Detailed Comparisons of Program, Erase and Data Retention Characteristics between P+- and N+-Poly SONOS NAND Flash Memory

In this paper, one of the future nonvolatile memory candidates, SONOS with p₊-poly gate, has been fully characterized in cell program/erase operation and data retention performance. Novel source-side injection programming and F-N erase schemes have been utilized on both n₊- and p₊-poly gate, and its characteristics are very satisfactory and can be easily used as a state-of-the-art flash memory. For data retention, our experimental result shows p₊-poly does have a slower charge decay rate than does n₊-poly gate. This is because of the work function difference between n₊- and p₊-poly gate that causes the different amount of trapped electrons between two of them. We also predict the charge loss characteristics with various baking temperature for n₊- and p₊-poly gate, which can tell us the concrete threshold voltage at any read delay time instead of the traditional and inaccurate long time projection from short time status