SBIR-STTR Award

Performance of current amorphous (A-Si) and even polycrystalline (Poly-Si) silicon thin film transistors (TFTs) made with low temperature processes ( 300°C on rigid glass or metal foil substrates with acceptable performance and yield, this is too high for traditional plastic substrates. Versatilis proposes to show high performing top gate based TFTs made of Zinc Oxide (ZnO) as an alternate semiconductor material, and made directly on a flexible polymer sheet at < 200°C. Such TFTs will be further patterned to <2µ features for high switching speeds using a novel multiwavelength photolithographic technique that will obviate sequential masking steps and fully eliminate registration and alignment challenges in working with flexible polymer substrates, and which will be compatible with a future R2R manufacturing paradigm for very low cost flexible electronics. Proposer will partner with the Display Research Lab at Lehigh University and adapt existing designs and techniques for Silicon based TFTs on metal foils to ZnO based TFTs on plastic.

Benefits:
The proposed technology will impact directly manufacturing methods and costs of future Flat Panel Displays (FPD), an enormous commercial market ($80 Billion including LCD and PDP TV), but where effectively all the manufacturing base is in the Far East. Yet rugged and low cost, flexible and conformal displays, as well as flexible electronics in general, are vital for the future warfighter; therefore, it is in the national interest to build a domestic manufacturing technology and infrastructure capable of supporting future military display needs. This well recognized need is supported by Congress through ARL and the Army ASU Flexible Displays Center, and the U.S. Displays Consortium (USDC). Versatilis believes it can obtain designs, methods and devices that clearly show higher performance, improved stability, higher yield, lower cost and improved scalability over the current state of the art, and which can easily be weaved into the ongoing work at the Army ASU Flexible Displays Center.

Keywords:
Thin film transistors, flexible substrates, displays, materials, device structures, processes, process tools

Performance of silicon thin film transistors (TFTs) made with low temperature processes (<200°C) on flexible polymer substrates cannot meet requirements for flexible electronics in rugged, low cost Army systems of the future. For example, higher performance and/or larger flexible displays require full motion video such as streaming data from a UAV or high information content and color imagery, presenting significant challenges for the AM TFT backplane and associated electronics.. While amorphous and polycrystalline silicon TFTs can be processed with acceptable performance and yield > 300°C on glass or metal foil substrates, this is still too high for traditional plastic substrates. In Phase I, Versatilis successfully showed the feasibility of using Zinc Oxide (ZnO) as an alternative to Silicon for the active semiconductor channel in such TFT arrays. ZnO is readily available and cheap, and can be processed at low temperatures with high yields while delivering carrier mobility adequate for increased current density vs. drain voltage, with little or no threshold voltage shift vs. stress. In Phase II, Versatilis will extend this work to develop a robust, reproducible method for manufacturing ZnO based AM TFT backplanes, including integrated driver circuits, and deliver a number of such backplanes to ARL for integration with OLED frontplanes, producing a 6 in., 100 dpi flexible display demonstrator, a higher performance, lower cost alternative to silicon. The technology would be transferable to the Army’s Flex Display Center at ASU for integration into Army’s display initiative and/or licensable to commercial entities.

Keywords:
Thin Film Transistors, Flexible Substrates, Flexible Displays, Displays, Flexible Materials, Zinc Oxide