Novel Materials and Integration Schemes for CMOS- Based Circuits for Flexible Electronics

The development of low temperature, thin film transistor processes that has enabled flexible displays also presents opportunities for flexible electronics and flexible integrated systems. Of particular interest are possible applications in flexible, low metal content, sensor systems for unattended ground sensors, smart medical bandages, electronic ID tags for geo-location, conformal antennas, neutron/gamma-ray/x-ray detectors, etc. In this talk, we review the state-of-the-art in flexible electronics materials and devices and present recent results in our efforts to fully integrate complementary metal oxide semiconductors. We conclude with a discussion of the constraints of thin film transistors and the remaining challenges. Introduction In the last few years, there have been substantial development efforts in reducing the amorphous silicon thin film transistor processing temperatures to be compatible with a plastic substrate (heat stabilized polyethylene napthalate or PEN) and for handling flexible substrates in standard processing equipment. The development of low temperature, thin film transistor also presents opportunities for flexible electronics and flexible integrated sensor systems. One limitation of amorphous silicon transistors is that only N-channel devices are possible that is only devices that are activated with positive voltages are available. P-channel devices – devices that are activated with negative voltages – are also needed to build low power CMOS circuits, the technology of choice for the silicon integrated circuit industry. The development of flexible CMOS is, therefore, essential to reduce the power consumption of portable, flexible integrated sensor systems. We have recently combined an N-channel amorphous silicon thin film transistor process with a Pchannel organic thin film transistor process to form CMOS circuits on a flexible plastic substrate (Fig. 1). Results and Discussion Our flexible CMOS process was achieved by fabricating the nMOS a-Si:H and the pMOS device on a flexible plastic substrate. The formation of vias enables the arbitrary connection of nMOS and pMOS devices to Gate Source Drain Gate Source Drain Pentacene