Three-coil inductively coupled plasma source with individually controlled coil currents from a single rf power generator
AssigneeApplied Materials, Inc.
InventorsLeonid Dorf, Shahid Rauf, Jonathan Liu, Jason A. Kenney, Andrew Nguyen, Kenneth S. Collins, Kartik Ramaswamy, Steven Lane
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Abstract
An inductively coupled plasma reactor has three concentric RF coil antennas and a current divider circuit individually controlling currents in each of the three coil antennas by varying only two reactive elements in the current divider circuit.
Claims20
A plasma reactor for processing a workpiece, comprising:
- a reactor chamber comprising a cylindrical side wall and a ceiling;
- an RF power generator and an impedance match coupled to said RF power generator;
- three coil antennas having respective driven ends and return ends, the return ends being connected to a common potential;
- a pair of current branches each comprising respective series and parallel reactance elements, the series reactance element of each of the current branches being coupled between said impedance match and the driven end of a respective one of said coil antennas, the parallel reactance element of each of the current branches being coupled in parallel with a respective one of said coil antennas;
- a third current branch coupled between said impedance match and the driven end of a third one of said three coil antennas;
- and
- a current apportionment controller governing reactances of said parallel reactance elements in accordance with a user-specified apportionment of currents among said coil antennas.
A method of individually controlling currents in three coils of a plasma reactor supplied from an RF generator output node of a single RF power generator through a single RF impedance match, comprising:
- providing parallel current divider branches between an output node of said RF generator and respective ones of said coils, each one of at least two of said current divider branches comprising a series reactance element connected between said RF generator output node and a respective one of said coils and a variable parallel reactance element connected in parallel with said respective coil;
- providing a model comprising a first set of equations defining voltage drops in said parallel branches in accordance with mutual inductances of said coils 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 coils relative to total current as 3-dimensional functions of reactance values of said variable parallel reactance elements in said at least two current divider branches;
- correlating information corresponding to said functions to a user-defined apportionment of currents in said coils.
A method of individually controlling currents in three coils of a plasma reactor supplied from an RF generator output node of an RF power generator through an RF impedance match, comprising:
- providing parallel current divider branches between an output node of said RF generator and respective ones of said coils, at least two of said current divider ranches comprising a series reactance element connected between said RF generator output node and a respective one of said coils and a variable parallel reactance element connected in parallel with said respective coil;
- correlating information, corresponding to coil currents as 3-dimensional functions of reactance values of said variable parallel reactance elements in said at least two current divider branches, to a user-defined apportionment of currents in said coils.
Dependencies are inferred from the claim text.