Polishing process of silicon wafer using silica dispersion

Abstract

Since a rapid development of technics in electronics and communication industry in twentieth century, silicon wafer which was manufactured from ingot as sliced has been a basic material in semiconductor fabrication industry. After slicing step wafer polishing was needed to remove surface damage occcurred by slicing and maintain a uniform wafer thickness and smooth wafer surface. Used as a polishing abrasive in wafer polishing process, silica slurry was fabricated with dispersing 20 ~200 nm size of silica particles into a high-purity alkali solution. In this study, silica particles were prepared using particle growth of fumed silica and colloidal silica as seeds by sol-gel method to control various sizes of particles and produce economically competitive goods. And it was an alternative to the silica particle manufacturing method suggested by St$ö$ber et al. which was a combination of hydrolysis and condensation of monomeric, tetrafunctional alkoxide precursors. In the case of colloidal silica like commercial Ludox, it was not adequate to an abrasive slurry of wafer polishing because of containing so small size of no more than 20 nm silica particles and metal ions such as $Na^+$ or $K^+$ etc. used for particles stabilizer. And in the case of fumed silica like Aerosil, it had too broad size distribution and irregular shapes of particles although it had a adequate size of 40 ~50 nm primary particles. For that reason, in this study particles were grown with hydrolysis and condensation of silica alkoxide, or Tetraethylorthosilicate (TEOS), and water using pre-treated fumed or colloidal silica particles as seeds. And sequentially alcohol-base solvent of silica slurry was substituted for water-base one and additives was added to accelerate a polishing rate or stabilize a particle dispersion electrostatically or sterically. And next these slurries were tested with one-armed polisher to compare with reference slurries, namely Nalco2371 G3900 which are commonly used...