Hyunmin Hong1,Min Jung Kim1,Dong-Joon Yi1,Dong Yeob Shin1,Kwangsik Jeong1,Kwun-bum Chung1
Dongguk University, Seoul, Korea1
Hyunmin Hong1,Min Jung Kim1,Dong-Joon Yi1,Dong Yeob Shin1,Kwangsik Jeong1,Kwun-bum Chung1
Dongguk University, Seoul, Korea1
Transparent oxide-based thin-film transistors (TFTs) have attracted much attention due to their excellent electrical and optical characteristics. In particular, amorphous indium gallium zinc oxide (a-IGZO) TFTs have shown a better threshold voltage (V<sub>TH</sub>) and field-effect mobility (μ<sub>FE</sub>) due to the lack of grain boundaries, making this type of transistor a very promising alternative to an amorphous silicon TFT (a-Si TFT). In fabricating the a-IGZO-based TFTs, IGZO is deposited widely using magnetron sputtering. This technique generally provides such benefits as high deposition rates and has low processing temperatures. Therefore, IGZO has great potential to replace the existing silicon-based semiconductors and organic-based semiconductors that are employed as an active layer of the TFT backplane in the flat panel display. However, despite these merits, magnetron sputtering occasionally results in lower TFT performances due to the increase in surface morphology roughness.<br/>The interfacial charge trapping, scattering, and rough surfaces cause a decrease in the saturation mobility (μ<sub>sat</sub>), on/off current ratio (I<sub>ON</sub>/I<sub>OFF</sub>), and stability. An additional supply of O<sub>2</sub> during deposition or annealing in an appropriate environment can provide the oxygen content needed to compensate for oxygen vacancies (V<sub>O</sub>) in the film. Although some studies have already reported the effect of oxygen vacancies on the electrical properties of IGZO thin films, the effective mechanism has hardly been clearly presented for this phenomenon.<br/>In this study, we investigated the device properties and defect states in Indium gallium zinc oxide (IGZO) as a function of the oxygen flow ratio and annealing temperature during deposition. To investigate the defects at the interface, light was incident without deformation or destruction of the device using an fs-laser, and the defect density was quantitatively analyzed through the intensity of nonlinear light. In addition, the correlation between the intensity of the nonlinear signal and the device characteristics was analyzed and consistency was verified using the existing qualitative/quantitative defect analysis method.