High temperature radiative properties of thin polysilicon films at the λ = 0.6328 μm wavelength

Abstract

To improve thin film laser processing methods and develop accurate process diagnostics for film microfabrication, it is necessary to understand and quantify light interaction with thin film structures. The radiation absorption analysis requires knowledge of the material complex refractive index. The thin film optical properties are strongly influenced by the presence of grain boundaries, disordered regions and inhomogeneities on the microstructural level. The film microstructure is in turn determined by the thin film deposition conditions and the properties of the substrate material. This work presents an experimental procedure for measuring radiative properties of thin polysilicon films deposited by Low Pressure Chemical Vapor Deposition on oxidized crystalline silicon wafers. The complex refractive index of polysilicon films at the HeNe laser light wavelength ( λ = 0.6328 μm) is determined in a temperature range from room temperature to approximately 1400 K, by combined ellipsometric and normal incidence reflectivity measurements in a reduced pressure, inert gas environment. The effects of the thickness and the deposition temperature of the polysilicon layer on the optical properties are discussed.