Screening of hot electron effect during plasma processing

Abstract

CMOS devices are subjected to high-field electron injection during plasma processing. This work investigates the screening of hot carrier stress degradation in an n-channel MOSFET when the device was exposed to plasma processing. Devices with various antenna ratios were subjected to current stress (both gate injection and substrate injection) while the source and drain terminals were reverse biased by a screening potential followed by hot carrier stress. It was observed that screening of the drain edge was effective for both gate injection and substrate injection at different screening potentials. For higher antenna ratio devices, the hot carrier screening potential is reduced due to pre-existing oxide traps. The hot carrier lifetime is directly related to interface state density (D/sub it/), measured by charge pumping method. These results suggest that hot electron degradation could be severe or mild for devices affected by plasma damage depending on their exposure to the level of screening potential.