45 GHz silicon MESFETs on a 0.15 µm SOI CMOS process

Fully integrated MESFETs have been shown to work on multiple commercial silicon-on-insulator (SOI) and silicon-on-sapphire (SOS) CMOS processes without changing a step in the process flow. The unique features of the MESFET including depletion mode operation, breakdown voltages in excess of 50 V, and easy to adjust, but well controlled threshold voltages have given the designers a cost-free way to achieve certain circuit design solutions that were previously cost inefficient or difficult to implement on their respective processes. Until now, silicon MESFET based circuit applications were limited in very high frequency applications due to either the technology they were designed on and/or key layout rules that affected the gate length, L
_g
, of the MESFETs but not the MOSFETs. The highest SOI MESFET f
_T
reported was ~10 GHz which was associated with an L
_g
= 0.4 mum on a 0.35 mum SOI CMOS process. The devices presented in this abstract were designed on a 0.15 mum process and represent the most aggressive scaling yet for SOI MESFETS. Devices with f
_T
> 45 GHz and L
_g
= 0.15 mum were achieved.