JP5906932B2 - Capacitive sensor - Google Patents

Description

  The present invention includes a sensor unit that detects displacement of a movable electrode due to application of a physical quantity to be measured based on a change in capacitance of a capacitor formed by a fixed electrode and a movable electrode, and a sensor unit in a first sealed space. The present invention relates to a capacitance type sensor having a first storage portion for storage.

  Conventionally, as shown in Patent Document 1, for example, a hermetic sealed package in which a hollow portion formed by a lid and a substrate is in a reduced pressure atmosphere and a device is installed in the hollow portion has been proposed. This hermetically sealed package includes pressure adjusting means for adjusting the pressure in the hollow portion and energy transmitting means for transmitting energy for driving the pressure adjusting means.

  The pressure adjusting means has a gas absorbing means that absorbs gas by receiving energy, and the gas absorbing means (pressure adjusting member) has a metal surface that does not contain a gas generating component such as a solder alloy. It is coated with an active metal film. When thermal energy is applied to the pressure adjusting member, the inert metal film diffuses into the solder alloy, and the solder alloy is exposed on the surface. Then, the solder alloy exposed on the surface reacts with the gas molecules in the hollow portion to form an oxide film, or the gas molecules are adsorbed on the surface of the solder alloy, and the gas molecules are absorbed by the solder alloy. As a result, the number of gas molecules in the hollow portion decreases and the degree of vacuum decreases.

JP 2008-182103 A

  By the way, as described above, the capacitance type sensor disclosed in Patent Document 1 is made hollow by reacting the solder alloy with gas molecules in the hollow portion or by adsorbing gas molecules on the surface of the solder alloy. The degree of vacuum in the section is reduced. However, for example, when a sensor that detects a physical quantity to be measured based on a change in capacitance of a capacitor constituted by a movable electrode and a fixed electrode due to application of the physical quantity to be measured is used as a device, the following problems are caused: May occur. That is, when the temperature changes, the pressure in the hollow portion varies and the viscosity in the hollow portion changes. As a result, the displacement amount of the movable electrode fluctuates and the detection accuracy of the physical quantity to be measured may be lowered. On the other hand, according to the invention described in Patent Document 1, since the internal pressure depends on the number of particles, the internal pressure can be kept constant by changing the number of particles. However, if the solder alloy and gas molecules are successively reacted according to the temperature that constantly changes depending on the environment, the life of the pressure adjusting member will be exhausted immediately. For this reason, the detection accuracy may decrease over time.

  In view of the above problems, an object of the present invention is to provide a capacitance type sensor in which a decrease in detection accuracy is suppressed.

In order to achieve the above object, the present invention provides a movable electrode (28), a sensor unit (15) having a fixed electrode (38) opposed to the movable electrode, and a movable electrode by applying a physical quantity to be measured. A displacement detection circuit (56) for detecting the displacement based on a change in capacitance of a capacitor constituted by a fixed electrode and a movable electrode, a bottomed cylindrical cylindrical portion (71), and an opening of the cylindrical portion A first storage portion (70) that has a lid portion (72) that closes the end, and that houses the sensor portion in a first sealed space (S1) constituted by the cylinder portion and the lid portion, and a first sealed space A change unit (90) that changes the shape of the lid so that the pressure of the second electrode is constant, and the sensor unit stores the movable electrode and the fixed electrode in the second sealed space (S2). And a part of the second storage part is formed between the first sealed space and the second sealed space. A movable film (63) that its shape by the force variation changes, the change unit, so that the pressure in the second enclosed space is the same as the pressure in the first enclosed space, the Rukoto change the shape of the lid portion Features.

  Thus, according to the present invention, by changing the shape of the lid (72) and changing the volume of the first sealed space (S1), the pressure of the first sealed space (S1) (hereinafter simply referred to as the internal pressure). Is shown). According to this, as a means for adjusting the internal pressure, the surface of the solder alloy is covered with an Au film, and the internal pressure is adjusted by means of adjusting the internal pressure by adsorbing gas molecules to the solder alloy. A decrease in the lifetime of a certain change portion (90) is suppressed. Thereby, as time passes, it is suppressed that the detection accuracy of the measured physical quantity of the sensor unit (15) decreases.

It is sectional drawing which shows schematic structure of an angular velocity sensor. It is a top view which shows schematic structure of a sensor chip. It is a block diagram which shows the circuit structure of an angular velocity sensor. It is sectional drawing which shows the modification of an angular velocity sensor. It is sectional drawing which shows the modification of an angular velocity sensor. It is sectional drawing which shows the modification of an angular velocity sensor.

Hereinafter, an embodiment in which the capacitance type sensor of the present invention is applied to an angular velocity sensor will be described with reference to the drawings.
(First embodiment)
The angular velocity sensor according to the first embodiment will be described with reference to FIGS. In the following, one direction along the facing surface 11a of the semiconductor substrate 11 is indicated as the x direction, a direction along the facing surface 11a and perpendicular to the x direction is indicated as the y direction, and x defined by the x and y directions. The direction perpendicular to the −y plane is denoted as the z direction. Further, as shown in FIG. 2, a virtual straight line VL along the y direction that bisects the sensor chip 10 in the x direction is indicated by a one-dot chain line. And in order to distinguish the floating part 16 and the fixing | fixed part 17 which are mentioned later, in FIG. 2, these are hatched.

  The angular velocity sensor 100 includes a sensor chip 10, a circuit chip 50, a storage unit 70, and a change unit 90 as main parts. The sensor chip 10 and the circuit chip 50 are mechanically and electrically connected via bumps 60, and the circuit chip 50 and the storage unit 70 are mechanically connected via an adhesive 61. The circuit chip 50 and the storage unit 70 are electrically connected via the wiring 62, and the sensor chip 10 and the circuit chip 50 are stored in the first sealed space S1 of the storage unit 70. In the present embodiment, the first sealed space S1 is in a low pressure state lower than 1 atm, and the main part (piezoelectric element 91) of the changing unit 90 is provided outside the first sealed space S1. Further, the sensor chip 10 and the circuit chip 50 are mechanically coupled not only by the bump 60 but also by the movable film 63 and the covering material 64. Each of the sensor chip 10, the circuit chip 50, the bump 60, the movable film 63, and the covering material 64 constitutes a second sealed space S2, and the second sealed space S2 is also similar to the first sealed space S1, The pressure is lower than 1 atm.

  As shown in FIG. 2, the sensor chip 10 has a symmetric structure via a virtual straight line VL. Therefore, in the following, in order to avoid complicated description, only the left side or the right side of the page of the sensor chip 10 divided by the virtual straight line VL will be described.

  As shown in FIG. 1, the sensor chip 10 includes a semiconductor substrate 11 in which a first semiconductor layer 12, an insulating layer 13, and a second semiconductor layer 14 are sequentially stacked, and a circuit chip 50 in the semiconductor substrate 11. And a sensor unit 15 formed using a known exposure technique on the opposite surface 11a side.

  As shown in FIG. 2, the sensor unit 15 includes a floating unit 16 in which the second semiconductor layer 14 floats with respect to the first semiconductor layer 12 without the insulating layer 13, and the first semiconductor layer through the insulating layer 13. 12 includes a fixing portion 17 to which the second semiconductor layer 14 is fixed, and a sensor pad 18 formed on the fixing portion 17. The floating portion 16 can be displaced (vibrated) in the x direction and the y direction with respect to the first semiconductor layer 12, but the fixed portion 17 and the sensor pad 18 cannot be displaced with respect to the first semiconductor layer 12. .

  As shown in FIG. 2, the floating portion 16 connects the vibrator 19, the displacement portion 20, the first connection portion 21 that connects the vibrator 19 and the displacement portion 20, and the displacement portion 20 to the fixed portion 17. A second connecting portion 22. As described above, the vibrator 19 is connected to the fixed portion 17 via the first connection portion 21, the displacement portion 20, and the second connection portion 22.

  The vibrator 19 includes a weight portion 23 extending in the x direction, beams 24 and 25 extending from the weight portion 23 in the y direction, and electrodes 26 and 27 extending from the beams 24 and 25 in the x direction. The first monitor beams 24 are formed at both ends of the weight portion 23, and the first drive beams 25 are formed at portions of the weight portion 23 sandwiched between the two first monitor beams 24. A plurality of first monitor electrodes 26 extend in a comb shape from the side surface of the first monitor beam 24 on the side of the center P (part indicated by a cross in FIG. 2) of the weight portion 23, and the first drive electrode 27 is a first drive electrode 27. A plurality of comb teeth are extended from the side surface of the beam 25 on the center P side. Each of the constituent elements 23 to 27 of the vibrator 19 has a planar rectangular shape.

  The displacement unit 20 includes a first detection electrode 28 and a first detection beam 29. The first detection beam 29 extends in the y direction, and the first detection electrode 28 extends from the first detection beam 29 in the x direction. The first detection electrode 28 and the first detection beam 29 each have a planar rectangular shape, and a plurality of the first detection electrodes 28 extend in a comb shape from the back surface of the side surface of the first detection beam 29 on the vibrator 19 side. .

  The first connecting portion 21 includes a planar L-shaped arm portion 30 connected to the first detection beam 29, and a spring portion 31 provided between the arm portion 30 and the first detection beam 29. As shown in FIG. 2, the arm portion 30 includes a first portion 30a extending in the x direction from the side surface of the first detection beam 29 on the vibrator 19 side, and y toward the vibrator 19 from the tip of the first portion 30a. A second portion 30b extending in the direction. The spring portion 31 includes a third portion 31a along the x direction and a fourth portion 31b extending in the y direction from the side surface of the third portion 31a on the vibrator 19 side.

  In the present embodiment, the four fourth portions 31b extend from the third portion 31a and are arranged in the x direction. Of the four fourth parts 31b arranged in the x direction, the tip of the fourth part 31b on the first drive beam 25 side is connected to the second part 30b, and the tip of the fourth part 31b on the first detection beam 29 side is connected. The first detection beam 29 is connected. The tips of the remaining two fourth portions 31 b are connected to the first monitor beam 24.

  With the above configuration, the spring portion 31 is easily elastically deformed in the x direction and is difficult to elastically deform in the y direction. Therefore, the vibration in the x direction of the vibrator 19 is hardly transmitted to the displacement portion 20 via the spring portion 31, and the vibration (displacement) in the y direction of the vibrator 19 via the spring portion 31 (connecting portion 21). Thus, it is easy to be transmitted to the displacement portion 20. As will be described later, when the vibrator 19 is displaced (vibrated) in the y direction by the Coriolis force, the displacement unit 20 is also displaced (vibrated) in the y direction.

  The second connecting portion 22 has a shape extending in the x direction from the side surface on the vibrator 19 side of the first detection beam 29 toward the anchor 32 of the fixing portion 17. The other components 19 to 21 of the floating portion 16 excluding the second connecting portion 22 are fixed to the fixing portion 17 via the second connecting portion 22.

  The fixing portion 17 includes an anchor 32, beams 33 to 35 whose main portions extend in the y direction, electrodes 36 to 38 extending from the beams 33 to 35 in the x direction, floating portions 16, anchors 32, and beams 33 to 35. And a base 39 surrounding the electrodes 26 to 28 and 36 to 38.

  The second monitor beam 33 is provided between the first drive beam 25 and the first monitor beam 24 on the displacement unit 20 side, and the second monitor electrode 36 is connected to the first monitor beam 24 in the second monitor beam 33. A plurality of comb-like shapes extend from the facing surface toward the first monitor beam 24. The monitor electrodes 26 and 36 are meshed with each other so as to face each other in the y direction to constitute a monitor capacitor.

  The second drive beam 34 is provided between the two first drive beams 25, and the second drive electrode 37 is a first side facing the side surface from the side surface away from the center P of the second drive beam 34. A plurality of comb teeth are extended toward the drive beam 25. The drive electrodes 27 and 37 are engaged with each other so as to face each other in the y direction to constitute a drive capacitor.

  The second detection beam 35 is provided between the first detection beam 29 and a part of the base 39 along the y direction, and the second detection electrode 38 is on the first detection beam 29 side of the second detection beam 35. From the side surface, a plurality of comb teeth are extended toward the first detection beam 29. The detection electrodes 28 and 38 are engaged with each other so as to face each other in the y direction to constitute a detection capacitor.

  The sensor pad 18 includes a first sensor pad 40 formed on the anchor 32, a second sensor pad 41 formed on the second monitor beam 33, a third sensor pad 42 formed on the second drive beam 34, It has the 4th sensor pad 43 formed in the 2nd detection beam 35, and the 5th sensor pad 44 formed in the base 39. As shown in FIG. 2, the sensor pads 40 to 44 are arranged in the x direction, and each of the sensor pads 40 to 43 is formed on the eight fixing portions 17 and the fifth sensor pad 44 is formed on the two fixing portions 17. Has been.

  A DC voltage is input to the first sensor pad 40. This DC voltage is input to the floating portion 16 via the anchor 32. Thereby, the floating part 16 is equipotential with the DC voltage.

  From the second sensor pad 41, a change in capacitance of the monitor capacitor constituted by the monitor electrodes 26 and 36 is output. Since the first monitor electrode 26 which is a part of the floating portion 16 has the same potential as the DC voltage, it is expected that a signal depending on the DC voltage is output from the second sensor pad 41.

  The third sensor pad 42 is supplied with a drive voltage Vd whose polarity varies at a constant period. Since the first drive electrode 27 which is a part of the floating portion 16 is equipotential with the DC voltage, an electrostatic force depending on the DC voltage and the drive voltage Vd is applied to the drive capacitor formed by the drive electrodes 27 and 37. (Driving force Fd) is generated. Due to the force along the x direction in the driving force Fd, the first driving beam 25 (vibrator 19) on which the first driving electrode 27 is formed is displaced in the x direction. Since the polarity of the drive voltage Vd varies at a constant cycle, the direction of the drive force Fd acting on the first drive electrode 27 also varies at a constant cycle in the x direction. Thereby, the vibrator 19 vibrates at a constant period in the x direction.

  From the fourth sensor pad 43, the capacitance change of the detection capacitor constituted by the detection electrodes 28 and 38 is output.

  A constant voltage is input to the fifth sensor pad 44. With this constant voltage, the potential of the base 39 (sensor chip 10) is kept constant.

  As shown in FIG. 1, the circuit chip 50 includes a semiconductor substrate 51, a circuit unit 52 configured on one surface 51 a of the semiconductor substrate 51 for processing an output signal of the sensor chip 10, and an electrical connection with the circuit unit 52. And a pad 53 connected to the.

  As shown in FIG. 3, the circuit unit 52 includes a monitor circuit 54 that detects a vibration state (vibration amplitude and vibration frequency) of the vibrator 19 in the x direction, a drive circuit 55 that generates a drive voltage Vd, and the vibrator 19. A displacement detection circuit 56 for detecting a displacement amount (vibration amplitude) in the y direction.

  The monitor circuit 54 detects the vibration state (vibration amplitude) of the vibrator 19 in the x direction based on the change in the capacitance of the monitor capacitor input from the second sensor pad 41.

  The drive circuit 55 generates a drive voltage Vd (drive force Fd) in which the vibration amplitude and vibration frequency in the x direction are constant based on the output signal of the monitor circuit 54, and the generated drive voltage Vd is used as the third sensor pad. 42. Thus, even if the vibration state of the vibrator 19 changes due to changes in internal pressure, temperature, etc., the vibration state in the x direction of the vibrator 19 is kept constant.

  The displacement detection circuit 56 converts the displacement amount (vibration amplitude) in the y direction of the displacement unit 20 (vibrator 19) into an electric signal based on the capacitance change of the detection capacitor input from the fourth sensor pad 43. Is.

  In addition to the above components, the circuit unit 52 includes a DC voltage application circuit (not shown) that inputs a DC voltage to the first sensor pad 40 and a constant voltage generation circuit that inputs a constant voltage to the fifth sensor pad 44. (Not shown).

  The pad 53 includes a circuit pad 57 corresponding to the sensor pad 18 and an external pad 58 electrically connected to an internal terminal 73 described later. The sensor pad 18 and the circuit pad 57 are mechanically and electrically connected via the bump 60, and the internal terminal 73 and the external pad 58 are electrically connected via the wiring 62.

  As shown in FIG. 1, each of the sensor pad 18, the circuit pad 57, and the bump 60 is covered with a covering material 64, and the sensor chip 10 and the circuit chip 50 are mechanically interposed via a movable film 63. It is connected. As described above, a plurality of sensor chips 10 are arranged in the x direction. Similarly, a plurality of circuit pads 57 and bumps 60 are arranged in the x direction, and the coating material 64 extends in the x direction. . On the other hand, the movable film 63 has a shape extending in the y direction, its end is covered with the coating material 64, and the overall shape of the above-described components 18, 57, 60, 64, 43 is annular. Is made. The annular member, the sensor chip 10, and the circuit chip 50 constitute a second sealed space S <b> 2, and the internal pressure is variable by the movable film 63. The movable film 63 has such a rigidity that it changes following the internal pressure of the first sealed space S1, and the respective internal pressures of the first sealed space S1 and the second sealed space S2 are movable film 63. It becomes the composition which becomes equal by modification of.

  As shown in FIG. 1, the storage unit 70 includes a bottomed cylindrical tube portion 71 and a lid portion 72 that closes an opening of the tube portion 71. The cylinder portion 71 is provided with an internal terminal 73 provided on the inner surface of the side portion, an internal wiring 74 provided inside the side portion, and an external terminal 75 provided on the outer surface of the bottom portion. As described above, the internal terminal 73 and the external pad 58 are electrically connected via the wiring 62, and the electrical signal of the circuit chip 50 is transmitted from the external pad 58, the wiring 62, the internal terminal 73, the internal wiring 74, And it outputs to the outside via the external terminal 75. The cylinder portion 71 and the lid portion 72 are mechanically and electrically connected, and the lid portion 72 is fixed to the ground potential. As shown in FIG. 1, the lid portion 72 is formed with a thin portion 72 a that is locally thin.

  Next, the principle of angular velocity detection will be described. When an angular velocity is applied in the z direction while the vibrator 19 is vibrating in the x direction by the driving force Fd, a Coriolis force Fc is generated in the vibrator 19 in the y direction. When the transducer 19 is displaced in the y direction by the Coriolis force Fc, the displacement portion 20 (first detection electrode 28) coupled to the transducer 19 via the first coupling portion 21 is displaced in the y direction. To do. As a result, the relative distance between the detection electrodes 28 and 38 varies, and the capacitance of the detection capacitor changes. This change in capacitance is input to the circuit chip 50 through the second sensor pad 41, the bump 60, and the pad 53 formed on the second detection electrode 38.

  Next, the changing unit 90 that is a characteristic point of the angular velocity sensor 100 according to the present embodiment will be described. The changing part 90 changes the shape of the lid part 72 so that the pressure in the first sealed space S1 is constant. The change unit 90 includes a piezoelectric element 91, a temperature sensor 92, and a supply unit 93. The piezoelectric element 91 is an element that generates a pressure according to a current flowing through the piezoelectric element 91, and has a property that a pressure generation direction varies depending on a direction of the flowing current. The piezoelectric element 91 according to this embodiment has a property of generating pressure in one direction and the opposite direction. The piezoelectric element 91 is fixed to the thin portion 72a of the lid portion 72 via an insulating member (not shown), and is installed outside the first sealed space S1. When a current in a certain direction (hereinafter referred to as a first current) flows through the piezoelectric element 91, the piezoelectric element 91 bends the thin portion 72 a in the z direction so as to move away from the sensor chip 10. The volume of S1 is expanded and the pressure is reduced. On the contrary, when a current in the direction opposite to the first current (hereinafter referred to as a second current) flows through the piezoelectric element 91, the piezoelectric element 91 moves the thin portion 72 a to z so as to approach the sensor chip 10. By bending in the direction, the volume of the first sealed space S1 is contracted and the pressure is increased.

  The temperature sensor 92 measures the temperature of the first sealed space S1. Since the pressure in the first sealed space S1 depends on the temperature, the pressure in the first sealed space S1 can be measured based on the output signal of the temperature sensor 92.

  Based on the output signal of the temperature sensor 92, the supply unit 93 allows current to flow through the piezoelectric element 91 so that the pressure in the first sealed space S <b> 1 is constant. The supply unit 93 determines that the internal pressure has increased when the output signal of the temperature sensor 92 exceeds the threshold value, and supplies the first current to the piezoelectric element 91. In addition, when the output signal of the temperature sensor 92 falls below the threshold value, the supply unit 93 determines that the internal pressure has decreased and supplies the second current to the piezoelectric element 91.

  When the first current flows through the piezoelectric element 91, the volume of the first sealed space S1 expands, and the movable film 63 also changes accordingly. As a result, the volume of the second sealed space S2 is also expanded, and the internal pressures of the two sealed spaces are similarly reduced. On the contrary, when the second current flows through the piezoelectric element 91, the volume of the first sealed space S1 contracts, and the movable film 63 also changes accordingly. As a result, the volume of the second sealed space S2 is also contracted, and the internal pressures of the two sealed spaces are similarly reduced. From the above, when the shape of the lid 71 is changed so that the pressure in the first sealed space S1 is constant, the movable film 63 is also changed so that the pressure in the second sealed space S2 is constant. Therefore, the internal pressure of each of the first sealed space S1 and the second sealed space S2 is kept constant.

  Next, functions and effects of the angular velocity sensor 100 according to the present embodiment will be described. As described above, by changing the shape of the lid 72 and changing the volume of the first sealed space S1, the pressures in the first sealed space S1 and the second sealed space S2 (hereinafter simply referred to as internal pressure) are constant. It is said. According to this, as a means for adjusting the internal pressure, the surface of the solder alloy is covered with an Au film, and the internal pressure is adjusted by means of adjusting the internal pressure by adsorbing gas molecules to the solder alloy. A reduction in the lifetime of a certain change portion 90 is suppressed. Thereby, it is suppressed that the detection accuracy of the angular velocity of the sensor part 15 falls over time.

  The lid 72 is fixed to the ground potential, and the piezoelectric element 91 is outside the first sealed space S1. According to this, unlike the configuration in which the piezoelectric element is in the first sealed space S1, the piezoelectric element 91 and the sensor unit 15 are physically separated. Therefore, when a part of the members constituting the piezoelectric element 91 is peeled off, the peeled part is suppressed from affecting the sensor unit 15. Further, it is possible to suppress the noise generated from the current flowing through the piezoelectric element 91 from being applied to the sensor unit 15. Therefore, the detection accuracy of the sensor unit 15 is suppressed from being lowered as compared with the configuration in which the piezoelectric element is in the first sealed space S1.

  The pressure (internal pressure) of the sealed space is a low pressure state lower than 1 atm. In this case, the fluctuation of the Qs value representing the vibration state of the vibrator 19 in the y direction and the Qd value representing the vibration state in the x direction are larger than when the internal pressure is 1 atm. Therefore, as described above, a configuration in which the internal pressure is adjusted to be constant is preferable.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In this embodiment, the supply part 93 showed the example which sends an electric current to the piezoelectric element 91 so that the internal pressure of 1st sealed space S1 may become fixed based on the output signal of the temperature sensor 92. FIG. However, as shown in FIG. 4, the supply unit 93 employs a configuration in which a current is passed through the piezoelectric element 91 so that the internal pressure of the first sealed space S <b> 1 is constant based on the output signal of the drive circuit 55. You can also. The vibration amplitude A in the x direction of the vibrator 19 depends on the Qd value representing the vibration state in the x direction and the driving force Fd that causes the drive circuit 55 to vibrate the vibrator 19 in the x direction. When the Qd value varies due to the internal pressure variation, the drive circuit 55 varies the drive force Fd in order to keep the vibration amplitude A constant. The value of the driving force Fd is determined by the output signal of the driving circuit 55. Therefore, the pressure in the first sealed space S1 can be made constant by changing the shape of the lid 72 based on the output signal of the drive circuit 55. In the case of this configuration, as shown in FIG. 4, the change unit 90 does not need to have the temperature sensor 92, and the output signal of the drive circuit 55 is input to the supply unit 93.

  In the present embodiment, an example in which the movable film 63 is provided between the sensor chip 10 and the circuit chip 50 is shown. However, the movable film 63 may be formed on the sensor chip 10 as shown in FIG. In this modification, the movable film 63 is formed by reducing the thickness of a part of the first semiconductor layer 12.

  In the present embodiment, an example in which the piezoelectric element 91 is provided outside the first sealed space S1 is shown. However, as shown in FIG. 6, a configuration in which the piezoelectric element 91 is provided in the first sealed space S1 may be employed.

  In the present embodiment, an example in which the second sealed space S2 is configured in the first sealed space S1 has been described. However, as shown in FIG. 6, the second sealed space S2 may not be provided.

  In this embodiment, the example which employ | adopted the angular velocity sensor as an electrostatic capacitance type sensor was shown. However, the use of the capacitive sensor is not limited to the above example, and may be employed for an acceleration sensor, for example.

DESCRIPTION OF SYMBOLS 15 ... Sensor part 28 ... Movable electrode 38 ... Fixed electrode 56 ... Displacement detection circuit 70 ... 1st accommodating part 71 ... Cylindrical part 72 ... Cover part 90 ... Change Part S1 ... first sealed space 100 ... angular velocity sensor

Claims (6)

A sensor unit (15) having a movable electrode (28) and a fixed electrode (38) facing the movable electrode;
A displacement detection circuit (56) for detecting displacement of the movable electrode due to application of a physical quantity to be measured based on a change in capacitance of a capacitor constituted by the fixed electrode and the movable electrode;
A first sealed space (S1) that includes a cylindrical portion with a bottom (71) and a lid portion (72) that closes an open end of the cylindrical portion, and includes the cylindrical portion and the lid portion. A first storage portion (70) for storing the sensor portion therein;
A change unit (90) that changes the shape of the lid so that the pressure in the first sealed space is constant ,
The sensor unit includes a second storage unit that stores the movable electrode and the fixed electrode in a second sealed space (S2),
A part of the second storage part is a movable film (63) whose shape changes due to pressure fluctuations in the first sealed space and the second sealed space,
It said change unit is configured so that the pressure in the second enclosed space is the same as the pressure of the first sealed space, the capacitance type sensor according to claim Rukoto change the shape of the lid.   The changing part includes a piezoelectric element (91) provided in the lid part, and a supply part (93) for supplying a current corresponding to a pressure change in the first sealed space to the piezoelectric element. The capacitive sensor according to claim 1. The lid is fixed to a ground potential;
The capacitive sensor according to claim 2, wherein the piezoelectric element is outside the first sealed space. The changing part has a temperature sensor (92) for measuring the temperature in the first sealed space,
The said change part changes the shape of the said cover part so that the pressure of a said 1st sealed space may become constant based on the output signal of the said temperature sensor. The capacitance type sensor according to item. The sensor unit is
A vibrator (19) that is displaceable in each of an x-direction and a y-direction that are orthogonal to each other;
A drive circuit (55) for vibrating the vibrator in the x direction;
A monitor circuit (54) for detecting a vibration amplitude in the x direction of the vibrator,
The displacement detection circuit detects a change in capacitance of the capacitor due to displacement of the vibrator in the y direction,
The drive circuit adjusts the vibration amplitude in the x direction to be constant based on the output signal of the monitor circuit,
The said change part changes the shape of the said cover part so that the pressure of a said 1st sealed space may become constant based on the output signal of the said drive circuit. The capacitance type sensor according to item. The first closed space and the second closed space each inner pressure, an electrostatic capacitance type sensor according to any one of claims 1-5, characterized in a low low pressure der Rukoto than 1 atm.

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