JPH0218376A - Granular silicon raw material supply device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a silicon single crystal manufacturing apparatus using the Czochralski method in which a granular silicon raw material is supplied while pulling a silicon single crystal, in which the granular silicon raw material is placed in a crucible. The present invention relates to a raw material supply device for supplying raw materials.

[Prior art] Silicon single crystals (hereinafter sometimes simply referred to as single crystals) are manufactured using the so-called Czochralski method, in which a single crystal is pulled from a silicon melt held in a crucible using a seed crystal. (CZ Law) is widely implemented.

In this method, for the purpose of controlling the resistivity of the silicon single crystal, boron for a p-type semiconductor, phosphorus, antimony, etc. for an n-type semiconductor are added to the silicon melt in advance. However, when the silicon melt solidifies into a single crystal, these additive elements are incorporated into the single crystal at a constant rate, and the rest is discharged into the remaining silicon melt. As the silicon melt decreases as the single crystal is pulled, the dopant concentration in the silicon melt increases, and therefore the dopant concentration in the pulled single crystal gradually increases from the head to the tail of the single crystal. . Therefore, the low efficiency also changes, and when silicon wafers are manufactured from single crystals, the electrical efficiency varies from wafer to wafer, and if the requirements are strict,
The yield of usable wafers may be less than 50%.

For this reason, a method has been proposed in which a silicon raw material corresponding to the amount of silicon single crystal pulled is poured into the silicon melt in a crucible and melted, and the liquid level and dopant concentration of the silicon melt are always kept constant. has been done.

In this method, one end of a guide tube provided inside the heating furnace is connected to a material supply device provided outside the heating furnace to supply granular silicon raw material to the silicon melt. However, in this method, the dropped granular silicon raw material causes ripples in the silicon melt, or the dropped granular silicon raw material adheres to the silicon single crystal grown in the center before it is completely melted. For this reason, a problem arises in that the growing silicon single crystal becomes dislocated.

Therefore, in order to prevent such problems, a ring-shaped partition that is concentric with the crucible and has a communication section at the bottom is installed inside the crucible, and the single crystal growth section is placed inside the partition, and the raw material is supplied outside the partition. A method is proposed in which a part is formed and a granular silicon raw material is supplied to this raw material supply part. For example, in the device disclosed in Japanese Utility Model Application Publication No. 59-141578, the opening of the guide tube into which the granular silicon raw material is introduced is located above the liquid level of the silicon melt in the raw material supply section. In the invention disclosed in Japanese Patent Application Laid-Open No. 58-130195, the tip of the guide tube is inserted into the silicon melt in the raw material supply section.

[Problems to be Solved by the Invention] In the invention disclosed in Japanese Utility Model Application Publication No. 59-141578, the collision of falling granular silicon raw materials,
There is a problem in that a large amount of granular silicon raw material enters the single crystal growth zone due to splashing on the melt surface, and the growing silicon single crystal becomes dislocated. Therefore, silicon single crystals are grown continuously. The problem is that I can't.

Furthermore, in the invention disclosed in JP-A No. 58-13095, when the granular silicon raw material is introduced, there is a high possibility that the silicon melt will solidify in the guide tube due to the thermal environment in the crucible, so this method is not practical. Have difficulty.

The present invention has been made to solve the above problems, and there is no fear that the granular silicon raw material fed into the raw material supply section will enter the single crystal growth section, so that the grown silicon single crystal will have dislocations. The object of the present invention is to obtain a supply device for a granular silicon raw material that does not become oxidized.

[Means for Solving the Problems] The present invention has been made to achieve the above object, and includes a crucible having a ring-shaped partition, pulling a silicon single crystal from inside the partition, and pulling the silicon single crystal from the inside of the partition. In an apparatus for manufacturing silicon single crystals by continuously supplying granular silicon raw material to the outside of a partition through a guide tube, a shielding portion larger than the outer diameter of the guide tube is provided at the tip of the guide tube, and the shielding portion is A supply device for granular silicon raw material, which is disposed close to or partially immersed in the surface of the silicon melt outside the partition of the crucible. And, in the above-mentioned apparatus, there is provided a supplying device for granular silicon raw material, which is provided with a falling speed reducing section for the granular silicon raw material in the middle of the guide tube.

[Function] By providing a shielding part at the tip of the guide tube, even if the introduced granular silicon raw material hits the silicon melt and rebounds, it will hit the shielding part and fall again to the outside of the partition, and it will fall inside the partition. will not invade.

Further, by providing a falling speed reducing part in the middle of the guide tube, the falling speed of the granular silicon raw material is reduced, and the rebound when it hits the surface of the silicon melt is reduced.

[Embodiments of the Invention] FIG. 1 is a cross-sectional view of an example of a silicon single crystal production apparatus equipped with a granular silicon supply apparatus according to the present invention. In the figure, reference numeral 1 denotes a crucible made of quartz, which is set in a graphite crucible 2 supported by a support shaft 3 so as to be rotatable and movable up and down. Reference numeral 4 denotes a partition ring made of quartz provided in the crucible 1. A flow hole 4a for the silicon melt 5 is provided in the lower part of the partition ring 4, and the upper part is slightly exposed from the surface of the silicon melt 5.

The crucible 1 is divided by this partition ring 4 into an inner single crystal growth section A and an outer raw material supply section B. 6 is a columnar silicon single crystal pulled from the silicon melt 5. Reference numeral 7 denotes a heater arranged around the outer periphery of the graphite crucible 2 to heat the silicon melt, 8 a heat insulating material provided outside the heater 7, and 9 a housing of the heating furnace.

Reference numeral 10 represents a supply device for supplying granular silicon raw material provided inside and outside the housing 9, reference numeral 11 represents a hopper, and reference numeral 12 represents a guide tube connected to the hopper 11 at one end. As shown in FIG. 2, the guide tube 12 is provided with a disc-shaped shielding portion 13 at its tip end, the diameter of which is larger than the diameter of the lower portion of the guide tube 12. As shown in FIG. This shielding part 1
3 is desirably arranged with its lower surface as close as possible to the liquid surface of the silicon melt 5, and in the embodiment, the shielding part 13
The distance between the lower surface of the silicon melt 5 and the liquid level of the silicon melt 5 was 5 long.

Next, the operation of the silicon single crystal manufacturing apparatus configured as described above will be explained. First, a lump of silicon polycrystal is charged into the crucible 1, and the crucible 1 is heated by the heater 7 to melt it. Next, the seed crystal is lowered and brought into contact with the surface of the silicon melt 5 in the single crystal growth section A, and is gradually pulled up while rotating, thereby growing a columnar silicon single crystal 6. On the other hand, a granular silicon raw material in an amount commensurate with the amount of silicon single crystal 6 pulled is introduced into the raw material supply section B from the raw material supply device IO through the guide pipe 12. The input granular silicon raw material is immediately melted, and the silicon melt 5 corresponding to the amount of silicon single crystal 6 pulled moves from the flow hole 4a to the single crystal growth section A, and is then transferred to the single crystal growth section A and the single crystal supply section B. The liquid level of the silicon melt 5 is always kept constant.

By the way, in the present invention, the guide pipe 12 of the raw material supply device
is configured as described above, even if the granular silicon raw material falls onto the surface of the silicon melt 5 and bounces off, it will hit the shielding part 13 and fall into the raw material supply part B again and be melted, thereby preventing single crystal growth. There is no risk of it entering Part A.

In this embodiment, the side of the shielding part 18 perpendicular to the radial direction of the crucible 1, that is, both sides of the crucible 1 in the rotational direction, are cut off as shown by the dashed line in FIG. 2(b) to form an oval shape. may be formed.

FIG. 3 shows another embodiment of the shielding part 13 according to the present invention, in which an outer tube 14 is provided at the lower part of the guide tube 12, and its lower end is located below the lower end of the guide tube 12. It is.

Further, FIG. 4 shows still another embodiment of the shielding part 13 according to the present invention. 15 is a shielding part 13 whose outer wall is formed in a semicylindrical shape and has openings 16 on both sides in the rotational direction of the crucible 1, and which is connected to the guide tube 12 so that its lower end is located below the lower end of the guide tube 12. This is especially effective when a large amount of granular silicon raw material is introduced.

In the embodiment shown in FIG. 4, the granular silicon raw material may be supplied while the shielding part 13 is immersed in the silicon melt 5 of the raw material supply part B.

Next, the raw material supply device according to the present invention explained in FIG.
Conventional raw material supply device shown in Fig. 6
The results of experiments using the devices (corresponding to the device disclosed in Japanese Patent No. 578) will be explained.

First, as shown in FIG. 6, when a granular silicon raw material was continuously introduced into the raw material supply B using the raw material supply device 10 having the N guide tube 12 with its tip cut at right angles to the length direction, a large amount The granular silicon raw material was scattered and entered the single crystal growth section A, and the growing single crystal 6 immediately became polycrystalline. In this case, the distance between the tip of the guide tube 12 and the surface of the silicon melt 5 was 30 m+*.

Next, as shown in FIG. 7, the tip of the guide tube 12 is cut obliquely so that the inclined surface faces the inner wall of the crucible 1, and the tip is brought as close as possible to the surface of the silicon melt 5. (In the experimental example, the distance between the two was 5 mm), and the granular silicon raw material was continuously introduced into the raw material supply device. As a result, most of the granular silicon raw material fell into raw material supply section B, but
As expected, some of it splashed on the surface of the silicon melt 5 and entered the single crystal growth section A. In this example, the silicon single crystal 6 became polycrystalline some time after the introduction of the granular silicon raw material.

The experimental results using the raw material supply device according to the present invention are as described above, and there is no intrusion of granular silicon raw material into the single crystal growth section A, so even if the operation continues for a long time, the silicon single crystal 6 becomes polycrystalline. There was no conversion.

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

30 is a falling speed reducing part of the granular silicon raw material provided in the large diameter part of the guide tube 12a, which includes a funnel-shaped chute 31;
This chute 31 is supported by a plurality of support frames 32,
It is composed of a distribution plate 33 having a slightly smaller diameter than the inner diameter of the large diameter portion of the guide tube 12a, and a hemispherical upper surface and an inverted dish shape.

In the guide tube 12a equipped with the falling speed reducing section 30 configured in this way, the granular silicon raw material introduced from the raw material supply device IO is rectified by the chute 31 and falls onto the distribution plate 33. As a result, the granular silicon raw material whose falling energy has been attenuated descends while rolling on the upper surface of the distribution plate 33, passes through the gap formed between the inner wall of the guide tube 12a and the outer periphery of the distribution plate 33, and passes through the raw material 0 (supply section B). In this way, the falling speed of the granular silicon raw material that has fallen from the raw material supply device 10 is reduced to near zero by the falling speed reduction section 30, and the silicon melt 5 falls again. The falling speed when falling onto a surface is significantly reduced, thus preventing scattering.

In the above embodiment, the present invention was applied to the silicon single crystal manufacturing apparatus shown in FIG. The present invention can also be implemented in the configuration of. Further, the shielding portion may be provided on a guide tube provided with a falling speed reducing portion, or may be provided on a guide tube without a falling speed reducing portion. Furthermore, the structure of the shielding part is not limited to the above-mentioned embodiment, and any structure can be used as long as it can prevent the fallen granular silicon raw material from hitting the liquid surface of the silicon melt and rebounding and entering the single crystal growth part. It may have the structure of

[Effects of the Invention] As is clear from the above description, the present invention provides a shielding portion at the tip of the guide tube that supplies the granular silicon raw material to the raw material supply section, so that the granular silicon raw material fed into the single crystal growth section Since it is possible to prevent the silicon single crystal being grown from becoming dislocated. Therefore, a high quality silicon single crystal with a uniform dopant concentration from the head to the foot can be obtained.

In addition, by providing a part that reduces the falling speed of the granular silicon raw material in the middle of the guide tube, the falling speed of the granular silicon raw material being introduced is reduced, and the rebound when it hits the surface of the silicon melt is reduced. This further ensures prevention of intrusion into the single crystal growth section.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an example of a silicon single crystal manufacturing apparatus equipped with a raw material supply device according to the present invention, and FIGS. 2 and 3 show an embodiment of the main part of the present invention. (b) is a bottom view, FIG. 4 shows another embodiment of the main part of the present invention, (a) is a perspective view, (b)
) is a bottom view, FIG. 5 is a sectional view showing another embodiment of the present invention, FIG. 6 is a schematic diagram showing an example of a conventional silicon single crystal manufacturing apparatus, and FIG. 7 is a schematic diagram of another example. FIG. 1: Crucible, 4: Partition ring, 5: Silicon melt, 6
: Silicon single crystal, 7: Heater, 10: Raw material supply device,
12.12a: Guide tube, 13: Shielding section, 30: Falling speed reduction section, A: Single crystal growth section, B: Raw material supply section. Agent Patent Attorney So Sasaki Chart Diagram 5

Claims (2)

[Claims] (1) A crucible having a ring-shaped partition is provided, and a silicon single crystal is pulled up from inside the partition, and a granular silicon raw material is continuously supplied to the outside of the partition through a guide tube to produce a silicon single crystal. In the apparatus, a shielding portion larger than the outer diameter of the guide tube is provided at the tip of the guide tube, and the shielding portion is placed close to the liquid surface of the silicon melt outside the partition of the crucible or a part thereof is immersed. A supply device for a granular silicon raw material, characterized in that the device is arranged at (2) The apparatus for supplying granular silicon raw material according to claim 1, characterized in that a part for reducing the falling speed of the granular silicon raw material is provided in the middle of the guide tube.