Experimental characterization of critical high-electric field spots in power semiconductors by planar and scanning collimated alpha sources

Abstract

The occurrence of critical spots, where carriers' multiplication occurs due to the local high-electric field can be very detrimental for the robustness and the reliability of power devices, since catastrophic failure mechanisms like Single Event Burnout can be initiated at these locations. Traditional analytical techniques like DC analysis, photoemission microscopy, electron, and optical probing are not the first choice to detect the presence and in particular to locate such critical spots because they either lack in sensitivity, or they suffer from relevant penalties due to the thick metallization layers at the surface of the devices. In recent years, successful attempts have been made by finely focused high-energy ion beams. However, such nuclear probing techniques require advanced complex facilities like particle accelerators, operate under high vacuum conditions, and are not immune to radiation damage effects. In this paper, we propose the use of planar and collimated alpha sources to assess the presence and to locate critical high-field spots in power semiconductors. It is shown, that the proposed technique just requires basic spectrometry equipment and provides sufficient sensitivity and space resolution to fulfill all analytical requirements.