High Performance of Ultralow Temperature Polycrystalline Silicon Thin Film Transistor on Flexible Metal Foil Substrate
A high performance ultralow temperature polycrystalline silicon (poly-Si) thin film transistor (TFT) was obtained on a flexible metal foil substrate using the optimization of a benzocyclobutene (BCB) planarization process for a rough flexible metal foil substrate surfaces, the high quality SiO 2 int...
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| Published in | Japanese Journal of Applied Physics Vol. 49; no. 5; pp. 056502 - 056502-4 |
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| Main Author | |
| Format | Journal Article |
| Language | English |
| Published |
The Japan Society of Applied Physics
01.05.2010
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| Online Access | Get full text |
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| Summary: | A high performance ultralow temperature polycrystalline silicon (poly-Si) thin film transistor (TFT) was obtained on a flexible metal foil substrate using the optimization of a benzocyclobutene (BCB) planarization process for a rough flexible metal foil substrate surfaces, the high quality SiO 2 interface layer formation between the gate dielectric film and the poly-Si film using plasma oxidation, and a successful crystallization of large grain poly-Si films with a sequential lateral solidification (SLS) method. High performances with field effect mobilities of 196 and 95 cm 2 V -1 s -1 , threshold voltages of 1.6 and $-1.5$ V and sub-threshold swings of 0.53 and 0.45 V/decade were obtained for n-channel metal--oxide--semiconductor (nMOS) and p-channel metal--oxide--semiconductor (pMOS) TFT on flexible metal foil substrate, respectively. |
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| Bibliography: | Schematic diagram of the cross-sectional TFT structure. Images of stainless steel foil surfaces. (a) as-received, unsuccessful (b) SOG, and (c) anonymous organic material planarization (note the scale bar), (d) BCB planarization. A comparison of align accuracy between layers fabricated on plastic substrate [(a) PAR, (b) PES, (c) PEN] and (d) stainless steel foil. The roughness of film was measured with the aid of the Tencor surface profiler Alpha-Step 500. Ar content within the a-Si film and the maximum laser energy density over which the a-Si film is damaged by explosive Ar gas effusion with pressure variation. The TEM photo of a successfully SLS crystallized poly-Si film on a BCB planarized stainless substrate which shows super lateral growth. Thickness variation of SiO 2 and Al 2 O 3 layer with the plasma oxidation power obtained from TEM observation. The inset shows TEM images of interface layer, 8 nm SiO x , and 50 nm Al 2 O 3 deposition layer. Changes in the dielectric constants and hysteresis values of 70 nm grown gate dielectric with a plasma oxidation power variation using $C$--$V$ measurement. Transfer characteristics of the nMOS/pMOS TFT with $W/L=30$ \mbox{$\mu$m}/30 \mbox{$\mu$m}. |
| ISSN: | 0021-4922 1347-4065 |
| DOI: | 10.1143/JJAP.49.056502 |