Aggressive sige channel gate stack scaling by remote oxygen scavenging: Gate-first pFET performance and reliability

Abstract

We demonstrate that aggressive gate dielectric scaling in hafniumbased high-k/metal gate (HKMG) p-channel metal-oxidesemiconductor field-effect transistors (pFETs) with biaxially strained silicon germanium (SiGe) channels can be achieved in gate-first integration via remote interfacial SiO2 scavenging by metal-doped titanium nitride gates. We show that an inversion thickness (Tinv) of 0.86 nm can be reached, corresponding to an equivalent oxide thickness (EOT) of about 0.45-0.5 nm. We then provide a detailed study of interlayer-scaling-induced pFET threshold voltage increase and hole mobility reduction, and we establish an exponential interlayer thickness dependence of negative bias temperature instability (NBTI), resulting in shrinking reliability margins that will require gate stack optimization or reduced operating voltage. Previously shown to be effective for nFETs, our results demonstrate that remote oxygen scavenging is an attractive scaling option for dual-channel CMOS. © The Electrochemical Society.