There is provided an illumination system. The method comprises pre-cleaning a semiconductor wafer to remove native oxide, such as by applying hydrofluoric acid to form an HF-last surface, pre-treating the HF-last surface with ozonated deionized water, forming a dielectric stack on the pre-treated surface and providing a flow of NH3 in a process zone surrounding the wafer. The first electrode and a second electrode are disposed over the reference plane.