RF Performance and TID Hardness Tradeoffs in Annular 45-nm RF SOI CMOS Devices

The operability and total-ionizing-dose (TID) response of 45-nm annular RF silicon-on-insulator (SOI) nFETs are evaluated and compared with standard layouts. All devices were exposed to 10-keV X-rays, up to a dose of 1 Mrad(SiO2), at both high-gate/low-drain and low-gate/high-drain irradiation conditions. Differences in damage response to dc and small-signal performance between samples are observed as a result of TID-sensitive oxides and their proximity to key transport regions of the devices. Annular FETs are more TID tolerant than standard nFETs while showing small RF performance tradeoffs as well as lower drive currents and higher threshold voltages. Technology computer-aided design (TCAD) is used to isolate critical oxides and damage mechanisms in annular and standard layouts to help confirm experimental data and observed damage trends. Taken together, these results suggest that annular FETs represent a valid TID-hardening approach in small-lithography RF silicon-on-insulator complementary metal-oxide semiconductor technology platforms for both dc and RF applications.