Physical quantity sensor element and physical quantity sensor device

Abstract

It performs accurate self-diagnosis simultaneously based on acceleration in the X-axis direction and acceleration in the Y-axis direction. [Solution] The device comprises a first fixed comb electrode connected to a first electrode fixing part, having a body extending in a first direction parallel to a support substrate and comb teeth extending in a second direction parallel to the support substrate and perpendicular to the first direction; a second fixed comb electrode connected to a second electrode fixing part, having a body extending in the second direction and comb teeth extending in the first direction; a first movable comb electrode connected to a movable electrode fixing part, facing the first fixed comb electrode; and a second movable comb electrode facing the second fixed comb electrode. During self-diagnosis, a signal identical to the resonant frequency of the first movable comb electrode and the second movable comb electrode is applied between the first movable comb electrode and the first fixed comb electrode, and between the second movable comb electrode and the second fixed comb electrode, respectively.

Description

Technical Field

[0001] The present invention relates to a physical quantity sensor element and a physical quantity sensor device.

Background Art

[0002] Conventionally, sensors for detecting physical quantities along two orthogonal axes have been known. For example, in Patent Document 1, a capacitive physical quantity sensor in which a fixed electrode and a movable electrode face each other in parallel and the distance between the fixed electrode and the movable electrode changes according to a physical quantity, a configuration is disclosed in which two sets of the pair of the fixed electrode and the movable electrode corresponding to two axes are formed to detect physical quantities along the two axes. In Patent Document 1, when performing self-diagnosis with such a sensor, input voltages of different frequencies are applied to each of a first detection unit that detects acceleration in the X-axis direction and a second detection unit that detects acceleration in the Y-axis direction, and a configuration for simultaneously performing self-diagnosis in the first detection unit and the second detection unit is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described conventional technology, in order to apply input voltages of different frequencies to each of a first detection unit that detects acceleration in the X-axis direction and a second detection unit that detects acceleration in the Y-axis direction, there is a possibility that the displacement during self-diagnosis of either one becomes small.

Means for Solving the Problems

[0005] A physical quantity sensor element for solving the above problems includes a first electrode fixing portion, a second electrode fixing portion, and a movable electrode fixing portion extending in a direction perpendicular to the support substrate; a first fixed comb electrode connected to the first electrode fixing portion and comprising a body extending in a first direction parallel to the support substrate and comb teeth extending in a second direction parallel to the support substrate and perpendicular to the first direction; a second fixed comb electrode connected to the second electrode fixing portion and comprising a body extending in the second direction and comb teeth extending in the first direction; and a movable electrode fixing portion The device comprises a first movable comb electrode facing the first fixed comb electrode and a second movable comb electrode facing the second fixed comb electrode, wherein the resonance frequencies of the first and second movable comb electrodes are the same, and during self-diagnosis, a signal is applied between the first movable comb electrode and the first fixed comb electrode, and between the second movable comb electrode and the second fixed comb electrode, respectively, to displace the first and second movable comb electrodes, with a frequency equal to the resonance frequency. [Brief explanation of the drawing]

[0006] [Figure 1] A plan view of the physical quantity sensor device of this embodiment. [Figure 2] A plan view of the XY directional acceleration sensor element of this embodiment. [Figure 3] A schematic diagram illustrating the displacement of a movable body. [Figure 4] Plan view of the movable comb-tooth electrode and the fixed comb-tooth electrode. [Figure 5] Plan view of the movable comb-tooth electrode and the fixed comb-tooth electrode. [Figure 6] A plan view showing the configuration of the movable body. [Figure 7] A diagram illustrating the circuit used to detect acceleration. [Figure 8] This figure shows the signal waveform when switching from normal acceleration detection to self-diagnosis mode. [Figure 9] An enlarged view of the signal waveform during acceleration detection. [Figure 10] A diagram showing the resonant frequency characteristics of the movable electrode. [Figure 11]A diagram showing the relationship between voltage and displacement. [Modes for carrying out the invention]

[0007] The following describes this embodiment. Note that the embodiment described below does not unduly limit the scope of the claims. Furthermore, not all of the configurations described in this embodiment are necessarily essential components.

[0008] (1) Configuration of the physical quantity sensor device: The physical quantity sensor device 100 of this embodiment is housed in a substantially rectangular parallelepiped package. Figure 1 is a plan view showing the physical quantity sensor device 100 as viewed in a direction perpendicular to the largest face of the rectangular parallelepiped. Viewing each part in this direction is called a plan view. The physical quantity sensor device 100 according to this embodiment comprises a plurality of physical quantity sensor elements. Specifically, the physical quantity sensor device 100 comprises a Z-direction acceleration sensor element 101 and an XY-direction acceleration sensor element 1. Each sensor element is a MEMS (Micro Electro Mechanical Systems) device.

[0009] In this specification, mutually orthogonal directions are referred to as the first direction DR1 and the second direction DR2, the opposite direction of the first direction DR1 is referred to as the third direction DR3, and the opposite direction of the second direction DR2 is referred to as the fourth direction DR4. The first direction DR1 and the second direction DR2 are, for example, the X-axis direction and the Y-axis direction, respectively, but are not limited to these. For example, the first direction DR1 corresponding to the X-axis direction and the second direction DR2 corresponding to the Y-axis direction are directions parallel to the largest face of the rectangular parallelepiped formed by the physical quantity sensor device 100. In cases where there is no particular need to distinguish the opposite direction, for example, the third direction DR3 can be considered as a direction along the first direction DR1. Furthermore, "orthogonal" includes not only intersections at 90° but also intersections at angles slightly tilted from 90°.

[0010] Figure 1 also shows the multiple pads provided by the physical quantity sensor device 100. Pad Pgnd is a pad electrically connected to the ground. Pad Pxy is a pad electrically connected to the movable comb-tooth electrode, which will be described later, provided by the XY direction acceleration sensor element 1, and is set to a common potential in the XY direction. Pad Py1 is a pad electrically connected to the fixed comb-tooth electrode, which will be described later, provided by the XY direction acceleration sensor element 1, and is set to a potential for detecting acceleration in the Y direction. Pad Py2 is a pad electrically connected to the fixed comb-tooth electrode, which will be described later, provided by the XY direction acceleration sensor element 1, and is set to a potential opposite in phase to pad Py1 in order to detect acceleration in the Y direction.

[0011] Pad Px1 is a pad electrically connected to the fixed comb-tooth electrode of the XY direction acceleration sensor element 1 (described later), and is set to a potential for detecting acceleration in the X direction. Pad Px2 is a pad electrically connected to the fixed comb-tooth electrode of the XY direction acceleration sensor element 1 (described later), and is set to a potential with the opposite phase to pad Px1 in order to detect acceleration in the X direction.

[0012] Pad Pz is electrically connected to a first movable comb electrode and a second movable comb electrode (not shown) provided by the Z-direction acceleration sensor element 101. Pad Pz1 is electrically connected to a first fixed comb electrode (not shown) provided by the Z-direction acceleration sensor element 101 and is set to a potential for detecting acceleration in the Z direction. Pad Pz2 is electrically connected to a second fixed comb electrode (not shown) provided by the Z-direction acceleration sensor element 101 and is set to a potential opposite to that of pad Pz1 in order to detect acceleration in the Z direction.

[0013] Figure 2 schematically shows an example of the XY directional acceleration sensor element 1 of this embodiment in a plan view. In the XY directional acceleration sensor element 1 of Figure 2, a frame-shaped movable body MB is connected to the support substrate 10. In the plan view of Figure 2, the movable body MB is shown forming a single closed loop, but it may be partially open. Other configurations connected to the support substrate 10 or the movable body MB will be described later in Figures 4, 5, and 6. More specifically, the configuration shown in the dotted line frame A1 of Figure 2 corresponds to the configuration shown in A11 of Figure 4, which will be described later; the configuration shown in the dotted line frame A2 of Figure 2 corresponds to the configuration shown in A12 of Figure 4, which will be described later; the configuration shown in the dotted line frame B1 of Figure 2 corresponds to the configuration shown in B11 of Figure 6, which will be described later; the configuration shown in the dotted line frame A3 of Figure 2 corresponds to the configuration shown in A13 of Figure 5, which will be described later; and the configuration shown in the dotted line frame A4 of Figure 2 corresponds to the configuration shown in A14 of Figure 5, which will be described later. Furthermore, the configuration shown in the dotted box B2 in Figure 2 is the same as the configuration in B1 in Figure 2, but reversed symmetrically with respect to a line parallel to the second direction DR2. Also, the configuration shown in the dotted box B3 in Figure 2 is the same as the configuration in B2 in Figure 2, but reversed symmetrically vertically with respect to a line parallel to the first direction DR1. Furthermore, the configuration shown in the dotted box B4 in Figure 2 is the same as the configuration in B1 in Figure 2, but reversed symmetrically vertically with respect to a line parallel to the first direction DR1.

[0014] Furthermore, in implementing the method of this embodiment, not all of the configurations shown in Figure 2 are essential, and some may be omitted. Specifically, for example, the configurations shown in A3, A4, B2, B3, and B4 in Figure 2 may be omitted or modified as appropriate.

[0015] The support substrate 10 is, for example, a silicon substrate made of semiconductor silicon or a glass substrate made of a glass material such as borosilicate glass. However, the constituent material of the support substrate 10 is not particularly limited, and a quartz substrate or an SOI (Silicon On Insulator) substrate may be used. Note that the shape of the support substrate 10 may be various shapes. For example, a cavity may be formed in a direction perpendicular to the first direction DR1 and the second direction DR2. The predetermined region AR is a region where the first electrode fixing portion, the second electrode fixing portion, the movable electrode fixing portion, etc. are concentrated and connected to the support substrate 10, and can also be called a fixing portion connection region.

[0016] The XY-direction acceleration sensor element 1 of the present embodiment is, for example, an inertial sensor as a MEMS (Micro Electro Mechanical Systems) device, and detects physical quantities in the first direction DR1 and the second direction DR2. That is, the XY-direction acceleration sensor element 1 detects physical quantities by the operation mode shown in M10 of FIG. 3. M10 is an operation mode in which each component included in the movable body MB and the movable body MB operates along the direction shown in M11 or the direction shown in M12. The direction shown in M11 coincides with the direction along the first direction DR1, and the direction shown in M12 coincides with the direction along the second direction DR2. Thereby, physical quantities in the first direction DR1 and the second direction DR2 are detected by the method described later. Strictly speaking, the XY-direction acceleration sensor element 1 may also generate an operation mode shown in M20 of FIG. 3, for example. The operation mode shown in M20 is an operation mode corresponding to an operation in which the movable body MB rotates as the axis shown in M21 with respect to the plane including the support substrate 10, and can also be called an in-plane rotation mode. However, the XY-direction acceleration sensor element 1 of the present embodiment is configured such that the operation based on the operation mode shown in M20 is small enough to be ignored with respect to the operation of the operation mode shown in M10.

[0017] Hereinafter, mainly taking the case where the physical quantity detected by the XY-direction acceleration sensor element 1 is acceleration as an example for explanation, the physical quantity is not limited to acceleration, and may be other physical quantities such as velocity, pressure, displacement, posture, angular velocity, or gravity. The XY-direction acceleration sensor element 1 may also be used as a pressure sensor or a MEMS switch, etc. Also, in any of the figures of the present embodiment, the dimensions of each member, the intervals between members, etc. are schematic illustrations for the convenience of explanation and do not indicate actual dimensions, intervals, etc. Further, the XY-direction acceleration sensor element 1 of the present embodiment is illustrated with some components such as electrodes and wirings appropriately omitted.

[0018] As shown in A11 of FIG. 4, the XY-direction acceleration sensor element 1 of the present embodiment includes a first fixed comb electrode 110 and a first movable comb electrode 210. The first movable comb electrode 210 includes a first connecting portion 410. The first connecting portion 410 is configured as a part of the movable body MB and extends along the second direction DR2.

[0019] The first fixed comb electrode 110 is fixed to the support substrate 10 and is connected to a first electrode fixing portion 111 that extends in a direction perpendicular to the support substrate 10. The first fixed comb electrode 110 includes a main body 113 that is connected to the first electrode fixing portion 111 and extends in the first direction DR1, and a plurality of comb teeth 115. Also, the comb teeth 115 of the first fixed comb electrode 110 are portions that extend from the main body 113 in the second direction DR2 (including the fourth direction DR4). In the present embodiment, the length of the comb teeth 115 extending in the second direction DR2 and the length of the comb teeth 115 extending in the fourth direction DR4 are the same. Here, "the lengths are the same" includes not only the case where the actual lengths are the same, but also the case where they can be regarded as the same considering manufacturing errors. That is, the first fixed comb electrode 110 is line-symmetric with respect to the line segment LS113 in FIG. 4. The line segment LS113 is a line segment passing through the first electrode fixing portion 111 and along the first direction DR1. Such a first fixed comb electrode 110 is fixed to the support substrate 10 via the first electrode fixing portion 111 and serves as a probe electrode.

[0020] Note that the first electrode fixing portion 111 shown in A11 of Figure 4 merely conceptually indicates that the main body 113 is fixed to the support substrate 10, and does not specify the concrete structure of the first electrode fixing portion 111. The same applies to the second electrode fixing portion 121 and the like, which will be described later.

[0021] The first movable comb electrode 210 has a plurality of comb teeth 215. The comb teeth 215 extend in the second direction DR2 (including the fourth direction DR4) and face the comb teeth 115. In this embodiment, as shown in A11 of Figure 4, the comb teeth 215 on the second direction DR2 side and the comb teeth 215 on the fourth direction DR4 side are configured to be symmetrical with respect to the line segment LS113. Although not strictly illustrated, by providing a movable electrode on the side surface of the comb teeth 215 and a fixed electrode on the side surface of the comb teeth 115, it can function as a probe electrode. The first movable comb electrode 210 plays the role of a probe electrode that can move together with the movable body MB.

[0022] It can be considered that a set of physical quantity detection units is formed by this combination of the first fixed comb electrode 110 and the first movable comb electrode 210. Hereafter, the physical quantity detection unit will be simply referred to as the detection unit. In other words, Figure 2 can be considered to include the detection unit shown in the dotted line frame A1, the detection unit shown in the dotted line frame A2, the detection unit in the dotted line frame A3, and the detection unit shown in the dotted line frame A4. The number of comb teeth 115 and comb teeth 215 is not limited to the numbers shown in Figures 2 and 4, but it is assumed that in a plan view of the support substrate 10, comb teeth 115 are arranged on both sides of the comb teeth 215. This allows the operation of the movable body MB to be stabilized.

[0023] An example of operation by a detection unit consisting of a combination of a first fixed comb electrode 110 and a first movable comb electrode 210, as shown in A11 of Figure 4, will be explained. For example, when acceleration occurs in the direction along the X-axis, which is the first direction DR1, the comb teeth 215 are displaced along the X-axis, and the distance between the comb teeth 215 and the comb teeth 115 in the direction along the X-axis changes, which in turn changes the capacitance. In other words, the detection unit consisting of a combination of a first fixed comb electrode 110 and a first movable comb electrode 210, as shown in A11 of Figure 4, is a detection unit that can detect acceleration in the direction along the X-axis.

[0024] On the other hand, if acceleration occurs in the direction along the second direction DR2, for example, the area of ​​contact between the comb teeth 115 and 215 extending from the main body 113 toward the second direction DR2 increases, but the area of ​​contact between the comb teeth 115 and 215 extending from the main body 113 toward the fourth direction DR4 decreases. Similarly, if acceleration occurs in the direction along the fourth direction DR4, the area of ​​contact between the comb teeth 115 and 215 extending from the main body 113 toward the second direction DR2 decreases, but the area of ​​contact between the comb teeth 115 and 215 extending from the main body 113 toward the fourth direction DR4 increases. In other words, whether acceleration occurs in the direction along the second direction DR2 or the direction along the fourth direction DR4, the area of ​​contact between the comb teeth 115 and 215 remains generally unchanged. In other words, the detection unit consisting of the combination of the first fixed comb electrode 110 and the first movable comb electrode 210 shown in A11 of Figure 4 is configured so as not to detect acceleration in the direction along the Y axis.

[0025] Thus, by having the comb teeth 115 extend from the main body 113 in the second direction DR2 and the fourth direction DR4, a detection unit is constructed that detects acceleration along the X-axis direction but does not detect acceleration along the Y-axis direction. In other words, the detection unit consisting of the combination of the first fixed comb tooth electrode 110 and the first movable comb tooth electrode 210 shown in A11 of Figure 4 can be said to have suppressed sensitivity in other axes.

[0026] Furthermore, as shown in A12 of Figure 4, the XY directional acceleration sensor element 1 of this embodiment includes a second fixed comb electrode 120 and a second movable comb electrode 220. The second movable comb electrode 220 includes a second connecting portion 420. The second connecting portion 420 is configured as part of a movable body MB and extends along the first direction DR1.

[0027] The second fixed comb electrode 120 is fixed to the support substrate 10 and connected to a second electrode fixing portion 121 that extends perpendicular to the support substrate 10. The second fixed comb electrode 120 is connected to the second electrode fixing portion 121 and includes a body 123 that extends in the second direction DR2 and a plurality of comb teeth 125. The comb teeth 125 of the second fixed comb electrode 120 are the portion that extends from the body 123 in the first direction DR1 (including the third direction DR3). In this embodiment, the length of the comb teeth 125 extending in the first direction DR1 is the same as the length of the comb teeth 125 extending in the third direction DR3. The second fixed comb electrode 120 is symmetric with respect to the line segment LS123 in Figure 4. The line segment LS123 is a line segment that passes through the second electrode fixing portion 121 and lies along the second direction DR2. Such a second fixed comb-tooth electrode 120 is fixed to the support substrate 10 via the second electrode fixing part 121 and serves as a probe electrode.

[0028] The second movable comb electrode 220 has a plurality of comb teeth 225. The comb teeth 225 extend in the first direction DR1 (including the third direction DR3) and face the comb teeth 125. In this embodiment, as shown in A12 of Figure 4, the comb teeth 225 on the first direction DR1 side and the comb teeth 225 on the third direction DR3 side are configured to be symmetrical with respect to the line segment LS123. The second movable comb electrode 220 plays the role of a probe electrode that can move together with the movable body MB.

[0029] As is clear from Figure 4, the detection unit consisting of the second fixed comb electrode 120 and the second movable comb electrode 220 shown in A12 of Figure 4 can be considered identical to the detection unit consisting of the first fixed comb electrode 110 and the first movable comb electrode 210 shown in A11, rotated 90° counterclockwise. Therefore, although some detailed explanations will be omitted, the detection unit consisting of the second fixed comb electrode 120 and the second movable comb electrode 220 shown in A12 of Figure 4 is a detection unit capable of detecting acceleration in the direction along the Y axis, and its sensitivity to other axes is suppressed.

[0030] The configuration shown in the dotted line frame at A3 in Figure 2 corresponds to the configuration shown at A13 in Figure 5, which will be described later. The configuration shown at A13 in Figure 5 is the configuration shown at A11 in Figure 4, reversed symmetrically with respect to a line parallel to the second direction DR2. That is, the first fixed comb electrode 130 is fixed to the support substrate 10 and connected to the first electrode fixing part 131 which extends in a direction perpendicular to the support substrate. The first fixed comb electrode 130 includes a main body 133 which is connected to the first electrode fixing part 131 and extends in the third direction DR3, and a plurality of comb teeth 135. The comb teeth 135 of the first fixed comb electrode 130 are the parts that extend from the main body 133 in the second direction DR2 (including the fourth direction DR4). The first movable comb electrode 230 includes a third connecting part 430. The third connecting part 430 is configured as part of the movable body MB and extends along the second direction DR2. The first movable comb electrode 230 has a plurality of comb teeth 235. The comb teeth 235 extend in the second direction DR2 (including the fourth direction DR4) and face the comb teeth 135.

[0031] The configuration shown in the dotted line frame at A4 in Figure 2 corresponds to the configuration shown at A14 in Figure 5, which will be described later. The configuration shown at A14 in Figure 5 is the configuration shown at A11 in Figure 4, reversed symmetrically with respect to a line parallel to the first direction DR1. That is, the second fixed comb electrode 140 is fixed to the support substrate 10 and connected to the second electrode fixing part 141 which extends in a direction perpendicular to the support substrate 10. The second fixed comb electrode 140 includes a main body 143 which is connected to the second electrode fixing part 141 and extends in the fourth direction DR4, and a plurality of comb teeth 145. The comb teeth 145 of the second fixed comb electrode 140 are the parts that extend from the main body 143 in the first direction DR1 (including the third direction DR3). The second movable comb electrode 240 includes a fourth connecting part 440. The fourth connecting part 440 is configured as part of the movable body MB and extends along the first direction DR1. The second movable comb electrode 240 has a plurality of comb teeth 245. The comb teeth 245 extend in the first direction DR1 (including the third direction DR3) and face the comb teeth 145.

[0032] On the other hand, as shown in B11 of Figure 6, the XY directional acceleration sensor element 1 of this embodiment further includes a movable electrode fixing portion 311, a first movable electrode support portion 313, and a first spring 317. The movable electrode fixing portion 311 is fixed to the support substrate 10 and is a portion that extends in a direction perpendicular to the support substrate 10.

[0033] Furthermore, the XY directional acceleration sensor element 1 shown in Figure 2 has a movable electrode fixing part with a similar configuration in addition to the movable electrode fixing part 311. These can be collectively referred to as the movable electrode fixing part 301. Therefore, B11 in Figure 6 can be appropriately interpreted as the XY directional acceleration sensor element 1 of this embodiment further including the movable electrode fixing part 301, the first movable electrode support part 313, and the first spring 317. Also, as will be described later, in the example shown in Figure 2, the XY directional acceleration sensor element 1 includes four movable electrode fixing parts 301, but the number of movable electrode fixing parts 301 is not limited to four, and various modifications can be implemented.

[0034] The first spring 317 is in the shape of a thin wire in a plan view of the support substrate 10, and one end of it is connected to the first movable electrode support portion 313. The location to which the other end of the first spring 317 is connected is not particularly limited as long as it can support the first connecting portion 410 and the second connecting portion 420, but it may be connected to the corner of the movable body MB shown at B111 in Figure 6, for example. The corner shown at B111 can also be considered as the point where the first connecting portion 410 and the second connecting portion 420 intersect. Due to the bellows-like shape of the thin wire, the first spring 317 has the properties of a folded spring and can be distorted and deformed in the XY plane.

[0035] The first movable electrode support portion 313 extends from the movable electrode fixing portion 301 (movable electrode fixing portion 311) in the first intersecting direction DR11 and is connected to one side of the first spring 317. As shown in Figure 6, the first intersecting direction DR11 is the direction that intersects the first direction DR1 and the second direction DR2. In other words, the first intersecting direction DR11 is not parallel to the X-axis (first direction DR1, third direction DR3), nor is it parallel to the Y-axis (second direction DR2, fourth direction DR4). Alternatively, it can be said that the first intersecting direction DR11 is inclined with respect to the X-axis and also inclined with respect to the Y-axis.

[0036] In this way, the movable electrode fixing part 301 (movable electrode fixing part 311), the first movable electrode support part 313, the first spring 317, the corner of the movable body MB shown in B111, the first connecting part 410, and the first movable comb electrode 210 are connected in order. Similarly, the movable electrode fixing part 301 (movable electrode fixing part 311), the first movable electrode support part 313, the first spring 317, the corner of the movable body MB shown in B111, the second connecting part 420, and the second movable comb electrode 220 are connected in order. Since the first connecting part 410 and the second connecting part 420 are connected to the first movable comb electrode 210 and the second movable comb electrode 220, it can be said that the first movable comb electrode 210 and the second movable comb electrode 220 are supported by the support substrate 10.

[0037] Furthermore, for ease of understanding, the first spring 317 is highlighted in Figure 6, but the first spring 317 may be made smaller. More specifically, for example, the length L313 of the first movable electrode support 313 may be longer than the length of the first spring 317. The length of the first spring 317 is the length based on the longest point of the intersection when the area occupied by the first spring 317 in the XY plane intersects with a straight line in a direction parallel to the first intersecting direction DR11. In this way, the first spring 317 can be positioned further outward. This allows the length L313 of the first movable electrode support 313 to be made as long as possible. This reduces the moment of inertia based on the first movable electrode support 313, thereby suppressing the operation of the movable body MB in in-plane rotation mode (operation mode of M20 in Figure 2).

[0038] Furthermore, for example, a certain relationship may be established between the length L313 of the first movable electrode support 313, the length L113 of the main body 113, and the length L123 of the main body 123. Specifically, for example, the main body 113, the main body 123, and the first movable electrode support 313 may be configured such that the relationship "length L313 > length L113, and length L313 > length L123" is met. By doing so, an XY direction acceleration sensor element 1 can be constructed that clearly defines the standard for the length of the first movable electrode support 313 necessary to suppress operation due to the in-plane rotation mode. This makes it possible to suppress operation due to the in-plane rotation mode when deformation occurs in the first spring 317.

[0039] Furthermore, as shown in Figure 6, by aligning the first intersecting direction DR11 with the direction from the movable electrode fixing part 301 (movable electrode fixing part 311) toward the corner shown in B111, a relationship can be established in which the first spring 317 is positioned further outward. This allows the length L313 of the first movable electrode support part 313 to be maximized. As a result, the moment of inertia based on the first movable electrode support part 313 can be reduced, thereby suppressing the operation of the movable body MB in in-plane rotation mode (operation mode of M20 in Figure 2).

[0040] In the above configuration, capacitance is formed by the opposition between the first fixed comb electrode 110 and the first movable comb electrode 210, and between the opposition between the second fixed comb electrode 120 and the second movable comb electrode 220. Specifically, in the first fixed comb electrode 110, the first movable comb electrode 210, the second fixed comb electrode 120, and the second movable comb electrode 220, specific faces of the opposing comb teeth function as electrodes. For example, assume that an electrode is formed on the face of the comb tooth 115 of the first fixed comb electrode 110 on the side facing the third direction DR3, and an electrode is formed on the face of the comb tooth 215 of the first movable comb electrode 210 on the side facing the first direction DR1. In this case, an electrode is formed on the face of the comb tooth 135 of the first fixed comb electrode 130 on the side facing the first direction DR1, and an electrode is formed on the face of the comb tooth 235 of the first movable comb electrode 230 on the side facing the third direction DR3. In this case, as the acceleration along the first direction DR1 increases, the distance between the electrodes of comb teeth 115 and 215 increases, while the distance between the electrodes of comb teeth 135 and 235 decreases, causing a change in capacitance.

[0041] Furthermore, it is assumed that electrodes are formed on the surface of the comb teeth 125 of the second fixed comb electrode 120 facing the fourth direction DR4, and electrodes are formed on the surface of the comb teeth 225 of the second movable comb electrode 220 facing the second direction DR2. In this case, electrodes are formed on the surface of the comb teeth 145 of the second fixed comb electrode 140 facing the second direction DR2, and electrodes are formed on the surface of the comb teeth 245 of the second movable comb electrode 240 facing the fourth direction DR4. In this case, as the acceleration along the second direction DR2 increases, the distance between the electrodes of comb teeth 125 and 225 increases, and the distance between the electrodes of comb teeth 145 and 245 decreases, causing a change in capacitance. The XY direction acceleration sensor element 1 detects changes in acceleration along the first direction DR1 and the second direction DR2 based on the above-described change in capacitance.

[0042] The Z-direction acceleration sensor element 101 is an element that detects acceleration in the Z direction, which is perpendicular to the first direction DR1 and the second direction DR2. The Z-direction acceleration sensor element 101 only needs to be able to detect acceleration in the Z direction, and various known configurations can be adopted.

[0043] (2) Detection circuit: Next, a circuit for detecting changes in acceleration along the first direction DR1 and the second direction DR2 using the above configuration will be described. Note that the Z-direction acceleration sensor element 101 can detect acceleration in the Z direction using a circuit similar to the acceleration detection circuit using the XY-direction acceleration sensor element 1. Here, a circuit for detecting changes in acceleration along the first direction DR1 and the second direction DR2 using the XY-direction acceleration sensor element 1 will be described. The XY-direction acceleration sensor element 1 is used in connection with a control IC (not shown). The control IC includes a circuit for detecting acceleration based on the signal output from the XY-direction acceleration sensor element 1. Figure 7 is a diagram illustrating this circuit. In Figure 7, the XY-direction acceleration sensor element 1 is shown along with the elements and wiring that constitute the circuit.

[0044] However, in Figure 7, the details of the structure of the XY direction acceleration sensor element 1 are omitted, and the comb teeth 215, 235, 225, 245 that serve as movable electrodes and the comb teeth 115, 135, 125, 145 that serve as fixed electrodes are schematically shown.

[0045] The comb teeth 215, 235 and 115, 135 constitute a parallel plate capacitor oriented perpendicular to the first direction DR1. The comb teeth 215, 235 are electrodes that move in the first direction DR1 in response to acceleration in the X direction, which is the first direction DR1. The positions of the comb teeth 115, 135 do not change. When the comb teeth 215, 235 are displaced in the first direction DR1 in response to acceleration in the X direction, which is the first direction DR1, the capacitance formed by the comb teeth 215 and 115, and the capacitance formed by the comb teeth 235 and 135, change.

[0046] The comb teeth 225, 245 and 125, 145 constitute a parallel plate capacitor oriented perpendicular to the second direction DR2. The comb teeth 225, 245 are electrodes that move in the second direction DR2 in response to acceleration in the Y direction, which is the second direction DR2. The positions of the comb teeth 125, 145 do not change. When the comb teeth 225, 245 are displaced in the second direction DR2 in response to acceleration in the Y direction, which is the second direction DR2, the capacitance formed by the comb teeth 225 and 125, and the capacitance formed by the comb teeth 245 and 145, change.

[0047] Furthermore, as shown in Figure 1, the XY directional acceleration sensor element 1 is equipped with multiple pads, and Figure 7 shows the connection relationships between pads Pxy, Px1, Px2, Py1, Py2 and circuit components, as well as the connection relationships between comb teeth 215, 235, 225, 245 and comb teeth 115, 135, 125, 145.

[0048] Here, the configuration for detecting acceleration in the X direction, which is the first direction DR1, is referred to as the first detection unit, and the configuration for detecting acceleration in the Y direction, which is the second direction DR2, is referred to as the second detection unit. The first detection unit has a detection circuit 20 that detects acceleration based on the change in differential capacitance due to comb teeth 215, 235 and comb teeth 115, 135. The second detection unit has a detection circuit 30 that detects acceleration based on the change in differential capacitance due to comb teeth 225, 245 and comb teeth 125, 145.

[0049] The detection circuits 20 and 30 are equipped with CV conversion circuits 21 and 31, switch circuits 22 and 32, signal processing circuits 23 and 33, and a control signal generation circuit 60.

[0050] The CV conversion circuits 21 and 31 are circuits that convert the change in differential capacitance formed by comb teeth 215-245 and comb teeth 115-145 into a voltage. Specifically, the CV conversion circuits 21 and 31 include operational amplifiers 21a and 31a, capacitors 21b and 31b, and switches 21c and 31c.

[0051] The inverting input terminals of the operational amplifiers 21a and 31a are electrically connected to the comb teeth 215 and 235, 225 and 245, respectively. Capacitors 21b and 31b and switches 21c and 31c are connected in parallel between the inverting input terminals and the output terminals. Switch 21c is driven by signal S1X from the control signal generation circuit 60, and switch 31c is driven by signal S1Y from the control signal generation circuit 60. The non-inverting input terminals of the operational amplifiers 21a and 31a are input via switch circuits 22 and 32 to either a voltage V1 which is half the voltage applied to the comb teeth 115 to 145 (i.e., the midpoint voltage, 2.5V in this embodiment) or a voltage V2 which is different from this midpoint voltage (4V in this embodiment).

[0052] Switch circuits 22 and 32 input voltages from respective voltage sources (not shown) to the non-inverting input terminals of the operational amplifiers 21a and 31a in the CV conversion circuits 21 and 31. Specifically, switch circuit 22 includes switches 22a and 22b, and switch circuit 32 includes switches 32a and 32b. Of these, switches 22a and 22b are driven based on the signal S2X from the control signal generation circuit 60, and switches 32a and 32b are driven based on the signal S2Y from the control signal generation circuit 60, so that when one is closed, the other is open.

[0053] The signal processing circuits 23 and 33 each include LPF (low-pass filter) circuits 23a and 33a and GAIN circuits 23b and 33b. The LPF circuits 23a and 33a remove high-frequency components from the output of the CV conversion circuits 21 and 31, extracting only components within a predetermined frequency band. The GAIN circuits 23b and 33b amplify the output after it has passed through the LPF circuits 23a and 33a and output it as acceleration signals GoutX and GoutY.

[0054] The control signal generation circuit 60 outputs signals (carrier waves) P1X, P2X, P1Y, P2Y indicating the timing of voltage application to the comb teeth 115 to 145, signals S2X, S2Y indicating the switching timing of the switches in the switch circuits 22 and 32, and signals S1X, S1Y indicating the switching timing of switches 21c and 31c.

[0055] The various signals generated by this control signal generation circuit 60 change between normal acceleration detection (when not self-diagnostic) and self-diagnostic. Specifically, the control signal generation circuit 60 outputs various signals based on the clock signal CLK, but outputs an acceleration detection signal when the self-diagnostic command signal is at a low level, and outputs a self-diagnostic signal when the self-diagnostic command signal is at a high level.

[0056] The self-diagnosis process involves inputting a self-diagnosis signal to the XY directional acceleration sensor element 1. If the obtained output falls within a predetermined range, it is considered normal; if it falls outside this range, it is considered abnormal. In other words, if the obtained output falls outside the predetermined range, it can be assumed that an abnormality, such as damage to the comb teeth of the XY directional acceleration sensor element 1, has occurred.

[0057] The operation of the acceleration sensor configured in this way will be explained with reference to the signal waveform diagrams shown in Figures 8 and 9. Figure 8 shows the signal waveform when switching from normal acceleration detection to self-diagnosis, and Figure 9 is an enlarged view of the signal waveform during acceleration detection.

[0058] First, as shown in Figure 8, during normal acceleration detection, the self-diagnosis command signal is set to a low level, and acceleration detection is performed. The operation at this time will be explained based on Figure 9. Although not shown in Figure 9, during normal acceleration detection, based on signals S2X and S2Y, switches 22a and 32a are opened and switches 22b and 32b are closed, and a midpoint voltage V1 (2.5V in this embodiment) is applied to the non-inverting input terminals of the operational amplifiers 21a and 31a, and the comb teeth 215 to 245 are set to the midpoint voltage V1.

[0059] The signals P1X, P2X and P1Y, P2Y output from the control signal generation circuit 60 are signals with amplitudes V (5V in this embodiment) whose voltage levels are inverted relative to each other, and are constant amplitude rectangular wave signals whose Hi level and Low level change over four periods t1 to t4. Note that the voltage V is not limited to 5V. For example, the voltage V may be 3V, the midpoint voltage V1 may be 1.5V, etc. Of course, in this case, the voltage V2 will also change and will be a value between 3V and 1.5V.

[0060] First, during the first period t1, based on signals P1X, P2X and P1Y, P2Y, the potentials of comb teeth 115 and 125 are set to V, and the potentials of comb teeth 135 and 145 are set to 0. At the same time, the signals S1X and S1Y from the control signal generation circuit 60 close switches 21c and 31c. As a result, the operational amplifiers 21a and 31a bias the comb teeth 215 to 245 to a potential of V / 2, and the charge stored between the electrodes of the feedback capacitors 21b and 31b is discharged.

[0061] In this case, if the capacitance C1 between comb teeth 215, 225 and comb teeth 115, 125 and the capacitance C2 between comb teeth 235, 245 and comb teeth 135, 145 satisfy the relationship C1 > C2, then, based on this relationship and the relationship between the potential applied to comb teeth 115~145, comb teeth 215~245 will have a predominantly negative charge.

[0062] Next, during the second period t2, based on signals P1X, P2X and P1Y, P2Y, the potentials of comb teeth 115 and 125 are kept at V, and the potentials of comb teeth 135 and 145 remain at 0. At the same time, switches 21c and 31c are opened by signals S1X and S1Y from the control signal generation circuit 60. As a result, charges corresponding to the state of comb teeth 215 to 245 are stored in capacitors 21b and 31b. When voltage values ​​corresponding to the charges stored in capacitors 21b and 31b are output from CV conversion circuits 21 and 31, the outputs GoutX and GoutY at this time are sampled via LPF circuit 23a and GAIN circuit 23b.

[0063] Next, during the third period t3, the potentials of the comb teeth 115 and 125 are swapped based on signals P1X, P2X and P1Y, P2Y, so that the potential of the comb teeth 135 and 145 becomes 0 and the potential of the comb teeth 135 and 145 becomes V. At the same time, switches 21c and 31c are kept open by signals S1X and S1Y from the control signal generation circuit 60.

[0064] At this time, the charge state of the comb teeth 215-245 is reversed from that of the second period t2 due to the reversal of signals P1X, P2X and P1Y, P2Y. That is, if the relationship C1 > C2 is satisfied as described above, the reversal of the applied potential to the comb teeth 115-145 results in a state where the comb teeth 215-245 have a large positive charge.

[0065] However, at this time, a closed circuit is formed between the comb teeth 215-245 and capacitors 21b and 31b, and the amount of charge in the first period t1 is conserved. Therefore, the charge that overflows from the balance of charge in the comb teeth 215-245 moves to and is stored in capacitors 21b and 31b. Then, from the relationship Q=CV, a voltage value proportional to the amount of charge that has moved and inversely proportional to the capacitance C of capacitors 21b and 31b is output from the CV conversion circuits 21 and 31.

[0066] Furthermore, during the fourth period t4, the potentials of comb teeth 115 and 125 are kept at 0 and the potentials of comb teeth 135 and 145 are kept at V based on the signals P1X, P2X and P1Y, P2Y, and once the outputs of the CV conversion circuits 21 and 31 are sufficiently stable, the values ​​at this time are output to GoutX and GoutY via the LPF circuits 23a and 33a and the GAIN circuits 23b and 33b.

[0067] Finally, the outputs GoutX and GoutY sampled in the second period t2 and the outputs GoutX and GoutY sampled in the fourth period t4 are differentially calculated. Based on this, acceleration detection is performed according to the displacement of the comb teeth 215 to 245.

[0068] Next, the operation during self-diagnosis will be explained based on Figure 8. During self-diagnosis, the self-diagnosis command signal input to the control signal generation circuit 60 is set to a Hi level, and various signals for self-diagnosis are output from the control signal generation circuit 60. In this embodiment, self-diagnosis in the first detection unit and self-diagnosis in the second detection unit are performed simultaneously.

[0069] During self-diagnosis, a potential difference is formed between the comb teeth 115, 125 and 135, 145 based on signals P1X, P2X and P1Y, P2Y. For the first detection unit, based on signal S2X, switch 22a of the switch circuit 22 is closed and switch 22b is opened. Therefore, a voltage V2 (4V in this embodiment), different from the midpoint voltage V1 of the comb teeth 115, 135, is applied to the non-inverting input terminal of the operational amplifier 21a for self-diagnosis.

[0070] As a result, the potential difference between comb teeth 235 and 135 (4V) becomes greater than the potential difference between comb teeth 215 and 115 (1V), increasing the electrostatic force. This electrostatic force forces comb teeth 215 and 235 to move away from their center point. Subsequently, at time T1, the switch circuit 22 switches based on the signal S2X, and the midpoint voltage V1 of comb teeth 115 and 135 is applied to the non-inverting input terminal of the operational amplifier 21a, just as in normal acceleration detection.

[0071] Regarding the second detection unit, based on the signal S2Y, switch 32a of the switch circuit 32 is closed and switch 32b is opened. For this reason, a voltage V2 (4V in this embodiment), which is different from the midpoint voltage V1 of the comb teeth 125 and 145, is applied to the non-inverting input terminal of the operational amplifier 31a for self-diagnosis.

[0072] As a result, the potential difference between comb teeth 245 and 145 (4V) becomes greater than the potential difference between comb teeth 225 and 125 (1V), increasing the electrostatic force. This electrostatic force forces comb teeth 225 and 245 to move away from their center point. Subsequently, at time T1, the switch circuit 32 switches based on the signal S2Y, and the midpoint voltage V1 of comb teeth 125 and 145 is applied to the non-inverting input terminal of the operational amplifier 31a, just as in normal acceleration detection.

[0073] In this embodiment, the signals for displacing the first fixed comb electrodes 110, 130 and the second movable comb electrodes 220, 240 are the same in both the first and second detection units. That is, the frequency of the signal is the same in both the first and second detection units, and the time variation of the signal is also the same in both the first and second detection units. As a result, as shown in Figure 8, the input voltage to the first detection unit and the input voltage to the second detection unit change at the same timing. Therefore, in this embodiment, the first fixed comb electrodes 110, 130 and the second movable comb electrodes 220, 240 can be changed in a synchronized manner.

[0074] Through the above process, the comb teeth 215, 235, 225, and 245 can be displaced by electrostatic force. In this embodiment, the period of the drive signal S2X of the switch circuit 22 is set to control the time for generating the electrostatic force so that the amount of displacement can be sufficiently detected. For example, the resonance frequency characteristics of the vibration of the comb teeth 215, 235, 225, and 245 with respect to the input frequency of the voltage applied to the comb teeth 215, 235, 225, and 245 are shown in Figure 10. In this embodiment, the frequency of the input signal, that is, the frequency of the input voltage to the first detection unit shown in Figure 8, is set to be the resonance frequency f0. As a result, vibration in the comb teeth 215 and 235 occurs at the frequency in which the comb teeth 215, 235, 225, and 245 resonate, that is, at the frequency in which the displacement range is greatest.

[0075] Subsequently, the first and second detection units operate in the same manner as the conventional acceleration detection described above, and outputs GoutX and GoutY are obtained corresponding to the displacement amounts of the comb teeth 215, 235, 225, and 245. At this time, the displacement amounts of the comb teeth 215, 235, 225, and 245 due to the electrostatic force are uniquely determined by the voltage applied to the non-inverting input terminal of the operational amplifier 21a. Therefore, the output corresponding to the displacement amounts of the comb teeth 215, 235, 225, and 245 is also uniquely determined, and self-diagnosis is performed on the first and second detection units by comparing the obtained output with the uniquely determined self-diagnosis amount (output).

[0076] In this embodiment, the comb teeth 215, 235, 225, and 245 are made of silicon. Therefore, their Q-factor is low. For example, the Q-factor of a quartz crystal oscillator, which is widely used in gyro sensors, is on the order of 30,000, but the Q-factor of the comb teeth 215, 235, 225, and 245, which are constructed as silicon MEMS, is about 20. As a result, the vibrations forcibly induced during the self-diagnosis of the first and second detection units subside in a very short time.

[0077] In this embodiment, the first movable comb electrodes 210, 230 and the second movable comb electrodes 220, 240 have the same shape. Furthermore, the mass and material of each electrode are also the same. Therefore, the resonant frequencies f0 of the first movable comb electrodes 210, 230 and the second movable comb electrodes 220, 240 are the same. As described above, during self-diagnosis, a signal is applied between the first movable comb electrodes 210, 230 and the first fixed comb electrodes 110, 130, and between the second movable comb electrodes 220, 240 and the second fixed comb electrodes 120, 140, respectively, to displace the first movable comb electrodes 210, 230 and the second movable comb electrodes 220, 240, with a frequency equal to the resonant frequency.

[0078] Specifically, the resonance frequency characteristics of the vibration of the first movable comb electrodes 210, 230 and the second movable comb electrodes 220, 240 with respect to the input frequency of the voltage applied to the first fixed comb electrodes 110, 130 and the second fixed comb electrodes 120, 140 are shown in Figure 10. In this embodiment, the frequencies of the input signals (V1, V2) for displacing the first movable comb electrodes 210, 230 and the second movable comb electrodes 220, 240, i.e., the frequencies of the input voltages to the first and second detection units shown in Figure 8, are set to be the resonance frequency f0. As a result, vibrations in the first movable comb electrodes 210, 230 and the second movable comb electrodes 220, 240 occur at the frequency in which the first movable comb electrodes 210, 230 and the second movable comb electrodes 220, 240 resonate, i.e., at the frequency in which the displacement range is greatest.

[0079] With the above configuration, the displacement of the first movable comb electrodes 210, 230 and the second movable comb electrodes 220, 240 is large, making it easy to detect changes in displacement due to slight damage to the comb teeth. Figure 11 shows the displacement with respect to voltage between the first fixed comb electrodes 110, 130 and the second fixed comb electrodes 120, 140. In Figure 11, the solid line shows an example where the voltage frequency is the resonant frequency, and the dashed line shows an example where the voltage frequency is not the resonant frequency (1 Hz in the example shown). The displacement is the value of gravitational acceleration detected by the displacement of the first movable comb electrodes 210, 230 and the second movable comb electrodes 220, 240.

[0080] As shown in Figure 11, for example, if the input signal voltage is 3V, a displacement equivalent to 5G will occur if the input signal frequency is 1Hz. On the other hand, if the input signal frequency is the resonant frequency, a displacement equivalent to 20G will occur. Therefore, even slight damage to the comb teeth will result in a difference in the amount of displacement, making it highly likely that the abnormality can be accurately detected.

[0081] (3) Other embodiments, etc.: The above embodiments are examples of carrying out the invention. Therefore, the configuration of each part can be replaced with any configuration having a similar function. Furthermore, any other arbitrary components may be added to the present invention.

[0082] The first electrode fixing portion, the second electrode fixing portion, and the movable electrode fixing portion are parts that extend perpendicularly to the support substrate and can be any part that supports other parts. That is, the support substrate is a substrate that supports other structures, and each part of the physical quantity sensor element is supported directly or indirectly by the support substrate. The first electrode fixing portion, the second electrode fixing portion, and the movable electrode fixing portion are parts that are directly supported by the support substrate.

[0083] An electrode that is considered fixed and does not move relative to the support substrate is a fixed electrode, and an electrode that moves relative to the support substrate or a part fixed to the support substrate is a movable electrode. The first electrode fixing part and the second electrode fixing part are parts that support the first fixed comb electrode and the second fixed comb electrode, respectively. The first electrode fixing part and the second electrode fixing part only need to be able to connect to other parts and support other parts, and their shape, size, and position on the support substrate can be in various forms.

[0084] Each of the first and second movable comb electrodes is connected to a movable electrode fixing part and is configured to face each of the first and second fixed comb electrodes, respectively. That is, there may be one or more movable electrode fixing parts. The first and second movable comb electrodes may be directly or indirectly connected to one or more movable electrode fixing parts. In any case, the first and second movable comb electrodes are configured to face each of the different fixed comb electrodes, and as a whole, they may be movable in either the first or second direction.

[0085] The first movable comb electrode and the first fixed comb electrode only need to face each other. Furthermore, the first fixed comb electrode is fixed relative to the support substrate, and the first movable comb electrode is configured to be displaceable relative to the first fixed comb electrode. In other words, the displacement of the first movable comb electrode should cause a displacement in the distance between the capacitor formed by the first movable comb electrode and the first fixed comb electrode.

[0086] The second movable comb electrode and the second fixed comb electrode only need to face each other. Furthermore, the second fixed comb electrode should be fixed relative to the support substrate, and the second movable comb electrode should be configured to be displaceable relative to the second fixed comb electrode. In other words, the displacement of the second movable comb electrode should cause a displacement in the distance of the capacitor formed by the second movable comb electrode and the second fixed comb electrode.

[0087] The first and second movable comb electrodes have the same resonant frequency. Although the orientations of the first and second movable comb electrodes differ by 90°, at least one of their mass, size, structure, or material is identical, and they are configured to resonate at the same frequency.

[0088] During self-diagnosis, signals are applied to displace the first movable comb electrode and the first fixed comb electrode, and between the second movable comb electrode and the second fixed comb electrode, respectively. The frequency of these signals is set to be the same as the resonant frequency, so that both the first and second movable comb electrodes resonate with the signal, and the amount of displacement is greater than when they are not resonating. [Explanation of symbols]

[0089] 1...XY direction acceleration sensor element, 10...Support substrate, 20...Detection circuit, 21...Conversion circuit, 21a...Operational amplifier, 21b...Capacitor, 21c...Switch, 22...Switch circuit, 22a...Switch, 22b...Switch, 23...Signal processing circuit, 23a,33a...LPF circuit, 23b,33b...GAIN circuit, 30...Detection circuit, 31...Conversion circuit, 31a...Operational amplifier, 31b...Capacitor, 31c...Switch, 32...Switch circuit, 32a,32b...Switch, 33...Signal processing circuit, 60...Control signal generation circuit, 100...Physical quantity sensor device, 101...Z direction acceleration sensor element, 110...First fixed comb-tooth electrode, 111...First electrode fixing part, 113...Main body, 115...comb teeth, 120...second fixed comb tooth electrode, 121...second electrode fixing part, 123...main body, 125...comb teeth, 130...first fixed comb tooth electrode, 131...first electrode fixing part, 133...Main body, 135...Comb tooth, 140...Second fixed comb tooth electrode, 141...Second electrode fixing part, 143...Main body, 145...Comb tooth, 210...First movable comb tooth electrode, 215...Comb tooth, 220...Second movable comb electrode, 225...Comb tooth, 230...First movable comb electrode, 235...Comb tooth, 240...Second movable comb electrode, 245...Comb tooth, 301...Movable electrode fixing part, 311...Movable electrode fixing part, 313...First movable electrode support part, 317...First spring, 410...First connecting part, 420...Second connecting part, 430...Third connecting part, 440...Fourth connecting part

Claims

1. A first electrode fixing portion, a second electrode fixing portion, and a movable electrode fixing portion extending perpendicular to the support substrate, A first fixed comb electrode is connected to the first electrode fixing portion and comprises a body extending in a first direction parallel to the support substrate and comb teeth extending in a second direction parallel to the support substrate and perpendicular to the first direction, A second fixed comb electrode is connected to the second electrode fixing portion and comprises a body extending in the second direction and comb teeth extending in the first direction, It comprises a first movable comb electrode connected to the movable electrode fixing portion and facing the first fixed comb electrode, and a second movable comb electrode facing the second fixed comb electrode, The resonance frequencies of the first movable comb electrode and the second movable comb electrode are the same. During self-diagnosis, a signal is applied between the first movable comb electrode and the first fixed comb electrode, and between the second movable comb electrode and the second fixed comb electrode, respectively, which is a signal for displacing the first movable comb electrode and the second movable comb electrode, and whose frequency is the same as the resonant frequency. A physical quantity sensor element.

2. A physical quantity sensor element according to claim 1, During normal operation, which is not self-diagnostic, a signal for detecting capacitance changes is periodically applied between the first movable comb electrode and the first fixed comb electrode, and between the second movable comb electrode and the second fixed comb electrode. During self-diagnosis, instead of the signal for detecting capacitance changes, a signal of the resonant frequency is periodically applied between the first movable comb electrode and the first fixed comb electrode, and between the second movable comb electrode and the second fixed comb electrode, in order to perform self-diagnosis. This is a control signal generation circuit. A C-V conversion circuit that outputs a voltage corresponding to the change in capacitance between the first movable comb electrode and the first fixed comb electrode and the change in capacitance between the second movable comb electrode and the second movable comb electrode, The system includes a signal processing circuit that processes the output voltage of the C-V conversion circuit and outputs a signal corresponding to the change in a physical quantity. Physical quantity sensor device.

3. The signals applied between the first movable comb electrode and the first fixed comb electrode, and between the second movable comb electrode and the second fixed comb electrode, respectively, for displacing the first and second movable comb electrodes, are signals whose frequency is the same as the resonant frequency and whose time variation is the same. The physical quantity sensor device according to claim 2.

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