JPH0244690A - Preparation of multicolor thin film el device - Google Patents

Abstract

PURPOSE:To make it easy to manufacture EL decides by using an etching gas mainly containing halogen gases such as chlorine, bromine, iodine, etc., or halides for dry etching of a fluorescent layer of mainly a sulfide. CONSTITUTION:A first fluorescent film 13 of ZnS:Tb, F and a second fluorescent film 15 of CaS:Eu are successively formed on a glass substrate 10 bearing a transparent electrode 11 and a first insulating layer 12 patterned into desired patterns and when these fluorescent films are etched, a gas mainly containing halogen gases such as chlorine, bromine, iodine, etc., or halides such as chloride, bromide, iodide, etc., is used as an etching gas. By using the etching gas, dry etching of fluorescent films mainly consisting of ZnS, CaS, or SrS is carried out at high speed and reproducibly. As a result, a plurality of fluorescent films having original luminous efficiency can be formed between a pair of electrode films.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a multicolor thin film EL device using a thin film mainly composed of a sulfide such as zinc sulfide, calcium sulfide, or strontium sulfide as a phosphor layer. It is related to.

Conventional technology The phosphor film layer of a conventional thin film EL element is ZnS:Mn.
However, recently materials other than ZnS:Mn with high brightness have been developed. For example, ZnS:Tb, F is green, SrS:Ce is blue, CaS:
Eu emits bright red light. Therefore, many thin film EL devices with multicolor display using these materials have been proposed.

When producing a thin film EL element with multicolor display, there are two methods: sandwiching an electrode layer and optionally a dielectric thin film layer between multiple phosphor layers, and another method arranging multiple phosphor layers in a predetermined pattern. is possible. The mask method requires multiple sets of electrode layers, making the device structure very complicated and also tends to have unstable characteristics. On the other hand, in the latter case, it is a practical method from the viewpoint of simplicity of element structure and stability of characteristics. However, if the pattern is large, it is possible to form each phosphor film layer using a metal mask, but if the pattern is fine, it is practically difficult to form it using a metal mask.

In order to form a thin film layer in a Y/Fine pattern, a common method is to form a thin film uniformly over the entire surface, then form a photoresist pattern and chemically or physically remove (etch) unnecessary parts of the thin film. It is true. As a chemical etching method, etching can be performed using an acidic solution such as dilute sulfuric acid or dilute hydrochloric acid. As physical methods, a sputter etching method using an inert gas such as argon, a reactive sputter etching method using a reactive gas, etc. have been proposed.

Problems to be Solved by the Invention However, chemical etching is strongly influenced by film quality, and the etching characteristics tend to become unstable.

Furthermore, Cab and SrS thin films are extremely sensitive to acid and moisture, and from this point of view, chemical etching is not suitable. Therefore, a physical method (tri-etching) is considered desirable for etching the above-mentioned sulfide thin film, but there is no method for etching a thin film mainly composed of Cab and SrS at a sufficient speed and with good reproducibility. Therefore, it has been extremely difficult to realize a multicolor thin film EL element.

The present invention aims to solve the problems of the prior art.

Means for Solving the Problems The present invention provides a method for manufacturing a thin film EL device comprising a light emitting layer formed on a substrate and electrode layers sandwiching the light emitting layer. When forming a pattern, a process of performing reactive dry etching using a gas whose main component is a halogen gas such as chlorine, bromine, or iodine, or a gas whose main component is a halide gas such as chlorine, bromine, or iodine. By including the above, multicolor thin film EL devices can be manufactured easily and with good reproducibility.

Effect: According to the method of the present invention, a halogen element is dissociated from a halogen gas or a halide gas activated by plasma, and a phosphor film of ZnS, C is formed on the substrate surface.
It reacts with aS or SrS to form a halide of Zn-Cas or S. These compounds have a low boiling point, so they evaporate easily and can perform good etching. By using the method described above, The phosphor film of a thin film EL device using sulfide in the phosphor layer can be easily patterned, and a multicolor thin film EL device can be easily manufactured with good reproducibility.

Example The present invention will be explained in detail below.

FIG. 1 is a schematic structural diagram of a dry etching apparatus used in the method of manufacturing a multicolor thin film EL device of the present invention. Inside the vacuum container 1, an electrode pair cathode 2 and an anode 3 are arranged. A substrate 4 is placed on the cathode 2 . A high frequency power source 6 is connected to the cathode 2 via a matching circuit 5, and an alternating current voltage is applied thereto. Further, a gas introduction lower a is attached to the anode 3, and gas whose flow rate is controlled to a desired level by flowmeters 8a, 8b, and 8C is uniformly distributed on the substrate 4 through a large number of fine holes 7b provided in the anode 3. It has a structure that can supply a gas flow.

The gas pressure within the vacuum container 1 is controlled by a vacuum exhaust system 9.

A case in which a multicolor thin film EL element is manufactured using the above-mentioned apparatus will be described in detail. First, as shown in FIG. 2(a), a transparent electrode 11 with a desired pattern and a first insulator [
A first phosphor film 1 is formed on the glass substrate 10 on which 12 is formed.
As No. 3, a ZnS:Tb,F film was uniformly formed over the entire surface by co-evaporation. After heat-treating the ZnS:Tb, F film at 500°C for 1 hour, a photoresist 14 is applied on the ZnS:Tb, F film, and the first
The photoresist 14 is patterned so that stripes of the phosphor film 13 are formed. This glass substrate 10 is placed on the cathode 2 of the above-mentioned dry etching apparatus. 1. Inside the vacuum container 1. After exhausting to OX 1O-5 Torr, a mixed gas of carbon tetrachloride and nitrogen is introduced from the gas introduction lower a. For carbon tetrachloride and nitrogen gas, use flowmeters 8a and 8C.
Each flow rate is controlled to a desired flow rate. Further, the pressure inside the vacuum container 1 is maintained at a predetermined constant pressure by a vacuum exhaust system 9. The high frequency type R6 is operated and a predetermined AC voltage is applied to the cathode 2 through the matching circuit 5. Plasma is generated between the electrodes by applying an alternating voltage, and the ZnS:Tb,F film is etched. Zn
When the etching of the S:Tb and F films is completed, the operation of the high frequency power supply 6 is stopped and the glass substrate 10 is taken out.
b)), removing the resist on the ZnS:Tb,F film (
(not shown). The flow rates of carbon tetrachloride and nitrogen were set to 28. O5
CCM, and 2. O5CCM, when the gas pressure during etching is 20mTorr, the etching speed is 60n
It showed a very high value of m/min.

Next, as shown in FIG. 2(c), a CaS:Eu film, which is the second phosphor film 15, is uniformly formed over the entire surface by electron beam evaporation to the same thickness as the ZnS:Tb,F film. , 50
Heat treatment was performed at 0°C for 1 hour. A photoresist 16 is applied thereon, and the photoresist 16 is patterned so that stripes of the photoresist 16 remain in areas where the first phosphor film 13 is not formed. This glass substrate 10 is placed on the anode 2 of the above-mentioned dry etching apparatus, and the inside of the vacuum container 1 is heated 1. OX 1O-5To
Exhaust to rr. A mixed gas of bromine and nitrogen, each controlled to a desired flow rate by the flowmeters 8b and 8C, is introduced from the gas introduction lower a, and the inside of the vacuum vessel 1 is maintained at a predetermined constant pressure. The high frequency power supply 6 is operated, and the matching circuit 5
A predetermined AC voltage is applied to the cathode 2 through the Cab.
: Etching the Eu film. When the etching of the CaS:Eu film is completed, the operation of the high frequency power supply 6 is stopped and the glass substrate 10 is taken out.
Remove the resist on the film (not shown).

The flow rate of bromine and nitrogen was set to 20. O5CCM, and 2. O
5CCM, gas pressure during etching & 15mTorr
The etching rate was as high as 50 nm/min.

The multicolor thin film EL element has a second layer as shown in FIG. 2(e).
This is completed by forming the insulating layer 17 and the back electrode 1B patterned in stripes so as to be orthogonal to the transparent electrode 11. When this element was driven, the first
When voltage is applied only to the electrode on which the phosphor film 13 is formed, green light is emitted, and when voltage is applied only to the electrode on which the second phosphor film 15 is formed, red light is emitted. Furthermore, when a voltage was applied to all electrodes, a mixed color of light was obtained for both stools. In addition, the luminous efficiency of each phosphor film is
The same luminous efficiency as when an EL element was formed using each phosphor film alone was obtained.

In the above embodiments, when etching the first phosphor film 13 and the second phosphor film 15, a mixed gas of carbon tetrachloride and nitrogen and bromine and nitrogen were used as the etching gas, but halogen used as the etching gas The gas or halide gas is not limited to carbon tetrachloride or bromine gas. Table 1 shows examples of gases that can be used for dry etching the phosphor film in the method of manufacturing a multicolor thin film EL device of the present invention. The table also shows the boiling point of each halide. Needless to say, the gases listed in the table can be used for reactive dry etching of other sulfide phosphor films, as well as the phosphor films shown in the above embodiments.

Among these, halides with relatively low boiling points can be gasified by reducing pressure, and halides with high boiling points can be gasified by heating or bubbling. . The halogen or halide gas is not limited to one type, and a mixture of two or more types of gases may be used. Furthermore, the gases shown in the table are just examples, and similar effects can be expected if other halide gases are used.

The flow rate of the halogen or halide gas affects the etching rate and other etching characteristics, and is generally 100 SCCM or less for gases that are gases at room temperature, and 605 SCCM or less for gases that are easily gasified by reducing the pressure. Alternatively, if bubbling is required, 40 SCCM or less is appropriate. The pressure during etching also affects the etching rate and other etching characteristics, and the optimum value is determined depending on the vapor pressure of the reaction product between the object to be etched and the halogen element and the vapor pressure of the gas used for etching, and is approximately 50 mT.
orr or less is appropriate.

In this example, a mixture of carbon tetrachloride gas, bromine gas, and a trace amount of nitrogen was used as the etching gas.
It is not necessary to mix nitrogen gas.

Generally, a higher etching rate can be obtained by not mixing a halogen gas or a gas other than a halide gas. As an example, FIG. 3 shows the dependence of the etching rate on the carbon tetrachloride concentration when a 2',nS:Tb,F film is etched with a mixed gas of carbon tetrachloride and nitrogen.

As seen in FIG. 3, the etching rate increases as the carbon tetrachloride concentration increases. however,
When the carbon tetrachloride concentration is high, the damage to the resist is also large.

Therefore, in this example, a gas mixed with a trace amount of nitrogen gas was used. The gas to be mixed is not limited to nitrogen gas,
Any gas that causes less damage to the resist may be used.

Furthermore, depending on the type of resist, it is not necessarily necessary to mix gases other than halogen gas or halide gas. A good etching rate can be obtained as long as the amount of gas other than the halogen gas or halide gas to be mixed is approximately 50% or less.

In addition, in this example, ZnS:Tb, F film, and CaS:
Although a case has been described in which a multicolor thin film EL device is formed using two types of phosphor films such as Eu films, the multicolor thin film EL device of the present invention can also be used when three or more types of phosphor film layers are formed. It goes without saying that the manufacturing method is effective.

Effects of the Invention According to the method for manufacturing a multicolor thin film EL device of the present invention, dry etching of a phosphor film containing ZnS, CaS, or SrS as a main component, which has been extremely difficult in the past, can be performed at high speed and with high reproducibility. I can do it well. This allows multiple phosphor film layers with the original luminous efficiency to be combined into a pair of electric F! without multilayering the phosphor layers. ! It has become possible to provide a highly reliable multicolor thin film EL element that can be formed between layers.

[Brief explanation of the drawing]

FIG. 1 is a schematic structural diagram of an apparatus used for dry etching a phosphor film in the method for manufacturing a multicolor thin film EL device according to an embodiment of the present invention, and FIG. Figure 3, a cross-sectional view for explaining the process of manufacturing a thin film EL element, shows the dependence of the etching rate on the carbon tetrachloride concentration when a ZnS:Tb,F film is etched with a mixed gas of carbon tetrachloride and nitrogen. This is a graph showing the characteristics. l...Vacuum container, 2...Cathode, 3...Anode, 4...Substrate, 5...Matching circuit, 6...
High frequency 7rLR17a...-Gas inlet, 7b... Fine hole, 8a, 8b, 8c...-Flow meter, 9... Vacuum exhaust system, 10... Glass substrate, 11... Transparent electrode, 1
2... First insulator layer, 13... First phosphor film, 14
...Photoresist, 15...Second phosphor film, 16
... Photoresist, 17 ... Second insulator film, 8 ... Back electrode.

Claims (5)

[Claims] (1) In a method for manufacturing a multicolor thin film EL device consisting of a light emitting layer formed on a substrate and electrode layers sandwiching the light emitting layer, when forming a phosphor film layer containing sulfide as a main component in a predetermined pattern. A method for manufacturing a multicolor thin film EL device, comprising the steps of performing reactive dry etching using a gas containing chlorine gas as a main component or a gas containing a chlorine-containing compound gas as a main component. (2) In a method for manufacturing a multicolor thin film EL device comprising a light emitting layer formed on a substrate and electrode layers sandwiching the light emitting layer, when forming a phosphor film layer containing sulfide as a main component in a predetermined pattern. A method for manufacturing a multicolor thin film EL device, comprising the steps of performing reactive dry etching using a gas whose main component is bromine gas or a gas of a compound containing bromine. (3) In a method for manufacturing a multicolor thin film EL device consisting of a light emitting layer formed on a substrate and electrode layers sandwiching the light emitting layer, when forming a phosphor film layer containing sulfide as a main component in a predetermined pattern. A method for manufacturing a multicolor thin film EL device, comprising the steps of performing reactive dry etching using a gas whose main component is iodine gas or a gas of a compound containing iodine. (4) When forming a phosphor film layer mainly composed of sulfide in a predetermined pattern, a gas mainly composed of chlorine gas, bromine gas, iodine gas, or a compound gas containing the above-mentioned halogen element is used. 4. The method of manufacturing a multicolor thin film EL device according to claim 1, wherein when performing reactive dry etching using a nitrogen gas, nitrogen gas is added to the gas. (5) The method for manufacturing a multicolor thin film EL device according to claim 4, characterized in that the proportion of nitrogen gas added is 50% or less.