JPH02160688A - Production of silicon single crystal and apparatus therefor - Google Patents

Abstract

PURPOSE:To prevent floating of partition member and obtain a silicon single crystal at a low cost by providing a partition member in a crucible with a specific manner, heating and melting a silicon raw material and simultaneously fusing lower end of the partition member with the crucible. CONSTITUTION:A partition member 11 is installed in a crucible 1 concentrically with the crucible 1 so as to surely bringing the lower end of partition member 11 into contact with the bottom of crucible 1 and then a bulky silicon raw material 18 is charged into the inside and outside of the partition member 31 so as to fix the partition member 11. Then when the silicon raw material 18 is melted by heating the crucible 1, the lower end of the partition member is completely fused with the bottom of crucible 1 in a state fixing the partition member 11 by the silicon raw material 18. Since melt liquid 4 of the outside of the partition member 11 can be quietly moved to the inside only through a small hole 12, the outside and inside (single crystal-growing part) of the partition member 11 can be sufficiently partitioned.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method and apparatus for producing a silicon single crystal using the Czochralski method.

[Prior Art] The Czochralski method for producing silicon single crystals has been practiced for a long time and has become an almost perfected technology.

As is well known, in this technology, a molten silicon raw material is placed in a quartz crucible, a seed crystal is brought into contact with the molten surface, and at the same time the seed crystal is rotated and pulled up gradually. As the contact surface solidifies, crystal growth occurs. In this way, a cylindrical silicon single crystal is obtained.

At this time, in order to transform the silicon single crystal into a P-type or N-type semiconductor depending on the purpose, an appropriate amount of doping material such as boron, antimony, or phosphorus is mixed into the molten raw material. However, the way these dopants are incorporated into the silicon single crystal is not constant, and the concentration in the lower part becomes high.

Furthermore, in addition to the dopant intentionally mixed into the silicon single crystal as described above, there is also a large presence of oxygen, which is unavoidably mixed during manufacturing. In other words, oxygen incorporated into the silicon single crystal can improve the characteristics and yield of the semiconductor, so it is desirable that the silicon single crystal contains oxygen uniformly from top to bottom. The concentration increases. For this reason, a silicon single crystal is manufactured based on the upper part of the silicon single crystal where the concentration of the dopant is low and the concentration of oxygen is high.

However, as the pulling of the silicon single crystal progresses, the liquid level of the melt in the crucible decreases and the temperature of the melt surface changes, so the melt in the crucible has a higher concentration of dopant and oxygen concentration becomes lower. As a result, the dopant present in the silicon single crystal that is pulled and grown gradually increases while the oxygen content decreases, resulting in a problem that the quality of the manufactured silicon single crystal fluctuates along the pulling direction. As a result, it has been difficult to improve the yield of products used as wafers.

Several methods have been proposed to solve these problems, and one of the representative methods considered to be practically possible is one using a double-structured crucible.

Figure 6 schematically shows a silicon single crystal manufacturing apparatus using a double-structured crucible, and (21) shows an outer crucible (22) and an inner crucible (23) made of high-purity quartz. Constructed crucible 1. (25) Silicon melt placed in Haruppo (21), (2B) is the inner crucible (3)
This is a silicon single crystal pulled up from the surface of the molten liquid. In addition, the outer crucible (20) is located at the bottom of the inner crucible (23).
and the inner crucible (22) is filled with silicon melt (25).
A hole (24) is drilled through which the fluid flows.

FIG. 3(a) shows that a silicon single crystal (26) is pulled up from the silicon melt in the inner crucible (23) (hereinafter referred to as single crystal growth section A), and the silicon single crystal (26) is pulled up from the outer crucible (22).
This is a batch type silicon single crystal manufacturing apparatus in which raw silicon is intermittently charged into the silicon melt between the crucible and the inner crucible (23) (hereinafter referred to as raw material supply section B).

In addition, in the case shown in FIG. 3(b), a silicon single crystal (26) is pulled up from the single crystal growth section A, and a single crystal pulled up from a melt having the same composition as this melt is transferred to the raw material supply section B. , and a raw material ingot (27) having the same form as the single crystal to be grown is inserted at a constant speed. Furthermore, what is shown in FIG. 3(C) is the single crystal growth part A.
The powdered raw material (29) is continuously supplied from the raw material supply pipe (28) to the raw material supply section B while pulling the silicon single crystal (26) from the raw material supply pipe (28).
(Refer to Publication No. 5), and all of these are aimed at keeping the dopant concentration in the melt in the single crystal growth section A constant.

[Problems to be Solved by the Invention] The crucible according to the prior art described above has an integral structure of the outer crucible and the inner crucible, so the quartz crucible, which is extremely expensive to process, must be further processed into a double structure. This results in an increase in costs, which cancels out the effect of improving product yield, resulting in a problem that no practical effect can be obtained.

In order to deal with this problem, it is possible to insert a cylindrical partition member made of high-purity quartz into the silicon melt to form a single crystal growth section and a raw material supply section, but quartz is preferable. Since it has a lower density than the silicon melt, it floats on top of the melt and does not function as a partition.The growth of the silicon single crystal is also inhibited.

The present invention has been made in order to solve the above-mentioned problems, and by thermally welding and integrating the partition member configured separately from the crucible to the crucible, silicone can be used at low cost and without the risk of the partition member floating. The purpose of this invention is to obtain a method and apparatus for producing single crystals.

[Means for Solving the Problems] The present invention provides a crucible into which a silicon melt is placed, a partition that surrounds a silicon single crystal to be pulled and has a small hole penetrated therein so that the silicon melt can move quietly. In a method for producing a silicon single crystal by partitioning the crucible with a member and pulling the single crystal from inside the partition member, the partition member is arranged in the crucible so that its lower end is in contact with the crucible, and the silicon raw material is placed in the crucible. A method for producing a silicon single crystal, the method comprising heating and melting the silicon raw material and welding the lower end of the partition member to a crucible.

and a method for producing a silicon single crystal, wherein the silicon single crystal is pulled from the inside while continuously supplying granular silicon raw material to the melt outside the partition member. Furthermore, the inside of the crucible into which the silicon melt is placed is partitioned with a partition member having a small hole penetrated therein so as to surround the silicon single crystal to be pulled and to allow the silicon melt to move quietly, An apparatus for producing a silicon single crystal by pulling a crystal, comprising: a crucible in which a lower end of the partition member is integrated by thermal welding.

The present invention also provides a silicon single crystal manufacturing apparatus, in which a granular silicon raw material supply device is provided close to the molten liquid surface outside the partition member.

[Function] Since the crucible and the partition member are integrated by thermal welding, there is no fear that the partition member will float due to the silicon melt.

[Example] Figure 1 is a sectional view schematically showing an example of the present invention, and Figure 2 is a cross-sectional view schematically showing an example of the present invention.
The figure is a sectional view taken along line I-1. In the figure, a quartz crucible 1 is set in a graphite crucible 2, and the graphite crucible 2 is supported on a pedestal 3 so as to be movable up and down and rotatable. 4 is a silicon melt placed in the crucible 1, from which a silicon single crystal 5 grown into a columnar shape is pulled. 6 is a heater surrounding the graphite crucible 2;
Reference numeral 7 denotes a hot zone heat insulating material surrounding this heater 6, which is basically the same as a single crystal pulling apparatus using the ordinary Czochralski method.

Reference numeral 11 denotes a cylindrical partition member made of high-purity quartz and integrated with the crucible 1 by heat welding.As shown in FIG. , at least one small hole 12 is passed through.

FIG. 4 shows an example of a procedure for arranging the partition member 11. First, as shown in figure (a), a partition member 1 is installed in the crucible 1 concentrically with the crucible 1 so that its lower end is securely in contact with the bottom of the crucible 1, and then as shown in figure (b). As shown, bulk silicon raw material 18 is charged inside and outside the partition member 11 so as to be fixed therein. Then, the crucible 1 is heated by the heater 6 to melt the silicon raw material 1.
8, the partition member 11 is fixed by the silicon raw material 18, and its lower end and the bottom of the crucible 1 are completely welded together.

Partition member 1 set in crucible 1 in this way
1 is immersed in the melt 4 so as to surround the single crystal 5 after the silicon raw material 18 is melted, and the upper part is slightly exposed from the surface of the melt. Further, the lower end portion is welded to the crucible 1 and will not float up. Therefore, the molten liquid 4 on the outside of the partition member 11 can quietly move inward only through the small holes 12, so that the outside and the inside (single crystal growth area) of the partition member 11 can be sufficiently partitioned.

Note that the shape of the partition member 11 may be arbitrary, and the outer diameter of the partition member 11 is determined depending on the potted silicon raw material melted in Luppo 1, and the volume of the silicon melt on the inside and outside. Calculate and eliminate the ratio.

Reference numeral 13 denotes a heat insulating cover, which is arranged to enhance the heat insulating effect of the melting of the partition member 11 and its outside.

In the present invention configured as described above, the partition member 11 is disposed inside the crucible 1, the silicon raw material 18 is charged inside and outside of the partition member 11, and the crucible 1 is heated with the heater 6 to melt the silicon raw material 18. At the same time, the lower end of the partition member 11 is welded to the bottom of the crucible 1. At this time, the molten liquid levels on the inside and outside of the partition member 11 are maintained at the same level. Now, if the seed crystal is brought into contact with the molten liquid surface inside the partition member (1) and gradually pulled up while rotating,
Crystal growth occurs as the contact liquid surface solidifies, and a cylindrical silicon single crystal 5 is obtained. During this time, the molten liquid inside and outside the partition member 11 moves quietly through the small holes 12, and the level of the molten liquid is always kept constant.

FIG. 5 is a longitudinal sectional view of another embodiment of the invention.

Note that parts having the same functions as those in the embodiment shown in FIG.

Reference numeral 9 denotes an opening provided in the chamber 8 corresponding to the molten liquid surface outside the partition member 11, and this opening 9 is filled with granular or lumpy silicon raw material (hereinafter referred to as granular silicon raw material).
A supply device (14) is inserted and fixed, and the tip of the supply device (4) is closely opposed to the surface of the molten liquid on the outside of the partition member 11. This supply device 14 is connected to a raw material supply chamber (not shown) provided outside the chamber 8,
Continuously supplies granular silicon raw material.

15 and 18 are temperature detectors such as radiation thermometers placed at the upper part of the chamber 8, one of which is temperature detector 5.
The temperature detector 16 measures the temperature of the molten liquid surface on the outside of the partition member 11, and the other temperature sensor 16 measures the temperature of the molten liquid surface on the inside.

In this embodiment, while the cylindrical silicon single crystal 5 is being pulled, the granular silicon raw material 17 is continuously supplied from the supply device 14 onto the molten liquid surface outside the partition member 11. is melted by the melt on the outside of the partition member 11, and gently moves inward through the micropores 12 of the partition member 11 in an amount corresponding to the silicon single crystal 5 being pulled up, thereby keeping the liquid level of the melt 4 constant. Hold constant.

[Effects of the Invention] As is clear from the above description, the present invention prevents floating of the partition member by thermally welding the separate partition member to the crucible, thereby reliably partitioning the inside and outside. Therefore, the cost of the crucible can be reduced, and furthermore, the yield of the product can be improved and the cost can be reduced, so the implementation has great effects.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view schematically showing an embodiment of the present invention, Fig. 2
The figure is a sectional view taken along line II, FIG. 3 is a side view of an embodiment of the partition member, FIGS. FIGS. 6(a) to 6(e), which are vertical sectional views schematically showing other embodiments of the invention, are explanatory diagrams showing an example of a conventional double-structured crucible. 1: crucible, 2: graphite crucible, 4: melt, 5: silicon single crystal, 6: heater, 11: partition member, 12: small hole, 14: raw material supply device, 17: granular silicon raw material.

Claims (4)

[Claims] (1) The inside of the crucible into which the silicon melt is placed is partitioned with a partition member that surrounds the silicon single crystal to be pulled and has small holes penetrated so that the silicon melt can move quietly, and from the inside of the partition member. In the method of producing a silicon single crystal by pulling a single crystal, a partition member is placed in the crucible so that its lower end is in contact with the crucible, a silicon raw material is charged into the crucible, and the silicon raw material is heated. A method for producing a silicon single crystal, comprising melting and welding a lower end of the partition member to a crucible. (2) The method for producing a silicon single crystal according to claim (1), characterized in that the silicon single crystal is pulled from the inside of the partition member while continuously supplying granular silicon raw material to the melt outside the partition member. (3) The inside of the crucible into which the silicon melt is placed is partitioned with a partition member that surrounds the silicon single crystal to be pulled and has small holes penetrated so that the silicon melt can move quietly, and from the inside of the partition member. An apparatus for producing a silicon single crystal by pulling a single crystal, comprising: a crucible in which the lower end of the partition member is integrated by thermal welding. (4) The apparatus for producing a silicon single crystal according to claim (3), further comprising a supply device for supplying granular silicon raw material close to the molten liquid surface outside the partition member.