Effect of abrasive material properties on polishing rate selectivity of nitrogen-doped Ge2Sb2Te5 to SiO2 film in chemical mechanical polishing

We investigated the polishing rate and selectivity of nitrogen-doped Ge2Sb2Te5 (NGST) to SiO2 film for different abrasive materials (colloidal silica, fumed silica, and ceria abrasives). They both were strongly dependant on abrasive material properties. The polishing rate of nitrogen-doped NGST decreased in the order ceria, fumed silica, and colloidal silica abrasives, which was determined by abrasive material properties, such as abrasive hardness, crystal structure, and primary and secondary abrasive sizes. In addition, the polishing rate slope of NGST film was not significantly different for different abrasive materials, indicating that the polishing of NGST film is mechanical dominant polishing. In contrast, the polishing rate slope of SiO2 film decreased in the order ceria, fumed silica, and colloidal silica abrasives, indicating that the polishing of SiO2 film is chemical dominant polishing. Furthermore, the difference in polishing rate slopes between NGST and SiO2 film gave a polishing rate selectivity of NGST to SiO2 film higher than 100:1 with colloidal silica abrasive.