Document Type

Thesis

Date of Award

8-31-1991

Degree Name

Master of Science in Chemistry - (M.S.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

James M. Grow

Second Advisor

Roland A. Levy

Third Advisor

R. P. T. Tomkins

Abstract

The depositions of amorphous and cubic-crystal SiC from a new chemical vapor deposition source, diethylsilane(DES), have been studied. Amorphous SiC thin films and crystalline cubic-SiC materials have been deposited on silicon wafers at temperature lower and higher than 850C, respectively. The activation energy and a reaction mechanism involving the production and subsequent desorption of diethylsilene has been suggested, which explains the observed deposition dependency with the temperature and reactor pressure. A model based on the polymerization of DES is offered and the deposition rate is found to be the result of a large number of simultaneously occuring deposition processes for all the polymers involved. The degree of polymerization is thought to determine the uniformity of the deposition rate: if the degree of polymerization is low, homogeneous thin films are deposited; if the degree is high, large thickness variations are observed. Based on the similarity of the pyrolysis of dialkylsilane and silane, DES shows a similar reaction mechanism in the CVD process to silane. A general method of estimation of the kind of reaction mechanism in a CVD process from the kinetics data has been proposed. In an etching study, the Si fraction of the films has been found to be effective on preventing the films from etching. A hypothesis, in which the silicon in amorphous SiC can react with KOH:H2O etching solution to form a porous film after the etching, has been suggested. In the film evaluation, the films chemical compositions, bonding and crystallinity were determined by RBS, IR and X-ray diffraction, respectively. The IR results show that the hydrogen content in the films can be ignored.

Included in

Chemistry Commons

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