Abstract
A new technique is proposed for measuring film structure based on the combination of time- and frequency-domain fitting and white-light scanning interferometry. The approach requires only single scanning and employs a fitting method to obtain the film thickness and the upper surface height in the frequency and time domains, respectively. The cross-correlation function is applied to obtain the initial value of the upper surface height, thereby making the fitting process more accurate. Standard films (SiO2) with different thicknesses were measured to verify the accuracy and reliability of the proposed method, and the three-dimensional topographies of the upper and lower surfaces of the films were reconstructed.
Highlights
Measurement of Film Structure UsingFabrication processes in the semiconductor and display industries invariably involve continuous deposition and etching to integrate thin films on silicon substrates or transparent glass, and measuring the film thickness and topography is essential for increasing yields and monitoring product quality
The film thickness and height can be estimated from the phase information of a white-light spectral interferometer (WSI) [8,9,10], but WSIs cannot be applied to full-field measurement and have low lateral resolution
The time domain here is the domain of the original vertical scanning interferometers (VSIs) signal, and the frequency domain is the domain of the VSI signal after Fourier transform
Summary
Fabrication processes in the semiconductor and display industries invariably involve continuous deposition and etching to integrate thin films on silicon substrates or transparent glass, and measuring the film thickness and topography is essential for increasing yields and monitoring product quality. De Groot and de Lega proposed a VSI signal model [17], and several researchers have used it to obtain the film reflectivity and thickness from Fourier-transform information [18,19,20] In those methods, the tested sample is compared with a reference sample to solve the film-thickness issue, but such approaches usually require the tested and reference samples to be scanned separately and the light-source intensity and experimental parameters to remain consistent in the two measurements, thereby setting higher requirements for the experimental equipment and operation [21,22,23,24]. Topographies of the upper and lowerPrinciple surfaces of the film are reconstructed
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