JP2001261480A - Method for restoring deformation and correcting local erosion of quartz crucible of single crystal pulling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for restoring deformation and correcting local erosion of a quartz crucible used in a single crystal pulling device, by which falling-down of the quartz crucible is restored or the local erosion can be corrected, and therefore factors impairing a single crystal, which are caused by the falling-down or the local erosion, can be eliminated, when the falling- down or the local erosion of the quartz crucible are occurred by heat. SOLUTION: When the deformation of a quartz crucible 10 is restored by utilizing the centrifugal force applied to the quartz crucible 10, the number of revolution of the quartz crucible 10 is controlled while appropriately controlling the amount of heat of a heater. For example, the number of revolution in adjusted so that the centrifugal force is >=92 N/m3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of treating a quartz crucible in a single crystal pulling apparatus, and more particularly to a method of restoring the collapse of a wall of a quartz crucible and correcting local erosion.

[0002]

2. Description of the Related Art In general, in a single crystal manufacturing apparatus using the pulling CZ method, a high pressure-resistant hermetic chamber is decompressed to about 10 torr to flow fresh Ar (argon) gas, and a quartz crucible provided below the chamber is provided. The polycrystal in the melt is heated and melted, the seed crystal is immersed from above in the surface of the melt, and the seed crystal and the quartz crucible are rotated, and the seed crystal is pulled up while moving up and down, so that the upper end is below the seed crystal. It is configured to grow a single crystal (a so-called ingot) composed of a conical upper cone portion protruding, a cylindrical body portion and a conical lower cone portion protruding at a lower end.

[0003]

In the case of pulling a silicon single crystal, in order to heat a polycrystalline silicon raw material in a quartz crucible, the quartz crucible is heated by using a heater arranged around the raw material. Thereby, the polycrystalline raw material is heated indirectly. The melting point of silicon is as high as 1420 ° C., and when the silicon raw material is completely melted, the temperature of the quartz crucible is higher than this melting point. At such a high temperature, the quartz crucible itself is softened and easily deformed due to the weight of the wall surface. This deformation generally occurs in such a manner that the upper edge of the quartz crucible is lowered from its normal position or falls down inside as shown in FIG. The fall of such a quartz crucible,
In the subsequent crystal growth, this may hinder the rise of the crucible or may disturb the gas flow, thereby hindering good single crystal growth.

[0004] If the surface position of the melt remains unchanged for a long time during the melting of the raw material, local melting occurs at the contact point between the quartz crucible and the melt surface. Once local erosion occurs, the following problems occur. That is, the local melting of the quartz crucible affects, and the meniscus at the contact point between the molten raw material and the inner wall of the quartz crucible becomes unstable at that portion. As a result, as shown in FIGS. 5 (a), 5 (b) and 5 (c), a wave is generated on the surface of the melt at this portion, and the seed crystal or the single crystal being formed thereunder is formed by the wave. Risk of wearing. If such a wave is applied, dislocations are likely to occur in a dash neck portion or the like, and when dislocations occur, the growth of a silicon single crystal is hindered, which causes a problem that a high-quality silicon single crystal cannot be pulled. As described above, when the shape of the meniscus is deformed in the process of pulling the single crystal, ripples are generated on the surface of the melt, which causes dislocation due to the seed crystal or the like.

Accordingly, the present invention provides a single crystal capable of correcting such deformation (including local melting) of a quartz crucible and preventing dislocation of the single crystal due to ripples caused by the deformation when such deformation (including local erosion) occurs. An object of the present invention is to provide a method for restoring the deformation of a quartz crucible of a lifting device and a method for correcting local erosion.

[0006]

In order to achieve the above object, in the present invention, the heat quantity of the heater is appropriately adjusted and the deformation is corrected by using the centrifugal force of the quartz crucible.

That is, according to the present invention, a method for recovering deformation of a quartz crucible of a single crystal pulling apparatus for pulling a single crystal from a melt of a polycrystalline raw material in a rotating quartz crucible using a seed crystal while being heated by a heater. And, when the wall surface of the quartz crucible falls down, after the melting process of the polycrystalline raw material is finished, the heat amount of the heater is adjusted so that the surface temperature of the melt becomes equal to or higher than the melting point of silicon. A first step of rotating the quartz crucible at a rotation speed such that a centrifugal force acting on the quartz crucible returns the collapsed portion of the quartz crucible to the original state;
And a method for restoring the deformation of the quartz crucible of the single crystal pulling apparatus.

Further, according to the present invention, local melting of a quartz crucible of a single crystal pulling apparatus for pulling a single crystal from a melt of a polycrystalline raw material in a rotating quartz crucible using a seed crystal while being heated by a heater. In the correction method, when local erosion occurs in the quartz crucible, after the melting process of the polycrystalline raw material is completed, the calorific value of the heater is adjusted so that the surface temperature of the melt becomes equal to or higher than the melting point of silicon. The first step of adjusting and rotating the quartz crucible at a speed higher than the rotation speed at the time of normal pulling, so that the meniscus portion of the melt in the quartz crucible rises by about several mm from that at the time of normal pulling. And a second step of rotating at a high rotational speed as described above.

According to the present invention, there is also provided a single crystal pulling apparatus for pulling a single crystal from a melt of a polycrystalline raw material in a rotating quartz crucible using a seed crystal while being heated by a heater. In the correction method, when local melting of the quartz crucible occurs and ripples occur on the surface of the melt, after the melting process of the polycrystalline raw material is completed, the surface temperature of the melt is changed to the melting point of silicon. As described above, the first step of adjusting the amount of heat of the heater, and the quartz crucible at a higher speed than the normal rotation speed at the time of pulling,
And a second step of rotating the melt at a high rotational speed so as to reduce the number of occurrences of ripples on the surface of the melt.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart showing a control process of a method for restoring a quartz crucible in a single crystal pulling apparatus according to the present invention. FIG. 2 is a schematic sectional view of a quartz crucible showing the effect of the present invention. Now, it is assumed that there is a polycrystalline raw material in the quartz crucible 10, and a heater (not shown) arranged around the quartz crucible 10 is energized to heat the polycrystalline raw material and start melting (step S1). . It is assumed that after heating for a predetermined time, the silicon raw material is completely melted to form a melt 14 (step S2). Note that the control of step S1 and step S2 may actually include monitoring of the temperature and monitoring by a camera, but the melting of the raw material itself is not related to the features of the present invention, and therefore, the control is simplified as described above. Explained.

Next, in step S3, it is determined whether or not the quartz crucible 10 is deformed. This is performed by capturing an image of the edge of the quartz crucible 10 with a monitoring camera (not shown) and performing matching with a predetermined pattern. In addition,
Visual observation or visual observation can be used in combination. If it is determined in step S3 that there is no deformation, step S3
Is repeatedly executed. If deformation (including local erosion) has occurred, temperature control is performed by controlling the amount of heat of the heater in step S4 such that the temperature of the melt surface 18 is equal to or higher than the melting point of silicon. Next, in step S5, the rotational speed of the quartz crucible is increased from the normal time, and speed control is performed to rotate the quartz crucible at a high speed. That is, the quartz crucible 10 is rotated at such a rotational speed as to apply a centrifugal force to the quartz crucible 10 to return the collapsed portion of the quartz crucible 10 to the original state.

Thereafter, in step S6, it is determined whether or not the quartz crucible has been deformed and has returned to the original shape. This can also be performed in the same manner as in step S3 described above. If the deformation has not returned to the original state, the flow returns to step S4, and steps S4 and S5 are executed again. The steps S4 to S6 are repeated until the deformation returns to the original state. When it is determined in step S6 that the deformation has returned to the original state, the control is terminated.

The centrifugal force acting on the quartz crucible 10 is basically determined by the radius and the rotation speed of the quartz crucible 10,
The centrifugal force for returning the collapsed portion of the quartz crucible 10 to the original state is, for example, a case where the diameter of the quartz crucible 10 is 3
At 6 inches, it can be set to 192 N / m ³ or more. In the above embodiment, the rotation speed of the quartz crucible 10 is controlled using the centrifugal force as a parameter, but the present invention is not limited to this, and other parameters may be used.

As an example of control using other parameters, the meniscus portion 16 of the melt 14 in the quartz crucible 10 is used.
Some of them are rotated at a high rotation speed such that it rises by several mm from the time of normal lifting. The magnitude of the meniscus rise is preferably about 5 mm to 8 mm when the diameter of the quartz crucible 10 is 36 inches. That is,
The rise of the meniscus is measured with a camera or visually, and the number of rotations is controlled. Further, as an example of control using still other parameters, there is a method of rotating at a high rotation speed such that the number of times (frequency) of ripples generated on the melt surface 18 is reduced. In each case, the quartz crucible 1
It is common that 0 is rotated at a higher speed than the normal rotation speed. Also in this case, the number of occurrences (frequency) of ripples is measured by a camera or by visual observation to control the number of rotations.

The control shown in FIG. 1 corresponds to step S in FIG.
5. By changing the contents of S6, the control can be basically executed by the same control as the flowchart of FIG. In addition, even in the control using these parameters, until the falling or deformation of the quartz crucible 10 is corrected as in FIG.
Temperature control and speed control are continued. FIG.
In the case of local erosion in which the inner wall of the quartz crucible 10 has a depression as shown in (1), the meniscus rises according to the present invention, and the length of the depression in the vertical direction increases, so that the radius of curvature of the depression increases.
As a result, the meniscus is stabilized. In the present invention, this is referred to as correction of local erosion.

The control of the amount of heat and the rotation speed for heating the quartz crucible 10 according to the present invention is continued during the growth process of the single crystal to correct the deformation of the quartz crucible 10, and is performed during the formation of the cone portion or the body portion. It continues to the process of reaching.

<Comparison between Example and Comparative Example> An example and a comparative example of controlling the amount of heat and the rotation speed for heating the quartz crucible 10 according to the present invention will be described. Now, using a quartz crucible 10 having a diameter of 36 inches and a thickness of 15 mm, the crucible was rotated at 0.2 rpm as a comparative example, and was rotated at 6 rpm for performing control according to FIG. 1 as an example. When the calorific value of the heater was adjusted so that the surface temperature was equal to or higher than the melting point of silicon, the displacement of the wall surface was as follows.

[0018]

[Table 1] Displacement of wall surface in comparative example ... 40 mm Displacement amount of wall surface in embodiment ... 5 mm

At the same time, the number of occurrences (frequency) of ripples on the melt surface was as follows.

[0020]

[Table 2] Ripple occurrence frequency in the comparative example: 30 times / minute Ripple occurrence frequency in the example: 2 times / minute

As described above, the displacement amount of the wall surface of the quartz crucible 10 and the number of occurrences (frequency) of ripples on the melt surface 18 were improved. In this example, the number of occurrences (frequency) of ripples on the melt surface 18 was improved as a result of the control of the number of rotations. However, as described above, the number of occurrences (frequency) of ripples on the melt surface was improved. May be measured, and the rotation speed of the quartz crucible may be controlled so as to obtain the improvement. Similarly, the degree of meniscus rise may be measured, and the rotation speed of the quartz crucible may be controlled so as to improve the meniscus.

[0022]

As described above, according to the present invention, the deformation of the quartz crucible is restored or corrected by controlling the amount of heat and the rotation speed for heating the quartz crucible of the single crystal pulling apparatus. So, the quartz crucible is stopped rising due to the falling of the quartz crucible, or the growth of the single crystal is inhibited by disturbing the flow of argon gas, or the seed crystal etc. The conventional disadvantage of dislocation can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a preferred embodiment of a method for restoring deformation of a quartz crucible in a single crystal pulling apparatus according to the present invention.

FIG. 2 is a schematic diagram showing a state of a melt inside a quartz crucible as a result of control by one example of the embodiment of FIG. 1;

FIG. 3 is a schematic diagram showing a state of a melt inside a quartz crucible in a comparative example.

FIG. 4 is an image showing a state in which a quartz crucible has fallen.

FIG. 5 is a schematic view showing how a meniscus and waves are generated on the surface of a melt inside a quartz crucible.

[Explanation of symbols]

 10 Quartz crucible 14 Melt 16 Meniscus part 18 Surface of melt

Claims (9)

[Claims] 1. A method for recovering deformation of a quartz crucible of a single crystal pulling apparatus for pulling a single crystal from a melt of a polycrystalline raw material in a rotating quartz crucible by using a seed crystal while being heated by a heater, A first step of adjusting the calorific value of the heater so that the surface temperature of the melt becomes equal to or higher than the melting point of silicon, after the melting process of the polycrystalline raw material is completed, when the wall surface of the quartz crucible has fallen; A second step of rotating the quartz crucible at a rotational speed such that a centrifugal force acting on the quartz crucible returns the folded portion of the quartz crucible to the original state. Deformation restoration method. 2. The method according to claim 1, wherein the quartz crucible is rotated at a rotation speed such that the centrifugal force is 192 N / m ³ or more. 3. The single crystal pulling apparatus according to claim 1, wherein the first step and the second step are continued until the falling of the quartz crucible is corrected. Deformation restoration method. 4. The method according to claim 1, wherein the first step and the second step are continued during a process of growing the single crystal and are continued until a process of forming a cone portion or a body portion is performed. 3. The method for restoring the deformation of a quartz crucible of the single crystal pulling apparatus according to item 1. 5. A method for correcting local erosion of a quartz crucible in a single crystal pulling apparatus for pulling a single crystal from a melt of a polycrystalline raw material in a rotating quartz crucible using a seed crystal while being heated by a heater. When local melting of the quartz crucible occurs, after the melting process of the polycrystalline raw material is completed, the calorific value of the heater is adjusted so that the surface temperature of the melt becomes equal to or higher than the melting point of silicon. Step, by rotating the quartz crucible at a higher speed than the number of revolutions at the time of normal pulling, high-speed rotation such that the meniscus portion of the melt in the quartz crucible rises about several mm than at the time of normal pulling. And a second step of rotating the quartz crucible in a single crystal pulling apparatus. 6. A method according to claim 5, wherein said several mm is 5 to 8 mm.
3. The method for correcting local erosion of a quartz crucible in the single crystal pulling apparatus according to item 1. 7. A method for correcting local erosion of a quartz crucible of a single crystal pulling apparatus for pulling a single crystal from a melt of a polycrystalline raw material in a rotating quartz crucible by using a seed crystal while being heated by a heater. When local erosion occurs in the quartz crucible and ripples occur on the surface of the melt, after the melting process of the polycrystalline raw material is completed, the surface temperature of the melt becomes equal to or higher than the melting point of silicon, A first step of adjusting the amount of heat of the heater; rotating the quartz crucible at a speed higher than the speed at the time of normal pulling, and at a high speed such that the number of ripples on the surface of the melt decreases. A method for correcting local erosion of a quartz crucible in a single crystal pulling apparatus. 8. The quartz of the single crystal pulling apparatus according to claim 5, wherein the first step and the second step are continued until the local erosion of the quartz crucible is corrected. Method for correcting local melting of crucibles. 9. The method according to claim 5, wherein the first step and the second step are continued during a single crystal growth process, and are continued until a process of forming a cone portion or a body portion is performed. 3. The method for correcting local erosion of a quartz crucible in the single crystal pulling apparatus according to item 1.