La-ni-o sputtering target, powder, and method for producing sputtering target

Abstract

The present disclosure addresses the problem of providing a high-density La-Ni-O sputtering target, a powder, and a method for producing the sputtering target. Provided is a La-Ni-O sputtering target comprising lanthanum (La), nickel (Ni), and oxygen (O), having a dimensional density of 5.9 g / cm3 or more. Also provided is a La-Ni-O powder comprising an La2NiO4 crystal phase, wherein the X-ray diffraction peak intensity ratio of the La2NiO4 crystal phase (103) is 15 or more.

Description

La-Ni-O sputtering target, powder, and method for manufacturing the sputtering target

[0001] This disclosure relates to a La-Ni-O sputtering target, a powder, and a method for manufacturing the sputtering target.

[0002] Lead-based PZT (lead zirconate titanate), which exhibits excellent piezoelectric properties, is used as a piezoelectric material in sensors and actuators. Although PZT has good and stable piezoelectric properties, it contains lead, which has a significant environmental impact. Therefore, there is a growing trend to replace it with lead-free materials. KNN (potassium sodium niobate) is one such lead-free piezoelectric material that has been developed.

[0003] Piezoelectric materials are fabricated by forming thin films such as PZT or KNN with lanthanum nickelate (La-Ni-O) as an intermediate layer. For example, Patent Document 1 discloses a technique for forming a PZT thin film on a buffer layer made of lanthanum nickelate provided on a platinum electrode layer. Patent Document 2 discloses a piezoelectric laminate having an alkali niobium oxide piezoelectric film on a film made of lanthanum nickelate provided on an electrode film.

[0004] Japanese Patent Publication No. 2019-52326 Japanese Patent Publication No. 2021-27132

[0005] La-Ni-O films can be formed using a La-Ni-O sputtering target (Patent Document 1). However, lanthanum nickelate absorbs moisture from the atmosphere and La(OH) ３ This resulted in the generation of a problem that caused deterioration. Also, the raw material La ２ O ３ It absorbs moisture from the atmosphere, and some of it becomes La(OH) ３ As a result, dehydration occurred during sintering, making it prone to cracking and difficult to achieve high density.

[0006] The object of this disclosure is to provide a high-density La-Ni-O sputtering target, powder, and a method for manufacturing the sputtering target.

[0007] The gist of the present disclosure is as follows. [1] A La—Ni—O sputtering target containing lanthanum (La), nickel (Ni), and oxygen (O) and having a dimensional density of 5.9 g / cm ３ or more. [2] A La ２ NiO ４ crystalline phase, and the La ２ NiO ４ The La—Ni—O sputtering target according to [1], wherein the X-ray diffraction peak intensity ratio of the crystalline phase (103) is 10 or more. [3] When left in the air for 24 hours in an environment of a temperature of 40° C. and a relative humidity of 90%, the X-ray diffraction peak intensity ratio of La(OH) ３ (100) is 3 or less. The La—Ni—O sputtering target according to [1] or [2]. [4] A La ２ NiO ４ crystalline phase, and the La ２ NiO ４ La—Ni—O powder in which the X-ray diffraction peak intensity ratio of the crystalline phase (103) is 15 or more. [5] When left in the air for 24 hours in an environment of a temperature of 40° C. and a relative humidity of 90%, the intensity ratio of the La(OH) ３ crystalline phase (100) is 3 or less. The La—Ni—O powder according to [4]. [6] Mixing La ２ O ３ powder and NiO powder, calcining the obtained mixed powder at a temperature exceeding 1300° C. and not exceeding 1500° C. to synthesize La—Ni—O powder, shaping the obtained synthesized powder to produce a shaped body, and sintering the shaped body at 1400° C. or higher under normal pressure in the air. A method for manufacturing a La—Ni—O sputtering target.

[0008] According to the present disclosure, it is possible to provide a high-density La—Ni—O sputtering target, powder, and a method for manufacturing the sputtering target.

[0009] Hereinafter, specific embodiments of the present disclosure will be described with examples. However, each configuration and their combinations in each embodiment are merely examples, and within the scope not departing from the gist of the present disclosure, addition, omission, substitution, and other changes of the configuration are possible as appropriate.

[0010] [La-Ni-O sputtering target] The La-Ni-O sputtering target according to the embodiment of the present disclosure (also referred to as this embodiment) contains lanthanum (La), nickel (Ni), and oxygen (O). The composition ratio of La to Ni preferably satisfies the following formula. In the following formula, La and Ni represent the atomic percentages of lanthanum and nickel contained in the sputtering target, respectively. 0.8 ≤ La / (La + Ni) ≤ 1.2 (1) In formula (1), the lower limit is preferably 0.8, more preferably 0.9. The upper limit is preferably 1.2, more preferably 1.1.

[0011] The La-Ni-O sputtering target according to this embodiment has a dimensional density of 5.9 g / cm³. ３ This concludes the explanation. High-density sputtering targets are expected to suppress particle generation during sputtering because they have fewer pores (voids) that cause arcing. Furthermore, since film deposition is possible at higher power, an improvement in the deposition rate is expected. Note that the true density changes depending on the crystalline phase produced, making it difficult to specify the relative density; therefore, it is specified by dimensional density. The dimensional density is preferably 6.0 g / cm³. ３ The above is more more accurate, 6.1 / cm ３ That's all.

[0012] The La-Ni-O sputtering target according to this embodiment is La ２ NiO ４ The crystalline phase is included, and the La ２ NiO ４ It is preferable that the X-ray diffraction peak intensity ratio of the crystalline phase (103) is 10 or more. ２ NiO ４ The crystalline phase is a crystalline phase that does not easily absorb moisture from the atmosphere, therefore La ２ NiO ４ An increase in the proportion of the crystalline phase improves weather resistance, and La(OH) can cause arcing. ３ It can suppress the generation of La(OH) ３This makes it possible to suppress surface roughness of the sputtering target caused by the occurrence of La ２ NiO ４ The X-ray diffraction peak intensity ratio of the crystalline phase (103) is preferably 13 or higher, more preferably 15 or higher, and even more preferably 20 or higher.

[0013] The La-Ni-O sputtering target according to this embodiment, when left in the air for 24 hours at a temperature of 40°C and a relative humidity of 90%, produces La(OH) ３ It is preferable that no generation occurs. The La-Ni-O sputtering target absorbs moisture from the atmosphere, and La(OH) ３ When this occurs, the surface of the sputtering target becomes rough, which can cause arcing. La(OH) ３ The presence or absence of La(OH) is analyzed using X-ray diffraction. ３ If the X-ray diffraction peak intensity ratio of the crystalline phase (100) is 3 or less, then La(OH) ３ We determine that no such occurrence occurred.

[0014] The sputtering target in this embodiment can be a disc-shaped plate, a rectangular plate-shaped plate, or a cylindrical shape, and can be joined to a backing plate with a bonding material. The sputtering target can have a thickness of 20 mm or less, preferably 3.0 to 15 mm, and more preferably 6.0 to 12 mm. The surface area to be sputtered is 182 cm². ２ It is preferable that the above conditions are met.

[0015] [Method for Manufacturing a La-Ni-O Sputtering Target] A method for manufacturing a La-Ni-O sputtering target according to the embodiments of this disclosure is described below. However, it is clear that the following manufacturing conditions are not limited to the disclosed scope, and some omissions and modifications may be made. In order to avoid making the disclosed manufacturing method unnecessarily unclear, detailed explanations of well-known manufacturing processes and processing operations are omitted.

[0016] (1. Raw material powder) As raw material powder, La ２ O ３Prepare powder and NiO powder. There are no particular limitations on the particle size of the raw material powder, but finer powder is preferable to promote the reaction during synthesis. Specifically, particle size D ５０ The median diameter is preferably 100 μm or less, more preferably 10 μm or less, and even more preferably 3 μm or less.

[0017] (2. Mixing process) La ２ O ３ The powder and NiO powder are weighed to achieve the desired composition ratio. After weighing, they are mixed to obtain a mixed powder. To obtain a dense and uniform sintered body, fine grinding and uniform mixing may be thoroughly performed using a mixer such as a ball mill or attritor.

[0018] (3. Synthesis process) La ２ O ３ The powder absorbs moisture from the air, and some of it becomes La(OH) ３ As a result, dehydration occurs during the subsequent sintering process, making the sintered body prone to cracks and roughness. Therefore, La is used beforehand. ２ NiO ４ The weather resistance is improved by synthesizing a crystalline phase. The synthesis is preferably carried out by calcining the mixed powder in air at a temperature exceeding 1300°C. A calcination temperature of 1350°C or higher is more preferable. However, if the temperature is too high, grain growth occurs, making it difficult to increase the density of the sintered body during the sintering process. Therefore, a calcination temperature of 1550°C or lower is preferable. Furthermore, a calcination time of 5 hours or more is preferable.

[0019] In the aforementioned synthesis step, La ２ NiO ４ A La-Ni-O powder containing a crystalline phase (hereinafter sometimes referred to as synthetic powder) can be obtained. From the viewpoint of weather resistance, the synthetic powder is made of the aforementioned La ２ NiO ４ It is preferable that the X-ray diffraction peak intensity ratio of the crystalline phase (103) is 15 or more. More preferably, the X-ray diffraction peak intensity ratio is 20 or more, and even more preferably, the X-ray diffraction peak intensity ratio is 30 or more. Furthermore, when the synthetic powder is left in the air for 24 hours at a temperature of 40°C and a relative humidity of 90%, La(OH) ３ It is preferable that the generation of La(OH) is not present.３ The presence or absence of La(OH) is analyzed using X-ray diffraction. ３ If the X-ray diffraction peak intensity ratio of the crystalline phase (100) is 3 or less, then La(OH) ３ We determine that no such occurrence occurred.

[0020] (4. Grinding process: Optional) After synthesis, the synthesized powder may be dry-ground. Particle size D ５０ It is preferable to grind the material until the median diameter is 2 μm or less.

[0021] (5. Molding Process) The molding process involves filling a mold with synthetic powder and applying a press pressure of 300-400 kgf / cm². ２ It is preferable to perform this procedure. Afterwards, cold hydrostatic pressurization (CIP) may be performed. The CIP pressure should be 1000 to 2000 kgf / cm². ２ It is preferable to carry out the process in this manner. Alternatively, the molding process may be carried out using a hot press machine with a surface pressure of 250 kgf / cm². ２ The above process may be carried out at temperatures of 500 to 1000°C. If the hot press temperature during molding is too high, the reduction of NiO will proceed, and metallic Ni will precipitate. As a result, La ２ O ３ Precipitation can occur, leading to a loss of weather resistance.

[0022] (6. Sintering Process) The molded body is sintered in air at atmospheric pressure. The sintering temperature is preferably 1400°C or higher. If the temperature is below 1400°C, the density of the sintered body may not increase sufficiently. There is no particular upper limit to the sintering temperature, but from the viewpoint of energy cost, it is preferably 1600°C or lower.

[0023] (7. Finishing Process) The sintered body obtained through the above sintering process can be processed into the desired PVD material using a surface grinder, cylindrical grinder, machining center, or other processing machine as needed. In the case of a sputtering target, it can be in the shape of a disc, rectangular, cylindrical, etc. Since the sputtering target is made by machining the sintered body, the dimensional density and crystalline phase are substantially the same as those measured on the sintered body.

[0024] The following explanation is based on examples and comparative examples. However, these examples are merely illustrative and do not limit the invention in any way. That is, the present invention is limited only by the claims and encompasses various variations other than those included in the examples of this disclosure.

[0025] The evaluation methods used in the examples and comparative examples are as follows: (Compositional analysis) The composition of the sintered body was analyzed using the following apparatus: Apparatus: SPS3500DD manufactured by SII Corporation Method: ICP-OES (Inductively coupled plasma emission spectrometry)

[0026] (Regarding dimensional density) A piece of the sintered body was cut to a predetermined size (approximately 20 x 20 x 10 mm), its length, width, and thickness were measured, and its volume was calculated. The weight of the sintered body was also measured, and its dimensional density (g / cm³) was determined. ３ ) = weight / volume was calculated.

[0027] (Analysis of Crystalline Phase) The crystalline phase of the synthetic powder and sintered body was analyzed using the following apparatus: Principle: X-ray diffraction apparatus: Rigaku Smart Lab tube: Cu-Kα ray tube Voltage: 40kV Current: 30mA Measurement method: 2θ-θ reflection method Scan speed: 20° / min Sampling interval: 0.02° Measurement range (2θ): 10° to 60° Divergence slit: 1° Divergence longitudinal limiting slit: 10mm Scattering slit: 8mm Receiving slit: Open Goniometer: Horizontal type Sample measurement location: Sputtered surface side

[0028] (La ２ NiO ４ (Analysis of crystalline phase) La ２ NiO ４ The XRD peak intensity in the range of 31.0° ≤ 2θ ≤ 31.5° that belongs to the crystalline phase (103) is I(La ２ NiO ４ ) and the average value of the XRD intensity in the range of 20.0° ≤ 2θ ≤ 20.5° is taken as background I (BG), and from the following formula, La ２ NiO ４ The X-ray diffraction peak intensity ratio of the crystalline phase (103) was calculated. La２ NiO ４ X-ray diffraction peak intensity ratio of the crystal phase (103) = I(La ２ NiO ４ ) / I(BG)

[0029] (Analysis of crystal phase) La(OH) ３ For the analysis of the crystal phase, the XRD peak intensity in the range of 15.0° ≤ 2θ ≤ 16.0° attributed to the crystal phase (100) of La(OH) ３ was defined as I{La(OH) ３}, and the average value of the XRD intensity in the range of 20.0° ≤ 2θ ≤ 20.5° was defined as the background I(BG). From the following formula, the X-ray diffraction peak intensity ratio of the crystal phase (100) of La(OH) ３ was calculated. La(OH) ３ X-ray diffraction peak intensity ratio of the crystal phase (103) = I{La(OH) ３} / I(BG)

[0030] (Weather resistance test) The synthetic powder and the sintered body were left in the atmosphere at a temperature of 40°C and a relative humidity of 90% for 24 hours, and the presence or absence of the generation of La(OH) ３ was confirmed by X-ray diffraction. For those without the generation of La(OH) ３ , it was judged that they had excellent weather resistance. For the synthetic powder, the presence or absence of whitening considered to be caused by the generation of La(OH) ３ was also confirmed, and for the sintered body, the change in shape was also confirmed.

[0031] (Synthesis example 1) La ２ O ３ powder and NiO powder were weighed so that La:Ni = 1:1 (atomic %), and then mixed in a blade rotation type dry mixer. The rotation speed of the blade was 3000 rpm, and the mixing was carried out for 3 minutes. Then, this mixed powder was calcined at 1400°C to synthesize La-Ni-O powder. After synthesis, the powder was analyzed by X-ray diffraction method. As a result, the La ２ NiO ４ crystal phase and the NiO crystal phase were confirmed. Also, the X-ray peak intensity ratio of the La ２ NiO ４ crystal phase was 38.3. When the weather resistance test was carried out, La(OH) ３There was no occurrence, and whitening could not be confirmed. The above results are shown in Table 1.

[0032]

[0033] (Synthesis Examples 2 to 4) In Synthesis Examples 2 to 4, only the calcination temperature was changed from Synthesis Example, and La-Ni-O powder was synthesized. After synthesis, the powders were analyzed by X-ray diffraction method respectively. As a result, in Synthesis Example 2, ４ Ni ３ O １０ crystalline phase and NiO crystalline phase were confirmed, and the X-ray peak intensity ratio of the La ２ NiO ４ crystalline phase was 1.2. In Synthesis Example 3, La ３ Ni ２ O ７ crystalline phase was confirmed, and the X-ray peak intensity ratio of the La ２ NiO ４ crystalline phase was 1.3. In Synthesis Example 4, La ３ Ni ２ O ７ crystalline phase, La ２ NiO ４ , NiO crystalline phase were confirmed, and the X-ray peak intensity ratio of the La ２ NiO ４ crystalline phase was 13.3. Also, when the weather resistance test was conducted, the occurrence of La(OH) ３ was confirmed in all synthesis examples, and partial whitening was confirmed. The above results are shown in Table 1.

[0034] (Examples 1, 2) The La-Ni-O powder prepared in Synthesis Example 1 was filled into carbon dice, and pressed at a temperature of 800 °C and a surface pressure of 250 kgf / cm ２ for 5 hours to be molded. Then, the obtained molded body was subjected to atmospheric pressure sintering at 1450 °C (Example 1) and 1550 °C (Example 2) under an oxygen flow to produce a sintered body. In Example 1, the dimensional density of the sintered body was 6.11 g / cm ３ , and in Example 2, the dimensional density of the sintered body was 6.42 g / cm ３ . Also, in both Examples 1 and 2, La ２ NiO ４ crystalline phase, La ３ Ni ２ O ７Crystalline phase and NiO crystalline phase were confirmed. In Example 1, La ２ NiO ４ The X-ray peak intensity ratio of the crystalline phase was 27.8, while in Example 2 it was 14.9. Weathering tests were performed, and in both Examples 1 and 2, La(OH) ３ No defects occurred, and the shape of the sintered body was maintained (no deterioration). The results are shown in Table 2.

[0035]

[0036] (Comparative Examples 1 and 2) The La-Ni-O powder prepared in Synthesis Example 1 was packed into a carbon die and subjected to a surface pressure of 250 kgf / cm in an Ar atmosphere. ２ Sintered bodies were produced by hot-press sintering at 1300°C (Comparative Example 1) and 1400°C (Comparative Example 2) for 5 hours. In both Comparative Examples 1 and 2, La ２ O ３ Crystalline phase and Ni crystalline phase were confirmed, and La was found in both Comparative Examples 1 and 2. ２ NiO ４ The X-ray peak intensity ratio of the crystalline phase is 1.0, and La ２ NiO ４ The crystalline phase could not be confirmed. Furthermore, when weather resistance tests were performed, both Comparative Examples 1 and 2 showed La(OH) ３ The following occurred. Furthermore, in both Comparative Examples 1 and 2, the shape of the sintered body was distorted, making it impossible to process them into sputtering targets. The results are shown in Table 2.

[0037] According to this disclosure, it is possible to obtain high-density sputtering targets, which may improve product yield. Improved product yield leads to a stable supply of products and a reduction in the loss of metal raw materials, which are limited resources. Therefore, this disclosure may contribute to Goal 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster technological innovation," and Goal 12, "Ensure sustainable consumption and production patterns," both of which are led by the United Nations. The sputtering target relating to this disclosure is useful for forming lanthanum nickelate (La-Ni-O) thin films that can be applied as an intermediate layer in piezoelectric materials.

[0038] According to this disclosure, a high-density sputtering target containing lanthanum, nickel, and oxygen can be obtained. Furthermore, a La-Ni-O thin film formed using the La-Ni-O sputtering target according to this disclosure is useful as an intermediate layer in piezoelectric materials.

Claims

1. Contains lanthanum (La), nickel (Ni), and oxygen (O), with a dimensional density of 5.9 g / cm³. ３ The above describes the La-Ni-O sputtering target.

2. La ２ NiO ４ The crystalline phase is included, and the La ２ NiO ４ The La-Ni-O sputtering target according to claim 1, wherein the X-ray diffraction peak intensity ratio of the crystalline phase (103) is 10 or more.

3. When left in the air for 24 hours under conditions of 40°C and 90% relative humidity, La(OH) ３ The La-Ni-O sputtering target according to claim 1 or 2, wherein the X-ray diffraction peak intensity ratio of (100) is 3 or less.

4. La ２ NiO ４ comprising a crystal phase, wherein the X-ray diffraction peak intensity ratio of the La ２ NiO ４ crystal phase (103) is 15 or more, and La-Ni-O powder.

5. When left in the air for 24 hours under conditions of 40°C and 90% relative humidity, La(OH) ３ The La-Ni-O powder according to claim 4, wherein the intensity ratio of the crystalline phase (100) is 3 or less.

6. La ２ O ３ A method for manufacturing an La-Ni-O sputtering target, comprising: mixing powder and NiO powder; calcining the resulting mixed powder at a temperature above 1300°C and below 1500°C to synthesize La-Ni-O powder; molding the resulting synthesized powder to produce a molded body; and sintering the molded body in air at atmospheric pressure at a temperature of 1400°C or higher.

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