Measurement of Nanograin Orientations: Application to Cu Interconnects

Nowadays the orientation maps of polycrystalline material are necessary for a better understanding of, for example, the formation of voids in the interconnects of modern electronic devices. As new generation of devices has dramatically reduced in size, new tools are required to meet these spatial resolution specifications. In this work two electron microscopy techniques are used to study the voids nucleation sites. Orientation maps were acquired with Electron BackScattered Diffraction (EBSD) technique and with NanoBeam Electron Diffraction (NBED) coupled with the ASTAR technique [1]. Experiments were performed on a Zeiss LEO1530 Scanning Electron Microscope (SEM) and on a JEOL 2010 FEF Transmission Electron Microscope (TEM), both equipped with a FEG (Field Emission Gun). The orientation maps were acquired with a probe size of 15 nm for EBSD and 2.7 nm for NBED. The present study is carried out on polycrystalline copper interconnections as used in the 45 nm technological node. The orientation maps were acquired on the same cross‐section sample allowing a precise comparison of the EBSD and ASTAR techniques. This study confirms the localization of the voids nucleation sites (along the Cu/dielectric interface and grain boundaries) and gives new information concerning the orientation in the neighborhood of the voids.