# Towards inline real-time characterization

# Towards in-line real-time characterization of roll-to-roll produced ZTO/Ag/ITO thin films by hyperspectral imaging

<p class="callout info">Please view the full paper via [https://do<span style="color: rgb(53, 152, 219);">i.org/</span>](https://doi.org/10.1088/1361-6463/acd8c9)<span style="caret-color: rgb(51, 51, 51); color: rgb(53, 152, 219); font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Noto Sans', Ubuntu, 'Droid Sans', 'Helvetica Neue', sans-serif; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; display: inline !important; float: none;">[10.1088/1361-6463/acd8c9](https://doi.org/10.1088/1361-6463/acd8c9) (open access)</span></p>

Large area manufacturing processes of thin films such as large-area vacuum roll-to-roll coating of dielectric and gas permeation barrier layers in industry require a precise control of e.g. film thickness, homogeneity, chemical compositions, crystallinity and surface roughness. In order to determine these properties in real time, hyperspectral imaging is a novel, cost-efficient, and fast tool as in-line technology for large-area quality control. We demonstrate the application of hyperspectral imaging to characterize the thickness of thin films of the multilayer system ZTO/Ag/ITO produced by roll-to-roll magnetron sputtering on 220 mm wide polyethylene terephthalate substrate. X-ray reflectivity measurements are used to determine the thickness gradients of roll-to-roll produced foils with sub nanometer accuracy that serve as ground truth data to train a machine learning model for the interpretation of the hyperspectral imaging spectra. Based on the model, the sub-layer thicknesses on the complete substrate foil area were predicted which demonstrates the capabilities of this approach for large-scale in-line real-time quality control for industrial applications.