Abstract
In this study, Quality of grain boundaries which caused briffle fracture was discussed experimentally. The authors conducted tensile and fatigue tests of annealed films to clarify the relationship between their mechanical properties and microstructure including grain boundaries and grain size. The fracture strain of the film annealed at 400℃ increased from initial about 7% to 25% and at the same time their yield stress decreased from about 300 MPa to 100 MPa. In addition, it was found that there were two fatigue fracture modes. One was a typical ductile fracture mode with plastic deformation and the other was brittle one. When brittle fracture occurred, the crack propagated along weak or porous grain boundaries which were formed during electroplating. These result clearly indicated that that the mechanical properties of electroplated copper thin films vaty drastically depending on their microsiructure. In addition, their grain boundaries were evaluated by measurement of ciystal orientation based on EBSD (Electron Back Scatter Diffraction). We created new evaluation method of quality of porous grain boundaries which caused briffle fracture. So it was found that the crack propagation path during a fatigue test was dominated by the quality of the grain boundaries and grain size.
