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Core/shell structured PS/mSiO2 hybrid particles: Controlled preparation, mechanical property, and their size-dependent CMP performance

Ailian Chen,Yang Chen,Xiaobing Zhao,Yayun Wang

For chemical and mechanical polishing/planarization (CMP) applications, the finished surface roughness , polishing efficiency, and defectivity critically depend on the type of abrasive particles and their physical and surface chemical characteristics. Both of core/shell structured inorganic/organic hybrids and porous particles exhibit important potentials in achieving high-efficiency and damage-free CMP. In this work, the polystyrene (PS)-core/mesoporous silica (mSiO 2 )-shell hybrid particles with a comparable shell thickness and tunable core size were synthesized via a modified Stöber process using cetyltrimethylammonium bromide as the template and tetraethyl orthosilicate as the silica precursor. The as-obtained PS/mSiO 2 hybrid particles were characterized by XRD , FT-IR, FESEM , HRTEM , STEM-EDX, HAADF-STEM, DLS, and N 2 sorption-desorption measurements. The mechanical properties (elastic moduli) of PS/mSiO 2 hybrids were investigated via atomic force microscopy (AFM) nano-indentation using Hertz contact model. The effect of the abrasive particle size of PS/mSiO 2 hybrids on CMP performances for oxidized silicon wafers was investigated in terms of root-mean-square ( RMS ) roughness and material removal rate ( MRR ). The PS/mSiO 2 hybrid abrasives presented a reduced roughness and an enhanced MRR with respect to non-porous solid silica abrasives with a comparable particle size. The improved CMP performance might be attributed to the reduction of overall hardness and/or elastic modulus and the improvement of interfacial tribo-chemical wear, resulting from the abundant meso-channels in the silica shells. Furthermore, the RMS roughness and MRR decreased as the PS core size decreased for PS/mSiO 2 hybrids with a comparable mSiO 2 shell thickness. The presented work describes our effort to engineer hybrid abrasives by regulating their polymer core size in order to optimize the CMP performance.