Improving performance and reliability of NOR-Flash arrays by using pulsed operation

Pulsed Operation (PO) is a new writing methodology based on a sequence of high voltage ultra-short pulses allowing of improving both performance and reliability of Flash memories. Measurements performed on 4Mb NOR-Flash test chips show the features of this methodology. Reliability, and in particular data retention, is shown to improve significantly for a whole array of cells with respect to standard FN writing operations that are based on sequences of box-shaped low voltage long pulses. Results show that PO allows for obtaining very compact threshold voltage distributions improving read margins and reducing the use of soft-programming techniques.