| AVS 54th International Symposium | |
| Electronic Materials and Processing | Wednesday Sessions |
| Session EM-WeM |
| Session: | Contacts, Interfaces and Defects in Semiconductors |
| Presenter: | T. Sun, University of Central Florida |
| Authors: | T. Sun, University of Central Florida B. Yao, University of Central Florida V. Kumar, Carnegie Mellon University A.P. Warren, University of Central Florida K.R. Coffey, University of Central Florida K. Barmak, Carnegie Mellon University |
| Correspondent: | Click to Email |
Surface and grain boundary electron scattering contribute greatly to resistivity as the dimensions of polycrystalline metal thin films and interconnects are reduced to and below the length of the electron mean free path. A quantitative measurement of the relative contributions of surface and grain boundary scattering to the resistivity is very challenging, requiring not only the preparation of suitably small conductors having independent variation of the two relevant length scales, namely, the sample critical dimension and the grain size, but also independent, experimental quantification of these two length scales. Since for most work to date the sample grain size has been either assumed equal to conductor dimension or measured for only a small number of grains, the quantification of the classical size effect still suffers from an uncertainty in the relative contributions of surface and grain boundary scattering. A methodology is reported to independently evaluate surface and grain boundary scattering in dielectric encapsulated polycrystalline Cu thin films. The film resistivity measured at both room temperature and at 4K is compared for samples having different grain sizes (determined from 400 to 1,500 grains per sample) and film thicknesses. The experimental data is compared to existing and empirical models of surface and grain boundary scattering in thin films. The resistivity measured at room temperature and 4K is observed to follow similar trends. We find that the resistivity contribution from grain boundary scattering to be significantly greater than that of surface scattering for Cu thin films having Cu/SiO2 surfaces and grain sizes similar to their thickness. We also find that the resistivity at room temperature is not equal to the simple sum of the low temperature resistivity and the room temperature phonon resistivity contribution, suggesting that either Matthiessen’s rule can not be applied, or that the grain boundary and/or surface scattering has a temperature dependence.