Influence of ion/atom arrival ratio and ion energy on residual stress of BN films were investigated using the dual ion beam sputtering (DIBS) method. The dual ion beam deposition system comprises two Kaufman type ion sources. The sputtering ion source, which is directed to a target, can provide an ion beam at a selected energy in the range of 1000-1500 eV and a current density of 0.5-1.5 mA/cm 2 . The assisting ion source having two grids provides an ion beam at a selected energy in a range of 100-800 eV and a current density of ~ 100 μA/cm 2 . The internal stress was estimated by a bending method. A coated silicon substrate has curvature caused by the deposition. The curvature was measured by a surface profilometer with a stylus tracking force of 10 mgf. RBS analysis was conducted with 4 2He + ions as the projectile which were extracted from a 2 MeV Van de Graaff accelerator, with a total scattering angle of 168° and a beam incident angle to the substrate normal or 60 deg, so that the composition of the prepared BN thin films including Ar content was measured. With regard to the influence of the ion/B arrival ratio on the stress of BN films, it was found that (a) the Ar content increased to 8 at.% with increasing ion/B arrival ratio, whereas (b) the stress of the BN films increased to around 3.8 MPa at an ion/B arrival ratio of 0.75,then decreased with the increase of the ion/B arrival ratio. It has been suggested that the increase of stress at lower ion/B arrival ratios could be caused by lattice strain produced by the change of composition and crystal structure from boron to BN, and after the composition and crystal structure reach BN, excess energy may be used to create Ar and N 2 bubbles, resulting in stress relief. From a series of experiments varying the ion energy from 300 to 850 eV keeping others constant, it was found that the Ar content and stress of the BN films decreased with increasing ion energy. It has been suggested that the decrease is due to the annealing effect by supplying higher energy.