Magnetoresistive sensor integrated in a chip for detecting magnetic fields perpendicular to the chip and manufacturing process thereof
An integrated magnetoresistive sensor, formed in a chip including a substrate having a surface and an insulating region covering the surface of the substrate. A magnetoresistor, of a first ferromagnetic material, is formed in the insulating region and has a sensitivity plane parallel to the surface. A concentrator of a second ferromagnetic material is formed in the substrate and has at least one arm extending in a transverse direction to the sensitivity plane. The arm has one end in contact with the magnetoresistor.
1. An integrated magnetoresistive sensor, comprising:
a chip including a substrate having a surface and an insulating region covering the surface of the substrate
a ferromagnetic first magnetoresistor formed in the chip, the first magnetoresistor extending lengthwise in a direction parallel to the surface and having a sensitivity plane parallel to the surface, the first magnetoresistor being configured to conduct a current; and
a ferromagnetic first concentrator formed in the chip, the first concentrator including an arm extending in a transverse direction to the sensitivity plane and having an end in contact with the first magnetoresistor.
2. The sensor according to claim 1 , wherein the first magnetoresistor extends into the insulating region, the substrate has a trench opening on the surface, the arm of the first concentrator extends within the trench, and the end of the arm projects from the trench and extends into the insulating region.
3. The sensor according to claim 1 , wherein the first magnetoresistor and first concentrator are of at least one of a cobalt-based alloy and a Fe-Ni alloy.
4. The sensor according to claim 1 , wherein the end of the arm has a bent portion directed parallel to the sensitivity plane and in contact with the first magnetoresistor.
5. The sensor according to claim 1 , wherein the first magnetoresistor includes a magnetoresistive strip, the magnetoresistive strip and the first concentrator being formed in a same ferromagnetic material layer.
6. The sensor according to claim 1 , wherein the first magnetoresistor has an elongated shape having a longitudinal direction, and the first concentrator includes a plurality of concentrator segments in contact with the first magnetoresistor, separated from each other, and aligned with each other in the longitudinal direction.
7. The sensor according to claim 1 , comprising:
a plurality of magnetoresistors including the first magnetoresistor, the magnetoresistors being connected to form a Wheatstone bridge and each including a magnetoresistive strip and a plurality of conductive transverse strips arranged on top of the magnetoresistive strip; and
a plurality of concentrators including the first concentrator, the concentrators extending parallel to and in contact with the magnetoresistive strips, respectively.
8. The sensor according to claim 1 , wherein the substrate is of silicon semiconductor material.
9. The sensor according to claim 1 , forming an integrated electronic compass or a high-sensitivity magnetic-field detector.
10. The sensor according to claim 1 , wherein a first end of the first magnetoresistor is electrically coupled to a power supply input and a second end of the first magnetoresistor is electrically coupled to an output terminal.
11. The sensor according to claim 1 , wherein the first magnetoresistor and the concentrator are made of different materials with respect to each other.
12. A process, comprising:
manufacturing a magnetoresistive sensor integrated in a chip having a substrate and an insulating region, the substrate having a surface, the manufacturing including:
forming, in the chip, a magnetoresistor of a first ferromagnetic material extending lengthwise in a direction parallel to the surface and having a sensitivity plane parallel to the surface, the first magnetoresistor being configured to conduct a current; and
forming, in the chip, a concentrator of a second ferromagnetic material and having an arm extending in a transverse direction to the sensitivity plane and in contact with the magnetoresistor.
13. The process according to claim 12 , wherein the magnetoresistor has an elongated shape having a longitudinal direction, and the concentrator is formed by a plurality of concentrator segments in contact with the magnetoresistor, separated from each other and aligned with each other in the longitudinal direction.
14. The process according to claim 12 , wherein forming a magnetoresistor and forming a concentrator comprise forming a trench in the substrate from the surface, coating walls of the trench and the surface with a ferromagnetic layer, and patterning the ferromagnetic layer.
15. The process according to claim 14 , comprising, after coating the walls, filling the trench with insulating material before or after patterning.
16. The process according to claim 12 , wherein forming a concentrator comprises: forming a trench in the substrate from the surface; coating walls of the trench and a portion of the surface adjacent to the trench with a first ferromagnetic layer; and forming the magnetoresistor at least partially on the first ferromagnetic layer.
17. The process according to claim 16 , comprising:
after coating the walls and before forming the magnetoresistor, forming a protective layer above the first ferromagnetic layer, wherein forming the magnetoresistor comprises depositing a second ferromagnetic layer and patterning the second ferromagnetic layer; and
filling the trench with insulating material.
18. The process according to claim 12 , comprising:
depositing a first insulating layer on the surface;
forming the magnetoresistor on the first insulating layer;
forming a trench in the substrate, through the first insulating layer and laterally to the magnetoresistor; and
depositing a ferromagnetic layer on walls of the trench and on a portion of the magnetoresistor.
19. The process according to claim 12 , including electrically coupling a first end of the first magnetoresistor to a power supply input and electrically coupling a second end of the first magnetoresistor to an output terminal.
20. The process according to claim 12 , wherein the first magnetoresistor and the concentrator are made of different materials with respect to each other.
21. An integrated magnetoresistive sensor, comprising:
a chip including a substrate having a surface and an insulating region covering the surface of the substrate
a ferromagnetic first magnetoresistor formed in the chip, the first magnetoresistor having a sensitivity plane parallel to the surface;
a ferromagnetic first concentrator formed in the chip, the first concentrator including an arm extending in a transverse direction to the sensitivity plane and having an end in contact with the first magnetoresistor;
a plurality of magnetoresistors including the first magnetoresistor, the magnetoresistors being connected to form a Wheatstone bridge and each including a magnetoresistive strip and a plurality of conductive transverse strips arranged on top of the magnetoresistive strip; and
a plurality of concentrators including the first concentrator, the concentrators extending parallel to and in contact with the magnetoresistive strips, respectively.
22. The sensor according to claim 21 , wherein the first magnetoresistor extends into the insulating region, the substrate has a trench opening on the surface, the arm of the first concentrator extends within the trench, and the end of the arm projects from the trench and extends into the insulating region.
23. The sensor according to claim 21 , wherein a first end of the first magnetoresistor is electrically coupled to a power supply input and a second end of the first magnetoresistor is electrically coupled to an output terminal.