Enhanced tunneling characteristics of PECVD silicon-rich-oxide (SRO) for the application in low voltage flash EEPROM

High tunneling efficiency is indispensable for the application of low voltage flash EEPROM. In this study the enhanced tunneling characteristics of the thin silicon-Rich-Oxide (SRO) films deposited using Plasma Enhanced Chemical Vapor Deposition (PECVD) as a tunneling injector was first reported. By optimizing the reactant gas ratios of [N2O]/[SiH4] during SRO deposition, the tunneling voltage of flash EEPROM can be 1/3 lower than that without PECVD SRO films. The significant tunneling efficiency is found to be caused by the micro Si-islands in SRO films. Micro Si-islands in SRO films enhance the electrical field of the tunneling oxide in flash EEPROM. A modified WKB tunneling approximation have been successfully applied to model the SRO tunneling characteristics. The field enhancement factor of SRO is also found to depend on the oxide electrical field, and is proportion to the inverse of oxide electrical field.