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Total photoyield emission spectroscopy (TPYS) was applied to study the evolution of sub-gap states in hydrogen-treated amorphous In-Ga-Zn-O (a-IGZO) thin films. The a-IGZO thin films were subjected to hydrogen radicals and subsequently annealed in ultra-high vacuum (UHV) conditions. A clear onset of the electron emission was observed at around 4.3 eV from the hydrogen-treated a-IGZO thin films. After successive UHV annealing at 300 °C, the onset in the TPYS spectra was shifted to 4.15 eV, and the photoelectron emission from the sub-gap states was decreased as the annealing temperature was increased. In conjunction with the results of thermal desorption spectrometer, it was deduced that the hydrogen atoms incorporated in the a-IGZO thin films induced metastable sub-gap states at around 4.3 eV from vacuum level just after the hydrogenation. It was also suggested that the defect configuration was changed due to the higher temperature UHV annealing, and that the hydrogen atoms desorbed with the involvement of Zn atoms. These experiments produced direct evidence to show the formation of sub-gap states as a result of hydrogen incorporation into the a-IGZO thin films.

In this study, adhesion of the Cu/Cu-Mn stacked interconnections to glass (SiO2) substrates was evaluated and the results were correlated with a detailed analysis of the reaction layer between the Cu-Mn and the chemical vapour deposited SiO2. When the Mn concentrations were varied, an abrupt change in the adhesion properties was observed; the practical adhesion properties were obtained in the Cu/Cu-Mn interconnections with Mn concentrations at 8% and higher. To clarify the chemical nature and the microstructure of the reaction layer at the interface between the Cu-x Mn (x = 4, 10 at. %) and the SiO2 layers was analysed using angle-resolved x-ray photoelectron spectroscopy and transmission electron microscope-electron energy loss spectroscopy. These observations indicated that the cross-sectional structure along the reaction layer of the Cu–10 at. % Mn sample can be divided into two regions: in the high Mn region, the Mn-Si complex oxide and the SiO2 mixture phase are preferable due to a decrease in the ox...

Metal-oxide-semiconductor (MOS) diodes with various gate insulators (G/Is) were characterized by capacitance–voltage characteristics and isothermal capacitance transient spectroscopy (ICTS) to evaluate the effect of H and OH desorption and diffusion on the electronic structures in amorphous In–Ga–Zn–O (a-IGZO) thin films. The density and the distribution of the space charge were found to be varied depending on the nature of the G/I. In the case of thermally grown SiO2 (thermal SiO2) G/Is, a high space-charge region was observed near the a-IGZO and G/I interface. After thermal annealing, the space-charge density in the deeper region of the film decreased, whereas remained unchanged near the interface region. The ICTS spectra obtained from the MOS diodes with the thermal SiO2 G/Is consisted of two broad peaks at around 5 × 10−4 and 3 × 10−2 s before annealing, while one broad peak was observed at around 1 × 10−4 s at the interface and at around 1 × 10−3 s in the bulk after annealing. Further, the trap densi...

Electron traps in amorphous In–Ga–Zn–O (a-IGZO) thin films were studied using isothermal capacitance transient spectroscopy (ICTS). Broad peaks that shifted toward a longer elapsed time with an increase in the filling pulse width were detected from the ICTS spectra for metal-oxide-semiconductor diodes consisting of a Mo/SiO2/a-IGZO structure. The time constant of the peak position at 180 K was found to be from ∼1 m to ∼100 ms, corresponding to a range of energy level from ∼170 to ∼230 meV below the conduction band edge. The total trap density around the peak was estimated to be ∼1 × 1016 cm−3·eV−1. Further, according to the biasing voltage dependence of the ICTS signal, the density of the trap states increases by about three orders of magnitude near the interface between the a-IGZO and the gate dielectric layers. The electron transport in electronic devices using an a-IGZO could be influenced by the trap states detected in the present study.