Control of macrostress σ in reactively sputtered Mo–Al–N films by total gas pressure

This article reports on the effect of the energy delivered to a growing film by bombarding ions and fast neutrals on the macrostress σ and the structure of sputtered films. To demonstrate this effect, we selected Mo–Al–N films with a low (⩽20 at.%) Al content reactively sputtered using an unbalanced dc magnetron with a target of 100 mm diameter at a high total pressure pT=3Pa, low substrate bias Us=-20V and a high substrate ion current density is=1mA/cm2. The main goal of this study was to show the reduction of σ in films sputtered at high pressures of several Pa. Under the conditions given above approximately 4 μm thick Mo–Al–N films with enhanced hardness H≈35 GPa and a very low (⩽−0.5 GPa) macrostress σ were successfully prepared. This result demonstrates that the enhanced hardness H of Mo–Al–N films is not caused by σ but is due to its nanostructure as shown in the XRD patterns of these films. The Mo–Al–N films with enhanced hardness are composed of a mixture of grains of different crystallographic orientations.