Piezoelectric micromechanical ultrasonic transducer, method of fabrication and electrical product

Abstract

The embodiment of the present application provides a piezoelectric micromachined ultrasonic transducer, a manufacturing method and an electrical product. The piezoelectric micromachined ultrasonic transducer comprises a substrate provided with a cavity; at least one piezoelectric film layer, the piezoelectric film layer is provided with an electrode layer on both sides, and the electrode layer below the piezoelectric film layer closest to the substrate is located on the substrate; wherein, from the direction parallel to the substrate, the piezoelectric film layer and the electrode layers on both sides thereof are curved surfaces, and the curved surfaces are formed by electrostatic force among the top electrode, the bottom electrode and the substrate. The present application makes the diaphragm layer of the piezoelectric micromachined ultrasonic transducer curved through the electrostatic force among the electrode layers and between the electrode layer and the substrate, so that the PMUT diaphragm layer with higher bending degree is obtained. In addition, by adjusting the direct current voltage applied to the electrode, different electrostatic forces can be obtained, and then the bending degree of the PMUT diaphragm layer can be controlled, greatly expanding the application range of the piezoelectric micromachined ultrasonic transducer.

Description

Technical Field

[0001] This application relates to the field of electronic technology, and in particular to a piezoelectric micromechanical ultrasonic transducer, its manufacturing method, and electrical products. Background Technology

[0002] A piezoelectric micromachined ultrasonic transducer (PMUT) is a micro-electromechanical system that utilizes the direct and inverse piezoelectric effects of piezoelectric materials to vibrate a piezoelectric thin film, thereby emitting or receiving ultrasonic signals. PMUTs can function as actuators to emit sound waves or as sensors to receive sound waves. In addition, mass production processes based on MEMS standard technology and wafer-level packaging technology make PMUTs low in production costs, making them very suitable for large-scale commercial applications.

[0003] The transmission and reception performance of a PMUT is a key indicator that determines the quality of the product. Existing PMUTs typically consist of a bottom electrode, a piezoelectric layer, a top electrode, a support layer, a substrate, and a cavity. Generally, the PMUT diaphragm layer (the film layer that bends during PMUT operation, including the piezoelectric thin film layer and the electrode layers on both sides) has a planar structure. Its working principle is that when an alternating signal is applied to the electrodes, due to the inverse piezoelectric effect, the piezoelectric thin film layer in the PMUT diaphragm layer above the cavity generates d31 mode stretching and contraction vibrations, causing the PMUT diaphragm layer to vibrate in a bending mode, thereby exciting ultrasonic waves. Summary of the Invention

[0004] Research has found that the emission performance of existing PMUTs is insufficient, and the ultrasonic waves they generate have too short a propagation distance, which limits the large-scale commercial application of PMUTs. Therefore, it is necessary to improve the emission performance of PMUTs.

[0005] Research has found that when the PMUT diaphragm layer is curved, its emission performance is improved by orders of magnitude. However, curved PMUTs are extremely difficult to manufacture, making them difficult to apply to the research and development of large-scale PMUTs.

[0006] On the other hand, once the product is formed, the radius of curvature of the PMUT diaphragm layer with a curved surface becomes a fixed value and cannot be changed. In this case, although the ultrasonic emission performance of the obtained PMUT will be improved, its performance cannot be controlled, thus limiting the application of PMUT.

[0007] To address at least one or more of the aforementioned problems, embodiments of this application provide a piezoelectric micromechanical ultrasonic transducer, a manufacturing method, and an electrical product. On one hand, it enables the formation of a PMUT with a large degree of curvature, thereby achieving excellent ultrasonic performance. On the other hand, the piezoelectric micromechanical ultrasonic transducer provided by these embodiments allows for adjustment of the curvature of the PMUT diaphragm layer as needed, thus expanding the PMUT's application range.

[0008] According to a first aspect of the embodiments of this application, a piezoelectric micromechanical ultrasonic transducer is provided, comprising:

[0009] The substrate has a cavity.

[0010] At least one piezoelectric thin film layer, with electrode layers disposed on both sides of the piezoelectric thin film layer, and the electrode layer below the piezoelectric thin film layer closest to the substrate is located on the substrate;

[0011] When viewed from a direction parallel to the substrate, the piezoelectric thin film layer and the electrode layers on both sides thereof are curved surfaces, which are formed by the electrostatic force between the electrode layers and the substrate.

[0012] According to a second aspect of the embodiments of this application, the ratio of the minimum width of the surface on the horizontal cross-section of the piezoelectric micromechanical ultrasonic transducer to the depth of the surface is greater than 1 / 40.

[0013] According to a third aspect of the embodiments of this application, the piezoelectric micromechanical ultrasonic transducer further includes:

[0014] An insulating layer is located between the electrode layer, which is below the piezoelectric thin film layer closest to the substrate, and the substrate;

[0015] A DC voltage is applied between the electrode layer below the piezoelectric thin film layer closest to the substrate and the substrate;

[0016] The electrostatic force is formed by the DC voltage.

[0017] According to a fourth aspect of the embodiments of this application, the piezoelectric micromechanical ultrasonic transducer further includes:

[0018] The support layer is located at at least one of the following positions: between the electrode layer below the piezoelectric thin film layer closest to the substrate and the insulating layer, and above the electrode layer above the piezoelectric thin film layer furthest from the substrate.

[0019] According to a fifth aspect of the present application, the insulating layer is disposed along the surface of the substrate and the surface of the cavity between the electrode layer below the piezoelectric thin film layer closest to the substrate and the substrate.

[0020] According to a sixth aspect of the embodiments of this application, the piezoelectric micromechanical ultrasonic transducer further includes:

[0021] A first electrostatic electrode is located on an insulating layer at the bottom of the cavity, and a DC voltage is applied between the first electrostatic electrode and an electrode layer below the piezoelectric thin film layer closest to the substrate.

[0022] The dielectric layer is located at at least one of the following positions: between the electrode layer and the insulating layer below the piezoelectric thin film layer closest to the substrate, and above the first electrostatic electrode.

[0023] According to a seventh aspect of the embodiments of this application, the piezoelectric micromechanical ultrasonic transducer further includes:

[0024] An insulating post is disposed on the first electrostatic electrode.

[0025] According to an eighth aspect of the embodiments of this application, the piezoelectric micromechanical ultrasonic transducer further includes:

[0026] A dielectric layer is located between the electrode layer and the insulating layer, below the piezoelectric thin film layer closest to the substrate.

[0027] A second electrostatic electrode is located below the dielectric layer, and a DC voltage is applied between the second electrostatic electrode and the substrate.

[0028] According to a ninth aspect of the present application, when the dielectric layer is located between the electrode layer below the piezoelectric thin film layer closest to the substrate and the insulating layer, it further includes:

[0029] A third electrostatic electrode is located between the dielectric layer and the insulating layer, and a DC voltage is applied to the third electrostatic electrode and at least one of the first electrostatic electrode or the substrate.

[0030] According to a tenth aspect of the embodiments of this application, the substrate comprises at least one of the following materials: single-crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, highly conductive doped silicon, and diamond.

[0031] According to the eleventh aspect of the embodiments of this application, the electrode layer, the first electrostatic electrode, the second electrostatic electrode, and the third electrostatic electrode comprise at least one of the following materials: highly conductive silicon, molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or a composite or alloy of the above materials.

[0032] According to a twelfth aspect of the embodiments of this application, the piezoelectric thin film layer comprises at least one of the following materials:

[0033] Polycrystalline aluminum nitride, polycrystalline zinc oxide, polycrystalline lead zirconium titanate, polycrystalline lithium niobate, polycrystalline lithium tantalate, polycrystalline potassium niobate, monocrystalline aluminum nitride, monocrystalline gallium nitride, monocrystalline lithium niobate, monocrystalline lead zirconium titanate, monocrystalline potassium niobate, monocrystalline quartz film, monocrystalline lithium tantalate, and rare earth elements with a preset atomic ratio.

[0034] According to a thirteenth aspect of the present application, the support layer comprises at least one of the following materials: silicon nitride, silicon dioxide, and silicon.

[0035] According to a fourteenth aspect of the embodiments of this application, a method for manufacturing a piezoelectric micromechanical ultrasonic transducer having any one of the first to thirteenth aspects described above is provided, comprising:

[0036] A DC voltage is applied between a substrate and / or a first electrostatic electrode and at least one of the following layers: an electrode layer below the piezoelectric thin film layer closest to the substrate, a second electrostatic electrode, and a third electrostatic electrode;

[0037] Wherein: the first electrostatic electrode is located on the insulating layer at the bottom of the cavity; the second electrostatic electrode is located below the dielectric layer; the third electrostatic electrode is located between the dielectric layer and the insulating layer; the dielectric layer is located at at least one of the following positions: between the electrode layer below the piezoelectric thin film layer closest to the substrate and the insulating layer, and above the first electrostatic electrode;

[0038] When the first electrostatic electrode is present, there is a dielectric layer and / or an insulating layer and / or an insulating pillar between it and the electrode layer below the piezoelectric thin film layer closest to the substrate, the second electrostatic electrode, and the third electrostatic electrode;

[0039] The electrostatic force generated by the DC voltage causes the electrode layer, piezoelectric thin film layer, first electrostatic electrode, second electrostatic electrode, and third electrostatic electrode to form curved surfaces.

[0040] According to a fifteenth aspect of the embodiments of this application, an electrical product is provided, the electrical product having a piezoelectric micromechanical ultrasonic transducer as described in any one of the first to thirteenth aspects above.

[0041] One of the beneficial effects of the embodiments of this application is that: the piezoelectric micromechanical ultrasonic transducer, manufacturing method and electrical product proposed in this application, in the process of manufacturing the piezoelectric micromechanical ultrasonic transducer, the diaphragm layer of the piezoelectric micromechanical ultrasonic transducer is made curved by the electrostatic force between the electrode layers and between the electrode layers and the substrate, so that a PMUT diaphragm layer with a high degree of curvature can be obtained. In addition, by adjusting the DC voltage applied to the electrodes, different electrostatic forces can be obtained, thereby controlling the curvature of the PMUT diaphragm layer, which greatly expands the application range of the piezoelectric micromechanical ultrasonic transducer.

[0042] Embodiments of this application are disclosed in detail with reference to the following description and accompanying drawings. It should be understood that the scope of embodiments of this application is not limited thereto. Within the spirit and scope of the appended claims, embodiments of this application include many changes, modifications, and equivalents.

[0043] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0044] It should be emphasized that the term "including / contains / has" as used herein refers to the presence of a feature, whole or component, but does not exclude the presence or addition of one or more other features, wholes or components. Attached Figure Description

[0045] The above and other objects, features and advantages of the embodiments of this application will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0046] Figure 1 This is an intention of existing piezoelectric micromechanical ultrasonic transducers;

[0047] Figure 2 This is a schematic diagram of a piezoelectric micromechanical ultrasonic transducer according to an embodiment of this application;

[0048] Figure 3 This is another schematic diagram of the piezoelectric micromechanical ultrasonic transducer according to an embodiment of this application;

[0049] Figure 4 This is another schematic diagram of the piezoelectric micromechanical ultrasonic transducer according to an embodiment of this application;

[0050] Figure 5 This is another schematic diagram of the piezoelectric micromechanical ultrasonic transducer according to an embodiment of this application;

[0051] Figure 6 This is another schematic diagram of the piezoelectric micromechanical ultrasonic transducer according to an embodiment of this application;

[0052] Figure 7 This is another schematic diagram of the piezoelectric micromechanical ultrasonic transducer according to an embodiment of this application;

[0053] Figure 8 This is another schematic diagram of the piezoelectric micromechanical ultrasonic transducer according to an embodiment of this application;

[0054] Figure 9 This is another schematic diagram of the piezoelectric micromechanical ultrasonic transducer according to an embodiment of this application;

[0055] Figure 10This is another schematic diagram of the piezoelectric micromechanical ultrasonic transducer according to an embodiment of this application;

[0056] Figure 11 This is another schematic diagram of the piezoelectric micromechanical ultrasonic transducer according to an embodiment of this application;

[0057] Figure 12 This is another schematic diagram of the piezoelectric micromechanical ultrasonic transducer according to an embodiment of this application;

[0058] Figure 13 This is a schematic flowchart of the fabrication method of the piezoelectric micromechanical ultrasonic transducer according to an embodiment of this application;

[0059] Icon labels:

[0060] 100 substrate;

[0061] 101 cavity;

[0062] 110 insulation layer;

[0063] 200 bottom electrode;

[0064] 300 and 500 piezoelectric thin film layers;

[0065] 400, 600 top electrodes

[0066] 800, 120 dielectric layers;

[0067] 900 Second electrostatic electrode;

[0068] 1000 First electrostatic electrode;

[0069] 1100 Third electrostatic electrode. Detailed Implementation

[0070] Referring to the accompanying drawings, the foregoing and other features of this application will become apparent from the following description. Specific embodiments of this application are specifically disclosed in the description and drawings, illustrating partial implementations in which the principles of this application may be adopted. It should be understood that this application is not limited to the described embodiments; rather, it includes all modifications, variations, and equivalents falling within the scope of the appended claims.

[0071] In embodiments of this application, the term "and / or" includes any one and all combinations of one or more of the terms listed in association. The terms "comprising," "including," "having," etc., refer to the presence of the stated features, elements, components, or assemblies, but do not exclude the presence or addition of one or more other features, elements, components, or assemblies.

[0072] In the embodiments of this application, the singular forms "a," "the," etc., may include the plural forms and should be broadly understood as "a kind" or "a class" rather than limited to the meaning of "an." Furthermore, the term "described" should be understood to include both the singular and plural forms unless the context explicitly indicates otherwise. Additionally, the term "according to" should be understood as "at least partially based on…," and the term "based on" should be understood as "at least partially based on…," unless the context explicitly indicates otherwise. Furthermore, the terms "proximity" and "distance" in this application are only used to describe the relative positional relationship of the components and do not indicate the magnitude or specific degree of distance. For example, "distance" can also be referred to as "away from," etc.

[0073] Furthermore, in the following description of this application, for ease of explanation, one side of the substrate (also referred to as a base plate or substrate), support layer, bottom electrode, piezoelectric thin film layer, and bonding layer will be referred to as the upper side or top side, and the other side of the top electrode, support layer, bottom electrode, piezoelectric thin film layer, and bonding layer will be referred to as the lower side or bottom side. However, it should be noted that these are only for ease of explanation and do not limit the orientation of the piezoelectric micromechanical ultrasonic transducer of the embodiments of this application during manufacturing and use.

[0074] Figure 1 This is a typical cross-sectional view of a PMUT. For example... Figure 1 As shown, the PMUT includes: a substrate 100, a bottom electrode 200, a piezoelectric thin film layer 300, and a top electrode 400. The substrate 100 contains a cavity 101 to provide space for the PMUT diaphragm layer to bend and vibrate. In the prior art, the pressure inside the cavity 101 is the same as or equivalent to the external environmental pressure of the PMUT, meaning the pressure on both sides of the PMUT diaphragm layer is equivalent, thus making it essentially planar. Even when the PMUT product is molded and its diaphragm layer is bent, the degree of upward or downward bending is limited and difficult to control due to the relatively high rigidity of the diaphragm layer.

[0075] The embodiments of this application will now be described with reference to the accompanying drawings.

[0076] like Figure 2 As shown, the piezoelectric micromechanical ultrasonic transducer provided in this application embodiment includes:

[0077] Substrate 100, with cavity 101 provided;

[0078] At least one piezoelectric thin film layer 300, with electrode layers on both sides of the piezoelectric thin film layer 300 (for ease of description, the electrode layer 500 above the piezoelectric thin film layer 400 furthest from the substrate 100 is referred to as the top electrode, and the other electrode layers 300 are referred to as the bottom electrode), and the electrode layer 200 below the piezoelectric thin film layer 300 closest to the substrate 100 is located above the substrate 100.

[0079] See Figure 3 When viewed from a direction parallel to the substrate 100, the piezoelectric thin film layer 300 and the electrode layers (200 and 400) on both sides of it are curved surfaces, which are formed by the electrostatic force between the electrode layer (400) and the substrate 100.

[0080] The aforementioned electrostatic force can be achieved by applying a DC voltage to the bottom electrode 200 and the substrate 100, thereby generating an electrostatic force through the DC voltage. Furthermore, the curved surface mentioned above refers to the state of the PMUT during operation, i.e., when an electrostatic force exists between the top electrode 400, the bottom electrode 200, and the substrate 100. When this electrostatic force is absent, the piezoelectric thin film layer 300 and its two adjacent electrode layers (200, 400) are planar. It should be noted that when the PMUT is operating, an AC voltage also needs to be applied between the top electrode 400 and the bottom electrode 200 to drive the PMUT's diaphragm layer to vibrate.

[0081] Additionally, it is understandable that when a DC voltage is applied between the bottom electrode 200 and the substrate 100, the substrate 100 needs to have high conductivity, for example, it is made of highly conductive doped silicon.

[0082] In this embodiment of the application, the ratio of the minimum width of the curved surface on the horizontal cross-section of the piezoelectric micromechanical ultrasonic transducer to the depth of the curved surface is greater than 1 / 40.

[0083] Since the shape of the curved surface is not limited in this application, the minimum width mentioned above refers to the minimum distance between two points on the horizontal cross-section of the piezoelectric micromechanical ultrasonic transducer, where a straight line passing through the center (or approximately the center) of the curved surface intersects the curved surface. In a more preferred embodiment, the ratio of the minimum width of the curved surface to its depth is greater than 1 / 20 or 1 / 10.

[0084] In the piezoelectric micromechanical ultrasonic transducer provided in the embodiments of this application, the value of the DC voltage V applied to the bottom electrode 200 and the substrate 100 can be adjustable, that is, its value can be set according to the degree of curvature that the PMUT diaphragm layer is to be achieved, thereby obtaining a PMUT with adjustable frequency and acoustic performance and a curved structure.

[0085] It should be noted that, in this embodiment of the application, there is no limitation on the position of the cavity 101 on the substrate 100. It can be located at the center of the substrate 100, or on the left or right side of the substrate 100.

[0086] In summary, the piezoelectric micromechanical ultrasonic transducer provided in this application embodiment achieves a curved diaphragm layer by utilizing the electrostatic forces between electrode layers and between the electrode layers and the substrate. This results in a PMUT diaphragm layer with a high degree of curvature. Furthermore, by adjusting the DC voltage applied to the electrodes, different electrostatic forces can be obtained, thereby controlling the curvature of the PMUT diaphragm layer and greatly expanding the application range of the piezoelectric micromechanical ultrasonic transducer.

[0087] In some embodiments, see Figure 4 To ensure electrical isolation between the bottom electrode 200 and the substrate 100, the piezoelectric micromechanical ultrasonic transducer also includes:

[0088] An insulating layer 110 is located between the electrode layer 200 and the substrate 100, below the piezoelectric thin film layer 300 which is closest to the substrate 100;

[0089] An AC voltage is applied between the electrode layers (200, 400), and a DC voltage is applied between the electrode layer 200 below the piezoelectric thin film layer closest to the substrate and the substrate 100.

[0090] Electrostatic force is generated by alternating current voltage and direct current voltage.

[0091] Specifically, in the above embodiments, when the number of piezoelectric thin film layers 300 is 1, see [reference needed]. Figure 4 An insulating layer 110 is located between the bottom electrode 200 and the substrate 100; similarly, an AC voltage is applied to the top electrode 400 and the bottom electrode 200, and a DC voltage is applied to the bottom electrode 200 and the substrate 100.

[0092] In some embodiments, the piezoelectric micromechanical ultrasonic transducer further includes:

[0093] A support layer is located at at least one of the following positions: between the electrode layer 200 below the piezoelectric thin film layer 300 closest to the substrate 100 and the insulating layer 110, and above the electrode layer 400 above the piezoelectric thin film layer 300 furthest from the substrate 100. The function of this support layer is to offset the neutral layer of the diaphragm layer of the piezoelectric micromechanical ultrasonic transducer from the center of mass plane of the piezoelectric thin film layer 300. The diaphragm layer includes the support layer, the piezoelectric thin film layer 300, and the electrode layers (200 and 400) on both sides thereof.

[0094] It is understandable that when the materials of each layer are uniform, and the electrode layers on both sides of the piezoelectric thin film layer 300 have equal thickness and are made of the same material, the neutral layer of the diaphragm layer composed of the piezoelectric thin film layer 300 and the electrode layers (200 and 400) on both sides is the center of mass plane of the piezoelectric thin film layer 300, that is, its central axial plane. Figure 5(as shown by the dashed line), but after adding a support surface, the neutral layer of the diaphragm layer can be deviated from this surface.

[0095] It should be noted that in the piezoelectric micromechanical ultrasonic transducer provided in the embodiments of this application, the support layer is not necessary; for example... Figure 2 In this embodiment, the bottom electrode 200 is thicker than the top electrode 400, thus the bottom electrode 200 serves as both a support layer and an electrode layer. Even if the bottom electrode 200 and the top electrode 400 have the same thickness, the diaphragm layer of the piezoelectric micromechanical ultrasonic transducer provided in this application embodiment has a curved surface structure, which still enables it to excite and receive ultrasonic waves.

[0096] In some embodiments, see Figure 4 as well as Figure 6 The insulating layer 110 is laid between the bottom electrode 200 and the substrate 100 along the surface of the substrate 100 and the surface of the cavity 101, that is, the insulating layer 110 is roughly in the shape of a "U" in cross section.

[0097] In some embodiments, see Figure 7 The piezoelectric micromechanical ultrasonic transducer also includes:

[0098] The first electrostatic electrode 1000 is located on the insulating layer 110 at the bottom of the cavity 101, and a DC voltage is applied between the first electrostatic electrode 1000 and the electrode layer 200 below the piezoelectric thin film layer 300 closest to the substrate.

[0099] The dielectric layer 800 is located at at least one of the following locations: between the electrode layer 200 and the insulating layer 110 below the piezoelectric thin film layer 300 closest to the substrate 100, and above the first electrostatic electrode 1000.

[0100] Specifically, the dielectric layer 800 is located in at least one of the following positions: between the bottom electrode 200 and the insulating layer 110, and only covering the first electrostatic electrode 1000 (not shown in the figure in this case).

[0101] The dielectric layer 800 serves to prevent the bottom electrode 200 from contacting the first electrostatic electrode 1000, similar to the function of the insulating pillar. Of course, both the insulating pillar and the dielectric layer can be simultaneously placed in the piezoelectric micromechanical ultrasonic transducer. It should be noted that when the dielectric layer 800 is located between the bottom electrode 200 and the insulating layer 110, it bends along with the PMUT diaphragm layer (when the PMUT is operating). When the dielectric layer 800 covers the first electrostatic electrode 1000, its shape remains unchanged.

[0102] See Figure 8 ,and Figure 3Similarly, the first electrostatic electrode 1000 can be omitted and disposed within the substrate 100, i.e., a DC voltage is applied between the substrate 100 and the bottom electrode 200. Specifically, the first electrostatic electrode 1000 is located on the insulating layer 110 at the bottom of the cavity 101, and a DC voltage is applied between the first electrostatic electrode 1000 and the bottom electrode 200. This embodiment is essentially... Figure 3 In this invention, a DC voltage is applied to the bottom electrode 200 and the substrate 100. Alternatively, a DC voltage is applied to the first electrostatic electrode 1000 and the bottom electrode 200. In order to ensure the insulation between the bottom electrode 200 and the first electrostatic electrode 1000, an insulating layer 110 is provided between the bottom electrode 200 and the substrate 100. Of course, the insulating layer 110 may not be added, and the present invention is not limited thereto.

[0103] In some embodiments, the piezoelectric micromechanical ultrasonic transducer further includes:

[0104] An insulating post is disposed above the first electrostatic electrode 1000. It is used to prevent the electrode layer 200 from contacting the first electrostatic electrode 1000 when the PMUT diaphragm layer bends during PMUT operation, which could lead to device failure.

[0105] In some embodiments, see Figure 9 When the dielectric layer 800 is located between the electrode layer 200 and the insulating layer 110 below the piezoelectric thin film layer 300 closest to the substrate 100, it further includes:

[0106] The second electrostatic electrode 900 is located below the dielectric layer 800, wherein an AC voltage is applied between the electrode layers (200, 400) and a DC voltage is applied between the second electrostatic electrode 900 and the substrate 100.

[0107] Specifically, in the above embodiment, when the dielectric layer 800 is located between the bottom electrode 200 and the insulating layer 110, the piezoelectric micromechanical ultrasonic transducer further includes: a second electrostatic electrode 900, located below the dielectric layer 800 (the two are connected), wherein an AC voltage is applied between the top electrode 400 and the bottom electrode 200, and a DC voltage is applied between the second electrostatic electrode 900 and the substrate 100. Additionally, it should be noted that... Figure 9 The insulating layer 110 in the cavity may be absent. In addition, the first electrostatic electrode 1000 cannot be placed on the insulating layer 110 at the bottom of the cavity 101, because if the first electrostatic electrode 1000 and the second electrostatic electrode 900 are present at the same time, there is a great risk of contact between them when the PMUT is working.

[0108] In some embodiments, see Figure 10 When the dielectric layer 800 is located between the electrode layer 200 and the insulating layer 110 below the piezoelectric thin film layer 300 closest to the substrate 100, it further includes:

[0109] The third electrostatic electrode 1100 is located between the dielectric layer 800 and the insulating layer 110, wherein an alternating voltage is applied between the electrode layers (200, 400), and a direct current voltage is applied between the third electrostatic electrode 1100 and at least one of the first electrostatic electrode 1000 or the substrate 100. Figure 10 as well as Figure 11 (As shown).

[0110] Specifically, when the dielectric layer 800 is located between the bottom electrode 200 and the insulating layer 110, the piezoelectric micromechanical ultrasonic transducer further includes: a third electrostatic electrode 1100 located between the dielectric layer 800 and the insulating layer 110, wherein an AC voltage is applied to the top electrode 400 and the bottom electrode 200, and a DC voltage is applied to the third electrostatic electrode 1100 and at least one of the electrostatic electrode 1000 or the substrate 100.

[0111] Figure 11 The piezoelectric ultrasonic transducer (PMUT) includes an electrostatic attraction component comprising a first electrostatic electrode 1000 and a second electrostatic electrode 900 for applying a DC voltage signal. By applying a DC voltage to this electrode pair and an AC voltage to the top electrode 400 and bottom electrode 200, an electrostatic attraction is generated, causing the PMUT diaphragm layer to bend towards the cavity 101, forming a PMUT with a curved surface structure. A dielectric layer 800 exists between the bottom electrode 200 and the second electrostatic electrode 900 of the PMUT, allowing the two electrode pairs to operate independently without shared electrodes, thus reducing mutual interference. Furthermore, the insulating layer 110 shown in the figure is not essential and can be omitted.

[0112] During operation, when a large degree of bending is required, to prevent the second electrostatic electrode 900 in the PMUT diaphragm layer from short-circuiting with the first electrostatic electrode 1000 due to excessive bending, which could damage the device, a dielectric layer 120 is added between the second electrostatic electrode 900 and the first electrostatic electrode 1000. This avoids the possibility of direct contact between the two electrodes. Alternatively, this layer can cover the first electrostatic electrode 1000 instead of just being adjacent to the dielectric layer 800, or a certain amount of insulating pillars can be added between the dielectric layer 800 and the first electrostatic electrode 1000 to prevent the bottom electrode 200 from contacting the first electrostatic electrode 1000 during PMUT operation, thus preventing device failure. Such designs can be applied to all the above embodiments.

[0113] In some embodiments, Figure 12 This is an embodiment where there are multiple piezoelectric thin film layers. Figure 12(Taking two as an example, this application is not limited to this), where 300 and 500 are piezoelectric thin film layers, 200 and 400 are bottom electrodes, and 600 is a top electrode located on both sides of piezoelectric thin film layers 300 and 500. Figures 1 to 11 Compared to the previous embodiment, this PMUT contains a double piezoelectric thin film layer, whose simultaneous vibration can generate a stronger ultrasonic signal.

[0114] During operation, a DC voltage V is applied between the electrode pair substrate 100 and the bottom electrode 200, causing the PMUT diaphragm layer to bend under electrostatic attraction. Simultaneously, an AC voltage is applied between the bottom electrode 400 and the top electrode 600, generating an electrostatic force between the bottom electrode 200 and the substrate 100, thereby exciting the piezoelectric thin film layer to vibrate and generate ultrasonic waves. The applied DC voltage V can be different, thus controlling the degree of bending of the PMUT diaphragm layer to obtain a PMUT with adjustable frequency and acoustic performance and a curved structure. Understandably, due to the double-layer piezoelectric thin film layer and the curved structure, the ultrasonic emission performance of the PMUT is greatly improved.

[0115] In the diagram, 400 and 200 represent two bottom electrodes, which can be the same or different. Similarly, 300 and 500 represent two piezoelectric thin film layers, which can also be the same or different. Figure 12 In this design, due to the use of dual piezoelectric thin film layers, the simultaneous vibration of these two layers (300° and 500°) generates a stronger ultrasonic signal. Furthermore, [the following text appears to be incomplete and requires further context: "same..."] Figure 9 Similarly, the first electrostatic electrode 1000 cannot be placed on the insulating layer 110 at the bottom of the cavity 101, because if the first electrostatic electrode 1000 and the bottom electrode 200 are present at the same time (without an insulating layer or dielectric layer between them), there is a great risk of contact between them when the PMUT is working.

[0116] In the embodiments of this application, the substrate includes at least one of the following materials: single crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, highly conductive doped silicon (silicon on insulator (SOI)), and diamond.

[0117] In the embodiments of this application, the electrode layer, the first electrostatic electrode, the second electrostatic electrode, and the third electrostatic electrode comprise at least one of the following materials: highly conductive silicon, molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or a composite or alloy of the above materials.

[0118] In the embodiments of this application, the piezoelectric thin film layer includes at least one of the following materials: optional materials include polycrystalline aluminum nitride (AlN), polycrystalline zinc oxide, polycrystalline lead zirconate titanate (PZT), polycrystalline lithium niobate (LiNbO3), polycrystalline lithium tantalate (LiTaO3), polycrystalline potassium niobate (KNbO3), etc., or single-crystal aluminum nitride, single-crystal gallium nitride, single-crystal lithium niobate, single-crystal lead zirconate titanate, single-crystal potassium niobate, single-crystal quartz film, or single-crystal lithium tantalate, rare earth elements with a predetermined atomic ratio (e.g., scandium-doped aluminum nitride).

[0119] In the embodiments of this application, the support layer includes at least one of the following materials: silicon nitride, silicon dioxide, and silicon.

[0120] Additionally, it should be noted that, Figures 1 to 12 The cross-sectional area of ​​the top electrode 500 is smaller than that of the piezoelectric thin film layer 400, the bottom electrode 300, the support layer 200, and the insulating layer 800. This is just for illustration and is not a limitation. That is, the cross-sectional area of ​​the top electrode 500 can be the same as or different from that of the piezoelectric thin film layer 400, the bottom electrode 300, the support layer 200, and the bonding layer 800, and can also be other shapes, such as circles, triangles, and rings.

[0121] by Figure 3 For example, the piezoelectric micromechanical ultrasonic transducer provided in this application embodiment, under a certain cavity radius D, can first obtain a high degree of bending h through the stretching effect of electrostatic force, which meets the requirement of a large degree of bending of the PMUT diaphragm layer, such as h / D≥0.5%, especially h / D≥1%. In addition, by adjusting the DC voltage V applied to the electrode, different electrostatic forces can be obtained, thereby obtaining the desired degree of bending of the PMUT diaphragm layer.

[0122] The structure of the embodiments of this application has been described above, but this application is not limited thereto. Specific details of each device or component can be found in related technologies; furthermore, additional [devices / components] may be added. Figures 1 to 12 Devices or components not shown, or reduced Figures 1 to 12 One or more devices or components in it.

[0123] The above embodiments are merely illustrative examples of embodiments of this application, but this application is not limited thereto, and appropriate modifications can be made based on the above embodiments. For example, the above embodiments can be used alone, or one or more of the above embodiments can be combined.

[0124] In some embodiments, see Figure 13 According to this application, a method for manufacturing the above-mentioned piezoelectric micromechanical ultrasonic transducer is also provided, the method comprising:

[0125] Step 100: Apply a DC voltage between the substrate and / or the first electrostatic electrode and at least one of the following layers: the electrode layer below the piezoelectric thin film layer closest to the substrate, the second electrostatic electrode, and the third electrostatic electrode;

[0126] Wherein: the first electrostatic electrode is located on the insulating layer at the bottom of the cavity; the second electrostatic electrode is located below the dielectric layer; the third electrostatic electrode is located between the dielectric layer and the insulating layer; the dielectric layer is located at at least one of the following positions: between the electrode layer below the piezoelectric thin film layer closest to the substrate and the insulating layer, and above the first electrostatic electrode;

[0127] When the first electrostatic electrode is present, there is a dielectric layer and / or an insulating layer and / or an insulating pillar between it and the electrode layer below the piezoelectric thin film layer closest to the substrate, the second electrostatic electrode, and the third electrostatic electrode.

[0128] Step 200: The electrostatic force generated by the DC voltage causes the electrode layer, piezoelectric thin film layer, first electrostatic electrode, second electrostatic electrode and third electrostatic electrode to be curved.

[0129] In step 200, when viewed from a direction parallel to the substrate, the electrode layer, the piezoelectric thin film layer, the first electrostatic electrode, the second electrostatic electrode, and the third electrostatic electrode are curved surfaces;

[0130] It should be noted that the fabrication methods for piezoelectric micromechanical ultrasonic transducers also include:

[0131] Step 300: Apply an alternating voltage between the electrode layers on both sides of the piezoelectric thin film layer to cause the diaphragm layer driving the PMUT to vibrate.

[0132] This application also provides an electrical product having the piezoelectric micromechanical ultrasonic transducer described above. This electrical product includes, for example, ultrasonic imagers, ultrasonic radars, sonar detectors, robotic vacuum cleaners, ultrasonic smoke detectors, etc., but this application is not limited to these.

[0133] It is worth noting that the above description is merely illustrative of the embodiments of this application, but the embodiments of this application are not limited thereto, and appropriate modifications can be made based on the above embodiments. Furthermore, the above description is merely illustrative of the various components, but the embodiments of this application are not limited thereto, and the specific content of each component can be referred to related technologies; in addition, components not shown in the figures can be added, or one or more components in the figures can be removed.

[0134] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the embodiments of the device implementation method are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0135] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0136] While this specification provides method steps as illustrated in the embodiments or flowcharts, more or fewer steps may be included based on conventional or non-inventive means. The order of steps listed in the embodiments is merely one possible order of execution among many steps and does not represent the only possible order. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, product, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, product, or apparatus. Without further limitations, the presence of additional identical or equivalent elements in a process, method, product, or apparatus that includes elements is not excluded.

[0137] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, system embodiments are basically similar to method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. In the description of this specification, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the embodiments in this specification. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0138] The above are merely embodiments of the examples in this specification and are not intended to limit the scope of the embodiments in this specification. For those skilled in the art, various modifications and variations can be made to the embodiments in this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the embodiments in this specification should be included within the scope of the claims of the embodiments in this specification.

[0139] The embodiments of this application have been described above with reference to specific implementation methods. However, those skilled in the art should understand that these descriptions are exemplary and not intended to limit the scope of protection of the embodiments of this application. Those skilled in the art can make various modifications and variations to the embodiments of this application based on the spirit and principles of the embodiments, and these modifications and variations are also within the scope of the embodiments of this application.

[0140] Preferred embodiments of the present application have been described above with reference to the accompanying drawings. Many features and advantages of these embodiments are apparent from this detailed description, and therefore the appended claims are intended to cover all such features and advantages falling within the true spirit and scope of these embodiments. Furthermore, since many modifications and alterations will readily occur to those skilled in the art, the embodiments of the present application are not intended to be limited to the precise structures and operations illustrated and described, but rather to encompass all suitable modifications and equivalents falling within their scope.

Claims

1. A piezoelectric micromechanical ultrasonic transducer, characterized in that, include: The substrate has a cavity. At least one piezoelectric thin film layer, with electrode layers disposed on both sides of the piezoelectric thin film layer, and the electrode layer below the piezoelectric thin film layer closest to the substrate is located on the substrate; When viewed from a direction parallel to the substrate, the piezoelectric thin film layer and the electrode layers on both sides thereof are curved surfaces, which are formed by the electrostatic force between the electrode layers and the substrate. An insulating layer is located between the electrode layer, which is below the piezoelectric thin film layer closest to the substrate, and the substrate; A DC voltage is applied between the electrode layer below the piezoelectric thin film layer closest to the substrate and the substrate; The electrostatic force is formed by the DC voltage.

2. The piezoelectric micromechanical ultrasonic transducer according to claim 1, characterized in that, The ratio of the minimum width of the surface to the depth of the surface on the horizontal cross-section of the piezoelectric micromechanical ultrasonic transducer is greater than 1 / 40.

3. The piezoelectric micromechanical ultrasonic transducer according to claim 1, characterized in that, Also includes: The support layer is located at at least one of the following positions: between the electrode layer below the piezoelectric thin film layer closest to the substrate and the insulating layer, and above the electrode layer above the piezoelectric thin film layer furthest from the substrate.

4. The piezoelectric micromechanical ultrasonic transducer according to claim 1, characterized in that, The insulating layer is laid along the surface of the substrate and the surface of the cavity between the electrode layer below the piezoelectric thin film layer closest to the substrate and the substrate.

5. The piezoelectric micromechanical ultrasonic transducer according to claim 1, characterized in that, Also includes: A first electrostatic electrode is located on an insulating layer at the bottom of the cavity, and a DC voltage is applied between the first electrostatic electrode and an electrode layer below the piezoelectric thin film layer closest to the substrate. The dielectric layer is located at at least one of the following locations: between the electrode layer and the insulating layer below the piezoelectric thin film layer closest to the substrate, and above the first electrostatic electrode.

6. The piezoelectric micromechanical ultrasonic transducer according to claim 5, characterized in that, Also includes: An insulating post is disposed on the first electrostatic electrode.

7. The piezoelectric micromechanical ultrasonic transducer according to claim 1, characterized in that, Also includes: A dielectric layer is located between the electrode layer and the insulating layer, below the piezoelectric thin film layer closest to the substrate. A second electrostatic electrode is located below the dielectric layer, and a DC voltage is applied between the second electrostatic electrode and the substrate.

8. The piezoelectric micromechanical ultrasonic transducer according to claim 5, characterized in that, When the dielectric layer is located between the electrode layer below the piezoelectric thin film layer closest to the substrate and the insulating layer, it further includes: A third electrostatic electrode is located between the dielectric layer and the insulating layer, and a DC voltage is applied to the third electrostatic electrode and at least one of the first electrostatic electrode or the substrate.

9. The piezoelectric micromechanical ultrasonic transducer according to claim 1, characterized in that, The substrate comprises at least one of the following materials: single-crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, highly conductive doped silicon, and diamond.

10. The piezoelectric micromechanical ultrasonic transducer according to claim 8, characterized in that, The electrode layer, the first electrostatic electrode, the second electrostatic electrode, and the third electrostatic electrode comprise at least one of the following materials: highly conductive silicon, molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or a composite or alloy of the above materials.

11. The piezoelectric micromechanical ultrasonic transducer according to claim 1, characterized in that, The piezoelectric thin film layer comprises at least one of the following materials: Polycrystalline aluminum nitride, polycrystalline zinc oxide, polycrystalline lead zirconium titanate, polycrystalline lithium niobate, polycrystalline lithium tantalate, polycrystalline potassium niobate, monocrystalline aluminum nitride, monocrystalline gallium nitride, monocrystalline lithium niobate, monocrystalline lead zirconium titanate, monocrystalline potassium niobate, monocrystalline quartz film, monocrystalline lithium tantalate, and rare earth elements with a preset atomic ratio.

12. The piezoelectric micromechanical ultrasonic transducer according to claim 3, characterized in that, The support layer comprises at least one of the following materials: silicon nitride, silicon dioxide, and silicon.

13. A method for fabricating a piezoelectric micromechanical ultrasonic transducer as described in any one of claims 1 to 12, characterized in that, include: A DC voltage is applied between a substrate and / or a first electrostatic electrode and at least one of the following layers: an electrode layer below the piezoelectric thin film layer closest to the substrate, a second electrostatic electrode, and a third electrostatic electrode; Wherein: the first electrostatic electrode is located on the insulating layer at the bottom of the cavity; the second electrostatic electrode is located below the dielectric layer; the third electrostatic electrode is located between the dielectric layer and the insulating layer; the dielectric layer is located at at least one of the following positions: between the electrode layer below the piezoelectric thin film layer closest to the substrate and the insulating layer, and above the first electrostatic electrode; When the first electrostatic electrode is present, there is a dielectric layer and / or an insulating layer and / or an insulating pillar between it and the electrode layer below the piezoelectric thin film layer closest to the substrate, the second electrostatic electrode, and the third electrostatic electrode; The electrostatic force generated by the DC voltage causes the electrode layer, piezoelectric thin film layer, first electrostatic electrode, second electrostatic electrode, and third electrostatic electrode to form curved surfaces.

14. An electrical product, characterized in that, The electrical product has a piezoelectric micromechanical ultrasonic transducer as described in any one of claims 1 to 12.

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