Application of Field-Enhanced Rapid Thermal Annealing to Activation of Doped Polycrystalline Si Thin Films
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Application of Field-Enhanced Rapid Thermal Annealing to Activation of Doped Polycrystalline Si Thin Films B.S. So1, Y.H.You1, H.J. Kim1, Y.H. Kim1, J.H. Hwang1, D.H. Shin2, S.R. Ryu2, K. Choi3and Y.C. Kim4 1 Department of Materials Science and Engineering, Hongik University, Seoul, Korea 2 Viatron Technologies, Seoul, Korea 3 Thin Film Materials Lab., KICET, Seoul, Korea 4 Department of Advanced Materials Engineering, Korea University of Technology and Education Chunan, Korea ABSTRACT Activation of polycrystalline silicon (poly-Si) thin films doped as n-type using selective ion implantation of phosphorous was performed employing field-enhanced rapid thermal annealing where rapid thermal annealing of halogen lamps is combined with alternating magnetic fields. The ion activation was evaluated using Hall effect measurements incorporating the resistivity, the charge carrier concentration, and the mobility. Statistical design of experiments is attempted in order to clarify the effects and interactions of processes variables on field-enhanced rapid thermal annealing towards ion activation: the three processing variables are furnace temperature, power of halogen lamp, and the alternating magnetic field. Hall effect measurements indicate that the furnace temperature and RTA power are found to be dominant in activating the doped polycrystalline Si in dose. The activation process results from the competition between charge carrier concentration and mobility: the increase in mobility is larger than the decrease in charge carrier concentration. INTRODUCTION Polycrystalline silicon (poly-Si) thin film transistors (TFT's) on glass substrates are essential components for active matrix organic light-emitting diodes (AMOLED). The poly-Si TFTs offers much higher mobility compared to that of amorphous Si TFTs, leading to the excellent combination with organic light-emitting diodes (OLEDs) which incorporates excellent color coordinates, self-emission, fast responses, and wide viewing-angle. The superior TFT characteristics can be extend to the panel ASIC, memories, photodiodes, functional sensors, etc. Highly functional applications require the stringent controls in TFT characteristics, such as mobilities, threshold voltage, s-slope, leakage currents, etc. The above device parameters are critically dependent on gate dielectrics, Si crystallization, and ion-doping and activation. After ion-doping, various activation processes have been researched: furnace annealing, rapid thermal annealing, excimer laser annealing, etc [1-3]. None of them can be adapted to the manufacturing processes, due to their respective demerits, e.g. long processing time, thermal shock leading to fatal mechanical deformation, narrow processing regimes, high cost, etc. The doping/activation process for a source-drain contact should also be carried out at low temperature, due to the inherent limitation of glass substrates. A novel processing was developed for activation after ion-doping, where the rapid thermal annealing process are modified and combined wi
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