The study of mechanical stress in NEMS heterostructures

Mechanical stress is increasingly applied in microelectronics. For instance, strained silicon technology is widely used to improve carrier mobility and driver current for advanced MOS transistors. For micro electromechanical systems, piezoresistive efiects are widely used in pressure sensors. In this paper we present an original method for studying mechanical stress in nanodevices placed on ultra-thin membranes, which has several advantages compared with the conventional fourpoint-bending method. Using this architecture, we use FEM simulations of an innovative NEMS pressure sensor to investigate its static and dynamic modes. We study the optimal orientation and position of a nanowire on the membrane We show that a large improvement in pressure measurement sensitivity can be obtained by adopting tunnel junction technology. We also investigate the dynamic multi-bends of the nanostructure in its dynamic deformation modes and introduce the transport matrix method to calculate the tunnel current. Finally, our work helps to understand the electrical and mechanical properties of the nanostructure under the in∞uence of large mechanical stress and to design innovative NEMS pressure sensors.