Relation of the polymeric ion species in plasma to the hardness of a-C:H film made by PSII&D

The amorphous carbon (a-C:H) films formed by plasma source ion implantation and deposition (PSII&D) have expanded the tribological properties. Especially, the hardness can be widely changed by adequately selecting RF power, pulse bias voltage, gas species and gas pressure. Previously, we reported that a-C:H film hardness depended on the electron temperature in C2H2 plasma which was ignited with pulsed RF power, and that the hardness was in inverse proportion to the electron temperature in the range of less than 2.5 eV. We have discovered that the film hardness is, in some cases, changing even if the electron temperature is constant. This suggests that there are some new factors to determine the film hardness besides the electron temperature in the plasma. In this study, we employ a quadrupole mass spectrometer to measure the intensity of each polymeric ion in C2H2. The film hardness is determined by the synergy of the polymeric ion abundances and ion irradiation.