Iron trichloride as oxidizer in acid slurry for chemical mechanical polishing of Ge2Sb2Te5

Abstract

The effect of iron trichloride (FeCl3) on chemical mechanical polishing (CMP) of Ge2Sb2Te5 (GST) film is investigated in this paper. The polishing rate of GST increases from 38 nm/min to 144 nm/min when the FeCl3 concentration changes from 0.01 wt% to 0.15 wt%, which is much faster than 20 nm/min for the 1 wt% H2O2-based slurry. This polishing rate trends are inversely correlated with the contact angle data of FeCl3-based slurry on the GST film surface. Thus, it is hypothesized that the hydrophilicity of the GST film surface is associated with the polishing rate during CMP. Atomic force microscope (AFM) and optical microscope (OM) are used to characterize the surface quality after CMP. The chemical mechanism is studied by potentiodynamic measurements such as Ecorr and Icorr to analyze chemical reaction between FeCl3 and GST surface. Finally, it is verified that slurry with FeCl3 has no influence on the electrical property of the post-CMP GST film by the resistivity–temperature (RT) tests.