Roughness scaling of cyclical electrodeposition/dissolution of copper

Successful application of copper electrodeposition in nano-interconnects strongly depends on its surface roughness scattering. The understanding of the individual deposition/dissolution processes and their combined effects during multiple cycling is fundamentally important for both technological applications and natural phenomena. Previous study of surface roughness dealt with a single process of growth or recession, however in many natural phenomena and technological applications, both processes of deposition and dissolution alternate to generate a rough surface.; The kinetic roughening of copper during cyclical electrodeposition/dissolution in CuSO4 solution was experimentally studied. The scaling exponents alpha and beta of the primary processes were determined and compared to those obtained from cycling. In the early time regime, the roughness is predicted to grow as nbeta. Roughness saturates to a maximum value in the late-time regime and scales with the system size L as Lalpha, where n is the number of cycles, alpha and beta are the roughness and growth exponent respectively. This study focuses on kinetic surface roughness in two interesting directions, namely the effect of the number of cycles on surface roughness and the effect of the relative duration of the individual processes within each cycle. The relations between the cyclical exponents and corresponding exponents of the primary processes are also studied. The roughness is found to increase as a power law of n, consistent with the anticipated theoretically scaling behavior. The results also show a crossover of the growth exponent beta from self-affine to mounded regime after a critical thickness of copper deposit is attained.; The scope of this work also includes finding an alternative to the use of organic additives in copper plating bath to achieve super filling of trenches/vias. As bath additives are slowly consumed, they must be continuously monitored and periodically replenished, this proves to be a difficult task to maintain. An additive free process would lower cost and monitoring of both additives and the actual process. Super filling of trenches/vias was investigated by electroplating from a copper sulfate bath containing a complexing agent, completely eliminating the need for additives. Acetonitrile as a complexing agent has been experimented with and found to aid super filling without the undesired precipitation of the cuprous complex.