Stress of c-BN thin films: a parameter investigation

Boron nitride thin films were ion-beam-assisted deposited on bare silicon substrates or silicon cantilever structures. The resulting film stress was studied by determination of the resulting bending of the beam using either a profilometer or optical microscopy, respectively. Employing the latter method, the reliability of the stress measurement on the BN-coated cantilever structure could be increased. The theoretically predicted E-ION(-2/3) dependence of the resulting film stress on the ion energy was verified. Generally, the stress of the coatings increased with increasing content of cubic boron nitride (c-BN) in the sample. However; no correlation between the c-BN infrared peak position and the film stress could be observed. In addition. the development of stress - i.e., the distribution of the total film stress - was studied. Therefore, an as-deposited coating containing c-BN was subsequently resputtered and examined after each sputter step. The total stress of the non-cubic base layer increased gradually with increasing thickness. lifter the onset of c-BN growth, the film stress exhibited only a marginal increase. So far, any reduction of film stress after c-BN nucleation has not been observed. (C) 1999 Elsevier Science S.A. All rights reserved.