Fully depleted extremely thin SOI for mainstream 20nm low-power technology and beyond

Abstract

Extremely thin SOI (ETSOI) MOSFET is an attractive candidate for 22nm technology and beyond due to its excellent short channel control, low leakage current, and immunity to random dopant fluctuation [1–5]. Short channel effects are mainly controlled by channel thickness, so there is no need for aggressive scaling of the gate dielectric. Thus the gate leakage is reduced beyond what is achievable in high-k bulk technologies. Low-power operation is further enhanced by negligible GIDL current due to the undoped channel. In addition, ETSOI devices have inherently no junction leakage by the virtue of thin silicon channel. Higher gate voltage overdrive is achieved for a given supply voltage compared to bulk technologies due to smaller subthreshold slope. This enables low-VDD logic operation. Moreover, low-VDD SRAM functionality is supported by small VT- mismatch in undoped channel [5]. In conventional CMOS technologies, complete device redesign is needed if VT changes are required. In ETSOI, however, threshold voltage is tuned through gate workfunction modulation without change in the channel doping. Thus VT tuning is to a large extent decoupled from device scaling.