JPH06132082A - Thin film electroluminescence element and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an electroluminescence element wherein environmental resistance is improved without performing sealing required for the conventional electroluminescence element. CONSTITUTION:In a thin film electroluminescence element having a lower part insulation layer, emission layer and an upper part insulation layer constituted of a thin film, the density of each thin film layer is provided with its difference within 5% as compared with the difference in the case of constituting this thin film of monocrystal material. Further in the case that a material of constituting the thin film is a compound, its composition is a stoichiometric composition, and further as desired in a surface of at least one layer of the lower part insulation layer, emission layer and the upper part insulation layer, a monoatomic layer of at least one kind of a fluorine atom, carbon atom and a sulfur atom or a compound layer containing at least one kind atom of the before-mentioned atoms is provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a technical field of an electroluminescence device having improved environment resistance and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, an EL element having a double insulating structure in which a semiconductor light emitting layer such as ZnS: Mn is sandwiched with a dielectric layer has been developed, and it has been confirmed that light emitting characteristics are improved. The basic device structure of a thin film EL device is shown in FIG. A transparent electrode 102 made of ITO, SnO ₂ or the like is formed on a glass substrate 101, and a lower insulating layer 103 made of Y ₂ O ₃ , TiO ₂ , Si ₃ N ₄ or the like is formed thereon.
To form. Next, a light emitting layer 104 made of ZnS: Mn is formed, an upper insulating layer 105 made of Y ₂ O ₃ , TiO ₂ , Si ₃ N ₄ or the like is sequentially formed on the light emitting layer 104, and finally an upper electrode 106 made of Al or the like is formed. And complete. Since each layer forming the EL element is usually composed of a polycrystalline film and has a laminated structure, the upper layer has many defects such as pinholes and microcracks in the film. Therefore, moisture or the like penetrates into the ZnS: Mn 104 through these defects, which causes problems such as deterioration of device characteristics and delamination of layers.

In order to solve this problem, it has been proposed to protect the moisture by the sealing structure shown in FIG. 2 (Actual Kaihei 3-32080). This sealing structure will be described with reference to FIG. A back glass 203 is arranged opposite to a glass substrate 201 via a spacer 202, and each component is fixed and sealed with an adhesive to form an envelope. An EL element 204 is built in the envelope, and an EL element protection fluid such as silicon oil or vacuum grease is filled and sealed to complete the sealing structure. As the sealing agent, a sealing agent which has excellent permeability to pinholes in the insulating layer and moisture resistance and which does not react with the EL element constituting film is used. Furthermore, recently, SrS has been attracting attention as a base material of a light emitting layer of a blue light emitting EL element. Since this SrS is a material having a very high hygroscopicity, the EL element sealing technology by the sealing structure described above is indispensable for the blue light emitting element using SrS as a base material. However, there are some problems with this sealing structure. First, the EL element manufacturing process is complicated. That is, in order to manufacture the envelope filled with the sealing agent, the steps of processing the spacer and the rear glass, positioning each component, adhering, and drying are required. After manufacturing the envelope, the steps of filling the sealing agent, vacuum degassing, and sealing the filled portion are required. As described above, many steps are required to manufacture the sealing structure, which is a major obstacle to mass production. Further, there is a drawback that the size of the device cannot be avoided. Compared with the dispersion type EL element, the thin film EL element has an advantage that the thickness of the element can be made as thin as possible. However, in the case of the sealing structure, the thickness of the spacer and the back glass is taken into consideration in addition to the EL element forming substrate. Therefore, the element thickness is not so different from the dispersion type EL element. further,
There is also a problem of diffusion of constituent atoms of the sealing agent or impurity atoms in the sealing agent. The sealing agent penetrates to the vicinity of the light emitting layer through pinholes in the insulating layer. The constituent atoms or impurity atoms of the sealing agent diffuse into the light emitting layer due to heat generated by driving the EL element. The diffused atoms form a level in the light emitting layer, which causes deterioration of EL element characteristics.

[0004]

[Objective] The present invention is intended to improve the environmental resistance of the element without performing the sealing which is conventionally required for the electroluminescent element, and is thin and excellent in the environmental resistance in a simple manufacturing process. It is an object of the present invention to provide an EL device having the following characteristics.

[0005]

[Structure] The thin-film electroluminescent device of the present invention uses a single crystal semiconductor layer or a single crystal semiconductor layer formed on an insulating substrate as a substrate, and the density of each layer is higher than that of a bulk single crystal. When the deviation is within 5% and the constituent of each layer is a compound, it is formed to have a stoichiometric composition. The basic configuration is that a lower insulating layer, a light emitting layer, and an upper insulating layer are sequentially provided. The density of each layer of the electroluminescent device of the present invention is
Since the density is close to that of the bulk single crystal and has a stoichiometric composition, the upper insulating layer located on the outermost surface of the device has
There are few defects such as pinholes and microcracks, and ingress of water and the like is suppressed. Even in this state, the element structure is superior in moisture resistance as compared with the conventional element. It is preferable to adopt an epitaxial growth method for each layer constituting the electroluminescence device, which can form a thin film having very few defects such as pinholes and microcracks.

In the present invention, by adopting the above-mentioned layer structure, it has sufficient environmental resistance.
Further, by providing a fluorine, carbon or sulfur monoatomic layer or a compound layer containing at least one atom of fluorine, sulfur or carbon atom on the surface layer of the element and / or the boundary surface of each layer, the environment resistance is further improved. Can be improved. The outermost surface of the EL element surface-treated with the fluorine, carbon or sulfur monoatomic layer or the compound containing at least one of fluorine, sulfur or carbon atom is
It is in a very inactive state because there are no dangling bonds. Therefore, it is possible to prevent adsorption of water and impurities to the EL element. The surface treatment for providing the monoatomic layer of fluorine, carbon or sulfur atoms or the compound layer containing at least one atom of fluorine, carbon or sulfur atoms is performed on the entire surface portion of the electroluminescent element. However, not only the surface of the upper insulating layer, the lower insulating layer, or the light emitting layer portion, or the surface layer of the device, but also the interface between the light emitting layer and the upper insulating layer, the light emitting layer and the lower insulating layer are preferable. Interface with the material layer or the interface between the substrate and the lower insulating layer,
Further, it may be provided at a plurality of the above-mentioned locations. The most preferable treatment is a fluorination treatment to form a fluorine atom layer or a fluoride layer. For example, it can be obtained by treating an oxide having a large dielectric constant with hydrofluoric acid vapor and water vapor. When the oxide material is PbTiO ₃ , β-PbF ₂ , BaTiO ₃ to BaF ₂ , SrT
SrF ₂ can be formed from iO ₃ and TaF ₃ can be formed from Ta ₂ O ₃ .

Next, the materials used for the layers constituting the EL device according to the present invention and the method for forming the same will be described with reference to FIG. The substrate 301 is a single crystal semiconductor substrate such as Si or Ge, or a quartz substrate or a glass substrate on which a single crystal Si or Ge is formed by a stripe heater method, a high frequency induction heating method, a lamp heating method, a laser heating method, or the like. An SOI substrate on which a thin film is formed is used. Since this single crystal substrate or SOI substrate is used as a lower electrode in addition to the EL element forming substrate, the resistivity of Si or Ge is 1 or less.
It is preferably in the range of 0 ⁻⁴ to 10 ² (Ω · cm).

As described above on the substrate 301, the density thereof is 5% or less, preferably 1% or less as compared with the density of the bulk single crystal, and in the case of a compound, a lower portion having a stoichiometric composition. The insulator layer 302 is formed. As the insulating material, PbTiO ₃ , PLT, PLZT, BaTi
O ₃ , SrTiO ₃ , Y ₂ O ₃ , YSZ, Ta ₂ O ₃ , Sn ₂
O ₃ , Al ₂ O ₃ , MgO, MgAl ₂ O ₃ or the like can be used. As a forming method, it is excellent in composition controllability of constituent elements,
This method is suitable for epitaxial growth. Methods such as a metal organic thermal decomposition method (MOCVD method) and a molecular beam epitaxial growth method (MBE method) are used.

A light emitting layer is formed on the insulator 302.
The density of the layer is within 5%, preferably 1% or less as compared with the density when it is formed of a bulk single crystal, and when the material forming the layer is a compound, the stoichiometric composition Is to have. As the light emitting layer material, ZnS, Zn
ZnS: Mn, ZnSe: with Se, ZnSxSey (y = 1-x) or the like as a base material and Mn added as an emission center.
A material such as Mn, ZnSxSey: Mn (y = 1-x),
Alternatively, a ZnS: Cu-based material obtained by adding Cu to the above base material, or a rare earth fluoride (TbF ₃ , E
rF ₃ , NdF ₃ , TmF ₃ , PrF ₃ , SmF ₃ , Dy
A material to which F ₃ , HoF ₃ etc.) is added is used. Also,
Ce, Sm, Tb, Dy,
A material to which Er, Tm, Pr, Mn or the like is added, or a material in which CaS is a base material and Er is added to the emission center is used as the light emitting layer. Each of the above materials is formed in a single layer or a multi-layer structure by MOCVD, MBE or the like.

An upper insulating layer 304 is formed on the light emitting layer 303.
To form. Similarly, the density of the layer is 5% or less, preferably 1% or less as compared with the density when the layer is formed of a bulk single crystal, and when the material forming the layer is a compound, the stoichiometry is It has a theoretical composition. The same material and layer forming means as the lower insulating layer can be used.

Next, the transparent electrode 3 is formed on the upper insulating layer 304.
As the transparent electrode material forming 05, ITO, In ₂
Thin films of O ₃ , SnO ₂ , ZnO: Al, Au, etc. can be used, and layers of these materials are formed by MOCVD, MBE, sputtering, plasma CVD, vacuum deposition, or the like. After forming the layer, it is processed into a desired electrode shape by, for example, photolithography.

[0012]

The details of the present invention will be described with reference to Examples. Example 1 An example of the present invention will be described. An SOI substrate 401 is used as the EL element formation substrate and the lower electrode. The SOI substrate is formed by melting and recrystallizing a polycrystalline Si thin film formed on a quartz substrate by laser heating. The melt recrystallization conditions are adjusted to form a (100) oriented single crystal Si thin film. Next, a SrTiO ₃ thin film is epitaxially grown on the above substrate using the MBE method to form a lower insulating layer 402.
The thickness of the SrTiO ₃ thin film is 3000 Å. Then Sr
SrS: Ce was formed on the TiO ₃ thin film using the MOCVD method.
The thin film 403 is epitaxially grown to a thickness of 4000Å to form a light emitting layer. The concentration of Ce, which is the emission center, in the film is
It is set to 0.2 mol%. Next, an SrTiO ₃ thin film 404 is grown on SrS: Ce by the MBE method to a thickness of 3000 Å to form an upper insulating layer. Finally, an ITO thin film 405 is formed on the upper insulating layer by sputtering to have a film thickness of 1000 Å to complete the EL device structure. Table 1 shows the composition ratio of each layer constituting the EL device and the reduction rate of the density from the bulk single crystal. The composition ratio is based on the Rutherford backscattering method (RB
S) was used to determine the intensity ratio of the scattering spectrum of each atom. In addition, the reduction rate of the density with respect to the bulk single crystal material is
It was measured using the RBS method. It is obtained by comparison with the bulk single crystal material having the minimum yield of channeling (χmin). As shown in Table 1, all thin films have almost the same stoichiometric composition, and the reduction rate from the density of the bulk single crystal material is 1
Within%. As described above, the EL element of Example 1 is composed of a thin film having no compositional deviation and having no grain boundary in a state close to the density of a single crystal. Next, a method of treating the surface of the EL element will be described. The processing is performed in the device shown in FIG. HF solution and H ₂ O were used for the treatment, and each was treated with N ₂
Bubble gas and introduce into the vacuum chamber. H ₂ O and HF
HF molecule is ionized by the reaction of, and HF ₂ ⁻ ion is generated. Since HF ₂ ⁻ ions are very active, Sr
It reacts with TiO ₃ to form an F monoatomic layer or SrF ₂ layer 406 bonded to Sr on the outermost surface. F the EL element surface
By terminating with atoms or coating with SrF ₂ film,
A state resistant to corrosion can be formed without being replaced by another gas. The EL element of Example 1 is completed by the above method. FIG. 6 shows the luminance-voltage characteristics of the EL element of Example 1.
FIG. 7 shows the change in luminance with time. Conventional blue light emitting devices using SrS: Ce as a light emitting layer have a problem in the moisture resistance of SrS as a base material, and a sufficient device life has not been obtained. On the other hand, as shown in FIG. 7, the EL element of the present invention shows a characteristic that the luminance is slightly reduced even after continuous driving for a long time and the stability is excellent.

[0013]

[Table 1]

[0014]

[Effect] According to the present invention, moisture resistance equivalent to or higher than that of the conventional element can be obtained without using the sealing structure required by the conventional EL element by the sealing agent. As a result, the thickness of the element can be the thickness of the quartz substrate used as the support, and the element can be thinned.

[Brief description of drawings]

FIG. 1 is a model view showing a basic element configuration of a conventional thin film EL element.

FIG. 2 is a diagram schematically showing a basic element structure and sealing structure of a conventional thin film EL element.

FIG. 3 is a diagram schematically showing a basic element configuration of a thin film EL element of the present invention and a manufacturing process thereof.

FIG. 4 is a diagram showing a thin film EL element of Example 1 of the present invention.

FIG. 5 shows a schematic view of an example of a fluorination treatment apparatus used in the present invention.

FIG. 6 shows a relationship between luminance-voltage characteristics of the thin film EL element of Example 1 of the present invention.

FIG. 7 shows a change with time in emission luminance at a threshold voltage of +80 V of the thin film EL element of Example 1 of the present invention.

[Explanation of symbols]

101 glass substrate 102 transparent electrode 103 lower insulating layer 104 light emitting layer 105 upper insulating layer 106 upper electrode 201 glass substrate 202 spacer 203 back glass 204 light emitting element 205 upper insulating layer 206 upper electrode 301 single crystal semiconductor layer 302 lower insulating layer 303 light emission Layer 304 Upper insulator layer 401 SOI substrate 402 SrTiO ₃ thin film 403 SrS: Ce thin film 404 SrTiO ₃ thin film 405 ITO 406 SrF ₂ layer 501 N ₂ gas 502 mass flow controller 503 HF solution 504 H ₂ O 505 EL element 506 rotary pump

Claims (5)

[Claims] 1. In a thin film electroluminescent device having a lower insulating layer, a light emitting layer and an upper insulating layer formed of thin films, the density of each thin film layer is compared with the density when the thin film is made of a single crystal material. Then, the difference is within 5%, and when the material forming the thin film is a compound, the composition is a stoichiometric composition, and the thin film electroluminescent device is characterized. 2. A monoatomic layer of at least one of a fluorine atom, a carbon atom and a sulfur atom or at least one of the atoms is formed on the surface of at least one layer of the lower insulating layer, the light emitting layer and the upper insulating layer. The thin film electroluminescent device according to claim 1, further comprising a layer of a compound containing one kind of atom. 3. A fluorine atom, a carbon atom and a sulfur atom are present at at least one of the interface between the light emitting layer and the upper insulating layer, the interface between the light emitting layer and the lower insulating layer, and the interface between the substrate and the lower insulating layer. 3. A thin film electroluminescent device according to claim 1, further comprising a monoatomic layer of at least one of the above, or a layer of a compound containing at least one of the atoms. 4. The thin film electroluminescent device according to claim 2, wherein the layer provided on the surface of at least one of the lower insulating layer and the upper insulating layer is a fluoride. 5. The oxide layer forming the lower insulating layer and / or the upper insulating layer is treated with hydrofluoric acid vapor and water vapor to form a fluoride layer on the surface of the oxide layer. The method for manufacturing a thin film electroluminescent device according to claim 4.