Multimode cavity type MPACVD reactor for large area diamond film deposition

A novel microwave plasma-assisted CVD reactor for large area diamond film deposition is described. Reactor is based on cylindrical cavity with diameter that allows exciting of three axially symmetric modes ТМ01n, ТМ02n and ТМ03n at frequency 2.45 GHz. Upper and lower walls of the cavity act as mode converters. On the lower wall of the cavity, outside the quartz dome and near the side wall of the cavity, is a ledge of variable profile with an external diameter equal to inner diameter of cavity and inner diameter selected so that the TM03n mode decays along the axis over a section of cavity with the ledge. As a result of superposition of three modes: TM01n, TM02n and decaying TM03n, the distribution of the near electric field is formed in the cavity over the substrate with diameter 80 mm so that the diamond films deposited in H2 + CH4 mixture have 5% thickness difference over a diameter of 75 mm. Based on numerical simulations the CVD reactor equipped pulsed magnetron operating with a 5 kW mean power have been realized. Deposition of high quality diamond films with diameter 80 mm and thickness 0.5–2 mm, having not more than ±5% thickness uniformity over a diameter of 75 mm, have been demonstrated in pulsed mode operation of CVD reactor.