Frequency tuning for pulsed radio frequency plasma processing
AssigneeAdvanced Energy Industries, Inc.
InventorsMichael Mueller, Myeong Yeol Choi
Life of this patent
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Abstract
This disclosure describes systems, methods, and apparatus for pulsed RF power delivery to a plasma load for plasma processing of a substrate. In order to maximize power delivery, a calibration phase using a dummy substrate or no substrate in the chamber, is used to ascertain a preferred fixed initial RF frequency for each pulse. This fixed initial RF frequency is then used at the start of each pulse during a processing phase, where a real substrate is used and processed in the chamber.
Claims17
A method of selecting a fixed initial RF frequency for each of a plurality of RF pulses provided to a plasma load, the method comprising:
- providing pulsed RF power to a plasma load, where each pulse comprises RF power having a controllable frequency, and where a plasma having the plasma load interacts with a dummy substrate, or no substrate, in a plasma chamber;
- tuning an initial RF frequency for each pulse in a string of pulses, pulse to pulse, in a calibration process, by minimizing a difference between a characteristic indicative of the pulsed RF power at a start of each pulse and a desired characteristic of the pulsed RF power at a start of each pulse until the difference between the characteristic for a start to two consecutive pulses is below a threshold;
- then
- selecting the initial RF frequency as a fixed initial RF frequency for use in a processing run using a real substrate;
- and
- tuning the RF frequency during processing within each pulse but returning to the fixed initial RF frequency at a start of each pulse.
A non-transitory, tangible computer readable storage medium, encoded with processor readable instructions to perform a method for frequency tuning a power source to optimize delivered power to a plasma load, the method comprising:
- in a calibration phase,
- tuning an initial RF frequency at a start of each pulse in a string of RF pulses, pulse to pulse, until a difference between a characteristic indicative of power at the start of each pulse and a desired characteristic of the power at the start of each pulse, for a start to two consecutive pulses, is below a threshold;
- then
- selecting the initial RF frequency as a fixed initial RF frequency to be used during a processing phase;
- and
- in the processing phase,
- setting an initial RF frequency for all pulses in the processing phase equal to the fixed initial RF frequency selected during the calibration phase;
- and
- tuning the RF frequency of pulsed RF power during each pulse, but returning to the fixed initial RF frequency at a start of each pulse.
A power delivery system comprising:
- a power source configured to provide pulsed RF power to a plasma load via a matching network;
- a sensor configured to sample a characteristic indicative of the pulsed RF power;
- a controller in communication with the sensor and the power source and executable to:
- in a calibration phase,
- tuning an initial RF frequency at a start of each pulse in a string of RF pulses, pulse to pulse, until a difference between a characteristic indicative of power at the start of each pulse and a desired characteristic of the power at the start of each pulse, for a start to two consecutive pulses, is below a threshold;
- then
- selecting the initial RF frequency as a fixed initial RF frequency to be used during a processing phase;
- and
- in the processing phase,
- setting an initial RF frequency for all pulses in the processing phase equal to the fixed initial RF frequency selected during the calibration phase;
- and
- tuning the RF frequency of pulsed RF power during each pulse, but returning to the fixed initial RF frequency at a start of each pulse.
Dependencies are inferred from the claim text.