Confocal optoelectronic holography microscope for structural characterization and optimization of MEMS

In this paper, we describe confocal optoelectronic holography microscopy (COEHM) technique specifically being developed for characterizing the shape of MEMS and microelectronics. This is particularly important because shape is directly related to the functionality, performance, and integrity of the microstructures of interest. A specific feature of COEHM is that it allows characterization of high aspect ratio MEMS and microelectronics. Representative applications demonstrating the capabilities of COEHM are presented. It is shown that measurement resolution is highly dependent on the numerical aperture (NA) of the optical components comprising COEHM and on the quality of image digitization. By utilizing optical components characterized by a magnification factor of 50x and a NA of 0.45, measurement resolution of 25 nm is achieved. The resolution can be increased to 8 nm when utilizing optical components characterized by a magnification factor of 100x and a NA of 0.73.