Defects in Polycrystalline Silicon Thin-Films Crystallized by Solid Phase and Excimer Laser Annealing

摘要

The optical-phonon modes and local-vibration modes in Raman spectra were investigated as a probe for defects in polycrystalline-Si (poly-Si) thin films. Poly-Si films were fabricated by two techniques, i.e. solid-phase crystallization and excimer-laser annealing. Defects were detected by utilizing the hydrogen termination of dangling bonds resulting in appearance of local-vibration modes. In the case of SPC, only the ～2000 cm~(-1) band was detected. For solid-phase crystallization at 600 ℃, the ordering of amorphous Si networks and the disappearance of dangling bonds were observed in prior to onset of crystallization. For solid-phase crystallization at higher temperature, local-vibration mode intensity tends to increase with temperature. In the case of excimer-laser annealing, two bands were observed at ～2000 and ～2100 cm~(-1). The variations of their intensity with laser-energy density and post-annealing temperature were examined. Results obtained for solid-phase crystallization and excimer-laser annealing indicate that the 2000 cm~(-1) band were mainly attributed to dangling bonds at grain boundaries. Thus the 2000 cm~(-1) band-related defects are regarded to be identical to those detected by electron-spin resonance. The 2100 cm~(-1) band was attributed to nonequilibrium defects in grains. The relationship between defects and the width of the ～520 cm~(-1) optical-phonon mode was also discussed.