基于多场耦合效应的多孔介质填铜协同机制研究

The use of electrodeposited copper for filling micro-vias 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, the speed of signal transmission become faster and which decrease the reliability of the structure system, 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 through-hole and blind/buried microvia filling by copper electroplating are the electric field distribution. Furthermore, the uniformity of the electric field inside the hole is mainly determined by the synergistic interactions of those factors(the adsorption of chemical additives/current density/temperature field /vibration frequency), especially for the field synergy analysis. 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 multi-field coupling. This tempted us to investigate the filling mechanism in blind/buried microvias and through-hole metallization by copper electroplating with the different structural characteristics of the organic additives and its field synergy analysis for a copper interconnection system. The synergistic interactions of the multi-field in a copper plating solution for bottom-up filling of the blind/buried microvias and butterfly technology of through-hole filling 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 its field synergy analysis such as the structural properties of diverse additives have been further studied. The probability models of the multi-field coupling 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/buried microvias and butterfly technolgy of through-hole filling.

基于多场耦合效应的多孔介质填铜协同机制研究是制约高密度互连印制电路板和集成电路封装基板高阶高密度任意层互连特性及可靠性进一步发展的瓶颈，是目前国际上研究的热点和难点。经过前期的研究我们发现,影响微埋盲孔、通孔电镀填铜的主要问题在于二次电场线非等同性分布,而电镀添加剂、电流、温度、振动是影响电场线分布的关键因素,但基于多场耦合效应的多孔介质填铜协同机国内外还没有形成相应的理论,这使得电镀填铜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电镀添加剂、电场和温度场之间协同交互作用规律，研究Cu 互连微埋盲孔、通孔填充过程中多场耦合机制对铜沉积过程的影响，进一步建立相应的电场、温度场、电镀添加剂同电结晶铜作用机理模型，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，逐步完善多场耦合效应对多孔介质填铜的影响及其协同机制研究。

基于多场耦合效应的多孔介质填铜协同机制研究是制约高密度互连印制电路板和集成电路封装基板高阶高密度任意层互连特性及可靠性进一步发展的瓶颈，是目前国际上研究的热点和难点。基于多场耦合效应的填铜协同机理尚未完全清楚，本项目围绕高密度互连印制电路板电镀铜互连技术开展盲孔填铜、通孔电镀铜的研究，经过研究发现：（1）以三嵌段聚合物PEP作为抑制剂，SPS作为加速剂，使用旋转圆盘电极，研究了各种添加剂的独立作用以及相互作用。研究表明，PEP 与 Cl-之间存在显著的协同作用，在镀液含有Cl-及SPS时，对流越强，PEP 的抑制作用越强，抑制剂能抑制面铜沉积反应速率的同时加速剂能加速盲孔孔底沉铜速率，表明PEP在提高镀液填孔效果方面有优秀的表现：当电流密度 2A/dm2，液温 25℃，及空气搅拌速率为2.5L/min, 电镀60min后125um直径盲孔被沉铜层均匀填满，没有空洞和缝隙，且样品表面平整光亮。 （2）采用理论与实践相结合方法构建印制电路盲孔填铜模型，进行电镀盲孔填铜物理场之间的耦合。通过采用酸铜电镀组成的基础镀液体系进行盲孔铜填充。数值模拟结果表明，电场线在孔口聚集所形成的高电流密度区会导致夹断效应的产生，最终使孔内填铜形成空洞。而采用酸铜基础液和SPS、EO/PO 与 PEOPI的镀液体系进行盲孔填铜，盲孔孔底发生铜沉积反应使孔内有效沉积区域减小，这样单位体积内的SPS相对吸附量显著增加，从而加速孔底铜的沉积，加快孔内部铜的生长。在填铜后期，PEOPI 与SPS 存在竞争吸附，部分替代SPS有效抑制过填充现象。因此，通过 SPS、EO/PO 与 PEOPI 之间的协同作用可以实现盲孔填铜，研究表明盲孔填铜实验结果与数值模拟结论相一致。（3）此外，通孔填孔方面分别研究了气流量、硫酸、氯离子、整平剂、抑制剂浓度等对通孔填充效果的影响。研究表明气流量于填充效果具有重要影响，研究也表明高浓度SPS条件下，通孔填孔过程为蝴蝶式填充，而在低浓度加速剂条件下，铜沉积的总体趋势为沿着气流方向生长，为非蝴蝶式填充模式。