电子电镀铜新体系中添加剂对铜电沉积及镀层结构的影响机制

以低主盐浓度、 弱碱性、 复合配位的柠檬酸盐电子电镀铜新体系为研究对象, 阐明了新型添加剂XNS(聚胺类化合物和含氮化合物的混合物)在新电沉积铜体系中的作用. 恒电流沉积实验结果表明, 添加剂XNS能够提高铜沉积的电流效率, 特别是在2.0 A/dm²电流密度下, 添加剂XNS使铜沉积电流效率达到95.4%, 提高了17.5%. 电化学实验的结果表明, 添加剂XNS改变了铜沉积的电极过程, 由原来的两步单电子还原过程 Cu(Ⅱ)+e→Cu(Ⅰ)+e→Cu]转变为一步两电子还原过程Cu(Ⅱ)+2e→Cu]. 虽然添加剂XNS呈现促进铜电沉积的特征, 即还原电流增大, 但铜镀层颗粒却更细小、 更致密均匀. 在2.0 A/dm²电流密度下, 铜镀层晶体结构由无添加剂时的(111)晶面重构为高择优取向的(200)晶面.

Effects of Additive on the Electrodeposition and Coating Structure in a Novel System of Electronic Copper Electroplating

Electronic copper electroplating has important applications in the advanced electronic manufactu-ring industry. In this work， the effects of the additive XNS（a mixture of polyamine and nitrogen-containing compounds） on the coating structure in the novel， weakly alkaline and citrate-based multi-coordination system for copper electronic electroplating with low concentration of main salts（10 g/L copper sulfate） was investiga-ted. The constant current deposition experiments indicate that the additive XNS can increase the current efficiency of copper electrodeposition， which achieves 95.4% at a current density of 2.0 A/dm² and increases by 17.5% comparing to the electroplating system without XNS. Electrochemical experiments prove that the additive XNS can change the cathodic reduction of Cu（Ⅱ） cations， i.e.， in presence of XNS which is a one-step two-electron process［Cu（Ⅱ）+2e→Cu］， and in absence of XNS which is a two-step one-electron processes ［Cu（Ⅱ）+e→Cu（Ⅰ）+e→Cu］， and improves the reduction current density of Cu electrodeposition. Although additive XNS can accelerate copper electrodeposition rate， the coating surface of Cu becomes much finer and neater. At the current density of 2.0 A/dm²， the crystal structure of copper coating is reconstructed from Cu（111） facet to Cu（200） facet， presenting highly preferred crystal orientation in the presence of XNS.