An electrochemical study on the effects of electrolyte additives on metal electrodeposition

Abstract

The electrolyte additives have a significant effect on the improvement of the properties of the electroplating. Especially, copper electroplating is widely used in the fabrication of semiconductors and printed circuit boards (PCBs), because of it excellent electric conductivity and high productivity. Recently, with the development of fifth-generation (5G) communication modules, there is increasing interest in 5G mm-wave antenna-in package (AiP) substrate consisting of more than 10 layers. For the production of high-density multi-layer PCB, a microvias are used to connect adjacent layers. The fully filled microvias have the advantage of increasing substrate density and signal transmission. To fill the microvias, low concentration of chemical additives such as a suppressor, an accelerator and a leveler are contained the copper electroplating solution. However, during the electroplating, the additives are decomposed and the filling performance are decreased. In general, the plating solutions contain hundreds of ppm of suppressor and less than 10 ppm of an accelerator and leveler. With the highest concentration, suppressors have the most significant effects on the filling performance of the microvias. The suppressors with a larger molecular weight (MW) inhibits the Cu reduction on the substrate surface more effectively, leading to higher filling performance. However, during the electroplating process, PEG molecules are decomposed through a hydrolysis reaction at the cathode and the filling performance is decreased. Therefore, it is necessary to study the accuracy improving the filling performance prediction and improvement of filling performance on plating solutions contained decomposed suppressors. Furthermore, a study was performed to improve the cycle stability by controlling the dendrite growth of lithium metal electrode by applying an additive that is used for electrolytic copper plating. Herein, three individual studies are conducted on improving accuracy microvias filling performance prediction of solution contained decomposed suppressor, improvement of filling performance in copper electroplating, and on the stability enhancement of lithium metal secondary batteries. In the first part, the filling performance prediction of electroplating solutions containing the decomposition suppressor conducted using an electrochemical characterization. The filling performance of electroplating solutions increase high accuracy considering both the cathodic potential and potential difference. The second part is the study of effects of suppressor MW on the filling performance in Cu electroplating. When the MW of suppressors increased, the optimal chloride concentration increased. The in the third part, the cycle stability of lithium secondary batteries are improved by adding suppressor and leveler to electrolyte.