Effects of flash EEPROM floating gate morphology on electrical behavior of fast programming bits

The effects of Flash EEPROM Floating Gate morphology on the generation and density of fast programming bits on a 2-MBit Flash EEPROM array has been characterized. These fast programming bits exhibit identical subthreshold characteristics similar to that of a normal bit after UV-erase, thus establishing that the initial charge stored on the floating gate of both fast and normal bit is the same. This clearly indicates that the fast programming phenomena result from an interaction of the programming process and the floating gate. An in depth experimentation reveals that the floating gate poly deposition and doping process are crucial for controlling the desired Fowler-Nordheim (FN) tunneling. A correlation is established between the fast bit density observed in the 2-MBit array, the FN tunneling currents, the floating gate deposition and doping processes. The fast programming bit threshold voltage distribution and density can be modulated with the floating gate deposition and doping processes.