Finite-element analysis (FEA) modal results of 3C-SiC lateral resonant devices anchored to a Si substrate are presented as resonant frequency versus temperature. The suspended elements are etched from a 2 mm, 3C-SiC film grown at 1600 K on a 500 mm-thick, Si substrate. The analysis includes, temperature-dependent properties, shape change due to volume expansion with temperature, and thermal stress caused by differential thermal expansion of different materials. Two designs are considered: type I has anchor locations close to the geometric centroid and a small shuttle, type II has a large shuttle with anchors far from the centroid. The resonant frequency decreases approximately 3.5% over a 1000 K temperature increase for the type-I device, and behaves according to theory. The resonant frequency of the type-II device decreases by 2% over the first 400 K, then rises slightly over the remaining 600 K. This device deviates from theory because of the high thermal stress induced in the beams. The thermal stress is caused by the differential thermal expansion of the suspended element relative to the substrate. The results show that the device geometry must be properly chosen if the resonant frequency of that device will be used to calculate the temperature coefficient of Youngís modulus. These results apply only to resonators of one material on a substrate of a different material.
Journal: TechConnect Briefs
Volume: Technical Proceedings of the 1999 International Conference on Modeling and Simulation of Microsystems
Published: April 19, 1999
Pages: 644 - 647
Industry sector: Sensors, MEMS, Electronics
Topicss: Chemical, Physical & Bio-Sensors, MEMS & NEMS Devices, Modeling & Applications