JP4211558B2 - Sputtering target material, manufacturing method thereof, and manufacturing method of transparent conductive film using the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a sputtering target material, a method for producing the same, and a method for producing a transparent conductive film using the same, and a sputtering target material capable of forming an extremely smooth and low-resistance transparent electrode film at high speed and stably. The present invention relates to a method for forming a low resistance and smooth transparent conductive film.

  Transparent conductive films have high conductivity and high transmittance in the visible light region, so they are used for solar cells, liquid crystal display elements, electrodes for various other light receiving elements, and other heat ray reflections for automobiles and buildings. It is also used as a transparent heating element for various types of antifogging, such as a film, an antistatic film, and a frozen showcase.

In recent years, flat panel displays such as a liquid crystal display and a plasma display (PDP) have been widely used. However, electroluminescence elements (hereinafter also referred to as EL elements) have attracted attention as next-generation flat panel displays.
The EL element is an element using electroluminescence, has high visibility because of self-emission, and is excellent in impact resistance because it is a complete solid element. The EL element includes an inorganic EL element using an inorganic compound as a light emitting material and an organic EL element using an organic compound. Among these, the organic EL element is characterized in that it can be easily downsized by greatly reducing the driving voltage. The structure of this organic EL element is based on a laminated structure of anode / light emitting layer / cathode, and a structure in which a transparent conductive film (anode) is formed on a transparent insulating substrate such as a glass plate is usually employed.

The transparent conductive film includes tin oxide (SnO ₂ ) containing antimony or fluorine as a dopant, zinc oxide (ZnO) containing aluminum or gallium as a dopant, indium oxide (In ₂ O ₃ ) containing tin as a dopant, or the like. Widely used. This indium oxide film (In ₂ O ₃ —Sn-based film) containing tin as a dopant is called an ITO (Indium tin oxide) film, and is widely used because a film having a particularly low resistance can be easily obtained. .

As a method for producing these transparent conductive films, a sputtering method is often used. The sputtering method is an effective method when film formation of a material having a low vapor pressure or precise film thickness control is required, and since the operation is very simple, it is widely used industrially.
In the sputtering method, a target is used as a raw material for film components. In this method, generally, under a gas pressure of about 10 Pa or less, a substrate is used as an anode, a target is used as a cathode, a glow discharge is generated between them to generate argon plasma, and argon cations in the plasma are converted into cathode targets. The target component particles that are caused to collide with the substrate and be blown off by this are deposited on the substrate to form a film.
Sputtering methods are classified according to the method of generating argon plasma. Those using high-frequency plasma are called high-frequency sputtering methods, and those using DC plasma are called DC sputtering methods. In addition, a method of depositing a magnet on the back side of the target to concentrate plasma on the target and increasing the generation efficiency of argon ions even at a low gas pressure is called a magnetron sputtering method. In general, the direct current sputtering method is widely used industrially for reasons such as a higher film forming speed, lower power supply facilities, and easier film forming operation than a high frequency sputtering method.

Usually, an ITO sintered body target is obtained by a powder sintering method, that is, a method in which indium oxide or tin oxide is substantially blended into a desired composition, pressure-molded, and then sintered at a temperature of 1400 ° C. or higher. It is manufactured.
Conventionally, an ITO sintered body containing about 10% by weight of tin oxide (SnO ₂ ) as a material for an ITO sintered body target is manufactured by processing an ITO sintered body having a density of less than 6 g / cm ³ . However, recently, in order to improve the film forming performance of ITO, development of a higher density ITO sintered body and a sputtering target using the same has been studied.

  If a high-density ITO sintered body is used for sputtering, the initial stage can be satisfactorily formed. However, when approaching the end stage, blackened matter called nodules is generated on the target surface, causing abnormal discharge and the like (sputtering). (Rate) decreases. This is because the pore distribution of the sintered body is not controlled, and it means that the effect cannot be ignored when spattering for a long time.

  In addition, a method for uniformly controlling the surface roughness of the target is known, and if a target prepared by this method is used, a stable film formation rate can be achieved with little abnormal discharge at the initial stage of sputtering, but from the middle to the later stage. At the stage, there was a problem that a new surface appeared, nodules were generated on the target surface, abnormal discharge occurred, and it was not stable until the end.

By the way, ITO, which is a transparent conductive film, has a low resistance, but has a low crystallization temperature of around 150 ° C., and unevenness occurs on the surface of the film without heating the substrate. A black spot is generated in the element due to the unevenness on the surface, which causes a defect. Therefore, when ITO is used as the transparent conductive film, it is used after forming the ITO film on the substrate and smoothing the surface by removing irregularities on the surface by polishing or the like. A transparent conductive film formed using a ZnO-based or SnO ₂ -based target is not suitable as a transparent electrode because its resistance is not as low as that of ITO.

On the other hand, regarding an indium oxide-based transparent conductive film, an In ₂ O ₃ -based transparent conductive film containing additives other than Sn has been studied, and several materials having characteristics not found in ITO have been found.
An indium oxide-based sintered body containing silicon oxide and / or germanium oxide has been proposed as a raw material for producing the indium oxide-based film (see Patent Document 1), and such silicon oxide and / or germanium oxide is proposed. A technique for forming a Si-added indium oxide film or the like by a high-frequency sputtering method and an electron beam vapor deposition method using an indium oxide-based sintered body containing Si has been proposed (see Patent Document 2).

According to this method, an Si-added indium oxide film or the like in which film defects are eliminated can be obtained, but even if a target obtained from such a sintered body is used, silicon oxide and / or germanium oxide is contained in the sintered body. Therefore, it corresponds to the case where direct current sputtering is performed using a target containing a high-resistance substance in the base of the conductive substance, and arcing or the like occurs to stably form a film. Can not.
Further, if a large amount of DC power is input, charging of a high-resistance substance is likely to occur, and the frequency of arcing during film formation increases. Therefore, it is difficult to obtain a high film formation rate by applying high power. Further, since the crystal structure of the film is not specified, it is considered that a film having a smooth surface cannot be obtained even by high-frequency sputtering film formation in pure argon gas by this method.

On the other hand, the applicant of the present invention uses a Si-added In ₂ O ₃ film, a Si and W-added In ₂ O ₃ film, a Si and Sn-added In ₂ O ₃ useful as a transparent conductive film for various display devices such as LCDs. A membrane was proposed (see Patent Document 3).
These films tend to have an amorphous structure and do not crystallize when heated to 200 ° C., for example, not only when the substrate temperature during film formation is room temperature. Therefore, there is an advantage that a transparent conductive film excellent in surface smoothness can be easily produced stably. The transparent conductive film uses a composite target in which Si chips are evenly arranged on the surface of an In ₂ O ₃ sintered body target, a W-added In ₂ O ₃ sintered body target, and a Sn-added In ₂ O ₃ sintered body target. It is preferably manufactured by direct current sputtering.

  However, if the film is formed continuously by this method, the Si chip is reduced in weight and the film composition is changed, or if the DC input power is increased in order to increase productivity, there is sufficient conduction between the Si chip and the target. In some cases, arcing occurs and stable film formation may not be possible.

Recently, a transparent conductive thin film having a smooth surface and a low resistance is required for electrodes for LCDs and organic EL devices. In particular, in an electrode of a display using an organic EL element, an ultra-thin film of an organic compound is formed on the electrode, so that an excellent surface smoothness is required for the transparent conductive thin film.
However, there is no industrially useful direct current sputtering method that can stably form a low-resistance Si and W-added In ₂ O ₃ film at a high speed, and a useful sputtering target material for this purpose is eagerly desired.
JP 61-136954 A (Claims) JP 62-202415 A (Claims) Japanese Patent Application No. 2002-196840 (Claims)

  An object of the present invention is to provide a sputtering target material capable of forming a very smooth and low resistance transparent electrode film at high speed and stably, a method for producing the same, and a method for forming a low resistance and smooth transparent conductive film by sputtering. It is to provide.

  As a result of intensive studies to solve the above problems, the present inventor formed transparent conductive films having various compositions by a sputtering method, and examined the crystal structure, electrical characteristics, and optical characteristics of the obtained films. When a target containing indium oxide as a main component and containing a specific amount of Si and W is used, the obtained film has excellent surface smoothness and low electrical resistivity. The present inventors have found that it is suitable as a conductive film and have completed the present invention.

That is, according to the first invention of the present invention, it contains 0.3 to 5% by weight of W and 0.2 to 5% by weight of Si, and the balance is substantially made of In ₂ O _3. A sputtering target material is provided.

According to the second invention of the present invention, there is provided a sputtering target material characterized in that, in the first invention, the sintered density is 6.3 g / cm ³ or more.

  Furthermore, according to the third aspect of the present invention, there is provided a sputtering target material characterized in that, in the first aspect, at least a part of W and Si is contained as a conductive compound of W-Si.

According to the fourth invention of the present invention, in any one of the first to third inventions, the raw material powder of W, the raw material powder of Si, and the powder of In ₂ O ₃ are mixed, and this powder mixture is formed into a mold. And a hot-pressing in an inert gas atmosphere of 800 to 1100 ° C. and 9.8 MPa or more is provided.

  According to a fifth aspect of the present invention, there is provided the method for producing a sputtering target material according to the fourth aspect, wherein the mold for charging the powder mixture is made of carbon.

  Furthermore, according to the sixth invention of the present invention, there is provided a target obtained by grinding and processing the sputtering target material of any one of the first to third inventions.

  On the other hand, according to the seventh aspect of the present invention, after the target and the substrate according to the sixth aspect are arranged in the sputtering apparatus, the substrate is subjected to direct current sputtering in an inert gas atmosphere containing oxygen gas. There is provided a method for producing a transparent conductive film, wherein a transparent conductive film made of indium oxide containing Si and W is formed thereon.

If the sputtering target material of the present invention is used, the surface of the film after sputtering film formation is so smooth that processing such as polishing is not required, and a low-resistance transparent electrode film can be formed at high speed and stably.
The transparent conductive film thus formed has excellent surface smoothness, low resistance, and high transmittance in the visible light region. In addition, the transparent conductive substrate on which the transparent conductive film is formed is not only an organic EL element that requires a transparent electrode with a smooth surface and low resistance, but also an electronic circuit packaging for display device elements such as inorganic EL elements and LCDs. It is extremely useful as a part.

1. Sputtering Target Material The sputtering target material of the present invention is a sintered body containing 0.3 to 5% by weight of W and 0.2 to 5% by weight of Si, with the balance being substantially made of In and O.

When the amount of W contained in the sputtering target material is less than 0.3% by weight or the amount of Si is less than 0.2% by weight, the crystallization temperature is lowered at the same time as the resistance value is increased, and the surface is smoothed. The film is crystallized even in room temperature film formation, resulting in unevenness on the surface.
On the other hand, if the amount of W and Si exceeds 5% by weight, respectively, the crystallization temperature becomes high, so that a film having excellent surface smoothness can be obtained, but the resistance value becomes high and is not suitable as a transparent conductive film. It becomes.

The sputtering target material of the present invention has a sintered density of 6.3 g / cm ³ or more and is based on a sintered body substantially made of indium oxide. “Substantially” means that indium oxide is 90% or more and W and Si contain almost no impurities. However, molybdenum, rhenium, hafnium, germanium, zirconium, titanium, silver, gold, palladium, platinum, copper, or the like may be added within a range not impairing the object of the present invention.

2. Manufacturing method of sputtering target material The process of manufacturing the W * Si addition indium oxide sintered compact which is sputtering target material of this invention consists of (1) the process of forming a molded object from raw material powder, and (2) this molded object. A step of sintering in a sintering furnace is included.

(1) Formation of molded body In the step of forming a molded body from raw material powder, indium oxide is used as the raw material powder, and Si and W raw material powders are mixed and molded.

  The indium oxide as the raw material powder has an average particle size of 0.5 μm or less, preferably 0.4 μm or less (particle size distribution is 85% by weight or more of particles having a particle size of 0.1 to 0.8 μm, more preferably, Powder (occupying 95% or more).

  As Si, high purity metal Si can be used as a raw material. Among them, it is preferable to use high-purity metal Si having an average particle diameter of 300 μm or less and having a purity of, for example, 99.99% by weight or more. Moreover, as W, high purity metal W can be used as a raw material. Among them, it is preferable to use a high-purity metal W having an average particle diameter of 300 μm or less and having a purity of, for example, 99.99% by weight or more.

The raw material powder of Si and W is mixed with indium oxide using a known apparatus, stirred, granulated by adding a binder (PVA), etc., and then adjusted to a range of 10 to 100 μm. Press molding at a pressure of 1000 kg / cm ³ or more to obtain a molded body.
By pressing the raw material powder with a metal mold, the powder is compressed to become high-density condensed particles, the bulk density is improved, and a higher-density sintered body target can be obtained. If the pressure is lower than 1000 kg / cm ² , the bulk density is not sufficiently improved, and a satisfactory density improvement effect cannot be expected.

(2) Sintering of molded body The sintering process following the molding process is a process in which the molded body is put into a sintering furnace to be sintered. A pressure furnace of HIP (hot isostatic pressing) method can be employed.

  In the case of using an atmospheric furnace, the molded body obtained in the above process is placed on a hearth plate or setter in the furnace and then sintered in an oxygen atmosphere. As the type of the normal pressure furnace used in the sintering process of the present invention, an electric furnace in which the heating atmosphere is easily controlled is usually employed. In advance, the molded body is placed in the furnace with a sufficient space for oxygen gas to flow between the lower surface of the molded body and the hearth plate and between the upper surface of the molded body and the ceiling plate. By circulating oxygen gas over the surface of the molded body at the above temperature, the sintering is carried out by maintaining the sintering temperature at 1400 ° C. or higher while replacing the oxygen atmosphere in the furnace.

  When the temperature inside the furnace was raised to 1000 ° C., the flow of oxygen gas was started on the upper and lower surfaces of the molded body at normal pressure, and the oxygen atmosphere inside the furnace was replaced. Hold at the sintering temperature for 1 hour or more, preferably 5 to 20 hours. Thereafter, the flow of oxygen gas is substantially stopped and finally cooled. During sintering, care is taken to keep the temperature variation within 20 ° C. within the compact.

The distribution time may be less than 30 minutes if it is a small sintered body, but a large indium oxide target (for example, a large and thick one whose sintered body size exceeds 300 mm on a side and 5 mm in thickness) It is difficult to control the temperature distribution, so that the temperature distribution is preferably maintained over 60 minutes.
As a result, the plane direction and the thickness direction are heated almost uniformly, and it is possible to greatly reduce the variation in the sintered density and the average number of pores. Reduced by the weight of the sintered body.
After the main sintering step, the heating is stopped and the flow of oxygen gas is substantially stopped and the cooling step is started. After finishing the cooling step, re-sintering may be performed by heating the sintered body again to the sintering temperature.

  In addition to sintering at normal pressure as described above, a hot pressing method and a HIP method can be adopted for the manufacturing process of the oxide sintered body, but in the present invention, it can be manufactured by the hot pressing method. preferable.

In the hot press method, it is desirable to use a carbon mold in order to apply a large force to the pressing mold at a high temperature. In the present invention, at the time of hot pressing, sintering can be performed by placing inclusions in part or all of the portion where the carbon mold and the molded body (sintered body) are in contact. Thereby, it can prevent that a sintered compact and a carbon type | mold adhere | attach firmly during sintering.
As the material of the inclusion, any material can be used without particular limitation as long as it does not react or adhere to carbon during sintering and does not affect the sintered body. For example, iron foil, a carbon sheet, stainless steel foil, nickel foil, tantalum foil, etc. are mentioned.

Hot pressing is preferably performed in a temperature range of 800 ° C to 1100 ° C, particularly 850 ° C to 1000 ° C. When the temperature is lower than 800 ° C., the sintering is insufficient, the density is lowered, and the resistance value of the sintered body is increased. In addition, a target manufactured from a sintered body obtained under these conditions is not preferable because a film formation rate is slow and problems such as abnormal discharge occur during sputtering. On the other hand, when the temperature exceeds 1100 ° C., the reduction of In ₂ O ₃ proceeds, the metal In is locally observed in the sintered body, and a uniform sintered body cannot be obtained.

The pressure is preferably 9.8 MPa or more, particularly preferably 14 MPa or more. Even if sintered at a pressure lower than 9.8 MPa, a sintered body having a high density cannot be obtained.
An inert gas such as argon, helium, or xenon can be used as the hot press atmosphere, but it is particularly preferably performed in an argon atmosphere. If it is performed in a vacuum, the density of the sintered body does not increase because the reduction of In ₂ O ₃ proceeds excessively. The inert gas pressure is preferably 0.05 MPa or more and atmospheric pressure or less. If it is less than 0.05 MPa, the sintered density cannot be increased.

The inventor of the present invention uses a carbon container during hot pressing to cause oxygen deficiency due to reduction in the sintered body, and to the sintered body, a W-Si compound (a phase composed of W and Si). ) Was found to exist uniformly. In the atmospheric pressure sintering method, W is dissolved in In ₂ O ₃ if the addition amount is small and becomes WO ₃ if the addition amount is large. It is presumed that Si is similarly dissolved in In ₂ O ₃ or becomes SiO ₂ . On the other hand, in the hot press method, it was found that Si and W preferentially form a W—Si conductive compound, and excess W and Si are dissolved in In ₂ O ₃ .

The sintered body manufactured by the above method is processed by surface grinding or the like to obtain a predetermined size, and then adhered to a backing plate, whereby the sputtering target of the present invention can be obtained. If necessary, several sintered bodies may be divided into divided shapes to form a large area target.

3. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms a transparent conductive film on a substrate by arranging a substrate and a sputtering target in a sputtering apparatus and then performing direct current sputtering in an inert gas atmosphere containing a certain amount of oxygen gas. It is a method to do.

  That is, the method of the present invention uses a target obtained from the Si / W-added indium oxide sintered body and adopts sputtering conditions such as a specific substrate temperature, pressure, oxygen concentration, etc. This is a method of forming a transparent conductive film made of indium oxide containing W.

  As described above, the target is based on an indium oxide sintered body to which Si and W are added. There are a single target and a composite target. A single target is preferable because the film formation rate and film uniformity can be improved as compared with the conventional target.

  In order to form a transparent conductive film according to the present invention, it is necessary to use direct current sputtering using a mixed gas of an inert gas such as argon and oxygen as a sputtering gas. It is important that the oxygen gas is introduced at 1% or more, preferably 1 to 5%. If the oxygen gas is less than 1%, the transparency of the resulting film is low and the dopant is easily detached from the surface of the film, causing a composition shift. On the other hand, if it exceeds 5%, the resistance value is increased, which is not preferable.

  Moreover, the inside of a sputtering device can make surface smoothness favorable by sputtering by the pressure of 0.1-1 Pa, especially 0.3-0.8 Pa. If it is less than 0.1 Pa, it is difficult to be amorphous, and if it exceeds 1 Pa, a dense film cannot be obtained.

  In the present invention, film formation without heating the substrate is possible, but an amorphous film can be obtained by heating the substrate to 100 to 300 ° C., particularly 100 to 200 ° C. This effect is further effective by adding Si and W as dopants.

  According to the method for forming a transparent conductive film of the present invention, since Si and W are added to indium oxide by direct current sputtering adopting specific conditions (substrate temperature, pressure, etc.), the lattice distortion is larger than when Sn is added. Since the film becomes large, the crystallization temperature of the film rises, and a film having an amorphous structure is easily obtained.

Since the ion radius of Si ⁴⁺ is smaller than 0.39Å and 0.92Å of the ion radius of In ³⁺ , the lattice is easily distorted when Si is added to indium oxide. In addition, since W is also included in indium oxide, the covalent bond between In—O is increased, and an amorphous structure can be stably obtained, and a film having an amorphous structure can be stably obtained. The specific resistance of the film also decreases.

  Previously, a conventional technique for producing a transparent conductive thin film made of Si and Sn-added indium oxide by high frequency sputtering has been described. However, in such a high frequency sputtering method, a transparent conductive thin film having an amorphous and smooth structure is formed. It is impossible to obtain stably.

  The present inventor tried an experiment to form a film by high frequency sputtering using a sintered body target containing silicon oxide in indium oxide and pure argon gas (sputtering gas). A crystalline thin film with severe surface irregularities was obtained. This tendency was the same even when a sintered body target containing silicon oxide and tin oxide in indium oxide was used.

  In general, it is known that high-frequency sputtering has significantly higher plasma energy than direct-current sputtering, and a film obtained by high-frequency sputtering has high crystallinity. Needless to say, a film with high crystallinity has severe irregularities on the film surface and poor smoothness. Also, high-frequency sputtering is performed in pure argon gas, and under the film-forming conditions in which oxygen is not included in the film-forming gas, oxygen taken into the film is only part of oxygen supplied from the target. It becomes an oxide thin film with extremely many defects.

  As the amount of oxygen vacancies in indium oxide increases, In—O bonding becomes metallic, and crystal growth easily occurs due to the effect of heat received from plasma during film formation. In other words, in high-frequency sputtering, if oxygen is not introduced into the sputtering gas and the film is formed only with pure argon, the film becomes a good film without heating the substrate, and the film surface becomes uneven. . Conditions for obtaining an amorphous film include not only Si and W in the film, but also DC sputtering with low plasma energy as a film forming method, and an inert gas (at least 1% oxygen mixed in the sputtering gas) It can be said that it is essential to use a mixed gas of argon) and oxygen.

  In the case of an indium oxide film containing Si, or an indium oxide film containing Si and Sn, a crystal film can be obtained by producing high-frequency sputtering using pure argon gas as a sputtering gas. If indium oxide containing W is also used, an amorphous film can be stably obtained even under such film formation conditions, and the specific resistance of the film can be lowered.

The present inventor has confirmed that when W is contained in indium oxide, the covalent bond between In—O is increased by calculating material physical properties by a molecular orbital calculation method by the DV-Xα method. As the covalent bond between In-O increased, the crystallization temperature was estimated to increase and could be confirmed by experiments.
The crystallization temperature of the In ₂ O ₃ film is about 150 ° C., but it is clear from the high temperature X-ray diffraction measurement of the film that the crystallization temperature rises to about 200 ° C. when 0.3 wt% of W is included. It became. Therefore, it can be said that an amorphous film having a smooth surface can be stably obtained by using indium oxide containing not only Si but also W as the composition of the thin film.

  In the case of conventional ITO, it was necessary to perform sputtering film formation under high gas pressure without heating the substrate and reducing the energy of sputtered particles in order to obtain an amorphous film. However, indium oxide to which Si and W are added as in the present invention, for example, even if the gas pressure is low, it is easy to obtain a completely amorphous film. That is, as the amount of Si and W in the film increases, the crystallization temperature of the film increases. Therefore, even if the substrate temperature is substantially increased by sputtering or the substrate is heated as described above, the film composition is increased. If the temperature is lower than the crystallization temperature corresponding to the above, the obtained film has an amorphous structure.

Thus, if each condition of adoption of direct-current sputtering method, dopant content, substrate temperature, pressure, oxygen gas concentration is variously changed within the above range, Si and W are mainly contained in indium oxide. The transparent conductive thin film which does not contain the crystal layer to perform can be obtained.
Oxygen vacancies and the presence of a conductive compound lower the resistance value of the sintered body, thereby reducing the input power during sputtering. Further, the sputtering rate is increased, which shortens the sputtering process and is practical. On the other hand, it is considered that the target manufactured by atmospheric pressure sintering has a higher resistance than the target manufactured by the hot press method and the sputter rate is slower because of less oxygen deficiency.

4). Transparent conductive film The transparent conductive film obtained by the above method is a transparent conductive film containing indium oxide as a main component and containing specific amounts of Si and W as dopants.

  Until now, an ITO thin film, that is, an indium oxide thin film doped with Sn, has been exclusively used as a transparent conductive film in solar cells and various display panels. The conductive mechanism is described as follows. Sn is likely to be a tetravalent ion. When tetravalent Sn is substituted and dissolved in the trivalent In ion position of indium oxide, carrier electrons are emitted and the conductivity is improved.

  In addition, oxygen defects are easily generated in indium oxide, which causes carrier electrons to be emitted. Therefore, in order to increase the carrier electron density of ITO, not only the addition of Sn but also an appropriate amount of oxygen defects is required. However, since the mobility of carrier electrons decreases as the number of oxygen vacancies increases, it is easy to obtain a tetravalent valence like Sn in order to minimize the electrical resistivity. It is conceivable to employ an element to be released as a dopant, and Si is a powerful element.

The ion radii of In ³⁺ and Sn ⁴⁺ are 0.81Å and 0.71Å, respectively, and Sn ions are slightly smaller than In ions. However, the ion radius of Si ⁴⁺ is 0.41 Å, which is extremely small compared to In ³⁺ . Therefore, it is considered that when Si substitutes and dissolves in the In site of indium oxide, the lattice distortion is larger than when Sn substitutes and dissolves, and an amorphous film is easily obtained.

  Therefore, in the present invention, Si is used as a dopant to indium oxide instead of Sn, and the content of Si is 0.2 to 5% by weight, preferably 0.5 to 4.5% by weight. The conductivity of the film can be improved. If the Si content is less than 0.2% by weight, it is difficult to obtain an amorphous film. On the other hand, if it exceeds 5% by weight, the specific resistance becomes too large, which is not preferable.

  Even when W is doped into indium oxide, 4- to 6-valent W is substituted and dissolved in the trivalent In ion position of indium oxide, and carrier electrons are emitted. Can do. An amorphous transparent conductive film can be obtained by further adding W to the Si-doped indium oxide.

  When W is contained in an amount of 0.3 to 5% by weight, preferably 0.5 to 4.5% by weight, more preferably 0.8 to 4.5% by weight, the conductivity of the film can be improved. If the W content is less than 0.3% by weight, it is difficult to obtain an amorphous film. On the other hand, if it exceeds 5% by weight, the specific resistance becomes too large, which is not preferable.

  In the present invention, Sn can be further added to the transparent conductive film containing indium oxide as a main component and Si and W as dopants. According to the conductive mechanism, it can be said that an ITO thin film containing indium oxide, which is a conventional transparent conductive film as a main component, and Sn as a dopant, further contains Si and W.

The specific resistance of the transparent conductive film of the present invention is 9.0 × 10 ⁻⁴ Ω · cm or less, preferably 6.0 × 10 ⁻⁴ Ω · cm or less, and 3 × It can also be 10 ⁻⁴ Ω · cm or less. The specific resistance of the conventional amorphous ITO film is limited to 6 × 10 ⁻⁴ to 8 × 10 ⁻⁴ Ω · cm, and requires a special film formation method as described above. ADVANTAGE OF THE INVENTION According to this invention, the electrically conductive film with low surface resistance suitable as a transparent electrode for LCD and the display of an organic EL element is provided. If the specific resistance exceeds 9.0 × 10 ⁻⁴ Ω · cm, the film must be formed thick, which is not preferable.

  In the present invention, the thickness of the transparent conductive film is not particularly limited, but is 100 to 500 nm, preferably 150 to 450 nm, and more preferably 200 to 400 nm. If the thickness is less than 100 nm, a sufficient specific resistance cannot be ensured. On the other hand, if it exceeds 500 nm, a problem of coloring of the film occurs, which is not preferable.

  Moreover, the transmittance | permeability in the average visible light (400-800 nm) of a transparent conductive film is 85% or more, Preferably it is 90% or more, More preferably, it is 95% or more. When the average transmittance is less than 85%, application to an organic EL element or the like becomes difficult.

  A major feature of the transparent conductive film obtained by the present invention is that the surface is smooth, that is, the center line average roughness (Ra) of the film surface is 1.0 nm or less. Further, if the film forming conditions are optimized, an extremely smooth thin film with Ra of 0.5 nm or less is provided.

  Here, the centerline average roughness (Ra) is measured with an atomic force microscope, specifically, measured in an area of 1 μm × 1 μm for each of 10 arbitrary positions on the film surface. The average value is calculated. When Ra exceeds 1.0 nm, particularly when used as an electrode for organic EL, it becomes impossible to form an ultra-thin film of an organic compound thereon, and therefore a smoothing process such as etching or polishing of the film must be added. This is not preferable.

5. Transparent conductive base material If the transparent conductive thin film is formed on any base material (substrate) selected from a glass plate, a quartz plate, a resin plate or a resin film, a transparent conductive base material is obtained. it can.

  This transparent conductive substrate allows the transparent conductive film to function as an anode and / or a cathode of a display panel such as an LCD, PDP, or EL element. Since the substrate also serves as a light-transmitting support, it needs to have a certain strength and transparency.

  Examples of the material constituting the resin plate or resin film include polyethylene terephthalate (PET), polyethersulfone (PES), polyarylate, polycarbonate (PC), etc., and a structure in which an acrylic resin is coated on these surfaces The resin plate or resin film may be used.

  Although the thickness of a base material is not necessarily limited, if it is a glass plate or a quartz plate, it is 0.5-10 mm, Preferably it is 1-5 mm, and in the case of a resin plate or a resin film, it is 0.00. 1 to 5 mm, preferably 1 to 3 mm. If it is thinner than this range, the strength is weak and handling is difficult. On the other hand, if it is thicker than this range, not only the transparency is poor, but also the weight is unfavorable.

  Any of an insulating layer, a semiconductor layer, a gas barrier layer, and a protective layer can be formed on the substrate. The insulating layer includes a silicon oxide (Si—O) film or a silicon nitride oxide (Si—O—N) film, and the semiconductor layer includes a thin film transistor (TFT) and is mainly formed on a glass substrate. The gas barrier layer is formed on a resin plate or resin film as a water vapor barrier film or the like. The protective layer is for protecting the surface of the substrate from scratches and impacts, and various coatings such as Si-based, Ti-based, and acrylic resin-based are used. Note that the layers that can be formed over the base material are not limited to these, and a thin conductive metal film or the like can also be applied.

  The transparent conductive substrate obtained by the present invention has a transparent conductive film having excellent properties such as specific resistance, light transmittance, and surface flatness, so that it can be used as a component of various display panels. Very useful. Moreover, as an electronic circuit mounting component provided with the said transparent conductive base material, a laser component etc. other than an organic EL element can be mentioned.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited at all by these Examples.

The physical properties of the transparent conductive film were measured by the following methods.
(1) The specific resistance of the transparent conductive film was measured by the four probe method.
(2) The centerline average roughness (Ra) of the film surface was measured with an atomic force microscope. Ra was measured in an area of 1 μm × 1 μm for 10 arbitrary positions on the film surface, and the average value was calculated.

(Examples 1 to 3) (Comparative Examples 1 to 3)
As raw material powder, In ₂ O ₃ powder having an average particle size of 0.1 to 5 μm (purity 99.99 wt%), metal W (purity 99.99 wt%) pulverized to 300 μm or less, metal Si pulverized to 300 μm or less (Purity 99.99% by weight) was prepared.
These raw material powders were uniformly mixed by a dry ball mill, a V blender or the like, fed into a carbon container, and subjected to hot press sintering in an argon gas atmosphere while changing the sintering temperature and pressure.
Table 1 shows the sintering conditions and the density of the obtained sintered body. The sintering density varied with temperature, sintering pressure, and Ar pressure. In addition, even if it changed the composition of the sintered compact in the range from which W becomes 0.3 to 5 weight% and Si becomes 0.2 to 5 weight%, it was the same result.

(Examples 4 and 5) (Comparative Examples 4 and 5)
Sintered bodies having different sintering densities were manufactured using a hot press or an atmospheric furnace. After processing this into a target, the target was attached to the nonmagnetic target cathode of the DC magnetron sputtering apparatus, and a glass substrate was placed at a position facing the target.
A part of the glass substrate immediately above the center of the target was marked with magic ink. Then, the distance between the target and the substrate is set to 60 mm, pure Ar gas is introduced, O ₂ gas is mixed by 1%, the gas pressure is set to 0.5 Pa, DC plasma is generated at DC 160 W, and the substrate is placed on the target. Then, sputtering was carried out for 10 minutes without heating the substrate while still facing the surface.
After the film formation, the marked magic ink and the film deposited thereon were removed with acetone, and the step formed by removing the magic ink, that is, the film thickness was measured with a surface roughness meter. The film formation rate was calculated from the film thickness / film formation time. Further, the number of abnormal discharges was measured as the number of occurrences per 10 minutes after 10 hours of sputtering. The results are shown in Table 2.

(Examples 6 to 9) (Comparative Examples 6 to 10)
In order to investigate the characteristics of the film obtained by sputtering using each target having different concentrations of W and Si, it is determined by the above method without marking with magic ink and heating the substrate temperature. A transparent conductive film having a film thickness of about 150 nm was prepared according to the film formation rate.
The surface resistance of the film was measured by a four-end needle method to calculate the specific resistance, the surface shape was observed with an atomic force microscope, and the surface roughness was measured.
For comparison, an ITO thin film (In ₂ O ₃ -10% by mass SnO ₂ ) was also measured (Comparative Example 10). The composition in the film was measured by EPMA.

From Table 1 above, it is understood that the sintering temperature in the hot press method is preferably 850 to 1000 ° C., the pressure is 9.8 MPa or more, and the hot press atmosphere is preferably Ar atmosphere.
As is clear from Table 2, a target having a relative density of 90% or more (sintering density of 6.3 g / cm ³ or more) produced by a hot press method has a high film forming rate and a low abnormal discharge. Although the target produced by the atmospheric pressure method shown in Comparative Example 5 had a relative density of 90%, no W-Si compound was observed in this sintered body, so no W-Si compound was present. In addition, it is presumed that the small number of oxygen vacancies may be the cause of the low film formation rate of the target produced by the atmospheric sintering method. Further, even when the hot pressing method was used, the number of abnormal discharges increased when the relative density was lower than 90%.
As is apparent from Table 3, if the composition range is such that W is 0.3 to 5% by weight and Si is 0.2 to 5% by weight, a specific resistance equal to or less than that of ITO (Comparative Example 10), ITO and A film having a smaller surface roughness can be obtained.

Claims (7)

A sputtering target material comprising 0.3 to 5% by weight of W and 0.2 to 5% by weight of Si, the balance being substantially made of In ₂ O ₃ . The sputtering target material according to claim 1, wherein the sintered density is 6.3 g / cm ³ or more.   The sputtering target material according to claim 1, wherein at least part of W and Si is contained as a conductive compound of W—Si. W raw material powder, Si raw material powder and In ₂ O ₃ powder are mixed, this powder mixture is charged into a mold, and hot pressed in an inert gas atmosphere at 800 to 1100 ° C. and 9.8 MPa or more. The manufacturing method of the sputtering target material in any one of Claims 1-3 characterized by the above-mentioned.   The method for producing a sputtering target material according to claim 4, wherein the mold for charging the powder mixture is made of carbon.   A target obtained by grinding and processing the sputtering target material according to claim 1.   A transparent substrate made of indium oxide containing Si and W is formed on the substrate by direct current sputtering in an inert gas atmosphere containing oxygen gas after arranging the target and the substrate according to claim 6 in a sputtering apparatus. A method for producing a transparent conductive film, comprising forming a conductive film.