Chemical Vapor Deposition of Electronic Materials

Abstract

Chemical vapor deposition (CVD), as the name implies, involves the formation of a deposit on a substrate caused by the reaction of chemicals transported to the substrate in the vapor phase. It is a very old technique which dates at least as far back as the chemical transport studies of Bunsen (1) and Sainte-Claire Deville (2) in the mid-nineteenth century, and which achieved commercial significance as long ago as 1880 when it was used for coating filaments in the incandescent lamp industry (3). Over the course of approximately 100 years it has developed into a very important method for material synthesis and today has application to a broad spectrum of compounds ranging from relatively easily prepared amorphous and polycrystalline deposits used as protective coatings to highly sophisticated epitaxial single crystalline films used in semiconductor devices. The growing importance of CVD is derived from the inherent versatility of this synthesis method which permits the preparation of virtually any material in essentially any geometry. In addition, CVD has a number of unique advantages, in comparison with most synthesis techniques, which include the ability to synthesize materials at relatively low temperatures and to directly synthesize compounds represented by any region of a phase diagram. This latter ability is very important for the preparation of compounds having incongruent melting points and for the synthesis of solid solutions or alloys. The ability to prepare materials at low temperatures is beneficial for achieving high purity since contamination resulting from diffusion processes and unwanted reactions can be minimized. Also, homogeneity and stoichiometry can be more easily controlled in compounds which have high equilibrium dissociation pressures near their melting temperatures, and the integrity of substrate materials can be more easily assured. An additional advantage of CVD is that it readily accommodates the