SYMPOSIA PAPER Published: 01 January 2001

Mechanical Tests of Free-Standing Aluminum Microbeams for MEMS Application


We studied mechanical properties and alloy effects of free-standing aluminum microbeams (50 × 500 × 2 μm) in a piezo-actuator-driven test apparatus with a load resolution of ±0.2 mN and a displacement resolution of ±10 nm. Pure Al and Al-2%Ti microbeams were fabricated using micromachining techniques. In tensile tests, we found the yield strength to be approximately 120 MPa for the pure Al beams, and approximately 75% higher for the alloyed beams. We examined the results with respect to those of bulk materials and thin films adhered to substrates. In stress relaxation tests, we observed a load drop of 56% over 10 min for the pure Al beams. We attributed this to grain boundary sliding and the nature of a free-standing thin film, i.e., the absence of a substrate. For the alloyed beams, the load drop was only 16%. We believed the difference was due to Al3Ti precipitates formed at grain boundaries, which hindered dislocation movements. We used TEM to reveal the microstructural features of the microbeams.

Author Information

Zhang, P
Stanford University, Stanford, CA
Lee, H-J
Lucent Technologies, Inc., Reading, PA
Bravman, JC
Stanford University, Stanford, CA
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Developed by Committee: E08
Pages: 203–213
DOI: 10.1520/STP10990S
ISBN-EB: 978-0-8031-5458-2
ISBN-13: 978-0-8031-2889-7