Variation in natural threshold voltage of NVM circuits due to dopant fluctuations and its impact on reliability

The statistical distribution of the natural threshold voltage (V/sub T0/) of 512k-bit NVM circuit arrays has been studied for two different technologies. The major source of the V/sub T0/ variation is dopant fluctuations of the NVM well. An analytical model for the dopant fluctuations provides excellent agreement with the measured circuit V/sub T0/ variation and NVM cell mismatch for both technologies. The reliability implications of the V/sub T0/ variation are considered using charge leakage models for data retention.