# US 11,029,227 B2 · CSOI MEMS pressure sensing element with stress equalizers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,029,227 B2 - Document ID: US11029227B2 - Status: Granted - Kind: B2 - Application number: 16/123,367 - Filed: 2018-09-06 - Published: 2019-12-05 - Granted: 2021-06-08 - Earliest claimed: 2018-06-04 - Assignees: Vitesco Technologies USA, LLC - Applicants: Continental Automotive Systems, Inc. - Inventors: Jen-Huang Albert Chiou; Shiuh-Hui Steven Chen - Web page: https://patentgrep.com/patent/US11029227B2 ## CPC - G01L 9/0054: {integral with a semiconducting diaphragm} - G01L 9/0042: {Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms (details about the integration or bonding of piezoresistor in or on the diaphragm G01L9/0052 and G01L9/0057 respectively)} - G01L 9/0045: {Diaphragm associated with a buried cavity} - G01L 9/06: of piezo-resistive devices - G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G) ## Abstract A pressure sensing element includes a supporting substrate including a cavity. A device layer is bonded to the supporting substrate, with a diaphragm of the device layer covering the cavity in a sealed manner. A plurality of piezoresistors is coupled to the diaphragm. A plurality of metal stress equalizers is disposed on the device layer such that each stress equalizer is generally adjacent to, but separated from, a corresponding piezoresistor. A plurality of metal bond pads is disposed on the device layer. The plurality of stress equalizers are constructed and arranged to reduce thermal hysteresis of the pressure sensing element caused by stress relaxation of the metal bond pads during a cooling and heating cycle of the pressure sensing element. ## Claims ### Claim 1 A pressure sensing element, comprising: a supporting substrate including a cavity; a device layer bonded to the supporting substrate, with a diaphragm of the device layer covering the cavity in a sealed manner; a plurality of piezoresistors coupled to the diaphragm; a plurality of metal stress equalizers disposed on the device layer such that each stress equalizer is generally adjacent to, but separated from, a corresponding piezoresistor, and a plurality of metal bond pads disposed on the device layer, wherein the plurality of stress equalizers are constructed and arranged to reduce thermal hysteresis of the pressure sensing element caused by stress relaxation of the metal bond pads during a cooling and heating cycle of the pressure sensing element. ### Claim 2 (depends on 1) The pressure sensing element of claim 1, wherein the plurality of stress equalizers is constructed and arranged on the device layer so as to increase radial stresses on the plurality of piezoresistors and decrease tangential stresses on the plurality of piezoresistors during the cooling and heating cycle. ### Claim 3 (depends on 2) The pressure sensing element of claim 2, wherein four piezoresistors are provided on the diaphragm near a circumferential edge thereof and in a Wheatstone Bridge arrangement, and four corresponding stress equalizers are provided on the device layer outside the circumferential edge of the diaphragm. ### Claim 4 (depends on 3) The pressure sensing element of claim 3, wherein the four stress equalizers are arranged symmetrically on the device layer. ### Claim 5 (depends on 2) The pressure sensing element of claim 2, wherein the metal of each of the plurality of bond pads and of each of the plurality of stress equalizers is aluminum. ### Claim 6 (depends on 4) The pressure sensing element of claim 4, wherein each of the stress equalizers is in a rectangular shape. ### Claim 7 (depends on 4) The pressure sensing element of claim 4, wherein each of the stress equalizers is in at least one of an elliptical shape and a T shape. ### Claim 8 (depends on 1) The pressure sensing element of claim 1, wherein the plurality of stress equalizers is separated from the plurality of bond pads. ### Claim 9 (depends on 3) The pressure sensing element of claim 3, wherein two of the piezoresistors and two of the corresponding stress equalizers are disposed on a first axis and the other two piezoresistors and other two corresponding stress equalizers are disposed on a second axis that is perpendicular to the first axis. ### Claim 10 A method of controlling thermal hysteresis of a pressure sensing element, the method comprising the steps of: providing a pressure sensing element having a supporting substrate including a cavity; a device layer bonded to the supporting substrate, with a diaphragm of the device layer covering the cavity in a sealed manner; a plurality of piezoresistors coupled to the diaphragm; and a plurality of metal bond pads disposed on the device layer, and controlling thermal hysteresis of the pressure sensing element caused by stress relaxation of the metal bond pads during a heating and cooling cycle by increasing radial stress and decreasing tangential stress on each of the plurality of piezoresistors on the pressure sensing element. ### Claim 11 (depends on 10) The method of claim 10, wherein the step of controlling thermal hysteresis includes: providing plurality of metal stress equalizers disposed on the device layer such that each stress equalizer is generally adjacent to, but separated from, a corresponding piezoresistor. ### Claim 12 (depends on 11) The method of claim 11, wherein four piezoresistors are provided on the diaphragm near a circumferential edge thereof and in a Wheatstone Bridge arrangement, and the method provides four corresponding stress equalizers on the device layer outside the circumferential edge of the diaphragm. ### Claim 13 (depends on 12) The method of claim 12, wherein the four stress equalizers are arranged symmetrically on the device layer. ### Claim 14 (depends on 11) The method of claim 11, wherein the metal of each of the plurality of bond pads and of each of the plurality of stress equalizers is aluminum. ### Claim 15 (depends on 11) The method of claim 11, wherein each of the stress equalizers is provided in a rectangular shape. ### Claim 16 (depends on 11) The method of claim 11, wherein each of the stress equalizers is provided in an elliptical shape. ### Claim 17 (depends on 11) The method of claim 11, wherein each of the stress equalizers is provided in a T shape. ### Claim 18 (depends on 11) The method of claim 11, wherein the plurality of stress equalizers is separated from the plurality of bond pads. ### Claim 19 (depends on 12) The method of claim 12, wherein two of the piezoresistors and two of the corresponding stress equalizers are disposed on a first axis and the other two piezoresistors and other two corresponding stress equalizers are disposed on a second axis that is perpendicular to the first axis.