In-Situ Measurements of Stress during Electrodeposition of Copper Nanofilms: Effect of Growth Rate and Additives

Stress was measured in situ during electrodeposition of copper nanofilms. Grain size was measured using both in-situ AFM and ex-situ SEM imaging and showed that grain size increased with time for about the first 10 depositions and thereafter became approximately constant. Films deposited at low growth rates had compressive stress while films deposited at higher growth rates had tensile stress. The transition from compressive to tensile stress occurred at a growth rate of ~1 nm s-1, in reasonable agreement with the literature. Our data supports Chason's model for stress development during thin film deposition. Addition of chloride gives decreased stress, a rougher surface and larger grains. Addition of PEG alone has very little effect on the stress in the deposit. The reduction in stress due to chloride is still observed when PEG is also added and this greatly reduces the surface roughness which occurs with the addition of chloride alone.