薄SiO_2层击穿特性与临界陷阱密度

The Breakdown Character of Thin Oxide Film and Critical Trap Density

薄栅氧化层的退化、击穿与氧化层中和界面陷阱的产生相关 .本文研究了在恒电流TDDB(Time Depen dentDielectricBreakdown)应力条件下 8 9nm薄氧化层的电学特性退化、击穿情况 .研究表明 ,电子在穿越SiO2 晶格时与晶格相互作用产生陷阱 ,当陷阱密度达到某一临界密度Nbd时 ,氧化层就击穿 .Nbd可以用来表征氧化层的质量 ,与测试电流密度无关 .击穿电量Qbd随测试电流密度增大而减小可用陷阱产生速率的增长解释 .临界陷阱密度Nbd随测试MOS电容面积增大而减小 ,这与统计理论相符 .统计分析表明 ,对于所研究的薄氧化层 ,可看作由面积为 2 5 6× 10 -14cm2 的“元胞”构成 ,当个别“元胞”中陷阱数目达到 13个时 ,电子可通过陷阱直接隧穿 ,“元胞”内电流突然增大 ,产生大量焦耳热 ,形成欧姆通道 ,氧化层击穿 .

The degradation and breakdown of thin gate oxide film are related with the generation of traps in oxide layer.In this work,the electric characteristics of 8 9nm thin oxide film have been studied using TDDB (Time Dependent Dielectric Breakdown) measurement method.In stress experiments,part of the kinetic energy of the injected electrons is dissipated by interaction with SiO 2 lattice and converted into some sort of defects in oxide film that behave as traps. When the density of traps reaches a critical density N bd ,the thin oxide film breaks down. N bd decreases as the area of test MOS capacitor increases.This phenomenon can be explained using statistic theory. N bd can be used as an oxide quality parameter.