Chemical Mechanical Polishing of Exfoliated III-V Layers

Abstract

The chemical mechanical polishing of III-V materials including GaAs, InP, InAs, and GaSb is investigated with sodium hypochlorite and citric acid solutions. It is found that the surfaces can be polished to below 0.5 nm RMS surface roughness without the induction of crystalline damage using similar abrasive-free polishing solutions for all the materials with controlled polishing rates of 10 nm / min which is important for touch polishing of exfoliated III-V layers. The optimal composition of the slurry is adjusted for the particular material. A balance between reduced sub-surface mechanical damage and smooth surface morphology is obtained by adjusting the amount of citric acid. However, the damage-free planarization in these cases may be aided by an oxide formation as predicted by Pourbaix diagrams. Additionally, triple axis x-ray diffraction is found to be an extremely sensitive, non-destructive method for evaluating damage induced by the CMP process.