JP2009063430A - Two-axis capacitive acceleration sensor, and two-axis capacitive accelerometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-axis capacitive acceleration sensor that can suppress the occurrence of another axis sensitivity without enlarging the size of the sensor, and has high linearity. <P>SOLUTION: The two-axis capacitive acceleration sensor includes a substrate 110 where one or more X-axis fixed electrodes 111 and one or more Y-axis fixed electrodes 112 are formed on the same plate surface, and a structure 120. The structure 120 has a frame 121 that is facedly arranged to the substrate 110 in parallel and is disposed at the outer rim, an X-axis movable electrode 123 that is displaceably supported in the X axis direction by a plurality of beams 122 inside the flame 121, and establishes a predetermined relation between the displacement in the X axis direction and the variation of the area facing the X-axis fixed electrodes 111, and a Y-axis movable electrode 125 that is displaceably supported in the Y axis direction by a plurality of beams 124 inside the X-axis movable electrode 123, and establishes a predetermined relation between the displacement in the Y axis direction and the variation of the area facing the Y-axis fixed electrodes 112. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a biaxial capacitive acceleration sensor for detecting biaxial acceleration from changes in capacitance between electrodes due to relative displacement of opposing electrode pairs, and biaxial static using the same. The present invention relates to a capacitive accelerometer.

  Conventionally known capacitance type acceleration sensors can be broadly divided into a detection method based on a change in the distance between opposing electrodes and a detection method based on a change in the opposing area of the electrodes.

  FIG. 13 is a cross-sectional view illustrating a configuration example of the capacitive acceleration sensor 10 that detects acceleration based on a change in electrode spacing. The capacitive acceleration sensor 10 includes a substrate 11, a fixed electrode 12 fixed to the substrate 11, a movable electrode 13, and a beam 14 that supports the movable electrode 13 so as to be displaceable with respect to the substrate 11. . A parallel plate capacitor is formed by the fixed electrode 12 and the movable electrode 13, and the capacitance C generated there can be expressed by the following equation.

C = ε · S / d (1)
Here, ε is the dielectric constant of the space between the fixed electrode 12 and the movable electrode 13, S is the facing area between the fixed electrode 12 and the movable electrode 13, and d is the distance between the fixed electrode 12 and the movable electrode 13. It is. When acceleration in the direction shown in FIG. 13 is applied to the capacitive acceleration sensor 10, the beam 14 bends, the movable electrode 13 is displaced, and the distance d changes. Therefore, the acceleration in the direction shown in FIG. 13 can be obtained by detecting the displacement of the movable electrode 13 as a change in capacitance. Known techniques that employ such a detection method are disclosed in Patent Documents 1 and 2 and the like.

  However, the detection method based on the change in the distance between the electrodes has an advantage that the capacitance C can be detected with high sensitivity even when the change in the distance d is small as can be seen from the equation (1). Linearity is poor because it is proportional to / d.

On the other hand, the detection method based on the change in the area where the electrodes face each other is inferior to the detection method based on the change in the electrode interval in terms of sensitivity when the displacement is small, but the capacitance C is proportional to the opposed area S. Good linearity. FIG. 14A is a plan view showing a configuration example of a capacitive acceleration sensor 20 that detects acceleration based on a change in the area where the electrodes face each other, and FIG. 14B is a plan view of FIG. It is sectional drawing of the part of a '. The capacitive acceleration sensor 20 includes a frame 21, a fixed electrode 22, a weight 23, a movable electrode 24 that is integrally displaced with the weight 23, and a beam 25 that supports the weight 23 so as to be displaceable with respect to the frame 21. It consists of. When acceleration in the direction shown in FIG. 14 (a) is applied to the capacitive acceleration sensor 20, the movable electrode 24 vibrates with the weight 23 and a displacement occurs in the length L where the fixed electrode 22 and the movable electrode 24 face each other. . The opposing area S of the electrode is S = L × H (H is the height of the electrode), and changes in proportion to the displacement of L. Therefore, this change in S is detected as a change in capacitance. Thus, the acceleration in the displacement direction can be obtained. Known techniques employing such a detection method are disclosed in Patent Documents 3 and 4 and the like.
JP 2001-4658 A JP 2002-365306 A JP 2000-266777 A Japanese Patent Laid-Open No. 9-89927

  The capacitive acceleration sensor 20 in FIG. 14 is configured to detect acceleration in one axial direction based on a change in the facing area of electrodes. When this configuration is applied to a biaxial capacitive acceleration sensor 30 that performs biaxial detection, for example, the configuration is as shown in FIG. The configuration disclosed in Patent Document 4 is similar to this. However, in the case of the configuration shown in FIG. 15A, for example, when the displacement occurs in the X-axis direction as shown in FIG. 15B, the fixed electrode and the movable electrode face each other in the X-axis direction detection unit 31. Not only the displacement of ΔL occurs in the length, but also the movable electrode is integrated, so that a displacement of Δd also occurs in the interval between the fixed electrode and the movable electrode in the Y-axis direction detection unit 32. Therefore, although there is actually no displacement in the Y-axis direction, it is erroneously detected that there is also an acceleration in the Y-axis direction. Similarly, misdetection of the acceleration in the X-axis direction can occur with respect to the displacement in the Y-axis direction.

  Furthermore, such a problem of the occurrence of other-axis sensitivity can also occur in a method of detecting acceleration by a change in the distance between the electrodes, as in the configuration disclosed in Patent Document 2, A countermeasure of separating the sensor and the sensor for the Y-axis direction is also conceivable. However, if the sensor is simply separated, the size of the sensor is doubled. If the sensor is separated and stored in the same size, the space allocated to the detection unit of each axis will be halved. Must be reduced, resulting in a loss of sensitivity.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a biaxial capacitive acceleration sensor having good linearity and capable of suppressing the occurrence of other-axis sensitivity without increasing the size of the sensor, and a biaxial capacitive using the same. The realization of a type accelerometer.

  The biaxial capacitive acceleration sensor of the present invention includes a substrate on which one or more X-axis fixed electrodes and one or more Y-axis fixed electrodes are formed on the same plate surface, in parallel with the substrate. A frame disposed on the outer peripheral edge, and supported by a plurality of beams inside the frame so as to be displaceable in the X-axis direction; displacement in the X-axis direction; and change in area facing the X-axis fixed electrode; An X-axis movable electrode that establishes a predetermined relationship between them, and is supported inside the X-axis movable electrode so as to be displaceable in the Y-axis direction by a plurality of beams, and the displacement in the Y-axis direction and the Y-axis fixed electrode And a structure having a Y-axis movable electrode in which a predetermined relationship is established between the facing area and the change in the facing area.

  A parallel plate capacitor is formed of an X-axis fixed electrode and an X-axis movable electrode, and a Y-axis fixed electrode and a Y-axis movable electrode, respectively. When acceleration in the X-axis direction and the Y-axis direction is applied, the X-axis movable electrode, Y A displacement occurs in each of the shaft movable electrodes. The displacement is detected as a change in capacitance.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the sensitivity of another axis | shaft can be suppressed without enlarging the size of a sensor, and the 2-axis electrostatic capacitance type acceleration sensor with good linearity, and a biaxial electrostatic capacitance type using the same An accelerometer can be realized.

[First Embodiment]
FIG. 1 is an exploded plan view of a configuration example of a biaxial capacitive acceleration sensor 100 of the present invention. The biaxial capacitive acceleration sensor 100 includes a substrate 110 and a structure 120. FIGS. 1A and 1B show the biaxial capacitive acceleration sensor 100 as a substrate 110 and a structure 120, respectively. It has been disassembled. 2A is a perspective view of the biaxial capacitive acceleration sensor 100, FIG. 2B is an exploded perspective view, FIG. 3A is a plan view, and FIGS. 3B and 3C are FIG. It is aa 'sectional drawing of (a), and bb' sectional drawing.

  For example, a glass substrate is used as the substrate 110, and one or more X-axis fixed electrodes 111 and one or more Y-axis fixed electrodes 112 are formed on the plate surface.

  The structure 120 is made of, for example, an SOI wafer, and each part thereof is supported by a frame 121 provided on the outer peripheral edge and a plurality of beams 122 inside the frame so as to be displaceable in the X-axis direction. The X-axis movable electrode 123 in which a predetermined relationship is established between the displacement to the X-axis and the change in the area facing the X-axis fixed electrode, and the X-axis movable electrode 123 inside the Y-axis direction by a plurality of beams 124. And a Y-axis movable electrode 125 in which a predetermined relationship is established between the displacement in the Y-axis direction and the change in the area facing the Y-axis fixed electrode. Thus, the sensor size can be reduced by using a gimbal structure in which the Y-axis movable electrode 125 is included in the X-axis movable electrode 123. The structure 120 faces the substrate 110 in parallel and is joined to the X-axis fixed electrode 111 and the Y-axis fixed electrode 112 so as to form capacitors. If the beam 122 and the beam 124 have the same shape, the X-axis movable electrode 123 includes the Y-axis movable electrode 125, so that the ease of displacement differs, and as a result, the sensitivity is not equal. When it is desired to make the sensitivity to the acceleration in the X-axis direction equal to the sensitivity to the acceleration in the Y-axis direction, the ease of displacement of the X-axis movable electrode 123 due to the acceleration in the X-axis direction and the Y-axis movable due to the acceleration in the Y-axis direction. For example, the length of the beam 124 in the X-axis direction is longer than the length of the beam 122 in the Y-axis direction. In order to suppress the occurrence of sensitivity to acceleration in the Z-axis direction, it is desirable that the beam 122 has a shape that is sufficiently longer in the Z-axis direction than the thickness in the X-axis direction. Specifically, since the difficulty of displacement of the beam is generally proportional to the cube of the thickness of the beam, for example, if the length in the Z-axis direction is 10 times the thickness in the X-axis direction, Can be made 1000 times harder to move than in the X-axis direction. Similarly, the beam 124 can be made difficult to move in the Z-axis direction by sufficiently increasing the length in the Z-axis direction compared to the thickness in the Y-axis direction.

  The entire structure 120 has a ground potential, and the X-axis movable electrode 123 and the Y-axis movable electrode 125, which are constituent parts thereof, constitute a capacitor in a portion facing the X-axis fixed electrode 111 and the Y-axis fixed electrode 112, respectively. . When acceleration in the X-axis direction and the Y-axis direction is applied to the biaxial capacitive acceleration sensor 100, an inertial force is generated by acting on the mass of each movable electrode, and the X-axis movable electrode 123 and the Y-axis movable electrode 125 are respectively Displacement in −X axis direction and −Y axis direction. In the present invention, the capacitance is changed by changing the facing area between the fixed electrode and the movable electrode by this displacement. As an electrode shape forming method for changing the facing area, for example, as shown in FIG. 1, a method of forming a hole 126 in the X-axis movable electrode 123 and a hole 127 in the Y-axis movable electrode 125 at appropriate positions is conceivable. Specifically, in the range where each movable electrode is displaced, as shown in FIG. 3, a part of each hole is formed at a position facing the fixed electrode. When the movable electrode is displaced in such a direction that the portion where the fixed electrode faces the hole becomes large as shown in FIG. 4 (b), by opening the hole at such a position, the facing area between the fixed electrode and the movable electrode When the movable electrode is displaced in a direction in which the portion where the fixed electrode faces the hole becomes smaller as shown in FIG. 4C, the area where the fixed electrode and the movable electrode face each other is increased. Can be made. In addition to making a hole, for example, by changing the outer shape of the movable electrode as shown in FIG. 5, the facing area can be changed on the same principle as when the hole is made.

  In order to obtain the acceleration from the change in capacitance caused by the displacement of each axis movable electrode, the displacement of each axis movable electrode in each axis direction and the change in the area where each axis fixed electrode and each axis movable electrode face each other It is necessary to determine the position and size of the holes so that a predetermined relationship, basically a proportional relationship, is established. For example, as shown in FIG. 1, the X-axis fixed electrode 111 has a rectangular shape with the Y-axis direction as the longitudinal direction, and the X-axis movable electrode 123 has the same number of Y-axis directions as the X-axis fixed electrode 111 as the longitudinal direction. In the range where the X-axis movable electrode 123 is displaced, a part of each of the holes 126 faces the X-axis fixed electrode 111 in a one-to-one relationship and the X-axis movable electrode 123 is displaced. The positions and sizes are determined and opened so that the direction of increase / decrease in the area of the facing portion between the shaft fixing electrode 111 and the hole 126 is the same for all the holes 126. Also, the Y-axis fixed electrode 112 has a rectangular shape whose longitudinal direction is the X-axis direction, and the Y-axis movable electrode 125 has a rectangular hole 127 whose longitudinal direction is the same number of X-axis directions as the Y-axis fixed electrode 112. In a range in which the movable shaft electrode 125 is displaced, a part of each hole 127 faces the Y-axis fixed electrode 112 on a one-to-one basis, and the Y-axis fixed electrode 112 and the hole 127 generated by the displacement of the Y-axis movable electrode 125. The positions and sizes of the holes 127 are determined and opened so that the direction of increase / decrease of the area of the facing portion is the same for all the holes 127. In this way, both the fixed electrode and the hole are rectangular, and within a range in which the movable electrode is displaced, a part of each hole is opposed to each fixed electrode on a one-to-one basis, and the fixed electrode and the hole generated by the displacement of the movable electrode By deciding the position and size of the hole so that the direction of increase / decrease of the area of the opposing part is the same for all the holes, the displacement of the movable electrode and the change of the area where the fixed electrode and the movable electrode face each other Can have a proportional relationship.

  When the fixed electrode and a part of the hole face each other on a one-to-one basis, capacitors corresponding to the number of the fixed electrode and the hole are formed. For example, as shown in FIG. 6A, in the case where there is one fixed electrode and one hole, one capacitor is formed in a portion of L width where the fixed electrode and the movable electrode face each other. When the displacement of ΔL occurs in the movable electrode as shown in FIG. 6B, if the length of the electrode in the longitudinal direction is M, the amount of change in capacitance ΔC due to the displacement is represented by the following equation (1). Asking.

ΔC = ε · S / d = ε · ΔL · M / d (2)
On the other hand, when the fixed electrode and the hole are finely divided, for example, when there are four each as shown in FIG. 6C, the change amount ΔC ′ of the capacitance due to the displacement ΔL can be obtained as follows.

ΔC ′ = ε · 4ΔL · M / d = 4ΔC (3)
As described above, by dividing the fixed electrode and the hole finely to increase the number, the change in the capacitance can be obtained even with the same amount of displacement.

  With the configuration as described above, it is possible to suppress the generation of sensitivity in the Y-axis direction during sensing in the X-axis direction without increasing the size of the sensor, and to provide a highly linear biaxial capacitive acceleration sensor. Can be realized.

[Second Embodiment]
In the configuration of the first embodiment, since the Y-axis movable electrode 125 is inside the X-axis movable electrode 123, the occurrence of sensitivity in the X-axis direction can be suppressed during sensing in the Y-axis direction. When sensing in the axial direction, sensitivity in the Y-axis direction may occur. For example, when the Y-axis fixed electrode 112 and the Y-axis movable electrode 125 have the same length in the longitudinal direction and are opposed to each other as shown in FIG. When displacement occurs in 123, the Y-axis movable electrode 125 integrated inside the X-axis movable electrode 123 via the beam 124 is also displaced as shown in FIG. 7 (a-2). As a result, as shown in FIG. 7A-2, the facing area is increased, and the capacitance between the Y-axis fixed electrode 112 and the Y-axis movable electrode 125 is increased even when no displacement occurs in the Y-axis direction. It will change.

  Therefore, in the configuration of the second embodiment, the length in the longitudinal direction of the Y-axis fixed electrode 112 is made longer than the length in the longitudinal direction of the hole 127 of the Y-axis movable electrode 125 in consideration of the amount of displacement in the X-axis direction. Is. Specifically, since the electrostatic capacitance between the Y-axis fixed electrode 112 and the Y-axis movable electrode 125 should not be changed even if the displacement in the X-axis direction occurs, the X-axis movable electrode 123 is When the length a is movable in both directions, the longitudinal length of the Y-axis fixed electrode 112 is longer on both sides than the longitudinal length of the hole 127 of the Y-axis movable electrode 125 as shown in FIG. The total length is increased by at least 2 × a. With this configuration, as shown in FIG. 7B, the length of the portion that does not reach the hole can be kept constant (2 × a) regardless of whether or not the X-axis movable electrode 123 is displaced. Thus, it is possible to prevent a change in capacitance between the Y-axis fixed electrode 112 and the Y-axis movable electrode 125 due to the displacement in the X-axis direction.

  When the longitudinal length of the hole 127 of the Y-axis movable electrode 125 is longer than the longitudinal length of the Y-axis fixed electrode 112, the displacement of the X-axis movable electrode 123 is longer than the movable length of the X-axis movable electrode 123. Even if this occurs, the area of the opposing portion does not change. Therefore, in such a case, since the electrostatic capacitance between the Y-axis fixed electrode 112 and the Y-axis movable electrode 125 is constant, the longitudinal length of the Y-axis fixed electrode 112 is increased as described above. Is unnecessary.

  As described above, with the configuration of the second embodiment, it is possible to suppress the occurrence of other-axis sensitivity for both the X-axis direction acceleration and the Y-axis direction acceleration.

[Third Embodiment]
In order to establish a proportional relationship between the displacement of each axis movable electrode in each axial direction and the change in the area where each axis fixed electrode and each axis movable electrode face each other, the movable electrode is within the range in which the movable electrode is displaced. When a hole is drilled so that a part of each hole faces the fixed electrode on a one-to-one basis, as shown in FIG. 8 (a), the hole faces the fixed electrode only slightly when no displacement occurs. In this case, for example, when the movable electrode is displaced beyond the left end of the fixed electrode in the drawing, the opposing area changes from increasing to decreasing (or a constant value), and thus the proportional relationship is impaired. Therefore, in order to establish a proportional relationship when a hole is drilled in such a positional relationship, the allowable displacement width becomes small as shown in FIG. 8A, and the acceleration detection range is narrowed. Therefore, in the third embodiment, as shown in FIG. 8 (b), the hole is formed such that the hole faces the fixed electrode by approximately half the length when there is no displacement. By drilling holes in such a positional relationship, the entire width of the fixed electrode can be made the allowable displacement width of the movable electrode as shown in FIG. 8B, so that the acceleration detection range can be increased.

[Fourth Embodiment]
The biaxial capacitive accelerometer 200 can be configured using the biaxial capacitive acceleration sensor 100 described in any one of the first to third embodiments. FIG. 9 is a configuration example of the biaxial capacitive accelerometer 200 of the present invention. The biaxial capacitive accelerometer 200 includes a biaxial capacitive acceleration sensor 100, an X axis signal processing unit 201, and a Y axis signal processing unit 202. The X-axis signal processing unit 201 and the Y-axis signal processing unit 202 are different except that the connected capacitance is an X-axis capacitance or a Y-axis capacitance as shown in FIG. The configuration is exactly the same. Hereinafter, the operation principle of each signal processing unit will be described. Each signal processing unit constitutes a pair of CR delay circuits in which a resistance element is loaded on each axis capacitance and offset capacitance element to be measured. The rectangular wave given to the input terminal is branched into two paths on each axis electrostatic capacity side and offset capacitive element side, and merges again with the EX-OR element. At this time, a phase difference (t3-t1) determined by the time constant of each delay circuit is generated in the two paths, and this phase difference appears as signal waveforms at the end points X1 and X2 in FIG. 9, as shown in FIG. Further, a pulse waveform having a width corresponding to the phase difference between the signals at the input terminals X1 and X2 appears at the terminal Y of the EX-OR element as shown in FIG. That is, the pulse width changes with the change in the difference between the capacitance of each axis and the offset capacitance. The output from the terminal Y is smoothed by a smoothing circuit, and an analog output corresponding to the change in capacitance can be obtained at the output terminal.

[Production method]
An example of a manufacturing method of the biaxial capacitive acceleration sensor of the present invention will be described along the flow shown in FIG.

(1) A pattern of the structure 120 is formed on the device layer of the SOI wafer by ICP etching.
(2) Etching with KOH from the handle layer side.
(3) The sacrificial layer is etched.
(4) A step for the gap between the electrodes is formed on the substrate 110 by HF etching.
(5) An Au film is formed by sputtering, and an electrode pattern is formed in the step by photolithography.
(6) The substrate 110 and the structure 120 are bonded together by anodic bonding.

〔analysis〕
The biaxial capacitive acceleration sensor 100 of the present invention was analyzed based on the following dimensions and the like.

◎ Dimensions External dimensions and electrode configuration are shown in FIG. FIG. 12A shows the outer dimensions, and the electrode configuration is simply shown. Details of the electrode configuration are shown in FIG.
-Number of X-axis fixed electrodes 111 and holes 126 = 344 each
-Number of Y-axis fixed electrodes 112 and holes 127 = 94 each
・ Dimension of X-axis fixed electrode 111 = 0.8 mm × 0.01 mm
The size of the electrode part paired with the X-axis fixed electrode 111 formed by the hole 126 in the X-axis movable electrode 123 = 0.78 mm × 0.01 mm
・ Dimension of Y-axis fixed electrode 112 = 2.88 mm × 0.01 mm
The size of the electrode part paired with the Y-axis fixed electrode 112 formed by the hole 127 in the Y-axis movable electrode 125 = 2.86 mm × 0.01 mm
-Arrangement interval of each axis fixed electrode, and length of each hole in short direction = 0.002 mm
-Thickness of movable electrode (dimension in the Z-axis direction) = 0.15 mm
・ Number of beams 122 and beams = 4 each

◎ Analysis result It was found that the X-axis and Y-axis were equivalent in terms of displacement sensitivity and capacity sensitivity, and good results were obtained.
Electrode area (no displacement): X-axis electrode 1.34 mm ² , Y-axis electrode 1.34 mm ²
Nominal capacity: X-axis electrode 5.94 pF, Y-axis electrode 5.95 pF
Displacement sensitivity: X-axis electrode 1.9 μm / G, Y-axis electrode 1.63 μm / G
Capacitance sensitivity: X-axis electrode 2.26 pF / G, Y-axis electrode 1.94 pF / G

  The present invention is useful when it is desired to detect acceleration in two axes with high accuracy and easy signal processing using a small sensor.

The disassembled top view of the structural example of the biaxial capacitive acceleration sensor of this invention. The perspective view of the structural example of the biaxial capacitive acceleration sensor of this invention, and a disassembled perspective view. Sectional drawing of the structural example of the biaxial capacitive acceleration sensor of this invention. The figure which shows the change of the opposing state of a fixed electrode and a movable electrode. The figure which shows the example of another structure of the biaxial capacitive acceleration sensor of this invention. The figure which shows the improvement effect of the detection sensitivity by increasing the number of electrodes. The figure which shows the effect by the widening of a Y-axis fixed electrode. The figure which shows the effect by making substantially half of a fixed electrode oppose a movable electrode. The block diagram which shows the example of the biaxial electrostatic capacitance type accelerometer of this invention. The figure which shows the content of the logical operation in a signal processing part. The manufacturing flowchart of the biaxial capacitive acceleration sensor of this invention. The block diagram of the biaxial capacitive acceleration sensor which analyzed. The figure which shows the structural example of the conventional electrostatic capacitance type acceleration sensor. The figure which shows another structural example of the conventional electrostatic capacitance type acceleration sensor. The figure which shows the structural example of the biaxial capacitive acceleration sensor by a prior art.

Claims (6)

X axis, Y axis and Z axis are orthogonal to each other,
The normal of the plate surface is the Z-axis direction,
One or more X-axis fixed electrodes;
One or more Y-axis fixed electrodes;
Are formed on the same plate surface, and
Arranged in parallel to the substrate,
A frame provided on the outer periphery;
A predetermined relationship is established between the displacement in the X-axis direction and the change in the area facing the X-axis fixed electrode. An X-axis movable electrode;
A predetermined relationship between the displacement in the Y-axis direction and the change in the area facing the Y-axis fixed electrode is supported inside the X-axis movable electrode so as to be displaceable in the Y-axis direction by a plurality of beams. A Y-axis movable electrode where
A structure having
A biaxial capacitive acceleration sensor. The biaxial capacitive acceleration sensor according to claim 1,
The X-axis fixed electrode is a rectangle whose longitudinal direction is the Y-axis direction,
The Y-axis fixed electrode is a rectangle whose longitudinal direction is the X-axis direction,
The X-axis movable electrode has the same number of rectangular holes as the X-axis fixed electrode, the longitudinal direction of which is the Y-axis direction. Each of the X-axis fixed electrodes face each other in a one-to-one relationship, and the direction of increase / decrease of the facing portions caused by the displacement of the X-axis movable electrode is the same for all holes,
The Y-axis movable electrode has the same number of rectangular holes with the X-axis direction as the longitudinal direction as the Y-axis fixed electrode, and a part of each hole is within the range in which the Y-axis movable electrode is displaced. A biaxial capacitive acceleration characterized by facing each Y-axis fixed electrode on a one-to-one basis and having the same increase / decrease direction for all the holes due to the displacement of the Y-axis movable electrode. Sensor. The biaxial capacitive acceleration sensor according to claim 2,
The biaxial capacitive acceleration characterized in that the length in the longitudinal direction of the Y axis fixed electrode and the length in the longitudinal direction of the hole in the Y axis movable electrode have a difference greater than or equal to the movable length of the X axis movable electrode. Sensor. The biaxial capacitive acceleration sensor according to claim 2 or 3,
The X-axis fixed electrode and the hole of the X-axis movable electrode are substantially half the length in the short direction of the X-axis fixed electrode with no displacement of the X-axis movable electrode. A biaxial capacitive acceleration sensor. A biaxial capacitive acceleration sensor according to any one of claims 2 to 4,
In a state where the Y-axis movable electrode is not displaced, the Y-axis fixed electrode and the hole of the Y-axis movable electrode are substantially half the length in the short direction of the Y-axis fixed electrode. A biaxial capacitive acceleration sensor. A biaxial capacitive acceleration sensor according to any one of claims 1 to 5,
An X-axis signal processing unit for detecting an electrostatic capacitance between the X-axis fixed electrode and the X-axis movable electrode and calculating an acceleration in the X-axis direction;
A Y-axis signal processing unit for detecting an electrostatic capacitance between the Y-axis fixed electrode and the Y-axis movable electrode and calculating an acceleration in the Y-axis direction;
A biaxial capacitive accelerometer.