JPH0850992A - Manufacture of thin film electroluminescent element - Google Patents

Abstract

PURPOSE:To obtain a thin film electroluminesceut element with an excellent bight-emitting luninance by a new manufacturing method of a luminous layer. CONSTITUTION:The zinc is evaporated from a metal evaporation source 1, and the manganese is evaporated from a metal evaporation source 2. Hydrogen or a hydrogen sulfide, or both of them are bubbled in a sulfur cylinder 3 passing through a heatproof bulb 11. A reaction gas including a sulfur gas is heated to a specific temperature by a nozzle heater 8, and injected parallel to a substrate 4 from the tip of a nozzle 15. The above specific temperature is made 200 to 300 deg.C. The zinc sulfide crystals which have large crystal particles, and a good stoichiometry are grown up on the substrate 4.

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 a light emitting layer of a thin film electroluminescent device, and more particularly to a method for manufacturing a thin film electroluminescent device having good emission brightness by reactive vapor deposition.

[0002]

2. Description of the Related Art A double-insulation type thin film electroluminescent display (hereinafter referred to as a thin film electroluminescent device) in which both surfaces of a light emitting layer which is a phosphor having Mn as an emission center are sandwiched by a transparent electrode ITO and a back electrode with an insulating layer interposed therebetween. Is called high-intensity light emission,
Since it is capable of high resolution and large capacity display, it is attracting attention as a display panel for thin display.

FIG. 8 is a sectional view showing a conventional double insulation type thin film electroluminescent device. The thin film electroluminescent device includes a glass substrate 22, a transparent electrode 23, alumina Al ₂ O ₃ and silica SiO _2.
Alternatively, the first insulating layer 24 made of silicon nitride Si ₃ N ₄ etc.
A light emitting layer 21 made of zinc sulfide or strontium sulfide, a second insulating layer 25 made of the same material as the first insulating layer, and a back face made of Al arranged in parallel and orthogonal to the transparent electrode 23. The electrode 26 constitutes a thin film electroluminescent device. The thickness of each of these layers is 20 to 1000.
Set to nm. The transparent electrode 23, the first insulating layer 24, and the second insulating layer 25 are generally produced by a sputtering method, and the light emitting layer 21 made of zinc sulfide or strontium sulfide is an ALE method which is one of a vacuum vapor deposition method and a CVD method. It is manufactured by a sputtering method or an electron beam evaporation method.

The zinc sulfide light emitting layer 21 of such a thin film electroluminescent device is composed of a zinc sulfide ZnS film as a base material and a small amount of Mn or TbOF as an emission center added thereto.
In the strontium sulfide light emitting layer, strontium sulfide is doped with cerium Ce. The emission center in each emission layer has the optimum concentration (e.g., manganese Mn is 0 for zinc sulfide ZnS).
4 to 0.6 wt%, cerium Ce for strontium sulfide SrS is maintained at 0.3 mol%) to form a film, and then heat treatment is performed at a specified temperature to improve the crystallinity of the light emitting layer and to improve the emission center. The dispersibility of is improved.

[0005]

However, when the light emitting layer of the thin film electroluminescent device is manufactured by the conventional method as described above, there is a problem that the obtained thin film electroluminescent device has low emission brightness. For example, by the vacuum deposition method, zinc sulfide ZnS
When forming the light-emitting layer, zinc metal is evaporated in a vacuum device and sulfur gas is supplied into the device to deposit zinc sulfide ZnS on the substrate.
However, due to the reactive vapor deposition that produces the crystals, a dead layer consisting of small crystal grains occurs at the initial stage of film formation, and the crystals of zinc sulfide ZnS that grow thereafter have crystal defects due to sulfur depletion, and the crystal composition is The phenomenon of deviation from the stoichiometric composition occurs. If the crystal grains are small or there are sulfur vacancies, the acceleration of electrons in the crystal is not sufficient and the excitation of the luminescence center is weak, resulting in low emission brightness.

When a crystal of zinc sulfide ZnS is formed, a zinc atom and a sulfur atom each occupy a predetermined site to form a crystal lattice. Sulfur gas is composed of S ₈ in which eight sulfur atoms are connected in a ring shape. It is composed of molecules, and the dissociation of S ₈ molecules is required during the growth of zinc sulfide ZnS crystal. Zinc sulfide
The small ZnS crystal grains and the presence of sulfur vacancies are considered to be due to the small number of dissociated low-molecular-weight sulfur molecules.

The present invention has been made in view of the above points, and an object thereof is to promote the dissociation of S ₈ sulfur molecules and prevent the occurrence of dead layers and crystal defects when the metal sulfide crystals of the light emitting layer are generated by reactive vapor deposition. Accordingly, it is an object of the present invention to provide a method for manufacturing a thin film electroluminescent device having excellent emission brightness.

[0008]

According to the present invention, there is provided a method for producing a thin film electroluminescent device using a base metal sulfide thin film to which an element serving as an emission center is added, as a light emitting layer. The component metal or sulfide of the thin film and the dopant containing the element serving as the emission center are evaporated, respectively, and the mixed gas of the carrier gas and the sulfur gas is heated to a predetermined temperature and supplied onto the substrate, and the reactive vapor deposition is performed. This is achieved by forming a metal sulfide thin film on the substrate.

In the method of manufacturing a thin film electroluminescent device described above, a group II element is used as the metal element of the metal sulfide thin film.
The carrier gas is at least one of hydrogen sulfide gas and hydrogen gas, and is bubbled into the molten sulfur. Further, the mixed gas of sulfur gas and hydrogen sulfide gas is heated to a temperature of 300 ° C or higher, and the mixed gas of sulfur gas and hydrogen gas is 300 ° C.
The mixture gas of sulfur gas, hydrogen sulfide gas, and hydrogen gas is heated to the above temperature, and is heated to a temperature of 200 ° C. or more.

Group II elements include zinc, strontium,
Calcium or the like is used, and as the dopant, manganese, which is an element serving as an emission center, or sulfides, fluorides, chlorides of rare earth elements, and the like are used.

[0011]

[Function] Sulfur molecules having a small molecular weight enhance the growth rate of metal sulfide crystals and improve stoichiometry. Sulfur exists molecules _{S 8, S 6, S 4} , S 2. At the melting point of sulfur, S ₈ sulfur molecules evaporate, but as the temperature rises, those having a smaller molecular weight become dominant. When at least one of hydrogen sulfide gas and hydrogen gas is used as a carrier gas for sulfur gas, sulfur molecules having a small molecular weight are likely to be formed. In this case, good metal sulfide crystal growth occurs at a temperature of 200 to 300 ° C.

[0012]

EXAMPLE FIG. 6 shows a thin film electroluminescence according to an example of the present invention.
It is sectional drawing which shows an element. Thin film electroluminescent device is 1m thick
m glass substrate 22A and 0.2 μm thick indium
Transparent electrode 23A made of tin oxide and a film thickness of 0.3 μm
Silicon nitride Si ₃N_FourA first insulating layer 24A composed of
Similar to the light emitting layer 21A made of zinc sulfide and the first insulating layer
The second insulating layer 25A made of the above material and the film thickness made of Al
To be parallel and orthogonal to the transparent electrode 23A at 0.5 μm
A thin film electroluminescent device is constructed from the arrayed back electrodes 26A.
To be done.

Such a thin film electroluminescent device is prepared as follows. First, the transparent electrode 23A made of indium tin oxide is formed by sputtering. Next, the silicon target is sputtered with oxygen and nitrogen to form the first insulating layer 24A. Subsequently, the light emitting layer 21A is formed. Further, the second insulating layer 24A is formed by sputtering.
Finally, the back electrode 26A made of aluminum is deposited by vapor deposition. The light emitting layer is formed as follows.

FIG. 1 is a layout view showing a reactive vapor deposition apparatus for producing a thin film electroluminescent device according to an embodiment of the present invention.
Sulfur is melted in the sulfur cylinder 3 heated by the heater 7, and hydrogen in the hydrogen cylinder 9 and / or hydrogen sulfide in the hydrogen sulfide cylinder 10 are introduced into the sulfur cylinder 3 through the heat resistant valve 11. The molten sulfur is carried as vapor by the bubbled gas, heated to a predetermined temperature by the nozzle heater 8 and jetted in parallel from the tip of the nozzle 15 toward the substrate 4. For example, zinc metal is housed in the metal evaporation source 1 and heated by the heater 7 to evaporate zinc metal. A dopant is contained in the metal evaporation source 2 and heated by a heater to evaporate. For example, manganese sulfide is used as the dopant. Metal evaporation source 1,
2 can supply the mixed gas of the carrier gas and the sulfur gas into the chamber 12 through the introduction pipe 14 from the nozzle arranged at the center thereof.

At least one of hydrogen sulfide gas and hydrogen gas flows through the sulfur cylinder 3. The sulfur gas supplied into the chamber 12 is discharged from the discharge port 13 and the inside of the chamber 12 is maintained at a constant gas pressure. A heat resistant valve 11 is installed at a predetermined portion of the gas line to control the flow of gas. The gas nozzle can be illuminated with an infrared lamp or an ultraviolet lamp.

After the pressure inside the chamber 12 was set to 10 ^-6 torr, the substrate and the line were heated to discharge gas.
After that, metal evaporation source 1, metal evaporation source 2, substrate heater 6,
The temperature of the nozzle heater 8 and the vacuum pressure were controlled to adjust the chemical composition of the light emitting layer to a stoichiometric composition. When supplying only the reaction gas with sulfur gas, when transferring the sulfur gas by bubbling with hydrogen sulfide gas, when transferring the sulfur gas with bubbling with hydrogen gas, the sulfur gas is transferred with hydrogen sulfide gas and hydrogen gas. When carrying in a bubble,
Experiments were conducted on four cases. Nozzle heater 8
The temperatures are 200 ° C, 300 ° C and 500 ° C. During the film formation, the amount of sulfur supplied and the vacuum pressure were kept constant. The temperature of the substrate heater 6 is 200 to 250 ° C. The X-ray diffraction spectrum of the manganese-doped zinc sulfide crystal formed by this method was measured.

2, 3 and 4 are diagrams showing X-ray diffraction spectra of the light emitting layer in the thin film electroluminescent device according to the embodiment of the present invention. The light emitting layers of the thin film electroluminescent device shown in FIGS. 2, 3 and 4 are such that the temperature of the nozzle heater 8 is set to 200 ° C., 300 ° C. and 500 ° C., respectively. When only sulfur gas was transported, a manganese-doped zinc sulfide crystal having a stoichiometric composition and (100) orientation was obtained at a temperature of 500 ° C. or higher.

When sulfur gas was bubbled by hydrogen sulfide gas to be transported, manganese-doped zinc sulfide crystals having a stoichiometric composition and (100) orientation were obtained at a temperature of 300 ° C. or higher. When sulfur gas was bubbled by hydrogen gas and conveyed, manganese-doped zinc sulfide crystals having a stoichiometric composition and a (100) orientation were obtained at a temperature of 300 ° C. or higher.

When the sulfur gas was bubbled by hydrogen sulfide gas and hydrogen gas and transported, a manganese-doped zinc sulfide crystal having a stoichiometric composition and (100) orientation was obtained at a temperature of 200 ° C. or higher. FIG. 5 is a diagram showing an X-ray diffraction spectrum of a light emitting layer of a thin film electroluminescent device according to another embodiment of the present invention.

In this example, the nozzle 15 is heated simultaneously with the heating of the substrate.
The reaction gas inside was irradiated with an infrared lamp or an ultraviolet lamp having a wavelength of 256 nm. It can be seen that the crystallinity is slightly improved by irradiation with an infrared lamp or an ultraviolet lamp having a wavelength of 256 nm. In the thin film electroluminescent device obtained by the above-mentioned method, an AC voltage was applied between the transparent electrode 23A and the back electrode 26A to measure the emission brightness.
The emission brightness was 400 cd / m ² or more, and good characteristics were obtained.

FIG. 7 is a diagram showing an element profile of a cross section of a thin film electroluminescent device according to an embodiment of the present invention. It can be seen that the elemental profile is almost constant. Normal E
It can be seen that in the method B, the composition ratio in the cross-sectional direction is greatly different, whereas in the case of reactive vapor deposition, the stoichiometry in the cross-sectional direction is stable. The reaction gas is caused to flow horizontally from the nozzle 15 to the substrate in order to uniformly grow crystals in the substrate, and the same effect can be obtained even if the reaction gas is supplied from the metal evaporation source 1 and the metal evaporation source 2.

Further, the light emitting layer is not limited to zinc sulfide, and even in the case of strontium sulfide or the like, a dopant such as a rare earth element can be selected and formed by the above method. The metal sulfide thin film can be used not only for a thin film electroluminescent device but also for a phosphor such as a CRT.

[0023]

According to the present invention, the constituent elements are vaporized and the mixed gas of the carrier gas and the sulfur gas is heated to a predetermined temperature and supplied onto the substrate, and the metal sulfide thin film is deposited on the substrate by reactive vapor deposition. As a film is formed, a reaction gas rich in sulfur molecules with a small molecular weight is supplied to the substrate surface, and as a result, the growth rate of the metal sulfide crystal increases and the chemical composition of the crystal approaches the stoichiometric composition, resulting in good metal sulfide. As a result, a thin film electroluminescent device is obtained which is excellent in emission brightness.

[Brief description of drawings]

FIG. 1 is a layout view showing a reactive vapor deposition apparatus for producing a thin film electroluminescent device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an X-ray diffraction spectrum of a light emitting layer in a thin film electroluminescent device according to an example of the present invention.

FIG. 3 is a diagram showing an X-ray diffraction spectrum of a light emitting layer in a thin film electroluminescent device according to an example of the present invention.

FIG. 4 is a diagram showing an X-ray diffraction spectrum of a light emitting layer in a thin film electroluminescent device according to an example of the present invention.

FIG. 5 is a diagram showing an X-ray diffraction spectrum of a light emitting layer in a thin film electroluminescent device according to another embodiment of the present invention.

FIG. 6 is a sectional view showing a thin film electroluminescent device according to an embodiment of the present invention.

FIG. 7 is a diagram showing an element profile of a cross section of a thin film electroluminescent device according to an example of the present invention.

FIG. 8 is a cross-sectional view showing a conventional thin film electroluminescent device.

[Explanation of symbols]

 1 Metal Evaporation Source 2 Metal Evaporation Source 3 Sulfur Cylinder 4 Substrate 5 Substrate Holder 6 Substrate Heater 7 Heater 8 Nozzle Heating Heater 9 Hydrogen Cylinder 10 Hydrogen Sulfide Cylinder 11 Heat Resistant Valve 12 Chamber 13 Exhaust Port 14 Inlet Tube Heater 15 Nozzle 21 Light Emitting Layer 22 Glass substrate 23 Transparent electrode 24 First insulating layer 25 Second insulating layer 26 Back electrode 21A Light emitting layer 22A Glass substrate 23A Transparent electrode 24A First insulating layer 25A Second insulating layer 26A Back electrode

Claims (6)

[Claims] 1. A method for manufacturing a thin film electroluminescent device using a metal sulfide thin film to which an element which becomes an emission center is added as a light emitting layer, wherein a component metal or sulfide of the metal sulfide thin film and an element which becomes an emission center are included. It is characterized by vaporizing each of the dopants containing it, heating a mixed gas of a carrier gas and a sulfur gas to a predetermined temperature and supplying it onto a substrate, and forming a metal sulfide thin film on the substrate by reactive vapor deposition. Method for manufacturing thin film electroluminescent device. 2. The method for manufacturing a thin film electroluminescent device according to claim 1, wherein the metal of the base metal sulfide is a Group II element metal. 3. The manufacturing method according to claim 1 or 2, wherein the carrier gas is at least one of hydrogen sulfide gas and hydrogen gas, and is bubbled in the molten sulfur. Method for manufacturing thin film electroluminescent device. 4. The method for manufacturing a thin film electroluminescent device according to claim 3, wherein the mixed gas containing hydrogen sulfide gas as a carrier gas is heated to a temperature of 300 ° C. or higher. 5. The method for manufacturing a thin film electroluminescent device according to claim 3, wherein the mixed gas containing hydrogen gas as a carrier gas is heated to a temperature of 300 ° C. or higher. 6. The manufacturing method according to claim 3, wherein the mixed gas containing hydrogen sulfide gas and hydrogen gas as a carrier gas is 200 ° C.
A method for manufacturing a thin film electroluminescent device, which comprises heating to the above temperature.