Growth Mechanism and Dislocation Characterization of Silicon Carbide Epitaxial Films
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0911-B05-27
Growth Mechanism and Dislocation Characterization of Silicon Carbide Epitaxial Films Govindhan Dhanaraj1, Yi Chen1, Hui Chen1, William M Vetter1, Hui Zhang2, and Michael Dudley1 1 Department of Materials Science and Engineering, Stony Brook University, Stony Brook, NY, 11794-2275 2 Department of Mechanical Engineering, Stony Brook University, Stony Brook, NY, 117942300
ABSTRACT SiC homo-epitaxial layers were grown in a chemical vapor deposition process using silicon tetrachloride and propane precursors with hydrogen as a carrier gas. Growth rates were found to increase as temperatures increased at high carrier gas flow rate, while at lower carrier gas flow rate growth rates were observed to decrease as temperature increased. Based on the equilibrium model, “thermodynamically controlled growth” accounts for the growth rate reduction. The grown epitaxial layers were characterized using various techniques. Reduction in the threading screw dislocation (SD) density in the epilayers was observed. Suitable models were developed for explaining the reduction in the screw dislocation density as well as the conversion of basal plane dislocations (BPD) into threading edge dislocations (TED). INTRODUCTION Silicon carbide (SiC) is a promising advanced semiconductor material possessing excellent electronic and physical properties including high thermal conductivity, high breakdown field and high electron drift velocity [1, 2, 3]. The unique combination of these properties makes SiC a suitable material for certain critical applications such as high voltage, high power and high temperature devices. Epitaxial layers of thickness more than 100 µm are needed for high voltage SiC devices and hence higher growth rates are desirable for cost effective production. Hightemperature chemical vapor deposition (HTCVD) was developed to obtain thick films and even boules up to several millimeters thick grown at temperatures (1800-2200oC) close to physical vapor transport (PVT) process [4]. Recently, CVD using halide precursor was used in SiC epitaxial growth due to the higher decomposition temperature of silicon tetrachloride (SiCl4) in comparison to commonly used silane [5, 6]. Although epitaxial layers at growth rates of 100-200 µm/hr could be grown using the halide CVD at temperatures similar to those used in epilayer growth using silane, better understanding of growth process and mechanism are needed for well controlled halide CVD. The defect reduction in the epitaxial layer requires better knowledge of the growth and defect propagation. This paper presents our results on growth mechanism, and geometrical modeling on how the dislocations get redirected during the epitaxial growth process. EXPERIMENTAL PROCEDURE Epitaxial films were grown in our custom-made CVD system [7,8] using silicon tetrachloride (SiCl4) and propane (C3H8) as silicon and carbon precursors, respectively. Hydrogen was used as the carrier gas. Numerical modeling was used to obtain the temperature field in the hot-zone. Hydrogen was bubbled through silicon tetra
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