JPH0281028A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display device which obviates the decrease in the opening ratios of respective picture elements by providing electrodes for auxiliary capacities consisting of transparent conductive films electrically connected to gate metallic films of thin-film transistors (TFTR) to prevent the deterioration of display. CONSTITUTION:The electrodes 2 for auxiliary capacities consisting of the transparent conductive films electrically connected to the gate metallic films 3 are provided on the insulating substrate of the constitution disposed in matrix shape with the TFTRs each consisting of the gate metallic film, insulating film for gate, amorphous semiconductor, and metallic films for drain nd source on the insulating substrate. Since the transparent conductive films 2 are used as the electrodes for auxiliary capacities, the opening rate of the respective picture elements is entirely prevented from lowering even if the electrodes for auxiliary capacities are lowering even if the electrodes for auxiliary capacities are so patterned as to overlap on the transparent electrodes 7 for display which are counter electrodes. The degradation of the display lightness is thus prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to an active matrix type liquid crystal display device.

(b) Conventional technology In recent years, amorphous semiconductor materials, especially amorphous dinocon (
Amorphous materials such as a-5i (hereinafter abbreviated as a-5i) films, which are impossible to achieve with conventional single-crystal silicon (c-5i), take advantage of their physical properties and the advantages of the plasma CVD method. We are developing applications for existing fields. Especially a
Since the -5i film can be formed by a formation method called plasma reaction, it is applied to switching elements for solar cells and large-area liquid crystal TVs.

A-5i to active matrix type) alpha product TV
The application of thin film transistor (hereinafter referred to as TPT) switching elements takes advantage of the ease of large-area plasma reaction, but at the same time, the same reaction method also produces nitride that becomes the gate insulating film and passivation film that make up the TPT. It also takes advantage of the fact that a Zinocon (hereinafter referred to as 5INx) film and a silicon oxide (hereinafter referred to as "Sin") film can be formed simply by changing the reaction gas.

However, in a liquid crystal TV using TPT, images are displayed using the charge accumulation effect of the liquid crystal, which is regarded as a capacitor. Therefore, the charged charge of the liquid crystal, which is updated every frame of the video signal, must be maintained during that frame, but if the holding voltage of the liquid crystal decreases due to leakage during this period, the display quality will deteriorate. invite.

For this reason, a structure has heretofore been proposed in which an auxiliary capacitor is provided in parallel with the liquid crystal capacitor to prevent display deterioration (Japanese Patent Laid-Open No. 57-3088).

There are generally two types of structures for attaching such auxiliary capacity: One is to provide a transparent electrode for auxiliary capacitance (2) between an insulating substrate and a transparent 'it electrode for display (7) coupled to TPT (0), as shown in Fig. 5, through an insulating film. The transparent electrode for display (7) and the transparent electrode for auxiliary capacitance (2) are made to face each other. In this case, the transparent electrode for auxiliary capacitance (2
) was generally grounded. Another structure, as shown in FIG. 6, extends an adjacent gate metal film (3) between the display transparent electrode (7) and the glass substrate, and uses this as an auxiliary capacitor@pole. This extended gate metal film (3) and a display transparent electrode (7) are opposed to each other with an insulating film interposed therebetween.

(c) Problems to be Solved by the Invention The liquid crystal display device using the gate metal film (3) as the auxiliary capacitance electrode as shown in FIG. Since the device structure is simpler than the one with 2), it is particularly effective for manufacturing large-area display panels. However, in the case of the device shown in FIG.
Since each device component is composed of a gate metal film (3), as the capacitance value of the auxiliary capacitance increases, it becomes necessary to increase the area of the opaque gate metal film (3), which makes it difficult to use the opaque gate metal film (3) like a general LCD TV. However, the translucent liquid crystal display device has a disadvantage in that the aperture ratio of each pixel decreases, resulting in a decrease in display brightness.

The present invention has been made to eliminate these drawbacks.

(d) Means for Solving the Problems In the liquid crystal display device of the present invention, thin film transistors each consisting of a gate metal film, a gate insulating film, an amorphous semiconductor, and a drain and source metal film are arranged in a matrix on an insulating substrate. However, a display electrode is coupled to each transistor, and an auxiliary capacitance electrode made of a transparent conductive film is electrically connected to the gate metal film.

(E) Function According to the present invention, by using the transparent conductive film which is electrically connected to the gate metal film and Tf as the pole for the auxiliary capacitance,
Even if the auxiliary capacitor electrode is patterned so as to overlap the display transparent electrode serving as the counter electrode, it is possible to provide an effective auxiliary capacitor without reducing the aperture ratio at all.

(F) Embodiment FIG. 1 shows a partial plan view of an embodiment of the liquid crystal display device of the present invention, and the manufacturing process in the AA' line cross section and the BB' line cross section of the same figure is shown in FIG. Shown in Figure 2.

The structure of the liquid crystal display device of the present invention shown in FIG. 1 will be described in detail below based on the manufacturing steps shown in FIGS. 2(a) to 2(g).

On an insulating edge substrate (1) made of a glass plate, a transparent conductive film (2) of ITO for auxiliary capacitance is formed and patterned [Second
Figure (a)].

Next, a gate metal film (3) is formed using a two-layer film of Au/Cr so as to be in electrical contact with the transparent conductive film (2), and patterned into a shape that partially overlaps the transparent conductive film (2). [Figure 2(b)].

By adopting a plasma reaction method, for example, Si
A gate insulating film (4) is formed using Nx, a semiconductor thin film (5) is formed using, for example, a-5, and an impurity semiconductor film (6) is formed using, for example, n''a-5i doped with impurities [Figure 2 (C)]. .

Next, the semiconductor thin film (5) and the gate insulating film (4)
27 in a desired pattern so as to be located on the gate metal film (3) [FIG. 2(d)].

Thereafter, a transparent conductive film (7) for display is formed using ITO and patterned [see FIG. 2(e)].

Furthermore, a drain and source metal film (8) was formed on the impurity semiconductor film (6) and patterned [Fig. 2(f)]
] After that, the impurity semiconductor film (6) at the channel position between the drain and source metal films (8) is removed by etching to complete the process [FIG. 2(g)].

In the above embodiment, the transparent conductive film for auxiliary capacitance (2) was formed before the gate metal film (3), but there is no problem even if the order of forming these films is reversed.

FIG. 3 shows another embodiment of the present invention, and its manufacturing process is shown in c.
It is shown in (a) to (f) of Figure 4 along the line -c'.

In the liquid crystal display device shown in the figure, first, a transparent conductive film for auxiliary capacitance (2) and a metal film for gate (3) are successively formed on an insulating substrate (1), and then a metal film for gate (3) is applied to the gate. The lugist (9) is patterned using a pattern in which the pattern of the transparent conductive film for auxiliary capacitance (2) is overlapped with the pattern of [Figure 4 (a)]
].

Next, the second resist (10) is patterned to form an auxiliary capacitance transparent conductive film (2) so that the portion requiring transparency is opened (FIG. 4(b)).

Next, after removing the unnecessary metal film (3) on the transparent conductive film (2) using an etchant for the gate metal film (3), the gate insulating film (4) is removed as in the case of FIG. , a semiconductor thin film (5), and an impurity semiconductor film (6) are sequentially formed [Fourth
Figure (C)].

The following steps may be the same as those in Figure 2, and Figure 4(d)
4(e) shows the patterning of the transparent conductive film for display (7) using the resist (11), and FIG. ) shows a state in which the removal of the resist l-(11) and the impurity semiconductor film (6) of the channel L have been completed.

In such a manufacturing method, a transparent conductive film (2) for auxiliary capacitance is formed entirely under the metal film (3) for gate (different from the case shown in Fig. 2).
), the occurrence of poor contact between the two is reduced, and the yield can be improved.

In addition, the metal film for gate of the transparent conductive film for auxiliary capacitance (2) (
3) The opening from 3), that is, the area of the auxiliary capacitor with light-transmitting properties, is determined by the first resist pattern (9) and the second resist pattern (11), and the auxiliary capacitor is not used. Determined by the material of the insulating film and its thickness,
Furthermore, since it is determined by the overlapping area of the transparent conductive film for auxiliary capacitance (2) and the transparent conductive film for display (7) in the subsequent process, the second resist pattern (10) is applied to the transparent conductive film for display (7). It can be used as a lift-off resist in patterning. Lift in this case
The process before the off-processing is shown in FIG. 4(g).

(g) Effects of the Invention The present invention improves the aperture ratio by using a transparent material for the auxiliary capacitance electrode in the portion that overlaps the display transparent electrode when the gate adjacent to the display transparent electrode is used as an auxiliary capacitor. It becomes possible to realize a liquid crystal display device without degradation.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an embodiment of the liquid crystal display device of the present invention, FIGS. 2(a) to (g) are manufacturing process diagrams of the device of the present invention shown in FIG. 1, and FIG. FIG. 4 is a plan view of the embodiment of FIG. 3, FIG. 4 is a manufacturing process diagram of the device of the present invention shown in FIG. 3, and FIGS. 5 and 6 are plan views of the conventional device, respectively. (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, (7)・
・・Transparent conductive film for display, (8) ・・Metal film, (9)・
...First resist, (10)...Second resist, (11
)...Resist.

Claims (1)

[Claims] (1) Gate metal film, gate insulating film on an insulating substrate,
In a liquid crystal display device in which thin film transistors each consisting of an amorphous semiconductor and a metal film for drain and source are arranged in a matrix and a display electrode is connected to each transistor, a transparent conductor electrically connected to the gate metal film is used. A liquid crystal display device characterized by being equipped with a transparent electrode for auxiliary capacitance made of a film.