Nitride materials and piezoelectrics made therefrom, as well as MEMS devices using the piezoelectrics; the nitride materials and ferroelectrics made therefrom, as well as electronic components using the ferroelectrics.

Abstract

This invention provides a scandium-added gallium nitride material, a piezoelectric material thereof, a MEMS device using the piezoelectric material, the scandium-added gallium nitride material and a ferroelectric material thereof, and an electronic component using the ferroelectric material. Furthermore, it provides a method for manufacturing the scandium-added gallium nitride material, which has a piezoelectric constant d exceeding 14 pC / N. 33 It has a piezoelectric constant d exceeding 16.9 pC / N. 33 In particular, it has a higher maximum piezoelectric constant d than aluminum nitride with added scandium. 33 The piezoelectric constant d with a value of 27.6 pC / N 33 A nitride material, composed of the chemical formula Sc x Ga 1‑x N represents the range where x is above 0.39 and below 0.54, and the length of the c-axis in the crystal structure is 4.94 × 10⁻⁶. ‑10 m or more and less than 5.2 × 10 ‑10 The range of m.

Description

Technical Field

[0001] The present invention relates to a gallium nitride material with added scandium, a piezoelectric body made therefrom, a MEMS device using the piezoelectric body, the gallium nitride material and the ferroelectric body made therefrom, and an electronic component using the ferroelectric body. Background Technology

[0002] Devices utilizing piezoelectricity are applied in a wide range of fields, and their use is expanding in mobile devices such as mobile phones where miniaturization and power saving are critical. One example is the FBAR filter, which uses a film bulk acoustic resonator (FBAR).

[0003] FBAR filters are filters based on resonators using the longitudinal vibration modes of a thin film exhibiting piezoelectric response, enabling them to resonate in the gigahertz band. FBAR filters with these characteristics have low loss and can operate over a wide bandwidth, thus promising to contribute to further high-frequency compliance, miniaturization, and power saving in mobile devices.

[0004] Furthermore, examples of piezoelectric materials used in piezoelectric films for such FBARs include scandium-doped aluminum nitride (see Patent Document 1) and scandium-doped gallium nitride (Patent Document 2). In particular, scandium-doped aluminum nitride exhibits a high piezoelectric constant (d). 33 Scandium-added aluminum nitride is used as a high-frequency filter in fifth-generation mobile communication systems (5G). Additionally, scandium-added aluminum nitride is expected to be used in various MEMS (microelectromechanical system) devices, including physical sensors such as pressure sensors, accelerometers, and gyroscopes, actuators, microphones, speakers, ultrasonic oscillators, ultrasonic sensors, fingerprint authentication sensors, and vibration generators. Existing technical documents Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2009-10926 Patent Document 2: Japanese Patent No. 6698159 Non-patent literature

[0006] Non-patent literature 1: Uehara et al., Applied Physics letters 114,012902,2019. Non-patent literature 2: Tholander al., Physical Review B 87,094107 2013. Non-patent literature 3: Akiyama et al., Applied Physics letters 95, 162107, 2009. Summary of the Invention The problem that the invention aims to solve

[0007] However, gallium nitride (Sc) with added scandium x Ga 1-x The maximum piezoelectric constant d of N) 33 The piezoelectric constant d has a value of 14 pC / N (refer to Non-Patent Literature 1) and a value exceeding that. 33 Sc x Ga 1-x The problem is that N does not exist. It should be noted that Sc is calculated using first principles... x Ga 1-x The maximum piezoelectric constant of N, d 33 The value is 16.9 pC / N (refer to non-patent literature 2).

[0008] Therefore, there are more aluminum nitride (Sc) with added scandium than those mentioned above. x Al 1-x The maximum piezoelectric constant d of N) 33 (27.6 pC / N) (Refer to Non-Patent Literature 3) Sc x Ga 1-x N is of course not a problem.

[0009] In view of the above, the present invention aims to provide a gallium nitride material with added scandium, a piezoelectric body thereof, a MEMS device using the piezoelectric body, the gallium nitride material and a ferroelectric body thereof, and an electronic component using the ferroelectric body. Furthermore, the present invention provides a method for manufacturing the scandium-added gallium nitride material, wherein the scandium-added gallium nitride material has a piezoelectric constant d exceeding 14 pC / N. 33 It has a piezoelectric constant d exceeding 16.9 pC / N. 33 In particular, it has a higher maximum piezoelectric constant d than aluminum nitride with added scandium. 33 The piezoelectric constant d with a value of 27.6 pC / N 33 . Methods for solving problems

[0010] The inventors of this invention have conducted in-depth research on the above-mentioned problems and have discovered that gallium nitride (Sc) with scandium (Sc) added (doped) within a specified concentration range and having a c-axis (c-axis in crystal structure) length within a specified range is a suitable solution. x Ga 1-x N), with a higher Sc than the above-mentioned traditional x Ga 1-x The maximum piezoelectric constant of N, d33 (14pC / N), and higher than the Sc calculated using the first principle described above. x Ga 1-x The maximum piezoelectric constant of N, d 33 (16.9 pC / N), further exceeding the maximum piezoelectric constant d of scandium-added aluminum nitride. 33 The piezoelectric constant d is 27.6 pC / N. 33 Furthermore, it possesses high ferroelectricity, thus leading to the invention of epoch-making nitride materials such as the following. It should be noted that the contents of Japanese Patent Application No. 2023-188952 are incorporated herein as part of this specification.

[0011] The first aspect of the present invention for solving the above-mentioned problems is a nitride material, which is composed of the chemical formula Sc x Ga 1-x N indicates that the characteristic is that x is in the range of 0.39 or higher and 0.54 or lower, and the length of the c-axis in the crystal structure is 4.94 × 10⁻⁶. -10 m or more and 5.2 × 10 -10 The range below m.

[0012] Among them, the "c-axis" refers to the axis that forms a 90-degree angle with the other two axes among the three axes of the hexagonal crystal system, such as wurtzite-type crystals.

[0013] According to this first method, a piezoelectric constant d with a value exceeding 16.9 pC / N can be provided. 33 Gallium nitride with added scandium.

[0014] The second aspect of the present invention is the nitride material described in the first aspect, characterized in that x is in the range of 0.45 or higher and 0.54 or lower.

[0015] According to this second approach, a higher maximum piezoelectric constant d can be provided. 33 Gallium nitride with added scandium.

[0016] The third aspect of the present invention is the nitride material described in the first aspect, characterized in that x is in the range of 0.5 or more and 0.54 or less.

[0017] According to this third approach, a high maximum piezoelectric constant d can be provided. 33 Gallium nitride with added scandium.

[0018] The fourth aspect of the present invention is the nitride material described in the first aspect, characterized in that the length of the c-axis is 4.94 × 10⁻⁶. -10 m or more and 5.05×10 -10 The range below m.

[0019] According to this fourth approach, a higher maximum piezoelectric constant d can be provided. 33 Gallium nitride with added scandium.

[0020] The fifth aspect of the present invention is the nitride material described in the first aspect, characterized in that the length of the a-axis in the crystal structure is 3.4 × 10⁻⁶. -10 m or more and 3.5 × 10 -10 The range below m.

[0021] Here, "a-axis" refers to the two axes that form a 90-degree angle with the aforementioned c-axis, and they have the same lattice constant.

[0022] According to this fifth method, a higher piezoelectric constant d can be provided. 33 Gallium nitride with added scandium.

[0023] The sixth aspect of the present invention is the nitride material described in the first aspect, characterized in that the length of the a-axis is 3.44 × 10⁻⁶. -10 m or more and 3.48 × 10 -10 The range below m.

[0024] According to this sixth method, a further higher maximum piezoelectric constant d can be provided. 33 Gallium nitride with added scandium.

[0025] The seventh aspect of the present invention is the nitride material described in the first aspect, characterized in that the thickness is in the range of 1 nm to 3000 nm.

[0026] According to this seventh method, a piezoelectric constant d can be provided. 33 Gallium nitride with added scandium.

[0027] The eighth aspect of the present invention is a piezoelectric material composed of any one of the nitride materials described in the first to seventh aspects.

[0028] According to this eighth method, a piezoelectric constant d can be provided. 33 Piezoelectric material.

[0029] The ninth aspect of the present invention is a piezoelectric material, characterized in that the nitride material of any one of the first to seventh aspects is disposed on a substrate, and at least one intermediate layer is disposed between the nitride material and the substrate.

[0030] According to this ninth method, due to the increased crystallinity (crystallinity) of the piezoelectric material, a piezoelectric material with higher piezoelectricity can be provided.

[0031] The tenth aspect of the present invention is the piezoelectric body described in the ninth aspect, characterized in that a diffusion layer is further provided between the intermediate layer and the piezoelectric body, the diffusion layer comprising a substance constituting the intermediate layer and a substance constituting the piezoelectric body.

[0032] According to this tenth method, similarly to the ninth method, a piezoelectric material with high piezoelectricity can be provided.

[0033] The eleventh aspect of the present invention is a MEMS device that uses the piezoelectric element described in the eighth aspect.

[0034] The term "MEMS device" is not specifically limited as long as it refers to a microelectromechanical system. Examples include high-frequency filters such as FBAR filters and SMR (Solidly Mounted Resonator), oscillators, pressure sensors, accelerometers, gyroscopes, actuators, microphones, speakers, ultrasonic oscillators, ultrasonic sensors, fingerprint authentication sensors, vibration generators, and energy harvesters.

[0035] According to this eleventh method, high-frequency, miniaturized, and power-saving MEMS devices can be provided. Especially when the MEMS device is a high-frequency filter, it can provide a high-frequency filter with low loss and the ability to operate over a wide bandwidth compared to traditional high-frequency filters.

[0036] The twelfth aspect of the present invention is a ferroelectric material, wherein the ferroelectric material is composed of any one of the nitride materials described in the first to seventh aspects.

[0037] According to this twelfth method, a ferroelectric material with high ferroelectricity can be provided.

[0038] The thirteenth aspect of the present invention is an electronic component that uses the ferroelectric material described in the twelfth aspect.

[0039] Among them, "electronic components" include ferroelectric non-volatile memory (including field-effect ferroelectric non-volatile memory), resistance-varying non-volatile memory, piezoresistive transistors, energy storage elements, piezoelectric elements, pyroelectric elements, piezoelectric sensors, and electrothermal effect elements.

[0040] According to this thirteenth method, due to its high ferroelectricity, it is possible to provide small and high-performance electronic components.

[0041] The fourteenth aspect of the present invention is a method for manufacturing a nitride material, wherein the nitride material described in any one of the first to seventh aspects is manufactured by sputtering, characterized in that the sputtering gas contains nitrogen, and the sputtering target is a target made of scandium and a target made of gallium nitride, a target made of scandium and a target made of an alloy containing scandium and gallium, a target made of gallium nitride and a target made of an alloy containing scandium and gallium, or a target made of an alloy containing scandium and gallium.

[0042] According to this fourteenth method, it is possible to manufacture a product with a high piezoelectric constant d. 33 Piezoelectric material.

[0043] The fifteenth aspect of the present invention is a method for manufacturing nitride material as described in the fourteenth aspect, characterized in that the heating temperature during film formation of the substrate for forming the nitride material is in the range of 25°C or higher and less than 400°C.

[0044] According to this fifteenth method, it is possible to manufacture products with a higher piezoelectric constant d. 33 Piezoelectric material. Attached Figure Description

[0045] Figure 1 This is a schematic cross-sectional view of the piezoelectric thin film of Embodiment 1. Figure 2 This is a table showing the conditions for forming each piezoelectric film in Film Example 1 and the data for each piezoelectric film. Figure 3 This represents the substrate heating temperature and piezoelectric constant d during the film formation of each piezoelectric thin film in Example 1. 33 A diagram showing the relationship between the two. Figure 4 This is a table showing the data of each piezoelectric thin film in Example 2. Figure 5 This is a table showing the data of each piezoelectric thin film in Example 3. Figure 6 This is a table showing the conditions for forming each piezoelectric film in Film Example 4 and the data for each piezoelectric film. Figure 7 This is a table showing the conditions for forming each piezoelectric film in Film Example 5 and the data for each piezoelectric film. Figure 8 This is a table showing the conditions for forming each piezoelectric film in Film Example 6 and the data for each piezoelectric film. Figure 9 This refers to the piezoelectric thin films of Examples 1-6, showing the relationship between the concentration of Sc and the piezoelectric constant d. 33 A diagram showing the relationship between the two. Figure 10 This refers to the piezoelectric thin films of Examples 1-6, where the length of the c-axis and the piezoelectric constant d are shown.33 A diagram showing the relationship between the two. Figure 11 This refers to the piezoelectric thin films of Examples 1-6, where the length of the a-axis and the piezoelectric constant d are shown. 33 A diagram showing the relationship between the two. Figure 12 This is a schematic cross-sectional view of the piezoelectric thin film of Embodiment 2. Figure 13 This is a table showing the data for each ferroelectric thin film of Example 7. Figure 14 This is a graph showing the hysteresis loop of the ferroelectric thin film No.3 in Example 7. Detailed Implementation

[0046] Hereinafter, embodiments of the nitride material of the present invention will be described with reference to the accompanying drawings. It should be noted that the present invention is not limited to the following embodiments.

[0047] (Implementation Method 1) Figure 1 This is a schematic side view of a piezoelectric thin film made of the nitride material of this embodiment. As shown in the figure, the piezoelectric thin film 1 is formed on the substrate 10.

[0048] The thickness and material of the substrate 10 are not particularly limited as long as a piezoelectric thin film 1 can be formed on its surface. Examples of substrates 10 include silicon, heat-resistant alloys such as Inconel alloy, and resin films such as polyimide.

[0049] The piezoelectric thin film 1 is composed of a nitride material, wherein the nitride material is of the chemical formula Sc x Ga 1-x N indicates that the characteristic is that x is in the range of 0.39 or higher and 0.54 or lower, and the length of the c-axis in the crystal structure is 4.94 × 10⁻⁶. -10 m or more and 5.2 × 10 -10 The range below m.

[0050] Such a piezoelectric thin film 1 has at least higher properties than conventional Sc x Ga 1-x The maximum piezoelectric constant of N, d 33 The value (14 pC / N) is higher than the Sc calculated using first-principles calculations. x Ga 1-x The maximum piezoelectric constant of N, d 33 The maximum piezoelectric constant d is 16.9 pC / N. 33 .

[0051] Among them, the piezoelectric thin film 1, in the above chemical formula, has a higher maximum piezoelectric constant d when x is in the range of 0.45 or more and 0.54 or less.33 Therefore, preferably, the piezoelectric thin film 1 with x in the range of 0.5 or higher and 0.54 or lower also has a high maximum piezoelectric constant d. 33 Therefore, it is the preferred choice.

[0052] Furthermore, the length of the c-axis in these crystal structures is 4.94 × 10⁻⁶. -10 m or more and 5.05×10 -10 The piezoelectric thin film 1 in the range below m has a higher Sc content than Sci. x Al 1-x The maximum piezoelectric constant of N, d 33 The piezoelectric constant d is 27.6 pC / N. 33 The value of is therefore particularly preferred. Furthermore, the length of the a-axis in these crystal structures is 3.40 × 10⁻⁶. -10 m or more and 3.5 × 10 -10 Piezoelectric thin films 1 with a range below m have higher piezoelectric constants d. 33 The value is therefore more preferably 3.44 × 10. -10 m or more and 3.48 × 10 -10 Piezoelectric thin films 1 with a range below m have a further higher piezoelectric constant d. 33 The value of is therefore particularly preferred.

[0053] It should be noted that the thickness of the piezoelectric thin film 1 is not particularly limited, but is preferably 1nm to 3000nm, more preferably 10nm to 1000nm, and particularly preferably 100nm to 1000nm.

[0054] Furthermore, the piezoelectric thin film 1 may contain rare gases such as argon (Ar) and neon (Ne), with Ar being particularly preferred. Examples of piezoelectric thin films 1 containing Ar include those made of the chemical formula (Sc... x Ga 1-x ) 1-y Ar y The N-denoted nitride material has the following piezoelectric constants: x is 0.39 or higher and 0.54 or lower, y is 0.0016 or higher and 0.006 or lower; x is 0.45 or higher and 0.54 or lower, y is 0.0016 or higher and 0.006 or lower; and x is 0.5 or higher and 0.54 or lower, y is 0.0016 or higher and 0.006 or lower. Similarly, the piezoelectric thin film made of this Ar-containing nitride material also has a high piezoelectric constant d. 33 .

[0055] Moreover, with Sc x Al 1-xCompared to high-frequency filters composed of N, high-frequency filters using these piezoelectric thin films 1 have lower losses and can operate over a wider bandwidth. As a result, mobile devices can achieve higher frequency response, miniaturization, and power saving. It should be noted that the structure of the high-frequency filter is not particularly limited and can be manufactured using known structures.

[0056] Next, the manufacturing method of the piezoelectric thin film 1 according to this embodiment will be described. The piezoelectric thin film 1, like a general piezoelectric thin film, can be manufactured using methods such as sputtering or vapor deposition. Specifically, for example, it can be manufactured by simultaneously sputtering two targets onto a substrate 10 (e.g., a silicon (Si) substrate) under a nitrogen (N2) atmosphere or a mixed atmosphere of nitrogen (N2) and argon (Ar). The combination of these two targets can be a target made of scandium and a target made of gallium nitride (GaN), a target made of scandium and a target made of an alloy containing scandium and gallium, or a target made of gallium nitride and a target made of an alloy containing scandium and gallium.

[0057] It should be noted that, as a sputtering target, a target made solely of an alloy containing scandium and gallium (a target monomer made of an alloy containing scandium and gallium) may also be used. For example, there are no particular limitations on the alloy containing scandium and gallium, provided that the ratio of Sc to the total amount of Sc and Ga in the sputtering target is 25 atomic% or more and less than 100 atomic%. Specifically, examples of alloys containing scandium and gallium include one or more intermetallic compounds selected from the group consisting of Ga3Sc, Ga2Sc, Ga3Sc2, GaSc, Ga4Sc5, and Ga3Sc5.

[0058] In addition, the sputtering gas can also contain rare gases other than Ar. By using sputtering gases containing rare gases such as Ar, it is easy to fabricate gases with high piezoelectric constants d. 33 Sc x Ga 1-x N. It should be noted that the rare gas can be a single gas such as Ar, or a mixture of multiple rare gases such as a mixture of Ar and Kr. Among these rare gases, Ar is particularly preferred. By including Ar in the sputtering gas, it is easier to manufacture piezoelectric thin films made of the nitride material of the present invention.

[0059] The concentration of rare gases contained in the sputtering gas is not particularly limited, but is preferably in the range of 5 mol% or more and 95 mol% or less, more preferably in the range of 20 mol% or more and 95 mol% or less, and even more preferably in the range of 50 mol% or more and 90 mol% or less.

[0060] Furthermore, if the temperature during film formation (substrate heating temperature) of the substrate for forming the piezoelectric thin film 1 is in the range of room temperature (25°C) or higher and less than 400°C, the piezoelectric thin film 1 can be easily manufactured. Therefore, it is preferable that the temperature is in the range of 100°C to 350°C, and even more preferable that the temperature is in the range of 150°C to 300°C, which makes the piezoelectric thin film 1 even easier to manufacture. Therefore, it is particularly preferred.

[0061] Furthermore, the pressure of the sputtering gas is not particularly limited, but is preferably below 1 Pa, more preferably in the range of 0.1 Pa to 0.7 Pa, and particularly preferably in the range of 0.2 Pa to 0.5 Pa. <Example 1>

[0062] Using the following apparatus and sputtering target, a substrate with added Hf intermediate layer (thickness ≤ 0.02 Ω·cm) is fabricated on a conductive silicon substrate (0.02 Ω·cm or less) pre-formed with an Hf intermediate layer (thickness 100 nm to 130 nm). Figure 2 The scandium-gallium nitride piezoelectric thin film shown is (Sc x Ga 1-x N).

[0063] Sputtering film deposition apparatus (manufactured by ULVAC) Sc sputtering target (purity: 99.99%) GaN powder sintered sputtering target (purity: 99.99%) Gas: A mixture of nitrogen (purity: ≥99.99995%) and argon (purity: ≥99.9999%) (mixing ratio (nitrogen:argon) 30:70) Sputtering gas pressure: 0.25 Pa Substrate heating temperature: 35~200℃

[0064] The substrate heating temperature and piezoelectric constant d during the formation of each obtained piezoelectric thin film are represented. 33 The relationship is represented in a graph. Figure 3 As shown in the figure, the piezoelectric films of Example 1 (piezoelectric films formed at a substrate heating temperature of 35~200°C) have a higher Sc value than that calculated using the first principle. x Ga 1-x The maximum piezoelectric constant of N, d 33 The piezoelectric constant d is 16.9 pC / N. 33 It should be noted that the piezoelectric constant d 33 After attaching a 2.5 mm diameter Al electrode as the upper electrode using vapor deposition, the results were evaluated using a piezoelectric meter (PM300 (Alpha Corporation)). <Example 2>

[0065] Using the following equipment and sputtering target, etc., the following will be added Figure 4 The scandium-gallium nitride piezoelectric thin film shown is (Sc x Ga 1-x N) Direct film formation on a conductive silicon substrate (below 0.02 Ω·cm).

[0066] Sputtering film deposition apparatus (manufactured by ULVAC) Sc sputtering target (purity: 99.99%) GaN powder sintered sputtering target (purity: 99.99%) Gas: A mixture of nitrogen (purity: ≥99.99995%) and argon (purity: ≥99.9999%) (mixing ratio (nitrogen:argon) 30:70) Sputtering gas pressure: 0.25 Pa Substrate heating temperature: 150℃ <Example 3>

[0067] Using the following equipment and sputtering target, etc., the following will be added Figure 5 Scandium gallium nitride piezoelectric thin films (Sc x Ga 1- x N) Direct film formation on a conductive silicon substrate (below 0.02 Ω·cm). Sputtering film deposition apparatus (manufactured by ULVAC) ScGa alloy sputtering target (Sc:Ga=50:50, purity: 99.99%) Sc metal sputtering target (purity: 99.99%) Gas: A mixture of nitrogen (purity: ≥99.99995%) and argon (purity: ≥99.9999%) (mixing ratio (nitrogen:argon) 30:70) Sputtering gas pressure: 0.25 Pa Substrate heating temperature: 200℃ <Example 4>

[0068] Using the following equipment and sputtering target, etc., the following will be added Figure 6 The scandium-gallium nitride piezoelectric thin film shown is (Sc x Ga 1-x N) Direct film formation on a conductive silicon substrate (below 0.02 Ω·cm).

[0069] Sputtering film deposition apparatus (manufactured by ULVAC) Sc sputtering target (purity: 99.99%) GaN powder sintered sputtering target (purity: 99.99%) Gas: A mixture of nitrogen (purity: above 99.99995%) and argon (purity: above 99.9999%) (mixing ratio (nitrogen:argon) 10:90~30:70) Sputtering gas pressure: 0.45 Pa Substrate heating temperature: 200℃ <Example 5>

[0070] Using the following equipment and sputtering target, etc., the following will be added Figure 7 The scandium-gallium nitride piezoelectric thin film shown is (Sc x Ga 1-x N) Direct film formation on a conductive silicon substrate (below 0.02 Ω·cm).

[0071] Sputtering film deposition apparatus (manufactured by ULVAC) ScGa alloy sputtering target (Sc:Ga=50:50, purity: 99.9%) Sc metal sputtering target (purity: 99.99%) Gas: A mixture of nitrogen (purity: above 99.99995%) and argon (purity: above 99.9999%) (mixing ratio (nitrogen:argon) 10:90~50:50) Sputtering gas pressure: 0.45 Pa Substrate heating temperature: 200℃ <Example 6>

[0072] Using the following equipment and sputtering target, etc., the following will be added Figure 8 The scandium-gallium nitride piezoelectric thin film shown is (Sc x Ga 1-x N) Direct film formation on a conductive silicon substrate (below 0.02 Ω·cm).

[0073] Sputtering film deposition apparatus (manufactured by ULVAC) Sc sputtering target (purity: 99.99%) GaN powder sintered sputtering target (purity: 99.99%) Gas: A mixture of nitrogen (purity: ≥99.99995%) and argon (purity: ≥99.9999%) (mixing ratio (nitrogen:argon) 12:88) Sputtering gas pressure: 0.45 Pa Substrate heating temperature: 150~300℃

[0074] Next, regarding the piezoelectric thin films of Examples 1-6, the relationship between the concentration of Sc and the piezoelectric constant d will be explained. 33 The relationship is represented in a graph. Figure 9 The length of the c-axis and the piezoelectric constant d will be represented by...33 The relationship is represented in a graph. Figure 10 It should be noted that the data in Non-Patent Document 1 in these figures represent the data recorded in the aforementioned Non-Patent Document. The same applies below.

[0075] As can be seen from these figures, the piezoelectric constant d of each piezoelectric thin film in Examples 1-6 is... 33 Higher than the conventional Sc described in Non-Patent Document 1 x Ga 1-x The maximum piezoelectric constant of N, d 33 (14pC / N). That is, we know that x is in the range of 0.39 and 0.54, and the length of the c-axis is 4.94 × 10⁻⁶. -10 m or more and less than 5.2 × 10 -10 piezoelectric thin films in the range of m, at least higher than conventional Sc x Ga 1-x The maximum piezoelectric constant of N, d 33 (14pC / N), and higher than the Sc calculated using first-principles calculations. x Ga 1-x The maximum piezoelectric constant of N, d 33 (16.9pC / N).

[0076] Furthermore, it can be seen that x is in the range of 0.45 and 0.54, and the length of the c-axis is 4.94 × 10⁻⁶. -10 m or more and less than 5.05 × 10 -10 A piezoelectric thin film in the range of m, having a higher content than that of aluminum nitride (Sc) with added scandium as described in Non-Patent Document 3 above. x Al 1-x The maximum piezoelectric constant d of N) 33 The piezoelectric constant d is 27.6 pC / N. 33 .

[0077] Furthermore, regarding the piezoelectric thin films of Examples 1-6, the length representing the a-axis and the piezoelectric constant d will be... 33 The relationship is represented in a graph. Figure 11 As shown in the figure, the length of the a-axis is 3.4 × 10⁻⁶. -10 m or more and 3.5 × 10 -10 Piezoelectric thin films in the range below μm, higher than traditional Sc x Ga 1-x The maximum piezoelectric constant of N, d 33 (14pC / N), and higher than the Sc calculated using first-principles calculations. x Ga 1-x The maximum piezoelectric constant of N, d 33 (16.9pC / N). Furthermore, it can be known that the length of the a-axis is 3.44 × 10. -10 m or more and less than 3.48 × 10 -10 A piezoelectric thin film in the range of m, having a higher content than that of aluminum nitride (Sc) with added scandium as described in Non-Patent Document 3 above. x Al 1-x The maximum piezoelectric constant d of N) 33 The piezoelectric constant d is 27.6 pC / N. 33 .

[0078] (Implementation Method 2) In Embodiment 1 described above, a piezoelectric thin film was directly fabricated on the substrate, but the present invention is not limited thereto. For example, such as Figure 12 As shown, an intermediate layer 20 can also be provided between the substrate 10 and the piezoelectric film 1A.

[0079] As for the intermediate layer 20, its material, thickness, etc. are not particularly limited as long as a piezoelectric thin film 1A can be formed on the intermediate layer 20. For example, intermediate layers with a thickness of 1 to 200 nm can be made of aluminum nitride (AlN), gallium nitride (GaN), indium nitride (InN), titanium nitride (TiN), scandium nitride (ScN), ytterbium nitride (YbN), molybdenum (Mo), tungsten (W), hafnium (Hf), titanium (Ti), ruthenium (Ru), ruthenium oxide (RuO2), chromium (Cr), chromium nitride (CrN), platinum (Pt), gold (Au), silver (Ag), copper (Cu), aluminum (Al), tantalum (Ta), iridium (Ir), palladium (Pd), and nickel (Ni), as well as intermediate layers with a thickness of 50 to 200 nm made of these materials.

[0080] By providing such an intermediate layer 20 on the substrate 10, the crystallinity (crystallinity) of the piezoelectric film 1A is improved, thus enabling the formation of a piezoelectric constant d that is even higher than that of the piezoelectric film of Embodiment 1. 33 Sc x Ga 1-x N.

[0081] (Implementation Method 3) In Embodiment 2 described above, a piezoelectric thin film is formed directly on the intermediate layer, but the present invention is not limited thereto. For example, a diffusion layer comprising a material constituting the intermediate layer and a material constituting the piezoelectric thin film may be further provided between the intermediate layer and the piezoelectric thin film. It should be noted that the diffusion layer may be formed, for example, by heating the piezoelectric thin film after it has been formed on the intermediate layer. Even with the diffusion layer provided in this way, the same effect as in Embodiment 2 can be obtained.

[0082] (Implementation Method 4) In the above embodiments, the use of the nitride material of the present invention as a piezoelectric material has been described, but the present invention is not limited thereto. The nitride material of the present invention has ferroelectric properties and can also be used as a ferroelectric material. <Example 7>

[0083] Using the following apparatus and sputtering target, a ferroelectric thin film of gallium nitride (Sc) with added scandium is formed. x Ga 1-x N) Direct film formation on a conductive silicon substrate (below 0.02 Ω·cm).

[0084] Sputtering film deposition apparatus (manufactured by ULVAC) Sc sputtering target (purity: 99.99%) GaN powder sintered sputtering target (purity: 99.99%) Gas: A mixture of nitrogen (purity: ≥99.99995%) and argon (purity: ≥99.9999%) (mixing ratio (nitrogen:argon) 12:88) Sputtering gas pressure: 0.45 Pa Substrate heating temperature: 250℃

[0085] The resulting ferroelectric thin films are shown in Figure 13 For the ferroelectric thin film No. 3, after attaching a 100 μm diameter Pt electrode as the top electrode via vapor deposition, the ferroelectricity (electric field-polarization characteristics) was measured using an FCE10-S / 400-A (manufactured by Dongyang Technology Co., Ltd.). The results are shown below. Figure 14 As can be seen from the figure, the ferroelectric thin film No. 3 exhibits a distinct hysteresis loop, thus demonstrating ferroelectricity.

[0086] (Other implementation methods) In Embodiment 1, a piezoelectric thin film using the nitride material of the present invention was described as an example, but the present invention is not limited thereto. For example, the nitride material of the present invention can also be applied to electronic components such as MEMS devices and ferroelectric memories. The structure of the MEMS device and electronic component can adopt a known structure.

[0087] Compared with conventional ferroelectric memories, ferroelectric memories using the nitride material of the present invention have high spontaneous polarization and high storage performance. Explanation of reference numerals in the attached figures

[0088] 1, 1A: Piezoelectric thin film; 10: Substrate; 20: Intermediate layer.

Claims

1. A nitride material, composed of the chemical formula Sc x Ga 1-x N represents, characterized in that, x is in the range of 0.39 and 0.

54. The length of the c-axis in the crystal structure is 4.94 × 10⁻⁶. -10 m or more and 5.2 × 10 -10 The range below m.

2. The nitride material according to claim 1, characterized in that, The x value is in the range of 0.45 or higher and 0.54 or lower.

3. The nitride material according to claim 1, characterized in that, The x value is in the range of 0.5 or higher and 0.54 or lower.

4. The nitride material according to claim 1, characterized in that, The length of the c-axis is 4.94 × 10. -10 m or more and 5.05×10 -10 The range below m.

5. The nitride material according to claim 1, characterized in that, The length of the a-axis in the crystal structure is 3.4 × 10⁻⁶. -10 m or more and 3.5 × 10 -10 The range below m.

6. The nitride material according to claim 5, characterized in that, The length of the a-axis is 3.44 × 10. -10 m or more and 3.48 × 10 -10 The range below m.

7. The nitride material according to claim 1, characterized in that, The thickness ranges from 1nm to 3000nm.

8. A piezoelectric element, characterized in that, The piezoelectric element is composed of the nitride material according to any one of claims 1 to 7.

9. A piezoelectric element, characterized in that, The nitride material according to any one of claims 1 to 7 is disposed on a substrate, and at least one intermediate layer is disposed between the nitride material and the substrate.

10. The piezoelectric element according to claim 9, characterized in that, A diffusion layer is further disposed between the intermediate layer and the piezoelectric element, the diffusion layer comprising the material constituting the intermediate layer and the material constituting the piezoelectric element.

11. A MEMS device, characterized in that, The MEMS device uses the piezoelectric element as described in claim 8.

12. A ferroelectric material, characterized in that, The ferroelectric material is composed of any one of the nitride materials according to claims 1 to 7.

13. An electronic component, characterized in that, The electronic component uses the ferroelectric material as described in claim 12.

14. A method for manufacturing a nitride material, comprising manufacturing the nitride material according to any one of claims 1 to 7 using a sputtering method, characterized in that, As a sputtering gas, it contains nitrogen. As sputtering targets, targets made of scandium and targets made of gallium nitride, targets made of scandium and targets made of alloys containing scandium and gallium, targets made of gallium nitride and targets made of alloys containing scandium and gallium, or targets made of alloys containing scandium and gallium are used.

15. The method for manufacturing the nitride material according to claim 14, characterized in that, The heating temperature during film formation of the substrate of the nitride material is in the range of 25°C or higher and less than 400°C.

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