Nanoscale in-plane displacement evaluation by AFM scanning and digital image correlation processing

A quantitative evaluation of the structure deformation of microfabricated electromechanical systems is important for the design and functional control of microsystems. When the displacement measurement of the microstructure's surface is to be made in a domain smaller than a few microns, both spatial sampling resolution and measuring sensitivity should reach nanoscale levels. In this paper, an atom force microscope (AFM) is used to scan surface topographies of silicon beam structures under electrostatic actuation, and then the AFM images are utilized to evaluate the in-plane deformation field based on digital image correlation (DIC) processing. It is shown that the AFM topographic maps provide a kind of carrier pattern to include the displacement information of the deformed surface, whose high scanning resolution and good image correlation makes it possible to search the in-plane displacement components on the nanometre scale from the images with statistics resembling grey level distributions. By using the proposed DIC algorithms, the deformation fields in the beam-end regions are obtained for the folded silicon flexures actuated by electrostatic comb drives.