JPH07272852A - Manufacture of electroluminescent element - Google Patents

Abstract

PURPOSE:To establish a film growing method with which the film thickness can be well controlled using a puttering process base board transport type puttering process. CONSTITUTION:According to a sputtering process in the base board transport system, the film thickness growing speed decreases monotonously, wherein the speed sinks relatively quickly to approx. ten times and is saturated by and by to become steady substantially at 30th times. A program to regulate the base board transport speed and the number of reversals at each batch is prepared on the basis of the described pattern of growing speed, and a light emission layer is formed. That is, the program should be such that the moving speed of a board transporting tray is regulated for attaining the specified film thickness and that the number of reversals is made 2-3 according to necessity. The program may be conducted by giving a command value for the tray driving system from a microcomputer which is used conventionally.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electroluminescence device (hereinafter referred to as an EL device), and particularly to an EL device.
The present invention relates to a method of forming a light emitting layer of a device.

[0002]

2. Description of the Related Art Conventionally, when a large-sized substrate is used to form an EL element, the substrate is placed on a transfer tray, and a desired layer is formed by passing the front surface of a target to form a desired layer. Is used. In this method, since the substrates are placed one by one on the tray, they are formed by batch processing.
The light-emitting layer of the EL element is also formed by this substrate-conveying sputtering method. As shown in FIG. 5, the thickness of this light-emitting layer greatly contributes to the light-emitting characteristics of the EL element. Is desired. Usually, the sputtering is performed by using a material to be grown as a target and discharging it by using high frequency power. Since the discharge of this sputtering is not stable immediately after energization, the sputtering is performed under a steady discharge state while monitoring the voltage. Sputtering in a stable discharge state is considered to be stable in deposition, and it is said that a constant film thickness can be obtained.

[0003]

Since the substrate is moved in the substrate transfer type sputtering method, the film thickness monitor used in other fixed substrate type or vapor deposition methods cannot be used. Therefore, the film thickness to be formed can only be controlled by the film formation time (sputtering time, hereinafter referred to as sputtering time). However, the growth rate of this sputtering, the inventors actually substrate-type sputtering method, ZnS: Tb and ZnS: Sm and other materials,
When the number of batches was increased using the same target, it was found that the growth rate was not constant, as shown in FIG. 1, although the mechanism was unknown. Therefore, it is necessary to strictly control the film thickness of this light emitting layer in order to obtain a constant light emitting characteristic of the EL element in production. Therefore, it is necessary to strictly control the film thickness by the conventional substrate transfer type sputtering method. Desired.

Therefore, an object of the present invention is to provide a growth method capable of controlling the film thickness by the substrate transfer type sputtering method.

[0005]

Since the characteristic shown in FIG. 1 has a substantially constant reduction rate, stable sputtering can be realized by forming a film in consideration of this characteristic. Therefore, in order to solve the above problems, the structure of the present invention has a first electrode, a first insulating layer, a light emitting layer, a second insulating layer and a second electrode on a support substrate, at least a light emitting layer, a second insulating layer and a second insulating layer. In the method for manufacturing an electroluminescent device in which two electrodes are sequentially laminated with an optically transparent one, in the step of forming the light emitting layer, for each batch treatment, the sputtering time is changed to the light emitting layer growth rate depending on the number of batch treatments. That is, the light emitting layer is grown by a corresponding program, and the light emitting layer having the same thickness is formed in each batch process. Further, the structure of the related invention is characterized in that the correspondence of the sputtering time is adjusted by a program for adjusting the substrate transfer speed and the number of reciprocations in the substrate transfer-type sputtering method, or alternatively, the correspondence of the sputtering time is adjusted by the shutter-type sputtering. The opening and closing time of the shutter that covers the target of the device is controlled by a program to form a light emitting layer having an equal thickness in each batch process. The configuration of the present invention is also characterized in that the light emitting layer growth rate is measured in advance by a sputtering apparatus for growing the light emitting layer.

[0006]

In the substrate transport type sputtering method, the film thickness growth rate monotonously decreases, the rate drops relatively large up to about 10 batches, gradually saturates and becomes almost steady around the 30th batch ( Figure 3. However, the number of times depends on the sputtering equipment used). Therefore, based on this growth rate, a program for adjusting the substrate transport speed and the number of reciprocations is set for each batch process to form the light emitting layer. In the actual number of batch processes, the sputtering apparatus is overhauled up to about 30 times, and the number of batch processes becomes the film growth rate from 1 again.

[0007]

EFFECTS OF THE INVENTION Since the sputtering time is adjusted by the substrate transport speed and the number of substrate reciprocations, the film is formed in accordance with the film thickness growth rate, so that the variation in the film thickness of the light emitting layer is suppressed between the batch processes, and the light emission characteristics are improved. A uniform EL element is formed.

[0008]

EXAMPLES The present invention will be described below based on specific examples. As shown in FIG. 3, the inventors found that the change in the film formation rate with respect to the number of batches of film formation measured by the substrate transfer type sputtering apparatus as shown in FIG. It was found that the change was stable up to about 10 times, and was stable up to about 30 batches, and the film deposition rate was almost constant. The detailed mechanism for this is currently unknown. However, when the layer to be formed is the light emitting layer of the EL element, the fact that the film forming rate is not constant greatly affects the characteristics of the EL element.

FIG. 2 is a schematic configuration diagram of a substrate transfer type sputtering apparatus 200 used in the present invention. A gate valve 22 is provided at an end of a film forming chamber 21, and a substrate heating chamber 23 for preheating a substrate is provided outside the gate valve 22. It is provided. After the substrate 20 is placed on the substrate tray and heated in the substrate heating chamber 23, the gate valve 22 is opened to carry it into the film forming chamber 21 and the gate valve 22 is closed. A slight amount of argon (Ar) / helium (He) gas is introduced into the chamber. After the sputter discharge is started and stabilized, the substrate 20 is brought in front of the target 25 to form a film. The transportation of the substrate 20 is automatically processed by a computer. Usually, the transport speed is controlled to be constant in order to maintain the uniformity of film formation. Therefore, since the time for passing in front of the target 25 is determined by the transport speed, the film thickness is also determined by the transport speed of the substrate 20. Therefore, in order to obtain a predetermined film thickness, the number of reciprocations is programmed to be 2-3 times as necessary. The program can be executed by outputting an instruction value to the drive system of the tray by a microcomputer which is usually used.

Here, the light emitting layer deposition rate of the sputtering apparatus is actually measured in advance using a dummy substrate or the like before it is used, and is programmed using the data.

The light emitting layer which is often formed by sputtering is
As shown in FIG. 5, if the film thickness varies, the emission intensity and the emission start voltage also vary, and the quality deteriorates. Therefore, it is necessary to keep the thickness of the light emitting layer constant for manufacturing. Therefore, based on the characteristics of FIG. 3, the sputtering time for each batch is adjusted to drive the substrate transfer tray 20 (FIG. 2) of the sputtering apparatus so that the film thickness becomes constant.
That is, in the first few batches where the film forming speed is fast, the conveying speed is increased according to the film forming speed, and as the number of batches increases, the conveying speed is slowed down according to the decreased film forming speed, and slowly. If not possible, the number of reciprocations of the tray is also selected to be increased, and the substrate transfer speed and the number of reciprocations of the tray are determined so that the film thickness is constant. Here, the number of reciprocations means that the mechanism of the substrate-conveying-type sputtering apparatus shown in FIG. 2 forms a film on the target so that the target passes through the tray. This is because the film is formed, and after passing, it quickly returns to the position just before the gate valve and then passes through the target region again at a low speed.

FIG. 4 shows a thin film EL formed by the manufacturing method of the present invention.
6 is a schematic view showing a vertical cross section of a display device 400. FIG. In the thin film EL display element 400 of FIG. 4, light is extracted in the arrow direction.

The thin film EL display element 400 is constructed by bonding a thin film EL display element 500 that emits yellow-orange light and a thin film EL display element 600 that emits green light in a mounting process. One of the thin film EL display elements 500 is a glass substrate 6 which is an insulating substrate.
The following thin films are sequentially laminated and formed on the substrate 1.

A first transparent electrode (first electrode) 62 made of optically transparent zinc oxide (ZnO) is formed on a glass substrate 61, and an optically transparent tantalum pentoxide ( Ta ₂ O ₅ ) first insulating layer 63, manganese (Mn) -doped zinc sulfide (ZnS) light emitting layer 64, optically transparent tantalum pentoxide (Ta ₂ O ₅ ) second layer Insulation layer 6
5. An upper transparent electrode (second electrode) 66 made of optically transparent zinc oxide (ZnO) is formed.

The other thin film EL display element 600 is
The thin film EL display element 500 basically has the same layer structure. That is, the thin film EL display element 600 is formed on the glass substrate 21 in order of the first transparent electrode (first electrode) 2
2, a first insulating layer 23, a light emitting layer 24, a second insulating layer 25, and a thin film of a second transparent electrode (second electrode) 26 are laminated. Of these, only the composition and amount of the luminescent center added to the luminescent layer 24 are different. Specifically, in the thin film EL display element 600, the thin film EL display element 50
0, a light emitting layer 24 made of zinc sulfide (ZnS) added with terbium (Tb) is formed instead of the light emitting layer 14 made of zinc sulfide (ZnS) added with manganese (Mn). . Then, both thin film EL display elements 500, 600
Are sealed by injecting silicone oil 80 into these intermediate portions and bonding them together.

Next, the above-mentioned thin film EL display element 50.
The manufacturing method of No. 0 will be described below. (1) First, the first transparent electrode 62 was formed on the glass substrate 61. As the vapor deposition material, zinc oxide (ZnO) powder to which gallium oxide (Ga ₂ O ₃ ) was added and mixed and molded into pellets was used. An ion plating device was used as a film forming device. Specifically, the temperature of the glass substrate 61 is set to 1
5 × in the ion plating device while maintaining at 50 ℃
The gas was exhausted to 10 ^-3 Pa. After that, argon (Ar) gas was introduced to maintain 6.5 × 10 ⁻¹ Pa and the film formation rate was 1.0 to 3.0 Å
The beam power and the high frequency power were adjusted to be within the range of / sec.

(2) Next, a first insulating layer 63 made of tantalum pentoxide (Ta ₂ O ₅ ) was formed on the first transparent electrode 62 by sputtering. Specifically, the temperature of the glass substrate 61 is set to 200
Hold the temperature at ℃, maintain the inside of the sputtering equipment at 1.0 Pa, introduce a mixed gas of argon (Ar) and oxygen (O ₂ ) into the equipment (200 cc / min), and deposit at a high-frequency power of 1 kW at a rate of 2Å / sec.
It went on condition of.

(3) Zinc sulfide (Zn) is formed on the first insulating layer 13.
A zinc sulfide: manganese (ZnS: Mn) light emitting layer 64, in which S) was used as a base material and manganese (Mn) was added as an emission center, was formed by vapor deposition. Specifically, the temperature of the glass substrate 61 is set to 1
The temperature was maintained at 20 ° C., the inside of the vapor deposition apparatus was maintained at 5 × 10 ⁻⁴ Pa or less, and electron beam vapor deposition was performed at the deposition rate of 1.0 to 3.0 Å / sec.

(4) Next, a second insulating layer 65 made of tantalum pentoxide (Ta ₂ O ₅ ) is formed on the light emitting layer 64 and a first insulating layer 6 is formed.
It was formed in the same manner as in No. 3. (5) After forming the above layers on the glass substrate 61, 5 × 10 ⁻⁴
A heat treatment was performed at 400 to 600 ° C. for 2 hours in a vacuum of Pa.
By this heat treatment, the crystallinity of the light emitting layer 64 was improved and the emission luminance was increased. (6) After the heat treatment, the second transparent electrode 66 made of a zinc oxide (ZnO) film is formed by the same method as the above-mentioned first transparent electrode 62.
It was formed on the second insulating layer 65. (7) The film thickness of each layer is 30 for the first and second transparent electrodes 62, 66.
00Å, the first and second insulating layers 63 and 65 are 4000Å, the light emitting layer 6
4 is 6000Å. The thickness of each layer is described with reference to the central portion thereof.

As described above, the thin-film EL display device 600 has the same layer structure as the thin-film EL display device 500 except for the light-emitting layer 74, so only the method for manufacturing the light-emitting layer 74 will be described.

The light emitting layer 74 is made of zinc sulfide (ZnS) as a base material, and zinc sulfide: terbium (ZnS: Tb) added with terbium (Tb) as an emission center is used as a target in the substrate transfer type sputtering apparatus shown in FIG. It was formed by high frequency sputtering. Specifically, the temperature of the glass substrate 71 is maintained at 200 ° C, and the inside of the sputtering device is set to 0.5 to 10
It was maintained at Pa and sputtered. Sputtering is performed 5 times in batch (here, 1 substrate / 5 times in 1 batch)
When the light emitting layer is continuously formed, the substrate transfer speed of the tray on which the substrate is placed is determined based on the change in the film thickness shown in FIG.
Set 40 to 55 mm / min and the number of conveyances to 2 to 3 times,
The thickness of the light emitting layer was programmed to be the same. In addition,
This program is included in the drive system of the sputtering apparatus in FIG. 2, and automatically controls this sputtering apparatus to automatically treat the target film formation.

(Second Embodiment) The method of the present invention can be carried out not only by the substrate-conveying type sputtering apparatus but also by a batch type sputtering apparatus. That is, immediately after the sputter discharge is started between the substrate 30 and the target 35 in the batch type sputtering apparatus 300 shown in FIG. 6, the film formation is not uniform in an unstable state. Keep the film from growing. Then, when stable sputter discharge is reached, the shutter 31 is opened to start film formation. After a predetermined time, the shutter 31 is closed to complete the film formation. Here, the opening / closing time of the shutter 31 is programmed so that the film thickness becomes uniform corresponding to the number of batches, and the sputtering is performed. As a matter of course, if the sputtering apparatus is different, the film forming rate for each batch also differs. Therefore, the programming is performed based on the film forming rate value actually measured in advance.

By the way, the sputtering time in the claims is
It refers to the time during which the target material is deposited near the target being discharged, and the time during which the substrate is carried to the tray and passes near the target. Therefore,
The substrate transfer type sputtering apparatus can adjust the substrate transfer speed and the number of reciprocations, and the batch type sputtering apparatus can adjust the sputtering time by a shutter. Due to the structure of the apparatus, the substrate transportation speed needs to have an appropriate speed value according to the sputtering apparatus used, and when the speed cannot be compensated, the sputtering time is adjusted by the number of reciprocations. However, the adjustment by the combination method of them is free. Needless to say, the number of reciprocations may be 1 or less (0.5 times) when the desired film thickness is thin or when the film formation rate is high.

The thin film EL shown in FIG. 4 used in the present invention.
The display element is not limited to the configuration shown in the above embodiment, and various modifications as described below are possible. (1) Zinc sulfide: manganese (Z
Instead of nS: Mn), for example, strontium sulfide: cerium (SrS: Ce) that emits blue-green light is used. And thin film EL
As the oil-soluble dye, for example, an azo-based or anthraquinone-based blue dye intermediate may be dissolved and dispersed in the silicone oil covering the light extraction side of the display element. In the thin-film EL display device having such a structure, the blue dye intermediate acts as a blue filter, and a blue color having a good color purity can be obtained as a whole. (2) The first and second insulating layers 63, 65, 73 and 75 were made of tantalum pentoxide (Ta ₂ O ₅ ), but Al ₂ O ₃ , PbTiO ₃ , Y ₂ O ₃ and Si were used.
It may be composed of ON, Si ₃ N ₄ .

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a batch number dependence of a film thickness of a sputtering apparatus.

FIG. 2 is a schematic configuration diagram of a substrate transfer type sputtering apparatus.

FIG. 3 is an explanatory diagram showing the dependence of the film forming speed on the number of round trips.

FIG. 4 is a schematic structural cross-sectional view of a thin film EL display element embodying the present invention.

FIG. 5 is an explanatory diagram showing the light emitting film thickness dependence of the light emitting characteristics of an EL element.

FIG. 6 is a schematic configuration diagram of a batch type sputtering apparatus.

[Explanation of symbols]

 200 substrate transfer type sputtering device 21 film forming chamber 22 gate valve 23 substrate heating chamber 24 heater 25 sputter target 300 batch type sputtering device 31 shutter 34 heater 35 sputter target 400 thin film EL display element 500 first EL element 600 second EL Element 61 Glass substrate (insulating substrate) 62 First transparent electrode (first electrode) 63 First insulating layer 64 Light emitting layer 65 Second insulating layer 66 Second transparent electrode (second electrode)

Claims (4)

[Claims] 1. A first substrate, a first insulating layer, a light emitting layer, a second insulating layer and a second electrode, at least a light emitting layer, a second insulating layer and a second electrode being optically transparent on a supporting substrate. In the method for manufacturing an electroluminescent element in which the light emitting layers are sequentially stacked in, in the step of forming the light emitting layer, the light emitting layers are formed by a program in which the sputtering time is associated with the light emitting layer growth rate depending on the number of batch processes in each batch process. A method for manufacturing an electroluminescence device, which comprises growing the light emitting layer to have an equal thickness in each batch process. 2. The method for manufacturing an electroluminescence element according to claim 1, wherein the correspondence of the sputtering time is adjusted by a program for adjusting a substrate transfer speed and the number of reciprocations in the substrate transfer-type sputtering method. 3. Corresponding to the sputtering time, the opening / closing time of a shutter for covering a target of a shutter type sputtering apparatus is adjusted by a program to form a light emitting layer having an equal thickness in each batch process. Item 2. A method for manufacturing an electroluminescent element according to Item 1. 4. The method for manufacturing an electroluminescent element according to claim 1, wherein the growth rate of the light emitting layer is measured by a sputtering apparatus for growing the light emitting layer in advance.