An apparatus and method for actively reducing the temperature gradient of a substrate. A substrate may be in spaced relation to the flat portion of the plate such that the protrusion extends toward the substrate and such that the flat portion and the substrate define, at least in part, a chamber. The electrical length from the ground connection to the feed point is about of a wavelength of the first frequency creating a virtual open at the feed point. Upon receiving a dispatch request, a critical ratio for each lot is calculated and compared with the planned factory cycle time value.