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Monodispersed mesoporous silica (mSiO2) spheres as abrasives for improved chemical mechanical planarization performance

Chen, Yang, Li, Zefeng, Qin, Jiawei, Chen, Ailian
Journal of materials science 2016 v.51 no.12 pp. 5811-5822
Fourier transform infrared spectroscopy, X-ray diffraction, abrasives, cetyltrimethylammonium bromide, desorption, hardness, microstructure, nitrogen, porous media, powders, roughness, scanning electron microscopes, scanning electron microscopy, silica, silicon, surface area, surface roughness, synergism, transmission electron microscopy
Inorganic mesoporous particles as polishing powders have been developed for achieving high-efficiency chemical mechanical planarization (CMP). For improving the surface quality and material removal rate (MRR) in oxide-CMP processes, the submicrometer spherical mesoporous silica (mSiO₂) particles with a controlled size (200–500 nm) and a specific surface area of up to 1400 m²/g were synthesized using cetyltrimethylammonium bromide as the template agent and tetraethyl orthosilicate as the silica source. The microstructures of the obtained samples were analyzed by low-angle X-ray diffraction, N₂ sorption/desorption, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. The CMP performances of the obtained mSiO₂ and solid silica (sSiO₂) particles for oxidized silicon wafers were investigated. The surface characteristics of the substrates before and after CMP were characterized by atomic force microscope, scanning electron microscope, and 3D non-contact surface profiler. The results indicated that the mSiO₂ particles exhibited a higher MRR (62–84 nm), a lower surface average roughness (0.14–0.19 nm), and a lower topographical variation (±0.4 to ±0.6 nm) than sSiO₂ particles (34 nm/min, 0.33, and ±1.5 nm, respectively) under the same CMP conditions. Moreover, the lowest average surface roughness (0.142 nm) was achieved with the mSiO₂ particles with the smallest size (263 ± 15 nm), while the highest MRR (84 nm/min) was obtained for the mSiO₂ particles with the smallest mesopore channel (2.4 nm) and highest specific surface area (1462.8 m²/g). It might be attributed to the low hardness (H), low Young’s modulus (E), and high specific surface area of the mSiO₂ particles, resulted from their abundant mesoporous structure. The low H and E are in favor of decreasing the indentation depth of an abrasive particle onto a substrate surface, which is contributed to the decrease of surface roughness. The high specific area is beneficial to enhancing the chemical reactivity in the real contact region between abrasives and substrates, which is be propitious to the improvement of MRR. The improved polishing characteristics may be resulted from the synergetic effect of the mechanical action and the chemical action for the mSiO₂ particles.