Single crystal pulling apparatus and method for manufacturing single crystal

Abstract

To suppress introduction of a CO gas or the like to a silicon melt when closing a gate valve to suppress a rise in carbon concentration of a single crystal to pull.SOLUTION: A control unit 11 introduces an inert gas G to a main chamber 10A from a first gas introduction port 10a with inert gas supply means 17 while a gate valve 18 is open and introduces an inert gas toward a silicon melt M stored in a crucible 3 from a second gas introduction port 20c with the inert gas supply means while the gate valve is closed to separate a pull chamber 10B from the main chamber.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a single crystal pulling apparatus and a method for manufacturing a single crystal, which pull a single crystal using the Czochralski method.

Background Art

[0002] Conventionally, a single crystal pulling apparatus as shown in FIG. 8 has been used for growing silicon single crystals by the Czochralski method (CZ method). This single crystal pulling apparatus includes a quartz glass crucible 51 that houses a silicon melt M, a main chamber 50A that houses the quartz glass crucible 51, a heater 52 provided around the quartz crucible 51, and a pull chamber 50B that is stacked on the main chamber 50A and from which a single crystal C is pulled up.

[0003] At the upper part of the pull chamber 50B, a gas inlet 50a for supplying an inert gas G into the chamber is provided, and a flow of the inert gas G is formed from the pull chamber 50B toward the main chamber 50A (the inert gas G is exhausted from an outlet 50b provided in the main chamber 50A). By forming a flow of the inert gas G in the main chamber 50A in this way, SiO gas evaporated from the silicon melt M or CO gas generated from members disposed in the main chamber 50A such as the heater 52 is discharged outside the chamber without being trapped in the chamber.

[0004] In addition, in order to enhance the cooling effect of the single crystal C being grown, a radiation shield 55 that surrounds the periphery of the single crystal C is disposed above the silicon melt M formed in the crucible 51. Furthermore, in order to improve the cooling effect, a cylindrical rectifying cylinder 56 extending downward from the ceiling portion of the main chamber 50A may be provided as disclosed in Patent Document 1. The single crystal C is pulled up through the rectifying cylinder 56.

[0005] In the single crystal pulling apparatus configured as described above, polysilicon as a raw material is filled into the quartz crucible 51 installed in the main chamber 50A, and the polysilicon is heated and melted by the heater 52 provided around the quartz crucible 51 to obtain a silicon melt M. Thereafter, the seed crystal P (seed) attached to the seed chuck is immersed in the silicon melt M, and the silicon single crystal C is grown by pulling the seed chuck up into the pull chamber 50B while rotating the seed chuck and the quartz crucible 51 in the same direction or in the opposite direction.

[0006] By the way, in pulling the single crystal C by the CZ method, there is a multi-pulling method of continuously pulling a plurality of single crystals C from one chamber 50A. In this multi-pulling method, when pulling of one silicon single crystal C is completed, as shown in FIG. 9, the main chamber 50A is sealed by the gate valve 54 provided at the lower part of the pull chamber 50B (for the chamber configuration using the gate valve, see, for example, Patent Document 2). Next, the recharge tube 60 is carried into the pull chamber 50B. The recharge tube 60 is filled with, for example, nugget-shaped raw polysilicon 70, and the raw polysilicon 70 is held in the tube by a conical valve 61 provided at the lower part of the recharge tube 60.

[0007] When the recharge tube 60 is set in the pull chamber 50B, as shown in FIG. 10, the gate valve 54 is opened, and the recharge tube 60 is lowered into the main chamber 50A by the wire 65. Here, the position of the recharge tube 60 is fixed by the flange protrusion 60a provided on the outer peripheral surface of the recharge tube 60 engaging with the protrusion 50b provided on the inner peripheral surface of the pull chamber 50B. Subsequently, when only the conical valve 61 is lowered by the wire 65, the lower surface of the recharge tube 60 is opened, and the polysilicon 70 falls from the tube into the quartz crucible 51, and the raw polysilicon 70 is additionally loaded into the silicon melt M remaining in the quartz crucible 51. Then, the polysilicon 70 is heated and melted by the heater 52 provided around the quartz crucible 51, and the silicon melt M in an amount necessary for growing the single crystal C is obtained. Then, the pulling of the silicon single crystal C is performed again. Patent Document 1 discloses a configuration in which a second gas inlet for introducing an inert gas is provided at the upper part of the main chamber 50A along the outer peripheral surface of the rectifying cylinder 56 and the inner peripheral surface of the main chamber 50A from the outside of the upper part of the rectifying cylinder 56.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] By the way, for example, in the multi-pulling method, while the recharge tube 60 is installed in the pull chamber 50B, the gate valve 54 is closed. Also, in addition to the multi-pulling method, the gate valve 54 is closed even during additional charging when silicon raw material is added to the silicon melt M. However, when the gate valve 54 is closed, the inert gas G introduced from the gas inlet 50a provided in the pull chamber 50B is blocked by the gate valve 54 and thus is not introduced into the main chamber 50A. Therefore, the CO gas generated from the members arranged in the main chamber 50A such as the heater 52 is not discharged outside the chamber and is likely to dissolve and be introduced into the silicon melt M. As a result, there is a problem that the carbon concentration in the silicon melt M increases and the carbon concentration of the single crystal C to be pulled becomes higher.

[0010] An object of the present invention is to provide a silicon single crystal pulling apparatus and a method for manufacturing a silicon single crystal that can suppress the introduction of CO gas or the like into the silicon melt when the gate valve is closed and suppress the increase in the carbon concentration of the pulled single crystal.

Means for Solving the Problems

[0011] The single crystal pulling apparatus according to the present invention, which has been made to solve the above problems, includes a crucible for containing a silicon melt, a heater for heating the silicon melt, a main chamber for containing the crucible and the heater, a pull chamber disposed above the main chamber and separable from the main chamber, an openable and closable gate valve for separating the main chamber and the pull chamber, a first gas introduction path provided on the pull chamber side for supplying an inert gas to the main chamber, and a rectifying cylinder provided on the main chamber side for rectifying the inert gas supplied to the main chamber. The single crystal pulling apparatus has a second gas introduction path provided on the main chamber side and having a vertically downward opening for supplying an inert gas along the inner peripheral surface of the rectifying cylinder to the main chamber, an inert gas supply device for introducing an inert gas into the first gas introduction path and the second gas introduction path, and a control unit for controlling the inert gas supply device. The control unit causes the inert gas supply device to introduce an inert gas from the first gas introduction path into the main chamber while the gate valve is open, and causes the inert gas supply device to introduce an inert gas from the second gas introduction path toward the silicon melt contained in the crucible while the gate valve is closed and the pull chamber and the main chamber are separated.

[0012] In addition, it further has a radiation shield provided in the main chamber for shielding the radiant heat from the heater to the growing silicon single crystal, and it is desirable that the opening of the second gas introduction path does not overlap the radiation shield in the vertical direction. Alternatively, it further has a radiation shield provided in the main chamber for shielding radiant heat from the heater to the growing silicon single crystal, and it is desirable that the opening of the second gas introduction path is located near the tip of the radiation shield in the vertical direction. Also, it is desirable that the opening is in an annular slit shape, or the opening may be formed by a plurality of holes arranged along the annular shape.

[0013] According to such a configuration, even when the main chamber is closed by the gate valve in order to add new raw material polysilicon to the crucible, an inert gas introduced from the second gas inlet having a vertically downward opening flows vertically downward along the inner peripheral surface of the rectifying cylinder in the main chamber. As a result, the inert gas flows so as to cover the liquid surface of the silicon melt, and in particular, a sufficient gas flow is formed also on the liquid surface of the silicon melt on the outer peripheral side. Thereby, even if CO gas is generated from a device such as a heater arranged in the chamber, it is discharged to the outside of the chamber by the gas flow of the inert gas, so that the dissolution of CO gas into the silicon melt is suppressed, and an increase in the carbon concentration of the pulled-up silicon single crystal can be suppressed.

[0014] Also, a method for manufacturing a single crystal according to the present invention, which is made to solve the above problems, includes a crucible that houses a silicon melt formed by heating with a heater, a main chamber that houses the crucible and the heater, a pull chamber that is disposed above the main chamber and from which a silicon single crystal is pulled up and that can be separated from the main chamber by a gate valve, and a rectifying cylinder that is provided on the main chamber side and rectifies an inert gas supplied to the main chamber. In the method for manufacturing a single crystal that pulls up a silicon single crystal by the Czochralski method in a single crystal pulling apparatus including these components, the method includes a step of supplying an inert gas from a first gas introduction path provided on the pull chamber side to the main chamber and growing a silicon single crystal from the silicon melt, and a step of closing the gate valve to separate the main chamber from the pull chamber and introducing an inert gas toward the silicon melt housed in the crucible from a second gas introduction path that is provided on the main chamber side and has a vertically downward opening for supplying the inert gas along the inner peripheral surface of the rectifying cylinder. The method is characterized by including these steps.

[0015] In addition, in the step of closing the gate valve to separate the main chamber from the pull chamber and introducing an inert gas toward the silicon melt housed in the crucible from a second gas introduction path that is provided on the main chamber side and has a vertically downward opening for supplying the inert gas along the inner peripheral surface of the rectifying cylinder, it is desirable to supply the inert gas from the opening formed in an annular slit shape. Alternatively, in the step of closing the gate valve to separate the main chamber from the pull chamber and introducing an inert gas toward the silicon melt housed in the crucible from a second gas introduction path that is provided on the main chamber side and has a vertically downward opening for supplying the inert gas along the inner peripheral surface of the rectifying cylinder, the inert gas may be supplied from the opening formed as a plurality of holes arranged along an annular shape.

[0016] According to such a method, even when the main chamber is closed by the gate valve in order to additionally load new raw material polysilicon into the crucible, an inert gas introduced from a second gas inlet having a vertically downward opening flows vertically downward along the inner peripheral surface of the rectifying cylinder in the main chamber. As a result, the inert gas flows so as to cover the liquid surface of the silicon melt, and a sufficient gas flow is particularly formed on the liquid surface of the silicon melt on the outer peripheral side. Thus, even if CO gas is generated from a device such as a heater disposed in the chamber, it is discharged to the outside of the chamber by the gas flow of the inert gas, so that the CO gas is prevented from dissolving in the silicon melt, and an increase in the carbon concentration of the silicon single crystal to be pulled up can be suppressed.

Advantages of the Invention

[0017] According to the present invention, it is possible to provide a single crystal pulling apparatus and a method for manufacturing a single crystal that can suppress the introduction of CO gas into the silicon melt when the gate valve is closed and suppress an increase in the carbon concentration of the single crystal to be pulled up.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

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Figure 8

Figure 9

Figure 10

Figure 11

BEST MODE FOR CARRYING OUT THE INVENTION

[0019] Hereinafter, the single crystal pulling apparatus and the method for manufacturing a single crystal according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of the single crystal pulling apparatus according to the present invention. This single crystal pulling apparatus 1 includes a furnace body 10 formed by stacking a pull chamber 10B on a cylindrical main chamber 10A. Inside the furnace body 10, there are provided a carbon crucible (or graphite crucible) 2 that can rotate and move up and down around a vertical axis, and a quartz glass crucible 3 (hereinafter simply referred to as crucible 3) held by the carbon crucible 2. The crucible 3 is made to be rotatable around the vertical axis as the carbon crucible 2 rotates.

[0020] Also, below the carbon crucible 2, there are provided a rotation drive unit 14 such as a rotation motor for rotating the carbon crucible 2 around the vertical axis, and a lifting drive unit 15 for moving the carbon crucible 2 up and down. A rotation drive control unit 14a is connected to the rotation drive unit 14, and a lifting drive control unit 15a is connected to the lifting drive unit 15.

[0021] The single crystal pulling apparatus 1 also includes a heater 4 for melting the semiconductor raw material (raw material polysilicon) loaded in the crucible 3 into a silicon melt M by resistance heating, and a pulling mechanism 9 for winding up the wire 6 and pulling up the grown single crystal C. A seed crystal P is attached to the tip of the wire 6 of the pulling mechanism 9. Further, a heater control unit 4a for controlling the amount of power supplied to the heater 4 is connected to the heater 4, and a rotation drive control unit 9a for controlling the rotation drive of the lifting mechanism 9 is connected to the lifting mechanism 9.

[0022] In addition, the single crystal pulling apparatus 1 includes a first gas inlet (first gas introduction passage) 10a at the upper part of the pull chamber 10B, and an inert gas G such as argon gas is supplied to the first gas inlet 10a from the inert gas supply means 17. In the furnace 10, the inert gas G is introduced from the first gas inlet 10a toward the lower main chamber 10A at a flow rate of, for example, 300 L / min. During the pulling of the single crystal, the inert gas G introduced into the furnace from the first gas inlet 10a flows downward along the outer peripheral surface of the single crystal C toward the silicon melt M. When the inert gas G hits the liquid surface of the silicon melt M, it flows radially outward so as to cover the entire liquid surface, and when it exits the crucible 3, it is exhausted to the outside of the chamber through the gas outflow pipe 19. By forming the flow of the inert gas G in this way, the SiO gas evaporated from the silicon melt M or the CO gas generated from the members arranged in the main chamber 10A such as the heater 4 is discharged to the outside of the furnace without being trapped in the furnace.

[0023] Further, above the silicon melt M formed in the crucible 3, a radiation shield 7 surrounding the single crystal C is arranged. The radiation shield 7 has openings formed at the upper and lower parts, and shields unnecessary radiant heat from the heater 4, the silicon melt M, etc. for the growing single crystal C, and rectifies the gas flow in the furnace. The gap between the lower end (tip) of the radiation shield 7 and the melt liquid surface is controlled to maintain a predetermined distance (for example, 50 mm) constant according to the desired characteristics of the single crystal to be grown.

[0024] Furthermore, in the present embodiment, in the vicinity of the ceiling portion of the main chamber 10A, a straightening cylinder 16 is extended downward so as to surround the single crystal C in order to improve the cooling effect of the silicon single crystal C to be pulled up. During the pulling of the single crystal, the inert gas G introduced from the first gas inlet 10a passes through the inside of the rectifying cylinder 16 and flows downward along the outer peripheral surface of the single crystal C toward the silicon melt M.

[0025] Also, at the lower part inside the pull chamber 10B, above the rectifying cylinder 16, a gate valve 18 that can be opened and closed by a gate valve driving unit 18a is provided. By closing this gate valve 18 (closing the valve), the inside of the main chamber 10A can be sealed. That is, the pull chamber 10B and the main chamber 10A are configured to be separable by the gate valve 18. Also, below the gate valve 18 and above the rectifying cylinder 16, a gas introduction jig 20 having a second gas inlet 20c formed therein is provided. This gas introduction jig 20 is used when the gate valve 18 is closed and the main chamber 10A is sealed.

[0026] Fig. 2(a) is a plan view of the gas introduction jig 20, and Fig. 2(b) is a cross-sectional view thereof. The gas introduction jig 20 is formed by an L-shaped cross-sectional pipe body in an annular shape, and in the main chamber 10A, the annular main body is arranged to be parallel (i.e., horizontal) to the liquid surface of the silicon melt M. As shown in Fig. 2(a), on the outer peripheral surface of the gas introduction jig 20, a plurality (two locations in the figure) of gas introduction pipes 20a are provided so as to protrude outward. These gas introduction pipes 20a are arranged so as to protrude out of the chamber from the side wall of the main chamber 10A as shown in Fig. 1. An inert gas at a predetermined flow rate is supplied to the gas introduction pipes 20a from the inert gas supply device 17 as required.

[0027] Also, an annular slit pipe 20b extending downward is formed at the inner peripheral edge of the gas introduction jig 20, and the outer peripheral surface of this slit pipe 20b is arranged along the inner peripheral surface of the rectifying cylinder 16. That is, the outer diameter of the annularly arranged slit pipe 20b is formed to substantially match the inner diameter of the rectifying cylinder 16. At the tip of the slit tube 20b, a second gas inlet 20c, which is an annular opening, is formed. Thereby, the inert gas introduced into the gas introduction jig 20 from the gas introduction pipe 20a passes through the slit 20b and is introduced into the furnace 10 from the second gas inlet 20c. The second gas introduction pipe 20a, the slit 20b, and the second gas inlet 20c, which is an opening, serve as a second gas introduction path for introducing the inert gas G into the main chamber. That is, the inert gas G introduced from the second gas inlet 20c is configured to flow downward along the inner peripheral surface of the rectifying cylinder 16 toward the lower main chamber 10A side. Also, the opening of the second gas introduction path (the second gas inlet 20c) is positioned so as not to overlap with the radiation shield 7 in the vertical direction. However, the opening of the second gas introduction path may be positioned near the tip of the radiation shield 7 in the vertical direction.

[0028] In this way, as the inert gas G flows downward (vertically downward) along the inner peripheral surface of the rectifying cylinder 16, the inert gas flow hits the liquid surface of the silicon melt M, and then the inert gas G is configured to flow along the liquid surface so as to cover the entire liquid surface. This is because, compared with the case where the inert gas G is applied to the center of the liquid surface and then flows radially outward along the liquid surface (when the single crystal C is not being pulled up), a gas flow can be formed in which the inert gas G surely reaches the outer peripheral portion of the liquid surface, and the diffusion of the inert gas can be prevented.

[0029] In addition, it is desirable that the flow rate of the inert gas introduced from the second gas inlet 20c is 300 L / min. Also, the slit width of the slit tube 20b is preferably 6 mm to 13 mm. If the slit width is greater than 13 mm, the inert gas flowing into the crucible directly below is likely to stay, and it becomes difficult to flow in the circumferential direction of the crucible, which is not preferable. Also, the introduction direction of the inert gas from the second gas inlet 20c is determined by the inclination direction of the slit tube 20b in a cross-sectional view, but as shown in Fig. 2(b), it is preferably in the vertically downward direction (a direction of 90° with respect to the silicon melt surface).

[0030] Further, this single crystal pulling apparatus 1 includes a controller 11 (control unit) having a storage device 11a and an arithmetic control device 11b. The rotation drive control unit 14a, the lifting drive control unit 15a, the rotation drive control unit 9a, and the gate valve drive unit 18a are each connected to the arithmetic control device 11b.

[0031] In the single crystal pulling apparatus 1 configured as described above, for example, when continuously growing a single crystal C with a diameter of 200 mm by the multi-pulling method, the pulling is performed as follows. Note that the present invention is not limited to the multi-pulling method and is also applicable to an additional charge in which a polysilicon raw material is added to a silicon melt and melted. First, raw material polysilicon (for example, 150 kg) is loaded into the crucible 3 (step S1 in FIG. 3), and a crystal growth process is started based on a program stored in the storage device 11a of the controller 11.

[0032] Next, the controller 11 drives the inert gas supply means 17 and introduces an inert gas (for example, argon gas) into the chamber from the first gas inlet 10a at a flow rate of 300 L / min. The inside of the chamber 10 is set to a predetermined atmosphere (for example, a furnace internal pressure of 60 to 110 torr) (step S2 in FIG. 3). Then, with the crucible 3 being rotated in a predetermined direction at a predetermined rotational speed (rpm), the raw material polysilicon loaded in the crucible 3 is melted by heating with the side heater 4 to form a silicon melt M (step S3 in FIG. 3).

[0033] Also, the pulling conditions are adjusted with parameters such as the power supplied to the side heater 4, the pulling speed, and the magnetic field application intensity, and the seed crystal P starts to rotate at a predetermined rotational speed around the axis. The rotational direction is opposite to the rotational direction of the crucible 3. Then, the wire 6 is lowered and the seed crystal P is brought into contact with the silicon melt M. After the tip of the seed crystal P is melted, necking is performed to form a neck portion.

[0034] Then, the single crystal pulling process is started. That is, the crystal diameter is gradually increased to form a shoulder, and the process proceeds to form a straight body portion that becomes the product part. The growth of the single crystal continues. When the single crystal is pulled up to the desired length without dislocation, the growth of the single crystal is completed. That is, when the straight body portion is formed to a predetermined length, the process proceeds to the final tail portion process. In this tail portion process, the contact area between the lower end of the crystal and the silicon melt M is gradually reduced, and the single crystal C and the silicon melt M are separated to produce a silicon single crystal (step S4 in Fig. 3).

[0035] When the pulling of one single crystal C is completed and the next single crystal is continuously pulled up (step S5), the gate valve 18 is closed, and the main chamber 10A and the pull chamber 10B are separated (step S6 in Fig. 3). When the gate valve 18 is closed and the main chamber 10A is sealed, the controller 11 stops the introduction of the inert gas from the first gas inlet 10a, and starts to introduce an inert gas G (for example, argon gas) at a flow rate of, for example, 300 L / min from the second gas inlet 20c into the main chamber 10A by the inert gas supply means 17. As a result, a predetermined gas flow by the inert gas G is formed in the main chamber 10A as shown by the arrow in Fig. 4 (step S7 in Fig. 3).

[0036] More specifically, the inert gas G introduced from the second gas inlet 20c flows downward along the inner peripheral surface of the rectifying tube 16 as shown in Fig. 4, and forms a cylindrical gas flow (with a diameter larger than the diameter of the single crystal to be grown), which hits the liquid surface of the silicon melt M remaining in the crucible 3. Then, the inert gas G forms a gas flow that flows radially outward so as to cover the entire liquid surface of the silicon melt M. The inert gas that reaches the outer peripheral portion of the melt surface M climbs over the upper end of the crucible and flows to the side of the crucible, then flows downward in the chamber, and is exhausted to the outside of the chamber by the gas outlet pipe 19.

[0037] While the main chamber 10A is closed by the gate valve 18 in this way, an inert gas introduced from the second gas inlet 20c forms a gas flow in the main chamber 10A that flows to cover the surface of the silicon melt M. This way, even if CO gas is generated from a device such as a heater arranged in the chamber, it is discharged outside the chamber by the gas flow of the inert gas G.

[0038] On the other hand, when the gate valve 18 is closed, a recharge tube (not shown) filled with raw polysilicon is set in the pull chamber 10B (step S8 in FIG. 3), and then the gate valve 18 is opened again (step S9 in FIG. 3). The controller 11 stops the introduction of the inert gas from the second gas inlet 20c, and starts introducing an inert gas G (for example, argon gas) at a flow rate of, for example, 300 L / min into the main chamber 10A from the first gas inlet 10a by the inert gas supply means 17 (step S10 in FIG. 3). Then, the recharge tube is lowered, and new raw polysilicon is put into and loaded into the crucible (step S11 in FIG. 3). After that, it returns to step S3 in FIG. 3, and subsequently, the next single crystal C is continuously pulled up.

[0039] As described above, according to the present embodiment, in order to additionally load new raw polysilicon into the crucible 3, when the main chamber 10A is closed by the gate valve 18, in the main chamber 10A, an inert gas G introduced from the second gas inlet 20c forms a gas flow that flows to cover the entire surface of the silicon melt M and is then exhausted outside the chamber. Thereby, even if CO gas is generated from a device such as a heater arranged in the chamber, it is discharged outside the chamber by the gas flow of the inert gas G. Therefore, the dissolution of CO gas into the silicon melt M is suppressed, and an increase in the carbon concentration of the silicon single crystal to be pulled up can be suppressed.

[0040] In the above-described embodiment, an annular slit tube 20b extending downward is formed at the inner peripheral edge of the gas introduction jig 20. However, in the present invention, the configuration is not limited to this. For example, as shown in the plan view of FIG. 5(a) and the cross-sectional view of FIG. 5(b), instead of the slit tube 20b, a large number of rod-shaped tubes 20d are arranged in the circumferential direction (porous method), and an inert gas may be allowed to flow vertically downward from a second gas inlet 20e formed at the lower ends of the plurality of tubes 20d. Alternatively, instead of arranging a large number, only two rod-shaped tubes 20d may be arranged on the circumference, and an inert gas may be allowed to flow vertically downward from the second gas inlet 20e. In addition, the inert gas supply devices 17 for introducing inert gas into the first gas inlet and the second gas inlet may be provided separately.

Example

[0041] The single crystal pulling apparatus and the single crystal manufacturing method according to the present invention will be further described based on examples. In this example, in the configuration of FIG. 1, a quartz crucible with a diameter of 32 inches was filled with 300 kg of silicon raw material, the furnace internal pressure was 65 torr, and argon gas was flowed into the main chamber 10A from the first gas inlet 10a at a flow rate of 300 L / min. Then, the crucible rotation speed was set to 5 - 6 rpm, the crystal rotation speed was set to 8 rpm (in the opposite direction to the crucible rotation), and single crystal growth was performed with a pulling speed of 1.4 mm / min aiming for a crystal diameter of 12 inches.

[0042] After pulling up the first single crystal, the gate valve 18 was closed, the supply of argon gas was switched from the first gas inlet 10a to the second gas inlet 20c, and argon gas was introduced into the main chamber at a flow rate of 300 L / min from this second gas inlet 20c. In addition, the gate valve was opened and the supply of argon gas was switched from the second gas inlet 20c to the first gas inlet 10a, and raw material polysilicon was added into the crucible. The second single crystal was pulled up under the same pulling conditions as those of this order, the tail portion of this single crystal was cut out, and the carbon concentration was measured and evaluated by FT-IR (Fourier transform infrared spectrophotometer).

[0043] (Example 1) In Example 1, the second gas inlet was formed at the lower end of a slit tube as shown in FIG. 2 (slit method), and argon gas was flowed directly downward (90° with respect to the silicon melt surface). The slit width was 13 mm. (Example 2) In Example 2, the second gas inlet was formed at the lower ends of 12 rod-shaped tubes as shown in FIG. 5 (porous method), and argon gas was flowed directly downward (90° with respect to the silicon melt surface). The diameter of the inlet was 13 mm.

[0044] (Comparative Example 1) In Comparative Example 1, as shown in FIG. 6(a), the second gas inlet 20c was formed at the tip of the slit tube 20b (slit method), and argon gas G was flowed toward the center of the chamber (parallel to the silicon melt surface (180°)). The slit width was 13 mm. (Comparative Example 2) In Comparative Example 2, as shown in FIG. 6(b), the second gas inlet 20c was formed at the tip of the slit tube 20b (slit method), and argon gas G was flowed obliquely downward at 45° with respect to the silicon melt surface. The slit width was 13 mm. (Comparative Example 3) In Comparative Example 3, as shown in FIG. 6(c), the second gas inlet 20c was formed at the tip of the slit tube 20b (slit method), and argon gas G was flowed obliquely downward at 75° with respect to the silicon melt surface. The slit width was 13 mm.

[0045] The results of the examples are shown in the graph of FIG. 7. In the graph of FIG. 7, the vertical axis represents the carbon concentration (arb. unit), and the horizontal axis represents Examples 1 and 2 and Comparative Examples 1, 2, and 3. In Examples 1 and 2 and Comparative Examples 1, 2, and 3, single crystals could be pulled up without dislocation. However, in Examples 1 and 2, the carbon concentration was 1.0 arb.unit or less, and the carbon concentration was significantly lower than that in Comparative Examples 1, 2, and 3. According to this example, it was confirmed that in the multi-pulling method, the carbon concentration of the single crystal pulled up after the second time in Example 1 could be suppressed to the same level as that of the first single crystal. Similarly, for Example 2, it was also confirmed that the carbon concentration of the single crystal pulled up after the second time could be suppressed to almost the same level as that of the first single crystal.

Explanation of Signs

[0046] 1 Single crystal pulling device 2 Carbon crucible 3 Quartz glass crucible 4 Heater 6 Wire 7 Radiation shield 10A Main chamber 10B Pull chamber 10a First gas inlet 11 Controller (control unit) 16 Rectifier tube 18 Gate valve 20 Gas introduction jig 20a Gas introduction pipe 20b Slit pipe 20c Second gas inlet 19 Gas outflow pipe M Silicon melt C Silicon single crystal

Claims

1. A single crystal pulling apparatus comprising a crucible for containing a silicon melt, a heater for heating the silicon melt, a main chamber for containing the crucible and the heater, a pull chamber disposed above the main chamber and separable from the main chamber, an openable and closable gate valve for separating the main chamber and the pull chamber, a first gas introduction path provided on the pull chamber side for supplying an inert gas to the main chamber, and a rectifying cylinder provided on the main chamber side for rectifying the inert gas supplied to the main chamber, a second gas introduction path provided on the main chamber side and having a vertically downward opening for supplying an inert gas along the inner peripheral surface of the rectifying cylinder to the main chamber, an inert gas supply device for introducing an inert gas into the first gas introduction path and the second gas introduction path, a control unit for controlling the inert gas supply device, wherein the control unit causes the inert gas supply device to introduce an inert gas into the main chamber from the first gas introduction path while the gate valve is open, and causes the inert gas supply device to introduce an inert gas from the second gas introduction path toward the silicon melt contained in the crucible while the gate valve is closed and the pull chamber and the main chamber are separated.

2. further comprising a radiation shield provided in the main chamber for shielding radiant heat from the heater to the growing silicon single crystal, wherein the opening of the second gas introduction path does not overlap the radiation shield in the vertical direction. The single crystal pulling apparatus according to claim 1.

3. further comprising a radiation shield provided in the main chamber for shielding radiant heat from the heater to the growing silicon single crystal, wherein the opening of the second gas introduction path is located near the tip of the radiation shield in the vertical direction. The single crystal pulling apparatus according to claim 1.

4. The single crystal pulling apparatus according to any one of claims 1 to 3, wherein the opening has an annular slit shape.

5. The single crystal pulling apparatus according to any one of claims 1 to 3, wherein the opening is formed by a plurality of holes arranged along an annular shape.

6. A crucible for containing a silicon melt formed by heating with a heater, a main chamber for containing the crucible and the heater, a pull chamber disposed above the main chamber, from which a single crystal of silicon is pulled up and which can be separated from the main chamber by a gate valve, and a rectifying cylinder provided on the main chamber side for rectifying an inert gas supplied to the main chamber. A method for producing a single crystal of silicon by the Czochralski method, comprising: Supplying an inert gas from a first gas introduction path provided on the pull chamber side to the main chamber and growing a single crystal of silicon from the silicon melt; Closing the gate valve to separate the main chamber from the pull chamber, and introducing an inert gas toward the silicon melt contained in the crucible from a second gas introduction path provided on the main chamber side and having a vertically downward opening for supplying the inert gas along the inner peripheral surface of the rectifying cylinder; A method for producing a single crystal of silicon, characterized by comprising the above steps.

7. In the step of closing the gate valve to separate the main chamber from the pull chamber and introducing an inert gas toward the silicon melt contained in the crucible from a second gas introduction path provided on the main chamber side and having a vertically downward opening for supplying the inert gas along the inner peripheral surface of the rectifying cylinder, The method for producing a single crystal of silicon according to claim 6, characterized in that the inert gas is supplied from the opening formed in an annular slit shape.

8. In the step of closing the gate valve to separate the main chamber from the pull chamber and introducing an inert gas toward the silicon melt contained in the crucible from a second gas introduction path provided on the main chamber side and having a vertically downward opening for supplying the inert gas along the inner peripheral surface of the rectifying cylinder, The method for producing a single crystal of silicon according to claim 6, characterized in that the inert gas is supplied from the opening formed as a plurality of holes arranged along an annular shape.

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