The Role of the Ion Implanted Emitter State on 6H-SiC Power Diodes Behavior. A Statistical Study

Abstract

Two device runs of high voltage bipolar 6H-SiC p + n diodes were fabricated. Emitter and JTE (Junction Termination Extension) periphery were both realized by aluminum ion implantation, at room temperature (RT) for JTE, and both RT and 300°C for emitters. All diodes Current-Voltage characteristics were systematically measured in forward (0 → 5V) and reverse bias (0 → -50V). Breakdown voltages were also measured on a part of diodes. The emitter quality after implantation and annealing seems to be important for the diode behavior in forward and in reverse bias also. For the 300°C implanted diodes higher current densities (200 A.cm -2 at 5V) are obtained in forward bias, with a more homogeneous distribution, showing better doping activation and layer quality. Compared to the RT implanted diodes, a less number of 300°C implanted diodes with high leakage currents is obtained. Those with the smallest emitter and the largest JTE length sustain more than 1100V. The breakdown voltage value (V BR ) is similar to the calculated value and independent on the testing ambient. This indicates a breakdown in the bulk volume, confirmed by a lower V BR for the RT implanted diodes. This lower V BR value is due to the presence of an amorphous layer after implantation and thus residual defects at the emitter-epilayer junction interface.

SiC power semiconductor devices for new applications in power electronics

“…Indeed 70% of the 1.3kV diodes with an emitter implanted at 300˚C and a long JTE (120 m) exhibit a breakdown voltage higher than 1100V (up to 1300V ) without any impact of the ambient conditions (air or SF6 gas or dielectric liquid). The ambient conditions impact breakdown voltage only for diodes with short JTE length (50m) [8]. These results show in the same time that post-implantation annealing realized in the lab furnace [8] allows a full activation of dopants in JTE.…”

“…The ambient conditions impact breakdown voltage only for diodes with short JTE length (50m) [8]. These results show in the same time that post-implantation annealing realized in the lab furnace [8] allows a full activation of dopants in JTE. In forward state, current densities and efficiency have been improved (200 A/cm2 @ 5 V at room temperature) also due to the improvement of metallization step and subsequent annealing at IMM Bologne [9].…”

High energy N+ ion implantation in 4H–SiC

“…Moreover, the conception of SiC-based power and high temperature devices, requires the formation of deep junctions (formation of Junction Termination Extension (JTE) [2] for bipolar devices, thick channels and deeper gate buried layers in Junction-FET transistors [3] . .…”