| AVS 56th International Symposium & Exhibition | |
| MEMS and NEMS | Thursday Sessions |
| Session MN+IJ+TR-ThA |
| Session: | Multi-scale Interactions of Materials and Fabrication at the Micro- and Nano-scale I |
| Presenter: | F. Liu, University of California, Berkeley |
| Authors: | F. Liu, University of California, Berkeley I. Laboriante, University of California, Berkeley C. Carraro, University of California, Berkeley R. Maboudian, University of California, Berkeley |
| Correspondent: | Click to Email |
Recent developments in the MEMS field have created a growing interest in the reliability of these miniaturized devices. Along with the reliability issues such as stiction, corrosion and friction, wear is an important failure mechanism in these microsystems. Repetitive contact between microelectromechanical systems (MEMS) surfaces can lead to device failure, making it highly desirable to develop a microfabricated instrument to study the effects of impact and wear in MEMS for a wide range of structural layers, contact mechanics, coatings, and ambients.
This paper describes the design, and testing of a microinstrument that allows the surfaces of two microstructures to come into contact, after which the surfaces are separated sufficiently in the substrate plane to allow nondestructive surface analysis and then, for the first time, re-engagement of the contact. The device is designed to achieve large enough in-plane deflection for in situ analysis and controllable contact load. Using this microinstrument, the time-dependent assessment of the contacting surfaces is achieved by scanning probe microscopy, including atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM), as well as scanning Auger electron microscopy (SAEM) and electrical contact resistance measurements. The microinstrument design also allows for the study of a wide range of materials, coatings and environmental conditions under controlled loads. The contact resistance initially decreases during the first tens of millions of impacts and then increase gradually, a behavior attributed to the wear. The fracture of Si grains shows up at around 24 billion impacts and grows to 5-6 grains in diameter after about 100 billion impacts, associated with the interfacial oxidation. Based on these results, potential wear mechanisms at the microscale are proposed.