Method of preparing crucible for growing of monocrystalline silicon ingot

FIELD: production of semiconductor material monocrystals.

SUBSTANCE: method involves formation of barium-containing coating of barium hydroxide on inner and/or outer surface of heated quartz crucible, said coating being formed by spraying suspension of barium hydroxide in air atmosphere on surface of quartz crucible heated to temperature of 100-150 C.

EFFECT: improved uniformity and homogeneity of coating to thereby increase yield of product and reduce discard in production of monocrystalline silicon ingots.

4 ex

 

The invention relates to the field of obtaining single crystals of semiconductor materials, in particular to the preparation of the crucible for growing silicon single crystals from the melt by the Czochralski method.

Single-crystal silicon by the Czochralski get by pulling the ingot from the molten silicon in a quartz crucible. The process is carried out in a sealed chamber in an atmosphere of inert gas at low pressure and high temperature.

The standard wall of the quartz crucible used in the production of ingots of silicon single crystals, have a structure with internal bubble free layer thickness of 2-7 mm in contact with the melt, and an outer layer containing bubbles.

In the process of obtaining the melt and the growth of the silicon single crystal quartz crucible is heated to a temperature of 1500-1600°C. under reduced pressure and high temperature bubbles walls of the crucible increase in volume and due to the concentration gradient bubbles diffuse to the inner surface of the crucible in contact with the melt, and come to the surface of the crucible.

At the exit to the inner surface of the crucible of two or more nearby bubbles on the inside surface are formed adjacent to each other depressions in the form of bowls. Impact melt leads to thinning of the jumpers this is x recesses and the subsequent separation of the pieces of quartz from the inner surface of the crucible.

Pieces of quartz, not had time to fully dissolve in the melt, can get in the region of the crystallization front, which leads to breakage dislocation of crystal growth. This effect is particularly evident when growing ingots of single crystal of a large diameter.

Known crucibles and methods for their preparation, are described in U.S. patent No. 4956208 and No. 4935046, with an opaque outer surface and a transparent inner quartz surface that is highly purified from bubbles.

This structure crucible prevents separation of particles of quartz from its walls, however, does not prevent the deformation of the walls under the influence of high temperatures, which also leads to impaired growth of the single crystal.

The closest is the method of preparation of the crucible for growing a single crystal ingot by the Czochralski method, which involves the formation of a barium-containing coating of barium hydroxide on the inner and/or outer surface of the heated quartz crucible, is known from U.S. patent No. 5980629 published 9.11.1999 [1]. In the known method on the surface of a quartz crucible heated to a temperature of 200-300°, is applied by spraying a solution of barium hydroxide when applying carbon dioxide. The barium hydroxide immediately sticks to the surface of the crucible and partially converted into barium carbonate when to the stage with carbon dioxide. After that, the surface at the same time pollinate water and carbon dioxide to complete the conversion of the hydroxide of barium in the barium carbonate. PH pH-covered surface supported within 8-9,5.

Obtained by a known method, the coating of the quartz crucible of barium carbonate in the process of heating the crucible upon receipt of the melt is converted to barium oxide, which reacts with the silica on the surface of the crucible with the formation of silicates of barium.

There is a method of preparation of the crucible for growing a single crystal ingot by the Czochralski helps to strengthen the walls of the quartz crucible and to prevent separation of particles of quartz from its walls. However, the thus obtained coating is often uneven, that in the future, in the process of obtaining the melt and the growing ingot, lead to flaking of the coating and decrease the yield of the product. In some cases there is a contamination of the ingot on the carbon, resulting in the marriage of carbon. In connection with this known method is preferred when coating only the outer surface of the crucible.

Object of the invention is the improvement of the method of preparation of the crucible for growing a single crystal ingot by the Czochralski method, in which due to the proposed conditions of application pok is itia crucible improves the uniformity and homogeneity, which leads to an increase of the yield of the product and reduction of defects in the produce ingots of single crystal silicon.

The problem is solved by the proposed method training crucible for growing a single crystal ingot by the Czochralski method, including the formation of barium-containing coating of barium hydroxide on the inner and/or outer surface of the heated quartz crucible, which indicated the formation of the barium-containing coating is carried out on the surface of the quartz crucible heated to a temperature of 100-150°C.

Barium-containing coating may be formed on inner and outer surface of the crucible, on the inner surface of the crucible or on the outer surface of the crucible. Thus the formation of the barium-containing coating is preferably carried out in an atmosphere of air.

Experimentally we found that during the application of barium hydroxide on the surface of a quartz crucible heated to a temperature of 100-150°the last is fully converted to barium carbonate with the formation of a uniform and homogeneous layer, which improves the quality of the coating. For the conversion of barium hydroxide barium carbonate in these conditions, a sufficient concentration of carbon dioxide in the air. Further in the process of obtaining the melt and the growing silicon single crystal passage is t reaction conversion of short-lived barium carbonate into barium oxide and at higher temperatures in uniform ceramic coating BaSiO 3.

The method is as follows.

Quartz crucible is installed in the camera heat and heated to the surface temperature of the crucible 100-150°C.

Willing suspension of barium hydroxide selected concentration is stirred for 9-12 minutes and transfer to a spray bottle.

Quartz crucible heated to a temperature of 100-150°placed in a cell deposition, which is the air.

On the surface of the crucible by means of a spray evenly applied the calculated amount of suspension of barium hydroxide, which is on the surface of the crucible is converted into barium carbonate, forming a homogeneous uniform layer.

For a more uniform deposition of barium hydroxide rotate the crucible. Suspension of barium hydroxide is applied on the side walls of the crucible and the bottom part. If the coating is applied to both surfaces of the crucible, first put a coating on the inner surface and outer surface. During the application of barium hydroxide on the external surface of the crucible is turned upside down and mounted on the ring.

The proposed method allows to prepare a crucible for growing a single crystal ingot by the Czochralski method, which have a uniform homogeneous coating. This coating is not destroyed and does not flake in the process of obtaining the melt and the growing ingot of single crystal.

10 quartz crucible with a diameter of 18′′ (45.72 cm) was placed in the chamber of the heat and heated until the surface temperature of the crucible 100°C.

Preparing a suspension of barium hydroxide by dissolving 50 mM barium hydroxide in 500 ml of deionized water. The suspension was stirred for 10 minutes and transferred into a spray bottle.

Heated quartz crucible was placed in a cell deposition and evenly applied on the inner surface of the crucible suspension of barium hydroxide on the side walls and bottom part. The application was carried out using a spray in the air. Waited drying the applied layer and said application layer before spending 50 ml suspension of barium hydroxide to each crucible.

Prepared crucibles have a uniform homogeneous coating.

Crucibles coated was used for growing monocrystalline silicon ingots.

Example 2.

10 quartz crucible with a diameter of 18′′ (45.72 cm) was placed in the chamber of the heat and heated until the surface temperature of the crucible 120°C.

Preparing a suspension of barium hydroxide by dissolving 130 mM barium hydroxide in 1300 ml of deionized water. The suspension was stirred for 12 minutes and transferred into a spray bottle.

Heated quartz crucible was placed in a cell deposition and evenly applied on the inner surface of the crucible suspe is the Zia hydroxide barium on the side walls and bottom part. The application was carried out using a spray in the air. Waited drying the applied layer and said application layer before spending 50 ml of the suspension on the inner surface of one of the crucible. Then the crucibles turned and struck a uniform layer of slurry on the outer surface of each crucible. Waited layer and drying was repeated application before spending 80 ml of suspension.

Prepared crucibles have a uniform homogeneous coating.

Crucibles coated was used for growing monocrystalline silicon ingots.

Example 3.

10 quartz crucible with a diameter of 20′′ (50.8 cm) was placed in the chamber of the heat and heated until the surface temperature of the crucible 130°C.

Preparing a suspension of barium hydroxide by dissolving 62 mM barium hydroxide in 620 ml of deionized water. The suspension was stirred for 10 minutes and transferred into a spray bottle.

Heated quartz crucible was placed in a cell deposition and evenly applied on the inner surface of the crucible suspension of barium hydroxide on the side walls and bottom part. The application was carried out using a spray in the air. Waited drying the applied layer and said application layer before spending 62 ml suspension of barium hydroxide to each crucible.

Training the military crucibles have a uniform homogeneous coating.

Crucibles coated was used for growing monocrystalline silicon ingots.

Example 4.

10 quartz crucible with a diameter of 20′′ (50.8 cm) was placed in the chamber of the heat and heated until the surface temperature of the crucible 150°C.

Preparing a suspension of barium hydroxide by dissolving 160 mM barium hydroxide in 1600 ml of deionized water. The suspension was stirred for 12 minutes and transferred into a spray bottle.

Heated quartz crucible was placed in a cell deposition and evenly applied on the inner surface of the crucible suspension of barium hydroxide on the side walls and bottom part. The application was carried out using a spray in the air. Waited drying the applied layer and said application layer before spending 60 ml suspension on the inner surface of one of the crucible. Then the crucibles turned and struck a uniform layer of slurry on the outer surface of each crucible. Waited layer and drying was repeated application before spending 100 ml of suspension.

Prepared crucibles have a uniform homogeneous coating.

Crucibles coated was used for growing monocrystalline silicon ingots.

The use of crucibles prepared by the present method for growing a single crystal ingot by the Czochralski method, call the lilo:

to increase the yield of bullion by 10-15%;

to avoid flaking of the coating during the process of growing a single crystal ingot;

to exclude the appearance of marriage associated with contamination of the ingot on carbon.

Thus, the claimed method can improve the uniformity and homogeneity of the coating of the quartz crucible, which leads to an increase of the yield of the product and reduction of defects in the produce ingots of single crystal silicon.

The method of preparation of the crucible for growing a single crystal silicon ingot by the Czochralski method, including the formation of barium-containing coating of barium hydroxide on the inner and/or outer surface of the heated quartz crucible, wherein the barium-containing coating is formed by spraying a suspension of barium hydroxide in an atmosphere of air on the surface of the quartz crucible heated to a temperature of 100-150°C.



 

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