Positive dc bias-enhanced diamond nucleation with high CH4 concentration

A two-step process, positive dc biasing during the substrate nucleation sta ge but no biasing during growth stage, was used in this study. The diamond nucleation by positive dc bias enhancement on (100) silicon substrate in ho rizontal microwave plasma chemical vapor deposition from a CH4 + H-2 gas mi xture was investigated by scanning electron microscopy, Raman spectroscopy, atomic force microscopy and transmission electron microscopy. It was found that high methane concentration is needed during positive bias step for hi gh nucleation density (> 10(10)/cm(2)). Diamond phase was formed during the biasing step. High quality and polycrystalline diamond was achieved by con trolling biasing and deposition conditions. Dense plasma was formed at high methane content in positive BEN step. The changes of various species such as atomic hydrogen and carbonaceous radicals in the CH4-H-2 plasma during p ositive dc bias have been identified using optical emission spectroscopy (O ES). (C) 2001 Elsevier Science B.V. All rights reserved.