Optimum voltage scaling methodology for low voltage operation of CHE type flash EEPROMs with high reliability, maintaining the constant performance

摘要

The optimum voltage scaling method is presented to achieve the low voltage operation of Channel Hot Electron type flash EEPROMs with high reliability, maintaining the constant performance and the constant tunnel oxide thickness. In this rule, the maximum electric field reduces with the constant tunnel oxide thickness for suppressing the oxide reliability problems. Moreover the electric field at tow level is fixed to keep the program and the erase time constant. Furthermore low voltage operation is achieved by increasing the coupling ratio and the p/sup 0/-pocket impurity concentration. This new rule is derived by clarifying the relation between the coupling ratio, the supply voltages and the sense levels from simple analytical equations. It is found that the flash performance is kept almost the same and the disturb characteristics is improved by following this methodology.