Yong-Mo Choi

PECVD‐based nanocrystalline‐silicon TFT backplanes for large‐sized AMOLED displays

— A 14.1-in. AMOLED display using nanocrystalline silicon (nc-Si) TFTs has been developed. Nanocrystalline silicon was deposited using conventional 13.56-MHz plasma-enhanced chemical vapor deposition (PECVD). Detailed thin-film characterization of nc-Si films was followed by development of nc-Si TFTs, which demonstrate a field-effect mobility of about 0.6–1.0 cm2/V-sec. The nc-Si TFTs show no significant shift in threshold voltage when over 700 hours of constant current stress is applied, indicating a stable TFT backplane. The nc-Si TFTs were successfully integrated into a 14.1-in. AMOLED display. The display shows no significant current decrease in the driving TFT of the 2T-1cap circuit because the TFTs are highly stable. In addition to the improved lifetime of AMOLED displays, the development of nc-Si TFTs using a conventional 13.56-MHz PECVD system offers considerable cost advantages over other laser and non-laser polysilicon-TFT technologies for large-sized AMOLEDs.

70.4: A 14.1inch AMOLED Display using Highly Stable PECVD based Microcrystalline Silicon TFT Backplane

We have developed a 14.1 inch AMOLED display using microcrystalline silicon (mc-Si) TFTs. Microcrystalline silicon was deposited using conventional 13.56MHz Plasma Enhanced Chemical Vapor Deposition (PECVD). Detailed thin film characterization of mc-Si films was followed by development of mc-Si TFTs which show a field effect mobility of around 0.7∼1.0cm2/V.s. The mc-Si TFTs show no significant shift in threshold voltage when applied with a long time constant current stress, indicating a stable TFT backplane. The mc-Si TFTs were successfully integrated in a 14.1 inch AMOLED display. The display shows no significant current decrease in the driving TFT of the 2T circuit, even after long time of lifetime tests. Along with improved lifetime for AMOLED display, the development of mc-Si TFTs using conventional 13.56 MHz PECVD system offers significant cost advantages over other laser or non-laser polysilicon TFT technologies for AMOLED.