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

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 (
$\rho _{c}$
) of as-fabricated devices with different Co:Ti atomic ratios. Achieved results demonstrate that as a single barrier/liner, Co
_0.65
Ti
_0.35
is highly effective in preventing Co diffusion into Si substrate, thus realizing a uniform Co
_0.65
Ti
_0.35
/n
⁺
-Si interface, spike-free contacts, and ultralow
$\rho _{c}$
of
$2.3 \times 10^{-8} \Omega {-}cm^{2}$
.