JPH06203962A - Manufacture of electroluminescent element - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing an EL element having high luminance and high reliability. CONSTITUTION:A base 9 is arranged on a susceptor 8 in the reaction furnace 1 of a MOCVD (organometal vapor phase development) device 10. Each gas of the groups II, IV, rare earth and halogen elements for thin film vapor phase development is supplied through nozzles 2, 3, 4, 5 to the vicinity of the base 9 so that they are never mutually reacted. Each gas is separately supplied by the different nozzles in this way, whereby the presence ratio of rare earth element to halogen element in a light emitting layer can be set to 21 proper value. Therefore, the size of crystal grain of an emission central material in the base is increased, and the grain boundary of the light emitting layer can be reduced. Thus, an EL element manufactured by this manufacturing method of EL element can perform efficient excitation of the emission center of the light emitting layer, and has high luminance and high reliability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electroluminescence element (hereinafter referred to as an EL element) used as a surface emitting source for a backlight of instruments, for example.

[0002]

2. Description of the Related Art Conventionally, an EL element utilizes a phenomenon in which a phosphor such as zinc sulfide (ZnS) emits light when an electric field is applied to the EL element, and has attracted attention as a constituent of a self-luminous flat display. . FIG. 5 is a schematic view showing a typical sectional structure of a conventional EL element 500. EL element 50
0 is a first electrode 52 made of an optically transparent ITO film, a first insulating layer 53 made of tantalum pentoxide (Ta ₂ O ₅ ) and a light emitting layer 54 on a glass substrate 51 which is an insulating substrate.
The second insulating layer 55 and the second electrode 56 made of an ITO film are sequentially laminated and formed.

An ITO (Indium Tin Oxide) film is a transparent conductive film obtained by doping indium oxide (In ₂ O ₃ ) with tin (Sn) and has been widely used for transparent electrodes since it has a low resistivity. ing. As the light emitting layer 54, for example,
A material in which zinc sulfide (ZnS) is used as a base material and manganese (Mn) or terbium trifluoride (TbF ₃ ) is added as an emission center is used. The emission color of the EL element is zinc sulfide (ZnS)
It depends on the kind of the additive therein, for example, yellow-orange emission is obtained when manganese (Mn) is added as the emission center, and green emission is obtained when terbium trifluoride (TbF ₃ ) is added.

As a method of manufacturing the above-mentioned EL element, metal organic chemical vapor deposition (Metal Organic Chemical Vapor Depositio) using an organic zinc compound and H ₂ S or an organic sulfur compound is used.
n: hereinafter referred to as MOCVD) is attracting attention as a high-quality thin film having a uniform size and a large area can be manufactured at low cost.

Here, MOCVD as shown in FIG.
The device is known. In the MOCVD equipment 60, zinc sulfide (ZnS) and samarium chloride (SmCl ₃ ) are used as the base materials.
Emission layer 5 of EL element using emission center substance 67
The case of forming No. 4 will be described below. It should be noted that hydrogen (H) is used as a gas for reducing the emission center substance 67 made of samarium chloride (SmCl ₃ ) and transporting it into the reaction furnace 61.
_{Use 2} ). The main raw materials for forming the base material are diethyl zinc (DEZ: organozinc compound) and hydrogen sulfide.
Thin film (emissive layer) composed of ZnS: Sm using (H ₂ S)
To manufacture. The MOCVD apparatus 60 has a nozzle 62 for supplying DEZ and a nozzle 63 for supplying H ₂ S from the lower part of the reaction furnace 61. A rotatable susceptor 68 is provided on the upper portion, and a substrate 69 on which a thin film is formed is arranged on the susceptor 68. In addition, the emission center substance 67 is perpendicular to the substrate 69 (downward).
A nozzle 64 is provided for supplying the gas into the reaction furnace 61. Further, the emission center substance 6 is provided on the upstream side of the nozzle 64.
A reaction chamber 65 for reducing 7 is arranged. A heater 66 is provided around the nozzle 64 and the reaction chamber 65 to keep the internal atmospheric temperature constant.
Is wrapped around. Furthermore, a vacuum pump (not shown) is connected to the reaction furnace 61.

[0006]

By the way, in order to improve the emission brightness of the EL element 500 having the above structure, it is important to improve the crystallinity of the light emitting layer 54.
Generally, the light emitting layer 54 is composed of a polycrystalline II-VI compound semiconductor such as zinc sulfide (ZnS). Therefore, many crystal grain boundaries exist in the light emitting layer 54. This grain boundary acts as a scatterer for the electrons accelerated by the application of the electric field, which hinders efficient excitation of the emission center. Further, at the crystal grain boundaries, the lattice distortion is large due to the shift of the crystal orientation, and many non-radiative recombination centers harmful to EL light emission exist. From these facts, in order to improve the crystallinity of the light emitting layer 54, it is necessary to increase the grain size of the constituent material and reduce the grain boundary.

Here, in order to form the light emitting layer by the vapor phase epitaxy method, a gas containing a halogen element is generally used as a source gas for the semiconductor thin film constituent element and the rare earth element. Therefore, a large amount of halogen element is contained in the light emitting layer when the raw material gas decomposes on the surface of the substrate and crystal growth occurs. These large amounts of halogen elements serve as nuclei for the generation of crystal grains and generate a large number of crystal grains. These crystal grains interfere with each other when they grow, and thus the grain size of the light emitting layer is prevented from increasing. Also, zinc sulfide (Zn
It is known that semiconductor thin films such as S) are attacked by acid. Therefore, halogen or hydrogen halide produced in large amounts on the surface of the substrate, for example, zinc sulfide (ZnS) due to hydrogen chloride (HCl) gas, is etched at the same time as the growth thereof, and thus the crystal growth of the light emitting layer is prevented. Will be hindered. On the other hand, in order to obtain high brightness and high reliability of the EL element, the atomic ratio (at%) of the rare earth element contained in the light emitting layer is required.
It is known that the light emitting layer must also contain an appropriate amount of a halogen element in addition to the fact that However, in the MOCVD apparatus 60 as shown in FIG. 6, it is difficult to increase the crystal grain size in the light emitting layer and control the amount of the halogen element contained in the light emitting layer.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method of manufacturing an EL element having high brightness and high reliability.

[0009]

The first feature of the constitution of the invention for solving the above-mentioned problems is that the first electrode, the first insulating layer, the light emitting layer, the second insulating layer and the second electrode are formed on the insulating substrate. A method for manufacturing an electroluminescent element, in which electrodes are sequentially laminated with at least a material on the light extraction side being optically transparent, in the step of forming the light emitting layer made of a semiconductor thin film containing a rare earth element by a MOCVD method. As a raw material gas for the rare earth element and the semiconductor thin film constituent element, a gas containing no halogen element is used, and halogen or hydrogen halide gas is introduced independently of the raw material gas so as not to react with each other up to the vicinity of the insulating substrate. It is to be.

In addition to the first feature, the second feature is
The halogen or the hydrogen halide gas is chlorine or hydrogen chloride gas.

[0011]

According to the above means, a gas containing no halogen element is used as a raw material gas for forming a light emitting layer made of a semiconductor thin film containing a rare earth element by the MOCVD method. Separately, halogen or hydrogen halide gas is introduced and the amount thereof is controlled. These gases are introduced so as not to react with each other up to the vicinity of the insulating substrate arranged in the reaction furnace. The present invention employs technical means based on experimental results found by the inventors that the amount of halogen element contained in the light emitting layer can be controlled. As a result, the atomic ratio of the rare earth element and the halogen element existing in the light emitting layer formed of the formed semiconductor thin film can be set to an appropriate value. Further, since the introduction amount of halogen or hydrogen halide can be controlled independently, the introduction amount can be made to be a necessary minimum amount. Therefore, unnecessary etching of the light emitting layer made of a semiconductor thin film by hydrogen halide or the like can be suppressed as much as possible. Further, the crystal grain size is increased by the MOCVD method using a gas not containing a halogen element as a source gas of the rare earth element and the semiconductor thin film constituent element, and the grain boundary in the light emitting layer is reduced. You can Therefore, according to the method for manufacturing an EL element of the present invention, in the case of using a MOCVD method which has been generally used in the past, as compared with the case where a halide of a rare earth element is used as a raw material, the excitation of the emission center of the light emitting layer is efficiently performed. And an EL element having high brightness and high reliability can be realized.

[0012]

EXAMPLES The present invention will be described below based on specific examples. FIG. 2 is a schematic view showing a cross-sectional structure of an EL element 100 formed by using the EL element manufacturing method according to the present invention. The EL element 100 extracts light in the direction of the arrow. The EL element 100 is configured by sequentially laminating the following thin films on a glass substrate 11 which is an insulating substrate. In addition, the film thickness of each layer is described below based on the central portion thereof. A first transparent electrode (first electrode) 12 made of optically transparent zinc oxide (ZnO) is formed, and a first insulating layer made of tantalum pentoxide (Ta ₂ O ₅ ) is optically transparent on its upper surface. 13, a light emitting layer 14 made of zinc sulfide (ZnS) added with samarium (Sm) as an emission center, and a second insulating layer 1 made of optically transparent tantalum pentoxide (Ta ₂ O ₅ ).
5. A second transparent electrode (second electrode) 16 made of optically transparent zinc oxide (ZnO) is formed.

FIG. 1 is a schematic diagram showing a MOCVD apparatus 10 which is an apparatus for manufacturing the EL element 100 described above. MO
A rotatable susceptor 8 is provided in the upper part of the reaction furnace 1 of the CVD apparatus 10, and a substrate 9 on which a thin film is formed is arranged on the susceptor 8. In the lower part of the reaction furnace 1, a nozzle 2 for supplying a group II element from a direction perpendicular to the substrate 9 (downward), a nozzle 3 for supplying a group VI element, a nozzle 4 for supplying a rare earth element, and a halogen. And a nozzle 5 for supplying an element. The nozzles 2, 3,
The gas supplied from each of the substrates 4 and 5 is the substrate 9
The openings are inserted into the reaction furnace 1 so as not to react to the vicinity. Further, a vacuum pump (not shown) is connected to the reaction furnace 1. Incidentally, FIG. 4 is a schematic view showing another embodiment of the MOCVD apparatus which is a manufacturing apparatus of the EL element 100 described above. This MOCVD apparatus 20 is shown in FIG.
The nozzles 4 and 5 in the MOCVD apparatus 10 of
Only the configuration arranged from the lower part to the lateral side is different, and the other components are the same and the same reference numerals are given and the description thereof is omitted.

Next, a method of manufacturing the above-mentioned EL element 100 will be described below. First, the first transparent electrode 12 was formed on the glass substrate 11. As a vapor deposition material, zinc oxide (ZnO)
Gallium oxide (Ga ₂ O ₃ ) was added to the powder and mixed, and the mixture was molded into pellets. An ion plating device was used as a film forming device. Specifically, while maintaining the temperature of the glass substrate 11 at 150 ° C., the inside of the ion plating apparatus was evacuated to 5 × 10 ⁻³ Pa. After that, argon (Ar) gas was introduced to maintain the pressure at 6.5 × 10 ⁻¹ Pa, and the beam power and the high frequency power were adjusted so that the film formation rate was in the range of 0.1 to 0.3 nm / sec.

Next, a first insulating layer 13 made of tantalum pentoxide (Ta ₂ O ₅ ) was formed on the first transparent electrode 12 by sputtering. Specifically, the temperature of the glass substrate 11 is set to 200 ° C.
And maintain the inside of the sputtering system at 1.0 Pa, and introduce a mixed gas of argon (Ar) and oxygen (O ₂ ) into the sputtering system (200c
c / min), high frequency power was applied, and the deposition rate was 0.2 nm / sec.

On the first insulating layer 13, zinc sulfide (Zn
S) was used as a base material, and samarium (Sm), which is a rare earth element, and chlorine (Cl), which is a halogen element, were added as emission centers to form a light emitting layer 14 by the MOCVD apparatus 10 in FIG. Specifically, the glass substrate 11 is heated to 450 ° C.
And the inside of the reaction furnace 1 was placed under a reduced pressure atmosphere, and hydrogen (H ₂ ) was used as a carrier gas for diethyl zinc (Zn (C ₂ H _{2
5) 2)} diluted hydrogen sulfide (H ₂ S) was flowed from the nozzle 3 200 cc / min at 250 cc / min through a nozzle 2, hydrogen (H _2).
Moreover, the source temperature of samarium tridipivaloyl methanide (Sm (DPM) ₃ ) is 150 ° C. for the addition of the emission center.
It is heated to the above temperature, and hydrogen (H
₂ ) and a flow rate of 25 cc / min was flown from the nozzle 4. Further, in order to add a halogen element, hydrogen chloride (HCl) gas is diluted with hydrogen (H ₂ ), and this mixed gas is supplied from the nozzle 5 to the reactor 1.
50cc / min was introduced inside. Then, the pressure in the reactor 1 is set to 100
The light emitting layer 14 was formed while maintaining Pa.

At this time, the concentrations of the added samarium (Sm) and chlorine (Cl) in the zinc sulfide (ZnS) film are both 0.2 at%.
EPMA (Electron Probe Micro Anarysi)
s: electron beam microanalysis). That is, this E
The atomic ratio (Cl / Sm) of chlorine (Cl) as a halogen element contained in the light emitting layer 14 of the L element 100 to samarium (Sm) as a rare earth element was 1.

Next, a second insulating layer 15 made of tantalum pentoxide (Ta ₂ O ₅ ) was formed on the light emitting layer 14 in the same manner as the first insulating layer 13. Then, the second transparent electrode 16 made of a zinc oxide (ZnO) film was formed on the second insulating layer 15 by the same method as the above-mentioned first transparent electrode 12. The film thickness of each layer is 300 for the first transparent electrode 12 and the second transparent electrode 16.
nm, the first insulating layer 13 and the second insulating layer 15 are 400 nm, and the light emitting layer 14 is 1000 nm.

FIGS. 7 (a), (b) and (c) show the surface of the zinc sulfide (ZnS) light emitting layer when a mixed gas of hydrogen chloride and hydrogen was flowed at 0 cc / min, 25 cc / min and 50 cc / min, respectively. It is an electron micrograph of. It was confirmed by EPMA that the chlorine element concentrations in the zinc sulfide (ZnS) film at this time were 0 at%, 0.2 at%, and 0.5 at%, respectively, and the samarium (Sm) concentrations were all the same. It was also confirmed that the crystal grain size on the surface of these samples became smaller as the flow rate of the mixed gas of hydrogen chloride and hydrogen increased.

FIG. 8 shows a conventional MOC as shown in FIG.
Zinc sulfide: samarium chloride (ZnS: SmCl ₃ ) which is a light-emitting layer formed by a method of adding samarium trichloride (SmCl ₃ ) vapor as a raw material of a luminescence center in a VD device 60 to zinc sulfide (ZnS). It is an electron micrograph of the film surface. That is, although the crystal grain size of the light emitting layer surface of the present invention becomes smaller as the flow rate of the mixed gas of hydrogen chloride and hydrogen increases, the crystal grain size thereof is smaller than that of the conventional light emitting layer surface. It turns out that it is extremely large.

FIG. 3 is a characteristic diagram showing the relationship between the applied voltage of the EL element and the emission brightness. The characteristics of the EL device 100 having the light emitting layer (atomic ratio (Cl / Sm) = 1) manufactured by the above-described method were shown as a product of the present invention. For comparison, a conventional device uses a vapor of samarium trichloride (SmCl ₃ ) as a raw material for an emission center and has a light emitting layer (atomic ratio (Cl / Sm)> 3) added to zinc sulfide (ZnS). The EL element is a conventional product (1), and a light emitting layer (atomic ratio (Cl / S) is formed of a zinc sulfide: samarium (ZnS: Sm) film containing no chlorine element.
The characteristics of the EL device having m) = 0) are shown as the conventional product (2). In order to obtain higher brightness in the EL device according to the present invention than in the past, the atomic ratio of the halogen element contained in the light emitting layer to the rare earth element needs to be in the range of 0.5 to 3, and the preferable atomic ratio is Was found to be close to 1 by the inventors' experimental research. Therefore, in the manufacturing process, hydrogen chloride (HC1) and hydrogen (HC1) are adjusted so that the atomic ratio (Cl / Sm) of chlorine (Cl) to samarium (Sm) in the zinc sulfide (ZnS) film becomes 1, which is the optimum value. The amount of the mixed gas of H ₂ ) introduced was adjusted. As a result, the product of the present invention has a remarkably higher emission brightness than the conventional products (1) and (2) having a light emitting layer having an atomic ratio (Cl / Sm) outside the range of 0.5 to 3. And a high luminous efficiency was obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an MOCVD apparatus that achieves a method for manufacturing an EL device according to a specific embodiment of the present invention.

FIG. 2 is a schematic view showing a cross-sectional structure of an EL element formed by the device of the example.

FIG. 3 is a characteristic diagram showing the relationship between the applied voltage and the light emission luminance in EL devices of the present invention product and the conventional product.

FIG. 4 shows an M for achieving the method for manufacturing an EL device according to the present invention.
It is the schematic which showed the other Example of the OCVD apparatus.

FIG. 5 is a schematic diagram showing a typical cross-sectional structure of a conventional EL element.

FIG. 6 is a schematic view of a MOCVD apparatus for forming a conventional EL element.

FIG. 7 is an electron micrograph showing the texture of the surface of the light emitting layer of the EL device according to the present invention.

FIG. 8 is an electron micrograph showing a texture of a surface of a light emitting layer of a conventional EL device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Reactor 2 ... (Group II element supply) nozzle 3 ... (Group VI element supply) nozzle 4 ... (Rare earth element supply) nozzle 5 ... (Halogen element supply) nozzle 11 ... Glass substrate (insulating substrate) 12 ... No. DESCRIPTION OF SYMBOLS 1 transparent electrode (1st electrode) 13 ... 1st insulating layer 14 ... light emitting layer 15 ... 2nd insulating layer 16 ... 2nd transparent electrode (2nd electrode) 100 ... EL element (electroluminescence element)

Front Page Continuation (72) Inventor Yu Hattori, 1-1, Showa-cho, Kariya city, Aichi Prefecture

Claims (2)

[Claims] 1. A first electrode, a first insulating layer, and
A method for manufacturing an electroluminescence device, in which a light-emitting layer, a second insulating layer, and a second electrode are sequentially laminated with at least a material on the light extraction side being optically transparent, wherein a rare earth element is formed by a metal organic chemical vapor deposition method. In the step of forming the light-emitting layer comprising a semiconductor thin film containing, a gas containing no halogen element is used as a source gas for the rare earth element and the semiconductor thin film constituent element, and halogen or hydrogen halide is used independently of the source gas. A method for manufacturing an electroluminescence device, characterized in that gases are introduced into the vicinity of the insulating substrate so as not to react with each other. 2. The method for manufacturing an electroluminescent element according to claim 1, wherein the halogen or the hydrogen halide gas is chlorine or hydrogen chloride gas.