Search

The amorphous InGaZnO (a-IGZO) is widely accepted as a promising channel material for thin-film transistor (TFT) applications owing to their outstanding electrical properties [1, 2]. However, a-IGZO TFTs have still suffer from their bias instability with illumination [1-4]. Up to now, many researchers have studied the sub-gap density of states (DOS) as the root cause of instability. It is well known that defect states can influence on the performances and stabilities of a-IGZO TFTs. The defects states should be closely related with the deposition condition, including sputtering power, and pressure. Nevertheless, it has not been reported how these defects are created during conventional RF magnetron sputtering. In general, during conventional RF magnetron sputtering process, negative oxygen ions (NOIs) can be generated by electron attachment in oxygen atom near target surface and then accelerated up to few hundreds eV by a self-bias; at this time, the high energy bombardment of NOIs induce defects in oxide thin films. Recently, we have reported that the properties of IGZO thin films are strongly related with effects of NOIs which are generated during the sputtering process [5]. From our previous results, the electrical characteristics and the chemical bonding states of a-IGZO thin films were depended with the bombardment energy of NOIs. And also, we suggest that the deep sub-gap states in a-IGZO as well as thin film properties would be influenced by the bombardment of high energetic NOIs during the sputtering process. In this study, we have studied the gate bias instability and their density of states (DOSs) of a-IGZO TFTs as depending on the bombardment of NOIs during conventional magnetron sputtering. Finally, we will introduce our novel technology named as Magnetic Field Shielded Sputtering (MFSS) process to prevent the NOIs bombardment effects and present how much to be improved the instability of a-IGZO TFTs by this new deposition method. 1. M.G. Kim, M.G. Kanatzidis, A. Facchetti, and T.J. Marks, Nat. Mater. 10, 382 (2011). 2. K.K. Banger, Y. Yamashita, K. Mori, R.L. Peterson, T. Leedham, J. Rickard, and H. Sirringhaus, Nat. Mater. 10, 45 (2011). 3. M.D.H. Chowdhury, P. Migliorato, and J. Jang, Appl. Phys. Lett. 98, 153511 (2011). 4. X. Xiao, W. Deng, S. Chi, Y. Shao, X. He, L. Wang, and S. Zhang, IEEE Trans. Electron Devices 60, 4159 (2013). 5. D.H. Kim, J.N. Jang, S.B. Yoon, and MunPyo Hong, Appl. Phys. Express 7, 031401 (2014).

We have investigated the effect of hydrogen neutral beam(H-NB) on the nano-crystalline silicon (nc-Si) thin films using the neutral beam assisted chemical vapor deposition (NBaCVD) system. In traditional hydrogenated silicon deposition, the gas mixture ratio of hydrogen and silane (SiH4) controls the phase of the thin films, including that from hydrogenated amorphous silicon (a-Si:H) to microcrystalline silicon (μc-Si). However, poor migration of deposition precursor and the absence of nucleation sites cause silicon background to be amorphous in the early stage of growth. Conversely, The NBaCVD technology controls the energy of neutral particles (mainly hydrogen atoms) in the range of 0-300 eV to enhance the crystallinity during thin film deposition at low temperature (2 Halogen Lamp) condition, while the field effect mobility was up to 3.2 cm2/Vs: threshold voltage shift was smaller than 1 V after 104sec under the PBIS conditions.

not Available.