JPH09208363A - Single crystal pulling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single crystal-pulling up apparatus enabling the rapid growth of solid layer before the pulling up of a single crystal and the fusing of the solid layer so that the interface of the single crystal is smoothen during pulling up of the single crystal. SOLUTION: A first heater 6 having a cylindrical shape and heated by resistance heating is placed outside a crucible 1 in a configuration concentric with the crucible 1. Further, a ring-shaped second heater 7 is placed below the crucible 1 in a figure coaxial with the crucible 1. The first heater 6 and the second heater 7 are stored in a graphite-made heat-insulating container 8 of a cylindrical shell-shape. On the inner peripheral surface of the heat-insulating container 8, a ring-shaped protrusion, which protrudes into between the first heater 6 and the second heater 7, is attached. The front end of the protruding part 8a exists at the center-side of the heat-insulating container 8 from the main heater 6.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to DLCZ (Doubl
The present invention relates to an apparatus for pulling a single crystal by the e-Layered Czochralski method.

[0002]

2. Description of the Related Art FIG. 3 is a schematic side sectional view showing a main part of a conventional single crystal pulling apparatus disclosed in Japanese Patent Application No. 8-8238 by the present applicant. A crucible 1 for feeding raw materials is arranged in a metal chamber 19. In the crucible 1, a quartz outer container 3 having a bowl-shaped lower portion at the lower end of a cylindrical body is fitted with a graphite outer container 3 having a similar shape to the inner container 2.
The crucible 1 is rotated by a graphite support member 5 having substantially the same thermal conductivity as that of the outer container 3, and is also moved up and down. On the outside of the crucible 1, a resistance heating type cylindrical first heater 6 is concentrically arranged with the crucible 1, and below the crucible 1, an annular second heater 7 is coaxial with the crucible 1. It is located at.

The first heater 6 and the second heater 7 are housed in a cylindrical shell-shaped heat insulating container 18. A hole having a diameter slightly larger than the diameter of the crucible 1 is formed on the upper surface of the heat insulating container 18,
A hole having a diameter slightly larger than the diameter of the shaft of the support member 5 is formed on the bottom surface of the support member 5. The support member 5 described above is the second annular member.
The bottom of the chamber 19 is penetrated through a hole formed in the bottom of the heater 7 and the heat insulating container 18. On the other hand, a rod-shaped or wire-shaped pulling shaft 14 is arranged on the central axis of the crucible 1, and a seed crystal 15 is attached to the lower end of the pulling shaft 14.

In order to pull a single crystal by the DLCZ method with such an apparatus, the first heater 6 and the second heater 7 are used.
After melting the raw material charged into the crucible 1 to form a molten liquid, the power of the first heater 6 is reduced, and the power of the second heater 7 is set to zero to set the solid layer S from the bottom of the crucible 1 to a predetermined height. Are grown to form two layers, a solid layer S and a melt layer L.

When the formation of the two layers is completed, the power of the first heater 6 is increased to maintain the surface temperature of the molten liquid layer L at a temperature slightly higher than the melting point of the raw material, and the power of the second heater 7 is also increased. Temperature distribution at the interface of the solid layer S is made uniform, and the seed crystal 15 attached to the lower end of the pulling shaft 14 is brought into contact with the surface of the melt layer, and the pulling shaft 14 and the supporting member 5 are rotationally driven in opposite directions. While pulling the pulling shaft 14 at a predetermined speed, the single crystal 16 is grown below the seed crystal 15. Then, as the melt liquid layer L is reduced by pulling up the single crystal 16, the supporting member 5 raises the crucible 1 to keep the surface height of the melt liquid layer L substantially constant and melt the solid layer S. The melt layer L
By keeping the concentration of oxygen and the dopant in the above, etc. constant, a single crystal 16 of uniform quality in the axial direction is obtained.

[0006]

However, the conventional single crystal pulling apparatus has the following problems.

During pulling up of the single crystal 16, the power of the first heater 6 is controlled so that the surface temperature of the melt layer L becomes constant. The crucible 1 is raised with the decrease in the melt liquid layer L due to the pulling of the single crystal 16, and the solid layer S is melted by the heat transfer from the first heater 6, but the solid layer S is melted only by this heat transfer. Is melted first from the peripheral portion and becomes a conical shape with the central portion remaining, so that when the melt liquid layer L further decreases,
In some cases, the center of the solid layer S and the lower end of the single crystal 16 were fixed and the pulling had to be stopped. for that reason,
The central portion of the solid layer S is heated by the heat transfer from the second heater 7, the melting of the portion is promoted, the interface of the solid layer S is flattened, and the center of the solid layer S and the lower end of the single crystal 16 are formed. Prevented sticking.

However, since the upper part of the crucible 1 has heat input by radiation from the second heater 7 in addition to heat input by radiation from the first heater 6, the surface temperature of the melt layer L is kept constant. Therefore, the power of the first heater 6 must be smaller than that when the second heater 7 does not heat the power. for that reason,
There is a problem that the amount of heat conducted from the first heater 6 to the central portion of the solid layer S is reduced, and the flattening of the interface of the solid layer S is suppressed. This is because, for example, when the diameter of the crucible 1 is increased to obtain a single crystal having a diameter exceeding 8 inches, the power of the second heater 7 must be increased and the power of the first heater 6 must be reduced accordingly. Therefore, it becomes an even bigger problem.

On the other hand, in the step of forming the two layers of the solid layer S and the molten liquid layer L, the power of the second heater 7 is set to zero, but the lower part of the crucible 1 receives much heat due to the radiation from the first heater 6. ,
There is also a problem that the growth of the solid layer S is slow and, as a result, the efficiency of single crystal production is low. As in the previous case, if the diameter of the crucible 1 is increased and the weight of the crucible 1 is not increased so much, the molten liquid becomes shallow and the distance between the lower part of the crucible 1 and the first heater 6 becomes shorter. Since the amount of heat input from the first heater 6 increases, it becomes a further serious problem.

The present invention has been made in view of the above circumstances, and its object is to provide a heat insulator provided with a first heater facing the side surface of the crucible and a second heater facing the bottom of the crucible. A projecting portion projecting between the first heater and the second heater is provided on the inner side surface of the container, and the projecting portion projects radiant heat from the first heater to the bottom of the crucible and from the second heater to the upper portion of the crucible. Provided is a single crystal pulling apparatus capable of melting the solid layer so that the solid layer grows quickly before pulling the single crystal by blocking radiant heat and the interface becomes flat during pulling of the single crystal. To do.

[0011]

A single crystal pulling apparatus according to the present invention comprises a first heater facing a side portion of a crucible filled with a raw material in a heat insulating container, and a second heater facing a bottom portion of the crucible. Is provided, the raw material is melted, and a solid layer obtained by solidifying the melt and a melt layer thereabove coexist, and the solid layer is melted by heating from both heaters to form a single crystal from the melt layer. In the single crystal pulling apparatus for pulling up, the heat insulating container is provided on its inner surface with a protruding portion protruding between the first heater and the second heater.

In the single crystal pulling apparatus of the present invention,
The first placed so as to face the side surface of the crucible into which the raw materials are put.
A heater and a second heater below the first heater and arranged to face the bottom of the crucible are provided in the heat insulating container, and the first heater and the second heater are provided on the inner surface of the heat insulating container.
Since the protrusion that protrudes into the heater is provided,
Radiant heat from the heater is blocked by the protrusion, and the amount of heat reaching below the protrusion is reduced. Therefore, by setting the bottom of the crucible below the protrusion, the solid layer can be grown quickly. Further, the radiant heat from the second heater is also shielded by the protrusion, and the amount of heat reaching above the protrusion is reduced. Therefore, it is not necessary to reduce the power of the first heater during pulling of the single crystal, and the solid layer can be melted so that the interface becomes flat.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic side sectional view showing an essential part of a single crystal pulling apparatus according to the present invention, in which 19 is a metal chamber. In the chamber 19, a crucible 1 for introducing raw materials is arranged. In the crucible 1, a quartz outer container 3 having a bowl-shaped lower portion at the lower end of a cylindrical body is fitted with a graphite outer container 3 having a similar shape to the inner container 2. The crucible 1 is rotated by a graphite support member 5 having substantially the same thermal conductivity as that of the outer container 3, and is also moved up and down. A rod-shaped or wire-shaped pulling shaft 14 is arranged on the central axis of the crucible 1, and a seed crystal 15 is attached to the lower end of the pulling shaft 14.

On the outside of the crucible 1, a resistance heating type cylindrical first
A heater 6 is arranged concentrically with the crucible 1, and an annular second heater 7 is arranged below the crucible 1 coaxially with the crucible 1. The first heater 6 and the second heater 7 Is stored in a cylindrical shell-shaped heat insulating container 8 made of graphite. A hole having a diameter slightly larger than the diameter of the crucible 1 is formed on the upper surface of the heat insulation container 8, and a hole having a diameter slightly larger than the diameter of the support member 5 is formed on the bottom surface of the heat insulation container 8. Support member 5 described above
Penetrates the bottom of the chamber 19 through a hole formed in the bottom surface of the annular second heater 6 and the heat insulating container 7.

An annular projecting portion 8a is provided on the inner peripheral surface of the heat insulating container 8 so as to project between the first heater 6 and the second heater 7, and the tip of the projecting portion 8a is located above the first heater 6. Insulation container 8
On the center side of. An example of the size and installation position of the protruding portion 8a is as follows. Insulation container: Inner diameter 900 x Outer diameter 1000 x Height 1200
mm First heater: inner diameter 700 × outer diameter 750 × height 200 mm Dimension between lower end and bottom of heat insulating container 500 mm Second heater: inner diameter 200 × outer diameter 500 × thickness 20 mm Between lower surface and bottom of heat insulating container Dimension 400 mm crucible: When the outer diameter is 600 mm and the height is 400 mm, the thickness is 50 mm or more and 100 mm or less, and the protruding portion 8a having the longest possible protruding length without contacting the crucible is attached to the first heater 6. 20mm or more from the lower end 1
It is provided at a position of 00 mm or less.

Under the above-mentioned conditions, the thickness of the protruding portion 8a is 50
When the thickness is less than or equal to mm, the effect of shutting off the radiant heat from the first heater 6 or the second heater 7 is low, and when it is greater than or equal to 100 mm, the heat removal due to the radiation from the lower portion of the crucible 1 is obstructed, and the solid layer S formation rate Will be late. When the position where the protruding portion 8a is provided is 20 mm or less from the lower end of the first heater 6,
It is difficult to attach the first heater 6, and the first heater 6
When the distance is 100 mm or more from the lower end of, the effect of blocking radiant heat from the first heater 6 or the second heater 7 is low.

In order to pull a single crystal by the DLCZ method with such an apparatus, the first heater 6 and the second heater 7 are used.
After melting the raw material charged into the crucible 1 to form a molten liquid, the power of the first heater 6 is reduced, and the power of the second heater 7 is set to zero to set the solid layer S from the bottom of the crucible 1 to a predetermined height. Are grown to form two layers, a solid layer S and a melt layer L. At this time, the radiation from the first heater 6 is blocked by the protruding portion 8a, and the amount of heat input from the first heater 6 to the lower portion of the crucible 1 due to the radiation is small, so that the solid layer S grows quickly.

When the formation of the two layers is completed, the power of the first heater 6 is increased to maintain the surface temperature of the molten liquid layer L at a temperature slightly higher than the melting point of the raw material, and the power of the second heater 7 is also increased. Temperature distribution at the interface of the solid layer S is made uniform, the seed crystal 15 attached to the lower end of the pulling shaft 14 is brought into contact with the surface of the melt layer, and the pulling shaft 14 and the supporting member 26 are rotationally driven in opposite directions. While pulling the pulling shaft 14 at a predetermined speed, the single crystal 16 is grown below the seed crystal 15. Then, as the melt liquid layer L is reduced by pulling up the single crystal 16, the supporting member 5 raises the crucible 1 to keep the surface height of the melt liquid layer L substantially constant and melt the solid layer S. The melt layer L
By keeping the concentration of oxygen and the dopant in the above, etc. constant, a single crystal 16 of uniform quality in the axial direction is obtained. At this time, the radiation from the second heater 7 is blocked by the protruding portion 8a, and the second heater 7
Since the amount of heat input to the upper part of the crucible 1 by radiation is small, the heating by the second heater 7 does not affect the power adjustment of the first heater 6. As a result, the solid layer S is melted so that its interface becomes flat.

[0019]

EXAMPLES Next, the results of comparative tests will be described. In order to pull up a single crystal having a diameter of 12 inches, an apparatus of the present invention having the following dimensions and a conventional apparatus having the same dimensions as the apparatus of the present invention except that a protrusion is not provided in the heat insulating container are used as raw materials. High-purity polycrystalline silicon 200
Then, 2 kg of a molten liquid layer and a solid layer was tried by charging kg and 0.6 g of phosphorus-silicon alloy. Insulation container: Inner diameter 900 x Outer diameter 1000 x Height 1200
mm Projection part: Projection length 120 × thickness 50 mm Dimension 30 mm between the upper surface and the lower end of the first heater First heater: Inner diameter 700 × Outer diameter 750 × Height 200 mm Dimension between the lower end and the bottom of the heat insulating container 780 mm 2 heater: inner diameter 200 x outer diameter 500 x thickness 20 mm 330 mm dimension between the lower surface and the bottom surface of the heat insulating container crucible: outer diameter 600 x height 400 mm

As a result, in the conventional apparatus, the solid layer could not be grown without forming a solidified film on the surface of the melt layer. On the other hand, in the device of the present invention, the solid layer could be formed from the bottom of the crucible to the required height.

FIG. 2 shows the results of measuring the resistivity of the single crystal at an appropriate interval in the axial direction by pulling a single crystal having a diameter of 12 inches by 1 m from the melt layer while melting the solid layer. As is clear from FIG. 2, a single crystal having a diameter of 12 inches could be pulled with a substantially uniform resistivity over the entire length. On the other hand, during this pulling operation, the solid layer was melted so that its interface became flat, and the solid layer and the single crystal did not stick to each other until the pulling was completed.

[0022]

As described in detail above, in the apparatus for pulling a single crystal according to the present invention, since the radiant heat from the first heater or the second heater is blocked by the protrusion provided on the inner surface of the heat insulating container, a solid layer is formed. In the two-layer forming step of the melt layer and the solid layer, the solid layer grows to a predetermined height in a short time, and the production efficiency of the single crystal is improved. Further, during the pulling of the single crystal, the interface of the solid layer is melted flat, and the solid layer and the single crystal are prevented from sticking until the end of the pulling of the crystal.
The present invention has excellent effects.

[Brief description of drawings]

FIG. 1 is a schematic side sectional view showing a main part of a single crystal pulling apparatus according to the present invention.

FIG. 2 is a graph showing a change in resistivity of a single crystal in the axial direction.

FIG. 3 is a schematic side sectional view showing a main part of a conventional single crystal pulling apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crucible 2 Inner container 3 Outer container 5 Supporting member 6 First heater 7 Second heater 8 Insulating container 8a Protruding portion L Melt liquid layer S Solid layer

Claims (1)

[Claims] 1. A heat insulating container is provided with a first heater facing a side portion of a crucible filled with a raw material and a second heater facing a bottom portion of the crucible for melting the raw material to obtain a molten liquid. Coexist with a solid layer solidified with a melt layer on it,
In a single crystal pulling device for melting a solid layer by heating from both heaters and pulling a single crystal from a molten liquid layer, a projecting portion that projects between the first heater and the second heater on an inner surface of the heat insulating container. An apparatus for pulling a single crystal characterized by being provided with.