Thin film resistive device for use in an integrated circuit, an integrated circuit including a thin film resistive device
Thin film resistive sensors typically include a number of resistive components. These components should be well matched in order for the sensor to provide accurate readings. When a sensor is incorporated within an integrated circuit, the resistive components may be formed over, or under, metallic traces that form part of other components. As a result, the thin film resistive components are subjected to different levels of stress. This disclosure provides a structure that is arranged to mitigate the effects of stress.
1. A thin film magnetoresistive device with stress equalization for use in an integrated circuit, the thin film magnetoresistive device comprising:
thin film magnetoresistive elements formed in a first layer of the thin film magnetoresistive device so as to form a sensor; and
a stress equalization structure comprising stress equalization elements formed in a second layer of the thin film magnetoresistive device, the stress equalization elements arranged so as to equalize stress imposed on the thin film magnetoresistive elements.
2. A thin film magnetoresistive device according to claim 1 , wherein the stress equalization elements are arranged in a periodic arrangement.
3. A thin film magnetoresistive device according to claim 1 , wherein the stress equalization elements are elongate and arranged in parallel with each other.
4. A thin film magnetoresistive device according to claim 1 , wherein each thin film magnetoresistive element has a corresponding stress equalization element of substantially similar shape and aligned therewith.
5. A thin film magnetoresistive device according to claim 4 , wherein the thin film magnetoresistive elements and the stress equalization elements are arcuate.
6. A thin film magnetoresistive device according to claim 1 , wherein the thin film magnetoresistive elements and the stress equalization elements are arranged in groups, and the thin film magnetoresistive element groups are aligned with respective stress equalization element groups.
7. A thin film magnetoresistive device according to claim 1 , further comprising interconnectors, wherein the stress equalization elements are coupled together by the interconnectors so as to form one or more electrical paths.
8. A thin film magnetoresistive device according to claim 7 , wherein the stress equalization elements are arranged to heat the device by passing current through the one or more electrical paths.
9. A thin film magnetoresistive device according to claim 1 , wherein the stress equalization structure further includes a third layer of the thin film magnetoresistive device including additional stress equalization elements.
10. A thin film magnetoresistive device according to claim 1 , further comprising conductive interconnectors arranged to couple the thin magnetoresistive elements together and an isolation layer disposed between the first and second layers.
11. A monolithic integrated circuit with stress equalization, the monolithic integrated circuit comprising:
magnetoresistive thin film elements arranged as a sensor in a first layer of the monolithic integrated circuit; and
metallic elements in a second layer of the monolithic integrated circuit, the second layer being adjacent to the first layer, and the metallic elements being disposed in positions of the second layer that correspond to positions of each of the magnetoresistive thin film elements in the first layer.
12. The monolithic integrated circuit of claim 11 , wherein the metallic elements cover an area of the second layer that is similar to an area of the first layer covered by the magnetoresistive thin film elements.
13. The monolithic integrated circuit of claim 11 , wherein the sensor is a magnetoresistive sensor sensitive to changes in an external magnetic field.
14. The monolithic integrated circuit of claim 11 , wherein the metallic elements are configured to pass current to heat the magnetoresistive thin film elements to approximately the same temperature.
15. The monolithic integrated circuit of claim 11 , wherein the magnetoresistive thin film elements comprise a group of magnetoresistive thin film elements in the first layer, and wherein the metallic elements comprise a group of metallic elements in the second layer each of which extends across the group of the magnetoresistive thin film elements in the first layer.
16. The monolithic integrated circuit of claim 11 , wherein the magnetoresistive thin film elements comprise a group of parallel elongate magnetoresistive elements having lengths aligned along a first direction, wherein the metallic elements comprise a group of parallel elongate metallic elements having lengths aligned along a second direction, and wherein the first direction is substantially perpendicular to the second direction.
17. A thin film resistive device with stress equalization, the thin film resistive device comprising:
a plurality of thin film magnetoresistive elements arranged as a magnetoresistive sensor; and
means for reducing a difference in stress imposed on different thin film magnetoresistive elements of the magnetoresistive sensor, wherein the means for reducing are arranged such that each of the thin film magnetoresistive elements is exposed to substantially the same stress.
18. The thin film resistive device of claim 17 , wherein the means for reducing is included in a patterned metal layer, and wherein only an isolation layer is disposed between the patterned metal layer and a layer that includes the plurality of thin film magnetoresistive elements.
19. The thin film resistive device of claim 17 , wherein the thin film magnetoresistive elements are arranged such that the magnetoresistive sensor is sensitive to changes in direction of an external magnetic field applied to the magnetoresistive sensor.
20. The thin film resistive device of claim 17 , wherein the thin film magnetoresistive elements are arranged as at least one bridge circuit.