基于Cu互连微埋盲孔填充的形成机制及电化学性能研究

The use of electrodeposited copper for filling blind/buried microvias has become a new research hotspot in the field of the Cu interconnected of any layer of both HDI printed circuit boards and IC package substrates. As both microvia dimensions and trace widths become smaller, and the speed of signal transmission become faster, the ability of copper filling processes to consistently produce void-free copper filled microvias and traces with acceptable cross sectional profiles comes under increasing pressure. After a long research we found that the main factors which determine the microvia filling performance of the copper electroplating are the electric field distribution. Furthermore, the uniformity of the electric field inside the hole is mainly determined by the adsorption of chemical additives, especially for the suppressor. Although various experimental techniques and orthogonal design methods have been developed to ensure proper concentration of every additive in the copper plating solution, little is known about the relation between the electric field distribution and structural properties of diverse additives in such a complicated formula. This tempted us to investigate the filling mechanism in blind and buried microvias metallization by copper electroplating with the different structural characteristics of the organic additives for a copper interconnection system..The synergistic interactions of three components (suppressor/accelerator/ leveler) in a copper plating solution for bottom-up filling of the blind and buried microvias have been characterized by electrochemical experiment、quantum chemical calculations and scanning electronic microscopy (SEM).Compared with the theory analysis of single via filling and the actual process of plating, the mechanisms of interaction between the electric field distribution and structural properties of diverse additives have been further studied. The probability models are correspondly established based on the experimental results. After completion of the project, it will break the development bottleneck in the field of high-end HDI PCB and IC package substrates and provides theoretical basis for bottom-up filling of the blind and buried microvias.

Cu互连微埋盲孔电镀填充机理研究是制约高密度互连印制电路板和集成电路封装基板多阶任意层互连性能及信号传输速率进一步发展的瓶颈，是目前国际上研究的热点和难点。经过长期的研究我们发现,影响微埋盲孔电镀填铜的主要问题在于二次电场线分布,而电镀添加剂是影响电场线分布的关键因素,但电镀添加剂与电场线分布的相互作用规律国内外还没有形成相应的理论,这使得电镀添加剂的研究变得极为困难。本项目旨在已有的基础上应用电化学分析方法、量子化学及表面分析技术深入探讨各类平整剂、加速剂和抑制剂之间协同交互作用规律，研究Cu互连微埋盲孔填充过程中不同活性结构化合物（电镀添加剂）对铜沉积过程的影响，进一步建立相应的电镀添加剂同电场线作用机理模型，从理论上阐释各类添加剂官能团结构衍生物对电场线分布的影响规律及作用机理，逐步完善微埋盲孔填充理论，为打破Cu互连微埋盲孔电镀填充技术瓶颈提供基础理论依据。

Cu互连微埋盲孔电镀填充机理研究是制约高密度互连印制电路板和集成电路封装基板多阶任意层互连性能及信号传输速率进一步发展的瓶颈，目前电镀添加剂抑制-吸附机理尚未完全清楚，经过研究发现：（1）Nyquist图由高频区代表电荷转移过程的一个大容抗弧，和特定浓度下低频区的扩散控制过程造成的Warburg阻抗构成，实验获得了铜电极界面的抑制剂分子的吸附热力学参数及分子结构等同抑制剂效率之间关系的阻抗谱图解析结果，其传质机制与温度、浓度、抑制剂介质吸脱附有关；（2）对影响PCB板深孔电镀的因素进行了分析，利用Minitab统计分析软件对硫酸铜浓度，电流密度，有机添加剂组成，震动频率等因素研究表明：光亮剂和辅助剂的综合作用，不但可提高深镀能力，而且还能增强镀层延展性；（3）吸附等温模型研究结果表明所研究的抑制剂分子在硫酸介质中取代铜棒表面的水分子数时分别服从 Dhar-Flory-Huggins 和 Bockris-Swinkels 吸附等温模型，随着温度是升高，取代水分子的数目 X 及吸-脱附平衡常数 K 呈现先增加后减小的趋势且在 298K 时取代水分子的个数出现峰值。当抑制剂浓度接近约 10-3mol/L 时，抑制效率随温度的升高而发生呈现先增加后减小的趋势表明抑制剂在较高的实验温度下都能很好的在铜棒表面吸附，并改变了相应的电场分布。