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

Abstract

An ultrasound transducer (100) includes a vibration plate (2) and a housing (1). The vibration plate (2) is capable of vibrating. The housing (1) is connected to the vibration plate (2). The vibration plate (2) has an opening (OP). The housing (1) has an internal space (IS). The internal space (IS) communicates with the opening (OP). The vibration plate (2) and the housing (1) constitute an acoustic resonance structure for amplifying, with the opening (OP) and the internal space (IS), ultrasound generated by the vibration of the vibration plate (2) and are monolithically formed.

Description

[Technical Field]

[0001] The present disclosure relates to an ultrasonic transducer, a distance measuring device, and a method for manufacturing an ultrasonic transducer. [Background technology]

[0002] Ultrasonic transducers are used as distance sensors for peripheral monitoring in automobiles and transport vehicles, as well as for contactless device operation. Bulk lead zirconate titanate (PZT: Pb(Zr,Ti)O3) is often used in commonly used ultrasonic transducers. However, miniaturization of ultrasonic transducers using bulk PZT is limited by the machining accuracy. For this reason, MEMS (Micro Electro Mechanical Systems) ultrasonic transducers have been developed as ultrasonic transducers that can be miniaturized.

[0003] The most common MEMS ultrasonic transducers use a thin-film diaphragm (membrane). The material used for the structure of the MEMS ultrasonic transducer, including the diaphragm, is silicon (Si), a semiconductor. MEMS ultrasonic transducers are processed using semiconductor technology such as deep reactive ion etching (DRIE). Applying semiconductor technology with high dimensional accuracy to the processing of the diaphragm makes it possible to miniaturize MEMS ultrasonic transducers.

[0004] For example, Japanese Patent Publication No. 2010-515335 (Patent Document 1) describes a sound source tracking microphone (ultrasonic transducer) that includes a MEMS microphone and an acoustic resonant structure. The acoustic resonant structure has a cavity and a sound entrance passage. The acoustic resonant structure is configured to amplify sound that enters the acoustic resonant structure by the cavity and the entrance passage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2010-515335 Summary of the Invention [Problem to be solved by the invention]

[0006] In the above publication, a MEMS microphone is disposed in a cavity of an acoustic resonator structure. Therefore, the acoustic resonator structure must be formed after the microphone is disposed in the cavity of the acoustic resonator structure. This makes it difficult to manufacture the acoustic resonator structure with high accuracy. This results in a decrease in the dimensional accuracy of the acoustic resonator structure.

[0007] The present disclosure has been made in consideration 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 a decrease in the dimensional accuracy of an acoustic resonant structure. [Means for solving the problem]

[0008] The ultrasonic transducer of the present disclosure includes a diaphragm and a housing. The diaphragm is vibrable. The housing is connected to the diaphragm. An opening is provided in the diaphragm. The housing is provided with an internal space. The internal space is in communication with the opening. The diaphragm and the housing are integrally configured to form an acoustic resonance structure in which ultrasonic waves generated by vibration of the diaphragm are amplified by the opening and the internal space. [Effects of the Invention]

[0009] According to the ultrasonic transducer of the present disclosure, it is possible to suppress a decrease in the dimensional accuracy of the acoustic resonance structure. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view schematically illustrating a configuration of an ultrasonic transducer according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] 1 is a cross-sectional view that schematically shows a state in which a lower electrode, a piezoelectric thin film, and an upper electrode are laminated on a substrate used in manufacturing the ultrasonic transducer according to the first embodiment. [Figure 4] 3 is a cross-sectional view schematically showing a state in which an opening is provided in a substrate used in manufacturing the ultrasonic transducer according to the first embodiment. FIG. [Figure 5] 3 is a cross-sectional view schematically showing an internal space provided in a substrate used in manufacturing the ultrasonic transducer according to the first embodiment. FIG. [Figure 6] FIG. 10 is a perspective view schematically illustrating the configuration of an ultrasonic transducer according to a second embodiment. [Figure 7] FIG. 10 is a top view schematically showing the configuration of an ultrasonic transducer according to a second embodiment. [Figure 8] FIG. 7 is a cross-sectional view taken along line VIII-VIII in FIG. 6. [Figure 9] 10 is a cross-sectional view schematically showing a state in which the center and beams of the ultrasonic transducer according to the second embodiment have moved away from the bottom of the housing. FIG. [Figure 10] 10 is a cross-sectional view schematically showing a state in which the center and beams of the ultrasonic transducer according to the second embodiment have moved closer to the bottom of the housing. FIG. [Figure 11] 10 is a cross-sectional view schematically showing the configuration of a first substrate used in manufacturing an ultrasonic transducer according to a second embodiment. FIG. [Figure 12] 10 is a cross-sectional view schematically showing a state in which openings and slits are provided in a first substrate used in manufacturing an ultrasonic transducer according to a second embodiment. FIG. [Figure 13] 10 is a cross-sectional view schematically showing the configuration of a second substrate used in manufacturing an ultrasonic transducer according to a second embodiment. FIG. [Figure 14] 10 is a cross-sectional view schematically showing an internal space provided in a second substrate used in manufacturing an ultrasonic transducer according to a second embodiment. FIG. [Figure 15]10 is a cross-sectional view that schematically shows a state in which a first substrate and a second substrate used in manufacturing an ultrasonic transducer according to a second embodiment are bonded together. FIG. [Figure 16] 10 is a cross-sectional view schematically showing a state in which a fifth silicon layer has been removed from a first substrate and a second substrate used in manufacturing an ultrasonic transducer according to a second embodiment. FIG. [Figure 17] 10 is a cross-sectional view schematically showing a state in which a lower electrode, a piezoelectric thin film, and an upper electrode are laminated on a first substrate used in manufacturing an ultrasonic transducer according to a second embodiment. FIG. [Figure 18] FIG. 10 is a top view schematically showing the configuration of an ultrasonic transducer according to a third embodiment. [Figure 19] 10 is a schematic cross-sectional view showing a state in which a beam of the ultrasonic transducer according to the third embodiment is deformed. FIG. [Figure 20] 10 is a schematic cross-sectional view showing a state in which a beam of the ultrasonic transducer according to the second embodiment is deformed. FIG. [Figure 21] FIG. 10 is a cross-sectional view schematically showing the configuration of an ultrasonic transducer according to a fourth embodiment. [Figure 22] FIG. 10 is a cross-sectional view schematically illustrating the configuration of an ultrasonic transducer according to a fifth embodiment. [Figure 23] FIG. 13 is a top view schematically showing the configuration of an ultrasonic transducer according to a sixth embodiment. [Figure 24] FIG. 13 is a schematic diagram illustrating the configuration of a distance measuring device according to a seventh embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be described with reference to the drawings. In the following, the same or corresponding parts will be denoted by the same reference numerals, and overlapping descriptions will not be repeated.

[0012] Embodiment 1 The configuration of an ultrasonic transducer 100 according to the first embodiment will be described with reference to FIGS.

[0013] As shown in Fig. 1, the ultrasonic transducer 100 includes a housing 1 and a diaphragm 2. The ultrasonic transducer 100 according to this embodiment further includes a first piezoelectric element 3. For ease of explanation, the side surface of the first piezoelectric element 3 is shown as flat in Fig. 1, but as shown in Fig. 2, a step is provided on the side surface of the first piezoelectric element 3.

[0014] As shown in FIG. 2, the housing 1 is connected to the diaphragm 2. The housing 1 has an internal space IS. The housing 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. In FIG. 2, the boundary between the peripheral wall portion 11 and the bottom portion 12 is indicated by a dashed line. The peripheral wall portion 11 is connected to the bottom portion 12 so as to rise from the bottom portion 12. The peripheral wall portion 11 surrounds the internal space IS. The bottom portion 12 sandwiches the internal space IS between the peripheral wall portion 11 and the diaphragm 2. The first oxide film 41 is stacked on the peripheral wall portion 11. The first oxide film 41 is sandwiched between the peripheral wall portion 11 and the diaphragm 2. The external shape of the housing 1 may be a rectangular parallelepiped or a cylindrical shape.

[0015] The diaphragm 2 is connected to the housing 1 so as to cover the internal space IS. This structure is sometimes called a cavity structure. An opening OP is provided in the diaphragm 2. The opening OP penetrates the diaphragm 2. Preferably, the opening OP is provided so as to pass through the center of the diaphragm 2 in the in-plane direction. The internal space IS is in communication with the opening OP. The shape of the opening OP may be circular or rectangular.

[0016] The diaphragm 2 is vibrable. Specifically, the diaphragm 2 is vibrable by the first piezoelectric element 3. The diaphragm 2 is configured to generate ultrasonic waves by vibration. The principle by which the diaphragm 2 generates ultrasonic waves will be described later.

[0017] The diaphragm 2 includes a second silicon layer 52 and a second oxide film 42. An opening OP penetrates 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.

[0018] The housing 1 and the diaphragm 2 form an acoustic resonance structure that amplifies ultrasonic waves generated by vibration of the diaphragm 2 through the opening OP and the internal space IS. The acoustic resonance structure is integrally formed. The acoustic resonance structure may be, for example, a Helmholtz resonator. The acoustic resonance structure will be described in detail later.

[0019] The housing 1 and the diaphragm 2 are integrally formed. In other words, the housing 1 and the diaphragm 2 are connected without any gaps. More specifically, the first oxide film 41 of the housing 1 and the second silicon layer 52 of the diaphragm 2 are connected without any gaps. In this embodiment, "integrally formed" and "connected without any gaps" mean that they are connected by atomic or molecular bonds such as covalent bonds. Preferably, the housing 1 and the diaphragm 2 are integrally formed using MEMS technology. A manufacturing method for the housing 1 and the diaphragm 2 using MEMS technology will be described later.

[0020] The material for the peripheral wall 11 and bottom 12 (first silicon layer 51) of the housing 1 and the second silicon layer 52 of the diaphragm 2 is preferably silicon (Si), which is a material that is easily applicable to semiconductor manufacturing techniques and has excellent mechanical properties as an elastic material. The first oxide film 41 and the second oxide film 42 are, for example, silicon (Si) oxide films.

[0021] The first piezoelectric element 3 is connected to the vibration plate 2. The first piezoelectric element 3 is disposed on the vibration plate 2. Specifically, the first piezoelectric element 3 is disposed on the second oxide film 42 of the vibration plate 2. The first piezoelectric element 3 is disposed on the opposite side of the vibration plate 2 from the internal space IS. In other words, the first piezoelectric element 3 is disposed outside the internal space IS. As shown in FIG. 1, the first piezoelectric element 3 has a ring shape. The first piezoelectric element 3 is disposed so as to expose the opening OP.

[0022] The first piezoelectric element 3 is configured as an actuator for vibrating the diaphragm 2. The first piezoelectric element 3 is configured to vibrate the diaphragm 2 when transmitting ultrasonic waves. The first piezoelectric element 3 is also configured as a strain sensor for measuring the strain of the diaphragm 2. The first piezoelectric element 3 is configured to function as a strain sensor for the diaphragm 2 when receiving ultrasonic waves. This allows the vibration of the diaphragm 2 to be measured when receiving ultrasonic waves. The ultrasonic transducer 100 is configured to apply a voltage to the first piezoelectric element 3. A power source (not shown) may be electrically connected to the first piezoelectric element.

[0023] As shown in Fig. 2, the first piezoelectric element 3 includes a lower electrode 3A, a piezoelectric thin film 3B, and an upper electrode 3C. The lower electrode 3A and the upper electrode 3C sandwich the piezoelectric thin film 3B. The lower electrode 3A is disposed on the vibration plate 2. The piezoelectric thin film 3B is disposed on the opposite side of the lower electrode 3A from the internal space IS. The lower electrode 3A, the piezoelectric thin film 3B, and the upper electrode 3C have larger outer diameters in this order.

[0024] The piezoelectric thin film 3B may be made of, for example, lead zirconate titanate (PZT: Pb(Zr,Ti)O3), aluminum nitride (AlN), or potassium sodium niobate (KNN: (K,Na)NbO3). The lower electrode 3A and the upper electrode 3C are preferably made of a laminated film of titanium (Ti) and platinum (Pt), which is commonly used in piezoelectric elements. The lower electrode 3A and the upper electrode 3C may be made of other laminated films, provided they have sufficient conductivity as an electrode and good adhesion to the substrate. An oxide electrode film, such as a strontium oxide (SrO) film, which has the effect of reducing polarization fatigue, may be disposed between the upper electrode 3C and the piezoelectric thin film 3B.

[0025] Next, the operation of the ultrasonic transducer 100 according to the first embodiment will be described. When a voltage is applied between the lower electrode 3A and the upper electrode 3C, the piezoelectric thin film 3B contracts. The contraction of the piezoelectric thin film 3B bends the diaphragm 2. When a voltage of a frequency close to the resonant frequency of the diaphragm 2 is applied to the piezoelectric thin film 3B, the diaphragm 2 vibrates by resonant vibration. In this embodiment, the frequency close to the resonant frequency of the diaphragm 2 refers to a frequency where the vibration displacement of the diaphragm 2 is 2 times the maximum displacement (peak displacement). -1 / 2 more than 2 times 1 / 2 This is the frequency range where the frequency is less than 1 / 2 of the original frequency. This generates ultrasound.

[0026] Furthermore, when the ultrasonic transducer 100 is used as an ultrasonic sensor, the vibration of the diaphragm 2 vibrated by ultrasonic waves is acquired as a voltage signal via the first piezoelectric element 3.

[0027] The dimensions of the internal space IS of the housing 1 and the opening OP of the diaphragm 2 are set so that the resonance frequency of the housing 1 approaches the resonance frequency of the diaphragm 2. In this embodiment, the resonance frequency of the housing 1 approaches the resonance frequency of the diaphragm 2 when the vibration displacement of the diaphragm 2 is 2 times the maximum displacement. -1 / 2 more than 2 times 1 / 2This means that the frequency is set to a range where the frequency is equal to or less than 1 / 2 of the frequency of the ultrasonic wave generated by the vibration of the diaphragm 2. As a result, the sound pressure of the ultrasonic wave generated by the vibration of the diaphragm 2 is amplified by the acoustic resonance structure.

[0028] The resonance frequency of the acoustic resonance structure is determined by 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 The area Sm of the opening OP in the in-plane direction is expressed by the following equation (2): c is expressed by the following equation (3).

[0029]

number

[0030]

number

[0031]

number

[0032] Furthermore, when the ultrasonic transducer 100 is used as an ultrasonic sensor, the sound pressure of the received ultrasonic waves is amplified by acoustic resonance, increasing the vibration of the diaphragm 2. This increases the distortion of the first piezoelectric element 3, and an amplified signal is acquired.

[0033] Next, a method for manufacturing the ultrasonic transducer 100 according to the first embodiment will be described with reference to FIGS.

[0034] As shown in FIG. 3, in the preparation step, a substrate 9 is prepared. The substrate 9 is an SOI substrate (SOI: Silicon On Insulator). The ultrasonic transducer 100 according to this embodiment is manufactured by processing the SOI substrate. The 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, 1 00 μm or more 6 The thickness of the second silicon layer 52 is, for example, 1 μm or more 1 The second oxide film 42 is formed as a surface oxide film. The second oxide film 42 is preferably formed by thermal oxidation, which can reduce surface roughness.

[0035] 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.

[0036] Subsequently, as shown in FIG. 4, the lower electrode 3A, the piezoelectric thin film 3B, the upper electrode 3C, the second oxide film 42 and the second silicon layer 52 are patterned.

[0037] Specifically, photolithography using a resist film as a protective film is suitable for patterning the upper electrode 3C. Reactive ion etching (RIE) or photoetching using an etchant is used for etching the upper electrode 3C. Regardless of the etching method, conditions must be set to ensure a sufficient etching selectivity between the upper electrode 3C and the underlying film. For example, if PZT is used as the piezoelectric thin film 3B and a laminated film of titanium (Ti) and platinum (Pt) films is used as the upper electrode 3C, a chlorine (Cl2) / argon (Ar)-based gas is suitable for patterning the laminated film by reactive ion etching. After patterning the upper electrode 3C, the resist film is removed. Oxygen (O2) ashing or other suitable method is used to remove the resist film.

[0038] Next, the piezoelectric thin film 3B is patterned by photolithography and etching. The etching process may be, for example, reactive ion etching or wet etching. The etching process must be performed under conditions that ensure a sufficient etching selectivity between the piezoelectric thin film 3B and the underlying layer. For example, the lower electrode 3A and the piezoelectric thin film 3B may be formed of a stacked film of titanium (Ti) and platinum (Pt) films, and PZT, respectively, and the stacked film may be patterned by reactive ion etching. In this case, chlorine (Cl2), boron chloride (BCl2), or hydrogen chloride (CH4)-based gases are suitable. After patterning the piezoelectric thin film 3B, the resist film is removed by oxygen (O2) ashing or the like.

[0039] Next, the lower electrode 3A is patterned by photolithography and etching. The etching process is, for example, reactive ion etching or wet etching. The etching process must be performed under conditions that ensure a sufficient etching selectivity between the lower electrode 3A and the underlying layer. For example, if a stacked film of titanium (Ti) and platinum (Pt) is used as the lower electrode 3A, a chlorine (Cl2) / argon (Ar)-based gas is suitable for patterning the stacked film by reactive ion etching. After patterning the lower electrode 3A, the resist film is removed by oxygen (O2) ashing or the like.

[0040] Subsequently, the second oxide film 42 formed on the second silicon layer 52 is patterned by photolithography and etching. The etching is, for example, reactive ion etching or wet etching. When the second oxide film 42 is patterned by reactive ion etching, chlorine (Cl-based) gas is suitable.

[0041] Subsequently, the second silicon layer 52 is subjected to an etching process. As a result, in forming step S102, an opening OP is formed in the diaphragm 2 (second silicon layer 52). The etching process is preferably, for example, deep reactive ion etching (DRIE). The deep etching is performed by the Bosch method, which allows etching with a high aspect ratio. The etching process is performed until the first oxide film 41 is exposed. After the etching process, the resist film is removed by oxygen (O2) ashing or the like.

[0042] Next, as shown in FIG. 5, the first silicon layer 51 is patterned by photolithography and etching. As a result, in forming step S102, an internal space IS is formed in the housing 1 (see FIG. 2) (first silicon layer 51). The etching is, for example, a reactive ion etching process or a wet etching process. Preferably, the etching is Bosch deep etching (DRIE). The etching is performed until the first oxide film 41 is exposed. Then, the exposed first oxide film 41 is removed by etching. The etching of the first oxide film 41 is a reactive ion etching process or a wet etching process. When the first oxide film 41 is patterned by reactive ion etching, a chlorine (Cl2)-based gas is suitable.

[0043] 2 and 5, a second substrate, which is a silicon substrate, is bonded to the substrate 9. The second substrate becomes the bottom 12 of the housing 1. Surface activated bonding or room temperature activated bonding is used to bond the substrate 9 and the second substrate.

[0044] As described above, in forming step S102, the housing 1 and diaphragm 2 are integrally molded from a substrate using MEMS manufacturing technology. The housing 1 and diaphragm 2 are formed to form an acoustic resonance structure that amplifies the sound generated by vibration of the diaphragm 2 through the opening OP and the internal space IS.

[0045] Next, the substrate is cut into chip sizes by, for example, dicing, and the MEMS ultrasonic transducer 100 is completed.

[0046] 4, an SOI substrate is prepared as the substrate 9, but the substrate 9 is not limited to this. For example, a CSOI (Cavity Silicon On Insulator) substrate having a hollow structure from the initial state may be used as the substrate. When a CSOI substrate is used, the first piezoelectric element 3 and the opening OP are formed on the hollow structure, so the patterning process of the second silicon layer 52 and the bonding process of the second substrate do not need to be performed. This makes it easier to fabricate the ultrasonic transducer 100.

[0047] Next, the effects of this embodiment will be described. According to the ultrasonic transducer 100 of the first embodiment, as shown in FIG. 2, the housing 1 and the diaphragm 2 constitute an acoustic resonance structure and are integrally configured. This allows the acoustic resonance structure to be manufactured with high precision. Specifically, the acoustic resonance structure can be manufactured with higher precision than when the housing 1 and the diaphragm 2 are separate bodies. In particular, the acoustic resonance structure can be manufactured with higher precision than when the acoustic resonance structure is manufactured by fitting the housing 1 and the diaphragm 2, which are separate bodies, together. This prevents a decrease in the dimensional precision of the acoustic resonance structure. In other words, the dimensional precision of the acoustic resonance structure can be improved.

[0048] 2, the first piezoelectric element 3 is connected to the diaphragm 2. Therefore, the diaphragm 2 can be vibrated by the first piezoelectric element 3. The first piezoelectric element 3 can also measure the distortion of the diaphragm 2. Therefore, the frequency of the ultrasonic waves received by the acoustic resonant structure can be measured based on the distortion of the diaphragm 2.

[0049] As shown in Figure 2, the housing 1 and diaphragm 2 are integrally constructed using MEMS manufacturing technology. This allows the acoustic resonance structure to be manufactured with high precision. For example, the acoustic resonance structure can be manufactured with dimensional precision within an error range of 1 μm to 10 μm.

[0050] According to the manufacturing method of the ultrasonic transducer 100 according to the first embodiment, as shown in Fig. 3, the housing 1 and the diaphragm 2 are integrally molded from the substrate 9 using MEMS manufacturing technology. This allows the acoustic resonance structure to be manufactured with high precision. Specifically, the acoustic resonance structure can be manufactured with higher precision than when the housing 1 and the diaphragm 2 are separate bodies. This prevents the dimensional precision of the acoustic resonance structure from decreasing.

[0051] As shown in Fig. 3, the housing 1 and diaphragm 2 are integrally molded from the substrate 9 using MEMS manufacturing technology. This allows for a lower assembly cost for the ultrasonic transducer 100 than when, for example, the housing 1 and diaphragm 2 are assembled by fitting together a separately manufactured housing 1 and diaphragm 2. Also, for example, a more precise assembly process is not required than when, for example, the housing 1 and diaphragm 2 are assembled by fitting together a separately manufactured housing 1 and diaphragm 2. This allows for an acoustic resonance structure to be easily manufactured.

[0052] Embodiment 2 Next, the configuration of an ultrasonic transducer 100 according to embodiment 2 will be described with reference to Figures 6 to 10. Unless otherwise specified, embodiment 2 has the same configuration, manufacturing method, and effects as embodiment 1. Therefore, the same components as embodiment 1 above are denoted by the same reference numerals, and description thereof will not be repeated.

[0053] As shown in FIGS. 6 and 7, the diaphragm 2 of the ultrasonic transducer 100 according to this embodiment includes a central portion 21, a 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 due to the first piezoelectric element 3. The peripheral portion 22 is disposed around the central portion 21. The beam 6 connects the central portion 21 and the peripheral portion 22 between them. A slit SL is provided in the diaphragm 2. The slit SL is provided around the beam 6. Therefore, the beam 6 can bend along the direction in which the housing 1 and the diaphragm 2 are connected. The dimension of the slit SL in the short direction is, for example, 10 μm. For ease of explanation, the side surface of the first piezoelectric element 3 is shown flat in FIG. 6, but steps are provided on the side surface of the first piezoelectric element 3 as shown in FIGS. 7 and 8.

[0054] As shown in Figures 8 to 10, the housing 1 and the diaphragm 2 are configured so that the volume of the internal space IS can be changed. As shown in Figure 9, the housing 1 and the diaphragm 2 are configured so that the volume of the internal space IS can be changed by the deformation of the beams 6 so that they move away from the bottom 12 of the housing 1. More specifically, as the beams 6 deform so that they move away from the bottom 12 of the housing 1, the central portion 21 moves away from the bottom 12 of the housing 1. This increases the volume of the internal space IS.

[0055] 10, the housing 1 and the diaphragm 2 may be configured so that the volume of the internal space IS can be changed by the deformation of the beam 6 so that it approaches the bottom 12 of the housing 1. More specifically, by the deformation of the beam 6 so that it approaches the bottom 12 of the housing 1, the central portion 21 moves so that it approaches the bottom 12 of the housing 1. This reduces the volume of the internal space IS.

[0056] The amount of deformation of the beam 6 may be larger than the maximum displacement due to resonance of the diaphragm 2. The amount of deformation of the beam 6 may be equal to or smaller than the maximum displacement due to resonance of the diaphragm 2. Preferably, the shape of the deformed beam 6 does not change due to the vibration of the central portion 21.

[0057] The material of the beam 6 is preferably silicon (Si), which is easy to apply semiconductor manufacturing techniques to and has excellent mechanical properties as an elastic material.

[0058] As shown in FIG. 6, the beam 6 includes a plurality of beam portions 60. The plurality of beam portions 60 are bendable along the direction in which the housing 1 and the diaphragm 2 are connected. In the present embodiment, the 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 in which the housing 1 and the diaphragm 2 are connected. The first beam portion 61 and the second beam portion 62 may have the same shape.

[0059] As shown in Fig. 7, when viewed from the direction from the diaphragm 2 toward the housing 1 (see Fig. 6), the first beam portion 61 and the second beam portion 62 each have a C-shape. The first beam portion 61 and the second beam portion 62 are each arranged along the circumferential direction of the central portion 21. The first beam portion 61 and the second beam portion 62 are arranged spaced apart from each other via a slit SL. More specifically, the first beam portion 61 and the second beam portion 62 are arranged spaced apart from each other via a portion of the slit SL that extends in the radial direction of the central portion 21.

[0060] The slits SL include a first slit portion SL1 and a second slit portion SL2. The first slit portion SL1 is provided around the first beam portion 61. The second slit portion SL2 is provided around the second beam portion 62. Each of the first slit portion SL1 and the second slit portion SL2 has a first slit portion, a second slit portion, and a third slit portion. The first slit portion is located on the central portion 21 side of the beam 6. The second slit portion is located on the outer periphery 22 side of the beam 6. The third slit portion connects the first slit portion and the second slit portion. Each of the first slit portion and the second slit portion is C-shaped. The first slit portion and the second slit portion are provided along the circumferential direction of the central portion 21. The third slit portion is provided along the radial direction of the central portion 21. The third slit portion is linear.

[0061] The ultrasonic transducer 100 further 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.

[0062] The first piezoelectric element 3 and the second piezoelectric element 30 are formed of a common lower electrode 3A, upper electrode 3C, and 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 a first beam portion 61. The second element 32 is connected to a second beam portion 62.

[0063] Next, the operation of the ultrasonic transducer 100 according to the second embodiment will be described with reference to FIGS.

[0064] As shown in FIGS. 8 to 10, when a voltage is applied to the second piezoelectric element 30, the second piezoelectric element 30 is deformed. The principle by which the second piezoelectric element 30 is deformed is the same as the principle by which the first piezoelectric element 3 is deformed, and therefore will not be described. The deformation of the second piezoelectric element 30 bends the beam 6. Specifically, when a voltage is applied to each of the first element 31 and the second element 32, the first element 31 and the second element 32 are deformed. The deformation of the first element 31 and the second element 32 bends the first beam portion 61 and the second beam portion 62, 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 is changed.

[0065] Next, a method for manufacturing the ultrasonic transducer 100 according to the second embodiment will be described with reference to FIGS. 8 and 11 to 17. FIG.

[0066] As shown in FIG. 11, in the preparation step, a first substrate 91, which is a substrate 9, is prepared. The first substrate 91 is a three-layer SOI substrate. The diaphragm 2 (see FIG. 8) is formed from the first substrate 91. 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 stacked in this order. The thicknesses of the third silicon layer 53 and the fourth silicon layer 54 are, 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.

[0067] 12, in forming step S102, the first surface oxide film 43 and the third silicon layer 53 are etched and patterned, thereby forming openings OP and slits SL.

[0068] 13, in the preparation step, a second substrate 92, which is the substrate 9, is prepared. The second substrate 92 is a two-layer SOI substrate. The housing 1 (see FIG. 8) is formed from the second substrate 92. 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 in this order. The thickness of the sixth silicon layer 56 is, for example, not less than 100 μm and not more than 600 μm. The thickness of the seventh silicon layer 57 is, for example, not less than 1 μm and not more than 100 μm.

[0069] 14, the second surface oxide film 46 and the sixth silicon layer 56 are etched and patterned, thereby forming an internal space IS.

[0070] 15, 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.

[0071] 15 and 16, the fifth silicon layer 55 is removed by etching, thereby exposing the fourth oxide film 45.

[0072] 17, the lower electrode 3A, the piezoelectric thin film 3B, and the upper electrode 3C are laminated in this order on the fourth oxide film 45. Then, as shown in FIG.

[0073] Subsequently, as shown in FIG. 8, the lower electrode 3A, the piezoelectric thin film 3B and the upper electrode 3C are etched to form the first piezoelectric element 3 and the second piezoelectric element 30.

[0074] 11, a three-layer SOI substrate is used as the first substrate 91, but the fifth silicon layer 55 is used only to support the substrate and is not included in the final structure, so the first substrate 91 is not limited to a three-layer SOI substrate. For example, if the wafer has a high enough rigidity that it does not interfere with transportation during semiconductor processing, a two-layer SOI substrate may be used as the first substrate 91. Also, a dummy wafer may be used as the fifth silicon layer 55.

[0075] Next, the effects of this embodiment will be described. According to the ultrasonic transducer 100 of the second embodiment, as shown in Figs. 9 and 10, the housing 1 and the diaphragm 2 are configured so that the volume of the internal space IS can be changed. Therefore, the height dimension from the bottom 12 of the housing 1 to the diaphragm 2 can be changed. This makes it possible to change the resonance frequency of the acoustic resonance structure. Therefore, for example, the resonance frequency of the acoustic resonance structure can be changed so as to correct the deviation between the resonance frequency of the diaphragm 2 and the resonance frequency of the housing 1 due to manufacturing errors or the like. Therefore, the sound caused by resonance can be reduced. sound This can prevent the amplification effect from decreasing.

[0076] 8 to 10, the beam 6 is bendable along the direction in which the housing 1 and the diaphragm 2 are connected. Therefore, the height dimension from the bottom 12 of the housing 1 to the diaphragm 2 can be changed by moving the center portion 21 due to deformation of the beam 6. Therefore, the resonance frequency of the acoustic resonance structure can be changed by deformation of the beam 6. Therefore, the deformation of the beam 6 can suppress a decrease in the acoustic amplification effect due to resonance.

[0077] 8, the second piezoelectric element 30 is connected to the beam 6. Therefore, when a voltage is applied to the second piezoelectric element 30, the beam 6 can be deformed.

[0078] As shown in FIG. 6, the beam 6 includes a plurality of beam portions 60. As shown in FIGS. 7 to 10, the plurality of beam portions 60 are bendable along the direction in which the housing 1 and the diaphragm 2 are connected. This allows the volume of the internal space IS to be changed by deformation of the plurality of beam portions 60. This makes it easier to change the volume of the internal space IS than when there is a single beam 6. This makes it easier to prevent a reduction in the acoustic amplification effect due to resonance.

[0079] Embodiment 3 Next, the configuration of the ultrasonic transducer 100 according to embodiment 3 will be described with reference to Fig. 18. Unless otherwise specified, embodiment 3 has the same configuration, manufacturing method, and effects as embodiment 2. Therefore, the same components as embodiment 2 above are denoted by the same reference numerals, and description thereof will not be repeated.

[0080] 18, 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, each of the first element 31 and the second element 32 is divided into a plurality of element portions 39.

[0081] The plurality of element portions 39 are arranged at intervals SP from one another along the longitudinal direction of the beam 6. In other words, the plurality of element portions 39 are physically isolated from one another. The plurality of element portions 39 are configured to receive input signals that are independent of one another.

[0082] In this embodiment, the first element 31 includes, for example, two element portions 39. Each of the two element portions 39 of the first element 31 is connected to the first beam portion 61. The two element portions 39 of the first element 31 are arranged along the longitudinal direction of the first beam portion 61 with a distance SP therebetween.

[0083] The second element 32 includes, for example, two element portions 39. Each of the two element portions 39 of the second element 32 is connected to the second beam portion 62. The two element portions 39 of the second element 32 are arranged along the longitudinal direction of the second beam portion 62 with a distance SP therebetween.

[0084] Next, as shown in FIG. 19, the operation of the ultrasonic transducer 100 according to the third embodiment will be described.

[0085] Voltages of opposite phases are applied to each of the two element portions 39 of the first element 31. As a result, as shown in Fig. 19, each of the two element portions 39 of the first element 31 and each of the two element portions 39 of the second element 32 deform. The deformation of one of the two element portions 39 of the first element 31 is symmetrical with respect to the deformation of the other, with the center of the first beam portion 61 in the longitudinal direction as the center. Since the first beam portion 61 is deformed by the symmetric deformation of the two element portions 39 of the first element 31 with respect to the center of the first beam portion 61 in the longitudinal direction, the sign of the curvature of the deformation of the first beam portion 61 is reversed at the center in the longitudinal direction.

[0086] Although not shown, similarly to the first element 31, the deformation of one of the two element portions 39 of the second element 32 is point-symmetric with respect to the deformation of the other, with the center in the longitudinal direction of the second beam portion 62 as the center. Since the second beam portion 62 is deformed by the symmetric deformation of the second beam portion 62 of the two element portions 39 of the second element 32 with respect to the center in the longitudinal direction, the sign of the curvature of the deformation of the second beam portion 62 is reversed at the center in the longitudinal direction.

[0087] Next, the effects of this embodiment will be described. According to the ultrasonic transducer 100 of the third embodiment, as shown in FIG. 18, the plurality of element portions 39 are arranged at a distance SP from one another along the longitudinal direction of the beam 6. Therefore, as shown in FIG. 19, the stress applied to the beam 6 when the two element portions 39 of the first element 31 are deformed is released at the distance SP (gap) between the two element portions 39 of the first element 31. Therefore, the stress applied to the beam 6 when the plurality of element portions 39 are deformed is smaller than the stress applied to the beam 6 when the second piezoelectric element 30 is made up of a single element portion (see FIG. 20). Therefore, the stress applied to the beam 6 can be reduced. Note that the stress is also small in the two element portions 39 of the second element 32, similar to that in the first element 31.

[0088] Embodiment 4 Next, the configuration of the ultrasonic transducer 100 according to embodiment 4 will be described with reference to Fig. 21. Unless otherwise specified, embodiment 4 has the same configuration, manufacturing method, and effects as embodiment 2. Therefore, the same components as embodiment 2 above are denoted by the same reference numerals, and description thereof will not be repeated.

[0089] As shown in FIG. 21, the ultrasonic transducer 100 according to this embodiment further includes a membrane portion 7. The membrane portion 7 is connected to the beam 6. The ultrasonic transducer 100 does not include the second piezoelectric element 30 (see FIG. 8). In other words, the ultrasonic transducer 100 includes the membrane portion 7 as a substitute for the second piezoelectric element 30. The membrane portion 7 has a different thermal expansion coefficient from that of the diaphragm 2. The membrane portion 7 is, for example, a metal membrane. The ultrasonic transducer 100 is configured to pass a current through the membrane portion 7.

[0090] In this embodiment, the film portion 7 includes a first film portion 71 and a second film portion 72. The first film portion 71 is connected to the first beam portion 61. The second film portion 72 is connected to the second beam portion 62. The first film portion 71 and the second film portion 72 each have a different thermal expansion coefficient from the diaphragm 2.

[0091] Next, the operation of the ultrasonic transducer 100 according to the fourth embodiment will be described. When a current is passed through the membrane 7, the membrane 7 and the beam 6 are heated by Joule heat. The temperature rise causes the membrane 7 and the beam 6 to expand. Because the membrane 7 has a different thermal expansion coefficient from the diaphragm 2, the amount of deformation of the membrane 7 differs from the amount of deformation of the diaphragm 2. The difference between the amount of deformation of the membrane 7 and the amount of deformation of the diaphragm 2 causes the beam 6 to bend.

[0092] Next, the effects of this embodiment will be described. According to the ultrasonic transducer 100 of the fourth embodiment, as shown in FIG. 21, the membrane 7 has a different thermal expansion coefficient from the diaphragm 2. Therefore, when the membrane 7 and the beam 6 are heated, the amount of deformation of the membrane 7 differs from the amount of deformation of the diaphragm 2. Therefore, the diaphragm 2 is deformed as if pulled by the membrane 7, which is deformed by heating. In other words, the beam 6 can be bent by heating. Therefore, the beam 6 can be bent without using the second piezoelectric element 30 (see FIG. 8).

[0093] Embodiment 5 Next, the configuration of the ultrasonic transducer 100 according to embodiment 5 will be described with reference to Fig. 22. Unless otherwise specified, embodiment 5 has the same configuration, manufacturing method, and effects as embodiment 2. Therefore, the same components as embodiment 2 above are denoted by the same reference numerals, and description thereof will not be repeated.

[0094] As shown in FIG. 22, the ultrasonic transducer 100 according to this embodiment further includes a cover portion 8. The cover portion 8 has lower rigidity than the diaphragm 2. Therefore, the cover portion 8 is deformable in response to deformation of the diaphragm 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.

[0095] The cover portion 8 is disposed on the diaphragm 2 so as to cover the slit SL. The cover portion 8 is disposed on the diaphragm 2 so as to expose the opening OP. The cover portion 8 is disposed on the diaphragm 2 so as to cover the first slit portion SL1 and the second slit portion SL2. The shape and arrangement of the cover portion 8 may be determined as appropriate, as long as the first slit portion SL1 and the second slit portion SL2 are covered. The cover portion 8 may have, for example, a ring shape that covers the entire slit SL. The cover portion 8 may be disposed on the diaphragm 2 so as to cover, for example, the central portion 21, the outer circumferential portion 22, and the entire surface of the beam 6 of the diaphragm 2. In this embodiment, the second piezoelectric element 30 is connected to the beam 6 via the cover portion 8.

[0096] In the present embodiment, the cover unit 8 includes a first cover portion 81 and a second cover portion 82. The first cover portion 81 and the second cover portion 82 each cover the first slit portion SL1 and the second slit portion SL2, respectively.

[0097] Next, a method for manufacturing the ultrasonic transducer 100 according to the fifth embodiment will be described. The cover portion 8 is placed on the wafer (substrate 9 (see FIG. 4)) before the second piezoelectric elements 30 are formed. The placed cover portion 8 is then patterned. For example, the cover portion 8 may be placed by a technique such as inkjet printing at an appropriate timing, such as after the patterning of the second piezoelectric elements 30 and after processing of the silicon layer.

[0098] Next, the effects of this embodiment will be described. According to the ultrasonic transducer 100 of the fifth embodiment, as shown in FIG. 22, the cover 8 is disposed on the diaphragm 2 so as to cover the slit SL. This prevents air in the internal space IS from leaking out of the internal space IS through the slit SL. Air in the internal space IS is likely to leak out if the width of the slit SL is too wide. This prevents the amplification effect due to acoustic resonance from being reduced due to air leakage.

[0099] Embodiment 6 Next, the configuration of the ultrasonic transducer 100 according to embodiment 6 will be described with reference to Fig. 23. Unless otherwise specified, embodiment 6 has the same configuration, manufacturing method, and effects as embodiment 2. Therefore, the same components as embodiment 2 above are denoted by the same reference numerals, and description thereof will not be repeated.

[0100] As shown in FIG. 23, each of the beams 60 of the ultrasonic transducer 100 according to this embodiment includes a silicon (Si) substrate having a (1,1,1) crystal plane.

[0101] In this embodiment, the multiple beam portions 60 include a first beam portion 61, a second beam portion 62, and a third beam portion 63. Each of the first beam portion 61, the second beam portion 62, and the third beam portion 63 includes 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 first beam portion 61, the second beam portion 62, and the third beam portion 63 have the same shape and length.

[0102] 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 connected to the first beam portion 61, the second beam portion 62, and the third beam portion 63, respectively. The first element 31, the second element 32, and the third element 33 can vibrate the first beam portion 61, the second beam portion 62, and the third beam portion 63, respectively. The first element 31, the second element 32, and the third element 33 are configured to be able to measure the strain of the first beam portion 61, the second beam portion 62, and the third beam portion 63, respectively.

[0103] Next, the effects of this embodiment will be described. According to the ultrasonic transducer 100 of the sixth embodiment, as shown in FIG. 23, each of the beams 60 includes a silicon (Si) substrate having a (1,1,1) crystal plane. The (1,1,1) mechanical properties of the silicon (Si) substrate are three-fold symmetric. Therefore, when the same stress is applied to each of the beams 60, the deformation amounts of the beams 60 can be made equal to each other. Therefore, even if the silicon (Si) substrate has crystalline anisotropy, the deformation amounts of the beams 60 can be made equal to each other.

[0104] Embodiment 7 Next, the configuration of a distance measuring device 200 according to embodiment 7 will be described with reference to Fig. 24. Unless otherwise specified, the ultrasonic transducer 100 of the distance measuring device 200 according to embodiment 7 has the same configuration, manufacturing method, and effects as those of embodiment 1 above. Therefore, the same components as those of embodiment 1 above will be given the same reference numerals, and descriptions thereof will not be repeated.

[0105] As shown in FIG. 24, a distance measuring device 200 according to this embodiment includes the ultrasonic transducer 100 according to any one of the first to sixth embodiments.

[0106] The distance measuring device 200 is a distance measuring device 200 for measuring the distance from the distance measuring device 200 to the object 300. The distance measuring device 200 is configured to measure the distance from the distance measuring device 200 to the object 300 using a time-of-flight method. That is, the distance measuring device 200 is configured to transmit an ultrasonic wave W1 to the object 300. The distance measuring device 200 is also configured to receive an ultrasonic wave W2 reflected by the object. The distance measuring device 200 is configured to measure the distance from the distance measuring 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.

[0107] When an electric signal is input to the first piezoelectric element 3, the first piezoelectric element 3 vibrates the diaphragm 2 at the resonant frequency, generating an ultrasonic wave W1 at the resonant frequency. The ultrasonic wave W1 is amplified by the acoustic resonant structure. The amplified ultrasonic wave W1 is transmitted from the ultrasonic transducer 100 toward the object 300 as a transmission 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 ultrasonic wave W2 that has reached the object is amplified by the acoustic resonant structure. The amplified ultrasonic wave W2 vibrates the diaphragm 2 by resonance. The vibration of the diaphragm 2 is received as an electric signal by a piezoelectric element arranged on the diaphragm 2. When the distance from the ultrasonic transducer 100 to the object 300 is L, the time from transmission to reception of the sound wave is t, and the speed of sound is c, the distance L can be calculated using equation (4).

[0108] L=c×t / 2 Equation (4) Next, the effects of this embodiment will be described.

[0109] According to the distance measuring device 200 of the seventh embodiment, as shown in Fig. 24, the distance measuring device 200 includes the ultrasonic transducer 100 of any one of the first to sixth embodiments. Therefore, as in any one of the first to sixth embodiments, it is possible to suppress a decrease in the dimensional accuracy of the ultrasonic transducer 100. Therefore, it is possible to suppress a decrease in the dimensional accuracy of the distance measuring device 200. Therefore, it is possible to suppress a decrease in the generated sound pressure and sensitivity of the ultrasonic transducer 100, and therefore it is possible to suppress a decrease in the detection distance of the distance measuring device 200.

[0110] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0111] 1 housing, 2 vibration plate, 3 first piezoelectric element, 6 beam, 7 membrane portion, 8 cover portion, 9 substrate, 21 central portion, 22 peripheral portion, 30 second piezoelectric element, 39 element portion, 60 beam portion, 100 ultrasonic transducer, 200 distance measuring device, IS internal space, OP opening, SL slit.

Claims

1. A vibrating diaphragm; A housing connected to the diaphragm, The diaphragm has an opening, The housing has an internal space communicating with the opening, The diaphragm and the housing form an acoustic resonance structure that amplifies ultrasonic waves generated by vibration of the diaphragm through the opening and the internal space, and are integrally formed; the diaphragm 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 diaphragm is provided with a slit, The slit is provided around the beam, the beam is bendable along a direction in which the diaphragm and the housing are connected, Further comprising a first piezoelectric element and a second piezoelectric element, the first piezoelectric element is disposed on the diaphragm between the central portion and the opening and is connected to the diaphragm; a gap is provided between an end of the first piezoelectric element on the outer periphery side and an end of the beam on the central portion side, The second piezoelectric element is disposed on the beam separately from the first piezoelectric element and connected to the beam.

2. The ultrasonic transducer according to claim 1 , wherein the vibration plate and the housing are configured so that the volume of the internal space can be changed.

3. The second piezoelectric element includes a plurality of element portions, The ultrasonic transducer according to claim 1 , wherein the plurality of element portions are arranged at intervals from one another along a longitudinal direction of the beam.

4. Further comprising a membrane portion connected to the beam, 4. The ultrasonic transducer according to claim 1, wherein the film portion has a different thermal expansion coefficient from that of the vibration plate.

5. A cover portion having a lower rigidity than the diaphragm is further provided, The ultrasonic transducer according to any one of claims 1 to 4, wherein the cover portion is disposed on the vibration plate so as to cover the slit.

6. The beam includes a plurality of beam portions, 6. The ultrasonic transducer according to claim 1, wherein the plurality of beam portions are bendable along a direction in which the vibration plate and the housing are connected.

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

8. A distance measuring device comprising the ultrasonic transducer according to any one of claims 1 to 7.

9. A method for manufacturing an ultrasonic transducer, comprising: The ultrasonic transducer includes: A vibrating diaphragm; A housing connected to the diaphragm, The diaphragm has an opening, The housing has an internal space communicating with the opening, The diaphragm and the housing form an acoustic resonance structure that amplifies ultrasonic waves generated by vibration of the diaphragm through the opening and the internal space, and are integrally formed; the diaphragm 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 diaphragm is provided with a slit, The slit is provided around the beam, the beam is bendable along a direction in which the diaphragm and the housing are connected, Further comprising a first piezoelectric element and a second piezoelectric element, the first piezoelectric element is disposed on the diaphragm between the central portion and the opening and is connected to the diaphragm; a gap is provided between an end of the first piezoelectric element on the outer periphery side and an end of the beam on the central side, the second piezoelectric element is disposed on the beam separately from the first piezoelectric element and connected to the beam; A substrate is provided; a step of integrally molding the vibration plate and the housing from the substrate using MEMS manufacturing technology, forming the opening in the vibration plate, and forming the internal space in the housing that communicates with the opening.

Images