Investigation of novel leveler Rhodamine B on copper superconformal electrodeposition of microvias by theoretical and experimental studies

Achieving void-defect copper filling by electrodeposition on microvias is essentially important. Rhodamine B (RhB) is of excellent suppressing ability based on electrochemical analysis. Convection-dependent adsorption analysis demonstrates that 100 mg/L was the optimum value to achieve bottom-up growth. The interaction among sodium 3,3′-dithiodipropane sulfonate, polyethylene glycol, and RhB was investigated and competition adsorption between RhB and SPS is observed. Meanwhile, copper electrodeposition obeys 3D diffusion-controlled progressive nucleation process at low potential but obeys 3D diffusion-controlled instantaneous nucleation process at high overpotential. Density functional theory and in situ Raman spectra were used to study the adsorption behavior of RhB. The calculated results indicates that RhB can effectively increase the energy barrier during copper electrodeposition. The surface morphology is improved and surface roughness is lowered with proper RhB concentration. The influence of RhB on orientation and grain size was analyzed and proper RhB (100 mg/L) is conducive to the formation of Cu (1 1 1) surface and lowering the grain size. Besides, the introduction of RhB can improve the wettability, which is conducive to the bottom-up growth. The electroplating process is optimized and void-defect copper interconnect line with high quality is obtained.