Real‐Time Metrology for Roll‐To‐Roll and Advanced Inline Manufacturing: A Review

Abstract

Roll‐to‐Roll (R2R) manufacturing is changing how state‐of‐the‐art technology is made. Roll‐to‐Roll is part of a family of advanced scalable inline manufacturing techniques that make traditional and state‐of‐the‐art products at high yield and reduced cost. R2R manufacturing has grown rapidly and is fundamental to several advanced technologies such as functional materials and films, sensors for medicine, biology, and environment monitoring, energy harvesting devices, and flexible electronics. Advantages of R2R manufacturing include ease of machine design, adaptability to a wide range of additive processing methods, and very high throughput. To keep up with advances in R2R manufacturing, novel methods have emerged to measure important product metrics (thickness, roughness, conductivity) and monitor quality (uniformity, defects) inline and in real‐time. This review provides an overview of the state‐of‐the‐art for real‐time inline metrology and quality control in modern R2R manufacturing. The survey considers both established inline metrology techniques such as line‐scan imaging and reflectometry, and techniques recently adapted or that show promise for real‐time inline R2R metrology such as ellipsometry, hyper‐spectral imaging, and Raman spectroscopy.

Recent Progress in Printed Photonic Devices: A Brief Review of Materials, Devices, and Applications

“…A continuous R2R production can be evolved by additive processes, printing, and self-assembly [ 117 ]. New quality control and metrology forms are needed to store, monitor, and analyze real-time production data [ 118 ]. Process drift can be corrected in real time using artificial intelligence and other deep-learning techniques [ 119 ].…”

“…Future inline metrology will increasingly incorporate techniques derived from big data analysis. They provide instant morphology for a wide variety of materials and products, with a spatial resolution on the order of 10 μm and requiring minimal calibration [ 118 ]. It has been reported that eddy current sensors are the best choice for noncontact inline R2R electrode quality monitoring [ 120 ].…”

“…For lab-scale inline R2R measurement, spectroscopic ellipsometry, hyperspectral single point, imaging reflectometry, and Raman spectroscopy are being developed. Polarimetry, digital holography microscopy, and optical coherence tomography are promising methods for inline R2R metrology [ 118 ].…”