US Patent 9745660 Method for controlling a plasma chamber

An system and method for controlling a plasma chamber includes operably coupling an RF generator to the plasma chamber, the RF generator providing an RF signal to a chamber input of the plasma chamber; measuring a parameter at the chamber input; determining a rate of change based on the measured parameter; detecting an excessive rate of change condition comprising the rate of change exceeding a reference rate of change; detecting a repetitive change condition comprising a predetermined number of the excessive rate of change conditions in a predetermined time; upon detection of the repetitive change condition, decreasing a power of the RF signal provided to the chamber input.