Film structure, piezoelectric film, and superconductor film

Abstract

According to the present application, for various piezoelectric materials, a piezoelectric film having a crystal structure of a single crystal can be formed on the film structure of the present application. The film structure of the present application has: a substrate; a buffer film having a crystal structure of tetragonal zirconia formed on the substrate; a metal film containing a platinum group element epitaxially grown on the buffer film; and a film containing Sr(Ti 1‑x , Ru x )O3 (0≤x≤1) epitaxially grown on the metal film.

Description

Technical Field

[0001] The present invention relates to a membrane structure having a buffer membrane capable of forming a single crystal piezoelectric membrane or superconducting membrane on a substrate by epitaxial growth, the piezoelectric membrane, and the superconducting membrane. Background Technology

[0002] In today's Internet of Things (IoT) era, where everything is connected to the internet, sensors play a vital role. The global market size is $20 billion and is expanding at a growth rate of 7-8%, with up to 90 billion sensors produced worldwide annually. Efforts using MEMS sensor technology, particularly piezoelectric materials like PZT, are especially active, with wide applications in gyroscope sensors for autonomous driving, piezoelectric microphones, high-frequency filters for 5G communications, vibration-generating components, and many other applications.

[0003] With the development of IoT technology, MEMS sensor technology using piezoelectric materials needs to be miniaturized / thinned and made more sensitive year by year. On the other hand, to achieve high sensitivity, uniform polarization is required to ensure sufficient piezoelectricity, but for piezoelectric materials that are usually polycrystalline ceramic sintered bodies, the polarization is not uniform. In addition, there are limitations to thin-film production for ceramic sintered bodies. Therefore, in recent years, attempts have been made to obtain piezoelectric materials as thin films by epitaxial growth of single crystals (for example, see Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 5-072428 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In efforts to achieve single-crystal piezoelectric materials, since most are oxides, it is difficult to achieve single-crystal piezoelectric materials through epitaxial growth, for example, when using a single-crystal Si substrate. Therefore, oxide crystals such as YSZ (Yttria-stabilized zirconia) are sometimes used as buffer layers. However, this oxide crystal has a different crystal system than the piezoelectric material, so the piezoelectric material is affected by the crystal system of the buffer layer during crystal formation, making it difficult to achieve in-plane single-crystallinity as a thin film. Furthermore, since the lattice constants of different piezoelectric materials vary, it is necessary to study the composition of the buffer layer for each piezoelectric material, making the selection of the buffer layer difficult.

[0009] Methods for solving problems

[0010] To address the aforementioned issues, the membrane structure of the present invention comprises: a substrate; a buffer film with a tetragonal crystal structure containing zirconium oxide formed on the substrate; an epitaxially grown metal film containing platinum group elements formed on the buffer film; and an epitaxially grown Sr(Ti)-containing metal film formed on the metal film. 1-x Ru x O3 (0≤x≤1) membrane.

[0011] Invention Effects

[0012] According to the present invention, for various piezoelectric materials and superconducting materials, a film having a single-crystal crystal structure can be formed on the film structure of the present invention. Attached Figure Description

[0013] Figure 1 This is a cross-sectional view of the substrate with a buffer film formed according to the present invention.

[0014] Figure 2 This is a cross-sectional view of the substrate of the present invention having a lower electrode formed on a buffer film.

[0015] Figure 3 This is a cross-sectional view of the membrane structure including the buffer membrane of the present invention.

[0016] Figure 4 (a) is a STEM image obtained by observing the cross-section of a ZrO2 film formed on substrate 11 as a buffer film 12; (b) is an electron diffraction pattern of substrate 11 in the lower part and an electron diffraction pattern of buffer film 12 in the upper part.

[0017] Figure 5 The following are STEM images obtained by observing the cross-sections of the buffer film 12 with the following thicknesses: (a) 1 nm; (b) 12 nm; (c) 15 nm; (d) 25 nm.

[0018] Figure 6 The results are shown based on the XRD-based θ-2θ spectrum of membrane structure 101.

[0019] Figure 7 These are STEM images obtained by observing cross-sections of conductive films 13 with the following thicknesses: (a) 10 nm; (b) 20 nm; (c) 150 nm.

[0020] Figure 8 The results are shown by measuring the θ-2θ spectrum of the membrane structure 101 of Example 1 using the XRD method.

[0021] Figure 9 This is a STEM-based lattice diagram obtained by observing the cross-section of PZT (30 / 70) as piezoelectric film 14 in Example 1.

[0022] Figure 10 (a) is a pole figure of the Si (220) plane of the membrane structure 101 of Example 1, (b) is a pole figure of the ZrO2 (220) plane, (c) is a pole figure of Pt (220), and (d) is a pole figure of PZT (202).

[0023] Figure 11 This is a graph showing the voltage dependence of the polarization of the piezoelectric film 14 in Example 1.

[0024] Figure 12 The results are shown by measuring the θ-2θ spectrum of the membrane structure 101 of Example 2 using the XRD method.

[0025] Figure 13 (a) is a diagram showing the X-ray diffraction pattern of the substrate 11 of the membrane structure 101 of Example 2 based on φ scanning, and (b) is a diagram showing the X-ray diffraction pattern of the piezoelectric membrane 14 of the membrane structure 101 of Example 2 based on φ scanning.

[0026] Figure 14 The image shows a STEM-based lattice pattern obtained by observing a cross-section of the BTO in the piezoelectric film 14 of Example 2.

[0027] Figure 15 This is a graph showing the voltage dependence of the polarization of the piezoelectric film 14 in Example 2.

[0028] Figure 16 This is a diagram showing the piezoelectricity of BTO in the piezoelectric film 14 of Example 2.

[0029] Figure 17 The results are shown by measuring the θ-2θ spectrum of the membrane structure 101 of Example 3 using the XRD method.

[0030] Figure 18 (a) is a diagram showing the X-ray diffraction pattern of the substrate 11 of the membrane structure 101 of Example 3 based on φ scanning, and (b) is a diagram showing the X-ray diffraction pattern of the piezoelectric membrane 14 of the membrane structure 101 of Example 3 based on φ scanning.

[0031] Figure 19 The image shows a STEM-based lattice pattern obtained by observing the cross-section of the BFO of the piezoelectric film 14 as Example 3.

[0032] Figure 20 This is a graph showing the voltage dependence of the polarization of the piezoelectric film 14 in Example 3.

[0033] Figure 21 This is a graph showing the piezoelectricity of the BFO of the piezoelectric film 14 as Example 3.

[0034] Figure 22 The results are shown by measuring the out-of-plane θ-2θ spectrum of the membrane structure 101 of Example 4 using the XRD method.

[0035] Figure 23 (a) is a diagram showing the X-ray diffraction pattern of the substrate 11 of the membrane structure 101 of Example 4 based on φ scanning, and (b) is a diagram showing the X-ray diffraction pattern of the piezoelectric membrane 14 of the membrane structure 101 of Example 4 based on φ scanning.

[0036] Figure 24 The image shows a STEM-based lattice pattern obtained by observing the cross-section of the BLT of the piezoelectric film 14 as Example 4.

[0037] Figure 25 This is a graph showing the voltage dependence of the polarization of the piezoelectric film 14 in Example 4.

[0038] Figure 26 This is a graph showing the piezoelectricity of the BLT of the piezoelectric film 14 as Example 4.

[0039] Figure 27 The results are shown by measuring the θ-2θ spectrum of the membrane structure 101 of Example 5 using the XRD method.

[0040] Figure 28 This is a diagram showing the φ-scan-based X-ray diffraction pattern of the membrane structure 101 of Example 5.

[0041] Figure 29 The results are shown by measuring the θ-2θ spectrum of the membrane structure 101 of Example 6 using the XRD method.

[0042] Figure 30 This is a diagram showing the φ-scan-based X-ray diffraction pattern of the membrane structure 101 of Example 6.

[0043] Figure 31 The results are shown by STEM observation of the cross-sections of the buffer film 12 and the conductive film 13 of the PZT (30 / 70) film of Example 1.

[0044] Figure 32 The results are shown by STEM observation of the cross-sections of the buffer film 12 and the conductive film 13 of the BFO film of Example 3.

[0045] Figure 33 The results are shown by STEM observation of the cross-sections of the buffer film 12 and the conductive film 13 of the BLT film of Example 4.

[0046] Figure 34(a) is a lattice diagram showing a cross-sectional view of the interface between conductive film 13 and film 16 when forming a BFO film in film-forming example 3, and (b) is a lattice diagram showing a cross-sectional view of the interface between conductive film 13 and film 16 when forming a BLT film in film-forming example 4.

[0047] Figure 35 The results are shown for the membrane structure 101 of Example 7, obtained by measuring the X-ray diffraction pattern of AlN based on the XRD method with φ scanning.

[0048] Figure 36 The results shown are obtained by measuring the X-ray diffraction pattern of LiNbO3 based on φ scanning using the XRD method for the membrane structure 101 of Example 8. Detailed Implementation

[0049] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0050] It should be noted that the disclosed content is merely an example, and appropriate modifications that can be easily conceived by those skilled in the art while maintaining the spirit of the invention are of course included within the scope of this invention. Furthermore, in the accompanying drawings, to make the description clearer, there are illustrative representations of the width, thickness, shape, etc., of various parts compared to the embodiments, but these are merely examples and do not limit the interpretation of this invention.

[0051] In addition, in this specification and in the figures, the same symbols are sometimes given to the same elements that have appeared in previous figures as described above, and detailed descriptions are appropriately omitted.

[0052] Furthermore, in the accompanying drawings used in the embodiments, there are instances where additional shading lines used to distinguish structures are omitted based on the drawings.

[0053] (Implementation Method)

[0054] Figure 1 This is a cross-sectional view of the substrate with the buffer film formed according to the present invention. Figure 1 As shown, a buffer film 12 is formed on the substrate 11.

[0055] Substrate 11 is, for example, a silicon (Si) substrate. Besides Si, it can also be, for example, an SOI (Silicon on Insulator) substrate, a substrate formed from various semiconductor crystals other than Si, a substrate formed from various oxide single crystals such as sapphire, or a substrate formed from garnet Al3Fe2Si3O4. 12 Substrates, or glass substrates with a polycrystalline silicon film formed on their surface, etc. These substrates can be 4 inches, 6 inches, or 8 inches in size.

[0056] The orientation of substrate 11 can be arbitrary. If it is a Si substrate, then Si(100), Si(110), Si(111), etc. can be used.

[0057] The buffer film 12 comprises zirconium oxide (ZrO2) epitaxially grown on the substrate 11, and is composed of a film portion 12a and a protrusion 12b. It is known that ZrO2 undergoes a phase transition from monoclinic to tetragonal to cubic crystal depending on the applied energy; in this invention, the buffer film 12 has a tetragonal crystal structure. It should be noted that the buffer film 12 is preferably epitaxially grown according to the orientation of the substrate 11.

[0058] It should be noted that, regarding piezoelectric materials, it has been reported that performance is improved if the crystal system is tetragonal, or even if it is not tetragonal but contains tetragonal crystals. It is believed that by setting tetragonal zirconium oxide as a buffer film, it plays a beneficial role in the formation of single crystals of piezoelectric materials.

[0059] Single-crystal ZrO2 contains up to 8% crystal defects. It is believed that, in the presence of crystal defects, the vacancies and neighboring atoms exert elastic forces in the direction of reducing lattice strain. The degree of these elastic forces is believed to be proportional to the vacancy concentration. The buffer film 12 of the present invention can utilize these elastic forces to perform a function that allows for a variable crystal structure.

[0060] like Figure 1 As shown, the buffer film 12 has a protrusion 12b. It is believed that the protrusion 12b is formed in this way because, during the film formation process of the buffer film 12, when the raw material concentration is supersaturated, the crystal grows anisotropically along a certain axis or edge to form a pyramid structure and carry out crystal growth.

[0061] The buffer membrane 12 can contain not only ZrO2, but also rare earth elements and alkaline earth elements. Among these, ZrO2 can contain oxygen vacancies. In addition, to improve properties, transition metal elements such as Al, Sc, Mn, Fe, Co, and Ni can be included.

[0062] Preferably, the membrane portion 12a is 10 nm or more, and the protrusion portion 12b is 3 to 8 nm.

[0063] Figure 2 Displayed Figure 1 The diagram shows a cross-sectional view of a substrate on which a lower electrode is formed on a buffer film 12. The lower electrode comprises conductive films 13 and 16 epitaxially grown on the buffer film 12. The conductive film 13 can be formed using various metals, such as Ru, Rh, Pd, Os, Ir, and Pt, which are platinum group elements. These materials are known to have similar physical / chemical properties to each other.

[0064] The membrane 16 comprises a composite oxide represented by the following general formula (Chemical Formula 1), such as strontium titanate (STO), strontium ruthenium titanate (STRO), or strontium ruthenium oxide (SRO). It should be noted that 0 ≤ x ≤ 1 is satisfied.

[0065] Sr(Ti 1-x Ru x O3…(Chemical Formula 1)

[0066] Regarding the lower electrode, it is preferable that its surface is planar, and the conductive film 13 should be at least 20 nm thick. Regarding the film 16, its thickness should be thinner than that of the conductive film 13.

[0067] Figure 3 Displayed Figure 2 The diagram shows a cross-sectional view of the film structure 101 of the present invention, on which a piezoelectric film 14 and a conductive film 15 serving as an upper electrode are further formed on the substrate.

[0068] The material of the piezoelectric film 14 is, for example, a perovskite oxide such as lead zirconate titanate (PZT) or barium titanate (BaTiO3). Alternatively, for example, bismuth ferrite (BiFeO3) of the trigonal crystal system can be used. Similarly, lithium niobate (LiNbO3) or lithium tantalate (LiTaO3) of the trigonal crystal system can be used. In addition, for example, aluminum nitride (AlN) of the hexagonal crystal system can be used.

[0069] Alternatively, for example, a tungsten bronze-type strong dielectric film or a bismuth layered structure strong dielectric film can be used as the piezoelectric film 14. For example, a material with a crystal structure having a tungsten bronze-type strong dielectric film could be Ba₂NaNb₅O. 15 .

[0070] The crystal structure of a bismuth layered high-dielectric film is based on the general formula (Bi₂O₂). 2+ (A m-1 B m O 3m+1 ) 2- (m = 1~5), or Bi2A m-1 B m O 3m+3 (m=1~5) represents, and in (Bi2O2) 2+ The layers contain multiple perovskite-like structures. A strong dielectric material for bismuth layered structures is, for example, bismuth titanate (Bi₄Ti₃O₄). 12 Alternatively, lanthanum bismuth titanate (Bi) can be used, for example. 4-x La x Ti3O 12 (0 < x < 1).

[0071] Not limited to the piezoelectric film 14 mentioned above, yttrium-based superconductors such as YBa2Cu3O7 (YBCO) with perovskite structure, or Bi2SrCa2Cu3O4 with piezoelectric structure can also be used. 10 Superconducting films are made using bismuth-based superconductors such as (BSCCO) as materials.14

[0072] If a material for forming such a piezoelectric film or superconductor film is used, a single-crystal piezoelectric film 14 or superconductor film 14 can be formed on the buffer film 12.

[0073] A conductive film 15 is formed on the piezoelectric film 14. The conductive film 15 can be made of the same material as the conductive film 13. It should be noted that the film 16 can be used to improve the adhesion between the conductive film 13 and the piezoelectric film 14.

[0074] Example

[0075] The following describes this embodiment in more detail based on examples. It should be noted that the present invention is not limited to the following examples.

[0076] In Examples 1-4, a (100) oriented Si substrate was used as substrate 11 for fabrication. Figure 3 The membrane structure 101 is shown. Regarding the piezoelectric membrane 14, Example 1 uses PZT(30 / 70)(Pb(Zr)) 0.3 Ti 0.7 Example 2 uses BTO (BaTiO3), Example 3 uses BFO (BiFeO3), and Example 4 uses BLT (Bi... 3.25 La 0.75 Ti3O 12 It is used as a sputtering material for film formation.

[0077] First, a ZrO2 film is formed on substrate 11 as a buffer film 12 by electron beam evaporation. The conditions at this time are as follows.

[0078] Apparatus: Electron beam evaporation apparatus

[0079] Pressure: 7.0 × 10 -3 Pa

[0080] Evaporation source: Zr + O2

[0081] O2 flow rate: 10 sccm

[0082] Accelerating voltage / emission current: 7.5kV / 1.8mA

[0083] Thickness: 25nm

[0084] Substrate temperature: 600℃

[0085] Figure 4 (a) is a STEM image obtained by observing the cross-section of a ZrO2 film formed on substrate 11 as a buffer film 12. Figure 4 (b) The following figure is the electron diffraction pattern of substrate 11. Figure 4 (b) The upper part is the electron diffraction pattern of buffer film 12.

[0086] like Figure 4 As shown in (a), the buffer membrane 12 has a protrusion 12b with a pyramidal surface, and is composed of a membrane portion 12a and a protrusion 12b. Figure 4 As shown in the figure above (b), the buffer film 12 is an aggregate of fine ZrO2 single crystals, which is epitaxially grown on the upper surface of the substrate 11.

[0087] Figure 5 STEM-based cross-sectional views showing the various film formation times of the buffer membrane 12. Figure 5 (a) Shows the appearance of the 1nm buffer film 12. Figure 5 (b) Shows the appearance of the 12nm buffer film 12. Figure 5 (c) Shows the appearance of the 15nm buffer film 12. Figure 5 (d) Shows the appearance of the 25nm buffer film 12. It should be noted that... Figure 5 In (b)-(d), the shape of the protrusion 12b is emphasized with white dashed lines to illustrate its shape.

[0088] like Figure 5 As shown in (a), it can be seen that the protrusion 12b was not formed immediately after the buffer membrane 12 was formed. The film formation time at this time was 3 seconds. Next, a sample was prepared after the buffer membrane 12 had been formed for 1 minute, and its cross-section was observed. Figure 5 (b)). For example Figure 5 As shown in (b), the height of the protrusion 12b is uneven. Next, a sample was prepared after the buffer membrane 12 had been deposited for 5 minutes, and its cross-section was observed. Figure 5 (c)). For example Figure 5 As shown in (c), the height of the protrusion 12b is greater than that of the protrusion. Figure 5 (b) The protrusion 12b shown is more uniform. Next, a sample was prepared by forming the buffer film 12 for 8 minutes, and its cross-section was observed. Figure 5 (d)). For example Figure 5 As shown in (d), the height of the protrusion 12b is greater than that of the protrusion. Figure 5 The protrusion 12b shown in (b) or (c) is more uniform.

[0089] about Figure 5 The height of the protrusion 12b shown in (b)-(d) is calculated as an average based on each image.Figure 5 (b) is 2.2 nm. Figure 5 (c) is 3.33 nm. Figure 5 (d) is 4.67 nm. Furthermore, regarding the protrusion 12b, which is a square pyramid, the length of the diagonal of the base is... Figure 5 (b) is 3.3 nm. Figure 5 (c) is 5.0 nm. Figure 6 (d) is 7.0 nm.

[0090] Based on the above results, as the buffer film 12 is formed, the size of the square pyramid increases, and the height of the protrusion 12b increases with the film formation time. Furthermore, when the buffer film 12 is formed for 0.05 minutes (3 seconds)... Figure 6 When the buffer membrane 12 in (a) is considered a plane and its surface area is set to 1.0, Figure 7 The surface area of ​​the buffer membrane 12 in (b)-(d) is 1.30 to 1.60 times.

[0091] Calculate the film formation rate. Figure 7 (a) The value is 3.33 [nm / second]. Figure 7 (b) is 2.0 [nm / second], Figure 7 (c) is 0.50 [nm / second], Figure 7 (d) is 0.52 [nm / second]. Thus, based on the film formation rates of different thicknesses of the buffer film 12, it can be seen that if a film thicker than 15 nm is formed, the film formation rate becomes constant.

[0092] Figure 7 The results are shown below, obtained by measuring the XRD-based θ-2θ spectra of conductive films 13 and 16 after deposition using the methods described later in this text. Figure 7 As shown, based on the position of the peak, it can be known that ZrO2, which serves as buffer film 12, has a tetragonal crystal structure oriented in the (200) plane.

[0093] Next, a platinum (Pt) film is formed on the buffer film 12 as a conductive film 13 by sputtering. The conditions at this time are as follows.

[0094] Equipment: DC sputtering equipment

[0095] Pressure: 1.2 × 10 -1 Pa

[0096] Evaporation source: Pt

[0097] Power consumption: 100W

[0098] Thickness: 150nm

[0099] Substrate temperature: 450~600℃

[0100] Figure 8 The image is a STEM image obtained by observing the cross-section of a Pt film formed on the buffer film 12 as a conductive film 13. Figure 8 (a) Shows the appearance of the 10nm conductive film 13. Figure 9 (b) Shows the appearance of the 20nm conductive film 13. Figure 9 (c) Shows what the 150nm conductive film 13 looks like when it is formed.

[0101] like Figure 10 As shown in (a), even with a film thickness of 10 nm, the surface of the conductive film 13 is approximately planarized. Furthermore, as... Figure 10 As shown in (b), by setting the film thickness to 20 nm, the surface of the conductive film 13 becomes more flattened, even if a 150 nm film is formed in this state, as... Figure 10 (c) shows that the terrain remains flat.

[0102] Next, a SrRuO3 (SRO) film is formed on the conductive film 13 by sputtering as film 16. The conditions at this time are as follows.

[0103] Apparatus: RF magnetron sputtering apparatus

[0104] Power: 300W

[0105] Gas: Ar

[0106] Pressure: 1.8 Pa

[0107] Thickness: 20nm

[0108] Substrate temperature: 600℃

[0109] Next, a piezoelectric film 14 is formed on the film 16. In Examples 1 to 4, the formation conditions are the same, only the sputtering materials are different.

[0110] Apparatus: RF magnetron sputtering apparatus

[0111] Materials: [Example 1: PZT(30 / 70)]Pb(Zr) 0.3 Ti 0.7 O3、

[0112] [Example 2: BTO]BaTiO3,

[0113] [Example 3: BFO]BiFeO3,

[0114] [Example 4: BLT](Bi) 3.25 La 0.75 Ti3O 12

[0115] Power: 1500W

[0116] Gas: Ar / O2

[0117] Pressure: 1.0 Pa

[0118] Substrate temperature: 450℃

[0119] (Example 1)

[0120] In Example 1, the film structure 101 was formed using a Si / ZrO2 / Pt / SRO / PZ / Pt configuration. The substrate 11 used was Si (100). It should be noted that after forming the PZT (30 / 70) piezoelectric film 14, its thickness was measured using XRF with a Rigaku X-ray fluorescence analyzer (AZX400), and the result was 1.0 μm.

[0121] Figure 10 The results are shown by measuring the θ-2θ spectrum of the membrane structure 101 of Example 1 using XRD. Figure 10 As shown, PZT(30 / 70) preferentially oriented along the c-axis. Based on this X-ray diffraction pattern, the lattice constants a and c were determined, and the c / a axis ratio was calculated, yielding a result of 1.046.

[0122] Figure 10 This shows a STEM-based lattice diagram of the PZT (30 / 70) piezoelectric film 14 in a cross-section of the membrane structure 101. (See image.) Figure 11 As shown, it was confirmed that there were no lattice disturbances such as dislocations in the piezoelectric film 14, indicating that it is a single crystal.

[0123] Figure 11 The results show the findings of investigating the in-plane orientation relationships of each layer of the membrane structure 101 in Example 1 by measuring the pole figures based on the XRD method. Figure 12 (a) is the pole figure of the Si(220) plane. Figure 12 (b) is the pole figure of the ZrO2(220) surface. Figure 12 (c) is the pole figure of Pt(220). Figure 13 (d) is the pole figure of PZT(202).

[0124] like Figure 13 As shown in (a)-(d), four symmetrical peaks can be seen, indicating that epitaxial growth is performed with the orientation in-plane consistent with the substrate.

[0125] Figure 14 This is a graph showing the voltage dependence of the polarization of the piezoelectric film 14 in Example 1. (As shown...) Figure 14 As shown, the piezoelectric film 14 of Example 1 exhibits good properties, with a residual polarization Pr of 50 μC / cm.2 The coercive electric field Ec is 180 kV / cm.

[0126] (Example 2)

[0127] In Example 2, a film was formed using a Si / ZrO2 / Pt / SRO / BTO configuration. The substrate 11 was Si(100). It should be noted that after forming the BTO film 14 as a piezoelectric film, its thickness was measured by XRF, and the result was 1.0 μm.

[0128] Figure 15 The results are shown based on the XRD-based θ-2θ spectrum of the membrane structure 101 of Example 2. Figure 15 In the diagram, the upper curve shows the results of out-of-plane measurements, and the lower curve shows the results of in-plane measurements.

[0129] like Figure 16 As shown, the piezoelectric film 14 is preferentially oriented in the (001) plane. Furthermore, the a-axis length and c-axis length of the piezoelectric film 14 were calculated from these measurements, resulting in an a-axis length of 0.4012 nm and a c-axis length of 0.4262 nm. Therefore, the c / a ratio is 1.044, indicating that the c-axis length is longer compared to the bulk value of 1.01.

[0130] Figure 16 Images showing the φ-scan-based X-ray diffraction pattern of the film structure 101 of Example 2. (a) is the pattern of the substrate 11, and (b) is the pattern of the piezoelectric film 14. Figure 17 It can also be seen that the piezoelectric film 14 has four axes of symmetry at the same angle as the substrate 11, and it can be seen that the piezoelectric film 14 is formed in a cube-on-cube manner.

[0131] Figure 17 This shows a STEM-based lattice pattern of BTO, which serves as the piezoelectric film 14, in a cross-section of the membrane structure 101 of Example 2. (See attached image.) Figure 17 As shown, it was confirmed that there were no lattice disturbances such as dislocations in the piezoelectric film 14, indicating that it is a single crystal.

[0132] Figure 18 This is a graph showing the voltage dependence of the polarization of the piezoelectric film 14. For example... Figure 18 As shown, the piezoelectric film 14 of Example 2 exhibits strong dielectric properties.

[0133] Figure 19This diagram confirms the piezoelectricity of the piezoelectric film 14 using a d33 meter. The d33 meter is a d33 constant measuring device (model: LTFA-01) manufactured by Lead Techno Co., Ltd., which can measure d33 even without the conductive film 15 serving as the upper electrode. Specifically, it is a device that applies force to the film structure 101 and detects changes in charge using an integrating circuit; if piezoelectricity is present, then... Figure 19 As shown, by applying or not applying force at certain time intervals, a pulse-shaped waveform can be observed. It should be noted that the d33 value is 24.88 (pC / N) at this time.

[0134] (Example 3)

[0135] In Example 3, a film was formed using a Si / ZrO2 / Pt / SRO / BFO configuration. The substrate 11 was Si(100). It should be noted that after forming the BFO as a piezoelectric film 14, its thickness was measured by XRF, and the result was 2.1 μm.

[0136] Figure 20 The results are shown based on the XRD-based θ-2θ spectrum of the membrane structure 101 of Example 3. Figure 20 In the diagram, the upper curve shows the results of out-of-plane measurements, and the lower curve shows the results of in-plane measurements. For example... Figure 21 As shown, the piezoelectric film 14 is preferably oriented on the (001) plane.

[0137] Figure 21 Is the display based on Images of the scanned X-ray diffraction patterns. (a) is the pattern of substrate 11, and (b) is the pattern of piezoelectric film 14. Figure 22 It can also be seen that after the piezoelectric film 14 is formed, it has four axes of symmetry at the same angle as the substrate 11. It can be seen that the piezoelectric film 14 is formed in a cube-on-cube manner.

[0138] Figure 22 This shows a STEM-based lattice diagram of the BFO (bipolar free radical) acting as the piezoelectric film 14 in a cross-section of the membrane structure 101. (See image.) Figure 22 As shown, it was confirmed that there were no lattice disturbances such as dislocations in the piezoelectric film 14, indicating that it is a single crystal.

[0139] Figure 23 This is a graph showing the voltage dependence of the polarization of the piezoelectric film 14. For example... Figure 24 As shown, the piezoelectric film 14 of Example 3 exhibits good properties, with a residual polarization Pr of 60 μC / cm. 2 The coercive electric field Ec is 100 kV / cm.

[0140] Figure 24This is a graph showing the measurement results of the piezoelectric film 14 according to the d33 meter. (See figure.) Figure 24 As shown, the piezoelectric film 14 exhibits piezoelectric properties. It should be noted that the d33 value at this time is 16.69 (pC / N).

[0141] (Example 4)

[0142] In Example 4, a film was formed using a Si / ZrO2 / Pt / SRO / BLT configuration. The substrate 11 was Si(100). It should be noted that after forming the BLT as a piezoelectric film 14, its thickness was measured by XRF, and the result was 1.0 μm.

[0143] Figure 25 The results are shown by measuring the θ-2θ spectrum of the membrane structure 101 of Example 4 using the XRD method. Figure 25 Display the results of out-of-plane measurements. For example... Figure 25 As shown, the piezoelectric film 14 is preferably oriented on the (001) plane.

[0144] Figure 26 Is the display based on Images of the scanned X-ray diffraction patterns. (a) shows the pattern of substrate 11, and (b) shows the pattern formed up to the piezoelectric film 14. Figure 26 It can also be seen that after the piezoelectric film 14 is formed, it has four axes of symmetry at the same angle as the substrate 11, and the piezoelectric film 14 is formed in a cube-on-cube manner.

[0145] Figure 27 This shows a STEM-based lattice image of the BLT (Bipolar Light-Lens) layer, which serves as the piezoelectric film 14, observed in a cross-section of the membrane structure 101. (See image.) Figure 27 As shown, it was confirmed that no lattice disorder such as dislocations appeared in the piezoelectric film 14, indicating that it is a single crystal. It should be noted that... Figure 28 In the diagram, W1 is the perovskite layer and W2 is the bismuth oxide layer.

[0146] Figure 28 This is a graph showing the voltage dependence of the polarization of the piezoelectric film 14. For example... Figure 29 As shown, the piezoelectric film 14 of Example 4 exhibits strong dielectric properties, with a residual polarization Pr of 4 μC / cm. 2 The coercive electric field Ec is 4.5 kV / cm.

[0147] Figure 29 This is a graph showing the measurement results of the piezoelectric film 14 according to the d33 meter. (See figure.) Figure 30 As shown, the piezoelectric film 14 exhibits piezoelectric properties. It should be noted that the d33 value at this time is 164.7 (pC / N).

[0148] (Example 5)

[0149] In Example 5, a film was formed using a Si / ZrO2 / Pt / SRO / PZT configuration. The substrate 11 used was Si (111). It should be noted that after forming the PZT as the piezoelectric film 14, its thickness was measured by XRF, and the result was 1.0 μm. It should also be noted that a Pb / Zr / Ti (130 / 52 / 48) target was used as the PZT material.

[0150] Figure 30 The results of XRD-based θ-2θ spectra measurements of the samples prepared in Example 5 are shown. Figure 31 As shown, the substrate 11, buffer film 12, conductive film 13, and piezoelectric film 14 are all oriented on the (111) plane.

[0151] Figure 31 The XRD-based results of the sample prepared in Example 5, with the (111) plane as the diffraction plane, are shown. The results of the scan. For example... Figure 31 As shown, the substrate 11, conductive film 13, and piezoelectric film 14 exhibit triple symmetry. It should be noted that although the peak of conductive film 13 is shifted by 60°, it is still an epitaxially grown single-crystal film, and piezoelectric film 14 is also an epitaxially grown single-crystal film.

[0152] (Example 6)

[0153] In Example 6, a film was formed using a Si / ZrO2 / Pt / SRO / PZT configuration. The substrate 11 used was Si (110). It should be noted that after forming the PZT as the piezoelectric film 14, its thickness was measured by XRF, and the result was 1.0 μm. It should also be noted that a Pb / Zr / Ti (130 / 52 / 48) target was used as the PZT material.

[0154] Figure 32 The results of XRD-based θ-2θ spectra measurements of the samples prepared in Example 6 are shown. Figure 32 As shown, the substrate 11 and the conductive film 13 are preferably oriented on the (110) plane.

[0155] Figure 32 The XRD-based results of the sample prepared in Example 6, with the (111) plane as the diffraction plane, are shown. The results of the scan. For example... Figure 33 As shown, the substrate 11, conductive film 13, and piezoelectric film 14 exhibit double symmetry. Therefore, it can be said that the piezoelectric film 14 is an epitaxially grown single-crystal film.

[0156] As can be seen from the results of Examples 1-6, the buffer film 12 is epitaxially grown according to the orientation of the substrate 11, and various piezoelectric films 14 formed on it are also epitaxially grown. It is believed that this is because, as will be explained below, after the buffer film 12 is formed, the crystal structure of the buffer film 12 changes accordingly to the piezoelectric material formed on it.

[0157] Figure 33 The results are shown by STEM observation of the cross-sections of the buffer film 12 and the conductive film 13 of the sample formed with the PZT(30 / 70) film of Example 1. Figure 33 As shown in (a), the length between the protrusions 12b is 4.2 nm. Figures 31-33 (b) is an enlarged view of the protrusion 12b.

[0158] Figure 32 The results are shown by STEM observation of the cross-sections of the buffer film 12 and the conductive film 13 on a sample of the BFO film formed in Example 3. Figure 31 As shown in (a), the length between the protrusions 12b is 3.9 nm. Figure 33 (b) is an enlarged view of the protrusion 12b.

[0159] Figure 32 The results are shown by STEM observation of the cross-sections of the buffer film 12 and the conductive film 13 on a sample of the BLT film formed in Example 4. Figure 33 As shown in (a), the length between the protrusions 12b is 5.5 nm. Figure 31 (b) is an enlarged view of the protrusion 12b.

[0160] like Figure 32 As shown, the height of the protrusion 12b varies according to the lattice constant of the piezoelectric film 14. For example, Figure 33 The lattice constant of the a-axis of the BFO shown is 0.3971 nm, which is consistent with... Figure 34 PZT and Figure 34 The BLT is the shortest. At this point, as... Figure 34 As shown in (b), the height of the protrusion 12b is 6.3 nm. It is believed that during the film formation process of BFO as piezoelectric film 14, the protrusion 12b extends upward in conjunction with the short lattice constant of BFO.

[0161] on the other hand, Figure 34 The lattice constant of the a-axis of the BLT shown is 0.5411 nm, which is consistent with... Figure 35 PZT and Figure 35 The BFO is the longest. At this point, as... Figure 35As shown in (b), the height of the protrusion 12b is 2.8 nm. It is believed that during the film formation process of the BLT, which serves as the piezoelectric film 14, the protrusion 12b is compressed downward in conjunction with the BLT with a long lattice spacing.

[0162] In this way, the buffer film 12, especially the protrusion 12b, is deformed according to the type of piezoelectric film 14, and consequently the lattice spacing of the conductive film 13 and film 16 on the buffer film 12 also changes. Figure 36 (a) is a lattice diagram showing a cross-section of the interface between conductive film 13 and film 16 when the BFO film is formed. Figure 35 (b) is a lattice diagram showing the cross-section of the interface between conductive film 13 and film 16 when the BLT film is formed.

[0163] Regarding ​ (b) shows the molecular spacing between conductive films 13 and 16 when a BLT film is formed, for example... ​ (a) shows that the conductive films 13 and 16, when BFO films are formed, have longer molecular spacing.

[0164] (Example 7)

[0165] In Example 7, a film was formed using the Si / ZrO2 / Pt / SRO / AlN configuration. The substrate 11 used was Si(100). The manufacturing conditions up to the SRO film were the same as in Examples 1-6. AlN was formed under the following conditions.

[0166] Apparatus: RF magnetron sputtering apparatus

[0167] Power: 200W

[0168] Gas: Ar

[0169] Pressure: 0.5 Pa

[0170] Film formation time: 60 minutes

[0171] Substrate temperature: 200℃

[0172] ​ The results shown are obtained by measuring the φ-scan X-ray diffraction pattern of AlN based on XRD for the membrane structure 101 of Example 7. ​ As shown, the AlN film exhibits 6-fold symmetry, a single orientation at (0001), and is monocrystalline. It should be noted that... ​ The circular numbers 1 and 2 shown are displayed rotated 90° within the plane.

[0173] (Example 8)

[0174] In Example 8, a film was formed using the Si / ZrO2 / Pt / SRO / LiNbO3 (LN) method. The substrate 11 used was Si (100). The manufacturing conditions up to the SRO film were the same as in Examples 1-6. The LN film was formed under the following conditions.

[0175] Apparatus: RF magnetron sputtering apparatus

[0176] Power: 160W

[0177] Gas: Ar / O2 ratio 2%

[0178] Pressure: 0.8 Pa

[0179] Film formation time: 9 hours

[0180] Substrate temperature: 400℃

[0181] ​ The results of LN determination based on the φ-scan X-ray diffraction pattern obtained by XRD method for the membrane structure 101 of Example 8 are shown. ​ As shown, the LN film exhibits 4-fold symmetry, with a single orientation at (001), and is monocrystalline.

[0182] As can be seen from the results of Examples 1 to 8 above, if an epitaxially grown Pt film and SRO film are formed on a zirconium-containing buffer film, and a piezoelectric film is formed on top of it, a single-crystallized piezoelectric film can be formed.

[0183] Explanation of reference numerals in the attached figures

[0184] 11: Substrate;

[0185] 12: Buffer membrane;

[0186] 12a: Membrane portion;

[0187] 12b: Protrusion;

[0188] 13, 15: Conductive film;

[0189] 14: Piezoelectric film / superconductor film;

[0190] 16: membrane;

[0191] 101: Membrane structure.

Claims

1. A membrane structure comprising: substrate; A buffer film containing zirconium oxide and having a tetragonal crystal structure, formed on the substrate and consisting of a film portion and protrusion portions; An epitaxially grown metal film containing platinum group elements formed on the buffer film; and The epitaxially grown Sr(Ti)-containing film formed on the metal film 1-x Ru x O3 membrane, in which, 0≤x≤1。 2. The membrane structure according to claim 1, wherein, The thickness of the metal film is 20nm to 150nm.

3. The membrane structure according to claim 1 or 2, wherein, The buffer membrane further contains rare earth elements or alkaline earth elements.

4. The membrane structure according to claim 1 or 2, wherein, The surface area of ​​the buffer membrane is 1.30 to 1.60 compared to the plane.

5. The membrane structure according to claim 1 or 2, wherein, The substrate is oriented on the (100) plane, (110) plane, or (111) plane.

6. The membrane structure according to claim 1 or 2, wherein, The buffer film is epitaxially grown according to the orientation of the substrate.

7. A single-crystal piezoelectric film formed on the film according to any one of claims 1 to 6.

8. The piezoelectric film according to claim 7, having a trigonal crystal structure.

9. The piezoelectric film according to claim 8, wherein, The materials for the piezoelectric film are BiFeO3, LiNbO3, or LiTaO3.

10. The piezoelectric film according to claim 7, having a hexagonal crystal structure.

11. The piezoelectric film according to claim 10, wherein, The material of the piezoelectric film is AlN.

12. The piezoelectric film according to claim 7, having a tungsten bronze-type crystal structure.

13. The piezoelectric film according to claim 7, wherein it has a bismuth layered crystal structure.

14. The piezoelectric film according to claim 13, wherein, The material of the piezoelectric film is Bi4Ti3O 12 Or (Bi) 4-x La x Ti3O 12 , where 0 ≤ x < 1.

15. The piezoelectric film according to claim 7, wherein it is a perovskite oxide represented by ABO3.

16. The piezoelectric film according to claim 7, wherein, The material of the piezoelectric film is lead zirconate titanate.

17. The piezoelectric film according to claim 16, wherein, The lead zirconate titanate is Pb(Zr) 0.3 Ti 0.7 )O3.

18. A single-crystal superconducting film formed on the film according to any one of claims 1 to 6.

19. The superconducting film according to claim 18, wherein it is a bismuth-based superconductor.

20. The superconducting film according to claim 19, wherein, The superconducting film is made of Bi₂SrCa₂Cu₃O 10 .

21. The superconducting film according to claim 18, wherein it is a yttrium-based superconductor.

22. The superconducting film according to claim 21, wherein, The material of the yttrium-based superconductor is YBa2Cu3O7.

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