Abstract
An amorphous TaxMnyOz layer with 1.0 nm thickness was studied as an alternative Cu diffusion barrier for advanced interconnect. The thermal and electrical stabilities of the 1.0-nm-thick TaxMnyOz barrier were evaluated by transmission electron microscopy (TEM) and current density–electric field (J–E) and capacitance–voltage (C–V) measurements after annealing at 400 °C for 10 h. X-ray photoelectron spectroscopy revealed the chemical characteristics of the TaxMnyOz layer, and a tape peeling test showed that the TaxMnyOz barrier between the Cu and SiO2 layers provided better adhesion compared to the sample without the barrier. TEM observation and line profiling measurements in energy-dispersive X-ray spectroscopy after thermal annealing revealed that Cu diffusion was prevented by the TaxMnyOz barrier. Also, the J–E and C–V measurements of the fabricated metal-oxide-semiconductor sample showed that the TaxMnyOz barrier significantly improved the electrical stability of the Cu interconnect. Our results indicate that the 1.0-nm-thick TaxMnyOz barrier efficiently prevented Cu diffusion into the SiO2 layer and enhanced the thermal and electrical stability of the Cu interconnect. The improved performance of the TaxMnyOz barrier can be attributed to the microstructural stability achieved by forming ternary Ta-Mn-O film with controlled Ta/Mn atomic ratio. The chemical composition can affect the atomic configuration and density of the Ta-Mn-O film, which are closely related to the diffusion behavior. Therefore, the 1.0-nm-thick amorphous TaxMnyOz barrier is a promising Cu diffusion barrier for advanced interconnect technology.
Highlights
A copper (Cu) interconnect can transmit clock and other signals for providing power/ground functions to various microelectronic devices
To confirm the elemental distribution in the as-deposited MOS capacitor with the TaxMnyOz barrier, the scanning transmission electron microscopy (TEM)-electron energy loss spectroscopy (STEM-EELS) spectrum was obtained in the energy loss range for each region with Cu (L2,3 edge:[931] eV), Ta (O1 edge:[71] eV), Mn (L3 edge:[640] eV), O (K edge:[532] eV), and Si (K edge:[99] eV)
We investigated the effectiveness of an amorphous TaxMnyOz layer as an ultrathin diffusion barrier for advanced Cu interconnects
Summary
A copper (Cu) interconnect can transmit clock and other signals for providing power/ground functions to various microelectronic devices. A dual Ta/TaN barrier formed by physical vapor deposition (PVD) is generally used as a diffusion barrier as it leads to good adhesion between Cu and the ILD materials, in addition to ensuring thermal stability and blocking the diffusion of Cu into the ILD material[2,3]. Instead of a dual Ta/TaN barrier which has polycrystalline structure with inherent grain boundary diffusion pathways, an amorphous Ta2O5 barrier was investigated as a potential single barrier for Cu interconnects[8,9]. This oxide has a high thermal stability and is not reactive with Cu or SiO2. An alternative Cu diffusion barrier is required to meet various requirements such as good adhesion between
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