Dielectric Degradation of Cu/ SiO2/Si Structure during Thermal Annealing

Abstract

The impact of Cu on the dielectric layer was studied using a Cu//Si metal oxide semiconductor capacitor and rapid thermal annealing (RTA) treatment. With the RTA treatment, no chemical reaction was observed up to 900°C; however, dielectric degradation occurred following RTA at 300°C for 60 s and became worse with the increase of annealing temperature. The interface‐trap density at the /Si interface also increased from 5 × 1010 to after 800°C RTA treatment. The RTA anneal introduced a large number of positive Cu ions into the dielectric layer. Under bias‐temperature stress, Cu ions drift quickly in the layer and may drift across the /Si interface and enter the Si substrate. With the use of 1200 Å thick TiN and TiW barrier layers, respectively, the dielectric strength of the Cu/(barrier)//Si structures was able to remain stable up to 500 and 600°C.