Paul E. Kladitis

Microswitches with sputtered Au, AuPd,Au-on-AuPt, and AuPtCu alloy electric contacts

This paper is the first to report on a new analytic model for predicting microcontact resistance and the design, fabrication, and testing of microelectromechanical systems (MEMS) metal contact switches with sputtered bimetallic (i.e., gold (Au)-on-Au-platinum (Pt), (Au-on-Au-(6.3at%)Pt)), binary alloy (i.e., Au-palladium (Pd), (Au-(3.7at%)Pd)), and ternary alloy (i.e., Au-Pt-copper (Cu), (Au-(5.0at%)Pt-(0.5at%)Cu)) electric contacts. The microswitches with bimetallic and binary alloy contacts resulted in contact resistance values between 1-2Omega. Preliminary reliability testing indicates a 3times increase in switching lifetime when compared to microswitches with sputtered Au electric contacts. The ternary alloy exhibited approximately a 6times increase in switch lifetime with contact resistance values ranging from approximately 0.2-1.8Omega

Micro-switches with sputtered Au, AuPd, Au-on-AuPt, and AuPtCu alloy electric contacts

This work is the first to report on a new analytic model for predicting micro-contact resistance and the design, fabrication, and testing of microelectromechanical systems (MEMS) metal contact switches with sputtered bi-metallic (i.e. gold (Au)-on-Au-platinum (Pt), (Au-on-Au-(6%)Pt)), binary alloy (i.e. Au-palladium (Pd), (Au-(2%)Pd)), and tertiary alloy (i.e. Au-Pt-copper (Cu), (Au-(5%)Pt-(0.5%)Cu)) electric contacts. The micro-switches with bi-metallic and binary alloy contacts resulted in contact resistance between 1-2 /spl Omega/ and, when compared to micro-switches with sputtered Au electric contacts, exhibited a 3.3 and 2.6 times increase in switching lifetime, respectively. The tertiary alloy exhibited a 6.5 times increase in switch lifetime with contact resistance ranging from 0.2-1.8 /spl Omega/.

Self-recovery of stressed nanomembranes

Long-term stability and self-recovery properties were studied for the compliant nanomembranes with a thickness of 55nm free suspended over openings of several hundred microns across. These nanomembranes were assembled with spin-assisted layer-by-layer routines and were composed of polymer multilayers and gold nanoparticles. In a wide pressure range, the membranes behave like completely elastic freely suspended plates. Temporal stability was tested under extreme deformational conditions close to ultimate strain and very modest creep behavior was observed. A unique “self-recovery” ability of these nanomembranes was revealed in these tests. We observed a complete restoration of the initial nanomembrane shape and properties after significant inelastic deformation. These unique micromechanical properties are suggested to be the result of strong Coulombic interaction between the polyelectrolyte layers combined with a high level of biaxial orientation of polymer chains and in-plane prestretching stresses.

Nanoindentation technique for characterizing cantilever beam style RF microelectromechanical systems (MEMS) switches

A nanoindentation technique was used to mechanically actuate a radio frequency micro-switch along with the measurement of contact resistance to investigate its applicability to characterize deflection and contact resistance behaviors of micro-sized cantilever beam switches. The resulting load?displacement relationship showed a discontinuity in slope when the micro-switch closed. The measured spring constants reasonably agreed with theoretical values obtained from the simple beam models. The change in contact resistance during test clearly indicated micro-switch closure but it did not coincide exactly with the physical contact between two electric contacts due to a resistive contaminated film.

Uncertainty in Manufacture and Assembly of Multiple-Joint Solder Self-Assembled Microelectromechanical Systems (MEMS)

Surface-micromachined microelectromechanical systems (MEMS) are two dimensional in their “as fabricated” form. Surface-micromachined MEMS can be assembled after fabrication to realize systems with a more three-dimensional form and function. One reliable method of assembly, suited to commercial mass production, is to use the surface tension of microsized droplets of molten solder to assemble the microsized structures, otherwise known as “solder selfassembly.” In other works, single-joint solder self-assembled structures have been demonstrated without emphasis on the uncertainty involved in the assembly position. In this work, a reliable process for manufacturing multiple-joint solder self-assembled MEMS was developed, and the impact of process and component tolerances on assembly precision was investigated using statistical and worst-case tolerance analysis techniques. It was determined that assembly precision was affected, from greatest to least impact, by the following assembly variables: solder volume, scavenging and overwetting, residual stress in bilayer structures, temperature, structure dimension, solder pad warpage, hinge play, and residual stress in single-layer structures, respectively. Guidelines on increasing assembly precision are discussed.