Radically- and Thermally- cured High-SiOH Methylvinylsiloxane Polymer Thin Film for Electric Insulator Applications for
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1247-C08-08
Radically- and Thermally- cured High-SiOH Methylvinylsiloxane Polymer Thin Film for Electric Insulator Applications for TFT Tadashi Nakano, An KiHwan and Jung SoRa APM, Inc. 150-50 Gajwa-dong, Seo-gu, Incheon 464-810, Korea ABSTRACT Hydrolytically polymerized poly(methyl-co-vinyl)siloxane is cross-linked by radically and dehydrolytically at elevated temperature. Peroxide-type thermal radical generator is found to cross-link the polymer at the vinyl and methyl pendant groups. In parallel, free silanol (SiOH) end groups in the polymer also contribute to cross-linking by dehydrolytic polycondensation. By use of these two-fold cross-linking mechanisms, we were able to deposit highly cross-linked siloxane polymer film which provides excellent optical and electrical properties. Cured film of 500 nm thickness exhibited the pencil hardness of 9H on glass with > 95% visible light transmittance. These excellent features are applied to optical hard coating for flexible displays and touch panels. The cured film also exhibited excellent electric properties. The leakage current of the film is as low as that of CVD dielectric film, and the break down field is exceeded 3 MV/cm, which enabled the film to be applied to insulator in thin film transistor. We carried out analyses of the polymer in film and powder form with 13C- and 29SiNMR MAS, FT-RAMAN and FTIR-ATR methods to investigate curing mechanism. The analysis results clearly indicated that the cured film contains unique Si-(CH)n-Si bonds generated by radical crosslinking, and all the Si-OH bonds are consumed by hydrolytic polycondensation as well. The Si-(CH)n-Si bonds are more rigid and less polar than Si-O-Si bond, which should be the major reasons that radical condensation remarkably reinforced the film. This radically and thermally cured poly(methyl-co-vinyl)siloxane film was applied to Mo-gate thin film transistor fabricated on glass as the gate insulator. The I-V characteristics from the transistor were equivalent to those made using CVD-SiN insulator. INTRODUCTION Polysiloxane materials, having Si-O-Si chain as the backbone, are known to provide high thermal stability, high optical transmittance and excellent electric insulation. Properties of polysiloxane can be tuned by altering chemistry of pendant group directly attaching to Si atom. For example, poly(dimethylsiloxane), two methyl groups attached to Si, is transparent fluid, whereas poly(monomethylsiloxane), single methyl group attached to Si, is typically hard and brittle resinous solid. Electronic industries require insulation film with great thermal stability. The best polymer candidate should be polysiloxane. For real world applications, the chemistry of the pendant groups of polysiloxane must be carefully tailored, for example, poly (alkylsilicate) film (rich in 4-oxygen-surrounded silicon; Si[Q]) provides significantly high hardness at 100ºC or so, while the film tends to crack even at < 0.3 µm, while poly(monoalkylsiloxane) film (rich in 3-oxygenand 1-carbond surround silicon; Si[T]) has less int
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