Patent ID: 8334213

Claim:
A method of patterning a bottom electrode layer in a MRAM structure, said bottom electrode layer is formed on a substrate including an insulation layer dielectric (ILD), comprising: (a) providing an array of MTJ elements on said bottom electrode layer wherein each of said MTJ elements has a bottom portion contacting the bottom electrode layer, a top portion having a top surface, and sidewalls connecting said top surface to the bottom electrode layer; (b) forming a protective dielectric layer that serves as a hard mask on the top surface and sidewalls of the MTJ elements and on the bottom electrode layer between adjacent MTJ elements; (c) forming a stack of layers on the protective dielectric layer, comprising: (1) a bottom anti-reflective coating (BARC) which contacts the protective dielectric layer; and (2) a photoresist layer on the BARC layer; (d) patterning the photoresist layer to form a plurality of openings between adjacent MTJ elements; (e) transferring said plurality of openings through the BARC layer and through the protective dielectric layer with a dielectric etch process; (f) transferring said plurality of openings through the bottom electrode layer with a metal etch process to form a patterned bottom electrode below each of said plurality of MTJ elements, said metal etch includes a certain amount of overetching that removes a top portion of the ILD at the bottom of each of the plurality of openings; and (g) removing the photoresist and BARC layers following the metal etch through the bottom electrode, the photoresist and BARC are removed with a stripping process that is a sequence of wet, dry, and wet stripping methods, comprising: (1) a first method which is a first wet strip that includes immersing or spraying the substrate with a solution including one or more organic solvents; (2) a dry ashing step following the first wet strip that includes exposing the substrate to an O 2 plasma; and (3) a second wet strip following the dry ashing step that includes treatment of the substrate with a water based solution.