Funnel-shaped comb teeth and MEMS accelerometer

Abstract

The funnel-shaped comb tooth comprises funnel-shaped comb tooth structures, comb tooth root filling blocks, a fixed polar plate and a movable polar plate, the fixed polar plate and the movable polar plate are oppositely arranged, the funnel-shaped comb tooth structures are arranged on the side faces, facing each other, of the fixed polar plate and the movable polar plate, and the comb tooth root filling blocks are arranged on the side faces, facing each other, of the fixed polar plate and the movable polar plate. The funnel-shaped comb tooth structures are arranged on the fixed polar plate and the movable polar plate at intervals, and the comb tooth root filling blocks are arranged at intervals of the funnel-shaped comb tooth structures; the wider end of the funnel-shaped comb tooth structure is respectively connected with the fixed polar plate and the movable polar plate, and the end part of the narrower end of the funnel-shaped comb tooth structure is a plane. According to the funnel-shaped comb tooth and the MEMS accelerometer, the funnel-shaped comb tooth structure with the horizontal top end is adopted, compared with a tip end of a sawtooth-shaped comb tooth, the fringe capacitance is reduced, the linearity is improved, the intervals of the funnel-shaped comb tooth structure are filled with the comb tooth root filling blocks, and the capacitance is increased.

Description

Technical Field

[0001] The invention relates to a funnel-shaped comb tooth and a MEMS accelerometer, belonging to the technical field of MEMS capacitive sensors. Background Art

[0002] MEMS (Micro-electric mechanical systems) is short for micro-electromechanical systems. It refers to a micro-integration technology that integrates mechanical and electronic components using micromachining techniques based on integrated circuit technology. MEMS devices are mainly divided into microsensors, microactuators, and microcontrollers. Their feature sizes range from a few microns to several millimeters. They offer advantages such as miniaturization, mass production, microelectronic integration, and high-precision parallel manufacturing.

[0003] Among MEMS accelerometers, capacitive micromachined accelerometers are currently the most widely used. These micromachined capacitive accelerometers measure acceleration by detecting changes in capacitance. Capacitive micromachined capacitors are typically composed of several pairs of overlapping comb-shaped plates.

[0004] From physics, we know that the approximate calculation formula for the capacitance of a capacitor composed of two parallel metal plates is: (1); Among them, ε is the dielectric constant of the two plate media, S is the relative effective area of ​​the two plates, and d is the distance between the two plates.

[0005] There are three ways to change the capacitance C. The first is to change the distance d between the two plates; the second is to change the effective area S that forms the capacitor; and the third is to change the dielectric constant ε of the medium.

[0006] A variable-pitch capacitive accelerometer measures acceleration by changing the capacitance by varying the spacing between the plates. Because the width of the capacitor plates is much larger than the spacing between the plates, the capacitance change of the variable-pitch structure is much greater than that of the variable-area structure when the nominal capacitance is the same. This means the variable-pitch capacitive accelerometer has higher sensitivity. However, the acceleration measured by the variable-pitch type is not linear with the sensitive displacement, resulting in a nonlinear problem.

[0007] A variable-area capacitive accelerometer measures acceleration by varying the capacitance by changing the relative effective area between the plates. The measured acceleration is linearly related to the sensitive displacement, resulting in high linearity but low sensitivity. Micromachined capacitive accelerometers generally do not use a variable dielectric type.

[0008] To achieve an accelerometer with both high sensitivity and high linearity, the comb capacitor structure needs to be improved. Ideally, the relationship between the output voltage and acceleration of an accelerometer should be linear, described by the device's sensitivity. However, in practice, due to limitations in materials, processes, and inherent mechanisms, accelerometers often exhibit certain nonlinear errors. Nonlinearity measures the deviation between actual sensitivity and the ideal constant sensitivity and is expressed relative to the full-scale range (%FSR or PPM). Improving linearity helps simplify signal processing and improve measurement accuracy.

[0009] In order to obtain a high-performance accelerometer, relevant researchers proposed an improved structure of the comb teeth: Patent CN 114814293 A "A MEMS accelerometer with a sawtooth comb structure" discloses a MEMS accelerometer with a sawtooth comb structure. The sensitive comb teeth pair are sawtooth comb teeth. When subjected to acceleration motion, they almost only produce synovial damping, reducing thermomechanical noise. The sawtooth comb teeth also increase the change in the capacitance of the MEMS accelerometer, effectively improving sensitivity and resolution.

[0010] However, the sharp shape of the top of the sawtooth comb teeth leads to a large charge density, obvious charge tip effect, and a large edge effect capacitance. The change in the edge capacitance at the top of the sawtooth comb teeth is nonlinear with the acceleration, which aggravates the nonlinear effect of the comb capacitance and reduces the linearity of the accelerometer. It can be seen that in order to improve the linearity of acceleration, a funnel-shaped comb tooth and a MEMS accelerometer are urgently needed. Summary of the Invention

[0011] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a funnel-shaped comb tooth and a MEMS accelerometer. The funnel-shaped comb tooth structure with a horizontal top is adopted. Compared with the tip of the sawtooth comb tooth, the edge capacitance is reduced and the linearity is improved. The gaps in the funnel-shaped comb tooth structure are filled with filling blocks at the root of the comb tooth to increase the capacitance.

[0012] In order to achieve the above objectives / solve the above technical problems, the present invention is implemented by adopting the following technical solutions: In a first aspect, the present invention provides a funnel-shaped comb tooth, comprising a funnel-shaped comb tooth structure, a filling block at the root of the comb tooth, and a fixed electrode plate and a movable electrode plate arranged opposite to each other, wherein: The fixed electrode plate and the movable electrode plate are both provided with a funnel-shaped comb tooth structure on one side facing the other, the funnel-shaped comb tooth structure is arranged at intervals on the fixed electrode plate and the movable electrode plate, and the comb tooth root filling blocks are arranged at the intervals between the funnel-shaped comb tooth structures; The wider end of the funnel-shaped comb-tooth structure is connected to the fixed electrode plate and the movable electrode plate respectively, and the narrower end of the funnel-shaped comb-tooth structure is a flat surface; The ends of the fixed electrode plate and the movable electrode plate are aligned, the funnel-shaped comb tooth structure on the fixed electrode plate and the funnel-shaped comb tooth structure on the movable electrode plate are staggered with each other, and the comb tooth gap between the fixed electrode plate and the movable electrode plate remains consistent.

[0013] Furthermore, the initial capacitance of the funnel-shaped comb-tooth structure is the sum of the sidewall capacitance, top capacitance and bottom corner capacitance of the funnel-shaped comb-tooth structure.

[0014] Furthermore, the initial capacitance is calculated by the following formula: (1); Where, is the initial capacitance, is the side wall capacitance, is the top capacitance, is the funnel-shaped branch bottom corner capacitance, N is the number of funnel-shaped comb-tooth structures, ε is the dielectric constant of the two plate media, d is the distance between the two plates, T is the thickness of the plate, L is the overlapping length of two adjacent funnel-shaped comb-tooth structures, and W is the width of the top of the funnel-shaped comb-tooth structure. is the height of the filling block at the root of the comb teeth, It is the bottom angle of the funnel-shaped comb structure.

[0015] Furthermore, when the moving plate is subjected to acceleration, it will move Finally, the capacitance C of the funnel-shaped comb structure is expressed by the following formula: (2); Where, is the displacement of the moving plate.

[0016] Furthermore, the fixed electrode plate and the movable electrode plate are rectangular flat plates.

[0017] Furthermore, when the fixed electrode plate and the movable electrode plate are aligned at both ends, the top of the funnel-shaped comb-tooth structure on one electrode plate corresponds to the comb-tooth root filling block on the other electrode plate.

[0018] Furthermore, the fixed electrode plate and the movable electrode plate are arranged one above the other.

[0019] In a second aspect, the present invention provides a MEMS accelerometer comprising the funnel-shaped comb teeth described in the first aspect.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The funnel-shaped comb teeth provided by the present invention have a horizontal top surface under the conditions of the same gap and the same gap variation. Compared with the tips of sawtooth-shaped comb teeth, the edge capacitance is reduced and the linearity is improved. The filling block at the root of the comb teeth can reduce the gap between the top of the funnel-shaped comb tooth structure and the overlapping electrode plate, thereby increasing the comb tooth capacitance value and further increasing the capacitance variation. Under the conditions of the same gap and the same gap variation, compared with traditional flat comb teeth, the initial capacitance value is increased, and the capacitance sensitivity of the funnel-shaped comb tooth structure is improved. The MEMS accelerometer provided by the present invention can have both high sensitivity and high linearity by adapting to the above-mentioned funnel-shaped comb teeth, which helps to simplify the signal processing process and improve measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic structural perspective view of the funnel-shaped comb teeth provided by the present invention; Figure 2 yes Figure 1 A schematic top view of the structure of the funnel-shaped comb teeth shown; Figure 3 yes Figure 1 A schematic structural diagram of the fixed plate shown; Figure 4 yes Figure 1 The structural diagram of the movable plate shown; Figure 5 yes Figure 1 Schematic diagram of local detail dimensions of the middle comb tooth structure.

[0022] In the figure: 1. Funnel-shaped comb structure; 2. Filler block at the root of the comb; 3. Fixed plate; 4. Moving plate. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0024] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0025] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances. Example 1

[0026] like Figures 1 to 5 As shown, this embodiment provides a funnel-shaped comb tooth, including a funnel-shaped comb tooth structure 1, a comb tooth root filling block 2, and a fixed electrode plate 3 and a movable electrode plate 4 arranged opposite to each other, wherein: The fixed electrode plate 3 and the movable electrode plate 4 are both provided with a funnel-shaped comb tooth structure 1 on one side facing the other. The funnel-shaped comb tooth structure 1 is arranged at intervals on the fixed electrode plate 3 and the movable electrode plate 4. The comb tooth root filling blocks 2 are arranged at the intervals between the funnel-shaped comb tooth structures 1. The wider end of the funnel-shaped comb-tooth structure 1 is connected to the fixed electrode 3 and the movable electrode 4 respectively, and the narrower end of the funnel-shaped comb-tooth structure 1 is a plane. The two ends of the fixed electrode plate 3 and the movable electrode plate 4 are aligned, the funnel-shaped comb tooth structure 1 on the fixed electrode plate 3 and the funnel-shaped comb tooth structure 1 on the movable electrode plate 4 are staggered with each other, and the comb tooth gap between the fixed electrode plate 3 and the movable electrode plate 4 remains consistent.

[0027] In the above technical solution, under the conditions of the same gap and the same gap change, the top of the funnel-shaped comb tooth structure 1 is a horizontal plane. Compared with the tip of the serrated comb tooth, the edge capacitance is reduced and the linearity is improved. The filling block 2 at the root of the comb tooth can reduce the gap d between the top of the funnel-shaped comb tooth structure 1 and the overlapping electrode (fixed electrode 3 or movable electrode 4), thereby increasing the comb tooth capacitance value and then increasing the capacitance change. Under the conditions of the same gap and the same gap change, compared with the traditional flat comb tooth, the initial capacitance value is increased and the capacitance sensitivity of the funnel-shaped comb tooth structure is improved.

[0028] By adjusting the shape of the protruding branches, the capacitance of the comb structure can be changed, and thus the sensitivity and linearity of the accelerometer can be adjusted. Example 2

[0029] like Figures 1 to 5 As shown, the funnel-shaped comb teeth provided in this embodiment differ from the funnel-shaped comb teeth provided in the first embodiment in that: The initial capacitance of the funnel-shaped comb-tooth structure 1 is the sum of the sidewall capacitance, top capacitance, and bottom corner capacitance of the funnel-shaped comb-tooth structure 1. The initial capacitance is calculated by the following formula: (1); Where, is the initial capacitance, is the side wall capacitance, is the top capacitance, is the funnel-shaped branch bottom corner capacitance, N is the number of funnel-shaped comb-tooth structures 1, ε is the dielectric constant of the two plate media, d is the distance between the two plates, T is the thickness of the plate, L is the overlapping length of two adjacent funnel-shaped comb-tooth structures 1, W is the width of the top of the funnel-shaped comb-tooth structure 1, is the height of the filling block 2 at the root of the comb teeth, It is the bottom angle of the funnel-shaped comb structure 1.

[0030] Furthermore, when the moving plate 4 is subjected to acceleration, it will be displaced. Finally, the capacitance C of the funnel-shaped comb structure 1 is expressed by the following formula: (2); Where, is the displacement of the moving plate 4.

[0031] The fixed electrode plate 3 and the movable electrode plate 4 are rectangular flat plates.

[0032] When the fixed electrode plate 3 and the movable electrode plate 4 are aligned at both ends, the top of the funnel-shaped comb structure 1 on one electrode plate corresponds to the comb root filling block 2 on the other electrode plate.

[0033] The fixed electrode plate 3 and the movable electrode plate 4 are arranged one above the other.

[0034] The funnel-shaped comb teeth provided by this embodiment are introduced below in conjunction with the specific operation process during implementation. The specific steps are as follows: Step 1: Take a fixed upper plate, attach the funnel-shaped comb structure and the comb root filling block to the lower end of the upper plate (such as Figure 3 shown).

[0035] Step 2: Take a movable lower plate, attach the funnel-shaped comb structure and the comb root filling block to the upper end of the lower plate (such as Figure 4 shown).

[0036] Step 3: Align the ends of the fixed upper plate and the movable lower plate, overlap them, and place them with a comb gap of d (such as Figure 2 and Figure 5 shown).

[0037] Step 4: Calculate the initial capacitance of the funnel-shaped comb structure , this capacitor is composed of three parts: the side wall capacitor of the funnel-shaped branch , the top capacitance of the funnel-shaped branch , Funnel-shaped branch bottom corner capacitor , ; Where N is the number of funnel-shaped comb-tooth structures 1, ε is the dielectric constant of the two plate media, d is the distance between the two plates, T is the thickness of the plate, L is the overlapping length of two adjacent funnel-shaped comb-tooth structures 1, and W is the width of the top of the funnel-shaped comb-tooth structure 1. is the height of the filling block 2 at the root of the comb teeth, is the bottom angle of the funnel-shaped comb structure 1 (e.g. Figure 5 shown).

[0038] Step 5: When the moving plate 4 is displaced by acceleration, the capacitance C of the funnel-shaped comb structure 1 is expressed by the following formula: (2); Where, is the displacement of the moving plate 4.

[0039] Step 6: In COMSOL simulation software, three-dimensional structural models of funnel-shaped comb teeth, sawtooth-shaped comb teeth, and traditional flat comb teeth were established. The comb gap, comb length, and structural thickness of the three models were the same. An electromechanical interface was added, and the simulation results are shown in Table 1. Under the conditions of the same gap and the same gap variation, the funnel-shaped comb teeth have a 0.92% lower sensitivity than the sawtooth-shaped comb teeth, but the nonlinearity of the funnel-shaped comb teeth is reduced by 4%. Compared with the traditional flat comb teeth, the funnel-shaped comb teeth have a 2.26% higher sensitivity and a 31.93% lower nonlinearity.

[0040] Table 1 COMSOL electromechanical simulation results

[0041] Example 3

[0042] This embodiment provides a MEMS accelerometer that, by adapting the funnel-shaped comb teeth described in the first or second embodiment, can have both high sensitivity and high linearity, thereby helping to simplify the signal processing process and improve measurement accuracy.

[0043] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A funnel-shaped comb, characterized in that: It comprises a funnel-shaped comb tooth structure (1), a comb tooth root filling block (2), and a fixed pole plate (3) and a movable pole plate (4) arranged opposite to each other, wherein: The fixed electrode plate (3) and the movable electrode plate (4) are both provided with a funnel-shaped comb tooth structure (1) on one side facing the other, the funnel-shaped comb tooth structure (1) is arranged at intervals on the fixed electrode plate (3) and the movable electrode plate (4), and the comb tooth root filling block (2) is arranged at the intervals between the funnel-shaped comb tooth structure (1); The wider end of the funnel-shaped comb-tooth structure (1) is connected to the fixed electrode plate (3) and the movable electrode plate (4), respectively, and the narrower end of the funnel-shaped comb-tooth structure (1) is a plane. The two ends of the fixed pole plate (3) and the movable pole plate (4) are aligned, the funnel-shaped comb tooth structure (1) on the fixed pole plate (3) and the funnel-shaped comb tooth structure (1) on the movable pole plate (4) are interlaced, and the comb tooth gap between the fixed pole plate (3) and the movable pole plate (4) remains consistent.

2. The funnel-shaped comb teeth according to claim 1, characterized in that: The initial capacitance of the funnel-shaped comb-tooth structure (1) is the sum of the sidewall capacitance, top capacitance and bottom corner capacitance of the funnel-shaped comb-tooth structure (1).

3. The funnel-shaped comb teeth according to claim 2, characterized in that: The initial capacitance is calculated by the following formula: （1）； Where, is the initial capacitance, is the side wall capacitance, is the top capacitance, is the bottom angle capacitance of the funnel-shaped branch, N is the number of the funnel-shaped comb-tooth structures (1), ε is the dielectric constant of the two plate media, d is the distance between the two plates, T is the thickness of the plate, L is the overlapping length of two adjacent funnel-shaped comb-tooth structures (1), W is the width of the top of the funnel-shaped comb-tooth structure (1), is the height of the filling block (2) at the root of the comb teeth, and is the bottom angle of the funnel-shaped comb-tooth structure (1).

4. The funnel-shaped comb teeth according to claim 1, characterized in that: When the moving plate (4) is subjected to acceleration, it will move Finally, the capacitance C of the funnel-shaped comb structure (1) is expressed by the following formula: （2）； Where, is the displacement of the moving plate (4).

5. The funnel-shaped comb teeth according to claim 1, characterized in that: The fixed electrode plate (3) and the movable electrode plate (4) are rectangular flat plates.

6. The funnel-shaped comb teeth according to claim 1, characterized in that: When the fixed electrode (3) and the movable electrode (4) are aligned at both ends, the top of the funnel-shaped comb-tooth structure (1) on one electrode plate corresponds to the comb-tooth root filling block (2) on the other electrode plate.

7. The funnel-shaped comb teeth according to claim 1, characterized in that: The fixed electrode plate (3) and the movable electrode plate (4) are arranged one above the other.

8. A MEMS accelerometer, characterized in that: The invention comprises the funnel-shaped comb teeth according to any one of claims 1 to 7.

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