JP4985554B2 - Silicon melting crucible and silicon single crystal pulling device - Google Patents

Description

  The present invention relates to a silicon melting crucible and a silicon single crystal pulling apparatus used when a silicon single crystal is manufactured by the Czochralski method (CZ method).

  Conventionally, the CZ method is known as one of methods for growing a semiconductor single crystal such as silicon or gallium arsenide. This CZ method is characterized by the fact that a single crystal having a large diameter and high purity can be easily obtained with no dislocations or very few lattice defects. is there.

  An apparatus for producing a silicon single crystal by this CZ method is known as shown in FIG. In this figure, reference numeral 21 is a chamber filled with an inert gas, 22 is a crucible disposed in the chamber, 23 is a heating element disposed around the crucible 22, and 24 is disposed above the crucible 22. This is a silicon single crystal pulling device which can be rotated up and down.

  The crucible 22 includes a quartz inner crucible 33 in which molten silicon 32 is accommodated, and a carbon outer crucible 34 fitted to the outer surface of the inner crucible 33. The lower surface of the crucible 22 is attached to the upper side of the shaft 30.

  The silicon single crystal pulling device 24 includes a shaft that is disposed above the crucible 22 and that can freely move up and down. A chuck 39 is attached to the lower end of the shaft. The chuck 39 holds a silicon seed crystal 40.

  When a silicon single crystal is manufactured using the silicon single crystal growth apparatus having such a configuration, first, solid silicon is accommodated in the crucible 22. Then, an inert gas flows into the chamber 21 from the upper part of the chamber, and the crucible 22 in the chamber 21 is heated by the heating element 23. In this way, after the solid silicon in the crucible 22 is made into the molten silicon 32, the silicon single crystal pulling device 24 is lowered and the seed crystal 40 is immersed in the molten silicon 32. In this state, the silicon single crystal pulling device 24 and the crucible 23 are rotated in opposite directions, and the silicon single crystal pulling device 24 is slowly raised. In this way, the seed crystal 40 grows, and a large rod-shaped silicon single crystal 41 is grown below the seed crystal 40.

  In such a method for producing a silicon single crystal by the CZ method, a quartz crucible has conventionally been used as the most suitable crucible for melting and storing solid silicon as a raw material.

  However, quartz crucibles do not have sufficient strength at high temperatures, so they are usually fitted with a carbon outer crucible to maintain their shape, and the carbon outer crucible reacts with the quartz crucible. There was a problem that carbon oxide gas was generated. When the carbon monoxide gas is taken into the molten silicon, the carbon concentration in the silicon ingot is increased.

  The present invention has been made in view of the above-described circumstances, and when melting and containing solid silicon, the reaction with the outer crucible made of carbon is suppressed, and the generation of carbon monoxide is reduced. Another object of the present invention is to provide a silicon single crystal pulling apparatus using the same.

In order to achieve the above object, the crucible for melting silicon according to the present invention comprises a binder crucible composed mainly of amorphous silica powder and a stucco layer composed of amorphous silica sand alternately on the outer surface of the quartz crucible any number of times. is laminated an outer layer portion is formed, the outer layer portion, is calcined by keeping 0.5-12 hours heating at 600 to 1200 ° C., the silica between crystalline are the molded body diffusion bonding by sintering The outer surface of the outer layer portion has irregularities due to silica sand .

  In this case, the outer layer portion is composed of silica powder as a main component, and the binder layer from which the solvent is volatilized from the slurry layer and the stucco layer made of silica sand are alternately laminated any number of times, and then fired, thereby having a stable structure. It is a molded body in which crystalline silica particles having diffusive bonds are bonded together. That is, since the silicon melting crucible according to the present invention is reinforced with the strength of a conventionally used quartz crucible, softening at high temperatures is suppressed.

  Further, in the silicon melting crucible according to the present invention, the portion accommodated in direct contact with the molten silicon is made of a conventionally used quartz crucible which is most suitable for it. It is utilized as it is.

  Furthermore, since the outer surface of the outer layer portion has irregularities due to silica sand, the convex portion of the outer surface of the silicon melting crucible is supported in a point contact state with the inner surface of the carbon outer crucible or the carbon support tool. . In this case, since the contact area is small, the reaction between them is suppressed, and the amount of generated carbon monoxide is reduced.

  In the case of a silicon single crystal pulling apparatus comprising a silicon melting crucible according to the present invention and a carbon member that supports the bottom surface of the crucible in a radially open state, the outer surface of the silicon melting crucible Since it is in a point contact state with the carbon member, the reaction between them can be suppressed and the generation of carbon monoxide can be reduced. In this case, the carbon monoxide is the lower part of the outer side of the silicon melting crucible. Since the gas flows from the upper part of the chamber and flows into the lower part as it flows from the upper part of the chamber and is exhausted out of the chamber, the amount taken into the molten silicon in the silicon melting crucible is small. Further, since the carbon member does not face the heating element disposed on the side surface portion of the silicon melting crucible, the suppression of the heating by the heating element also suppresses the reaction and reduces the generation of carbon monoxide.

  The silicon melting crucible and silicon single crystal pulling apparatus according to the present invention have the following effects.

  The outer layer portion of the silicon melting crucible according to the present invention is composed of silica powder as a main component, and the binder layer from which the solvent is volatilized from the slurry layer and the stucco layer made of silica sand are alternately laminated any number of times and then fired. In other words, it is a molded body in which crystalline silica particles having a stable structure are diffusion-bonded to each other. Therefore, the strength of the conventionally used quartz crucible is reinforced. Therefore, there is an advantage that softening at high temperature is suppressed.

  In addition, since the silicon melting crucible according to the present invention is made of a quartz crucible that is most suitable for the portion that comes into direct contact with the molten silicon, the advantage of the quartz crucible is utilized as it is.

Furthermore, the silicon melting crucible according to the present invention is supported by the irregularities due to the silica particles on the outer surface of the outer layer portion being in contact with the inner surface of the carbon outer crucible in a point contact state, so that the reaction between them is supported. It is suppressed and generation of carbon monoxide can be reduced.

  In the case of the silicon single crystal pulling apparatus equipped with the silicon melting crucible according to the present invention, the generation of carbon monoxide due to the reaction between the silicon melting crucible and the carbon outer crucible is reduced. Ingots can be manufactured.

  In the case of the silicon single crystal pulling apparatus including the silicon melting crucible according to the present invention and the carbon member supporting the bottom surface of the crucible in the open state in the radial direction, carbon monoxide is generated. However, since it is from the outside lower part of the silicon melting crucible, it is flowed to the lower part by the argon gas flow flowing from the upper part of the chamber and exhausted out of the chamber, so that the amount taken into the molten silicon in the silicon melting crucible is small. Further, since the carbon member does not face the heating element disposed on the side surface portion of the silicon melting crucible, the suppression of the heating by the heating element also suppresses the reaction and reduces the generation of carbon monoxide.

  Preferred embodiments of a crucible for melting silicon and a method for producing the same according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a flowchart of a method for manufacturing a crucible for melting silicon according to the present invention. First, in step S01, a conventional quartz crucible is prepared. Next, in step S02, the quartz crucible is dipped in a slurry obtained by mixing silica powder and colloidal silica and then pulled up to form a slurry layer on the outer surface. Next, in step S03, silica sand having an average particle size smaller than the thickness of the slurry layer is sprayed on the surface of the slurry layer to form a stucco layer. Next, the steps S02 and S03 are repeated any number of times, and the slurry layers and the stucco layers are alternately laminated, and finally the slurry layer is formed to form the outer layer portion.

  Next, in step S04, the quartz crucible on which the outer layer portion is formed is heated and held at 600 to 1200 ° C. for 0.5 to 12 hours to be baked, thereby completing a silicon melting crucible. The silicon melting crucible thus produced has high strength and suppresses high temperature softening.

  FIG. 2 is a schematic diagram of an enlarged cross section of the silicon melting crucible 1. In an actual silicon melting crucible, a large number of layers are usually laminated on the outer layer, but in this schematic diagram, three binder layers 2 and two stucco layers 3 are drawn. The silicon melting crucible 1 formed in this way has irregularities due to the silica sand 7 formed on its outer surface 1 b, that is, the surface actually in contact with and supported by the carbon outer crucible 10. Since the unevenness is so large that the unevenness of the inner surface 10 a of the carbon outer crucible 10 can be ignored, the convex portion 8 of the outer surface 1 b of the silicon melting crucible 1 makes point contact with the inner surface 10 a of the carbon outer crucible 10. Supported. On the other hand, the inner surface of the quartz crucible portion 4 of the silicon melting crucible 1 (not shown) is flat as in the case of the conventional quartz crucible.

  In the case of a conventional quartz crucible, the quartz crucible is supported in surface contact with the flat surface 4a of the quartz crucible portion 4 and the flat inner surface 10a of the carbon outer crucible 10 in FIG. It will be.

  Since the amount of carbon monoxide generated depends on the contact area between the silicon melting crucible and the carbon outer crucible, the contact area should be as small as possible. Therefore, the silicon melting crucible of the present invention that makes point contact with the conventional silicon melting crucible in surface contact with the outer carbon crucible can suppress the generation of carbon monoxide, and the carbon concentration in the silicon ingot Can be reduced.

  FIG. 3 is a schematic view of the vicinity of a silicon melting crucible and a carbon member of the silicon single crystal pulling apparatus according to the present invention. Since the silicon melting crucible of the present invention has high strength and is suppressed from being softened at a high temperature, a carbon outer crucible for fitting the silicon melting crucible from the entire outside is not required. Therefore, in this example, the bottom surface of the silicon melting crucible is only supported by the carbon member.

  Since the carbon member 16 faces only the bottom surface portion 15a of the silicon melting crucible and supports the silicon melting crucible 15, the carbon member 16 is generated by reacting with the carbon member 16 at the bottom surface portion 15a of the silicon melting crucible 15. Since the carbon monoxide gas (arrow A in the figure) is caused to flow downward by the argon gas (arrow B in the figure) flowing from the top of the silicon single crystal pulling apparatus, the silicon 32 melted in the silicon melting crucible 15 The amount taken in is suppressed. Further, since the carbon member 16 does not face the heating element 17 disposed on the side surface portion 15b of the silicon melting crucible 15, the heating by the heating element 17 is suppressed, and the reaction with the silicon melting crucible 15 is reduced.

It is a flowchart which shows one Embodiment which concerns on the manufacturing method of the crucible for silicon melting of this invention. It is a schematic diagram of the one part expanded cross section of the crucible for silicon melting of this invention. It is a figure which shows one Embodiment of the crucible for silicon melting of this invention, and the member made from carbon. It is a figure which shows one Embodiment of the conventional silicon single crystal manufacturing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon melting crucible 1b Outer side surface 2 Binder layer 3 Stucco layer 4 Quartz crucible part 4a Flat surface 7 Silica sand 8 Convex part 10 Carbon outer crucible 10a Inner surface 15 Silicon melting crucible 15a Bottom surface part 15b Side surface part 16 Carbon member 17 Heating element 21 Chamber 22 Crucible 23 Heating element 24 Silicon single crystal pulling device 30 Shaft 32 Molten silicon 40 Seed crystal 41 Silicon single crystal A Flow of carbon monoxide gas B Flow of argon gas

Claims (3)

A binder layer mainly composed of amorphous silica powder and a stucco layer made of amorphous silica sand are alternately laminated on the outer surface of the quartz crucible an arbitrary number of times to form an outer layer portion. It is heated and fired at 1200 ° C. for 0.5 to 12 hours, and is a molded body in which crystalline silicas are diffusion-bonded by sintering ,
A crucible for melting silicon, wherein the outer surface of the outer layer portion has irregularities due to silica sand .   A silicon single crystal pulling apparatus comprising the crucible for melting silicon according to claim 1.   A silicon single crystal pulling apparatus comprising: the crucible for melting silicon according to claim 1; and a carbon member that supports a bottom surface of the crucible with its radially outer side open.

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