Non-silicon MOSFETs for mainstream CMOS?

Further scaling of silicon MOSFET feature size is projected to provide diminishing performance enhancements resulting in an increasing performance gap beyond the 45 nm node of the International Technology Roadmap for Semiconductors (ITRS). To close this gap, the industry is contemplating a paradigm shift to channel materials with carrier mobility substantially higher than offered by silicon. MOSFETs based on Ge or III-V channel materials including InGaAs and even more exotic solutions such as graphene are proposed. Beyond unresolved technology and viability issues of such non-silicon devices for CMOS, this most challenging endeavor is further complicated by implementation on silicon substrate which is dictated by economics. This plenary talk outlines the challenges associated with non-silicon MOSFETs and their introduction onto silicon substrate for CMOS applications. In accordance with the topic of the conference, particular emphasis is placed on III-V MOSFETs. Freescale´s GaAs MOSFET technology, developed for RF power applications, features a unique device quality oxide/GaAs interface, high-fUcirc dielectric and metal gate. Enhancement-mode MOSFETs manufactured in collaboration with the University of Glasgow have demonstrated competitive and exceptional performance compared to GaAs PHEMTs. Most important, MOSFETs potentially bring unprecedented integration capability to RF frontends: power amplification, RF switching, power control, and digital functions can all be monolithically integrated. While typical channel electron mobilities in GaAs MOSFETs range from 5,000 to 6,000 cm2/Vs, electron mobilities in CMOS relevant MOSFET channels with high In concentration have exceeded 10,000 cm2/Vs, a factor of 40 higher than afforded by Si n-channel MOSFETs. With proof of concept for CMOS in mind, first thin body MOSFETs with In0.75Ga0.25As channels have been fabricated on InP substrate. Convergence of silicon and non-silicon semiconductors will require a concerted effort - - and substantial resources. Tremendous challenges lie ahead of us.