JP4911726B2 - Surface treatment method for quartz glass articles - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is used for a quartz glass article having a rough surface, for example, a quartz glass article having a recess that is difficult to mechanically polish, a quartz glass substrate having a step or unevenness, or a semiconductor heat treatment having a curved surface. The present invention relates to a surface treatment method for improving the surface roughness of a quartz glass tube, a quartz glass jig, such as a groove portion of a quartz glass boat.

  In order to form a very smooth surface in a quartz glass mask substrate or a quartz glass substrate for semiconductor film deposition, high-precision polishing using an abrasive such as cerium oxide has been performed. These are widely used because they can form a very smooth surface with a surface roughness Ra value (the definition will be described later) of about 5 angstroms (0.5 nm), and also can ensure the flatness of the entire substrate. These polishing methods are for polishing a quartz glass substrate on one side or both sides simultaneously while flowing abrasive grains on a rotating platen. It is impossible to carry out on uneven and uneven surfaces.

In addition, because the surfaces of quartz glass tubes and quartz glass rods are curved and the above-mentioned polishing is impossible, the accuracy is lowered, but the flame partially melts with the oxyhydrogen burner flame. Polishing (fire polishing) is performed.
When performing such flame polishing, the surface condition of the surface is improved, but the quartz glass article is exposed to a high-temperature flame (usually said to be about 2200 ° C.), so that partial deformation or gas pressure causes partial There is a drawback that the surface shape is deformed due to the formation of general irregularities.

  Similarly, the groove portion of the quartz glass boat is formed by mechanically grinding the groove on the quartz glass rod at regular intervals. Flame polishing is used for this groove surface because the above-described polishing treatment is impossible, but the problem of fluttering of the groove due to flame polishing is often a problem.

On the other hand, Patent Document 1 describes a method of heat-treating a silica glass jig at a temperature of at least 800 ° C. in a water vapor atmosphere as a treatment method aimed at doping silica glass with OH groups. However, Patent Document 1 does not consider surface roughness and thermal denaturation, and does not describe anything about surface roughness.
JP-A-8-250572 Physical Science data 15 handbook of glass data Part A silica glass and binary silicate glasses, ELSEVIER 1983 PP.79 Fig.96

  The present invention is the same as that of flame polishing on the surface of a quartz glass substrate or curved surface having a step or unevenness that cannot be mechanically polished, a quartz glass tube or rod having a groove, and a quartz glass jig using them. It is an object of the present invention to provide a surface treatment method for a quartz glass article, which can be smoothed without causing a change in shape of the surface to a certain degree of surface roughness.

  As a result of intensive studies to solve such problems, the inventors have found that the surface roughness is improved by heating and holding quartz glass having a rough surface in the presence of water vapor, and the surface roughness is reduced. The present invention was completed by finding that the improvement is expressed as a function of temperature and time, and at the same time, the change in surface roughness is in a competitive relationship with the viscous deformation of quartz glass, and finding appropriate conditions.

That is, in the surface treatment method for a quartz glass article of the present invention, the quartz glass article having a rough surface is maintained at 800 ° C. or more and 1250 ° C. or less in an atmosphere including a water vapor partial pressure of 0.001 MPa or more and 0.1 MPa or less, A method for treating a surface of a quartz glass article that improves the surface roughness (surface roughness) of the quartz glass article by treating the surface of the quartz glass article,
The surface roughness before processing of the quartz glass article is 130 nm to 400 nm in terms of Ra value, and the surface roughness after processing is 1 nm to 120 nm in terms of Ra value,
The lower limit value t _min of the processing time of the quartz glass article is determined by the following formula (1), and the upper limit value t _max of the processing time of the quartz glass article is determined by the following formula (2) .
[In the above formulas (1) and (2), t _min is the lower limit value (time) of the processing time , t _max is the upper limit value (time) of the processing time, R is the surface roughness Ra value (nm) before processing, T is the processing temperature (° C)]

  In the present invention, it is preferable that the surface roughness of the quartz glass article before processing is 130 nm to 400 nm in terms of Ra value, and the surface roughness after processing is 1 nm to 120 nm in terms of Ra value. In the present invention, the surface roughness of the quartz glass article before treatment is referred to as initial surface roughness.

In the present invention, it is preferable that the lower limit value t _min of the processing time of the quartz glass article is determined by the following mathematical formula (1). In addition, it is preferable that the upper limit value t _max of the processing time of the quartz glass article is determined by the following mathematical formula (2).

[In the above formulas (1) and (2), t _min is the lower limit value (time) of the processing time, t _max is the upper limit value (time) of the processing time, R is the surface roughness Ra value (nm) before processing, T is the processing temperature (° C)]

  According to the present invention, a conventional quartz glass substrate having a step or unevenness that cannot be mechanically polished, a curved surface, or a quartz glass tube or rod having a groove, and a surface of a quartz glass jig using them are flame-polished. The surface can be smoothed to the same degree of surface roughness without causing a change in shape of the surface.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the illustrated examples are illustrative only, and various modifications can be made without departing from the technical idea of the present invention. .

  In the surface treatment method for a quartz glass article of the present invention, the quartz glass article having a rough surface is held at a high temperature of 800 ° C. or more and 1250 ° C. or less in an atmosphere containing a water vapor partial pressure of 0.001 MPa or more and 0.1 MPa or less, The surface roughness of the quartz glass article is improved by heat-treating the surface of the quartz glass article.

  In the present invention, the evaluation based on the surface roughness Ra was performed as an index quantitatively indicating the decrease in the surface roughness of the sample obtained by the heat treatment. This surface roughness Ra is defined by the following mathematical formula (3).

In the mathematical formula (3), the grid points on the surface of the vertical M point and the horizontal N point are measurement points, the average of the height is represented by u, and the coordinates of each measurement point are (x _k , y _i ), The height there is z.
In the present invention, the apparatus for measuring the surface roughness Ra value is not particularly limited, and a known surface roughness measuring machine, for example, a stylus type surface roughness meter or a laser microscope can be used.

  In the present invention, the water vapor partial pressure condition in the surface treatment is 0.001 MPa or more and 0.1 MPa or less, and preferably 0.01 MPa or more and 0.1 MPa or less. In the present invention, the surface roughness can be improved by setting the water vapor partial pressure to 0.001 MPa or more. However, by setting the water vapor partial pressure to 0.01 MPa or more, the surface roughness can be increased more quickly and efficiently. This can be improved and is more preferable. In order to make the water vapor partial pressure exceed 0.1 MPa (that is, atmospheric pressure), a large-scale apparatus is required and costs are high. However, the present invention can achieve the object without applying pressure, so that it is industrial. Very advantageous.

  In the present invention, the temperature condition in the surface treatment is 800 ° C. or more and 1250 ° C. or less, and more preferably 1100 ° C. or more and 1200 ° C. or less. In the present invention, surface smoothing proceeds under a temperature condition of 800 ° C. or higher. However, when the temperature condition exceeds 1250 ° C., thermal deformation of the quartz glass article increases, so that the processing temperature is set to 800 ° C. or higher and 1250 ° C. or lower. Since thermal deformation of quartz glass becomes substantially significant at 1100 ° C. or higher, management of heat treatment time is important in a processing temperature range of 1100 ° C. or higher and 1250 ° C. or lower.

  Regarding the improvement of the surface roughness according to the present invention, details of the flattening mechanism are unclear, but from the results of Example 1 in which the processing time described later is changed, the change in the processing time and the surface roughness Ra is approximated by a primary reaction. It was found that the Arrhenius type can be applied to the rate constant of the flattening reaction (Table 2 and FIG. 9). That is, the value x (nm) of the surface roughness Ra shown in FIG. 9 is expressed by the following mathematical formula (4). FIG. 9 is a graph showing the results of the surface roughness with respect to the processing time of Sample A (initial surface roughness Ra value: about 150 nm) of Example 1.

The equation (4) is a time-dependent change equation of the surface roughness Ra. In the equation (4), x is the surface roughness Ra (unit: nm), t is a processing time (unit: hour), A and k ₁ Is a constant. From the result of the sample A of Example 1, the constant A = 156 nm and the reaction rate constant k ₁ = 2.04 × 10 ⁻² (h ⁻¹ ), and the broken line in FIG. 9 can be obtained.
In addition, when the initial surface roughness is 300 nm and the equation (4) is A = 300 nm, the result of Example 1 gives very good consistency as well, so that the equation (4) represents the initial surface roughness R. And can be expressed as the following mathematical formula (5).

In the above equation (5), x is the surface roughness Ra (Unit: nm), t is treatment time (unit: hour), R is the initial surface roughness Ra (Unit: nm), _{k 1} is a constant.
Furthermore, since the reaction rate constant is an Arrhenius type, the reaction rate constant k ₁ is expressed by the following formula (6) using the activation energy E, the absolute temperature T ₁ (K), and the constant k ₀ .

In Equation (6), k ₁ is a reaction rate constant, E is an activation energy, T ₁ is an absolute temperature (unit: K), and k ₀ is a constant.
From the results of surface roughness in Example 1 (treatment temperature: 1200 ° C.) and Example 3 (treatment temperature: 1000 ° C.) with different treatment temperatures, which will be described later, the reaction rate constant kn at a certain temperature T _n is _expressed by the following formula ( It was found that it was given in 7).

In the equation (7), _{T n} is the processing temperature (unit: K), _{k n} is the reaction rate constant in the processing temperature _{T n.}
Further, from the results of Examples 1 and 5 and 6 in which the water vapor partial pressure described later was changed, although the water vapor partial pressure has some influence on the reaction rate, the influence is small compared to the temperature condition, and the water vapor partial pressure In the range of 0.012 MPa to 0.085 MPa, it was found that there is no practical problem even if the above formulas (5) to (7) are applied. However, as shown in Example 7, the reaction becomes slow when the water vapor partial pressure is 0.004 MPa or less. Therefore, in order to apply these equations, it is preferable to set the water vapor partial pressure to 0.01 MPa or more.

  The surface treatment method of the present invention is suitable for improving the surface roughness of a quartz glass article having an initial surface roughness Ra value of 130 nm or more. Usually, when the Ra value is 130 nm or more, as shown in FIG. 2A, the object on the other side looks slightly blurred due to light scattering on the surface. FIG. 2A is a photograph of a quartz glass plate (sample A before processing in Example 1) having a surface roughness Ra value of about 150 nm.

According to the present invention, the surface roughness after processing of the quartz glass article can be 120 nm or less in terms of Ra value. When the Ra value is 120 nm or less, as shown in FIG. 2 (b), the quartz glass article is sufficiently transparent so that the other side can be visually recognized, and has almost the same appearance as the quartz glass article subjected to flame polishing. Can be presented. FIG. 2B is a photograph of a quartz glass plate having a surface roughness Ra value of 56 nm (Sample A after 48 hours treatment in Example 1).
The lower limit of the surface roughness after the treatment of the quartz glass article is not particularly limited, but it is preferable to set the Ra value to 1 nm or more. When the initial surface roughness is an Ra value of 130 nm or more, the treatment time is unnecessarily long to achieve a surface roughness after treatment of less than 1 nm, which is not industrially preferable.

  The upper limit value of the initial surface roughness of the quartz glass article applied to the surface treatment method of the present invention is not particularly limited, but when obtaining a quartz glass article having a Ra value of 120 nm or less after the treatment, the initial surface roughness is obtained. It is preferable to select a quartz glass article having a Ra value of 400 nm or less.

  In the present invention, the minimum processing time required for the surface roughness after processing to achieve a desired numerical value can be calculated using Equation (5) and Equation (7). For example, the minimum processing time necessary for obtaining a quartz glass article having a surface roughness after treatment of 120 nm or less in Ra value is expressed by the following equation using Equation (5) and Equation (7). Can do. That is, substituting x = 120 into Equation (5) and solving Equation (5) and Equation (7) for t yields the following Equation (1).

In the formula (1), t _min is a processing time (unit: hour) until the surface roughness of the quartz glass article reaches 120 nm in terms of Ra value, T is a processing temperature (unit: ° C.), and R is an initial surface roughness. Ra (unit: nm) is shown.
The surface roughness Ra of the quartz glass surface can be flattened to 120 nm or less by applying a treatment time equal to or greater than t _min calculated by the mathematical formula (1).

  Since the improvement of the surface roughness in the present invention is accompanied by a change in the structure of the quartz glass at a high temperature, plastic deformation accompanying the viscous flow of the entire quartz glass also proceeds simultaneously. In order to achieve the improvement of the surface roughness while suppressing the deformation of the entire quartz glass, which is the object of the present invention, it is necessary to set the heat treatment to a condition in which the plastic deformation of the quartz glass is within an allowable range.

  Viscosity is the most important factor in knowing the viscous deformation of quartz glass, but the viscosity of quartz glass has been investigated in detail in the past. For example, Non-Patent Document 1 describes a diagram showing a temperature change of viscosity in quartz glass. A graph showing the relationship between the viscosity and the temperature in the quartz glass described in FIG. 96 of Non-Patent Document 1 is shown in FIG. As shown in FIG. 11, from Non-Patent Document 1, the following formula (8) can be obtained for the viscosity and temperature of quartz glass. In the following mathematical formula (8), η is the viscosity (unit: poise), and T is the temperature (° C.).

10A and 10B are schematic explanatory views showing an example of a method for measuring thermal deformation of quartz glass. FIG. 10A shows a state before heat treatment, and FIG. 10B shows a state after heat treatment. In FIG. 10, 30 is a quartz glass sample, 32a and 32b are jigs, for example, SiC jigs, L is the distance between the jigs 32a and 32b, b is the length of the quartz glass sample, and d is the quartz glass sample. Thickness Y is the amount of deformation.
As shown in FIG. 10 (a), the opposing end face of the quartz glass sample 30 is not fixed and is held by the jigs 32a and 32b and heat-treated. Thus, the quartz glass sample 30 is thermally deformed, and the deformation amount Y is measured.

  As shown in FIG. 10, a quartz glass plate having a width a (cm), a length b (cm), and a thickness d (cm) and having a viscosity η can be freely deformed at intervals L (cm). When held and heat-treated, the deformation amount y (cm) per hour is considered to be proportional to the fourth power of the interval L and inversely proportional to the thickness and viscosity, and is expressed by the following formula (9). Actually, a and b are deleted and do not appear in the equation.

In the equation (9), y is the deformation amount (cm) per hour, A is a constant, L is the distance between the jigs 32a and 32b (cm), d is the thickness of the quartz glass (cm), and η is the viscosity. (Poise).
Table 5 to be described later shows the results of thermal deformation amounts of Examples 8 to 11 in which the processing temperature and the processing time are changed, and the viscosity obtained from the mathematical formula (8). Substituting the deformation amount and the viscosity η shown in Table 5 into the equation (9), and obtaining the constant A by the least square method, A = 6.747 × 10 ⁴ is obtained. Therefore, the mathematical formula (9) becomes the following mathematical formula (10). In the following formula (10), y, L, d and η are the same as those in the formula (9).

In the present invention, the upper limit value of the processing time for setting the deformation amount of the treated quartz glass to be equal to or less than a desired numerical value can be calculated using the formulas (8) to (10).
Specifically, in the present invention, as a limit setting of the thermal deformation of quartz glass, a 6025 type quartz glass mask substrate (width 152 mm × length 152 mm × thickness) generally used as a quartz glass mask substrate is used. The deformation amount Y when the 6.25 mm square glass substrate) is thermally deformed by the method shown in FIG. 10 described above is preferably 100 μm or less.

In the present invention, the quartz glass plate is usually heat-treated by standing on a flat surface, or is heat-treated standing upright in order to minimize the influence of gravity. Since it does not occur, it is considered appropriate to set the deformation amount of 100 μm to the maximum value.
On the other hand, in the case of a quartz glass article having a circular cross section such as a quartz glass tube or a rod, the amount of deformation is substantially reduced to about 1/10 compared to the case of holding a flat plate as shown in FIG. The amount setting is still reasonable.

As described above, the processing time t until the allowable deformation amount is reached when the allowable deformation amount Y of the quartz glass in the heat treatment is 1 × 10 ⁻² (cm), d = 0.63 (cm), and L = 15 (cm). When (time) is obtained, it is the following formula (11), so these values are substituted into formulas (8) to (11), and η is deleted to obtain the following formula (2).

  In the formula (11), t is a processing time (unit: hour), and y is an amount of change per hour (unit: cm).

In the formula (2), t _max is a treatment time (unit: hour) in which the deformation amount of the quartz glass due to the heat treatment becomes the above-described allowable deformation amount [1 × 10 ⁻² (cm)], and T is a treatment temperature ( Unit: ° C).
In the present invention, by setting the processing time to t _max or less calculated by the above formula (2), the thermal deformation of the quartz glass can be suppressed to the allowable deformation amount or less.

In the present invention, it is preferable to determine the minimum processing time and the maximum processing time for each temperature according to the mathematical formulas (1) and (2).
Table 1 shows the lower limit t _{min of the} processing time determined by the equation (1) at each temperature and the upper limit of the processing time determined by the equation (2) when the initial surface roughness is 150 nm (R = 150) as the Ra value. t _max is shown.

As shown in Table 1, a quartz glass article having an initial surface roughness Ra of 150 nm is surface-treated at a treatment temperature of 800 ° C. to 1250 ° C. and a treatment time of t _min or more and t _max or less. By doing so, thermal deformation can be suppressed and the surface roughness can be improved to 120 nm or less in terms of Ra.
As shown in Example 2, which will be described later, since the surface smoothing proceeds at a temperature of 800 ° C. or higher, the treatment temperature is set to 800 ° C. or higher in the present invention. A long processing time is required for the surface roughness Ra to be 120 nm or less. Further, as shown in Tables 1 and 5, the thermal deformation of the quartz glass becomes substantially significant at 1100 ° C. or higher. In the processing temperature range of 1100 ° C or higher, it is important to manage the heat treatment time. At 1250 ° C, the surface roughness can be improved in a short time, but the process tolerance is smaller, so the management of the processing time is extremely important. It becomes.
If the temperature exceeds 1250 ° C., the rate of thermal deformation becomes almost the same as the rate of the surface smoothing reaction, so that the process tolerance cannot be obtained. Further, at the processing temperature of 1300 ° C., the maximum processing time t for preventing thermal deformation _{Since max} is larger than the minimum processing time t _min for achieving surface smoothing and deformation is dominant, the upper limit of the processing temperature is considered to be 1250 ° C.

FIG. 1 is a schematic explanatory diagram showing an example of the configuration of an apparatus used in the present invention.
The apparatus used for the surface treatment method of the present invention is not particularly limited, and any apparatus that can control the treatment temperature and water vapor partial pressure can be used suitably. For example, the apparatus shown in FIG. 1 can be used. .

In FIG. 1, 100 is an apparatus used in the processing method of the present invention, 10a and 10b are heat treatment furnaces, 12 is a sample holder, 20 is a quartz glass sample, and 22a and 22b are thermocouples. The introduction of water vapor into the heat treatment furnace 10 is not particularly limited. For example, as shown in FIG. 1, a gas cleaning bottle 16 containing pure water W is placed in an oil bath 14 and dry air is allowed to flow through the cleaning bottle 16. Thus, the heat treatment furnace can be easily made into a steam atmosphere. At this time, the water vapor partial pressure can be adjusted by adjusting the temperature of the oil bath 14.
It is preferable that ribbon heaters 18a and 18b are respectively wound around the water vapor introduction part and the exhaust part in the furnace 10 to keep all the pipes at 100 ° C. or higher to prevent water vapor condensation. Thereby, it can prevent that water vapor | steam condenses and water vapor partial pressure falls from a setting value.

  The present invention will be described more specifically with reference to the following examples. However, it is needless to say that these examples are shown by way of illustration and should not be construed in a limited manner.

Example 1
<Sample preparation>
A quartz glass plate having a width of 20 mm, a length of 20 mm, and a thickness of 2 mm is subjected to high-precision polishing using cerium oxide, the surface roughness is adjusted to 0.5 nm or less, and then coarse abrasive grains (for example, carborundum) are used. The surface was readjusted to a uniform surface roughness.
At this time, by using two types of abrasive grains having different particle sizes, the surface roughness after readjustment was measured with a surface roughness meter, and two types of samples (samples A and B) having an Ra value of about 300 nm and 150 nm. It was created.

<Heat treatment of sample>
The quartz glass plates (samples A and B) having the rough surface were subjected to ultrasonic cleaning in pure water for 10 minutes and further subjected to ultrasonic cleaning in acetone for 10 minutes for the purpose of avoiding residual abrasive grains.
The quartz glass sample was placed on a quartz glass sample holder, and the holder was placed in the heat treatment furnace shown in FIG. The temperature of the furnace was raised to a predetermined temperature over about 3 hours, and then heat treatment was performed by flowing air containing water vapor.
The introduction of water vapor was performed by putting a gas washing bottle containing pure water into an oil bath and flowing dry air through the washing bottle at a flow rate of 200 ml / min. At this time, the water vapor partial pressure was adjusted by adjusting the temperature of the oil bath. Ribbon heaters were wound around the water vapor introduction part and the exhaust part in the furnace to keep all the pipes at 100 ° C. or higher to prevent water vapor condensation.

  As heat treatment condition 1, the temperature was set to 1200 ° C., and the water vapor partial pressure was set to 0.047 MPa (the oil bath temperature was set to 80 ° C.). Under these conditions, 15 quartz glass samples each having a surface roughness Ra value of 150 nm (sample A) and 300 nm (sample B) are prepared, and 5 samples are set as 1 set for 3 hours for 1 hour and 3 hours respectively. , 12 hours, 24 hours and 48 hours. This is for observing a change in surface roughness with time due to heat treatment.

  FIG. 2 is a photograph showing the results of Example 1, (a) is a photograph of Sample A before heat treatment, and (b) is a photograph of Sample A that has been heat treated for 48 hours. As can be seen from this photograph, the scattering due to the unevenness of the surface almost disappeared by the heat treatment for 48 hours, and a transparent glass sample was obtained.

<Measurement of surface roughness>
In order to observe the surface shape of a quartz glass sample, the surface shape and height profile of the sample at a magnification of 9000 times using a VK-9510 laser microscope [model: controller unit VK-9500, measurement unit VK-9510] manufactured by KEYENCE. The surface roughness was measured. The surface roughness Ra of three samples under the same heat treatment conditions was measured to obtain an average value. Table 2 shows the processing conditions of Example 1 and the measurement results of the surface roughness Ra before and after the processing. FIG. 9 is a graph showing the change over time of the surface roughness Ra with respect to the processing time of the sample A of Example 1.

  As shown in Table 2 and FIG. 9, it was found that the change in the processing time and the surface roughness Ra was approximated by a first order reaction, and that the Arrhenius type was applicable to the rate constant of the flattening reaction.

<Surface shape and height profile by laser microscope>
The image and height profile which observed the surface of the sample A of Example 1 with the laser microscope (9000-times multiplication factor) are shown to FIGS. 3 and 4 are images and height profiles of Sample A before heat treatment, FIGS. 5 and 6 are images and height profiles of Sample A that has been heat treated for 12 hours, and FIGS. 7 and 8 are heat treated for 48 hours. It is the image and height profile of the sample A which were given.
In the sample before the treatment, the surface shape (FIG. 3) has many irregularities of various sizes, and it was found from the height profile (FIG. 4) that sharp irregularities are conspicuous. The surface of the sample treated for 12 hours under the heat treatment condition 1 (FIG. 5) appears to be bonded by melting the small particulate irregularities seen on the sample surface before the treatment. In the height profile (FIG. 6), it can be seen that the sharp irregularities seen before the treatment are eliminated and the number of irregularities is reduced. It was found that the sample surface treated for 48 hours (FIG. 7) became smooth, and the unevenness was hardly visible from the height profile (FIG. 8).

(Examples 2 to 4)
In the same manner as in Example 1, a sample having a surface roughness Ra value of about 150 nm was prepared. The heat treatment was carried out except that the treatment temperature was set to 800 ° C. (Example 2), 1000 ° C. (Example 3) or 1250 ° C. (Example 4) without changing the water vapor partial pressure, and the heat treatment was performed for 48 hours. The prepared sample was subjected to a surface treatment in the same manner as in Example 1, and the change in surface shape was measured. Table 3 shows the treatment conditions of Examples 2 to 4 and the measurement results of the surface roughness Ra before and after the treatment.

  As shown in Table 3, it was found that the surface roughness was improved according to the treatment temperature at the treatment temperature of 800 ° C. to 1250 ° C.

(Examples 5-7)
In the same manner as in Example 1, a sample having a surface roughness Ra value of about 150 nm was prepared. The heat treatment conditions were such that the temperature was fixed at 1200 ° C., the water vapor partial pressure was 0.012 MPa (Example 5, the oil bath temperature was set to 50 ° C.), and 0.085 MPa (Example 6, the oil bath temperature was 95 ° C.). Set to 0.degree. C.) or 0.004 MPa (Example 7, oil bath temperature set to 30.degree. C.), and the surface treatment of the prepared sample was performed in the same manner as in Example 1 except that heat treatment was performed for 48 hours. And the change of the surface shape was measured. Table 4 shows the treatment conditions of Examples 5 to 7 and the measurement results of the surface roughness Ra before and after the treatment.

  As shown in Table 4, the surface roughness was improved at a water vapor partial pressure of 0.004 MPa to 0.085 MPa. In particular, at the water vapor partial pressures of 0.012 MPa and 0.085 MPa, the surface roughness was rapidly improved, and the influence of the change in the water vapor partial pressure was small.

(Examples 8 to 11 and Experimental Example 1)
<Sample preparation>
In order to investigate the degree of viscous deformation of quartz glass by heat treatment, a quartz glass plate having a width of 20 mm, a length of 160 mm, and a thickness of 0.63 mm was prepared. Since this quartz glass plate was cut out from a 6025 type quartz glass mask, the surface was subjected to high-precision polishing. The quartz glass plate was treated by the same method as in Example 1 to adjust the surface roughness so that the surface roughness was about 150 nm in terms of Ra value.

<Measurement of deformation by heat treatment>
The quartz glass plate is placed on a silicon carbide jig as shown in FIG. 10 (jig distance L = 15 cm), and the whole is set in the heat treatment furnace shown in FIG. 1, and the water vapor partial pressure is set to 0.047 MPa. However, heat treatment for a predetermined time shown in Table 5 at 800 ° C. (Example 8), 1000 ° C. (Example 9), 1200 ° C. (Example 10), 1250 ° C. (Example 11) or 1300 ° C. (Experimental Example 1) And the amount of deformation was measured with a three-dimensional measuring device. Further, the surface roughness Ra of the quartz glass plate before and after the heat treatment was measured. Table 5 shows the processing conditions of Examples 8 to 11 and Experimental Example 1, the deformation amount of the quartz glass sample, and the surface roughness Ra before and after the processing.
Table 5 shows the viscosity η at each processing temperature calculated from the formula (8) and the deformation calculated from the formula (10) and the processing time. Note that the numerical values substituted into the formula (10) when calculating the deformation amount are L = 15 (cm), d = 0.063 (cm), and η is the calculated value obtained from the formula (8). .

  As shown in Table 5, the surface roughness was improved and the amount of deformation was suppressed at the processing temperature of 800 ° C. to 1250 ° C. applied in the present invention, whereas the deformation was remarkable at the processing temperature of 1300 ° C. .

It is a schematic explanatory drawing which shows an example of the apparatus used by this invention. It is a photograph which shows the result of Example 1, (a) is a photograph of the sample A before heat processing, (b) is a photograph of the sample A which heat-processed for 48 hours. It is the image which observed the surface shape of the sample A before heat processing of Example 1 with the laser microscope (magnification 9000 times). It is the height profile which observed the surface of the sample A before the heat processing of Example 1 with a laser microscope (magnification 9000 times). It is the image which observed the surface shape of the sample A which heat-processed for 12 hours of Example 1 with the laser microscope (magnification 9000 times). It is the height profile which observed the surface of the sample A which heat-processed for 12 hours of Example 1 with the laser microscope (magnification 9000 times). It is the image which observed the surface shape of the sample A which performed the heat processing for 48 hours of Example 1 with the laser microscope (magnification 9000 times). It is the height profile which observed the surface of the sample A which heat-processed for 48 hours of Example 1 with the laser microscope (9000-times multiplication factor). 4 is a graph showing the change over time in the surface roughness with respect to the processing time of Sample A in Example 1. It is a schematic explanatory drawing which shows an example of the thermal deformation measuring method of quartz glass, (a) shows before heat processing and (b) shows after heat processing, respectively. It is a graph which shows the relationship between the viscosity and temperature in quartz glass.

Explanation of symbols

  10: heat treatment furnace, 12: sample holder, 14: oil bath, 16: gas washing bottle, 18a, 18b: ribbon heater, 20, 30: quartz glass sample, 22a, 22b: thermocouple, 32a, 32b: jig, 100: Apparatus, W: Pure water.

Claims (1)

The quartz glass article having a rough surface is maintained at 800 ° C. or more and 1250 ° C. or less in an atmosphere containing a water vapor partial pressure of 0.001 MPa or more and 0.1 MPa or less, and the surface of the quartz glass article is treated to treat the quartz glass article. A surface treatment method for a quartz glass article for improving the surface roughness of the article ,
The surface roughness before processing of the quartz glass article is 130 nm to 400 nm in terms of Ra value, and the surface roughness after processing is 1 nm to 120 nm in terms of Ra value,
The lower limit value t _min of the processing time of the quartz glass article is determined by the following formula (1), and the upper limit value t _max of the processing time of the quartz glass article is determined by the following formula (2). A method for surface treatment of glass articles.
[In the above formulas (1) and (2), t _min is the lower limit value (time) of the processing time , t _max is the upper limit value (time) of the processing time, R is the surface roughness Ra value (nm) before processing, T is the processing temperature (° C)]