JPS60182690A - Method of producing el element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (1.1 Technical Field of the Invention The present invention relates to a method for manufacturing a thin film EL device, and in particular to a method for manufacturing a thin film EL device, in particular
The present invention relates to a manufacturing method for obtaining a highly efficient EL thin film by sputtering using He gas instead of r gas.

(2) Background of the technology As a method for producing EL thin films, the sputtering method is superior to the vapor deposition method, and furthermore, when He gas is used instead of the conventional Ar gas during sputtering, there are fewer defect levels inside the film. Previous research has revealed that it is possible to obtain an EL element with higher luminous efficiency than conventional ones.
No. 5.7-231297 and Japanese Patent Application No. 5.7-231297.

(3) Prior art and problems However, when sputtering is performed using He gas instead of conventional Ar gas, the sputtering rate decreases because the mass of He atoms is small, and the sputter rate becomes slower than in the case of Ar gas. However, there is a drawback that various conditions such as sputtering gas pressure and sputtering power are not sufficiently optimized.

Furthermore, since the properties of the heat treatment performed to improve crystallinity after film formation are different, there is a drawback that the optimum conditions are different when using Ar gas and He gas.

(4) Purpose of the invention The purpose of the present invention is to eliminate the above-mentioned conventional drawbacks, and to
In a method of manufacturing an EL element by sputtering using gas, sputtering gas pressure.

By optimizing the manufacturing conditions such as heat treatment after film formation to obtain a film of higher quality than the conventional Ar gas sputtering film, and by finding heat treatment conditions suitable for this film, it is possible to create high-efficiency, high-brightness EL elements. It provides a manufacturing method.

(5) Structure of the Invention The object of the present invention is to solve the following problems:
A method for manufacturing an EL (electroluminescent) element made of a ZnS thin film, characterized in that the ZnS thin film is formed by sputtering using He gas, and the pressure during sputtering is maintained at 2 x 10 torr or less during discharge. This is achieved by a method for manufacturing E and L elements, which is characterized in that the method for manufacturing the device and the heat treatment after forming the ZnS film are carried out at 400° C. or lower.

(6) Embodiments of the Invention Preferred embodiments of the invention will now be described in more detail with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing the structure of an EL display device manufactured by applying the present invention, in which a mixed vapor-deposited film of indium oxide and tin oxide (ITO
A transparent electrode 2 made of ZnS (film) is provided on which
It has a structure in which an EL thin film 3 of TbF3 and a back electrode 4 of Aβ are laminated. However, the configuration itself in Figure 1 is D.
This is a well-known representative example of a C' (direct current) light emitting type EL element, and generally there is a DC current between the transparent electrode 2 and the back electrode 4.
By connecting the voltage source 5, the EL thin film 3 emits light and the display can be observed from the glass substrate 1 side.

According to the present invention, the ELM film 3 is produced by a high frequency sputtering method. That is, FIG. 2 is a conceptual diagram showing a high frequency sputtering pattern according to an embodiment of the present invention, in which a target material 8 is placed in a quartz petri dish 7 on a target holder 6. In this case, the Cougett material 8 includes ZnS powder as a luminescent base material and T as a luminescent center.
It is prepared in the form of a mixed powder to which bF powder is added at a ratio of around 4 wt%, and its diameter is about 105mm. On the other hand, a substrate 1 is placed on a substrate holder 10 having a heater 9 on its back side so as to face the target at a distance of about 40 mm.

A base component such as a transparent electrode 2 is formed in advance on the surface of the substrate l.

In the above configuration, first, the target material 8 is evacuated while the bell jar (not shown) of the sputtering apparatus is evacuated.
The Couget material is degassed by heating for 8 minutes. After that, as an example, He gas was injected into the bell jar at 2X10 tor.
The substrate temperature was set at 150° C., and the sputtering power was adjusted to 300 W for sputtering. The sputtering speed at this time is 2
00 people/min.

In this sputtering method, atoms on the target surface are sputtered layer by layer and attached to the substrate, so TbF3 does not exist in clusters as in the electron beam evaporation method, and the TbF3 concentration distribution in ZnS is uniform. Become something. In this way, Zns:'FbFB thin film 3
After forming, a heat treatment is performed to recover the damage caused by sputtering and improve the crystallinity of the film, and finally, a back electrode 4 of /l is formed by vacuum evaporation to obtain the device shown in FIG.

Fig. 3 is a graph showing the relationship between the luminous efficiency of the EL element prepared as described above and the gas pressure in the sputtering, and the efficiency is Q until the sputtering gas pressure is 1.5X10 torr.
, 31 m/w, but the efficiency decreases rapidly at pressures exceeding 1.5XIQ torr, and good luminous efficiency can no longer be obtained at pressures higher than 2X10 torr. We investigated the reason why this luminous efficiency decreases at pressures higher than 2.0X10-'torr, and found that when the gas pressure is increased to over 2.0X10-'torr during discharge, Zn, which is used as a target material, S+T
b It became clear that this was caused by the deterioration of the F3 powder.

Therefore, during both sputtering film formation and press sputtering, the gas pressure must be increased to 2xlQ tor during discharge.
If it is more than r, a device with high luminous efficiency cannot be obtained. Also, because the quality of Kugetto wood changes, 2X10
The target when the pressure is increased above -'torr will no longer be usable.

Figure 4 shows ZnS:'rb sputtered under the same conditions.
It is a graph showing the relationship between luminous efficiency and temperature when a thin film is heat-treated in vacuum.

As is clear from Fig. 4, the efficiency is almost constant at heat treatment temperatures up to 400°C, but when the temperature exceeds 400°C, the efficiency tends to become extremely poor.

The phenomenon in which efficiency decreases due to high-temperature treatment is significantly different from the phenomenon observed during heat treatment of a general deposited film of ZnS:Mn. In other words, in the case of a ZnS:Mn film, it is said that the higher the heat treatment temperature is, the better, from the viewpoint of promoting the diffusion of Mn as a luminescent center to make the concentration distribution uniform and improving the crystallinity of ZnS. In most cases, it has become common to perform heat treatment at 500''C or higher, with a typical temperature of 580°C determined from the allowable heating temperature of glass substrates.

However, in the case of the zn3:TbFB film that is the subject of this invention, since TbF as a luminescent center cannot be diffused by heat treatment like Mn, the film is deliberately formed by sputtering, and the TbF in ZnS b
Since the F'5 concentration distribution is already uniform,
Heat treatment fully recovers sputtering damage and improves
It has the meaning of improving the crystallinity of the L thin film. Conventional A
When sputtering with R gas, the efficiency gradually improves even in the low temperature range and reaches the maximum luminous efficiency at 480°C, but when sputtering with He, the efficiency is almost constant in the low temperature range and 400°C.
The efficiency decreases rapidly when the temperature exceeds ℃.

The reason for this is that films sputtered with Ar gas have insufficient crystallinity, which can be recovered by heat treatment in a low temperature range, but films sputtered with He gas already have sufficient crystallinity after sputtering, so they cannot be heated in a low temperature range. It is considered that no significant dependence on the heat treatment effect is observed.

Furthermore, as mentioned above, the customer efficiency of ZnS:TbF membrane is 4.
At present, the detailed reason for the sudden deterioration caused by heat treatment above 00°C is unknown, but one reason is that
T of the luminescent center TbF3 that should exist in a molecular state in ZnS
It is conceivable that the bond between b and F is broken by heat treatment at 500° C. or higher, F atoms dissociate, and the crystal structure collapses, resulting in a decrease in luminous efficiency.

By the way, the embodiments of the EL thin film using ZnS as the luminescent base material and rbF3 as the luminescent center have been described above, but in addition to TbF3, this invention also includes S m F (red-orange), DyF5 (yellow), B r F3 (green).

T (OF (green), Pr F3 (white border), NbF (orange).

It can be applied to the formation of EL thin films in which various rare earth fluorides such as "l' m +'5 (blue) are the luminescent center, and Zn5e or a mixture thereof Zn5xSe7- can be used instead of ZnS as the luminescent base material. χ can be used.

Furthermore, EL display devices to which this invention can be applied are not limited to the C drive element as illustrated in FIG. Naturally, the AC drive element of the configuration is also a target.

(7) As described in detail, according to the method for manufacturing an EL device of the present invention, a highly efficient green-emitting EL device can be obtained with good reproducibility, so it is particularly suitable for multicolor E'L panels. effective.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing the structure of an EL display device manufactured by applying the present invention, FIG. 2 is a conceptual diagram of sputtering according to an embodiment of the present invention, and FIG. 3 is a light emission of an EL element. Graph showing the relationship between efficiency and gas pressure in spuck, 4th
The figure shows a graph showing the relationship between heat treatment (annealing) temperature after film formation and luminous efficiency. In the figure, 1 is a substrate, 2 is a transparent electrode, 3 is an EI-thin film, 4 is an electrode, 5 is a voltage source, 6 is a cathode, 7 is a Petri dish, 8 is a notebook plate, and 9 is a heater. 10 does not indicate a substrate boulder. Dinner 1 Figure ＼ ! Specialized? B

Claims (1)

[Claims] (1) Zinc sulfide (ZnS) or selenium sulfide (ZnSe) added with rare earth elements, or a mixture thereof (ZnS)
EL (
In a method for manufacturing an electroluminescent (electroluminescent) element,
The EL thin film was formed by sputtering using He gas, and the pressure during sputtering was changed to 2×10' during discharge.
A method for manufacturing an EL element characterized by maintaining the temperature below torr. (The method for manufacturing an EL element according to claim 1, characterized in that the heat treatment after forming the 21E'L film is carried out at 400°C or less. (3) Using Tb (terbium) as the rare earth element. A method for manufacturing an EL element according to claim 1 or 2, characterized in that: