Characterization of ageing failures on power MOSFET devices by electron and ion microscopies

Extreme electro-thermal fatigue tests have been performed to failure on power MOSFET devices that were later observed using electron and ion microcopy. At variance with devices from the former technology generation, fatigue-induced ageing of these components is observed only in the source metallization zone. An increase in drain–source resistance may originate from both a loss of contact between the wire bondings and the Al layer and/or an extensive decohesion between the metal grains. Failure modes include local melting of the Al and creation of eutectic alloys.