Patent ID: 7863060

Claim:
A method of fabricating a MTJ element having essentially vertical sidewalls and with a top surface having an area determined by a first dimension along a first axis and a second dimension along a second axis, said MTJ element has a stack of layers comprised of a seed layer, AFM layer, pinned layer, tunnel barrier, free layer, hard mask spacer layer, and composite hard mask layer with a lower NiCr layer and an upper Ta layer formed in order from bottom to top on a substrate, comprising: (a) forming the MTJ stack of layers on said substrate; (b) patterning a first photoresist layer on the composite hard mask layer to form a first parallel line pattern wherein each line has a width that is the first dimension along the first axis; (c) transferring said first parallel line pattern through the composite hard mask layer with a first etch sequence comprising: (1) performing a first fluorocarbon plasma etch step to form a parallel line pattern in the upper hard mask layer; (2) removing the first photoresist layer with an oxygen plasma; (3) performing a first CH 3 OH plasma etch to transfer the parallel line pattern in the upper hard mask layer through the lower hard mask layer; and (4) performing an oxygen plasma to treat exposed surfaces following the first CH 3 OH plasma etch, (d) patterning a second photoresist layer on the parallel line pattern and hard mask spacer layer to form a second parallel line pattern wherein each line in the second parallel line pattern intersects the hard mask parallel lines and has a width that is the second dimension along the second axis; (e) transferring said second parallel line pattern through the composite hard mask layer by a second etch sequence to form a post pattern wherein each post has an area determined by the first dimension and second dimension, said second etch sequences comprises; (1) performing a second fluorocarbon plasma etch step to form a post pattern in the upper hard mask layer; (2) removing the second photoresist layer with an oxygen plasma; and (3) performing a second CH 3 OH plasma etch to transfer the post pattern in the upper hard mask layer through the lower hard mask layer; and (f) continuing the second CH 3 OH step to transfer the post pattern through the remaining layers in the MTJ stack of layers to form a plurality of MTJ elements.