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16 May 2003 Thin film transistors made of nanocrystalline silicon for CMOS on plastic
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Our motivation is to realize CMOS on plastic foil. We report the development of thin film transistors (TFTs) made of nanocrystalline silicon (nc-Si:H). nc-Si:H is compatible with present a-Si:H thin film technology. Because of the structural evolution of nc-Si:H with film thickness, it requires extensive experimentation with device geometry. For comparison we fabricate TFTs in (a) conventional coplanar top-gate, top-source/drain geometry and (b) staggered top-gate, bottom source/drain geometry. A seed layer is introduced in the latter case serves to develop the crystallinity of the intrinsic channel layer. While the coplanar geometry provides the shortest carrier path in the most crystalline channel region, the inverted staggered geometry ensures that the active channel is formed in the last-to-grow nc-Si:H layer, and also avoids exposure of the channel to reactive ion etching (RIE). The highest process temperature is 150°C. Both intrinsic and doped nc-Si:H layers are grown by plasma-enhanced chemical vapor deposition with an excitation frequency of 80MHz. Present p-channel TFTs reach a hole field-effect mobility of ~ 0.2 cm2V-1s-1 in the staggered geometry, and an electron field-effect mobility of ~ 40 cm2V-1s-1 in both geometries. These results suggest that directly deposited nc-Si:H is an attractive candidate material for CMOS capable electronics on plastic substrates.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
I-Chun Cheng and Sigurd Wagner "Thin film transistors made of nanocrystalline silicon for CMOS on plastic", Proc. SPIE 5004, Poly-Silicon Thin Film Transistor Technology and Applications in Displays and Other Novel Technology Areas, (16 May 2003);

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