Papers by Author: W. Luangtip

Abstract: 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.

Abstract: A silver film was deposited on silicon wafer by DC unbalance magnetron sputtering system. The temperature dependence of the silver film was investigated. The spectroscopic ellipsometry (SE) with the heating of sample stage (HTC100) was employed for the in situ SE measurement under annealing cycles of the sample from room temperature to 300°C in dry nitrogen gas. The results show that the pseudo dielectric constants (<ε1>, < ε2>) of the sample varied with an annealing temperature. The real part of pseudo dielectric constant (<ε1>) of annealed Ag film was slightly changed and the imaginary part (< ε2>) was strongly increased at a photon energy below the optical band gap (3.5-4.5 eV). Furthermore, the pseudo dielectric constant of imaginary part at low energy region was changed due to the enhancement of crystallinity of Ag film at 300°C. All measured SE spectra were fitted by Drude-Lorentz optical model, the scattering time and resistivity were obtained.