The effect of electron-beam aluminization on the Si-sapphire interface

We have used extended-range MIS C (V) measurements of Al-sapphire-Si capacitor structures to study the effect of metallization in an e-beam (electron-beam) evaporator on the Si-sapphire interface. Our results show that (1) this step causes the development of positive charge at or near the Si-sapphire interface, and (2) the charge is partially but not entirely removed by annealing at 400 °C in forming gas. We believe that the observed positive charge is due to (1) generation of electron-hole pairs in the sapphire by ionizing radiation (probably soft x rays) emanating from the e-beam evaporation unit, and (2) more effective trapping of holes than electrons within the sapphire. These results have important implications for CMOS/SOS technology.