Piezoelectric film laminate and method for manufacturing the same

Abstract

To provide a piezoelectric film laminate including a ScAlN film that has reduced the generation of abnormal grains.SOLUTION: A piezoelectric film laminate comprises a SiN film 14 having an undercoat surface 14a, and a ScAIN film 15 arranged in contact with the undercoat surface 14a. The surface roughness of the undercoat surface 14a is 0.5 nm or less in a value of arithmetic average roughness. According to this, the ScAIN film 15 is formed in contact with the undercoat surface 14a having a surface roughness of 0.5 nm or less. Consequently, generation of abnormal grains in the ScAIN film can be reduced compared to a case where the ScAIN film is formed in contact with the undercoat surface having a surface roughness larger than 0.5 nm.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a piezoelectric film laminate in which a piezoelectric film and a base material are laminated, and a method for manufacturing the same.

Background Art

[0002] Patent Document 1 discloses a piezoelectric film laminate including a base material and a ScAlN film which is a piezoelectric film.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The ScAlN film is hexagonal and has a polycrystalline crystal structure having a plurality of crystal grains. When a large number of c-axis oriented crystal grains in which the c-axis of the hexagonal crystal is oriented perpendicular to the film surface of the ScAlN film are included in the plurality of crystal grains, the piezoelectricity of the ScAlN film becomes high. On the other hand, when a large number of abnormal grains in which the orientation of the c-axis of the hexagonal crystal is random are included in the plurality of crystal grains, the piezoelectricity of the ScAlN film becomes low. There is a relationship that the fewer abnormal grains present in the ScAlN film, the more c-axis oriented crystal grains present in the ScAlN film. Therefore, it is desirable to suppress the generation of abnormal grains in the ScAlN film.

[0005] In view of the above points, an object of the present invention is to provide a piezoelectric film laminate including a ScAlN film in which the generation of abnormal grains is suppressed, and a method for manufacturing the same.

Means for Solving the Problems

[0006] To achieve the above object, according to the invention described in claim 1~11 the piezoelectric film laminate is <​​Substrate material (14, 21, 22, 23, 24, 25, 26) having a substrate surface (14a, 21a, 22a, 23a, 24a, 25a, 26a), It comprises a ScAlN film (15) positioned in contact with the substrate surface, The surface roughness of the substrate surface is 0.5 nm or less in terms of arithmetic mean roughness.

[0007] According to this method, the ScAlN film is formed in contact with a substrate surface having a surface roughness of 0.5 nm or less. This suppresses the generation of abnormal grains in the ScAlN film compared to the case where the ScAlN film is formed in contact with a substrate surface having a surface roughness greater than 0.5 nm. Therefore, it is possible to provide a piezoelectric film laminate having a ScAlN film in which the generation of abnormal grains is suppressed.

[0008] Furthermore, claims 12~14 According to the invention described, The method for manufacturing a piezoelectric film laminate is: Prepare a base material (14, 21, 22, 23, 24, 25, 26) having a base surface (14a, 21a, 22a, 23a, 24a, 25a, 26a) (S1, S2, S3), To flatten the substrate surface (S4), The process includes flattening the substrate surface and then forming a ScAlN film (15) in contact with the substrate surface (S5), For the flattening process, the surface roughness of the substrate surface should be 0.5 nm or less in terms of arithmetic mean roughness.

[0009] According to this method, the ScAlN film is formed in contact with a substrate surface having a surface roughness of 0.5 nm or less. This suppresses the generation of abnormal grains in the ScAlN film compared to the case where the ScAlN film is formed in contact with a substrate surface having a surface roughness greater than 0.5 nm. Therefore, it is possible to manufacture a piezoelectric film laminate having a ScAlN film in which the generation of abnormal grains is suppressed.

[0010] Furthermore, claims 15 According to the invention described, The method for manufacturing a piezoelectric film laminate is: (S1, S2) prepare a conductive material (13) having a surface (13a), Planarizing the surface of the conductive material (S2-1), After flattening the surface, a base material having a base surface is formed in contact with the conductive material (S3), This includes forming a ScAlN film in contact with the substrate surface (S5), In planarization, the surface roughness of the conductive material is made 0.5 nm or less in terms of arithmetic mean roughness, thereby making the surface roughness of the substrate surface 0.5 nm or less in terms of arithmetic mean roughness.

[0011] According to this method, the ScAlN film is formed in contact with a substrate surface having a surface roughness of 0.5 nm or less. This suppresses the generation of abnormal grains in the ScAlN film compared to the case where the ScAlN film is formed in contact with a substrate surface having a surface roughness greater than 0.5 nm. Therefore, it is possible to manufacture a piezoelectric film laminate having a ScAlN film in which the generation of abnormal grains is suppressed.

[0012] The reference numerals in parentheses attached to each component indicate an example of the correspondence between that component and the specific components described in the embodiments described later. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view of the piezoelectric film laminate in the first embodiment. [Figure 2] This is a flowchart showing the method for manufacturing a piezoelectric film laminate according to the first embodiment. [Figure 3] This is a diagram showing the crystal structure of ScAlN. [Figure 4] This figure shows the relationship between surface roughness Ra and crystallinity of the substrate surface in Examples 1-3 and Comparative Examples 1-3. [Figure 5A] This is an SEM image of the ScAlN film from Example 1. [Figure 5B] This is an SEM image of the ScAlN film from Example 2. [Figure 5C]SEM image of the ScAlN film of Example 3. [Figure 5D] SEM image of the ScAlN film of Comparative Example 1. [Figure 5E] SEM image of the ScAlN film of Comparative Example 2. [Figure 6] The figure showing the relationship between the surface roughness Ra of the base surface and the piezoelectric performance in Examples 1 to 3 and Comparative Examples 1 to 3. [Figure 7] The figure showing the relationship between the surface roughness Ra of the base surface and tanδ in Examples 1 to 3 and Comparative Examples 1 to 3. [Figure 8] The figure showing the relationship between the surface roughness Ra of the base surface and the crystallinity in Examples 1 to 4 and Comparative Examples 1 to 3. [Figure 9] Cross-sectional view of the piezoelectric film laminate in the second embodiment. [Figure 10] Cross-sectional view of the piezoelectric film laminate in the third embodiment. [Figure 11] Cross-sectional view of the piezoelectric film laminate in the fourth embodiment. [Figure 12] Cross-sectional view of the piezoelectric film laminate in the fifth embodiment. [Figure 13] The figure showing the relationship between the surface roughness Ra of the base surface and the crystallinity in Examples 1 to 3, 5 and Comparative Examples 1 to 4. [Figure 14] Cross-sectional view of the piezoelectric film laminate in the sixth embodiment. [Figure 15] Cross-sectional view of the piezoelectric film laminate in the seventh embodiment. [Figure 16] Flowchart showing the manufacturing method of the piezoelectric film laminate in the eighth embodiment.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described based on the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals for description.

[0015] (First Embodiment) As shown in Figure 1, the piezoelectric film laminate 10 of this embodiment comprises a Si substrate 11, an AlN film 12, a Mo film 13, a SiN film 14, and a ScAlN film 15. These films are laminated.

[0016] The Si substrate 11 is a substrate mainly composed of Si, a semiconductor material. A substrate composed of semiconductor materials other than Si may also be used.

[0017] The AlN film 12 is placed on the upper side of the Si substrate 11, in contact with the surface of the Si substrate 11. The AlN film 12 is a film mainly composed of AlN. The AlN film 12 is used as a base material for the Mo film 13 to improve its crystallinity.

[0018] The Mo film 13 is positioned above the AlN film 12, in contact with the surface of the AlN film 12. In other words, the Mo film 13 is positioned below the SiN film 14, in contact with the SiN film 14. The side below the SiN film 14 is the opposite side of the SiN film 14 from the ScAlN film 15 side.

[0019] The Mo film 13 is a film mainly composed of Mo, a conductive material. The Mo film 13 is used as a lower electrode to enable the piezoelectric function of the ScAlN film 15. The Mo film 13 has a surface 13a that is in contact with the SiN film 14. Instead of the Mo film 13, a film composed of a conductive material other than Mo, such as a metallic material, may be used.

[0020] The SiN film 14 is positioned on the upper side of the Mo film 13, in contact with the surface 13a of the Mo film 13. The SiN film 14 is a base material for the ScAlN film 15 and is in the form of a film. The base material for the ScAlN film 15 is in contact with the ScAlN film 15 and supports it. The SiN film 14 is mainly composed of SiN, an amorphous insulating material.

[0021] Amorphous refers to a state of matter that does not have a crystalline structure, and is also called non-crystalline. The amorphous nature of a film's constituent material can be confirmed by performing electron diffraction measurements on the film. If the measurement result is a halo pattern, the film's constituent material is amorphous. In this specification, insulating properties refer to a state where the electrical resistivity (i.e., volume resistivity) is 10⁻¹⁰. 4 This means it is greater than or equal to Ω·m.

[0022] If the thickness of the insulating SiN film 14 becomes too thick, the overall piezoelectric properties of the composite film containing the ScAlN film 15 and the SiN film 14 will be impaired. Therefore, to prevent a significant impairment of the piezoelectric properties of this composite film, the thickness of the SiN film 14 is preferably 1 / 10 or less of the thickness of the ScAlN film 15, and more preferably 1 / 50 or less of the thickness of the ScAlN film 15. This makes it possible to suppress a decrease in the overall piezoelectric properties of the composite film containing the ScAlN film 15 and the SiN film 14.

[0023] The SiN film 14 has a surface (i.e., a base surface) 14a that is in contact with the ScAlN film 15. The surface roughness of the base surface 14a is 0.5 nm or less in terms of arithmetic mean roughness. The arithmetic mean roughness is defined in JIS B 0601. The surface roughness can be measured by scanning the surface using an atomic force microscope, a stylus-type surface roughness meter, etc. Also, if another film is formed on the surface to be measured, the surface roughness can be measured by performing cross-sectional observation with a transmission electron microscope and determining the shape of the interface to be measured.

[0024] The ScAlN film 15 is positioned above the SiN film 14, in contact with the underlying surface 14a of the SiN film 14. The ScAlN film 15 is a piezoelectric film mainly composed of ScAlN (i.e., scandium-containing aluminum nitride). The ScAlN film 15 has a surface 15a opposite to the SiN film 14 side.

[0025] The Sc concentration of the ScAlN film 15 may be greater than 0 atomic percent and less than or equal to 45 atomic percent. Sc concentration is the ratio of Sc atoms to the total amount of Sc atoms and Al atoms (100 atomic percent). Atomic percent refers to fractions of an atom. The Sc concentration is measured by RBS. RBS is an abbreviation for Rutherford Backscattering Spectrometry. The Sc concentrations shown in this specification are values ​​measured using the following apparatus under the following measurement conditions. Device name: Pelletron 3SDH, manufactured by National Electrostatics Corporation Measurement conditions RBS measurement Incident ion: 4He++ Incident energy: 2300 keV Incident angle: 0deg Scattering angle: 160deg Sample current: 13nA Beam diameter: 2mmφ In-plane rotation: None Irradiance: 70μC

[0026] Next, the manufacturing method of the piezoelectric film laminate 10 of this embodiment will be described. As shown in Figure 2, the manufacturing method of the piezoelectric film laminate 10 includes the steps of forming an AlN film 12 (S1), forming a Mo film 13 (S2), forming a SiN film 14 (S3), planarizing the SiN film 14 (S4), and forming a ScAlN film 15 (S5).

[0027] First, in the AlN film 12 formation step S1, the AlN film 12 is formed on the surface of the Si substrate 11 by reactive DC sputtering. Subsequently, the Mo film 13 formation step S2 is performed.

[0028] In step S2, the formation of the Mo film 13, the Mo film 13 is formed on the surface of the AlN film 12 by DC sputtering. Subsequently, step S3, the formation of the SiN film 14, is performed.

[0029] In the SiN film formation step S3, the SiN film 14 is formed on the upper side of the Mo film 13 in contact with the surface 13a of the Mo film 13 using plasma CVD. Subsequently, the SiN film 14 is planarized in step S4.

[0030] In the planarization step S4 of the SiN film 14, the underlying surface 14a of the SiN film 14 is planarized by etching using Ar plasma. At this time, the longer the etching time, the lower the surface roughness of the underlying surface 14a. The etching time is set so that the surface roughness of the underlying surface 14a is 0.5 nm or less in terms of arithmetic mean roughness. After planarizing the underlying surface 14a, the formation step S5 of the ScAlN film 15 is performed.

[0031] In step S5, the formation of the ScAlN film 15, the ScAlN film 15 is formed on the upper side of the SiN film 14 in contact with the substrate surface 14a using a reactive DC sputtering method. In this way, the piezoelectric film laminate 10 with the structure shown in Figure 1 is manufactured.

[0032] In this embodiment, the AlN film 12 formation step S1, the Mo film 13 formation step S2, and the SiN film 14 formation step S3 correspond to preparing the substrate material. The SiN film 14 planarization step S4 corresponds to planarizing the substrate surface. The ScAlN film 15 formation step S5 corresponds to forming the ScAlN film in contact with the substrate surface.

[0033] Furthermore, the surface of the Mo film 13 may be planarized after the Mo film 13 formation step S2 and before the SiN film 14 formation step S3. In this case as well, the SiN film 14 planarization step S4 is performed so that the surface roughness of the base surface 14a is ultimately 0.5 nm or less in terms of arithmetic mean roughness.

[0034] The ScAlN film 15 has a hexagonal crystal structure as shown in Figure 3, as well as a polycrystalline structure with multiple crystal grains. The piezoelectricity of the ScAlN film is high when many of the multiple crystal grains contain c-axis oriented crystal grains, in which the c-axis of the hexagonal crystal is oriented perpendicular to the surface 15a of the ScAlN film 15. On the other hand, the piezoelectricity of the ScAlN film 15 is low when many of the multiple crystal grains contain abnormal grains, in which the orientation of the c-axis of the hexagonal crystal is random. There is a relationship where the fewer abnormal grains present in the ScAlN film 15, the more c-axis oriented crystal grains present in the ScAlN film 15. Therefore, it is desirable to suppress the generation of abnormal grains in the ScAlN film 15.

[0035] As described below, the inventors have found that one of the factors causing the occurrence of abnormal grains is the surface roughness of the substrate surface 14a. They have also found that by forming a ScAlN film 15 in contact with the substrate surface 14a having a surface roughness of 0.5 nm or less, the occurrence of abnormal grains in the ScAlN film 15 can be suppressed.

[0036] Therefore, the piezoelectric film laminate 10 of this embodiment comprises a SiN film 14 having a base surface 14a, and a ScAlN film 15 disposed in contact with the base surface 14a. The surface roughness of the base surface 14a in contact with the ScAlN film 15 is 0.5 nm or less in terms of arithmetic mean roughness.

[0037] The method for manufacturing the piezoelectric film laminate 10 of this embodiment includes preparing a SiN film 14 having a base surface 14a, planarizing the base surface 14a, and forming a ScAlN film 15 in contact with the base surface 14a. In planarizing, the surface roughness of the base surface 14a is set to 0.5 nm or less in terms of arithmetic mean roughness.

[0038] According to these findings, the ScAlN film 15 is formed in contact with a substrate surface 14a having a surface roughness of 0.5 nm or less. This suppresses the generation of abnormal grains in the ScAlN film 15 compared to the case where the ScAlN film is formed in contact with a substrate surface having a surface roughness greater than 0.5 nm.

[0039] Furthermore, the piezoelectric film laminate 10 of this embodiment provides the following effects. The SiN film 14, which is the base material for the ScAlN film 15, is an amorphous insulating material.

[0040] Unlike this embodiment, when the Mo film 13 is used as a base material for the ScAlN film 15, that is, when the ScAlN film 15 is formed in contact with the surface 13a of the Mo film 13, abnormal grains are likely to occur in the ScAlN film 15. The following reasons are considered to be for this.

[0041] Generally, Mo films formed on the surface of an AlN film tend to be (101) oriented. That is, the plane direction parallel to the surface of a Mo film formed on the surface of an AlN film tends to be the (101) plane. In this case, the symmetry of the atomic arrangement of Mo in the plane direction parallel to the surface 13a of the Mo film 13 approximates the symmetry of the atomic arrangement of ScAlN in the plane direction parallel to the surface 15a of the ScAlN film 15 when the c-axis of the hexagonal crystal is perpendicular to the surface 15a of the ScAlN film 15 and multiple crystal grains are oriented. In addition, the lattice constant of Mo does not match the lattice constant of ScAlN by a range of a few percent. Therefore, when the ScAlN film 15 is formed, undesirable strain, i.e., stress, is generated in the ScAlN film 15. These are considered to be the causes of the occurrence of abnormal grains in the above case.

[0042] In contrast, according to this embodiment, the atomic arrangement of SiN in the plane direction parallel to the substrate surface 14a of the SiN film 14 is different from the atomic arrangement of ScAlN in the plane direction parallel to the surface 15a of the ScAlN film 15 when the above-mentioned plurality of crystal grains are oriented. Therefore, the symmetry of the atomic arrangement in the plane direction parallel to the substrate surface 14a is the same as the symmetry of the atomic arrangement in the plane direction parallel to the surface 15a of the ScAlN film 15, and the generation of abnormal grains caused by the mismatch between the lattice constant of the substrate material and the lattice constant of ScAlN can be avoided. Thus, the generation of abnormal grains in the ScAlN film 15 can also be suppressed by the substrate material being an amorphous insulating material.

[0043] Here, the experimental results obtained by the inventors will be described. The inventors manufactured the piezoelectric film laminates 10 of Examples 1 to 3 using the manufacturing method described above. Furthermore, the inventors manufactured the piezoelectric film laminates 10 of Comparative Examples 1 to 3 by changing the conditions of the planarization step S4 of the SiN film 14 compared to the manufacturing method described above. The inventors then measured the surface roughness Ra of the underlying surface of the SiN film 14, and the crystallinity, piezoelectric performance, and tanδ of the ScAlN film 15 in each of the piezoelectric film laminates 10 of Examples 1 to 3 and Comparative Examples 1 to 3.

[0044] The manufacturing conditions for the piezoelectric film laminates 10 of Examples 1-3 and Comparative Examples 1-3 are as follows.

[0045] [Process for forming SiN film 14] Equipment: Parallel plate type RF plasma device Introduced gases: SiH4, NH3, N2 Gas pressure: 5 Tor RF power: 300W Substrate temperature: 330℃

[0046] [Planarization process of SiN film 14] Equipment: Parallel plate type RF plasma device Introduced gas: Ar, RF power: 50W Etching time: 0-200 sec

[0047] [Etching time and surface roughness Ra in the planarization process of SiN film 14] In Example 1, the etching time was 200 sec and the surface roughness Ra was 0.29 nm. In Example 2, the etching time was 90 sec and the surface roughness Ra was 0.44 nm. In Example 3, the etching time was 40 sec and the surface roughness Ra was 0.51 nm. In Comparative Example 1, the etching time was 30 sec and the surface roughness Ra was 0.57 nm. In Comparative Example 2, the etching time was 23 sec and the surface roughness Ra was 0.71 nm. In Comparative Example 3, the etching time was 0 sec and the surface roughness Ra was 1.01 nm.

[0048] [ScAlN film 15 formation process] Target type: ScAl target, Sc concentration 40% Target size: 300mm in diameter Distance between Si substrate and target: 60 mm DC Power: 8kW Gas flow rates: N2: 26 sccm, Ar: 19 sccm Gas pressure: 0.3 Pa Si substrate temperature: 335℃ Board RF bias power: 20W The inventors measured the Sc concentration of the ScAlN films using RBS, and found that the Sc concentration of each of the ScAlN films in Examples 1-3 and Comparative Examples 1-3 was 40%.

[0049] [Thickness of each film] AlN film thickness 12: 30 nm Mo film thickness 13: 25 nm Thickness of SiN film 14: 10-30 nm Film thickness of ScAlN film 15: 500 nm Examples 1-3 and Comparative Examples 1-3 have different film thicknesses of the SiN film 14. This is because the etching times are different.

[0050] Figure 4 is a graph showing the relationship between the surface roughness Ra of the substrate surface 14a and the crystallinity of the ScAlN film 15. The vertical axis of Figure 4 represents the peak height and full width at half maximum of the rocking curve for the X-ray diffraction peak of the (0002) plane of the ScAlN crystal, measured by an X-ray diffractometer. The horizontal axis of Figure 4 represents the surface roughness Ra of the substrate surface 14a.

[0051] In Figure 4, A1 to A3 represent the results for Examples 1 to 3, respectively. B1 to B3 represent the results for Comparative Examples 1 to 3, respectively. The larger the peak intensity value and the smaller the full width at half maximum value, the better the crystallinity of ScAlN. "Good crystallinity of ScAlN" means that the ScAlN film 15 contains few abnormal grains and many c-axis oriented crystal grains. In other words, it means that the crystal structure of ScAlN is a highly oriented crystal structure in which the hexagonal c-axis is oriented perpendicular to the surface 15a of the ScAlN film 15.

[0052] Figure 4 shows that as the surface roughness Ra decreases, the peak intensity tends to increase and the full width at half maximum tends to decrease, meaning that the crystallinity tends to improve. In particular, when the surface roughness Ra changes from 0.57 in B1 to 0.51 in A3, the crystallinity improves dramatically. Rounding 0.51 to two decimal places gives 0.5, and rounding 0.57 to two decimal places gives 0.6. From these findings, it can be concluded that when the surface roughness Ra of the substrate surface is 0.5 or less, a ScAlN film 15 with better crystallinity can be obtained than when the surface roughness Ra of the substrate surface is greater than 0.5.

[0053] The surface roughness Ra of the substrate surfaces 14a in Examples 1 to 3 falls within the range of 0.5 nm or less. The surface roughness Ra of the substrate surfaces 14a in Comparative Examples 1 to 3 falls within the range of greater than 0.5 nm.

[0054] Figures 5A to 5C are SEM images of the ScAlN films 15 of Examples 1 to 3, respectively. Figures 5D and 5E are SEM images of the ScAlN films 15 of Comparative Examples 1 and 2, respectively. SEM images are images acquired by a scanning electron microscope. The multiple small fragments present in each figure are abnormal grains. From Figures 5A to 5E, it was confirmed that the number of abnormal grains in the ScAlN films 15 of Examples 1 to 3 was less than that in the ScAlN films 15 of Comparative Examples 1 and 2.

[0055] Figure 6 is a graph showing the relationship between the surface roughness Ra of the substrate surface 14a and the piezoelectric performance of the ScAlN film 15. The vertical axis of Figure 6 represents the piezoelectric constant d33. A larger value for the piezoelectric constant d33 is desirable. From Figure 6, it was confirmed that the piezoelectric constant d33 of the ScAlN films 15 in Examples 1 to 3 was larger than that of the ScAlN films 15 in Comparative Examples 1 to 3.

[0056] Figure 7 is a graph showing the relationship between the surface roughness Ra of the substrate surface 14a and the tanδ of the ScAlN film 15. A small tanδ value is desirable. From Figure 7, it was confirmed that the tanδ of the ScAlN film 15 in Examples 1-3 was smaller than that of the ScAlN film 15 in Comparative Examples 1-3.

[0057] Furthermore, the inventors manufactured the piezoelectric film laminate 10 of Example 4. In Example 4, the Sc concentration of the ScAlN film 15 is 24%. The surface roughness Ra of the underlying surface 14a of the SiN film 14 is 0.25 nm. The other manufacturing conditions for the piezoelectric film laminate 10 are the same as in Examples 1 to 3.

[0058] Then, the inventors measured the crystallinity of the ScAlN film 15 of Example 4, similar to Examples 1-3. Figure 8 shows the measurement results of surface roughness Ra and crystallinity of Example 4, added to the graphs of Examples 1-3 and Comparative Examples 1-3. A4 in Figure 8 is the measurement result for Example 4. The surface roughness Ra of the substrate surface 14a of Example 4 is 0.5 nm or less. From Figure 8, it was confirmed that in Example 4 as well, the relationship that crystallinity is good when the Ra of the substrate surface is 0.5 or less is satisfied.

[0059] The results from Examples 1-4 confirmed that when the Sc concentration of the ScAlN film 15 is between 24 atomic% and 40 atomic%, the occurrence of abnormal grains in the ScAlN film 15 can be suppressed when the surface roughness Ra of the substrate surface 14a is 0.5 nm or less, compared to when the surface roughness Ra is greater than 0.5 nm. It is believed that a similar effect can be obtained not only in this case, but also when the Sc concentration is less than 24 atomic%.

[0060] However, unlike the manufacturing method of the piezoelectric film laminate 10 in this embodiment, it has been found that abnormal grains are likely to occur, especially when the Sc concentration is high, such as 24 atomic percent or more, if the substrate surface 14a is not flattened. For this reason, as shown in the experimental results above, it is particularly effective to have a surface roughness Ra of 0.5 nm or less when the Sc concentration is 24 atomic percent or more.

[0061] In this embodiment, a SiN film 14 is used as the base material for the ScAlN film 15, but a film made of an amorphous insulating material other than SiN may also be used. Examples of amorphous insulating materials other than SiN include SiO2. A film made of amorphous SiO2 is formed by depositing it on a conductive material such as a Mo film 13.

[0062] (Second Embodiment) As shown in Figure 9, in the piezoelectric film laminate 10A of this embodiment, an AlN film 21 is used as the base material for the ScAlN film 15 instead of the SiN film 14 of the first embodiment. This AlN film 21 is a film mainly composed of AlN. The AlN constituting this AlN film 21 is a polycrystalline material containing multiple crystal grains, and each of the multiple crystal grains has an unoriented structure, making it an insulating material. "Unoriented" means that the orientation distribution of each of the multiple crystal grains is uniform. In actual measurements, "unoriented" means that when the rocking curve for an arbitrary crystal plane is measured in X-ray diffraction, no peak is shown. In the measurement of the rocking curve, the horizontal axis is the angle ω of the sample with respect to the incident X-ray, and the vertical axis is the diffraction intensity. Not showing a peak means that the diffraction intensity is approximately constant with respect to the change in ω.

[0063] The AlN film 21 has a surface (i.e., a base surface) 21a that is in contact with the ScAlN film 15. The surface roughness of the base surface 21a is 0.5 nm or less in terms of arithmetic mean roughness, as in the first embodiment. The other components of the piezoelectric film laminate 10A are the same as in the first embodiment.

[0064] The method for manufacturing the piezoelectric film laminate 10A in this embodiment is the same as the method for manufacturing the piezoelectric film laminate 10 in the first embodiment, except that an AlN film 21 is used instead of a SiN film 14. The AlN film 21 is formed by sputtering under conditions that result in multiple crystal grains being unoriented.

[0065] According to this embodiment, the same effects as in the first embodiment are achieved by making the surface roughness of the substrate surface 21a 0.5 nm or less in terms of arithmetic mean roughness. Furthermore, the piezoelectric film laminate 10A of this embodiment provides the following effects.

[0066] The AlN film 21, which is the base material for the ScAlN film 15, is a polycrystalline film of insulating material containing multiple crystal grains, each of which has an unoriented structure. As a result, the atomic arrangement of the AlN film 21 in the plane direction parallel to the base surface 21a is different from the atomic arrangement of ScAlN in the plane direction parallel to the surface 15a of the ScAlN film 15 when multiple crystal grains are oriented, because the orientation of the hexagonal c-axis is perpendicular to the surface 15a of the ScAlN film 15. Therefore, similar to the first embodiment, the symmetry of the atomic arrangement is the same, and the generation of abnormal grains caused by the lattice constant of the base material not matching the lattice constant of ScAlN can be avoided.

[0067] In this embodiment, an AlN film 21 is used as the base material for the ScAlN film 15. However, as the base material for the ScAlN film 15, an insulating material other than the AlN film 21 may be used, which is a polycrystalline material containing multiple crystal grains, and each of the multiple crystal grains has an unoriented structure.

[0068] (Third embodiment) As shown in Figure 10, in the piezoelectric film laminate 10B of this embodiment, a MoO3 film 22 is used as the base material for the ScAlN film 15 instead of the SiN film 14 of the first embodiment. The MoO3 film 22 is a film mainly composed of MoO3 (i.e., molybdenum oxide). The MoO3 constituting the MoO3 film 22 is an insulating material having an orthorhombic crystal structure. The MoO3 film 22 may be polycrystalline or single-crystal.

[0069] The MoO3 film 22 has a surface (i.e., a base surface) 22a that is in contact with the ScAlN film 15. The surface roughness of the base surface 22a is 0.5 nm or less in terms of arithmetic mean roughness, as in the first embodiment. The other components of the piezoelectric film laminate 10B are the same as in the first embodiment.

[0070] The method for manufacturing the piezoelectric film laminate 10B in this embodiment is the same as the method for manufacturing the piezoelectric film laminate 10 in the first embodiment, except that a MoO3 film 22 is used instead of a SiN film 14.

[0071] According to this embodiment, the same effects as in the first embodiment are achieved by making the surface roughness of the substrate surface 22a 0.5 nm or less in terms of arithmetic mean roughness. Furthermore, the piezoelectric film laminate 10B of this embodiment provides the following effects.

[0072] When the c-axis of the hexagonal crystal is oriented perpendicular to the surface 15a of the ScAlN film 15, and multiple crystal grains are oriented, the crystal plane in the plane parallel to the surface 15a of the ScAlN film 15 is the (0001) plane. In this case, the atomic arrangement of ScAlN in the plane parallel to the surface 15a of the ScAlN film 15 is 6-fold rotationally symmetric. Therefore, unlike in this embodiment, when the substrate material of the ScAlN film 15 has a hexagonal crystal structure, and the c-axis of the hexagonal crystal is oriented perpendicular to the surface 15a of the ScAlN film 15, and multiple crystal grains are oriented, abnormal grains are generated due to a mismatch in lattice constants, as described in the first embodiment.

[0073] Furthermore, unlike this embodiment, if the substrate material has a cubic crystal structure, and the crystal plane in the plane direction parallel to the surface of the substrate material in contact with the ScAlN film 15 is the (111) plane, then the atomic arrangement in the plane direction parallel to the surface of the substrate material is 6-fold rotational symmetry, or an arrangement that is pseudo-6-fold rotational symmetry. As a result, abnormal grains are generated due to the aforementioned mismatch in lattice constants.

[0074] In contrast, according to this embodiment, the MoO3 film 22, which is the base material for the ScAlN film 15, is a film made of an insulating material having a crystal structure that is neither hexagonal nor cubic. Therefore, it is possible to avoid the generation of abnormal grains caused by mismatches in lattice constants that can occur when the base material for the ScAlN film 15 has a hexagonal or cubic crystal structure.

[0075] In this embodiment, a MoO3 film 22 is used as the underlayment for the ScAlN film 15. However, as the underlayment for the ScAlN film 15, an insulating material other than the MoO3 film 22, which has a crystal structure that is neither hexagonal nor cubic, may be used.

[0076] (Fourth Embodiment) As shown in Figure 11, in the piezoelectric film laminate 10C of this embodiment, a BN film 23 is used as the base material for the ScAlN film 15 instead of the SiN film 14 of the first embodiment. The BN film 23 is a film mainly composed of BN (i.e., boron nitride). The BN film 23 has a surface (i.e., base surface) 23a that is in contact with the ScAlN film 15. The surface roughness of the base surface 23a is 0.5 nm or less in terms of arithmetic mean roughness, similar to the first embodiment.

[0077] The BN constituting the BN film 23 is an insulating material having a hexagonal crystal structure as well as a polycrystalline structure with multiple crystal grains. The multiple crystal grains include crystal grains whose crystal axes are oriented in a specific direction. The orientation of the c-axis of the oriented crystal grains is not perpendicular to the substrate surface 23a. In other words, the BN constituting the BN film 23 has a structure that excludes the structure in which the c-axis of the hexagonal crystal is oriented perpendicular to the substrate surface 23a.

[0078] The BN constituting the BN film 23 may have a single-crystal structure. In this case as well, the BN film 23 has a structure other than one in which the orientation of the hexagonal c-axis is perpendicular to the substrate surface 23a. That is, the crystal planes of the BN film 23 in the plane direction parallel to the substrate surface 23a are not c-planes.

[0079] The other components of the piezoelectric film laminate 10C are the same as those of the first embodiment. The method for manufacturing the piezoelectric film laminate 10C in this embodiment is the same as the method for manufacturing the piezoelectric film laminate 10 in the first embodiment, except that a BN film 23 is used instead of a SiN film 14.

[0080] According to this embodiment, the same effects as in the first embodiment are achieved by making the surface roughness of the substrate surface 23a 0.5 nm or less in terms of arithmetic mean roughness. Furthermore, the piezoelectric film laminate 10C of this embodiment provides the following effects.

[0081] When the substrate material for the ScAlN film 15 has a hexagonal crystal structure, as described in the first embodiment, when the orientation of the c-axis of the hexagonal crystal is perpendicular to the surface 15a of the ScAlN film 15, abnormal grains are generated due to a mismatch in lattice constants.

[0082] In contrast, the BN film 23, which is the base material for the ScAlN film 15, is a film made of an insulating material that has a hexagonal crystal structure, and has a structure that excludes structures in which the c-axis of the hexagonal crystal is oriented perpendicular to the base surface 23a. Therefore, it is possible to avoid the generation of abnormal grains due to mismatch in lattice constants that may occur when the base material for the ScAlN film 15 has a hexagonal crystal structure. Note that, as the base material for the ScAlN film 15, an insulating material other than the BN film 23 may be used, which has a hexagonal crystal structure, and has a structure that excludes structures in which the c-axis of the hexagonal crystal is oriented perpendicular to the base surface 23a.

[0083] Furthermore, instead of the BN film 23 in this embodiment, a SiC film may be used as the base material for the ScAlN film 15. The SiC film is a film mainly composed of SiC (i.e., silicon carbide). The SiC film has a surface that is in contact with the ScAlN film 15 (i.e., a base surface). In this case as well, the same effects as in the first embodiment can be obtained if the surface roughness of the base surface is 0.5 nm or less in terms of arithmetic mean roughness.

[0084] In this case, the SiC constituting the SiC film is an insulating material having a cubic crystal structure as well as a polycrystalline structure with multiple crystal grains. These multiple crystal grains include crystal grains whose crystal axes are oriented in a specific direction. The orientation of the <111> axis of the cubic crystal of the oriented crystal grains is such that it is aligned with the substrate surface. on In contrast, the orientation is not perpendicular. That is, the SiC that makes up the SiC film has a structure in which the orientation of the <111> axis of the cubic crystal is perpendicular to the substrate surface.

[0085] The SiC constituting the SiC film may have a single-crystal structure. In this case as well, the SiC constituting the SiC film has a structure other than one in which the orientation of the <111> axis of the cubic crystal is perpendicular to the substrate surface. That is, the crystal planes in the plane direction parallel to the substrate surface of the SiC film are not (111) planes.

[0086] According to this, it is possible to avoid the generation of abnormal grains due to mismatch in lattice constants that can occur when the substrate material has a cubic crystal structure, as described in the third embodiment. In addition, as the substrate material for the ScAlN film 15, a film may be used that is an insulating material other than a SiC film, which has a cubic crystal structure and a structure other than one in which the orientation of the <111> axis of the cubic crystal is perpendicular to the substrate surface.

[0087] (Fifth embodiment) As shown in Figure 12, in the piezoelectric film laminate 10D of this embodiment, a polySi film 24 is used as the base material for the ScAlN film 15 instead of the SiN film 14 of the first embodiment. The polySi film 24 is placed on the upper side of the Si substrate 11 in contact with the surface of the Si substrate 11.

[0088] The polySi film 24 is a film mainly composed of polySi (i.e., polycrystalline silicon), which is a conductive material. The polySi film 24 is used as a lower electrode to enable the piezoelectric function of the ScAlN film 15. The polySi constituting the polySi film 24 has a polycrystalline structure containing multiple crystal grains. Each of the multiple crystal grains is unoriented. Phosphorus or boron may be added to the polySi constituting the polySi film 24. The addition of these enhances conductivity and improves its function as a lower electrode.

[0089] The polySi film 24 has a surface (i.e., a base surface) 24a that is in contact with the ScAlN film 15. The surface roughness of the base surface 24a is 0.5 nm or less in terms of arithmetic mean roughness. The other components of the piezoelectric film laminate 10D are the same as in the first embodiment.

[0090] The manufacturing method for the piezoelectric film laminate 10D of this embodiment includes a step of forming a polySi film 24, a step of planarizing the polySi film 24, and a step of forming a ScAlN film 15. First, in the step of forming the polySi film 24, the polySi film 24 is formed on the surface of the Si substrate 11 using a thermal CVD apparatus. Then, the polySi film 24 is planarized. In the polySi film 24 planarization step, the underlying surface 24a of the polySi film 24 is planarized. At this time, the surface roughness of the underlying surface 24a is made to be 0.5 nm or less in terms of arithmetic mean roughness by the same method as in the planarization step S4 of the SiN film 14 of the first embodiment. Then, the ScAlN film 15 is formed. The ScAlN film 15 formation step is the same as in the first embodiment.

[0091] According to this embodiment, the same effects as in the first embodiment are achieved by making the surface roughness of the substrate surface 24a 0.5 nm or less in terms of arithmetic mean roughness. Furthermore, the piezoelectric film laminate 10D of this embodiment provides the following effects.

[0092] The polySi film 24, which is the base material for the ScAlN film 15, is a polycrystalline material containing multiple crystal grains, each of which has an unoriented structure. conductive This is a film of a material. According to this, the atomic arrangement of the polySi film 24 in the plane direction parallel to the substrate surface 24a is different from the atomic arrangement of ScAlN in the plane direction parallel to the surface 15a of the ScAlN film 15 when the orientation of the hexagonal c-axis is perpendicular to the surface 15a of the ScAlN film 15 and multiple crystal grains are oriented. Therefore, similar to the first embodiment, the symmetry of the atomic arrangement is the same, and the generation of abnormal grains caused by the mismatch between the lattice constant of the substrate material and the lattice constant of ScAlN can be avoided.

[0093] The inventors manufactured the piezoelectric film laminate 10D of Example 5 using the manufacturing method described above. Furthermore, the piezoelectric film laminate of Comparative Example 4 was manufactured by changing the conditions of the planarization step of the polySi film 24 compared to the manufacturing method described above. The surface roughness Ra of the base surface 24a of the polySi film 24 was 0.45 nm for Example 5 and 1.14 nm for Comparative Example 4. The formation conditions for the ScAlN film 15 were the same as in Examples 1 to 3. The Sc concentration of the ScAlN film 15 was 40 atomic percent for both Example 5 and Comparative Example 4. The thickness of each formed film was 70 nm for the polySi film 24 and 500 nm for the ScAlN film 15.

[0094] Then, similar to Examples 1-3, the inventors measured the surface roughness Ra of the base surface 24a of the polySi film 24 and the crystallinity of the ScAlN film 15 for Example 5 and Comparative Example 4, respectively. Figure 13 shows the measurement results of surface roughness Ra and crystallinity for Example 5 and Comparative Example 4, added to the graphs of Examples 1-3 and Comparative Examples 1-3 shown in Figure 4. A5 in Figure 13 is the measurement result for Example 5. B4 in Figure 13 is the measurement result for Comparative Example 4. The surface roughness Ra of the base surface 24a in Example 5 is 0.5 nm or less. From Figure 13, it was confirmed that in Example 5 as well, the relationship that crystallinity is good when the surface roughness Ra of the base surface is 0.5 nm or less is satisfied.

[0095] In this embodiment, the polySi film 24 is positioned on the upper side of the Si substrate 11, in contact with the surface of the Si substrate 11. However, this is not limited to this case, and an insulating film made of SiO2 or the like may be interposed between the Si substrate 11 and the polySi film 24.

[0096] In this embodiment, a polySi film 24 is used as the underlayment for the ScAlN film 15. However, the invention is not limited to this case, and a conductive material other than the polySi film 24 may be used as the underlayment for the ScAlN film 15, which is a polycrystalline material containing multiple crystal grains, and in which the multiple crystal grains have an unoriented structure.

[0097] (Sixth Embodiment) As shown in Figure 14, in the piezoelectric film laminate 10E of this embodiment, an a-Mo film 25 is used as the underlayment for the ScAlN film 15 instead of the SiN film 14 of the first embodiment. The a-Mo film 25 is placed on top of the Mo film 13 and in contact with the surface 13a of the Mo film 13. The Mo film 13 is placed on top of the Si substrate 11 and in contact with the surface of the Si substrate 11, but as in the first embodiment, it may also be placed on top of the AlN film 12 and in contact with the AlN film 12. The Si substrate 11, Mo film 13, and ScAlN film 15 are the same as in the first embodiment.

[0098] The a-Mo film 25 is a film mainly composed of amorphous Mo, which is a conductive material. In this specification, conductivity means that the electrical resistivity (i.e., volume resistivity) is 10 -2 This means that the density is Ω·m or less. The a-Mo film 25 is used as a lower electrode together with the Mo film 13. The a-Mo film 25 has a surface (i.e., a base surface) 25a that is in contact with the ScAlN film 15. The surface roughness of the base surface 25a is 0.5 nm or less in terms of arithmetic mean roughness, as in the first embodiment.

[0099] The manufacturing method of the piezoelectric film laminate 10E of this embodiment includes a step of forming a Mo film 13, a step of forming an a-Mo film 25, a step of planarizing the a-Mo film 25, and a step of forming a ScAlN film 15. First, in the step of forming the Mo film 13, the Mo film 13 is formed on the surface of the Si substrate 11 in the same manner as in the Mo film 13 formation step S2 of the first embodiment. Then, the step of forming the a-Mo film 25 is performed. In the step of forming the a-Mo film 25, the a-Mo film 25 is formed by ion implantation or plasma treatment of the Mo film 13.

[0100] In ion implantation of the Mo film 13, metal ions, rare gas ions, etc., are used as ion implantation species. By applying an energy of several tens to 100 keV to the surface layer of the Mo film 13, an a-Mo film 25 with a thickness of several tens to 100 nm can be formed. By using metal ions, rare gas ions, etc., as ion implantation species, the conductivity of the ion-implanted Mo can be maintained.

[0101] Plasma treatment of the Mo film 13 is performed using a chamber configuration commonly used for dry etching (i.e., a layout in which the substrate and counter electrode are arranged in parallel). In this chamber configuration, plasma is generated by high-frequency discharge, similar to a normal dry etching process. At this time, by introducing only Ar gas as the material gas, etching of the Mo film 13 is minimized, and amorphous formation of the surface layer of the Mo film 13 becomes possible.

[0102] Subsequently, a planarization step of the a-Mo film 25 is performed. In the planarization step of the a-Mo film 25, the underlying surface 25a of the a-Mo film 25 is planarized. At this time, the surface roughness of the underlying surface 25a is made 0.5 nm or less in terms of arithmetic mean roughness by the same method as in the planarization step S4 of the SiN film 14 in the first embodiment. Subsequently, a ScAlN film 15 formation step is performed. The formation step of the ScAlN film 15 is the same as in the first embodiment. Note that instead of the planarization step of the a-Mo film 25, a planarization step of the Mo film 13 may be performed. In this case, the formation step of the Mo film 13, the planarization step of the Mo film 13, and the formation step of the a-Mo film 25 are performed in this order. In the planarization step of the Mo film 13, similar to the eighth embodiment described later, the surface roughness of the Mo film 13 is made 0.5 nm or less in terms of arithmetic mean roughness, thereby making the surface roughness of the a-Mo film 25 formed in the subsequent a-Mo film 25 formation step 0.5 nm or less in terms of arithmetic mean roughness.

[0103] According to this embodiment, the same effects as in the first embodiment are achieved by making the surface roughness of the substrate surface 25a 0.5 nm or less in terms of arithmetic mean roughness. Furthermore, the piezoelectric film laminate 10E of this embodiment provides the following effects.

[0104] The a-Mo film 25, which is the underlayment for the ScAlN film 15, is a film of amorphous conductive material. According to this, the atomic arrangement of the a-Mo film 25 in the plane direction parallel to the underlayment surface 25a differs from the atomic arrangement of ScAlN in the plane direction parallel to the surface 15a of the ScAlN film 15 when multiple crystal grains are oriented, with the orientation of the hexagonal c-axis perpendicular to the surface 15a of the ScAlN film 15. Therefore, similar to the first embodiment, the symmetry of the atomic arrangement is the same, and the generation of abnormal grains caused by a mismatch between the lattice constant of the underlayment and the lattice constant of ScAlN can be avoided.

[0105] In the piezoelectric film laminate 10E of this embodiment, an a-Mo film 25 is used as the underlayment for the ScAlN film 15. However, other amorphous conductive materials may be used as the underlayment for the ScAlN film 15. Examples of other amorphous conductive materials include conductive metal oxides and conductive metal nitrides. Examples of conductive metal oxides include Ru oxide and ITO. ITO is an abbreviation for Indium Tin Oxide.

[0106] (Seventh Embodiment) As shown in Figure 15, in the piezoelectric film laminate 10F of this embodiment, a Ru film 26 is used as the base material for the ScAlN film 15 instead of the SiN film 14 of the first embodiment. The Ru film 26 is placed on the upper side of the Si substrate 11 in contact with the surface of the Si substrate 11. The Ru film 26 has a surface (i.e., a base surface) 26a that is in contact with the ScAlN film 15. The surface roughness of the base surface 26a is 0.5 nm or less in terms of arithmetic mean roughness, similar to the first embodiment.

[0107] The Ru film 26 is a film mainly composed of Ru (i.e., ruthenium), a conductive material. The Ru film 26 is used as a lower electrode to enable the piezoelectric function of the ScAlN film 15. The Ru constituting the Ru film 26 has a hexagonal crystal structure as well as a polycrystalline structure with multiple crystal grains. Among the multiple crystal grains are crystal grains whose crystal axes are oriented in a specific direction. The orientation of the c-axis of the oriented crystal grains is not perpendicular to the substrate surface 26a. In other words, the Ru film 26 has a structure that excludes the structure in which the c-axis of the hexagonal crystal is oriented perpendicular to the substrate surface 26a.

[0108] The Ru constituting the Ru film 26 may have a single-crystal structure. In this case as well, the Ru film 26 has a structure other than one in which the orientation of the hexagonal c-axis is perpendicular to the underlying surface 26a. That is, the crystal planes of the Ru film 26 in the plane direction parallel to the underlying surface 26a are not c-planes.

[0109] The manufacturing method of the piezoelectric film laminate 10F of this embodiment includes a step of forming a Ru film 26, a step of planarizing the Ru film 26, and a step of forming a ScAlN film 15. First, in the step of forming the Ru film 26, the Ru film 26 is formed on the surface of the Si substrate 11. Then, the Ru film 26 is planarized. In the Ru film 26 planarization step, the underlying surface 26a of the Ru film 26 is planarized. At this time, the surface roughness of the underlying surface 26a is made to be 0.5 nm or less in terms of arithmetic mean roughness by the same method as in the planarization step S4 of the SiN film 14 of the first embodiment. Then, the ScAlN film 15 is formed. The ScAlN film 15 formation step is the same as in the first embodiment.

[0110] According to this embodiment, similar to the first embodiment, the substrate surface 2 6 The effect obtained by making the surface roughness of a 0.5 nm or less in terms of arithmetic mean roughness. Furthermore, the piezoelectric film laminate 10 of this embodiment F According to the report, it produces the following effects.

[0111] When the substrate material for the ScAlN film 15 has a hexagonal crystal structure, as described in the first embodiment, when the orientation of the c-axis of the hexagonal crystal is perpendicular to the surface 15a of the ScAlN film 15, abnormal grains are generated due to a mismatch in lattice constants.

[0112] In contrast, the Ru film 26, which is the base material for the ScAlN film 15, has a hexagonal crystal structure, and its structure excludes structures where the c-axis of the hexagon is oriented perpendicular to the base surface 26a. Therefore, it is possible to avoid the generation of abnormal grains due to lattice constant mismatch that can occur when the base material for the ScAlN film 15 has a hexagonal crystal structure. Alternatively, a conductive material other than the Ru film 26 may be used as the base material for the ScAlN film 15, which has a hexagonal crystal structure, and its structure excludes structures where the c-axis of the hexagon is oriented perpendicular to the base surface 26a.

[0113] Furthermore, instead of the Ru film 26 in this embodiment, a Mo film may be used as the base material for the ScAlN film 15. The Mo film is a film mainly composed of Mo (i.e., molybdenum). The Mo film has a surface that is in contact with the ScAlN film 15 (i.e., a base surface). In this case as well, the same effects as in the first embodiment can be obtained if the surface roughness of the base surface is 0.5 nm or less in terms of arithmetic mean roughness.

[0114] In this case, the Mo constituting the Mo film is a conductive material having a body-centered cubic crystal structure and a polycrystalline structure with multiple crystal grains. The multiple crystal grains include crystal grains whose crystal axes are oriented in a specific direction. The orientation of the <101> axis of the oriented crystal grains is such that it is aligned with the substrate surface. on In contrast, the orientation is not perpendicular. That is, the Mo constituting the Mo film has a structure other than one in which the orientation of the <101> axis of the body-centered cubic crystal is perpendicular to the substrate surface. The Mo constituting the Mo film may also have a single crystal structure. In this case as well, the Mo constituting the Mo film has a structure other than one in which the orientation of the <101> axis of the body-centered cubic crystal is perpendicular to the substrate surface. That is, the crystal planes in the plane direction parallel to the substrate surface of the Mo film are not (101) planes.

[0115] When the substrate material has a body-centered cubic crystal structure, and the orientation of the <101> axis of the body-centered cubic crystal is perpendicular to the substrate surface, the atomic arrangement in the plane parallel to the surface of the substrate material is 6-fold rotational symmetry, or at least close to 6-fold rotational symmetry. As a result, abnormal grains are generated due to the aforementioned mismatch in lattice constants.

[0116] In contrast, the above-mentioned Mo film has a body-centered cubic crystal structure, and the orientation of the <101> axis of the body-centered cubic crystal is aligned with the substrate surface. on In contrast, this structure excludes structures oriented perpendicular to the surface. Therefore, it is possible to avoid the generation of abnormal grains due to lattice constant mismatch that can occur when the substrate material for the ScAlN film 15 has a body-centered cubic crystal structure. The substrate material for the ScAlN film 15 is a conductive material other than a Mo film, which has a body-centered cubic crystal structure, and the orientation of the <101> axis of the body-centered cubic crystal is such that it is not aligned with the surface of the substrate. on Alternatively, a film made of a conductive material having a structure that excludes vertically oriented structures may be used.

[0117] Furthermore, instead of the Ru film 26 in this embodiment, a Pt film may be used as the underlayment for the ScAlN film 15. The Pt film is a film mainly composed of Pt (i.e., platinum). The Pt film has a surface that is in contact with the ScAlN film 15 (i.e., an underlayment surface). In this case as well, the same effects as in the first embodiment can be obtained if the surface roughness of the underlayment surface is 0.5 nm or less in terms of arithmetic mean roughness.

[0118] In this case, the Pt constituting the Pt film is a conductive material having a face-centered cubic crystal structure as well as a polycrystalline structure with multiple crystal grains. The multiple crystal grains include crystal grains whose crystal axes are oriented in a specific direction. The orientation of the <111> axis of the oriented crystal grains is not perpendicular to the substrate surface. In other words, the Pt constituting the Pt film has a structure that excludes the structure in which the orientation of the <111> axis is perpendicular to the substrate surface.

[0119] The Pt constituting the Pt film may have a single-crystal structure. In this case as well, the Pt constituting the Pt film has a structure other than one in which the orientation of the face-centered cubic <111> axis is perpendicular to the substrate surface. That is, the crystal planes in the plane direction parallel to the substrate surface of the Pt film are not (111) planes.

[0120] When the substrate material has a face-centered cubic crystal structure, and the orientation of the <111> axis of the face-centered cubic crystal is perpendicular to the substrate surface, the atomic arrangement in the plane parallel to the surface of the substrate material is 6-fold rotational symmetry, or at least close to 6-fold rotational symmetry. As a result, the aforementioned mismatch in lattice constants leads to the generation of abnormal grains.

[0121] In contrast, the above-mentioned Pt film has a face-centered cubic crystal structure, and its structure excludes structures in which the orientation of the <111> axis of the face-centered cubic crystal is perpendicular to the substrate surface 26a. Therefore, it is possible to avoid the generation of abnormal grains due to lattice constant mismatch that may occur when the substrate material of the ScAlN film 15 has a face-centered cubic crystal structure. Alternatively, a film may be used as the substrate material for the ScAlN film 15, which is a conductive material other than the Pt film, and which has a face-centered cubic crystal structure, and its structure excludes structures in which the orientation of the <111> axis of the face-centered cubic crystal is perpendicular to the substrate surface 26a.

[0122] (Eighth embodiment) In this embodiment, the method for manufacturing the piezoelectric film laminate 10 includes, as shown in Figure 16, a step S1 for forming an AlN film 12, a step S2 for forming a Mo film 13, a step S2-1 for planarizing the Mo film 13, a step S3 for forming a SiN film 14, and a step S5 for forming a ScAlN film 15. This embodiment differs from the first embodiment in that the Mo film 13 planarization step S2-1 is performed instead of the SiN film 14 planarization step S4. The steps other than the Mo film 13 planarization step S2-1 are the same as in the first embodiment.

[0123] Following the formation step S2 of the Mo film 13, a planarization step S2-1 of the Mo film 13 is performed. In the planarization step S2-1 of the Mo film 13, the surface 13a of the Mo film 13 is planarized by etching using Ar plasma. At this time, the etching time is set so that the surface roughness of the surface 13a of the Mo film 13 is 0.5 nm or less in terms of arithmetic mean roughness. As a result, the surface roughness of the surface 13a of the Mo film 13 is 0.5 nm or less in terms of arithmetic mean roughness. After planarizing the surface 13a of the Mo film 13, a formation step S3 of the SiN film 14 is performed. In the formation step S3 of the SiN film 14, a SiN film 14 having a base surface is formed in contact with the Mo film 13. After that, a formation step S5 of the ScAlN film 15 is performed.

[0124] In this embodiment, the AlN film 12 formation step S1 and the Mo film 13 formation step S2 correspond to preparing a conductive material having a surface. The Mo film 13 planarization step S2-1 corresponds to planarizing the surface of the conductive material. The SiN film 14 formation step S3 corresponds to forming the base material in contact with the conductive material. The ScAlN film 15 formation step S5 corresponds to forming the ScAlN film in contact with the base surface.

[0125] In this embodiment, in the planarization step S2-1 of the Mo film 13, the surface roughness of the Mo film 13 is made to 0.5 nm or less in terms of arithmetic mean roughness, thereby making the surface roughness of the SiN film 14 formed in the subsequent SiN film 14 formation step S3 0.5 nm or less in terms of arithmetic mean roughness. In this way, when forming a substrate material in contact with the surface of a conductive material, the surface roughness of the conductive material may be reflected in the surface roughness of the substrate material. In such cases, by making the surface roughness of the conductive material 0.5 nm or less, the surface roughness of the substrate surface of the substrate material can be made 0.5 nm or less in terms of arithmetic mean roughness. Since the surface roughness of the substrate surface is 0.5 nm or less in terms of arithmetic mean roughness, the same effect as in the first embodiment can be obtained with this embodiment as well.

[0126] In this embodiment, an amorphous insulating material, a SiN film 14, is formed as the base material for the ScAlN film 15. However, other materials may be formed as the base material for the ScAlN film 15. The other material may be either an insulating material or a conductive material, as in the second to seventh embodiments, and may have either an amorphous or polycrystalline structure.

[0127] (Other embodiments) (1) In the first to seventh embodiments, the planarization of the substrate surface is performed by dry etching using Ar plasma. However, the planarization of the substrate surface may be performed by other methods. Other methods include CMP (i.e., chemical mechanical polishing). Also, when a silicon oxide film doped with B and P is used as the substrate material for the ScAlN film 15, a method of heating and fluidizing it can be used.

[0128] Similarly, in the eighth embodiment, the surface planarization of the conductive material such as the Mo film 13 is performed by etching using Ar plasma, but it may also be performed by other methods such as CMP.

[0129] (2) In each of the above embodiments, the base material for the ScAlN film 15 has a film shape. However, the base material may have a shape other than a film.

[0130] (3) The present invention is not limited to the embodiments described above, and can be modified as appropriate within the scope of the claims, and includes various modifications and variations within the equivalent scope. Furthermore, the embodiments described above are not unrelated to each other, and can be combined as appropriate, except in cases where the combination is clearly impossible. In addition, it goes without saying that the elements constituting the embodiments in the embodiments described above are not necessarily essential, except in cases where they are explicitly stated to be particularly essential or where they are clearly considered essential in principle.

[0131] (Features of the present invention) [Claim 1] A piezoelectric film laminate, Substrate material (14, 21, 22, 23, 24, 25, 26) having a substrate surface (14a, 21a, 22a, 23a, 24a, 25a, 26a), The system comprises a ScAlN film (15) positioned in contact with the aforementioned substrate surface, A piezoelectric film laminate, wherein the surface roughness of the substrate surface is 0.5 nm or less in terms of arithmetic mean roughness. [Claim 2] The piezoelectric film laminate according to claim 1, wherein the base material (14) is an amorphous insulating material. [Claim 3] The piezoelectric film laminate according to claim 1, wherein the base material (21) is a polycrystalline insulating material comprising a plurality of crystal grains, each of which has an unoriented structure. [Claim 4] The piezoelectric film laminate according to claim 1, wherein the base material (22) is an insulating material having a crystal structure that is neither hexagonal nor cubic. [Claim 5] The aforementioned base material (23) is an insulating material having a hexagonal or cubic crystal structure, and also having a polycrystalline or single-crystal structure with multiple crystal grains. The plurality of crystal grains include crystal grains whose crystal axes are oriented in a specific direction. If the substrate material has a hexagonal crystal structure, the substrate material has a structure other than one in which the orientation of the c-axis of the hexagonal crystal is perpendicular to the substrate surface. The piezoelectric film laminate according to claim 1, wherein, if the substrate material has a cubic crystal structure, the substrate material has a structure other than one in which the orientation of the <111> axis of the cubic crystal is perpendicular to the substrate surface. [Claim 6] The aforementioned base material is in the form of a film, The piezoelectric film laminate according to any one of claims 2 to 5, wherein the film thickness of the base material is 1 / 10 or less of the film thickness of the ScAlN film. [Claim 7] The piezoelectric film laminate according to any one of claims 2 to 6, wherein the piezoelectric film laminate comprises a conductive material (13) disposed in contact with the base material on the side opposite to the ScAlN film side with respect to the base material. [Claim 8] The conductive material has a surface (13a) that is in contact with the substrate material, The piezoelectric film laminate according to claim 7, wherein the surface roughness of the surface of the conductive material is 0.5 nm or less in terms of arithmetic mean roughness. [Claim 9] The piezoelectric film laminate according to claim 1, wherein the base material (25) is an amorphous conductive material. [Claim 10] The piezoelectric film laminate according to claim 1, wherein the base material (24) is a polycrystalline conductive material comprising a plurality of crystal grains, each of which has an unoriented structure. [Claim 11] The aforementioned base material (26) is a conductive material having a hexagonal, body-centered cubic, or face-centered cubic crystal structure, and having a polycrystalline or single-crystal structure with multiple crystal grains. The plurality of crystal grains include crystal grains whose crystal axes are oriented in a specific direction. If the substrate material has a hexagonal crystal structure, the substrate material has a structure other than one in which the orientation of the c-axis of the hexagonal crystal is perpendicular to the substrate surface (26a). If the substrate material has a body-centered cubic crystal structure, the structure is one in which the orientation of the <101> axis of the body-centered cubic crystal is perpendicular to the substrate surface. The piezoelectric film laminate according to claim 1, wherein, in the case of the substrate material having a face-centered cubic crystal structure, the structure excludes a structure in which the orientation of the <111> axis of the face-centered cubic crystal is perpendicular to the surface of the substrate. [Explanation of Symbols]

[0132] 10 Piezoelectric film laminate 14 SiN film 14a Substrate surface 15 ScAlN membrane

Claims

1. A piezoelectric film laminate, A base material (14) having a base surface (14a), The system comprises a ScAlN film (15) positioned in contact with the substrate surface, The surface roughness of the aforementioned substrate surface is 0.5 nm or less in terms of arithmetic mean roughness. The aforementioned substrate material is a piezoelectric film laminate, which is an amorphous insulating material.

2. A piezoelectric film laminate, A base material (21) having a base surface (21a), The system comprises a ScAlN film (15) positioned in contact with the substrate surface, The surface roughness of the aforementioned substrate surface is 0.5 nm or less in terms of arithmetic mean roughness. The piezoelectric film laminate is an AlN film made of an insulating material that is polycrystalline and contains a plurality of crystal grains, each of which has an unoriented structure.

3. A piezoelectric film laminate, A base material (22) having a base surface (22a), The system comprises a ScAlN film (15) positioned in contact with the substrate surface, The surface roughness of the aforementioned substrate surface is 0.5 nm or less in terms of arithmetic mean roughness. The aforementioned substrate material is a piezoelectric film laminate, which is an insulating material having a crystal structure that is neither hexagonal nor cubic.

4. A piezoelectric film laminate, A base material (23) having a base surface (23a), The system comprises a ScAlN film (15) positioned in contact with the substrate surface, The surface roughness of the aforementioned substrate surface is 0.5 nm or less in terms of arithmetic mean roughness. The aforementioned substrate material is an insulating material having a hexagonal or cubic crystal structure, and also having a polycrystalline or single-crystal structure with multiple crystal grains. The plurality of crystal grains include crystal grains whose crystal axes are oriented in a specific direction. If the substrate material has a hexagonal crystal structure, the substrate material has a structure other than one in which the orientation of the c-axis of the hexagonal crystal is perpendicular to the substrate surface. In the case where the substrate material has a cubic crystal structure, the piezoelectric film laminate has a structure other than one in which the orientation of the <111> axis of the cubic crystal is perpendicular to the substrate surface.

5. The aforementioned base material is in the form of a film, The piezoelectric film laminate according to any one of claims 1 to 4, wherein the film thickness of the base material is 1 / 10 or less of the film thickness of the ScAlN film.

6. The piezoelectric film laminate according to any one of claims 1 to 4, wherein the piezoelectric film laminate comprises a conductive material (13) arranged in contact with the base material on the side opposite to the ScAlN film with respect to the base material.

7. The conductive material has a surface (13a) that is in contact with the substrate material, The piezoelectric film laminate according to claim 6, wherein the surface roughness of the surface of the conductive material is 0.5 nm or less in terms of arithmetic mean roughness.

8. A piezoelectric film laminate, A base material (25) having a base surface (25a), The system comprises a ScAlN film (15) positioned in contact with the substrate surface, The surface roughness of the aforementioned substrate surface is 0.5 nm or less in terms of arithmetic mean roughness. The aforementioned substrate material is a piezoelectric film laminate, which is an amorphous conductive material.

9. A piezoelectric film laminate, A base material (24) having a base surface (24a), The system comprises a ScAlN film (15) positioned in contact with the substrate surface, The surface roughness of the aforementioned substrate surface is 0.5 nm or less in terms of arithmetic mean roughness. The substrate material is a piezoelectric film laminate, which is a polycrystalline material containing a plurality of crystal grains, each of which crystal grains has an unoriented structure.

10. A piezoelectric film laminate, A base material (26) having a base surface (26a), The system comprises a ScAlN film (15) positioned in contact with the substrate surface, The surface roughness of the aforementioned substrate surface is 0.5 nm or less in terms of arithmetic mean roughness. The aforementioned substrate material is a conductive material having a hexagonal, body-centered cubic, or face-centered cubic crystal structure, and having a polycrystalline or single-crystal structure with multiple crystal grains. The plurality of crystal grains include crystal grains whose crystal axes are oriented in a specific direction. If the substrate material has a hexagonal crystal structure, the substrate material has a structure other than one in which the orientation of the c-axis of the hexagonal crystal is perpendicular to the substrate surface (26a). If the substrate material has a body-centered cubic crystal structure, the structure is one in which the orientation of the <101> axis of the body-centered cubic crystal is perpendicular to the substrate surface. A piezoelectric film laminate in which, when the substrate material has a face-centered cubic crystal structure, the structure excludes a structure in which the orientation of the <111> axis of the face-centered cubic crystal is perpendicular to the surface of the substrate.

11. The piezoelectric film laminate according to any one of claims 1 to 4 and 8 to 10, wherein the ScAlN film has an Sc concentration of 24 atomic percent or more and 40 percent or less.

12. A method for manufacturing a piezoelectric film laminate, Prepare a base material (14, 21, 22, 24, 25) having a base surface (14a, 21a, 22a, 24a, 25a) (S1, S2, S3), The aforementioned substrate surface is flattened (S4), The process includes flattening the substrate surface and then forming a ScAlN film (15) in contact with the substrate surface (S5), In the planarization process, the surface roughness of the substrate surface is set to 0.5 nm or less in terms of arithmetic mean roughness. A method for manufacturing a piezoelectric film laminate, wherein the base material is one of the following: an amorphous insulating material, an AlN film made of a polycrystalline insulating material containing a plurality of crystal grains, each of which has an unoriented structure, an insulating material having a crystal structure that is neither hexagonal nor cubic, an amorphous conductive material, or a polycrystalline conductive material containing a plurality of crystal grains, each of which has an unoriented structure.

13. A method for manufacturing a piezoelectric film laminate, Prepare a base material (23) having a base surface (23a) (S1, S2, S3), The aforementioned substrate surface is flattened (S4), The process includes flattening the substrate surface and then forming a ScAlN film (15) in contact with the substrate surface (S5), In the planarization process, the surface roughness of the substrate surface is set to 0.5 nm or less in terms of arithmetic mean roughness. As the aforementioned base material, an insulating material having a hexagonal or cubic crystal structure and a polycrystalline or single-crystal structure with multiple crystal grains is used. The plurality of crystal grains include crystal grains whose crystal axes are oriented in a specific direction. If the substrate material has a hexagonal crystal structure, the substrate material has a structure other than one in which the orientation of the c-axis of the hexagonal crystal is perpendicular to the substrate surface. A method for manufacturing a piezoelectric film laminate, wherein, when the substrate material has a cubic crystal structure, the substrate material has a structure other than one in which the orientation of the <111> axis of the cubic crystal is perpendicular to the substrate surface.

14. A method for manufacturing a piezoelectric film laminate, Prepare a base material (26) having a base surface (26a) (S1, S2, S3), The aforementioned substrate surface is flattened (S4), The process includes flattening the substrate surface and then forming a ScAlN film (15) in contact with the substrate surface (S5), In the planarization process, the surface roughness of the substrate surface is set to 0.5 nm or less in terms of arithmetic mean roughness. As the base material, a conductive material having a hexagonal, body-centered cubic, or face-centered cubic crystal structure, and having a polycrystalline or single-crystal structure with multiple crystal grains, is used. The plurality of crystal grains include crystal grains whose crystal axes are oriented in a specific direction. If the substrate material has a hexagonal crystal structure, the substrate material has a structure other than one in which the orientation of the c-axis of the hexagonal crystal is perpendicular to the substrate surface. If the substrate material has a body-centered cubic crystal structure, the structure is one in which the orientation of the <101> axis of the body-centered cubic crystal is perpendicular to the substrate surface. A method for manufacturing a piezoelectric film laminate, wherein, when the substrate material has a face-centered cubic crystal structure, the structure excludes a structure in which the orientation of the <111> axis of the face-centered cubic crystal is perpendicular to the surface of the substrate.

15. A method for manufacturing a piezoelectric film laminate, The process involves preparing a conductive material (13) having a surface (13a) (S1, S2), The surface of the conductive material is flattened (S2-1), After flattening the surface, a base material having a base surface is formed in contact with the conductive material (S3), This includes forming a ScAlN film in contact with the aforementioned substrate surface (S5), A method for manufacturing a piezoelectric film laminate, wherein, in the planarization process, the surface roughness of the surface of the conductive material is made 0.5 nm or less in terms of arithmetic mean roughness, thereby making the surface roughness of the substrate surface 0.5 nm or less in terms of arithmetic mean roughness.

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