Influence of annealing, oxidation and doping on conduction-band near interface traps in 4H-SiC characterized by low temperature conductance measurements

Current power MOSFET devices on Silicon Carbide show a limited inversion channel mobility, which can be a result of the expected very high density of interface states near the conduction band [1]. In the current work, the effect of the post implantation annealing temperature, the thermal oxidation and the nitrogen doping concentration of the n-epi layer on the density of these interface traps is investigated using capacity-conductance measurements. Instead of the usage of very high frequencies as used in [2], in this investigation the measurements were performed in liquid nitrogen to decrease the recharging times of the interface traps. Due to different processing parameters the samples showed a wide spreading of the inversion channel mobility. Especially for the low temperature measurements, the conductance measurements reveal a characteristic peak caused by interface traps near the conduction band. But these traps could not be correlated to mobility variations. Instea d, a correlation to the nitrogen doping of the epi layer could be observed indicating that the traps near conductance band seen by the low temperature conduction measurement originated from nitrogen in the epi layer and/or the NO oxidation