Three-dimensional positioning piezoelectric MEMS microphone and manufacturing method thereof

Abstract

This invention provides a three-dimensional positioning piezoelectric MEMS microphone and its fabrication method. It 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 and second back cavities are correspondingly arranged and connected; a piezoelectric diaphragm structure corresponding to the back cavity; 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 by a main support beam; each main cantilever beam has a cantilever beam groove, and the Y-direction high-sensitivity sensing cantilever beam assembly is disposed at the cantilever beam groove of each main cantilever beam, the Y-direction high-sensitivity sensing cantilever beam assembly including one or more pairs of secondary cantilever beams, and each pair of secondary cantilever beams being fixed to the main cantilever beams by secondary support beams.

Description

Technical Field

[0001] This invention belongs to the field of semiconductors, and in particular relates to a three-dimensional positioning piezoelectric MEMS microphone and its fabrication method. Background Technology

[0002] A microphone is an energy conversion device that can convert sound signals into electrical signals in different ways. MEMS microphones are widely used in smart wearable devices and smartphones due to their advantages such as 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 by multiple microphones distributed in an array). The number of array elements (i.e., 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 to material properties and diaphragm structure design, the signal-to-noise ratio (SNR) of a MEMS microphone is also related to its cavity volume; theoretically, a larger cavity volume results in a higher SNR. In existing technologies, MEMS microphones utilize deep silicon etching to form the cavity structure. However, due to technological limitations, deep silicon etching cannot achieve perfectly perpendicular etching, and the tilt angle can sometimes reach approximately 1°. Furthermore, because the cavity of a MEMS microphone is quite deep, a tilt angle of around 1° can cause fluctuations of tens of micrometers within the cavity, significantly impacting device performance at the cavity boundaries. Summary of the Invention

[0005] The purpose of this invention is to provide a three-dimensional positioning piezoelectric MEMS microphone and its fabrication method, so as to realize 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, the three-dimensional positioning piezoelectric MEMS microphone comprising:

[0007] 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 disposed and the first back cavity and the second back cavity are connected;

[0008] A piezoelectric diaphragm structure is provided corresponding to the back cavity;

[0009] The piezoelectric diaphragm structure includes:

[0010] The frame, the X-direction high-sensitivity sensing cantilever beam combination, and the Y-direction high-sensitivity sensing cantilever beam combination;

[0011] 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 by a main support beam; each main cantilever beam has a cantilever beam groove, and the Y-direction high-sensitivity sensing cantilever beam assembly is located at the cantilever beam groove of each main cantilever beam. The Y-direction high-sensitivity sensing cantilever beam assembly includes one or more pairs of secondary cantilever beams, and each pair of secondary cantilever beams is fixed to the main cantilever beam by a secondary support beam.

[0012] Optionally, the piezoelectric diaphragm structure includes an electrode layer that is interconnected at the frame. The interconnected electrode layers are used to extract signals from the X-direction high-sensitivity sensing cantilever beam combination and the Y-direction high-sensitivity sensing cantilever beam combination.

[0013] Optionally, the cross-sectional area of ​​the first back cavity is larger than the cross-sectional area of ​​the second back cavity.

[0014] Optionally, the depth of the first back cavity is less than the depth of the second back cavity.

[0015] Optionally, the depth of the first back cavity is 2 to 5 micrometers.

[0016] Optionally, the piezoelectric diaphragm structure is a monocrystalline piezoelectric diaphragm structure or a bicrystalline piezoelectric diaphragm structure.

[0017] Optionally, when the piezoelectric diaphragm structure adopts a single-crystal piezoelectric diaphragm structure, the substrate is an SOI substrate; when the piezoelectric diaphragm structure adopts a dual-crystal piezoelectric diaphragm structure, the substrate is a high-resistivity silicon substrate.

[0018] Secondly, a method for fabricating a three-dimensional positioning piezoelectric MEMS microphone is provided, including:

[0019] Provide substrate;

[0020] A first back cavity is formed on the substrate;

[0021] A sacrificial layer is filled into the first back cavity;

[0022] A piezoelectric diaphragm structure is fabricated on the side of a substrate with a 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 has a cantilever beam groove. The Y-direction high-sensitivity sensing cantilever beam assembly is located at the cantilever beam groove of each main cantilever beam. The Y-direction high-sensitivity sensing cantilever beam assembly includes one or more pairs of secondary cantilever beams, and each pair of secondary cantilever beams is fixed to the main cantilever beam via a secondary support beam.

[0023] A second cavity is created on the side of the substrate away from the sacrificial layer, exposing the sacrificial layer.

[0024] Remove the sacrificial layer to obtain the first cavity.

[0025] Optionally, the step of fabricating the piezoelectric diaphragm structure on the side of the substrate having the sacrificial layer includes:

[0026] A seed layer and a first electrode layer are sequentially stacked on the substrate surface;

[0027] The first electrode layer is patterned.

[0028] Fabrication of the first piezoelectric layer;

[0029] The first piezoelectric layer is patterned to obtain the first interconnect groove;

[0030] A patterned second electrode layer is fabricated, and the second electrode layer is connected to the first electrode layer through a first interconnecting groove;

[0031] A passivation layer is fabricated on the surface of the second electrode layer;

[0032] The first piezoelectric layer is patterned to obtain the frame, the X-direction high-sensitivity sensing cantilever beam combination, and the Y-direction high-sensitivity sensing cantilever beam combination.

[0033] Optionally, the step of fabricating a piezoelectric structure layer corresponding to the first and second back cavities on the side of the substrate having a sacrificial layer includes:

[0034] A seed layer and a first electrode layer are sequentially stacked on the substrate surface;

[0035] The first electrode layer is patterned;

[0036] Fabrication of the first piezoelectric layer;

[0037] The first piezoelectric layer is patterned to obtain the first interconnect groove;

[0038] A patterned second electrode layer is fabricated, and the second electrode layer is connected to the first electrode layer through a first interconnecting groove;

[0039] A second piezoelectric layer is fabricated on the surface of the second electrode layer;

[0040] The second piezoelectric layer is patterned to obtain the second interconnect groove and the third interconnect groove;

[0041] A graphical third electrode layer is fabricated, which is interconnected with the second electrode layer through the second interconnect groove and the third interconnect groove;

[0042] A passivation layer is fabricated on the surface of the third electrode layer;

[0043] The first and second piezoelectric layers are patterned to obtain a frame, a combination of high-sensitivity sensing cantilever beams in the X direction, and a combination of high-sensitivity sensing cantilever beams in the Y direction.

[0044] The unexpected technical effects of this invention are:

[0045] Fruit flies in nature possess an unusual auditory mechanism. Their tympanic membranes are spatially separated by approximately 450-520 μm, symmetrically distributed on both sides and coupled from the center. They localize sound through binaural intensity difference (IID) and binaural time difference (ITD). Because the two tympanic membranes are internally coupled, their vibrations form two modes: a rocking mode where the two membranes are out of phase, and a bending mode where they are in phase. This invention, however, modifies the structure of the microphone's piezoelectric diaphragm to create a microphone with a fruit fly-inspired structure. Utilizing the unique auditory mechanism of the fruit fly's tympanic membrane, a unique biomimetic pickup structure is designed, significantly reducing the size of acoustic localization applications (on the order of micrometers). In other words, the microphone provided in this application can achieve acoustic localization with a single microphone, eliminating the need for traditional microphone arrays (multiple microphone structures). This drastically reduces the size of the acoustic localization structure (this application can shrink it to a few hundred micrometers, while traditional microphone arrays are on the order of meters).

[0046] In addition, to address the back cavity boundary problem caused by the deep silicon etching process, this invention employs a first back cavity and a second back cavity (or more back cavities) stacked in the vertical direction. Thus, the first back cavity (the back cavity close to the piezoelectric diaphragm structure) plays a role in determining the back cavity boundary. Regardless of whether the area of ​​the second back cavity is larger or smaller than that of the first back cavity, the boundary of the back cavity is always determined by the first back cavity. Compared to forming a single back cavity through a single deep silicon etching process, forming the first and second back cavities through two separate deep silicon etching processes can reduce the impact of deep silicon etching on the cavity boundaries. (With the total cavity depth remaining constant, forming a single back cavity would cause the cavity width to decrease sequentially at a certain tilt angle, resulting in a significant change in the width of the cavity near the piezoelectric diaphragm structure, leading to a large variation in the cavity boundary. By forming the first and second back cavities separately through two deep silicon etching processes, the cavity boundary is determined only by the first back cavity near the piezoelectric diaphragm structure. This means that although the width of the first back cavity decreases at a certain tilt angle, its shallow depth results in a smaller reduction in width.) This reduces the impact of deep silicon etching on the boundaries of a single back cavity, ensuring device performance. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0048] Figure 1 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention;

[0049] Figure 2 A schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention;

[0050] Figure 3 A schematic diagram of another three-dimensional positioning piezoelectric MEMS microphone provided by the present invention;

[0051] Figure 4 Simulation results of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention;

[0052] Figure 5 A flowchart illustrating a method for fabricating a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0053] Figure 6 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0054] Figure 7 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0055] Figure 8 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0056] Figure 9 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0057] Figure 10 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0058] Figure 11 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0059] Figure 12 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0060] Figure 13 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0061] Figure 14 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0062] Figure 15 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0063] Figure 16 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0064] Figure 17 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0065] Figure 18 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0066] Figure 19 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0067] Figure 20 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0068] Figure 21 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0069] Figure 22 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0070] Figure 23 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0071] Figure 24 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0072] Figure 25 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0073] Figure 26A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0074] Figure 27 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0075] Figure 28 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0076] Figure 29 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0077] Figure 30 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0078] Figure 31 A schematic diagram illustrating the fabrication process of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention;

[0079] Figure 32 This invention provides a layout of the first electrode layer of a three-dimensional positioning piezoelectric MEMS microphone;

[0080] Figure 33 This invention provides a layout of the second electrode layer of a three-dimensional positioning piezoelectric MEMS microphone;

[0081] Figure 34 A layout of the third electrode layer of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention;

[0082] Figure 35 This invention provides a layout of the first to third electrode layers stacked together for a three-dimensional positioning piezoelectric MEMS microphone.

[0083] The attached figures are labeled as follows:

[0084] 1: Substrate; 11: Sacrificial layer; 1000: Back cavity; 1001: First back cavity; 1002: Second back cavity;

[0085] 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: Sub-frame; 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 Implementation

[0086] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0087] Figure 1 This is a schematic diagram of the structure of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention.

[0088] Figure 2 This is a top view of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention.

[0089] Figure 3 This is a top view of another three-dimensional positioning piezoelectric MEMS microphone provided by the present invention.

[0090] See also Figures 1 to 3 The three-dimensional positioning piezoelectric MEMS microphone includes:

[0091] Substrate 1, said substrate 1 having a back cavity 1000 (in Figure 19 (as shown in the figure), 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 disposed and the first back cavity and the second back cavity are connected;

[0092] The piezoelectric diaphragm structure 2 is disposed corresponding to the back cavity 1000 (the piezoelectric diaphragm structure 2 is stacked on the substrate 1).

[0093] Among them, the piezoelectric diaphragm structure 2 includes:

[0094] Frame 201, X-direction high-sensitivity sensing cantilever beam assembly 202 and Y-direction high-sensitivity sensing cantilever beam assembly 203;

[0095] The X-direction high-sensitivity sensing cantilever beam assembly 202 includes one or more pairs of main cantilever beams 2021, each pair of main cantilever beams 2021 being fixed to the frame 201 by a main support beam 2022; each main cantilever beam 2021 has a cantilever beam groove 2023, and the main cantilever beam forms a sub-frame 2024 at the cantilever beam groove 2023; the Y-direction high-sensitivity sensing cantilever beam assembly 203 is disposed at the cantilever beam groove 2023 of each main cantilever beam 2021; 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 by a secondary support beam 2032.

[0096] 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 X-direction sound pickup; 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 Y-direction sound pickup, which is formed in the main cantilever beam by opening a groove, and is symmetrically suspended on both sides of the coupling secondary beam.

[0097] Fruit flies in nature possess an unusual auditory mechanism. Their tympanic membranes are spatially separated by approximately 450-520 μm, symmetrically distributed on both sides and coupled from the center. They localize sound through binaural intensity difference (IID) and binaural time difference (ITD). Because the two tympanic membranes are internally coupled, their vibrations form two modes: a rocking mode where the two membranes are out of phase, and a bending mode where they are in phase. This invention creates a microphone similar to the structure of a fruit fly. Utilizing the unique auditory mechanism of the fruit fly's tympanic membrane, a unique biomimetic pickup structure is designed, significantly reducing the size of acoustic localization applications (on the order of micrometers). That is, the microphone provided in this application can achieve acoustic localization with a single microphone, eliminating the need for traditional microphone arrays (multiple microphone structures). This greatly reduces the size of the acoustic localization structure (this application can shrink it to a few hundred micrometers, while traditional microphone arrays are on the order of meters).

[0098] In addition, to address the back cavity boundary problem caused by deep silicon etching, this invention employs a first back cavity and a second back cavity (or more back cavities) stacked vertically. Thus, the first back cavity (the back cavity closest to the piezoelectric diaphragm structure) plays a role in determining the back cavity boundary. Regardless of whether the area of ​​the second back cavity is larger or smaller than that of the first back cavity, the boundary of the back cavity is always determined by the first back cavity. Compared to forming a single back cavity through a single deep silicon etching process, forming the first and second back cavities through two separate deep silicon etching processes can reduce the impact of deep silicon etching on the cavity boundaries. (With the total cavity depth remaining constant, forming a single back cavity would cause the cavity width to decrease sequentially at a certain tilt angle, resulting in a significant change in the width of the cavity near the piezoelectric diaphragm structure, leading to a large variation in the cavity boundary. By forming the first and second back cavities separately through two deep silicon etching processes, the cavity boundary is determined only by the first back cavity near the piezoelectric diaphragm structure. This means that although the width of the first back cavity decreases at a certain tilt angle, its shallow depth results in a smaller reduction in width.) This reduces the impact of deep silicon etching on the boundaries of a single back cavity, ensuring device performance.

[0099] In this embodiment, the piezoelectric diaphragm structure 2 includes an electrode layer (i.e., a first electrode layer, a second electrode layer, and a third electrode layer). Figure 19 As shown in the figure, the electrode layers are interconnected at frame 201, and the interconnected electrode layers are used to extract the signals of the X-direction high-sensitivity sensing cantilever beam assembly 202 and the Y-direction high-sensitivity sensing cantilever beam assembly 203.

[0100] 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.

[0101] In this embodiment, the depth of the first back cavity 1001 is less than the depth of the second back cavity.

[0102] In this embodiment, the depth of the first back cavity 1001 is 2 to 5 micrometers, for example, 3 micrometers.

[0103] In this embodiment, the piezoelectric diaphragm structure 2 is a single-crystal piezoelectric diaphragm structure or a dual-crystal piezoelectric diaphragm structure.

[0104] In this embodiment, when the piezoelectric diaphragm structure 2 adopts a single-crystal piezoelectric diaphragm structure, the substrate 1 is an SOI substrate; when the piezoelectric diaphragm structure 2 adopts a dual-crystal piezoelectric diaphragm structure, the substrate 1 is a high-resistivity silicon substrate.

[0105] Figure 4 The simulation results of a three-dimensional positioning piezoelectric MEMS microphone provided by the present invention are shown in the figure.

[0106] Finite element analysis clearly demonstrates the effective positioning performance of this structure. A point sound source is added in the air domain, positioned diagonally above the three-dimensional positioning piezoelectric MEMS microphone. Sound waves are excited by the point sound source, and the diaphragms on the three-dimensional positioning piezoelectric MEMS microphone generate corresponding electrical signals upon receiving the sound waves. For example... Figure 4 As shown in (a), the amplitude and phase of the electrical signal generated by the cantilever beam diaphragm in the X direction have significant differences; as Figure 4 (b) and Figure 4 As shown in (c), the amplitude and phase of the electrical signal generated by the cantilever beam diaphragm in the Y direction are identical, indicating that the point sound source is located in a direction perpendicular to the Y-direction diaphragm; Figure 4 As shown in (d), the amplitude and phase of the electrical signals generated by the diaphragms of the cantilever beam in the Y direction opposite each other are significantly different. By analyzing the amplitude and phase of the electrical signals from each diaphragm, the sound source can be accurately located.

[0107] Figure 5 A flowchart illustrating the fabrication method of a three-dimensional positioning piezoelectric MEMS microphone provided by this invention. See also... Figure 5 ,include:

[0108] S101, Provide substrate.

[0109] The substrate is either an SOI (Silicon-On-Insulator) substrate or a high-resistivity silicon substrate.

[0110] In one example, when fabricating a microphone with a bicrystalline piezoelectric diaphragm structure, a high-resistivity silicon substrate is used. See also... Figure 6 This is a schematic diagram of the structure of a substrate provided by the present invention. The substrate 1 is a high-resistivity silicon substrate.

[0111] In another example, when fabricating a microphone with a single-crystal piezoelectric diaphragm structure, an SOI substrate is used. See also... Figure 20 This is a schematic diagram of another substrate provided by the present invention. The substrate 1 is an SOI substrate.

[0112] It should be noted that SOI substrates typically include a Si layer and an oxide layer disposed within the Si layer, which can be a SiO2 layer.

[0113] S102. Create a first back cavity on the substrate.

[0114] In one example, step S102 includes:

[0115] The first step is to fabricate a patterned etch barrier layer on the substrate surface, with the patterned etch barrier layer protruding from the substrate surface and the area to be etched corresponding to the first back cavity.

[0116] The etching barrier layer can be a photoresist layer.

[0117] The second step involves using deep silicon etching to etch the area to be etched on the substrate, creating the first back cavity on the substrate.

[0118] In one example, the depth of the first back cavity is 2 to 5 micrometers. For example, it is 3 micrometers.

[0119] In one example, a schematic diagram of the first back cavity 1001 obtained when fabricating a microphone with a bicrystalline piezoelectric diaphragm structure is shown below. Figure 7 As shown.

[0120] In another example, a schematic diagram of the first back cavity 1001 obtained when fabricating a microphone with a single-crystal piezoelectric diaphragm structure is shown below. Figure 21 As shown.

[0121] S103. Fill the first back cavity with a sacrificial layer.

[0122] In one example, step S103 includes:

[0123] The first step is to fill the first dorsal cavity with a sacrificial layer.

[0124] The sacrificial layer may be slightly higher than the first back cavity, and the sacrificial layer may be an oxide layer, including silicon dioxide.

[0125] The second step is to flatten the sacrificial layer.

[0126] Among these processes, chemical mechanical grinding (CMP) can be used for planarization.

[0127] In one example, a schematic diagram of the sacrificial layer 11 obtained when fabricating a microphone with a bicrystalline piezoelectric diaphragm structure is shown below. Figure 8 As shown.

[0128] In another example, a schematic diagram of the sacrificial layer 11 obtained when fabricating a microphone with a single-crystal piezoelectric diaphragm structure is shown below. Figure 22 As shown.

[0129] S104. A piezoelectric diaphragm structure is fabricated on the side of the substrate with a 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 is fixed to the frame by a main support beam; each main cantilever beam has a cantilever beam groove, the Y-direction high-sensitivity sensing cantilever beam assembly is disposed at the cantilever beam groove of each main cantilever beam, the Y-direction high-sensitivity sensing cantilever beam assembly includes one or more pairs of secondary cantilever beams, and each pair of secondary cantilever beams is fixed to the main cantilever beam by a secondary support beam.

[0130] In one example, when fabricating a microphone with a bicrystalline piezoelectric diaphragm structure, step S104 includes:

[0131] Step 1: Create a seed layer and a first electrode layer stacked sequentially on the substrate surface.

[0132] The seed layer can be an aluminum nitride layer with a thickness of 20nm~30nm, for example, a thickness of 25nm.

[0133] Of course, the seed layer material given here is only an example and is not intended to limit this disclosure. In actual situations, the seed layer material can be selected as needed.

[0134] The first electrode layer can be made of one of molybdenum, titanium, gold, and copper, or an alloy of one or more of molybdenum, titanium, gold, and copper.

[0135] Step 2: Perform patterning on the first electrode layer.

[0136] Patterning can be achieved through photolithography and etching techniques.

[0137] In one example, when fabricating a microphone with a dual-crystal piezoelectric diaphragm structure, a schematic diagram of the first electrode layer 21 obtained is shown below. Figure 9 As shown.

[0138] Step 3: Fabricate the first piezoelectric layer.

[0139] In this embodiment, the piezoelectric layer is made of piezoelectric material. Piezoelectric materials are a large class of single-crystal or polycrystalline solid materials that generate electrical charges on their two end faces when subjected to pressure. They are important carriers for energy conversion and signal transmission. Piezoelectric materials themselves have excellent dynamic characteristics, rich vibration modes, and the acoustic emission spectra of various materials cover almost the entire frequency band. Due to their excellent electromechanical coupling effect, piezoelectric materials can respond quickly to external forces.

[0140] In this embodiment, the piezoelectric layer can be fabricated using a deposition process.

[0141] In one example, a schematic diagram of the first piezoelectric layer 22 obtained when fabricating a microphone with a bicrystalline piezoelectric diaphragm structure is shown below. Figure 10 As shown.

[0142] Step 4: The first piezoelectric layer is patterned to obtain the first interconnect groove.

[0143] In one example, a schematic diagram of the first interconnecting groove 221 obtained when fabricating a microphone with a bicrystalline piezoelectric diaphragm structure is shown below. Figure 11 As shown.

[0144] Step 5: Fabricate a patterned second electrode layer, which is connected to the first electrode layer via a first interconnect groove.

[0145] In one example, a schematic diagram of the second electrode layer 23 obtained when fabricating a microphone with a bicrystalline piezoelectric diaphragm structure is shown below. Figure 12 As shown.

[0146] Step 6: Fabricate a second piezoelectric layer on the surface of the second electrode layer.

[0147] A schematic diagram of the second piezoelectric layer 24 obtained when fabricating a microphone with a bicrystalline piezoelectric diaphragm structure is shown below. Figure 13 As shown.

[0148] Step 7: The second piezoelectric layer is patterned to obtain the second interconnect groove and the third interconnect groove.

[0149] In one example, a schematic diagram of the second interconnecting groove 241 and the third interconnecting groove 242 obtained when fabricating a microphone with a dual-crystal piezoelectric diaphragm structure is shown below. Figure 14 As shown.

[0150] Step 8: Create a graphical third electrode layer, which is interconnected with the second electrode layer through the second interconnect groove and the third interconnect groove.

[0151] In one example, a schematic diagram of the graphical third electrode layer 25 obtained when fabricating a microphone with a dual-crystal piezoelectric diaphragm structure is shown below. Figure 15 As shown.

[0152] Step 9: Create a passivation layer on the surface of the third electrode layer.

[0153] In one example, a schematic diagram of the passivation layer 26 obtained when fabricating a microphone with a bicrystalline piezoelectric diaphragm structure is shown below. Figure 16 As shown.

[0154] The passivation layer can be an oxide layer or a film formed from other insulating materials.

[0155] After the passivation layer is fabricated, electrode pads 27 can be fabricated. Figure 16 Electrode pads 27 fabricated on a passivation layer are also shown, and the electrode pads 27 are electrically connected to multiple electrode layers.

[0156] Step 10: The first piezoelectric layer and the second piezoelectric layer are graphically processed to obtain the frame, the X-direction high-sensitivity sensing cantilever beam combination, and the Y-direction high-sensitivity sensing cantilever beam combination.

[0157] In one example, the first and second piezoelectric layers are patterned to obtain a trench 200, thereby forming a frame, an X-direction high-sensitivity sensing cantilever beam assembly, and a Y-direction high-sensitivity sensing cantilever beam assembly. For the trench 200 obtained when fabricating a microphone with a dual-crystal piezoelectric diaphragm structure, please refer to [reference needed]. Figure 17 .

[0158] In another example, when fabricating a microphone with a single-crystal piezoelectric diaphragm structure, step S104 includes:

[0159] Step 1: Create a seed layer and a first electrode layer stacked sequentially on the substrate surface.

[0160] The seed layer can be an aluminum nitride layer with a thickness of 20nm~30nm, for example, 25nm.

[0161] Of course, the seed layer material given here is only an example and is not intended to limit this disclosure. In actual situations, the seed layer material can be selected as needed.

[0162] The first electrode layer can be made of one of molybdenum, titanium, gold, and copper, or an alloy of one or more of molybdenum, titanium, gold, and copper.

[0163] Step 2: Perform patterning on the first electrode layer.

[0164] In one example, when fabricating a microphone with a single-crystal piezoelectric diaphragm structure, a schematic diagram of the resulting patterned first electrode layer 21 is shown below. Figure 23 As shown.

[0165] Step 3: Fabricate the first piezoelectric layer.

[0166] In this embodiment, the piezoelectric layer is made of piezoelectric material. Piezoelectric materials are a large class of single-crystal or polycrystalline solid materials that generate electrical charges on their two end faces when subjected to pressure. They are important carriers for energy conversion and signal transmission. Piezoelectric materials themselves have excellent dynamic characteristics, rich vibration modes, and the acoustic emission spectra of various materials cover almost the entire frequency band. Due to their excellent electromechanical coupling effect, piezoelectric materials can respond quickly to external forces.

[0167] In this embodiment, the piezoelectric layer can be fabricated using a deposition process.

[0168] In one example, a schematic diagram of the first piezoelectric layer 22 obtained when fabricating a microphone with a single-crystal piezoelectric diaphragm structure is shown below. Figure 24 As shown.

[0169] Step 4: The first piezoelectric layer is patterned to obtain the first interconnect groove.

[0170] In one example, a schematic diagram of the first interconnect groove 221 obtained when fabricating a microphone with a single-chip piezoelectric diaphragm structure is shown below. Figure 25 As shown.

[0171] Step 5: Fabricate a patterned second electrode layer, which is connected to the first electrode layer via a first interconnect groove.

[0172] In one example, a schematic diagram of the second electrode layer 23 obtained when fabricating a microphone with a single-crystal piezoelectric diaphragm structure is shown below. Figure 26 As shown.

[0173] Step 6: Create a passivation layer on the surface of the second electrode layer.

[0174] In one example, a schematic diagram of the passivation layer 26 obtained when fabricating a microphone with a single-crystal piezoelectric diaphragm structure is shown below. Figure 27 As shown.

[0175] Step 7: The first piezoelectric layer is patterned to obtain the frame, the X-direction high-sensitivity sensing cantilever beam combination, and the Y-direction high-sensitivity sensing cantilever beam combination.

[0176] In one example, the first piezoelectric layer is patterned to obtain trench 200, thereby forming a frame, an X-direction high-sensitivity sensing cantilever beam combination, and a Y-direction high-sensitivity sensing cantilever beam combination.

[0177] Please see Figure 28 After the passivation layer is made, electrode pads 27 can be made, and the electrode pads are electrically connected to multiple electrode layers.

[0178] In one example, when fabricating a microphone with a single-crystal piezoelectric diaphragm structure, the resulting groove 200 is as follows: Figure 29 As shown.

[0179] S105. A second cavity is formed on the side of the substrate away from the sacrificial layer, exposing the sacrificial layer.

[0180] The second cavity can be obtained through deep silicon etching.

[0181] In one example, when fabricating a microphone with a bicrystalline piezoelectric diaphragm structure, the resulting second cavity 1002 is as follows: Figure 18 As shown.

[0182] In another example, when fabricating a microphone with a single-crystal piezoelectric diaphragm structure, the resulting second cavity 1002 is as follows: Figure 30 As shown.

[0183] S106. Remove the sacrificial layer to obtain the first cavity.

[0184] The sacrificial layer can be removed using either buffered oxide etching (BOE) or vapor hydrogen fluoride (VHF) dry etching.

[0185] In one example, when fabricating a microphone with a bicrystalline piezoelectric diaphragm structure, the resulting second cavity 1001 is as follows: Figure 19 As shown.

[0186] In another example, when fabricating a microphone with a single-crystal piezoelectric diaphragm structure, the resulting second cavity 1001 is as follows: Figure 31 As shown.

[0187] It should be noted that, Figures 6 to 31 To make such Figure 2 When the microphone is shown, along Figure 2 Cross-sectional view of the dashed line AA'.

[0188] The present invention also provides Figure 3 The diagram shows 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.

[0189] Please see Figure 32 The present invention provides Figure 3 The layout of the first electrode layer corresponding to the structure in the diagram.

[0190] Please see Figure 33 The present invention provides Figure 3 The layout of the second electrode layer corresponding to the structure in the diagram.

[0191] Please see Figure 34 The present invention provides Figure 3 The layout of the third electrode layer corresponding to the structure in the diagram.

[0192] Please see Figure 35 The present invention provides Figure 3 The layout is formed by stacking the first, second, and third electrode layers corresponding to the structure in the diagram.

[0193] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the 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 disposed and the first back cavity and the second back cavity are connected; A piezoelectric diaphragm structure is provided corresponding to the back cavity; The piezoelectric diaphragm structure includes: The frame, the X-direction high-sensitivity sensing cantilever beam combination, and the Y-direction high-sensitivity sensing cantilever beam combination; 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 by a main support beam; each main cantilever beam has a cantilever beam groove, and the Y-direction high-sensitivity sensing cantilever beam assembly is located at the cantilever beam groove of each main cantilever beam. The Y-direction high-sensitivity sensing cantilever beam assembly includes one or more pairs of secondary cantilever beams, and each pair of secondary cantilever beams is fixed to the main cantilever beam by a secondary support beam.

2. The three-dimensional positioning piezoelectric MEMS microphone according to claim 1, characterized in that, The piezoelectric diaphragm structure includes an electrode layer that is interconnected at the frame. The interconnected electrode layers are used to extract 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 that of the second back cavity.

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

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

6. The three-dimensional positioning piezoelectric MEMS microphone according to any one of claims 1 to 5, characterized in that, The piezoelectric diaphragm structure can be a single-crystal piezoelectric diaphragm structure or a dual-crystal piezoelectric diaphragm structure.

7. The three-dimensional positioning piezoelectric MEMS microphone according to claim 6, characterized in that, When a single-crystal piezoelectric diaphragm structure is used, the substrate is an SOI substrate; when a dual-crystal piezoelectric diaphragm structure is used, the substrate is a high-resistivity silicon substrate.

8. A method for fabricating a three-dimensional positioning piezoelectric MEMS microphone, characterized in that, include: Provide substrate; A first back cavity is formed on the substrate; A sacrificial layer is filled into the first back cavity; A piezoelectric diaphragm structure is fabricated on the side of a substrate with a 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 has a cantilever beam groove. The Y-direction high-sensitivity sensing cantilever beam assembly is located at the cantilever beam groove of each main cantilever beam. The Y-direction high-sensitivity sensing cantilever beam assembly includes one or more pairs of secondary cantilever beams, and each pair of secondary cantilever beams is fixed to the main cantilever beam via a secondary support beam. A second cavity is created on the side of the substrate away from the sacrificial layer, exposing the sacrificial layer. Remove the sacrificial layer to obtain the first cavity.

9. The method for fabricating a three-dimensional positioning piezoelectric MEMS microphone according to claim 8, characterized in that, The steps for fabricating a piezoelectric diaphragm structure on the side of a substrate with a sacrificial layer include: A seed layer and a first electrode layer are sequentially stacked on the substrate surface; The first electrode layer is patterned. Fabrication of the first piezoelectric layer; The first piezoelectric layer is patterned to obtain the first interconnect groove; A patterned second electrode layer is fabricated, and the second electrode layer is connected to the first electrode layer through a first interconnecting groove; A passivation layer is fabricated on the surface of the second electrode layer; The first piezoelectric layer is patterned to obtain the frame, the X-direction high-sensitivity sensing cantilever beam combination, and the Y-direction high-sensitivity sensing cantilever beam combination.

10. The method for fabricating a three-dimensional positioning piezoelectric MEMS microphone according to claim 8, characterized in that, The step of fabricating a piezoelectric structure layer corresponding to the first back cavity and the second back cavity on the side of the substrate having a sacrificial layer includes: A seed layer and a first electrode layer are sequentially stacked on the substrate surface; The first electrode layer is patterned. Fabrication of the first piezoelectric layer; The first piezoelectric layer is patterned to obtain the first interconnect groove; A patterned second electrode layer is fabricated, and the second electrode layer is connected to the first electrode layer through a first interconnecting groove; A second piezoelectric layer is fabricated on the surface of the second electrode layer; The second piezoelectric layer is patterned to obtain the second interconnect groove and the third interconnect groove; A graphical third electrode layer is fabricated, which is interconnected with the second electrode layer through the second interconnect groove and the third interconnect groove; A passivation layer is fabricated on the surface of the third electrode layer; The first and second piezoelectric layers are patterned to obtain a frame, a combination of high-sensitivity sensing cantilever beams in the X direction, and a combination of high-sensitivity sensing cantilever beams in the Y direction.

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