# US 10,375,481 B2 · MEMS device and process > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,375,481 B2 - Document ID: US10375481B2 - Status: Granted - Kind: B2 - Application number: 15/665,996 - Filed: 2017-08-01 - Published: 2017-12-14 - Granted: 2019-08-06 - Earliest claimed: 2012-09-24 - Assignees: Cirrus Logic, Inc. - Applicants: Cirrus Logic International Semiconductor Ltd. - Inventors: Colin Robert Jenkins; Tsjerk Hans Hoekstra; Euan James Boyd - Web page: https://patentgrep.com/patent/US10375481B2 ## CPC - H04R 19/005: {using semiconductor materials} - 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)} - B81B 3/0075: {For improving wear resistance} - B81C 1/00158: {Diaphragms, membranes (manufacture process for semi-permeable inorganic membranes B01D67/0039)} - H04R 1/222: {for microphones (H04R1/24, H04R1/26 take precedence)} - H04R 23/006: {using solid state devices (solid state devices per se H10)} - B81B 2201/0257: Microphones or microspeakers - B81B 2201/0264: Pressure sensors - 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 - H04R 2201/003: Mems transducers or their use - H10N 30/20: with electrical input and mechanical output, e.g. functioning as actuators or vibrators - H10N 30/204: {using bending displacement, e.g. unimorph, bimorph or multimorph cantilever or membrane benders} - H10W 90/724: {between a chip and a stacked insulating package substrate, interposer or RDL} - Y10T 29/49005: Acoustic transducer - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) - 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) - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR - H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10 - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract A MEMS capacitive transducer with increased robustness and resilience to acoustic shock. The transducer structure includes a flexible membrane supported between a first volume and a second volume, and at least one variable vent structure in communication with at least one of the first and second volumes. The variable vent structure includes at least one moveable portion which is moveable in response to a pressure differential across the moveable portion so as to vary the size of a flow path through the vent structure. The variable vent may be formed through the membrane and the moveable portion may be a part of the membrane, defined by one or more channels, that is deflectable away from the surface of the membrane. The variable vent is preferably closed in the normal range of pressure differentials but opens at high pressure differentials to provide more rapid equalisation of the air volumes above and below the membrane. ## Claims ### Claim 1 A MEMS transducer comprising: a flexible membrane; and at least one variable vent structure wherein said variable vent structure provides a flow path between a first volume on one side of the flexible membrane and a second volume on the other side of the flexible membrane, the vent structure having a size that varies according to a non-linear relationship with pressure differential across the membrane. ### Claim 2 (depends on 1) A MEMS transducer as claimed in claim 1, wherein said variable vent structure comprises at least one moveable portion which is moveable in response to a pressure differential across the moveable portion so as to vary the size of a flow path through the vent structure and wherein the equilibrium position of the at least one moveable portion corresponds to a minimum size of flow path. ### Claim 3 (depends on 2) A MEMS transducer as claimed in claim 2, wherein the at least one moveable portion is configured such that there is substantially no movement of the moveable portion from the equilibrium position at pressure differentials below a first threshold. ### Claim 4 (depends on 2) A MEMS transducer as claimed in claim 2, wherein the first threshold is greater than 150 Pa. ### Claim 5 (depends on 2) A MEMS transducer as claimed in claim 2, wherein the first threshold is greater than 1 kPa. ### Claim 6 (depends on 1) A MEMS transducer as claimed in claim 1, wherein at least one said variable vent structure provides substantially no significant variation in flow path size for pressure differentials in the range of 0 Pa-200 Pa. ### Claim 7 (depends on 2) A MEMS transducer as claimed in claim 2, wherein the at least one moveable portion is configured such that there is substantial movement of the moveable portion from the equilibrium position at pressure differentials above a second threshold. ### Claim 8 (depends on 7) A MEMS transducer as claimed in claim 7, wherein the second threshold is lower than 100 kPa. ### Claim 9 (depends on 1) A MEMS transducer as claimed in claim 1, wherein at least one said variable vent structure provides substantially a significant increase in flow path size for pressure differentials in the range of 100 kPa-200 kPa, compared to the flow path size at equilibrium. ### Claim 10 (depends on 1) A MEMS transducer as claimed in claim 1, wherein at least one said variable vent structure comprises at least one moveable portion which is moveable in response to a pressure differential across the moveable portion of at least 100 kPa. ### Claim 11 (depends on 2) A MEMS transducer as claimed in claim 2, wherein the equilibrium position of the at least one moveable portion corresponds to the flow path being substantially closed. ### Claim 12 (depends on 1) A MEMS transducer as claimed in claim 1, wherein at least one said variable vent structure is formed in the flexible membrane and the flow path is a path through the flexible membrane. ### Claim 13 (depends on 12) A MEMS transducer as claimed in claim 12, wherein the at least one moveable portion comprises a portion of the flexible membrane which is able to be deflected away from the surface of the rest of the flexible membrane. ### Claim 14 (depends on 13) A MEMS transducer as claimed in claim 13, wherein said moveable portion of the flexible membrane is connected to the rest of the flexible membrane via a beam structure. ### Claim 15 (depends on 14) A MEMS transducer as claimed in claim 14, wherein said beam structure is able to bend and/or twist to allow said moveable portion of the flexible membrane to be deflected away from the surface of the rest of the flexible membrane. ### Claim 16 (depends on 1) A MEMS transducer as claimed in claim 1, wherein at least one said variable vent structure comprises at least two moveable portions of the flexible membrane, the at least two moveable portions being able to be deflected away from the surface of the rest of the flexible membrane to expose a hole in the flexible membrane. ### Claim 17 (depends on 1) A MEMS transducer as claimed in claim 1, wherein at least one said variable vent structure is formed with a flow-path that bypasses the flexible membrane. ### Claim 18 (depends on 17) A MEMS transducer as claimed in claim 17, wherein the flow-path that bypasses the flexible membrane runs through at least part of a sidewall of a transducer structure that supports the flexible membrane. ### Claim 19 (depends on 1) A MEMS transducer as claimed in claim 1, comprising a back-plate structure wherein the flexible membrane is supported with respect to said back-plate structure. ### Claim 20 (depends on 1) A MEMS transducer as claimed in claim 1, wherein the transducer is a capacitive microphone.