螯合剂与氧化剂协同降低CMP中Co/Cu电偶腐蚀

Reduction of Galvanic Corrosion between Cobalt and Copper in CMP by Chelation and Oxidation

钴（Co）作为10 nm及以下技术节点的铜互连极大规模集成电路（GLSI）的新型阻挡层材料,在阻挡层化学机械抛光（CMP）中易与铜（Cu）发生电偶腐蚀。本文采用电化学、CMP、静态腐蚀实验以及扫描电镜（SEM）表征方法,研究了弱碱性抛光液中螯合剂和氧化剂在Co/Cu电偶腐蚀中的协同作用。研究表明：抛光液中的氧化作用,使得Co和Cu表面生成一层由氧化物及氢氧化物组成的钝化膜,抑制了Co和Cu的静态腐蚀;多羟多胺螯合剂浓度增加,抛光液pH升高,Co和Cu表面钝化膜的生成加快;CMP过程中,Co和Cu腐蚀电位均有明显降低,去除速率均加快。抛光液组分为1.5 ml·L-1H2O2、0.1%FA/O螯合剂、30%AEO-9、5%硅溶胶（质量分数）时,Co的腐蚀电位低于Cu的腐蚀电位;研磨状态下,Co/Cu腐蚀电位差降到-6 m V,电偶腐蚀电流很小,极大地减弱Co/Cu电偶腐蚀。同时,Co的去除速率为130 nm·min-1,Cu的去除速率为76.5 nm·min-1,Co与Cu的静态腐蚀均不明显,可以很好地满足阻挡层CMP要求。

Cobalt as the copper-interconnects barrier in the 10 nm Node（or next techniques node） great-large scale integrated circuit（GLSI）,was prone to have galvanic corrosion during chemical-mechanical polishing（CMP） with copper. The synergistic reaction of chelating agent and hydrogen peroxide on Co/Cu galvanic corrosion in weak alkaline slurry were investigated. The results of electrochemical experiments,polishing experiments and static corrosion experiments indicated that the passive film was composed of oxide and hydroxide on the surface of cobalt and cooper could inhibit the corrosion due to the enhanced oxidation by increasing hydrogen peroxide concentration. The formation of passive film became faster as a result of the pH rise because of the increasing multi hydroxyl polyamine chelating agent concentration; during the CMP process,both the corrosion potential of cobalt and copper decreased and the removal rate of cobalt and copper were increased. When the slurry was composed by 1. 5 ml·L-1 hydrogen peroxide,0. 1% FA/O,30% AEO-9,5% silica（mass fraction）,copper had higher corrosion potential than cobalt and the galvanic corrosion could be reduced effectively when the difference of open circuit potential between them decreased to-6 m V. Meanwhile,the removal rate of Co was 130 nm·min-1,the removal rate of Cu was 76. 5 nm·min-1,and the static corrosion of Co/Cu was very weak which could be very good for meeting the requirements of barrier CMP.