Negatively charged silicon nitride films for improved p-type silicon surface passivation by low-temperature rapid thermal annealing

The effect of post-deposition rapid thermal annealing (RTA) on p-type Czochralski silicon surface passivation by plasma-enhanced chemical vapor deposited nitrogen-rich silicon nitride (SiNx) films has been investigated. The effective carrier lifetime is significantly improved after annealing at low temperature (400 degrees C-450 degrees C) for 15-30 s. This improvement is associated with a decrease of N-H and Si-H bond densities in SiNx films and, a resultant decreased density of states at the SiNx/Si interface. More importantly, the polarity of fixed charges is converted from positive to negative in the annealed SiNx films. It is demonstrated that a release of hydrogen atoms to the SiNx/Si interface combined with a tuning of charges during low-temperature RTA, is very beneficial for p-type silicon surface passivation.