JP2580197B2 - Single crystal pulling device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a single crystal pulling apparatus for pulling and growing a single crystal rod by the Czochralski method.

[Conventional technology]

Conventionally, this type of single crystal pulling apparatus includes an upper flat annular rim that protrudes outward from the edge of the crucible, and is attached to the annular rim and inclined downwardly into a cylindrical shape from the inner edge. Alternatively, a crucible and a semiconductor melt contained in the crucible are partially covered with a cover device comprising a conical tapered connecting portion (see Japanese Patent Publication No. 57-40119). ).

This cover device protects the single crystal rod by reflecting the heat radiation from the exposed wall surface of the crucible, and this temperature shield enables a high pulling speed.

[Problems to be solved by the invention]

However, in the single crystal pulling apparatus, the entire amount of the inert gas introduced into the apparatus from the top of the apparatus passes through the gap between the edge of the cover connecting portion and the single crystal rod, and then melts the semiconductor melt. It is discharged out of the crucible along with the silicon monoxide (SiO) generated from the melt through the liquid surface. However, on the lower surface of the flat annular rim of the cover, the monoxide generated from the melt is evaporated. There is a problem that silicon is condensed and solidified particles fall on the surface of the melt to hinder single crystallization.

In addition, since the surface of the melt near the inner peripheral wall of the crucible is covered with the annular rim, the situation cannot be observed from the outside, and the upper end of the crucible is thermally deformed or recrystallized near the inner peripheral wall of the crucible. There is also a problem that even if a problem such as adhesion of silicon or silicon occurs, it cannot be promptly dealt with.

The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent silicon monoxide generated from a melt in a crucible from being easily condensed, and solidified particles falling onto the surface of the melt. It is an object of the present invention to provide a single crystal pulling apparatus in which the factors that hinder single crystallization can be eliminated, and the surface of the melt near the inner peripheral wall of the crucible can be easily observed.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a single crystal pulling apparatus by a Czochralski method for pulling and growing a single crystal rod from a crucible in a downflow atmosphere of an inert gas in a chamber. A cylindrical main body having a diameter smaller than the inner diameter, and an inclined cylindrical part tapering inward following the lower end of the cylindrical main body and having a tapered tip edge larger than the diameter of the single crystal rod; A reflector formed so as to surround the crystal rod is provided, and the flow of the inert gas supplied from above the chamber flows through the inside of the cylinder main body, flows through the gap between the tip edge of the inclined cylinder part and the single crystal rod, and melts. A structure that branches into a first gas flow discharged to the outside of the crucible after being guided to the liquid surface, and a second gas flow guided to the outside of the crucible from outside the cylinder main body and merges with the first gas flow. A single crystal pulling device characterized by To.

[Action]

Explaining the flow of the inert gas in the single crystal pulling apparatus of the present invention, the downward flow of the inert gas supplied from the upper part of the chamber branches into the inside of the reflector and the gap between the inner surface of the chamber and the outer surface of the reflector. The inert gas branched into the reflector descends in the cylinder main body of the reflector, then the gap between the tip edge of the inclined cylinder portion of the reflector and the single crystal rod, and then the gap between the tip edge of the inclined cylinder portion and the melt surface. The gas passes through the gap, is guided to the surface of the melt surface, and is discharged out of the crucible through the gap between the outer peripheral surface of the cylindrical body and the crucible with the silicon monoxide evaporated from the melt surface (first gas). Flow). On the other hand, the inert gas (second gas flow) branched into the gap between the inner surface of the chamber and the outside of the reflector passes through the outside of the cylinder main body, merges with the first gas flow outside the upper end edge of the crucible, and then out of the apparatus. Is to be discharged.

As described above, by dividing the flow of the inert gas supplied into the chamber into the first gas flow flowing inside the cooling cylinder and the second gas flow flowing outside the cooling cylinder, the surface of the melt surface is The flow rate and flow rate of the flowing inert gas can be controlled. Further, in the vicinity of the upper edge of the crucible, an aspiration effect is generated by the second gas flow. Therefore, as a result of sucking the inside of the crucible, an atmosphere containing silicon monoxide is involved from the surface of the melt and discharged to the outside of the crucible.

Therefore, it is possible to prevent silicon monoxide from adhering to the reflector as much as possible, to maintain a uniform oxygen concentration distribution on the melt surface, and to obtain a high-quality single crystal.

In addition, since there is a gap between the inner peripheral surface of the crucible and the reflector, and the surface of the melt near the inner peripheral wall of the crucible is not covered, if a viewing window is provided at the upper part of the apparatus so that the inside can be seen through,
The melt surface can be directly observed.

〔Example〕

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

1 and 2 show an embodiment of the present invention. FIG. 1 is a schematic configuration diagram, and FIG. 2 is a sectional view taken along line AA 'in FIG.

In these figures, a quartz crucible 2 is provided substantially at the center of a chamber 1. And quartz crucible 2
Is mounted on a lower shaft 3 which is rotatable and vertically movable via a graphite susceptor 2 '. Around the quartz crucible 2, a heater 5 for controlling the temperature of the silicon melt 4 in the quartz crucible 2 is installed.
A heat retaining cylinder 6 is disposed between the heater 5 and the chamber 1. A ring-shaped support member 7 is provided on the upper surface of the heat retaining cylinder 6, and the reflector 8 is supported by the support member 7.

The reflector 8 has a cylindrical portion 9a whose outer diameter is set slightly smaller than the inner diameter of the quartz crucible 2, and an inclined cylindrical portion gradually tapering inward as it goes downward following the lower end of the cylindrical portion 9a.
A reflector body 9 integrally formed with or separately assembled from a reflector 9b, and three curved hooks (equally spaced at the upper end edge of the cylindrical portion 9a of the reflector body 9 and supported on the upper surface of the support member 7). Locking portion) 10.

A cooling cylinder 11 is provided vertically above the chamber 1 so as to communicate with the opening of the chamber, and the inert gas flowing down from the opening of the chamber is guided to the pulled single crystal rod 12 to cool the single crystal rod 12. It is supposed to. The lower edge of the cooling cylinder 11 slightly enters the upper end opening of the cylindrical portion 9a, and the upper inner peripheral surface of the cylindrical portion 9a and the lower outer peripheral surface of the cooling cylinder 11 are separated to form a gap G4 therebetween. . The gap G4 is a passage for guiding the flow of the inert gas flowing down from above the chamber to the outside of the cylindrical portion 9a. In this case, since the lower edge of the cooling cylinder 11 is slightly entering the cylindrical portion 9a, the downward flow of the inert gas once rises in the gap G4 and then flows outside the cylindrical cylinder 9a. , A resistance portion of a second gas flow described later.

The diameter of the tip end of the inclined cylindrical portion 9b is formed slightly larger than the diameter of the single crystal rod 12, and the inclined cylindrical portion 9b, the tip end and the single crystal rod are formed.
12, a gap G1 is formed between the melt G and the surface of the melt 4 in the crucible 2. A gap G3 is also formed between the outer peripheral surface of the cylindrical portion 9a and the inner surface of the crucible 2, and an inert gas flows through these gaps G1, G2, G3.

In this case, as the single crystal rod 12 is pulled up, the melt surface lowers,
Accordingly, when the crucible 2 is raised so as to keep the gap between the lower surface of the inclined cylindrical portion 9b and the melt surface constant, the cylindrical portion
9a enters the crucible 2, but since the cylindrical portion 9a is formed in the vertical direction and the outer diameter is smaller than the inner diameter of the crucible 2, the gap G3 with the inner surface of the crucible 2 is kept constant. It has become.

In the single crystal pulling apparatus configured as described above,
As in the conventional case, after the seed crystal is immersed in the silicon melt 4 in the quartz crucible 2 and the seed crystal is pulled up, the single crystal rod 12 grows sequentially at the lower end of the seed crystal. Here, the flow of the inert gas in the lifting device of the present invention will be described.

The inert gas, for example, argon gas, supplied into the cooling cylinder 11 of the chamber 1 passes through the first gas flow F1 descending in the reflector main body 9 as it is, and passes through the gap G4 between the cooling cylinder 11 and the reflector main body 9 to form the reflector main body. It branches into a second gas flow F2, which descends outward from the outside.

The argon gas of the first gas flow F1 flows between the inner peripheral surface of the cylindrical portion 9a and the single crystal rod 11, and cools the single crystal rod 11. Then, the argon gas flows through the narrow gap G1 between the tip edge of the inclined cylindrical portion 9b and the single crystal rod 12, and is guided to the melt 4 surface.
9b flows through the gap G2 between the leading edge and the melt 4 surface, and contains silicon monoxide which flows horizontally on the melt 4 surface and evaporates from the melt 4 surface. Argon gas with silicon monoxide is
Next, the gap G3 between the inner surface of the crucible 2 and the outer peripheral surface of the cylindrical portion 9a rises and is discharged to the outside of the crucible 2.

On the other hand, the argon gas of the second gas flow F2 descends through the gap between the outer surface of the cylindrical portion 9a and the heat retaining material 6 and reaches the edge of the crucible 2, where it merges with the argon gas of the first gas flow F1.

The merged argon gas is discharged to the outside of the chamber 1 after descending through the gap G5 between the crucible 2 and the heat insulating material 6.

Here, the resistance in the first gas flow F1 mainly depends on the inclined cylindrical portion.
The gap G1 between the leading edge of the single crystal rod 12 and the single crystal rod 12, the gap G2 between the leading edge of the inclined cylindrical portion 9b and the surface of the melt 4, and the gap G3 between the cylindrical portion 9a and the crucible 2 in the second gas flow. Resistance is mainly the cooling cylinder
This is a gap G4 between 11 and the cylindrical portion 9a. Therefore, by adjusting these gaps, the flow rates of the first gas flow F1 and the second gas flow F2 can be adjusted, and the flow rate and the flow rate of the first gas flow F1 flowing on the surface of the silicon melt can be reduced. It has a controllable structure.

Further, an aspiration effect is generated in the vicinity of the upper edge of the crucible 2 by the second gas flow F2. Therefore, as a result of sucking the inside of the crucible 2, the atmosphere containing silicon monoxide is involved from the surface of the melt and discharged to the outside of the crucible 2. . Therefore, the attachment of silicon monoxide to the reflector 8 can be prevented as much as possible, the oxygen concentration distribution on the surface of the melt 4 is maintained uniformly, and the oxygen concentration contained in the single crystal 12 can be controlled.
High quality single crystals can be obtained.

Moreover, the surface of the silicon melt 4 near the inner peripheral wall of the quartz crucible 2 can be visually recognized from the viewing window 13 of the furnace main body 1 through the gap between the curved hooks 10, so that recrystallization occurs in the inner peripheral wall. When this occurs, it is easy to confirm and an appropriate operation can be performed immediately.

In the above embodiment, the description has been made using the curved hook 10 as the locking portion for supporting the reflector main body 9. However, the present invention is not limited to this. For example, as shown in FIG. 3 and FIG. The same effect can be obtained even if the hook 14 is used.

〔The invention's effect〕

The single crystal pulling apparatus according to the present invention makes it difficult for silicon monoxide to be condensed, so that it is possible to eliminate the factors that hinder single crystallization, and to remove the melt in the crucible through the gap between the locking portions. It has an excellent effect that the surface can be visually recognized.

[Brief description of the drawings]

1 and 2 show an embodiment of the present invention.
FIG. 2 is a schematic structural view, FIG. 2 is a sectional view taken along the line AA 'of FIG. 1, FIGS. 3 and 4 show another embodiment of the present invention, and FIG. FIG. 4 is a plan view of the reflector. 1 ... chamber, 2 ... crucible, 6 ... thermal insulation cylinder, 7 ...
Supporting member, 8 Reflector, 9 Reflector body,
9a ... cylindrical part, 9b ... inclined cylinder part, 10 ... curved hook (locking part), 11 ... cooling cylinder, 12 ... single crystal rod, 14 ... L
Shaped hook.

Claims (1)

(57) [Claims] A single crystal pulling apparatus by a Czochralski method for pulling and growing a single crystal rod from a crucible in a down-flow atmosphere of an inert gas in a chamber, wherein a cylindrical body having an outer diameter smaller than an inner diameter of the crucible. And a slanted tube portion tapered inward following the lower end of the tube main body, the tapered tip edge of which is formed larger than the diameter of the single crystal rod, and surrounds the pulling single crystal rod. With the formed reflector, the flow of the inert gas supplied from above the chamber was guided to the melt surface through the gap between the tip edge of the inclined cylinder portion and the single crystal rod through the interior of the cylinder body. The first gas flow discharged to the outside of the crucible and the second gas flow guided to the outside of the crucible from the outside of the cylinder main body and merged with the first gas flow are branched. Single crystal pulling device.