Method to fabricate a magnetic head including ion milling of read gap using dual layer hard mask

1. A method to manufacture a magnetic head, the method comprising:

providing a first layered structure including a magnetic layer, a first hard mask layer immediately adjacent and contacting the magnetic layer, a second hard mask layer immediately adjacent and contacting the first hard mask layer; and a first stepping layer immediately adjacent and contacting the second hard mask layer;

etching through the first stepping layer to create a sidewall of the first stepping layer;

depositing a mask-width definition layer on and adjacent to the sidewall, until a mask-width definition layer thickness is achieved adjacent to the sidewall;

removing the mask-width definition layer except on the sidewall;

removing the first stepping layer;

etching away the second hard mask layer except for a remainder of the second hard mask layer beneath the mask-width definition layer;

etching away the first hard mask layer around the remainder of the second hard mask layer to define a remainder of the first hard mask layer beneath the remainder of the of the second hard mask layer, to form a dual layer hard mask comprising the remainder of the second hard mask layer and the remainder of the first hard mask layer; and

ion milling the magnetic layer around the dual hard mask.

2. The method of claim 1 , wherein the first layered structure further comprises a second stepping layer immediately adjacent and contacting the first stepping layer, and wherein the act of etching through the first stepping layer also etches a continuation of the sidewall through the second stepping layer, a total height of the sidewall equaling a sum of a thickness of the first stepping layer plus a thickness of the second stepping layer.

3. The method of claim 2 , wherein ion etching is used to etch the sidewall through the first and second stepping layers.

4. The method of claim 2 , wherein the second stepping layer comprises tantalum having a thickness in the range of 1 nm to 10 nm.

5. The method of claim 2 , wherein providing the first layered structure includes depositing a plurality of layers onto a substrate, the plurality of layers including the magnetic layer, the first hard mask layer, the second hard mask layer, and the first and second stepping layers.

6. The method of claim 1 , wherein ion milling the magnetic layer around the dual hard mask defines a reader width of the magnetic head that depends upon the mask-width definition layer thickness.

7. The method of claim 6 , wherein the mask-width definition layer thickness and the reader width of the magnetic head are less than 30 nm.

8. The method of claim 1 , wherein ion milling the magnetic layer around the dual hard mask also removes the remainder of the second hard mask layer.

9. The method of claim 1 , further comprising removal of the remainder of the first hard mask layer using an oxygen plasma, after ion milling the magnetic layer around the dual hard mask.

10. The method of claim 1 , further comprising depositing a patterned partial overlayer of photoresist material on the first hard mask layer, before etching away the first hard mask layer around the remainder of the second hard mask layer.

11. The method of claim 1 , wherein the first stepping layer comprises amorphous carbon having a thickness in the range of 20 nm to 200 nm.

12. The method of claim 1 , wherein the first hard mask layer comprises amorphous carbon having a thickness in the range of 10 nm to 50 nm.

13. The method of claim 12 , wherein oxygen plasma is used for etching away the first hard mask layer around the remainder of the second hard mask layer.

14. The method of claim 1 , wherein the second hard mask layer comprises silicon carbide having a thickness in the range of 5 nm to 50 nm.

15. The method of claim 14 , wherein the mask-width definition layer comprises silicon dioxide having a thickness in the range of 3 nm to 30 nm.

16. The method of claim 1 , wherein the mask-width definition layer comprises alumina having a thickness in the range of 3 nm to 30 nm.

17. The method of claim 16 , wherein the second hard mask layer comprises silicon dioxide or silicon nitride.

18. The method of claim 1 , wherein the magnetic layer is a tunneling magnetoresistive laminate comprising a plurality of sublayers.

19. The method of claim 1 , wherein the first hard mask layer comprises a cured photoresist material.

20. The method of claim 1 , wherein reactive ion etching is used to remove the mask-width definition layer except on the sidewall.