Magnesium silicon nitride film, piezoelectric body, and piezoelectric element

Abstract

To provide a magnesium silicon nitride film having piezoelectric characteristics, a piezoelectric body, and a piezoelectric element.SOLUTION: A magnesium silicon nitride film contains magnesium, silicon, and nitrogen, and a crystalline phase contains hexagonal crystal. A piezoelectric body and a piezoelectric element include the magnesium silicon nitride film. The magnesium silicon nitride film may contain aluminum. The hexagonal crystal contained in the magnesium silicon nitride film may have a wurtzite type structure. A thickness of the magnesium silicon nitride film may be 2,000 nm or lower.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a magnesium silicon nitride film, a piezoelectric body, and a ferroelectric element.

Background Art

[0002] Magnesium silicide is known as one of the thermoelectric conversion materials used in thermoelectric conversion elements. For example, Patent Document 1 proposes a thermoelectric conversion material in which an aluminum-concentrated layer having a higher Al concentration than the inside of the magnesium silicide phase is formed between the magnesium silicide phase and the magnesium oxide layer. On the other hand, various materials are being studied as piezoelectric materials used in piezoelectric elements such as pressure sensors and vibration sensors.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide at least one of a magnesium silicon nitride film having piezoelectric properties, a piezoelectric body, and a piezoelectric element.

Means for Solving the Problems

[0005] The inventors of the present invention examined various materials in order to find a novel material exhibiting piezoelectric properties. As a result, it was found that when Mg and Si are contained in a certain composition ratio instead of Al contained in hexagonal aluminum nitride, the hexagonal crystal is maintained and piezoelectric properties are exhibited. The content of the present invention is as described in the claims, and the gist of the present disclosure is as follows.

[0006] [1] A magnesium silicon nitride film containing magnesium, silicon, and nitrogen, and having a crystal phase including a hexagonal crystal. [2] The magnesium silicon nitride film according to [1], which contains aluminum. [3] The magnesium silicon nitride film according to [1] or [2], wherein the hexagonal crystal has a wurtzite structure. [4] The magnesium silicon nitride film according to any one of [1] to [3], having a thickness of 2000 nm or less. [5] The magnesium silicon nitride film according to any one of [1] to [4], having a thickness of 250 nm or less. [6] The magnesium silicon nitride film according to any one of [1] to [5], having a thickness greater than 250 nm. [7] A piezoelectric body comprising the magnesium silicon nitride film according to any one of [1] to [6] above. [8] A piezoelectric element comprising the magnesium silicon nitride film according to any one of [1] to [6] above.

Advantages of the Invention

[0007] According to the present disclosure, at least one of a magnesium silicon nitride film having piezoelectric characteristics, a piezoelectric body, and a piezoelectric element is provided.

Brief Description of the Drawings

[0008]

Figure 1

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Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0009] Some examples of the embodiments of the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments.

[0010] <Magnesium silicon nitride film> The magnesium silicon nitride film contains magnesium, silicon and nitrogen, and the crystal phase includes a hexagonal crystal. In the magnesium silicon nitride film, magnesium, silicon and nitrogen may form a hexagonal crystal lattice. The magnesium silicon nitride film may contain aluminum. As a result, the proportion of hexagonal crystals in the crystal phase can be made sufficiently high, so that the piezoelectric performance is likely to be improved. In this case, in the magnesium silicon nitride film, magnesium, silicon, aluminum and nitrogen may form a hexagonal crystal lattice.

[0011] The crystal phase contained in the magnesium silicon nitride film may have a structure in which Al atoms (valence electron number: 3) in hexagonal aluminum nitride are substituted with Mg atoms (valence electron number: 2) and Si atoms (valence electron number: 4). Furthermore, it is preferable that two Al atoms are substituted with one Mg atom and one Si atom. Since the magnesium silicon nitride film contains magnesium and silicon having different valence electron numbers, charge bias occurs in the hexagonal crystal and residual polarization occurs, which is considered to be a factor showing ferroelectricity and piezoelectric properties. In particular, since the c / a of the crystal lattice is smaller than that of aluminum nitride, the relative permittivity is considered to increase and the piezoelectric properties are improved. However, the factor showing the piezoelectric properties is not limited to this.

[0012] The crystal phase in the magnesium silicon nitride film may contain a crystal phase different from the hexagonal crystal. The crystal phase may contain, for example, a tetragonal crystal. The hexagonal crystal preferably has a wurtzite structure. The fact that the crystal phase contains a hexagonal crystal and that the hexagonal crystal has a wurtzite structure can be confirmed by selected area electron diffraction using TEM, two-dimensional mapping of the X-ray diffraction image of the magnesium silicon nitride film, measurement of the X-ray diffraction profile by the Out-of-Plane method, etc.

[0013] In the two-dimensional mapping of the X-ray diffraction image, the diffraction peaks derived from (100), (101), and (002) of the hexagonal crystal of magnesium silicon nitride are detected at the following positions. When diffraction peaks are detected at all the following positions, it can be determined that the crystal phase of the magnesium silicon nitride film contains a hexagonal crystal. The measurement conditions of X-ray diffraction are as described in the examples.

[0014] (100): 2θ = 32° - 34°, Ψ = 85° - 90° (101): 2θ = 36° - 38°, Ψ = 58° - 63° (002): 2θ = 35° - 37°, Ψ = 0° - 5°

[0015] In the two-dimensional mapping of the X-ray diffraction image, when diffraction peaks of the hexagonal crystal of magnesium silicon nitride and diffraction peaks of a different phase different from this are detected as the crystal phase of the magnesium silicon nitride film, for example, the ratio [H1 / (H1 + H2)] of the peak height (H1) of (002) of the hexagonal crystal to the total (H1 + H2) of the peak height (H1) of the hexagonal crystal and the height (H2) of the highest diffraction peak among the diffraction peaks of the different phase may be 60% or more, 70% or more, 80% or more, 90% or more, 95% or more, 98% or more, 99% or more, or 100%. By increasing the ratio of the hexagonal crystal in the crystal phase of the magnesium silicon nitride film, the piezoelectric characteristics can be made sufficiently high.

[0016] The crystal contained in the magnesium silicon nitride film may have strain. The crystal contained in the magnesium silicon nitride film preferably has an internal parameter u defined by the following formula (I) of less than 1.0. Internal parameter u = (a 2 / 3c 2 ) + 0.25 ··· (I)

[0017] In the above formula (I), a represents the lattice constant (Å) of the a-axis, and c represents the lattice constant (Å) of the c-axis. The internal parameter u is one of the indicators showing the strain of the crystal, and the smaller its value, the greater the strain. As the internal parameter becomes smaller, the piezoelectric performance improves. The internal parameter u is preferably 0.30 or more and 0.50 or less, and more preferably 0.35 or more and 0.40 or less.

[0018] The magnesium silicon nitride film may have a composition represented by, for example, the following compositional formula (II) or (III). Such a magnesium silicon nitride film tends to have a high ratio of hexagonal crystals in all crystal phases and has excellent piezoelectric characteristics.

[0019] (Mg x Si y )N ··· (II) In the above compositional formula (II), x may be 0.4 or more and 0.6 or less, and y may be 0.4 or more and 0.6 or less. At this time, x + y = 1. The lower limit of x may be 0.42, 0.45, or 0.47. The upper limit of x may be 0.58, 0.56, or 0.53. The lower limit of y may be 0.42, 0.45, or 0.47. The upper limit of y may be 0.58, 0.56, or 0.53. As x and y approach 0.5, the ratio of hexagonal crystals in the crystal phase can be increased.

[0020] (Mg x1 Si y1 Al z )N ··· (III) In the above compositional formula (III), x1 may be 0.1 or more and 0.6 or less, y1 may be 0.1 or more and 0.6 or less, and z may be 0 or more and 0.75 or less. At this time, x1 + y1 + z = 1. x1 / (x1 + y1) may be 0.4 or more and 0.6 or less. Also, the lower limit of x1 / (x1 + y1) may be 0.42, 0.45, or 0.47. The upper limit of x1 / (x1 + y1) may be 0.58, 0.56, or 0.53.

[0021] The thickness of the magnesium silicon nitride film is not particularly limited and may be 10000 nm or less, 2000 nm or less, 1500 nm or less, 1000 nm or less, 500 nm or less, or 250 nm or less. The thickness of the magnesium silicon nitride film may be 1 nm or more, 2 nm or more, 3 nm or more, 50 nm or more, 100 nm or more, or 175 nm or more. An example of the range of the thickness of the magnesium silicon nitride film is 1 nm or more and 10000 nm or less.

[0022] Since the magnesium silicon nitride film contains magnesium and silicon with different valence electrons, the residual polarization can be increased by the charge bias in the hexagonal crystal. Therefore, it exhibits ferroelectricity and piezoelectric properties. Accordingly, the magnesium silicon nitride film may constitute a ferroelectric or a piezoelectric.

[0023] When the above magnesium silicon nitride film is used as a ferroelectric, a thinner thickness is preferred. Specifically, the thickness of the magnesium silicon nitride film may be 250 nm or less. Thereby, the ferroelectric element can be used with lower power consumption. The thickness of the magnesium silicon nitride film may be 200 nm or less, 150 nm or less, 100 nm or less, 50 nm or less, or 20 nm or less. The thickness of the magnesium silicon nitride film may also be 1 nm or more, 2 nm or more, 3 nm or more, or 5 nm or more. An example of the range of the thickness of the magnesium silicon nitride film as a ferroelectric is 1 nm or more and 200 nm or less.

[0024] When using a magnesium silicon nitride film as a piezoelectric body, the thickness of the magnesium silicon nitride film may be greater than 250 nm. The thickness of the magnesium silicon nitride film may be 400 nm or more, or 500 nm or more. The thickness of the magnesium silicon nitride film may also be 10,000 nm or less, 5,000 nm or less, or 1,000 nm or less. An example of the thickness range of the magnesium silicon nitride film that is a piezoelectric body is greater than 250 nm and 10,000 nm or less.

[0025] <Method for manufacturing a magnesium silicon nitride film> An example of a method for manufacturing a magnesium silicon nitride film includes a film formation step of forming a film by sputtering a magnesium target and a silicon target, or a magnesium silicon target in an atmosphere containing nitrogen gas. In the film formation step, a magnesium silicon nitride film may be formed on a substrate by sputtering the target. In one example of the film formation step, a magnesium silicon nitride film containing magnesium, silicon, and nitrogen may be obtained using a magnesium target and a silicon target. In another example of the film formation step, a magnesium silicon nitride film containing magnesium, silicon, and nitrogen may be obtained using only a magnesium silicon target. In yet another example of the film formation step, a magnesium silicon nitride film containing magnesium, silicon, aluminum, and nitrogen may be obtained using a magnesium target, a silicon target, and an aluminum target. In still another example of the film formation step, a magnesium silicon nitride film containing magnesium, silicon, aluminum, and nitrogen may be obtained using a magnesium silicon target and an aluminum target.

[0026] The magnesium target contains magnesium as the main component. The silicon target contains silicon as the main component. The magnesium-silicon target contains magnesium and silicon as the main components. The aluminum target contains aluminum as the main component. Each target may contain a dopant in addition to the main component. Examples of the dopant contained in the magnesium target include Ca (calcium), Sr (strontium), and Ba (barium). Examples of the dopant contained in the silicon target include Ge (germanium), Sn (tin), and Pb (lead). Examples of the dopant contained in the magnesium-silicon target include Ca, Sr, Ba, Ge, Sn, and Pb. Examples of the dopant contained in the aluminum target include In (indium), Ga (gallium), and Si (silicon). The magnesium-silicon nitride film may contain the above-mentioned dopants.

[0027] Each target may have a bulk containing each main component and a backing plate joined to the bulk. Each target may be provided with a bonding material between the bulk and the backing plate. Various materials can be used as the material of the bonding material. The material may be indium from the viewpoint of suppressing thermal diffusion and thermal expansion during sputtering.

[0028] The substrate used for film formation may include a support substrate. The material of the support substrate is not particularly limited. Examples of the substrate include a silicon substrate, a silicon carbide substrate, a glass substrate including non-alkali glass or quartz, a substrate having a wurtzite-type crystal structure such as a gallium nitride substrate, and an oxide crystal substrate such as sapphire or magnesia. Among these, a silicon substrate is preferred.

[0029] The above substrate may further have an oxide layer on the support substrate as needed. Examples of the oxide constituting the oxide layer include titania and silica. The oxide layer may be a single layer or a laminate of a plurality of layers.

[0030] As the sputtering method, one or more selected appropriately from the group consisting of DC sputtering method, RF sputtering method, AC sputtering method, DC magnetron sputtering method, RF magnetron sputtering method, ECR sputtering method, pulsed laser deposition method, and ion beam sputtering method can be selected. Among these, the DC magnetron sputtering method and the RF magnetron sputtering method are preferable in that they can form a film uniformly and at high speed over a large area.

[0031] The gas pressure during sputtering is not particularly limited and may be, for example, 20 mTorr or less. The lower the gas pressure during sputtering, the easier it is for the particles (sputter particles) released from the target to reach the substrate with high energy and to be rearranged epitaxially. As a result, it becomes easier to obtain a magnesium silicon nitride film with a high ratio of hexagonal crystals.

[0032] The temperature of the substrate during film formation may be 700 °C or lower, or 600 °C or lower. By setting the temperature of the substrate during film formation within such a temperature range, the film formation time is shortened and the throughput is improved. The temperature of the substrate during film formation may be 150 °C or higher, or 200 °C or higher.

[0033] The gas to be introduced may contain a gas other than nitrogen gas together with nitrogen gas. Various gases that cause sputtering by discharge can be used. Examples of the gas other than nitrogen gas include argon gas.

[0034] The power during discharge may be adjusted appropriately for each target. The power density applied to the target is, for example, 0.45 W / cm 2 or more and 10.0 W / cm 2 or less, and may be 0.45 W / cm 2 or more and 5.45 W / cm 2 or less. By setting it within such a range, it is possible to make it difficult to peel off coarse target particles from the target. When the power during discharge is 2 W / cm 2If the above conditions are met, the plasma is stable and the film deposition rate is likely to increase. By adjusting the power of each target, the respective ratios of magnesium, silicon, aluminum, and nitrogen can be adjusted.

[0035] The film deposition time may be appropriately adjusted according to the thickness of the magnesium silicon nitride film. The greater the film deposition time, the greater the thickness of the magnesium silicon nitride film can be.

[0036] <Piezoelectric Body and Piezoelectric Element> The piezoelectric body and the piezoelectric element include the above-described magnesium silicon nitride film. The piezoelectric body and the piezoelectric element have, for example, the cross-sectional structure shown in FIG. 1. The piezoelectric element 10 in FIG. 1 includes a first electrode 12, a magnesium silicon nitride film 13 (piezoelectric body), and a second electrode 14 in this order on a substrate 11. The piezoelectric element 10 including the magnesium silicon nitride film 13 as the piezoelectric body exhibits a stable piezoelectric response. The piezoelectric element 10 may be used in a pressure sensor, a vibration sensor, or an actuator. The ferroelectric body and the ferroelectric element may also have the same structure as the piezoelectric body and the piezoelectric element.

[0037] As described above, some embodiments of the present disclosure have been described, but the present disclosure is not limited to the above embodiments in any way.

Example

[0038] Hereinafter, the content of 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.

[0039] [Fabrication of Magnesium Silicon Nitride Film] (Example 1) A silica (SiO2) film with a thickness of 100 nm was formed on a support substrate made of a crystalline silicon substrate with dimensions of 5 mm × 5 mm × a thickness of 600 μm (the Miller index of the surface: (001)). Subsequently, a titania (TiO2) film with a thickness of 50 nm was formed on the silica film. Next, a platinum (Pt) film with a thickness of 100 nm (the Miller index of the surface: (111)) was formed on the titania film by electron beam evaporation. Thus, a film-forming substrate with a thickness of 0.6 mm was obtained.

[0040] The above film-forming substrate, a magnesium target and a silicon target prepared as follows were attached to a sputtering apparatus, and reactive sputtering was performed using a high-frequency (RF) power supply. The sputtering apparatus was fabricated using a vacuum chamber manufactured by Preco and a sputter source manufactured by MeiVac. The film-forming conditions were as follows. As a result, a magnesium silicon nitride film was formed on the Pt film of the film-forming substrate, and a laminate having a magnesium silicon nitride film on the platinum film was obtained.

[0041] · Magnesium target Product name: Mg, diameter × thickness: 50.8 mm × 5 mm, purity: 4N (99.99 mass%), manufactured by High Purity Chemical Research Institute Co., Ltd. · Silicon target Product name: High-purity silicon wafer for research, purity: 5N or higher (: 99.999 mass% or higher), manufactured by Misumi Co., Ltd.

[0042] <Film-forming conditions> · Magnetic field strength: 6100 Gauss · Distance between the magnesium target and the film-forming substrate: 120 mm · Distance between the silicon target and the film-forming substrate: 120 mm · Power density applied to the magnesium target: 4.93 W / cm 2 (100 W) · Power density applied to the silicon target: 4.93 W / cm 2 (100 W) · Substrate temperature during film formation: 400 °C · Film-forming time: 120 minutes · Type of introduced gas (sputtering atmosphere): Nitrogen gas (N2 gas) · Flow rate of introduced gas: 75 sccm · Gas pressure during sputtering: 6 mTorr

[0043] (Example 2) In addition to the magnesium target and silicon target used in Example 1, the following aluminum target was prepared. A film-forming substrate fabricated by the same procedure as in Example 1, and the magnesium target, silicon target, and aluminum target were attached to the same sputtering apparatus as in Example 1. Then, reactive sputtering (high-frequency triple simultaneous reactive magnetron sputtering) using a high-frequency (RF) power supply was performed. The film-forming conditions were as follows. As a result, a magnesium silicon nitride film was formed on the Pt film of the film-forming substrate.

[0044] · Aluminum target A target in which polycrystalline Al (sintered body) was joined to a backing plate via an indium-based joining material (manufactured by High Purity Chemical Laboratory Co., Ltd.)

[0045] <Film-forming conditions> · Magnetic field strength: 6100 Gauss · Distance between the magnesium target and the film-forming substrate: 120 mm · Distance between the silicon target and the film-forming substrate: 120 mm · Distance between the aluminum target and the film-forming substrate: 120 mm · Power density applied to the magnesium target: 7.40 W / cm 2 (150 W) · Power density applied to the silicon target: 7.40 W / cm 2 (150 W) · Power density applied to the aluminum target: 2.47 W / cm 2 (50 W) · Substrate temperature during film formation: 500 °C · Film-forming time: 120 minutes · Type of introduced gas (sputtering atmosphere): Nitrogen gas (N2 gas) · Flow rate of introduced gas: 50 sccm · Gas pressure during sputtering: 5 mTorr

[0046] (Example 3) Among the film formation conditions of Example 2, the power applied to the magnesium target, the power applied to the silicon target, and the power applied to the aluminum target were all changed to 100 W. Film formation was performed under the same conditions as in Example 2 except for this condition, and a magnesium silicon nitride film was formed on the Pt film of the film formation substrate.

[0047] (Example 4) Among the film formation conditions of Example 1, the power applied to the magnesium target was changed to 47 W. Film formation was performed under the same conditions as in Example 1 except for this condition, and a magnesium silicon nitride film was formed on the Pt film of the film formation substrate.

[0048] (Comparative Example 1) Sputtering was performed using only an aluminum target without using a magnesium target and a silicon target. The film formation substrate prepared by the same procedure as in Example 1 and the aluminum target were attached to the same sputtering apparatus as in Example 1. Then, sputtering using a high-frequency (RF) power source was performed. The film formation conditions were as follows. As a result, an aluminum film was formed on the Pt film of the film formation substrate. The film formation conditions were as follows.

[0049] <Film formation conditions> · Magnetic field strength: 6100 Gauss · Distance between the aluminum target and the film formation substrate: 120 mm · Power density applied to the aluminum target: 4.93 W / cm 2 (100 W) · Substrate temperature during film formation: 500 °C · Film formation time: 120 minutes · Type of introduced gas (sputtering atmosphere): Nitrogen gas (N2 gas) · Flow rate of introduced gas: 50 sccm · Gas pressure during sputtering: 5 mTorr

[0050] [Evaluation of the film] (1) Selected area electron diffraction Observation by TEM (transmission electron microscope) Using a TEM (manufactured by JEOL Ltd., trade name: JEM-F200), selected area electron diffraction of the magnesium silicon nitride films formed in Examples 1 to 4 and the aluminum film formed in Comparative Example 1 was performed. Fig. 2 shows the selected area diffraction pattern of the magnesium silicon nitride film of Example 4. From these results, it was confirmed that the magnesium silicon nitride film of Example 4 contained hexagonal crystals. The magnesium silicon nitride films of Examples 1, 2, and 3 and the aluminum film of Comparative Example 1 also contained hexagonal crystals.

[0051] (2) X-ray diffraction X-ray diffraction measurements were performed on the magnesium silicon nitride films formed in Examples 1 to 4 and the aluminum film formed in Comparative Example 1. As the measuring apparatus, ‘X’Pert MRD (trade name) manufactured by PANalytical equipped with a 0-dimensional detector was used. X-ray diffraction measurements were performed while changing 2θ by 0.04° and Ψ by 1° each.

[0052] The results of the two-dimensional mapping measurement of X-ray diffraction were as shown in Fig. 3 (Example 1), Fig. 4 (Example 2), Fig. 5 (Example 3), Fig. 6 (Example 4), and Fig. 7 (Comparative Example 1). In these results, in the range of 2θ = 30° to 40° or 30° to 45° and Ψ = 0° to 90°, the relative intensities of the diffraction peaks are shown in color. The background is shown in blue (black in each figure), and the diffraction peaks are shown in green, yellow, or red (gray in each figure). The high-intensity diffraction peaks have a red center and are surrounded by yellow and green in that order from the center side. In each figure, the red part at the center is dark gray, the yellow part is the lightest gray, and the green part is the intermediate gray between these. The low-intensity diffraction peaks are only green (intermediate gray in each figure).

[0053] Diffraction peaks derived from (100), (101), and (002) of the hexagonal crystal of magnesium silicon nitride are detected at the following positions. (100): 2θ = 32° to 34°, Ψ = 85° to 90° (101): 2θ = 36° to 38°, Ψ = 58° to 63° (002): 2θ = 35° to 37°, Ψ = 0° to 5°

[0054] In the X-ray diffraction profiles of the magnesium silicon nitride films formed in Examples 1 to 4, in addition to the diffraction peak of (111) of the Pt film, the diffraction peaks of (100), (101), and (002) in the hexagonal crystal of magnesium silicon nitride were detected.

[0055] As shown in Figure 3, in Example 1, in addition to the diffraction peaks of (100), (101), and (002) in the hexagonal crystal of magnesium silicon nitride, three diffraction peaks of unidentified heterogeneous phases (indicated as "UN" in the figure) were detected.

[0056] As shown in Figures 4, 5, and 6, in Examples 2, 3, and 4, only the diffraction peaks of (100), (101), and (002) in the hexagonal crystal of magnesium silicon nitride were detected in addition to Pt. Therefore, it was confirmed that the crystal phase of magnesium silicon nitride is only hexagonal. On the other hand, in Comparative Example 1, as shown in Figure 7, the diffraction peaks of the hexagonal crystal of magnesium silicon nitride were not detected.

[0057] The internal parameter u of the magnesium silicon nitride films of Examples 1 to 4 and the aluminum film of Comparative Example 1 was determined. The internal parameter u was determined by the following procedure. The X-ray diffraction profiles of the magnesium silicon nitride films of the laminates of Examples 1 to 4 and the aluminum films of the laminates of Comparative Example 1 were measured by the Out-of-Plane method. Based on the measurement results, the type of crystal structure, the lattice constant a (Å) of the a-axis of the unit cell, the lattice constant c (Å) of the c-axis, c / a, and the internal parameter u were examined. The Out-of-Plane method is a technique for evaluating the lattice plane parallel to the surface of the sample, and a θ-2θ scan was performed using X'pert MRD (manufactured by PANalytical) to conduct X-ray diffraction measurement.

[0058] As a result, in the X-ray diffraction profiles obtained by the Out-of-Plane method for all of Examples 1 to 4, a diffraction peak of (002) of the hexagonal phase of magnesium silicon nitride was observed. From this, it was found that the magnesium silicon nitride film contains a wurtzite-type crystal phase. The lattice constants of the a-axis and c-axis, and the internal parameter u of each example were as shown in Table 1.

[0059]

Table 1

[0060] (2) Measurement of crystal phase composition and film thickness The composition and film thickness of the magnesium silicon nitride films of Examples 1 to 4 and the aluminum film of Comparative Example 1 were measured using a wavelength dispersive fluorescence X-ray analyzer (product name: PW4400, manufactured by PANalytical). The results are shown in Table 2. In the ternary phase diagram in Fig. 8, the molar ratios of Mg:Si:Al of each example and comparative example were plotted. As shown in Fig. 8, Examples 1, 2, 3, and 4 were all located near the dotted line showing a molar ratio of Mg:Si = 0.5:0.5.

[0061] (3) Evaluation of piezoelectric properties On the magnesium silicon nitride films of the laminates of Examples 1 to 4, platinum (Pt) electrodes with a diameter of 50 μm and a thickness of 75 ± 25 nm were formed at room temperature using the electron beam evaporation method to obtain samples of piezoelectric elements. For Comparative Example 1 as well, platinum (Pt) electrodes were formed on the aluminum films of the laminates in the same manner as in Examples 1 to 4 to obtain samples of piezoelectric elements. d 33 meter (product name: "PM300", manufactured by Piezo Test, Ltd.) was used to measure the piezoelectric constant d 33 of each sample at room temperature to evaluate the piezoelectric properties. The results are shown in Table 2.

[0062]

Table 2

[0063] As shown in Table 2, the absolute values of the piezoelectric constants d of the magnesium silicon nitride films of Examples 1 to 4 33 were all greater than 0. Therefore, it was confirmed that the magnesium silicon nitride film of the present disclosure has piezoelectric properties.

Description of Reference Numerals

[0064] 11... Substrate, 12... First electrode, 13... Magnesium silicon nitride film, 14... Second electrode, 10... Piezoelectric element.

Claims

1. A magnesium silicon nitride film containing magnesium, silicon, and nitrogen, and having a crystal phase containing a hexagonal crystal.

2. The magnesium silicon nitride film according to Claim 1, further containing aluminum.

3. The magnesium silicon nitride film according to Claim 1 or 2, wherein the hexagonal crystal has a wurtzite structure.

4. The magnesium silicon nitride film according to Claim 1 or 2, having a thickness of 2000 nm or less.

5. The magnesium silicon nitride film according to Claim 1 or 2, having a thickness of 250 nm or less.

6. The magnesium silicon nitride film according to Claim 1 or 2, having a thickness greater than 250 nm.

7. A piezoelectric body comprising the magnesium silicon nitride film according to Claim 1 or 2.

8. A piezoelectric element comprising the magnesium silicon nitride film according to Claim 1 or 2.

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