RU2378421C1 - Method of silicon crystals growth - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: method includes melting, growing of silicon crystal from melt in furnace chamber 2 with following cooling and removing of residues of silicon melt from melting pot 1 by means of creation of pressure difference between furnace chamber 2 and chamber 5 of tank- storage 4 with simultaneous pumping-over of silicon melt residues by tube 3, one end of which is placed into the rest of melt in melting pot 1, and the other end - into water-cooled tank- storage 4, herewith the rest of silicon melt, abandoned in quartz melting pot, should not exceed 10 mm.

EFFECT: reduction of consumptions ensured by excluding of destruction of quartz melting pots and increasing of its usage multiplicity, ability of secondary usage of silicon residues at following cycle of crystals growing.

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Description

The invention relates to a technology for producing semiconductor materials and can be used for growing silicon crystals from quartz crucibles according to the Czochralski method.

A known method of growing silicon crystals from a quartz crucible according to the Czochralski method, including melting and growing crystals, solidification of silicon residues in a crucible during cooling (B. Sakharov et al. Metallurgy and technology of semiconductor materials. M .: Metallurgy, 1972. - 544 S. )

However, the known method does not allow the use of a quartz crucible after cooling twice, which leads to an increase in the cost of the process of growing silicon crystals.

The closest set of essential features is the method of growing crystals, including silicon, including melting, growing a silicon crystal from a melt in a furnace chamber, followed by cooling and removing residual silicon melt from a crucible (JP 45014892 B, May 26, 1970).

However, the use of this method does not prevent the destruction of the quartz crucible. A quartz crucible is well wetted by molten silicon, and after cooling, the hardened silicon residues and the crucible are mechanically firmly bonded to each other, and since the thermal expansion coefficients of quartz and silicon differ significantly, they break apart when cooled. Therefore, a quartz crucible can be used to grow one or several crystals only in a semi-continuous process, and in a batch process only once, which significantly increases the cost of growing silicon crystals.

The main objective of the invention is to reduce the cost of growing silicon crystals by eliminating the destruction of quartz crucibles and increasing the frequency of their use, as well as the possibility of recycling silicon residues in the subsequent periodic process of crystal growth.

To solve the problem in a method of growing silicon crystals from a quartz crucible according to the Czochralski method, which includes melting, growing a silicon crystal from a melt in a furnace chamber, followed by cooling and removing silicon melt residues from a crucible, removing molten residues is carried out by creating a pressure differential between the furnace chambers and storage tank with simultaneous pumping of the remains of the silicon melt through a tube, one end of which is placed in the remainder of the melt in the crucible, and the other end in water cooling emy storage tank, wherein the molten silicon residue left in the quartz crucible should not exceed 10 mm.

The Czochralski method of growing silicon crystals from a quartz crucible involves melting, growing a silicon crystal from a melt in a furnace chamber, followed by cooling, and immediately after growing the crystal, the remainder of the silicon melt is removed from the crucible by creating a pressure differential between the furnace chambers and the storage tank with by simultaneously pumping the remainder of the silicon melt through a quartz tube, one end of which is placed in the melt of the silicon residue in the crucible, and the other in a water-cooled cutter UAR storage.

In relation to the prototype, the proposed method has the following distinctive features: after growing the crystal, the remainder of the silicon melt is removed from the crucible by creating a pressure differential between the furnace chambers and the storage tank while pumping the remainder of the silicon melt using a quartz tube, while the remaining silicon melt left in a quartz crucible, should not exceed 10 mm.

Pumping the remnants of the silicon melt from the quartz crucible by creating a pressure differential in the furnace chambers and the storage tank eliminates the destruction of the quartz crucible and increases the frequency of its use due to the fact that thermal stresses between solid quartz and silicon do not occur in the crucible purified from silicon residues.

The drawing shows a device for implementing the method.

A quartz crucible 1 placed in the chamber of the furnace 2 is charged with a portion of silicon, melted, and then a silicon crystal is grown.

Then, one end of the quartz tube 3 is placed in the crucible of the silicon melt in the crucible using a manipulator, and the other end is placed in the storage tank 4 installed in the chamber 5 connected to the chamber of the furnace 2 into a single system through a partition 6 through a gaseous medium. A pressure drop is created by evacuating the storage tank chamber or increasing the pressure in the furnace chamber and at the same time transfer the remaining silicon melt from the quartz crucible to the storage tank. The size of a drop of silicon left in a quartz crucible should not exceed 10 mm. If the droplet size is more than 10 mm, thermal stresses are formed between solid quartz and silicon, which leads to cracking of the crucible upon cooling. After cooling, silicon in the form of an ingot is removed from a storage tank having a shape close to the shape of a quartz crucible, but smaller, which is transferred to a quartz crucible after external etching for subsequent use in growing silicon crystals.

The proposed method in comparison with the prototype allows to increase the frequency of use of a quartz crucible for growing silicon crystals in a batch process by 10 times by eliminating cracking of the crucible, and also to reduce the consumption of silicon due to the secondary use of silicon residues in the subsequent process of growing silicon crystals and, as a result, reduce the cost of producing silicon crystals.

The cost of growing silicon crystals only for the purchase of quartz crucibles in the prototype is more than $ 80,000 per installation per year (for example, when loading 60 kg of silicon, a quartz crucible with a diameter of 500 mm at a cost of $ 550 is used, the growth process takes about two days).

When using the crucible ten times according to the proposed method, the annual savings will be more than $ 7200 per installation.

Claims (1)

A method of growing silicon crystals from a quartz crucible according to the Czochralski method, including melting, growing a silicon crystal from a melt in a furnace chamber, followed by cooling and removing silicon melt residues from a crucible, characterized in that the removal of melt residues is carried out by creating a pressure differential between the furnace chambers and the tank -stores with simultaneous pumping of the remains of the silicon melt through a tube, one end of which is placed in the remainder of the melt in the crucible, and the other end is placed in a water-cooled reservoir p-store, with the silicon melt residue left in the quartz crucible should not exceed 10 mm.