Measurement of thin film thickness using diffraction Lloyd mirror interferometer

Monika Rani; Raj Kumar

doi:10.1117/12.2669806

11 May 2023 Measurement of thin film thickness using diffraction Lloyd mirror interferometer

Monika Rani, Raj Kumar

Proceedings Volume 12638, Women in Optics and Photonics in India 2022; 126380A (2023) https://doi.org/10.1117/12.2669806
Event: Women in Optics and Photonics in India, 2022, Bangalore, India

Conference Poster

Abstract

Thin films are used in many applications including holography, integrated optical circuits, polarizers, low-pass filters, beam splitters, and antireflection coatings. Refractive index and thickness of thin films are important parameters to understand its optical characteristics. In this work, thickness of thin film is measured by diffraction Lloyd mirror interferometer (DLMI). This interferometer works on the principle of superimposing two diffracted waves and direct geometric waves to generate the interference pattern. In comparison to the conventional Lloyd mirror interferometer, the interference pattern obtained by proposed interferometer covers a large area due to the presence of diffracted light in almost 4π region. The main idea of this work is to check the feasibility of DLMI to measure the thickness of films in single step. Three different test samples containing different step heights are used as a Lloyd mirror. The fringe patterns obtained from intereference of direct diffracted wavefront and reflected wavefront from samples are recorded using CMOS sensor. Recorded fringe patterns were further processed to extract phase by the application of Fourier transform. The 3D and 2D line profile of retrieved phase information are utilized to find the thickness of the film. The measured values of the thin film thickness by DLMI are compared with that of a standard mechanical profilometer. The experimental findings verify the usefulness of the proposed method.

Citation Download Citation

Monika Rani and Raj Kumar "Measurement of thin film thickness using diffraction Lloyd mirror interferometer", Proc. SPIE 12638, Women in Optics and Photonics in India 2022, 126380A (11 May 2023); https://doi.org/10.1117/12.2669806

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