The mechanical properties of the thin film materials used in RF-MEMS are crucial for the reliability and proper functioning of the devices. In this paper we study a large number of aluminum alloys as possible RF-MEMS thin film materials. The yield strength and creep properties are measured using nano-indentation. The results show that the mechanical properties of thin aluminum films can be improved substantially by alloying elements. Of the alloys studied in this paper, AlCuMgMn in particular seems quite promising as a thin film material for RF MEMS, having both high yield strength and little creep. Using X-ray diffraction and electron microscopy, the observed effects are partly explained.
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This work is supported by the EC project MEMS2TUNE (IST 28231). Thanks go to Robert Modlinski, Petar Ratchev, and Ingrid de Wolf of IMEC for TEM measurements and discussions.
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den Toonder, J.M., van Dijken, A.R. Optimization of mechanical properties of thin free-standing metal films for RF-MEMS. MRS Online Proceedings Library 820, 13–18 (2004). https://doi.org/10.1557/PROC-820-O8.3