Investigation of Barrier Property of Amorphous Co–Ti Layer as Single Barrier/Liner in Local Co Interconnects

Abstract

The scaling of interconnect dimensions is becoming increasingly difficult due to the fast rise of line/via resistance. To alleviate this problem, Co has a high potential as an alternative material to Cu or W in metallization schemes. In this article, Co is used as local interconnects, and Co–Ti is proposed as a single barrier/liner to replace the conventional thick TiN/Ti bilayer. The samples with and without Co–Ti were fabricated to investigate the barrier property of Co–Ti. Meanwhile, the reaction mechanism between Co/Co–Ti and Si was comprehensively studied. In order to further evaluate the barrier property of Co–Ti, the samples were annealed at 500 °C for different durations, including 1, 30, and 60 min. Interfacial quality, elemental distribution, and Co spikes were analyzed by cross-sectional and plane-view transmission electron microscopy (TEM) in combination with corresponding electron energy loss spectroscopy (EELS) mapping. Furthermore, refined transmission line model (RTLM) structures were employed to extract the specific contact resistivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rho _{c}$ </tex-math></inline-formula> ) of as-fabricated devices with different Co:Ti atomic ratios. Achieved results demonstrate that as a single barrier/liner, Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.65</sub> Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.35</sub> is highly effective in preventing Co diffusion into Si substrate, thus realizing a uniform Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.65</sub> Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.35</sub> /n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -Si interface, spike-free contacts, and ultralow <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rho _{c}$ </tex-math></inline-formula> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.3 \times 10^{-8} \Omega {-}cm^{2}$ </tex-math></inline-formula> .