George G. Adams
Nicol E. McGruer
Date of Award
Master of Science
Department or Academic Unit
College of Engineering, Department of Mechanical and Industrial Engineering
mechanical engineering, adhesion, AFM, contact switch, MEMS, plasma cleaning, testing
The testing of micro-contacts at low forces (below 1mN) is critical for understanding the contact evolution of MEMS contact-switches. Testing is achieved with a specially designed micro-contact-test assembly based on an AFM. The micro-contact-test assembly consists of a Si force sensor with an integrated micro-bump and a mating silicon pillar. Both sides of the contact can be coated with various combinations of metals to provide a wide range of metal-contact pairs for testing. When fabricated with different lengths, these force sensors cover a wide range of forces from 10µN to 1mN. Both force and resistance can be measured simultaneously during the contact tests. To protect the contacts from contamination, assemblies were first cleaned using Ar and O2 plasmas, or UV/ozone, followed by testing under a constant stream of nitrogen. Cleaning efficiencies of Ar and O2 plasma, and UV/ Ozone were compared by performing in-situ and ex-situ experiments on a variety of metal-pairs. Experiments were conducted on Au, Ru, Ir and V2O5-Au, and Au-Ni with three different compositions under different forces. It is proposed that integration of electrical properties of Au with the mechanical properties of Ru can promote an electromechanically sound and long lasting metal contact pair. Two strategies were followed to verify this proposition 1) using a layered stack of Ru of different thicknesses on Au for the entire test assembly 2) using a Au-coated force sensor over a Ru-coated pillar for conducting contact tests. The simulation results for the four-wire resistances of contacts using finite element analysis show good agreement with the recordings from the system.
Joshi, Nikhil, "An SPM based tester for the study of microcontacts" (2010). Mechanical Engineering Master's Theses. Paper 34. http://hdl.handle.net/2047/d20000955
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