提出了一种基于反射法的化学机械抛光(CMP)在线终点判定方法。首先通过改进的单纯形混合遗传算法(GA),对SiO2薄膜的膜厚与折射率进行了拟合,再以200～1200nm波段内反射率平均值作为特征值,得到了不同膜厚条件下的反射率平均值参照表。以实时反射率与预设膜厚反射率的差方和、特征值大小及其变化趋势这2个条件作为CMP终点判定条件。实验结果表明:混合算法拟合膜厚平均相对误差小于0.21%,折射率平均相对误差小于1.07%;特征值计算速度快,满足在线动态抛光的时间要求。
Abstract
In order to improve the accuracy and efficiency of chemical mechanical polishing (CMP) endpoint detection, a method based on reflection method for CMP online endpoint determination was proposed. Firstly, the film thickness and refractive index of SiO2 film were fitted by the improved simplex hybrid genetic algorithm (GA). Secondly, the average reflectance in the range of 200～1200nm was used as the eigenvalue, and a reference table of reflectance average values under different film thickness conditions was obtained. The difference between the real-time reflectance and the preset film thickness reflectance, and the eigenvalue with its changing trend were used as the CMP endpoint detection conditions. The experimental results demonstrate that the average relative error of the hybrid algorithm is less than 0.21%, the average relative error of the refractive index is less than 1.07%, and the eigenvalue calculation speed is fast, which meets the time requirement of online dynamic polishing.
关键词
计量学 /
薄膜厚度 /
化学机械抛光 /
终点判定 /
遗传算法 /
反射率
Key words
metrology /
film thickness /
CMP /
endpoint detection /
genetic algorithm /
reflectance
{{custom_sec.title}}
{{custom_sec.title}}
{{custom_sec.content}}
参考文献
［1］Cui J, Huang H L, Zhuang Y, et al. XPS Study of Tungsten and Barrier Film Transition at Various Stages of Chemical Mechanical Polishing Endpoint and of Surface Compositions Post-CMP Cleaning ［J］. ECS Journal of Solid State Science and Technology, 2017, 6(9): 633-640.
［2］Zhou Y, Pan G S, Zou C L, et al. Chemical Mechanical Polishing (CMP) of SiC Wafer Using Photo-Catalyst Incorporated Pad ［J］. ECS Journal of Solid State Science and Technology, 2017, 6(9): 603-608.
［3］宋文超, 柳滨, 种宝春. 一种基于光学干涉原理的CMP在线终点检测装置 ［J］. 电子工业专用设备, 2007, 36(10): 10-13.
Song W C, Liu B, Zhong B C. An Apparatus for CMP in Situ End Point Detection Based on Optics Interference Principle ［J］. Equipment for Electronic Products Manufacturing, 2007, 36(10): 10-13.
［4］刘彬, 张春燃, 孙超, 等. 多种群遗传算法在篦冷机二次风温预测中的应用 ［J］. 计量学报, 2019, 40(2): 252-258.
Liu B, Zhang C R, Sun C, et al. The Application of Multi-population Genetic Algorithm in Secondary Air Temperature of Grate Cooler ［J］. Acta Metrologica Sinica, 2019, 40(2): 252-258.
［5］王跃灵, 旺玥, 王琪, 等. 基于自适应粒子群遗传算法的柔性关节机器人动力学参数辨识 ［J］. 计量学报, 2020, 41(1): 60-66.
Wang Y L, Wang Y, Wang Q, et al. Dynamic Parameter Identification of Flexible Joint Robot Based on Adaptive Particle Swarm Optimization-genetic Algorithm ［J］. Acta Metrologica Sinica, 2020, 41(1): 60-66.
［6］Güngr T, Saka B. Calculation of the optical constants of a thin layer upon a transparent substrate from the reflection spectrum using a genetic algorithm ［J］. Thin Solid Films, 2004, 467(1-2): 319-325.
［7］Guo T, Chen Z, Li M H, et al. Film thickness measurement based on nonlinear phase analysis using a Linnik microscopic white-light spectral interferometer ［J］. Applied optics, 2018, 57(12): 2955-2961.
［8］El-Naggar A M, El-Zaiat S Y, Hassan S M. Optical parameters of epitaxial GaN thin film on Si substrate from the reflection spectrum ［J］. Optics and Laser Technology, 2008, 41(3): 334-338.
［9］宋敏, 李波欣, 郑亚茹. 利用光学方法测量薄膜厚度的研究 ［J］. 光学技术, 2004, 30(1): 103-106.
Song M, Li B X, Zheng Y R. Study of optical methods for measuring the thickness of the thin films ［J］. Optical Technique, 2004, 30(1): 103-106.
［10］Zhu W H, Zheng G, Cao S, et al. Thermal conductivity of amorphous SiO2 thin film: A molecular dynamics study ［J］. Scientific reports, 2018, 8(1): 10537.
［11］Elena R G, Alfonso P G, Sergio A, et al. Engineered TiO2 and SiO2-TiO2 films on silica-coated glass for increased thin film durability under abrasive conditions ［J］. International Journal of Applied Ceramic Technology, 2017, 14(1): 39-49.
［12］Michael Q. A Practical Guide to Optical Metrology for Thin Films ［M］. New York: Wiley, 2012: 59-67.
［13］Hlubina P, Ciprian D, Lunacek J, et al. Thickness of SiO2 thin film on silicon wafer measured by dispersive white-light spectral interferometry ［J］. Applied Physics B, 2006, 84(3): 511-516.
［14］张寅辉, 任玲玲, 高慧芳, 等. 纳米尺度HfO2薄膜的光谱椭偏模型建立 ［J］. 计量学报, 2017, 38(5): 548-552.
Zhang Y H, Ren L L, Gao H F, et al. Establish of Spectroscopic Ellipsometry Model of Nanoscale
HfO2 Thin Films［J］. Acta Metrologica Sinica, 2017, 38(5): 548-552.
［15］Ramirez G C F, Castao Y J D, Rodriguez G M E. Porosity and roughness determination of porous silicon thin films by genetic algorithms ［J］. Optik, 2018, 173: 271-278.
［16］Kitahara T, Mizuno S. A bound for the number of different basic solutions generated by the simplex method ［J］. Mathematical Programming, 2013, 137(1-2): 579-586.
［17］Zhang J H, Zhou Z G. An improved genetic algorithm and its applications to the optimisation design of an aspirated compressor profile ［J］. International Journal for Numerical Methods in Fluids, 2015, 79(12): 640-653.
