关键词: 电镀铜, 印制电路板, 超级填孔, 多物理场耦合, 有机添加剂, 竞争吸附

Abstract:

Copper electroplating is the key technology for manufacturing of integrated circuit, packaging substrate, printed circuit board, and other electronic interconnection components. However, the electrochemistry and mechanism of deposition growth have not been fully elucidated, and the development of additives and bath maintenance are inseparable from a large number of experiments. This article reviews recent fundamental research and application progress in copper electroplating for printed circuit board industry, and these works are mainly dedicated by the research group of Printed Circuit and Printed Electronics from University of Electronic Science and Technology of China. First of all, a brief history of copper plating in printed circuit board is given. Then, modeling and simulation studies are introduced. A multi-physics coupling model is built on the basis of an electroplating bath, and an additive related parameter is introduced into the model to connect the convection intensity and the voltammetric response of the electrolyte. Base on tertiary current distribution, a relational model with the growth process of cathode surface related to micro-scale hole structure, plating current, convection intensity, additives etc., is obtained. Some applications using the above model are presented successively. By simplifying this model, a fast electrochemical evaluation method is developed to screen leveler candidates. Two dependent indicators, polarization overpotential of leveler injection (Δη) and deposition potential difference with low and high convection (ΔEr), are introduced, and the chemical having both high Δη and Δ Er may be an appropriate leveler. Fix the parameters of plating conditions and set TP as the index, the additive related parameter, size and structure of micro-scale hole are varied. It is feasible for a specific copper electroplating application couple to an appropriate additives’ pack. Then, a multi-physics modeling helping to optimize plating parameters of fine circuit pattern plating to meet the requirement of high thickness uniformity over the whole board has been demonstrated. Secondly, the mechanism of competitive adsorption of the organic additives has been discussed from the electrochemical results. The adsorption amount of the accelerator is independent of solution convection, but it shows dependency on the suppressor, and the adsorption strength of the accelerator is weaker than that of the suppressor. From that, a fast via-filling process is developed. Molecules of accelerator are selectively replaced from board surface but remained on via bottom by a mass-transport controlled pre-dip step of oxidant or suppressor, and the plating time of via filling is significantly shortened. Thirdly, the structure-electrochemistry relationship of series nitrogen heterocyclic oligomers is studied, and applications of the levelers and redox additive are discussed. Finally, a prospect on the research and application of copper electroplating has been made.

Key words: copper electroplating, electronic interconnection, super-filling, multi-physics coupling, organic additives, competitive adsorption