm ² and 100 Hz for 30 minutes in both comparative methods 1 and 2. In addition, the presence or absence of fluorescence emission is defined as “no fluorescence emission” when the spectral irradiance of fluorescence peaks in the 280 nm band, 390 nm band, and 650 nm band is 5 pW / cm ³ / nm or less when irradiated under these irradiation conditions. If it exceeds ⁵ pW / cm ³ / nm, “fluorescent emission is present”.

<Contrast between Example and Comparative Example>
As shown in Table 1, in the synthetic quartz glass before hydrogen impregnation, in the comparative example, fluorescence emission was observed in all the wavelength ranges, whereas in the example, there was no fluorescence emission in the wavelength ranges other than the 650 nm band. It was confirmed.

<Contrast between Example and Comparative Example>
As shown in Table 2, in the synthetic quartz glass after hydrogen impregnation, in the comparative example, it was recognized that there was fluorescence emission in a wavelength range other than the 650 nm band, whereas in Examples 1 to 3, It was confirmed that there was no fluorescence emission in the wavelength range. Further, in the examples, it was confirmed that the transmittance was higher than that of the comparative example and that there was no deterioration with time in the comparative example.

  From the above results, in the manufacturing method in which the process D in the above-described hydrogen impregnation process condition is performed through the process B in the sintering condition 4 as in the comparative example, the fluorescence emission can be suppressed only in the 650 nm band. As described above, it has been proved that the manufacturing method in which the process D in the above-described hydrogen impregnation process condition is performed through the process B using the sintering conditions 1 to 3 can suppress the fluorescence emission in all wavelength ranges.

  In other words, it was proved that it is effective to use the process of sintering conditions 1 to 3 in the process B for suppressing the fluorescence emission in the 280 nm band and the 390 nm band. Moreover, by subjecting the synthetic quartz glass composed of the sintered glass particles sintered in the process B including the sintering conditions 1 to 3 to the process D in the above-described hydrogen impregnation process conditions, fluorescence emission in the 650 nm band is obtained. It was proved that all the fluorescent light emission contained was suppressed, and that the synthetic quartz glass had high transmittance and no deterioration with time.

  Therefore, according to the process B using the sintering conditions 1 to 3, which is an example of the production method of the present invention, a synthetic quartz glass in which fluorescence emission in the 280 nm band and the 390 nm band is suppressed can be produced. Furthermore, if the treatment of step D under the hydrogen impregnation treatment conditions, which is an example of the production method of the present invention, is performed, it is possible to produce a synthetic quartz glass in which all the fluorescence emission is suppressed and good transmittance and no deterioration with time are produced. it can. Therefore, it is possible to provide a synthetic quartz glass capable of producing an optical member that has few defects and can maintain good transmission performance over a long period of time, and a method for producing the same.

  In the above-described embodiment, the KrF excimer laser (248 nm) is exemplified as the irradiation light. However, the synthetic quartz glass manufactured by the manufacturing method of the present embodiment is not limited to this KrF excimer laser, but an ArF excimer laser. (193 nm), F2 excimer laser (157 nm), YAG-FHG laser (266 nm), Xe2 excimer lamp (172 nm), ArF excimer lamp (193 nm), and the like can obtain the same effect.

Claims (7)

The synthetic quartz glass before the hydrogen impregnation treatment has suppressed defects corresponding to the fluorescence peak in the 280 nm band and defects corresponding to the fluorescence peak in the 390 nm band,
By the hydrogen impregnation treatment, defects corresponding to the fluorescence peak in the 280 nm band, defects corresponding to the fluorescence peak in the 390 nm band, and defects corresponding to the fluorescence peak in the 650 nm band are suppressed.
Synthetic quartz glass. The synthetic quartz glass before hydrogen impregnation treatment has a spectral irradiance of 5 pW / cm ³ / nm for the fluorescence peaks in the 280 nm band and 390 nm band when irradiated with a KrF excimer laser at 20 mJ / Pulse / cm ² and 100 Hz for 30 minutes. Is
The synthetic quartz glass according to claim 1. Synthetic quartz glass before hydrogen impregnation treatment has a spectral irradiance of 5 pW / cm ³ / nm for fluorescence peaks in the 280 nm band and 390 nm band when irradiated with ArF excimer laser at 5 mJ / Pulse / cm ² and 100 Hz for 30 minutes. Is
The synthetic quartz glass according to claim 1. The hydrogen content is 3 × 10 ¹⁷ molecules / cm ³ or more,
The synthetic quartz glass according to any one of claims 1 to 3. A method for producing a synthetic quartz glass according to any one of claims 1 to 4,
Producing a quartz glass fine particle deposit by vapor phase synthesis;
A sintering step of sintering the quartz glass deposit while raising the temperature,
In the sintering step, the time during which the quartz glass is exposed to an atmosphere of 1100 ° C. to 1350 ° C. is 180 minutes or less,
A method for producing synthetic quartz glass. In the sintering step, the pressure when the quartz glass is exposed to an atmosphere of 1100 ° C. to 1350 ° C. is 1 Pa or more.
The method for producing synthetic quartz glass according to claim 5.   A synthetic quartz glass obtained by the production method according to claim 5, further comprising a hydrogen impregnation treatment step in a hydrogen atmosphere at 500 ° C. or less.