The Growth And Characterization Of Beta Silicon Carbide Beta Sic Thin Films By Chemical Vapor Deposition In A Low Pressure Vertical Reactor

Thin films of beta silicon carbide were prepared on alpha silicon carbide substrates by the chemical vapor deposition (CVD) technique involving the hydrogen reduction of silane and propane. The films were prepared under a variety of conditions and subsequently subjected to thermal annealing cycles between 1600 degrees C and 2000 degrees C. It is shown that the single crystallinity of the beta films improved with continued annealing. The beta polytype was found to be stable over the entire range of temperatures studied.

The project involves the development of low pressure chemical vapor deposition and r-f sputtering techniques for the synthesis of single crystal thin films of beta-SiC. The CVD apparatus is being produced in-house and a detailed description of the design is provided herein. Theoretical CVD phase diagrams of the Si-C-H system are also being produced as a function of Si/Si+C and total pressure. Both reactive sputtering of Si in CH4 and normal sputtering of a SiC target are being readied. (Author).

Beta silicon carbide has the potential of becoming an important semiconductor device material for hazardous military environments such as high temperature and radiation. This report is concerned with a study of the growth of thin single crystal films of beta silicon carbide through molten metal intermediates. Thin films of nickel, cobalt, chromium and iron were deposited by vacuum deposition on to the (0001) faces of single crystals of alpha silicon carbide. Then heteroepitaxial layers of beta silicon carbide were deposited through the molten metal films by the hydrogen reduction of methyltrichlorosilane. The deposited films were studied by electron microscopy, electron diffraction and electron beam microprobe analysis to determine the growth mechanism and to arrive at optimum conditions for heteroepitaxial growth. From the results obtained it was concluded that nickel and cobalt were equally effective in promoting epitaxial growth. Films of nickel only 20A in thickness were as effective as those up to 300A. Results with chromium and iron were disappointing for different reasons. Chromium did not etch the substrate surface uniformly because of poor wetting. With iron, whisker growth of beta silicon carbide occurred at the surface. Although in many respects the growth of mechanism resembled that of the vapor-liquid-solid method, certain differences were observed which make the actual growth mechanism using nickel and cobalt films still uncertain. (Author).