Micromechanical device with piezoelectric and electrostatic actuation and method therefor

• US 7,830,066 B2
• Filed: 07/26/2007
• Issued: 11/09/2010
• Est. Priority Date: 07/26/2007
• Status: Expired due to Fees

• Current Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Liu, Lianjun
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US11/828,902
• Publication Number:
  US 20090026880A1
• Time in Patent Office: 1,202 Days
• Field of Search: 310/328, 310330-332, 310/311
• US Class Current: 310/309
• CPC Class Codes: H01G 5/18 due to change in inclination, e.g. by flexing, by spiral wrapping
• CPC Class Codes: H02N 1/008 Laterally driven motors, e.g. of the comb-drive type
• CPC Class Codes: H10N 30/2042 Cantilevers, i.e. having one fixed end

Abstract

A MEMS device uses both piezoelectric actuation and electrostatic actuation and also provides enough electrostatic force to enable very low voltage operation. As the electrostatic actuation uses DC and the piezoelectric actuation uses high frequency, the structure of the device minimizes the coupling of the two actuator structures to reduce noise. In addition, for some embodiments, the location of the physical structures of the piezoelectric actuator and electrostatic actuator generates higher contact force with lower voltage. For some embodiments, the piezoelectric actuator and electrostatic actuator of the device are connected at the contact shorting bar or capacitor plate location. This makes the contact shorting bar or capacitor plate the focal point of the forces generated by all of the actuators, thereby increasing the switch contact force.

Claims

1. A device for coupling an input signal to an output signal, comprising:

a piezoelectric actuator comprising a support layer, a first piezoelectric electrode overlying the support layer, a piezoelectric material layer overlying the first piezoelectric electrode layer, and a second piezoelectric electrode overlying the piezoelectric material layer; and

an electrostatic actuator comprising a contact shorting bar formed over the support layer, wherein the contact shorting bar is coupled to receive the input signal, a first electrostatic actuator portion overlying the support layer and a second electrostatic actuator portion overlying the support layer, wherein the piezoelectric actuator is coupled to the electrostatic actuator at the contact shorting bar, and wherein the first electrostatic portion comprises a first electrode and a second electrode and the second electrostatic portion comprises a third electrode and a fourth electrode, and wherein each of the first electrode and the third electrode is coupled to a power supply voltage and wherein each of the second electrode and the fourth electrode is coupled to a ground voltage, and wherein the piezoelectric actuator and the electrostatic actuator are arranged in a manner that they are separated physically from each other both in a first direction and a second direction that is perpendicular to the first direction.

2. The device of claim 1, wherein the contact shorting bar is configured as a capacitor electrode.

3. The device of claim 1, wherein a layout of the first electrostatic actuator portion and a layout of the second electrostatic actuator portion are approximately symmetrical with respect to the contact shorting bar.

4. The device of claim 2, and wherein a layout of the first electrostatic actuator portion and a layout of the second electrostatic actuator portion are approximately symmetrical with respect to the capacitor electrode.

5. The device of claim 1 further comprising a first voltage pad and a second voltage pad, wherein an actuation voltage is coupled to the piezoelectric actuator via the first voltage pad and the second voltage pad.

6. The device of claim 5, wherein the input signal received by the device is coupled to the output signal in response to the actuation voltage causing a movement of the piezoelectric actuator.

7. A device for coupling an input signal received via a first conductor to an output signal received via a second conductor, comprising:

a piezoelectric actuator comprising a support layer, a first piezoelectric electrode overlying the support layer, a piezoelectric material layer overlying the first piezoelectric electrode layer, and a second piezoelectric electrode overlying the piezoelectric material layer; and

an electrostatic actuator comprising a contact shorting bar formed over the support layer, wherein the contact shorting bar is coupled to receive the input signal, a first electrostatic actuator portion overlying the support layer and a second electrostatic actuator portion overlying the support layer, wherein the piezoelectric actuator is coupled to the electrostatic actuator only at the contact shorting bar, and wherein the first conductor and the second conductor are aligned in a straight line along a first direction, and wherein the piezoelectric actuator and the electrostatic actuator are arranged in a manner that they are separated physically from each other both in the first direction and a second direction that is perpendicular to the first direction.

8. The device of claim 7, wherein the contact shorting bar is configured as a capacitor electrode, and wherein the piezoelectric actuator is coupled to the electrostatic actuator at the capacitor electrode.

9. The device of claim 7, wherein a layout of the first electrostatic actuator portion and a layout of the second electrostatic actuator portion are approximately symmetrical with respect to the contact shorting bar.

10. The device of claim 8, wherein a layout of the first electrostatic actuator portion and a layout of the second electrostatic actuator portion are approximately symmetrical with respect to the capacitor electrode.

11. The device of claim 7 further comprising a first voltage pad and a second voltage pad, wherein an actuation voltage is coupled to the piezoelectric actuator via the first voltage pad and the second voltage pad.

12. The device of claim 11, wherein the input signal received by the device is coupled to the output signal in response to the actuation voltage causing a movement of the piezoelectric actuator.

13. A device for coupling an input signal received via an input conductor to an output signal provided via an output conductor, comprising:

a piezoelectric actuator comprising a first piezoelectric actuator portion and as second piezoelectric actuator portion, wherein the first piezoelectric actuator portion comprises a support layer, a first piezoelectric electrode overlying the support layer, a piezoelectric material layer overlying the first piezoelectric electrode layer, and a second piezoelectric electrode overlying the piezoelectric material layer, and wherein the second piezoelectric actuator portion comprises a support layer, a first piezoelectric portion, and a second piezoelectric portion, and wherein the first piezoelectric actuator portion and the second piezoelectric actuator portion are located at a peripheral location compared to a location of the input conductor and the output conductor; and

an electrostatic actuator comprising a contact shorting bar formed over the support layer, wherein the contact shorting bar is coupled to receive the input signal, a first electrostatic actuator portion overlying the support layer and a second electrostatic actuator portion overlying the support layer, wherein the piezoelectric actuator is coupled to the electrostatic actuator at the contact shorting bar, and wherein the first electrostatic portion comprises a first electrode and a second electrode and the second electrostatic portion comprises a third electrode and a fourth electrode, and wherein each of the first electrode and the third electrode is coupled to a power supply voltage and wherein each of the second electrode and the fourth electrode is coupled to a ground voltage, and wherein the piezoelectric actuator and the electrostatic actuator are arranged in a manner that they are separated physically from each other both in a first direction and a second direction that is perpendicular to the first direction.

14. The device of claim 13, wherein the contact shorting bar is configured as a capacitor electrode, and wherein the piezoelectric actuator is coupled to the electrostatic actuator at the capacitor electrode.

15. The device of claim 13, wherein a layout of the first electrostatic actuator portion and a layout of the second electrostatic actuator portion are approximately symmetrical with respect to the contact shorting bar.

16. The device of claim 15, wherein a layout of the first electrostatic actuator portion and a layout of the second electrostatic actuator portion are approximately symmetrical with respect to the capacitor electrode.

17. The device of claim 13 further comprising a first voltage pad and a second voltage pad, wherein an actuation voltage is coupled to the piezoelectric actuator via the first voltage pad and the second voltage pad.

18. The device of claim 17, wherein the input signal received by the device is coupled to the output signal in response to the actuation voltage causing a movement of the piezoelectric actuator.

19. The device of claim 13, wherein a layout of the first piezoelectric actuator portion and a layout of the second piezoelectric actuator portion are approximately symmetrical with respect to the contact shorting bar.

20. The device of claim 14, wherein a layout of the first piezoelectric actuator portion and a layout of the second piezoelectric actuator portion are approximately symmetrical with respect to the capacitor electrode.