Method for uniform deposition of polystyrene particles on wafer surface

ZHANG Ziheng; REN Jun; LIU Yue; LIU Junjie

doi:10.13732/j.issn.1008-5548.2025.06.003

Abstract：Objective The scanning surface inspection system(SSIS)for wafer surface is an essential tool for quality control in semiconduc-tor manufacturing processes,and its performance evaluation requires calibration using standard wafer(SW)materials.To achieve independent calibration,there is an urgent need for China to develop SW materials that meet calibration requirements.This will address the low domestic production rate of SSIS equipment and further advance the research and application of wafer standard materials in China. Methods In this paper,a generation-deposition system for SW preparation was developed.The system utilized a differential mobility classifier(DMC)to screen polystyrene aerosols of the desired particle size and a scanning mobility particle sizer(SMPS)to analyze particle size distribution.Through theoretical and experimental analysis,the physical parameters of the depo-sition chamber were optimized and validated through numerical simulations in Ansys Fluent.Moreover,the influence of opera-tional parameters on uniform deposition and deposition efficiency was investigated. Results and Discussion When the particle size ranged from 100 to 300 nm,uniform physical parameters of the deposition cham-ber could achieve similar deposition results.However,for particles with sizes between 40 and 70 nm,different combinations of deposition chamber parameters were required.Deposition uniformity was influenced by the relative rotation position.Under the same conditions,particle size monodispersity was negatively correlated with the flow-to-time ratio.Increasing the deposition time improved deposition efficiency but had no impact on particle size monodispersity.Thermophoretic effect improved deposi-tion efficiency but caused contamination,rendering the contaminated SW unsuitable for SSIS calibration.Rotation increased the deposition spot area by 26％and decreased the concentration by 10％,reducing deposition efficiency but facilitating better con-trol of deposition time and improving distribution uniformity.Differences in particle size distribution between SSIS and SMPS were observed due to their distinct calibration principles. Conclusion Based on the simulation and experimental results,a 2-inch wafer standard with 200 nm polystyrene particles was successfully prepared,meeting the calibration requirements.The wafer standard materials prepared using this generation-deposition system have traceable particle sizes and a quantity distribution that meets the calibration requirements of the SSIS.