Large size plasma generation using multicathode direct current geometry for diamond deposition

The deposition area of diamond film is increased by applying a geometry of multiple cathodes and a single anode in direct current (dc) plasma assisted chemical vapor deposition (PACVD). Each cathode is made of Ta and connected independently to its own dc power supply. The operating pressure is 1.3 × 10⁴ Pa (100 Torr), and methane-hydrogen mixed gas is used as reaction gas. The voltage and the current applied to each cathode are 650 V and 4 A, respectively. The transition from a diffuse glow to an arc is prevented by maintaining cathode temperatures above 2000 °C, which inhibits carbon deposition on the cathodes. Translucent diamond film of 3 in. diameter, thicker than 200 μm, is grown using seven cathodes with 3% CH₄–H₂ mixed gas for 110 h. The deposition area can be increased further by increasing the number of cathodes.