JPH05238875A - Pull apparatus for single crystal - Google Patents

Abstract

PURPOSE:To provide the subject apparatus designed to uniformize the in-plane oxygen concentration distribution for a single crystal rod by controlling, through a convection control means, the direction of a convection developed within a specified range of depth just under the surface of a crystal melt due to the revolution of a quartz crucible. CONSTITUTION:A quartz crucible 5 is put revolvably in a chamber 2 and loaded with polycrystalline silicon followed by heating with a heater 5 to produce a silicon melt 13; concurrently, a convection control jig 15 made of quartz is suspended with four wires 16 and immersed in the melt 13. This jig 15 is virtually cylindrical, the lower end side of the cylindrical part 15A is provided with plural curved plates 15C of guide blade form, and each of the curved plates 15C is specifically tilted relatively to the radial direction of the cylindrical form. Thereby, the direction of a convection developed within a specified range of depth just under the surface of the melt 13 due to the revolution of the crucible 5 can be controlled. Thence, a single crystal rod 14 is pulled from the melt 13 and grown.

Description

Detailed Description of the Invention

[0001]

The present invention relates to, for example, homogenizing the oxygen concentration distribution in the plane of a silicon single crystal rod, or controlling the shape of the solid-liquid interface between the silicon single crystal rod and the silicon melt. The present invention relates to a CZ (Czochralski) method single crystal pulling apparatus capable of homogenizing the in-plane dopant concentration of a crystal rod.

[0002]

2. Description of the Related Art Conventionally, an apparatus for pulling a single crystal by the CZ method, which is suitable for manufacturing a cylindrical silicon single crystal ingot having a large diameter, holds a chamber and a silicon melt rotatably provided in the chamber. A quartz crucible, a heater that surrounds the quartz crucible and heats the silicon melt, and a pulling mechanism that is rotatably provided above the quartz crucible and that pulls up a silicon single crystal rod. And, this single crystal pulling apparatus, a seed crystal of a silicon single crystal is immersed in a silicon melt, and the seed crystal is gradually pulled up while rotating,
A large-diameter silicon single crystal ingot having the same orientation as the seed crystal is grown.

[0003]

However, in the conventional CZ method single crystal pulling apparatus, the rotation speed of the quartz crucible and the rotation speed of the silicon single crystal rod at the time of pulling are changed respectively. However, the homogeneity control of the in-plane oxygen concentration of the silicon single crystal ingot was only performed. As a result, convections of the silicon melts having different molten oxygen concentrations generated in the quartz crucible collide with each other near the solid-liquid interface between the silicon single crystal rod and the silicon melt, and in the silicon melt near the solid-liquid interface. However, there is a problem that the concentration of molten oxygen cannot be controlled. In addition, in this single crystal pulling apparatus, it was not possible to control Marangoni convection that occurs at a shallow position just below the surface of the silicon melt during pulling. Moreover, since the shape of the silicon single crystal rod at the interface between the silicon single crystal rod and the silicon melt cannot be flattened,
There is also a problem that the dopant concentration becomes inhomogeneous in the plane of the silicon single crystal rod.

Therefore, according to the present invention, it is possible to homogenize the oxygen concentration distribution in the plane of the silicon single crystal ingot and the dopant concentration in the plane of the silicon single crystal ingot.
As a result of these, an object is to provide a single crystal pulling apparatus capable of improving the quality of a silicon single crystal ingot.

[0005]

In a single crystal pulling apparatus according to claim 1, a rotatable quartz crucible for holding a crystal melt and a pulling mechanism for pulling a single crystal rod from the crystal melt. And a heater for heating the crystal melt, in a single crystal pulling apparatus, which controls the direction of convection generated in a predetermined depth range immediately below the surface of the crystal melt by rotating the quartz crucible. It is provided with a convection control means.

The invention described in claim 2 is the same as claim 1
In the single crystal pulling apparatus according to, the convection control means, within a predetermined depth range immediately below the surface of the crystal melt, a plurality of guide blade-shaped jigs provided so as to surround the single crystal rod. I have.

[0007]

In the single crystal pulling apparatus according to the present invention, convection is generated in the crystal melt by the rotation of the quartz crucible. The direction of this convection is controlled by a convection control means, for example, a guide blade-shaped jig provided in the crystal melt. For example, the direction of convection of the crystal melt near the interface between the single crystal rod and the crystal melt is changed to the centripetal direction or the centrifugal direction. By making this convection a centrifugal flow, the oxygen concentration in the crystal melt in the vicinity of the interface can be made uniform, and the Marangoni flow can be prevented from occurring. On the other hand, as a result of controlling convection in the centripetal direction, the temperature distribution of the crystal melt can be made uniform near the interface with the single crystal rod, and the shape of the solid-liquid interface of the single crystal rod can be flattened. it can.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a sectional view of a single crystal pulling apparatus according to an embodiment of the present invention.

As shown in this figure, a single crystal pulling apparatus 1
Has a chamber 2. A shaft 3 which is rotated by a motor (not shown) is provided at the center of the chamber 2. At the upper end of the shaft 3, a cylindrical graphite susceptor 4 with a bottom is provided.
Is attached. Inside this graphite susceptor 4,
The quartz crucible 5 is detachably held. The quartz crucible 5 has a substantially hemispherical shape. A silicon melt 13 is melted inside the quartz crucible 5. In this silicon melt 13, a convection control jig 15 made of quartz is suspended by four suspending wires 16 suspended from the upper part of the chamber 2.

As shown in FIG. 1, the convection control jig 15 has a substantially cylindrical shape and has a cylindrical portion 15A having a predetermined diameter on the upper end side. On the lower end side of the cylindrical portion 15A,
A plurality of guide vane-shaped curved plates 15C are formed. Each of these curved plates 15C is formed to have a predetermined inclination with respect to the radial direction of the cylindrical body, and each curved plate 15C is curved with a predetermined curvature. Also,
These curved plates 15C are configured to have a plane including the axis of the cylindrical body, that is, a vertical plane, and the length thereof is set to a predetermined value, for example, a length such that convection can be effectively controlled. Has been done. Further, a predetermined gap is formed between the curved plates 15C so that the inside of the cylindrical body communicates with the outside thereof. Therefore, the convection control jig 15 is inserted into the silicon melt 13 so that the curved plate 15C is located at a predetermined depth from the surface of the silicon melt 13, and the silicon melt 13 in this depth range is inserted. The quartz crucible 5 is divided into a central portion and a peripheral portion. Then, the convection of the silicon melt 13 generated by the relative rotation of the quartz crucible 5 and the silicon single crystal ingot 14 comes into contact with the curved plate 15C of the convection control jig 15, whereby the direction of the convection is controlled. It is something. For example, a convection that normally flows in a circle in a horizontal plane is controlled either by a centripetal flow that flows from the peripheral part toward the central part, or conversely by a centrifugal flow that flows from the central part toward the peripheral part. Is.

The control of the convection of the silicon melt 13 is shown in FIG.
Will be explained. FIG. 2 is an enlarged view of a main part (a part showing an interface between the silicon single crystal ingot 14 and the silicon melt 13) of FIG. As shown in this figure, when the quartz crucible 5 rotates in one direction and the silicon single crystal ingot 14 rotates in the other direction, convection generated in the silicon melt 13 in a predetermined depth range from the surface is: The direction is changed by the curved plate 15C of the convection control jig 15, and as shown by an arrow B in the figure, the silicon melt 1
It flows from the peripheral portion of 3 toward the central portion (the portion directly below the silicon single crystal ingot 14) (centripetal flow). Conversely,
When the quartz crucible 5 rotates in the other direction and the silicon single crystal ingot 14 rotates in the one direction, the convection control jig 15 causes the convection in the silicon melt 13 to flow in the direction opposite to the arrow B (centrifugal flow). Is.

Further, in this single crystal pulling apparatus 1,
As in the conventional case, a heater 6 for heating the silicon melt 13 and a heat shield member 7 are arranged outside the graphite susceptor 4 so as to surround the graphite susceptor 4. Further, a pulling mechanism (not shown) and an inlet 8 are provided on the upper portion of the chamber 2. This inlet 8
Is for introducing argon gas into the chamber 2. By this pulling mechanism, the pulling wire 9 is configured to move up and down above the quartz crucible 5 while rotating in the opposite direction to the quartz crucible 5. A seed crystal 11 of a silicon single crystal is attached to the tip of the pulling wire 9 via a seed chuck 10. An exhaust port 12 for argon gas or the like is provided in the lower portion of the chamber 2. The exhaust port 12 is connected to a vacuum device (not shown).
Then, the seed crystal 11 is immersed in the silicon melt 13 and then raised. As a result, the silicon single crystal ingot 14 that is grown sequentially from the seed crystal 11 as the starting point and has the same crystal orientation as the seed crystal 11 can be pulled in an argon atmosphere.

Next, a method for pulling a silicon single crystal using the single crystal pulling apparatus 1 will be described. Prior to the pulling, high-purity polycrystalline silicon and a small piece of silicon crystal doped with boron at a high concentration are put into a quartz crucible 5 in the graphite susceptor 4. All of these are attached to the shaft 3. The inside of the chamber 2 is evacuated by a vacuum device, an argon gas is supplied to the inlet 8, and the inside of the chamber 2 is 10 to 20 Tor.
The atmosphere of argon is r. The heater 6 is directly energized to heat the quartz crucible 5 and melt the raw material silicon or the like. Then, a seed crystal 11 of silicon single crystal is placed on the seed chuck 10.
The seed crystal 11 is brought into contact with the center of the silicon melt 13. Simultaneously with this contact, the motor rotates the shaft 3 in one direction at a predetermined crucible rotation speed, and the pulling mechanism slowly rotates the seed crystal 11 while rotating in the other direction at a predetermined crystal rotation speed. As a result, the silicon single crystal ingot 14 grows from the seed crystal 11 and is pulled up.

At this time, the convection generated in the silicon melt 13 changes its direction by the curved plate 15C of the convection control jig 15, and at the upper part of the silicon melt 13 (from the surface to a predetermined depth range). It flows from the periphery to the center. As a result, the silicon single crystal rod 1
The temperature just below the interface between 4 and the silicon melt 13 and in the vicinity thereof is made uniform. Therefore, the solid-liquid interface shape between the silicon single crystal ingot 14 and the silicon melt 13 is flattened. And
The diameter of the silicon single crystal ingot 14 is monitored by a diameter control optical sensor (not shown) diagonally above the quartz crucible 5, and the pulling rate of the pulling mechanism is changed (average 1.0 to 1.5 mm / min). So that its diameter is always constant.

Next, the case where the rotation direction of the quartz crucible 5 and the rotation direction of the silicon single crystal ingot 14 are opposite to the above will be described. In this case, a flow (centrifugal flow) in the direction opposite to the convective flow (centripetal flow) of FIG. 2 is generated in the silicon melt 13. More specifically, centrifugal convection occurs just below the interface between the silicon single crystal ingot 14 and the silicon melt 13 and in the vicinity thereof. As a result, it is possible to control the amount of molten oxygen from the quartz crucible 5 in the silicon melt 13 flowing just below the interface between the silicon single crystal ingot 14 and the silicon melt 13, and in the vicinity thereof. 14
It is possible to control the amount of oxygen taken up into. Therefore, the in-plane oxygen concentration distribution of the silicon single crystal ingot 14 is homogenized. In addition, the convection in the centrifugal direction can suppress the generation of Marangoni flow. The convection control jig 15
The same effect can be obtained by reversing the curve of the curved plate 15C having the guide vane shape.

[0016]

As described above, the apparatus for pulling a single crystal according to the present invention can homogenize the oxygen concentration distribution in the plane of a single crystal rod. Further, the temperature in the vicinity of the interface between the single crystal rod and the crystal melt can be made uniform, and the solid-liquid interface shape of the single crystal rod can be flattened. As a result, the quality of the single crystal ingot can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view of a convection control jig of a single crystal pulling apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of an essential part of a single crystal pulling apparatus according to an embodiment of the present invention.

FIG. 3 is a sectional view of a single crystal pulling apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 5 Quartz Crucible 6 Heater 13 Silicon Melt (Crystal Melt) 14 Silicon Single Crystal Rod 15 Convection Control Jig

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Shimanuki 3-8-16 Iwamotocho, Chiyoda-ku, Tokyo Sanritsu Material Silicon Co., Ltd. Address Central Research Laboratory, Mitsubishi Materials Corporation

Claims (2)

[Claims] 1. A single crystal puller comprising a rotatable quartz crucible for holding a crystal melt, a pulling mechanism for pulling a single crystal rod from the crystal melt, and a heater for heating the crystal melt. The upper apparatus comprises a convection control means for controlling the direction of convection generated in a predetermined depth range immediately below the surface of the crystal melt by rotating the quartz crucible. 2. The convection control means comprises a plurality of guide blade-shaped jigs provided so as to surround the single crystal rod within a predetermined depth range immediately below the surface of the crystal melt. The single crystal pulling apparatus according to claim 1.