JP3306923B2 - Liquid crystal device manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an MIM type nonlinear element used for a liquid crystal display device or the like.

[0002]

2. Description of the Related Art In general, in an active matrix type liquid crystal display device, a non-linear element is provided for each pixel region to form a matrix array and a substrate on the other side on which a color filter is formed. Is filled with liquid crystal, and predetermined information is displayed by controlling the alignment state of the liquid crystal in each pixel region. Here, as a nonlinear element, TF
T terminal or two terminal such as MIM type nonlinear element
Although a terminal element is used, a system using an MIM type non-linear element is advantageous in order to meet demands such as a large screen and low cost for a liquid crystal display panel. In the case where an MIM type nonlinear element is used, a scanning line can be provided on one substrate on which a matrix array is formed and a signal line can be provided on the other substrate. There is also an advantage that an over short circuit does not occur.

In an active matrix type liquid crystal display device using an MIM type nonlinear element, as shown in FIG. 5, a MIM type nonlinear element is provided between each scanning line 501 and each signal line 502 in each pixel region 503. 504 (shown by a varistor in the figure) and a liquid crystal display element 505 (shown by a capacitor in the figure) are connected in series, and based on signals applied to scanning lines and signal lines. The display operation is controlled by switching the liquid crystal display element between a selected state (display state) and a non-selected state (non-display state).

Conventional Example 1 Conventionally, as shown in FIGS. 3 and 5, a Ta electrode layer 302 (conductively connected to a scanning circuit (driving circuit) via a scanning line 501 for each pixel region 503 in a matrix array. A first metal electrode layer) and this Ta
Ta ₂ formed on the surface of the electrode layer 302 by anodic oxidation
O ₅ film 303 (element insulating film) and this element insulating film 303
A transparent substrate 301 on which a Ta ₂ O ₅ layer 301a (Ta thermal oxide film) is formed in advance by a Cr electrode layer 304 (second metal electrode layer) conductively connected to a pixel electrode 305 made of ITO A MIM type non-linear element is formed on the surface of.

(Conventional Example 2) In the structure of the MIM type nonlinear element of the above-mentioned Conventional Example 1, the symmetry of the element characteristics is poor, and the display quality of the liquid crystal display device is deteriorated. In order to solve the problem relating to this characteristic, a method of connecting MIM type nonlinear elements having characteristics in opposite directions in series (Back-to-B
ack scheme) has been proposed.

In this method, until the formation of an element insulating film,
This is the same as Conventional Example 1. After the formation of the element insulating film, the element part is separated from the wiring part by etching, and the part for forming the MIM type nonlinear element is left in an island shape.

Next, a Cr electrode layer which is conductively connected to the pixel electrode is formed.

Further, in both of the conventional examples 1 and 2, a simplified process of forming the second metal electrode layer and the pixel electrode from the same material and the same layer may be possible.

[0009]

In the back-to-back method described in the prior art 2, the number of steps is increased as compared with the conventional method of manufacturing a MIM type nonlinear element. One of the cost advantages was not fully utilized.

[0010]

Means taken to solve the above problems in the present invention are as follows: a first metal electrode layer is formed on a substrate, and an anodic oxidation layer formed on the surface of the first metal electrode layer is formed. In a method for manufacturing a liquid crystal device including a non-linear element constituted by a film and a second metal electrode layer formed on the surface of the anodic oxide film, the first metal electrode layer supplies a drive signal to the non-linear element. A step of forming an anodic oxide film on the surface of the first metal electrode layer, comprising a wiring portion to be supplied and an element portion constituting the nonlinear element connected to the wiring portion; Anodizing is selectively performed on only the element portion among the wiring portion of the electrode layer and the element portion connected to the wiring portion. Further, in the method for manufacturing a liquid crystal device, after the step of forming an anodic oxide film on the surface of the first metal electrode layer, the method further includes a step of separating the wiring section and the element section, The step of separating the element portion from the element portion is characterized in that the first metal electrode layer and the second metal electrode layer are simultaneously etched using the same mask. In the method for manufacturing a liquid crystal device, the first metal electrode layer is an aluminum layer, and the second metal electrode layer is ITO.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing an MIM type nonlinear element according to the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing a process of the MIM type nonlinear element of the present invention, and FIG. 2 is a sectional view taken along lines AB and C in FIG.
3D is a cross-sectional view of the MIM type nonlinear element,
FIG. 4 is a cross-sectional view of an IM-type non-linear element, FIG. 4 is a cross-sectional view of an MIM-type non-linear element using an already proposed method of connecting elements having reverse characteristics in series, and FIG. FIG. 3 is an equivalent circuit diagram of an active matrix type liquid crystal display device.

In the MIM type nonlinear element according to the present invention,
First, after an Al layer is formed on the surface of the transparent substrate 201 by sputtering, this is patterned to form an Al electrode layer 202. At this time, the Al electrode layer is patterned as shown in FIG.

Next, a photoresist is applied to the entire surface of the substrate, exposed and developed, and the photoresist is removed only from the portion of the Al electrode layer 101 where the MIM type nonlinear element is to be formed. The photoresist as a mask, by performing selective anodic oxidation by applying a voltage so that a predetermined thickness on the Al electrode layer 202 of the portion to be a MIM nonlinear device is obtained, the surface layer Al ₂ O _Three layers 203 (element insulating films) are formed. At this time, as shown in FIG. 1B, only the portion 102 is anodized. The photoresist used as a mask for anodization is removed after the anodization using a stripping solution.

Next, after forming an ITO layer by sputtering, M
A portion forming an IM type nonlinear element, a portion used for wiring, and a portion serving as a pixel electrode are collectively patterned to form an ITO electrode layer 204 and a pixel electrode 205. At this time, a portion of the ITO electrode layer 204 used for wiring is used.
Is formed on the Al electrode layer 202a formed in the previous step, covers the entire Al electrode layer 202a,
01 and conductively connected to the scanning circuit. By completely covering the Al electrode layer 202a of the wiring with the ITO electrode layer 204, it is possible to prevent Al corrosion and disconnection due to the ITO etchant.

The Al ₂ O ₃ is due to its high chemical resistance, for corrosion by etchant ITO, no care needs to be taken.

It is a well-known fact that the contact resistance between Al and ITO is high irrespective of the stacking order, and this may cause a problem in some cases. This is not particularly a problem because the structure is such that the wiring is directly connected and the ITO and Al are capacitively coupled and conductively connected to the scanning circuit.

At the same time as the patterning of the ITO electrode layer, the wiring section and the MIM type nonlinear element section are separated. In this element separation step, the Al electrode layer 202a and the Al electrode layer 202b are separated using the same mask as the ITO electrode layer 204,
The MIM type nonlinear element portion is left in an island shape. At this time, Al is also etched by the ITO etchant, so that a separate step for element isolation is not required unlike the MIM type non-linear element manufacturing process of Conventional Example 2.

Al etching may be performed using an Al etching solution after the ITO etching. Further, the photoresist applied at the time of patterning the ITO electrode layer and the pixel electrode may be peeled off at any of a stage where the etching of ITO is completed and a stage where etching of Al is completed. For simplification of the process, Al is preferably etched using an ITO etchant, and then the photoresist is removed.

In the conventional manufacturing process of the MIM type nonlinear element, etching of the Ta electrode layer and element isolation are performed by dry etching. At this time, it is pointed out that contamination or the like by a photoresist or a re-deposited substance may affect the element characteristics of the MIM type nonlinear element. Further, at this time, the Ta thermal oxide film is also etched, and uneven etching due to the Ta thermal oxide film not being uniformly etched appears on the substrate, which affects the display quality of the liquid crystal display device. In an embodiment of the present invention,
Since no dry etching step is performed, such a problem does not occur.

The device section ITO electrode layers 104 and 105
The spacing, so are at a sufficient distance than the thickness of the Al ₂ O ₃ film, with respect to the leakage current through the Al ₂ O ₃ film
There is no particular problem.

In the simplification process of the MIM type nonlinear element of the conventional example 2, the sputtering process is performed twice, the photolithography process is performed three times, and the etching process is performed three times. The process is performed twice, the photolithography process is performed three times, and the etching process is performed twice.

According to the embodiment of the present invention, the total number of manufacturing steps can be reduced by suppressing the number of etching steps to two, so that the cost advantage, which is one of the major characteristics of the MIM type nonlinear element, can be utilized.

[0024]

As described above, according to the present invention, the wiring has a two-layer structure of Al as the first metal electrode layer and ITO as the second metal electrode layer constituting the MIM type non-linear element. Anodization is selectively performed only on the Al electrode layer of the portion constituting the type nonlinear element, the wiring and the element portion are separated, the second metal electrode layer and the pixel electrode are made of the same material, and the MIM having the reverse characteristics is provided. It is characterized in that it has a structure in which type nonlinear elements are connected in series.

According to the present invention, the same mask as that of ITO is used to separate the wiring section and the MIM type nonlinear element section from the ITO.
Is performed at the same time as the etching, so that there is an effect that the manufacturing process can be simplified.

[Brief description of the drawings]

FIG. 1 is a plan view showing a process of an MIM type nonlinear element of the present invention.

FIG. 2 (a) shows the M of the present invention in the section AB in FIG. 1;
FIG. 3 is a cross-sectional view of an IM type nonlinear element. FIG. 2B is a cross-sectional view of the MIM type nonlinear element of the present invention, taken along a line CD in FIG.

FIG. 3 is a cross-sectional view of a MIM type nonlinear element of Conventional Example 1.

FIG. 4 is a cross-sectional view of a MIM type nonlinear element of Conventional Example 2.

FIG. 5 is an equivalent circuit diagram of an active matrix type liquid crystal display device using an MIM type nonlinear element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 101 Al electrode layer 102 Al electrode layer anodic oxidation part 103 MIM type nonlinear element part 104 Element part ITO electrode layer 105 Element part ITO electrode layer 201 Transparent substrate 202 Al electrode layer 202a Al electrode layer wiring part 202b Al electrode layer element part 203 Al ₂ O ₃ film (element insulating film) 204 ITO electrode layer 205 Pixel electrode 301 Transparent substrate 301 a Ta ₂ O ₅ layer (Ta thermal oxide film) 302 Ta electrode layer 303 Ta ₂ O ₅ film (anodic oxide film) 304 Cr electrode layer 305 Pixel electrode 501 Scan line 502 Signal line 503 Pixel area 504 MIM type nonlinear element 505 Liquid crystal display element

Continuation of the front page (56) References JP-A-4-251825 (JP, A) JP-A-3-259226 (JP, A) JP-A-2-170137 (JP, A) JP-A-6-29534 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/1362 H01L 49/02

Claims (3)

(57) [Claims] A first metal electrode layer, an anodic oxide film formed on the surface of the first metal electrode layer, and a second metal electrode layer formed on the surface of the anodic oxide film. In the method for manufacturing a liquid crystal device provided with a nonlinear element constituted by the above, the first metal electrode layer is a wiring section for supplying a drive signal to the nonlinear element, and an element constituting the nonlinear element connected to the wiring section And forming an anodic oxide film on the surface of the first metal electrode layer, wherein the wiring portion of the first metal electrode layer and the element portion connected to the wiring portion A method for manufacturing a liquid crystal device, comprising selectively anodizing only the element portion. 2. The method for manufacturing a liquid crystal device according to claim 1, further comprising a step of separating the wiring section and the element section after the step of forming an anodic oxide film on the surface of the first metal electrode layer. Wherein the step of separating the wiring section and the element section comprises simultaneously etching the first metal electrode layer and the second metal electrode layer with the same mask. Device manufacturing method. 3. The method of manufacturing a liquid crystal device according to claim 1, wherein said first metal electrode layer is an aluminum layer, and said second metal electrode layer is an ITO layer.
A method for manufacturing a liquid crystal device, comprising: