MEMS sensor based on half cymbal structure and preparation method thereof

Abstract

The invention discloses an MEMS sensor based on a half cymbal structure and a preparation method thereof. The preparation method comprises the following steps: providing a substrate; a first structure layer is formed on one side of the substrate and comprises an end cover layer, the end cover layer comprises a first horizontal part, an inclined part and a second horizontal part, the two ends of the inclined part are integrally connected with the first horizontal part and the second horizontal part respectively, the first horizontal part is located on the substrate, and the second horizontal part is parallel to the first horizontal part; a first gap is formed between the substrate and the end cover layer; sequentially forming a lower electrode layer, a piezoelectric layer and an upper electrode layer on one side, far away from the substrate, of the first structure layer; a second gap exists between the lower electrode layer and the end cover layer. Through the method, the preparation process of the micron-sized MEMS sensor is simplified, and the production yield and the production efficiency of the MEMS sensor are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of MEMS sensors, and in particular to a MEMS sensor based on a half-cymbal structure and a preparation method thereof. Background Art

[0002] At present, MEMS (Micro-Electro-Mechanical System) technology has achieved rapid development. MEMS devices have the characteristics of small size and thin thickness in structure. The products can be mass-produced, and fully automated assembly has cost advantages. Many macroscopic large-size sensors and actuators have turned to MEMS structures.

[0003] At present, the preparation of micron-level MEMS sensors is usually based on the cymbal structure. Although this process can solve the disadvantage of small displacement of the circular membrane structure and avoid the low low-frequency performance of the cantilever beam structure due to many slits, the cymbal structure has a small lateral size due to its own proportion problem. The process steps of micro-machining in MEMS sensors are very complicated, and the process of photolithography and etching errors is very difficult, which will cause the upper and lower end covers to be unable to align, resulting in a decrease in the performance of the MEMS sensor and a low yield. Summary of the invention

[0004] The present invention provides a MEMS sensor based on a half-cymbal structure and a preparation method thereof, so as to utilize the micron-scale half-cymbal structure and apply the micron-scale half-cymbal structure to the MEMS sensor, thereby greatly simplifying the process steps, reducing the process difficulty, and improving the production yield of the MEMS sensor.

[0005] In a first aspect, the present invention provides a method for preparing a MEMS sensor based on a half-cymbal structure, comprising:

[0006] providing a substrate;

[0007] A first structural layer is formed on one side of the substrate, the first structural layer includes an end cap layer, the end cap layer includes a first horizontal portion, an inclined portion, and a second horizontal portion, two ends of the inclined portion are respectively connected to the first horizontal portion and the second horizontal portion as a whole, the first horizontal portion is located on the substrate, the second horizontal portion is parallel to the first horizontal portion, and is located on a side of the first horizontal portion away from the substrate, and a first gap exists between the substrate and the end cap layer;

[0008] A lower electrode layer, a piezoelectric layer and an upper electrode layer are sequentially formed on a side of the first structural layer away from the substrate; and a second gap exists between the lower electrode layer and the end cover layer.

[0009] Optionally, forming a first structural layer on a surface of one side of the substrate includes:

[0010] Depositing a first silicon oxide layer on a surface of one side of the substrate;

[0011] Patterning and etching the first silicon oxide layer to form a first sacrificial layer in which the first silicon oxide layer is recessed toward the substrate;

[0012] An end cap layer is deposited on a surface of the first sacrificial layer away from the substrate.

[0013] Optionally, before sequentially forming a lower electrode layer, a piezoelectric layer and an upper electrode layer on a side of the first structural layer away from the substrate, the method further includes:

[0014] Depositing a second silicon oxide layer on the surface of the end cap layer away from the substrate;

[0015] The second silicon oxide layer is etched to form a second sacrificial layer.

[0016] Optionally, a lower electrode layer, a piezoelectric layer and an upper electrode layer are sequentially formed on a side of the first structural layer away from the substrate, including:

[0017] Forming a lower electrode layer on the surface of the end cap layer and the second sacrificial layer away from the substrate;

[0018] Patterning and etching the lower electrode layer and the end cap layer so that the edge of the lower electrode layer coincides with the edge of the end cap layer;

[0019] Forming a piezoelectric layer and a second metal layer on a surface of the lower electrode layer away from the substrate;

[0020] Patterning and etching the second metal layer to form an upper electrode layer, wherein the edge of the upper electrode layer overlaps with the edge of the end cover layer;

[0021] The second sacrificial layer and the first sacrificial layer are removed to form a first gap and a second gap.

[0022] Optionally, before removing the second sacrificial layer and the first sacrificial layer to form the first gap and the second gap, the method further includes:

[0023] Etching to form a first release groove, wherein the first release groove penetrates the piezoelectric layer to expose the first sacrificial layer;

[0024] A second release groove is formed by etching, and the second release groove sequentially penetrates the upper electrode layer, the piezoelectric layer, and the lower electrode layer until the second sacrificial layer is exposed.

[0025] Optionally, removing the second sacrificial layer and the first sacrificial layer to form a first gap and a second gap includes:

[0026] Etching and removing a portion of the first sacrificial layer through the first release groove to form a first gap between the substrate and the end cover layer;

[0027] The second sacrificial layer is removed by etching through the second release groove, so as to form a second gap between the end cap layer and the lower electrode layer.

[0028] Optionally, after the lower electrode layer, the piezoelectric layer and the upper electrode layer are sequentially formed on the side of the first structure layer away from the substrate, the method further includes:

[0029] A protective layer is deposited on the surface of the upper electrode layer away from the substrate.

[0030] Optionally, after the lower electrode layer, the piezoelectric layer and the upper electrode layer are sequentially formed on the side of the first structure layer away from the substrate, the method further includes:

[0031] Depositing an ethyl silicate layer on the surface of the end cap layer away from the substrate;

[0032] The ethyl silicate layer is patterned and etched to form a sealing layer.

[0033] Optionally, after the lower electrode layer, the piezoelectric layer and the upper electrode layer are sequentially formed on the side of the first structure layer away from the substrate, the method further includes:

[0034] etching the piezoelectric layer to expose a portion of the lower electrode layer;

[0035] Two electrode lead pads are formed on a portion of the upper electrode layer and an exposed portion of the lower electrode layer.

[0036] In a second aspect, the present invention provides a MEMS sensor based on a half-cymbal structure, comprising a substrate and a plurality of half-cymbal structures arranged in an array on a surface direction of one side of the substrate, wherein the half-cymbal structure comprises a first structural layer, a lower electrode layer, a piezoelectric layer and an upper electrode layer sequentially arranged in a vertical direction;

[0037] The first structural layer includes a first sacrificial layer and an end cover layer, the end cover layer includes a first horizontal portion, an inclined portion and a second horizontal portion, two ends of the inclined portion are respectively connected to the first horizontal portion and the second horizontal portion as a whole, the first horizontal portion is located on the substrate; the second horizontal portion is parallel to the first horizontal portion, and is located on the side of the first horizontal portion away from the substrate, and a first gap exists between the substrate and the end cover layer; there is a second gap between the lower electrode layer and the end cover layer.

[0038] The technical solution of the present invention is to provide a substrate; form a first structural layer on one side of the substrate, the first structural layer includes an end cap layer, the end cap layer includes a first horizontal portion, an inclined portion and a second horizontal portion, the two ends of the inclined portion are respectively connected to the first horizontal portion and the second horizontal portion as a whole, the first horizontal portion is located on the substrate, the second horizontal portion is parallel to the first horizontal portion and is located on the side of the first horizontal portion away from the substrate, and there is a first gap between the substrate and the end cap layer; form a lower electrode layer, a piezoelectric layer and an upper electrode layer in sequence on the side of the first structural layer away from the substrate; there is a second gap between the lower electrode layer and the end cap layer. Through the above method, a micron-scale semi-cymbal structure is used, and the micron-scale semi-cymbal structure is applied to MEMS sensors, which greatly simplifies the process steps, reduces the process difficulty, improves the production yield of MEMS sensors, and at the same time improves the volume displacement of MEMS sensors under voltage.

[0039] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 A flowchart of a method for preparing a MEMS sensor based on a half-cymbal structure provided in Embodiment 1 of the present invention;

[0042] Figure 2 A flowchart of a preparation process of a MEMS sensor based on a half-cymbal structure provided in Embodiment 1 of the present invention;

[0043] Figure 3 A flow chart of a second method for preparing a MEMS sensor based on a half-cymbal structure provided in Embodiment 1 of the present invention;

[0044] Figure 4 A flowchart of a method for preparing a MEMS sensor based on a half-cymbal structure provided in Embodiment 2 of the present invention;

[0045] Figure 5 A flow chart of a preparation process of a MEMS sensor based on a half-cymbal structure provided in Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0047] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0048] Embodiment 1

[0049] Figure 1 A flowchart of a method for preparing a MEMS sensor based on a half-cymbal structure provided in Embodiment 1 of the present invention, Figure 2 The present invention provides a flowchart of a preparation process of a MEMS sensor based on a half-cymbal structure according to the first embodiment of the present invention. This embodiment can be applied to the case where the half-cymbal structure is applied to a MEMS sensor to reduce the process difficulty and improve the production yield of the MEMS sensor, such as Figure 1 and Figure 2 As shown, the preparation method comprises:

[0050] S110, providing a substrate.

[0051] Among them, reference Figure 2 As shown in FIG. a), substrate 1 is the basic structure of the MEMS sensor, and mainly plays a supporting role so that a semi-cymbal structure can be subsequently formed on one side of the substrate 1. Exemplarily, the material of the substrate 1 may include silicon.

[0052] S120, forming a first structural layer on one side of the substrate.

[0053] Among them, reference Figure 2As shown in FIG. b), the first structural layer 2 includes an end cap layer 22, and the end cap layer 22 includes a first horizontal portion 221, an inclined portion 222, and a second horizontal portion 223. The two ends of the inclined portion 221 are respectively connected to the first horizontal portion 221 and the second horizontal portion 223 as a whole. The first horizontal portion 221 is located on the substrate 1, and the second horizontal portion 223 is parallel to the first horizontal portion 221 and is located on the side of the first horizontal portion 221 away from the substrate 1. The inclined portion 222 is used to change displacement in the longitudinal direction. In this embodiment, the first sacrificial layer 21 mainly plays a role of separation and support, and part of the first sacrificial layer 21 will be removed later to form a first gap between the substrate 1 and the end cap layer 22. The remaining first sacrificial layer 21 is used to support the half-cymbal structure to make the prepared half-cymbal structure stable.

[0054] Specifically, after providing the substrate 1, a first sacrificial layer 21 is formed on one side of the substrate 1 by deposition, wherein the method of depositing the first sacrificial layer 21 may include but is not limited to chemical deposition and other processes. After the first sacrificial layer 21 is formed on one side of the substrate 1, an end cap layer 22 may be formed on the surface of the first sacrificial layer 21 away from the substrate 1 by deposition. The method of depositing the end cap layer 22 may include but is not limited to magnetron sputtering and other processes, and the formed end cap layer 22 protrudes toward one side of the substrate 1 to form an inclined portion 222, a second horizontal portion 223 and a first horizontal portion 221. The material deposited to form the first sacrificial layer 21 may include but is not limited to polycrystalline silicon, single crystal silicon, silicon nitride or silicon oxide, and the material deposited to form the end cap layer 22 may include but is not limited to metal materials with a large Young's modulus such as molybdenum, copper or tungsten. In addition, the formed first sacrificial layer 21 can be finally removed by an etching process.

[0055] S130, forming a lower electrode layer, a piezoelectric layer and an upper electrode layer in sequence on a side of the first structure layer away from the substrate.

[0056] Among them, reference Figure 2 As shown in Figure c), the lower electrode layer 3 and the upper electrode layer 5 can be used for an external power supply, and the lower electrode layer 3 and the upper electrode layer 5 are usually opposite electrodes. If the power supply external to the lower electrode layer 3 is a positive electrode, the upper electrode layer 5 is externally connected to a negative electrode; or if the power supply external to the upper electrode layer 5 is a positive electrode, the lower electrode layer 3 is externally connected to a negative electrode, so that a current loop is formed between the upper electrode layer 5 and the lower electrode layer 3. The piezoelectric layer 4 is arranged between the upper electrode layer 5 and the lower electrode layer 3, and is used for when a certain voltage is applied to the upper electrode layer 5 and the lower electrode layer 3, the piezoelectric layer 4 can produce a corresponding displacement change in the lateral direction according to the voltage. There is a second gap 24 between the lower electrode layer 3 and the end cover layer 22, and the second gap 24 can be used for the end cover layer 22 to deform and produce a space that changes when the displacement changes.

[0057] Specifically, after forming the first structural layer 2, the surface of the first structural layer 2 away from the substrate 1, that is, the end cover layer 22 is deposited on the side away from the substrate 1, so as to form the lower electrode layer 3. After forming the lower electrode layer 3, the deposition is continued on the side of the lower electrode layer 3 away from the substrate 1, so as to form the piezoelectric layer 4. After forming the piezoelectric layer 4, the upper electrode layer 5 is deposited on the side of the piezoelectric layer 4 away from the substrate 1. In this way, the lower electrode layer 3, the piezoelectric layer 4 and the upper electrode layer 5 are sequentially formed on the side of the first structural layer 2 away from the substrate 1. There is a second gap 24 between the formed lower electrode layer 3 and the end cover layer 22, so that a micrometer-level semi-cymbal structure is prepared. Among them, the method of depositing the lower electrode layer 3, the piezoelectric layer 4 and the upper electrode layer 5 can include but is not limited to magnetron sputtering and other methods for deposition. In addition, the materials used for depositing the lower electrode layer 3 and the upper electrode layer 5 can include but are not limited to metal materials with a large Young's modulus such as molybdenum, copper or tungsten, and the materials used for depositing the piezoelectric layer 4 can include but are not limited to aluminum nitride, scandium-doped aluminum nitride, zinc oxide or lead zirconate titanate and other piezoelectric materials. In addition, the MEMS sensor may include one half-cymbal structure or multiple half-cymbal structures. When the MEMS sensor includes multiple half-cymbal structures, the above method can be used to simultaneously prepare multiple half-cymbal structures on one side of the substrate 1, and the half-cymbal structures can be arranged in an array on the substrate 1, which greatly simplifies the preparation process and reduces production costs.

[0058] In addition, the working principle of the prepared half-cymbal structure is as follows: by applying a certain voltage to the upper electrode layer 5 and the lower electrode layer 3 in the half-cymbal structure, the piezoelectric layer 4 can be deformed to a certain extent in the lateral direction, resulting in a displacement change, and the displacement change will drive the end cover layer 22 to deform in the longitudinal direction at the same time, resulting in a displacement change. Conversely, the longitudinal displacement of the end cover layer 22 can also be converted into the lateral displacement of the piezoelectric layer 4. In other words, the mutual conversion between the lateral displacement of the piezoelectric layer 4 and the longitudinal displacement of the end cover layer 22 is achieved, ensuring that the MEMS sensor meets the performance requirements when used as a receiving end and a transmitting end.

[0059] The technical solution of the embodiment of the present invention is provided by providing a substrate; forming a first structural layer on one side of the substrate, the first structural layer including an end cap layer, the end cap layer including a first horizontal portion, an inclined portion and a second horizontal portion, the two ends of the inclined portion are respectively connected to the first horizontal portion and the second horizontal portion as a whole, the first horizontal portion is located on the substrate, the second horizontal portion is parallel to the first horizontal portion and is located on the side of the first horizontal portion away from the substrate, and a first gap exists between the substrate and the end cap layer; forming a lower electrode layer, a piezoelectric layer and an upper electrode layer in sequence on the side of the first structural layer away from the substrate; and a second gap exists between the lower electrode layer and the end cap layer. Through the above method, a micron-scale semi-cymbal structure is realized, and the micron-scale semi-cymbal structure is applied to MEMS sensors, which greatly simplifies the process steps, reduces the process difficulty, improves the production yield of MEMS sensors, and at the same time improves the volume displacement of MEMS sensors under voltage.

[0060] In another specific embodiment, Figure 3 A flowchart of a second method for preparing a MEMS sensor based on a cymbal structure provided in the first embodiment of the present invention is provided. Figure 3 As shown, optionally, after forming a lower electrode layer, a piezoelectric layer and an upper electrode layer in sequence on the side of the first structural layer away from the substrate, it also includes: depositing an ethyl silicate layer on the surface of the upper electrode layer away from the substrate; patterning and etching the ethyl silicate layer to form a sealing layer.

[0061] Among them, reference Figure 3 As shown, when the MEMS sensor is applied to the MEMS hydrophone, it is also necessary to form a sealing layer 6 on the surface of the upper electrode layer 5 away from the substrate to ensure that the MEMS sensor can work normally in water. Specifically, an ethyl silicate layer is deposited on the surface of the upper electrode layer 5 away from the substrate 1. After the ethyl silicate layer is formed, the formed ethyl silicate layer is patterned and etched to form the sealing layer 6. In this embodiment, the patterned etching method may include processes such as chemical etching, so that the formed sealing layer 6 does not cover the position of the upper electrode layer 5 where the external power supply is connected.

[0062] Embodiment 2

[0063] Figure 4 A flowchart of a method for preparing a MEMS sensor based on a half-cymbal structure provided in the second embodiment of the present invention, Figure 5 This is a flow chart of a manufacturing process of a MEMS sensor based on a half-cymbal structure provided in the second embodiment of the present invention. This embodiment refines the implementation of the manufacturing method of the MEMS sensor based on the half-cymbal structure. The contents not yet detailed in this embodiment can be referred to the above embodiments, and will not be repeated here. Figure 4 and Figure 5 As shown, the method includes:

[0064] S210, providing a substrate.

[0065] S211, depositing a first silicon oxide layer on a surface of one side of the substrate.

[0066] The deposition method may include but is not limited to chemical deposition and other processes.

[0067] S212, pattern-etching the first silicon oxide layer to form a first sacrificial layer in which the first silicon oxide layer is recessed toward the substrate.

[0068] Specifically, refer to Figure 5 As shown in FIG. b), after forming the first silicon oxide layer, the first silicon oxide layer is patterned and etched so that the center of the first silicon oxide layer is recessed toward the substrate 1, thereby forming a first sacrificial layer 21. The angle formed between the inclined edge of the first sacrificial layer 21 and the surface of the substrate 1 is α.

[0069] S213, depositing a cap layer on the surface of the first sacrificial layer away from the substrate.

[0070] Specifically, refer to Figure 5 As shown in FIG. c), after the first sacrificial layer 21 is formed, a deposition is performed on the surface of the first sacrificial layer 21 away from the substrate 1 to form an end cap layer 22 having a certain thickness. Since the first sacrificial layer 21 is recessed on the side facing the substrate 1, the end cap layer 22 formed on the surface of the first sacrificial layer 21 will protrude toward the side of the substrate 1, so that the formed end cap layer 22 includes an inclined portion 222, a first horizontal portion 221, and a second horizontal portion 223.

[0071] S214, depositing a second silicon oxide layer on the surface of the end cap layer away from the substrate.

[0072] For details, please refer to Figure 5 As shown in FIG. c), after the end cap layer 22 is formed, deposition is performed on the surface of the end cap layer 22 away from the substrate 1 to form a second silicon oxide layer. The deposition method may include but is not limited to chemical deposition and other processes.

[0073] S215, etching the second silicon oxide layer to form a second sacrificial layer.

[0074] Among them, etching includes chemical mechanical polishing, photolithography etching and BOE solution etching. Chemical Mechanical Polishing (CMP) is the simultaneous chemical etching and mechanical grinding. During the polishing process, sodium hydroxide reacts with the silicon surface to form sodium silicate. Through grinding with silica colloidal sol, sodium silicate enters the polishing liquid. The two processes are carried out simultaneously without interruption to achieve the purpose of polishing. Photolithography technology is a technology that transfers the pattern on the mask to the substrate with the help of photoresist (photoresist) under the action of light. BOE solution etching, that is, buffered oxide etchant (Buffered Oxide Etch), is a liquid corrosive agent commonly used in semiconductor manufacturing processes. By precisely controlling the etching time and temperature, BOE solution can effectively remove silicon oxide film and is a key link in the semiconductor manufacturing process.

[0075] For details, please refer to Figure 5 As shown in FIG. d), after the second silicon oxide layer is formed, the second silicon oxide layer is chemically mechanically polished to ensure that the surface of the second oxide layer is flat. After the surface of the second silicon oxide layer is flat, the second silicon oxide layer in the edge area is patterned and etched using a photolithography process to remove part of the second silicon oxide layer at the edge. Finally, the excess second oxide layer is corroded and removed using a BOE solution to form a second sacrificial layer, and the formed second sacrificial layer is flush with both ends of the end cap layer 22.

[0076] S216, forming a lower electrode layer on the surface of the end cover layer and the second sacrificial layer away from the substrate.

[0077] S217, pattern-etching the lower electrode layer and the end cover layer so that the edge of the lower electrode layer overlaps with the edge of the end cover layer.

[0078] Specifically, refer to Figure 5 As shown in Figure e), after the lower electrode layer 3 is formed by deposition on the surface of the end cover layer 22 and the second sacrificial layer away from the substrate 1, the edges of the lower electrode layer 3 and the end cover layer 22 are patterned and etched, and the edge of the lower electrode layer 3 formed after etching coincides with the edge of the end cover layer 22.

[0079] S218, forming a piezoelectric layer and a second metal layer on the surface of the lower electrode layer away from the substrate.

[0080] S219, pattern-etching the second metal layer to form an upper electrode layer, wherein an edge of the upper electrode layer overlaps an edge of the end cover layer.

[0081] Specifically, refer to Figure 5As shown in FIG. f), after the lower electrode layer 3 is formed, a piezoelectric layer and a second metal layer are continuously deposited on the surface of the lower electrode layer 3 away from the substrate 1. After the second metal layer is formed, the second metal layer is patterned and etched to remove part of the second metal layer. After the etching is completed, an upper electrode layer 5 is formed. The edge of the formed upper electrode layer 5 coincides with the edge of the end cover layer 22.

[0082] S220, etching the piezoelectric layer to expose a portion of the lower electrode layer.

[0083] Specifically, refer to Figure 5 As shown in FIG. g), since the upper electrode layer 5 partially covers the piezoelectric layer 4, the uncovered piezoelectric layer 4 will be exposed. When the upper electrode layer 5 and the lower electrode layer 3 are connected to an external power source, two electrode lead pads 11 need to be provided to achieve electrical connection with the external power source through the electrode lead pads 11, thereby achieving power supply to the upper electrode layer 5 and the lower electrode layer 3. In this embodiment, the exposed piezoelectric layer 4 can be etched, and the etching can be achieved by chemical etching and other processes. After the etching of the piezoelectric layer 4 is completed, part of the lower electrode layer 3 can be exposed.

[0084] S221 , forming two electrode lead pads on the upper electrode layer and the exposed portion of the lower electrode layer.

[0085] The method for preparing the electrode lead pad includes but is not limited to a stripping process, wherein the stripping process is to obtain a patterned photoresist structure or a metal mask on the substrate 1 by a photolithography process, plate a metal pad on the mask by a coating process, and then use a degumming liquid or a stripping liquid to dissolve the photoresist to obtain the electrode lead pad. In this embodiment, the stripping process may include a lift-off stripping process.

[0086] For details, please refer to Figure 5 As shown in Figure g), after part of the lower electrode layer 3 is exposed, a stripping process can be used to form two electrode lead pads 11 on the upper electrode layer 5 and the exposed part of the lower electrode layer 3, so that the two electrode lead pads 11 can be connected to an external power source to supply power to the upper electrode layer 5 and the lower electrode layer 3.

[0087] S222 , etching to form a first release groove, wherein the first release groove penetrates the piezoelectric layer to expose the first sacrificial layer.

[0088] For details, please refer to Figure 5As shown in FIG. 5( g), after forming the first sacrificial layer 21, the end cap layer 22, the second sacrificial layer, the lower electrode layer 3, the piezoelectric layer 4 and the upper electrode layer 5 on one side of the substrate 1, in order to remove part of the first sacrificial layer 21, it is necessary to etch the piezoelectric layer 4 at one edge of the piezoelectric layer 4, and a first release groove 9 is formed after the etching is completed. In this embodiment, the etching method may include but is not limited to chemical etching and other processes, and after the etching is completed, a part of the first sacrificial layer 21 located on the side of the end cap layer 22 facing the substrate 1 is exposed, so that a part of the first sacrificial layer 21 can be subsequently etched through the first release groove 9.

[0089] It should be noted that the etching to form the first release groove in this step can be performed simultaneously with the etching of the piezoelectric layer in S220 to expose part of the lower electrode layer in the actual preparation process, so as to simplify the etching process and shorten the preparation time.

[0090] S223, etching to form a second release groove, the second release groove sequentially penetrates the upper electrode layer, the piezoelectric layer, and the lower electrode layer until the second sacrificial layer is exposed.

[0091] For details, please refer to Figure 5 As shown in Figure g), in order to remove the second sacrificial layer, it is necessary to etch in sequence in the direction of the upper electrode layer 5 toward the substrate 1 to form a second release groove 10. The formed second release groove 10 sequentially penetrates the upper electrode layer 5, the piezoelectric layer 4 and the lower electrode layer 3, so that the second sacrificial layer can be completely exposed, so that the second sacrificial layer can be removed subsequently through the second release groove 10.

[0092] S224, etching and removing the first sacrificial layer through the first release groove to form a first gap between the substrate and the end cover layer.

[0093] Specifically, refer to Figure 5 As shown in FIG. 3 h), after the first release groove 9 is formed, part of the first sacrificial layer 21 can be etched through the first release groove 9. The etching method may include but is not limited to dry etching and other processes. After the first sacrificial layer 21 is dry-etched, a first gap 23 can be formed between the substrate 1 and the end cover layer 22.

[0094] S225 , etching and removing the second sacrificial layer through the second release groove, so as to form a second gap between the end cover layer and the lower electrode layer.

[0095] For details, please refer to Figure 5As shown in FIG. 1h), after the second release groove 10 is formed, the second sacrificial layer can be etched through the second release groove 10. The etching method may include but is not limited to dry etching and other processes. After the second sacrificial layer is etched, a second gap 24 can be formed between the end cover layer 22 and the lower electrode layer 3. The structure formed after removing the second sacrificial layer and part of the first sacrificial layer 21 is a micron-scale semi-cymbal structure.

[0096] It should be noted that the process flow of forming the first gap in S224 and the process flow of forming the second gap in S225 can be simultaneously etched and removed during the actual preparation process to form the first gap and the second gap, so as to simplify the process flow and shorten the preparation time.

[0097] The technical solution of the embodiment of the present invention realizes the preparation of the micron-scale half-cymbal structure and applies the micron-scale half-cymbal structure to the MEMS sensor, which greatly simplifies the process steps, reduces the process difficulty, improves the production yield of the MEMS sensor, and at the same time increases the volume displacement of the MEMS sensor under the action of voltage.

[0098] In another specific embodiment, optionally, after forming a lower electrode layer, a piezoelectric layer and an upper electrode layer in sequence on a side of the first structure layer away from the substrate, the further embodiment further includes: depositing a protective layer on a surface of the end cover layer away from the substrate.

[0099] The protective layer 7 is used to protect the upper electrode layer 5 to prevent the upper electrode layer 5 from being oxidized.

[0100] Specifically, refer to Figure 5 As shown in FIG. 1 , after the upper electrode layer 5 is formed, since the material used for the upper electrode layer 5 is generally a metal material, oxidation will occur when it is placed in the air for a long time. Therefore, in order to prevent the upper electrode layer 5 from being oxidized, it is necessary to deposit on the surface of the upper electrode layer 5 away from the substrate 1, thereby forming a protective layer 7 on the surface of the upper electrode layer 5 away from the substrate. The material of the protective layer 7 can be the same as that of the piezoelectric layer 4, but the thickness is thinner than that of the piezoelectric layer 4.

[0101] It should be noted that when etching to form the second release groove 10, the second release groove 10 will first penetrate the protective layer 7, and then sequentially penetrate the upper electrode layer 5, the piezoelectric layer 4 and the lower electrode layer 3 until the second sacrificial layer is exposed. Similarly, when forming the electrode lead pad 11 on the upper electrode layer 5, the protective layer 7 needs to be patterned and etched to expose part of the upper electrode layer 5, and the electrode lead pad 11 is prepared on the exposed upper electrode layer 5 by a stripping process.

[0102] Based on the same inventive concept, the embodiment of the present invention further provides a MEMS sensor based on a half-cymbal structure, referring to Figure 2As shown in Figure c), the MEMS sensor includes a substrate 1 and a plurality of half-cymbal structures arranged in an array on the surface direction of one side of the substrate 1, the half-cymbal structure includes a first structure layer 2, a lower electrode layer 3, a piezoelectric layer 4 and an upper electrode layer 5 arranged in sequence along the vertical direction; the first structure layer 2 includes a first sacrificial layer 21 and an end cover layer 22, the end cover layer 22 includes a first horizontal portion 221, an inclined portion 222 and a second horizontal portion 223, the two ends of the inclined portion 222 are respectively integrally connected to the first horizontal portion 221 and the second horizontal portion 223, the first horizontal portion 221 is located on the substrate 1; the second horizontal portion 223 is parallel to the first horizontal portion 221, and is located on the side of the first horizontal portion 221 away from the substrate 1, and there is a first gap between the substrate 1 and the end cover layer 22; there is a second gap between the lower electrode layer 3 and the end cover layer 22.

[0103] Specifically, the MEMS sensor provided in this embodiment can be applied in different MEMS sensor fields, for example, including but not limited to sensor fields such as MEMS microphones or MEMS speakers, and when the application fields of the MEMS sensor are different, the corresponding working principles will also have certain differences. In this embodiment, when the MEMS sensor is applied to a MEMS speaker, taking a half-cymbal structure provided on the substrate 1 as an example, its working principle is: the lower electrode layer 3 and the upper electrode layer 5 are respectively connected to an external power supply, and a certain voltage is applied to the upper electrode layer 3 and the lower electrode layer 5, which will cause the piezoelectric layer 4 located between the upper electrode layer 3 and the lower electrode layer 5 to produce a certain displacement in the lateral direction, and the displacement change will drive the end cover layer 22 to undergo a certain displacement change in the longitudinal direction, and the magnitude of the displacement change will affect the output response of the MEMS speaker. Specifically, when the displacement change of the piezoelectric layer 23 in the transverse direction is positive, that is, the piezoelectric layer 23 is stretched, it will drive the stretching of the end cap layer 22, so that the distance of the end cap layer 22 in the longitudinal direction is reduced; wherein, the second gap 24 is used to achieve the displacement change of the end cap layer 22 in the longitudinal direction, generating a displacement change; when the displacement change of the piezoelectric layer 4 in the transverse direction is negative, that is, the piezoelectric layer 4 is contracted, it will drive the extrusion of the end cap layer 22, so that the distance of the end cap layer 22 in the longitudinal direction increases. After the end cap layer 22 generates a displacement change in the longitudinal direction, the displacement change can be converted into a sound pressure signal emitted outward, and the greater the displacement change, the greater the output response of the sound pressure signal, and the better the performance of the MEMS speaker. After testing, under the same conditions, if the diameters of the existing cymbal structure and the semi-cymbal structure of this embodiment are both 50um, by applying a terminal voltage excitation of 15V between the upper electrode and the lower electrode of the MEMS sensor based on the cymbal structure and the MEMS sensor based on the semi-cymbal structure, the volume displacement change of the MEMS sensor based on the cymbal structure is 0.88991um3, while the volume displacement change of the MEMS sensor based on the semi-cymbal structure of this application is 1.1383um3. It can be seen that the displacement change of the MEMS sensor prepared in this embodiment has obvious advantages.

[0104] When the MEMS sensor is applied to a MEMS microphone, its working principle is as follows: when a user speaks using a MEMS microphone, sound pressure is generated, and the sound pressure is transmitted to the MEMS sensor. After receiving the sound pressure signal, the half-cymbal structure in the MEMS sensor converts the received sound pressure signal into a displacement change of the end cover layer 22 in the longitudinal direction, causing the end cover layer 22 to produce a certain amount of displacement change. The displacement change of the end cover layer 22 in the longitudinal direction will drive the piezoelectric layer 4 to undergo a corresponding expansion and contraction deformation of a certain amount in the transverse direction, thereby producing a displacement change. After the piezoelectric layer 4 undergoes a displacement change in the transverse direction, the displacement change produced by the piezoelectric layer 4 is converted into an induced electrical signal, so that an induced voltage is generated between the upper electrode layer 3 and the lower electrode layer 5. The greater the induced voltage generated, the greater the output voltage of the MEMS microphone, the higher the sensitivity, and the wider the range of use. In this way, the output voltage and sensitivity of the MEMS sensor can be effectively improved without reducing the output response of the MEMS sensor at low frequencies. In addition, if a plurality of half-cymbal structures are provided on one side of the substrate 1, the half-cymbal structures may be connected in series or in parallel, which is not specifically limited here. When the half-cymbal structures are connected in series, the output voltage of the MEMS sensor is the sum of the output voltages of the half-cymbal structures; when the half-cymbal structures are connected in parallel, the output voltage of the MEMS sensor is the output voltage of a single half-cymbal structure.

[0105] The MEMS sensor based on the half-cymbal structure provided by the embodiment of the present invention has the same technical features and beneficial effects as the preparation method of the MEMS sensor based on the half-cymbal structure.

[0106] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0107] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a MEMS sensor based on a half-cymbal structure, characterized in that: include: providing a substrate; A first structural layer is formed on one side of the substrate, the first structural layer includes an end cap layer, the end cap layer includes a first horizontal portion, an inclined portion, and a second horizontal portion, two ends of the inclined portion are respectively connected to the first horizontal portion and the second horizontal portion as a whole, the first horizontal portion is located on the substrate, the second horizontal portion is parallel to the first horizontal portion, and is located on a side of the first horizontal portion away from the substrate, and a first gap exists between the substrate and the end cap layer; A lower electrode layer, a piezoelectric layer and an upper electrode layer are sequentially formed on a side of the first structural layer away from the substrate; a second gap is provided between the lower electrode layer and the end cover layer.

2. The preparation method according to claim 1, characterized in that: A first structural layer is formed on a surface of one side of the substrate, comprising: Depositing a first silicon oxide layer on a surface of one side of the substrate; Patterning and etching the first silicon oxide layer to form a first sacrificial layer in which the first silicon oxide layer is recessed toward the substrate; The end cap layer is deposited on a surface of the first sacrificial layer away from the substrate.

3. The preparation method according to claim 2, characterized in that: Before sequentially forming a lower electrode layer, a piezoelectric layer and an upper electrode layer on a side of the first structural layer away from the substrate, the method further comprises: Depositing a second silicon oxide layer on the surface of the end cap layer away from the substrate; The second silicon oxide layer is etched to form a second sacrificial layer.

4. The preparation method according to claim 3, characterized in that: A lower electrode layer, a piezoelectric layer and an upper electrode layer are sequentially formed on a side of the first structural layer away from the substrate, including: forming the lower electrode layer on the surface of the end cap layer and the second sacrificial layer away from the substrate; Patterning and etching the lower electrode layer and the end cover layer so that the edge of the lower electrode layer overlaps with the edge of the end cover layer; Forming the piezoelectric layer and the second metal layer on the surface of the lower electrode layer away from the substrate; Patterning and etching the second metal layer to form the upper electrode layer, wherein the edge of the upper electrode layer overlaps with the edge of the end cover layer; The second sacrificial layer and the first sacrificial layer are removed to form the first gap and the second gap.

5. The preparation method according to claim 4, characterized in that: Before removing the second sacrificial layer and the first sacrificial layer to form the first gap and the second gap, the method further includes: Etching to form a first release groove, wherein the first release groove penetrates the piezoelectric layer to expose the first sacrificial layer; A second release groove is formed by etching, wherein the second release groove sequentially penetrates the upper electrode layer, the piezoelectric layer, and the lower electrode layer until the second sacrificial layer is exposed.

6. The preparation method according to claim 5, characterized in that: Removing the second sacrificial layer and a portion of the first sacrificial layer to form the first gap and the second gap comprises: etching and removing the first sacrificial layer through the first release groove, so as to form the first gap between the substrate and the end cover layer; The second sacrificial layer is removed by etching through the second release groove, so as to form the second gap between the end cap layer and the lower electrode layer.

7. The preparation method according to claim 1, characterized in that: After a lower electrode layer, a piezoelectric layer and an upper electrode layer are sequentially formed on a side of the first structural layer away from the substrate, the method further includes: A protective layer is deposited on a surface of the end cover layer away from the substrate.

8. The preparation method according to claim 1, characterized in that: After a lower electrode layer, a piezoelectric layer and an upper electrode layer are sequentially formed on a side of the first structural layer away from the substrate, the method further includes: Depositing an ethyl silicate layer on a surface of the upper electrode layer away from the substrate; The ethyl silicate layer is pattern-etched to form a sealing layer.

9. The preparation method according to claim 1, characterized in that: After a lower electrode layer, a piezoelectric layer and an upper electrode layer are sequentially formed on a side of the first structural layer away from the substrate, the method further includes: Etching the piezoelectric layer to expose a portion of the lower electrode layer; Two electrode lead pads are formed on a portion of the upper electrode layer and an exposed portion of the lower electrode layer.

10. A MEMS sensor based on a half-cymbal structure, characterized in that: It comprises a substrate and a plurality of half-cymbal structures arranged in an array on a surface direction of one side of the substrate, wherein the half-cymbal structure comprises a first structural layer, a lower electrode layer, a piezoelectric layer and an upper electrode layer arranged in sequence along a vertical direction; The first structural layer includes an end cover layer, and the end cover layer includes a first horizontal portion, an inclined portion, and a second horizontal portion. Two ends of the inclined portion are respectively connected to the first horizontal portion and the second horizontal portion as a whole, and the first horizontal portion is located on the substrate; the second horizontal portion is parallel to the first horizontal portion, and is located on a side of the first horizontal portion away from the substrate, and a first gap exists between the substrate and the end cover layer; and a second gap exists between the lower electrode layer and the end cover layer.

Images