Impact of radiation-induced nonuniform damage near MOSFET junctions

Laterally nonuniform distributions of radiation-induced oxide charge and interface traps near MOSFET junctions have been found in a variety of samples. As revealed by three independent measurement techniques, the degree of nonuniformity depends strongly on the process technology. Such lateral nonuniformity could arise from the lateral variation of the oxide field near the channel edges during irradiation and the different diode properties in these regions compared to those in the main channel region. These channel edge effects can significantly affect MOSFET device parameters such as the threshold voltage, transconductance, channel resistance, and effective channel length. This is especially the case for submicron devices. Results from computer simulation indicate that the edge damage alone could contribute to a major portion of the transconductance degradation in irradiated submicron devices.