Magnetic reader sensor device for reading magnetic stripes and method for manufacturing the sensor device
The present disclosure concerns a magnetic reader (MR) sensor device for reading magnetic stripes, the MR sensor device comprising a substrate provided on a wafer, a back-end-of-line (BEOL) interconnect layer and a plurality of magneto-resistive sensor elements embedded within the BEOL interconnect layer; the MR sensor device comprising a protective layer having a Vickers hardness of at least 3 GPa. The present disclosure further concerns a method for manufacturing the MR sensor device. The MR sensor device can be brought close to the surface to the magnetic stripe so that the magnetic stripe can be read with an increased resolution.
1. A magnetic reader (MR) sensor device for reading magnetic stripes, the MR sensor device comprising:
a substrate provided on a wafer;
a back-end-of-line (BEOL) interconnect layer;
a plurality of magneto-resistive sensor elements embedded within the BEOL interconnect layer; and
a protective layer having a Vickers hardness of at least 3 GPa,
wherein the protective layer is on the BEOL interconnect layer.
2. The MR sensor device according to claim 1 , wherein the protective layer has a friction coefficient μ that is lower than 1.
3. The MR sensor device according to claim 1 , wherein the protective layer has a friction coefficient μ that is lower than 0.5.
4. The MR sensor device according to claim 1 , wherein the protective layer has a wear rate below 10−7 mm3 N−1 m−1.
5. The MR sensor device according to claim 1 , wherein the protective layer comprises a diamond like carbon (DLC) layer.
6. The MR sensor device according to claim 1 , wherein the MR sensor device is interconnected to a packaging substrate.
7. The MR sensor device according to claim 6 , comprising solder balls providing interconnection between the MR sensor device and the packaging substrate.
8. The MR sensor device according to claim 7 ,
wherein the BEOL interconnect layer is between the substrate and the protective layer; and
wherein the MR sensor device comprises vias passing through the substrate such that the vias and the solder balls provide interconnection between the MR sensor device and the packaging substrate.
9. The MR sensor device according to claim 7 ,
wherein the BEOL interconnect layer is between the protective layer and the substrate; and
wherein the solder balls are between the substrate and the package substrate.
10. The MR sensor device according to claim 1 , further comprising a chamfered profile.
11. The MR sensor device according to claim 1 , further comprising a magnetic flux concentrator.
12. A method for manufacturing a magnetic reader (MR) sensor device comprising a substrate provided on a wafer, at least one back-end-of-line (BEOL) interconnect layer, a plurality of magneto-resistive sensor elements embedded within the at least one BEOL interconnect layer, and a protective layer having a Vickers hardness of at least 3 GPa; the method comprising:
providing the wafer;
forming the substrate on the wafer;
forming at least one BEOL interconnect layer;
forming at least one MR sensor circuit comprising the plurality of magneto-resistive sensor elements embedded within at least one BEOL interconnect layer; and
forming the protective layer having a Vickers hardness of at least 3 GPa on the BEOL interconnect layer.
13. The method according to claim 12 , wherein forming the protective layer comprises forming a diamond like carbon (DLC) layer.
14. The method according to claim 13 , wherein the protective layer is between 1 nm and 1 μm in thickness.
15. The method according to claim 12 , further comprising dicing the wafer to obtain individual dices, each die containing a MR sensor circuit.
16. The method according to claim 15 , further comprising
placing at least one of the dices on a packaging substrate; and
providing interconnections between the at least one BEOL interconnect layer of one of the dices and the packaging substrate.
17. The method according to claim 16 , wherein said providing interconnections comprises forming solder balls on the MR sensor device.
18. The method according to claim 17 ,
wherein said at least one BEOL interconnect layer is formed over the substrate and the protective layer is formed over said at least one BEOL interconnect layer; and
wherein said providing interconnections further comprises providing through-silicon vias in the substrate such that the vias and the solder balls provide interconnection between the MR sensor device and the packaging substrate.
19. The method according to claim 17 ,
wherein the at least one BEOL interconnect layer is formed between the protective layer and the substrate; and
wherein the solder balls are formed on the substrate.
20. The method according to claim 17 , further comprising
a step of flipping the MR sensor device on the packaging substrate after the solder balls are formed, and
wherein the protective layer is formed on top of the substrate after flipping the MR sensor device.
21. The method according to claim 12 , further comprising providing a chamfered profile to the packaging substrate.