JPS61188967A - Thin film transistor - Google Patents

Abstract

PURPOSE:To prevent a source electrode from improperly disconnecting and to shorten the photoetching step by superposing a transparent conductive film as a picture element electrode on the surface of the source and drain electrodes. CONSTITUTION:A thin metal film of Ta or Al is formed on the entire surface of an insulating substrate 2, patterned by photoetching to form a gate electrode 3. An Si3N4 film 4a to become a gate insulating film 4 is formed on the entire surface of the substrate 2 which contains the electrode 3, an amorphous Si film 5a to become a semiconductor film 5 and further thin metal film 7a to become N<+> type amorphous Si film 6, a source electrode 7 and a drain electrode 8 are respectively formed. Then, a transparent conductive film (In2O3) 10 to become a picture element electrode 9 is formed on the entire surface of the substrate 2 which contains source and drain electrode pattern 13. Then, a photoresist is coated on the entire surface of the film 10, and a photoresist 11 is patterned in the pattern of the electrodes 7, 8 and 9 with one photomask.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thin film transistor applied to a liquid crystal display device.

(Prior art) An example of the conventional structure of a thin film transistor is shown in FIGS. 6(a) and 6(b).
).

In the drawing, a is an insulating substrate, b is a gate electrode, C is a gate insulating film, d is a semiconductor film, e is an n-amorphous Si film, f is a source electrode, 1g is a drain electrode, h is a pixel electrode, i is the channel opening. The picture element electrode layer is formed to cover a part of the upper surface of the drain electrode g.

In the structure of this thin film transistor, the semiconductor film d has a source electrode f and a drain electrode g except for the channel opening i.
Since it has the same pattern as the previous one, it is possible to keep the storage capacity to a minimum.

There is an advantage that the contact portions between the semiconductor film d and the source electrode f and drain electrode g can be protected from contamination generated during the manufacturing process.

However, in order to improve the resolution of one display panel, it is necessary to increase the number of picture element electrodes, which inevitably requires a reduction in the source electrode width l.

In this case, in order to suppress the increase in the resistance of the source pass line and improve the manufacturing yield of two display panels, it is necessary to take measures against disconnection of the source electrode f and to simplify the manufacturing process.

(Purpose of the invention) The zero discharge prevents disconnection of the source electrode, and
The purpose is to shorten the photo-etching process and provide a thin film transistor with a new structure that is stable and has excellent characteristics.

(Structure of the invention) The thin film transistor of the present invention is provided on an insulating substrate.

In a structure in which a gate electrode, a gate insulating film, a semiconductor film, and a metal thin film are sequentially laminated, and the metal thin films are formed on a source electrode and a drain electrode, the surface of the source electrode and drain electrode also serves as a picture element electrode. It is formed by overlapping transparent conductive films.

(Function) The source electrode and drain electrode have a two-layer structure of a metal thin film and a transparent conductive film, and the source electrode.

The drain electrode and the pixel electrode are patterned simultaneously by the same photoetching process.

(Example) FIG. 1 fa) (b) shows the structure of a thin film transistor according to the present invention.

In this thin film transistor 1, a transparent conductive film 10 which also serves as a picture element electrode 9 is formed on the entire surface of a source electrode 7 and a drain electrode 8, and the other structure is the same as the conventional structure described above. Namely.

2 is an insulating substrate, 3 is a gate electrode, 4 is a gate insulating film,
5 is a semiconductor film (amorphous Si film), and 6 is an n9-amorphous Si film.

Next, the manufacturing process of the thin film transistor 1 described above will be explained with reference to FIGS. 2(a) and 5(b) to FIGS. 5(a) and 5(b).

■ Ta or A is deposited on the entire surface of the insulating substrate 2 made of a glass substrate or the like by sputtering or electron beam evaporation.
A metal thin film such as I is formed and patterned by photoetching to form the gate electrode 3 [Fig. 2(a) (b)
)reference〕.

(2) Next, on the entire surface of the insulating substrate 2 including the gate electrode 3, a Si3N4 film 4a, which will become the gate insulating film 4, is formed to a thickness of 1000 nm by plasma CVD. 5a by plasma CVD
Furthermore, metal thin films 7a, which will become the n''-amorphous Si film 6, the source electrode 7, and the drain electrode 8, are formed by plasma CVD or sputtering [Fig. 3(a) (b)].
)reference〕.

■ Next, the metal thin film 7a, the n''-amorphous Si film 6
．． The amorphous Si film 5a and the 5izN4 film 4a are etched continuously from the upper layer, and the metal thin film 7a is formed in the source/drain electrode pattern 13 where the channel opening 12 [see FIG. 1(b)] has not yet been formed. [See Figures 4(a) and (b)].

■ Next, a transparent conductive film (r
nzo*) 10 is formed by sputtering or electron beam evaporation [see FIG. 5 fa) (b)]. After that, photoresist is applied to the entire surface of the transparent conductive film 10 using a single photomask.

Source electrode7. Drain electrode8. Then, photoresist 11 is patterned in the pattern of picture element electrode 9, and then transparent conductive film 10. Source/drain electrode pattern 13.
The n''-amorphous Si film 6 is etched in order to form a thin film transistor 1 having the structure shown in FIG. 1 (al(b)).

(Effects of the Invention) As explained above, according to the thin film transistor of the present invention, the transparent conductive film formed on the entire surface of the source electrode and the drain electrode and the transparent conductive film that becomes the pixel electrode can be patterned at the same time. So.

The number of photomasks that conventionally required four can be reduced to three. Furthermore, since the source electrode has a two-layer structure of a metal thin film and a transparent conductive film, disconnections of the source electrode are reduced, and the yield of thin film transistors can be improved.

[Brief explanation of the drawing]

FIGS. 1(a) and (h) are a plan view and a vertical cross-sectional view of a thin film transistor of the present invention, and FIGS. 2(a) and (b) to FIG.
a) (b) are process diagrams explaining the manufacturing process of the thin film transistor shown in Fig. 1 (a) (bl), Fig. 2 (a),
Figures 3(a) and 4(a). Figure 5 (a) is a plan view, Figure 2 (b), Figure 3 (b),
Figure 4 (b), Figure 5 (bl is a vertical sectional view, Figure 6 (al
(bl is a plan view of a conventional thin film transistor and '#
FIG. 1 is a sectional view. l...Thin film transistor 5...Semiconductor film 6...
・No-amorphous Si film 7... Source voltage % 7a... Metal thin film meter... Drain electrode 9... Picture element electrode 10...
Transparent conductive film and 1 other person Figure 7 (a) Figure 2 (a) Figure 2 (b) Figure 3 s a ) Figure 4 (a) Figure 4 (b) Prisoner 5 (a)

Claims (1)

[Claims] 1) A gate electrode, a gate insulating film, a semiconductor film, and a metal thin film are sequentially laminated on an insulating substrate, and the metal thin film is formed as a source electrode and a drain electrode, wherein: A thin film transistor characterized in that a transparent conductive film that also serves as a pixel electrode is formed on the surfaces of a source electrode and a drain electrode.