An Evaluation for Quality Inspection of Epitaxial Layer and Heavily-doped 4H-SiC Substrate by Simple Schottky Barrier Diode and MOS Capacitor

Reducing the crystal defects in SiC is an important issue. In this work, we propose a short turn-around method using simple SBD and MOSC devices to reflect the electrically-active defect density in the substrate. Simple SBD and MOSC structures are fabricated on n(-) epi-layer/n(+) substrate or pure n(+) substrate that have different defect densities. The n(-) epi-layer SBDs for high-defect wafers generate high yield loss, a more comprehensive leakage current distribution, and a stronger bias-dependent leakage current than low-defect alternatives. The pure n(+) substrate SBDs of high-defect wafers only reveal a higher leakage level than the low-defect alternatives. This phenomenon may be caused by the variation of doping concentration or Schottky barrier height. The pure n(+) substrate MOSCs show a higher yield loss than the n(-) epi-layer MOSCs based on TZDB, where the leakage level is identical for both the high-defect and the low-defect wafers. It is suggested that the epitaxial quality can be evaluated by using the simple SBD, where the heavily-doped substrate is not suitable. Both the n(-) epi-layer and the pure n(+) substrate MOSCs cannot reflect electrically-active defect densities for the TZDB phenomena.