JP6142554B2 - Capacitive sensor - Google Patents

Description

  The technology disclosed in the present application relates to a capacitive sensor configured as MEMS (Micro Electro Mechanical Systems).

  Conventionally, some physical quantity sensors manufactured using MEMS technology use capacitance. For example, there is a substrate that includes a substrate and a vibration mass body, and the vibration mass body is rotatably held with respect to a torsion bar provided on a support portion standing on the substrate (for example, Patent Document 1) ). In the sensor disclosed in Patent Document 1, the vibration mass body is formed in a flat plate shape so as to be spaced apart from and parallel to the plane of the substrate, and to rotate about the extending direction of the torsion bar as the rotation axis. Yes. The vibration mass body includes a first wing portion and a second wing portion at positions symmetrical with respect to the rotation axis. The substrate is provided with first and second fixed electrodes on a substrate facing each of the first and second wing portions of the torsion bar. In the sensor, a capacitor is constituted by each wing and each fixed electrode. The vibrating mass rotates, for example, according to a physical quantity (acceleration in the literature) that acts in a direction perpendicular to the planar direction of the substrate. In the sensor, the distance between each wing portion and each fixed electrode varies according to the rotation of the vibrating mass body, and the acceleration is detected from the amount of change in the capacitance accompanying the variation in distance.

  Further, in the vibration mass body of the sensor disclosed in Patent Document 1, through holes having different hole diameters are formed in each of the first wing portion and the second wing portion. Therefore, the vibrating mass body rotates according to the acceleration acting on the sensor, with different moments acting on the first wing and the second wing.

Special table 2009-537803 gazette

  By the way, in the capacitance type sensor as described above, each physical quantity is detected from the amount of change in capacitance by applying a voltage between each wing and each fixed electrode. In the case of using a sensor, an alternating voltage of a pulse wave having an opposite phase between, for example, the first wing part and the second wing part is applied between each wing part and each fixed electrode prior to detection, and the vibrating mass body Is in the initial state. When a voltage is applied between each wing part and each fixed electrode, the vibrating mass body has an electrostatic force between the first wing part and the first fixed electrode, and the second wing part and the second fixed electrode. Rotational torque is generated according to the difference between the two electrostatic forces and the electrostatic force between the two. Therefore, as an initial state for starting detection, the vibration mass body needs to be in a stable state in which vibrations are settled at a position within a predetermined range from a state in which the vibration mass body is rotated (vibrated) by a rotational torque caused by a difference in electrostatic force. is there.

  However, in Patent Document 1 described above, it is described that the through holes formed in each wing portion are formed with different hole diameters. There is no mention of what the electrostatic force will look like. For this reason, in the case where each through-hole is formed by paying attention only to the moment acting on the vibrating mass, it is uncertain what the electrostatic force will act on the vibrating mass at startup. As a result, there is a problem that the time required for the vibration of the vibrating mass to shift to a stable state is not optimized and the start-up time becomes unnecessarily long.

  The technology disclosed in the present application has been proposed in view of the above problems. It is an object of the present invention to provide a capacitive sensor capable of shortening the startup time.

  A capacitance-type sensor according to a technique disclosed in the present application includes a substrate, a torsion bar provided in a support portion fixed to the substrate, and a substrate that is rotatably provided with the extending direction of the torsion bar as a rotation axis. A flat plate-like vibrating mass provided at a position facing the substrate plane and spaced apart from each other, first and second wings provided at each of positions where the rotation axis of the vibrating mass is sandwiched, and provided on the substrate A first fixed electrode facing the first wing portion and outputting the amount of change in the first capacitance between the first wing portion and the second wing portion provided on the substrate, A plurality of second fixed electrodes that output the amount of change in the second capacitance between the wings and a plurality of second electrodes that are provided on the first wings and penetrate between the two main surfaces of the plate-like vibrating mass body. 1 through hole, and the first through hole has a hole diameter at which the first capacitance is substantially the same as the second capacitance. A.

  In the capacitance type sensor, the first wing portion and the second wing portion are provided at each of the positions sandwiching the rotation axis with respect to the vibration mass body provided rotatably with respect to the torsion bar. The capacitance type sensor includes a first capacitance between the first fixed electrode on the substrate and the first wing portion, and a second capacitance between the second fixed electrode on the substrate and the second wing portion. A physical quantity (for example, acceleration) is detected by outputting a change amount of each capacitance with the capacitance. The first wing portion is provided with a plurality of first through holes penetrating between the two main surfaces of the flat plate-like vibration mass body.

  In the vibrating mass, the first through hole is provided in the first wing part and is lighter than the second wing part, and a difference in mass between the wing parts causes different moments to each wing part. The vibration mass body rotates according to the physical quantity acting on the sensor by applying different moments to the wing parts. Here, there may be a difference between the first capacitance and the second capacitance due to the formation of the first through hole in the first wing portion. As a result, depending on the difference between the electrostatic force between the first wing part and the first fixed electrode and the electrostatic force between the second wing part and the second fixed electrode, the vibrating mass body is A rotational torque is generated, and the startup time of the sensor becomes long.

  Accordingly, the capacitance type sensor is configured such that the first capacitance is substantially the same as the second capacitance by adjusting the diameter of the first through hole formed in the first wing portion. To do. The first capacitance is mainly a component of a parallel plate capacitance due to electric lines of force connecting the first fixed electrode and the plane of the vibrating mass body constituting the first wing part. In addition to the parallel plate capacitance, the capacitance due to the wrapping of electric lines of force connecting the inner surface of the first through hole and the first fixed electrode also contributes as the capacitance. The decrease in the parallel plate capacity due to the decrease in the flat plate area due to the first through-hole opened in the first wing portion is compensated by the wraparound capacity due to the inner surface of the first through-hole. By adjusting the hole diameter of the first through hole, it is possible to make up for the capacity substantially the same as the decrease in the parallel plate capacity by the wraparound capacity. Thereby, a 1st electrostatic capacitance and a 2nd electrostatic capacitance can be made into the substantially same electrostatic capacitance. In such a configuration, the electrostatic force acting on each wing during start-up can be made the same, and the time required for the vibration of the vibrating mass to shift to a stable state can be optimized. it can. As a result, it is possible to shorten the startup time of the capacitive sensor.

  Note that the capacity due to the wraparound is generated according to the electric force lines connecting the inner side surface of the first through hole and the first fixed electrode, and the electric force lines are strongly deeper at a shallow position on the inner side surface of the first through hole. It gets smaller as you enter. Therefore, the capacity due to the wraparound is mainly due to the lines of electric force generated at the periphery of the inner wall surface near the opening. Therefore, the decrease in the capacity of the parallel plate that is reduced by the opening of the through hole is proportional to the opening area of the through hole. It will be proportional to the length. Compensation by the capacity by the wraparound is effective when the through hole has a small diameter.

  In the capacitive sensor according to the technology disclosed in the present application, a plurality of plural sensors formed in the second wing portion and penetrating between the two main surfaces of the vibrating mass body and having a total area different from that of the first through hole. The first through hole is provided with a second through-hole, and each of the first and second through-holes is formed to have a total area size in which the first capacitance and the second capacitance have substantially the same capacitance. Also good. In addition, the total area here is the total of the areas of the respective opening portions of the first through hole and the second through hole when the flat vibrating mass is viewed from a direction perpendicular to the plane. It says size.

  In the capacitive sensor, a second through hole is formed in the second wing portion in addition to the first through hole. A 2nd wing | blade part penetrates between two main surfaces of a vibration mass body, and the some 2nd through-hole used as the whole area different from a 1st through-hole is provided. In the vibrating mass body, different total moments are generated in the respective wing portions due to different total areas of the first and second through holes. The difference in moment acting on each of the first and second wing parts is, for example, when the first and second through holes having different hole diameters are provided in the first and second wing parts. This is due to the difference in the mass of each wing. Further, for example, when the vibration mass body is housed in a case filled with a medium such as nitrogen, the vibration mass body is caused by a difference in damping torque caused by the medium flowing through each through hole.

  And a vibration mass body rotates according to the physical quantity which acts on a sensor by a different moment acting on each wing | blade part. Here, as a case where the total areas of the two through holes are different, a case where the hole diameters of the through holes are different or the interval (pitch) of the through holes is different is assumed. Even in this case, the start-up time becomes longer if there is a difference between the first capacitance and the second capacitance.

  Therefore, in the capacitance type sensor, the second through hole opened in the second wing part is reduced by the parallel plate capacity due to the opening, as in the case of the first through hole in the first wing part. It is assumed that the hole is made up of a hole diameter that is compensated by the volume of the surroundings. Further, in each of the first and second wing parts, the decrease in the parallel plate capacity is completely compensated by the wraparound capacity, and the decrease in the parallel plate capacity in the first wing part and the wraparound. What is necessary is just to comprise with the total area where the sum with the capacity | capacitance part is substantially the same as the sum of the reduction | decrease part for the parallel plate capacity | capacitance in a 2nd wing | blade part, and the compensation part for a surrounding capacity part. Thereby, a through-hole in which the first capacitance and the second capacitance are substantially the same is formed. In such a configuration, the electrostatic force acting on each wing portion at the time of activation can be made the same, and the activation time can be shortened.

  Further, in the capacitive sensor according to the technique disclosed in the present application, the second fixed electrode may have a configuration in which an opening or a slit corresponding to the first through hole is formed.

  In the capacitance type sensor, an opening or a slit is formed in the second fixed electrode in order to compensate for the difference between the first capacitance and the second capacitance. When the first through hole is formed in the first wing part, the first electrostatic capacitance is constituted by a parallel plate capacity part of the first wing part and the first fixed electrode and a surrounding capacity part. On the other hand, since the second wing portion and the second fixed electrode have the same configuration as the first wing portion and the first fixed electrode, an opening or a slit is provided in the second fixed electrode. As a result, the second capacitance is also composed of the parallel plate capacitance and the wraparound capacitance. At this time, if the opening or slit formed in the second fixed electrode is formed corresponding to the first through-hole, the sum of the decrease in the parallel plate capacity and the supplement in the wrap-around capacity is calculated. The first wing portion and the second wing portion can be adjusted substantially the same. As a result, it is easy to make both electrostatic capacitances the same, and it is possible to easily shorten the startup time.

  Further, in the capacitive sensor according to the technology disclosed in the present application, the first through hole is formed with a smaller total area than the second through hole, and the first fixed electrode includes the first through hole and the second through hole. It is good also as a structure in which the opening or slit of a magnitude | size based on the difference of the whole area with a through-hole is formed.

  In the capacitance type sensor, an opening or a slit is formed in the first fixed electrode in order to compensate for the difference between the first capacitance and the second capacitance. More specifically, the first through hole is formed with a small area compared to the second through hole. For example, when the hole diameter of the first through hole is smaller than that of the second through hole, the area of the surface where the first wing portion faces the first fixed electrode is larger than the area where the second wing portion faces the second fixed electrode. It becomes relatively larger than the area of the surface to be processed, and the capacity of the parallel plate increases. Further, as described above, the relationship between the increase in the wraparound capacity due to the through hole and the decrease in the parallel plate capacity is dominant as the hole diameter increases, so that the second through hole having a larger hole diameter is used. In the second wing part in which the hole is opened, the compensation by the amount of the wraparound capacity is further insufficient. From this point, the first capacitance may be larger. As a result, the first capacitance is more likely to increase than the second capacitance. Therefore, in the sensor, an opening or a slit having a size based on the difference in the total area of the two through holes is formed in the first fixed electrode that is likely to have a relatively large capacitance. As a result, the capacitance of the parallel plate is decreased in the first capacitance and the amount of wraparound is increased, making it easy to make both capacitances the same.

  Further, in the capacitive sensor according to the technology disclosed in the present application, the first wing portion and the second wing portion are configured in substantially the same shape, and the first fixed electrode and the second fixed electrode are substantially the same. It is good also as a structure provided on the said board | substrate comprised by the shape and having the same distance from the said rotation axis.

  In such a configuration, the amount of change in capacitance that occurs between the first capacitance and the second capacitance with the rotation of the vibrating mass body is the same. For example, the first capacitance can be obtained using a fully differential circuit. In addition, a processing circuit that can detect an arbitrary physical quantity with high accuracy from the amount of change in the second capacitance can be configured.

  Further, in the capacitive sensor according to the technology disclosed in the present application, in a state where no voltage is applied between each of the first wing portion and the first fixed electrode, and the second wing portion and the second fixed electrode, A configuration in which a hole diameter having a size that takes into account the amount of change between the first capacitance and the second capacitance when the vibration mass body is tilted by the moment generated in the first wing portion and the second wing portion is set. It is good.

  When the first through hole is formed in the first wing part, or when the first and second through holes having different total areas are formed in both wing parts, a voltage is applied between each wing part and each fixed electrode. When the voltage is not applied, different moments may be generated due to the difference in mass between the blades, and the vibrating mass may be tilted. Therefore, in the capacitance type sensor, the amount of change between the first capacitance and the second capacitance when the vibration mass body is tilted is taken into consideration, and the capacitance is so large that both capacitances are the same. Each through hole is formed with the hole diameter and the total area. As a result, the first capacitance and the second capacitance can be made to coincide with each other with high accuracy, and shortening at the time of startup can be achieved more reliably.

  According to the technology disclosed in the present application, it is possible to provide a capacitive sensor that can shorten the startup time.

It is a top view which shows schematic structure of the electrostatic capacitance type sensor of 1st Embodiment. It is the sectional view on the AA line of FIG. It is sectional drawing for demonstrating the manufacturing process of a sensor. It is sectional drawing for demonstrating the manufacturing process of a sensor. It is sectional drawing for demonstrating the manufacturing process of a sensor. It is sectional drawing for demonstrating the manufacturing process of a sensor. It is sectional drawing for demonstrating the manufacturing process of a sensor. It is sectional drawing for demonstrating the manufacturing process of a sensor. It is a top view which shows schematic structure of the electrostatic capacitance type sensor of 2nd Embodiment. FIG. 10 is a sectional view taken along line B-B in FIG. 9. It is sectional drawing of another electrostatic capacitance type sensor. It is a top view which shows schematic structure of another electrostatic capacitance type sensor.

(First embodiment)
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings. Note that, for convenience of explanation, the accompanying drawings include portions that are illustrated differently from actual dimensions and scales.
FIG. 1 shows a schematic configuration of a capacitive sensor according to the present embodiment manufactured by using a micro electro mechanical systems (MEMS) technique. As shown in FIG. 1, a capacitive sensor (hereinafter referred to as “sensor”) 10 includes a vibrating mass body 11 and a substrate 12 (see FIG. 2). The vibration mass body 11 is formed in a substantially rectangular plate shape in plan view. In the following description, as indicated by an arrow in FIG. 1, the direction along the long side of the vibrating mass body 11 is the X direction, and the direction along the short side of the vibrating mass body 11 is perpendicular to the X direction. The Y direction, and the direction perpendicular to both the X direction and the Y direction (the direction perpendicular to the plate surface of the vibrating mass 11) is referred to as the Z direction and will be described.

  In the sensor 10, a frame portion 13 is formed so as to surround the outer edge of the vibration mass body 11. The frame portion 13 is formed in a rectangular frame shape in plan view, and is separated from the outer peripheral portion of the vibration mass body 11 provided with an inner wall on the inner side. As shown in FIG. 2, the frame portion 13 has a base end portion in the Z direction formed integrally with the substrate 12 and extends from the substrate 12 along the Z direction. The tip end surface 13A in the Z direction of the frame portion 13 has the same position in the Z direction as the upper surface 11A (the upper surface in FIG. 2) of the vibration mass body 11.

  The substrate 12 has an insulating layer 22 formed so as to cover the upper surface of the flat core substrate 21 in the Z direction. On the insulating layer 22, a pad 23, a first fixed electrode 25, and a second fixed electrode 26 are formed. The pad 23 is formed at the center of the substrate 12, and the support portion 14 is provided on the upper surface. The support portion 14 has a rectangular parallelepiped shape standing on the substrate 12 and extending in the Z direction, and a base end portion is electrically connected to the pad 23. The first and second fixed electrodes 25 and 26 are formed at symmetrical positions in the X direction with respect to the support portion 14 at the center of the substrate 12.

  As shown in FIG. 1, the support portion 14 has a pair of torsion bars 15 formed on each side surface 14 </ b> A in the Y direction. The torsion bar 15 has a bar shape formed along the Y direction, in other words, along the direction perpendicular to the side surface 14A. In addition, the torsion bar 15 has a cross-sectional shape cut along a plane along a direction orthogonal to the Z direction, and a long side of the torsion bar 15 has a rectangular shape along the Y direction. The torsion bar 15 has one end portion in the Y direction formed integrally with the side surface 14 </ b> A and the other end portion formed integrally with the vibrating mass body 11.

  The vibration mass body 11 is a central portion in the X direction, and a rotation fulcrum portion 18 formed at each of both end portions in the Y direction is supported by the support portion 14 via a torsion bar 15. As a result, the vibration mass body 11 is rotatably supported with respect to the support portion 14 via the torsion bar 15. The vibrating mass 11 rotates around the rotation axis along the Y direction passing through the center of the torsion bar 15 in the X direction. The vibrating mass 11 has a first wing part 31 formed on one side (left side in FIG. 1) in the X direction with respect to the rotation axis, and a second wing part 32 formed on the other side (right side in FIG. 1). Yes. The first and second wing portions 31 and 32 rotate in different Z directions around the rotation axis. Incidentally, the support part 14 is formed with extended parts 14B on side surfaces 14A on both side parts in the X direction of the torsion bar 15, respectively. Each extending portion 14B is formed in a rod shape branched into a plurality along the Y direction. For example, the extending portion 14B functions as a resistance portion that generates a damping torque due to friction with air or a medium when the vibrating mass 11 rotates, or introduces an etching solution when etching a sacrificial layer described later. It functions as a part for adjusting the mouth (introduction amount). In addition, the extension part 14B is good also as a structure extended in the Y direction toward each support point 14 from each rotation fulcrum part 18. As shown in FIG. Moreover, the sensor 10 is good also as a structure which does not provide the extended part 14B.

  The first and second wing portions 31 and 32 have the same outer edge shape in plan view, while the first wing portion 31 is formed with a first through hole 34. More specifically, the first wing portion 31 has a substantially rectangular shape in plan view with the long side extending in the Y direction. Further, the first fixed electrode 25 is formed in a substantially rectangular shape in plan view with the long side facing the first wing portion 31 in the Z direction and along the Y direction. The first wing portion 31 has a plurality of first through holes 34 formed in a matrix shape in a region facing the first fixed electrode 25 in the Z direction. The first through-hole 34 passes through two main surfaces facing each other in the Z direction of the first wing portion 31, and has a circular cross-sectional shape cut in the plane direction of the vibration mass body 11. Moreover, the 2nd wing | blade part 32 makes | forms a substantially rectangular shape in planar view in which the long side followed the Y direction. The second fixed electrode 26 is formed in a substantially rectangular shape in plan view with the long side facing the second wing part 32 in the Z direction and along the Y direction. Therefore, the first and second fixed electrodes 25 and 26 have the same shape and are formed at the same distance in the X direction from the rotation axis in the plan view of the substrate 12.

  As shown in FIG. 2, the first through hole 34 is formed with a hole diameter of the size of the first width L1. Note that the shape and number of the first through holes 34 are examples, and may be changed as appropriate. For example, the first through hole 34 may have a square cross-sectional shape. Moreover, you may comprise the 1st through-hole 34 as a slit along an X direction or a Y direction, for example. In this case, the hole diameter is appropriately set according to the shape of the first through hole 34.

  Incidentally, as shown in FIG. 1, the first and second wing portions 31 and 32 are convex portions formed at the outer ends in the X direction and projecting outward in the X direction at both ends in the Y direction. A part 19 is provided. The convex portion 19 has an area where each wing portion 31, 32 contacts the bottom portion of the substrate 12 when each wing portion 31, 32 of the vibrating mass 11 rotates toward the substrate 12 and contacts the bottom portion of the substrate 12. It functions as a part to be reduced. In addition, the sensor 10 is good also as a structure which does not provide the convex part 19. FIG.

  The sensor 10 configured as described above has an electrostatic capacity (hereinafter referred to as “first electrostatic capacity”) C1 between the first wing part 31 and the first fixed electrode 25 as the vibration mass body 11 rotates. Then, acceleration is detected based on the electrostatic capacity (hereinafter referred to as “second electrostatic capacity”) C2 between the second wing portion 32 and the second fixed electrode 26. More specifically, in the vibrating mass 11, the first and second wing parts 31 and 32 are electrically connected to the substrate 12 through the rotation fulcrum part 18, the torsion bar 15 and the support part 14. The 1st wing | blade part 31 opposes the 1st fixed electrode 25 in a Z direction, and the capacitor | condenser of 1st electrostatic capacitance C1 is comprised. Further, the second wing portion 32 is opposed to the second fixed electrode 26 in the Z direction, and a capacitor of the second capacitance C2 is formed.

  The first and second capacitances C <b> 1 and C <b> 2 are the distances between the first wing portion 31 and the first fixed electrode 25 when the vibrating mass body 11 rotates according to the acceleration acting on the sensor 10 in the Z direction. The first and second electrostatic capacitances C1 and C2 change with the change of D1 (see FIG. 2) and the distance D2 between the second wing portion 32 and the second fixed electrode 26. For example, in FIG. 2, when the vibrating mass 11 rotates clockwise, the capacitance C1 decreases as the distance D1 increases, while the second capacitance decreases as the distance D2 decreases. C2 increases. In the sensor 10, for example, an alternating voltage of an antiphase pulse wave is applied between the first and second wing parts 31 and 32 and the first and second fixed electrodes 25 and 26. In the sensor 10, the amount of change in the first and second capacitances C1 and C2, which changes as the vibration mass body 11 rotates, is connected to a processing circuit (not shown) (for example, a fully differential circuit) via wiring. The output is detected and acceleration is detected.

Next, conditions for forming the first through hole 34 will be described.
First, the first wing part 31 is formed in substantially the same shape as the second wing part 32, and the first through hole 34 is formed only in the first wing part 31. It becomes lightweight and a difference arises in the mass between the 1st and 2nd wing parts 31 and 32. For this reason, the moment acting on the second wing part 32 based on the distance from the torsion bar 15 is larger than the moment acting on the first wing part 31 based on the distance from the torsion bar 15. . Accordingly, the first wing part 31 rotates in a direction away from the substrate 12 and the second wing part 32 rotates in a direction approaching the substrate 12 in accordance with the acceleration along the Z direction acting on the sensor 10, that is, FIG. Rotate clockwise at.

  Prior to the acceleration detection, an alternating voltage of a pulse wave is applied between the first and second wing parts 31 and 32 and the first and second fixed electrodes 25 and 26, and the vibrating mass body 11 is brought into an initial state. The When an AC voltage is applied between the wing portions 31 and 32 and the fixed electrodes 25 and 26, the vibrating mass body 11 is based on the electrostatic force based on the first capacitance C1 and the second capacitance C2. A rotational torque is generated according to the difference between the two electrostatic forces and the electrostatic force, and vibration is generated. As an initial state for starting detection, since it is necessary to be in a stable state in which the vibration of the vibrating mass 11 falls within a predetermined range, the startup time becomes long.

  Therefore, in the sensor 10 of the present embodiment, the first capacitance C1 is adjusted to the second electrostatic capacity by adjusting the hole diameter (first width L1) of the first through hole 34 formed in the first wing portion 31. It is configured to be the same as or substantially the same as the capacitor C2. Here, as indicated by a one-dot chain line in FIG. 2, for example, in the lines of electric force generated from the first fixed electrode 25 toward the first wing part 31, the first capacitance C <b> 1 is the same as the first fixed electrode 25. A main component is a parallel plate capacity component by an electric force line 41 connecting the plane of the vibrating mass 11 constituting the first wing part 31. In addition to the electric force lines 41 corresponding to the parallel plate capacity, the capacity due to the wrapping of the electric force lines 42 connecting the inner surface of the first through-hole 34 and the first fixed electrode 25 also contributes as the capacitance. The decrease in the parallel plate capacity (electric field lines 41) due to the decrease in the plate area by the first through hole 34 opened in the first wing portion 31 is the capacity of the wraparound by the inner surface of the first through hole 34. It will be supplemented by the minute (electric force line 42). By adjusting the first width L1 of the first through hole 34, it is possible to make up for the capacity that is substantially the same as the decrease in the parallel plate capacity by the wraparound capacity. Thereby, the 1st electrostatic capacitance C1 and the 2nd electrostatic capacitance C2 can be made into the substantially same electrostatic capacitance.

  In such a configuration, the electrostatic forces acting on the wing parts 31 and 32 at the time of activation can be made the same or substantially the same. Therefore, it is preferable that the capacitances coincide with each other, and the vibration generated in the vibration mass body 11 at the time of startup is eliminated. As a result, it is possible to shorten the startup time. The conditions of the first width L1 for making both the capacitances C1 and C2 the same or substantially the same are the shape of the first through hole 34, the wings 31 and 32, and the fixed electrodes 25 and 26. It can be determined by changing the distances D1 and D2 and the areas where the fixed electrodes 25 and 26 and the wings 31 and 32 face each other and performing a simulation or the like.

  As described above, since the mass of the second wing part 32 is larger than that of the first wing part 31, the moment acting on the second wing part 32 is larger than that of the first wing part 31. For this reason, in the state where the voltage for starting is not applied, the first wing part 31 rotates in the direction away from the substrate 12 and the second wing part 32 rotates in the direction approaching the substrate 12, and the vibration is very small but not. There is a case where the mass body 11 is inclined in the clockwise direction. Therefore, in the sensor 10 of the present embodiment, both capacitances C1 and C2 are taken into account in consideration of the amount of change in the first capacitance C1 and the second capacitance C2 due to the tilting of the vibration mass body 11. The first through hole 34 is formed with a hole diameter of the same size. As a result, the first capacitance C1 and the second capacitance C2 can be made to coincide with each other with high accuracy, and the startup can be shortened more reliably.

  Furthermore, in the sensor 10 of this embodiment, the 1st and 2nd wing | blade parts 31 and 32 are comprised by the same shape. Further, the first and second fixed electrodes 25 and 26 are configured in the same shape, and are formed at the same distance from the rotation axis in the X direction. An alternating voltage of an antiphase pulse wave is applied between the first and second wing parts 31 and 32 and the first and second fixed electrodes 25 and 26. Therefore, the amount of change in capacitance that occurs in the first capacitance C1 and the second capacitance C2 with the rotation of the vibrating mass 11 is the same. In such a configuration, a fully differential circuit that can be detected with higher accuracy than a single-ended circuit can be used, and acceleration can be detected with high accuracy from the amount of change in the first and second capacitances C1 and C2. A processing circuit can be configured. The single-ended circuit here is a circuit having one output terminal of the differential amplifier circuit, and the fully differential circuit is a circuit having two output terminals and symmetry.

Next, an example of a method for manufacturing the sensor 10 will be described.
First, the core substrate 200 shown in FIG. 3 is prepared. The core substrate 200 is a wafer made of single crystal silicon, for example. The sensor 10 is manufactured by forming a large number of sensor elements on the core substrate 200 and then dicing them into a plurality of sensors 10.

  An insulating layer 210 is formed on the surface of the core substrate 200. The insulating layer 210 is formed by, for example, silicon nitride (SiNx) or a film obtained by stacking silicon nitride on a silicon dioxide film by using a thermal oxidation method or a deposition method. Next, on the surface of the insulating layer 210, for example, a first fixed electrode 211, a second fixed electrode 212, a pad 213, and a wiring (not shown) that connect these arbitrarily patterned using a photolithography technique are formed. For each of the fixed electrodes 211, 212, etc., a material that is resistant to etching of a later-described sacrificial layer 215 such as polysilicon is used. When aluminum generally used in LSI technology is used for the first fixed electrode 211 or the like, for example, a silicon nitride film is stacked on the aluminum to increase resistance to etching of the sacrificial layer 215. It is preferable. The insulating layer 210, the first fixed electrode 211, the second fixed electrode 212, the pad 213, and the wiring (not shown) may be formed in a plurality of layers.

  Next, as illustrated in FIG. 4, a sacrificial layer 215 is formed so as to cover the insulating layer 210, the first fixed electrode 211, the second fixed electrode 212, and the pad 213. The sacrificial layer 215 is formed by depositing silicon dioxide by, for example, a chemical vapor deposition (CVD) method. Next, as shown in FIG. 5, a hole 216 </ b> A is formed so that a part of the surface of the pad 213 is exposed to the sacrificial layer 215. A hole 216 </ b> B corresponding to the position of the frame portion 13 is formed in the sacrificial layer 215. The holes 216A and 216B are formed using, for example, a photolithography technique.

  Next, as illustrated in FIG. 6, an electrode layer 217 is formed on the sacrificial layer 215. A part of the electrode layer 217 is filled in the holes 216A and 216B. The electrode layer 217 is formed by depositing polysilicon by, for example, the CVD method. Next, as shown in FIG. 7, the electrode layer 217 is etched to form a first wing part 220 in which a first through hole 219 is formed, a second wing part 222, a frame part 224, and a support part 225. And form. For the etching of the electrode layer 217, for example, a resist (not shown) formed by arbitrary patterning using a photolithography technique is formed on the electrode layer 217, and Deep is applied to the region exposed from the opening of the resist. -Anisotropic etching is performed using a reactive ion etching (RIE) method. Although not shown, the torsion bar 15 is formed in the same process as the first and second wing portions 220 and 222 described above, for example.

  Next, as shown in FIG. 8, the sacrificial layer 215 is etched. Etching of the sacrificial layer 215 is performed, for example, from the first through-hole 219 formed in the first wing 220, the gap between the frame 224 and the second wing 222, the gap between the extended portions 14B described above, or the like. Etching is performed by introducing an etching solution (for example, buffered hydrofluoric acid (BHF)). In this way, the sensor 10 shown in FIG. 1 is formed.

As described above, according to the first embodiment described above, the following effects are provided.
(1) The first wing part 31 of the vibrating mass 11 is formed in substantially the same shape as the second wing part 32, and the first through hole 34 is formed in the first wing part 31. Compared to the portion 32, the weight is reduced, and a difference occurs in mass between the first and second wing portions 31 and 32. Therefore, since different moments are generated in the first wing portion 31 and the second wing portion 32, the vibrating mass body 11 rotates according to the acceleration acting on the sensor 10. On the other hand, the sensor 10 includes a first electrostatic capacitance C1 between the first wing portion 31 and the first fixed electrode 25, and a second electrostatic capacitance between the second wing portion 32 and the second fixed electrode 26. A first through hole 34 is formed with a hole diameter (first width L1) that is the same as the capacity C2. In such a configuration, the electrostatic force acting on each of the wing parts 31 and 32 at the time of starting can be made the same, and the starting time can be shortened by eliminating the rotational torque generated in the vibration mass body 11 at the time of starting. Is possible.

(2) In addition, the first through hole 34 is formed with a hole diameter having such a size that both the capacitances C1 and C2 are the same in consideration of the inclination of the vibration mass body 11 when no voltage is applied. Has been. As a result, the first capacitance C1 and the second capacitance C2 can be made to coincide with each other with high accuracy, and the startup can be shortened more reliably.
(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. 9 and 10. In addition, the same code | symbol is attached | subjected about the thing similar to 1st Embodiment, and the description is abbreviate | omitted suitably. The vibration mass body 11 according to the second embodiment is different from the first embodiment in that a through hole (second through hole 35) is also formed in the second wing part 32.

  As shown in FIG. 9, in the sensor 10 </ b> A, the first and second through holes 34 and 35 having different hole diameters are formed in the first and second wing parts 31 and 32, respectively, while having substantially the same shape. . In the second wing portion 32, a plurality of second through holes 35 are formed in a matrix in a region facing the second fixed electrode 26 in the Z direction. The second through-hole 35 penetrates through two main surfaces facing each other in the Z direction of the second wing portion 32 and has a circular cross-sectional shape cut in the plane direction of the vibration mass body 11.

  The same number of second through holes 35 as the first through holes 34 are formed. Further, as shown in FIG. 10, the second through hole 35 is formed with a hole diameter having a size of a second width L <b> 2 that is larger than the first width L <b> 1 of the first through hole 34. Therefore, in the vibrating mass 11, the total area of the first through hole 34 is smaller than the total area of the second through hole 35. The total area here means the total area of the opening portions of the first through hole 34 and the second through hole 35 when the flat vibrating mass 11 is viewed from the direction perpendicular to the plane. Refers to the size. The shape and number of the first and second through holes 34 and 35 are examples, and may be changed as appropriate. For example, the vibration mass body 11 may have a configuration in which the interval (pitch) forming each of the first and second through holes 34 and 35 is different from each other, and the first and second through holes 34 are different if their total areas are different. , 35 may be appropriately changed to other configurations.

Next, conditions relating to the total area of the first and second through holes 34 and 35 will be described.
First, since the first wing part 31 is formed in substantially the same shape as the second wing part 32 and the first through hole 34 has a smaller total area than the second through hole 35, the second wing part The mass is larger than 32. For this reason, the moment acting on the first wing part 31 based on the distance from the torsion bar 15 is larger than the moment acting on the second wing part 32 based on the distance from the torsion bar 15. . Therefore, according to the acceleration along the Z direction acting on the sensor 10, the first wing portion 31 rotates in a direction approaching the substrate 12, and the second wing portion 32 rotates in a direction away from the substrate 12, that is, FIG. Rotate counterclockwise at.

  Prior to the acceleration detection, an alternating voltage of a pulse wave is applied between the first and second wing parts 31 and 32 and the first and second fixed electrodes 25 and 26, and the vibrating mass body 11 is brought into an initial state. The When an AC voltage is applied between the wing portions 31 and 32 and the fixed electrodes 25 and 26, the vibrating mass body 11 is based on the electrostatic force based on the first capacitance C1 and the second capacitance C2. A rotational torque is generated according to the difference between the two electrostatic forces and the electrostatic force, and vibration is generated. As an initial state for starting detection, since it is necessary to be in a stable state in which the vibration of the vibrating mass 11 falls within a predetermined range, the startup time becomes long.

  Therefore, in the sensor 10A of the present embodiment, the second through hole 35 opened in the second wing portion 32 has the parallel plate capacity component due to the opening as in the case of the first through hole 34 of the first embodiment. It is composed of a hole diameter (second width L2) that compensates for the decrease in (electric force line 41) by a surrounding capacity (electric force line 42). Further, in each of the first and second wing parts 31 and 32, the reduction in the parallel plate capacity in the first wing part 31 as well as the reduction in the parallel plate capacity in the first wing part 31 are completely compensated by the wraparound capacity. Is the same as or substantially the same as the sum of the decrease in the parallel plate capacity in the second wing portion 32 and the supplement in the wrap-around capacity. It consists of the entire area. Thereby, each through-hole 34 and 35 in which the 1st electrostatic capacitance C1 and the 2nd electrostatic capacitance C2 become the same is formed. In such a configuration, the electrostatic forces acting on the wing parts 31 and 32 at the time of activation can be made the same or substantially the same. Therefore, it is preferable that the capacitances coincide with each other, and the vibration generated in the vibration mass body 11 at the time of startup is eliminated. As a result, it is possible to shorten the startup time. In the sensor 10A, it is preferable that the hole diameter and the entire area of the first and second through holes 34 and 35 are formed in consideration of the inclination of the vibration mass body 11 in a state where no voltage is applied. In addition, the conditions of the total area of the first and second through holes 34 and 35 can be determined by changing the first and second widths L1 and L2 of the through holes 34 and 35 and performing simulations.

As described above, according to the above-described second embodiment, the following effects can be obtained.
(1) The sensor 10 includes a first width L1 of a hole diameter of the first through hole 34 formed in the first wing part 31 and a first hole diameter of the second through hole 35 formed in the second wing part 32. The two widths L2 are different. The first and second through holes 34 and 35 have different total areas. Similar to the first through hole 34, the second through hole 35 is configured with a hole diameter that compensates for the decrease in the parallel plate capacity (electric field lines 41) due to the opening with the surrounding capacity (electric field lines 42). ing. And each through-hole 34 and 35 is the part for the reduction | decrease by the parallel plate capacity | capacitance in the 1st and 2nd wing | blade parts 31 and 32 so that 1st electrostatic capacitance C1 and 2nd electrostatic capacitance C2 may become the same. And the total area that makes the sum of the supplementary amount in the surrounding capacity equal to each other. In such a configuration, the electrostatic force acting on each of the wing parts 31 and 32 at the time of starting can be made the same, and the starting time can be shortened by eliminating the rotational torque generated in the vibration mass body 11 at the time of starting. Is possible.

Note that the present invention is not limited to the above-described embodiment, and it goes without saying that various improvements and modifications can be made without departing from the spirit of the present invention.
For example, in each of the embodiments described above, the sensors 10 and 10A are configured as capacitive sensors capable of detecting acceleration, but may be configured to detect other physical quantities (for example, angular velocity).

  Further, for example, a slit corresponding to the difference in the hole diameter and the total area of the first and second through holes 34 and 35 may be formed in each of the fixed electrodes 25 and 26 in the first and second fixed electrodes 25 and 26. . For example, as shown in FIG. 11, a slit 301 is formed in the second fixed electrode 26 in the sensor 10B. The slit 301 is formed so as to connect both ends of the second fixed electrode 26 in the Y direction along the Y direction with an arbitrary width in the X direction. A plurality of slits 301 are formed at predetermined intervals in the X direction. Note that the shape, number, position, and the like of the slit 301 are merely examples, and may be changed as appropriate. For example, a plurality of openings (through holes) may be formed in the second fixed electrode 26 instead of the slit 301.

  Here, in the sensor 10B, the first through hole 34 is formed only in the first wing portion 31, and the second electrostatic capacity C2 is likely to be relatively increased as compared to the first electrostatic capacity C1. Become. Therefore, in the sensor 10B, a slit 301 is formed in the second fixed electrode 26 in order to compensate for the difference between the first capacitance C1 and the second capacitance C2. When the first through hole 34 is formed in the first wing part 31, the first capacitance C1 is equal to the parallel plate capacity of the first wing part 31 and the first fixed electrode 25 and the wraparound capacity. Consists of. On the other hand, since the second wing portion 32 and the second fixed electrode 26 have the same configuration as the first wing portion 31 and the first fixed electrode 25, a slit 301 is provided for the second fixed electrode 26. ing. As a result, the second capacitance C2 is also composed of the parallel plate capacity and the wraparound capacity. At this time, if the slit 301 formed in the second fixed electrode 26 is formed corresponding to the hole diameter (first width L1) of the first through-hole 34, etc., the reduced amount of the parallel plate capacity and the wraparound capacity The sum of the minute supplement and the first wing portion 31 and the second wing portion 32 can be adjusted to be the same. As a result, it is easy to make both electrostatic capacitances C1 and C2 the same, and it is possible to easily shorten the startup time.

  In the sensor 10A of the second embodiment described above, the first fixed electrode 25 may be provided with a slit 301. More specifically, in the sensor 10 </ b> A, the hole diameter of the first through hole 34 is smaller than that of the second through hole, and the area of the surface where the first wing part 31 faces the first fixed electrode 25 is the second wing part 32. Is relatively larger than the area of the surface facing the second fixed electrode 26, and the capacity of the parallel plate is increased. Further, as described above, the relationship between the increase in the wraparound capacity by the through holes 34 and 35 and the decrease in the parallel plate capacity is as the hole diameter (first and second widths L1 and L2) is larger. Therefore, in the second wing portion 32 in which the second through-hole 35 having a large hole diameter is opened, the compensation by the amount of the wraparound capacity is further insufficient. From this point, the first capacitance may be larger. As a result, there is a higher possibility that the first capacitance C1 will increase compared to the second capacitance C2. When the slits 301 are provided in the sensor 10 </ b> A having such a configuration, the first through-hole 34 and the second through-hole 35 are all disposed with respect to the first fixed electrode 25 that is likely to have a relatively large capacitance. It is preferable to form a slit 301 or the like having a size based on the difference in area. Even in such a configuration, the same effect as described above can be obtained.

  Moreover, in each said embodiment, although the 1st and 2nd wing | blade part 31 and 32 was comprised so that the shape of the outer edge in planar view might become the same shape, it is not limited to this. For example, as in the sensor 10 </ b> C of FIG. 12, the width of the first wing part 31 in the X direction may be larger than that of the second wing part 32. In this case, the second through hole 35 is formed only in the second wing portion 32. That is, the sensor 10 </ b> C is configured such that the first wing part 31 whose mass is relatively large without forming a through hole is larger than the second wing part 32. In such a configuration, the moment acting on the first wing portion 31 is made larger than that on the second wing portion 32, and the amount of change in the rotational direction of the vibrating mass 11 with respect to the same acceleration acting on the sensor 10C is further increased. By increasing the sensitivity, the sensitivity can be improved.

  In this case, it is expected that the inclination of the vibration mass body 11 in a state where no voltage is applied is further increased. Therefore, it is preferable to form the second through hole 35 in consideration of this inclination. Further, it is preferable that the distance from the rotation axis of the first fixed electrode 25 and the distance from the rotation axis of the second fixed electrode 26 are the same.

  In the above embodiment, although not particularly mentioned, the vibration mass body 11 may be housed in a case filled with a medium such as nitrogen. In this case, it is preferable to set the hole diameter and the total area of each through hole 34, 35 including the magnitude and difference of the damping torque generated by the medium flowing in each through hole 34, 35.

  Further, the shape and configuration of each member is an example, and may be changed as appropriate. For example, it is good also as a structure provided with two or more support parts 14. FIG. Further, for example, a configuration in which a through-hole for ventilation is formed in the frame portion 13 or a part of the frame portion 13 so that air or a medium is not compressed in the frame portion 13 with the rotation of the vibration mass body 11. It may be configured such that is cut away.

  Incidentally, the sensors 10, 10A, 10B, and 10C are examples of capacitive sensors, the vibration mass body 11 is an example of a vibration mass body, the substrate 12 is an example of a substrate, and the support portion 14 is a support portion. As an example, the torsion bar 15 is an example of a torsion bar, the first fixed electrodes 25 and 211 are an example of a first fixed electrode, the second fixed electrodes 26 and 212 are an example of a second fixed electrode, The first wings 31 and 220 are examples of the first wings, the second wings 32 and 222 are examples of the second wings, and the first through holes 34 and 219 are examples of the first through holes. The second through hole 35 is an example of a second through hole, the first capacitance C1 is an example of a first capacitance type, and the second capacitance C2 is an example of a second capacitance. It is done.

DESCRIPTION OF SYMBOLS 10 Capacitance type sensor, 11 Vibrating mass body, 12 Substrate, 14 Support part, 15 Torsion bar, 25, 25 First and second fixed electrode, 31, 32 First and second wing part, 34, 35 First And the second through hole, C1, C2 first and second capacitances.

Claims (5)

A substrate,
A torsion bar provided in a support portion fixed to the substrate;
A flat plate-like vibration mass body provided rotatably at the extending direction of the torsion bar as a rotation axis, and provided at a position separated from the substrate and facing the substrate plane;
First and second wing portions provided at each of positions where the rotational axis of the vibrating mass body is sandwiched therebetween,
A first fixed electrode provided on the substrate, opposed to the first wing portion, and from which the amount of change in the first capacitance between the first wing portion and the first fixed electrode is output;
A second fixed electrode provided on the substrate, facing the second wing, and outputting a change amount of the second capacitance between the second wing and the second wing,
A plurality of first through holes provided in the first wing portion and penetrating between two main surfaces of the flat plate-like vibration mass body;
With
It said first through hole is to have a hole diameter of the first capacitance is the second capacitance and substantially the same capacitance,
In a state in which no voltage is applied between each of the first wing portion and the first fixed electrode and each of the second wing portion and the second fixed electrode, the first wing portion and the second wing portion capacitance by resulting moment wherein Rukoto set the hole diameter of a size obtained by adding the amount of change between the first capacitance and the second capacitance when the inclined said oscillating mass Type sensor. A plurality of second through holes provided in the second wing portion, penetrating between the two main surfaces of the vibrating mass body, and having a total area different from the first through holes;
Each of the first and second through holes is formed with a size of the total area where the first capacitance and the second capacitance are substantially the same capacitance. The capacitive sensor according to claim 1.   The capacitive sensor according to claim 1, wherein the second fixed electrode has an opening or a slit corresponding to the first through hole. The first through hole is formed with the entire area smaller than the second through hole,
3. The opening according to claim 2, wherein the first fixed electrode is formed with an opening or a slit having a size based on a difference in the total area between the first through hole and the second through hole. Capacitive sensor. The first wing portion and the second wing portion are configured in substantially the same shape,
5. The device according to claim 1, wherein the first fixed electrode and the second fixed electrode are configured to have substantially the same shape and are provided on the substrate at the same distance from the rotation axis . The capacitive sensor according to one.

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