Radio‐frequency sputter deposition of boron nitride based thin films

Thin films (≊2 μm) of boron nitride, titanium boron nitride, and titanium aluminum boron nitride have been grown on molybdenum, niobium, and cemented carbide substrates employing nonreactive as well as reactive rf magnetron sputter deposition from either a BN, a TiN‐BN, or a TiN–AlN–BN target. Substrates have been rf biased, with dc potentials up to −200 V. By means of nonreactive sputtering mixed‐phase structures with dominant phases B₄₈B₂N₂ (using a BN target), or B₄₈B₂N₂ and hexagonal Ti–B–N (using a TiN–BN or a TiN–AlN–BN target) are formed. Reactive deposition leads to the existence of hexagonal BN in all deposition modes. In the cases of Ti–B–N and Ti–Al–B–N films this phase is accompanied by fcc Ti–B–N. SEM cross sections revealed very fine grained to fracture‐amorphous film structures. Hardness measurements gave the following maximum HV 0.02 values: B–N films 2800, Ti–B–N films 2750, and Ti–Al–B–N films 1650.