Deposition of diamond-like carbon films by a hollow cathode multi-jet rf plasma system

Diamond-like carbon (DLC) films were deposited on silicon and polycarbonate substrates with diameters up to 5 inches. Deposition temperatures and nega tive rf-bias were 60 degreesC and 250-450 V, respectively. The central part of the deposition system is a novel scaleable 13.56 MHz rf hollow cathode multi-jet plasma source operating typically at 400 W and a pressure of 100 Pa. He was used as carrier gas in the primary hollow cathode discharge with a standard flow of 400 seem. Downstream from a second gas distribution lev el close to the primary plasma outlet, methane (CH4) and acetyIene (C2H2) s erving as the carbon supply were effectively dissociated and activated. The measured maximum ion concentrations depend on the systems operation mode. When powering the substrate holder only, up to 4.7 x 10(10) cm(-3) ions wer e measured. Simultaneous operation of the hollow cathode plasma source and powering of the substrate holder, however, increases the ion density up to 2 x 10(11) cm(-3). As expected, high ion concentrations yield high depositi on rates with 70-80 and 160-200 nm min(-1) for methane and acetylene (stati onary deposition mode), respectively. The DLC films were characterized by m icro-Raman spectroscopy, ellipsometry and microhardness measurements. It wa s found that even in the stationary deposition mode, film thickness variati ons across a 5-inch wafer did not exceed +/-3.5%. The highest deposition ra te and best film quality were obtained at a substrate holder bias of - 350 to - 420 V. Methane-derived films showed refractive indices ranging from 2. 1 to 2.3 at 632 nn and a Vickers microhardness of up to 30 GPa. (C) 2000 Pu blished by Elsevier Science B.V. All rights reserved.