Acceleration-sensitive measuring device and method for manufacturing the same

Abstract

The application provides an acceleration sensitive measuring device and a manufacturing method thereof. The acceleration sensitive measuring device is a passive device and serves as an acceleration sensitive module in a micro-accelerometer. The acceleration sensitive measuring device comprises a sensitive mass and a frame. A plurality of cantilever beams for supporting the sensitive mass are connected to the sensitive mass. One end of each cantilever beam is connected to the sensitive mass, and the other end of each cantilever beam is connected to a loading mechanism for extruding the cantilever beam. The loading mechanism is connected to the frame. The frame is provided with a through slot. The sensitive mass is movably arranged in the through slot. An amplifier for amplifying the displacement of the sensitive mass is arranged between the frame and the sensitive mass. The frame is fixedly installed on a substrate provided with a recess. The device and the manufacturing method have the advantages of low elastic coefficient and ultrahigh acceleration displacement sensitivity, and can ensure high tape-out rate and processing precision.

Description

Technical Field

[0001] This invention relates to the field of micro-accelerometer technology, and more specifically, to an acceleration-sensitive measuring device and its manufacturing method. Background Technology

[0002] Precise measurement of local acceleration changes plays a crucial role in applications such as natural disaster prediction, resource exploration, topographic mapping, and geophysical research. Low-cost miniature accelerometers will further contribute to Earth research, making the design and fabrication of miniaturized, high-performance accelerometers a current research focus. The basic measurement principle of an accelerometer is based on Newton's second law, and it typically consists of two parts: an acceleration-sensitive mechanism and a displacement readout system. The sensitive mass in the acceleration-sensitive mechanism generates a displacement related to the external acceleration, which is then amplified by a micro-lever mechanism, converting acceleration into displacement. The displacement readout system measures this displacement to obtain the acceleration value. The performance indicators of the accelerometer are determined by both parts. To achieve ultra-high acceleration measurement sensitivity, an acceleration-sensitive mechanism with ultra-high acceleration displacement sensitivity is essential.

[0003] Currently reported microelectromechanical system (MEMS) accelerometers' acceleration sensing mechanisms cannot achieve a sensitivity of 500 μm / Gal. For example, US Patent No. US010802042B2, "Measurement of acceleration," discloses an acceleration measurement device for use in accelerometers or gradiometers. The acceleration sensing mechanism of this device consists of three arc-shaped cantilever beams and a sensitive mass block. A pair of symmetrical arc-shaped cantilever beams support the bottom of the sensitive mass block, and one arc-shaped cantilever beam connects to the top of the sensitive mass block. In a vertical state, the resonant frequency of the structure is approximately 2.3 Hz.

[0004] Furthermore, US Patent No. US20200284940A1, "MEMS gravimeter," discloses a gravity accelerometer capable of operating globally. The acceleration-sensing mechanism includes a sensitive mass block, a pair of serpentine cantilever beams connecting the bottom of the sensitive mass block, and a pair of cosine cantilever beams connecting the top of the sensitive mass block. The resonant frequency of the structure in a vertical state is approximately 3.1 Hz. To improve the acceleration-displacement sensitivity of the acceleration-sensing mechanism, a sensitive mass block with the largest possible mass and an elastic mechanism with the smallest possible elastic coefficient are needed, but this is constrained by area and manufacturing processes. Existing micro-accelerometers cannot achieve ultra-high acceleration measurement sensitivity because they lack an acceleration-sensing mechanism with ultra-high acceleration-displacement sensitivity. Summary of the Invention

[0005] The main technical problem solved by this invention is to provide an acceleration-sensitive measuring device that achieves low elastic coefficient and ultra-high acceleration-displacement sensitivity.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an acceleration-sensitive measuring device, wherein the acceleration-sensitive measuring device is a passive device and acts as an acceleration-sensitive module in a micro accelerometer. The acceleration-sensitive measuring device includes a sensitive mass block and a frame. A plurality of cantilever beams for supporting the sensitive mass block are connected to the sensitive mass block. One end of each cantilever beam is connected to the sensitive mass block, and the other end of each cantilever beam is connected to a loading mechanism for pressing the cantilever beam. The loading mechanism is connected to the frame. A through groove is provided in the frame, and the sensitive mass block is movably disposed in the through groove. An amplifier for amplifying the displacement of the sensitive mass block is provided between the frame and the sensitive mass block. The frame is fixedly mounted on a substrate with grooves.

[0007] The beneficial effects of this invention are as follows: by setting a loading mechanism, the cantilever beam can be compressed by a certain distance, thereby reducing the elastic coefficient of the cantilever beam, improving the output of acceleration-displacement signals, and avoiding energy consumption. By setting an amplifier, the conversion and amplification from acceleration to displacement can be realized, effectively improving the acceleration-displacement sensitivity of the device. The sensitive mass block is set in the through slot of the frame and connected to the frame through the cantilever beam and the loading mechanism, improving the connection stability of the sensitive mass block. The frame is set on a substrate with grooves, improving the stability of the device and suspending the sensitive mass block and amplifier on the substrate. When they move, there is a movement gap between them and the substrate, reducing friction and improving measurement accuracy.

[0008] Preferably, there are four cantilever beams and four loading mechanisms. A connecting protrusion is provided at the center of each of the front and rear sides of the sensitive mass block. Each connecting protrusion connects to one end of a cantilever beam on its left and right sides, and the other end of each cantilever beam connects to a corresponding loading mechanism. This allows the four loading mechanisms to be spaced apart at the four corners of the sensitive mass block. By employing this structure, the number of cantilever beams and loading mechanisms is limited, as is their positional relationship with the sensitive mass block. This enables the sensitive mass block to move with acceleration in the front-rear direction, facilitating measurement and improving measurement stability.

[0009] Preferably, the amplifier includes a lever arm, one end of which is connected to one of the connecting protrusions via an input beam, and the other end of which is provided with an output terminal for outputting a displacement signal. By adopting the above structure, when the sensitive mass block undergoes a slight acceleration displacement, the input beam can input the slight displacement signal into the lever arm, which is then amplified and output by the output terminal at the other end of the lever arm, thus improving the displacement conversion and amplification effect.

[0010] Preferably, a pivot beam for supporting the lever arm is provided on the side of the lever arm near the input beam. One end of the pivot beam is connected to the lever arm, and the other end is connected to the frame. By adopting the above structure, the connection on the side of the lever arm near the input beam is stable, improving the stability of the lever arm in use.

[0011] Preferably, the loading mechanism includes a locking tooth structure for defining the left and right positions of the cantilever beam and a brake for pushing the locking tooth structure. One side of the locking tooth structure is connected to the cantilever beam, and the other side is connected to the brake. One side of the brake is connected to the locking tooth structure, and the other side is connected to the frame. By employing this structure, the brake pushes the locking tooth structure, which in turn pushes the cantilever beam towards the sensitive mass block, effectively reducing the elastic coefficient of the cantilever beam, stabilizing the structural connection, effectively improving the output of the acceleration-displacement signal, and avoiding energy consumption.

[0012] Preferably, the locking tooth structure includes a connecting block connected between the cantilever beam and the brake. Locking teeth extend from both the front and rear sides of the connecting block, and the frame has several grooves for the locking teeth to engage. By employing this structure, when the locking teeth on the connecting block engage with one of the grooves near the sensitive mass block, the cantilever beam experiences a large compression, resulting in a low elastic coefficient. The compressive force is maintained by a locking mechanism, effectively preventing energy loss.

[0013] Preferably, a connecting beam for supporting the connecting block is provided between the connecting block and the frame, with one end of the connecting beam connected to the connecting block and the other end connected to the frame. This structure ensures stable connection of the connecting block and improves the locking stability of the locking tooth structure.

[0014] Preferably, the brake includes two first beams and a second beam. The first beam has an arc-shaped structure, and the second beam has a multi-bend structure. One end of the first beam is connected to a connecting block, and the other end is connected to one end of the second beam. One end of the second beam is connected to the frame. The two first beams and the second beam are distributed symmetrically along the axis of symmetry of the connecting block. The irregular structure of the first beams and the second beam can effectively push the connecting block, enabling the connecting block to move towards the cantilever beam. At the same time, the symmetrical distribution of the first beams and the second beam further improves the pushing effect.

[0015] A method for manufacturing an acceleration-sensitive measuring device as described above includes the following steps: S1: Take a sample silicon wafer and clean its surface;

[0016] S2: Spin-coat a photoresist layer onto the upper plane of the sample silicon wafer, and pattern the photoresist layer using a photolithography process;

[0017] S3: An aluminum layer is prepared on the lower plane of the sample silicon wafer;

[0018] S4: The aluminum layer is attached to a carrier silicon wafer via an adhesive layer on its lower surface.

[0019] S5: Etch the sample silicon wafer using a deep reactive ion beam;

[0020] S6: Immerse the etched sample silicon wafer in acetone, peel the sample silicon wafer off the carrier silicon wafer, and then treat it with alkali to remove the aluminum layer, so that the sensitive mass block, cantilever beam, loading mechanism, amplifier and frame are formed on the sample silicon wafer 10.

[0021] S7: Take another sample silicon wafer to make a substrate, and etch grooves on the substrate at the positions corresponding to the sensitive mass block, cantilever beam, loading mechanism and amplifier.

[0022] S8: Bond the frame to the substrate to obtain the acceleration-sensitive measurement device.

[0023] The advantages of the above manufacturing method are: the sample silicon wafer can ensure a high aspect ratio and sidewall perpendicularity, and is compatible with IC process. At the same time, it avoids vibration and pressure and stress mismatch after the acceleration sensitive measuring device is formed. The maskless design ensures a high wafer yield and processing accuracy.

[0024] Preferably, the sample silicon wafers are fabricated in multiple arrays on the same monolithic silicon wafer. By adopting the above method steps, production efficiency can be effectively improved, and the device can be easily removed from the monolithic silicon wafer thanks to the maskless design. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of an acceleration-sensitive measuring device according to the present invention;

[0026] Figure 2 This is a schematic diagram of the loading mechanism;

[0027] Figure 3 This is a schematic diagram of the amplifier's structure;

[0028] Figures 4-11 This is a flowchart of the manufacturing method for an acceleration-sensitive measurement device;

[0029] Explanation of reference numerals in the attached figures:

[0030] 1. Sensitive mass block; 11. Connecting protrusion; 2. Cantilever beam; 3. Loading mechanism; 31. Gear structure; 311. Connecting block; 312. Gear; 313. Connecting beam; 32. Brake; 321. First beam; 322. Second beam; 4. Frame; 41. Through slot; 42. Gear groove; 5. Amplifier; 51. Lever arm; 52. Input beam; 53. Output end; 54. Pivot beam; 6. Substrate; 61. Groove; 10. Sample silicon wafer; 20. Photoresist layer; 30. Aluminum layer; 50. Adhesive layer. Detailed Implementation

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] In the description of this invention, it should be noted that the terms "upper", "lower", "left", "right", "front", "rear", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0033] like Figure 1-11 As shown, this invention provides an acceleration-sensitive measuring device, which is a passive device serving as the acceleration-sensitive module in a micro accelerometer. The device includes a sensitive mass block 1 and a frame 4. Several cantilever beams 2 for supporting the sensitive mass block 1 are connected to the sensitive mass block 1. Each cantilever beam 2 is a slender curved beam. One end of each cantilever beam 2 is connected to the sensitive mass block 1, and the other end is connected to a loading mechanism 3 for compressing the cantilever beam 2. The loading mechanism 3 is connected to the frame 4. A through groove 41 is provided within the frame 4, and the sensitive mass block 1 is movably disposed within the through groove 41. The frame 4 and the sensitive mass block 1 are connected to the frame 4. An amplifier 5 for amplifying the displacement of the sensitive mass block 1 is provided between the mass blocks 1. The frame 4 is fixedly installed on the substrate 6 with a groove 61. Specifically, the groove 61 has the same shape as the through groove 41. There are four cantilever beams 2 and four loading mechanisms 3. A connecting protrusion 11 is provided in the middle of the front and rear sides of the sensitive mass block 1. Each connecting protrusion 11 is connected to one end of a cantilever beam 2 on the left and right sides respectively. The other end of the cantilever beam 2 is connected to a loading mechanism 3, so that the four loading mechanisms 3 are distributed at intervals at the four corners of the sensitive mass block 1. The two cantilever beams 2 connected to each connecting protrusion 11 are symmetrically arranged on the left and right.

[0034] The thickness of the sensitive mass block 1, cantilever beam 2, amplifier 5, loading mechanism 3 and frame 4 are the same, and their center horizontal planes coincide. The acceleration sensing direction of the acceleration sensing measurement device is parallel to the length direction of the sensitive mass block 1, so that the center of gravity of the sensitive mass block 1 is located on the center plane of the cantilever beam 2. This ensures that the accelerometer has a small off-axis crosstalk.

[0035] The amplifier 5 includes a lever arm 51. One end of the lever arm 51 is connected to one of the connecting protrusions 11 via an input beam 52. The other end of the lever arm 51 is provided with an output terminal 53 for outputting displacement signals. When the sensitive mass block 1 undergoes a slight acceleration displacement, the input beam 52 can input the slight displacement signal into the lever arm 51, which is then amplified and output by the output terminal 53 at the other end of the lever arm 51, thereby improving the displacement conversion and amplification effect. In order to improve the stability of the lever arm 51, a pivot beam 54 for supporting the lever arm 51 is provided on the side of the lever arm 51 near the input beam 52. One end of the pivot beam 54 is connected to the lever arm 51, and the other end is connected to the frame 4.

[0036] The loading mechanism 3 includes a toothed structure 31 for defining the left and right positions of the cantilever beam 2 and a brake 32 for pushing the toothed structure 31. One side of the toothed structure 31 is connected to the cantilever beam 2 and the other side is connected to the brake 32. One side of the brake 32 is connected to the toothed structure 31 and the other side is connected to the frame 4. The toothed structure 31 includes a connecting block 311, which is connected between the cantilever beam 2 and the brake 32. The front and rear sides of the connecting block 311 are respectively provided with toothed teeth 312. The frame 4 is provided with a plurality of toothed grooves 42 for the toothed teeth 312 to engage. The plurality of toothed grooves 42 are arranged in two rows on the front and rear sides of the connecting block 311, and the plurality of toothed grooves 42 in each row are spaced apart in the left and right direction.

[0037] To improve the stability of the toothed structure 31, a connecting beam 313 for supporting the connecting block 311 is provided between the connecting block 311 and the frame 4. One end of the connecting beam 313 is connected to the connecting block 311 and the other end is connected to the frame 4.

[0038] The brake 32 includes two first beams 321 and a second beam 322. The first beam 321 has an arc-shaped structure, and the second beam 322 has a multi-bend structure. One end of the first beam 321 is connected to the connecting block 311, and the other end is connected to one end of the second beam 322. The other end of the second beam 322 is connected to the frame 4. The two first beams 321 and the second beam 322 are distributed symmetrically along the axis of symmetry of the connecting block 311. In use, the brake 32 pushes the locking tooth structure 31, which pushes the cantilever beam 2 to compress towards the sensitive mass block 1, thereby effectively reducing the elastic coefficient of the cantilever beam 2, stabilizing the structural connection, effectively improving the output of the acceleration displacement signal, and avoiding energy consumption.

[0039] A method for manufacturing an acceleration-sensitive measuring device as described above includes the following steps:

[0040] S1: Take a sample silicon wafer 10 and clean its surface;

[0041] S2: Spin-coat a photoresist layer 20 onto the upper plane of the sample silicon wafer 10, and pattern the photoresist layer 20 using a photolithography process;

[0042] S3: An aluminum layer 30 is prepared on the lower plane of the sample silicon wafer 10;

[0043] S4: The aluminum layer 30 is attached to a carrier silicon wafer via an adhesive layer 50 on its lower surface.

[0044] S5: The sample silicon wafer 10 is etched using a deep reactive ion beam;

[0045] S6: Immerse the etched sample silicon wafer 10 in acetone, peel the sample silicon wafer 10 off the carrier silicon wafer, and then remove the aluminum layer 30 by alkaline treatment, so that the sensitive mass block 1, cantilever beam 2, loading mechanism 3, amplifier 5 and frame 4 are formed on the sample silicon wafer 10.

[0046] S7: Take another sample silicon wafer 10 to make a substrate 6. The substrate 6 has grooves 61 etched on the positions corresponding to the sensitive mass block 1, cantilever beam 2, loading mechanism 3 and amplifier 5.

[0047] S8: Bond the frame 4 to the substrate 6 to obtain the acceleration-sensitive measurement device.

[0048] Specifically, before proceeding to step S1, the sample silicon wafer 10 needs to undergo dimensional testing to ensure the accuracy of the thickness.

[0049] In step S2, the pattern of the acceleration-sensitive measurement device is transferred onto the photoresist layer 20 using a mask. Finally, a stripping process is used to remove the film layer in the non-structured area. Meanwhile, the thickness of the photoresist layer 20 needs to reach more than 10 μm to ensure the depth of deep silicon etching. The photoresist can be AZ9260.

[0050] In step S3, an aluminum layer 30 is prepared using an evaporation process.

[0051] Before proceeding with step S4, the carrier silicon wafer must be placed on a 100°C heating plate for 2 minutes to ensure good adhesion between the two wafers.

[0052] During step S7, a substrate 6 with grooves 61 is fabricated by deep reactive ion beam etching of another silicon wafer using thick AZ4620 photoresist.

[0053] After step S8, the residual stress in the acceleration-sensitive measuring device is released by degumming and annealing.

[0054] The sample silicon wafers were fabricated in an array of more than 10 arrays on the same whole silicon wafer.

[0055] In the manufacturing method of this invention, during the residual stress release and adhesive removal process of the acceleration-sensitive measuring device, due to the extremely small elastic coefficient of the device itself, vibration and stirring processes should be avoided. During adhesive removal, organic water bath heating and dry plasma adhesive removal methods are combined to ensure the integrity of the structure.

[0056] The acceleration-sensitive measurement device of the present invention is designed to achieve an acceleration-displacement sensitivity of over 500 μm / Gal, and can also achieve an ultra-small elastic coefficient and ultra-high acceleration-displacement sensitivity while ensuring that the maximum stress in the structure does not exceed the yield limit of single-crystal silicon.

[0057] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. An acceleration-sensitive measuring device, wherein the acceleration-sensitive measuring device is a passive device, serving as the acceleration-sensitive module in a micro accelerometer, characterized in that, The acceleration sensitive measuring device includes a sensitive mass block (1) and a frame (4). Several cantilever beams (2) for supporting the sensitive mass block (1) are connected to the sensitive mass block (1). One end of the cantilever beam (2) is connected to the sensitive mass block (1), and the other end of the cantilever beam (2) is connected to a loading mechanism (3) for squeezing the cantilever beam (2). The loading mechanism (3) is connected to the frame (4). A through groove (41) is provided in the frame (4). The sensitive mass block (1) is movably disposed in the through groove (41). An amplifier (5) for amplifying the displacement of the sensitive mass block (1) is provided between the frame (4) and the sensitive mass block (1). The frame (4) is fixedly installed on a substrate (6) with a groove (61). The number of cantilever beams (2) and loading mechanisms (3) are four. A connecting protrusion (11) is provided in the middle of the front and rear sides of the sensitive mass block (1). Each connecting protrusion (11) is connected to one end of a cantilever beam (2) on the left and right sides respectively. The other end of the cantilever beam (2) is connected to a loading mechanism (3) so that the four loading mechanisms (3) are distributed at intervals at the four corners of the sensitive mass block (1). The two cantilever beams (2) connected to each connecting protrusion (11) are symmetrically arranged on the left and right sides. The thickness of the sensitive mass block (1), cantilever beam (2), amplifier (5), loading mechanism (3) and frame (4) is the same, and their center horizontal planes coincide. The acceleration sensing direction of the acceleration sensing measuring device is parallel to the length direction of the sensitive mass block (1), so that the center of gravity of the sensitive mass block (1) is located on the center plane of the cantilever beam (2). The loading mechanism (3) includes a toothed structure (31) for defining the left and right positions of the cantilever beam (2) and a brake (32) for pushing the toothed structure (31). One side of the toothed structure (31) is connected to the cantilever beam (2) and the other side is connected to the brake (32). One side of the brake (32) is connected to the toothed structure (31) and the other side is connected to the frame (4). The tooth structure (31) includes a connecting block (311), which is connected between the cantilever beam (2) and the brake (32). The front and rear sides of the connecting block (311) are respectively provided with toothed teeth (312), and the frame (4) is provided with a number of toothed grooves (42) for the toothed teeth (312) to engage. The brake (32) includes two first beams (321) and a second beam (322). The first beam (321) has an arc-shaped structure, and the second beam (322) has a multi-bend structure. One end of the first beam (321) is connected to the connecting block (311), and the other end is connected to one end of the second beam (322). The other end of the second beam (322) is connected to the frame (4). The two first beams (321) and the second beam (322) are distributed in a front-to-back symmetrical relationship along the axis of symmetry of the connecting block (311).

2. The acceleration-sensitive measuring device according to claim 1, characterized in that, The amplifier (5) includes a lever arm (51), one end of which is connected to one of the connecting protrusions (11) via an input beam (52), and the other end of which is provided with an output terminal (53) for outputting a displacement signal.

3. The acceleration-sensitive measuring device according to claim 2, characterized in that, The lever arm (51) is provided with a pivot beam (54) on one side near the input beam (52) for supporting the lever arm (51). One end of the pivot beam (54) is connected to the lever arm (51) and the other end is connected to the frame (4).

4. The acceleration-sensitive measuring device according to claim 1, characterized in that, A connecting beam (313) for supporting the connecting block (311) is provided between the connecting block (311) and the frame (4). One end of the connecting beam (313) is connected to the connecting block (311) and the other end is connected to the frame (4).

5. A method for manufacturing an acceleration-sensitive measuring device as described in any one of claims 1-4, characterized in that... Includes the following steps: S1: Take a sample silicon wafer (10) and clean its surface; S2: A photoresist layer (20) is spin-coated onto the upper plane of the sample silicon wafer (10), and the photoresist layer (20) is patterned using a photolithography process; S3: An aluminum layer (30) is prepared on the lower plane of the sample silicon wafer (10). S4: The lower surface of the aluminum layer (30) is attached to a carrier silicon wafer by an adhesive layer (50); S5: The sample silicon wafer (10) is etched using a deep reactive ion beam. S6: Immerse the etched sample silicon wafer (10) in acetone, peel the sample silicon wafer (10) off the carrier silicon wafer, and then treat with alkali to remove the aluminum layer (30) so that the sensitive mass block (1), cantilever beam (2), loading mechanism (3), amplifier (5) and frame (4) are formed on the sample silicon wafer (10). S7: Take another sample silicon wafer (10) to make a substrate (6). The substrate (6) has grooves (61) etched on the positions corresponding to the sensitive mass block (1), cantilever beam (2), loading mechanism (3) and amplifier (5). S8: Bond the frame (4) to the substrate (6) to obtain the acceleration-sensitive measurement device.

6. The method for manufacturing the acceleration-sensitive measuring device according to claim 5, characterized in that, The sample silicon wafers (10) are fabricated in multiple arrays on the same whole silicon wafer.

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