JPH0564357B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a so-called active matrix display in which active elements such as thin film transistors are formed within a display panel, among flat display devices using liquid crystals, electroluminescence, etc. .

[Background of the invention]

An active matrix display device, for example, an active matrix display device using a display material with an electro-optic effect such as a liquid crystal, consists of a transparent substrate on which switch elements and matrix-shaped wiring electrodes are formed, and a substrate on which a common electrode is also formed. It has a display section with a display material sandwiched in between, and has the advantage of being able to display high-definition, high-quality images. In particular, active matrix displays constructed from thin film transistors (hereinafter abbreviated as TFT) using polycrystalline silicon or recrystallized silicon thin films formed on transparent substrates have a large drain conductance gm. It is possible to miniaturize each display pixel while keeping the aperture ratio (the ratio of the effective display area) of the display pixel to a large value.
Furthermore, since there is a high possibility that a driving circuit can be formed in the periphery of the display, the TFT element is particularly suitable for high-definition displays. In addition, polycrystalline silicon
Items related to active matrix displays using TFTs or recrystallized silicon TFTs are described in Japanese Patent Application Laid-open No. 58-90690 or Japanese Patent Application Laid-Open No. 59-31055.

These publications improve the aperture ratio by devising the TFT shape, but for example, polycrystalline silicon
For TFTs and recrystallized silicon TFTs, which have high carrier mobility in semiconductor films and can form long-channel structured TFT devices,
There is room for improvement.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an active matrix display in which self-aligned thin film transistors are formed in a display panel to improve the aperture ratio of the display portion.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG. That is,
On an insulating substrate such as glass or quartz, signal electrode wiring 2 having a plurality of constant widths is used to apply a signal voltage to pixels in the column direction, and a scanning pulse is applied to scan the pixels in the row direction of the display section. A plurality of scanning electrode wirings 3 having a constant width are formed to intersect with each other, and near the crossing point, the signal electrode wiring 2 and the display electrode 4 for applying voltage to the liquid crystal are used as source or drain electrodes. , a transistor having a structure in which the scanning electrode wiring 3 is used as a gate electrode is formed. A semiconductor thin film 1 is formed under the signal wiring 2 and the scanning wiring 3, and the portion connected to the display electrode 4 is formed under the signal wiring 2 and the scanning wiring 3.
It has a structure in which it comes out from below the and scanning wiring 3. Also, the channel part of this transistor is connected to the scanning wiring 3.
The channel direction is the same as the direction of the scanning wiring. Therefore, the channel length I of the transistor is longer than the channel width W, and the transistor becomes a long channel type transistor. By adopting such a structure, most of the thin film transistors can be formed in the wiring portion, the proportion of the area occupied by the display electrodes 4 in the display portion becomes large, and a display with good display characteristics can be constructed. In addition, by making the planar shape of the signal electrode wiring and scanning electrode wiring uniform without unevenness and making the width constant, the manufacturing process can be simplified by introducing printing methods, etc., and it has the effect of realizing a low-cost active matrix display. be.

FIG. 2 shows the manufacturing process of the thin film transistor of the present invention. This is a cross section taken along the - arrow in FIG. (a) A semiconductor thin film 7 such as polycrystalline silicon, amorphous silicon, or crystallized silicon is placed on an insulating substrate 6 such as glass or quartz.
form and leave the necessary parts as islands. (b) Gate insulating film 8 is formed by a method such as thermal oxidation, CVD method, sputtering, or plasma oxidation. Note that the gate insulating film 8 may be formed continuously with the semiconductor thin film 7, and then the semiconductor thin film 7 and the gate insulating film 8 may be formed together into an island shape. (c) Gate electrode 9, which also serves as a scanning electrode, is formed of polycrystalline silicon or various metal silicides. (d) Part of the gate insulating film 8 is removed, and source and drain parts are formed by ion implantation, thermal diffusion, deposition, or other methods. (e) An insulating film 11 that serves both as an interlayer insulating film for the two-layer wiring between the gate electrode and the signal wiring and as passivation for the thin film transistor is formed by a CVD method, sputtering method, spin-on method, etc., and contact holes are formed in the source and drain regions. Open. (f) Signal wiring 13 and pixel electrode 12, which also serve as source and drain electrodes, are formed. Both of these electrodes have a structure made of transparent electrodes such as ITO,
A structure in which the signal wiring 13 is made of metal such as aluminum is conceivable.

In this example, the gate has a self-aligned structure, and even if the position of the scanning wiring is slightly shifted, the channel length L and channel width W of the thin film transistor do not change, so it is possible to obtain an element with uniform characteristics. can.

In addition, although the structure of the self-aligned gate electrode was described in the example, the source and drain contact portions were formed using known techniques such as thermal diffusion of impurities and ion implantation before forming the gate electrode. After that, the gate insulating film and the gate electrode may be formed in this order.

In addition, in the figure, 10 is an impurity diffusion part, and 12 is a display electrode and a source electrode.

FIG. 3 shows a structure in which the channel length L of the thin film transistor is shortened in the structure shown in FIG. 1. 1st
As can be seen by comparing the figure and FIG. 3, in the structure of the present invention, the aperture ratio is constant regardless of the channel length L, and is particularly effective when the channel length L is long. Furthermore, even if the channel length L is changed by changing the design of the transistor, the semiconductor island 1
By simply changing the pattern and the pattern of the contact 5, the same pattern can be used for the other patterns, making it easy to change the design and reducing the number of mask layers.

〔Effect of the invention〕

According to the present invention, since the thin film transistor is formed in the scanning wiring section and the signal wiring section, the ratio of the area occupied by the display electrode can be increased, and since the gate electrode can be formed in a self-aligned manner, characteristics can be made uniform between pixels. Since a thin film transistor can be obtained, an active matrix display with good display characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the structure of the present invention, FIG. 2 is a sectional view taken along the - arrow in FIG. 1 showing the manufacturing process, and FIGS. 3 and 4 are structural views of a thin film transistor. 1...Semiconductor thin film, 2...Signal wiring/drain electrode, 3...Scanning wiring/gate electrode, 4...Display electrode/source electrode, 5...Contact hole.

Claims (1)

[Scope of Claims] 1. A plurality of signal wirings having a constant width on the surface of an insulating substrate, a plurality of scanning wirings having a constant width intersecting the signal wirings, and an intersection between the signal wiring and the scanning wiring. The first substrate includes a thin film transistor nearby, a display electrode formed in a region surrounded by the wiring, a second substrate formed with a common electrode, and a substance having an electro-optical effect. and a second substrate, the thin film transistor is of a long channel type, and the gate electrode is connected to a part of the scanning wiring. An active matrix display characterized in that drain electrodes are each formed from a part of the signal wiring, and source electrodes are provided in the display electrode section. 2. The active matrix display according to claim 1, wherein the substance having an electro-optical effect is a liquid crystal.