Pulsed RF power delivery for plasma processing

A method for delivering pulsed RF power to a plasma, the method comprising:

• generating a pulse train comprising a series of pulses, each pulse being characterized by a pulse period;
• generating a frequency-varied RF oscillation which varies in frequency within the pulse period;
• modulating the frequency-varied RF oscillation with the pulse train to generate a frequency-varied pulsed RF signal;
• transmitting the frequency-varied pulsed RF signal to the plasma;
• sensing a phase error signal comprising a phase difference between the frequency-varied pulsed RF signal being transmitted to the plasma and a reflected signal coming back from the plasma;
• and
• utilizing the phase error signal for frequency control over the frequency-varied RF oscillation,
• wherein the frequency-varied RF oscillation varies in frequency within the pulse period in accordance with a frequency profile.

A system for delivering pulsed RF power to a plasma, the system comprising:

• a pulse generator adapted to generate a pulse train comprising a series of pulses, each pulse being characterized by a pulse period;
• a variable-frequency oscillator adapted to generate a frequency-varied RF oscillation which varies in frequency within the pulse period;
• an amplitude modulator adapted to modulate the frequency-varied RF oscillation with the pulse train to generate a frequency-varied pulsed RF signal;
• and
• a transmission medium adapted to transmit the frequency-varied pulsed RF signal to the plasma.

A system for delivering pulsed RF power to a plasma, the system comprising:

• a pulse generator adapted to generate a pulse train comprising a series of pulses, each pulse being characterized by a pulse period;
• a variable-frequency oscillator adapted to generate a frequency-varied RF oscillation which varies in frequency within the pulse period;
• an amplitude modulator adapted to modulate the frequency-varied RF oscillation with the pulse train to generate a frequency-varied pulsed RF signal;
• a transmission medium adapted to transmit the frequency-varied pulsed RF signal to the plasma;
• a phase error sensor coupled to the transmission medium and adapted to sense a phase error signal comprising a phase difference between the frequency-varied pulsed RF signal being transmitted to the plasma and a reflected signal coming back from the plasma;
• and
• a feedback mechanism adapted to send the phase error signal to a frequency control input of the voltage-controlled oscillator.

A method for delivering pulsed radio frequency (RF) power to a plasma, the method comprising:

• generating a RF oscillation;
• generating a pulse train comprising a series of pulses, each pulse being characterized by a pulse height;
• varying the pulse height from pulse to pulse in the pulse train to form a pulse train having varied pulse heights;
• modulating the RF oscillation with the pulse train having varied pulse heights to form a pulsed RF signal having varied pulse heights;
• and
• transmitting the pulsed RF signal having varied pulse heights to the plasma.

A method for delivering pulsed radio frequency (RF) power to a plasma, the method comprising:

• generating a RF oscillation;
• generating a pulse train comprising a series of pulses, each pulse being characterized by a pulse height;
• varying the pulse height from pulse to pulse in the pulse train to form a pulse train having varied pulse heights;
• modulating the RF oscillation with the pulse train having varied pulse heights to form a pulsed RF signal having varied pulse heights;
• and
• transmitting the pulsed RF signal having varied pulse heights to the plasma,
• wherein varying the pulse height from pulse to pulse comprises ramping the pulse height upward over a plurality of pulses from a smaller value at a leading end of the pulse train to a larger value further into the pulse train.

A system for delivering pulsed radio frequency (RF) power to a plasma, the system comprising:

• a RF oscillator adapted to generate a RF oscillation;
• a pulse generator adapted to generate a pulse train comprising a series of pulses, each pulse being characterized by a pulse height;
• a train adjuster adapted to vary the pulse height from pulse to pulse in the pulse train to form a pulse train having varied pulse heights;
• an amplitude modulator adapted to modulate the RF oscillation with the pulse train having varied pulse heights to form a pulsed RF signal having varied pulse heights;
• and
• a transmission medium adapted to transmit the pulsed RF signal having varied pulse heights to the plasma.

A method for delivering pulsed radio frequency (RF) power to a plasma, the method comprising:

• generating a first continuous wave RF signal and a second continuous wave RF signal;
• generating a pulse train comprising a series of pulses;
• modulating the first continuous wave RF signal with the pulse train to form a pulsed RF signal;
• and
• transmitting simultaneously both the pulsed RF signal and the second continuous wave RF signal to the plasma.

A system for delivering pulsed radio frequency (RF) power to a plasma, the system comprising:

• a RF oscillator subsystem adapted to generate a first continuous wave RF signal and a second continuous wave RF signal;
• a pulse generator adapted to generate a pulse train comprising a series of pulses;
• an amplitude modulator adapted to modulate the first continuous wave RF signal with the pulse train to form a pulsed RF signal;
• and
• a transmission medium adapted to transmit simultaneously both the pulsed RF signal and the second continuous wave RF signal to the plasma.

A method for delivering pulsed RF power to a plasma, the method comprising:

• transmitting a pulsed MF signal by way of an impedance matching network to the plasma, the pulsed RF signal including a series of pulses, each pulse being characterized by a pulse period;
• sensing a magnitude error signal related to a magnitude of a reflected signal coming back from the plasma;
• and
• utilizing the magnitude error signal for control over a variable shunt capacitor in the impedance matching network, where capacitance of the variable shunt capacitor is varied within the pulse period.

A method for delivering pulsed RF power to a plasma, the method comprising:

• transmitting a pulsed RF signal by way of an impedance matching network to the plasma, the pulsed RF signal including a series of pulses, each pulse being characterized by a pulse period;
• sensing a magnitude error signal related to a magnitude of a reflected signal coming back from the plasma;
• and
• utilizing the magnitude error signal for control over a variable shunt capacitor in the impedance matching network,
• where capacitance of the variable shunt capacitor is varied within the pulse period wherein the shunt capacitor comprises a binary coded capacitor bank, and a high-speed switch is used to switch the pulsed RF signal away from being delivered to the plasma while the shunt capacitor transitions from a first capacitance to a second capacitance.

A system for delivering pulsed RF power to a plasma, the system comprising:

• an RF power generator adapted to generate a pulsed RF signal, the pulsed RF signal including a series of pulses, each pulse being characterized by a pulse period;
• a transmission medium coupled to the RF power generator and adapted to carry the pulsed RF signal;
• an impedance matching network coupled between the transmission medium and the plasma;
• a variable shunt capacitor within the impedance matching network;
• a sensor coupled to the transmission medium and adapted to sense a magnitude error signal related to a magnitude of a reflected signal coming back from the plasma;
• and
• a mechanism adapted to send the magnitude error signal from the sensor to a control input of the variable shunt capacitor, where the magnitude error signal is used to vary capacitance of the variable shunt capacitor within the pulse period.

A system for delivering pulsed radio frequency (RF) power to a plasma and for measuring power absorbed by the plasma, the system comprising:

• a pulsed RF power generator configured to generate forward RF pulses;
• a RF cable having a first end coupled to the pulsed RF power generator, the RF cable being adapted to carry the forward RF pulses;
• a reaction chamber coupled to a second end of the RF cable, the reaction chamber being adapted to contain the plasma and to couple the forward RF pulses to the plasma;
• a directional coupler coupled to the RF cable, the directional coupler being adapted to generate a first attenuated signal proportional to the forward RF pulses and a second attenuated signal proportional to backward RF pulses;
• and
• a time-averaging mechanism coupled to the directional coupler and adapted to time-average the first attenuated signals to generate a first time-averaged signal and to time-average the second attenuated signal to generate a second time averaged signal, where the power absorbed by the plasma is proportional to the difference between the first and second time-averaged signals.

A method for delivering pulsed radio frequency (RF) power to a plasma and for measuring power absorbed by the plasma, the method comprising:

• generating forward RF pulses;
• containing a plasma within a reaction chamber;
• transmitting the forward RF pulses to the plasma by way of a transmission medium;
• reflecting backward RF pulses from the plasma;
• coupling to the transmission medium to generate a first attenuated signal proportional to the forward RF pulses and a second attenuated signal proportional to the backward RF pulses;
• applying time-averaging to the first attenuated signal to generate a first time-averaged signal;
• applying time-averaging to the second attenuated signal to generate a second time-averaged signal;
• and
• forming a difference signal from a difference between the first and second time-averaged signals, where said difference signal is proportional to RF power absorbed by the plasma.

An apparatus for delivering and measuring pulsed radio frequency (RF) power to a plasma, the apparatus comprising:

• a pulsed RF generator;
• a directional coupler coupled to the pulsed RF generator;
• and
• a time-averager coupled to the directional coupler, where the time averager measures forward and backward pulsed RF power and produces a signal representative of a time-averaged difference between the forward and backward pulsed RF power.