Systems and methods for controlling soft bias thickness for tunnel magnetoresistance readers
View Patent ↗Systems and methods for controlling a thickness of a soft bias layer in a tunnel magnetoresistance (TMR) reader are provided. One such method involves providing a magnetoresistive sensor stack including a free layer and a bottom shield layer, performing contiguous junction milling on the sensor stack, depositing an insulating layer on the sensor stack, depositing a spacer layer on the insulating layer, performing an angled milling sub-process to remove preselected portions of the spacer layer, depositing a soft bias layer on the sensor stack, and depositing a top shield layer on the sensor stack and the soft bias layer. The method can further involve adjusting an alignment of a top surface of the spacer layer with respect to the free layer. In one such case, the top surface of the spacer layer is adjusted to be below the free layer.
1. A tunnel magnetoresistance reader comprising:
a magnetoresistive sensor stack comprising a free layer and a bottom shield layer and having angled sides;
a soft bias structure adjacent to the sensor stack, wherein the soft bias structure comprises:
a portion of the bottom shield layer;
an insulating layer on the portion of the bottom shield layer and on the angled sides of the sensor stack;
a non-magnetic spacer layer directly on the insulating layer;
a soft bias layer directly on the spacer layer; and
a top shield layer directly on the soft bias layer;
wherein the spacer layer is entirely below the free layer.
2. The tunnel magnetoresistance reader of claim 1 :
wherein the soft bias structure comprises an air bearing surface;
wherein a rear area of the soft bias structure is substantially free of the soft bias layer; and
wherein the soft bias structure is positioned between the rear area and the air bearing surface.
3. The tunnel magnetoresistance reader of claim 1 , wherein the sensor stack comprises:
an anti-ferromagnetic pinning layer on the bottom shield layer;
a pinned layer on the anti-ferromagnetic pinning layer;
a barrier layer on the pinned layer;
the free layer on the barrier layer; and
a capping layer on the free layer.
4. The tunnel magnetoresistance reader of claim 3 :
wherein the bottom shield layer comprises one or more materials selected from the group consisting of NiFe, NiCo, CoFe, NiFeCo, CoB, CoFeB, and combinations thereof;
wherein the anti-ferromagnetic pinning layer comprises one or more materials selected from the group consisting of IrMn, IrMnCr, and combinations thereof;
wherein the pinned layer comprises one or more materials selected from the group consisting of CoFe, CoB, CoFeB, and combinations thereof;
wherein the barrier layer comprises one or more materials selected from the group consisting of MgO, AlOx, and combinations thereof, where x is a positive integer;
wherein the free layer comprises one or more materials selected from the group consisting of NiFe, NiCo, CoFe, Fe, NiFeCo, CoB, CoFeB, Ru, Ta, and combinations thereof; and
wherein the capping layer comprises one or more materials selected from the group consisting of Ru, Ta, Ti, MgO, and combinations thereof.
5. The tunnel magnetoresistance reader of claim 4 , wherein the non-magnetic spacer layer comprises one or more materials selected from the group consisting of NiFeCr, NiCr, Ta, Ru, Cr, oxides of NiFeCr, NiCr, Ta, and Cr, and combinations thereof.
6. The tunnel magnetoresistance reader of claim 5 , wherein the soft bias layer comprises one or more materials selected from group consisting of NiFe, NiCo, CoFe, NiCoFe, CoB, CoFeB, Ru, and combinations thereof.
7. The tunnel magnetoresistance reader of claim 4 , wherein the insulating layer comprises one or more materials selected from group consisting of alumina, MgO, SiN, SiO2, and combinations thereof.
8. The tunnel magnetoresistance reader of claim 1 , wherein the non-magnetic spacer layer consists of a substantially flat layer.
9. A tunnel magnetoresistance reader comprising:
a magnetoresistive sensor stack comprising a free layer and a bottom shield layer and having angled sides;
a soft bias structure adjacent to the sensor stack, wherein the soft bias structure comprises:
a portion of the bottom shield layer;
an insulating layer on the portion of the bottom shield layer and on the angled sides of the sensor stack;
a spacer layer on the insulating layer;
a soft bias layer on the spacer layer; and
a top shield layer on the soft bias layer;
wherein the spacer layer is entirely below the free layer;
wherein the soft bias structure comprises an air bearing surface;
wherein a rear area of the soft bias structure is substantially free of the soft bias layer;
wherein the soft bias structure is positioned between the rear area and the air bearing surface; and
wherein a portion of the insulating layer forms the rear area of the soft bias structure.
10. A tunnel magnetoresistance reader comprising:
a magnetoresistive sensor stack comprising a free layer and a bottom shield layer and having angled sides;
a soft bias structure adjacent to the sensor stack, wherein the soft bias structure comprises:
a portion of the bottom shield layer;
an insulating layer on the portion of the bottom shield layer and on the angled sides of the sensor stack;
a spacer layer on the insulating layer;
a soft bias layer on the spacer layer; and
a top shield layer on the soft bias layer;
wherein the spacer layer is entirely below the free layer;
wherein the soft bias structure comprises an air bearing surface; and
wherein a depth of the spacer layer from the air bearing surface is greater than a depth of the soft bias layer from the air bearing surface.
11. The tunnel magnetoresistance reader of claim 10 , wherein a depth of the insulating layer from the air bearing surface is greater than the depth of the spacer layer from the air bearing surface.