JPS646158B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a silica glass crucible, and is particularly used for pulling silicon single crystals. Silicon single crystals are usually pulled in the following manner. That is, silicon polycrystals are loaded into a quartz glass crucible and placed inside a graphite crucible. This crucible is heated from the surroundings to approximately 1450℃.
A silicon single crystal ingot is obtained by melting a silicon polycrystal while maintaining the same temperature, dipping a silicon single crystal seed crystal, and slowly cooling it while pulling it up. However, with this method, corrosion of the quartz glass crucible that is in contact with molten silicon cannot be avoided, and impurities from the crucible are mixed into the pulled silicon single crystal. In particular, when the concentration of Group 1 alkali metals or copper is high, lattice defects occur in silicon single crystals, which is one of the causes of lower manufacturing yields. In addition, since it is used at a high temperature of approximately 1450℃,
If the viscosity of the quartz glass crucible is low, the crucible will bend and distort violently, making the flow of molten silicon irregular and increasing the amount of erosion of the crucible, making it difficult to pull high-quality silicon single crystals. It was hot. The present invention has been made in order to eliminate the above-mentioned drawbacks, and aims to provide a quartz glass crucible that can produce high quality silicon single crystals. That is, the quartz glass crucible of the present invention is used when pulling a silicon single crystal by applying a magnetic field to molten silicon.
The alkali metal content of Na, K, and Li is
0.2ppm or less, Cu content is 0.02ppm or less,
And the viscosity at 1450℃ is 10 ^{to 10} poise or more, 1200
It is characterized by an electrical resistance of 1.4×10 ⁷ Ω·m or more at °C. In the quartz glass crucible of the present invention, Na, Li,
The reason why the content of K and Cu is limited to below the above values is that when these values are exceeded, the content of alkali metals and copper in the silicon single crystal that is pulled increases, and the high quality used for manufacturing VLSI is This is because it becomes impossible to manufacture silicon single crystals. Also,
The reason why the viscosity at 1450°C was limited to the value above is that if it is less than this value, it will be easily deformed during pulling and the quartz glass crucible will be eroded to a large extent, making it impossible to produce high quality silicon single crystals. . Furthermore, the electrical resistance at 1200℃ was limited to the value above, because if it is less than the above value, when pulling the molten silicon by applying a magnetic field (the so-called MCZ method), it may cause the movement of alkali metals, etc. This is to facilitate silicon convection. Examples of the present invention will be described below. First, crush the natural crystal and adjust it to 50~80#,
Refined by flotation method. This refined powder was molded by arc rotation melting to produce a quartz glass crucible. Next, the top and bottom of this crucible are placed in a 1300℃ furnace.
A direct current of 10 kV was applied to electrolyze for 5 minutes or more, and the alkali metal and copper were transferred. The chemical analysis values, viscosity and electrical resistance values of this crucible are shown in Table 1 below. In addition, as a comparative example, we crushed natural crystal and
After adjusting the powder to # and refining it by the flotation method, this refined powder was molded by arc rotation melting to produce two types of conventional silica glass crucibles. The chemical analysis values, viscosity, and electrical resistance values of these crucibles are also listed in Table 1 below. Furthermore, the silica glass crucible manufactured by the above method was actually used to pull silicon single crystals by the MCZ method, which applies a magnetic field to molten silicon, and the chemical analysis values of the silicon single crystals obtained as a result are shown in the second section below.
Shown in the table.

【table】

[Table] As is clear from Table 1, the crucible in the example was
The alkali metal content of Na, Li, and K is 0.2 ppm or less, the Cu content is 0.02 ppm or less, and 1450
The viscosity at ℃ is 10 ¹⁰ poise or more, and the electrical resistance at 1200 ℃ is 1.4×10 ⁷ Ω・m or more. That is, since the crucible of the example has a low content of alkali metal and copper, it is possible to pull a high quality silicon single crystal. Furthermore, since the alkali metal ions that modify the network of silica glass have been removed from the crucible of the example, it has a high viscosity and is not easily deformed even at high temperatures, and is also resistant to corrosion. Therefore, the flow of molten silicon is not obstructed when pulling a silicon single crystal, and a high quality silicon single crystal can be pulled. Furthermore, in the method of applying a magnetic field to molten silicon (MCZ method), the higher the electrical resistance of the crucible, the more the amount dissolved into molten silicon can be reduced. In other words, at a high temperature of 1450°C, not only the molten silicon but also the silica glass crucible itself has electrical conductivity, and in the presence of a strong magnetic field, current is generated in both, causing complex convection. When the electrical resistance is high as in a crucible, convection of molten silicon can be suppressed, so the amount of erosion on the inner surface of the crucible is reduced, and the amount of dissolved oxygen can be reduced. In addition, 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 results of pulling silicon single crystals by the MCZ method that the above-mentioned effects can be obtained. As described in detail above, the quartz glass crucible of the present invention can pull silicon single crystals of extremely high quality, and has remarkable effects such as being able to improve the manufacturing yield of semiconductor devices.

Claims (1)

[Claims] 1. In the quartz glass crucible used when pulling a silicon single crystal by applying a magnetic field to molten silicon, the alkali metal content of Na, K, and Li is 0.2 ppm or less, and the Cu content is 0.02 ppm or less. , and the viscosity at 1450℃ is 10 ¹⁰ poise or more, and the electrical resistance at 1200℃ is 1.4×10 ⁷ Ω・m
A quartz glass crucible characterized by the above.