JPH0348821A - Production of nonlinear element - Google Patents

Abstract

PURPOSE:To form the element which decreases leak current and has uniform element characteristics by forming a lower layer metal on a substrate, than forming an insulator on the lower layer metal and heat treating the surface of the insulator in an oxygen atmosphere under irradiation with UV rays, then forming an upper layer metal. CONSTITUTION:The lower layer metal 2 consisting of Ta and wirings are formed on the glass substrate 1. The Ta is then anodized and TaO is formed as the insulator 3 on the surface of the lower layer metal 2. The surface of the insulator 3 is heat treated in the oxygen atmosphere under the irradiation with the UV rays to embed the defect 7 on the insulator 3 surface, such as oxygen hole, which is the cause for the leak current; thereafter, the insulator is diffused in the film by heat to embed to defects in the insulator 3 as well, by which the leak current is decreased. An upper layer metal 4 and ITO as picture element electrodes for liquid crystal driving are then formed. The nonlinear element having a MIM element structure to be used for the liquid crystal switching element having high quality and high density is obtd.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a nonlinear element having a metal-insulator-metal structure (hereinafter referred to as MIM) used in a liquid crystal switching element in an active matrix type liquid crystal display panel. Regarding the manufacturing method.

[Conventional technology]

Liquid crystal display panels have been put into practical use, and higher density is currently desired. This is possible in the active multi-'J-socks type using MIM elements.

In MIM elements, the conductor can be considered a metal,
For example, tantalum (Ta) - tantalum oxide (Tag) -
Metal-insulators such as indium tin oxide (ITO)
When an MIM element having a conductor (metal) structure is used in a liquid crystal display panel, it can be manufactured by the following steps. FIG. 4(a) is a plan view showing a liquid crystal display panel, and FIG. 4 (bl is an enlarged sectional view of the AB section in FIG. 4(a).

Hereinafter, explanation will be given with reference to (4) and (b) alternately.

Ta is formed on a glass substrate 1 by sputtering, and lower metal 2 and wiring 5 of the MIM element are formed by photoetching.

Next, in a 0.1% citric acid aqueous solution, Ta
is anodized, and TaO is applied as an insulator 6 to the surface of the lower metal 2.
form. Next, ITO is formed by sputtering, and then the upper metal layer 4 of the MIM element and the pixel electrode 6 for driving the liquid crystal are formed by photoetching.

[Problem to be solved by the invention]

It is said that the anodic oxidation method produces relatively fewer pinholes in the insulator than other insulator formation methods such as plasma chemical vapor deposition and sputtering. However, the anodic oxidation method is sensitive to the surface condition of the metal before anodization, and it is difficult to form a uniform, defect-free insulator.

FIG. 3(b) is a current-voltage characteristic diagram of the MIM element. The device characteristics of an MIM device are largely determined by the film thickness and film quality of the insulator, and if there is a defect in the insulator, the voltage decreases by 10''A on the low voltage side as shown in Figure 3(b).
A leakage current of ~10''12A occurs, and variations in element characteristics occur for each element in the low voltage region.

An object of the present invention is to solve these problems and provide a method for manufacturing a high-quality, high-density liquid crystal display panel by forming an element with low leakage current and uniform device characteristics.

[Means to solve the problem]

The purpose of the above is to form a lower metal layer, then form an insulator on the lower metal layer, and then form an upper layer metal on the insulator. This problem can be solved by using a process of heat treatment in a lower oxygen atmosphere.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Figures 1(a) to (C) show the MI manufactured according to this example.
FIG. 4 is a cross-sectional view showing the manufacturing method of a liquid crystal display panel using an M element in order of steps, and corresponds to the A-B cross section in FIG. 4 (al). Hereinafter, FIGS. This will be explained with reference to fa).

As shown in FIG. 1(a), Ta is deposited on a glass substrate 1.
Thickness 200nm to 11000n by sputtering method
Formed and patterned by photo etching,
A lower metal layer 2 made of Ta and a wiring 5 are formed. The planar pattern shape of the lower metal 2 and the wiring 5 is shown in FIG.
).

Next, as shown in Fig. 1 fb), Ta is anodized at a voltage of 30 V in a 0.1% citric acid aqueous solution to form 'P on the surface of the lower metal 2 and TaO as the edge 6 to a thickness of 50 nm. do.

Next, heat treatment is performed in an oxygen atmosphere under ultraviolet irradiation under the conditions described below.

Substrate heating: 250'C to 400°C Pressure: near 60 torr Ultraviolet wavelength: 254 nm Ultraviolet cut: 10 mW/c111 to 60 mW
/cn1 hour: 0.5h ~ 3h Oxygen partial pressure: l 50 torr ~ 76 Q tor
r As shown in Figure 2, when UV irradiation is performed in an oxygen atmosphere, oxygen becomes very active oxygen radicals (0"). Active oxygen radicals (0") are the source of leakage current. Defects 7 on the surface of the insulator 6, such as oxygen vacancies, are filled in, and then the oxygen is diffused through the film by heat to fill in the defects in the insulator 6, thereby reducing leakage current.

Next, as shown in FIG. 1(C), ITO was deposited as the upper layer metal 4 and the pixel electrode 6 for driving the liquid crystal using a sputtering method.
A thickness of 200 nm=1 OOO nm is formed, and the upper metal layer 4 of the MIM element made of ITO and the pixel electrode 6 for driving the liquid crystal are formed by photoetching. The planar pattern shape of the upper layer metal 4 and the liquid crystal driving pixel electrode 6 is as follows:
It is shown in FIG. 4(a).

FIG. 3(a) shows the device characteristics of the MIM device manufactured according to this example. The leakage current on the low voltage side is 10-”A
It was possible to suppress the temperature to below, and uniform device characteristics were obtained.

In this example, an example using an insulator formed by an anodic oxidation method has been described, but an insulator made of a silicon oxide film, a silicon nitride film, etc. However, it has the effect of reducing leakage current.

Further, in this embodiment, Ta is used as the lower layer metal 2, and Ta is used as the upper layer metal 4.
Although TaO was used as the ITO 1 insulator 3, MIM elements can also be manufactured using other metals such as aluminum, chromium, tungsten, and nickel as the upper and lower layer metals, and silicon nitride or silicon oxide as the insulator. I can do it.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, defects in the insulator surface and film are filled, and leakage current is reduced by 10-"13
Since M of uniform device characteristics can be suppressed to below A,
It is possible to produce an I M element, and a high-quality, high-density liquid crystal display panel can be obtained.

[Brief explanation of drawings]

Figures 1 (a) to fc) are cross-sectional views showing the manufacturing method of a liquid crystal display panel using an MIM element manufactured according to the implementation sequence of the present invention in order of steps, and Figure 2 is a cross-sectional view showing a method of manufacturing a liquid crystal display panel using an MIM element manufactured according to the implementation sequence of the present invention. An explanatory diagram modeling the reaction inside, Figure 3 is MI
Figure 3 (a) is a graph showing the current-voltage characteristics of the M element.
3(b) is a graph showing the device characteristics of the M element manufactured by the manufacturing method of the present invention, and FIG.
A graph showing the device characteristics of the device, FIG. 4 shows a liquid crystal display panel using the MIM device, FIG. 4(a) is a plan view, and FIG. 4(b) is a It is a sectional view of cross section B. 1...Glass substrate, 2...Lower metal,
6... Insulator, 4... Upper layer metal,...
・・・Wiring, ・・・Pixel electrode for driving liquid crystal. Figure 1 (CI) (b) (C) Figure 3 (G) Figure 3 (b)

Claims (1)

[Claims] In the method for manufacturing a nonlinear element, in which a lower metal layer is formed on a glass substrate, an insulator is formed on the lower metal layer, and an upper metal layer is then formed on the insulator, after the insulator is formed, the insulator A method for manufacturing a nonlinear element, comprising the step of heat-treating the surface in an oxygen atmosphere under ultraviolet irradiation.