低原生缺陷密度的HfN/HfO2高K栅结构中界面反应导致的PBTI和NBTI特性

In this paper, HfN/HfO2 gated n-FETs and p-FETs with low preexisting traps density in the HfN/HfO2 gate stacks were fabricated by using a high temperature process. The positive and negative bias temperature instability (PBTI and NBTI) characteristics in the HfN/HfO2 gate stacks are studied systematically. The characteristics of the Vt instability mainly caused by the stress-polarity instead of the substrate type -dependent are observed both in n-FETs and p-FETs. The negative threshold voltage (Vt) shifts, which can be well fitted by a generalized reaction-diffusion (R-D) model, are observed under both positive and negative bias temperature (NBT) stressing. The mechanisms of the interfacial reactions induced by the injected electrons or holes from substrates are proposed to explain the observed PBTI and NBTI characteristics: under PBT stressing, the injected electrons from the substrates induce the breaking of the Si-O bonds in the interfacial layer between HfO2 layer and Si substrates, which causes the PBTI characteristics; under NBT stressing, the injected holes from the substrate induce the breaking of the Si-H bonds at Si interface, which causes the NBTI characteristics. The consistency between the measured data and the ones predicted by the mechanisms confirms the validity of the interfacial reactions mechanisms.