Ultrasonic transducer, distance measuring device, and method for manufacturing ultrasonic transducer

Abstract

An ultrasonic transducer (100) has a vibrating plate (2) and a frame (1). The vibrating plate (2) is capable of vibrating. The frame (1) is connected to the vibrating plate (2). An opening portion (OP) is provided in the vibrating plate (2). An internal space (IS) is provided in the frame (1). The internal space (IS) communicates with the opening portion (OP). The vibrating plate (2) and the frame (1) constitute an acoustic resonance structure that amplifies ultrasonic waves generated by vibration of the vibrating plate (2) using the opening portion (OP) and the internal space (IS), and are integrated.

Description

Technical Field

[0001] This disclosure relates to an ultrasonic transducer, a ranging device, and a method for manufacturing an ultrasonic transducer. Background Technology

[0002] Distance sensors, used for perimeter monitoring in automobiles and transport vehicles as well as for non-contact operation of devices, typically employ ultrasonic transducers. Commonly used ultrasonic transducers often utilize bulk lead zirconate titanate (PZT: Pb(Zr,Ti)O3). However, the miniaturization of ultrasonic transducers using bulk PZT is limited by machining precision requirements. Therefore, MEMS (Micro Electro Mechanical Systems) ultrasonic transducers are being developed as a means to achieve miniaturization of ultrasonic transducers.

[0003] The most common MEMS ultrasonic transducers use thin-film vibrating plates (diaphragms). The structure of a MEMS ultrasonic transducer containing a vibrating plate is made of silicon (Si), a semiconductor. MEMS ultrasonic transducers are fabricated using semiconductor technologies such as deep reactive ion etching (DRIE). By applying semiconductor technologies with high dimensional accuracy to the fabrication of the vibrating plate, miniaturization of MEMS ultrasonic transducers can be achieved.

[0004] For example, Japanese Patent Publication No. 2010-515335 (Patent Document 1) describes a sound source tracking microphone (ultrasonic transducer) equipped with a MEMS microphone and an acoustic resonance structure. The acoustic resonance structure has a cavity and a sound inlet passage. The acoustic resonance structure is configured to amplify the sound entering the acoustic resonance structure through the cavity and the inlet passage.

[0005] Prior art literature

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Publication No. 2010-515335 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] The aforementioned announcement describes placing a MEMS microphone within a cavity of the acoustic resonant structure. Therefore, the acoustic resonant structure needs to be formed after placing the microphone within the cavity. Consequently, manufacturing the acoustic resonant structure with high precision is very difficult. Therefore, the dimensional accuracy of the acoustic resonant structure is reduced.

[0010] This disclosure is made in view of the above-mentioned problems, and its purpose is to provide an ultrasonic transducer, a ranging device, and a method for manufacturing an ultrasonic transducer that can suppress the reduction of dimensional accuracy of acoustic resonant structures.

[0011] Solution for solving the problem

[0012] The disclosed ultrasonic transducer includes a vibrating plate and a frame. The vibrating plate is capable of vibration. The frame is connected to the vibrating plate. An opening is provided in the vibrating plate. An internal space is provided in the frame. The internal space communicates with the opening. The vibrating plate and the frame constitute an acoustic resonant structure and are integrally formed. This acoustic resonant structure amplifies the ultrasonic waves generated by the vibration of the vibrating plate by utilizing the opening and the internal space.

[0013] The effects of the invention

[0014] According to the ultrasonic transducer disclosed herein, it is possible to suppress the reduction in dimensional accuracy of acoustic resonant structures. Attached Figure Description

[0015] Figure 1 This is a perspective view that schematically illustrates the structure of the ultrasonic transducer involved in Embodiment 1.

[0016] Figure 2 It is along Figure 1 A sectional view along line II-II.

[0017] Figure 3 This is a cross-sectional view that schematically shows the appearance of a substrate with a lower electrode, a piezoelectric film and an upper electrode stacked on it in the manufacture of the ultrasonic transducer according to Embodiment 1.

[0018] Figure 4 This is a cross-sectional view that schematically shows the appearance of the substrate with an opening in the manufacture of the ultrasonic transducer according to Embodiment 1.

[0019] Figure 5 This is a cross-sectional view that schematically shows the appearance of the substrate used in the manufacture of the ultrasonic transducer according to Embodiment 1 having an internal space.

[0020] Figure 6 This is a perspective view that schematically represents the structure of the ultrasonic transducer involved in Embodiment 2.

[0021] Figure 7 This is a top view that schematically shows the structure of the ultrasonic transducer involved in Embodiment 2.

[0022] Figure 8 It is along Figure 6 A cross-sectional view of line VIII-VIII.

[0023] Figure 9This is a cross-sectional view that schematically shows the central part of the ultrasonic transducer according to Embodiment 2 and the beam moving away from the bottom of the frame.

[0024] Figure 10 This is a cross-sectional view that schematically shows the central portion of the ultrasonic transducer according to Embodiment 2 and the beam moving toward the bottom of the frame.

[0025] Figure 11 This is a cross-sectional view that schematically shows the structure of the first substrate used in the manufacture of the ultrasonic transducer according to Embodiment 2.

[0026] Figure 12 This is a cross-sectional view that schematically shows the appearance of the first substrate used in the manufacture of the ultrasonic transducer according to Embodiment 2, which has an opening and a slit.

[0027] Figure 13 This is a cross-sectional view that schematically shows the structure of the second substrate used in the manufacture of the ultrasonic transducer according to Embodiment 2.

[0028] Figure 14 This is a cross-sectional view that schematically shows the appearance of the second substrate used in the manufacture of the ultrasonic transducer according to Embodiment 2 having an internal space.

[0029] Figure 15 This is a cross-sectional view that schematically shows how the first substrate and the second substrate used in the manufacture of the ultrasonic transducer according to Embodiment 2 are joined together.

[0030] Figure 16 This is a schematic cross-sectional view showing the first and second substrates used in the manufacture of the ultrasonic transducer according to Embodiment 2 with the fifth silicon layer removed.

[0031] Figure 17 This is a cross-sectional view that schematically shows the appearance of a first substrate used in the manufacture of the ultrasonic transducer according to Embodiment 2, on which a lower electrode, a piezoelectric film, and an upper electrode are stacked.

[0032] Figure 18 This is a top view that schematically shows the structure of the ultrasonic transducer involved in Embodiment 3.

[0033] Figure 19 This is a schematic cross-sectional view that roughly shows the deformed appearance of the beam of the ultrasonic transducer involved in Embodiment 3.

[0034] Figure 20 This is a schematic cross-sectional view that roughly shows the deformed appearance of the beam of the ultrasonic transducer according to Embodiment 2.

[0035] Figure 21 This is a cross-sectional view that schematically shows the structure of the ultrasonic transducer involved in Embodiment 4.

[0036] Figure 22 This is a cross-sectional view that schematically shows the structure of the ultrasonic transducer according to Embodiment 5.

[0037] Figure 23 This is a top view that schematically shows the structure of the ultrasonic transducer involved in Embodiment 6.

[0038] Figure 24 This is a schematic diagram that roughly illustrates the structure of the ranging device involved in Embodiment 7. Detailed Implementation

[0039] The following description of the embodiments is based on the accompanying drawings. It should be noted that, in the following description, the same or corresponding parts are labeled with the same reference numerals, and repeated descriptions are omitted.

[0040] Implementation method 1.

[0041] use Figure 1 as well as Figure 2 The structure of the ultrasonic transducer 100 according to Embodiment 1 is explained.

[0042] like Figure 1 As shown, the ultrasonic transducer 100 includes a frame 1 and a vibrating plate 2. The ultrasonic transducer 100 according to this embodiment also includes a first piezoelectric element 3. It should be noted that, for ease of explanation, although... Figure 1 The flat map shows the side of the first piezoelectric element 3, but as... Figure 2 As shown, a step is provided on the side of the first piezoelectric element 3.

[0043] like Figure 2 As shown, the frame 1 is connected to the vibrating plate 2. An internal space IS is provided in the frame 1. The frame 1 includes a first silicon layer 51 and a first oxide film 41. The first silicon layer 51 has a peripheral wall portion 11 and a bottom portion 12. It should be noted that... Figure 2 The boundary between the peripheral wall 11 and the bottom 12 is indicated by a dashed line. The peripheral wall 11 is connected to the bottom 12 in a way that it rises from the bottom 12. The peripheral wall 11 surrounds the internal space IS. The bottom 12 and the vibrating plate 2 sandwich the internal space IS. A first oxide film 41 is stacked on the peripheral wall 11. The first oxide film 41 is sandwiched between the peripheral wall 11 and the vibrating plate 2. It should be noted that the shape of the frame 1 can be either a cuboid or a cylinder.

[0044] The vibrating plate 2 is connected to the frame 1 in a manner that covers the internal space IS. This structure is sometimes referred to as a chamber structure. An opening OP is provided in the vibrating plate 2. The opening OP penetrates the vibrating plate 2. Ideally, the opening OP should be positioned at its center in the in-plane direction through the vibrating plate 2. The internal space IS communicates with the opening OP. It should be noted that the shape of the opening OP can be either circular or rectangular.

[0045] The vibrating plate 2 can vibrate. Specifically, the vibrating plate 2 can vibrate under the action of the first piezoelectric element 3. The vibrating plate 2 is configured to generate ultrasonic waves through vibration. It should be noted that the principle of ultrasonic wave generation by the vibrating plate 2 will be explained later.

[0046] The vibrating plate 2 includes a second silicon layer 52 and a second oxide film 42. An opening OP penetrates both the second silicon layer 52 and the second oxide film 42. The second silicon layer 52 is stacked on the first oxide film 41. The second oxide film 42 is stacked on the second silicon layer 52.

[0047] The frame 1 and the vibrating plate 2 constitute an acoustic resonance structure. This structure amplifies the ultrasonic waves generated by the vibration of the vibrating plate 2 using the opening OP and the internal space IS. The acoustic resonance structure is integrated as a single unit. For example, the acoustic resonance structure can be a Helmholtz resonator. It should be noted that the acoustic resonance structure will be described in detail later.

[0048] The frame 1 and the vibrating plate 2 are integrally formed. In other words, the frame 1 and the vibrating plate 2 are connected without gaps. More specifically, the first oxide film 41 of the frame 1 and the second silicon layer 52 of the vibrating plate 2 are connected without gaps. It should be noted that in this embodiment, "integrated" and "connected without gaps" refer to the connection through the bonding of atomic or molecular units such as covalent bonds. It is desirable that the frame 1 and the vibrating plate 2 are integrally formed using MEMS technology. It should be noted that the method for manufacturing the frame 1 and the vibrating plate 2 using MEMS technology will be described later.

[0049] It is desirable that the peripheral wall 11 and bottom 12 (first silicon layer 51) of the frame 1 and the second silicon layer 52 of the vibrating plate 2 are made of silicon (Si). Silicon (Si) is a material that is easily applied to semiconductor manufacturing technology and has excellent mechanical properties as an elastic material. The first oxide film 41 and the second oxide film 42 are, for example, oxide films of silicon (Si).

[0050] The first piezoelectric element 3 is connected to the vibrating plate 2. The first piezoelectric element 3 is disposed on the vibrating plate 2. Specifically, the first piezoelectric element 3 is disposed on the second oxide film 42 of the vibrating plate 2. The first piezoelectric element 3 is disposed on the side opposite to the internal space IS relative to the vibrating plate 2. In other words, the first piezoelectric element 3 is disposed outside the internal space IS. Figure 1As shown, the first piezoelectric element 3 has an annular shape. The first piezoelectric element 3 is configured to expose the opening OP.

[0051] The first piezoelectric element 3 is configured as an actuator for vibrating the vibrating plate 2. The first piezoelectric element 3 is configured to vibrate the vibrating plate 2 when transmitting ultrasonic waves. Additionally, the first piezoelectric element 3 is configured as a strain sensor for measuring the strain of the vibrating plate 2. The first piezoelectric element 3 is configured to function as a strain sensor for the vibrating plate 2 when receiving ultrasonic waves. Thus, the vibration of the vibrating plate 2 is measured when receiving ultrasonic waves. The ultrasonic transducer 100 is configured to apply a voltage to the first piezoelectric element 3. The first piezoelectric element can be electrically connected to a power source (not shown).

[0052] like Figure 2 As shown, the first piezoelectric element 3 includes a lower electrode 3A, a piezoelectric film 3B, and an upper electrode 3C. The lower electrode 3A and the upper electrode 3C sandwich the piezoelectric film 3B. The lower electrode 3A is disposed on the vibrating plate 2. The piezoelectric film 3B is disposed on the side opposite to the internal space IS relative to the lower electrode 3A. The lower electrode 3A, the piezoelectric film 3B, and the upper electrode 3C have successively decreasing outer diameters.

[0053] The material of the piezoelectric thin film 3B is, for example, lead zirconate titanate (PZT: Pb(Zr,Ti)O3), aluminum nitride (AlN), or potassium sodium niobate (KNN: (K,Na)NbO3). It is desirable that the materials of the lower electrode 3A and the upper electrode 3C be a laminate of titanium (Ti) and platinum (Pt) films commonly used in piezoelectric elements. It should be noted that the materials of the lower electrode 3A and the upper electrode 3C can be other laminated films, as long as they have sufficient conductivity to function as electrodes and good adhesion to the substrate. Alternatively, an oxide electrode film, such as a strontium oxide (SrO) film, which has the effect of reducing polarization fatigue, can be disposed between the upper electrode 3C and the piezoelectric thin film 3B.

[0054] Next, the operation of the ultrasonic transducer 100 according to Embodiment 1 will be explained.

[0055] By applying a voltage between the lower electrode 3A and the upper electrode 3C, the piezoelectric film 3B contracts. This contraction of the piezoelectric film 3B causes the vibrating plate 2 to bend. By applying a voltage to the piezoelectric film 3B at a frequency close to the resonant frequency of the vibrating plate 2, the vibrating plate 2 vibrates under the influence of resonant vibration. It should be noted that, in this embodiment, a frequency close to the resonant frequency of the vibrating plate 2 refers to a frequency where the vibration displacement of the vibrating plate 2 is twice the maximum displacement (peak displacement). -1 / 2 More than twice and 2 1 / 2 The frequency range is less than 10 times that of ultrasound.

[0056] In addition, when the ultrasonic transducer 100 is used as an ultrasonic sensor, the vibration of the vibrating plate 2 under the action of ultrasonic waves is obtained via the first piezoelectric element 3 and used as a voltage signal.

[0057] The dimensions of the internal space IS of the frame 1 and the opening OP of the vibrating plate 2 are set such that the resonant frequency of the frame 1 is close to the resonant frequency of the vibrating plate 2. It should be noted that, in this embodiment, "the resonant frequency of the frame 1 is close to the resonant frequency of the vibrating plate 2" means that the resonant frequency of the frame 1 is set to be 2 times the maximum displacement of the vibrating plate 2. -1 / 2 More than twice and 2 1 / 2 The frequency range is less than 10 times. Therefore, the sound pressure of the ultrasonic waves generated by the vibration of the vibrating plate 2 is amplified by using an acoustic resonance structure.

[0058] The resonant frequency of the acoustic resonance structure is determined using the diameter D1 of the internal space IS, the diameter D2 of the opening OP, the height L1 of the internal space IS, the height L2 of the opening OP, the opening correction a, and the in-plane area S of the opening OP. m The volume V of the internal space IS c It is expressed by the following equation (1). It should be noted that the area S in the in-plane direction of the opening OP... m It is expressed by the following equation (2). The volume V of the internal space IS c It is expressed by the following formula (3).

[0059] Mathematical Formula 1

[0060]

[0061] Mathematical formula 2

[0062] S m =π(d / 2) 2 Equation (2)

[0063] Mathematical Formula 3

[0064] V c =π(D / 2) 2 l2 Equation (3)

[0065] Furthermore, when the ultrasonic transducer 100 is used as an ultrasonic sensor, the sound pressure of the received ultrasonic wave is amplified through acoustic resonance, thereby increasing the vibration of the vibrating plate 2. As a result, the strain of the first piezoelectric element 3 increases, thus obtaining an amplified signal.

[0066] Next, using Figures 2-5 The manufacturing method of the ultrasonic transducer 100 according to Embodiment 1 is explained.

[0067] like Figure 3As shown, in the preparation process, substrate 9 is prepared. Substrate 9 is an SOI substrate (SOI: Silicon On Insulator). The ultrasonic transducer 100 according to this embodiment is manufactured by processing an SOI substrate. Substrate 9 includes, for example, a first silicon layer 51, a second silicon layer 52, a first oxide film 41, and a second oxide film 42. The thickness of the first silicon layer 51 is, for example, 100 μm or more and 600 μm or less. The thickness of the second silicon layer 52 is, for example, 1 μm or more and 100 μm or less. The second oxide film 42 is configured as a surface oxide film. The method for forming the second oxide film 42 is suitable for thermal oxidation, which can reduce surface roughness.

[0068] Next, the lower electrode 3A, the piezoelectric thin film 3B, and the upper electrode 3C are sequentially formed on the second oxide film 42. The lower electrode 3A, the piezoelectric thin film 3B, and the upper electrode 3C are formed by sputtering or CSD (Chemical Solution Deposition). The thickness of the lower electrode 3A and the upper electrode 3C is, for example, 0.1 μm. The thickness of the piezoelectric thin film 3B is, for example, 1 μm or more and 9 μm or less.

[0069] Next, as Figure 4 As shown, the lower electrode 3A, piezoelectric film 3B, upper electrode 3C, second oxide film 42, and second silicon layer 52 are patterned.

[0070] Specifically, photolithography using a resist film as a protective film is suitable for patterning the upper electrode 3C. The etching process for the upper electrode 3C can be performed using reactive ion etching (RIE) or photolithography using an etchant. Regardless of the etching process used, conditions must be set to achieve a sufficient etch selectivity ratio for both the upper electrode 3C and the substrate film. For example, when using PZT as the piezoelectric thin film 3B and a stack of titanium (Ti) and platinum (Pt) films as the upper electrode 3C, and the stack is patterned using reactive ion etching, a chlorine (Cl2) / argon (Ar) gas is suitable. After patterning the upper electrode 3C, the resist film is removed. The resist film is removed using methods such as oxygen (O2) ashing.

[0071] Next, a pattern is formed on the piezoelectric thin film 3B using photolithography and etching. The etching process can be, for example, reactive ion etching or wet etching. During etching, conditions need to be set to achieve a sufficient etch selectivity between the piezoelectric thin film 3B and the substrate layer. For example, a stack of titanium (Ti) and platinum (Pt) films, along with PZT, can be used as the lower electrode 3A and the piezoelectric thin film 3B, respectively, and the stack can be patterned using reactive ion etching. In this case, chlorine (Cl2), boron chloride (BCl2), or hydrogen chloride (CH4) based gases are suitable. After the patterning of the piezoelectric thin film 3B, the resist film is removed by oxygen (O2) ashing or similar processes.

[0072] Next, the lower electrode 3A is patterned using photolithography and etching. The etching process can be, for example, reactive ion etching or wet etching. During etching, conditions need to be set to achieve a sufficient etch selectivity between the lower electrode 3A and the substrate layer. For example, when a stack of titanium (Ti) and platinum (Pt) films is used as the lower electrode 3A, and the stack is patterned by reactive ion etching, a chlorine (Cl2) / argon (Ar) gas is suitable. After the patterning of the lower electrode 3A is formed, the resist film is removed by oxygen (O2) ashing or similar processes.

[0073] Next, the second oxide film 42 formed on the second silicon layer 52 is patterned using photolithography and etching. The etching process can be, for example, reactive ion etching or wet etching. When the second oxide film 42 is patterned using reactive ion etching, a chlorine (Cl2-based) gas is suitable.

[0074] Next, the second silicon layer 52 is etched. Thus, in formation step S102, an opening OP is formed on the vibrating plate 2 (the second silicon layer 52). The desired etching process is, for example, deep reactive ion etching (DRIE). DRIE is performed using the Bosch method, which allows etching at a high aspect ratio. The etching process continues until the first oxide film 41 is exposed. After etching, the resist film is removed by oxygen (O2) ashing or similar treatment.

[0075] Next, as Figure 5 As shown, a pattern is formed on the first silicon layer 51 using photolithography and etching processes. Thus, in the formation process S102, a pattern is formed on the frame 1 (refer to...). Figure 2The first silicon layer 51 forms the internal space IS. The etching process is, for example, reactive ion etching or wet etching. Deep reactive ion etching (DRIE) using the Bosch method is preferred. The etching process continues until the first oxide film 41 is exposed. Next, the exposed first oxide film 41 is removed by etching. The etching process for the first oxide film 41 is either reactive ion etching or wet etching. When the first oxide film 41 is patterned by reactive ion etching, a chlorine (Cl2) based gas is suitable.

[0076] Next, as Figure 2 as well as Figure 5 As shown, a second substrate, which serves as a silicon substrate, is bonded to substrate 9. The second substrate forms the bottom 12 of the frame 1. The bonding between substrate 9 and the second substrate is achieved using surface activation bonding or room temperature activation bonding.

[0077] As described above, in the forming process S102, the frame 1 and the vibrating plate 2 are integrally formed from the substrate using MEMS manufacturing technology. Furthermore, the frame 1 and the vibrating plate 2 are formed to constitute an acoustic resonance structure, which amplifies the sound generated by the vibration of the vibrating plate 2 by utilizing the opening OP and the internal space IS.

[0078] Next, for example, the MEMS ultrasonic transducer 100 is completed by cutting the substrate to chip size.

[0079] It should be noted that, in Figure 4 In this embodiment, an SOI substrate is prepared as substrate 9, but substrate 9 is not limited to this. For example, a CSOI substrate (CSOI: Cavity Silicon On Insulator) with a hollow structure from the initial state can be used as the substrate. When using a CSOI substrate, since the first piezoelectric element 3 and the opening OP are formed on the hollow structure, the patterning process of the second silicon layer 52 and the bonding process of the second substrate can be omitted. Therefore, it is easier to manufacture the ultrasonic transducer 100.

[0080] Next, the effects of this implementation method will be explained.

[0081] According to the ultrasonic transducer 100 involved in Embodiment 1, such as Figure 2As shown, the frame 1 and the vibrating plate 2 constitute an acoustic resonance structure and are integrated as one unit. Therefore, the acoustic resonance structure can be manufactured with high precision. Specifically, compared to the case where the frame 1 and the vibrating plate 2 are separate units, the acoustic resonance structure can be manufactured with high precision. In particular, compared to the case where the acoustic resonance structure is manufactured by fitting the separate frame 1 and the vibrating plate 2 together, the acoustic resonance structure can be manufactured with high precision. Therefore, the reduction in the dimensional accuracy of the acoustic resonance structure can be suppressed. In other words, the dimensional accuracy of the acoustic resonance structure can be improved.

[0082] like Figure 2 As shown, the first piezoelectric element 3 is connected to the vibrating plate 2. Therefore, the vibrating plate 2 can be vibrated by the first piezoelectric element 3. In addition, the strain of the vibrating plate 2 can be measured by the first piezoelectric element 3. Therefore, the frequency of the ultrasonic waves received by the acoustic resonance structure can be determined based on the strain of the vibrating plate 2.

[0083] like Figure 2 As shown, the frame 1 and the vibrating plate 2 are integrated using MEMS manufacturing technology. Therefore, it is possible to manufacture acoustic resonant structures with high precision. For example, acoustic resonant structures can be manufactured with dimensional accuracy within an error range of 1 μm to 10 μm.

[0084] According to the manufacturing method of the ultrasonic transducer 100 involved in Embodiment 1, such as Figure 3 As shown, the frame 1 and the vibrating plate 2 are manufactured in a single piece from the substrate 9 using MEMS manufacturing technology. Therefore, the acoustic resonance structure can be manufactured with high precision. Specifically, compared to the case where the frame 1 and the vibrating plate 2 are separate components, the acoustic resonance structure can be manufactured with high precision. Therefore, the reduction in the dimensional accuracy of the acoustic resonance structure can be suppressed.

[0085] like Figure 3 As shown, the frame 1 and the vibrating plate 2 are integrally molded from the substrate 9 using MEMS manufacturing technology. Therefore, for example, compared to assembling by fitting separately manufactured frame 1 and vibrating plate 2 together, the assembly cost of the ultrasonic transducer 100 can be reduced. Furthermore, for example, compared to assembling by fitting separately manufactured frame 1 and vibrating plate 2 together, a precise assembly process is not required. Therefore, an acoustic resonance structure can be easily manufactured.

[0086] Implementation method 2.

[0087] Next, using Figures 6-10 The structure of the ultrasonic transducer 100 according to Embodiment 2 will be described. Unless otherwise specified, Embodiment 2 has the same structure, manufacturing method, and effects as Embodiment 1 described above. Therefore, the same reference numerals are used to refer to the same structures as in Embodiment 1, and repeated descriptions are omitted.

[0088] like Figure 6 as well as Figure 7 As shown, the vibrating plate 2 of the ultrasonic transducer 100 according to this embodiment includes a central portion 21, an outer peripheral portion 22, and a beam 6. A first piezoelectric element 3 is connected to the central portion 21. The central portion 21 is configured to vibrate under the action of the first piezoelectric element 3. The outer peripheral portion 22 is disposed around the central portion 21. The beam 6 connects the central portion 21 and the outer peripheral portion 22 between the central portion 21 and the outer peripheral portion 22. A slit SL is provided in the vibrating plate 2. The slit SL is provided around the beam 6. Therefore, the beam 6 can be bent along the direction in which the frame 1 and the vibrating plate 2 are connected. The dimension of the short side of the slit SL is, for example, 10 μm. It should be noted that, for ease of explanation, Figure 6 In the diagram, the side of the first piezoelectric element 3 is shown as flat, but... Figure 7 as well as Figure 8 As shown, a step is provided on the side of the first piezoelectric element 3.

[0089] like Figures 8-10 As shown, the frame 1 and the vibrating plate 2 constitute a variable internal space IS volume. Figure 9 As shown, the frame 1 and the vibrating plate 2 are configured such that the volume of the internal space IS can be changed by deforming the beam 6 away from the bottom 12 of the frame 1. More specifically, by deforming the beam 6 away from the bottom 12 of the frame 1, the central portion 21 moves away from the bottom 12 of the frame 1. As a result, the volume of the internal space IS increases.

[0090] like Figure 10 As shown, the frame 1 and the vibrating plate 2 can be configured to change the volume of the internal space IS by deforming the beam 6 in a manner that brings it closer to the bottom 12 of the frame 1. More specifically, by deforming the beam 6 in a manner that brings it closer to the bottom 12 of the frame 1, the central portion 21 moves in a manner that brings it closer to the bottom 12 of the frame 1. As a result, the volume of the internal space IS decreases.

[0091] It should be noted that the deformation of beam 6 can be greater than the maximum displacement caused by the resonance of vibrating plate 2. Alternatively, the deformation of beam 6 can be less than the maximum displacement caused by the resonance of vibrating plate 2. It is desirable that the shape of the deformed beam 6 will not change due to the vibration of the central portion 21.

[0092] The desired material for beam 6 is, for example, silicon (Si), which is readily applicable to semiconductor manufacturing technology and possesses excellent mechanical properties as an elastic material.

[0093] like Figure 6As shown, beam 6 includes multiple beam portions 60. The multiple beam portions 60 are bendable along the direction connecting the frame 1 and the vibrating plate 2. In this embodiment, beam 6 includes a first beam portion 61 and a second beam portion 62. The first beam portion 61 and the second beam portion 62 are bendable along the direction connecting the frame 1 and the vibrating plate 2. The first beam portion 61 and the second beam portion 62 may have the same shape.

[0094] like Figure 7 As shown, from the vibrating plate 2 toward the frame 1 (refer to...) Figure 6 When viewed from the direction of the central portion 21, the first beam portion 61 and the second beam portion 62 are each C-shaped. The first beam portion 61 and the second beam portion 62 are arranged along the circumference of the central portion 21. The first beam portion 61 and the second beam portion 62 are separated from each other by a slit SL. More specifically, the first beam portion 61 and the second beam portion 62 are separated from each other by the radially extending portion of the slit SL of the central portion 21.

[0095] The slit SL includes a first slit portion SL1 and a second slit portion SL2. The first slit portion SL1 is located around the first beam portion 61. The second slit portion SL2 is located around the second beam portion 62. The first slit portion SL1 and the second slit portion SL2 each have a first slit portion, a second slit portion, and a third slit portion. The first slit portion is positioned relative to the beam 6 on the central portion 21 side. The second slit portion is positioned relative to the beam 6 on the outer peripheral portion 22 side. The third slit portion connects the first slit portion and the second slit portion. The first slit portion and the second slit portion are each C-shaped. The first slit portion and the second slit portion are arranged along the circumferential direction of the central portion 21. The third slit portion is arranged radially along the central portion 21. The third slit portion is straight in shape.

[0096] The ultrasonic transducer 100 also includes a second piezoelectric element 30. The second piezoelectric element 30 is connected to the beam 6. The second piezoelectric element 30 is configured as an actuator for deforming the beam 6.

[0097] The first piezoelectric element 3 and the second piezoelectric element 30 are formed from a common lower electrode 3A, an upper electrode 3C, and a piezoelectric thin film 3B. In this embodiment, the second piezoelectric element 30 includes a first element 31 and a second element 32. The first element 31 is connected to the first beam portion 61. The second element 32 is connected to the second beam portion 62.

[0098] Next, using Figures 8-10 The operation of the ultrasonic transducer 100 according to Embodiment 2 is explained.

[0099] like Figures 8-10As shown, the second piezoelectric element 30 deforms when a voltage is applied to it. It should be noted that the principle of deformation of the second piezoelectric element 30 is the same as that of deformation of the first piezoelectric element 3, and therefore will not be explained further. The deformation of the second piezoelectric element 30 causes the beam 6 to bend. Specifically, the first element 31 and the second element 32 deform when voltages are applied to them respectively. The deformation of the first element 31 and the second element 32 causes the first beam portion 61 and the second beam portion 62 to bend respectively. This changes the volume of the internal space IS. The ultrasonic transducer 100 is configured to receive or transmit ultrasonic waves when the volume of the internal space IS has changed.

[0100] Next, using Figure 8 as well as Figures 11-17 The manufacturing method of the ultrasonic transducer 100 according to Embodiment 2 is explained.

[0101] like Figure 11 As shown, in the preparation process, a first substrate 91, which serves as substrate 9, is prepared. The first substrate 91 is a three-layer SOI substrate. Vibration plate 2 (refer to...) Figure 8 The first substrate 91 is formed. The first substrate 91 includes a third silicon layer 53, a fourth silicon layer 54, a fifth silicon layer 55, a first surface oxide film 43, a third oxide film 44, and a fourth oxide film 45. The first surface oxide film 43, the third silicon layer 53, the third oxide film 44, the fourth silicon layer 54, the fourth oxide film 45, and the fifth silicon layer 55 are sequentially stacked. The thickness of the third silicon layer 53 and the fourth silicon layer 54 is, for example, 1 μm or more and 100 μm or less. The thickness of the fifth silicon layer 55 is, for example, 100 μm or more and 600 μm or less.

[0102] Next, as Figure 12 As shown, in the formation process S102, the first surface oxide film 43 and the third silicon layer 53 are etched to form a pattern. This forms the opening OP and the slit SL.

[0103] In addition, such as Figure 13 As shown, in the preparation process, a second substrate 92, which serves as substrate 9, is prepared. The second substrate 92 is a double-layer SOI substrate. (Refer to frame 1) Figure 8 The second substrate 92 is formed from a third substrate. The second substrate 92 includes a sixth silicon layer 56, a seventh silicon layer 57, a second surface oxide film 46, and a fifth oxide film 47. The second surface oxide film 46, the sixth silicon layer 56, the fifth oxide film 47, and the seventh silicon layer 57 are stacked sequentially. The thickness of the sixth silicon layer 56 is, for example, 100 μm or more and 600 μm or less. The thickness of the seventh silicon layer 57 is, for example, 1 μm or more and 100 μm or less.

[0104] Next, as Figure 14As shown, the second surface oxide film 46 and the sixth silicon layer 56 are etched to form a pattern. This forms the internal space IS.

[0105] Next, as Figure 15 As shown, the etched first substrate 91 and the etched second substrate 92 are bonded together. Specifically, the third silicon layer 53 of the first substrate 91 and the second surface oxide film 46 of the second substrate 92 are bonded together.

[0106] Next, as Figure 15 as well as Figure 16 As shown, the fifth silicon layer 55 is removed by etching. As a result, the fourth oxide film 45 is exposed.

[0107] Next, as Figure 17 As shown, a lower electrode 3A, a piezoelectric film 3B, and an upper electrode 3C are sequentially stacked on the fourth oxide film 45.

[0108] Next, as Figure 8 As shown, the first piezoelectric element 3 and the second piezoelectric element 30 are formed by etching the lower electrode 3A, the piezoelectric thin film 3B and the upper electrode 3C.

[0109] It should be noted that, as Figure 11 As shown, a three-layer SOI substrate is used as the first substrate 91, but the final structure, which is only used to support the substrate, does not contain a fifth silicon layer 55. Therefore, the first substrate 91 is not limited to a three-layer SOI substrate. For example, if the rigidity of the wafer is high enough that there are no obstacles to handling during semiconductor processes, a two-layer SOI substrate can also be used as the first substrate 91. Alternatively, a dummy wafer can be used as the fifth silicon layer 55.

[0110] Next, the effects of this implementation method will be explained.

[0111] According to the ultrasonic transducer 100 involved in Embodiment 2, such as Figure 9 as well as Figure 10 As shown, the frame 1 and the vibrating plate 2 are configured to have a variable internal space IS volume. Therefore, the height dimension from the bottom 12 of the frame 1 to the vibrating plate 2 can be changed. This allows for the change of the resonant frequency of the acoustic resonance structure. Thus, for example, the resonant frequency of the acoustic resonance structure can be changed to correct the deviation between the resonant frequency of the vibrating plate 2 and the resonant frequency of the frame 1 caused by manufacturing errors, etc. Consequently, the reduction in sound amplification effect relying on resonance can be suppressed.

[0112] like Figures 8-10As shown, beam 6 can be bent along the direction connecting frame 1 and vibrating plate 2. Therefore, the central part 21 can be moved by the deformation of beam 6, thereby changing the height dimension from the bottom 12 of frame 1 to vibrating plate 2. Thus, the resonant frequency of the acoustic resonance structure can be changed by the deformation of beam 6. Therefore, the reduction of sound amplification effect relying on resonance can be suppressed by the deformation of beam 6.

[0113] like Figure 8 As shown, the second piezoelectric element 30 is connected to the beam 6. Therefore, the beam 6 can be deformed by applying a voltage to the second piezoelectric element 30.

[0114] like Figure 6 As shown, beam 6 comprises multiple beam sections 60. (As...) Figures 7-10 As shown, multiple beams 60 can be bent along the direction connecting the frame 1 and the vibrating plate 2. Therefore, the volume of the internal space IS can be changed by deforming the multiple beams 60. Thus, compared to the case where there is only one beam 6, the volume of the internal space IS can be easily changed. Consequently, it is easier to suppress the reduction of sound amplification effect relying on resonance.

[0115] Implementation method 3.

[0116] Next, using Figure 18 The structure of the ultrasonic transducer 100 according to Embodiment 3 will be described. Unless otherwise specified, Embodiment 3 has the same structure, manufacturing method, and effects as Embodiment 2 described above. Therefore, the same reference numerals are used to refer to the same structures as in Embodiment 2, and repeated descriptions are omitted.

[0117] like Figure 18 As shown, the second piezoelectric element 30 of the ultrasonic transducer 100 according to this embodiment includes a plurality of element portions 39. In this embodiment, the first element 31 includes a plurality of element portions 39. The second element 32 includes a plurality of element portions 39. In other words, the first element 31 and the second element 32 are each divided into a plurality of element portions 39.

[0118] Multiple component sections 39 are arranged at intervals SP along the long side of beam 6. In other words, the multiple component sections 39 are physically isolated from each other. Each of the multiple component sections 39 is configured to be subjected to an independent input signal.

[0119] In this embodiment, the first element 31 includes, for example, two element portions 39. The two element portions 39 of the first element 31 are respectively connected to the first beam portion 61. The two element portions 39 of the first element 31 are arranged at a distance SP from each other along the long side direction of the first beam portion 61.

[0120] The second element 32 includes, for example, two element portions 39. The two element portions 39 of the second element 32 are respectively connected to the second beam portion 62. The two element portions 39 of the second element 32 are arranged with a gap SP between them along the long side of the second beam portion 62.

[0121] Next, as Figure 19 The operation of the ultrasonic transducer 100 according to Embodiment 3 is illustrated below.

[0122] Voltages with opposite phases are applied to the two element sections 39 of the first element 31. Thus, as... Figure 19 As shown, the two element portions 39 of the first element 31 deform individually, and the two element portions 39 of the second element 32 also deform individually. The deformation of one of the two element portions 39 of the first element 31 is symmetrical about the center of the long side of the first beam portion 61 with respect to the deformation of the other. Through the symmetrical deformation of the two element portions 39 of the first element 31 with respect to the center of the long side of the first beam portion 61, the first beam portion 61 is deformed, and therefore, the sign of the curvature of the deformation of the first beam portion 61 is reversed at the center of the long side.

[0123] Furthermore, although not illustrated, similar to the first element 31, the deformation of one of the two element portions 39 of the second element 32 is point-symmetrical about the center of the long side of the second beam portion 62 with respect to the deformation of the other. Through the symmetrical deformation of the two element portions 39 of the second element 32 with respect to the center of the long side of the second beam portion 62, the second beam portion 62 is deformed; therefore, the sign of the curvature of the deformation of the second beam portion 62 is reversed at the center of the long side.

[0124] Next, the effects of this implementation method will be explained.

[0125] According to the ultrasonic transducer 100 involved in Embodiment 3, such as Figure 18 As shown, multiple component sections 39 are arranged at intervals SP apart from each other along the long side of beam 6. Therefore, as Figure 19 As shown, the stress exerted on the beam 6 when the two element portions 39 of the first element 31 deform is released at the interval SP (gap) between the two element portions 39 of the first element 31. Therefore, the stress exerted on the beam 6 when multiple element portions 39 deform is less than that when the second piezoelectric element 30 is composed of a single element portion (see reference). Figure 20 The stress applied to beam 6 is reduced. It should be noted that the stress on beam 6 is also reduced in the two element portions 39 of the second element 32, similar to that of the first element 31.

[0126] Implementation method 4.

[0127] Next, using Figure 21The structure of the ultrasonic transducer 100 according to Embodiment 4 will be described. Unless otherwise specified, Embodiment 4 has the same structure, manufacturing method, and effects as Embodiment 2 described above. Therefore, the same reference numerals are used to refer to the same structures as in Embodiment 2, and repeated descriptions are omitted.

[0128] like Figure 21 As shown, the ultrasonic transducer 100 according to this embodiment also includes a diaphragm 7. The diaphragm 7 is connected to the beam 6. The ultrasonic transducer 100 does not include a second piezoelectric element 30 (see reference). Figure 8 In other words, the ultrasonic transducer 100 includes a diaphragm 7 in place of the second piezoelectric element 30. The diaphragm 7 has a different coefficient of thermal expansion than the vibrating plate 2. The diaphragm 7 is, for example, a metallic membrane. The ultrasonic transducer 100 is configured to allow current to flow through the diaphragm 7.

[0129] In this embodiment, the membrane portion 7 includes a first membrane portion 71 and a second membrane portion 72. The first membrane portion 71 is connected to the first beam portion 61. The second membrane portion 72 is connected to the second beam portion 62. The first membrane portion 71 and the second membrane portion 72 each have a different coefficient of thermal expansion than the vibrating plate 2.

[0130] Next, the operation of the ultrasonic transducer 100 according to Embodiment 4 will be explained.

[0131] By flowing an electric current through the membrane 7, Joule heating is applied to both the membrane 7 and the beam 6. This temperature rise causes the membrane 7 and beam 6 to expand. The membrane 7 has a different coefficient of thermal expansion than the vibrating plate 2, therefore the deformation of the membrane 7 is different from that of the vibrating plate 2. The beam 6 is bent by utilizing the difference between the deformation of the membrane 7 and the vibrating plate 2.

[0132] Next, the effects of this implementation method will be explained.

[0133] According to the ultrasonic transducer 100 involved in Embodiment 4, such as Figure 21 As shown, the membrane 7 has a different coefficient of thermal expansion than the vibrating plate 2. Therefore, the deformation of the membrane 7 and the vibrating plate 2 are different when the beam 6 is heated. Thus, the vibrating plate 2 deforms by being pulled by the heated membrane 7. That is, the beam 6 can be bent by heating. Therefore, the second piezoelectric element 30 is not used. Figure 8 (Referencing) this will allow beam 6 to be bent.

[0134] Implementation method 5.

[0135] Next, using Figure 22The structure of the ultrasonic transducer 100 according to Embodiment 5 will be described. Unless otherwise specified, Embodiment 5 has the same structure, manufacturing method, and effects as Embodiment 2 described above. Therefore, the same reference numerals are used to refer to the same structures as in Embodiment 2, and repeated descriptions are omitted.

[0136] like Figure 22 As shown, the ultrasonic transducer 100 according to this embodiment also includes a cover portion 8. The cover portion 8 has lower rigidity than the vibrating plate 2. Therefore, the cover portion 8 can deform in accordance with the deformation of the vibrating plate 2. The cover portion 8 is, for example, an organic film such as parylene. The cover portion 8 may also be, for example, a thin-film silicon layer.

[0137] The cover 8 is disposed on the vibrating plate 2 to cover the slit SL. The cover 8 is disposed on the vibrating plate 2 such that the opening OP is exposed. The cover 8 is disposed on the vibrating plate 2 to cover the first slit SL1 and the second slit SL2. The shape and arrangement of the cover 8 can be appropriately determined as long as it can cover the first slit SL1 and the second slit SL2. For example, the cover 8 may be annular, covering the entire slit SL. For example, the cover 8 may be disposed on the vibrating plate 2 to cover the central portion 21, the outer peripheral portion 22, and the entire surface of the beam 6. In this embodiment, the second piezoelectric element 30 is connected to the beam 6 via the cover 8.

[0138] In this embodiment, the cover portion 8 includes a first cover portion 81 and a second cover portion 82. The first cover portion 81 and the second cover portion 82 respectively cover the first slit portion SL1 and the second slit portion SL2.

[0139] Next, the manufacturing method of the ultrasonic transducer 100 according to Embodiment 5 will be described.

[0140] The cover portion 8 is disposed on the wafer (substrate 9, reference) before the second piezoelectric element 30 is deposited. Figure 4 Next, the configured cover 8 is patterned. For example, the cover 8 can be configured at an appropriate time, such as after the pattern of the second piezoelectric element 30 is formed or after the silicon layer is processed, by means of inkjet printing or other techniques.

[0141] Next, the effects of this implementation method will be explained.

[0142] According to the ultrasonic transducer 100 involved in Embodiment 5, such as Figure 22 As shown, the cover 8 is positioned on the vibrating plate 2 to cover the slit SL. Therefore, it is possible to suppress the leakage of air from the internal space IS to the outside of the internal space IS through the slit SL. Air in the internal space IS tends to leak out if the width of the slit SL is too large. Therefore, it is possible to suppress the reduction of the amplification effect relying on acoustic resonance due to air leakage.

[0143] Implementation method 6.

[0144] Next, using Figure 23 The structure of the ultrasonic transducer 100 according to Embodiment 6 will be described. Unless otherwise specified, Embodiment 6 has the same structure, manufacturing method, and effects as Embodiment 2 described above. Therefore, the same reference numerals are used to refer to the same structures as in Embodiment 2, and repeated descriptions are omitted.

[0145] like Figure 23 As shown, the multiple beam portions 60 of the ultrasonic transducer 100 according to this embodiment each include a silicon (Si) substrate having a (1,1,1) crystal plane.

[0146] In this embodiment, the plurality of beam portions 60 include a first beam portion 61, a second beam portion 62, and a third beam portion 63. The first beam portion 61, the second beam portion 62, and the third beam portion 63 each include a silicon (Si) substrate having a (1,1,1) crystal plane. The first beam portion 61, the second beam portion 62, and the third beam portion 63 are arranged on the circumference of a circle centered on the opening OP. The shapes and lengths of the first beam portion 61, the second beam portion 62, and the third beam portion 63 are equal to each other.

[0147] The second piezoelectric element 30 includes a first element 31, a second element 32, and a third element 33. The first element 31, the second element 32, and the third element 33 are respectively connected to the first beam portion 61, the second beam portion 62, and the third beam portion 63. The first element 31, the second element 32, and the third element 33 are capable of causing the first beam portion 61, the second beam portion 62, and the third beam portion 63 to vibrate. The first element 31, the second element 32, and the third element 33 are configured to measure the strain of each of the first beam portion 61, the second beam portion 62, and the third beam portion 63.

[0148] Next, the effects of this implementation method will be explained.

[0149] According to the ultrasonic transducer 100 of embodiment 6, such as Figure 23 As shown, each of the multiple beam portions 60 includes a silicon (Si) substrate with a (1,1,1) crystal plane. The mechanical properties of the (1,1,1) plane of the silicon (Si) substrate are 3-fold symmetric. Therefore, it is possible to make the deformation of the multiple beam portions 60 equal to each other when the same stress is applied to each of the multiple beam portions 60. Thus, even with a silicon (Si) substrate having crystal anisotropy, it is possible to make the deformation of the multiple beam portions 60 equal to each other.

[0150] Implementation method 7.

[0151] Next, using Figure 24The structure of the ranging device 200 according to Embodiment 7 will be described. Unless otherwise specified, the ultrasonic transducer 100 of the ranging device 200 according to Embodiment 7 has the same structure, manufacturing method, and operating effect as that of Embodiment 1 described above. Therefore, the same reference numerals are used to refer to the same structures as in Embodiment 1 described above, and repeated descriptions are omitted.

[0152] like Figure 24 As shown, the ranging device 200 involved in this embodiment includes the ultrasonic transducer 100 involved in any of embodiments 1 to 6.

[0153] The ranging device 200 is used to determine the distance from the ranging device 200 to the object 300. The ranging device 200 is configured to determine the distance from the ranging device 200 to the object 300 using a time-of-flight method. That is, the ranging device 200 is configured to transmit an ultrasonic wave W1 towards the object 300. Additionally, the ranging device 200 is configured to receive an ultrasonic wave W2 reflected by the object. The ranging device 200 is configured to determine the distance from the ranging device 200 to the object 300 based on the time from the transmission of the ultrasonic wave W1 to the reception of the ultrasonic wave W2.

[0154] The first piezoelectric element 3, after receiving an input electrical signal, causes the vibrating plate 2 to vibrate at its resonant frequency, thereby generating an ultrasonic wave W1 at the resonant frequency. The ultrasonic wave W1 is amplified by the acoustic resonance structure. The amplified ultrasonic wave W1 is transmitted from the ultrasonic transducer 100 to the object 300 as a transmitted wave. The ultrasonic wave W1 is reflected by the object 300. The reflected ultrasonic wave W2 reaches the ultrasonic transducer 100 as a reflected wave. The arrived ultrasonic wave W2 is amplified by the acoustic resonance structure. The amplified ultrasonic wave W2 causes the vibrating plate 2 to vibrate through resonance. The vibration of the vibrating plate 2 is received as an electrical signal by the piezoelectric element disposed on the vibrating plate 2. When the distance from the ultrasonic transducer 100 to the object 300 is L, the time from the transmission to the reception of the sound wave is t, and the speed of sound is c, the distance L is calculated by equation (4).

[0155] L = c × t / 2 (4)

[0156] Next, the effects of this implementation method will be explained.

[0157] According to the ranging device 200 of Embodiment 7, such as Figure 24As shown, the ranging device 200 includes the ultrasonic transducer 100 described in any of embodiments 1 to 6. Therefore, similar to any of embodiments 1 to 6, the reduction in the dimensional accuracy of the ultrasonic transducer 100 can be suppressed. Thus, the reduction in the dimensional accuracy of the ranging device 200 can be suppressed. Consequently, the reduction in the generated sound pressure and sensitivity of the ultrasonic transducer 100 can be suppressed, and the reduction in the detection distance of the ranging device 200 can be suppressed.

[0158] The embodiments disclosed herein should be considered exemplary in all respects and are not limiting. The scope of this disclosure is not shown by the foregoing description but by the claims, and is intended to include all modifications in the sense and scope equivalent to the claims.

[0159] Explanation of reference numerals in the attached figures

[0160] 1. Frame; 2. Vibrating plate; 3. First piezoelectric element; 6. Beam; 7. Membrane section; 8. Cover section; 9. Substrate; 21. Central section; 22. Outer periphery section; 30. Second piezoelectric element; 39. Element section; 60. Beam section; 100. Ultrasonic transducer; 200. Distance measuring device; IS internal space; OP opening; SL slit.

Claims

1. An ultrasonic transducer, wherein, The ultrasonic transducer includes a vibrating plate and a frame connected to the vibrating plate. The vibrating plate is provided with an opening. The frame has an internal space that communicates with the opening. The vibrating plate and the frame constitute an acoustic resonance structure and are integrated as one unit. This acoustic resonance structure utilizes the opening and the internal space to amplify the ultrasonic waves generated by the vibration of the vibrating plate. The vibrating plate includes a central portion, an outer peripheral portion disposed around the central portion, and a beam connecting the central portion and the outer peripheral portion between the central portion and the outer peripheral portion. The vibrating plate is provided with a slit. The slit is located around the beam. The beam can be bent along the direction in which the vibrating plate connects to the frame. The ultrasonic transducer also includes a piezoelectric element. The piezoelectric element is connected to the beam.

2. The ultrasonic transducer according to claim 1, wherein, The vibrating plate and the frame are configured to change the volume of the internal space.

3. The ultrasonic transducer according to claim 1 or 2, wherein, The ultrasonic transducer also includes a first piezoelectric element. The first piezoelectric element is connected to the vibrating plate.

4. The ultrasonic transducer according to claim 1 or 2, wherein, The piezoelectric element includes multiple element parts. The plurality of components are arranged at intervals along the long side of the beam.

5. The ultrasonic transducer according to claim 1 or 2, wherein, The ultrasonic transducer also includes a cover that has lower rigidity than the vibrating plate. The cover is configured on the vibrating plate in a manner that covers the slit.

6. The ultrasonic transducer according to claim 1 or 2, wherein, The beam comprises multiple beam sections. The plurality of beams can be bent along the direction in which the vibrating plate and the frame are connected.

7. The ultrasonic transducer according to claim 6, wherein, The plurality of beams each include a silicon substrate having a (1,1,1) crystal plane.

8. A ranging device, wherein, The ranging device comprises the ultrasonic transducer according to any one of claims 1 to 7.

9. A method for manufacturing an ultrasonic transducer, wherein, The ultrasonic transducer includes a vibrating plate and a frame connected to the vibrating plate. The vibrating plate is provided with an opening. The frame has an internal space that communicates with the opening. The vibrating plate and the frame constitute an acoustic resonance structure and are integrated as one unit. This acoustic resonance structure utilizes the opening and the internal space to amplify the ultrasonic waves generated by the vibration of the vibrating plate. The vibrating plate includes a central portion, an outer peripheral portion disposed around the central portion, and a beam connecting the central portion and the outer peripheral portion between the central portion and the outer peripheral portion. The vibrating plate is provided with a slit. The slit is located around the beam. The beam can be bent along the direction in which the vibrating plate connects to the frame. The ultrasonic transducer also includes a piezoelectric element. The piezoelectric element is connected to the beam. The method for manufacturing the ultrasonic transducer includes: The process of preparing the substrate; and The process of fabricating the vibrating plate and the frame from the substrate in an integral manner using MEMS manufacturing technology, forming an opening in the vibrating plate, and forming an internal space in the frame that communicates with the opening.

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