Nanocrystalline Silicon Diodes for Rectifiers on Flexible RFID Tags
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1066-A06-09
Nanocrystalline Silicon Diodes for Rectifiers on Flexible RFID Tags Ian Chi Yan Kwong, Hyun Jung Lee, and Andrei Sazonov Department of Electrical and Computer Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1, Canada ABSTRACT There has been an on-going effort to produce low cost radio frequency identification (RFID) tags as a replacement for traditional barcodes. One method to achieve low cost production is to integrate the manufacturing of the substrate, antenna and active devices into one single continuous process. Hydrogenated nanocrystalline silicon (nc-Si:H) is a suitable material for manufacturing the active devices in such a process. We present a nc-Si:H diode suitable for use in rectifiers on RFID tags. It consists of a Cr bottom contact, an undoped layer of nc-Si:H, an n-doped nc-Si:H and an Al top contact. We demonstrate the current-voltage characteristics of the nc-Si:H diode are much improved over aSi:H diodes. Current density of 10 A/cm2 and ON/OFF ratio greater than 106 was measured at 2 V forward bias. Output DC voltage of 2.6 V was achieved using four nc-Si:H diodes in a fullwave bridge rectifier. The input AC signal was a sine wave at 14 MHz and 2 VRMS amplitude. INTRODUCTION The use of RFID technology on the commercial market is being lauded as the next big revolution in enhancing business intelligent. However, the deployment of RFID by business has been slow and one major factor is the cost associated with deploying large number of RFID tags. However, advanced RFID tags that provide data processing and writable storage capability requires many transistors. Currently, these advanced RFID tags uses traditional CMOS chips and are still too expensive for wide deployment [1]. Recent research in RFID tags manufacturing has been centered on different technology in reducing the cost of manufacturing tags with many transistors [2-4]. One method to reduce the manufacturing cost of RFID tags is to switch to using large area electronics manufacturing methods and technology. Current RFID tags are manufactured using a packaged CMOS chip made on crystalline silicon which is then bonded to an antenna and substrate of the tag. The packaging cost of the CMOS chip, the bonding cost and the subsequent testing cost of the final tag adds to the total cost of the finished RFID tag. By switching to large area electronics technology, where the antenna and active circuitry are manufactured in one integrated process, there is much potential for cost savings. Research has been done on using amorphous silicon and organic semiconductors in making the active components for RFID tags [2-4]. Our approach is to use hydrogenated nanocrystalline silicon (nc-Si:H) in an integrated process for manufacturing the same active component. Previous research has demonstrated that nc-Si:H possesses higher electron and hole mobilities than a-Si:H and organic semiconductors, which will lead to superior performing devices, necessary for RFID tags operating at 13.56 MHz and above. We demonstr
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