(An) EEPROM with self-aligned structure using thermal nitride tunneling film

Abstract

We have proposed Self-Aligned EEPROM using Thermal Nitride Tunneling Film. Thermal Nitride shows low tunneling barrier height and yields large tunneling current.The low-barrier nitride enables the complete self-aligned process between FG and the channel and between FG and CG, leading to increase the integrity of EEPROMs. In this paper we have fabricated a Self-Aligned EEPROM and investigated its electrical characteristics. The programming characteristics of the self aligned EEPROM with thermal oxide thickness of 6nm. With the control-gate voltage of -14V, the electrons are injected from the control gate to the floating gate. The threshold voltage moves from 0V to +2.5V. These programming characteristics are just opposite to normal stacked EEPROM``s. This is due to same overlap area between floating gate and channel, and rougher inter-poly oxide interface. On the other hand, the EEPROM with thermal nitride film does show normal programming and erasing characteristics. The programming characteristics of the EEPROM with ring type gate electrode and thermal nitride thickness of 6nm. With the control-gate voltage of 11 V and 1 msec duration pulse, the electrons are injected from the channel to the floating gate. The threshold voltage moves from -4.5 V to -2.8 V. Compared with EEPROM with thermal oxide in programming characteristics, EEPROM with thermal nitride requires much lower the control-gate voltage. This result is consistent with the lower energy barrier height of thermal nitride. All of these demonstrate the potentiality of self-aligned EEPROM with thermal nitride as high density fast EEPROM application.