Atomic insights of material removal mechanism in chemical mechanical polishing for silicon using developed abrasive-free slurry

Atomic surface of silicon (Si) wafers without particulate contamination achieved by chemical mechanical polishing (CMP) is highly desired for advanced chip manufacturing. Traditional CMP processes usually employ abrasive-containing slurries, resulting in significant particulate residues and high-cost post-treatments. To settle this challenge, a novel abrasive-free CMP slurry only including designated chain-length alkylamine was developed based on the observed dependence between the Si surface roughness and alkylamine chain length. After polishing by the long-chain hexylamine slurry, an atomic surface without particulate contamination is achieved with surface roughness as low as 0.13 nm, which is 85% lower than that obtained using short-chain methylamine slurry, while maintaining a material removal rate of 57.7 nm/min. Then, we established an atomic mechanistic framework that integrates interfacial chemistry with mechanical action to understand how alkylamine chain length modulates mechanochemistry in abrasive-free Si CMP. Density functional theory calculations show that long-chain alkylamines adsorb more readily but have a milder weakening effect on Si–Si bonds, whereas short-chain counterparts, despite weaker adsorption, more effectively weaken these bonds. Nanowear tests and X-ray photoelectron spectroscopy corroborate that the dynamic equilibrium between the adsorption strength and bond weakening promotes the formation of a mechanically vulnerable reaction layer composed by O_x–Si–N_y compounds amenable to abrasive-free removal for atomic smoothness. Our findings shift the mechanistic paradigm from conventional abrasive-involved interfacial interactions to abrasive-free, chemically driven, adsorption-controlled removal processes. These insights offer valuable theoretical guidelines for both academic research and industrial practice in ultra-precision manufacturing and advanced semiconductor processing.