JPS63144501A - Thin film nonlinear resistance element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an M I M having a metal-insulator-metal structure.
(Metal In5ulator Metal) element.

Conventional clamping Conventional MIM elements utilize their nonlinear resistance characteristics to
It is used as a switching element to increase the display capacity of liquid crystal display devices. The insulator of this MIM element is generally formed by anodic oxidation of the lower metal because it is easy to obtain uniform characteristics over a large area. However, due to the principle of anodic oxidation, this MIM element
Individuals have an asymmetry in that voltage-current characteristics differ when the polarity of the voltage differs. If there is asymmetry, a direct current component will remain in the liquid crystal portion, which will deteriorate the display quality of the liquid crystal and shorten the life of the liquid crystal, which is not preferable.

Therefore, conventionally, the asymmetry was canceled out by connecting two 1MIM elements in series in opposite directions, as shown in Japanese Patent Application Laid-Open No. 60-241022 (Figure 3).
, In Fig. 3, 31 is a substrate, 33 is a first gold shoulder electrode, 35 is an insulator, 37 is a second metal electrode, 39 is a photoresist for insulation, and 41 is a pixel electrode.6 In Fig. 3, A4B If a current flows in the direction, the current will be M-)I→M→I-+ M (
M: Metal, I: In5ul-ator
), and the asymmetry is certainly offset.

However, as can be seen in FIG. 3, the contact between the second gold R electrode 37 and the insulator 35 is a planar contact. Assuming that the unit pixel is a square and the pixel size is 0.3 to 0.5III, the contact area of the MIM element is 50 mm due to the capacitance.
It is required that the thickness be less than μ112, preferably less than 25 μm2. This corresponds to C<7 μm in FIG. 3, assuming that the contact surface between the second metal electrode 37 and the insulator 35 is square. This is difficult to achieve using normal photolithography, and there is also a problem in that the use of precision photolithography techniques used in LSIs increases costs.

On the other hand, the lateral MIM element shown in Figure 4 is known as a method of reducing the contact area between the metal electrode and the insulator of the MIM element without requiring precise photolithography technology (Television Society of Japan Technology Report IPD83
-8. (Announced on December 15, 1982). In Figure 4, 51
53 is a substrate, 53 is a lower metal electrode, 55 is an MIM element insulator layer, 57 is an insulator such as polyimide, and 59 is a lower metal electrode.

61 is a pixel electrode. This method takes advantage of the fact that the length of the thin film in the film thickness direction can be easily adjusted, and etches the side surface of the lower metal electrode 53 into a tapered shape, and then anodizes this tapered part to insulate the MIM element. By forming the body layer 55, it is possible to reduce the contact area between the insulator layer 55 and the upper gold-conductive dielectric layer 59 without using precision photolithography technology.

However, although this method is useful, since the insulating layer is formed by anodic oxidation as described above, there is a problem that the V-1 characteristics are asymmetrical.

2 Precepts The present invention connects two of the above-mentioned lateral elements in opposite directions.
-■ The present invention provides an MIM element whose characteristics are symmetrical and whose manufacture does not require precision photolithography technology.

3 weeks 40'' The MIM element of the present invention has an insulating layer for controlling the anodic oxidation area of the first metal electrode formed on the upper surface, and both sides of the insulating layer and the first metal electrode form tapered slopes, +'* is applied to the first metal electrode layer in which the tapered portion is anodized to form an insulator layer for MIM element P, and the insulator layer for MIM element formed in the tapered portions on both sides. It is characterized by having two second metal electrode layers.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an embodiment in which the MIM element of the present invention is used as a substrate for a liquid crystal display element. A pixel electrode 15 is formed on the substrate 11 and connected to the signal line electrode 13 via an MIM element 21 . The MIM element 21 includes an MIM element insulator layer 25127 formed by oxidizing the tapered portions on both sides of the first metal electrode 23, and a second gold electrode 29.31 electrically connected to the insulator layer 25.27, respectively. It consists of An insulator [33] is provided above the first metal electrode 23 to control the anodized area of the first metal electrode 23 and to prevent electrical conduction between the second electrodes 21 and 3.

When a voltage is applied to the signal line electrode 13, the current flows as follows: second metal electrode 29 (M) → MIM element insulator layer 25 (1) → first metal electrode 23 (M) → MIM element insulator layer 27 (1) → Flow from the second metal electrode 31 (M) to the pixel electrode 15, M-I-
M-IM, which means that two MIM elements are connected in series in opposite directions.

In the configuration shown in FIG. 1, the second metal electrode 29°31 and M
Since the contact portion with the IM element insulator layer 25, 27 has a tapered portion, it is easy to miniaturize the contact area. Even if the thickness of the first metal electrode is 5000 mm, the length of the tapered portion of the MIM element insulator layer 25.27 is at most 700 mm.
0 to 8,000 people. Therefore, the contact area is 20μff
Even if it is +2, the width is 25 μm (20 μm2 ÷ 0.8 μf
f1), which can be easily achieved using current photolithography technology.

In addition, in the present invention, two MIM elements are connected in series in opposite directions, which causes problems such as shortening of the life of the liquid crystal due to the asymmetry of the V-1 characteristic, which was a problem with the bow chiral element shown in Fig. 4. is resolved. This also makes use of the lateral structure having two tapered portions for one line of the first metal electrode. As will become clear from the description of the manufacturing method below, the number of steps is the same as that of the conventional lateral element. Therefore, the MIM element of the present invention can be manufactured without using precision photolithography technology and without increasing the number of steps, and has a significant effect in improving yield and characteristics.

The MIM device of the present invention can be manufactured by sequentially performing each of the first steps.

(1) Step of sequentially forming a first metal electrode thin film and an insulating layer thin film on a substrate.

(2) The laminated film obtained in step (1) is patterned and etched so that both sides are tapered to form a laminated body of the first metal electrode and an insulating layer for controlling the anodized area. The process of doing.

(3) Anodizing the tapered parts on both sides of the first metal electrode,
Step of forming an insulator layer for MIM element.

(4) A step of patterning and forming two second metal electrodes so as to be connected to the MIM element insulator layers of the tapered portions on both sides, respectively.

Next, the manufacturing method will be explained in more detail by taking a substrate for a liquid crystal display element as an example.

First, the first metal electrode thin film 22 and the insulating layer thin film 32 are sequentially formed on the substrate 11 (FIG. 2A).

This laminated thin film is dry-etched under the condition that one side has a tapered shape to form a laminated body of the first metal electrode 23 and the insulating layer 33 for controlling the anodic oxidation area (FIG. 2B).
,.

The first metal electrode 23 is anodized to form an insulator layer 25, 27 for the MIM element (FIG. 2C). At this time, the insulating layer 33 acts as a protective film and the tapered part is selectively anodized, so by regulating the length of the tapered part, the contact area between the second metal electrode and the MIM element insulating layer can be reduced. Can be adjusted.

A transparent conductive material such as IT○ is made into a thin film by sputtering or vapor deposition, and a transparent pixel electrode 15 and a signal line electrode 13 are formed by one step of photolithography (Fig. 1D).
.

A thin film for the second metal electrode is formed, and a single photolithography process is used to form the transparent pixel electrode 15 and the MIM element insulator layer 27, as well as the signal line electrode 13 and the MIM element insulator layer 25. The second metal electrodes 29, 31 are formed by patterning to make them conductive (FIG. 2E).

As the first metal electrode, a metal that can be anodized, for example, A
Q, Ta, Cr, etc. are used.

As the second metal electrode, Cr, Ni, NiCr, Au, Ag, etc. are used.

The insulating layer is made of polyimide, A2□0. .

Ta2O,, Cr2O,, SiO,, Sin.

TiO□ etc. may be used, and the film thickness is 1000~t.
Approximately oooo people.

The MIM device of the present invention can be manufactured without requiring precision photolithography technology, compared to a conventional MIM device in which two MIM devices are connected in series in opposite directions. Furthermore, compared to conventional lateral MIM devices, an MfM device with no asymmetry in V-1 characteristics can be produced without increasing the number of steps, which has a significant effect in improving yield and characteristics.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the MIM element of the present invention. 2A to 2E are explanatory diagrams showing the method for manufacturing the MIM element of the present invention. Figures 3 and 4 are. FIG. 2 is a sectional view showing a conventional structure. 11... Substrate 15... Pixel electrode 21...
MIM element 23...first metal electrode 25.27...
MIM element insulator layer 29, 31... second metal electrode 33... insulating layer

Claims (1)

[Claims] 1. Nonlinear resistance element with metal-insulator-metal structure (
(hereinafter referred to as an MIM element), an insulating layer for controlling the anodic oxidation area of the first metal electrode is formed on the upper surface, and both sides of the insulating layer and the first metal electrode form tapered slopes,
A first metal electrode whose tapered portion is anodized to form an MIM element insulating layer, and two second metal electrodes each connected to the MIM element insulating layer formed on the tapered portions on both sides. A thin film nonlinear resistance element characterized by having an electrode.