Effects of hot-carrier stress on the RF performance of 0.18 /spl mu/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/sub T/ decreases as the transconductance g/sub m/ and gate-source capacitance C/sub gs/ of the transistor are degraded with stress time. It is observed that the degradation of f/sub T/ versus stress time is faster than that of the g/sub m/ degradation. This was found to be due to the increase of the C/sub gs/ with stress. The threshold voltage V/sub th/ and the output conductance g/sub ds/ increase and the intrinsic voltage gain of the device A/sub /spl nu/,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/sub 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 transistor power gain G/sub T/, input matching /spl Gamma//sub in/, noise figure NF and stability factor /spl mu/ of a low noise amplifier made of these NMOSFETs.