Patent ID: 8911637

Claim:
A method for processing a substrate in a capacitively-coupled plasma processing system, said capacitively-coupled plasma processing system having a plasma processing chamber and at least an upper electrode and a lower electrode, said substrate being disposed on said lower electrode during plasma processing, comprising: providing at least a first RF signal from a first RF signal generator to said lower electrode, said first RF signal having a first RF frequency, said first RF signal coupling with a plasma in said plasma processing chamber, thereby inducing an induced RF signal on said upper electrode; providing a phase-mirroring arrangement to probe said lower electrode to detect said first RF signal and to adjust one of phase or amplitude of the first RF signal to define a control signal, the control signal provided as an input to a second RF signal generator; providing a second RF signal from said second RF signal generator to said upper electrode, said second RF signal also having said first RF frequency, a phase of said second RF signal being offset from a phase of said first RF signal by a value that is less than 10%, wherein said phase and said first frequency of the second RF signal being generated based upon the input from the control signal to the second RF signal generator without probing said upper electrode; and processing said substrate while said second RF signal is provided to said upper electrode, wherein the first and second RF signal generators consist of separate RF signal generators.