基于稳定pH值的硅衬底晶圆抛光液成分优化

Component Optimization of Polishing Slurry for Silicon Substrate Wafer Based on Stable pH Value

目的探究不同配比方案配制pH值相同的抛光液对抛光去除速率、抛光液寿命和表面粗糙度的影响,优化硅衬底晶圆抛光液,使其满足半导体产业的发展要求。方法以二氧化硅水溶胶为磨料,通过设置有机碱、pH缓冲剂、pH稳定剂的不同配比来调节和稳定抛光液的初始pH值(11.0~12.0),在最佳工艺参数下循环使用抛光液对2英寸(1英寸≈2.54 cm)硅衬底晶圆进行抛光实验。研究不同配比下抛光液pH值、抛光去除速率随抛光液循环使用时间的变化情况。对比实验结果,分析各种成分在抛光过程中的作用,以及对抛光效果产生的影响,得出最佳配比方案,优化抛光液方案。结果通过优化硅衬底晶圆的抛光液方案,使抛光去除速率达到0.804μm/min,抛光液的寿命延长了约114.29%,抛光后硅衬底晶圆的表面粗糙度最低为0.156 nm。结论得到了抛光液的最佳配比方案,有机碱的质量分数为1.0%,pH缓冲剂的质量分数为1.1%,并加入pH稳定剂调节pH,使其抛光去除速率、抛光液寿命、表面粗糙度都得到很大提升。

In order to solve the problem that the pH value of polishing slurry on silicon substrate wafer is slowly decreasing with the increase of service time and poor buffering ability,and that the domestic nano-silica hydrosol has a large gap with the international level,the work aims to explore the effects of different proportioning formulas on polishing rate,service life of polishing slurry and surface roughness under the same pH value and optimize the polishing slurry for silicon wafer to meet the development requirements of semiconductor industry.From the point of stabilizing the pH value of the polishing slurry,the pH value of the polishing slurry was adjusted and stabilized in the range of 11.0-12.0 by setting different proportions of organic base,pH buffer and pH stabilizer with the domestic nano-silica hydrosol as the abrasive.The polishing experiments of 2 inch silicon substrate wafer were carried out under the optimum polishing parameters.The changes of pH value and polishing rate of polishing slurry with the circulating time of polishing slurry at different proportions were studied.By comparing the experimental results,the effects of various components in the polishing process and their effects on the polishing effect were analyzed,and the best proportioning formula was obtained to optimize the polishing slurry.By setting up comparative experiments,the effects of mass fraction of organic base and pH buffer,usage and pH stabilizer on polishing rate and service life of polishing slurry were investigated.The surface roughness of the polished silicon substrate wafer was measured.The results showed that:The function of the pH buffer was to generate an equal amount of conjugated acid and base to stabilize the pH of the polishing slurry system to a certain range.However,a large number of pH buffers could destroy the original chemical stability of the colloid system,such as coagulation and crystallization.A large number of organic base could continuously provide OH—for the system,the rate of chemical reaction was increased,and the products of organic base reacting with the surface of silicon substrate wafer were macromolecules,which were easy to detach from the reaction surface and accelerate the mechanical removal process.In addition,the chemical etching effect after organic base infiltration was weak,which could protect the crystal circle depression of the silicon substrate wafer.The combination of organic base and pH buffer could ensure that the pH value of polishing slurry did not decrease rapidly and effectively avoid the formation of plough groove structure.The hydrolysis of pH stabilizer was weakly alkaline,which could work together with the pH buffer to ensure the pH stability,and its hydrolysis by-product was H2CO_(3).It could overcome the disadvantage of excessive pH buffer to cause the agglutination of silica hydrosol and ensure the full mechanical action of silica hydrosol abrasives and the raised surface of silicon substrate wafer.For the polishing slurry optimized for silicon substrate wafer,the polishing rate reached 0.804μm/min,the service life was prolonged by 114.29%,and the surface roughness of the polished silicon substrate wafer was as low as 0.156 nm.The optimum proportion of polishing slurry is:organic base 1.0wt.%and pH buffer 1.1wt.%.pH stabilizer can be added to adjust and stabilize the pH value.The polishing rate,service life of polishing slurry and surface roughness are all improved greatly.