Method of fabricating magnetoresistive bit from magnetoresistive stack

1. A method of fabricating a magnetoresistive bit from a magnetoresistive stack including at least two magnetic regions, an intermediate region positioned between two magnetic regions of the at least two magnetic regions, and a multi-layer hard mask region, the method comprising:

(a) etching through at least a first layer of the multi-layer hard mask region to create a first set of exposed areas in the form of multiple parallel strips extending in a first direction;

(b) after the etching in step (a), etching through at least the first layer of the multi-layer hard mask region to create a second set of exposed areas in the form of multiple parallel strips extending in the first direction, wherein the multiple parallel strips of the first set are spaced apart from the multiple parallel strips of the second set;

(c) after the etching in step (b), etching through at least the first layer of the multi-layer hard mask region to create a third set of exposed areas in the form of multiple parallel strips extending in a second direction different from the first direction;

(d) after the etching in step (c), etching through at least the first layer of the multi-layer hard mask region to create a fourth set of exposed areas in the form of multiple parallel strips extending in the second direction, wherein the multiple parallel strips of the third set are spaced apart from the multiple parallel strips of the fourth set; and

(e) after the etching in step (d), etching through at least a portion of the thickness of the magnetoresistive stack through the first set, the second set, the third set, and the fourth set of exposed areas.

2. The method of claim 1 , wherein the first direction is transverse to the second direction.

3. The method of claim 1 , wherein the first set of exposed areas includes multiple parallel strips spaced substantially equidistant from each other, and the second set of exposed areas includes multiple parallel strips spaced substantially equidistant from each other.

4. The method of claim 1 ,

wherein the parallel strips of the first set of exposed areas are substantially equally spaced apart from the parallel strips of the second set of exposed areas.

5. The method of claim 1 , wherein

each parallel strip of the first set of exposed areas is positioned between two parallel strips of the second set of exposed areas, and

each parallel strip of the fourth set of exposed areas is positioned between two parallel strips of the third set of exposed areas.

6. The method of claim 1 , wherein the multi-layer hard mask region includes a thickness in the range of approximately 600-1200 Å.

7. The method of claim 1 , wherein the multi-layer hard mask region includes a first layer disposed over a second layer, wherein the first layer has a higher etch rate than the second layer.

8. The method of claim 1 , wherein the multi-layer hard mask region includes a first layer having a higher etch rate to a chemical reagent disposed over a second layer having a lower etch rate to the chemical reagent, and wherein the etching in steps (a)-(d) includes etching through the first layer of the multi-layer hard mask region using an etching process that utilizes the chemical reagent.

9. The method of claim 1 , wherein the multi-layer hard mask region includes a first layer having a higher etch rate to a chemical reagent disposed over a second layer having a lower etch rate to the chemical reagent, and wherein the etching in steps (a)-(d) includes etching through the first layer of the multi-layer hard mask region using chemical etching or a partially chemical etching, and the method further included etching through at least the second layer of the multi-layer hard mask region using a physical etch before the etching in step (e).

10. The method of claim 1 , wherein the multi-layer hard mask region includes a first layer disposed above a second layer and a third layer disposed below the second layer, and wherein the first and the third layers have a higher etch rate to a chemical reagent than the second layer.

11. The method of claim 1 , wherein the etching in steps (a)-(d) includes a chemical etching process or a partially chemical etching process utilizing a chemical reagent, and the etching in step (e) includes a physical etching process.

12. A method of fabricating a magnetoresistive bit from a magnetoresistive stack including at least two magnetic regions, an intermediate region positioned between two magnetic regions of the at least two magnetic regions, and a multi-layer hard mask region, the method comprising:

(a) etching through at least a first layer of the multi-layer hard mask region to create a first set of exposed areas in the form of a plurality of substantially parallel strips extending in a first direction;

(b) after the etching in step (a), etching through at least the first layer of the multi-layer hard mask region to create a second set of exposed areas in the form of a plurality of substantially parallel strips extending in the first direction, wherein the substantially parallel strips of the first set are equally spaced apart from the substantially parallel strips of the second set;

(c) etching through at least the first layer of the multi-layer hard mask region to create a third set of exposed areas in the form of a plurality of substantially parallel strips extending in a second direction transverse to the first direction;

(d) after the etching in step (c), etching through at least the first layer of the multi-layer hard mask region to create a fourth set of exposed areas in the form of a plurality of substantially parallel strips extending in the second direction, wherein the substantially parallel strips of the third set are equally spaced apart from the substantially parallel strips of the fourth set;

(e) after the etching in steps (a)-(d), etching through a second layer of the multi-layer hard mask region positioned below the first layer using an etching process different from the etching process of steps (a)-(d); and

(f) after the etching in step (e), etching through at least a portion of the thickness of the magnetoresistive stack.

13. The method of claim 12 , wherein the multi-layer hard mask region includes at least the first layer disposed over the second layer, the first layer having a higher etch rate than the second layer to a same chemical reagent, and wherein the etching in steps (a)-(d) includes a chemical etching process or a partially chemical etching process using the chemical reagent.

14. The method of claim 12 , wherein (i) the etching in steps (a)-(d) includes etching through the first layer using an etching process utilizing a chemical reagent, and (ii) the etching in step (e) includes etching through the second layer using a physical etching process.

15. The method of claim 12 , wherein (i) the etching in steps (a)-(d) uses reactive ion etching, and (ii) the etching in step (e) uses ion beam etching.

16. The method of claim 12 , wherein the multi-layer hard mask region includes the first layer disposed above the second layer and a third layer disposed below the second layer, and wherein the first and the third layers have a higher etch rate than the second layer to a same chemical reagent.

17. The method of claim 12 , wherein the multi-layer hard mask region includes the first layer disposed above the second layer, and wherein, after the etching in steps (a)-(d), the first layer forms an array of substantially square or substantially rectangular shapes.

18. The method of claim 12 , wherein the multi-layer hard mask region includes the first layer disposed above the second layer, and wherein, after the etching in steps (a)-(d), the first layer forms an array of substantially square or substantially rectangular shapes, and the method further includes further etching the first layer to smooth at least some of the corners of the substantially square or substantially rectangular shapes.

19. The method of claim 12 , wherein the multi-layer hard mask region includes a thickness in the range of approximately 600-1200 Å.

20. The method of claim 12 , wherein the multi-layer hard mask region includes the first layer disposed above the second layer and a third layer disposed below the second layer, wherein (i) the first layer includes a thickness of approximately 100-1000 Å, (ii) the second layer includes a thickness of approximately 10-400 Å, and (iii) the third layer includes a thickness of approximately 100-2000 Å.