A Investigation into X-ray Radiation of VDMOS

In this study, the investigation into X-ray radiation of VDMOS is described. A radiation test of VDMOS was made by X-ray at various loads. The different radiation behavior of VDMOS was observed. The "rebound" of the threshold voltage shift of VDMOS at a larger load with X-ray radiation was larger than that without X-ray radiation, indicating that a radiation annealing effect happened to VDMOS at a powerful load. In terms of transconductance, all the radiated samples showed an increase in interface traps (Qit). At 9.84 X 10⁵ rad (Si), the interface traps increments at a large load and at a small load were 6.3 X 10¹¹cm² and 5.12 X 10¹¹/cm², respectively. A timely annealing effect is a major factor contributing to the "rebound" of the threshold voltage shift, and caused by anneal of VDMOS weak inversion interface traps whose equivalent charge is -2.31 X 10¹¹/cm².