Laser phase-shifting interference triangulation micro-displacement measuring device and method

Abstract

The invention relates to a laser phase-shift interference triangular micro displacement measuring device and method, belongs to the technical field of ultra-precise measurement, and aims at realizinglarge-range high-precision micro displacement measurement by combining phase shift interference with laser triangle technologies. The device mainly comprises a Ronchi grating light splitting based synchronous phase shift interference subsystem and a laser triangular displacement measuring subsystem. According to principles of phase shift interference and laser triangular range finding, four pathsof interference signals between which the phase shift is 90 degree are obtained synchronously by grating light splitting and a four-quadrant polarization analyzer group, the laser triangular subsystemuses part of diffuse reflection light to obtain coarse measurement data of displacement, and when a laser triangular measuring error is lower than 1 / 4 of the interference displacement signal period,an accurate displacement value can be obtained by certain resolution. The device and method are high in measuring precision and anti-interference capability and large in measuring range, and suitablefor measuring the step height, film thickness and displacement of movement parts in micro-structure devices.

Description

technical field [0001] The invention relates to a laser phase-shifting interference triangular micro-displacement measuring device and method, which belongs to the field of ultra-precision measurement, and mainly relates to the application of ultra-precision non-contact measurement of geometric characteristic dimensions of microstructure devices. Background technique [0002] With the continuous development of processing and manufacturing technology, the demand for micro-displacement non-contact sensors with high precision and large range continues to increase. For example, in lithography technology, various geometric parameters in silicon wafer etching are important factors affecting device quality and yield, measurement and verification of line width, spacing, step height, film thickness, etc. in chips and masks, and The unification and traceability of these geometric dimensions have become particularly important in the processing and manufacturing of integrated circuits. ...

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Problems solved by technology

However, the system requires a precise piezoelectric ceramic displacement device to complete high-resolution and large-range measurement, which greatly limits its application range.

[0005] The document "A Method of Improving the Measurement Accuracy of Step Height Using Optical Frequency Comb" (Acta Physica Sinica, 2012) proposes a method based on the principle of synthetic wavelength ranging, using an optical frequency comb and a tunable semiconductor laser to improve the measurement accuracy of step height. The method has a large measurement range and high measurement accuracy, but the system has a complex structure and is easily affected by ambient temperature, vibration, etc.

[0006] The patent "Pupil-Split Phase-shifting Interferometric Differential Confocal Micro-displacement Measuring Device" (CN201610317208.5) proposes to integrate phase-shifting interferometry and confocal differential detection in the same optical path, which can realize micro-displacement measurement in a large measurement range. However, due to the limitation of the numerical aperture of the microscope objective lens, the working distance of this method is relatively short, and the expansion of the measurement range also has certain limitations.

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