JPH03179690A - Thin film electroluminescence element and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a high luminance emission characteristic, and to achieve driving at a low voltage by including 0.1-5.0 volume % of hydrogen in a luminous layer thin film. CONSTITUTION:0.1-5.0 volume % of hydrogen is included in a luminous layer thin film. Namely, when the amount of hydrogen in the luminous layer thin film is less than 0.1 volume % or exceeds 5 volume %, the reduction in luminance is remarkable, while it is not less than 100fL when the amount is in the range from 0.1 volume % to 5 volume %, whereby the luminance is stabilized in a good condition. The luminance becomes twice that or more, achieved by a conventional method, while an emission element of low driving voltage can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a thin film EL (electroluminescence) element that has high luminance luminescence characteristics and can be driven at low voltage, and a method for manufacturing the same.

[Prior Art] Recently, electroluminescent (hereinafter referred to as EL) elements have been put into practical use as displays for graphics and messages, and are used as broadcasting equipment.

A typical example of a thin film EL element is shown in FIG.

In the figure, 1 is a glass substrate, 2 is a transparent electrode, 3 is a high dielectric layer, 4 is a light emitting layer, 5 is a back electrode, and 6 is an AC electrode.

A S n 02 film was deposited to a thickness of about 3000 as a transparent electrode 2 on a glass substrate 1, and then a 5 ia film was deposited as a high dielectric film 3.
A film of N4 is formed to a thickness of about 3000 nm, and a rare earth material is added to ZnS as the light emitting layer 4.

For example, a film added with fluoride molecules such as Tb
0 people are each vacuum evaporated. Furthermore, 2 Si3N4
000 thin film is formed, and furthermore, as the back electrode 5, an opaque vapor-deposited film of aluminum metal is formed. The color of the emitted light varies depending on the rare earth fluoride substance introduced as the luminescent center.

The principle of light emission is that an alternating current voltage is applied between the S n O2 transparent electrode 2 and the rear aluminum metal electrode 5 through an alternating current electrode 6, and when the voltage exceeds a certain level, the light emission becomes stronger. Due to the structure of the device, the emitted light is reflected by the aluminum electrode 5 on the back side and is entirely radiated toward the glass substrate 1 side. Typical elements, such as Z n S
: Maximum 100 rL when using T b F 3
(f'L: Foot Lambert) green light emission is obtained.

Conventionally, the following manufacturing methods have been used to increase the brightness and drive voltage of these thin film EL elements.

The following methods have been used to improve the quality of the light-emitting layer.

(1-1) Vapor deposition m called atomic layer epitaxy (ALE)
Both the light emitting layer and the dielectric layer are manufactured using the ALEa.

(1-2) An EL thin film is manufactured by molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD).

As another method, (2-1) pbTI using an insulating layer for low voltage drive.
A method using a high dielectric constant material such as O3.

(2-2) Lower the voltage by placing the insulating layer on one side.

(2-3) DC-driven EL element.

(2-4) In addition, consider the structures of the electrode layer, insulating layer, and light emitting layer to lower the voltage and increase the brightness. For example, there is a method of using a black dielectric material as an insulating layer.

[Problems to be Solved by the Invention] The conventional method for manufacturing a thin film EL element as described above has the following problems.

1) With the conventional light-emitting layer production method, it is not possible to significantly increase brightness and reduce voltage. With ZnS and Mn, which emit yellow-orange light, high brightness can be obtained using normal thin film production methods, but high brightness cannot be obtained with red, especially blue, and this is a major reason why full color cannot be produced.

Furthermore, white EL, which has recently been expected to be used as a light source for color displays or liquid crystals, has not been put into practical use because high brightness cannot be obtained. The reason for this is presumed to be that although the crystal quality of the base material of the light-emitting layer is improved, the distribution state of the substance at the luminescence center is not improved.

In addition, in other methods (2-1), in order to create a highly insulating PbTiO3 film, the substrate must be heated to a high temperature of 600°C or higher, so the light emitting layer is affected by this high temperature heating. receive.

(2-2) One-side insulation type elements have slow response when voltage is applied, that is, a slow rise in brightness, and have low luminance.

(2-3) Although it is possible to lower the voltage of the DC drive element, the amount of current is large, resulting in large power consumption and poor stability.

(2-4) There are problems such as the fact that even if the film structure of EL is improved, it is not possible to significantly lower the voltage and increase the brightness.

An object of the present invention is to provide a thin film EL device and a method for manufacturing the same, which solves the problems of the conventional methods described above.

[Means for Solving the Problems] A first aspect of the present invention is a thin film EL device characterized in that a light emitting layer thin film contains 0.1 to 5.0% by volume of hydrogen; 2 is a method for manufacturing a thin film EL device characterized by laminating a light emitting layer by an electron cyclotron resonance (ECR) sputtering method, and furthermore, in the sputtering method, hydrogen gas of 10% by volume or more is used as a sputtering gas. This is a method of manufacturing a thin film EL device characterized by using the present invention.

[Function] The thin film EL device of the present invention is characterized in that the light emitting layer is laminated by an electron cyclotron resonance (ECR) sputtering method, and the reason for this is as follows.

One of the reasons why high brightness cannot be obtained in thin film EL devices is that when a luminescent center is doped into the luminescent layer matrix, an impurity level is formed due to charge imbalance, and this is caused by electrons accelerated in a high electric field. is trapped in this impurity level and does not fall into the acceptor level or valence band.

In order to reduce impurity levels, it is not only necessary to reduce impurities in the emitter, but also to reduce distortions and defects in the crystal structure.

Furthermore, in order to obtain high brightness, it is necessary to uniformly and finely distribute the luminescent centers.

As described above, the inventor of the present invention believes that in order to obtain high brightness, it is necessary to reduce distortions and defects in the luminescent material and to uniformly and finely disperse the luminescent centers. (ECR) discovered that it was sufficient to create a thin film using the sputtering method,
This led to the present invention.

Furthermore, if a gas containing hydrogen is used as the sputtering gas at this time, the effect will be even greater, and as a result, a hydrogen-containing EL light emitter will be good.

Considering the reason for this, it is thought that hydrogen compensates for the impurity level that causes the charge imbalance mentioned above.

Electron cyclotron resonance sputtering using a hydrogen-containing sputtering gas is most suitable for producing this hydrogen-containing EL luminescent material.

The reason why the thin film EL device of the present invention exhibits high luminance is that, as described in the examples below, a good crystal base material is first formed by ECR, and the luminescent centers are uniformly and finely dispersed. It is.

Further, in the thin film EL device of the present invention, the amount of hydrogen in the thin film of the light emitting layer is 0, as is clear from the graph of the relationship between hydrogen volume % in the light emitting layer and brightness (fL) in FIG. .1
When the amount is less than 5% by volume or more than 5% by volume, the brightness decreases significantly, and in the range of 0.1% to 5% by volume, the brightness becomes 100 fL or more, which is preferable because the brightness is stable. Therefore, 0.1~
It was specified that it contained 5.0% by volume of hydrogen.

The reason for this is that a certain amount of hydrogen is required to compensate for the impurity level caused by minute defects introduced during thin film formation, and beyond a certain level, the impurity level is generated more than the hydrogen itself, reducing the brightness. It will be done.

Further, as the hydrogen concentration increases, the luminance increases, but there is a drawback that the film formation rate decreases, so it is preferable to use a mixed gas of hydrogen and Ar as the sputtering gas.

Next, examples of the present invention will be described.

[Example] [Example 1] FIG. 1 is an explanatory diagram of an apparatus for carrying out the present invention, and FIG. 2 is a structural diagram of a double-structure thin film EL element which is an embodiment of the present invention.

In the figure, 3a is a lower insulating film, 3b is an upper insulating film, 11 is a microwave, 12 is a plasma chamber, 13 is an exciting coil, 14 is a reaction chamber, 15 is a sample stage, 16 is a plasma, and 17 is a target. , 18 and 1 are sputtering gas inlets ① and ①, 20 is a glass substrate plate, and other symbols that are the same as those in FIG. 6 indicate the same or corresponding parts, so a description thereof will be omitted.

As shown in FIG. 1, inside the reaction chamber 4, I n 20
Transparent electrode 2, thickness of 2000, Y2O3 thickness 200
A sample stage 15 and a target 17 are installed on which a transparent insulating substrate plate 20 having a layered lower insulating film 3a is placed.

The plasma 16 generates approximately 1O due to the interaction between the 2.45 GHz microwave 11 and the magnetic field generated by the excitation coil 13.
High-density plasma is generated in the plasma chamber 12 which is in a vacuum of -3 torr.

Plasma chamber 1 is used as the sputtering gas introduction port.
There are both a sputtering gas inlet 18 at 2 and a sputtering gas inlet 19 at the reaction chamber 14.

ZnS and S m Fa were used as the target 17, and argon gas was used as the sputtering gas.

By this sputtering method, Z
A light emitting layer 4 made of n S ; S m Fa is formed.

Thereafter, an upper insulating film 3b having a thickness of 2000 and made of Y 20 a, which is the same as the lower insulating film 3a, and an aluminum back electrode 5 are successively laminated to form a thin film EL light emitting device with a thickness of 1.4 g.

FIG. 3 shows the results of measuring the brightness characteristics by applying an AC voltage from an AC voltage source 6 between the transparent electrode 2 and the lower electrode of the thin film EL element thus formed. In this case the frequency is 1 kHz.

Figure 3 shows the characteristic curves of the thin film EL device created based on the present invention and the characteristic curve of the thin film EL device created based on the conventional method of electron beam evaporation, and the horizontal axis is the AC drive with a drop between the electrodes. The voltage (V) is shown on the vertical axis, and the luminance (f'L: foot lambert) is shown on the vertical axis.

As is clear from FIG. 3, the E formed according to the present invention
The L element is superior to the conventional thin film EL element because the film quality is improved due to the reduction in electron or ion irradiation to the film surface during the sorrel/vine process, and because S m F s, which is the luminescent center, is uniformly and finely dispersed. The brightness is higher and the driving voltage is lower than that of the previous model.

[Example 2] A thin film EL device was produced in the same manner as in Example 1.

SrS containing Ce and Eu was used as the target 17, and a mixed gas of carbon argon and hydrogen was used as the sputtering gas.

A thickness of I n 20 a 2 on a transparent glass insulating substrate 1
The transparent electrode film of 000 people's transparent electrode 2 is made of Si3N4
A light-emitting layer 4 of SrS:Ce, Eu with a thickness of 5000 mm was formed on a substrate 1 on which a lower insulating film 3a of 2000 mm thick was sequentially laminated using the ECR sputtering apparatus shown in FIG.

After that, as in Example 1, the thickness of S l a N 4 was 2
The upper insulating film 3b and the aluminum back electrode 5 were laminated to form an EL light emitting device.

A 1 kHz AC voltage was applied between the transparent electrode 2 and the lower electrode of this light emitting element to measure the brightness.

FIG. 4 shows the luminance (fL) versus hydrogen volume % in the sputtering gas. Note that the driving voltage was 180 .mu.m.

As is clear from FIG. 4, when the volume fraction of hydrogen is 10% or more, the brightness is 100 rL.

SrS:Ce and Eu, which are the light emitters of this example, exhibit spontaneous luminescence and can be used as light emitting elements of color display materials if the luminance is 100 rL or more.

An investigation into the improvement in brightness and reduction in driving voltage of the EL light emitting element according to the present invention revealed the following.

As described in Example 1, a base material with a good crystalline structure is first formed by ECR film formation, and the luminescence centers are uniformly and finely dispersed, so that the brightness is improved.

In addition to this, we investigated the causes of further increase in brightness and found that
It has become clear that the amount of hydrogen in the light-emitting thin film is related.

FIG. 5 shows a graph of the relationship between hydrogen volume % in the light emitting layer and brightness (n).

As shown in FIG. 5, it can be seen that in the hydrogen content range of 0.1% to 5%, the brightness is at least twice as high as 1oorL or more.

In this embodiment, the manufacturing of the double insulating film thin film EL device shown in FIG. 2 has been described, but the present invention is not limited to these examples and can of course be applied to thin film EL devices having other structures.

In addition, similar effects such as lower driving voltage under high brightness were obtained with other luminescent substances.

[Effects of the Invention] According to the thin film EL device and the manufacturing method thereof of the present invention, it is possible to obtain a light emitting device that has twice as high luminance as the conventional method and also has a low driving voltage, and can be used as a display for broadcasting equipment. It is useful as

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an apparatus for carrying out the present invention, and FIG. 2 is a structural diagram of a double structure thin film EL element which is an embodiment of the present invention.
FIG. 3 is a characteristic diagram of an EL element manufactured in an example of the present invention,
FIG. 4 is a diagram showing the relationship between luminance and hydrogen volume % in the sputtering gas in the example, FIG. 5 is a diagram showing the relationship between hydrogen volume % in the light emitting layer and brightness in the example, and FIG. 1 is an explanatory diagram of a typical structural example of a thin film EL element. In the figure, 1 glass substrate, 3: high dielectric insulating film, 3a: lower insulating film, 5: back electrode, 2: transparent electrode, 4: light emitting layer, 3b = upper insulating film, 6: AC voltage source, 11: micro Wave, 12: Plasma chamber, 13: Excitation coil, 14: Reaction chamber, 15: Sample stage, 1
6: plasma, 17: target, 18: sputtering gas inlet ■, 1 varnish sputtering gas population ■, 20: substrate plate.

Claims (3)

[Claims] (1) A thin film EL device characterized in that the light emitting layer thin film contains 0.1 to 5.0% by volume of hydrogen. (2) Thin film E characterized by laminating a light-emitting layer by electron cyclotron resonance (ECR) sputtering method
Manufacturing method of L element. (3) The thin film EL according to claim 2, characterized in that hydrogen gas of 10% by volume or more is used as the sputtering gas.
Device manufacturing method.