JP2000169281A - Apparatus for pulling crystal substance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce effects of radiant heat on a pulled crystal substance and raise the pulling speed of the crystal substance by installing a heat insulating material on the outer peripheral surface of a melting crucible located above a filling zone for a raw material melt just before starting the pulling of the crystal substance. SOLUTION: A graphite crucible 2 is arranged on the inside of a graphite heater 1 as a heat source for feeding thermal energy to a quartz glass crucible 3 as a crucible for melting a raw material and the quartz glass crucible 3 is held in the interior of the graphite crucible 2. A raw material melt 4 is stored in the interior of the quartz glass crucible 3 and a crystal substance 5 is pulled from the melt 4. An annular heat insulator 6 ending at a position just above the liquid surface of the raw material melt 4 just before the pulling and protruding upward therefrom is installed to cover the outer peripheral surface of the quartz glass crucible 3. Thereby, a great heat load is applied to a lower part of the graphite crucible 2, i.e., a part for retaining the temperature of the raw material melt 4 and a small heat load is applied to the part of the crystal substance 5. Thereby, the large temperature gradient in the pulling shaft direction can be ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal pulling apparatus for a semiconductor single crystal or the like by the Czochralski method (CZ method), and more particularly to a crystal pulling apparatus for producing a high-purity and homogeneous crystal. is there.

[0002]

2. Description of the Related Art For growing a semiconductor single crystal, a CZ method for growing a columnar crystal from a raw material melt in a crucible is used. As the diameter of the crystal increases during the growth of the single crystal, the size of parts in the furnace also increases. As the crucible diameter increases, the heat loss from the melt surface also increases, and the electric power of the resistance heater also increases to compensate for this. For this reason, the radiant heat from the resistance heater hits the crystal, and the temperature gradient in the crystal pulling axis direction decreases,
There was a problem that the pulling speed of the single crystal was not increased and the productivity was poor. Conventionally, in order to solve this kind of problem, a heat radiation plate has been arranged so as to surround the crystal so that radiation from a resistance heater is not directly irradiated to the crystal.

On the other hand, Japanese Utility Model Publication No. 3-43250 discloses that
A crucible used in the CZ method, which has a structure in which a side wall portion made of a cylindrical carbon fiber reinforced carbon material and a pedestal portion made of a graphite material are removably combined, is disclosed.

[0004]

In the conventional method of surrounding a crystal with a heat radiating plate, the surface temperature of the crystal of the heat radiating plate on the side of the heat radiating plate is radiated by the resistance heater unless the heat insulating property of the heat radiating plate is perfect. And the temperature gradient in the direction of the crystal pulling axis is reduced accordingly.

In the crucible disclosed in Japanese Utility Model Publication No. 3-43250, the side wall portion is made of carbon fiber reinforced carbon material which is more heat-insulating than graphite material, and heat is radiated to the crystal by that much. However, the crucible has the drawback that it also blocks the heat necessary to melt the raw material and maintain it in a molten state, and this crucible was originally specified in the same publication as the cooling process. The purpose is to prevent the graphite crucible from being damaged, to reduce the thickness of the crucible itself and to reduce the weight, and the intention is different from the present invention.

According to the present invention, even if the diameter of the pulled crystal is increased and the diameter of the crucible is enlarged, the power for maintaining the temperature of the raw material melt is not consumed more than necessary, and An object of the present invention is to improve the productivity by reducing the influence of radiant heat on the crystal and increasing the pulling speed of the crystal.

[0007]

In order to achieve the above object, in a crystal pulling apparatus according to the present invention, a raw material melting crucible held in a graphite crucible and a raw material melting crucible provided around the graphite crucible are provided. A heat source for supplying heat energy to the melting crucible, a pulling mechanism for pulling a crystal from the raw material melt melted by the heat energy from the heat source,
, Wherein a heat insulating material is provided on the outer peripheral surface of the molten crucible located above the raw material melt filling area immediately before the start of the crystal pulling.

Further, as another crystal pulling apparatus, a raw material melting crucible held in a graphite crucible, a heat source provided to surround the graphite crucible and supplying thermal energy to the raw material melting crucible, and a heat source from the heat source are provided. A pulling mechanism for pulling a crystal from the raw material melt melted by thermal energy, wherein the pulling mechanism is located above a raw material melt filling area immediately before the pulling of the crystal. A crystal pulling apparatus in which a heat insulating material is provided on an inner peripheral surface of the graphite crucible.

The heat insulating material used in each of the two crystal pulling apparatuses is preferably a carbon / carbon fiber composite material. That is, this kind of material is available in high purity, has high mechanical strength, and has thermal conductivity in the direction perpendicular to the laminating direction of carbon fiber which is several minutes smaller than that of carbon constituting a normal graphite crucible. It is one of Although it is conceivable to use a coated carbon fiber felt material or a carbon fiber felt material surrounded by a carbon material, the quartz crucible is deformed during pulling of the crystal and is damaged by stress. Further, a ceramic heat insulating material is not preferably used because it has a high possibility of reacting with quartz glass or being reduced by carbon and contaminating the crystal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the drawings to provide an understanding of the present invention. FIG. 1 is a cross-sectional view showing an outline of a crystal pulling apparatus of the present invention. A graphite crucible 2 is disposed inside a graphite heater 1 as a heat source for supplying thermal energy to a quartz glass crucible 3 as a raw material melting crucible. The quartz glass crucible 3 is held inside the graphite crucible 2. The raw material melt 4 is stored in the quartz glass crucible 3, and the crystal 5 is pulled up from the raw material melt 4 by the pulling mechanism 100. The pulling mechanism 100 includes a seed crystal jig 12,
It comprises a cable 11, a cable winding drum 10, and the like. The graphite crucible 2 terminates immediately above the liquid surface of the raw material melt 4 immediately before being pulled up, and has an annular heat insulating material 6 as shown in FIG. Is covered. In addition,
Reference numeral 7 in FIG. 1 is a heat shielding plate that does not directly relate to the present invention, but blocks radiant heat from surroundings to the crystal body 5. Here, an example of a pulling mechanism of the crystal 5 will be described with reference to FIG. This pulling mechanism encloses the quartz glass crucible 3 as the crucible for melting the raw material shown in FIG. 1 and members around the quartz glass crucible, and is connected to a hoisting motor 9 installed above a vacuum chamber 8 extending upward. A seed crystal holder 12 is attached to the lower part of the cable 11 suspended from the cable hoisting drum 10, and the seed crystal 13 attached below the same seed crystal holder 12 is removed from the raw material melt shown in FIG. This is a mechanism that is immersed in the liquid 4 and pulled up. Reference numeral 14 in FIG.
Denotes a crucible shaft rotation driving motor, and reference numeral 15 denotes a crucible shaft vertical driving motor. The crystal pulling speed is substantially proportional to the temperature gradient mainly in the crystal pulling axial direction near the solid-liquid interface. In order to increase the temperature gradient, there are measures to prevent radiant heat from the heater from being applied to the crystal and to prevent radiant heat from the melt surface from being applied to the crystal. At this time, the heat radiation plate alone has a disadvantage that the heat radiation plate itself has heat due to radiant heat from the heater and the surface of the melt, and the crystal cannot be cooled.
In the present invention, as shown in FIG. 1, since the outer peripheral surface of the quartz glass crucible 3 above the raw material melt 4 is covered with the heat insulating material 6, the heat load is reduced as shown by the arrow in FIG. , That is, the portion where the temperature of the raw material melt 4 is to be maintained is large, and the portion where the temperature of the crystal 5 is small is solved.

Next, as another embodiment, as shown in FIG. 4, the thickness of the upper 1/3 to 1/4 portion of the graphite crucible 2 is reduced to about 1/2, and an annular ring is formed inside the crucible. There is a single crystal pulling apparatus having a configuration in which the heat insulating material 6 is fitted.

FIG. 5 is a cross-sectional view showing the structure of the heat insulating member 6. As the heat insulating material, a carbon / carbon fiber composite material 6-1 is optimal, and the carbon / carbon fiber composite material is shown in FIG. By using the apparatus as shown, the crystal pulling speed, which was conventionally 0.7 to 0.8 mm / min., Was improved to 0.9 mm / min.
By the way, the test outline in this case is 560
mm, height 70 mm, thickness 10 mm.

[0013]

As described above, according to the present invention,
Only the outer peripheral surface of the quartz glass crucible above the surface of the raw material melt immediately before the start of crystal pulling is composed of a heat insulating material, and the graphite crucible below it is used to maintain the temperature of the melt. In addition to applying the necessary and sufficient heat load to the melt, it does not apply unnecessary heat load to the crystal, so that the temperature gradient in the crystal pulling axial direction can be increased and the pulling speed can be increased. This has the effect of improving productivity. Further, the material of the heat insulating material used in the present invention has a feature that it is not broken even if it is made thinner because it has a higher strength than a normal graphite material.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an outline of an apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of a heat insulating material according to one embodiment of the present invention.

FIG. 3 is a schematic diagram of a pulling mechanism used in the device according to one embodiment of the present invention.

FIG. 4 is a sectional view of a main part of an apparatus according to another embodiment of the present invention.

FIG. 5 is a sectional view of a heat insulating material used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Graphite heater 2 Graphite crucible 3 Quartz glass crucible 4 Raw material melt 5 Crystal 6 Thermal insulation 7 Heat shielding plate 8 Vacuum chamber 9 Winding motor 10 Cable winding drum 11 Cable 12 Seed crystal holder 13 Seed crystal 14 Rotation of crucible shaft Driving motor 15 Crucible shaft vertical driving motor 100 Winding mechanism

Claims (3)

[Claims] 1. A raw material melting crucible held by a graphite crucible, a heat source provided surrounding the graphite crucible and supplying thermal energy to the raw material melting crucible, and a raw material melt melted by the heat energy from the heat source A pulling mechanism for pulling up the crystal further, comprising: a heat-insulating system for the raw material melting crucible located above the raw material melt filling area immediately before the start of the crystal pulling. A crystal pulling device comprising a material. 2. A raw material melting crucible held by a graphite crucible, a heat source provided surrounding the graphite crucible and supplying thermal energy to the raw material melting crucible, and a raw material melt melted by the thermal energy from the heat source. A pulling mechanism for pulling up the crystal further, comprising a heat insulating material on an inner peripheral surface of the graphite crucible located above a raw material melt filling area immediately before the crystal pulling. A crystal pulling device comprising: 3. The crystal pulling apparatus according to claim 1, wherein the heat insulating material is made of a carbon / carbon fiber composite material.