Stability of silver thin films on various underlying layers at elevated temperatures

Abstract

The stability of silver thin films on various substrates has been studied and the results are compared to the copper films under the similar conditions. The compatibility of silver with underlying substrate materials is important for device performance and reliability. Ag and Cu films are deposited on various barrier materials such as TiN, Ti(O)N, TaN, TiW and on dielectrics viz. phosphorus silicate glass, boron phosphorus silicate glass, and tetraethylorthosilane. The morphology and effect of thermal stability at high temperatures are studied using backscattering analysis method and also electrical resistance is monitored with four point probe measurements. The silver films are stable on the most of the barrier layer up to 700 °C for 30 min in vacuum while films on dielectrics are less stable. The copper films show similar behavior though in some cases its more stable compared with silver. The film stability seems to be affected by the underlying materials which in turn affects microstructure, diffusion characteristics, and stress levels of the silver or copper films deposited on the top.