Core/shell structured sSiO2/mSiO2 composite particles: The effect of the core size on oxide chemical mechanical polishing

Abstract

In a typical chemical mechanical polishing (CMP) process, the type, morphology, structure, mechanical, and surface characteristics of abrasive particles play an important role in influencing the material removal process. The novel abrasive particles with special mechanical and/or tribochemical properties have been introduced into CMP processes for the improvement of surface quality and finishing efficiency. In this work, the composite particles containing solid silica (sSiO2) cores and mesoporous silica (mSiO2) shells were prepared via a developed Stöber method using cetyltrimethylammonium bromide as a structure-templating surfactant. The as-synthesized core/shell structured sSiO2/mSiO2 composite particles were characterized by powder X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and nitrogen sorption–desorption measurements. The effect of the sSiO2 core size of the composite particles on oxide CMP performance was evaluated in terms of surface roughness and material removal rate (MRR). The root-mean-square surface roughness (0.15–0.31nm) of the polished substrates slightly increased with increasing of the sSiO2 core size (168–353nm) of the composites with a comparable mSiO2 shell thickness (16–18nm). The sSiO2/mSiO2 composite particles with a relatively smaller or larger core presented a relatively high MRR for silicon oxide films. These oxide CMP results could be rationalized according to the contact area mechanism and indentation-based mechanism, incorporating the total contact area and chemical reactivity between particles and wafers, and the indentation depth of an abrasive particle onto the substrate surface.