An effective triblock copolymer as a suppressor for microvia filling via copper electrodeposition

In this work, an effective suppressor was found in copper electroplating solution for microvia filling. The suppressor is a triblock copolymer comprised of ethylene oxide (EO)-propylene oxide (PO)-ethylene oxide (EO) with a molecular weight of 2900 (EPE 2900). In terms of the obtained filling performance evaluated by observing the obtained cross-sectional views of the microvias after electroplating, the electroplating solution was systematically studied as functions of Cl− concentration, EPE 2900 concentration, and convection conditions. It was found that filling performance was greatly dependent on these key factors. In the developed copper electroplating formulation, EPE 2900 was able to yield sufficient filling performance in a broad Cl− concentration ranging from 3 to 200 ppm, although the optimized value was determined to be about 30 ppm in terms of the best filling performance. During the microvia filling process, Cl− concentration, EPE 2900 concentration, and forced convection would affect each other. Their interactions were studied based on the anchor effect of Cl− on the adsorption of EPE 2900 on Cu substrates. In doing so, extensive electrochemical experiments including galvanostatic measurements, linear sweep voltammetry, electrochemical impedance spectroscopy and cyclic voltammetry were employed to study the adsorption behavior of EPE 2900 on the cathode during both the copper electrodeposition and dissolution processes. An adsorbing mechanism of EPE 2900 on cathode was proposed to elucidate the promotional role in improving the microvia filling performance.