JP3114835B2 - Quartz glass article and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quartz glass article having a projection formed on at least one surface of a quartz glass body and a method of manufacturing the same, and more particularly to a projection often used in a vertical boat used for heat treatment of semiconductor wafers. , A method of efficiently manufacturing a top lid and / or a bottom plate having a fitting portion.

[0002]

2. Description of the Related Art In recent years, heat treatment means for semiconductor wafers has
From the viewpoint of saving installation area and facilitation of automatic loading, the conventional horizontal furnace has been shifted to a vertical furnace, and in response, the wafer boat loaded in the furnace has also shifted from a horizontal to a vertical furnace. I have. And in this type of vertical boat,
In many cases, the entire boat is rotated in order to facilitate uniform contact of the processing gas on the wafer surface and uniform heating. In this case, in order to engage with the rotating shaft suspended from above ) Or an installation type, a design in which a cylindrical projection is formed on the upper lid for the purpose of centering or the like has been devised and put to practical use.

Further, in a vertical boat of an installation type, in a furnace, the heat is soaked in the axial direction of the boat, and the heat treatment atmosphere space in which the boat is installed and the flange mounting portion below the heat treatment atmosphere space. In many cases, it is installed on a pedestal made of a cylindrical heat insulator, and in this case, fitting of a complicated shape to the boat bottom plate side to enable fitting with the cylindrical heat insulator and accurate fitting to a predetermined position. Projections may be provided.

In the case of manufacturing a top cover and a bottom plate having a complicated shape on the upper surface of such a vertical boat, conventionally, a welding rod made of quartz glass is heated and fused by a burner heating to a quartz glass flat plate, and successive build-up is performed. After that, the build-up portion was ground to form a predetermined shape.

[0005]

However, in the overlaying process using a welding rod, the working time is extremely long, and if the adjustment of the welding speed and the heating temperature is not performed properly, bubbles may be smeared, requiring a high level of skill in the work. However, there was a problem that the working environment was poor because of the long-time fire working.
In addition, since the quartz glass article manufactured as described above has a thermal strain, the strain must be removed by heat treatment by annealing prior to grinding, and the annealing process for removing the strain is generally performed. The object is heated and held at a temperature higher than or equal to the strain point of quartz glass, specifically, at 1000 to 1200 ° C. At this time, the material of the quartz glass differs between the built-up portion and the flat plate as described above. Therefore, it is extremely difficult to remove the strain generated at the interface between the two materials, and it is not possible to remove the strain on the interface even if the heating time is very long or the temperature is slightly increased. Due to the distortion, peeling or cracking is likely to occur from the interface particularly during grinding. In order to eliminate such disadvantages,
If the temperature during the annealing treatment is too high, the quartz article will be deformed.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a quartz glass article and a method for manufacturing the same, which can produce bubble-free and very high-quality projections very efficiently and at low cost. I do. Another object of the present invention is to provide a quartz glass article and a method of manufacturing the same that enable smooth annealing without causing internal strain at the interface between the projection and the quartz glass body without unnecessarily increasing the temperature during the annealing process. The purpose is to provide.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a quartz glass article having a projection formed on at least one surface of a quartz glass body while supplying quartz glass powder or quartz powder onto the quartz glass body heated at a high temperature. The first point is to form a projection (facing part) on the quartz glass body by heat fusion.
The second feature is that the OH difference between the projection and the quartz glass body is set to 30 ppm or less or within 50% of the OH value of the quartz glass body, whichever is greater. It is characterized by the following. The present invention is suitably applied to the case where the quartz glass article is used as a top cover and / or a bottom plate of a vertical boat for heat treatment of a semiconductor wafer, but is not limited thereto.

[0008] Such a quartz glass article is obtained by rotating a quartz glass body, which is installed in a heating furnace, while rotating it.
A step of heating and fusing while supplying quartz glass powder or quartz powder to the upper surface side while heating to a high temperature of 00 ° C. or more to form a built-up portion, and forming the built-up portion into a predetermined shape by machining. Selecting a means for heating and melting the quartz glass powder or quartz powder to an oxyhydrogen flame or an electric arc flame according to the OH content of the quartz glass body, for example, being contained in the quartz glass body. In the region where the OH group is 100 ppm or more, an oxyhydrogen flame, 50 ppm
This is achieved by selecting either an oxyhydrogen flame or an electric arc in the region of 100 ppm or less and an electric arc flame in the region of 50 ppm or less.

[0009]

In the present invention, as shown in FIG. 1, for example, a quartz glass body serving as a base of a quartz article to be manufactured is placed on a rotating table in a furnace kept sufficiently warm, and a Bernui is formed according to the shape of the projection. A protrusion is formed by a powder fusion method according to the method. For example, when the shape of the projection to be designed is located at the center of the flat plate, as shown in FIG. Protrusions can be obtained efficiently. In the case where the projections are ring-shaped, as shown in FIG. 2, the focal point for fusing the powder is shifted by a predetermined distance from the center and the powder is fused to easily obtain a ring-shaped projection having good shape accuracy. be able to. Therefore, according to such a technical means, the projecting portion conventionally formed by the build-up of the welding rod is fused to the target quartz glass body by a method of fusing powder according to the Bernoulli method. A very high-quality, bubble-free projection can be produced very efficiently and inexpensively.

On the other hand, since the quartz glass article manufactured in this way has thermal strain, it must be annealed and removed prior to the grinding process. As described above, it is extremely difficult to remove the strain generated at the interface of the substrate. Therefore, the present invention has found that the cause of the difference in thermal strain at the interface during the annealing treatment is determined by the amount of OH contained in the quartz glass in the case of high-purity quartz glass used in the semiconductor industry. Heating means for fusing powder in accordance with the content of OH groups in the flat plate, an oxyhydrogen flame burner when the quartz flat plate is a water type silica glass, and By appropriately selecting an electric arc flame burner, the OH groups between the projection portion and the quartz glass body to be the base are substantially matched,
As a result, it has been found that heat distortion does not remain at the interface even by the annealing treatment, and that a vertical boat or other quartz glass articles of stable quality can be manufactured.

That is, fused silica glass having a large residual amount of OH groups generally contains 100 to 300 ppm of OH groups. Is formed, the OH content may be given to the protrusions that are similar to the extent that the strain can be removed in the annealing step.Specifically, the heating means for fusion is performed by an oxyhydrogen flame burner. Just do it. If an oxyhydrogen burner is used as a heat source, the amount of OH contained in the formed projections depends on the particle size when using quartz powder, and on the particle size and the amount of OH contained when using quartz glass powder. 100 ppm or more and 1000 ppm depending on the growth rate of the fused body and the balance of oxygen and hydrogen forming a flame.
Adjustment to about ppm is possible.

On the other hand, anhydrous quartz glass is usually O
H is not contained at all or OH of 20 ppm or less is contained. In order to carry out the present invention using such a quartz glass as a substrate, any annealing treatment is necessary unless the OH content of the quartz glass contained in the projections obtained by fusion is similarly extremely low. Removal of distortion becomes difficult. For this purpose, an electric arc flame may be suitably selected as a heating means for the fusion. Here, even when the heating means is selected as an electric arc flame burner, when quartz powder is used as a raw material, its particle size and atmosphere are
When quartz glass powder is used as a raw material, the amount of OH can be adjusted to about 0 to 100 ppm by using quartz glass powder substantially containing no OH and appropriately selecting the particle size and atmosphere. In particular, when forming a fused body substantially free of OH, it is necessary to use a relatively coarse powder having a particle size of 100 μ or more and to carry out the present invention in a dry air or nitrogen atmosphere having a dew point of −30 ° C. or less. There is.

However, in practice, the amount of OH between the quartz glass substrate and the fused silica glass, which is a projection, does not necessarily have to be exactly the same, and even if the OH of the substrate is 0 ppm. Up to about 30 ppm or ± 100 when OH is about 200 ppm
It was found that if the difference was about ppm, the strain could be removed by annealing. Generally, the higher the OH included, the higher this tolerance will be, but at least ± 50.
%. Therefore, it has been found that, as an embodiment of the present invention, if the OH content of the quartz glass substrate is 100 ppm or more, an oxyhydrogen flame may be used as a heat source, and if it is 50 ppm or less, an electric arc flame may be used as a heat source. Either heat source may be used when the OH of the quartz glass substrate is 50 to 100 ppm, but it is preferable to use an oxyhydrogen flame as the heat source from the viewpoint of simplicity of implementation.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. It's just FIG. 1 is a basic configuration diagram for fusing a projection to a quartz glass flat plate. Reference numeral 1 denotes a burner for melting quartz powder or quartz glass powder. The number of OH groups contained in the plate 2 is 10
In the region of 0 ppm or more, the oxyhydrogen burner 1A is set to
In the region of not less than m and not more than 100 ppm, either the oxyhydrogen burner 1A or the electric arc burner 1B is
In the region below ppm, the electric arc burner 1B is selected. Each of the burners 1 is supplied with a powder 5 such as quartz powder from above the center, is heated and melted by the burner flame, and is fused on the quartz glass flat plate 2.

On the other hand, a quartz glass flat plate 2 to be a substrate is set on a rotating table 4 in a heating furnace 3 to be described later, and is rotated at 1900 ° C. while rotating the quartz glass flat plate 2.
By heating and fusing the quartz glass powder or quartz powder 5 heated and melted by the burner 1 from the upper surface side while heating to the above high temperature, for example, the shape of the designed projection 6 is In the case of the central portion, as shown in FIG. 1A, the focus for fusing the powder is set to the center of rotation of the quartz flat plate 2 and fusing is performed, so that the cylindrical projection 6 having an arm-shaped cross section is formed. Can be obtained efficiently.
Then, as shown in FIG. 1 (B), the projections 6 remove unnecessary portions 60 by grinding after annealing to form quartz glass articles having a predetermined shape.

When the projection 6 is ring-shaped, FIG.
As shown in (A), the focus at which the powder is fused is shifted by a predetermined distance from the center to produce a ring-shaped projection 6 having an arm-shaped cross section. By removing the quartz glass article, a quartz glass article having good shape accuracy can be easily obtained. Then, after the quartz glass article formed as described above is annealed to remove internal strain, it is formed into a predetermined shape by grinding as shown in FIG.

Then, various quartz glass articles were manufactured by the above method. For example, FIG. 3 shows an embodiment using an oxyhydrogen burner 1A. FIG. 3 (A) shows the equipment, and the oxyhydrogen burner 1A is composed of supply pipes 11 and 12 for oxygen and hydrogen. Through the oxygen supply pipe 12
It is configured to be supplied / fused onto the quartz glass plate 2 from the outlet A, and the quartz glass plate 2 is placed on a rotatable table 4 in a heating furnace 3 and, for example, contains OH groups contained therein. Is placed on a rotating table 4 in a heating furnace 3 at 2200 ° C. with an oxyhydrogen burner 1A.
Heated to the above high temperature, and the particle size in the upper hopper 8 was 100 μm.
200μ quartz powder 5 together with oxygen gas
A was fed into the flame at a rate of 200 g / hour, and a flat hemispherical quartz glass projection 6 having a diameter of 8 cm and a height of 4 cm was formed in about 1.5 hours. In this case, the weight of the projection 6 of quartz glass was 220 g. The quartz glass flat plate 2 thus obtained is
After annealing at 0 ° C. for 30 minutes, the unnecessary portion 60 is removed by grinding to the shape shown in FIG. 3B, and the upper cover for a vertical boat having a two-stage cylindrical projection 6 is formed. Was manufactured. Here, the O contained in the protrusion 6
The amount of H was 220 ppm, and the strain was completely removed by the annealing treatment.

FIG. 4 shows another embodiment using an electric arc burner 1B. The arc burner 1B comprises an arc electrode 14 and a quartz glass introducing tube 15, and the quartz powder 5 retained in the hopper 8 is supplied with a quartz glass introducing tube. The quartz glass flat plate 2 is configured to be supplied / fused onto the quartz glass flat plate 2 from between the tips of the electrodes 14 via 15, and the quartz glass flat plate 2 is mounted on a rotatable table 4 in the heating furnace 3. And for example containing OH
Is placed on a rotating table 4 in a heating furnace 3 and heated to a high temperature of 2200 ° C. or more by an arc flame by a three-phase alternating current arc electrode 14. After heating, the quartz powder 5 having a particle diameter of 100 μm to 200 μm in the upper hopper 8 is entrained by nitrogen into the central portion of the arc flame by the quartz glass introduction tube 15 (the nitrogen introduction tube is not shown in the figure). It was fed at a rate of 150 g / h into the flame. In about 2.5 hours, a flat hemispherical quartz glass projection 6 having a diameter of 8 cm and a height of 4 cm was formed. In this case, the weight of the quartz glass projection 6 was 220 g. After the thus obtained quartz glass member is annealed at 1150 ° C. for 30 minutes,
By grinding to the shape shown in FIG. 3B, a quartz glass member for the upper lid of a vertical boat for semiconductor heat treatment having a cylindrical projection 6 was manufactured. Here, the O contained in the protrusion 6
The amount of H was 30 ppm, and the strain was completely removed by the annealing treatment.

Next, using the equipment of the oxyhydrogen burner 1A shown in FIG.
A quartz glass disk having a thickness of 5 mm was placed on a rotating table 4 in the same furnace as in Example 1, and the same crystal material was used. Under the same conditions, a hemisphere having a diameter of 8 cm and a height of 4 cm was slightly crushed. A projection 6 of quartz glass having a shape was formed. The quartz glass member thus obtained is heated at 1150 ° C. for 1 hour.
After performing the annealing treatment for 20 minutes, when grinding is performed to the shape shown in FIG. 3B, the interface of the quartz plate 2 is broken due to the remaining distortion, and a desired quartz glass member is formed. Could not. Here, when the amount of OH contained in the protrusions 6 was examined, it was 220 ppm, and it was confirmed that the strain could not be completely removed by annealing.

[0020]

As described above, according to the present invention, a bubble-free and very high-quality projection can be produced very efficiently and inexpensively, and the temperature at the time of annealing can be increased without unnecessarily increasing the temperature. In addition, the present invention has various remarkable effects, such as being able to obtain a quartz glass article which can be smoothly annealed and ground without causing internal strain at the interface between the projection and the quartz glass body.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram for fusing a projection to the center of a quartz glass flat plate, where (A) is a facility for fusing,
(B) shows a fused quartz glass article.

FIGS. 2A and 2B are basic configuration diagrams for fusing a ring-shaped projection around a quartz glass flat plate, wherein FIG. 2A shows a facility for fusing and FIG. 2B shows a fused quartz glass article.

FIG. 3 shows an embodiment using an oxyhydrogen burner, wherein (A) shows the equipment and (B) shows a quartz glass article manufactured by the equipment.

FIG. 4 shows another embodiment using an electric arc burner.

[Explanation of symbols]

 2 quartz glass flat plate 1A oxyhydrogen burner 1B electric arc burner 3 heating furnace 5 quartz glass powder or quartz powder 6 protrusion

Continuation of front page (56) References JP-A-1-219030 (JP, A) JP-A-63-282133 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C03B 20 / 00 C03C 17/04 H01L 21/22

Claims (5)

(57) [Claims] 1. A quartz glass article having a projection formed on at least one surface of a quartz glass body, wherein the quartz glass article is heated and fused while supplying quartz glass powder or quartz powder onto the quartz glass body heated at a high temperature. A projection is formed on the body, and O between the projection and the quartz glass body is formed.
A quartz glass article characterized in that the H difference falls within 30 ppm or less or within ± 50% of the OH value of the quartz glass body, whichever is greater. 2. When at least the OH group contained in the quartz glass body is 50 ppm or less, the projection is formed using an electric arc flame, and the OH group contained in the quartz glass body is 100 ppm or more. 2. The quartz glass article according to claim 1, wherein the projection is formed using an oxyhydrogen flame. 3. The quartz glass article according to claim 1, wherein the quartz glass article is a top cover and / or a bottom plate of a vertical boat for heat treatment of a semiconductor wafer. 4. A method for manufacturing a quartz glass article in which a projection is formed on at least one surface of a quartz glass body, wherein the quartz glass body installed in a heating furnace while rotating is rotated by 19%.
A step of heating and fusing while supplying quartz glass powder or quartz powder to the upper surface side while heating to a high temperature of 00 ° C. or more to form a built-up portion, and forming the built-up portion into a predetermined shape by machining. And a step of selecting the means for heating and melting the quartz glass powder or quartz powder to an oxyhydrogen flame or an electric arc flame according to the OH content of the quartz glass body. . 5. An oxyhydrogen flame in a region where the OH group contained in the quartz glass body is 100 ppm or more,
5. The method for producing a quartz glass article according to claim 4, wherein either an oxyhydrogen flame or an electric arc is selected in a region of not less than 100 ppm and an electric arc flame is selected in a region of not more than 50 ppm.