Microstructure Surface Topography Measurement Methods Based On Color Images Of White Light Interference

Microstructure surface topography is a key aspect of micro-nano measuringresearch for it has an obvious influence on the performance and the quality of devices.White light interferometry, as a non-contact optical method, is widely used inmeasuring and calibrating microstructures ranging from nanometer scale tomicrometer scale for it has several advantages, such as high precision, non-damage,and high efficiency. A color CCD camera, rather than a black-and-white CCD camera,can be utilized to acquire white light interference images, which could obtain RGBchannels information. In this thesis, RGB phase-crossing method and RGBphase-shifting method were proposed respectively to accomplish surface topographymeasurement. The main achievements of this thesis are as follows.1. Firstly, the conventional methods of surface topography measurement werecompared and the state-of-the-art development related to white light interferometry byprocessing color images was described in detail. Then two methods were proposed byprocessing color images of white light interference.2. Secondly, RGB phase-crossing method was proposed to measuremicrostructure surface profiling. Based on acquired color interference images,wavelet transform method was employed to calculate phases of correspondingchannel in each scanning position. Then zero-optical-path-difference position wasaccurately determined via a constructed evaluation function and the least squaremethod. Besides, relevant simulations were performed to verify RGB phase-crossingmethod. Meanwhile, the results showed that the accuracy was higher via color imagesthan gray images in RGB phase-crossing method.3. Thirdly, RGB phase-shifting method was proposed to realize microstructuresurface topography measurement. This method could acquire different wavelengthinformation simultaneously by using a color CCD camera. The center wavelengths ofRGB channels were calculated by wavelet analysis and the phases of correspondingchannel were obtained by a certain phase-shifting algorithm with the least error. Thenthe algorithms of the effective wavelength method, the slope method and the fringeorder method were utilized to calculate surface topography. Furthermore, relevantsimulations were performed to compare the above-mentioned algorithms, and theresults showed that processing color images by the fringe order method could achieve high precise and high repeatable measurement.4. Finally, the white-light-interference measuring system was established, whichcontained an imaging section, a scanning section, an acquisition section and aprogram section. Besides, programs were written based on the proposed methods torealize image acquisition and processing. The proposed testing methods werevalidated by measuring a silicon wafer and a VLSI step height standard which wastraceable to NIST (The National Institute of Standards and Technology).