JP2616976B2 - Active matrix and its manufacturing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix driven by a non-linear element such as a thin film transistor (hereinafter, referred to as TFT) and a method for manufacturing the same.

[Conventional technology]

Liquid crystal display (LCD) using liquid crystal as display medium
Since they are lighter and thinner than CRT displays and have features such as low power consumption, research and development are being promoted as alternatives to the above CRT displays, and some of them have begun to be put into practical use. In particular, the active matrix method in which a non-linear element is provided for each pixel and driven can realize high image quality comparable to that of a CRT display. Next, an active matrix type LCD will be described, and the most frequently used TFT is used for the non-linear element.

In an LCD using an active matrix method, a basic unit (pixel) composed of a TFT and a pixel electrode is arranged in a matrix, and a scanning line for controlling the TFT operation around the pixel and a scanning line for controlling the TFT operation around the pixel. The liquid crystal is sandwiched between an active matrix substrate in which data lines for supplying display data to lines and pixel electrodes are arranged in a grid pattern, and a counter substrate in which a single potential is supplied to the entire surface. Here, a portion where a liquid crystal is sandwiched between a pixel electrode and a counter substrate and a display is performed is referred to as a liquid crystal display cell, and a TFT provided for each pixel is referred to as a pixel TFT. FIG. 4 shows an equivalent circuit of the active matrix. 1 is a scanning line, 2 is a data line,
3 is a TFT, and 11 is a liquid crystal display cell.

In an active matrix type LCD, a voltage is applied to the liquid crystal by charging a capacitor formed by the liquid crystal display cell with electric charge, and display is performed by a change in transmittance accompanying a change in liquid crystal alignment. However, the charging time of a specific pixel is extremely short compared to the time until the next time display data is written to the same pixel, and after charging, the TFT is turned off until the next display data is written. It is necessary to maintain the state of the liquid crystal display cell. If the voltage applied to the liquid crystal fluctuates within a prescribed holding time, a change in the display state occurs, and a problem in display quality such as a decrease in contrast occurs. In particular, when gradation display is performed to achieve full color, or when the pixel size is reduced to achieve a higher definition screen, that is, when the capacity of the liquid crystal display cell is reduced, this charge retention characteristic becomes a problem. Since the charged electric charge leaks due to the leak current of the TFT or the like, the retention characteristics of the liquid crystal display cell are determined by the capacity of the liquid crystal display cell and the amount of charge leak due to the leak current of the TFT and the like.

In order to solve the above problem, a method of increasing the effective capacitance of the liquid crystal display cell by forming an additional capacitance 12 in parallel with the liquid crystal display cell 11 as shown in FIG. 5 is generally used. This method has the advantage that if the amount of charge leakage is constant, the fluctuation of the voltage value applied to the liquid crystal can be reduced due to an increase in the capacity of the liquid crystal display cell. Examples using such additional capacitors are described in the literature (for example, Shirai et al., “High-quality Full-Color Liquid Crystal Panels”, Research Report on Electronics and Communications, Vol. 86, No. 65, p.
p65-69,1986, Y.Oana “A240 × 320Elements Active Matr
ix LCD with Integrated Gate−Bus Drivers Using P
oly-Si TFTs "SID International Symposium Technical Paper Abstract, pp31
2-315, 1984, etc.). In these examples, as shown in FIG. 6, the pixel electrode 4 and the additional capacitance wiring 5 form an additional capacitance with the additional capacitance insulating film 6 interposed therebetween.
The same potential as that of the counter electrode is supplied to the additional capacitance wiring 5. For this reason, it is inevitable that the additional capacitance line 5 crosses the scanning line 1, the data line 2, or both.

[Problems to be solved by the invention]

FIG. 7 shows the concept of an active matrix in the case where an additional capacitor is formed. FIG. 7A shows a case where the additional capacitance wiring 5 and the data line 2 intersect, and FIG. 7B shows a case where both the scanning line 1 and the data line 2 intersect the additional capacitance wiring 5. Although FIG. 7 does not show the case where the scanning line 1 intersects with the additional capacitance line 5, the concept is the same as the case of FIG.

Therefore, in the active matrix in which the additional capacitance is formed, a wiring capacitance is newly generated at the intersection of the additional capacitance wiring 5 and the data line 2 or the scanning line 1.
In the conventional method, electrical insulation between the additional capacitance wiring and the data line (or the scanning line) is performed only by the insulating film forming the additional capacitance. Therefore, in order to increase the additional capacitance value, the thickness of the insulating film has to be reduced, and therefore the wiring capacitance of the data line or the scanning line is increased, and the load of the peripheral circuit for driving the active matrix is increased. However, there is a drawback that the number increases.

SUMMARY OF THE INVENTION It is an object of the present invention to obtain an active matrix configuration in which the wiring capacitance of a data line or a scanning line is reduced, and a simple manufacturing method thereof.

[Means for solving the problem]

The above object is achieved at the intersection between the additional capacitance wiring formed of a transparent conductive film and the data line and / or the scanning line.
This is achieved by electrically insulating with an insulating film for forming an additional capacitance and a negative photosensitive resin layer.

[Action]

In the pixel structure in which the additional capacitance is formed as described above, an increase in wiring capacitance is a major problem. In order to reduce the wiring capacitance, it is conceivable to reduce the wiring capacitance by providing a new insulating layer at the intersection of the additional capacitance wiring and the data line and the scanning line. In order to reduce the wiring capacitance of the scanning line, an insulating layer made of a photosensitive resin layer is newly provided at the wiring intersection by a simple method to form an active matrix structure.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. First
FIG. 2 is a plan view of a pixel showing an embodiment of the active matrix according to the present invention, FIG. 2 is a cross-sectional view of the above embodiment taken along line AA, and FIGS. It is a figure explaining each manufacturing method of. The pixels of the active matrix of the embodiment shown in FIG. 1 are composed of scanning lines 1, data lines 2, TFTs 3, pixel electrodes 4 and additional capacitance lines 5, as in FIG. As a sectional structure, as shown in FIG. 2, an additional capacitance insulating film 6 for forming an additional capacitance structure exists between the additional capacitance wiring 5 and the pixel electrode 4 as in FIG. The sectional view shown in FIG.
To make it easier to understand the characteristics of the active matrix,
The cross-sectional view in the direction of the arrow A-A 'and the cross-sectional view in the direction of the arrow A'-A are combined. At the intersection of the data line 2 and the additional capacitance wiring 5, a photosensitive resin layer 7 is provided in addition to the additional capacitance insulating film 6. Has been reduced.

Next, a method of manufacturing the active matrix having the above configuration will be described with reference to FIG. FIG. 3 (a) shows on a transparent substrate 10.
A cross section of a pixel after forming a scanning line 1 also serving as a TFT 3 and a gate electrode of the TFT and an interlayer insulating film 8 is shown. (A) above
Up to this point, a conventional active matrix manufacturing method can be used. Here, the transparent conductive film, specifically, ITO (I
A 500 .ANG.-thick ndium TIn Oxide) film is deposited by a sputtering method, a resist pattern of the additional capacitance wiring 5 is formed by a usual photo process, and the ITO film is processed with an aqueous solution containing hydrochloric acid and nitric acid to form the additional capacitance wiring 5. . An insulating film 6 for additional capacitance, specifically SiO ₂ , for forming an additional capacitance is deposited by a sputtering method or the like, and a structure shown in FIG. 3B is manufactured.

Next, in order to form the pixel electrode 4, a two-layer film of a transparent conductive film and an opaque film, for example, the ITO film 500 # and the Mo film 10 are formed.
After a continuous deposition of 00 ° by a sputtering method, a resist pattern of the pixel electrode 4 is formed by a normal photo process, and then the Mo film is processed by a reactive ion etching method using a mixed gas of CCl ₂ F ₂ and O _2. Subsequently, the ITO film is processed with a hydrochloric acid / nitric acid-based acid solution in the same manner as in the above-described processing of the additional capacitance wiring pattern to produce the structure shown in FIG. 3 (c).

Next, a negative photosensitive resin such as Toray's negative photosensitive polyimide UR-3600 is applied by a spin coating method, and the recommended 83
The photosensitive resin layer 7 was formed by pre-baking at ℃. Subsequently, as shown in FIG. 3 (d), 1000 mj / cm ²
The photosensitive polyimide is exposed to ultraviolet light. afterwards,
Remove the photosensitive polyimide in the unexposed area with the recommended developer,
A heat treatment at 250 ° C. or higher is performed to cause an imidization reaction. Then, as shown in FIG. 3 (e), the photosensitive polyimide is unexposed on the scanning lines 1, TFT3 and pixel electrodes 4 which are opaque parts, so that the photosensitive polyimide is removed and other parts are removed. Then, the photosensitive resin layer 7 is formed.

Finally, as shown in FIG. 2, in order to electrically connect the TFT 3 with the data line 2 and the pixel electrode 4, three holes are formed in the interlayer insulating film 8 and the additional capacitance insulating film 6 to form a metal such as Al. A film is deposited, and a wiring pattern of the data line 2 is formed. In these steps, a method used for a normal active matrix can be applied. Further, the unnecessary Mo film which is an opaque film on the pixel electrode 4 may be removed by a reactive ion etching method using a mixed gas of CCl ₂ F ₂ and O ₂ . Through the above steps, the active matrix of the present invention can be manufactured.

The wiring capacitance between the data line 2 and the active matrix manufactured by the above-described method is determined by adding the additional capacitance insulating film 6 to the SiO ₂ film 10.
When the film thickness of the photosensitive polyimide was 3000 mm and the film thickness of the photosensitive polyimide was 3000 mm, the wiring capacitance could be reduced to about 1/6 as compared with the case where only the insulating film 6 for additional capacitance was used. In addition, the thickness of the photosensitive polyimide is set to 6
When the thickness was increased to 000 mm, there was an effect that the wiring capacitance could be reduced to about 1/10.

The gist of the present invention is to significantly reduce the wiring capacity of the data line by interposing an insulating film of a photosensitive resin between the data line and the additional capacitance wiring. Since the above-mentioned additional capacitance wiring is formed of a transparent conductor, a single layer of opaque material is provided on the pixel electrode, and the photosensitive resin is exposed from the back, so that the desired data line and the additional capacitance can be easily formed without a photomask. An object of the present invention is to form a photosensitive resin insulating film between the wirings. Therefore, the above-mentioned photosensitive resin only needs to be present only at the wiring intersection, and even if the TFT or the scanning line portion is light-shielding and the photosensitive resin is not formed, there is no problem for the purpose of the present invention. Absent.

In this embodiment, only the case where the additional capacitance wiring intersects only with the data line has been described. If the process is changed so that the data lines and the scanning lines are formed after the formation of the resin layer, it is obvious that the same can be applied.

Furthermore, although a negative photosensitive polyimide was used as the photosensitive resin, the present invention is not limited to a specific photosensitive resin, and other negative photosensitive resins such as a polyisoprene-based resist ( It is clear that Nippon Synthetic Rubber CBR series) and rubber-based resists (Tokyo Oka OMR series) can be applied.

〔The invention's effect〕

As described above, the active matrix according to the present invention includes:
In an active matrix in which a non-linear element and a pixel electrode are provided for each pixel, and a part of the pixel electrode is used as one electrode of an additional capacitor, an additional capacitor wiring formed of a transparent conductive film and both a data line and a scanning line or Since the intersection with one side is electrically insulated by the insulating film for forming the additional capacitance and the negative photosensitive resin layer, it is not necessary to consider an increase in the wiring capacitance, and the film of the insulating film forming the additional capacitance is not required. There is an advantage that the thickness can be set arbitrarily. In addition, there are irregularities on the surface due to the presence of conventional wiring such as active matrix TFTs and scanning lines.Therefore, the wiring formed on those irregularities has a high probability of breaking at those steps, and the yield is high. There was a drawback of lowering. However, in the active matrix of the present invention, since the Si and the wiring material constituting the TFT are opaque films, the photosensitive resin layer is not formed, and if the thickness of the photosensitive resin layer is adjusted, the step portion is flattened. Therefore, there is an advantage that the yield is improved.

[Brief description of the drawings]

FIG. 1 is a plan view of a pixel showing an embodiment of an active matrix according to the present invention, FIG. 2 is a cross-sectional view of the above embodiment taken along the line AA, and FIGS. FIGS. 4A and 4B are diagrams illustrating a manufacturing method of the embodiment, FIG. 4 is an equivalent circuit diagram of an active matrix, FIG. 5 is an equivalent circuit diagram of an active matrix when an additional capacitor is formed, and FIG. FIG. 7 is a conceptual diagram of an active matrix when an additional capacitance is formed. FIG. 7A is a diagram showing a case where a data line and an additional capacitance line intersect, and FIG. FIG. 10 is a diagram illustrating a case where an additional capacitance line intersects both a line and a data line. DESCRIPTION OF SYMBOLS 1 ... Scanning line 2 ... Data line 3 ... Non-linear element 4 ... Pixel electrode 5 ... Additional capacitance wiring 6 ... Insulating film for additional capacitance formation 7 ... Negative photosensitive resin layer

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Noboru Hagiwara Nippon Telegraph and Telephone Corporation, 1-6-1, Uchisaiwaicho, Chiyoda-ku, Tokyo (56) References JP-A-1-283519 (JP, A) JP-A Sho 60−230118 (JP, A)

Claims (2)

(57) [Claims] In an active matrix in which a non-linear element and a pixel electrode are provided for each pixel, and a part of the pixel electrode is used as one electrode of an additional capacitor, an additional capacitor wiring formed of a transparent conductive film, a data line and An active matrix, wherein an intersection of both or one of the scanning lines is electrically insulated by an additional capacitance forming insulating film and a negative photosensitive resin layer. 2. A method of manufacturing an active matrix in which a non-linear element and a pixel electrode are provided for each pixel, and a part of the pixel electrode is used as one electrode of an additional capacitor, wherein a transparent conductive film is formed on a main surface of a transparent substrate. After forming an additional capacitance line, an insulating film for forming an additional capacitance is deposited, a pixel electrode is formed with a two-layer film of a transparent conductive film and an opaque conductive film, and a negative photosensitive resin is applied to the substrate. Exposure from the back surface of the opaque conductive film and the like, the negative photosensitive resin layer is formed on a region other than the light-shielding portion, and the region includes the negative photosensitive resin layer and the insulating film for forming an additional capacitance. Form an insulating film,
A method for manufacturing an active matrix, comprising a step of forming a data line and / or a scanning line on the insulating film.