JPH077712B2 - Method of manufacturing thin film EL device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] This is an improvement in the method of manufacturing a thin film EL element, and is an improvement in improving the luminous efficiency and luminance characteristics of the thin film EL element.

By controlling the composition ratio of the rare earth element and the halogen element that are added as emission centers in the zinc sulfide that is the base material, and making the composition ratio of them to be 1: 1, the zinc sulfide as the base material and the halogen of the rare earth element are used. Independently separates zinc sulfide, rare earth element halides, and rare earth element sulfides by utilizing the newly discovered property of controlling the luminous efficiency and brightness of thin film EL devices centered on halides. EL using the deposition method (sputtering method, vacuum evaporation method, etc.) used as the source of
It is an improvement of a method for manufacturing a thin film EL element for forming a film, wherein, among deposits, a rare earth element halide or a mixture of a rare earth element halide and a rare earth element sulfide,
This is a method of manufacturing a thin film EL element that is deposited by the diode sputtering method.

[Industrial application field]

TECHNICAL FIELD The present invention relates to an improvement in a method for manufacturing a thin film EL element, which makes it possible to improve the luminous efficiency and luminance characteristics of the thin film EL element. Furthermore, a thin film that can be selected to a desired value within a range in which the luminous efficiency and luminance characteristics of the thin film EL element can be realized.
The present invention relates to improvement of a manufacturing method of an EL element.

[Conventional technology]

A thin film EL device applies an electric field to a polycrystalline thin film of a phosphor such as zinc sulfide containing a rare earth element functioning as an emission center such as terbium, samarium, thulium, praseodymium, europium and halogen elements such as fluorine and chlorine. However, it is a light emitting element that emits light based on the electroluminescence phenomenon, and conventionally, a direct current drive type as shown in FIG. 2 and an alternating current drive type as shown in FIG. 3 are known.

See Fig. 2. In the DC drive type thin film EL device, a transparent electrode 2 made of ITO or the like and having a thickness of about 2,000 Å is formed on a glass substrate 1 and the rare earth element that functions as an emission center is formed on the transparent electrode 2. An EL film 4 made of zinc sulfide or the like containing an element such as terbium and a halogen element such as fluorine is formed, and a counter electrode 6 made of aluminum or the like is further formed thereon.

See FIG. 3. In the AC drive type thin film EL device, in addition to the layer structure shown in FIG. 2, the EL film 4 is sandwiched between silicon oxynitride, aluminum oxide, yttrium oxide, etc. A first insulating film 3 and a second insulating film 5 having a thickness of about 2,000 Å are formed.

By the way, of the rare earth elements that function as emission centers,
Terbium emits green light, samarium and europium emit red light, thulium emits blue light, and praseodium emits white light, but their luminous efficiency and brightness are not satisfactory except for terbium. Even the best terbium has a luminous efficiency of 0.
It is 1 to 0.2 lumen / W, and the brightness is 30 foot lamberts, so it is hard to say that they are completely satisfactory, and the reproducibility is poor. Therefore, it is difficult to realize an additive color mixing type color EL element.

As a means for solving this problem, the inventor of the present invention has
There is a correlation between the composition ratio of the rare earth element and the halogen element contained in the film and the luminous efficiency / luminance, and when the number of atoms of the rare earth element and the number of atoms of the halogen element are the same, the best luminous efficiency / Brightness can be realized, and the composition ratio of the rare earth element contained in the EL film to the halogen element is adjusted so that the composition ratio of the rare earth element is at least larger than the stoichiometric composition ratio. By discovering that this is effective, we have completed the invention of a thin film EL device with excellent luminous efficiency and brightness.

A thin film in which the composition ratio of the rare earth element contained in the EL film to the halogen element is made larger than at least the stoichiometric composition ratio, and desirably, the number of atoms of the rare earth element and the number of atoms of the halogen element are the same. As one of the methods for manufacturing an EL device, the inventor of the present invention uses zinc sulfide and a rare earth element halide or a mixture of a rare earth element halide and a rare earth element sulfide as an independent source. We have developed a method for manufacturing a thin film EL element that forms an EL film using a sputtering method or a vacuum deposition method, and filed a patent application (Japanese Patent Application No. 60-282320).

In this improved thin film EL device manufacturing method, it is practically advantageous to perform the magnetron sputtering method using the above-mentioned two or three independent targets. This is because it is possible to prevent the temperature of the substrate from rising excessively.

[Problems to be solved by the invention]

When using a zinc sulfide source and a rare earth element halide source as the source, the composition ratio of the rare earth element and the halogen element is not necessarily 1: 1, but as the source, a zinc sulfide source and the rare earth element halide and the rare earth element By using the mixed source with sulfide of, the composition ratio of the rare earth element and the halogen element can be about 1: 1, and the luminous efficiency and luminance characteristics can be improved considerably compared with the conventional technology. it can.

However, their luminous efficiency and luminance characteristics are still not sufficiently satisfactory, and there is still room for improvement, and the development of an even better thin-film EL device manufacturing method has been desired.
An object of the present invention is to meet this requirement, and a sputtering method using zinc sulfide and a rare earth element halide or a mixture of a rare earth element halide and a rare earth element sulfide as an independent source or We have further improved the manufacturing method of thin-film EL elements that form an EL film using the vacuum deposition method, and have further improved thin film with excellent luminous efficiency and brightness characteristics.
An object of the present invention is to provide a method for manufacturing a thin film EL element capable of manufacturing an EL element.

[Means for solving problems]

Means adopted by the present invention to achieve the above object, the above-mentioned deposit (zinc sulfide, a rare earth element halide or a mixture of a rare earth element halide and a rare earth element sulfide), A thin film EL is prepared by depositing a rare earth element halide or a mixture of a rare earth element halide and a rare earth element sulfide by the diode sputtering method.
It is to manufacture the device.

[Function] The cause of the above-mentioned defect (the composition ratio of the rare earth element and the halogen element is approximately 1: 1 but the luminous efficiency and the brightness characteristics are still not sufficiently good) is that zinc and the halogen element are easily bonded. Therefore, it is presumed that the bond between zinc and a halogen element such as fluorine is realized, and as a result, the halogen element such as fluorine is located at the position where sulfur should otherwise exist, resulting in an EL film with large strain. To be done.

In the present invention, the rare earth element halide or the mixture of the rare earth element halide and the rare earth element sulfide is diode-sputtered, so that electrons are rapidly transmitted to the region where the rare earth element and the halogen element are deposited. Irradiated,
It is considered that since the temperature of the region is locally high, the bond between zinc and the halogen element (fluorine) does not occur and an EL film having no strain is formed.

According to the result of the experiment, FIG. 4 shows the luminance (luminance threshold) in the case of the conventional technique (when both the zinc sulfide target and the mixture target of the rare earth element halide and the rare earth element sulfide are magnetron sputtered). Value voltage 30V
The brightness of the thin film EL element manufactured by the method for manufacturing a thin film EL element according to the present invention (the brightness for a voltage exceeding the light emission threshold voltage of 30 V) (B) is compared with the brightness for the voltage exceeding (A). As shown, this brightness is improved about 3 times.

〔Example〕

Hereinafter, referring to the drawings, a thin film according to an embodiment of the present invention
The method for manufacturing the EL element will be further described.

See Fig. 1. Sputtering method is used to make a thickness of about 2,000 on the glass substrate 1.
A transparent electrode 2 made of Å ITO film and a first insulating film 3 made of aluminum oxide and having a thickness of about 2,000 Å are formed.

Subsequently, using a zinc sulfide target and a terbium trifluoride target, the zinc sulfide target forms magnetron sputter, and the terbium trifluoride target forms diode sputter to form zinc sulfide containing terbium and fluorine. The film is formed to a thickness of 6,000Å.

At this time, the power of each target is controlled so that the content of each of terbium and fluorine becomes, for example, 2 mol% of the content of zinc sulfide. For example, the power of each target is controlled so that the deposition rate of zinc sulfide is 300Å / min and the deposition rate of terbium trifluoride is 12Å / min. Then, heat treatment is performed at about 600 ° C. for about 1 hour to form the EL film 41.

Next, the second insulating film 5 made of yttrium oxide and having a thickness of about 2,000Å is formed by using the electron beam evaporation method, and further, the counter electrode made of aluminum is formed by using the evaporation method or the sputtering method. 6 is formed.

The EL film 41 of the thin-film EL device manufactured through the above steps has a composition ratio of terbium and fluorine that is approximately 1: 1 and, moreover, terbium is located at the position of zinc and has no distortion. It is a film, and since fluorine is weakly bound to terbium and exists in the space between the lattice points, the luminous efficiency and luminance (luminance corresponding to a voltage exceeding the emission threshold voltage of 30 V) is Each is 1.2 lumens / W and 220 foot transvers, which is about 3 times higher than the conventional technology.

〔The invention's effect〕

As described above, in the method for producing a thin film EL element according to the present invention, in order to produce the EL film, zinc sulfide, a halide of a rare earth element or a halide of a rare earth element and a sulfide of a rare earth element are used. A mixture of targets is used, and among these targets, the target of a rare earth element halide or a mixture of a rare earth element halide and a rare earth element sulfide is sputtered, so the rare earth element of the EL film is The composition ratio of elements and halides is said to be about 1: 1, and moreover,
The rare earth element is located at the position of zinc and has no distortion, and the halide is weakly bound to the rare earth element and exists in the space between the lattice points, so that the luminous efficiency and the brightness characteristics are improved. .

Furthermore, by selecting the material of the emission center, it is possible to select the desired value within the range where the emission efficiency and brightness characteristics of the thin film EL element can be realized. It is also possible to realize an additive color mixing thin film EL element that combines EL elements.

[Brief description of drawings]

FIG. 1 is a structural diagram of an AC driving type thin film EL element according to one embodiment of the present invention, FIG. 2 is a structural diagram of a DC driving type thin film EL element according to the prior art, and FIG. FIG. 4 is a structural diagram of such an AC-driven thin film EL element, and FIG. 4 shows the luminance (emission threshold voltage) of the AC driven thin film EL element manufactured by the method for manufacturing a thin film EL element according to an embodiment of the present invention. Luminance (voltage corresponding to a voltage exceeding 30 V) to the voltage relationship (B), and luminance (luminance corresponding to a voltage exceeding the light emission threshold voltage of 30 V) to a voltage relationship (A) in the related art.
It is a graph compared and represented. In FIG. 1, 1 ... Transparent substrate (glass substrate), 2 ... Transparent electrode (ITO electrode), 3 ... First insulating film (silicon nitride, aluminum oxide, yttrium oxide), 41 ...... EL film (composition of zinc sulfide, rare earth element and halogen element), 5 ... Second insulating film (silicon oxynitride, aluminum oxide, yttrium oxide), 6 ... Counter electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Watanabe 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Kenji Okamoto 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Seito Sato 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Within Fujitsu Limited (72) Inventor Keihiro Hamakawa 3-17-4 Minamihanayashiki, Kawanishi-shi, Hyogo (56) References 62-140394 (JP, A) JP 61-245489 (JP, A) JP 61-34890 (JP, A)

Claims (3)

[Claims] 1. A mixture of zinc sulfide and a halide of a rare earth element or a halide of a rare earth element and a sulfide of a rare earth element after forming a transparent electrode (2) on a transparent substrate (1). Is used as an independent source to form an EL film (41) on the transparent electrode (2), and a counter electrode (6) is formed on the EL film (41). In the method of manufacturing a thin film EL element to be formed, the deposition of the rare earth element halide or a mixture of a rare earth element halide and a rare earth element sulfide is performed by performing a diode sputtering method. Device manufacturing method. 2. The method according to claim 1, further comprising the step of forming a first insulating film (3) and a second insulating film (5) with the EL film (41) interposed therebetween. A method for producing the thin film EL element described in the above. 3. The method for manufacturing a thin film EL element according to claim 1, wherein the deposition of zinc sulfide is performed by executing a magnetron sputtering method.