Lifetime estimation of SiC MOSFETs under high temperature reverse bias test

Reliability physics of silicon carbide (SiC) metal-oxide semiconductor field-effect transistor (MOSFET) is not sufficiently clear; therefore an accurate estimation method of lifetime has been strongly required. The relationship between the failure time of 4H-SiC double implanted MOSFETs under high temperature reverse bias test and the doping concentration in a drift layer was studied to clarify the failure physics. The failure time of the device showed dependence on the doping concentration in the 150 mm wafer. The breakdown occurred at the gate oxide over the threading dislocation in the JFET region. The electric field simulation indicated that the oxide electric field linearly depends on the doping concentration, which means the failure time depends on the oxide electric field. According to these results, the electric field acceleration tests were conducted with the samples in the uniform area of the doping concentration so as to exclude the distribution of the oxide electric field in each sample. The lifetime showed dependence on the oxide electric field varied by the drain bias intentionally. These results revealed the importance of the doping concentration uniformity of the epitaxial layer and we established the method to estimate the lifetime accurately.