A plasma processing apparatus for processing a substrate with a plasma is
disclosed. The apparatus includes a first RF power source having a first
RF frequency, and a process chamber. Further, the apparatus includes a
substantially circular antenna operatively coupled to the first RF power
source and disposed above a plane defined by the substrate when the
substrate is disposed within the process chamber for processing. The
substantially circular antenna being configured to induce an electric
field inside the process chamber with a first RF energy generated by the
first RF power source. The substantially circular antenna including at
least a first pair of concentric loops in a first plane and a second pair
of concentric loops in a second plane. The first pair of concentric loops
and the second pair of concentric loops being substantially identical and
symmetrically aligned with one another. The substantially circular antenna
forming an azimuthally symmetric plasma inside the process chamber. The
apparatus also includes a coupling window disposed between the antenna and
the process chamber. The coupling window being configured to allow the
passage of the first RF energy from the antenna to the interior of the
process chamber. The coupling window having a first layer and a second
layer. The second layer being configured to substantially suppress the
capacitive coupling formed between the substantially circular antenna and
the plasma. The substantially circular antenna and the coupling window
working together to produce a substantially uniform process rate across
the surface of the substrate.