ICMCTF2013 Session C5-1: Thin Films for Active Devices

Wednesday, May 1, 2013 2:10 PM in Room Sunset

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2:10 PM C5-1-1 Investigation on Plasma Treatment in Transparent Al-Zn-Sn-O Thin Film Transistor Application
Chih-Hsiang Chang, Po-Tsung Liu, Yu-Ta Wu, Chur-Shyang Fuh (National Chiao Tung University, Taiwan, Republic of China)

Recently, the thin film transistors (TFTs) with a-IGZO thin film as active layer perform higher mobility and better reliability than conventional hydrogenated amorphous silicon TFT (a-Si: H TFT). In addition, the uniformity of a-IGZO TFT is also superior to low temperature polycrystalline silicon TFT (LTPS TFT). Therefore, the a-IGZO TFTs have been widely considered to be the most promising candidate for the next generation display technology. a-IGZO TFTs showed good electrical performance, however, containing the rare-dispersive elements(In, Ga), will be an important issue for the long-term application. In this work, we developed rare elements-free oxide semiconductors--- amorphous Al-Zn-Sn-O thin film transistor (a-AZTO TFT).

We investigated on the physical characteristics and electrical performance of a-AZTO TFT under temperature effect of annealing process and plasma post treatment. The higher annealing temperature could strengthen the oxygen bonding, therefore the quality of the a-AZTO film improves. The electrical performance enhanced under high temperature of annealing process, as well. Moreover, O2 and N2O plasma could oxidize the AZTO film and eliminate some of the oxygen deficient. As a result, the reliability of the devices under GBS improved significantly after O2 and N2Oplasma post treatment. The optical energy gap of a-AZTO films untreated and with O2 or N2O plasma treatment were about 3.5 eV which indicated that all of the a-AZTO films were insensitive to visible light.These results showed the application potentials of a-AZTO TFT device on flat panel display technology.
2:30 PM C5-1-2 IGZO Deposition - Sputtering Technologies Comparison
Pawel Ozimek, Wojciech Glazek, Andrzej Klimczak, Piotr Rozanski (Huettinger Electronic, Poland)
In the paper are compared results of sputtering of indium gallium zinc oxide by DC, pulsed DC, but also by MF and Bipolar - dual magnetron industrial sputtering technologies. Comparison including detailed results such as process parameters stability, deposition rates, and coatings quality are compared for full range of industrially available high rate sputtering deposition technologies.The sputtering technologies presented in the publication are realized by new range of power supplies equipped with advanced process stabilization solutions, ultra-fast arc management characterized by very low stored energy (in range down to 0.1mJ/kW) , and digital control platform enabling highly flexible software algorithms design, all this with intention to improve overall result of the process.
2:50 PM C5-1-3 Low Temperature Electrochemical Hydrocarbon Sensor Based on Reactive Magnetron Co-sputtering Deposited Layers
Eloi Dereeper, Pascal Briois, Alain Billard (IRTES-LERMPS-UTBM, France)
Hydrocarbon vapours released by car exhausts or industrial activities can be either irritating or carcinogenic, flammable or explosives. Their monitoring thus relates to health and security issues. Electrochemical sensors are widely studied for the detection of oxidizable gases in an atmosphere: they are easy to miniaturize and exhibit good response time and sensitivity. However, oxide-based sensors generally require a rather high working temperature (600°C) to enable ionic conductivity through the electrolyte. The work presented here is about the fabrication of a hydrocarbon sensor able to work at lower temperature of about 300°C in ambient air. In a first step, attention has been paid to the synthesis of BITAVOX solid state electrolyte (Bi2TaxV1-xO5.5), which makes oxide ion conduction possible at this temperature. It has been deposited on alumina pellets and on MSP 769 commercial sensor platform. The influence of tantalum substitution rate on the conduction performance of the material has been assessed by electrochemical impedance spectroscopy. Then, lanthanum perovskite and platinum have been sputtered to play the role of electrodes. The impact of deposition parameters on their microstructure and on the electrode / electrolyte interface has been assessed by X-ray diffraction and SEM observations. Finally, the sensor performances are investigated via four probe measurements under air-HC mixtures.
3:10 PM C5-1-4 Growth of Carbon Nanotubes/ Diamond Double Layers for High Stable Field Electron Emission
Lezhi Yang, Chunzi Zhang, Yuanshi Li, Qiaoqin Yang (University of Saskatchewan, Canada)
Thin films of Diamond and carbon nanotubes (CNTs) are promising candidates as cold cathode field electron emitter. However, because of the poor electrical conductivity, diamond emitters usually present a high turn-on field. CNTS emitters fail with high emission current due to the heat accumulation at the contact surface caused by a poor contact to substrate. To improve the emitter’s stability with better emission properties, a double-layered nanostructure consisting of a layer of vertically aligned CNTs and a layer of diamond has been synthesized on silicon substrate by hot filament chemical vapor deposition (HFCVD). The synthesis was achieved by firstly depositing an inner layer of diamond on silicon then a top layer of vertically aligned carbon nanotubes by applying a negative bias on the substrate holder. The growth of CNTs was catalyzed by a thin layer of spin coated Iron nitride. The morphology and structure of the CNT/diamond double layered material were characterized by Scanning Electron Microscope, X-ray diffraction, Transmission Electron Microscope and Raman Spectroscopy. The field electron emission properties were measured by KEITHLEY 237 high voltage measurement unit. This double layered material has a direct C-C bonding between vertically aligned CNTs and diamond and shows better field electron emission properties than single layered diamond films, and higher stability than CNT films. The high density CNTs arrays supply high emission density and large field enhancement factor while the diamond layer enhances the emission stability due to its high thermal conductivity.
3:30 PM C5-1-5 The Effect of Moisture on Oxygen Adsorption of InGaZnO Thin Film Transistors under Bias Stress
Yu-Chun Chen, Ting-Chang Chang (National Sun Yat-Sen University, Taiwan, Republic of China)
This paper investigates the asymmetric degradation behaviors of amorphous InGaZnO thin film transistors (TFTs) in oxygen and moisture ambient under gate bias stress. In InGaZnO TFTs, the electrical characteristic of passivation-free device is a strongly function with the ambient gas, however, the influence combined with moisture and oxygen (O2/H2O) on the bias-induced instability of amorphous InGaZnO TFTs is studied rarely. Experimental results show the threshold voltage shifts of devices under positive and negative gate bias stress are increased and suppressed in O2/H2O ambient, respectively, when compared to that in only oxygen or moisture ambient . A physical model is proposed to explain the the dynamic relationship between the electrical instability of TFTs and ambient O2/H2O in environment, which may provide a better understanding of the adsorbed/desorbed gas phenomenon of the IGZO TFTs in atmospheric ambient .
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