High Conductivity and Adhesion of Cu-Cr-Zr Alloy for TFT Gate Electrode

Abstract

Abstract:The characteristics of Cu alloy (0.3 wt. % Cr, 0.2 wt. % Zr) thin film deposited by direct current (DC) magnetron sputtering deposition were investigated. The conductivity and adhesion of the Cu-0.3%Cr-0.2%Zr films were optimized by increasing the sputter power to 150 W and reducing the sputter pressure to 2 mTorr. With an annealing process (at 300 • C for 1 h in argon ambient atmosphere), the resistivity of the alloy film decreased from 4.80 to 2.96 µΩ·cm, and the adhesion classification increased from 2B to 4B on glass substrate. X-ray photoelectron spectroscopy (XPS) analysis showed that Cr aggregated toward the surface of the film and formed a self-protection layer in the annealing process. Transmission electron microscopy (TEM) indicated the aggregation and migration of Cr in the annealing process. A further X-ray diffraction (XRD) analysis showed that Cu 2 O appeared when the annealing temperature reached above 350 • C, which accounts for the increase of the resistivity. Based on Al 2 O 3 and SiO 2 substrate surfaces, the Cu-0.3%Cr-0.2%Zr film also showed high conductivity and adhesion, which has a potential in the application of Cu gate electrodes for thin film transistor (TFT).

Alloy-Electrode-Assisted High-Performance Enhancement-Type Neodymium-Doped Indium-Zinc-Oxide Thin-Film Transistors on Polyimide Flexible Substrate

“…Figure 5 shows the element distribution by XPS depth profile analysis, and the inset shows the interface between the CCZ S/D electrode and NdIZO active layer. It can be seen that Zr and Cr, as refractory metals, do not form intermetallic compounds with Cu and segregate on the surface and interface, which is consistent with our previous work [ 42 ]. Moreover, this morphology acting as a self-aligned barrier buffer layer can effectively block the diffusion of Cu atoms into the NdIZO active layer, thereby preventing the activity of the NdIZO active layer from being affected by the Cu deep-level acceptor trap.…”

A Flash‐Induced Robust Cu Electrode on Glass Substrates and Its Application for Thin‐Film μLEDs

“…Cu is an attractive material for thin‐film μLED electrodes due to its remarkable conductivity (5.98 × 10 5 S cm –1 ), [ 24 ] high robustness, [ 25,26 ] and cheap price (≈6500 times cheaper than Au), [ 27 ] as proven by the industrial application of copper interconnects in a‐Si TFT‐LCD. [ 28–30 ] Nonetheless, poor Cu adhesion on glass substrates induces the electrode delamination under minor environmental stresses of temperature and humidity, leading to the breakdown of current‐driven μLEDs. [ 28,29,31 ] Metal interlayers such as Mo, Cr, and Ti at Cu/glass interface have been proposed; however, they possess a drawback of galvanic reaction during the wet etching process, causing the damage and disconnection of metal lines.…”

“…[ 28–30 ] Nonetheless, poor Cu adhesion on glass substrates induces the electrode delamination under minor environmental stresses of temperature and humidity, leading to the breakdown of current‐driven μLEDs. [ 28,29,31 ] Metal interlayers such as Mo, Cr, and Ti at Cu/glass interface have been proposed; however, they possess a drawback of galvanic reaction during the wet etching process, causing the damage and disconnection of metal lines. [ 31–33 ] To solve the inherent atomic mismatch, chemical and physical reactions at the interface between Cu/glass should be investigated.…”

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

“…Amorphous indium–gallium–zinc oxide (a-IGZO) is the most appropriate oxide semiconductor for thin-film transistors (TFT) for high-end display technology owing to its superior electrical and optical transparency properties. − These a-IGZO characteristics enable fast response of the active matrix, which is essential in large-area and high-resolution displays. 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.…”