Optimizing hardness of CNx thin films by dc magnetron sputtering and a statistical approach

We have investigated the effects of seven sputtering control factors on the hardness of carbon nitride (CNx) thin films by design of experiments and t he analysis of variance (ANOVA) to synthesize hard CNx thin films. It was d etermined statistically that the substrate temperature, the sputtering pres sure and the target to substrate distance are significant control factors f or the hardness of the CNx thin films within the experimental range of this study. Especially, the distance is the most important control factor of th e seven factors; the hardest films are obtained at the distance of 4.5 cm. On the other hand, the effects of the substrate treatment, the dc power, th e nitrogen concentration and the sputtering time are not statistically sign ificant. It is suggested that these statistical methods are effective to co mpare the importance of many sputtering control factors. The CNx thin films deposited under the optimized sputtering conditions exhibit a relatively h igh hardness value of 55 +/- 11 GPa, Young's modulus of 228 +/- 21 GPa and an elastic recovery (%R) of 98%. The compressive stress in the films is a l ow value of 0.3 GPa. (C) 2001 Kluwer Academic Publishers.