Statistical approach for optimizing sputtering conditions of highly oriented aluminum nitride thin films

Design of experiments and the analysis of Variance (ANOVA) are very efficient methods to optimize the sputtering conditions for highly c-axis oriented aluminum nitride (AlN) thin films. The effects of the five sputtering control factors. substrate temperature, nitrogen concentration, rf power, sputtering pressure and sputtering time, were simultaneously investigated by only 16 experiments. It could be proved statistically at the 5% level that the substrate temperature, the rf power and the sputtering pressure are significant control factors for the crystal orientation of the films. Especially, the rf power is the most important control factor. On the other hand, the effects of the nitrogen concentration and the sputtering time are not statistically significant. Our results were ascertained at the 95% confidence level. The full width at half-maximum (FWHM) of the X-ray rocking curves of the film deposited under the optimized sputtering conditions was 2.7 degrees (sigma=1.6 degrees). The orientation of the film was the highest of the films deposited on glass substrates reported to our knowledge. (C) 1998 Elsevier Science S.A.