Bulk Growth of SiC
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Bulk Growth of SiC Peter Wellmann1, Ralf Müller1, Sakwe Aloysius Sakwe1, Ulrike Künecke1, Philip Hens1, Mathias Stockmeier2, Katja Konias2, Rainer Hock2, Andreas Magerl2, Michel Pons3 1 Institute for Materials Department 6, Electronic Materials, University of Erlangen-Nürnberg, GERMANY. 2 Institute for Crystallography, University of Erlangen-Nürnberg, GERMANY. 3 LTPCM, INPG, Grenoble, FRANCE corresponding author: [email protected] ABSTRACT The paper reviews the basics of SiC bulk growth by the physical vapor transport (PVT) method and discusses current and possible future concepts to improve crystalline quality. In-situ process visualization using x-rays, numerical modeling and advanced doping techniques will be briefly presented which support growth process optimization. The „pure“ PVT technique will be compared with related developments like the so called Modified-PVT, Continuous-Feeding-PVT, High-Temperature-CVD and Halide-CVD. Special emphasis will be put on dislocation generation and annihilation and concepts to reduce dislocation density during SiC bulk crystal growth. The dislocation study is based on a statistical approach. Rather than following the evolution of a single defect, statistic data which reflect a more global dislocation density evolution are interpreted. In this context a new approach will be presented which relates thermally induced strain during growth and dislocation patterning into networks. INTRODUCTION Commercial silicon carbide (SiC) substrates for electronic device applications are generally grown by the so-called PVT (physical vapor transport) growth, also called seeded sublimation technique. The growth process takes place in a quasi-closed graphite crucible system at elevated temperatures above 2000°C. Today 2", 3" and 4" substrates of the two polytypes 4H-SiC and 6HSiC are commercially available with low defect density. Depending on the application, nitrogen doped n-type and semi-insulating materials are available. In the case of p-type doping only medium conducting material is on the market. 3C-SiC is currently not commercially available in big volume. VAPOR GROWTH OF BULK SiC CRYSTALS Fundamental Growth Process Other than the widely used semiconductor materials silicon and gallium arsenide, silicon carbide single crystals cannot be grown from the melt. SiC decomposes peritectically at approx. 2800°C (figure 1a) into a Si melt with approx. 13% of dissolved C and into pure C which forms graphite clusters. At around 2000°C to 2400°C, however, sublimation of silicon carbide and defined re-crystallization may be carried out. This so called physical vapor transport (PVT) or seeded sublimation technique was first developed by Tairov and Tsvetkov [1] in 1978, who
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