1.2 kV silicon carbide Schottky barrier diode embedded MOSFETs with extension structure and titanium-based single contact

摘要

Recently, to avoid forward-voltage degradation of body diodes, which is caused by the expansion of stacking faults due to hole-current conduction through the body diodes, silicon carbide (SiC) Schottky barrier diode (SBD) embedded metal-oxide-semiconductor field effect transistors have been actively studied. However, most studies focus on designs that do not allow hole current to flow when reverse current flows from the source to drain, and there are few reports that mention the contact-formation process or contact reliability. A low-resistance ohmic contact and a highly reliable Schottky contact were formed simultaneously by combining the recrystallization of an N+ heavily implanted region to 3C-SiC, opening of a contact hole by dry etching and formation of a titanium electrode followed by post-annealing. Moreover, gate leakage current can be reduced by improving the crystallinity and morphology near the channel by introducing an extension structure, even if the process for simultaneously forming the ohmic and Schottky contacts is applied to the MOSFETs fabrication process. The developed process minimizes the increase in cell pitch due to the incorporation of the SBD and suppresses the conventional increase in on-resistance to about 10%. Regarding diode characteristics, expansion of the stacking faults could be suppressed by eliminating the hole-current conduction, even in the case of a large current density of 500 A cm(-2) at 175 degrees C. (C) 2020 The Japan Society of Applied Physics