Achieving highly selective polishing of polysilicon over oxide and nitride films via ethylenediamine-modulated interfacial mechanochemistry

Polysilicon (poly-Si) has been extensively employed in advanced chip manufacturing, where the selective removal of poly-Si over underlying oxide/nitride films with a high material removal rate (MRR) while achieving an ultra-clean and sub-nano smooth surface by chemical mechanical polishing (CMP) is crucial. In this study, the underlying mechanism of –NH 2 functional groups of ethylenediamine (EDA) in the selective CMP process was investigated. The –NH 2 functional groups in EDA interact synergistically with OH − ions, promoting the formation of a hydrophilic reactive layer on the poly-Si surface. Nanowear tests confirmed that this reactive layer has lower mechanical wear resistance, making it more susceptible to removal during polishing. Density functional theory calculations provide atomic-scale insights, showing that the energy barriers for reactions between –NH 2 functional groups and the chemically inert oxide/nitride surfaces are substantially higher than with the reactive poly-Si, resulting in a negligible MRR. Based on these findings, an optimized abrasive-free slurry composed of EDA was developed, achieving a poly-Si MRR exceeding 1000 nm/min (an increase of over 700 %) with minimal MRR for oxide/nitride surfaces, whilst delivering a poly-Si surface roughness as low as 0.3 nm. These results provide mechanistic insights into the role of the –NH 2 functional groups in poly-Si CMP, and highlight the potential of the new EDA-based abrasive-free slurry as a cost-effective solution for the ultra-high-precision polishing of poly-Si in the semiconductor industry.