Etching Characteristics and Changes in Surface Properties of IGZO Thin Films by O2 Addition in CF4/Ar Plasma

Abstract

Plasma etching processes for multi-atomic oxide thin films have become increasingly important owing to the excellent material properties of such thin films, which can potentially be employed in next-generation displays. To fabricate high-performance and reproducible devices, the etching mechanism and surface properties must be understood. In this study, we investigated the etching characteristics and changes in the surface properties of InGaZnO4 (IGZO) thin films with the addition of O2 gases based on a CF4/Ar high-density-plasma system. A maximum etch rate of 32.7 nm/min for an IGZO thin film was achieved at an O2/CF4/Ar (=20:25:75 sccm) ratio. The etching mechanism was interpreted in detail through plasma analysis via optical emission spectroscopy and surface analysis via X-ray photoelectron microscopy. To determine the performance variation according to the alteration in the surface composition of the IGZO thin films, we investigated the changes in the work function, surface energy, and surface roughness through ultraviolet photoelectron spectroscopy, contact angle measurement, and atomic force microscopy, respectively. After the plasma etching process, the change in work function was up to 280 meV, the thin film surface became slightly hydrophilic, and the surface roughness slightly decreased. This work suggests that plasma etching causes various changes in thin-film surfaces, which affects device performance.

Influence of Channel Surface with Ozone Annealing and UV Treatment on the Electrical Characteristics of Top-Gate InGaZnO Thin-Film Transistors

“…Nevertheless, the influence of the PR/stripper treatment on the IGZO surface was expected to be A UPS analysis was conducted to further understand the correlation between the different electrical properties of IGZO TFTs due to the various surface treatments and the energy state of valence electrons participating in chemical bonding in IGZO. UPS is a useful analysis technology for identifying IGZO valence band states like XPS by finely grasping the electron emission energy in the valence band [46,47]. Figure 12a,b shows secondary electron cut-off energy (E cut-off ) and valence band maximum (E V ) in the UV photoelectron spectroscopy of IGZO films with different treatments on the IGZO surface.…”

Plasma etching and surface characteristics depending on the crystallinity of the BaTiO3 thin film

“…By contrast, wet etching is difficult to apply to certain nano-sized patterns due to its isotropic etching characteristics [13]. Hence, it is essential to apply a plasma etching process that provides anisotropic and elaborate etching characteristics [14,15]. In addition, a post-deposition annealing process is essential to obtain high-κ, high-crystallinity BTO thin films [16,17].…”

Indium-Gallium-Zinc-Oxide-Based Photoelectric Neuromorphic Transistors for Spiking Morse Coding

“…A smooth channel surface and low leakage current are favorable for the charge carrier transport in semiconductor channel, which also improve the devices' comprehensive performance. [24,25] Figure 1(c) shows the transfer curve (𝐼 DS versus 𝑉 GS ) of the device with 𝑉 DS fixed at 2.0 V. During the model of reverse 𝑉 GS scanning, the 𝐼 DS can be effectively modulated, and a clockwise hysteresis loop of ∼0.2 V can be obtained, possibly due to the electron trapping near the IGZO/Al 2 O 3 interface or within the IGZO channel film. [26] A high channel current ON/OFF ration (𝐼 ON /𝐼 OFF ) is estimated to be 5.…”