1. Field of the Invention
The present invention relates to a low resistance wiring structure and a liquid crystal display device using the same, and more particularly, to a low resistance wiring structure including copper applied to a semiconductor and a display element and a liquid crystal display device using the same.
2. Description of the Related Art
In general, a liquid crystal display (LCD) is a representative semiconductor-related device employing copper-containing low resistance wirings.
The LCD, a light thin film type flat panel display (FPD) that replaces the existing display device CRT (Cathode Ray Tube), is a device for displaying images by using optical anisotropy of liquid crystal and is actively applied to a notebook computer, a desk top monitor, or the like, because of its good resolution, color display and picture quality.
The LCD includes a color filter substrate, an array substrate, and a liquid crystal layer formed between the color filter substrate and the array substrate.
An active matrix (AM) driving method commonly used for the LCD is a method in which liquid crystal molecules in a pixel part are driven by using amorphous silicon thin film transistors (a-Si TFTs) as switching elements.
FIG. 1 is an exploded perspective view showing an LCD device according to the related art.
As shown in FIG. 1, the LCD includes a color filter substrate 5, an array substrate 10 and a liquid crystal layer 30 formed between the color filter substrate 5 and the array substrate 10.
The color filter substrate 5 includes a color filter (C) including a plurality of sub-color filters 7 that implement red, green and blue colors, a black matrix 6 for dividing the sub-color filters 7 and blocking light transmission through the liquid crystal layer 30, and a transparent common electrode 8 for applying voltage to the liquid crystal layer 30.
The array substrate 10 includes gate lines 16 and data lines 17 which are arranged vertically and horizontally to define a plurality of pixel areas (P), TFTs (T) which are switching elements formed at respective crossings of the gate lines 16 and the data lines 17, and pixel electrodes 18 formed on the pixel areas (P).
The color filter substrate 5 and the array substrate 10 are attached in a facing manner by a sealant (not shown) formed at an edge of an image display region to form a liquid crystal panel, and the attachment of the color filter substrates 5 and the array substrate 10 is made by an attachment key formed on the color filter substrate 5 or the array substrate 10.
In the LCD, a metal is used as a material for forming the metal wirings such as the gate lines or the data lines serving to intermediate signals, and in this case, as the metal has a low resistivity and high corrosion resistance, the reliability and price competitiveness of the product can be increased. As such metal wiring material, aluminum (Al) or an aluminum alloy is typically used.
However, as the LCD is enlarged in size and its resolution increased to resolutions such as SVGA, XGA, SXGA, VXGA or the like, a scanning time is shortened and a signal processing speed is increased. Thus, in order to cope with such trend, it is required to form metal wirings with a metal material of low resistivity.
Recently, copper is actively proposed as a substitute of the existing metal wiring material because it has better resistivity and electromigration characteristics.
However, copper has a weak bonding force with glass substrates and readily spreads to an insulation layer or to a semiconductor layer even at a relatively low temperature (−200° C.), so it is not proper to applied copper as a single metal wiring material.
In an effort to solve such problem, a copper wiring structure, in which a barrier metal layer is additionally disposed of between the glass substrate and a gate wiring and between the semiconductor layer and a data wiring to thereby improve adhesion (bonding) characteristics and prevent spreading of the copper to the semiconductor layer, has been proposed.
With this method, however, if pure molybdenum is used as the barrier metal layer in fabricating a semiconductor and display element, a galvanic corrosion phenomenon occurs at an interface of Mo and Cu during a wet etching process as shown in FIG. 2. For reference, FIG. 2 shows, for example, a gate electrode 21 disposed on the array substrate 10. A dual-layer copper wiring structure includes a first gate electrode 21a made of copper and a second gate electrode 21b made of pure molybdenum. This structure has a problem in that a galvanic corrosion is generated from the interface of the first and second gate electrodes 21a and 21b, degrading the reliability of the element.
Thus, instead of the pure metal material, a metal alloy such as a molybdenum alloy is used.
However, compared with the pure metal material, the purity of the metal alloy is low because of a target fabrication method and thus the alloy contains much foreign materials. This causes a foreign material defect and an increase in fabrication cost for the target.