%0 Journal Article
%T Characterization of Defects and Stress in Polycrystalline Silicon Thin Films on Glass Substrates by Raman Microscopy
%A Kuninori Kitahara
%A Toshitomo Ishii
%A Junki Suzuki
%A Takuro Bessyo
%A Naoki Watanabe
%J International Journal of Spectroscopy
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/632139
%X Raman microscopy was applied to characterize polycrystalline silicon (poly-Si) on glass substrates for application as thin-film transistors (TFTs) integrated on electronic display panels. This study examines the crystallographic defects and stress in poly-Si films grown by industrial techniques: solid phase crystallization and excimer laser crystallization (ELC). To distinguish the effects of defects and stress on the optical-phonon mode of the Si每Si bond, a semiempirical analysis was performed. The analysis was compared with defect images obtained through electron microscopy and atomic force microscopy. It was found that the Raman intensity for the ELC film is remarkably enhanced by the hillocks and ridges located around grain boundaries, which indicates that Raman spectra mainly reflect the situation around grain boundaries. A combination of the hydrogenation of films and the observation of the Si-hydrogen local-vibration mode is useful to support the analysis on the defects. Raman microscopy is also effective for detecting the plasma-induced damage suffered during device processing and characterizing the performance of Si layer in TFTs. 1. Introduction Raman microscopy has been used in the field of semiconductor technologies to characterize lattice defect, damage, and stress introduced during crystallization and device processing. Amorphous silicon (a每Si) films and polycrystalline silicon (poly-Si) films on glass substrates have been extensively researched for application as thin-film transistors (TFTs) integrated on liquid crystal display (LCD) panels. The use of poly-Si instead of conventional a每Si allows for high-definition LCD and the integration of driver circuits into the panels [1]. The primary advantage of poly-Si is the electron and hole mobility at least two orders of magnitude larger than those of a每Si. Poly-Si TFTs are also applied in organic light-emitting diode panels. In the future, the applications of the thin-film poly-Si technology will extend to flexible displays, microprocessor-display-combined devices, and solar cells. Poly-Si films on glass substrates are generally fabricated by the recrystallization of an a每Si precursor. The recrystallization is industrially performed by solid-phase crystallization (SPC) or excimer laser crystallization (ELC) [2, 3]. Using these techniques, the film quality is degraded by large density defects due to the seed less growth and restriction of growth temperature. Moreover, stress is caused by the differences of the film and substrate materials. Thus, characterization of the defects and stress is
%U http://www.hindawi.com/journals/ijs/2011/632139/