Investigation of SiO2 Cap for Al Implant Activation in 4H-SiC

The effect of using SiO2 capping layer during Al implant activation anneal on the performance of 4H-SiC P-i-N diodes has been investigated. Two sets of 4H-SiC pin diode samples, one with SiO2 cap and another with graphite cap, were annealed under high temperatures of 1500 degrees C for activation after Al implantation at 650 degrees C to form the p-type active region and the JTE region. The surface stoichiometry of annealed SiC was examined by x-ray photoelectron spectroscopy (XPS). Various material and device parameters including surface roughness, sheet resistance, minimum forward leakage current and maximum breakdown voltage have been extracted for comparison. The results show that SiO2 cap effectively protects the SiC surface during high temperature implant annealing.