NBTI behavior of Ge/HFO2/Al gate stacks

In this paper negative bias temperature instability (NBTI) characteristics of Al/HfO₂/Ge MOS gate stack with nitrided Ge surface was compared with the non-nitrided Ge surface at high temperatures (125degC). Results show that nitridation creates additional bulk traps even though it shows initial improvements. The authors, therefore, noticed that nitrided Ge has higher DeltaV_FB shift and stress induced leakage current than non-nitrided samples. NBTI degradation of nitrided germanium surface is also consistent with literature regarding NBTI on nitrided Si devices. Optimization on nitrogen content and nitridation procedure may improve sensitivity to NBTI.