Effect of β-cyclodextrin and Citric Acid on Chemical Mechanical Polishing of Polycrystalline Ge₂Sb₂Te₅in H₂O₂Containing Slurry

Abstract

The effect of citric acid (CA) and β-cyclodextrin (CD) used as chelating agents on the chemical mechanical polishing (CMP) process of polycrystalline Ge2Sb2Te5 (pc-GST) film was investigated for a H2O2 containing slurry. CD would be better used in slurry than CA in pc-GST CMP, because a higher polishing rate of over 1000 Å/min as well as a low RMS roughness of 0.44 nm for a pc-GST film would be possible. A very smooth surface with a passive film was formed after the pc-GST film was polished with the addition of CD. According to a surface analysis conducted using scanning electron microscopy and X-ray photoelectron spectroscopy, there was only negligible formation of chemical oxides with an increase in CA in the H2O2 containing slurry, while they were formed continuously for CD. The potentiodynamic curves measured for the CA addition showed that there was insufficient oxidizing power for the forming the passive film. However, the oxidizing power of the slurry containing H2O2 with CD was sufficient enough to form the passive film due to the sufficient evolution of O2 on the surface of the pc-GST film. The additions of CA and CD largely affected the anodic and cathodic polarization, respectively.

The effect of slurry pH on the chemical mechanical planarization of a carbon-doped Ge2Sb2Te5 phase change material

“…Difference in oxidizability between germanium, antimony, tellurium, and carbon leads to the accumulation of tellurium, which would increase the surface roughness. 24 The slurry pH affects the equilibrium of passivation and corrosion reaction, which in turn affects the mechanism of CMP. Therefore, the pH level is of fundamental importance in the development of a slurry for CMP.…”