Chlorinated silicon carbide CVD revisited for polycrystalline bulk growth
Silicon carbide is interesting for high power, high temperature and high frequency applications but its development is limited by the low quality and high cost of single-crystalline wafers. The transfer by wafer-bonding of single-crystalline SiC thin films to a polycrystalline SiC support is an attractive way for lowering the cost. This transfer requires high quality polycrystalline substrates fabricated with high growth rate, controlled morphology (columnar, dense, well-oriented layers), and very low surface roughness (RMS < 5 nm), to achieve tailored bulk properties.
Compared to the Physical Vapour Transport technique which is limited by the low number of process parameters (temperature, pressure, crucible design), high temperature Chemical Vapour Deposition represents an easier and more efficient way of controlling high growth rate, morphology, crystalline quality via the gas phase composition (Si/C ratio, supersaturation…) and temperature. Typical deposition conditions using methyltrichlorosilane (MTS) has been revisited at higher temperature (above 1500 °C) to achieve high growth rate. Advantages of chlorine system vs. organosilane system have been highlighted by thermodynamic calculations in the range of 1000–2000 °C. Thermodynamic and thermal simulations have been performed to describe the methyltrichlorosilane decomposition. Finally, bulk silicon carbide layers are synthesized between 1200 °C and 1600 °C at various H2/MTS ratios. The observed morphologies are correlated to calculated thermodynamic supersaturations.
- Silicon carbide;
- Thermodynamic and thermal modelling; silicon carbide ceramics
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