Effect of substrate rotation on the analog performance of triple-gate FinFETs

This paper studies the influence of the 45deg substrate rotation on the analog parameters of n-type and p-type triple-gate FinFETs with HfSiON gate dielectric, TiN gate material and undoped body. Tall triple-gate n-type and p-type FinFETs were fabricated on SOI wafers with 150 nm thick buried oxide. The fin height (H
_Fin
) is 65 nm for all devices. It has been demonstrated that the substrate rotation improves the transconductance of narrow nFinFETs increasing the unity gain frequency. The output conductance of nFinFETs is weakly sensitive to substrate rotation. The improvement of the transconductance is marginally transferred to the voltage gain, leading to similar values for both substrate orientations. For the pFinFETs the substrate rotation strongly degrades the carrier mobility and hence the transconductance, independently if narrow or wide devices are used. This degradation affects also the transconductance over drain current ratio and the voltage gain of narrow devices is smaller by 3 dB with respect to standard substrate orientation.