Investigation of Barrier Property of Amorphous Co–Ti Layer as Single Barrier/Liner in Local Co Interconnects
Dan Zhang, Anyan Du, Chao Zhao, Jianfeng Gao, Shujuan Mao, Jing Xu, Shihai Gu, Yaodong Liu, Xue Gang Luo, Yongliang Li, Junfeng Li, Wenwu Wang, Dapeng Chen, Tianchun Ye, Jun Luo
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> .