Diamond-like carbon film preparation using a high-repetition nanosecond pulsed glow discharge plasma at gas pressure of 1 kPa generated by a SiC-MOSFET inverter power supply

Abstract

A high-repetition nanosecond pulsed glow discharge plasma at a gas pressure of 1 kPa was generated using a SiC-MOSFET inverter power supply for diamond-like carbon (DLC) film preparation. At a high repetition frequency above 50 kHz, the period of the nanosecond voltage pulse became shorter than the decay time of the afterglow plasma, and many ions and radicals remained in the gap space. The deposition rate was 0.1 µm/min, which was 5 times higher than that of a conventional plasma CVD process. An increase in hardness to 13 GPa and a decrease in hydrogen content in the DLC film were confirmed by increasing the repetition frequency to 200 kHz.

Effects of Substrate Temperature on Film Hardness and Hydrogen Content in Diamond-like Carbon Films Prepared with a Repetitive Nanosecond Pulsed Glow Hydrogen/Methane Discharge Plasma

“…As T s increased from 90 • C to 170 • C, film hardness increased; however, it decreased slightly at 190 • C. Such a substrate temperature effect was not observed in the deposition experiment with the He/CH 4 plasma. Furthermore, the maximum hardness was 15 GPa, which was higher than 13 GPa obtained in our previous study [3]. The deposition rate of the DLC film, approximately 0.13 µm/min, was approximately six times higher than that of a conventional low-gas pressure plasma chemical vapor deposition experiment [4].…”

“…Highspeed DLC film deposition experiments using nanosecond pulsed plasmas at sub-atmospheric/ atmospheric pressures have been conducted [2], but uniform deposition was difficult to achieve because of the use of streamer discharges. We have recently performed a high-speed DLC deposition experiment using a repetitive nanosecond pulsed glow helium (He)/methane (CH 4 ) discharge [3]. Although using He, which is expensive, as a dilution gas can obtain a stable glow discharge, an alternative gas would reduce costs.…”

“…Details of the experimental setup can be found in [3]. In the present study, a mixture of H 2 and CH 4 with a gas pressure of 1.2 kPa was used for the process gas.…”

Preparation of hydrogenated amorphous carbon films using a microsecond-pulsed DC capacitive-coupled plasma chemical vapor deposition system operated at high frequency up to 400 kHz

“…37) Such a decrease in hydrogen content in high-frequency operation of pulsed glow discharge plasma is observed in the DLC films prepared from methane gas. 25) For the investigation of the microstructure of the deposited a-C:H films, Raman spectra were fitted by two Gaussian distributions for the D and G peaks after deducting the PL background. The G peak position, the full width at half maximum (FWHM) of the G peak, and the intensity ratio of the D peak to the G peak [I(D)=I(G)] were evaluated.…”

“…However, several studies 15,[21][22][23] have been carried out for the preparation of a-C:H films by conventional pulsed plasma CVDs, in which the pulse frequencies and widths were 20-40 kHz and 10-30 µs, respectively. In contrast, very few works 24,25) have been reported for the deposition of a-C:H films using high-frequency pulsed DC plasma discharge, in which the maximum operating pulse frequency was limited to 250 kHz. In addition, the impact of plasma-generated hydrocarbon species on the formation of films was not discussed.…”