The effects of stress on interfacial properties and flatband voltage instability of 4H-SiC MOS structures

Strain engineering technology is expected to improve the poor SiO2/4H-SiC interface. The paper investigated the effects of curvature induced stress on interfacial properties and flatband voltage instability of 4H-SiC MOS capacitors. The slightest stress sample demonstrated the best calculation results and the superior properties in terms of interface state density, FN barrier, and effective near-interface traps density, which means the “stress free” or small compressive stress oxide film might be helpful for the realization of high performance of 4H-SiC MOS structures. The behavior of Vfb instability under various bias temperature stress and voltage stress at different durations was also studied. The more significant compressive/tensile stress led to worse reliability at high temperatures, which was caused by the combined effect of mobile ions and charge trapping. The trapping and de-trapping time constants of interface and oxide traps were calculated to clarify the relationship between temperature and Vfb instability. Moreover, the results of the measured Raman shift of the SiC bond implied that stresses tend to be unanimous in the subsequent processes while the influences on interfacial properties and Vfb instability still exist. These results are considered necessary for strain engineering technology, which is expected to lower the interface states density in SiO2/4H-SiC interface and reach the optimal performances of 4H–SiC.