MICROELECTROMECHANICAL SYSTEM DEVICE INCLUDING A METAL PROOF MASS AND A PIEZOELECTRIC COMPONENT

• US 20120234093A1
• Filed: 03/15/2011
• Published: 09/20/2012
• Est. Priority Date: 03/15/2011
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Black, Justin Phelps, Ganapathi, Srinivasan Kodaganallur, Stephanou, Philip Jason, Acar, Cenk, Shenoy, Ravindra Vaman, Buchan, Nicholas Ian, Petersen, Kurt Edward
• Granted Patent: US 9,000,656 B2
• Time in Patent Office: Days
• US Class Current: 73/504.08
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81B 3/0078 Constitution or structural means for improving mechanical properties not provided for in B81B3/007 - B81B3/0075
• CPC Class Codes: G01C 19/5769 Manufacturing; Mounting; Housings
• CPC Class Codes: H10N 30/00 Piezoelectric or electrostrictive devices integrated devices or assemblies of multiple devices H10N39/00
• CPC Class Codes: H10N 30/10513 characterised by the underlying bases, e.g. substrates
• CPC Class Codes: H10N 30/302 Sensors

Abstract

This disclosure provides systems, apparatus, and devices and methods of fabrication for electromechanical devices. In one implementation, an apparatus includes a metal proof mass and a piezoelectric component as part of a MEMS device. Such apparatus can be particularly useful for MEMS gyroscope devices. For instance, the metal proof mass, which may have a density several times larger than that of silicon, is capable of reducing the quadrature and bias error in a MEMS gyroscope device, and capable of increasing the sensitivity of the MEMS gyroscope device.

Claims

1. An apparatus comprising:

a metal layer;

a first dielectric layer disposed on the metal layer;

a first electrode layer disposed on the first dielectric layer;

a piezoelectric layer disposed on the first electrode layer, the piezoelectric layer configured to respond to at least one of an electric field or a mechanical force;

a second electrode layer disposed on the piezoelectric layer, the first electrode layer and the second electrode layer configured to apply the electric field across the piezoelectric layer or to sense an electric field generated by the piezoelectric layer due to the mechanical force; and

a second dielectric layer disposed on the second electrode layer.

2. The apparatus of claim 1, where the metal layer is configured as a proof mass.

3. The apparatus of claim 1, further comprising:

a second metal layer disposed on the second dielectric layer.

4. The apparatus of claim 1, wherein a thickness of the metal layer is greater than about 5 micrometers.

5. The apparatus of claim 1, wherein a thickness of the piezoelectric layer is in the range of about 0.5 to 3 micrometers.

6. The apparatus of claim 1, wherein at least one of a thickness of the first electrode layer or a thickness of the second electrode layer are in the range of about 100 to 300 nanometers.

7. The apparatus of claim 1, wherein at least one of a thickness of the first dielectric layer or a thickness of the second dielectric layer are in the range of about 100 to 300 nanometers.

8. The apparatus of claim 1, wherein a thickness of the metal layer is greater than a combined thickness of the first dielectric layer, the first electrode layer, the piezoelectric layer, the second electrode layer, and the second dielectric layer.

9. The apparatus of claim 1, wherein the metal layer includes at least one of nickel, a nickel-manganese alloy, and a nickel-cobalt alloy.

10. The apparatus of claim 1, wherein the piezoelectric layer includes aluminum nitride.

11. The apparatus of claim 1, wherein the first electrode layer and the second electrode layer include a metal selected from the group consisting of copper, platinum, molybdenum, tungsten, ruthenium, gold and aluminum.

12. The apparatus of claim 1, wherein the first dielectric layer and the second dielectric layer include silicon oxide.

13. The apparatus of claim 1, wherein a root mean square roughness of the piezoelectric layer is less than about 1 nanometer.

14. An electromechanical gyroscope apparatus comprising:

a first device configured as a drive component of the electromechanical gyroscope apparatus, the first device including;

a metal layer;

a first dielectric layer disposed on the metal layer;

a first electrode layer disposed on the first dielectric layer;

a piezoelectric layer disposed on the first electrode layer, the piezoelectric layer configured to respond to an electric field;

a second electrode layer disposed on the piezoelectric layer, the first electrode layer and the second electrode layer configured to apply an electric field across the piezoelectric layer; and

a second dielectric layer disposed on the second electrode layer.

15. The apparatus of claim 14, further comprising:

a second device configured as a sense component of the electromechanical gyroscope apparatus, the second device including the metal layer, the first dielectric layer, the first electrode layer, the piezoelectric layer, the second electrode layer, and the second dielectric layer;

wherein the piezoelectric layer is further configured to respond to a mechanical force, and wherein the first electrode layer and the second electrode layer are further configured to sense an electric field generated by the piezoelectric layer due to the mechanical force.

16. The apparatus of claim 14, wherein the metal layer is configured as a proof mass.

17. The apparatus of claim 14, wherein a thickness of the metal layer is greater than about 5 micrometers.

18. The apparatus of claim 14, wherein a thickness of the metal layer is greater than a combined thickness of the first dielectric layer, the first electrode layer, the piezoelectric layer, the second electrode layer, and the second dielectric layer.

19. An apparatus of an electromechanical device, the apparatus comprising:

a metal layer;

a first dielectric layer disposed on the metal layer;

a first electrode layer disposed on the first dielectric layer;

a first piezoelectric layer disposed on the first electrode layer, the first piezoelectric layer configured to respond to a mechanical force;

a second electrode layer disposed on the first piezoelectric layer, the first electrode layer and the second electrode layer configured to sense a first electric field generated by the first piezoelectric layer in response to the mechanical force;

a second piezoelectric layer disposed on the second electrode layer, the second piezoelectric layer configured to respond to the mechanical force;

a third electrode layer disposed on the second piezoelectric layer, the second electrode layer and the third electrode layer configured to sense a second electric field generated by the second piezoelectric layer in response to the mechanical force, a differential signal capable of being provided by the combination of the sensed first electric field and the sensed second electric field; and

a second dielectric layer disposed on the third electrode layer.

20. The apparatus of claim 19, further comprising:

a second metal layer, the second metal layer disposed on the second dielectric layer.

21. The apparatus of claim 19, wherein the metal layer is configured as a proof mass.

22. The apparatus of claim 19, wherein a thickness of the metal layer is greater than about 5 micrometers.

23. The apparatus of claim 19, wherein a thickness of the metal layer is greater than a combined thickness of the first dielectric layer, the first electrode layer, the piezoelectric layer, the second electrode layer, and the second dielectric layer.

24. A method comprising:

forming a sacrificial layer on a substrate;

forming a first dielectric layer on the sacrificial layer;

forming a first electrode layer on the first dielectric layer;

forming a piezoelectric layer on the first electrode layer;

forming a second electrode layer on the piezoelectric layer;

forming a second dielectric layer on the second electrode layer; and

forming a metal layer on the second dielectric layer.

25. The method of claim 24, wherein the metal layer is configured to be a proof mass.

26. The method of claim 24, wherein the metal layer is formed with an electroplating process.

27. The method of claim 24, wherein the metal layer is formed with a sputtering process.

28. The method of claim 24, wherein the piezoelectric layer is formed with a sputtering process.

29. The method of claim 24, further comprising:

providing a photoresist layer on the second dielectric layer;

patterning the photoresist layer before forming the metal layer; and

removing the photoresist layer after forming the metal layer.

30. The method of claim 24, further comprising:

removing the sacrificial layer after forming the metal layer.

31. An apparatus comprising:

an electromechanical system device, the electromechanical system device including;

a first dielectric layer;

a first electrode layer disposed on the first dielectric layer;

a piezoelectric layer disposed on the first electrode layer, the piezoelectric layer configured to respond to at least one of an electric field or a mechanical force;

a second electrode layer disposed on the piezoelectric layer, the first electrode layer and the second electrode layer configured to apply the electric field across the piezoelectric layer or to sense an electric field generated by the piezoelectric layer due to the mechanical force;

a second dielectric layer disposed on the second electrode layer; and

a metal layer disposed on the second dielectric layer.

32. The apparatus of claim 31, further comprising:

a display;

a processor that is configured to communicate with the display, the processor being configured to process image data; and

a memory device that is configured to communicate with the processor.

33. The apparatus of claim 32, further comprising:

a driver circuit configured to send at least one signal to the display.

34. The apparatus of claim 33, further comprising:

a controller configured to send at least a portion of the image data to the driver circuit.

35. The apparatus of claim 32, further comprising:

an image source module configured to send the image data to the processor.

36. The apparatus of claim 35, wherein the image source module includes at least one of a receiver, transceiver, and transmitter.

37. The apparatus of claim 32, further comprising:

an input device configured to receive input data and to communicate the input data to the processor.