Effects of Electrical Stress on the Frequency Performance of $0.18\,\mu{\rm m}$ Technology NMOSFETs

The effects of DC hot-carrier stress on DC and RF performance of submicron LDD NMOSFETs are investigated. It is shown that transit frequency $f_{T}$ decreases as transconductance $g_{m}$ of the transistor is degraded with stress but it is observed that degradation of $f_{T}$ versus stress time is faster than that of $g_{m}$. This was found to be due to the increase of the gate-source capacitances $C_{gs}$ with stress. Threshold voltage $V_{th}$ and output conductance $g_{ds}$ increase and voltage gain of the device $\mu_{f}$ decreases with stress. Stability factors $K$ and Δ also change toward higher stability with stress.