Apparatus for Frequency Tuning in a RF Generator

A radio-frequency (RF) generator, comprising:

• means for generating a signal, the signal oscillating at an initial frequency;
• means for amplifying the signal to produce an amplified oscillating signal;
• means for filtering the amplified oscillating signal to produce an output signal that supplies power to a plasma load in a plasma processing chamber;
• means for sensing at least one property of the plasma load;
• and
• means for frequency tuning that includes a non-transitory, tangible, machine-readable medium encoded with instructions to perform a method, the method including:
• receiving an impedance trajectory of the plasma load as a function of frequency;
• receiving a reference point in a complex-reflection-coefficient plane, the reference point lying on a reference vector that passes through the reference point and an origin of the complex-reflection-coefficient plane;
• receiving, from the means for sensing, a measured impedance of the plasma load, the measured impedance lying along the received impedance trajectory;
• determining a measurement angle between the reference vector and a line passing through the reference point and a point in the complex-reflection-coefficient plane corresponding to the measured impedance, as expressed in terms of complex reflection coefficient;
• scaling the measurement angle by a predetermined constant to produce a frequency step;
• adding the frequency step to the initial frequency to produce an adjusted frequency;
• and
• causing the means for generating a signal to generate a signal that oscillates at the adjusted frequency.