A new technique for 3D profilometry of MEMS

摘要

Based on physical optics models of light propagation, scattering and transfer, a new fast computerized non-interferometric technique for 3D image reconstruction using wide-field microscopy is developed and tested that allows profilometry of M(O)EMS without compromising accuracy and spatial resolution attained by well established interferometry techniques. This non-destructive technique associated with using conventional microscope setups allows obtaining high-quality 3D profiles of structures like protecting membranes for packaging of MEMS with subsequent measurements of their mechanical properties. The comparison with conventional phase-shift interferometry-based measurements yielded encouraging results. The technique finds its potential whenever using of laser scanning confocal microscopy or phase-shifting techniques is compromised by the need to perform vibration-insensitive studies, or whenever stringent acquisition time requirements are of concern. This software technique being fully automatic, no changes to the existing hardware in the optical paths of microscopes is required. Moreover, the image acquisition protocol associated with the technique allows for simpler and cheaper measuring devices than interferometers and open the possibility for creating portable devices. The technique is tested on images acquired to control of packaging of MEMS by measuring deformations in MEMS protection membranes. The method's simplicity, its lower implementation cost and better insensitivity to vibrations with respect to established interferometric techniques makes it a potentially promising procedure for routine MEMS quality control hi industrial environments.