JPH09241093A - Quartz crucible having double layer structure for fusing of silicon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a quartz crucible to fuse silicon which does bend inward at its upper part even in a high temp. atmosphere so that a single crystal having a larger diameter can be obtd., and a single crystal without dislocation can be drawn, by forming a two-layer structure of transparent and translucent quartz glass for the crucible to be inserted in a carbon crucible. SOLUTION: A quartz crucible 1 to fuse silicon to be inserted inside of a carbon crucible 5 has a two-layer structure fusing crucible 6 consisting of an upper transparent quartz glass 2 and a lower translucent quartz glass 3 integrated into one body. The transparent quartz glass means that it has <=0.01vol.% air bubbles, while the translucent quartz glass means it has >=0.1vol.% air bubbles. The upper part comprising the transparent glass has length corresponding to at least 25% of the crucible height from the upper edge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon melting quartz crucible used for pulling a silicon single crystal,
More specifically, it relates to a quartz crucible for melting silicon, which prevents deformation of the upper part of the crucible during pulling.

[0002]

2. Description of the Related Art In order to manufacture a silicon single crystal, a method of melting a high-purity silicon raw material in an argon atmosphere under reduced pressure and solidifying it while pulling it upward with a seed crystal is widely used.

FIG. 2 is a longitudinal sectional view showing a silicon single crystal manufacturing apparatus for solidifying while pulling. Reference numeral 9 in the figure
Is a chamber for depressurizing the pulling atmosphere of the silicon single crystal 12, a melting crucible 6 is arranged inside the chamber, and a heating heater 7 composed of an induction heating coil is provided outside the crucible so as to surround it. Further, on the outer side thereof, a heat insulating cylinder 8 formed of a heat insulating material in a cylindrical shape is arranged. In the melting crucible, raw material for crystal growth melted by a heater,
That is, the melt 10 of the silicon raw material is contained. Seed crystal attached to the surface of the melt at the tip of pulling wire 13
The lower end of 11 is brought into contact and the seed crystal is pulled upward to grow a silicon single crystal 12 in which the melt is solidified at the lower end thereof.

At this time, the melting crucible is rotated by the rotating shaft 16, and the silicon single crystal is rotated by the rotating mechanism (not shown) provided above the pulling wire in opposite directions. The melting crucible has a double structure and the inside is made of quartz glass.
(Hereinafter, this is referred to as "quartz crucible"), and the outer side is composed of a carbon container 5 (hereinafter referred to as "carbon crucible").

The inside of the decompression chamber is decompressed to about 10 torr, argon gas is supplied from the gas supply port 14, and SiO gas generated from the surface of the silicon melt and CO gas generated from the carbon crucible and the heater are exhausted. Discharge through mouth 15.

FIG. 3 is a view showing a cross section of a conventionally used crucible for melting silicon, (a) is a vertical cross section of the crucible, and (b) is a cross section.
FIG. 6 is a diagram showing a state in which a single crystal is tilted inward during pulling. As shown in (a), the upper end portion of the melting crucible is configured such that the side wall of the quartz crucible is higher than the side wall of the carbon crucible. Then, during the pulling of the silicon single crystal, the temperature of the portion of the quartz crucible where the silicon melt does not exist becomes higher than the portion where the silicon melt exists. Therefore, when a single crystal with a diameter of 8 inches or more is pulled up, the upper part of the quartz crucible in which the silicon melt does not exist collapses inward as shown in FIG. . Further, SiO gas is generated from the molten liquid of silicon and invades between the quartz crucible and the carbon crucible, and carbon (C) of the carbon crucible undergoes a silicidation reaction (SiO + C → SiC) as shown in FIG. Therefore, the life of the carbon crucible is reduced.

FIG. 1B shows a collapsed portion 17 in which the upper part of the quartz crucible is collapsed inward, and a silicified portion 19 of the carbon crucible. SiO gas adheres to the inner surface 18 of the collapsed portion of the quartz crucible, and the SiO gas is solidified and drops into the silicon melt. If the solidified material that has dropped falls into the silicon single crystal, it becomes difficult to pull up the dislocation-free crystal. Further, when collapse occurs, SiO is formed at the interface 20 between the carbon crucible and the quartz crucible.
Gas easily enters and the carbon crucible is silicified and cannot be reused.

To solve this problem, Japanese Patent Laid-Open No. 63-315263 proposes a melting crucible in which a flange extending outward is integrally provided on the upper end of a cylindrical side wall of a quartz crucible. However, the process of integrally providing the flange is complicated and costly. Therefore, Japanese Patent Application Laid-Open No. 3-290393 proposes a melting crucible in which a quartz ring covering the cylindrical side wall of the melting crucible is provided on the upper end of the side wall. However, when exposed to high temperatures, the quartz ring fuses with the quartz crucible and cannot be removed, and this quartz ring cannot be reused.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to increase the diameter of a single crystal so that the upper part of the quartz crucible does not collapse even in a high temperature atmosphere, and a single crystal without dislocation can be pulled up. To provide.

[0010]

As a result of various investigations on the cause of the collapse of the upper part of the crucible, the present inventor has found that the higher the transparency of quartz glass, that is, the lower the existence rate of bubbles, the less the occurrence of the collapse. Then, the present invention was completed.

The gist of the present invention resides in the following quartz crucible for melting silicon shown in FIG.

A carbon crucible 5 as a double structure melting crucible 6
1. A quartz glass crucible for melting silicon 1, which is inserted inside a quartz melting crucible 1 for melting, wherein upper part 2 is made of transparent quartz glass and lower part 3 is made of semitransparent quartz glass.

Here, the transparent quartz glass has a bubble existence rate of 0.01% or less in volume ratio, and the semitransparent quartz has a bubble existence rate of 0.
It means 1% or more. The upper part made of transparent quartz glass means having a length of at least 25% from the upper end with respect to the crucible height.

[0014]

1 is a longitudinal sectional view showing a silicon melting crucible having a quartz crucible of the present invention inserted therein. As shown in the figure, the melting crucible 6 of the present invention has a double structure in which a quartz crucible 1 is inserted inside an outer carbon crucible 5.

The quartz crucible has an upper part 2 made of transparent quartz glass,
The lower part is composed of semitransparent quartz glass. Since the upper part is made of transparent quartz glass with a bubble existence rate of 0.01% by volume or less, it has good radiant heat permeability, and the temperature rise is reduced by about 100 ° C compared to the conventional crucible. As a result, there is no buckling of the upper part of the crucible due to its own weight and no fall into the crucible. The lower part is composed of semi-transparent quartz glass with a bubble existence rate of 0.1 vol% or more.

The quartz crucible of the present invention is manufactured by melting and shaping quartz powder by a usual arc melting method. For the production, the following conventional methods can be used.

A raw material quartz powder is deposited on the inner peripheral surface of the mold. At this time, by making the particle size of the quartz powder forming the upper part of the crucible sufficiently smaller than the particle size of the quartz powder forming the lower part, the transparency of the upper part can be promoted. Next, the quartz powder deposited on the bottom surface of the mold with a certain thickness is melted by, for example, arc heating, the surface of the deposited quartz layer is melted and vitrified, and the pressure is reduced from the mold side.
Air inside the quartz layer is sucked to the outside through a vent hole provided in the mold to form a transparent glass layer on the surface portion of the quartz layer. After that, the position of the heating source is adjusted, the heating source is brought close to the upper part, and the upper part is remelted under reduced pressure to make the upper part transparent.

In the quartz crucible manufactured by this method, no clear boundary appears in the upper and lower joints 4, but it is confirmed by the change in the abundance ratio of the bubbles. As another method, a quartz partition plate may be provided on the upper and lower portions during manufacturing, and the upper and lower portions may be made transparent and the lower portion may be made semi-transparent by changing the upper and lower vacuum levels. Then, the crucible can be finished by removing the quartz partition plate.

[0019]

【Example】

(Example 1) A quartz crucible having an upper and lower two-layer structure as shown in Table 1 was used as a melting crucible of a single crystal manufacturing apparatus shown in FIG. 2 to perform a test for pulling a silicon single crystal having a diameter of 12 inches. From the observation window of the pulling device, the amount of deformation of the upper part of the quartz crucible (the amount of collapse of the upper part) was measured and the presence or absence of dislocation (defect) was observed, and the results are shown in Table 1.

[0020]

[Table 1]

In Invention Examples 1 to 5, in the upper part of the crucible, the bubble existence rate is set.
Since 0.01% by volume or less of transparent quartz glass was used, the upper part of the crucible did not collapse and dislocation (defect) was not observed in the pulled single crystal.

On the other hand, in Comparative Example 6, since the length of the upper part made of transparent quartz glass is as small as 50 mm, there is a collapse of 50 mm in the upper part of the crucible, and dislocations (defects) occur in a part of the single crystal.
Was observed.

In Comparative Examples 7 and 8, since the transparent quartz glass in the upper part of the crucible was poor in transparency, collapse or buckling of 35 mm was observed in the upper part of the crucible, and dislocations (defects) were observed in the single crystal in all cases. .

In Comparative Examples 9 and 10, the conventional crucible was used, but buckling was observed in the upper part of the crucible, and dislocations (defects) were observed in the single crystal.

(Embodiment 2) Approximately in the height direction from the top of the crucible.
200 mm is a transparent quartz glass with a bubble existence rate of 0.01 vol% or less, and a lower part is a semi-transparent quartz glass with a bubble existence rate of 0.1 vol% or more, and a quartz crucible with an inner diameter of 750 mm and a height of 400 mm is 25 mm. I made a body.

Using a melting crucible in which the above quartz crucible is inserted into a carbon crucible, 200 kg of polycrystalline silicon is melted,
A single crystal with a diameter of 12 inches and a length of 800 mm was produced. Also,
As a comparative example, a conventional silicon crucible as shown in FIG. 3 (a) was used to manufacture the same silicon single crystal.

When the melting quartz crucible of the present invention using transparent quartz glass in the upper portion is used, no deformation or buckling of the quartz crucible was observed in the pulling of 25 single crystals.
The dislocation-free silicon single crystal was pulled up. On the other hand, in the comparative example using the conventional melting crucible, deformation or buckling of the quartz crucible was observed in 18 of the 25 pulls,
Of those 18, eight stopped pulling up.

[0028]

According to the apparatus for producing a silicon single crystal in which the quartz crucible for melting silicon of the present invention is arranged, the diameter of the single crystal is increased without causing the upper part of the quartz crucible to collapse or buckle. Also, a dislocation-free silicon single crystal can be pulled.

[Brief description of drawings]

FIG. 1 is a longitudinal section showing a double crucible for melting silicon, in which a quartz crucible of the present invention is inserted.

FIG. 2 is a vertical sectional view showing a silicon single crystal manufacturing apparatus for solidifying while pulling.

FIG. 3 is a view showing a cross section of a conventionally used silicon melting crucible, (a) is a vertical cross section of the crucible, and (b) is a view showing a state in which the single crystal is tilted inward during pulling.

[Explanation of symbols]

 1. Quartz crucible 2. Upper 3. Lower part 4. Joint 5. Carbon crucible 6. Double structure melting crucible 7. Heater for heating 8. Heat insulation tube 9. Chamber 10. Silicon melt 11. Seed crystal 12. Silicon single crystal 13. Pull bar 14. Gas supply port 15． Gas outlet 16. Rotating shaft 17． Falling part of quartz crucible 18. Inner surface that fell down 19. Siliconized part of carbon crucible 20. Interface between quartz crucible and carbon crucible

Claims (1)

[Claims] 1. A quartz crucible for melting silicon, which is inserted into a carbon crucible as a double-structured crucible, wherein an upper part is made of transparent quartz glass and a lower part is made of semitransparent quartz glass. A quartz crucible for melting silicon.