Organic Thin Film Transistor Integration - A Hybrid Approach

Research on organic electronics (or plastic electronics) is driven by the need to create systems that are lightweight, unbreakable, and mechanically flexible. With the remarkable improvement in the performance of organic semiconductor materials during the past few decades, organic electronics appeal to innovative, practical, and broad-impact applications requiring large-area coverage, mechanical flexibility, low-temperature processing, and low cost. Thus, organic electronics appeal to a broad range of electronic devices and products including transistors, diodes, sensors, solar cells, lighting, displays, and electronic identification and tracking devices A number of commercial opportunities have been identified for organic thin film transistors (OTFTs), ranging from flexible displays, electronic paper, radio-frequency identification (RFID) tags, smart cards, to low-cost disposable electronic products, and more are continually being invented as the technology matures. The potential applications for ?plastic electronics? are huge but several technological hurdles must be overcome. In many of these applications, transistor serves as a fundamental building block to implement the necessary electronic functionality. Hence, research in organic thin film transistors (OTFTs) or organic field effect transistors (OFETs) is eminently pertinent to the development and realization of organic electronics. This book presents a comprehensive investigation of the production and application of a variety of polymer based transistor devices and circuits. It begins with a detailed overview of Organic Thin Film Transistors (OTFTs) and discusses the various possible fabrication methods reported so far. This is followed by two major sections on the choice, optimization and implementation of the gate dielectric material to be used. Details of the effects of processing on the efficiency of the contacts are then provided. The book concludes with a chapter on the integration of such devices to produce a variety of OTFT based circuits and systems. The key objective is to examine strategies to exploit existing materials and techniques to advance OTFT technology in device performance, device manufacture, and device integration. Finally, the collective knowledge from these investigations facilitates the integration of OTFTs into organic circuits, which is expected to contribute to the development of new generation of all-organic displays for communication devices and other pertinent applications. Overall, a major outcome of this work is that it provides an economical means for organic transistor and circuit integration, by enabling the use of a well-established PECVD infrastructure, while not compromising the performance of electronics. The techniques established here are not limited to use in OTFTs only; the organic semiconductor and SiNx combination can be used in other device structures (e.g., sensors, diodes, photovoltaics). Furthermore, the approach and strategy used for interface optimization can be extended to the development of other materials systems.

Flora M. Li is a Research Associate at the Centre of Advanced Photonics and Electronics (CAPE) at the University of Cambridge, UK. She received her Ph.D. degree in Electrical and Computer Engineering from the University of Waterloo, Canada in 2008. She was a Visiting Scientist at Xerox Research Centre of Canada (XRCC) from 2005-2008. Her research interests are in the field of nano- and thin-film technology for applications in large area and flexible electronics, including displays, sensors, photovoltaics, circuits and systems. She has co-authored a book entitled CCD Image Sensors in Deep-Ultraviolet (2005), and published in various scientific journals.

Arokia Nathan holds the Sumitomo/STS Chair of Nanotechnology at the London Centre for Nanotechnology, University College London, UK. He is also the CTO of Ignis Innovation Inc., Waterloo, Canada, a company he founded to commercialize technology on thin film silicon backplanes on rigid and flexible substrates for large area electronics. He received his Ph.D. in Electrical Engineering from the University of Alberta, Canada, in 1988. In 1987, he joined LSI Logic Corp., Santa Clara, CA, USA where he worked on advanced multi-chip packaging techniques. Subsequently, he was at the Institute of Quantum Electronics, ETH Zurich, Switzerland. In 1989, he joined the Department of Electrical and Computer Engineering, University of Waterloo. In 1995, he was a Visiting Professor at the Physical Electronics Laboratory, ETH Zurich, Switzerland. In 1997 he held the DALSA/NSERC Industrial Research Chair in sensor technology, and was a recipient of the 2001 Natural Sciences and Engineering Research Council E.W.R. Steacie Fellowship. In 2004 he was awarded the Canada Research Chair in nano-scale flexible circuits. In 2005/2006, he was a Visiting Professor in the Engineering Department, University of Cambridge, U.K. In 2006, he joined the London Centre for Nanotechnology and is a recipient of the Royal Society Wolfson Research Merit Award. He has published extensively in the field of sensor technology, CAD, and thin film transistor electronics, and has over 40 patents filed/awarded. He is the co-author of two books, Microtransducer CAD and CCD Image Sensors in Deep-Ultraviolet, published in 1999 and 2005, respectively, and serves on technical committees and editorial boards at various capacities.

1. Introduction
1.1 Organic Electronics: History and Market
2. Organic Thin Film Transistors (OTFT): Overview
2.1 Organic Semiconductor Overview
2.2 OTFT Operation and Characteristics
2.3 OTFT Device Architecture
2.4 OTFT Device Material Selection
2.5 Summary
3. OTFT Integration Strategies
3.1 Technological Challenge inOTFT Integration
3.2 Overview of Processing and Fabrication Techniques
3.3 OTFT Fabrication Schemes
3.4 Summary
4. Gate Dielectric by Plasma Enhanced Chemical Vapor Deposition (PECVD)
4.1 Overview of Gate Dielectrics
4.2 Experimental Details and Characterization Methods
4.3 Material Characterization of PECVD SiNx Films
4.4 Electrical Characterization of OTFTs with PECVD Gate Dielectrics
4.5 Summary
5. Dielectric Interface Engineering
5.1 Background
5.2 Experimental Details
5.3 Impact of Dieletric Surface Treatments
5.4 Impact of Oxygen Plasma Exposure Conditions
5.5 Summary
6. Contact Interface Engineering
6.1 Background
6.2 Experimental Details
6.3 Impact of Contact Surface Treatment by Thiol SAM
6.4 Impact of Execution Sequence of Surface Treatment
6.5 Summary
7. OTFT Circuits and Systems
7.1 OTFT Requirements for Circuit Applications
7.2 Applications
7.3 Circuit Demonstration
7.4 Summary, Contributions, and Outlook
8. Outlook and Future Challenges