HeeHwan Choe

A Study of Parameters Related to the Etch Rate for a Dry Etch Process Using NF3/O2 and SF6/O2

The characteristics of the dry etching of :H thin films for display devices using SF6/O2 and NF3/O2 were investigated using a dual-frequency capacitively coupled plasma reactive ion etching (CCP-RIE) system. The investigation was carried out by varying the RF power ratio (13.56 MHz/2 MHz), pressure, and gas flow ratio. For the :H film, the etch rates obtained using NF3/O2 were higher than those obtained using SF6/O2 under various process conditions. The relationships between the etch rates and the usual monitoring parameters—the optical emission spectroscopy (OES) intensity of atomic fluorine (685.1 nm and 702.89 nm) and the voltages and —were investigated. The OES intensity data indicated a correlation between the bulk plasma density and the atomic fluorine density. The etch rate was proportional to the product of the OES intensity of atomic fluorine and the square root of the voltages on the assumption that the velocity of the reactive fluorine was proportional to the square root of the voltages.

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.

A comparative study of algorithm for fluid simulation of high density plasma discharges

A new algorithm for steady-state fluid simulation of high density, low temperature plasma discharge is suggested. The restriction on simulation time step and a new method to overcome it is discussed. For a comparison of the new method with a previous other method, a one-dimensional fluid simulation of inductively coupled plasma discharge is studied.

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-22: Electrical Stability of ZnO TFT during Gate-Bias Stress

We fabricated TFTs with ZnO thin film as an active layer. Electrical bias stress test of ZnO TFT was also carried out. The results of stress test of ZnO TFT differed from those of a-Si:H TFT. Therefore, the instability of ZnO TFT cannot be explained by conventional degradation mechanisms of a-Si:H TFT. The variance of some factors in the fabrication process showed a certain trend in the results of bias stress. A possible mechanism of abnormal behavior under the gate bias stress was discussed.

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.

P‐67: Brief Study of an Electric Force on a Glass Substrate in a Dry Etching System

Substrate holding systems are widely used in TFT fabrication. As a basic study of ESC system, we have investigated the electric force on a glass substrate in dry etching system. Brief calculation shows that there might be an upward electric force against the gravitational force. This electric force depends on dry etching system and process conditions.