Research Projects

For several applications such as material characterization, precision mechanics, thin film metrology, biomechanics and semiconductor wafer condition monitoring, precision measurement of surface properties such as topography, morphology and deformation of a test object is an important problem with significant practical relevance. In this domain, such measurements are usually performed using techniques such as scanning electron microscope, atomic force microscope, coordinate measuring machine and stylus device. However, these methods are usually constrained by one or more of the following limitations: (1) invasive probe based operation, (2) bulky, sophisticated and high cost design, (3) limited throughput due to point or line scan operations and (4) requirement of specialized and trained operators. In addition, as the primary output of these techniques is stored in the form of a digital image, and consequently, the imaging artifacts related to sharp surface features, noise and local image abnormalities also constitute an important challenge. Accordingly, the primary aim of this proposal is to develop a robust and compact technique for non-contact, high throughput and full field inspection of surface micro-structures. Our proposed technique is based on a common path optical interferometric design where the desired information about the surface properties would be encoded in an optical interferogram. This would be supplanted with the development of interferogram demodulation approaches based on robust signal processing algorithms which have high computational performance, and are resilient to severe noise, non-uniform intensity fluctuations and local image abnormalities. In addition, these algorithms would provide the capability for identifying sharp surface features such as step structures and edges as well as automated localization of defects. Finally, the developed technique would be tested for practical applications related to precision surface topography, sub-micron deformation testing and micro-scale surface defect identification. Using the proposed method, the ability for non-invasive inspection of large surface areas without the requirement of multiple line/point scan operations would be valuable for dynamic surface metrology. Overall, the proposed has the potential to provide practical impact in the domain of non-destructive material characterization, semiconductor condition monitoring and precision mechanics.