High-selectivity reactive ion etching with CO/NH3/Xe gas for micro/nanostructuring of 20% Fe-Ni, Au, Pt, and Cu

Highly selective etch process for conductive metals (Au, Pt, and Cu) and magnetic metal (20%Fe-Ni) has been developed on a magnetron reactive ion etching system which uses a CO/NH₃/Xe chemistry. Etch selectivities of these metals to titanium greater than 80:1 for Au, 40:1 for Pt, 30:1 for Cu, and 15:1 for Permalloy (20%Fe-Ni) were achieved at a titanium etch rate of 1.0 nm/min. These etchings were carried out at a room temperature. We found out that a little addition of Xe to CO/NH₃ gases (molar ratio=1/7) shows both ion assist etching of these metals and nitridation of titanium mask thus resulting in the good selectivity. These etch selectivities were enhanced about three times greater than that obtained without Xe.