Three-dimensional positioning piezoelectric MEMS microphone and preparation method thereof

Abstract

The invention provides a three-dimensional positioning piezoelectric MEMS microphone and a preparation method thereof. Comprising a substrate which is provided with a back cavity; the back cavity comprises a first back cavity and a second back cavity which are arranged in the direction perpendicular to the substrate; the first back cavity and the second back cavity are correspondingly arranged and are communicated with each other; the piezoelectric vibrating diaphragm structure is arranged corresponding to the back cavity; the piezoelectric diaphragm structure comprises a frame, an X-direction high-sensitivity sensing cantilever beam combination and a Y-direction high-sensitivity sensing cantilever beam combination; the X-direction high-sensitivity sensing cantilever beam combination comprises one or more pairs of main cantilever beams, and each pair of main cantilever beams is fixed to the frame through a main supporting beam. Each main cantilever beam is provided with a cantilever beam groove, the Y-direction high-sensitivity sensing cantilever beam combination is arranged at the cantilever beam groove of each main cantilever beam, the Y-direction high-sensitivity sensing cantilever beam combination comprises one or more pairs of secondary cantilever beams, and each pair of secondary cantilever beams are fixed on the main cantilever beams through secondary supporting beams.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductors, and in particular relates to a three-dimensional positioning piezoelectric MEMS microphone and a preparation method thereof. Background Art

[0002] A microphone is an energy conversion device that converts sound signals into electrical signals through various methods. MEMS microphones are widely used in smart wearable devices and smartphones due to their small size, stable performance, high signal-to-noise ratio, good sensitivity, and fast response speed.

[0003] One use case for microphones is acoustic positioning. Current acoustic positioning applications typically use multi-channel arrays (that is, acoustic positioning is achieved through multiple microphones distributed in an array). The number of array elements (that is, microphones) is large, and the array size is large (generally on the order of meters), making it difficult to achieve miniaturized application scenarios.

[0004] In addition, the signal-to-noise ratio of a MEMS microphone is related not only to material properties and diaphragm structure design, but also to its back cavity volume. In theory, the larger the back cavity volume, the greater the signal-to-noise ratio. In existing technologies, MEMS microphones use a deep silicon etching process to form the back cavity structure. However, due to process limitations, deep silicon etching cannot achieve completely vertical etching, and the inclination angle can sometimes reach around 1°. Furthermore, due to the deep back cavity of a MEMS microphone, an inclination angle of around 1° can cause the back cavity range to fluctuate by tens of microns, and the back cavity boundary greatly affects device performance. Summary of the Invention

[0005] The object of the present invention is to provide a three-dimensional positioning piezoelectric MEMS microphone and a preparation method thereof, so as to realize the acoustic positioning function through a single microphone and improve the device performance of the microphone.

[0006] In a first aspect, a three-dimensional positioning piezoelectric MEMS microphone is provided, wherein the three-dimensional positioning piezoelectric MEMS microphone comprises: A substrate having a back cavity; the back cavity includes a first back cavity and a second back cavity arranged in a direction perpendicular to the substrate; the first back cavity and the second back cavity are correspondingly arranged and communicate with each other; a piezoelectric diaphragm structure, arranged corresponding to the back cavity; Among them, the piezoelectric diaphragm structure includes: Frame, X-direction high-sensitivity sensing cantilever beam combination and Y-direction high-sensitivity sensing cantilever beam combination; The X-direction high-sensitivity sensing cantilever beam combination includes one or more pairs of main cantilever beams, each pair of main cantilever beams is fixed to the frame through a main support beam; each main cantilever beam is provided with a cantilever beam groove, and the Y-direction high-sensitivity sensing cantilever beam combination is arranged in the cantilever beam groove of each main cantilever beam, and the Y-direction high-sensitivity sensing cantilever beam combination includes one or more pairs of secondary cantilever beams, and each pair of secondary cantilever beams is fixed to the main cantilever beam through a secondary support beam.

[0007] Optionally, the piezoelectric diaphragm structure includes an electrode layer, the electrode layers are interconnected at the frame, and the interconnected electrode layers are used to lead out signals from the X-direction high-sensitivity sensing cantilever beam combination and the Y-direction high-sensitivity sensing cantilever beam combination.

[0008] Optionally, the cross-sectional area of ​​the first back cavity is greater than the cross-sectional area of ​​the second back cavity.

[0009] Optionally, the first back cavity depth is smaller than the second back cavity depth.

[0010] Optionally, the depth of the first back cavity is 2-5 microns.

[0011] Optionally, the piezoelectric diaphragm structure is a single-chip piezoelectric diaphragm structure or a double-chip piezoelectric diaphragm structure.

[0012] Optionally, when the piezoelectric diaphragm structure adopts a single-chip piezoelectric diaphragm structure, the substrate is an SOI substrate; when the piezoelectric diaphragm structure adopts a dual-chip piezoelectric diaphragm structure, the substrate is a high-resistance silicon substrate.

[0013] In a second aspect, a method for preparing a three-dimensional positioning piezoelectric MEMS microphone is provided, comprising: providing a substrate; opening a first back cavity on the substrate; filling a sacrificial layer in the first back cavity; A piezoelectric diaphragm structure is fabricated on the side of the substrate having the sacrificial layer; the piezoelectric diaphragm structure includes: a frame, an X-direction high-sensitivity sensing cantilever beam assembly, and a Y-direction high-sensitivity sensing cantilever beam assembly; the X-direction high-sensitivity sensing cantilever beam assembly includes one or more pairs of main cantilever beams, each pair of main cantilever beams being fixed to the frame via a main support beam; each main cantilever beam is provided with a cantilever beam groove, and the Y-direction high-sensitivity sensing cantilever beam assembly is disposed in the cantilever beam groove of each main cantilever beam, and the Y-direction high-sensitivity sensing cantilever beam assembly includes one or more pairs of secondary cantilever beams, each pair of secondary cantilever beams being fixed to the main cantilever beam via a secondary support beam; A second cavity is formed on a side of the substrate away from the sacrificial layer to allow the sacrificial layer to leak out; The sacrificial layer is removed to obtain a first cavity.

[0014] Optionally, the step of fabricating a piezoelectric diaphragm structure on a side of the substrate having the sacrificial layer includes: Forming a seed layer and a first electrode layer stacked in sequence on the surface of the substrate; performing patterning on the first electrode layer; fabricating a first piezoelectric layer; Performing patterning on the first piezoelectric layer to obtain first interconnected grooves; forming a patterned second electrode layer, wherein the second electrode layer is connected to the first electrode layer via a first interconnection groove; forming a passivation layer on the surface of the second electrode layer; The first piezoelectric layer is patterned to obtain a frame, an X-direction high-sensitivity sensing cantilever beam combination, and a Y-direction high-sensitivity sensing cantilever beam combination.

[0015] Optionally, the step of manufacturing a piezoelectric structure layer corresponding to the first back cavity and the second back cavity on the side of the substrate having the sacrificial layer includes: Forming a seed layer and a first electrode layer stacked in sequence on the surface of the substrate; performing patterning on the first electrode layer; fabricating a first piezoelectric layer; Performing patterning on the first piezoelectric layer to obtain first interconnected grooves; forming a patterned second electrode layer, wherein the second electrode layer is connected to the first electrode layer via a first interconnection groove; fabricating a second piezoelectric layer on the surface of the second electrode layer; Performing a patterning process on the second piezoelectric layer to obtain a second interconnection groove and a third interconnection groove; forming a patterned third electrode layer, wherein the third electrode layer is interconnected with the second electrode layer through the second interconnection groove and the third interconnection groove; forming a passivation layer on the surface of the third electrode layer; The first piezoelectric layer and the second piezoelectric layer are patterned to obtain a frame, an X-direction high-sensitivity sensing cantilever beam combination, and a Y-direction high-sensitivity sensing cantilever beam combination.

[0016] The unexpected technical effects of the present invention are: Fruit flies possess an unusual hearing mechanism. Their eardrums are spatially separated by approximately 450–520 μm, with two symmetrically spaced eardrums coupled in the middle. Sound localization is achieved through interaural intensity difference (IID) and interaural time difference (ITD). Because the eardrums are internally coupled, they vibrate in two modes: a rocking mode, in which the two eardrums are out of phase; and a bending mode, in which the two eardrums are in phase. The present invention, however, modifies the structure of the microphone's piezoelectric diaphragm to create a microphone with a fruit fly-inspired structure. Leveraging the unique hearing mechanism of the fruit fly eardrum, a unique biomimetic sound pickup structure is designed, significantly reducing the size of acoustic localization applications (on the order of microns). This means that the microphone provided in this application can achieve acoustic localization with a single microphone, eliminating the need for a traditional microphone array (multiple microphones). This significantly reduces the size of the acoustic localization structure (down to hundreds of microns, compared to meters for traditional microphone arrays).

[0017] In addition, to address the back cavity boundary problem caused by the deep silicon etching process, the present invention adopts a first back cavity and a second back cavity (or more back cavities) stacked in the vertical direction, so that the first back cavity (the back cavity close to the piezoelectric diaphragm structure) plays the role of determining the back cavity boundary. Regardless of whether the area of ​​the second back cavity is larger or smaller than the first back cavity, the boundary of the back cavity is always determined by the first back cavity. Compared with forming a single back cavity through a single deep silicon etching process, forming the first back cavity and the second back cavity through two separate deep silicon etching processes can reduce the impact of the deep silicon etching process on the back cavity boundary (the total depth of the back cavity remains unchanged. If a single back cavity is formed, the width of the back cavity will decrease in sequence according to a certain inclination angle. Finally, the width of the back cavity close to the piezoelectric diaphragm structure will change greatly, resulting in a large change in the back cavity boundary. The two separate deep silicon etching processes form the first back cavity and the second back cavity respectively. The back cavity boundary is only determined by the first back cavity close to the piezoelectric diaphragm structure. This is equivalent to that although the width of the first back cavity decreases according to a certain inclination angle, the depth of the first back cavity is shallower, and the degree of reduction in its width will also be smaller). This can reduce the impact of the deep silicon etching process on the boundary of a single back cavity and ensure the performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 A schematic structural diagram of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention; Figure 2 A schematic structural diagram of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention; Figure 3 A schematic structural diagram of another three-dimensional positioning piezoelectric MEMS microphone provided by the present invention; Figure 4 A diagram showing simulation results of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention; Figure 5 A flow chart of a method for manufacturing a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention; Figure 6 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 7 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 8 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 9 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 10 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 11 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 12 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 13 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 14 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 15 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 16 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 17 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 18 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 19 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 20 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 21 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 22 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 23 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 24 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 25 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 26 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 27 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 28 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 29 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 30 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 31 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone during the manufacturing process provided by the present invention; Figure 32 A layout of the first electrode layer of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention; Figure 33 A layout of the second electrode layer of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention; Figure 34 A layout of the third electrode layer of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention; Figure 35A layout formed by stacking the first to third electrode layers of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention.

[0020] The reference numerals are as follows: 1: substrate; 11: sacrificial layer; 1000: back cavity; 1001: first back cavity; 1002: second back cavity; 2: Piezoelectric diaphragm structure; 200: Groove; 201: Frame; 202: X-direction high-sensitivity sensing cantilever beam assembly; 2021: Main cantilever beam; 2022: Main support beam; 2023: Cantilever beam groove; 2024: Subframe; 203: Y-direction high-sensitivity sensing cantilever beam assembly; 2031: Secondary cantilever beam; 2032: Secondary support beam; 20: Seed layer; 21: First electrode layer; 22: First piezoelectric layer; 221: First interconnect groove; 23: Second electrode layer; 24: Second piezoelectric layer; 241: Second interconnect groove; 242: Third interconnect groove; 25: Third electrode layer; 26: Passivation layer; 27: Electrode pad; DETAILED DESCRIPTION To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0021] Figure 1 This is a structural schematic diagram of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention.

[0022] Figure 2 This is a top view of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention.

[0023] Figure 3 A top view of another three-dimensional positioning piezoelectric MEMS microphone provided by the present invention.

[0024] See also Figures 1 to 3 , three-dimensional positioning piezoelectric MEMS microphones include: Substrate 1, the substrate 1 having a back cavity 1000 (in Figure 19 The back cavity 1000 includes a first back cavity 1001 and a second back cavity 1002 arranged in a direction perpendicular to the substrate; the first back cavity and the second back cavity are correspondingly arranged and the first back cavity and the second back cavity are connected; A piezoelectric diaphragm structure 2 is provided corresponding to the back cavity 1000 (the piezoelectric diaphragm structure 2 is stacked on the substrate 1); The piezoelectric diaphragm structure 2 includes: Frame 201, X-direction high-sensitivity sensing cantilever beam assembly 202 and Y-direction high-sensitivity sensing cantilever beam assembly 203; The X-direction high-sensitivity sensing cantilever beam assembly 202 includes one or more pairs of main cantilever beams 2021, and each pair of main cantilever beams 2021 is fixed to the frame 201 through a main support beam 2022; each main cantilever beam 2021 is provided with a cantilever beam groove 2023, and the main cantilever beam forms a sub-frame 2024 at the cantilever beam groove 2023, and the Y-direction high-sensitivity sensing cantilever beam assembly 203 is arranged at the cantilever beam groove 2023 of each main cantilever beam 2021, and the Y-direction high-sensitivity sensing cantilever beam assembly 203 includes one or more pairs of secondary cantilever beams 2031, and each pair of secondary cantilever beams 2031 is fixed to the main cantilever beam 2021 through a secondary support beam 2032.

[0025] In this embodiment, the main support beam 2022 in the piezoelectric diaphragm structure is also a coupling main beam, which is suspended on the back cavity of the substrate; the main cantilever beam is symmetrically suspended on both sides of the coupling main beam for picking up sound in the X direction; the secondary cantilever beam is also a coupling secondary beam, which is formed in the main cantilever beam by opening a groove, and the coupling secondary beam is perpendicular to the coupling main beam; and the secondary cantilever beam is used for picking up sound in the Y direction, which is formed in the main cantilever beam by opening a groove, and is symmetrically suspended on both sides of the coupling secondary beam.

[0026] Fruit flies possess an unusual hearing mechanism. Their eardrums are spatially separated by approximately 450–520 μm, with two symmetrically spaced eardrums coupled in the middle. Sound localization is achieved through interaural intensity difference (IID) and interaural time difference (ITD). Because the eardrums are internally coupled, they vibrate in two modes: a rocking mode, in which the two eardrums are out of phase; and a bending mode, in which the two eardrums are in phase. The present invention employs a microphone with a structure similar to that of a fruit fly. Leveraging the unique hearing mechanism of the fruit fly eardrums, a unique biomimetic sound pickup structure is designed, significantly reducing the size of acoustic localization applications (on the order of microns). This means that the microphone provided in this application can achieve acoustic localization using a single microphone, eliminating the need for a traditional microphone array (multiple microphones). This significantly reduces the size of the acoustic localization structure (down to hundreds of microns, compared to meters for traditional microphone arrays).

[0027] In addition, to address the back cavity boundary problem caused by the deep silicon etching process, the present invention adopts a first back cavity and a second back cavity (or more back cavities) stacked in the vertical direction, so that the first back cavity (the back cavity close to the piezoelectric diaphragm structure) plays the role of determining the back cavity boundary. Regardless of whether the area of ​​the second back cavity is larger or smaller than the first back cavity, the boundary of the back cavity is always determined by the first back cavity. Compared with forming a single back cavity through a single deep silicon etching process, forming the first back cavity and the second back cavity through two separate deep silicon etching processes can reduce the impact of the deep silicon etching process on the back cavity boundary (the total depth of the back cavity remains unchanged. If a single back cavity is formed, the width of the back cavity will decrease in sequence according to a certain inclination angle. Finally, the width of the back cavity close to the piezoelectric diaphragm structure will change greatly, resulting in a large change in the back cavity boundary. The two separate deep silicon etching processes form the first back cavity and the second back cavity respectively. The back cavity boundary is only determined by the first back cavity close to the piezoelectric diaphragm structure. This is equivalent to that although the width of the first back cavity decreases according to a certain inclination angle, the depth of the first back cavity is shallower, and the degree of reduction in its width will also be smaller). This can reduce the impact of the deep silicon etching process on the boundary of a single back cavity and ensure the performance of the device.

[0028] In this embodiment, the piezoelectric diaphragm structure 2 includes electrode layers (ie, a first electrode layer, a second electrode layer, and a third electrode layer). Figure 19 As shown in FIG, the electrode layers are interconnected at the frame 201, and the interconnected electrode layers are used to lead out the signals of the X-direction high-sensitivity sensing cantilever beam combination 202 and the Y-direction high-sensitivity sensing cantilever beam combination 203.

[0029] In this embodiment, the cross-sectional area of ​​the first back cavity 1001 is larger than the cross-sectional area of ​​the second back cavity.

[0030] In this embodiment, the depth of the first back cavity 1001 is less than the depth of the second back cavity.

[0031] In this embodiment, the depth of the first back cavity 1001 is 2-5 microns, for example, 3 microns.

[0032] In this embodiment, the piezoelectric diaphragm structure 2 is a unimorph piezoelectric diaphragm structure or a bimorph piezoelectric diaphragm structure.

[0033] In this embodiment, when the piezoelectric diaphragm structure 2 adopts a single-chip piezoelectric diaphragm structure, the substrate 1 is an SOI substrate; when the piezoelectric diaphragm structure 2 adopts a dual-chip piezoelectric diaphragm structure, the substrate 1 is a high-resistance silicon substrate.

[0034] Figure 4 This is a simulation result diagram of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention.

[0035] Finite element simulation can clearly show the effective positioning effect of the structure. A point sound source is added in the air domain, and the point sound source is located obliquely above the three-dimensional positioning piezoelectric MEMS microphone. The point sound source excites the sound wave, and each diaphragm on the three-dimensional positioning piezoelectric MEMS microphone generates a corresponding electrical signal after receiving the sound wave. Figure 4 As shown in (a) in the figure, the amplitude and phase of the electrical signal generated by the cantilever beam membrane in the X direction have obvious differences; Figure 4 (b) and Figure 4 As shown in (c), there is no difference in the amplitude and phase of the electrical signal generated by the cantilever beam diaphragm in the Y direction, indicating that the point sound source is located in the direction perpendicular to the diaphragm in the Y direction; Figure 4 As shown in (d) of the figure, the amplitude and phase of the electrical signals generated by the diagonally opposite cantilever beam diaphragms in the Y direction are significantly different. The amplitude and phase of the electrical signals from each diaphragm can be used to accurately locate the sound source.

[0036] Figure 5 This is a flow chart of a method for preparing a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention. Figure 5 ,include: S101. Provide a substrate.

[0037] The substrate is a SOI (Silicon-On-Insulator) substrate or a high-resistance silicon substrate.

[0038] In one example, when manufacturing a microphone with a dual-chip piezoelectric diaphragm structure, a high-resistance silicon substrate is used as the substrate. Figure 6 , is a structural schematic diagram of a substrate provided by the present invention, wherein the substrate 1 is a high-resistance silicon substrate.

[0039] In another example, when manufacturing a microphone with a single-chip piezoelectric diaphragm structure, the substrate is an SOI substrate. Figure 20 , is a schematic structural diagram of another substrate provided by the present invention, wherein the substrate 1 is an SOI substrate.

[0040] It should be noted that the SOI substrate generally includes a Si layer and an oxide layer disposed in the Si layer, and the oxide layer may be a SiO2 layer.

[0041] S102, opening a first back cavity on the substrate.

[0042] In one example, step S102 includes: In the first step, a patterned etch stop layer is formed on the surface of the substrate, and the patterned etch stop layer leaks out of the to-be-etched area on the surface of the substrate corresponding to the first back cavity.

[0043] The etch stop layer may be a photoresist layer.

[0044] In the second step, a deep silicon etching process is used to etch the area to be etched on the substrate, and a first back cavity is opened on the substrate.

[0045] In one example, the depth of the first back cavity is 2-5 microns, for example, 3 microns.

[0046] In one example, when manufacturing a microphone having a dual-chip piezoelectric diaphragm structure, the schematic diagram of the first back cavity 1001 is as follows: Figure 7 shown.

[0047] In another example, when manufacturing a microphone having a single-chip piezoelectric diaphragm structure, the schematic diagram of the first back cavity 1001 is as follows: Figure 21 shown.

[0048] S103 , filling a sacrificial layer in the first back cavity.

[0049] In one example, step S103 includes: In the first step, a sacrificial layer is filled in the first back cavity.

[0050] The sacrificial layer may be slightly higher than the first back cavity, and the sacrificial layer may be an oxide layer, and the oxide layer includes silicon dioxide.

[0051] The second step is to planarize the sacrificial layer.

[0052] Among them, a chemical mechanical polishing process can be used for planarization.

[0053] In one example, when manufacturing a microphone having a dual-chip piezoelectric diaphragm structure, the schematic diagram of the sacrificial layer 11 is as follows: Figure 8 shown.

[0054] In another example, when manufacturing a microphone having a single-chip piezoelectric diaphragm structure, the schematic diagram of the sacrificial layer 11 is as follows: Figure 22 shown.

[0055] S104. Fabricate a piezoelectric diaphragm structure on the side of the substrate having the sacrificial layer; wherein the piezoelectric diaphragm structure includes: a frame, an X-direction high-sensitivity sensing cantilever beam assembly, and a Y-direction high-sensitivity sensing cantilever beam assembly; the X-direction high-sensitivity sensing cantilever beam assembly includes one or more pairs of main cantilever beams, each pair of main cantilever beams being fixed to the frame via a main support beam; each main cantilever beam is provided with a cantilever beam groove, and the Y-direction high-sensitivity sensing cantilever beam assembly is disposed in the cantilever beam groove of each main cantilever beam, and the Y-direction high-sensitivity sensing cantilever beam assembly includes one or more pairs of secondary cantilever beams, each pair of secondary cantilever beams being fixed to the main cantilever beam via a secondary support beam.

[0056] In one example, when manufacturing a microphone having a dual-chip piezoelectric diaphragm structure, step S104 includes: Step 1: forming a seed layer and a first electrode layer stacked in sequence on the surface of a substrate.

[0057] The seed layer may be an aluminum nitride layer, and the thickness may be 20 nm to 30 nm, for example, 25 nm.

[0058] Of course, the material of the seed layer given here is only an example and is not intended to limit the present disclosure. In actual situations, the material of the seed layer can be selected as needed.

[0059] The first electrode layer may be made of one of molybdenum, titanium, gold, and copper, or an alloy composed of one or more of molybdenum, titanium, gold, and copper.

[0060] Step 2: performing patterning on the first electrode layer.

[0061] Among them, the graphic processing can be achieved through photolithography technology and etching technology.

[0062] In one example, when manufacturing a microphone having a dual-chip piezoelectric diaphragm structure, the schematic diagram of the patterned first electrode layer 21 is as follows: Figure 9 shown.

[0063] Step 3: fabricate the first piezoelectric layer.

[0064] In this embodiment, the piezoelectric layer is made of piezoelectric material. Piezoelectric materials are a broad class of single-crystal or polycrystalline solid materials that develop charges on their end faces when subjected to pressure. They are important vehicles for energy conversion and signal transmission. Piezoelectric materials inherently possess excellent dynamic characteristics and a rich variety of vibration modes. The acoustic emission spectra of various materials cover nearly the entire frequency range. Piezoelectric materials, due to their excellent electromechanical coupling effect, can rapidly respond to external forces.

[0065] In this embodiment, the piezoelectric layer can be prepared by a deposition process.

[0066] In one example, when manufacturing a microphone having a dual-chip piezoelectric diaphragm structure, the schematic diagram of the first piezoelectric layer 22 is as follows: Figure 10 shown.

[0067] Step 4: perform patterning on the first piezoelectric layer to obtain first interconnected grooves.

[0068] In one example, when manufacturing a microphone having a dual-chip piezoelectric diaphragm structure, a schematic diagram of the first interconnected groove 221 is obtained as shown in FIG. Figure 11 shown.

[0069] Step 5: manufacturing a patterned second electrode layer, wherein the second electrode layer is connected to the first electrode layer via the first interconnection groove.

[0070] In one example, when manufacturing a microphone having a dual-chip piezoelectric diaphragm structure, the schematic diagram of the patterned second electrode layer 23 is as follows: Figure 12 shown.

[0071] Step 6: fabricate a second piezoelectric layer on the surface of the second electrode layer.

[0072] When manufacturing a microphone with a dual-chip piezoelectric diaphragm structure, the schematic diagram of the second piezoelectric layer 24 is as follows: Figure 13 shown.

[0073] Step 7: perform patterning on the second piezoelectric layer to obtain a second interconnection groove and a third interconnection groove.

[0074] In one example, when manufacturing a microphone having a dual-chip piezoelectric diaphragm structure, a schematic diagram of the second interconnected groove 241 and the third interconnected groove 242 is shown as follows: Figure 14 shown.

[0075] Step 8: manufacturing a patterned third electrode layer, wherein the third electrode layer is interconnected with the second electrode layer through the second interconnection groove and the third interconnection groove.

[0076] In one example, when manufacturing a microphone having a dual-chip piezoelectric diaphragm structure, the schematic diagram of the patterned third electrode layer 25 is as follows: Figure 15 shown.

[0077] Step 9: forming a passivation layer on the surface of the third electrode layer.

[0078] In one example, when manufacturing a microphone having a dual-chip piezoelectric diaphragm structure, the schematic diagram of the passivation layer 26 is as follows: Figure 16 shown.

[0079] The passivation layer may be an oxide layer or a film layer formed of other insulating materials.

[0080] After the passivation layer is made, the electrode pad 27 can be made. Figure 16 Also shown is an electrode pad 27 manufactured on the passivation layer, which is electrically connected to the multiple electrode layers.

[0081] Step 10: Graphically process the first piezoelectric layer and the second piezoelectric layer to obtain a frame, an X-direction high-sensitivity sensing cantilever beam combination, and a Y-direction high-sensitivity sensing cantilever beam combination.

[0082] In one example, the first piezoelectric layer and the second piezoelectric layer are patterned to obtain grooves 200, thereby forming a frame, an X-direction high-sensitivity sensing cantilever beam combination, and a Y-direction high-sensitivity sensing cantilever beam combination. When manufacturing a microphone with a dual-chip piezoelectric diaphragm structure, the grooves 200 obtained are shown in FIG. Figure 17 .

[0083] In another example, when manufacturing a microphone having a single-chip piezoelectric diaphragm structure, step S104 includes: Step 1: forming a seed layer and a first electrode layer stacked in sequence on the surface of a substrate.

[0084] The seed layer may be an aluminum nitride layer, and its thickness may be 20 nm to 30 nm, for example, 25 nm.

[0085] Of course, the material of the seed layer given here is only an example and is not intended to limit the present disclosure. In actual situations, the material of the seed layer can be selected as needed.

[0086] The first electrode layer may be made of one of molybdenum, titanium, gold, and copper, or an alloy composed of one or more of molybdenum, titanium, gold, and copper.

[0087] Step 2: performing patterning on the first electrode layer.

[0088] In one example, when manufacturing a microphone having a single-chip piezoelectric diaphragm structure, the schematic diagram of the patterned first electrode layer 21 is as follows: Figure 23 shown.

[0089] Step 3: fabricate the first piezoelectric layer.

[0090] In this embodiment, the piezoelectric layer is made of piezoelectric material. Piezoelectric materials are a broad class of single-crystal or polycrystalline solid materials that develop charges on their end faces when subjected to pressure. They are important vehicles for energy conversion and signal transmission. Piezoelectric materials inherently possess excellent dynamic characteristics and a rich variety of vibration modes. The acoustic emission spectra of various materials cover nearly the entire frequency range. Piezoelectric materials, due to their excellent electromechanical coupling effect, can rapidly respond to external forces.

[0091] In this embodiment, the piezoelectric layer can be prepared by a deposition process.

[0092] In one example, when manufacturing a microphone having a single-chip piezoelectric diaphragm structure, the schematic diagram of the first piezoelectric layer 22 is as follows: Figure 24 shown.

[0093] Step 4: perform patterning on the first piezoelectric layer to obtain first interconnected grooves.

[0094] In one example, when manufacturing a microphone having a single-chip piezoelectric diaphragm structure, a schematic diagram of the first interconnected groove 221 is obtained as shown in FIG. Figure 25 shown.

[0095] Step 5: manufacturing a patterned second electrode layer, wherein the second electrode layer is connected to the first electrode layer via the first interconnection groove.

[0096] In one example, when manufacturing a microphone having a single-chip piezoelectric diaphragm structure, the schematic diagram of the patterned second electrode layer 23 is as follows: Figure 26 shown.

[0097] Step 6: forming a passivation layer on the surface of the second electrode layer.

[0098] In one example, when manufacturing a microphone having a single-chip piezoelectric diaphragm structure, the schematic diagram of the passivation layer 26 is as follows: Figure 27 shown.

[0099] Step 7: Performing graphic processing on the first piezoelectric layer to obtain a frame, an X-direction high-sensitivity sensing cantilever beam combination, and a Y-direction high-sensitivity sensing cantilever beam combination.

[0100] In one example, the first piezoelectric layer is patterned to obtain the groove 200 , thereby forming a frame, an X-direction high-sensitivity sensing cantilever beam combination, and a Y-direction high-sensitivity sensing cantilever beam combination.

[0101] See Figure 28 After the passivation layer is formed, an electrode pad 27 may be formed, and the electrode pad is electrically connected to the plurality of electrode layers.

[0102] In one example, when manufacturing a microphone having a single-chip piezoelectric diaphragm structure, the groove 200 obtained is as follows: Figure 29 shown.

[0103] S105 , forming a second cavity on a side of the substrate away from the sacrificial layer to expose the sacrificial layer.

[0104] The second cavity can be obtained by a deep silicon etching process.

[0105] In one example, when manufacturing a microphone having a dual-chip piezoelectric diaphragm structure, the second cavity 1002 is obtained as follows: Figure 18 shown.

[0106] In another example, when manufacturing a microphone having a single-chip piezoelectric diaphragm structure, the second cavity 1002 is obtained as follows: Figure 30 shown.

[0107] S106 , removing the sacrificial layer to obtain a first cavity.

[0108] The sacrificial layer can be removed by using a buffered oxide etch (BOE) technique or a vapor hydrogen fluoride (VHF) dry etching technique.

[0109] In one example, when manufacturing a microphone having a dual-chip piezoelectric diaphragm structure, the second cavity 1001 obtained is as follows: Figure 19 shown.

[0110] In another example, when manufacturing a microphone having a single-chip piezoelectric diaphragm structure, the second cavity 1001 is obtained as follows: Figure 31 shown.

[0111] It should be noted that Figures 6 to 31 To make Figure 2 When the microphone is Figure 2 Cross-sectional view along the dashed line AA'.

[0112] The present invention also provides Figure 3 The layout of the first electrode layer, the second electrode layer, and the third electrode layer of the microphone, as well as the stacked layout of the first electrode layer, the second electrode layer, and the third electrode layer are shown in FIG.

[0113] See Figure 32 , provided by the present invention Figure 3 The structure in FIG. 1 corresponds to the layout of the first electrode layer.

[0114] See Figure 33 , provided by the present invention Figure 3 The layout of the second electrode layer corresponds to the structure in FIG.

[0115] See Figure 34 , provided by the present invention Figure 3 The layout of the third electrode layer corresponding to the structure in FIG.

[0116] See Figure 35 , provided by the present invention Figure 3 The layout is formed by stacking the first, second and third electrode layers corresponding to the structure in FIG.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A three-dimensional positioning piezoelectric MEMS microphone, characterized in that: The three-dimensional positioning piezoelectric MEMS microphone includes: A substrate having a back cavity; the back cavity includes a first back cavity and a second back cavity arranged in a direction perpendicular to the substrate; the first back cavity and the second back cavity are correspondingly arranged and communicate with each other; a piezoelectric diaphragm structure, arranged corresponding to the back cavity; Among them, the piezoelectric diaphragm structure includes: Frame, X-direction high-sensitivity sensing cantilever beam combination and Y-direction high-sensitivity sensing cantilever beam combination; The X-direction high-sensitivity sensing cantilever beam combination includes one or more pairs of main cantilever beams, each pair of main cantilever beams is fixed to the frame through a main support beam; each main cantilever beam is provided with a cantilever beam groove, and the Y-direction high-sensitivity sensing cantilever beam combination is arranged in the cantilever beam groove of each main cantilever beam, and the Y-direction high-sensitivity sensing cantilever beam combination includes one or more pairs of secondary cantilever beams, and each pair of secondary cantilever beams is fixed to the main cantilever beam through a secondary support beam.

2. The three-dimensional positioning piezoelectric MEMS microphone according to claim 1, characterized in that: The piezoelectric diaphragm structure includes electrode layers, which are interconnected at the frame. The interconnected electrode layers are used to lead out signals from the X-direction high-sensitivity sensing cantilever beam combination and the Y-direction high-sensitivity sensing cantilever beam combination.

3. The three-dimensional positioning piezoelectric MEMS microphone according to claim 1, characterized in that: The cross-sectional area of ​​the first back cavity is greater than the cross-sectional area of ​​the second back cavity.

4. The three-dimensional positioning piezoelectric MEMS microphone according to claim 1, characterized in that: The first back cavity depth is smaller than the second back cavity depth.

5. The three-dimensional positioning piezoelectric MEMS microphone according to claim 4, characterized in that: The depth of the first back cavity is 2-5 microns.

6. The three-dimensional positioning piezoelectric MEMS microphone according to any one of claims 1 to 5, characterized in that: The piezoelectric diaphragm structure is a single-chip piezoelectric diaphragm structure or a double-chip piezoelectric diaphragm structure.

7. The three-dimensional positioning piezoelectric MEMS microphone according to claim 6, characterized in that: When the piezoelectric diaphragm structure adopts a single-chip piezoelectric diaphragm structure, the substrate is an SOI substrate; when the piezoelectric diaphragm structure adopts a double-chip piezoelectric diaphragm structure, the substrate is a high-resistance silicon substrate.

8. A method for preparing a three-dimensional positioning piezoelectric MEMS microphone, characterized in that: include: providing a substrate; opening a first back cavity on the substrate; filling a sacrificial layer in the first back cavity; A piezoelectric diaphragm structure is fabricated on the side of the substrate having the sacrificial layer; the piezoelectric diaphragm structure includes: a frame, an X-direction high-sensitivity sensing cantilever beam assembly, and a Y-direction high-sensitivity sensing cantilever beam assembly; the X-direction high-sensitivity sensing cantilever beam assembly includes one or more pairs of main cantilever beams, each pair of main cantilever beams being fixed to the frame via a main support beam; each main cantilever beam is provided with a cantilever beam groove, and the Y-direction high-sensitivity sensing cantilever beam assembly is disposed in the cantilever beam groove of each main cantilever beam, and the Y-direction high-sensitivity sensing cantilever beam assembly includes one or more pairs of secondary cantilever beams, each pair of secondary cantilever beams being fixed to the main cantilever beam via a secondary support beam; A second cavity is formed on a side of the substrate away from the sacrificial layer to allow the sacrificial layer to leak out; The sacrificial layer is removed to obtain a first cavity.

9. The method for preparing a three-dimensional positioning piezoelectric MEMS microphone according to claim 8, characterized in that: The steps of fabricating a piezoelectric diaphragm structure on a side of a substrate having a sacrificial layer include: Forming a seed layer and a first electrode layer stacked in sequence on the surface of the substrate; performing patterning on the first electrode layer; fabricating a first piezoelectric layer; Performing patterning on the first piezoelectric layer to obtain first interconnected grooves; forming a patterned second electrode layer, wherein the second electrode layer is connected to the first electrode layer via a first interconnection groove; forming a passivation layer on the surface of the second electrode layer; The first piezoelectric layer is patterned to obtain a frame, an X-direction high-sensitivity sensing cantilever beam combination, and a Y-direction high-sensitivity sensing cantilever beam combination.

10. The method for preparing a three-dimensional positioning piezoelectric MEMS microphone according to claim 8, characterized in that: The step of manufacturing a piezoelectric structure layer corresponding to the first back cavity and the second back cavity on a side of the substrate having the sacrificial layer comprises: Forming a seed layer and a first electrode layer stacked in sequence on the surface of the substrate; performing patterning on the first electrode layer; fabricating a first piezoelectric layer; Performing patterning on the first piezoelectric layer to obtain first interconnected grooves; forming a patterned second electrode layer, wherein the second electrode layer is connected to the first electrode layer via a first interconnection groove; fabricating a second piezoelectric layer on the surface of the second electrode layer; Performing a patterning process on the second piezoelectric layer to obtain a second interconnection groove and a third interconnection groove; forming a patterned third electrode layer, wherein the third electrode layer is interconnected with the second electrode layer through the second interconnection groove and the third interconnection groove; forming a passivation layer on the surface of the third electrode layer; The first piezoelectric layer and the second piezoelectric layer are patterned to obtain a frame, an X-direction high-sensitivity sensing cantilever beam combination, and a Y-direction high-sensitivity sensing cantilever beam combination.

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