The crystalline quality, resistivity, chemical composition, and surface morphology of a ZrN film deposited on a Si(100) substrate by an ion assisted deposition method were investigated as functions of the incident angle of an ion beam. By this method, metallic Zr is deposited by electron-beam evaporation while simultaneously bombarding the film with nitrogen ions having an energy of 400-600 eV. The incident angle was changed from 15 degrees to 90 degrees between the ion beam and the plane of the substrate. It was found that the crystalline quality of the ZrN film improved by decreasing the incident angle from 90 degrees to 48 degrees. This is partly because, by lowering the incident angle, the normal momentum component of the ion beam to the growing film is decreased so that the radiation damage due to ion bombardment is reduced and partly because the horizontal component is increased to enhance the migration of the adatoms on the surface of the film. Also, it was found that the resistivity decreased by lowering the incident angle. However, at incident angles less than or equal to 30 degrees, the surface of the growing film was roughened at the initial deposition stage and eventually the film peeled off the substrate because of the formation of zirconium silicide at the interface between the ZrN film and the Si substrate. On the other hand, the chemical composition of the ZrN film was found to be almost stoichiometric for any incident angle. It was concluded that the optimum incident angle of an ion beam is around 45 degrees for the highest crystalline quality, lowest resistivity, and smoothest surface morphology.