Study on the Influence of Iron-Based Catalysts on the Planarization of GaN Wafers During Electro-Fenton Assisted CMP Polishing

Abstract

Electro-Fenton assisted chemical mechanical polishing (CMP) has been demonstrated as an effective technique for enhancing the surface oxidation efficiency of gallium nitride (GaN) substrates, where the valence and phase states of iron-based catalysts directly determine the oxidation capability of the system. Herein, the effects of three types of iron-based catalysts (i.e., homogeneous ferrous sulfate (FeSO₄), homogeneous iron sulfate (Fe₂(SO₄)₃), and heterogeneous ferroferric oxide (Fe₃O₄)) on the performance of electro-Fenton assisted GaN CMP were systematically investigated. ·OH generation kinetics and the formation behavior of the oxide layer were comprehensively characterized through fluorescence spectrophotometry, potentiodynamic polarization tests, and X-ray photoelectron spectroscopy (XPS). Iron cycling mechanisms in the electro-Fenton system were examined through elemental analysis of iron deposition on GaN surfaces. Experimental results indicated significant differences in polishing performance among the catalyst systems, with clear linear relationships observed among ·OH concentration, corrosion potential, and material removal rate (MRR). Based on these findings, an oxidation kinetics model of the GaN surface was established to elucidate the origin of these linear correlations.