JPH02255589A - Method and device for producing silicon single crystal - Google Patents

Abstract

PURPOSE:To prevent the splashing of a melt and to stably grow a single crystal at the time of pulling up the single crystal by the Czochralski process while supplying silicon grains into the melt by reducing the falling speed of the grains. CONSTITUTION:Molten silicon 5 is charged into a quartz crucible 1, and a partition wall having a small hole 4a is provided in the crucible 1 coaxially with the crucible 1. Consequently, the inner chamber A and the outer chamber B communicating with each other through the small hole 4a are formed. Granular silicon is supplied into the molten silicon 5 in the outer chamber B from a feed pipe 12. A mechanism 13 for reducing the speed of the granular silicon is set in the feed pipe 12 to reduce the falling speed of granular silicon to be supplied into the molten silicon 5. A silicon single crystal 6 is pulled up from the molten silicon 5.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a method and apparatus for producing a silicon single crystal in which silicon single crystals are continuously pulled by the Czochralski method while supplying granular silicon. It is related to.

[Prior Art] Conventionally, several methods have been proposed for providing a coaxial partition wall in a quartz crucible and pulling a single crystal from the melt inside while supplying raw materials to the outside of the partition wall. There is. However, there are almost no concrete examples of methods for supplying granular raw materials.
This publication merely discloses a method for supplying the raw material through a supply pipe immersed in the silicon melt outside the partition wall.

[Problems to be Solved by the Invention] In the continuous charge Czochralski method in which single crystals are grown while supplying granular raw materials, raw granular silicon is stored above the furnace where it is not exposed to radiant heat from the heater or silicon melt. Ru. In this case, the distance (height difference) from the dispensing position of the hopper or the like to the silicon melt surface becomes large, and the falling speed of the granular silicon when it enters the silicon melt becomes considerably faster. Therefore, a large amount of droplets are generated from the silicon melt hit by the falling granular silicon. The droplets remain in a molten state, or are cooled in the air and become solid fine powder, which is then scattered into the furnace. In addition to adhering to or bouncing off partition walls and quartz crucible walls, they also adhere to the surfaces of furnace components such as heaters, and react with them to produce SiC in the case of graphite and metal silicide in the case of metals. . In addition, scattered particles may accumulate on the heater surface, causing electrical discharge and current leakage. In either case, the life of the furnace components such as the heater will be significantly shortened.

In addition, flying objects (droplets and fine powder) may cross the partition walls and enter the inner chamber, and if they adhere to the single crystal surface, they may cause dislocations, and they may also touch the surface of the silicon melt. If it falls, it may become a nucleus for solidification and cause a solidified film to form on the surface of the melt.

No measures against such problems have been proposed so far. In the method disclosed in JP-A-58-130195, the tip of the raw material supply pipe is immersed below the surface of the silicon melt in the outer chamber.
Although scattering can be prevented, the melt in the immersed part of the supply pipe may be locally cooled and solidified, or the granular silicon may remain unmelted and accumulate on the surface of the melt in the supply pipe.
Eventually, there are problems such as clogging of the supply pipe.

This invention was made to solve these problems, and it is possible to charge silicon granules without interfering with single crystal growth or adversely affecting the furnace components such as the heater. An object of the present invention is to obtain a method for manufacturing a silicon single crystal and an apparatus therefor, which can continuously pull a single crystal.

[Means for solving the problem] In the method for manufacturing a silicon single crystal according to the present invention,
The falling speed of the granular silicon that is supplied into the silicon melt in the outer chamber partitioned by a partition wall in the quartz crucible containing the silicon melt is slowed down, and the granular silicon is supplied into the melt at a gentle speed that almost no splashes are generated. do.

Furthermore, the silicon single crystal manufacturing apparatus according to the invention includes a deceleration mechanism that is installed in the supply pipe that supplies granular silicon into the silicon melt in the outer chamber and reduces the falling speed of the granular silicon.

This speed reduction mechanism is constructed by arranging a plurality of rods in a direction approximately perpendicular to the falling direction of the granular silicon, or by arranging a plurality of inclined plates approximately alternately.

[Function] In the silicon single crystal manufacturing method and device according to the present invention, the granular silicon plunges into the silicon melt with its falling speed reduced, so the impact force is small and the droplets are small. This makes it possible to reduce the occurrence of oxidation, thereby preventing deterioration of the components in the furnace and disturbance during single crystal growth.

In addition, in the granular silicon deceleration mechanism of the silicon single crystal production apparatus according to the present invention, the plurality of rods arranged in a direction approximately perpendicular to the falling direction of the granular silicon allow the granular silicon to directly reach the silicon melt surface. It prevents the person from falling and reduces the speed of the fall. That is, the falling granular silicon hits these rods, and the falling speed is significantly reduced due to the reduction in energy received during the repulsion.

Further, in the granular silicon deceleration mechanism of the silicon single crystal production apparatus according to the present invention, the plurality of inclined plates in the supply pipe prevent the granular silicon from directly falling, and prevent the granular silicon from falling directly. In addition to reducing the speed, the falling speed of the granular silicon is reduced by rolling or sliding down the inclined plate rather than falling through the air.

[Example] FIG. 1 is a cross-sectional explanatory diagram schematically showing an example of the present invention. A quartz crucible 1 is set and supported within a graphite crucible 2, and contains a silicon melt 5 therein. 3 is a crucible support shaft (pedestal) that supports the graphite crucible 2 so as to be movable up and down and rotatable. Reference numeral 4 denotes a ring-shaped partition wall made of, for example, high-purity silica glass and provided coaxially with respect to the quartz crucible 1, thereby separating the quartz crucible 1 into an inner chamber A and an outer chamber B. The inner chamber A and the outer chamber B communicate with each other through a small hole 4a formed in the partition wall 4. While the silicon single crystal 6 is pulled up from the inner chamber A, granular silicon is supplied to the outer chamber B into the silicon melt 5 through the supply pipe 12. Further, a dopant is supplied to the outer chamber B by a dopant supply pipe (not shown). In response to the pulling of the single crystal 6, the silicon melt in the outer chamber B flows into the inner chamber A, making it possible to keep the impurity concentration of the silicon melt in the inner chamber A substantially constant. This makes it possible to continuously pull single crystals with constant resistivity, and to produce silicon single crystals that are significantly superior to silicon single crystals produced by the conventional Czochralski method in terms of both quality and yield. It is possible.

7 is a heater surrounding the graphite crucible 2; 8 is a hot zone insulation material surrounding this heater 7; 9 is a furnace chamber, and lO 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.

Reference numeral 13 denotes a granular silicon deceleration device provided at the lower part of the supply pipe 12, which reduces the falling speed of the granular silicon. Thereby, the falling speed of the granular silicon entering the silicon melt in the outer chamber B can be significantly reduced, and the generation of droplets from the silicon melt can be prevented.

FIG. 2(A) is a perspective view showing the structure of one embodiment of the granular silicon deceleration mechanism 13. This granular silicon speed reduction mechanism 1
3 indicates the falling direction 1 of the granular silicon inside the supply pipe 12.
It is constructed by providing a plurality of rods 14 in a direction approximately perpendicular to the rod 7. It is preferable that this rod 14 be provided as close as possible to the opening 15 of the supply pipe 12 in order to reduce the falling speed of the granular silicon.

FIG. 2 CB) is a schematic diagram illustrating an example of how granular silicon falls in the deceleration mechanism 13 of FIG. , due to the reduction in energy incurred during its rebound, its falling speed is significantly reduced.

FIG. 3(A) is a perspective view showing the structure of another embodiment of the granular silicon deceleration mechanism 13. This granular silicon deceleration mechanism 13 is constructed by providing a plurality of inclined plates 1B approximately alternately inside the supply pipe 12.

FIG. 3(B) is a schematic diagram illustrating an example of the form of falling granular silicon in the deceleration mechanism 13 of FIG. 3(A), in which the granular silicon falls from the direction indicated by 18
In addition to being decelerated by hitting the inclined plate 16, it is also decelerated by rolling or sliding along the inclined plate 16.

The operation of this embodiment will be explained below. When manufacturing a silicon single crystal using the manufacturing apparatus shown in FIG. 1, a 20-inch quartz crucible 1 was equipped with an 18-inch ring-shaped quartz partition wall 4, and 30 kg of silicon melt 5 was contained therein. A small hole 4a having a diameter of 5 mm is provided in the partition wall 4, and the molten liquid level in the inner chamber A and the outer chamber B is maintained at the same level. A 6-inch silicon single crystal 6 was pulled from the silicon melt in the inner chamber A.

Then, in response to pulling this silicon single crystal 6,
Granular silicon is supplied into the silicon melt in the outer chamber B through the supply pipe 12 made of quartz, is melted by the melt in the outer chamber B, which is the raw material melting section, and passes through the small hole 4a of the partition wall 4 to the single crystal pulling section. The liquid level of the silicon melt 5 is maintained constant.

Although the granular silicon is continuous with the pulling furnace,
It is designed to be led to a supply pipe 12 from a separate granular silicon storage chamber 11 which is not affected by the heat in the furnace.

Initially, when granular silicon was supplied without providing the granular silicon deceleration mechanism 13, a large amount of droplets were generated, some of which crossed the partition wall 4 and entered the inner chamber A side, causing the single crystal 6
Some adhered to the surface of the silicon melt and formed a coagulated film on the surface of the silicon melt.

Further, a large amount of silicone was deposited on the upper part of the heater 7, the upper part of the heat insulating tube 8, etc. due to the droplets.

On the other hand, a granular silicon deceleration mechanism 13 of the mechanism shown in FIG. 2(A) was provided across the lower part 15 (to) of the supply pipe 12, and was used to pull the silicon single crystal. As a result, almost no droplets were generated, and the above phenomenon was not observed at all.

Further, when the speed reduction mechanism 13 of the mechanism shown in FIG. 3(A) was used, a droplet prevention effect equal to or greater than that was obtained. In addition, in the deceleration mechanism of the mechanism shown in FIG. 3(A), the angle of the inclined plate (made of quartz>10) was set to 25# with respect to the horizontal.

It goes without saying that these speed reduction mechanisms 13 can be provided as close as possible to the silicon melt surface to obtain a great effect.

That is, it is desirable to have the opening 15 of the supply pipe 12 as close to the silicon melt surface as possible and to provide the deceleration mechanism 13 close to the opening 15 of the supply pipe 12.

Further, this invention is applicable to FIGS. 1, 2 (A), and 3 (A).
) It goes without saying that the present invention is not limited to the embodiments shown in the drawings, and includes modifications as appropriate depending on the purpose of the present invention.

[Effects of the Invention] As described above, according to the present invention, the falling speed of the granular silicon to be supplied into the silicon melt is sufficiently reduced before it is supplied into the silicon melt. This not only eliminates the negative effects on single crystal growth and realizes stable single crystal production, but also prevents deterioration due to droplets adhering to the components in the furnace, allowing long-term This has the effect of making it possible to pull the single crystal many times.

In addition, since the components inside the furnace are made of expensive materials such as high-purity graphite, quartz glass, and high-melting point metals, the lifespan of these components has a direct impact on manufacturing costs. By preventing the generation of droplets, the product's lifespan is extended, which is also highly effective in terms of cost.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a silicon single crystal manufacturing apparatus according to an embodiment of the present invention, and FIGS. 2(A) and 2(B) are perspective views showing an embodiment of a deceleration mechanism for granular silicon and its granular silicon. Schematic diagram showing an example of a falling situation, Figure 3 (A) (B
) is a perspective view showing another embodiment of the granular silicon deceleration mechanism and a schematic diagram showing an example of the falling state of the granular silicon. In the figure, 1 is a quartz crucible, 2 is a graphite crucible, 3 is a crucible support shaft, 4 is a partition wall, 4a is a small hole, 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, 10 is a granular silicon supply device, 11 is a granular silicon storage chamber, 12 is a supply pipe, 13 is a granular silicon moderator, 14 is a moderation rod, 15 is an opening of the supply pipe,
1B is an inclined plate for deceleration, 17 is the falling direction of the silicon granules, and 1g is the falling path of the silicon granules. Agent Patent Attorney Muneharu Sasaki Fig. 9;

Claims (4)

[Claims] (1) A partition wall coaxial with the quartz crucible and having a small hole is provided in the quartz crucible containing the silicon melt, and the partition wall is separated into an inner chamber and an outer chamber that communicate with each other through the small hole. In a method for producing a silicon single crystal in which the silicon single crystal is pulled up from the silicon melt in the inner chamber while supplying the granular silicon into the silicon melt, the falling speed of the granular silicon supplied into the silicon melt is reduced. A method for producing a silicon single crystal characterized by: (2) A partition wall that is coaxial with the quartz crucible and has a small hole is provided in the quartz crucible containing the silicon melt, and is separated into an inner chamber and an outer chamber that communicate with each other through the small hole. In a silicon single crystal production device that pulls up silicon single crystals from the silicon melt in the inner chamber while supplying granular silicon into the silicon melt, a supply pipe for supplying the granular silicon into the silicon melt in the outer chamber is provided. What is claimed is: 1. A silicon single crystal manufacturing apparatus, comprising: a deceleration mechanism for decelerating the falling speed of granular silicon. (3) The silicon single crystal manufacturing apparatus according to claim 2, wherein the deceleration mechanism includes a plurality of rods arranged in a direction substantially perpendicular to the falling direction of the granular silicon. (4) The silicon single crystal manufacturing apparatus according to claim 2, wherein the deceleration mechanism is formed by approximately alternately arranging a plurality of inclined plates.