The role of nitridation of nc-Si dots for improving performance of nc-Si nonvolatile memory

Abstract

We report a nc-Si nonvolatile memory (NVM) device with nitrided nc-Si dots embedded in a floating gate. LPCVD was used to deposit a layer of nc-Si on the tunnel oxide layer at the pressure of 350mTorr. Subsequently as-deposited nc-Si dots were nitrided at 780°C in NH3 ambient. The role of the nitridation of nc-Si dots for improving performance of nc-Si NVM was investigated. First of all, enlarged memory windows have been observed from nitrided nc-Si NVM compared with that of un-nitrided nc-Si NVM because of the reduction of the surface defect states of nc-Si. Secondly, a faster program speed is achieved because the effective gate bias is increased in nitrided nc-Si NVM. Furthermore, the Si nitride cover layer also acts as a potential barrier which enhanced the memory retention time. The mechanism of improving performance of nitrided nc-Si NVM has been discussed.