Low-Stress, Adherent Cubic Boron Nitride Films with Oxygen Addition

Abstract #






J. Ye; Forschungszentrum Karlsruhe, IMF I, Germany



S. Ulrich; Forschungszentrum Karlsruhe, IMF I, Germany



C. Ziebert; Forschungszentrum Karlsruhe, IMF I, Germany





Well-adhered, low-stress cubic boron nitride (c-BN) films were successfully grown on to silicon substrates by means of controlled addition of oxygen into the films. The deposition was based on the radio-frequency magnetron sputtering of a hexagonal boron nitride (h-BN) target, and was accomplished in a reactive mode using gas mixtures of argon/nitrogen/oxygen at 0.3 Pa pressure, 400 C growth temperature, and -250 V substrate bias. In the present study, systematic results are shown with respect to the critical influences of oxygen partial pressure during deposition upon the stress, cubic phase fraction, as well as nanohardness of the deposited films. Although the formation of c-BN was completely hindered at oxygen fractions above 1.5 vol.% in the gas mixture, there existed only marginal influences on the c-BN fraction, yet strong impact on the film stress on the other hand, when limiting the oxygen content within 1 vol.%. Cubic-phase dominated films (containing 70~80 vol.% c-BN) with their compressive stress three times reduced were thus produced through careful control of oxygen partial pressure, showing an excellent plastic hardness of almost 60 GPa. For such films, a post-deposition thermal treatment at 900 C was found to bring about an additional drastic stress relaxation leading to an ultimate stress that is almost 10 times lower than that of as-deposited c-BN films without intentional oxygen addition. Furthermore, owing to the reduced film stress, adherent, m-thick c-BN films were achieved, with an adequate buffer layer, on to silicon substrates.

Note: Requested a Poster Session.