Influence of quantum-mechanical boundary roughness resistance on copper nanolines

TL;DR

This paper investigates how quantum-mechanical surface roughness affects copper nanoline resistivity, revealing a significant increase in resistance for lines narrower than 100 nm, which impacts future electronic device performance.

Contribution

It introduces a quantum mechanical model for surface roughness scattering that explains the linewidth dependence of resistivity in copper nanolines below 100 nm.

Findings

Quantum roughness scattering causes a 40% resistivity increase in 20 nm lines.

Finite size effects alone do not fully explain the linewidth dependence.

Surface roughness effects become dominant below the mean free path.

Abstract

Copper nanolines fabricated by the damascene process are commonly used as interconnects in advanced electronic devices. The copper resistivity increases above the bulk value because of confinement, in detriment of performance. Recent electronic transport measurements clearly exhibit this effect for nanolines whose widths range between 80 and 500 nm at low and room temperatures. An interpretation in terms of finite size effects that consider semiclassical models for electron-surface and grain-boundary scattering was presented, but the fits do not capture the strong linewidth dependence in the data below 100 nm. The present letter explains how the excess resistivity arises from a quantum mechanical surface roughness effect that begins to contribute strongly in lines narrower than the mean free path. This type of roughness scattering would contribute a 40% increase in resistivity for future 20 nm-interconnects.