That's a pretty low pressure for a plasma, I would consider it likely that the plasma starts flickering and when that happens, you may have irregularities of your growth mode.
Using magnetron electrodes you can sputter around 4 to 5 milli torr. But still it is a low pressure, and you have to carefully stabilize the pressure. Anyway the lower the pressure, you have energetic species bombarding the substrate, ejected species with higher kinetic energy, and lot of stress build up in the deposited film.
You didn't specify what type of evaporator you are using? For example, when using Resistive evaporator, pressure in vacuum does not matter at all. Check type of your evaporative system.