MEMS microphone and manufacturing method therefor
By using a MEMS microphone design with a three-diaphragm dual-backplane structure, the contradiction between improving sensitivity and signal-to-noise ratio and miniaturizing integration of MEMS silicon microphones was resolved, resulting in a high-performance and easy-to-manufacture MEMS microphone.
Patent Information
- Application Number
- PCT/CN2023/128058
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-06-20
- Filing Date
- 2023-10-31
- Publication Date
- 2026-01-22
AI Technical Summary
Existing MEMS silicon microphones present a contradiction in terms of improving sensitivity and signal-to-noise ratio. It is difficult to achieve both device miniaturization and increased integration. Furthermore, the manufacturing process of the new structure is complex, making it difficult to achieve large-scale production and cost reduction.
The three-diaphragm dual-backplane structure is adopted. By directly bonding the diaphragms of the microphone structure with dual diaphragms and single backplane to form a common diaphragm, a three-diaphragm dual-backplane capacitive MEMS microphone structure is formed, which increases the capacitor area and reduces the manufacturing difficulty.
It improves the sensitivity and signal-to-noise ratio of MEMS microphones, has a small size and excellent performance, reduces the difficulty of manufacturing processes, and is suitable for mass production.
Smart Images
Figure CN2023128058_22012026_PF_FP_ABST
Abstract
Description
MEMS Microphones and Their Manufacturing Methods
[0001] This application claims priority to Chinese Patent Application No. 2023107391950, filed on June 20, 2023, entitled “A MEMS Microphone and a Method for Manufacturing the Same”, the entire contents of which are incorporated herein by reference. Technical Field
[0002] This application relates to the field of semiconductor technology, and more specifically to a MEMS microphone and a method for manufacturing the same. Background Technology
[0003] Micro-Electro-Mechanical Systems (MEMS) technology is a rapidly developing high-tech field in recent years. It utilizes advanced semiconductor manufacturing processes to achieve mass production of devices such as sensors and actuators. Compared to their traditional counterparts, MEMS devices offer significant advantages in terms of size, power consumption, weight, and price. In the market, major applications of MEMS devices include pressure sensors, accelerometers, and silicon microphones.
[0004] MEMS silicon microphones are acoustic sensors that convert sound pressure into analog signals. They consist of a MEMS sensor and an ASIC (Application Specific Integrated Circuit) chip. Current technology uses wire bonding to create electrical contacts between the two and place them in a single package. The MEMS sensor is a variable capacitor with a fixed backplate and a vibrating diaphragm. When sound pressure is applied to the MEMS sensor, the diaphragm vibrates with the sound, changing the distance between the backplate and the diaphragm, and thus changing the capacitance of the variable capacitor. This capacitance change is determined by acoustic parameters and is converted into an analog signal, which is then input to the ASIC for further analysis and processing.
[0005] To further improve the performance of MEMS silicon microphones, the following methods are currently mainly adopted: First, increase the size of the device to improve sensitivity and SNR (Signal-to-Noise Ratio), but this goes against the trend of miniaturization and is not conducive to improving the integration of the device; Second, design a new silicon microphone structure model to achieve differential signal output, thereby reducing noise and achieving high signal-to-noise ratio performance, but the new structure products have complex processes and high manufacturing difficulty, which is not conducive to the large-scale production and cost reduction of the products.
[0006] Summary of the Invention
[0007] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. This summary section is not intended to limit the key and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.
[0008] This application provides a MEMS microphone, including a first microphone structure, a second microphone structure, and a common diaphragm;
[0009] The first microphone structure includes a first diaphragm, a first back plate, and a second diaphragm spaced apart from bottom to top, wherein a first cavity is formed between the first diaphragm and the second diaphragm, and the first back plate is arranged parallel to the first diaphragm and the second diaphragm and passes through the first cavity;
[0010] The second microphone structure includes a third diaphragm, a second back plate, and a fourth diaphragm spaced apart from top to bottom, wherein a second cavity is formed between the third diaphragm and the fourth diaphragm, and the second back plate is arranged parallel to the third diaphragm and the fourth diaphragm and passes through the second cavity;
[0011] The common diaphragm is formed by directly bonding the second diaphragm and the fourth diaphragm.
[0012] In one embodiment, the first diaphragm, the first backplate, the common diaphragm, the second backplate, and the third diaphragm serve as the first electrode, the second electrode, the third electrode, the fourth electrode, and the fifth electrode of the MEMS microphone, respectively.
[0013] In one embodiment, the first cavity is further provided with a plurality of first support columns, the two ends of which are respectively connected to the first diaphragm and the second diaphragm; the second cavity is further provided with a plurality of second support columns, the two ends of which are respectively connected to the third diaphragm and the fourth diaphragm.
[0014] In one embodiment, the plurality of first support columns are arranged perpendicularly to the first diaphragm and the second diaphragm and penetrate the first cavity; the plurality of second support columns are arranged perpendicularly to the third diaphragm and the fourth diaphragm and penetrate the second cavity.
[0015] In one embodiment, a plurality of first acoustic holes are formed in the first back plate, and the plurality of first support columns pass through the first acoustic holes; a plurality of second acoustic holes are formed in the second back plate, and the plurality of second support columns pass through the second acoustic holes.
[0016] In one embodiment, a first support portion is further formed between the first diaphragm and the first back plate, and a second support portion is further formed between the second diaphragm and the first back plate. The first diaphragm, the second diaphragm, the first support portion, and the second support portion surround each other to form the first cavity. A third support portion is further formed between the third diaphragm and the second back plate, and a fourth support portion is further formed between the fourth diaphragm and the second back plate. The third diaphragm, the fourth diaphragm, the third support portion, and the fourth support portion surround each other to form the second cavity.
[0017] In one embodiment, the first microphone structure is formed on a first substrate, and a first isolation layer is further formed between the first substrate and the first diaphragm.
[0018] This application also provides a MEMS microphone and a method for manufacturing the same, including:
[0019] A first microphone structure and a second microphone structure are provided. The first microphone structure includes a first diaphragm, a first back plate, and a second diaphragm spaced apart from bottom to top. A first cavity is formed between the first diaphragm and the second diaphragm. The first back plate is arranged parallel to and passes through the first diaphragm and the second diaphragm. The second microphone structure includes a second and a third diaphragm, a second back plate, and a fourth diaphragm spaced apart from top to bottom. A second cavity is formed between the third diaphragm and the fourth diaphragm. The second back plate is arranged parallel to and passes through the second cavity.
[0020] The second diaphragm and the fourth diaphragm are directly bonded to form a common diaphragm.
[0021] In one embodiment, setting the first microphone structure and the second microphone structure includes:
[0022] One or more of the first microphone structures are fabricated on a first substrate; and,
[0023] One or more of the second microphone structures are formed on the second substrate.
[0024] In one embodiment, fabricating one or more of the first microphone structures on a first substrate includes:
[0025] A first diaphragm is formed on the first substrate;
[0026] A first support layer is formed on the first diaphragm;
[0027] A first backplate layer is formed on the first support layer, and the first backplate layer is patterned to form the first backplate, wherein a plurality of first acoustic holes are formed in the first backplate.
[0028] A second support layer is formed on the first back plate;
[0029] The first support layer and the second support layer are etched to form a plurality of first through holes through the first support layer and the second support layer, the plurality of first through holes passing through the plurality of first acoustic holes;
[0030] Fill the plurality of first through holes to form a plurality of first support pillars;
[0031] A second diaphragm layer is formed on the second support layer, and the second diaphragm layer is patterned to form the second diaphragm, and a plurality of diaphragm holes are formed on the second diaphragm.
[0032] The first support layer and the second support layer are etched to form the first cavity between the first diaphragm and the second diaphragm. The remaining portion of the first support layer forms the first support portion, and the remaining portion of the second support layer forms the second support portion.
[0033] In one embodiment, fabricating one or more of the second microphone structures on a second substrate includes:
[0034] A third diaphragm is formed on the second substrate;
[0035] A third support layer is formed on the third diaphragm;
[0036] A second backplate layer is formed on the third support layer, and the second backplate layer is patterned to form the second backplate, wherein a plurality of second acoustic holes are formed in the second backplate;
[0037] A fourth support layer is formed on the second back plate;
[0038] The third support layer and the fourth support layer are etched to form a plurality of second through holes penetrating the third support layer and the fourth support layer, the plurality of second through holes passing through the plurality of second acoustic holes;
[0039] Fill the plurality of second through holes to form a plurality of second support columns;
[0040] A fourth diaphragm layer is formed on the fourth support layer, and the fourth diaphragm layer is patterned to form the fourth diaphragm, wherein a plurality of diaphragm holes are formed on the fourth diaphragm;
[0041] The third support layer and the fourth support layer are etched to form the second cavity between the third diaphragm and the fourth diaphragm. The remaining portion of the third support layer forms the third support portion, and the remaining portion of the fourth support layer forms the fourth support portion.
[0042] In one embodiment, the method further includes: directly bonding the second diaphragm and the fourth diaphragm to form a common diaphragm,
[0043] Remove the second substrate to expose the third diaphragm;
[0044] The first substrate is etched to expose the region of the first diaphragm corresponding to the first cavity.
[0045] According to the MEMS microphone and its manufacturing method provided in this application, a first microphone structure and a second microphone structure with dual diaphragms and a single backplate are firstly manufactured. Then, the diaphragms of the first microphone structure and the second microphone structure are directly bonded to form a common diaphragm, thereby forming a microphone structure with three diaphragms and a dual backplate. This improves the performance of the MEMS microphone and reduces the manufacturing process difficulty of the MEMS microphone. Attached Figure Description
[0046] The following drawings, which are incorporated herein by reference and are used to understand this application, illustrate embodiments of the invention and their descriptions to explain the principles of the invention.
[0047] In the attached image:
[0048] Figure 1 is a schematic diagram of the structure of a MEMS microphone according to an embodiment of this application;
[0049] Figure 2 is a flowchart of a MEMS microphone manufacturing method according to an embodiment of this application;
[0050] Figure 3 is a flowchart of a method for manufacturing a first microphone structure according to an embodiment of this application;
[0051] Figures 4A-4E are cross-sectional schematic diagrams of the structures obtained by sequentially implementing the manufacturing method of the first microphone structure according to the embodiments of this application;
[0052] Figure 5 is a cross-sectional schematic diagram of the structure obtained by bonding the first microphone structure and the second microphone structure according to an embodiment of this application. Detailed Implementation
[0053] The following description provides numerous specific details to offer a more thorough understanding of this application. However, it will be apparent to those skilled in the art that this application can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described to avoid confusion with this application.
[0054] It should be understood that this application can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of this application to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated. The same reference numerals denote the same elements throughout.
[0055] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this application, the first element, component, area, layer, or portion discussed below may be referred to as the second element, component, area, layer, or portion.
[0056] Spatial relation terms such as “below,” “under,” “below,” “under,” “above,” “above,” etc., are used herein for convenience of description to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, then the element or feature described as “below” or “under” the other element or feature will be oriented “above” the other element or feature. Therefore, the exemplary terms “below” and “under” can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or otherwise) and the spatial descriptive terms used herein will be interpreted accordingly.
[0057] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising” and / or “including,” when used in this specification, identify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.
[0058] To fully understand this application, detailed steps and structures will be presented in the following description to illustrate the technical solutions proposed in this application. Preferred embodiments of this application are described in detail below; however, in addition to these detailed descriptions, this application may have other implementation methods.
[0059] To address the aforementioned issues, this application provides a MEMS microphone, as shown in Figure 1, comprising a first microphone structure 110, a second microphone structure 120, and a common diaphragm 130.
[0060] The first microphone structure 110 includes a first diaphragm 111, a first back plate 112, and a second diaphragm 113 spaced apart from bottom to top. A first cavity 114 is formed between the first diaphragm 111 and the second diaphragm 113. The first back plate 112 is arranged parallel to the first diaphragm 111 and the second diaphragm 113 and passes through the first cavity 114.
[0061] The second microphone structure 120 includes a third diaphragm 121, a second back plate 122, and a fourth diaphragm 123 spaced apart from top to bottom. A second cavity 124 is formed between the third diaphragm 121 and the fourth diaphragm 123. The second back plate 122 is arranged parallel to the third diaphragm 121 and the fourth diaphragm 123 and passes through the second cavity 124.
[0062] The common diaphragm 130 is formed by bonding the second diaphragm 113 and the fourth diaphragm 123.
[0063] For example, a plurality of first support columns 115 are also provided in the first cavity 114, and the two ends of the plurality of first support columns 115 are respectively connected to the first diaphragm 111 and the second diaphragm 113. In one embodiment, the plurality of first support columns 115 are arranged perpendicularly to the first diaphragm 111 and the second diaphragm 113 and penetrate through the first cavity 114.
[0064] For example, a plurality of second support columns 125 are also provided in the second cavity 124, and the two ends of the plurality of second support columns 125 are respectively connected to the third diaphragm 121 and the fourth diaphragm 123. In one embodiment, the plurality of second support columns 125 are arranged perpendicularly to the third diaphragm 121 and the fourth diaphragm 123 and penetrate through the second cavity 124.
[0065] In one embodiment, a plurality of first acoustic holes 1121 are formed in the first back plate 112, and a plurality of first support columns 115 pass through the first acoustic holes 1121, and the plurality of first support columns 115 do not contact the first back plate 112. A plurality of second acoustic holes 1221 are formed on the second back plate 122, and a plurality of second support columns 125 pass through the second acoustic holes 1221, and the plurality of second support columns 125 do not contact the second back plate 122.
[0066] In one embodiment, a first support portion 116 is formed between the first diaphragm 111 and the first back plate 112, and a second support portion 117 is formed between the second diaphragm 113 and the first back plate 112. The first diaphragm 111, the second diaphragm 113, the first support portion 116, and the second support portion 117 surround each other to form a first cavity 114.
[0067] In one embodiment, a third support portion 126 is formed between the third diaphragm 121 and the second back plate 122, and a fourth support portion 127 is formed between the fourth diaphragm 123 and the second back plate 122. The third diaphragm 121, the fourth diaphragm 123, the third support portion 126, and the fourth support portion 127 surround each other to form a second cavity 124.
[0068] In one embodiment, a first microphone structure 110 is formed on a first substrate 101, and a first isolation layer 102 is also formed between the first substrate 101 and the first diaphragm. The first substrate 101 and the first isolation layer 102 are only provided in the regions corresponding to the first support portion 116 and the second support portion 117, while the region corresponding to the first cavity 114 does not have the first substrate 101 and the first isolation layer 102.
[0069] In one embodiment, the pressure in the first cavity 114 and the second cavity 124 can be set as needed, for example, to a low-pressure state or a vacuum state.
[0070] For example, the first diaphragm 111, the first backplate 112, the common diaphragm 130, the second backplate 122, and the third diaphragm 121 serve as the first electrode P1, the second electrode P2, the third electrode P3, the fourth electrode P4, and the fifth electrode P5 of the MEMS microphone, respectively. When P1, P3, and P5 are electrically connected, and P2 and P4 are electrically connected, a single-ended ultra-large capacitance output can be formed, increasing the capacitance area and effectively improving sensitivity. P1, P2, and P3 can output differential capacitance signals, and P3, P4, and P5 can also form differential capacitance signals. Superimposing the two differential capacitance signals can effectively improve the signal-to-noise ratio.
[0071] In this application, the common diaphragm 130 is formed by directly bonding the second diaphragm 113 and the fourth diaphragm 123. The three-diaphragm / dual-backplate capacitive MEMS microphone structure is formed by directly bonding the first microphone structure 110 and the second microphone structure 120 with dual diaphragms and single backplate face to face through cavity direct bonding. It has high sensitivity, small size, high signal-to-noise ratio (SNR) and excellent performance.
[0072] This application also provides a method for manufacturing a MEMS microphone, as shown in Figure 2, including the following steps:
[0073] Step S210: Set up a first microphone structure and a second microphone structure; wherein, the first microphone structure includes a first diaphragm, a first back plate and a second diaphragm spaced apart from bottom to top, wherein a first cavity is formed between the first diaphragm and the second diaphragm, and the first back plate is arranged parallel to the first diaphragm and the second diaphragm and passes through the first cavity; the second microphone structure includes a third diaphragm, a second back plate and a fourth diaphragm spaced apart from top to bottom, wherein a second cavity is formed between the third diaphragm and the fourth diaphragm, and the second back plate is arranged parallel to the third diaphragm and the fourth diaphragm and passes through the second cavity.
[0074] Step S220: Directly bond the second diaphragm and the fourth diaphragm to form a common diaphragm.
[0075] For example, the first microphone structure in step S210 is formed on the first substrate, and one or more first microphone structures can be fabricated on the first substrate at the same time.
[0076] Exemplarily, the first substrate can be any suitable semiconductor substrate, such as a silicon substrate, and can also be at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, or other III / V compound semiconductors, including multilayer structures composed of these semiconductor materials, or silicon-on-insulator (SOI), silicon-on-insulator stacked (SSOI), silicon-on-insulator stacked (S-SiGeOI), silicon-on-insulator (SiGeOI), and germanium-on-insulator (GeOI), or it can also be a double-side polished wafer (DSP), or a ceramic substrate such as alumina, a quartz, or a glass substrate. In one embodiment, the first substrate is selected with a crystal orientation of <100> Monocrystalline silicon.
[0077] For example, the spacing between the first diaphragm and the second diaphragm and the spacing between the third diaphragm and the fourth diaphragm can be the same or different.
[0078] In one embodiment, a first isolation layer is further formed on the first substrate. In one embodiment, the first isolation layer can be formed using a physical vapor deposition process or a chemical vapor deposition process. The first isolation layer includes, but is not limited to, a silicon oxide layer. The thickness of the first isolation layer ranges from 0.5 μm to 2 μm.
[0079] Referring to Figure 3, the steps of fabricating one or more first microphone structures on the first substrate include:
[0080] Step S310: Form a first diaphragm on the first substrate;
[0081] Step S320: Form a first support layer on the first diaphragm;
[0082] Step S330: A first backplate layer is formed on the first support layer, and the first backplate layer is patterned to form a first backplate, wherein a plurality of first acoustic holes are formed in the first backplate;
[0083] Step S340: Form a second support layer on the first backing plate;
[0084] Step S350: Etch the first support layer and the second support layer to form a plurality of first through holes through the first support layer and the second support layer, the plurality of first through holes passing through a plurality of first acoustic holes;
[0085] Step S360: Fill the plurality of first through holes to form a plurality of first support pillars;
[0086] Step S370: A second diaphragm layer is formed on the second support layer, and the second diaphragm layer is patterned to form a second diaphragm, and a plurality of diaphragm holes are formed on the second diaphragm;
[0087] Step S380: Etch the first support layer and the second support layer to form a first cavity between the first diaphragm and the second diaphragm, the remaining portion of the first support layer forms the first support portion, and the remaining portion of the second support layer forms the second support portion.
[0088] The manufacturing method of the first microphone structure of this application will now be described in detail with reference to Figures 4A to 4E, wherein Figures 4A to 4E are cross-sectional schematic diagrams of the structures obtained by sequentially implementing the manufacturing method of the first microphone structure according to the embodiments of this application.
[0089] First, step S310 is performed, as shown in FIG4A, to form a first diaphragm 411 on the first substrate 401.
[0090] In one embodiment, a diaphragm material is deposited on the surface of the first isolation layer 402 using conventional semiconductor processing methods to form a first diaphragm 411, which covers the first isolation layer 402. The material of the first diaphragm 411 includes, but is not limited to, doped polysilicon. The thickness of the first diaphragm 411 ranges from 0.2 μm to 1 μm.
[0091] In one embodiment, the conventional semiconductor process method for forming the first isolation layer 402 can be selected as needed, such as low-pressure chemical vapor deposition (LPCVD), laser ablation deposition (LAD), and selective epitaxial growth (SEG) formed by chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD), or low-temperature chemical vapor deposition (LTCVD), thermally rapid chemical vapor deposition (RTCVD), and plasma-enhanced chemical vapor deposition (PECVD). Low-pressure chemical vapor deposition (LPCVD) is preferred here.
[0092] Next, step S320 is performed, as shown in Figure 4B, to form a first support layer 416' on the first diaphragm 411.
[0093] In one embodiment, a first support layer 416' is formed on the first diaphragm 411 using conventional semiconductor processes such as LPCVD or PECVD, and the first support layer 416' covers the first diaphragm 411. The material of the first support layer 416' includes, but is not limited to, silicon dioxide. The thickness of the first support layer 416' ranges from 1 μm to 3 μm.
[0094] Next, step S330 is performed, as shown in FIG4B, a first back plate layer is formed on the first support layer 416', and the first back plate layer is patterned to form a first back plate 412, wherein a plurality of first acoustic holes 4121 are formed in the first back plate 412.
[0095] In one embodiment, a first backplane layer is formed on the surface of the first support layer 416' using conventional semiconductor processes such as LPCVD or PECVD. The material of the first backplane layer includes, but is not limited to, doped polysilicon. In one embodiment, the first backplane layer can be a single-layer doped polysilicon layer, or a combination of a doped polysilicon layer and a passivation layer. The material of the passivation layer includes, but is not limited to, silicon nitride, silicon carbide, and silicon oxynitride. The first backplane layer can be patterned using photolithography to form the first backplane 412, which will not be elaborated further here. The thickness of the first backplane 412 ranges from 0.5 μm to 2 μm.
[0096] Next, step S340 is performed, as shown in Figure 4C, to form a second support layer 417' on the first back plate 412.
[0097] In one embodiment, a second support layer 417' is formed on the first backplane 412 using conventional semiconductor processes such as LPCVD or PECVD, and the second support layer 417' covers the first backplane 412. The material of the second support layer 417' includes, but is not limited to, silicon dioxide. The thickness of the second support layer 417' ranges from 1 μm to 3 μm.
[0098] Next, step S350 is performed, as shown in FIG4C, to etch the first support layer 416' and the second support layer 417' to form a plurality of first through holes 415' through the first support layer 416' and the second support layer 417', and the plurality of first through holes 415' through a plurality of first acoustic holes 4121.
[0099] In one embodiment, a photolithography process can be used to pattern the first support layer 416' and the second support layer 417' to form a plurality of first through holes 415' penetrating the first support layer 416' and the second support layer 417' until the first diaphragm 411 is exposed. It should be noted that the plurality of first through holes 415' pass through the plurality of first acoustic holes 4121 of the first back plate 412, therefore the first through holes 415' do not contact the first back plate 412.
[0100] Next, step S360 is performed, as shown in Figure 4D, to fill a plurality of first through holes 415' to form a plurality of first support posts 415.
[0101] In one embodiment, a layer of material is deposited using conventional semiconductor processes such as LPCVD to completely fill the plurality of first vias 415'. Then, a CMP process is used to remove the surface material, with the second support layer 417' serving as the stop layer. The remaining material fills the plurality of first vias 415' to form a plurality of first pillars 415. The first pillars 415 can be made of conductive or non-conductive material. The diameter of the first pillars 415 ranges from 0.5 μm to 3 μm.
[0102] Next, step S370 is performed, as shown in FIG4D, a second diaphragm layer is formed on the second support layer 417', and the second diaphragm layer is patterned to form a second diaphragm 413, on which a plurality of diaphragm holes (not shown) are formed.
[0103] In one embodiment, a diaphragm material (i.e., a second diaphragm layer) is deposited on the second support layer 417' and the first support pillar 415 using conventional semiconductor processes such as LPCVD. The diaphragm material is then patterned using photolithography to form a second diaphragm 413 with multiple diaphragm holes. The material of the second diaphragm 413 includes, but is not limited to, doped polysilicon. The thickness of the second diaphragm 413 ranges from 0.2 μm to 0.5 μm.
[0104] In one embodiment, the second diaphragm layer is patterned using a photolithography process. In one embodiment, a photoresist layer (not shown) with a diaphragm hole pattern is formed on the second diaphragm layer. This photoresist layer with the diaphragm hole pattern can be formed by spin coating, followed by exposure, development, and cleaning processes. Then, the second diaphragm layer is etched using the photoresist layer with the diaphragm hole pattern as a mask to form a second diaphragm 413 with multiple diaphragm holes.
[0105] It should be noted that after forming the second diaphragm 413, the process also includes depositing an oxide film on the surface of the second diaphragm 413 using conventional semiconductor processes such as LPCVD or PECVD, and then grinding it to the surface of the second diaphragm 413 using a CMP process to obtain a bonding surface with the required roughness.
[0106] Next, step S380 is performed, as shown in FIG4E, to etch the first support layer 416' and the second support layer 417' to form a first cavity 414 between the first diaphragm 411 and the second diaphragm 413, the remaining portion of the first support layer forms the first support portion 416, and the remaining portion of the second support layer forms the second support portion 417.
[0107] In one embodiment, the first cavity 414 is formed by wet etching. Specifically, the support layer is released by HF or BOE solution or Vapor HF, resulting in the structure shown in FIG4E.
[0108] For example, the second microphone structure in step S210 is formed on the second substrate, and one or more second microphone structures can be fabricated on the second substrate at the same time.
[0109] Exemplarily, the step of fabricating one or more second microphone structures on a second substrate includes: forming a third diaphragm on the second substrate; forming a third support layer on the third diaphragm; forming a second backplate layer on the third support layer; patterning the second backplate layer to form a second backplate, wherein a plurality of second acoustic holes are formed in the second backplate; forming a fourth support layer on the second backplate; etching the third support layer and the fourth support layer to form a plurality of second through-holes penetrating the third support layer and the fourth support layer, wherein the plurality of second through-holes pass through the plurality of second acoustic holes; filling the plurality of second through-holes to form a plurality of second support pillars; forming a fourth diaphragm layer on the fourth support layer; patterning the fourth diaphragm layer to form a fourth diaphragm, wherein a plurality of diaphragm holes are formed on the fourth diaphragm; etching the third support layer and the fourth support layer to form a second cavity between the third diaphragm and the fourth diaphragm, wherein the remaining portion of the third support layer forms a third support portion, and the remaining portion of the fourth support layer forms a fourth support portion.
[0110] The specific process can be referred to the steps of fabricating one or more of the first microphone structures on the first substrate, which will not be repeated here.
[0111] Next, step S220 is performed, in which the second diaphragm 413 of the first microphone structure obtained through the above steps is directly bonded to the fourth diaphragm 423 of the second microphone structure to form a common diaphragm 430, as shown in Figure 5.
[0112] In one embodiment, the pressure in the first cavity 414 and the second cavity can be set as needed, for example, to a low-pressure state or a vacuum state.
[0113] After step S220, the process further includes removing the second substrate and the second isolation layer by methods such as CMP until the third diaphragm 421 is exposed; and thinning the first substrate by methods such as CMP, then performing pad wires by TSV process, and etching the first substrate and the first isolation layer by back-side etching process to expose the area of the first diaphragm corresponding to the first cavity, thereby forming the MEMS microphone device structure shown in FIG1.
[0114] For example, the first diaphragm 111, the first backplate 112, the common diaphragm 130, the second backplate 122, and the third diaphragm 121 serve as the first electrode P1, the second electrode P2, the third electrode P3, the fourth electrode P4, and the fifth electrode P5 of the MEMS microphone, respectively. When P1, P3, and P5 are electrically connected, and P2 and P4 are electrically connected, a single-ended ultra-large capacitance output can be formed, increasing the capacitance area and effectively improving sensitivity. P1, P2, and P3 can output differential capacitance signals, and P3, P4, and P5 can also form differential capacitance signals. Superimposing the two differential capacitance signals can effectively improve the signal-to-noise ratio.
[0115] This concludes the introduction of the key steps in the manufacturing method of the semiconductor device of this application. The complete device fabrication may require several other processes, which will not be elaborated here.
[0116] It is worth mentioning that the order of the above steps is only for example. Without conflict, the order of the above steps can be changed or performed alternately.
[0117] According to the MEMS microphone and its manufacturing method provided in this application, a first microphone structure and a second microphone structure with dual diaphragms and a single backplate are first manufactured. Then, the diaphragms of the first microphone structure and the second microphone structure are directly bonded to form a common diaphragm to form a microphone structure with three diaphragms and a dual backplate, which improves the performance of the MEMS microphone and reduces the process difficulty of manufacturing the MEMS microphone.
[0118] This application has been described through the above embodiments. However, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit this application to the scope of the described embodiments. Furthermore, those skilled in the art will understand that this application is not limited to the above embodiments, and many more variations and modifications can be made based on the teachings of this application, all of which fall within the scope of protection claimed in this application. The scope of protection of this application is defined by the appended claims and their equivalents.
Claims
1. A MEMS microphone, comprising a first microphone structure, a second microphone structure and a common diaphragm; The first microphone structure includes a first diaphragm, a first back plate, and a second diaphragm which are spaced from bottom to top, wherein, a first cavity is formed between the first diaphragm and the second diaphragm, and the first back plate is arranged in parallel with the first diaphragm and the second diaphragm and penetrates through the first cavity; the second microphone structure comprises a third diaphragm, a second back plate and a fourth diaphragm arranged in sequence from top to bottom, wherein a second cavity is formed between the third diaphragm and the fourth diaphragm, and the second back plate is arranged in parallel with the third diaphragm and the fourth diaphragm and penetrates through the second cavity; the common diaphragm is directly bonded by the second diaphragm and the fourth diaphragm.
2. The MEMS microphone of claim 1, wherein, The first diaphragm, the first back plate, the common diaphragm, the second back plate and the third diaphragm are respectively a first electrode, a second electrode, a third electrode, a fourth electrode and a fifth electrode of the MEMS microphone.
3. The MEMS microphone of claim 1, wherein, A plurality of first support columns are arranged in the first cavity, and two ends of the plurality of first support columns are respectively connected to the first diaphragm and the second diaphragm;A plurality of second support columns are arranged in the second cavity, and two ends of the plurality of second support columns are respectively connected to the third diaphragm and the fourth diaphragm.
4. The MEMS microphone of claim 3, wherein, The plurality of first support columns are arranged in perpendicular to the first diaphragm and the second diaphragm and penetrate through the first cavity;The plurality of second support columns are arranged in perpendicular to the third diaphragm and the fourth diaphragm and penetrate through the second cavity.
5. The MEMS microphone of claim 3, wherein, A plurality of first sound holes are formed in the first back plate, and the plurality of first support columns pass through the first sound holes;A plurality of second sound holes are formed in the second back plate, and the plurality of second support columns pass through the second sound holes.
6. The MEMS microphone of claim 1, wherein, A first support part is further formed between the first diaphragm and the first back plate, a second support part is further formed between the second diaphragm and the first back plate, and the first diaphragm, the second diaphragm, the first support part and the second support part surround to form the first cavity;A third support part is further formed between the third diaphragm and the second back plate, a fourth support part is further formed between the fourth diaphragm and the second back plate, and the third diaphragm, the fourth diaphragm, the third support part and the fourth support part surround to form the second cavity.
7. The MEMS microphone of claim 1, wherein, The first microphone structure is formed on a first substrate, and a first isolation layer is further formed between the first substrate and the first diaphragm. 8.A MEMS microphone and a manufacturing method thereof, comprising: setting a first microphone structure and a second microphone structure; wherein the first microphone structure comprises a first diaphragm, a first back plate and a second diaphragm arranged in sequence from bottom to top, wherein a first cavity is formed between the first diaphragm and the second diaphragm, and the first back plate is arranged in parallel with the first diaphragm and the second diaphragm and penetrates through the first cavity;The second microphone structure comprises a third diaphragm, a second back plate and a fourth diaphragm arranged in sequence from top to bottom, wherein a second cavity is formed between the third diaphragm and the fourth diaphragm, and the second back plate is arranged in parallel with the third diaphragm and the fourth diaphragm and penetrates through the second cavity; bonding the second diaphragm and the fourth diaphragm directly forms a common diaphragm.
9. The production method as claimed in claim 8, wherein, The setting first microphone structure and second microphone structure comprises: manufacturing one or more of the first microphone structures on a first substrate; and manufacturing one or more of the second microphone structures on a second substrate.
10. The production method as claimed in claim 9, wherein, manufacturing one or more of the first microphone structures on a first substrate comprises: forming a first diaphragm on the first substrate; forming a first support layer on the first diaphragm; forming a first backplate layer on the first support layer, and patterning the first backplate layer to form the first backplate, the first backplate having a plurality of first acoustic holes formed therein; forming a second support layer on the first backplate; etching the first support layer and the second support layer to form a plurality of first through holes penetrating through the first support layer and the second support layer, the plurality of first through holes passing through the plurality of first acoustic holes; filling the plurality of first through holes to form a plurality of first support columns; forming a second diaphragm layer on the second support layer, and patterning the second diaphragm layer to form the second diaphragm, the second diaphragm having a plurality of diaphragm holes formed therein; etching the first support layer and the second support layer to form the first cavity between the first diaphragm and the second diaphragm, a remaining portion of the first support layer forming a first support portion, and a remaining portion of the second support layer forming a second support portion.
11. The production method as claimed in claim 9, wherein, manufacturing one or more of the second microphone structures on a second substrate comprises: forming a third diaphragm on the second substrate; forming a third support layer on the third diaphragm; forming a second backplate layer on the third support layer, and patterning the second backplate layer to form the second backplate, the second backplate having a plurality of second acoustic holes formed therein; forming a fourth support layer on the second backplate; etching the third support layer and the fourth support layer to form a plurality of second through holes penetrating through the third support layer and the fourth support layer, the plurality of second through holes passing through the plurality of second acoustic holes; filling the plurality of second through holes to form a plurality of second support columns; forming a fourth diaphragm layer on the fourth support layer, and patterning the fourth diaphragm layer to form the fourth diaphragm, the fourth diaphragm having a plurality of diaphragm holes formed therein; etching the third support layer and the fourth support layer to form the second cavity between the third diaphragm and the fourth diaphragm, a remaining portion of the third support layer forming a third support portion, and a remaining portion of the fourth support layer forming a fourth support portion.
12. The manufacturing method of claim 10, further comprising: after the second diaphragm and the fourth diaphragm are bonded directly to form a common diaphragm, removing the second substrate to expose the third diaphragm; etching the first substrate to expose a region of the first diaphragm corresponding to the first cavity.