Trade-Offs Between RF Performance and Total-Dose Tolerance in 45-nm RF-CMOS

The hot carrier and ionizing radiation responses of 45-nm SOI RF nMOSFETs are investigated. Devices with "tight" source/drain (S/D) contact spacing have improved RF performance but degraded hot carrier reliability and radiation tolerance. Devices with "loose" gate finger-to-gate finger spacing have improved RF performance and also improved hot carrier and radiation tolerance. The effects of finger width on the hot carrier stress and ionizing radiation degradation of strained silicon-on-insulator RF MOSFETs are also investigated. Enhanced degradation is observed for devices with wide finger widths and is attributed to the greater channel-region mechanical stress induced impact ionization. This result is contrary to the previous studies which showed that narrow channel width devices should exhibit greater damage. Taken together, these results have serious consequences for RF circuits that require large widths for sufficient RF gain. Finally, devices with symmetric halo doping are observed to exhibit greater total-dose degradation than devices with asymmetric halo doping.