Ca-Doped CuO Diffusion Barrier for High-Performance <italic>a</italic>-IGZO Transistors With Cu-Based Source/Drain Material

Tailored Self-Assembled Monolayer using Chemical Coupling for Indium–Gallium–Zinc Oxide Thin-Film Transistors: Multifunctional Copper Diffusion Barrier

“…After the chemical-tailoring process on SAMs, the diffused length of the Cu ion in the Cu electrode was reduced to less than 0.1 nm (Figure e–h). These results agreed with those in the previously reported literature. ,, …”

“…reported that a 5 nm-thick MoTi alloy DB improved the performance of an a-IGZO TFT device with a carrier mobility (μ FE ) of 14.8 cm 2 /V·s and a reduced subthreshold swing (SS) of 0.41 V/decade compared to an a-IGZO TFT without DB (μ FE = 3.5 cm 2 /V·s and SS = 1.51 V/decade) . Lee et al achieved the highest μ FE value of 20.7 cm 2 /V·s using thermally stable 5 nm-thick Ca-doped CuO as DB on the a-IGZO TFT with a SS of 0.42 V/decade . However, according to the International Technology Roadmap for Devices and Systems, a much thinner (<1.5 nm) and new well-blocking DB material is highly required for high integration…”

“…Moreover, faster devices require highly conductive interconnectors that minimize contact resistance between the source/drain electrode and the oxide channel, which reduce the response time. − Copper (Cu) is an attractive interconnect material owing to its low resistivity. − However, Cu interconnectors inevitably come with a diffusion barrier (DB) due to the high diffusivity of Cu, which can create trap levels in the sub-bandgap region that degrade the device performance. ,− As DB for a Cu/a-IGZO device, several requirements are needed, such as low contact resistance, no interdiffusion between the Cu and a-IGZO films, and good mechanical adhesion without chemical reactions. Generally, refractory metals are used as a DB layer by deposition using a high-vacuum process. − For example, Kim et al. reported that a 5 nm-thick MoTi alloy DB improved the performance of an a-IGZO TFT device with a carrier mobility (μ FE ) of 14.8 cm 2 /V·s and a reduced subthreshold swing (SS) of 0.41 V/decade compared to an a-IGZO TFT without DB (μ FE = 3.5 cm 2 /V·s and SS = 1.51 V/decade) .…”

“…17 Lee et al achieved the highest μ FE value of 20.7 cm 2 /V•s using thermally stable 5 nmthick Ca-doped CuO as DB on the a-IGZO TFT with a SS of 0.42 V/decade. 18 However, according to the International Technology Roadmap for Devices and Systems, a much thinner (<1.5 nm) and new well-blocking DB material is highly required for high integration. Recently, two-dimensional materials, including graphene, h-BN, and self-assembled monolayers (SAMs), have emerged as new candidates for low-dimensional Cu DB.…”

Vacuum-free solution-based metallization (VSM) of a-IGZO using trimethylaluminium solution

“…If the metallic Al was precipitated on the surface of the TFTs, the entire surface of the TFTs should be conductive. Functioning TFTs cannot be achieved with the existence of uncontrollable current pathways, 42 which include leakage paths from the gate electrode to the S&D electrodes and from the source electrode to the drain electrode.…”