Surface structuring and phase formation in thin metallic layers deposited at various temperatures

Scanning electron microscopy, atomic force microscopy and XRD analyses were performed for the study of the influence of the substrate temperature during deposition on the surface structuring and phase formation on thin metallic double layers. Thin layers of Au, Cr, Al and Cr were deposited at 150 and 300 °C on 30-nm Cu layers evaporated on (100) wafer Si substrates. Possible applications of such layers are Raman active surfaces and model layers for diffusion experiments. The topographical investigation revealed an increase with temperature of surface structuring that is related to the formation of intermetallic and oxide phases. At 150 °C deposition temperature, the average roughness of the films was determined to 2 – 3 nm and the surfaces appeared smooth. In agreement with previous ion beam analysis measurements, a significant surface roughness occurred at 300 °C depending on the type of the metallic films. The lowest average surface roughness value was measured for the Al/Cu/Si system (Ra = 14.1 nm). About double the roughness was measured for the Au/Cu/Si and Cr/Cu/Si layer systems. In contrast, single Cu layers a high value of Ra = 93.0 nm was determined. The combined analyses showed that the formation of intermetallic phases, such as AlCu and CuAl2, reduces a surface roughening. However, the formation of oxide phases, such as CuO2, increase the average surface roughness.