Common-path self-calibration film thickness measuring device and measuring method based on polarization multiplexing

Abstract

The invention provides a common-path self-calibration film thickness measuring device and a measuring method based on polarization multiplexing. The measuring device includes a light source output module, a film thickness measuring probe module, a demodulation interferometer module, a polarization beam splitter module, and an acquisition and control module. The polarization multiplexing technology is used in the invention, and two probes use orthogonal polarized light. The measuring probes can transmit and reflect transferred light. When there is no film to be measured, the absolute distance H between the two probes can be measured. When a film to be measured is placed between the two probes, the absolute distances H1 and H2 between the two probes and the front and back surfaces of the film to be measured can be measured. The thickness d of the film to be measured is determined according to the formula d=H-(H1+H2). The thickness of a film to be measured can be measured without a calibration object. Through a common-path design, the influence of the mechanical instability inside the system and the change in external environment on the measurement process is overcome. The measuring device and the measuring method have the advantages of self-calibration, simple feature white light interference peak identification, large dynamic range, traceable measurement result, and the like.

Description

technical field [0001] The invention relates to an optical measuring device, in particular to a film thickness measuring device. Specifically, it is a polarization multiplexing common optical path self-calibration film thickness measuring device. Background technique [0002] With the vigorous development of material science and technology, in order to meet the urgent needs of microelectronics, optoelectronics, new energy and other fields, thin films are used in optical engineering, mechanical engineering, communication engineering, biological engineering, aerospace engineering, chemical engineering, medical engineering and other fields. widely used. One of the core and key parameters of thin film materials is thickness, which not only plays a key role in the preparation of thin films, but also basically determines the mechanical, electromagnetic, photoelectric and optical properties of thin films. [0003] In 1961, N. Schwartz and others proposed a contact probe method th...

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Problems solved by technology

[0004] In 2013, Ma Xizhi and others from Nanjing University of Aeronautics and Astronautics disclosed an ultrasonic film thickness measuring instrument and its measurement method (Chinese patent application number: 201310198294.9). Measure the correlation characteristics of the reflected pulse to measure the thickness of the oil film; however, this method is only suitable for the measurement of the liquid mode, and different models need to be established for films with different thickness ranges, and the demodulation is difficult

In 2014, Jia Chuanwu of Shandong University and others disclosed a system for measuring film thickness by wide-spectrum optical interferometry (Chinese patent application number: 201410290494.1). Luo interferometer, by measuring the Fabry-Perot cavity length before and after placing the film under the mirror, the thickness of the film to be tested can be obtained. This method has a simple structure and high measurement accuracy, but due to the need to The film is placed under the mirror, which is easy to damage the morphology of the film surface

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