Robert L. Cobene

Advances in roll-to-roll imprint lithography for display applications

A solution to the problems of roll-to-roll lithography on flexible substrates is presented. We have developed a roll-toroll imprint lithography technique to fabricate active matrix transistor backplanes on flexible webs of polyimide that have a blanket material stack of metals, dielectrics, and semiconductors. Imprint lithography produces a multi-level 3- dimensional mask that is then successively etched to pattern the underlying layers into the desired structures. This process, Self-Aligned Imprint Lithography (SAIL), solves the layer-to-layer alignment problem because all masking levels are created with one imprint step. The processes and equipment required for complete roll-to-roll SAIL fabrication will be described. Emphasis will be placed on the advances in the roll-to-roll imprint process which have enabled us to produce working transistor arrays.

Fabrication of three-dimensional imprint lithography templates by colloidal dispersions

Self-aligned imprint lithography (SAIL) enables the patterning and alignment of submicron-sized features on metre-scaled flexible substrates in the roll-to roll (R2R) environment. SAIL solves the problem of precision interlayer registry on a moving web by encoding all the geometry information required for the entire patterning steps into a monolithic three-dimensional mask that is imprinted on the thin film stack deposited on a flexible substrate. Soft molds made of plastics or elastomers cast on a silicon master have been used as stamps to pattern the 3D masks because of their low cost and ease of fabrication. However, the durability of these stamps is one factor that limits their efficiency in a R2R process. Fluorothermoplastics are low cost imprint stamp materials with great mechanical strength and chemical compatibility but with low gas permeability that trap air bubbles in the photopolymer during the imprint process. This paper describes the strategy for increasing gas permeability of fluorothermoplastics by introducing voids or pores in the stamp material by fabricating the stamps with aqueous colloidal dispersions of tetrafluoroethylene–hexafluoropropylene copolymer (FEP) nanoparticles. The basic idea is that the hard fluorinated particles, whose modulus is too high to deform during drying, remain as hard spheres and lead to a porous packing when drying is complete. The selection of suitable additives to eliminate cracks created by capillary stresses during water evaporation is also described in this paper.

77.3: Invited Paper: Roll‐to‐Roll Manufacturing of Backplanes for Paper‐Like Displays

HP and Phicot are planning the worlds first R2R (roll-to-roll) manufacturing line for display backplanes based on the SAIL (Self-Aligned Imprint Lithography) process. Economic benefits for R2R compared to batch, cost comparisons of different R2R processes, comparison of substrate options, and necessary supply chain infrastructure developments are presented.