AVS 52nd International Symposium
    Thin Films Friday Sessions
       Session TF-FrM

Invited Paper TF-FrM1
Thin Film Electronics on Flexible Polymer and Steel Substrates

Friday, November 4, 2005, 8:20 am, Room 306

Session: Thin Films on Flexible and Polymer Substrates
Presenter: S. Wagner, Princeton University
Authors: S. Wagner, Princeton University
I.-C. Cheng, Princeton University
S.P. Lacour, Princeton University
H. Gleskova, Princeton University
J.C. Sturm, Princeton University
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The flat panel display industry, growing rapidly, is developing flexible displays for its next technology generation. Flexible displays are attractive for light weight and resistance to fracture. They can be bent, conformally shaped, and possibly even stretched elastically. While the optoelectronic functions of flexible displays are similar to those of rigid displays, many of their materials, fabrication processes, and mechanics are new. We will concentrate on transferring the processes for display fabrication from glass plates to flexible substrates, and on the mechanics of flexible substrates. A manufacturer can choose from several display technologies, but only silicon is available for the transistors of the active-matrix transistor backplane. Therefore, the design of a flexible backplane begins with the selection of a foil substrate that is compatible with the silicon thin-film transistor process. The substrate may be an organic polymer or steel. It may need a planarization layer, and must have a layer that provides adhesion, chemical passivation, and electrical insulation. Converting from the chemistry of the substrate foil to the chemistry of a silicon nitride or silicon dioxide passivation layer enables the adoption of many processes developed for glass substrates. The mechanics of flexible substrates plays a role during processing, where it affects device film integrity and mask overlay alignment, and during post-process shaping. Shaping by bending is straightforward and is done in the elastic regime; the device films remain intact. Shaping to a spherical surface, or elastic stretching over an arbitrary surface, produce mechanical strain so large that devices break. A new physical architecture based on rigid device islands has been developed to prevent fracture. Flexible electronics offers a unique combination of materials, processes, devices, and mechanics.