Microelectromechanical systems surface characterization based on white light phase shifting interferometry

This paper describes a new peak detecting algorithm combined Carre phase shifting interferometry with white light interferometry. The new method can carry the fast, accurate, and noncontact measurements. The testing system employs a Mirau objective on a piezoelectric transducer based on a Zeiss microscope. Several numerical simulations are first carried to analyze its phase calculation errors due to the visibility variation in the white light correlogram. Afterwards, the centroid method is adopted to concentrate the phase extraction on the zero-order fringe, which not only decreases the phase error, but also frees the data processing from the phase unwrapping procedure. The capabilities of the system and the proposed algorithm are evaluated through the measurements of a microresonator and two standard step heights. In the measurement of the 44-nm standard step height, no overshoot shows up on or close to the edge of the sample. At last, three different methods include: white light phase shifting interferometry, phase shifting interferometry and white light interferometry are employed to make a comparison on the measurement precision. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3577694]