JP4702898B2 - Method for producing quartz glass crucible for pulling silicon single crystal - Google Patents

Description

  The present invention relates to a method for producing a quartz glass crucible for pulling a silicon single crystal, and more specifically, foam expansion on the inner surface of the crucible that occurs when pulling a single crystal at a high temperature and under reduced pressure is suppressed, and a silicon single crystal formed by a peeled quartz glass piece The present invention relates to a method for producing a quartz glass crucible that can pull up a silicon single crystal with a high yield without crystal transition.

  Conventionally, a so-called Czochralski method (CZ method) has been widely used for the production of silicon single crystals. In this CZ method, a silicon polycrystal is melted in a crucible made of quartz glass, a silicon single crystal seed crystal is immersed in the silicon melt, and the seed crystal is gradually pulled up while rotating the crucible. Is grown using seed crystals as nuclei. The single crystal produced by the CZ method is required to have a high purity and to be able to produce a silicon wafer with a high yield. As a quartz glass crucible used for the production, an inner layer containing no bubbles and an opaque material including bubbles are opaque. A double-structured quartz glass crucible composed of an outer layer is used. This quartz glass crucible is made from high-purity synthetic silica powder, synthetic cristobalite powder, or highly purified natural silica powder obtained by the sol-gel method. A so-called arc rotation melting method in which a powder layer is formed along the inside and heated and melted by an arc from the inside to form a quartz glass crucible, and then the arc is stopped and cooled to room temperature while continuing to rotate the mold. It is common to be manufactured by. Although the inner layer of the double-structured quartz glass crucible is a transparent layer without bubbles, bubbles are generated when the silicon single crystal is pulled up under reduced pressure and high temperature to expand, and the inner surface of the crucible peels off. However, the peeled quartz piece adheres to the single crystal being pulled, and there is a defect that a high quality silicon single crystal cannot be produced due to the transition from that portion.

Therefore, as a quartz glass crucible to solve the above disadvantages, the heating conditions when melting the crucible base and the silica powder used for forming the transparent layer are selected to suppress the bubble expansion below 1 mm inside the crucible after pulling up the silicon single crystal. A quartz glass crucible is proposed in Patent Document 1 and a quartz glass crucible manufactured by introducing water vapor into a crucible substrate during at least a part of the inner layer forming step of the quartz glass crucible is proposed in Patent Document 2, respectively. ing. However, the former quartz glass crucible has the disadvantage that it cannot be applied to all types of crucibles because the heating conditions and silica powder are specified. In the latter case, there is a problem that the OH group concentration of the entire crucible increases and the viscosity of the quartz glass tends to decrease.
JP 2000-44386 JP2001-348240

In view of the current situation, the present inventors have conducted extensive research, and as a result, used amorphous silica powder doped with hydrogen molecules in a specific range as a raw material powder for forming at least the inner surface layer of the quartz glass crucible. Therefore, it is not necessary to specify the silica powder or heating conditions, and it can be applied to the production of all types of crucibles. Moreover, the foam expansion on the inner surface of the crucible can be suppressed without decreasing the viscosity of the quartz glass due to the increase of OH group concentration. The present invention has been completed by finding that a silica glass crucible in which silicon single crystal can be pulled at a high yield can be produced without causing transition of the silicon single crystal due to separation of the quartz glass piece. Ie

In order to achieve the above object, the present invention introduces silica powder into a rotating mold, forms it into a crucible shape by centrifugal force, and then heat-melts to form a translucent quartz glass crucible base, which is being formed or formed. A hydrogen-doped amorphous silica powder and a hydrogen-undoped crystal having a specific range of concentration obtained by heat treatment at a temperature of 300 ° C. to 800 ° C. under a hydrogen pressure of 0.1 MPa to 10 MPa in a later heating atmosphere A method for producing a quartz glass crucible for pulling a silicon single crystal, characterized by forming a transparent quartz glass layer at least 0.5 mm from the inner surface side of a translucent quartz glass crucible substrate by mixing and supplying porous silica powder .

The silica powder used in the present invention includes crystalline or amorphous natural silica powder, or crystalline or amorphous synthetic silica obtained by a sol-gel method, hydrothermal synthesis method, oxyhydrogen flame synthesis method, or the like. Powder. These silica powders can be used alone or as a mixture. The non TadashiAkira silica powder in the silica powder, 0.1 MPa or more 10MPa or less of the hydrogen pressure, 300 ° C. to 800 ° C. of the temperature at the heat treatment was 5 × ¹⁰ the hydrogen concentration of the hydrogen-doped silica powder 17 ~8 × ¹⁰ 19 molecules / Cm ^3, and hydrogen undoped crystalline silica powder in a weight ratio of 2: 1 to 1: 500 is mixed with the mixture to obtain an average hydrogen concentration of 1 × 10 ^{17 to} 5 × 10 ¹⁹ molecules / cm ³ . Using the mixed silica powder, a transparent quartz glass layer is formed at least 0.5 mm from the inner surface of the quartz glass crucible. By forming this transparent quartz glass layer, there is no occurrence of bubble expansion on the inner surface even when pulling up the silicon single crystal under high temperature and reduced pressure, and there is no transition of the single crystal due to separation of the quartz piece due to bubble expansion. Single crystals can be produced with good yield. According to the study by the present inventors, it is known that the bubble expansion is caused by free oxygen which is weakly associated with the glass structure contained in the silica powder itself or taken from the molten atmosphere when forming the inner surface layer. . And by making the hydrogen concentration in silica powder into the above-mentioned range, the doped hydrogen molecule reacts with free oxygen to form OH group, which is fixed in the glass and suppresses bubble expansion. At this time, the OH group concentration slightly increases but is not a value that affects the viscosity. If the hydrogen concentration is less than 5 × 10 ¹⁷ molecules / cm ³ , the reaction between hydrogen molecules and free oxygen is not sufficiently performed, and there is no effect. If the hydrogen concentration exceeds 8 × 10 ¹⁹ molecules / cm ³ , the hydrogen molecules have a glass structure. It reacts with the oxygen in it, the OH group concentration becomes high, water is formed, and foam expansion resulting from it occurs. Moreover, if the transparent quartz glass layer formed with hydrogen dope silica powder is less than 0.5 mm, there is little suppression effect of bubble expansion and it is not preferable.

  The hydrogen concentration is measured by a known gas emission method, and a specific example thereof is shown in Illumination Society Vol. 74, No. 9, pp. 27-32, 1990.

The hydrogen gas used in the production of the hydrogen-doped amorphous silica powder used in the present invention may be pure hydrogen gas or a mixed gas with an inert gas. As the inert gas, any gas that is non-reactive with hydrogen and silica glass can be used, but nitrogen gas, helium gas, and the like can be used from the economical viewpoint. And when the said inert gas is included, the said hydrogen gas pressure means hydrogen gas partial pressure. Moreover, as a heating furnace used for heat processing, the pressurization processing furnace (autoclave furnace) is preferable from the point of the efficiency of hydrogen dope. When the heating temperature is less than 300 ° C., sufficient dope of hydrogen molecules is not observed, and the effect of suppressing the bubble expansion cannot be expected. When the heating temperature exceeds 800 ° C., oxygen of SiO ₂ structure is OH grouped, which is not preferable. Also, if the hydrogen gas pressure is less than 0.1 MPa, the amount of hydrogen doping is small and the effect of suppressing bubble expansion cannot be expected, and if it exceeds 10 MPa, excess hydrogen is doped, and when creating a crucible, OH groups are added to oxygen in the glass structure. And foam expansion due to water is undesirable.

  When the silicon single crystal is pulled up using the quartz glass crucible for silicon single crystal obtained by the production method of the present invention, bubble expansion does not occur on the inner surface of the crucible, and separation of the quartz glass piece does not occur. As a result, the transition of the silicon single crystal due to the separation of the quartz glass piece does not occur, and a high-quality silicon single crystal can be manufactured with a high yield.

Hereinafter, although an embodiment of the present invention is described in detail, the present invention is not limited to this.

  As a means for producing the quartz glass crucible for pulling up the silicon single crystal of the present invention, known production means can be used, but the production method by the arc melting method shown in FIG. 1 is particularly preferable. In the arc melting method, as shown in FIG. 1, silica powder is put into a rotary mold 1 and formed into a crucible shape by centrifugal force, and then melted by heating with an arc electrode 6 to form a translucent quartz glass crucible base 5. Then, the hydrogen-doped silica powder 4 is supplied from the powder supply means 7 in the heating atmosphere during or after the formation of the crucible base 5, and the transparent quartz glass layer 10 is formed on the inner surface side of the crucible base 5. When using mixed powder as the hydrogen-doped silica powder 4, the mixed powder obtained by mixing with a V mixer or the like in advance may be used, or two crucible manufacturing devices are provided with two powder supply means, and a heated atmosphere When supplying silica powder, hydrogen-doped silica powder and undoped silica powder may be supplied from the respective powder supply means so as to obtain a desired average hydrogen concentration.

Reference example 1
(Production of hydrogen-doped amorphous silica powder)
High-purity synthetic silica powder (particle size: 100 to 350 μm) obtained by the sol-gel method was placed in an autoclave furnace, the hydrogen gas pressure in the furnace was set to 2 MPa, the temperature in the furnace was set to 600 ° C., and heat treatment was performed for 10 hours. The hydrogen concentration in the obtained silica powder was 8 × 10 ¹⁸ molecules / cm ³ .

(Manufacture of quartz glass crucibles)
Using the apparatus shown in FIG. 1, high-purity natural silica powder is put into a rotary mold 1 and formed into a quartz glass crucible shape by centrifugal force, and an arc electrode 6 is inserted therein, and an opening is formed. 9 was covered with a ring-shaped lid body 8, the inside of the cavity 3 was made into a high-temperature gas atmosphere by the arc electrode 6, melted into glass, and cooled to prepare a translucent quartz glass crucible base 5. Next, after the mold 1 is rotated, the arc-transparent quartz glass crucible base 5 is heated to a high temperature atmosphere by the arc electrode 6 and then the hydrogen-doped amorphous silica powder 4 obtained above is supplied little by little. 5 A transparent quartz glass layer 10 of about 2 mm was formed by fusing and integrating with the inner surface. The diameter of the obtained quartz glass crucible was 22 inches.

Reference example 2
In the production of the hydrogen-doped amorphous silica powder of Reference Example 1, a hydrogen-doped silica powder was produced in the same manner as in Example 1 except that the hydrogen partial pressure was 0.1 MPa, the heating temperature was 400 ° C., and the treatment time was 40 hours. . The hydrogen concentration in the obtained quartz powder was 6 × 10 ¹⁷ molecules / cm ³ .

A quartz glass crucible having a diameter of 22 inches was prepared using the hydrogen-doped amorphous silica powder in the same manner as in Reference Example 1, and the silicon single crystal was pulled up. After the operation for about 90 hours, the transparent quartz glass layer of the quartz glass crucible was visually observed, and no bubble expansion was observed in the vicinity of the inner surface.

Example 1
In Reference Example 1, the silica powder forming the transparent quartz glass layer was subjected to heat treatment at a hydrogen partial pressure of 10 MPa and 300 ° C. for 40 hours, and the synthetic silica powder (hydrogen concentration 8 × 10 ¹⁹ molecules / cm ³ ) A quartz glass crucible having a diameter of 22 inches was prepared in the same manner as in Reference Example 1 except that silica powder (average hydrogen concentration 2 × 10 ¹⁷ molecules / cm ³ ) mixed with dope natural silica powder at a weight ratio of about 1: 400 was used. The silicon single crystal was pulled up. After the operation for about 90 hours, the transparent quartz glass layer of the quartz glass crucible was visually observed, and no bubble expansion was observed in the vicinity of the inner surface.

Comparative Example 1
Using a hydrogen-undoped synthetic silica powder as the quartz glass powder, a 22-inch quartz glass crucible was prepared in the same manner as in Reference Example 1, and the silicon single crystal was pulled up. After about 60 hours of operation, the single crystal was disturbed and the pulling was stopped. When the transparent quartz glass layer of the quartz glass crucible was visually observed after use, countless bubble expansion was observed near the inner surface. The curved (r) portion of the quartz glass was cut to a thickness of 3.0 mm and the cross-sectional shape was observed with a microscope as shown in FIG.

Comparative Example 2
The same treatment as in Reference Example 1 was performed except that the silica powder of Reference Example 1 was treated at a hydrogen pressure of 0.1 MPa and a heating temperature of 1000 ° C. for 10 hours. The hydrogen concentration in the obtained silica powder was 5 × 10 ¹⁶ molecules / cm ³ . Using this silica powder, a 22-inch quartz glass crucible was prepared in the same manner as in Reference Example 1, and the silicon single crystal was pulled up. After about 70 hours, the single crystal was disturbed, and the pulling was stopped. . When the transparent quartz glass layer of the quartz glass crucible was visually observed after use, countless bubble expansion was observed near the inner surface. The curved (r) portion of the quartz glass was cut to a thickness of 3.0 mm and the cross-sectional shape was observed with a microscope as shown in FIG.

Comparative Example 3
Using the hydrogen-doped amorphous silica powder alone of Example 1, a quartz glass crucible having a diameter of 22 inches was prepared in the same manner as in Reference Example 1, and the silicon single crystal was pulled up. After about 30 hours, the single crystal was disturbed and the pulling was stopped. When the transparent quartz glass layer of the quartz glass crucible was visually observed after use, enormous countless bubble expansion was observed near the inner surface. The curved (r) portion of the quartz glass was cut to a thickness of 3.0 mm and the cross-sectional shape was observed with a microscope as shown in FIG.

  By using the quartz glass crucible produced in the present invention, the bubble expansion of the inner surface of the crucible generated when pulling the single crystal under high temperature and reduced pressure is suppressed, and the silicon single crystal is separated by peeling of the quartz glass piece based on the bubble expansion. There is no transition and the silicon single crystal can be pulled with a high yield.

It is a schematic sectional drawing of the apparatus which manufactures the quartz glass crucible of this invention. It is a microscope picture of the section section of a quartz glass crucible after pulling up a silicon single crystal using the quartz glass crucible of the present invention. It is a microscope picture of a quartz glass crucible section section after pulling up a silicon single crystal using a quartz glass crucible in which an inner surface layer was formed with hydrogen undoped silica powder. Silica glass crucible section cross-section after pulling up a silicon single crystal using a silica glass crucible in which an inner surface layer is formed using silica powder obtained by treating hydrogen pressure at 0.1 MPa and heating temperature at 1000 ° C. for 10 hours FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotation mold 2 Rotation mechanism 3 Cavity 4 Hydrogen dope silica powder 5 Quartz glass crucible base 6 Arc electrode 7 Powder supply means 8 Lid 9 Opening 10 Transparent quartz glass layer 11 Arc power supply

Claims (3)

Silica powder is put into a rotating mold and formed into a crucible shape by centrifugal force, then heated and melted to form a translucent quartz glass crucible base, and 0.1 MPa in the heating atmosphere during or after the formation A hydrogen-doped amorphous silica powder having a hydrogen concentration of 5 × 10 ¹⁷ to 8 × 10 ¹⁹ molecules / cm ^{3 and} a hydrogen - undoped crystalline material obtained by heat treatment at a temperature of 300 ° C. to 800 ° C. under a hydrogen pressure of 10 MPa or less. Silica powder was mixed at a weight ratio of 2: 1 to 1: 500 and an average hydrogen concentration of 1 × 10 ^{17 to} 5 × 10 ¹⁹ molecules / cm ³ was supplied, and the inner surface of the translucent quartz glass crucible substrate A method for producing a quartz glass crucible for pulling a silicon single crystal, wherein a transparent quartz glass layer is formed at least 0.5 mm from the side. 3. The method for producing a quartz glass crucible for pulling up a silicon single crystal according to claim 2, wherein the mixing of the hydrogen-doped amorphous silica powder and the hydrogen-undoped crystalline silica powder is carried out before being supplied to the powder supply means. 3. A quartz glass crucible for pulling up a silicon single crystal according to claim 2, wherein the hydrogen-doped amorphous silica powder and the hydrogen-undoped crystalline silica powder are supplied from separate powder supply means and mixed in a high temperature atmosphere. Manufacturing method.