Optical and electrical properties of amorphous carbon films deposited using filtered cathodic vacuum arc with pulse biasing

Passive devices using metal containing amorphous (a-C) films have been successfully fabricated. However, difficulties in the etching of these films as well as their inferior inertness compared to pure a-C films led us to study the electrical and optical properties of pure a-C films. The films were deposited using a filtered cathodic vacuum arc system (FCVA) in conjunction with high substrate pulse biasing. It is possible to control the sp2 content and hence the properties, by varying the substrate pulse bias voltage. In this study, the a-C films were prepared by varying the high substrate bias between 3 and 11 kV using a Plasma immersion ion implantation (PI3) system. Characterization of these samples gives us an indication about the suitability of the films for integrated passive devices and other applications. Four-point probe measurement has been carried out to study the resistivity of the films deposited on quartz and SiO2. The resistivity decreases with increasing pulse bias voltage, which is likely attributed to the sp2 fraction in the film as well as the substrates’ resistivity. The sp2 content in the films is estimated using XPS and Raman spectroscopy. Optical properties of the films are characterized using spectroscopic phase-modulated ellipsometry. The band gap decreases from 2.3 to 1.49 with increasing bias voltage.