JPH0352277A - Manufacture of nonlinear element - Google Patents

Abstract

PURPOSE:To obtain an active matrix liquid crystal display device employing MIM elements having high display quality by forming an insulating film on the side face of an insulator after the insulator is formed through anodic oxidation. CONSTITUTION:An under layer metal 6, an insulator 7, an insulating film 9 and a transparent conductor 10 are provided. Here, after the metal 6 is patterned, the insulator 7 is formed through anodic oxidation, and the film 9 is formed on the side face of the insulator. In this case, current-voltage characteristic of the insulator 7 is controlled to reduce irregularity of the current- voltage characteristic between MIM(Metal Insulator Meter) elements due to the irregularity of the etching shape on the side face of the metal 6. Thus, an active matrix liquid crystal display device employing MIM element having high display quality can be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a lower metal-insulator-upper metal structure, or a lower metal-insulator-transparent conductive structure used in a liquid crystal switching element in an active matrix liquid crystal display device. The present invention relates to the structure of a nonlinear element having a physical structure (hereinafter these two structures will be referred to as MIM).

[Conventional technology]

A MIM element is, for example, a Ta-anodized film (Tag's
) It has a three-layer structure of indium tin monoxide (ITO), a lower metal layer, an insulator, and a transparent conductor.
．． When the MIM element having the 05-ITO structure is used in a liquid crystal display device, it can be manufactured through the steps described with reference to FIG.

FIG. 6(a) is a plan view showing the MIM element, and FIG. 6(b) is a sectional view taken along line CD in FIG. 6(a). Ta2 is formed on the glass substrate 1 by sputtering or patterned by etching.
The lower electrode and wiring of the MIM element consisting of a2 are formed. The planar pattern shape of Ta2 is shown by the solid line 11 in FIG. 6(a). Next, an insulator 6 was formed on the Ta2 surface by anodic oxidation. form. Next, transparent conductor 4
As a result, ITO is shaped by sputtering and patterned by photoetching to form an M made of ITO.
The shape of the upper electrode of the IM element and the pixel electrode for driving the liquid crystal is determined. The planar pattern shape of this transparent conductor 4 is shown in FIG. 6(a).
This is indicated by a broken line 12. The cross section between Ta2 and the transparent conductor 4 becomes an MIM element.

[Problem to be solved by the invention]

Figure 7 shows the MIM fabricated on the same substrate using the conventional method.
It is a graph showing current-voltage characteristics of 100 elements, and the polarity of the horizontal axis indicating voltage corresponds to the polarity of the lower electrode Ta. When Ta is used as the negative electrode, the variation (range surrounded by the maximum value and minimum value) shown by the arrow 15 in the current-voltage characteristics between each element becomes significantly large. This is because the reproducibility and stability of the etched cross section on the Ta side surface is extremely poor compared to the normal film surface, so variations in current-voltage characteristics on the side surface affect the current-voltage characteristics of the entire device. The reason is that there is.

The present invention has solved these problems, and an object of the present invention is to provide a method for manufacturing an active matrix liquid crystal display device using MIM elements with high display quality.

[Means for Solving the Problems] In an MIM element, the present invention forms an insulator by an anodic oxidation method after patterning a lower metal layer, and then forms an insulating film on the side surface of the insulator. By making the current-voltage characteristics of the MIM element dominant, variations in the current-voltage characteristics between MIM elements due to variations in the etching shape of the side surfaces of the underlying metal are reduced.

〔Example〕

Hereinafter, details of the present invention will be explained based on examples.

(Example 1) FIG. 2 is a plan view showing the MIM device manufactured according to this example, and FIGS. 1(a) to (e) are process cross-sectional views showing the A-B cross section in FIG. be. The following description will be given with reference to FIG. 1 and FIG. 2 alternately.

First, as shown in FIG. 1(a), Ta was deposited on a glass substrate 5 as a lower metal layer 6 to a thickness of 200 mm by sputtering.
(nm) shape. This is buttered by normal photo-etching. The planar pattern shape of the lower metal layer 6 is shown by a solid line 16 in FIG.

Next, as shown in Figure 1(b), citric acid 0.1 [%]
Ta, which is the lower layer metal 6, is anodized at a voltage of 30 (V) in an aqueous solution, and the Ta which is the insulator 7 is applied to the surface of the lower layer metal 6.
,0, with a thickness of 50 [nm].

Next, as shown in FIG. 1(C), a resist 8 is applied to the entire surface, and the resist 8 is formed on the upper surface of the insulator 7 by back exposure in which the entire surface is exposed from the back surface of the glass substrate 5, and then plasma CVD is applied. An insulating film 9 of SiNx is formed to a thickness of 200 nm over the entire surface by a method.

Next, as shown in FIG. 1(d), the insulating film 9 on the resist 8 is peeled off by a lift-off method in which when the resist 8 is removed, the insulating film 9 on the upper surface of the resist 8 is simultaneously removed.

Next, as shown in FIG. 1(e), as a transparent conductor 10, for example, ITO is sputtered to a thickness of 200 [
nm) is formed, and the transparent conductor 10 is patterned by ordinary photoetching. This transparent conductor 10
The planar pattern shape of is shown by the broken line 14 in FIG.

Note that the area of the manufactured MIM element portion was 16 [μM].

Figure 3 shows 100 MIM elements fabricated on the same substrate.
This shows the voltage-current characteristics of . Compared to the conventional method shown in FIG. 7, the variation in characteristics among MIM elements shown by the arrow 16 when Ta negative electrode is used is reduced.

(Example 2) A second example of the present invention will be described using FIGS. 4(a) to (e).

As shown in FIGS. 4(a) and 4(b), an insulator 7 is formed on the surface of the lower metal 6 on the glass substrate 5 in the same manner as in Example 1. Next, as shown in FIG. 4(C), as an insulating film 9, SiNx is deposited over the entire surface to a thickness of 200 (
n m ) form. Next, as shown in FIG. 4(d), this insulating film 9 is subjected to reactive ion etching (RI).
E) Ecchibug from I/c. In this RIE, the side surfaces of the lower gold layer R6 become negative and ions do not reach them, so that the insulating film 9 remains on the side surfaces without being etched. Next, as shown in FIG. 4(e), the same results as in Example 1 can be obtained by shaping the transparent conductor 10.

(Example 3) A third example of the present invention will be described using FIGS. 5(a) to (e).

As shown in FIGS. 5(a) and 5(b), an insulator 7 is formed on the surface of the lower metal 6 on the glass substrate 5 in the same manner as in Example 1. Next, as shown in FIG. 5(C), SiNx is deposited to a thickness of 300 Cn over the entire surface by plasma CVD as an insulating film 9.
m) shape, and then apply resist 8 to a thickness of 5 over the entire surface.
00 (nm) is formed. The resist 8 has the effect of alleviating the difference in level, and the surface of the resist 8 becomes substantially flat.

Next, as shown in FIG. 5(d), the insulating film 9 and the resist 8
The resist 8 and the insulating film 9 are etched under conditions such that the etching rate is the same as that of the resist 8 and the insulating film 9 until the insulator 7 is exposed. Thereafter, the same results as in Example 1 can be obtained by shaping the transparent conductor 10 as shown in FIG. 5(e).

〔Effect of the invention〕

As explained above, by forming an insulator by anodic oxidation in the MIM device or process, and then forming an insulating film on the side surface of the insulator, only the insulator on the upper surface of the lower metal can affect the current-voltage characteristics of the device. Since this is dominant, it is possible to achieve uniform electrical characteristics and to obtain an active matrix liquid crystal display device using an MIM element with high display quality. Further, the same effect can be obtained in an MIM element having a metal-insulator-metal structure other than the metal-insulator-transparent conductor structure.

[Brief explanation of drawings]

1(a) to (e) are cross-sectional views showing the method for manufacturing a nonlinear element according to the first embodiment of the present invention in order of steps; FIG. 2 is a plan view illustrating the method for manufacturing a nonlinear element according to the present invention; FIG. 3 is a graph showing the current-voltage characteristics of the nonlinear element according to the present invention, FIGS. 5(a) to (el are cross-sectional views showing the manufacturing method of a nonlinear element according to the third embodiment of the present invention in order of steps;
The figures show a conventional Ta-Ta205-ITO structure MIM element, FIG. 6(a) is a plan view, FIG. 6(b) is a cross-sectional view for explaining the manufacturing method, and FIG. 7 is a conventional Ta-Ta205-ITO structure MIM element. T
It is a graph showing current-voltage characteristics of an MIM element having a205-I To structure. 6... Lower layer metal, 7... Insulator, 9... Insulating film, 10... Transparent conductor. Figure 1 Figure 4 Figure 5 Figure 6 (b)

Claims (1)

[Claims] In a method for manufacturing a nonlinear element in which an insulator is provided on a lower metal layer by anodizing, and an upper metal layer or a transparent conductor is further provided on the insulator, the insulator is formed on the lower metal layer by an anodizing method. . A method of manufacturing a nonlinear element, comprising: next forming an insulating film on a side surface of the insulator.