CMOS ultrasonic transducers and related apparatus and methods

• US 10,518,292 B2
• Filed: 01/11/2018
• Issued: 12/31/2019
• Est. Priority Date: 02/05/2013
• 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): Baghdasaryan, Hovhannes
• Application Number:
  US15/868,989
• Publication Number:
  US 20180133756A1
• Time in Patent Office: 719 Days
• Field of Search: None
• 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 2203/0127 Diaphragms, i.e. structures separating two media that can control the passage from one medium to another; Membranes, i.e. diaphragms with filtering function
• CPC Class Codes: B81B 2203/0315 Cavities
• CPC Class Codes: B81B 2207/015 the micromechanical device and the control or processing electronics being integrated on the same substrate
• CPC Class Codes: B81B 3/0021 Transducers for transforming electrical into mechanical energy or vice versa dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00
• CPC Class Codes: B81B 7/0077 Other packages not provided for in groups B81B7/0035 - B81B7/0074
• CPC Class Codes: B81C 1/00158 Diaphragms, membranes manufacture process for semi-permeable inorganic membranes B01D67/0039
• CPC Class Codes: B81C 2201/013 Etching
• CPC Class Codes: B81C 2203/0118 Bonding a wafer on the substrate, i.e. where the cap consists of another wafer
• 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: G10K 11/18 Methods or devices for transmitting, conducting or directing sound G10K11/02, G10K11/36 take precedence
• CPC Class Codes: G10K 9/12 electrically operated

Abstract

CMOS Ultrasonic Transducers and processes for making such devices are described. The processes may include forming cavities on a first wafer and bonding the first wafer to a second wafer. The second wafer may be processed to form a membrane for the cavities. Electrical access to the cavities may be provided.

Claims

1. A method, comprising:

forming a cavity on a top region of a complementary metal oxide semiconductor (CMOS) substrate, the cavity surrounded by a lip region;

disposing a membrane over the lip region to substantially seal the cavity;

forming a first electrical contact on a top side of the membrane, wherein the top side of the membrane is disposed distal the cavity, and wherein a bottom side of the membrane and the first electrical contact are doped with substantially a same dopant;

forming a second electrical contact on the CMOS substrate; and

connecting the second electrical contact to the first electrical contact.

2. The method of claim 1, wherein the first electrical contact and the second electrical contact comprise a metal.

3. The method of claim 1, wherein the first electrical contact and the second electrical contact comprise aluminum.

4. The method of claim 1, further comprising forming an interface layer between the first electrical contact and the top side of the membrane.

5. The method of claim 1, wherein the first electrical contact is common to two or more membranes of two or more cavities.

6. The method of claim 1, wherein forming the second electrical contact comprises etching the CMOS substrate to expose the second electrical contact.

7. The method of claim 1, further comprising forming a third electrical contact on the CMOS substrate, wherein the third electrical contact is electrically coupled to a substrate electrode disposed on an opposite side of the cavity from the membrane, with the cavity between the substrate electrode and the membrane.

8. The method of claim 1, wherein the membrane and the first electrical contact are doped with substantially a same dopant.

9. The method of claim 1, wherein the CMOS substrate comprises processing circuitry configured to:

actuate the membrane to transmit an ultrasound wave; and

detect a received ultrasound wave based on vibration of the membrane.

10. An ultrasound structure, comprising:

a complementary metal-oxide-semiconductor (CMOS) substrate having a cavity formed therein, the cavity surrounded by a lip region;

a membrane disposed over the lip region to substantially seal the cavity;

a first electrical contact on a top side of the membrane, wherein the top side of the membrane is disposed distal to the cavity, and wherein a bottom side of the membrane and the first electrical contact are doped with substantially a same dopant; and

a second electrical contact on the CMOS substrate;

wherein

the second electrical contact and the first electrical contact are connected.

11. The ultrasound structure of claim 10, wherein the first electrical contact and the second electrical contact comprise a metal.

12. The ultrasound structure of claim 10, wherein the first electrical contact and the second electrical contact comprise aluminum.

13. The ultrasound structure of claim 10, further comprising an interface layer between the first electrical contact and the top side of the membrane.

14. The ultrasound structure of claim 10, wherein the first electrical contact is common to two or more membranes of two or more cavities.

15. The ultrasound structure of claim 10, further comprising a third electrical contact on the CMOS substrate, wherein the third electrical contact is electrically coupled to a substrate electrode disposed on an opposite side of the cavity from the membrane, with the cavity between the substrate electrode and the membrane.

16. The ultrasound structure of claim 10, wherein the membrane and the first electrical contact are doped with substantially a same dopant.

17. The ultrasound structure of claim 10, wherein the CMOS substrate comprises processing circuitry configured to:

actuate the membrane to transmit an ultrasound wave; and

detect a received ultrasound wave based on vibration of the membrane.