Effect of L-isoleucine on the Removal Rate Selectivity of SiO₂/Si₃N₄ in Chemical Mechanical Polishing of Shallow Trench Isolation

The shallow trench isolation chemical mechanical polishing (STI CMP) technique is critical to ensure the flatness of the isolation layer and the merit of the device performance. The need for a moderate and adjustable silicon oxide and silicon nitride removal rate selectivity ratio to avoid deep oxide dishing pits and severe silicon nitride loss in polishing remains a challenge. Regarding the difficulty in regulating the selectivity ratio of the removal rate (RR) of SiO 2 and Si 3 N 4 in STI CMP, this paper innovatively employs L-isoleucine as an inhibitor, achieving a moderately adjustable selectivity ratio in the nano-CeO 2 abrasive system. The RRs of SiO 2 and Si 3 N 4 were respectively reduced to 238 and 11 nm min −1 , with a selectivity ratio of 21.6, and the surface roughness (Sq) was decreased to 0.32 and 0.19 nm, respectively. Coefficient of friction, X-ray photoelectron spectroscopy, and theoretical calculations indicated that the L-isoleucine molecule can adsorb on the surface of SiO 2 and Si 3 N 4 wafers to form a passivation layer, while also adsorbing on the surface of CeO 2 abrasive to retard the wear effect.