Maarten P de Boer | Search PubMed

PubMed2005

Long-working-distance incoherent-light interference microscope.

We describe the design and operation of a long-working-distance, incoherent light interference microscope that has been developed to address the growing demand for new microsystem characterization tools. The design of the new microscope is similar to that of a Linnik interference microscope and thus preserves the full working distance of the long-working-distance objectives utilized. However, in contrast to a traditional Linnik microscope, the new microscope does not rely on the use of matched objectives in the sample and the reference arms of the interferometer. An adjustable optical configuration has been devised that allows the total optical path length, wavefront curvature, and dispersion of the reference arm to be matched to the sample arm of the interferometer. The reference arm configuration can be adjusted to provide matching for 5x, 10x, and 20x long-working-distance objectives in the sample arm. In addition to retaining the full working distance of the sample arm objectives, the new design allows interference images to be acquired in situations in which intervening windows are necessary, such as occur with packaged microsystems, microfluidic devices, and cryogenic, vacuum, or environmental chamber studies of microsystem performance. The interference microscope is compatible with phase-shifting interferometry, vertical scanning interferometry, and stroboscopic measurement of dynamic processes.

Equipment Design↗

PubMed2005

The role of van der Waals forces in adhesion of micromachined surfaces.

Interfacial adhesion and friction are important factors in determining the performance and reliability of microelectromechanical systems. We demonstrate that the adhesion of micromachined surfaces is in a regime not considered by standard rough surface adhesion models. At small roughness values, our experiments and models show unambiguously that the adhesion is mainly due to van der Waals dispersion forces acting across extensive non-contacting areas and that it is related to 1/Dave2, where Dave is the average surface separation. These contributions must be considered because of the close proximity of the surfaces, which is a result of the planar deposition technology. At large roughness values, van der Waals forces at contacting asperities become the dominating contributor to the adhesion. In this regime our model calculations converge with standard models in which the real contact area determines the adhesion. We further suggest that topographic correlations between the upper and lower surfaces must be considered to understand adhesion completely.

Journal Article↗