JPH056793A - Manufacture of thin film el element - Google Patents

Abstract

PURPOSE:To provide a manufacturing method capable of easily manufacturing a large-sized thin film EL element having a high dielectric voltage resistance which is excellent in driving reliability. CONSTITUTION:An aluminium thin film 6 is formed on a base 1, a resist 7 is applied thereto followed by patterning, aluminium anode oxidation of two stages is conducted to form a lower dielectric thin film 3 having a satisfactory step coverage to an aluminium electrode stripe. Then, a phosphor thin film 4, an upper dielectric thin film 5, and an ITO transparent electrode thin film 2 are successively laminated to complete a thin film EL element.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thin film E used in office automation equipment such as word processors and personal computers and FA equipment such as various measuring instruments.
The present invention relates to a method for manufacturing an L element.

[0002]

2. Description of the Related Art Conventionally, in a thin film EL element, a transparent electrode thin film is formed on a glass substrate by a sputtering method, and then processed into a stripe-shaped electrode pattern by a photolithography process, and then a sputtering method, an electron beam heating evaporation method or CVD
Dielectric thin film, phosphor thin film, dielectric thin film are sequentially laminated by the method, and finally aluminum metal thin film is formed, and the metal thin film is also photolithographically processed and the striped electrodes orthogonal to the striped transparent electrode thin film are formed. It was processed and manufactured.

The lowermost layer of the laminated film, that is, the transparent electrode thin film pattern, is desired to have a stripe with a lower resistance as the element becomes larger. Therefore, it is necessary to increase the film thickness for that purpose.
A step becomes prominent at the pattern edge. Therefore, the thickness of the dielectric thin film laminated on the edge portion tends to be smaller than that of other portions. This state is shown in FIG.

[0004]

A thin film EL element manufactured by the manufacturing method described in the prior art is a base electrode, that is, a transparent electrode usually made of indium tin oxide (hereinafter referred to as I
2 is abbreviated as TO), which is located in the lowermost layer of the laminated thin film and is processed into a stripe shape, so that there is a step at the edge.
Unless the step coverage of the dielectric thin film 3 laminated on this portion is good, the electrical breakdown voltage thereof is insufficient, and there is a problem that dielectric breakdown easily occurs at the time of driving. In addition,
1 is a glass substrate, 4 is a phosphor thin film, 5 is an upper dielectric thin film, and 6 is an aluminum metal electrode thin film.

Further, when the size of the device is increased, the electric resistance of the lengthened ITO stripe becomes high and the input electric signal is delayed, resulting in uneven brightness along the ITO electrode 2 during driving. That is, the power supply terminal side is brighter, and becomes darker as the distance from the terminal increases. In order to deal with this, if the film thickness of ITO 2 is increased, there is a problem that the step difference of the edge is further increased in the conventional structure, which is not preferable.

The present invention is to solve the above-mentioned problems of the conventional thin film EL device,
That is, it is an object of the present invention to provide a method for manufacturing a thin film EL element that solves the problems of breakdown voltage and size increase.

[0007]

According to the present invention, a step of forming an aluminum metal thin film for an electrode on an insulating substrate, a resist is applied to a portion on which an electrode pattern is to be formed, and a portion other than the above is applied. A step of completely anodizing to form an aluminum anodized thin film, and then peeling off the resist,
A step of partially anodizing from the surface of the electrode pattern portion to a predetermined depth to form an aluminum anodic oxide film, and a phosphor thin film on the upper surface of the aluminum anodic oxide film,
And a step of sequentially forming a dielectric thin film and a patterned transparent electrode thin film.

[0008]

According to the manufacturing method of the present invention, the influence of the pattern edge of the electrode-like aluminum metal thin film and the influence of the resistance of the transparent electrode thin film electrode can be reduced. Due to this effect, a large-sized thin film EL element having an excellent withstand voltage can be manufactured.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram sequentially showing one embodiment of a method of manufacturing a thin film EL element of the present invention. Figure 1
(A) shows a cross-sectional view after forming an aluminum metal thin film 6 on a glass substrate 1 to a thickness of 2500 Å, spin-coating a resist 7 on it, and patterning it in stripes by a photolithography process. Is. The resist 7 has a cross section perpendicular to the length direction of the stripe. In this state, use aluminum as the anode 240
A voltage up to V was gradually applied while controlling a constant current of 1 mA / cm ² to form an anodized thin film of aluminum. The chemical conversion solution used was a solution in which a 0.1 molar ammonium tartrate aqueous solution and ethylene glycol were mixed at a volume ratio of 1: 9, and a small amount of an ammonia aqueous solution was added to adjust the pH to 7.0. Unlike the acidic aqueous solution, when such a neutral solution is used as the aluminum conversion solution, a so-called dense barrier type anodic oxide film is obtained. A similar thin film can be obtained by using adipate, borate, phosphate, phthalate, maleate or citrate instead of ammonium tartrate. The temperature of the chemical conversion liquid is 40-50 ° C.
To prevent the resist from deteriorating during formation because it was too high. Since an anodic oxide film having a thickness of 14 Å can be formed per 1 V of applied voltage, it is possible to completely change the aluminum having a thickness of 2500 Å to an anodic oxide film at 240 V. That is, normally, when anodizing aluminum, an anodized film 3 having a thickness about 1.3 times that of aluminum is obtained. However, the portion not covered with the resist is completely anodized to obtain the original aluminum thickness of 2500 Å. It was converted to an aluminum anodic oxide film 3 having a thickness of 3300Å. Figure 1 shows the cross section at that time.
It is shown in (b). Next, after the resist 7 was peeled off, anodic oxidation of aluminum was performed again by applying a voltage of 93V. As a result, the anodic oxide film 3 having a thickness of 1300 Å was formed on the aluminum metal 6 having a thickness of 1500 Å, and the cross-sectional structure shown in FIG. 1C was obtained. The thickness of the aluminum anodic oxide film on the aluminum metal can be changed by controlling the applied voltage. As is clear from the cross-sectional view, the aluminum metal stripe 6 has a structure in which the aluminum anodic oxide film 3 is embedded, and the anodic oxide film dielectric does not become relatively thin even on the edge of the aluminum stripe. It is becoming thicker from the edge to the outside of the stripe near the edge. That is, by forming the dielectric thin film of the aluminum anodic oxide film 3 by the above method, very good step coverage can be realized for the aluminum electrode stripe 6. This structure was heat-treated at 300 ° C. for 1 hour in an air atmosphere in order to remove volatile components such as water contained in the anodic oxide film 3. Then, as shown in FIG. 1D, ZnS: Mn
Phosphor thin film (0.8 atomic% Mn content) 4 5000
Å Similarly, 330 aluminum anodized dielectric thin film 5
Finally, the ITO transparent electrode stripe 2 orthogonal to the aluminum electrode stripe 6 was laminated at 6000 Å to complete a thin film EL device. The dielectric thin film 5 is not limited to the above-mentioned aluminum anodic oxide film, and since the step coverage of the lower dielectric thin film 3 is important, other types of dielectric thin films by other methods may be used.
However, it is advantageous to use the same aluminum anodic oxide film as the lower dielectric thin film 3 in consideration of manufacturing facility costs and ease of manufacturing. Similarly, use of a tantalum anodic oxide film having excellent characteristics as an anodic oxide film is also advantageous in terms of ease of production. Further, unlike the structure of FIG. 2, the ITO transparent electrode thin film 2 is arranged at the uppermost part because it is necessary to take out light emission from the side opposite to the glass substrate 1 as shown by the arrow, but the thin film EL element Since it is located at the uppermost portion of the laminated film that does not participate in the step formation, the thickness can be changed according to the requirements of the electrical resistance of the stripe. Generally, it is 3 for a large EL display device with a diagonal of 10 inches.
An ITO transparent electrode with a thickness of 000 to 6000Å is used. A higher definition display device requires a thicker ITO electrode thin film.

With the method described above and each film thickness, the aluminum electrode stripe and the ITO transparent electrode stripe are 300 × 300 lines (line pitch 0.33 mm, line width 0.23 mm) at 10 cm square (diagonal 5.6 inch). A relatively large EL display device was produced. At the same time, an EL display element of the same size and the same number of lines as that of the type of FIG. 2 in which the thin film laminated structure of FIG. That is, the glass substrate / ITO transparent electrode (6
000Å) / Aluminum oxide dielectric (3300Å) /
ZnS: Mn phosphor (5000Å) / aluminum oxide dielectric (1300Å) / aluminum metal electrode (150
A thin film EL device having a structure of 0Å) was prepared for comparison. The aluminum oxide dielectric is formed by high frequency magnetron sputtering with aluminum oxide as the target. An AC pulse (pulse width: 30 μsec) of 500 Hz was applied to both of them, and both were driven by full surface emission at the same average luminance of 500 cd / m ² , and the number of pinholes of dielectric breakdown after 5000 hours was examined and compared with each other. As a result, 123 dielectric breakdown pinholes were generated in the conventional thin-film EL element manufactured by the ordinary method, whereas only 2 thin-film EL elements manufactured by the method of the present invention were manufactured. Only pinholes were observed. Also,
The mode of the dielectric breakdown was not the propagation type but the local dielectric breakdown. In this way, the method of forming the base electrode of aluminum and simultaneously producing the aluminum anodic oxide dielectric thin film by anodic oxidation was applied. Also,
In order to reduce the resistance of the ITO stripe even if the thin film EL element is enlarged, the thickness of the thin film EL element can be increased as much as possible.
The TO electrode was placed on top of the laminated film. Although such a structure generally facilitates propagation type dielectric breakdown, insulation is obtained by forming a structure in which the influence of the edge of the electrode pattern does not occur and using a dielectric material by the anodization method that is generally homogeneous and has few defects. Prevented destruction.

[0012]

As described above, since the thin film EL element manufactured by the manufacturing method of the present invention has a much higher dielectric breakdown voltage than the thin film EL element manufactured by the conventional method, stable and highly reliable driving is possible. .

Further, the restriction of the increase in size due to the electric resistance of ITO can be avoided by the structure of the thin film EL element manufactured by the manufacturing method of the present invention. Therefore, I
Even if the resistance of the TO electrode stripe is reduced and the thickness thereof is increased, the size can be easily increased without affecting the withstand voltage.

Further, the production method of the present invention is technically mature,
Moreover, since the anodic oxidation technology, which is relatively low in cost, is applied as an oxide film forming apparatus, it is a significant method in industrial production.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for sequentially explaining one embodiment of a method of manufacturing a thin film EL element of the present invention.

FIG. 2 is a cross-sectional view of a thin film EL element manufactured by a conventional method.

[Explanation of symbols]

1 glass substrate 2 ITO transparent electrode thin film 3 Lower dielectric thin film 4 Phosphor thin film 5 Upper dielectric thin film 6 Aluminum metal electrode thin film 7 Resist

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Jun Kuwata             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd.

Claims (3)

[Claims] 1. An aluminum anode in which a step of forming an aluminum metal thin film for an electrode on an insulating substrate, a resist is applied to a portion on which an electrode pattern is to be formed, and the other portion is completely anodized. A step of forming an oxide thin film,
Subsequently, a step of peeling off the resist and partially anodizing from the surface of the electrode pattern portion to a predetermined depth to form an aluminum anodic oxide film, and a phosphor thin film and a dielectric on the upper surface of the aluminum anodic oxide film. A method of manufacturing a thin film EL element, comprising the steps of sequentially forming a thin film and a patterned transparent electrode thin film. 2. The method for manufacturing a thin film EL element according to claim 1, wherein the dielectric thin film sandwiched between the phosphor thin film and the transparent electrode thin film is produced by an anodic oxidation method. 3. The method of manufacturing a thin film EL element according to claim 2, wherein the dielectric thin film is an anodized film of aluminum or tantalum.