Low-temperature deposition of cubic BN:C films by unbalanced direct current magnetron sputtering of a B4C target

Abstract

Controllable-unbalanced dc magnetron sputtering of a B4C target in mixed Ar–N2 discharges has been used to deposit BN:C thin films with carbon concentrations in the range of 5–21 at. % on Si(001) substrates. The variation of the nitrogen gas consumption with nitrogen partial pressure was used to determine the sorption capacity of the sputtering source and was then correlated to the film elemental composition. An additional axially symmetric magnetic field was used to vary the discharge plasma density near the substrate in a wide range. Hence, the ion flux Ji of primary Ar+ and N+2 ions accelerated to the substrate by an applied negative substrate bias could be varied while keeping the deposition flux Jn (the sum of film building species, B, C, and N atoms) near constant. BN:C films were grown at large ion-to-neutral flux ratios 3≤Ji/Jn≤24, ion energies Ei≤500 eV, and substrate temperatures 150≤Ts≤350 °C. The phase and elemental composition of as-deposited BN:C films were characterized by Fourier transform infrared spectroscopy and wavelength dispersive x-ray spectroscopy, respectively. Deposition of cubic phase c-BN:C containing 5–7 at. % of C is demonstrated under conditions of low energy (110 eV) ion bombardment, a high ion-to-atom arrival rate ratio (Ji/Jn∼24), and low growth temperatures (∼150 °C).