JP5998976B2 - Cutting position determination method, single crystal ingot cutting method, and cutting position determination system - Google Patents

Description

  The present invention relates to a technique for cutting a single crystal ingot, and more particularly to a cutting position determination method and a determination system for reliably obtaining a dislocation-free single crystal from a partially crystallized single crystal ingot.

For example, when a silicon single crystal is manufactured by the CZ method (Czochralski method), dislocation may occur in the middle due to foreign matters mixed in the crystal or poor control of the pulling operation parameters.
Generally, it is known that when a growing silicon single crystal undergoes dislocation in the middle, the crystal portion after the dislocation is crystallized. Also, slip dislocation extends from the dislocation site to the upper single crystal region that is not dislocated (hereinafter sometimes referred to as slipback), and the extension length is generally the diameter of the silicon single crystal that is pulled up. It is known to reach length.

When dislocations are formed at a relatively early stage of the production process of the single crystal, the grown single crystal is redissolved and the single crystal is grown again. On the other hand, in the case where dislocations are formed in the latter half of single crystal growth, the slip-back portion is cut and removed, and the portion without slip dislocation is used (see, for example, Patent Document 1).
Conventionally, when cutting such a slip-back portion, a skilled worker visually confirms the slip dislocation appearing on the outer peripheral surface of the ingot and determines the cutting position of the ingot. When determining the cutting position of the ingot, considering the difference in slip dislocation length between the crystal center and the crystal periphery, the position of the boundary between the slip dislocation and non-dislocation portions (hereinafter referred to as the dislocation boundary). A position obtained by adding a predetermined length to the position) is defined as a cutting position.

JP 2011-225408 A

However, in recent years, slip dislocations that are difficult to visually observe on the outer peripheral surface of a single crystal ingot to be pulled are increasing due to further increase in the diameter of the single crystal ingot, change in pulling conditions, and the like. Therefore, in the visual confirmation, the dislocation part may be missed, or the dislocation part may be mistakenly determined as the dislocation part, and the position determination is not accurate and the product yield varies greatly. There is. Therefore, when the dislocation part is missed, the number of times of cutting increases and the process time increases.
Furthermore, from the recognition that the slip dislocation length at the outer periphery of the as-grown ingot and the slip dislocation inside the crystal do not coincide with each other due to the difference in the cooling rate, the dislocation boundary position is observed as described above. Since a position obtained by adding a predetermined length to the cutting position is used as a cutting position, there is a problem that the product yield is significantly reduced.

  The present invention has been made to solve such a problem, and can accurately determine the dislocation boundary position on the outer peripheral surface of a single crystal ingot that has undergone dislocation in the middle, and determine an appropriate cutting position. An object of the present invention is to provide a method and system for determining a cutting position and a method for cutting a single crystal ingot, which can improve the product yield and prevent waste of processes.

  In order to achieve the above object, according to the present invention, there is provided a method for determining a cutting position of a dislocated single crystal ingot, wherein the outer peripheral surface of the single crystal ingot is irradiated with laser light, and reflected light is received. There is provided a method for determining a cutting position, comprising the steps of: detecting a slip dislocation length; and determining a cutting position of the single crystal ingot based on the detected slip dislocation length.

  With such a method for determining the cutting position, it is possible to accurately detect the slip dislocation length of the outer peripheral surface and accurately determine the dislocation boundary position. Based on this position, the optimum cutting position can be determined with high accuracy.

At this time, it is preferable to irradiate the laser beam so as to scan a predetermined range of the outer peripheral surface of the ingot using a polygon mirror.
In this way, the slip dislocation length can be detected more accurately.

Further, the single crystal ingot can be an asgron ingot.
In the present invention, even when the single crystal ingot is an as-grown ingot, it is possible to accurately detect the slip dislocation length of the outer peripheral surface and accurately determine the dislocation boundary position.

Further, in the step of detecting the slip dislocation length, image data is created from the intensity of the reflected light, only the slip dislocation line of 45 ° ± 3 ° with respect to the crystal habit line is selected, and the other lines are scratched. It is preferable to detect the slip dislocation length from the image data after performing the filtering process to be excluded.
In this way, the slip dislocation length can be detected more accurately.

  Further, according to the present invention, there is provided a single crystal ingot cutting method for cutting a dislocated single crystal ingot, wherein the cutting position of the single crystal ingot is determined by the above-described cutting position determination method, and the determination is performed. A method for cutting a single crystal ingot is provided, wherein the single crystal ingot is cut at a cutting position.

  With such a single crystal ingot cutting method, an appropriate cutting position can be determined and the product yield can be stably maintained at a high level, and recutting can be prevented and waste of the process can be eliminated.

  Further, according to the present invention, a system for determining a cutting position of a dislocated single crystal ingot, a projector that irradiates a laser beam to the outer peripheral surface of the single crystal ingot, a light receiver that receives reflected light, Length detecting means for detecting a slip dislocation length from the received reflected light, and a cutting position determining means for determining a cutting position of the single crystal ingot based on the detected slip dislocation length. A featured cutting position determination system is provided.

  With such a cutting position determination system, it is possible to accurately detect the slip dislocation length on the outer peripheral surface and accurately determine the dislocation boundary position. Based on this position, a cutting position capable of improving the product yield can be accurately determined.

At this time, it is preferable that the projector emits the laser light so as to scan a predetermined range of the outer peripheral surface of the ingot using a polygon mirror.
With such a configuration, the slip dislocation length can be detected more accurately.

Further, the length detection means creates image data from the intensity of the reflected light, selects only slip dislocation lines at 45 ° ± 3 ° with respect to the crystal habit line, and filters out other lines as scratches It is preferable that the slip dislocation length is detected from the image data after the processing.
With such a configuration, the slip dislocation length can be detected more accurately.

  In the present invention, in determining the cutting position of a single crystal ingot partially dislocated, the outer peripheral surface of the single crystal ingot is irradiated with laser light, the reflected light is received to detect the slip dislocation length, and the detection Since the cutting position of the single crystal ingot is determined based on the length of the slip dislocation, the dislocation boundary position can be accurately determined by accurately detecting the slip dislocation length of the outer peripheral surface. Based on this position, the optimum cutting position can be determined with high accuracy. In particular, if the dislocation boundary position is the cutting position, the product yield can be greatly improved. In addition, since the number of times of recutting can be reduced, it is possible to prevent waste of processes.

It is the schematic which shows an example of the determination system of the cutting position of this invention. It is the schematic which shows an example of the light projector of the determination system of the cutting position of this invention. It is a flowchart from a manufacture of a single crystal ingot to obtaining a dislocation-free ingot by the cutting position determination method and cutting method of the present invention. It is a figure which shows a mode that a laser beam is irradiated and received in the determination method of the cutting position of this invention. It is a figure which shows an example of the detection method of the slip dislocation length by the length detection means of the determination system of the cutting position of this invention.

Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to this.
Conventionally, when manufacturing a wafer by cutting a single crystal ingot, if the single crystal ingot is partially dislocation, a skilled worker visually confirms the slip dislocation that appeared on the outer peripheral surface of the asgron ingot, The dislocation part is removed by cutting. At this time, based on the recognition that the slip dislocation length at the outer periphery of the as-grown ingot and the slip dislocation length inside the crystal were not the same, a predetermined length was added as a correction value to the visually confirmed slip dislocation position. The position is the cutting position.

However, the confirmation of slip dislocation by visual inspection is inaccurate, resulting in large variations in product yield. In addition, if cutting is performed again, the cutting process increases, leading to an increase in cost.
Therefore, the present inventors have made extensive studies to solve such problems. As a result, first, it was found that the length of slip dislocations on the outer peripheral portion of the as-grown ingot and the length of slip dislocations inside the crystal almost coincide. Furthermore, if the length of slip dislocations on the outer periphery is accurately detected based on the intensity of the reflected light of the irradiated laser light, the length of slip dislocations inside the crystal can also be specified accurately, so the cutting position is determined. At this time, the present inventors have found that it is not necessary to add a predetermined length, which has been conventionally performed, and completed the present invention.

First, the cutting position determination system of the present invention will be described.
As shown in FIG. 1, the cutting position determination system 1 of the present invention includes a projector 2, a light receiver 3, an amplifier unit 4, a control unit 5, a length detection means 6, and a cutting position determination means 7.
The projector 2 irradiates the outer peripheral surface 8 of the single crystal ingot with laser light. For example, the projector 2 can be configured using a rotating polygon mirror as shown in FIG.

The projector 2 shown in FIG. 2 includes a laser light source 21, a polygon mirror (rotating polygon mirror) 22, and an fθ lens 23. As the laser light source 21, for example, it can be used red laser with a wavelength of 650 to 690 nm, without being limited thereto, may be a source of blue-violet region having a wavelength of 390 to 430 nm.
The polygon mirror 22 has a polygonal shape with, for example, 4 to 6 mirror surfaces. For example, a single crystal ingot emits laser light emitted from the laser light source 21 while rotating at a high speed of 6,000 to 12,000 rpm. Is reflected on the outer peripheral surface 8 and scans a predetermined range (for example, 300 mm width) of the outer peripheral surface 8.

The fθ lens 23 is a lens designed so that the scanning speed of the laser light is always constant while preventing a scanning position shift that occurs when there is an angular error (surface tilt) such as the mirror surface of the polygon mirror 22 is tilted.
The light receiver 3 receives the reflected light of the laser light emitted from the projector 2, and transmits the received reflected light signal to the amplifier unit 4. Here, the angle between the projector 2 and the light receiver 3 can be set so that the incident angle of the laser beam with respect to the central axis of the single crystal ingot is 45 ° ± 10 ° and the reflection angle is 30 ° to 80 °.

The amplifier unit 4 amplifies the reflected light signal received from the light receiver 3 and transmits it to the control unit 5. The control unit 5 controls the irradiation of the laser light of the projector 2 and transmits the reflected light signal received from the amplifier unit 4 to the length detection means 6.
The length detector 6 receives the reflected light signal transmitted from the control unit 5 and detects the length of the slip dislocation based on the intensity of the reflected light. For example, the length detection means 6 can be configured as a program that operates on a computer and performs image processing on a received reflected light signal.

  The cutting position determination means 7 calculates the dislocation boundary position (the position of the boundary between the slip dislocation portion and the non-dislocation portion) from the slip dislocation length detected by the length detection means 6 and the end position data of the single crystal ingot. Determine the cutting position of the single crystal ingot. At this time, it is preferable to set the cutting position as the determined boundary position because the product yield can be further improved. However, the present invention is not limited to this, and within a permissible range, the cutting position may be determined by adding a predetermined length to the boundary position in view of safety.

Next, the cutting position determination method and single crystal ingot cutting method of the present invention using the above-described cutting position determination system of the present invention will be described with reference to FIG.
As a preparation step, for example, a single crystal is manufactured by the CZ method (FIG. 3A) and taken out from the manufacturing apparatus (FIG. 3B).
The target single crystal ingot 9 using the cutting position determination method of the present invention is one in which slip dislocations 10 are generated during the growth. For example, the outer periphery may be processed by cylindrical grinding or the like, but an as-grown ingot may be used in order to shorten the processing time and reduce the cost.

  First, as shown in FIG. 4, the single crystal ingot 9 is placed on the rotating roller 11. While rotating the rotating roller 11 to rotate the single crystal ingot 9 around its central axis A, the single crystal ingot 9 is composed of a projector 2 composed of, for example, a laser light source, a polygon mirror, and an fθ lens as shown in FIG. The outer peripheral surface 8 is irradiated with laser light, and the reflected light from the outer peripheral surface 8 is received by the light receiver 3 ((c) in FIG. 3). Here, the laser light source used, the wavelength, the incident / reflection angle, and the like can be the same as the conditions described in the cutting position determination system.

  Next, the slip dislocation length is detected by the length detection means 6 based on the intensity of the received reflected light. At this time, for example, as shown in FIG. 5, in order to specify the slip dislocation length, image data is created from the intensity of the reflected light, and only the slip dislocation line of 45 ° ± 3 ° with respect to the crystal habit line is selected. A filtering process for excluding other lines as scratches can be performed on the image data, and the slip dislocation length can be detected from the filtered image data. In the present invention, the slip dislocation length can be accurately detected by such an optical method.

Next, the cutting position of the single crystal ingot 9 is determined by the cutting position determining means 7 based on the slip dislocation length accurately detected as described above. At this time, the position obtained by adding the slip dislocation length to the end position of the single crystal ingot 9 can be determined as the dislocation boundary position.
Since it is known that the slip dislocation length observed on the outer peripheral surface of the single crystal ingot is substantially equal to the slip dislocation length inside the crystal, if the determined boundary position is the cutting position, as described above, Dispersion-free single crystal ingots can be reliably obtained while greatly improving product yield

In the method for cutting a single crystal ingot of the present invention, the single crystal ingot is cut at the cutting position determined by the above-described cutting position determination method of the present invention ((d) in FIG. 3). Then, by removing the dislocation portion (FIG. 3 (e)), a single crystal ingot consisting of only a dislocation-free portion can be obtained reliably (FIG. 3 (f)).
Specifically, the single crystal ingot is horizontally placed on the cutting table, and the single crystal ingot is positioned at the cutting position determined above. Thereafter, the ingot is cut by sending the blade 12 from the upper side to the lower side relative to the single crystal ingot.

Here, examples of the blade that can be used include a general inner peripheral blade and a band saw, and the cutting conditions other than the cutting position can be the same as those in the related art.
In the present invention, since the cutting position of the single crystal ingot is determined based on the slip dislocation length detected with high accuracy as described above, it is possible to suppress the dislocation-free crystals from being included more than necessary in the portion to be cut and removed. Yield can be greatly improved. Moreover, it is possible to reliably prevent the necessity of cutting at the dislocation portion and recutting.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to these.

(Example)
Using the cutting position determination system of the present invention as shown in FIG. 1, the cutting position of a partially dislocated 300 mm diameter azgron silicon single crystal ingot was determined according to the cutting position determination method of the present invention. Thereafter, the ingot was cut at the determined cutting position, and the cone portion was cut to make only the straight body portion, and then the cutting position relative to the slip dislocation position was evaluated. The cutting position was the same as the dislocation boundary position.

  Here, the cutting position was evaluated as follows. First, the dislocation boundary position is divided into two parts in the ingot center axis direction by cutting the ingot after cutting into the ingot center axis direction with reference to the crystal habit line, and then a 2 mm thick sample is cut out in the ingot center axis direction, and the cut sample is selectively etched And the surface was observed to obtain “selective etching no dislocation position”. Thereafter, the obtained position was compared with the cutting position.

  Table 1 shows the evaluation results for six ingots. The cutting position shown in the table indicates the distance from the position of the end portion on the side without slip dislocation (the end portion obtained by cutting the cone portion), that is, the length of the ingot obtained as a non-dislocation portion. As shown in Table 1, in the example, it was found that the difference between the selective etching no dislocation position and the cutting position was small compared to the comparative example described later, and an appropriate cutting position could be determined very accurately. Moreover, it turned out that the yield improvement for 57 mm can be achieved by the average value.

  As described above, according to the present invention, it was confirmed that the dislocation boundary position of the ingot having dislocations can be accurately determined, and the product yield can be improved by determining an appropriate cutting position.

(Comparative example)
The as-grown silicon single crystal ingot was cut in the same manner as in the example except that the dislocation boundary position was visually confirmed by a skilled person and the cutting position was determined, and evaluated in the same manner as in the example.
As a result, the dislocation portion was determined to be a dislocation boundary position, and the number of cuts sometimes increased. Therefore, a position obtained by adding a predetermined length of 85 mm to the determined dislocation boundary position was determined as the cutting position.
The results are shown in Table 1. As shown in Table 1, compared with the example, the difference between the selective etching no dislocation position and the cutting position was large, and the product yield was greatly deteriorated.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

DESCRIPTION OF SYMBOLS 1 ... Cutting position determination system, 2 ... Light projector, 3 ... Light receiver, 4 ... Amplifier unit,
5 ... Control unit, 6 ... Length detection means, 7 ... Cutting position determination means,
8 ... outer peripheral surface, 9 ... single crystal ingot, 10 ... slip dislocation,
11 ... Rotating roller, 12 ... Blade, 21 ... Laser light source,
22 ... Polygon mirror, 23 ... fθ lens.

Claims (8)

A method for determining a cutting position of a dislocated single crystal ingot,
The irradiated with a laser beam to the outer peripheral surface of the single crystal ingot, based on the length of the region where the step of detecting the length of the region where the slip dislocation is present by receiving the reflected light, slip dislocations the detected present A method for determining a cutting position, comprising a step of determining a cutting position of the single crystal ingot.   The method for determining a cutting position according to claim 1, wherein the laser beam is irradiated so as to scan a predetermined range of the outer peripheral surface of the ingot using a polygon mirror.   The method for determining a cutting position according to claim 1 or 2, wherein the single crystal ingot is an asgron ingot. In the step of detecting the length of the region where the slip dislocation exists, image data is created from the intensity of the reflected light, and only the slip dislocation line of 45 ° ± 3 ° with respect to the crystal habit line is selected. The cutting position according to any one of claims 1 to 3, wherein a length of a region where slip dislocation exists is detected from image data after performing filtering processing to exclude lines as scratches. How to determine. A method of cutting a single crystal ingot for cutting a dislocated single crystal ingot,
The cutting position of the single crystal ingot is determined by the cutting position determination method according to any one of claims 1 to 4, and the single crystal ingot is cut at the determined cutting position. A method of cutting a single crystal ingot. A system for determining a cutting position of a dislocated single crystal ingot,
A projector for irradiating a laser beam on the outer peripheral surface of the single crystal ingot; a receiver for receiving reflected light; a length detecting means for detecting the length of a region where slip dislocations exist from the received reflected light; and A cutting position determining system, comprising: a cutting position determining means for determining a cutting position of the single crystal ingot based on a length of a region where the detected slip dislocation exists .   The cutting position determination system according to claim 6, wherein the projector irradiates the laser beam so as to scan a predetermined range of the outer peripheral surface of the ingot using a polygon mirror. The length detection means creates image data from the intensity of the reflected light, selects only a slip dislocation line of 45 ° ± 3 ° with respect to the crystal habit line, and performs a filtering process to exclude other lines as scratches The cutting position determination system according to claim 6 or 7, wherein the length of a region where slip dislocation exists is detected from image data after being performed.

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