On the Output Conductance Dispersion due to Traps and Self-Heating in Large Bulk, FDSOI and FinFET nMOS Devices

We report experimental investigations on the AC small signal output conductance ($g_{D D}$) of large nMOSFETs with bulk, FDSOI, and bulk FinFET architecture. The $g_{D D}$ frequency spectra reveal opposite trends at low and high gate voltage $\mathrm{V}_{\mathrm{GS}}$. Furthermore, an unexpected anomaly is observed at $\mathrm{V}_{\mathrm{GS}}$ close to the value where the sensitivity to temperature of the DC IV transfer characteristics changes sign.Self-heating is scrutinized as a possible unique origin of the $\mathrm{g}_{\mathrm{DD}}$ dispersion. An additional non-negligible role of trap states is put in evidence by numerical simulations taking self-consistently into account electrothermal effects and the possible presence of gate dielectric traps.The results can reduce inaccuracies in determining the thermal resistances from the $g_{D D}$ frequency dispersion data, and support better design of large FETs and circuits for RF applications.