Key Technology And System Of White Light Interference Based Atomic Force Microscopy For Micro-nano Surface Measurement

With the development of advanced manufacturing technology,various surfaces with micro-nano scale and precision appear constantly,such as integrated circuit surface,optical surface,surface of information storage,etc.Micro-nano surface quality assurance and manufacturing process analysis depends on accurate measurement instruments for micro-nano surface morphology and structure measurement.At present,the observation of micro-nano surfaces is mainly conducted by scanning electron microscope(SEM),scanning tunneling microscope(STM)and atomic force microscope(AFM),which is unable to meet the requires of the micro-nano surface measurement.It is necessary to research and develop instrument with measuring significance for micro-nano surface morphology and structure measurement.This dissertation has studied the micro-nano surface measurement methods and key technologies of atomic force probe scanning based on white light interference.An atomic force probe scanning microscope based on white light interference is developed,which can realize traceable measurement for micro-nano surface.The main research contents are as follows:An accurate and robust zero-order fringe localization algorithm based on gradient compression and Hilbert transform is presented.Since the interference signal on the surface of the cantilever is distorted in the process of measurement,which leads to inapplicability of the common zero-order fringe location algorithms.The gradient compression algorithm is applied to eliminate the distortion of the interference signal and the Hilbert transform for phase solution is applied to obtain the position of zero-order fringe,which effectively guarantee the robustness and accuracy of zero-order fringe localization.The model of atomic force probe cantilever bending and the corresponding zero order fringe position of white light interference is established.A real-time traceable atomic force probe displacement calibration method based on this model and the displacement measurement of laser interference is proposed.The relation model of displacement of the probe,cantilever bending and zero order fringe positions of white light interference is established based on statics analysis of atomic force probe.The discrete calibration data of vertical displacements of the probe and the corresponding series of zero order fringe positions of white light interference are fitted based on this model.The traceable calibration curve between the zero order fringe position on the probe cantilever and vertical displacement of the probe is obtained for measurement.A rapid piezoelectric ceramic scanning method based on Bouc-Wen model to compensate the hysteresis is proposed.The Bouc-Wen model is used to fit the inverse hysteresis data obtained by scanning the piezoelectric ceramics beforehand.The parameters of the inverse hysteresis compensated Bouc-Wen model are obtained by genetic algorithm.By applying the model to the piezoelectric ceramic for open-loop feedforward control,it can realize accurate and rapid linearization scanning of the piezoelectric ceramic.An atomic force probe scanning dynamic model is established.A scanning measurement strategy for measured parameters optimization based on this model is presented to improve the stability of the measurement system.In order to avoid the atomic force probe tip separating from the sample surface in the process of scanning measurement and resulting measurement errors.By establishing the dynamic model of the probe in the process of scanning measurement and combining the typical surface contour model,the numerical simulation is conducted for analysis of the influence of the elastic coefficient of the probe,the equivalent mass and the preloading on critical scanning speed to realize the measured parameters optimization of scanning speed and preloading.An atomic force probe scanning instrument system based on white light interference is developed for micro-nano surface measurement based on the research results of the above key technologies.The accuracy,speediness and stability of the developed instrument are verified by series of experiments.The good characteristics of the developed instrument are proved by the testing of National Institute of Metrology and related applications.