Influence of Nitrogen on Negative Bias Temperature Instability in Ultrathin SiON

Negative bias temperature instability (NBTI) and its recovery phenomenon in ultrathin silicon oxynitride (SiON₂) films were investigated. To discuss the influence of nitrogen incorporation into silicon dioxide films, we used NO-nitrided SiON and plasma-nitrided SiON. As a result, it was found that the recovery for plasma-nitrided SiON is less marked than that for NO-nitrided SiON, although NBTI can be suppressed by plasma nitridation. It is also experimentally confirmed that hydrogen plays an important role in these phenomena. On the basis of these results, we proposed nitrogen-originated NBT degradation involving hydrogen at SiON/Si interface and hole trapping/detrapping. Furthermore, NBTI under ac stress was investigated. Not only NBTI was more suppressed under ac stress than under dc stress as already reported, but also, this behavior of dynamic NBTI is independent of nitrogen distribution in SiON.