Mems pressure sensing element with stress adjustors to minimize thermal hysteresis induced by electrical field

1. A pressure sensing element, comprising:

a supporting substrate

a cavity integrally formed as part of the supporting substrate;

a device layer bonded to the supporting substrate;

a diaphragm being part of the device layer, the diaphragm covering the cavity in a sealed manner;

a plurality of piezoresistors coupled to the diaphragm;

a plurality of bond pads disposed on the device layer;

an electrical field shield bonded to an outer surface of the device layer such that the electrical field shield is on top of the device layer and at least one of the bond pads; and

at least one stress adjustor being part of the electrical field shield;

wherein the at least one stress adjustor is constructed and arranged to reduce thermal hysteresis of the pressure sensing element caused by stress relaxation of the electrical field shield during a cooling and heating cycle of the pressure sensing element.

2. The pressure sensing element of claim 1 , the at least one stress adjustor further comprising a plurality of stress adjustors.

3. The pressure sensing element of claim 1 , wherein the at least one stress adjustor is integrally formed as part of the electrical field shield so as to decrease radial stresses on the plurality of piezoresistors and increase tangential stresses on the plurality of piezoresistors during the cooling and heating cycle.

4. The pressure sensing element of claim 1 , wherein the at least one stress adjustor is integrally formed as part of the electrical field shield so as to increase radial stresses on the plurality of piezoresistors and decrease tangential stresses on the plurality of piezoresistors during the cooling and heating cycle.

5. The pressure sensing element of claim 1 , the at least one stress adjustor further comprising a cut-out.

6. The pressure sensing element of claim 5 , the cut-out further comprising a portion of the electrical field shield which has been removed.

7. The pressure sensing element of claim 5 , wherein the cut-out is L-shaped.

8. The pressure sensing element of claim 5 , wherein the cut-out is square-shaped.

9. The pressure sensing element of claim 5 , wherein the cut-out is circular-shaped.

10. The pressure sensing element of claim 5 , wherein the cut-out is rectangular-shaped.

11. The pressure sensing element of claim 5 , wherein the cut-out is cross-shaped.

12. The pressure sensing element of claim 5 , wherein the cut-out is T-shaped.

13. The pressure sensing element of claim 5 , the cut-out further comprising a plurality of cut-outs, each of the plurality of cut-outs are rectangular shaped, and at least two of the plurality of cut-outs are arranged in an L-shaped configuration.

14. The pressure sensing element of claim 1 , at least one stress adjustor further comprising a thin film, where the thin film deposited on the electrical field shield.

15. The pressure sensing element of claim 14 , wherein the thin film applies residual stress to the plurality of piezoresistors.

16. A pressure sensing element, comprising:

a substrate having a cavity;

a device layer coupled to the substrate;

a diaphragm being part of the device layer;

a plurality of piezoresistors coupled to the diaphragm;

a plurality of bond pads disposed on the device layer;

an electrical field shield bonded to an outer surface of the device layer and at least one of the bond pads; and

at least one stress adjustor being part of the electrical field shield;

wherein the at least one stress adjustor is constructed and arranged to reduce thermal hysteresis of the pressure sensing element caused by stress relaxation of the electrical field shield during a cooling and heating cycle of the pressure sensing element.

17. The pressure sensing element of claim 16 , the at least one stress adjustor further comprising a plurality of stress adjustors.

18. The pressure sensing element of claim 16 , wherein the at least one stress adjustor is integrally formed as part of the electrical field shield so as to decrease radial stresses on the plurality of piezoresistors and increase tangential stresses on the plurality of piezoresistors during the cooling and heating cycle.

19. The pressure sensing element of claim 16 , wherein the at least one stress adjustor is integrally formed as part of the electrical field shield so as to increase radial stresses on the plurality of piezoresistors and decrease tangential stresses on the plurality of piezoresistors during the cooling and heating cycle.

20. The pressure sensing element of claim 16 , the at least one stress adjustor further comprising a cut-out.

21. The pressure sensing element of claim 20 , the cut-out further comprising a portion of the electrical field shield which has been removed.

22. The pressure sensing element of claim 20 , wherein the cut-out is L-shaped.

23. The pressure sensing element of claim 20 , wherein the cut-out is square-shaped.

24. The pressure sensing element of claim 20 , wherein the cut-out is circular-shaped.

25. The pressure sensing element of claim 20 , wherein the cut-out is rectangular-shaped.

26. The pressure sensing element of claim 20 , wherein the cut-out is cross-shaped.

27. The pressure sensing element of claim 20 , wherein the cut-out is T-shaped.

28. The pressure sensing element of claim 20 , the cut-out further comprising a plurality of cut-outs, each of the plurality of cut-outs are rectangular shaped, and at least two of the plurality of cut-outs are arranged in an L-shaped configuration.

29. The pressure sensing element of claim 16 , at least one stress adjustor further comprising a thin film, where the thin film deposited on the electrical field shield.

30. The pressure sensing element of claim 29 , wherein the thin film applies residual stress to the plurality of piezoresistors.