JP6881214B2 - Method for manufacturing silicon single crystal - Google Patents

Description

The present invention relates to a method for producing a silicon single crystal.

Cs in the silicon single crystal becomes Ci in the device process and combines with Oi to form a CiOi defect. CiOi defects cause device failure.
Here, the carbon concentration in the crystal is determined by controlling the contamination rate of CO mixed in the raw material melt from a high-temperature carbon member such as a heater in a furnace and a graphite crucible and the evaporation rate of CO from the raw material melt. It is known to reduce. CO (gas) from the high temperature carbon member is generated based on the following reaction formula.
SiO (gas) + 2C (solid) → CO (gas) + SiC (solid)

Therefore, in Patent Document 1, an inert gas such as argon gas is introduced into the quartz crucible from above the pulling device, and the gas containing CO is guided above the upper end and below the lower end of the heater to pull the device. The technology for discharging from below is disclosed.

Japanese Unexamined Patent Publication No. 05-319976

However, in the technique described in Patent Document 1, since the upper exhaust port is located at a high position, exhaust by the upper exhaust port is not sufficiently performed, and it cannot always be said that the gas containing CO can be efficiently exhausted. .. Therefore, there is a problem that Cs in the silicon single crystal cannot be sufficiently reduced.

An object of the present invention is to provide a method for producing a silicon single crystal capable of efficiently exhausting a gas containing CO to reduce Cs in the silicon single crystal.

The method for producing a silicon single crystal of the present invention uses a pulling device provided with a chamber, a quartz rubbing provided in the chamber, and a heater arranged so as to surround the quartz rubbing and heating the quartz rubbing. It is a method for producing a silicon single crystal for producing a silicon single crystal, and the pulling device includes an upper exhaust port for exhausting gas introduced into the pulling device from the upper part of the heater and exhaust from the lower part of the heater. The lower exhaust port is formed, and the gas exhaust amount from the upper exhaust port is 1: 3 ≦ the gas exhaust amount from the lower exhaust port ≦ 6: 1.
In the present invention, it is preferable that 1: 2 ≦ the amount of gas discharged from the upper exhaust port: the amount of gas discharged from the lower exhaust port ≦ 3: 1.

According to the present invention, the amount of gas exhausted from the upper exhaust port is set to 1: 3 ≤ the amount of gas exhausted from the upper exhaust port: the amount of gas exhausted from the lower exhaust port ≤ 6: 1. , Exhaust from the upper exhaust port can be given priority. Therefore, the gas containing CO that has flowed into the surface of the silicon melt in the quartz crucible can be efficiently discharged, and Cs in the silicon single crystal can be reduced.
In particular, by setting 1: 2 ≤ gas displacement from the upper exhaust port: gas displacement from the lower exhaust port ≤ 3: 1, the gas containing CO in the quartz crucible can be efficiently discharged. it can.

In the present invention, it is preferable that the amount of gas exhausted from the upper exhaust port and the lower exhaust port is adjusted by changing the opening area of each exhaust port.
According to the present invention, the amount of gas exhausted from each exhaust port can be adjusted simply by changing the opening areas of the upper exhaust port and the lower exhaust port, so that the gas exhaust amount from the upper exhaust port and the lower exhaust port can be easily adjusted. The amount of gas exhaust can be adjusted.

In the present invention, it is preferable that the pulling device is arranged in the chamber, the upper exhaust port and the lower exhaust port are formed, and an exhaust flow path composed of a carbon member is provided.
According to the present invention, since the pulling device is provided with an exhaust flow path, the gas containing CO can be exhausted without leaking to other parts, so that Cs in the pulled silicon single crystal can be reliably ensured. Can be reduced to.

The schematic diagram which shows the structure of the silicon single crystal pulling apparatus which concerns on embodiment of this invention. FIG. 5 is a vertical cross-sectional view showing the structure of the exhaust flow path in the embodiment. The horizontal sectional view which shows the structure of the exhaust flow path in the said embodiment. The graph which shows the change of the carbon concentration in a silicon single crystal according to the displacement of the gas of the upper exhaust port and the lower exhaust port in an Example. The graph which shows the simulation result which changed the ratio of the gas displacement of the upper exhaust port and the gas displacement of the lower exhaust port in the exhaust flow path.

[1] Structure of Silicon Single Crystal Pulling Device 1 FIG. 1 shows a schematic view showing an example of the structure of a silicon single crystal pulling device 1 to which the method for producing a silicon single crystal according to the embodiment of the present invention can be applied. Has been done. The pulling device 1 is a device for pulling the silicon single crystal 10 by the Czochralski method, and includes a chamber 2 forming an outer shell and a crucible 3 arranged in the center of the chamber 2.
The crucible 3 has a double structure composed of an inner quartz crucible 3A and an outer graphite crucible 3B, and is fixed to the upper end of a support shaft 4 capable of rotating and raising and lowering.

A resistance heating type heater 5 surrounding the crucible 3 is provided on the outside of the crucible 3, and a heat insulating material 6 serving as an outer cylinder is provided on the outside of the heater 5 along the inner surface of the chamber 2.
Above the crucible 3, a pull-up shaft 7 such as a wire that rotates coaxially with the support shaft 4 in the opposite direction or the same direction at a predetermined speed is provided. A seed crystal 8 is attached to the lower end of the pulling shaft 7.

A tubular heat shield 12 is arranged in the chamber 2.
The heat shield 12 blocks the high-temperature radiant heat from the silicon melt 9 in the crucible 3, the heater 5, and the side wall of the crucible 3 with respect to the growing silicon single crystal 10, and the solid liquid as the crystal growth interface. In the vicinity of the interface, it suppresses the diffusion of heat to the outside and plays a role of controlling the temperature gradient in the pulling axial direction of the central portion of the single crystal and the outer peripheral portion of the single crystal.
Further, the heat shield 12 also has a function as a rectifying cylinder that exhausts the evaporation part from the silicon melt 9 to the outside of the furnace by the inert gas introduced from above the furnace.

A gas introduction port 13 for introducing an inert gas such as argon gas (hereinafter referred to as Ar gas) into the chamber 2 is provided in the upper part of the chamber 2. An exhaust port 14 is provided in the lower part of the chamber 2 to suck and discharge the gas in the chamber 2 by driving a vacuum pump (not shown).
The inert gas introduced into the chamber 2 from the gas introduction port 13 descends between the growing silicon single crystal 10 and the heat shield 12, and the lower end of the heat shield 12 and the liquid level of the silicon melt 9. After passing through the gap between the two, the gas flows toward the outside of the heat shield 12 and further toward the outside of the crucible 3, then descends the outside of the crucible 3 and is discharged from the exhaust port 14.

When the silicon single crystal 10 is produced using such a pulling device 1, the heater 5 uses a solid raw material such as polycrystalline silicon filled in the crucible 3 while maintaining the inside of the chamber 2 in an inert gas atmosphere under reduced pressure. Is melted by heating to form a silicon melt 9. When the silicon melt 9 is formed in the crucible 3, the pulling shaft 7 is lowered to immerse the seed crystal 8 in the silicon melt 9, and the crucible 3 and the pulling shaft 7 are rotated in a predetermined direction while the pulling shaft is rotated. 7 is gradually pulled up, thereby growing a silicon single crystal 10 connected to the seed crystal 8.

[2] Structure of the exhaust flow path FIG. 2 and FIG. 3 show the structure of the exhaust flow path formed in the above-mentioned pulling device 1. FIG. 2 is a vertical sectional view, and FIG. 3 is a horizontal sectional view.
As shown in FIG. 3, the exhaust duct 15 is composed of a long member having a C-shaped cross section, and the C-shaped flange tip of the exhaust duct 15 is joined to an inner cylinder 16 arranged outside the heater 5. .. The exhaust ducts 15 are provided at four locations around the inner cylinder 16, and the adjacent exhaust ducts 15 are arranged so as to form an angle of 90 ° with the center of the quartz crucible 3A as the center.

The inner cylinder 16 is a cylindrical body made of a carbon member such as graphite. As shown in FIG. 2, the inner cylinder 16 has an upper exhaust port 16A formed above the upper end of the heater 5 and a lower exhaust port 16B formed below the lower end of the heater 5.
The amount of gas exhausted from the four upper exhaust ports 16A and the amount of gas exhausted from the lower exhaust port 16B of the four exhaust ducts 15 are 1: 3 ≤ the amount of gas exhausted from the upper exhaust port 16A: the lower exhaust port 16B. Gas displacement ≤ 6: 1, preferably 1: 2 ≤ gas displacement from the upper exhaust port 16A: gas displacement ≤ 3: 1 at the lower exhaust port 16B.

In the present embodiment, the exhaust ducts 15 are provided at four locations, but the present invention is not limited to this, and the exhaust ducts 15 may be provided at three locations or eight locations, as long as there are a plurality of exhaust ducts 15. Further, the amount of gas exhausted from the upper exhaust port 16A and the lower exhaust port 16B can be adjusted by changing the opening areas of the upper exhaust port 16A and the lower exhaust port 16B.

In such an exhaust flow path, the inert gas introduced from the gas introduction port 13 (see FIG. 1) at the upper part of the quartz crucible 3A diffuses outward along the melt surface of the silicon melt 9, and CO. The gas containing the above rises along the inner peripheral surface of the quartz crucible 3A.
Then, as shown in FIG. 2, a part of the gas containing CO flows into the space surrounded by the inner cylinder 16 and the heat shield 12, and forms a high CO gas concentration atmosphere region. The gas containing CO in the high CO gas concentration atmosphere region enters the inside of the exhaust duct 15 from the upper exhaust port 16A, flows downward, and is discharged from the exhaust port 14.

On the other hand, the other part of the gas containing CO flows inside the heater 5 and forms a high CO gas concentration atmosphere region below the crucible 3 as shown in FIG. The gas containing CO in the CO gas concentration atmosphere region enters the inside of the exhaust duct 15 from the lower exhaust port 16B, flows downward, and is discharged from the exhaust port 14.
Then, by adjusting the displacement of the gas exhausted from the upper exhaust port 16A and the displacement of the gas exhausted from the lower exhaust port 16B, the CO that has flowed into the surface of the silicon melt 9 in the quartz rut 3A is removed. The contained gas can be efficiently discharged, and as a result, Cs in the raised silicon single crystal 10 can be reduced.

Next, examples of the present invention will be described. The present invention is not limited to the examples described below.
[1] Change in Carbon Concentration of Silicon Single Crystal 10 Depending on Exhaust Position Using the silicon single crystal 10 pulling device 1 described in the embodiment, the exhaust flow paths from the upper exhaust port 16A and the lower exhaust port 16B are changed. , The silicon single crystal 10 was pulled up, and the carbon concentration in the pulled up silicon single crystal 10 was measured.

Example: The upper exhaust port 16A was opened and the lower exhaust port 16B was opened. The amount of gas discharged from the upper exhaust port 16A: the amount of gas discharged from the lower exhaust port 16B = 4: 1.
Comparative Example 1: The upper exhaust port 16A was closed and the lower exhaust port 16B was opened.
Comparative Example 2: The upper exhaust port 16A was opened and the lower exhaust port 16B was closed.
In Examples 1 and 2, the raw material charge amount was 400 kg, and 390 kg of the silicon single crystal 10 was pulled up. The flow rate of argon gas was set to 200 L / min, and the pressure inside the furnace was set to 4000 Pa (value converted to 30 Torr). The results are shown in FIG.

As can be seen from FIG. 4, it can be confirmed that the carbon concentration in the silicon single crystal 10 is significantly reduced in the case of the upper + lower exhaust of the example as compared with the case of only the lower exhaust of Comparative Example 1. It was.
On the other hand, in the case of only the upper exhaust of Comparative Example 2, the carbon concentration in the silicon single crystal 10 increased as compared with the case of only the lower exhaust of Comparative Example 1. This is because all the CO gas generated by the reaction of the quartz crucible 3A and the graphite crucible 3B is sucked up to the upper part, so that the CO concentration in the vicinity of the silicon melt 9 increases, and as a result, the carbon concentration in the silicon single crystal 10 increases. It is considered to be connected.

[2] Ratio of gas exhaust amount of upper exhaust port 16A and lower exhaust port 16B Next, using STR's heat flow analysis program CGSim, the ratio of gas exhaust amount of upper exhaust port 16A and lower exhaust port 16B is calculated. It was simulated how the carbon concentration in the silicon melt 9 changes when the gas is changed. The results are shown in Table 1 and FIG.

^{As can be seen from Table 1 and FIG. 5, the carbon concentration in the silicon melt 9 is 5 × 10 15} (at the displacement of gas in the upper exhaust port 16A: the displacement of gas in the lower exhaust port 16B = 1: 3). atoms / cm ³ ) Reduced to below.
On the other hand, it was confirmed that the gas displacement of the upper exhaust port 16A: the gas displacement of the lower exhaust port 16B = 6: 1 ^{can be reduced to 5 × 10 15} (atoms / cm ^{3) or less.}
In particular, in the range of 1: 2 ≤ gas displacement of the upper exhaust port 16A: gas displacement of the lower exhaust port 16B ≤ 3: 1, it can be reduced to ^{4 × 10 15} (atoms / cm ^{3) or less.} , The carbon concentration in the silicon melt 9 could be significantly reduced.
Therefore, the carbon concentration in the silicon melt 9 can be reduced by appropriately changing the gas displacement of the upper exhaust port 16A: the gas displacement of the lower exhaust port 16B. It was confirmed that the carbon concentration in the crystal 10 could be reduced.

1 ... Pulling device, 2 ... Chamber, 3 ... Crucible, 3A ... Quartz crucible, 3B ... Graphite crucible, 4 ... Support shaft, 5 ... Heater, 6 ... Insulation material, 7 ... Pulling shaft, 8 ... Seed crystal, 9 ... Silicon Melt, 10 ... silicon single crystal, 12 ... heat shield, 13 ... gas inlet, 14 ... exhaust port, 15 ... exhaust duct, 16 ... inner cylinder, 16A ... upper exhaust port, 16B ... lower exhaust port.

Claims (4)

Manufacture of a silicon single crystal for producing a silicon single crystal by using a lifting device including a chamber, a quartz crucible provided in the chamber, and a heater arranged so as to surround the quartz crucible and heating the quartz crucible. It ’s a method,
Wherein the pulling device, the disposed in the chamber, an exhaust passage to exhaust the introduced gas into the pulling apparatus is formed,
The exhaust flow path includes an upper exhaust port for introducing the gas from the upper part of the heater into the exhaust flow path, a lower exhaust port for introducing the gas from the lower part of the heater into the exhaust flow path, and the upper exhaust. An exhaust port and an exhaust port for discharging the gas introduced from the lower exhaust port are formed.
1: 3 ≤ Gas displacement from the upper exhaust port: Gas displacement from the lower exhaust port ≤ 6: 1 .
A method for producing a silicon single crystal , wherein the amount of gas exhausted from the upper exhaust port and the lower exhaust port is adjusted by changing the opening areas of the upper exhaust port and the lower exhaust port, respectively. In the method for producing a silicon single crystal according to claim 1,
1: 2 ≤ Gas displacement from the upper exhaust port: A method for producing a silicon single crystal, characterized in that the gas displacement from the lower exhaust port is ≤ 3: 1. In the method for producing a silicon single crystal according to claim 1 or 2.
The ratio of the gas exhaust amount from the upper exhaust port and the lower exhaust port changes the ratio of the gas exhaust amount from the upper exhaust port and the lower exhaust port, and simulates the carbon concentration in the silicon melt. A method for producing a silicon single crystal, which is characterized by being adjusted from the results obtained. In the method for producing a silicon single crystal according to any one of claims 1 to 3.
The exhaust passage, the method for manufacturing a silicon single crystal, wherein the benzalkonium consists of carbon members.

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