Optical constant of CoFeB thin film measured with interference enhancement method

Optical constants (n and k) of Co20Fe60B20 (CoFeB) thin films (2~40nm) are measured by using interference enhancement method with spectroscopic ellipsometry in the wavelength range of 270~1600nm. The effects of film thickness, protection layer and annealing process on the optical constant of CoFeB film are investigated. In the range of 40~10nm, both n and k decrease with the decrease of thickness. The protection layer of SiO2 on the CoFeB film is helpful for the precise measurement of the n and k values. The annealing process has less effect on the optical constant of the film with the protection layer as compared to the one without it. © 2014 Optical Society of America OCIS codes: (160.4760) Optical properties; (240.0310) Thin films; (260.2130) Ellipsometry and polarimetry. http://dx.doi/org/10.1364/AO.99.099999