Distortion mechanism of patterning positions in the soft roller printing process for realizing large-area overlay printing

Soft roller printing techniques such as rolling mask soft lithography and offset printing are prominent as high-resolution, high-throughput patterning technologies. The overlay accuracy of soft roller printing becomes critical in large-area fabrications since many factors causing overlay errors tend to be proportional to the patterning area. In this study, the mechanism of overlay distortion was investigated in the soft roller printing process using both lab testing and finite element simulations. The overlay distortion is closely related to the deformation of PDMS in soft roller printing and it is key to investigate how PDMS is deformed under various disturbances from equipment and process. Two kinds of major disturbances, 'nip motion error' and 'roundness error', are defined and their effect on the overlay distortion is discussed. The methodology to improve overlay accuracy in the soft roller printing process is also presented and verified. For the nip motion error, the compensation method, in which the nip motion error is modeled based on the previous printed position errors and the modeled error is compensated by the alignment stage, are proposed. It is proven that high compressibility of cushioning can help to relieve the position errors caused by roundness errors by reducing the deformation of PDMS. Finally, printing position errors can be reduced to the level of a few micrometers when the overlay distortion mechanisms investigated in this study are well controlled.