JP2644360B2 - Silicon single crystal pulling device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon single crystal pulling apparatus capable of improving the crystallization rate of a silicon single crystal, particularly an antimony-doped silicon single crystal. .

[Conventional technology]

When pulling up a silicon single crystal, a quartz crucible is installed inside and a main chamber with an upper part as a neck part, a gate valve part, a pull chamber and a pulling mechanism part provided above the upper neck part of this main chamber It is widely known to use a device for pulling a silicon single crystal from a silicon melt in a quartz crucible by a pulling means such as a cylinder or a wire. This main chamber has a water jacket structure as a whole, and cools the inside of the main chamber. The stainless steel low temperature surface of the neck is usually exposed.

[Problems to be solved by the invention]

When this conventional pulling apparatus is used, silicon oxide (and in the case of antimony-doped silicon single crystal, antimony oxide) evaporates from the silicon melt of the quartz crucible, and the above-mentioned low-temperature upper neck surface This causes a problem that these precipitates fall and fall into the silicon melt to lower the crystallization rate of the silicon single crystal.

The present invention has been made in order to solve the above-mentioned problems in the prior art, and reduces the precipitation of silicon oxide (antimony oxide in the case of antimony-doped silicon single crystal) in the upper neck portion of the main chamber. The present invention provides a silicon single crystal pulling apparatus capable of increasing the yield of silicon single crystals, particularly antimony-doped silicon single crystals, that is, increasing the single crystallization rate by preventing falling of precipitated substances. The purpose is to do.

[Means for solving the problem]

In order to solve the above-mentioned problems, in the silicon single crystal pulling apparatus of the present invention, a quartz crucible is installed inside and a main chamber having an upper portion as a neck portion, and a main portion provided above the upper neck portion of the main chamber. In a device having a gate valve, a pull chamber and a pulling mechanism, and pulling a silicon single crystal from a silicon melt in a quartz crucible by pulling means, the inner peripheral surface of the neck portion is made of, for example, carbon. This is shielded by a thin cylindrical protective cover.

The thin-walled cylindrical protective cover has a rough inner surface, that is, the surface is made of carbon having a maximum roughness of 1 to 30 μm, or the surface is coated with SiC or Si ₃ N ₄ , or SiC or S
It may be made of i ₃ N ₄ itself. The thin cylindrical protective cover is installed so that the lower end is supported by a small projection or the like at the lower end of the neck portion and substantially fits on the inner surface of the neck portion. Of course, this protective cover is removable for replacement, and it is of course effective to cover only the lower part of the neck portion.

By providing such a protective cover, the temperature of the surface of the upper neck portion of the main chamber, that is, the surface of the protective cover increases, and silicon oxide (and in the case of antimony-doped silicon single crystal, antimony oxide further increases)
Is reduced, and the fall of the precipitate is also reduced.

[Action]

By providing such a protective cover, the temperature of the neck surface, that is, the surface of the protective cover increases, and silicon oxide (in the case of antimony-doped silicon single crystal,
Further, the effect of reducing the precipitation of antimony oxide) and the drop of the deposited substance are also reduced.

The decrease in the fall of the precipitate can be further inferred as follows. On the surface of the protective cover of the present invention, silicon oxide is uniformly and relatively densely deposited and adhered, and the inert gas flowing down the neck, that is, the argon gas flow, prevents the above-mentioned precipitate from peeling off. On the other hand, when the protective cover of the present invention is not used, the precipitate is unevenly formed on the inner surface of the neck portion, that is, only a specific portion is deposited more than others, and the precipitate grows, for example, in the form of a thread, and its tip Part or most of it is cut, and the chance of falling with the gas flow is increased. In addition, since the protective cover does not have the water cooling effect of the neck portion, it is considered that the inner surface of the protective cover becomes high temperature, the above-mentioned precipitates are densified, and the precipitates themselves are reduced.

It is known that a tubular body called a purge tube is suspended below the neck of the main chamber so as to guide an inert gas to be introduced. It is completely different from the protective cover.

〔Example〕

An embodiment of the present invention will be described below with reference to the accompanying drawings.

In the drawing, reference numeral 2 denotes a silicon single crystal pulling apparatus according to the present invention. The lifting device 2 has a main chamber 6 having an upper portion as a neck portion 4. This main chamber 6
A pull chamber (not shown) and a pull-up mechanism (not shown) are provided above the upper neck part 4 via a gate valve part 8. The pull chamber and the pulling-up mechanism are well-known, and description thereof is omitted.

A quartz crucible 12 is provided inside the main chamber 6 via a support shaft 10. Polycrystalline silicon is melted in the quartz crucible 12 to form a silicon melt 14.
16 is a heater provided around the quartz crucible 12,
Reference numeral 18 denotes a heat shield plate provided around the heater 16.
Reference numeral 20 denotes an upper lid forming the upper part of the main chamber 6, and the upper part of the upper lid 20 is narrowed to form the above-mentioned neck part 4. Reference numeral 22 denotes a monitoring window provided on an upper portion of the upper cover 20, which is used for monitoring the inside of the main chamber 6. The entire main chamber 6 has a water jacket structure in order to prevent the temperature from rising, and the temperature of the inner peripheral wall surface of the neck portion 4 is also reduced. Reference numeral 24 denotes a pulling means which is suspended vertically from the pull chamber 8, and in the illustrated example, a pulling shaft. A seed crystal 26 is attached to the tip of the pulling shaft, and the seed crystal 26 is immersed in the silicon melt 14. By gradually pulling up the pulling shaft 24, the silicon single crystal 28 is grown and pulled up. As the lifting means 24, one using a flexible means such as a wire in addition to the lifting shaft is used.

Reference numeral 30 denotes a protective cover fitted to the inner peripheral wall surface of the neck portion 4 and is formed of carbon. As the structure of the protective cover 30, for example, a short tubular member may be attached, or the inner peripheral surface of the neck portion 4 may be covered with carbon. As a material of the protective cover 30, carbon coated with SiC or Si ₃ N ₄ can be applied in addition to carbon. Further, as the material of the protective cover, a material made of only SiC or Si ₃ N ₄ can be used. What is important is that the surface of the protective cover is effectively rough, and it is preferable that the maximum surface roughness (Rmax) is 1 to 30 μm. If the surface is as smooth as a mirror surface, problems such as the metal surface under the neck occur, and if it is too rough, the same phenomenon often occurs. The size of the protective cover does not necessarily have to cover the entire surface of the neck portion, and the effect of the present invention can be obtained by blocking the lower portion adjacent to the main chamber.

By providing such a protective cover 30, the temperature of the surface of the neck portion 4, that is, the surface of the protective cover 30 rises, and the precipitation of silicon oxide (and in the case of antimony-doped silicon single crystal, antimony oxide) further increases. The effect is obtained that the amount of the precipitate decreases and the fall of the precipitate also decreases.

An exhaust port 32 is connected to a vacuum pump (not shown) and is used for adjusting the pressure of the inert gas in the main chamber and exhausting the same.

Main chamber 6 with the above protective cover 30 attached
An example of an experiment using the lifting device 2 including the following will be described below.

Experimental Example 25 kg of polycrystalline material is set in a quartz crucible. The inside of the main chamber is replaced with a vacuum, and an inert gas (argon) is introduced to set the pressure to about 50 mb. An electric current is applied to the heater to melt the polycrystalline raw material in the quartz crucible. After melting, 200 g of antimony particles are charged into the silicon melt. A seed crystal was attached to the tip of the pulling shaft, and the pulling shaft was lowered to allow the seed crystal to adapt to the silicon melt. The pulling shaft was gradually raised to pull up a silicon single crystal rod having a predetermined diameter. By this operation, for each of the three types of 4 ″, 5 ″, and 6 ″ diameters, 20
The pulling operation of the silicon single crystal rod was performed several times. The results of this experiment are shown in Table 1. The silicon single crystal rod was pulled up by the same operation when the protective cover was not attached, and the results are also shown in Table 1.

Table 1 shows the effect of the presence or absence of the protective cover on the pulling of three types of single crystals of 4 ", 5", and 6 "in diameter. The single crystallization ratio was compared, and the comparison value with the case without the protective cover was shown assuming that the case with the protective cover was 100, where the single crystallization ratio was defined as the single crystallization ratio after 20 times of pulling. Only the crystals pulled up by the crystal were counted and expressed as a percentage, and it was found that each of the protective covers was effective at each diameter, and was particularly effective at a large diameter. The material of the protective cover used had a maximum surface roughness of about 5 to 10 μm, and the material was carbon.

〔The invention's effect〕

As described above, according to the present invention, the precipitation of silicon oxide (antimony oxide in the case of antimony-doped silicon single crystal) at the upper neck portion of the main chamber is reduced, and the fall of the deposited material is also reduced. The yield of the silicon single crystal, particularly the antimony-doped silicon single crystal, that is, a large effect of increasing the single crystallization ratio can be achieved.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing an embodiment of the present invention. 2 ... Lifting device, 4 ... Neck, 6 ... Main chamber, 8 ... Gate valve, 12 ... Quartz crucible, 14 ...
… Silicon melt, 16… Heater, 24… Pull-up shaft, 26
…… Seed crystal, 28 …… Silicon single crystal, 30 …… Protective cover.

Claims (4)

(57) [Claims] 1. A main chamber having a quartz crucible therein and an upper portion as a neck portion, and a gate valve, a pull chamber, and a pulling mechanism portion provided above the upper neck portion of the main chamber. In a device for pulling a silicon single crystal from a silicon melt in a quartz crucible by a pulling means, a thin cylindrical protective cover made of a heat-resistant material having a rough surface of 1 to 30 μm (Rmax) is provided on the inner surface of the neck portion. An apparatus for pulling a silicon single crystal, which is shielded by fitting. 2. The apparatus for pulling a silicon single crystal according to claim 1, wherein said protective cover is made of carbon. 3. The silicon single crystal pulling apparatus according to claim 1, wherein said protective cover is made of carbon coated with SiC or Si ₃ N ₄ . 4. The apparatus according to claim 1, wherein said protective cover is made of SiC or Si ₃ N ₄ .