Effects of erase source bias on Flash EPROM device reliability

This paper is concerned with the effects of the source bias during the erase operation on the reliability of Flash EPROM devices. It will be shown that positive charge in the tunnel oxide, mostly generated by the erase operation, is a major cause of the unintentional charge loss/gain mechanisms that disturb the data content of the memory cell. The effects of the erase source bias are evaluated in the context of the positive oxide charge generation and the resulting enhancement of the gate current that causes the data loss. An optimal source bias during erase, around 2 V for our samples, is shown to cause the least positive oxide charge. A model based on the band-to-band tunneling-induced hole generation in Si and subsequent hole injection during the erase operation is presented and discussed