The Use of Electron Backscatter Diffraction for the Investigation of Nano Crystalline Materials and the Move Towards Orientation Imaging in the TEM

Electron backscatter diffraction is shown to have a spatial resolution between 5nm and 10nm and is well suited for the investigation of nano crystalline materials. A study of texture and mesotexture in copper Damascene interconnect lines is used as an illustration. Samples were prepared by electro deposition from baths of different compositions and under various power cycles. The resulting grain structures were visually smaller than the 0.3 micron interconnect line width. However, if twin boundaries were considered as substructure rather than true grain boundaries, the effective grain size become larger than the line width. The bath composition affected the 111 texture component from times 5 random to 26 times random whereas different power cycles affected the texture much less. For structures with a grain size smaller than 20nm a new transmission electron microscope technique has been developed. Automated examination of a sequence of dark field images collected from a selected area lead to the reconstruction of a diffraction pattern for each pixel within the area. These patterns are indexed automatically, permitting crystal orientation as a function of spatial positioning to be mapped. The resulting orientation information is equivalent to that obtained using electron backscatter patterns. The practical resolution limit of this technique approaches 1 to 2 nanometers.