Chemical Vapor Deposition of Beta Silicon Carbide Epilayers Using the Single Source Precursor 1,2-Disilylethane
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CHEMICAL VAPOR DEPOSITION OF BETA SILICON CARBIDE EPILAYERS USING THE SINGLE SOURCE PRECURSOR 1,2-DISILYLETHANE J. D. PARSONS*, D.A. ROBERTS**, J.G. WU*, A.K. CHADDA*, H-S. CHEN* and H. HOCKENHULL** * Department of Electrical Engineering and Applied Physics, Oregon Graduate Institute of Science and Technology, Beaverton, OR 97006 ** Schumacher, 1969 Palomar Oaks Way, Carlsbad, CA 92009 ABSTRACT A B-SiC epitaxial growth process, using 1,2-disilylethane (DES), was developed. DSE was selected because it contains an equal number of C and Si atoms and its reported decomposition characteristics suggest that C and Si could be obtained from it at approximately equal rates. Repeatable nucleation and epitaxial growth conditions, giving complete substrate coverage and controlled growth, were established by atmospheric pressure CVD, in an inverted-vertical reactor. A substrate temperature of 1290± 10'C was found to be optimum for B-SiC epilayer nucleation and growth. The maximum B-SiC epitaxial growth rate obtained was 1014ms/hr. Undoped 13-SiC epilayers were n-type (n - 10"6 cm-3 ). DSE synthesis, CVD growth parameters, SiC deposition characteristics and B-SiC epitaxial film properties are described. INTRODUCTION The SiC crystalline form having the cubic, zinc blend structure (6-SiC or 3C-SiC) has the potential to become the most important semiconductor material since Si. This potential is due to its many outstanding properties which are important for electron device integrated circuit (IC) performance. These properties - presented in the Table- can extend the range of solid state electronic applications well beyond present power, powerfrequency, temperature and radiation fluence limits. More than 170 different polymorphic forms of SiC have been identified. The include four crystal structures and .polytypes of the hexagonal2", rhombohedral2' and trigonal22 structures. Beta-SiC has no polytypic23', 4 forms. Synthesis of bulk B-SiC crystals in substantial size or quantity is not yet possible. Thus, the primary focus of B-SiC synthesis has been epitaxial growth of thin films onto 31 Si" , 6Haz-SiC 32'22 , AIN3, and TiC35"38 substrates. TiC was used as a substrate because it possesses unique advantages for nucleation and growth of B-SiC epilayers 35' 36' 39 . and for vertical device structures. The use of DSE as a single source CVD precursor for B-SiC growth on TiC has been reported 38,40 ,41 . However, the morphological properties of B-SiC obtained from pyrolyzed DSE are very sensitive to the TiC preheat process and to the CVD parameters used for B-SiC nucleation and growth. The purpose of this work was to determine CVD parameters which yield device quality B-SiC epitaxial films. In this paper we discuss: (1) the synthesis of DSE, (2) the CVD process used to grow SiC form pyrolyzed DSE, (3) the morphology and crystallinity of SiC as a function of CVD growth parameters, (4) the optimized CVD conditions for B-SiC epitaxial growth, and (5) the crystallinity, morphology and carrier concentration of B-SiC grown at the optimized CVD g
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