The CAP-reactor, a novel microwave CVD system for diamond deposition

The development and improvement of efficient microwave plasma reactors for diamond CVD is still an important topic and a prerequisite for the reliable production of high quality diamond films and wafers. We report on a novel reactor concept, the circumferential antenna plasma (CAP) reactor, which was developed on the basis of numerical FEM simulations. The electromagnetic field enters the plasma chamber through a ring-shaped circumferential window. The microwave power is guided to the window by radially expanding a coaxial waveguide. The design and simulation results of the CAP-reactor as well as a first prototype system powered by 6 kW microwave of 2.45 GHz will be described. The electric field distribution has been measured with a miniature microwave field probe and was found in perfect agreement with the FEM simulations. The CAP-reactor has been optimized to obtain a homogenous flat plasma distribution above the substrate holder. Under these conditions CVD-diamond films and wafers have been deposited. Preliminary results will be presented.