Patent ID: 8652298

Claim:
A wafer processing apparatus including a first top electrode and a bottom electrode inside a processing chamber, the wafer processing apparatus comprising: a second top electrode coupled to electrical ground; a first radio frequency (RF) power source, a second RF power source, and a third RF power source, the first, second, and third power sources being coupled to the bottom electrode; a fourth RF power source with a low RF frequency in a range from 100 kHz to less than 2 MHz; and a switch operable to be in one of a first position or a second position, the first position causing the first top electrode to be connected to a first voltage, and the second position causing the first top electrode to be connected to the fourth RF power source, wherein a power level of the fourth RF power source is defined for each wafer processing operation to control a chemistry in the processing chamber while keeping a potential at the wafer substantially constant.