JP5332019B2 - A sample for quality evaluation of a quartz glass crucible, a method for producing the sample, an evaluation method using the sample, and a device for producing the sample. - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sample for the quality evaluation of a quartz glass crucible, a production method of the sample, an evaluation method of the quality and the like using the sample, and a production apparatus of the sample. <P>SOLUTION: A quartz glass crucible is cut out into a U shape or J shape in the direction containing the center of the crucible to make a primary sample. The primary sample is cut out in the direction perpendicular to the cutting-out direction of the primary sample and in the thickness direction of the primary sample to make a secondary sample. While the inner wall surface and the outer wall surface of the crucible are left, a plurality of grooves are cut between the inner wall surface and the outer wall surface, whereby a sample for the quality evaluation having a plurality of strip-shaped portions thus provided is produced, and is used for the evaluation. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention provides a sample for evaluating the quality and characteristics of a crucible made of high-purity quartz, a method for producing the sample, and a device for producing the sample, and also provides a method for evaluating the quality of the entire crucible. It is what.

 Silicon wafers are indispensable for the electronics technology that supports today's IT society and for the manufacture of semiconductor devices used there. One of the features of this silicon wafer is microdefects such as oxygen precipitates, dislocations, and oxygen stacking faults. While these micro defects have the beneficial effect of capturing heavy metal contamination that occurs in the device process, they can also cause device failure. Therefore, the oxygen concentration in the crystal needs to be adjusted to a predetermined concentration according to the type of device or the device process used. Also, depending on the distribution of air bubbles inside the crucible wall, especially the distribution of impurities on the inner surface, when the single crystal silicon is pulled out of the crucible, the quartz piece on the surface of the crucible peels off, or the inner surface of the quartz glass crucible In some cases, the impurity existing in the silicon melts and diffuses into the silicon, which causes a decrease in the manufacturing yield of single crystal silicon.

Currently, quartz glass crucibles are manufactured mainly by the arc melting method. In this arc melting method, quartz powder as a raw material is supplied to the inner surface of a rotating mold made of carbon from above the mold wall to fill the entire carbon mold wall. Next, a method for producing a quartz glass crucible by forming a quartz powder molded body having a predetermined thickness by centrifugal force due to rotation of the mold, and heating and melting the quartz powder by an arc discharge of an electrode placed on the inner upper side of the mold to vitrify it. (Rotary molding method).
In the above manufacturing method, in order to remove bubbles on the inner wall surface side of the glass layer, there is a method in which the quartz powder is melted while sucking from the mold side under reduced pressure and degassing the quartz powder molded body, and the bubbles are moved to the outer wall surface side. (See Patent Document 1 and Patent Document 2).

 As described above, attempts have been made to produce a quartz glass crucible in which no bubbles are present in the vicinity of the inner surface by moving bubbles to the outer wall surface side. . Therefore, in order to manage the state of the bubbles in stages, that is, to manage the production conditions for the deaeration described above, the bubbles move from the inner wall surface of the crucible toward the thickness direction of the outer wall surface. It is necessary to grasp step by step in the thickness direction at the site.

  Conventionally, in the method of inspecting the distribution state of bubbles, a part of the quartz glass crucible is cut out, and the presence or absence of bubbles is inspected by observing the cross section with the naked eye. However, the quartz glass crucible with a part cut away is not representative of the entire crucible, and the bubble distribution state should be inspected step by step at the bubble movement site of the quartz glass crucible. I couldn't.

  Furthermore, in the destructive inspection as described above, when the quartz glass crucible is cut out, the quartz glass tends to produce fine fragments compared to normal glass, and thick protective gloves are used to handle the sample for inspection. There was a problem that it had to be used and workability was poor.

  On the other hand, various nondestructive inspection methods have been proposed. For example, Patent Document 3 discloses a method of observing and detecting bubbles contained in the vicinity of the inner surface of the crucible by scanning by moving the focal point in the depth direction of the vessel wall using an optical detection means. Has been.

Japanese Patent Laid-Open No. 06-191986 Japanese Patent Laid-Open No. 10-025184 Japanese Patent Publication No. 8-13340 Japanese Patent Laid-Open No. 11-228283

  However, Patent Document 3 described above proposes a method of detecting bubbles using a non-destructive optical method by applying irradiation light to the inner surface of a quartz glass crucible and its depth direction. There is no mention of how to recognize bubbles. That is, after detecting the presence of a bubble by an optical method, the possibility of detecting something other than a bubble as a bubble cannot be denied when determining whether or not the bubble is indeed a bubble.

  Further, Patent Document 4 proposes a nondestructive device equipped with an optical camera. However, since a crucible made of quartz glass is increased in size today, the conventional nondestructive inspection method increases the size of equipment. There is a need. Nevertheless, there remains a problem that the characteristics in the thickness direction from the inner wall surface to the outer wall surface of the crucible cannot be directly confirmed.

  Furthermore, when using the conventional destructive inspection method, as described above, there is a problem in the representativeness of sampling, and it is necessary to use a protective glove and handle a crucible made of quartz glass that is a heavy object exceeding 80 kg. Therefore, it is extremely difficult to cut out a sample for quality evaluation of any part of a quartz glass crucible, especially a sample for quality evaluation from a part where bubbles move to the outer wall surface. there were.

  The present invention has been developed in view of the above situation, and corresponds to a large quartz glass crucible (diameter: 500 mm or more) that has been difficult with the conventional inspection method, and from the inner wall surface of the crucible toward the outer wall surface. A quartz glass crucible quality evaluation sample that can be accurately inspected in the thickness direction is provided together with the sample preparation method and the sample preparation device, and the evaluation sample at a desired position throughout the crucible It is an object of the present invention to provide a quality evaluation method that can easily and appropriately perform sampling.

The inventors have conducted various examinations from the shape of the sample that has conventionally used some notches and verified the shape of the sample, the cutting method, etc., and at the same time, a shape that is easy to handle even with thick protective gloves It was investigated.
As a result, in order to perform the destructive inspection most efficiently, not only the shape of the sample, but also a method for cutting out the sample and an apparatus for its production are found, and the sample is applied to an evaluation method for quality, etc. The invention has been completed.

That is, the gist configuration of the present invention based on the above knowledge is as follows.
(1) A sample for quality evaluation of a quartz glass crucible, wherein a primary sample cut into a U shape or a J shape in a direction including the center of the quartz glass crucible is perpendicular to the cutting direction of the primary sample and the A plurality of strips provided by leaving a plurality of notches between the inner wall surface and the outer wall surface of the quartz glass crucible while leaving the inner wall surface and the outer wall surface of the quartz glass crucible in the secondary sample cut in the thickness direction of the primary sample. A quartz glass crucible quality evaluation sample characterized by having a portion.

  (2) As a sample for quality evaluation of a quartz glass crucible, a primary sample is produced from the quartz glass crucible by cutting it into a U shape or a J shape in a direction including the center, and then perpendicular to the cutting direction of the primary sample. In addition, a secondary sample is prepared by cutting in the thickness direction of the primary sample, and a plurality of cuts are made between the inner wall surface and the outer wall surface while leaving the inner wall surface and the outer wall surface of the quartz glass crucible. A method for producing a sample for quality evaluation of a quartz glass crucible, characterized in that a plurality of strip-shaped portions are formed to obtain a sample for quality evaluation.

  (3) The quality evaluation sample as described in (1) above is cut out from at least three places of the straight body part, corner part and bottom part of the quartz glass crucible, and each strip-like part is inspected for each of these samples. And the quality evaluation method of the crucible made from quartz glass characterized by evaluating the quality of the thickness direction of each site | part of quartz glass.

  (4) The quality evaluation sample preparation apparatus according to (1), wherein a cutting blade fixed to the apparatus body, a holding jig for the quality evaluation sample, and the holding jig are fixed. A means for moving forward and backward with respect to the cutting blade and a means for moving the holding jig laterally, and intermittently cutting the material to be cut through the forward and backward moving means and the lateral movement means of the holding jig. A sample preparation device for quality evaluation of quartz glass crucibles, characterized in that it can be introduced.

  By using the method and apparatus according to the present invention, a quality evaluation sample that safely and easily measures various qualities such as bubble distribution, impurity analysis, OH group measurement, photographs, etc. in the thickness direction of a quartz glass crucible. Can be produced. Further, according to the quality evaluation method according to the present invention, the above-described various qualities can be accurately evaluated over the entire quartz glass crucible at a desired part, a bubble moving part, and the like of the quartz glass crucible.

It is a crucible made from quartz glass and its sectional view. It is a schematic diagram of the primary sample cut out to U type or J type. It is a schematic diagram of a secondary sample according to the present invention and a sample with a plurality of cuts. It is a schematic diagram of the sample preparation apparatus for the quality evaluation of the quartz glass crucible according to the present invention. It is a figure of the holding jig of the sample for quality evaluation according to this invention. It is a figure which shows the preparation procedures of the sample for quality evaluation according to this invention. It is a figure of the sample for quality evaluation according to this invention. It is the photograph of each part using the sample for quality evaluation according to this invention.

Hereinafter, the present invention will be specifically described.
In the present invention, a sample for quality evaluation of a quartz glass crucible is prepared by cutting a U-shaped or J-shaped primary sample in a direction including the center of the quartz glass crucible, and then perpendicular to the cutting direction of the primary sample. A secondary sample cut in the thickness direction of the primary sample was prepared, and the inner wall and the outer wall of the quartz glass crucible were left on the secondary sample, and a plurality of cuts were provided between the inner wall and the outer wall. It is characterized in that it has a plurality of strip-shaped portions.

The above-described quality evaluation sample will be described together with its production method.
First, as the crucible made of quartz glass used in the present invention, any conventionally known crucible used in the CZ method can be used. In particular, it is a large one having a diameter of 500 mm or more, as shown in FIG. Can be suitably used. In the figure, reference numeral 1 is a quartz glass crucible, 2 is an opening edge (rim part) of the quartz glass crucible, 3 is a straight body part, 4 is a corner part, and 5 is a bottom part.

  FIG. 1 shows a crucible made of quartz glass that can be used in the present invention, a cylindrical straight body portion 3 having an edge opened on the upper surface, a corner portion 4 having a relatively large curvature, and a straight line or a relatively small curvature. An example of the bottom portion 5 made of a curve is shown in a cross section including the center portion of the bottom portion 5. In the present invention, the corner portion 4 refers to a portion from a point where the tangent line of the curve overlaps the straight body portion 3 of the crucible to a point having a common tangent line with the bottom portion 5.

  A quartz glass crucible as shown in FIG. 1 is cut into a U shape or a J shape as shown in FIG. In particular, by cutting into a U-shape or J-shape passing through the center of the bottom of the crucible, the above-described straight body portion 3, corner portion 4 and bottom portion 5 can be sampled at a time, and in the same cross-sectional direction while being at an arbitrary position of the crucible. On the other hand, it becomes possible to sample. Moreover, this cutting method can be cut out by using a commercially available cutter, for example, a diamond cutter movable in the XYZ axial directions, with the opening edge of the crucible fixed downward.

Next, as shown in Fig. 3 (a), the cube-shaped secondary sample is further cut out (or referred to as sampling), and finally a plurality of cuts as shown in Fig. 3 (b) are made for quality evaluation. This sample. By further cutting into the shape of such a cubic secondary sample, a sample for quality evaluation having the inner wall surface and the outer wall surface of the same part of the quartz glass crucible can be produced.
In addition, by making strip-like cuts in the secondary sample, a single sample can be used to make a series of changes such as bubbles that occur in the thickness direction from the inner wall surface to the outer wall surface of the crucible. A sample for crucible quality evaluation can be produced.

The number of strip-like portions (or plates) remaining in the plate shape by this cutting can be set to any number depending on the thickness of the quartz glass crucible to be evaluated, the evaluation items, and the like.
In addition, the sampling position of the secondary sample can be cut out from a place where a special layer is provided in the quartz glass crucible. Furthermore, as for the size of the secondary sample, one side is the thickness of the crucible, which is about 10 to 15 mm. The remaining two sides are not particularly limited, but are preferably about 40 mm × 15 mm.

 The above-mentioned special layer means that when a large-sized single crystal silicon (300 mm diameter) is pulled up in recent years, the molten silicon surface is several minutes between where the necking is formed and where the shoulder is formed. The phenomenon of oscillating (vibrating) for about several hours occurs. As a countermeasure, it is provided as a region for preventing molten metal surface vibration.

One example is a special layer made of quartz containing bubbles. The bubble in this case means a bubble that can be detected with the naked eye using light scattering. At this time, the average diameter of the bubbles is about 30 μm, and the existence density is about 40 / cm ² . The thickness of the region is about 2 mm from the inner wall surface, and the width in the height direction is about 40 mm.

  In the present invention, a method for forming a cut in a secondary sample can use a conventionally known quartz glass cutting machine, and in particular, a fixed diamond cutting blade and a quartz glass crucible as a material to be cut. It is important to provide a sample holding jig for quality evaluation, a means for moving the holding jig forward and backward with respect to the cutting blade, and a means for moving laterally for each forward and backward movement.

When forming the incision in the secondary sample, by using the holding jig for the secondary sample according to the present invention, even if wearing protective gloves, it is easy and accurate without impairing workability. A sample for quality evaluation can be produced aiming at a site with foreign matter.
In addition, when a quartz glass crucible is cut by a conventional cutting method, a so-called chattering phenomenon is likely to occur in the vicinity of the inner wall surface and the outer wall surface. It was extremely difficult to cut thinly at the same time. However, when the holding jig for the secondary sample according to the present invention is used, the vicinity of the inner wall surface and the outer wall surface of the quartz glass crucible can be easily and thinly cut simultaneously with one sample.
Further, conventionally, it is possible to directly observe an arbitrary position from the inner wall surface to the outer wall surface of the quartz glass crucible that can only be indirectly observed.

In the present invention, the quality evaluation sample produced as described above can be used as it is when the quality of the quartz glass crucible is evaluated. By doing so, as described above, a series of changes such as bubbles generated in the thickness direction from the inner wall surface of the crucible toward the outer wall surface can be observed step by step with a single sample. Moreover, various inspections can be performed safely and effectively by using a portion that is not in a strip shape and mounting a portion that is not in a strip shape on an inspection device or the like.
In addition, when performing a more precise evaluation, it is also possible to separate the strip-shaped plates one by one and perform the evaluation in plate units.

  In this separation operation, the quality evaluation sample is fixed using the quality evaluation sample holding jig described above, and the movement is restricted by wearing a protective glove, for example, by simply folding a strip-shaped portion. Even an operator who is present can easily and accurately produce an inspection plate having a desired thickness.

  In the present invention, it is desirable to sample a sample for quality evaluation from each part of the straight body part 3, the corner part 4 and the bottom part 5 shown in FIG. 1, but when evaluating the entire crucible, at least one from each part. It is necessary to sample the secondary sample described above. This is because the above-mentioned three places are the places where the properties are most likely to change for the quartz glass crucible, and the tendency of the bubble distribution and the like is different from each other.

  In the present invention, an apparatus as shown in FIG. 4 can be used as an apparatus for producing a sample for quality evaluation of a quartz glass crucible. In the figure, 11 is an entire sample preparation apparatus for quality evaluation of a quartz glass crucible, 12 is a sample holding jig, 13 is a diamond cutting blade, 14 is a means for moving forward and backward, and 15 is a means for moving laterally for each forward and backward movement It is.

The quality evaluation sample preparation apparatus according to the present invention will be described with reference to FIG.
The sample holding jig 12 is desirably made of stainless steel suitable for holding quartz glass. Further, when the secondary sample is fixed to the sample holding jig 12, as shown in FIG. 5, it is desirable to have a function of adjusting the width of the surface in contact with the secondary sample using an adjusting screw. In particular, it is desirable to use a simple adjusting screw such as a one-touch clamp. By having this function, the secondary sample can be fixed to the sample holding jig 12 easily and safely even when wearing thick protective gloves. It should be noted that a sample for quality evaluation according to the present invention can be produced in a safer manner without slipping when rubber or the like is attached to the contact surface with the secondary sample.
What is necessary is just to produce the magnitude | size of the sample holding jig 12 according to the magnitude | size of a secondary sample.

  Any diamond cutting blade 13 can be used as long as it is a conventionally known blade for cutting quartz, but the thickness of the blade is particularly a strip-like shape remaining in a plate shape by cutting the cutting blade. Although it is advantageous to set according to the thickness of the portion, about 0.6 mm is preferable.

As the advancing / retreating means 14, any conventionally known advancing / retreating means can be preferably used.
As the means 15 for lateral movement for each advancement / retraction movement, any conventionally known means for lateral movement for each advancement / retraction movement can be used. Is preferable. Further, when there is a desired position such as a bubble or a defect, a cut can be made so as to leave the place. Depending on the purpose of the evaluation, there is no problem even if the thickness of each plate is changed.

In the present invention, for example, the apparatus 11 shown in FIG. 4 is used, and the secondary sample described above is fixed to the apparatus 11 by the sample holding jig 12 shown in FIG. Cut with the cutter 13.
Here, the thickness of the plate is preferably about 1 mm in view of the accuracy of quality evaluation, and the number of cuts is preferably about 3 to 10 in view of the production efficiency of the sample for quality evaluation.

  As the evaluation items of the quartz glass crucible using the quality evaluation sample according to the present invention, it is preferable to suitably evaluate the evaluation items having changes in the above-described parts (the straight body part 3, the corner part 4 and the bottom part 5). Although there are specific evaluation items such as bubble distribution, impurity analysis, OH group measurement, and cross-sectional photograph, each item will be described below.

Bubble distribution As a method for measuring bubble distribution, any conventionally known technique can be suitably used, and it can be applied to the techniques described in the above-mentioned Patent Documents 1 and 2 by separating individual plates. .
Further, according to the method of the present invention, a series of bubble distribution data with respect to the thickness direction of the same part of the quartz glass crucible corresponding to each sample for quality evaluation can be obtained accurately and stepwise. It can be used not only for management of manufacturing conditions such as vacuum degassing during production and crucible quality control, but also for data collection when developing a new crucible.

Impurity analysis As a measurement method for impurity analysis, any conventionally known technique can be suitably used. Inductively coupled plasma mass spectrometry (ICP-MS), energy dispersive X-ray analysis (SEM-EDX), atomic absorption analysis Law (AAS) etc. can be suitably used.
The measurement elements are Na, K, Li, Fe, Cu, Mg, Ca, Ti and the like. Here, according to the method of the present invention, since data in the thickness direction of the crucible can be acquired, it can be used not only for quality control but also for data collection when developing a new crucible.

  In addition, when colored foreign matter is included in the glass, the part containing the foreign matter is cut out as a secondary sample, and the portion is subjected to impurity analysis step by step, so that the components of the mixed foreign matter can be accurately grasped. It is also useful for estimating the process of mixing.

OH group measurement As a measurement method for OH group measurement, any conventionally known technique can be preferably used, and in particular, infrared spectroscopy can be preferably used.

Cross-sectional photograph In the present invention, since a sample having an arbitrary thickness can be produced, a photograph that allows light to pass through is also possible, and it can also be used for image analysis and the like.

  In the present invention, a strip-shaped cut was made between the inner wall surface and the outer wall surface to produce a sample for quality evaluation, but a sample with a slit perpendicular to the direction of the inner wall surface and the outer wall surface can also be produced. . In this case, one plate can include a variation in the vertical direction between the inner and outer wall surfaces (the direction from the opening side to the bottom side of the quartz glass crucible) in one sample.

  A crucible made of high-purity quartz glass having a diameter of 560 mm was used as a quality evaluation sample provided with a J-shaped primary sample, a rectangular parallelepiped secondary sample, and a strip-shaped cut by the procedure shown in FIG. Note that the quality evaluation sample preparation apparatus shown in FIG. 4 was used in the preparation of the quality evaluation sample in which strip-shaped portions were formed.

FIG. 7 shows a diagram in which a quality evaluation sample according to the present invention is fixed to a sample holding jig 12.
The following tests were conducted using this quality evaluation sample. In the following examples, an example was shown in which a plate was separated from a quality evaluation sample, but even if it was not separated, a series of data such as a series of bubble distributions with respect to the thickness direction of the same part was accurately and stepwise. You can get it.

1. Bubble distribution Table 1 shows the measurement results of the bubble distribution using the sample for quality evaluation according to the present invention.

The sample was made from each of the straight body part, the corner part, and the bottom part. Finally, each plate was sliced horizontally in the thickness direction to a thickness of 1 mm, and then the front and back surfaces were precisely polished with a polishing machine. The number of plates was 4 for the straight body and the bottom, and 6 for the corner.
These polished samples were photographed using an optical microscope, and the ratio of bubbles contained per unit area was calculated from the photographed images using image processing software.

2. Impurity analysis Impurity analysis was performed using the sample for quality evaluation according to the present invention. Table 2 shows the measurement results of the impurity concentration distribution in the depth direction of the straight body portion and the bottom portion. The number of plates was 6 for both the straight body and the bottom.

  In the above impurity measurement, each layer sample is washed with hydrofluoric acid to remove impurities adhering to the glass surface, and then quartz glass is dissolved using hydrofluoric acid, and then an atomic absorption device (AAS) and high-frequency plasma are dissolved. The impurity concentration of each sample was measured using an emission spectroscopic analyzer (ICP).

3. OH group measurement Table 3 shows the measurement results of OH groups using the sample for quality evaluation according to the present invention.
For the measurement, Fourier transform infrared spectroscopy (FT-IR) was used, and the number of plates was 4 on the straight body and bottom, and 6 on the corner.

4). Photo FIG. 8 shows the result of taking a picture of each part using the sample for quality evaluation according to the present invention.

The sample was made from each of the straight body part, the corner part, and the bottom part. Finally, each plate was sliced horizontally in the thickness direction to a thickness of 1 mm, and then the front and back surfaces were precisely polished with a polishing machine. The number of plates was 4 for the straight body and the bottom, and 6 for the corner.
The polished sample was photographed with an optical microscope with a scale.

  As described above, the evaluation items related to the quality of the quartz glass crucible for each of the straight body part, the corner part, and the bottom part, which are important for quality control of the same part of the quartz glass crucible, It can be seen that it can be evaluated.

  The present invention can safely sample an arbitrary part of a quartz glass crucible and can grasp its quality step by step. As a result, it contributes to providing a suitable quartz glass crucible for pulling up a silicon single crystal.

1 Crucible glass crucible 2 Opening edge (rim) of quartz glass crucible
3 Straight body part 4 Corner part 5 Bottom part
11 Sample preparation equipment for quality evaluation of quartz glass crucibles
12 Sample holding jig
13 Diamond cutting blade
14 Means to move forward and backward
Means to move horizontally every 15 forwards and backwards

Claims (4)

  A sample for quality evaluation of a quartz glass crucible, wherein a primary sample cut into a U shape or a J shape in a direction including the center of the quartz glass crucible is perpendicular to the cutting direction of the primary sample and the primary sample In the secondary sample cut in the thickness direction, the inner wall surface and the outer wall surface of the quartz glass crucible are left, and a plurality of strip portions are provided by making a plurality of cuts between the inner wall surface and the outer wall surface. A sample for quality evaluation of a quartz glass crucible characterized by the above.   As a sample for quality evaluation of a quartz glass crucible, a primary sample is produced from the quartz glass crucible by cutting it into a U shape or a J shape in a direction including the center, and then perpendicular to the cutting direction of the primary sample and the A secondary sample is produced by cutting in the thickness direction of the primary sample, and a plurality of incisions are made between the inner wall surface and the outer wall surface by leaving the inner wall surface and the outer wall surface of the quartz glass crucible. A method for producing a sample for quality evaluation of a quartz glass crucible, characterized in that a strip-like portion is formed as a sample for quality evaluation.   The sample for quality evaluation according to claim 1 is cut out from at least three places of a straight body part, a corner part and a bottom part of a crucible made of quartz glass, and each strip-like part is inspected for each of these samples to obtain quartz glass. A method for evaluating the quality of a crucible made of quartz glass, characterized in that a series of quality in the thickness direction of each part is evaluated stepwise.   2. The quality evaluation sample preparation apparatus according to claim 1, wherein the cutting blade fixed to the apparatus body, the holding jig for the quality evaluation sample, and the holding jig are moved forward and backward with respect to the cutting blade. And a means for moving the holding jig laterally, and intermittent cutting can be introduced into the material to be cut through the advancing / retreating movement means and the lateral movement means of the holding jig. A sample preparation device for quality evaluation of quartz glass crucibles.

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