Transducer and method for manufacturing the same

Abstract

To keep the amount of displacement of a cantilever portion 7 small even when a high voltage is applied to a piezoelectric element 3 in a vibration mode in which a vibrating membrane 1 having a cantilever structure is displaced in a Y direction intersecting with an X direction connecting a fixed end 1a and a free end 1b of the vibrating membrane 1.SOLUTION: A transducer includes a cantilever portion 7 having a vibrating membrane 1 and a piezoelectric element 3 arranged on a main surface 1A of the vibrating membrane 1, a support portion 2 connected to a fixed end 1a of the vibrating membrane 1, and a resin film 8 arranged on at least one of a first main surface 7A of the cantilever portion 7 and a second main surface 7B of the cantilever portion 7 facing the opposite direction to the first main surface 7A.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to transducers and methods of manufacturing transducers. [Background technology]

[0002] Piezoelectric MEMS transducers that transmit or receive sound waves or ultrasonic waves are known (see Patent Document 1). Piezoelectric MEMS transducers are composed of a laminated structure of a piezoelectric film that deforms when an electric field is applied and a base made of silicon or the like that does not deform, and are micromechanisms that convert electric fields and motion by utilizing a mechanism in which the laminated film warps depending on whether the film is deformed. Patent Document 1 describes a transducer equipped with a cantilever-type vibrating film that has a free end and a fixed end. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-56253

[0004] [overview] In a vibration mode in which a cantilever-type diaphragm is displaced in a direction intersecting the direction connecting the fixed end and the free end (hereinafter referred to as the "butterfly mode"), applying a high voltage to the piezoelectric element may cause the displacement of the diaphragm to exceed the allowable range.

[0005] The object of the present disclosure is to provide a transducer and a method for manufacturing the transducer that keep the amount of displacement of the cantilever portion small even when a high voltage is applied to a piezoelectric element in a vibration mode in which the vibration membrane having a cantilever structure is displaced in a direction intersecting the direction connecting the fixed end and free end of the vibration membrane.

[0006] In order to solve the above-mentioned problems, one aspect of the present disclosure is a transducer having a cantilever portion having a vibrating membrane and a piezoelectric element arranged on a main surface of the vibrating membrane, a support portion connected to a fixed end of the vibrating membrane, and a resin film arranged on at least one of a first main surface of the cantilever portion and a second main surface of the cantilever portion facing in the opposite direction to the first main surface. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a plan view showing the configuration of a transducer 100 according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the transducer 100 taken along the line II-II of FIG. [Figure 3] FIG. 3 is a cross-sectional view of the transducer 100 taken along the line III-III of FIG. [Figure 4] FIG. 4 is a cross-sectional view of a process showing an example of a method for manufacturing the transducer 100 (part 1). [Figure 5] 5A to 5C are cross-sectional views of steps showing an example of a method for manufacturing the transducer 100 (part 2). [Figure 6] 6A to 6C are cross-sectional views of steps showing an example of a method for manufacturing the transducer 100 (part 3). [Figure 7] 7A to 7C are cross-sectional views of steps showing an example of a method for manufacturing the transducer 100 (part 4). [Figure 8] FIG. 8 is a graph showing, for each sample, the impedance angle (θ) in the resonance frequency range in which a resonance mode occurs that has a characteristic shape of displacement in the longitudinal direction (X direction) of the cantilever portion 7. [Figure 9] FIG. 9 is a graph showing the relationship between the Q value calculated from the peak of the impedance angle (θ) in FIG. 8 and the film thickness of the polyparaxylene film. [Figure 10] FIG. 10 is a graph showing the relationship between the breakdown voltage (breakdown Vpp) and the Q value in the butterfly mode. [Figure 11]FIG. 11 is a graph showing the relationship between the breakdown voltage (breakdown Vpp) and the film thickness of the polyparaxylene film. [Figure 12] FIG. 12 is a cross-sectional view showing the configuration of a transducer 101 according to another embodiment. [Figure 13] FIG. 13 is a plan view showing the configuration of a transducer 102 according to another embodiment. [Figure 14] FIG. 14 is a cross-sectional view of the transducer 102 taken along the II-II section of FIG. [Figure 15] FIG. 15 is a contour diagram showing the displacement shape of the diaphragm 1 when it is resonating in the butterfly mode BF.

[0008] [Detailed explanation] Hereinafter, a transducer and a manufacturing method thereof according to an embodiment will be described in detail with reference to the drawings. However, it should be noted that the drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each part, etc., differ from the actual ones. Furthermore, it goes without saying that the drawings also include parts with different dimensional relationships or ratios.

[0009] The embodiments described below are comprehensive or specific examples. The numerical values, shapes, materials, components, installation positions, and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the scope of the present disclosure. Furthermore, among the components in the following embodiments, components that are not recited in the independent claims that represent the highest concepts are described as optional components. Furthermore, the dimensional proportions in the drawings are exaggerated for the sake of explanation and may differ from the actual proportions. Furthermore, the following embodiments and their variations may include similar components, and the same reference numerals will be used to denote similar components, and redundant explanations will be omitted.

[0010] Fig. 1 is a plan view showing the configuration of a transducer 100 according to an embodiment. Fig. 2 is a cross-sectional view of the transducer 100 taken along the II-II cross section of Fig. 1. Fig. 3 is a cross-sectional view of the transducer 100 taken along the III-III cross section of Fig. 1. The configuration of the transducer 100 will be described with reference to Figs. 1 to 3.

[0011] The transducer 100 according to the embodiment has a cantilever portion 7 , a support portion 2 , and a resin film 8 .

[0012] The cantilever section 7 has a cantilever-type diaphragm 1 and a piezoelectric element 3 arranged on a main surface 1A of the diaphragm 1. The diaphragm 1 is a flexible thin film made of single-crystal silicon. The diaphragm 1 has a cantilever structure. That is, one end 1a of the diaphragm 1 in the longitudinal direction (X direction) is a fixed end, and the other end 1b is a free end. The planar shape of the diaphragm 1 is not particularly limited, but may be, for example, a rectangular shape as shown in FIG. 1A. In this case, the fixed end 1a is located on one of the four sides, and the free end 1b is located on the side opposite this one side.

[0013] The direction from the fixed end 1a to the free end 1b (X direction) is the longitudinal direction of the diaphragm 1. On the main surface 1A of the diaphragm 1, the direction perpendicular to the X direction (Y direction) is the lateral direction of the diaphragm 1. The length of the diaphragm 1 in the X direction and the width of the diaphragm 1 in the Y direction are not particularly limited. For example, in the transducer 100 shown in FIGS. 1 and 2, the length of the diaphragm 1 is 3 mm, and the width of the diaphragm 1 is 2 mm.

[0014] As shown in Fig. 1, when viewed from the normal direction (Z direction) of main surface 1A, support portion 2 has a frame-like shape that surrounds the outer periphery of cantilever portion 7. Slits 5 (gaps) are formed between the inner periphery of support portion 2 and the outer periphery (three sides) of vibrating membrane 1 excluding fixed end 1a (one side) of vibrating membrane 1. Vibrating membrane 1, whose fixed end 1a is fixed to support portion 2, can freely elastically deform relative to support portion 2 due to slits 5.

[0015] A fixed end 1a of the vibration membrane 1 is connected to the support part 2. As shown in Fig. 2, the support part 2 has a laminated structure of an upper layer part 2b that is positioned in the same Z direction (film thickness direction) as the vibration membrane 1, and a lower layer part 2a that is connected to the upper layer part 2b. The transducer 100 has a cavity (hollow part) 9 that is surrounded by the inner circumferential surface of the cylindrical support part 2 and the second main surface 7B of the cantilever part 7.

[0016] The piezoelectric element 3 is disposed over the entire main surface 1A of the diaphragm 1. In reality, the outer shapes of the diaphragm 1 and the piezoelectric element 3 are patterned in different processes. Due to limitations in pattern processing accuracy, such as mask alignment accuracy, the maximum outer shape of the piezoelectric element 3 formed on the main surface 1A of the diaphragm 1 is narrower than the outer shape of the diaphragm 1 by a certain margin. The passivation film that covers the diaphragm 1 and the piezoelectric element 3 is omitted from Figures 1 to 3.

[0017] Although not shown, the transducer 100 may include a silicon (Si) subframe for reinforcing the strength of the support portion 2. The Si subframe is connected to the upper end of the support portion 2.

[0018] Although not shown, the piezoelectric element 3 has a laminated structure of a pair of electrodes and a piezoelectric film sandwiched between the pair of electrodes. Each of the pair of electrodes is formed of a thin film of a conductive metal such as aluminum (Al) or copper (Cu). Alternatively, the lower electrode of the pair of electrodes may have a laminated structure in which titanium (Ti) and platinum (Pt) are laminated in this order. The upper electrode of the pair of electrodes may have a laminated structure in which iridium oxide (IrO2) and iridium (Ir) are laminated in this order. The piezoelectric film is composed of, for example, a lead zirconate titanate (PZT) film. In addition to lead zirconate titanate, the piezoelectric film may also be made of aluminum nitride (AlN), zinc oxide (ZnO), lead titanate (PbTiO3), potassium sodium niobate (KNN), or the like.

[0019] In the embodiment, resin film 8 covers the entire exposed surfaces of the above-described cantilever portion 7 and support portion 2. For example, with respect to cantilever portion 7, resin film 8 is disposed on first main surface 7A (upper surface) of cantilever portion 7, second main surface 7B (lower surface) of cantilever portion 7 facing in the opposite direction to first main surface 7A (upper surface), and side surface of cantilever portion 7 connecting first main surface 7A and second main surface 7B. The side surface of cantilever portion 7 is the surface exposed to slit 5 adjacent to three sides of cantilever portion 7 excluding fixed end 1a.

[0020] In the embodiment, the resin film 8 is also formed on the supporting portion 2, but the resin film 8 does not have to be formed on the supporting portion 2. Formation of the resin film 8 on the supporting portion 2 is optional.

[0021] The resin film 8 is made of at least one of the group consisting of a polyparaxylene film, a resist film, and a polyimide film. It may be a single-layer film or a laminated film of multiple layers. When the resin film 8 covers the entire exposed surface of the cantilever portion 7 and the support portion 2, a polyparaxylene film that can be formed using a vapor deposition method is suitable. A polyparaxylene film with a uniform thickness can be formed over the entire exposed surface. Note that a resist film for photolithography or a resist film for screen printing is suitable as the resist film.

[0022] The basic operation of the transducer 100 will be described. When an AC voltage is applied to a pair of electrodes, an electric field is generated between the pair of electrodes. This electric field causes the piezoelectric membrane to expand or contract in a direction parallel to the XY plane, displacing the free end 1b of the diaphragm 1 so that it warps in the Z direction or its opposite direction. Repeated application of a voltage causes the diaphragm 1 to alternately displace in the Z direction and in the opposite direction to the Z direction. This vibration of the diaphragm 1 causes the air around the diaphragm 1 to vibrate, and the air vibrations are output as audible sound waves or ultrasonic waves. In this way, the transducer 100 functions as a vibration generator that generates vibrations in the diaphragm 1 by inputting a voltage signal to the piezoelectric element 3 to deform the piezoelectric element 3. Furthermore, the transducer 100 functions as an acoustic transducer, such as a piezoelectric speaker or crystal earphone, by converting the vibration of the diaphragm 1 into audible sound waves or ultrasonic waves, which are vibrations of the surrounding air. The frequency of the audible sound waves or ultrasonic waves is controlled by the frequency of the AC voltage.

[0023] Next, an example of a method for manufacturing the transducer shown in FIGS. 1 to 3 will be described.

[0024] The diaphragm 1 and support portion 2 can be formed simultaneously from a single single-crystal silicon substrate. The silicon substrate is etched between the periphery (three sides) of the diaphragm 1, excluding the fixed end 1a, and the upper layer portion 2b. This separates the periphery (three sides) of the diaphragm 1 from the upper layer portion 2b, forming a slit 5. Then, by etching the silicon substrate from its bottom surface (the side of the lower layer portion 2a), a cavity (hollow portion) 9 is formed, as shown in FIG. 2.

[0025] When an SOI (Silicon On Insulator) substrate is used instead of a bulk single crystal silicon substrate, the Si active layer of the SOI substrate can be used as the vibrating membrane 1 and upper layer 2b, and the Si support substrate of the SOI substrate can be used as the lower layer 2a.

[0026] A manufacturing method using an SOI substrate will be described below with reference to FIGS. 4 to 7. First, as shown in FIG. 4, an SOI substrate 12 is prepared, in which a Si active layer 12b is stacked on a Si support substrate 12a via a silicon oxide film (SiO2 film: not shown). As shown in FIG. 5, a piezoelectric element 3 is formed on the surface 12A of the Si active layer of the SOI substrate 12. Specifically, a lower electrode is formed using a deposition method or a sputtering method, and the lower electrode is patterned into a predetermined planar shape using a photolithography method. Then, a piezoelectric film and an upper electrode are sequentially formed on the lower electrode and patterned. This results in the formation of a piezoelectric element 3 having a layered structure consisting of a pair of electrodes and a piezoelectric film sandwiched between the pair of electrodes. Note that the drawings only show the piezoelectric element 3 formed on the vibration membrane 1, but wiring connected to the pair of electrodes and extending to the support portion 2 via the fixed end 1a, and electrode pads for external connection connected to the ends of the wiring are also formed, but these are not shown or described here.

[0027] Next, as shown in FIG. 6, a portion of the Si active layer 12b of the SOI substrate 12 is etched to form a slit 5. Specifically, a mask material made of a silicon oxide film is formed and patterned. Using the patterned mask material as a mask, a portion of the Si active layer 12b is etched by dry etching such as reactive ion etching (RIE), thereby forming the slit 5. The SiO2 film of the SOI substrate 12 can function as an etching stopper layer for detecting the completion of etching of the Si active layer 12b. Thereafter, the mask material is removed by washing with hydrofluoric acid.

[0028] Next, as shown in FIG. 7, a portion of the Si support substrate 12a is etched from the back surface of the SOI substrate 12 to form a cavity (hollow portion) 9. The portion of the Si support substrate 12a that will become the support portion 2a is left, and the portion that overlaps with the vibrating membrane 1 and the slit 5 in a planar view is etched. The specific technique is the same as when etching a portion of the Si active layer 12b to form the slit 5, and therefore a description thereof will be omitted. After that, the SiO2 film of the SOI substrate 12 that is exposed on the bottom surface of the cavity is removed using hydrofluoric acid. As a result, a hole penetrating the front and back surfaces of the SOI substrate 12 is formed in the portion where the cavity (hollow portion) 9 and the slit 5 overlap in a planar view. That is, a cantilever structure is formed in which the fixed end 1a of the vibrating membrane 1 is connected to the support portion 2, and the support portion 2 and the cantilever portion (1, 3) are separated by the slit 5 and the cavity 9.

[0029] Thereafter, a polyparaxylene film is formed by vapor deposition as the resin film 8. Because the polyparaxylene film can be vapor deposited as a gas, it can be formed even after the thin film processing of the vibrating membrane 1 shown in Fig. 7. Therefore, as shown in Figs. 1 to 3, it can be formed on the first main surface 7A, the second main surface 7B, and the side surfaces of the cantilever portion 7.

[0030] The polyparaxylene film serving as resin film 8 has a thickness of, for example, 5 μm or more and 10 μm or less. By forming the film on both first main surface 7A and second main surface 7B of cantilever portion 7, the effect of suppressing the vibration amplitude of cantilever portion 7 in butterfly mode is enhanced compared to when the film is formed on only one surface.

[0031] We will now explain the "butterfly mode." A cantilever-type transducer can have not only a resonance mode characterized by the shape of the displacement in the length direction (X direction) of the cantilever part 7, but also a vibration mode characterized by the shape of the displacement in the width direction (Y direction) of the cantilever part 7, depending on the frequency of the applied voltage. The latter is called the "butterfly mode" to distinguish it from the normal resonance mode. A cantilever-type transducer is characterized by being easily broken in this butterfly mode.

[0032] For example, as shown in FIG. 15, in butterfly mode BF, diaphragm 1 is bent in the short direction (Y direction) at free end 1b. Central portion 1b-1 of one side of diaphragm 1 that forms free end 1b is displaced in the +Z direction relative to frame 6, while both end portions 1b-2 and 1b-3 of one side of diaphragm 1 that form free end 1b are displaced in the -Z direction relative to frame 6. Frame 6 indicates the position where the Z coordinate is 0, i.e., the XY plane. Central portion 1b-1 and both end portions 1b-2 and 1b-3 are displaced alternately in the Z direction. Note that FIG. 15 shows an example of butterfly mode BF in which diaphragm 1 is displaced at free end 1b, but the term "butterfly mode" is not limited to this and also includes a mode in which diaphragm 1 is displaced midway between fixed end 1a and free end 1b.

[0033] (Regarding the thickness of the resin film 8) Hereinafter, the effect of suppressing the vibration amplitude of cantilever portion 7 and the effect of improving the breakdown pressure resistance of cantilever portion 7 when a polyparaxylene film is formed as resin film 8 will be described with reference to experimental data.

[0034] The inventors of the present application prepared multiple transducer 100 samples with different thicknesses of the polyparaxylene film (an example of the resin film 8). The length of the cantilever portion 7 in the short direction (Y direction) was 2 mm, and the length in the long direction (X direction) was 3 mm. The polyparaxylene film was formed on both the first principal surface 7A and the second principal surface 7B of the cantilever portion 7. Multiple samples (P1, P5, P10) with polyparaxylene film thicknesses of 1 μm, 5 μm, and 10 μm were prepared, as well as a sample (P0) with no polyparaxylene film formed. The thickness of the polyparaxylene film refers to the thickness of the polyparaxylene film disposed on each of the first principal surface 7A and the second principal surface 7B.

[0035] The inventors first applied an AC voltage in the resonant frequency range to the piezoelectric element 3, measured the impedance angle (θ) in the resonant frequency range, and calculated the Q value at the resonant frequency. Figure 8 is a graph showing the impedance angle (θ) for each sample in the resonant frequency range where a resonant mode occurs, characterized by the shape of the displacement in the longitudinal direction (X direction) of the cantilever portion 7. The impedance angle (θ) represents the ease of displacement of the cantilever portion 7. A peak (maximum value) of the impedance angle (θ) occurs at the resonant frequency where the resonant mode occurs. Sample P0, which does not have a polyparaxylene film, exhibited the highest peak, followed by samples P1, P5, and P10 in that order. Note that for ease of viewing, Figure 8 shows only one representative impedance angle (θ) for each of samples P0, P1, P5, and P10.

[0036] The inventors calculated the Q value from the peak of the impedance angle (θ) of each sample. The results are shown in Figure 9. The vertical axis of Figure 9 represents the Q value, and the horizontal axis represents the film thickness of the polyparaxylene film. The Q value was calculated by dividing the peak height of the impedance angle (θ) by the half-width. The half-width was defined as half the height of the peak. The peak height of the impedance angle (θ) was defined as the height from a baseline drawn by a straight line connecting two points at both ends of the measurement range shown in Figure 8.

[0037] 9 shows several samples in which the thickness (length in the Z direction) of the diaphragm 1 is 12 μm and the width W5 of the slit 5 is 50 μm, several samples in which the thickness of the diaphragm 1 is 12 μm and the width W5 of the slit 5 is 3 μm, and several samples in which the thickness of the diaphragm 1 is 8 μm and the width W5 of the slit 5 is 50 μm. As shown in FIG. 9, regardless of the thickness of the diaphragm 1 and the width W5 of the slit, the Q value decreased as the thickness of the polyparaxylene film increased.

[0038] The inventors applied an AC voltage of a specific frequency that generates butterfly mode vibration in the cantilever portion 7 to the sample, and increased the voltage value to measure the voltage at which the cantilever portion 7 broke down (breakdown Vpp). The sample used had the same film thickness (length in the Z direction) of the diaphragm 1 and the same width W5 of the slit 5 as in FIG. 9. The vertical axis of FIG. 10 represents the breakdown voltage (breakdown Vpp), and the horizontal axis represents the Q value. The Q value in FIG. 10 corresponds to the Q value in FIG. 9. As shown in FIG. 10, regardless of the film thickness of the diaphragm 1 or the width W5 of the slit, the smaller the Q value, the higher the breakdown voltage (breakdown Vpp).

[0039] By combining the relationship between the Q value and the thickness of the polyparaxylene film shown in FIG. 9 and the relationship between the breakdown voltage (breakdown Vpp) and the Q value shown in FIG. 10, the relationship between the breakdown voltage (breakdown Vpp) and the thickness of the polyparaxylene film shown in FIG. 11 can be derived. The vertical axis of FIG. 11 represents the breakdown voltage (breakdown Vpp), and the horizontal axis represents the thickness of the polyparaxylene film. As shown in FIG. 11, regardless of the thickness of the vibrating membrane 1 and the slit width W5, the thicker the polyparaxylene film, the higher the breakdown voltage (breakdown Vpp). In particular, the breakdown voltage (breakdown Vpp) of samples with a thickness of 5 μm to 10 μm was higher than that of samples without a polyparaxylene film and samples with a polyparaxylene film thickness of 1 μm. Thus, the effect of suppressing the vibration amplitude of the cantilever portion 7 and the effect of improving the breakdown voltage resistance of the cantilever portion 7 were confirmed for transducer 100 having a polyparaxylene film of a predetermined thickness.

[0040] The relationship between the thickness of resin film 8 and the thickness of diaphragm 1 may be determined using their respective Young's moduli. Specifically, the value obtained by multiplying the thickness of resin film 8 by its Young's modulus may be set to 1 / 10 or less of the value obtained by multiplying the thickness of diaphragm 1 by the Young's modulus of single-crystal silicon (approximately 170 GPa). The Young's modulus of polyparaxylene film is approximately 3.5 GPa, approximately 1 / 50 of that of single-crystal silicon. Therefore, it is considered appropriate for the thickness of the polyparaxylene film to be approximately five times the thickness of diaphragm 1. However, if resin film 8 is formed on both first and second main surfaces 7A and 7B of cantilever portion 7, the thickness of resin film 8 is the sum of the thicknesses of both first and second main surfaces 7A and 7B. If the thickness of diaphragm 1 is 12 μm, the total thickness of the polyparaxylene film is preferably 60 μm or less (thickness on one side is 30 μm or less).

[0041] (Regarding the location where the resin film 8 is formed) In the transducer 100 shown in FIGS. 1 to 3, the resin film 8 is formed on the entire exposed surface of the cantilever portion 7, i.e., on the first principal surface 7A, the second principal surface 7B, and the side surfaces. However, the resin film 8 may be formed on at least one of the first principal surface 7A and the second principal surface 7B. For example, as in the transducer 101 shown in FIG. 12, the resin film 8 may be formed only on the first principal surface 7A of the cantilever portion 7 on which the piezoelectric element 3 is formed. The resin film 8 may be formed on the entire first principal surface 7A of the cantilever portion 7, or on only a portion of the first principal surface 7A. Of course, the resin film 8 may be formed only on the second principal surface 7B.

[0042] Next, an example of a method for manufacturing the transducer 101 will be described. As shown in FIG. 5, after forming the piezoelectric element 4 on the surface 12A of the Si active layer 12b, or as shown in FIG. 6, after forming the slit 5, a polyparaxylene film may be formed on the piezoelectric element 4 by a vapor deposition method. The polyparaxylene film can be patterned using a lift-off method or the like. The polyparaxylene film can be selectively formed only on the first main surface 7A.

[0043] Instead of or in combination with the polyparaxylene film, a resist film or a polyimide film may be formed. That is, the resin film 8 may be a single-layer film made of at least one of the group consisting of a polyparaxylene film, a resist film, and a polyimide film, or a laminated film made of two or more of these. The resist film and the polyimide film may be formed by, for example, spin coating, spray coating, or the like.

[0044] Resin film 8 may be disposed only in a portion where cantilever portion 7 is displaced in a direction (e.g., Y direction) intersecting with the X direction connecting fixed end 1a and free end 1b of vibrating membrane 1. Specifically, resin film 8 may be formed only in a portion where the amplitude of the butterfly mode is particularly large. This reduces the amount of displacement of cantilever portion 7.

[0045] 15, the amplitude of the vibration membrane 1 on the free end 1b side increases. Therefore, for example, as shown in FIGS. 13 and 14, a resin film 8 may be selectively formed on a part of the first main surface 7A on the free end 1b side, a part of the second main surface 7B, and the side surface of the cantilever portion 7 on the free end 1b side.

[0046] Although the present disclosure has been described in detail above, it will be apparent to those skilled in the art that the present disclosure is not limited to the embodiments described herein. One or more elements of one embodiment may be combined with one or more elements of another embodiment. The present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the present disclosure, as defined by the claims. Therefore, the description of the present disclosure is intended to be illustrative and explanatory and is not intended to be limiting of the present disclosure.

[0047] [Note] The technical ideas that can be understood from the present disclosure are described below. Note that, for the purpose of aiding understanding and not intending to be limiting, the components described in the appendices are given the reference numerals of the corresponding components in the embodiments. The reference numerals are shown as examples to aid understanding, and the components described in each appendix should not be limited to the components indicated by the reference numerals.

[0048] (Appendix 1) Transducers 100, 101, and 102 each include a cantilever portion 7 having a vibrating membrane 1 and a piezoelectric element 3 arranged on a main surface 1A of vibrating membrane 1, a support portion 2 connected to fixed end 1a of vibrating membrane 1, and a resin film 8 arranged on at least one of a first main surface 7A of cantilever portion 7 and a second main surface 7B of cantilever portion 7 facing in the opposite direction from first main surface 7A. The presence of resin film 8 reduces the displacement of cantilever portion 7 in the normal resonance mode, thereby reducing the Q value. Therefore, even when a high voltage is applied to piezoelectric element 3 in the butterfly mode, the amount of displacement of cantilever portion 7 can be kept small.

[0049] (Appendix 2) In the transducer 101 described in Supplementary Note 1, the resin film 8 may be disposed only on the first main surface 7A of the cantilever portion 7. The resin film 8 can be formed before the cavity 9 is formed. Therefore, the resin film 8 is not limited to a polyparaxylene film, and a resist film or a polyimide film can be selected.

[0050] (Appendix 3) In the transducers 101 and 102 described in Supplementary Note 1 or 2, the resin film 8 may be disposed on each of the first main surface 7A and the second main surface 7B of the cantilever portion 7. After the cavity 9 is formed, the uniform resin film 8 can be formed.

[0051] (Appendix 4) In transducers 100 and 102 described in Supplementary Note 1 or 3, resin film 8 may also be disposed on the side surface of cantilever portion 7 connecting first main surface 7A and second main surface 7B. This makes it possible to minimize the amount of displacement of cantilever portion 7 originating from minute cracks on the side surface of vibration membrane 1 made of single crystal silicon.

[0052] (Appendix 5) In transducer 102 described in any one of Supplementary Notes 1 to 4, resin film 8 is disposed only in a portion where cantilever portion 7 is displaced in the Y direction, which intersects with the X direction connecting fixed end 1a and free end 1b of vibrating membrane 1. This makes it possible to keep the amount of displacement of cantilever portion 7 small.

[0053] (Appendix 6) In transducer 102 described in Supplementary Note 5, the portion of cantilever portion 7 that is displaced in the Y direction, which intersects with the X direction connecting fixed end 1a and free end 1b, includes the side surface of cantilever portion 7 on the free end 1b side. This makes it possible to keep the amount of displacement of cantilever portion 7 small in butterfly mode BF shown in FIG.

[0054] (Appendix 7) In transducer 100 described in Supplementary Note 3, the thickness of resin film 8 disposed on each of first main surface 7A and second main surface 7B of cantilever portion 7 is 5 μm or more and 10 μm or less, thereby making it possible to keep the amount of displacement of cantilever portion 7 small.

[0055] (Appendix 8) In the transducers 100, 102 described in any one of Appendices 1 to 7, the vibrating membrane 1 is made of single crystal silicon, and the value obtained by multiplying the film thickness (total value of both sides) of the resin film 8 by the Young's modulus of the resin film 8 may be 1 / 10 or less of the value obtained by multiplying the film thickness of the vibrating membrane 1 by the Young's modulus of single crystal silicon.

[0056] (Appendix 9) In the transducers 100, 101, and 102 described in any one of Supplementary Notes 1 to 8, the resin film 8 is made of at least one of a group consisting of a polyparaxylene film, a resist film, and a polyimide film. The resist film includes a photoresist film and a screen printing resist film.

[0057] (Appendix 10) A method for manufacturing transducers 100-102 according to any one of Supplementary Notes 1 to 9, comprising a step of depositing a polyparaxylene film as resin film 8 by vapor deposition. This allows for the deposition of a uniform resin film 8 on both sides of cantilever portion 7. Since the film can be deposited even after thin film processing of vibration membrane 1, it is also possible to deposit a film on second main surface 7B of cantilever portion 7.

[0058] (Appendix 11) In the method for manufacturing transducers 100 to 102 described in Supplementary Note 10, resin film 8 is formed on first main surface 7A and second main surface 7B of cantilever portion 7. By forming the film on both sides of cantilever portion 7, the effect of suppressing butterfly mode can be enhanced. [Explanation of symbols]

[0059] 1. Vibration membrane 1a fixed end 1b free end 2 Support part 3 Piezoelectric element 5 Slits 7 Cantilever part 7A 1st main surface 7B Second main surface 8 Resin film 9 Cavity (hollow part) 12 SOI substrate 12a Si support substrate 12b Si active layer 100~102 transducer W5 width

Claims

1. a cantilever portion having a vibration membrane and a piezoelectric element disposed on a main surface of the vibration membrane; a support portion connected to a fixed end of the vibration membrane; a resin film disposed on at least one of a first main surface of the cantilever portion and a second main surface of the cantilever portion facing in a direction opposite to the first main surface; A transducer having:

2. The transducer according to claim 1 , wherein the resin film is disposed only on the first main surface of the cantilever portion.

3. The transducer according to claim 1 , wherein the resin film is disposed on each of the first main surface and the second main surface of the cantilever portion.

4. The transducer according to claim 1 , wherein the resin film is also disposed on a side surface of the cantilever portion connecting the first main surface and the second main surface.

5. 2. The transducer according to claim 1, wherein the resin film is disposed only in a portion where the cantilever portion is displaced in a direction intersecting a direction connecting the fixed end and the free end of the vibration membrane.

6. 6. The transducer according to claim 5, wherein a portion of the cantilever portion that is displaced in a direction intersecting a direction connecting the fixed end and the free end includes a side surface of the cantilever portion on the free end side.

7. 4. The transducer according to claim 3, wherein the resin film disposed on each of the first and second principal surfaces has a thickness of 5 [mu]m or more and 10 [mu]m or less.

8. the vibration membrane is made of single crystal silicon, 4. The transducer according to claim 3, wherein the value obtained by multiplying the thickness of said resin film by the Young's modulus of said resin film is 1 / 10 or less of the value obtained by multiplying the thickness of said vibration film by the Young's modulus of single crystal silicon.

9. 2. The transducer according to claim 1, wherein the resin film is made of at least one of a group consisting of a polyparaxylene film, a resist film, and a polyimide film.

10. A method for manufacturing a transducer according to any one of claims 1 to 9, comprising: forming a polyparaxylene film as the resin film by a vapor deposition method; A method for manufacturing a transducer.

11. The method for manufacturing a transducer according to claim 10 , wherein the resin film is formed on the first main surface and the second main surface of the cantilever portion.

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