Effect of cations on the improvement of material removal rate of silicon wafer in chemical mechanical polishing

Abstract

For obtaining a sub-nanometer surface, the material removal rate (MRR) is usually very low. It is challenging to achieve sub-nanometer surface with high MRR. To overcome this challenge, in this work, different cations are considered to improve the MRR during CMP for silicon (Si) wafer. When the concentration of NH4+ ions is 125 mmol/L, the MRR of Si wafer reaches 1687 Å/min, increasing 107.8 % compared with the controlled group. It is noted that nanometer silica abrasives remain at a good monodisperse state in CMP. The surface roughness Sa after CMP on a Si wafer is 0.744 nm under a measurement area of 868 × 868 µm2. COF data and X-ray photoelectron spectroscopy indicate that NH4+ ions reduce the electrostatic repulsion between silica nanoparticles and Si, whilst accelerating chemical reactions between Si and developed slurry. This work suggests a novel approach to fabricating sub-nanometer surface of Si wafer with high MRR, which is beneficial for the potential use in semiconductor and microelectronics industries.