JPS62259434A - Quartz glass jig - Google Patents

Abstract

PURPOSE:To effectively enhance uniform thermal effect and to obtain a jig having excellent thermal resistance and dimensional stability by forming 1/10 or more of the total number of air bubbles in elliptically spherical shape. CONSTITUTION:In a fine air bubble-containing quartz glass jig, 1/10 or more of the total number of air bubbles are of elliptically spherical shape. A cylindrical thick tube which contains spherical air bubbles produced by arc melting is thermally softened in a molding furnace, and then oriented in the longitudinal direction. Then, quartz glass which contains elliptically spherical air bubbles oriented in the longitudinal direction can be obtained. For example, the elliptically spherical air bubbles oriented in the longitudinal direction of the core tube reflect at random incident light in a circumferential direction to enhance the uniform thermal effect in the circumferential direction, and the elliptically spherical air bubbles oriented in the circumferential direction reversely reflect the light at random in the longitudinal direction to enhance the uniform thermal effect in the longitudinal direction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is a quartz glass jig that is used in the semiconductor industry and has excellent heat uniformity, heat resistance, and dimensional stability.

For example, it relates to furnace core tubes, forks, chambers, pelgers, boats, etc., and is particularly aimed at providing furnace core tubes.

(Conventional technology and its problems) Conventionally, quartz glass jigs used in the semiconductor industry, such as furnace core tubes, have poor heat uniformity and heat resistance.

Dimensional stability has become a problem, and in particular, there is a strong desire to solve the problem of bending and deformation of the furnace core tube during the process of heat treating semiconductor wafers at 1100° C. or higher. For this reason, attempts have been made to use thick transparent quartz glass or opaque quartz glass, but jigs made of such quartz glass suffer from undesirable phenomena such as uneven heating. In particular, opaque quartz glass has a disadvantage of poor purity and is not suitable for the semiconductor industry.

In addition, as the diameter of semiconductor wafers continues to increase, the size of the furnace core tube and other jigs used also increases.As a result, the temperature distribution within the furnace core tube tends to become uneven, making it difficult to uniformly heat the semiconductor wafers. It has become difficult to do so, and yields have decreased.

(Structure and Effects of the Invention) It is already known that conventional bubble-filled quartz glass has better properties such as heat uniformity and heat resistance than transparent quartz glass that does not contain bubbles. As a result of intensive research by the inventors, (a) bubbles contained in the layered structure of quartz glass reflect incident light diffusely, but the size, shape, number, etc. of the bubbles in this case are determined by the uniformity of the glass. (b) The shape of the bubbles can be changed by adjusting the manufacturing conditions of quartz glass, etc.
Surprisingly, it was found that the uniform heating effect was significantly improved by changing from the normal spherical shape to an elliptical spherical shape.

The present invention has been completed based on the above findings, and is directed to a quartz glass jig with fine bubbles, characterized in that 1000 or more of the total number of bubbles are ellipsoidal bubbles. It is related to.

This is caused by the bubble having an ellipsoidal shape.

Although the reason for the above-mentioned effect is not necessarily clear, it is thought to be as follows.

In other words, the case of a furnace core tube was considered based on the inference that ellipsoidal bubbles diffusely reflect the light incident on the quartz glass at an angle of 90'' to the long axis direction of the bubbles, increasing the heat uniformity effect in the direction of diffuse reflection. Then, the ellipsoidal bubbles arranged in the length direction of the furnace core tube diffusely reflect the incident light in the circumferential direction, increasing the uniform heating effect in one circumferential direction, and the ellipsoidal bubbles arranged in the circumferential direction This seems to be due to the fact that the bubbles diffusely reflect light in the length direction, increasing the heat uniformity effect in the length direction.

In this case, the effect is insufficient if the proportion of ellipsoidal bubbles present in the quartz glass is less than 1/10 of the total number of bubbles, and the effect increases as this proportion increases.

The ellipsoidal shape used in the present invention is conceptually a sinusoidal shape, but the dimensions of this ellipsoidal sphere are preferably such that the major axis is 15 to 1000 μm; Even if it exceeds 1000 μm, no effect can be expected, and the ratio of stretching from the base material to the furnace core tube during manufacturing becomes large, which is inconvenient and economical for manufacturing large diameter furnace core tubes.

Efficiently undesirable.

The short axis is not particularly specified, but it is sufficient that the shape of the bubble is not a true sphere, and the shape of the elliptical sphere does not have to be a true elliptical sphere, but may be a shape that approximates it.

There are various methods for producing quartz glass containing ellipsoidal bubbles, but for example, it can be produced efficiently and economically by the following method.

First, a cylindrical thick-walled tube containing spherical bubbles manufactured by arc melting is heated and softened in a forming furnace.

If the tube is then stretched in the length direction, a quartz glass tube containing ellipsoidal bubbles arranged in the length direction can be obtained. Furthermore, by stretching in the circumferential direction, quartz glass containing ellipsoidal bubbles arranged in the circumferential direction can be obtained.

The orientation direction of the elliptical spheres may be changed depending on the usage method and purpose of each jig such as a quartz glass furnace core tube.

Although the purity of the quartz glass was not specifically defined, in semiconductor processing processes where the degree of integration is increasing, the lower the content of radioactive elements such as alkali, alkaline earth, or uranium, the higher the yield of wafers. Moreover, it is not necessary to use natural silica as a raw material, it may be manufactured from a synthetic quartz glass raw material, and the OH group content may be controlled.

Although the above description has mainly been about the furnace core tube for semiconductor processing, this is not limited to the furnace core tube only, and of course includes various other jigs such as boats, forks, pelgers, and chambers.

The present invention will be explained in detail below.

(Example 1) The total number of bubbles included is in the range of 15 to 500 μm in size, approximately 115 of the total number of bubbles are elliptical spheres, and the ratio of the major axis to the minor axis of the elliptical sphere is 115 to 1/1/2. A quartz glass furnace core tube having an outer diameter of 240 mm, an inner diameter of 225 m, and a length of 1700 n* was made, with the orientation direction being the length direction. This was installed in a horizontal furnace for semiconductor wafer heat treatment with a soaking length of 700 m++, a thermocouple for measuring the temperature inside the furnace was attached to the automatic semiconductor wafer transfer device, and the furnace was heated to 1050°C with a Kanthal heating element and maintained for 2 hours. . Next, platinum-
A thermocouple made of 13% platinum-rhodium was inserted, and the lengthwise direction of the soaking zone was divided into seven equal parts, and the circumferential direction was divided into eight equal parts, and the temperature at each point was measured.

(Example 2) Compared to Example 1, a quartz glass furnace core tube having the same dimensions as Example 1 was produced using a larger diameter base material, increasing the drawing ratio, and at a lower temperature. Total bubbles included are size 10
It is in the range of 0 to 1000 μm, and about 1/1 of the total number of bubbles is
No. 2 was an elliptical sphere, the ratio of the major axis to the minor axis of the elliptical sphere was in the range of 1150 to 1/100, and the orientation direction of the elliptical sphere was the length direction.

The temperature distribution of this was measured in the same manner as in Example 1.

(Example 3) A quartz glass furnace core tube having the same dimensions as in Example 1 was produced by pressurizing the inside of a base material with a smaller diameter than in Example 1 and stretching it in the circumferential direction. The total bubble size included is 15~
Approximately 1710 of the total number of bubbles are in the range of 200 μm, and the ratio of the major axis to the minor axis of the elliptical sphere is 1/1.
It was in the range of 2 to 1/20, and the orientation direction of the 9w1 sphere was in the circumferential direction. The temperature distribution of this was measured in the same manner as in Example 1.

(Comparative Example) Temperature distribution was measured in the same manner as in Example 1 in the case of a quartz glass furnace core tube in which about 1/20 of the total bubbles contained were elliptical spheres and the rest were approximately spherical.

The above Example 1, Example 2. The temperature distributions measured in Example 3 and Comparative Example are shown in FIGS. 1 and 2.

The positions of each measurement point on the furnace core tube are as shown in FIGS. 3(a) and 3(b).

From these results, when the ellipsoidal bubbles are arranged in the length direction (Examples 1 and 2), the heat uniformity effect is high in the circumferential direction of the furnace core tube. The smaller the ratio of the short axis, the higher the effect.0 When arranged in the circumferential direction (Example 3), the heat uniformity effect is high in the length direction, and the ellipsoidal bubbles account for 1/20 of the total bubbles, leaving the rest. If is spherical (
It is clear that the comparative example) has poor heat uniformity effect in all directions.

(Effects of the Invention) As explained in detail above, according to the present invention, by using quartz glass containing ellipsoidal bubbles in a semiconductor processing jig, it is possible to efficiently improve the uniform heating effect, and as a result, Furthermore, we were able to realize a jig with excellent heat resistance and 1-dimensional stability.

The present invention has industrial significance in that it has developed a quartz glass that is extremely suitable for use in current semiconductor processing jigs.

[Brief explanation of drawings]

FIG. 1 shows Example 1. Example 2. FIG. 2 shows the temperature distribution in the circumferential direction, and FIG. 3(a) shows the temperature distribution in the longitudinal direction of the furnace core tube in Example 3 and Comparative Example.
(b) shows the positions of measurement points in the circumferential direction. ■ -, 1 Measurement point position in length direction 1'2'3'4'5'5' 7
'8' Sub-fixed point position in circumferential direction

Claims (1)

[Scope of Claims] 1) A quartz glass jig with fine bubbles, characterized in that 1/10 or more of the total number of bubbles are ellipsoidal bubbles. 2) The quartz glass jig according to claim 1, wherein the ellipsoidal bubble has a major axis of 15 to 1000 μm. 3) A quartz glass jig according to claim 1 or 2, which is used in a heat treatment process for semiconductor wafers.