JP3031056B2 - Matrix display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matrix type display device.

[0002]

2. Description of the Related Art A matrix type display device is generally constructed such that a display material such as a liquid crystal is sandwiched between two opposing substrates, and a voltage is selectively applied to the display material. At least one of the substrates is provided with a pixel electrode made of a transparent conductive film arranged in a matrix, and holds a switching element such as a transistor for selectively applying a voltage to each of the pixel electrodes and a charge. Charge holding capacity is provided. In order to reduce short-circuit defects in the gate insulating film of the transistor and the insulating film for charge storage capacitor, these insulating films
Formed in layers. As this type of conventional device,
There is one shown in 3 and 4. FIG. 4 is a plan view of a pixel of a conventional matrix type display device, and FIG. 3 is a sectional view thereof.

Referring to FIGS. 3 and 4 , a lower electrode 2 for a charge storage capacitor connected to a gate electrode line 3 and a gate electrode 3a and a gate electrode line 3 connecting them are formed on a transparent insulating substrate 1. A first gate insulating film 16 of a first layer and a second gate insulating film 17 of a second layer are formed thereon. On the second gate insulating film 17, a non-doped layer is formed on the gate electrode 3a. Amorphous silicon layer 7, phosphorus-doped amorphous silicon layer 9, source electrode
10a and a source electrode line 10 and a drain electrode 11 connecting them are sequentially formed. Further, in the charge storage capacitor portion, the first and second gate insulating films 16 and 17 are extended on the charge storage capacitor lower electrode 2 to form first and second charge storage capacitor insulating films, respectively. 16a and 17a are formed, a pixel electrode 12 made of a transparent conductive film connected to the drain electrode 11 is formed thereon, and a protective film 13 is formed on both surfaces.

In the conventional matrix type display device, as described above, the charge storage capacitor and the insulating film of the thin film transistor are formed in two layers in order to reduce a short circuit failure due to a foreign substance or a pinhole. Moreover, in order to suppress an increase in the number of steps, as described above, the gate insulating film and the charge storage capacitor insulating film are formed of the same material and the same thickness.

Next, the manufacturing process will be described. First, after the gate electrode 3a, the gate electrode line 3, and the lower electrode 2 for charge storage capacitor are formed on the transparent insulating substrate 1, the first gate insulating film 16 of the first layer and the first charge of the first layer are formed. A first insulating film serving as a storage capacitor insulating film 16a is formed, and a second insulating film 17a serving as a second-layer second gate insulating film 17 and a second-layer second charge holding capacitor insulating film 17a is formed. Form a film. Further, a non-doped amorphous silicon layer 7 and a phosphorus-doped amorphous silicon layer 9 are formed and patterned into islands 18. After that, a pixel electrode 12 is formed, a source electrode 10a, a source electrode line 10, and a drain electrode 11 are formed, an unnecessary phosphorus-doped amorphous silicon layer 9 on a channel is removed, and a protective film 13 is formed to form a matrix type. A display device is manufactured.

[0006]

The conventional matrix type display device reduces a charge holding capacity and a short-circuit defect due to a defect of an insulating film of a thin film transistor, and reduces a gate insulating film and a charge holding capacity in order to reduce a manufacturing process. The same insulating film is used as the same insulating film, and the insulating film is formed of two layers. However, it is difficult to optimize the material and film thickness so as to satisfy all the specifications required for the gate insulating film and the insulating film for the charge storage capacitor if the insulating film is also used in this way, and it is possible to reduce short-circuit defects. The measures are not enough. That is, as the gate insulating film, good characteristics of the thin film transistor and reduction of short-circuit defect failure can be obtained. As the charge-holding capacitor insulating film, a high dielectric constant for reducing area and a high withstand voltage for reducing short-circuit defect can be obtained. There is a problem that it is difficult to select an insulating film that satisfies both of the requirements of the above.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems.
The gate insulating film and conductive load holding capacitor insulating film multilayered,
Moreover, it is an object of the present invention to realize a matrix type display device which can be optimized for each insulating film and has high yield and high display characteristics.

[0008]

According to the present invention, there is provided a matrix type display device, wherein a gate insulating film and a charge-holding capacitor insulating film are formed in two layers, respectively, and a second-layer second charge-holding capacitor insulating film is provided. And the first gate insulating film of the first layer are also used, and the first insulating film for the charge storage capacitor of the first layer and the second gate insulating film of the second layer are formed as dedicated insulating films. ing.

[0009]

[0010]

[0011]

The matrix-type display device constructed as described above has a dual-purpose insulating film in which the gate insulating film and the insulating film for the charge storage capacitor are formed of the same film, respectively, and a dedicated insulating film suitable for each insulating film. Since it is formed, the combination of insulating films is free, and a multilayer insulating film optimal as a gate insulating film and a multilayer insulating film optimal as an insulating film for a charge storage capacitor can be obtained. In addition, since the part of the insulating film is formed of the same material and the same thickness and is also used, the increase in the number of steps can be minimized. Therefore, the characteristics of the charge storage capacitor insulating film and the gate insulating film can be satisfied, and a multilayer insulating film required for reducing short-circuit defects can be formed by suppressing an increase in the number of steps. A matrix display device is obtained.

[0012]

1 and 2 show an embodiment of the present invention.
This will be described with reference to FIG.

The thin-film transistor portion of the matrix type display device of the present invention comprises a gate electrode 3a on a transparent insulating substrate 1.
And a gate electrode line 3 are formed thereon. The dual-purpose insulating film 5 as a first gate insulating film 5a, the gate-insulating exclusive insulating film 6 as a second gate insulating film, and the semiconductor layers 7, 9
Are sequentially formed, and a source electrode 10a, a source electrode line 10, and a drain electrode 11 are formed. In the charge storage capacitor portion, a lower electrode 2 for a charge storage capacitor is formed on a transparent insulating substrate 1 at a place different from the thin film transistor portion, and a first insulating film for the charge storage capacitor is formed thereon. Dedicated insulating film 4, a dual-purpose insulating film 5 as a second charge storage capacitor insulating film 5b, and a pixel electrode 12 are sequentially formed. The dual-purpose insulating film 5 is formed simultaneously with the gate insulating film of the thin film transistor portion. As the first insulating film,
In the charge storage capacitor portion, it is used as a second charge storage capacitor insulating film.

As the insulating film, Si, Al, Ta,
Oxides such as Ti and Zr (eg, SiO ₂ , Ta ₂ O ₅
), A nitride (eg, Si ₃ N ₄ ), an oxide of an alloy of these metals (eg, an oxide of a TaMo alloy), or a ternary oxide (eg, BaTiO ₃₎
, LiTaO _3, etc.).

According to the present invention, a part of the insulating film formed of a plurality of layers in the thin film transistor portion and the charge holding capacitor portion of the matrix type display device is formed in common, and the other films are dedicated to satisfy the respective characteristics. By using the film, a matrix-type display device having high characteristics and a small number of manufacturing steps can be obtained, and other electrodes, transparent insulating substrates, and the like that are conventionally used can be similarly used. In addition, a plasma CVD method, which has been conventionally used for forming an insulating film,
It can be formed by a sputtering method, an EB evaporation method, or the like.

In the above description, the insulating film of the thin film transistor portion and the insulating film of the charge storage capacitor portion are each described as having two layers.
One insulating film satisfying one property may be used as a single-layer insulating film, and the other insulating film may be formed as a plurality of layers using a dual-purpose insulating film and a dedicated insulating film, or may be formed as three or more layers. Also in this case, the features of the present invention can be obtained by using the dual-purpose insulating film and the dedicated insulating film.

Further, it is preferable that all of the plurality of gate insulating films and the plurality of dedicated insulating films of the charge storage capacitor insulating films are formed of different materials from the viewpoint of chemical resistance and selectivity to an etching gas.

[Embodiment 1] Next, a specific manufacturing method of the matrix type display device of this embodiment will be described.

First, a film of Cr or the like is formed on the transparent insulating substrate 1 by a sputtering method or the like. Next, the patterns of the gate electrodes 3a, the gate electrode lines 3 connecting them, and the lower electrodes 2 for charge storage capacitors are formed by photolithography. Next, as a dedicated insulating film 4 for the charge storage capacitor, T
a ₂ O ₅ or the like is formed, and the gate electrode is removed by photolithography and etching. Further, an insulating film such as Si ₃ N _{4 serving} as the insulating film 5 serving as the gate insulating film 5a and the charge storage capacitor insulating film 5b is formed by a plasma CVD method or the like. Next, a transparent electrode material such as ITO is formed into a film, and the pixel electrode 12 is formed by partially overlapping the lower electrode 2 for the charge storage capacitor. At this point, the charge storage capacitor is formed by the first and second insulating films of the two layers of the dedicated insulating film 4 and the dual-purpose insulating film 5, respectively. Further, a second gate insulating film 6 serving as a dedicated gate insulating film is formed of SiO ₂ or the like,
A non-doped amorphous silicon layer 7 and a channel protection film 8 are successively formed. At this time, the dual-purpose insulating film 5
And the first and second gate insulating films formed of the gate insulating insulating film 6. Next, the channel protective film is patterned to form a phosphorus-doped amorphous silicon layer 9. Further, an opening 14 for connecting the pixel electrode 12 and the drain electrode 11 is formed by patterning, and a source electrode 10a and Cr and Al which become the source electrode line 10 and the drain electrode 11 continuous with them are continuously formed. And patterning. Next, the amorphous silicon layer on the channel and the pixel electrode 12 is etched to form the protective film 13.
Is formed thereon to complete a thin film transistor (TFT) substrate.

In the present embodiment, the insulating film for the charge storage capacitor
The first insulating film is formed of a dedicated insulating film, and the second insulating film has a two-layer structure formed of the same material as the first gate insulating film. In addition, Gate insulating film,
The first gate insulating film of the lower layer portion is a two-layer insulating film with the second insulating film of the upper layer portion forming the combined insulating a film, and the amorphous silicon 7 and the interface between the insulating film of the charge storage capacitor. Therefore, the gate insulating film and the insulating film for the charge storage capacitor can be formed into two layers with different film configurations only by increasing the film forming process by one step. A two-layer structure can be achieved, and the yield can be improved by the two-layer structure and the display characteristics can be improved by optimizing the insulating film.

In this example, the first gate insulating film and the second charge holding capacitor insulating film are formed of the same material as a dual purpose insulating film. In the part, it can be formed on the pixel electrode,
Since it can be formed without the need for patterning ,
Process increase is minimized .

[0022]

[0023]

[0024]

As described above, according to the present invention, the gate insulating film and the charge-holding capacitor insulating film are each formed of two layers, and the second-layer second charge-holding capacitor insulating film and one layer are formed. The first gate insulating film of the first layer is also formed, and the first gate insulating film of the first layer is formed.
Since the second gate insulating film of the insulating film and the second layer for charge storage capacitor is formed as a dedicated insulating film, one dedicated insulating film even without least may be formed without patterning,
While minimizing the increase in the number of manufacturing steps, short circuit defects can be reduced by multilayering, and the yield is improved. In addition, since the gate insulating film and the charge storage capacitor insulating film can have different film configurations, each can be optimized and display characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view (a cross-sectional view taken along line AA in FIG. 2) of a pixel portion of a matrix display device according to an embodiment of the present invention.

FIG. 2 is a plan view of a pixel portion of a matrix type display device according to an embodiment of the present invention.

FIG. 3 shows a pixel portion of a conventional matrix type display device.
FIG. 5 shows a configuration sectional view (a sectional view taken along line CC of FIG. 4).

FIG. 4 shows a pixel portion of a conventional matrix type display device.
FIG.

[Explanation of symbols]

1 transparent insulating substrate, 2 lower electrode for charge storage capacitor,
3 gate electrode line, 3a gate electrode, 4 dedicated insulating film for charge storage capacitor, 5 dual purpose insulating film, 6 dedicated insulating film for gate insulation, 10 source electrode line, 10a source electrode, 11 drain electrode, 12 pixel electrode.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-97385 (JP, A) JP-A-4-128823 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1368

Claims (1)

(57) [Claims] 1. A thin film transistor comprising: a gate insulating film in which a gate electrode, a first and a second gate insulating film are sequentially formed on a transparent insulating substrate; a semiconductor layer; and a source electrode and a drain electrode. A charge storage capacitor electrode, a charge storage capacitor insulating film in which first and second charge storage capacitor insulating films are sequentially formed on the transparent insulating substrate, and a transparent electrode connected to the drain electrode. A charge holding portion having a pixel electrode formed thereon is arranged in a matrix, and a second charge holding capacitor insulating film and a first gate insulating film are also formed to serve as the first charge holding capacitor. A matrix display device, wherein the insulating film and the second gate insulating film are formed as dedicated insulating films .