Test device and method for measurement of tunneling magnetoresistance properties of a manufacturable wafer by the current-in-plane-tunneling technique

1. A combined manufacturable wafer and test device for measuring a tunneling-magnetoresistance property of a tunneling-magnetoresistance, sensor-layer structure, said combined manufacturable wafer and test device comprising:

a tunneling-magnetoresistance, sensor-layer structure disposed on a substrate; and

a plurality of partially fabricated tunneling-magnetoresistance sensors, at least one of said partially fabricated tunneling-magnetoresistance sensors disposed at one of a plurality of first locations;

wherein said test device is disposed on said substrate at a second location different from said plurality of first locations; and

wherein said test device allows measurement of said tunneling-magnetoresistance property of said tunneling-magnetoresistance, sensor-layer structure using a current-in-plane-tunneling technique.

2. The test device of claim 1 , wherein said test device further comprises:

a first electrical-contact layer; and

a second electrical-contact layer disposed on and in electrical contact with said tunneling-magnetoresistance, sensor-layer structure;

wherein said tunneling-magnetoresistance, sensor-layer structure is disposed on and in electrical contact with said first electrical-contact layer.

3. The test device of claim 2 , wherein said first electrical-contact layer further comprises:

a first shield layer wherein said first shield layer is patterned for localizing a testing current substantially within said test device.

4. The test device of claim 2 , wherein said first electrical-contact layer further comprises:

a layer comprising nickel and iron wherein said layer is patterned for localizing a testing current substantially within said test device.

5. The test device of claim 2 , wherein said first electrical-contact layer further comprises:

a layer having a sheet resistance less than about 0.2 Ohm per square.

6. The test device of claim 2 , wherein said second electrical-contact layer further comprises:

an electrically conductive mask alignment layer.

7. The test device of claim 2 , wherein said second electrical-contact layer further comprises:

a layer comprising copper.

8. The test device of claim 2 , wherein said second electrical-contact layer further comprises:

a layer having a sheet resistance less than about 0.2 Ohm per square.

9. The test device of claim 1 , wherein said test device further comprises:

an approximately rectangular, probe-contact region, a length of said rectangular, probe-contact region greater than approximately 1.5 mm.

10. The test device of claim 1 , wherein said tunneling-magnetoresistance property further comprises said tunneling-magnetoresistance property selected from a group consisting of a tunneling-magnetoresistance ratio of said tunneling-magnetoresistance, sensor-layer structure and a resistance-area product of said tunneling-magnetoresistance, sensor-layer structure.

11. A method for measuring a tunneling-magnetoresistance property of a tunneling-magnetoresistance, sensor-layer structure of a manufacturable wafer with a test device, said method comprising:

depositing a tunneling-magnetoresistance, sensor-layer structure on a substrate;

fabricating a plurality of partially fabricated tunneling-magnetoresistance sensors on said substrate, at least one of said partially fabricated tunneling-magnetoresistance sensors disposed at one of a plurality of first locations;

fabricating at least one test device disposed on said substrate at a second location different from said plurality of first locations; and

measuring, from said test device, said tunneling-magnetoresistance property of said tunneling-magnetoresistance, sensor-layer structure using a current-in-plane-tunneling technique.

12. The method as recited in claim 11 , further comprising:

fabricating on said substrate a first electrical-contact layer; and

fabricating on said substrate a second electrical-contact layer disposed on and in electrical contact with said tunneling-magnetoresistance, sensor-layer structure;

wherein said tunneling-magnetoresistance, sensor-layer structure is disposed on and in electrical contact with said first electrical-contact layer.

13. The method as recited in claim 12 , wherein said fabricating said first electrical-contact layer further comprises:

depositing a first shield layer; and

patterning said first shield layer for localizing a testing current substantially within said test device.

14. The method as recited in claim 12 , wherein said fabricating said first electrical-contact layer further comprises:

depositing a layer comprising nickel and iron; and

patterning said layer comprising nickel and iron for localizing a testing current substantially within said test device.

15. The method as recited in claim 12 , further comprising:

performing a hydrogen/nitrogen, plasma ashing of a surface of said tunneling-magnetoresistance, sensor-layer structure before fabricating on said surface said second electrical-contact layer.

16. The method as recited in claim 12 , wherein said fabricating said second electrical-contact layer further comprises:

depositing an electrically conductive mask alignment layer.

17. The method as recited in claim 12 , wherein said fabricating said second electrical-contact layer further comprises:

depositing a layer of copper.

18. The method as recited in claim 11 , wherein said measuring with said test device further comprises:

measuring said tunneling-magnetoresistance property selected from a group consisting of a tunneling-magnetoresistance ratio of said tunneling-magnetoresistance, sensor-layer structure and a resistance-area product of said tunneling-magnetoresistance, sensor-layer structure.

19. The method as recited in claim 11 , wherein said measuring with said test device said tunneling-magnetoresistance property of said tunneling-magnetoresistance, sensor-layer structure further comprises:

measuring a transfer curve of said tunneling-magnetoresistance, sensor-layer structure; and

determining a transfer-curve parameter of said tunneling-magnetoresistance, sensor-layer structure selected from a group consisting of a transfer-curve slope, a transfer-curve hysteresis, and a transfer-curve, hysteresis-loop area.

20. A combined manufacturable wafer and wafer-testing means for measuring a tunneling-magnetoresistance property of a tunneling-magnetoresistance, sensor-layer structure, said combined manufacturable wafer and wafer-testing means comprising:

a tunneling-magnetoresistance, sensor-layer structure disposed on a substrate; and

a plurality of partially fabricated tunneling-magnetoresistance sensors, at least one of said partially fabricated tunneling-magnetoresistance sensors disposed at one of a plurality of first locations;

wherein said wafer-testing means is disposed on said substrate at a second location different from said plurality of first locations; and

wherein said wafer-testing means for measuring said tunneling-magnetoresistance property of said tunneling-magnetoresistance, sensor-layer structure allows measurements using a current-in-plane-tunneling technique.