Dae-Yong Moon

Effects of oxygen contents in the active channel layer on electrical characteristics of ZnO-based thin film transistors

The authors report the fabrication and characteristics of thin film transistors with ZnO channel layers (ZnO TFTs) having different oxygen contents. Also, the authors define the operation mechanism of ZnO TFTs as the variation of oxygen contents in the ZnO channel layer. The ZnO thin films were deposited on SiO2∕n-Si substrate by dc magnetron sputtering at various oxygen partial pressures. Effects of oxygen contents in ZnO thin films on the electrical performance of ZnO TFTs with bottom gate structure were investigated. The ZnO thin films deposited at oxygen partial pressures of 40% exhibit a nonstoichiometric system in an oxygen rich state, resulting in resistivity as high as 105Ωcm. ZnO TFTs with this channel layer exhibited depletion mode, turn on voltage of −15V, on-off current ratio of ∼106, and field effect mobility of 0.88cm2∕Vs. This research implied that an attractive application for TFTs involves their use as select transistors in individual pixels of an active-matrix liquid-crystal display.

Titanium Oxide Thin Films Prepared by Plasma Enhanced Atomic Layer Deposition Using Remote Electron Cyclotron Resonance Plasma for Organic Devices Passivation

We examined titanium oxide films and their barrier characteristics. Titanium oxide films were deposited at room temperature with electron cyclotron resonance plasma power of 300 W. We measured the growth rate of the titanium oxide film to be 1.8 A/cycle. Barrier layers on poly(ether sulfon) (PES) substrates were observed to provide activation energy for water permeation. Activation energy of 12.4 kJ/mol was added by applying a titanium oxide coating with a thickness of 100 nm. The passivation performance of the titanium oxide film was also investigated using organic light-emitting diodes (OLEDs). The relative luminance of a 400-nm-thick-coated OLED device was diminished by 11.6% for 20 h.

Copper seed layer using atomic layer deposition for Cu interconnect

Cu has replaced Al for interconnection material in ultra large integrated circuit (ULSI), resulting in reducing the RC delay and achieving higher electro-migration reliability. However, it becomes more difficult to form reliable Cu wire as the feature size more decreases. For successful electrochemical plating (ECP) filling, continuous Cu seed layer with low resistivity and conformallity is essentially required. We have studied a Cu seed layer deposited using plasma enhanced atomic layer deposition (PE-ALD). The electrical property of sub-10 nm thickness Cu thin film was determined by the continuity and morphology of thin film. Based on these results, Cu seed layers were deposited on the 32 nm sized Ta/SiO2 trench substrate, and ECP was performed under the conventional conditions. It was observed that the continuous seed layer was deposited using PE-ALD and the trench was perfectly filled.

Water Vapor Permeation Properties of Al 2 O 3 /TiO 2 Passivation Layer Deposited by Atomic Layer Deposition

In this study, and films was deposited on to PES (poly(ethersulfon) substrate by using atomic layer deposition as functions of deposition temperature and plasma power. The density and carbon contents of and films was changed by varying process conditions. High density thin films was achieved through optimizing the process conditions. Buffer layer was deposited prior to the processing of upper thin films to avoid PES surface destruction during the high power plasma process and to enhances the tortuous path for water vapor permeation for the defect decoupling effect. The water vapor transmission rate by using MOCON test was investigated to analyze the effect. Water vaper permeation properties was improved by using the inorganic multi-layer passivation layer and activation energy of the water vapor permeation was increased.

Phosphorus Doping Effect in a Zinc Oxide Channel Layer to Improve the Performance of Oxide Thin-Film Transistors

In this study, we fabricated phosphorus-doped zinc oxide-based thin-film transistors (TFTs) using direct current (DC) magnetron sputtering at a relatively low temperature of 100°C. To improve the TFT device performance, including field-effect mobility and bias stress stability, phosphorus dopants were employed to suppress the generation of intrinsic defects in the ZnO-based semiconductor. The positive and negative bias stress stabilities were dramatically improved by introducing the phosphorus dopants, which could prevent turn-on voltage (VON) shift in the TFTs caused by charge trapping within the active channel layer. The study showed that phosphorus doping in ZnO was an effective method to control the electrical properties of the active channel layers and improve the bias stress stability of oxide-based TFTs.