JP2513641Y2 - Graphite crucible for semiconductor single crystal pulling equipment - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION This invention relates to improvement of a graphite crucible for a semiconductor single crystal pulling apparatus.

[0002]

2. Description of the Related Art As a method for producing a semiconductor single crystal, for example, a high-purity silicon single crystal, polycrystalline silicon is charged into a quartz crucible held by a graphite crucible,
A method is known in which the polycrystalline silicon is melted by a heater, and the silicon melt is gradually pulled up and solidified based on a seed crystal to be solidified. As shown in FIG. 4, the graphite crucible conventionally used in this method is a graphite crucible 9 when the semiconductor material in the quartz crucible 5 is melted.
The upper surface of the graphite crucible 5 was higher than the upper surface of the quartz crucible 5, and the upper surface of the graphite crucible 9 was flat.

[0003]

Although the upper surface of the conventional graphite crucible 9 is horizontally cut, since the temperature of the upper surface of the graphite crucible 9 is low, the silicon monoxide vaporized from the silicon melt 6 becomes graphite. The crucible 9 was deposited on the upper surface of the crucible 9 to form a residue, which was easy to attach 10. Further, since the upper surface of the quartz crucible 5 is lower than the upper surface of the graphite crucible 9 during melting of silicon, when a turbulent air flow occurs in the atmospheric gas, the silicon monoxide deposit 10 on the upper surface of the graphite crucible 9 grows into a silicon single crystal. The shape is such that it easily drops onto the surface, and because of these, the defect-free ratio of the silicon single crystal was not necessarily sufficiently high.

Therefore, the present invention suppresses the deposition of silicon monoxide on the upper surface of the graphite crucible, and even if it deposits, it prevents the deposition of silicon monoxide deposits on the silicon single crystal growth surface. An object is to provide a graphite crucible for a semiconductor single crystal pulling apparatus having a high defect crystal ratio.

[0005]

According to the present invention, the upper surface of a graphite crucible is formed lower than the upper surface of the quartz crucible when the semiconductor material in the quartz crucible is melted, and at least the outer peripheral portion of the upper surface of the graphite crucible is outside. The above object is achieved by forming the plate so that the height thereof decreases toward one side.

[0006]

[Function] Since at least the outer peripheral portion of the upper surface of the graphite crucible is formed so as to decrease in height toward the outside, silicon monoxide which tends to adhere to the upper surface of the graphite crucible easily falls to the outside of the graphite crucible, Adhesion of silicon monoxide to the upper surface of the graphite crucible is suppressed. Even if silicon monoxide adheres to the upper surface of the graphite crucible, since the upper surface of the quartz crucible is higher than the upper surface of the graphite crucible, the drop of silicon monoxide onto the growth surface of the silicon single crystal is suppressed, and thus, no defect occurs. A semiconductor single crystal with a high ratio can be obtained.

[0007]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a vertical sectional view showing an example of a semiconductor single crystal pulling apparatus using an embodiment of a graphite crucible according to the present invention.
A heat insulation tube 2 is arranged inside the container coaxially with the decompression container 1, a heater 3 is arranged inside the heat insulation tube 2 coaxially with the heat insulation tube 2, and a heater is provided inside the heater 3. A graphite crucible 4 is coaxially and rotatably arranged with the quartz crucible 3, and a quartz crucible 5 is held in the graphite crucible 4. Polycrystalline silicon is introduced into the quartz crucible 5, the polycrystalline silicon is heated by the heater 3 to become a silicon melt 6, and the silicon melt 6 is gradually pulled up based on the seed crystal 7. The single crystal 8 is obtained.

FIG. 2 is an enlarged cross-sectional view of portion A in FIG. 1. The inner peripheral portion of the upper surface of the graphite crucible 4 of this embodiment is formed into a flat surface 4a, but the outer peripheral portion of the upper surface of the graphite crucible 4 is tapered. , That is, the conical surface 4b. The upper surface of the quartz crucible 5 when the semiconductor material in the quartz crucible 5 is melted is formed higher than the upper surface of the graphite crucible 4. This protrusion amount h can be set to 2 to 5 mm. Before heating the semiconductor material, the quartz crucible 5 is placed between the outer surface of the quartz crucible 5 and the inner surface of the graphite crucible 4.
There is a gap that can fit inside. Further, when the material is heated, the quartz crucible 5 softens and conforms to and adheres to the inner surface of the graphite crucible 4. Therefore, as the semiconductor material is heated, the quartz crucible 5 sinks into the graphite crucible 4. In this embodiment, the upper surface of the quartz crucible 5 is higher than the upper surface of the graphite crucible 4 even if the quartz crucible 5 sinks into the graphite crucible 4 due to heating.

This embodiment is formed as described above,
Since the outer peripheral portion of the upper surface of the graphite crucible 4 is chamfered,
The silicon monoxide that tends to adhere to the upper surface of the graphite crucible 4 easily falls to the outside of the graphite crucible 4, and therefore the adhesion of silicon monoxide to the upper surface of the graphite crucible 4 is suppressed. Even if silicon monoxide adheres to the upper surface of the graphite crucible 4, since the upper surface of the quartz crucible 5 is higher than the upper surface of the graphite crucible 4, it functions as a barrier, and the silicon monoxide on the growth surface of the silicon single crystal grows. Fall is suppressed, and as a result, a semiconductor single crystal having a high defect-free ratio can be obtained.

Table 1 below shows whether or not silicon monoxide is attached to the upper surface of the graphite crucible 4 in comparison with the case where the conventional graphite crucible 9 shown in FIG. 4 is used. As is apparent, in this example, the adhesion of silicon monoxide to the upper surface of the graphite crucible 4 could be significantly reduced.

[0011]

[Table 1]

Further, by comparing the above-mentioned embodiment with the conventional example shown in FIG. 4, the improvement rate of the defective number and the improvement rate of the single crystallization rate were obtained. The defective line rate and its improvement rate are the number of defective lines = n / N x 100% when the number of collapsed n-crystals is increased when pulling N single crystals. Improvement rate = (rate of defective lines in the conventional example)- (Percentage of defective lines in this example). The single crystallization rate and its improvement rate were d = 1 for a defect-free single crystal and d = 0.5 for a crystal that collapsed during pulling.
Those collapsed tail as d = 0.8, the single crystallization ratio _{= Σ N d / N × 100} % improvement rate = (single crystallization rate of the present example) - in (single crystallization rate of the prior art) I asked. As a result, the improvement rate of the defective line rate ≈7% and the improvement rate of the single crystallization rate ≈4% were obtained. That is, according to this example, it was possible to considerably improve the defective line rate and the single crystallization rate.

In the above embodiment, the inner peripheral portion of the upper surface of the graphite crucible 4 is formed on the flat surface 4a and the outer peripheral portion is formed on the conical surface 4b. However, the entire upper surface of the graphite crucible 4 may be formed on the conical surface 4b. Further, the upper surface of the graphite crucible 4 can be formed to have an arc surface 4c in cross section as shown in FIG. That is, the upper surface of the graphite crucible 4 may be formed so that at least the outer peripheral portion of the graphite crucible 4 is reduced in height toward the outside.

[0014]

[Effects of the Invention] The present invention suppresses the adhesion of silicon monoxide to the upper surface of the graphite crucible, and even if the silicon monoxide adheres to the upper surface of the graphite crucible, the drop of silicon monoxide on the growth surface of the silicon single crystal is suppressed. Therefore, a graphite crucible capable of producing a semiconductor single crystal having a high defect-free ratio was obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an example of a semiconductor single crystal pulling apparatus using an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of the main part of the embodiment.

FIG. 3 is a longitudinal sectional view of a main part of another embodiment.

FIG. 4 is a vertical sectional view of a main part of a conventional example.

[Explanation of symbols]

1 ... Decompression container 2 ... Insulation cylinder 3 ... Heater
4 ... Graphite crucible 4a ... Plane 4b ... Cone surface 4c ... Cross section arc surface 5 ... Quartz crucible 6 ... Silicon melt 7 ... Seed crystal 8 ... Silicon single crystal 9 ... Graphite crucible 10 ... Silicon monoxide deposit

Claims (1)

(57) [Scope of utility model registration request] 1. A graphite crucible for a semiconductor single crystal pulling apparatus holding a quartz crucible, wherein the upper surface of the graphite crucible when the semiconductor material in the quartz crucible is melted is lower than the upper surface of the quartz crucible, and the graphite A graphite crucible for a semiconductor single crystal pulling apparatus, characterized in that at least an outer peripheral portion of an upper surface of the crucible is formed so as to decrease in height outward.