Method and device for measuring OCD (optical critical dimension)

Abstract

The invention discloses a method and device for improving the matching reliability and measurement precision of a spectrum curve in OCD measurement equipment. The method comprises the steps: carrying out the sensitivity analysis of theoretical spectrums of all to-be-measured structure parameters at full-wavelength points, and obtaining the sensitivity wavelength distribution; carrying out the normalization processing of the sensitivity wavelength distribution of all to-be-measured structure parameters; flexibly configuring a normalized weighting coefficient, and carrying out the normalized processing of the sensitivity wavelength distribution after normalization; setting a matching weighting coefficient in the matching process of a theoretical spectrum and a measurement spectrum, and carrying out the estimation optimization operation of the theoretical spectrum and the measurement spectrum, so as to judge the matching degree of the theoretical spectrum and the measurement spectrum. Therefore, the method achieves the optimized design of matching estimation, and achieves the improvement of the fitting value precision of the to-be-measured structure parameters.

Description

Technical field [0001] The invention relates to the measurement of optical critical dimensions of a semiconductor manufacturing process, and more specifically, to a measurement method for improving the reliability of spectral curve matching and measurement stability in optical critical dimension OCD (Optical Critical Dimension) measuring equipment. Background technique [0002] In the integrated circuit industry, with the shrinking of process nodes and the complexity and diversification of device structures, the manufacturing and production of very large-scale integrated circuits have higher and higher requirements for the accuracy and sensitivity of measuring equipment. As an important critical dimension measurement technology, OCD (Optical Critical Dimension) measurement technology has gradually occupied a dominant position in the production of logic devices and memory at 65nm and below process nodes. [0003] With the development of the semiconductor integrated circuit manufactu...

AI Technical Summary

Problems solved by technology

[0010] OCD measurement equipment includes many hardware system parameter designs. In the optical measurement process, engineers are striving to achieve high-precision control of the system parameters of each OCD measurement equipment, reducing hardware errors (such as the accuracy limit of moving parts and precision positioning subsystems) It causes deviation to the diffracted light signal collected in the measurement, but the ideal zero error cannot be realized, and the total spectral noise formed by system noise, uncertainty and random error is inevitable

The existence of noise leads to a decrease in the matching degree between the measured spectrum and the theoretical spectrum, and at the same time causes the fitting value of the measured structural parameters to deviate from the true value, and more importantly, affects the repeatability and accuracy of industrial measurement

[0011] Due to different semiconductor manufacturing processes and changes in the structure of the device to be tested, it is generally difficult to consider the sensitivity difference of the spectral signal at each wavelength in the design process of the system parameters of the usual OCD measurement equipment

In the process of evaluating the matching between the measured spectrum and the theoretical spectrum, the weight of all wavelength points participating in the matching is used to adopt an indiscriminate matching method, which restricts the improvement of sensitivity, signal-to-noise ratio and accuracy of measurement results

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