Effect of the dielectric thickness and the metal deposition technique on the mobility for HfO2/TaN NMOS devices

In this paper the effects from the high-¿dielectric thickness and the metal gate deposition technique on the mobility of n-channel MOS transistors are investigated. The results reveal mobility degradation due to an increase of charge density in the dielectric and / or at the material interfaces, not efficiently compensated by the screening effect from the gate. We correlate this mobility degradation to the reduction observed in a comparison between metal and poly-Si gated MOSFETs. It is shown that the mobility can be improved by using different metals deposition technique, which indicates that the mobility reduction is related to the deposition technique.