氮化硅介质中双层纳米硅薄膜的两级电荷存储

Double-level charge storage in self-aligned doubly-stacked Si nanocrystals in SiN_x dielectric

研究镶嵌在超薄非晶氮化硅(a-SiNx)层之间的双层纳米硅(nc-Si)的电荷存储现象.利用等离子体增强化学气相淀积(PECVD)技术在硅衬底上制备a-SiNx/a-Si/a-SiNx/a-Si/a-SiNx多层薄膜结构.采用常规热退火方法使非晶硅(a-Si)层晶化,形成包含双层nc-Si的金属-氮化物-半导体(MIS)结构.通过电容电压(C-V)特性测量,观测到该结构中由于电荷存储引起的C-V回滞现象,并在室温下成功观察到载流子基于Fowler-Nordheim(F-N)隧穿注入到第一层、第二层nc-Si的两级电荷存储状态.结合电流电压(I-V)特性的测量,对电荷存储的机理进行了深入分析.

Doubly stacked layers of amorphous silicon （a-Si） between amorphous silicon nitride （a-SiNx ） layers have been fabricated by plasma enhanced chemical vapor deposition （PECVD）technique. Si nanocrystal （nc-Si） layers were formed by thermal crystallization of a-Si layers after a furnace annealing at 1100℃ for 30 min in N2 ambient. The phenomena of charge trapping and storage in nc-Si layers were observed in both capacitance-voltage （C-V） and current-voltage （I-V） measurements at room temperature. The structure has revealed a double-level charging process. Two stages of charge storage were evident in the series of C-V curves. The phenomena and mechanism of charge storage were discussed in detail.