Silicon microforce sensors, to be used as a transferable standard for micro force and depth scale calibrations of hardness testing instruments, are developed using silicon bulk micromachining technologies. Instead of wet chemical etching, inductively coupled plasma (ICP) cryogenic deep reactive ion etching (DRIE) is employed in the sensor fabrication process leading to more precise control of 300 μm deep structures with smooth sidewall profiles. Double meander springs are designed flanking to the boss replacing the conventional rectangular springs and thereby improving the system linearity. Two full p-SOI piezoresistive Wheatstone bridges are added on both clamped ends of the active sensors. To realize passive force sensors two spring-mass elements are stacked using glue and photoresist as joining materials. Correspondingly, although plastic deformation seems to occur when the second spring is contacted, the kink effect (i.e., abrupt increase of stiffness) is obviously observed from the first test of the passive stack sensor.

Date Published: 21 May 2015
PDF: 9 pages
Proc. SPIE 9517, Smart Sensors, Actuators, and MEMS VII; and Cyber Physical Systems, 95171X (21 May 2015); doi: 10.1117/12.2180117

Published in SPIE Proceedings Vol. 9517:
Smart Sensors, Actuators, and MEMS VII; and Cyber Physical Systems
José Luis Sánchez-Rojas; Riccardo Brama, Editor(s)