JP5806941B2 - Method for producing a silica sintered crucible - Google Patents

Description

The present invention relates to a method of manufacturing a sheet silica sintered crucible relates particularly the method for producing a silica sintered crucible varies silica glass silica sintered by melt heat of polysilicon.

  Semiconductor single crystals such as silicon are mainly manufactured by the Czochralski (CZ) method. In the manufacture of a silicon single crystal by the CZ method, a silicon single crystal seed crystal is deposited on a silicon raw material melt obtained by melting polysilicon, and is gradually pulled up while rotating to grow a silicon single crystal ingot. Is done. In such pulling of a silicon single crystal, a silica glass crucible is used as a container for heating and melting a silicon raw material.

  A method for producing the silica glass crucible will be described with reference to FIG. FIG. 6 shows each step of manufacturing a conventional silica glass crucible in order by cross-sectional views, and the upper half in FIGS. 6 (a) to 6 (e) is shown in a central cross-sectional state in the vertical direction. The lower half in FIGS. 6A to 6D is shown in the state of the central cross section in each horizontal direction.

  A reference numeral 103 shown in FIG. 6A is a hopper as a raw material powder supply device for supplying a quartz glass raw material powder. A partition plate 103 a that divides the hopper 103 into two is provided inside the hopper 103. ing. Different raw material powders G1 and G2 are accommodated in the hopper divided into two parts, and the raw material powders G1 and G2 are supplied from the raw material supply port 103b of the hopper 103. A purified natural silica raw material powder is used as the raw material powder G1, and a high-purity synthetic silica raw material powder is used as the raw material powder G2.

  As shown in FIG. 6B, the material supply port 103b of the hopper 103 is located above the narrow gap portion of the gap formed by the outer frame 101 and the inner frame 102 that are both rotated. The raw material powders G1 and G2 are supplied between the outer frame 101 and the inner frame 102 through the narrow gap portion. Then, the raw material powders G1 and G2 supplied between the outer frame 101 and the inner frame 102 are separated from the outer peripheral surface of the inner frame 102 in an eccentric state, in particular, by the portion close to the inner peripheral surface of the outer frame 101. A plurality of powder layers G1 and G2 made of different raw materials are formed in the thickness direction of the gap by the centrifugal force.

With the raw powder layers G1 and G2 formed on the inner peripheral surface of the outer frame 101 in this way, as shown in FIG. 6C, the shaft center 1a of the outer frame 101 and the shaft center 2a of the inner frame 102 are shown. And the inner frame 102 is pulled out from the outer frame 101 by moving the inner frame 102 upward as shown in FIG.
Subsequently, as shown in FIG. 6 (e), an arc discharge device comprising electrodes 104a, 104b and 104c as heating means is inserted into the outer frame 101 in a rotating state from above, and the electrodes 104a, 104b and 104c. The raw material powders G1 and G2 are vitrified by arc melting by the arc discharge heat generated in the arc.
Then, as shown in FIG. 7, the silica glass crucible 100 made of the synthetic silica glass layer F <b> 2, which is an apparently opaque natural silica glass layer F <b> 1 and the inner layer is transparent, which includes a large number of pores by the above-described manufacturing method. Is manufactured.

JP 2000-169164 A

By the way, since the transparent synthetic silica glass layer F2 of the inner layer of the silica glass crucible 100 is formed by arc melting in the atmosphere, not a few bubbles remain in the synthetic silica glass layer F2.
When such a silica glass crucible is used to pull up a silicon single crystal under reduced pressure, since the inside of the bubble A is atmospheric pressure, as shown in FIGS. A swells. When the transparent synthetic silica glass layer F2 on the inner surface side is eroded by the molten silicon melt, the bubbles A are mixed in the silicon melt, and the bubbles are taken into the pulled silicon single crystal.
As a result, there has been a technical problem that the bubbles taken into the silicon single crystal cause dislocations (crystal defects) due to crystal dislocations and reduce the single crystallization rate.

Further, a technique in which separation or chipping occurs in the transparent synthetic silica glass layer F2 of the silica glass crucible, and small pieces of the synthetic silica glass layer F2 are mixed into the silicon melt, thereby reducing the single crystallization rate. There was a problem.
Further, since the silica glass crucible is manufactured by arc melting, a large amount of carbon electrode is consumed during the manufacturing. For this reason, there is a technical problem that the cost of the carbon electrode increases and it takes time to replace the carbon electrode, which is not suitable for mass production.

In order to solve the above technical problem, the present inventors suppress bubbles existing in the inner layer as much as possible, suppress dislocation (crystal defects) due to crystal dislocation, and improve the single crystallization rate. Researched crucibles that are inexpensive and suitable for mass production. As a result, it was conceived that the inner peripheral surface of the crucible was a silica sintered body, and the silica sintered body was changed from silica sintered body to silica glass by the heat of fusion of polysilicon or the like to obtain a silica glass crucible.
However, when the crucible is silica glass, there is a problem that cracks and peeling occur when the silica sintered body on the inner peripheral surface of the crucible is densified or crystallized. As a result, the crucible body is also made of a silica sintered body, an inner layer made of a silica sintered body is provided on the inner peripheral surface of the outer layer made of silica sintered body, and the outer layer is crystallized by the heat of fusion of polysilicon or the like. The present inventors have completed the present invention by conceiving that a silica glass crucible is changed from a silica sintered body to a silica glass and a single crystal pulling is performed using this silica glass crucible.

It is an object of the present invention to provide a method for producing a silica sintered crucible that is inexpensive in cost and suitable for mass production.

In order to solve the problems described above, a method for producing a silica sintered crucible according to the present invention is obtained by molding a silica powder having a predetermined particle diameter, firing the molded body, and firing. A molded layer containing spherical silica particles having a predetermined particle diameter is formed on the inner peripheral surface of the sintered body, the molded layer is fired, and an inner layer of the sintered body is formed on the inner peripheral surface of the sintered body. And a step of forming a silica sintered body crucible.
In the silica sintered body crucible manufactured by such a method for manufacturing a silica sintered body crucible according to the present invention, when heat is applied, at least the inner layer of the silica sintered body crucible becomes dense and changes to silica glass.
Therefore, for example, at least the inner layer of the silica sintered crucible can be densified and converted to silica glass by heat generated when the polysilicon accommodated in the silica sintered crucible is melted. That is, in the pulling process of the silicon single crystal, it is possible to form a crucible in which the portion that comes into contact with the silicon melt is converted to silica glass.
Therefore, since the crucible can be formed without using a conventional means such as arc discharge, it can be manufactured inexpensively and efficiently.

  Here, a step of molding silica powder having a particle size of 0.1 μm or more and 5.0 mm or less, a step of removing the molded body from the mold and firing, and an inner peripheral surface of the sintered body obtained by the firing The inner layer coating liquid containing spherical silica particles having an average particle size of 10 μm or less and a full width at half maximum of 10 μm or more is applied to form a molding layer, and the molding layer is fired in the atmosphere. It is desirable to provide the process of forming the inner layer which consists of a sintered compact in an inner peripheral surface, and forming a silica sintered compact crucible.

  In addition, a slurry in which silica powder having a particle size of 0.1 μm or more and 5.0 mm or less is dispersed is supplied to a casting mold, and the molding is performed by depositing silica powder on the mold surface and molding the molded body from the casting mold. After removing the molded body and drying the molded body, spherical silica particles having an average particle diameter of 10 μm or less and a full width at half maximum of 10 μm or more are formed on the inner peripheral surface of the sintered body obtained by the firing. An inner layer coating solution is applied to form a molded layer, the molded layer is fired in the atmosphere, an inner layer made of a sintered body is formed on the inner peripheral surface of the sintered body, and a silica sintered crucible is formed. And forming the step.

In addition, the silica sintered compact crucible manufactured by the manufacturing method of the silica sintered compact crucible concerning this invention is filled with the raw material polysilicon lump in the said silica sintered compact crucible, and silica sintered compact under reduced pressure. disposed around the crucible, by heating the heater, at least an inner layer of silica sintered body crucible is densified, you change the silica glass.

As described above, in order to change from a sintered silica to silica glass in the melting step (heating step) of the polysilicon lump that is performed under reduced pressure, even if bubbles are mixed in the densified inner layer, silicon The bubbles do not expand in the single crystal pulling process, dislocation formation (crystal defects) due to crystal dislocation can be suppressed, and the single crystallization rate can be improved.
Further, in the silicon single crystal pulling process, since the bubbles in the densified inner layer do not expand, peeling or chipping is suppressed, and small pieces of the inner layer are also prevented from being mixed into the silicon melt. Dislocation (crystal defects) can be suppressed and the single crystallization rate can be improved.

Here, it is desirable that the inner layer of the sintered silica is at least densified and the outer layer is partially crystallized before the polysilicon lump starts to melt by the heating.
Further, it is desirable that the inner layer of the silica sintered body is at least densified by the heating before the polysilicon lump starts to melt, and then crystallized. The crystallization of the inner layer is preferably completed at the same time as the crystallization of the outer layer.

The present invention is economically cheap, it is possible to obtain a manufacturing method of a good optimal shea silica sintered crucible for mass production.

FIG. 1 is a flow chart sheet diagram showing the manufacturing process of the sintered silica crucible according to the present invention. FIG. 2 is a flowchart sheet showing a second manufacturing process of the sintered silica crucible according to the present invention. FIG. 3 is a partial cross-sectional view showing a silica sintered body crucible according to the present invention. FIG. 4 is a diagram showing the inner layer formation of the mouth portion of the sintered silica crucible according to the present invention. FIG. 5 is a schematic view showing a change from a sintered silica crucible to a silica glass crucible according to the present invention, and is a schematic view of a portion X in FIG. FIG. 6 is a diagram showing a manufacturing process of a conventional silica glass crucible. FIG. 7 is a cross-sectional view showing a conventional silica glass crucible. FIG. 8 is a schematic diagram showing a conventional silica glass crucible, which is a schematic diagram of a portion X in FIG. 7, (a) is a schematic diagram showing a state before pulling a single crystal, and (b) is under reduced pressure. It is a schematic diagram which shows the silicon single crystal pulling state in FIG.

Hereinafter, the manufacturing method of the silica sintered compact crucible concerning this invention is demonstrated based on FIG. 1 thru | or FIG. The method for producing the outer layer of the sintered silica crucible according to the present invention is a method for producing CIP (cold isostatic pressing), so-called casting (pressure casting, gel casting, slip casting, etc.), etc. Is adaptable.
First, a method for producing the outer layer (base) of the sintered silica crucible will be described.
CIP (cold isostatic pressing method) is a method in which a powder is filled between a metal inner mold (mandrel) and an outer mold, and molding is performed by applying hydrostatic pressure. This is a molding method in which the raw material powder having a blended particle size is filled in a rubber mold and pressed by dry molding so that the density of the molded body obtained is uniform.

  The slip casting method refers to casting a slip (also called slurry or slurry) prepared by mixing and dispersing raw material powder, dispersion medium, dispersant, binder, etc. into a mold made of a porous material such as gypsum. In this method, the liquid in the slip is absorbed by the capillary phenomenon of the mold, and solid particles are deposited on the surface of the mold to perform the wall forming.

[Outer layer manufacturing method 1]
First, a method for producing an outer layer (base) of a sintered silica crucible by CIP (cold isostatic pressing) will be described.
As shown in FIG. 1, a glycol plasticizer as a binder is mixed with silica powder having a particle size of 0.1 μm or more and 5.0 mm or less, and granulated by spray drying to prepare a granule raw material powder (S1 in FIG. 1). .
If the granule raw material powder contains a silica powder with a particle size of less than 0.1 μm, the powder particles are too fine and it is difficult to sufficiently fulfill the role as an aggregate for maintaining the strength of the crucible molding. It becomes. On the other hand, when the particle size contains more than 5.0 mm, the powder particles are too coarse, and voids are generated between the particles, which causes breakage of the crucible.

This raw material powder is filled between a metal inner mold having a crucible shape and a rubber mold (S2 in FIG. 1) and filled with a vibrator (S3 in FIG. 1). Thereafter, this rubber mold is molded at a pressure of 150 MPa or less with a cold isostatic press (S4 in FIG. 1). The molded body is removed from the mold (S5 in FIG. 1), and the molded body is fired in the air at 1200 ° C. or lower in an electric furnace (S6 in FIG. 1).
The outer layer (base) of the crucible is formed as a porous sintered body having a bulk specific gravity of 1.6 to 2.2 and a porosity of 7 to 15%. The thickness (wall thickness) of the outer layer (base) of the crucible is 5 mm to 20 mm.

[Outer layer manufacturing method 2]
Next, a method for producing the outer layer (base) of the sintered silica crucible by the slip casting method will be described.
As shown in FIG. 2, a slurry is prepared in addition to a solution in which silica powder having a particle size of 0.1 μm or more and 5.0 mm or less is dispersed (S21 in FIG. 2).
When the silica powder added to the slurry contains a silica powder having a particle size of less than 0.1 μm, the powder particles are too fine to sufficiently serve as an aggregate for maintaining the strength of the crucible molded body. It becomes difficult. On the other hand, when the particle size contains more than 5.0 mm, the powder particles are too coarse, and voids are generated between the particles, which causes breakage of the crucible.

The slurry is prepared by adding 90% by weight of the silica powder, which is a constituent material of the crucible, and 10% by weight of ion-exchanged water, followed by stirring and mixing.
In addition, as additives other than the crucible constituent materials such as the binder and the dispersant, those which are burned off during firing and do not affect the purity of the fused silica are used.

The slurry is supplied to a casting mold (gypsum mold) (S22 in FIG. 2), moisture in the slurry is absorbed by the capillary action of the mold (S23 in FIG. 2), and fused silica powder is deposited on the mold surface. Let the meat form.
Thereafter, the molded body is removed from the mold (S24 in FIG. 2), dried (S25 in FIG. 2), and then fired in the atmosphere at a temperature of 1200 ° C. or less (S26 in FIG. 2).
The outer layer (base) of the crucible is formed as a porous sintered body having a bulk specific gravity of 1.6 to 2.2 and a porosity of 7 to 15%. The thickness (wall thickness) of the outer layer (base) of the crucible is 5 mm to 20 mm.

The silica powder may be natural silica powder, synthetic silica powder, fused silica powder, or the like.
The silica powder is preferably high-purity silica powder. By using such high-purity silica powder, impurity contamination due to alkali metal or the like can be suppressed.
However, the silica powder constituting the outer layer (base) of the crucible may be low-purity silica. Impurity contamination may be suppressed by using a high-purity inner layer silica powder to be described later.

Next, a method for forming an inner layer on the sintered body will be described. The inner layer of the sintered body (outer layer) is manufactured by a so-called coating method (drainage method), spray coating method, spin coating method, or the like.
In the coating method (sludge method), the sintered body is immersed in the inner layer coating liquid, and a molding layer is formed on the inner peripheral surface of the sintered body by the inner layer coating liquid.
In the spray coating method, an inner layer coating liquid is sprayed on the inner peripheral surface of the sintered body, and a molding layer is formed on the inner peripheral surface of the sintered body with the inner layer coating liquid.
In the spin coating method, the inner layer coating liquid is put on the inner peripheral surface of the sintered body, and the sintered body is rotated to spread the inner layer coating liquid on the inner peripheral surface of the sintered body. To form.

[Inner layer manufacturing method]
The inner layer coating liquid is prepared by mixing and dispersing inner layer raw material powder (S7 in FIG. 1, S27 in FIG. 2), binder (S8 in FIG. 1, S28 in FIG. 2), a dispersion medium, and a dispersing agent. A molding layer is formed by the liquid (S9 in FIG. 1, S29 in FIG. 2).
Here, spherical silica particles are used as the inner layer raw material powder. For example, spherical silica particles having an average particle diameter of 10 μm or less and a full width at half maximum of 10 μm or more are used. You may use what mixed two or more spherical silica particles from which an average particle diameter differs so that an average particle diameter may be 10 micrometers or less and a full width at half maximum will be 10 micrometers or more.

Here, the spherical silica particles having an average particle diameter of 10 μm or less and a full width at half maximum of 10 μm or more are used to increase the filling rate of the molded body, reduce firing shrinkage, and prevent deformation.
The spherical silica particles used as the inner layer raw material powder are preferably high purity. By using a high-purity material in this way, it is possible to suppress impurity contamination of the single crystal that is pulled up.
Moreover, as said binder, an acrylic binder is used suitably, for example.

The inner layer coating solution thus adjusted is stirred and uniformly dispersed (S10 in FIG. 1 and S30 in FIG. 2).
Then, the inner layer coating liquid is applied to the inner surface of the manufactured sintered body, spray coating, and spin coating to form a molding layer by the inner layer coating liquid on the inner peripheral surface of the sintered body (outer layer) ( S11 in FIG. 1, S31 in FIG. This molding layer is formed to a thickness of 0.5 mm to 5 mm.
When forming this molding layer, as shown in FIG. 4, the molding layer may be formed in the mouth portion 1c of the crucible 1 to form the inner layer 1b. In this manner, by forming the inner layer 1 b at the mouth portion 1 c of the crucible 1, peeling of the inner layer 1 b formed on the inner peripheral surface of the crucible 1 can be suppressed. The inner layer 1b of the mouth portion 1c can be formed by immersing the mouth portion 1c in the inner layer coating liquid C stored in the tank 10.

Further, after drying the sintered body coated on the inner peripheral surface (S12 in FIG. 1, S32 in FIG. 2), the sintered body is fired in the atmosphere at a temperature of 1200 ° C. or less (S13 in FIG. 1, S33 in FIG. 2). . Thereby, the said shaping | molding layer (inner layer) is also formed as a sintered compact.
This inner peripheral surface (inner layer) is formed as a porous sintered body having a bulk specific gravity of 1.6 to 2.0 and a porosity of 19%. The inner peripheral surface (inner layer) has a thickness (wall thickness) of 0.5 mm to 5.0 mm.

In this way, the crucible 1 in which the outer layer (base) 1a and the inner layer 1b as shown in FIG. 3 are formed of a silica sintered body is manufactured.
In this silica sintered body crucible 1, the outer layer (substrate) 1a of the silica sintered body crucible is manufactured by CIP (cold isostatic pressing method) or slip cast method, and the inner layer 1b is formed by a coating method. It is inexpensive in cost and suitable for mass production.
In addition, although the coating liquid for inner layers was apply | coated to the inner surface of the manufactured sintered compact, the case where a shaping | molding layer (inner layer) was formed in the internal peripheral surface of a sintered compact (outer layer) was demonstrated. The method is not particularly limited, and for example, a method such as spray coating, brush coating, or dipping can be used, and any method can be used as long as the inner layer can be formed with a uniform thickness.
In the above production method, after molding silica powder having a predetermined particle diameter, firing the molded body, a molded layer containing spherical silica particles having a predetermined particle diameter on the inner peripheral surface of the sintered body The molding layer was fired to form an inner layer on the inner peripheral surface of the sintered body.
However, the production method according to the present invention is not limited to the above production method, and silica powder having a predetermined particle diameter is formed, and spherical silica particles having a predetermined particle diameter are contained on the inner peripheral surface of the formed body. A molded layer may be formed, the molded body on which the molded layer is formed is fired, and an inner layer may be formed on the inner peripheral surface of the sintered body. In this case, the sintered ceramic crucible can be efficiently manufactured with only one firing step.

Next, the usage method in the pulling process of the single crystal of the said silica sintered compact crucible is demonstrated. As the single crystal pulling apparatus, a general pulling apparatus can be used.
The sintered silica crucible 1 is placed in a single crystal pulling apparatus. As shown in FIG. 5A, the raw material polysilicon lump P is filled in the silica sintered crucible 1 and heated by a heater (single crystal pulling device) arranged around the sintered crucible. At this time, the inside of the single crystal pulling apparatus is in a reduced pressure state, and heating by the heater is performed under a reduced pressure. The reduced pressure state is preferably lower than the pressure at the time of pulling the single crystal.
When the temperature of the silica sintered body crucible 1 is increased by this heating, the inner layer 1b of the silica sintered body crucible 1 starts to be densified (reference numeral 1b1 in the figure indicates a densified portion). Further, the outer layer 1a begins to crystallize (reference numeral 1a1 in the drawing partially indicates a crystallized portion).
In addition, since the temperature of the silica sintered body crucible 1 is raised under reduced pressure, even if the air bubbles A inside the silica sintered body crucible 1 exist, the air bubbles A do not expand and are densified. (See FIGS. 5B to 5E).

Then, as shown in FIG. 5 (b), the inner layer 1b finishes densification until the temperature of the silica sintered body crucible 1 rises to 1400 ° C. (before the polysilicon lump starts to melt), and the silica sintered body The crucible 1 is formed as a silica glass crucible.
Further, the outer layer 1a is partially crystallized (reference numeral 1a1 in the figure indicates a part of the crystallized portion). That is, before the polysilicon lump starts to melt, the inner layer of the sintered silica is at least densified and a part of the outer layer is crystallized.

Further, as shown in FIG. 5C, crystallization (cristo ballasting) of the inner layer 1b starts.
When the temperature of the sintered silica crucible 1 exceeds 1420 ° C. (polysilicon lump starts to melt), the inner layer 1b and the outer layer 1a crystallize (cristobalite) and the raw material polysilicon P melting begins. In the figure, PL indicates a melt of the raw material polysilicon P.
Reference numerals 1a2 and 1b2 in the figure indicate crystallized portions. Then, as shown in FIG. 5 (d), the sintered silica crucible 1 is 1450 ° C., the melting of the raw material polysilicon P is completed, and this state of 1450 ° C. is maintained for 2 hours, thereby sintering the silica. Crystallization (cristoballasting) of the inner layer 1b and the outer layer 1a of the body crucible 1 is completed (see FIG. 5 (e)).
By this crystallization (cristoballasting), the mechanical strength is increased and the buckling deformation can be suppressed.

  After the sintered silica crucible 1 is formed as a silica glass crucible, the single crystal is pulled up by a general pulling method. Specifically, the crucible is rotated by a crucible rotation raising / lowering mechanism, the seed crystal attached to the chuck provided on the wire of the pulling mechanism is lowered, immersed in a raw material silicon melt, and then the wire is pulled by the pulling mechanism. Is gradually rolled up to grow a silicon single crystal.

Thus, in the densification and transparency of the sintered silica crucible 1, even if the bubbles A are taken into the inner layer 1b, the temperature of the sintered crucible 1 is increased under reduced pressure. The bubbles inside the body crucible 1 do not expand, and the bubbles A are not mixed into the silicon melt PL, and the bubbles are not taken into the pulled silicon single crystal.
In addition, since the so-called bubble bulging does not occur as described above, the inner layer 1b is hardly peeled off or chipped, and the accompanying decrease in the single crystallization rate can be suppressed. In addition, since the silica glass crucible is not manufactured by arc melting, the crucible can be manufactured inexpensively and efficiently without consuming a large amount of carbon electrodes during manufacturing.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not restrict | limited by the following Example.
[Example 1]
As shown in FIG. 1, a glycol plasticizer as a binder is mixed with fused silica powder having a particle size of 0.1 μm or more and 5.0 mm or less to prepare a raw material powder. This raw material powder was filled between a metal inner mold having a crucible shape and a rubber mold, and filled with a vibrator. Thereafter, this rubber mold was molded at a pressure of 150 MPa or less with a cold isostatic press. The molded body was removed from the mold, and the molded body was fired in the air at 1200 ° C. or lower in an electric furnace.
In addition, the thickness of this porous sintered body (outer layer) was formed to 5 mm to 20 mm.

A molding layer was formed on the inner peripheral surface of the sintered body (outer layer) obtained by this firing by a so-called coating method (a mud draining method). The inner layer coating solution for forming the molding layer was prepared by adding spherical silica powder having an average particle size of 10 μm (full width at half maximum: 15.5 μm) and an acrylic binder to prepare a slurry. Then, the inner layer coating liquid is applied to the inner circumferential surface of the manufactured sintered body (outer layer), thereby forming a 0.5 mm to 5.0 mm thickness on the inner circumferential surface of the sintered body (outer layer). A layer was formed.
The sintered body coated with the inner peripheral surface was dried at 100 ° C. or higher and then fired in the air at 1200 ° C. or lower. In this manner, a crucible having an outer layer (base) and an inner layer formed of a porous silica sintered body was formed.

  This sintered silica crucible was placed in a single crystal pulling apparatus. Then, the raw material polysilicon lump was filled in the silica sintered crucible, and heated under a reduced pressure from a heater (single crystal pulling device) arranged around the silica sintered crucible. The silica sintered crucible was maintained at 1450 ° C. for 2 hours, and the inner layer of the silica sintered crucible was densified and the outer layer was crystallized (cristo ballast).

Subsequently, the silicon single crystal was pulled under predetermined conditions. The pulling of the silicon single crystal was performed using 10 crucibles manufactured in the same manner. And about each crucible, the magnitude | size of the bubble contained in the inner layer after pulling up a silicon single crystal was observed with the optical microscope. In addition, when the silicon single crystal was pulled up by each crucible, the number of times of crystal remelting (meltback) due to occurrence of dislocation (crystal defects) was recorded. The results are shown in Table 1.
The size of the bubbles contained in the inner layer after pulling the silicon single crystal was 50 μm or less, and it was confirmed that the bubbles did not bulge. Further, meltback occurred in 1 out of 10 and was good.

[Example 2]
As shown in FIG. 2, a slurry in which silica powder having a particle size of 0.1 μm or more and 5.0 mm or less is dispersed is prepared. This slurry is prepared by adding 90% by weight of the silica powder, which is a constituent material of the crucible, and 10% by weight of ion-exchanged water, followed by stirring and mixing.
This slurry was supplied to a casting mold (gypsum mold) and then molded by depositing silica powder on the mold surface. The molded body was removed from the mold, and the molded body was dried at 100 ° C. or higher, and then fired in the air at a temperature of 1200 ° C. or lower in an electric furnace.
In addition, the thickness of this sintered compact (outer layer) was formed in 5 mm-20 mm.

An inner layer was formed on the inner peripheral surface of the sintered body (outer layer) obtained by this firing by a so-called coating method (a mud draining method). The inner layer coating solution for forming the inner layer was prepared by adding spherical silica particles having an average particle diameter of 10 μm (full width at half maximum: 15.5 μm) and an acrylic binder to prepare a slurry. Then, the inner layer coating liquid is applied to the inner circumferential surface of the manufactured sintered body (outer layer), thereby forming a 0.5 mm to 5.0 mm thickness on the inner circumferential surface of the sintered body (outer layer). A layer was formed.
In addition, the sintered body on which the molding layer is formed is dried at 100 ° C. or higher and then fired in the atmosphere at a temperature of 1200 ° C. or lower. In this manner, a crucible having an outer layer (base) and an inner layer formed of a porous silica sintered body was formed.

This silica sintered crucible was placed in a single crystal pulling apparatus in the same manner as in Example 1, the inner layer of the silica sintered crucible was densified, and the outer layer was crystallized (cristoballast). Crystals were pulled up. The pulling of the silicon single crystal was performed using 10 crucibles manufactured in the same manner. And about each crucible, the magnitude | size of the bubble contained in the inner layer after pulling up a silicon single crystal was observed with the optical microscope. In addition, when the silicon single crystal was pulled up by each crucible, the number of times of crystal remelting (meltback) due to occurrence of dislocation (crystal defects) was recorded. The results are shown in Table 1.
The size of the bubbles contained in the inner layer after pulling the silicon single crystal was 50 μm or less, and it was confirmed that the bubbles did not bulge. In addition, meltback occurred in 0 out of 10 and was good.

[Example 3]
An inner layer was formed on the inner peripheral surface of the sintered body (outer layer) formed in the same manner as in Example 2 by a so-called spray coating method. The inner layer coating liquid for forming the inner layer was prepared by adding spherical silica powder having an average particle size of 10 μm (full width at half maximum: 15.5 μm) and an acrylic binder to prepare a slurry. The slurry viscosity was adjusted to 0.5 poise or less. And by applying this inner layer coating liquid to the inner peripheral surface of the sintered body (outer layer) with a gravity air spray gun, the inner peripheral surface of the sintered body (outer layer) has a thickness of 0.5 mm to A 5.0 mm molded layer was formed.
The sintered body on which the molding layer was formed was dried at 100 ° C. or higher and then fired in the air at 1200 ° C. or lower. In this manner, a crucible having an outer layer (base) and an inner layer formed of a porous silica sintered body was formed.

This silica sintered crucible was placed in a single crystal pulling apparatus in the same manner as in Example 1, the inner layer of the silica sintered crucible was densified, and the outer layer was crystallized (cristoballast). Crystals were pulled up. The pulling of the silicon single crystal was performed using 10 crucibles manufactured in the same manner. And about each crucible, the magnitude | size of the bubble contained in the inner layer after pulling up a silicon single crystal was observed with the optical microscope. In addition, when the silicon single crystal was pulled up by each crucible, the number of times of crystal remelting (meltback) due to occurrence of dislocation (crystal defects) was recorded. The results are shown in Table 1.
The size of the bubbles contained in the inner layer after pulling the silicon single crystal was 50 μm or less, and it was confirmed that the bubbles did not bulge. Further, meltback occurred in 1 out of 10 and was good.

[Example 4]
An inner layer was formed on the inner peripheral surface of the sintered body (outer layer) formed in the same manner as in Example 2 by a so-called spin coating method. The inner layer coating liquid for forming the inner layer was prepared by adding spherical silica powder having an average particle size of 10 μm (full width at half maximum: 15.5 μm) and an acrylic binder to prepare a slurry. The slurry viscosity was adjusted to 0.75 poise or less.
Then, the sintered body (outer layer) is inserted into an automatic spin coating apparatus having an eccentric rotation drive, and after the inner layer coating liquid slurry is charged, the sintered body (outer layer) is rotated at a rotation speed of 200 rpm or less to be sintered. By applying to the inner peripheral surface of the body (outer layer), a molded layer having a thickness of 0.5 mm to 5.0 mm was formed on the inner peripheral surface of the sintered body (outer layer).
The sintered body on which the molding layer was formed was dried at 100 ° C. or higher and then fired in the air at 1200 ° C. or lower. In this manner, a crucible having an outer layer (base) and an inner layer formed of a porous silica sintered body was formed.

This silica sintered crucible was placed in a single crystal pulling apparatus in the same manner as in Example 1, the inner layer of the silica sintered crucible was densified, and the outer layer was crystallized (cristoballast). Crystals were pulled up. The pulling of the silicon single crystal was performed using 10 crucibles manufactured in the same manner. And about each crucible, the magnitude | size of the bubble contained in the inner layer after pulling up a silicon single crystal was observed with the optical microscope. In addition, when the silicon single crystal was pulled up by each crucible, the number of times of crystal remelting (meltback) due to occurrence of dislocation (crystal defects) was recorded. The results are shown in Table 1.
The size of the bubbles contained in the inner layer after pulling the silicon single crystal was 50 μm or less, and it was confirmed that the bubbles did not bulge. Further, meltback occurred in 1 out of 10 and was good.

[Comparative Example 1]
In the same manner as in the prior art, ten silica glass crucibles were produced by molding and arc melting, and the silicon single crystal was pulled under the same conditions as in Example 1.
And about each crucible, the magnitude | size of the bubble contained in the inner layer after pulling up a silicon single crystal was observed with the optical microscope. In addition, when the silicon single crystal was pulled up by each crucible, the number of times of crystal remelting (meltback) due to occurrence of dislocation (crystal defects) was recorded. The results are shown in Table 1.
The size of bubbles contained in the inner layer after pulling the silicon single crystal was 500 μm to 1 mm, and it was confirmed that the bubbles were swollen. Further, meltback occurred in 3 out of 10 pieces, and the pulling efficiency of the silicon single crystal was low due to the meltback, which was not good.

  Thus, in Examples 1 to 4, it was recognized that dislocations (crystal defects) due to crystal dislocations were suppressed and the single crystallization rate was improved.

DESCRIPTION OF SYMBOLS 1 Silica sintered body crucible 1a Outer layer 1a1 Outer layer part crystallization part 1a2 Outer layer crystallization part 1b Inner layer 1b1 Inner layer densification part 1b2 Inner layer crystallization part A Bubble C Inner layer coating liquid P Polysilicon lump PL Silicon melt PL

Claims (3)

A method for producing a silica sintered crucible,
Forming a silica powder having a predetermined particle size;
Firing the molded body;
A molded layer containing spherical silica particles having a predetermined particle diameter is formed on the inner peripheral surface of the sintered body obtained by the firing, the molded layer is fired, and the inner peripheral surface of the sintered body is sintered. Forming an inner layer of the body and forming a silica sintered body crucible;
A method for producing a sintered silica crucible, comprising: Forming a silica powder having a particle size of 0.1 μm or more and 5.0 mm or less;
Removing the molded body from the mold and firing;
On the inner peripheral surface of the sintered body obtained by the firing, an inner layer coating liquid containing spherical silica particles having an average particle diameter of 10 μm or less and a full width at half maximum of 10 μm or more is applied to form a molding layer, Firing the molding layer in the atmosphere, forming an inner layer made of the sintered body on the inner peripheral surface of the sintered body, and forming a silica sintered body crucible;
A method for producing a sintered silica crucible according to claim 1, comprising: Supplying a slurry in which silica powder having a particle size of 0.1 μm or more and 5.0 mm or less is dispersed to a casting mold, and depositing the silica powder on the mold surface to form the slurry;
Removing the molded body from the casting mold, drying the molded body, and then firing;
On the inner peripheral surface of the sintered body obtained by the firing, an inner layer coating liquid containing spherical silica particles having an average particle diameter of 10 μm or less and a full width at half maximum of 10 μm or more is applied to form a molding layer, Firing the molding layer in the atmosphere, forming an inner layer made of the sintered body on the inner peripheral surface of the sintered body, and forming a silica sintered body crucible;
A method for producing a sintered silica crucible according to claim 1, comprising:

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