JPH10274785A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold the area that the source wire of a pixel area occupies as minimum as possible and to obtain a high aperture rate by arranging and wiring thin film transistors in more than one layer. SOLUTION: On the entire top surface of a glass substrate 1, an insulating protection film 2 is formed of, for example, silicon dioxide. On its top surface, a semiconductor film 3 is formed and then patterned to form an active layer. Then a gate insulating film 4 and a gate wire 5 are formed on the top surface of the glass substrate 1 including this active layer. A source area 6 and a drain area 7 is developed in the active layer by a method such as ion doping from above it. Silicon dioxide is filmed as an inter-layer insulating film 8 on the top surface and a contact hole is bored in the inter-layer insulating film 8 and the source area of the gate insulating film 4 by using photolithography and etching technology. Then a conductive metal material is filmed as a source wire material to fill the contact hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an active matrix type liquid crystal display device using a thin film transistor and other display devices.

[0002]

2. Description of the Related Art In recent years, as a display device used for various office machines such as computers and measuring instruments, instead of a conventionally used CRT, a lightweight liquid crystal display, EL (electroluminescence) display, plasma display or the like is used. In addition, demand for a thin display device is increasing. Among them, a liquid crystal display is particularly important from the viewpoint of low power consumption and low cost.

As a typical example of this type of conventional thin film transistor manufacturing method, a method of manufacturing a polycrystalline silicon thin film transistor will be briefly described with reference to the manufacturing process diagram of FIG. First, a glass substrate (1) is usually used as a light-transmitting substrate. An insulating protective film (2) is formed on the upper surface of the glass substrate, and an amorphous silicon film is further formed on the upper surface by a method such as a CVD method, which is polycrystalline by a method such as laser annealing. After forming the silicon film (3), patterning is performed to form an active layer. Next, a gate insulating film (4) and a gate electrode (5) are formed on the upper surface of the glass substrate including the active layer. Further, a source region (6) and a drain region (7) are developed in the active layer from above by using a technique such as ion doping. Further, after an interlayer insulating film (8) is formed on the upper surface by a method such as a CVD method, a contact hole is opened in the insulating layer by using ordinary photolithography and etching techniques. Then, after depositing a suitable metal, for example, aluminum, a transparent pixel electrode typified by ITO is used as a source electrode (9) and a drain electrode in the case of a liquid crystal display device by photolithography and etching techniques. By forming (11), a thin film transistor having a structure as shown in FIG. 1 is obtained. Further, in order to obtain a color display, a color filter is arranged corresponding to the position of each transparent pixel electrode.

[0004]

However, in the conventional structure, the existence of the source line between the pixel electrodes causes a large negative factor in the aperture ratio.

Generally, in order to realize a high-definition or high-quality display image, the number of pixels may be increased. For example, a liquid crystal display device having a display area of a diagonal of 2.4 inches has about 640 × 480 pixels, but a finer pixel size is required to support high-definition color display and the like. In order to realize this requirement, it is only necessary to reduce the distance between the wirings and the width of the wirings.

However, there is naturally a limit in reducing the wiring width, and even if the wiring interval is reduced by the width, only the aperture ratio is reduced, and this does not solve the problem.

Accordingly, the present invention aims at solving the above-mentioned problems, and an object of the present invention is to provide a structure capable of further increasing the aperture ratio of an active matrix type liquid crystal display device using a thin film transistor and other display devices. Is to do.

[0008]

According to the present invention, there is provided a display device having a plurality of thin film transistors on a single insulating substrate, wherein the thin film transistors are arranged and wired in a multilayer structure. The first feature is that the display device uses polysilazane as an insulating film, and the display device further includes a source line and a gate when viewed from a direction perpendicular to a substrate surface. The third feature is that the lines overlap with each layer. Finally, when the display device is viewed from a direction perpendicular to the substrate surface, the source lines overlap with each layer.

[0009]

Therefore, the inventor of the present application has made it possible to keep the area occupied by the source wiring in the pixel region as small as possible, and to further increase the active matrix type liquid crystal display device using thin film transistors and other display devices. The present invention has been completed from the viewpoint that the aperture ratio can be increased.

According to the configuration of the present invention described above, when viewed from the direction perpendicular to the substrate surface, the source line overlaps with each of the layers, and if the number of layers is n, the source line overlaps from the direction perpendicular to the substrate surface When viewed, the apparent occupied area of the source line can be reduced to 1 / n.

Further, by using a silicon-containing polymer liquid typified by polysilazane as the insulating film, it is possible to obtain flatter layers, to reduce the disorder of the orientation of the liquid crystal layer on the pixel electrode, The area can be used more effectively.

As a result, it is possible to keep the area occupied by the source wiring in the pixel region as small as possible, and to further increase the aperture ratio of an active matrix type liquid crystal display device using a thin film transistor and other display devices. It is possible to plan.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that the drawings merely schematically show the shapes, dimensions, and arrangements of the components to the extent that the present invention can be understood.

FIG. 2 is a sectional view of an active matrix type liquid crystal display device using thin film transistors as an embodiment of the present invention. The pixel array was obtained by the following steps.

A glass substrate (1) is usually used as a light-transmitting substrate having an insulating property. An insulating protective film (2) made of, for example, silicon dioxide is formed on the entire upper surface of the glass substrate. This film thickness may be any thickness as long as the purpose as the insulating protective film can be achieved.
Angstrom is most preferred.

After forming a semiconductor film (3) on the upper surface, patterning is performed to form an active layer. The thickness may be any thickness as long as the purpose as the active layer can be achieved, but is most preferably about 1000 Å.

Next, a gate insulating film (4) and a gate line (5) are formed on the upper surface of the glass substrate including the active layer.
The thickness of the gate insulating film may be any thickness as long as the purpose as the insulating film can be achieved.
Most preferably, it is about 0 Å. Most preferably, the thickness of the gate line is about 7,000 angstroms.

Further, a source region (6) and a drain region (7) are developed in the active layer by a technique such as ion doping from above. Further, a silicon dioxide film is formed as an interlayer insulating film (8) on the upper surface, and the source regions of the interlayer insulating film (8) and the gate insulating film (4) are formed by using ordinary photolithography and etching techniques. Open the first contact hole.

The means for opening the first contact hole may be any one of the two methods of wet etching and reactive ion etching.

As for etching conditions, an etching solution of hydrogen fluoride / ammonium fluoride / acetic acid system was used for wet etching. As for the etching conditions, the liquid temperature is 40 ° C., depending on the shape of the step after etching and the etching rate.
The etching time is most preferably 300 seconds.

For reactive ion etching, trifluoromethane was used as an etching gas. The results of etching vary depending on various conditions such as the flow rate of the etching gas, the degree of vacuum in the reaction chamber, and the high-frequency discharge applied to the electrodes. At this time, trifluoromethane was introduced as an etching gas into the reaction chamber at a flow rate of 200 sccm, and a 13.56 MHz high-frequency discharge was applied to the electrodes at a power of 1.5 kW for 3 seconds.
The condition of applying for 00 seconds is most preferable. At this time, the etching selectivity between silicon dioxide and non-single-crystal silicon was about 25. Further, the etching rate is about 80
0 Å / min.

Next, a conductive metal material or a conductive organic compound is formed as a source wire to fill the contact hole. The conductive metal material or the conductive organic compound used here is a material capable of forming a desired pattern using general photolithography and etching techniques, and is a typical source electrode. It is necessary to have properties that can withstand the aluminum-based etching conditions used for the above. Materials satisfying these conditions include aluminum and aluminum as metal materials.
In addition to copper, titanium, tantalum, gold, silver, and zirconium, various metals, precious metals, and alloys thereof are included. Examples of the organic compound include polyacetylene, polyparaphenylenevinylene, and polyparaphenylene sulfide, all of which have been subjected to a chemical doping treatment to impart conductivity.

Thereafter, a metal suitable as a source electrode,
For example, after depositing aluminum, a source line (9) is formed by ordinary photolithography and etching techniques. The thickness of the source electrode may be any thickness as long as its purpose can be achieved, but is most preferably about 8000 Å.

Subsequently, silicon dioxide is formed on the upper surface as an insulating protective film (10). This film thickness may be any thickness as long as the purpose as the insulating protective film can be achieved, but is most preferably about 5,000 Å.

Further, by using various insulating films made of a silicon-containing polymer liquid represented by polysilazane, it is possible to obtain flatter layers and to adjust the orientation of the liquid crystal layer on the pixel electrodes. Disturbance can be reduced, and the pixel area can be more effectively utilized.

Thereafter, the units (3) to (10) are stacked as one unit according to the number of layers required on the upper surface, and the units are stacked. In the embodiment, a three-layer structure is used.

After lamination, a second contact hole is formed on the drain region of the insulating protective film (10), the interlayer insulating film (8) and the gate insulating film (4) by using ordinary photolithography and etching techniques. Open the file.

The means for opening the second contact hole may be any one of the two methods of wet etching and reactive ion etching.

As for etching conditions, a hydrogen fluoride / ammonium fluoride / acetic acid-based etchant was used for wet etching. The etching temperature is most preferably 40 ° C. depending on the shape of the step after etching and the etching rate.

For reactive ion etching, trifluoromethane was used as an etching gas. The result of etching varies depending on various conditions such as the flow rate of the etching gas, the degree of vacuum in the reaction chamber, and the high-frequency discharge applied to the electrodes. At this time, it is most preferable that trifluoromethane is introduced as an etching gas into the reaction chamber at a flow rate of 200 sccm, and a high-frequency discharge of 13.56 MHz is applied to the electrodes at a power of 1.5 kW. At this time, the etching selectivity between silicon dioxide and non-single-crystal silicon is about 25.
Met. Further, the etch rate was about 800 Å / min.

Further, after a metal suitable for the drain electrode, for example, indium tin oxide is deposited from the upper surface, a drain electrode (11) is formed by ordinary photolithography and etching techniques. The thickness of the drain electrode may be any thickness as long as its purpose can be achieved, but is most preferably about 1600 Å. Further, in order to obtain a color display, a color filter is arranged corresponding to the position of each transparent pixel electrode.

Through the above steps, a thin film transistor of the present invention having a structure as shown in FIG. 2 can be obtained.

FIG. 3 shows the display pixel portion of the structure shown in FIG. 2 in a direction perpendicular to the substrate surface.

When viewed from the direction perpendicular to the substrate surface, the gate line (5) does not necessarily have to overlap with each of the layers. For example, as shown in FIG. ) When viewed from the direction perpendicular to the substrate surface,
By appropriately displacing the arrangement, the thickness of the entire structure can be further reduced.

Further, the direction in which the drain electrode (11) is drawn out with respect to the gate line (5) does not necessarily need to be the same in each layer, and there is no problem even if the structure shown in FIG. 5 is used as an example. .

The above-described embodiments of the present invention are merely preferred examples, and therefore, the present invention is not limited to the above-described embodiments, and many modifications and changes can be made. For example, tantalum is used as the gate wire (5), but other metals may be used. In addition, the above-described materials, shapes, numerical values, and other conditions other than forming the active layer with a non-single-crystal or polycrystalline silicon layer are merely preferred examples, and are not limited thereto.

[0037]

As can be seen from the above description, according to the structure of the display device of the present invention, when viewed from the direction perpendicular to the substrate surface, the source line overlaps with each layer, so that the number of layers can be reduced. n, the apparent occupation area of the source line is 1 / when viewed from the direction perpendicular to the substrate surface.
n.

Further, by using a silicon-containing polymer liquid typified by polysilazane as the insulating film, it is possible to obtain flatter layers, to reduce the disorder of the orientation of the liquid crystal layer on the pixel electrode, The area can be used more effectively.

As a result, it is possible to keep the area occupied by the source wiring in the pixel region as small as possible, and to further increase the aperture ratio of an active matrix type liquid crystal display device using thin film transistors and other display devices. It is possible to plan.

[Brief description of the drawings]

FIG. 1 is a diagram showing a manufacturing process of a conventional thin film transistor and its structure.

FIG. 2 is a sectional structural view of a display device according to an embodiment of the present invention.

FIG. 3 is a structural diagram of a display pixel unit in a direction perpendicular to a substrate surface of a display device according to an embodiment of the present invention.

FIG. 4 is a view showing an example of a structure of a display pixel portion in a direction perpendicular to a substrate surface of a display device according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of a structure of a display pixel portion in a direction perpendicular to a substrate surface of a display device according to an embodiment of the present invention.

Claims (4)

[Claims] 1. A display device having a plurality of thin film transistors on a single substrate, wherein the thin film transistors are arranged in multiple layers and arranged and wired. 2. The display device according to claim 1, wherein the display device includes an insulating film formed of a silicon-containing polymer liquid. 3. The display device according to claim 1, wherein the source line and the gate line overlap with each other when viewed in a direction perpendicular to the substrate surface in the display device. 4. The display device according to claim 1, wherein when viewed from a direction perpendicular to the surface of the substrate, the source line overlaps with each layer in the display device.