JP2017186581A - Oxide sintered body sputtering target for forming positive electrode film and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering target for forming a positive electrode film, capable of continuing electric discharge without generating arcing even under the condition of supplying high DC power to stably deposit a film when the positive electrode of a thin film lithium secondary battery is manufactured by a sputtering method.SOLUTION: The oxide sintered body sputtering target for forming a positive electrode film consists of at least one or more kinds of transition metals selected from nickel, cobalt, and manganese and an oxide sintered body including aluminum. The oxide sintered body is mostly constituted of a transition metal oxide phase, and does not include an aluminum oxide phase or has a size of 100 nm or less even when included.SELECTED DRAWING: None

Description

  The present invention relates to an oxide sintered body sputtering target for forming a positive electrode film and a method for producing the same, and more specifically, even when a positive electrode of a thin film lithium secondary battery is produced by a sputtering method, Furthermore, the present invention relates to an oxide sintered body sputtering target for forming a positive electrode film, which is capable of forming a stable film without causing arcing, and a method for producing the same.

  In recent years, development of thin film lithium secondary batteries has been promoted. A thin-film lithium secondary battery has a structure in which a solid electrolyte is sandwiched between a positive electrode and a negative electrode. A lithium phosphate nitride film is used for the solid electrolyte, a metal lithium film is used for the negative electrode, and a positive electrode is used for the positive electrode. A positive electrode film composed of a compound of a transition metal such as lithium cobaltate, lithium nickelate or lithium manganate and lithium, or a positive electrode film composed of a solid solution of these compounds is used. In addition, attempts have been made to improve the characteristics of secondary batteries by replacing a part of the transition metal in the positive electrode with aluminum.

For example, the positive electrode material of LiNi _0.8 Co _0.15 Al _0.05 O ₂ has a composition in which Al is replaced with a part of a transition metal, so that a secondary battery having excellent cycle characteristics and safety can be realized. Therefore, it is known as a positive electrode material that is extremely useful in practice (Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3).
In addition, it is known that the LiNi _1/3 Mn _1/3 Co _1/3 O ₂ positive electrode material is also improved in thermal behavior and cycle stability when Co is partially substituted with Al (Non-patent Document 5). ).

LiMn ₂ O ₄ reduces the theoretical capacity when Mn is partially substituted with Al, but prevents Mn from being excessively reduced than the average oxidation state of 3.5 during charge and discharge, and the Jahn-Teller effect The risk of leading to the formation of a tetragonal phase due to is greatly reduced (Non-patent Documents 6 and 7).
The positive electrode film is generally formed by mixing a positive electrode active material with a binder or a solvent and applying it to a substrate. Industrially, an oxide sintered body containing a constituent element of the active material was used as a target. Sputtering is also a useful formation method.

In such a sputtering method, one target containing all the constituent metals of the positive electrode material is used as a target. For example, Patent Document 1 describes a lithium cobaltate target, and a method for forming a lithium cobaltate film on a substrate by sputtering using a direct current pulsing method is proposed. However, although it is described here that it is preferable that at least a part of the LiCoO ₂ layer formed on the substrate includes a crystalline structure, the target used for the film formation may be an oxide or the like as a material. There is no specific explanation.

Also, Patent Document 2 and Patent Document 3 propose a method for producing a lithium cobaltate sputtering target. These describe that a target having a relative density of 95% or more and an average particle diameter of 10 to 30 μm is produced by pressure sintering under specific conditions using LiCoO ₂ powder as a raw material powder. ing. However, the film obtained by using this has not yet exhibited a sufficient function as a positive electrode film for a lithium secondary battery.

  In addition to the above general sputtering method, an oxide sintered compact target including a metal excluding lithium among constituent metals of the positive electrode material, that is, at least one transition metal selected from nickel, cobalt, and manganese and aluminum Sputtering simultaneously from two targets, an oxide sintered body target (hereinafter referred to as a positive electrode film forming oxide sintered body target) and a lithium metal target (hereinafter referred to as a positive electrode film forming metal Li target) There is a method of forming a positive electrode film by film formation, which is effective. This method is called co-sputtering, and the excess or deficiency of lithium can be easily controlled by changing the ratio of electric power applied to both targets.

  In general, the sputtering method uses a substrate as an anode and a target as a cathode under an argon gas pressure of about 10 Pa or less, generates a glow discharge between them to generate an argon plasma, and generates an argon cation in the plasma. This is a method in which a film is obtained by colliding with a cathode target, thereby repelling target component atoms and depositing them on a substrate. Usually, a magnet is arranged on the back side of the target, and the plasma density generated on the upper surface of the target is increased and stabilized even at a low gas pressure of about 2.0 Pa or less, and sputtering film formation is performed. This method is called a magnetron sputtering method and is industrially mainstream.

  Further, the sputtering method is classified according to the generation method of the argon plasma, and when the direct current plasma is used, it is called the direct current sputtering method. The DC sputtering method is industrially the most useful method because the DC power source for generating plasma is inexpensive and the film is formed at a high speed. The DC magnetron sputtering method using the above-described magnetron is the best. It is used.

  On the other hand, the direct-current magnetron sputtering method can generally stably produce a film only when a conductive target is used. This is because when an insulating or high-resistance target is used, positive charging occurs on the target surface from argon generated from plasma, and arcing occurs. Among DC sputtering methods, arcing can be suppressed by a method in which a negative voltage applied to the target is periodically stopped and a low positive voltage is applied to neutralize positive charges with electrons in the plasma. This method is called a direct current pulsing method and is included in the direct current sputtering method in a broad sense. However, there is a limit to the suppression of arcing when an attempt is made to obtain high-speed film formation by applying high power.

  High-frequency sputtering methods that have been known for a long time are useful for stable film formation using insulating and high-resistance targets. High frequency sputtering is a method of forming a film by inserting an impedance matching circuit composed of a coil and a capacitor between a high frequency power source and a target, and generating high frequency plasma between the target and the substrate. This is because even if a part of the target is charged, the polarity of the target is periodically reversed, so that electrons in the plasma are attracted and neutralized. However, the high-frequency sputtering has many industrial demerits such as high power supply cost, complicated adjustment of the film forming operation because the impedance matching circuit needs to be adjusted, and low film forming speed.

  As described above, the DC magnetron sputtering method is useful because the apparatus is inexpensive and easy to operate, and the film formation speed is high. However, considering the productivity, the input power for generating plasma is increased as much as possible. Thus, the film formation rate is increased to form a film. Therefore, there is a need for a sputtering target that maintains a stable plasma and continues high-speed film formation even when high DC power is applied.

As described above, in the secondary battery, when a positive electrode material containing at least one transition metal selected from nickel, cobalt, and manganese and further containing aluminum is used, charge / discharge cycle characteristics and safety are improved. It is effective for.
And in such a method for producing a thin film of the positive electrode material, a sputtering method is common, and among the constituent metals of the positive electrode material, at least one transition metal selected from nickel, cobalt and manganese excluding lithium and A cathode film is obtained by sputtering simultaneously from two targets: an oxide target containing aluminum (oxide sintered body target for positive electrode film formation) and a lithium metal target (metal Li target for positive electrode film formation). A sputtering method is effective. In mass production, it is useful to manufacture by a direct current sputtering method (hereinafter also including a direct current magnetron sputtering method) because high-speed film formation is obtained.

  Even with the target, the positive electrode film forming metal Li target can stably perform direct current sputtering, but the positive electrode film forming oxide sputtering target contains aluminum. Sputtering cannot be performed. In particular, in the DC sputtering method under the condition that high DC power is applied in consideration of productivity improvement, arcing frequently occurs and discharge does not continue, and thus it cannot be manufactured stably.

Therefore, a sputtering target containing Al is required when such a positive electrode film is stably manufactured by a direct current sputtering method (hereinafter also including a direct current magnetron sputtering method) effective for mass productivity.
However, sputtering targets containing Al have not yet been distributed on the market. This is because in the DC sputtering method under the condition that high DC power is applied in consideration of productivity improvement, when a sputtering target containing Al is used, arcing occurs and the positive electrode film cannot be stably manufactured.

JP 2008-45213 A WO2011-086649 WO2011-086650 gazette

Dahn, J. et al. R. Fuller, E .; W. Obrovac, M .; Von Sacken, U .; , Solid State Ionics, 1994, 69, 265. Albrecht, S .; Kumpers, J .; Kruft, M .; Malcus, S .; Vogler, C .; Wahl, M .; Wohlfahrt-Mehrens, M .; , J. et al. Power Sources, 2003, 119-121, 178. Chen, C.I. H. Liu, J .; Stoll, M .; E. Henriksen, G .; Vissers, D .; R. Amine, K .; , J. et al. Power Sources, 2004, 128, 278. Kostecki, R.A. Lei, J .; McLarnon, F .; Shim, J .; Striebel, K .; , J. et al. Electrochem. Soc. 2006, 153, A669. Wilcox, J .; D. Rodriguez, E .; E. Doeff, M .; M.M. , J. et al. Electrochem. Soc. , 2009, 156, A1011. Gummow, R.A. J. et al. De Kock, A .; Thuckeray, M .; M.M. , Solid State Ionics, 1994, 69, 59. Ariyoshi, K. et al. Iwata, E .; Kuniyoshi, M .; Wakabayashi, H .; Ohzuku, T .; , Electrochem. Solid St. , 2006, 9, A557.

  In view of the above-described problems of the prior art, an object of the present invention is to provide a positive electrode film-forming oxide sintered sputtering target capable of producing a positive electrode film containing aluminum that can be stably used even by a direct current sputtering method, and a method for producing the same. Is to provide.

  As a result of diligent research to solve the above problems, the present inventor has obtained oxide sintering produced from an oxide sintered body containing at least one transition metal selected from nickel, cobalt, and manganese and aluminum. When a body sputtering target was used to form a film by a direct current sputtering method, the occurrence of arcing largely depends on the form of aluminum present in the sintered body. In particular, if an aluminum oxide phase is present, arcing frequently occurs. The inventors have devised that the generation of arcing can be suppressed by using a very fine particle size of aluminum oxide in an oxide sintered body containing aluminum, and the present invention has been completed. .

  That is, according to the first invention of the present invention, the oxide sintered body sputtering for positive electrode film formation comprising an oxide sintered body containing at least one transition metal selected from nickel, cobalt and manganese and aluminum. In the target, the oxide sintered body is mostly composed of a transition metal oxide phase and does not contain an aluminum oxide phase or has a size of 100 nm or less. An oxide sintered sputtering target is provided.

According to the second invention of the present invention, in the first invention, the oxide sintered body has an aluminum content of 1 to 15 atomic% with respect to the total of all transition metal oxides. The oxide sintered compact sputtering target for positive electrode film formation characterized by this is provided.
According to the third invention of the present invention, in the first invention, the oxide sintered body is composed only of nickel, cobalt, and an aluminum-containing transition metal oxide, and the aluminum element is in the transition metal oxide phase. An oxide sintered body sputtering target for forming a positive electrode film, characterized by being dissolved, is provided.

  According to the fourth invention of the present invention, in the first invention, the oxide sintered body is composed only of nickel, cobalt, manganese, and an aluminum-containing transition metal oxide, and the aluminum element is a transition metal oxide. An oxide sintered body sputtering target for forming a positive electrode film, characterized by being dissolved in a phase, is provided.

  According to a fifth aspect of the present invention, in the first aspect, the oxide sintered body is characterized in that the presence of an aluminum oxide phase is not confirmed even when observed with an EPMA (Electron Probe Microanalyzer). An oxide sintered sputtering target for positive electrode film formation is provided.

According to the sixth aspect of the present invention, after using at least one transition metal oxide powder selected from nickel, cobalt, and manganese and aluminum oxide powder as raw material powder, mixing, and sufficiently pulverizing A method for producing a positive electrode film forming oxide sintered sputtering target including a step of forming an oxide sintered body by pressure molding and firing the obtained molded body,
Provided is a method for producing an oxide sintered sputtering target for forming a positive electrode film, characterized in that the sizes of the transition metal oxide and aluminum oxide in the raw material powder are 5 μm or less in average particle size.

  According to a seventh aspect of the present invention, in the sixth aspect, the raw material powder is heated at a rate of temperature increase of 3 ° C. or less up to a firing temperature of at least 1100 ° C. A method of manufacturing an oxide sintered body sputtering target is provided.

Further, according to the eighth invention of the present invention, the oxide film-forming sintered sputtering target for positive electrode film formation of any one of the first to fifth inventions is charged into a direct current sputtering apparatus, and under a gas pressure of 10 Pa or less, There is provided a method for forming a positive electrode film, wherein DC power of 2.757 W / cm ² or more is input to a target to form a positive electrode film on a substrate without causing arcing.

  The oxide sintered compact sputtering target for forming a positive electrode film of the present invention uses an extremely small particle size of aluminum oxide in the oxide sintered body, and there is substantially no aluminum oxide phase. By using this, arcing is suppressed even in the direct current sputtering method, and the positive electrode film can be stably formed with high productivity. Since the positive electrode film containing aluminum thus formed is much thinner than that obtained by the conventional coating method, the size of the lithium secondary battery can be reduced.

  Hereinafter, modes for carrying out the present invention will be described. However, the present invention is not limited to the following embodiments, and various modifications and substitutions may be made to the following embodiments unless the object of the present invention is impaired. Can be added.

1. Oxide Sintered Body and Sputtering Target An oxide sintered body sputtering target comprising an oxide sintered body containing at least one transition metal selected from nickel, cobalt, and manganese of the present invention and aluminum is a sintered body. When the particle size of aluminum oxide is as fine as 100 nm or less, the aluminum oxide phase is substantially free of aluminum oxide. Preferably it is 50 nm or less, More preferably, it is 20 nm or less.

In the conventional sputtering target of lithium cobaltate, as described above, the LiCoO ₂ powder is used as a raw material powder, and the relative density of 95% or more and the average particle size of 10 to 30 μm are obtained by pressure sintering under specific conditions. Thus, a positive electrode film for a lithium secondary battery could be formed relatively stably even by a direct current sputtering method.
However, in order to obtain a positive electrode film for a lithium secondary battery that exhibits a sufficient function, it is necessary to contain aluminum. However, when an oxide sintered body for a target is manufactured, a large aluminum oxide phase is included in the crystal phase. Has occurred.

In general, when a metal oxide is subjected to a heat reduction treatment performed in a non-oxidizing atmosphere such as nitrogen at a high temperature, oxygen deficiency is introduced and conductivity is imparted. Since the bond with oxygen is strong, it is difficult to effectively impart conductivity by introducing oxygen vacancies. This tendency is the same regardless of whether the aluminum oxide phase is crystalline or amorphous, and this aluminum oxide phase causes arcing because it is a high resistance phase or an insulating phase. In DC sputtering, the high resistance or insulating aluminum oxide phase is charged by irradiation with argon ions, and the DC discharge is not stabilized and arcing occurs.
The aluminum oxide phase has such problems, but the transition metal oxide phase other than that is a conductive phase even when aluminum is contained, and charging that causes arcing does not occur.

In the sputtering target for forming a positive electrode film of the present invention, it is preferable that the target does not substantially contain an aluminum oxide phase.
In the present invention, the absence of an aluminum oxide phase means that a diffraction peak does not appear by XRD, and an aluminum oxide region having a size exceeding 100 nm is not confirmed by EPMA (Electron Probe Microanalyzer) observation. Yes.

  In addition, if a part of other metal constituting the target is dissolved in the aluminum oxide phase, arc resistance tends to occur because it exhibits high resistance or insulation. It is not included in the oxide sintered compact sputtering target for positive electrode film formation of this invention.

(Oxide sintered body)
As described above, the oxide sintered body sputtering target for forming a positive electrode film of the present invention uses an oxide sintered body containing at least one transition metal selected from nickel, cobalt, and manganese and aluminum. .

  The oxide sintered body is substantially free of an aluminum oxide phase, but may contain a metal oxide phase such as nickel oxide, manganese oxide, cobalt oxide or the like that can impart conductivity by the above heat reduction treatment. Absent. Further, metals other than nickel, cobalt, manganese, aluminum, and lithium, for example, Mg, Ca, Ti, V, Cr, Zr, Nb, Mo, W, and the like may be included so long as the object of the present invention is not impaired.

  In the present invention, it is preferable that both Ni and Co are included as the transition metal. Ni is 10 to 90 atomic% and Co is 10 to 50% with respect to the total amount of the transition metal represented by the above composition formula. It is preferably atomic%. More preferably, Ni is 20 to 90 atomic%, and Co is 10 to 40 atomic%.

  In the oxide sintered body, part of oxygen may be substituted with F, Cl, etc., and part of the transition metal is Fe, Cr, Ti, Nb, W, Mo, Li, Na, K. It may be substituted with another metal such as Mg, Ca. Further, Li may be excessive or deficient with respect to the stoichiometric composition of the compound, and oxygen may be deficient with respect to the stoichiometric composition.

  In any of these, the oxide sintered sputtering target including all metals except for lithium among the constituent metals of the positive electrode film is an object, and as described above, the aluminum oxide is observed by EPMA (Electron Probe Microanalyzer). The particle size is as fine as 100 nm or less. If the particle diameter of aluminum oxide exceeds 100 nm, arcing is likely to occur due to the aluminum oxide phase, which is not preferable.

A more preferable embodiment of the present invention is that it is composed only of at least one transition metal selected from nickel, cobalt, and manganese and an aluminum oxide, and the aluminum element is dissolved in the lithium-containing transition metal oxide. .
Even if a metal oxide phase such as nickel oxide, manganese oxide, cobalt oxide, etc. that can be rendered conductive in the target exists in the target, it does not cause arcing, but if it is not dissolved, the metal element This is because the uniformity of the film is inferior and causes a variation in the composition of the film obtained by film formation. In a target having a phase structure as in the present invention, each metal element is uniform at the atomic level, and a constant element can be always sputtered to make the film composition constant.

2. Manufacturing method of oxide sintered body sputtering target for forming positive electrode film The oxide sintered body sputtering target for forming a positive electrode film of the present invention is obtained by mixing and firing using a metal oxide powder of a constituent element of the target as a starting material. The oxide sintered body is manufactured by sintering and processed into a predetermined size to obtain a sputtering target.

  In the present invention, unlike the conventional manufacturing method, attention is paid to selection of raw material powder and optimization of mixing conditions and firing conditions. That is, the present invention uses at least one kind of transition metal oxide selected from nickel, cobalt, and manganese and aluminum oxide as a raw material powder, and after sufficiently pulverizing the mixture, it is pressure-molded, and the obtained molded body Is a method for producing a cathode film-forming oxide sintered sputtering target including a step of forming an oxide sintered body by firing, and the raw material powder has an average particle size of transition metal oxide and aluminum oxide The diameter should be 5 μm or less.

  As the raw material powder for the oxide sintered body, at least one transition metal oxide selected from nickel, cobalt, and manganese and aluminum oxide are used. As the starting material, a metal powder or a metal salt powder may be blended within a range not impairing the object of the present invention.

  If the average particle size exceeds 5 μm, it takes time to grind, which is not preferable. It is desirable that the raw material powders are sufficiently mixed with each other to increase the reactivity. It is efficient to mix while grinding. In the case of ball mill mixing, it is preferable to carry out sufficient pulverization and mixing for 10 hours or longer, particularly 12 hours or longer.

The starting material of the aluminum component is aluminum oxide powder, and a powder having an average secondary particle size of 5 μm or less, preferably 3 μm or less is used. Particularly preferred is 0.2 to 1 μm.
The content of aluminum in the oxide sintered body is preferably 1 to 15 atomic%, more preferably 3 to 10 atomic%, based on the total of all transition metals and aluminum. For this purpose, 1 to 20 mol% of aluminum oxide powder is used with respect to the total amount of the transition metal powder.

  As described above, when mixing with other raw material powders by ball mill mixing, it is desirable to perform sufficient grinding and mixing for 10 hours or more. By performing sufficient pulverization and mixing, the aluminum oxide can be completely dissolved in the lithium-containing transition metal oxide by subsequent firing.

  Then, it puts into a reaction container and fires. The baking temperature is 800 to 1150 ° C., oxygen is sufficiently supplied, and baking is performed for 5 to 12 hours in an atmosphere of nitrogen or inert gas containing 20% by volume or more of oxygen. The baking temperature is preferably 850 to 1100 ° C., oxygen is sufficiently supplied, and baking is preferably performed for 8 to 12 hours in a nitrogen or inert gas atmosphere containing 30% by volume or more of oxygen.

  In the liquid phase generated by firing, an oxide of at least one transition metal selected from nickel, cobalt, and manganese is preferentially melted and deposited, but aluminum oxide is not melted, so aluminum oxide is segregated. End up. Even if the aluminum oxide powder is sufficiently uniformly mixed in the mixture before firing, a large lump of aluminum oxide is formed due to such segregation, so that the oxide sintered body in which an aluminum oxide phase exists after firing. Become.

  In the present invention, specifically, in order to avoid this, it is effective to set the rate of temperature rise at the time of firing slower, and to repeat the calcination and calcination step below the melting point. The rate of temperature increase during firing in which aluminum oxide is not segregated depends on the mixed state, but is preferably 3 ° C./min or less.

  When the average particle diameter of the aluminum oxide raw material powder is 1 μm or less, the obtained oxide sintered body is substantially free of the aluminum oxide phase. In addition, since aluminum is dissolved in another metal constituting the target, the resistance value does not increase and it is suitable for forming a positive electrode film by sputtering.

3. Formation of Positive Electrode Film by Sputtering A sputtering target produced from the oxide sintered body of the present invention is used when producing a positive electrode of a thin film lithium secondary battery by a sputtering method.

The oxide sintered compact sputtering target for positive electrode film formation of this invention can be utilized when obtaining the following positive electrode films.
In the α-NaFeO ₂ type layered structure LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , the spinel type structure LiMn ₂ O ₄ , the olivine type LiFePO ₄ , and two or more solid solutions of these compounds, a part of the transition metal is Al is substituted. Further, LiNi _0.8 Co _0.15 Al _0.05 O ₂ or LiNi _1/3 Mn _1/3 Co _1/3 O ₂ in which a transition metal is partially substituted with Al, a lithium-excess solid solution A cathode material in which a part of the transition metal of the Li ₂ MnO ₃ —LiMO ₂ system (M: Ni, Co, and / or Mn) called “Al” is substituted with Al can be obtained. A part of oxygen may be substituted with F, Cl, etc., and a part of the transition metal may be Fe, Cr, Ti, Nb, W, Mo, Li, Na, K, Mg, Ca, etc. It may be substituted with any metal. Further, Li may be excessive or deficient with respect to the stoichiometric composition of the compound, and oxygen may be deficient with respect to the stoichiometric composition. In any of these positive electrode films, the oxide sintered body sputtering target including all metals except for lithium among the constituent metals of the positive electrode film is a target, and it is not included in the present invention that the aluminum oxide phase is not included as described above. This is a feature of the invention.

  First, the sputtering target produced from the oxide sintered body of the present invention and the positive electrode film forming metal Li target are charged together with the substrate into the sputtering apparatus. Subsequently, the inside of the apparatus is evacuated, and then glow discharge is generated between the electrodes under an inert gas pressure such as argon of 10 Pa or less, preferably 5 Pa or less, using the substrate as the anode and the target as the cathode. As a result, argon plasma is generated, the argon cations in the plasma collide with the cathode target, the target component atoms are repelled, and a film is deposited on the substrate.

  When using a magnetron sputtering apparatus in which a magnet is placed on the back side of the target, the plasma density generated on the upper surface of the target is increased and stabilized at a low gas pressure of 2.0 Pa or less, preferably 1 Pa or less, and sputtering film formation is performed. To do. This device does not have a function of suppressing arcing, and even if high DC power is applied, arcing cannot be sufficiently prevented in many cases.

However, in the case of the target of the present invention, arcing occurs in the positive electrode film even under a condition where the input power per unit area of the sputtering surface, that is, the input power density is high, such as 2.757 W / cm ² or more. Without discharge, the film can be stably formed with sustained discharge. The thickness of the film can be adjusted by controlling input power, film formation time, and the like, and can be set to 1 to 10 μm, for example.
According to the present invention, since it is an inexpensive film formation method and the operation method is simple, even if it is used in an industrially useful DC sputtering method, stable film formation is possible without causing arcing. The manufacturing cost of the positive electrode film containing can be significantly reduced.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited only to the following examples.

Example 1
NiO powder, CoO powder with an average secondary particle size of 5 μm, and Al ₂ O ₃ powder with an average secondary particle size of 1 μm or less were used as the raw material powder. As shown in Table 1, the metal was 80:15 : 5 in a molar ratio, put in a resin pot, and dry ball mill mixed. At this time, hard ZrO ₂ balls were used, and the mixing time was 10 hours. After mixing, the obtained powder mixture was taken out and subjected to uniaxial pressure molding at 3 ton / cm 2 using a mold molding machine to obtain a molded body.
Next, this molded body was heated to 1100 ° C. at 1 ° C./min in the air and sintered at this temperature for 10 hours. Cooling after sintering was performed by lowering the temperature to 700 ° C. at 5 ° C./min, and then gradually cooling to room temperature.
From the powder X-ray diffraction measurement and the local analysis using a scanning electron microscope and EPMA (Electron Probe Microanalyzer), the sintered compact is substantially composed of NiCoAl ₂ O ₃ . As shown in Table 1, the size was less than 100 nm.
The obtained sintered body was processed into a size of 152 mm in diameter and 5 mm in thickness, and the sputter surface was polished with a cup grindstone. A sputter target was produced by bonding to a backing plate made of oxygen-free copper using metal indium.
A sputtering target was attached to the cathode of a DC magnetron sputtering apparatus equipped with a DC power supply without an arcing suppression function, a glass substrate was placed at the position facing the target, and the distance between the target substrates was 60 mm. After evacuating the target and the substrate to 1 × 10 ⁻⁴ Pa or less, pure Ar gas was introduced to set the gas pressure to 0.5 Pa, and DC power was supplied to the target to generate plasma between the target substrates. .
A predetermined DC power was applied for 10 minutes, and the number of occurrences of a phenomenon in which the discharge voltage instantaneously dropped due to arcing was observed. The DC input power density was calculated when gradually increasing from “DC power ÷ target sputtering surface area”. The results are shown in Table 1. When the DC input power density was 1.103 to 2.757 W / cm ² , no arcing occurred and stable discharge could be performed. The composition of the obtained film was also equivalent to the target composition. This is because the sintered body is composed of NiO, CoO, and Al ₂ O _{3 with} a raw material blending ratio of 80: 15: 5 in terms of metal molar ratio. This is because there was an aluminum phase, but the presence of a high resistance phase and an insulating phase can be ignored. Such a sputtering target can be used stably even in mass production.

(Comparative Example 1)
In Example 1, a sintered body having the same composition was prepared in the same manner except that a powder having an average secondary particle diameter of 5 μm was used as the Al ₂ O ₃ raw material powder, and the sintered body was subjected to the same technique. It was evaluated with. As a result, as shown in Table 1, an aluminum oxide phase of 1 to 3 μm was present in the sintered body. Moreover, the target was produced from this sintered body by the same method as in Example 1, and the occurrence of arcing was evaluated. As shown in Table 1, arcing occurred at 1.654 W / cm ² and the discharge was unstable. Such a sputtering target cannot be used in mass production.

(Comparative Example 2)
A sintered body having the same composition was prepared in the same manner as in Example 1 except that a powder having an average particle size of secondary particles of 10 μm was used as the Al ₂ O ₃ raw material powder. As a result, an aluminum oxide phase of 2 to 5 μm was present in the sintered body. Moreover, the target was produced from this sintered body by the same method as in Example 1, and the occurrence of arcing was evaluated. The results are shown in Table 1. Arcing occurred at 1.103 W / cm ² and the discharge was unstable. Such a sputtering target cannot be used in mass production.

(Example 2)
A target for producing a positive electrode film of LiNi _0.32 Co _0.32 Mn _0.32 Al _0.04 O ₂ by co-sputter deposition was produced by the following procedure.
In addition to the raw material powder of Example 1, a sintered body was produced under the same conditions as in Example 1 except that MnO powder having an average secondary particle size of 5 μm was also used. The raw material compounding amounts of NiO, CoO, MnO, and Al ₂ O ₃ were 32: 32: 32: 4 in terms of metal molar ratio. From the powder X-ray diffraction measurement and local analysis by scanning electron microscope and EPMA, this sintered body has very little aluminum oxide phase in the crystal phase. The size was less than 100 nm as shown in Table 1.
Table 1 shows the results of measuring the occurrence of arcing using a sputtering target produced from this sintered body in the same manner as in Example 1. The DC input power density is 1.103 to 2.757 W. At / cm ² , arcing did not occur at all and stable discharge could be performed. Further, the composition of the obtained film was equivalent to the target composition, and there was a very small amount of the aluminum oxide phase, but the presence of a high resistance phase or an insulating phase can be ignored. Such a sputtering target can be used stably even in mass production.

(Comparative Example 3)
In Example 2, a sintered body having the same composition was produced in the same manner as in Example 1 except that a powder having an average particle size of secondary particles of 3 μm was used as the Al ₂ O ₃ raw material powder. Was evaluated by the same method, it was found that an aluminum oxide phase of 1 to 3 μm was present in the sintered body. Moreover, the target was produced from this sintered body by the same method as in Example 1, and the occurrence of arcing was evaluated. The results are shown in Table 1. Arcing occurred at 2.757 W / cm ² and the discharge was unstable. Such a sputtering target cannot be used in mass production.

(Comparative Example 4)
In Example 2, a sintered body having the same composition was prepared in the same manner as in Example 1 except that a powder having an average particle size of secondary particles of 7 μm was used as the Al ₂ O ₃ raw material powder. Was evaluated by a similar method, and an aluminum oxide phase of 1 to 4 μm was present in the sintered body. Moreover, the target was produced from this sintered body by the same method as in Example 1, and the occurrence of arcing was evaluated. The results are shown in Table 1. Arcing occurred at 1.654 W / cm ² and the discharge was unstable. Such a sputtering target cannot be used in mass production.

The sputtering target of this invention can be used when producing the positive electrode of a thin film lithium secondary battery by sputtering method.
According to the present invention, it is possible to employ a direct current sputtering method that is an inexpensive film formation method and a simple operation method, and at this time, stable film formation is possible without causing arcing. Membrane manufacturing costs can be greatly reduced.

Claims (8)

In an oxide sintered body sputtering target for forming a positive electrode film comprising at least one transition metal selected from nickel, cobalt, and manganese, and an oxide sintered body containing aluminum,
The oxide sintered body is mostly composed of a transition metal oxide phase, and does not contain an aluminum oxide phase or has a size of 100 nm or less, but does not contain an aluminum oxide phase. Combined sputtering target.   The oxide sintered body according to claim 1, wherein the oxide sintered body has an aluminum content of 1 to 15 atomic% with respect to the total of all transition metal oxides. Combined sputtering target.   2. The positive electrode film according to claim 1, wherein the oxide sintered body is composed only of nickel, cobalt, and an aluminum-containing transition metal oxide, and the aluminum element is dissolved in the transition metal oxide phase. Oxide sintered sputtering target for forming.   The oxide sintered body is composed only of nickel, cobalt, manganese, and an aluminum-containing transition metal oxide, and the aluminum element is solid-dissolved in the transition metal oxide phase. Oxide sintered sputtering target for positive electrode film formation.   2. The oxide sintered body sputtering target for forming a positive electrode film according to claim 1, wherein the oxide sintered body does not confirm the presence of an aluminum oxide phase even when observed with an EPMA (Electron Probe Microanalyzer). 3. . At least one transition metal oxide powder selected from nickel, cobalt, and manganese and aluminum oxide powder are used as raw material powders, mixed, sufficiently pulverized and then pressure-molded, and the resulting molded body is fired It is a manufacturing method of the oxide sintered compact sputtering target for positive electrode film formation including the process of making it into oxide sintered compact,
A method for producing an oxide sintered body sputtering target for forming a positive electrode film, wherein the transition metal oxide and the aluminum oxide in the raw material powder have an average particle size of 5 μm or less.   The method for producing an oxide sintered body sputtering target for forming a positive electrode film according to claim 6, wherein the raw material powder is heated at a temperature rising rate of 3 ° C. or lower until a firing temperature of at least 1100 ° C. The oxide sintered compact sputtering target for forming a positive electrode film according to any one of claims 1 to 5 is charged into a DC sputtering apparatus, and a DC power of 2.757 W / cm ² or more is applied to the target under a gas pressure of 10 Pa or less. And forming a positive electrode film on the substrate without generating arcing.