Interfacial phases and the adhesion of amorphous hydrogenated carbon films deposited by r.f. chemical vapour deposition onto (100) silicon

Abstract

Using a plan-orientation taper sectioning technique, the interfacial region between amorphous hydrogenated carbon (a-C:H) films deposited by r.f. chemical vapour deposition and (100) silicon substrates was investigated by transmission electron microscopy. Interfacial films approximately 2 nm thick were characterized as silicon carbide. However, depending upon deposition conditions the interfacial film was observed to be either a continuous film of crystalline 4H–6H SiC or to occur as isolated small islands of 4H SiC. It is possible that the formation of this SiC interfacial phase is governed by sputtering of silicon atoms from the substrate into the plasma from which the carbon films are deposited, conditions resulting in higher than expected sputter yields of silicon producing the continuous interfacial film. The role of these films in nucleation of the subsequent carbon film is still unclear. However, film adhesion, as characterized by indentation and scratch techniques, correlates with the amount of SiC present, continuous films producing well adherent coatings and patchy films resulting in poor adhesion.