Alterung von Leistungshalbleitermodulen im Temperatur-Feuchte-Spannungs-Test

Abstract

For a power semiconductor chip the most critical region is its junction termination. By the formation of a closed water film (monolayer electrolytic solution) linking the chip metallisation of the active area and the channel stopper metallisation or any other structure near the chip edge, a corrosion cell builds up. In case of copper and silver, the electro-chemical migration (ECM) occurs and forms dendrites of the metals at the active area metallisation. In case of aluminium, metal corrosion occurs leading to corrosion of the active area metal and precipitation at the outer part of the junction. This kind of degradation is usually investigated by means of accelerated testing, in this case by the High Humidity, High Temperature, Reverse Bias (H3TRB) test. Traditionally, end-of-life testing was done, but degradation occurs much earlier and, thus, this kind of test strategy is not sufficient. Instead, leakage monitoring and intermediate blocking measurements yield a much better estimation of the degradation status. The more detailed methods reveal a more complex degradation scenario.