Piezoelectric device

Abstract

To provide a piezoelectric device capable of preventing detection accuracy from being reduced.SOLUTION: A piezoelectric device comprises: a piezoelectric element 1 including a plurality of vibration regions 22 each configured by including a piezoelectric film 40 and an electrode film 50, and a control unit 2. In the plurality of vibration regions 22, the vibration regions 22 are separated from each other by a slit 30. The electrode film 50 includes: a pressure electrode film 510 connected with the piezoelectric film 40 and outputting a pressure detection signal corresponding to the charge of the piezoelectric film 40; a capacity electrode film 520 outputting a capacity detection signal corresponding to the capacity between the adjacent vibration regions 22; and a drive electrode film 530 to which a drive voltage is applied for displacing a tip end in the vibration region 22 at an opposite side of a support region 21a along a stacking direction of a support 10 and the vibration region 22. The control unit 2 regulates the drive voltage to be applied to the drive electrode film 530 so as to maximize the capacity detection signal based on the capacity detection signal in predetermined timing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a piezoelectric device including a piezoelectric element having a vibration region.

Background Art

[0002] Conventionally, a piezoelectric element having a vibration region has been proposed (see, for example, Patent Document 1). Specifically, this piezoelectric element has a structure in which a piezoelectric film and an electrode film connected to the piezoelectric film are laminated on a support. And, a recess is formed in the support, and a part of the piezoelectric film and the electrode film forms a floating region floating from the support. Further, in this piezoelectric element, a slit is formed in the floating region, so that the floating region is divided into a plurality of regions to form a vibration region. And each vibration region is in a state of being cantilever-supported by the support.

[0003] Such a piezoelectric element is manufactured as follows. That is, first, a piezoelectric film and an electrode film are formed on a support. Next, a slit is formed in the piezoelectric film to form a vibration region forming portion. Then, a recess is formed in the support, and the vibration region forming portion is floated to form a vibration region, whereby the above piezoelectric element is manufactured.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the piezoelectric element as described above, the vibrating region may be warped due to residual stress during the manufacture of the piezoelectric element. Further, since the linear expansion coefficients of the piezoelectric film and the electrode film are different in the piezoelectric element, it may be warped depending on the use environment. And when the vibrating region is warped in this way, the slit width between adjacent vibrating regions becomes wider, so that the pressure easily escapes through the slit, and in particular, the detection accuracy at low frequencies is likely to decrease.

[0006] In view of the above points, an object of the present invention is to provide a piezoelectric device capable of suppressing a decrease in detection accuracy.

Means for Solving the Problems

[0007] Claim 1 for achieving the above object is a piezoelectric device including a piezoelectric element (1) having a vibrating portion (20), the piezoelectric device including a support (10), a configuration including a piezoelectric film (40) and an electrode film (50) disposed on the support, a support region (21a) supported by the support, and a plurality of vibrating regions (22) connected to the support region and having a portion on the opposite side of the support region floating from the support. The piezoelectric element includes a control unit (2) that performs a predetermined process. The plurality of vibrating regions are separated from each other by a slit (30). The electrode film includes a pressure electrode film (510) connected to the piezoelectric film and outputting a pressure detection signal corresponding to the charge of the piezoelectric film, a capacitance electrode film (520) outputting a capacitance detection signal corresponding to the capacitance between adjacent vibrating regions, and a drive electrode film (530) to which a drive voltage for displacing the tip portion on the opposite side of the support region in the vibrating region along the lamination direction of the support and the vibrating region is applied. The control unit adjusts the drive voltage applied to the drive electrode film so that the capacitance detection signal is maximized based on the capacitance detection signal at a predetermined timing.

[0008] According to this, at a predetermined timing, the control unit adjusts the driving voltage applied to the driving electrode film based on the capacitance detection signal so that the capacitance detection signal becomes maximum. That is, at a predetermined timing, the control unit adjusts the driving voltage applied to the driving electrode film so that the warp of the vibration region is reduced. Therefore, it is possible to suppress detecting the pressure in a state where the vibration region is warped, and it is possible to suppress a decrease in detection accuracy.

[0009] Note that the reference signs with parentheses attached to each component etc. indicate an example of the correspondence relationship between the component etc. and the specific components etc. described in the embodiments described later.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 3C

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are identical or equivalent to each other will be described with the same reference numerals.

[0012] (First Embodiment) The piezoelectric device of the first embodiment will be described with reference to FIGS. 1, 2A, and 2B. Note that the piezoelectric device of this embodiment is preferably mounted and used in a smartphone, an AI (abbreviation for artificial intelligence) speaker, or the like. Although FIG. 1 is not a cross-sectional view, for ease of understanding, hatching is applied to the pressure electrode film 510, the capacitance electrode film 520, and the drive electrode film 530, which will be described later.

[0013] The piezoelectric device of this embodiment includes a piezoelectric element 1 and a control unit 2. First, the configuration of the piezoelectric element 1 will be described.

[0014] The piezoelectric element 1 includes a support 10 and a vibrating portion 20, and has a rectangular planar shape. The support 10 includes a support substrate 11 having a first surface 11a and a second surface 11b, and an insulating film 12 formed on the first surface 11a of the support substrate 11. Note that the support substrate 11 is formed of, for example, a silicon substrate or the like, and the insulating film 12 is formed of an oxide film or the like.

[0015] The vibrating portion 20 is disposed on the support 10. A recess 10a is formed in the support 10 to float the inner edge side of the vibrating portion 20. Therefore, the vibrating portion 20 has a configuration including a support region 21a disposed on the support 10 and a floating region 21b that is connected to the support region 21a and floats on the recess 10a. Note that the recess 10a of this embodiment has a planar rectangular shape at the opening end on the vibrating portion 20 side. Therefore, the entire floating region 21b has a planar rectangular shape.

[0016] In the floating region 21b, a slit 30 penetrating the floating region 21b in the thickness direction is formed. The slit 30 of the present embodiment is formed so as to divide the floating region 21b into four parts. Specifically, two slits 30 are formed so as to pass through the central portion C of the floating region 21b and extend toward the opposite corner portions of the floating region 21b. In other words, the slits 30 extend from each corner portion of the floating region 21b having a planar rectangular shape toward the central portion C, and the slits 30 intersect at the central portion C. As a result, the floating region 21b is separated into four vibration regions 22 having a substantially planar triangular shape. Although not particularly limited, in the present embodiment, the interval between the vibration regions 22 (that is, the width of the slit 30) is about 1 μm.

[0017] And each vibration region 22 is configured as a cantilever having a fixed end at the end on the support region 21a side and a free end at the tip portion on the side opposite to the support region 21a (hereinafter also simply referred to as the tip portion). Hereinafter, the surface of the vibration region 22 on the side opposite to the support 10 will be described as one surface 22a of the vibration region 22, and the surface of the vibration region 22 on the support 10 side will be described as the other surface 22b of the vibration region 22.

[0018] The vibrating portion 20 is configured to include a piezoelectric film 40 and an electrode film 50 connected to the piezoelectric film 40. Specifically, the piezoelectric film 40 includes a lower piezoelectric film 41 and an upper piezoelectric film 42 laminated on the lower piezoelectric film 41. 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).

[0019] The electrode film 50 is formed at a predetermined position in the vibration region 22 so as to be connected to the piezoelectric film 40, and is composed of molybdenum, copper, platinum, platinum, titanium, etc. In the present embodiment, as the electrode film 50, 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 are formed. The lower electrode film 51 and the intermediate electrode film 52 are arranged so as to face each other with the lower piezoelectric film 41 interposed therebetween. The intermediate electrode film 52 and the upper electrode film 53 are arranged so as to face each other with the upper piezoelectric film 42 interposed therebetween. The lower electrode film 51, the intermediate electrode film 52, and the upper electrode film 53 have the same shape in the normal direction with respect to one surface 22a of the vibration region 22. Hereinafter, the arrangement position of the electrode film 50 in the present embodiment will be described in more detail.

[0020] First, when the vibration region 22 as described above is cantilever-supported, the stress generated when the vibration region 22 (that is, the piezoelectric film 40) vibrates is more likely to be larger on the fixed end side where the vibration region 22 is supported than on the free end side. For this reason, the vibration region 22 is divided into a first region R1 where the stress is likely to increase and a second region R2 where the stress is likely to decrease. In the present embodiment, the electrode film 50 is formed in each of the first region R1 and the second region R2. The electrode film 50 formed in the first region R1 and the electrode film 50 formed in the second region R2 are insulated from each other in order to exhibit different functions.

[0021] The electrode film 50 formed in the first region R1 functions as a pressure electrode film 510 that detects the vibration of the vibration region 22. Hereinafter, the lower electrode film 51 formed in the first region R1 will be described as the lower pressure electrode film 511, the intermediate electrode film 52 as the intermediate pressure electrode film 512, and the upper electrode film 53 as the upper pressure electrode film 513. And, since the charge of the upper piezoelectric film 42 and the lower piezoelectric film 41 changes when the vibration region 22 vibrates, the pressure electrode film 510 outputs a pressure detection signal corresponding to the change in the charge. Specifically, although not particularly shown, the lower pressure electrode film 511, the intermediate pressure electrode film 512, and the upper pressure electrode film 513 are connected to an electrode for connection to the control unit 2 via wiring or the like formed in the support region 21a. And, in the present embodiment, the respective lower pressure electrode films 511, intermediate pressure electrode films 512, and upper pressure electrode films 513 in each vibration region 22 are connected to the electrode so as to output the change in charge in the first region R1 of each vibration region 22 as one pressure detection signal.

[0022] In the second region R2, electrode films 50 are formed on the outer edge side and the inner edge side. However, the electrode film 50 formed on the outer edge side and the electrode film 50 formed on the inner edge side are insulated from each other.

[0023] The electrode film 50 formed on the outer edge side of the second region R2 functions as a capacitance electrode film 520 that detects the capacitance between adjacent vibration regions 22. Note that the adjacent vibration regions 22 in the present embodiment mean the vibration regions 22 adjacent in the circumferential direction with respect to the center portion C as a reference. In other words, the adjacent vibration regions 22 in the present embodiment mean the vibration regions 22 adjacent without sandwiching the center portion C. Hereinafter, the lower electrode film 51 formed on the outer edge of the second region R2 will be described as the lower capacitance electrode film 521, the intermediate electrode film 52 as the intermediate capacitance electrode film 522, and the upper electrode film 53 as the upper capacitance electrode film 523.

[0024] Then, the lower capacitive electrode film 521, the intermediate capacitive electrode film 522, and the upper capacitive electrode film 523, which are formed in adjacent vibration regions 22 and face each other, output a capacitance detection signal corresponding to the capacitance between the adjacent vibration regions 22. Specifically, the lower capacitive electrode film 521, the intermediate capacitive electrode film 522, and the upper capacitive electrode film 523 are connected to an electrode for connection to the control unit 2 via a lead wiring 61 formed in the vibration region 22 and wirings (not shown) formed in the support region 21a. In this embodiment, the lower capacitive electrode film 521, the intermediate capacitive electrode film 522, and the upper capacitive electrode film 523 formed in each vibration region 22 are connected so that the capacitance between each vibration region 22 is output as a capacitance detection signal. Note that the capacitance detection signal may be such that the sum of the capacitance between the lower capacitive electrode films 521, the capacitance between the intermediate capacitive electrode films 522, and the capacitance between the upper capacitive electrode films 523 is output, or each capacitance may be output separately.

[0025] Also, the electrode film 50 formed on the inner edge side of the second region R2 functions as a drive electrode film 530 to which a drive voltage for displacing (i.e., driving) the vibration region 22 is applied. Hereinafter, the lower electrode film 51 formed on the inner edge of the second region R2 will be described as the lower drive electrode film 531, the intermediate electrode film 52 as the intermediate drive electrode film 532, and the upper electrode film 53 as the upper drive electrode film 533.

[0026] The lower drive electrode film 531, the intermediate drive electrode film 532, and the upper drive electrode film 533 are connected to an electrode for connection to the control unit 2 via a lead wiring 62 formed in the vibration region 22 and wirings (not shown) formed in the support region 21a. Then, as will be described later, a predetermined drive voltage is applied to each of the drive electrode films 531 to 533 based on the capacitance detection signal.

[0027] In this embodiment, the lower pressure electrode film 511, the lower capacitance electrode film 521, and the lower drive electrode film 531 are each disposed below the lower piezoelectric film 41 and are formed by patterning a common metal film. Similarly, the intermediate pressure electrode film 512, the intermediate capacitance electrode film 522, and the intermediate drive electrode film 532 are each disposed between the lower piezoelectric film 41 and the upper piezoelectric film 42 and are formed by patterning a common metal film. Further, the upper pressure electrode film 513, the upper capacitance electrode film 523, and the upper drive electrode film 533 are each disposed above the upper piezoelectric film 42 and are formed by patterning a common metal film.

[0028] Furthermore, the vibrating portion 20 of this embodiment has a base film 70 on which the lower piezoelectric film 41 and the lower electrode film 51 are disposed. That is, on the support 10, the piezoelectric film 40 and the electrode film 50 are disposed via the base film 70. The base film 70 is not necessarily required, but is provided to facilitate crystal growth when forming the lower piezoelectric film 41 and the like. In this embodiment, the base film 70 is made of aluminum nitride or the like. The piezoelectric film 40 has a thickness of about 1 μm, and the base film 70 has a thickness of about several tens of nm. That is, the base film 70 is extremely thin compared to the piezoelectric film 40.

[0029] The above is the configuration of the piezoelectric element 1 in this embodiment. The control unit 2 is composed of a microcomputer or the like including a CPU and a storage unit such as a ROM, a RAM, and a non-volatile RAM, and is connected to the piezoelectric element 1. Then, the control unit 2 realizes various control operations by the CPU reading and executing a program from the ROM or the non-volatile RAM. Note that various data (for example, initial values, look-up tables, maps, etc.) used during the execution of the program are stored in advance in the ROM or the non-volatile RAM. The storage medium such as the ROM is a non-transitory physical storage medium. The CPU is an abbreviation for Central Processing Unit, the ROM is an abbreviation for Read Only Memory, and the RAM is an abbreviation for Random Access Memory.

[0030] Specifically, the control unit 2 grasps the warping state of the vibration region 22 based on the capacitance detection signal from the capacitance electrode film 520. Specifically, the capacitance between adjacent vibration regions 22 is maximized because the distance between the capacitance electrode films 520 is shortest when the adjacent vibration regions 22 are not warped. And the capacitance between adjacent vibration regions 22 becomes smaller because the distance between the capacitance electrode films 520 becomes longer when the vibration region 22 warps. Therefore, the control unit 2 grasps the warping state of the vibration region 22 based on the magnitude of the capacitance detection signal.

[0031] Then, the control unit 2 performs a reduction process to reduce the warping of the vibration region 22 by applying a driving voltage to the driving electrode film 530 based on the capacitance detection signal to displace the piezoelectric film 40. Hereinafter, a method for reducing the warping of the vibration region 22 will be described with reference to FIGS. 3A to 3C. Note that FIGS. 3A to 3C show schematic diagrams in which the pressure electrode film 510 and the capacitance electrode film 520 are omitted. Also, in FIGS. 3A to 3C, the direction along the lamination direction of the lower piezoelectric film 41 and the upper piezoelectric film 42 is defined as the Y-axis direction, and the direction along the surface direction of the lower piezoelectric film 41 and the upper piezoelectric film 42 is defined as the X-axis direction. Also, hereinafter, in the Y-axis direction, the side from the lower piezoelectric film 41 toward the upper piezoelectric film 42 is defined as the positive side, and the side from the upper piezoelectric film 42 toward the lower piezoelectric film 41 is defined as the negative side.

[0032] First, as shown in FIG. 3A, a case where the intermediate driving electrode film 532 is at the ground potential and no driving voltage is applied to the lower driving electrode film 531 and the upper driving electrode film 533 will be described. In this case, the dipoles D in the lower piezoelectric film 41 and the dipoles D in the upper piezoelectric film 42 are in a neutral state.

[0033] Then, as shown in FIG. 3B, when a positive driving voltage is applied to the lower driving electrode film 531 and the upper driving electrode film 533, in the upper piezoelectric film 42, the positive electrode side of the dipole D repels the upper driving electrode film 533 and the negative electrode side is attracted to the upper driving electrode film 533. For this reason, the upper piezoelectric film 42 rotates such that the dipole D rotates in the negative side in the Y-axis direction as indicated by the arrow in the figure and tries to extend in the X-axis direction. On the other hand, in the lower piezoelectric film 41, the positive electrode side of the dipole D repels the lower driving electrode film 531 and the negative electrode side is attracted to the lower driving electrode film 531. For this reason, the lower piezoelectric film 41 rotates such that the dipole D rotates in the positive side in the Y-axis direction as indicated by the arrow in the figure and tries to contract in the X-axis direction. Therefore, the tip of the vibration region 22 is displaced to the negative side in the Y-axis direction. That is, when a positive driving voltage is applied to the lower driving electrode film 531 and the upper driving electrode film 533, the tip of the vibration region 22 is displaced to the other surface 22b side of the vibration region 22.

[0034] Also, as shown in FIG. 3C, when a negative driving voltage is applied to the lower driving electrode film 531 and the upper driving electrode film 533, in the upper piezoelectric film 42, the positive electrode side of the dipole D is attracted to the upper driving electrode film 533 and the negative electrode side repels the upper driving electrode film 533. For this reason, the upper piezoelectric film 42 rotates such that the dipole D rotates in the positive side in the Y-axis direction as indicated by the arrow in the figure and tries to contract in the X-axis direction. On the other hand, in the lower piezoelectric film 41, the positive electrode side of the dipole D is attracted to the lower driving electrode film 531 and the negative electrode side repels the lower driving electrode film 531. For this reason, the lower piezoelectric film 41 rotates such that the dipole D rotates in the negative side in the Y-axis direction as indicated by the arrow in the figure and tries to extend in the X-axis direction. Therefore, the tip of the vibration region 22 is displaced to the positive side in the Y-axis direction. That is, when a negative driving voltage is applied to the lower driving electrode film 531 and the upper driving electrode film 533, the tip of the vibration region 22 is displaced to the one surface 22a side of the vibration region 22.

[0035] Therefore, when the control unit 2 determines that the vibration region 22 is warped based on the capacitance detection signal from the capacitance electrode film 520, the control unit 2 performs a reduction process of adjusting the voltage applied to the drive electrode film 530 to reduce the warp of the vibration region 22. In the present embodiment, four vibration regions 22 are configured. Therefore, the control unit 2 performs a reduction process on each vibration region 22 so that the warp of each vibration region 22 is reduced. For example, first, the control unit 2 performs a reduction process of reducing the warp by increasing or decreasing the drive voltage applied to two adjacent vibration regions 22. Next, for one vibration region 22 that has undergone the process of reducing the warp and a vibration region 22 adjacent to the vibration region 22 that has not undergone the process of reducing the warp, the control unit 2 performs a reduction process of reducing the warp by increasing or decreasing the drive voltage applied thereto. Thereafter, the control unit 2 sequentially performs the same process on the remaining vibration regions 22, and performs a reduction process of reducing the warp by increasing or decreasing the drive voltage applied to all the vibration regions 22.

[0036] Further, when the control unit 2 performs the reduction process, a reference drive voltage may be stored in a storage unit or the like, and the reference drive voltage may be applied first, and then the drive voltage to be applied may be finely adjusted. The reference drive voltage is, for example, a drive voltage that minimizes the warp due to residual stress or the like when the piezoelectric element 1 is manufactured. In other words, the reference drive voltage is, for example, a drive voltage at which the capacitance detection signal is maximized immediately after the piezoelectric element 1 is manufactured. According to this, the time related to the reduction process can be shortened, and the program on the control unit 2 side can be simplified.

[0037] Incidentally, the reference drive voltage may be set as follows. First, a positive voltage is applied to one capacitive electrode film 520 in adjacent vibration regions 22, and a negative voltage is applied to the other capacitive electrode film 520. Thereby, an electrostatic attraction force is generated between the adjacent vibration regions 22. When the vibration region 22 is warped, the vibration region 22 is displaced and the warp is reduced. When the vibration region 22 is displaced, an adjustment signal based on the displacement is output from the drive electrode film 530. Also, when the vibration region 22 is not warped, even if the voltage applied to the capacitive electrode films 520 of the adjacent vibration regions 22 is increased, the adjustment signal does not change. Therefore, the magnitude of the voltage applied to the adjacent capacitive electrode films 520 may be adjusted, and the reference drive voltage may be set based on the voltage at which the adjustment signal no longer changes.

[0038] Furthermore, when the reduction process is periodically performed as described later, the reference drive voltage may be updated each time the reduction process of the vibration region 22 is performed, or the drive voltage set in the previous reduction process may be used as the reference drive voltage. According to this, it is possible to obtain the effect of setting the reference drive voltage even with respect to the warp over time in the vibration region 22.

[0039] The above is the configuration of the piezoelectric device in this embodiment. Next, the operation of the piezoelectric device will be described.

[0040] First, the control unit 2 performs the reduction process of the vibration region 22 as described above at a predetermined timing before detecting a pressure such as a sound pressure. This process is performed, for example, when the piezoelectric device is produced in a factory or the like. Also, this process is performed periodically, for example, immediately after the device on which the piezoelectric device is mounted is turned on from the off state or at predetermined intervals.

[0041] Then, the piezoelectric device detects the pressure (e.g., sound pressure) applied to the vibration region 22 in a state where the warpage of the vibration region 22 is reduced. Specifically, when pressure is applied to the vibration region 22, the vibration region 22 vibrates. Then, charges are generated in the lower piezoelectric film 41 and the upper piezoelectric film 42 based on the stress corresponding to the displacement of the vibration region 22. Therefore, the piezoelectric device detects the pressure applied to the vibration region 22 based on the pressure detection signal from the pressure electrode film 510. At this time, since the warpage of the vibration region 22 is reduced, it is possible to suppress a decrease in detection accuracy.

[0042] According to the present embodiment described above, the control unit 2 performs a reduction process for reducing the warpage of the vibration region 22 based on the capacitance detection signal. Therefore, it is possible to suppress detecting pressure in a state where the vibration region 22 is warped, and it is possible to suppress a decrease in detection accuracy. Further, in order to reduce the warpage of the vibration region 22 in this way, by periodically performing the reduction process by the control unit 2, it is also possible to suppress the warpage of the vibration region 22 over time.

[0043] (1) In this embodiment, the pressure electrode film 510, the capacitance electrode film 520, and the drive electrode film 530 are each arranged in the same manner with respect to the piezoelectric film 40. That is, the lower pressure electrode film 511, the lower capacitance electrode film 521, and the lower drive electrode film 531 are each arranged below the lower piezoelectric film 41. The intermediate pressure electrode film 512, the intermediate capacitance electrode film 522, and the intermediate drive electrode film 532 are each arranged between the lower piezoelectric film 41 and the upper piezoelectric film 42. The upper pressure electrode film 513, the upper capacitance electrode film 523, and the upper drive electrode film 533 are each arranged above the upper piezoelectric film 42. Therefore, when arranging the lower pressure electrode film 511, the lower capacitance electrode film 521, and the lower drive electrode film 531, the lower pressure electrode film 511, the lower capacitance electrode film 521, and the lower drive electrode film 531 can be arranged simultaneously by arranging a metal film and then patterning the metal film. Similarly, when arranging the intermediate pressure electrode film 512, the intermediate capacitance electrode film 522, and the intermediate drive electrode film 532, the intermediate pressure electrode film 512, the intermediate capacitance electrode film 522, and the intermediate drive electrode film 532 can be arranged simultaneously by arranging a metal film and then patterning the metal film. When arranging the upper pressure electrode film 513, the upper capacitance electrode film 523, and the upper drive electrode film 533, the upper pressure electrode film 513, the upper capacitance electrode film 523, and the upper drive electrode film 533 can be arranged simultaneously by arranging a metal film and then patterning the metal film. Therefore, the manufacturing process of the piezoelectric element 1 can be simplified.

[0044] (2) In this embodiment, when the control unit 2 performs reduction processing related to the warpage of the vibration region 22, by using a reference drive voltage, the time related to the reduction processing can be shortened and the program on the control unit 2 side can be simplified.

[0045] (3) In this embodiment, based on the capacitance detection signal, the control unit 2 performs reduction processing related to the warpage of the vibration region 22. Therefore, for example, compared with the case of trying to reduce the warpage of the vibration region 22 by adjusting the thickness of the piezoelectric film 40, the electrode film 50, etc. when forming the vibration region 22, the manufacturing process can be simplified and the reduction in yield can be suppressed.

[0046] (Second Embodiment) The second embodiment will be described. In this embodiment, the configuration of the capacitive electrode film 520 is changed with respect to the first embodiment. Since other aspects are the same as those of the first embodiment, the description thereof is omitted here.

[0047] In the piezoelectric element 1 of this embodiment, as shown in FIG. 4, when the surface exposed from the slit 30 in the vibration region 22 is defined as the side surface 22c, side surface capacitive electrode films 524 as the capacitive electrode film 520 are formed on the respective side surfaces 22c in the second region R2 of the vibration region 22. Note that in this embodiment, the capacitive electrode film 520 is not formed below the lower piezoelectric film 41, between the lower piezoelectric film 41 and the upper piezoelectric film 42, or above the upper piezoelectric film 42. FIG. 4 corresponds to a cross-sectional view taken along line IIB-IIB in FIG. 1.

[0048] Then, the control unit 2 of this embodiment performs a reduction process for reducing the warp of the vibration region 22 based on a capacitance detection signal corresponding to the capacitance between the side surface capacitive electrode films 524 in adjacent vibration regions 22.

[0049] According to the present embodiment described above, since the warp of the vibration region 22 is reduced based on the capacitance detection signal, the same effects as those of the first embodiment can be obtained.

[0050] (1) In this embodiment, the capacitive electrode film 520 is formed on each side surface 22c in the second region R2 of the vibration region 22. Therefore, it becomes easy to increase the area of the opposing capacitive electrode films 520 in adjacent vibration regions 22, and the capacitance between the opposing capacitive electrode films 520 can be increased. Accordingly, the signal-to-noise ratio (SN ratio), which is the ratio of the signal to the noise, can be increased, and the influence of the noise can be reduced.

[0051] (Third Embodiment) The third embodiment will be described. In this embodiment, the configuration of the capacitive electrode film 520 is changed with respect to the second embodiment. Since other aspects are the same as those of the second embodiment, the description thereof is omitted here.

[0052] In the piezoelectric element 1 of the present embodiment, as shown in FIG. 5, the side surface capacitance electrode film 524 is divided into a one-side capacitance electrode film 524a located on the one-side 22a side of the vibration region 22 and a the other-side capacitance electrode film 524b located on the other-side 22b side of the vibration region 22. Then, the piezoelectric element 1 outputs a first capacitance detection signal corresponding to the capacitance between the one-side capacitance electrode films 524a formed in adjacent vibration regions 22, and outputs a second capacitance detection signal corresponding to the capacitance between the other-side capacitance electrode films 524b formed in adjacent vibration regions 22.

[0053] Note that FIG. 5 corresponds to a cross-sectional view taken along line IIB-IIB in FIG. 1. Also, although not particularly limited, in the present embodiment, the one-side capacitance electrode film 524a and the other-side capacitance electrode film 524b are divided at the boundary between the lower piezoelectric film 41 and the upper piezoelectric film 42.

[0054] The control unit 2 determines the direction of the warp of the vibration region 22 based on the first capacitance detection signal and the second capacitance detection signal, and adjusts the drive voltage applied to the drive electrode film 530. Specifically, when the vibration region 22 warps toward the one-side 22a side, the distance between the opposing one-side capacitance electrode films 524a in the adjacent vibration regions 22 becomes longer than the distance between the opposing other-side capacitance electrode films 524b. For this reason, the first capacitance detection signal becomes smaller than the second capacitance detection signal. On the other hand, when the vibration region 22 warps toward the other-side 22b side, the distance between the opposing one-side capacitance electrode films 524a in the adjacent vibration regions 22 becomes shorter than the distance between the opposing other-side capacitance electrode films 524b. For this reason, the first capacitance detection signal becomes larger than the second capacitance detection signal.

[0055] Therefore, the control unit 2 determines the warping direction of the vibrating region 22 based on the first capacitance detection signal and the second capacitance detection signal, and adjusts the driving voltage applied to the driving electrode film 530 based on the determination result. Specifically, when the first capacitance detection signal is smaller than the second capacitance detection signal, the control unit 2 determines that the tip of the vibrating region 22 is warped toward the one surface 22a side. Then, as described with reference to FIG. 3B above, the control unit 2 applies a positive driving voltage to the upper driving electrode film 533 and the lower driving electrode film 531 to displace the tip of the vibrating region 22 toward the other surface 22b side. Further, when the first capacitance detection signal is larger than the second capacitance detection signal, the control unit 2 determines that the tip of the vibrating region 22 is warped toward the other surface 22b side. Then, as described with reference to FIG. 3C above, the control unit 2 applies a negative driving voltage to the upper driving electrode film 533 and the lower driving electrode film 531 to displace the tip of the vibrating region 22 toward the one surface 22a side.

[0056] According to the present embodiment described above, since the warping of the vibrating region 22 is reduced based on the capacitance detection signal, the same effects as those of the first embodiment can be obtained.

[0057] (1) In the present embodiment, the control unit 2 determines the warping direction of the vibrating region 22 and adjusts the driving voltage applied to the lower driving electrode film 531 and the upper driving electrode film 533 based on the determination result. Therefore, the time related to the warping reduction process can be shortened.

[0058] (Fourth Embodiment) The fourth embodiment will be described. This embodiment combines the lower capacitance electrode film 521 and the upper capacitance electrode film 523 of the first embodiment with the second embodiment. Since the other aspects are the same as those of the first embodiment, the description thereof is omitted here.

[0059] The piezoelectric element 1 of this embodiment combines the lower-layer capacitive electrode film 521 and the upper-layer capacitive electrode film 523 of the first embodiment in the second embodiment. Specifically, as shown in FIG. 6, the capacitive electrode film 520 is configured to have a lower-layer capacitive electrode film 521, an upper-layer capacitive electrode film 523, and a side capacitive electrode film 524. The piezoelectric element 1 outputs a side-side capacitance detection signal related to the capacitance between the side capacitive electrode films 524 formed in adjacent vibration regions 22. The piezoelectric element 1 outputs an upper-layer capacitance detection signal related to the capacitance between the upper-layer capacitive electrode films 523 formed in adjacent vibration regions 22. The piezoelectric element 1 outputs a lower-layer capacitance detection signal related to the capacitance between the lower-layer capacitive electrode films 521 formed in adjacent vibration regions 22. Note that FIG. 6 corresponds to a cross-sectional view taken along line IIB-IIB in FIG. 1. Also, in this embodiment, the intermediate capacitive electrode film 522 is not formed.

[0060] Based on the side-side capacitance detection signal, the upper-layer capacitance detection signal, and the lower-layer capacitance detection signal, the control unit 2 determines the direction of the warp of the vibration region 22 and adjusts the drive voltage applied to the drive electrode film 530.

[0061] Specifically, as shown in FIG. 7, when the vibration region 22 is largely warped, the opposing area of the side capacitive electrode film 524 becomes smaller, and thus the capacitance between the side capacitive electrode films 524 becomes smaller. In this case, in the example of FIG. 7, since the vibration region 22 is largely warped toward one surface 22a side, the opposing area of the lower-layer capacitive electrode film 521 becomes larger, and the lower-layer capacitance detection signal becomes larger. On the other hand, although not particularly shown, when the vibration region 22 is largely warped toward the other surface 22b side, the opposing area of the upper-layer capacitive electrode film 523 becomes larger, and the upper-layer capacitance detection signal becomes larger.

[0062] Therefore, based on the side capacitance detection signal, the upper layer capacitance detection signal, and the lower layer capacitance detection signal, the control unit 2 determines the warping direction of the vibrating region 22, and adjusts the driving voltage applied to the driving electrode film 530 based on the determination result. Specifically, similar to the third embodiment, when the control unit 2 determines that the tip of the vibrating region 22 is warped toward the one surface 22a side, a positive driving voltage is applied to the upper layer driving electrode film 533 and the lower layer driving electrode film 531, thereby displacing the tip of the vibrating region 22 toward the other surface 22b side. Further, when the control unit 2 determines that the tip of the vibrating region 22 is warped toward the other surface 22b side, a negative driving voltage is applied to the upper layer driving electrode film 533 and the lower layer driving electrode film 531, thereby displacing the tip of the vibrating region 22 toward the one surface 22a side.

[0063] According to the present embodiment described above, since the warping of the vibrating region 22 is reduced based on the capacitance detection signal, the same effect as that of the first embodiment can be obtained.

[0064] (1) In this embodiment, the control unit 2 determines the warping direction of the vibrating region 22, and adjusts the driving voltage applied to the lower layer driving electrode film 531 and the upper layer driving electrode film 533 based on the determination result. Therefore, similar to the third embodiment, the time related to the warping reduction process can be shortened.

[0065] (2) In this embodiment, in addition to the side capacitance electrode film 524, the lower layer capacitance electrode film 521 and the upper layer capacitance electrode film 523 are also formed. Therefore, even when the side capacitance detection signal becomes small due to the large warping of the vibrating region 22, the warping of the vibrating region 22 can be suitably reduced.

[0066] (Other Embodiments) Although the present disclosure has been described in accordance with the embodiments, it is understood that the present disclosure is not limited to the embodiments and structures. The present disclosure includes various modifications and variations within an equivalent range. In addition, various combinations and forms, and further other combinations and forms including only one element, more than one element, or less than one element thereof, are within the scope and spirit of the present disclosure.

[0067] For example, in each of the above embodiments, the floating region 21b may have a polygonal shape such as a pentagonal shape, a hexagonal shape, or an octagonal shape instead of a rectangular shape in plan view. Also, the number of vibration regions 22 formed in the floating region 21b can be appropriately changed. Further, the piezoelectric element 1 may have a polygonal shape such as a pentagonal shape or a hexagonal shape instead of a rectangular shape in plan view.

[0068] Furthermore, in each of the above embodiments, the positions where the pressure electrode film 510, the capacitance electrode film 520, and the drive electrode film 530 are formed can be appropriately changed. For example, the pressure electrode film 510 may be formed in the second region R2, or the capacitance electrode film 520 and the drive electrode film 530 may be formed in the first region R1. Also, the capacitance electrode film 520 may be formed on the free end side in each vibration region 22. In this case, the control unit 2 may perform a reduction process for reducing the warp of the vibration region 22 based on the capacitance detection signals between adjacent vibration regions 22 across the central portion C in the floating region 21b.

[0069] And the above embodiments may be appropriately combined. For example, the third embodiment may be combined with the fourth embodiment, and the side surface capacitance electrode film 524 may be configured to include a one-side capacitance electrode film 524a and an other-side capacitance electrode film 524b.

[0070] The control unit and its method described in the present disclosure may be implemented by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the control unit and its method described in the present disclosure may be implemented by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Or, the control unit and its method described in the present disclosure may be implemented by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured by one or more hardware logic circuits. Also, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executable by a computer.

Description of Signs

[0071] 1 Piezoelectric element 2 Control unit 10 Support 21a Support region 22 Vibration region 30 Slit 40 Piezoelectric film 50 Electrode film 510 Pressure electrode film 520 Capacitance electrode film 530 Drive electrode film

Claims

1. A piezoelectric device comprising a piezoelectric element (1) having a vibrating portion (20), a support (10), a structure disposed on the support and including a piezoelectric film (40) and an electrode film (50), a support region (21a) supported by the support, and a plurality of vibrating regions (22) connected to the support region and having a portion on the opposite side of the support region floating from the support, and the piezoelectric element including the vibrating portion, a control unit (2) for performing a predetermined process, the plurality of vibrating regions are separated from each other by a slit (30), the electrode film has a pressure electrode film (510) connected to the piezoelectric film and outputting a pressure detection signal corresponding to the charge of the piezoelectric film, a capacitance electrode film (520) outputting a capacitance detection signal corresponding to the capacitance between adjacent vibrating regions, and a drive electrode film (530) to which a drive voltage for displacing a tip portion on the opposite side of the support region in the vibrating region along the lamination direction of the support and the vibrating region is applied, the control unit adjusts the drive voltage applied to the drive electrode film based on the capacitance detection signal so that the capacitance detection signal becomes maximum at a predetermined timing.

2. the vibrating region has a portion on the support region side as a first region (R1) and a portion on the opposite side of the support region as a second region (R2), the pressure electrode film is formed in the first region, the capacitance electrode film and the drive electrode film are formed in the second region. The piezoelectric device according to claim 1.

3. the piezoelectric film has a lower-layer piezoelectric film (41) and an upper-layer piezoelectric film (42) disposed on the lower-layer piezoelectric film, the pressure electrode film has an intermediate pressure electrode film (512) disposed between the lower-layer piezoelectric film and the upper-layer piezoelectric film, a lower-layer pressure electrode film (511) disposed on the opposite side of the intermediate pressure electrode film with the lower-layer piezoelectric film interposed therebetween, and an upper-layer pressure electrode film (513) disposed on the opposite side of the intermediate pressure electrode film with the upper-layer piezoelectric film interposed therebetween, The capacitive electrode film has an intermediate capacitive electrode film (522) disposed between the lower piezoelectric film and the upper piezoelectric film, a lower capacitive electrode film (521) disposed on the opposite side of the intermediate capacitive electrode film with the lower piezoelectric film interposed therebetween, and an upper capacitive electrode film (523) disposed on the opposite side of the intermediate capacitive electrode film with the upper piezoelectric film interposed therebetween. The control unit adjusts the drive voltage based on the capacitance detection signals of the intermediate capacitive electrode film, the capacitance detection signal of the lower capacitive electrode film, and the capacitance detection signal of the upper capacitive electrode film, which are respectively formed in the adjacent vibration regions sandwiching the slit. The piezoelectric device according to claim 1 or 2.

4. The piezoelectric film has a lower piezoelectric film (41) and an upper piezoelectric film (42) disposed on the lower piezoelectric film. The capacitive electrode film has side surface capacitive electrode films (524) respectively formed on the opposing side surfaces (22c) of the adjacent vibration regions sandwiching the slit. The control unit adjusts the drive voltage based on the capacitance detection signals of the side surface capacitive electrode films respectively formed on the side surfaces of the adjacent vibration regions. The piezoelectric device according to claim 1 or 2.

5. When the capacitive electrode film has one surface (22a) as the surface on the side opposite to the support side in the vibration region and the other surface (22b) as the surface on the support side in the vibration region, it is divided into a one - surface - side capacitive electrode film (524a) and an other - surface - side capacitive electrode film (524b). The control unit determines the direction of warping of the vibration region based on the capacitance detection signal of the one - surface - side capacitive electrode film and the capacitance detection signal of the other - surface - side capacitive electrode film, and adjusts the drive voltage based on the determination result. The piezoelectric device according to claim 4.

6. The piezoelectric film has a lower piezoelectric film (41) and an upper piezoelectric film (42) disposed on the lower piezoelectric film. The pressure electrode film has an intermediate pressure electrode film (512) disposed between the lower piezoelectric film and the upper piezoelectric film, a lower pressure electrode film (511) disposed on the side opposite to the intermediate pressure electrode film with the lower piezoelectric film interposed therebetween, and an upper pressure electrode film (513) disposed on the side opposite to the intermediate pressure electrode film with the upper piezoelectric film interposed therebetween. The capacitance electrode film has a lower capacitance electrode film (521) disposed on the side opposite to the upper piezoelectric film with the lower piezoelectric film interposed therebetween, an upper capacitance electrode film (523) disposed on the side opposite to the lower piezoelectric film with the upper piezoelectric film interposed therebetween, and side capacitance electrode films (524) respectively formed on the opposing side surfaces of the adjacent vibration regions with the slit interposed therebetween. The control unit determines the direction of warping of the vibration region based on the lower capacitance detection signal of the lower capacitance electrode film, the capacitance detection signal of the upper capacitance electrode film, and the side capacitance detection signal of the side capacitance electrode film, and adjusts the drive voltage based on the determination result. The piezoelectric device according to claim 1 or 2.

7. The control unit stores a predetermined reference drive voltage that brings the capacitance detection signal closest to the maximum. When adjusting the drive voltage, after applying the reference drive voltage to the drive electrode film, the drive voltage is adjusted based on the capacitance detection signal. The piezoelectric device according to any one of claims 1 to 6.

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