Real-Time In Situ Tracking of Gas-Phase Carbon-to-Silicon Ratio During Hot-Wall CVD Growth of SiC

The carbon-to-silicon ratio influences the background doping level of silicon carbide grown by hot-wall chemical vapor deposition (HWCVD). A quadrupole mass spectrometer was used to measure the process composition in the exhaust stream of a HWCVD reactor. The 26 amu mass-to-charge acetylene peak showed the strongest dynamic response to intentional changes in the precursor partial pressure at growth temperature. Methane peaks showed a similar but weaker dynamic response. The acetylene peaks have a direct linear correlation to variations in the propane and silane precursors, and thus can be tracked to give real-time in situ measurement of changes in the C/Si ratio.