多晶硅后热退火引起SiO_2栅介质可靠性下降的原因分析及其抑制方法

Gate Oxide Reliability Degradation by Post Poly-Sil icon Annealing and Suppression Method

实验研究表明 ,多晶硅后的高温退火明显引起热 Si O2 栅介质击穿电荷降低和 FN应力下电子陷阱产生速率增加 .采用 N2 O氮化则可完全消除这些退化效应 ,而且氮化栅介质性能随着退火时间增加反而提高 .分析认为 ,高温退火促使多晶硅内 H扩散到 Si O2 内同 Si— O应力键反应形成 Si— H是多晶硅后 Si O2 栅介质可靠性退化的主要原因 ;氮化抑制退化效应是由于 N “缝合”了 Si O2 体内的 Si— O应力键缺陷 .

Effects of post poly-Si annealing (PPA) o n gate oxide reliability are studied experimentally.It is shown that PPA causes significant increase in the electron trap's generation rate under FN stress and decrease in the number of charge-to-breakdown.This kind of degradation can be suppressed by N 2O nitridation.The PPA degradation effect is considered to be a ttributed to the diffusion of H atoms into gate oxide and the reaction with stra ined Si-O bonds.Suppression of PPA degradation by N 2O nitridation is assumed due to the replacement of strained Si-O bonds by Si-N bonds.