Yongjie Li, Longxiang Li, Hongda Wei, Xingchang Li, Xuejun Zhang
Scratches are key bottleneck limiting the improvement of the laser-induced damage threshold (LIDT) of optical components and the performance of large-scale integrated circuits. Chemical mechanical polishing (CMP) has shown great potential in scratch removal. However, as one of the core elements of CMP, the impact of polishing pads with different hardness on scratch removal efficiency has not been studied in depth. In this study, reactive ion beam etching (RIE) is used to create uniformly sized scratches. Two different hardnesses of pitch were used to remove scratches. Dynamic shear rheometer (DSR) and nanoindentation were used to comprehensively analyze the viscoelastic properties and hardness of the pitch. Relationship between material removal and scratch removal depth has been systematically tracked. Environmental scanning electron microscope (ESEM) and laser confocal microscopy were used to study the surface state of pitch. Temperature rise caused by pitch has been analyzed using thermal imaging camera. Combining the theory of elastoplastic contact, the removal characteristics of pitch at different stages have been explained. The results indicate that soft pitch demonstrated higher material removal efficiency in short period, while hard pitch is more effective over longer duration. Scratch removal efficiency of hard pitch is higher, and it is weaker in expanding scratches, while soft pitch can better conform to optical components. This study provides guidance for understanding the characteristics of pitch and establishing rapid removal strategies for scratches.