NBTI 열화의 Channel Length Dependency 에 대한 Mechanical Stress Effect 평가

Abstract

The effect of mechanical stress in the channel which was induced by the shallow trench isolation, on negative bias temperature instability (NBTI) degradation of a p-MOSFET with an ultra-thin gate dielectrics was investigated. As the channel length decrease, it was observed that the length-normalized linear current, transconductance, saturation current and intrinsic carrier concentration (ni) decrease. These experimental results indicate that channel region subjected to a tensile stress. The tensile stress increases, the threshold voltage (Vth) because it increases the band gap (Eg). Vth of short channel p-MOSFETs was higher than that of the long channel p-MOSFETs. When the stress voltage was compensated for the changes of Vth , both MOSFETs had same NBTI degradation. This results show that the observed differences of NBTI degradation characteristics between the long and short MOSFETs were caused by the mechanical stress in the channel region.