High-speed and uniform deposition of amorphous carbon on inner surface of metal tube with microwave-excited high-density plasma column

For high-speed diamond-like carbon (DLC) coating on the inner wall of tubular shape, a new method employing azimuthally symmetric surface wave-excited plasma (SWP) was proposed. In the coating equipment, a quartz tube antenna 20 mm in outer diameter was inserted along the center axis of a stainless-steel pipe 58 mm in inner diameter, 100 mm in length. 2.45-GHz microwaves were injected through the antenna, along which high-density plasma column (plasma electron density, n_e>10¹¹ cm^-3) was generated uniformly inside the pipe. The highest deposition rate of DLC was 5.8 mm/h with an input microwave power of 200 W at a total pressure of 40 Pa, where the gas flow rates of Ar, CH4, and tetra methyl silane were 10, 10, and 2 seem, respectively. The hardness of the DLC film was 21 GPa at a substrate bias of-250 V. These results proved that uniform and high-speed coating of DLC on the inner wall of a substrate pipe is obtained by using high-density SWP column with microwaves.