Dry etching of YMnO3 thin films in Ar/Cl2 and CF4/Cl2 plasmas

Ferroelectric YMnO3 thin films were etched with Ar/Cl-2 and CF4/Cl-2 plasmas. The maximum etch rate of the YMnO3 thin films was 300 Angstrom/min at a Cl-2/Ar of 8/2, an RF power of 800 W, a dc bias of -200 V, a chamber pressure of 15 mTorr, and a substrate temperature of 30 C-circ. From the X-ray photoelectron spectroscopy (XPS) analysis, yttrium could be etched by chemical reactions with Cl radicals as well as by Ar ion bombardments in the Ar/Cl-2 plasma. In the CF4/Cl-2 plasma, yttrium was formed of nonvolatile YFx compounds and remained on the etched surface. Manganese could be etched effectively by chemical reactions with Cl and F radicals. From the X-ray diffraction (XRD) analysis, the (0004) diffraction peak intensity of the YMnO3 thin film etched in Ar/Cl-2 plasma showed a lower value than that etched in CF4/Cl-2 plasma, which indicates that the damage by the Ar-ion bombardment to the crystallinity of the YMnO3 thin film is more severe than the damage caused by the changes in the stoichiometry due to nonvolatile etch by-products.