Physical quantity sensor

Abstract

To provide a physical quantity sensor which can be downsized.SOLUTION: A physical quantity sensor 1 includes: a substrate 10; a fixation electrode 24 relatively fixed to the substrate 10; a movable electrode 25 relatively displaced to the substrate 10; and a spring 30 having a first end 31 relatively fixed to the substrate 10 and a second end 32 relatively connected to the movable electrode 25. The spring 30 has a meander structure that folds back along the vertical direction of the main surface 11 of the substrate 10.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a physical quantity sensor. [Background technology]

[0002] In recent years, physical quantity sensors have been developed that detect physical quantities such as acceleration as changes in capacitance of a movable part. For example, Patent Document 1 discloses such a physical quantity sensor in which the movable part has a spring that folds back along a substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-071097 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the physical quantity sensor described in Patent Document 1, in order to reduce the spring constant so that the movable part can be easily displaced, it is necessary to increase the length of the spring or the number of times it is folded back, which increases the area occupied by the spring on the plane of the movable part, resulting in a problem of an increase in the size of the physical quantity sensor. [Means for solving the problem]

[0005] The physical quantity sensor includes a substrate, a fixed electrode fixed relative to the substrate, a movable electrode displaceable relative to the substrate, and a spring having one end fixed relative to the substrate and the other end connected relatively to the movable electrode, the spring having a meandering structure that extends along a main surface of the substrate and folds back along a plane perpendicular to the main surface. [Brief description of the drawings]

[0006] [Figure 1]FIG. 1 is a plan view showing a schematic structure of a physical quantity sensor according to a first embodiment. [Diagram 2] 2 is a cross-sectional view taken along line A1-A1 in FIG. 1. [Diagram 3] An enlarged view of part B1 in FIG. [Figure 4] FIG. 11 is a cross-sectional view showing the structure of a spring included in the physical quantity sensor according to the second embodiment. [Diagram 5] FIG. 11 is a cross-sectional view showing the structure of a spring included in the physical quantity sensor according to the third embodiment. [Figure 6] FIG. 13 is a plan view showing a schematic structure of a physical quantity sensor according to a fourth embodiment. [Figure 7] FIG. 7 is a cross-sectional view taken along line A2-A2 in FIG. [Figure 8] An enlarged view of part B2 in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] 1. First embodiment First, the physical quantity sensor 1 according to the first embodiment will be described with reference to FIGS. 1, 2, and 3, taking as an example an acceleration sensor that detects acceleration in a direction along the main surface 11 of the substrate 10. FIG.

[0008] For ease of explanation, the following plan views and cross-sectional views show an X-axis, a Y-axis, and a Z-axis as three mutually orthogonal axes. The direction along the X-axis is called the "X direction", the direction along the Y-axis is called the "Y direction", and the direction along the Z-axis is called the "Z direction". The tip side of the arrow in each axial direction is also called the "plus side", the base side is called the "minus side", the plus side of the Z direction is also called the "upper", and the minus side of the Z direction is also called the "lower". The Z direction is perpendicular to the main surface 11 of the XY plane.

[0009] 1, 2, and 3, the physical quantity sensor 1 according to this embodiment can detect acceleration in the Y direction along a main surface 11 of a substrate 10. Such a physical quantity sensor 1 includes the substrate 10, a movable part 20 fixed to the substrate 10 and having a movable electrode 25, and a fixed electrode 24 fixed to the substrate 10.

[0010] As shown in Fig. 1, the substrate 10 is a rectangle extending in the X and Y directions, and has a thickness in the Z direction. As shown in Fig. 2, the substrate 10 is formed with two first fixed portions 12 protruding upward from the main surface 11 of the substrate 10, and a plurality of second fixed portions 13 protruding upward from the main surface 11 of the substrate 10. A support portion 22 of the movable portion 20 is fixed to the first fixed portions 12, and a fixed electrode 24 is fixed to the second fixed portions 13.

[0011] The substrate 10 may be, for example, a silicon substrate. However, the substrate is not particularly limited to this, and may be, for example, a glass substrate or a quartz substrate.

[0012] As shown in FIGS. 1 and 2, the movable portion 20 includes a base portion 21, a support portion 22, a connecting portion 23, a plurality of movable electrodes 25, and a spring 30.

[0013] The base 21 is disposed in the center of the movable part 20, extends in the Y direction, and is connected at both ends in the Y direction to a connecting part 23 disposed on the positive side of the Y direction and a connecting part 23 disposed on the negative side of the Y direction, respectively. In addition, a plurality of movable electrodes 25 extending in the positive X direction and a plurality of movable electrodes 25 extending in the negative X direction are connected to both ends in the X direction of the base 21, respectively.

[0014] Two fixed electrodes 24 are arranged between two movable electrodes 25 arranged in the Y direction, with the first fixed electrode 24a arranged on the positive side of the Y direction and the second fixed electrode 24b arranged on the negative side of the Y direction. The first fixed electrode 24a and the movable electrode 25, and the second fixed electrode 24b and the movable electrode 25 are arranged so as to be parallel to each other. The fixed electrode 24 arranged on the positive side of the X direction of the base 21 has an end in the positive X direction fixed to the second fixed part 13 of the substrate 10. The fixed electrode 24 arranged on the negative side of the X direction of the base 21 has an end in the negative X direction fixed to the second fixed part 13 of the substrate 10. Therefore, the fixed electrode 24 is fixed relatively to the substrate 10 via the second fixed part 13.

[0015] The support portion 22 is disposed in the center of a connecting portion 23 that surrounds the support portion 22 and the spring 30, and is connected to the connecting portion 23 via the spring 30. The center of the support portion 22 is fixed to the first fixed portion 12 of the substrate 10.

[0016] The springs 30 are disposed on both sides of the support 22 in the X direction, with one end 31 on the support 22 side connected to the support 22 and the other end 32 on the connecting portion 23 side connected to the connecting portion 23. Therefore, one end 31 of the spring 30 is relatively fixed to the substrate 10 via the support 22, and the other end 32 of the spring 30 is relatively connected to the movable electrode 25 via the connecting portion 23 and the base 21. As shown in FIG. 2 and FIG. 3, the spring 30 has a meander structure that is folded back along a plane perpendicular to the main surface 11 of the substrate 10. That is, the spring 30 has a plurality of bent portions 33 that are curved in the Z direction, which is the thickness direction of the movable portion 20, and the intervals W between the bent portions 33 are arranged at approximately equal intervals, and act as an elastic portion that can deform in the Y direction, which is the direction of the arrow a. Therefore, when acceleration in the Y direction is applied, the spring 30 elastically deforms in the Y direction, and the connecting portion 23, the base 21, and the movable electrode 25 are displaced in the Y direction. Therefore, the movable electrode 25 is displaced relative to the substrate 10 .

[0017] Such a physical quantity sensor 1 detects acceleration in the Y direction as follows. That is, when acceleration in the Y direction is applied to the physical quantity sensor 1, the movable part 20 is displaced in the Y direction while elastically deforming the spring 30 based on the magnitude of the acceleration. With such displacement, the magnitudes of the capacitance between the movable electrode 25 and the first fixed electrode 24a and the capacitance between the movable electrode 25 and the second fixed electrode 24b each change. Therefore, it is possible to detect acceleration based on the amount of change in these capacitances.

[0018] The movable part 20 and the fixed electrode 24 are simultaneously formed by etching the same substrate, for example, a conductive silicon substrate doped with impurities such as phosphorus, boron, etc., by vertical processing using the Bosch process, which is a deep etching technique. Note that the movable part 20 in this embodiment is formed by processing a part of the bent part 33 by deep etching from the negative Z direction side of the movable part 20, fixing it to the substrate 10, and then deep etching from the positive Z direction side of the movable part 20.

[0019] The spring constant of the spring 30 can be adjusted by adjusting the plate thickness of the movable part 20 and the length L in the Z direction of the bent part 33. In addition, since the plate thickness of the movable part 20 is increased, the opposing area between the movable electrode 25 and the fixed electrode 24 is increased, and the amount of change in capacitance due to acceleration can be increased, thereby improving the detection sensitivity.

[0020] As described above, the physical quantity sensor 1 of this embodiment has a meandering structure in which the spring 30 is folded back along a plane perpendicular to the main surface 11 of the substrate 10, and therefore, compared to a meandering structure in which the spring 30 is folded back along the main surface 11, the area occupied by the spring 30 is smaller, the area of ​​the movable part 20 in the XY plane can be reduced, and the physical quantity sensor 1 can be made more compact. In addition, since the plate thickness of the movable part 20 is thicker, the opposing area between the movable electrode 25 and the fixed electrode 24 is larger, and the amount of change in capacitance due to acceleration can be increased, and a highly accurate physical quantity sensor 1 can be obtained.

[0021] 2. Second embodiment Next, a physical quantity sensor 1a according to a second embodiment will be described with reference to Fig. 4. Fig. 4 is a cross-sectional view taken at a position corresponding to Fig. 3.

[0022] The physical quantity sensor 1a of this embodiment is similar to the physical quantity sensor 1 of the first embodiment, except that the structure of the spring 30a is different from that of the physical quantity sensor 1 of the first embodiment. Note that the following description will focus on the differences from the first embodiment described above, and descriptions of similar points will be omitted.

[0023] 4, in the physical quantity sensor 1a, the spring 30a has a plurality of intervals W1 to W3 between adjacent bent portions 33a to 33d in the length in the X direction, which is the extension direction of the spring 30a. That is, the interval W1 is between bent portions 33a and 33b, the interval W2 is between bent portions 33b and 33c, and the interval W3 is between bent portions 33c and 33d, such that W3>W1>W2. By adjusting the intervals W1 to W3 between bent portions 33a to 33d, the spring constant of 30a can be freely adjusted.

[0024] With this configuration, the spring constant of the spring 30a can be adjusted, and the same effect as that of the physical quantity sensor 1 of the first embodiment can be obtained.

[0025] 3. Third embodiment Next, a physical quantity sensor 1b according to a third embodiment will be described with reference to Fig. 5. Fig. 5 is a cross-sectional view taken at a position corresponding to Fig. 3.

[0026] The physical quantity sensor 1b of this embodiment is similar to the physical quantity sensor 1 of the first embodiment, except that the structure of the spring 30b is different from that of the physical quantity sensor 1 of the first embodiment. Note that the following description will focus on the differences from the first embodiment described above, and descriptions of similar points will be omitted.

[0027] 5, the physical quantity sensor 1b has a plurality of lengths L1 to L3 of bent portions 33a to 33d adjacent to each other in the Z direction, which is a direction perpendicular to the main surface 11 of the substrate 10 of the spring 30b. That is, the bent portion 33a has a length L1, the bent portion 33b has a length L2, and the bent portion 33d has a length L3, where L1>L3>L2. The length of the bent portion 33c is the same as the length L1 of the bent portion 33a. By adjusting the lengths L1 to L3 of the bent portions 33a to 33d, the spring constant of 30b can be freely adjusted.

[0028] With this configuration, the spring constant of the spring 30b can be adjusted, and the same effect as that of the physical quantity sensor 1 of the first embodiment can be obtained.

[0029] 4. Fourth embodiment Next, a physical quantity sensor 1c according to a fourth embodiment will be described with reference to FIGS.

[0030] A physical quantity sensor 1c of this embodiment is similar to the physical quantity sensor 1 of the first embodiment, except that the structure of the spring 30c is different from that of the physical quantity sensor 1 of the first embodiment. Note that the following description will focus on the differences from the first embodiment described above, and descriptions of similar points will be omitted.

[0031] 6, 7, and 8, the physical quantity sensor 1c is configured with a meander structure in which the spring 30c is folded back along the perpendicular direction to the main surface 11 of the substrate 10, and a meander structure in which the spring 30c is folded back along the main surface 11 of the substrate 10. The spring 30c has a plurality of bent portions 34a curved in the Z direction, which is the thickness direction of the movable part 20, on one end 31 side, and a plurality of bent portions 34b curved in the Y direction along the main surface 11 of the substrate 10 on the other end 32 side. The bent portions 34a on the other end 32 side and the bent portions 34b on the one end 31 side are connected at their respective ends.

[0032] With this configuration, the spring constant of the spring 30c can be adjusted, and the same effect as that of the physical quantity sensor 1 of the first embodiment can be obtained. [Explanation of symbols]

[0033] 1, 1a, 1b, 1c...physical quantity sensor, 10...substrate, 11...main surface, 12...first fixed portion, 13...second fixed portion, 20...movable portion, 21...base, 22...support portion, 23...connecting portion, 24...fixed electrode, 24a...first fixed electrode, 24b...second fixed electrode, 25...movable electrode, 30...spring, 31...one end, 32...other end, 33...bent portion, a...arrow, L, L1, L2, L3...length, W, W1, W2, W3...spacing.

Claims

1. A substrate; a fixed electrode fixed relatively to the substrate; a movable electrode that is displaceable relative to the substrate; a spring having one end fixed relatively to the substrate and another end connected relatively to the movable electrode; Equipped with The spring has a meandering structure that extends along a main surface of the substrate and folds back along a plane perpendicular to the main surface. Physical quantity sensor.

2. The spring has a curved bend. The physical quantity sensor according to claim 1 .

3. The spring has a plurality of lengths as intervals between adjacent bent portions in the extension direction. The physical quantity sensor according to claim 2 .

4. The spring has a plurality of lengths as lengths of the bent portions adjacent to each other in a direction perpendicular to the main surface of the substrate. The physical quantity sensor according to claim 2 .

5. The spring further has a meander structure folded back along the main surface of the substrate. The physical quantity sensor according to claim 1 .

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