1700V/30A 4H-SiC MOSFET with low cut-in voltage embedded diode and room temperature boron implanted termination

In this paper, a SiC MOSFET embedded with a low cut-in voltage Schottky diode was proposed. The 1V cut-in voltage of embedded Schottky diode, which is lower than the 3V cut-in voltage of parasitic body diode, can prevent the potential failures caused by the transformation of dislocation defects into stacking faults due to the recombination of injected minority carriers when parasitic body diode in SiC MOSFET was turned on. The voltage drop of forward biased embedded diode at a current density of 75 A/cm² is 1.7V, compared to the 4.9V in the parasitic body diode, is helpful to reduce the energy loss. The terminations with floating guard rings formed by aluminum implantations at 500°C and an extended coupling band formed by boron implantations at room temperatures were able to achieve a blocking voltage of up to 1889V with a drift layer of 11μm thickness and 6×10¹⁵ cm^-3 doping concentration. This termination provided a very tight distribution of blocking voltages with an average value of 1797V and a sigma of 43V or a mean to sigma value of only 2.4%, for 28 devices across the wafer. The working of the extended coupling band formed by room temperature implantation is speculated different from the ordinary junction termination extension (JTE) as the single zone JTEs formed by the room temperature boron implantations could provide blocking voltages of about 500V, which is essentially of the same level for devices without terminations. A highly resistive region formed due to unrecoverable damages caused by room temperature implantations was considered to provide stable coupling between guard rings and thus improve the blocking voltage.