等离子清洗对Cu/Al引线键合焊点表面状态和力学性能的影响  

Influence of plasma cleaning on the surface state and mechanical properties of Cu/Al wire bonding joint

作　　者：李晓 杜亚红 高丽茵 袁晓虹 周文艳 康菲菲 刘志权 LI Xiao;DU Yahong;GAO Liyin;YUAN Xiaohong;ZHOU Wenyan;KANG Feifei;LIU Zhiquan(Shenzhen Institute of Advanced Technology,Chinese Academy of Sciences,Shenzhen,518055,China;Institute of Metal Research,Chinese Academy of Sciences,Shenyang,110016,China;Sino-Platinum Metals Co.,LTD.,Kunming,650106,China)

机构地区：[1]中国科学院深圳先进技术研究院,深圳518055 [2]中国科学院金属研究所,沈阳110016 [3]云南省贵金属新材料控股集团股份有限公司,昆明650106

出　　处：《焊接学报》2024年第12期14-19,共6页Transactions of The China Welding Institution

基　　金：稀贵金属综合利用新技术国家重点实验室开放课题(SKL-SPM-201803);广东省基础与应用基础研究基金面上项目(2022A1515011485);云南省刘志权专家工作站(202005AF150045);云南贵金属实验室科技计划基础研究项目(YPML-2022050222)。

摘　　要：等离子清洗作为一种前处理工艺广泛应用在引线键合、铜-铜键合和混合键合等半导体领域,基于微观表征、统计分析和性能测试等方法研究了等离子清洗对引线键合焊点表面状态和力学性能的影响,结果发现经过处理后,焊盘表面水滴接触角由96°降低至12.6°,每个焊盘表面平均污染颗粒数量由18.7±9.9个下降至3.7±1.6个,平均剪切力由165.6±5.9mN提升至179.3±3.9 mN.另外随着处理时间的适当延长可以提高焊球剪切力和稳定性,对经过3次回流+高温存储测试后失效的焊点(试验前未进行等离子处理)进行分析,发现裂纹萌生于铝焊盘和铜焊球界面处,裂纹沿着CuAl2界面拓展并导致键合失效,分析原因是焊盘表面有机污染促进了界面处柯肯达尔空洞的形成,进而在热机械应力的影响下形成裂纹并失效.结果表明,等离子清洗可以有效提高焊盘表面清洁度并提升键合可靠性,可在引线键合工艺中优化推广.As a pretreatment process,plasma cleaning is widely used in semiconductor industry such as wire bonding,copper-to-copper bonding and hybrid bonding.The effects of plasma cleaning on the surface state and mechanical properties of Cu/Al wire bonding joints were studied by microscopic characterization,statistical analysis and performance testing.The results showed that after plasma treatment,the contact angle of water droplets on the pad surface decreased from 96°to 12.6°,the average number of contaminated particles on each pad surface decreased from 18.7±9.9 to 3.7±1.6,and the average shear force increased from 165.6±5.9 to 179.3±3.9mN.In addition,it is found that the shear force and stability of the welding ball can be improved with the proper extension of the processing time.The bonding joints that failed after three times reflow and high temperature storage tests(without plasma treatment before the experiment)were analyzed.It was found that the crack originated at the interface of aluminum pad and copper ball,and it expanded along the CuAl_(2) interface and led to bonding failure.The reason for the failure may be that the organic pollution on the surface of the pad promotes the formation of Kirkendall void,and then cracks are formed and the failure occurs under the influence of thermal mechanical stress.It is concluded that plasma cleaning can effectively improve the surface cleanliness of the pad and improve the bonding reliability.Highlights:(1)Statistical analysis was used to clarify the influence of plasma cleaning treatment on the number of contaminated particles on the pad surface and shear force of bonding joint.(2)Failure analysis was carried out on the multiple reflow and high-temperature storage bonding joints without plasma cleaning treatment to clarify the failure mode and failure mechanism.

关 键 词：引线键合 等离子清洗 表面污染 剪切力 失效分析 

分 类 号：TG442[金属学及工艺—焊接]