Theoretical and experimental investigation of valence band offsets for direct silicon bond hybrid orientation technology

Abstract

Direct silicon bonding (DSB) for hybrid orientation technology has recently generated a lot of interest due to the significant performance enhancements reported for p-channel metal oxide semiconductor devices fabricated on alternative substrate orientations. This letter reports on the experimental observation and density functional theory (DFT) based theoretical prediction of a valence band offset between the (100) and (110) silicon surfaces directly bonded to each other. This constitutes a different type of junction created by the presence of two different surface orientations in close proximity to each other and not by doping or material variations. Experimentally, this band offset was observed as an asymmetry in the forward and reverse current-voltage characteristics of a two terminal device designed to flow a current across the DSB interface. Further, the valence band offset obtained from DFT simulations was used in a conventional device simulator (TAURUS-MEDICI) to simulate the behavior of this structure. MEDICI results are in qualitative agreement with the predicted band offset of ∼85meV between the (110) and (100) surfaces which result in a diodelike behavior of the current-voltage characteristics across the (110)∕(100) interface. Temperature dependence of the I-V characteristics is also discussed.