1. Introduction and overview 2. Film stress and substrate curvature 3. Stress in anisotropic and patterned films 4. Delamination and fracture 5. Film buckling, bulging and peeling 6. Dislocation formation in epitaxial systems 7. Dislocation interactions and strain relaxation 8. Equilibrium and stability of surfaces 9. The role of stress in mass transport.

Thin Film Materials: Stress, Defect Formation and Surface Evolution

Size effects in materials due to microstructural and dimensional constraints: a comparative review

Materials issues in microelectromechanical systems (MEMS)

http://nanomechanics.mit.edu/sites/default/files/documents/Gouldstone_2000.pdf

Discrete and continuous deformation during nanoindentation of thin films

This review examines the size effects observed in the mechanical strength of thin metal films and small samples such as single-crystalline pillars, whiskers, and wires. Experimental results from mechanical testing and electron mi- croscopy studies, as well as recent insights from discrete dislocation dynam- ics simulations, are presented. The size dependency of deformation may be separated into three regimes: the nanometer regime of roughly 100 nm and below, an intermediate regime between 100 nm and approximately 1 μm, and a bulk-like regime. We argue that there is no scaling law with one uni- versal power-law exponent encompassing the entire range. Instead, there are a number of different mechanisms and underlying effects, e.g., the initial dislocation microstructure or loading conditions. The complex interaction of these mechanisms leads to the typically observed scaling behavior.

Plasticity in Confined Dimensions

Thermal stresses in thin Cu films on silicon substrates were examined as a function of film thickness and presence of a silicon nitride passivation layer. At room temperature, tensile stresses increased with decreasing film thickness in qualitative agreement with a dislocation constraint model. However, in order to predict the stress levels, grain-size strengthening, which is shown to follow a Hall–Petch relation, must be superimposed. An alternative explanation is strain-hardening due to the increase in dislocation density, which was measured by x-ray diffraction. At 600 °C, the passivation increases the stress by an order of magnitude; this leads to a substantially different shape of the stress-temperature curves, which now resemble those of aluminum with only a native oxide layer. The effect of passivation is shown to be very sensitive to the deposition and test conditions.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400044228

Quantitative analysis of strengthening mechanisms in thin Cu films: Effects of film thickness, grain size, and passivation

Stress–temperature behavior of unpassivated thin copper films

The textures of thin copper films were determined quantitatively by measuring (111) pole figures with x-ray diffraction. Measurements were performed on a variety of samples, differing in copper film thickness and deposition technique, diffusion barrier material, and the presence or absence of a cap layer. Texture changes due to an annealing treatment were also recorded and correlated with stress measurements by the wafer-curvature technique. It is found that the deposition method (PVD vs CVD) has a strong effect on texture, barrier layer effects range from negligible to significant depending on the barrier material, and the effect of a cap layer is insignificant.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400046409

Textures of thin copper films

In-situ transmission electron microscopy (TEM) was performed to study grain growth and dislocation motion during temperature cycles of Cu films with and without a cap layer. In addition, the substrate curvature method was employed to determine the corresponding stresstemperature curves from room temperature up to 600°C. The results of the in-situ TEM investigations provide insight into the microstructural evolution which occurs during the stress measurements. Grain growth occurred continuously throughout the first heating cycle in both cases. The evolution of dislocation structure observed in TEM supports an explanation of the stress evolution in both capped and uncapped films in terms of dislocation effects.

In-Situ Tem Investigation During Thermal Cycling of thin Copper Films

The powder milling (or mechanical alloying) process was investigated by milling pure Fe, single-phase Fe 60 Al 40 and Ni 3 Al powders with two different mills. To characterize the process, coherence lengths and rms-strains, using X-ray peak broadening analysis, and the shape factor and size of powder particles, using quantitative metallography, were measured. From the temporal evolution of these quantities it was concluded that the milling process can be subdivided into three periods. In the first period only plastic deformation occurs, followed by fracture of deformed particles. The second period is characterized by the onset of welding and a decrease in the amount of plastic deformation. The third, final and longest period is dominated by an equilibrium of fracture and welding mechanisms, whereas plastic deformation plays only a minor role. The time scale and the path leading to the final microstructure of the powders is shown to depend on the type of the mill utilized.

R.-M. Keller

Papers

Quantitative analysis of strengthening mechanisms in thin Cu films: Effects of film thickness, grain size, and passivation

Stress–temperature behavior of unpassivated thin copper films

Textures of thin copper films

In-Situ Tem Investigation During Thermal Cycling of thin Copper Films

Mechanisms of Powder Milling Investigated by X-ray Diffraction and Quantitative Metallography