Patent ID: 8133745

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 stack of layers comprised of a seed layer, AFM layer, pinned layer, tunnel barrier, free layer, hard mask spacer layer, and hard mask layer formed in order from bottom to top, comprising: (a) forming an unpatterned MTJ stack of layers on a substrate; (b) patterning a first photoresist layer on the 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 hard mask layer with a first etch step to form parallel hard mask lines on the hard mask spacer layer; (d) patterning a second photoresist layer on the parallel hard mask lines and hard mask spacer layer to form a second parallel line pattern wherein each line intersects the parallel hard mask lines and has a width that is the second dimension along the second axis, said second photoresist layer contacts a top surface of the parallel hard mask lines; (e) transferring said second parallel line pattern through the hard mask layer with a second etch step to form a post pattern in the hard mask layer wherein each post has an area determined by the first dimension and second dimension; and (f) performing a third etch step to transfer the hard mask post pattern through the hard mask spacer and remaining unpatterned layers in the MTJ stack of layers to form a plurality of MTJ elements, said first and second dimensions are formed simultaneously in the MTJ stack of layers below the hard mask layer, and said hard mask layer remains as an uppermost layer in the MTJ stack.