In this paper, a submicron linewidth measurement method based on computer microscopic imaging technology to improve the measuring precision is proposed. Firstly, the microscopic image of the standard line pair is taken at the magnification M, and the pixel representing distance (PRD) of the microscopic image is calibrated. Secondly, the noise of the image is eliminated by the median filtering technology, and then the minimum ambiguity criterion of direction information measurement is used to quickly identify the edge boundary points of linewidth. Then, the edge points of the linewidth are fitted and filled to form a regular geometry shape, which can be accurately located by using the cascaded Hough transform algorithm. Finally, in order to verify the validity of the method, several representative linewidths are selected on the standard sample plate to repeat the measurement nine times, the experimental results show that for line width greater than 2 μ m, the error of measuring linewidth with the method studied in this paper is less than 0.1 μ m. Therefore, this method reveals the possibility of high-precision measurement of linewidth through microscopic images, and makes it be a much better option to be employed for further micro-nano structures analysis applications.
In order to obtain high precision optical constants at in the ellipsometry measurement process, an optimization algorithm for solving the complex refractive index of nano films at visible wavelength is proposed. To improve the convergence rate and the ability to escape from local optimum of original algorithm, an Improved Particle Swarm Optimization (IPSO) has been proposed to deal with and analyze the ellipsometry parameters, this method combines the evolutionary algebraic attenuation factor with the adaptive genetic algorithm. The algorithm is used to calculate the film parameters of silicon dioxide nano film thickness standard template with standard value of 100.4±0.3 nm in this paper. The results show that the relative error of the calculation results of the optical constants refractive index error is less than 0.1 at visible wavelength. At the same time, it is verified by experiments that the IPSO algorithm model can effectively optimize the number of iterations and has the advantages of fast convergence speed and high measurement efficiency.
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