Calibration method of ellipsometer

Abstract

The invention discloses a calibration method of a polarization angle and a light incidence angle of an ellipsometer in an ellipse polarization measuring system and belongs to the technical field of optical measuring devices. The calibration method includes fitting by a least square method according to the Fourier coefficient and referring to a relation expression of an optical coefficient of a sample and work parameters of the ellipsometer to acquire calibration values of the work parameters of the ellipsometer. System parameters including polarization directions of a polarizer and an analyzer and the light incidence angle in the ellipsometer can be calibrated by the method, calibration process is simple and accurate, measurement can be achieved directly without adjusting parts of a system after calibration, and accordingly the measurement process is simplified, and precision in measurement is increased.

Description

technical field [0001] The invention relates to the technical field of optical measuring instruments, in particular to a method for calibrating the polarization angle and light incident angle of an ellipsometer in an ellipsometer system. Background technique [0002] With the rapid development of the semiconductor industry, it is very important to use optical measurement technology to accurately measure the critical dimensions, spatial morphology and material properties of the three-dimensional structure formed by single-layer or multi-layer thin films on the wafer. In order to make the measurement results effective, the measurement used The system should be able to measure film thickness and / or film composition with high accuracy. The ellipsometry method used in the prior art obtains the characteristic parameters of the reference sample by measuring the polarization of the light reflected by the reference sample. Since the ellipsometry method has the advantages of high sens...

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Problems solved by technology

In this calibration method, not only the analyzer needs to be rotated, but also the polarizer P needs to be rotated electrically or manually. When the polarization direction of the polarizer is determined, the angle of the polarizer needs to be adjusted manually or electrically. In this case, Due to the instability of the mechanical structure and / or the error of human operation, there will be an error between the actual angle and the angle that needs to be set, which will easily lead to the inaccuracy of the reference sample measurement

Therefore, when using this method, the angular calibration accuracy of the polarizer is relatively low, which limits the measurement accuracy of the ellipsometer

[0007] The incident angle of light in the ellipsometer can be obtained by manual measurement, but due to the limited accuracy of manual measurement, and some measurements need to measure the reference sample at different incident angles to obtain more information about the reference sample, manual measurement is easy Due to human adjustment errors or reading errors, the results of data analysis are wrong. The application number is 201010137774, which discloses a device for automatic detection of incident angles in ellipsometry systems. The device can realize automatic detection of incident angles, but the device requires Multiple position detection devices are installed in the system, which makes the system structure of the device complex, and the calibration of the position detection device itself is a relatively complicated process, which also limits the application of the automatic detection device in the ellipsometer

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