Pressure-resistant MEMS underwater acoustic sensor and manufacturing method thereof

Abstract

The invention provides a pressure-resistant MEMS underwater acoustic sensor and a manufacturing method thereof, and belongs to the field of semiconductors. The pressure-resistant MEMS underwater acoustic sensor comprises a first substrate and a second substrate, wherein the first substrate is provided with a first cavity; the second substrate is provided with a first surface and a second surface, the first surface is provided with a second cavity, and the second cavity is filled with a sound transmission material to form a waveguide structure; the functional layer is stacked on the second surface of the second substrate, and the functional layer comprises an electrode layer and a piezoelectric film layer; the bonding layer is formed on the functional layer, and the surface, provided with the first cavity, of the first substrate is bonded with the functional layer through the bonding layer, so that the first cavity is kept in a sealed state.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductors, and in particular relates to a pressure-resistant MEMS underwater acoustic sensor and a manufacturing method thereof. Background Art

[0002] An underwater acoustic transducer, also known as an underwater acoustic sensor, is a device that converts electrical signals into underwater acoustic signals or vice versa. Widely used for underwater communications, detection, target positioning, and tracking, underwater acoustic transducers are essential components of sonar and play a vital role in various fields, including scientific research, military defense, and resource management.

[0003] With the development of micro-electro-mechanical systems (MEMS) technology, MEMS-based piezoelectric underwater acoustic sensors have become a hot research topic in the field of underwater acoustic sensors. They offer advantages such as low power consumption, low cost, miniaturization, and lightweight design. However, existing piezoelectric underwater acoustic sensors suffer from low sensitivity and poor pressure resistance. Summary of the Invention

[0004] The present invention provides a pressure-resistant MEMS underwater acoustic sensor and a manufacturing method thereof, which can improve the sensitivity and pressure resistance of the underwater acoustic sensor.

[0005] In one aspect, a pressure-resistant MEMS underwater acoustic sensor is provided, comprising: a first substrate, wherein a first cavity is formed on the first substrate; a second substrate having a first surface and a second surface, wherein the first surface is provided with a second cavity, and the second cavity is filled with a sound-transmitting material to form a waveguide structure; a functional layer, stacked on the second surface of the second substrate, the functional layer comprising an electrode layer and a piezoelectric film layer; A bonding layer is formed on the functional layer, and the surface of the first substrate having the first cavity is bonded to the functional layer through the bonding layer, so that the first cavity is kept in a sealed state.

[0006] Optionally, the ratio of the area of the second cavity to the area of the first cavity is greater than a threshold, and the threshold is in the range of 0.8 to 1.

[0007] Optionally, a ratio of the depth of the second cavity to the thickness of the functional layer is 50:1 to 70:1.

[0008] Optionally, the second cavity has a depth of 350-550 μm.

[0009] Optionally, the sound-transmitting material includes a hydrophilic material or an oleophilic material, the hydrophilic material includes polydimethylsiloxane, Parylene, polyimide, and silicone rubber, and the oleophilic material includes polytetrafluoroethylene and polyethylene.

[0010] On the other hand, a method for manufacturing a pressure-resistant MEMS underwater acoustic sensor is provided, comprising: providing a first substrate and a second substrate; forming a first cavity on the surface of the first substrate; forming a functional layer on the second surface of the second substrate; forming a bonding layer on the surface of the functional layer, and bonding the surface of the first substrate having the first cavity to the functional layer through the bonding layer; forming a second cavity on the first surface of the second substrate; The second cavity is filled with a sound-transmitting material to form a waveguide structure.

[0011] Optionally, filling the second cavity with a sound-transmitting material to form a waveguide structure includes: performing pretreatment on the second cavity; Mixing the sound-transmitting material with the curing agent; filling the second cavity with a sound-transmitting material; Perform vacuum treatment to remove bubbles in the sound-transmitting material; Curing the sound-transmitting material; The sound-transmitting material is flattened to form a waveguide structure.

[0012] Optionally, pre-processing the second cavity includes: cleaning the second cavity; The second cavity is subjected to surface treatment; wherein, when the sound-transmitting material is a hydrophilic material, the second cavity is subjected to hydrophilic treatment; and when the sound-transmitting material is an oleophilic material, the second cavity is subjected to hydrophobic treatment.

[0013] Optionally, the sound transmission material is mixed with a curing agent, and the ratio of the sound transmission material to the curing agent is 9:1 to 11:1.

[0014] Optionally, the curing method includes thermal curing, UV light curing or chemical curing.

[0015] The beneficial effects brought about by the technical solution provided by the present invention are: During use, underwater acoustic sensors are usually in a high-pressure environment, which will cause the piezoelectric film layer of the underwater acoustic sensor to be deformed under the action of water pressure (for example, the piezoelectric film layer will be dented). The underwater acoustic sensor receives acoustic signals through the piezoelectric film layer. If the piezoelectric film layer is already in a deformed state before receiving the acoustic signal, the piezoelectric film layer will rupture when receiving the acoustic signal.

[0016] To address the above-mentioned issues, the present invention provides a pressure-resistant MEMS underwater acoustic sensor, comprising a second substrate in which a waveguide structure is formed. The waveguide structure prevents water pressure from directly acting on the piezoelectric film layer, thereby alleviating deformation of the piezoelectric film layer. Furthermore, the waveguide structure absorbs acoustic wave energy, and the vibration of the medium within the waveguide structure generates an additional acoustic field on the piezoelectric film layer, further amplifying weaker underwater acoustic signals. This allows the underwater acoustic sensor to receive these weaker signals, thereby enhancing the sensor's sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 A schematic structural diagram of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention; Figure 2 A flow chart of a method for manufacturing a pressure-resistant MEMS underwater acoustic sensor provided by the present invention; Figure 3 A schematic diagram of the structure of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention during the manufacturing process; Figure 4 A schematic diagram of the structure of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention during the manufacturing process; Figure 5 A schematic diagram of the structure of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention during the manufacturing process; Figure 6 A schematic diagram of the structure of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention during the manufacturing process; Figure 7 A schematic diagram of the structure of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention during the manufacturing process; Figure 8 A schematic diagram of the structure of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention during the manufacturing process; Figure 9 A schematic diagram of the structure of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention during the manufacturing process; Figure 10 A schematic diagram of the structure of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention during the manufacturing process; Figure 11A schematic diagram of the structure of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention during the manufacturing process; Figure 12 A schematic diagram of the structure of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention during the manufacturing process; Figure 13 A schematic diagram of the structure of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention during the manufacturing process; Figure 14 A schematic diagram of the structure of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention during the manufacturing process; Figure 15 A schematic diagram of the structure of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention during the manufacturing process; Figure 16 A schematic diagram of a packaging structure provided by the present invention; Figure 17 A schematic diagram of another packaging structure provided by the present invention; Figure 18 A top view of an array element provided by the present invention; Figure 19 A data diagram of an underwater acoustic sensor in a related technology provided by the present invention; Figure 20 This is a data chart of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention.

[0019] The reference numerals are as follows: 100: first substrate; 1000: first cavity; 101: SiO2 layer; 102: limiting structure; 103: negative electrode through hole; 104: positive electrode through hole; 105: negative electrode; 106: positive electrode; 20: functional layer; 200: second substrate; 2000: second cavity; 2001: first surface; 2002: second surface; 201: waveguide structure; 30: electrode layer; 300: lower electrode layer; 40: functional layer; 400: piezoelectric film layer; 401: AlN piezoelectric layer; 402: ScAlN piezoelectric layer; 500: negative electrode connection hole; 600: upper electrode layer; 601: positive electrode layer; 602: negative electrode connection layer; 700: bonding layer.

[0020] 801: circuit board; 802: chip; 803: array element. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0022] Figure 1 This is a schematic diagram of the structure of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention. Figure 1 , A first substrate 100, wherein a first cavity 1000 is defined on the first substrate 100; The second substrate 200 has a first surface 2001 and a second surface 2002 . The first surface 2001 defines a second cavity 2000 . The second cavity 2000 is filled with a sound-transmitting material to form a waveguide structure 201 . A functional layer 20 is laminated on the second surface 2002 of the second substrate 200 , and the functional layer 20 includes an electrode layer 30 and a piezoelectric film layer 40 ; The bonding layer 700 is formed on the functional layer 20 . The surface of the first substrate 100 having the first cavity 1000 is bonded to the functional layer 20 via the bonding layer 700 , so that the first cavity 1000 remains sealed.

[0023] During use, underwater acoustic sensors are usually in a high-pressure environment, which will cause the piezoelectric film layer of the underwater acoustic sensor to be deformed under the action of water pressure (for example, the piezoelectric film layer will be dented). The underwater acoustic sensor receives acoustic signals through the piezoelectric film layer. If the piezoelectric film layer is already in a deformed state before receiving the acoustic signal, the piezoelectric film layer will rupture when receiving the acoustic signal.

[0024] To address the above-mentioned issues, the present invention provides a pressure-resistant MEMS underwater acoustic sensor, comprising a second substrate in which a waveguide structure is formed. The waveguide structure prevents water pressure from directly acting on the piezoelectric film layer, thereby alleviating deformation of the piezoelectric film layer. Furthermore, the waveguide structure absorbs acoustic wave energy, and the vibration of the medium within the waveguide structure generates an additional acoustic field on the piezoelectric film layer, further amplifying weaker underwater acoustic signals. This allows the underwater acoustic sensor to receive these weaker signals, thereby enhancing the sensor's sensitivity.

[0025] In this embodiment, the first substrate 100 is a Si substrate. Of course, the material used for the first substrate 100 is only an example provided by the present invention. In actual situations, the material of the first substrate 100 can be selectively set.

[0026] In this embodiment, a limiting structure 102 is provided in the first cavity 1000 , and the limiting structure is used to limit the vibration of the piezoelectric film layer to prevent the piezoelectric film layer from being broken due to excessive vibration.

[0027] In this embodiment, the second substrate 200 is an SOI substrate.

[0028] In this embodiment, the ratio of the area of the second cavity 2000 to the area of the first cavity 1000 is greater than a threshold value, and the value range of the threshold value is 0.8-1.

[0029] Exemplarily, the ratio of the area of the second cavity to the area of the first cavity is greater than a threshold, and the value range of the threshold is 0.9.

[0030] In this embodiment, the area of the second cavity corresponds to the area of the waveguide structure, and the area of the first cavity corresponds to the area of the vibrating region of the piezoelectric film layer (the piezoelectric film layer corresponding to the first cavity vibrates within the first cavity after receiving an acoustic signal). This area ratio ensures the effectiveness of the waveguide structure.

[0031] In this embodiment, the ratio of the depth of the second cavity 2000 to the thickness of the functional layer 20 is 50:1 to 70:1.

[0032] Exemplarily, the ratio of the depth of the second cavity 2000 to the thickness of the functional layer 20 is 400:7.

[0033] In this embodiment, the above thickness ratio is adopted to ensure the isolation effect of the waveguide structure.

[0034] In this embodiment, the depth of the second cavity 2000 is 350-550 μm.

[0035] Exemplarily, the depth of the second cavity is 400 μm.

[0036] In this embodiment, the sound-transmitting material includes a hydrophilic material or an oleophilic material. The hydrophilic material includes polydimethylsiloxane, parylene, polyimide, and silicone rubber. The oleophilic material includes polytetrafluoroethylene and polyethylene.

[0037] In this embodiment, the above materials can achieve a sound transmission effect.

[0038] In this embodiment, the electrode layer 30 includes a negative electrode 105, a positive electrode 106, a lower electrode layer 300 and an upper electrode layer 600. After the upper electrode layer 600 is etched, a portion of the upper electrode layer 600 becomes the positive electrode layer 601, and another portion of the upper electrode layer 600 becomes the negative electrode connecting layer 602.

[0039] The first substrate 100 is provided with a negative electrode through-hole 103 and a positive electrode through-hole 104. A negative electrode 105 is disposed in the negative electrode through-hole 103 and connected to the negative electrode connecting layer 602. The negative electrode connecting layer 602 is connected to the lower electrode layer 300 via the negative electrode connecting hole 500. A positive electrode 106 is disposed in the positive electrode through-hole 104 and connected to the positive electrode layer 601.

[0040] In this embodiment, the materials used for the lower electrode layer 300, the upper electrode layer 600, the negative electrode 105, and the positive electrode 106 include molybdenum, aluminum, copper, or alloy materials. Of course, the above is only an example provided by the present invention, and the electrodes can also be formed of other materials.

[0041] In this embodiment, the piezoelectric film layer 40 includes an AlN piezoelectric layer 401 and a ScAlN piezoelectric layer 402 .

[0042] In this embodiment, the piezoelectric film layer 40 is provided with a negative electrode connection hole 500 , and the negative electrode connection hole 500 is connected to the lower electrode layer 300 .

[0043] Figure 2 This is a flow chart of the manufacturing method of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention. Figure 2 ,include: S10, providing a first substrate and a second substrate.

[0044] For materials of the first and second substrates, see Figure 1 The materials in it will not be repeated here.

[0045] Figure 3 and Figure 4 Schematic diagrams of the structures of the first substrate 100 and the second substrate 200 provided by the present invention respectively.

[0046] It is worth noting that the second substrate 200 is an SOI substrate, that is, a substrate including a stacked Si layer, a SiO2 layer, and a Si layer. Figure 4 The film layer of different colors in the middle of the second substrate 200 is a SiO2 layer.

[0047] S11, forming a first cavity on the surface of the first substrate.

[0048] In step S11, before forming the first cavity, the first substrate is subjected to thermal oxidation treatment to form a SiO2 layer 101 on the surface of the first substrate 100 (see Figure 5 ).

[0049] Subsequently, the first substrate 100 is etched to form a first cavity 1000 and a limiting structure 102 (see Figure 6 ).

[0050] The first cavity 1000 and the limiting structure 102 are formed by etching twice. The first etching forms the first cavity 1000 , and the second etching forms the limiting structure 102 at the bottom of the first cavity 1000 .

[0051] In this embodiment, the etching technology may be dry etching.

[0052] S12, fabricating a functional layer on the second surface of the second substrate.

[0053] In one example, step S12 includes: In the first step, an AlN seed layer (not shown), a lower electrode layer 300, an AlN piezoelectric layer 401 and a ScAlN piezoelectric layer 402 are sequentially formed on the second surface 2002 of the second substrate 200 (see Figure 7 ).

[0054] The AlN seed layer, the lower electrode layer 300 , the AlN piezoelectric layer 401 and the ScAlN piezoelectric layer 402 may be manufactured by a sputtering process or a deposition process.

[0055] In the second step, the AlN piezoelectric layer 401 and the ScAlN piezoelectric layer 402 are etched to form a negative electrode connection hole 500 (see Figure 8 ).

[0056] The third step is to make the upper electrode layer 600 (see Figure 9 ).

[0057] In the fourth step, the upper electrode layer 600 is etched to form a positive electrode layer 601 and a negative electrode connection layer 602 (see Figure 10 ).

[0058] The negative electrode connection layer 602 is connected to the lower electrode layer 300 through the negative electrode connection hole 500 .

[0059] S13, forming a bonding layer on the surface of the functional layer, and bonding the surface of the first substrate having the first cavity to the functional layer through the bonding layer.

[0060] The bonding layer 700 is a SiO2 layer, which can be manufactured by plasma enhanced chemical vapor deposition (PECVD) process. Figure 11 Then, the bonding layer 700 is bonded to the SiO2 layer 101 on the surface of the first substrate 100 at room temperature and pressure. The bonded structure is shown in FIG. Figure 12 .

[0061] S14. Fabricate a positive electrode and a negative electrode, wherein the positive electrode penetrates the first substrate and is connected to the positive electrode layer, and the negative electrode penetrates the first substrate and is connected to the negative electrode connecting layer.

[0062] In one example, step S14 includes: In the first step, a patterned photoresist layer is formed on the surface of the first substrate 100 .

[0063] Parts of the first substrate 100 not covered by the patterned photoresist layer are removed.

[0064] In the second step, the first substrate 100 is etched by etching technology to form the positive electrode through hole 104 and the negative electrode through hole 103 (see Figure 13 ).

[0065] The positive electrode through hole 104 is connected to the positive electrode layer 601 , and the negative electrode through hole 103 is connected to the negative electrode connecting layer 602 .

[0066] Exemplarily, the etching technique may be dry etching.

[0067] In the third step, a positive electrode 106 and a negative electrode 105 are fabricated in the positive electrode through hole 104 and the negative electrode through hole 103 respectively.

[0068] Before manufacturing the positive electrode 106 and the negative electrode 105 , an insulating layer (not shown in the figure) is also manufactured on the sidewalls of the positive electrode through hole 104 and the negative electrode through hole 103 . The insulating layer may be a SiO 2 layer.

[0069] Subsequently, a positive electrode 106 and a negative electrode 105 are fabricated in the positive electrode through hole 104 and the negative electrode through hole 103 by using processes such as electron beam evaporation and magnetron sputtering. The fabricated positive electrode 106 and negative electrode 105 are shown in FIG. Figure 14 .

[0070] S15. Fabricate a second cavity on the first surface of the second substrate.

[0071] In one example, step S15 includes: The first step is to create a patterned photoresist layer.

[0072] The areas not covered by the patterned photoresist layer are removed.

[0073] In the second step, the second substrate 200 is etched to form a second cavity 2000 (see Figure 15 ).

[0074] S16. Fill the second cavity with a sound-transmitting material to form a waveguide structure.

[0075] In one example, step S16 includes: Step 1: Pre-process the second cavity 2000.

[0076] In one example, step 1 includes: The first step is to clean the second cavity 2000 .

[0077] Deionized water may be used to clean the second cavity 2000 to remove residues in the second cavity 2000 and enhance the bonding strength between the subsequent sound transmission material and the second substrate 200 .

[0078] In the second step, the second cavity 2000 is subjected to surface treatment. When the sound-transmitting material is a hydrophilic material, the second cavity 2000 is subjected to hydrophilic treatment. When the sound-transmitting material is an oleophilic material, the second cavity 2000 is subjected to hydrophobic treatment.

[0079] Surface treatment of the second cavity can further enhance the bonding strength between the sound-transmitting material and the second substrate.

[0080] Step 2: Mix the sound transmission material and the curing agent.

[0081] The mixing ratio of the sound transmission material to the curing agent is 9:1 to 11:1. For example, the mixing ratio of the sound transmission material to the curing agent is 10:1.

[0082] In this embodiment, the above-mentioned proportion of mixing of the generating material and the curing agent can ensure the curing effect of the sound transmission material.

[0083] Step 3: Fill the second cavity 2000 with sound-transmitting material.

[0084] In step 3, the filling method of the sound transmission material includes spin coating, injection or vapor deposition.

[0085] Step 4: Perform vacuum treatment to remove bubbles in the sound-transmitting material.

[0086] Step 5: Curing the sound-transmitting material.

[0087] In one example, the curing method includes thermal curing, UV curing, or chemical curing. Depending on the sound transmission material, a suitable curing method can be selected for curing.

[0088] Step 6: Flatten the sound-transmitting material to form a waveguide structure 201 (see Figure 1 ).

[0089] Among them, grinding technology can be used to flatten the sound-transmitting material.

[0090] Figure 16 This is a schematic diagram of a packaging structure provided by the present invention. Figure 16 , including a circuit board 801, a chip 802 and an array element 803 (the array element 803 is also the pressure-resistant MEMS underwater acoustic sensor provided by the present invention).

[0091] Figure 17 A perspective view of a packaging structure provided by the present invention. Figure 17 , the array element 803 is connected to the circuit board through the positive electrode 106 and the negative electrode 105.

[0092] Figure 18 A top view of an array element provided by the present invention. Figure 18 , Figure 18 It is also a top view of the pressure-resistant MEMS underwater acoustic sensor provided by the present invention.

[0093] Figure 19 This is a data diagram of an underwater acoustic sensor in a related technology provided by the present invention. Figure 19 , where the horizontal axis represents frequency and the vertical axis represents sensitivity.

[0094] Figure 20 This is a data chart of a pressure-resistant MEMS underwater acoustic sensor provided by the present invention. Figure 20 , compared to Figure 19 In the above situation, the pressure-resistant MEMS underwater acoustic sensor provided by the present invention has higher sensitivity.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A pressure-resistant MEMS underwater acoustic sensor, characterized in that: include: a first substrate, wherein a first cavity is formed on the first substrate; a second substrate having a first surface and a second surface, wherein the first surface is provided with a second cavity, and the second cavity is filled with a sound-transmitting material to form a waveguide structure; a functional layer, stacked on the second surface of the second substrate, the functional layer comprising an electrode layer and a piezoelectric film layer; A bonding layer is formed on the functional layer, and the surface of the first substrate having the first cavity is bonded to the functional layer through the bonding layer, so that the first cavity is kept in a sealed state.

2. The pressure-resistant MEMS underwater acoustic sensor according to claim 1, characterized in that: The ratio of the area of the second cavity to the area of the first cavity is greater than a threshold, and the threshold is in the range of 0.8 to 1.

3. The pressure-resistant MEMS underwater acoustic sensor according to claim 1, characterized in that: A ratio of the depth of the second cavity to the thickness of the functional layer is 50:1 to 70:

1.

4. The pressure-resistant MEMS underwater acoustic sensor according to claim 1, characterized in that: The second cavity has a depth of 350-550 μm.

5. The pressure-resistant MEMS underwater acoustic sensor according to claim 1, characterized in that: The sound-transmitting material includes a hydrophilic material or an oleophilic material. The hydrophilic material includes polydimethylsiloxane, parylene, polyimide, and silicone rubber. The oleophilic material includes polytetrafluoroethylene and polyethylene.

6. A method for manufacturing a pressure-resistant MEMS underwater acoustic sensor, characterized in that: include: providing a first substrate and a second substrate; forming a first cavity on the surface of the first substrate; forming a functional layer on the second surface of the second substrate; forming a bonding layer on the surface of the functional layer, and bonding the surface of the first substrate having the first cavity to the functional layer through the bonding layer; forming a second cavity on the first surface of the second substrate; The second cavity is filled with a sound-transmitting material to form a waveguide structure.

7. The method for manufacturing a pressure-resistant MEMS underwater acoustic sensor according to claim 6, characterized in that: Filling the second cavity with a sound-transmitting material to form a waveguide structure, comprising: performing pretreatment on the second cavity; Mixing the sound-transmitting material with the curing agent; filling the second cavity with a sound-transmitting material; Perform vacuum treatment to remove bubbles in the sound-transmitting material; Curing the sound-transmitting material; The sound-transmitting material is flattened to form a waveguide structure.

8. The method for manufacturing a pressure-resistant MEMS underwater acoustic sensor according to claim 7, characterized in that: The second cavity is pre-treated, including: cleaning the second cavity; The second cavity is subjected to surface treatment; wherein, when the sound-transmitting material is a hydrophilic material, the second cavity is subjected to hydrophilic treatment; and when the sound-transmitting material is an oleophilic material, the second cavity is subjected to hydrophobic treatment.

9. The method for manufacturing a pressure-resistant MEMS underwater acoustic sensor according to claim 7, characterized in that: Mix the sound transmission material and the curing agent in a ratio of 9:1 to 11:

1.

10. The method for manufacturing a pressure-resistant MEMS underwater acoustic sensor according to claim 7, characterized in that: Curing methods include thermal curing, UV curing, or chemical curing.

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