JPH07196365A - Sintered ito, ito clear conductive layer and formation thereof - Google Patents

Abstract

PURPOSE:To obtain ITO clear, electrically conductive layer of low specific resistance and high light transmittance by adding specific amounts of SiO2 and Bi2O3 to the ITO sintered product and effecting the sputtering using the mixed product as a target material. CONSTITUTION:In sintered ITO, the ITO sintered product and the ITO clear conductive layer have the SiO2 and Bi2O3 composition in wt.% in the area surrounded to the lines connecting the points 1 to 5 in the SiO2-Bi2O3 binary component system in Figure 1, where point 1 (0.001; 9.0), point 2 (9.0; 9.0), point 3 (12.0; 6.0), point 4 (12.0; 0.001) and point 5 (0.001; 0.001). The sintered product is used as a target, and a mixed gas containing Ar, O2 and H2 is introduced into the vacuum tank so that the gas composition may become 0.2ppm to 20% in O2 and H2, respectively and the rest of Ar and the total pressure may be set to 1X10<-3> to 5X10<-2> torr and sputtering is performed to form the ITO clear, electrically conductive layer on the base plate.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is useful as a sputtering target material used for forming a transparent conductive film.
The present invention relates to a TO sintered body, an ITO transparent conductive film obtained from the sintered body, and a method for forming such a transparent conductive film. The ITO sintered body of the present invention has a high sintered body density,
A transparent conductive film having a low specific resistance can be obtained from this sintered body. This transparent conductive film is particularly suitable for use as a transparent electrode for liquid crystal displays, electroluminescence and electrochromic displays.

[0002]

2. Description of the Related Art As a transparent conductive film, a film in which a metal such as gold or platinum or an oxide such as tin oxide or indium oxide is formed on a substrate is known. Among them, the ITO used as a liquid crystal display is a mixture of indium oxide and tin oxide.
(Indium-Tin Oxide) is the mainstream.
This is because ITO has high transparency and low resistance, and also has good etching properties, chemical stability, and adhesion to substrates.

As a method for forming the transparent conductive film, there are physical vapor deposition methods such as vacuum vapor deposition, ion plating and sputtering, chemical vapor deposition method for forming a film by a chemical reaction such as thermal decomposition, coating method by spraying, tips and the like. is there. Among them, the physical vapor deposition method, especially the sputtering method is the mainstream because the film is dense and a low resistance film can be easily obtained. When forming an ITO film by a sputtering method, an ITO sintered body obtained by adding tin oxide to indium oxide is often used as a sputtering target.

[0004] The ITO sintered body is usually obtained by molding powder obtained by adding tin oxide to indium oxide or calcined powder by cold pressing, casting, etc., and molding the molded body at 1200 ° C or higher in the atmosphere. It is manufactured by a method such as firing. However, the ITO powder has poor sinterability, and this method has a density of at most 4.9 g / cm ³ (theoretical density of 7.0 g / c).
Only a sintered body having a relative density of about 70% when m ³ is obtained.

Further, as a technique for lowering the resistance of an ITO transparent conductive film by a semiconductorization mechanism based on valence control, there are the following examples. In JP-A-59-163707, ruthenium oxide, lead oxide, and copper oxide are added to ITO.
In -71205, phosphorus oxide is added to ITO.
In 94703 and JP-A-63-78404, aluminum fluoride is added to indium oxide and ITO, respectively.
In JP-A-3-178414, tellurium oxide is added to ITO.
In 4-10507, ITO is added with silicon oxide, and
In 283369, selenium oxide or tin fluoride is added to ITO, and in JP-A-3-199373, I and Br are added to ITO to reduce the resistance of the transparent conductive film.

On the other hand, as an example of reducing the resistance of a transparent conductive film by reducing the semiconductor, USP 4,399,
There is 194. In this example, 40-60 wt% of zirconium oxide is added to indium oxide to give a specific resistance of 4.4 × 10 4.
^It has the characteristics of ^-4 Ωcm and light transmittance of 80%.

When a low-density sintered body is used as a sputtering target, the amount of ITO that can be used in a single target of the same size is small, the target life is short, the target replacement frequency is high, and the sputtering device operating rate is high. Will be lower. Further, the lower the sintering density, the more marked the blackening phenomenon of the target surface that occurs during sputtering, the slower the film formation rate and the higher the specific resistance of the transparent conductive film. Therefore, since the blackened material on the surface is removed, the amount of the target used is substantially reduced and the operating rate of the sputtering apparatus is further reduced.

Therefore, in order to increase the usable amount of ITO per target, and to improve the operating rate of the sputtering apparatus and the stable operation, the density of the ITO sintered body target should be improved, at least the relative density of which exceeds 70%. It has been demanded. In order to meet this demand, in the conventional molding and firing process, hot pressing, HIP was used, or the firing atmosphere was controlled to achieve a higher density, and a maximum relative density of 98% was also obtained (JP-A-3- 20785
However, there is a problem that the equipment and the production cost are high.

A technique for controlling the particle size of the raw ITO powder to increase the density of the sintered body has been proposed (JP-A-62-12009, JP-A-3-218924, etc.).
However, the preparation of the raw material is very difficult and the cost is high, so it cannot be said to be practical. As a method of densifying the sintered body to eliminate the above-mentioned high cost, there is a method of adding a sintering aid.

Japanese Unexamined Patent Publication No. Sho 61-136954 (Japanese Patent Publication No. 1-254)
1109) Si and / or Ge as a sintering aid.
Oxide is added to obtain a sintered body having a maximum relative density of 90%. However, as a result of additional tests conducted by the present inventor, the best film property was that the composition was 0.5% GeO ₂ in ITO.
With the addition of wt%, the specific resistance of the film is 2.0 × 10 ^-4 Ω
cm, but the sintered body density remained at 79%. GeO
_{When 2} wt% of ₂ was added, the sintered body density became 90%, but the specific resistance of the film deteriorated to 2.9 × 10 ⁻⁴ Ωcm.

Further, Japanese Patent Laid-Open No. 59-198602 discloses an I
A transparent conductive film in which Al, W, Th, and Mo elements are added to TO is described, but the film resistance is 1.2 × 10 ^-2 〜.
As high as 2.42 × 10 ^-2 Ωcm, the inventors of the present invention made an additional test and found that the density of the sintered body was 70% relative to the theoretical density.
Less than and lower.

In addition, in recent years, liquid crystal displays have been widely used for word processors, televisions, etc., and the size of the liquid crystal screen has been increased. As a result, the conventional transparent conductive film does not deteriorate in the specific resistance value, and light transmission is possible. The need to improve rates has arisen. At this time, keeping the specific resistance value low can reduce the film thickness of the electrode, and thus also enable good etching properties. If the film thickness of the transparent conductive film exceeds 2000 angstroms, the etching time becomes longer and the pattern disconnection,
The deterioration of the film surface condition causes non-uniformity of resistance and the like, resulting in a decrease in yield.

[0013]

In view of the above situation, an object of the present invention is to provide a high density IT having a relative density of 90% or more.
An object of the present invention is to provide an ITO sintered body that is an O sintered body and can obtain a transparent conductive film having a low specific resistance. further,
Another purpose is to have a low specific resistance value that exceeds the specific resistance value of 2 × 10 ⁻⁴ Ωcm of the transparent conductive film that has been used conventionally, and has a high light transmittance of more than 90%, which is thin and shortened. An object of the present invention is to provide an ITO transparent conductive film that can be manufactured with a high yield with a controlled etching time.

[0014]

[Means for Solving the Problems] As a result of various studies to solve the above-mentioned problems, in the ITO sintered body, the following composition in the SiO ₂ —Bi ₂ O ₃ binary system diagram shown in FIG. 1 is shown. A sintered body containing a composition of SiO ₂ and Bi ₂ O ₃ corresponding to a region surrounded by 1, 2, 3, 4 and 5 has a high density and is useful for forming a transparent conductive film having a low specific resistance value. It turned out to be

With the ITO sintered body having the above composition as a target, a mixed gas of Ar gas, O ₂ gas and H ₂ gas was introduced into the vacuum chamber against the total pressure of O ₂ gas and H ₂ gas. Both contain 0.2 ppm to 20%, and the balance is Ar.
The total pressure is 1 × 10 ⁻³ torr to 5 × 1
It was found that an ITO transparent conductive film having a low specific resistance value can be advantageously formed by introducing the silicon oxide film so as to be 0 ^-2 torr and performing sputtering.

In the ITO sintered body and the ITO transparent conductive film, tin is present as a mixture or solid solution of oxide with respect to indium oxide, but in the sintered body and conductive film of the present invention, Bi and Si are respectively contained. Are mixed as oxides, but are believed to exist as complex oxides, as solid solutions, or in a mixture thereof. Since it is difficult to identify the state accurately, in the present invention,
For convenience, the composition of each oxide is shown.

The amount of tin oxide in the ITO sintered body of the present invention is 0.
05-25 wt% is preferable. If it is less than 0.05 wt% or more than 25 wt%, the specific resistance of the transparent conductive film produced thereby becomes large, which is not preferable. The sintered body and the transparent conductive film of the present invention are characterized by containing the amount of tin oxide in the above range and further containing Bi ₂ O ₃ and SiO ₂ in the above composition range.

Regarding the production of the sintered body, an oxide of In is generally used as a starting material for indium oxide.
Metals, hydroxides, fluorides, sulfates, nitrates and the like may be used. However, when a raw material other than an oxide is used, the oxide-based sintered body is obtained by calcining or firing in an oxidizing atmosphere. The starting material of tin oxide is generally an oxide, but Sn metal, hydroxide, fluoride, sulfide, sulfate, nitrate or the like may be used. Similarly to In, Sn is also an oxide finally. The starting material of bismuth oxide is generally an oxide, but Bi metal, hydroxide, iodide,
Sulfides, sulfates, nitrates and the like may be used. When a raw material other than the Bi oxide is used, the oxide may be formed by 950 ° C. at which sintering starts during firing. The starting material of germanium oxide is generally an oxide, but simple substance of Si, chloride, nitride, carbide, sulfide or the like may be used. Similar to Bi, Si may be an oxide by 950 ° C. during firing.

The raw material compounds of these four elements may be mixed at the same time, or the compounds of two or more elements may be mixed in advance and calcined, and the calcined powder and the compounds of other elements may be mixed. . For mixing the raw materials, mortar mixing, ball mill mixing and the like are used. The raw material powder is preferably 2 μm or less. When the mixed powder is calcined, it is performed at 400 to 1500 ° C.

Polyvinyl alcohol (P
VA), polyvinyl butyral (PVB) and other binders are added, and the mixture is granulated to a particle size of 1 to 50 μm with a spray dryer or the like and molded at a pressure of about 500 to 8000 kg / cm ² . Alternatively, it may be made into a slurry together with a binder such as PVA and then cast-molded. The molded body may be dried and degreased. Sintering of the obtained compact is 1200-
It is carried out at 1600 ° C. Sufficient densification can be achieved by sintering in the air, but of course hot pressing, HI
P may be fired by adjusting the atmosphere.

Generally, as a method for forming a transparent conductive film, a sputtering method and an electron beam vapor deposition method are adopted, but an ion plating method, a chemical vapor deposition method and a coating method are also used. A method suitable for the raw material for forming each film is selected. In the sputtering method and the electron beam evaporation method,
As a vapor deposition material (target), a sintered body of indium and an oxide of an additional element or an alloy thereof is used. When a film is formed by sputtering using a sintered body, the sintered body and the film formation substrate are set as a target, and 1 × 1
After vacuuming below 0 ^-5 torr, in the case of a sintered body, A
or r gas only, or a mixed gas composed of Ar gas and O ₂ gas, by introducing a mixed gas composed of Ar gas and O ₂ gas and H ₂ gas to form a film.

[0022] When sputtering using a sintered body of the present invention as a target, in a vacuum chamber, a mixed gas of Ar gas and O ₂ gas and H ₂ gas, O ₂ gas and H
_The total pressure is 1 × 10 ⁻³ torr to 5 × at a rate such that each of the ₂ gases contains 0.2 ppm to 20% and the balance is Ar.
It is introduced so that it becomes 10 ^-2 torr.

At this time, when the partial pressure of O ₂ in the sputtering gas is high, the transmittance is high and the resistance value is low, but when it is too high, the resistance value is conversely increased. Even if only Ar gas is used as the sputtering gas without adding O ₂ gas, oxygen in the oxide functions similarly to O ₂ gas in the mixed sputtering gas, so that the film characteristics such as the resistance value are not significantly deteriorated. However, it is more advantageous that O ₂ gas is present at a certain ratio or more, and therefore, in the conductive film forming method of the present invention, O ₂ gas is contained in the sputtering mixed gas at a ratio of 0.2 ppm to 20%. .

[0024] without introducing of H ₂ can be low resistance, the introduction of H _2, without impairing the light transmittance of the film can lower the resistance. H ₂ partial pressure is 1 × 10 ^-3 torr
When it exceeds r, the light transmittance decreases. Therefore, in the conductive film forming method of the present invention, H ₂ gas of 0.2 ppm to
It is contained in the sputtering mixed gas at a rate of 20%. When the total pressure of the sputtering gas is a low pressure of less than 1 × 10 ⁻³ torr, stable plasma is not generated, and
At a high pressure exceeding 5 × 10 ^-2 torr, the resistance value of the film deteriorates.

It is preferable that the substrate temperature is 150 to 500 ° C. and the target input power is 0.5 to 4 W / cm ² . Here, the input power refers to the power per 1 cm ² of the target, and is used to turn the sputtering gas into plasma and accelerate the ions forming the plasma.
If the substrate temperature is lower than 150 ° C, the resistance value is inferior, and if it exceeds 500 ° C, the substrate is deformed and cannot be used. If the applied power is less than 0.5 W / cm ² , the vapor deposition rate will be slow and production efficiency will be poor, while if it exceeds 4 W / cm ² , the resistance value will be poor.

The film formation rate is determined by the total pressure of the sputtering gas, the distance between the substrates, etc. in addition to the input power, but the film characteristics are superior or inferior even at the same film formation rate. In consideration of the above, it is preferable to select a sputtering condition in which the light transmittance of the film is 90% or more, and the resistance value is as high as possible and has the lowest resistance value.

Although it is inferior to the sputtering method, the film can be formed by the electron beam evaporation method. In this case, Ar gas is not introduced, but only O ₂ gas or O ₂ gas and H ₂ gas is introduced to heat the substrate.
Similar to sputtering, the deposition rate is determined by the electron beam voltage, current, and beam diameter. By appropriately selecting the hydrogen partial pressure, the substrate temperature and the vapor deposition rate, a film having a transmittance of 90% or more and the lowest resistance value can be obtained. First ultimate vacuum is 10 ^-5 torr
The following O ₂ gas partial pressure is 0.1 × 10 ^{−4 to} 5
× 10 ⁻⁴ torr, H ₂ gas partial pressure 0.1 × 10 ^{−5 to} 5 ×
Appropriate conditions are 10 ⁻⁵ torr, substrate temperature of 200 to 400 ° C., and vapor deposition rate of 0.5 × 10 Å / sec. As the film formation substrate, a glass or plastic sheet or film, or a substrate or a film having a protective film or a functional film applied thereto is used.

[0028]

Function: ITO in which only tin oxide is added to indium oxide
Since the vapor pressure during sintering is high, a sintering mechanism by evaporation and condensation is adopted, shrinkage does not easily occur, and densification of the sintered body does not proceed.

However, surprisingly, Bi ₂ O
_{When 3} is added as a sintering aid, a liquid phase is formed at about 830 ° C., and this liquid phase prevents evaporation (sublimation) of ITO,
Sintering due to evaporation and condensation is suppressed, and sintering proceeds by the liquid phase sintering mechanism described below. That is, in the liquid phase sintering, due to the existence of the liquid phase, mass transfer occurs, shrinkage occurs, and the density of the sintered body increases. However, when only Bi ₂ O ₃ was added alone without adding SiO ₂ , the densification effect was not sufficient, and the relative density remained at 79% even if 16 wt% of Bi ₂ O ₃ was added. The SiO _{2 of the} present invention
In the —Bi ₂ O ₃ composition, this liquid phase sintering is accelerated and further densified, so that a good transparent conductive film is considered to be formed.

As will be demonstrated in Examples described later, by combining ITO with the above specific SiO ₂ —Bi ₂ O ₃ composition, a high density sintered body having a relative density of more than 90% was obtained, and further, By carrying out sputtering using this sintered body as a target, it is possible to industrially obtain an ITO conductive film having a very low specific resistance value and a large visible light transmittance.

The above specific SiO ₂ --Bi ₂ O ₃ composition is critical, and for example, when Bi ₂ O ₃ is not added (Comparative Examples 10 to 13: relative density of sintered bodies 72 to 88, conductive film). Specific resistance of 2.0 to 2.3 × 10 ⁻⁴ Ωcm),
When Bi ₂ O ₃ is included in a predetermined amount (Examples 21 to 24:
Sintered body relative density 95-93, conductive film specific resistance 1.2-1.
In 3), the density of the sintered body is high and the specific resistance of the conductive film is considerably low.

[0032]

EXAMPLES The sintered body of the present invention, the transparent conductive film, and the method for forming the film will be specifically described below with reference to Examples and Comparative Examples. Examples 1 to 47, Comparative Examples 1 to 23 Indium oxide (indium oxide N manufactured by Dowa Chemical Co., purity 99.99%, average particle size d ₅₀ = 0.93 μm) 900
g and tin oxide (manufactured by Shin Nippon Metal, purity 99.9%, particle size d ₅₀
(0.72 μm) was mixed in a ball mill having a capacity of 4.8 liters for 24 hours and then calcined in the air at 1450 ° C. for 15 hours to obtain ITO powder. Bismuth oxide (manufactured by Mitsuwa Chemical Co., purity 99.9)
%, Particle size d ₅₀ = 0.78 μm) and silicon oxide (manufactured by Wako Pure Chemical Industries, purity 99.9999%, particle size d ₅₀ = 1.1 μm)
Were mixed in the proportions shown in Table 1. In Tables 1 to 3, the mixing amount of bismuth oxide and silicon oxide is shown by weight%, and the balance is ITO. Mixing was done with a ball mill. A 0.05 wt% PVA solution was added to each of these mixed powders to form a slurry having a solid content concentration of 20 wt%, and this slurry was spray-dried with a spray dryer to obtain an average particle size of 2
The granules were 0 μm.

The granules were uniaxially pressure-molded at 1 ton / cm ² to obtain a disk-shaped molded body having a diameter of 90 mmφ and a thickness of 3.5 mm. This molded body was fired in the air at 1450 ° C. for 10 hours. Tables 1 to 3 show the composition (chemical analysis) and relative density of the sintered body.

Each of these sintered bodies was set as a target in a DC magnetron sputtering apparatus,
After evacuating to 1 × 10 ⁻⁶ torr, H ₂ gas was 3 × 10 ⁻⁷ torr and O while monitoring with a partial pressure vacuum gauge.
₂ gas was introduced at 3 × 10 ⁻⁶ torr, and then Ar gas was introduced until the total pressure became 5 × 10 ⁻³ torr. A slide glass (size: 76 × 26 × 1 mm) substrate was heated to 300 ° C., and a transparent conductive film was formed under the conditions of an input power of 100 W and a substrate-to-substrate distance of 65 mm.

The blackening of the targets was thin even when the sputtering was repeated in all the targets of the examples, and the sputtering rate was almost unchanged at 10 Å / sec. It was confirmed by EPMA that the composition of the obtained transparent conductive film was almost the same as the composition of the target. Tables 1 to 3 show the thickness, average transmittance of visible light and specific resistance of the obtained transparent conductive film.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

Examples 48 to 50, Comparative Examples 24 and 25 Samples were prepared by using the same raw material powders as in Example 1 and varying the amount of tin oxide. The amounts of indium oxide and tin oxide mixed were as shown in Table 4, and calcined under the same conditions as in Example 1, and I
TO powder was used. Each ITO powder was further mixed with silicon oxide 0.1 wt% and bismuth oxide 1.5 wt%. Other conditions were the same as in Example 1 to obtain a sintered body, and a transparent conductive film was produced. Table 4 shows the composition, density and film characteristic values of the sintered body.

[0040]

[Table 4]

Examples 51 to 94, Comparative Examples 26 to 39 Using the targets obtained in Example 14, a mixed gas containing O ₂ gas, H ₂ gas and the balance Ar gas in the amounts shown in Tables 5 and 6 was used. A transparent conductive film was produced under the same conditions as in Example 1 except that was used as the sputtering gas. The film characteristic values are shown in Tables 5 and 6.
Shown in.

[0042]

[Table 5]

[0043]

[Table 6]

[0044]

As described above, the above specific SiO ₂ -B is used.
According to the i ₂ O ₃ composition, the relative density is easily and stably 90%.
% High density ITO sintered body is obtained, and an ITO transparent conductive film having low resistance and high transparency can be obtained from this sintered body. When a transparent conductive film is formed from a sintered body by sputtering, the target surface is not blackened, the film forming speed does not decrease with time, and the specific resistance of the film does not deteriorate. Further, industrially, the problem that the operating rate of the sputtering apparatus is lowered because the target is removed for the purpose of removing the blackened substance on the surface, or the target life is short and the target is frequently replaced, is solved. . In addition, the transparent conductive film can be made thinner, the etching time can be shortened, and the yield can be improved.

[Brief description of drawings]

FIG. 1 is a two-component system diagram of SiO ₂ —Bi ₂ O ₃ , showing the SiO ₂ and Bi ₂ O ₃ contents of an ITO sintered body and an ITO transparent conductive film defined in the claims.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C23C 14/34 8414-4K G09F 9/30 339 7610-5G H01B 5/14 A 13/00 B 7244 -5G

Claims (3)

[Claims] 1. In an ITO sintered body, S corresponding to a region surrounded by points 1, 2, 3, 4 and 5 showing the following composition in the SiO ₂ —Bi ₂ O ₃ binary system shown in FIG.
An ITO sintered body containing a composition of iO ₂ and Bi ₂ O ₃ . Point 1: SiO ₂ = 0.001 wt%, Bi ₂ O ₃ = 9.
0 wt% Point 2: SiO ₂ = 9.0 wt%, Bi ₂ O ₃ = 9.0
wt% Point 3: SiO ₂ = 12.0 wt%, Bi ₂ O ₃ = 6.0
wt% Point 4: SiO ₂ = 12.0 wt%, Bi ₂ O ₃ = 0.0
01 wt% point 5: SiO ₂ = 0.001 wt%, Bi ₂ O ₃ = 0.
001wt% 2. In an ITO transparent conductive film, SiO ₂ corresponding to the region surrounded by points 1, 2, 3, 4 and 5 showing the following composition in the SiO ₂ —Bi ₂ O ₃ binary system shown in FIG. And an ITO transparent conductive film containing a Bi ₂ O ₃ composition. Point 1: SiO ₂ = 0.001 wt%, Bi ₂ O ₃ = 9.
0 wt% Point 2: SiO ₂ = 9.0 wt%, Bi ₂ O ₃ = 9.0
wt% Point 3: SiO ₂ = 12.0 wt%, Bi ₂ O ₃ = 6.0
wt% Point 4: SiO ₂ = 12.0 wt%, Bi ₂ O ₃ = 0.0
01 wt% point 5: SiO ₂ = 0.001 wt%, Bi ₂ O ₃ = 0.
001wt% 3. A mixed gas comprising Ar gas, O ₂ gas and H ₂ gas in a vacuum chamber, wherein the sintered body according to claim 1 is used as a target, and O ₂ gas and H ₂ gas are respectively supplied to the total pressure. ITO transparent, characterized by containing 0.2 ppm to 20% and introducing Ar so that the balance is Ar so that the total pressure is 1 × 10 ⁻³ torr to 5 × 10 ⁻² torr and performing sputtering. Method for forming conductive film.