Complementary metal oxide semiconductor (CMOS) ultrasonic transducers and methods for forming the same

• US 10,710,873 B2
• Filed: 03/01/2019
• Issued: 07/14/2020
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: BFLY Operations, Inc. (Butterfly Network, Inc.)
• Original Assignee: Butterfly Network, Inc.
• Inventors: Rothberg, Jonathan M., Fife, Keith G., Ralston, Tyler S., Charvat, Gregory L., Sanchez, Nevada J.
• Primary Examiner(s): Smoot, Stephen W
• Application Number:
  US16/290,188
• Publication Number:
  US 20190210869A1
• Time in Patent Office: 501 Days
• Field of Search: 257416, 257419
• CPC Class Codes: B06B 1/02 making use of electrical energy B06B1/18, B06B1/20 take precedence
• CPC Class Codes: B06B 1/0292 Electrostatic transducers, e.g. electret-type
• CPC Class Codes: B81B 7/007 Interconnections between the MEMS and external electrical signals
• CPC Class Codes: B81C 1/00134 comprising flexible or deformable structures manufacture of MEMS devices for specific applications, see relevant places, e.g. gyroscopes G01C19/5719, pressure sensors G01L9/0042, accelerometers G01P15/0802, acoustic transducers or diaphragms therefor H04R31/00
• CPC Class Codes: B81C 1/00158 Diaphragms, membranes manufacture process for semi-permeable inorganic membranes B01D67/0039
• CPC Class Codes: B81C 1/00246 Monolithic integration, i.e. micromechanical structure and electronic processing unit are integrated on the same substrate
• CPC Class Codes: B81C 1/00301 Connecting electric signal lines from the MEMS device with external electrical signal lines, e.g. through vias
• CPC Class Codes: B81C 2201/0195 the layer being unstructured
• CPC Class Codes: B81C 2203/0735 Post-CMOS, i.e. forming the micromechanical structure after the CMOS circuit
• CPC Class Codes: B81C 2203/0771 Stacking the electronic processing unit and the micromechanical structure
• CPC Class Codes: G01N 29/2406 Electrostatic or capacitive probes, e.g. electret or cMUT-probes
• CPC Class Codes: H01L 29/84 controllable by variation of applied mechanical force, e.g. of pressure
• CPC Class Codes: H04R 19/005 using semiconductor materials

Abstract

Complementary metal oxide semiconductor (CMOS) ultrasonic transducers (CUTs) and methods for forming CUTs are described. The CUTs may include monolithically integrated ultrasonic transducers and integrated circuits for operating in connection with the transducers. The CUTs may be used in ultrasound devices such as ultrasound imaging devices and/or high intensity focused ultrasound (HIFU) devices.

Claims

1. An ultrasonic transducer apparatus, comprising:

a substrate comprising;

an integrated circuit; and

a metal layer electrically connected to the integrated circuit;

one or more standoff structures disposed on an uppermost portion of the substrate;

a membrane bonded to the one or more standoff structures such that a sealed cavity exists between the uppermost portion of the substrate and a bottommost portion of the membrane, thereby defining, at least in part, an ultrasonic transducer; and

a conductive material extending from the metal layer, through one of the one or more standoff structures, and to an uppermost portion of the membrane.

2. The ultrasonic transducer apparatus of claim 1, wherein the conductive material includes titanium nitride.

3. The ultrasonic transducer apparatus of claim 1, further comprising one or more passivation layers formed on the conductive material on the uppermost portion of the membrane.

4. The ultrasonic transducer apparatus of claim 1, wherein:

the membrane comprises;

a first layer on the bottommost portion of the membrane; and

a second layer that is coupled to the first layer, wherein the second layer comprises silicon.

5. The ultrasonic transducer apparatus of claim 4, wherein:

the membrane comprises a third layer that is coupled to the second layer; and

the third layer comprises a buried oxide layer from a silicon-on-insulator (SOI) substrate.

6. The ultrasonic transducer apparatus of claim 1, wherein the substrate comprises a metal electrode aligned with the sealed cavity.

7. The ultrasonic transducer apparatus of claim 6, wherein the metal electrode is electrically connected to the integrated circuit.

8. The ultrasonic transducer apparatus of claim 1, wherein the one or more standoff structures comprise sidewalls of the sealed cavity.

9. The ultrasonic transducer apparatus of claim 1, further comprising electrical contacts disposed on the uppermost portion of the membrane.

10. A method, comprising:

forming one or more first standoff structures on an uppermost portion of a substrate, the substrate comprising;

an integrated circuit; and

a metal layer electrically connected to the integrated circuit;

bonding a membrane to the one or more first standoff structures such that a sealed cavity exists between the uppermost portion of the substrate and a bottommost portion of the membrane, thereby defining, at least in part, an ultrasonic transducer; and

forming a conductive material extending from the metal layer, through one of the one or more first standoff structures, and to an uppermost portion of the membrane.

11. The method of claim 10, wherein the conductive material includes titanium nitride.

12. The method of claim 10, further comprising forming one or more passivation layers deposited on the conductive material on the uppermost portion of the membrane.

13. The method of claim 10, wherein:

the membrane comprises;

a first layer on the bottommost portion of the membrane; and

a second layer that is coupled to the first layer, wherein the second layer comprises silicon.

14. The method of claim 13, wherein:

the membrane comprises a third layer that is coupled to the second layer; and

the third layer comprises a buried oxide layer from a silicon-on-insulator (SOI) substrate.

15. The method of claim 10, wherein the substrate comprises a metal electrode aligned with the sealed cavity.

16. The method of claim 15, wherein the metal electrode is electrically connected to the integrated circuit.

17. The method of claim 10, wherein the one or more first standoff structures comprise sidewalls of the sealed cavity.

18. The method of claim 10, further comprising forming electrical contacts on the uppermost portion of the membrane.

19. An ultrasonic transducer apparatus, comprising:

a substrate comprising;

an integrated circuit; and

a metal layer electrically connected to the integrated circuit;

one or more standoff structures disposed on an uppermost portion of the substrate;

a membrane bonded to the one or more standoff structures such that a sealed cavity exists between the uppermost portion of the substrate and a bottommost portion of the membrane, thereby defining, at least in part, an ultrasonic transducer, and such that the one or more standoff structures create a standoff between the substrate and the membrane; and

a layer disposed in a portion of the sealed cavity such that the portion of the sealed cavity has a smaller depth than another portion of the sealed cavity.

20. The ultrasonic transducer apparatus of claim 19, wherein the layer comprises a patterned layer.

21. The ultrasonic transducer of claim 19, wherein the layer is disposed on the uppermost portion of the substrate.