ELECTRICAL TUNING OF PARAMETERS OF PIEZOELECTRIC ACTUATED TRANSDUCERS

• US 20150358740A1
• Filed: 06/04/2014
• Published: 12/10/2015
• Est. Priority Date: 06/04/2014
• Status: Abandoned Application

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Tsai, Julius Ming-Lin, Lloyd, Stephen
• Application Number:
  US14/295,881
• Publication Number:
  US 20150358740A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2562/02 Details of sensors specially adapted for in-vivo measurements
• CPC Class Codes: A61B 5/1172 using fingerprinting
• CPC Class Codes: G01N 29/36 Detecting the response signal , e.g. electronic circuits specially adapted therefor
• CPC Class Codes: H04R 17/00 Piezoelectric transducers; Electrostrictive transducers piezoelectric or electrostrictive elements in general H10N30/00; details of piezoelectric or electrostrictive motors, generators or positioners H10N30/00
• CPC Class Codes: H04R 2201/003 Mems transducers or their use
• CPC Class Codes: H04R 2217/03 Parametric transducers where sound is generated or captured by the acoustic demodulation of amplitude modulated ultrasonic waves
• CPC Class Codes: H04R 29/001 for loudspeakers H04R29/007 takes precedence
• CPC Class Codes: H04R 3/04 for correcting frequency response

Abstract

Parameters, such as, quality factor and/or resonance frequency of an acoustic transducer can be electrically tuned. The acoustic transducer can include a piezoelectric layer deposited on a silicon supporting layer, a first electrode layer deposited on the piezoelectric layer, and a second electrode layer deposited between the silicon supporting layer and piezoelectric layer. In one aspect, a resonant frequency of the piezoelectric actuated transducer is electrically tuned based on modifying a voltage across at least a portion of the first electrode layer and the second electrode layer. In another aspect, a quality factor of the piezoelectric actuated transducer is electrically tuned based on modifying a resistance across at least another portion of the first electrode layer and the second electrode layer.

Claims

1. A piezoelectric actuated transducer, comprising:

a piezoelectric layer deposited on a silicon supporting layer;

a first electrode layer deposited on the piezoelectric layer; and

a second electrode layer deposited between the silicon supporting layer and the piezoelectric layer, wherein at least a portion of the first electrode layer and the second electrode layer are coupled to a direct current voltage source to facilitate electrical tuning of a resonant frequency of the piezoelectric actuated transducer.

2. The piezoelectric actuated transducer of claim 1, wherein the second electrode layer comprises a supporting silicon layer having a doping level that exceeds a defined threshold.

3. The piezoelectric actuated transducer of claim 1, wherein a voltage of the direct current voltage source is programmable.

4. The piezoelectric actuated transducer of claim 1, wherein a voltage of the direct current voltage source is time variant.

5. The piezoelectric actuated transducer of claim 4, wherein the voltage is modified based on a mode of operation of the piezoelectric actuated transducer.

6. The piezoelectric actuated transducer of claim 1, further comprising:

a released structure comprising the silicon supporting layer, wherein a shape of the released structure is defined in-plane with a microelectromechanical systems (MEMS) membrane that comprises the piezoelectric layer, the first electrode layer and the second electrode layer.

7. The piezoelectric actuated transducer of claim 6, wherein the released structure operates in at least one of vacuum, air, or a liquid.

8. The piezoelectric actuated transducer of claim 1, wherein a shape of at least the portion of the first electrode layer and the second electrode layer is defined in-plane with a microelectromechanical systems (MEMS) membrane that comprises the piezoelectric layer, the first electrode layer and the second electrode layer.

9. The piezoelectric actuated transducer of claim 1, wherein at least the portion of the first electrode layer and the second electrode layer are placed at a location associated with a constraint of a microelectromechanical systems (MEMS) membrane that comprises the piezoelectric layer, the first electrode layer and the second electrode layer, wherein the constraint is a flexible structure in connection to an anchor of the MEMS membrane.

10. The piezoelectric actuated transducer of claim 9, wherein the MEMS membrane is a circular MEMS membrane and the location is at a periphery of the circular MEMS membrane.

11. The piezoelectric actuated transducer of claim 1, wherein the portion is a first portion and at least a second portion of the first electrode layer and the second electrode layer are coupled to a variable resistor to facilitate electrical tuning of a quality factor of the piezoelectric actuated transducer.

12. A piezoelectric actuated transducer, comprising:

a piezoelectric layer deposited on a silicon supporting layer;

a first electrode layer deposited on the piezoelectric layer; and

a second electrode layer deposited between the silicon supporting layer and the piezoelectric layer, wherein at least a portion of the first electrode layer and the second electrode layer are coupled to a resistor to facilitate electrical tuning of a quality factor of the piezoelectric actuated transducer.

13. The piezoelectric actuated transducer of claim 12, wherein the second electrode layer comprises a supporting silicon layer having a doping level that exceeds a defined threshold.

14. The piezoelectric actuated transducer of claim 12, wherein a resistance of the resistor is programmable.

15. The piezoelectric actuated transducer of claim 12, wherein a resistance of the resistor is time variant.

16. The piezoelectric actuated transducer of claim 15, wherein the resistance is modified based on a mode of operation of the piezoelectric actuated transducer.

17. The piezoelectric actuated transducer of claim 12, further comprising:

a released structure comprising the silicon supporting layer, wherein a shape of the released structure is defined in-plane with a microelectromechanical systems (MEMS) membrane that comprises the piezoelectric layer, the first electrode layer and the second electrode layer.

18. The piezoelectric actuated transducer of claim 17, wherein the released structure operates in at least one of vacuum, air, or a liquid.

19. The piezoelectric actuated transducer of claim 12, wherein a shape of at least the portion of the first electrode layer and the second electrode layer is defined in-plane with a microelectromechanical systems (MEMS) membrane that comprises the piezoelectric layer, the first electrode layer and the second electrode layer.

20. The piezoelectric actuated transducer of claim 12, wherein the first electrode layer and the second electrode layer are placed at a defined area of a microelectromechanical systems (MEMS) membrane that comprises the piezoelectric layer, the first electrode layer and the second electrode layer, wherein the defined area satisfies a specified strain criterion.

21. The piezoelectric actuated transducer of claim 20, wherein the MEMS membrane is a circular MEMS membrane and the defined area is at a center of the circular MEMS membrane.

22. The piezoelectric actuated transducer of claim 12, wherein the first electrode layer and the second electrode layer are coupled to a voltage source to facilitate electrical tuning of a resonant frequency of the piezoelectric actuated transducer.

23. A method, comprising:

depositing a piezoelectric layer on a silicon supporting layer;

forming a first electrode layer on the piezoelectric layer and a second electrode layer between the silicon supporting layer and the piezoelectric layer to form a piezoelectric actuated transducer; and

tuning a resonant frequency of the piezoelectric actuated transducer based on controlling a voltage signal across at least a portion of the first electrode layer and the second electrode layer.

24. The method of claim 23, wherein the forming the second electrode layer comprises doping a supporting silicon layer, wherein a doping level of the supporting silicon layer exceeds a defined threshold.

25. The method of claim 23, wherein the controlling the voltage signal comprises controlling the voltage signal based on a mode of operation of the piezoelectric actuated transducer.

26. The method of claim 23, further comprising:

forming a released structure comprising the silicon supporting layer, the piezoelectric layer, the first electrode layer and the second electrode layer; and

operating the released structure in at least one of vacuum, air, or a liquid.

27. The method of claim 23, wherein the forming the first electrode layer and the second electrode layer comprises forming at least the portion of the first electrode layer and the second electrode layer at a location associated with a constraint of a microelectromechanical systems (MEMS) membrane that comprises the piezoelectric layer, the first electrode layer and the second electrode layer, wherein the constraint is a flexible structure in connection to an anchor of the MEMS membrane.

28. The method of claim 23, wherein the portion is a first portion and the method further comprises:

tuning a quality factor of the piezoelectric actuated transducer based on controlling a resistance across at least a second portion of the first electrode layer and the second electrode layer.

29. The method of claim 28, wherein the forming the first electrode layer and the second electrode layer comprises forming at least the second portion of the first electrode layer and the second electrode layer at a location of a microelectromechanical systems (MEMS) membrane that comprises the piezoelectric layer, the first electrode layer and the second electrode layer, wherein the location is determined to satisfy a defined strain criterion.

30. A biometric sensing method, comprising:

transmitting an ultrasonic signal by an acoustic sensing element having a voltage source coupled across a first electrode that is deposited on a piezoelectric layer and a second electrode that is deposited below the piezoelectric layer;

sensing, by the piezoelectric layer, an interference signal that is generated based on an interference of the ultrasonic signal with an object; and

controlling a voltage of the voltage source to tune a resonant frequency of the piezoelectric layer.

31. The biometric sensing method of claim 30, comprising a fingerprint sensing method, wherein the object comprises a finger.