PIEZOELECTRIC ARRAY EMPLOYING INTEGRATED MEMS SWITCHES

• US 20140232241A1
• Filed: 02/15/2013
• Published: 08/21/2014
• Est. Priority Date: 02/15/2013
• Status: Active Grant

• Current Assignee: Fujifilm Dimatix, Inc. (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Dimatix, Inc. (Fujifilm Holdings Corporation)
• Inventors: HAJATI, Arman
• Granted Patent: US 9,096,422 B2
• Time in Patent Office: Days
• US Class Current: 310/317
• CPC Class Codes: B06B 1/0207 Driving circuits specially adapted for particular applications, see the relevant subclass, e.g. G01; circuits for steering transducer arrays G10K11/34; basic circuits H03
• CPC Class Codes: B06B 1/0629 Square array
• CPC Class Codes: B06B 2201/20 Application to multi-element transducer
• CPC Class Codes: B81B 7/008 MEMS characterised by an electronic circuit specially adapted for controlling or driving the same B81B7/0087 takes precedence; arrangements for starting, regulating, braking, or otherwise controlling an actuator H02N; control arrangements or circuits for visual indicators G09G3/00
• CPC Class Codes: B81B 7/02 containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS] B81B7/04 takes precedence
• CPC Class Codes: G01N 29/262 by electronic orientation or focusing, e.g. with phased arrays phased arrays per se G10K11/34
• CPC Class Codes: G01S 15/8925 the array being a two-dimensional transducer configuration, i.e. matrix or orthogonal linear arrays
• CPC Class Codes: G01S 7/52017 particularly adapted to short-range imaging G01S7/53 takes precedence
• CPC Class Codes: G10K 11/346 using phase variation
• CPC Class Codes: H01H 1/0036 Switches making use of microelectromechanical systems [MEMS] for electromagnetic relays H01H50/005; for electrostatic relays H01H59/0009
• CPC Class Codes: H10N 30/1071 with electrical and mechanical input and output, e.g. having combined actuator and sensor parts
• CPC Class Codes: H10N 30/2047 Membrane type
• CPC Class Codes: H10N 39/00 Integrated devices, or assemblies of multiple devices, comprising at least one piezoelectric, electrostrictive or magnetostrictive element covered by groups H10N30/00 – H10N35/00

Abstract

Switchable micromachined transducer arrays are described where a MicroElectroMechanical Systems (MEMS) switch, or relay, is monolithically integrated with a transducer element. In embodiments, the MEMS switch is implemented in the same substrate as the transducer array to implement one or more logic, addressing, or transducer control function. In embodiments, each transducer element of an array is a piezoelectric element coupled to at least one MEMS switch to provide element-level addressing within the array. In certain embodiments the same piezoelectric material employed in the transducer is utilized in the MEMS switch.

Claims

1. A piezoelectric micromachined transducer (pMUT) array, comprising:

a transducer substrate;

a plurality of piezoelectric transducers disposed over a first area of the transducer substrate; and

a plurality of MEMS switches coupled to the plurality of transducers, wherein states of the MEMS switches control access to individual transducers of the plurality.

2. The pMUT array of claim 1, wherein the MEMS switch comprises a piezoelectric, electrostatic or electromagnetic switching member and wherein the MEMS switches are disposed over a second area of the transducer substrate.

3. The pMUT array of claim 2, wherein the array is a two dimensional (2D) array, wherein the plurality of transducer elements are resonant within the ultrasonic frequency band, and wherein the MEMS switch comprises a piezoelectric member employing a same piezoelectric material as the plurality of transducers.

4. The pMUT of claim 3, wherein the MEMS switch is a capacitive switch comprising a cantilever or fixed beam further comprising the piezoelectric material.

5. The pMUT of claim 3, wherein the plurality of MEMS switches comprises a MEMS switch connected in series with at least one of a drive/sense electrode and a ground electrode of an individual transducer element.

6. The pMUT of claim 5, wherein the plurality of MEMS switches comprises a MEMS switch connected in series with the drive/sense electrode of an individual transducer element, the MEMS switch disposed between the transducer element and a drive/sense channel and operable to selectably pass a drive/sense voltage.

7. The pMUT of claim 1, wherein the array comprises a plurality of transducers having drive/sense electrodes selectably coupled to a first drive/sense channel by the MEMS switches, wherein each of the plurality of MEMS switches is coupled to one or more MEMS switch controllers that are to control states of the MEMS switches to couple an individual transducer to the first drive/sense channel.

8. The pMUT of claim 7, wherein the array further comprises a first column of transducers, each transducer in the first column coupled to a first drive/sense channel through one of first MEMS switches, and wherein states of the first MEMS switches are to couple a first transducer of the first column to the first drive/sense channel at a first time while decoupling all other transducers of the first column from the first drive/sense channel.

9. The pMUT of claim 8, wherein states of the first MEMS switches are to couple a second transducer of the first column to the first drive/sense channel at a second time while decoupling all other transducers of the first column from the first drive/sense channel.

10. The pMUT of claim 9, wherein the array is a two dimensional array further comprising a second column of transducers with individual transducers of the second column aligned into rows with individual transducers in the first column, wherein each transducer in the second column is coupled to a second drive/sense channel through at least one of second MEMS switches, and wherein states of the second MEMS switches are to match the states of the first MEMS switches to couple a first transducer of the second column to the second drive/sense channel at the first time and to couple a second transducer of the second column to the second drive/sense channel at the second time.

11. The pMUT of claim 7, wherein the one or more MEMS switch controllers further comprise additional MEMS switches disposed over a third area of the transducer substrate or CMOS transistors disposed over a CMOS substrate.

12. The pMUT of claim 1, wherein the MEMS switch is connected to a sample and hold circuit connected to a drive/sense electrode of the transducer.

13. The pMUT of claim 12, wherein the sample and hold circuit further comprises a capacitor disposed over the transducer substrate.

14. The pMUT of claim 12, wherein the sample and hold circuit comprises a plurality of MEMS switches connected to a transducer drive/sense channel, each of the MEMS switches further coupled to a capacitive element with the plurality operable to sequentially store a sample of a time varying drive/sense voltage on the channel to one of the capacitors and enable analog beamforming directly at the transducer.

15. An apparatus for generating and sensing pressure waves in a medium, the apparatus comprising:

the pMUT array of claim 1;

one or more signal generator coupled to the pMUT array to apply an electrical drive signal on a first drive/sense channel;

one or more receiver coupled to the pMUT array to receive an electrical response signal from the first drive/sense channel;

one or more switch controller connected to at least a first of the MEMS switches to couple different ones of the piezoelectric transducers to the first drive/sense channel over time; and

at least one signal processor coupled to the receiver to process a plurality of electrical response signals received from the drive/sense channel.

16. The apparatus of claim 15, wherein the pMUT array is a two-dimensional array with a first plurality of transducers along a first dimension coupled to the first drive/sense channel, a second plurality of transducers along the first dimension coupled to a second drive/sense channel, and wherein the first and second plurality of transducers form rows of transducers along a second dimension with the at least one switch controller to set a plurality of switches to a same state coupling all transducers of a same row to the drive/sense channels concurrently.

17. The apparatus of claim 15, wherein the generator is coupled to a first pole of at least a first of the MEMS switches and is to apply an electrical drive signal to cause a transducer connected through a MEMS switch to resonate at frequencies between 1 MHz and 50 MHz.

18. A method of generating and sensing pressure waves in a medium, the method comprising:

coupling a first piezoelectric micromachined transducer (pMUT) of a pMUT array disposed over a transducer substrate to a first drive/sense channel during a first time period by setting a first MEMS switch to a first state while setting a second MEMS switch to a second, complementary, state;

applying an electrical drive signal on the first drive/sense channel during a first portion of the first time period;

receiving an electrical response signal from the first drive/sense channel during a second portion of the first time period; and

coupling a second pMUT of the array to the first drive/sense channel during a second time period by setting the second MEMS switch to the first state while setting the first MEMS switch to the second, complementary, state.

19. The method of claim 18, further comprising:

reapplying the electrical drive signal on the first drive/sense channel during the second time period; and

receiving another electrical response signal from the first drive/sense channel.

20. The method of claim 18, further comprising:

coupling a third pMUT of the array to a second drive/sense channel during the first portion of the first time period by setting a third MEMS switch, also disposed over the transducer substrate, to the first state;

applying an electrical drive signal on the second drive/sense channel during the first portion of the first time period; and

receiving an electrical response signal from the second drive/sense channel during the second portion of the first time period.

21. The method of claim 18, wherein setting the first MEMS switch comprises applying a voltage to an electrode coupled to a piezoelectric member of the MEMS switch sufficient to short circuit or capacitively couple the first pMUT to the first drive/sense channel.

22. The method of claim 18, wherein coupling the first pMUT to the first drive/sense channel further comprises

coupling a drive/sense electrode of the first pMUT to a capacitor by setting the first MEMS switch to the first state;

and

discharging the capacitor to the first drive/sense channel.

23. The method of claim 18, wherein setting the first MEMS switch to the first state during the first time period and setting the second MEMS switch to the first state during the second time period comprises scanning a first dimension of the array and wherein at least one of the electrical drive signal applied on the second drive/sense channel during the first portion the first time period or the electrical response single received from the second drive/sense channel during the second portion of the first time period is time delayed relative the corresponding electrical drive or sense signal on the first drive/sense channel to phase the array along a second dimension.