Interface states and deep-level centers in silicon-on-insulator structures

Deep-level centers in a split-off silicon layer and trap levels were studie d by deep-level transient spectroscopy both at the Si/SiO2 interface obtain ed by direct bonding and also at the Si(substrate)/< thermal SiO2> interfac e in the silicon-on-insulator structures formed by bonding the silicon wafe rs and delaminating one of the wafers using hydrogen implantation. It is sh own that the Si/< thermal SiO2> interface in a silicon-on-insulator structu re has a continuous spectrum of trap states, which is close to that for cla ssical metal-insulator-semiconductor structures. The distribution of states in the upper half of the band gap for the bonded Si/SiO2 interface is char acterized by a relatively narrow band of states within the range from E-c - 0.17 eV to E-c - 0.36 eV. Furthermore, two centers with levels at E-c - 0. 39 eV and E-c - 0.58 eV are observed in the split-off silicon layer; these centers are concentrated in a surface layer with the thickness of up to 0.2 1 mum and are supposedly related to residual postimplantation defects. (C) 2001 MAIK "Nauka/ Interperiodica".