A method of producing silicon single crystals in violation of the single-crystal growth

 

(57) Abstract:

The invention relates to the field of obtaining single crystals of semiconductor materials and can be used to obtain silicon single crystal by Czochralski method. The inventive method includes pulling the ingot from the melt on a seed crystal, alienating it from the melt, separating the strand from the seed, feeding of the melt and pulling the next ingot, in which pulling the ingot control the morphology of its surface and by fixing the disappearance or interruption of the growth faces of the single crystal carry out the specified separation of the ingot from the melt. The invention improves the yield of product by increasing the purity of the melt and to reduce the polycrystalline part in the grown ingot and can also be used raw material with a greater degree of contamination. table 1.

The invention relates to the field of obtaining single crystals of semiconductor materials and can be used to obtain silicon single crystal by Czochralski method.

A known method of producing silicon single crystals, including pulling the ingot from a melt of polycrystalline silicon on monocrystalline. - K., 1997, S. 7) [1]. The seed crystal and the crucible are rotated in opposite directions to provide radial uniformity of the temperature field that defines the homogeneity of the parameters of the growing crystal.

However, in practice often a violation of the single-crystal growth of silicon ingots. The graphite particles, quartz and various kinds of refractory compounds that fall outside or were included with the download comes at the expense of conventional and diffusion from the melt to the surface crystallization, disrupting the process of single crystal growth. In pulling the ingot is formed of single-crystal region with a high content of dislocations, resulting in a region with a polycrystalline structure. Such ingots significantly reduce the percentage yield (% SE) at high energy consumption, crucibles, graphite. Depending on the quality used to load the raw material, the purity class production facilities, technical equipment level, the number of ingots with impaired single-crystal growth is from 15 to 40% of the total number of heats.

A known method of producing silicon single crystals, including the pulling of the ingot on a seed crystal of n is alloy pulling the next ingot of not more than 2/3 of the melt, and so forth several cycles and, finally, the ingot is pulled from the entire melt (SU inventor's certificate 1773955, M CL 30 In 15/02, 29/06, publ. 07.11.1992) [2]. This method is chosen for the prototype because it is the closest method of producing silicon single crystals in violation monocrystalline growth.

The disadvantage of this method is that known method is provided for pulling the ingot from the melt regardless sustainable or broken monocrystalline growth. It is not possible to avoid a significant reduction in percentage of yield of product on the bars with the broken single-crystal growth. As shown in the table, % SE by a known method does not exceed 61%.

The objective of the invention is to provide such a method of producing silicon single crystals in violation of the single-crystal growth, which by definition of the moment of separation of the ingot from the melt is achieved by increasing the percentage yield of the product by improving the purity of the melt and the elimination of polycrystalline part in the grown ingot. In addition, the proposed method allows the use is achieved by the proposed method of producing single crystal silicon in violation of the single-crystal growth, including pulling the ingot from the melt on a seed crystal, alienating it from the melt, separating the strand from the seed, feeding of the melt and pulling the next ingot, in which pulling the ingot control the morphology of its surface and by fixing the disappearance or interruption of the growth faces of the single crystal carry out the specified separation from the melt.

Violation of the single-crystal growth in accordance with technological regime and the absence of failures in the equipment is, if the surface crystallization fall debris coming at the expense of diffusion and conventional flow from the melt. We found that the most favorable is the separation of the ingot from the melt immediately after the disappearance or interruption on the surface of the ingot growth faces of the crystal, because at this point most of the foreign particles from the melt passed in the near-surface region of the bottom part of the ingot. The remaining melt is more clean from particles. When the uploading of such melt content of particles less critical and the next ingot is grown in most cases without violating the single-crystal growth. In the grown ingot.

Loading consisting of polycrystalline silicon and return ingot is melted in a quartz crucible. The seed required orientation controlled by the speed of the pull bar. The process is carried out in a sealed chamber in a stream of argon at a pressure in the chamber is not more than 150 PA. When extruding the ingot conduct visual monitoring of the growth faces of the single crystal. When fixing the disappearance or the interruption of the growth faces of the single crystal to produce a separation of the ingot from the melt, move it, separating the ingot from seed and unload it from the camera. Then perform the uploading of the crucible, melted polycrystalline silicon and pull the next strand on the same seed, as a rule, from the melt, as if pulling the next crystal violation of the single crystal growth was observed.

The percentage yield of product (% SE), i.e. dislocation single crystal, calculated according to the formula

< / BR>
where Li- the length of the dislocation single crystal part i-the strand extruded from a single crucible, cm;

i - the number of bars, extruded from a single crucible;

D is the diameter of the calibrated ingot (in these experiments is equal to 15 cm);

- density monomer. In each of the 80 crucibles were loaded with 25 kg of polycrystalline silicon and 7 kg of returns. For 4 h was carried out fusion download. Each crucible was pulled ingot with a diameter of 155 mm on a monocrystalline seed crystal orientation (100). The rise of the 4 faces of the single crystal was carried out by visual inspection. Fifteen crucibles of 80 has been a violation of the single-crystal growth: an interrupt or disappearance. When fixing interrupt or disappearance of the growth faces of the single crystal in each of the fifteen crucibles was carried out by separation of the ingot from the melt and the separation of the ingot from the seed. Then spent uploading these crucibles necessary number of from 17 to 24 kg content in each of them 32 kg load silicon. After melting so pulled another strand on the seed used by the pulling of the first ingot from the crucible. By pulling the second ingot from the crucible in all cases when the observation was not recorded interrupt or disappearance of the growth faces of the single crystal. Were obtained ingots with just melt without breaking the single-crystal growth.

The characteristic obtained in these crucibles crystals and the yield of product is given in the table. As a view of the finding allows to increase the yield of product, to reduce energy consumption and to use lower quality raw materials.

A method of producing silicon single crystals in violation monocrystalline growth, including pulling the ingot from the melt on a seed crystal, alienating it from the melt, separating the strand from the seed, feeding of the melt and pulling the next ingot, characterized in that the pulling of the ingot control the morphology of its surface and by fixing the disappearance or interruption of the growth faces of the single crystal carry out the specified separation of the ingot from the melt.

 

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