On twin density and resistivity of nanometric Cu thin films

Abstract

Crystal orientation mapping in the transmission electron microscope was used to quantify the twin boundary length fraction per unit area for five Ta38Si14N48/SiO2 encapsulated Cu films with thicknesses in the range of 26–111 nm. The length fraction was found to be higher for a given twin-excluded grain size for these films compared with previously investigated SiO2 and Ta/SiO2 encapsulated films. The quantification of the twin length fraction per unit area allowed the contribution of the twin boundaries to the size effect resistivity to be assessed. It is shown that the increased resistivity of the Ta38Si14N48 encapsulated Cu films compared with the SiO2 and Ta/SiO2 encapsulated films is not a result of increased surface scattering, but it is a result of the increase in the density of twin boundaries. With twin boundaries included in the determination of grain size as a mean-intercept length, the resistivity data are well described by 2-parameter Matthiessen's rule summation of the Fuchs-Sondheimer and Mayadas Shatzkes models, with p and R parameters that are within experimental error equal to those in prior reports and are p = 0.48(+0.33/−0.31) and R = 0.27 ± 0.03.

Effect of De-Twinning on Tensile Strength of Nano-Twinned Cu Films

“…Furthermore, many researchers reported that twin boundaries can be produced by means of the electroplating [ 9 , 12 , 21 , 22 , 23 ]. The amount and density of the twin boundaries can be manipulated by the specific additives, pulse current modes, and different types of electroplating solution [ 9 , 24 , 25 , 26 ]. Typically, two kinds of twin grains can be produced in the electroplated Cu films: the equi-axised twin grains (typically dispersing in the Cu matrix) and columnar twin grains (the Cu columns grow perpendicularly to the plating substrate) [ 27 , 28 , 29 , 30 ].…”

Relative Grain Boundary Energies from Triple Junction Geometry: Limitations to Assuming the Herring Condition in Nanocrystalline Thin Films

“…The grain structure of polycrystalline materials and the properties of their grain boundaries play a key role in determining electrical [1][2][3], mechanical [4], and chemical properties [5,6] in a variety of systems. The grain boundary character distribution (GBCD), which measures the relative areas of boundary types in a sample, has been shown to correlate with macroscopic properties in a variety of systems [7].…”

“…The grain boundary character distribution (GBCD), which measures the relative areas of boundary types in a sample, has been shown to correlate with macroscopic properties in a variety of systems [7]. As an example, twin boundaries have been shown to contribute significantly less to resistivity than boundaries of different types [1][2][3]. To fully define the crystallography of a boundary, its character must be specified over 5 five macroscopic degrees of freedom; three of these parameters define the misorientation between the two neighboring crystallites, and two define the geometric plane which divides them.…”

Epitaxial metals for interconnects beyond Cu

“…1,2 Furthermore, as the critical dimensions of interconnects are scaled towards, and then below the mean free path of Cu (39 nm at room temperature), the resistivity is found to increase. [2][3][4][5][6][7] The increase in resistivity, termed the resistivity size-effect, results in resistance scaling beyond Ohm's law dimensional scaling and leads to even larger power consumption and further limits improvements in computing performance.…”

“…Furthermore, for polycrystalline interconnects where the grain size is of the order of λ, grain boundary scattering is expected to be the dominant scattering mechanism and has been shown to be the case for Cu films and lines. 3,5,13 Therefore, the development of interconnects beyond Cu points to the need for elimination of grain boundaries and the implementation of epitaxial metals as interconnects. This motivates the current work on experimental studies of the resistivity behavior of epitaxial, single crystal Co and Ru films.…”