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We demonstrated the nonvolatile memory functionality of nano-crystalline silicon (nc-Si) field effect transistors (FETs) using mobile protons that are generated by very short time (within 2 minutes) hydrogen neutral beam (H-NB) treatment at room temperature (25 °C). Some researches try to hydrogen insertion process via long time (40 minutes) high-pressure hydrogen annealing (HPHA) at high temperature (400 °C) that also need several steps such as poly silicon deposition, HPHA process, and poly silicon etching process. However our hydrogen insertion process does not need any other additional process but only H-NB process during normal thin film transistor fabrication. Also the whole memory fabrication process kept under 50 °C (except SiO2deposition process; 300 °C). These nc-Si devices exhibited reproducible hysteresis, reversible switching, and nonvolatile memory behaviors in comparison with those of the conventional FET devices. We think that the memory characteristics are attributed to the movement of protons between the Si(gate)/SiO2(gate insulator) interface and the SiO2/nc-Si thin film (active layer) interface by the applied gate electric field. Our study will further provide a useful route of creating memory functionality and incorporating proton-based storage elements onto a modified CMOS platform for FET memory devices using nanomaterials, and probability of next generation flexible memorable electronics.

The neutral beam assisted chemical vapor deposition (NBaCVD) system can control the crystalline phase and the doping efficiency simultaneously by the energy of impinge neutral particle beam. During the deposition process, energetic hydrogen (H) neutral atoms transport their energy to the surface of depositing film to enhance crystallization (crystal volume fraction (Xc) up to 85%) and dopant activation (~1X1020 #/cm3, ~30 cm2/Vs) with low H ratio at near room temperature on the substrate. The increase of H neutral beam flux induces transition of crystal orientation from [111] to [311] at constant Xc and changes the carrier transport path from “grain boundary path” to “grain-to-grain percolation path” and enhances bulk mobility of the Si thin film. The various analysis data of the thin films (XRD, Raman, temperature dependent conductivity, Hall measurement) represent the evidence of very high doping efficiency at near room temperature, obvious nano-crystalline embedded polymorphous phase, and mixed transport (band and percolation) characteristics.

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.

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