表面沾污对金铝键合脱键影响的微观机理分析

Microscopic Mechanism Analysis of the Influence of Surface Contamination on Disbonding in Gold-Aluminum Bonding

金铝键合脱键是一种电子元器件使用过程中严重的失效模式,其中键合表面沾污是一种导致该问题的常见原因。对表面沾污及无沾污样品分别进行粗铝丝键合和高温烘烤,然后对键合拉力、表面形貌、表面成分、聚焦离子束(FIB)剖面等进行测试对比,总结沾污导致键合失效的机理和特点。研究结果表明:表面无沾污的样品经历烘烤后键合拉力为720~801 g,失效模式为键合丝断裂;同样的条件下表面沾污样品的键合拉力为0~90 g,失效模式为脱键。通过对其表面及剖面分析发现,表面无沾污样品经过150℃下烘烤120 h后,金和铝之间可以充分扩散,形成均匀的金属间化合物;而表面沾污样品的污染物阻挡了金、铝扩散,或者限制了扩散区域,导致金和铝之间有效结合面积变小,使得该界面处形成缺陷源,以至于在后续高温烘烤过程中,金铝键合界面形成脆性的金属间化合物,同时产生内应力,进一步产生裂纹,最终发生金铝键合失效。

Disbonding in gold-aluminum bonding is a serious failure mode during the use of electronic components,the bonding surface contamination is a common cause of this problem.The coarse aluminum wire bonding and high temperature baking of samples with and without surface contamination were performed,and the bond pull force,surface morphology,surface composition,focused ion beam(FIB)cross-section were tested and compared to summarize the mechanism and characteristics of bonding failure caused by contamination.The study results show that the bond pull force of samples without surface contamination is 720-801 g after baking,the failure mode is the fracture of the bonded wire.Under the same conditions,the bond pull force of samples with surface contamination is 0-90 g,the failure mode is disbonding.Through analysis of surface and cross-section,it is found that after baking of samples without surface contamination at 150℃for 120 h,there is sufficient diffusion between gold and aluminum to form a uniform intermetallic compound.However,the pollutants of samples with surface contamination hinder the diffusion of gold and aluminum,or restrict the diffusion area,resulting in a smaller effective bonding area between gold and aluminum,resulting in the formation of a defect source at the interface,so that in the subsequent high temperature baking process,a brittle intermetallic compound forms at the gold-aluminum bonding interface,while generating internal stress and further leading to crack formation,and finally the gold-aluminum bonding failure occurs.