Fluorinated indium‐gallium‐zinc oxide thin‐film transistor with reduced vulnerability to hydrogen‐induced degradation

Abstract

Thin‐film transistors (TFTs) based on amorphous indium‐gallium‐zinc oxide channels with or without fluorination were fabricated. The sensitivity of their electrical characteristics to hydrogen exposure was compared. It is shown that TFTs built with fluorinated channels exhibit significantly improved intrinsic resistance against hydrogen‐induced degradation; hence, they are potentially better suited for integration with hydrogen‐containing devices such as photo‐diodes based on amorphous hydrogenated silicon and TFTs based on low‐temperature polycrystalline silicon. The observed improvement correlates well with a reduced population of oxygen‐related defects and reduced hydrogen incorporation in the fluorinated channels.

Compact Integration of Hydrogen–Resistant a–InGaZnO and Poly–Si Thin–Film Transistors

“…However, the on-state current (I on ) of such strongly oxidized a-IGZO TFT was degraded after the hydrogenation, especially for the 5-µm-L transistor, a result suggesting a significantly increased source/drain (S/D) resistance (R SD ). Most plausibly, although the resistivity of strongly oxidized a-IGZO can still be effectively reduced by the argon plasma-induced donor defects [17,20], the additional H dopants suppress these donor defects rather than further supply donors; this process could result in an elevated R SD . As illustrated in Figure 1a, the L SD is even longer for the shorter-L transistor, causing an even larger R SD and thus seriously limiting the I on of 5-µm-L TFT (Figure 2b).…”

“…Furthermore, the H-resistant capability of the AOS channel needs fundamental enhancements. The fluorine (F) plasma treatment has been demonstrated to effectively suppress oxygen-related native defects and enhances the H-resilience of a-IGZO [11,14,17]. Given the corrosive effect of F on common dielectrics, a more moderate pretreatment was developed to realize the H-resistant AOS.…”

Suppression of the redox reaction between the IGZO surface and the reducing agent TMA using fluorine oxidizing agent treatment

“…[15][16][17] Furthermore, the presence of F reduces the vulnerability of IGZO to H penetration from plasma enhanced chemical vapor deposited (PECVD)-SiO 2 . 18 The type and concentration of H species from the adjacent insulator are another major issue in discussing the device performance of IGZO TFT. 19 Therefore, attention should be paid to the gate insulator (GI) material, preparation, and process sequence.…”

Enhancing the Contact between a-IGZO and Metal by Hydrogen Plasma Treatment for a High-Speed Varactor (>30 GHz)

“…Various doping methods have been studied with a-IGZO. − Argon plasma bombardment was used in self-aligned top-gated TFTs, and the fluorine plasma process exhibited stable electron doping in a-IGZO . However, since both plasma treatments etch a-IGZO, even a slight difference in plasma density may cause large nonuniformity in electrical properties and surface roughness. , Hydrogen doping in a-IGZO has been widely studied with various approaches: thermal annealing, plasma treatment, and diffusion from a hydrogen-rich layer. , Hydrogen passivates native defects in a-IGZO and increases the electron density; however, unstable bonding between hydrogen and a-IGZO elements, which results in temporal instability even at room temperature, is yet to be solved. − …”