Silicon Carbide Growth: C/Si Ratio Evaluation and Modeling
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0911-B04-02
Silicon Carbide Growth: C/Si Ratio Evaluation and Modeling Michel Pons1, Shin-Ichi Nishizawa2, Peter Wellmann3, Elisabeth Blanquet1, Didier Chaussende1, and Jean Marc Dedulle1 1 CNRS, INPGrenoble, 1130 rue de la Piscine, BP 75, Saint Martin D'Heres, Rhone-Alpes, 38402, France 2 National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Japan, Ibaraki 305-8568, Japan 3 Materials Department 6, Erlangen University, Martensstr. 7, Erlangen, Germany, 91058, Germany ABSTRACT Modeling and simulation of the SiC growth processes, Physical Vapor Transport (PVT), Chemical Vapor Deposition (CVD) and hybrid techniques, are sufficiently mature to be used as a training tool for engineers as well as a growth machine design tool, e.g. when building new process equipment or up-scaling old ones. It is possible (i) to simulate accurately temperature and deposition distributions, as well as doping (ii) to quantify the limiting phenomena, (iii) to understand the important role of different precursors in CVD and hydrogen additions in PVT. The first conclusion of this paper is the importance of the "effective" C/Si ratio during CVD epitaxy in hot-wall reactors and its capability to explain the doping concentrations. The second conclusion is the influence of the C/Si ratio in alternative bulk growth technique involving gas additions. Preliminary results show that fine tuning of H2 or precursor additions allow a better control of concentrations of residual and intentional doping.
INTRODUCTION Nowadays, gas-solid chemical reactions are most commonly used for the growth of bulk silicon carbide single crystals and epitaxial layers. One important challenge is the control of residual and intentional doping. One way to change it is the control of the effective C/Si ratio. In the mid-1990s, the site-competition theory proposed by Larkin [1] described the dependence of the doping atom incorporation with the ratio of available silicon and carbon atoms (C/Si ratio) in the gas phase. The site-competition epitaxy working model is based on the competition between the SiC and dopant source gases for the available substitutional lattice sites on the growing SiC crystal surface. Dopant incorporation is controlled by appropriately adjusting the C/Si ratio within the growth reactor to affect the amount of dopant atoms incorporated into these sites. Specifically, Larkin's model is based on the principle of competition between nitrogen and carbon for the C sites and between aluminum and silicon for the Si sites during the growth of the epilayer. In summary, the nitrogen donor concentration in the grown epilayer is inversely proportional to the C/Si ratio during epilayer growth, whereas the aluminum acceptor concentration is proportional to the C/Si ratio. This paper will address two issues on modeling and simulation. The first one is the study of doping phenomena in hot-wall CVD reactor used for epitaxial growth at low growth rate (3-10
µm/h), around 1900 K using silane and propane diluted in H2.
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