JP2639980B2 - Liquid crystal display - Google Patents

Description

The present invention relates to an active matrix type liquid crystal display device.

(B) Conventional technology In recent years, amorphous semiconductor materials, particularly amorphous materials such as amorphous silicon (hereinafter abbreviated as a-Si) films, have been characterized by their physical properties and the advantages of the plasma CVD method. We are exploring applications in fields that were not feasible with conventional single crystal silicon (c-Si). Especially a-Si
Since the film can be formed by a formation method called a plasma reaction, it is applied to a switching element for a solar cell or a large-area liquid crystal TV.

The application of a-Si thin film transistor (hereinafter referred to as TFT) switching elements to active matrix liquid crystal televisions takes advantage of the ease of increasing the plasma reaction area.
A silicon oxide (hereinafter SiNx) film or a silicon oxide (hereinafter Si) that will be a gate insulating film or passivation film that constitutes a TFT
It also has the advantage that an O ₂ ) film can be formed simply by changing the reaction gas.

However, in a liquid crystal TV using a TFT, an image is displayed by using a charge storage effect in which the liquid crystal is regarded as a capacitor. Therefore, the charge of the liquid crystal, which is updated for each frame of the video signal, must be held during that frame. However, if the holding voltage of the liquid crystal decreases during this period due to leakage, the display quality deteriorates. Invite. For this reason, conventionally, a structure has been proposed in which an auxiliary capacitor is provided in parallel with the liquid crystal capacitor to prevent display degradation [
No. 57-3088].

Generally, there are the following two types of structures for providing such auxiliary capacitors. One is to provide a storage capacitor transparent electrode (2) between the display transparent electrode (7) coupled to the TFT (0) and the insulating substrate as shown in FIG. The transparent electrode for storage (7) and the transparent electrode for auxiliary capacitance (2) are opposed to each other. In this case, the transparent electrode for auxiliary capacitance (2) was generally grounded, for example. Another structure is to extend an adjacent gate metal film (3) between a display transparent electrode (7) and a glass substrate as shown in FIG.
This is used as an auxiliary capacitance electrode, and the extended gate metal film (3) and the display transparent electrode (7) are opposed to each other via an insulating film.

(C) Problems to be Solved by the Invention A liquid crystal display device using the gate metal film (3) as an auxiliary capacitance electrode as shown in FIG. 6 described above uses another pair of auxiliary capacitance transparent electrodes (2) as shown in FIG. Since the device structure is simpler than that of the device having the method of (1), it is particularly effective for manufacturing a large-area display panel. However, in the case of the device of FIG. 6, since the capacitance component is constituted by the gate metal film (3), it is necessary to increase the area of the opaque gate metal film (3) as the capacitance value of the auxiliary capacitance increases. Becomes a general liquid crystal
In a translucent liquid crystal display device such as a TV, there is a drawback that the aperture ratio of each pixel is reduced and the display brightness is reduced.

The present invention has been made to solve such a drawback.

(D) Means for Solving the Problems In the liquid crystal display device of the present invention, a thin film transistor including a gate metal film, a gate insulating film, an amorphous semiconductor, a drain and a source metal film is arranged in a matrix on an insulating substrate. Then, in a liquid crystal display device in which a display electrode is coupled to each transistor, a transparent electrode for an auxiliary capacitor made of a transparent conductive film electrically connected to the gate metal film enhances transparency under the display electrode. It is located under the gate metal film from which a necessary portion has been removed.

(E) Function According to the present invention, the transparent conductive film electrically connected to the gate metal film is used as the auxiliary capacitance electrode, so that the pattern of the auxiliary capacitance electrode is overlapped with the display transparent electrode serving as the counter electrode. Therefore, it is possible to ground an effective auxiliary capacitance without lowering the aperture ratio at all, and to provide a transparent conductive film that is a conductive film for the auxiliary capacitance on the entire surface under the gate metal film. The occurrence of contact failure between the two can be eliminated.

(F) Example First, an example of the present invention will be described, and the manufacturing process will be described in C-.
2 (a) to 2 (f) are shown along the line C '.

In the liquid crystal display device shown in the figure, first, a transparent conductive film for an auxiliary capacitor (2) and a metal film for a gate (3) are provided on an insulating substrate (1) and then formed. The first resist (9) is patterned with a pattern in which the pattern of (1) and the pattern of the transparent conductive film for auxiliary capacitance (2) are overlapped. Metal film for gate (3) and transparent conductive film for auxiliary capacitance (2)
[FIG. 2 (a)].

Next, a second resist (10) is patterned as an auxiliary capacitance transparent conductive film (2) such that a portion requiring transparency is opened [FIG. 2 (b)].

Subsequently, after the unnecessary metal film (3) on the transparent conductive film (2) is removed with an etchant of the gate metal film (3),
By employing a plasma reaction method or the like, for example, a gate insulating film (4) of, for example, SiNx, a semiconductor thin film (5) of, for example, a-Si, and an impurity semiconductor film (6) of, for example, n ⁺ a-Si doped with impurities are formed. [FIG. 1 (c)].

Next, the semiconductor thin film (5) and the impurity semiconductor film (6) are etched into a desired pattern so as to be located on the gate metal film (3) [FIG. 1 (d)]. Thereafter, a transparent conductive film for display (7) is formed by ITO and patterned by a resist [FIG. 2 (e)].

Further, after forming a drain and source metal film (8) on the impurity semiconductor film (6) and patterning it (FIG. 2 (f)), a channel position between the drain and source metal film (8) is defined. The impurity semiconductor film (6) is etched and removed to complete (FIG. 2 (g)).

In such a manufacturing method, since the transparent conductive film used as the transparent conductive film (2) for the auxiliary capacitor is provided all under the metal film (3) for the gate, the occurrence of poor contact between the two is reduced. In other words, the yield can be improved.

The opening from the gate metal film (3) of the storage capacitor transparent conductive film (2), that is, the area as a light-transmitting storage capacitor, is determined by the first resist pattern (9) and the second resist pattern. That the auxiliary capacitance is determined by the material and thickness of the insulating film used,
Further, since the overlapping area of the transparent conductive film for auxiliary capacitance (2) and the transparent conductive film for display (7) in a later step is determined, the second resist pattern (10) is used for the transparent conductive film for display (7). It can be used as a lift-off resist in patterning. The process before the lift-off process in this case is shown in FIG.

(G) Effect of the Invention In the present invention, when the gate adjacent to the display transparent electrode is used as an auxiliary capacitor, the aperture ratio is reduced by using a transparent material for the auxiliary capacitor electrode that overlaps the display transparent electrode. In addition, it is possible to realize a liquid crystal display device free from defects, and to reduce the occurrence of contact failure between the gate metal film and the transparent conductive film for an auxiliary capacitor, thereby improving the yield.

[Brief description of the drawings]

FIG. 1 is a plan view of an embodiment of the liquid crystal display device of the present invention, FIGS. 2 (a) to 2 (g) are manufacturing process diagrams of the device of the present invention in FIG. 1, and FIGS. It is a top view of a conventional device. (0) ... thin film transistor, (1) ... insulating substrate,
(2): transparent conductive film for auxiliary capacitance; (3) metal film for gate; (4): insulating film for gate; (5): semiconductor thin film; (6): impurity semiconductor film; ... transparent conductive film for display, (8) ... metal film, (9) ... first resist,
(10)... Second resist, (11).

Claims (1)

(57) [Claims] 1. A liquid crystal in which thin film transistors comprising a gate metal film, a gate insulating film, an amorphous semiconductor, a drain and a source metal film are arranged in a matrix on an insulating substrate, and a display electrode is coupled to each transistor. In the display device, a transparent electrode for an auxiliary capacitor formed of a transparent conductive film electrically connected to the gate metal film is formed of the gate metal film in which a portion requiring transparency under the display electrode is removed. A liquid crystal display device characterized by being in a lower layer.