JPH0780716B2 - Quartz glass crucible manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a quartz glass crucible. In particular, it relates to a method for producing a quartz glass crucible used for pulling a silicon single crystal.

[0002]

2. Description of the Related Art The pulling of a silicon single crystal is usually carried out by loading a polycrystalline silicon into a quartz glass crucible which is contained in a graphite crucible.

That is, a quartz glass crucible loaded with a silicon polycrystal is heated from the surroundings to heat and melt the silicon polycrystal therein to about 1450 ° C. Then, a seed crystal is brought into contact with this and pulled up, and the silicon pulled up accordingly is gradually cooled, whereby an ingot of a silicon single crystal is obtained.

This method is the most widely used method at present for obtaining a silicon single crystal from other crystalline silicon. According to this method, the inner surface of the quartz glass crucible is always made of molten silicon. You are in direct contact.

Therefore, according to this method, the inner surface of the quartz glass crucible is always eroded by the molten polycrystalline silicon, and as a result, the pulled silicon single crystal contains the melted crucible inner surface portion. There was a risk that impurities that had been removed would be mixed in. In particular, when the purity of the quartz glass forming the crucible is not good, and the Group 1 alkali metal or copper is contained in a high concentration in the quartz glass, the silicon single crystal pulled by using this has a lattice A defect occurs,
It was also supposed to reduce the yield of silicon wafers to be manufactured.

Further, the pulling of the silicon single crystal is about 14
Since it is performed at a high temperature of 50 ° C, if the viscosity of the quartz glass crucible used for this is low, the deflection and distortion of the crucible become large, the flow of molten silicon in the crucible becomes irregular, and the inner surface of the crucible The amount of erosion is further increased, and these are great obstacles to pulling a high-quality silicon single crystal.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks, and an object of the present invention is to provide a method of manufacturing a quartz glass crucible which can manufacture a high-quality silicon single crystal. is there.

[0008]

That is, according to the present invention, natural quartz is crushed and refined, and this is formed into a crucible by arc rotary melting, and a high voltage is applied to the crucible, and alkali of Na, K and Li is applied. The metal content is 0.2 ppm or less, the Cu content is 0.02 ppm or less, and the viscosity at 1450 ° C. is 10 ¹⁰ poise or more and the electric resistance at 1200 ° C. is 1.4 × 10 ⁷ Ω · m or more. A method of manufacturing a quartz glass crucible characterized by the above. The present invention will be further described below.

The present invention is a method for producing a quartz glass crucible using natural quartz as a raw material. Quartz glass includes natural quartz as a raw material and synthetic quartz as raw material made of silicon tetrachloride. However, the present invention is limited to quartz glass made from natural quartz. Synthetic quartz is ridiculously expensive as compared with natural quartz, and a technique capable of manufacturing it at low cost has not been developed so far.

The reason why the synthetic quartz glass is excluded in the present invention is not only the cost. This is because the synthetic quartz glass has almost no pores inside and is significantly inferior in heat insulation and viscosity as compared with natural quartz glass. Further, when synthetic quartz glass is used, there is a problem that it is difficult to control the temperature of the fused quartz in the crucible. Usually, natural quartz glass has an apparent porosity of about 0.1% and a chlorine content of 1 ppm or less, and is distinguished from synthetic quartz glass.

In the method for producing a quartz glass crucible of the present invention, the contents of Na, Li, K and Cu are limited to the above-mentioned values or less because the alkali metal in the silicon single crystal which is pulled above these values and This is because the copper content increases and it becomes impossible to manufacture a high-quality silicon single crystal used for manufacturing a VLSI.

Further, the reason why the viscosity at 1450 ° C. is limited to the above value or more is that if the value is less than this value, the crucible is easily deformed at the time of pulling up, and the erosion amount of the quartz glass crucible is increased, so that high quality silicon single crystal is also expected. This is because crystals cannot be manufactured. Further, the electric resistance at 1200 ° C. is limited to the above-mentioned value or more because the movement of the remaining alkali metal or the like is taken into consideration when the magnetic field is applied to the molten silicon to pull it up (so-called MCZ) when the value is less than the above value. This is because it suppresses as much as possible and does not easily cause convection of molten silicon.

The above raw materials are crushed by a conventional method,
Purify. The pulverization is adjusted to, for example, 50 to 80 #, and the purification is performed by a flotation method according to a conventional method. Next, this is molded into a crucible and electrolyzed to remove impurities.

Molding into a crucible is carried out by ordinary arc rotary melting, and electrolysis is carried out by applying a high voltage, for example, a voltage of 10 KV, for 5 minutes or more above and below the crucible, whereby alkali metal and copper are crucible. Move out of. This treatment is carried out at a high voltage, but this makes it possible to remove the alkali impurities, and accordingly the viscosity of the crucible is improved and its electrical resistance is also increased. This treatment is determined by the relation between the treatment voltage and the treatment time, and its specification is given by the viscosity and electric resistance value of the obtained crucible.

[0015]

EXAMPLES Examples of the present invention will be described below.

First, natural quartz was crushed and adjusted to 50 to 80 #, and purified by a flotation method. This refined powder was molded by arc rotary melting to prepare a quartz glass crucible. Next, a high voltage of 10 KV above and below this crucible was applied in a furnace at 1300 ° C., and electrolysis was performed for 5 minutes or more to move the alkali metal and copper. The chemical analysis value, viscosity and electric resistance value of this crucible are also shown in Table 1 below.

Further, the quartz glass crucible manufactured by the above method was used for pulling a silicon single crystal by the MCZ method of actually applying a magnetic field to molten silicon. The chemical analysis values of the silicon single crystal obtained as a result are shown in Table 2 below.

[0018]

[Table 1]

[Table 2] As is clear from Table 1, the crucibles of the examples are Na,
Alkali metal content of K and Li is 0.2ppm or less, Cu
Content was 0.02 ppm or less, and the viscosity at 1450 ° C. was 10 ¹⁰ poise or more and the electric resistance at 1200 ° C. was 1.4 × 10 ⁷ Ω · m or more. Therefore, this crucible was capable of pulling a high-quality silicon single crystal because the content of alkali metal and copper was low.

Further, the crucibles of the examples had a high viscosity because the alkali metal, which is the network-modifying ion of quartz glass, was removed, so that the crucibles were not easily deformed even at high temperatures, and were not easily corroded. Therefore, this crucible was capable of pulling a high-quality silicon single crystal without hindering the flow of molten silicon when pulling a silicon single crystal.

Further, in the method of applying a magnetic field to molten silicon (MCZ method), the higher the electric resistance of the crucible, the more the amount of melting into the molten silicon can be reduced. That is, at a high temperature of 1450 ° C., not only the molten silicon but also the quartz glass crucible itself has electrical conductivity, and in the presence of a strong magnetic field, an electric current is generated in both of them to cause complicated convection. When the electric resistance is high as in a crucible, the convection of molten silicon can be controlled, so that the amount of melting loss on the inner surface of the crucible can be reduced and the amount of dissolved oxygen can be reduced. In addition, the migration of alkali metals and the like does not occur, and the content of various metals in the silicon single crystal can be reduced.

In fact, it can be seen from Table 2 showing the result of pulling a silicon single crystal by the MCZ method that the above effects can be obtained.

Of course, the quartz glass crucible obtained by the present invention can be used even when no magnetic field is applied to the molten silicon.

[0023]

As described above in detail, the quartz glass crucible of the present invention has a remarkable effect of improving the manufacturing yield of semiconductor devices.

Claims (1)

[Claims] 1. Natural quartz is crushed and refined, and this is molded into a crucible by arc rotary melting. Then, a high voltage is applied to the crucible to adjust the alkali metal contents of Na, K and Li to 0.
2 ppm or less, Cu content of 0.02 ppm or less, and viscosity at 1450 ° C. of 10 ¹⁰ poise or more, 120
A method for producing a silica glass crucible, which has an electric resistance of 1.4 × 10 ⁷ Ω · m or more at 0 ° C.