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

• US 10,266,401 B2
• Filed: 03/02/2018
• Issued: 04/23/2019
• 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:
  US15/910,776
• Publication Number:
  US 20180186628A1
• Time in Patent Office: 417 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;

a membrane bonded to the substrate such that a sealed cavity exists between an uppermost portion of the substrate and the membrane, thereby defining, at least in part, an ultrasonic transducer, with the sealed cavity disposed between the membrane and the substrate, the membrane comprising a first layer on a bottommost portion of the membrane, a second layer coupled to the first layer, and a buried oxide layer coupled to the second layer, the second layer comprising silicon; and

one or more first standoff structures disposed on the uppermost portion of the substrate, wherein the one or more first standoff structures create a standoff between the substrate and the membrane and comprise a same material as the first layer on the bottommost portion of the membrane.

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

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

4. An ultrasonic transducer apparatus, comprising:

a substrate comprising an integrated circuit;

a membrane bonded to the substrate such that a sealed cavity exists between an uppermost portion of the substrate and the membrane, thereby defining, at least in part, an ultrasonic transducer, with the sealed cavity disposed between the membrane and the substrate, the membrane comprising a first layer on a bottommost portion of the membrane and a second layer coupled to the first layer, the second layer comprising silicon; and

one or more first standoff structures disposed on the uppermost portion of the substrate, wherein the one or more first standoff structures create a standoff between the substrate and the membrane and comprise a same material as the first layer on the bottommost portion of the membrane,

wherein the membrane comprises one or more second standoff structures contacting the one or more first standoff structures.

5. The ultrasonic transducer apparatus of claim 4, wherein the one or more second standoff structures are bonded to the one or more first standoff structures.

6. The ultrasonic transducer apparatus of claim 5, wherein the one or more second standoff structures are bonded to the one or more first standoff structures such that the one or more second standoff structures are aligned with the one or more first standoff structures.

7. The ultrasonic transducer apparatus of claim 4, wherein the one or more second standoff structures comprise a same material as the one or more first standoff structures.

8. The ultrasonic transducer apparatus of claim 4, wherein the substrate comprises a metal electrode aligned with the sealed cavity.

9. The ultrasonic transducer apparatus of claim 4, wherein the one or more first standoff structures comprise sidewalls of the sealed cavity.

10. A method, comprising:

forming one or more first standoff structures on an uppermost portion of a substrate comprising an integrated circuit; and

bonding the substrate with a membrane such that a sealed cavity exists between the uppermost portion of the substrate and the membrane, thereby defining, at least in part, an ultrasonic transducer, with the sealed cavity disposed between the membrane and the substrate, wherein the membrane comprises a first layer on a bottommost portion of the membrane, a second layer coupled to the first layer, and a buried oxide layer coupled to the second layer, the second layer comprising silicon,

wherein the one or more first standoff structures create a standoff between the substrate and the membrane and comprise a same material as the first layer on the bottommost portion of the membrane.

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

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

13. A method, comprising:

forming one or more first standoff structures on an uppermost portion of a substrate comprising an integrated circuit; and

bonding the substrate with a membrane such that a sealed cavity exists between the uppermost portion of the substrate and the membrane, thereby defining, at least in part, an ultrasonic transducer, with the sealed cavity disposed between the membrane and the substrate, wherein the membrane comprises a first layer on a bottommost portion of the membrane and a second layer coupled to the first layer, the second layer comprising silicon,

wherein;

the one or more first standoff structures create a standoff between the substrate and the membrane and comprise a same material as the first layer on the bottommost portion of the membrane,

the membrane comprises one or more second standoff structures, and

bonding the substrate with the membrane comprises bonding the one or more first standoff structures with the one or more second standoff structures.

14. The method of claim 13, wherein bonding the one or more first standoff structures with the one or more second standoff structures comprises aligning the one or more first standoff structures with the one or more second standoff structures.

15. The method of claim 13, wherein the one or more second standoff structures comprise a same material as the one or more first standoff structures.

16. The method of claim 13, wherein the substrate comprises a metal electrode aligned with the sealed cavity.

17. The method of claim 13, wherein the one or more first standoff structures comprise sidewalls of the sealed cavity.