JPH0633106A - Production of sputtering target for production of light emitting layer of thin-film electroluminrescence element - Google Patents

Abstract

PURPOSE:To provide the sintered body target having a high and fine density by mixing a light emission center additive and sulfur powder with SrS powder, then heat treating the mixture with a sulfurizing gaseous atmosphere and hot pressing the mixture in an inert gaseous atmosphere. CONSTITUTION:The light emission center additive, such as CeF3, and the sulfur powder are mixed with the SrS powder and the mixture is heat treated at 300 to 1500 deg.C in the sulfurizing gaseous atmosphere. The powder is hot pressed at about 500 to 2000 deg.C in the inert gaseous atmosphere or after the powder is molded by a press machine in the same atmosphere, the molding is subjected to a heating treatment. As a result, the sputtering target for forming the light emission layer with which the EL element emitting light with high luminance is obtainable is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film electroluminescent device (hereinafter referred to as "E") which emits light in response to an electric field applied.
The present invention relates to a method for producing a sputter target used for producing a light emitting layer.

[0002]

2. Description of the Related Art M is used for compound semiconductors such as ZnS and ZnSe.
The phenomenon of electroluminescence in which light is emitted by applying a high voltage to a material to which a luminescence center such as n is added has been known for a long time. In recent years, due to the development of the double insulating layer type EL device, the brightness and the life have been dramatically improved, and the thin film EL device has been applied to a thin display, and has come to the market now.

The emission color of the EL element is determined by the combination of the semiconductor matrix forming the light emitting layer and the doped emission center.
For example, when ZnS host is doped with Mn as an emission center, yellow electroluminescence is obtained, and when Tb is added, green electroluminescence emission (hereinafter abbreviated as EL emission) is obtained. EL light emission is obtained when the SrS host is doped with Ce as the emission center and blue is emitted when the CaS host is doped with Eu as the emission center.

However, only the yellow-orange system in which Mn is added to the ZnS matrix is the one that has reached the practical level of brightness at present. When a full-color thin film display is manufactured using EL elements, EL elements that emit three primary colors of blue, green, and red are required, and EL that emits each color with high brightness.
The development of the device is being actively pursued. SrS is useful as a base material in developing such a color EL device. For example, SrS obtained by doping Ce with SrS:
Blue-green in the Ce light-emitting layer, Sr with Eu doped in SrS
It is known that red light emission can be obtained in the S: Eu light emitting layer.

The light emitting layer is formed by a resistance heating vapor deposition method, an electron beam heating vapor deposition method, a sputter vapor deposition method, an MOCVD method (metal organic chemical vapor deposition method), an MBE method (molecular beam epitaxial method), The ALE method (atomic layer epitaxial method) or the like is used. As a relationship between the crystallinity of the light emitting layer formed by these methods and the brightness of the EL element, it is known that the EL element having a highly crystallized light emitting layer has high brightness.

It is presumed that this is because the electrons accelerated by the electric field applied to the light emitting layer efficiently excite the luminescence center. A highly crystalline thin film is obtained from a ZnS: Mn light-emitting layer manufactured by MOCVD, ALE, or MBE, and an EL element which emits light with high brightness is manufactured. However, in a system using a compound semiconductor other than ZnS as a matrix, for example, in a SrS: Ce light emitting layer that emits blue light, an element that emits light with high brightness has not been obtained.

The MOCVD method, the ALE method, and the MBE method are promising methods for producing a highly crystalline thin film, but it is difficult to uniformly disperse the emission centers, and a large-area EL emission layer is used. There is a problem that it is inferior to the electron beam heating vapor deposition method and the sputter vapor deposition method in that it is economically difficult to manufacture. In order to increase the crystallization of the light-emitting layer, which is one of the promising conditions for manufacturing an EL device exhibiting high-brightness emission, the substrate temperature during the production of the light-emitting layer is increased, or after the light-emitting layer is produced in a vacuum or at Methods such as high temperature heat treatment in an active gas atmosphere have been taken. However, in many cases, thin film EL elements use glass as a substrate, and therefore, when heat-treated at a high temperature of 850 ° C. or higher, there is a problem such as glass distortion. Further, when SrS, which is a sulfide, is used as a base material of the light emitting layer, the amount of S in the film decreases due to the high temperature heat treatment, which deviates from the stoichiometric composition,
In addition, it is also a big problem that a highly crystallized light emitting layer cannot be formed due to a defect caused by the escape of S.

Japanese Examined Patent Publication No. 63-461117, JP-A-1
-272093 and Japanese Patent Laid-Open No. 3-225792 describe heat treatment in H ₂ S after forming a light emitting layer. Particularly, in JP-A-3-225792, after forming a light emitting layer by a sputtering method,
By heat treatment of H ₂ S at 0 ° C. or higher for 1 hour or longer, SrS:
Ce system maximum brightness 12000 cd / m ² , SrS: C
7,000 cd / m ² was obtained for the e and Eu systems.

Conventionally, as a method for producing a target used for sputtering, after mixing an emission center additive with SrS powder, hot pressing in an inert gas atmosphere, after mixing an emission center additive with SrS powder. , A method of molding under pressure in an inert gas atmosphere, and the like.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a sputtering target for producing a light emitting layer, which can obtain an EL element that emits light with particularly high brightness.

[0011]

[Means for Solving the Problems] Under such circumstances,
The inventors of the present invention have made earnest studies on a method of manufacturing a sputter target used for manufacturing a light emitting layer of an EL device exhibiting high-luminance light emission, and as a result, after mixing an emission center additive and sulfur powder with SrS powder, a sulfurous gas atmosphere was used. By hot pressing the heat-treated powder in an inert gas atmosphere, sintering between powder particles is promoted as compared with the conventional technique, and a sintered compact target having a high density can be obtained. In addition, after the light emitting layer is formed by the sputtering method using the target, the light emitting layer is heat-treated in a sulfide gas atmosphere, so that the crystal grains of the light emitting layer grow large, thereby increasing the brightness of the EL device. The present invention has been completed by discovering that the above-mentioned is significantly improved.

That is, according to the present invention, in a method of manufacturing a sputter target for producing a light emitting layer in which an SrS base material is doped with an emission center, after mixing an emission center additive and sulfur powder with SrS powder, it is heated at 300 ° C. to 1500 ° C. in a sulfur gas atmosphere. In the method for producing a sputter target, which is characterized by heat-treating at ℃, hot pressing the powder in an inert gas atmosphere, or molding with a press in an inert gas atmosphere, and then heat-treating in the same atmosphere. is there.

The present invention will be described in detail below. Under the manufacturing conditions of the sputter target used for manufacturing the light emitting layer, after mixing the emission center additive and the sulfur powder with the SrS powder, the mixture is heat-treated in a sulfide gas atmosphere, and then hot-pressed in an inert gas atmosphere. It is important to mold with a press machine under an active gas atmosphere and heat-treat under the same atmosphere. The material and element of the luminescence center added to the SrS host are not particularly limited. For example, in the case of a Ce luminescence center that can obtain blue-green luminescence, CeF ₃ , Ce ₂ O ₃ , Ce ₂ S as the luminescence center additive material are used. ₃ etc. The concentration of the luminescent center added to the host is not particularly limited, but if it is too low, the emission brightness does not increase, and
If it is too much, the crystallinity of the light emitting layer is deteriorated, or concentration quenching occurs and the brightness does not increase. Therefore, SrS: C
As a specific example of e, it is preferably in the range of 0.01 to 5 mol% and more preferably in the range of 0.05 to 2 mol% with respect to SrS of the entire light emitting layer base material. The amount of the sulfur powder mixed with the SrS powder is not particularly limited, but is preferably 0.5 wt% with respect to the SrS powder.
˜30%, more preferably 2 wt% to 15 wt%
Is. Hydrogen sulfide, carbon disulfide,
Sulfur vapor, ethyl mercaptan, methyl mercaptan,
There are dimethylsulfur, diethylsulfur, and the like. Among them, hydrogen sulfide gas is preferable because it has a large effect of improving brightness. The concentration of the sulfurizing gas is not particularly limited, but a concentration of 10% or more is preferable in order to obtain the heat treatment effect in the sulfurizing gas atmosphere. An inert gas such as argon or helium is used as the diluent gas. Further, since the heat treatment effect is exhibited in the sulfide gas atmosphere, the heat treatment time needs to be 1 hour or more. The heat treatment temperature in the sulfide gas atmosphere is 300 ° C to 1500 ° C, more preferably 400 ° C to 1200 ° C. Examples of the inert gas which is an atmosphere in hot pressing, pressure molding by a pressing machine, and heat treatment after molding include argon, helium, nitrogen and the like. The temperature of the heat treatment during hot pressing or after pressure molding is 500 ° C to 2000 ° C,
More preferably, it is 700 ° C to 1200 ° C. The pressing pressure for hot pressing or pressure molding with a pressing machine is 1 to 1000 kg / cm ² , and more preferably 10 to 1000 kg / cm ² . The hot press or pressure molding time by a press machine is 0.01 to 180 minutes, preferably 0.05.
~ 90 minutes.

The target thus obtained is used to form a light emitting layer by sputtering.
The light-emitting layer produced by heat-treating this film in a sulfurized gas atmosphere has a large crystal grain and is highly crystallized as compared with the case where sputtering is performed using a target by the conventional manufacturing method. Therefore, the brightness of the thin film EL element is significantly improved.

As the sulfide gas atmosphere used for the heat treatment of the light emitting layer, as described above, there are hydrogen sulfide, carbon disulfide, sulfur vapor, ethyl mercaptan, methyl mercaptan, dimethyl sulfur, diethyl sulfur and the like. Hydrogen gas is preferable because it has a large effect of improving brightness. The heat treatment concentration in the sulfurizing gas atmosphere is not particularly limited, but is 0.01 to 100%, more preferably 0.1 to 30.
%. An inert gas such as argon or helium is used as the diluent gas. Further, in order for the effect of the sulfurizing gas to be prominent, the heat treatment temperature must be 650 ° C. or higher and the time must be 1 hour or longer. However, heat treatment at a temperature of 800 ° C. or higher causes problems such as distortion of the substrate glass, high resistance of ITO used as a transparent electrode, and necessity of using an expensive quartz glass substrate.

[0016]

EXAMPLES Examples of the present invention will be specifically described below. Luminance of the EL element in the examples was measured by LUMINANCE COLORIMATE in a dark room.
It was performed using RBM-7 (manufactured by TOPCON).

[0017]

Example 1 Glass substrate [Hoya Co., Ltd., NA-4
0] by a reactive sputtering method to a thickness of about 100 nm.
The ITO electrode of was formed. On top of that, a Ta target and a SiO ₂ target are used to form Ta with a thickness of 400 nm.
₂ O ₅ and SiO ₂ having a thickness of 100 nm were sequentially formed by a sputter deposition method to form an insulating layer. Subsequently, a ZnS thin film having a thickness of about 100 nm was prepared as a buffer layer by sputter deposition in an argon gas using a ZnS target. Next, 0.3 mol% C relative to SrS and SrS
After mixing eF ₃ and KCl, 5 wt% sulfur powder,
A powder heat-treated in 100% H ₂ S at 500 ° C. for 6 hours was subjected to argon gas atmosphere at 900 ° C. and 100 kg / c.
A target hot-pressed with m ² was prepared. Using this target, sputter deposition was performed while maintaining the substrate temperature at about 300 ° C. to form a light emitting layer thin film having a thickness of about 800 nm. Then, heat treatment was performed at 700 ° C. for 4 hours in an argon gas atmosphere containing 2 mol% hydrogen sulfide. Further, a laminated film was formed on the light emitting layer in the order of ZnS, SiO ₂ , and Ta ₂ O ₅ by the above method to construct a double insulating structure. Finally, Al electrodes were formed in a stripe shape by a resistance heating vapor deposition method using a metal mask. As the lower electrode, a part of the light emitting layer and the insulating layer was peeled off to expose the ITO electrode, which was used.

The SrS (200) was obtained by measuring the X-ray diffraction spectrum of the light emitting layer after the heat treatment under the above conditions and measuring the width of the point having an intensity half the maximum value of the obtained diffraction peak. The half-widths of the peaks of the () plane and the (220) plane are 0.12 degrees and 0.16 degrees, respectively, which are smaller than the peak half-widths of Comparative Example 1 which is a conventional technique.

The maximum brightness of the EL device manufactured from this light emitting layer is 16500 cd / m ^{2 when} driven by a 5 kHz sin wave.
Met.

[0020]

[Example 2] SrS and 0.3 mol% CeF ₃ and KCl with respect to SrS were mixed, and the mixture was placed in an argon gas atmosphere.
Press molding was performed at room temperature and 100 kg / cm ² for 5 minutes, and then the molded product was heat-treated at 900 ° C. in an argon gas atmosphere to prepare a sputter target. An element was manufactured in the same manner as in Example 1 using the target. Example 1
SrS (200) after heat treatment obtained by the same method as
The FWHMs of the peaks of the (220) plane and the (220) plane are 0.12
The degree was 0.16 degrees. In addition, the maximum brightness of the EL element manufactured from this light emitting layer is 1 at 5 kHz sin wave drive.
It was 6400 cd / m ² .

[0021]

[Comparative Example 1] SrS and 0.3 mol% of CeF ₃ and KCl with respect to SrS were mixed, and the mixture was placed in an argon gas atmosphere.
A sputter target was produced by press molding at room temperature and 100 kg / cm ² for 5 minutes. An element was manufactured in the same manner as in Example 1 using the target. The half-value widths of the peaks of the SrS (200) plane and (220) plane after heat treatment, which were obtained by the same method as in Example 1, were each 0.17.
It was 0.24 degrees. In addition, the maximum brightness of the EL element manufactured from this light emitting layer is 1 at 5 kHz sin wave drive.
It was 2000 cd / m ² .

[0022]

[Comparative Example 2] SrS and SrS were mixed with 0.3 mol% CeF ₃ and KCl, and 5 wt% sulfur powder, and then the powder was heat-treated at 500 ° C. for 6 hours in 100% H ₂ S atmosphere. In a gas atmosphere, room temperature, 100 kg
Press molding was carried out for 5 minutes at / cm ² to prepare a sputter target. An element was manufactured in the same manner as in Example 1 using the target. The half widths of the peaks of the SrS (200) plane and the (220) plane after heat treatment, which were obtained by the same method as in Example 1, were 0.18 degrees and 0.25 degrees, respectively. The maximum brightness of the EL device produced from this light emitting layer was 11000 cd / m ^{2 when} driven by a 5 kHz sin wave.

[0023]

Comparative Example 3 SrS and 0.3 mol% CeF ₃ with respect to SrS were mixed, and then 900
A sputter target was prepared by hot pressing at 100 ° C. and 100 kg / cm ² for 5 minutes. An element was manufactured in the same manner as in Example 1 using the target. The half-value widths of the peaks of the SrS (200) plane and (220) plane after the heat treatment obtained by the same method as in Example 1 were each 0.18.
Was 0.25 degrees. In addition, the maximum brightness of the EL element manufactured from this light emitting layer is 1 at 5 kHz sin wave drive.
It was 1000 cd / m ² .

[0024]

Example 3 SrS and SrS were mixed with 0.3 mol% CeF ₃ and KCl, 10 wt% sulfur powder, and then heat treated in 100% H ₂ S at 800 ° C. for 6 hours. 900 ℃, 100kg under gas atmosphere
/ Cm ² was hot-pressed for 5 minutes to prepare a sputter target. An element was manufactured in the same manner as in Example 1 using the target. EL manufactured from this light emitting layer
The maximum brightness of the element is 1600 when driven by a 5 kHz sin wave.
It was 0 cd / m ² .

[0025]

Example 4 SrS and SrS were mixed with 0.3 mol% CeF ₃ and KCl, 5 wt% sulfur powder, and then heat treated in 100% H ₂ S at 500 ° C. for 6 hours. In a gas atmosphere, 1200 ° C, 300k
Hot pressing was performed at g / cm ² for 5 minutes to prepare a sputter target. An element was manufactured in the same manner as in Example 1 using the target. E produced from this light emitting layer
Maximum brightness of L element is 162 at 5kHz sin wave drive
It was 00 cd / m ² .

[0026]

Example 5: SrS and SrS with 0.3 mol% CeF ₃ and KCl, and 0.02 mol% EuF ₃ ,
After mixing 5 wt% sulfur powder, 100% H ₂ S
Inside, a powder heat-treated at 500 ° C. for 6 hours was hot-pressed at 900 ° C. and 100 kg / cm ² for 5 minutes in an argon gas atmosphere to prepare a sputter target. That target
Using Get, in the same manner as in Example 1, SrS: Ce,
An Eu white device was produced. EL manufactured from this light emitting layer
The maximum brightness of the element is 9000 with 5kHz sin wave drive
It was cd / m ² .

[0027]

According to the present invention, S
It is possible to obtain a highly dense sintered body target in which sintering between rS powder particles is further promoted. Also, the target
After the light emitting layer is formed using the get, the light emitting layer can be heat-treated in a sulfurizing gas atmosphere to obtain a highly crystallized light emitting layer with a large crystal grain size. An EL element which emits light with higher luminance than the manufactured element can be manufactured.

Claims (1)

[Claims] 1. A method for producing a sputtering target for producing a light emitting layer, comprising a SrS base material doped with an emission center, comprising:
After mixing the luminescent center additive and the sulfur powder with the S powder, heat treatment is performed at 300 ° C. to 1500 ° C. in a sulfide gas atmosphere, and the powder is hot pressed in an inert gas atmosphere or pressed in an inert gas atmosphere. A method for manufacturing a sputter target, which comprises performing heat treatment in the same atmosphere after molding by a machine.