# US 9,040,427 B2 · Method of plasma etching > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,040,427 B2 - Document ID: US9040427B2 - Status: Granted - Kind: B2 - Application number: 14/043,818 - Filed: 2013-10-01 - Published: 2014-04-10 - Granted: 2015-05-26 - Earliest claimed: 2012-10-03 - Assignees: SPTS Technologies Limited - Applicants: Spts Technologies Limited - Inventors: Huma Ashraf; Anthony Barker - Web page: https://patentgrep.com/patent/US9040427B2 ## CPC - C23F 1/12: Gaseous compositions - H01J 37/32449: {Gas control, e.g. control of the gas flow} - H10P 50/242: {of Group IV materials} - H10P 50/692: {characterised by their composition, e.g. multilayer masks or materials} - C23F: NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE (working metal by laser beams B23K26/00; desurfacing by applying flames B23K7/00; working of metal by electro-erosion B23H; producing decorative effects by removing surface material, e.g. by engraving, by etching, B44C1/22; electrolytic etching or polishing C25F); INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25 - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 ## Abstract A method of plasma etching a silicon carbide workpiece includes forming a mask on a surface of the silicon carbide workpiece, performing an initial plasma etch on the masked surface using a first set of process conditions, wherein the plasma is produced using an etchant gas mixture which includes i) oxygen and ii) at least one fluorine rich gas which is present in the etchant gas mixture at a volume ratio of less than 50%, and subsequently performing a bulk plasma etch process using a second set of process conditions which differ from the first set of process conditions. ## Claims ### Claim 1 A method of plasma etching a silicon carbide wafer, including the steps of: forming a mask on a surface of the silicon carbide wafer; performing an initial plasma etch comprising etching the masked surface using plasma under a first set of process conditions, wherein the plasma is produced using an etchant gas mixture which includes i) oxygen and ii) at least one fluorine rich gas which is present in the etchant gas mixture at a volume ratio of less than 50%; and subsequently performing a bulk plasma etch process comprising etching the silicon carbide wafer using plasma under a second set of process conditions which differ from the first set of process conditions. ### Claim 2 (depends on 1) A method according to claim 1 in which the fluorine rich gas is present in the etchant gas mixture at a volume ratio in the range 0.1-20%. ### Claim 3 (depends on 1) A method according to claim 1 in which the at least one fluorine rich gas is CF4 and/or SF6. ### Claim 4 (depends on 1) A method according to claim 1 in which the plasma etching of the silicon carbide wafer is performed to provide one or more vias. ### Claim 5 (depends on 1) An apparatus for etching a silicon carbide workpiece including: a chamber; a workpiece support positioned in the chamber; a gas supply and pumping arrangement for providing etchant gases to the chamber; and a control arrangement configured to control the apparatus, including the gas supply and pumping arrangement, to perform a method according to claim 1. ### Claim 6 (depends on 1) A method according to claim 1 in which the fluorine rich gas is present in the etchant gas mixture at a volume ratio in the range 0.1-10%. ### Claim 7 (depends on 1) A method according to claim 1 in which the fluorine rich gas is present in the etchant gas mixture at a volume ratio in the range of 0.5-7%. ### Claim 8 (depends on 1) A method according to claim 1 in which the fluorine rich gas is present in the etchant gas mixture at a volume ratio of about 1.5%. ### Claim 9 (depends on 1) A method according to claim 1 in which the mask is a metallic mask. ### Claim 10 (depends on 9) A method according to claim 9 in which the mask is a nickel mask. ### Claim 11 (depends on 1) A method according to claim 1 in which the surface of the silicon carbide wafer on which the mask is formed is unpolished. ### Claim 12 (depends on 11) A method according to claim 11 in which the surface of the silicon carbide wafer on which the mask is formed is lapped. ### Claim 13 (depends on 1) A method according to claim 1 in which the initial plasma etch is performed to an etch depth of at least 250 nm. ### Claim 14 (depends on 13) A method according to claim 13 in which the initial plasma etch is performed to an etch depth of at least 700 nm. ### Claim 15 (depends on 1) A method according to claim 1 in which the etchant gas mixture further includes an inert carrier gas. ### Claim 16 (depends on 15) A method according to claim 15 in which the inert carrier gas is a noble gas. ### Claim 17 (depends on 15) A method according to claim 15 in which the inert carrier gas is argon.