Design of a precision multi-layer roll-to-roll printing system

Abstract

Roll-to-roll (R2R) printing technologies have been widely adopted in a variety of engineering fields, e.g., organic photovoltaics and flexible electronics, owing to the advantages of cost and throughput. Although a minimum feature size of 100 nm has been demonstrated on R2R systems, the layer to layer registration accuracy (i.e., overlay accuracy) still remains as low as tens of microns, which prevents the fabrication of common electronic and functional devices, such as transistors. To realize the full potential of R2R technologies, the registration accuracy must be improved to match the printing resolution, i.e., 100s nm. To address the issue, we have developed a multi-layer R2R system with multiple-input multiple-output (MIMO) closed-loop control that achieves submicron level alignment precision for large-scale continuous printing processes. The enabling elements in the multi-layer R2R system include: (1) new vision-based alignment algorithm/method, which provides 100s nm position detection capability based on low-cost cameras; and (2) custom-built five-axis compliant roller positioner. Experimental results show that the compliant roller positioner has a ±1 mm range with 100s nm precision in X, Y, and Z axes respectively. For correcting in-plane web errors, the roller positioner can achieve a range of 1 mm with < 1 μm precision, realizing multi-layer R2R printing with submicron overlay accuracy. Based on the new methods, a gate/source-drain multi-layer electrode structure for field-effect transistors (FETs) has been designed and fabricated on a 4-inch PET web, demonstrating better than 1 μm overlay precision in fabricating flexible electronics on a R2R platform for the first time.