Protection of selectively implanted and patterned silicon carbide surfaces with graphite capping layer during post-implantation annealing
A graphite capping layer has been evaluated to protect the surface of patterned and selectively implanted 4H–SiC epitaxial wafers during post-implantation annealing. AZ-5214E photoresist was spun and baked in vacuum at temperatures ranging from 750 to 850 °C to form a continuous coating on both planar and mesa-etched SiC surfaces with features up to 2 µm in height. Complete conversion of the hydrogenated polymer-like film into nanocrystalline graphite layer was verified by Raman spectroscopy. The graphite capping layer remained undamaged and protected both planar and mesa-etched SiC surfaces during subsequent annealing in argon ambient at temperatures up to 1650 °C for 30 min. It effectively suppressed step bunching and dopant out-diffusion in implanted regions and simultaneously ensured that the un-implanted surface of the 4H–SiC epitaxial wafer remained free of contamination. Schottky barrier diodes formed on the un-implanted annealed surfaces displayed almost ideal characteristics.