CN110820040B

CN110820040B - Quartz glass crucible and method for producing quartz glass crucible

Info

Publication number: CN110820040B
Application number: CN201910725841.1A
Authority: CN
Inventors: 须藤俊明; 佐藤忠广; 北原江梨子; 北原贤
Original assignee: Sumco Corp
Current assignee: Sumco Corp
Priority date: 2018-08-07
Filing date: 2019-08-07
Publication date: 2022-05-10
Anticipated expiration: 2039-08-07
Also published as: JP7150250B2; CN110820040A; JP2020023411A

Abstract

[ problem ] to]The purpose is to provide a quartz glass crucible which can prevent the falling and deformation of the quartz glass crucible to the inner side of the straight body part caused by the large-scale of the quartz glass crucible, and further prevent the peeling caused by the density difference at the boundary part where the layers are directly contacted in the quartz glass crucible with a plurality of layers with different characteristics; and a method for producing the silica glass crucible. [ solution means ] to]A silica glass crucible for pulling a silicon single crystal, which comprises a straight body portion and a bottom portion, wherein the density of the top portion of the straight body portion is low and the density of the bottom portion is high. A silica glass crucible for pulling a silicon single crystal, which comprises a straight body part and a bottom part, wherein in the silica glass crucible for pulling a silicon single crystal comprising a plurality of layers, the difference in density of each layer at the boundary part where the outer layer and the inner layer are in contact is 0.0014g/cm³The following.

Description

Quartz glass crucible and method for producing quartz glass crucible

Technical Field

The present invention relates to a silica glass crucible, particularly a silica glass crucible for pulling a silicon single crystal, and relates to a large-diameter large-capacity silica glass crucible in which deformation such as inward tilting occurring at a high temperature during pulling of a silicon single crystal, occurrence of peeling at a boundary portion between an outer layer including natural silica glass and an inner layer including synthetic silica glass, and the like are suppressed; and a method for manufacturing a silica glass crucible.

In the present specification, the heat treatment including arc melting and the subsequent cooling treatment that is continuously performed is referred to as "arc heat treatment", and the heat treatment performed to remove internal strain and homogenize the quartz glass crucible that is a new product that is temporarily produced or the quartz glass crucible used for growing single crystals by the CZ method is referred to as "annealing treatment".

Background

Silicon single crystals used for substrates of semiconductors and the like are generally produced by the Czochralski method (CZ method) using a quartz glass crucible. The CZ method is a method in which a polycrystalline silicon raw material is introduced into a quartz glass crucible, heated and melted to produce a silicon melt, a seed crystal is brought into contact with the silicon melt from above, and the seed crystal is slowly pulled while rotating the quartz glass crucible, thereby obtaining a silicon single crystal.

As described in patent document 1, for example, the quartz glass crucible for pulling a silicon single crystal is produced by a rotating arc melting method in which a quartz raw material powder is supplied into a rotating mold for molding a quartz glass crucible to form a crucible-shaped molded body, and arc melting is performed while applying a reduced pressure to the crucible-shaped molded body from the inner surface toward the outer surface and rotating the crucible-shaped molded body, thereby producing a quartz glass crucible having a transparent layer on the inner surface side and a bubble layer on the outer surface side.

The transparent layer is a layer from which bubbles are removed by pressure reduction in arc melting, and the bubble layer is a layer in which bubbles remain.

In view of the required properties of the material of such a silica glass crucible, it has been proposed to provide a natural silica glass layer (a layer formed by melting natural silica powder) as an outer surface side layer and a synthetic silica glass layer (a layer formed by melting synthetic silica powder) as an inner surface side layer (patent document 2); a three-layer structure in which an outer layer is a natural quartz powder layer, an intermediate layer is a natural quartz powder layer or a high-purity synthetic quartz powder layer, and an inner layer is a high-purity synthetic quartz powder layer (patent documents 3 and 4).

Here, the layers based on the material are different, that is, the natural quartz glass layer and the synthetic quartz glass layer; and the difference based on the layer with or without bubbles, i.e. the bubble layer and the transparent layer, are defined independently.

For example, a transparent layer and a bubble layer are present in the natural quartz glass layer, and further, a synthetic quartz glass layer and a natural quartz glass layer are present in the transparent layer.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2010-105881

Patent document 2: japanese patent application laid-open No. 2010-126423

Patent document 3: japanese patent laid-open No. 2000-247778

Patent document 4: japanese patent laid-open publication No. 2015-127287

Patent document 5: japanese patent laid-open No. 2012 and 17242

Patent document 6: japanese laid-open patent publication No. 2009-298652

Patent document 7: japanese patent laid-open No. 5-58667.

Patent document 8: japanese laid-open patent publication No. 2008-297154

Non-patent document

Non-patent document 1: phys. Rev. B Vol.28 No.6, p.3266-3271, Sept., 1983.

Disclosure of Invention

Problems to be solved by the invention

In recent years, studies have been made to further improve the yield of silicon single crystals and use large-diameter and large-capacity quartz glass crucibles have been progressing, but as a result, when the molten state of the silicon melt in the crucible reaches a long time, the heating load on the quartz glass crucible increases, and when the crucible is exposed to a high temperature higher than the glass softening point, a problem of falling to the inside of the straight body portion of the quartz glass crucible and thermal deformation occurs has been pointed out.

That is, as described above, the quartz glass crucible for pulling a silicon single crystal is produced by, for example, the rotating arc melting method, but generally, after the arc melting, the crucible is cooled from the upper portion thereof, and therefore, the virtual temperature, that is, the density is high at the upper portion of the crucible, and the virtual temperature gradually decreases from the straight portion of the crucible to the bottom portion, and as a result, the density decreases as the distance from the bottom portion decreases. Therefore, conventionally, as described in, for example,

patent documents

5 and 6, a quartz glass crucible is supported in contact with a susceptor made of graphite or carbon, and a centrifugal force is applied to a straight body of the quartz glass crucible while rotating the susceptor, thereby preventing the quartz glass crucible from falling inward.

However, since the difference in the virtual temperatures between the upper and lower portions of the crucible is increased and the density difference is increased as the quartz glass crucible is increased in size, the crucible is supported only by the conventional susceptor and cannot cope with deformation such as falling, and falling is caused, and further measures for solving the problem have been required.

Further, as described above, the silica glass crucible is generally composed of a plurality of layers of natural silica glass and synthetic silica glass, but the densities of the respective glass layers at the virtual temperature are different at the boundary portions thereof, and therefore, even if the respective glass layers have the same virtual temperature, there is pointed out a problem that the respective glass layers are abnormally expanded due to the difference in the densities thereof to cause separation of the glass layers, and it is required to cope with separation of the different glass layers in addition to occurrence of the above-described falling.

Accordingly, an object of the present invention is to provide a quartz glass crucible in which density distributions at the upper and bottom portions of the quartz glass crucible are optimized by adjusting virtual temperatures at respective positions of the crucible, and the quartz glass crucible can prevent falling and deformation to the inner side of the straight body portion, and further, in a quartz glass crucible having a plurality of layers made of different kinds of quartz glass, for example, natural quartz glass and synthetic quartz glass, the density distributions at the boundary portions between the natural quartz glass layer and the synthetic quartz glass layer are optimized by adjusting virtual temperatures of the respective quartz glasses, and the separation of the natural quartz glass layer and the synthetic quartz glass layer can be prevented; and a method for producing the silica glass crucible.

Means for solving the problems

In order to solve the above problems, the present inventors have made extensive studies on a quartz glass crucible while adjusting the densities of the upper part and the bottom part of the quartz glass crucible and the density at the boundary part between the natural quartz glass layer and the synthetic quartz glass layer based on the virtual temperatures of the quartz glass, and as a result, have obtained the following findings.

Namely, it was found that: 1) the quartz glass crucible having a high density at an upper virtual temperature and a low density at a bottom can be manufactured by performing an appropriate annealing treatment on each of the upper portion, the straight portion, and the bottom of the quartz glass crucible having a high density at an upper virtual temperature and a low density at a bottom virtual temperature, which is manufactured by a normal arc melting method or the like.

Further, it was found that 2) in order to prevent peeling of the natural silica glass layer and the synthetic silica glass layer, it is necessary to adjust the density of each silica glass layer so as to eliminate the density difference of each silica glass layer at the boundary portion, but in the natural silica glass and the synthetic silica glass, the relationship between the virtual temperature and the density is observed, and in the virtual temperature range which is equal to or lower than the melting temperature of the silica glass and can be adjusted, that is, the temperature range of 1000 ℃ to 1400 ℃ to 1500 ℃, although the density of each silica glass increases in accordance with the increase in the virtual temperature, the density when observed for the same virtual temperature is generally high for the natural silica glass and low for the synthetic silica glass, and therefore, the density difference can be reduced by setting the virtual temperature of the synthetic silica glass to be high and setting the virtual temperature of the natural silica glass to be low.

Further, 3) the silica glass crucible having the characteristics obtained according to the findings of 1) and/or 2) is produced by subjecting the silica glass crucible in a high-temperature state just obtained by the rotating arc melting method to a specific cooling treatment, and in addition to this, a new silica glass crucible which is temporarily produced by a normal method by the rotating arc melting method or the like can be produced by subjecting the silica glass crucible to a cooling treatment after a reheating annealing treatment, and further, a silica glass crucible which has been used for growing a single crystal by the CZ method can be produced by subjecting the quartz glass crucible to an annealing treatment.

The present invention has been made based on the above findings, and is characterized in that,

"(1) A silica glass crucible for pulling a silicon single crystal, wherein the silica glass crucible for pulling a silicon single crystal has a straight body portion and a bottom portion, and is characterized in that the density is low at the upper portion of the straight body portion and high at the bottom portion.

(2) The silica glass crucible for pulling up a silicon single crystal according to the item (1), which comprises a natural silica glass layer or a synthetic silica glass layer.

(3) The silica glass crucible for pulling up a silicon single crystal according to the item (1), which comprises a natural silica glass layer as an outer layer and a synthetic silica glass layer as an inner layer.

(4) The silica glass crucible for pulling up a silicon single crystal according to the item (1) or (3), which has a natural silica glass layer as an outer layer, a natural silica glass layer or a synthetic silica glass layer as an intermediate layer, and a synthetic silica glass layer as an inner layer.

(5) A silica glass crucible for pulling a silicon single crystal, characterized in that it comprises a body portion and a bottom portionThe crucible has a natural quartz glass layer as an outer layer and a synthetic quartz glass layer as an inner layer, and the density difference of the layers is 0.0014g/cm at the boundary between the outer layer and the inner layer³The following.

(6) A silica glass crucible for pulling up a silicon single crystal, comprising a straight body part and a bottom part, wherein the silica glass crucible for pulling up a silicon single crystal has a natural silica glass layer as an outer layer, a natural silica glass layer or a synthetic silica glass layer as an intermediate layer, and a synthetic silica glass layer as an inner layer, and wherein at a boundary part where layers containing different kinds of silica glass are in direct contact, a density difference at the boundary part of the layers is 0.0014g/cm³The following.

(7) The silica glass crucible for pulling a silicon single crystal according to the item (5) or (6), wherein the silica glass crucible for pulling a silicon single crystal having a straight body portion and a bottom portion has a low density at an upper portion of the straight body portion and a high density at the bottom portion.

(8) A method for manufacturing a silica glass crucible for pulling up a silicon single crystal, characterized in that raw material silica powder is supplied into a rotating mold for molding the silica glass crucible, stacked to a predetermined thickness, then the whole inner surface of the stacked raw material silica powder is arc-melted from the inside of the mold, then rapidly cooled from the bottom of the silica crucible, and then sequentially cooled to the upper side of a straight body part, and a temperature gradient of a virtual temperature is provided so that the virtual temperature is high at the bottom and gradually decreases from the bottom to the upper part of the straight body part, whereby the density at the bottom is high and gradually decreases from the lower part to the upper part of the straight body part.

(9) The method for producing a silica glass crucible for pulling a silicon single crystal according to item (8), wherein the step of rapidly cooling the crucible from the bottom and then cooling the crucible sequentially to the upper side of the straight body portion is carried out by: after the arc melting treatment, a cooling gas obtained by cooling nitrogen gas or the like is introduced into the quartz glass crucible through a cooling tube movable in the vertical direction, and the cooling tube is sequentially moved from the bottom of the crucible inside the crucible to the upper portion of the straight crucible portion.

(10) The method for producing a silica glass crucible for pulling a silicon single crystal according to the item (8) or (9), wherein the step of rapidly cooling the crucible from the bottom and then cooling the crucible sequentially to the upper side of the straight body portion is carried out by: a mold for manufacturing a quartz glass crucible is provided with a plurality of cooling holes for cooling the quartz glass crucible from the outside, and the quartz glass crucible is forcibly cooled at the bottom of the crucible at each cooling position from the bottom of the crucible to the upper part of a straight body part of the crucible, and is gradually cooled toward the upper part of the straight body part of the crucible, or is immediately cooled at the bottom of the crucible at the start time of cooling after the end of an arc, and is then sequentially cooled until the upper part of the straight body part of the crucible after a certain period of time of holding the temperature, thereby performing the process.

(11) A method for manufacturing a silica glass crucible for pulling up a silicon single crystal, characterized in that raw material silica powder for forming a rotating silica glass crucible forming mold is supplied in the order of an outer layer and an inner layer, or in the order of an outer layer, an intermediate layer and an inner layer, stacked to a predetermined thickness, then the whole inner surface of the stacked raw material silica powder is arc-melted from the inside of the forming mold, and then, at a boundary portion where two kinds of silica glass layers are in contact, in order to reduce a density difference between the two kinds of silica glass layers, a layer having natural silica glass with a density higher than that of synthetic silica glass at the same virtual temperature is adjusted to have a low density at the boundary portion by lowering the virtual temperature, while a layer having synthetic silica glass is adjusted to have a high density at the boundary portion by raising the virtual temperature, thereby setting the density difference between the two layers at the boundary portion to 0.0014g/cm³The following.

(12) A method for manufacturing a silica glass crucible for pulling up a silicon single crystal, characterized in that raw material silica powder for forming a rotating silica glass crucible forming mold is supplied in the order of an outer layer and an inner layer or in the order of an outer layer, an intermediate layer and an inner layer, stacked to a predetermined thickness, and then the whole inner surface of the stacked raw material silica powder is arc-melted from the inside of the forming mold, and then quenched from the bottom of the silica crucible, and then sequentially cooled until the inside is cooled to a predetermined thicknessCooling the upper part of the straight body so as to set a temperature gradient of the virtual temperature in such a manner that the virtual temperature is high at the bottom part and the virtual temperature is gradually lower from the bottom part toward the upper part of the straight body, thereby performing arc heat treatment in which the density is high at the bottom and gradually decreases from the lower portion toward the upper portion of the straight body, simultaneously, at the interface where the different kinds of quartz glass layers are in contact with each other simultaneously with the arc heat treatment, in order to reduce the density difference between the two quartz glass layers, for a layer of natural quartz glass having a higher density at the same fictive temperature relative to synthetic quartz glass, the density at the boundary portion is adjusted to be low by lowering the virtual temperature, while the density at the boundary portion is adjusted to be high by raising the virtual temperature with respect to the layer having the synthetic quartz glass, the difference in density between the two layers at the boundary was set to 0.0014 g/cm.³The following. "

Effects of the invention

The present invention relates to a silica glass crucible used for pulling a silicon single crystal, in which a virtual temperature of silica glass is lowered and a density is lowered in an upper portion of the silica glass crucible, and the virtual temperature of silica glass is raised and the density is raised in a bottom portion of the silica glass crucible, whereby an inclination in a straight portion of the crucible, deformation, and breakage of the crucible can be prevented.

Further, in the silica glass crucible having a plurality of different kinds of silica glass layers such as natural silica glass and synthetic silica glass, by adjusting the virtual temperature of each of the different kinds of silica glass, the density difference at the boundary portion between these layers is reduced, thereby preventing the peeling at the boundary portion.

Since the silica glass crucible according to the present invention is excellent in deformation resistance and peeling resistance and has a long life, a high-quality silicon single crystal can be produced with high energy efficiency by using the silica glass crucible.

In the production of a silicon single crystal, the quartz glass crucible is accommodated in the susceptor, whereby further stabilization and efficiency of production are achieved, and a high-quality silicon single crystal can be stably obtained.

Drawings

Fig. 1 shows the relationship between the fictive temperature (horizontal axis) and the density (vertical axis) in the natural silica glass (■ (U), □ (He),. tangle-solidup (H), ● (JR),. smallcircle (J)) and the synthetic silica glass (Δ (SpH), □ (SpV),. smallcircle (S)). (Journal of Non-Crystalline solids 5(1970) p137) for the production of natural quartz glass and synthetic stone

The quartz glass has a uniform density, the synthetic quartz glass has a fictive temperature of 1450 ℃ or lower, the natural quartz glass has a fictive temperature of 1200 ℃ or lower, and the density value at this time is about 2.2030g/cm³The following.

FIG. 2 is a schematic view showing an example of an apparatus for producing a silica glass crucible by a rotating arc melting method.

FIG. 3 is a schematic view showing another example of an apparatus for producing a silica glass crucible by a rotating arc melting method.

FIG. 4 is a schematic view showing an example of an annealing apparatus for annealing after the production of a silica glass crucible.

FIG. 5 is a schematic view showing another example of an annealing apparatus for annealing after the production of a silica glass crucible.

Detailed Description

Hereinafter, in order to carry out the present invention, a step of manufacturing a silica glass crucible for silicon single crystal pulling having a predetermined density distribution by adjusting a virtual temperature of silica glass by arc heat treatment or the like, and a manufacturing method including a specific mode of the silica glass crucible for silicon single crystal pulling and an annealing method for manufacturing the silica glass crucible for these will be described, and specific embodiments will be described together.

< method for adjusting Density distribution at Upper and bottom of Quartz glass crucible >

In general, a quartz glass crucible for pulling a silicon single crystal is manufactured by a rotating arc melting method, and as a result of charging natural silica glass or synthetic silica glass from the upper portion of the crucible, and arc melting and natural cooling from the upper portion, the virtual temperature at the upper portion and the straight portion of the crucible among the obtained natural silica glass layer and synthetic silica glass layer is higher than that at the bottom portion of the crucible, and a crucible having a high density at the upper portion and the straight portion and a low density at the bottom portion is manufactured.

As described above, in accordance with recent increase in size of a silica glass crucible for silicon single crystal, densification of the upper portion of the silica glass crucible has a problem that a straight body portion is inclined inward and thermally deformed, and in order to cope with this problem, it has been proposed to increase a virtual temperature of the bottom portion of the crucible by annealing the silica glass crucible after manufacturing the silica glass crucible by an arc melting method, thereby obtaining a silica glass crucible having a high density from the upper portion toward the bottom portion.

For example, in a method of manufacturing a silica glass crucible by a rotating arc melting method, after heating and melting the entire inner surface of silica powder by arc discharge from the inside of a mold, the bottom portion of the crucible is rapidly cooled at the time of cooling, and the cooling rate is controlled to be reduced to a level above a straight body portion, whereby a silica glass crucible having a high density of the bottom portion with respect to the upper portion and the straight body portion can be obtained.

Fig. 2 shows an example of an apparatus for manufacturing a crucible using a rotating arc melting method.

In fig. 2, a cooling tube having a rotating mechanism capable of cooling from the bottom of the crucible to the straight body and a cooling nozzle is inserted into the crucible by a remotely operated robot or the like immediately after the arc melting, and is cooled while controlling the cooling rate at each position in the crucible. Here, the cooling tube or the rotation mechanism of the cooling nozzle for cooling the bottom portion and the straight body portion of the crucible is a mechanism in which the cooling nozzle is rotated on the bottom portion side and the straight body portion side with respect to the horizontal axis, and a mechanism in which the cooling tube is rotated around the tube axis thereof is used, whereby the bottom portion of the crucible is rapidly cooled by remote operation or the like, and cooling control is performed so that the cooling rate is reduced to above the straight body portion, and a quartz glass crucible having a high density with respect to the upper portion and the straight body portion at the bottom portion is obtained.

In addition, by providing cooling holes at necessary portions of the mold and adjusting the purge amount of the cooling gas, it is possible to perform more precise cooling control from the outside of the crucible, and by cooling from the cooling holes provided at the lower portion of the mold, it is possible to obtain a high-density quartz glass crucible at the bottom.

Fig. 3 shows another example of an apparatus for manufacturing a crucible using the rotating arc melting method.

In fig. 3, a quartz glass crucible having a bottom portion with a high density with respect to the upper portion and the straight portion was obtained by inserting and arranging a cooling tube having a flow rate variable nozzle at each of a plurality of positions to be controlled for cooling into the crucible immediately after arc melting, adjusting the flow rate of the cooling gas from the flow rate variable nozzle at each position of the crucible, and cooling while controlling the cooling rate, along the shape of the inner surface of the bottom portion.

The control of the cooling rate further includes providing cooling holes at necessary portions of the mold, and adjusting the purge amount of the cooling gas by changing the density of the cooling holes (the number of holes per unit area of the mold surface) at each position of the crucible as necessary; alternatively, a quartz glass crucible having a high density at the bottom can be obtained by providing a holding heater in the straight body of the crucible to moderate supercooling and performing fine cooling control from the outside of the crucible.

Further, a general quartz glass crucible manufactured by a conventional rotating arc melting method or the like is once heated to a temperature region of not less than a temperature at which a change in temperature is assumed (a temperature at which a glass structure changes) and not more than a melting temperature, then the bottom of the crucible is rapidly cooled, and annealing treatment is performed to slow down control of a cooling rate to above the straight body portion, whereby a quartz glass crucible having a high density in the bottom portion with respect to the upper portion and the straight body portion can be obtained.

Since the melting temperature of the quartz powder in the conventional rotating arc melting method is 1700 ℃ or higher, the glass of the ordinary quartz glass crucible manufactured by the method has an assumed temperature in the range of about 1000 ℃ to 1500 ℃, and thus the assumed temperature can be controlled by the annealing treatment with the maximum temperature of about 1000 ℃ to 1500 ℃.

In this case, for example, by heating the quartz glass crucible to a maximum temperature of 1200 ℃ using an electric furnace shown in fig. 4 and then performing an annealing treatment in which the cooling temperature is controlled, the quartz glass crucible having a high density at the bottom of the crucible and a low density at the upper part of the straight body of the crucible can be manufactured.

That is, in the electric furnace, the quartz glass crucible is disposed on the mounting table such that only the lowermost portion of the bottom portion of the crucible is supported, and after heating to a predetermined temperature by the heaters disposed on the upper portion and the side surface portion of the crucible, the cooling gas purge cooling pipe having the tip nozzle for cooling the inner surface of the crucible and the cooling gas purge cooling pipe having the tip nozzle for cooling the outer surface of the crucible are moved while purging the cooling gas from the bottom portion of the crucible to the straight portion and the upper portion in this order, whereby the quartz glass crucible having a high density at the bottom portion of the crucible and a relatively low density at the straight portion and the upper portion of the crucible can be obtained.

Further, the quartz glass crucible was heated to a maximum temperature of 1200 ℃ using an electric furnace shown in fig. 5, and then subjected to an annealing treatment in which the cooling temperature was controlled, whereby a quartz glass crucible having a high density at the bottom of the crucible and a low density at the upper part of the straight body of the crucible could be manufactured.

That is, in the electric furnace, the quartz glass crucible is arranged on the mounting table such that only the lowermost portion of the bottom portion of the crucible is supported, and after heating to a predetermined temperature by the heaters arranged on the upper portion and the side portion of the crucible, the cooling gas is purged from the bottom portion of the crucible to the straight portion and the upper portion in this order while synchronizing the cooling gas purge cooling pipe having the tip nozzle for cooling the inner surface of the crucible and the cooling gas purge cooling pipe having the tip nozzle for cooling the outer surface of the crucible, whereby the quartz glass crucible having a high density at the bottom portion of the crucible and a relatively low density at the straight portion and the upper portion of the crucible can be obtained.

The cooling tube can be inserted into the crucible even immediately after the arc melting by using a robot or the like, and as a cooling means for the quartz glass crucible, the cooling tube is cooled while moving the entire cooling tube from the bottom portion to the straight portion and the upper portion in order; alternatively, after the crucible is inserted, the cooling control can be performed by fixing the position of the entire cooling pipe and sequentially changing the maximum flow rate of the cooling medium in each cooling pipe from the cooling pipe at the bottom to the cooling pipe at the straight body and the upper.

< method for adjusting difference in interlayer density at boundary portion of quartz glass crucible including multiple layers >

The quartz glass crucible for pulling a single crystal is generally composed of a plurality of layers of natural quartz glass and synthetic quartz glass, but has a problem that, even if the virtual temperatures of the respective glass layers are the same at the boundary portions, the densities corresponding to the virtual temperatures are different among the respective glasses, and therefore, abnormal expansion occurs due to the difference in density and density, and the glass layers are peeled off.

Here, a means for solving the problems such as peeling by adjusting the virtual temperature in each glass layer to minimize the density difference between the glass layers will be described.

Fig. 1 shows the relationship between the fictive temperature (horizontal axis) and the density (vertical axis) of each of the natural silica glass and the synthetic silica glass.

When the relationship between the virtual temperature and the density of the natural quartz glass and the synthetic quartz glass is observed, it is found that in a virtual temperature range which is not higher than the melting temperature of the quartz glass and can be adjusted, that is, a temperature range of 1000 ℃ to 1400 ℃ to 1500 ℃, although the density of each quartz glass increases in accordance with the increase in the virtual temperature, the density when observed for the same virtual temperature is generally high for the natural quartz glass and low for the synthetic quartz glass, and therefore, the difference in the density between the natural quartz glass and the synthetic quartz glass can be reduced by setting the virtual temperature of the synthetic quartz glass to be high and the virtual temperature of the natural quartz glass to be low.

In order to match the densities of the natural silica glass and the synthetic silica glass, the density values of the natural silica glass are about 2.2030g/cm in both the natural silica glass and the synthetic silica glass, for example, by setting the virtual temperature of the synthetic silica glass to 1450 ℃ and the virtual temperature of the natural silica glass to 1200 ℃³The density difference can be made almost 0, and a silica glass crucible having excellent peeling resistance can be obtained.

By using such a means, in the silica glass crucible having a multilayer structure including the natural silica glass layer and the synthetic silica glass layer, the virtual temperature of each layer is also adjusted to minimize the density difference between the adjacent two layers, whereby the silica glass crucible having excellent peeling resistance can be manufactured.

Further, in the silica glass crucible including the plurality of silica glass layers, by combining the annealing treatment, the density of the bottom portion with respect to the upper portion is increased, and the silica glass crucible which minimizes the density difference between the layers, has excellent peeling resistance, and is free from falling or deformation can be manufactured.

Hereinafter, the following description will be given of embodiments 1 to 4, and examples thereof, that is, examples 1 to 6 and examples 11 to 15, will be described while comparing them with comparative examples 1 to 3 and comparative examples 11 to 13.

< embodiment 1 >

The silica glass crucible of embodiment 1 is a silica glass crucible for pulling up a silicon single crystal, which has a cylindrical straight body portion and a bottom portion and is composed of a single layer of a natural silica glass layer or a synthetic silica glass layer, and can solve the problem of falling inside of the straight body portion of the crucible, and can be used while being supported by a carbon susceptor as needed. (hereinafter, the same applies to the quartz glass crucibles according to embodiments 2 to 4, as far as they can be supported by a susceptor made of carbon and used as needed).

The quartz glass crucible is produced by, for example, a rotating arc melting method, and specifically, a quartz glass crucible having a high bottom density and a relatively low density at the upper part of a straight body is obtained by supplying natural quartz powder or synthetic quartz powder as a raw material to the inner surface of a carbon mold for producing a rotating crucible, stacking the quartz powder or synthetic quartz powder to a predetermined thickness, then performing arc discharge from the inside of the mold to heat and melt the entire inner surface of the quartz powder, rapidly cooling the quartz powder from the bottom of the crucible, and then sequentially cooling the quartz powder to the upper part of the straight body.

As the mold for manufacturing the silica glass crucible, a water-cooled stainless steel mold or the like may be used in addition to the carbon mold.

Regarding the cooling method of the silica glass crucible, the method of quenching from the bottom of the crucible and cooling from the bottom of the crucible to the upper side of the straight body portion of the crucible in order can be realized by, for example: after the arc interruption, a cooling gas obtained by cooling nitrogen gas or the like is introduced into the quartz glass crucible through a cooling tube movable in the vertical direction, and the cooling tube is sequentially moved from the bottom of the crucible inside the crucible to the upper part of the straight body part of the crucible, thereby achieving a desired gradient of the virtual temperature from the bottom to the upper part of the straight body part.

Further, a plurality of cooling holes for cooling the quartz glass crucible from the outside are provided in the mold for producing the quartz glass crucible, and the crucible bottom portion is strongly cooled at each cooling position from the crucible bottom portion to the upper portion of the straight crucible portion, and gradually cooled toward the upper portion of the straight crucible portion, or immediately cooled at the crucible bottom portion at the cooling start time after the end of the arc, and thereafter, the cooling is started sequentially until the upper portion of the straight crucible portion after the temperature is held for a certain time, and the like, whereby a gradient of a desired virtual temperature from the bottom portion to the upper portion of the straight crucible portion can be obtained in the crucible outer portion.

The crucible can be manufactured by the manufacturing apparatus using the rotating arc melting method shown in fig. 2 or 3.

As described above, in the conventional rotating arc melting method and the like, the present invention may be applied to a conventional rotary arc melting method and the like, particularly, to a conventional rotary arc melting method and a conventional rotary arc melting method, in which a quartz glass crucible is not provided with a virtual temperature gradient and density gradient in the vertical direction; the quartz glass crucible that has been used for growing a single crystal by the CZ method or the like is manufactured by, for example, temporarily heating the quartz glass crucible to a temperature region of a virtual temperature or higher and a melting temperature or lower, and then applying the cooling method according to embodiment 1 described above, a quartz glass crucible having a gradient of the virtual temperature, a high density at the bottom of the crucible, and a low density at the upper part of the straight body of the crucible can be obtained, and therefore, occurrence of falling-in and thermal deformation can be prevented.

Can be manufactured by performing an annealing process using an electric furnace shown in fig. 4 or 5.

It should be noted that the virtual temperature can be confirmed by, for example, collecting a sample piece from the middle position in the thickness direction of each layer in a quartz crucible manufactured under the same conditions, and measuring the sample piece by using a laser raman spectroscopy (see patent document 7, patent document 8, and non-patent document 1).

The density at each position of the silica glass crucible can be directly measured by an archimedes method or the like. The difference in the correct density can also be determined by direct measurement. In this case, the results of measuring the density of the samples cut out from the respective positions by the archimedes method are fed back to the production conditions of the silica glass crucible, whereby the silica glass crucible containing glass having a desired density at the respective positions can be produced. Further, if bubbles are present in the sample, the density of the glass itself cannot be measured, and therefore it is necessary to extract the sample from a portion where no bubbles are present.

< embodiment 2 >

The silica glass crucible according to embodiment 2 is a silica glass crucible for pulling up a silicon single crystal, which can solve the problem of the fall-in of the straight body portion of the crucible and the like, similarly to the silica glass crucible according to embodiment 1, and is a silica glass crucible having a cylindrical straight body portion and a bottom portion and formed of a plurality of layers including a two-layer structure or a three-layer structure.

Specifically, for example, the present invention includes: a quartz glass crucible having a natural quartz glass layer made of natural quartz glass as an outer layer and a synthetic quartz glass layer made of synthetic quartz glass as an inner layer; a quartz glass crucible comprising a plurality of layers, which has a natural quartz glass layer as an outer layer, a natural quartz glass layer or a synthetic quartz glass layer as an intermediate layer, and a synthetic quartz glass layer as an inner layer.

The quartz glass crucible is manufactured by, for example, a rotating arc melting method, as in embodiment 1, and specifically, natural quartz powder and synthetic quartz powder as raw materials are sequentially supplied from the quartz powder for the outer layer to the inner surface of a carbon mold for manufacturing a rotating crucible, stacked to a predetermined thickness, arc-discharged from the inside of the mold, the entire inner surface of the quartz powder is heated and melted, then rapidly cooled from the bottom of the crucible, and then sequentially cooled to the upper side of the straight body portion, whereby the quartz glass crucible is provided at a gradient of an imaginary temperature in which the imaginary temperature at the bottom is high and the imaginary temperature at the upper portion of the straight body portion is low, and a quartz glass crucible having a high density at the bottom and a relatively low density at the upper portion of the straight body portion is obtained.

Further, in embodiment 2, since the silica glass crucible is formed in a plurality of layers, the outer layer is also subjected to the cooling method from the outside as shown in embodiment 1, for example, and the density of the outer layer is also increased at the bottom portion and relatively decreased at the upper portion of the straight body portion, whereby an excellent silica glass crucible which is less likely to fall back can be manufactured.

Similarly to embodiment 1, the crucible can be manufactured by using the apparatus for manufacturing a crucible by the rotating arc melting method shown in fig. 2 or 3.

In addition, as in embodiment 1, the silica glass crucible according to the present invention may be a silica glass crucible which is a general new product in which no virtual temperature gradient or density gradient is provided in the vertical direction of the silica glass crucible; a quartz glass crucible that has been used for growing a single crystal by the CZ method or the like is produced, and after these quartz glass crucibles are once heated to a temperature region of a virtual temperature or higher and a melting temperature or lower, by applying the cooling method according to embodiment 1 described above, a quartz glass crucible that forms a gradient of the virtual temperature, has a high density at the bottom of the crucible, and has a low density at the upper part of the straight body of the crucible can be obtained, and therefore, occurrence of falling-in and thermal deformation can be prevented.

In this case, the substrate can be manufactured by performing annealing treatment using an electric furnace shown in fig. 4 or 5.

The measurement position and the confirmation method for the virtual temperature are the same as those in embodiment 1.

< embodiment 3 >

The silica glass crucible according to embodiment 3 is a silica glass crucible for pulling up a silicon single crystal, which has a cylindrical straight body portion and a bottom portion and is formed of a plurality of layers including a two-layer structure or a three-layer structure, and which can avoid a problem of separation due to a difference in density of each layer at a boundary portion between layers including silica glasses having different materials.

Specifically, examples thereof include: a quartz glass crucible having a natural quartz glass layer made of natural quartz glass as an outer layer and a synthetic quartz glass layer made of synthetic quartz glass as an intermediate layer or an inner layer in contact with the outer layer; a quartz glass crucible having a multilayer structure comprising a natural quartz glass layer as an intermediate layer and a synthetic quartz glass layer as the No. 2 intermediate layer or inner layer in contact with the intermediate layer.

As has been shown as a finding matter, in order to prevent separation of the natural silica glass layer and the synthetic silica glass layer, the problem can be solved by adjusting the density difference between the respective silica glass layers so as to eliminate the density difference between the respective silica glass layers at the boundary portion, and therefore, the density difference can be reduced by adjusting the density at the boundary portion to be low by lowering the virtual temperature for the natural silica glass having a relatively high density with respect to the synthetic silica glass at the same virtual temperature, and by adjusting the density to be high by raising the virtual temperature for the synthetic silica glass, for example, by setting the density difference to 0.0014g/cm³Hereinafter, an excellent silica glass crucible can be produced which can avoid the occurrence of defects such as peeling and cracks at the boundary portion.

In general, in a silica glass crucible having a plurality of layers, since a natural silica glass layer is generally provided on the outer layer side and a synthetic silica glass layer is generally provided on the inner layer side, for example, by using a cooling mechanism from the inside of a mold and a cooling mechanism from the outside of the mold as described in embodiment 1 and embodiment 2, the inner portion having the synthetic silica glass layer is rapidly cooled to increase the virtual temperature and achieve a high density, while the outer portion having the natural silica glass layer is gradually cooled to decrease the virtual temperature and decrease the density, whereby the difference in density at the boundary portion between the adjacent two layers can be reduced and peeling at the boundary portion can be prevented.

Similarly to embodiment 1 and embodiment 2, the crucible can be manufactured using the apparatus for manufacturing a crucible by the rotating arc melting method shown in fig. 2 or fig. 3.

Further, when the synthetic quartz glass layer is provided on the outer layer side and the natural quartz glass layer is provided on the inner layer side, the density difference at the boundary portion can be reduced and peeling at the boundary portion can be prevented by slowly cooling the inner layer and rapidly cooling the outer layer.

In addition, among the silica glass crucibles according to the present invention, a silica glass crucible of a general new product in which no virtual temperature gradient or density gradient is provided in the vertical direction of the silica glass crucible; the quartz glass crucibles that have been used for growing single crystals by the CZ method and the like are produced by heating these quartz glass crucibles to a temperature range of not lower than the virtual temperature and not higher than the melting temperature once, and then adjusting the virtual temperature at the boundary portion between the respective quartz glass layers so as to eliminate the density difference between the respective quartz glass layers at the boundary portion as described above, thereby preventing the separation at the boundary portion.

In this case, the electric furnace shown in fig. 4 or 5 can be used for manufacturing, as in embodiment 2.

In the measurement of the virtual temperature, it is confirmed by collecting a sample piece from a boundary position in the thickness direction of each layer of a quartz crucible manufactured under the same conditions, and measuring the sample piece by using a laser raman spectroscopy.

The density of each layer of the silica glass crucible can be directly measured by archimedes method or the like. The difference in the correct density can also be determined by direct measurement. At this time, the results of measuring the density of the samples cut out at the positions of the respective layers by the archimedes method were fed back to the production conditions of the silica glass crucible, thereby obtaining a silica glass crucible containing glass having a desired density in each layer. Further, if bubbles are present in the sample, the density of the glass itself cannot be measured, and therefore it is necessary to extract the sample from a portion where no bubbles are present.

< embodiment 4 >

The silica glass crucible according to embodiment 4 is a silica glass crucible for pulling up a silicon single crystal, which can simultaneously solve the problem of deformation such as an inward fall occurring in the straight body portion of the silica glass crucible in which the problem has been solved in embodiment 2 and the problem of delamination occurring between layers in the silica glass crucible formed of a plurality of layers including silica glasses having different materials in which the problem has been solved in embodiment 3.

Specifically, the quartz glass crucibles shown in embodiment 2 and embodiment 3, for example, have a natural quartz glass layer using natural quartz glass as a raw material as an outer layer, a synthetic quartz glass layer in contact with the outer layer and using synthetic quartz glass as a raw material as an intermediate layer or an inner layer; a quartz glass crucible having a multilayer structure with a natural quartz glass layer as an intermediate layer, in contact with the intermediate layer, and a synthetic quartz glass layer as the 2 nd intermediate layer or inner layer.

The silica glass crucible is manufactured by, for example, a rotating arc melting method, as in

embodiments

2 and 3, and specifically, a natural silica powder and a synthetic silica powder as raw materials are sequentially supplied from the silica powder for the outer layer to the silica powder for the inner layer to the inner surface of a carbon mold for manufacturing a rotating crucible, are stacked to a predetermined thickness, arc discharge is performed from the inside of the mold, the entire inner surface of the silica powder is heated and melted, then, temperature control is performed for each layer from the inner layer side and the outer layer side, and virtual temperatures at each part of each layer are adjusted, thereby obtaining a silica glass crucible in which the density of the bottom part is high in each layer of the silica glass crucible, the density of the upper part of the straight body part is low, and the density difference in each part from the upper part to the bottom part of the straight body part is small at the boundary part of each layer.

As already described in the findings, the raw material quartz powder stacked in the mold is heated and melted, and then rapidly cooled from the bottom of the crucible to the upper portion of the straight body portion in order from the bottom of the crucible to either or both of the inner layer side and the outer layer side of the crucible, or cooled from the bottom of the crucible to the upper portion of the straight body portion by providing a cooling gradient having a higher cooling capacity as the temperature of the crucible is closer to the bottom of the crucible, whereby the density is increased by increasing the virtual temperature at the bottom of the quartz glass crucible, and the virtual temperature is relatively decreased and decreased with respect to the bottom of the quartz glass crucible at the upper portion of the straight body portionLow density, suppressing the occurrence of falling and thermal deformation to the inside of the straight body, and rapidly cooling the inside portion having the synthetic quartz glass layer at the boundary portion between the natural quartz glass layer on the outer layer side and the synthetic quartz glass layer on the inner layer side which are in direct contact, using the cooling means from the inside of the mold, the cooling means from the outside of the mold, and the like shown in embodiments 1 and 2, thereby increasing the virtual temperature and relatively increasing the density of the synthetic quartz glass layer, while slowly cooling or holding the outside portion having the natural quartz glass layer for a certain period of time, thereby decreasing the virtual temperature and relatively decreasing the density of the natural quartz glass layer, thereby decreasing the density difference at the boundary portion between the adjacent two layers, preferably setting the density difference to 0.0014g/cm³This makes it possible to avoid the occurrence of defects such as separation and cracks at the boundary.

Similarly to embodiment 1 and embodiment 2, the crucible can be manufactured using the apparatus for manufacturing a crucible by the rotating arc melting method shown in fig. 2 or fig. 3. In addition, when the synthetic quartz glass layer is provided on the outer layer side and the natural quartz glass layer is provided on the inner layer side adjacent thereto, the cooling capacity of the outer layer is increased relative to the inner layer, so that the density difference at the boundary between the two layers is reduced, and the occurrence of defects such as peeling and cracking at the boundary can be prevented.

In addition, among the silica glass crucibles according to the present invention, a silica glass crucible of a general new product in which no virtual temperature gradient or density gradient is provided in the vertical direction of the silica glass crucible; in the production of a silica glass crucible which has been used for growing a single crystal by the CZ method or the like, after these silica glass crucibles are heated once to a temperature region of not lower than the virtual temperature and not higher than the melting temperature, the virtual temperature at the boundary portion of each silica glass layer is adjusted as described above so as to eliminate the difference in density between the silica glass layers at the boundary portion, and the virtual temperature is adjusted at the bottom portion of the silica glass crucible so that the virtual temperature is high and the virtual temperature is low at the upper portion of the straight body portion in each silica glass layer, whereby the silica glass crucible having a high density at the bottom portion and a relatively low density at the upper portion of the straight body portion is produced, whereby the occurrence of falling and thermal deformation to the inside of the straight body portion is suppressed, and the occurrence of separation at the boundary portion can be prevented together.

The electric furnace shown in fig. 4 or 5 can be used for manufacturing the same as in embodiment 2.

Examples

The present invention will be described below by referring to examples in comparison with comparative examples.

It should be noted that the present invention is not limited to these examples.

In the examples, the quartz glass crucible of the present invention having a diameter of 32 inches (bore diameter 800mm) and a height of 500mm was produced directly by the rotating arc melting method, or the quartz glass crucible of the same shape was produced once by the ordinary rotating arc melting method and then subjected to the annealing treatment.

Table 1 shows examples 1 to 6, Table 2 shows comparative examples 1 to 3, Table 3 shows examples 11 to 15, and Table 4 shows comparative examples 11 to 13.

Examples 1 to 4 are the silica glass crucibles of embodiment 1 formed of a single silica glass layer, solving the problem of falling inside of the crucible and the like. Here, the single silica glass layer of example 1 and example 2 refers to a natural silica glass layer, and the single silica glass layer of example 3 and example 4 refers to a synthetic silica glass layer, in which a bubble layer and a transparent layer are present.

In examples 1 and 3, when the silica glass crucible was produced by the rotating arc melting method, the quartz glass crucible having a low density in the upper part and a high density in the bottom part of the straight body was directly produced by adjusting the virtual temperature of the silica glass layer.

The virtual temperature of the silica glass layer was adjusted using the manufacturing apparatus by the rotating arc melting method shown in fig. 2. Immediately after the arc melting, a cooling tube was inserted into the crucible, and the cooling gas (air) was purged inward at a rate of 10L/sec and moved from the bottom toward the top.

In examples 2 and 4, a normal silica glass crucible produced by the rotating arc melting method was reheated to a temperature equal to or higher than the virtual temperature and equal to or lower than the melting temperature, and then the virtual temperature of the silica glass layer was adjusted by annealing treatment, thereby producing a silica glass crucible having a low density in the upper part and a high density in the bottom part of the straight body part.

The adjustment of the virtual temperature of the silica glass layer was performed using the annealing apparatus shown in fig. 4. During cooling in the annealing treatment, a cooling tube was inserted into the crucible, and the crucible was moved from the bottom toward the top while blowing cooling gas (air) inward at a rate of 10L/sec.

As shown in table 1, the quartz glass crucible obtained by these production methods did not cause inner fall or thermal deformation when pulling up a single crystal, and the quality of the produced single crystal was also good.

On the other hand, in the quartz glass crucibles of comparative examples 1 and 2 obtained by the conventional rotating arc melting method, the virtual temperature was not adjusted during the production (no cooling tube was inserted), and therefore, the occurrence of the fall-back was observed when pulling the single crystal.

Examples 5 and 6 are the silica glass crucibles formed of a plurality of silica glass layers in embodiment 2, in which the problem of the fall-in of the crucible and the like is solved.

In example 5, when a silica glass crucible formed of a plurality of silica glass layers was manufactured, the silica glass crucible having a low density in the upper part and a high density in the bottom part of the straight body part was directly manufactured by adjusting the virtual temperature of the silica glass layer in the case of manufacturing the silica glass crucible by the rotating arc melting method, as in examples 1 and 3.

The virtual temperature of the silica glass layer was adjusted using the manufacturing apparatus by the rotating arc melting method shown in fig. 3. Immediately after the arc melting, a cooling tube was inserted into the crucible, and while blowing cooling gas (air) inward at a rate of 10L/sec, the cooling tube was moved from the bottom to the upper part, and while blowing cooling gas (air) inward at a rate of 0.1L/sec from the mold to the bottom of the silica glass, at a rate of 1L/sec to the corner, and at a rate of 10L/sec to the straight body.

In example 6, similarly to examples 2 and 4, a normal silica glass crucible temporarily manufactured by a rotating arc melting method was heated to a temperature not lower than the virtual temperature and not higher than the melting temperature, and then the virtual temperature of the silica glass layer was adjusted by annealing treatment, thereby manufacturing a silica glass crucible having a low density in the upper part and a high density in the bottom part of the straight body part.

The adjustment of the virtual temperature of the silica glass layer was performed using the annealing apparatus shown in fig. 5. During cooling in the annealing treatment, a cooling tube was inserted into the crucible, and cooling gas (air) was blown into the crucible at a rate of 10L/sec and moved from the bottom toward the top, while cooling gas (air) was blown from the cooling tube outside the crucible at a rate of 5L/sec and moved from the bottom toward the top.

In contrast, in the quartz glass crucible of comparative example 3 obtained by the conventional rotating arc melting method, since the adjustment of the virtual temperature is not performed during the production (the cooling tube is not inserted), the density of the upper portion of the crucible with respect to the bottom portion of the crucible becomes high, and the occurrence of the fall-in is observed when pulling up the single crystal.

Example 11 is a silica glass crucible formed of a plurality of layers according to embodiment 3, which solves the problem of delamination caused by a difference in density of each layer at a boundary portion between layers formed of silica glass having different properties.

In example 11, when a quartz glass crucible was produced by a rotating arc melting method in the production of a quartz glass crucible formed of a plurality of quartz glass layers having different characteristics, the virtual temperature of each quartz glass layer was adjusted to reduce the density difference at the boundary between the plurality of layers, and the density difference was set to 0.0014g/cm³The following procedure was conducted.

In the silica glass crucible produced by such a method, as shown in table 2, defects such as peeling and cracking can be prevented from occurring at the boundary portion between the silica glass layers having different characteristics.

On the other hand, in the quartz glass crucibles of comparative examples 11 to 13 obtained by the conventional rotating arc melting method, since the adjustment of the virtual temperature was not performed at the time of production (no cooling tube was inserted), more than 0.0014g/cm was generated at the boundary portion between the quartz glass layers having different characteristics³The occurrence of delamination was observed at the boundary between these layers.

Examples 12 to 15 are the silica glass crucibles according to embodiment 4, which are formed of a plurality of layers, and which solve both the problem of deformation such as a fall-back which may occur in a straight body portion of the silica glass crucible and the problem of peeling due to a difference in density of each layer at a boundary portion between layers formed of silica glass having different properties.

Further, in examples 12 and 14, when the quartz glass crucibles formed of a plurality of quartz glass layers having different characteristics were manufactured, and when the quartz glass crucibles were manufactured by the rotating arc melting method, the virtual temperatures of the respective quartz glass layers were adjusted to lower the density of the upper part of the straight body part and to increase the density of the bottom part, and the density difference between the respective quartz glass layers was adjusted to be reduced at the boundary part of the quartz glass layers, thereby suppressing the occurrence of falling to the inside of the crucible of the straight body part and the occurrence of thermal deformation, and also avoiding the occurrence of defects such as peeling and cracking at the boundary part of the quartz glass layers.

The virtual temperature of the silica glass layer was adjusted using the manufacturing apparatus by the rotating arc melting method shown in fig. 2. Immediately after the arc melting, a cooling tube was inserted into the crucible, and while blowing cooling gas (air) inward at a rate of 10L/sec, the cooling tube was moved from the bottom to the upper part, and while blowing cooling gas (air) inward at a rate of 0.2L/sec from the mold to the bottom of the silica glass, at a rate of 1L/sec to the corner, and at a rate of 5L/sec to the straight body.

In examples 13 and 15, the quartz glass crucible produced by the rotating arc melting method was reheated to a temperature not lower than the virtual temperature and not higher than the melting temperature, and then the virtual temperature of the quartz glass layer was adjusted by annealing treatment to lower the density of the upper part of the straight body part and to increase the density of the bottom part, and at the boundary part between the quartz glass layers, the density difference between the respective quartz glass layers was adjusted so as to be small, thereby suppressing the occurrence of falling to the inside of the crucible in the straight body part and the occurrence of defects such as cracks and the like, and also avoiding the occurrence of peeling at the boundary part between the quartz glass layers and the occurrence of defects such as cracks.

The adjustment of the virtual temperature of the silica glass layer was performed using the annealing apparatus shown in fig. 4. During cooling in the annealing treatment, a cooling tube was inserted into the crucible, and cooling gas (air) was blown into the crucible at a rate of 10L/sec and moved from the bottom toward the top, while cooling gas (air) was blown from the cooling tube outside the crucible at a rate of 5L/sec and moved from the bottom toward the top.

As shown in table 2, the quartz glass crucible obtained by the above-described production method did not cause falling or thermal deformation when pulling a single crystal, and the quality of the produced single crystal was good, and also delamination did not occur between layers of a plurality of different quartz glass layers.

On the other hand, in the quartz glass crucibles of comparative examples 11 to 13 obtained by the conventional rotating arc melting method, since the adjustment of the virtual temperature was not performed at the time of production (no cooling pipe was inserted), the inner fall occurred, and more than 0.0014g/cm was generated at the boundary portion between the quartz glass layers having different characteristics³The occurrence of peeling was found.

Industrial applicability

As described above, the present invention relates to a silica glass crucible, particularly a silica glass crucible for pulling a silicon single crystal, and provides a large-diameter large-capacity silica glass crucible in which deformation such as inward inclination generated at a high temperature during pulling of a silicon single crystal, occurrence of separation at a boundary portion between an outer layer including natural silica glass and an inner layer including synthetic silica glass, and the like are suppressed; and a method for producing a silica glass crucible, and is therefore extremely useful in the field of production of various silica glass crucibles for pulling up silicon single crystals.

Description of the reference numerals

1 mould

2 arc electrode

3 Cooling tube

4 adjusting valve

5 mould rotating mechanism

6 mould cooling hole

7 nozzle reversing mechanism

8 crucible

9 electric stove

10 heater

11 stations.

Claims

1. A silica glass crucible for pulling a silicon single crystal, comprising a straight body portion and a bottom portion, wherein the density of a glass itself not containing bubbles in the upper portion of the straight body portion is low, the density of a glass itself not containing bubbles in the bottom portion is high, and the density is gradually reduced from the lower portion toward the upper portion of the straight body portion.

2. The silica glass crucible for pulling up a silicon single crystal as set forth in claim 1, comprising a natural silica glass layer or a synthetic silica glass layer.

3. A silica glass crucible for pulling up a silicon single crystal as set forth in claim 1, wherein a natural silica glass layer is provided as an outer layer and a synthetic silica glass layer is provided as an inner layer.

4. The silica glass crucible for pulling up a silicon single crystal as set forth in claim 1 or 3, wherein the crucible has a natural silica glass layer as an outer layer, a natural silica glass layer or a synthetic silica glass layer as an intermediate layer, and a synthetic silica glass layer as an inner layer.

5. A silica glass crucible for pulling a silicon single crystal, comprising a straight body part and a bottom part, wherein the silica glass crucible for pulling a silicon single crystal comprises a natural silica glass as an outer layer and a synthetic silica glass layer as an inner layer, and the difference in density between the glass itself containing no bubbles in each layer at a boundary part where the outer layer and the inner layer are in contact is 0.0014g/cm³The following.

6. A silica glass crucible for pulling up a silicon single crystal, comprising a straight body part and a bottom part, wherein the silica glass crucible for pulling up a silicon single crystal has a natural silica glass layer as an outer layer, a natural silica glass layer or a synthetic silica glass layer as an intermediate layer, and a synthetic silica glass layer as an inner layer, and at a boundary part where layers containing different kinds of silica glass are in direct contact, a density difference of a glass itself containing no bubbles at the boundary part of each layer is 0.0014g/cm³The following.

7. The silica glass crucible for pulling a silicon single crystal according to claim 5 or 6, wherein in the silica glass crucible for pulling a silicon single crystal having a straight body portion and a bottom portion, the density of the glass itself containing no bubbles in an upper portion of the straight body portion is low, and the density of the glass itself containing no bubbles in a bottom portion is high.

8. A method for manufacturing a silica glass crucible for pulling up a silicon single crystal, characterized in that raw material silica powder is supplied into a rotating mold for molding a silica glass crucible, stacked to a predetermined thickness, then the whole inner surface of the stacked raw material silica powder is arc-melted from the inside of the mold, then rapidly cooled from the bottom of the silica crucible, and then sequentially cooled to the upper side of a straight body part, and a temperature gradient of a virtual temperature is provided so that the virtual temperature is high at the bottom and gradually decreases from the bottom to the upper part of the straight body part, whereby the density of glass itself containing no bubbles at the bottom is high and gradually decreases from the lower part to the upper part of the straight body part.

9. A method of manufacturing a silica glass crucible for pulling a silicon single crystal as set forth in claim 8, wherein the step of quenching the crucible from the bottom and then cooling the crucible sequentially to the upper side of the straight body portion is performed by: after the arc melting treatment, a cooling gas obtained by cooling nitrogen gas or the like is introduced into the quartz glass crucible through a cooling tube movable in the vertical direction, and the cooling tube is sequentially moved from the bottom of the crucible inside the crucible to the upper portion of the straight crucible portion.

10. The method of manufacturing a silica glass crucible for pulling a silicon single crystal as set forth in claim 8 or 9, wherein the step of quenching from the bottom of the silica crucible and then cooling the crucible sequentially to the position above the straight body portion is performed by: a mold for manufacturing a quartz glass crucible is provided with a plurality of cooling holes for cooling the quartz glass crucible from the outside, and the quartz glass crucible is forcibly cooled at the bottom of the crucible at each cooling position from the bottom of the crucible to the upper part of a straight body part of the crucible, and is gradually cooled toward the upper part of the straight body part of the crucible, or is immediately cooled at the bottom of the crucible at the start time of cooling after the end of an arc, and is then sequentially cooled until the upper part of the straight body part of the crucible after a certain period of time of holding the temperature, thereby performing the process.

11. A method for manufacturing a silica glass crucible for pulling up a silicon single crystal, characterized in that raw material silica powder for forming the layers is supplied in the order of an outer layer and an inner layer, or in the order of an outer layer, an intermediate layer and an inner layer, stacked to a predetermined thickness, in a rotating mold for molding a silica glass crucible, then the whole inner surface of the stacked raw material silica powder is arc-melted from the inside of the mold, and then, in a boundary portion where the two kinds of silica glass layers are in contact, in order to reduce a density difference between the two kinds of silica glass layers, a layer having natural silica glass having a density higher than that of synthetic silica glass at the same virtual temperature is adjusted to have a low density of the glass itself not containing bubbles at the boundary portion by lowering the virtual temperature, while a layer having synthetic silica glass is adjusted to have a high density of the glass itself not containing bubbles at the boundary portion by raising the virtual temperature, thereby setting the density difference between the two layers at the boundary portion to 0.0014g/cm³The following.

12. A method for manufacturing a silica glass crucible for pulling a silicon single crystal, characterized in thatIn order to reduce the difference in density between two types of quartz glass layers at the boundary between the different types of quartz glass layers, the arc heat treatment is performed by supplying raw quartz powder for forming the outer layer and the inner layer in this order, stacking the quartz powder to a predetermined thickness, arc-melting the entire inner surface of the stacked raw quartz powder from the inside of the mold, rapidly cooling the quartz powder from the bottom of the quartz crucible, cooling the quartz powder to the upper side of the straight body in this order, cooling the quartz powder to a temperature gradient such that the virtual temperature at the bottom is higher and the virtual temperature at the bottom is lower in this order, and arc-heating the quartz powder having a high density at the bottom and a lower density in this order from the lower side of the straight body to the upper side of the straight body, the density of the glass itself containing no bubbles at the boundary portion is adjusted to be low by lowering the virtual temperature for a layer of natural quartz glass having a higher density than that of synthetic quartz glass at the same virtual temperature, and the density of the glass itself containing no bubbles at the boundary portion is adjusted to be high by raising the virtual temperature for a layer of synthetic quartz glass, whereby the difference in density between the two layers at the boundary portion is set to 0.0014g/cm³The following.