Effects of Hot-Carrier Stress on the RF Performance of $0.18\ \mu {\rm m}$ Technology NMOSFETs and Circuits

The effects of DC hot-carrier stress on DC and RF performance of submicron LDD NMOSFETs are investigated. It is shown that the unity current gain frequency $f_{T}$ decreases as the transconductance $g_{m}$ and gate-source capacitor $C_{gs}$ of the transistor are degraded with stress time. It is observed that the degradation of $f_{T}$ versus stress time is faster than that of the $g_{m}$ degradation. This was found to be due to the increase of the gate-source capacitance $C_{gs}$ with stress. The threshold voltage $V_{th}$ and the output conductance $g_{ds}$ increase and the intrinsic voltage gain of the device $A_{v, int}$ decreases by stress. The effect of hot carrier stress on the noise performance of the device is investigated by calculating the minimum noise figure of the device $NF_{min}$ before and after stress, using the calibrated small signal model of the transistors. The results of the hot carrier experiments on single devices are used to analyze the hot carrier effects on the transducer power gain $G_{T}$ input matching $\Gamma_{{\rm in}}$, noise figure $NF$ and stability factor µ of a low noise amplifier made of these NMOSFETs.