JPH05299436A - Thin-film transistor and liquid crystal display using the thin-film transistor - Google Patents

Abstract

PURPOSE:To obtain a low-cost active matrix liquid crystal display by a method wherein the resist is patterned on an intrinsic semiconductor film and then an extrinsic semiconductor film and a source/drain electrode are deposited and after that, the resist is removed and the extrinsic semiconductor film and the source/drain electrode are patterned. CONSTITUTION:The resist is patterned on an intrinsic semiconductor film 'i'. Then, an extrinsic semiconductor film n<+> and a source/drain electrode Cr are deposited. After that, the extrinsic semiconductor film n<+> and the source/drain electrode Cr are patterned by removing the resist. In this TET manufacturing method, the extrinsic semiconductor film n<+> is not etched and therefore a channel protective film is not required to be inserted and eventually the intrinsic semiconductor film 'i' can be formed very thin. Consequently, the number of masks is reduced and the number of layers of the TFT is also reduced and therefore the active matrix liquid crystal display manufacturing cost can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to cost reduction of an active matrix liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, a device structure of a thin film transistor (hereinafter abbreviated as TFT) used in an active matrix liquid crystal display device is described in, for example, "Flat Panel Display '91" edited by Nikkei Electronics, Nikkei Microdevices. As described above, the extrinsic semiconductor film is inserted between the intrinsic semiconductor film and the source / drain electrodes. FIG. 4 shows a conventional TFT device structure. In the figure, Cr below is a gate electrode, SiN below is a gate insulating film, i is an intrinsic semiconductor film, SiN above is a channel protective film, and n + is an extrinsic semiconductor. Membrane, upper Cr is source /
It is a drain electrode. Here, the intrinsic semiconductor film thickness of the TFT is usually 0.1 μm or less. In the TFT, when the intrinsic semiconductor film thickness becomes extremely thin, the on-current of the TFT increases and the off-current decreases.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
It had the following problems.

That is, in the above device structure, a channel protective film is added so as to prevent the i layer serving as a channel portion from being etched when the n + layer is patterned. This is because there is no selection ratio between the n + layer and the i layer in etching. This increases the number of masks and the number of TFT layers, which increases the cost of the active matrix liquid crystal display device.

An object of the present invention is to solve the above problems and provide a low cost active matrix liquid crystal display device.

[0006]

In order to solve the above problems, the present invention provides a method for manufacturing a field effect type thin film transistor, in which a resist is patterned on an intrinsic semiconductor film, and then an extrinsic semiconductor film and a source are formed. This invention proposes a thin film transistor and a liquid crystal display device using the thin film transistor, which has a manufacturing method of patterning an extrinsic semiconductor film and a source / drain electrode by depositing a / drain electrode and then removing the resist.

[0007]

In the TFT manufacturing method described above, since the etching of the extrinsic semiconductor film is not used, the intrinsic semiconductor film can be made extremely thin without inserting the channel protective film. Therefore, the number of masks is reduced and the number of TFT layers is reduced, so that the cost of the active matrix liquid crystal display device can be reduced.

[0008]

The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a manufacturing procedure of the TFT of the present invention. That is, a resist is patterned on the intrinsic semiconductor film (see (a)), then an extrinsic semiconductor film and source / drain electrodes are deposited (see (b)), and then the resist is removed to remove the extrinsic semiconductor. Pattern the film and the source / drain electrodes ((c))
Refer to) Manufacturing procedure. In the above-mentioned TFT manufacturing method, since the etching of the extrinsic semiconductor film is not used, the intrinsic semiconductor film thickness can be made extremely thin without inserting the channel protective film. Therefore, the number of masks is reduced, and the TFT
Since the number of layers is reduced, the cost of the active matrix liquid crystal display device can be reduced.

2, FIG. 3 and FIG. 4 show a manufacturing procedure when the TFT of the present invention is applied to an active matrix liquid crystal display.

First, ITO (Indiu) is formed on a glass substrate.
m Tin Oxide), Ti, and Al-Si-Ti are sputtered and patterned (see (a)).
Next, SiN, i is continuously deposited (see (b)), and i, S
iN, Al-Si-Ti, and Ti are patterned (see (c)). Next, a resist is patterned on the i layer, then an n + layer and a Cr electrode are deposited (see (d)), and then the resist is removed to remove n +.
The layer and the Cr electrode are patterned. Next, a PAS film is deposited and patterned (see (e)), and then a liquid crystal process is performed (see (f)).

As described above, when the TFT of the present invention is used, the TFT substrate can be formed with four masks. Therefore, the cost of the active matrix liquid crystal display device can be reduced.

FIG. 5 shows the structure of a terminal portion when the TFT of the present invention is applied to an active matrix liquid crystal display. As shown in the figure, only the ITO is exposed at the connection terminal portion, so the reliability is high.

[0014]

As is apparent from the above description, according to the present invention, since the etching of the extrinsic semiconductor film is not used, the intrinsic semiconductor film thickness can be made extremely thin without inserting the channel protective film. Therefore, the number of masks is reduced, and
Since the number of TFT layers is reduced, the cost of the active matrix liquid crystal display device can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing procedure of a TFT of the present invention.

FIG. 2 is a diagram showing a manufacturing procedure when the TFT of the present invention is applied to an active matrix liquid crystal display.

FIG. 3 is a diagram showing a manufacturing procedure of the same.

FIG. 4 is a diagram showing a manufacturing procedure of the same.

FIG. 5 is a structural diagram of a terminal portion when the TFT of the present invention is applied to an active matrix liquid crystal display.

FIG. 6 is a device structure diagram of a conventional TFT.

[Explanation of symbols]

Cr ... Chromium, SiN ... Silicon nitride film, i ... Intrinsic semiconductor film, ITO ... Indium tin oxide, Ti
... Titanium, Al-Si-Ti ... Aluminum-silicon-titanium, PAS film ... Protective film, n + ... Extrinsic semiconductor film.

Front page continued (72) Inventor Ryoji Oritsuki 3300 Hayano, Mobara-shi, Chiba Hitachi Ltd. Mobara factory

Claims (3)

[Claims] 1. A method of manufacturing a field effect thin film transistor, wherein a resist is patterned on an intrinsic semiconductor film, and then an extrinsic semiconductor film and source / drain electrodes are deposited, and then the resist is removed to remove the extrinsic film. A thin film transistor characterized by patterning a semiconductor film and source / drain electrodes. 2. The thin film transistor according to claim 1, wherein the intrinsic semiconductor film thickness is 0.1 μm or less. 3. A liquid crystal display device using the thin film transistor according to claim 2 as a pixel transistor.