Low-temperature electron spin resonance investigations of silicon paramagnetic defects in silicon nitride

We have reproduced and extended some recently reported electron spin resonance (ESR) measurements related to the nature of the dominant charge traps in silicon nitride. We detected defect centers at low temperatures using ESR, in both as-deposited and ultraviolet-irradiated silicon nitride powders and films prepared by low-pressure chemical vapor deposition (LPCVD). Only two silicon dangling bond defects were observed in the silicon nitride, one at g=2.003 (⋅Si≡N3), and the other at g=2.005 (⋅Si≡Si3). The signal intensity at g=2.003 is by far the dominant signal in the LPCVD films and powders subjected to UV illumination; the signal at g=2.005 is only about 3% of its intensity. These results support the idea that there is just one dominant silicon paramagnetic center (⋅Si≡N3), which is responsible for charge trapping in silicon nitride.