JP2008081373A - Silica glass crucible and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica glass crucible which is excellent in deformation resistance and also excellent from the viewpoint of cost, and which provides the sample thereof formed from a synthetic silica raw material in which a layer formed from a natural silica raw material does not coexist and which hence provides exact result of measurement of impurity concentration, and to provide a method for producing the same. <P>SOLUTION: The silica glass crucible is provided with an opening part area 2c having predetermined lengths in the depth direction and the circumferential direction from the upper end of the opening and a side-bottom surface part areas 2a, 2b ranging from the opening part area 2c to the bottom part of the crucible. In the opening part area 2c and the side-bottom surface part area 2a, 2b, the silica glass crucible has a constant thicknesses (t1+t2=t3+t4). In the opening part area 2c, a thickness t3 part having a thickness of at least 2 mm from inner surface is formed from a synthetic silica raw material, and the remaining thickness t4 part is formed from a natural silica raw material. In the side-bottom surface part area 2a, 2b, a thickness t1 part having a thickness of at least 0.5-1.5 mm from the inner surface is formed from the synthetic silica raw material, and the remaining thickness t2 part is formed from the natural silica raw material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a silica glass crucible used for pulling a silicon single crystal and a method for producing a silica glass crucible.

  The Czochralski method (CZ method) is widely used for the growth of silicon single crystals. In this method, the seed crystal is brought into contact with the surface of the silicon melt contained in the crucible, the crucible is rotated, and the seed crystal is pulled upward while rotating in the opposite direction. A single crystal is formed.

Conventionally, a silica glass crucible has been used as a crucible for producing this silicon single crystal. This silica glass crucible has a two-layer structure, and an outer layer is an opaque layer and an inner layer is a transparent layer.
The outer opaque layer contains a large number of bubbles and is formed of a natural silica raw material having a lower purity than that of synthetic silica glass but excellent in heat resistance, and the inner transparent layer is formed of a high-purity synthetic silica raw material. . Since this synthetic silica glass has the advantage that there are few impurities and a DF rate (single crystallization rate) is good, in recent years, the ratio of silica glass crucibles using so-called synthetic silica glass for the inner transparent layer has increased. .

As shown in FIG. 5, in the conventional silica glass crucible 30, the thickness of the inner transparent layer 31 is generally about 0.5 mm to 8 mm, and the thickness of the outer opaque layer 32 is 8 mm. It is formed in about ~ 16mm.
As described above, since the impurity concentrations in the inner and outer layers 31 and 32 are different from each other, if the thickness of the inner transparent layer 31 is increased so as to obtain a high-purity crucible, a difference in viscosity occurs between the inner and outer layers 31 and 32. The silica glass crucible 30 may be deformed due to the thermal history when pulling up the crystalline silicon. Moreover, the high-purity synthetic silica raw material is expensive, and the thickness of the inner transparent layer is thin from the viewpoint of cost reduction.
JP 2003-20234 A

By the way, it is necessary to measure and confirm whether the manufactured silica glass crucible 30 is within a desired impurity concentration range, and it is necessary to accumulate the data.
Therefore, in the silica glass crucible 30, the sample A is sampled from the inner layer 31, and the impurity concentration is measured. As shown in FIG. 5, the silica glass crucible 30 is completed by cutting the upper end portion of the silica glass crucible 30 along the cutting line C below the sampling region A.

  However, as described above, in the silica glass crucible 30, if the thickness of the inner transparent layer is thin from the viewpoint of deformation resistance and cost reduction, the sample A is sampled from the inner layer 31 and the impurity concentration is measured. In this case, since the inner layer 31 is thin, sampling may be performed including a part of the outer layer 32, and there is a technical problem that an accurate impurity concentration result cannot be obtained.

  The present invention has been made in order to solve the above technical problems, and is excellent in deformation resistance and cost. Further, a sample collected from a portion formed by a synthetic silica raw material is used as a natural silica raw material. An object of the present invention is to provide a silica glass crucible and a method for producing a silica glass crucible in which the formed portion is not mixed and an accurate impurity concentration result is obtained.

  A silica glass crucible according to the present invention is made to solve the above technical problem. In a bottomed silica glass crucible having an upper end surface of an opening, the depth direction and the circumferential direction from the upper end surface of the opening. An opening region having a predetermined length and a side bottom surface region continuing from the lower end of the opening region to the bottom of the crucible, and the silica glass crucible has a substantially constant thickness in the opening region and the side bottom surface region. In the opening region, at least 2 mm thick portion from the inner surface is formed of a synthetic silica raw material and the remaining thickness portion is formed of a natural silica raw material, and in the side bottom surface region, A thickness portion of at least 0.5 to 1.5 mm from the inner surface is formed of a synthetic silica raw material, and the remaining thickness portion is formed of a natural silica raw material.

Thus, in the opening region, at least 2 mm thick portion is formed from the synthetic silica raw material from the inner surface, and in the side bottom surface region, at least 0.5 to 1.5 mm thick portion from the inner surface is synthetic silica. It is made of raw materials.
That is, the thickness formed of the synthetic silica raw material in the opening region is at least 2 mm, and the dimension is larger than the thickness formed of the synthetic silica raw material in the side bottom surface region.

Here, in the opening region, the synthetic silica raw material formed a thickness portion of at least 2 mm from the inner surface. The minimum thickness of the sample to be sampled is 2 mm, which is the minimum dimension for performing the purity analysis. is there. In addition, the part formed by this synthetic silica raw material is not limited to transparent silica glass, and may contain opaque silica glass.
Since it is constituted in this way, when sampling a sample in the opening region, it is possible to sample without being affected by the natural silica raw material. As a result, an appropriate impurity concentration measurement can be performed.

  On the other hand, in the side bottom surface region, the synthetic silica raw material formed a thickness portion of at least 0.5 mm or more from the inner surface because the transparent silica glass portion formed from the synthetic silica raw material is thin below 0.5 mm. In addition, when the single crystal silicon is pulled, the portion is eroded, and the portion formed by the natural silica raw material is exposed, which is against the request for high purity of the inner surface of the crucible. Moreover, if the erosion occurs in the vicinity of the melt surface in the crucible, it causes a liquid surface vibration, which is not preferable.

  In addition, in the side bottom surface region, the synthetic silica material is used to form a portion having a thickness of at least 1.5 mm or less from the inner surface. The portion formed with the synthetic silica raw material is unnecessarily thicker than the minimum thickness that does not erode to the portion formed with the raw material, which is not preferable in terms of manufacturing cost. Moreover, it is because when the part formed with the said synthetic silica raw material exceeds 1.5 mm, high temperature viscosity will fall and heat-resistant deformation property will be inferior, and it is unpreferable.

Here, the opening region is preferably 10 mm or more and 30 mm or less in the depth direction from the upper end surface of the opening and is formed over the entire circumference.
The reason why the opening region is formed to be 10 mm or more in the depth direction from the upper end surface of the opening is that the minimum vertical dimension of the sample to be sampled is 10 mm, which is the minimum dimension for performing the purity analysis. In addition, the opening region is formed to be 30 mm or less in the depth direction from the upper end surface of the opening. When the opening region is formed to exceed 30 mm, the portion formed of the synthetic silica raw material in the opening region becomes large and the cost increases. At the same time, the high temperature viscosity is lowered and the heat deformation resistance is inferior.
Since the crucible is manufactured while being rotated, the opening region can be manufactured more easily if it is formed over the entire periphery of the upper end of the opening than if it is formed on a part of the upper end of the opening.

The above-mentioned bottomed silica glass crucible having the upper end surface of the opening has a two-layer structure comprising an inner layer made of a substantially bubble-free transparent silica glass and an outer layer made of an opaque silica glass containing many bubbles. The silica glass crucible is preferred.
Here, “substantially bubble-free” means that the bubble number density is 2 / mm ³ or less.

  The method for producing a silica glass crucible according to the present invention is made to solve the above technical problem, and is a bottomed silica glass crucible having an opening upper end surface, from the upper end surface of the opening. An opening region having a predetermined length in the depth direction and the circumferential direction, and a side bottom surface region that extends from the bottom of the opening region to the bottom of the crucible, and has a substantially constant thickness in the opening region and the side bottom surface region. In the method for producing a silica glass crucible having a thickness, a natural silica raw material and a synthetic silica raw material are supplied into a crucible molding die rotated at a high speed, and at least 0.5 to 1.5 mm from the inner surface in the side bottom surface region. And the remaining thickness portion is made of natural silica raw material, and at least 2 mm thick portion from the inner surface in the opening area is made of synthetic silica. Forming a remaining thickness so as to form the raw material of natural silica material, a raw material heating and melted in the crucible mold inside, is characterized by a step of subsequently cooling.

  Here, after the cooling step, the step of collecting a sample from the opening region of the silica glass crucible, and after the step, the upper end portion of the silica glass crucible is cut at a position below the position where the sample was collected. It is desirable to include the process of carrying out.

Thus, the thickness of the portion formed of the synthetic silica raw material in the opening region of the silica glass crucible is thicker than the portion of the side bottom surface region formed of the synthetic silica raw material.
Therefore, in order to collect the sample from the opening area (sampling area) using the opening area as a sampling area, the part formed from the synthetic silica raw material is sampled without being affected by the part formed from the natural silica raw material. can do.
As a result, an appropriate impurity concentration measurement can be performed. In addition, the portion formed of the synthetic silica raw material in the side bottom surface region of the silica glass crucible is formed to a minimum thickness so that the natural silica raw material is not exposed by being eroded when pulling up the single crystal silicon. The amount of raw material used can be reduced, and the manufacturing cost can be reduced.

Further, it is desirable to cut the silica glass crucible while leaving a part of the opening region formed at the upper end portion of the silica glass crucible.
As described above, when a part of the opening region remains, when a silicon single crystal is pulled up using a silica glass crucible, if a problem occurs in the pulled silicon single crystal. A sample can be taken from the remaining opening region, and the impurity concentration and the bubble inclusion state of the transparent layer can be measured.
The substantially constant thickness means within ± 15% of the average thickness of the entire crucible.

  According to the present invention, it is excellent in deformation resistance and cost, and a sample collected from a portion formed from a synthetic silica raw material does not include a portion formed from a natural silica raw material, and an accurate impurity It aims at providing the manufacturing method of the silica glass crucible which can obtain a density | concentration result, and a silica glass crucible.

Next, a first embodiment of the invention according to the present invention will be described based on FIG. 1 and FIG.
As shown in FIG. 1, this silica glass crucible 1 is a two-layered silica glass crucible composed of an inner layer 2 and an outer layer 3, and the inner layer 2 is formed of a transparent layer and the outer layer 3 is formed of an opaque layer. The opaque layer of the outer layer 3 contains a large number of bubbles and is formed of a natural silica raw material that is lower in purity than synthetic silica glass but has excellent heat resistance. The transparent layer of the inner layer 2 is formed of a high-purity synthetic silica raw material. Is done.

  Also, in the side bottom region of the side wall 2a and the bottom wall 2b of the silica glass crucible 1, the thickness t1 of the inner layer 2 is formed thinner than the thickness t2 of the outer layer 3. Specifically, the thickness t1 of the inner transparent layer is generally formed to be about 0.5 mm to 1.5 mm, and is formed thinner than the thickness t14.5 mm to 16.0 mm of the outer opaque layer. ing.

Moreover, the opening part area | region 2c which has a predetermined area | region in the depth direction from the opening upper end surface is formed over the perimeter of the upper end part of the said silica glass crucible 1.
The thickness (t3 + t4) of the inner layer 2 and the outer layer 3 in the opening region and the thickness (t1 + t2) of the inner layer 2 and the outer layer 3 in the side bottom surface region are substantially equal, that is, formed to have a substantially constant thickness. ing. Further, the thickness t3 of the inner layer 2 in the opening region 2c has a thickness of at least 2 mm, and is formed thicker than the thickness t1 of the inner layer 2a in the side bottom region of the side wall 2a and the bottom wall 2b. .
The thickness t3 of the inner layer 2 in the opening region 2c is formed to be larger than the thickness t5 of the sample A1 (the cutting depth t5 (2 mm or less) when sampling). Therefore, when the sample A1 of the inner layer 2 is collected from the region A1 shown in FIG. 1, the outer layer 3 is not mixed and the sample A1 consisting only of the inner layer 2 can be collected.
In general, since the crucible is formed to have a thickness of about 15 mm to 17.5 mm, the thickness t4 of the outer layer 3 of the opening region 2c is formed to a thickness of 15.5 mm or less.

  Further, the opening region 2c is formed in a depth direction from the upper end surface of the opening to a length l of 10 mm or more and 30 mm or less and over the entire circumference. The reason why the opening region 2c is formed to be 10 mm or more in the depth direction from the upper end surface of the opening in this manner is that the minimum vertical dimension of the sample to be sampled is 10 mm, which is the minimum dimension for performing the purity analysis. . Also, the opening region 2c is formed to be 30 mm or less in the depth direction from the upper end surface of the opening. When the opening region 2c is formed to exceed 30 mm, the portion formed of the synthetic silica raw material in the opening region becomes large, and the cost is increased. In addition to being bulky, the high temperature viscosity is lowered, and the heat deformation resistance is inferior. Further, since the crucible is manufactured while being rotated, the opening region 2c can be manufactured more easily if it is formed over the entire periphery of the upper end of the opening than if it is formed on a part of the upper end of the opening.

  In addition, the dimension shape of the sample A1 is generally 10 mm in length, 20 mm in width, and thickness t2 mm. Further, the thicknesses of the inner layer 2 and the outer layer 3 in FIG. 1 are exaggerated for easy understanding.

Next, the manufacturing method of the silica glass crucible concerning this invention is demonstrated.
First, the manufacturing method of the silica glass crucible concerning this invention is implemented using the manufacturing apparatus 10 of the silica glass crucible shown in FIG. The apparatus 10 includes a crucible molding die (rotating body) 11 having a space portion 11a for forming a silica glass crucible and a through hole 11b opening inside and outside the space portion 11a, and a space of the crucible molding die 11. And heating means 14 for melting the raw material M supplied into the portion 11a.
Further, an intake means 12 having an intake pipe 12a for sucking the inside of the crucible molding die 11 from the through hole 11b and a communication pipe 12b communicating with the intake pipe 12a when heated by the heating means 14 (during crucible molding), And cooling means 13 for cooling the crucible molding die 11.

In the production of the silica glass crucible using such an apparatus, first, a natural silica raw material for forming the outer layer 3 and a synthetic silica raw material for forming the inner layer 2 are supplied as the raw material M into the crucible molding die 11 rotated at high speed. .
Next, the inside of the crucible molding die 11 is sucked by the suction means 12, and the layered natural silica raw material and synthetic silica raw material in the crucible molding die 11 are heated and melted by the heating means 14 almost simultaneously with the suction processing. At that time, the crucible molding die 11 is cooled by the cooling means 13. And the silica glass crucible 1 shown in FIG. 1 is formed.

Subsequently, the sample A1 of the opening region 2c at the upper end of the silica glass crucible 1 is collected, and the impurity concentration and the bubble inclusion state of the transparent layer are measured. This measurement result is accumulated and stored as analysis data of each silica glass crucible 1.
At this time, as described above, the thickness t3 of the opening region (sampling region) 2c is formed larger than the thickness t5 of the sample A1 (the cutting depth t5 when sampling), so the sample A1 is collected. In this case, the outer layer is not mixed, the sample A1 consisting only of the inner layer can be collected, and an accurate impurity concentration and bubble-containing state can be measured.

  After that, the opening region 2c is cut below the sampling position of the sample A1. That is, as shown in FIG. 1, the upper end portion of the silica glass crucible 1 is cut along the cutting line L1, and the region from which the sample A1 has been taken is removed to obtain a finished product.

  Further, when a silicon single crystal is pulled using the silica glass crucible 1, if a problem occurs in the pulled silicon single crystal, the sample is removed from the remaining opening region 2c as shown in FIG. A2 is sampled, and the impurity concentration and the bubble inclusion state of the transparent layer are measured. This measurement result is compared with the analysis data of the silica glass crucible 1 described above and used for investigation of the cause.

Next, a second embodiment will be described based on FIG.
In this embodiment, as shown in FIG. 3, the inner layer 2 and the outer layer 3 are characterized in that they are formed with substantially constant thicknesses (t1, t2) in the opening region 2c and the side bottom region, respectively. have. That is, in the side bottom region, the inner layer 2 (formed from the raw material of the synthetic silica glass 21) is formed with a thickness of t1 from the inner surface, and the outer layer 3 (formed of the natural silica raw material 20) with a thickness of t2 outside thereof. Are formed. Further, the inner part of the outer layer 3 in the opening region 20 is formed of the synthetic silica raw material 22, and the outer part of the outer layer 3 is formed of the natural silica raw material 20. In the opening region 20 as well, the inner layer 2 is formed of a raw material of synthetic silica glass 21 with a thickness of t1 from the inner surface.

  As described above, the inner layer 2 and the outer layer 3 are formed of the synthetic silica raw material in the opening region 2c even if the opening region 2c and the side bottom region are formed to have substantially constant thicknesses (t1, t2). The thickness t10 of the portion can be formed thicker than the thickness t1 of the portion formed of the synthetic silica raw material in the side bottom region.

  In order to manufacture this crucible, when forming the outer layer 3 in the opening region, the synthetic silica raw material 22 is supplied after the natural silica raw material 20, and the inner portion of the outer layer 3 in the opening region is formed with the synthetic silica raw material. To do. Then, this crucible can be manufactured by forming the inner layer 2 with a synthetic silica raw material.

  Even in this second embodiment, a thickness (t10) of at least 2 mm from the inner surface in the opening region is formed from the synthetic silica raw material and the remaining thickness (t11) is formed from the natural silica raw material, In addition, a crucible is obtained in which the thickness (t1) of at least 0.5 to 1.5 mm from the inner surface is formed from the synthetic silica raw material and the remaining thickness (t2) is formed from the natural silica raw material in the side bottom surface region. be able to.

Further, a third embodiment will be described with reference to FIG.
Even in this embodiment, as in the second embodiment, as shown in FIG. 4, the inner layer 2 and the outer layer 3 have a substantially constant thickness (t1, t2) in the opening region 2c and the side bottom region, respectively. ) Is characterized in that it is formed.
That is, in the side bottom region, the inner layer 2 (the inner side is formed of the synthetic silica raw material 24 and the outer side is formed of the natural silica raw material 25) is formed with a thickness of t1 from the inner surface, and the outer layer is formed with the thickness of t2 on the outer side. 3 (formed with natural silica raw material 23) is formed.
Further, the outer portion of the inner layer 2 in the opening region 2 c is formed of a natural silica raw material 25, and the inner portion of the inner layer 2 is formed of a synthetic silica raw material 24. In addition, also in the opening part area | region 2c, the outer layer 3 is formed with the thickness of t2 with the natural silica raw material 23. FIG.

  As described above, the inner layer 2 and the outer layer 3 are formed of the synthetic silica raw material in the opening region 2c even though the opening region 2c and the side bottom region are formed to have substantially constant thicknesses (t1, t2), respectively. The thickness t10 of the portion to be formed can be thicker than the thickness t12 of the portion formed of the synthetic silica raw material in the side bottom region.

  In order to manufacture this crucible, an outer layer is formed with a natural silica raw material to a thickness of t2, and subsequently, when forming the inner layer 2, a natural silica raw material 25 is supplied, and the natural silica raw material of the inner layer 3 in the opening region The crucible can be manufactured by forming the portion thinner than the natural silica raw material portion of the inner layer 3 in the side bottom region and then forming the entire inner layer 2 with the synthetic silica raw material at t1. it can.

  Even in this third embodiment, a thickness (t10) of at least 2 mm from the inner surface in the opening region is formed from the synthetic silica raw material and the remaining thickness (t11) is formed from the natural silica raw material, In addition, a crucible in which a thickness (t12) of at least 0.5 to 1.5 mm from the inner surface is formed from the synthetic silica raw material and the remaining thickness (t1 + t2-t12) is formed from the natural silica raw material in the side bottom surface region. Can be obtained.

  Other configurations in the second and third embodiments described above, such as the size of the opening region, are the same as those in the first embodiment, and thus the description thereof is omitted. The effects of the second and third embodiments are also the same as those of the first embodiment, and a description thereof will be omitted.

The product of the present invention shown in FIG. 3 and the conventional product shown in FIG. 5 were manufactured using the silica glass crucible manufacturing apparatus shown in FIG. Here, the opening region of the product of the present invention was 20 mm in the depth direction from the upper end surface of the opening.
In this opening region, transparent silica glass was formed from a synthetic silica raw material with a thickness of 0.5 mm from the inner surface to form an inner layer. Further, an opaque silica glass with a synthetic silica raw material having a thickness of 1.5 mm was formed on the outer side of the inner layer, and an opaque silica glass with a natural silica raw material having a thickness of 14.5 mm on the outer side to form an outer layer. In addition, the side bottom part area | region formed the opaque silica glass with the natural silica raw material with a thickness of 16 mm, and made it the outer layer. Further, a transparent silica glass was formed from a synthetic silica raw material with a thickness of 0.5 mm from the inner surface to form an inner layer.

The conventional product shown in FIG. 5 has an inner layer of 1.5 mm and is formed of a synthetic silica raw material. Moreover, the outer layer was 15 mm and formed from a natural silica raw material.
And the sample of length 10mm, width 20mm, and thickness 2mm was extract | collected from the opening part area | region of this invention product, and the impurity concentration was measured. In the conventional product, a sample having the same shape as the above sample was taken at a position 10 mm deep from the upper end surface of the opening, and the impurity concentration was measured in the same manner.

  As a result, in the product of the present invention, A1 (0.01 ppm), Ti (<0.01 ppm), Ca (<0.01 ppm), and in the conventional product, A1 (1.2 ppm), Ti (0.6 ppm) , Ca (0.1 ppm), and in the conventional product, the impurity concentration was affected by the natural silica raw material and showed a tendency to be higher than the impurity concentration of the synthetic silica raw material. Impurity concentration.

FIG. 1 is a cross-sectional view showing an embodiment of a silica glass crucible according to the present invention. FIG. 2 is a schematic view showing a configuration of a production apparatus for producing a silica glass crucible according to the present invention. FIG. 3 is a cross-sectional view of an essential part showing a second embodiment of the silica glass crucible according to the present invention. FIG. 4 is a cross-sectional view of an essential part showing a third embodiment of the silica glass crucible according to the present invention. FIG. 5 is a cross-sectional view showing a conventional silica glass crucible.

Explanation of symbols

1 Silica glass crucible 2 Inner layer (transparent layer)
2a Side wall 2b Bottom wall 2c Opening area (sampling area)
3 Outer layer (opaque layer)
A1, A2 Sample t1 Inner layer thickness t2 Outer layer thickness t3 Opening region (sampling region) inner layer thickness t4 Opening region (sampling region) outer layer thickness t5 Sample thickness (cutting out sample) depth)
t10 Thickness of the portion formed of the synthetic silica raw material t11 Thickness of the portion formed of the natural silica raw material t12 Thickness of the portion formed of the synthetic silica raw material L1, L2, L3 Cutting line l Depth of the opening region Direction length

Claims (6)

In a bottomed silica glass crucible having an open top surface,
An opening region having a predetermined length in the depth direction and the circumferential direction from the upper end surface of the opening, and a side bottom surface region continuing from the lower end of the opening region to the bottom of the crucible, and the opening region and the side bottom surface portion. In the region, the silica glass crucible has a substantially constant thickness;
In the opening region, a thickness portion of at least 2 mm from the inner surface is formed of a synthetic silica raw material and the remaining thickness portion is formed of a natural silica raw material,
And in the side bottom face region, at least 0.5 to 1.5 mm thick portion from the inner surface is formed of synthetic silica raw material and the remaining thickness portion is formed of natural silica raw material. Silica glass crucible.   2. The silica glass crucible according to claim 1, wherein the opening region is 10 mm or more and 30 mm or less in the depth direction from the upper end surface of the opening, and is formed over the entire circumference.   A bottomed silica glass crucible having an open upper end surface is a two-layer silica glass crucible provided with an inner layer made of a substantially silica-free transparent silica glass and an outer layer made of an opaque silica glass containing many bubbles. The silica glass crucible according to claim 1 or 2, wherein A bottomed silica glass crucible having an opening upper end surface, an opening region having a predetermined length in the depth direction and the circumferential direction from the upper end surface of the opening, and a side continuing from the lower portion of the opening region to the bottom of the crucible In the method for producing a silica glass crucible having a bottom surface region, and having a substantially constant thickness in the opening region and the side bottom surface region,
A natural silica raw material and a synthetic silica raw material are supplied into a crucible molding die rotated at a high speed, and at a side bottom surface region, a thickness portion of at least 0.5 to 1.5 mm from the inner surface is formed from the synthetic silica raw material. And forming the remaining thickness portion with a natural silica raw material, forming a thickness portion of at least 2 mm from the inner surface in the opening region with a synthetic silica raw material, and forming the remaining thickness with a natural silica raw material,
A method for producing a silica glass crucible, comprising a step of heating and melting the raw material in the crucible molding die and then cooling. After the cooling step, collecting a sample from the opening region of the silica glass crucible;
The method for producing a silica glass crucible according to claim 3, further comprising a step of cutting an upper end portion of the silica glass crucible at a position below the position where the sample is collected after the step.   The method for producing a silica glass crucible according to claim 4, wherein the silica glass crucible is cut while leaving a part of an opening region formed at an upper end portion of the silica glass crucible.

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