JPS5849519B2 - Quartz glass crucible for pulling silicon single crystals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a silica glass crucible used for pulling up molten silicon to form a single crystal for use in semiconductors and the like.

A silicon single crystal pulling apparatus usually consists of the following components.

That is, a quartz glass crucible is filled with silicon polycrystals.

Since the quartz glass crucible is expensive, it is made thin and inserted into a graphite crucible to reinforce its strength.

The crucible filled with silicon is rotated and heated to about 1450° C. using a heat source such as high-frequency induction heating to melt the silicon.

A silicon single crystal seed supported by a pulling machine at the top of the crucible is immersed in the melt, and the polycrystal is turned into a single crystal by slowly cooling it while pulling it up.

This single crystal needs to be extremely pure in order to take advantage of its semiconducting properties, and the quartz glass that comes into direct contact with the molten material is corroded by silicon, causing some of the quartz glass (S i
02) enters the molten silicon, its purity is always taken care of.

The present inventors have conducted various studies on manufacturing methods for silicon single crystals with few impurities.In order to reduce the total amount of impurities mixed in silicon single crystals, it is necessary to not only pay attention to the total amount of impurities in quartz glass, but also to The present invention was developed as a result of focusing on a method of reducing the amount of silicon eroded by silicon and attempting to control the amount of impurities mixed in by reducing the amount of erosion.

That is, it was found that the amount of melting loss is approximately proportional to the viscosity of the quartz glass, and that this viscosity is greatly influenced by the content ratio of B203 and OH groups in the quartz glass.

Alkali metal oxides are known to be factors that reduce the viscosity of quartz glass, but experiments have shown that the relationship between the proportion of these oxides and the amount of melting damage has been determined in the field of ultra-high purity products with a total impurity level of ppm order. It is difficult to ignore the influence of B203 and OH groups, and therefore it is desirable that the amount of alkali metal oxides and other impurities be as low as possible, but S203
and 1 ppm and 30 ppm for OH group, respectively.
0 ppm or less, and as a result, the quartz glass of such a composition must have a viscosity of 109 poise at 1450°C.

That is, according to experiments, B2 in silicon single crystal pulling
The relationship between the amount of 03 and OH groups, the viscosity of quartz glass, and the amount of erosion is shown in Table 1. Table 2 shows the relationship between the amount of A103 and the amount of erosion when the amount of B203 was kept constant.

The data on the amount of melting loss in Tables 1 and 2 is based on the test piece quartz glass tube (outer 30 φ, inner 20 φ).
Measurements were taken in a 3N4 crucible by immersing it in a silicon melt at 1450°C for 20 hours.

The test pieces used in the experiment shown in Table 10B203 had a total amount of metal oxides of 10 ppm or less and OH groups of 10 ppm or less.

The test pieces used in the OH group experiments in Table 1 had a total amount of metal oxides of 10 ppm or less, B, 2 030. 1pp
m or less.

The test pieces in Table 2 have a total amount of metal oxides excluding A1203 of 10 ppm or less and OH groups of 10 ppm or less.

Therefore, in order to minimize the total amount of impurities transferred to molten silicon, it is recognized that quartz glass with a specified amount of B203 and OH groups is preferable, so in fact, quartz glass that is called a conventional high-purity product is Compared to silica glass, corrosion-resistant quartz glass contains less than 1 ppm of boron oxide, less than 300 ppm of OH groups, and less than 100 ppm of aluminum oxide, iron oxide, titanium oxide, and alkali metal oxide. The viscosity at 1450°C is 10
It turned out that 9 things were needed.

For example, particles made of high-purity crystalline quartz pulverized to a particle size of about 150 to 420 μm are filled into a mold that rotates around a vertical axis, heated from the inside with an arc flame, and
35mm, outer diameter 154mm, height 135 peaks, weight 701
The above-mentioned hemispherical quartz glass crucible of ' is manufactured, and 2,500 ? It was filled with polycrystalline silicon and heated to 1450°C to raise the silicon to a single crystal by 2000P.

Furthermore, conventional quartz glass was molded in the same manner, and silicon single crystals were pulled under the same conditions.

The results are shown in Table 3. As is clear from Table 3, the quartz glass crucible for pulling silicon single crystals of the present invention has a melting loss of 1
1, which is significantly less than the weight loss of 3 g under the same conditions using a conventional quartz glass crucible.

The characteristics of the obtained silicon single crystals were also compared, and as shown in Table 4, the influence on the specific resistance of the silicon single crystal was significantly different between the example and the comparative example.The quartz glass crucible of the comparative example had a high specific resistance. becomes very difficult.

The oxygen concentration is also affected by the amount of erosion loss, and it is preferable to suppress the amount of erosion loss in order to lower the oxygen concentration.

Claims (1)

[Claims] 1 Boron oxide 1 ppm or less, OH group 300 ppm
Quartz for pulling silicon single crystals, characterized in that the total amount of aluminum oxide, iron oxide, titanium oxide, and alkali metal oxide is 100 ppm or less, and has a viscosity of 109 poise or more at 1450°C. glass crucible.