JPH05152075A - Thin film el element and manufacture thereof - Google Patents

Abstract

PURPOSE:To enhance the luminescence and reliability of a thin film EL element. CONSTITUTION:A first dielectric layer 3 and a second dielectric layer are, both or either one, a composite dielectric layer in which an oxide 3a, a nitride 3b and an oxide 3c are laminated one upon another, of these oxides, the one 3c adjacent to a luminescent layer 4 is a deposition layer formed by a chemical gas vapor growth process. With this arrangement, the insulative withstant voltage mad be enhanced, and further, uneveness caused by protrusions or the like on the dielectric layers may be removed so as to obtain an uniform film thickness. Moreover, the electric filed strength may be made to be uniform, thereby it is possible to enhance the insulative withstand voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film EL device and a method for manufacturing the same.

[0002]

2. Description of the Related Art A thin film EL device has excellent advantages such as a self-luminous device and a thin planar light emitting device, and has been developed in the field of display panels with the recent development of the information industry and the image industry. Applications are progressing mainly.

FIG. 5 shows the basic structure of a conventional thin film EL element. This structure has an indium tin oxide (Indium Tin Oxide: hereinafter referred to as ITO) formed on the surface of the translucent insulating substrate 1 by using a DC sputtering device.
A transparent electrode 2, a first dielectric layer 3 formed by sequentially laminating SiO ₂ and Si ₃ N ₄ manufactured by using a high frequency magnetron sputtering device (hereinafter referred to as an RF sputtering device), and an electron. Light emitting layer 4 of ZnS: Mn manufactured using a linear vapor deposition apparatus (hereinafter referred to as an EB vapor deposition apparatus).
And a second dielectric layer 5 made of Al ₂ O ₃ manufactured by using an RF sputtering device, and a back electrode 6 made of aluminum (Al) manufactured by using a vapor deposition device. At this time, the translucent electrode 2 and the back electrode 6 are formed in a stripe shape by photolithography so as to intersect with each other.

In the thin film EL element shown above, by applying an AC voltage of about 150 V between the transparent electrode 2 and the back electrode 6, the light emitting layer sandwiched between these two electrodes. The area 4 (pixel) emits light.
FIG. 6 shows the luminance-voltage characteristic.

[0005]

However, the thin film EL element manufactured by the conventional manufacturing method as described above does not have a sufficient withstand voltage. That is, since the dielectric layer 3 which mainly bears the withstand voltage of the thin film EL element is formed by the RF sputtering apparatus, it has defects such as pinholes and clusters in the film, and the withstand voltage is low. In order to compensate for the above, the dielectric layer 3 has a two-layer structure in the above-mentioned conventional example, but the dielectric strength is still insufficient.
Further, irregularities such as protrusions are formed on the surface of the dielectric layer, which makes the film thickness nonuniform and further lowers the dielectric strength voltage. As a result, the manufactured thin-film EL device cannot apply a sufficient voltage, and thus has a defect that the brightness is low like the brightness-voltage characteristics shown in FIG.

An object of the present invention is to solve the above problems, and to provide a thin film EL device having improved dielectric strength and high withstand voltage and high reliability, and a manufacturing method thereof.

[0007]

In order to achieve the above object, the present invention provides that the dielectric layer is a composite dielectric layer in which an oxide, a nitride and an oxide are sequentially laminated, and the same composite dielectric. Among the two oxide layers forming the layer, the oxide layer on the side in contact with the light emitting layer is a deposited layer formed by the chemical vapor deposition method.

[0008]

With this structure, the withstand voltage of the dielectric layer is improved by the three-layer structure, and the unevenness due to the protrusions and the like on the surface of the dielectric layer is removed, so that the film thickness can be made uniform. The electric field strength applied to the body layer becomes uniform, and the dielectric strength is further improved. Therefore, the dielectric strength is dramatically improved as compared with the conventional manufacturing method,
As a result, a thin film EL element with high brightness and high reliability can be realized.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of an essential part for explaining a thin film EL element in one embodiment of the first invention of the present invention, and FIG. 2 is a cross sectional view for explaining a thin film EL element in one embodiment of the second invention. 3 is a partial sectional view, FIG. 3 is a sectional view in the order of steps of a main part for explaining a method of manufacturing a thin film EL element according to an embodiment of the third invention, and FIG. It is a figure which shows the brightness | luminance-voltage characteristic of an element.

In these FIGS. 1, 2 and 3, the parts having the same functions as those of the conventional example shown in FIG. 5 are designated by the same reference numerals.

In the description of this embodiment, the third invention will be described generally with reference to FIG. 3, of which the first and second inventions will be described with reference to FIGS. Will be explained.

First, as shown in FIG. 3 (a), glass,
After a transparent conductive layer of ITO or the like having a thickness of about 0.1 μm is formed on the translucent insulating substrate 1 made of quartz or the like by a DC sputtering device, the photoresist is used as a mask to form a stripe-shaped translucent light-transmitting device The electrode 2 is formed.

Next, as shown in FIG. 3B, a Ta ₂ O ₅ layer 3a having a thickness of about 0.2 μm is formed by an RF sputtering device.
Si ₃ N ₄ layer 3b having a thickness of about 0.1 μm and a thickness of 0.1
A SiO ₂ layer 3c having a thickness of about μm is sequentially laminated, and then, as shown in FIG.
The first dielectric layer 3 shown in is formed.

After this, as shown in FIG. 3D, an SrS: Ce, Sm film having a thickness of about 1.0 μm was formed by an EB vapor deposition apparatus.
The light emitting layer 4 is formed. At this time, it is desirable to evaporate sulfur simultaneously from another crucible or the like to supplement the re-evaporation of sulfur (S), or to perform heat treatment to improve the crystallinity of the light emitting layer 4.

Then, as shown in FIGS. 3 (f) and 3 (g), a second dielectric layer 5 and a back electrode 6 are formed to form a composite dielectric in which an oxide, a nitride and an oxide are sequentially laminated. The thin film EL element of the first invention having the layer as the first dielectric layer 3 is obtained. A cross-sectional view of the main part is shown in FIG. The thin-film EL device of the first invention thus obtained exhibited the luminance-voltage characteristics as shown by the alternate long and short dash line in FIG. For reference, the characteristics of a similar thin film EL element manufactured by the conventional manufacturing method are indicated by dotted lines in the figure.

However, in the thin film EL element of the first invention, the dielectric layer 3 is a deposited layer formed by a sputtering method which is a physical vapor deposition method, so that the coating property on a steep step is inferior. However, depending on the shape of the dielectric layer, the film thickness distribution may become non-uniform and the characteristics may fluctuate. The second invention further improves this point.

As shown in FIGS. 3A to 3D, after the translucent electrode 2, the first dielectric layer 3 and the light emitting layer 4 are sequentially formed on the translucent insulating substrate 1, the figure As shown in FIG. 3 (e), a low pressure CVD (Chemical Vapor Deposition) apparatus is used for T
A SiO ₂ layer 5a having a thickness of about 0.1 μm by a chemical vapor deposition method using EOS (Tetraethyloxysilane) gas as a main material, and an S ₂ layer having a thickness of about 0.2 μm by an RF sputtering device.
i ₃ N ₄ layer 5b and SiO ₂ layer 5 having a thickness of about 0.1 μm
c are sequentially laminated to form the second dielectric layer 5 shown in FIG.
To form.

Finally, as shown in FIG. 3 (g), a metal conductive layer made of Al--Si or the like having a thickness of about 0.1 μm is formed by a DC sputtering device, and the transparent electrode 2 and the transparent electrode 2 are formed by photolithography. The back electrodes 6 are formed in stripes by an etching device so as to intersect.

As described above, when the dielectric layer is composed of the composite dielectric layer in which the oxide layer, the nitride layer and the oxide layer are sequentially laminated, of the two oxide layers constituting the dielectric layer. The thin film EL element of the second invention is obtained by applying to the second dielectric layer 5 a method in which the oxide layer on the side in contact with the light emitting layer is a deposited layer formed by chemical vapor deposition. ..
A cross-sectional view of the main part is shown in FIG. The thin-film EL device of the second invention thus obtained exhibited the luminance-voltage characteristics as shown by the solid line in FIG.

As described above, according to this embodiment, of the two oxide layers forming the composite dielectric layer in which the oxide, the nitride, and the oxide are sequentially stacked, the oxide on the side in contact with the light emitting layer. Since the layer is a deposited layer formed by the chemical vapor deposition method, the dielectric strength of the dielectric layer can be easily improved by the manufacturing method.

In the examples of the first, second and third inventions of the present invention, SrS: Ce, Sm was used as the light emitting layer, but the light emitting matrix of the light emitting layer was ZnS, CaS and Sm.
Any material may be used as long as it contains at least one of rS. Also, the activation material is not limited to C
Both aS: Eu and SrS: Sm Ca _x Sr _1-x S: Pr
It may be (0 ≦ x ≦ 1). In addition, Si is used as an oxide layer formed by the RF sputtering device that constitutes the dielectric layer.
O ₂ and Ta ₂ O ₅ were used, and Si ₃ N ₄ was used as the nitride, but the material is not particularly limited, and Al ₂ O ₃ , SrTiO ₃ , BaTa ₂ O ₆ and PZT are used as the oxide layer. Needless to say, the nitride may be AlN, SiON, or the like.

Further, in the embodiment of the first invention, the composite dielectric layer in which the oxide, the nitride and the oxide are sequentially laminated is used as the first dielectric layer, but as the second dielectric layer. You may implement. In addition, in the embodiment of the second invention, when the dielectric layer is composed of the composite dielectric layer in which the oxide layer, the nitride layer and the oxide layer are sequentially laminated, the two oxides forming the dielectric layer are formed. Of the layers, the method in which the oxide layer on the side in contact with the light emitting layer is a deposited layer formed by chemical vapor deposition was applied to the second dielectric layer, but this was not the only limitation. Needless to say, it may be implemented as the first dielectric layer.

Further, in the third embodiment of the present invention, when forming a composite dielectric layer in which an oxide layer, a nitride layer and an oxide layer are sequentially stacked below or above the light emitting layer, the composite dielectric layer is in contact with the light emitting layer. The step of forming the oxide layer on the side by chemical vapor deposition was performed by applying it to the second dielectric layer, but it was also applied to the first dielectric layer, or the first and second dielectric layers. It may be applied to both body layers. In addition, as the chemical vapor deposition method, a SiO ₂ layer containing TEOS gas as a main raw material by a low pressure CVD apparatus was used.
D equipment may be used, or the gas may be monosilane (Si
H ₄ ) or SiO ₂ layer using disilane (Si ₂ H ₆ ), or several mol% of phosphine (PH ₃ ) or diborane (B ₂ H
₆ ) PSG (Phosphosilicate Glass)
Layer, BSG (Borosilicate Glass) layer and BPSG (Boro
A phosphosilicate glass) layer or the like may be used. That is,
Any layer may be used as long as it is a deposited layer formed by chemical vapor deposition.

[0024]

As described above, according to the present invention, the dielectric layer is a composite dielectric layer in which an oxide, a nitride, and an oxide are sequentially stacked, and two oxides forming the composite dielectric layer. Among the layers, the oxide layer on the side in contact with the light emitting layer is a deposited layer formed by the chemical vapor deposition method, so that the dielectric breakdown voltage of the dielectric layer is improved by the three-layer structure, and
Since the unevenness due to the protrusions or the like on the surface of the dielectric layer is removed, the film thickness can be made uniform, the electric field strength applied to the dielectric layer becomes uniform, and the dielectric strength voltage is further improved. Therefore, the withstand voltage is dramatically improved as compared with the conventional manufacturing method. As a result, a thin film EL element having high brightness and high reliability can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part of a thin film EL element according to an embodiment of the present invention.

FIG. 2 is a sectional view of a main part of another example of the same thin film EL element.

3A to 3C are cross-sectional views in order of steps, illustrating a main part of the method for manufacturing the same thin-film EL device.

FIG. 4 is a diagram showing luminance-voltage characteristics of the thin film EL element.

FIG. 5 is a partial cross-sectional view of a conventional thin film EL device.

FIG. 6 is a diagram showing luminance-voltage characteristics of the thin film EL element.

[Explanation of symbols]

 1 translucent insulating substrate 2 translucent electrode (first electrode) 3 first dielectric layer 4 light emitting layer 5 second dielectric layer 6 back electrode (second electrode)

Claims (3)

[Claims] 1. Two electrodes, at least one of which is a translucent electrode, are arranged on a translucent insulating substrate, and a first dielectric layer, a light emitting layer and a second dielectric layer are interposed between the two electrodes. In a thin film EL device in which at least one of the first and second dielectric layers is a composite dielectric layer in which an oxide layer, a nitride layer and an oxide layer are sequentially stacked. Characteristic thin film EL device. 2. The oxide layer on the side in contact with the light emitting layer of the two oxide layers constituting the composite dielectric layer is a deposited layer formed by a chemical vapor deposition method. The thin film EL device described. 3. A step of forming a light-transmitting or non-light-transmitting first electrode on a light-transmitting insulating substrate, and a step of forming a first dielectric layer on the first electrode. A step of forming a light emitting layer on the first dielectric layer, a step of forming a second dielectric layer on the light emitting layer, and a translucency functioning as a back electrode on the second dielectric layer. Alternatively, in the method of manufacturing a thin film EL element for forming a non-translucent second electrode, the first and second
At least one of the steps of forming the dielectric layer comprises sequentially stacking an oxide layer, a nitride layer, and an oxide layer, and chemically synthesizing an oxide layer of the two oxide layers on a side in contact with the light emitting layer. A method of manufacturing a thin film EL element, which is a step of forming by a physical vapor deposition method.