| With the widely application of micro-nano device,the research on the micro-nano device detection technology becomes deep.Based on the optical theory,the non-contact measurement with the advantages of non-destruction,high speed and accuracy,is widely used in the surface topography measurement.The spectrally resolved whitelight interferometer obtaining the surface information with just one image has a great prospect in the on-line detection.Therefore,the model of a Michelson line-type whitelight spectral microscopic interferometer was put forward.Besides,the phase extraction algorithms and absolute distance calculation algorithms were discussed and the method of line-by-line spectral calibration was proposed to reduce the effect of distortion.Finally,the system was validated through the measurements of the step height and the thin film thickness.The main work of this paper is as follows:1.A Michelson line-type white-light spectral microscopic interferometer was developed and the software parts of image acquisition based on Lab VIEW and data processing based on MATLAB were completed.The system performances including the field of view,resolution and the noise level were tested.And the nanometer accuracy of the system was demonstrated by the absolute distance experiment.2.The effect of phase shift errors due to the scanner and the environment noise on different temporal phase-shifting methods were analyzed by simulation.Besides,temporal phase-shifting method and Fourier transform method were compared in terms of phase extraction accuracy and the surface calculation accuracy by simulation.The slope method and the single-wavelength method were compared in absolute distance calculation.Finally,the simulation analysis was demonstrated by the practical measurement.3.The simulation was done to analyze the influence of the wavenumber calibration and the wavelength calibration on measurement.And the sensitivity of the calibration coefficients for measurement was also discussed.The distortion degrees at different wavelengths and different optical path difference positions were discussed by simulation.Besides,the impact of distortion on measurement was analyzed.Compared with the single-point spectral calibration,the line-by-line calibration was proved to reduce the effect of the spectral distortion and improve the measurement accuracy by the experiment.4.The repeatability and the reproducibility experiments on the step height were carried out.And the surface topography result of the step by scanning was close to that of the white-light vertical scanning interferometer,which shows that the system can be applied in the nano-accuracy measurement for surface topography.The system also achieved the thin film thickness measurement with the nonlinear phase optimal fitting.And both the temporal phase-shifting method and Fourier transform method were applied and discussed in the thin film measurement. |
