Cubic boron nitride (c-BN) films were deposited on Si substrate with poor adhesion using magnetically enhanced active reaction evaporation (ME-ARE). An attempt has been made to enhance the adhesion strength between c-BN film and substrate by nitrogen plasma based ion implantation (PBII) into c-BN film. Nitrogen ion doses range from 5 x 10(16) to 1 x 10(17) ions cm(-2) at an implant voltage of 50 kV The nitrogen ion implanted c-BN films were analyzed using FTIR, scratch test, and XPS to investigate the change of structure, adhesion strength of c-BN film, and interfacial mixing between the initial turbostratic BN (t-BN) film layer and substrate caused by nitrogen ion implantation. FTIR spectra showed little change of c-BN phase content in the films under the above implantation conditions but XPS depth elemental profile of N+-implanted boron nitride films displayed a mixed layer consisting of elements from film and substrate formed at interface. A highly optimized dynamic Monte Carlo program TAMIX was used to simulate the PBII process in a good agreement with above measured depth elemental profile. The scratch test showed that the adhesion strength evaluated in terms of the critical load of N+-implanted c-BN film was 1.4 times higher than that of as deposited c-BM film. (C) 2004 Elsevier Ltd. All rights reserved.