TW201917237A - Method for manufacturing silicon single crystal - Google Patents

Abstract

To provide a method for manufacturing a silicon single crystal capable of efficiently evacuating gas containing CO and reducing Cs within the silicon single crystal. A silicon single crystal manufacturing method for manufacturing a silicon single crystal by using a pulling apparatus having a chamber, a quartz crucible 3A provided in the chamber, and a heater 5 arranged so as to surround the quartz crucible 3A and heating the quartz crucible 3A, wherein an upper vent 16A for exhausting the gas introduced into the pulling device from the upper portion of the heater 5 and a lower vent 16B for exhausting from the lower portion of the heater 5 are formed in the pulling apparatus, wherein 1:3 ≤ volume of the gas exhausted via the upper vent 16A: volume of the gas exhausted via the lower vent 16B ≤ 6:1.

Description

Manufacturing method of silicon single crystal

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

Cs in the silicon single crystal becomes Ci in the device manufacturing process, and then combines with Oi to form CiOi defects. CiOi defects can cause component failure. Here, it is known that carbon in crystals can be reduced by controlling the pollution rate of CO that is mixed into the raw material melt from high-temperature carbon members such as furnace heaters and graphite crucibles, and the evaporation rate of CO from the raw material melt. concentration. The 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, Patent Document 1 discloses a technology that introduces an inert gas such as argon into a quartz crucible from above the pulling device, and directs a gas containing CO above the upper end of the heater and below the lower end of the heater, so that It is discharged from under the pulling device. Prior technical literature Patent literature:

Patent Document 1: Japanese Patent Application Laid-Open No. 05-319976

Invent the problem to be solved

However, in the technique described in the aforementioned patent document 1, since the upper exhaust port is located at a high position, exhaust from the upper exhaust port cannot be performed sufficiently, and it is not always possible to efficiently exhaust a gas containing CO. Therefore, there is a problem that Cs in the silicon single crystal cannot be sufficiently reduced.

The invention provides a method for manufacturing silicon single crystal, which can efficiently exhaust a gas containing CO to reduce Cs in the silicon single crystal. Problem solving

The method for producing a silicon single crystal according to the present invention is to use a quartz crucible provided with a reaction chamber, the quartz crucible provided in the pre-reaction chamber, and a pulling device arranged to surround the pre-quartz crucible and heat the pre-quartz crucible to produce A method for manufacturing a silicon single crystal of a silicon single crystal includes forming an upper exhaust port for exhausting gas that has been introduced into the former drawing apparatus from the upper part of the former heater, and exhausting the lower part of the former heater from the upper part of the former heater. The lower exhaust port of the gas; where 1: 3 ≦ the exhaust volume of the gas from the upper exhaust port of the previous record: the exhaust volume of the gas from the lower exhaust port of the previous record ≦ 6: 1. In the present invention, it is preferable that 1: 2 ≦ the exhaust gas amount from the upper exhaust port in the foregoing description: the exhaust gas amount from the lower exhaust port in the previous description ≦ 3: 1.

According to this invention, the exhaust volume of the gas exhausted from the upper exhaust port is 1: 3 ≦ the exhaust volume of the gas exhausted from the upper exhaust port: the exhaust volume of the gas exhausted from the lower exhaust port ≦ 6: 1 With this, it is possible to make the exhaust from the upper exhaust port preferential. Therefore, the CO-containing gas flowing 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, it is set to 1: 2 ≦ the exhaust gas volume from the upper exhaust port: the exhaust gas volume from the lower exhaust port ≦ 3: 1, so that the CO contained in the quartz crucible can be efficiently discharged. gas.

In the present invention, this is preferable: by changing the opening area of each exhaust port, the amount of gas exhausted from the upper exhaust port and the lower exhaust port of the preamble is adjusted. According to this invention, as long as the opening areas of the upper and lower exhaust ports are changed, the amount of gas exhausted from each exhaust port can be adjusted, so the gas from the upper and lower exhaust ports can be easily adjusted. Displacement.

In the present invention, it is preferable that the pre-drawing device includes an exhaust flow path, which is arranged in the pre-reaction chamber, forms the pre-exhaust upper exhaust port and the pre-lower exhaust vent, and is composed of a carbon member. According to this invention, the pulling device has an exhaust flow path, so that the gas containing CO can be exhausted without leaking to other parts, and Cs in the drawn silicon single crystal can be reliably reduced.

[1] Structure of silicon single crystal pulling device 1 FIG. 1 is a schematic diagram showing an example of a structure of a silicon single crystal pulling device 1 to which a method for manufacturing a silicon single crystal according to an embodiment of the present invention can be applied. The pulling device 1 is a device for pulling silicon single crystals 10 according to the Chuklasky method, and includes a reaction chamber 2 constituting an outer profile, and a crucible 3 disposed at a center portion of the reaction chamber 2. The crucible 3 has a double-layer structure composed of an inner quartz crucible 3A and an outer graphite crucible 3B, and is fixed to an upper end portion of the support shaft 4 which can be rotated and raised.

A resistance heating heater 5 surrounding the crucible 3 is provided on the outside of the crucible 3, and a heat insulating material 6 along the inner surface of the reaction chamber 2 as an outer tube is provided on the outside. Above the crucible 3 is provided a pulling shaft 7 of a wire or the like which rotates at a predetermined speed coaxially with the support shaft 4 in the reverse direction or the same direction. A seed crystal 8 is attached to the lower end of the pulling shaft 7.

A cylindrical heat shield 12 is arranged in the reaction chamber 2. The role of the heat shield 12 is to: for the silicon single crystal 10 being grown, shield the high temperature radiant heat from the silicon melt 9 in the crucible 3 or the heater 5 or the side wall of the crucible 3, and for the solid-liquid as the interface for crystal growth In the vicinity of the interface, thermal diffusion to the outside is suppressed, and the temperature gradient in the direction of the pull axis of the single crystal central portion and the single crystal outer peripheral portion is controlled. In addition, the heat shield 12 also functions as a rectifier, and exhausts the evaporation portion from the silicon melt 9 to the outside of the furnace by an inert gas introduced from above the furnace.

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

When a silicon single crystal 10 is produced using such a pulling device 1, the polycrystalline silicon and the like filled in the crucible 3 are heated by the heater 5 while the inside of the reaction chamber 2 is maintained under an inert gas atmosphere under reduced pressure. The solid material is melted to form a silicon melt 9. When the silicon melt 9 is formed in the crucible 3, the pulling shaft 7 is lowered, and the seed crystal 8 is immersed in the silicon melt 9, the crucible 3 and the pulling shaft 7 are rotated in a predetermined direction, and the pulling shaft 7 is slowly By pulling, a silicon single crystal 10 connected to the seed crystal 8 is produced.

[2] Structure of Exhaust Flow Path FIG. 2 and FIG. 3 show the structure of the exhaust flow path formed in the pulling device 1 described above. FIG. 2 is a vertical sectional view, and FIG. 3 is a horizontal sectional view. The exhaust pipe 15 is composed of a long member having a C-shaped cross section as shown in FIG. 3. The C-shaped flange of the exhaust pipe 15 is joined to the inner tube 16 disposed outside the heater 5 at the tip. The exhaust pipe 15 is disposed at four positions around the inner cylinder 16, with the center of the quartz crucible 3A as the center, and the adjacent exhaust pipes 15 are at an angle of 90 °.

The inner tube 16 is a cylindrical body made of a carbon member such as graphite. As shown in FIG. 2, in the inner cylinder 16, an upper exhaust port 16A is formed above the upper end of the heater 5, and a lower exhaust port 16B is formed below the lower end of the heater 5. The exhaust gas volume of the four upper exhaust ports 16A and the lower gas exhaust port 16B of the four exhaust pipes 15 is 1: 3 ≦ the exhaust gas volume of the gas from the upper exhaust port 16A : Exhaust gas from the lower exhaust port 16B ≦ 6: 1, preferably 1: 2 ≦ exhaust gas from the upper exhaust port 16A: exhaust gas from the lower exhaust port 16B The amount is ≦ 3: 1.

Furthermore, in this embodiment, the exhaust pipes 15 are provided at four places, but it is not limited thereto, and may be three or eight, as long as there are a plurality of exhaust pipes 15. In addition, the gas exhaust amounts of 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 system introduced from the gas introduction port 13 (see FIG. 1) above the quartz crucible 3A diffuses outward along the melt surface of the silicon melt 9, and the gas containing CO flows The inner peripheral surface of the quartz crucible 3A rises. Then, as shown in FIG. 2, a part of the CO-containing gas flows into the space surrounded by the inner tube 16 and the heat shield 12 to form a high CO gas concentration environment region. The CO-containing gas in the high CO gas concentration environment region enters the inside of the exhaust pipe 15 from the upper exhaust port 16A, flows downward, and is discharged from the exhaust port 14.

On the other hand, another part of the CO-containing gas flows through the inside of the heater 5 and, as shown in FIG. 2, an environment region with a high CO gas concentration is formed below the crucible 3. The CO-containing gas in the CO gas concentration environment region enters the inside of the exhaust pipe 15 from the lower exhaust port 16B, flows downward, and is discharged from the exhaust port 14. Furthermore, by adjusting the amount of gas exhausted from the upper exhaust port 16A and the amount of gas exhausted from the lower exhaust port 16B, the silicon melt flowing into the quartz crucible 3A can be efficiently discharged. The gas containing CO on the surface of 9 can reduce Cs in the silicon single crystal 10 obtained by drawing. [Example]

Next, embodiments of the present invention will be described. The present invention is not limited to the embodiments described below. [1] Change in carbon concentration of silicon single crystal 10 due to exhaust position Using the pulling device 1 of silicon single crystal 10 described in the embodiment, the discharge from the upper exhaust port 16A and the lower exhaust port 16B is changed. The air flow path pulls the silicon single crystal 10 and measures the carbon concentration in the pulled silicon single crystal 10.

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

As can be seen from FIG. 4, it can be confirmed that the carbon concentration in the silicon single crystal 10 is significantly lowered in the case of the upper + lower exhaust than in the case of only the lower exhaust in Comparative Example 1. On the other hand, in the case where only the upper exhaust gas is used in Comparative Example 2, the carbon concentration in the silicon single crystal 10 is higher than that in the case where only the lower exhaust gas is used in Comparative Example 1. This is because the CO gas generated by the reaction of the quartz crucible 3A and the graphite crucible 3B is sucked to the upper part, so the CO concentration near the silicon melt 9 increases, and as a result, the carbon concentration in the silicon single crystal 10 increases.

[2] The ratio of the exhaust gas volume of the upper exhaust port 16A and the lower exhaust port 16B is followed by using the thermal flow analysis program CGSim of STR to simulate the change of the upper exhaust port 16A and the lower exhaust port 16B. How the carbon concentration in the silicon melt 9 changes when the ratio of the gas exhaust amount is changed. The results are shown in Table 1 and Fig. 5.

[Table 1]

As can be seen from Table 1 and FIG. 5, when the gas exhaust volume of the upper exhaust port 16A: the gas exhaust volume of the lower exhaust port 16B = 1: 3, the carbon concentration in the silicon melt 9 is reduced to 5 × 10. ¹⁵ (atoms / cm ³ ) or less. On the other hand, it can be confirmed that the exhaust gas amount of the gas at the upper exhaust port 16A: the exhaust gas amount of the gas at the lower exhaust port 16B = 6: 1, and can be reduced to 5 × 10 ¹⁵ (atoms / cm ³ ) or less . In particular, in the range of 1: 2 ≦ the upper exhaust port 16A gas exhaust volume: lower exhaust port 16B gas exhaust volume ≦ 3: 1, it can be reduced to 4 × 10 ¹⁵ (atoms / cm ³ ) Below, the carbon concentration in the silicon melt 9 can be significantly reduced.

Therefore, it can be confirmed that the carbon concentration in the silicon melt 9 can be reduced by appropriately changing the gas exhaust amount of the gas at the upper exhaust port 16A and the gas exhaust amount of the lower exhaust port 16B. Carbon concentration in the drawn silicon single crystal 10.

1‧‧‧Pull device

2‧‧‧ reaction chamber

3‧‧‧ crucible

3A‧‧‧Quartz Crucible

3B‧‧‧Graphite Crucible

4‧‧‧ support shaft

5‧‧‧ heater

6‧‧‧Insulation

7‧‧‧ Pull shaft

8‧‧‧ crystals

9‧‧‧ silicon melt

10‧‧‧ silicon single crystal

12‧‧‧ heat shield

13‧‧‧Gas inlet

14‧‧‧ exhaust port

15‧‧‧ exhaust pipe

16‧‧‧ Inner tube

16A‧‧‧ Upper exhaust port

16B‧‧‧Lower exhaust port

[Fig. 1] A schematic diagram showing a structure of a silicon single crystal pulling device according to an embodiment of the present invention. [FIG. 2] A vertical cross-sectional view showing the structure of an exhaust gas flow path in the foregoing embodiment. [Fig. 3] A horizontal cross-sectional view showing a structure of an exhaust flow path in the foregoing embodiment. [Fig. 4] A graph showing a change in the carbon concentration in a silicon single crystal corresponding to the exhaust gas amount of the gas in the upper exhaust port and the lower exhaust port in the example. [Fig. 5] A graph showing a simulation result obtained by changing a ratio of an exhaust gas amount of an upper exhaust port and an exhaust gas amount of a lower exhaust port in an exhaust flow path.

Claims (5)

A method for manufacturing a silicon single crystal is to use a quartz crucible provided with a reaction chamber, the quartz crucible provided in the preceding reaction chamber, and a pulling device arranged to surround the preceding quartz crucible and heat the preceding quartz crucible to produce the silicon single crystal. In a method for producing crystalline silicon single crystal, an upper exhaust port for exhausting gas that has been introduced into the former pull apparatus from the upper part of the former heater and a gas exhaust from the lower part of the former heater are formed in the former pull device. Lower exhaust port; where 1: 3 ≦ exhaust gas from the upper exhaust port of the previous note: exhaust gas from the lower exhaust port of the previous note ≦ 6: 1. The method for manufacturing a silicon single crystal according to item 1 of the scope of the patent application, wherein 1: 2 ≦ exhaust gas amount of the gas from the upper exhaust port in the foregoing description: exhaust gas amount of the gas from the lower exhaust port in the previous description ≦ 3 :1. The method for manufacturing a silicon single crystal according to item 1 of the scope of the patent application, wherein the amount of gas discharged from the upper exhaust port and lower exhaust port is adjusted by changing the opening area of each exhaust port. . The method for manufacturing a silicon single crystal according to item 2 of the scope of patent application, wherein the amount of gas exhausted from the upper exhaust port and lower exhaust port is adjusted by changing the opening area of each exhaust port. . As described in the method for manufacturing a silicon single crystal according to any one of the claims 1 to 4, the pre-drawing device includes an exhaust flow path, which is arranged in the pre-reaction chamber, forming the pre-exhaust upper exhaust port and The lower exhaust port mentioned above is made of carbon components.