Patent ID: 8728333
Filing Date: 2014-05-20
Classification: B82Y,G01R,G11B,H01F,H01L,Y10T

Abstract:
1. A method of reducing a critical dimension in a magnetoresistive sensor, comprising: (a) providing a magnetic tunnel junction (MTJ) stack of layers on a substrate including a pinned layer, a free layer, a non-magnetic spacer between the pinned layer and free layer, and an uppermost capping layer; (b) patterning the MTJ stack of layers to form a MTJ element having a top surface and an essential vertical sidewall along all of the layers in the MTJ element that connects the top surface with the substrate, said free layer has a critical dimension which is a first width along a plane that is parallel to the MTJ element top surface, and the pinned layer, and non-magnetic spacer have the same sidewall as that along the free layer; (c) performing a first low energy ion beam etch (IBE) step with an ion beam incident angle less than about 20° with respect to a plane perpendicular to the substrate to trim the sidewall such that the free layer has a second width less than the first width; (d) performing a second low energy IBE step with a sweeping motion and with an ion beam incident angle greater than about 60° with respect to a plane perpendicular to the substrate to remove residue formed during the first IBE step and further trim the sidewall such that the free layer has a third width less than the second width; and (e) performing a third low energy IBE step with an ion beam incident angle less than about 20° with respect to a plane perpendicular to the substrate to remove damaged portions of the sidewall resulting from the second IBE step and to further trim the sidewall such that the free layer has a final width less than the third width, the sidewall has a slope of about 90 degrees or less with respect to the substrate, and the first, second, and third low energy IBE steps are performed in consecutive order after the sidewall is formed along the pinned layer and non-magnetic spacer.