Understanding and controlling bias-temperature instability in SiC metal-oxide-semiconductor devices induced by unusual generation of mobile ions

Unusual behavior of bias-temperature instabilities in SiC metal-oxide-semiconductor (MOS) devices is studied. Electrical measurements of SiC-MOS capacitors are used to investigate details of self-generated mobile ions in thermal oxides on 4H-SiC(0001) substrates, such as their polarity, density, distribution, and impact on interface properties. It is found that positive bias-temperature stress (BTS) accumulates self-generated positive mobile ions at the bottom SiO2/SiC interface with an areal density of several 1012 cm−2, and that they induce additional electron trap formation at the interface. Using this knowledge, we demonstrate effective removal of the positive mobile ions with a combination of negative BTS and subsequent etching of the oxide surface.