Low Temperature Deposition of Si-based Thin Films on Plastic Films Using Pulsed-Discharge PECVD under Near Atmospheric P
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1066-A05-05
Low Temperature Deposition of Si-based Thin Films on Plastic Films Using PulsedDischarge PECVD under Near Atmospheric Pressure Mitsutaka Matsumoto1, Yohei Inayoshi1, Maki Suemitsu1, Setsuo Nakajima2, Tsuyoshi Uehara2, and Yasutake Toyoshima3 1 Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan 2 Sekisui Chemicals Co. Ltd, 2-3-17 Toranomon, Minato-ku, Tokyo, 105-8450, Japan 3 Energy Technology Research Institute, AIST, 1-1-1 Umezono, Tsukuba, Tukuba, 305-8568, Japan ABSTRACT Low temperature (150 °C) deposition of doped and undoped polycrystalline Si (poly-Si) as well as SiNX films on polyethylene terephthalate (PET) films has been achieved with practical deposition rates by using pulsed-plasma CVD under near-atmospheric pressure. The precursor is SiH4 diluted in H2 for poly-Si while N2 has been additionally used for SiNx. No inert gases such as He was used. A short-pulse based power system has been employed to maintain a stable discharge in the near-atmospheric pressures. With this technique, deposition of poly-Si thin film with virtually no incubation layer is possible, which in the case of P-doped poly-Si shows a Hall mobility (μH) of 1.5 cm2/V·s. INTRODUCTION Recently, low-temperature depositions of silicon-based thin films, such as amorphous Si [1], polycrystalline Si [2] and SiNX [3], have been reported on plastic films, which have attracted much attention because they form an essential part of the fabrication process in flexible electronics such as for flexible solar cells and flexible displays. Despite the ever increasing needs for flexible electronics, however, conventional low-temperature deposition techniques such as represented by plasma enhanced chemical vapor deposition (PECVD), still require temperatures that are significantly higher than the melting points of most plastic films (>300 °C). Here, we demonstrate that a pulsed-discharge (PD)-PECVD under near atmospheric pressure provides a quite feasible method to form various Si-based thin films on plastic substrates. Plasma operation under Near atmospheric pressure is advantageous since the amount of the density of the gas molecules or radicals is considerably increased from the conventional PECVD operated at lower pressures, leading to an increased in the deposition rate and a reduction in the process cost. Actually, a high rate deposition (~60 nm/min) of poly-Si thin film has been achieved on glass substrates [4] using the same plasma. In this report, we show that a high rate deposition of polySi films, its n-type doping with phosphine (PH3), and a low-temperature (~100 °C) deposition of SiNX films can be realized on polyethylene terephthalate (PET) substrates using PD-PECVD under near atmospheric pressure.
EXPERIMENT Figure 1 shows the schematic diagram of the PECVD apparatus. The discharge plasma is generated by applying a pulsed electric bias on the hot electrode pair (20×20 mm2 each) located opposite to the substrate on the grounded electrode. The H2/SiH4/N2/PH3 mixture
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