Date
Place
- Room A (Room 325)
- 55. Advanced TFT Backplane Technologies VI
- August 21, 2015 (Friday)
- 15:30 ~ 16:55
- [55-3]
- 16:10 ~ 16:25
- Title:Effect of Low Temperature Annealing of Sputtered SiO2 for Gate Insulator in Poly-Si TFTs
- Hikaru Tamashiro, Kimihiko Imura, Tatsuya Okada, and Takashi Noguchi (Univ. of the Ryukyus, Japan)
Abstract: Poly-Si Thin Film Transistors (TFTs) are used for displays of TV panels or smartphones. High quality gate insulating film with high breakdown voltage at low leakage current is required. Insulation strength of the gate oxide film can be realized by adding small amount of oxygen during deposition by sputtering and improvement in ?poly-Si TFT characteristics by hydrogen annealing at low temperature has been reported [1, 2]. It is considered that the defects density in SiO2 film and at Si/SiO2 interface are reduced by hydrogen annealing. However, the influence of hydrogen on sputtered SiO2 film as a gate oxide has not been understood yet in detail. ?For Al / SiO2 structure, the post metallization annealing (PMA) is known in the SiO2 film deposited by chemical vapor deposition (CVD). Al electrode reacts with H2O or OH of the SiO2 Film when annealing at 400¢ªC. Dangling bonds are terminated by the generated hydrogen atoms [3]. SiO2 film was deposited by radio frequency (RF) sputtering on p type Si substrate (4~10 ¥Øcm). Al electrodes were formed on the surface (0.5 mm¥õ) and on the back-surface. The SiO2 film was annealed at 400¡É for 30 min in H2/N2 (4%) ambient. As is shown, hysteresis decreased down to 5¡¿10-10 A/cm2 by performing the hydrogen annealing after the Al electrode formation. The result suggests that the dangling bonds at the SiO2 film surface are terminated with hydrogen atoms. It is estimated that PMA acts effectively even for the sputtered SiO2 film. Furthermore, after the annealing, the flat-band voltage shifted to ideal level of -0.9V from C-V characteristics. Reduced of leak current and shift of the flat band voltage to suggest that dangling bonds in the SiO2 film were terminated effectively. From these results, insulating characteristics of the SiO2 film are considered to be improved by hydrogen annealing after the formation of Al electrodes. It is expected that practical poly Si TFT performance on glass should be improved stably.
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