Study on Pitch Performance Deterioration in Chemical Mechanical Polishing of Fused Silica

Abstract

Fused silica (FS) has been widely applied in astronomical telescopes, laser systems, and optical communication. The excellent fabrication of a fused silica surface requires high efficiency and high smoothness. Here, based on the ceria slurry and the pitch lap, the study of chemical mechanical polishing (CMP) of FS surface was carried out. The variations of the polishing removal rate (RR) and polished surface roughness Rq of FS with the polishing time were investigated. Meanwhile, the variations of the pitch performance during the CMP process were analyzed. Compared with the original pitch, the Rq of the used pitch presented an obvious decrement and the thickness of the used pitch was reduced. Scanning electronic microscopy was used to observe the morphologic change of the pitch. Attenuated total reflection-Fourier transform infrared spectroscopy was used to evaluate the chemical change of the pitch. The surface roughness Rq of the pitch was characterized. The viscoelastic characteristics of the pitch were investigated by dynamic shear rheometer tests. The relative mechanism of the pitch performance deterioration was discussed.