Image Number 15 for United States Patent #6322662.
In a plasma treatment system, the increase of the electric field of a treatment space facing the central portion of a flat antenna member is relieved, and the ununiformity of the density of plasma in a plasma forming region is relieved.Microwave generated by a microwave generator 50 are supplied from a waveguide 52 to a flat antenna member 44. The flat antenna member 44 has a plurality of slots 60. The space between adjacent two of the slots 60 is longer than the guide wavelength of microwaves in the waveguide 52, and the length of each of the slots 60 is shorter than half of the guide wavelength. The slots 60 are arranged in a region other than the central portion of the flat antenna member 44 so as not to be axisymmetric.