Large area deposition of thick diamond film by direct-current PACVD

Thick diamond films with a diameter of 100 mm are deposited by two types of modified dir direct-current (DC) plasma assisted chemical vapor deposition methods, a multi-cathodes geometry and a large single cathode geometry. In the case of the first method, we have used a seven cathode array, whose te mperature is maintained over 2100 degrees C to inhibit carbon deposition on the cathodes. Each cathode is connected to an independent DC power supply, which supplies voltage and current between 500 and 700 V and between 3 and 5 A per cathode, respectively at 100 Torr of chamber pressure during the d eposition. The diffuse glow formed by this method is very stable, enough to grow diamond films thicker than 1 mm. In the case of the secund method, we have used a single large cathode, whose temperature is about 1100 degrees C. At this temperature, the carbon deposition can also be inhibited. We hav e used a pulsed power supply, since an are cannot be prohibited without it. The cathode diameter is 120 mm, which makes the diffuse glow large enough to deposit diamond on the substrate of 100 mm diameter. The diffuse glow is maintained very stable also. The quality of thick diamond films varies fro m white to dark gray according to their methane concentration. The depositi on rate varies, ranging from 2 mu m/h to 10 mu m/h. (C) 1999 Elsevier Scien ce S.A. All rights reserved.