Influences of process parameters on chemical mechanical polishing effect of ZnGeP2 crystal

To obtain the ultra-smooth surface of ZnGeP2 crystal (ZGP), the workpiece-abrasive-polishing pad contact model during polishing was established to calculate the load Fw and the cutting depth hw of a single abrasive. The influences of polishing methods, abrasive hardness, abrasive size, polishing pressure, polishing time and other factors on the polishing effect were studied, and the mechanism underpinning the formation of surface morphology after polishing was revealed, and the mathematical model between material removal rate (MRR) and surface roughness (Ra) was established. The results show that the critical cutting depth hc of ZnGeP2 crystal is 95.21 nm, when the polishing load is 5 N, the material removal under mechanical polishing and chemical mechanical polishing entails plastic removal. Compared with mechanical polishing, the MRR of chemical mechanical polishing is increased by 23.4% and Ra is decreased by 26.5%. The increases of abrasive hardness, abrasive size and polishing load will increase the cutting depth hw of the abrasive, resulting in the increases of MRR and Ra, but the influence forms of various factors are different. After optimizing the process parameters, the minimum Ra of ZnGeP2 crystal is 0.76 nm. MRR and Ra will decrease significantly with the increase of polishing time, and there is a significant correlation between them.