A method for preparing a piezoelectric structure

Abstract

The present application provides a method for preparing a piezoelectric structure, which relates to the field of semiconductor technology. The method for preparing the piezoelectric structure includes: providing a base structure, and forming a first piezoelectric layer on the base structure; forming a metal layer on the first piezoelectric layer; forming a second piezoelectric layer on the metal layer; etching the second piezoelectric layer, the metal layer and the first piezoelectric layer at one time using an etching gas to form a first gap that runs through the second piezoelectric layer, the metal layer and the first piezoelectric layer. The method for preparing the piezoelectric structure utilizes the "redeposition effect" that exists in the etching process of piezoelectric materials. By adding a metal layer between the first piezoelectric layer and the second piezoelectric layer, and then cooperating with a one-step etching, the protective effect of the redeposition effect on the side wall of the first gap is increased, and a larger inclination angle of the first gap can be achieved. By adjusting the ratio of metal etching gas and piezoelectric etching gas in the etching menu, while preparing a first gap with a small line width, the free control of the bottom width of the first gap is also achieved.

Description

Technical Field

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

[0002] Piezoelectric MEMS microphones have been widely used in electronic products due to their simple structure, waterproof and dustproof, low power consumption, etc. Piezoelectric MEMS microphones are mainly composed of a piezoelectric structure and an ASIC circuit. A gap is provided on the piezoelectric structure, and the gap runs through the piezoelectric structure to form a cantilever beam.

[0003] During the manufacturing process of piezoelectric MEMS microphones, the thickness of the piezoelectric layer often needs to be above 1µm, so that sufficient charge output can be achieved and device performance can be guaranteed. However, due to the relatively small etching selectivity of piezoelectric materials and photoresists, when etching a piezoelectric layer of 1µm or more thickness, the thickness of the photoresist used needs to be at least 4 times the thickness of the piezoelectric layer (that is, the thickness of the photoresist is required to be no less than 4µm). However, for the photolithography process of cantilever beam gaps, if gaps of 1µm or less are to be prepared, the thickness of the photoresist is required to be 3 times or less of the gap width (that is, the thickness of the photoresist is required to be less than 3µm). It can be seen from the above data that there is a certain conflict in the process implementation between preparing small gap structures and ensuring device performance. Summary of the invention

[0004] The purpose of the present application is to provide a method for preparing a piezoelectric structure in view of the above-mentioned deficiencies in the prior art, which can achieve a small gap width while ensuring the performance of the piezoelectric MEMS microphone device.

[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 structure, comprising: providing a base structure, and forming a first piezoelectric layer on the base structure; forming a metal layer on the first piezoelectric layer, wherein the metal layer completely covers the first piezoelectric layer or covers a portion of the first piezoelectric layer; forming a second piezoelectric layer on the metal layer; and etching the second piezoelectric layer, the metal layer, and the first piezoelectric layer at one time using an etching gas to form a first gap that runs through the second piezoelectric layer, the metal layer, and the first piezoelectric layer.

[0007] Optionally, providing a base structure and forming a first piezoelectric layer on the base structure includes: providing a base structure and forming a first electrode layer on the base structure; forming a first piezoelectric layer on the first electrode layer; using an etching gas to etch the second piezoelectric layer, the metal layer and the first piezoelectric layer at one time to form a first gap that passes through the second piezoelectric layer, the metal layer and the first piezoelectric layer. The first piezoelectric layer includes: using an etching gas to etch the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time to form a first gap that passes through the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer.

[0008] Optionally, after forming the second piezoelectric layer on the metal layer, the method further includes: forming a second electrode layer on the second piezoelectric layer; etching the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time using an etching gas to form a first gap that penetrates the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer. The method further includes: etching the second electrode layer, the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time using an etching gas to form a first gap that penetrates the second electrode layer, the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer.

[0009] Optionally, after forming the second piezoelectric layer on the metal layer, the method further includes: forming a second electrode layer on the second piezoelectric layer; etching the second electrode layer using an etching gas to form a second gap extending through the second electrode layer; etching the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time using an etching gas to form a first gap extending through the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer, including: introducing an etching gas into the second gap to etch the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time to form a first gap extending through the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer.

[0010] Optionally, after forming the second piezoelectric layer on the metal layer, the method also includes: alternately forming a third electrode layer and a third piezoelectric layer on the second piezoelectric layer; etching the third electrode layer and the third piezoelectric layer using an etching gas to form a third gap that penetrates the third electrode layer and the third piezoelectric layer; etching the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time using an etching gas to form a first gap that penetrates the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer, including: introducing an etching gas into the third gap to etch the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time to form a first gap that penetrates the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer.

[0011] Optionally, the side of the uppermost third piezoelectric layer facing away from the second piezoelectric layer has a third electrode layer.

[0012] Optionally, the etching gas includes metal etching gas and piezoelectric etching gas.

[0013] Optionally, the metal etching gas is a fluorine-containing gas, and the piezoelectric etching gas is a chlorine-containing gas.

[0014] Optionally, the thickness of the metal layer is smaller than the thickness of the first piezoelectric layer and the thickness of the second piezoelectric layer, respectively.

[0015] Optionally, after etching the second piezoelectric layer, the metal layer and the first piezoelectric layer at one time using an etching gas to form a first gap that penetrates the second piezoelectric layer, the metal layer and the first piezoelectric layer, the method further includes: cleaning the first gap to remove a redeposition layer formed on the surface of the first gap due to a redeposition effect.

[0016] The beneficial effects of this application include:

[0017] The present application provides a method for preparing a piezoelectric structure, comprising: providing a base structure, and forming a first piezoelectric layer on the base structure; forming a metal layer on the first piezoelectric layer, wherein the metal layer completely covers the first piezoelectric layer or covers part of the first piezoelectric layer; forming a second piezoelectric layer on the metal layer; etching the second piezoelectric layer, the metal layer and the first piezoelectric layer at one time using an etching gas to form a first gap that penetrates the second piezoelectric layer, the metal layer and the first piezoelectric layer. The method for preparing the piezoelectric structure utilizes the "redeposition effect" existing in the etching process of the piezoelectric material. By adding a metal layer between the first piezoelectric layer and the second piezoelectric layer, and then cooperating with a one-step etching, the protective effect of the redeposition effect on the side wall of the first gap is increased, and a larger inclination angle of the first gap can be achieved. Without reducing the thickness of the first piezoelectric layer and the second piezoelectric layer, the bottom width of the first gap can also be made smaller. In addition, by adjusting the ratio of the metal etching gas and the piezoelectric etching gas in the etching menu, while preparing the first gap with a small line width, the free control of the bottom width of the first gap is also achieved. 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 One of the flow charts of the method for preparing a piezoelectric structure provided in an embodiment of the present application;

[0020] Figure 2 One of the schematic diagrams of the preparation process of the piezoelectric structure provided in the embodiment of the present application;

[0021] Figure 3 The second schematic diagram of the preparation process of the piezoelectric structure provided in the embodiment of the present application;

[0022] Figure 4 One of the structural schematic diagrams of the piezoelectric structure provided in the embodiment of the present application;

[0023] Figure 5 This is a SEM diagram of the sidewall tilt angle of the first gap after etching through the metal layer;

[0024] Figure 6 Flow chart 2 of the method for preparing a piezoelectric structure provided in an embodiment of the present application;

[0025] Figure 7 The second structural schematic diagram of the piezoelectric structure provided in the embodiment of the present application;

[0026] Figure 8 Flow chart 3 of the method for preparing a piezoelectric structure provided in an embodiment of the present application;

[0027] Fig. 9 Schematic diagram of the piezoelectric structure provided in the embodiment of the present application Figure 3 ;

[0028] Fig.10 Flow chart 4 of the method for preparing a piezoelectric structure provided in an embodiment of the present application;

[0029] Fig.11 Schematic diagram of the piezoelectric structure provided in the embodiment of the present application Figure 4 ;

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

[0031] Fig.13 Schematic diagram of the piezoelectric structure provided in the embodiment of the present application Figure 5 ;

[0032] Fig.14 Flow chart six of the method for preparing a piezoelectric structure provided in an embodiment of the present application;

[0033] Fig.15 Schematic diagram of the piezoelectric structure provided in the embodiment of the present application Figure 6 .

[0034] Icon: 10-substrate structure; 21-first piezoelectric layer; 22-second piezoelectric layer; 23-third piezoelectric layer; 30-metal layer; 40-patterned mask layer; 41-mask opening; 50-redeposition layer; 61-first electrode layer; 62-second electrode layer; 63-third electrode layer; 100-first gap; 200-second gap; 300-third gap; θ-tilt angle; B-bottom width of the first gap. DETAILED DESCRIPTION

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] Please refer to Figure 1 , the present application embodiment provides a method for preparing a piezoelectric structure, comprising:

[0041] S100: providing a substrate structure, and forming a first piezoelectric layer on the substrate structure.

[0042] Please refer to Figure 2The base structure 10 can provide a growth surface for the film layer and can also provide support for the film layer. The material of the first piezoelectric layer 21 may include aluminum nitride (AlN), scandium-doped aluminum nitride (AlScN), lithium niobate (LiNbO3), lithium tantalate (LiTaO3), lead zirconate titanate (PZT), zinc oxide (ZnO), quartz crystal and other materials. The thickness of the first piezoelectric layer 21 may be 0.1μm~2μm.

[0043] Illustratively, forming the first piezoelectric layer on the substrate structure includes: depositing a layer of piezoelectric material on the substrate structure using a deposition process to form the first piezoelectric layer.

[0044] Illustratively, the substrate structure 10 includes a substrate layer and other film layers disposed on the substrate layer.

[0045] The material of the base layer may include silicon oxide (SiO x ), silicon nitride (SiN) and silicon (Si), etc. The materials of other film layers may include metal materials (such as molybdenum, copper, titanium, etc.), non-metallic materials (such as silicon nitride, silicon oxide, etc.), and composite materials formed by any stacking combination of the above materials.

[0046] S200: forming a metal layer on the first piezoelectric layer, wherein the metal layer completely covers the first piezoelectric layer or covers a portion of the first piezoelectric layer.

[0047] A metal layer 30 is formed on the side of the first piezoelectric layer 21 facing away from the substrate structure 10. The metal layer 30 can completely cover the first piezoelectric layer 21 (eg, Figure 2 As shown in FIG. 1 ), or only part of the first piezoelectric layer 21 may be covered (as shown in FIG. Figure 3 When the metal layer 30 only covers a portion of the first piezoelectric layer 21 , the metal layer 30 needs to cover at least the region on the first piezoelectric layer 21 for forming the first slit 100 .

[0048] The metal layer 30 may be a single-layer metal film layer, or a composite film layer formed by stacking two or more metal film layers.

[0049] The material of the metal layer 30 may include metal materials such as molybdenum (Mo), ruthenium (Ru), aluminum (Al), copper (Cu), etc. The thickness of the metal layer 30 may be 10 nm to 1 μm.

[0050] S300: forming a second piezoelectric layer on the metal layer.

[0051] The second piezoelectric layer 22 is formed on the side of the metal layer 30 away from the base structure 10. The second piezoelectric layer 22 can be formed by a deposition process. If the metal layer 30 completely covers the first piezoelectric layer 21, the second piezoelectric layer 22 preferably completely covers the metal layer 30; if the metal layer 30 covers a portion of the first piezoelectric layer 21, the second piezoelectric layer 22 preferably completely covers the metal layer 30 and completely covers the first piezoelectric layer 21 exposed by the metal layer 30.

[0052] The material of the second piezoelectric layer 22 may be the same as or different from that of the first piezoelectric layer 21 . The thickness of the second piezoelectric layer 22 may be the same as or different from that of the first piezoelectric layer 21 .

[0053] S400: etching the second piezoelectric layer, the metal layer and the first piezoelectric layer at one time using an etching gas to form a first gap penetrating the second piezoelectric layer, the metal layer and the first piezoelectric layer.

[0054] The second piezoelectric layer 22, the metal layer 30 and the first piezoelectric layer 21 are etched with an etching gas, and the etching is performed only once, and the second piezoelectric layer 22, the metal layer 30 and the first piezoelectric layer 21 are completely penetrated in one time, thereby forming a first slit 100. If the base structure 10 will be removed in a subsequent process, only the first slit 100 needs to penetrate the first piezoelectric layer 21 in one etching; if the base structure 10 will not be removed in a subsequent process, the first slit 100 also needs to penetrate the base structure 10 in one etching.

[0055] For example, etching the second piezoelectric layer, the metal layer and the first piezoelectric layer at one time using an etching gas includes: forming a patterned mask layer 40 on the second piezoelectric layer 22, wherein the patterned mask layer 40 has a mask opening 41; and introducing the etching gas into the mask opening 41 to etch the second piezoelectric layer 22, the metal layer 30 and the first piezoelectric layer 21 at one time. After the etching is completed, the patterned mask layer 40 can be removed.

[0056] The etching gas includes a metal etching gas and a piezoelectric etching gas. Among them, under the premise of the same machine parameter setting and only changing the type of gas, the metal etching gas is mainly used to etch the metal layer 30, and its etching rate for the metal layer 30 is significantly higher than that for the first piezoelectric layer 21 and the second piezoelectric layer 22. The piezoelectric etching gas is mainly used to etch the piezoelectric layer, and its etching rate for the first piezoelectric layer 21 and the second piezoelectric layer 22 is significantly higher than that for the metal layer 30.

[0057] Please refer to Figure 4During the ion beam processing, the sputtered atoms and some reaction products will be redeposited on the surface to form a protective film (redeposition layer 50) to prevent the ion beam from directly etching the bottom surface and side walls. In the etching edge area, due to the change in the ion beam incident angle, the thickness of the redeposition layer 50 will increase significantly. This non-uniform redeposition layer 50 will cause the etching speed to be different in different areas, thereby forming a non-vertical morphology and causing the side wall of the first gap 100 to be tilted.

[0058] Due to the existence of the above-mentioned redeposition effect, the side wall of the first gap 100 will be tilted and there will be a redeposition layer 50, and the first gap 100 will present a morphological structure that is wide at the top and narrow at the bottom. However, for the etching of a single material film layer, the thickness of the redeposition layer 50 and the protective effect on the side wall of the first gap 100 are limited. Therefore, in order to enhance the redeposition effect, the present application divides the single piezoelectric layer into a first piezoelectric layer 21 and a second piezoelectric layer 22, and a metal layer 30 is provided between the first piezoelectric layer 21 and the second piezoelectric layer 22. When etching to the metal layer 30, due to the introduction of new metal elements into the reaction product, the volatility of the reaction product will be reduced, resulting in an increase in the thickness and yield of the redeposition layer 50 compared to when etching a single piezoelectric layer, which will further enhance the protection of the side wall of the first gap 100, thereby obtaining a first gap 100 that is obviously wide at the top and narrow at the bottom.

[0059] Figure 5 The effect of etching the metal layer 30 on the sidewall tilt angle θ of the first slit 100 after the metal layer 30 is introduced is shown. When the etching process reaches and passes through the metal layer 30, the sidewall tilt angle θ of the first slit 100 changes significantly, and the sidewall tilt angle θ of the first slit 100 decreases to about 14 to 15 degrees.

[0060] Generally, when the proportion of metal etching gas increases compared to that of piezoelectric etching gas, volatile reaction products increase, the redeposition effect weakens, the inclination angle θ of the side wall of the first slit 100 increases, and the first slit bottom width B increases; when the proportion of metal etching gas decreases compared to that of piezoelectric etching gas, volatile reaction products decrease, the redeposition effect increases, the inclination angle θ of the side wall of the first slit 100 decreases, and the first slit bottom width B decreases. It can be seen that by reducing the proportion of metal etching gas, enhancing the redeposition effect, and reducing the inclination angle θ of the side wall of the first slit 100, the first slit bottom width B can be reduced, thereby achieving a smaller bottom slit opening under the same mask opening 41, breaking through the photolithography process.

[0061] The preparation method of the piezoelectric structure above utilizes the "redeposition effect" existing in the etching process of the piezoelectric material. By adding a metal layer 30 between the first piezoelectric layer 21 and the second piezoelectric layer 22, and then cooperating with a one-step etching, the protective effect of the redeposition effect on the side wall of the first slit 100 is increased, and a larger tilt angle θ of the first slit 100 can be achieved. It is not necessary to reduce the thickness of the first piezoelectric layer 21 and the second piezoelectric layer 22, and the bottom width B of the first slit can also be made smaller. In addition, by adjusting the ratio of the metal etching gas and the piezoelectric etching gas in the etching menu, while preparing the first slit 100 with a small line width, the free control of the bottom width B of the first slit is also achieved.

[0062] Optionally, the etching gas includes a metal etching gas and a piezoelectric etching gas, and the proportion of the piezoelectric etching gas is greater than the proportion of the metal etching gas. In a certain embodiment, the proportion of the piezoelectric etching gas is 8 to 10 times the proportion of the metal etching gas. Within this range, the redeposition effect is strong, and it can be ensured that the first gap 100 penetrates the first piezoelectric layer 21.

[0063] It should be noted that the above gas ratio range is only the ratio obtained in a certain example. For different models and types of operating machines and different operating menus, the obtained gas ratio range will be different.

[0064] Optionally, the metal etching gas is a fluorine-containing gas, and the piezoelectric etching gas is a chlorine-containing gas.

[0065] Optionally, the thickness of the metal layer 30 is smaller than the thickness of the first piezoelectric layer 21 and the thickness of the second piezoelectric layer 22 .

[0066] Such an arrangement allows the reaction products generated when etching the metal layer 30 to be smoothly deposited on the sidewall of the first slit 100 located in the second piezoelectric layer 22 , so as to reduce the bottom width B of the first slit.

[0067] Optionally, see Figure 6 , providing a substrate structure, and forming a first piezoelectric layer on the substrate structure comprises:

[0068] S110: providing a substrate structure, and forming a first electrode layer on the substrate structure.

[0069] S120: forming a first piezoelectric layer on the first electrode layer.

[0070] Etching the second piezoelectric layer, the metal layer, and the first piezoelectric layer at one time using an etching gas to form a first gap penetrating the second piezoelectric layer, the metal layer, and the first piezoelectric layer comprises:

[0071] S410: etching the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time using an etching gas to form a first gap penetrating the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer.

[0072] Please refer to Figure 7 , a first electrode layer 61 may be provided between the first piezoelectric layer 21 and the base structure 10. The material of the first electrode layer 61 may be the same as or different from the material of the metal layer 30. The thickness of the first electrode layer 61 may be the same as or different from the thickness of the metal layer 30. When the first electrode layer 61 is present, the etching gas needs to penetrate the second piezoelectric layer 22, the metal layer 30, the first piezoelectric layer 21 and the first electrode layer 61 at the same time during one etching process, thereby obtaining a first gap 100 that is wide at the top and narrow at the bottom. Whether it is necessary to penetrate the base structure 10 depends on whether the base structure 10 is removed in the subsequent process.

[0073] Optionally, see Figure 8 After forming a second piezoelectric layer on the metal layer, the method further comprises:

[0074] S510: forming a second electrode layer on the second piezoelectric layer.

[0075] Etching the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time using an etching gas to form a first gap that penetrates the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer comprises:

[0076] S420: etching the second electrode layer, the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time using an etching gas to form a first gap penetrating the second electrode layer, the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer.

[0077] Please refer to Figure 7 , a second electrode layer 62 is formed on the second piezoelectric layer 22, so that a piezoelectric stack structure in the form of "electrode layer-piezoelectric layer-electrode layer" can be formed. It can be understood that when the metal layer 30 completely covers the first piezoelectric layer 21, the metal layer 30 can be regarded as an intermediate electrode layer. Fig. 9 When the metal layer 30 covers a portion of the first piezoelectric layer 21, the first piezoelectric layer 21 and the second piezoelectric layer 22 can be regarded as one piezoelectric layer. An etching gas is used to perform one etching, thereby forming a first gap 100 that simultaneously penetrates the second electrode layer 62, the second piezoelectric layer 22, the metal layer 30, the first piezoelectric layer 21 and the first electrode layer 61.

[0078] Optionally, see Fig.10 After forming a second piezoelectric layer on the metal layer, the method further comprises:

[0079] S510: forming a second electrode layer on the second piezoelectric layer.

[0080] S520: etching the second electrode layer using an etching gas to form a second gap penetrating the second electrode layer.

[0081] Etching the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time using an etching gas to form a first gap that penetrates the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer comprises:

[0082] S430: Introducing an etching gas into the second slit to etch the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time to form a first slit that penetrates the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer.

[0083] Please refer to Fig.11 After forming the second electrode layer 62, the second electrode layer 62 is first etched to form a second slit 200 penetrating the second electrode layer 62, and then the second piezoelectric layer 22, the metal layer 30, the first piezoelectric layer 21 and the first electrode layer 61 are etched once to form a first slit 100 that is connected to the second slit 200 and simultaneously penetrates the second piezoelectric layer 22, the metal layer 30, the first piezoelectric layer 21 and the first electrode layer 61. Etching the second electrode layer 62 alone can avoid the failure to form the first slit 100 that can penetrate the first electrode layer 61 due to etching too many film layers at one time.

[0084] It should be noted that the components of the etching gas used for etching the second slit 200 and the etching of the first slit 100 and the proportion of each component may be different.

[0085] Optionally, see Fig.12 After forming a second piezoelectric layer on the metal layer, the method further comprises:

[0086] S530: alternately forming a third electrode layer and a third piezoelectric layer on the second piezoelectric layer.

[0087] S540: etching the third electrode layer and the third piezoelectric layer using an etching gas to form a third gap penetrating the third electrode layer and the third piezoelectric layer.

[0088] Etching the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time using an etching gas to form a first gap that penetrates the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer comprises:

[0089] S440: Introducing an etching gas into the third slit to etch the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time to form a first slit that penetrates the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer.

[0090] Please refer to Fig.13 , a third electrode layer 63 and a third piezoelectric layer 23 are alternately formed on the second piezoelectric layer 22, and a piezoelectric stack structure with multiple film layers can be obtained. When the number of film layers is large, it is difficult to ensure that all film layers are penetrated by one etching, or it is difficult to control the bottom width B of the first slit, the film layer above the second piezoelectric layer 22 can be etched separately. That is, the film layer above the second piezoelectric layer 22 is first etched with an etching gas. The etching of this part of the film layer can be performed only once, or twice or more times. This embodiment is not limited to this, as long as the third slit 300 that penetrates all film layers above the second piezoelectric layer 22 can be finally achieved. Then, the second piezoelectric layer 22, the metal layer 30, the first piezoelectric layer 21 and the first electrode layer 61 are etched once to form a first slit 100 that is connected to the third slit 300 and penetrates the second piezoelectric layer 22, the metal layer 30, the first piezoelectric layer 21 and the first electrode layer 61 at the same time.

[0091] Optionally, the third piezoelectric layer 23 of the uppermost layer has a third electrode layer 63 on a side facing away from the second piezoelectric layer 22. In this way, both sides of each piezoelectric layer can have electrode layers.

[0092] After forming the first slit 100, two solutions can be adopted: performing or not performing a cleaning process to determine whether the redeposited layer 50 on the sidewall of the first slit 100 is retained. Figure 4 As shown, if the cleaning process is not performed, the side wall of the first gap 100 will retain the redeposited layer 50, which can further reduce the bottom width B of the first gap, thereby further improving the low-frequency performance of the piezoelectric MEMS microphone, and the redeposited layer 50 and the etched material are in a coupling relationship, and will not fall off or peel off during the application of the piezoelectric MEMS microphone. Therefore, for the piezoelectric MEMS microphone, the retention of the redeposited layer 50 is beneficial to improving the performance of the product.

[0093] Of course, the cleaning process after etching is also a normal process in the manufacturing process of piezoelectric MEMS microphones. Its main purpose is to keep the etched surface neat and smooth and remove residual elements, which is conducive to the smooth progress of subsequent deposition, lithography and other processes, and facilitates the formulation of standards for post-etching inspection and standardization of the process flow.

[0094] Optionally, see Fig.14 , after etching the second piezoelectric layer, the metal layer and the first piezoelectric layer at one time using an etching gas to form a first gap penetrating the second piezoelectric layer, the metal layer and the first piezoelectric layer, the method further includes:

[0095] S600: cleaning the first slit to remove a redeposition layer formed on the surface of the first slit due to a redeposition effect.

[0096] Please refer to Fig.15 After the re-deposition layer 50 is removed, the sidewall of the first slit 100 is flat, but the width B of the bottom of the first slit becomes larger. Fig.11 and Fig.13 If there is a second gap 200 or a third gap 300 , the redeposition layer 50 on the surface of the second gap 200 or the third gap 300 can also be removed at the same time.

[0097] Illustratively, a wet cleaning process is used to remove the redeposition layer 50 .

[0098] The wet cleaning process includes: wet solution cleaning, alcohol or ketone solution cleaning, deionized water cleaning and drying. The specific wet cleaning process can be composed of multiple repetitions and different order combinations of the above steps.

[0099] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, 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 structure, characterized in that: include: Providing a base structure, and forming a first piezoelectric layer on the base structure; forming a metal layer on the first piezoelectric layer, wherein the metal layer completely covers the first piezoelectric layer or covers a portion of the first piezoelectric layer; forming a second piezoelectric layer on the metal layer; The second piezoelectric layer, the metal layer and the first piezoelectric layer are etched at one time using an etching gas to form a first gap that penetrates the second piezoelectric layer, the metal layer and the first piezoelectric layer, wherein the sidewall of the first gap is covered with a redeposited layer and is inclined, and the upper end width of the first gap is greater than the lower end width of the first gap.

2. The method for preparing a piezoelectric structure according to claim 1, characterized in that: The step of providing a substrate structure and forming a first piezoelectric layer on the substrate structure comprises: Providing a substrate structure, and forming a first electrode layer on the substrate structure; forming a first piezoelectric layer on the first electrode layer; The etching of the second piezoelectric layer, the metal layer and the first piezoelectric layer at one time using an etching gas to form a first gap penetrating the second piezoelectric layer, the metal layer and the first piezoelectric layer comprises: The second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer are etched at once using an etching gas to form a first gap that penetrates the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer.

3. The method for preparing a piezoelectric structure according to claim 2, characterized in that: After forming the second piezoelectric layer on the metal layer, the method further comprises: forming a second electrode layer on the second piezoelectric layer; The etching of the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time using an etching gas to form a first gap penetrating the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer comprises: The second electrode layer, the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer are etched at once using an etching gas to form a first gap that penetrates the second electrode layer, the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer.

4. The method for preparing a piezoelectric structure according to claim 2, characterized in that: After forming the second piezoelectric layer on the metal layer, the method further comprises: forming a second electrode layer on the second piezoelectric layer; Etching the second electrode layer using an etching gas to form a second gap penetrating the second electrode layer; The etching of the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time using an etching gas to form a first gap penetrating the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer comprises: An etching gas is introduced into the second gap to etch the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time to form a first gap that penetrates the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer.

5. The method for preparing a piezoelectric structure according to claim 2, characterized in that: After forming the second piezoelectric layer on the metal layer, the method further comprises: forming a third electrode layer and a third piezoelectric layer alternately on the second piezoelectric layer; Etching the third electrode layer and the third piezoelectric layer using an etching gas to form a third gap penetrating the third electrode layer and the third piezoelectric layer; The etching of the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time using an etching gas to form a first gap penetrating the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer comprises: An etching gas is introduced into the third gap to etch the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer at one time to form a first gap that penetrates the second piezoelectric layer, the metal layer, the first piezoelectric layer and the first electrode layer.

6. The method for preparing a piezoelectric structure according to claim 5, characterized in that: The side of the uppermost third piezoelectric layer facing away from the second piezoelectric layer comprises the third electrode layer.

7. The method for preparing a piezoelectric structure according to claim 1, characterized in that: The etching gas includes metal etching gas and piezoelectric etching gas.

8. The method for preparing a piezoelectric structure according to claim 7, characterized in that: The metal etching gas is a fluorine-containing gas, and the piezoelectric etching gas is a chlorine-containing gas.

9. The method for preparing a piezoelectric structure according to claim 1, characterized in that: The thickness of the metal layer is smaller than the thickness of the first piezoelectric layer and the thickness of the second piezoelectric layer, respectively.

10. The method for preparing a piezoelectric structure according to claim 1, characterized in that: After etching the second piezoelectric layer, the metal layer and the first piezoelectric layer at one time using an etching gas to form a first gap penetrating the second piezoelectric layer, the metal layer and the first piezoelectric layer, the method further includes: The first gap is cleaned to remove a redeposition layer formed on the surface of the first gap due to a redeposition effect.

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