Effect of Potassium Periodate Oxidizer on Germanium Chemical Mechanical Planarization Using Fumed Silica as Abrasive

Abstract

The chemical mechanical planarization (CMP) removal rate (RR) of germanium using potassium periodate as oxidizer with fumed silica based slurries have been investigated. Static etch rate (ER) of germanium was performed as a function of solution temperature, pH and concentration of potassium periodate. Change in the enthalpy (ΔHact) and entropy (ΔSact) of activation for the Ge in the proposed oxidizer was found to be 11.029 kJ/mol and −271.06 J/mol.K, respectively. The values suggest that the dissolution of germanium in the proposed oxidizer is endothermic in nature and the etching is controlled by activation complex. The effect of slurry pH, KIO4 concentration, turntable speed and down pressure on Ge RR were studied. ER and RR of Ge was found to increase with pH. In the absence of oxidizer, polishing of germanium with 3 wt% fumed silica showed almost zero removal. With the addition of 1 wt% KIO4 + 0.1M KOH to 3 wt% fumed silica slurry, significant increase in the RR of Ge was observed for complete range of pH. Ge is oxidized to form germanium dioxide in the presence of KIO4, which on subsequent oxidation resulted in the formation of soluble species.