Using an Ammonia Treatment to Improve the Floating-Gate Spacing in Split-Gate Flash Memory

Abstract

In the split-gate flash memory process, during poly oxidation, the bird's beak encroaches under the SiN film, especially along the poly grain boundary, and that will cause nonuniform floating-gate (FG) spacing, even bridging, which is an obstacle to cell shrinkage. In this paper, we show that employing an ammonia treatment on the poly can nitridize the poly surface, thereby avoiding bird's beak bridging. After the ammonia treatment, FG spacing is quite uniform and can be improved from 0.09 to 0.03 m. The XPS analysis on the ammonia treated poly shows the oxynitride thickness is less than 5 nm.

Performance evaluation of field-enhanced P-channel split-gate flash memory

“…1(a) [3], [5], [10]. After shallow trench isolation and N-well formation, the first gate oxide, i.e., FG oxide, was grown on the Si-substrate, then the poly and SiN layers were deposited sequentially using LPCVD.…”