Chemical Vapor Deposition of Diamond Film at High Gas Pressure by Using Pulsed Discharge Plasma

Formation of diamond films at gas pressure (Pg) higher than 300 Torr was succeeded by means of a new method of pulsed discharge plasma chemical vapor deposition (CVD). The pulsed discharge was performed by a pulse power supply fabricated by means of chopping the output of DC power supply with Intelligent Power Module (IPM) and elevating the voltage by a transformer. The switching time of the pulse was shortened to get high discharge beginning voltage, and discharge and non-discharge time in each period of the pulse were adjusted to get stable discharge at high Pg. The deposited films, investigated with scanning electron microscope and Raman spectroscopy, showed that the crystalline quality became superior and the deposition rate increased when Pg increased from 300 to 500 Torr. When a rod-shaped cathode was used against the substrate (anode), the plasma during the deposition was constricted to small diameter with increasing Pg. Emission intensities of Hα and Hβ from the plasma, which were measured with a spectrometer and CCD array sensor, were also increased when Pg increased. By using this method using rod-shaped cathode, the diamond film could be deposited to small area at low substrate temperature.