HV Gate Oxide Over-Oxidation Process Optimization for SONOS 1.5T Flash Cell

In this paper, HV gate-oxide process has been optimized for solving SONOS 1.5T Flash cell Over-oxidation issue. In this type SONOS, TEOS was used as flash cell poly spacer, which has poorer ability blocking O2 diffusion during high temperature process. For this problem, traditional SONOS flash cell formation sequence was changed, N-pass HV gate oxide was preferential fabricated before flash cell. This method has demonstrated to dramatically prevent flash cell from suffering over-oxidation issue.