Effects of hot-carrier stress on the performance of CMOS low-noise amplifiers

The effects of direct current (dc) hot-carrier stress on the characteristics of NMOSFETs and a fully integrated low-noise amplifier (LNA) made of NMOSFETs in an 0.18-mu m complementary MOS (CMOS) technology are investigated. The increase in threshold voltage and decrease in mobility caused by hot carriers lead to a drop in the biasing current of the transistors. These effects lead to a decrease in the transconductance and an increase of the output conductance of the device. No measurable change in the parasitic gate-source and gate-drain capacitances in the devices under test were observed due to hot carriers. In the LNA, the important effects caused by hot carriers were a drop of the power gain and an increase of the noise figure. A slight increase in the input and output matching S-11 and S-22, respectively, after hot-carrier stress was observed. The linearity parameter IIP3 of the LNA improved after stress. This is believed to be due to the improvement of the linearity of the I-V characteristics of the transistors in the LNA at the particular operating point where the measurements were performed.