CMOS ultrasonic transducers and related apparatus and methods

• US 9,499,392 B2
• Filed: 02/04/2014
• Issued: 11/22/2016
• 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): Smith, Zandra
• Assistant Examiner(s): TYNES JR., LAWRENCE C
• Application Number:
  US14/172,383
• Publication Number:
  US 20140217478A1
• Time in Patent Office: 1,022 Days
• Field of Search: 257/254, 438/459, 438/53
• 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 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:

depositing a first conductive layer on a silicon wafer;

depositing a second conductive layer on the first conductive layer;

depositing a first layer of SiO₂ on the second conductive layer;

etching at least one cavity in the first layer of SiO₂, a bottom surface of the at least one cavity corresponding to the second conductive layer;

depositing a second layer of SiO₂ on the first layer of SiO₂;

planarizing the second layer of SiO₂;

bonding a second wafer comprising silicon to the silicon wafer with a fusion bond;

thinning a backside of the second wafer distal the at least one cavity to form a membrane over the at least one cavity; and

depositing a third conductive layer on the membrane.

2. The method of claim 1, wherein the first conductive layer comprises aluminum.

3. The method of claim 1, wherein the second conductive layer comprises TiN.

4. The method of claim 1, wherein depositing the first layer of SiO₂ is performed via TEOS.

5. The method of claim 1, wherein the method does not involve any steps performed at higher than 450°

C.

6. The method of claim 1, wherein the silicon wafer has a complementary metal oxide semiconductor (CMOS) circuit formed therein, and wherein the method further comprises electrically connecting the third conductive layer to the CMOS circuit.