Hybrid plasma system for diamond-like carbon film deposition

A novel hybrid plasma apparatus optimized for diamond-like carbon (DLC) film deposition is presented. A plasma was generated by use of a jet matrix plasma source (JeMPS) operated at 13.56 MHz and up to 1 kW. The 48 plasma jets were arranged as a hexagonal matrix within a 15-cm diameter circle. In the center of an argon plasma at pressure of 1 mbar the ion concentration is 4.82×1011 cm−3. At a distance of 6 cm from the plasma source a water-cooled substrate holder biased with 13.56 MHz power was positioned. A plasma-enhanced chemical vapor deposition (PECVD) process was used. Helium was used as a carrier gas excited in the jet matrix plasma source. Methane, used as a source of carbon, was introduced in the zone between the plasma source and the substrate holder. A fractal carrier and process gas distribution system allowed high film homogeneity. Typical gas flows were 500 and 100 sccm, respectively; typical process pressure was 1 mbar. A Root’s blower with a pumping speed of 250 m3 h−1 was used. A deposition rate of 78 nm min−1 at room temperature was achieved. The film thickness variation over a 5 inch wafer was less than 7%. As the dc bias of the substrate holder increased from 350 to 400 V the sp2/sp3 ratio increased from 0.79 to 0.88. The refractive index of almost 2.4 and a Vickers hardness of 3000 were evidence of high quality DLC films.