Characterization of Defects and Stress in Polycrystalline Silicon Thin Films on Glass Substrates by Raman Microscopy

Abstract

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–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.

5.8‐inch QHD flexible AMOLED display with enhanced bendability of LTPS TFTs

“…Figure shows that polycrystalline Si has a weak but preferred crystal orientation of (100). In the electron backscattering diffraction pattern of the surface normal direction, the {001} orientation has a high portion in the surface orientation of (100), (110), and (111) . Also, Raman spectrum shows that the poly‐Si film on plastic/glass substrate has a residual stress of 750–850 MPa biaxial tensile stress.…”

“…In the electron backscattering diffraction pattern of the surface normal direction, the {001} orientation has a high portion in the surface orientation of (100), (110), and (111). 16,17 Also, Raman spectrum shows that the poly-Si film on plastic/glass substrate has a residual stress of 750-850 MPa biaxial tensile stress. The crystalline Si peak was red-shifted (to the lower frequency) with an amount of 3-3.5 cm À1 (compared with the 520 cm À1 of non-strained c-Si).…”

Depth-Sensitive Raman Investigation of Metal-Oxide-Semiconductor Structures: Absorption as a Tool for Variation of Exciting Light Penetration Depth

“…Position of the maximum recorded for c-Si was used as a reference. The type of stress in polycrystalline Si layer depends also on the substrate [54]. If glass plate is used as a substrate thermal effects related to cooling of the sample lead to tensile stress [54].…”

“…The type of stress in polycrystalline Si layer depends also on the substrate [54]. If glass plate is used as a substrate thermal effects related to cooling of the sample lead to tensile stress [54]. Application of sapphire as a substrate changes the type of stress to compressive [54].…”

Oriented Lateral Growth and Defects in Polycrystalline-Silicon Thin Films on Glass Substrates

“…In contrast, optical techniques are suitable for simple, non-destructive characterization. We analyzed the defects and stress in a poly-Si/glass system by Raman scattering spectroscopy (Kitahara et al, 2002(Kitahara et al, , 2003(Kitahara et al, , 2011a. Micro-Raman spectroscopy was conducted by using a Renishaw System 1000 in the backscattering geometry under excitation with a 514.5 nm Ar ion laser.…”