By Melbourne Centre for Nanofabrication
Spectral Reflectance is an optical characterisation technique, and is used to characterise thickness and reflective index of transparent films. Light is reflected as it crosses the interface of different materials, the top and bottom of a thin film, in the case of film characterisation. The reflected light from the top and bottom of the thin film is either added constructively or destructively, and this is a function of the film's thickness, optical properties and wavelength. Film thickness and reflective index can then be determined over a range of wavelengths. Spectral Reflectance is primarily used to characterise transparent film thickness, such as semiconductor process films, or optical coatings, as well as the film's optical constants. MCN's spectral reflectance instrumentation is the Filmetrics F20, F40 and F50. The F20 is a bench top spectral reflectometer, and characterises films in the range of 15nm to 70µm. The F20 is attached to a microscope and can measure film thickness using small spot areas in the the range of 20nm to 40μm. The F50 maps film thickness in the range of 20nm to 70µm.
