Preparations of silica slurry for wafer polishing via controlled growth ofcommercial silica seeds

Silica slurry in aqueous medium for wafer polishing was prepared by sol-gel reaction of silicon alkoxide utilizing commercial silica particles as seed s that were grown stepwise through intermittent additions of tetraethy 1-or thosilicate (TEOS) as a silica precursor. Before the growth reaction, the c ommercial silica particles were pre-treated in the vibratory mill partially filled with zirconia ball and the sonicator to ensure good dispersion. The alcohol left after growth reaction was removed by vacuum distillation and repeated washings with distilled water followed by centrifugations. Then, t he alcohol-free silica particles were redispersed in water. The dispersion stability of the silica slurries was examined by measuring surface charge o f silica particles and rheological properties. Finally, wafer-polishing per formance of the prepared silica slurries was considered by measuring the po lishing (or removal) rate, and RMS (root mean square) roughness of the poli shed wafer surface. For the polishing, MEA (monoethanolamine) and TMAH (tet ramethylammonium. hydroxide) were used as polishing accelerators. The polis hing result showed that the removal rate was nearly independent of the conc entrations of MEA and TMAH in the range of 0.3-0.5 wt% and 100-500 ppm, res pectively. One of the most interesting features is that hydrothermal treatm ent of the prepared silica slurries in autoclave increased the removal rate as high as ten times. Although the removal rate was increased by the incre ased size of the abrasive particle, surface roughness of the polished wafer surface was deteriorated.