Preparation method of piezoelectric stack structure

Abstract

The invention provides a preparation method of a piezoelectric stack structure, and relates to the technical field of semiconductors. The preparation method of the piezoelectric stack structure comprises the steps that a substrate structure is provided, a composite film layer is formed on the substrate structure in the first preset direction, and the composite film layer comprises at least two electrode layers arranged in a stacked mode in the first preset direction and piezoelectric layers arranged between the two adjacent electrode layers; slits are formed in the composite film layer, the slits penetrate through the two opposite surfaces of the composite film layer in the first preset direction respectively, the slits comprise at least two first slits and at least one second slit, and the two opposite sides of the second slit in the first preset direction are connected with the first slits respectively. According to the preparation method of the piezoelectric stack structure, the piezoelectric stack structure with the slit width as small as possible, better low-frequency response and better low-frequency signal transmission effect can be easily obtained.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a method for preparing a piezoelectric stack structure. Background Art

[0002] As an advanced acoustic sensor technology, cantilever microphones have been rapidly developed due to their many advantages such as low power consumption, fast response, and high reliability. A slit is provided on the piezoelectric stack structure of the cantilever microphone, and the slit runs through the piezoelectric stack structure to form a cantilever beam. The design of the slit has a great influence on the low-frequency response capability of the cantilever microphone. Among them, the slit width is a parameter that directly affects the low-frequency response of the cantilever microphone. The smaller the slit width, the lower the low-frequency response of the cantilever microphone and the wider the response range. A smaller slit width can help the cantilever microphone capture and reproduce low-frequency sounds more accurately, and achieve a wider frequency response to enable the cantilever microphone system to sense more natural and clear sounds.

[0003] However, in the actual process of preparing a cantilever microphone, the width of the slit depends on the minimum processing width of the processing equipment. In addition, the slit has a large aspect ratio and the piezoelectric stack structure contains piezoelectric materials that are difficult to etch. It is extremely difficult to obtain the smallest possible slit width. As the thickness of the cantilever beam increases, the difficulty of processing the slit increases further. Therefore, it is extremely difficult to process a slit with the smallest possible width using existing processes. Summary of the invention

[0004] The purpose of the present application is to provide a method for preparing a piezoelectric stack structure in view of the deficiencies in the above-mentioned prior art, which can relatively easily obtain a piezoelectric stack structure with a slit width as small as possible, a better low-frequency response, and a better low-frequency signal transmission effect.

[0005] To achieve the above purpose, the technical solution adopted in the embodiment of the present application is as follows:

[0006] An embodiment of the present application provides a method for preparing a piezoelectric stack structure, including: providing a base structure, and forming a composite film layer on the base structure along a first preset direction, wherein the composite film layer includes at least two electrode layers stacked along the first preset direction and a piezoelectric layer arranged between two adjacent electrode layers, and a slit is provided in the composite film layer, and the slit passes through two opposite surfaces of the composite film layer in the first preset direction respectively, so as to divide the composite film layer into at least two cantilever beams, and the slit includes at least two first slits and at least one second slit, the number of the second slits is one less than the number of the first slits, and the second slits are respectively connected to the first slits on two opposite sides of the first preset direction.

[0007] Optionally, the width of the first gap is greater than the depth of the second gap.

[0008] Optionally, a vertical distance between mutually adjacent side surfaces of two first gaps connected to the same second gap is greater than a depth of the first gap.

[0009] Optionally, forming a composite film layer on the substrate structure along a first preset direction includes: alternately forming the same number of first sacrificial layers and second sacrificial layers on the substrate structure along the first preset direction, and forming a first composite film layer wrapping the first sacrificial layer and the second sacrificial layer on the substrate structure along the first preset direction, wherein the first sacrificial layer is connected to the second sacrificial layer, the first sacrificial layer penetrates the surface of the first composite film layer facing the substrate structure, and the second sacrificial layer penetrates the surface of the first composite film layer facing away from the substrate structure, and if the number of first sacrificial layers is at least two, the orthographic projections of two adjacent first sacrificial layers on the substrate structure do not overlap; forming a second composite film layer covering the second sacrificial layer on the surface of the first composite film layer facing away from the substrate structure, and forming a third groove in the second composite film layer, wherein the third groove respectively penetrates two opposite surfaces of the second composite film layer, the third groove is connected to the second sacrificial layer, and the orthographic projections of the third groove and the first sacrificial layer adjacent to it on the substrate structure do not overlap; removing the first sacrificial layer and the second sacrificial layer to form a slit.

[0010] Optionally, an equal number of first sacrificial layers and second sacrificial layers are alternately formed on the base structure along a first preset direction, and a first composite film layer wrapping the first sacrificial layers and the second sacrificial layers is formed on the base structure along the first preset direction, including: forming a first composite film layer on the base structure; forming an equal number of first grooves and second grooves in the first composite film layer, and filling the first groove with the first sacrificial layer, and filling the second groove with the second sacrificial layer.

[0011] Optionally, an equal number of first sacrificial layers and second sacrificial layers are alternately formed on the base structure along a first preset direction, and a first composite membrane layer wrapping the first sacrificial layer and the second sacrificial layer is formed on the base structure along the first preset direction, including: forming a first composite sub-membrane layer on the base structure; forming a first groove and a second groove in the first composite sub-membrane layer, and filling the first groove with the first sacrificial layer, and filling the second groove with the second sacrificial layer; forming another first composite sub-membrane layer on the surface of the first composite sub-membrane layer facing away from the base structure; forming a first groove and a second groove in the other first composite sub-membrane layer, and filling the first groove with the first sacrificial layer, and filling the second groove with the second sacrificial layer; repeating the steps of forming the first composite sub-membrane layer, the first groove, the second groove, the first sacrificial layer, and the second sacrificial layer until all the first sacrificial layers and the second sacrificial layers are formed.

[0012] Optionally, forming the same number of first grooves and second grooves in the first composite film layer, and filling the first groove with a first sacrificial layer, and filling the second groove with a second sacrificial layer includes: forming a second groove on the surface of the first composite film layer facing away from the substrate structure, and forming a first groove at the bottom of the second groove, wherein the bottom of the first groove penetrates the surface of the first composite film layer facing the substrate structure; filling the first groove and the second groove with sacrificial materials to form a first sacrificial layer filling the first groove and a second sacrificial layer filling the second groove.

[0013] Optionally, forming a first groove and a second groove in a first composite sub-membrane layer, and filling the first groove with a first sacrificial layer, and filling the second groove with a second sacrificial layer includes: forming a second groove on a surface of the first composite sub-membrane layer facing away from the substrate structure, and forming a first groove at the bottom of the second groove, wherein the bottom of the first groove penetrates the surface of the first composite sub-membrane layer facing the substrate structure; filling the first groove and the second groove with sacrificial material to form a first sacrificial layer filling the first groove and a second sacrificial layer filling the second groove; forming a first groove and a second groove in another first composite sub-membrane layer, and filling the first sacrificial layer in the first groove, and filling the second groove with the second sacrificial layer includes: forming a second groove on a surface of another first composite sub-membrane layer facing away from the substrate structure, and forming a first groove at the bottom of the second groove, wherein the bottom of the first groove penetrates the surface of the other first composite sub-membrane layer facing the substrate structure; filling the first groove and the second groove with sacrificial material to form a first sacrificial layer filling the first groove and a second sacrificial layer filling the second groove.

[0014] Optionally, two opposite surfaces of the first sacrificial layer in the first preset direction are respectively flush with opposite ends of the first groove in the first preset direction, and two opposite surfaces of the second sacrificial layer in the first preset direction are respectively flush with opposite ends of the second groove in the first preset direction.

[0015] Optionally, providing a base structure and forming a composite film layer on the base structure along a first preset direction includes: providing a substrate, and sequentially forming a protective layer and a composite film layer on the surface of the substrate along the first preset direction; after forming the composite film layer on the base structure along the first preset direction, the method further includes: forming a first back cavity on the surface of the substrate away from the protective layer, the first back cavity passing through two opposite surfaces of the substrate; removing the area on the protective layer corresponding to the first back cavity to form a second back cavity on the protective layer, wherein the first back cavity, the second back cavity and the slit are sequentially connected.

[0016] The beneficial effects of this application include:

[0017] The present application provides a method for preparing a piezoelectric stack structure, comprising: providing a base structure, and forming a composite film layer on the base structure along a first preset direction, wherein the composite film layer comprises at least two electrode layers stacked along the first preset direction and a piezoelectric layer arranged between two adjacent electrode layers, a slit is provided in the composite film layer, and the slit respectively penetrates two surfaces of the composite film layer opposite to each other in the first preset direction to divide the composite film layer into at least two cantilever beams, the slit comprises at least two first slits and at least one second slit, the number of the second slits is one less than the number of the first slits, and the second slits are respectively connected to the first slits on opposite sides of the first preset direction. The above-mentioned method for preparing a piezoelectric stack structure can relatively easily obtain a piezoelectric stack structure with a slit width as small as possible, a better low-frequency response, and a better low-frequency signal transmission effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A schematic diagram of the structure of a piezoelectric stack structure provided in an embodiment of the present application;

[0020] Figure 2 A schematic diagram of the deformation of the cantilever beam of the piezoelectric stack structure provided in an embodiment of the present application;

[0021] Figure 3 One of the schematic diagrams of the preparation process of the piezoelectric stack structure provided in the embodiment of the present application;

[0022] Figure 4 One of the flow charts of the method for preparing the piezoelectric stack structure provided in the embodiment of the present application;

[0023] Figure 5 A second schematic diagram of the preparation process of the piezoelectric stack structure provided in an embodiment of the present application;

[0024] Figure 6 A third schematic diagram of the preparation process of the piezoelectric stack structure provided in an embodiment of the present application;

[0025] Figure 7 Flow chart 2 of the method for preparing a piezoelectric stack structure provided in an embodiment of the present application;

[0026] Figure 8 A fourth schematic diagram of the preparation process of the piezoelectric stack structure provided in an embodiment of the present application;

[0027] Fig. 9 A fifth schematic diagram of the preparation process of the piezoelectric stack structure provided in an embodiment of the present application;

[0028] Fig.10 Flow chart 3 of the method for preparing a piezoelectric stack structure provided in an embodiment of the present application;

[0029] Fig.11 Flow chart 4 of the method for preparing a piezoelectric stack structure provided in an embodiment of the present application;

[0030] Fig.12 Flow chart 5 of the method for preparing a piezoelectric stack structure provided in an embodiment of the present application;

[0031] Fig.13 Schematic diagram six of the preparation process of the piezoelectric stack structure provided in the embodiment of the present application;

[0032] Fig.14 Schematic diagram of the preparation process of the piezoelectric stack structure provided in the embodiment of the present application;

[0033] Fig.15 An eighth schematic diagram of the preparation process of the piezoelectric stack structure provided in an embodiment of the present application;

[0034] Fig.16 A ninth schematic diagram of the preparation process of the piezoelectric stack structure provided in an embodiment of the present application;

[0035] Fig.17 Flow chart six of the method for preparing a piezoelectric stack structure provided in an embodiment of the present application;

[0036] Fig.18 A schematic diagram of the structure of a MEMS acoustic device provided in an embodiment of the present application.

[0037] Icons: 10-piezoelectric stack structure; 11-composite film layer; 111-first composite film layer; 1111-first composite sub-film layer; 1112-second composite sub-film layer; 112-second composite film layer; 113-electrode layer; 114-piezoelectric layer; 115-other film layers; 116-support layer; 12-slit; 121-first slit; 122-second slit; 13-cantilever beam; 14-acoustic channel; 151-first sacrificial layer; 152-second sacrificial layer Layer; 161-first groove; 162-second groove; 163-third groove; 20-base structure; 21-substrate; 211-first back cavity; 22-protective layer; 221-second back cavity; X-first preset direction; Y-second preset direction; Z-third preset direction; B-width of the first gap; H-depth of the second gap; T-vertical distance between the sides of two first gaps connected to the same second gap that are close to each other; L-depth of the first gap. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0039] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. It should be noted that, in the absence of conflict, the various features in the embodiments of the present application can be combined with each other, and the combined embodiments are still within the scope of protection of the present application.

[0040] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0041] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the application is usually placed when in use. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0042] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0043] The embodiment of the present application provides a method for preparing a piezoelectric stack structure, comprising: providing a base structure, and forming a composite film layer on the base structure along a first preset direction. The composite film layer comprises at least two electrode layers stacked along the first preset direction and a piezoelectric layer arranged between two adjacent electrode layers, and a slit is provided in the composite film layer, and the slit passes through two surfaces of the composite film layer opposite to each other in the first preset direction, so as to divide the composite film layer into at least two cantilever beams, and the slit comprises at least two first slits and at least one second slit, the number of the second slits is one less than the number of the first slits, and the second slits are respectively connected to the first slits on two opposite sides of the first preset direction.

[0044] Please refer to Figure 1 , with the base structure 20 as support, a composite film layer 11 is formed on the base structure 20. The composite film layer 11 includes multiple film layers, and the multiple film layers are stacked on the base structure 20 along the first preset direction X. Among the multiple film layers, at least two layers are electrode layers 113 and one layer is a piezoelectric layer 114, and the piezoelectric layer 114 is located between two adjacent electrode layers 113, thereby forming a film layer structure of a piezoelectric stack. In addition, the multiple film layers may also include other film layers 115, such as a support layer 116, etc.

[0045] The composite film layer 11 is provided with slits 12, and the slits 12 include at least two first slits 121 and at least one second slit 122. The at least two first slits 121 are arranged at intervals in the composite film layer 11, and two adjacent first slits 121 are connected through the second slit 122. One surface of the composite film layer 11 in the first preset direction X is penetrated by one first slit 121, and the other opposite surface is penetrated by another first slit 121. When the number of slits 12 is one, one slit 12 divides the composite film layer 11 into two cantilever beams 13; when the number of slits 12 is two or more, two or more slits 12 cooperate with each other to divide the composite film layer 11 into two or more cantilever beams 13.

[0046] The composite film layer 11 including the slits 12 is the piezoelectric stack structure 10 to be prepared. After the piezoelectric stack structure 10 is prepared, the base structure 20 can be removed or retained, depending on actual needs.

[0047] The gap (the first gap 121 or the second gap 122) has dimensions in three directions, wherein the dimension of the gap in the first preset direction X is the depth of the gap, the dimension in the second preset direction Y is the width of the gap, and the dimension in the third preset direction Z is the length of the gap. The first preset direction X, the second preset direction Y, and the third preset direction Z are perpendicular to each other.

[0048] In the piezoelectric stack structure 10 prepared by the above-mentioned method for preparing a piezoelectric stack structure, the slit 12 does not extend in a straight line along the thickness direction (i.e., the first preset direction X) of the piezoelectric stack structure 10, but has at least two turns inside the piezoelectric stack structure 10 to change the extension direction. The width of the slit 12 mainly depends on the depth H of the second slit, and the depth H of the second slit is no longer limited by the minimum processing width of the processing equipment. Reducing the depth H of the second slit will increase the flow rate of the sound wave, increase the viscosity, and thus increase the acoustic impedance. The greater the acoustic impedance, the more difficult it is for the sound to pass through the second slit 122, and the possibility of low-frequency signals leaking through the slit 12 is smaller, and the prepared piezoelectric stack structure 10 has the opportunity to receive signals in a wider frequency range. It is relatively easy to obtain a smaller depth H of the second slit in terms of technology, such as by growing an extremely thin film and releasing it, or by setting the photolithography depth to be smaller.

[0049] The area between the sides of the two first slits 121 connected to the second slit 122 in the slit 12 is the sound channel 14 ( Figure 1 Increasing the length of the sound channel 14 (i.e., increasing the vertical distance T between the sides of the two first slits connected to the same second slit) will increase the propagation path of the sound wave in the sound channel 14, thereby increasing the contact opportunity between the sound wave and the wall of the sound channel 14, increasing the viscosity, and increasing the acoustic impedance. Obtaining a larger length of the sound channel 14 is also relatively easy to achieve in terms of technology, as long as the distance between the two first slits 121 is increased.

[0050] In addition, the existence of the second gap 122 enables the two cantilever beams 13 to have a projection overlap area in the first preset direction X ( Figure 1 The area within the dotted line frame) Figure 2 When the cantilever beam 13 is deformed by the environment or external force, the prepared piezoelectric stack structure 10 can still maintain a small slit 12 width to ensure the transmission effect of low-frequency signals. However, the slit of the piezoelectric stack structure prepared by the existing method extends along a straight line, and when the cantilever beam is deformed by the environment or external force, the slit width will increase significantly.

[0051] Therefore, the piezoelectric stack structure preparation method described above can easily obtain a piezoelectric stack structure 10 with a slit 12 width as small as possible, a better low-frequency response, and a better low-frequency signal transmission effect.

[0052] It should be noted that the first slit 121 and the second slit 122 can be formed by etching grooves in the composite film layer 11 by processing equipment. Figure 3It can also be formed by forming a first sacrificial layer 151 and a second sacrificial layer 152 on the base structure 20, and releasing the first sacrificial layer 151 and the second sacrificial layer 152 after the composite film layer 11 wraps the first sacrificial layer 151 and the second sacrificial layer 152. The optional scheme will be described in detail later.

[0053] Optionally, the width B of the first gap is greater than the depth H of the second gap.

[0054] The processing of the first slit 121 is limited by the processing equipment, and its width is greater than or equal to the minimum processing width of the processing equipment. However, the depth H of the second slit is independent of the minimum processing width of the processing equipment, and a very small depth H of the second slit can be obtained relatively easily. The width of the slit 12 mainly depends on the depth H of the second slit. Therefore, limiting the depth H of the second slit to be less than the width B of the first slit can make the width of the slit 12 smaller, and the prepared piezoelectric stack structure 10 can have a better low-frequency response.

[0055] Optionally, a vertical distance T between mutually adjacent side surfaces of two first gaps connected to the same second gap is greater than a depth L of the first gap.

[0056] With such an arrangement, the two cantilever beams 13 of the prepared piezoelectric stack structure 10 have a larger projection overlap area in the first preset direction X. When the cantilever beam 13 is deformed by environmental influences or external forces, the piezoelectric stack structure 10 can still maintain a smaller slit 12 width, thereby ensuring the transmission effect of the low-frequency signal.

[0057] It should be noted that, in the present application, the sizes of at least two first slits 121 are not limited to be equal, nor are the sizes of at least two second slits 122 limited to be equal. Therefore, a certain parameter mentioned above may have multiple values, but all values ​​should satisfy the above size relationship. For example, when the number of first slits 121 is two and the widths B of the two first slits are not equal, the width B of the first slit has two values. At this time, the two values ​​of the width B of the first slit are both greater than the depth H of the second slit.

[0058] It can be understood that the smaller the depth H of the second gap, the larger the vertical distance T between the sides of the two first gaps connected to the same second gap that are close to each other, and the better the low-frequency response of the prepared piezoelectric stack structure 10. Therefore, when B>>H and / or T>>L, the prepared piezoelectric stack structure 10 can achieve better low-frequency response. However, the depth H of the second gap cannot be infinitely small, and the vertical distance T between the sides of the two first gaps connected to the same second gap that are close to each other cannot be infinitely large. Therefore, under the premise of taking into account the process difficulty, the size of the piezoelectric stack structure 10 and the low-frequency response, optionally, the vertical distance T between the sides of the two first gaps connected to the same second gap that are close to each other is 10 times or more than 10 times the depth L of the first gap.

[0059] Optionally, see Figure 4 , forming a composite film layer on the base structure along a first preset direction includes:

[0060] S100: Alternately forming the same number of first sacrificial layers and second sacrificial layers on the base structure along a first preset direction, and forming a first composite film layer wrapping the first sacrificial layer and the second sacrificial layer on the base structure along the first preset direction, wherein the first sacrificial layer is connected to the second sacrificial layer, the first sacrificial layer penetrates the surface of the first composite film layer facing the base structure, and the second sacrificial layer penetrates the surface of the first composite film layer facing away from the base structure, and if the number of the first sacrificial layers is at least two, the orthographic projections of two adjacent first sacrificial layers on the base structure do not overlap.

[0061] Please refer to Figure 3 and Figure 5 , the number of the first sacrificial layer 151 and the second sacrificial layer 152 is equal, and can be one, two or more. When the number of the first sacrificial layer 151 and the second sacrificial layer 152 are both one, the first sacrificial layer 151 is located on the side of the second sacrificial layer 152 facing the substrate structure 20, and is connected to the second sacrificial layer 152. When the number of the first sacrificial layer 151 and the second sacrificial layer 152 are both two or more, along the first preset direction X, the arrangement of the first sacrificial layer 151 and the second sacrificial layer 152 is: first sacrificial layer 151-second sacrificial layer 152-first sacrificial layer 151-...-second sacrificial layer 152, and the first sacrificial layer 151 and the second sacrificial layer 152 are connected in sequence.

[0062] The first composite film layer 111 is a part of the composite film layer 11. The first composite film layer 111 includes at least one film layer. When the number of film layers is two or more, each film layer is stacked along the first preset direction X. Figure 1, the membrane layer may be an electrode layer 113, a piezoelectric layer 114 or other membrane layer 115 (such as a support layer 116). Each membrane layer may be formed in sequence by thin film deposition. The first composite membrane layer 111 wraps the first sacrificial layer 151 and the second sacrificial layer 152. The first sacrificial layer 151 closest to the substrate structure 20 penetrates the surface of the first composite membrane layer 111 toward the substrate structure 20, and the second sacrificial layer 152 farthest from the substrate structure 20 penetrates the surface of the first composite membrane layer 111 away from the substrate structure 20.

[0063] In the subsequent process, the first sacrificial layer 151 is removed to form the first gap 121 in the first composite membrane layer 111, and the second sacrificial layer 152 is removed to form the second gap 122 in the first composite membrane layer 111. When there are two or more first sacrificial layers 151, the first sacrificial layers 151 on both sides of the same second sacrificial layer 152 are staggered, and the orthographic projections of the two on the base structure 20 have no overlapping area, so that the transverse sound channel 14 can be formed in the first composite membrane layer 111 after the first sacrificial layer 151 and the second sacrificial layer 152 are removed.

[0064] The first sacrificial layer 151 and the second sacrificial layer 152 are connected to ensure that the first gap 121 formed after the subsequent release is connected to the second gap 122. Under the premise of ensuring that the first sacrificial layer 151 and the second sacrificial layer 152 are connected, the first sacrificial layer 151 and the second sacrificial layer 152 can have a variety of relative positional relationships, so that the obtained first gap 121 and the second gap 122 also have a variety of relative positional relationships. For example, Figure 3 As shown, the end of the first sacrificial layer 151 is connected to the lower surface of the second sacrificial layer 152, and the right side surface of the first sacrificial layer 151 is flush with the right side surface of the second sacrificial layer 152. Figure 6 As shown, the first sacrificial layer 151 and the second sacrificial layer 152 may also be cross-connected, and the side surface of the first sacrificial layer 151 may not be flush with the side surface of the second sacrificial layer 152 .

[0065] In this embodiment, the preparation order of the first composite film layer 111, the first sacrificial layer 151 and the second sacrificial layer 152 is not limited. For example, the complete first composite film layer 111 may be prepared first, and then the first sacrificial layer 151 and the second sacrificial layer 152 may be prepared in the first composite film layer 111; or part of the first composite film layer 111 may be prepared first, and then the first sacrificial layer 151 and the second sacrificial layer 152 may be prepared, and then part of the first composite film layer 111 may be prepared. The first sacrificial layer 151 and the second sacrificial layer 152 may be formed by thin film deposition and etching. The first composite layer may be formed by thin film deposition.

[0066] S200: A second composite film layer covering the second sacrificial layer is formed on the surface of the first composite film layer facing away from the substrate structure, and a third groove is formed in the second composite film layer, wherein the third groove respectively penetrates two opposite surfaces of the second composite film layer, the third groove is connected to the second sacrificial layer, and the orthographic projection of the third groove and the first sacrificial layer adjacent thereto on the substrate structure do not overlap.

[0067] The second composite film layer 112 is also a part of the composite film layer 11. The second composite film layer 112 includes at least one film layer. When the number of film layers is two or more, each film layer is stacked along the first preset direction X. The film layer may be an electrode layer 113, a piezoelectric layer 114 or other film layer 115 (such as a support layer 116). Each film layer may be formed in sequence by thin film deposition.

[0068] The third groove 163 is formed in the second composite film layer 112 and penetrates the two opposite surfaces of the second composite film layer 112 in the first preset direction X. The third groove 163 is connected to the second sacrificial layer 152 farthest from the base structure 20. The third groove 163 is the second uppermost slit 122 in the piezoelectric stack structure 10 to be prepared. The outer contour formed by all the first sacrificial layers 151, all the second sacrificial layers 152 and the third groove 163 is the outer contour of the slit 12 to be formed in the piezoelectric stack structure 10. At the same time, the third groove 163 also exposes the second sacrificial layer 152 so as to release the second sacrificial layer 152 and the first sacrificial layer 151 connected to the second sacrificial layer 152 through the third groove 163.

[0069] The third groove 163 and the first sacrificial layer 151 located on both sides of the same second sacrificial layer 152 are staggered, and their orthographic projections on the base structure 20 have no overlapping area. In this way, a horizontal sound channel 14 can be formed after the first sacrificial layer 151 and the second sacrificial layer 152 are removed.

[0070] The third groove 163 can be formed by thin film etching. The third groove 163 can have a variety of relative position relationships with the second sacrificial layer 152, such as Figure 3 As shown, the end of the third groove 163 is connected to the upper surface of the second sacrificial layer 152, and the left side of the third groove 163 is flush with the left side of the second sacrificial layer 152. In other embodiments, the third groove 163 and the second sacrificial layer 152 may also be cross-connected, and the side of the third groove 163 may not be flush with the side of the second sacrificial layer 152.

[0071] S300: removing the first sacrificial layer and the second sacrificial layer to form a slit.

[0072] By removing all the first sacrificial layers 151 and the second sacrificial layers 152 , the slit 12 penetrating the first composite film layer 111 and the second composite film layer 112 can be obtained.

[0073] In the preparation method of the above-mentioned piezoelectric stack structure, the top second gap 122 is prepared separately, and the remaining equal number of first gaps 121 and second gaps 122 are obtained by forming a first sacrificial layer 151 and a second sacrificial layer 152 in the first composite film layer 111 and releasing them. The process is simple and easy to implement.

[0074] Optionally, see Figure 7 , alternately forming the same number of first sacrificial layers and second sacrificial layers on the base structure along a first preset direction, and forming a first composite film layer wrapping the first sacrificial layers and the second sacrificial layers on the base structure along the first preset direction, comprising:

[0075] S110: forming a first composite film layer on the base structure.

[0076] S120: forming the same number of first grooves and second grooves in the first composite film layer, and filling the first grooves with a first sacrificial layer, and filling the second grooves with a second sacrificial layer.

[0077] In this embodiment, please refer to Figure 8 and Fig. 9 First, a first composite film layer 111 is formed on the base structure 20, and then a first groove 161 and a second groove 162 are processed in the first composite film layer 111, and then the first groove 161 and the second groove 162 are filled with a sacrificial material, and finally a first sacrificial layer 151 and a second sacrificial layer 152 are formed which are wrapped by the first composite film layer 111. The first groove 161 and the second groove 162 can be formed by etching.

[0078] Optionally, see Fig.10 , forming the same number of first grooves and second grooves in the first composite film layer, filling the first grooves with a first sacrificial layer, and filling the second grooves with a second sacrificial layer comprises:

[0079] S121: forming a second groove on a surface of the first composite film layer facing away from the substrate structure, and forming a first groove at the bottom of the second groove, wherein the bottom of the first groove penetrates the surface of the first composite film layer facing the substrate structure.

[0080] S122: Filling the first groove and the second groove with a sacrificial material to form a first sacrificial layer filling the first groove and a second sacrificial layer filling the second groove.

[0081] Please refer to Figure 8 and Fig. 9When the number of the first groove 161 and the second groove 162 are both one, a complete first composite film layer 111 is directly formed on the base layer, and then the first groove 161 and the second groove 162 are processed. In this embodiment, a second groove 162 is processed on the surface of the first composite film layer 111 away from the base structure 20, and then a first groove 161 is directly processed at the bottom of the second groove 162. After that, the first sacrificial layer 151 and the second sacrificial layer 152 can be obtained at the same time by filling a single sacrificial material, and the process is simple and the processing efficiency is high.

[0082] In another embodiment, optionally, a first groove 161 is formed on the surface of the first composite film layer 111 away from the substrate structure 20, and a second groove 162 is formed on the surface of the first composite film layer 111 away from the substrate structure 20, wherein the first groove 161 penetrates the surface of the first composite film layer 111 facing the substrate structure 20, the second groove 162 is connected to the first groove 161, the width of the second groove 162 is greater than the width of the first groove 161, and the depth of the second groove 162 is less than the depth of the first groove 161.

[0083] That is, a first groove 161 is first processed through two opposite surfaces of the first composite film layer 111 in the first preset direction X, and then a second groove 162 which is wider and shallower than the first groove 161 is processed at the notch of the first groove 161. In this way, a first groove 161 and a second groove 162 can also be formed in the first composite film layer 111.

[0084] Of course, it is also possible to first form a first groove 161 in the first composite film layer 111 that penetrates two surfaces of the first composite film layer 111 that are opposite to each other in the first preset direction X, then fill the first groove 161 with a sacrificial material, and then process a second groove 162 that is wider and shallower than the first groove 161 at the notch of the first groove 161, and then fill the second groove 162 with a sacrificial material. In this way, the first sacrificial layer 151 and the second sacrificial layer 152 can also be obtained, but the efficiency is low.

[0085] When the number of the first groove 161 and the second groove 162 is two or more, optionally, please refer to Fig.11 , alternately forming the same number of first sacrificial layers and second sacrificial layers on the base structure along a first preset direction, and forming a first composite film layer wrapping the first sacrificial layers and the second sacrificial layers on the base structure along the first preset direction, comprising:

[0086] S130: forming a first composite sub-membrane layer on the base structure.

[0087] In this embodiment, please refer to Figure 5According to the number of the first sacrificial layers 151 and the second sacrificial layers 152, the first composite film layer 111 is divided into at least two first composite sub-film layers 1111 along the first direction, and the number of the first composite sub-film layers 1111 is equal to the number of the first sacrificial layers 151. By repeatedly preparing the first composite sub-film layers 1111, the first composite film layer 111 is finally obtained.

[0088] S140: forming a first groove and a second groove in the first composite sub-membrane layer, and filling the first groove with a first sacrificial layer, and filling the second groove with a second sacrificial layer.

[0089] A first groove 161 and a second groove 162 are first processed in the first composite sub-membrane layer 1111 , and then the first groove 161 and the second groove 162 are filled with sacrificial material, so as to finally form a first sacrificial layer 151 and a second sacrificial layer 152 wrapped by the first composite sub-membrane layer 1111 .

[0090] S150: forming another first composite sub-membrane layer on a surface of the first composite sub-membrane layer facing away from the base structure.

[0091] Another first composite sub-membrane layer 1111 is formed on the first composite sub-membrane layer 1111 , and the other first composite sub-membrane layer 1111 also includes at least one film layer. However, the compositions of the two first composite sub-membrane layers 1111 may be different, and the number of film layers may also be different.

[0092] S160: forming a first groove and a second groove in another first composite sub-film layer, and filling the first groove with a first sacrificial layer, and filling the second groove with a second sacrificial layer.

[0093] A first groove 161 and a second groove 162 are first processed in another first composite sub-membrane layer 1111 , and then the first groove 161 and the second groove 162 are filled with sacrificial material, so as to finally form a first sacrificial layer 151 and a second sacrificial layer 152 wrapped by another first composite sub-membrane layer 1111 .

[0094] S170: Repeat the steps of forming a first composite sub-membrane layer, a first groove, a second groove, a first sacrificial layer, and a second sacrificial layer until all the first sacrificial layers and the second sacrificial layers are formed.

[0095] Repeat steps S150 and S160 until all the first sacrificial layers 151 and the second sacrificial layers 152 are formed, and thus the first composite film layer 111 that simultaneously wraps at least two first sacrificial layers 151 and at least two second sacrificial layers 152 can be obtained. By dividing the first composite film layer 111 into a plurality of first composite sub-film layers 1111, only one first sacrificial layer 151 and second sacrificial layer 152 are prepared in one first composite sub-film layer 1111 each time, which can significantly reduce the difficulty of preparing the first sacrificial layer 151 and second sacrificial layer 152.

[0096] Optionally, see Fig.12 , forming a first groove and a second groove in the first composite sub-film layer, and filling the first groove with a first sacrificial layer, and filling the second groove with a second sacrificial layer comprises:

[0097] S141: forming a second groove on the surface of the first composite sub-membrane layer facing away from the base structure, and forming a first groove at the bottom of the second groove, wherein the bottom of the first groove penetrates the surface of the first composite sub-membrane layer facing the base structure.

[0098] S142: Filling the first groove and the second groove with a sacrificial material to form a first sacrificial layer filling the first groove and a second sacrificial layer filling the second groove.

[0099] Forming a first groove and a second groove in another first composite sub-film layer, and filling the first groove with a first sacrificial layer, and filling the second groove with a second sacrificial layer comprises:

[0100] S161: forming a second groove on a surface of another first composite sub-membrane layer facing away from the base structure, and forming a first groove at the bottom of the second groove, wherein the bottom of the first groove penetrates the surface of another first composite sub-membrane layer facing the base structure.

[0101] S162: Filling the first groove and the second groove with a sacrificial material to form a first sacrificial layer filling the first groove and a second sacrificial layer filling the second groove.

[0102] In this embodiment, please refer to Figure 5 A second groove 162 is processed on the surface of the first composite sub-membrane layer 1111 away from the substrate structure 20, and then a first groove 161 is directly processed at the bottom of the second groove 162. After that, the first sacrificial layer 151 and the second sacrificial layer 152 can be obtained at the same time by filling a single sacrificial material. The process is simple and the processing efficiency is high.

[0103] In another embodiment, optionally, a first groove 161 is formed on the surface of the first composite sub-membrane layer 1111 facing away from the substrate structure 20, and then a second groove 162 is formed on the surface of the first composite sub-membrane layer 1111 facing away from the substrate structure 20, wherein the first groove 161 penetrates the surface of the first composite sub-membrane layer 1111 facing the substrate structure 20, the second groove 162 is connected to the first groove 161, the width of the second groove 162 is greater than the width of the first groove 161, and the depth of the second groove 162 is less than the depth of the first groove 161.

[0104] That is, first, a first groove 161 is processed through the two opposite surfaces of the first composite sub-membrane layer 1111 in the first preset direction X, and then a second groove 162 which is wider and shallower than the first groove 161 is processed at the notch of the first groove 161. In this way, a first groove 161 and a second groove 162 can also be formed in the first composite sub-membrane layer 1111.

[0105] Of course, it is also possible to first form a first groove 161 in the first composite sub-membrane layer 1111 that penetrates two surfaces of the first composite sub-membrane layer 1111 that are opposite to each other in the first preset direction X, and then fill the first groove 161 with a sacrificial material, and then process a second groove 162 that is wider and shallower than the first groove 161 at the notch of the first groove 161, and then fill the second groove 162 with a sacrificial material. In this way, the first sacrificial layer 151 and the second sacrificial layer 152 can also be obtained, but the efficiency is low.

[0106] In the aforementioned embodiments, a film structure is first formed, a groove is then machined in the film structure, and then a sacrificial material is used to fill the groove to obtain the first sacrificial layer 151 and the second sacrificial layer 152. In other embodiments, a sacrificial layer may be prepared first, and then a film structure that wraps the sacrificial layer may be prepared.

[0107] Optionally, please refer to Figures 13 to 15 , Fig. 9 , firstly, a first sacrificial layer 151 is formed on the base structure 20, then a second composite sub-membrane layer 1112 is formed to wrap the first sacrificial layer 151, then a second sacrificial layer 152 is formed on the second composite sub-membrane layer 1112, and then another second composite sub-membrane layer 1112 is formed to wrap the second sacrificial layer 152. The above process is repeated until all the first sacrificial layers 151 and the second sacrificial layers 152 are prepared.

[0108] All the second composite sub-layers 1112 together constitute the first composite layer 111. The first sacrificial layer 151, the second sacrificial layer 152 and the second composite sub-layer 1112 can be formed by deposition and etching of thin films.

[0109] Fig. 9In the embodiment, the first sacrificial layer 151 does not exceed the range of the first groove 161, that is, the first sacrificial layer 151 is entirely located in the first groove 161, and the second sacrificial layer 152 does not exceed the range of the second groove 162, that is, the second sacrificial layer 152 is entirely located in the second groove 162. However, in the actual preparation process, Fig.16 As shown, the first sacrificial layer 151 may exceed the range of the first groove 161, that is, the upper surface of the first sacrificial layer 151 protrudes from the first groove 161, and the second sacrificial layer 152 may also exceed the range of the second groove 162, that is, the upper surface of the second sacrificial layer 152 protrudes from the second groove 162. If there are first sacrificial layers 151 exceeding the range of the first groove 161 among the preset number of first sacrificial layers 151, and / or, there are second sacrificial layers 152 exceeding the range of the second groove 162 among the preset number of second sacrificial layers 152, the upper surface of the first composite film layer 111 and the surface of the film layer formed on the first composite film layer 111 in the subsequent steps may be uneven. Therefore, preferably, the two opposite surfaces of the first sacrificial layer 151 in the first preset direction X are respectively flush with the opposite ends of the first groove 161 in the first preset direction X, and the two opposite surfaces of the second sacrificial layer 152 in the first preset direction X are respectively flush with the opposite ends of the second groove 162 in the first preset direction X.

[0110] Optionally, see Fig.17 , providing a base structure, and forming a composite film layer on the base structure along a first preset direction includes:

[0111] S10: providing a substrate, and sequentially forming a protective layer and a composite film layer on a surface of the substrate along a first preset direction.

[0112] After forming the composite film layer on the base structure along the first preset direction, the method further includes:

[0113] S20: forming a first back cavity on a surface of the substrate away from the protective layer, wherein the first back cavity penetrates two opposite surfaces of the substrate.

[0114] S30: removing the area on the protective layer corresponding to the first back cavity to form a second back cavity on the protective layer, wherein the first back cavity, the second back cavity and the slit are sequentially connected.

[0115] Please refer to Fig.18 The first back cavity 211 on the substrate 21 and the second back cavity 221 on the protective layer 22 provide a stable sound pressure environment for the cantilever beam 13, ensuring that the vibration of the cantilever beam 13 can be accurately detected. The first back cavity 211 can be formed by a back etching process, and the second back cavity 221 can be formed by a thin film etching process. The protective layer 22 is used to avoid damage to the composite film layer 11 when forming the first back cavity 211. For example, the material of the protective layer 22 is silicon oxide.

[0116] It should be understood that, although the steps in each flowchart are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a part of the steps in each flowchart may include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0117] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. The present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a piezoelectric stack structure, characterized in that: include: A base structure is provided, and a composite film layer is formed on the base structure along a first preset direction, wherein the composite film layer includes at least two electrode layers stacked along the first preset direction and a piezoelectric layer arranged between two adjacent electrode layers, and a slit is provided in the composite film layer, and the slit respectively penetrates two opposite surfaces of the composite film layer in the first preset direction to divide the composite film layer into at least two cantilever beams, and the slit includes at least two first slits and at least one second slit, the number of the second slits is one less than the number of the first slits, and the second slits are respectively connected to the first slits on two opposite sides in the first preset direction.

2. The method for preparing a piezoelectric stack structure according to claim 1, wherein: The width of the first gap is greater than the depth of the second gap.

3. The method for preparing a piezoelectric stack structure according to claim 2, wherein: A vertical distance between mutually adjacent side surfaces of two first slits connected to the same second slit is greater than a depth of the first slit.

4. The method for preparing a piezoelectric stack structure according to claim 1, wherein: The forming of a composite film layer on the base structure along a first preset direction comprises: An equal number of first sacrificial layers and second sacrificial layers are alternately formed on the base structure along a first preset direction, and a first composite film layer wrapping the first sacrificial layer and the second sacrificial layer is formed on the base structure along the first preset direction, wherein the first sacrificial layer is connected to the second sacrificial layer, the first sacrificial layer penetrates the surface of the first composite film layer facing the base structure, and the second sacrificial layer penetrates the surface of the first composite film layer facing away from the base structure, and if the number of the first sacrificial layers is at least two, the orthographic projections of two adjacent first sacrificial layers on the base structure do not overlap; A second composite film layer covering the second sacrificial layer is formed on a surface of the first composite film layer facing away from the base structure, and a third groove is formed in the second composite film layer, wherein the third groove penetrates two opposite surfaces of the second composite film layer respectively, the third groove is connected to the second sacrificial layer, and the third groove and the orthographic projection of the first sacrificial layer adjacent thereto on the base structure do not overlap; The first sacrificial layer and the second sacrificial layer are removed to form a slit.

5. The method for preparing a piezoelectric stack structure according to claim 4, characterized in that: The method of alternately forming the same number of first sacrificial layers and second sacrificial layers on the base structure along a first preset direction, and forming a first composite film layer wrapping the first sacrificial layers and the second sacrificial layers on the base structure along the first preset direction comprises: forming a first composite film layer on the base structure; The same number of first grooves and second grooves are formed in the first composite film layer, and the first grooves are filled with a first sacrificial layer, and the second grooves are filled with a second sacrificial layer.

6. The method for preparing a piezoelectric stack structure according to claim 5, characterized in that: The method of alternately forming the same number of first sacrificial layers and second sacrificial layers on the base structure along a first preset direction, and forming a first composite film layer wrapping the first sacrificial layers and the second sacrificial layers on the base structure along the first preset direction comprises: forming a first composite sub-membrane layer on the base structure; Forming a first groove and a second groove in the first composite sub-film layer, and filling the first groove with a first sacrificial layer, and filling the second groove with a second sacrificial layer; forming another first composite sub-film layer on a surface of the first composite sub-film layer away from the base structure; forming a first groove and a second groove in another first composite sub-film layer, and filling the first sacrificial layer in the first groove and filling the second sacrificial layer in the second groove; The steps of forming the first composite sub-membrane layer, the first groove, the second groove, the first sacrificial layer and the second sacrificial layer are repeated until all the first sacrificial layer and the second sacrificial layer are formed.

7. The method for preparing a piezoelectric stack structure according to claim 5, characterized in that: The forming of the same number of first grooves and second grooves in the first composite film layer, and filling the first grooves with a first sacrificial layer, and filling the second grooves with a second sacrificial layer comprises: A second groove is formed on the surface of the first composite film layer facing away from the base structure, and a first groove is formed at the bottom of the second groove, wherein the bottom of the first groove penetrates the surface of the first composite film layer facing the base structure; A sacrificial material is filled into the first groove and the second groove to form a first sacrificial layer filling the first groove and a second sacrificial layer filling the second groove.

8. The method for preparing a piezoelectric stack structure according to claim 6, wherein: The forming of a first groove and a second groove in the first composite sub-film layer, and filling the first groove with a first sacrificial layer, and filling the second groove with a second sacrificial layer comprises: A second groove is formed on the surface of the first composite sub-membrane layer facing away from the base structure, and a first groove is formed at the bottom of the second groove, wherein the bottom of the first groove penetrates the surface of the first composite sub-membrane layer facing the base structure; Filling the first groove and the second groove with a sacrificial material to form a first sacrificial layer filling the first groove and a second sacrificial layer filling the second groove; The forming of the first groove and the second groove in another first composite sub-film layer, and filling the first sacrificial layer in the first groove and filling the second sacrificial layer in the second groove comprises: A second groove is formed on the surface of another first composite sub-film layer facing away from the base structure, and a first groove is formed at the bottom of the second groove, wherein the bottom of the first groove penetrates the surface of another first composite sub-film layer facing the base structure; A sacrificial material is filled into the first groove and the second groove to form a first sacrificial layer filling the first groove and a second sacrificial layer filling the second groove.

9. The method for preparing a piezoelectric stack structure according to claim 5, characterized in that: Two opposite surfaces of the first sacrificial layer in the first preset direction are respectively flush with opposite ends of the first groove in the first preset direction, and two opposite surfaces of the second sacrificial layer in the first preset direction are respectively flush with opposite ends of the second groove in the first preset direction.

10. The method for preparing a piezoelectric stack structure according to claim 1, wherein: The step of providing a base structure and forming a composite film layer on the base structure along a first preset direction comprises: Providing a substrate, and sequentially forming a protective layer and a composite film layer on a surface of the substrate along a first preset direction; After forming the composite film layer on the base structure along the first preset direction, the method further includes: forming a first back cavity on a surface of the substrate facing away from the protective layer, wherein the first back cavity penetrates two opposite surfaces of the substrate; An area on the protective layer corresponding to the first back cavity is removed to form a second back cavity on the protective layer, wherein the first back cavity, the second back cavity and the slit are connected in sequence.

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