Liquid crystal display device and fabrication method thereof

Abstract

The present invention provides a novel photolithography processes using photoresist pattern having at least two areas which has different thickness from each other for a fabrication method for a liquid crystal display device having reversed staggered and channel-etched type thin film transistors, reduce a number of photolithography processes required for whole of the fabrication process of the liquid crystal display device, and improve brightness of the liquid crystal display device.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display device and, for example, to one of a pair of substrates between which a liquid crystal layer is interposed, i.e., a so-called TFT substrate on which thin film transistors (hereinafter referred to as TFTs) are formed, as well as to a fabrication method for such a TFT substrate. [0003] 2. Description of the Related Art [0004] In the case of a related art liquid crystal display device, as described in Japanese Patent Laid-Open No. 202153 / 1994, its TFT substrate is fabricated by forming openings in the gate insulating film and the protective film laminated on the TFT substrate, through one photo-process (a process which includes the photolithography of forming a photomask on a work and partly removing the photomask according to a processing pattern), and carrying out patterning through a total of five photo-processes. In the TFT substrate obtained by this fabrica...

AI Technical Summary

Benefits of technology

[0010] The TFT liquid crystal display device described in Japanese Patent Laid-Open No. 90404 / 1997 has the protective film made of the organic material, and the drain wiring lines are used as light-shielding electrodes, and pixel electrodes are disposed to overlap the drain wiring lines above the organic protective film of low dielectric constant, thereby improving the aperture ratio. However, patterning processing needs at least five photo-processes.

[0071] Although the metal films of the drain wiring lines, the source electrodes and the drain electrodes are removed through two separate etching processes, it is possible to improve the processing accuracy of the drain wiring lines by performing dry etching as the first process and wet etching as the second process.

Problems solved by technology

Moreover, in Japanese Patent Laid-Open No. 232409 / 1998, although the TFT glass substrate of a lateral electric field type, i.e., the IPS display mode, of liquid crystal display device is formed through four photo-processes, the terminals of its gate and drain wiring lines are not coated with a transparent conductive film such as Indium-Tin-Oxide (hereinafter, ITO), so that the terminals suffer the problem of electrical corrosion due to humidity.

In addition, since comb-teeth like pixel (source) electrodes are disposed close to the gate wiring lines, there is the problem that parasitic capacitance becomes large.

During a charge-holding period in such driving, electrons are emitted from the i-type semiconductor and the capacitance value fluctuates and lowers to a capacitance value which is a value for the thickness of the i-type semiconductor, resulting in the problem that image retention occurs in the liquid crystal.

Images