New optoelectronic methodology for nondestructive evaluation of MEMS at the wafer level

Abstract

One of the approaches to fabrication of MEMS involves surface micromachining to define dies on single crystal silicon wafers, dicing of the wafers to separate the dies, and electronic packaging of the individual dies. Dicing and packaging of MEMS accounts for a large fraction of the fabrication costs, therefore, nondestructive evaluation at the wafer level, before dicing, can have significant implications on improving production yield and costs. In this paper, advances in development of optoelectronic holography (OEH) techniques for nondestructive, noninvasive, full-field of view evaluation of MEMS at the wafer level are described. With OEH techniques, quantitative measurements of shape and deformation of MEMS, as related to their performance and integrity, are obtained with sub-micrometer spatial resolution and nanometer measuring accuracy. To inspect an entire wafer with OEH methodologies, measurements of overlapping regions of interest (ROI) on a wafer are recorded and adjacent ROIs are stitched together through efficient 3D correlation analysis algorithms. Capabilities of the OEH techniques are illustrated with representative applications, including determination of optimal inspection conditions to minimize inspection time while achieving sufficient levels of accuracy and resolution.

Analysis and Optomechanical Characterisation of a MEMS Micromirror Device

“…In our investigations, noninvasive, remote and full‐field‐of‐view quantitative optical methods are applied to investigate the reflective membrane and suspension mechanism of the MEMS micromirror device by means of accurate measurements of deformations and shape. Specifically, measurements and characterisation of load‐displacement responses are based on optoelectronic holographic microscopy (OEHM), being developed by us [23–27].…”

Dynamic characterization of AFM probes by laser Doppler vibrometry and stroboscopic holographic methodologies

“…depicts major components of an optoelectronic holographic microscope (OEHM), currently under development, specifically set up to perform high-resolution shape and deformation measurements of MEMS and for the investigations of the micromechanics of materials used in their fabrication7,12,13 . The OEHM is defined in a Linnik configuration and with capabilities to operate with laser diodes and short-coherence light sources having wavelengths in the visible range.…”

“…The OEHM is defined in a Linnik configuration and with capabilities to operate with laser diodes and short-coherence light sources having wavelengths in the visible range. Optoelectronic holography microscope (OEHM) specifically set up to perform highresolution shape and deformation measurements of MEMS materials and devices7,12,13 .…”