# US 2013/0278142 A1 · Three-coil inductively coupled plasma source with individually controlled coil currents from a single rf power generator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0278142 A1 - Document ID: US20130278142A1 - Status: Published application - Kind: A1 - Application number: 13/863,614 - Filed: 2013-04-16 - Published: 2013-10-24 - Earliest claimed: 2012-04-24 - Assignees: Applied Materials, Inc. - Applicants: Applied Materials, Inc. - Inventors: Leonid Dorf; Shahid Rauf; Jonathan Liu; Jason A. Kenney; Andrew Nguyen; Kenneth S. Collins; Kartik Ramaswamy; Steven Lane - Web page: https://patentgrep.com/patent/US20130278142A1 ## CPC - H01J 37/32183: {Matching circuits} - H01J 37/32082: {Radio frequency generated discharge (H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence)} - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract An inductively coupled plasma reactor has three concentric coil antennas and a current divider circuit individually controlling currents in each of the three coil antennas by varying two variable impedance elements in the current divider circuit in response to a desired current apportionment among the coil antennas received from a user interface. ## Claims ### Claim 1 A plasma reactor for processing a workpiece, comprising: an RF power generator and an impedance match coupled to said RF power generator; three coil antennas having respective driven ends and return ends, said return ends being connected to a common potential; three current divider branches coupled between said impedance match and the driven ends of respective ones of said coil antennas, each one of a pair of said three current divider branches comprising a respective variable impedance element; and a current apportionment controller controlling impedances of said variable impedance elements of said pair of current divider branches in response to a user-specified apportionment of currents among said three coil antennas. ### Claim 2 (depends on 1) The reactor of claim 1 wherein said current apportionment controller comprises: a look-up table storing a sequence of pairs of impedance values of said variable impedance elements. ### Claim 3 (depends on 2) The reactor of claim 2 wherein said sequence of pairs of values defines a linear programming sequence. ### Claim 4 (depends on 3) The reactor of claim 3 wherein said user interface is adapted, to record a user-selected point along said path and transmit said user-selected point to said current apportionment controller. ### Claim 5 (depends on 3) The reactor of claim 3 wherein said sequence of pairs of values defines a path in a 2-dimensional space whose dimensions are the impedance values of said variable impedance elements. ### Claim 6 (depends on 5) The reactor of claim 5 wherein said path includes: a reference point at which currents in said three coil antennas are at least approximately equal, a first point at which current in a first one of said coil antennas, relative to currents a second and third one of said coil antennas, is near a maximum, a second point at which current in said second coil antenna, relative to currents in said first and third coil antennas, is near a maximum, and a third point at which current in said third coil antenna, relative to currents in said first and second coil antennas, is near a maximum, ### Claim 7 (depends on 1) The reactor of claim 1 wherein said apportionment controller comprises: a memory containing data representing respective currents in said three coil antennas relative to total current as functions of values of said variable impedance elements; a processor for determining from said data the impedance values of said variable impedance elements at which said respective currents in said three coil antennas at least nearly correspond to said user-specified apportionment. ### Claim 8 A method of individually controlling currents in three coil antennas of a plasma reactor supplied from an RF generator through an RF impedance match, comprising: providing respective current divider branches between said impedance match and respective ones of said coil antennas, each of at least two of said current divider branches comprising a respective variable impedance element; providing a model comprising a first set of equations defining voltage drops in said current divider branches in accordance with mutual inductances of said coil antennas and corresponding portions of a plasma in said reactor and a second set of equations defining voltage drops in said corresponding portions of said plasma in accordance with said mutual inductances; solving said first and second sets of equations for currents in said coil antennas relative to total current as 3-dimensional functions of impedance values of said variable impedance elements in said at least two current divider branches; correlating information corresponding to said functions to a user-defined apportionment of currents in said coil antennas. ### Claim 9 (depends on 8) The method of claim 8 wherein said correlating comprises: searching said functions for respective points in a space representing pairs of values of said variable impedance elements at which coil currents are maximum for respective ones of said coil antennas; defining a linear programming path that includes said respective points; responding to a user selection of a location on said linear programming path by controlling impedance values of said variable impedance elements in accordance with said location. ### Claim 10 (depends on 9) The method of claim 9 wherein said correlating comprises: searching said functions for a set of impedance values of said variable impedance elements corresponding to an apportionment of currents among said coil antennas that at least nearly approximates a user-defined apportionment. ### Claim 11 A method of individually controlling currents in three coil antennas of a plasma reactor supplied from an RF generator through an RF impedance match, comprising: providing respective current divider branches between said impedance match and respective ones of said coil antennas, at least two of said current divider branches comprising a respective variable impedance element; correlating information, corresponding to coil antenna currents as 3-dimensional functions of impedance values of said variable impedance elements, to a user-defined apportionment of currents in said coil antennas. ### Claim 12 (depends on 11) The method of claim 11 wherein said correlating comprises: defining respective points in a space representing pairs of values of said variable impedance elements at which coil antenna currents are maximum for respective ones of said coil antennas; defining a linear programming path that includes said respective points; responding to a user selection of a location on said linear programming path by controlling impedance values of said variable impedance elements in accordance with said location. ### Claim 13 A plasma reactor for processing a workpiece, comprising: an Pop power generator and an impedance match coupled to said RF power generator; three coil antennas having respective driven ends and return ends, said return ends being connected to a common potential; a pair of current divider branches each comprising respective series and parallel impedance elements, the series impedance element of each of said pair of current divider branches being of an impedance value other than zero or infinity and being coupled between said impedance match and the driven end of a respective one of said, coil antennas, the parallel impedance element of each of said pair of current divider branches being of an impedance value other than zero and being coupled in parallel with a respective one of said coil antennas; a third current divider branch coupled between said impedance match the driven end of a third one of said three coil antennas; and a current apportionment controller controlling impedances of either (a) said series impedance elements of said pair of current divider branches or (b) said parallel impedance elements of said pair of current divider branches, in response to a user-specified apportionment of currents to said three coil antennas received from said user interface. ### Claim 14 (depends on 13) The reactor of claim 13 wherein said current apportionment controller comprises: a look-up table storing a sequence of pairs of impedance values of said first and second variable impedance elements. ### Claim 15 (depends on 14) The reactor of claim 14 wherein said sequence of pairs of values defines a linear programming sequence. ### Claim 16 (depends on 15) The reactor of claim 15 wherein said user interface is adapted to record a user-selected point along said path and transmit said user-selected point to said current apportionment controller. ### Claim 17 (depends on 15) The reactor of claim 15 wherein said sequence of pairs of values defines a path in a 2-dimensional space whose dimensions are the impedance values of said variable impedance elements. ### Claim 18 (depends on 17) The reactor of claim 17 wherein said path includes: a reference point at which currents in said three RF coil antennas are at least approximately equal, a first point at which current in said a first one of said coil antennas, relative to currents in said second and third ones of said coil antennas, is near a maximum, a second point at which current in said second coil antenna, relative to currents in said first and third coil antennas, is near a maximum, and a third point at which current in said third coil antenna, relative to currents in said first and second coil antennas, is near a maximum. ### Claim 19 (depends on 13) The reactor of claim 13 wherein said apportionment controller comprises: a memory containing data representing respective currents in said three RF coil antennas relative to total current as functions of values of said variable impedance elements; a processor for determining from said data the values of said variable impedance elements at which said respective currents in said three coil antennas at least nearly correspond to said user-specified apportionment. ### Claim 20 (depends on 13) The reactor of claim 13 wherein said three coil antennas are concentric and wherein an outermost one of said three coil antennas comprises a side coil antenna, and said reactor comprises a cylindrical side window around which said side coil antenna is disposed.