Particle bombardment effects on thin‐film deposition: A review

In many atomistic film deposition processes, concurrent energetic particle bombardment (ions, atoms, molecules, atom clusters) may occur inadvertently and uncontrollably or bombardment may be used to deliberately modify film properties. These energetic particles can arise from (i) the acceleration of charged particles, (ii) high‐energy neutrals from reflection from bombarded surfaces, or (iii) charge exchange processes. Particle bombardment effects that can affect film formation and growth include (a) modifying the substrate surface (cleaning, defect formation), (b) momentum transfer processes in the surface region (sputtering, desorption, recoil implantation, defect formation), (c) addition of heat to the surface region, and (d) formation of secondary elelctrons that can affect chemical reactions. These in turn affect film properties such as adhesion, residual film stress, film morphology, density, grain size and orientation, surface coverage, pinhole density, and surface area. The understanding of these effects and how to use them advantageously is important to those utilizing processes where concurrent energetic particle bombardment is occurring or can be made to occur.