Classical size effect in oxide-encapsulated Cu thin films: Impact of grain boundaries versus surfaces on resistivity

A methodology is developed to independently evaluate surface and grain boundary scattering in silicon dioxide-encapsulated, polycrystalline Cu thin films. The room-temperature film resistivity for samples with film thicknesses in the range of 27 to 1 65 nm and different grain sizes (determined from approximately 400 to 1500 grains per sample) is compared to existing and empirical models of surface and grain boundary scattering. For the combined effects of surface and grain boundary scattering, the surface specularity parameter p is 0.6 +/- 0.2 and the grain boundary reflectivity coefficient R is 0.45 +/- 0.03. It is thereby shown that the resistivity contribution from grain boundary scattering is significantly greater than that of surface scattering for Cu thin films having Cu/SiO2 surfaces and grain sizes similar to film thickness. (C) 2008 American Vacuum Society

Surface and grain-boundary scattering in nanometric Cu films

We report a quantitative analysis of both surface and grain-boundary scattering in Cu thin films with independent variation in film thickness (27 to 158 nm) and grain size (35 to 425 nm) in samples prepared by subambient temperature film deposition followed by annealing. Film resistivities of carefully characterized samples were measured at both room temperature and at 4.2 K and were compared with physical models that include the effects of surface and grain-boundary scattering. Grain-boundary scattering is found to provide the strongest contribution to the resistivity increase. However, a weaker, but significant, role is observed for surface scattering. We find that the data are best fit when the Mayadas and Shatzkes\u27 model of grain-boundary scattering and the Fuchs and Sondheimer\u27s model of surface scattering resistivity contributions are combined using Matthiessen\u27s rule (simple addition of resistivities). This finding implies that grain-boundary scattering preserves the component of electron momentum parallel to the grain-boundary plane. Using Matthiessen\u27s rule, we find our data are well described by a grain-boundary reflection coefficient of 0.43 and a surface specularity coefficient of 0.52. This analysis finds a significantly lower contribution from surface scattering than has been reported in previous works and we attribute this difference to the careful quantitative microstructural characterization performed on our samples. The effects of surface roughness, impurities, voids, and interactions between surface and grain-boundary scattering are also examined and their importance is evaluated

Surface and grain boundary scattering in nanometric Cu thin films: A quantitative analysis including twin boundaries

The relative contributions of various defects to the measured resistivity in nanocrystalline Cu were investigated, including a quantitative account of twin-boundary scattering. It has been difficult to quantitatively assess the impact twin boundary scattering has on the classical size effect of electrical resistivity, due to limitations in characterizing twin boundaries in nanocrystalline Cu. In this study, crystal orientation maps of nanocrystalline Cu films were obtained via precession-assisted electron diffraction in the transmission electron microscope. These orientation images were used to characterize grain boundaries and to measure the average grain size of a microstructure, with and without considering twin boundaries. The results of these studies indicate that the contribution from grain-boundary scattering is the dominant factor (as compared to surface scattering) leading to enhanced resistivity. The resistivity data can be well-described by the combined Fuchs-Sondheimer surface scattering model and Mayadas-Shatzkes grain-boundary scattering model using Matthiessen\u27s rule with a surface specularity coefficient of p = 0.48 and a grain-boundary reflection coefficient of R = 0.26

Classical size effect in copper thin films: Impact of surface and grain boundary scattering on resistivity

Surface and grain boundary electron scattering contribute significantly to resistivity as the dimensions of polycrystalline metallic conductors are reduced to, and below, the electron mean free path. A quantitative measurement of the relative contributions of surface and grain boundary scattering to 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. In 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. Thus, the quantification of the classical size effect still suffers from an uncertainty in the relative contributions of surface and grain boundary scattering. In this work, a quantitative analysis of both surface and grain boundary scattering in Cu thin films with independent variation of film thickness (27 nm to 158 nm) and grain size (35 nm to 425 nm) in samples prepared by sub-ambient temperature film deposition followed by annealing is reported. Film resistivities of carefully characterized samples were measured at both room temperature and at 4.2 K and were compared with several scattering models that include the effects of surface and grain boundary scattering. Grain boundary scattering is found to provide the strongest contribution to the resistivity increase. However, a weaker, but significant, role is also observed for surface scattering. Several of the published models for grain boundary and surface scattering are explored and the Matthiessen’s rule combination of the Mayadas and Shatzkes’1 model of grain boundary scattering and Fuchs 2 and Sondheimer’s3 model of surface scattering resistivity contributions is found to be most appropriate. It is found that the experimental data are best described by a grain boundary reflection coefficient of 0.43 and a surface specularity coefficient of 0.52. This analysis finds a significantly lower contribution from surface scattering than has been reported in previous works, which is in part due to the careful quantitative microstructural characterization of samples performed. The data does suggest that there is a roughness dependence to the surface scattering, but this was not conclusively demonstrated. Voids and impurities were found to have negligible impact on the measured resistivities of the carefully prepared films. 1A. F. Mayadas and M. Shatzkes, Phys Rev. B 1, 1382 (1970). 2K. Fuchs, Proc. Cambridge Philos. Soc. 34, 100 (1938). 3E. H. Sondheimer, Adv. Phys. 1. 1, (1952)

Thin Gold Films Sputter Deposition and Optical Characterization

(Statement of Responsibility) by Tik Sun(Thesis) Thesis (B.A.) -- New College of Florida, 2005(Electronic Access) RESTRICTED TO NCF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE(Bibliography) Includes bibliographical references.(Source of Description) This bibliographic record is available under the Creative Commons CC0 public domain dedication. The New College of Florida, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.(Local) Faculty Sponsor: Sendova, Marian

The critical study of political pbligation in Zhou Shu of Shang Shu and Liji = "Shang shu, zhou shu" ji "li ji" 'zheng zhi yi wu' zhi yan jiu

In ancient Chinese political philosophy, it seems that political obligation does not play a vital role in political discourse. Although it may be a mistaken belief, the image of primitive, tyrannical and moral distasteful on ancient Chinese governmentality were sharing between modern philosophers, such as Leibniz or Hegel. However, that image may not be justified if we examine those historical literatures concerning Zhou dynasty. In this essay, I shall provide a theory of political obligation in pre-Qin Chinese political philosophy. Two classical Chinese texts, Zhou Shu of Shan Shu and Liji, would be studied to outline the system of political obligation. I shall reorganize those fragments related to political obligation in the texts and provide a systematic explanation on the content and practice of political obligation. After reviewing theories of political obligation and clarifying some preliminarily remarks of this study, I shall discuss the historical background of the studied texts. The political crises during the Zhou dynasty provide reasons for recognizing the importance of praising political obligation. Then, I shall try to explain two underlying social systems which are providing criterion of judgment of political obligation. The side of Tian Dao provide transcended basis and authority for political obligation. On the side of Li, its properties create a social, moral and concrete basis for practicing and regulating proper social conduct of different social roles. After that, I shall discuss political obligations in terms of three social roles, which are ruler, officer and ordinary people. The political obligations of each social role reflect the moral considerations of right-ordering society and political burden of those are powerful.published_or_final_versionChinese Language and LiteratureMasterMaster of Art

Impact Of Surface And Grain Boundary Scattering On The Resistivity Of Nanometric Cu Interconnects

This work addresses the resistivity increase in Cu interconnects with decreasing line width. Recent published resistivity data for Cu interconnect lines is found to be accurately modeled by a fixed surface scattering specularity parameter, p=0.52, and a grain boundary reflection coefficient, R=0.43. In this model, the resistivity contribution from surface scattering at the line top and bottom surfaces, the contribution from surface scattering at the line sidewalls, and the contribution of grain boundary scattering from within the line are simply summed with the phonon and impurity resistivity contributions following Matthiessen\u27s rule. The more recent line resistivity reports were found to have reduced impurity contributions to resistivity and larger grain sizes than earlier reports. It is concluded that a significant mitigation of the Cu resistivity increase with decreasing line width is possible, if the grain size can be maintained larger than the electron mean free path (39 nm at room temperature). © 2010 American Institute of Physics

High Contrast Hollow-Cone Dark Field Transmission Electron Microscopy For Nanocrystalline Grain Size Quantification

In this paper, we describe hollow-cone dark field (HCDF) transmission electron microscopy (TEM) imaging, with a slightly convergent beam, as an improved technique that is suitable to form high contrast micrographs for nanocrystalline grain size quantification. We also examine the various factors that influence the HCDF TEM image quality, including the conditions of microscopy (alignment, focus and objective aperture size), the properties of the materials imaged (e.g., atomic number, strain, defects), and the characteristics of the TEM sample itself (e.g., thickness, ion milling artifacts). Sample preparation was found to be critical and an initial thinning by wet etching of the substrate (for thin film samples) or tripod polishing (for bulk samples), followed by low-angle ion milling was found to be the preferred approach for preparing high-quality electron transparent samples for HCDF imaging. © 2009 Elsevier Ltd. All rights reserved

Resistivity Size Effect In Encapsulated Cu Thin Films

The work addresses the resistivity increase in Cu interconnects with decreasing linewidth. The surface and grain boundary scattering parameters in Cu thin films encapsulated in SiO 2 with and without Ta barrier layers are quantified, and grain boundary scattering is shown to be much greater than surface scattering. 21 samples and 17,882 Cu grains were measured to provide the grain size data. This work indicates that significant mitigation of the Cu resistivity increase with decreasing linewidth is possible, if the grain size can be maintained larger than the electron mean free path (39 nm at room temperature). ©2008 IEEE