Effect of the epitaxial layer features on the reliability of medium blocking voltage power VDMOSFET during heavy ion exposure

In this paper we present an experimental study of the effect of the epi-layer parameters on the reliability of medium voltage power VDMOSFET to sustain single event effects caused by the impact of heavy ions. The impact of energetic particles is accompanied by a charge generation that we experimentally detected and can cause the premature failure of the device. The tested devices have been specifically constructed by using different epi-regions and the typical gate structure used in 200V VDMOSFET.lt is experimentally proven that the failure event involves a damage of the gate oxide due to the development of a large electric field at the silicon surface underneath the gate oxide. A statistical analysis we have performed shows that the rupture mechanism is quite independent of the charge generated (ion energy and species) and strongly dependent on the epi-layer doping profile. The failure mechanisms reported in the literature and based on a flow of holes through a surface path underneath the gate does not completely explain this experimental behavior.