Methods of manufacturing a magnetic field sensor
A semiconductor process integrates three bridge circuits, each include magnetoresistive sensors coupled as a Wheatstone bridge on a single chip to sense a magnetic field in three orthogonal directions. The process includes various deposition and etch steps forming the magnetoresistive sensors and a plurality of flux guides on one of the three bridge circuits for transferring a “Z” axis magnetic field onto sensors orientated in the XY plane.
1. A method of manufacturing an integrated magneto-resistive sensor, the method comprising:
forming a plurality of magneto-resistive sensor elements over a substrate, wherein forming the plurality of magneto-resistive sensor elements includes:
forming a reference layer,
forming a sensing layer, and
forming an intermediate layer between the reference layer and the sensing layer;
forming conductors to electrically connect the plurality of magneto-resistive sensor elements;
depositing a first insulating material over the plurality of magneto-resistive sensor elements; and
forming flux guides on or in the first insulating material, wherein the flux guides (i) comprise a magnetic material and (ii) are adjacent to and offset from associated magneto-resistive sensor elements.
2. The method of claim 1 , wherein the magnetic material of the flux guides comprises one or more of nickel, iron and cobalt and/or an alloy including one or more of nickel, iron and cobalt.
3. The method of claim 1 , wherein the intermediate layer of each magneto-resistive sensor element is a dielectric material.
4. The method of claim 1 , wherein the reference layer of each magneto-resistive sensor element includes a pinning direction; and
wherein forming the sensing layer of each magneto-resistive sensor element includes:
depositing the magnetic material over the intermediate layer, and thereafter, patterning the magnetic material into the sensing layer, wherein the magnetic material includes an easy axis of a magnetization direction that is orthogonal to the pinning direction of the reference layer.
5. The method of claim 1 , wherein each magneto-resistive sensor element is a magnetic tunnel junction sensor element.
6. The method of claim 1 , wherein forming conductors to electrically connect the magneto-resistive sensor elements includes forming conductors to electrically interconnect the magneto-resistive sensor elements into a bridge circuit including input conductors and output conductors.
7. The method of claim 6 , further including:
providing a detection circuit; and
electrically connecting the output conductors of the bridge circuit to the detection circuit.
8. The method of claim 7 , wherein the detection circuit, using a voltage difference generated by the bridge circuit, determines an applied magnetic field along an axis that is perpendicular to a surface of the substrate over which the plurality of magneto-resistive sensor elements are formed.
9. The method of claim 7 , wherein the detection circuit includes a voltage meter.
10. The method of claim 6 , the method further including electrically connecting the input conductors of the bridge circuit to electrical power terminals.
11. The method of claim 1 , wherein forming the flux guides on or in the first insulating material includes forming a plurality of bars, comprising a magnetic material, adjacent to and offset from associated magneto-resistive sensor elements.
12. The method of claim 1 , wherein forming the flux guides on or in the first insulating material includes forming a plurality of bars, comprising a magnetic material, adjacent to and offset from one or more edges of each associated magneto-resistive sensor element.
13. The method of claim 1 , wherein forming the flux guides on or in the first insulating material includes forming a plurality of bars, comprising a nickel-iron alloy, wherein each bar is adjacent to and offset from a side of at least one associated magneto-resistive sensor element.
14. The method of claim 1 , wherein forming flux guides on or in the first insulating material includes:
etching trenches in the first insulating material, wherein each trench includes at least two side walls, and wherein each trench is adjacent to and offset from at least one associated magneto-resistive sensor element; and
depositing a magnetic material in the trenches to form the flux guides.
15. A method of manufacturing an integrated magneto-resistive sensor, the method comprising:
forming a plurality of magneto-resistive sensor elements over a substrate, wherein forming the plurality of magneto-resistive sensor elements includes:
forming a reference layer,
forming a sensing layer, and
forming an intermediate layer between the reference layer and the sensing layer;
forming conductors to electrically interconnect (i) a first subset of the magneto-resistive sensor elements into a first bridge circuit and (ii) a second subset of magneto-resistive sensor elements into a second bridge circuit;
depositing a first insulating material over the magneto-resistive sensor elements; and
forming flux guides on or in the first insulating material, wherein the flux guides (i) comprise a magnetic material and (ii) are adjacent to and offset from associated magneto-resistive sensor elements of the first subset of the magneto-resistive sensor elements.
16. The method of claim 15 , wherein the magnetic material of the flux guides comprises one or more of nickel, iron and cobalt.
17. The method of claim 15 , wherein each magneto-resistive sensor element is a magnetic tunnel junction sensor element.
18. The method of claim 15 , wherein the intermediate layer of each magneto-resistive sensor element is a dielectric material.
19. The method of claim 15 , wherein the reference layer of each magneto-resistive sensor element includes a pinning direction; and
wherein forming the sensing layer of each magneto-resistive sensor element includes:
depositing the magnetic material over the intermediate layer, and thereafter, patterning the magnetic material into the sensing layer, wherein the magnetic material includes an easy axis of a magnetization direction that is orthogonal to the pinning direction of the reference layer.
20. The method of claim 15 , wherein forming the flux guides on or in the first insulating material includes forming a plurality of bars, comprising a magnetic material, adjacent to and offset from associated magneto-resistive sensor elements.
21. The method of claim 15 , wherein forming the flux guides on or in the first insulating material includes forming a plurality of bars, comprising a magnetic material, adjacent to and offset from one or more edges of each associated magneto-resistive sensor element.
22. The method of claim 15 , wherein forming flux guides on or in the first insulating material includes:
etching trenches in the first insulating material, wherein each trench includes at least two side walls, and wherein each trench is adjacent to and offset from at least one associated magneto-resistive sensor element; and
depositing a magnetic material in the trenches to form the flux guides.
23. The method of claim 15 , wherein forming conductors to electrically interconnect a first subset of the magneto-resistive sensor elements into a first bridge circuit further includes forming conductors to electrically interconnect the first subset of the magneto-resistive sensor elements into the first bridge circuit having input conductors and output conductors, wherein the method further includes:
providing a detection circuit; and
electrically connecting the output conductors of the first bridge circuit to the detection circuit.
24. The method of claim 23 , wherein the detection circuit, using a voltage difference generated by the bridge circuit, determines an applied magnetic field along an axis that is perpendicular to a surface of the substrate over which the plurality of magneto-resistive sensor elements are formed.
25. The method of claim 23 , wherein the detection circuit includes a voltage meter.
26. The method of claim 15 , wherein forming conductors to electrically interconnect a first subset of the magneto-resistive sensor elements into a first bridge circuit further includes forming conductors to electrically interconnect the first subset of the magneto-resistive sensor elements into a first bridge circuit having input conductors and output conductors, wherein the method further includes:
electrically connecting the input conductors of the first bridge circuit to electrical power terminals.