# US 2026/0086065 A1 · Ion sensing with deep trench isolation varactors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2026/0086065 A1 - Document ID: US20260086065A1 - Status: Published application - Kind: A1 - Application number: 19/179,106 - Filed: 2025-04-15 - Published: 2026-03-26 - Earliest claimed: 2024-09-25 - Assignees: Microchip Technology Incorporated - Applicants: Microchip Technology Inc. - Inventors: Mazhar Hoque; Amit Rai; Samir Fuke; Joseph Rascon; Arthur B. Eck; Randy Yach - Web page: https://patentgrep.com/patent/US20260086065A1 ## CPC - G01N 27/4148: {Integrated circuits therefor, e.g. fabricated by CMOS processing} - G01N 27/226: {Construction of measuring vessels; Electrodes therefor} - G01N 27/4145: {specially adapted for biomolecules, e.g. gate electrode with immobilised receptors} - G01N 27/74: of fluids (G01N24/00 takes precedence) - H10D 1/20: Inductors - H10D 1/64: Variable-capacitance diodes, e.g. varactors - 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) - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES ## Abstract Aspects provide a device comprising: a substrate doped to form a first well; a first deep trench etched in the substrate; a dielectric in the first deep trench; a first conductor within the dielectric in the first deep trench and biased to create a first depletion region in the substrate proximate the first deep trench, wherein the substrate forms a bottom electrode of a first deep trench isolation varactor and the conductor in the first deep trench forms a top electrode of the first deep trench isolation varactor; a sense electrode operable to become electrically charged when interacting with an ionized fluid, wherein the sense electrode is operable to electrically charge the first deep trench isolation varactor; and a fluid property measurement circuit operable to determine a change in the capacitance of the first deep trench isolation varactor and output a fluid property signal. ## Claims ### Claim 1 A device comprising: a substrate doped to form a first well; a first deep trench etched in the substrate; a dielectric in the first deep trench; a first conductor within the dielectric in the first deep trench and biased to create a first depletion region in the substrate proximate the first deep trench, wherein the substrate forms a bottom electrode of a first deep trench isolation varactor and the conductor in the first deep trench forms a top electrode of the first deep trench isolation varactor; a sense electrode operable to become electrically charged when interacting with an ionized fluid, wherein the sense electrode is electrically connected to the top electrode of the deep trench isolation varactor, wherein the sense electrode is operable to electrically charge the first deep trench isolation varactor; and a fluid property measurement circuit operable to determine a change in the capacitance of the first deep trench isolation varactor and output a fluid property signal. ### Claim 2 (depends on 1) The device of claim 1, comprising a sensing membrane connected to the sense electrode and operable to electrically communicate with the sense electrode, wherein the sensing membrane is sensitive to a specific ion type in the ionized fluid. ### Claim 3 (depends on 1) The device of claim 1, comprising a sensing membrane connected to the sense electrode and operable to electrically communicate with the sense electrode, wherein the sensing membrane is sensitive to a plurality of ion types in the ionized fluid. ### Claim 4 (depends on 1) The device of claim 1, comprising a second deep trench isolation varactor of the integrated circuit comprising: a second deep trench etched in the substrate; a dielectric in the second deep trench; and a second conductor within the dielectric in the second deep trench, wherein the substrate forms a bottom electrode of a second deep trench isolation varactor and the second conductor in the second deep trench forms a top electrode of the second deep trench isolation varactor, wherein the fluid property measurement circuit is operable to measure a capacitance on the second deep trench isolation varactor and output a fluid property signal. ### Claim 5 (depends on 3) The device of claim 3, wherein the first deep trench isolation varactor and the second deep trench isolation varactor are connected differentially to form a differential deep trench isolation varactor. ### Claim 6 (depends on 1) The device of claim 1, comprising a control gate connected between the sense electrode and the first deep trench isolation varactor and operable to reset or calibrate the first deep trench isolation varactor. ### Claim 7 (depends on 4) The device of claim 4, wherein the second deep trench isolation varactor is electrically insulated from the ionized fluid, whereby the second deep trench isolation varactor is a reference varactor. ### Claim 8 (depends on 1) The device of claim 1, comprising: a second well surrounding the substrate and configured to isolate the substrate; and a buried layer proximate the substrate and configured to isolate the substrate, whereby the isolated substrate is biased, wherein the sense electrode is configured to electrically connect with the isolated substrate of the first deep trench isolation varactor. ### Claim 9 (depends on 1) The device of claim 1, comprising: a silicon base; and an insulator layered on the silicon base, wherein the substrate is layered on the insulator. ### Claim 10 A method, comprising: sensing an ionized fluid via a sense electrode; charging a first varactor via the sense electrode based on the sensing an ionized fluid, wherein the first varactor comprises a conductor in a dielectric in a deep trench in a substrate, the conductor biased to create a depletion region in the substrate proximate the deep trench; measuring a capacitance on the first varactor; and outputting a fluid property signal corresponding to the measured capacitance on the first varactor. ### Claim 11 (depends on 10) The method of claim 10, wherein sensing an ionized fluid via a sense electrode comprises sensing a specific ion type. ### Claim 12 (depends on 10) The method of claim 10, comprising: measuring a capacitance on a reference varactor; and comparing the measured capacitance on the first varactor with the measured capacitance on the reference varactor. ### Claim 13 (depends on 10) The method of claim 10, comprising resetting or calibrating the first varactor via a control gate. ### Claim 14 (depends on 10) The method of claim 10, comprising isolating the first varactor to form an isolated well and biasing the isolated well to connect it to the sense electrode to create a depletion region in the isolated substrate proximate the deep trench. ### Claim 15 A fluid property sensor made by a process comprising: doping a substrate to form a first well; etching a deep trench in the substrate; forming a dielectric in the deep trench; forming a conductor within the dielectric in the deep trench, wherein the substrate forms a bottom electrode of a deep trench isolation varactor and the conductor in the deep trench forms a top electrode of the deep trench isolation varactor; and electrically communicating with the top electrode of the deep trench isolation varactor a sense electrode operable to become electrically charged when interacting with an ionized fluid. ### Claim 16 (depends on 15) The fluid property sensor made by the process of claim 15, comprising: surrounding the substrate with a second well and configuring the second well to isolate the substrate; burying a buried layer proximate the substrate and configuring the buried layer to isolate the substrate, whereby the isolated substrate is biased; and configuring the sense electrode to electrically communicate with the isolated substrate of the deep trench isolation varactor. ### Claim 17 (depends on 15) The fluid property sensor made by the process of claim 15, comprising electrically insulating a second deep trench isolation varactor from the ionized fluid, whereby the second deep trench isolation varactor is a reference varactor. ### Claim 18 (depends on 17) The fluid property sensor made by the process of claim 17, comprising configuring the fluid property measurement circuit to compare the measured capacitance of the first deep trench isolation varactor with the measured capacitance of the reference varactor and output a fluid property signal. ### Claim 19 (depends on 15) The fluid property sensor made by the process of claim 15, comprising configuring a control gate to reset or calibrate an electrical communication between the sense electrode and the deep trench isolation varactor. ### Claim 20 (depends on 15) The fluid property sensor made by the process of claim 15, comprising connecting a sensing membrane to the sense electrode and configured to electrically communicate with the sense electrode, wherein the sensing membrane is configured to be sensitive to a specific ion type in the ionized fluid.