Digital phase controller for two-phase operation of a plasma reactor
AssigneeApplied Materials, Inc.
InventorsSatoru Kobayashi, Kartik Ramaswamy, Shahid Rauf, Kenneth S. Collins
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Abstract
Phase angle between opposing electrodes in a plasma reactor is controlled in accordance with a user selected phase angle. Direct digital synthesis of RF waveforms of different phases for the different electrodes is employed. The synthesis is synchronized with a reference clock. The address generator employed for direct digital synthesis is synchronized with an output clock signal that is generated in phase with the reference clock using a phase lock loop. The phase lock loop operates only during a limited initialization period.
Claims20
A plasma reactor for processing a workpiece, comprising:
- a pair of electrodes coupled to a pair of RF power amplifiers having an RF phase angle between them;
- a feedback controller having a phase correction signal output dependent upon said RF phase angle and a user-defined target phase angle;
- a clock generator comprising:
- (a) an oscillator responsive to a control signal corresponding to a phase difference between said oscillator and a reference clock, and (b) an output clock derived from an output of said oscillator;
- an address generator comprising a pair of address outputs incremented in synchronism with said output clock and separated by an address difference dependent upon said phase correction signal output;
- a pair of waveform-containing read only memories coupled to receive respective ones of said pair of address outputs, and coupled to respective ones of said RF power amplifiers.
A plasma reactor for processing a workpiece, comprising:
- a pair of electrodes facing a processing zone and a pair of RF power amplifiers coupled to respective ones of said electrodes, there being an RF phase angle between said pair of electrodes;
- a feedback controller having a phase correction signal output that is a function of said RF phase angle and a user-defined target phase angle;
- a clock generator comprising:
- (a) an oscillator responsive to a control signal corresponding to a phase difference between said oscillator and a reference clock, and (b) an output clock derived from an output of said oscillator, said control signal being unchanging following a limited initialization period;
- an address generator comprising a pair of address outputs incremented in synchronism with said output clock and separated by an address difference that is a function of said phase correction signal output;
- a pair of waveform-containing read only memories coupled to receive respective ones of said pair of address outputs, and coupled to respective ones of said RF power amplifiers.
A plasma reactor for processing a workpiece, comprising:
- a pair of electrodes facing a processing zone and a pair of RF power amplifiers coupled to respective ones of said electrodes and having an RF phase angle between said pair of electrodes, and an oscillator providing a reference clock directly to one of said pair of RF power amplifiers;
- a feedback controller having a phase correction signal output that is a function of said RF phase angle and a user-defined target phase angle;
- a clock generator comprising:
- (a) an oscillator responsive to a control signal corresponding to a phase difference between said oscillator and a reference clock, and (b) an output clock derived from an output of said oscillator;
- an address generator comprising an address output incremented in synchronism with said output clock and having an address that is a function of said phase correction signal output;
- a waveform-containing read only memory coupled to receive said address outputs, and coupled to respective ones of said RF power amplifiers.
Dependencies are inferred from the claim text.