Effect of chlorine on gold-titanium thin films

Abstract

In this study the effect of a small concentration of chlorine on gold-titanium metallization was investigated. Samples were prepared by deposition of gold and titanium layers on a glass substrate. Samples were exposed at 75, 135 and 175° C for 53 days to an argon atmosphere and to an argon atmosphere containing 50 ppm chlorine. In all cases the electrical resistance of the exposed samples decreased and the addition of chlorine made this decrease even larger. Depending on the conditions, migration of the titanium atoms and formation of preferred oriented structure took place. At 135 and 175° C in the argon atmosphere containing 50 ppm chlorine, a very active migration of titanium atoms from the gold layer to the external surface of the samples was observed. Migration of titanium was not observed in the samples exposed to the pure argon atmosphere. This strongly suggests that chlorine acts as an agent bringing titanium from the gold layer to the external surface by a process known as chemisorption-induced segregation; on the surface titanium forms an oxide. When samples were exposed for 53 days at 175° C, preferred oriented structure in the gold layer was developed. Formation of the preferred oriented structure was neither conditioned nor related to the presence of chlorine in the atmosphere.