Common-path tandem interferometer for thin-film thickness measurements

Abstract

Conventional optical interferometers utilized for gauging thin-film thickness can offer non-contact, high-resolution, and full-field measurements but have to endure the noise caused by environmental perturbations. Possessing not only the superior performance of conventional interferometers but also the advantages of high measurement repeatability and high tolerance to environmental disturbances, a common-path tandem interferometer was proposed. In this paper, the interferometer’s measurement theory and experimental setup are demonstrated, and the experimental results from the uses of the experimental setup are then presented and discussed. The experimental results validate the interferometer and show a measurement repeatability of up to 3 nm, curve fitting inaccuracy is one reason causing the measurement error; in addition, the results agree with the interferometer’s high resistance to environmental perturbations.