TWI548762B - Alumina film containing tantalum - Google Patents

Description

Alumina film containing ruthenium

This invention relates to an aluminum oxide film containing Ta. The alumina film containing Ta of the present invention not only provides properties inherent in alumina having excellent electrical insulating properties, gas barrier properties such as blocking oxygen or water vapor, but also excellent productivity by sputtering. Film formation is thus useful as a replacement film for alumina.

Therefore, the film of the present invention can be suitably used in various technical fields applicable to the above characteristics of alumina. Specifically, for example, an insulating film (including a protective film or the like) or a gas mask film used in a display device, a magnetic recording device, a solar power generation device, a semiconductor element, or the like; and an insulation of a magnetic head mounted on a magnetic recording device; A film (including a spacer layer, a protective film, or the like) or a gas mask film; a material used for a gas-shielding packaging material used in a field of packaging materials such as foods, precision electronic parts, and pharmaceuticals.

Alumina (sometimes referred to as alumina) has excellent properties such as electrical insulating properties, gas barrier properties, corrosion resistance, non-magnetic properties, and abrasion resistance. Therefore, these properties can be widely used in various fields. Typically, alumina can be applied to: a gate insulating film for protecting a thin film transistor (TFT) or a passivation film (protective film) of a source electrode-drain electrode; an insulating film mounted on a magnetic head of a magnetic recording device; It is used in a gas-shielding packaging material for packaging contents, such as electronic parts, pharmaceuticals, foods, and the like.

Among them, since the masking property of alumina is higher than that of the insulating film or the protective film of SiO ₂ or SiN, in particular, in a display device containing an oxide as a semiconductor layer, an insulating film of aluminum oxide or Protective film. Further, when the oxide semiconductor layer is used as described above, the oxide used in the semiconductor layer and the alumina used in the insulating film or the like can be produced in the same vacuum chamber, and therefore, there is an advantage that the production efficiency is improved. The oxide is typically an oxide containing at least one element selected from the group consisting of In, Ga, Zn, and Sn. A display device having such an oxide semiconductor has a high carrier mobility and a large optical band gap and can form a film at a low temperature as compared with a conventional amorphous germanium (a-Si). It is applied to next-generation displays with high performance, high resolution, and high-speed drive, and resin substrates with low heat resistance.

The above-mentioned aluminum oxide film can be used for an insulating film, a protective film, a gas mask film, or the like of various parts, but there is an increasing demand for improvement in film formation efficiency and improvement in productivity. For example, Patent Document 1 discloses a technique of manufacturing an aluminum oxide film at low cost by using a simple device without using a high-priced device such as a vacuum device. In the above-mentioned Patent Document 1, a common method for forming an aluminum oxide film is a thermal spraying method, a vapor deposition method, a sputtering method, a CVD method, or a wet method using a precursor such as an aluminum alkoxide. Method, sol-gel method, anodic oxidation method of metal aluminum, etc., and pointed out the problems of each film formation method, etc., and also pointed out that the deposition rate of the vapor deposition method, the sputtering method, and the CVD method is slow, so film formation is required. Long time, no economic and other issues. There has not been disclosed a technique for producing a film having the same characteristics as an aluminum oxide film with good productivity by a preferable sputtering method.

Prior art literature

Patent Document 1: Japanese Laid-Open Patent Publication No. 2007-210825

The present invention has been made in view of the above problems, and it is an object of the invention to provide a new technique which is useful as a substitute film for alumina and which has a higher film forming speed and more excellent productivity than alumina.

The alumina film of the present invention obtained by solving the above problems has a point of containing Ta.

In a preferred embodiment of the present invention, the aluminum oxide film contains Ta in a range of 30 atom% or less.

In a preferred embodiment of the present invention, the aluminum oxide film is a film obtained by a sputtering method.

In a preferred embodiment of the present invention, the aluminum oxide film is a film used as an insulating film or a gas mask film.

In a preferred embodiment of the present invention, the alumina film is a film used in a film transistor, a magnetic recording device, or a photovoltaic power generation device.

In a preferred embodiment of the present invention, the semiconductor layer of the thin film transistor is made of an oxide, and the oxide contains at least one element selected from the group consisting of In, Ga, Zn, and Sn.

In the present invention, the aluminum oxide described in any of the above is thin A display device for a film is also included in the scope of the present invention. The display device can be typically exemplified by a thin display device such as a liquid crystal display device, a plasma display device, an electroluminescence display device, or a field emission display device.

According to the present invention, it is possible to provide an alternative technique of alumina which exhibits the same characteristics (excellent insulating properties, gas masking properties, etc.) as those of alumina. The film shape, film properties, and the like after the wet etching process can be favorably maintained by appropriately controlling the amount of Ta in the Ta-containing alumina film of the present invention.

The oxide film containing Ta of the present invention is preferably formed by sputtering, and since the film formation speed at the time of sputtering can be further improved as compared with alumina, productivity can be improved.

The alumina film containing Ta of the present invention is preferably used in the technical field in which alumina is preferably used, and is not particularly limited as long as it is a technical field capable of effectively exhibiting the original characteristics of alumina. An insulating film (including a protective film) of a TFT having a display device having an oxide semiconductor layer, a gas mask film used in the field of foods or pharmaceuticals, and an insulating film such as a magnetic head. As described above, the wet etching property of the film of the present invention can be favorably maintained. Therefore, for example, a wet etching process of a wiring film such as an insulating film can be used in many technical fields without any need.

The inventors of the present invention have focused on providing an alternative to an alumina thin film which can form a film at a higher speed than aluminum oxide and can improve productivity, and has excellent insulating properties, gas masking properties, and the like, and is wet. For reasons such as good etching properties, alumina thin films which are commonly used in various technical fields have been repeatedly studied. As a result, it has been found that when an aluminum oxide film containing Ta (hereinafter sometimes referred to as a Ta-containing aluminum oxide film) is used, the desired object can be achieved without impairing the original characteristics of the above-described alumina, and thus completed. this invention.

As described above, the film of the present invention is characterized in that Ta is contained in alumina. In the present invention, attention is paid to Ta because Ta is an element useful for improving corrosion resistance or heat resistance, and the oxide of Ta has insulating properties. An element other than Ta, for example, an element such as Li, Na, or Ag, becomes conductive when it forms an oxide, and it is unsuitable because it impairs the original properties (electrical insulation, etc.) of the alumina. In addition, Ta is an element which is useful for improving corrosion resistance or heat resistance, and the film of the present invention containing Ta can exhibit the above-described characteristics by Ta in addition to the original properties of alumina, and is therefore very useful.

Further, unexpectedly, it has been found that the oxide film containing Ta of the present invention can be formed at a very high deposition rate as compared with the conventional aluminum oxide film not containing Ta. As described above, the film of the present invention is preferably formed by sputtering, and when the film is formed by sputtering, it is preferable to use an Al alloy sputtering target containing Ta (for example, Japanese Patent Application No. 2011-221005) The sputtering target described in the number is detailed as described later). When a reactive sputtering using a reactive gas formed by mixing an appropriate amount of oxygen in an inert gas such as Ar as a sputtering gas to perform sputtering is performed, it is found that alumina is formed by reactive sputtering using an Al sputtering target. The film formation rate at the time of the film was significantly higher than that of the alumina film containing Ta (see the examples described later). The effect of increasing the film formation speed at the time of sputtering based on Ta has not been known until now.

In order to effectively exhibit the above-described action by Ta (the effect of increasing the film formation rate, the effect of improving heat resistance or corrosion resistance, etc.), the lower limit of the amount of Ta in the alumina containing Ta is preferably It is 0.01 atom% or more. Here, "the amount of Ta in the alumina containing Ta" means the content (atomic %) of Ta with respect to all the metal elements contained in the alumina. Further, it has been found that the more the amount of Ta, the more the above-mentioned effects increase. The upper limit of the amount of Ta is not particularly limited, but when the content of Ta is increased, the original excellent properties of alumina such as insulating properties and wet etching properties may be lowered. Further, when a film of the present invention is formed by using an Al alloy sputtering target containing Ta, for example, an Al-Ta-based intermetallic compound (details will be described later) which contributes to an increase in film formation rate is increased, and the compound is compounded. Since the melting point is a high melting point of 1500 ° C or higher, productivity or production possibility on an industrial scale may be lowered. In consideration of these factors, the upper limit of the amount of Ta in the alumina containing Ta is preferably controlled to be substantially 30 atom% or less. More preferably, the content of Ta is 0.02 atom% or more and 25 atom% or less, and more preferably 0.04 atom% or more and 20 atom% or less.

In the present invention, the alumina in the "alumina containing Ta" is preferably present in a state in which oxygen and aluminum satisfy the stoichiometric composition ratio (also referred to as Al ₂ O ₃ , generally referred to as alumina), but is not limited thereto. Thus, for example, as long as the ratio of O/Al is in the range of about 1 to 1.5, it is allowed. That is, the above alumina may include alumina in which Al is oxidized to a level lower than the stoichiometric composition ratio, and conversely, alumina in which Al is oxidized to a stoichiometric composition ratio and is present in a so-called peroxide state. In short, all of the existing states are included as long as the original properties of the above alumina can be exhibited.

In the present invention, the state of existence of Ta in the "alumina containing Ta" is not particularly limited. That is, at least a part (may be all) of Ta may exist in the form of an oxide, may exist in the form of Ta metal, or may exist in a form in which the above two are mixed. In summary, a Ta-containing alumina having the same characteristics as alumina, regardless of the state of existence of Ta, is included in the scope of the present invention.

In the present specification, the "insulating film" may be an insulating film (typically, a gate insulating film or the like) used in a display device or the like or a semiconductor element. The purpose of the invention is that the insulating film also includes a protective film (representatively, a passivation film overlying the semiconductor layer, etc.) used in the field of a display device or the like or a semiconductor element.

When the film of the present invention is used as an insulating film, it is preferably used in an insulating film for a film transistor, and more preferably used in an insulating film made of an oxide for a semiconductor layer of a film transistor. In this case, since both the insulating film and the semiconductor layer are made of an oxide, it is possible to obtain a manufacturing advantage in which film formation or the like can be performed using the same vacuum chamber. Further, in the thin film transistor having the oxide semiconductor layer, alumina has an advantage of being able to obtain higher insulation and masking properties than SiO ₂ or SiN which is generally used.

The oxide is preferably an oxide containing at least one element selected from the group consisting of In, Ga, Zn, and Sn. Specific examples thereof include an oxide semiconductor containing In (In—Ga—Zn—O, In—Zn—Sn—O, In—Zn—O, etc.), and a Zn-containing oxide semiconductor containing no In ( ZnO, Zn-Sn-O, Ga-Zn-Sn-O, Al-Ga-Zn-O, etc.). The composition ratio described above is not particularly limited, and the composition ratio of the range generally used can be used.

In the present specification, the "gas mask film" is used to block oxygen, water vapor, etc., and is preferably a medicine, an electronic device, a food, a magnetic recording device, a solar power generation device, or the like. A membrane of a gas component that is blocked in the field.

The aluminum oxide film of the present invention consists essentially of only alumina and Ta, and the remainder is an unavoidable impurity. Examples of the unavoidable impurities include impurities that are inevitably mixed in a film forming process such as sputtering.

In addition, the selection component other than the above (a well-known component which can exhibit other characteristics, etc.) can also be added in the range which does not impair the effect of this invention. In practice, it is preferred to appropriately add the optional component to the application to which the aluminum oxide film of the present invention is applied.

For example, when the alumina film of the present invention is used for an insulating film, it is recommended to add an element which does not adversely affect at least the insulating property, and conversely, an element which adversely affects the insulating property is not added. For example, a rare earth element such as Nd or La or Hf or Zr is an element which forms an insulating oxide, and when it is sputtered under reactive sputtering conditions containing oxygen, it does not bring insulation to the film after film formation. Worry about adverse effects, so it can be used as an ingredient To use. Further, although an oxide of Ge, Co, Ni, Ti, or Mg can form a semiconductor, it can be used as a selective component if it is added only in a small amount (about 2 atom% or less). On the other hand, since the oxide of Li, Na, and Ag is highly likely to form a conductor, it cannot be used as a selective component.

The aluminum oxide film of the present invention preferably has a thickness of about 100 to 500 nm. Specifically, the thickness of the above film is preferably appropriately controlled depending on the application to which the film is applied or the like.

Next, a method of producing the aluminum oxide film of the present invention (forming the film of the present invention) will be described.

The oxide film containing Ta of the present invention is preferably formed by a sputtering method using a sputtering target. If the sputtering method is used, there is an advantage that the amount of the additive element can be easily controlled, and a film having substantially the same composition as that of the sputtering target can be easily obtained (the difference in composition between the sputtering target and the film after film formation) Less), the alloy component in the film is easily homogenized. In particular, in the present invention, it is preferable to form the thin film by using an Al alloy sputtering target containing Ta as a sputtering target, whereby the formation at the time of sputtering can be remarkably improved as compared with the case of forming an aluminum oxide thin film. Film speed.

Hereinafter, the sputtering conditions used in the preferred embodiment of the present invention will be described.

First, the sputtering target used in the sputtering method is not particularly limited as long as it is a sputtering target having the same composition as the aluminum oxide film containing Ta of the present invention. Specifically, a metal sputtering target (the remainder: an unavoidable impurity that is inevitably mixed in at the time of production) containing at least a part of Ta and Al constituting the film of the present invention, and a film constituting the present invention can be used. At least a part of Ta and Al are oxidized oxide sputtering targets or both.

For example, in order to obtain a metal sputtering target using a Ta-containing Al alloy sputtering target (single sputtering target) described in Japanese Patent Application No. 2011-221005 (hereinafter, referred to as the prior application) The desired oxide film may be formed by a reactive sputtering method in which oxygen is introduced into an inert gas such as Ar or Ne to perform sputtering. According to this method, there is an advantage that the film formation speed is improved as compared with alumina.

Preferred reactive sputtering conditions when using the above single sputtering target are as described above.

Preferably, oxygen is used as the reactive gas, and the flow ratio of the inert gas to oxygen (oxygen flow rate (sccm) / {oxygen flow rate (sccm) + inert gas flow rate (sccm)) is controlled to be in the range of 5 to 50%. If the flow ratio of the inert gas to oxygen is insufficient, the aluminum after sputtering cannot be sufficiently oxidized. The better one is 10% or more. On the other hand, when the flow rate ratio exceeds 50%, stable and sufficient plasma is not generated, and the film formation rate is lowered, so that it is preferably 50% or less. More preferably 30% or less. Further, the gas pressure is preferably controlled to be in the range of 0.5 to 20 mTorr. When the gas pressure is less than 0.5 mTorr, stable plasma cannot be produced. On the other hand, when the gas pressure exceeds 20 mTorr, the film formation rate is lowered.

Hereinafter, in the invention of the present application, a Ta-containing Al alloy sputtering target described in the preferred application of the invention will be described. However, the sputtering target used in the present invention is not limited thereto.

The above Al alloy sputtering target containing Ta contributes to the film formation speed It is very useful because it is high and is preferably effective in preventing the occurrence of spatter (finely fused particles). In the above-described sputtering target, Ta is bonded to Al and distributed as an Al—Ta-based intermetallic compound, and it has been confirmed that it contributes to a large increase in the film formation rate in film formation. Further, Ta is also an element useful for improving the corrosion resistance and heat resistance of a film formed by using the above-described sputtering target.

The content of Ta contained in the sputtering target is preferably controlled so as to obtain a desired Ta-containing alumina film, and is preferably about 0.01 at% or more and 30 at% or less.

The sputtering target contains Ta and the remainder is Al and unavoidable impurities. However, as described above, the Ta-containing alumina film of the present invention may contain a rare earth element such as Nd or La, an element which forms an insulating oxide such as Hf or Zr, and Ge, Co, Ni, Ti, Mg or the like as an optional component. These optional components may also be included in the above sputtering target.

In the sputtering target, the average particle diameter of the Al—Ta-based intermetallic compound is preferably 0.005 μm or more and 1.0 μm or less, and the average interparticle distance of the Al—Ta-based intermetallic compound is preferably 0.01 μm or more and 10.0 μm or less. . A sputtering target that satisfies both of the above requirements can achieve a higher film formation speed than when a pure Al is used to form an aluminum oxide film.

Here, the above-mentioned Al-Ta-based intermetallic compound means a compound containing at least Al and Ta. In the above-mentioned intermetallic compound, an element other than Al and Ta (for example, the above-mentioned preferred selection element) may be contained depending on the composition of the Al alloy sputtering target containing Ta, the production conditions, and the like, and may further contain The case of these elements is also included in the Al-Ta gold Within the scope of intergeneric compounds.

In addition, the average particle diameter of the above-mentioned intermetallic compound (0.005 μm or more and 1.0 μm or less) can be made fine to the average particle diameter of the above-mentioned intermetallic compound to a nanometer level of 1.0 μm or less. The sputtering phenomenon is uniformly generated, and the film formation speed can be increased. In order to effectively exhibit the above-described effects, the average particle diameter of the above-mentioned intermetallic compound is preferably as small as possible, and the lower limit is about 0.005 μm in consideration of the possibility of production on an industrial scale.

Incidentally, the above "average particle diameter" means an average value of the equivalent circle diameters.

Furthermore, in addition to controlling the average particle diameter, the average interparticle distance (0.01 μm or more and 10.0 μm or less) of the intermetallic compound is controlled, and the dispersion state of the Al—Ta-based intermetallic compound is appropriately controlled. Thereby, the sputtering state of the sputtering surface can be made uniform, and the film formation speed can be further increased. In order to effectively exhibit the above-described effects, the average interparticle distance of the intermetallic compound is preferably as small as possible, but the lower limit is about 0.01 μm in consideration of the possibility of production on an industrial scale.

The average particle diameter and the average interparticle distance (dispersion state) of the above Al-Ta-based intermetallic compound were measured by microscopic observation and image processing as described below.

Specifically, the type of the microscope is changed according to the size (equivalent circle diameter) of the Al-Ta intermetallic compound observed in the visual field, and the Al-Ta intermetallic compound is calculated by the following methods (1) and (2). Size and dispersion state, then calculate their average value, and use the average value as Al-Ta The average particle diameter of the intermetallic compound and the average interparticle distance.

(1) Measurement of average particle diameter and average interparticle distance when an equivalent circle diameter of an Al-Ta-based intermetallic compound exceeds 1.0 μm

At this time, the above compound was observed by FE-SEM (magnification: 1,000 times).

First, a sample for measurement was prepared in the following manner. First, the sputtering target is cut so that the measurement surface of the sputtering target (the surface parallel to the rolling direction in the cross section perpendicular to the rolling surface, and the surface portion of the thickness t of the sputtering target) (1/4) × t portion, (1/2) × t portion) are exposed, and then, in order to smooth the measurement surface, polishing is performed by sandpaper or polishing with a diamond polishing paste or the like to obtain a sample for FE-SEM measurement. .

Next, the sample for measurement was subjected to FE-SEM (magnification: 1000 times), and on the surface layer side in the thickness direction of the sputtering target, (1/4) × t portion, (1/2) × t portion A total of three positions were taken, and five fields of view were taken for each position (one field of view was about 80 μm in length × about 100 μm in width). At this time, analysis of each intermetallic compound was carried out using EDS, and an intermetallic compound in which a Ta peak was detected was extracted. Next, the compound in which the Ta peak was detected in each photograph was determined to be an Al-Ta-based intermetallic compound containing at least Al and Ta, and the compound was quantitatively analyzed by image processing, and the equivalent circle diameter was obtained for each photograph. The average value thereof is referred to as "the average particle diameter of the Al-Ta-based intermetallic compound".

Further, the number density (the number of the second dimension, the number of each unit area) of the compound determined to be an Al-Ta-based intermetallic compound is obtained for each photograph, and the average value thereof is calculated, and the following conversion formula is obtained. Al-Ta The average interparticle distance of intermetallic compounds.

Average interparticle distance of Al-Ta intermetallic compounds = 2 × {1÷π÷ [number density (2 dimensions)]} ^1/2

(2) Measurement of average particle diameter and average interparticle distance when the equivalent circle diameter of the Al-Ta-based intermetallic compound is 1.0 μm or less

At this time, the above compound was observed by TEM (magnification: 7500 times). First, a sample for measurement was produced in the following manner. First, from the measurement surface of the sputtering target (the surface parallel to the rolling surface, the surface parallel to the rolling direction, the surface layer portion of the thickness t of the sputtering target, (1/4) × t The part, (1/2) × t part), respectively, cut out a sample having a thickness of about 0.8 mm. Further, each sample was ground with a sandpaper, a diamond slurry or the like to have a thickness of about 0.1 mm, and then processed into a disk shape having a diameter of 3 mm, and a 30% nitric acid-methanol solution was prepared using Tenurpol-5 by Struers. Electrolytic etching was carried out as an electrolytic solution to obtain a sample for TEM observation.

Then, TEM (magnification: 7500 times) was used for the sample for measurement, and the surface layer side in the thickness direction of the sputtering target, (1/4) × t portion, and (1/2) × t portion totaled 3 At each position, five fields of view were taken at each position (one field of view was about 10 μm in length × 14 μm in width). At this time, analysis of each intermetallic compound was carried out using EDS, and an intermetallic compound in which a Ta peak was detected was extracted. Next, the compound in which the Ta peak was detected in each photograph was determined to be an Al-Ta-based intermetallic compound containing at least Al and Ta, and the compound was quantitatively analyzed by image processing, and the equivalent circle diameter was obtained for each photograph. The average value thereof is referred to as "the average particle diameter of the Al-Ta-based intermetallic compound".

Furthermore, the number density (3rd order, the number of each unit volume) of the compound which was judged to be an Al-Ta-based intermetallic compound was obtained for each photograph, and the average value thereof was calculated, and Al was obtained by the following conversion formula. The average interparticle distance of the -Ta-based intermetallic compound. In addition, the film thickness of the TEM sample at the observation position was measured in the TEM using a foreign matter/spot method, and multiplied by the field of view area (one field of view is about 10 μm in length × about 14 μm in width) to obtain a volume. Using the obtained volume, the number density (3 dimensions) of the compound was calculated for each photograph.

Average interparticle distance of Al-Ta intermetallic compounds = 2 × {(3/4) ÷ π ÷ [number density (3 tens)]] ^1/3

Further, after the size and dispersion state of the Al—Ta-based intermetallic compound are calculated by the methods (1) and (2), the average value thereof is calculated, and the average value is defined as the average particle diameter of the Al—Ta-based intermetallic compound. And the average distance between particles.

Further, the sputtering target preferably has a Vickers hardness (Hv) of 26 or more, thereby preventing occurrence of spatter. Although the detailed reason why the occurrence of spatter can be suppressed by increasing the Vickers hardness as described above is not clear, it is presumed as follows. In other words, when the Vickers hardness of the sputtering target is low, the microscopic smoothness of the machined surface when machining using a milling machine or a lathe used in the production of the sputtering target is poor, in other words, the surface of the material is complicatedly deformed. Since it is thick, stains such as cutting oil used in machining are mixed and remain on the surface of the sputtering target. Such stains are difficult to remove sufficiently even if surface cleaning is performed in a subsequent process. It is considered that these stains remaining on the surface of the sputtering target are the starting point of the initial splash at the time of sputtering. Moreover, in order not to leave these stains on the surface of the sputtering target, it is necessary to improve the machining. The processability (fast blunt) makes the surface of the raw material not thick. Therefore, it is preferable to increase the Vickers hardness of the sputtering target.

The Vickers hardness of the sputtering target is preferably as high as possible from the viewpoint of preventing occurrence of spatter, and is preferably 35 or more, more preferably 40 or more, and further preferably 45 or more. In addition, the upper limit of the Vickers hardness is not particularly limited, but if it is too high, it is necessary to increase the rolling ratio of the cold rolling for the Vickers hardness adjustment, and it becomes difficult to perform rolling. Therefore, it is preferably 160 or less. The ratio is preferably 140 or less, and further preferably 120 or less.

The Vickers hardness (Hv) of the above-mentioned sputtering target can be measured at a load of 50 g using a Vickers hardness tester (AVK-G2, manufactured by Akashi Akashi).

Next, a method of producing the Ta-containing Al alloy sputtering target will be described.

In the method for producing a sputtering target, for example, it is recommended to obtain an alloy ingot having a predetermined composition by a spray foaming method, a powder metallurgy method, or the like, and then heat-treating by heat as needed. A densification process such as HIP (Hot Isostatic Pressing), followed by forging, hot rolling, and annealing. After the above steps, cold rolling→annealing (second rolling→annealing step) can be performed.

In the process of obtaining an alloy ingot of a predetermined composition, it is preferred to apply a spray foaming method from the viewpoint of easily controlling the size or dispersion state of the above-mentioned Al-Ta-based intermetallic compound. Here, the spray foaming method means blowing into an Al alloy melt stream in a vacuum chamber in an inert gas atmosphere. A method in which a high-pressure inert gas is sprayed and quenched to a semi-molten state, a semi-solidified state, and a solid phase state to obtain particles, and the obtained particles are deposited to obtain a predetermined shape of a preform (preform). The present applicant has disclosed a number of spray-foaming methods, for example, Japanese Laid-Open Patent Publication No. Hei 9-248665, Japanese Laid-Open Patent Publication No. Hei No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. It is described in JP-A-2008-127623, and these descriptions can be referred to.

Specifically, as a preferable spray foaming condition for obtaining a desired Al—Ta-based intermetallic compound, a melting temperature: 700 to 1400 ° C, a gas/metal ratio of 10 Nm ³ /kg or less, and more The best is 5~8Nm ³ /kg.

Further, in the step of obtaining an alloy ingot by a spray foaming method or the like, in order to obtain a desired Al—Ta-based intermetallic compound, it is preferred to appropriately control hot rolling conditions (for example, rolling start temperature and rolling). At least one of annealing temperature (one-time maximum reduction ratio, total reduction ratio, etc.), annealing conditions (annealing temperature, annealing time, etc.). Specifically, in the above steps, the rolling start temperature is preferably controlled to 250 to 500 ° C, and the annealing temperature is controlled to be in the range of 200 to 450 ° C.

Further, in the present invention, in order to adjust to a preferable Vickers hardness, it is recommended to control the annealing condition by controlling the cold rolling ratio to be in the range of about 5 to 40% in the second rolling-annealing step. It is in the range of about 1 to 5 hours at about 150 to 250 ° C.

Example

Hereinafter, the present invention will be more specifically described by the examples, but the present invention is not limited to the above-described examples, and may be modified within the scope of the above and the following objects, which are all included in the technology of the present invention. Within the scope.

(Example 1)

In the present embodiment, in order to examine the effect of improving the film formation rate by the addition of Ta and the influence of the addition of Ta on the wet etching property, the Ta content of the sputtering target was changed and compared. According to the following method, a Ta-containing alumina film containing Ta in the same amount as the Ta content of the sputtering target used was obtained.

Specifically, various sputtering targets (Al-Ta sputtering targets (remaining parts: unavoidable impurities)) shown in Table 1 were produced by the following methods.

First, an Al alloy preform containing Ta was obtained under the spray foaming conditions described below.

(spray foaming conditions)

Melting temperature: 1300 ° C

Atomizing gas: nitrogen

Gas/metal ratio: 7Nm ³ /kg

Spray distance: 1050mm

Gas atomization exit angle: 1°

Collector angle: 35°

Next, the obtained preform is sealed in a sealed container, and then Degassing and densification with a HIP device. The HIP treatment was carried out under the conditions of a HIP temperature of 550 ° C, a HIP pressure of 85 MPa, and a HIP time of 2 hours.

The Al-based alloy dense body obtained in the above manner was forged under the conditions of a heating temperature of 500 ° C before forging, a heating time of 2 hours, and an average upsetting rate of 10% or less to obtain a slab (size). It has a thickness of 60 mm, a width of 540 mm, and a length of 540 mm).

Next, rolling (condition: rolling start temperature: 400 ° C, total reduction ratio: 85%) and annealing (condition: 200 ° C × 4 hours) were carried out, and then machining was performed to produce an Al alloy sheet (thickness: 9 mm, width: 150 mm, Length 150mm).

Next, the above Al alloy sheet was subjected to punching processing and lathe processing to obtain a disk-shaped Al-alloy sputtering target (having a thickness of 5 mm) having a diameter of 4 inches.

The average particle diameter (average value of the equivalent circle diameter) and the dispersion state (average distance between particles) of the Al-Ta intermetallic compound were measured by the above-described methods for various Ta-containing Al alloy sputtering targets obtained as described above. It is preferable to satisfy the sputtering target (the average particle diameter of the Al-Ta intermetallic compound is 0.005 μm or more and 1.0 μm or less, and the average interparticle distance of the Al-Ta intermetallic compound is 0.01 μm or more and 10.0 μm or less). In addition, the Vickers hardness (Hv) of the above-described Ta-containing Al alloy sputtering target was measured using a Vickers hardness meter (manufactured by Akashi Akashi, AVK-G2) under a load of 50 g, and both of them satisfied the present invention. Preferred (26Hv or more).

Further, in the present embodiment, for the sake of comparison, it is manufactured by a melting method. Pure Al sputtering target with a purity of 4N. Specifically, an ingot having a thickness of 100 mm was ingot cast by a DC casting method, and then heat treated at 400 ° C for 4 hours, followed by cold working at a cold rolling ratio of 75% at room temperature. Then, it was heat-treated at 200 ° C for 4 hours, and cold rolled at a cold rolling rate of 40% at room temperature.

(Measurement of film formation rate ratio with pure Al)

Various sputtering targets (Al-Ta sputtering targets and pure Al sputtering targets) shown in Table 1 were used, and sputtering was performed under the following conditions to form various films.

Specifically, first, DC sputtering was performed on an EAGLE XG glass substrate (size: 4 inches in diameter × thickness 0.70 mm) manufactured by Corning using various sputtering targets obtained by changing the content of Ta as shown in Table 1. plating. As the sputtering apparatus, a sputtering apparatus of "Sputtering System HSR-542S" manufactured by Shimadzu Corporation was used. The sputtering conditions are as described above.

Reaching vacuum: 7×10 ^-6 Torr

Air pressure: 2mTorr

Discharge power: 260W

Ar gas flow: 27sccm

Oxygen flow: 3sccm

Oxygen flow ratio = 10%

Distance between poles: 50mm

Substrate temperature: room temperature

Film formation time (sputtering time): 20 minutes

The film thickness of the produced film was measured with a stylus type step meter ("alpha-step 250" manufactured by TENCOR INSTRUMENTS). Determination of film thickness The film thickness was measured from the center of the film at intervals of 5 mm in the radial direction, and the film thickness at three points was measured in total, and the average value was defined as "thickness of the film" (nm). The average film formation rate (nm/min) was calculated by dividing the "thickness of the film" thus obtained by the sputtering time (minutes).

In the present embodiment, the film formation rate ratio of the average film formation rate when a film is formed using an Al-Ta sputtering target of each composition is calculated based on the average film formation rate when a film is formed using a pure Al sputtering target. The larger the film formation rate ratio thus obtained, the faster the film formation speed.

(Evaluation of wet etching property)

Various thin films were formed by sputtering using various sputtering targets (Al-Ta sputtering targets and pure Al sputtering targets) shown in Table 1. The sputtering method was the same as the above-described method in the column of "measurement of film formation rate ratio of pure Al", except that the ruthenium substrate was used instead of the XG glass substrate. However, the film thickness was set to 100 nm (constant).

Then, each of the aluminum oxide films thus obtained was immersed in 1% by weight of dilute hydrofluoric acid for 1 minute to carry out a wet etching treatment, and the reflectance after wet etching was measured. The reflectance of the visible light of the alumina film was measured by a spectrophotometer (V-570 spectrophotometer manufactured by JASCO Corporation) to measure the reflectance of visible light having a wavelength of 550 nm. For comparison, the reflectance of the tantalum substrate (that is, the reflectance when the aluminum oxide film was not provided) was calculated in the same manner as described above, and the difference in reflectance from the aluminum oxide film was determined. In the present example, the wet etching properties of the respective aluminum oxide films were evaluated by the following criteria, and ◎, ○, and Δ were evaluated as acceptable (excellent wet etching property).

◎The above difference is less than 3.0%

○ The above difference is 3.0% or more and less than 6.0%

△ The above difference is 6.0% or more and less than 10.0%

×The above difference is 10.0% or more

Incidentally, as described above, in the present embodiment, the reflectance was measured in order to evaluate the wet etching property, because the thickness of the aluminum oxide film was as thin as 100 nm as in the present example, and the wetness was usually performed. The method for evaluating the etching property (typically, the method for evaluating the film thickness before and after wet etching using a step gauge or the like) is inferior in accuracy.

The above results are shown together in Table 1. For reference, FIG. 1 shows a graph of the results of the film formation rate when the content of Ta is 0 to 40 atom%. The horizontal axis of Fig. 1 represents the content of Ta (atomic %), and the vertical axis represents the film formation rate of the film.

First, the film formation speed was examined. As is clear from Table 1 and Fig. 1, the amount of Ta in the alumina film containing Ta [in the present embodiment, the ratio (atomic %) of Ta to all metal elements (Al + Ta) is increased to form a film. The speed is also improved. Specifically, when an Al alloy sputtering target containing Ta is used, and an oxide thin film containing Ta is formed by a reactive sputtering method in which oxygen is added to Ar gas, a pure Al sputtering target is used. In the case of the film, the film formation speed ratio was 1.13 to 2.18, which was greatly improved.

On the other hand, when the amount of Ta in the aluminum oxide film containing Ta exceeds 30 atom%, the wet etching property is lowered (evaluation in Table 1). Therefore, when considering the wet etching property, it is recommended to set the upper limit of the amount of Ta to 30 atom% or less.

(Example 2)

In the present embodiment, the oxygen flow rate ratio at the time of sputtering was changed, and the effect of improving the film formation rate by the addition of Ta was compared.

Specifically, an Al-1.5% Ta sputtering target (remaining: unavoidable impurities) containing 1.5 atom% of Ta and a pure Al sputtering target were produced in the same manner as in the above-described Example 1. Next, according to the manner shown in Table 2, the oxygen flow ratio [ratio of the flow rate of oxygen (sccm) to the total flow rate of the gas of Ar and oxygen (sccm)] is varied in the range of 0 to 0.6, and the DC magnetron is simultaneously performed. Each film was formed in the same manner as in Example 1 except that the film thickness was changed to about 600 nm. The average film formation rate and the film formation rate ratio were calculated in the same manner as in the above Example 1. This implementation In the example, a Ta-containing alumina film containing Ta in the same amount as the Ta content (1.5 atom%) of the sputtering target used can be obtained.

The above results are collectively shown in Table 2. In the present embodiment, the average film formation rate when the film was formed using a pure Al sputtering target (see (b) of Table 2) was used to calculate the average value when forming a film using an Al-1.5% Ta sputtering target. Film formation rate [see Table 2 (a)] film formation rate ratio [= (a) ÷ (b)].

For reference, FIG. 2 plots the results of the oxygen flow ratio = 0.1 to 0.6. The horizontal axis of Fig. 1 represents the oxygen flow ratio, and the vertical axis represents the film formation speed (● and □) of each film. Specifically, ● is a film forming speed at the time of film formation using an Al-1.5% Ta sputtering target, and □ is a film forming speed at the time of film formation using a pure Al sputtering target.

These results can be examined as described above.

First, the case where the oxygen flow ratio is 0 (no oxygen is added) is discussed. When a film is formed using an Al alloy sputtering target containing Ta, the film formation rate ratio is 1.68 as compared with the case of forming a film using a pure Al sputtering target not containing Ta, and the film formation rate is greatly improved.

In the above, since the film is formed without adding oxygen to the sputtering gas, the film after the film formation is not the Ta-containing aluminum oxide film which is the object of the present invention, but the Ta-containing object which is the object of the present invention is as described below. When the aluminum oxide film is formed into a film, the effect of increasing the film formation rate based on the addition of Ta is similarly found.

That is, in the process of performing sputtering by using an Al alloy sputtering target containing Ta, a reaction is carried out by adding oxygen to the Ar gas and changing the oxygen flow ratio in the range of 0.1 to 0.6 (=10 to 60%). The film formation by the sputtering method is similar to the case where the film formation is performed using a pure Al sputtering target containing no Ta, and the film formation rate ratio is greatly improved from 1.44 to 1.87.

Incidentally, in the reactive sputtering method, the film formation rate (absolute value) is usually lowered by introduction of oxygen. In the present embodiment, when only the absolute value of the film formation rate is compared, it is found that the film formation rate is lowered at a time when oxygen is introduced, and the film formation rate is lowered as the oxygen flow rate ratio is increased. However, the film formation rate is decreased as described above. Ta, so that the film formation speed ratio is improved as compared with the case where Ta is not added. In particular, under the conditions of the present embodiment, the effect of increasing the film formation rate ratio based on the addition of Ta was most remarkable when the oxygen flow ratio was at least 0.1 (=10%).

Incidentally, the film formation rate at the oxygen flow ratio = 0.1 (10%) in Table 2 of the present example and the film formation rate of Al-1.5% Ta in Table 1 of the above-described Example 1 theoretically obtained the same value. (The reason is that the same sputtering target was used and sputtering was performed under the same conditions), but in fact, the same result was not obtained. Similarly, the film formation rate when using a pure Al sputtering target There are also a few differences between Table 1 and Table 2. However, these slight differences are within the range allowed by the calculation of the film formation speed, and there is no substantial difference, as long as the comparison is made in the same experimental group, the film formation speed is improved for the addition of Ta-based addition. The conclusion of such a role has no effect.

The embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention as set forth in the appended claims.

Fig. 1 is a graph showing the relationship between the Ta content and the film formation speed of various films in the case where various changes in the Ta content are caused in Example 1 to form various films.

Fig. 2 is a graph showing the relationship between the oxygen flow ratio and the film formation speed of various films when the oxygen flow ratio is varied and the various films are formed in the second embodiment.

Claims (8)

An aluminum oxide film characterized by containing Ta in a range of 0.01 at% or more and 30 at% or less. An alumina film according to the first aspect of the invention is a film obtained by film formation by a sputtering method. An alumina film as claimed in claim 2, which is a film used as an insulating film or a gas mask film. An alumina film as claimed in claim 3, which is a film for an insulating film of a film transistor. The aluminum oxide film according to claim 4, wherein the semiconductor layer of the thin film transistor is made of an oxide, and the oxide contains at least one element selected from the group consisting of In, Ga, Zn, and Sn. A display device having an alumina film according to any one of claims 1 to 5. An alumina film as claimed in claim 3, which is a film for a magnetic recording device. An alumina film as claimed in claim 3, which is a film for a photovoltaic power generation device.