Sound sensor

Abstract

Provided is an acoustic sensor provided with: a support body (10); and a vibration unit (20) that is disposed on the support body (10), that has a support region (21a) supported by the support body (10) and a vibration region (22) that is continuous with the support region (21a) and is capable of vibration, and that outputs a detection signal corresponding to the deformation of the vibration region (22). A recessed portion (10a) is formed in a portion of the support body (10) facing the vibration region (22), the vibration region (22) has a portion in which compressive stress is formed, and a stress relaxation hole portion (81) is formed in the vibration portion (20).

Description

Technical Field

[0001] This disclosure relates to sound sensors. Background Technology

[0002] Previously, piezoelectric sensors with vibration regions have been proposed as sound sensors (for example, see Patent Document 1). Specifically, the piezoelectric sensor includes a vibrating part having a vibration region and a support region, and a support body supporting the support region of the vibration part, wherein the vibration region is suspended from the support body.

[0003] Such a piezoelectric sensor is configured such that the vibrating part includes a piezoelectric film and an electrode film. Furthermore, the piezoelectric film and electrode film are formed, for example, by sputtering. Therefore, the vibrating part is configured with residual internal stress. Moreover, if compressive stress, as an internal stress, is generated in the vibrating region, the sound sensor will become structurally stiff due to buckling in the vibrating region, thereby reducing its sensitivity. Therefore, in this piezoelectric sensor, the vibrating region is locally thickened to prevent buckling.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent No. 2010-247295 Summary of the Invention

[0005] However, when the vibration region is locally thickened, the thickened portion becomes difficult to deform. Therefore, in this structure, although the decrease in sensitivity caused by buckling can be suppressed, the sensitivity may decrease due to the thickened portion, and it may not be able to sufficiently suppress the decrease in sensitivity.

[0006] The purpose of this disclosure is to provide a sound sensor capable of suppressing reduced sensitivity.

[0007] According to one aspect of this disclosure, a sound sensor includes: a support body; and a vibrating part disposed on the support body, having a support region supported on the support body and a vibration region connected to the support region and capable of vibration, and outputting a detection signal corresponding to the deformation of the vibration region; the support body has a recessed portion in the portion opposite to the vibration region, the vibration region has a portion that generates compressive stress, and the vibrating part has a stress-relieving hole.

[0008] Accordingly, stress-relieving holes are formed in the vibrating section. Therefore, the compressive stress in the vibration region can be released from the stress-relieving holes, suppressing buckling of the vibration region. Furthermore, since it is not necessary to thicken the vibration region, the sensitivity is not reduced by the stress-relieving holes. Thus, a decrease in sensitivity can be suppressed.

[0009] Furthermore, the bracketed reference numerals used to indicate each constituent element, etc., represent an example of the correspondence between that constituent element, etc., and the specific constituent elements, etc., described in the embodiments described later. Attached Figure Description

[0010] Figure 1 This is a top view of the piezoelectric sensor according to the first embodiment.

[0011] Figure 2 It is along Figure 1 A sectional view along line II-II in the diagram.

[0012] Figure 3 It is a three-dimensional diagram representing a vibration region.

[0013] Figure 4 It is a graph representing the displacement of the vibration region.

[0014] Figure 5A It means Figure 1 The diagram shows a cross-sectional view of the manufacturing process of the piezoelectric sensor.

[0015] Figure 5B It continues Figure 5A The figure shows a cross-sectional view representing the manufacturing process of a piezoelectric sensor.

[0016] Figure 6 This is a cross-sectional view of the piezoelectric sensor according to the second embodiment.

[0017] Figure 7 This is a top view of the piezoelectric sensor according to the third embodiment.

[0018] Figure 8 It is along Figure 7 A cross-sectional view of line VIII-VIII in the diagram.

[0019] Figure 9 This is a top view of the piezoelectric sensor according to the fourth embodiment.

[0020] Figure 10 It is along Figure 9 A sectional view of the XX line.

[0021] Figure 11 It is a graph representing the displacement of the vibration region.

[0022] Figure 12A It means Figure 10 The diagram shows a cross-sectional view of the manufacturing process of the piezoelectric sensor.

[0023] Figure 12B It continues Figure 12A The figure shows a cross-sectional view representing the manufacturing process of a piezoelectric sensor.

[0024] Figure 12C It continues Figure 12B The figure shows a cross-sectional view representing the manufacturing process of a piezoelectric sensor.

[0025] Figure 12D It continues Figure 12C The figure shows a cross-sectional view representing the manufacturing process of a piezoelectric sensor.

[0026] Figure 12E It continues Figure 12D The figure shows a cross-sectional view representing the manufacturing process of a piezoelectric sensor. Detailed Implementation

[0027] Hereinafter, embodiments of the present disclosure will be described based on the accompanying drawings. Furthermore, in the following embodiments, the same or equivalent parts will be described using the same reference numerals.

[0028] (First Implementation) The sound sensor of the first embodiment will be described. Furthermore, in this embodiment, a piezoelectric sensor used in microphones and the like will be used as an example of a sound sensor.

[0029] like Figures 1-3 As shown, the piezoelectric sensor includes a support body 10 and a vibrating part 20, and has a rectangular shape when viewed from above. The support body 10 includes a support substrate 11 having one side 11a and another side 11b, and an insulating film 12 formed on one side 11a of the support substrate 11. Furthermore, the support substrate 11 is made of, for example, a silicon substrate, and the insulating film 12 is made of, an oxide film, or the like. Additionally, hereinafter, a direction along the surface direction of the vibrating part 20 will be referred to as the X-axis direction, and a direction orthogonal to the X-axis direction along the surface direction of the vibrating part 20 will be referred to as the Y-axis direction. Figure 1 In the diagram, the left-right direction of the paper is the X-axis, and the up-down direction of the paper is the Y-axis.

[0030] The vibrating part 20 is disposed on the support body 10. Furthermore, a recess 10a is formed on the support body 10 for suspending the inner edge of the vibrating part 20. Therefore, the vibrating part 20 is configured to have a support region 21a disposed on the support body 10 and a suspension region 21b connected to the support region 21a and suspended on the recess 10a. In other words, in the vibrating part 20, the portion overlapping the recess 10a in the stacking direction of the support body 10 and the vibrating part 20 is the suspension region 21b, and the region different from the suspension region 21b is the support region 21a. That is, the recess 10a is formed in the portion opposite to the suspension region 21b (i.e., the vibrating region 22 described later).

[0031] Furthermore, in this embodiment, the recess 10a is formed such that it penetrates the support substrate 11 and the insulating film 12, exposing the vibrating part 20. The shape of the opening end on the vibrating part 20 side is rectangular when viewed from above. Therefore, the suspension region 21b as a whole is rectangular when viewed from above. More specifically, the suspension region 21b as a whole is a square shape with equal lengths in the X-axis and Y-axis directions. In addition, the so-called stacking direction of the support 10 and the vibrating part 20, in other words, is the same as the normal direction relative to one side 22a of the vibration region 22 described later.

[0032] In this embodiment, a slit 30 is formed in the suspension region 21b, extending through the suspension region 21b in the thickness direction. The slit 30 in this embodiment is formed to divide the suspension region 21b into four parts. Specifically, two slits 30 are formed such that they extend from the center C1 of the suspension region 21b to opposite corners of the suspension region 21b. In other words, the slits 30 are formed to extend from each corner of the suspension region 21b, which is rectangular in shape when viewed from above, towards the center C1, and the slits 30 intersect at the center C1. Thus, the suspension region 21b is separated into four vibration regions 22 that are approximately triangular in shape when viewed from above. Furthermore, in this embodiment, the slits 30 are formed to reach the recess 10a, but the slits 30 may also be configured to terminate within the suspension region 21b. That is, the vibration regions 22 may also be partially connected on the side of the recess 10a. In addition, although not specifically limited, in this embodiment, the interval between each vibration region 22 (i.e., the width W of the slit 30) is about 1 μm.

[0033] Each vibration region 22 is a cantilever structure in which one end 221 on the support region 21a side is a fixed end and the other end 222 on the opposite side of the support region 21a, i.e., the front end, is a free end. Hereinafter, the surface of the vibration region 22 opposite to the support body 10 will be referred to as one surface 22a of the vibration region 22, and the surface of the vibration region 22 on the support body 10 side will be referred to as the other surface 22b of the vibration region 22. Furthermore, in this embodiment, one end 221 of the vibration region 22 can also be described as the part that coincides with the opening end on the vibration part 20 side of the recess 10a in the normal direction.

[0034] The vibrating part 20 is a dual piezoelectric wafer structure having a piezoelectric film 40 and an electrode film 50 connected to the piezoelectric film 40. Specifically, the piezoelectric film 40 has a lower piezoelectric film 41 and an upper piezoelectric film 42 stacked on the lower piezoelectric film 41. Furthermore, the lower piezoelectric film 41 and the upper piezoelectric film 42 are made of lead-free piezoelectric ceramics such as scandium aluminum nitride (ScAlN) and aluminum nitride (AlN).

[0035] The electrode film 50 is formed at a predetermined location in the vibration region 22 in a manner connected to the piezoelectric film 40, and is made of materials such as molybdenum, copper, platinum, and titanium. In this embodiment, the electrode film 50 comprises a lower electrode film 51 formed below the lower piezoelectric film 41, an intermediate electrode film 52 formed between the lower piezoelectric film 41 and the upper piezoelectric film 42, and an upper electrode film 53 formed above the upper piezoelectric film 42.

[0036] Furthermore, the lower electrode film 51 and the intermediate electrode film 52 are arranged opposite each other with the lower piezoelectric film 41 in between. The intermediate electrode film 52 and the upper electrode film 53 are arranged opposite each other with the upper piezoelectric film 42 in between. Moreover, the lower electrode film 51, the intermediate electrode film 52, and the upper electrode film 53 have the same shape in the normal direction (hereinafter also simply referred to as the normal direction) relative to one side 22a of the vibration region 22. In other words, "in the normal direction relative to one side 22a of the vibration region 22" can also be interpreted as when viewed from the normal direction relative to one side 22a of the vibration region 22. Furthermore, the statement that the lower electrode film 51, the intermediate electrode film 52, and the upper electrode film 53 have the same shape means not only that they are completely identical in shape, but also that they include some differences in shape.

[0037] Here, when the vibration region 22 is cantilevered as in this embodiment, the stress generated when the vibration region 22 (i.e., the piezoelectric film 40) vibrates is more likely to be greater on the fixed end side supporting the vibration region 22 than on the free end side. In other words, the stress generated when the vibration region 22 (i.e., the piezoelectric film 40) vibrates is more likely to be greater on one end 221 side than on the other end 222 side. Therefore, it can also be said that the vibration region 22 is configured to have a first region R1 on the end 221 side where the stress is more likely to increase and a second region R2 on the other end 222 side where the stress is less likely to increase. Furthermore, in this embodiment, electrode films 50 are formed in both the first region R1 and the second region R2. However, in this embodiment, the electrode film 50 formed in the first region R1 and the electrode film 50 formed in the second region R2 are mutually insulated.

[0038] like Figure 3 As shown, the electrode film 50 formed in the first region R1 is connected to an electrode portion (not shown) disposed in the support region 21a via an external wiring 61 formed in the support region 21a. In this embodiment, in order to output a detection signal as a change in charge in the first region R1 of each vibration region 22, each lower electrode film 51, intermediate electrode film 52, and upper electrode film 53 in each vibration region 22 are connected to the electrode portion via the external wiring 61, etc.

[0039] Furthermore, in this embodiment, the upper electrode film 53 formed in the first region R1 is divided into first and third upper electrode films 531 to 533. The first to third upper electrode films 531 to 533 are connected in series via internal wiring 71 formed in the support region 21a. Additionally, in... Figure 1 In this diagram, external wiring 61 and internal wiring 71 are omitted. Although not specifically illustrated, the intermediate electrode film 52 and the lower electrode film 51 have the same shape as the first and third upper electrode films 531-533, and are respectively divided into first and third intermediate electrode films and first and third lower electrode films. Furthermore, the first and third intermediate electrode films and the first and third lower electrode films are connected in series via internal wiring (not shown). In this embodiment, by dividing the electrode film 50 formed in the first region R1 into multiple capacitors connected in parallel, an improvement in detection sensitivity can be achieved. Hereinafter, in the first region R1 of the vibration region 22, the portion along the normal direction where the first upper electrode film 531 is disposed is designated as the first portion R11, the portion along the normal direction where the second upper electrode film 532 is disposed is designated as the second portion R12, and the portion along the normal direction where the third upper electrode film 533 is disposed is designated as the third portion R13.

[0040] The lower electrode film 51, the intermediate electrode film 52, and the upper electrode film 53 formed in the second region R2 are not electrically connected to each electrode portion and are in a floating state. Therefore, the lower electrode film 51, the intermediate electrode film 52, and the upper electrode film 53 formed in the second region R2 are not necessary. In this embodiment, they are provided to protect the portions of the lower piezoelectric film 41 and the upper piezoelectric film 42 located in the second region R2.

[0041] Furthermore, although not specifically illustrated, the piezoelectric sensor may also have a base film on which the lower piezoelectric film 41 and the lower electrode film 51 are disposed. That is, the piezoelectric sensor may also have the piezoelectric film 40 and the electrode film 50 disposed on the base film. The base film is provided to facilitate crystal growth during the formation of the lower piezoelectric film 41, and is, for example, made of aluminum nitride. In the case of the base film, its thickness is approximately tens of nanometers (nm), which is extremely thin relative to the piezoelectric film 40. Therefore, in the case of a structure with a base film, the base film located in the suspension region 21b also constitutes each vibration region 22, thus the vibration region 22 is a structure that includes the base film.

[0042] Furthermore, as described later, the vibration section 20 is formed by patterning a piezoelectric film 40 and an electrode film 50 using a sputtering method or the like. It is reported that the piezoelectricity of the piezoelectric film 40 tends to decrease when tensile stress increases. Therefore, the piezoelectric sensor is configured such that compressive stress remains in the vibration region 22. However, if compressive stress exists in the vibration region 22, the sensitivity may decrease if the vibration region 22 is bent. In this embodiment, the free end of the vibration region 22 is open, making it difficult for it to be bent due to compressive stress, but the fixed end may be bent due to compressive stress. In other words, in the vibration region 22 of this embodiment, the first region R1 is more prone to bending than the second region R2.

[0043] Therefore, in this embodiment, a through hole 81 is formed in the first region R1, which passes through one side 22a and the other side 22b of the vibration region 22. In this embodiment, three through holes 81 are formed in each vibration region 22, respectively passing through the first part R11, the second part R12, and the third part R13. In addition, the through holes 81 in this embodiment are cylindrical with a perfectly circular opening, and are formed along the normal direction. Moreover, in the opening of the through hole 81 in this embodiment, the width (i.e., diameter) d of the opposing portion is greater than or equal to the width W of the slit. Furthermore, in this embodiment, the through hole 81 corresponds to a stress-relieving hole.

[0044] The above describes the structure of the piezoelectric sensor according to this embodiment. In this piezoelectric sensor, when sound pressure is applied to each vibration region 22, each vibration region 22 vibrates. In this case, for example, if the free end of each vibration region 22 displaces upward, tensile stress is generated on the lower piezoelectric film 41, and compressive stress is generated on the upper piezoelectric film 42, causing a change in the charge of the lower and upper piezoelectric films 41 and 42. Therefore, the sound pressure applied to the vibration region 22 is detected based on the charge of the lower and upper piezoelectric films 41 and 42.

[0045] At this time, regarding the stress generated in the vibration region 22 (i.e., the piezoelectric film 40), since the stress is released at the free end, the stress at the fixed end is greater than the stress at the free end. That is, less charge is generated at the free end, and the signal-to-noise ratio (SN ratio) tends to decrease. Therefore, in the piezoelectric sensor of this embodiment, as described above, each vibration region 22 is divided into a first region R1 where stress tends to increase and a second region R2 where stress tends to decrease. Furthermore, in the piezoelectric sensor, the charge generated in the lower piezoelectric film 41 and the upper piezoelectric film 42 located in the first region R1 is extracted from the lower electrode film 51, the upper electrode film 53, and the intermediate electrode film 52 disposed in the first region R1. As a result, the influence of noise can be suppressed.

[0046] Furthermore, in this embodiment, a through-hole 81 is formed in the first region R1, which is the area where charge is extracted and where compressive stress is prone to increase. Therefore, the compressive stress in the first region R1 can be released through the through-hole 81, and buckling in the vibration region 22 can be suppressed. Thus, the decrease in sensitivity of the piezoelectric sensor can be suppressed.

[0047] Here, the inventors have conducted an in-depth study on the displacement of the vibration region 22 in the piezoelectric sensor of this embodiment, and obtained... Figure 4 The results are shown. Furthermore, in Figure 4 In this example, a piezoelectric sensor without the through-hole 81 as in this embodiment but with the same structure as this embodiment is used as a comparative example. The displacement of each vibration region 22 without applying sound pressure to the vibration region 22 is shown. Furthermore, Figure 4 It shows along Figure 3 The displacement of the IV-IV line portion is represented with the boundary between the support 10 and the vibrating part 20 as a reference (i.e., 0), and the displacement of the vibrating region 22 towards the support 10 is negative. Furthermore, Figure 4 Is it like this? Figure 1 As shown, the length L of one end 221 in the vibration region 22 is set to 900 μm, the width d of the through hole 81 is set to 60 μm, and the position of 400 μm is represented as the center of the second part R12.

[0048] like Figure 4 As shown, in this embodiment, it can be confirmed that the displacement of the vibration region 22 can be reduced due to the formation of the through hole 81. That is, it can be confirmed that the vibration region 22 is less prone to deformation caused by buckling.

[0049] Furthermore, although the through hole portion 81 in this embodiment is set as a cylindrical shape with a perfectly circular opening, the shape of the opening can be appropriately changed; it can be either an elliptical shape or a polygonal shape. Additionally, the number of through holes 81 can be appropriately changed.

[0050] Next, the manufacturing method of the above-mentioned piezoelectric sensor will be briefly explained.

[0051] First, such as Figure 5A As shown, a support 10 without the recess 10a is prepared, and a piezoelectric film 40 and an electrode film 50 are disposed by appropriate sputtering, etching, or other methods. At this time, by appropriately adjusting the sputtering conditions, the piezoelectric film 40 is formed such that compressive stress remains at least in the portion that becomes the vibration region 22. Next, as... Figure 5BAs shown, a resist (not shown) or similar material is applied to the vibrating part 20, and a slit 30 and a through hole 81 are appropriately formed by etching or the like. Then, although not specifically shown, a recess 10a is formed by etching or the like from the other side 11b of the support substrate 11 to form a suspension region 21b (i.e., the vibrating region 22), thereby manufacturing the piezoelectric sensor described above.

[0052] According to the embodiment described above, a through hole 81 is formed in the vibrating section 20. Therefore, the compressive stress of the vibration region 22 can be released from the through hole 81, and buckling of the vibration region 22 can be suppressed. In addition, since it is not necessary to thicken the vibration region 22, the sensitivity will not decrease due to the through hole 81. Therefore, the decrease in sensitivity can be suppressed.

[0053] (1) In this embodiment, the vibration region 22 is a cantilever structure, and the through hole 81 is formed in a first region R1 on the side of an end 221. That is, the through hole 81 is formed in a region that is prone to buckling due to compressive stress. Therefore, the decrease in sensitivity can be further suppressed.

[0054] (Second Implementation) The second embodiment will be described. This embodiment differs from the first embodiment in that the shape of the through hole 81 is changed. Other aspects are the same as in the first embodiment, and therefore will not be described here.

[0055] In the piezoelectric sensor of this embodiment, such as Figure 6 As shown, the through-hole portion 81 is formed obliquely in the normal direction. Therefore, compared with the case where the through-hole portion 81 is formed along the normal direction as in the first embodiment described above, the length of the through-hole portion 81 is longer, and the hole resistance (i.e., piping resistance) related to sound passage is greater. Specifically, the through-hole portion 81 is formed such that the hole resistance is greater than the slit resistance (i.e., piping resistance) related to sound passage of the slits 30 that divide each vibration region 22. Therefore, by forming the through-hole portion 81, sound escape from the through-hole portion 81 can be suppressed, and sensitivity reduction and detection frequency band changes can be suppressed.

[0056] Furthermore, the through-hole 81 is formed, for example, in a manner where the resistance of the hole is approximately 10 times the resistance of the slit. Additionally, in Figure 6 The diagram shows a structure in which the through hole portion 81 is formed from the other side 22b towards the other side 22a, toward the other end 222. However, the through hole portion 81 may also be formed from the one side 22a towards the other side 22b, toward the other end 222.

[0057] According to the above-described embodiment, since a through hole 81 is formed in the vibration region 22, the same effect as the first embodiment described above can be obtained.

[0058] (1) In this embodiment, the through hole 81 is formed such that the resistance of the hole is greater than the resistance of the slit. Therefore, by forming the through hole 81, it is possible to suppress sound from escaping from the through hole 81. That is, by forming the through hole 81, it is possible to suppress the decrease in sensitivity and the change in the detection frequency band.

[0059] (Third Implementation) The third embodiment will be described. This embodiment differs from the first embodiment in that the shape of the through hole 81 is changed. Other aspects are the same as in the first embodiment, and therefore will not be described here.

[0060] In the piezoelectric sensor of this embodiment, such as Figure 7 and Figure 8 As shown, the through-hole 81 is formed along the normal direction. However, the width d of the through-hole 81 is narrower than the width W of the slit 30. Therefore, compared to the case in the first embodiment described above where the width d of the through-hole 81 is greater than or equal to the width W of the slit 30, the resistance of the hole increases. Specifically, the through-hole 81 in this embodiment is formed such that the resistance of the hole is greater than the resistance of the slit. Therefore, by forming the through-hole 81, it is easy to suppress sound from escaping from the through-hole 81. Furthermore, the through-hole 81 is formed, for example, such that the resistance of the hole is about 10 times the resistance of the slit.

[0061] Furthermore, in this embodiment, since the width d of the through hole 81 is reduced, the function of releasing the compressive stress of the vibration region 22 may be reduced. Therefore, in this embodiment, the number of through holes 81 is increased compared to the first embodiment described above.

[0062] According to the above-described embodiment, since a through hole 81 is formed in the vibration region 22, the same effect as the first embodiment described above can be obtained.

[0063] (1) In this embodiment, the through hole 81 is formed such that the resistance of the hole is greater than the resistance of the slit. Therefore, by forming the through hole 81, it is possible to suppress sound from escaping from the through hole 81. That is, by forming the through hole 81, it is possible to suppress the decrease in sensitivity and the change in the detection frequency band.

[0064] (Fourth Implementation) The fourth embodiment will be described. This embodiment differs from the first embodiment in that the structure of the stress-relieving hole is modified. Other aspects are the same as in the first embodiment and therefore will not be described here.

[0065] In this embodiment, such as Figure 9 and Figure 10As shown, no through hole 81 is formed in the vibration region 22, but a through hole 83 is formed in the support region 21a. Specifically, in this embodiment, a cavity 82 is formed on the side of the recess 10a in the insulating film 12 of the support body 10, serving as a hole communicating with the recess 10a. More specifically, the cavity 82 is composed of a recess formed by removing the surface on the side of the vibration part 20 in the insulating film 12.

[0066] Furthermore, the depth t of the cavity 82 is smaller than the width W of the slit 30, so that the resistance of the cavity (i.e., the piping resistance) related to the passage of sound is greater than the resistance of the slit. For example, the depth t of the cavity 82 is adjusted so that the piping resistance in the pressure relief hole formed in communication with the through hole 83 described later is about 10 times the resistance of the slit.

[0067] Furthermore, in this embodiment, the cavity portion 82 is formed at one end 221 of each vibration region 22 such that the inner edge 221a of that end 221 is supported by the support body 10 (i.e., the insulating film 12). In other words, the cavity portion 82 is not formed in such a way that the inner edge 221a of one end 221 in each vibration region 22 is suspended.

[0068] Furthermore, in this embodiment, the cavity portion 82 is formed at one end 221 of each vibration region 22 such that the outer edge 221b of that end 221 is supported by the support body 10 (i.e., the insulating film 12). In other words, the cavity portion 82 is not formed in such a way that the outer edge 221b of one end 221 in each vibration region 22 is suspended.

[0069] Therefore, in this embodiment, one end 221 of the support region 21a side in the vibration region 22 is a support portion supported by the support body 10, a suspended portion suspended from the support body 10, a support portion supported by the support body 10, a suspended portion suspended from the support body 10, and a support portion supported by the support body 10.

[0070] Here, when the piezoelectric film 40 and the electrode film 50 are stacked to form the vibration region 22 as in this embodiment, the internal stress will vary due to the different stacking structures. For example, at one end 221 of the vibration region 22, the internal stress differs between the portion where the electrode film 50 is disposed and the portion where the electrode film 50 is not disposed. That is, at one end 221 of the vibration region 22, there is a region with high compressive stress and a region with lower compressive stress. Furthermore, the region with low compressive stress also includes a region where tensile stress is formed.

[0071] Furthermore, in this embodiment, the compressive stress is higher in the portion where the electrode film 50 is not disposed compared to the portion where the electrode film 50 is disposed. For example, the vibration region 22 in this embodiment is configured such that the compressive stress is higher in the region between the first portion R11 and the second portion R12, and in the region between the second portion R12 and the third portion R13, compared to the first portion R11, the second portion R12, and the third portion R13. Furthermore, the cavity portion 82 in this embodiment is formed in such a way that the region between the first portion R11 and the second portion R12, and the region between the second portion R12 and the third portion R13, where the compressive stress at one end 221 is higher, is suspended.

[0072] Furthermore, in this embodiment, two cavities 82 are formed such that each vibration region 22 is supported by the support body 10 as described above. Specifically, one cavity 82 is formed such that its inner edge 221a at one end 221 is suspended between its outer edge 221b. The other cavity 82 is formed such that its inner edge 221a is suspended between its outer edge 221b. Additionally, the cavity 82 in this embodiment is formed in a generally triangular shape in the normal direction.

[0073] Furthermore, the through hole 83 formed in the support region 21a is formed to communicate with the cavity 82. In addition, the through hole 83 in this embodiment is formed with a width d equal to or greater than the width W of the slit 30. Furthermore, in this embodiment, a stress-relieving hole is formed including both the through hole 83 and the cavity 82, and the stress-relieving hole is formed to pass through the vibration section 20. Moreover, in this embodiment, since the cavity resistance (i.e., piping resistance) is greater than the slit resistance, the overall piping resistance of the stress-relieving hole is greater than the slit resistance.

[0074] The above describes the structure of the piezoelectric sensor according to this embodiment. In such a piezoelectric sensor, compressive stress can be released from the through hole 83 and the cavity 82, and buckling in the vibration region 22 can be suppressed. Therefore, the decrease in sensitivity of the piezoelectric sensor can be suppressed.

[0075] Here, the inventors have conducted an in-depth study on the displacement of the vibration region 22 in the piezoelectric sensor of this embodiment, and obtained... Figure 11 The results are shown. Furthermore, in Figure 11 In this example, a piezoelectric sensor without the through hole 83 and cavity 82 as in this embodiment, but with the same structure as this embodiment, is used as a comparative example. The displacement of each vibration region 22 without applying sound pressure to the vibration region 22 is shown. Furthermore, Figure 11 It shows along Figure 9The displacement of the XI-XI line portion is represented with the boundary between the support 10 and the vibrating part 20 as a reference (i.e., 0), and the displacement of the vibrating region 22 towards the support 10 is negative. Furthermore, in Figure 11 In this design, the length L of one end 221 of the vibration region 22 is set to 900 μm, and the width d of the through hole 81 is set to 60 μm. Additionally, Figure 11 The result shows the situation where the length L1 of a cavity 82 along the length direction of one end 221 is set to 300 μm, the length L2 in the direction intersecting the length direction is set to 150 μm, and the position at 400 μm is taken as the center of the second part R12. Furthermore, Figure 11 The results are shown when a tensile stress of 50 MPa is generated in the portion where the electrode film 50 is configured, and a compressive stress of 100 MPa is generated in the portion where the electrode film 50 is not configured.

[0076] like Figure 11 As shown, in this embodiment, since the through hole 83 and the cavity 82 are formed, it can be confirmed that the displacement of the vibration region 22 can be reduced overall. That is, it can be confirmed that the vibration region 22 is less likely to undergo deformation caused by buckling.

[0077] Next, the manufacturing method of the above-mentioned piezoelectric sensor will be described.

[0078] In this embodiment, firstly, as Figure 12A As shown, a support body 10 without the recess 10a is prepared. Then, as... Figure 12B As shown, a resist (not shown) is disposed on the insulating film 12 and patterned. The resist is then used as a mask for etching, thereby removing the portion of the insulating film 12 that constitutes the void 82. Next, as... Figure 12C As shown, the cavity 82 is filled with a landfill material 90, which is composed of a nitride film or the like that is easier to etch than the insulating film 12.

[0079] Then, as Figure 12D As shown, after applying piezoelectric film 40 and electrode film 50 using appropriate sputtering, etching, or other methods, a slit 30 and a through-hole 83 are formed. Furthermore, the through-hole 83 is formed in the portion that becomes the support region 21a, in a manner that allows access to the landfill material 90. Then, as... Figure 12E As shown, the recess 10a is formed by etching or the like from the other side 11b of the support substrate 11. In this embodiment, the filler material 90 is made of a material that is easier to etch than the insulating film 12. Therefore, by performing lateral etching when forming the recess 10a, the filler material 90 is removed, thus forming the void portion 82.

[0080] As described above in this embodiment, a through hole 83 and a cavity 82 are formed as stress-relieving holes. Therefore, the compressive stress of the vibration region 22 can be released from the through hole 83 and the cavity 82, and the same effect as in the first embodiment described above can be obtained.

[0081] (1) In this embodiment, no through hole 81 is formed in the vibration region 22. Therefore, the structure of the vibration region 22 is the same as in the past, and the usage method can be easily made the same as in the past.

[0082] (2) In this embodiment, the cavity 82 is formed such that the inner edge 221a of one end 221 of the vibration region 22 is supported by the support body 10. Therefore, the length of the actual vibration region 22 is the same as that in the first embodiment described above, and the resonant frequency of the vibration region 22 is difficult to change. Therefore, the usage method can be easily made the same as in the past.

[0083] (3) In this embodiment, the cavity 82 is formed such that the outer edge 221b of one end 221 of the vibration region 22 is supported by the support body 10. Therefore, it is possible to further suppress changes in the resonant frequency of the vibration region 22.

[0084] (4) In this embodiment, the stress-relieving orifice is formed such that the piping resistance is greater than the slit resistance. Therefore, by forming the cavity 82 and the through hole 83 that serve as the stress-relieving orifice, sound can be suppressed from escaping from the stress-relieving orifice. That is, by forming the stress-relieving orifice, the decrease in sensitivity and the change in the detection frequency band can be suppressed.

[0085] (5) In this embodiment, the cavity 82 is formed in such a way that the region with high compressive stress in one end 221 of the vibration region 22 is suspended. Therefore, buckling in the vibration region 22 can be further suppressed.

[0086] (Other implementation methods) While this disclosure has been described with reference to embodiments, it should be understood that this disclosure is not limited to those embodiments or constructions. This disclosure also includes various modifications and equivalent variations. Furthermore, various combinations and arrangements, as well as other combinations and arrangements containing only one element, more or fewer elements, also fall within the scope and spirit of this disclosure.

[0087] For example, in the embodiments described above, a piezoelectric sensor was used as an example of a sound sensor. However, any structure having a vibration region 22 is acceptable, and the sound sensor could also be a capacitive sensor, for example.

[0088] Furthermore, in the above embodiments, an example of a structure in which the vibration region 22 is cantilevered has been described. However, the vibration region 22 may also be a structure in which both ends are supported.

[0089] Furthermore, in the above embodiments, the recess 10a may be formed such that a portion of the support 10 remains, and the vibration region 22 may be configured to include a portion of the support 10. For example, the recess 10a may be formed such that the support substrate 11 is removed while the insulating film 12 remains, and the vibration region 22 may be configured to include the insulating film 12.

[0090] Furthermore, in the above embodiments, the electrode film 50 formed in the second region R2 can also be electrically connected to the electrode film 50 formed in the first region R1.

[0091] Furthermore, in the first to third embodiments described above, the structure of the through hole 81, which serves as a stress-relieving hole, penetrating the vibration section 20 was explained. However, the through hole 81 may not be formed to penetrate the vibration section 20. Similarly, in the fourth embodiment described above, the structure of the vibration section 20 penetrating by connecting the cavity 82, which serves as a stress-relieving hole, and the through hole 83 was explained. However, the cavity 82 and the through hole 83 may be formed separately, or only one of them may be formed.

[0092] Alternatively, in the first to third embodiments described above, the through hole 81 may also be formed in the second region R2.

[0093] Furthermore, in the fourth embodiment described above, the cavity 82 can also be formed such that the resistance of the cavity is less than the resistance of the slit. In addition, the formation location and shape of the cavity 82 can be appropriately modified. For example, the cavity 82 can be formed such that the inner edge 221a of the vibration region 22 is suspended, or it can be formed such that the outer edge 221b of the vibration region 22 is suspended.

[0094] Furthermore, the above embodiments can be combined. For example, the second and third embodiments can be combined, such that the through hole 81 is inclined relative to the normal direction and its width d is narrower than the width W of the slit. The second and fourth embodiments can also be combined, such that the through hole 83 is inclined relative to the normal direction. Additionally, the fourth and third embodiments can be combined, such that the width of the through hole 83 is narrower than the width W of the slit 30. That is, the through hole 83 can also be formed such that the hole resistance is greater than the slit resistance. Furthermore, the first and fourth embodiments can be combined, such that the through hole 81 is formed in the vibration region 22, the cavity 82 is formed in the support 10, and the through hole 83 is formed in the support region 21a. Moreover, combinations of the above embodiments can be further combined with each other.

Claims

1. A sound sensor, characterized in that, have: Support body; and The vibration unit is disposed on the support body, has a support area supported on the support body and a vibration area connected to the support area and capable of vibration, and outputs a detection signal corresponding to the deformation of the vibration area; The support body has a recess in the portion opposite to the vibration region. The vibration region has a portion that generates compressive stress. Stress-relieving holes are formed in the vibrating part.

2. The sound sensor according to claim 1, characterized in that, The vibrating part is configured to include: A piezoelectric film having a lower piezoelectric film and an upper piezoelectric film disposed on the lower piezoelectric film; and An electrode film having a lower electrode film connected to the lower piezoelectric film, an intermediate electrode film connected to the lower piezoelectric film and the upper piezoelectric film, and an upper electrode film connected to the upper piezoelectric film, and extracting the charge generated by the deformation of the piezoelectric film.

3. The sound sensor according to claim 2, characterized in that, The vibration region is connected to the support region, and multiple vibration regions are formed by dividing the vibration region from the suspended region of the support body using slits. The vibration zone is a cantilever structure with one end fixed to the support body and the other end free.

4. The sound sensor according to claim 3, characterized in that, The region at one end of the vibration region is a first region, and the region at the other end of the vibration region is a second region. The electrode film is formed at least in the first region. The stress-relieving hole is a through hole that penetrates the vibration region formed in the first region.

5. The sound sensor according to claim 4, characterized in that, The resistance of the through hole to sound transmission is greater than the resistance of the slit to sound transmission.

6. The sound sensor according to claim 5, characterized in that, The through hole is formed at an angle relative to the stacking direction of the support and the vibrating part.

7. The sound sensor according to claim 5, characterized in that, The width of the opening of the through hole is narrower than the width of the slit between adjacent vibration regions.

8. The sound sensor according to claim 3, characterized in that, The support body has a cavity on the vibrating part side that communicates with the recess. A through hole is formed in the support region, which communicates with the cavity. The stress-relieving hole is configured to include the cavity and the through hole.

9. The sound sensor according to claim 8, characterized in that, The cavity's resistance to sound transmission is greater than the slit's resistance to sound transmission.

10. The sound sensor according to claim 8, characterized in that, The depth of the cavity is smaller than the width of the slit between adjacent vibration regions.

11. The sound sensor according to claim 8, characterized in that, The cavity is formed with the inner edge of one end of the vibration region supported by the support body.

12. The sound sensor according to claim 8, characterized in that, The cavity is formed with the outer edge of one end of the vibration region supported by the support body.

13. The sound sensor according to claim 8, characterized in that, The vibration region has a region of high compressive stress and a region of low compressive stress on one end side. The cavity is formed in such a way that the region with high compressive stress is suspended.

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