JP7280160B2 - Silica glass crucible - Google Patents

Description

TECHNICAL FIELD The present invention relates to a vitreous silica crucible for pulling a silicon single crystal by the Czochralski method (hereinafter referred to as "CZ method").

The CZ method is widely used for growing silicon single crystals. In this method, a seed crystal is brought into contact with the surface of a silicon melt contained in a silica glass crucible, the crucible is rotated, and the seed crystal is pulled upward while rotating in the opposite direction. A single crystal is formed at the lower end of the .

By the way, silica glass crucibles are getting larger year by year. By increasing the size of the silica glass crucible in this way, it is possible to increase the amount of polycrystalline silicon that is contained in the silica glass crucible and converted into a silicon melt by heating. Elongation has the advantage of improving throughput.
However, on the other hand, it has to be used in a severe environment such as being exposed to higher temperatures than before due to the longer melting time of polycrystalline silicon into a silicon melt and the increased output of a carbon heater for heating. The adverse effect on the glass crucible is also great.
For example, a conventional vitreous silica crucible has a low viscosity value in a high temperature range, and it is difficult to maintain its shape for a long time in a thermal environment of 1400° C. or higher. Therefore, there are problems in the silicon single crystal pulling process, such as fluctuations in the melt surface of molten silicon due to deformation of the silica glass crucible and a decrease in the single crystallization rate (ratio of the weight of the pulled silicon single crystal to the polycrystalline silicon filling weight). was occurring.

In order to solve the above problem, Patent Document 1 proposes a quartz glass crucible with a three-layer structure comprising an Al-added quartz layer as an outer layer, a natural quartz layer as an intermediate layer, and a high-purity synthetic quartz layer as an inner layer. This crucible crystallizes into cristobalite when the outer layer is heated at a constant temperature of 1200° C. or higher in the heating process of the silicon single crystal pulling process. In the growth process of cristobalite, the viscosity is improved and further crystallized, so that high durability can be obtained, and the problems such as deformation and breakage of the crucible can be solved as described above.

In addition, if the outer layer particles to which the crystallization accelerator is added are mixed with the inner surface of the crucible, it will affect the durability of the crucible and the single crystallization rate. The present applicant has proposed in Patent Document 2 to suppress the mixing of outer layer particles to which a crystallization accelerator is added into the inner surface of the crucible when adsorbing and desorbing the opening of the crucible.
Specifically, in Patent Document 2, in order to suppress the mixing of the outer layer particles to which the crystallization accelerator is added into the inner surface of the crucible, an outer layer added with a crystallization accelerator is provided in a region of 30 to 50 mm from the upper end of the crucible. Crucibles that do not form have been proposed.

JP-A-2000-247778 JP 2010-275151 A

By the way, in the crucible described in Patent Document 2, since the outer layer containing the crystallization accelerator is not formed in the region of 30 to 50 mm from the upper end of the crucible, the outer layer particles containing the crystallization accelerator are not formed. Mixing into the inner surface of the crucible was suppressed, and the durability and the single crystallization rate were improved.
If the upper end region of the crucible deforms (falls down) inwardly during the process of pulling the silicon single crystal, the flow of gas in the pulling apparatus is obstructed, and the pulled silicon single crystal cannot obtain the necessary crystal properties. Moreover, if the upper end region of the crucible is extremely deformed, the upper end region of the crucible may come into contact with the ingot (silicon single crystal) and the pulling of the upper end region of the crucible may not be continued.

In addition, in the crucible described in Patent Document 1, since a layer containing a crystallization accelerator is formed up to the upper end of the opening of the crucible (upper end of the mouth), when crystallized, the upper end of the opening of the crucible Cracks are generated from the outer peripheral side of the crucible, and the expansion of the cracks toward the bottom side of the crucible may cause melt leakage.

In order to solve these problems, the present inventors specified a region where no crystallization accelerator is added and does not form an outer layer, thereby suppressing cracks generated from the crucible opening (upper end of the crucible) and The present inventors have made intensive research on how to suppress the inward deformation (falling down) of the upper end region of the frame, and have arrived at the present invention.

The present invention has been made under the circumstances as described above. An object of the present invention is to provide a vitreous silica crucible in which inward deformation (tilting) of the upper end region is suppressed.

In order to solve the above-described problems, a silica glass crucible according to the present invention is a silica glass crucible having a bottom, a bottom corner formed around the bottom, and a side extending upward from the bottom corner, The crucible upper end region is a region of 5 mm or more downward from the crucible upper end and equal to or less than the length obtained by adding 10 mm to the thickness of the upper end, wherein the crucible upper end region comprises an opaque outer layer made of natural raw silica glass and natural raw silica It consists of a two-layer structure formed of a transparent inner layer made of glass or synthetic raw material silica glass, an outer layer made of silica glass added with a crystallization accelerator from the lower end of the crucible upper end region, and an opaque outer layer of the crucible upper end region. It is characterized by having at least a three-layer structure, which is formed by an opaque intermediate layer formed by the above method and the transparent inner layer.

As described above, the outer layer of the crystallization accelerator-added silica glass is not formed in the upper end region of the crucible that is 5 mm or more downward from the upper end of the crucible and equal to or less than the thickness of the upper end plus 10 mm.
Therefore, cracks generated from the crucible opening (upper end of the crucible) can be suppressed, and inward deformation (falling down) of the upper end region of the crucible can be suppressed. Further, it is possible to improve the crucible durability, improve the single crystallization rate, and solve the crystal quality abnormality of the silicon single crystal caused by the inward deformation (collapse) of the upper end region of the crucible.
If the crucible upper end region is less than 5 mm downward from the crucible upper end, cracks are generated from the outer peripheral side near the crucible upper end, which is not preferable. If the crucible top end region exceeds the thickness of the crucible top end plus 10 mm, the crucible top end region will deform (fall down) inward of the crucible, which is not preferable.

The crystallization accelerator added to the outer layer is specifically Al and Ca. The Al concentration in the crystallization accelerator is preferably 9 wtppm or more and 20 wtppm or less, the Ca concentration is preferably 0.1 wtppm or more and 0.6 wtppm or less, and the Al/Ca concentration ratio (Al/Ca) is in the range of 15≦Al/Ca≦200. is desirable.
Here, it is preferable that an opaque outer layer made of natural raw material silica glass is laminated on the outside of the outer layer made of the crystallization accelerator-added silica glass to form a four-layer structure.

Moreover, it is desirable that the thickness of the upper end is 10 mm or more and 18 mm or less. If the thickness of the upper end of the crucible is less than 10 mm, there is a risk of breakage and the durability is poor, which is not preferable. Moreover, if the thickness of the upper end exceeds 18 mm, the weight increases more than necessary, which is not preferable. When the thickness of the top end is 10 mm or more and 18 mm or less, the crucible top end region is 5 mm or more downward from the crucible top end and 20 mm to 28 mm or less from the top end.
In this case, an outer layer containing a crystallization accelerator is formed in a region of 30 to 50 mm from the upper end of the crucible described in Patent Document 2, so when removing the packaging of the crucible opening before use or by adsorption When adsorbing and desorbing the opening of the crucible with a pad, it is necessary to prevent the outer layer particles to which the crystallization accelerator is added from entering the inner surface of the crucible.

According to the present invention, in a silica glass crucible having an outer layer to which a crystallization accelerator is added, cracks generated from the crucible opening (upper end of the crucible) are suppressed, and inward deformation (falling down) of the upper end region of the crucible ) can be obtained.

FIG. 1 is a cross-sectional view of a vitreous silica crucible according to the present invention. FIG. 2 is a partially enlarged cross-sectional view of the silica glass crucible of FIG. FIG. 3 is a partially enlarged cross-sectional view for explaining the thickness dimension of each layer of the silica glass crucible of FIG. FIG. 4 is a sectional view of a silica glass crucible manufacturing apparatus for manufacturing the silica glass crucible of FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of silica glass crucibles according to the present invention will be described based on the drawings. FIG. 1 is a sectional view of a vitreous silica crucible 1 according to the present invention. FIG. 2 is a partially enlarged cross-sectional view of the silica glass crucible of FIG.
This silica glass crucible 1 is used, for example, in a single crystal pulling apparatus (not shown), and is used in a state of being held by a carbon susceptor (not shown) within the apparatus.
That is, in the single crystal pulling apparatus, the polycrystalline silicon accommodated in the silica glass crucible 1 is melted, and the silicon single crystal is pulled from the silicon melt.

The silica glass crucible 1 is formed to have a diameter of 810 mm (32 inches), for example, and as shown in FIG. is done.
That is, the upper end region 10 of the crucible includes an opaque outer layer 5a made of a natural silica glass layer, and a synthetic silica glass (or natural silica glass) adjacent to the inner side of the opaque outer layer 5a and in contact with molten silicon when pulling a silicon single crystal. ) and a transparent inner layer 4 made of
Here, the term "opaque" means that silica glass has a large number of internal pores and appears to be cloudy. In addition, the natural raw material silica glass means silica glass produced by melting natural raw materials such as crystal, and the synthetic raw material silica glass means melting synthetic raw materials synthesized by hydrolysis of silicon alkoxide, for example. means silica glass produced by

Further, below the upper end region 10 of the crucible, the outer layer 2 made of crystallization accelerator-added silica glass is formed up to a predetermined range based on the curvature change point between the side portion 7 and the bottom portion 9 and the bottom corner 8. is provided.
The portion where the outer layer 2 is provided has a three-layer structure composed of an opaque intermediate layer 3 made of natural silica glass continuously formed from the opaque outer layer 5a and the transparent inner layer 4.

Further, the crucible bottom 9 comprises an opaque outer layer 5b made of natural silica glass continuously formed from the opaque intermediate layer 3, and an adjacent transparent inner layer 4 made of synthetic silica glass (or natural silica glass). It has a two-layer structure formed of

More specifically, as shown in the cross-sectional view of FIG. 2, a region from the crucible upper end 6 to a distance h is formed as a crucible upper end region 10 having a two-layer structure. In addition, the length is equal to or less than the thickness T of the upper end plus 10 mm.
Here, the thickness T of the upper end is generally 10 mm or more and 18 mm or less, and the crucible upper end region h is generally 5 mm or more downward from the crucible upper end and 20 mm or more from the upper end. 28 mm or less.

This is because the thermal expansion of cristobalite is much larger than that of quartz glass, so tensile stress acts on the outer peripheral surface, and the crucible upper end region 10 of the two-layer structure is below the crucible upper end 6 by less than 5 mm. In this case, cracks are generated from the outer peripheral side near the upper end of the crucible, which is not preferable.

Further, if the crucible upper end region exceeds the thickness of the crucible upper end plus 10 mm, the crucible upper end region will deform (fall down) inward of the crucible, which is not preferable.
This deformation of the upper end region of the crucible toward the inner side of the crucible is caused by a force that pulls the mouth of the upper end of the crucible inward due to the low viscosity of the transparent inner layer 4, and since the opaque outer layer 5a contains air bubbles, it is transparent. The expansion of the opaque outer layer 5a is greater than that of the inner layer 4, and a force acts to deform the upper end of the crucible inward (the force of collapsing inward acts).

Further, as shown in FIG. 2, the bottom 9 has a curvature (first curvature) with a radius R in the crucible, and the bottom corner 8 has a curvature (second curvature) with a radius r. . Also, the crucible side portion 7 is formed linearly in the vertical direction.
Here, the outer layer 2 is formed downward from the upper end 6 of the crucible, and the lower end of the outer layer 2 defines the curvature change point P between the bottom 9 (curvature radius R) and the bottom corner 8 (curvature radius r). It is formed within a predetermined range as a reference. More specifically, the lower end of the outer layer 2 is rotated ±5° around the center of curvature C, with the straight line L connecting the center of curvature C of the radius R and the curvature change point P set at 0°. It is formed to within the range.

This is because, when the downward direction (bottom direction) is the positive direction, if the lower end of the outer layer 2 is formed in a range of more than +5°, crystallization (cristobalite formation) proceeds rapidly, making it difficult to obtain the desired adhesion. This is because the support of the crucible by the carbon susceptor becomes unstable, and the silicon single crystallization rate tends to decrease.
On the other hand, if the lower end of the outer layer 2 is formed in a range of less than -5°, the ratio of the outer layer 2 to the entire crucible is small, and the heat deformation resistance tends to be low.

Further, as shown in FIG. 3, the outer layer 2 is formed so that both the thickness dimension et1 at the crucible side portion 7 and the thickness dimension et2 at the crucible bottom corner 8 are 0.5 to 5 mm (preferably 1 to 3 mm). be.
This is because if the thickness is more than 5 mm, cracks may occur due to the occurrence of large stress due to the difference in thermal expansion between the crucible wall layers. This is because it tends to be low.

Also, the concentration of the crystallization accelerator in the outer layer 2 is 35-100 ppm (preferably 50-80 ppm). This is because if the concentration of the crystallization accelerator is higher than 100 ppm, crystallization tends to proceed rapidly, and crystallization may be completed before the adhesion between the crucible and the carbon susceptor is stabilized.
On the other hand, if it is lower than 35 ppm, the crystallization speed becomes slow, and it is difficult to obtain the desired heat distortion resistance.

The opaque intermediate layer 3 made of natural silica glass has a thickness mt1 of 3 mm or more at the crucible side portion 7 and a thickness mt2 of 6 mm or more at the crucible bottom corner 8 .
The opaque outer layer 5a of the crucible upper end region 10 has a thickness mt4 of 10 mm or more and 18 mm or less, and the opaque outer layer 5b of the crucible bottom 9 has a thickness mt3 of 6 mm or more.

This is because when the thickness of the opaque intermediate layer 3 in the three-layer portion is less than 3 mm, the effect of preventing the scattering of the crystallization accelerator compound from the opaque intermediate layer 3 due to the irregular flow of the arc flame during melting of the silica glass powder. This is because the crystallization accelerator compound in the outer layer 2 passes through the opaque intermediate layer 3 and mixes into the transparent inner layer 4, increasing the concentration of the crystallization accelerator in the transparent inner layer 4.
The reason why the thickness mt4 of the opaque outer layer 5a in the crucible upper end region 10 is 10 mm or more and 18 mm or less is to suppress heat radiation from the crucible upper end.
If the thickness mt2 of the opaque intermediate layer 3 at the crucible bottom corner 8 and the thickness mt3 of the opaque outer layer 5b at the crucible bottom 9 are less than 6 mm, it is difficult to obtain sufficient heat deformation resistance, which is not preferable.

The transparent inner layer 4 is a transparent layer formed by melting synthetic raw material silica glass (or natural raw material silica glass) having a metal impurity content of Na, K, and Al of 1 ppm or less each and having substantially no air bubbles. be.
In the transparent inner layer 4, the thickness dimension it1 at the crucible upper end region 10 and the crucible side portion 7, the thickness dimension it2 at the crucible bottom corner 8, and the thickness dimension it3 at the crucible bottom portion 9 are all 3 mm or more. formed.
This is because if the thickness of the transparent inner layer 4 is less than 3 mm, the concentration of the crystallization accelerator on the inner surface of the transparent inner layer 4 in contact with the melted silicon is difficult to be sufficiently low, for example, 1 ppm or less.

In the above embodiment, a crucible having a three-layer structure consisting of an outer layer 2 made of silica glass containing a crystallization accelerator, an opaque intermediate layer 3 and a transparent inner layer 4 has been described as an example.
However, the present invention is not limited to this. The crucible may have a four-layer structure in which a second outer layer made of silica glass to which a crystallization accelerator is added is laminated on the outside of the first outer layer made of silica glass.
At this time, the first outer layer is formed up to the upper end 6 of the crucible, and the second outer layer is formed up to a region of 5 mm or more downward from the upper end 6 of the crucible and equal to or less than the thickness of the upper end plus 10 mm.

Next, a method for manufacturing the vitreous silica crucible 1 having the structure described above will be described.
A silica glass crucible 1 is manufactured using a silica glass crucible manufacturing apparatus 30 as shown in FIG. The crucible molding die 11 of the silica glass crucible manufacturing apparatus 30 includes, for example, a die having a plurality of through holes, or an inner member 12 made of a gas permeable member such as a highly purified porous carbon die. , and a holding body 14 for holding the inner member 12 with a ventilation portion 13 provided on the outer periphery thereof.

A rotating shaft 15 connected to rotating means (not shown) is fixed to the lower portion of the holder 14 to rotatably support the crucible molding die 11 . The ventilation part 13 is connected to an exhaust passage 17 provided in the center of the rotating shaft 15 via an opening 16 provided in the lower part of the holder 14 , and the exhaust passage 17 is connected to the decompression mechanism 18 . It is
An arc electrode 19 for arc discharge, a crystallization accelerator-added silica glass supply nozzle 20, a natural raw material silica glass supply nozzle 21, and a synthetic raw material silica glass supply nozzle 22 are provided in the upper part facing the inner member 12. there is

The crystallization accelerator-added silica glass powder used for the outer layer 2 is obtained as follows. For example, when the crystallization accelerator is Al, Al(NO ₃ ) ₃ prepared by dissolving Al nitrate (Al(NO ₃ ) ₃ ) in water in such an amount that the Al concentration of the silica glass powder becomes 35 to 100 ppm. The aqueous solution is added to the natural raw silica glass powder and stirred. The silica glass powder immersed in the Al(NO ₃ ) ₃ aqueous solution is heat-treated at 800 to 1100° C. for dehydration and acid removal.
When Mg, Ca or the like is used as a crystallization accelerator, it can be obtained by similarly adding an aqueous solution of nitrate to natural raw silica glass powder, stirring and heat-treating.
When adding Al and Ca as a crystallization accelerator, the Al concentration in the crystallization accelerator is 9 wtppm or more and 20 wtppm or less, the Ca concentration is 0.1 wtppm or more and 0.6 wtppm or less, and the Al and Ca concentration ratio (Al/Ca). is preferably 15≤Al/Ca≤200.

By adding the above-described crystallization accelerator, the variation in the viscosity of the silica glass powder is reduced, and in the obtained silicon crucible, cracks occurring from the upper end of the crucible are suppressed, and inward deformation (falling down) of the upper end region is suppressed. ).

When the silica glass crucible 1 is manufactured from the Al-added silica glass powder thus obtained using the silica glass crucible manufacturing apparatus 30 described above, a rotation drive source (not shown) is operated to rotate the rotating shaft 18 in the direction of the arrow. , thereby rotating the crucible molding die 11 at high speed.
Next, the Al-added silica glass powder obtained as described above is supplied from the crystallization accelerator-added silica glass supply nozzle 20 into the crucible molding die 11 . The supplied Al-added silica glass powder is pressed against the inner surface side of the inner member 12 by centrifugal force to form the outer layer 2 .
Here, the outer layer 2 is positioned at the top and bottom ends as described with reference to FIG. 2, and excess top and bottom portions are removed.

Next, an opaque intermediate layer 3 and an opaque outer layer 5a each having a thickness of 3 mm or more on the inner surface side of the outer layer 2 made of an Al-added silica glass layer, a thickness of 3 mm or more at the upper end region of the crucible, and a thickness of 6 mm or more at the bottom corners and bottom. , 5b are fed from the natural raw silica glass feed nozzle 21. As shown in FIG.
The supplied natural raw material silica glass powder is pressed against the inner surface side of the outer layer 2 and the inner member 12 by centrifugal force, and formed into a compact of the opaque intermediate layer 3 and the opaque outer layers 5a and 5b.

Next, synthetic raw materials each having a metal impurity content of Na, K, and Al of 1 ppm or less so as to form a transparent layer having a thickness of 3 mm or more on the inner surface side of the opaque intermediate layer 3 and the opaque outer layers 5a and 5b Silica glass powder (or natural raw silica glass powder) is supplied from synthetic raw material silica glass supply nozzle 22 .
The supplied synthetic raw material silica glass powder is pressed against the inner surfaces of the opaque intermediate layer 3 and the opaque outer layers 5a and 5b by centrifugal force, and formed into a compact of the transparent inner layer 4. FIG.

In this manner, a crucible molded body of the outer layer 2, the opaque intermediate layer 3, the opaque outer layers 5a and 5b, and the transparent inner layer 4 having a stepwise decreasing gradient of Al concentration is obtained.
Further, the inside of the inner member 12 is decompressed by the operation of the decompression mechanism 18, and the arc electrode 19 is energized to heat the crucible molded body from the inside, thereby forming the transparent inner layer 4, the opaque intermediate layer 3, and the opaque outer layers 5a and 5b of the crucible molded body. and the outer layer 2 are melted to manufacture the vitreous silica crucible 1 .

As described above, according to the present embodiment, the crucible upper end region 10 of the silica glass crucible 1 is 5 mm or more downward from the upper end of the crucible and equal to or less than the length obtained by adding 10 mm to the thickness of the upper end. The upper end region 10 is formed in a two-layer structure comprising an opaque outer layer 5a made of natural silica glass and a transparent inner layer 4 made of natural silica glass or synthetic silica glass.
Therefore, it is possible to suppress cracks generated from the crucible opening (upper end of the crucible) and to suppress inward deformation (falling down) of the upper end region of the crucible. Further, it is possible to improve the crucible durability, improve the single crystallization rate, and solve the crystal quality abnormality of the silicon single crystal caused by the inward deformation (collapse) of the upper end region of the crucible.

According to this silica glass 1 , in the initial stage of starting the pulling of the silicon single crystal, the bottom portion 9 (opaque outer layer 5 ) in a predetermined range where the outer layer 2 made of silica glass containing a crystallization accelerator does not exist softens, and the crucible 1 is in close contact with the carbon susceptor that supports the After that, from the start to the end of pulling, crystallization (cristobalite formation) of the outer layer 2 such as the bottom corners 8 and the side portions 7 in a predetermined range progresses due to high temperature heating, and the entire crucible 1 and its support. Adhesion stability with the carbon susceptor to be used is improved. In addition, the crystallization improves heat distortion resistance.
Therefore, the crucible 1 can be secured against heat deformation, and the adhesion stability of the support by the carbon susceptor can be obtained, and the single crystallization ratio of the silicon single crystal can be improved.

Next, the silica glass crucible according to the present invention will be further described based on examples. In this example, a silica glass crucible having the structure shown in the above embodiment was used to pull a silicon single crystal, and the crystallization rate (yield) of the obtained silicon single crystal and the silica glass crucible used. The amount of deformation at the upper end of the opening was verified.

(Experiment 1)
In Experiment 1, silica glass crucibles were manufactured using a 32-inch crucible under the conditions of the formation region of the crucible upper end region 10 in the above-described embodiment, and a single crystal was pulled for each of the manufactured silica glass crucibles.
As specific conditions, the upper end region of the crucible, which has a two-layer structure, is arranged downward from the upper end of the crucible to a region of up to 50 mm (Comparative Example 1), a region of up to 45 mm (Comparative Example 2), and a region of up to 40 mm (Comparative Example 3). ), area up to 35 mm (Comparative Example 4), area up to 30 mm (Comparative Example 5), area up to 25 mm (Example 1), area up to 20 mm (Example 2), area up to 15 mm (Example 3 ), a region up to 10 mm (Example 4), a region up to 5 mm (Example 5), and a region up to 0 mm (Comparative Example 6).

The thickness dimension of each layer of the silica glass crucible used at this time is as follows.
Referring to FIG. 3, the thickness it1 of the transparent inner layer 4 is 3 mm, the thickness it2 is 7 mm, and the thickness it3 is 3 mm.
Further, the thickness dimension mt4 of the opaque outer layer 5a is 12 mm, the thickness dimension mt2 is 17 mm, and the thickness dimension mt3 is 12 mm. Moreover, the thickness dimension et1 and the thickness dimension et2 of the outer layer 2 are 1 mm. The sum T of the thicknesses it1 and mt4 at the upper end of the opening of the crucible is 15 mm.

Referring to FIG. 2, the curvature of the radius R (first curvature) of the bottom portion 9 was 813 mm, and the curvature of the radius r (second curvature) of the bottom corner 8 was 160 mm. In addition, the lower end of the outer layer 2 is within a range obtained by rotating the straight line L connecting the curvature center C of the radius R and the curvature change point P by ±5° around the curvature center C, with the straight line L being 0°. formed.
Furthermore, the concentration of the crystallization accelerator in the outer layer 2 was set at 50 ppm.

The conditions for pulling the silicon single crystal are as follows.
A silicon single crystal is pulled, for example, by putting a raw material polycrystalline silicon block in a quartz glass crucible, holding it in an inert gas atmosphere, for example, an argon gas atmosphere of 10 torr to 200 torr, and raising it from room temperature to the pulling temperature of 1400° C. to 1550° C. , and held at this temperature for 10 hours to melt the polycrystalline silicon mass and form a silicon melt. A seed crystal (silicon single crystal) was immersed in this silicon melt (necking step), and the seed crystal was gradually pulled up while rotating the crucible to grow a silicon single crystal with the seed crystal as a nucleus.

Regarding Experiment 1, Table 1 shows the conditions and experimental results for each example and comparative example.
In Table 1, the amount of deformation indicates the amount of inward tilting of the upper end of the crucible. Yield indicates the single crystallization rate. In the remarks, "impossible" indicates that the silicon single crystal cannot be pulled continuously, "acceptable" indicates that the silicon single crystal can continue to be pulled, and "crack" indicates that a crack occurs and the silicon single crystal cannot be continued to be pulled. bottom.

From the results in Table 1, the upper end position of the outermost layer is in the range of 5 mm to 25 mm, that is, the region of 5 mm or more downward from the upper end of the crucible and the length (25 mm) or less obtained by adding 10 mm to the thickness of the upper end of 15 mm is the crucible. It was confirmed that cracks generated from the opening (upper end of the crucible) can be suppressed, and inward deformation (falling down) of the upper end region of the crucible can be suppressed.
Further, it is possible to improve the crucible durability, improve the single crystallization rate, and solve the crystal quality abnormality of the silicon single crystal caused by the inward deformation (collapse) of the upper end region of the crucible.

(Experiment 2)
Silica glass crucibles were produced using a 22-inch crucible in the same manner as in Experiment 1, and single crystal pulling was performed on each of the produced silica glass crucibles.
As specific conditions, the upper end region of the crucible, which has a two-layer structure, is a region of up to 50 mm (Comparative Example 7), a region of up to 45 mm (Comparative Example 8), and a region of up to 40 mm (Comparative Example 9) from the upper end of the crucible. ), area up to 35 mm (Comparative Example 10), area up to 30 mm (Comparative Example 11), area up to 25 mm (Comparative Example 12), area up to 20 mm (Example 6), area up to 15 mm (Example 7 ), a region up to 10 mm (Example 8), a region up to 5 mm (Example 9), and a region up to 0 mm (Comparative Example 13).

The thickness dimension of each layer of the silica glass crucible used at this time is as follows.
Referring to FIG. 3, the thickness it1 of the transparent inner layer 4 is 3 mm, the thickness it2 is 7 mm, and the thickness it3 is 3 mm.
Further, the thickness dimension mt4 of the opaque outer layer 5a is 10 mm, the thickness dimension mt2 is 16 mm, and the thickness dimension mt3 is 9 mm. Moreover, the thickness dimension et1 and the thickness dimension et2 of the outer layer 2 are 1 mm. The sum T of the thicknesses it1 and mt4 at the upper end of the opening of the crucible is 13 mm.

Referring to FIG. 2, the curvature of the radius R (first curvature) of the bottom portion 9 was 813 mm, and the curvature of the radius r (second curvature) of the bottom corner 8 was 160 mm. In addition, the lower end of the outer layer 2 is within a range obtained by rotating the straight line L connecting the curvature center C of the radius R and the curvature change point P by ±5° around the curvature center C, with the straight line L being 0°. formed.
Furthermore, the concentration of the crystallization accelerator in the outer layer 2 was set at 50 ppm.
The conditions for pulling the silicon single crystal were the same conditions as in Experiment 1.

Regarding Experiment 2, Table 2 shows the conditions and experimental results for each example and comparative example.
In Table 2, the amount of deformation indicates the amount of inward tilting of the upper end of the crucible. Yield indicates the single crystallization rate. In addition, in the remarks, "impossible" means that the pulling of the silicon single crystal cannot be continued, "acceptable" means that the pulling of the silicon single crystal can be continued, and "crack" means that the pulling of the silicon single crystal cannot be continued due to cracks. displayed.

From the results in Table 2, the upper end position of the outermost layer is in the range of 5 mm to 20 mm, that is, the region of 5 mm or more downward from the upper end of the crucible and the length (20 mm) or less obtained by adding 10 mm to the thickness of the upper end of 10 mm is the crucible. It was confirmed that cracks generated from the opening (upper end of the crucible) can be suppressed, and inward deformation (falling down) of the upper end region of the crucible can be suppressed.
Further, it is possible to improve the crucible durability, improve the single crystallization rate, and solve the crystal quality abnormality caused by the inward deformation (collapse) of the upper end region of the crucible.

From the experimental results of the above examples, a region of 5 mm or more downward from the upper end of the crucible and less than or equal to the length obtained by adding 10 mm to the thickness of the upper end suppresses cracks generated from the crucible opening (upper end of the crucible). In addition, it was confirmed that the inward deformation (falling down) of the upper end region of the crucible could be suppressed.

(Experiment 3)
In Example 4 in which the upper end region of the crucible having a two-layer structure was set to 10 mm downward from the upper end of the crucible, the concentration and the concentration ratio of the crystallization accelerator in the outer layer 2 were set to the numerical values shown in Table 3.
The results of Experiment 3 are shown in Table 3.
In Table 3, the amount of deformation indicates the amount of inward tilting of the upper end of the crucible, and the yield indicates the rate of single crystallization. In the remarks, "acceptable" indicates that the pulling of the silicon single crystal can be continued, and "impossible" indicates that the pulling of the silicon single crystal cannot be continued due to cracks.

REFERENCE SIGNS LIST 1 silica glass crucible 2 outer layer made of crystallization accelerator-added silica glass 3 opaque intermediate layer 4 transparent inner layer 5a opaque outer layer 5b opaque outer layer 6 crucible upper end 7 side 8 bottom corner 9 bottom 10 crucible upper end region 30 silica glass crucible manufacturing apparatus T Crucible top wall thickness h Length from crucible top

Claims (5)

A silica glass crucible having a bottom, a bottom corner formed around the bottom, and a side extending upward from the bottom corner,
The upper end region of the crucible is 5 mm or more downward from the upper end of the crucible and is equal to or less than the length obtained by adding 10 mm to the thickness of the upper end,
The upper end region of the crucible has a two-layer structure including an opaque outer layer made of natural silica glass and a transparent inner layer made of natural silica glass or synthetic silica glass, and the thickness of the upper end is 10 mm or more and 18 mm or less. can be,
At least three layers formed of an outer layer made of silica glass containing a crystallization accelerator added from the lower end of the crucible upper end region, an opaque intermediate layer continuously formed from the opaque outer layer of the crucible upper end region, and the transparent inner layer. A silica glass crucible characterized by comprising a structure. Al and Ca are added as the crystallization accelerator, the Al concentration in the crystallization accelerator is 9 wtppm or more and 20 wtppm or less, the Ca concentration is 0.1 wtppm or more and 0.6 wtppm or less, and the concentration ratio of Al and Ca 2. The vitreous silica crucible according to claim 1, wherein (Al/Ca) satisfies 15≤Al/Ca≤200. 3. The vitreous silica crucible according to claim 1 or 2, wherein an opaque outer layer made of natural raw material silica glass is further laminated outside the outer layer made of said crystallization accelerator-added silica glass to form a four-layer structure. A silica glass crucible having a bottom, a bottom corner formed around the bottom, and a side extending upward from the bottom corner,
The upper end region of the crucible is 5 mm or more downward from the upper end of the crucible and is equal to or less than the length obtained by adding 10 mm to the thickness of the upper end,
The upper end region of the crucible has a two-layer structure formed of an opaque outer layer made of natural silica glass and a transparent inner layer made of natural silica glass or synthetic silica glass,
At least three layers formed of an outer layer made of silica glass containing a crystallization accelerator added from the lower end of the crucible upper end region, an opaque intermediate layer continuously formed from the opaque outer layer of the crucible upper end region, and the transparent inner layer. consists of a structure
Al and Ca are added as the crystallization accelerator, the Al concentration in the crystallization accelerator is 9 wtppm or more and 20 wtppm or less, the Ca concentration is 0.1 wtppm or more and 0.6 wtppm or less, and the concentration ratio of Al and Ca A silica glass crucible, wherein (Al/Ca) satisfies 15≦Al/Ca≦200. A silica glass crucible having a bottom, a bottom corner formed around the bottom, and a side extending upward from the bottom corner,
The upper end region of the crucible is 5 mm or more downward from the upper end of the crucible and is equal to or less than the length obtained by adding 10 mm to the thickness of the upper end,
The upper end region of the crucible has a two-layer structure formed of an opaque outer layer made of natural silica glass and a transparent inner layer made of natural silica glass or synthetic silica glass,
At least three layers formed of an outer layer made of silica glass containing a crystallization accelerator added from the lower end of the crucible upper end region, an opaque intermediate layer continuously formed from the opaque outer layer of the crucible upper end region, and the transparent inner layer. consists of a structure
A silica glass crucible having a four-layer structure, wherein an opaque outer layer made of natural silica glass is laminated outside the outer layer made of silica glass added with a crystallization accelerator.

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