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Journal of Inorganic Materials

Journal of Inorganic Materials

   

Preparation and Performance of Ceria-Based Slurry for Ultra-Precision Polishing of Calcium Fluoride

JIA Wenqing1,2, ZHANG Zhenghao3, WANG Jun4, WANG Mengxia4, ZHANG Chuanqi1,2, JIANG Dapeng2,5, ZHANG Ling1,2, KOU Huamin2,5, WANG Wenzhong1,2,3   

  1. 1. State Key Laboratory of High Performance Ceramics, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China;
    2. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China;
    3. School of Chemistry and Materials Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China;
    4. Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China;
    5. State Key Laboratory of Functional Crystals and Device, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201899, China
  • Received:2026-01-21 Revised:2026-03-19
  • Contact: WANG Wenzhong, professor. E-mail: wzwang@mail.sic.ac.cn; KOU Huamin, professor. E-mail: huaminkou@mail.sic.ac.cn
  • About author:JIA Wenqing (2000-), male, Master candidate. E-mail: jiawenqing23@mails.ucas.ac.cn
  • Supported by:
    National Natural Science Foundation of China (52172256, 52372248,52450255); Shanghai Municipal Science and Technology Commission "Explorer" Project (25TS1416100)

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Abstract: The continuous downscaling of integrated circuit nodes demands atomic-level smoothness for calcium fluoride (CaF2) optical materials used in lithography systems. To overcome the limitations of conventional alkaline silica polishing slurries, namely low material removal rate (MRR) and corrosion issues, this study developed a high-efficiency, stable, and eco-friendly near-neutral ceria (CeO2) slurry for chemical mechanical polishing (CMP) of CaF2. Monodispersed spherical CeO2 abrasives with three particle sizes were synthesized via urea precipitation. Polishing slurries were prepared using sodium polyacrylate (PAAS) as dispersant and primary alcobol ethoxylate (AEO-9) as surfactant. Effects of calcination temperature, abrasive size, and additive content on polishing performance were systematically investigated. Optimal performance was achieved with CeO2 calcined at 500 ℃, 0.2% PAAS and 0.2% AEO-9 (in mass). Specifically, the slurry containing 140 nm abrasives delivered a MRR of 109 nm/min and a surface roughness after polishing (Ra) of 0.12 nm, while the slurry with 110 nm abrasives produced an ultra-smooth surface with an Ra as low as 0.09 nm, outperforming the traditional alkaline silica slurry. Laser-induced damage threshold tests revealed that CaF2 polished with the optimized slurry reached 6.4 J/cm2, significantly higher than the 4.9 J/cm2 obtained with the silica slurry. Electron paramagnetic resonance (EPR) and Fourier-transform infrared (FT-IR) spectroscopic analyses confirmed that Ce3+ species on the CeO2 surface is critical for enhancing chemical reactivity. The contact angle measurements with reduced contact angle showed PAAS and AEO-9 notably improved wettability. This study provides an efficient, eco-friendly strategy for ultraprecision machining of CaF2.

Key words: calcium fluoride, chemical mechanical polishing, spherical ceria, slurry, ultra-precision machining

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