Characterization of thin-film thickness

Abstract

Analysis methods and instrumentation for obtaining optical parameters and thickness profiles of thin-film samples from spectrophotometric and ellipsometric measurements are presented. Measured samples include thermally grown and evaporated SiO2 on a silicon substrate and a polymer photoresist layer on silicon. Experimental results at multiple sample positions give the thickness uniformity and optical constants of thin films. The thickness results obtained with spectrophotometry and ellipsometry agree within 1 nm for the 300 nm thick layer of SiO2 on silicon. For the 1600 nm thick resist sample the agreement of the measurement methods is within 8 nm. For the sample with a nominally 6000 nm thick layer of SiO2 on silicon, there is a deviation of ∼100 nm between the spectrophotometry and ellipsometry results. As an application, the optical parameters of a SiO2 layer on an induced junction silicon photodiode are determined by spectrophotometry and are used to confirm earlier values and uncertainties of the SiO2 refractive index and layer thickness non-uniformity.

Sub-400 nm film thickness determination from transmission spectra in organic distributed feedback lasers fabrication

“…One of the advantages of ellipsometry is that it is sensitive even for films of a few nanometers [7,8]. Spectrophotometry, even though has lower accuracy and is limited to thicker films, is cost-effective, and the analysis is simpler and requires less time [9]. In this paper we propose a simple method for determining filmthickness in the fabrication of DFB lasers.…”

Full-field film thickness measurement method based on reflection spectrum using AOTF

“…the source intensity is distributed over the film surface, and it can be seen that the distribution is non-uniformity. In equation (7), silicon wafer corresponds to the position point of the film in the image one by one during calculation, which can eliminate the influence of non-uniformity light intensity on the film surface. After the measurement, the reflection spectrum at each point of the film needs to be reconstructed, and the specific calculation procedure is shown in Figure 3.…”

“…In addition, there is a method to calculate the thickness from the diffuse reflectance spectroscopy of the sample [5]. Ellipsometry uses variations in the polarization state of linearly polarized light reflected from the sample surface to measure different thicknesses [6,7], which is necessary to develop theoretical mathematical models to obtain sample thickness information. Spectroscopic ellipsometry can extract multiple valid parameters and produce more reliable results [8].…”

Simultaneous Determination of Refractive Index and Thickness of Submicron Optical Polymer Films from Transmission Spectra

“…Ellipsometry is useful when high precision is required (four decimal places in n and accuracy within less than 1 nm in h ), even when dealing with films of a few nanometers [ 5 ]. Spectrophotometry has lower accuracy, but it is cost-effective and the analysis is simpler and requires less time [ 6 ].…”