The adhesive force acting on microstructures has been investigated by using an atomic force microscope (AFM). In the AFM system, a heterodyne interferometer is used to measure the deflection of the AFM probe precisely. We investigate the adhesive force (capillary force) acting between an Si3N4 probe and some kinds of material used for micromachining processes. When an SiO2 substrate and five kinds of solution are used, the adhesive forces are in the range 10 nN-1 μN. The adhesive forces generated by C2H5OH and CH3COCH3 are smaller than the others, which is consistent with the result that rinsing with C2H5OH or CH3COCH3 reduces the pinning of surface-micromachined cantilevers to a substrate. The results are discussed on the basis of the macroscopic adhesive theory. The adhesive force is independent of the repulsive force applied to the sample surface in the force range 10 nN-6 μN and is almost uniform in the measured area (6 μm × 6 μm). In addition, the adhesive force of solid bridging, which occurs by the deposition of insoluble impurities present in a small gap of the microstructures after the drying process, has been tested by peeling off a microcantilever pinned to a dried substrate.
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