JPH02255591A - Method and device for producing silicon single crystal - Google Patents

Abstract

PURPOSE:To decrease the disturbance of heat convection and to prevent the generation of crystal defects by cooling the high-temp. silicon melt in the raw material melting part on the outer side of the inside partition wall of a crucible to attain a prescribed temp. difference before this melt is mixed with the melt in the single crystal growing part on the inner side. CONSTITUTION:The crucible 1 in which molten silicon 5 is put is partitioned by a partitioning member 4 to the single crystal growing part B on the inner side and the raw material melting part A on the outer side, between which the molten silicon 5 is gently moved. A silicone raw material is continuously supplied via a supply pipe 12 to the above-mentioned melting part A. The high- temp. silicon melt 5 in the above-mentioned melting part A is cooled by a heat exchanger 15 to <=5 deg.C from the melt of the growing part B before this melt is mixed with the melt 5 in the single crystal growing part B on the inner side. The silicon single crystal 6 is then pulled up in the growing part B.

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] A silicon single crystal pulling method using the Czochralski method has been practiced for a long time and has become a nearly perfected technology.

As is well known, this technology involves placing a molten semiconductor raw material in a quartz crucible, touching the molten surface of the seed crystal, and at the same time rotating it and gradually pulling it up. As the contact surface solidifies, crystal growth occurs, creating a circular shape. A columnar single crystal can be obtained.

At this time, in order to make the single crystal a P-type or N-type semiconductor depending on the purpose, an appropriate amount of boron, antimony,
Contains doping agents such as phosphorus.

However, the way these dopants are incorporated into the single crystal is not constant, and the concentration becomes higher in the lower part.

In addition, with this method, the molten semiconductor raw material in the crucible decreases as the single crystal grows, so the amount of oxygen that enters during melting is reduced compared to quartz crucible material, and the oxygen concentration in the single crystal decreases at the bottom. It gets lower.

Due to the uneven distribution of the dopant and oxygen as described above, the yield of usable wafers may be less than 50% if the components are strictly used.

As an effective method for solving such problems, a method is known in which silicon raw material is continuously or intermittently supplied to a crucible to maintain a constant liquid level of the molten raw material. Especially recently, it has become possible to produce high-quality granular polycrystalline silicon, and it is thought that it is relatively easy to continuously supply a fixed amount of this granular silicon to the molten raw material, and several inventions and papers have been published. (Unexamined Japanese Patent Publication No. 1983-
No. 130195, JP-A-63-95195, U.S. Pat.
9-141578 invention and paper Ann, Rev.
Mater, Sci., 1987. Vol, 17゜P27
3-279).

In the above invention, a crucible containing molten silicon is partitioned into an inner single crystal growth section and an outer raw material melting section so that the molten silicon can move, and the silicon raw material is continuously fed into the outer raw material melting section. While supplying the silicon single crystal, the silicon single crystal is pulled up from the inner single crystal growth section.

[Problems to be Solved by the Invention] When pulling a single crystal while continuously and directly supplying granular silicon into a crucible based on the prior art as described above, the following problem occurs. In other words, the melt in the raw material melting section is
When supplied to the single crystal growth section, which is maintained at a high enough temperature to melt the supplied granular silicon raw material, or where this high temperature melt is maintained just above the melting point of silicon,
It disturbs thermal convection, causes defects in the single crystal due to thermal fluctuations, and inhibits single crystallization.

The present invention was made in order to solve the above problems, and it is possible to reliably melt the input raw material without inhibiting the growth of single crystals, and to reduce the concentration of dopant in the pulling direction without defects due to thermal fluctuations. Another object of the present invention is to provide a silicon single crystal manufacturing method and apparatus capable of manufacturing a single crystal having a substantially constant oxygen concentration.

[Means for Solving the Problems] In the silicon manufacturing method according to the present invention, before the high-temperature silicon melt in the raw material melting section mixes with the melt in the inner single crystal growth section, It is designed to be cooled so that the temperature difference with the melt is 5° C. or less.

In addition, the silicon manufacturing apparatus according to the present invention is provided with a heat exchanger that cools the high-temperature silicon melt in the raw material melting section and then mixes it with the melt in the inner single crystal growth section. The temperature difference between the melt and the melt in the single crystal growth section was set to be 5°C or less.

[Function] In the present invention, while the raw material melting section is kept at a high temperature that allows the supplied granular silicon raw material to be sufficiently melted, and the inner single crystal growth section is maintained at just above the melting point of silicon,
A granular raw material corresponding to the amount of crystals to be pulled is supplied to the raw material melting section. The silicon raw material melted in the raw material melting section passes through the partition and flows into the inner single crystal growth section.

The high-temperature melt flowing into this single-crystal growth section is cooled so that the temperature difference between it and the melt in the single-crystal growth section is 5°C or less before mixing with the melt in the inner single-crystal growth section. By this cooling, the raw material melting section can be kept at a high temperature that sufficiently melts the supplied granular silicon raw material, and it also reduces disturbances in thermal convection, preventing crystal defects and inhibition of single crystallization due to thermal fluctuations. To prevent.

[Example] FIG. 1 is a sectional view schematically showing an example of the present invention. In the figure, 1 is a quartz crucible, which is set and supported in a graphite crucible 2, with silicon melt 5 inside.
It accommodates. 3 is a pedestal that supports graphite Ruppo 2 so that it can move up and down and rotate. Reference numeral 4 denotes a ring-shaped partition member made of, for example, high-purity silica glass and provided coaxially with respect to the quartz crucible 1, which separates the quartz crucible 1 into a raw material melting section A and a single crystal growth section B. separated into The raw material melting section A and the single crystal growth section B communicate with each other via a heat exchanger 15 attached to the partition member 4. The silicon single crystal 6 is pulled up from the single crystal growth section B, and granular silicon is supplied into the silicon melt 5 through the supply pipe 12 to the raw material melting section A.

Further, a dopant is supplied to the raw material dissolving section A through a dopant supply pipe (not shown). In response to the pulling of the single crystal 6, the silicon melt in the raw material melting section A flows into the single crystal growing section B, making it possible to maintain the impurity concentration of the silicon melt in the single crystal growing section A almost constant. . This makes it possible to continuously pull single crystals with constant resistivity, improving quality.
It is possible to produce silicon single crystals that are significantly superior to silicon single crystals produced by the conventional Czochralski method in terms of yield.

7 is a heater surrounding the graphite crucible 2, and 8 is a hot zone insulation material surrounding this heater 7. 9 is a furnace chamber, and 10 is a granular silicon supply device installed through the furnace chamber 9, and is provided with a granular silicon storage chamber 11 and a supply pipe 12.

In this embodiment, in particular, a heat exchanger 1 made of quartz glass is used.
5 is installed on the single crystal growth section B side of the partition member 4, and the molten raw material in the raw material melting section A flows into the single crystal growth section B through this heat exchanger 15. The lower edge of this partition member 4 is fused to the quartz lupo 1 in advance or is fused by the heat generated when melting the silicon raw material, and the lower edge of the partition member 4 is
The high-temperature molten raw material passes only through this heat exchanger 15 and is cooled by the melt in single crystal growth section B.
flows into.

FIG. 2 is an explanatory diagram showing an embodiment of the heat exchanger 15, and FIG. 2(A) shows an example in which the inner wall of the partition member 4 is meandered in the vertical direction. FIG. 2B shows an example in which the inner wall of the partition member 4 is meandered along the circumferential direction.

Furthermore, the same figure (C) is an example when it is installed at the bottom of the quartz crucible 1.

Figure 3 is a characteristic diagram when a quartz glass tube with an inner diameter of 5 mm and an outer diameter of 10 m is used as the heat exchanger 15, and it can be seen that as the inflow rate increases, the length of the heat exchanger 15 needs to be made longer. .

FIG. 4 is a characteristic diagram showing the crystal defect (O5F) density with and without the heat exchanger 15 installed, and it is clear that the defect density decreases when the heat exchanger 15 is used. I understand.

Note that the configuration of the heat exchanger in the present invention is not limited to the shape shown in the above-mentioned embodiments, and the high temperature silicon melt in the raw material melting section is mixed with the melt in the inner single crystal growth section. It goes without saying that other configurations may be used as long as they can be cooled so that the temperature difference between the single crystal growth section and the melt is 5° C. or less.

[Effects of the Invention] As described above, according to the present invention, before the high temperature silicon melt in the raw material melting section mixes with the melt in the inner single crystal growth section,
Before the single crystal, it was cooled so that the temperature difference with the melt in the forming part was 5°C or less, so that the raw material melting part was heated to a high temperature that sufficiently melted the supplied granular silicon raw material. It was possible to maintain the temperature at a high temperature, reduce disturbances in thermal convection, and prevent crystal defects and inhibition of single crystallization due to thermal fluctuations.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view schematically showing an embodiment of the present invention;
FIG. 2 is an explanatory diagram showing an embodiment of the heat exchanger, FIG. 3 is a characteristic diagram of the heat exchanger, and FIG. 4 is a characteristic diagram showing an example of improvement of crystal defects by the heat exchanger. In the figure, 1 is a quartz crucible, 2 is a graphite crucible, 3 is a crucible support shaft, 4 is a partition wall, 5 is a silicon melt, 6 is a silicon single crystal, 7 is a heater, 8 is a heat insulating cylinder, 9 is a furnace chamber, Lo is a granular silicon supply device, 11 is a granular silicon storage chamber, 12 is a supply pipe, and 15 is a heat exchanger.

Claims (2)

[Claims] (1) A crucible containing molten silicon raw material is divided into an inner single crystal growth zone and an outer raw material melting zone so that the molten silicon can move quietly, and granular or lump silicon is placed in the raw material melting zone. In a method of manufacturing a silicon single crystal by pulling a silicon single crystal inside the raw material while continuously supplying the raw material, before the high temperature silicon melt in the raw material melting section mixes with the melt in the inner single crystal growth zone. A method for producing a silicon single crystal, characterized in that cooling is performed so that the temperature difference between the single crystal growth section and the melt is 5° C. or less. (2) The crucible containing the molten silicon raw material is divided into an inner single crystal growth section and an outer raw material melting section so that the molten silicon can move quietly, and granular or lump-like silicon is placed in the raw material melting section. In an apparatus for producing a silicon single crystal by pulling a silicon single crystal inside the raw material while continuously supplying the raw material, after cooling the high temperature silicon melt in the raw material melting section, the melt is added to the inner single crystal growth zone. 1. An apparatus for producing a silicon single crystal, characterized in that it is provided in a heat exchanger for mixing, and the temperature difference between the high-temperature silicon melt after cooling and the melt in the single crystal growth section is 5° C. or less.