Hot-carrier degradation of LDD n-channel MOSFETs at 77 K

Hot-carrier degradation in lightly-doped drain (LDD) n-channel MOSFETs stressed at 77 K and 300 K was studied. Both short (L=1.3 μm) and long (L=50 μm) channel devices were stressed with both DC and pulsed gate biases. Short channel devices were stressed with a drain voltage of 5 V. The DC gate bias was 2.4 V, and the pulsed gate signal was a 1 MHz square wave of 0 to 5 V. Long channel devices were stressed at a drain voltage of 6 V, with the gate pulsed from -7 to 15 V. Drain characteristics and charge-pumping measurements indicate interface state generation at the drain end of the channel. In addition, hole injection led to trapped holes in the oxide at the drain end of the channel. Electron trapping at trapped hole sites in the oxide was observed in the long channel devices