Heat and mass transfer modeling for a better knowledge of the large-area growth of homoepitaxial SiC by CVD
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Heat and mass transfer modeling for a better knowledge of the large-area growth of homoepitaxial SiC by CVD Michel Pons1, Jerome Mezière1, Jean Marc Dedulle3, Stephane Wan Tang Kuan, Elisabeth Blanquet1, Claude Bernard1, Pierre Ferret2, Lea Di Cioccio2, Thierry Billon2 and Roland Madar3 1
LTPCM- UMR 5614 (CNRS/INPG/UJF), Domaine Universitaire, B.P.75, F-38402 St. Martin d'Hères Cedex, France 2 LETI-CEA Grenoble, 38054 Grenoble Cedex 9, France 3 LMGP - UMR 5628 (CNRS/INPG), Domaine Universitaire, B.P. 46, F-38402 St. Martin d'Hères Cedex, France ABSTRACT The growth of thick epitaxial 4H-SiC layers with low defect density is an essential step for the fabrication of SiC based devices. Cold- and hot wall reactors using silane and propane diluted in hydrogen were used in this study. The typical growth temperature range is 1700-1900 K and total pressure range 10-100 kPa. The resulting epilayers exhibit low background doping, low defect density and good thickness uniformity. The main problem is that it is difficult with this first generation of reactors to ensure a constant temperature over large wafer. A 3D simulation approach of heat and mass transfer was used with three objectives. The first one is to have a visualization of the flow, temperature and gaseous species fields in the standard reactor. The second one is to propose solutions for the optimal control of the temperature field and the subsequent uniformity of the epilayers over large dimensions. The third one is to improve the kinetic databases in this temperature range which has been very little investigated.
INTRODUCTION In view of its excellent thermal, mechanical and electronic properties, silicon carbide is the semiconductor material of reference for high temperature, high frequency and high power devices. The 4H-SiC polytype is considered as the most attractive for the fabrication of such devices. The resulting applications have made tremendous progress primarily because of the commercial availability of SiC substrates of ever increasing diameter and quality. This triggers higher demands on the epitaxial process. The growth of thick epitaxial layers with low defect density and the control of the doping is an essential technique and the next step for the fabrication of devices. State-of-the-art silicon carbide devices structures are currently essentially grown by chemical vapor deposition techniques. A large variety of encouraging prototype device have been already demonstrated [1-2]. Vertical cold-wall reactors [4-6], chimney reactors [7], horizontal hot-wall [8-11] and cold-wall [3] reactors have enabled the growth 6H- and 4H-SiC epilayers at temperatures ranging from 1700 to 1900 K and pressures from 10 to 100 kPa. More recently, a new high temperature (2300-2500 K) CVD process (HTCVD) [7] based on a seeded vapor phase technique has enabled a fast growth (> 100 µm/h) of epitaxial layers with semi-
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insulating properties. Finally, planetary reactors enabling the loading of a large number of wafer were presented some months ago [12]. Our recent e
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