Character of defects at an ion-irradiated buried thin-film interface

In order to investigate the nature of defects produced by ion irradiation through a heterostructure, a silicon-on-insulator substrate with a buried SiO2 layer at a depth of ∼1.5 μm was irradiated. The implantation was done using 2 MeV Si+28 ions in the dose range of 0.2–1×1016 cm−2. The subsequent defect analysis was performed using the Au labeling technique. Besides the presence of an expected excess of vacancy-type defects in the Si overlayer (VSiex), an additional vacancy excess peak was observed at the frontside of the buried interface (VIntex). The VIntex is found to increase linearly with increasing dose of the high-energy implant. The presence of this VIntex peak near the interface is also predicted by the TRIM Monte Carlo code. Additional Monte Carlo simulations of damage production via high-energy implantation in Si/X-type structures show that the nature of the defects at the front Si/X interface can be changed from vacancy to interstitial-type by increasing the mass of atoms in the buried thin-film, X. These experiments provide quantitative verification of nonuniform defect production at an ion-irradiated buried interface in Si.