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

• US 9,061,318 B2
• Filed: 12/05/2014
• Issued: 06/23/2015
• 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:
  US14/561,384
• Publication Number:
  US 20150084053A1
• Time in Patent Office: 200 Days
• US Class Current: 1/1
• 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 apparatus, comprising:

a semiconductor wafer having a complementary metal oxide semiconductor (CMOS) integrated circuit;

an electrode;

an insulating material having a cavity formed at least partially therein;

a conductive membrane contacting the insulating material, sealing the cavity and having a first side proximate the cavity and a second side distal the cavity, wherein the electrode, cavity, and conductive membrane together define, at least in part, an ultrasonic transducer, with the cavity being between the electrode and the conductive membrane;

a conductive contact coupling the electrode to the CMOS integrated circuit; and

a conductive plug embedded in the insulating material and terminating on the first side of the conductive membrane proximate the cavity without extending through the conductive membrane such that a surface of the conductive plug forms at least part of a bonding interface between the first side of the conductive membrane and the insulating material, the conductive plug electrically connecting the conductive membrane to the CMOS integrated circuit,

wherein the electrode and the conductive plug are electrically isolated from each other, and

wherein the apparatus lacks an electrode that is on the second side of the conductive membrane and that overlies the cavity.

2. The apparatus of claim 1, wherein the insulating material, the electrode, and the conductive plug are on the semiconductor wafer.

3. The apparatus of claim 2, wherein the conductive membrane comprises doped silicon.

4. The apparatus of claim 3, wherein the doped silicon is single crystal silicon.

5. The apparatus of claim 3, wherein the doped silicon is polysilicon.

6. The apparatus of claim 3, wherein the doped silicon is amorphous silicon.

7. The apparatus of claim 3, wherein the conductive plug comprises tungsten.

8. The apparatus of claim 2, wherein the insulating material defines a sidewall of the cavity.

9. The apparatus of claim 8, wherein the electrode is at least partially within the insulating material.

10. The apparatus of claim 2, wherein the cavity has a depth between 0.1 microns and 10 microns and a width between 20 microns and 100 microns, and wherein the conductive membrane has a thickness less than 30 microns.

11. The apparatus of claim 1, wherein the conductive membrane comprises doped silicon.

12. The apparatus of claim 11, wherein the doped silicon is single crystal silicon.

13. The apparatus of claim 11, wherein the doped silicon is polysilicon.

14. The apparatus of claim 11, wherein the doped silicon is amorphous silicon.

15. The apparatus of claim 11, wherein the conductive plug comprises tungsten.

16. The apparatus of claim 1, wherein the insulating material defines a sidewall of the cavity.

17. The apparatus of claim 1, wherein a width of the electrode is smaller than a width of the cavity.

18. The apparatus of claim 1, wherein the cavity has a depth between 0.1 microns and 10 microns and a width between 20 microns and 100 microns, and wherein the conductive membrane has a thickness less than 30 microns.