Evaluating the via filling performance with thin surface Cu by the synergistic effect of different additives

Abstract

• 1-(4-Ethoxyphenyl)−5-mercapto-1H-tetrazole (EPTT) was investigated as a leveler. • Current density affects deposition potential and copper plating thickness. • A formulation with EPTT plated very thin copper on the surface. • Quantum chemical calculations predicted the reaction sites for EPTT. A small molecule compound 1-(4-Ethoxyphenyl)-5-mercapto-1H-tetrazole (EPTT) with sulfhydryl group was investigated as a leveler to develop an innovative DC acid copper via fill formulation for vertical continues plating applications. The synergistic effects of the electrodeposit current density and plating additives were investigated by galvanostatic measurements, optical microscope and cyclic voltammetry measurements. Molecular dynamics simulations show that EPTT is adsorbed on the copper surface in a parallel form. It is found that the electrodeposit current density not only affects the potential difference at different speeds of Cu rotating disk electrode, but also affects its deposition potential and the copper thickness on the surface. In combination with propyleneoxide-ethylene oxide-propylene oxide, Cl − , and bis-(3-sulfopropyl) disulfide, EPTT shows excellent microvia filling performances, which allow this formulation to plate very thin copper on the surface while filling the via. For instance, the via with a diameter of about 6 mils was seamlessly filled with only 19.7 μm Cu at the surface by the electrodeposit current density of 2 A/dm 2 .