Key Technologies On Microscopic Interferometry For Micro-Nano Structure Profilometry Measurement

Microscopic Interferometry technique is a profilometry measurement technology for micro-nano structure surface profile and has been employed widely in the static and dynamic measurement of Micro-electronics and Micro Electronic Mechanic System for its non-contact, fast speed and high accuracy. By studying the interferometry and micro-vision principle, this dissertation discuss the model and interference processing algorithm of Phase Shift Interferometry (PSI) and Vertical Scanning Interferometry (VSI) which are the main techniques of the microscopic interferometry technique, and developed a new VSI interference processing algorithm, Phase Envelop algorithm. On the basis of previous Stroboscopic Interferometry and Micro-vision System, some key technologies of microscopic interferometry technique are realized.The model of light interferometry was deduced from the Michelson interference model, and the equation of light interference intensity function, envelop function and phase function was confirmed, from which the PSI model and VSI model were infered. On the basis of these studies, the Phase Envelop algorithm was presented, which extract the position of zero optical path difference of light interference intensity function from the phase and envelop values of sample points, which could be calculated by Whittaker reconstructed technique of sampling theory based on the spectrum of light interference intensity function and its Hilbert transform function. The outcome of computer simulation verified that the Phase Envelop algorithm has a high precision in the measurement.On the basis of the Stroboscopic Interferometry and Micro-vision system a profilometer system was developed for micro-nano structure profile testing which could operate in either PSI mode or VSI mode. The light source is a broadband LED which could switch to a narrowband light source by a filter to satisfy both interferometry mode. A Linnik interferometer was adopted in this profilometer, in which the scanner and the phase shifter were integrated through scanning the reference mirror. The VSI software module was added in the Stroboscopic Interferometry and Micro-vision System software and could process sampling interference intensity data by Phase-Shifting algorithm, SEST algorithm, Spatial Frequency Domain algorithm and Phase Envelop algorithm, and an effective file format was proposed to store the three-dimensional surface profile data.The error mechanism of Linnik Interferometer in PSI measurement was studied by analyzing the error phenomena in the PSI measurement of the Stroboscopic Interferometry and Micro-vision System in which a measure error approximated to a conicoid was discovered. On the basis of PSI error mechanism study, the phase-shift error, camera error and optical wave matching error models were presented and some experiments were projected in which the plane was selected as the sample. The outcome of these experiments verified that the optical wave matching error was the main error source and the conicoid error was mainly caused by the focus axial matching error of the objectives in Linnik Interferometer. So the standard plane measurement could be used to compensate the outcome of PSI measurement.The standard step height of VEECO Corp. was measured by this system which employed two LED light source, and the experimental results which were processed by different VSI algorithm described above, were compared and analyzed. The error of Spatial Frequency Domain algorithm and Phase Envelop algorithm in the measurement were studied based on the analysis of phase spectum error and Phase Envelop algorithm was modifyed by two peak sum character.