Sub-100 nm² Cobalt Interconnects

Abstract

Co has elicited a strong interest to replace Cu for future interconnect applications in microelectronic circuits due to its potentially lower resistivity and better reliability at scaled dimensions. Here, we demonstrate Co wires with electrical cross-sectional areas as small as 34 nm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> using a simple subtractive patterning technique. Semiclassical resistivity modeling of the wire resistivity indicates that grain boundary scattering is the dominant contribution for cross-sectional areas of the order of 100 nm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , while the contribution of surface scattering increases drastically below 50 nm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Furthermore, wafer-level reliability tests of the Co wires show the high fusing current densities and a strong resistance to thermoelectric stress demonstrating the potential for robust reliability. The resistivity and the reliability of the Co wires are comparable with those of Ru wires.