JP3327146B2 - Liquid crystal panel, method of manufacturing the same, and electronic equipment using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a non-linear element and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, large-capacity matrix liquid crystal panels have begun to be used as display devices for various video-related devices, measuring instruments, information devices, and portable personal computers. When these liquid crystal panels are classified according to the address method, a simple matrix method, an active matrix method,
It is classified into an optical addressing method, a thermal addressing method, and the like. Among the above, the active matrix method is manufactured by various companies as a high-quality and large-capacity display and is on the market in large quantities. A typical active matrix liquid crystal panel is a TFT liquid crystal panel using amorphous silicon or polysilicon. The display quality of a liquid crystal panel using a non-linear element (TFD, MIM, varistor, etc.) related to this patent has been improved with the years, and is approaching a TFT. However, disconnection or short circuit occurs in a process of manufacturing the MIM element. I could not improve the yield of the panel. In the case of an MIM panel, the ratio of the pixel capacitance to the element capacitance is one factor that determines the contrast. Therefore, when manufacturing a large-capacity panel, it is necessary to reduce the element dimensions. The non-uniformity of the display called unevenness or spots is likely to become apparent, which also results in lowering the yield. As described above, the MIM panel, which is considered to be shorter in manufacturing process and easier to realize a lower cost than the TFT, actually has a high yield without increasing the yield.

A detailed description will be given below using a conventional example of an MIM panel.

FIG. 2 is a view showing a cross-sectional shape of a peripheral portion of an MIM element used in a conventional MIM panel.
A Ta film is laminated on a glass substrate 27 and thermally oxidized to form a base TaOx film 21. Thereafter, a Ta layer 22 serving as a lower metal of the MIM is laminated, patterned, and anodized to form TaOx layers 25 and 26 (I of the MIM).
Layer). Furthermore, on top of this, Cr serving as an MIM upper electrode is formed.
The MIM element shown in FIG. 2 can be obtained by laminating and patterning the layer 23 and electrically connecting the layer 23 to the pixel ITO electrode 24.
(However, steps such as annealing have been omitted.) In the MIM element having this shape, it is difficult to keep the yield of the panel high because disconnection or short-circuit easily occurs. Although some short-circuit defects of the element cannot be dealt with in terms of appearance, many of the short-circuit defects often differ from normal parts in appearance. In particular, the electric field tends to concentrate on the edge portions 28 and 29 of the element, and if there is a projection or the like there, dielectric breakdown occurs at that portion, which may lead to a short circuit.

FIG. 3 is a view showing a mechanism in which a disconnection failure occurs in a conventional MIM panel.

FIG. 1A shows an example in which a disconnection occurs at the edge of a Ta pattern. A step is formed between the anodized film 35 and the base oxide film 33, and the step coverage of the chromium film 32 to be subsequently sputtered is deteriorated. Become. In the anodized film, the shape of the lower edge of the Ta layer rapidly changed in level, so that disconnection was likely to occur.

FIG. 2B shows an example in which chromium breakage occurs at a slightly separated place instead of at the edge of the Ta pattern. This is due to the fact that the deposit 38 is laminated near the Ta pattern during dry etching and the chromium formed thereon is formed. This is a case where chromium breaks 37 are induced during etching due to poor adhesion of the film 32 or the like.

FIG. 4 is a graph showing the relationship between the driving voltage of the conventional MIM panel and the element dimensions (the capacitance ratio between the element and the pixel). The abscissa indicates the element size, but when the element size is changed, the capacitance ratio between the element and the pixel also changes in conjunction therewith, so both values are shown.

According to a curve 41 showing the relationship between the element size and the driving voltage of the panel, the MIM decreases as the element size decreases.
The driving voltage VOP of the panel gradually decreases, and the element size becomes 3.
The VOP is smallest when it is about 5 μm * 3.5 μm. As the element size is further reduced, VOP tends to increase sharply.

On the other hand, using an element having a size larger than the actual one,
The ratio of the element capacitance to the pixel capacitance is matched with the actual
The result of performing a hard simulation with the current characteristics optimized is shown by a broken line 42. Comparing this result with the curve 41 of the actual element, it can be seen that the rate of change of VOP is significantly different between the two in a region where the element size is small. This is M
The voltage-current characteristics of the IM element correspond to an extremely small current flowing through the element when the element size is small.

As described above, in a region where the element size is small, a slight change in the size leads to a large change in the driving voltage VOP, so that unevenness or spots are likely to occur on the panel. Since the magnitude of the inclination of the graph of the element size and the VOP can correspond to a narrow margin for unevenness and spots on the panel, it is preferable to make the inclination of this graph as small as possible.

The value of the current flowing through the MIM element is different between the flat portion on the top surface of the MIM element and the slope portion on the side surface, and the current value of the slope portion is smaller by about one digit than that of the flat portion having the same area. . If the element area is reduced, the area ratio of the flat portion on the upper surface of the element is reduced and the area ratio of the side inclined portion is increased. However, this alone is not enough to explain the magnitude of the decrease in the current value, and the current value actually changes more greatly.
In this regard, it seems better to consider that any of the manufacturing processes has some effect on the change in element characteristics (reduction in current value).

[0013]

SUMMARY OF THE INVENTION The conventional MI
The M liquid crystal panel has the following problems as described in FIG. 2, FIG. 3, and FIG.

That is, it has a structure in which disconnection and short-circuit easily occur in the process of manufacturing the MIM element.
In addition, the panel also has a characteristic that unevenness and spots are easily made visible.

An object of the present invention is to provide a MIM in view of the above points.
It is an object of the present invention to provide a method for solving the above drawbacks of the panel.

[0016]

The liquid crystal panel of the present invention comprises:
A liquid crystal panel having a non-linear element composed of a lower electrode on a substrate, an anodic oxide film formed on an upper surface of the lower electrode, and an upper electrode, wherein a thermal oxide film is formed on side surfaces of the lower electrode. Is formed to be thicker than the anodic oxide film, and the upper electrode is formed on upper surfaces of the anodic oxide film and the thermal oxide film.

Further, the method for manufacturing a liquid crystal panel according to the present invention comprises:
A method for manufacturing a liquid crystal panel having a non-linear element comprising a lower electrode on a substrate, an anodic oxide film formed on the upper surface of the lower electrode, and an upper electrode formed on the upper surface of the anodic oxide film A step of forming the lower electrode on the substrate, a step of laminating and patterning a thermal oxidation preventing thin film on the lower electrode, and a step of laminating a thermal oxidation preventing thin film on the lower electrode. Forming a thermal oxide film by thermally oxidizing a non-existing region; removing the thermal oxidation preventing thin film; anodizing the upper surface of the lower electrode to form the anodic oxide film; Laminating and patterning the upper electrode on the oxide film and the anodic oxide film.

Further, Mo, Ti, W or an alloy of these metals, or a silicide or nitride of these metals, Cr, Si
It is characterized in that one of Ox and SiNx is used.

Further, the liquid crystal panel of the present invention is characterized in that the non-linear element has a back-to-back structure composed of two elements connected in opposite directions.

Further, an electronic device according to the present invention includes the liquid crystal panel according to the present invention.

[0021]

[0022]

Embodiments of the present invention will be described below.

FIG. 1 shows a plan view and a sectional view of an MIM element used in the liquid crystal panel of the present invention.

(Embodiment 1) FIG. 1A is a plan view showing the periphery of an MIM element to which the present invention is applied. The MIM element 11 is formed at a portion where the data line 12 and the upper metal layer (upper electrode) 13 are orthogonal to each other. This orthogonal structure makes it difficult for the element area to change even if the glass substrate expands and contracts due to the process temperature and the like. have. 14 is pixel IT
The O electrode is electrically connected to the upper metal layer 13 of the MIM element. FIG. 1B shows a cross-sectional structure taken along a dashed line 15 shown in FIG. 1A. A lower metal layer Ta16 as a lower electrode is provided on a glass substrate 19, and the side surface 1
Thermal oxidation TaOx17 is formed in 10 and the periphery.
The upper surface of the metal layer Ta16 is covered with the anodized TaOx film 18. An upper metal layer 13 (Cr, Ti, or the like is used as an upper electrode) on these oxide films 17 and 18.
And a pixel ITO electrode 14 are formed. As can be seen from this cross-sectional shape, the oxide films 17 and 18 are flat and have no sharp step structure, the pattern of the upper metal layer 13 is hard to be cut, and the pattern width can be reduced to miniaturize the element. I can do it. In addition, the periphery of the edge portions 111 and 112 of the lower metal layer Ta has a structure in which dielectric breakdown and the like hardly occur because the thickness of the TaOx film is large. Further, in the embodiment of the present invention, even if the element size is reduced, the element side inclined portion does not contribute to the voltage-current characteristics of the element, so that unevenness and spots on the display due to variations in pattern size and process conditions are reduced. .

(Embodiment 2) FIG. 5 is a cross-sectional view of another embodiment of the MIM element used in the MIM panel of the present invention. Lower metal layer T as lower electrode on glass substrate 58
The thermal oxidation TaOx 52 is formed on the side surface. The upper surface of the lower metal layer Ta51 is anodized TaOx.
It is covered with a film 53. On these oxide films 52 and 53, an upper metal layer 54 (using Cr, Ti or the like) serving as an upper electrode and a pixel ITO electrode 55 are formed. In this cross-sectional shape, the boundary between the lower metal layer Ta51 and the thermal oxide film 52 and the glass substrate 58 does not have an abrupt step structure, so that the upper metal layer 54 was hardly cut and the number of disconnection defects was extremely reduced.
The periphery of the edge portions 56 and 57 of the lower metal layer Ta is Ta.
Since the thickness of the Ox film is large, the structure is such that dielectric breakdown and the like hardly occur.

FIG. 6 is a diagram showing an example of a manufacturing process of the MIM element used in the MIM panel of the present invention shown in FIG.

A lower metal layer Ta film 61 is formed on a glass substrate 66.
Are laminated to a thickness of 1000 to 2000 ° by sputtering. Next, a Mo film 62 for preventing thermal oxidation is laminated thereon by sputtering, and is patterned into a predetermined shape by photoetching.

Thereafter, in an oxygen atmosphere, at 400 ° C. to 500 ° C.
At this temperature, a thermal oxide film 63 of Ta is formed. At this time, the thermal oxide film 63 has a thickness of 1500 to 3000 °.

Next, after removing the Mo film 62 for preventing thermal oxidation, an anodic oxide film 64 of the lower metal layer Ta61 is formed on the surface.

After annealing the device, the upper metal is sputtered on the anodic oxide film 64 using Cr, Mo, Ti, W, etc., and is patterned to form an upper metal layer 65. Is formed.

(Embodiment 3) FIG. 7 is a diagram showing a plane pattern of an MIM element according to another embodiment of the present invention. M
The IM elements 71 and 72 are two elements connected in opposite directions, and have such a structure in order to eliminate a polarity difference. The elements 71 and 72 have upper metal layers 74 and 7 as upper electrodes.
5 (74 is a data line) and a lower metal layer 73 whose surface is anodized are formed at a portion orthogonal to each other (this structure is called a back-to-back device). The data line 74 includes a lower metal layer 73 serving as a lower electrode of the MIM elements 71 and 72, an anodized layer, an upper metal layer 74,
75 is formed at the same time as being laminated. The pixel ITO electrode 76 is formed on the upper metal layer 75 of the MIM element.
The pixel liquid crystal molecules are moved in accordance with a signal written to the pixel ITO electrode 76 and display is performed. According to this element structure, it is difficult to apply a DC component to the liquid crystal layer of the pixel, and it is difficult to cause a defect called image sticking or an afterimage. Reference numeral 78 denotes a Ta layer and a Ta layer for separating the lower metal layer 73 from the lower metal layer of the data line 74 after anodizing the lower metal layer 73.
This is a pattern obtained by etching the Ox layer.

FIG. 8 is a dashed line 7 of the embodiment shown in FIG.
FIG. 7 is a diagram showing a cross-sectional structure of the MIM element at a portion 7. A lower metal layer Ta73 is formed on a glass substrate 87, and a thermal oxidation TaOx 82 is formed on a side surface 88 and a periphery thereof. The upper surface of the lower metal layer Ta73 is an anodic oxide TaOx film 8
5 covered. Upper metal layers 71, 72 (using Cr, Mo, Ti, W, etc.) are formed on these oxide films 82, 85. As can be seen from this cross-sectional shape, since the tops of the oxide films 82 and 85 are flat and there is no abrupt step structure, the pattern of the upper metal layer is hardly cut, and the pattern width can be reduced to miniaturize the element. .

An anodized TaOx film 8 serving as an insulating film
Since the current flows twice through the element 5, the thickness can be reduced to, for example, about half the thickness of the insulating film of the conventional single element shown in FIG.

Therefore, the lower metal layer 73 formed first and serving as the base material of the insulating film can be formed thin.

In the conventional device structure, the data line and the lower metal of the device are formed of the same metal. Therefore, considering the wiring resistance of the data line, the lower metal also needs to be formed relatively thick. In the structure of this embodiment, it is possible to select a lower resistance material different from the data line as the lower metal, so that the lower metal can be formed thinly, and the anodized TaOx 85 and the lower metal can be formed. The thickness of the metal layer 73 can be reduced to about 1000 °.

Accordingly, the film thickness of the thermally oxidized TaOx 82 is also reduced, so that the entire device portion can be made thinner and flatter than the conventional device.

The edge portions 89 and 81 of the lower metal layer Ta
In the vicinity of 0, the thickness of the TaOx film is relatively thick, so that the structure is unlikely to cause dielectric breakdown or the like.

Further, in this embodiment, since the dry etching step is not used when forming the pattern of the lower metal layer Ta73, the element current of the fine element is extremely reduced by the dry etching process as shown in FIG. No irregularities or spots were generated on the display due to variations in pattern dimensions and process conditions.

Reference numeral 78 denotes a pattern in which the Ta layer and the TaOx layer are etched to separate from the data line 74 after the lower metal layer 73 is anodized.

The MIM according to one embodiment of the present invention described above
A liquid crystal panel has stable and uniform characteristics of an MIM element, and thus is suitable as a display device used for, for example, a personal computer or a portable electronic device, and can display various information with high definition and high quality. .

Although a metal layer has been described as an example of the upper electrode, the present invention is not limited to metal, and ITO serving as a pixel electrode may be substituted for the metal layer. Also in that case, the effect of flattening the insulating film is produced.

[0042]

According to the present invention, in a liquid crystal panel in which a non-linear element is formed on at least one substrate, an anodic oxide film is formed on the upper surface of the lower electrode of the non-linear element on the substrate, and the upper surface is formed on the side surface. Since the thermal oxide film thicker than the anodic oxide film is formed, the electric field is concentrated at the edge of the lower electrode and short-circuit failure does not occur, and the upper electrode is not cut off by the step at the edge, so the yield is high. Is improved.

Also, since the upper electrode is difficult to cut and the upper electrode pattern of the non-linear element has a structure orthogonal to the lower electrode pattern, the element size can be reduced, and a large capacity and high definition panel can be manufactured. It has the effect that can be done. Furthermore, since the side portion of the lower electrode is covered with a thick anodic oxide film, it does not contribute to the conductive characteristics of the device, stabilizes the device characteristics in a fine device, and reduces defects such as unevenness and spots. Having.

[Brief description of the drawings]

FIG. 1 shows an MIM used in the MIM panel of the present invention.
It is the figure which shows the top view and cross section shape of an element. FIG. 1 (A)
Shows a plan view of the periphery of the MIM element of the present invention. FIG. 1B is a diagram showing a cross-sectional structure taken along a dashed line 15 shown in FIG.

FIG. 2 is a diagram showing a cross-sectional shape of a peripheral portion of an MIM element used in a conventional MIM panel.

FIG. 3 is a view showing a mechanism in which a disconnection failure occurs in a conventional MIM panel.

FIG. 4 is a graph showing a relationship between a driving voltage and a device size (capacitance ratio between a device and a pixel) of a conventional MIM panel.

FIG. 5 is a diagram showing a cross section of an MIM element of another embodiment used for the MIM panel of the present invention.

FIG. 6 is a diagram showing an example of a manufacturing process of the MIM element used in the MIM panel of the present invention shown in FIG.

FIG. 7 is a diagram showing a plane pattern of an MIM element according to another embodiment of the present invention.

8 is a diagram showing a cross-sectional structure of the MIM element at a portion indicated by a dashed line 77 in the embodiment shown in FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... MIM element 12 ... Data line 13 ... Lower metal layer 16 ... Lower metal layer 17 ... Thermal oxidation TaOx 18 ... Anodized TaOx

Claims (3)

(57) [Claims] 1. A liquid crystal panel having a non-linear element comprising a lower electrode on a substrate, an anodic oxide film formed on an upper surface of the lower electrode, and an upper electrode, wherein a side surface of the lower electrode is provided. A liquid crystal panel, wherein a thermal oxide film is formed thicker than the anodic oxide film in a portion, and the upper electrode is formed on an upper surface of the anodic oxide film and the thermal oxide film. 2. A non-linear element comprising a lower electrode on a substrate, an anodic oxide film formed on an upper surface of the lower electrode, and an upper electrode formed on an upper surface of the anodic oxide film. A method for manufacturing a liquid crystal panel, comprising: forming the lower electrode on the substrate; laminating and patterning a thermal oxidation preventing thin film on the lower electrode; Forming a thermal oxide film by thermally oxidizing a region where the thin film is not laminated; removing the thermal oxidation preventing thin film; anodizing the upper surface of the lower electrode to form the anodic oxide film A method for manufacturing a liquid crystal panel, comprising: a step of: laminating and patterning the upper electrode on the thermal oxide film and the anodic oxide film. 3. An electronic apparatus comprising the liquid crystal panel according to claim 1.