Design and fabrication of nanometer measurement platform for better understanding of silicon mechanical properties

Abstract

Semiconductor industry is experiencing unprecedented growth, still driven by Moore's law, which is continually delivering devices with improved performance at lower costs. The continuation of this development places the industry in a divergent trade-off between economic attractiveness, technological feasibility, and the need for further performance improvement. Since the mainstream semiconductor technologies are silicon-based, new disruptive innovations are needed to gain additional performance margins. The use of nanowires is the preferred approach for preserving electrostatic control in the MOS transistor channel, and the application of mechanical stress is a booster of carrier mobility. It is in this context that this paper presents the design, fabrication, theoretical modeling, and characterization of a measurement platform to characterize the mechanical tensile stress of extremely narrow Si nanowires as small as 14.2 ± 1.12 nm in width. The proposed measurement platform enables a precise control of uniaxial strain, in terms of both amplitude and location, through the implementation of a stoichiometric Si3N4 pulling strand exerting a high tensile force on silicon nanowires. Reported devices are fabricated using a silicon-on-insulator wafer with fully complementary metal–oxide–semiconductor-compatible processing and top-down approach. It is observed that the mechanical strength of nanostructured Si is size-dependent and increases with miniaturization. Characterization revealed a record tensile strength value of 7.53 ± 0.8% (12.73 ± 1.35 GPa) for the narrowest nanowires fabricated using a top-down approach.