In Situ Measurement of Nitrogen during Growth of 4H-SiC by CVD

Real-time analysis of downstream nitrogen process-gas flows during 4H-SiC growth is reported. A Hiden Analytical HPR-20 quadrupole mass-spectrometer (QMS) was used to measure the process gas composition in the gas-stream of a hot-wall chemical vapor deposition (CVD) reactor. Using the 28 amu peak, it was found that the nitrogen partial pressure measured by the mass spectrometer directly correlates to the expected partial pressure of nitrogen in the process cell based on input flows. Two staircase doping samples were grown to track doping variations. The nitrogen mass flow was varied and corresponded to doping levels ranging from 1x1015 cm-3 to 8x1018 cm-3. Electron and nitrogen concentrations in the epilayers were measured by capacitancevoltage (CV) profiling and secondary ion mass spectrometry (SIMS), respectively. These efforts show real-time QMS monitoring is effective during growth for determining relative changes in nitrogen concentration in the gas flow, and thus, the level of nitrogen incorporation into the growing layer.