Low-temperature SiO₂ film coatings onto Cu particles using the polygonal barrel-plasma chemical vapor deposition method

Surface coating of Cu particles with SiO₂ thin films was investigated at a low temperature of 100 °C using the polygonal barrel-plasma chemical vapor deposition (PB-PCVD) method. The Cu particles were treated at 250 W for 30 min while a hexagonal barrel containing the samples was oscillated at 5 rpm with an amplitude of ± 75°. The results show that the particle surfaces were uniformly coated with amorphous SiO₂ films at the flow rates of vaporized hexamethyldisilazane (used as a precursor) and O₂ gas of 6 and 120 ml/min, respectively. The thickness of the SiO₂ films (77 nm) changed linearly with the treatment time and the RF power, whereas for longer treatment times (>40 min at 250 W) and higher RF powers (>300 W for 30 min), impurities were regenerated, which was prevented by inserting a barrel-cleaning process during the treatment. The deposition rate of the SiO₂ films for PB-PCVD was 15 times higher than that of our original sputtering method, and the smoother films can be obtained by PB-PCVD, as compared to the sputtering method. Thus, this high-speed and controllable PB-PCVD method would be useful for ceramic coating researches such as electric device fields, although further investigations are required.