The insulating properties of a-C:H on silicon and metal substrates

Amorphous carbon has many important applications. In electronic terms, its use as a dielectric is receiving greater attention. This is particularly important for applications in magnetic head devices as a reader gap insulation layer. Results are presented for resistivity and breakdown fields for hydrogenated amorphous carbon on silicon, undoped and doped with nitrogen, using an atomic flux source. Current–voltage characteristics were analysed using a numerical algorithm to determine trap densities. The results indicated that such films can meet the breakdown specifications, on silicon, and that nitrogen doping improves their characteristics. Thickness trends indicate improvements are likely as gaps are scaled. The density of states determination indicated that high breakdown was correlated, in the undoped case, with high DOS but this was not so for the doped films. The DOS was found to increase as the thickness decreased. On substrates other than silicon, the films were observed to have increased roughness, poorer adhesion and a more polymer-like quality. These changes were reflected in a reduction in the observed breakdown field.