Device and method for measuring thickness and refractive index of thin film

Abstract

The invention provides a device and a method for measuring the thickness and the refractive index of a thin film, and belongs to the field of optical measurement. The device comprises a low-coherence light source, a light splitting assembly, a reflecting mirror, a sample groove, a spectrograph and a signal processing unit. Light emitted from the low-coherence light source enters the light splitting assembly, and the light is split into reference light and sample light through the light splitting assembly. The reference light irradiates on the reflecting mirror; sample light enters the sample groove perpendicular to the side face of the sample groove. The reference light reflected by the reflecting mirror and the sample light reflected by the sample groove and the sample to be detected are reflected into the light splitting assembly and are output into the spectrograph. The method comprises: demodulating by combining the frequency and phase of Fourier transform, respectively measuring the optical path after the sample groove is vacant and after the sample is placed, and pouring a liquid with known refractive index into the sample groove for measuring the optical path for the thin film. The measuring method based on phase-sensitive optical coherence tomography has the advantages of nanoscale precision, simplicity in operation and applicability to films in various states.

Description

technical field [0001] The invention relates to the technical field of optical measurement, in particular to a device and method for measuring the thickness and refractive index of a thin film. Background technique [0002] The thickness and refractive index of thin films are important parameters that determine their properties. Accurately measuring the refractive index and thickness of thin films is of great significance in the preparation and application of thin films. The current thin film measurement methods are mainly divided into two categories, non-optical methods and optical methods. Non-optical methods can usually only measure the thickness of the thin film, but cannot obtain the refractive index of the thin film. Optical methods have the advantages of high precision and non-contact, and can measure the thickness and refractive index of thin films without destroying the sample. The current optical methods involving film thickness and refractive index include: prism...

AI Technical Summary

Problems solved by technology

Since the Fourier transform is directly used to process the interference signal, the resolution of this method is limited by the Fourier transform resolution (micron level), so the thickness measurement accuracy is low, which in turn leads to low refractive index measurement accuracy;

For samples with unknown refractive index, this measurement method needs to determine the tilt angle of the film sample, which is difficult to operate, especially for soft or easily deformable films, it is very difficult to accurately determine the film angle, and the error is large

[0006]The current non-optical measurement method of film thickness cannot measure the thickness and refractive index of the film at the same time, but there are many optical methods that can measure the thickness and refractive index of the film at the same time Problems, such as high requirements on the state of the film, difficult operation, or low measurement accuracy

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