Comparison of Au and Au-Ni Alloys as Contact Materials for MEMS Switches

• Published in: Journal of microelectromechanical systems Vol. 18; no. 2; pp. 287 - 295
• Main Authors: Zhenyin Yang, Lichtenwalner, D.J., Morris, A.S., Krim, J., Kingon, A.I.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.04.2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adhesives; Alloying; Alloys; Applied sciences; Au-Ni alloys; Binary systems; Circuit properties; Contact; Contact resistance; Electric, optical and optoelectronic circuits; electrical contacts; Electronics; Exact sciences and technology; Gold; Gold alloys; Gold base alloys; Gold |m Binary systems; Inorganic materials; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mechanical instruments, equipment and techniques; Metallurgy; Microelectromechanical systems; microelectromechanical systems (MEMS); Micromechanical devices; Micromechanical devices and systems; microswitch; Microswitches; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Nickel; Nickel |m Binary systems; Physics; radio-frequency (RF) MEMS; Surface topography; Switches; Nickel alloys; Ruptures; Gold alloys; microelectromechanical systems (MEMS); Stiction; Metals; Switches; Alloys; Hardness; Experimental study; Adhesion; Heat treatments; Operating conditions; radio-frequency (RF) MEMS; microswitch; Solid solutions; Wear rate; Phase separation; Wear; electrical contacts; Microelectromechanical device; Au―Ni alloys
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2008.2010850

This paper reports on a comparison of gold and gold-nickel alloys as contact materials for microelectromechanical systems (MEMS) switches. Pure gold is commonly used as the contact material in low-force metal-contact MEMS switches. The top two failure mechanisms of these switches are wear and stiction, which may be related to the material softness and the relatively high surface adhesion, respectively. Alloying gold with another metal introduces new processing options to strengthen the material against wear and reduce surface adhesion. In this paper, the properties of Au-Ni alloys were investigated as the lower contact electrode was controlled by adjusting the nickel content and thermal processing conditions. A unique and efficient switching degradation test was conducted on the alloy samples, using pure gold upper microcontacts. Solid-solution Au-Ni samples showed reduced wear rate but increased contact resistance, while two-phase Au-Ni (20 at.% Ni) showed a substantial improvement of switching reliability with only a small increase of contact resistance. Discussion of the effects of phase separation, surface topography, hardness, and electrical resistivity on contact resistance and switch degradation is also included.