Polycrystalline SiC coating on large-sized SiC ceramics using Si vapor

Abstract

Polycrystalline SiC coating on large-sized SiC ceramics was investigated for its application to SiC susceptors for use in severe environments in LSI processes. The proposed coating process is simple and special gases are not used. SiC coating on the SiC substrate is achieved by positioning the ceramics above Si melt maintained in a carbon crucible in a furnace constructed using carbon materials. First, we evaluated the effect on the SiC grain size and the thickness of the SiC coating of varying the temperature and the distance maintained between a 1-inch diameter SiC substrate and the melt surface. We found that 6H-SiC grains several micrometers in size were densely deposited on the substrate, and the grain size and thickness of the SiC coating increased with increasing temperature. Next, based on these results, we achieved crystalline SiC coating on both sides of a 6-inch diameter SiC substrate. The number of carbon or SiC particles released from the SiC ceramic surface was evaluated with a submerged particle counter, and this number was found to be reduced by 99 % or more with a sample coated at 1800 °C as compared to the uncoated product. A discussion of possible chemical reactions for crystalline SiC formation is presented here based on the analysis of chemical species in the furnace using quadrupole mass spectrometers.