JP5608258B1 - Silica container for pulling single crystal silicon and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress melt surface vibration of a silicon melt in a silica container at a high temperature and suppress generation of void defects called voids and pinholes in single crystal silicon in all steps of pulling single crystal silicon. Provided is a silica container for pulling single crystal silicon, and a method for producing such a silica container.
A single crystal silicon pulling silica container having a straight body part, a curved part, and a bottom part, wherein the outer side of the container is made of opaque silica glass containing bubbles and the inner side of the container is made of transparent silica glass. In the body portion, the curved portion, and the inner surface layer portion of the bottom portion, the bottom portion has a mixed silica layer in which a phase in which crystalline silica powder is melted and a phase in which amorphous silica powder is melted are mixed in a granular form. A silica container for pulling a single crystal silicon having a bottom silica glass layer on the inner surface.
[Selection] Figure 1

Description

  The present invention relates to a silica container for pulling up single crystal silicon and a method for manufacturing the same.

Conventionally, as a method for producing a silica crucible for pulling a single crystal silicon, production methods as described in Patent Document 1 and Patent Document 2 have been used. In these methods, high-purity quartz powder is put into a rotating mold, and after molding, an electrode is pushed in from the top and an electric discharge is applied to the electrode to cause an arc discharge. In the melting temperature range (estimated to be about 1800 to 2100 ° C.) to melt and sinter the quartz powder. However, when using such a manufactured silica crucible, molten silicon and the silica crucible react to produce silicon monoxide (SiO) gas, which is taken in as bubbles (gas bubbles) into the single crystal silicon, and voids and There were problems in the quality of single crystal silicon such as the formation of void defects called pinholes.

In particular, in the CZ method (Czochralski method), which is a general pulling method of single crystal silicon, a seed is used as a molten silicon melt surface in a silica container called a crucible (hereinafter also simply referred to as “hot water surface”). Crystal seeding (seeding), then growing the seed crystal with a slightly reduced diameter (necking), then expanding the diameter to produce a large diameter single crystal silicon (shoulder ring), followed by the large diameter single crystal silicon A single crystal silicon having a long axis dimension is taken out by pulling up while keeping the diameter constant. During this pulling up, a phenomenon that the molten silicon melt surface vibrates (hereinafter, this phenomenon is simply referred to as “molten surface vibration”) occurs. When this molten metal surface vibration occurs, seeding, necking and shouldering cannot be performed, and a part of single crystal silicon is polycrystallized during pulling. As one of the causes, molten metal surface vibration due to generation of silicon oxide (SiO) gas has been considered. In the silica crucible manufactured in Patent Documents 1 and 2, a large container having a diameter of 30 inches (75 cm) to 54 inches (135 cm) for pulling large-diameter single crystal silicon having a diameter of 12 inches (30 cm) to 18 inches (45 cm). In such a case, since a strong hot water surface vibration is frequently generated, an immediate solution has been demanded. Hereinafter, silica crucible and quartz crucible are synonymous. Silica glass and quartz glass are synonymous.

Patent Document 3 discloses that the IR (infrared) transmittance of the wall of the crucible is set to 3 to 30% as a quartz glass crucible that does not cause molten metal surface vibration of molten silicon. However, even when a large quartz glass crucible having such a wide transmittance range of properties is used, the molten metal surface vibration during pulling up of the large-diameter single crystal silicon cannot be suppressed.

In Patent Document 4, as a method for producing a quartz glass crucible in which no molten silicon surface vibration occurs, it is shown that water vapor is introduced into the atmosphere inside the crucible during crucible production, and the OH group concentration in the entire surface layer inside the crucible is shown. It is said that it is preferable to increase the hot water surface vibration. However, even if a large-sized quartz glass crucible by such a manufacturing method is used, the effect of suppressing the molten metal surface vibration when pulling up the large-diameter single crystal silicon is insufficient. In addition, the crucible inner surface was severely eroded (etched) by the silicon melt, and the life of the crucible was short.

Patent Document 5 shows that in a quartz glass crucible when pulling up single crystal silicon, molten metal surface vibration can be prevented by using only natural belt-like portions on the inner surface of the quartz glass crucible near the molten silicon surface. . However, this crucible is such that the molten metal surface vibration is relatively less than that of the fully synthetic quartz glass crucible, and the effect of suppressing the molten metal surface vibration when pulling up the large-diameter single crystal silicon is insufficient.

In Patent Document 6, it is shown that the molten metal surface vibration can be prevented by distributing a portion having a large bubble content on the inner surface of the quartz glass crucible near the molten metal surface of the molten silicon in a band shape. However, although this crucible shows a certain level of molten metal surface vibration suppression effect, the amount of erosion (etching) by the molten silicon in the band-shaped portion having a high bubble content is large, and the life of the crucible has become short. In addition, there is a high probability that bubbles contained in the band-like portion are taken into the single crystal silicon, and void defects such as voids and pinholes are often generated in the single crystal silicon.

In Patent Document 7, it is shown that the melt level of molten silicon can be prevented by homogenizing the bubble content, thickness, and transmittance of a quartz glass crucible having rotational axis symmetry over the circumference. It is considered that it is fundamentally important to make various physical properties of the crucible symmetrically about the axis of rotation with high precision from the viewpoint of preventing the molten metal surface vibration. However, it has been required to prevent the molten metal surface vibration even if some physical property fluctuation occurs.

Patent Document 8 shows that by providing a plurality of minute recesses on the inner surface of the quartz glass crucible near the molten silicon melt surface, and by providing a plurality of bubbles below it, the melt surface vibration can be prevented. However, although this crucible can suppress the initial molten metal surface vibration in the production of single crystal silicon, there is a problem that vibration occurs again after the minute recess is dissolved. In particular, when a plurality of single crystal silicons are pulled up (multiple pulling), there is a case where the molten metal surface vibration during the second and subsequent manufacturing becomes intense.

In Patent Document 9, it is shown that a rough surface region can be produced in a band shape by performing sand blasting treatment using quartz powder on the inner surface of the quartz glass crucible, and the molten metal surface vibration can be prevented. However, although such a crucible can suppress the initial surface vibration during the production of single crystal silicon, the effect does not last long. In addition, it was difficult to perform multiple pulling with one crucible.

Patent Document 10 shows that molten metal surface vibration can be prevented by melting silica powder on the inner surface of a quartz crucible with an oxyhydrogen flame and depositing a silica glass layer containing 500 to 1500 ppm of OH groups. Yes. However, this manufacturing method not only makes the process complicated and expensive, but also causes the disadvantage that the etching with the silicon melt near the molten metal surface is large, so that the molten metal surface vibration gradually increases and the crucible life is shortened. It was.

Japanese Patent Publication No.4-222861 Japanese Patent Publication No. 7-29871 JP 2000-219593 A JP 2001-348240 A Japanese Patent No. 4338990 Japanese Patent No. 4390461 JP 2010-30884 A JP 2011-105552 A International Publication No. WO2011 / 158712 Pamphlet JP 2012-17240 A

  The present invention has been made in view of the above-described problems. In all steps of pulling up the single crystal silicon, it is possible to suppress the surface vibration of the silicon melt in the silica container at a high temperature, and in the single crystal silicon. An object of the present invention is to provide a single crystal silicon pulling silica container capable of suppressing the generation of void defects called voids and pinholes, and a method for producing such a silica container.

  The present invention has been made in order to solve the above problems, and is a method for producing a silica container for pulling a single crystal silicon having a straight body portion, a curved portion, and a bottom portion. For producing a crystalline silica powder having a particle size of 10 to 1000 μm, and as a second raw material powder, a crystalline silica powder having a particle size of 50 to 2000 μm and an amorphous silica powder having a particle size of 50 to 2000 μm And a step of preparing a crystalline silica powder having a particle size of 10 to 1000 μm as the third raw material powder, and the first raw material powder to form a mold having rotational symmetry And forming the first temporary molded body made of the first raw material powder in the mold frame by rotating the mold frame and temporarily forming it into a predetermined shape corresponding to the inner wall of the mold frame. And a first step of forming the second raw material powder in the mold A second temporary molded body having a portion made of the first raw material powder and a portion made of the second raw material powder put into the inside of the temporary molded body is shaped according to the shape of the silica container to be manufactured, and Forming the portion made of the second raw material powder at a position corresponding to the inner surface layer portion of the straight body portion, the curved portion, and the bottom portion of the silica container to be manufactured, and rotating the mold Meanwhile, by heating from the inside of the second temporary molded body by the electric discharge heating melting method, a portion of the second temporary molded body made of the second raw material powder is melted with the crystalline silica powder. A straight silica body, curved, with a mixed silica layer in which a phase in which amorphous silica powder is melted is mixed in a granular form, and the outside of the container is made of opaque silica glass containing bubbles and the inside of the container is made of transparent silica glass And A step of producing a silica container having a bottom part, and the third raw material powder is melted by a discharge heating melting method while spraying the third raw material powder from the upper part of the silica container, and the melted third raw material powder is applied to the inner surface portion of the bottom part And a step of forming a bottom silica glass layer to provide a method for producing a single crystal silicon pulling silica container.

  By the method for manufacturing a silica container having such a process, a phase in which the crystalline silica powder is melted and a phase in which the amorphous silica powder is melted are mixed in a granular form in the straight body portion, the curved portion, and the inner surface layer portion of the bottom portion. A single-crystal silicon pulling silica container having a bottom silica glass layer on the inner surface of the bottom mixed silica layer can be manufactured. The portion where the mixed silica layer is exposed that is not covered by the bottom silica glass layer is subjected to etching (erosion) by the silicon melt when the raw silicon melt is held inside the silica container. In this etching, the phase in which the amorphous silica powder is melted is faster and the etching amount is larger than the phase in which the crystalline silica powder is melted. Due to this difference in etching effect, minute irregularities are formed on the surface of the mixed silica layer (interface with the raw material silicon melt). Due to the presence of the minute irregularities, it is possible to suppress the surface vibration of the silicon melt in the silica container at a high temperature. In addition, even if etching of the mixed silica layer proceeds due to the use at high temperature for a long time, the minute irregularities continue to exist without disappearing, so that the molten metal surface vibration of the silicon melt is suppressed for a long time. be able to.

  In addition, since the mixed silica layer is exposed on the inner surface of the silica container in the straight body part and the curved part, this silica container is an initial stage of the method of pulling up the single crystal silicon (seeding, necking, shoulder ring, etc. ) And subsequent stages (pulling, tailing) of the melt surface of the silicon melt can be effectively suppressed. Further, since the bottom of the silica container is covered with the bottom silica glass layer, the bottom does not have irregularities due to the mixed silica layer, and there is no growth of gas bubbles. Therefore, generation | occurrence | production of the void defect called the void and pinhole in single crystal silicon resulting from the gas bubble in a silicon melt can be suppressed.

  In this case, it is preferable to form the mixed silica layer as a silica container having a thickness in the thickness direction of 2 mm or more.

  By forming the mixed silica layer having such a thickness, it is possible to more reliably suppress the molten metal surface vibration of the raw material silicon melt in the manufactured silica container and maintain the effect.

  Moreover, it is preferable to heat the second temporary molded body by a discharge heating melting method while reducing the pressure from the outside of the second temporary molded body.

By performing the heating while reducing the pressure in this way, the opaque silica glass on the outside of the container and the transparent silica glass on the inside of the container can be efficiently produced.

  In the second raw material powder, it is preferable that the crystalline silica powder has an OH group concentration of 50 mass ppm or less, and the amorphous silica powder has an OH group concentration of 200 to 2000 ppm.

  By setting the OH group concentration in both silica powders constituting the second raw material powder in this way, the phase of the mixed silica layer to be produced is a phase in which the crystalline silica powder is melted and a phase in which the amorphous silica powder is melted. The etching rate difference with respect to the silicon melt can be made more prominent, and irregularities on the inner surface of the silica container can be more reliably formed.

  The concentration of the impurity element of the second raw material powder is 100 massppb or less for each of Li, Na, and K, 50 massppb or less for each of Ca and Mg, Ti, Cr, Fe, Ni, Cu, Zn, Zr, Mo , W and Pb are preferably 20 massppb or less.

  If the impurity element concentration of the second raw material powder is set in this way, the impurity element taken into the raw material silicon melt when the mixed silica layer to be produced is etched can be reduced.

  Further, the present invention is a single crystal silicon pulling silica container having a straight body part, a curved part, and a bottom part, the container outer side is made of opaque silica glass containing bubbles, and the container inner side is made of transparent silica glass, In the inner surface layer portion of the straight body portion, the curved portion, and the bottom portion, a mixed silica layer in which the phase in which the crystalline silica powder is melted and the phase in which the amorphous silica powder is melted is mixed in a granular form, and the bottom portion is mixed There is provided a silica container for pulling up single crystal silicon, characterized by having a bottom silica glass layer on the inner surface of a silica layer.

  The silica container having such a configuration of the mixed silica layer and the bottom silica glass layer has minute irregularities formed on the surface of the mixed silica layer by etching with the silicon melt when the raw material silicon melt is held inside. The Due to the presence of the minute irregularities, it is possible to suppress the surface vibration of the silicon melt in the silica container at a high temperature. Further, in this silica container, since the mixed silica layer is exposed on the inner surface of the silica container in the straight body part and the curved part, the silicon fusion in the initial stage of the method of pulling up the single crystal silicon and the stage after that. Liquid surface vibration of the liquid can be effectively suppressed. In addition, by covering the bottom of the silica container with the bottom silica glass layer, it is possible to suppress the occurrence of void defects called voids or pinholes in the single crystal silicon caused by gas bubbles in the silicon melt.

  In this case, it is preferable that the mixed silica layer is formed using a mixed powder of crystalline silica powder having an OH group concentration of 50 massppm or less and amorphous silica powder having an OH group concentration of 200 to 2000 ppm as a raw material.

  The mixed silica layer is formed by using a mixed powder of two types of silica powder having a difference in OH group concentration as a raw material, so that the crystalline silica powder of the mixed silica layer is melted and amorphous The difference in etching rate with respect to the silicon melt of the phase in which the silica powder is melted can be made more prominent, and irregularities on the inner surface of the silica container can be more reliably formed.

  The concentration of the impurity element in the mixed silica layer is 100 massppb or less for each of Li, Na, and K, 50 massppb or less for each of Ca and Mg, Ti, Cr, Fe, Ni, Cu, Zn, Zr, Mo, W, It is preferable that it is 20 massppb or less for each of Pb.

  By setting the impurity element concentration of the mixed silica layer in this way, it is possible to reduce the impurity element taken into the raw silicon melt when the mixed silica layer is etched.

  According to the manufacturing method of the silica container for pulling up single crystal silicon according to the present invention, the phase in which the crystalline silica powder is melted and the phase in which the amorphous silica powder is melted are obtained in the straight body portion, the curved portion, and the inner surface layer portion of the bottom portion. A single crystal silicon pulling silica container having a mixed silica layer mixed in a granular form and having a bottom silica glass layer on the inner surface of the bottom mixed silica layer can be produced.

  In the silica container for pulling single crystal silicon according to the present invention having such a mixed silica layer and a bottom silica glass layer, the amorphous silica powder constituting the mixed silica layer is formed when the raw material silicon melt is held inside. Due to the difference in etching effect between the melted phase and the phase in which the crystalline silica powder is melted, minute irregularities are formed on the surface of the mixed silica layer. Due to the presence of the minute irregularities, it is possible to suppress the surface vibration of the silicon melt in the silica container at a high temperature. In addition, even if etching of the mixed silica layer proceeds due to the use at high temperature for a long time, the minute irregularities continue to exist without disappearing, so that the molten metal surface vibration of the silicon melt is suppressed for a long time. The effect can be maintained. Since the effect of preventing the molten metal surface vibration for a long time continues, it is particularly effective for multi-pulling of single crystal silicon, and the life of the silica container can be extended. Further, in this silica container, since the mixed silica layer is exposed on the inner surface of the silica container in the straight body part and the curved part, the silicon fusion in the initial stage of the method of pulling up the single crystal silicon and the stage after that. Liquid surface vibration of the liquid can be effectively suppressed. In addition, by covering the bottom of the silica container with the bottom silica glass layer, it is possible to suppress the occurrence of void defects called voids or pinholes in the single crystal silicon caused by gas bubbles in the silicon melt.

It is a schematic sectional drawing which shows typically an example of the structure of the silica container which concerns on this invention. It is a schematic sectional drawing which shows typically another example of the structure of the silica container which concerns on this invention. It is a flowchart which shows the outline of an example of the manufacturing method of the silica container which concerns on this invention. It is a schematic sectional drawing which shows an example of the mold which can be used in the manufacturing method of the silica container which concerns on this invention. It is a schematic sectional drawing which shows another example of the formwork which can be used in the manufacturing method of the silica container which concerns on this invention. It is a schematic sectional drawing which shows typically an example of the process of forming the 1st temporary molded object in the manufacturing method of the silica container which concerns on this invention. It is a schematic sectional drawing which shows typically an example of the process of forming the 2nd temporary molded object in the manufacturing method of the silica container which concerns on this invention. It is a schematic sectional drawing which shows typically a part of example of the process of heating the 2nd temporary molded object (before discharge heating melting) in the manufacturing method of the silica container which concerns on this invention. It is a schematic sectional drawing which shows typically a part (during discharge heating melting) of an example of the process of heating the 2nd temporary molded object in the manufacturing method of the silica container which concerns on this invention. It is a schematic sectional drawing which shows typically an example of the process of forming the bottom part silica glass layer in the manufacturing method of the silica container which concerns on this invention. It is a schematic sectional drawing which shows the structure of the silica container of the comparative example 1 typically. It is a schematic sectional drawing which shows the structure of the silica container of the comparative example 2 typically. It is a schematic sectional drawing which shows typically the structure of the silica container of the comparative example 3. It is a schematic sectional drawing which shows the structure of the silica container of the comparative example 4 typically.

  The silica container for pulling single crystal silicon according to the present invention contains therein polycrystalline silicon or the like as a raw material for single crystal silicon, and melts the polycrystalline silicon or the like to form a raw material silicon melt. It is for pulling up crystalline silicon. The silica container of the present invention can be used as a silica container for pulling up single crystal silicon used for large-scale integrated circuits (LSIs) or photovoltaic power generation (solar cells, PV).

  Hereinafter, the silica container for pulling a single crystal silicon according to the present invention and the manufacturing method thereof will be described in detail with reference to the drawings, but the present invention is not limited thereto. Hereinafter, a crucible of a large-diameter silica container for producing single crystal silicon will be described as an example. In addition, the silica container of this invention shows a silica crucible.

Examples of the structure of the single crystal silicon pulling silica container according to the present invention are shown in FIGS. As shown in FIG. 1, the silica container 74 according to the present invention has a crucible shape having rotational axis symmetry, and includes a straight body portion 61, a curved portion 62, and a bottom portion 63. At this time, 1/3 of the outer diameter (D ₁ ) of the silica container 74 is defined as the diameter (D ₂ ) of the bottom 63 for convenience. The bottom 63 is a circular portion. The straight body portion 61 is a cylindrical portion between the upper edge of the silica container 74 and a height portion that is 1/3 of the height (H ₁ ) (height H ₁ -H ₂ ). Further, the portion other than the bottom portion 63 is defined as the curved portion 62 from the height portion of 1/3 of the height (H ₁ ) of the silica container 74 to the bottom portion 63 (height H ₂ ).

  The silica container 74 has a mixed silica layer 53 in the inner surface layer portion of the straight body portion 61, the curved portion 62, and the bottom portion 63, and has a bottom silica glass layer 55 on the inner surface of the mixed silica layer 53 in the bottom portion 63. . The mixed silica layer 53 is formed by mixing a phase in which crystalline silica powder is melted and a phase in which amorphous silica powder is melted in a granular form. The mixed silica layer 53 is not uniform and has a fine granular structure in units of several hundred μm to several thousand μm. More specifically, the phase in which the crystalline silica powder constituting the mixed silica layer 53 is melted is made of crystalline silica powder such as quartz powder, quartz powder, cristobalite powder, etc., and the amorphous constituting the mixed silica layer 53. The phase in which the porous silica powder is melted is made of an amorphous silica powder such as a synthetic silica glass powder by a flame hydrolysis method or a fused silica glass powder by a Bernoulli oxyhydrogen method. That is, the mixed silica layer 53 is a silica layer obtained by melting and mixing these mixed powders.

The silica container 74 is made of opaque silica glass containing bubbles on the outside of the container, and transparent silica glass on the inside of the container. By adopting such a two-layer structure in the silica container 74, it is possible to ensure heat uniformity inside the silica container 74 when the silica container at a high temperature is used. This opaque silica glass is usually white opaque. Transparent silica glass is transparent because it contains substantially no bubbles, and is usually colorless and transparent. The bulk density of the opaque silica glass 51 is about 1.90 to 2.15 (g / cm ³ ), and the bulk density of the transparent silica glass 52 is approximately 2.20 (g / cm ³ ). In order to show the position of the mixed silica layer 53, for the sake of convenience, the opaque silica glass 51 and the transparent silica glass 52 are shown in the drawing for portions other than the mixed silica layer 53. Actually, the mixed silica layer 53 is also made of opaque silica glass in the portion located in the outer region of the container, and made of transparent silica glass in the region located in the inner region of the container.

  When a silicon melt is held as a raw material for pulling up single crystal silicon in the silica container 74, the silica container is caused by a reaction (melting reaction) between the silica component constituting the inner surface of the silica container 74 and the silicon melt. The inner surface of 74 is subjected to etching (erosion) by silicon melt. At this time, in the portion where the mixed silica layer 53 is exposed, which is not covered with the bottom silica glass layer 55, the etching amount of the phase in which the crystalline silica powder is melted is more than the phase in which the amorphous silica powder is melted ( Since the erosion amount is small (that is, the etching rate is low), the part of the granular structure of the phase in which the crystalline silica powder is melted becomes a convex part, and the phase in which the amorphous silica powder is melted becomes a concave part. Due to the difference in the etching effect, minute irregularities are formed on the surface of the mixed silica layer 53 (interface with the raw material silicon melt), which changes to a rough surface. Due to the generation of this rough surface, it is difficult for fine vibrations to occur on the molten silicon surface in the silica container at high temperatures, and even if it occurs, the surface vibrations generated like waves are suppressed by the rough surface. It will be possible. This is similar to the phenomenon that the wave of the sea surface can be stopped by placing a tetrapod wave block on the coast. Thus, the mixed silica layer 53 functions as a molten metal surface vibration suppression layer.

  Further, even if the mixed silica layer 53 is etched due to the use at a high temperature for a long time, in the silica container 74 of the present invention, since the mixed silica layer 53 has a certain thickness, minute unevenness (roughness) The surface) continues to exist without disappearing, and the molten metal surface vibration of the silicon melt can be suppressed for a long time. Since the effect of preventing molten metal surface vibration continues for a long time, it is particularly effective for multi-pulling of single crystal silicon.

  The mixed silica layer 53 is formed so as to be located on the straight body portion, the curved portion, and the inner surface layer portion of the bottom portion of the silica container 74. As shown in FIG. 1, the mixed silica layer 53 does not have to be formed in a certain range from the upper end of the straight body portion not in contact with the silicon melt, but the silica container 74 holds the raw silicon melt. It includes a position on the inner surface corresponding to the initial melt surface (initial hot water surface). Further, as shown in FIG. 2, all of the straight body portion, the curved portion, and the inner surface layer portion of the bottom portion of the silica container 74 may be a mixed silica layer 53. In FIG. 2, the transparent silica glass (“transparent silica glass 52” in FIG. 1) is not shown for the sake of convenience, but in reality, the portion of the mixed silica layer 53 located in the region inside the container is transparent silica. There is a part made of glass.

  In the silica container 74, since the mixed silica layer 53 is exposed on the inner surface in the straight body portion 61 and the curved portion 62, the initial stage of the method for pulling up the single crystal silicon (seeding, necking, shoulder ring, etc.) and the It is possible to effectively suppress the melt level vibration of the silicon melt at a later stage (pulling, tailing). Since the molten metal surface vibration in all steps of single crystal silicon pulling can be suppressed, it is particularly suitable for multi-pulling of three or more single crystal silicon.

  The reason why the bottom silica glass layer 55 is formed on the inner surface of the bottom 63 of the silica container 74 is that the diameter of the bottom 63 of the silica container 74 approximates the diameter of single crystal silicon to be manufactured. When the surface of the mixed silica layer 53 is present at the bottom 63 of the silica container 74, irregularities are also generated on the inner surface of the bottom 63 during the production of the single crystal, and the surface changes to a rough surface. When silica glass reacts with the silicon melt in this state, silicon oxide (SiO) gas is generated, gas bubbles grow on the uneven surface of the bottom 63, and then the gas bubbles rise into the silicon melt. Therefore, it is taken into the growing single crystal silicon, and void defects called voids and pinholes are likely to occur. Since the bottom 63 of the silica container 74 of the present invention is covered with the bottom silica glass layer 55, the inner surface of the bottom 63 does not have irregularities due to the mixed silica layer 55, and there is no growth of gas bubbles. Therefore, generation | occurrence | production of the void defect called the void and pinhole in single crystal silicon resulting from the gas bubble in a silicon melt can be suppressed.

  In the case of the silica container 74 according to the present invention, a large diameter of 30 inches (75 cm) to a diameter of 54 inches (135 cm) for pulling a large diameter single crystal silicon having a diameter of 12 inches (30 cm) to a diameter of 18 inches (45 cm). Even in the large-diameter silica container, the molten metal surface vibration can be suppressed over the entire process of pulling up the single crystal silicon.

  The mixed silica layer 53 preferably has a thickness in the thickness direction of the silica container 74 of 2 mm or more. The mixed silica layer 53 is gradually etched and thinned during use of the silica container at a high temperature while holding the raw material silicon melt. By making the thickness of the mixed silica layer 53 2 mm or more, It is possible to more reliably suppress the molten metal surface vibration of the raw material silicon melt for a long time.

  The mixed silica layer 53 is preferably formed from a mixed powder of crystalline silica powder having an OH group concentration of 50 massppm or less and amorphous silica powder having an OH group concentration of 200 to 2000 ppm. The mixed silica layer 53 is formed by using a mixed powder of two types of silica powder having a difference in OH group concentration as a raw material, so that the crystalline silica powder of the mixed silica layer 53 is melted and non-phased. The etching rate difference with respect to the silicon melt of the phase in which the crystalline silica powder is melted can be made more remarkable, and the irregularities on the inner surface of the silica container 74 can be more reliably formed. The OH group concentration of the phase in which the crystalline silica powder is melted corresponds to the OH group concentration of the crystalline silica powder, and the OH group concentration of the phase in which the amorphous silica powder is melted corresponds to the OH group concentration of the amorphous silica powder. However, since the silica container 74 is manufactured through a high-temperature process such as about 1800 ° C. or more, it is estimated that there is some variation. When the OH group concentration of the entire mixed silica layer 53 is measured, the average value of the OH group concentrations of both raw material powders is obtained.

  The mixed silica layer 53 is etched from the interface when the raw material silicon melt is held. Therefore, it is preferable to reduce the amount of impurity elements taken into the raw silicon melt from the mixed silica layer 53 by making the mixed silica layer 53 highly pure. Specifically, the concentration of the impurity element in the mixed silica layer 53 is 100 massppb or less for each of Li, Na, and K, 50 massppb or less for each of Ca and Mg, Ti, Cr, Fe, Ni, Cu, Zn, Zr, Mo , W and Pb are each preferably 20 massppb or less.

  The bottom silica glass layer 55 is also preferably highly pure. Specifically, the impurity element concentration is 50 massppb or less for each of Li, Na, and K, 25 massppb or less for each of Ca and Mg, Ti, Cr, Fe, Each of Ni, Cu, Zn, Zr, Mo, W, and Pb is 10 massppb or less, and preferably has a thickness of 200 to 2000 μm.

The purity of portions other than the mixed silica layer 53 and the bottom silica glass layer 55 (hereinafter, also referred to as “normal silica portion”) in the silica container 74 of FIGS. 1 and 2 is silica (SiO ₂ ), depending on the application. ) The purity is preferably 99.99 mass% or more for pulling a solar single crystal and 99.999 mass% or more for pulling a single crystal for LSI. In addition, when the silica raw material powder containing about 10 mass ppm of each of the alkali metal elements Li, Na, and K is used as the raw material powder for producing the normal silica portion, for example, the OH group concentration of the normal silica portion By setting Al to 10-50 massppm and simultaneously setting Al to 5-30 massppm, it is possible to adsorb and confine elements with a large diffusion coefficient such as alkali metal elements in the thickness of the silica container. It becomes. As an effect of containing OH groups, there is a good effect of adsorbing and fixing metal impurity elements, but there is also a negative effect of reducing the viscosity at high temperature and deforming the silica container, so the above range is set. It is preferable. Al has the effect of adsorbing and fixing metal impurity elements and the effect of improving the viscosity of silica glass at high temperatures, but also has the negative effect of contaminating the silicon melt of the object to be treated with Al. . Therefore, even when Al is contained, it is preferable to set it in the range of 5 to 30 massppm (more preferably 10 to 20 massppm) as described above.

  Below, the manufacturing method of the silica container for single crystal silicon pulling of this invention which can manufacture the above silica containers 74 is demonstrated concretely.

  A method for producing the silica container 74 shown in FIGS. 1 and 2 will be described with reference to FIG.

  As shown in FIGS. 3A, 3B, and 3C, the first raw material powder 11, the second raw material powder 12, and the third raw material powder 22 are prepared and prepared (step (a)). Step (b) and Step (c)). The first raw material powder 11 may be prepared before the step of forming a first temporary molded body 41 described later, and the second raw material powder 12 is prepared before the step of forming a second temporary molded body 43 described later. do it. What is necessary is just to prepare the 3rd raw material powder 22 before the formation process of the bottom part silica glass layer 55 mentioned later.

(Preparation of the first raw material powder 11)
The first raw material powder 11 is a material constituting a portion (usually a silica portion) of the silica container 74 other than the mixed silica layer 53 and the bottom silica glass layer 55. As the first raw material powder 11, a crystalline silica powder having a particle size of 10 to 1000 μm is prepared and prepared (step (a)). Although the 1st raw material powder 11 can be produced by grind | pulverizing and sizing a silica stone lump as follows, for example, it is not limited to this.

  First, a natural quartzite block (naturally produced crystal, quartz, quartzite, siliceous rock, opal stone, etc.) with a diameter of about 5 to 50 mm is heated in the temperature range of 600 to 1000 ° C. for about 1 to 10 hours in an air atmosphere. To do. Next, the natural silica mass is put into water, taken out after rapid cooling, and dried. This process facilitates the subsequent crushing and sizing process using a crusher or the like, but the process may proceed to the crushing process without performing the heating and quenching process.

  Next, the natural silica stone lump is pulverized and sized by a crusher or the like, and the particle size is adjusted to 10 to 1000 μm, preferably 50 to 500 μm to obtain natural silica stone powder.

Next, this natural silica powder is put into a rotary kiln composed of a silica glass tube having an inclination angle, and the inside of the kiln is made into an atmosphere containing hydrogen chloride (HCl) or chlorine (Cl ₂ ) gas, and is heated to 800 to 1100 ° C. For about 1 to 100 hours. However, in a product application that does not require high purity, the process may proceed to the next process without performing the purification process.

  The first raw material powder 11 obtained after the above steps is crystalline silica. In addition, various crystalline silica powders such as high-purity synthetic cristobalite powder can also be used.

The particle size of the first raw material powder 11 is 10 to 1000 μm as described above. The particle size is preferably 50 to 500 μm. The silica purity (SiO ₂ ) of the first raw material powder 11 is preferably 99.99 mass% or more, and more preferably 99.999 mass% or more.

  When the purity of the first raw material powder 11 is low (bad), the first raw material powder 11 is used to prevent the migration and diffusion of the impurity metal element from the manufactured silica container 74 to the inner surface and further to the silicon melt to be accommodated. The raw material powder 11 can contain a predetermined amount of Al and OH groups. Al can be obtained, for example, by putting nitrate, acetate, carbonate, chloride or the like into water or an alcohol solution, putting silica powder in these solutions, immersing them, and then drying them. The OH group can be adjusted depending on the gas atmosphere, treatment temperature, and time in the subsequent drying step, which is included in the natural silica from the beginning, or moisture mixed in the intermediate step. The content of Al in the first raw material powder 11 for constituting the opaque silica glass 51 and the transparent silica glass 52 is preferably 5 to 30 mass ppm as described above. Although the OH group concentration of the first raw material powder 11 can be 10 to 50 mass ppm, the OH group concentration can be adjusted in the subsequent steps as described above.

  The details of the mechanism for preventing the migration and diffusion of impurity metal elements in silica glass due to the inclusion of these Al and OH groups are unknown, but Al replaces Si with cation (cation) of impurity metal elements in silica. It is presumed to prevent adsorption and diffusion from the viewpoint of maintaining the charge balance of the glass network. In addition, it is presumed that the OH group has an effect of adsorbing or preventing diffusion of these impurity metal elements by substitution of hydrogen ions and metal ions.

(Production of second raw material powder)
The second raw material powder 12 is a material for constituting the mixed silica layer 53. As the second raw material powder 12, a mixed powder of crystalline silica powder 13 having a particle size of 50 to 2000 μm and amorphous silica powder 14 having a particle size of 50 to 2000 μm is prepared (step (b)). . Crystalline silica powder 13 and amorphous silica powder 14 are separately prepared, and the second raw material powder 12 can be prepared and prepared by mixing them.

(Preparation of crystalline silica powder 13)
The production of the crystalline silica powder 13 can be basically performed in the same manner as the production of the first raw material powder 11, but the particle size is 50 to 2000 μm. Such a relatively rough one is preferable because it is difficult to be etched by the silicon melt when the crystalline silica powder of the mixed silica layer 53 is melted. More preferably, the particle size is 300 to 1000 μm. Further, the OH group concentration of the crystalline silica powder 13 is preferably 50 mass ppm or less as described later. Although the phase itself in which the crystalline silica powder is melted is difficult to be etched with respect to the silicon melt, the crystalline silica powder 13 is a raw material constituting the mixed silica layer 53. In view of contamination of the silicon melt by Al itself, it is better not to contain Al element. However, in some cases, the crystalline silica powder 13 may contain Al.

(Preparation of amorphous silica powder 14)
As the material of the amorphous silica powder 14, a highly purified natural quartz powder, natural quartz powder, or cristobalite powder is fused with an oxyhydrogen flame to form a silica glass lump, and then crushed and sized, Examples thereof include silica glass powder obtained by pulverizing and sizing a synthetic silica glass lump by an oxyhydrogen flame hydrolysis method of a silicon compound such as silicon tetrachloride (SiCl ₄ ). The particle size of the second raw material powder 12 is 50 to 2000 μm, preferably 300 to 1000 μm. The purity is 99.999 mass% or more of silica component (SiO ₂ ), more specifically, the impurity element concentration is 100 massppb or less for each of Li, Na, and K, 50 massppb or less for each of Ca and Mg, Ti, Cr, Fe , Ni, Cu, Zn, Zr, Mo, W, and Pb are preferably 20 massppb or less.

(Mixing adjustment of the second raw material powder 12)
The second raw material powder 12 can be produced and prepared by mixing the crystalline silica powder 13 and the amorphous silica powder 14 produced as described above. In order to make the structure of the rough surface when the mixed silica layer 53 is etched into the silicon melt suitable, the mixing ratio of the two types of silica powder is preferably 90 to 20 mass% for the crystalline silica powder 13. 80 to 50 mass% is more preferable. The remaining ratio is amorphous silica powder 14.

In the second raw material powder 12, it is preferable that the crystalline silica powder 13 has an OH group concentration of 50 massppm or less and the amorphous silica powder 14 has an OH group concentration of 200 to 2000 ppm. The OH group concentration of the crystalline silica powder 13 can be adjusted as described above. The amount of water vapor released from the crystalline silica powder 13 is preferably 2 × 10 ¹⁷ (H ₂ O molecule / g) or less. Various known methods can be used to adjust the OH group concentration of the amorphous silica powder 14. For example, when the above-purified natural quartz powder, natural quartz powder, or cristobalite powder is melted in an oxyhydrogen flame, the amorphous silica powder is adjusted by adjusting the oxygen and hydrogen flow rates of the oxyhydrogen flame. The OH group concentration in 14 can be adjusted. Further, in the case of production of silicon tetrachloride silicon compound by oxyhydrogen flame hydrolysis method, the flow rate of oxygen and hydrogen in the amorphous silica powder 14 is increased by increasing the flow rate of oxygen and hydrogen compared to the flow rate of silicon tetrachloride as a raw material. OH group concentration can be increased.

(Production of third raw material powder)
The third raw material powder 22 is a raw material for the bottom silica glass layer 55. A crystalline silica powder having a particle size of 10 to 1000 μm is prepared as the third raw material powder 22 (step (c)). The third raw material powder 22 can be prepared and prepared by the same method as the first raw material powder 11. The third raw material powder 22 is preferably highly pure. The purity is 99.999 mass% or more of silica component (SiO ₂ ), more specifically, the impurity element concentration is 50 massppb or less for each of Li, Na, and K, 25 massppb or less for each of Ca and Mg, Ti, Cr, Fe , Ni, Cu, Zn, Zr, Mo, W, and Pb are each preferably 10 massppb or less.

(Formation of first temporary molded body)
After producing at least the first raw material powder 11, as shown in FIG. 3 (d), the first raw material powder 11 is put inside the mold having rotational symmetry, and the mold is rotated. The first temporary molded body 41 made of the first raw material powder 11 is formed in the mold by temporary molding into a predetermined shape corresponding to the inner wall of the mold (step (d)). 4 and 5 are cross-sectional views showing an outline of a mold for temporarily forming the first raw material powder 11. The molds 101 and 101 ′ used in the present invention are made of, for example, a heat-resistant ceramic such as graphite or alumina or a heat-resistant metal having a cooling system, have rotational symmetry, and a mold rotation motor (not shown). ). In addition, as shown in FIG. 4, decompression holes 103 may be distributed and formed in the inner wall 102 of the mold 101. The decompression hole 103 is continuous with the decompression passage 104. Further, a pressure reducing passage 105 is also passed through a rotating shaft 106 for rotating the mold 101, and vacuuming can be performed from here. In the present invention, it is also possible to use a mold 101 ′ without a decompression equipment as shown in FIG. No pressure reducing hole is formed in the inner wall 102 ′ of the mold 101 ′, and there is no pressure reducing passage on the rotating shaft 106 ′. Hereinafter, the case where the mold 101 shown in FIG. 4 is used will be described as an example. However, the mold 101 ′ shown in FIG. 5 can be used in the same manner except that no decompression is performed.

  In the step (c), the first raw material powder 11 is introduced into the inner wall 102 of the mold 101 shown in FIG. 4, and the first raw material powder 11 is temporarily formed into a predetermined shape corresponding to the inner wall 102 of the mold 101. It shape | molds and it is set as the 1st temporary molding 41 (refer FIG. 6). Specifically, while rotating the mold 101, the first raw material powder 11 is gradually put into the inner wall 102 of the mold 101, and is formed into a container shape having a predetermined thickness using centrifugal force. Further, the thickness of the first temporary molded body 41 may be adjusted to a predetermined amount by bringing a plate-shaped inner mold (not shown) from the inside into contact with the rotating powder. At this time, in the next step, adjustment is performed leaving a portion for introducing the second raw material powder 12. FIG. 6 illustrates a case where the concave portion 42 is formed in the first temporary molded body 41. The method for supplying the first raw material powder 11 to the mold 101 is not particularly limited. For example, a hopper provided with a stirring screw and a measuring feeder can be used. In this case, the 1st raw material powder 11 with which the hopper was filled is stirred with the screw for stirring, and it supplies, adjusting a supply amount with a measurement feeder.

  Next, as shown in FIG. 3E, the second raw material powder 12 is charged into the recess 42 of the first temporary molded body 41 formed in the mold 101 (step (e)). As a result, a second temporary molded body 43 having a portion made of the first raw material powder 11 and a portion made of the second raw material powder 12 is formed. The shape of the second temporary molded body 43 is a shape corresponding to the shape of the silica container 74 to be manufactured, and a portion corresponding to the straight body portion, the curved portion, and the inner surface layer portion of the bottom portion of the silica container 74 to be manufactured. The second raw material powder 12 is formed. The second raw material powder 12 is introduced after the first temporary molded body 41 is formed by at least a part of the first raw material powder 11, but also after the second raw material powder 12 is introduced as necessary. A part of the first raw material powder 11 can be introduced to form the entire second temporary molded body 43.

  The example shown in FIG. 7 corresponds to the shape of the silica container 74 shown in FIG. In this case, the second raw material powder 12 is charged into the first temporary molded body 41 (recess 42). When the silica container 74 shown in FIG. 2 is manufactured, the shape of the second temporary molded body 43 is adjusted so as to have a shape corresponding to the silica container 74 of FIG.

  Next, as shown in (f) of FIG. 3, the second temporary molded body 43 is heated by the discharge heating melting method from the inside of the second temporary molded body 43 while rotating the mold 101. Among them, the portion made of the second raw material powder 12 is a mixed silica layer 53 in which a phase in which crystalline silica powder is melted and a phase in which amorphous silica powder is melted are mixed in a granular form, and the outside of the container contains bubbles. The silica container 73 is made of the opaque silica glass 51 and the inside of the container is made of the transparent silica glass 52 (step (f)). The heating of the second temporary molded body 43 by the discharge heating melting method is preferably performed while reducing the pressure from the outside of the second temporary molded body 43. By heating while reducing the pressure, the opaque silica glass on the outside of the container and the transparent silica glass on the inside of the container can be efficiently produced.

  The state of this process is specifically shown in FIGS. The apparatus for producing the silica container 73 includes a rotatable mold 101 having the rotational axis symmetry described above, a rotary motor (not shown), and discharge heating melting (also called arc melting or arc discharge melting). It includes a carbon electrode (carbon electrode) 212 serving as a heat source, an electric wire 212a, a high-voltage power supply unit 211, a lid 213, and the like. Two or three carbon electrodes 212 are generally used. Two types of power sources can be used: alternating current or direct current. Further, components for adjusting the atmospheric gas supplied from the inside of the second temporary molded body 43, for example, a hydrogen gas supply cylinder 411, an inert gas supply cylinder 412, a mixed gas supply pipe 420, a gas mixer And a flow controller 421 and the like.

As a procedure for melting and sintering the second temporary molded body 43, first, supply of a hydrogen-containing gas from the inside of the second temporary molded body 43 is started before charging is started between the carbon electrodes 212. Is preferred. Specifically, as shown in FIG. 8, hydrogen gas is supplied from a hydrogen gas supply cylinder 411, and inert gas (for example, nitrogen (N ₂ ), argon (Ar), helium is supplied from an inert gas supply cylinder 412. (He)) is supplied and mixed, and supplied from the inside of the second temporary molded body 43 through the mixed gas supply pipe 420. In addition, the white arrow shown with the code | symbol 510 shows the flow of mixed gas.

  Next, a degassing vacuum pump (not shown) is rotated while the mold 101 containing the second temporary molded body 43 is rotated at a constant speed while the supply of the mixed gas is continued as described above. Then, the pressure is reduced from the outside of the second temporary molded body 43 through the pressure reducing hole 103 and the pressure reducing passages 104 and 105, and charging is started between the carbon electrodes 212.

  When arc discharge (illustrated by reference numeral 220 in FIG. 9) is started between the carbon electrodes 212, the inner surface portion of the second temporary molded body 43 becomes a melting temperature range of silica powder (estimated to be about 1800 to 2000 ° C.). The melting starts from the outermost layer. When the outermost layer is melted, the degree of vacuum reduction by the degassing vacuum pump increases (the pressure suddenly decreases), and water, oxygen, etc. contained in the first raw material powder 11 and the second raw material powder 12 While the dissolved gas is degassed, the change to the fused silica glass layer proceeds from the inside to the outside.

  By applying electricity until the inner third to half of the total thickness of the second temporary molded body 43 are melted to become transparent silica glass, and the remaining outer third to about half are sintered opaque silica. Continue heating.

The atmospheric gas inside the container thick layer at the time of this discharge heating melting may contain an inert gas such as nitrogen (N ₂ ), argon (Ar), helium (He) as a main component for the purpose of reducing electrode consumption. However, in order to reduce the dissolved gas in the silica glass after melting, it is preferable that the atmosphere gas be a hydrogen-containing gas in this step as described above. This hydrogen-containing gas can be, for example, a mixed gas composed of hydrogen gas and an inert gas such as nitrogen gas (N ₂ ), argon (Ar), and helium (He). The content ratio of hydrogen gas (H ₂ ) is 1 vol. % Or more, preferably 1 to 10 vol. % Is more preferable. This is because, for example, oxygen gas (O ₂ ), which is difficult to degas, reacts with hydrogen to produce water (H ₂ O), and the water molecules have a larger diffusion coefficient than oxygen molecules, and are released to the outside of the outer layer. It is thought that it becomes easy to be done. Further, since hydrogen gas (H ₂ ) has a small molecular radius and a large diffusion coefficient, even if it is contained in the atmospheric gas, it is easily released to the outside of the outer layer.

  Through the steps so far, a silica container 73 having the mixed silica layer 53, the outer side of the container made of opaque silica glass containing bubbles, and the inner side of the container made of transparent silica glass is manufactured (see FIG. 9).

  Next, as shown in FIG. 3G, the bottom silica glass layer 55 is formed on the bottom of the silica container 73 to manufacture the silica container 74 of the present invention (step (g)). This process melt | dissolves the 3rd raw material powder (raw material powder for bottom part silica glass layer formation) 22 from the upper part of the silica container 73 by the discharge heating melting method, and melt | dissolves the 3rd raw material powder 22 in the silica container 73. The bottom silica glass layer 55 is formed by adhering to the inner surface portion of the bottom of the glass. The bottom silica glass layer 55 has an impurity element concentration of 50 massppb or less for each of Li, Na, and K, 25 massppb or less for each of Ca and Mg, Ti, Cr, Fe, Ni, Cu, Zn, Zr, Mo, W, Each Pb is preferably formed to have a thickness of 10 massppb or less and a thickness of 200 to 2000 μm.

  Thereby, the silica container 74 shown in FIG. 1 can be manufactured. The basic method of forming the bottom silica glass layer 55 by this step is similar to the contents shown in, for example, Patent Document 1 and Patent Document 2, but in the present invention, only the bottom portion of the inner surface of the silica container 73 is used. To form.

  The apparatus for forming the bottom silica glass layer 55 on the inner surface portion of the bottom of the silica container 73 shown in FIG. 10 is substantially the same as in step (f), and a silica container having rotational axis symmetry is installed. A rotatable mold 101, a rotary motor (not shown), a raw material powder hopper 303 containing the third raw material powder 22, a stirring screw 304, a metering feeder 305, and a carbon electrode 212 serving as a heat source for discharge heating and melting. , Electric wire 212a, high-voltage power supply unit 211, lid 213, and the like. When adjusting the atmospheric gas, as in the step (f), the hydrogen gas supply cylinder 411, the inert gas supply cylinder 412, the mixed gas supply pipe 420, the gas mixer and the flow controller 421 are further provided. Etc. may be provided. These devices can be used continuously from step (f).

  As a method of forming the bottom silica glass layer 55, first, the mold 101 is set to a predetermined rotation speed, and a high voltage is gradually applied from the high-voltage power supply unit 211. The raw material powder 22 is sprayed from the upper part of the silica container 73. At this time, the discharge is started between the carbon electrodes 212, and the inside of the silica container 73 is in the melting temperature range of silica powder (estimated to be about 1800 to 2000 ° C.). It becomes molten particles and adheres to the inner surface of the silica container 73. The carbon electrode 212, the raw material powder inlet, and the lid 213 installed in the upper opening of the silica container 73 have a mechanism that allows the position of the silica container 73 to be changed to some extent. By changing these positions, The bottom silica glass layer 55 can be formed at a predetermined thickness at a predetermined location on the bottom of the silica container 73.

The atmospheric gas inside the silica container 73 during arc discharge melting is mainly composed of an inert gas such as nitrogen gas (N ₂ ), argon (Ar), helium (He) in order to reduce the consumption of the carbon electrode. , Hydrogen gas (H ₂ ), 1 to 10 vol. %, The bottom silica glass layer 55 containing few bubbles is obtained.

When carbon fine particles generated during arc discharge melting, and carbon monoxide (CO) and carbon dioxide (CO ₂ ), which are compounds of carbon and oxygen, remain in the bottom silica glass layer 55, they are used as impurities when pulling up single crystal silicon. It can reoccur and be one of the causes that degrade the quality of the silicon. In order to suppress this, it is preferable to ventilate the inside of the melting silica container appropriately by discharging the gas inside the container at a constant flow rate while supplying a clean atmospheric gas from the outside of the silica container 73 at a constant flow rate. .

  EXAMPLES Hereinafter, although an Example and comparative example of this invention are shown and this invention is demonstrated more concretely, this invention is not limited by these.

Example 1
The silica container 74 for pulling up single crystal silicon shown in FIG. 1 was manufactured according to the steps (a) to (g) shown in FIG. As the first raw material powder 11, natural quartz powder (a) having a particle size of 50 to 500 μm and a purity of 99.999 mass% was prepared. The impurity concentration of this natural quartz powder (a) is shown in Table 6. As the second raw material powder 12, a mixed powder of crystalline silica powder 13 which is natural quartz powder (b) and amorphous silica powder 14 which is synthetic silica glass powder (a) was prepared. The amorphous silica powder 14 is a synthetic silica glass powder produced by an oxyhydrogen flame hydrolysis method of silicon tetrachloride SiCl ₄ . The impurity element concentration, OH group concentration, and H ₂ O molecule release amount of the natural quartz powder (b) and synthetic silica glass powder (a) are shown in Tables 7 and 8. The mixing ratio of the crystalline silica powder 13 and the amorphous silica powder 14 was 40:60 (mass% ratio).

The first raw material powder 11 and the second raw material powder 12 were charged while rotating the graphite mold 101 shown in FIGS. 4, 6, and 7, thereby obtaining a second temporary molded body 43. Next, using the apparatus shown in FIGS. 8 and 9, the inner atmosphere of the second temporary molded body 43 was dried N ₂ 95 vol. %, H _{2 5} vol. The silica container 73 was manufactured by performing discharge heating and melting inside the second temporary molded body 43 while reducing the intake pressure from the outer peripheral portion with a mixed gas of%. The bottom silica glass layer 55 is placed on the bottom of the silica container 73, and the molten atmosphere gas is N ₂ 95 vol. %, H _{2 5} vol. The silica container 74 shown in FIG. 1 was manufactured. The raw material powder (third raw material powder 22 ) for the bottom silica glass layer 55 at this time was the synthetic cristobalite powder (a) having the impurity concentration, OH group concentration and H ₂ O molecule release amount shown in Table 9. .

(Example 2)
The silica container 74 shown in FIG. 1 was manufactured. The production conditions are as follows: the mixing ratio of crystalline silica powder (natural quartz powder (b) and amorphous silica powder (synthetic silica glass powder (a)) is 60:40 (mass ratio), and the molten atmosphere gas is N ₂ 50 vol. %, H ₂ 10 vol.%, And He 40 vol.%, And the same as in Example 1 except that the bottom silica glass layer 55 is formed thicker than in Example 1.

(Example 3)
The silica container 74 shown in FIG. 1 was manufactured. The production condition is that the mixing ratio of crystalline silica powder (natural quartz powder (b) and amorphous silica powder (synthetic silica glass powder (a)) is 80:20 (mass ratio), and the bottom silica glass layer 55 is implemented. Example 1 is the same as Example 1 except that it is formed thicker than Example 1.

Example 4
The silica container 74 shown in FIG. 2, that is, the silica container 74 in which the mixed silica layer 53 was formed up to the upper end of the inner surface layer was manufactured. Other production conditions were that the synthetic silica glass powder (b) shown in Table 8 was used as the amorphous silica powder 14, and that the molten atmosphere gas was N ₂ 90 vol. %, H ₂ 10 vol. %, And the same as Example 1, except that the bottom silica glass layer 55 is formed thicker than Example 1.

(Example 5)
The silica container 74 shown in FIG. 2 was manufactured in the same manner as in Example 4, but the mixing of crystalline silica powder (natural quartz powder (b)) and amorphous silica powder (synthetic silica glass powder (b)) The ratio was 60:40 (mass ratio), and the molten atmosphere gas was N ₂ 95 vol. %, H _{2 5} vol. %.

(Example 6)
The silica container 74 shown in FIG. 2 was manufactured by the same method as in Example 5, but the mixing of crystalline silica powder (natural quartz powder (b)) and amorphous silica powder (synthetic silica glass powder (b)) The ratio was 80:20 (mass ratio).

(Comparative Example 1)
A silica container 91 shown in FIG. 11 was manufactured by a reduced pressure arc discharge melting method using natural quartz powder as a raw material powder. The silica container 91 does not have a portion corresponding to the mixed silica layer 53 of the present invention, the container outer side is made of opaque silica glass 81 containing bubbles, and the container inner side 82 is made of transparent silica glass.

(Comparative Example 2)
The silica container 92 shown in FIG. 12 was manufactured. First, by using natural quartz powder as a raw material powder, a silica container in which the outer side of the container is made of opaque silica glass 81 containing bubbles and the inner side of the container 82 is made of transparent silica glass is produced by atmospheric pressure arc melting method. A bottom silica glass layer 85 was formed on the bottom using synthetic cristobalite powder as a raw material.

(Comparative Example 3)
As shown in FIG. 13, a silica container 93 having a mixed silica layer 83 on the entire inner surface of the container and made of an opaque silica glass 81 on the outer side was manufactured. That is, the silica container 93 has the same configuration as that of Examples 4 to 6 except that the bottom silica glass layer is not formed. The specific manufacturing method is the same as that of Example 5 except that the synthetic silica glass powder (a) is used as the amorphous silica powder in addition to not forming the bottom silica glass layer.

(Comparative Example 4)
A silica container 94 shown in FIG. 14 was produced. The silica container 94 has a mixing ratio of crystalline silica powder (natural quartz powder (b)) and amorphous silica powder (synthetic quartz glass powder) of 50:50 (mass% ratio), and the mixed silica layer 53 is straight It was manufactured in the same manner as in Example 1 except that it was formed in a thickness of 2 mm only on the part (the height (width) in the straight body part was 150 mm) and the bottom silica glass layer 55 was not formed.

[Evaluation Methods in Examples and Comparative Examples]
The physical properties and characteristics of the raw material powder and the silica container produced in each Example and Comparative Example were evaluated as follows.

Particle size measurement of each raw material powder:
Two-dimensional shape observation and area measurement of each raw material powder were performed with an optical microscope or an electron microscope. Next, assuming that the shape of the particle is a perfect circle, the diameter was calculated from the area value. This method was repeated statistically and is shown in Tables 1 to 5 as values of the particle size range (containing 99 mass% or more of raw material powder in this range).

Layer thickness measurement of silica container:
The silica container was cut with a cutter, and the cross section was determined by measuring with a scale.

OH group concentration measurement:
The OH group concentration was measured by infrared absorption spectrophotometry. Conversion to OH group concentration follows the following literature.
Dodd, D.D. M.M. and Fraser, D.A. B. (1966) Optical determination of OH in fused silica. Journal of Applied Physics, vol. 37, P.I. 3911.

Impurity metal element concentration analysis:
When the impurity metal element concentration is relatively low (glass is highly pure), plasma emission spectrometry (ICP-AES) or plasma mass spectrometry (ICP-MS) is performed, and the impurity metal element concentration is relatively high ( In the case of low purity glass), it was performed by atomic absorption spectrophotometry (AAS). Concentration analysis of 15 elements of alkali metal elements Li, Na, K, alkaline earth metal elements Ca, Mg, transition metal elements Ti, Cr, Fe, Ni, Cu, Zn, Zr, Mo, W, and Pb was performed.

Measuring method of H ₂ O gas release amount:
About 2 g was sampled from each raw material powder, and this was placed in a vacuum chamber, and the amount of gas released under vacuum at 1000 ° C. was measured. Details follow the following literature.
Nasu, S .; et al. (1990) “Gas release of various kinds of vitreous silica”, Journal of Illuminating Engineering of Japan, vol. 74, no. 9, pp. 595-600.

Evaluation of surface vibration when pulling single crystal silicon:
Into a silica container having a diameter of 800 mm (32 inches), metal polysilicon having a purity of 99.99999999 mass% was charged and heated to obtain a silicon melt. At that time, in Examples 1 to 3, the silicon hot water surface was set to be close to the upper end of the mixed silica layer of the silica container. The atmosphere in the CZ apparatus was 100% argon (Ar) gas, and the seed crystal of single crystal silicon was moved downward while rotating, and seeding, necking, shoulder ring, pulling, and tailing were sequentially advanced. Evaluation of the level of hot water surface vibration was as follows. The evaluation before the first single crystal silicon pull-up is shown before the arrow, and the evaluation after the second single crystal silicon pull-up is shown after the arrow.
-There was no surface vibration, and seeding, necking, shoulder ring, pulling and tailing were all performed smoothly. ○ (Good)
・ There was some surface vibration, but shouldering, pulling, and tailing could be done by repeating the seeding and necking processes multiple times. △ (somewhat good)
・ It was impossible to perform seeding, necking, and shoulder ring due to severe vibration of the hot water surface. × (defect)

Single crystal silicon continuous pulling (multi pulling) evaluation:
Into the manufactured silica container, metal polysilicon having a purity of 99.99999999 mass% is charged, heated to a silicon melt, and then single crystal silicon is pulled up three times (multiple pulling) to grow single crystal silicon. Evaluated as a success rate. As for the pulling conditions, the inside of the pulling apparatus (CZ apparatus) is an atmosphere of 100% argon (Ar) gas, the pulling speed is 1 mm / min, the single crystal silicon dimensions are 300 mm in diameter, 900 mm in length, and the operation per single pulling of single crystal silicon. The time was about 30 hours. The classification of the success ratio of three times of single crystal silicon growth was as follows.
・ Successfully raised 3 single crystal silicon ingots ○ (Good)
・ Successfully raised two single crystal silicon ingots △ (somewhat good)
・ The single crystal silicon ingot was pulled up by one × (defect)

Evaluation of voids and pinholes:
Evaluation of voids and pinholes in the pulled single crystal silicon was performed as follows. In the single-crystal silicon continuous pulling, 200 double-side polished silicon wafers each having a diameter of 300 mm and a thickness of 200 μm were prepared from an arbitrary portion of the first single-crystal silicon after each single-crystal silicon multi-pull-up. Next, the number of voids and pinholes present on both surfaces of each silicon wafer was measured by a particle detector, and statistical processing was performed to obtain the number of defects free of 200 silicon wafers. As a result, the following evaluation was made according to the number of silicon wafers in which neither voids nor pinholes were detected. However, the detectable void and pinhole diameter was 50 μm or more.
・ Number of defect-free silicon wafers 200 to 199 ○ (good)
・ Number of defect-free silicon wafers: 198 to 197 △ (somewhat good)
・ Number of defect-free silicon wafers: 196 or less × (defect)

  The production conditions of each silica container produced in Examples 1 to 6 and Comparative Examples 1 to 4, the measured physical property values, and the evaluation results are summarized and shown in Tables 1 to 9 below.

  As can be seen from Tables 1 to 9, in Examples 1 to 6, it was possible to suppress the molten metal surface vibration during the single crystal silicon pulling, and the multi pulling could be performed smoothly. Moreover, in Examples 1-6, the void defect called a void and a pinhole was hardly introduce | transduced into the single crystal silicon. In Comparative Examples 1 and 2, the molten metal surface vibration was generated, and particularly generated from the initial stage of the pulling process. Also in Comparative Example 4, the molten metal surface vibration was generated particularly from the second single crystal silicon pulling step.

  In Comparative Example 3, there was almost no occurrence of molten metal surface vibration, but the evaluation of voids and pinholes was very bad.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

11 ... 1st raw material powder, 12 ... 2nd raw material powder, 13 ... Crystalline silica powder,
14 ... amorphous silica powder, 22 ... third raw material powder (raw material powder for bottom silica glass layer),
41 ... 1st temporary molded object, 42 ... Recessed part of 1st temporary molded object, 43 ... 2nd temporary molded object,
51 ... Opaque silica glass (outside of container), 52 ... Transparent silica glass (inside of container),
53 ... Mixed silica layer, 55 ... Bottom silica glass layer,
61 ... Straight body part, 62 ... Curved part, 63 ... Bottom part,
73 ... Silica container, 74 ... Silica container of the present invention,
101, 101 '... formwork, 102, 102' ... inner wall, 103 ... decompression hole,
104, 105 ... passage for decompression, 106, 106 '... rotating shaft,
211 ... High voltage power supply unit, 212 ... Carbon electrode, 212a ... Electric wire,
213 ... lid, 220 ... arc discharge,
303 ... Hopper, 304 ... Stirring screw, 305 ... Weighing feeder,
411 ... Hydrogen gas supply cylinder, 412 ... Inert gas supply cylinder,
420 ... Mixed gas supply pipe, 421 ... Gas mixer and flow controller,
510 ... Flow of mixed gas.

Claims (8)

A method of manufacturing a single crystal silicon pulling silica container having a straight body part, a curved part, and a bottom part,
Producing a crystalline silica powder having a particle size of 10 to 1000 μm as the first raw material powder;
Producing a mixed powder of a crystalline silica powder having a particle size of 50 to 2000 μm and an amorphous silica powder having a particle size of 50 to 2000 μm as a second raw material powder;
Producing a crystalline silica powder having a particle size of 10 to 1000 μm as a third raw material powder;
The first raw material powder is put inside a mold having rotational symmetry, and is temporarily molded into a predetermined shape corresponding to the inner wall of the mold while rotating the mold, Forming a first temporary molded body made of the first raw material powder;
The second raw material powder is introduced into the first temporary molded body formed in the mold, and has a portion made of the first raw material powder and a portion made of the second raw material powder. The second raw material powder in a shape corresponding to the shape of the silica container to be manufactured and at a position corresponding to the straight body part, the curved part, and the inner surface layer part of the bottom part of the silica container to be manufactured Forming a portion having a portion consisting of:
The portion made of the second raw material powder in the second temporary molded body is made of crystalline silica by heating from the inside of the second temporary molded body by the electric discharge heating melting method while rotating the mold. A mixed silica layer in which the phase in which the powder is melted and the phase in which the amorphous silica powder is melted is mixed in a granular form, the outer side of the container is made of opaque silica glass containing bubbles, and the inner side of the container is made of transparent silica glass Producing a silica container having a straight body portion, a curved portion, and a bottom portion,
Melting the third raw material powder from the top of the silica container by a discharge heating melting method, attaching the molten third raw material powder to the inner surface portion of the bottom, and forming a bottom silica glass layer; The manufacturing method of the silica container for single crystal silicon pulling characterized by including this.   The method for producing a single crystal silicon pulling silica container according to claim 1, wherein the mixed silica layer is formed with a thickness in the thickness direction of the silica container of 2 mm or more.   3. The single crystal silicon pulling-up according to claim 1, wherein the second temporary molded body is heated by a discharge heating melting method while reducing the pressure from the outside of the second temporary molded body. A method for producing a silica container.   4. The second raw material powder, wherein the crystalline silica powder has an OH group concentration of 50 mass ppm or less, and the amorphous silica powder has an OH group concentration of 200 to 2000 ppm. The manufacturing method of the silica container for single-crystal silicon pulling of any one of these.   The concentration of the impurity element of the second raw material powder is 100 massppb or less for each of Li, Na, and K, 50 massppb or less for each of Ca and Mg, Ti, Cr, Fe, Ni, Cu, Zn, Zr, Mo, W The method for producing a single crystal silicon pulling silica container according to any one of claims 1 to 4, wherein each of Pb and Pb is 20 massppb or less. A silica container for pulling a single crystal silicon having a straight body part, a curved part, and a bottom part,
The outside of the container is made of opaque silica glass containing bubbles, the inside of the container is made of transparent silica glass,
In the straight body portion, the curved portion, and the inner surface layer portion of the bottom portion, a mixed silica layer in which a phase in which crystalline silica powder is melted and a phase in which amorphous silica powder is melted is mixed in a granular form,
A silica container for pulling single crystal silicon, comprising a bottom silica glass layer on an inner surface of the bottom mixed silica layer.   The mixed silica layer is formed using a mixed powder of crystalline silica powder having an OH group concentration of 50 massppm or less and amorphous silica powder having an OH group concentration of 200 to 2000 ppm as a raw material. A silica container for pulling single crystal silicon as described.   The concentration of impurity elements in the mixed silica layer is 100 massppb or less for each of Li, Na, and K, 50 massppb or less for each of Ca and Mg, Ti, Cr, Fe, Ni, Cu, Zn, Zr, Mo, W, and Pb. The silica container for pulling up single crystal silicon according to claim 6 or 7, wherein each is 20 massppb or less.

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