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We have demonstrated the performance of circuits on stainless steel and compared them to those fabricated on quartz substrates. We have modeled the substrate dependence of the minimum and maximum operating frequency of a Shift Register, and found close agreement with our experimental measurements. This model can be used as a design guideline for future development of circuits on conducting substrates.

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In recent years, there has been an increased interest in the use of flexible substrates in microelectronic fabrication. Flexible substrates, such as polymers and metals have the potential to be utilized in roll-to-roll processing, resulting in low cost, rugged systems. Thin flexible stainless steel foils offer a number of advantages over polymers for device and circuit fabrication, most significantly in the increased thermal budget tolerance that they provide. This enables the utilization of high temperature processes in the fabrication and the production of high performance devices and circuits.Thin film transistors have been fabricated on thin stainless steel foils using a variety of crystallization and gate dielectric approaches. N-channel devices with average effective mobility values of 250cm2/Vs and p-channel devices with effective mobility values in the region of 90cm2/Vs were successfully fabricated. Both digital and analog circuits, such as operational amplifiers, ring oscillators and a variety of shift register designs were also fabricated, and their basic performance characteristics will be presented in this paper. The characteristics of ring oscillators having 19 inverter stages operating with speeds of 15MHz or higher, along with the characteristics of various shift register architectures with maximum operating frequencies above 1MHz, will be reported. The impact of process and design parameters on their operation was evaluated and will be addressed in this paper.The results that are presented in this paper constitute the first successful implementation of high performance circuitry having a high degree of scalability and complexity on thin metal foils, thus making the fabrication of efficient, inexpensive and versatile systems on flexible foils for a large variety of applications a realistic prospect.

The first successful integration of poly-Si thin-film-transistor (poly-Si TFT) backplane with polymer light-emitting diodes (PLEDs) onto a flexible stainless-steel foil is described, and a high-resolution (230 DPI) monochrome active-matrix polymer light-emitting diode (AM-PLED) display is demonstrated. The process technology required to implement this high-resolution AM-PLED display onto a flexible metal foil substrate is discussed. This technology primarily consists of the preparation of flexible metal foils, fabrication of the poly-Si TFT backplane, and integration with top-emitting PLEDs.