Factors Influencing the Growth Rate, Doping, and Surface Morphology of the Low-Temperature Halo-Carbon Homoepitaxial Gro
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1069-D05-03
Factors Influencing the Growth Rate, Doping, and Surface Morphology of the LowTemperature Halo-Carbon Homoepitaxial Growth of 4H SiC with HCl Additive Galyna Melnychuk, Huang De Lin, Siva Prasad Kotamraju, and Yaroslav Koshka Mississippi State University, 216 Simrall Hall, Box 9571, Mississippi State, MS, 39762 ABSTRACT In this work, a possibility to further suppress silicon vapor condensation and formation of Si clusters in order to improve the growth rate and morphology during the low-temperature halocarbon epitaxial growth of 4H-SiC was investigated. While a pronounced dissociating of Si clusters was clearly demonstrated, the enhancement of the growth rate and morphology was less significant then expected. In addition, the homogeneity of the growth rate and doping along the gas flow direction indicated that a significant and non-equal depletion of Si and C growth species takes place at sufficiently high HCl supply. HCl flow-dependent formation of polycrystalline Si and SiC deposits in the upstream portion of the hot zone was shown to be the source of this depletion. INTRODUCTION Use of chlorinated precursors, including addition of HCl, in the epitaxial growth of SiC has been extensively investigated recently [1-2]. Significant improvements in epilayer morphology and the growth rate have been demonstrated. Most of the reports attribute the improvements caused by chlorinated precursors to enhanced dissociation of silicon clusters in the gas phase [1-3]. However, a possibility of a significant enhancement of the surface migration of adatoms due to HCl-assisted suppression of 2D nucleation was also suggested [4]. Most of the previous reports provide predominantly indirect evidences in support of the proposed mechanisms for the effect of HCl and other chlorinated precursors. The evidences are typically based on interpretation of the growth rate and morphology trends. The incompleteness of our knowledge about the HCl effect is even more pronounced for the so called low-temperature halo-carbon epitaxial growth [5]. HCl addition during the halocarbon growth at 13000C was successful for (1) improving the growth rate for the same growth conditions, and (2) making it possible to additionally enhance the growth rate by increasing the precursor flow rates without morphology degradation [6]. However, the observed trends did not allow making a simple conclusion that the improvements are merely due to increase of the Si supply to the growth surface caused by HCl-induced Si cluster dissociation or suppressed formation. In this work, an attempt is made to provide direct experimental evidences for the mechanisms of cluster-etching by HCl during the low-temperature halo-carbon growth.
EXPERIMENT Low-temperature epitaxial growth experiments were conducted in a hot-wall CVD reactor at 100-200 Torr with H2 as the carrier gas, SiH4 (3% in H2) as the silicon source, and CH3Cl as the carbon source. Different flow rates of HCl gas were used during the growth A typical growth experiment utilized 10x10 mm square pieces of stan
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