JPS63148239A - Active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To make picture elements highly fine and large in area by composing the active matrix substrate of a 1st metallic thin film wire group, an anode oxide dielectric layer, a dry dielectric layer, a 2nd metallic thin film group, a semiconductor layer, an upper electrode, and a transparent picture element electrode, and providing a common electrode on an opposite substrate. CONSTITUTION:The counter electrode of a liquid crystal layer shown by the parallel circuit of liquid crystal capacity 5 and liquid crystal resistance 6 is the common electrode 7 which is the same among all picture elements. The picture elements electrode 1 which is the other electrode of this liquid crystal layer is connected to a TFD (thin film two-terminal element) shown by a parallel circuit of TFD capacity 3 and nonlinear resistance 2 and a storage capacitor shown by storage capacitor capacity 8. The TFD is connected to a 1st lead electrode 4 consisting of the metallic thin-film thin-wire group having anode oxide where the dielectric layer by a dry film forming method is not laminated and the storage capacitor is connected to a 2nd lead electrode 9 consisting of a metallic thin-film thin-wire group having anode oxide where the dielectric layer by the dry film forming method is laminated. Matrix addresses are constituted between those 1st and 2nd lead electrodes. Consequently, a highly fine display device which has large area and large display capacity is obtained at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active matrix type liquid crystal display device, and more particularly to an active matrix type liquid crystal display device in which switching means is formed on at least one substrate.

[Conventional technology]

Conventionally, various studies have been conducted regarding such active matrix liquid crystal display devices.

In recent years, the application of liquid crystal display devices (LCDs) mainly of twisted nematic type has been developed and is being used in large quantities in the fields of wristwatches and calculators.

Recently, matrix type LCDs that can display arbitrary characters such as two figures have also begun to be used.

In order to expand the field of application of this matrix type LCD, it is necessary to increase the display capacity. However, conventional LC
Since the rise of the voltage-transmittance change characteristic of D is not so steep, when the number of scans in multiplex drive is increased in order to increase the display capacity, the effective voltage ratio applied to each selected pixel and non-selected pixel decreases. , Therefore, a Talostalk occurs in which the transmittance of the selected pixel and the transmittance of the non-selected pixel decrease. As a result, the display contrast 1~ is significantly reduced, and the viewing angle at which a certain degree of contrast can be obtained becomes significantly narrower. Therefore, the number of scanning lines in a conventional LCD is about 60 lines at most.

Furthermore, in order to significantly increase the display capacity of the matrix type LCD, an active matrix type LCD has been devised in which a switching element is arranged in series in each pixel of the LCD. Thin film transistor elements (TFT) using amorphous silicon or polycrystalline silicon as semiconductor materials are often used as switching elements of active matrix LCDs that have been announced so far. On the other hand, since the manufacturing method and structure are relatively simple, the manufacturing process can be simplified, and the active Matrix type LCDs are also attracting attention.

Among the active matrix type LCDs (hereinafter referred to as TFD-LCDs) using such thin film two-terminal elements, the LCD that is considered to be closest to practical use is the TFD-LCD.
This is an LCD using a metal-semi-insulator-metal element (hereinafter referred to as an MIM element) in D. By connecting a TFD such as this MIM element in series with the liquid crystal, the rise of the voltage-transmittance change characteristic can be made steeper, making it possible to significantly increase the number of scans.

Regarding LCDs using such MIM elements, 19
Television Society technical report paper (IPDI13-8) published in December 1983, pp39-44, r25
A lateral MIM-LCD with 0x240 pixels is disclosed in JP-A-55-161273, etc., and its operating principle is also described in detail.

In the following, an MIM element, which is considered to be the closest to practical use as a TFD for LCD, will be explained as a representative example.

FIG. 11 is a conventional TFD for explaining the above-mentioned example.
- It is a sectional view of LCD.

As shown in FIG. 4, the lower glass substrate 10 and the upper glass substrate 16 are usually coated with a glass protective film 1 made of Ta205, Si02, or the like. However, this protective film can also be omitted. A lower electrode 13. is formed on the lower glass substrate 10 described above. An MIM element having a three-layer structure of a semi-insulator layer 14 and an upper electrode 15 and a pixel electrode 1 are formed to form an active matrix substrate. On the other hand, a counter transparent electrode 11 is formed on the upper glass substrate 16 to serve as a counter substrate. A TFD-LCD is constructed by sandwiching a liquid crystal layer 18 between the active matrix substrate and the counter substrate.

Next, FIG. 5 is a plan view of one pixel of the TFI-LCD shown in FIG. 4.

The first layer metal film of the MIM element mentioned in the explanation of FIG. 4 is typically a T sputtered film, and as shown in FIG. patterned into the shape of The surfaces of these electrodes are covered with a semi-insulating layer 14 formed by anodic oxidation or the like. Further, the lower electrode 13 corresponds to each pixel, and the semi-insulating layer 1
4 and intersects with the upper electrode 15. This upper electrode 15 is connected to the pixel electrode 1. The intersections formed in this way form an MIM element.

FIG. 6 is an electrical equivalent circuit diagram of the TFD-LCD shown in FIG. 4.

As shown in FIG. 6, this circuit is a circuit in which a TFD and a liquid crystal are connected in series. The components of the equivalent circuit shown in FIG. 6 are the TFD-L shown in FIGS. 4 and 5.
Corresponding to the structure of the CD, the first lead electrode 4 corresponds to the lower electrode 13 and the lead electrode 20, and the second lead electrode 9 corresponds to the opposing transparent type V511. The voltage applied to these electrodes is usually the same as the drive waveform of a simple 71-Socket LCD that does not use switching elements, and a scanning signal and a data signal are applied to the first lead electrode 4 and the second lead electrode 9. is applied. Also, this TFD
is expressed as a parallel circuit of a nonlinear resistor 2 and a TFD capacitor 3, while the liquid crystal is expressed as a parallel circuit of a liquid crystal capacitor 5 and a liquid crystal resistor 6. The pixel electrode 1 is the connection point between these TFDs and the liquid crystal.

The value ctp of the TFD capacitance 3 is the value CLc of the liquid crystal capacitance 5.
If it is sufficiently smaller than , this TFD-L CD operates ideally. At this time, all voltages corresponding to the difference between the scanning signal and the data signal are applied across the TFD, and a current flows through the TFD in accordance with the voltage. However, ctp
If CLc is not negligible compared to CLc, the voltage difference between the two signals is capacitively divided between ctp and CLC and applied to both the TFD and the liquid crystal. That is, CTF is CLC
When the value becomes approximately the same as , the TFD acts not as a nonlinear resistance but as a mere capacitor, and therefore no longer functions as a switching element. However, CL
The value of c is determined by the pixel size, liquid crystal layer thickness, and liquid crystal material, but since these values are almost fixed, the only way to realize a TFD-L'CD with a large display capacity is to reduce Ctp.

Incidentally, the CTF in the case of the above-mentioned MIM element is determined by the dielectric constant of the semi-insulating layer, its layer thickness, and the area of the junction of the MIM element. If this semi-insulator layer is made thicker, it becomes impossible to maintain the resistance switch-to-sotching ratio, so the area of the junction has to be reduced.

With such an MIM element structure, for example, the pixel portion has 200 pixels.
When displaying with a large display capacity of μm×200 μm, M
The IM element junction needs to be several μm square. It takes M
In order to form the IM element junction to such a size, LSI-level mask technology and photolithography technology are required, but it is difficult to create such a high-definition, large-capacity display without defects over a large area. It's almost impossible to make one.

FIG. 7 is a cross-sectional view of an active matrix substrate of a lateral structure M I M'=LCD for explaining another conventional example (see the above-mentioned Television Society technical paper) that solves this problem.

As shown in Figure 7, in a lateral structure MIM element,
The lower electrode 13. A semi-insulator layer 14 and a block insulator layer 21 are formed, and the block insulator layer 21 is further formed.
An upper electrode 15 is formed from above to above one glass protective film. Further, the pixel electrode 1 is formed on the glass protective film 19 so as to be connected to the upper electrode 15. In an MIM element having such a structure, a method is adopted in which the side wall 3 of the lower electrode 13 is machined and sown into a tapered shape to reduce the size of the MIM element joint, but it is difficult to obtain a uniform taper shape over the entire surface over a large area. Therefore, there was a problem that the yield could not be increased.

Therefore, as a structure to solve the above problem, a structure has been proposed in which a storage capacitor having a capacitance larger than the liquid crystal capacitance CLC is provided in parallel with the liquid crystal layer.

Figure 8 shows such a conventional storage capacitor parallel type TFD-L.
FIG. 2 is an electrical equivalent circuit diagram of a CD.

As shown in FIG. 8, this equivalent circuit has a configuration in which a storage capacitor 8 is added to the equivalent circuit shown in FIG. According to such a parallel structure of storage capacitors, the value CLC of the liquid crystal capacitor 5 on the equivalent circuit increases significantly and becomes the same as taking a constant value. This solves the drawback that the MIM element does not function as a switching element as described above.

(Problems to be Solved by the Invention) The above-mentioned conventional active matrix type liquid crystal display device can cope with an increase in display capacity, but has a problem that it cannot cope with an increase in pixel definition and a large area. be.

In particular, the equivalent circuit shown in Fig. 8 can be compared to an actual TFD-LCD.
However, it is not easy to realize this because the panel structure and the way to take out the terminals are complicated. That is, a major problem is that three sets of lead electrodes are required. In this way, the storage capacitor parallel type TFI)-L
Even for CDs, the structural complexity makes it difficult to create a practical, large-area, high-definition display device.

The purpose of the present invention is to realize higher definition and larger area than conventional pixels, and also to provide highly reliable active matrix I.
An object of the present invention is to provide a lix type liquid crystal display device.

[Means for solving problems]

The present invention provides an active matrix type liquid crystal display device having an active matrix substrate, a counter substrate facing the active matrix substrate, and a liquid crystal layer interposed between the active matrix substrate and the counter substrate so as to overlap each other. , the active matrix substrate includes a first metal thin film line group forming a capacitor counter electrode formed on this substrate, an anodic oxide dielectric layer formed on this first metal thin film line group, and this anode. a dry dielectric layer formed on the oxide dielectric layer; and a second metal thin film line formed on the dry dielectric layer so as to be perpendicular to the first metal thin film line group and serving as a lower electrode. a semi-insulating layer made of an anodic oxide formed on the second metal thin film wire group, an upper electrode formed on the semi-insulating layer, and a semi-insulating layer formed on the dry dielectric layer. and a transparent pixel electrode formed to be connected to the upper electrode, and the counter substrate is configured such that a common electrode exists on the counter substrate.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an electrical equivalent circuit diagram of an active matrix liquid crystal display device for explaining one embodiment of the present invention.

As shown in FIG. 1, this equivalent circuit is similar to the conventional storage capacitor parallel type TFD-L CD shown in FIG. 8, but differs greatly in the following points.

That is, the opposing electrode of the liquid crystal layer represented by the parallel circuit of the liquid crystal capacitor 5 and the liquid crystal resistor 6 in this equivalent circuit is the same common electrode 7 for all pixels. A pixel electrode 1, which is the other electrode of this liquid crystal layer, is connected to a TFD represented by a parallel circuit of a TFD capacitor 3 and a nonlinear resistor 2, and a storage capacitor represented by a storage capacitor 8. The TFD is connected to a first lead electrode 4 made of a metal thin film wire group having an anodic oxide without laminating a dielectric layer formed by a dry film formation method, and the storage capacitor is laminated with a dielectric layer formed by a dry film formation method. It is connected to a second lead electrode 9 made of a metal thin film wire group having positive TFI oxide, and a matrix address is formed between the first and second lead electrodes.

In comparison with the conventional TFD-LCD equivalent circuit shown in FIG. 6 mentioned above, the present invention has a structure in which a storage capacitor is placed in place of the liquid crystal layer, and the liquid crystal layer is connected to the contact between the TFD and the storage capacitor. This is the basic structure of TFD-LCD. Because of this shape, the TFD-LCD according to the present invention is sometimes called a storage capacitor addressing diode type LCD. In short, storage capacitor capacity 8 (C5T
) is TFD capacity 13 (Ctp) and liquid crystal capacity 5 (etc
), the potential of the pixel electrode 1 is hardly affected by the connection of the upper layer after 1. Therefore, the counter electrodes of the liquid crystal layer can be kept in common.

As described above, the TFD-LCl) according to the present invention is similar to the storage capacitor parallel type TFD described above, but the TFI)-LCD according to the present invention has a simpler panel structure. In particular, only two sets of lead electrodes are required as in the conventional case, and since all lead electrodes are formed on the same substrate, it is easy to take out the terminals.

Next, the storage capacitor, which is an important component of the TFD-LCD according to the present invention, will be explained.

This storage capacitor is located between the pixel electrode 1 and the second lead electrode 9. Therefore, storage capacitors are typically made by forming a dielectric layer on the second lead electrode and forming the pixel electrode thereon.

This dielectric layer has a two-layer structure of an anodic oxide layer and a dry dielectric layer. The typical anodic oxide layer is tantalum Ta anodic oxide, but this niobium N1
), aluminum A I , silconium Zr, hafnium Hf, tungsten W.

So-called valve metals such as bismuth Bi and antimony sb, and anodic oxides of alloys containing them are used. On the other hand, the dry dielectric layer can be made of various materials (Ta205, Si
o, S i 02 , S i3'N4, etc.) are used. The film formation methods are vacuum evaporation, ion blating, and ion cluster beam.

By using a dry film forming method in vacuum or reduced pressure such as sputtering method 9 In this way, by forming the dielectric layer into a laminated film of two types of thin films manufactured using different manufacturing methods, it is possible to Since short circuits between the counter electrode and the lower electrode and an increase in leakage current can be completely suppressed, a TFD-LCD with high amortization properties and no display defects can be realized.

FIG. 2 is a sectional view of one pixel of the display device in FIG. 1.

As shown in FIG. 2, the lower glass substrate 10 is made of Ta205
．． Although it is covered with a glass protective film such as St02, this protective film is not essential and is therefore omitted in FIG. On top of these, tantalum Ta was formed to a thickness of 4000 mm by sputtering or ion blating, and patterned into strips with a line width of 60 μm and a pitch of 200 μm by reactive etching using CF4 gas to form capacitor counter electrodes. 11 is formed. In short, this capacitor counter electrode 11 is composed of a metal thin film wire group having an anodic oxide. Next, Ta2
05 to a thickness of 1800 mm to form the dielectric layer 12. Next, a dry dielectric layer 30 is formed by coating T a 205 to a thickness of 4000 nm on the dielectric layer 12 by sputtering. Such dielectric layers 12 and 3
0 is formed on the entire upper surface of the lower glass substrate 10 except for the opposing transparent electrode, and a vapor deposition mask is used at this time.

The subsequent manufacturing process is almost the same as the MIM element manufacturing method described in the description of the conventional example.

First, Ta is again formed to a thickness of about 3000 on the dry dielectric layer by sputtering, and then patterned to form the lower electrode 13 by reactive ion etching using CF4 gas. This lower electrode 13 and the capacitor counter electrode 11 are orthogonal to each other with a dielectric layer interposed therebetween.

This lower glass substrate 10 is again immersed in 0.1% citric acid and anodized using the tantalum plate as a counter electrode to form a Ta205 semi-insulating layer 1.1 on the lower electrode 13. Cr is formed on this semi-insulator layer 14 using a vacuum evaporation method, and patterned using normal photolithography to form an upper electrode 15. Furthermore, ITO is formed by sputtering and patterning to form the pixel electrode 1.

The cross section of the lower electrode 13 and the upper electrode 15 is the MI
This becomes the M element junction, and the overlap between the pixel electrode 1 and the opposing transparent electrode via the dielectric layers 12 and 3.0 becomes a storage capacitor.

On the other hand, the E portion glass substrate 16 is the lower glass substrate 1 described above.
Although it is covered with a glass protective film like 0, it is omitted here because it is not essential.

ITO is formed on the entire surface of the display section on this upper glass substrate 1.6 to form a common transparent electrode 17.

The lower glass substrate 10 and the two-part glass substrate 16 are pasted together with a spacer such as a glass fiber and sealed with a common epoxy adhesive. Note that the thickness of this cell is approximately 9) tm.

Twisted nematic liquid crystal is injected into the cell formed by laminating such substrates together to form a liquid crystal layer 18, and the injection hole is sealed with an adhesive to complete a TFD-LCD.

FIG. 3 is a diagram of one pixel of the display device in FIG. 1.

As shown in FIG. 3, in the area of one pixel of this display device, the capacitor counter electrode 11 and the lower electrode 13
The lower electrode 13 and the upper electrode 15 are perpendicular to each other, and the upper electrode 15 is connected to the pixel electrode 1. Note that each component is the same as that explained in FIG. 2, so the explanation thereof will be omitted here.

In this embodiment, the dielectric layer between the capacitor counter electrode 11 and the pixel electrode 1, and between the capacitor counter electrode 11 and the lower electrode 13 has a two-layer structure of Ta2O by anodizing and Ta205 by sputtering. There are no problems such as displays between signal lines due to the presence of pinholes or display defects due to increased capacitor leakage current, etc., and the highly reliable rF D-1-CD t! -Can be obtained.

Further, in this embodiment, Ta2O5 was used as the dry dielectric layer by sputtering, but it can also be formed by ion blating. Furthermore, Ta20
By adding SiO□ to No. 5, the leakage current can be further reduced. Furthermore, similar results can be obtained by using S iz N,1 manufactured by plasma CVD method instead of Ta205 as the dry dielectric layer described above.

〔Effect of the invention〕

As explained above, according to the present invention, even when the pixel definition is high, the pattern accuracy of the TFD can be coarse, so it is possible to provide a large-area, high-definition, large-display capacity TpD-LcD3 with a low cost of 1 or more. This also means that the capacity of the liquid crystal is increased in terms of an equivalent circuit, so that there are effects such as a marked improvement in gradation display performance. In particular, by making the dielectric for the storage capacitor have a two-layer structure of an anodic oxide layer and a dry dielectric layer, the device of the present invention provides a highly reliable TFD-LCD with no display defects at a high yield. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is an electrical equivalent circuit diagram of an active matrix type liquid crystal display device for explaining one embodiment of the present invention, and FIG. 2 is a cross-sectional view of one pixel of the display device in FIG. 1.
3 is a diagram of one pixel of the display device in FIG. 1, FIG. 4 is a sectional view of a TFIl-LCD for explaining a conventional example, and FIG. 5 is a cross-sectional view of a TFIl-LCD shown in FIG. L CD
Figure 6 is a plan view of one pixel of the TFD-LC shown in Figure 4.
Dt7) Electrical equivalent circuit diagram, Figure 7 is a sectional view of the active matrix substrate of a lateral structure MIM-LCD to explain another conventional example, and Figure 8 is an electrical diagram of a conventional storage capacitor parallel type TFD-LCD. FIG. . 1... Pixel electrode, 2... Nonlinear resistance, 3... TI
" D capacitance, 4... First lead electrode, 5... Liquid crystal capacitance, 6... Liquid crystal resistance, 7... Common electrode, 8... Storage capacitor capacitance, 9... Second lead electrode , 10...
・Lower glass substrate, 11... Capacitor counter electrode, 1
2... Dielectric layer, 13... Lower electrode, 1/1...
- Semi-insulator layer, 15... Upper electrode, 16... Upper glass substrate, 17... Common transparent electrode, 18... Liquid crystal layer,
1...Glass protective film, 20...Lead electrode, 21
...Block insulator layer, 30...Drag eraser 1 Required 2 Figure 4 Figure 5 Figure 7 Chrysanthemum

Claims (1)

[Claims] An active matrix type liquid crystal display device having an active matrix substrate, a counter substrate facing the active matrix substrate, and a liquid crystal layer interposed so as to overlap between the active matrix substrate and the counter substrate,
The active matrix substrate includes a first metal thin film line group forming a capacitor counter electrode formed on the substrate;
An anodic oxide dielectric layer formed on this first metal thin film line group, a dry dielectric layer formed on this anodic oxide dielectric layer, and an anodic oxide dielectric layer formed on this first metal thin film line group; a second metal thin film line group formed perpendicularly to the metal thin film line group and serving as a lower electrode; a semi-insulator layer made of an anodic oxide formed on the second metal thin film line group; It has an upper electrode formed on the semi-insulating layer, and a transparent pixel electrode formed on the dry dielectric layer and connected to the upper electrode, while the counter substrate An active matrix liquid crystal display device characterized by having a common electrode on a substrate.