Investigation of Aluminium Diffusion into an Amorphous Silicon Thin Film at High Temperature by In Situ Spectroscopic Ellipsometry
This work is to study the diffusion of Al into amorphous silicon (a-Si) thin film at the elevated temperature by in-situ Spectroscopic Ellipsometry (SE). The sputtered a-Si film 60 nm thick on an optically opaque Al (100 nm) layer on silicon wafer was heated in a temperature controlled heating sample stage from room temperature to 300°C and slowly cooled down to room temperature while the dynamic SE data were measured. It was found that the ∆ and Ψ spectra began to change quickly at 200°C until the temperature reached 250°C, then continue to changed very slowly until 300°C. No significant change could be observed while the sample was cooling down to room temperature. The full spectral SE measurements were also taken at every 50°C steps and used to model the diffusion of Al into the top a-Si film. The interface layer due to diffusion was modeled by Bruggeman Effective Medium Approximation (EMA) theory as the mixture of Al and Si.
W. Luangtip et al., "Investigation of Aluminium Diffusion into an Amorphous Silicon Thin Film at High Temperature by In Situ Spectroscopic Ellipsometry", Advanced Materials Research, Vols. 55-57, pp. 449-452, 2008