JPH0244317A - Liquid crystal display device with auxiliary capacity - Google Patents

Abstract

PURPOSE:To sufficiently compensate a leak current of a switching element or a liquid crystal cell and to improve the reliability of a picture quality by constituting an auxiliary capacity by laminating plural capacities and connecting them in parallel. CONSTITUTION:As for an auxiliary capacity 5, the source side is placed in a shape that two pieces of electrodes are arranged in parallel, and a common electrode of the other side is connected by an auxiliary conductor 7, and the potential is fixed. In the auxiliary capacity 5, an auxiliary capacity use transparent electrode 10, an auxiliary capacity use insulating film 13 and an auxiliary capacity use common electrode 14 are formed, and one capacity is formed thereby. Subsequently, a layer insulating film 15 is formed, and by opening a contact window, a picture element use transparent electrode 17 is formed, and by the same material, a signal electrode 1 (drain electrode), a source electrode 16 and the auxiliary capacity use auxiliary conductor 7 are formed. In such a process, a second capacity is formed, and connected in parallel to the capacity which is embedded thereunder. In such a way, a large auxiliary capacity can be formed without increasing the number of processes, and the reliability of a picture quality of a liquid crystal display device can be raised.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an auxiliary capacitor of a liquid crystal display device, and particularly to a liquid crystal display device having an auxiliary capacitor suitable for obtaining a large capacity.

[Conventional technology]

Liquid crystal displays are characterized by being thin and low in power consumption, and have recently been commercialized as small TVs.

When high definition is achieved, there is also a use for projecting and enlarging images using a projector. In this case, 1. Since strong light is used, the leakage current of the switching element increases due to the light and heat.

Heat also lowers the resistance of the liquid crystal. For these reasons, an auxiliary capacitor for holding the applied voltage becomes essential.

Although the idea of forming an auxiliary capacity is old, a specific example is described in Japanese Patent Laid-Open No. 13228-1983.

A conventional example will be explained with reference to FIGS. 4 and 5.

In FIG. 4, switching elements 3 are arranged at each alternating point of the signal line 1 and the scanning line 2, and a liquid crystal cell 4 and an auxiliary capacitor 5 are connected in parallel on the source side. The liquid crystal cell 4 is composed of a common electrode 6 on a counter substrate. The other common electrode of the auxiliary capacitor 5 is connected by an auxiliary conductor 7, and the potential is fixed.

FIG. 5 shows a cross-sectional view of the switching element 3 and auxiliary capacitor 5. At the same time as the polycrystalline silicon gate 19, a auxiliary capacitor transparent electrode 20 is formed, and this is oxidized to form a gate insulating film 21 and an interlayer insulator. A film 22 is formed. Polycrystalline silicon is formed again on this, and the signal electrode 1 (drain), source electrode 23, and pixel transparent electrode 24 are formed. In this way, the auxiliary capacitor 5 is formed. In this example, a pixel transparent electrode 241, an interlayer insulating film 22. A set of capacitors is formed by the transparent electrode 20 for auxiliary capacitance.

[Problem to be solved by the invention]

In the above conventional example, the auxiliary capacitor is constituted by only a single capacitor, and a particularly large auxiliary capacitor cannot be realized when the capacitor is large.

An object of the present invention is to provide a means for forming a large storage capacity.

[Means to solve the problem]

The above object is achieved by stacking a plurality of capacitors and connecting them in parallel.

[Effect]

A large storage capacity is formed by the present invention.

Connected in parallel to the liquid crystal cell. Therefore, the leakage current of the switching element or the liquid crystal cell can be sufficiently compensated for, and the reliability of one image quality can be improved.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a partial configuration of an activate matrix according to the present invention, and shows signal lines 1. A switching element 3 is provided at the intersection of the scanning lines 2, and a liquid crystal cell 4 and an auxiliary capacitor 5 are connected in parallel on the source side. The liquid crystal cell 4 is composed of a common electrode 6 on a counter substrate. The auxiliary capacitor 5 has two electrodes arranged in parallel on the source side, and the other common electrode is connected by an auxiliary conductor 7, so that the potential is fixed.

FIG. 2 shows a cross-sectional view of the switching element 3 and auxiliary capacitor 5. Polycrystalline silicon 9 is formed on a glass substrate 8. As shown in FIG. Thereafter, the primary gate insulating film 11 is doped with phosphorus in the portion where the auxiliary capacitance 5 is to be formed. A gate electrode 12 is formed. In this process, the auxiliary capacitor 5 includes a auxiliary capacitor transparent electrode 10, an auxiliary capacitor insulating film 13. A common electrode 14 for auxiliary capacitance is formed, and one capacitance is formed here.

Next, an interlayer insulating film 15 is formed, a contact window is opened, and
A pixel transparent electrode 17 is formed. Signal electrode 1 made of the same material
(drain electrode), source electrode 16, and auxiliary conductor 7 for auxiliary capacitance are formed. In this process, a second capacitor is formed and connected in parallel with the underlying capacitor. What is particularly required in this process is the transparent electrode 1 for storage capacitance.
The only process required is zero doping, and the rest can be constructed using the same process as the switching element.

FIG. 3 shows an example of application of the present invention. The switching element 3 has a positive staggered structure. First, doped polycrystalline silicon or ITO is formed on the glass substrate 8, and the signal electrode 1 (
a drain), a drain electrode 16, and a transparent electrode 10 for pixels are formed. Second, the thin film semiconductor layer 18 which is an active layer.
．． A gate insulating film 11 and a gate 12 are formed. Thereafter, the auxiliary capacitor 5 can be formed in the same manner as shown in FIG.

In the above embodiments, switching elements using polycrystalline silicon have been described, but the present invention can also be applied to switching elements using single crystal or amorphous films. In addition, transparent electrode materials include semiconductor layers constituting switching elements, IT
O, thin film metal, conductive oxide, etc. can be arbitrarily selected.

[Effects of the Invention] According to the present invention described above, a large auxiliary capacitor can be formed without increasing the number of steps, and the reliability of the image quality of a liquid crystal display device can be improved.

[Brief explanation of the drawing]

FIG. 1 is a partial configuration diagram of an active matrix for explaining the present invention, FIGS. 2 and 3 are cross-sectional views of a switching element and an auxiliary capacitor section for explaining the present invention, and FIGS. 4 and 5 are FIG. 2 is a partial configuration diagram of an active matrix and a diagram showing a switching element and an auxiliary capacitance section, respectively, for explaining a conventional example. 3... Switching element, 5... Auxiliary capacitor, 10.
... Transparent electrode for auxiliary capacitance, 13... Insulating film for auxiliary capacitance, 14... Common electrode for auxiliary capacitance, 15... Interlayer insulating film, 17... Transparent electrode for pixel. Funeral map

Claims (1)

[Scope of Claims] 1. A liquid crystal display device having an auxiliary capacitor, characterized in that the auxiliary capacitor is made up of a plurality of stacked capacitors connected in parallel. 2. A liquid crystal display device having an auxiliary capacitor according to item 1, characterized in that a capacitor made of a gate insulating film of a switching element that drives the liquid crystal display device and a capacitor made of a protective film of the switching element are connected in parallel. 3. A liquid crystal display device having an auxiliary capacitor according to item 1 or 2, wherein the gate electrode of the switching element is a common electrode of the auxiliary capacitor. 4. A liquid crystal display device having an auxiliary capacitor according to item 1, 2 or 3, characterized in that the same material as the active layer or gate of the switching element is used as the transparent electrode of the auxiliary capacitor.