JP2009073965A - Phosphor thin film and film forming method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphor thin film favorable for use in an inorganic EL element and a PDP and having good color purity and high luminance, and a film forming method forming the film at a high film forming rate. <P>SOLUTION: The phosphor thin film is formed from a sulfide comprising zinc, barium, aluminum, sulfur and europium represented by composition formula: Zn<SB>x0</SB>Ba<SB>x1</SB>Al<SB>x2</SB>S<SB>x3</SB>Eu<SB>x4</SB>(wherein 0.01≤x0≤0.02, x1+x4=1, 2.01≤x2≤3.0, 4.0<x3≤4.3 and 0.03≤x4≤0.10), and the compound composition of the film comprises a phase consisting primarily of a compound phase represented by composition formula: BaAl<SB>2</SB>S<SB>4</SB>:Eu. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a phosphor thin film and a film forming method thereof, and more specifically, can emit light only from a compound whose composition formula is represented by BaAl ₂ S ₄ : Eu, that is, to increase the emission wavelength of fluorescence to a long wavelength. A phosphor thin film having good color purity and high brightness, suitable for inorganic EL (electroluminescence) and PDP (plasma display panel), having a small shift and high emission intensity, and hydrogen sulfide gas. The present invention relates to a film forming method that can be formed without using the film.

In recent years, inorganic EL elements have been actively developed as display elements for computer monitors and portable devices. Among them, a method for performing full-color display using a high-luminance blue phosphor as a phosphor thin film of an inorganic EL element has been proposed, and its practical application has attracted attention. As a promising phosphor thin film developed so far, a thin film mainly composed of a compound whose composition formula is represented by BaAl ₂ S ₄ : Eu is cited. This is obtained by substituting an element (Eu) serving as a light emission center by using a semiconductor material whose composition formula is represented by BaAl ₂ S ₄ as a base material. For example, a phosphor thin film in which EuS corresponding to 0.03-0.10 atomic% of Ba lattice position is added to a base material made of BaAl ₂ S ₄ has good color purity, and is expected as a phosphor for inorganic EL. ing.

As a method for producing such a phosphor thin film, a reactive sputtering method in which hydrogen sulfide gas is contained in a sputtering gas, a reactive vapor deposition method in which a vapor gas containing each constituent element is supplied to form a film, molecular beam epitaxy And chemical vapor deposition have been performed (see, for example, Patent Document 1). In addition, using a sintered body target composed of a compound whose composition formula is represented by BaAl ₂ S ₄ : Eu (hereinafter sometimes referred to as “BaAl ₂ S ₄ : Eu compound”), argon and hydrogen sulfide A method of sputtering in a mixed gas is proposed (for example, see Patent Document 2).
In addition, the composition formula includes at least a divalent metal element such as barium, a trivalent metal element such as aluminum, and a base material that can be represented by sulfur and an emission center material, and the oxygen content ratio is 5% by mass or less. Furthermore, a method is disclosed in which zinc is evaporated during sputtering by using a target containing zinc sulfide and sulfur is filled in the film (for example, see Patent Document 3).
Further, a method is disclosed in which an alloy target whose composition can be expressed by a divalent metal element such as barium or a trivalent metal element such as aluminum is sputtered in hydrogen sulfide (Patent Document 4).

  By the way, with the recent increase in the size of display screens, a phosphor thin film with good color purity and high brightness is desired by a sputtering method that is easy to increase in size. Therefore, it is suitable for film formation of such a phosphor thin film. There is a need for a suitable film formation method.

However, the conventional phosphor thin film forming method in which a sintered body target made of a BaAl ₂ S ₄ : Eu compound or a BaAl: Eu alloy target is sputtered in hydrogen sulfide has a technical problem to be solved. Has been.
For example, in a method in which an alloy target whose composition is represented by a divalent metal element such as barium or a trivalent metal element such as aluminum is sputtered in hydrogen sulfide, hydrogen sulfide is added during sputtering, so that hydrogen sulfide is added from the sputtering apparatus. Safety measures such as using special packing to prevent gas leakage, detecting hydrogen sulfide gas at the time of leakage, and automatically closing the cylinder are necessary. Moreover, hydrogen sulfide is decomposed by argon plasma, and the generated sulfur contaminates the chamber and the vacuum system. In particular, if sulfur adheres to the piping, vacuum ion gauge, or vacuum valve, the vacuum exhaust speed decreases, the ion gauge is disconnected, or the gas leakage of the vacuum valve occurs, resulting in poor maintainability and difficulty in mass production. Moreover, the film forming speed is also slow.

From the above situation, it is possible to form a phosphor thin film having a high color purity and a high luminance, which mainly contains a compound represented by the composition formula BaAl ₂ S ₄ : Eu, without using hydrogen sulfide gas. There is a need for a membrane method.

Japanese Patent Application Laid-Open No. 07-122364 (first page, second page) Japanese Patent Application Laid-Open No. 08-134440 (pages 1 to 3) JP 2001-118677 A (first page, second page) WO 2005/085493 A1 (pages 14-17)

An object of the present invention is to make it possible to emit light only from a compound whose composition formula is represented by BaAl ₂ S ₄ : Eu in view of the above-mentioned problems of the prior art, that is, the shift of the emission wavelength of fluorescence to a long wavelength A phosphor thin film which is small and has a high emission intensity, is suitable for inorganic EL (electroluminescence) and PDP (plasma display panel), has good color purity and high brightness, and uses hydrogen sulfide gas It is an object of the present invention to provide a film forming method that can be formed without any problems.

In order to achieve the above object, the present inventor has conducted extensive research on a phosphor thin film mainly comprising a compound phase represented by the composition formula: BaAl ₂ S ₄ : Eu and a method for forming the phosphor thin film. In a sulfide thin film having a compound structure consisting only of a compound phase represented by a composition formula: BaAl ₂ S ₄ : Eu, having a film composition represented by the following composition formula, the composition formula is derived from a BaAl ₂ S ₄ : Eu compound. It has been found that a blue phosphor thin film with good color purity and high brightness can be obtained because it can emit light only, has a characteristic that the shift of the emission wavelength of fluorescence to a long wavelength is small, and the emission intensity is high. The “phase” described here means, for example, that “BaAl ₂ S ₄ phase” is a precipitated phase composed of a compound whose composition formula is represented by BaAl ₂ S ₄ .

  Further, in the film formation method, when sputtering film formation is performed, first, a zinc sulfide film is formed at a specific substrate temperature using a target made of a sintered body of zinc sulfide, and then on the zinc sulfide film. In addition, an alloy film composed of barium, aluminum and europium is formed at a specific substrate temperature using an alloy target composed of barium, aluminum and europium and having a specific composition, and zinc sulfide is formed under specific conditions. As a result of sputtering, zinc sulfide (ZnS) reacts with the BaAlEu alloy, ZnS decomposes and the alloy is sulfided, and zinc evaporates to form a sulfide thin film having the above composition. It has been found that a blue phosphor thin film with brightness can be obtained. The present invention has been completed based on these findings.

That is, according to the first invention of the present invention, the following composition formula consisting of zinc, barium, aluminum, sulfur and europium:
Zn _x0 Ba _x1 Al _x2 S _x3 Eu _x4
(In the formula, x0 to x4 satisfy the requirements shown in the following (1) to (5).)
A phosphor thin film formed from a sulfide represented by:
There is provided a phosphor thin film characterized in that the compound structure is composed of a phase mainly including a compound phase represented by a composition formula: BaAl ₂ S ₄ : Eu.
(1) 0.01 ≦ x0 ≦ 0.02
(2) x1 + x4 = 1
(3) 2.01 ≦ x2 ≦ 3.0
(4) 4.0 <x3 ≦ 4.3
(5) 0.03 ≦ x4 ≦ 0.10

According to the second invention of the present invention, a zinc sulfide layer is formed while maintaining the substrate temperature at 300 to 600 ° C. in an argon gas atmosphere using the following sintered body target (A), Next, a BaAlEu alloy layer is formed on the zinc sulfide layer by sputtering using the following sintered body target (B) under an argon gas atmosphere while maintaining the substrate temperature at 400 to 650 ° C., On the BaAlEu alloy layer, the following sintered body target (A) was used, and while maintaining the substrate temperature at 550 to 720 ° C., the sputtering amount of zinc sulfide was the number of moles of barium in the BaAlEu alloy layer. There is provided a phosphor thin film deposition method according to the first invention, characterized in that zinc sulfide is sputtered so as to be 4.0 to 4.2 times.
(A) It is comprised from zinc sulfide.
(B) barium, aluminum, and the composition formula consists europium: Ba _y1 Al _y2 Eu _y3 (In the formula, Y1 to Y3 are, y1 + y3 = 1,1.5 ≦ y2 ≦ 3.0,0.03 ≦ y3 ≦ 0.10 is satisfied.).

As is clear from the above, the phosphor thin film of the present invention has a film composition represented by a predetermined composition formula in the first invention, and the compound structure is the composition formula: BaAl ₂ S ₄ : Eu. Since the sulfide thin film is mainly composed of the compound phase represented by formula (1), light is emitted only from the compound represented by the composition formula BaAl ₂ S ₄ : Eu, and the shift of the fluorescence emission wavelength to a long wavelength is small, and Since it has a characteristic of high emission intensity, color purity is good, and since the zinc concentration is low, not only the ZnS phase but also the ZnAl ₂ S ₄ phase is not detected, so that it is a high-luminance blue phosphor thin film.

Further, according to the second invention, which is a method for forming a phosphor thin film of the present invention, a ZnS layer is formed under the above film formation conditions using a sintered body target (A) composed of ZnS, Next, a BaAlEu alloy film is formed using a sintered body target (B) composed of a BaAlEu alloy having a predetermined composition, and then a ZnS film is formed thereon using a sintered body target (A). By sputtering, ZnS reacts with the BaAlEu alloy film and decomposes, and the BaAlEu alloy film is sulfided and zinc is evaporated, so that the thin film can be formed. Therefore, it is favorable for inorganic EL and PDP use. A phosphor thin film with good color purity and high brightness can be obtained.
Moreover, since zinc sulfide is sputtered and reacted while the substrate temperature is maintained at a temperature of 550 ° C. or higher, there is no residual zinc generated by the reaction, and the zinc concentration in the film decreases. At the same time, the deposition rate is increased and stable deposition can be performed. Furthermore, since no hydrogen sulfide gas is added, safety measures for the sputtering apparatus are reduced. Further, since there is no decomposition of hydrogen sulfide and generation of sulfur by plasma during sputtering, contamination of the sputtering chamber and the vacuum exhaust pipe by sulfur can be eliminated. From these things, the industrial value is very large.

Hereinafter, the phosphor thin film and the film forming method of the present invention will be described in detail.
1. Phosphor thin film The phosphor thin film of the present invention has the following composition formula composed of zinc, barium, aluminum, sulfur and europium: Zn _x0 Ba _x1 Al _x2 S _x3 Eu _x4 (wherein _{x0 to x4} are the following) (1) to the phosphor thin film formed from the sulfide represented by (5), wherein the compound structure is a compound represented by the composition formula: BaAl ₂ S ₄ : Eu. It is characterized by comprising a phase mainly containing a phase.
(1) 0.01 ≦ x0 ≦ 0.02
(2) x1 + x4 = 1
(3) 2.01 ≦ x2 ≦ 3.0
(4) 4.0 <x3 ≦ 4.3
(5) 0.03 ≦ x4 ≦ 0.10

In the phosphor thin film of the present invention, it is important that the compound structure of the thin film is mainly composed of a compound phase represented by the composition formula: BaAl ₂ S ₄ : Eu. As a result, a phosphor thin film having good color purity and good for inorganic EL and PDP can be obtained.

That is, normally, in the sputtering of sulfide, when the target composition and the film composition are compared, the ratio of Ba and Al varies greatly. For example, when the Al / Ba molar ratio of the target is 2.2, the Al / Ba molar ratio of the film varies from about 2.05 to 2.10. Thus, when the composition ratio of Ba and Al in the film is on the Al-excess side, a BaAl ₄ S ₇ phase is formed in the film, so that the fluorescence emission wavelength is shifted to the long wavelength side by about 5 nm, and the emission intensity is further increased. Is also about 20% lower.
On the other hand, in the present invention, the ZnS layer and the BaAlEu alloy film are separately formed, and ZnS is sputtered thereon, so that the controllability of the composition is very good.

The composition of the thin film is represented by a composition formula: Zn _x0 Ba _x1 Al _x2 S _x3 Eu _x4 , and _{x0 to x4} in the formula satisfy the following relational expressions (1) to (5). It is important to. As a result, since the zinc concentration in the film is low, a phosphor thin film having particularly high luminance, which is good for inorganic EL and PDP, can be obtained.
(1) 0.01 ≦ x0 ≦ 0.02
(2) x1 + x4 = 1
(3) 2.01 ≦ x2 ≦ 3.0
(4) 4.0 <x3 ≦ 4.3
(5) 0.03 ≦ x4 ≦ 0.10

First, the composition ratio (x0) of zinc satisfies the relational expression of 0.01 ≦ x0 ≦ 0.02. Within this range, a particularly bright film is formed. That is, when the composition ratio of zinc exceeds 0.02, since the amount of zinc remaining in the thin film is large, a ZnS phase is formed in addition to the ZnAl ₂ S ₄ phase. Become. On the other hand, if the composition ratio of zinc is less than 0.01, it cannot react with all of the BaAlEu alloy, so that an unreacted portion is formed in the film, the fluorescence emission intensity is reduced, and the luminance is deteriorated.

The composition ratio (x1) of barium and the composition ratio (x4) of europium satisfy the relational expressions x1 + x4 = 1 and 0.03 ≦ x4 ≦ 0.10. That is, europium is an element that emits fluorescence of the phosphor thin film, and replaces the lattice position of Ba of the base material whose composition formula is represented by BaAl ₂ S ₄ . Europium (Eu) is added so that the composition ratio is 0.03 to 0.10 with respect to barium (Ba). If the composition ratio of Eu is less than 0.03, the emission intensity of fluorescence is lowered and the luminance is deteriorated. On the other hand, if the Eu composition ratio exceeds 0.10, the crystallinity of the base material deteriorates, such being undesirable.

The composition ratio (x2) of aluminum is 2.01 ≦ x2 ≦ 3.0. That is, when the Al composition ratio is less than 2.01, a compound phase having a high Ba content ratio represented by Ba ₂ Al ₂ S ₅ is generated in the phosphor thin film, and the fluorescence peak wavelength is longer. Therefore, the color purity is deteriorated. On the other hand, if the Al composition ratio exceeds 3.0, a compound phase represented by the composition formula BaAl ₄ S ₇ is generated in the phosphor thin film, and the emission intensity of the base material is lowered and the luminance is deteriorated. It is not preferable.

  Moreover, the composition ratio (x3) of sulfur is 4.0 <x3 ≦ 4.3. That is, the composition ratio is greater than 4 which is the stoichiometric composition. When the composition ratio of sulfur is 4.0 or less, it becomes difficult to form the base material. On the other hand, if the composition ratio of sulfur exceeds 4.3, sulfur is precipitated in the film, and it becomes easy to form a polysulfide of Ba. This is not preferable because the formation of the compound structure of the thin film is not stable.

2. Method for Forming Phosphor Thin Film As a film forming method for obtaining the phosphor thin film of the present invention, the substrate temperature is set to 300 to 600 ° C. in an argon gas atmosphere using the following sintered body target (A). A zinc sulfide layer is formed while maintaining, and then a BaAlEu alloy is maintained on the zinc sulfide layer using the following sintered body target (B) while maintaining the substrate temperature at 400 to 650 ° C. in an argon gas atmosphere. The layer was formed by sputtering. Subsequently, on the BaAlEu alloy layer, the following sintered body target (A) was used, while maintaining the substrate temperature at 550 to 720 ° C., the sputtering amount of zinc sulfide was Zinc sulfide is sputtered so as to be 4.0 to 4.2 times the number of moles of barium in the BaAlEu alloy layer.
(A) It is comprised from zinc sulfide.
(B) barium, aluminum, and the composition formula consists europium: Ba _y1 Al _y2 Eu _y3 (In the formula, Y1 to Y3 are, y1 + y3 = 1,1.5 ≦ y2 ≦ 3.0,0.03 ≦ y3 ≦ 0.10 is satisfied.).

  In the film forming method, for example, two targets of a sintered body target (A) composed of ZnS and a sintered body target (B) composed of a BaAlEu alloy are mounted on two cathodes of a sputtering apparatus, and these A means for sputtering is suitable. In this way, by supplying ZnS and BaAlEu alloy to the substrate from one source, the composition in the film and the film formation rate are stabilized, and the film can be formed with good reproducibility.

  The substrate is not particularly limited, and a glass substrate such as a non-alkali glass for LCD or a soda-lime glass substrate for PDP, or a substrate in which an electrode layer and a dielectric layer are laminated on a glass substrate is used. It is done. A silicon substrate may be used as a small display substrate.

  As an apparatus used for the sputtering, a magnetron RF sputtering apparatus, for example, SPF210H manufactured by Anerva Co., Ltd., MB04-1055 manufactured by ULVAC, or the like is used, and the film formation is performed under a normal argon film pressure under a predetermined argon gas pressure.

In the film forming method, first, the sintered body target (A) composed of ZnS is used, and the substrate temperature is maintained at a temperature of 300 to 600 ° C., preferably 350 to 500 ° C. in an argon gas atmosphere. A zinc sulfide layer is formed. That is, although the ZnS film can be formed at room temperature, when the zinc sulfide film formed at room temperature is heated, ZnS crystal grains are generated and easily detached from the substrate. The detached powder adheres to the substrate and causes pinholes. By maintaining the substrate in the above temperature range during sputtering, the adhesion between the deposited zinc sulfide layer and the substrate is improved, so that the separation of ZnS crystal grains from the substrate is improved.
ZnS used here is a material suitable for film formation by sputtering because it has a high sputtering rate and hardly causes a compositional deviation. Here, since the atmosphere during sputtering is an argon gas atmosphere, there is no possibility that sulfur decomposed and generated by argon plasma will contaminate the chamber and the vacuum system as in the case of adding hydrogen sulfide.

  The method for producing the sintered body target (A) is not particularly limited, and for example, a method of sintering zinc sulfide powder is used. The zinc sulfide powder is not particularly limited, and commercially available powder having a purity of 99.9% by weight or more and an average particle size of 3 to 20 μm is used. The sintering method is not particularly limited. For example, zinc sulfide powder is placed in a mold made of carbon or the like, and is sintered in a hot-pressed atmosphere under an argon gas atmosphere or in a tubular furnace whose atmosphere can be controlled. To do. As said sintering temperature, it is 850-1200 degreeC, Preferably it is 900-1100 degreeC. That is, when the sintering temperature is less than 850 ° C., the sintering does not proceed, so the density of the sintered body is low, and the strength of the sintered body is also low, so that it is difficult to handle as a target. On the other hand, when the sintering temperature exceeds 1200 ° C., zinc sulfide is sublimated and a uniform target cannot be obtained.

  Next, a BaAlEu alloy layer is formed on the zinc sulfide layer by sputtering using the sintered body target (B) composed of the BaAlEu alloy while maintaining the substrate temperature at 400 to 650 ° C. in an argon gas atmosphere. Film. Since this sintered body target is a metal target, it can be formed by either direct current or high frequency sputtering, so that it can be formed at high speed. Here, since the atmosphere during sputtering is an argon gas atmosphere, there is no possibility that sulfur decomposed and generated by argon plasma contaminates the chamber and the vacuum system as in the case of adding hydrogen sulfide.

  At this time, the substrate is heated to a temperature of 400 to 650 ° C. during sputtering. That is, when the substrate temperature is less than 400 ° C., it does not react with the underlying ZnS layer. On the other hand, when the temperature of the substrate exceeds 650 ° C., barium in the BaAlEu alloy layer reacts to form BaS on the ZnS surface side, and vaporization of barium occurs on the other side, which is not preferable because the composition does not become uniform. .

The sintered body target (B) composed of the BaAlEu alloy is represented by a composition formula composed of barium, aluminum, and europium: Ba _y1 Al _y2 Eu _y3 , where y1 to y3 are y1 + y3 = Those satisfying the requirements of 1, 1.5 ≦ y2 ≦ 3.0 and 0.03 ≦ y3 ≦ 0.10 are used.
Here, regarding y2, the requirement of 1.5 ≦ y2 ≦ 3.0 is satisfied. That is, when y2 is less than 1.5, BaAl ₂ S ₄ which is a compound phase desired for the finally obtained phosphor film cannot be obtained. This is because excess aluminum evaporates as aluminum sulfide during annealing or reacts with zinc to become ZnBaAl ₂ S ₅ . However, since ZnBaAl ₂ S ₅ has little influence on the luminance, it is desirable that Al in the BaAlEu alloy layer formed on the ZnS layer has an excessive composition. On the other hand, when y2 exceeds 3.0, the luminance is lowered because the BaAl ₄ S ₇ phase remains in the finally obtained phosphor film.

  The method for producing the sintered body target (B) is not particularly limited, and for example, barium, aluminum, and europium are melted and alloyed by a predetermined amount. Next, it grind | pulverizes and sifts and produces 50-200 micrometers raw material powder. This raw material powder is packed and sintered using a vacuum hot press in an argon gas atmosphere.

Subsequently, on the BaAlEu alloy layer, ZnS is sputtered while maintaining the substrate temperature at 550 to 720 ° C. using the sintered body target (A), thereby forming a phosphor thin film. Here, sputtering of ZnS aims at sulfurization of barium and aluminum based on the following chemical formula (1).
Chemical formula (1): BaAl ₂ + 4ZnS = BaAl ₂ S ₄ + 4Zn
Note that the surface of the underlying ZnS layer is decomposed when BaAl ₂ is sputtered, and a part of Ba is sulfided, but it is difficult to sulfide Al. Therefore, it is desirable to adjust the sputtering amount of ZnS so as to be 4.0 to 4.2 times the number of moles of barium in the BaAlEu alloy layer. The sputtering amount was adjusted by the sputtering time by separately forming a ZnS and BaAlEu alloy film at room temperature and measuring the film weight to determine the sputtering rate.

  That is, if the sputtering amount of ZnS is less than 4.0, the BaAlEu alloy layer cannot be sulfided. On the other hand, if it exceeds 4.2 times, excess Zn and ZnS remain in the film, which is not preferable. Moreover, if the substrate temperature is less than 550 ° C., a sulfide film cannot be formed, which is not preferable. On the other hand, when the substrate temperature exceeds 720 ° C., the reaction does not proceed uniformly, and a trace of partial burning is not preferable. Also, in this temperature range, Zn produced by the reaction of ZnS with the BaAlEu alloy can be evaporated.

Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. The sintered body and film composition used in the examples and comparative examples, the structure of the sintered body, and the fluorescence emission wavelength and luminance evaluation method of the film obtained by sputtering are as follows.
(1) Analysis of composition of sintered body and film: ICP emission analysis was performed.
(2) Identification of the structure of the sintered body: It was carried out by X-ray diffraction (XRD).
(3) Measurement of fluorescence emission wavelength of film: Measurement was carried out with a spectrofluorescence intensity meter (FP-6500ST manufactured by Jusco) to obtain a peak wavelength.
(4) Measurement of film luminance: Measured with a spectrofluorometer (FP-6500ST manufactured by Jusco), and the emission intensity at the peak wavelength was determined. Relative luminance was compared to obtain relative luminance.

The sputtering method used in the examples and comparative examples is as described in [Sputtering method] below.
[Sputtering method]
The target was attached to the cathode of a magnetron RF sputtering apparatus (manufactured by ULVAC, MB04-1055) to form a film. After pulling to 2 Pa with a rotary pump, the vacuum was further pulled to 2 × 10 ⁻⁵ Pa with a molecular turbo pump. Thereafter, Ar gas was put in and discharged under the conditions of a sputtering pressure of 0.35 Pa and a sputtering power (RF power) of 100 W.
After the target was attached, pre-sputtering was performed for about 60 minutes to remove the surface layer. Further, a 2-inch silicon substrate was used as the substrate, and the resulting ZnS layer was formed to a thickness of about 300 nm and the BaAlEu alloy layer was formed to a thickness of about 200 nm. Moreover, the sputtering time was adjusted so that the sputtering amount of zinc sulfide on the BaAlEu alloy thin film became a desired amount in each example or comparative example.

Moreover, the sintered compact target (A) and (B) used by the Example and the comparative example were obtained with the following manufacturing method, respectively.
[Manufacture of sintered compact target (A)]
First, using ZnS powder (manufactured by Sakai Chemical), this was pulverized with a centrifugal ball mill (manufactured by Fritsch), and then sintered in a argon gas at a temperature of 1050 ° C. using a vacuum hot press (manufactured by Daiya Vacuum). . Thereafter, the surface of the obtained sintered body was polished by 100 μm, and then a target having a diameter of 2 inches (50 mm) was produced.

[Manufacture of sintered compact target (B)]
Ba (2N made by Kemetall), Al (4N made by high-purity chemical), and Eu (3N made by high-purity chemical) were melted in predetermined amounts to form an alloy. Next, it was pulverized by a stamp mill and sieved to prepare a raw material powder of 50 to 200 μm. This raw material powder was packaged and sintered at a temperature of 850 ° C. in an argon gas using a vacuum hot press (manufactured by Daia Vacuum). Thereafter, the surface of the obtained sintered body was polished by 100 μm, and then a target having a diameter of 2 inches (50 mm) was produced. The composition of the target was Ba _y1 Al _y2 Eu _y3 , and y1 = 0.94, y2 = 2.2, and y3 = 0.06.

Example 1
Sputtering was performed using the above target in accordance with the above [Sputtering method] to form a ZnS layer at a substrate temperature of 400 ° C., and then a BaAlEu alloy layer was formed thereon at a substrate temperature of 600 ° C. Subsequently, a phosphor thin film was obtained by sputtering zinc sulfide on the BaAlEu alloy layer at a substrate temperature of 700 ° C. Here, the sputtering amount of zinc sulfide is such that ZnS and BaAlEu alloy films are separately formed at room temperature, the film weight is measured, the sputtering speed is obtained, and the sputtering time is set to 4.0 times the number of moles of barium. Adjusted.
Then, according to the said evaluation method, the composition of the obtained film | membrane, the structure | tissue of a film | membrane, and the fluorescence emission wavelength and the brightness | luminance of the film | membrane were calculated | required. The results are shown in Tables 1, 2, and 3, respectively. In addition, the composition of Table 1 shows the composition ratio, assuming that Ba and Eu are added to 1.00. In Table 2, the peak of the compound in the X-ray diffraction method is a symbol in the table, where ◯ indicates that it is detected and × indicates that it is not detected.

(Example 2)
A phosphor thin film was obtained in the same manner as in Example 1 except that the substrate temperature at the time of sputtering zinc sulfide onto the BaAlEu alloy layer was 600 ° C. Then, according to the said evaluation method, the composition of the obtained film | membrane, the structure | tissue of a film | membrane, and the fluorescence emission wavelength and the brightness | luminance of the film | membrane were calculated | required. The results are shown in Tables 1, 2, and 3, respectively.

(Example 3)
A phosphor thin film was obtained in the same manner as in Example 1 except that the substrate temperature during the formation of the BaAlEu alloy layer was 550 ° C. Then, according to the said evaluation method, the composition of the obtained film | membrane, the structure | tissue of a film | membrane, and the fluorescence emission wavelength and the brightness | luminance of the film | membrane were calculated | required. The results are shown in Tables 1, 2, and 3, respectively.

Example 4
A phosphor thin film was obtained in the same manner as in Example 1 except that the substrate temperature during the formation of the ZnS layer was 500 ° C. Then, according to the said evaluation method, the composition of the obtained film | membrane, the structure | tissue of a film | membrane, and the fluorescence emission wavelength and the brightness | luminance of the film | membrane were calculated | required. The results are shown in Tables 1, 2, and 3, respectively.

(Example 5)
When zinc sulfide was sputtered onto the BaAlEu alloy layer, a phosphor thin film was obtained in the same manner as in Example 1 except that the sputtering amount of zinc sulfide was 4.15 times. Then, according to the said evaluation method, the composition of the obtained film | membrane, the structure | tissue of a film | membrane, and the fluorescence emission wavelength and the brightness | luminance of the film | membrane were calculated | required. The results are shown in Tables 1, 2, and 3, respectively.

(Comparative Example 1)
A phosphor thin film was obtained in the same manner as in Example 1 except that the substrate temperature at the time of sputtering zinc sulfide onto the BaAlEu alloy layer was changed to 760 ° C. Then, according to the said evaluation method, the composition of the obtained film | membrane, the structure | tissue of a film | membrane, and the fluorescence emission wavelength and the brightness | luminance of the film | membrane were calculated | required. The obtained film was discolored in the center and the film was thin. Moreover, the fluorescence was sparse and uniform fluorescence was not observed. The results are shown in Tables 1, 2, and 3, respectively.

(Comparative Example 2)
A phosphor thin film was obtained in the same manner as in Example 1 except that the substrate temperature when sputtering zinc sulfide onto the BaAlEu alloy layer was 500 ° C. Then, according to the said evaluation method, the composition of the obtained film | membrane, the structure | tissue of a film | membrane, and the fluorescence emission wavelength and the brightness | luminance of the film | membrane were calculated | required. In addition, fluorescence was not observed. The results are shown in Tables 1, 2, and 3, respectively.

(Comparative Example 3)
A phosphor thin film was obtained in the same manner as in Example 1 except that the substrate temperature during the formation of the BaAlEu alloy layer was 300 ° C. Then, according to the said evaluation method, the composition of the obtained film | membrane, the structure | tissue of a film | membrane, and the fluorescence emission wavelength and the brightness | luminance of the film | membrane were calculated | required. In addition, fluorescence was not observed. The results are shown in Tables 1, 2, and 3, respectively.

(Comparative Example 4)
A phosphor thin film was obtained in the same manner as in Example 1 except that the substrate temperature during the formation of the BaAlEu alloy layer was 700 ° C. Then, according to the said evaluation method, the composition of the obtained film | membrane, the structure | tissue of a film | membrane, and the fluorescence emission wavelength and the brightness | luminance of the film | membrane were calculated | required. In addition, fluorescence was not observed. The results are shown in Tables 1, 2, and 3, respectively.

(Comparative Example 5)
A phosphor thin film was obtained in the same manner as in Example 1 except that the substrate temperature during the formation of the ZnS layer was 100 ° C. The film could not be evaluated because it partially peeled.

(Comparative Example 6)
A phosphor thin film was obtained in the same manner as in Example 1 except that the substrate temperature during the formation of the ZnS layer was 650 ° C. Then, according to the said evaluation method, the composition of the obtained film | membrane, the structure | tissue of a film | membrane, and the fluorescence emission wavelength and the brightness | luminance of the film | membrane were calculated | required. In addition, fluorescence was not observed. The results are shown in Tables 1, 2, and 3, respectively.

(Comparative Example 7)
When sputtering zinc sulfide onto the BaAlEu alloy layer, a phosphor thin film was obtained in the same manner as in Example 1 except that the sputtering amount of zinc sulfide was 3.5. Then, according to the said evaluation method, the composition of the obtained film | membrane, the structure | tissue of a film | membrane, and the fluorescence emission wavelength and the brightness | luminance of the film | membrane were calculated | required. The results are shown in Tables 1, 2, and 3, respectively.

(Comparative Example 8)
When sputtering zinc sulfide onto the BaAlEu alloy layer, a phosphor thin film was obtained in the same manner as in Example 1 except that the sputtering amount of zinc sulfide was 4.5. Then, according to the said evaluation method, the composition of the obtained film | membrane, the structure | tissue of a film | membrane, and the fluorescence emission wavelength and the brightness | luminance of the film | membrane were calculated | required. The results are shown in Tables 1, 2, and 3, respectively.

(Comparative Example 9)
In order to confirm the state of film formation according to the conventional method, the sintered body target (B) is used, the substrate temperature is set to 600 ° C., hydrogen sulfide gas is allowed to flow at 0.5 Pa, Ar gas is further added, and the gas pressure is set to 0. Film formation was performed at 8 Pa and RF power of 100 watts.
As a result, the phosphor layer deposition rate was as low as 22% compared to the deposition rate of the BaAlEu alloy layer of Example 1. In addition, since hydrogen sulfide is decomposed by plasma, there is a problem that an ion gauge for measuring a vacuum degree cannot be turned on immediately after film formation, and sulfur is attached to an exhaust pipe when sputtering is performed for 2 hours. That is, in the sputtering method in hydrogen sulfide gas by such a conventional method, troubles due to sulfur occurred and the film formation rate was extremely low.

From Tables 1, 2, and 3, in Examples 1 to 5, the compound structure of the phosphor thin film formed according to the method of the present invention under the film forming conditions such as the target, atmosphere, and substrate temperature is the BaAl ₂ S ₄ phase. It can be seen that since the composition of the film satisfies the conditions of the present invention, the shift of the fluorescence emission wavelength to a long wavelength is small and the luminance is high. Thereby, a phosphor thin film with good color purity and high brightness is achieved. In Examples 1-5, since hydrogen sulfide gas was not used, troubles associated therewith did not occur.

  On the other hand, in Comparative Examples 1-4 and 6-8, either the substrate temperature during film formation or the sputtering amount of zinc sulfide was not performed according to the conditions of the method of the present invention. It turns out that satisfactory results are not obtained in the organization. Therefore, even if the fluorescence was observed, it was weak. In Comparative Example 5, the film could not be evaluated because the film was partially peeled off.

  As is clear from the above, the phosphor film of the present invention and the film forming method thereof are suitable for inorganic EL and PDPs and have a good color purity and a high-luminance phosphor thin film and a film forming method thereof.

Claims (2)

The following composition formula consisting of zinc, barium, aluminum, sulfur and europium:
Zn _x0 Ba _x1 Al _x2 S _x3 Eu _x4
(In the formula, x0 to x4 satisfy the requirements shown in the following (1) to (5).)
A phosphor thin film formed from a sulfide represented by:
A phosphor thin film characterized in that the compound structure is composed of a phase mainly comprising a compound phase represented by a composition formula: BaAl ₂ S ₄ : Eu.
(1) 0.01 ≦ x0 ≦ 0.02
(2) x1 + x4 = 1
(3) 2.01 ≦ x2 ≦ 3.0
(4) 4.0 <x3 ≦ 4.3
(5) 0.03 ≦ x4 ≦ 0.10 Using the following sintered body target (A), a zinc sulfide layer was formed while maintaining the substrate temperature at 300 to 600 ° C. in an argon gas atmosphere, and then the following sintering was performed on the zinc sulfide layer. Using the body target (B), a BaAlEu alloy layer was formed by sputtering while maintaining the substrate temperature at 400 to 650 ° C. in an argon gas atmosphere. Subsequently, the following sintered body was formed on the BaAlEu alloy layer. Using target (A), while maintaining the substrate temperature at 550 to 720 ° C., the amount of zinc sulfide sputtered was 4.0 to 4.2 times the number of moles of barium in the BaAlEu alloy layer. The method for forming a phosphor thin film according to claim 1, wherein zinc is sputtered.
(A) It is comprised from zinc sulfide.
(B) barium, aluminum, and the composition formula consists europium: Ba _y1 Al _y2 Eu _y3 (In the formula, Y1 to Y3 are, y1 + y3 = 1,1.5 ≦ y2 ≦ 3.0,0.03 ≦ y3 ≦ 0.10 is satisfied.).