JPH0693385B2 - Pattern forming method for multicolor thin film EL element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pattern forming method for a multicolor thin film EL element used for character or graphic display.

2. Description of the Related Art Recently, it has become possible to obtain high-luminance phosphor materials for thin film EL devices using materials other than ZnS: Mn. For example ZnS: TbF ₃
Emits green light, SrS: Ce emits blue light, and ZnS: SmF ₃ emits red light. Multi-color display thin film EL devices using these materials have been proposed.

When manufacturing a multi-color display thin film EL element, a method of sandwiching an electrode layer and a dielectric thin film layer as necessary between the phosphor layers that are superposed, and a plurality of phosphor layers in a predetermined pattern on the same plane It is conceivable to arrange them separately. In the former method,
Since a plurality of electrode layers are required, the device structure becomes very complicated and the characteristics tend to be unstable. On the other hand, the latter method is realistic in view of the simplicity of the device structure and the stability of characteristics. However, if the pattern is large, it is possible to pattern each phosphor layer using a metal mask, but if the pattern is fine, it is practically difficult to form using the metal mask.

Therefore, in order to form the phosphor layer in a fine pattern, a method of uniformly forming a thin film on the entire surface, then forming a photoresist pattern and chemically or physically removing (etching) unnecessary portions of the thin film is required. It is common. However, some phosphor thin films cannot be wet-etched depending on the material and film quality. In that case, etching is performed by reactive ion etching (RIE), but since the etching rate of the phosphor film is small, long-time etching is required, and thus the damage to the resist and the phosphor film surface is large at present. On the other hand, a method of forming a phosphor layer by lift-off has also been proposed (N. Yamauchi et.al) SID87 Digest p230 (198
7)). That is, after the first phosphor thin film is etched using a predetermined resist pattern, the second phosphor thin film is formed on the entire surface of the display portion, and the resist pattern is removed (lifted off). This is a method of obtaining the pattern of the second phosphor thin film in the portion.

However, in the lift-off method using a resist, the substrate temperature cannot be raised because of the resist pattern when the second phosphor layer is vapor-deposited, and it is easy to cause a decrease in brightness or uneven brightness of the device. However, the RIE method has a problem that the resist is greatly damaged by etching for a long time and the resist is difficult to peel off, and thus the underlying phosphor layer is greatly damaged. Damage to the phosphor layer causes uneven brightness.

Therefore, it is an object of the present invention to provide a pattern forming method of a multicolor thin film EL element which does not cause a decrease in light emission efficiency by the lift-off method and an etching damage on the phosphor film surface by the RIE method.

Means for Solving the Problems According to the present invention, after forming a first phosphor layer on a substrate, a resist having a good light-transmitting property is applied and prebaking is performed, and subsequently, a dry etching resistance is excellent. A resist is applied and prebaking is performed. After forming a resist pattern by a normal photolithography process, a predetermined phosphor pattern is formed by dry etching. After removing the resist, a second phosphor layer is formed, a predetermined resist pattern is similarly formed, and dry etching is performed.

Effect According to the present invention, since a thick film resist having good light transmittance is used, mask alignment is easy, and since a resist having good dry etching resistance is used, deterioration of the resist surface is small. In addition, since the resist film has a large thickness as described above, it also has an effect of preventing damage to the phosphor film surface due to ion bombardment, and thus it is possible to form a pattern without damaging the phosphor film surface.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

First Embodiment FIG. 1 shows a method for manufacturing a thin film EL device of the present invention. First, as shown in FIG. 1 (a), a tin-containing indium oxide (ITO film) 2 is formed on a glass substrate 1 by a DC magnetron sputtering method and processed into a stripe shape, and then a dielectric layer 3 is formed thereon. As an Sr (Zr _0.2 Ti _0.8 ) O ₃ film, was formed at a substrate temperature of 400 ° C. by the RF magnetron sputtering method. Next, ZnS: Tb for forming the first phosphor layer 4
The film 4 was uniformly formed on the entire surface at a substrate temperature of 200 ° C. by the RF sputtering method (FIG. 1 (a)). A thick film resist AZ4620A (manufactured by Hoechst Japan Co., Ltd.) having good light transmittance is applied thereon to form a first resist film 5 having a film thickness of 5 μm or more, and prebaking is performed at 90 ° C. for 30 minutes.
Subsequently, a resist S1713 (Chipley Co., Ltd.) resistant to chlorine plasma is applied as a second resist film 6 to a thickness of 2 μm. After prebaking at 90 ° C. for 15 minutes, exposure and development are performed to form a pattern (FIG. 1 (b)). As the developing solution, a 25% aqueous solution of 400K (manufactured by Hoechst Japan Co., Ltd.) was used. The thickness of ITO film 2 is 650 nm, Sr (Zr _0.2 Ti _0.8 ) O ₃
The film 3 was set to 500 nm, and the ZnS: Tb film 4 was set to 500 nm.

The width of the resist pattern was 200 μm and the pitch was 400 μm. Next, the ZnS: Tb film 4 was etched by RIE (FIG. 1 (c)). The etching gas was CCl ₄ , and the etching was performed for about 25 minutes. After the etching was completed, the photoresist was removed, and a ZnS: Sm film 7 was formed thereon by RF magnetron sputtering at a substrate temperature of 230 ° C. to a film thickness of 400 nm (FIG. 1 (d)). Next, in order to activate the phosphor, annealing was performed in vacuum at 450 ° C. for 1 hour. Similar to the pattern formation of the first phosphor layer, the first resist film 8 is applied and pre-baked, and then the second resist film 9 is applied, pre-baked, exposed and developed to form a predetermined resist pattern. Fig. 1 (e)). After etching with CCl ₄ for about 25 minutes by RIE, the resist was removed and a ZnS: Sm pattern was formed to complete the pattern of the phosphor layer (FIG. 1 (f)). Next, the BaTa ₂ O ₆ film 10 was formed by the RF magnetron sputtering method. The film thickness was 150 nm. Finally, the A ₁ electrode 11 was formed to complete the thin film EL device (FIG. 1 (g)).

When these elements were driven, the same emission luminance as that of an EL element formed of each phosphor thin film was obtained, and no luminance unevenness was observed.

Second Embodiment A method of manufacturing a thin film EL device according to a second embodiment of the present invention will be described with reference to FIG. First, as shown in FIG. 1A, an ITO film 2 was formed on a glass substrate 1 by a DC magnetron sputtering method and processed into a stripe shape. An Sr (Zr _0.2 Ti _0.8 ) O ₃ film was formed thereon as a dielectric layer 3 by an RF magnetron sputtering method at a substrate temperature of 400 ° C. Next, ZnS: Mn for forming the first phosphor layer 4
The film 4 was uniformly formed on the entire surface by the EB vapor deposition method at a substrate temperature of 200 ° C. AZ4903 as the first resist film 5 thereon
(Hoechst Japan Co., Ltd.) is applied and prebaked at 90 ° C. for 30 minutes, then OFPR800 (Tokyo Ohka Co., Ltd.) is applied as a second resist film 6 to a thickness of 2 μm and prebaked at 90 ° C. for 15 minutes. I went. Each film thickness is 650 nm for ITO film 2, Sr
(Zr _0.2 Ti _0.8 ) O ₃ was set to 500 nm and ZnS: Mn was set to 650 nm.

FIG. 1 (c) in which the ZnS: Mn film 4 is etched by RIE.
The etching gas was CH ₃ OH, and the etching was performed for about 25 minutes.
After the etching is completed, the photoresist is removed, and the ZnS: Tb film 7 is RF-sputtered on the photoresist and the substrate temperature is 20
At 0 ° C., the film thickness was formed to a thickness of 550 nm (FIG. 1 (d)). Next, after annealing in vacuum at 450 ° C. for 1 hour, resist films 8 and 9 were applied, exposed and developed to form a predetermined pattern (FIG. 1 (e)). CH ₃ OH by RIE
Then, after etching for about 25 minutes, the resist was removed to complete the phosphor pattern (FIG. 1 (f)). Next is BaTa ₂ O ₆
The film 10 was formed by the RF magnetron sputtering method. The film thickness was 150 nm. Finally, the Al electrode 11 is formed and the thin film E
The L element was completed (Fig. 1 (g)). This EL element also had a brightness equivalent to that of each phosphor single film, and no brightness unevenness was observed.

According to the present invention, it is possible to form a plurality of types of phosphor layers using different types of light emitting base materials in different patterns on the same plane. Therefore, it goes without saying that the present invention is also effective when three or more types of phosphor layers are formed.

EFFECTS OF THE INVENTION According to the present invention, it is possible to form a plurality of phosphor layers having original emission brightness in different patterns on the same plane, and to prevent uneven emission due to uneven etching of the phosphor.
EL element can be provided.

[Brief description of drawings]

1 (a) to 1 (g) are thin films in one embodiment of the present invention.
FIG. 6 is a process cross-sectional view showing the method of manufacturing an EL element. 1 ... glass substrate, 2 ... transparent electrode, 3 and 10 ... dielectric layer, 4 ... first phosphor layer, 5 and 8 ... first resist layer, 6 and 9 ... second Resist layer, 7 ... Second phosphor layer, 11 ... Al electrode.

Claims (1)

[Claims] 1. A first layer for selectively patterning a phosphor layer on a substrate by forming a predetermined pattern on the phosphor layer using a resist and performing dry etching using the resist as a mask. Is coated with a thick film resist having a large light transmittance, a second layer is coated with a resist excellent in dry etching resistance, and both are simultaneously exposed, developed and post-baked to form the resist pattern formed of a two-layer film. After that, a multicolor thin film characterized by performing dry etching
EL element pattern formation method.