Atomic surface of silicon wafers induced by grafted silica nanoparticles and sodium carbonate

Abstract

Atomic surface of silicon (Si) wafers is highly desired for integrated circuit (IC) industry. To meet this demand, traditional chemical mechanical polishing usually employs noxious slurries with complex compositions, containing oxidant, dispersant, inhibitor, surfactant, etc., resulting in the pollution of the environment and high-cost post-treatments. To settle this challenge, a novel green chemical mechanical polishing was developed, only including grafted silica nanoparticles and sodium carbonate. After CMP, surface roughness Sa of 0.219 and 0.247 nm are achieved on Si wafers using amine and methyl modified nanoparticles, respectively, corresponding to material removal rate (MRR) of 132.53 and 84.82 nm/min. Amino-modified nanoparticles increase 18.2 % MRR, and methyl modified ones reduce 24.4 % MRR, compared with those of unmodified nanoparticles. X-ray photoelectron spectroscopy reveals that amino-grafted nanoparticles have strong improvement for chemical reactions during CMP. Density functional theory calculations garner the electrostatic potential energy of 4.884 and 6.753 eV for amine and methyl-modified nanoparticles, respectively, corresponding to high and low effects for MRR. This work provides a new avenue to develop novel green simple CMP for Si wafers, reducing the pollution and cost for post-treatments.