JPH0558769A - Production of silicon single crystal - Google Patents

Abstract

PURPOSE:To reduce the number of granular silicon fragments generated and the probability of occurrence of dislocation in a silicon single crystal due to the fragments and to produce a silicon single crystal of a large diameter when a silicon single crystal is produced by the Czochralski method with granular silicon as starting material. CONSTITUTION:When the objective silicon single crystal is produced by the Czochralski method while continuously feeding granular silicon as starting material, granular silicon having >=1.5 fracture toughness KIC is used as the starting material. The generation of granular silicon fragments is inhibited and the rate of dislocation in the silicon single crystal can be remarkably reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a large diameter silicon single crystal by the Czochralski method while continuously supplying a granular silicon raw material.

[0002]

2. Description of the Related Art In the field of LSI, the diameter required for a silicon single crystal is increasing year by year. Today, state-of-the-art devices use 6 inch diameter silicon single crystals. It is said that a silicon single crystal having a diameter of 8 inches or more will be required in the future.

Czochralski method (hereinafter referred to as CZ method)
In, the silicon melt in the crucible decreases with the growth of the silicon single crystal. Therefore, as the silicon single crystal grows, the dopant concentration in the silicon single crystal increases and the oxygen concentration decreases. That is, as the silicon single crystal grows, the properties of the silicon single crystal change depending on the growth direction. As the diameter of the silicon single crystal increases, the dopant concentration segregation in the growth direction of the silicon single crystal increases, so that the effective single crystallization rate of the silicon single crystal having a diameter of 8 inches or more decreases significantly.

With the increase in the density of LSIs, the diameter of silicon single crystals has been increased, and the quality required for silicon single crystals has become severer year by year. Must be resolved.

As a means for solving this problem, C
The silicon melt in the quartz crucible in the Z method is partitioned by a cylindrical quartz partition member having small holes, and while the raw material polysilicon is supplied to the outside of the partition member, the cylindrical silicon single member is placed inside the partition member. The method for growing a crystal has long been disclosed in, for example, US Pat. No. 2,892,739. On the other hand, in recent years, granular polycrystalline silicon having a particle size distribution with a diameter of about 0.1 to 4.0 mm has been developed. In particular, the CZ method for continuously supplying a raw material using this has been actively researched and developed (for example, Kaihei 2-80392). But,
This method has a problem that the dislocation generation rate of the crystal is still higher than that of the ordinary CZ method, and therefore it has not reached a practical level yet.

[0006]

DISCLOSURE OF THE INVENTION In the method for producing a silicon single crystal by the CZ method while continuously supplying the above granular silicon raw material, the inventors of the present invention attributed to the crystal dislocation of the obtained single crystal. As a result of detailed research on the points, the following was found.

In the method of pulling a silicon single crystal by the above CZ method, when supplying a granular silicon raw material to a silicon melt, a phenomenon in which large-sized granular polysilicon particles are cracked and fly off is known. ..

Japanese Unexamined Patent Publication No. 1-282194 discloses that bursting and scattering of granular silicon generated on a silicon melt can be prevented by reducing the hydrogen content in the granular silicon to 7.5 ppm or less. However, even if an extremely small amount of raw material with a hydrogen content of 1 ppm or less in the granular silicon was used, the phenomenon of bursting and scattering occurred, and it was found that the amount of hydrogen in the granular silicon raw material was not essential for the above phenomenon. ..

The above-mentioned granular silicon shards sometimes fly to the upper part of the hot zone, and it is naturally expected that they also fall into the silicon melt. Under such circumstances, the granular silicon shards Are attached to the growing crystal or fall into the silicon melt near the crystal to generate dislocations.

The object of the present invention is to produce the above-mentioned granular silicon fragments by selecting the characteristics of the granular silicon raw material when the silicon single crystal is manufactured by the CZ method using the granular silicon raw materials having different raw material characteristics. The object of the present invention is to provide a method for producing a large-diameter silicon single crystal by reducing the number of particles and reducing the probability of occurrence of dislocations in the silicon single crystal due to granular silicon fragments.

[0011]

Means for Solving the Problems Based on the above-mentioned findings, the present inventors have investigated the physical properties of the granular silicon raw material in detail in order to achieve the object of the present invention. It was found that the burst and scattering phenomenon of granular silicon raw material can be arranged very well.

The fracture toughness value was adopted as the mechanical strength. This fracture toughness value is defined as the value of the stress intensity factor K _I corresponding to the condition for the initiation of crack propagation in Mode _I and is named K _IC in the ASTM plane strain fracture toughness test method. (Physics Dictionary) This fracture toughness value K _IC is obtained by calculating from the lengths of four cracks generated in the extension direction of the diagonal line of the indentation formed when the cross section of the granular silicon raw material is press-fitted using the pyramidal diamond indenter.

The present inventors have invented the following as a result of examining the fracture toughness value of this granular silicon raw material and the dislocation generation probability of the silicon single crystal. The present invention provides a Czochralski while continuously supplying a granular silicon raw material.
In the method for producing a silicon single crystal by the method of the present invention, the granular silicon raw material is used as the mechanical strength to obtain a fracture toughness value K _IC.
Is a raw material having a ratio of 1.5 or more.

[0014]

The method of producing a silicon single crystal according to the present invention uses the fracture toughness value K of the granular silicon raw material shown in FIG.
_From the relationship graph of _IC and dislocation free rate, the fracture toughness value K _IC is
If it is 1.5 or more, the dislocation-free rate of the silicon single crystal is 75.
It has become clear that it will be over%. Therefore, in the method for producing a silicon single crystal of the present invention, since granular silicon having a high fracture toughness having a fracture toughness value K _IC as a mechanical strength of 1.5 or more is used as a raw material, the granular silicon raw material is formed on the silicon melt. In the case of supplying, it is possible to prevent the burst and scattering phenomenon of the granular silicon generated on the silicon melt. By preventing this bursting and scattering phenomenon, the probability of dislocations occurring during crystal growth is drastically reduced, and stable crystal growth is achieved. Next, examples of the present invention will be described.

[0015]

EXAMPLE FIG. 2 is a sectional view schematically showing an apparatus for growing a silicon single crystal having a diameter of 6 inches in an example of the present invention.

In the figure, reference numeral 1 is a quartz crucible having a diameter of 20 inches, which is set in a graphite crucible 2 supported by a pedestal 4. The pedestal 4 is electrically operated outside the furnace.
It is connected to a motor (not shown) and serves to impart a rotational movement (10 rpm) to the graphite crucible 2. Reference numeral 3 is an electric resistance heater (heater) surrounding the graphite crucible 2. 5
Is a silicon single crystal, 6 is a heat retaining member in a hot zone made of a heat insulating material surrounding the electric resistance heating body 3, and 7 is a silicon molten raw material liquid contained in the quartz crucible 1.
From this, the columnar silicon single crystal 5 is pulled up while rotating (20 rpm). Atmospheric gas is introduced into the furnace from the pulling chamber 20 and finally the discharge port 19 at the bottom of the furnace.
Is discharged by a pressure reducing device (not shown). The pressure inside the furnace (chamber-upper lid 16 and chamber-body 17) is 0.01 to 0.03 atm. The above is basically the same as the silicon single crystal manufacturing apparatus by the normal CZ method.

Reference numeral 8 denotes a ring-shaped partition member made of high-purity quartz and concentrically arranged in the quartz crucible 1,
Its diameter is 35 cm. This partition member 8 has a small hole 1
0 is opened, and the molten raw material of the raw material melting portion 12 flows into the single crystal growth portion 13 through the small holes 10. The lower edge portion of the partition member 8 is fused with the quartz crucible 1 in advance, or is fused by the heat when melting the silicon raw material, and the high-temperature molten raw material of the raw material melting portion 12 has the small holes 10
It flows into the single crystal growth part 13 through only. 9 is a granular polysilicon raw material. Reference numeral 14 is a raw material supply pipe, which has an opening above the raw material melting section 12 and is provided with a granular silicon raw material 14
Is supplied to the raw material melting section 12 through the raw material supply pipe 14. The raw material supply pipe 14 is connected to a raw material supply chamber (not shown) provided outside the chamber upper lid 16 and continuously supplies the granular silicon raw material 14. 15
Is a heat insulating cover, which is housed in the chamber and is composed of a tantalum plate having a thickness of 0.2 mm, which suppresses the dissipation of heat from the partition member 8 and the raw material melting section 12. Reference numeral 17 is a chamber-body to form a chamber body with the chamber upper lid 16, and 19 is an outlet.

In the present invention, although not shown, a control means for surely controlling the temperatures of the raw material melting part 12 and the single crystal growing part 13, a single crystal pulling and rotating means, a crucible rotating means, an inert gas supply and It goes without saying that a discharge means is provided.

Next, the fracture toughness value was determined as follows. As described above, the fracture toughness value K _IC is obtained by calculating from the length of four cracks generated in the extension direction of the diagonal line of the indentation formed when the cross section of the granular silicon raw material is press-fitted using the pyramidal diamond indenter. Specifically, the diagonal length of the indentation is 2a, the length of the crack from the center of the indentation is c,
When the hardness is H and the Young's modulus is E, K _IC is expressed as follows. K _IC = 0.028 × c ^−1.5 × a ² (E · H) ^0.5

[Embodiment 1] The granular silicon fragments sometimes fly to the upper part of the hot zone, and it is naturally expected that they also fall into the silicon melt. Under such a situation, it is sufficiently conceivable that the granular silicon fragments adhere to the growing crystal or drop into the melt near the crystal to cause dislocation.

In the silicon single crystal manufacturing apparatus configured as described above, the growth conditions for the silicon single crystal are as follows: diameter 6 inches,
Body length is 1m and pulling speed is 1mm / min
Then, the silicon single crystal was pulled up at a feed rate of the granular silicon raw material of 45 g / min.

Table 1 shows the number of remaining granular silicon fragments in the apparatus after the pulling and the probability of dislocation generation of the silicon single crystal. Table 1 shows the relationship between the residual number of granular silicon fragments per 1 kg of the raw material supply amount calculated by the residual number of granular silicon fragments generated in one pulling experiment and whether dislocation occurred at that time. .. From Table 1, in Experiments 4 and 5 in which the residual number of granular polysilicon fragments was small, no crystal dislocation was generated. As a result, between the residual number of granular polysilicon fragments and the occurrence of dislocations at that time. Are found to be correlated. That is, it can be seen from Table 1 that the probability of dislocation formation is obviously low when the number of remaining granular silicon fragments is small.

In the present embodiment, the residual number of granular silicon fragments means that the silicon single crystal is grown as described above, and then the inside of the apparatus is opened to adhere to the hot zone portion inside the apparatus. Collect the particulate polysilicon fragments on the machine and the granular silicon fragments accumulated at the bottom of the device,
It refers to the number of remaining fragments.

[0024]

[Table 1]

Example 2 Using the same apparatus and growth conditions as in Example 1, silicon single crystals were pulled up four times with respect to four cases of granular silicon raw materials having different fracture toughness values.

The dislocation-free rate was obtained by pulling each raw material four times and counting the number of dislocation-free pieces when an ingot having a diameter of 6 inches and a length of 1 m or more was pulled up.

FIG. 1 shows the K _IC value of the fracture toughness value on the abscissa, and the ordinate shows the dislocation-free rate obtained as described above.

From FIG. 1, it is clear that if the fracture toughness value K _IC of the granular silicon raw material supplied during the pulling of the silicon single crystal is 1.5 or more, the dislocation-free rate of the silicon single crystal is 75% or more. Became. The granular silicon raw material used in the present invention can be applied by any method of monosilane or trichlorosilane, and the single crystal production apparatus is not limited to that shown in FIG. Any device that grows crystals may be used.

[0029]

According to the present invention, in the CZ method of the type of growing crystals while continuously supplying the granular silicon raw material, the fracture toughness value K _IC of the granular silicon raw material to be supplied is 1.5 or more. By
The generation of granular silicon fragments was suppressed and the dislocation rate of silicon single crystal was significantly reduced. This is a type of C that grows crystals while continuously supplying granular polysilicon raw material.
The effect is great in establishing the manufacturing method of the Z method.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a relationship between a fracture toughness value K _IC of a granular polysilicon raw material and a dislocation-free rate.

FIG. 2 is a schematic cross-sectional view of a single crystal manufacturing apparatus used in an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 quartz crucible, 2 graphite crucible, 3 electric resistance heating body (heater), 4 pedestal, 5 silicon single crystal, 6 heat retaining member, 7 molten raw material, 8 partitioning member, 9 granular silicon raw material, 10 small holes, 12 raw material Melting part, 13 single crystal growth part, 14 raw material supply pipe, 15 heat insulation cover, 16 chamber-top cover, 17 chamber-body, 19 discharge port, 20 pulling chamber-, 21 silicon melt.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasumitsu Nakahama 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (1)

[Claims] 1. A method for producing a silicon single crystal by the Czochralski method while continuously supplying a granular silicon raw material, wherein a raw material having a fracture toughness value K _IC of the granular silicon raw material of 1.5 or more is used. A method for producing a characteristic silicon single crystal.