A cymbal structure-based MEMS sensor and a preparation method thereof

Abstract

A MEMS sensor based on a cymbal structure and its fabrication method are disclosed, relating to the field of MEMS sensor technology. The fabrication method includes: providing a substrate; sequentially forming a seed layer and a first structural layer on one side of the substrate, the first structural layer comprising a first oxide layer, a first electrode layer, and a second oxide layer stacked sequentially; sequentially forming a lower electrode layer, a piezoelectric layer, and an upper electrode layer on the side of the first structural layer away from the substrate; forming a second structural layer on the side of the upper electrode layer away from the substrate, the second structural layer comprising a third oxide layer and a second electrode layer; and removing the first oxide layer, the second oxide layer, and the third oxide layer to form a first gap between the seed layer and the first electrode layer, a second gap between the first electrode layer and the lower electrode layer, and a third gap between the upper electrode layer and the second electrode layer. This fabrication method avoids substrate etching, improving the strain conversion efficiency and product yield of the MEMS sensor.

Description

Technical Field

[0001] This invention relates to the field of MEMS sensor technology, and more specifically, to a MEMS sensor based on a cymbal structure and its fabrication method. Background Technology

[0002] Introducing cymbal structures into microelectromechanical systems (MEMS) sensors can significantly improve mechanical response efficiency. This structure greatly enhances electromechanical conversion sensitivity by converting axial loads into radial strain of the piezoelectric material. Taking hydrophones as an example, traditional cantilever beam hydrophones are prone to acoustic pressure response attenuation due to seal failure, while circular diaphragm hydrophones have relatively weak output response due to limited changes in center displacement. In contrast, the cymbal structure efficiently converts longitudinal underwater acoustic vibrations into lateral expansion and contraction of the piezoelectric layer through a cavity with inclined planes, improving output voltage and sensitivity while maintaining low-frequency response advantages.

[0003] In existing MEMS sensors, when fabricating cymbal structures, an oxide layer is typically deposited directly on a silicon substrate, and this oxide layer is patterned and etched to initially form the cavity sidewall tilt angle, i.e., the initial slope of the cymbal structure. However, when etching the oxide layer, the underlying silicon substrate is easily etched simultaneously, resulting in the actual cavity sidewall tilt angle being significantly larger than the preset angle. This leads to a decrease in strain conversion efficiency and a reduction in product yield. Summary of the Invention

[0004] The purpose of this invention is to provide a MEMS sensor based on a cymbal structure and its fabrication method, which can avoid substrate etching and improve the strain conversion efficiency and product yield of the MEMS sensor.

[0005] The embodiments of the present invention are implemented as follows: In one aspect, the present invention provides a method for fabricating a MEMS sensor based on a cymbal structure, comprising: providing a substrate; sequentially forming a seed layer and a first structural layer on one side of the substrate, the first structural layer comprising a first oxide layer, a first electrode layer and a second oxide layer stacked sequentially, the first oxide layer comprising two first sub-oxide layers spaced apart on the seed layer, the opposite sidewalls of the first sub-oxide layers being inclined relative to the seed layer along a first included angle α; a first electrode layer being disposed covering at least a portion of the first oxide layer, and the first electrode layer located between the two first sub-oxide layers protruding toward the substrate to contact the seed layer, forming a recess; a second oxide layer being located on the first electrode layer and at least partially located within the recess, and the surface of the second oxide layer being flush with the substrate. The surface of the first electrode layer is flush with the surface of the first sub-oxide layer region; a lower electrode layer, a piezoelectric layer, and an upper electrode layer are sequentially formed on the side of the first structural layer away from the substrate; a second structural layer is formed on the side of the upper electrode layer away from the substrate, the second structural layer including a third oxide layer and a second electrode layer, the opposite sidewalls of the third oxide layer being inclined relative to the upper electrode layer along a second included angle β; a protrusion is formed in the second electrode layer in the direction away from the upper electrode layer, and the third oxide layer is located between the protrusion and the upper electrode layer; the first oxide layer, the second oxide layer, and the third oxide layer are removed to form a first gap between the seed layer and the first electrode layer, a second gap between the first electrode layer and the lower electrode layer, and a third gap between the upper electrode layer and the second electrode layer.

[0006] Optionally, forming a seed layer and a first structural layer sequentially on one side of the substrate includes: depositing a seed layer on the substrate; depositing a first oxide layer on the seed layer and patterning the first oxide layer to form two spaced-apart first sub-oxide layers, the opposite sidewalls of the first sub-oxide layers being inclined relative to the seed layer along a first included angle α; depositing a first electrode layer on the first oxide layer, the first electrode layer covering the seed layer; depositing a second oxide layer on the first electrode layer; and patterning the second oxide layer so that the surface of the second oxide layer is flush with the surface of the region of the first electrode layer corresponding to the first sub-oxide layer.

[0007] Optionally, a second structural layer is formed on the side of the upper electrode layer away from the substrate, including: depositing a third oxide layer on the upper electrode layer and patterning the third oxide layer so that the opposite sidewalls of the third oxide layer are inclined relative to the upper electrode layer along a second included angle β, wherein the second included angle β is equal to the first included angle α; depositing a second electrode layer on the third oxide layer, the second electrode layer covering the upper electrode layer.

[0008] Optionally, before patterning the second oxide layer, the method further includes: planarizing the surface of the second oxide layer.

[0009] Optionally, the surface smoothing treatment of the second oxide layer includes: performing chemical mechanical polishing on the second oxide layer to make the surface of the second oxide layer smooth; and adjusting the thickness of the second oxide layer by using an ion beam to make the thickness of the second oxide layer uniform.

[0010] Optionally, forming a lower electrode layer, a piezoelectric layer, and an upper electrode layer sequentially on the side of the first structural layer away from the substrate includes: depositing a lower electrode layer on the second oxide layer of the first structural layer, the lower electrode layer covering the first electrode layer and the second oxide layer; patterning and etching one edge of the lower electrode layer until at least a portion of the seed layer and the sidewall of any first sub-oxide layer are exposed; depositing a piezoelectric layer on the lower electrode layer, such that the piezoelectric layer covers the seed layer, the lower electrode layer, and the first sub-oxide layer, wherein the top surface of the piezoelectric layer corresponding to the region of the first oxide layer and the second oxide layer is a planar structure; and depositing an upper electrode layer on the planar structure of the piezoelectric layer.

[0011] Optionally, after forming a second structural layer on the side of the upper electrode layer away from the substrate, the method further includes depositing a passivation layer on the second electrode layer of the second structural layer, the passivation layer covering the upper electrode layer.

[0012] Optionally, after depositing a passivation layer on the second electrode layer of the second structural layer, the method further includes: etching to form a first release hole, the first release hole sequentially penetrating the passivation layer and the piezoelectric layer until the first electrode layer is exposed; etching to form a second release hole, the second release hole corresponding to the area of ​​the first electrode layer not covered by the first sub-oxide layer, the second release hole sequentially penetrating the passivation layer and the piezoelectric layer until at least a portion of the first sub-oxide layer is exposed; etching to form a third release hole, the third release hole sequentially penetrating the passivation layer, the second electrode layer, the upper electrode layer, the piezoelectric layer and the lower electrode layer to connect the second void and the third void.

[0013] Optionally, after etching to form the first release hole, the method further includes: depositing a first metal layer on the inner wall of the first release hole, the first metal layer at least partially covering the edge region of the passivation layer corresponding to the first release hole and the outer periphery of the passivation layer corresponding to the first release hole; patterning the passivation layer to expose at least a portion of the second electrode layer; and depositing a second metal layer on the passivation layer, the second metal layer covering the exposed second electrode layer.

[0014] In another aspect, the present invention provides a MEMS sensor based on a cymbal structure. It is fabricated using the aforementioned method for fabricating a MEMS sensor based on a cymbal structure.

[0015] The beneficial effects of this invention include: This application provides a method for fabricating a MEMS sensor based on a cymbal structure, comprising: providing a substrate; sequentially forming a seed layer and a first structural layer on one side of the substrate, wherein the seed layer prevents the first oxide layer of the first structural layer from over-etching the substrate below during etching at a first included angle α, thus avoiding the problem of an excessively large first included angle α caused by substrate etching in conventional processes; the first structural layer includes a first oxide layer, a first electrode layer, and a second oxide layer stacked sequentially, wherein the first oxide layer includes two first sub-oxide layers spaced apart on the seed layer, and the opposite sidewalls of the first sub-oxide layers are inclined relative to the seed layer along the first included angle α, thereby protecting the surface integrity of the substrate and ensuring that the first included angle α of the first sub-oxide layers is stably controlled within a preset small range, thus improving strain conversion efficiency; a first electrode layer is disposed on at least a portion of the first oxide layer, and the first electrode layer located between the two first sub-oxide layers protrudes toward the substrate to contact the seed layer, forming a recess; a second oxide layer is located on the first electrode layer and at least a portion of the first electrode layer is located on the first electrode layer. Within the recess, the surface of the second oxide layer is flush with the surface of the first electrode layer corresponding to the first sub-oxide layer region; a lower electrode layer, a piezoelectric layer, and an upper electrode layer are sequentially formed on the side of the first structural layer away from the substrate; a second structural layer is formed on the side of the upper electrode layer away from the substrate, the second structural layer including a third oxide layer and a second electrode layer, the opposite sidewalls of the third oxide layer being inclined relative to the upper electrode layer along a second included angle β; a protrusion is formed in the second electrode layer in the direction away from the upper electrode layer, and the third oxide layer is located between the protrusion and the upper electrode layer; the first electrode layer and the second electrode layer are respectively structurally matched by the first oxide layer and the second oxide layer to jointly form a cymbal structure; the first oxide layer, the second oxide layer, and the third oxide layer are removed to form a first gap between the seed layer and the first electrode layer, a second gap between the first electrode layer and the lower electrode layer, and a third gap between the upper electrode layer and the second electrode layer, the second gap and the third gap together forming a symmetrical double cavity structure, the cavity realizing the vibration space, and efficiently converting the longitudinal sound pressure vibration into the radial strain of the piezoelectric layer. The aforementioned MEMS sensor based on cymbal structure and its fabrication method can avoid substrate etching, thereby improving the strain conversion efficiency and product yield of the MEMS sensor. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is one of the flowcharts illustrating the fabrication method of a MEMS sensor based on a cymbal structure provided in an embodiment of the present invention; Figure 2 This is the second flowchart of the fabrication method of a MEMS sensor based on a cymbal structure provided in an embodiment of the present invention; Figure 3 The third flowchart illustrates the fabrication method of a MEMS sensor based on a cymbal structure provided in this embodiment of the invention. Figure 4 The fourth flowchart illustrates the fabrication method of a MEMS sensor based on a cymbal structure provided in this embodiment of the invention. Figure 5 The fifth flowchart illustrates the fabrication method of a MEMS sensor based on a cymbal structure provided in this embodiment of the invention. Figure 6 The sixth flowchart illustrates the fabrication method of a MEMS sensor based on a cymbal structure provided in this embodiment of the invention. Figure 7 The seventh flowchart illustrates the fabrication method of a MEMS sensor based on a cymbal structure provided in this embodiment of the invention. Figure 8 This is one of the structural schematic diagrams of a MEMS sensor based on a cymbal structure provided in an embodiment of the present invention; Figure 9 This is the second schematic diagram of the structure of a MEMS sensor based on a cymbal structure provided in an embodiment of the present invention; Figure 10 This is the third schematic diagram of the structure of a MEMS sensor based on a cymbal structure provided in an embodiment of the present invention; Figure 11 This is the fourth schematic diagram of the structure of a MEMS sensor based on a cymbal structure provided in an embodiment of the present invention; Figure 12 The fifth schematic diagram of the structure of the MEMS sensor based on the cymbal structure provided in the embodiments of the present invention; Figure 13 This is the sixth schematic diagram of the structure of a MEMS sensor based on a cymbal structure provided in an embodiment of the present invention; Figure 14 The seventh schematic diagram of the MEMS sensor based on the cymbal structure provided in the embodiments of the present invention; Figure 15 The eighth schematic diagram of the MEMS sensor based on the cymbal structure provided in the embodiments of the present invention; Figure 16 This is the ninth schematic diagram of the MEMS sensor based on the cymbal structure provided in the embodiments of the present invention.

[0018] Icons: 110-Substrate; 120-Seed layer; 130-First structural layer; 131-First oxide layer; 1311-First sub-oxide layer; 132-First electrode layer; 133-Second oxide layer; 140-Lower electrode layer; 150-Piezoelectric layer; 151-Planar structure; 160-Upper electrode layer; 170-Second structural layer; 171-Third oxide layer; 172-Second electrode layer; 180-Passivation layer; 181-First release hole; 1811-First metal layer; 182-Second release hole; 183-Third release hole; 184-Second metal layer; A-First void; B-Second void; C-Third void; 200-MEMS sensor based on cymbal structure. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0023] Please refer to Figure 1 This embodiment provides a method for fabricating a MEMS sensor based on a cymbal structure, the fabrication steps of which include: S100, Provide substrate 110; Substrate 110 mainly serves as a support so that a cymbal structure can be formed on one side of substrate 110 in the future. For example, the substrate material is silicon.

[0024] S200: A seed layer 120 and a first structural layer 130 are sequentially formed on one side of the substrate 110. The first structural layer 130 includes a first oxide layer 131, a first electrode layer 132, and a second oxide layer 133 stacked sequentially. The first oxide layer 131 includes two first sub-oxide layers 1311 spaced apart on the seed layer 120. The opposite sidewalls of the first sub-oxide layers 1311 are inclined relative to the seed layer 120 at a first included angle α. The first electrode layer 132 is disposed on at least a portion of the first oxide layer 131, and the first electrode layer 132 located between the two first sub-oxide layers 1311 protrudes toward the substrate 110 to contact the seed layer 120, forming a recess. The second oxide layer 133 is located on the first electrode layer 132 and at least a portion is located in the recess, and the surface of the second oxide layer 133 is flush with the surface of the first electrode layer 132 corresponding to the area of ​​the first sub-oxide layer 1311. Specifically, such as Figure 2 As shown, embodiments of this application can form a seed layer 120 and a first structural layer 130 through the following steps: Step S210: Deposit a seed layer 120 on the substrate 110. In traditional cymbal structures, the oxide layer is directly deposited on the substrate 110 during fabrication, and then patterned and etched to form the tilt angle of the cymbal structure. During etching, etching ions can easily penetrate the oxide layer and cause over-etching of the underlying substrate 110, resulting in an excessively large tilt angle of the cymbal structure and thus reducing strain conversion efficiency. In this application, the seed layer 120 covers one side of the substrate 110. The chemical stability of the seed layer 120 can block the erosion of the silicon substrate 110 by etching ions, avoiding surface damage to the substrate 110 and ensuring the accuracy of the cymbal structure tilt angle.

[0025] For example, the seed layer 120 can be an aluminum nitride layer. Of course, in addition to aluminum nitride, the seed layer 120 can also be made of other materials, such as a molybdenum layer. This application does not impose any restrictions on the specific material of the seed layer 120, as long as it can ensure that the substrate 110 is not etched.

[0026] After depositing the seed layer 120, proceed through step S220, as follows: Figure 8 As shown, a first oxide layer 131 is deposited on the seed layer 120, and the first oxide layer 131 is patterned and etched to form two first sub-oxide layers 1311 spaced apart. The opposite sidewalls of the first sub-oxide layers 1311 are inclined relative to the seed layer 120 along a first included angle α. For example, the first oxide layer 131 can be a silicon dioxide layer, which serves as a structural template for the subsequent fabrication of the cymbal structure and provides physical support for the tilt angle of the void sidewalls of the cymbal structure.

[0027] By patterning and etching the first oxide layer 131, it is separated into two spaced-apart first sub-oxide layers 1311. The edges of the first sub-oxide layers 1311 and the substrate 110 are spaced apart by a predetermined interval, and there is also a predetermined interval between the two first sub-oxide layers 1311, exposing the seed layer 120 located around the periphery of the two first sub-oxide layers 1311. The opposite sidewalls of the first sub-oxide layers 1311 are inclined relative to the seed layer 120 along a first included angle α, resulting in an isosceles trapezoidal structure for the first sub-oxide layers 1311. Preferably, the first included angle α is approximately 20° to improve the conversion efficiency of longitudinal vibration to transverse strain.

[0028] The spacing between the two first sub-oxide layers 1311 provides space for the recessed structure of the subsequent first electrode layer 132 and serves as a template; at the same time, it ensures that the angles of the inclined surfaces on both sides of the cavity formed later are consistent, avoiding vibration response imbalance caused by stress concentration on one side.

[0029] After depositing and patterning the first oxide layer 131, the process proceeds through step S230, as follows: Figure 9 As shown, a first electrode layer 132 is deposited on the first oxide layer 131, covering the first oxide layer 131 and simultaneously covering the seed layer 120 where the first oxide layer 131 is not disposed. Since the first oxide layer 131 has two spaced-apart first sub-oxide layers 1311, and the first sub-oxide layers 1311 are patterned and etched to form an isosceles trapezoidal structure with a first included angle α on the sidewalls, the structure of the first electrode layer 132 deposited on the first oxide layer 131 is the same as that of the first oxide layer 131, also forming an isosceles trapezoidal structure with two spaced protrusions. Because the seed layer 120 is exposed between the two first sub-oxide layers 1311 due to the predetermined interval, the first electrode layer 132 located in the region between the two first sub-oxide layers 1311 protrudes towards the substrate 110 to contact the seed layer 120, forming a recess.

[0030] After depositing the first electrode layer 132, proceed through step S240, as follows: Figure 9 As shown, a second oxide layer 133 is deposited on the first electrode layer 132; the second oxide layer 133 can be a silicon dioxide layer. Since the top surface profile of the first electrode layer 132 is the same as the top surface profile of the first oxide layer 131, similarly, the top surface profile of the second oxide layer 133 deposited on the first electrode layer 132 is also the same as the top surface profile of the first electrode layer 132.

[0031] In order to ensure the flatness of the top surface of the first structural layer 130, and to facilitate the subsequent deposition of the piezoelectric layer 150 and the flatness and stability of the first structural layer 130, and to ensure the yield of the device, the surface of the second oxide layer 133 can be flattened in step S250.

[0032] For example, the top surface of the second oxide layer 133 is first chemically mechanically polished to make the surface of the second oxide layer 133 smooth. Since chemical mechanical polishing may cause local thickness deviations due to uneven pressure distribution of the polishing pad, the surface material of the second oxide layer 133 can be removed by high-energy ions through ion beam etching after chemical mechanical polishing. Ion beam fine-tuning can achieve nanoscale precision etching, thereby ensuring uniform thickness of the second oxide layer 133 throughout.

[0033] After the surface of the second oxide layer 133 is smoothed, proceed to step S260, as follows: Figure 10 As shown, the second oxide layer 133 is patterned and etched so that the surface of the second oxide layer 133 is flush with the surface of the first electrode layer 132 corresponding to the first sub-oxide layer 1311 region. During the etching process, the etching endpoint can be automatically determined by monitoring the etching progress to ensure that the etching focus of the second oxide layer 133 is precisely located on the surface of the first electrode layer 132, thus avoiding incomplete or excessive etching. During the etching process, the second oxide layer 133 is deposited in the recesses of the first electrode layer 132, while the remaining parts of the first electrode layer 132 are etched to the exposed state.

[0034] Step S300: A lower electrode layer 140, a piezoelectric layer 150, and an upper electrode layer 160 are sequentially formed on the side of the first structural layer 130 away from the substrate 110. Specifically, such as Figure 3 As shown, embodiments of this application can form a lower electrode layer 140, a piezoelectric layer 150, and an upper electrode layer 160 through the following steps: Step S310, as follows Figure 11 As shown, a lower electrode layer 140 is deposited on the second oxide layer 133 of the first structural layer 130, and the lower electrode layer 140 covers the first electrode layer 132 and the second oxide layer 133, such that the lower electrode layer 140 can cover the exposed first electrode layer 132 and the second oxide layer 133 located in the recess of the first electrode layer 132.

[0035] Step S320, as Figure 11 As shown, one side edge of the lower electrode layer 140 is patterned and etched until at least a portion of the seed layer 120 and the sidewall of any first sub-oxide layer 1311 are exposed. Step S330, as Figure 12As shown, a piezoelectric layer 150 is deposited on the lower electrode layer 140, so that the piezoelectric layer 150 covers the seed layer 120, the lower electrode layer 140, and the first sub-oxide layer 1311 exposed after patterning and etching in step S320. In order to ensure the stability of the subsequent setting of the second structural layer 170 and improve the yield of the MEMS sensor 200 based on the cymbal structure, the area on the top surface of the piezoelectric layer 150 corresponding to the first oxide layer 131 and the second oxide layer 133 is a planar structure 151.

[0036] Step S340, Rui Figure 12 As shown, an upper electrode layer 160 is deposited on the planar structure 151 of the piezoelectric layer 150.

[0037] The lower electrode layer 140 and the upper electrode layer 160 can be used for an external power supply, and the lower electrode layer 140 and the upper electrode layer 160 are typically opposite electrodes to form a current loop between the upper electrode layer 160 and the lower electrode layer 140. A piezoelectric layer 150 is disposed between the upper electrode layer 160 and the lower electrode layer 140, and is used to generate a corresponding displacement change according to the voltage when a certain voltage is applied to the upper electrode layer 160 and the lower electrode layer 140.

[0038] Step S400, as follows Figure 13 As shown, a second structural layer 170 is formed on the side of the upper electrode layer 160 away from the substrate 110. The second structural layer 170 includes a third oxide layer 171 and a second electrode layer 172. The opposite sidewalls of the third oxide layer 171 are inclined relative to the upper electrode layer 160 along a second included angle β. The second electrode layer 172 forms a protrusion in the direction away from the upper electrode layer 160, and the third oxide layer 171 is located between the protrusion and the upper electrode layer 160. Specifically, such as Figure 4 As shown, embodiments of this application can form the second structural layer 170 through the following steps: Step S410, as follows Figure 12 As shown, a third oxide layer 171 is deposited on the upper electrode layer 160 and patterned and etched so that the opposite sidewalls of the third oxide layer 171 are inclined relative to the upper electrode layer 160 along the second included angle β to form an isosceles trapezoidal structure; wherein, the second included angle β is equal to the first included angle α. For example, the position of the third oxide layer 171 corresponds to the position of the second oxide layer 133 disposed in the recess, and the tilt angle of the opposite side walls of the third oxide layer 171 is the same as the tilt angle of the first oxide layer 131. Since the tilt angle of the side walls of the second oxide layer 133 disposed in the recess is realized by the structural contour of the first electrode layer 132, and the structural contour of the first electrode layer 132 is consistent with the structural contour of the first oxide layer 131, the tilt angle of the opposite side walls of the second oxide layer 133 is the same as the first included angle α of the opposite side walls of the first oxide layer 131 relative to the seed layer 120. It can be seen that the third oxide layer 171 and the second oxide layer 133 are symmetrically arranged with the piezoelectric layer 150 as the axis of symmetry.

[0039] Step S420, as Figure 13 As shown, a second electrode layer 172 is deposited on the third oxide layer 171, the second electrode layer 172 covers the third oxide layer 171, and the opposite sides of the second electrode layer 172 cover the area of ​​the upper electrode layer 160 where the third oxide layer 171 is not deposited.

[0040] Since the second electrode layer 172 is deposited on the third oxide layer 171, and the third oxide layer 171 has an isosceles trapezoidal structure, the structural outline of the second electrode layer 172 is consistent with the structural outline of the third oxide layer 171. Through the arrangement of the third oxide layer 171, the second electrode layer 172 forms a protrusion facing away from the upper electrode layer 160, and the structure of the second electrode layer 172 is symmetrically arranged with the structure of the first electrode layer 132 about the piezoelectric layer 150 as the axis of symmetry.

[0041] Step S500: Remove the first oxide layer 131, the second oxide layer 133 and the third oxide layer 171 to form a first gap A between the seed layer 120 and the first electrode layer 132, a second gap B between the first electrode layer 132 and the lower electrode layer 140, and a third gap C between the upper electrode layer 160 and the second electrode layer 172.

[0042] Specifically, the removal can be achieved through processes such as chemical etching. After removal, a first gap A is formed between the seed layer 120 and the first electrode layer 132, a second gap B is formed between the first electrode layer 132 and the lower electrode layer 140, and a third gap C is formed between the upper electrode layer 160 and the second electrode layer 172, thus forming a cymbal structure.

[0043] The second gap B can be used to create space when the first electrode layer 132 deforms and changes displacement, and the third gap C can be used to create space when the second electrode layer 172 deforms and changes displacement.

[0044] By applying a certain voltage to the upper electrode layer 160 and lower electrode layer 140 of the cymbal-based MEMS sensor 200, the piezoelectric layer 150 can undergo a certain deformation in the lateral direction, resulting in a displacement change. This displacement change causes the first electrode layer 132 and the second electrode layer 172 to deform simultaneously in the longitudinal direction, resulting in a displacement change. Conversely, the longitudinal displacement of the first electrode layer 132 and the second electrode layer 172 can also be converted into the lateral displacement of the piezoelectric layer 150. In other words, the mutual conversion between the lateral displacement of the piezoelectric layer 150 and the longitudinal displacement of the first electrode layer 132 and the second electrode layer 172 is realized. This amplifies the displacement change, generates a higher output voltage, and significantly improves the performance of the cymbal-based MEMS sensor 200.

[0045] In one possible embodiment of this application, in the fabrication method of the MEMS sensor 200 based on the cymbal structure, since the material used for the second electrode layer 172 is usually a metallic material, it is prone to oxidation when exposed to air for a long time. Therefore, in order to prevent the second electrode layer 172 from being oxidized, such as... Figure 5 As shown, the preparation method further includes step S600, depositing a passivation layer 180 on the second electrode layer 172 of the second structural layer 170, wherein the passivation layer 180 covers the upper electrode layer 160 to protect the second electrode layer 172. Preferably, as shown... Figure 14 As shown, the passivation layer 180 covers the top surface of the second electrode layer 172 and the exposed piezoelectric layer 150, so as to also protect the piezoelectric layer 150.

[0046] Furthermore, such as Figure 6 As shown, after depositing a passivation layer 180 on the second electrode layer 172 of the second structural layer 170, the method further includes: Step S710, as follows Figure 15 As shown, etching forms a first release hole 181, which sequentially penetrates the passivation layer 180 and the piezoelectric layer 150 until the first electrode layer 132 is exposed. The first electrode layer 132 can be connected to an external circuit through the first release hole 181, ensuring that the electrical signal generated by the piezoelectric layer 150 can be efficiently discharged. Similarly, during the etching of the first release hole 181, the etching focus can be monitored in real time in conjunction with the etching process. When a metal signal is detected in the first electrode layer 132, the etching is stopped to achieve high-precision etching and ensure the reliability of electrical contact.

[0047] Step S720, as follows Figure 15As shown, a second release hole 182 is formed by etching. The second release hole 182 corresponds to the area of ​​the first sub-oxide layer 1311 that is not covered by the first electrode layer 132. The second release hole 182 passes through the passivation layer 180 and the piezoelectric layer 150 in sequence until at least a portion of the first sub-oxide layer 1311 is exposed. Since the second release hole 182 can expose at least a portion of the first sub-oxide layer 1311, and the first sub-oxide layer 1311 is eventually removed to form the first void A, the second release hole 182 can communicate with the first void A.

[0048] Step S730, as follows Figure 15 As shown, a third release hole 183 is formed by etching. The third release hole 183 passes through the passivation layer 180, the second electrode layer 172, the upper electrode layer 160, the piezoelectric layer 150 and the lower electrode layer 140 in sequence to connect the second gap B and the third gap C.

[0049] The third release hole 183 can connect the second gap B and the third gap C. The connection between the second gap B and the third gap C can balance the pressure inside the cavity, avoid the vibration damping difference caused by the closure of one side of the gap, ensure that the cymbal structure deforms symmetrically under longitudinal sound pressure, and maintain the stability of low frequency response.

[0050] Furthermore, such as Figure 7 As shown, after etching to form the first release hole 181, the method further includes: Step S711, as follows Figure 16 As shown, a first metal layer 1811 is deposited on the inner wall of the first release hole 181. The first metal layer 1811 at least partially covers the edge region of the passivation layer 180 corresponding to the first release hole 181 and the outer periphery of the passivation layer 180 corresponding to the first release hole 181. The first metal layer 1811 is used for electrical connection path with external circuits. The outer periphery of the passivation layer 180 corresponding to the outer periphery of the first release hole 181, which covers the first metal layer 1811, forms a pad base, providing a stable connection point for subsequent wire bonding, and adapting to the mass production packaging requirements.

[0051] For example, the first metal layer 1811 is typically made of a highly conductive metal, such as aluminum.

[0052] Step S712: Pattern the passivation layer 180 to expose at least a portion of the second electrode layer 172, providing an electrical contact area for the deposition of the second metal layer 184. Step S713, as follows Figure 16As shown, a second metal layer 184 is deposited on the passivation layer 180, and the second metal layer 184 covers the exposed second electrode layer 172. The second metal layer 184, together with the first metal layer 1811, constitutes the positive and negative electrode lead-out structures of the sensor. The two metal layers together construct a complete electrical circuit, efficiently exporting the electrical signal generated by the piezoelectric layer 150 to the external detection circuit, ensuring the achievement of the sensitivity index.

[0053] Another aspect of the embodiments of this application, such as Figure 16 As shown, a MEMS sensor 200 based on a cymbal structure is also provided. It is fabricated using the aforementioned method for fabricating a MEMS sensor based on a cymbal structure. This fabrication method has been described in detail above and will not be repeated here.

[0054] It should be noted that the cymbal-based MEMS sensor 200 may include one or more cymbal structures. When the cymbal-based MEMS sensor 200 includes multiple cymbal structures, the above-described method can be used to simultaneously fabricate multiple cymbal structures on one side of the substrate 110. Furthermore, the cymbal structures can be arranged in an array on the substrate 110, greatly simplifying the fabrication process and reducing production costs. The aforementioned cymbal-based MEMS sensor 200 exhibits good strain conversion efficiency and product yield.

[0055] The above description is merely an optional embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0056] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A method for fabricating a MEMS sensor based on a cymbal structure, characterized in that, include: Provide substrate; A seed layer and a first structural layer are sequentially formed on one side of the substrate. The first structural layer includes a first oxide layer, a first electrode layer, and a second oxide layer stacked sequentially. The first oxide layer includes two first sub-oxide layers spaced apart on the seed layer. The opposite sidewalls of the first sub-oxide layers are inclined relative to the seed layer at a first included angle α. The first electrode layer is disposed on at least a portion of the first oxide layer, and the first electrode layer located between the two first sub-oxide layers protrudes toward the substrate to contact the seed layer, forming a recess. The second oxide layer is located on the first electrode layer and at least a portion is located within the recess, and the surface of the second oxide layer is flush with the surface of the first electrode layer corresponding to the region of the first sub-oxide layer. A lower electrode layer, a piezoelectric layer, and an upper electrode layer are sequentially formed on the side of the first structural layer away from the substrate; A second structural layer is formed on the side of the upper electrode layer away from the substrate. The second structural layer includes a third oxide layer and a second electrode layer. The opposite sidewalls of the third oxide layer are inclined relative to the upper electrode layer along a second included angle β. The second electrode layer forms a protrusion in the direction away from the upper electrode layer, and the third oxide layer is located between the protrusion and the upper electrode layer. The first oxide layer, the second oxide layer, and the third oxide layer are removed to form a first gap between the seed layer and the first electrode layer, a second gap between the first electrode layer and the lower electrode layer, and a third gap between the upper electrode layer and the second electrode layer.

2. The method for fabricating a MEMS sensor based on a cymbal structure according to claim 1, characterized in that, The step of sequentially forming a seed layer and a first structural layer on one side of the substrate includes: Deposit a seed layer on the substrate; The first oxide layer is deposited on the seed layer and patterned and etched to form two first sub-oxide layers spaced apart, wherein the opposite sidewalls of the first sub-oxide layers are inclined relative to the seed layer along a first included angle α. A first electrode layer is deposited on the first oxide layer, the first electrode layer covering the seed layer; A second oxide layer is deposited on the first electrode layer; The second oxide layer is patterned and etched so that the surface of the second oxide layer is flush with the surface of the first electrode layer corresponding to the first sub-oxide layer region.

3. The method for fabricating a MEMS sensor based on a cymbal structure according to claim 2, characterized in that, The formation of a second structural layer on the side of the upper electrode layer away from the substrate includes: The third oxide layer is deposited on the upper electrode layer and patterned and etched so that the opposite sidewalls of the third oxide layer are inclined relative to the upper electrode layer along a second included angle β, wherein the second included angle β is equal to the first included angle α; A second electrode layer is deposited on the third oxide layer, and the second electrode layer covers the upper electrode layer.

4. The method for fabricating a MEMS sensor based on a cymbal structure according to claim 2, characterized in that, Before patterning the second oxide layer, the method further includes: The surface of the second oxide layer is smoothed.

5. The method for fabricating a MEMS sensor based on a cymbal structure according to claim 4, characterized in that, The surface smoothing treatment of the second oxide layer includes: The second oxide layer is subjected to chemical mechanical polishing to make the surface of the second oxide layer smooth; The thickness of the second oxide layer is adjusted by using an ion beam to make the thickness of the second oxide layer uniform.

6. The method for fabricating a MEMS sensor based on a cymbal structure according to claim 1, characterized in that, The step of sequentially forming a lower electrode layer, a piezoelectric layer, and an upper electrode layer on the side of the first structural layer away from the substrate includes: The lower electrode layer is deposited on the second oxide layer of the first structural layer, and the lower electrode layer covers the first electrode layer and the second oxide layer; Patterned etching is performed on one side edge of the lower electrode layer until at least a portion of the seed layer and the sidewall of any of the first sub-oxide layers are exposed. A piezoelectric layer is deposited on the lower electrode layer, such that the piezoelectric layer covers the seed layer, the lower electrode layer and the first sub-oxide layer, wherein the top surface of the piezoelectric layer has a planar structure corresponding to the region of the first oxide layer and the second oxide layer; An upper electrode layer is deposited on the planar structure of the piezoelectric layer.

7. The method for fabricating a MEMS sensor based on a cymbal structure according to claim 6, characterized in that, After forming the second structural layer on the side of the upper electrode layer away from the substrate, the method further includes: A passivation layer is deposited on the second electrode layer of the second structural layer, the passivation layer covering the upper electrode layer.

8. The method for fabricating a MEMS sensor based on a cymbal structure according to claim 7, characterized in that, After depositing a passivation layer on the second electrode layer of the second structural layer, the method further includes: The first release hole is formed by etching, and the first release hole sequentially penetrates the passivation layer and the piezoelectric layer until the first electrode layer is exposed; A second release hole is formed by etching. The second release hole corresponds to the area of ​​the first electrode layer that is not covered by the first sub-oxide layer. The second release hole passes through the passivation layer and the piezoelectric layer in sequence until at least a portion of the first sub-oxide layer is exposed. A third release hole is formed by etching. The third release hole passes through the passivation layer, the second electrode layer, the upper electrode layer, the piezoelectric layer and the lower electrode layer in sequence to connect the second gap and the third gap.

9. The method for fabricating a MEMS sensor based on a cymbal structure according to claim 8, characterized in that, After the etching forms the first release hole, the method further includes: A first metal layer is deposited on the inner wall of the first release hole, the first metal layer at least partially covering the edge region of the passivation layer corresponding to the first release hole, and the outer periphery of the passivation layer corresponding to the first release hole; The passivation layer is patterned and etched to expose at least a portion of the second electrode layer; A second metal layer is deposited on the passivation layer, the second metal layer covering the exposed second electrode layer.

10. A MEMS sensor based on a cymbal structure, characterized in that, The MEMS sensor based on the cymbal structure described in any one of claims 1-9 is prepared.

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