Clipped sine wave channel erase method to reduce oxide trapping charge generation rate of flash EEPROM

摘要

A method to channel erase data from a flash EEPROM while electrical charges trapped in the tunneling oxide of a flash EEPROM are eliminated to maintain proper separation of the programmed threshold voltage and the erased threshold voltage after extended programming and erasing cycles. The method to channel erase a flash EEPROM cell begins by removing the charge from the floating gate of the flash EEPROM cell. The channel erasing consists of applying a relatively large clipped sinusoidal negative voltage pulse to the control gate of said EEPROM cell and concurrently applying a moderately large positive voltage pulse to a first diffusion region. At the same time a ground reference potential is applied to the semiconductor substrate, while the drain, the source and a second diffusion well are allowed to float.