Large-scale overlay: a study into accuracies in roll-to-plate nanoimprint lithography

Abstract

Roll-to-Plate (R2P) nanoimprint lithography (NIL) is a fabrication process with the potential for low-cost high-volume fabrication of micro- and nano-patterns on large areas. As a result, R2P is regarded as a promising production process for micro- and nano-scale features which exceed the conventional wafer sizes. In addition, the process has the potential to scale up the production of wafer based textures at a low costs, which would make the implementation of nano-features in products more accessible. To compete with alternative fabrication techniques, R2P NIL must meet requirements set by the industry for position accuracy and system repeatability. In this thesis, a study is performed on the positioning of micron- and nano-sized features in a two-dimensional plane in collaboration with Morphotonics, a company based in Veldhoven the Netherlands. The metrology of overlay from the semi-conductor industry is applied to NIL, to quantify the relative displacement and deformations of a given nano-pattern. Experimental results, obtained in a preliminary phase of the project, characterized the current overlay performance of machines available at Morphotonics. From the test results, a positioning error of the complete nano-pattern was found, in combination with a complex deformation which affected the relative distance of the imprinted features. Based on the characterization of overlay in R2P NIL, an interest in deformations of the flexible mould is developed. Concepts from roll-to-roll (R2R) production processes are used, to quantify the deformations observed in experiments. In R2R processes, deformation of a thin elastic material (web) is quantified by applying a beam model to the web. Using the beam model, the deformation of a web segment, constrained by two rollers, could be quantified in both quasi-static and dynamic conditions. The models based on literature of lateral web dynamics, combined with experimental results obtained at Morphotonics, have given insight in the behaviour of the elastic mould during the imprint process. The models describe the transverse motion of the web on a roller surface and the deformation of the web in between two consecutive rollers in a dynamic system. Verification of the model was performed on the machines of Morphotonics. The transverse motion of the elastic mould over the rollers was clearly observed in the measurement, including a repeatable deformation pattern of the imprints as a result of a forced disturbance exposed to the system. Both of which, were expected to be observed based on the modelled expectations. Nevertheless, the exact error magnitude did not meet the expectations and only a rough relation between model and experimental results was found. In spite of the verification results not perfectly matching the model, the theory applied in this thesis has given insight in the behaviour of elastic materials in roller based transport. From the observations and gathered knowledge of this thesis, the performance of overlay in large scale roll-to-plate nanoimprint lithography has been characterized and considerations for future imprint modules have been made.