JP2009190958A - Synthetic quartz glass body and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a synthetic quartz glass body containing hydrogen molecules, having high laser resistance and capable of being manufactured for a shorter time than ever before, and a method of manufacturing the same. <P>SOLUTION: The synthetic quartz glass body having a disk shape has a hydrogen molecule concentration of 2×10<SP>16</SP>to 4×10<SP>17</SP>molecules/cm<SP>3</SP>at least at the middle point of the central axis of the disk shape, of 2×10<SP>17</SP>to 2×10<SP>18</SP>molecules/cm<SP>3</SP>at least one side of the intersecting point of the central axis and the surface of the disk shape, and of a monotone increase toward the surfaces of the disk shape from the middle point of the central axis along the central axis. The method of manufacturing a synthetic quartz body for manufacturing such synthetic quartz body is also provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a synthetic quartz glass body and a method for producing the same, and more particularly to a synthetic quartz glass body containing hydrogen molecules and a method for producing the same.

  The optical lithography technology that transfers the pattern on the photomask onto the wafer using ultraviolet light is superior in terms of cost, throughput, etc. compared to other technologies that use electron beams or X-rays. It is widely used for an exposure apparatus for manufacturing an integrated circuit.

  In recent years, with the miniaturization and high integration of LSI, the wavelength of light sources for exposure has been shortened. Conventional g-line (wavelength 436 nm), i-line (wavelength 365 nm), or KrF excimer laser (wavelength 248. 3 nm), ArF excimer laser (wavelength 193.4 nm) has recently been used. And the optical member used for this ArF excimer laser lithography apparatus has stricter requirements for transparency, homogeneity, birefringence, laser resistance and the like than before.

  High-purity synthetic quartz glass has been used as a material for optical members that meet these requirements, and improvements in optical properties are being promoted by optimizing manufacturing conditions. In particular, it is known that synthetic quartz glass contains hydrogen molecules to improve laser resistance. During the quartz glass manufacturing process, hydrogen molecules are doped into silica glass (addition and introduction). The treatment to be done has been performed.

Temperature greatly affects the diffusion of hydrogen molecules in quartz glass.
For example, when the temperature is higher than 500 ° C., diffusion becomes easy, so that the time for containing hydrogen molecules is short, which is advantageous in terms of productivity. However, when hydrogen molecules are introduced at a high temperature, reductive defects are produced in the quartz glass, and absorption is induced in the ultraviolet region when irradiated with an excimer laser. This induced absorption is due to a permanent defect called an E ′ (e-prime) center, has an absorption band with a center wavelength of 210 to 215 nm, and greatly reduces laser resistance. For this reason, introduction of hydrogen molecules (hereinafter sometimes simply referred to as hydrogen doping) must be performed at a temperature as low as possible, but the diffusion rate of hydrogen molecules in quartz glass decreases at a low temperature, for example, below 500 ° C. Therefore, there is a problem that the time required for introducing hydrogen molecules (hereinafter, simply referred to as hydrogen doping time) becomes very long and the productivity is deteriorated.

  In addition, it has been found from previous studies that hydrogen molecules affect the homogeneity of the refractive index, and it has also been found that it is important to uniformly dope hydrogen molecules. In order to dope hydrogen molecules uniformly at a low temperature, a very long time may be required, and research has been conducted on the technique. For example, Patent Document 1 describes that when a synthetic quartz glass body is heat-treated in a hydrogen-containing atmosphere at a predetermined pressure, the pressure of the hydrogen-containing gas is changed continuously or stepwise. One of the purposes of this method is to contain hydrogen molecules in the quartz glass body as uniformly as possible, and studies have been made on the difference between the average hydrogen concentration and the maximum and minimum values of the hydrogen concentration. In Patent Document 2, the ratio of the maximum value and the minimum value is specified together with the range of the average hydrogen concentration, and a study for doping hydrogen molecules in as short a time as possible without affecting the homogeneity of the refractive index. Has been made.

However, there is a problem that even if the maximum value and the minimum value of the hydrogen molecule concentration in the quartz glass body are set within a predetermined range, the homogeneity of the refractive index may be adversely affected.
In addition, there is a problem that it is difficult to keep the hydrogen molecule concentration within a predetermined range at a relatively low temperature that does not deteriorate the laser resistance and within a time that does not impair the productivity.

JP 2002-316825 A JP 2007-84427 A

  The present invention has been made in view of such problems, and provides a synthetic quartz glass body containing hydrogen molecules and having high laser resistance, which can be produced in a shorter time than before, and a method for producing the same. For the purpose.

The present invention has been made in order to solve the above problems, and is a synthetic quartz glass body having a disk shape, and at least the hydrogen molecule concentration of the synthetic quartz glass body is a midpoint of the central axis of the disk shape. 2 × 10 ¹⁶ to 4 × 10 ¹⁷ molecules / cm ³ , and 2 × 10 ¹⁷ to 2 × 10 ¹⁸ molecules / cm ³ in at least one of the intersections between the central axis and the disk-shaped surface. A synthetic quartz glass body is provided which is monotonically increased from a midpoint of the central axis toward the disk-shaped surface along the central axis.

In the case of a disc-shaped synthetic quartz glass body having such a concentration distribution of hydrogen molecules, the processing time required for introducing hydrogen molecules during manufacture is high while it is a synthetic quartz glass body having high laser resistance. Can be made a synthetic quartz glass body that is much shorter than the conventional one.
Further, with such a synthetic quartz glass body, it becomes easy to cancel (cancel) the influence on the homogeneity of the refractive index by shape correction when processing into a shape suited to a desired application.

In this case, the distribution of the measured values when the hydrogen molecule concentration y [molecules / cm ³ ] at the position x [cm] is measured with the x axis on the central axis with the midpoint of the central axis as the origin is represented by two The coefficient of determination when regression analysis is performed by the following equation is preferably 0.9 to 1.0, and the coefficient of the quadratic term is preferably 5 × 10 ^{15 to} 3 × 10 ¹⁷ (Claim 2).
Thus, with respect to the hydrogen molecule concentration distribution on the central axis, the coefficient of determination when regression analysis is performed using a quadratic equation is 0.9 to 1.0, and the coefficient of the quadratic term is 5 × 10 ^{15 to} 3 ×. If it is 10 ¹⁷ , it becomes easier to cancel the influence on the homogeneity of the refractive index by shape correction when processing the shape.

Moreover, it is preferable that the average of the OH group concentration along the central axis is 1 to 150 wtppm, and the fluctuation range of the OH group concentration along the central axis is 30 wtppm or less.
Thus, if the average of the OH group concentration along the central axis is 1 to 150 wtppm and the fluctuation range of the OH group concentration along the central axis is 30 wtppm or less, the synthetic quartz having higher laser resistance It can be a glass body.

Further, the homogeneity of the refractive index in the central axis direction is 2 × 10 ⁻⁷ to 2 × 10 ⁻⁶ , and the homogeneity of the refractive index in the direction orthogonal to the central axis is 2 × 10 ⁻⁷ to 2 × 10 6. It is preferably ⁻⁶ (claim 4).
Thus, the homogeneity of the refractive index in the central axis direction is 2 × 10 ⁻⁷ to 2 × 10 ⁻⁶ , and the homogeneity of the refractive index in the direction orthogonal to the central axis is 2 × 10 ⁻⁷ to 2 × 10 6. If it is ⁻⁶ , it becomes easier to cancel the influence on the homogeneity of the refractive index by the shape correction when processing the shape.

Moreover, if it is the above synthetic quartz glass bodies, it can be used for an optical use (Claim 5).
The synthetic quartz glass body as described above has characteristics such as high laser resistance and is suitable as a material for optical quartz glass members.

  In addition, the present invention includes at least a step of producing a disc-shaped synthetic quartz glass body and a hydrogen molecule introduction step of containing hydrogen molecules in the synthetic quartz glass body, the disc shape is formed, and contains hydrogen molecules. In the method for producing a synthetic quartz glass body, the hydrogen molecule introducing step is performed at 50 to 850 at a hydrogen partial pressure of 0.5 to 1.5 MPa and a temperature of 350 to 450 ° C. at least with respect to the synthetic quartz glass body. A step of performing heat treatment for a period of time, a step of performing heat treatment for 150 to 2500 hours at a hydrogen partial pressure of 0.01 MPa or less and a temperature of 350 to 450 ° C., a hydrogen partial pressure of 0.05 to 0.5 MPa, and a temperature of A method for producing a synthetic quartz glass body is provided, which is performed at a temperature of 350 to 450 ° C. through a stage of heat treatment for 100 to 1500 hours.

  With such a method for producing a synthetic quartz glass body, it is possible to produce a synthetic quartz glass body having high laser resistance by significantly shortening the processing time required for introducing hydrogen molecules compared to the conventional method. . And if it is the synthetic quartz glass body manufactured by such a manufacturing method of a synthetic quartz glass body, it will become easy to cancel the influence which acts on the homogeneity of a refractive index by shape correction at the time of processing a shape.

As described above, the synthetic quartz glass body according to the present invention can be manufactured in a short time while ensuring the laser resistance, and the refractive index can be easily corrected when processing the lens shape or the like. .
Also, with the method for producing a synthetic quartz glass body according to the present invention, it is possible to produce a synthetic quartz glass body with high laser resistance and easy refractive index correction during shape processing into a lens shape or the like in a short time. it can.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.
As described above, even if the maximum and minimum values of the hydrogen molecule concentration in the quartz glass body are kept within the predetermined range, there is a problem that the homogeneity of the refractive index may be adversely affected, and the laser resistance. There is a problem that it is difficult to keep the hydrogen molecule concentration within a predetermined range at a relatively low temperature that does not deteriorate the pH and within a time that does not inhibit productivity.

  Therefore, the present inventor has conducted the following studies in order to find a synthetic quartz glass body into which hydrogen molecules have been introduced at a relatively low temperature that does not deteriorate the laser resistance and in a treatment time that does not impair productivity. It was.

  In general, when the shape of quartz glass is a disk shape, the diffusion of hydrogen molecules is more dominant in the central axis direction than in the radial direction. Therefore, the concentration gradient of hydrogen molecules doped from the outside tends to be tighter in the axial direction. Furthermore, since the concentration gradient in the radial direction appears in the vicinity of the outer periphery of the disc-shaped quartz glass body, it is possible to remove the portion with the concentration gradient by peripheral grinding or the like, whereas in the axial direction, the same means are used. It is difficult to take the method of removing the concentration gradient part. This is because, in such a disk-shaped quartz glass, the doping time necessary to secure the central hydrogen concentration depends on the axial distance, that is, the thickness of the quartz glass, so that the time in the hydrogen doping process can be as long as possible. This is because it is generally performed in a state in which quartz glass is processed to a necessary minimum thickness because of a request for shortening, and there is usually no room for further reducing the thickness.

  In other words, in order to improve the laser resistance in a disk-shaped quartz glass body, it is only necessary to pay attention to the hydrogen molecule concentration distribution in the central axis direction and make it flat. However, as described above, there is a problem that it is difficult to achieve this at a relatively low temperature that does not deteriorate the laser resistance and within a time that does not impair the productivity.

FIG. 2 schematically shows the shape of a disk-shaped quartz glass body. For the sake of convenience, a diagram in which a part of the disk shape is cut away and a cross section is shown is shown.
The disc-shaped quartz glass body 11 has rotational symmetry about the central axis 12. The disk shape is a columnar shape close to a parallel plate, and has a bottom surface diameter of about 2.5 to 8 times the height (the length of the central axis 12). Hereinafter, in this specification, the center point of the central axis 12 (that is, the center of the disk shape) is the point O, the intersection point P between the central axis 12 and the surface of the quartz glass body 11, and the line having the center O and the point P as both ends. A midpoint of the minute OP is a point M, and a position N closer to the point P than the point M on the line segment OP is defined and used. In addition, the disk-shaped quartz glass body particularly used for optical applications often has a diameter of 200 to 500 mm, but is not limited thereto.

According to the study of the present inventor, in view of the severe demand for optical properties of quartz glass optical members in recent years, the definition of the hydrogen molecule concentration found in Patent Document 1, Patent Document 2, etc. is insufficient. It was found that a clearer definition is necessary with an eye on the effect of refractive index on homogeneity.
That is, even if the maximum value and the minimum value of the hydrogen molecule concentration in the quartz glass body are kept within a predetermined range as in the prior art, the overall concentration distribution gradient is irregular as shown in FIG. Would adversely affect the homogeneity of the refractive index.

  Based on these findings, the present inventor has further studied, and as a result, even if the hydrogen molecule concentration distribution in the axial direction of the disc-shaped quartz glass body is not completely flat, as shown in FIG. It has been found that if the hydrogen molecule concentration is monotonically increasing along the line, the refractive index homogeneity sufficient for an optical synthetic quartz glass member can be obtained. In other words, the introduction of hydrogen molecules can be completed in a much shorter time than completely flattening the hydrogen molecule concentration distribution, and the hydrogen molecule concentration distribution is changing monotonically, so that optical synthesis is possible. The present invention has been completed by conceiving that it is possible to correct the shape when the quartz glass body is processed into a lens shape or the like, and to cancel the influence on the homogeneity of the refractive index.

  Hereinafter, the present invention will be described in more detail with reference to the drawings, but the present invention is not limited thereto.

First, the synthetic quartz glass body according to the present invention will be described with reference to FIG. The synthetic quartz glass body according to the present invention is a synthetic quartz glass body 11 having a disk shape, and the hydrogen molecule concentration is 2 × 10 ¹⁶ to 4 × 10 ¹⁷ molecules / in the middle point O of the center axis 12 of the disk shape. cm ³ , and 2 × 10 ¹⁷ to 2 × 10 ¹⁸ molecules / cm ³ in at least one of the intersections between the central axis 12 and the surface of the disc-shaped synthetic quartz glass body 11. Furthermore, it is a condition that the distribution of hydrogen molecule concentration along the central axis 12 is monotonically increasing from the midpoint O of the central axis 12 toward the surface of the disc-shaped synthetic quartz glass body 11.

  In the present invention, the hydrogen molecule concentration at the intersection (the vicinity of the outer surface) between the central axis and the disk-shaped surface indicates a value at a position 1.5 mm inside from the outer surface. This is because the change in the hydrogen molecule concentration is steep in a region at a distance of less than 1.5 mm from the outer surface, and a stable and accurate measurement result cannot be obtained.

  With a synthetic quartz glass body having such a hydrogen concentration distribution, the processing time required for introducing hydrogen molecules during production is high while having high laser resistance by containing hydrogen molecules. The synthetic quartz glass body can be made much shorter than that. In addition, since the concentration distribution of the hydrogen molecules contained is simple, the influence on the homogeneity of the refractive index is canceled by shape correction when processing a disc-shaped synthetic quartz glass body into a desired shape such as a lens shape. It becomes easy.

The concentration of hydrogen molecules at the center of the synthetic quartz glass body 11 is usually the smallest in the synthetic quartz glass body 11, but sufficient laser resistance is obtained when the hydrogen molecule concentration at this position is less than 2 × 10 ¹⁶ molecules / cm ³ . Can't get. On the other hand, when it seems to exceed 4 × 10 ¹⁷ molecules / cm ³ , it takes excessive time to introduce hydrogen molecules. 2 × 10 ¹⁶ to 4 × 10 ¹⁷ molecules / cm ³ is an optimal range in which the time required for introducing hydrogen molecules is not excessively lengthened while ensuring laser resistance.

Further, the hydrogen molecule concentration monotonously increases from the center O to the intersection P with the outer surface of the synthetic quartz glass body 11 along the central axis 12, and the intersection between the central axis 12 and at least one of the upper and lower outer surfaces. When the hydrogen molecule concentration in the part (near the point P) is smaller than 2 × 10 ¹⁷ molecules / cm ³ , this means that the hydrogen molecule concentration distribution is very flat. It is necessary to sufficiently diffuse hydrogen molecules from the surface to the inside, and it takes a long time to dope hydrogen, which is undesirable in production.
On the other hand, when the hydrogen molecule concentration at the intersection (near the point P) between the central axis 12 and the outer surface of the synthetic quartz glass body 11 is larger than 2 × 10 ¹⁸ molecules / cm ³ , the central axis 12 of the synthetic quartz glass body is obtained. The hydrogen molecule concentration gradient along the line becomes too large. In this case, it becomes difficult to cancel the influence of the shape correction on the homogeneity of the refractive index.

  In the present invention, the monotonous increase in the hydrogen molecule concentration means that the hydrogen molecule concentration continuously increases from the center point of the central axis toward the surface and does not decrease in the middle. With such a monotonically increasing distribution, even if there is a distribution in the hydrogen molecule concentration, it is possible to easily correct it by processing to obtain an optical member having desired characteristics.

In the synthetic quartz glass body of the present invention, the x axis is taken on the center axis 12 with the center O as the origin, and the hydrogen molecule concentration y [molecules / cm ³ ] at the position x [cm] is measured. The coefficient of determination when the distribution is subjected to regression analysis by a quadratic equation is preferably 0.9 to 1.0, and the coefficient of the quadratic term is preferably 5 × 10 ^{15 to} 3 × 10 ¹⁷ .
When this coefficient of determination is less than 0.9, the distribution of hydrogen molecule concentration along the central axis becomes distorted, and the refractive index is calculated from shape correction when processing a synthetic quartz glass body into a lens shape or the like. Since it becomes difficult to cancel the influence on the homogeneity, the coefficient of determination should be in the range of 0.9 to 1.0.
Further, the coefficient of the quadratic term indicates that the gradient is gentle when it is small, and the gradient is steep when it is large, but the thickness of the optical synthetic quartz glass body is usually about 40 mm to 160 mm. The range is suitably 5 × 10 ¹⁵ to 2 × 10 ¹⁷ .

The calculation method of the coefficient of determination and the quadratic term by the above regression analysis is as follows.
Taking the center of the synthetic quartz glass body (that is, the midpoint of the central axis of the disk shape) as the origin, taking the x-axis on the central axis, along the central axis from the vicinity of one outer surface to the vicinity of the other outer surface The hydrogen molecule concentration y [molecules / cm ³ ] at the position x [cm] is measured at preferably at least 20 points at equal intervals.
Next, a secondary expression represented by the following expression (1) is applied to each measurement value (x _i , y _i ) (where i = 1, 2, 3,..., N).

In order to obtain the quadratic expression represented by the expression (1), values of a, b, and c that minimize the expression (2) shown below may be obtained according to the principle of the least square method.

And in order to obtain | require the value of a, b, c which minimizes this Formula (2), what is necessary is just to solve the simultaneous equations of following Formula (3), (4), (5). However, the value (intercept) of c may be calculated by setting it equal to the hydrogen molecule concentration [molecules / cm ³ ] at the center of the disk-shaped synthetic quartz glass body.

When a, b, and c obtained in this way are used, a quadratic regression curve of y with respect to x (formula 2) is obtained. The value of a at this time is the coefficient of the secondary term. The determination coefficient is generally represented by R ^{2. In} this case, it is represented by the following formula (6).

  In the synthetic quartz glass body of the present invention, the average OH group concentration along the central axis 12 is 1 to 150 wtppm, and the fluctuation range of the OH group concentration along the central axis 12 is 30 wtppm or less. preferable. Since the OH group concentration is related to laser resistance, in order to use it as an optical member, it is preferable to define the OH group concentration as described above in addition to the hydrogen concentration distribution. In addition, since the fluctuation of the OH group concentration affects the homogeneity of the refractive index, the fluctuation width is preferably 30 wtppm or less.

Further, with respect to the homogeneity of the refractive index, in order to meet the recent demand for optical homogeneity of optical quartz glass members, 2 × both in the direction of the central axis 12 and in the direction orthogonal to the central axis 12. 10 ^{−7 to} 2 × 10 ⁻⁶ is desirable as an optical quartz glass member.

The measuring method of each parameter in the present invention is as follows.
(Hydrogen molecule concentration)
V. K. KHOTIMCHENKO, et al. , Determinating the content of hydrodissolved in quadz glassing the methods of Raman scattering and mass spectrometry, Journal of Applied Electronics. 46, no. 6, pp. A measurement method using a Raman spectrophotometer described in 632-635. The repeatability of the measured value at the same measurement point is ± 2 × 10 ⁻¹⁵ molecules / cm ³ .

(OH group concentration)
D. M.M. DODD and D.D. B. FRASER, Optical determination of OH in fused silica, Journal of Applied Physics, Vol. 37 (1966) p. Measurement method using infrared spectrophotometer described in 3911 document. Taking the x-axis on the central axis with the center of the quartz glass body as the origin, and measuring along the central axis from the vicinity of one outer surface to the vicinity of the other outer surface, preferably at least 20 points at equal intervals, The average OH group concentration is calculated. Further, the fluctuation range of the OH group concentration means the difference between the maximum value and the minimum value of the measured values.

(Homogeneity of refractive index)
Measurement with an optical interferometer (Mark GPI xp, manufactured by Zygo) using a He—Ne laser (wavelength 632.8 nm) as a light source based on the description of JIS R3252 “Method of measuring homogeneity by glass laser interferometry”. With respect to the central axis direction of the quartz glass body, measurement is performed on a concentric circle of the disk and a region having a diameter ratio of 90% or more. Further, in the direction perpendicular to the central axis, after performing hydrogen doping, orientation flat processing parallel to each other and parallel to the central axis is performed in the vicinity of the outer periphery of the disc-shaped synthetic quartz glass body as shown in FIG. The measurement was performed after applying to both sides. The processing thickness of the orientation flat is 10 mm or less, and both sides are equal in thickness. The measurement area is the entire orientation flat.

Next, a method for producing the above synthetic quartz glass body will be described.
An example of a method for producing a synthetic quartz glass body according to the present invention is shown in FIG.

First, as shown in FIG. 5A, a disc-shaped synthetic quartz glass body is produced (step a). For example, first, synthetic quartz glass is synthesized and formed into a disk shape.
In recent years, the synthetic method of synthetic quartz glass for optics is mainly the soot method in which silica fine particles obtained by flame hydrolysis of silica raw material are deposited and grown on a target and then converted into transparent glass. The invention is not limited to this.
Then, the synthesized synthetic quartz glass body is formed into a disk shape as shown in FIG. The disk shape here is, for example, a shape having a diameter of 200 to 500 mm and a diameter of about 2.5 to 8 times the height.

  Next, as shown in FIG. 5B, hydrogen molecules are contained in the disc-shaped synthetic quartz glass body thus manufactured (step b). At this time, in the method for producing a synthetic quartz glass body of the present invention, the hydrogen molecule introduction step is performed through at least the following three stages. That is, as a first stage, a hydrogen partial pressure is set to 0.5 to 1.5 MPa, a temperature is set to 350 to 450 ° C., and heat treatment is performed for 50 to 850 hours (stage b-1). Is set to 0.01 MPa or less, the temperature is set to 350 to 450 ° C., and heat treatment is performed for 150 to 2500 hours (step b-2). Subsequently, the hydrogen partial pressure is set to 0.05 to 0.5 MPa, 350 to 450 as the third step. A heat treatment is performed at 100 ° C. for 100-1500 hours (step b-3). The hydrogen partial pressure, temperature, and time at each stage are appropriately selected within the above range depending on the shape and dimensions of the disk.

Here, the role played by each of the above steps will be described.
The heat treatment in the first stage (stage b-1) is intended to contain a large amount of hydrogen molecules in the quartz glass. After the heat treatment at this stage, as shown in FIG. 3, many hydrogen molecules exist in the vicinity of the outer surface of the disc-shaped synthetic quartz glass body.

  The heat treatment in an atmosphere substantially free of hydrogen in the second stage (stage b-2) has the effect of diffusing hydrogen molecules inside the quartz glass and suppressing the concentration of hydrogen molecules near the outer surface from becoming excessively high. is there. Here, the atmosphere that does not substantially contain hydrogen refers to an atmosphere that is mostly made of non-hydrogen gas such as air, nitrogen, or helium, and has a hydrogen partial pressure of 0.01 MPa or less. FIG. 4 shows a distribution of hydrogen molecule concentration along the central axis of the synthetic quartz glass body at the end of the second stage. The concentration of hydrogen molecules at the intersection P between the central axis 12 and the outer surface of the disc-shaped synthetic quartz glass body 11 is almost 0, but the concentration increases toward the inside and takes a maximum value at the point N, from which the center O Gradually down towards The hydrogen molecule concentration at the center O increases after the first stage.

The subsequent third stage (stage b-3) heat treatment in a low hydrogen partial pressure increases the concentration of hydrogen molecules at the intersection P to a range of 2 × 10 ¹⁷ to 2 × 10 ¹⁸ molecules / cm ³ , The molecular concentration is in the range of 2 × 10 ¹⁶ to 4 × 10 ¹⁷ molecules / cm ³ , and the hydrogen molecule concentration along the central axis is finally from the center O toward the intersection P as shown in FIG. The distribution increases monotonically.
By the heat treatment through such a stage, for example, the x axis is taken on the center axis with the center as the origin, the hydrogen molecule concentration y [molecule / cm ³ ] at the position x [cm] is measured, and each measured value is secondarily measured. A synthetic quartz glass body having a coefficient of determination of 0.9 to 1.0 and a coefficient of a quadratic term of 5 × 10 ^{15 to} 3 × 10 ¹⁷ when regression analysis is performed using an equation can be obtained.

  In such a method for producing a synthetic quartz glass body, the heat treatment temperature in the step of introducing hydrogen molecules into the synthetic quartz glass body is set to a low temperature such as 450 ° C. or less. It is possible to suppress the deterioration of the laser resistance due to this reducing defect.

  Hereinafter, the present invention will be described in detail with reference to examples, comparative examples, and experimental examples. However, these examples are illustrative only, and the present invention should be limited by the following examples. is not.

Example 1
According to the method for producing a synthetic quartz glass body of the present invention as shown in FIG. 5, a synthetic quartz glass body was produced.
A porous soot body prepared by depositing silica soot by flame hydrolysis of silicon tetrachloride vaporized on a rotating target in oxyhydrogen was temporarily sintered at 1000 ° C. in a vacuum atmosphere, and then at 1600 ° C. in a vacuum atmosphere. A transparent vitrified quartz glass ingot was produced. The quartz glass ingot was fixed to a lathe and heated with an oxyhydrogen flame to obtain a cylindrical quartz glass body having a length of 550 mm and an outer diameter of 200 mm. The columnar quartz glass body is placed in a high-purity graphite container having an inner diameter of 420 mm and a height of 280 mm, and heated at 1800 ° C. in a vacuum atmosphere in a vacuum heating furnace to be deformed by its own weight, A disc-shaped quartz glass molded body having an outer diameter of 420 mm and a thickness of 120 mm was obtained, and an impurity-contaminated portion near the surface was removed to obtain a disc-shaped synthetic quartz glass body having an outer diameter of 360 mm and a thickness of 80 mm. Next, the disk-shaped synthetic quartz glass body is subjected to a slow strain treatment, held at 1150 ° C. for 45 hours in an atmospheric heating furnace, then gradually cooled to 900 ° C. at a cooling rate of 2 ° C./h, and then allowed to cool to room temperature. went.

This disk-shaped synthetic quartz glass body was doped with hydrogen at the hydrogen partial pressure, temperature, and time shown in Table 1 below. The refractive index homogeneity in the central axis direction after hydrogen doping is 1.7 × 10 ⁻⁶ , and the refractive index homogeneity in the direction orthogonal to the central axis direction is 1.8 × 10 ⁻⁶ . Suitability was good. Thereafter, the quartz glass body was disassembled and measured at 21 points at equal intervals from one outer surface vicinity portion to the other outer surface vicinity portion along the central axis. became. A regression analysis was performed on this distribution using a quadratic equation, and the coefficient of determination and the coefficient of the quadratic term were determined. Further, the OH group concentration was measured at the same measurement location as the hydrogen molecule concentration measurement, and the average OH group concentration and the fluctuation range of the OH group concentration were determined.

(Example 2)
A porous soot body prepared by depositing silica soot by flame hydrolysis of silicon tetrachloride vaporized on a rotating target in oxyhydrogen was temporarily sintered at 1100 ° C. in a vacuum atmosphere, and then at 1600 ° C. in a vacuum atmosphere. A transparent vitrified quartz glass ingot was produced. The quartz glass ingot was fixed to a lathe and heated with an oxyhydrogen flame to obtain a cylindrical quartz glass body having a length of 550 mm and an outer diameter of 200 mm. The columnar quartz glass body is placed in a high-purity graphite container having an inner diameter of 420 mm and a height of 280 mm, and heated at 1800 ° C. in a vacuum atmosphere in a vacuum heating furnace to be deformed by its own weight, A disc-shaped quartz glass molded body having an outer diameter of 420 mm and a thickness of 120 mm was obtained, and an impurity-contaminated portion near the surface was removed to obtain a disc-shaped synthetic quartz glass body having an outer diameter of 360 mm and a thickness of 80 mm. Next, the disk-shaped synthetic quartz glass body is subjected to a slow strain treatment, held at 1150 ° C. for 45 hours in an atmospheric heating furnace, then gradually cooled to 900 ° C. at a cooling rate of 2 ° C./h, and then allowed to cool to room temperature. went.

This disk-shaped synthetic quartz glass body was doped with hydrogen at the hydrogen partial pressure, temperature, and time shown in Table 1. The homogeneity of the refractive index in the central axis direction after hydrogen doping is 1.6 × 10 ⁻⁶ , and the homogeneity of the refractive index in the direction orthogonal to the central axis direction is 1.8 × 10 ⁻⁶ . Suitability was good. Thereafter, the quartz glass body was disassembled, and the hydrogen molecule concentration was measured at 21 points at equal intervals along the central axis from the vicinity of one outer surface to the vicinity of the other outer surface. The distribution shown in FIG. became. A regression analysis was performed on this distribution using a quadratic equation, and the coefficient of determination and the coefficient of the quadratic term were determined. Further, the OH group concentration was measured at the same measurement location as the hydrogen molecule concentration measurement, and the average OH group concentration and the fluctuation range of the OH group concentration were determined.

(Example 3)
A porous soot body prepared by depositing silica soot by flame hydrolysis of silicon tetrachloride vaporized on a rotating target in oxyhydrogen was temporarily sintered at 1100 ° C. in a vacuum atmosphere, and then at 1600 ° C. in a vacuum atmosphere. A cylindrical vitreous silica ingot was produced by vitrification. The quartz glass ingot was fixed to a lathe and heated with an oxyhydrogen flame to obtain a cylindrical quartz glass body having a length of 500 mm and an outer diameter of 100 mm. The columnar quartz glass body is placed in a high purity graphite container having an inner diameter of 260 mm and a height of 100 mm, and heated at 1800 ° C. in a vacuum atmosphere in a vacuum heating furnace to perform deformation by its own weight, A disc-shaped quartz glass molded body having an outer diameter of 260 mm and a thickness of 70 mm was obtained, and an impurity-contaminated portion near the surface was removed to obtain a disc-shaped synthetic quartz glass body having an outer diameter of 220 mm and a thickness of 40 mm. Next, the quartz glass body was kept at 1150 ° C. for 45 hours in an atmospheric heating furnace for slow strain treatment, then slowly cooled to 900 ° C. at a cooling rate of 2 ° C./h, and then allowed to cool to room temperature.

This disk-shaped synthetic quartz glass body was doped with hydrogen at the hydrogen partial pressure, temperature, and time shown in Table 1. The homogeneity of the refractive index in the central axis direction after hydrogen doping is 1.5 × 10 ⁻⁶ , and the homogeneity of the refractive index in the direction perpendicular to the central axis direction is 1.7 × 10 ⁻⁶ . Suitability was good. Thereafter, the quartz glass body was disassembled, and the hydrogen molecule concentration was measured at 21 points from the vicinity of one outer surface to the vicinity of the other outer surface along the central axis. As a result, the distribution shown in FIG. became. A regression analysis was performed on this distribution using a quadratic equation, and the coefficient of determination and the coefficient of the quadratic term were determined. Further, the OH group concentration was measured at the same measurement location as the hydrogen molecule concentration measurement, and the average OH group concentration and the fluctuation range of the OH group concentration were determined.

(Comparative Example 1)
A porous soot body prepared by depositing silica soot by flame hydrolysis of silicon tetrachloride vaporized on a rotating target in oxyhydrogen was temporarily sintered at 900 ° C. in a vacuum atmosphere, and then at 1600 ° C. in a vacuum atmosphere. A cylindrical vitreous silica ingot was produced by vitrification. The quartz glass ingot was fixed to a lathe and heated with an oxyhydrogen flame to obtain a cylindrical quartz glass body having a length of 550 mm and an outer diameter of 200 mm. The columnar quartz glass body is placed in a high-purity graphite container having an inner diameter of 420 mm and a height of 280 mm, and heated at 1800 ° C. in a vacuum atmosphere in a vacuum heating furnace to be deformed by its own weight, A disc-shaped quartz glass molded body having an outer diameter of 420 mm and a thickness of 120 mm was obtained, and an impurity-contaminated portion near the surface was removed to obtain a disc-shaped synthetic quartz glass body having an outer diameter of 360 mm and a thickness of 80 mm. Next, the quartz glass body was kept at 1150 ° C. for 45 hours in an atmospheric heating furnace for slow strain treatment, then slowly cooled to 900 ° C. at a cooling rate of 2 ° C./h, and then allowed to cool to room temperature.

This disk-shaped synthetic quartz glass body was doped with hydrogen at the hydrogen partial pressure, temperature, and time shown in Table 1. The homogeneity of the refractive index in the central axis direction after hydrogen doping is 4.5 × 10 ⁻⁶ , and the homogeneity of the refractive index in the direction perpendicular to the central axis direction is 5.7 × 10 ^−6. The suitability as a member was unsuitable. Thereafter, the quartz glass body was disassembled and measured at 21 points at equal intervals along the central axis from the vicinity of one outer surface to the vicinity of the other outer surface. As a result, the distribution shown in FIG. became. A regression analysis was performed on this distribution using a quadratic equation, and the coefficient of determination and the coefficient of the quadratic term were determined. Further, the OH group concentration was measured at the same measurement location as the hydrogen molecule concentration measurement, and the average OH group concentration and the fluctuation range of the OH group concentration were determined.

(Comparative Example 2)
A porous soot body prepared by depositing silica soot by flame hydrolysis of silicon tetrachloride vaporized on a rotating target in oxyhydrogen was temporarily sintered at 900 ° C. in a vacuum atmosphere, and then at 1600 ° C. in a vacuum atmosphere. A cylindrical vitreous silica ingot was produced by vitrification. The quartz glass ingot was fixed to a lathe and heated with an oxyhydrogen flame to obtain a cylindrical quartz glass body having a length of 500 mm and an outer diameter of 100 mm. The columnar quartz glass body is placed in a high purity graphite container having an inner diameter of 260 mm and a height of 100 mm, and heated at 1800 ° C. in a vacuum atmosphere in a vacuum heating furnace to perform deformation by its own weight, A disc-shaped quartz glass molded body having an outer diameter of 260 mm and a thickness of 70 mm was obtained, and an impurity-contaminated portion near the surface was removed to obtain a disc-shaped synthetic quartz glass body having an outer diameter of 220 mm and a thickness of 40 mm. Next, the quartz glass body was kept at 1150 ° C. for 45 hours in an atmospheric heating furnace for slow strain treatment, then slowly cooled to 900 ° C. at a cooling rate of 2 ° C./h, and then allowed to cool to room temperature.

This disk-shaped synthetic quartz glass body was doped with hydrogen at the hydrogen partial pressure, temperature, and time shown in Table 1. The homogeneity of the refractive index in the central axis direction after hydrogen doping is 3.4 × 10 ⁻⁶ , and the homogeneity of the refractive index in the direction perpendicular to the central axis direction is 4.1 × 10 ^−6. The suitability as a member was unsuitable. Then, the quartz glass body was disassembled, and the hydrogen molecule concentration was measured at equal intervals from the vicinity of one outer surface to the vicinity of the other outer surface along the central axis, and the distribution shown in FIG. became. A regression analysis was performed on this distribution using a quadratic equation, and the coefficient of determination and the coefficient of the quadratic term were determined. Further, the OH group concentration was measured at the same measurement location as the hydrogen molecule concentration measurement, and the average OH group concentration and the fluctuation range of the OH group concentration were determined.

(Comparative Example 3)
A porous soot body prepared by depositing silica soot by flame hydrolysis of silicon tetrachloride vaporized on a rotating target in oxyhydrogen is made into a transparent glass at 1600 ° C in a vacuum atmosphere to produce a cylindrical quartz glass ingot. did. The quartz glass ingot was fixed to a lathe and heated with an oxyhydrogen flame to obtain a cylindrical quartz glass body having a length of 550 mm and an outer diameter of 200 mm. The columnar quartz glass body is placed in a high-purity graphite container having an inner diameter of 420 mm and a height of 280 mm, and heated at 1800 ° C. in a vacuum atmosphere in a vacuum heating furnace to be deformed by its own weight, A disc-shaped quartz glass molded body having an outer diameter of 420 mm and a thickness of 120 mm was obtained, and an impurity-contaminated portion near the surface was removed to obtain a disc-shaped synthetic quartz glass body having an outer diameter of 360 mm and a thickness of 80 mm. Next, the quartz glass body was kept at 1150 ° C. for 45 hours in an atmospheric heating furnace for slow strain treatment, then slowly cooled to 900 ° C. at a cooling rate of 2 ° C./h, and then allowed to cool to room temperature.

This disk-shaped synthetic quartz glass body was doped with hydrogen at the hydrogen partial pressure, temperature, and time shown in Table 1. The homogeneity of the refractive index in the central axis direction after hydrogen doping is 3.8 × 10 ⁻⁶ , and the homogeneity of the refractive index in the direction orthogonal to the central axis direction is 4.9 × 10 ^−6. The suitability as a member was unsuitable. Thereafter, the quartz glass body was disassembled and measured at 21 points along the central axis from the vicinity of one outer surface to the vicinity of the other outer surface at equal intervals, and the distribution shown in FIG. became. A regression analysis was performed on this distribution using a quadratic equation, and the coefficient of determination and the coefficient of the quadratic term were determined. Further, the OH group concentration was measured at the same measurement location as the hydrogen molecule concentration measurement, and the average OH group concentration and the fluctuation range of the OH group concentration were determined.

(Experimental example)
A porous soot body prepared by depositing silica soot by flame hydrolysis of silicon tetrachloride vaporized on a rotating target in oxyhydrogen was temporarily sintered at 1000 ° C. in a vacuum atmosphere, and then at 1600 ° C. in a vacuum atmosphere. A transparent vitrified quartz glass ingot was produced. The quartz glass ingot was fixed to a lathe and heated with an oxyhydrogen flame to obtain a cylindrical quartz glass body having a length of 550 mm and an outer diameter of 200 mm. The columnar quartz glass body is placed in a high purity graphite container having an inner diameter of 420 mm and a height of 280 mm, and is subjected to a process of heating at 1800 ° C. in a vacuum atmosphere in a vacuum heating furnace to cause deformation by its own weight, A quartz glass molded body having an outer diameter of 420 mm and a thickness of 120 mm was obtained, and further, an impurity-contaminated portion near the surface was removed to obtain a quartz glass body having an outer diameter of 360 mm and a thickness of 80 mm. Next, the disk-shaped synthetic quartz glass body is subjected to a slow strain treatment, held at 1150 ° C. for 45 hours in an atmospheric heating furnace, then gradually cooled to 900 ° C. at a cooling rate of 2 ° C./h, and then allowed to cool to room temperature. went.

This disc-shaped synthetic quartz glass body was doped with hydrogen at the hydrogen partial pressure, temperature, and time shown in Table 1 below. The homogeneity of the refractive index in the central axis direction after hydrogen doping is 1.6 × 10 ⁻⁶ , and the homogeneity of the refractive index in the direction orthogonal to the central axis direction is 1.7 × 10 ⁻⁶ . Although the suitability was good, the time required for hydrogen dope was as extremely long as 5500 hours, which was unsuitable for industrial mass production. Thereafter, the quartz glass body was disassembled and measured at 21 points at equal intervals from one surface vicinity to the other surface vicinity along the central axis. The distribution shown in FIG. became. A regression analysis was performed on this distribution using a quadratic equation, and the coefficient of determination and the coefficient of the quadratic term were determined. Further, the OH group concentration was measured at the same location as the hydrogen molecule concentration measurement, and the average OH group concentration and the fluctuation range of the OH group concentration were determined.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

It is a graph which shows an example of the hydrogen molecule concentration along the central axis in the present invention. It is a schematic diagram which shows the shape of the synthetic quartz glass body of a disk shape in this invention including a cross section. It is a graph which shows an example of the hydrogen molecule concentration along the central axis at the time of completing the first stage of hydrogen doping in the present invention. It is a graph which shows an example of the hydrogen molecule concentration along the central axis at the time of completing the second stage of hydrogen doping in the present invention. It is a flowchart which shows an example of the manufacturing method of the synthetic quartz glass body in this invention. 3 is a graph showing the hydrogen molecule concentration along the central axis of Example 1. FIG. 6 is a graph showing the hydrogen molecule concentration along the central axis of Example 2. FIG. 10 is a graph showing the hydrogen molecule concentration along the central axis of Example 3. 5 is a graph showing the hydrogen molecule concentration along the central axis of Comparative Example 1. 10 is a graph showing the hydrogen molecule concentration along the central axis of Comparative Example 2. 10 is a graph showing the hydrogen molecule concentration along the central axis of Comparative Example 3. The example of the hydrogen molecule concentration along the central axis in the past is shown. It is a graph showing the hydrogen molecule concentration along the central axis of an experimental example. It is the schematic which looked at the disk-shaped synthetic quartz glass body from the top at the time of measuring the homogeneity of the refractive index in the direction orthogonal to the central axis.

Explanation of symbols

  11 ... quartz glass body, 12 ... central axis.

Claims (6)

A synthetic quartz glass body having a disk shape,
At least the hydrogen molecule concentration of the synthetic quartz glass body is
2 × 10 ¹⁶ to 4 × 10 ¹⁷ molecules / cm ³ at the midpoint of the central axis of the disk shape,
2 × 10 ¹⁷ to 2 × 10 ¹⁸ molecules / cm ³ in at least one of the intersections between the central axis and the disk-shaped surface;
A synthetic quartz glass body, which is monotonically increasing from the midpoint of the central axis toward the disk-shaped surface along the central axis. The distribution of measured values obtained by measuring the hydrogen molecule concentration y [molecules / cm ³ ] at the position x [cm] with the midpoint of the central axis as the origin and the x axis on the central axis is expressed by a quadratic expression 2. The synthetic quartz glass according to claim 1, wherein a coefficient of determination when regression analysis is performed is 0.9 to 1.0, and a coefficient of a quadratic term is 5 × 10 ^{15 to} 3 × 10 ^17. body.   The average of the OH group concentration along the central axis is 1 to 150 wtppm, and the fluctuation range of the OH group concentration along the central axis is 30 wtppm or less. The synthetic quartz glass body described. The homogeneity of the refractive index in the central axis direction is 2 × 10 ⁻⁷ to 2 × 10 ⁻⁶ , and the homogeneity of the refractive index in the direction orthogonal to the central axis is 2 × 10 ⁻⁷ to 2 × 10 ^−6. The synthetic quartz glass body according to any one of claims 1 to 3, wherein:   The synthetic quartz glass body according to any one of claims 1 to 4, wherein the synthetic quartz glass body is used for optical applications. Manufacturing a synthetic quartz glass body having a disk shape and containing hydrogen molecules, including at least a step of producing a disc-shaped synthetic quartz glass body and a hydrogen molecule introduction step of containing hydrogen molecules in the synthetic quartz glass body In the way to
The hydrogen molecule introduction step includes at least
The synthetic quartz glass body is subjected to a heat treatment at a hydrogen partial pressure of 0.5 to 1.5 MPa and a temperature of 350 to 450 ° C. for 50 to 850 hours,
A hydrogen partial pressure of 0.01 MPa or less, a temperature of 350 to 450 ° C., and a heat treatment in 150 to 2500 hours;
A method for producing a synthetic quartz glass body comprising: performing a heat treatment at a hydrogen partial pressure of 0.05 to 0.5 MPa and a temperature of 350 to 450 ° C. for 100 to 1500 hours.

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