JPH01274385A - Manufacture of membranous el element - Google Patents

Abstract

PURPOSE:To improve the luminous effect and the luminous brightness by forming an EL layer including a rare earth element and fluorine atoms on the ground of an insulating layer, and then, heat-treating it in the ambiance of a plasma-form fluorine compound. CONSTITUTION:On a glass substrate 11, the first electrode 12 is formed, and then the first insulating layer 13 which consists of a silicon oxide nitride layer is formed thereover. Moreover, an EL layer 14 with zinc sulfide as the luminous basic material and terbium fluoride as the luminous center is formed. After that, the substrate 11 on which the insulating layer 13 and the EL layer 14 are formed is installed in a reaction tube 21, and after evacuating by a vacuum pump, carbon tetrafluoride gas is led in and a high-frequency power is applied to a high-frequency induction coil provided around the reaction tube 21 to make the carbon tetrafluoride gas into a plasma condition. Furthermore, a current is applied to a heater 25 provided in the reaction tube 21 and the substrate 11 is heat-treated in the ambiance of the plasma- form carbon tetrafluoride gas. Then, after the second insulating layer 15 which consists of a silicone oxide nitride layer is formed to cover the EL layer 14, the second electrodes 16 are formed. By such a constitution, the luminous effect and the luminous brightness can be improved.

Description

[Detailed Description of the Invention] [Summary] Regarding the manufacturing method of a thin film EL device, it is necessary to prevent fluorine atoms from being liberated and extracted from a compound of a rare earth element and a fluorine atom, which is the luminescent center of the EL layer. For the purpose of manufacturing a thin film EL device with a structure in which an EL layer containing rare earth elements and fluorine atoms is sandwiched between insulating layers from both sides, after forming the EL layer on the underlying insulating layer, it is placed in a plasma-like fluorine compound atmosphere. Then, the underlying insulating layer is completely covered with an EL layer.

[Industrial application field]

The present invention relates to a thin film EL device, and more particularly to a method for manufacturing a thin film EL device that prevents fluorine atoms, which are a component of the luminescent center of the EL layer, from being extracted from the EL layer.

[Conventional technology]

Thin-film EL devices apply an electric field to a polycrystalline thin film of a phosphor such as zinc sulfide containing a rare earth element such as terbium, samarium, thulium, praseodymium, etc. and a halogen element such as fluorine, chlorine, etc., which functions as a luminescent center. It is a light emitting element that emits light based on the electroluminescence phenomenon, and conventionally there are two types: a DC drive type as shown in Figure 4, and a
An AC drive type as shown in the figure is known.

A DC-driven thin-film EL element as shown in FIG. 4 has a transparent electrode 2 made of ITO or the like having a thickness of approximately 2000 nm on a glass substrate 1, and a rare earth element that functions as a light emission center on top of the transparent electrode 2 made of ITO or the like. For example, an EL layer 4 made of zinc sulfide or the like containing terbium and a halogen element such as fluorine is formed, and a counter electrode (also referred to as a back electrode) 6 made of aluminum or the like is further formed thereon.

On the other hand, in an AC-driven thin film EL element as shown in FIG. 5, in addition to the structure shown in FIG.
, 60, a first insulating layer 3 and a second insulating layer 5 made of silicon oxynitride, aluminum oxide, yttrium oxide, etc. and having a thickness of about 2000 are formed.

By the way, among the rare earth elements that function as luminescent centers,
Terbium emits green light, samarium emits red light, thulium emits blue light, and praseodymium emits white light.
Except for terbium, none of them have satisfactory luminous efficiency and brightness.

Even with terbium, which has the best luminous efficiency and brightness, the luminous efficiency is 0.1 to 0.2 lumen/W, and the luminance is 14 foot lambert (fL), both of which are sufficiently satisfactory. It is difficult to say, and the reproducibility is also poor.

As a way to solve this problem, the applicant previously proposed that EL
There is a correlation between the composition ratio of rare earth elements and halogen elements contained in the layer, luminous efficiency, and brightness, and when the number of atoms of the rare earth element and the number of atoms of the halogen element are the same, the luminous efficiency is the best, The composition ratio of the rare earth element and the halogen element contained in the EL layer can be increased at least compared to the stoichiometric composition ratio. We discovered that it is effective and proposed a thin film EL device with excellent luminous efficiency and brightness.(Refer to Japanese Patent Application Laid-Open No. 76283/1983).Also, the purpose is to improve the crystallinity of the EL layer and reduce the defect density. A method has been adopted in which a substrate that has undergone the steps up to ELJi formation is heat-treated.

[Problem to be solved by the invention]

By the way, in the latter method, the heat treatment is performed in an atmosphere of sulfur hexafluoride (SF4) in order to prevent fluorine atoms from evaporating and being extracted from the EL layer during the heat treatment. This is desirable.

However, since the fluorine atoms in SF are stably bonded to sulfur atoms, they are not incorporated into the EL layer, and therefore cannot be effective in preventing fluorine atoms from evaporating and being extracted from the EL layer. cause problems.

The present invention solves the above-mentioned problems, and when a substrate on which an EL layer is formed is heat-treated, fluorine atoms in a compound of rare earth elements and fluorine atoms that form luminescent centers in the EL layer are liberated and
The object of the present invention is to provide a method for manufacturing a thin film EL element in which no leakage occurs outside the L layer.

[Means to solve the problem]

The method of the present invention for solving the above-mentioned problems is to form a first electric wire, a first insulating layer, and Ll'fi on an insulating substrate, and then heat-treat the substrate in a plasma-like fluorine compound atmosphere.

Further, the base insulating layer is completely covered with an EL layer so that it is not exposed.

[Function] In a fluorine compound gas in a plasma state, fluorine atoms are liberated from the compound and exist in the form of a single atom, a radical, or an ion. The fluorine atoms liberated in this way combine with zinc (Zn) and terbium (Tb) atoms on the bare surface of the ELJii, and further diffuse into the EL layer and are easily incorporated into the ELJi.

Therefore, even if fluorine atoms in the EL layer evaporate and are extracted during heat treatment, the EL
Fluorine atoms are replenished within the layer. As the supplied fluorine atoms move within the EL layer, they enter stable bonding positions of fluorine atoms within the EL layer.

As a result, fluorine atoms with weak bonding strength within the EL layer escape from the EL layer, but on the other hand, the number of fluorine atoms occupying stable atomic bonding positions increases.

The fluorine atom that stably contributes to the light emission is the EL element mentioned above.
Fluorine atoms occupy stable atomic bonding positions within the layer, and the method of the present invention prevents a decrease in the amount occupied by fluorine atoms within the EL layer, and also increases the number of fluorine atoms occupying stable atomic bonding positions. , an El-element with improved luminous efficiency and luminance can be obtained.

Also, the formation area of the first insulating layer is made smaller than ELJI, and E
By ensuring that the L layer completely covers everything including the ends of the first insulating layer so that the first insulating layer is not exposed,
This eliminates the possibility that the first insulating layer will be corroded during heat treatment of the substrate in a plasma fluorine compound gas atmosphere.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a thin film EL device manufactured by the method of the present invention, in which a first electrode 12 made of 170 transparent layers in a predetermined pattern is formed on a transparent glass substrate 11 using sputtering and photolithography. Form.

Next, silicon oxynitride (5
A first insulating layer 13 made of an iON) layer is formed to a thickness of 2000 nm.

Furthermore, two types of targets, a zinc sulfide (ZnS) target and a terbium oxide (TbOF) target, are used on the substrate, and high frequency power is applied separately to the two types of targets, so that sputtering is performed from the two types of targets. An E L layer 14 made of (ZnS:TbF) with ZnS as the luminescent base material and terbium fluoride (TbF) as the luminescent center is formed to a thickness of 6000 mm by a two-source sputtering method in which the speeds are different. .

Next, as shown in FIG. 3, the substrate 11 that has undergone the steps up to this point is placed in the reaction tube 21, and the inside of the reaction tube 21 is
After evacuation using a vacuum pump (not shown) connected to the evacuation pulp 22 until a vacuum level of -' torr is reached, the valve 23 of the gas introduction pipe is opened to introduce carbon tetrafluoride (CF, ) Introduce gas until the pressure reaches 10 torr.

Next, a high frequency induction coil 24 provided around the reaction tube 21
A high frequency power of 50 W is applied to the reaction tube 21 to turn the gas introduced into the reaction tube 21 into a plasma state.

Further, the temperature of the heater 25 installed in the reaction tube 21 is set to 600''C, and the substrate 11 is heat-treated in a plasma-like CF and gas atmosphere for 2 hours.

As shown in FIG. 1, a second insulating layer 15 made of a 5iON layer is formed on the heat-treated substrate so as to cover the EL layer 14 by a sputtering method, and then a second insulating layer 15 is formed using a sputtering method and a photolithography method. Eight! second electrode 1 of
6 to form an EL element.

The thin film EL device formed by the method of the present invention has a luminance of 60) compared to the thin film EL device formed by the conventional method.
A thin film EL element was obtained in which the value of 14 foot lamberts (fL) was improved to 20 fL at a driving frequency of 1z.

Further, a second embodiment of the method of the present invention will be described.

In the case of the first embodiment described above, the transparent electrode 12 is provided on the substrate 11.
After forming the first insulating layer 13 and ELLiO, heat treatment is performed in a plasma-like fluorine compound gas atmosphere.
A first insulating layer 13 is formed under ELLi2O,
The area of the first insulating layer 13 is larger than the area of the ELFii 14, and the insulating layer 13 is not completely covered with ELLi2O and has exposed portions.

By the way, since this first insulating layer 13 is formed of a 5iON layer, it has poor corrosion resistance against fluorine compound gas, and while the above-mentioned exposed portion is heat-treated in a plasma-like fluorine compound gas atmosphere. There is a problem in that the first insulating layer 13 eventually disappears and the reliability of the device decreases.

Therefore, as shown in FIG. 2, the formation area of the first insulating layer 13 is made smaller than that of ELLi2O, and the first insulating layer 13 is made to completely cover everything including the ends of the ELLi2O first insulating layer 13. Avoid exposure.

In this way, there is no fear that the first insulating layer 13 will be corroded during the heat treatment of the substrate in the plasma fluorine compound gas atmosphere, and a more reliable thin film EL element can be obtained than in the first embodiment.

Further, in the first embodiment shown in FIG. 1, the EL layer 14
Either cover the exposed portion of the first insulating layer that is not covered with a glass mask, or cover the exposed portion of the first insulating layer that is not covered with the first I! The edge layer 13 is formed of aluminum oxide, which is resistant to fluorine compound gases, or the exposed area is covered with a glass plate coated with a material resistant to fluorine compound gases, such as titanium nitride. You can use any method.

As described above, according to the method of the present invention, fluorine atoms will not be extracted from the EL layer during heat treatment, so that a highly reliable thin film E with good luminous efficiency and no decrease in luminous brightness can be produced.
An L element can be formed.

Also, as a fluorine compound gas, C
tFb (6-fluorinated ethane), C1Fll (8-fluorinated propane), CsP+z (12-fluorinated pentane), C11h (3
A fluorine compound gas such as methane fluoride), SF, (sulfur hexafluoride), SF, (sulfur tetrafluoride), and 5ps (nitrogen trifluoride) may be used at °C.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, fluorine atoms are not extracted from the EL layer during heat treatment, and this heat treatment produces a highly reliable thin film EL element with strong bonds between rare earth elements and fluorine atoms. There are benefits to be gained.

[Brief explanation of the drawing]

FIG. 1 shows a thin film EL formed by the first embodiment of the method of the present invention.
A cross-sectional view of the device, FIG. 2 is a thin film EL formed by the second embodiment of the method of the present invention.
FIG. 3 is a schematic diagram of an apparatus for carrying out the method of the present invention, and FIGS. 4 and 5 are cross-sectional views showing the structure of a thin film EL device. In the figure, 11 is a glass substrate, 12 is a first electrode, 13 is a first insulating layer, 14 is an EL layer, 15 is a second insulating layer, 16 is a second electrode,
21 is a reaction tube, 22 is an exhaust valve, 23 is a gas introduction valve, 24 is a high frequency coil, and 25 is a heater. 16 Ogoden Pui 2nd r: IIJ 7￥Hatsumekata Puunkyu I Kiyori tE: That role 1Φ Suibu 2nd 3rd
figure

Claims (2)

[Claims] (1) EL layer containing rare earth elements and fluorine atoms (14
) sandwiched between insulating layers (13, 15) from both sides. After forming the EL layer (14) on the underlying insulating layer (13), heat treatment is performed in a plasma-like fluorine compound atmosphere. 1. A method for manufacturing a thin film EL device, comprising the steps of: (2) Base insulating layer (1) formed on the substrate (11)
2. The method for manufacturing a thin film EL device according to claim 1, wherein the entire portion including the end portion of step 3) is covered with the EL layer (14).