A kinetic model for stress generation in thin films grown from energetic vapor fluxes

Abstract

We have developed a kinetic model for residual stress generation in thin films grown from energetic vapor fluxes, encountered, e.g., during sputter deposition. The new analytical model considers sub-surface point defects created by atomic peening, along with processes treated in already existing stress models for non-energetic deposition, i.e., thermally activated diffusion processes at the surface and the grain boundary. According to the new model, ballistically induced sub-surface defects can get incorporated as excess atoms at the grain boundary, remain trapped in the bulk, or annihilate at the free surface, resulting in a complex dependence of the steady-state stress on the grain size, the growth rate, as well as the energetics of the incoming particle flux. We compare calculations from the model with in situ stress measurements performed on a series of Mo films sputter-deposited at different conditions and having different grain sizes. The model is able to reproduce the observed increase of compressive stress with increasing growth rate, behavior that is the opposite of what is typically seen under non-energetic growth conditions. On a grander scale, this study is a step towards obtaining a comprehensive understanding of stress generation and evolution in vapor deposited polycrystalline thin films.

Tuning Material Properties of Oxides and Nitrides by Substrate Biasing during Plasma-Enhanced Atomic Layer Deposition on Planar and 3D Substrate Topographies

“…The corresponding behavior of the residual stress for TiO x in the first stage consisted of a change from tensile to compressive on applying a bias to the substrate, denoted by negative values on the vertical axis of Figure 3 d. This stress evolution from tensile to compressive is similar to that frequently reported in the literature for thin-film deposition using energetic particle bombardment. 19 , 34 − 37 The compressive stress reached a maximum as ⟨ V bias ⟩ was increased to −152 V, similar to the peaking of refractive index and mass density with biasing at the same voltage. The maximization of compressive stress for deposition using energetic particle bombardment has been reported in the literature to be related to the formation of bombardment induced point defects, such as interstitials in the film bulk.…”

SiNx coatings deposited by reactive high power impulse magnetron sputtering: Process parameters influencing the residual coating stress

“…5(a) and 5(b), it is evident that the compressive residual stress increases with the E pP , the applied pulse frequency, and the related SiN x growth rate. Similar observations were also reported by Chason et al 55 Using the same pulse frequency, an increased E pP implies an increasing average target power and hence elevated sputter rates and ionization. Therefore, an elevated compressive stress at increasing pulse energies can be partly ascribed to forward sputtering induced by ion bombardment as discussed above.…”

Electrodeposited Manganese Oxide on Tailored 3D Bimetallic Nanofoams for Energy Storage Applications

“…This behavior has been previously reported for electrodeposited metal and metal oxides and has been attributed to the generation of strain during film growth as a consequence of changes in the grain boundary area (microstructure evolution). [15] Clearly, such a phenomenon significantly www.advancedsciencenews.com www.entechnol.de restricted the thickness of the electrodeposited MnO x films on planar supports, limiting the mass loading of active material and, consequently, the practical importance of such electrodes. This issue can be avoided with a properly designed highsurface-area material, serving as a scaffold for MnO x distribution as evidenced in this work.…”