Carbon nitride thin films prepared by reactive r.f. magnetron sputtering

Nitrogenated amorphous carbon thin films (CN sub x ) were prepared by reactive r.f. magnetron sputtering from a graphite target in a nitrogen containing plasma (up to 4.4 at.%) on Si substrates. All main controllable deposition conditions (such as base and deposition pressure, power at target, target-substrate distance, substrate bias voltage) were kept constant throughout the series of experiments and the only variable parameter was the nitrogen flux (0-2 sccm). In situ spectroscopic ellipsometry (SE) in the energy region 1.5-5.5 eV in combination with Bruggeman's effective medium theory analysis was used per iterative deposition layer to monitor the film thickness and diamond character. The C:N chemical bonding characteristics of the films were also examined with the new Fourier transform IR ellipsometry technique. It was found that the films have a mixed character composed of Constituents (phases) of sp exp 3 and sp exp 2 type bonding. The film composition in terms of sp exp 3 , sp exp 2 and void concentration as a function of film thickness and nitrogen concentration in the plasma was determined. The plasma nitrogen concentration seems to directly affect the film deposition rate and diamond character of the films by favoring sp exp 3 bond formation.