Inkjet-configurable gate arrays: towards application specific printed electronic circuits

Abstract

Over the last decades, Organic Electronics has been emerging as a multidisciplinary and innovative way to generate electronic devices and systems. It is intended to provide a platform for low-cost, large-area, and low-frequency Printable Electronics on a variety of substrates, including flexible plastic substrates. Just as the first information revolution caused by integrated silicon circuits, PE is expected to cause another revolution characterized by the distribution of information systems in all aspects of life. Although the integrated circuits, based on Organic Thin Film Transistors (OTFT), are not meant to compete with the silicon-based high-end industry, their performance have already reached to a level enabling the use of organic technology to an ever-increasing number of emerging applications, such as flexible optical displays, sensors, and low-end microelectronics. Currently, most of the digital integrated circuits are yet designed by specifying the layout of each individual transistor and their interconnections. Full-custom design is extremely labor-intensive, time consuming for complex circuits and it requires advanced computer software in the design process, and several expensive mask sets in the fabrication process. Besides, taking the soft and hard faults at transistor level into account, the yield at system level is expected to be very low, since failure of one transistor causes the entire circuit to fail. This is more important for technologies based in non-crystalline materials (such as silicon) in which deposition and layer formation is more irregular. On the other side, organic electronics is more complex than Printed Circuit Boards (PCB) in the sense that these do not include active devices and do not reach high integration level. Furthermore, similar to any new-born technology, the performance of organic electronic circuits is degraded due to some limitations in technological and materials sides. That being said, the question arises as to whether circuit design techniques can be employed to compensate these bottlenecks so as to meet yield and performance requirements. The work presented in this thesis contributes to overcome the above-mentioned issues by proposing the novel concept of Inkjet-configurable Gate Array (IGA) as a designmanufacturing method for the direct mapping of digital functions on top of new prefabricated structures. IGA brings together the advantages of semi-custom gate array methodology, field-configurability, and fault-tolerance, and adopt it to Application Specific Printed Electronic Circuit (ASPEC), which is the equivalent term to Application Specific Integrated Circuit (ASIC), but for PE. This alternative has two main advantages. Firstly, it allows implementing individual circuit personalization at a very low cost through the best use of additive mask-less digital printing techniques (e.g. Inkjet, Superfine Jet, and etc.) "in the field", thus avoiding the need for One Time Programmable ROM-like (or E2PROM) devices. Secondly, fault tolerance technique allows the adoption of a failure map to use only working transistors for circuit implementation, thus, it helps to obtain high yield circuits out of mid-yield foils.