| AVS 61st International Symposium & Exhibition | |
| Materials Characterization in the Semiconductor Industry Focus Topic | Monday Sessions |
| Session MC+AP+AS-MoM |
| Session: | Characterization of 3D Structures, 2D films and Interconnects |
| Presenter: | Katayun Barmak, Columbia University |
| Authors: | X. Liu, Carnegie Mellon University D. Choi, Korea Railroad Research Institute, Republic of Korea N.T. Nuhfer, Carnegie Mellon University D.L. Yates, University of Central Florida T. Sun, University of Central Florida G.S. Rohrer, Carnegie Mellon University K.R. Coffey, University of Central Florida K. Barmak, Columbia University |
| Correspondent: | Click to Email |
The resistivity of Cu, the current interconnect material of choice, increases dramatically as the conductor’s dimensions decrease towards and below the mean free path of electrons (39 nm at the room temperature). Two scattering mechanisms that contribute to this resistivity size effect are surface scattering, evidenced by thickness dependence of resistivity, and grain boundary scattering, evidenced by grain size dependence of resistivity. Quantification of microstructural parameters, such as grain size, at the scale of the resistivity size effect necessitates the use of transmission electron microscopy (TEM). In this work, an electron diffraction-based orientation mapping system installed on the TEM is used to characterize not only nanometric Cu films, but also new materials, W, Ni, Ru and Co, that are potential candidates to replace Cu as the next-generation interconnect material. In this characterization technique, spot diffraction patterns are collected as the nano-sized beam scans the area of interest. The crystallographic orientation of each scanned pixel is determined by cross-correlation with pre-calculated diffraction patterns (termed, templates). Precession is used to reduce the dynamical scattering effects, increasing the reliability of the orientation mapping. The raw orientation data is then processed to yield the microstructural data via a well-defined procedure developed to parallel that used to process electron backscatter orientation data taken in scanning electron microscopes. This characterization yields full range of microstructural parameters including grain size, grain size distribution, orientation distribution, misorientation distribution, grain boundary and interface character and plane distribution that are extracted from the crystal orientation maps in a nearly fully-automated manner. These microstructural parameters, along with sample thicknesses, are used to evaluate the validity of the semiclassical resistivity size models for Cu and the new materials, and, where applicable, to determine the relative contributions of surface and grain boundary scattering to the resistivity increase.