Thermal stress in passivated blanket Cu and in passivated 0.2 μm wide damascene Cu lines have been characterized using x-ray diffraction and compared with that measured for 0.2 μm AlCu line structures. The microstructure plays an important role in controlling the thermal stress behavior, particularly for Cu due to its elastic anisotropy. Microstructural analysis of the blanket Cu revealed a strong (111) fiber texture. The damascene Cu lines had a strong (111) texture along with a weak in-plane (110) texture component that can be explained by surface energy considerations. The grain size of damascene Cu is constrained by the linewidth. The observed stress behavior of blanket Cu films shows stress hysteresis and plastic deformation. Under thermal cycling, the 0.2 μm wide Cu lines show a nearly hydrostatic triaxial stress state with linear elastic behavior. Compared with 0.2 μm wide AlCu lines, the principal stresses are generally lower in Cu lines and the difference can be attributed to the thermoelastic properties and confinement effect of the line structures. This indicates a weaker driving force for stress-induced void formation in Cu.

In the IFMIF-DONES facility of the future, the back-plate behind the Li target will receive strong irradiation from high-energy neutrons. The potential use of the back-plate for material specimens is attractive with respect to providing complementary irradiation data for Eurofer. In this work, DPA (displacement per atom) and gas production rates as well as DPA gradients and temperature distributions have been studied for the center segment of the back-plate, using both a nominal beam and a reduced beam footprint. It is shown that specimens can be produced with high DPA in similar conditions to the DEMO first-wall. Based on the size of the SSTT (small specimen test technology) specimens, the limited number of samples obtainable from the adopted arrangement scheme is driven by a major constraint: the thickness of the back-plate. A parametric study of the back-plate’s thickness provides an alternative arrangement scheme; thus, the DPA and gradient of the specimens are remarkably improved.