Jong Hyun Seo

The Effect of Passivation Layers on the Negative Bias Instability of Ga-In-Zn-O Thin Film Transistors under Illumination

Ga-In-Zn-O (GIZO) thin film transistors (TFTs) with disparate passivation structures were fabricated and their stabilities were compared. The devices were subjected to a negative bias stress with simultaneous exposure to visible light. TFT that incorporates a dual passivation composed of a SiO x layer grown at a relatively high temperature with an additional SiN x film deposited shows only -0.8 V V th shift, whereas a -5.7 V shift was observed for a TFT covered by a single SiO 2 film. The device degradation is susceptible to the ability of protecting external moisture, which may adsorb on the surface of the GIZO semiconductor to create donor states therein.

P-62: Wet Patterning of Copper/Molybdenum Thin Films in Phosphoric Acid Solution

Recently, copper metallization has been widely developed in TFT-LCD industry, because of its lowest electrical resistivity compared to other metal candidates such as aluminum and molybdenum. In addition, the copper metallization becomes more significant issue in a high frequency driving TFT-LCD with large sized panel. Since copper has a low adhesion force against the glass substrate, copper is inevitably used with an aid of an adhesive metal layer such as Ti, Ta and Mo. When dissimilar metals like copper and molybdenum are exposed together in a wet etchant, a typical galvanic reaction occurs and this results in an undercutting of copper line or partial stains on the metal surface after drying. Especially, it is well-known that the suitable taper angle of Cu/Mo is difficult to obtain. Such failures often lead to a bad performance of thin film transistor and the display quality. Wet galvanic corrosion behavior of DC magnetron sputtered the double layers of Mo alloys and copper on the glass substrate has been examined. Compared with Cu/Mo-Ti system, the pure Mo/Cu system shows recessed galvanic corrosion behavior.

P-61: A Study on the Galvanic Reaction between Cu and Mo as Well as MoW for TFT-LCDs by Using a Zero-Resistance Ammeter

Recently, copper metallization has been widely developed in TFT-LCD industry, because of its lowest electrical resistivity compared to aluminum and its alloys. In addition, the copper metallization becomes a more significant issue in a high frequency driving technology for large sized TFT-LCD panel. Since copper has a low adhesion force against the glass substrate, copper is inevitably used with an aid of an adhesive metal layer such as Ti, Ta and Mo. When dissimilar metals like copper and molybdenum are exposed together in a wet etchant, a typical galvanic reaction occurs and this results in an undercutting of copper line or partial stains on the metal surface after drying. The suitable taper angle of Cu line is difficult to obtain especially coupled with pure molybdenum. Such failures often lead to a bad performance of thin film transistor and the display quality. There are many literatures related to the copper metallization for TFT. However, a systematic approach on the galvanic reaction occurred in copper multilayered system has not been made. In this work, we investigated a feasibility of molybdenum alloy film (MoW) for copper metallization on the basis of the thin film analysis and the advanced electrochemical techniques such as Zero Resistance Ammeter (ZRA) method.

Study on wet patterning of thin films in vertical‐transfer wet station for thin‐film‐transistor manufacturing

— To overcome the “pseudo-puddling effect” in a low-angle-tilt transfer system with an oversized glass substrate over 2 m, a vertical transfer is suggested. The aim of the present work is to study the wet-etching behavior of an aluminum/molybdenum double layer deposited on the glass substrate in a vertical transfer wet etching system and compare it with a typical 5°-tilt-transfer system. Compared with the tilt-transfer wet station, the vertical etching system has three advantages, namely, 50% space savings, higher throughput due to the high etch rate, and good etch uniformity over the entire glass for thin-film-transistor application. The computational fluid-dynamics analysis is used to predict the change of the etch uniformity as a function of the tilt angle of the glass substrate.

79.2: Wet Patterning of Thin Films in Vertical Transfer Wet Station for TFT Manufacturing

Compared with tilt transfer wet station, vertical etching system has a many advantages that are 50% space savings, higher throughput and good etch uniformity over an entire glass for thin film transistor application. The aim of the present work is to analysis on a vertical etching system to improve the process factors. The computational fluid dynamics analysis is used to testify the change of the etch uniformity as a function of tilt angle of the glass substrate.

P‐67: Wet Etching of Gallium Indium Zinc Oxide (GIZO) Semiconductor for Thin Film Transistor Application

Recently, a significant progress has been made in the characterization of gallium indium zinc oxide (GIZO) as a new semiconductor layer instead of amorphous Si semiconductor used in thin film transistor. However, the wet behavior of GIZO thin film in the etching solutions which is conventionally used in TFT industry has not been reported yet. In this work, wet etch behavior of RF magnetron sputtered GIZO thin film in a new wet etchant was studied.

P-52: Wet Corrosion of Sputtered Molybdenum Thin Film on Glass Substrate in Various Acid Solutions

In this work, wet corrosion behavior of RF magnetron sputtered molybdenum thin films was studied using by electrochemical analysis. The effects of deposition parameters such as RF power and argon pressure on corrosion rate are also examined. The corrosion rate strongly depends both on the process parameters and the type of chemical solutions. Mo thin film dissolves fastest in the nitric acid solution among the various solutions. The dissolution rates increased with increasing RF power but decreased with argon pressure. The relationship between deposition parameter and corrosion rate was discussed in terms of thin film microstructure and susceptibility of corrosion.

Micro-Scratch Analysis on Adhesion between Thin Films and PES Substrate

In flexible display, reliability of the thin film/polymer interface is an important issue because adhesion strength dissimilar materials is often inherently poor, and residual stresses arising from thermal mismatches or pressure exerted by vaporized moisture often lead to delaminations of interfaces. In the present study we deposited various thin films such as silicon nitride (SiNx), aluminum metal layer, and indium tin oxide on polyether sulphone (PES) substrate. The film adhesion was determined by micro-scratch test. The adhesion strength, presented by the critical load, Lc, when the film starts to delaminate, was determined as a function of plasma pretreated on PES substrate.