Sublimation Growth of SiC

Sublimation is one of the main methods of growing silicon carbide. This method is employed for growth of the material for abrasive applications as well as for the growth of single crystals and epitaxial layers for use in semiconductor electronics. The idea of the method is fairly simple, and is based on material transport from a hot source of material to a substrate which rests at a somewhat lower temperature. The transport is performed by the intrinsic vapour of the material at a high temperature, usually in the range 1600-2700 °C. 

The high efficiency of the method is evidenced by the fact that the first sublimation method of growing the crystalline material, the Acherson method, was proposed at the beginning of the 20th century and it is used today with only small variations. The Acherson process yields material for abrasive use and the rate of production is really very high, more than half a million tons per year [1]. No other technique of growing silicon carbide can be compared with sublimation in its productivity and efficiency. 

A new approach to the directed crystallisation of silicon carbide has been proposed by Vodakov and Mokhov [6]. Their idea was to exclude the conditions which could permit any uncontrolled nucleation. They employ a nearly flat source positioned close to the substrate and perform the growth under near-equilibrium conditions. This has ensured a high quality of the grown material. The method was named the sublimation sandwich method and it appeared to be very effective. 

The studies of growth by the sandwich method have provided a better understanding of the sublimation growth peculiarities and they have formed the basis of the new approach to the bulk crystal growth of silicon carbide. The first successful results in this direction were reported by Tairov and Tsvetkov [7,8]. Currently, similar studies are being performed by a number of research groups and rather impressive progress has been achieved thus far see Datareview 8.1. 

B EQUIPMENT AND METHODS OF GROWING SILICON CARBIDE BY SUBLIMATION 

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S. Yu Karpov, N. Yu Makarov, M. S. Ramm. Simulation of sublimation growth of SiC single crystals. Physica Status Solidi B 202 201, 1997. 

In the commercial development of Si devices, diffusion is an important semiconductor fabrication process. This process does not play a major role (except in the case of the sublimation growth of SiC discussed in Chapter 8) in the development of SiC, because the diffusion coefficients for the most part are negligible at temperatures below approximately 1800 °C. As a result of this commercial insignificance, the diffusion process in SiC and its various polytypes has not received a great deal of scientific attention and diffusion data are incomplete. It does, however, appear that the solubility of impurities and their diffusive mobilities in different SiC polytypes are very similar. 

FIGURE 1 Schematic diagrams of furnaces for sublimation growth of SiC (a) resistive type furnace ... 

Sublimation growth of SiC TABLE 3 Solubility limits for impurities in SiC (cm 5). 

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