Al-Sc-Ga sputtering target and method for producing same

Abstract

The Al-Sc-Ga sputtering target is provided with a main body part which contains Al, Sc and Ga and does not contain a Ga phase. In the main body part, the atomic ratio (Sc / Ga) of Sc to Ga may be 0.5 or more. In the main body part, the atomic ratio (Sc / Ga) of Sc to Ga may be 20 or less. The Al-Sc-Ga sputtering target may further be provided with a back plate bonded to the main body section via a bonding material.

Description

Technical Field

[0001] The present disclosure relates to an Al—Sc—Ga sputtering target and a method for manufacturing the same. Background Art

[0002] In recent years, interest in non-volatile ferroelectric memories has increased, and aluminum scandium gallium nitride (hereinafter also referred to as "AlScGaN") films are expected to be suitable films for ferroelectric memories from the perspectives of high ferroelectric properties and reduced driving voltage (see Non-Patent Document 1).

[0003] Non-Patent Document 1 describes that the AlScGaN film is formed by a ternary simultaneous reactive sputtering method using an Al target, a Sc target, and a GaN target.

[0004] However, as described in Non-Patent Document 1, if three targets are used, the power of each target must be controlled separately during sputtering, which complicates the control. Therefore, it is desirable to use a single target, such as an Al—Sc—Ga sputtering target, for forming the AlScGaN film.

[0005] Prior art literature

[0006] Non-patent literature

[0007] Non-Patent Literature 1: Ohta Reika et al., “Crystal Structure and Strong Dielectric Properties of (Al1-x-yGaxScy)N Thin Films,” [online], September 20, 2022, Autumn Symposium of the Japanese Society of Applied Physics, 20p-B103-10, [retrieved February 10, 2022], Internet <URL: https: / / confit.atlas.jp / guide / event / jsap2022a / subject / 20p-B103-10 / tables?cryptoId=> Summary of the Invention

[0008] Problems to be solved by the invention

[0009] However, when an attempt was made to actually produce a sputtering target by using an Al—Sc—Ga alloy as the main body and bonding it to a backing plate via a bonding material, a problem occurred in which the main body separated from the backing plate during sputtering.

[0010] An object of the present disclosure is to provide at least one of an Al—Sc—Ga sputtering target capable of suppressing separation of a main body portion and a method for producing the same.

[0011] Solutions for solving problems

[0012] The inventors of the present disclosure studied the cause of the peeling of the main body. First, the inventors visually observed the surface of the main body and noticed that liquid metal was melting out. On the other hand, the cross-section of the main body was measured by powder X-ray diffraction, and the XRD peak of the (111) plane of metal Ga appeared near the diffraction angle 2θ=30.37°. In addition, the melting point of metal Ga is 29.8°C. Therefore, the inventors of the present disclosure believe that the metal Ga contained in the Al-Sc-Ga alloy may be melted and melted out during sputtering, and the melted metal Ga contacts the bonding material to form a low-melting-point alloy, and part of the bonding material melts, so the peeling of the main body occurs. In this way, the inventors came up with the technical solution of the present disclosure.

[0013] The contents of the present invention are as described in the claims, and the gist of the present disclosure is as follows.

[0014] (1) An Al—Sc—Ga sputtering target including a main body containing Al, Sc, and Ga and containing no Ga phase.

[0015] (2) The Al—Sc—Ga sputtering target according to (1), wherein in the main body portion, an atomic ratio of Sc to Al (Sc / Al) is 0.25 or more.

[0016] (3) The Al—Sc—Ga sputtering target according to (1) or (2), wherein in the main body, an atomic ratio of Sc to Ga (Sc / Ga) is 0.5 or more.

[0017] (4) The Al—Sc—Ga sputtering target according to any one of (1) to (3), wherein in the main body portion, an atomic ratio of Sc to Ga (Sc / Ga) is 20 or less.

[0018] (5) The Al—Sc—Ga sputtering target according to any one of (1) to (4), further comprising a backing plate joined to the main body via a joining material.

[0019] (6) A method for producing an Al—Sc—Ga sputtering target, the method comprising the following first step: producing a main body portion so as to contain Al, Sc, and Ga and not contain a Ga phase.

[0020] (7) The method for producing an Al—Sc—Ga sputtering target according to (6), wherein in the first step, the main body is produced so that the atomic ratio of Sc to Al (Sc / Al) is 0.25 or more.

[0021] (8) The method for producing an Al—Sc—Ga sputtering target according to (6) or (7), wherein in the first step, the main body is produced so that the atomic ratio of Sc to Ga (Sc / Ga) is 0.5 or more.

[0022] (9) The method for producing an Al—Sc—Ga sputtering target according to any one of (6) to (8), wherein in the first step, the main body is produced so that the atomic ratio of Sc to Ga (Sc / Ga) is 20 or less.

[0023] (10) The method for manufacturing an Al—Sc—Ga sputtering target according to any one of (6) to (9), further comprising a second step of bonding a backing plate to the main body via a bonding material.

[0024] Effects of the Invention

[0025] According to the present disclosure, at least one of an Al—Sc—Ga sputtering target capable of suppressing separation of a main body portion and a method for manufacturing the same is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 1 is a cross-sectional view showing one embodiment of the Al—Sc—Ga sputtering target disclosed herein.

[0027] Figure 2 These are diagrams showing an SEM image and an element mapping image of the sputtering target of Example 1.

[0028] Figure 3 It is a figure which shows the SEM image and element mapping image of the sputtering target of Comparative Example 1.

[0029] Figure 4 This is a graph showing the results of powder X-ray diffraction measurement in Example 1.

[0030] Figure 5 This is a graph showing the results of powder X-ray diffraction measurement in Example 2.

[0031] Figure 6 This is a graph showing the results of powder X-ray diffraction measurement in Example 3.

[0032] Figure 7 This is a graph showing the results of powder X-ray diffraction measurement in Example 4.

[0033] Figure 8 This is a graph showing the results of powder X-ray diffraction measurement in Example 5.

[0034] Figure 9 This is a graph showing the results of powder X-ray diffraction measurement in Example 6.

[0035] Figure 10 This is a graph showing the results of powder X-ray diffraction measurement in Example 7.

[0036] Figure 11 This is a graph showing the results of powder X-ray diffraction measurement in Example 8.

[0037] Figure 12 This is a graph showing the results of powder X-ray diffraction measurement of Comparative Example 1.

[0038] Figure 13 This is a graph showing the results of powder X-ray diffraction measurement of Comparative Example 2.

[0039] Figure 14 This is a diagram showing the results of measuring the peak pattern of X-ray diffraction of the Al—Sc—Ga—N film obtained using the sputtering target of Example 6. DETAILED DESCRIPTION

[0040] An example is given to illustrate the embodiments of the present disclosure in detail. However, the present disclosure is not limited to the following embodiments. In addition, the present disclosure includes any combination of the features and parameters disclosed in this specification. In addition, any combination range of the upper and lower limits of the numerical values ​​disclosed in this specification is also included in the present disclosure.

[0041] <Al-Sc-Ga溅射靶>

[0042] First, the edge reference Figure 1 One embodiment of the Al—Sc—Ga sputtering target disclosed herein will be described. Figure 1 1 is a cross-sectional view showing one embodiment of the Al—Sc—Ga sputtering target disclosed herein.

[0043] like Figure 1 As shown, an Al—Sc—Ga sputtering target (hereinafter, also simply referred to as “target”) 100 includes a main body 10 containing Al, Sc, and Ga and containing no Ga phase.

[0044] The target 100 may further include a backing plate 20 bonded to the main body 10 via a bonding material 30 .

[0045] According to the target 100, when the backing plate 20 is bonded to the main body 10 by means of the bonding material 30, even if the main body 10 is sputtered in this state and the temperature of the main body 10 rises, the metal Ga can be suppressed from melting on the surface, the formation of a low-melting-point alloy between the bonding material 30 and Ga can be suppressed, and the peeling of the main body 10 from the backing plate 20 due to the melting of the low-melting-point metal can be suppressed.

[0046] Furthermore, even when the target 100 is set in the sputtering apparatus with the main body 10 facing downward relative to the backing plate 20, the liquid metal Ga can be prevented from falling, thereby suppressing adverse effects on the sputtering apparatus caused by the falling metal Ga.

[0047] Furthermore, since the main body 10 does not contain a Ga phase with a melting point of 29.8°C, even when the main body 10 is heated, the Ga phase is prevented from dissolving and escaping from the main body 10 as liquid metallic Ga. Therefore, while the main body 10 of the target 100 is sputtered, the plasma during sputtering, which is caused by metallic Ga escaping onto the surface of the main body 10, can be prevented from becoming unstable. Consequently, when forming an AlScGaN film by reactive sputtering while supplying nitrogen into the sputtering apparatus, a decrease in the uniformity of the film's properties can be suppressed.

[0048] Hereinafter, the main body 10 , the back plate 20 , and the bonding material 30 will be described in detail.

[0049] (Main body)

[0050] The main body 10 contains Al, Sc and Ga, and does not contain a Ga phase. The Ga phase is a phase composed of metallic Ga. "Not containing a Ga phase" means that when a powder X-ray diffraction (hereinafter also referred to as "XRD") measurement is performed on a cross section in the thickness direction of the main body 10 under the following conditions, the XRD peak of the (111) plane of metallic Ga does not appear near 2θ=30.37°. Here, "no XRD peak appears" means "the XRD peak intensity is less than 10% of the maximum peak intensity at 2θ=20~40°". The XRD measurement can be performed, for example, using a crystallinity analysis X-ray diffraction device (device name: UltimaIV, manufactured by Rigaku Corporation).

[0051] <Condition>

[0052] Accelerating current and voltage: 40mA and 40kV

[0053] Radiation source: CuKα radiation

[0054] Measurement mode: continuous scanning

[0055] Scanning conditions: 2° / min

[0056] Measuring range: 2θ = 20° to 80°

[0057] Divergence longitudinal limiting slit: 10mm

[0058] Divergence / entrance slit: 1 / 2°

[0059] Light receiving slit: 0.3mm

[0060] The main body 10 may also include an alloy phase. Examples of alloy phases include phases composed of alloys containing two or more metal elements. Examples of such alloys include alloys of Sc and Al, and alloys of Sc and Ga. These alloys may contain two or more. Furthermore, the main body 10 may include at least one of an Al phase and a Sc phase.

[0061] The Al content in the main body 10 is not particularly limited, but is preferably 80% or less, and more preferably 70% or less, based on the total number of Al, Sc, and Ga atoms (100%). When the Al content is 80% or less, based on the total number of Al, Sc, and Ga atoms (100%), a sputtered thin film formed using the Al—Sc—Ga sputtering target disclosed herein can exhibit high dielectric properties.

[0062] Furthermore, the Al content is preferably 20% or more, more preferably 30% or more, based on the total number of atoms of Al, Sc, and Ga (100%).

[0063] The upper and lower limits may be any combination of the above.

[0064] The Sc content in the main body 10 is not particularly limited, but is preferably 30% or greater, more preferably 40% or greater, based on the total number of Al, Sc, and Ga atoms (100%). When the Sc atomic content is 30% or greater, based on the total number of Al, Sc, and Ga atoms (100%), the target can be easily processed because a metallic Ga phase is not present.

[0065] Furthermore, the content of Sc is preferably 90% or less, more preferably 80% or less, based on the total number of atoms of Al, Sc, and Ga (100%).

[0066] The upper and lower limits may be any combination of the above.

[0067] The Ga content in the main body 10 is not particularly limited, but is preferably 30% or less, more preferably 20% or less, based on the total number of atoms of Al, Sc, and Ga (100%). When the Ga content is 30% or less, based on the total number of atoms of Al, Sc, and Ga (100%), the target can be easily processed because a metallic Ga phase is not present.

[0068] Furthermore, the Ga content is preferably 5% or more, more preferably 10% or more, based on the total number of atoms of Al, Sc, and Ga (100%).

[0069] The upper and lower limits may be any combination of the above.

[0070] The total of the Al content, the Sc content, and the Ga content is 100%.

[0071] In the main body 10 , the atomic ratio of Sc to Ga (Sc / Ga) is not particularly limited as long as it is greater than 0, and may be greater than 0.25, preferably greater than 0.5, more preferably greater than 2, and particularly preferably greater than 4. When Sc / Ga is greater than 0.5, the melting of metallic Ga in the target 100 is effectively suppressed.

[0072] Sc / Ga is preferably not more than 20, more preferably not more than 10, and particularly preferably not more than 8. When Sc / Ga is not more than 20, the main body 10 can be manufactured at low cost.

[0073] The upper and lower limits may be any combination of the above.

[0074] The atomic ratio of Sc to Al (Sc / Al) is not particularly limited as long as it is greater than 0, but is preferably 0.25 or greater, and more preferably 0.5 or greater. When Sc / Al is 0.25 or greater, a sputtered thin film formed using the Al-Sc-Ga sputtering target disclosed herein can exhibit high dielectric properties. Sc / Al is preferably 2 or less, and more preferably 1.5 or less.

[0075] The upper and lower limits may be any combination of the above.

[0076] The thickness of the main body 10 is not particularly limited and may be 30 mm or less, 20 mm or less, 15 mm or less, 10 mm or less, or 8 mm or less.

[0077] In addition, the thickness of the main body 10 may be greater than 1 mm, greater than 2 mm, greater than 3 mm, or greater than 5 mm.

[0078] The upper and lower limits may be any combination of the above.

[0079] (Back panel)

[0080] The backing plate 20 is used to cool the main body 10 during sputtering of the main body 10 , and is made of, for example, oxygen-free copper, titanium, stainless steel, or the like.

[0081] (Joint material)

[0082] The bonding material 30 is not particularly limited as long as it is made of a material that can bond the main body 10 and the back plate 20, but in terms of suppressing thermal diffusion and thermal expansion during sputtering, it is preferred to use at least one of indium and tin (indium, tin, or an alloy of indium and tin).

[0083] <Al-Sc-Ga溅射靶的制造方法>

[0084] Next, a method for producing the Al—Sc—Ga sputtering target of the present disclosure will be described.

[0085] The method for producing an Al-Sc-Ga sputtering target disclosed herein includes a step (hereinafter also referred to as the "first step") of producing a main body 10 containing Al, Sc, and Ga and containing no Ga phase. Following the first step, the method for producing an Al-Sc-Ga sputtering target disclosed herein may further include a second step of bonding a backing plate 20 to the main body 10 via a bonding material 30 to obtain an Al-Sc-Ga sputtering target 100. Specifically, the main body 10 obtained in the first step may be used directly as an Al-Sc-Ga sputtering target, or a sputtering target obtained by bonding the backing plate 20 to the main body 10 via the bonding material 30 in the second step may be used as the Al-Sc-Ga sputtering target 100.

[0086] According to the above-described method for manufacturing an Al—Sc—Ga sputtering target, it is possible to manufacture an Al—Sc—Ga sputtering target 100 capable of suppressing separation of the main body 10 .

[0087] Hereinafter, the first step will be described in detail.

[0088] The main body 10 is specifically obtained by melting a mixture of an Al raw material, a Sc raw material, and a Ga raw material to form a melt, and then post-processing the melt as needed. In this case, it is difficult for the Ga raw material to form an alloy with the Al raw material, but it is easy to form an alloy with the Sc raw material. Therefore, by adjusting the atomic ratio of Al, Sc, and Ga in the Al raw material, the Sc raw material, and the Ga raw material in a well-balanced manner, it becomes easy to prevent the formation of a Ga phase. There is no particular limitation on the method for melting the mixture of the Al raw material, the Sc raw material, and the Ga raw material, and examples include melting and arc melting. These methods can easily produce a melt. As an example of post-processing of the melt, the following method can be cited: after the melt is formed into fine powder particles by gas atomization, the powder particles are sintered by any sintering method such as hot pressing. According to this post-processing method, a main body 10 with fine crystal grains can be obtained.

[0089] The raw material mixture is prepared so that Sc / Ga is, for example, greater than 0.25, preferably greater than 0.5, more preferably greater than 2, and particularly preferably greater than 4. When Sc / Ga is greater than 0.5, formation of a Ga phase can be easily prevented.

[0090] The mixture of the above raw materials is prepared so that Sc / Ga is preferably not more than 20, more preferably not more than 10, and particularly preferably not more than 8. When Sc / Ga is not more than 20, the main body 10 can be manufactured at low cost.

[0091] The upper and lower limits may be any combination of the above.

[0092] The raw material mixture is prepared such that the atomic ratio of Sc to Al (Sc / Al) is preferably 0.25 or greater, more preferably 0.5. When Sc / Al is 0.25 or greater, alloy formation between the Sc and Ga raw materials is facilitated, preventing the formation of a Ga phase.

[0093] The mixture of the above raw materials is prepared so that Sc / Al is preferably 2 or less, more preferably 1.5 or less.

[0094] The upper and lower limits may be any combination of the above.

[0095] The form of each raw material is not particularly limited, and may be in the form of powder, flake, or ingot.

[0096] The mixture of the Al raw material, the Sc raw material, and the Ga raw material can be heated, for example, by placing it in a container such as a crucible or a mold. The crucible and the mold can be made of any material that does not melt at the melting point of the Sc raw material, which has the highest melting point among the Al raw material, the Sc raw material, and the Ga raw material, and can be made of, for example, alumina, zirconia, or water-cooled copper.

[0097] The heating temperature of the raw materials can be any temperature above the temperature at which the Al, Sc, and Ga raw materials all melt. The Sc raw material has the highest melting point of 1541°C, so the heating temperature can be any temperature above 1541°C.

[0098] However, the heating temperature of the raw material is preferably 1800°C or lower, more preferably 1700°C or lower.

[0099] The upper and lower limits may be any combination of the above.

[0100] The heating time of the raw materials is not particularly limited and may be 0.25 hours or longer, 0.5 hours or longer, 1 hour or longer, or 3 hours or longer.

[0101] However, in consideration of production efficiency, the heating time of the raw materials may be 10 hours or less, or 8 hours or less, 6 hours or less, or 5 hours or less.

[0102] The upper and lower limits may be any combination of the above.

[0103] Post-processing includes, for example, processing the melt into a plate shape by grinding or cutting, etc. Specific processing means include machining machines such as surface grinders, cylindrical grinders, lathes, cutters, and machining centers.

[0104] Example

[0105] Hereinafter, the present disclosure will be described in more detail with reference to Examples and Comparative Examples, but the present disclosure is not limited to the following Examples.

[0106] (Example 1)

[0107] Al raw material, Sc raw material, and Ga raw material were prepared. Next, these raw materials were put into a crucible made of alumina in such a manner that the atomic ratio of Al, Sc, and Ga becomes Al:Sc:Ga = 30:50:20, and the crucible had an inner diameter of 25 mmφ, an outer diameter of 35 mmφ, and a height of 60 mm. At this time, the Al raw material, the Sc raw material, and the Ga raw material were arranged in order of melting point from high to low (i.e., the order of Sc, Al, and Ga) from the bottom surface of the crucible.

[0108] After that, the crucible was put into a heating furnace. Then, after the mixture was melted by heating at 1600°C for 0.5 hours under an Ar atmosphere, it was cooled to room temperature. In this way, by a melting method, an Al-Sc-Ga sputtering target was obtained in which an ingot in which the atomic ratio of Al, Sc, and Ga becomes Al:Sc:Ga = 30:50:20 was made as a main body.

[0109] (Example 2)

[0110] Al raw material, Sc raw material, and Ga raw material were prepared. Next, these raw materials were put into a crucible made of alumina in such a manner that the atomic ratio of Al, Sc, and Ga becomes Al:Sc:Ga = 30:60:10. At this time, the Al raw material, the Sc raw material, and the Ga raw material were arranged in order of melting point from high to low (i.e., the order of Sc, Al, and Ga) from the bottom surface of the crucible.

[0111] After that, the crucible was put into a heating furnace. Then, after the mixture was melted by heating at 1600°C for 0.5 hours under an Ar atmosphere, it was cooled to room temperature. In this way, by a melting method, an Al-Sc-Ga sputtering target was obtained in which an ingot in which the atomic ratio of Al, Sc, and Ga becomes Al:Sc:Ga = 30:60:10 was made as a main body.

[0112] (Example 3)

[0113] Al raw material, Sc raw material, and Ga raw material were prepared. Next, these raw materials were put into a crucible made of alumina in such a manner that the atomic ratio of Al, Sc, and Ga becomes Al:Sc:Ga = 50:30:20. At this time, the Al raw material, the Sc raw material, and the Ga raw material were arranged in order of melting point from high to low (i.e., the order of Sc, Al, and Ga) from the bottom surface of the crucible.

[0114] After that, the crucible was put into a heating furnace. Then, after the mixture was melted by heating at 1600°C for 0.5 hours under an Ar atmosphere, it was cooled to room temperature. In this way, by a melting method, an Al-Sc-Ga sputtering target was obtained in which the cast ingot in which the atomic ratio of Al, Sc, and Ga became Al:Sc:Ga = 50:30:20 was made the main body.

[0115] (Example 4)

[0116] An Al raw material, a Sc raw material, and a Ga raw material were prepared. Next, these raw materials were put into a crucible made of alumina having an inner diameter of 25 mmφ, an outer diameter of 35 mmφ, and a height of 60 mm, in such a manner that the atomic ratio of Al, Sc, and Ga became Al:Sc:Ga = 30:30:40. At this time, the Al raw material, the Sc raw material, and the Ga raw material were arranged in order of decreasing melting point from the bottom surface of the crucible (i.e., in the order of Sc, Al, Ga).

[0117] After that, the crucible was put into a heating furnace. Then, after the mixture was melted by heating at 1600°C for 0.5 hours under an Ar atmosphere, it was cooled to room temperature. In this way, by a melting method, an Al-Sc-Ga sputtering target was obtained in which the cast ingot in which the atomic ratio of Al, Sc, and Ga became Al:Sc:Ga = 30:30:40 was made the main body.

[0118] (Example 5)

[0119] An Al raw material, a Sc raw material, and a Ga raw material were prepared. Next, these raw materials were put into a 35 mmφ water-cooled copper casting mold having a height of 10 mm, in such a manner that the atomic ratio of Al, Sc, and Ga became Al:Sc:Ga = 30:30:40. At this time, the Al raw material, the Sc raw material, and the Ga raw material were arranged in order of decreasing melting point from the bottom surface of the casting mold (i.e., in the order of Sc, Al, Ga).

[0120] After that, the raw materials in the casting mold were melted by heating at 100 A for 5 minutes under an Ar atmosphere in an arc melting furnace, and then cooled to room temperature. In this way, by an arc melting method, an Al-Sc-Ga sputtering target was obtained in which the cast ingot in which the atomic ratio of Al, Sc, and Ga became Al:Sc:Ga = 30:30:40 was made the main body.

[0121] (Example 6)

[0122] An Al raw material, a Sc raw material, and a Ga raw material were prepared. Next, these raw materials were put into a 65 mmφ water-cooled copper casting mold having a height of 12 mm, in such a manner that the atomic ratio of Al, Sc, and Ga became Al:Sc:Ga = 40:50:10. At this time, the Al raw material, the Sc raw material, and the Ga raw material were arranged in order of decreasing melting point from the bottom surface of the casting mold (i.e., in the order of Sc, Al, Ga).

[0123] The raw material in the mold was then heated at 100 A for 5 minutes in an arc melting furnace under an Ar atmosphere to melt the material, followed by cooling to room temperature. In this manner, an Al-Sc-Ga sputtering target with an ingot as the main component and an atomic ratio of Al, Sc, and Ga of 40:50:10 was obtained by arc melting.

[0124] (Example 7)

[0125] Prepare Al, Sc, and Ga raw materials. Next, place these raw materials into a 35 mm diameter, 10 mm high, water-cooled copper mold so that the atomic ratio of Al, Sc, and Ga is 20:75:5. The Al, Sc, and Ga raw materials are arranged in descending order of melting point (i.e., Sc, Al, Ga) from the bottom of the mold.

[0126] The raw material in the mold was then heated at 100 A for 5 minutes in an arc melting furnace under an Ar atmosphere to melt it, and then cooled to room temperature. In this manner, an Al-Sc-Ga sputtering target containing a main body with an atomic ratio of Al, Sc, and Ga of 20:75:5 was obtained by arc melting.

[0127] (Example 8)

[0128] Prepare Al, Sc, and Ga raw materials. Next, weigh these raw materials so that the atomic ratio of Al, Sc, and Ga is 40:50:10. Place these raw materials into a 35 mm diameter, 10 mm high, water-cooled copper mold. Arrange the Al, Sc, and Ga raw materials in descending order of melting point (i.e., Sc, Al, Ga) from the bottom of the mold.

[0129] The raw materials in the mold were then melted using an arc melting method. Specifically, the raw materials in the mold were heated at 100 A for 5 minutes in an arc melting furnace under an Ar atmosphere to melt. This produced an ingot with an atomic ratio of Al, Sc, and Ga of Al:Sc:Ga = 40:50:10. The ingot was placed in an alumina crucible for gas atomization, and powder was produced under the following gas atomization conditions. In this way, a powder with an Al:Sc:Ga ratio of 40:50:10 was obtained using the gas atomization method.

[0130] <Gas Atomization Conditions>

[0131] Temperature: 1400℃

[0132] Gas: Ar

[0133] Air pressure: 3MPa

[0134] Thereafter, the powder was sintered by hot pressing under the following conditions to obtain an Al—Sc—Ga sputtering target having a main body composed of a sintered body having a composition of Al:Sc:Ga=40:50:10.

[0135] <Condition>

[0136] Temperature: 1050℃

[0137] Holding time: 3 hours

[0138] Atmosphere: Vacuum

[0139] Pressure: 20MPa

[0140] (Comparative Example 1)

[0141] Prepare Al and Ga raw materials. Next, place these raw materials into an alumina crucible so that the atomic ratio of Al to Ga is 80:20. Arrange the Al and Ga raw materials in descending order of melting point (i.e., Al and Ga) from the bottom of the crucible.

[0142] The crucible was then placed in a heating furnace. The mixture was then heated at 1200°C for 0.5 hours in an Ar atmosphere to melt it. This resulted in an Al-Ga sputtering target with an ingot as the main component, containing an Al:Ga atomic ratio of 80:20, using the melting method.

[0143] (Comparative Example 2)

[0144] Prepare Al, Sc, and Ga raw materials. Next, place these raw materials into an alumina crucible so that the atomic ratio of Al, Sc, and Ga is 25:15:60. The Al, Sc, and Ga raw materials are arranged in descending order of melting point (i.e., Sc, Al, Ga) from the bottom of the crucible.

[0145] The crucible was then placed in a heating furnace. The mixture was then heated at 1600°C for 0.5 hours in an Ar atmosphere to melt it. This resulted in an Al-Sc-Ga sputtering target with an ingot as the main body, containing an atomic ratio of Al, Sc, and Ga of 25:15:60.

[0146] <Confirmation of the Presence of Ga Phase>

[0147] Powder X-ray diffraction (XRD) measurements were performed on the thickness-direction cross-sections of the main bodies of the sputtering targets of Examples 1 to 8 obtained as described above at room temperature (25°C or lower) under the following conditions. XRD measurements were performed using a crystallographic analysis X-ray diffractometer (Ultima IV, manufactured by Rigaku Corporation).

[0148] <Condition>

[0149] Accelerating current and voltage: 40mA and 40kV

[0150] Radiation source: CuKα radiation

[0151] Measurement mode: continuous scanning

[0152] Scanning conditions: 2° / min

[0153] Measuring range: 2θ = 20° to 80°

[0154] Divergence longitudinal limiting slit: 10mm

[0155] Divergence / entrance slit: 1 / 2°

[0156] Light receiving slit: 0.3mm

[0157] On the other hand, regarding the sputtering targets of Comparative Examples 1 and 2 obtained as described above, since the main body thereof was broken and disintegrated into powder when the main body thereof was cut, XRD measurement was performed in the same manner as in Example 1 in the powdered state.

[0158] In the above measurement, the presence or absence of the XRD peak of the (111) plane of metallic Ga appearing near 2θ=30.37° was determined to confirm whether the main body of the sputtering target contained a Ga phase. The results are shown in Table 1. It should be noted that for Examples 1 to 8 and Comparative Examples 1 to 2, the results of the XRD measurement are shown in Table 1. Figures 4 to 13 .exist Figures 4 to 11 In the figure, no XRD peak of the (111) surface of metallic Ga was observed near 2θ=30.37°. Figures 12-13 In the figure, the XRD peak of the (111) plane of metallic Ga was observed near 2θ=30.37°.

[0159] It should be noted that the sputtering targets of Examples 1 to 8 and Comparative Examples 1 to 2 obtained as described above were cut along the thickness direction, the cross sections were mirror-polished, and the cross sections were observed using an SEM equipped with EDS (manufactured by JEOL Ltd., product name “JSM-IT800”) to obtain mapping images of the Ga element.

[0160] It should be noted that, for Example 1 and Comparative Example 1, the SEM images and elemental mapping images are shown in Figure 2 and Figure 3 .exist Figure 2 In the figure, (a) represents the SEM image, (b) represents the mapping image of the Al element, (c) represents the mapping image of the Sc element, and (d) represents the mapping image of the Ga element. Figure 3 In the figure, (a) shows a SEM image, (b) shows a mapping image of the Al element, and (c) shows a mapping image of the Ga element.

[0161] Figure 2 (d) shows an overall dark (dark) image with no distinct shades of color, indicating no segregation of the Ga element, that is, no Ga phase (single phase of the Ga element).

[0162] On the other hand, Figure 3 (c) shows different shades of color. Here, the darker (or darker) areas indicate that the Ga element is not segregated, meaning that no Ga phase exists. In contrast, the lighter areas indicate that the Ga element is segregated, meaning that a Ga phase exists.

[0163] Therefore, it can be seen that in Example 1, the main body portion does not contain the Ga phase, whereas in Comparative Example 1, the main body portion contains the Ga phase.

[0164] <Evaluation of Sputtering Target>

[0165] The sputtering targets of Examples 1 to 8 and Comparative Examples 1 to 2 were subjected to a metal Ga melting test. Specifically, the sputtering target was kept in a thermostat at 60°C for 3 hours, and the presence or absence of metal Ga melting was visually confirmed. After keeping the target, the target was taken out of the thermostat. If the liquid metal did not melt out at the location where the target was placed in the thermostat, the melting out of metal Ga was judged as "no". If the liquid metal melted out, the melting out of metal Ga was judged as "yes" after cooling. The results are shown in Table 1. XRD analysis was performed on the liquid metal melted in Comparative Examples 1 to 2 under the above conditions, and the XRD peak of the (111) plane of metal Ga near 2θ=30.37° was confirmed.

[0166] [Table 1]

[0167]

[0168] According to the results shown in Table 1, the melting of metallic Ga was not observed in the sputtering targets of Examples 1 to 8. In contrast, in Comparative Examples 1 and 2, the Ga phase was present.

[0169] From this, it was confirmed that, according to the Al—Sc—Ga sputtering target of the present disclosure, melting of metallic Ga can be suppressed by not including a Ga phase in the bulk portion.

[0170] Therefore, according to the Al-Sc-Ga sputtering target disclosed herein, even when joined to a backing plate by means of a joining material, the melted metal Ga will not come into contact with the joining material to form a low-melting-point alloy. Therefore, it is believed that the peeling of the main body caused by the melting of the low-melting-point alloy can be suppressed.

[0171] (Sputtering film formation)

[0172] The main body obtained in each example was bonded to a copper backing plate via an indium bonding material to produce a sputtering target. This target was then used in a film formation test under the following conditions. An 800nm ​​thick Al-Sc-Ga-N film was obtained, with no delamination between the main body and the backing plate. The ratio of Al, Sc, and Ga (Al:Sc:Ga) in the thin film was assumed to be the same as that in the main body (Al:Sc:Ga).

[0173] The ratio of nitrogen contained in the Al-Sc-Ga-N film is not particularly limited. For example, the ratio of the number of nitrogen atoms to the total number of atoms of Al, Sc, Ga, and N may be 20% or more, 30% or more, or 40% or more. Alternatively, the ratio may be 70% or less, 60% or less, or 50% or less. Further, the ratio may be 20% or more and 70% or less, 30% or more and 60% or less, or 40% or more and 50% or less.

[0174] <Condition>

[0175] Device used: CMS-6400 combined sputtering device

[0176] Film formation method: magnetron sputtering

[0177] Ultimate pressure: 1.0×10 -5 Pa

[0178] Sputtering gas: Ar+25%N2

[0179] Sputtering pressure: 0.3Pa

[0180] Substrate: Silicon

[0181] Lower electrode layer: Molybdenum (thickness: 200nm)

[0182] Upper electrode layer: Molybdenum (thickness: 100nm)

[0183] Film forming temperature: 500℃

[0184] Power: RF200W

[0185] (Thin film structure analysis)

[0186] The Al-Sc-Ga-N film obtained in Example 6 was subjected to structural evaluation by measuring the peak pattern of X-ray diffraction under the following conditions using an X-ray diffractometer (D8DISCOVER manufactured by Bruker AXS). The peak pattern of X-ray diffraction measured is shown in FIG. Figure 14 .Depend on Figure 14 The results shown show that the obtained Al—Sc—Ga—N film is a single layer having a hexagonal wurtzite structure.

[0187] <Condition>

[0188] Radiation source: CuKα radiation

[0189] Monochromator: Ge (220)

[0190] Pathfinder: Crystal3B

[0191] Measurement mode: 2θ-θ scanning

[0192] Measuring interval: 0.02 degrees

[0193] Measuring speed: 4 degrees / minute

[0194] Measuring range: 20 degrees ~ 80 degrees

[0195] (Piezoelectric characteristics evaluation)

[0196] The obtained Al-Sc-Ga-N film was evaluated using a piezoelectric wafer evaluation system. 33 The piezoelectric properties were evaluated using a piezoelectric coefficient d 33 It is 53pC / N.

[0197] <Condition>

[0198] Measuring temperature: room temperature

[0199] Upper electrode diameter: φ1mm

[0200] Probe diameter: 60 μm

[0201] Number of measurements: 50 times

[0202] This application is based on Japanese Patent Application No. 2023-039496 filed on March 14, 2023, the entirety of which is incorporated herein by reference. All references cited herein are incorporated herein in their entirety.

[0203] Industrial applicability

[0204] The Al—Sc—Ga sputtering target disclosed herein can be used as a sputtering target for forming an AlScGaN film used in, for example, a memory element such as a ferroelectric memory, or a piezoelectric element such as a pressure sensor or a vibration sensor.

[0205] Description of Reference Numerals

[0206] 10 ...main body, 20 ...back plate, 30 ...joining material, 100 ...Al-Sc-Ga sputtering target.

Claims

An Al—Sc—Ga sputtering target comprising a main body containing Al, Sc, and Ga and containing no Ga phase.

2. The Al-Sc-Ga sputtering target according to claim 1, wherein In the main body portion, the atomic ratio of Sc to Al, ie, Sc / Al, is 0.25 or more.

3. The Al-Sc-Ga sputtering target according to claim 1 or 2, wherein In the main body, the atomic ratio of Sc to Ga, ie, Sc / Ga, is 0.5 or more.

4. The Al-Sc-Ga sputtering target according to any one of claims 1 to 3, wherein In the main body, the atomic ratio of Sc to Ga, that is, Sc / Ga, is 20 or less. 5 . The Al—Sc—Ga sputtering target according to claim 1 , further comprising a backing plate joined to the main body portion via a joining material.

6. A method for producing an Al-Sc-Ga sputtering target, the method comprising a first step of producing a main body portion containing Al, Sc, and Ga and containing no Ga phase.

7. The method for producing an Al-Sc-Ga sputtering target according to claim 6, wherein: In the first step, the main body is manufactured so that the atomic ratio of Sc to Al, that is, Sc / Al, is 0.25 or more.

8. The method for producing an Al-Sc-Ga sputtering target according to claim 6 or 7, wherein: In the first step, the main body is manufactured so that the atomic ratio of Sc to Ga, that is, Sc / Ga, is 0.5 or more.

9. The method for producing an Al-Sc-Ga sputtering target according to any one of claims 6 to 8, wherein: In the first step, the main body is manufactured so that the atomic ratio of Sc to Ga, that is, Sc / Ga, is 20 or less. 10 . The method for producing an Al—Sc—Ga sputtering target according to claim 6 , further comprising a second step of bonding a backing plate to the main body portion via a bonding material.

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