# US 10,768,138 B2 · Protecting a substrate region during fabrication of a FET sensor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,768,138 B2 - Document ID: US10768138B2 - Status: Granted - Kind: B2 - Application number: 16/228,092 - Filed: 2018-12-20 - Published: 2019-06-27 - Granted: 2020-09-08 - Earliest claimed: 2017-12-21 - Assignees: Imec Vzw - Applicants: Imec Vzw - Inventors: Koen Martens; Nadine Collaert; Eddy Kunnen; Simone Severi - Web page: https://patentgrep.com/patent/US10768138B2 ## CPC - G01N 27/4146: {involving nanosized elements, e.g. nanotubes, nanowires} - G01N 27/4145: {specially adapted for biomolecules, e.g. gate electrode with immobilised receptors} - 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) ## Abstract Examples include a method for forming an intermediate in the fabrication of a field-effect transistor sensor, the method comprising: providing a substrate having a substrate region comprising a gate dielectric thereon and optionally a nanocavity therein, providing a sacrificial element over the substrate region, providing one or more layers having a combined thickness of at least 100 nm over the sacrificial element, opening an access to the sacrificial element through the one or more layers, and optionally selectively removing the sacrificial element, thereby opening a sensor cavity over the substrate region; wherein the sacrificial element is removable by oxidation and wherein selectively removing the sacrificial element comprises an oxidative removal. ## Claims ### Claim 1 A method for forming a field-effect transistor sensor, the method comprising: providing a substrate having a substrate region comprising a gate dielectric, providing a sacrificial element over the substrate region, providing one or more layers having a combined thickness perpendicular to the substrate of at least 100 nm over the sacrificial element, opening an access to the sacrificial element through the one or more layers, wherein the sacrificial element extends beyond the access in a direction that is parallel to the substrate, and removing the sacrificial element, thereby opening a sensor cavity over the substrate region, wherein removing the sacrificial element comprises removing the sacrificial element via oxidative removal, wherein the sacrificial element comprises a carbon-based material and wherein the oxidative removal comprises an oxygen-based plasma etching. ### Claim 2 (depends on 1) The method according to claim 1, wherein the sensor cavity has its smallest lateral dimension measuring at most 100 nm, and wherein the access has a dimension, in the direction of the smallest lateral dimension of the sensor cavity, larger than the smallest lateral dimension of the sensor cavity. ### Claim 3 (depends on 1) The method according to claim 1, wherein removing the sacrificial element comprises selectively removing the sacrificial element with respect to an exposed material comprising Al, Al2O3, Ti, or TixOy. ### Claim 4 (depends on 1) The method of claim 1, wherein the oxidative removal comprises contacting the sacrificial element with a peroxide solution. ### Claim 5 (depends on 1) The method according to claim 1, wherein opening the access comprises using a mask that is removable via removal of the sacrificial element. ### Claim 6 (depends on 1) The method of claim 1, wherein the substrate region comprises a nanocavity. ### Claim 7 (depends on 1) The method according to claim 1, wherein the sacrificial element comprises a metal. ### Claim 8 (depends on 7) The method according to claim 7, wherein the metal comprises one or more of TiN, W, or TaN. ### Claim 9 (depends on 1) The method according to claim 1, wherein the one or more layers have a combined thickness of at least 500 nm. ### Claim 10 (depends on 1) The method according to claim 1, wherein the one or more layers have a combined thickness of at least 1 μm. ### Claim 11 (depends on 1) The method according to claim 1, further comprising: providing a further sacrificial element over the sacrificial element, and removing the further sacrificial element. ### Claim 12 (depends on 11) The method according to claim 11, further comprising forming a fluidic channel by removing the further sacrificial element. ### Claim 13 A field-effect transistor (FET) obtained by a method comprising: providing a substrate having a substrate region comprising a gate dielectric, providing a sacrificial element over the substrate region, providing one or more layers having a combined thickness perpendicular to the substrate of at least 100 nm over the sacrificial element, opening an access to the sacrificial element through the one or more layers, wherein the sacrificial element extends beyond the access in a direction that is parallel to the substrate, and removing the sacrificial element, thereby opening a sensor cavity over the substrate region, wherein removing the sacrificial element comprises removing the sacrificial element via oxidative removal, wherein the sacrificial element comprises a carbon-based material and wherein the oxidative removal comprises an oxygen-based plasma etching. ### Claim 14 (depends on 13) The FET according to claim 13, wherein the sacrificial element further comprises a metal. ### Claim 15 (depends on 13) The FET according to claim 13, further comprising an exposed material comprising one or more of Al, Al2O3, Ti or TixOy, and wherein the sacrificial element is selectively removable by oxidation with respect to the exposed material. ### Claim 16 (depends on 13) The FET according to claim 13, further comprising a fluidic channel, the fluidic channel being filled with a further sacrificial element.