Dry Etching of Cr2MnO4 Thin Films for Forming p-n Junctions with β-Ga2O3

Abstract We report the dry etching characteristics of Cr2MnO4 thin films using Cl2-based inductively coupled plasmas (ICP) for applications in Ga2O3-based power electronics, where p-n heterojunctions offer advantages over Schottky diodes. Cr2MnO4, a thermally stable p-type oxide, was deposited via RF sputter beam epitaxy and etched using Cl2/Ar and BCl3/Ar plasmas, with the latter producing much lower etch rates. The etch rates and surface roughness were investigated as functions of Cl2 flow rate, RF power, and gas composition. Results reveal that increasing the Cl2 flow rate enhances etch rates but degrades surface roughness due to non-volatile chloride formation and redeposition. Higher RF power improves surface smoothness by increasing ion bombardment energy, promoting physical sputtering, and enabling uniform etching. The etch process is ion-flux limited, with threshold energies comparable to NiO. Post-etch X-ray photoelectron spectroscopy analysis confirms that NH4OH rinsing effectively removes chlorine residues by dissolving metal chlorides and neutralizing acidic species, ensuring a clean surface. These findings underscore the importance of optimizing plasma parameters and post-etch cleaning for fabricating high-quality Cr2MnO4/Ga2O3 heterojunctions, which hold promise for high-temperature, high-power electronic applications.