JP7820136B2 - Quartz glass crucible and its manufacturing method - Google Patents

Description

The present invention relates to a quartz glass crucible for pulling silicon single crystals by the Czochralski method, and a method for manufacturing the same.

To grow silicon single crystals using the Czochralski method, a quartz glass crucible placed inside a chamber is filled with polysilicon, which is then heated and melted using a heater installed around the quartz glass crucible to form molten silicon. A seed crystal (seed) attached to a seed chuck is then immersed in the molten silicon, and the seed chuck is pulled up while the seed chuck and quartz glass crucible are rotated in the same or opposite directions.

A quartz glass crucible used for pulling silicon single crystals is a quartz member that contains a silicon melt, and the inner surface of the crucible (inner crucible layer) that comes into contact with the melt must be a highly pure transparent layer. On the other hand, the outer surface of the crucible usually has an opaque outer layer (outer crucible layer) that generally contains many metal elements other than Si for the purposes of reducing costs and improving high-temperature mechanical properties.
Specifically, synthetic quartz powder is placed as a raw material in the inner layer of the crucible to form a transparent layer, and natural quartz powder is placed in two or more layers as a raw material in the outer layer of the crucible to form an opaque layer, and the formed molded body is melted by arc melting to produce a quartz glass crucible.

In the initial stage (before pulling) of the silicon single crystal pulling process, raw material polysilicon is heated to form a silicon melt, and then a stabilization step is carried out in which the quartz glass crucible is rotated to stabilize the flow of the silicon melt.
In this stabilization process, the edge of the silicon melt is in contact with the same location on the inner surface of the crucible for a long period of time. However, the contact area between the edge of the silicon melt and the inner surface of the crucible is exposed to the atmosphere and forms a three-phase interface, which causes etching of the inner layer of the crucible by the silicon melt due to a chemical reaction between the silicon melt and the quartz glass crucible.

In the stabilization step at the beginning of pulling the silicon single crystal, the longer the stabilization time, the greater the amount of etching. Therefore, as shown in Fig. 7, when the thickness of the crucible inner layer 51 (a layer made of synthetic quartz powder as a raw material) is thin, if the surface of the crucible inner layer is etched by the silicon melt M, there is a risk that the etching will reach the crucible outer layer 52 (a layer made of natural quartz powder as a raw material), exposing the crucible outer layer.
To solve this problem, it is necessary to have a crucible inner layer 51 that is thicker than the amount of etching by the silicon melt M, but the synthetic quartz powder that is the raw material for the crucible inner layer 51 is expensive, and there was a problem in that it was not realistic from a cost perspective to make the entire crucible inner layer 51 thick.
Furthermore, if the entire crucible inner layer 51 is formed thick, since it is a synthetic glass layer, it is likely to soften at high temperatures, causing deformation such as sagging downward and causing the crucible opening to collapse, which could interfere with the pulling-up operation.

Patent Document 1 discloses a quartz glass crucible that can solve these problems. The quartz glass crucible disclosed in Patent Document 1 has a transparent inner layer 51 and an opaque outer layer 52, as shown in Figure 8, and a mixed silica layer 53, in which a phase of fused crystalline silica powder and a phase of fused amorphous silica powder are mixed in particulate form, is arranged in an annular shape along the circumferential direction at least on the inner surface layer of the crucible inner layer in the straight body portion.
The mixed silica layer 53 is formed so as to include a position on the inner surface of the quartz glass crucible that is in contact with the initial melt surface M1 when the quartz glass crucible holds the silicon melt M (called the initial melt line), and is formed so that its thickness in the thickness direction is 2 mm or more.

According to this configuration, even if the mixed silica layer 53 becomes thin due to etching in the stabilization step, the silicon melt M can be prevented from reaching the crucible outer layer 52 .
Furthermore, since the mixed silica layer 53 is formed only partially in the crucible axial direction on the crucible inner layer 51 side, rather than over the entire straight body portion, the crucible inner layer 51 can be formed thinly using a synthetic glass layer, and collapse of the opening due to sagging of the crucible inner layer 51 can be prevented.

Japanese Patent Application Laid-Open No. 2014-201501

Incidentally, in the quartz glass crucible disclosed in Patent Document 1, the mixed silica layer 53 is provided to suppress vibration of the silicon melt surface M1 during pulling of a single crystal.
The mixed silica layer 53 is formed by fusing amorphous silica powder and crystalline silica powder, and the etching effects of the respective fused phases are different. Due to the difference in etching effects, minute irregularities are formed on the surface of the mixed silica layer 53. The existence of these minute irregularities suppresses the vibration of the surface of the silicon melt M.

However, in the configuration of the quartz glass crucible disclosed in Patent Document 1, in order to form the mixed silica layer 53, it is necessary to prepare a mixed raw material powder consisting of crystalline silica powder and amorphous silica powder, mold and place this in a recess formed on the inner layer side of the crucible, and melt it, which not only increases costs but also makes the manufacturing process complicated.
In view of the sole objective of preventing the crucible melt from reaching the outer layer of the crucible due to etching of the silicon melt into the inner layer of the crucible in the stabilization step, there is no need to use the mixed raw material powder consisting of the crystalline silica powder and amorphous silica powder in order to suppress vibration of the liquid surface during pulling. In other words, there has been a demand for a method of manufacturing a quartz glass crucible that can achieve this objective at lower cost and with greater ease.

The present invention was made in light of the above circumstances, and aims to provide a quartz glass crucible for pulling silicon single crystals by the Czochralski method, which prevents the outer layer of the crucible from being exposed due to etching of the inner layer of the crucible by silicon melt during the stabilization step before pulling the single crystal, and suppresses collapse due to deformation of the crucible opening, while also suppressing increases in manufacturing costs and making it easy to manufacture, as well as a method for manufacturing the same.

The quartz glass crucible of the present invention, which has been developed to solve the above problems, is a quartz glass crucible for holding a silicon melt and pulling a single crystal. It has an inner layer and at least one outer layer positioned outside the inner layer, and the inner layer on the side of the crucible has a thick inner layer portion formed in an annular shape along the circumferential direction at a position on the inner surface that contacts the molten silicon surface before the single crystal is pulled. The ratio of the thickness of the thick inner layer portion to the thickness of the remaining portion of the inner layer on the side of the crucible is 1:0.14 or greater and less than 1:1.

The inner thick layer portion is preferably formed to have a thickness of 0.7 mm or more and 5.0 mm or less.
Furthermore, it is desirable that the inner layer thick portion be formed with a width dimension of at least ±50 mm in the crucible axial direction, centered on a position on the inner surface of the crucible that contacts the molten surface of the silicon melt before the single crystal is pulled up.
Furthermore, it is desirable that the thick inner layer portion be formed in one of a rectangular cross-section, a trapezoidal cross-section, or a semicircular cross-section, and that an annular recess be formed along the circumferential direction on the inner surface of the side of the outer layer corresponding to the shape of the thick inner layer portion.

With this configuration, even if etching with the silicon melt progresses in the stabilization step, the silicon melt can be prevented from reaching the outer layer.
Furthermore, even if the thick inner layer portion of the inner layer on the side of the crucible is formed thick, other portions can be formed thin. Furthermore, a recess is formed on the inner surface of the outer layer to match the shape of the thick inner layer portion. By providing this recess, the softened inner layer catches on the lower surface (step portion) of the recess, suppressing sagging of the inner layer and preventing collapse and deformation of the crucible opening.

The method for manufacturing a quartz glass crucible according to the present invention, which has been devised to solve the above-mentioned problems, is characterized by comprising the steps of: supplying raw material powder containing natural quartz powder to a mold to form at least one outer layer; forming an annular recess along the circumferential direction on the inner side surface of the outer layer at a position corresponding to the molten surface of the silicon melt before pulling the single crystal; supplying raw material powder containing synthetic quartz powder inside the outer layer, filling the recess with the raw material powder, and forming an inner layer thereon to obtain a crucible molded body; and melting the inner and outer layers of the crucible molded body to form a quartz glass crucible.

With this method, when forming the crucible compact, the thick inner layer portion is part of the crucible inner layer, so the thick inner layer portion can be formed simultaneously by supplying synthetic quartz powder to the inside of the crucible outer layer to form the crucible inner layer. This minimizes increases in manufacturing costs and allows for easy manufacturing.

The present invention provides a quartz glass crucible for pulling silicon single crystals by the Czochralski method, which prevents the outer layer of the crucible from being exposed due to etching of the inner layer of the crucible by silicon melt during the stabilization step before pulling the single crystal, and suppresses collapse due to deformation of the crucible opening. It also provides a quartz glass crucible and a method for manufacturing the same that can be easily manufactured while suppressing increases in manufacturing costs.

FIG. 1 is a cross-sectional view of a quartz glass crucible according to the present invention. FIG. 2 is an enlarged cross-sectional view of a portion of the quartz glass crucible of FIG. FIG. 3 is a partially enlarged cross-sectional view of the quartz glass crucible of FIG. 1, showing the etching state. FIG. 4 is a partially enlarged cross-sectional view of the quartz glass crucible of FIG. 1, illustrating the effect of suppressing sagging of the transparent inner layer. 5(a) and 5(b) are cross-sectional views showing modified examples of the thick inner layer portion. FIG. 6 is a schematic diagram of an apparatus for manufacturing the quartz glass crucible of FIG. FIG. 7 is a partially enlarged cross-sectional view of a conventional quartz glass crucible, showing the state of etching. FIG. 8 is an enlarged cross-sectional view of a portion of another conventional quartz glass crucible.

Hereinafter, embodiments of a quartz glass crucible and a method for manufacturing the same according to the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view of a quartz glass crucible 1 according to the present invention. Fig. 2 is an enlarged cross-sectional view of a part of the quartz glass crucible of Fig. 1.
This quartz glass crucible 1 is used, for example, in a single crystal pulling apparatus (not shown) and is used in a state where it is held by a carbon susceptor (not shown) within the apparatus. That is, in the single crystal pulling apparatus, raw silicon is melted in the quartz glass crucible 1, and a silicon single crystal is pulled up from the melt.

The quartz glass crucible 1 is formed, for example, with a diameter (caliber) of 32 inches and a height of 500 mm, and has a bottom 9 with a predetermined curvature (first curvature), a bottom corner 8 formed around the bottom 9 and having a predetermined curvature (second curvature), and a side 7 extending upward from the bottom corner 8.
As shown in Figure 1, an outer layer 3 made of natural raw material quartz glass is formed on the outside of the side portion 7. Further, inside this outer layer 3, an inner layer 4 made of high-purity synthetic raw material quartz glass is formed, which comes into contact with the silicon melt when pulling up the silicon single crystal.

As shown in Figure 1, at the side portion 7, an inner layer thick portion 4a is formed in an annular shape along the crucible circumferential direction at the top of the inner layer 4, and is thicker than other portions. The position of this inner layer thick portion 4a in the crucible axial direction is set to include a position on the inner surface that contacts the initial melt surface M1 when silicon melt M is held in the crucible (referred to as the initial melt line), as shown in Figure 2.

Here, "opaque" means that numerous air bubbles (pores) are present in the quartz glass, resulting in an apparent cloudy appearance. Furthermore, a natural quartz layer refers to a silica glass layer manufactured by melting natural raw materials such as quartz, while a synthetic quartz layer refers to a silica glass layer manufactured by melting synthetic raw materials, such as those synthesized by the hydrolysis of silicon alkoxide.

As shown in the figure, the crucible bottom corners 8 and the crucible bottom 9 also have a two-layer structure formed by an outer layer 3 made of natural quartz glass that is formed continuously from the outer layer 3 of the side 7, and an inner layer 4 made of synthetic quartz glass (or natural quartz glass).

As shown in Figure 2, the outer layer 3 made of natural raw material silica glass has a thickness mt1 of 6 mm or more at the crucible side 7. However, at a position corresponding to the thick inner layer portion 4a provided in the inner layer 4 of the crucible side 7, the thickness mt2 is 1 mm or more. Furthermore, the thickness mt3 of the outer layer 3 at the crucible bottom corners 8 formed continuously from the outer layer 3 is 6 mm or more, and the thickness mt4 of the outer layer 3 at the crucible bottom 9 is 6 mm or more.
This is because if the thickness mt1 of the outer layer 3 at the crucible side 7, the thickness dimension mt3 of the outer layer 3 at the crucible bottom corner 8, and the thickness dimension mt4 of the outer layer 3 at the crucible bottom 9 are less than 6 mm, it is difficult to obtain sufficient durability.

The inner layer 4 is a transparent layer formed by melting the raw silica glass and substantially free of bubbles. The thickness it1 of the inner layer 4 at the crucible side portion 7 is, for example, 0.6 mm to 2.0 mm, excluding the thick inner layer portion 4a. By setting the thickness it1 at the crucible side portion 7 to 0.6 mm to 2.0 mm in this way, deformation (such as collapse) of the crucible opening and exposure of the outer layer of the crucible can be prevented.
The thickness it2 of the inner thick layer portion 4a is set so that the ratio (it2:it1) of it2 to it1 is 1:0.14 or more and less than 1:1. Specifically, in the case of the crucible size of this embodiment, the thickness it2 is set to 0.7 mm or more and 5.0 mm or less. By setting the thickness it2 of the inner thick layer portion 4a to 0.7 mm or more and 5.0 mm or less in this way, even if etching with the silicon melt progresses in the stabilization step as shown in FIG. 3 , it is possible to prevent the silicon melt from reaching the outer layer 3.

As mentioned above, the ratio of the thickness it2 of the thick inner layer portion 4a to the thickness it1 (it2:it1) is 1:0.14 or greater and less than 1:1. That is, in the inner layer 4 of the crucible side portion 7, the thick inner layer portion 4a is thick and the rest is thin. This is because if the entire crucible side portion 7 were made thick, the inner layer 4, which is a synthetic glass layer, would easily soften at high temperatures, causing it to sag downward and deformation such as collapsing of the opening, which could interfere with the pulling operation.

The height position in the axial direction of the crucible where the inner thick-layer portion 4a is arranged is set to a position on the inner surface of the crucible that comes into contact with the initial melt surface when silicon melt M is held in the crucible (referred to as the initial melt line) as shown in Fig. 2. Specifically, the inner thick-layer portion 4a is formed to have an axial width h of ±50 mm, more preferably ±30 mm, from the initial melt line as the center.
The width h of the thick inner layer portion 4a is specified in this manner because the internal volume of the quartz crucible varies and the melt surface changes depending on the internal volume of the crucible.
In addition, the inner layer 4 has a thickness it3 at the crucible bottom corner 8 and a thickness it4 at the crucible bottom 9 both of which are, for example, 0.6 mm or more.

As shown in the figure, the thick inner layer portion 4a is formed, for example, with a rectangular cross section. This shape helps prevent sinking of the inner layer 4 during high-temperature treatment. That is, the inner layer 4 has a lower viscosity than the outer layer 3. Therefore, at high temperatures, the inner layer 4 is prone to sagging at the crucible side 7, as indicated by the arrows in Figure 4. However, a recess 3a is formed on the inner surface of the outer layer 3 to match the shape of the thick inner layer portion 4a. In this recess 3a, the outer layer 3 and the inner layer 4 are in surface contact not only in the axial direction (vertical direction) but also in the radial direction. Because the recess 3a is formed on the natural outer layer 3 side, even if the softened inner layer 4 attempts to sag downward, the radial surface contact area of the recess 3a suppresses the downward force of the inner layer 4 due to the viscosity of the outer layer 3 (natural layer).

Although the thick inner layer portion 4a has a rectangular cross section, the present invention is not limited to this shape.
For example, as shown in Fig. 5(a), the thick inner layer portion 4a may be formed to have a trapezoidal cross section, or as shown in Fig. 5(b), it may be formed to have a semicircular cross section. In either case, the step portion 3a1 (recess 3a) in the outer layer 3 can suppress sinking of the inner layer 4.
5(a) and 5(b), the step 3a1 in the outer layer 3 is inclined downward in the radial direction, which weakens the grip of the inner layer 4. Therefore, it is desirable to form the step 3a1 in the outer layer 3 in a nearly horizontal state as shown in Fig. 5(c), or to form the step 3a1 in the outer layer 3 so that it is inclined upward in the radial direction as shown in Fig. 5(d).

Next, a method for manufacturing the vitreous silica crucible 1 having the above structure will be described.
The silica glass crucible 1 according to this embodiment is manufactured using, for example, a silica glass crucible manufacturing apparatus 10 as shown in FIG.
The crucible forming mold 11 of the quartz glass crucible manufacturing apparatus 10 is composed of an inner member 12 made of a gas-permeable material, such as a metal mold with multiple through holes or a highly purified porous carbon mold, and a holder 14 that holds the inner member 12 and has a ventilation section 13 on its outer periphery.

A rotating shaft 15 connected to a rotating means (not shown) is fixed to the lower part of the holder 14, and rotatably supports the crucible forming mold 11. The ventilation part 13 is connected to an exhaust path 17 provided in the center of the rotating shaft 15 via an opening 16 provided in the lower part of the holder 14, and this exhaust path 17 is connected to a pressure reducing mechanism 18.
An arc electrode 19 for arc discharge, a natural silica powder supply nozzle 20, and a synthetic silica powder supply nozzle 22 are provided on the upper portion facing the inner member 12.

When manufacturing a quartz glass crucible using the quartz glass crucible manufacturing apparatus 10, a rotary drive source (not shown) is operated to rotate the rotary shaft 18 in the direction of the arrow, thereby rotating the crucible forming mold 11 at high speed.
Next, natural silica powder (raw material powder) is supplied from the natural silica powder supply nozzle 20 into the crucible molding die 11. The supplied natural silica powder is pressed against the inner surface of the inner member 12 by centrifugal force, and is formed as an outer layer 30 having a thickness of 6 mm or more on the sides, bottom corners, and bottom.
Next, on the inner side of the outer layer 30 of the side, at a position corresponding to the thick inner layer portion 4a of the inner layer 4 shown in Figures 1 and 2, a recess 30a having a rectangular cross section and a depth of, for example, 2 mm and a width of 6 mm is processed and formed in a ring shape along the circumferential direction using a jig or the like.

Next, synthetic quartz powder (raw material powder) is supplied from the synthetic quartz powder supply nozzle 23 so that an inner layer 40 having a thickness of, for example, 3 mm is formed on the inner surface of the outer layer 30. Here, the recess 30a formed on the inner side of the outer layer 30 is filled with synthetic quartz powder, and synthetic quartz powder is further supplied on top of that so that an inner layer 40 having a thickness of 3 mm is formed.
The supplied synthetic quartz powder is pressed against the inner surface of the outer layer 30 by centrifugal force and formed into the inner layer 40 (molded body). As a result, the thick inner layer portion 40a (molded body) having a thickness of 5 mm and a width of 6 mm is obtained in the area corresponding to the thick inner layer portion 4a.

In this way, a crucible molded body consisting of two layers, the outer layer 3 and the inner layer 4, is obtained.
Furthermore, the pressure inside the inner member 12 is reduced by operating the pressure reduction mechanism 18, and electricity is passed through the arc electrode 19 to heat the crucible formed body from the inside, melting the inner layer 40 and outer layer 30 of the crucible formed body, thereby producing a quartz glass crucible 1 consisting of the inner layer 4 and outer layer 3.

As described above, according to this embodiment, in the inner layer 4 of the crucible, at a position on the inner surface that contacts the initial melt surface of the silicon melt (initial melt line), an inner layer thick portion 4a having a thickness of 0.7 mm or more and 5.0 mm or less is formed in a ring shape along the circumferential direction, with a width dimension of ±50 mm in the crucible axial direction centered on the initial melt line.
This makes it possible to prevent the silicon melt from reaching the outer layer 3 even if etching with the silicon melt progresses in the stabilization step.
Furthermore, even if the thick inner layer portion 4a of the inner layer 4 on the crucible side portion 7 is formed thick, other portions can be formed thin. Furthermore, a recess 3a is formed on the inner surface of the outer layer 3 to match the shape of the thick inner layer portion 4a, and a step 3a1 is formed on the underside thereof. By providing the recess 3a with this step 3a1, the softened inner layer 4 catches on the step 3a1, suppressing sagging of the inner layer 4 and preventing collapse and deformation of the crucible opening.
Furthermore, in forming the crucible compact, since the thick inner layer portion 4a is a part of the crucible inner layer 4, the compact 40a of the thick inner layer portion 4a can be formed at the same time as the crucible inner layer is formed by supplying synthetic quartz powder to the inside of the crucible outer layer. Therefore, the increase in manufacturing costs can be minimized and manufacturing can be easily performed.

In the above embodiment, the quartz glass crucible 1 has a two-layer structure consisting of outer layers 3 and 5 and an inner layer 4, but the present invention is not limited to this configuration, and the outer layer may be formed of more than two layers.

Next, the quartz glass crucible and the method for manufacturing the same according to the present invention will be further described based on examples.
In this example, a quartz glass crucible having the configuration shown in the above embodiment was manufactured, and a stabilization process was carried out to verify the effects of the present invention.

Example 1
A 32-inch, 500-mm-high quartz glass crucible was manufactured using the quartz glass crucible manufacturing apparatus shown in Figure 6. This quartz glass crucible had a two-layer structure, with an inner layer made of synthetic raw quartz glass and an outer layer made of natural raw quartz glass. The initial melt line in this quartz glass crucible was located 100 mm below the crucible opening, and the width of the thick inner layer in the axial direction of the crucible was ±50 mm from the initial melt line.
In Example 1, the thickness it2 of the thick inner layer portion shown in Figure 2 was 0.7 mm, and the thickness it1 of the other portion of the inner layer on the side of the crucible was 0.6 mm. The thickness mt2 of the outer layer at the position corresponding to the thick inner layer portion was 18.8 mm, and the thickness mt1 of the other portion of the outer layer on the side of the crucible was 16.9 mm.
The stabilization step was carried out at a furnace temperature of 1,420° C., a crucible rotation speed of 15 rpm, and a duration of 10 to 20 hours.
After the stabilization step was completed, the state of etching in the inner layer of the crucible and deformation of the opening of the crucible were observed.

Example 2
In Example 2, the thickness dimension it2 of the thick inner layer portion shown in Figure 2 was 1.7 mm, and the thickness dimension it1 of the other portion of the inner layer on the side of the crucible was 1.5 mm. The thickness dimension mt2 of the outer layer at the position corresponding to the thick inner layer portion was 16.4 mm, and the thickness dimension mt1 of the other portion of the outer layer on the side of the crucible was 16.6 mm. Other implementation conditions were the same as in Example 1.
Example 3
In Example 3, the thickness it2 of the thick inner layer portion shown in Figure 2 was 2.1 mm, and the thickness it1 of the other portion of the inner layer on the side of the crucible was 1.7 mm. The thickness mt2 of the outer layer at the position corresponding to the thick inner layer portion was 16.1 mm, and the thickness mt1 of the other portion of the outer layer on the side of the crucible was 16.5 mm. Other implementation conditions were the same as in Example 1.

Example 4
In Example 4, the thickness it2 of the thick inner layer portion shown in Figure 2 was 3.5 mm, and the thickness it1 of the other portion of the inner layer on the side of the crucible was 2.0 mm. The thickness mt2 of the outer layer at the position corresponding to the thick inner layer portion was 14.9 mm, and the thickness mt1 of the other portion of the outer layer on the side of the crucible was 16.4 mm. The other implementation conditions were the same as in Example 1.
Example 5
In Example 5, the thickness dimension it2 of the thick inner layer portion shown in Figure 2 was 4.3 mm, and the thickness dimension it1 of the other portion of the inner layer on the side of the crucible was 1.8 mm. The thickness dimension mt2 of the outer layer at the position corresponding to the thick inner layer portion was 13.2 mm, and the thickness dimension mt1 of the other portion of the outer layer on the side of the crucible was 15.7 mm. The other implementation conditions were the same as in Example 1.

Example 6
In Example 6, the thickness dimension it2 of the thick inner layer portion shown in Figure 2 was 5.0 mm, and the thickness dimension it1 of the other portion of the inner layer on the side of the crucible was 1.7 mm. The thickness dimension mt2 of the outer layer at the position corresponding to the thick inner layer portion was 12.6 mm, and the thickness dimension mt1 of the other portion of the outer layer on the side of the crucible was 15.9 mm. Other implementation conditions were the same as in Example 1.
Example 7
In Example 7, the thickness it2 of the thick inner layer portion shown in Figure 2 was 5.0 mm, and the thickness it1 of the other portion of the inner layer on the side of the crucible was 0.7 mm. The thickness mt2 of the outer layer at the position corresponding to the thick inner layer portion was 12.6 mm, and the thickness mt1 of the other portion of the outer layer on the side of the crucible was 16.9 mm. The other implementation conditions were the same as in Example 1.

(Comparative Example 1)
In Comparative Example 1, the thickness dimension it2 of the thick inner layer portion shown in Figure 2 was 0.6 mm, and the thickness dimension it1 of the other portion of the inner layer on the side of the crucible was 0.6 mm. The thickness dimension mt2 of the outer layer at the position corresponding to the thick inner layer portion was 17.7 mm, and the thickness dimension mt1 of the other portion of the outer layer on the side of the crucible was 17.7 mm. Other implementation conditions were the same as in Example 1.
(Comparative Example 2)
In Comparative Example 2, the thickness dimension it2 of the thick inner layer portion shown in Figure 2 was 5.2 mm, and the thickness dimension it1 of the other portion of the inner layer on the side of the crucible was 0.7 mm. The thickness dimension mt2 of the outer layer at the position corresponding to the thick inner layer portion was 13.2 mm, and the thickness dimension mt1 of the other portion of the outer layer on the side of the crucible was 17.7 mm. The other implementation conditions were the same as in Example 1.

The results of Examples 1 to 7 and Comparative Examples 1 and 2 are shown in Table 1.

As shown in Table 1, when the thickness of the thick inner layer portion was 0.6 mm (Comparative Example 1), exposure of the outer layer of the crucible occurred.
Furthermore, when the thickness of the thick inner layer portion was 0.7 mm or more and 5.0 mm or less, and the ratio of the thickness it2 of the thick inner layer portion to the thickness it1 of the other portion of the inner layer on the side of the crucible was 1:0.14 or more and less than 1 (Examples 1 to 7), the outer layer of the crucible was not exposed, and no deformation that would interfere with operation occurred.
Furthermore, when the thickness of the thick inner layer portion was 5.2 mm (Comparative Example 2), the outer layer of the crucible was not exposed, but the crucible collapsed and deformed.
As a result of the above examples, it was confirmed that by setting the ratio of the thickness it2 of the thick portion of the inner layer to the thickness it1 of the other portion of the inner layer on the side of the crucible to 1:0.14 or more and less than 1, it is possible to prevent the outer layer of the crucible from being exposed by etching of the inner layer of the crucible by the silicon melt, and to suppress the occurrence of deformation of the crucible by tipping over.

DESCRIPTION OF SYMBOLS 1 quartz glass crucible 3 outer layer 3a recess 3a1 step portion 4 inner layer 4a thick inner layer portion 5 outer layer 7 side portion 8 bottom corner 9 bottom portion 10 quartz glass crucible manufacturing apparatus

Claims (5)

In a quartz glass crucible for holding a silicon melt and pulling a single crystal,
The quartz glass crucible has a side, a bottom corner, and a bottom, and the side, the bottom corner, and the bottom have a multilayer structure formed of an inner layer and at least one outer layer arranged outside the inner layer,
the inner layer of the side portion has an inner layer thick portion formed of the same material as the material forming the inner layer, which is annularly formed along the circumferential direction at a position on the inner surface that contacts the melt surface of the silicon melt before the single crystal is pulled up;
A quartz glass crucible characterized in that the ratio of the thickness of the thick inner layer portion to the thickness of the other portion of the inner layer on the side is formed to be 1:0.14 or more and less than 1:1. The quartz glass crucible described in claim 1, characterized in that the inner thick layer portion is formed to a thickness of 0.7 mm or more and 5.0 mm or less. A quartz glass crucible as described in claim 1 or claim 2, characterized in that the inner layer thick portion is formed with a width dimension of at least ±50 mm in the crucible axial direction, centered on the position on the inner surface that contacts the molten surface of the silicon melt before the single crystal is pulled up. The inner thick portion is formed to have a rectangular cross section, a trapezoidal cross section, or a semicircular cross section,
A quartz glass crucible according to any one of claims 1 to 3, characterized in that an annular recess is formed along the circumferential direction on the inner surface of the side of the outer layer in correspondence with the shape of the thick portion of the inner layer. A method for manufacturing a quartz glass crucible according to any one of claims 1 to 4 ,
A step of supplying raw material powder containing natural quartz powder to a molding die to form at least one outer layer;
forming an annular recess along a circumferential direction on the inner surface of a side of the outer layer at a position corresponding to the surface of the silicon melt before pulling up the single crystal;
a step of supplying raw material powder containing synthetic quartz powder inside the outer layer, filling the recess with the raw material powder, and forming an inner layer thereon to obtain a crucible molded body;
a step of melting the inner layer and the outer layer of the crucible molded body to form a quartz glass crucible;
A method for manufacturing a quartz glass crucible, comprising: