# US 2020/0400620 A1 · Microfabricated ultrasonic transducers and related apparatus and methods > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2020/0400620 A1 - Document ID: US20200400620A1 - Status: Published application - Kind: A1 - Application number: 16/986,067 - Filed: 2020-08-05 - Published: 2020-12-24 - Earliest claimed: 2014-07-14 - Assignees: Butterfly Network, Inc. - Applicants: Butterfly Network, Inc. - Inventors: Jonathan M. Rothberg; Susan A. Alie; Keith G. Fife; Nevada J. Sanchez; Tyler S. Ralston - Web page: https://patentgrep.com/patent/US20200400620A1 ## CPC - G01N 29/2406: {Electrostatic or capacitive probes, e.g. electret or cMUT-probes} - A61B 8/4483: {characterised by features of the ultrasound transducer} - B06B 1/0292: {Electrostatic transducers, e.g. electret-type} - B81B 7/007: {Interconnections between the MEMS and external electrical signals} - B81C 1/00238: {Joining a substrate with an electronic processing unit and a substrate with a micromechanical structure} - B81C 1/00301: {Connecting electric signal lines from the MEMS device with external electrical signal lines, e.g. through vias} - B81B 2201/0271: Resonators; ultrasonic resonators - B81C 2201/019: Bonding or gluing multiple substrate layers - B81C 2203/036: Fusion bonding - B81C 2203/0792: Forming interconnections between the electronic processing unit and the micromechanical structure - H10W 72/5453: {connecting between multiple bond pads on a chip, e.g. daisy chain} - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - B06B: METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, {e.g.} FOR PERFORMING MECHANICAL WORK IN GENERAL (for particular applications, see the relevant subclasses, e.g. B07B1/40, B23Q17/12, B24B31/06; measurement of mechanical vibrations G01H; in direction finding, locating, distance or velocity measuring G01S; {generating seismic energy G01V1/02}; control of mechanical vibrations in general G05D; sound-producing devices, e.g. bells, sirens, whistles G10K, {e.g. methods or devices for transmitting, conducting, or directing sound in general G10K11/00}; generation of electrical oscillations H03B; electromechanical resonators in general H03H; electromechanical transducers {for communication techniques, e.g. microphones, speakers} H04R) - B81B: MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES (piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/00, H10N35/00) - B81C: PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS (making microcapsules or microballoons B01J13/02; processes or apparatus specially adapted for the manufacture or treatment of piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/01) - H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10 ## Abstract Micromachined ultrasonic transducers integrated with complementary metal oxide semiconductor (CMOS) substrates are described, as well as methods of fabricating such devices. Fabrication may involve two separate wafer bonding steps. Wafer bonding may be used to fabricate sealed cavities in a substrate. Wafer bonding may also be used to bond the substrate to another substrate, such as a CMOS wafer. At least the second wafer bonding may be performed at a low temperature. ## Claims ### Claim 1 (canceled) ### Claim 2 An ultrasound device, comprising: a membrane comprising a silicon layer; a complementary metal-oxide-semiconductor (CMOS) substrate including integrated circuitry; an electrode; and an ultrasonic transducer cavity; wherein: the ultrasonic transducer cavity is disposed between the membrane and the electrode; the electrode is disposed between the ultrasonic transducer cavity and the CMOS substrate; the electrode is electrically coupled to the integrated circuitry; and an opening extends from the ultrasonic transducer cavity and through the silicon layer. ### Claim 3 (depends on 2) The ultrasound device of claim 2, wherein the opening comprises a single opening that extends from the ultrasonic transducer cavity and through the silicon layer. ### Claim 4 (depends on 2) The ultrasound device of claim 2, wherein the opening comprises one of a plurality of openings that extend from the ultrasonic transducer cavity and through the silicon layer. ### Claim 5 (depends on 2) The ultrasound device of claim 2, wherein the opening extends vertically through the silicon layer. ### Claim 6 (depends on 2) The ultrasound device of claim 2, wherein the opening extends from the ultrasonic transducer cavity along a path comprising at least one non-vertical portion. ### Claim 7 (depends on 6) The ultrasound device of claim 6, wherein the opening extends to a trench disposed in the silicon layer at a periphery of the ultrasound device. ### Claim 8 (depends on 2) The ultrasound device of claim 2, wherein the opening is formed using etching. ### Claim 9 (depends on 2) The ultrasound device of claim 2, wherein the ultrasonic transducer cavity comprises one of a plurality of ultrasonic transducer cavities, the opening comprises one of a plurality of openings, and each of the plurality of openings extends to one of the plurality of ultrasonic transducer cavities. ### Claim 10 (depends on 2) The ultrasound device of claim 2, wherein the ultrasonic transducer cavity comprises one of a plurality of ultrasonic transducer cavities including a second ultrasonic transducer cavity that lacks an opening extending from it and through the silicon layer. ### Claim 11 (depends on 2) The ultrasound device of claim 2, wherein the membrane further comprises an oxide layer disposed between the silicon layer and the ultrasonic transducer cavity, and the opening extends through the oxide layer and the silicon layer. ### Claim 12 A method of forming an ultrasound device, wherein: the ultrasound device comprises a membrane comprising a silicon layer; a complementary metal-oxide-semiconductor (CMOS) substrate including integrated circuitry; an electrode; and an ultrasonic transducer cavity; wherein: the ultrasonic transducer cavity is disposed between the membrane and the electrode; the electrode is disposed between the ultrasonic transducer cavity and the CMOS substrate; and the electrode is electrically coupled to the integrated circuitry; and the method comprises forming an opening extending from the ultrasonic transducer cavity and through the silicon layer. ### Claim 13 (depends on 12) The method of claim 12, wherein forming the opening comprises forming a single opening that extends from the ultrasonic transducer cavity and through the silicon layer. ### Claim 14 (depends on 12) The method of claim 12, further comprising forming a plurality of openings that extend from the ultrasonic transducer cavity and through the silicon layer. ### Claim 15 (depends on 12) The method of claim 12, wherein forming the opening comprises forming the opening such that the opening extends vertically through the silicon layer. ### Claim 16 (depends on 13) The method of claim 13, wherein forming the opening comprises forming the opening such that the opening extends from the ultrasonic transducer cavity along a path comprising at least one non-vertical portion. ### Claim 17 (depends on 16) The method of claim 16, wherein forming the opening further comprises forming a trench in the silicon layer at a periphery of the ultrasound device such that the opening extends to the trench. ### Claim 18 (depends on 12) The method of claim 12, wherein forming the opening comprises using etching. ### Claim 19 (depends on 12) The method of claim 12, wherein the ultrasonic transducer cavity comprises one of a plurality of ultrasonic transducer cavities, and further comprising forming a plurality of openings such that each of the plurality of openings extends to one of the plurality of ultrasonic transducer cavities. ### Claim 20 (depends on 12) The method of claim 12, wherein the ultrasonic transducer cavity comprises one of a plurality of ultrasonic transducer cavities including a second ultrasonic transducer cavity that lacks an opening extending from it and through the silicon layer. ### Claim 21 (depends on 12) The method of claim 12, wherein the membrane further comprises an oxide layer disposed between the silicon layer and the ultrasonic transducer cavity, and forming the opening comprises forming the opening such that the opening extends through the oxide layer and the silicon layer.