Piezoelectric device, apparatus, and polarization processing method

Abstract

To provide a piezoelectric device and the like that can suppress the occurrence of temperature unevenness in a piezoelectric layer when the piezoelectric device is polarized.SOLUTION: A piezoelectric device 10 has a capacitor structure in which a first electrode layer 14 having two first electrode terminals 15A, 15B, a piezoelectric layer 13, and a second electrode layer 12 are stacked in this order, and the first electrode layer is heated by Joule heat due to the potential difference between the two first electrode terminals, and the piezoelectric layer is heated by the first electrode layer heated by Joule heat, while being polarized by an electric field generated by the potential difference between the first electrode layer and the second electrode layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to piezoelectric devices, apparatus, and poling methods. [Background technology]

[0002] A method is known in which a polarization process (poling process) is performed on the piezoelectric layer of a piezoelectric device having a capacitor structure in which a first electrode layer, a piezoelectric layer (piezoelectric element), and a second electrode layer are stacked in this order by applying a heating waveform (electric pulse) and a poling waveform (poling electric field) to the piezoelectric layer of the piezoelectric device (see, for example, Patent Document 1). In this case, the application of the heating waveform heats the piezoelectric layer of the piezoelectric device. Note that polarization process is a process in which a voltage is applied to a piezoelectric (piezoelectric element) to align the direction of spontaneous polarization. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2021-512492 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, since the piezoelectric layer of the piezoelectric device is heated by applying a heating waveform to the electrode terminals provided on the first electrode layer and the electrode terminals provided on the second electrode layer, there is a problem that temperature unevenness occurs in the piezoelectric layer of the piezoelectric device due to the arrangement and shape of the electrode terminals provided on the first electrode layer and the second electrode layer, resulting in variations in the characteristics (piezoelectric characteristics) of the piezoelectric layer of the piezoelectric device. There is also a problem that temperature unevenness occurs in the piezoelectric layer of the piezoelectric device due to variations in the film thickness of the piezoelectric layer, resulting in variations in the characteristics of the piezoelectric layer of the piezoelectric device.

[0005] The present disclosure has been made to solve such problems, and aims to provide a piezoelectric device, apparatus, and polarization processing method that can suppress the occurrence of temperature unevenness in the piezoelectric layer when the piezoelectric device is polarized. [Means for solving the problem]

[0006] The piezoelectric device according to the present disclosure is a piezoelectric device having a capacitor structure in which a first electrode layer having two first electrode terminals, a piezoelectric layer, and a second electrode layer are stacked in this order, and the first electrode layer is heated by Joule heat due to the potential difference between the two first electrode terminals, and the piezoelectric layer is heated by the first electrode layer heated by Joule heat, while being polarized by an electric field generated by the potential difference between the first electrode layer and the second electrode layer.

[0007] With this configuration, it is possible to prevent temperature unevenness from occurring in the piezoelectric layer when the piezoelectric device is polarized.

[0008] This is because the first electrode layer is heated by Joule heat due to the potential difference between the two first electrodes, and the piezoelectric layer is heated by the first electrode layer heated by Joule heat.

[0009] In the piezoelectric device, the two first electrode terminals may be arranged point-symmetrically with respect to the center of the first electrode layer.

[0010] In the piezoelectric device, one of the first electrode layer and the second electrode layer may be an anode electrode layer, and the other may be a cathode electrode layer.

[0011] The apparatus according to the present disclosure is an apparatus including the above-described piezoelectric device.

[0012] The polarization treatment method according to the present disclosure includes a first step of applying a heating voltage to two first electrode terminals of a piezoelectric device having a capacitor structure in which a first electrode layer having two first electrode terminals, a piezoelectric layer, and a second electrode layer are stacked in this order, thereby generating a potential difference between the two first electrode terminals and between the first electrode layer and the second electrode layer, thereby heating the first electrode layer by Joule heat and generating a polarization electric field; and a second step of heating the piezoelectric layer by the Joule heat-heated first electrode layer and polarizing the piezoelectric layer by the polarization electric field.

[0013] The polarization treatment method may further include a third step of applying a polarization voltage with a potential difference of 0 V to the two first electrode terminals after a predetermined period of time has elapsed, thereby generating a potential difference between the first electrode layer and the second electrode layer, thereby stopping Joule heating of the first electrode layer and generating a polarization electric field.

[0014] In the polarization treatment method, in the first step, a rectangular AC voltage may be applied as the heating voltage to one of the two first electrode terminals, and a rectangular AC voltage shifted in phase by 180 degrees may be applied as the heating voltage to the other first electrode terminal.

[0015] In the polarization treatment method, in the first step, a rectangular AC voltage may be applied as the heating voltage to one of the two first electrode terminals, and a DC voltage may be applied to the other first electrode terminal.

[0016] In the polarization treatment method, the frequency of the rectangular AC voltage may be a frequency that is determined so as not to cause a current to flow between the first electrode layer and the second electrode layer.

[0017] In the polarization treatment method, the two first electrode terminals may be arranged point-symmetrically with respect to the center of the first electrode layer.

[0018] In the polarization treatment method, one of the first electrode layer and the second electrode layer may be an anode electrode layer, and the other may be a cathode electrode layer.

[0019] In the above piezoelectric device, the device may be any one of a piezoelectric MEMS speaker, a piezoelectric MEMS mirror, and an inkjet printer head. [Effects of the Invention]

[0020] The present disclosure can provide a piezoelectric device, apparatus, and polarization method that can suppress temperature unevenness in a piezoelectric layer during polarization of a piezoelectric device. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic diagram of an apparatus 40 including a piezoelectric device 10. FIG. [Figure 2] FIG. 2 is a top view of the piezoelectric device 10. [Figure 3] 1 is an example of a heating / polarization potential difference generating circuit 20. [Figure 4] (a) An example of voltages Va and Vb generated by the heating / polarization potential difference generating circuit 20, (b) another example of voltages Va and Vb generated by the heating / polarization potential difference generating circuit 20. (b) An example of voltages Va and Vb generated by the heating / polarization potential difference generating circuit 20. [Figure 5] 1 is a flowchart of a polarization process (sequence process) for the piezoelectric device 10. [Figure 6] 10 is an example of a modified heating / polarization potential difference generating circuit 20A. [Figure 7] 10 is a diagram showing an example of voltages Va and Vb generated by a modified heating / polarization potential difference generating circuit 20A. [Figure 8] 10 is an example of a modified piezoelectric device 10A. [Figure 9] 3 is a cross-sectional view of FIG. 2 taken along line B-B. [Figure 10] This is an example of the configuration of a device 60 (re-polling station) different from the device 40. [Figure 11] 7 is a schematic diagram of a wafer W on which a plurality of piezoelectric devices 10 are formed before singulation, and a probe 70 that performs polarization processing (see FIG. 5) on each of the piezoelectric devices 10 before singulation. DETAILED DESCRIPTION OF THE INVENTION

[0022] A piezoelectric device 10 according to an embodiment of the present disclosure will now be described with reference to the accompanying drawings. Corresponding components in the various drawings are designated by the same reference numerals, and redundant description will be omitted.

[0023] <Piezoelectric device 10> First, the piezoelectric device 10 will be described.

[0024] Fig. 1 is a schematic diagram of an apparatus 40 including a piezoelectric device 10. The piezoelectric device 10 in Fig. 1 is a cross-sectional view taken along line AA in Fig. 2. Fig. 2 is a top view of the piezoelectric device 10.

[0025] As shown in FIGS. 1 and 2 , the piezoelectric device 10 has a capacitor structure in which a substrate 11, a cathode electrode layer 12, a piezoelectric body 13, and an anode electrode layer 14 are stacked in this order. An example in which the piezoelectric device of the present disclosure is applied to the piezoelectric device 10 for a piezoelectric MEMS speaker will be described below. As shown in FIG. 1 , the piezoelectric device 10 may be incorporated into an apparatus 40 together with a heating / polarization potential difference generating circuit 20, a control device 30, and a drive circuit 50. The apparatus 40 may be, for example, a piezoelectric MEMS speaker, a piezoelectric MEMS mirror, or an inkjet printer head. The apparatus 40 incorporating the piezoelectric device 10, the heating / polarization potential difference generating circuit 20, the control device 30, and the drive circuit 50 can be called an apparatus with a re-poling function (or an apparatus with a re-poling station).

[0026] The substrate 11 is made of, for example, Si (silicon substrate) and includes a substrate body 11a and a wall portion 11b provided along the edge of one surface (lower surface) of the substrate body 11a.

[0027] The cathode electrode layer 12 is, for example, an electrode layer made of Pt (an example of the second electrode layer of the present disclosure) and is laminated on the other surface (upper surface) of the substrate body 11a.

[0028] The piezoelectric body 13 is, for example, a piezoelectric layer (piezoelectric element) made of PZT, and is laminated on the cathode electrode layer 12.

[0029] The anode electrode layer 14 is, for example, an electrode layer made of Pt (an example of the first electrode layer of the present disclosure) and is laminated on the piezoelectric body 13. The outer shapes of the substrate 11, the cathode electrode layer 12, the piezoelectric body 13, and the anode electrode layer 14 are each rectangular and of approximately the same size when viewed from above.

[0030] Two first electrode terminals 15A and 15B are provided on the anode electrode layer 14 (see FIG. 1). The two first electrode terminals 15A and 15B are electrically connected to the anode electrode layer 14 by ohmic junction.

[0031] When performing a polarization process described below, a heating voltage, a polarization voltage, etc., described below, are applied to the two first electrode terminals 15A and 15B. On the other hand, when the piezoelectric device 10 is made to function as an actuator of the apparatus 40, etc., a predetermined drive voltage is applied to at least one of the two first electrode terminals 15A and 15B.

[0032] Two second electrode terminals 16A and 16B are provided on the cathode electrode layer 12 (see FIG. 9). FIG. 9 is a cross-sectional view taken along line BB in FIG. 2. The two second electrode terminals 16A and 16B are electrically connected to the cathode electrode layer 12 by ohmic junctions. Although the cathode electrode layer 12 is connected to GND, it may also be connected to GND via the second electrode terminals 16A and 16B. In the embodiment, the second electrode terminals 16A and 16B are connected to the GND of the drive circuit 50, but they may also be connected to the GND of the heating / polarization potential difference generating circuit 20.

[0033] The drive circuit 50 is electrically connected to the two first electrode terminals 15A, 15B (see FIG. 1) and the two second electrode terminals 16A, 16B (see FIG. 9). The drive circuit 50 drives the piezoelectric body 13 (for example, drives it as an actuator) by applying a drive voltage of the same potential to the two first electrode terminals 15A, 15B (at least one of them) under the control of the control device 30. The drive circuit 50 may also drive the piezoelectric body 13 (for example, drives it as an actuator) by applying a drive voltage between the two first electrode terminals 15A, 15B (at least one of them) and the two second electrode terminals 16A, 16B (at least one of them).

[0034] The two first electrode terminals 15A, 15B are, for example, Pt electrodes, and are arranged point-symmetrically with respect to the center of the anode electrode layer 14 in a top view (see FIG. 2). This has the following advantage: When a heating voltage is applied to the two first electrode terminals 15A, 15B to generate a potential difference between the two first electrode terminals 15A, 15B, a current path (see arrows AR1 and AR2 in FIG. 2) from one first electrode terminal 15A to the other first electrode terminal 15B is formed in the anode electrode layer 14. This current path is symmetrical with respect to the diagonal line L on its way from one first electrode terminal 15A to the other first electrode terminal 15B, and spreads uniformly (substantially uniformly) across the entire area (almost the entire area) of the anode electrode layer 14.

[0035] Therefore, by applying a heating voltage to the two first electrode terminals 15A and 15B and generating a potential difference between the two first electrode terminals 15A and 15B, it is possible to heat the entire area (almost the entire area) of the anode electrode layer 14 by Joule heat. As a result, the piezoelectric body 13 (at least the vibration portion) can be heated uniformly (almost uniformly) by the anode electrode layer 14 heated by Joule heat.

[0036] At this time, the center of the anode electrode layer 14 has a higher thermal resistance than the outer periphery of the anode electrode layer 14. This is because the wall portion 11b of the substrate 11, which has a low thermal resistance, is provided in a location corresponding to the outer periphery of the anode electrode layer 14. Therefore, heat from the outer periphery of the anode electrode layer 14 is mainly transferred to the wall portion 11b of the substrate 11, which has a low thermal resistance (see arrows AR3 to AR6 in FIG. 2). As a result, the center of the anode electrode layer 14 has a higher temperature than the outer periphery of the anode electrode layer 14, and this higher-temperature anode electrode layer 14 (center) can efficiently heat the piezoelectric body 13 (at least the vibration portion). Note that the vibration portion is the portion of the substrate main body 11a of the piezoelectric body 13 that is inside the wall portion 11b of the piezoelectric body 13 when viewed from above (the portion inside the rectangle indicated by symbol B in FIG. 2).

[0037] In addition, by applying a heating voltage to the two first electrode terminals 15A and 15B and generating a potential difference between the anode electrode layer 14 and the cathode electrode layer 12, a polarization electric field can be generated between the anode electrode layer 14 and the cathode electrode layer 12.

[0038] <Heating / polarization potential difference generating circuit 20> Next, the heating / polarization potential difference generating circuit 20 will be described.

[0039] Fig. 3 shows an example of the heating / polarization potential difference generating circuit 20. Fig. 4(a) shows an example of the voltages Va and Vb generated by the heating / polarization potential difference generating circuit 20, and Fig. 4(b) shows another example of the voltages Va and Vb generated by the heating / polarization potential difference generating circuit 20. The heating / polarization potential difference generating circuit 20 may be provided in the piezoelectric device 10 (substrate 11, which is a silicon substrate) or may be provided separately from the piezoelectric device 10. The same applies to the control device 30 and the drive circuit 50.

[0040] The heating / polarization potential difference generating circuit 20, under the control of the control device 30, receives a pulse of ±1.75 V (DC 0 V offset) @ 100 Hz as an input (input signal) and outputs (generates) voltages (AC voltages) to be applied to the two first electrode terminals 15A and 15B, specifically, a voltage Va to be applied to one first electrode terminal 15A and a voltage Vb to be applied to the other first electrode terminal 15B.

[0041] As shown in FIG. 4(a), the voltages Va and Vb output by the heating / polarization potential difference generating circuit 20 include a rectangular AC voltage applied to one of the first electrode terminals 15A and a rectangular AC voltage with a phase difference of 180 degrees applied to the other first electrode terminal 15B as heating voltages (see voltages Va and VB between times T2 and T3 in FIG. 4(a)). By applying this rectangular AC voltage (heating voltage) to the two first electrode terminals 15A and 15B and repeatedly alternating between the MAX voltage and the MIN voltage to generate a potential difference between the two first electrode terminals 15A and 15B, the anode electrode layer 14 can be heated by Joule heat. Because the potentials of the two first electrode terminals 15A and 15B also serve as polarization potentials, an AC voltage is used to apply between the two first electrode terminals 15A and 15B during heating in order to reduce polarization unevenness due to potential differences during heating.

[0042] Furthermore, the voltages Va and Vb output by the heating / polarization potential difference generating circuit 20 include a voltage with a potential difference of 0 V that is applied to the two first electrode terminals 15A and 15B as a polarization voltage (see voltages Va and VB between times T1 and T2 and between times T3 and T4 in FIG. 4(a)). By applying this voltage with a potential difference of 0 V (polarization voltage) to the two first electrode terminals 15A and 15B and generating a potential difference between the anode electrode layer 14 and the cathode electrode layer 12, a polarization electric field can be generated between the anode electrode layer 14 and the cathode electrode layer 12.

[0043] As shown in FIG. 4(b), the voltages Va and Vb output by the heating / polarization potential difference generating circuit 20 may be voltages that increase and decrease stepwise between time T2 and time T3.

[0044] The frequencies of the voltages Va and Vb (heating voltages) output by the heating / polarization potential difference generating circuit 20 are determined so as to prevent current from flowing (so as to avoid insufficient output) between the anode electrode layer 14 and the cathode electrode layer 12. Specifically, the frequencies of the voltages Va and Vb (heating voltages) output by the heating / polarization potential difference generating circuit 20 are desirably low (approximately less than 200 Hz) in consideration of the capacity of the piezoelectric body 13.

[0045] <An example of polarization treatment of the piezoelectric device 10> Next, an example of polarization processing of the piezoelectric device 10 having the above configuration will be described. The following processing is mainly realized by the heating / polarization potential difference generating circuit 20.

[0046] FIG. 5 is a flowchart of the polarization process (sequence process) of the piezoelectric device 10.

[0047] First, a polarization voltage (heating-OFF polarization voltage) with a potential difference of 0 V is applied to the two first electrode terminals 15A and 15B to generate a potential difference between the anode electrode layer 14 and the cathode electrode layer 12 (step S10). Specifically, as shown in FIG. 4(a), between time T1 and time T2, 18.25 V (see the thick solid line in FIG. 4(a)) is applied to one first electrode terminal 15A, and 18.25 V (see the thick dotted line in FIG. 4(a)) is applied to the other first electrode terminal 15B. This generates a polarization electric field (heating-OFF polarization electric field) between the anode electrode layer 14 and the cathode electrode layer 12. Note that between time T1 and time T2, the potential difference between the two first electrode terminals 15A and 15B is 0 V, and the potential difference between the anode electrode layer 14 and the cathode electrode layer 12 is 18.25 V. Between time T1 and time T2, the potential difference between the two first electrode terminals 15A and 15B is 0 V, and therefore the anode electrode layer 14 is not heated by Joule heat (heating is stopped).

[0048] Next, a heating voltage is applied to the two first electrode terminals 15A, 15B to generate a potential difference between the two first electrode terminals 15A, 15B and between the anode electrode layer 14 and the cathode electrode layer 12 (step S11). Specifically, as shown in Fig. 4, rectangular AC voltages Va and Vb (MAX voltage 20V, MIN voltage 16.5V) are applied as heating voltages to the two first electrode terminals 15A, 15B between time T2 and time T3.

[0049] By generating a potential difference between the two first electrode terminals 15A and 15B, the anode electrode layer 14 can be heated by Joule heat. In addition, by generating a potential difference between the anode electrode layer 14 and the cathode electrode layer 12, a polarization electric field can be generated between the anode electrode layer 14 and the cathode electrode layer 12.

[0050] As a result, the piezoelectric body 13 (at least the vibration portion) can be heated by the anode electrode layer 14 heated by Joule heat, while the piezoelectric body 13 (at least the vibration portion) can be polarized by the polarization electric field. That is, heating and polarization of the piezoelectric body 13 (at least the vibration portion) can be performed simultaneously. At this time, because the two first electrode terminals 15A, 15B are arranged point-symmetrically about the center of the anode electrode layer 14 in a top view (see FIG. 2), the entire area (almost the entire area) of the anode electrode layer 14 can be heated by Joule heat. As a result, the piezoelectric body 13 (at least the vibration portion) can be heated uniformly (almost uniformly) by the anode electrode layer 14 heated by Joule heat.

[0051] The process of step S11 is repeatedly executed until the polarization process time (for example, 1 to 5 minutes) has elapsed (step S12: NO).

[0052] On the other hand, if the polarization treatment time (e.g., 1 to 5 minutes) has elapsed (step S12: YES), that is, a polarization voltage with a potential difference of 0 V (polarization voltage when heating is OFF) is applied to the two first electrode terminals 15A and 15B, generating a potential difference between the anode electrode layer 14 and the cathode electrode layer 12 (step S13). This is the same as the process in step S10. Specifically, as shown in FIG. 4(a), between time T3 and time T4, 18.25 V (see the thick solid line in FIG. 4(a)) is applied to one first electrode terminal 15A, and 18.25 V (see the thick dotted line in FIG. 4(a)) is applied to the other first electrode terminal 15B. This generates a polarization electric field (polarization electric field when heating is OFF) between the anode electrode layer 14 and the cathode electrode layer 12. Between time T3 and time T4, the potential difference between the two first electrode terminals 15A and 15B is 0 V, and the potential difference between the anode electrode layer 14 and the cathode electrode layer 12 is 18.25 V. Between time T3 and time T4, the potential difference between the two first electrode terminals 15A and 15B is 0 V, so the anode electrode layer 14 is not heated by Joule heat (heating is stopped).

[0053] Next, the voltage with a potential difference of 0 V applied to the two first electrode terminals 15A and 15B is controlled to set the potential difference between the anode electrode layer 14 and the cathode electrode layer 12 to 0 V (step S14).

[0054] This completes the polarization process for the piezoelectric device 10.

[0055] As described above, according to this embodiment, it is possible to prevent temperature unevenness from occurring in the piezoelectric body 13 (piezoelectric body layer) when the piezoelectric device 10 is polarized.

[0056] This is because the anode electrode layer 14 (first electrode layer) is heated by Joule heat due to the potential difference between the two first electrode terminals 15A and 15B, and the piezoelectric body 13 is heated by the anode electrode layer 14 heated by Joule heat.

[0057] Furthermore, according to this embodiment, the potential difference between the two first electrode terminals 15A and 15B is for heating, and the potential difference between the anode electrode layer 14 and the cathode electrode layer 12 is for polarization, and these are independent of each other. Therefore, by using sequence processing (see FIG. 5), the heating can be controlled to be turned on / off while the polarization electric field is applied, and the polarization electric field can be controlled to be turned on / off before and after heating.

[0058] Furthermore, according to this embodiment, the polarization process can be performed while controlling the temperature of the device itself without using an external heating mechanism, so the number of processed chips is not limited by depolarization, which is an issue in the manufacturing process.

[0059] Furthermore, according to this embodiment, since no external heating mechanism is used, polarization treatment for ensuring characteristics can be performed even after product shipment.

[0060] Furthermore, according to this embodiment, the current path is the anode electrode layer 14 alone, and low frequencies that do not pass current through the piezoelectric body 13 can be used, thereby suppressing the heat generation and polarization unevenness caused by current variations within the capacitor, which were a conventional problem.

[0061] Furthermore, according to this embodiment, the owner (e.g., an individual who purchased the device 40) of the device 40 (device with a re-poling function or polling station) incorporating the piezoelectric device 10, the heating / polarization potential difference generating circuit 20, the control device 30, and the drive circuit 50 can perform polarization (local heating / polarization) without preparing a special heating furnace. In other words, the owner of the device 40 can individually perform polarization when an abnormality occurs in the operation of the piezoelectric device 10 incorporated in the device 40 owned by the owner (or periodically). This allows the owner to align the direction of spontaneous polarization of the piezoelectric device 10 incorporated in the device 40 owned by the owner, individually resolve the risk of depolarization of the piezoelectric body 13 due to changes over time, and restore the piezoelectric effect to factory-shipped levels.

[0062] Next, a modified example will be described.

[0063] Fig. 6 shows an example of a modified heating / polarization potential difference generating circuit 20A. Fig. 7(a) shows an example of a voltage Va generated by the modified heating / polarization potential difference generating circuit 20A, and Fig. 7(b) shows another example of a voltage Va generated by the modified heating / polarization potential difference generating circuit 20A.

[0064] The modified heating / polarization potential difference generating circuit 20A, under the control of the control device 30, outputs (generates) an alternating current (AC) voltage (rectangular wave (13 to 20 V)) to be applied to one first electrode terminal 15A and a direct current (DC) voltage of 16.5 V to be applied to the other first electrode terminal 15B, as shown in Figure 7(a).

[0065] As shown in FIG. 7(b), the voltage Va output by the heating / polarization potential difference generating circuit 20A may be a voltage that increases and decreases stepwise between time T2 and time T3.

[0066] According to this modification, the configuration of the heating / polarization potential difference generating circuit 20A can be simplified compared to the heating / polarization potential difference generating circuit 20 shown in FIG.

[0067] FIG. 8 shows an example of a modified piezoelectric device 10A.

[0068] In the above embodiment, an example in which two first electrode terminals 15A and 15B are provided on the anode electrode layer 14 has been described, but this is not limiting. For example, as shown in Fig. 8, two first electrode terminals 15A and 15B may be provided on the cathode electrode layer 12.

[0069] This modification also provides the same effects as the above embodiment.

[0070] Furthermore, in the above embodiment, an example of applying the piezoelectric device of the present disclosure to the piezoelectric device 10 for a piezoelectric MEMS speaker has been described, but the present disclosure is not limited thereto. For example, the piezoelectric device of the present disclosure may be applied to any type of piezoelectric device other than the piezoelectric device 10 for a piezoelectric MEMS speaker, such as a piezoelectric MEMS mirror or a piezoelectric device for an inkjet printer head. In this case, the piezoelectric device 10, the heating / polarization potential difference generating circuit 20, and the control device 30 may be configured as a re-poling station for the piezoelectric device. Alternatively, the piezoelectric device 10, the heating / polarization potential difference generating circuit 20, and the control device 30 may be configured as a poling device (polarization device) for a piezoelectric device (piezoelectric MEMS device) at the wafer level. This allows for localized heating and polarization without depolarizing adjacent chips, which is expected to shorten the cooling time due to the localized heating.

[0071] In the above embodiment, an example has been described in which the heating / polarization potential difference generating circuit 20 and the control device 30 are built into the device 40, but the present invention is not limited to this.

[0072] For example, as shown in Fig. 10, the heating / polarization potential difference generating circuit 20 and the control device 30 may be provided in a device 60 (re-poling station) separate from the device 40. Fig. 10 shows an example of the configuration of the device 60 (re-poling station) separate from the device 40.

[0073] 10, another apparatus 60 (re-poling station) includes a heating / polarization potential difference generating circuit 20, a control device 30, and a connector C2 electrically connected to the heating / polarization potential difference generating circuit 20. On the other hand, an apparatus 40 includes a piezoelectric device 10, a control device 30, a drive circuit 50, and a connector C1 electrically connected to two first electrode terminals 15A and 15B.

[0074] According to this modification, by connecting (physically and electrically) the connector C1 and the connector C2, the two first electrode terminals 15A, 15B can be electrically connected to the heating / polarization potential difference generating circuit 20, as in Figures 1 and 9. This allows the polarization process (see Figure 5) to be performed on the piezoelectric device 10 in the apparatus 40. In this case, although not shown, (at least one of) the second electrode terminals 16A, 16B is electrically connected to the GND of the apparatus 60.

[0075] This modification can also achieve the same effects as the above embodiment.

[0076] Furthermore, according to this modification, the retailer or manufacturer of the piezoelectric device 10 can provide the owner with after-sales service to restore the piezoelectric effect of the piezoelectric device 10 to the factory level.

[0077] In the above embodiment, the example in which the polarization process (see FIG. 5) is performed on the piezoelectric device 10 built into the apparatus 40 has been described, but the present invention is not limited to this.

[0078] For example, the polarization process (see FIG. 5) may be performed on the piezoelectric devices 10 before they are built into the apparatus 40. For example, as shown in FIG. 11, the polarization process (see FIG. 5) may be performed on each of the piezoelectric devices 10 at the stage of a wafer (e.g., a Si wafer) before it is singulated (cut into chips). FIG. 11 is a schematic diagram of a wafer W on which a plurality of piezoelectric devices 10 are formed before singulation, and a probe 70 that performs the polarization process (see FIG. 5) on each of the piezoelectric devices 10 before singulation. Note that each of the piezoelectric devices 10 is electrically insulated from one another.

[0079] As shown in FIG. 11, the probe 70 (poling device) includes a heating / polarization potential difference generating circuit 20, a control device 30, and contacts PA and PB (e.g., probe needles) electrically connected to the heating / polarization potential difference generating circuit 20.

[0080] According to this modification, the probe 70 is moved using a predetermined moving mechanism (not shown) to electrically connect the contacts PA, PB to the two first electrode terminals 15A, 15B of the piezoelectric device 10 before singulation, thereby electrically connecting the two first electrode terminals 15A, 15B to the heating / polarization potential difference generating circuit 20, as in Figures 1 and 9. This allows the polarization process (see Figure 5) to be performed on the piezoelectric device 10 before singulation.

[0081] For example, when a pair of contacts PA and PB is provided, the probe 70 can be moved using a predetermined moving mechanism (not shown) to electrically connect the pair of contacts PA and PB to the pair of first electrode terminals 15A and 15B of one piezoelectric device 10 before singulation, thereby performing a polarization process (see Figure 5) on one piezoelectric device 10 before singulation.

[0082] Furthermore, for example, when multiple sets of contacts PA, PB are provided, the probe 70 can be moved using a predetermined moving mechanism (not shown) to electrically connect the multiple sets of contacts PA, PB to the multiple sets of first electrode terminals 15A, 15B of the multiple pre-singled piezoelectric devices 10, thereby simultaneously performing polarization processing (see FIG. 5) on the multiple pre-singled piezoelectric devices 10. In this case, although not shown, the second electrode terminals 16A, 16B (at least one of them) are electrically connected to the GND of the apparatus 60.

[0083] This modification can also achieve the same effects as the above embodiment. Furthermore, this modification can be used for local heating and polarization treatment before shipping from a factory, and polarization treatment can be performed inexpensively without using equipment such as a heating furnace.

[0084] In the above embodiment, the device 40 incorporating the piezoelectric device 10, the heating and polarization potential difference generating circuit 20, and the control device 30 is a piezoelectric MEMS speaker, but the present invention is not limited to this. For example, the device 40 incorporating the piezoelectric device 10, the heating and polarization potential difference generating circuit 20, and the control device 30 may be any type of device other than a piezoelectric MEMS speaker, such as an inkjet printer.

[0085] All the numerical values ​​shown in the above embodiment are merely examples, and it goes without saying that other appropriate numerical values ​​can be used.

[0086] The above-described embodiments are merely examples in all respects. The present disclosure should not be construed as being limited by the description of the above-described embodiments. The present disclosure can be implemented in various other forms without departing from the spirit or main characteristics thereof. [Explanation of symbols]

[0087] 10, 10A...Piezoelectric device 11...Base material 11a...Base material body 11b...Wall part 12...Cathode electrode layer (second electrode layer) 13...Piezoelectric body (piezoelectric body layer) 14...Anode electrode layer (first electrode layer) 15A, 15B...1st electrode terminal 16A, 16B…Second electrode terminal 20, 20A...Polarization potential difference generating circuit 30...Control device 40...device L...Diagonal

Claims

1. A piezoelectric device having a capacitor structure in which a first electrode layer having two first electrode terminals, a piezoelectric layer, and a second electrode layer are laminated in this order, the first electrode layer is heated by Joule heat due to a potential difference between the two first electrode terminals; A piezoelectric device in which the piezoelectric layer is heated by the first electrode layer heated by Joule heat and polarized by an electric field generated by a potential difference between the first electrode layer and the second electrode layer.

2. The piezoelectric device according to claim 1 , wherein the two first electrode terminals are arranged point-symmetrically with respect to the center of the first electrode layer.

3. The piezoelectric device according to claim 1 , wherein one of the first electrode layer and the second electrode layer is an anode electrode layer, and the other is a cathode electrode layer.

4. An apparatus comprising the piezoelectric device according to claim 1.

5. a first step of applying a heating voltage to two first electrode terminals of a piezoelectric device having a capacitor structure in which a first electrode layer having two first electrode terminals, a piezoelectric layer, and a second electrode layer are laminated in this order, thereby generating potential differences between the two first electrode terminals and between the first electrode layer and the second electrode layer, thereby heating the first electrode layer by Joule heat and generating a polarization electric field; a second step of heating the piezoelectric layer with the first electrode layer heated by Joule heat and polarizing the piezoelectric layer with the polarization electric field.

6. and a third step of applying, after a predetermined period of time has elapsed, a polarization voltage having a potential difference of 0 V to the two first electrode terminals to generate a potential difference between the first electrode layer and the second electrode layer, thereby stopping Joule heating of the first electrode layer and generating a polarization electric field.

7. 6. The polarization treatment method according to claim 5, wherein in the first step, a rectangular AC voltage is applied as the heating voltage to one of the two first electrode terminals, and a rectangular AC voltage shifted by 180 degrees is applied as the heating voltage to the other first electrode terminal.

8. 6. The polarization treatment method according to claim 5, wherein in the first step, a rectangular AC voltage is applied as the heating voltage to one of the two first electrode terminals, and a DC voltage is applied to the other first electrode terminal.

9. 9. The polarization treatment method according to claim 7, wherein the frequency of the rectangular AC voltage is determined so as not to cause a current to flow between the first electrode layer and the second electrode layer.

10. The polarization treatment method according to claim 5 , wherein the two first electrode terminals are arranged point-symmetrically with respect to the center of the first electrode layer.

11. 6. The polarization method according to claim 5, wherein one of the first electrode layer and the second electrode layer is an anode electrode layer, and the other is a cathode electrode layer.

12. The device according to claim 4 , wherein the device is one of a piezoelectric MEMS speaker, a piezoelectric MEMS mirror, and an inkjet printer head.

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