Composite hard mask with upper sacrificial dielectric layer for the patterning and etching of nanometer size mram devices

Abstract

A composite hard mask is disclosed that prevents build up of metal etch residue in a MRAM device during etch processes that define an MTJ shape. As a result, MTJ shape integrity is substantially improved. The hard mask has a lower non-magnetic spacer, a middle conductive layer, and an upper sacrificial dielectric layer. The non-magnetic spacer serves as an etch stop during a pattern transfer with fluorocarbon plasma through the conductive layer. A photoresist pattern is transferred through the dielectric layer with a first fluorocarbon etch. Then the photoresist is removed and a second fluorocarbon etch transfers the pattern through the conductive layer. The dielectric layer protects the top surface of the conductive layer during the second fluorocarbon etch and during a substantial portion of a third RIE step with a gas comprised of C, H, and O that transfers the pattern through the underlying MTJ layers.