# US 9,716,140 B2 · Fluid sensor and method for examining a fluid > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,716,140 B2 - Document ID: US9716140B2 - Status: Granted - Kind: B2 - Application number: 14/674,850 - Filed: 2015-03-31 - Published: 2015-10-08 - Granted: 2017-07-25 - Earliest claimed: 2014-04-02 - Assignees: Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e. V. - Applicants: Fraunhofer Gesellschaft zur Foerderung der angewandten Forschung e. V. - Inventors: Ignaz Eisele - Web page: https://patentgrep.com/patent/US9716140B2 ## CPC - H10D 62/117: {Shapes of semiconductor bodies} - G01N 27/414: Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS - H10D 30/60: Insulated-gate field-effect transistors [IGFET] (H10D30/40 takes precedence) - H10D 84/811: {Combinations of field-effect devices and one or more diodes, capacitors or resistors} - H10D 84/813: {Combinations of field-effect devices and capacitor only} - Y10T 436/205831: Carbon monoxide only - Y10T 436/214: Acyclic [e.g., methane, octane, isoparaffin, etc.] - Y10T 436/22: Hydrogen, per se - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES - 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) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract Embodiments relate to a fluid sensor and a method for examining a fluid. A fluid sensor includes a substrate which comprises a recess for receiving a fluid to be examined, wherein the fluid sensor is implemented to detect electrical changes in the recess caused by the fluid to be examined. ## Claims ### Claim 1 A fluid sensor comprising a substrate including a recess for receiving a fluid to be examined, the fluid sensor further comprising an exterior electrode, wherein the exterior electrode at least partially surrounds the recess and is connected or connectable to a reference potential, and a transistor implemented to detect electrical changes in the recess caused by the fluid to be examined as electrical potential changes in the recess, wherein the transistor is an insulated gate field effect transistor, wherein an insulated gate of the insulated gate field effect transistor is arranged at least partially in the recess, wherein the fluid sensor further comprises a chemically sensitive layer at least partially arranged in the recess, wherein the insulated gate is at least partially arranged between the chemically sensitive layer and the exterior electrode, wherein the insulated gate is at least partially separated from the chemically sensitive layer and the exterior electrode by at least one insulation layer. ### Claim 2 (depends on 1) The fluid sensor according to claim 1, wherein the exterior electrode corresponds to a demarcated doped area of the substrate. ### Claim 3 (depends on 1) The fluid sensor according to claim 1, wherein at least a portion of the transistor is arranged outside the recess. ### Claim 4 (depends on 1) The fluid sensor according to claim 1, wherein the chemically sensitive layer in the recess forms a boundary layer to the fluid to be examined. ### Claim 5 (depends on 1) The fluid sensor according to claim 1, wherein the chemically sensitive layer surrounds the fluid to be examined in the recess at least partially and at least with respect to two spatial directions. ### Claim 6 (depends on 1) The fluid sensor according to claim 1, further comprising at least one insulation layer at least partially arranged between the substrate and the chemically sensitive layer. ### Claim 7 (depends on 1) The fluid sensor according to claim 1, wherein a gate oxide layer of the transistor is thinner than the at least one insulation layer. ### Claim 8 (depends on 1) The fluid sensor according to claim 1, wherein the recess comprises a vertical extent which is at least twice as large as a lateral extent of the recess along other spatial directions. ### Claim 9 (depends on 1) The fluid sensor according to claim 1, wherein the recess is implemented in the form of a trench, in the form of a passage or in the form of a gap. ### Claim 10 (depends on 1) The fluid sensor according to claim 1, wherein the recess is implemented as a passage through the substrate from a first side of the substrate to a second side of the substrate. ### Claim 11 (depends on 1) The fluid sensor according to claim 1, wherein the recess corresponds to a passage which is generally shaped as a hollow cylinder, wherein the insulated gate of the insulated gate field effect transistor at least partially extends along a wall of the hollow-cylinder-shaped passage of the substrate, and wherein the exterior electrode at least partially surrounds the passage. ### Claim 12 (depends on 1) The fluid sensor according to claim 1, wherein the substrate is at least a part of a semiconductor wafer. ### Claim 13 A fluid sensor comprising a recess for receiving a fluid to be examined, and a transistor which is implemented to detect an electrical change caused by the fluid to be examined, wherein the transistor is an insulated gate field effect transistor and an insulated gate of the insulated gate field effect transistor and the recess are at least partially surrounded by a common shielding electrode, wherein the insulated gate of the insulated gate field effect transistor is arranged at least partially in the recess, wherein the fluid sensor further comprises a chemically sensitive layer at least partially arranged in the recess, wherein the insulated gate is at least partially arranged between the chemically sensitive layer and the common shielding electrode, wherein the insulated gate is at least partially separated from the chemically sensitive layer and the common shielding electrode by at least one insulation layer. ### Claim 14 (depends on 13) The fluid sensor according to claim 13, wherein the recess lies outside a substrate on which the transistor is formed. ### Claim 15 A method for examining a fluid, comprising: passing the fluid through a recess of a substrate, wherein the recess is at least partially surrounded by an exterior electrode; detecting an electrical change in the recess using a chemically sensitive layer at least partially arranged in the recess and a transistor which is configured to detect the electrical change as a change of an electrical potential in the recess, wherein the transistor is an insulated gate field effect transistor, wherein an insulated gate of the insulated gate field effect transistor is arranged at least partially in the recess, wherein the insulated gate is at least partially arranged between the chemically sensitive layer and the exterior electrode, wherein the insulated gate is at least partially separated from the chemically sensitive layer and the exterior electrode by at least one insulation layer; and at least partially shielding the transistor in the recess using a reference potential.