JPS62296125A - Active-matrix type liquid-crystal display device - Google Patents

Abstract

PURPOSE:To prevent occurrence of unnecessary contact between electrodes, by using a transparent picture element electrode as a source electrode after extending the electrode to the top of a semiconductor layer and further forming an insulating layer at the top of the source electrode. CONSTITUTION:At the electrode forming locations on a semiconductor layer 33 impurity-doped amorphous Si films 34 and 35 are formed to prescribed thicknesses. Then a transparent picture element electrode 36 is formed by sputtering. At the time of formation, part of the electrode 36 is also formed on the upper surface of the Si film 35 and used as the source electrode of a thin-film transistor TFT 50. Moreover, an Si-nitride film 37 is formed on the upper surfaces of the source electrode part and electrode 36 as an insulating film. When such constitution is used, occurrence of unnecessary contact can be prevented between the electrodes even if some of data lines are overlapped on the transparent picture element electrode due to a faulty pattern when the data lines are formed.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to an active matrix liquid crystal display device using a thin film transistor (hereinafter referred to as TPT) as a switching element.

(Prior Art) Recently, display devices using liquid crystals or electroluminescence (EL) have been used for television displays, graphic displays, etc., and have a large capacity.

High-density active matrix liquid crystal display devices are being actively developed and put into practical use. This type of display device provides high-contrast display without crosstalk.
A semiconductor switch is used as a means for driving and controlling each pixel. As a semiconductor switch, single crystal S
There are MOS type FETs formed on i-substrates, TPTs formed on transparent substrates, which are capable of transmissive display, and can easily be made large in area.

FIG. 5 is a sectional view showing an example of a liquid crystal display device equipped with the above TPT array. In the same figure, glass substrate 1
A gate electrode 2 integral with the gate line is formed thereon, and an insulating film 3 is further formed to cover this. A semiconductor layer 4 made of, for example, amorphous silicon is formed at a predetermined position on the insulating film 3. A drain electrode 7 and a source electrode 8 are formed on this semiconductor layer 4 so as to sandwich this layer therebetween. In this case, the drain electrode 7 and the source electrode 8 are each formed via an impurity-doped amorphous silicon film 5.6 that has a function of making good contact with the semiconductor layer 4. Although not shown in the drawing, the drain electrode 7 is formed integrally with a predetermined data line. Further, the source electrode 8 is formed so as to be electrically connected to a transparent pixel electrode 9 formed on the insulating film 3.

Next, the above semiconductor layer 4, drain electrode 7, source electrode 8
The portion is covered with an insulating protective film 1o, and the entire surface of this upper portion is coated with liquid crystal alignment III. The first substrate 100 is configured in this manner.

On the other hand, in the second substrate 200, a common electrode 22 and a liquid crystal alignment film 23 are sequentially formed on a glass substrate 21.

The glass substrate 1.21 is sealed at its periphery with a gap of about 10 μm, and liquid crystal is sealed in this gap to form a liquid crystal layer 30.

FIG. 6 also shows a conventional liquid crystal display device, and the difference from the one in FIG. 5 is the portion constituting the TPT electrode. That is, the drain electrode 7a and the source electrode 8a are made of the same material as the transparent pixel electrode 9, and are formed in the same process as the transparent pixel electrode 9. The other parts are the 5th
Since the structure is the same as that of the TPT shown in the figure, the same reference numerals as in FIG. 5 will be given and the explanation will be omitted.

Among the liquid crystal display devices described above, the device shown in FIG. 5 has a problem in that the process of forming the transparent pixel electrode 9 and the process of forming the drain electrode 7 and source electrode 8 are different processes, and the number of steps is large. . On the other hand, the device shown in FIG.
At the same time when forming the transparent pixel electrode 9, the drain electrode 7
Since the as source electrode 8a can also be formed, there is an advantage in terms of the number of manufacturing steps. However, the transparent pixel electrode 9 is made of its material (lndiua+Tin Oxide, hereinafter referred to as I
Due to its properties (referred to as TO), it has poor workability and tends to have defects in electrical conductivity and resistance. On the other hand, the device shown in FIG. 5 is made of reminium (a) and does not have the problems of the device shown in FIG. 6.

(Problems to be Solved by the Invention) The conventional liquid crystal display devices described above all have the above-mentioned problems, but they also have a common problem.

That is, when forming the transparent pixel electrode 9, the drain electrode 7, and the source electrode 8, if a part of the electrode deviates from a predetermined position and extends to another electrode position due to a defective resist pattern or poor position, it may come into contact with that electrode. As a result, a device including such a part becomes a defective product as a whole. Moreover, even if it is used as a product, the product will include missing pixels and its product value will be inferior.

Therefore, this invention can prevent unnecessary contact between electrodes as much as possible without increasing the number of processes, and has high manufacturing safety, improves product yield, and at the same time improves product value. An object of the present invention is to provide an active matrix type liquid crystal display device that can be used as an active matrix type liquid crystal display device.

[Structure of the Invention] (Means for Solving the Problems) In an active matrix liquid crystal display device, a transparent pixel electrode is extended to the top of a semiconductor layer and used as a source electrode, and an insulating layer is provided on top of the source electrode. It forms the

(Function) With the above configuration, even if there is a pattern defect during electrode formation, since there is an insulating layer above the source electrode, unnecessary contact between the electrodes will not occur, and a good active A matrix type liquid crystal display device can be obtained without increasing the number of steps.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a diagram showing an equivalent circuit of an embodiment of the present invention. In the same figure, (Xi), (1-1°2,..., m)
is a plurality of data lines, (Yj).

(j-1, 2,..., n) are multiple gate lines perpendicular to these, and these data lines (Xi) and gate lines (
A TFT 50 is constructed at each intersection point of Yj). T
The drains of the FT 50 are connected to data lines (Xi) for each column, and the gates are connected to gate lines (Yj) for each row. 51
are transparent pixel electrodes, each connected to the source electrode of the TFT 50, and a liquid crystal 53 is sandwiched between the transparent pixel electrode 51 and the transparent counter electrode 52.

FIG. 1 is a sectional view showing an embodiment of the present invention, and its structure will be explained along the manufacturing process. First, the insulating substrate 30
1 After depositing, for example, molybdenum on a glass substrate to a thickness of about 1,500 yen by sputtering, a gate line (Y
j) A gate electrode 31 integral with the gate electrode 31 is patterned. Next, a gate insulating film 32 made of silicon dioxide, for example, is deposited to a thickness of approximately 4,000 nm so as to cover the gate electrode 31 by plasma CVD. Further, amorphous silicon is deposited to a thickness of approximately 3000 nm on the gate insulating film 32 by, for example, plasma CVD, and then a semiconductor layer 33 is patterned.

Next, impurity-doped amorphous silicon films 34 and 35 are formed to a thickness of about 500 nm at electrode formation positions on the semiconductor layer 33. Next, a transparent pixel electrode 36 is formed after depositing, for example, ITO to a thickness of about 1500 nm by sputtering. In this case, in this invention, the transparent pixel electrode 36
A portion is also formed on the upper surface of the impurity-doped amorphous silicon film 35 and also functions as the source electrode of the TFT 50. Furthermore, a silicon nitride film 37 as an insulating film is formed on the upper surface of this source electrode portion and on the transparent pixel electrode 36.

Further, for example, after aluminum is deposited on the entire surface to a thickness of about 1 μm, a drain electrode 38 integrated with the data line (Xi) is patterned. Then, after applying a protective film 39 made of polyimide to a thickness of about 2.5 μm over the entire surface, the polyimide and the silicon nitride film 37 on the upper surface of a predetermined position of the transparent pixel electrode 36 are removed. Furthermore, a liquid crystal aligning film 40 made of polyimide is formed over the entire upper surface by coating, and a first substrate 60 is obtained.

On the other hand, the second substrate 61 is an insulating substrate 45, for example, a glass substrate, on which a transparent counter electrode 46 made of, for example, ITO with a thickness of about 1500 μm and a liquid crystal alignment film 47 made of polyimide with a thickness of 1 μm, for example, are sequentially formed. It can be obtained by

The peripheral portions of the first substrate 60 and the second substrate 61 are sealed so that a gap of about 10 μm is maintained between the insulating substrates 45 and 31, and a liquid crystal 63 is further sandwiched within this gap. In this way, an active matrix liquid crystal display device is constructed.

FIG. 2 is a plan view showing one pixel portion of the display electrode array of this embodiment, and FIG. 1 corresponds to a cross section taken along line A-C-B in FIG. In order to avoid complexity, FIG. 2 shows only the parts completed before the formation of the protective film.

The operation of this liquid crystal display device will be described as follows. The gate line (Yj) is sequentially scanned and driven by an address signal, and when Tf is a frame scanning period, the TFTs 50 are sequentially turned on for (T f /n) periods for each row. On the other hand, in synchronization with the scanning of the gate line (Yj), for example, m parallel pixel signals are supplied to the data line (Xi). As a result, the signal voltage is applied to the transparent pixel electrode 5 row by row.
1, the liquid crystal 53 sandwiched between the transparent counter electrode 52 is excited and an image is displayed.

According to the device of the present invention described above, the insulating layer 37 is formed on at least the portion of the transparent pixel electrode that also serves as the source electrode before forming the drain electrode 38 integrated with the data line (Xi). For this reason, as shown in Fig. 4, for example, when a data line (X2) is formed, due to a pattern defect, a portion overlaps with the transparent pixel electrode as shown at 66°67. , thereby preventing electrical contact with the transparent pixel electrode. Furthermore, when forming a transparent pixel electrode, even if a portion overlaps with the data line (Xl) as shown at 68 due to a defective pattern, the data line (Xl) formed on top of this may occur.
1) is formed through an insulating layer, so no unnecessary contact occurs. The same applies to the digit 166.67. Conventionally, when there is a pattern defect as described above, this pixel portion becomes a completely defective portion, but by using the present invention, such defects can be prevented. This will also have a direct impact on yield improvement. Furthermore, improving product reliability and manufacturing.

It also leads to relaxation of patterning accuracy and has many advantages.

[Effects of the Invention] As explained above, the present invention can prevent unnecessary contact between electrodes as much as possible without increasing the number of steps, has high manufacturing safety, and improves product yield. It is possible to provide an active matrix liquid crystal display device that can be improved and at the same time its product value can also be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a plan view showing an example of the display electrode array of the invention, FIG. 3 is a diagram showing an example of an equivalent circuit of the invention, and FIG. Pattern explanatory diagrams shown for detailed explanation of this invention, FIGS. 5 and 6
Each figure is a sectional view showing an example of a conventional liquid crystal display device. 30.45... Insulating substrate, 31... Gate electrode,
32... Gate insulating film, 33... Semiconductor layer, 34°35... Impurity-doped amorphous silicon film, 36°51
... Transparent pixel electrode, 37... Insulating film, 38... Drain electrode, 39... Protective film, 40.47... Liquid crystal alignment film. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Δ Figure 2 Figure 3

Claims (1)

[Claims] A semiconductor layer is provided between a drain electrode and a source electrode at each intersection of a plurality of data lines provided on an insulating substrate and a plurality of gate lines perpendicular to the data lines, and the semiconductor layer and a first substrate on which a transparent electrode is arranged and a thin film transistor on which a protective film is formed to integrally cover and protect the drain and source electrodes, a second substrate on which a transparent counter electrode is formed, and the first substrate,
In an active matrix liquid crystal display device comprising a liquid crystal sandwiched between second substrates, the transparent electrode is extended to the top of the semiconductor layer and used as the source electrode, and an insulating electrode is provided above the source electrode. An active matrix liquid crystal display device characterized by forming layers.