ISBN 9783843938853

978-3-8439-3885-3, Reihe Elektrotechnik

Gerry Hamdana
MEMS piezoresistive force sensors based on micro- / nanostructured silicon components

234 Seiten, Dissertation Technische Universität Braunschweig (2018), Hardcover, A5

Zusammenfassung / Abstract

This dissertation presents the development of novel piezoresistive sensors based on icroelectromechanical systems (MEMS) for determining low forces that can be applied in various physical sensing and monitoring applications (e.g., material characterizations, robotics, automation systems, and during micromanipulation / -assembly of miniaturized structures). The developed micro force sensor mainly comprises double-meander-membrane structures and etched full Wheatstone bridge (WB) piezoresistors for enhancing the sensor performance and electrically sensing the applied forces, respectively. The use of double-layer silicon-on-insulator (DL-SOI) technology ensures precise realization of uniformly doped strain sensing elements by means of microlithography and inductively coupled plasma reactive ion etching (ICP-RIE) at cryogenic temperature. Correspondingly, the micro force sensor shows moderate stiffness, high sensitivity, and high resolution of ~30 nN with a maximum deviation of ~3 % due to varied force positions on the probing area. In addition, the inclusion of silicon pillar arrays into a force sensing device (i.e., micro-nano-integration) requires compatible, accurate, and reliable fabrication processes. Broad process window on various lithography techniques (i.e., photolithography, soft ultraviolet-based nanoimprint lithography (UV-NIL), colloidal lithography (CL), and electron beam lithography (EBL)) ensures accurate process control during the pattern transfer. As a result, silicon nanopillar structures with various pitches, tunable diameters down to ~58 nm, and an aspect ratio up to ~30 can be realized, in which they are then characterized in three-dimensional electrochemical capacitance-voltage (3-D ECV) measurements to investigate the doping concentration along the vertical direction of the pillars as well as in the atom probe tomography assessments to observe the atomic scale transport properties of silicon isotope (i.e., 28Si / 30Si). Besides, reproducible nanomechanical characteristics of silicon pillar structures as low-force transfer elements are investigated by high-precision nanoindentation tests (i.e., with standard deviations down to 5%).