<i>In Situ</i> Monitoring of Unintentionally Released Nitrogen Gas in the Initial PVT Silicon Carbide Growth Process Using Mass Spectrometry

Abstract

Different initial process steps during PVT crystal growth of SiC were monitored with a mass spectrometer. To measure the gas phase composition in the PVT growth machine during these steps the continuously pumped exhaust gas was analyzed by a quadrupole mass spectrometer (PrismaPro QMG 250). In order to reduce unintentionally doping of the crystal by contaminations in the growth setup the focus was on the release of nitrogen during the initial steps of the growth process. During the heat up of the growth setup in vacuum a substantial release of molecular nitrogen was observed at 800 °C. Further, the influence of pump and purge-steps on the amount of nitrogen in the gas phase was examined. After performing a pump and purge step, the intensity of the measurable nitrogen-related signal (m/z = 28) was approximately 20 % of the initial value. In-situ monitoring of the gas phase during the initial steps of crystal growth proved to be a versatile tool for the development of a process minimizing unintentionally doping through released nitrogen.