Process Control During Liquid Phase Rerowth of 3C-SiC on Si Substrates
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0911-B08-04
Process Control During Liquid Phase Rerowth of 3C-SiC on Si Substrates Mark P. Smith1, Matthias Voelskow2, Richard A. McMahon1, Andreas Muecklich2, Wolfgang Anwand2, and Wolgang Skorupa2 1 Department of Engineering, University of Cambridge, Trumpington Street, Cambridge, Cambridgeshire, CB2 1PZ, United Kingdom 2 Institute of Ion Beam Physics and Materials Research, Forschungszentrum Rossendorf, Dresden, Saxony, Germany ABSTRACT Flash lamp annealing in the millisecond regime of heteroepitaxial SiC on silicon structures involves melting the Si below the SiC layer, but the deep facetted nature of the solid-liquid interface leads to unacceptable long-range surface roughness. This paper describes a method of controlling melting by implanting a high dose of carbon or germanium at a controlled depth below the Si/SiC interface, which significantly alters the melting characteristics of the silicon. Results confirm the effectiveness of these approaches for increasing surface uniformity, making liquid phase processing compatible with standard device fabrication techniques. A thermal model has also been developed to describe this process and results indicate that the theoretical work is consistent with experimental evidence. The model is a valuable tool for predicting the onset of melting, maximum temperatures and process windows for liquid phase epitaxy.
INTRODUCTION Silicon carbide is an attractive material for power devices and for sensors operating in harsh environments, on account of its high thermal stability, thermal conductivity, wide band gap, theoretically high electron mobility and resistance to chemical attack. 3C-SiC has electrical characteristics among the best of the SiC polytypes, but a high defect density arising from growth has led to other polytypes being preferred. A successful method for forming 3C-SiC at low cost could enable the 3C polytype to gain a major share of the market. The growth of 3C-SiC on silicon substrates is the preferred method of preparation due to the low cost, large area and relatively high quality of the Si substrates. The current technology for growing 3C-SiC films epitaxially on (100) Si-substrates is based on CVD deposition at 1350 °C after carbonisation of the substrate surface at 1150 °C. However, due to the relatively high misfit between the lattice parameters the defect density in the SiC layer near the interface is very high [1]. Subsequent growth, to produce thicker (several microns) 3C-SiC layers, reduces the defect density by several orders of magnitude. Nevertheless, for the successful application of epitaxially grown 3C-SiC films, a further significant reduction of the defect density is necessary. Flash lamp annealing (FLA) of as-deposited thin SiC layers on silicon substrates with intense light pulses from an array of xenon flash lamps can give a marked improvement in the layer properties [1]. Results presented in reference [1] show in-depth comparison of the defect density in the SiC layers, before and after flash lamp treatment. Transient melting of the sil
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