JPS6159474A - Thin film transistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 transistors are formed within a display panel among flat display devices using liquid crystals, electroluminescence, etc. The present invention relates to a thin film transistor suitable for devices.

[Background of the invention]

An active matrix display device has a switch element formed in a display portion, and has the advantage of being able to display high definition and high quality images. In particular, active matrix displays configured with TPT using polycrystalline silicon formed on a transparent substrate or recrystallized silicon thin film can be made smaller because the drain conductance gm of the TPT element is large. In fact, it is possible to miniaturize each display pixel while keeping the display aperture ratio (the ratio of the effective light display area) to a large value, and it is also possible to form a drive circuit at the periphery of the display. Therefore, the TPT element is particularly suitable for high-definition displays. Note that matters related to active matrix displays using polycrystalline silicon TPT and recrystallized silicon TPT are described in JP-A-58-90690 or JP-A-59-31055. has been done.

In these publications, the TPT shape is devised to improve the aperture ratio, but for example, the mobility of the semiconductor film is large and the TPT element with a long channel structure, such as polycrystalline silicon TPT or recrystallized silicon TPT, is There is still room for improvement in what can be formed.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a self-aligned thin film transistor that has an improved aperture ratio in a display area in an active matrix display panel.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG. That is, the signal electrode wiring 2 for applying a signal voltage to the pixels in the column direction and the display electrode 4 for applying voltage to the liquid crystal are used as source or drain electrodes, and a scanning pulse is generated to scan the pixels in the row direction of the display area. This transistor has a structure in which the scanning electrode wiring 3 used to apply the voltage is used as a gate electrode. The semiconductor thin film 1 is formed under the signal wiring 2 and the scanning wiring 3, and has a structure in which a portion connected to the display electrode 4 comes out from below the signal wiring 2 and the scanning wiring 3. Further, the channel portion of this transistor is formed under the scanning wiring 3, so that the transistor has a channel length (2) longer than the channel width (W), making it a long channel type transistor. By adopting such a structure, most of the thin film transistors can be formed in the wiring portion, and a display with good display characteristics can be constructed in which the display electrode 4 occupies a large proportion of the area of the display portion.

FIG. 2 shows the manufacturing process of the thin film transistor of the present invention.

This is a cross section taken along the line n-tt in FIG.

(a) A semiconductor thin film 7 of polycrystalline silicon, amorphous silicon, crystallized silicon, etc. is formed on an insulating substrate 6 such as glass or quartz, and necessary portions are left in the form of islands. . (b) Gate insulating film 8 is formed by a method such as thermal oxidation, CVD, 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, various metal silicides, or the like. (d) Part of the gate insulating film 8 is removed, and the soda and drain parts are ion-implanted, thermally diffused,
It is formed by a method such as deposition. (e) CVD the insulating film 11 that serves as the interlayer insulating film of the two-layer wiring between the gate electrode and the signal wiring and the passivation of the thin film transistor.
A contact hole is formed in the source and drain portions by the D method, sputtering method, spin-on method, or the like.

(f) Signal wiring 13 and pixel electrode 12, which also serve as source and drain electrodes, are formed. Both of these electrodes are IT
Possible structures include a structure in which a transparent electrode such as O is used, and a structure in which the signal wiring 13 is made of a metal such as aluminum.

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 and channel width W of the thin film transistor will not change, making it possible to obtain an element with uniform characteristics. Can be done.

Although the structure of the self-aligned gate electrode has been described in the embodiment, the source and drain contact portions are 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 of the thin film transistor is shortened in the structure shown in FIG. 1. As can be seen by comparing FIG. 1 and FIG. 3, in the structure of the present invention, the aperture ratio is constant regardless of the length of the channel, especially when the channel length is long. By simply changing the pattern and the pattern of the contact holes 5, the number of other patterns that are the same can be reduced.

〔Effect of the invention〕

According to the present invention, since the thin film transistor is formed in the wiring electrode part and the proportion of the display electrode area can be increased, an active matrix display with good display characteristics can be obtained, and the gate electrode of the thin film transistor is self-aligned. Since it can be formed, an element with uniform characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 is a plan view of the structure of the present invention, and FIG. 2 is a sectional view taken along the line ■--■ in FIG. 1, showing the manufacturing process. DESCRIPTION OF SYMBOLS 1...Semiconductor thin film, 2...Signal wiring and drain electrode, 3...Scanning wiring and gate electrode, 4...Display electrode and source electrode, 5...Contact hole.

Claims (2)

[Claims] 1. An active matrix display in which multiple signal electrodes, multiple scanning electrodes that intersect with the signal electrodes, and thin film transistors connected to each intersection are formed on an insulating substrate, and are laminated with a material that has an electro-optical effect such as liquid crystal. The signal electrode and the scanning electrode are formed in a straight line, and the thin film transistor is formed along the signal electrode and the scanning electrode except for a connecting portion between the thin film transistor and the display electrode. Thin film transistor. 2. The thin film transistor according to claim 1, wherein a source electrode and a drain electrode are located on opposite sides of the scanning electrode.