Statistical evaluation of refractive index, growth rate, hardness and Young's modulus of aluminium oxynitride films

Abstract

Aluminium oxynitride films were produced by reactive dc-magnetron sputtering with compositions covering the concentration range from nitride to oxide. The altered deposition parameters were the sputtering power and the gas flow rates of argon, nitrogen and oxygen. The refractive index and the growth rate of the films were determined by spectroscopic ellipsometry, which showed negligible absorption. With indentation by a nano hardness tester the hardness and the Young's modulus of the films were obtained. The results of these measurements were evaluated by statistical software. The dependences of the physical properties on the deposition parameters and on the film thickness were evaluated and quantified. The thickness still had some influence on the results of the nano-indentation measurements resulting from the influence of the substrate. Furthermore, the dependences of the physical properties on the film composition represented by the oxygen content and the film thickness were evaluated. However, these evaluations only delivered useful results for the refractive index and the hardness. It is shown that the physical properties of aluminium oxynitride films can be controlled by utilising design of experiment and evaluation with statistical software, delivering the correct deposition parameters. For all of the mentioned properties graphs are given depicting actual measurement results of 26 evaluated films.