Evolution Of Cu/Sio2 And Cu/Ta Interface Roughness With Annealing

The scattering of conduction electrons by surface roughness has been considered a key contribution to increased resistivity of nanoscale Cu conductors. To study the evolution of surface (interface) roughness with annealing, a series of SiO2 and Ta/SiO2 encapsulated Cu thin films were prepared. Samples were subsequently annealed at 150° and 600° for 30 minutes in a reducing gas to assess the thermal stability of the Cu interfaces and the tendency for void formation. Specular X-ray reflectivity was used to separately determine the root mean square roughness for both the upper and the lower Cu/SiO2 (or Cu/Ta) interfaces. Notable differences in the roughness evolution between upper and lower interfaces were observed for SiO2 encapsulated thin films. The Ta/SiO2 encapsulated films are found to evolve little as compared to the SiO2 encapsulated films. © 2010 Materials Research Society