US Patent 6842147 Method and apparatus for producing uniform processing rates

An antenna arrangement for generating an rf field distribution at a plasma generating region inside a chamber wall of a process chamber of a plasma processing apparatus is described. The antenna arrangement includes an rf inductive antenna to which an rf power supply can be connected to supply an rf current to generate a first rf field extending into the plasma generating region. A passive antenna is also provided which is inductively coupled to the rf inductive antenna and configured to generate a second rf field modifying the first rf field. The rf field distribution at the plasma generating region increases the processing uniformity of the processing apparatus compared to that in the absence of the passive antenna.