Degradation of breakdown voltage of DMOS due to arsenic implant damage

We report the observation and detailed study of the degradation of breakdown voltage for a double-diffused power MOSFET (DMOS) in relation to the process of high dose arsenic implantation. We established a direct link between the breakdown voltage degradation and the dose and process conditions of the formation of the DMOS source. Starting from the observed electrical characteristics, we identified the particular cell site that exhibited the leakage by thermal imaging. Then, detailed silicon defect etching was performed on devices which showed leakage characteristics. We report, for the first time, the direct association of a double pit defect with the site of breakdown voltage degradation on numerous devices that exhibited the low breakdown voltage. We demonstrated that the conditions of the source implant have a direct influence on the formation of these defects, and we established a physical model of the interaction of the defect site with the spread of the depletion layer. Based on this model, we demonstrated experimentally that we can obtain devices with high breakdown voltages despite these defects. Additionally, the defects could be avoided by lowering the arsenic implant dose