Defect Passivation and Carrier Reduction Mechanisms in Hydrogen-Doped In-Ga-Zn-O (IGZO:H) Films upon Low-Temperature Annealing for Flexible Device Applications

Abstract

Low-temperature activation of oxide semiconductor materials such as In-Ga-Zn-O (IGZO) is a key approach for their utilization in flexible devices. We previously reported that the activation temperature can be reduced to 150 °C by hydrogen-doped IGZO (IGZO:H), demonstrating a strong potential of this approach. In this paper, we investigated the mechanism for reducing the activation temperature of the IGZO:H films. In situ Hall measurements revealed that oxygen diffusion from annealing ambient into the conventional Ar/O2-sputtered IGZO film was observed at >240 °C. Moreover, the temperature at which the oxygen diffusion starts into the film significantly decreased to 100 °C for the IGZO:H film deposited at hydrogen gas flow ratio (R[H2]) of 8%. Hard X-ray photoelectron spectroscopy indicated that the near Fermi level (EF) defects in the IGZO:H film after the 150 °C annealing decreased in comparison to that in the conventional IGZO film after 300 °C annealing. The oxygen diffusion into the film during annealing plays an important role for reducing oxygen vacancies and subgap states especially for near EF. X-ray reflectometry analysis revealed that the film density of the IGZO:H decreased with an increase in R[H2] which would be the possible cause for facilitating the O diffusion at low temperature.

High-mobility InSnZnO Thin Film Transistors via Introducing Water Vapor Sputtering Gas

“…The metal cations become very active, causing disruption of the equilibrium microstructure of the initial amorphous oxides. Velichko et al reported that the introduction of H enabled the low-temperature fabrication of IGZO TFTs by reducing the barrier for oxygen diffusion, which is similar to our explanation of increasing the activity of metal cations. Subsequently, the microstructure undergoes a rearrangement, resulting in a new configuration characterized by a strengthened M–O network and fewer defects.…”

“…44 Thus, numerous metal−hydrogen bonds (M−H) 45 form as evidenced by the optical absorption observation of additional H-related defects (such as H-DX − and H i − ). The bond dissociation energy required to break M−H bonds is approximately 1/3−2/3 of that needed for M−O bonds, 46 as detailed in Table S2. Therefore, a significant number of M−H bonds break before the obvious desorption of oxygen in the initial stage of the annealing process.…”

Charge Trapping and Emission Properties in CAAC-IGZO Transistor: A First-Principles Calculations

“…The supercell was obtained by setting lattice vectors to (420), (040), and (221) for the IGZO crystal and reducing the lattice constant c to one-third [ 29 ]. To have an insight into the capture process of the CAAC-IGZO FETs with Al 2 O 3 dielectric, a variety of different intrinsic defects are considered, which may widely exist and have been suggested as the cause of reliability issues [ 30 , 31 , 32 , 33 , 34 , 35 ] in oxide semiconductor materials, for instance, oxygen vacancy (V O ), oxygen interstitial (O i ), hydrogen interstitial (H i ), hydrogen substituted oxygen (H O ) and hydroxyl interstitial ((OH) i ), and so on. Here, the defect of Ho can be regarded as a coexistence of H i and V O .…”

Influence of Grain Boundary Scattering on the Field-Effect Mobility of Solid-Phase Crystallized Hydrogenated Polycrystalline In2O3 (In2O3:H)

“…In general, the SS value of a TFT is strongly affected by defects near the semiconductor Fermi level [ 2 , 12 ]. We recently reported from hard X-ray photoelectron spectroscopy analysis that intentionally introduced hydrogen is effective in reducing defects near the Fermi level in amorphous IGZO [ 40 , 41 , 42 , 43 , 44 ]. The SS values of the In 2 O 3 :H TFTs, shown in Figure 2 d, increased at a T ann of 400 °C and higher, indicating defect creation.…”