Fitting error interpolation based library matching method for optical scattering measurement

Abstract

The invention discloses a fitting error interpolation based library matching method for optical scattering measurement. The method comprises the following steps of: determining the variation range of to-be-measured structure parameters of a sample and carrying out discretization treatment on the variation range of the to-be-measured structure parameters of the sample, and storing obtained discretization gridding points and theory spectrum value corresponding to the discretization gridding points into a spectrum library; acquiring a measurement spectrum of the to-be-measured sample, calculating fitting errors between the measurement spectrum value corresponding to the discretization gridding points and the theory spectrum value, and then storing the fitting errors similarly to the spectrum library; setting threshold for the fitting errors and carrying out rough searching, constructing a candidate parameter set by utilizing the discretization gridding points corresponding to the searched fitting errors, and carrying out multidirectional interpolation treatment on the fitting errors, thereby obtaining a corresponding fitting error interpolation function; and carrying out fine searching and finding out the overall optimal point based on the fitting error interpolation function, wherein the parameter value corresponding to the overall optimal point is the finally determined optimal parameter. According to the invention, the measurement resolution and accuracy of the library matching process can be improved, and the fitting error interpolation based library matching method for optical scattering measurement has the advantage of being rapid and convenient in operation.

Description

technical field [0001] The invention belongs to the technical field of optical measurement, and more particularly relates to a library matching method based on fitting error interpolation for optical scattering measurement. Background technique [0002] The optical scattering measurement method (optical scatterometry), also known as the optical critical dimension measurement (optical critical dimension metrology) method, its basic principle is to project a beam of polarized light with a special polarization state onto the surface of the sample to be tested, and measure the surface of the sample to be tested. Zero-order diffracted light, thus obtaining the reflected light intensity under different polarization states or the change of the polarization state of polarized light before and after reflection, and then extracting the structural parameters of the sample to be tested, such as photolithography, etching and nanoimprinting patterns Line width, line height, side wall angl...

AI Technical Summary

Problems solved by technology

However, in this method, in order to obtain a complete spectral curve, it is necessary to interpolate each wavelength one by one for the wavelength-resolved spectral signal, and to interpolate each angle one by one for the angle-resolved spectral signal; in particular, If the output form of the spectral signal is a Stokes vector or a Mueller matrix, each element in the vector or matrix needs to be interpolated one by one. Therefore, the interpolation process of this method is very complicated, which makes the operation of the actual measurement process inconvenient.

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