JPH0535715B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a single crystal growth apparatus using the Czyochralski method.

[Prior art]

Figure 4 shows the general Czyochralski method (CZ method)
FIG. 2 is a schematic adiabatic cross-sectional view of a main part of a single crystal manufacturing apparatus according to the present invention. A crucible 1 is disposed in the center of the chamber 10, and a heater 2 made of graphite is placed outside the crucible 1.
Further, a heat insulating wall 3 is disposed concentrically on the outside thereof. The crucible 1 has a double structure in which a quartz container 1b is arranged inside a graphite container 1a, and a shaft 1c for rotating and moving the crucible up and down is connected to the center of its lower bottom. Crucible 1 again
A pulling shaft 7 having a seed crystal 6 fixed to its lower end is vertically disposed above the pull-up shaft 7.

In such a single crystal manufacturing apparatus, the raw material put into the crucible 1 is heated and melted by the heater 2, and after the seed crystal 6 is immersed in the melt, it is rotated by the pulling shaft 7. The single crystal 8 is grown at the lower end of the seed crystal 6.

Generally, when pulling a single crystal, the pulling speed is closely related to the temperature gradient of the single crystal in the pulling direction, and in order to pull the single crystal efficiently, set a temperature gradient above a certain level in the single crystal. There is a need to.

By the way, in the above-mentioned apparatus, around the single crystal 8 there is a radiant heat source such as the crucible 1, the heater 2, and a melt with an extremely high reflectance of 0.7, and the amount of radiant heat received from these is extremely large. The drawback was that the temperature gradient in the pulling direction was small, and the single crystal pulling efficiency was low.

As a countermeasure against this problem, conventionally, as shown in FIG. A configuration has been proposed in which a radiation screen 11 consisting of a tapered part 11c having a truncated conical shape and whose diameter decreases as it goes downward is disposed around the pulling area of the single crystal 8 (Japanese Patent Publication No. 57
−40119).

This radiant screen 11 blocks radiant heat from the crucible 1, heater 2, melt, etc., and
The temperature gradient in the pulling direction is increased, and at the same time, a carrier gas such as Ar, which is fed from above the chamber 10 toward the crucible 1, is guided into the crucible 1,
SiO gas and the like generated from the crucible 1 are guided to the periphery side of the crucible 1 and discharged from below the crucible 1 to the outside of the chamber 10.

[Problem that the invention seeks to solve]

In the case of the conventional device as described above, exhaust gases such as SiO can be effectively discharged, and the radiation screen 1
1, crucible 1, heater 2, melt etc. and single crystal 8
Although the primary radiant heat from these is blocked, the reflected heat radiated from the melt surface toward the single crystal and the radiant screen 11 itself heated to a high temperature result in secondary radiant heat being blocked. Radiant heat is emitted toward the single crystal 8, and the cooling effect on the single crystal 8 itself is insufficient, resulting in the time required for the temperature to pass through the temperature range of 550°C to 850°C, where crystal defects are likely to occur after device processing. As the crystal length increases, a decrease in crystal quality is inevitable.

Furthermore, although the radiation screen 11 itself is made of metal, it has a short lifespan due to melting and deterioration due to SiO gas generated from the melt or high temperatures, and the molten and deteriorated products fall into the melt in the crucible 1 and melt. There were problems such as contaminating the liquid and inducing polycrystallization due to the impact itself caused by dropping.

The present invention has been made in view of the above circumstances, and its purpose is to effectively block radiant heat from heaters, crucibles, melts, etc. without impairing the exhaust gas discharge function, and to effectively block radiant heat from the single crystal. It is an object of the present invention to provide a single crystal manufacturing apparatus that can form an appropriate temperature gradient in the upward direction, increase the pulling rate of the single crystal, and improve manufacturing efficiency.

[Means for Solving the Problems] The apparatus of the present invention includes a crucible for heating and melting a raw material for a single crystal to be produced, a means for pulling the single crystal from the melt in the crucible, and a In a single crystal production apparatus, the apparatus includes a heat shielding member disposed above the melt and around the single crystal pulling area,
The heat shielding member has an annular rim portion, and is suspended from the inner end of the annular rim portion over the melt surface and around the pulling region of the single crystal, and the inner surface facing the pulling region of the single crystal is suspended from the upper end side. A heat insulator formed in an inverted truncated conical ring shape whose diameter decreases toward the lower end, and whose thickness increases partially or entirely as it approaches the melt surface inside the inner and outer surfaces. and a heat shield having a material.

[Effect]

This blocks radiant heat, increases the temperature gradient in the pulling direction of the single crystal, increases the crystal pulling rate, and allows the crystal to pass through the temperature range where crystal defects occur frequently after device processing in a short time.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof. FIG. 1 is a schematic vertical cross-sectional view of a single crystal manufacturing apparatus according to the present invention (hereinafter referred to as the present invention apparatus), and FIG. 2 is a partially enlarged cross-sectional view of a heat shielding member, in which 1 is a crucible and 2 is a heater. , 3 is a heat insulation wall, 4
1 is a heat shielding member, 6 is a seed crystal, 8 is a single crystal, and 10 is a chamber. A crucible 1 is disposed in the center of the chamber 10, and a heater 2 is placed outside of the crucible 1.
However, a heat insulating wall 3 is further disposed concentrically on the outside thereof, and covers the heater 2, the heat insulating wall 3, and the crucible 1 from above the heat insulating wall 3 to the peripheral edge of the melt surface in the crucible 1. A heat shielding member 4 is provided.

The crucible 1 has a double structure in which a quartz container 1b is arranged inside a graphite container 1a, and a shaft 1c for rotating and raising and lowering the crucible 1 is connected to the center of the bottom of the crucible 1. .

Further, above the crucible 1, there is disposed a seed crystal 6 and a pulling shaft 7 for growing a single crystal 8 thereon and pulling it up. The heat shielding member 4 includes a support tube 42 provided on the lower surface of a thick annular rim portion 41 near the outer periphery, and an annular heat shield 43 having a right triangular cross section on the inner periphery. By bringing the support tube 42 into contact with the upper surface of the support plate 3a disposed on the heat retaining wall 3, the heat shield 43 is suspended above the surface of the melt in the crucible 1.

The heat shield 43 has an annular outer annular portion 43a having an L-shaped cross section and an inner annular portion 43b having an inverted truncated cone shape, which are overlapped inwardly and outwardly to form an annular space 43c having a right triangular cross section. Form this space 4
The outer ring part 43a and the inner ring part 43b have flange parts 43e and 43 that protrude outward at their upper ends, respectively.
By engaging the seat part 41a formed on the inner upper surface of the annular rim part 41, the annular rim part 4
It is suspended from 1.

In this state, the outer ring portion 4 of the heat shield 43
The cylindrical part 3a is vertically suspended along the inner side of the peripheral wall of the crucible 1 to just above the melt surface, and a heat insulating material 43d whose thickness increases as it approaches the melt surface is placed inside the heat shield 43. As it approaches the melt surface, the heat insulating function increases, and the horizontal ring edge is located approximately parallel to the melt surface, extending from the vicinity of the peripheral edge to the vicinity of the single crystal pulling region.

Both the outer ring part 43a and the inner ring part 43b are made of high-density graphite, and the heat insulating material 43d is made of a material with excellent heat resistance and low thermal conductivity, such as graphite felt or quartz felt.
By the way, graphite felt has a thermal conductivity of 0.2kcal/
m・hr・℃, and the thermal conductivity is 100kcal/m・
It has more than 500 times the insulation properties of graphite at hr/℃.

In addition, depending on the pulling equipment, the single crystal temperature may vary.
Since the temperature range of 550°C to 850°C is generated at different locations, the insulation material 43d may be used as appropriate depending on the pulling device.
It is possible to provide an appropriate temperature gradient depending on the pulling device by adjusting the thickness of the heat insulating material 43d or by changing the position of the heat insulating material 43d inside the inner ring part 43b and the outer ring part 43a. .

Figure 3 is a graph showing the results of a comparative test of the thermal insulation properties of a single crystal between the device of the present invention and a conventional device, with the horizontal axis representing the single crystal temperature (°C), and the vertical axis representing the distance from the melt surface ( mm). The results plotted with white circles in the graph are those of the apparatus of the present invention, and the results plotted with black circles are those of the conventional apparatus shown in FIG.

As is clear from this graph, the temperature of the single crystal can be significantly reduced using the apparatus of the present invention compared to when using the conventional apparatus. Further, in this test, it was confirmed that the single crystal pulling speed in the conventional apparatus was 1.6 mm/min, but it could be increased to 2.0 mm/min in the case of the apparatus of the present invention.

Furthermore, conventional equipment cannot handle the single crystal temperature range of 550 to 850°C, which is considered to be a temperature range where crystal defects are likely to occur.
The length was about 300 mm, but with the device of the present invention, it was possible to shorten it to 250 mm. As a result, the time the single crystal remained in the range of 550°C to 850°C was 188 minutes with conventional equipment, but
With the device of the present invention, the time could be shortened to 125 minutes. As a result,
Even if a single crystal is subjected to a device process, the density of internal microdefects can be reduced from 10 ⁶ defects/cm ² to less than 10 ⁴ defects/cm ² at an oxygen concentration of 15×10 ¹⁷ atm/cc, and at the same time It has also become possible to reduce the stacking fault density on the surface.

〔effect〕

As described above, in the apparatus of the present invention, the heat shielding member disposed between the crucible, heater, and heat insulating wall that are radiant heat sources and the single crystal to be pulled is arranged so that the front plate facing the single crystal is arranged from the upper end side to the lower end side. It is formed in the shape of an inverted truncated cone, with the inner diameter decreasing as it approaches the melt surface, and a heat insulating material that partially or entirely becomes thicker as it approaches the melt surface is interposed between the front plate and the outer plate. Therefore, the insulation effect increases as it approaches the melt surface, and by actively changing the temperature gradient of the single crystal during pulling, it is possible to shorten the time it takes for the device to pass through the temperature range where defective crystals are likely to occur. The present invention has excellent effects such as being able to reduce the crystal defect density after processing and significantly improving quality.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical sectional view of the device of the present invention, FIG. 2 is a partially enlarged sectional view of the heat shielding member, and FIG. 3 is a graph showing the results of a comparative test between the device of the present invention and a conventional device.
4 and 5 are schematic vertical cross-sectional views of the conventional device. DESCRIPTION OF SYMBOLS 1... Crucible, 2... Heater, 3... Heat insulation wall, 4... Heat shielding member, 6... Seed crystal, 8... Single crystal, 41... Annular rim part, 42... Support cylinder part, 43... Heat shielding body.

Claims (1)

[Scope of Claims] 1. A crucible for heating and melting a raw material for a single crystal to be produced, a means for pulling the single crystal from the melt in the crucible, and a means for pulling the single crystal from the melt in the crucible. In a single crystal manufacturing apparatus, the heat shielding member disposed around the pulling area of the single crystal is composed of an annular rim part and a heat shielding member hanging around the pulling area of the single crystal from the inner edge of the annular rim part, The heat shield is formed into an inverted truncated conical ring shape whose diameter decreases from the upper end to the lower end on the inner surface facing the pulling region of the single crystal, and between the inner surface and the outer surface there is a molten liquid. A single crystal production device characterized by having a heat insulating material whose thickness increases partially or entirely as it approaches the surface. 2. The single crystal manufacturing apparatus according to claim 1, wherein the heat insulating material is graphite felt or quartz felt.