JPH0348826A - Production of mim type nonlinear switching element - Google Patents

Abstract

PURPOSE:To eliminate the influence in the end parts of a metal and to avoid element fluctuations by subjecting the metal to a heat treatment in a nitrogen atmosphere or a plasma treatment in a compd. contg. nitrogen after patterning thereof at the time of forming the MIM type nonlinear switching element having a 3-layered structure consisting of the metal-insulator-metal of a liquid crystal element device. CONSTITUTION:The alpha-Ta metal 2 is formed at 100 to 500nm thickness by a reactive sputtering method in the gaseous Ar atmosphere added with 1 to 20% nitrogen on a glass substrate 1. Then, the metal 2 is patterned by a photoetching method. Plural sheets of such substrates 1 are then spaced from each other and are erected in a heating furnace, not shown, where the gaseous nitrogen is passed at >=1l/sec. The substrates are then subjected to the heat-treatment for 10 minutes to 3 hours at the temp. kept at 150 to 550 deg.C. Insulators 3 are otherwise deposited similarly over the entire exposed surface of the metals 2 by using tantalum oxide and these metals and insulators are embedded into transparent picture element electrodes 4 to be provided on the substrate 1.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an element having a three-layer structure of metal-insulator-metal, which is one of the switching elements installed in a liquid crystal display device.
Metal-Insulator-Metal.

The present invention relates to a method of manufacturing a MIM element (hereinafter referred to as an MIM element).

[Conventional technology]

MIM elements have electrical characteristics such as high resistance when the applied voltage is low and low resistance when the applied voltage is high, and can be easily formed on glass substrates, so they are used as switching elements in liquid crystal display devices. It is proposed to use.

The method of manufacturing this MIM element in the conventional example is shown in Fig. 6(a).
) and (b).

First, tantalum (T
a) form. After that, photosensitive resin is formed on the entire surface,
The photosensitive resin is patterned by exposure and development using a mask, and the metal 2 is patterned by so-called photo-etching, in which the patterned photosensitive resin is used as an etching mask to etch the metal 2.

Next, an insulator 6 is formed on this metal 2 using an anodic oxidation method, a thermal oxidation method, or the like.

Thereafter, a transparent conductive film is formed on the entire surface of the substrate, and this transparent conductive film is battered using photoetching to form a transparent pixel electrode 4, thereby manufacturing an MIM element. (Japanese Unexamined Patent Publication No. 57-196290) [Problem to be Solved by the Invention] When attempting to use an MIM element as a switching element installed in a liquid crystal display device, for example, Japanese Patent Application Laid-Open No. 59-13
According to the 1974 publication, in order to drive a pixel with a size of 014 mm square, an M I M element with a size of 5 μm square is required. As the density of display devices increases, the dimensions of pixels are required to be further miniaturized, and the dimensions of MIM elements are also required to be further miniaturized.

Furthermore, when forming tantalum as the aforementioned metal 2, a method is generally used in which α-Ta, which has a low resistivity, is formed by reactive sputtering in an atmosphere in which a small amount of nitrogen gas is added to argon gas. Even if the amount of nitrogen gas added is constant, the amount of nitrogen taken into the tantalum film will be small if the film formation rate is high, and the amount of nitrogen taken into the tantalum film will be large if the film formation rate is low. was found through experiments by the inventor.

Furthermore, it was also found that the current-voltage characteristics of the MIM device depended on the amount of nitrogen incorporated.

On the other hand, in so-called in-line sputtering, in which a substrate holder facing a sputter target performs sputtering while continuously moving over the sputter target, the deposition rate is high when the substrate holder is near the sputter target, and when the substrate holder is located far from the sputter target, There is a phenomenon in which the film formation rate decreases as the thickness increases.

For this reason, the inventor's analysis revealed that a large amount of nitrogen is incorporated into the upper layer 12 and lower layer 11 of the tantalum film, as shown in FIG. 6(b).

Due to these phenomena, the above-mentioned MIM element manufacturing method has the following problems.

(a) When the dimensions of the MIM element become smaller than 5 μm square, the effect on the current-voltage characteristics of the MIM element in Figure 6 (b)
) can no longer be ignored.

(b) At the end of the metal 2, there are both a layer in which a large amount of nitrogen is incorporated and a layer in which a small amount of nitrogen is incorporated.

(c) Due to the influence of the edge of metal 2, the current of the MIM element -
Large variations occur in voltage characteristics.

B) Due to the influence of the edge of the metal 2, the stability and reproducibility of the current-voltage characteristics of the MIM element are significantly reduced.

An object of the present invention is to eliminate the influence of the edge of the metal on the current-voltage characteristics caused by the existence of layers with a large amount of nitrogen introduced and layers with a small amount of nitrogen introduced at the edge of the metal, and to stabilize the current-voltage characteristics. MI that provides highly reproducible and consistent current-voltage characteristics
A method for manufacturing an M element is provided.

[Means to solve the problem]

In order to achieve the above object, the present invention performs at least one of a heat treatment in a nitrogen atmosphere or a plasma treatment using a compound containing nitrogen after patterning a metal.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a cross-sectional view showing a method for manufacturing an MIM device according to an embodiment of the present invention in the order of steps, and FIG. 2 is a plan view of the MIM device according to the present invention.

This will be explained below with reference to FIGS. 1 and 2.

First, as shown in FIG. 1(a), tantalum (α-Ta) was deposited as the metal 2 in a thickness of 10 Qnm to 10 Qnm on a glass substrate 1 using a reactive sputtering method in an argon gas atmosphere containing 1% to 20% nitrogen. It is formed to have a thickness of 500 nm. Next, as shown in FIG. 1(b), the metal 2 is patterned by etching tantalum using photoetching.

Thereafter, the glass substrate 61 is placed in a heating furnace 62 as shown in FIG.
, and heat treatment is carried out for 10 minutes to 3 hours while heating the sample to a temperature of 1506C to 550C with the heating wire 65 while exhausting air from the exhaust port 64. Or Figure 4 (
As shown in a), nitrogen (N!), ammonia (NH
3) Among compounds containing nitrogen such as laughing gas (NtO),
Introducing at least one type of gas from the gas introduction port 36,
An insulating seal 47 is installed inside the vacuum chamber 42 which is exhausted from the exhaust port 64.
A glass substrate 31 is placed on an electrode 46 which is electrically isolated from the surroundings by a pressure 10 and connected to a high frequency power source 49.
Pa ~ 100 Pa, high frequency power density 0.1 W/i ~
Perform plasma treatment at 5 W/crl for 1 to 30 minutes. Alternatively, as shown in FIG. 4(b), the plasma treatment may be performed by placing a substrate 61 on an electrically grounded electrode 45.

Incidentally, as shown in FIG. 5, a glass substrate 6 is placed inside the vacuum chamber 42.
1, the aforementioned gas is introduced from the gas inlet 46, exhausted from the exhaust port 44, and high frequency power is applied from the high frequency power source 49 to the electrode 46.The same effect can be obtained by using a so-called barrel type device. .

Thereafter, in order to obtain the insulator 6 as shown in FIG. 1(c), tantalum as the metal 2 was anodized in a citric acid solution of 0.5 g/l to 50 g/l).

Alternatively, instead of this anodizing method, a temperature of 200°C to 4°C can be used.
Tantalum oxide as the insulator 6 is formed by a so-called thermal oxidation method in which heat treatment is performed in an oxygen atmosphere at 50 DEG C. to a thickness of 5 nm to 1100 nm. Alternatively, tantalum oxide, silicon oxide, silicon nitride, or the like is formed over the entire surface to a thickness of 5 nm to 1100 nm using a sputtering method, a vapor deposition method, a chemical vapor deposition method, or the like.

Thereafter, as shown in FIG. 1(d), in order to form a transparent pixel electrode 4, a transparent conductive film such as ITO (I
n2O5*sno, ) is formed to a thickness of 50 nm to 500 nm using a sputtering method or a vapor deposition method, and the ITO is patterned by photoetching to form the MI.
Obtain M element.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to eliminate the influence of metal edges and to manufacture MIM elements stably, with good reproducibility, and without variation. If the present invention is applied to the manufacture of liquid crystal display devices, the effects will be tremendous.

[Brief explanation of drawings]

FIGS. 1(a) to 1(d) show MI in one embodiment of the present invention.
2 is a cross-sectional view showing the manufacturing method of the M element in the order of steps, FIG. 2 is a plan view of the M I M element in an embodiment of the present invention, and FIG. 3 is a diagram showing heat treatment in a nitrogen atmosphere in an embodiment of the present invention. 4(a), (b) and 5 are all schematic diagrams showing how plasma treatment is performed in an embodiment of the present invention, and FIG. 6(a) is a perspective view of the first drawing, and FIG. Figure 6(b) shows M by the conventional manufacturing method.
FIG. 3 is a cross-sectional view of an IM element. 1...Glass substrate, 2...Metal, 6...Insulator, 4...Transparent pixel electrode. Figure 2 Figure 3

Claims (1)

[Claims] A process of forming metal on the entire surface of the glass substrate and patterning the metal by first photoetching, and at least one of heat treatment in a nitrogen atmosphere or plasma treatment in a nitrogen-containing compound atmosphere. a step of forming an insulator on the surface of the metal; and a step of forming a transparent conductive film on the entire surface and patterning the transparent conductive film in the shape of a transparent pixel electrode by a second photo-etching. MI featuring
A method for manufacturing an M-type nonlinear switching element.