Hf-based barrier layers for Cu-metallization

It is well known that due to interaction between Cu and Si in the regions of source and drain copper interconnections should not be in direct contact with Si. In this study the barrier properties of Hf-based thin films were investigated. Hafnium nitride films (15nm) and multilayer Hf-Si structures (50 alternate 0,2 nm-Hf and 0,4 nm-Si layers) were prepared by electron beam evaporation. Hf-Si sandwiches were annealed at 700 degrees C and 900 degrees C for 2 min to form silicide. Then 100 nm thick copper layers were deposited on the samples. For the Cu/HfNx/Si contact system the interfacial reactions between Cu, Hf and Si were observed after annealing at 500 degrees C for 30 min by profile Auger analysis. The HfNx barrier fails and Cu atoms penetrate into the Si substrate. On the other hand Auger analysis results for Cu/HfSix/Si structure showed that there were not diffusion of Cu atoms in barrier layer and Si substrate. Findings demonstrate that hafnium silicide barrier layers can be used to prevent interfacial reactions between copper interconnections and silicon regions of source and drain.