Amorphous hydrocarbon based thin films for high-aspect-ratio MEMS applications

Methods to engineer the surfaces of micro-electro-mechanical systems (MEMS) are just beginning to be explored. Coating deposition is one such method. In cases where microdevices involve moving parts in contact, such as gear sets, combustion chambers, and mechanical seals, it may be necessary to impart the complex, highly non-planar surfaces with desired mechanical properties and tribological characteristics. In other cases, such as micro-heat exchangers or micro-catalytic converters, the chemical properties of the microdevice surfaces are important. Amorphous hydrocarbon (a-C:H) and metal-containing amorphous hydrocarbon (Me-C:H) thin films possess moderately high hardness, chemical inertness, low coefficient of friction and low wear rate, and are potentially useful in a wide range of microdevice applications. We report on the mechanical properties and tribological characteristics of Ti-C:H films as a function of the Ti composition. We further demonstrate the conformal deposition of Ti-C:H thin films over electrodeposited Ni high-aspect-ratio micro-scale structures (HARMS) fabricated by the deep X-ray lithography based microfabrication technique LIGA (Lithographie, Galvanoformung, Abformung). Conformal deposition of nanostructured ceramic thin films over HARMS offers possibilities for improving the tribological characteristics of HARMS based microdevices with parts in relative motion, and for using nanostructured ceramic thin films as structural materials for microdevices. As an example, we demonstrate the fabrication of freestanding, high-aspect-ratio Ti-C:H microtubes based on conformal deposition over electrodeposited Ni HARMS. (C) 2001 Elsevier Science B.V. All rights reserved.