Alteration of Cu conductivity in the size effect regime

Abstract

The resistivity of thin Cu films depends on film thickness as the dimensions approach the electron mean-free-path for Cu of 39 nm. The key size-dependent contributions are from electron–surface scattering, grain boundary scattering, and surface roughness-induced scattering. Measurements with pseudoepitaxial Cu films deposited on Si have been undertaken to reduce effects of grain boundaries and surface roughness and suggest an electron-scattering parameter of p=0.12. Overlayers of metal films on the Cu generally increase the resistivity for Ta and Pt overlayers, and may reduce the resistivity for Au and Al. The resistivity increase may also be reversed if the overlayer oxidizes.

Local fields in conductor surface electromigration: A first-principles study in the low-bias ballistic limit

“…[4][5][6] In particular, surface electromigration (EM) 7,8 often leads to the rapid breakdown of nanoscale conductors, 4,9 and is therefore a major reliability and performance concern in modern computer chip design. 3,9,10 For this reason, EM continues to attract a great deal of applied and fundamental research interest in physics, 4,11 chemistry, 5,11-13 materials science, 9,14 and nanoelectronics.…”

Microstructures of 50-nm Cu Interconnects along the Longitudinal Direction

“…Researchers have recently investigated cross-sectional microstructures and the resistivity of Cu films and interconnects [8][9][10][11][12] and reported experimental results for the microstructure have, e.g., an investigation of the grain sizes from the surface plane of Cu interconnects using an orientation imaging microscope (OIM) 8) or TEM (planeview measurement). 10) However, this investigation did not clarify the longitudinal grain size distribution that control resistivity.…”

Wire sizing with scattering effect for nanoscale interconnection

“…Since existing physics-based scattering models are too complicated for nanoscale interconnect optimization, we propose a simple yet high-fidelity width-dependent resistivitiy model based on the experimental data for copper wire [10], thin film [9], and from ITSR 2004 [14]. Our proposed model fits well compared to these data with the regression coefficient R 0.999.…”

“…The key observation is that the resistivity of copper wires will increase significantly as the wires width decreases [9][10][11][12][13][14]. While exploratory structures such as carbon nanotubes are being studied as possible replacement of copper interconnect [15][16][17], at least by 22nm technology, it is not likely that copper will be replaced by carbon nanotube or other materials [15].…”

“…While MS and FS models have been tested with measurement data for polycrystalline nanowires [6][7][8], very few experimental results on copper (Cu) film or interconnect have been reported until recently, e.g., the size effect of copper thin film was studied in [9], and the resistivity of copper wires with widths under 50nm was reported in [10][11][12][13]. The key observation is that the resistivity of copper wires will increase significantly as the wires width decreases [9][10][11][12][13][14].…”