Abstract
Currently, phase-shifting interferometry is widely used in MEMS (micro-electro-mechanical system) microsurface topography measurements, and an expensive and high-precision piezoelectric transducer (PZT) is often necessary to realize phase-shift operation. Because of the feature of a MEMS structure which always has a flat substrate, a practical algorithm to calculate phase shifts by fast Fourier transformation (FFT) from gathered interference fringes of the substrate is presented, then microsurface topography can be reconstructed according to the obtained phase shifts. By means of the presented algorithm, an expensive and high-precision PZT is unnecessary and the phase-shift operation can even be carried out by rotating the fine focus adjustment knob. The accuracy and feasibility of the method have been verified by experiments. Experiments indicated that the presented method can satisfy the needs of in situ MEMS topography measurements and is very simple.
Highlights
With the development of micro fabrication technology, accurate and simple three-dimensional MEMS surface topography metrology is becoming an urgent necessity.[1]
On the assumption that only linear error exists in a phase shifter, a self-calibration algorithm was suggested by Carré[4] and developed by Morgan[17] and others
In this paper, based on the feature of MEMS structure which always has a plane substrate, a practical algorithm to calculate phase shifts from the gathered interference fringes of the substrate is presented, microsurface topography can be reconstructed according to the obtained phase shifts
Summary
With the development of micro fabrication technology, accurate and simple three-dimensional MEMS surface topography metrology is becoming an urgent necessity.[1] Because of the advantages of noncontact and high-precision, optical metrology[2,3] has been widely applied in microsurface topography measurements such as phase-shifting interferometry(PSI),[4,5,6,7,8] white light interferometry,[9,10] heterodyne interferometry,[11,12] phase-locked interferometry,[13] and holography.[14,15] Among these, PSI plays a very important role. By means of the presented algorithm, an expensive and high-precision phase shifter is unnecessary and the phase-shift operation can even be carried out by rotating the fine focus adjustment knob. It is useful for in situ MEMS topography measurement
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