Electroanalytical Study of Organic Additive Interactions in Copper Plating and Their Correlation with Via Fill Behavior TIMOTHY B. HUANG , 1,3 HIMANI SHARMA, 1 RAHUL MANEPALLI, 2 SASHI KANDANUR, 2 VENKY SUNDARAM, 1 and RAO R. TUMMALA 1 1.—Packaging Research Center, Georgia Institute of Technology, 813 Ferst Dr NW, Atlanta, GA 30332, USA. 2.—Intel Corporation, 5000 W Chandler Blvd, Chandler, AZ 85226, USA. 3.—e-mail: tim.huang@gatech.edu In this study, individual interactions between various classes of organic additives in electrolytic copper plating solutions are characterized by elec- troanalytical methods. Cyclic voltammetry and chronopotentiometry were used to compare cases of sequential and competitive adsorption of additive combinations to the Cu cathode. Of the polyalkylene glycol (PAG) suppressors investigated, polypropylene glycol was in general a weaker suppressor than polyethylene glycol, showing weaker polarization of the Cu cathode and faster depolarization when combined with bis(sodium sulfopropyl)disulfide (SPS). The rapid depolarization of PAG with SPS resulted in a conformal Cu filling behavior in blind-vias. By itself, the leveler molecule polyvinyl pyrrolidone (PVP) shows very weak and slow suppression compared to the PAG-type suppressors, but depolarization of the Cu cathode is prevented when combined with SPS. The weak polarization of PVP combined with SPS resulted in sub- conformal filling behavior in blind-vias. The potential response of SPS, PAG, and PVP combined was found to be the sum of their individual interactions: PAG adsorbs rapidly to strongly polarize the cathode, but PVP prevents depolarization with time from SPS. This strong and consistent polarization outside the vias resulted in a superconformal filling behavior, with more than twice the thickness of Cu plated in the vias than outside. Key words: Copper, electroplating, metallization INTRODUCTION Increased demands for high-performance and multifunctional electronics in smaller form factors are driving the development of advanced packaging technologies. Achieving high logic-memory band- width and I/O density requires the IC package to support high wiring density and fine-pitch through- package-vias (TPVs) as seen in recent 2.5-D and 3-D system packages. 1 TPVs and blind-vias that are fully-filled with Cu are desired over conformally- plated copper due to lower DC resistance, improved power integrity, and superior thermal dissipation. 2 Fully-filled Cu blind-vias are typically fabricated by depositing a thin, conformal Cu seed layer followed by electrolytic Cu plating in an aqueous electrolyte comprised of an acid, Cu salt, and organic additives. The organic additives are crucial for modifying the Cu 2+ reduction rate in a way that achieves ‘‘bottom-up filling’’ or ‘‘superfilling’’ in vias, where Cu plating is promoted inside the vias while inhibiting plating on the surface regions outside the vias. 3 The effect of a given additive on the Cu 2+ reduction kinetics, and therefore the via filling profile, depends on where the additive molecules adsorb relative to the via geometry, its interaction with the Cu cathode surface, and other additives in the electrolyte. Akolkar and Moffat studied the interactions between common accelerator and sup- pressor additives and proposed a widely-accepted (Received October 11, 2017; accepted September 14, 2018) Journal of ELECTRONIC MATERIALS https://doi.org/10.1007/s11664-018-6680-0 Ó 2018 The Minerals, Metals & Materials Society