Tunable synthesis, characterization, and CMP performance of dendritic mesoporous silica nanospheres as functionalized abrasives

Abstract

The type, morphology, structure, size and distribution, surface chemistry, and mechanical behavior of particle abrasives play a key role in advanced chemical mechanical polishing (CMP) applications. In this work, dendritic mesoporous silica (D-mSiO2) nanospheres with tunable structures were synthesized via a modified n-hexane/water biliquid system coupled with a shearing assisted interfacial coassembly method. The resulting samples were characterized in terms of transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, powder X-ray diffraction, and nitrogen adsorption-desorption measurements. The spherical D-mSiO2 products presented three-dimensional and center-radial structures with particle size of 30–140 nm, pore diameter of 3–9 nm, surface area of ~780 m2/g, and pore volume of ~1.5 cm3/g. The elastic property and compressive elastic modulus of D-mSiO2 nanospheres were investigated by atomic force microscopy (AFM) nanoindentation. Oxide-CMP performances of the series of D-mSiO2 nanospheres as functionalized abrasives were tracked via high-resolution AFM and interferometric microscopy. The subtle differences of surface characteristics were systematically compared in terms of roughness, topographical variation, and image surface area difference (SAD). Sub-100 nm D-mSiO2 nanospheres achieved superior CMP qualities with the decreased surface roughness (less than 0.2 nm Rq and 0.3 nm Rz, within 5.0 × 5.0 µm2), the reduced maximum peak height/minimum valley depth (less than 0.5 nm), as well as the low image SAD (less than 0.009%). Furthermore, the interfacial contact behavior, water-involved tribochemical wear, and material removal mechanism of D-mSiO2 nanoabrasives were also discussed. The investigations are expected to open up the possibility of utilizing D-mSiO2 nanospheres as novel abrasives for advanced CMP applications.