探討快閃記憶體元件製程中退火氫氣濃度對抹寫特性影響分析之研究

Abstract

本篇論文主要研究退火過程中氫氣濃度對快閃記憶體元件抹寫之臨限電壓特性分析。氫氣添加在金屬氧化物半導體場效電晶體(MOSFET)的退火製程中被廣泛運用，氫離子的產生可以有效降低氧化層和基底間的表面能態。量測過程中發現，高濃度氫氣退火製程在寫入後的臨限電壓有異常分布。透過其他量測統計分析，發現在福勒-諾德漢穿隧 (FN tunneling ) 寫入機制中，高氫氣濃度製程有額外的電子注入。推測原因是高濃度氫氣製程造成正離子殘留於淺溝槽隔離中，又透過快閃記憶體結構造成的邊緣效應，放大了氧化層邊緣電子穿隧而形成。本論文研究機制可以應用在不同機制造成的電子注入異常，對未來元件製程微縮提供重要研究方向。

In this thesis, we investigate threshold voltage characteristic for different concentration of hydrogen during annealing in the process of NAND flash memory device. Hydrogen during annealing could reduce the dangling bonds that remain at silicon and silicon-oxide interface. However, our measurement shows that higher concentration of hydrogen during annealing treatments have wider threshold voltage distribution compare to lower one. Through the measurement with different conditions, we statistics concern the electron injection behavior and assume that there are positive charges remain in the shallow trench isolation which amplify the electric field at the edge of tunnel oxide with fringing effect. In this work, we provide a statistics way of abnormal electron injection that are caused by device shrinking.