Albert Jeans

Roll-to-roll manufacturing of electronics on flexible substrates using self-aligned imprint lithography (SAIL)

Abstract— The manufacture of large-area arrays of thin-film transistors on polymer substrates using roll-to-roll (R2R) processes exclusively is being developed. Self-aligned imprint lithography (SAIL) enables the patterning and alignment of submicron-sized features on meter-scaled flexible substrates in the 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 imprint with discrete thickness modulation. The pre-aligned multiple-step mask structure maintains its alignment regardless of subsequent substrate distortion. Challenges are encountered in relation to the novel nature of using flexible substrates and building toolsets for the R2R processing. In this paper, methods of the SAIL process, the resulting active-matrix backplanes, the trajectory of SAIL process development, and the remaining issues for production are presented.

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.

23.4: Invited Paper: Active‐Matrix Backplanes Produced by Roll‐to‐Roll Self‐Aligned Imprint Lithography (SAIL)

Progress in the development of a fully roll-to-roll self-aligned imprint process for producing active matrix backplanes with submicron aligned features on flexible substrates is reported. High performance transistors, crossovers and addressable active matrix arrays have been designed and fabricated using imprint lithography. Such a process has the potential of significantly reducing the costs of large area displays. The progress, current status and remaining issues of this new fabrication technology are presented.

Adaptation of roll-to-roll imprint lithography: from flexible electronics to structural templates

HP has previously demonstrated the roll-to-roll (R2R) fabrication of active-matrix display backplanes using the Self-Aligned Imprint Lithography (SAIL) process. This approach permits a single imprint step to create a multi level mask comprising all patterns required for subsequent etching steps, obviating the need for multiple alignment steps. In this paper the imprint lithography technique and aspects of SAIL are reviewed. New work using imprint processing to generate structural templates, with aspect ratios approaching 6:1, for fluid containment will be presented. Arrays of transparent well structures, formed on a flexible transparent substrate provide the basis for a color display filter matrix that is filled by inkjet deposition of pigmented resins. A primary benefit of this approach is precise color pattern definition. A separation between primary color fields of 4 microns is realized without risk of color mixing or overlap. Components patterned with high absolute precision by imprint lithography were readily integrated with parts from other sources to yield flexible color reflective display demonstrator panels. This work highlights the flexibility of imprint processing and its suitability for use with a wide variety of materials and in differing applications.

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.

Roll-to-roll fabrication and metastability in metal oxide transistors

A roll-to-roll process is used to fabricate amorphous silicon and amorphous multicomponent oxide (MCO) transistors on flexible substrates using self aligned imprint lithography (SAIL). SAIL solves the layer to layer alignment problem. The imprint lithography patterned MCO transistors had a mobility of 15 cm2V-1 sec-1 and an on-off ratio of 107. Full display arrays with data, gate, hold capacitors and cross-overs were patterned using SAIL technology. Studies of stability of the MCO transistors indicate the importance of controlling O vacancies in the material particularly the back channel. Devices subjected to -10V gate bias stress at 60C under illumination exhibited behavior consistent with state creation in the upper and lower half of the gap near the back channel interface possibly associated with O vacancy formation.

Electronics Produced by Roll-to-roll Self-Aligned Imprint Lithography

In this presentation, we present a method for fabrication using self-aligned imprint lithography (SAIL). The self-aligned process solves the layer-to-layer registration issues arising from the dimensionally changes of flexible substrates. The imprint process eliminates the need for photolithography and greatly lowers the cost for large area electronics because it is compatible with roll-to-roll processing. The basic concepts of the SAIL process are presented along with electrical characteristics of devices produced by roll-to-roll SAIL processes.

Defect analysis of roll-to-roll SAIL manufactured flexible display backplanes

HP and Phicot have made the worlds first roll-to-roll (R2R) manufactured active matrix displays. Currently we are developing a wrist-worn solar powered display for the U.S. Army. As we scale from research to preproduction on our 1/3 meter wide pilot line defect analysis and mitigation is our primary focus. In this presentation we will review the self-aligned imprint lithography (SAIL) process and discuss defects we observe, and the tools, and processes we have developed to detect and eliminate them

29.1: Invited Paper: Electrical Testing of Roll-to-Roll SAIL Manufactured Flexible Display Backplanes

HP and Phicot are making a fully roll-to roll fabricated display for a solar powered wrist display. We have developed methods for electrical testing of display backplanes on flexible substrates which are not bonded to a carrier. This has enabled improvement of yield through rapid electrical test feedback.