JPH07100671A - Processing method of silica glass body - Google Patents

Abstract

(57) [Summary] (Corrected) [Purpose] To provide a method for processing a silica glass body, particularly a laser processing method, which can be processed with high accuracy without cracks. When the virtual temperature of a processed portion during laser processing is A ° C., the virtual temperature of a silica glass body as a workpiece is (A-500) as a pre-process of the laser processing.
The heat treatment step of suppressing the temperature to be less than or equal to 1300 ° C.) is performed, or as a pre-step of laser processing, the fictive temperature of the silica glass body is set to 1300 ° C. to 1700 ° C. by using the silica glass body formed to have a wall thickness in the cutting direction of less than 20 mm A method for processing a silica glass body with an infrared laser, characterized in that there is a heat treatment step for setting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for accurately processing a silica glass body, and more particularly to a method for accurately processing a silica glass body using a CO ₂ laser or other infrared laser.

[0002]

2. Description of the Related Art In recent years, silica glass has not only been used as a jig and tool for manufacturing semiconductors, but also has been rapidly expanding in various fields such as optical systems. Along with this, there are various methods for processing silica glass, and various cutting processes are required in addition to conventional thermal processing. Particularly, in the grooving process of a wafer board as a semiconductor heat treatment jig, it is necessary to perform an accurate process, and a CO ₂ gas laser is often used for this type of process, other fine processes, and complicated processes. Came.

Since the CO ₂ laser can be automatically moved by a mirror, it has an advantage that it can be processed safely and accurately in a short time. On the other hand, in the case of a laser cutting machine,
A spot beam laser is incident on the silica glass,
The energy of the laser is absorbed and heat is generated to melt the silica glass, but at this time, the beam is a beam spot which is not diffused in the glass, and in particular, the wavelength of the CO ₂ laser is in the infrared region, so all the energy is absorbed. Is absorbed, so that there is a problem that a strain is locally generated and a crack is generated on the melting surface.

[0004]

Therefore, although the CO ₂ gas laser is a very efficient processing method, it has a problem that cracks are generated as described above. Especially, when cracks are generated during processing, crack repair is performed. Because of this, it takes time and efficiency becomes poor. In view of the above-mentioned drawbacks of the prior art, it is an object of the present invention to provide a method for processing a silica glass body, particularly a laser processing method, which can be processed with high accuracy without cracks.

[0005]

Means for Solving the Problems The present inventor diligently investigated the laser-processed surface of the silica glass body and studied the cause of the occurrence of cracks. It is true that the cracks generated in the silica glass body by the CO ₂ gas laser are the stresses (strains) generated during the laser processing. Particularly, silica glass has a strong property against compressive stress and a fragile property against tensile stress. Cracks occur when the stress strain becomes tensile stress. In order to solve this problem, it is necessary to prevent tensile stress from occurring in the silica glass. I thought that the cause of the tensile stress was the coefficient of thermal expansion, but the coefficient of thermal expansion of silica glass was 5 × 10 5.
It is as small as ^-7 mm / ° C, and it is unlikely that the difference in expansion coefficient will be large in the adjacent parts of the heat-processed surface.

Next, when the virtual temperature of the cracked portion was examined by a laser Raman spectrophotometer, it was found to be abnormally high. Therefore, the present inventor has found that the greater the difference between the fictive temperature of the material and the fictive temperature of the laser processed portion, the more likely the crack is to occur, and the present invention has been completed based on this finding. Here, the fictive temperature is, for example, when glass is rapidly cooled from a transition temperature range or a temperature range higher than that, for example, it is cooled to room temperature while the atomic arrangement and the density corresponding to the temperature T ₁ are frozen.
This temperature T ₁ is called an imaginary temperature. Then, the difference in fictive temperature appears as a difference in atomic arrangement and density, and as the fictive temperature changes, the silica glass material itself expands and contracts.

Since the expansion and contraction caused by the virtual temperature is irreversible unlike the thermal expansion coefficient, the expansion and contraction state caused by the virtual temperature remains as it is even when the temperature is lowered. It has been found that when the virtual temperature of the laser processing part is high and the virtual temperature of the material is low, the crack is more likely to occur as the deviation rate increases. That is, the inventors of the present invention measured the fictive temperature of the cracked portion of the silica glass body processed by the CO ₂ gas laser and found that it was 1800 ° C. to 1900 ° C., which was extremely high.

On the other hand, a heat treatment jig made of silica glass is generally manufactured by heating a silica glass with a flame of a burner at a temperature higher than its softening point to produce a predetermined shape, and then removing the strain from 1000 to 1000 in order to remove strain.
It is confirmed that the fictive temperature is around 1200 ° C. because it is manufactured by sufficiently annealing at a temperature of 1200 ° C. Therefore, the virtual temperature of the laser processed surface is 1800 ° C to 1900 ° C, while the virtual temperature of the jig material adjacent to the processed surface is 1200 ° C and the deviation rate thereof is 60.
It becomes extremely large at around 0 to 700 ° C.

Therefore, in order to suppress the occurrence of cracks, experiments were conducted by changing the fictive temperature of the jig material, and the fictive temperature of the jig material was 1300 ° C. to 1700.
It was found that the occurrence of cracks was small when the temperature was set to 0 ° C, more preferably 1400 ° C to 1600 ° C.

The fictive temperature of silica glass is 1300 ° C. to 1
Examining the cause that cracks are less likely to occur at 700 ° C. As described above, the occurrence of stress is reduced due to the decrease in the virtual temperature difference, and in particular, the degree of occurrence of tensile stress is decreased. May not occur. Also, in order to set the fictive temperature to 1800 ° C., it is basically necessary to heat it to 1800 ° C. or higher and then rapidly cool it, which causes the occurrence of internal strain, etc. Estimated to lead to.

However, a fictive temperature of 1400 ° C. to 160 ° C.
Since the crack generation rate can be most reduced at 0 ° C., it is considered that not only the effect due to the fictive temperature difference but also other factors, especially the stability of the glass structure density are included.
Then, in order to set the fictive temperature to 1300 ° C. to 1700 ° C., it is sufficient to heat the silica glass body at each temperature until the structure fits and then rapidly cool it.
If the silica glass body is continuously drawn out from the electric furnace heated to 1800 to 1800 ° C, the fictive temperature is 1400 to 16 ° C.
Can be set to 00 ° C.

A problem at this time is that the thickness of the silica glass body should be 20 mm or less, preferably about 10 mm. As the wall thickness increases, the heat capacity of the silica glass body increases, the temperature drop of the silica glass body slows down, and the fictive temperature decreases, and the fictive temperature distribution occurs in the wall thickness direction. Distortion occurs in itself. Further, since processing with a CO ₂ gas laser is conveniently difficult for a member having a large wall thickness, the wall thickness in the cutting direction is preferably 20 mm or less, more preferably 10 mm or less.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be exemplarily described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention only thereto, but merely illustrative examples. Nothing more than.

First, the silica glass material constituting the silica glass jig for semiconductor heat treatment is generally produced by oxyhydrogen flame or electric melting to melt the raw material crystal powder at a temperature of 1900 to 2100 ° C. to produce a silica glass ingot. 1900
A method of producing a silica glass tube or a silica glass rod by melting while drawing at a temperature of ~ 2100 ° C, and a method of producing a silica glass tube or a silica glass rod by sequentially melting at a temperature of 1900-2100 ° C while supplying a certain amount of raw material crystal powder. There is a method of pulling out a silica glass rod. The silica glass plate is formed in a plate shape by opening the glass tube while heating and softening the glass tube at a temperature of about 1600 to 1700. After the silica glass manufactured as described above is molded into a predetermined shape while being softened by heating at a temperature of around 1700,
It is annealed at a temperature of around 1000 to 1200 ° C., and its fictive temperature is generally 1200 ° C.

Therefore, in this example, six silica glass plates were prepared by cutting the annealed silica glass material into squares of 10 cm and a thickness of 3 mm. One sheet was heated at 1600 ° C. for 1 minute, then taken out from the electric furnace and naturally cooled (Example 1). Next, another plate was heated at 1400 ° C. for 1 hour, taken out from the electric furnace, and naturally cooled (Example 2). Another sheet was heated at 1100 ° C. for 24 hours, taken out from the electric furnace, and naturally cooled (Comparative Example 1). The last one is 1 at 1800 ℃
After heating for minutes, it was taken out of the electric furnace and rapidly cooled (Comparative Example 2). Further, two silica glass plates having a 10 cm square and a wall thickness of 20 mm were prepared. One sheet was heated at 1600 ° C. for 1 minute, then taken out of the electric furnace and naturally cooled (Example 3). Another sheet was heated at 1400 ° C. for 1 hour, taken out from the electric furnace, and naturally cooled (Comparative Example 3).

Next, the virtual temperatures of the silica glass plates of the above-mentioned examples and comparative examples are measured by a laser Raman spectrophotometer. That is, to explain the measuring method, a comparative sample obtained by cutting the silica glass plate into small pieces of a predetermined shape was used, and the sample was heated at 1200 ° C. for 2 hours and then rapidly cooled in water (in this case, a fictive temperature of 1200 ° C.). ) 1
Sample 2 heated at 000 ° C for 20 hours and then rapidly cooled in water
(Fictive temperature 1000 ° C.), sample heated at 900 ° C. for 120 hours and then rapidly cooled in water (virtual temperature 900 ° C.), 80
After heating at 0 ° C for 1200 hours and then rapidly cooling in water (virtual temperature 800 ° C), each sample is measured with a Raman spectrophotometer in the range of 150 to 650 cm ^-1 , and the following three peaks are measured. . 150-650 cm ^-1 (W1, peak area AW1), 470-520 cm ^-1 (D1, peak area AD1) 580-640 cm ^-1 (D2, peak area AD2) Next, from these three peak areas, the peak area of D2 The ratio (I) of is calculated. I = {AD2 / (AW1-AD1-AD2)} The relationship between this (I) and the fictive temperature is shown in a graph, and the fictive temperature is estimated from the I of the sample whose fictive temperature is unknown as a standard line (calibration curve). Is.

The fictive temperature of each of the silica glass plates is 1500 ° C. in Example 1 and 1350 in Example 2.
C., 1400 ° C. in Example 3 and 1100 in Comparative Example 1.
C., 1750 ° C. in Comparative Example 2, 1250 ° C. in Comparative Example 3
Met.

After the silica glass plate was cut into strips with a width of 2 cm by using a commercially available carbon dioxide laser cutting machine, the cracks on the machined surface were grasped. In Example 1, no crack was found. In Example 2, one crack was formed, in Comparative Example 1, five cracks were formed, and in Example 3, cutting with a laser took time. Although there were few cracks at three places, the volume lacked by the cracks was large. In Comparative Example 2, strain was left in the silica glass due to rapid cooling, and the glass was shattered during laser processing. In Comparative Example 3, cutting with a laser took time. The number of cracks was as large as 10 and the volume lacked by the cracks was very large. Next, the fictive temperature of the processed portion was measured and found to be 1800 to 1900 ° C.

[0019]

According to the present invention, therefore, the field of application of silica glass is rapidly expanding as described above, and the laser processing machine itself is rapidly advancing at the present time, while suppressing the occurrence of cracks. Laser processing is possible
This is a very meaningful technology for the silica glass processing industry, which will require more complicated processing in the future, and this will not require repair of cracks after cutting and will greatly improve productivity. It has various remarkable effects.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Minoru Saito 88 Kawakubo, Kanaya, Tamura-cho, Koriyama City, Fukushima Prefecture Shin-Etsu Quartz Co., Ltd.

Claims (2)

[Claims] 1. In a method of processing a silica glass body with an infrared laser, when a virtual temperature of a processed portion during laser processing is A ° C., a virtual of a silica glass body as a workpiece is pre-processed as the laser processing. Change the temperature to (A-5
A method of processing a silica glass body, characterized in that there is a heat treatment step of suppressing the temperature to within 100 ° C. 2. A method of processing a silica glass body with an infrared laser, wherein as a pre-step of the laser processing, a silica glass body formed to have a wall thickness in a cutting direction of less than 20 mm is used, and a virtual temperature of the silica glass body is adjusted. 1300 ° C ~ 17
A method for processing a silica glass body, characterized in that there is a heat treatment step of setting the temperature to 00 ° C.