Atomic surface of fused silica with high material removal rate produced by novel chemical mechanical polishing using composite rare earth oxides

Abstract

It is extremely difficult to garner atomic surface of fused silica with surface roughness less than 0.1 nm, due to its hard and brittle nature. For achieving such atomic surface, material removal rate (MRR) is usually sacrificed greatly. In this regard, surface roughness and MRR are a pare of contradiction eternally in manufacturing field. To solve this challenge, novel green chemical mechanical polishing (CMP) was developed, and the slurry consisted of ceria, erbia, sodium tripolyphosphate, choline chloride (CC) and deionized water. After CMP, atomic surface is acquired on fused silica with surface roughness Sa of 0.07 nm at a measurement area of 20 × 20 μm², and MRR is 37.53 μm/h. To the best of our knowledge, both the Sa and MRR are the best, compared with those published previously, breaking the contradiction between surface roughness and MRR. Transmission electron microscopy confirmed that the thickness of damaged layer is 3.25 nm. X-ray photoelectron spectroscopy (XPS) reveals that the concentration of Ce³⁺ increases from 24.17 % to 35.81 % and 41.54 % with addition of erbia and CC, respectively. Through incorporating CC, polydispersity index, zeta potential and contact angle varied from 0.213 to 0.168, −34.38 mV to −44.11 mV, and 51.996° to 34.757°, correspondingly, indicating the improvement of dispersity, stability and wettability, respectively. Fourier transform infrared spectroscopy and XPS demonstrate that hydroxylation happened on the surface of ceria and fused silica, forming Ce-OH and Si-OH bonds respectively, and generating Si-O-Ce bonds between them after dehydration condensation reaction. Our developed novel CMP on fused silica provides new insights to gain atomic surface with high MRR for a hard and brittle solid, which is beneficial for the potential application in high-performance devices.