Impact of electric field reconstruction on gate oxide degradation in 1200 V 4H–SiC MOSFET induced by heavy ion radiation

Abstract In this article, a degradation mechanism based on electric field reconstruction was proposed to evaluate the impact of heavy ion irradiation on the gate oxide of 1200 V SiC MOSFETs with planar gate structure. Experimental tests were firstly conducted by starting with a low V DS , which was gradually increased in steps of 20 V, using 181 Ta heavy ion species with an energy of 1483 MeV. Notably, the real-time monitoring data showed observable changes in the increasing rate of gate leakage current ( I GSS ) in the high V DS region (i.e. when V DS exceeded 320 V in this experiment). For mechanism analysis of such experimental phenomena, TCAD simulations were carried out. Simulation results revealed that the gate oxide degradation was influenced by the coupling of two mechanisms, with ion strikes generating two electric field peaks corresponding to different physical processes. The first peak was attributed to conventional hole accumulation in the JFET region, while the second peak resulted from electric field reconstruction caused by the activation of the parasitic bipolar junction transistor. It was found that the second electric field peak which continued to rise as V DS increased plays a dominant role in gate oxide degradation under high V DS conditions, resulting in a change in the increasing rate of I GSS . Furthermore, simulation results showed that the second electric field was less influenced by the ion strike position or the width of the JFET region, indicating that the electric field reconstruction could be triggered in almost any location within the active area and the traditional radiation hardness technique of optimizing JFET structures was ineffective.