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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 fT decreases as the transconductance gm and gate-source capacitance Cgs of the transistor are degraded with stress time. It is observed that the degradation of fT versus stress time is faster than that of the gm degradation. This was found to be due to the increase of the Cgs with stress. The threshold voltage Vth and the output conductance gds increase and the intrinsic voltage gain of the device Aν,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 NFmin 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 transistor power gain GT, input matching Γin, noise figure NF and stability factor μ of a low noise amplifier made of these NMOSFETs.
Date of Conference: 2002