An effective triblock copolymer as a suppressor for microvia filling viacopper electrodeposition

In this work, an effective suppressor was found in copper electroplating solution for microvia filling. Thesuppressor is a triblock copolymer comprised of ethylene oxide (EO)-propylene oxide (PO)-ethyleneoxide (EO) with a molecular weight of 2900 (EPE 2900). In terms of the obtained filling performanceevaluated by observing the obtained cross-sectional views of the microvias after electroplating, the elec-troplating 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 fac-tors. In the developed copper electroplating formulation, EPE 2900 was able to yield sufficient fillingperformance in a broad Cl-concentration ranging from 3 to 200 ppm, although the optimized value wasdetermined to be about 30 ppm in terms of the best filling performance. During the microvia filling pro-cess, Cl-concentration, EPE 2900 concentration, and forced convection would affect each other. Theirinteractions were studied based on the anchor effect of Cl-on the adsorption of EPE 2900 on Cu sub-strates. In doing so, extensive electrochemical experiments including galvanostatic measurements, linearsweep voltammetry, electrochemical impedance spectroscopy and cyclic voltammetry were employedto study the adsorption behavior of EPE 2900 on the cathode during both the copper electrodepositionand dissolution processes. An adsorbing mechanism of EPE 2900 on cathode was proposed to elucidatethe promotional role in improving the microvia filling performance.