Origins of residual stress in thin films: Interaction between microstructure and growth kinetics

Abstract

Thin films can develop large residual stresses during their growth that significantly impact their performance. Therefore, there is a need to understand how the stress is related to the developing film structure and underlying kinetic processes. In this work, we describe measurements of stress and the corresponding grain structure during electrodeposition of Ni and Cu films. For Ni deposition, the grain size stays nearly constant during growth and the stress reaches a nearly constant steady-state. For Cu deposition, the grain size grows as the thickness increases and the microstructural evolution affects the evolution of the stress. To remove the effect of subsurface grain growth on the stress, measurements were also done with periodic pauses that allowed the stress induced by grain growth to saturate. We interpret the results in terms of a kinetic model for stress evolution that focuses on the developing boundary between adjacent grains while the film is deposited. The effect of grain growth on stress for different types of microstructural evolution is also discussed. After accounting for the stress from subsurface grain growth, the results are consistent with the model for the dependence on growth rate and grain size at the surface.

Epitaxial growth of Cu(001) thin films onto Si(001) using a single-step HiPIMS process

“…3(b) : after a tensile maximum of 400 MPa, the stress rapidly decreases and becomes compressive, and reaches a constant value of −150 MPa (0 V) and −130 MPa (−130 V) with further film thickening (above 100 nm). The observation of a CTC behavior in the early stages of growth is consistent with literature data on stress evolution in Cu polycrystalline films 29 – 31 , though the critical thickness for film continuity and post-coalescence compressive stress magnitudes may vary depending on the kinetics and energetics of the deposition process 32 .

Figure 3 In situ intrinsic stress measurements during thin film growth.

…”

“…S1 ) 42 . The presence of V-shaped columns suggests that grain size changes primarily at the surface 31 and that bulk diffusion is rather limited. Another evidence of surface diffusion is noticed from the evolution of the intrinsic stress at the end of the deposition (see Supplementary Fig.…”

Influence of Cu Content on the Microstructure and Mechanical Properties of Cr-Cu-N Coatings

“…It is suggested that the energetic ion bombardment by increasing Cu target power does not all the times generate an increased tendency of compressive stress during deposition process. This phenomenon can be explained by the addition of Cu, which otherwise can be from a buffer area, leading to generating stress relief in the coatings [ 36 ].…”

Electrophoretic Coating of Octahedral Molybdenum Metal Clusters for UV/NIR Light Screening

“…The cracking phenomena of the Mo 6 film started to be recognized after 4 days of the dry process at the ambient conditions. The stabilization of the Mo 6 film was partially limited because the evaporation of acetone will create a residual stress, which break the hydrogen bonding between the cluster nanoparticles containing the Mo 6 6 cluster network [38,39]. The cracking point is grown from the tiny grain boundary, which is generated by the separation of the cluster phase and solvent phase.…”