Physico-chemical processes in Vertical-Double-Diffused Metal-Oxide-Semiconductor Field Effect Transistors induced by gamma-ray irradiation and post-irradiation annealing

Abstract

The behavior of commercial power Vertical-Double-Diffused Metal Oxide Semiconductor Field Effect Transistors (VDMOSFETs) during gamma-ray irradiation and subsequent annealing at room and elevated temperature was investigated. The densities of radiation-induced fixed traps and switching traps were determined from the sub-threshold I-V curves using the midgap technique. It was shown that the creation of fixed traps dominated during irradiation. The experimental results have also proved the existence of latent switching traps buildup process during annealing at an elevated temperature. This increase correlated with the decrease in fixed trap density. Physical and chemical processes responsible for the threshold voltage shift during irradiation have been analyzed on the basis of interactions between secondary electrons released by gamma photons with covalent bonds Sio - O and Sio - Sio. H-W model has been used for the explanation of processes leading to latent switching traps buildup at an elevated temperature and its passivation at late annealing times.