Impact of dual-k spacer on analog performance of underlap FinFET

Multigate structures have better short channel control than conventional bulk devices due to increased gate electrostatic control. FinFET is a promising candidate among multigate structures due to its ease of manufacturability. The RF performance of FinFET is affected by gate controlled parameters such as transconductance, output conductance and total gate capacitance. In this paper we have used dual-k spacers in underlap FinFETs to improve the gate electrostatic integrity. The inner high-k spacer helps in better screening out the gate sidewall fringing fields, thereby, increasing transconductance and reducing output conductance with increase in total gate capacitance. At 16 nm gate lengths, we have observed that, the intrinsic gain of dual-k spacer based FinFET can be increased by more than 100% (>6 dB) without affecting cutoff frequency and maximum oscillation frequency, as compared to conventional single spacer based FinFET. Improvement in cutoff frequency by 11% and maximum oscillation frequency by 5% can be achieved, when the gate lengths are scaled down to 12 nm, in addition to 2.75 times (8.8 dB) increase in intrinsic gain.