钴插塞化学机械平坦化的抛光液组分优化

目的提高Co在超大规模集成电路全局化学机械抛光过程中的去除速率及Co/Ti去除选择比,并对去除机理进行详细描述。方法研究不同浓度的磨料、多羟多胺络合剂(FA/OII)、氧化剂等化学成分及不同pH值对钴去除率的影响。利用电化学实验、表面化学元素分析(XPS)揭示钴实现高去除速率的机理,通过原子力显微镜(AFM)对钴抛光前后的表面形貌进行了观察,并采用正交实验法找到抛光液最佳组分配比。结果随磨料浓度的升高,钴去除速率增大。随pH值的升高,钴去除速率降低。随氧化剂浓度的提升,钴去除速率升高,但Co/Ti去除选择比先升后降。随螯合剂浓度的增大,钴去除速率及Co/Ti去除选择比均先升后降。正交试验找到了最佳的抛光液配比及条件(3%磨料+20 mL/L多胺螯合剂(FA/OⅡ)+5 mL/L氧化剂(H_2O_2),pH=8),实现了钴的高去除(～500 nm/min)及较好的Co/Ti去除选择比(100:1)。并且,表面的平坦化效果明显提高,原子力显微镜测试结果显示Co面粗糙度由原本的3.14 nm降低到0.637 nm。结论采用弱碱性抛光液能有效提升钴的去除速率,并保证腐蚀可控。抛光液中同时含有氧化剂和螯合剂时,通过强络合作用实现了钴的抛光速率和Co/Ti去除选择比的大幅度提升。

Component Optimization of Polishing Slurry on Chemical Mechanical Planarization of Cobalt Contact

The work aims to improve removal rate of Co and removal selection ratio of Co/Ti in global chemical mechanical polishing process of Very Large Scale Integration Circuit (VLSI), and describe removal mechanism of Co in detail. The effects of different concentrations of abrasives, polyhydroxypolyamine complexing agents (FA/O II) and oxidants, and different pH values on cobalt removal rate were studied. The mechanism of high Co removal rate was revealed by performing electrochemical experiments and surface chemical element analysis (XPS), and surface morphology of cobalt before and after polishing was observed by atomic force microscope (AFM). Optimum distribution ratio of polishing slurry was detected by performing orthogonal experiment. The removal rate of cobalt increased as the concentration of abrasive increased, and decreased as pH value increased. As oxidant concentration increased, removal rate of cobalt increased while removal selection ratio of Co/Ti firstly increased and then decreased. As the concentration of chelating agent increased, both removal rate of cobalt and removal selection ratio of Co/Ti firstly increased and then decreased. The orthogonal test found that the optimum distribution ratio of polishing slurry (3% abrasive, 20 mL/L polyamine chelating agent (FA/O II) and 5 mL/L oxidant (H2O2), pH=8) realized high removal rate of cobalt (~500 nm/min) and better removal selection ratio of Co/Ti (100:1). Besides, the planarization effect of surface was obviously improved. Atomic force microscope test results showed that Co surface roughness changed from 3.14 nm to 0.637 nm. The weakly alkaline polishing slurry can effectively improve removal rate of cobalt and ensure that corrosion is controllable. The combination of H2O2 and FA/O II in the polishing slurry could significantly improve polishing rate of cobalt and removal selection ratio of Co/Ti. It can be attributed to the strong complexation reaction on the surface of Co which results in the formation of the easily removable water-soluble complex.