Thin-film thickness profile and its refractive index measurements by dispersive white-light interferometry

Abstract

As an extension of the authors' previous report of Ref 1, we describe an improved version of dispersive white-light interferometry that enables us to measure the tomographical thickness profile of a thin-film layer through Fourier-transform analysis of spectrally-resolved interference signals. The group refractive index can also be determined without prior knowledge of the geometrical thickness of the film layer. Owing to fast measurement speed with no need of mechanical depth scanning, the proposed method is well suited for in-line 3-D inspection of dielectric thin film layers particularly for the semiconductor and flat-panel display industry.

White-light spectral interferometric technique to measure a nonlinear phase function of a thin-film structure

“…The method, which is much simpler compared to the techniques such as [7,8], is based on processing of the recorded channeled spectra to extract phase functions in two steps. One step is with a sample under study and the other step is with a reference sample of known phase change on reflection.…”

“…The use of white-light interferometry was extended into the spectral domain [6][7][8][9] where the phase of the reflected wave, which changes as a function of wavelength [10] and layer thickness, is inscribed in the recorded spectral interferogram (channeled spectrum). Some of the techniques [7,8] that are based on Fourier transforming of the channeled spectra enable a complete 3D tomographical reconstruction of a thinfilm layer. This reconstruction is possible using the retrieved time delays [7] or the spectrally resolved phases and reflectances [8].…”

“…Some of the techniques [7,8] that are based on Fourier transforming of the channeled spectra enable a complete 3D tomographical reconstruction of a thinfilm layer. This reconstruction is possible using the retrieved time delays [7] or the spectrally resolved phases and reflectances [8].…”

Determining the Thickness of a Trilayer Thin-Film Structure by Fourier-Transform Analysis

“…그러나 최근 박막의 기능이 다양하게 증가하 면서 다층박막의 두께를 결정하고자 하는 요구가 점차 증가 하고 있다. 다층박막의 두께를 측정하는 방법은 분광 타원분 광계(Spectroscopic Ellipsometer)를 사용하여 측정된 결과를 맞춤하는 방법 [4] , 분광광도계를 사용하여 측정한 결과를 역 설계 (reverse engineering) 기법으로 두께를 추정하는 방법 [5] , 그리고 백색광 간섭계를 사용하는 방법 [6,7] 등이 있다. 김상 열 [8] 은 …”

Absolute distance measurement method without a non-measurable range and directional ambiguity based on the spectral-domain interferometer using the optical comb of the femtosecond pulse laser

“…Spectral-domain interferometers (SDIs) have been utilized widely for 3D surface profile measurements because they can offer high measurement precision and speed without phase ambiguity. [1][2][3][4][5][6][7][8][9][10] For the practical realization of SDIs, incoherent wide-spectral light sources such as white-light lamps, light-emitting diodes, and superluminescent diodes have generally been used to produce spectrally resolved interference fringes. However, due to the short coherence length caused by their wide bandwidths, the working range of conventional SDIs is limited up to several mm.…”