JP2014209082A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration sensor capable of preventing reduction of detection accuracy while reducing influences of a thermal strain.SOLUTION: First and second movable parts 20 and 30 are formed in the same plane shape including torsion beams 23 and 33 which become rotation axes in the case of rotation and are supported on a support substrate 11 via anchor parts 24 and 34, respectively, and are disposed in rotational symmetry so as to match mutual virtual lines L which extend along the torsion beams 23 and 33, around a predetermined reference point 19 on the support substrate 11. The first and second movable parts 20 and 30 are then integrated via a connection beam 60 which is positioned on the virtual lines L.

Description

  The present invention relates to an acceleration sensor that detects acceleration applied in a normal direction to a surface direction of a support substrate.

  Conventionally, as this type of acceleration sensor, for example, the following acceleration sensor has been proposed in Patent Document 1.

  That is, in this acceleration sensor, the support substrate is disposed at a predetermined distance from the support substrate, and rotates according to the acceleration (seesaw motion) when acceleration is applied in the normal direction to the surface direction of the support substrate. Possible first and second movable parts are separately provided.

  Specifically, the first and second movable parts are each provided with a rectangular frame-like frame part in which an opening is formed inside, and the frame part so as to divide the opening, and the movable part rotates. And the same size. The torsion beam is provided on the support substrate by being supported by the support substrate via the anchor portion. Further, the frame portion is centered on the torsion beam so that the frame portion (first and second movable portions) can rotate about the torsion beam when the acceleration in the surface direction of the support substrate is applied. In contrast, the shape is asymmetric. The first and second movable parts are disposed rotationally symmetrically about a predetermined reference point on the support substrate.

  Further, lower electrodes facing the first and second movable parts are respectively arranged on the support substrate so as to form a predetermined capacity between the first and second movable parts.

  In such an acceleration sensor, when acceleration is applied in a direction normal to the surface direction of the support substrate, the first and second movable parts rotate about the torsion beam as a rotation axis. The capacitance between the lower electrode changes according to the acceleration. Therefore, acceleration is detected by detecting a change in capacitance.

  In the acceleration sensor, when thermal strain occurs in the support substrate, the distance between the first and second movable parts and the lower electrode changes due to the thermal strain, but the first and second movable parts have the same magnitude. In addition, the first and second movable parts are displaced in the same manner due to thermal distortion. For this reason, the influence of thermal distortion can be reduced by appropriately subtracting the capacitance between the first and second movable parts and the lower electrode.

JP2012-154919A

  However, since the acceleration sensor includes the two movable parts, ie, the first and second movable parts, separately, the acceleration sensor is accelerated against the normal direction of the support substrate and the acceleration relative to the surface direction of the support substrate. 1. The displacement of the second movable part may vary. For this reason, there exists a problem that detection accuracy may fall.

  An object of the present invention is to provide an acceleration sensor that can suppress a decrease in detection accuracy while reducing the influence of thermal distortion.

  In order to achieve the above object, according to the first aspect of the present invention, the support substrate (11) and the support substrate are arranged away from the support substrate in the normal direction to the surface direction of the support substrate, and acceleration is applied in the normal direction. The first and second movable parts (20, 30) that can be rotated according to the acceleration, and the lower electrodes (71 to 74) disposed on the support substrate in a state of facing the first and second movable parts. ), And is characterized by the following points.

  That is, the first and second movable parts each have a torsion beam (23, 33) that serves as a rotation axis when rotating and is supported on the support substrate via the anchor part (24, 34). The plane shapes are the same and are arranged in a rotationally symmetrical manner so that the virtual lines (L) extending along the torsion beam about the predetermined reference point (19) of the support substrate coincide with each other and positioned on the virtual line It is characterized by being integrated via the connecting beam (60).

  According to this, since the first and second movable parts have the same planar shape and are arranged in rotational symmetry, the influence of thermal distortion can be reduced as in the conventional case. And since the 1st, 2nd movable part is integrated via the connection beam, the 1st, 2nd movable part is displaced integrally. For this reason, it can suppress that the displacement of a 1st, 2nd movable part varies with respect to the acceleration with respect to the normal line direction of a support substrate, and the acceleration with respect to the surface direction of a support substrate, and can suppress that detection accuracy falls.

  In addition, since the connecting beam is disposed on a virtual line extending along the torsion beam, the first and second movable parts do not rotate differently when acceleration is applied in the normal direction of the support substrate. The detection accuracy is not lowered.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is a plane schematic diagram of the acceleration sensor in 1st Embodiment of this invention. It is sectional drawing along the II-II line | wire in FIG. It is sectional drawing along the III-III line in FIG. It is a figure which shows the circuit structure of the acceleration sensor shown in FIG. It is sectional drawing which shows the manufacturing process of the sensor part shown in FIG. It is a figure which shows the relationship between a torsion spring constant ratio and a thermal strain ratio. It is a plane schematic diagram of the sensor part in 3rd Embodiment of this invention. It is sectional drawing along the VIII-VIII line in FIG. It is a plane schematic diagram of the sensor part in 4th Embodiment of this invention. It is a figure which shows the circuit structure of the acceleration sensor in other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
A first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the acceleration sensor of this embodiment is configured by connecting a sensor unit 10 that detects acceleration to a circuit unit 100. First, the configuration of the sensor unit 10 will be described.

As shown in FIGS. 1 to 3, the sensor unit 10 is configured by using a substrate 15 in which a semiconductor layer 14 is disposed on a support substrate 11 via first and second insulating films 12 and 13. . For example, the support substrate 11 is a silicon substrate, the first and second insulating films 12 and 13 are made of SiO ₂ or SiN, and the semiconductor layer 14 is made of polysilicon or the like.

  The semiconductor layer 14 is subjected to micromachining to form first and second groove portions 16 and 17, and the first groove portion 16 divides the first and second movable portions 20 and 30, and the first Connection portions 41 to 45 are partitioned by the two groove portions 17. Further, a portion of the semiconductor layer 14 that is not partitioned by the first and second groove portions 16 and 17 is a peripheral portion 50.

  Here, each direction of the x axis, the y axis, and the z axis in FIGS. 1 to 3 will be described. 1 to 3, the x-axis direction is the left-right direction in FIG. 1, the y-axis direction is a direction orthogonal to the x-axis in the plane of the support substrate 11, and the z-axis direction is relative to the plane direction of the support substrate 11. Normal direction.

  The first and second movable parts 20 and 30 connect the rectangular frame-shaped frame parts 22 and 32 in which the planar rectangular openings 21 and 31 are formed, respectively, and the opposite side parts of the openings 21 and 31. The torsion beams 23 and 33 provided in the above are provided, and the planar shape has the same size. The torsion beams 23 and 33 are supported by the support substrate 11 by being connected to the anchor portions 24 and 34 supported by the second insulating film 13.

  Note that portions of the second insulating film 13 that face the frame portions 22 and 32 and the torsion beams 23 and 33 are removed to form openings 18. That is, the frame portions 22 and 32 are arranged apart from the support substrate 11 (first insulating film 12) by a predetermined distance in the z-axis direction, and are suspended from the support substrate 11 (first insulating film 12). 11 is supported.

  The torsion beams 23 and 33 are members that serve as rotation axes that serve as the rotation centers of the first and second movable parts 20 when acceleration in the z-axis direction is applied. In this embodiment, the openings 21 and 31 are divided into two. It is provided to divide. The torsion beams 23 and 33 are formed such that virtual lines L extending along the torsion beams 23 and 33 coincide with each other.

  The frame portions 22 and 32 have an asymmetric shape with respect to the torsion beams 23 and 33 so that the frames 22 and 32 can rotate about the torsion beams 23 and 33 when the acceleration in the z-axis direction is applied. In the present embodiment, the frame portions 22 and 32 are portions of the portions farthest from the torsion beams 23 and 33 in the first portions 22 a and 32 a of the frame portions 22 and 32 from the virtual line L extending along the torsion beams 23 and 33. The length L1 in the x-axis direction to the end is the x-axis from the torsion beams 23 and 33 to the end of the portion farthest from the torsion beams 23 and 33 in the second portions 22b and 32b of the frame portions 22 and 32. It is shorter than the direction length L2. For this reason, in this embodiment, the mass of 1st site | part 22a, 32a is made smaller than the mass of 2nd site | part 22b, 32b. In other words, the torsion beams 23 and 33 pass through the center of gravity of the first and second movable parts 20 and 30 and are aligned with the line segment moved in parallel in the x-axis direction from the center line extending in the y-axis direction. 32 can be said to be provided.

  Further, the first and second movable parts 20 and 30 are arranged rotationally symmetric about a predetermined reference point 19 on the support substrate 11. That is, the first and second movable parts 20 and 30 are arranged so as to coincide with the second movable part 30 when the first movable part 20 is rotated 180 ° with respect to the reference point 19.

  In FIG. 1, the left portion of the frame portion 22 corresponds to the first portion 22 a and the right portion of the frame portion 22 corresponds to the second portion 22 b. Further, the right part of the frame 32 corresponds to the first part 32a, and the right part of the paper corresponds to the second part 32b.

  The first and second movable parts 20 and 30 are integrated via a connecting beam 60. In the present embodiment, the connecting beam 60 is provided so as to coincide with the virtual line L. That is, it can be said that the torsion beams 23 and 33 and the connecting beam 60 are arranged on the same straight line passing through the rotation axis.

  The first and second movable parts 20 and 30 are connected to the connection part 41 via a common movable part wiring 25. Specifically, the movable portion wiring 25 is a portion of the first insulating film 12 that is located immediately below the connection portion 41 through a portion that is located directly below the anchor portion 34 from a portion that is located directly below the anchor portion 24. It is made into the planar rectangular shape extended to. The anchor portions 24 and 34 (first and second movable portions 20 and 30) and the connection portion 41 are connected to the movable portion wiring 25 through contact holes 13a formed in the second insulating film 13, respectively. ing.

  The first insulating film 12 is a portion where the second insulating film 13 is removed, and the first and fourth lower electrodes 71 to 74 are disposed on the portion facing the first and second movable parts 20 and 30. Is formed. Specifically, the first lower electrode 71 is disposed so as to face the first part 22a in the first movable part 20, and the second lower electrode 72 is arranged so as to face the second part 22b in the first movable part 20. Has been placed. In addition, a third lower electrode 73 is disposed so as to face the first portion 32a in the second movable portion 30, and a fourth lower electrode 74 is disposed so as to face the second portion 32b in the second movable portion 30. Yes.

  And the 1st, 4th lower electrodes 71-74 are connected with the connection parts 42-45 via the 1st-4th lower electrode wiring 71a-74a. Specifically, the first to fourth lower electrode wirings 71 a to 74 a are formed integrally with the first to fourth lower electrodes 71 to 74 on the first insulating film 12 and directly below the connection portions 42 to 45. It extends to the part located in. The connecting portions 42 to 45 are connected to the first to fourth lower electrode wirings 71 a to 74 a through contact holes 13 a formed in the second insulating film 13, respectively.

  Further, in the semiconductor layer 14, pads 81 to 86 connected to the circuit unit 100 are formed in the connection portions 41 to 45 and the peripheral portion 50, respectively, and the pads 81 to 86 are connected via wires 91 to 96. The circuit unit 100 is electrically connected. The pad 86 formed on the peripheral portion 50 is applied with a predetermined potential from the circuit portion 100 in order to fix the potential of the peripheral portion 50.

  The above is the configuration of the sensor unit in the present embodiment. Next, the circuit configuration of the acceleration sensor will be described with reference to FIG.

  As shown in FIG. 4, the circuit unit 100 includes a CV conversion circuit 110 including an operational amplifier 101, a capacitor 102, and a switch 103.

  Specifically, the capacitor 102 and the switch 103 are arranged in parallel between the inverting input terminal and the output terminal of the operational amplifier 101. The operational amplifier 101 has an inverting input terminal electrically connected to the first and second movable parts 20 and 30 via the pad 81, and a non-inverting input terminal having a voltage of Vcc / 2 (for example, Vcc = 5V). Is entered.

  The first and third lower electrodes 71 and 73 have a pulse-shaped first carrier wave P1 having an amplitude between the voltage Vcc and 0 V from the circuit unit 100 and having a predetermined frequency via the pads 82 and 84. It is designed to be entered. A second carrier wave P2 having the same amplitude and frequency as the first carrier wave P1 and having a phase difference of 180 ° is input to the second and fourth lower electrodes 72 and 74 via the pads 83 and 85. It has come to be.

In FIG. 4, the capacitance formed between the first part 22 a and the first lower electrode 71 in the first movable part 20 is a capacity C _s1, and the second part 32 b and the fourth lower part in the second movable part 30 are used. A capacitor formed between the electrode 74 and the electrode 74 is shown as a capacitor C _s2 . The capacity formed between the second part 22b and the second lower electrode 72 in the first movable part 20 is _defined as a capacity _Cs3, and the first part 32a and the third lower electrode 73 in the second movable part 30 The capacity formed between them is shown as _Cs4 . In the following _description , a capacitance formed between the first portion 22a and the first lower electrode 71 in the first movable portion 20 is referred to as a capacitance _Cs1, and the second portion 32b and the fourth lower electrode in the second movable portion 30 are used. The capacitor configured between the capacitor 74 and the capacitor 74 is described as a capacitor _Cs2 . The capacity formed between the second part 22b and the second lower electrode 72 in the first movable part 20 is _defined as a capacity _Cs3, and the first part 32a and the third lower electrode 73 in the second movable part 30 The capacity formed between them will be described as _Cs4 . Further, in such a circuit unit 100, acceleration is detected when the switch 103 is turned off, and the capacitor 102 is reset when the switch 103 is turned on (closed).

  Next, the operation of the acceleration sensor will be described. The acceleration sensor detects acceleration in a state where the first carrier wave P1 is input to the first and third lower electrodes 71 and 73 and the second carrier wave P2 is input to the second and fourth lower electrodes 72 and 74. Is called.

When acceleration in the z-axis direction from the support substrate 11 toward the first and second movable parts 20 and 30 is applied, the first and second movable parts 20 and 30 have the torsion beams 23 and 33 as the rotation axes. Integrate rotation according to acceleration. Specifically, the first and second portions 22a and 32a approach the first and third lower electrodes 71 and 73, and the second portions 22b and 32b move away from the second and fourth lower electrodes 72 and 74. 2 The movable parts 20 and 30 rotate. Therefore, the capacitors C _{s1 to} C _s4 are expressed as follows.

( _Formula 1) C _s1 = C ₀ + ΔC _a
(Expression 2) C _s2 = C ₀ −ΔC _a
(Expression 3) C _s3 = C ₀ −ΔC _a
( _Formula 4) C _s4 = C ₀ + ΔC _a
C ₀ is the initial capacity, and ΔC _a is an acceleration term that depends on the acceleration. Therefore, if the capacitance of the capacitor 102 is Cf, the sensor signal _Vout output from the operational amplifier 101 is expressed by the following equation.

(Expression 5) V _out = 4ΔC _a · Vdd / Cf
Further, when thermal distortion occurs in the support substrate 11, distortion terms depending on the distortion are added to the capacitors C _{s1 to} C _s4 , respectively. However, in the present embodiment, the first and second movable parts 20 and 30 have the same planar shape and are arranged rotationally symmetrically with respect to the reference point 19, so that the thermal distortion is the same as in the prior art. Can reduce the effects of

  Next, a method for manufacturing the sensor unit 10 will be described with reference to FIG. 5 is a cross-sectional view taken along line II-II in FIG.

  First, as shown in FIG. 5A, a first insulating film 12 is formed on a support substrate 11 by a CVD (Chemical Vapor Deposition) method or the like.

  Subsequently, as shown in FIG. 5B, a polysilicon, a metal film, or the like is formed on the first insulating film 12 by a CVD method or the like. Then, the movable part wiring 25, the first to fourth lower electrodes 71 to 74, and the first to fourth lower electrode wirings 71a to 74a are formed by appropriately patterning using a mask or the like (not shown).

  Thereafter, as shown in FIG. 5C, the CVD method or the like is performed so as to cover the movable portion wiring 25, the first to fourth lower electrodes 71 to 74, and the first to fourth lower electrode wires 71a to 74a. Thus, the second insulating film 13 is formed. Next, a contact hole 13a is formed in a portion corresponding to the portion connected to the anchor portions 24 and 34 and the connection portions 41 to 55 in the second insulating film 13.

  Subsequently, as shown in FIG. 5D, the substrate 15 is formed by forming the semiconductor layer 14 on the second insulating film 13 by CVD or the like while filling the contact hole 13a. And aluminum etc. are vapor-deposited on the semiconductor layer 14, and the pads 81-86 are formed in a cross section different from FIG. 5 by patterning using a mask.

  Next, as shown in FIG. 5E, the first and second movable parts 20 and 30 are formed by forming the first and second groove parts 16 and 17 in the semiconductor layer 14 using a mask (not shown). The connection portions 41 to 45 and the peripheral portion 50 are partitioned.

  Thereafter, as shown in FIG. 5F, a predetermined region of the second insulating film 13 is removed, and the first and second movable parts 20 and 30 are released from the support substrate 11 (first insulating film 12). Thus, the sensor unit 10 is formed. That is, the second insulating film 13 is a so-called sacrificial layer.

  As described above, in the present embodiment, since the first and second movable parts 20 and 30 have the same planar shape and are arranged rotationally symmetrically, the influence of thermal distortion can be reduced as in the conventional case. . And since the 1st, 2nd movable parts 20 and 30 are integrated via the connection beam 60, the 1st and 2nd movable parts 20 and 30 displace integrally. For this reason, when acceleration is applied in the x-axis direction, the y-axis direction, and the z-axis direction, variation in the displacement of the first and second movable parts 20 and 30 can be suppressed, and a decrease in detection accuracy can be suppressed. .

  Further, the torsion beams 23 and 33 and the connecting beam 60 are arranged on the same straight line passing through the rotation axis. For this reason, when acceleration in the z-axis direction is applied, the first and second movable parts 20 and 30 do not rotate differently, and the detection accuracy does not decrease.

(Second Embodiment)
A second embodiment of the present invention will be described. The present embodiment defines the relationship between the torsion spring constants of the torsion beams 23 and 33 and the torsion spring constant of the connecting beam 60 with respect to the first embodiment, and is otherwise the same as the first embodiment. Therefore, the description is omitted here.

  The basic configuration of the acceleration sensor of the present embodiment is the same as that of the first embodiment, but defines the torsion spring constants of the torsion beams 23 and 33 and the torsion spring constant of the connecting beam 60.

  Specifically, as shown in FIG. 6, when the torsion spring constant [k] of the connecting beam 60 with respect to the torsion spring constant [km] of the torsion beams 23 and 33 is a torsion spring constant ratio [km / k] As the spring constant ratio [km / k] increases, the thermal strain ratio decreases. FIG. 6 shows a simulation result when the thermal strain change of the entire movable part when the torsion spring constant ratio [km / k] is 0.5 is 1 (reference).

  Here, the reason why the thermal strain ratio decreases as the torsion spring constant ratio [km / k] increases will be described. That is, when thermal strain occurs in the support substrate 11, the thermal strain is applied to the torsion beams 23 and 33 via the anchor portions 24 and 34 and then applied to the connecting beam 60. Therefore, when thermal strain is applied to the torsion beams 23 and 33 via the anchor portions 24 and 34, the torsion beams 23 and 33 are more easily twisted as the torsion spring constant [km] of the torsion beams 23 and 33 is smaller. Thermal distortion can be reduced by twisting the beams 23 and 33. That is, the change in thermal distortion of the entire movable part can be reduced.

  For this reason, in this embodiment, the torsion spring constant [k] of the connecting beam 60 is made larger than the torsion spring constant [km] of the torsion beams 23 and 33. More specifically, as shown in FIG. 6, when the torsion spring constant ratio [km / k] is 1.5 or more, the thermal strain ratio decreases sharply. For this reason, in this embodiment, the torsion spring constant ratio [km / k] is 1.5 or more. Furthermore, it is preferable that the torsion spring constant ratio [km / k] is set to 2.0 or more in consideration of manufacturing errors and the like.

  The torsion spring constant [km] of the torsion beams 23 and 33 and the torsion spring constant [k] of the connecting beam 60 are adjusted as appropriate to the width, length, thickness, and the like of the torsion beams 23 and 33 and the connecting beam 60. Can be changed arbitrarily. For example, the torsion spring constant [k] can be increased by increasing the width of the connecting beam 60 (the length in the x-axis direction in FIG. 1).

  And since the torsion spring constant [k] of the connection beam 60 is made larger than the torsion spring constant [km] of the torsion beams 23 and 33, it is possible to suppress a decrease in detection accuracy.

  That is, since the torsion spring constant [k] of the connecting beam 60 is made larger than the torsion spring constant [km] of the torsion beams 23 and 33, the change in thermal strain of the entire movable part can be reduced as described above.

  In the case of an acceleration sensor in which the first and second movable parts 20 and 30 are integrated via the connecting beam 60, the torsion spring constant of the torsion beams 23 and 33 [km ] And the torsion spring constant [k] of the connecting beam 60 depends on the larger one. That is, when the torsion spring constant [k] of the connecting beam 60 is made larger than the torsion spring constant [km] of the torsion beams 23 and 33, it depends on the torsion spring constant [k] of the connecting beam 60.

  As described above, since the thermal strain can be reduced by twisting the torsion beams 23 and 33, the thermal strain applied to the connecting beam 60 can be reduced. For this reason, it can suppress that the torsion spring constant [k] of the connection beam 60 changes, and it can suppress that the torsion spring constant as the whole movable part changes. Therefore, it can suppress that detection accuracy falls.

  As described above, in this embodiment, the torsion spring constant [k] of the connecting beam 60 is made larger than the torsion spring constant [km] of the torsion beams 23 and 33. For this reason, the effect similar to the said 1st Embodiment can be acquired, suppressing further that detection accuracy falls by thermal distortion.

(Third embodiment)
A third embodiment of the present invention will be described. The present embodiment is provided with a cap portion with respect to the first embodiment, and the other aspects are the same as those of the first embodiment, and thus description thereof is omitted here.

  As shown in FIGS. 7 and 8, in the present embodiment, the sensor unit 10 includes a cap unit 200. Specifically, the cap unit 200 is formed of a silicon substrate or the like, and a recess 201 is formed in a portion facing the first and second movable units 20 and 30 in one surface 200 a facing the sensor unit 10. And it joins via the junction part 50a and the joining member 210 in the peripheral part 50 of the sensor part 10, and the 1st, 2nd movable parts 20 and 30 are sealed.

  Note that the bonding member 210 is made of, for example, an oxide film, low dielectric glass, metal, or the like. When a metal is used as the bonding member 210, an insulating film for insulating the sensor unit 10 and the cap unit 200 is formed on the one surface 200a.

  According to this, it is possible to obtain the same effect as that of the first embodiment while suppressing foreign matter from adhering to the first and second movable parts 20 and 30.

(Fourth embodiment)
A fourth embodiment of the present invention will be described. In the present embodiment, the shapes of the first and second movable parts 20 and 30 are changed with respect to the first embodiment, and the other aspects are the same as those in the first embodiment, and thus the description thereof is omitted here. .

  As shown in FIG. 9, in this embodiment, the frame portions 22 and 32 are the ends of the portions farthest from the torsion beams 23 and 33 in the first portions 22 a and 32 a of the frame portions 22 and 32 from the virtual line L. The length L1 in the x-axis direction up to the portion and the length in the x-axis direction from the torsion beams 23 and 33 to the end of the portion farthest from the torsion beam 23 in the second portions 22b and 32b of the frame portions 22 and 32 The length L2 is made equal. The second portions 22b and 32b are formed with through holes 22c and 32c that penetrate the frame portions 22 and 32 in the thickness direction, so that the mass is smaller than that of the first portions 22a and 32a. In the present embodiment, the through holes 22c and 32c correspond to the notches of the present invention.

  According to this, when the acceleration which goes to the 1st, 2nd movable part 20, 30 side from the support substrate 11 is applied, and the 2nd site | part 22b, 32b rotates so that the support substrate 11 may be approached, (2) Rotation of the first and second movable parts 20 and 30 when acceleration is applied from the movable parts 20 and 30 side toward the support substrate 11 and the first parts 22a and 32a rotate so as to approach the support substrate 11 The possible range can be made equal. For this reason, the case where the acceleration which goes to the 1st, 2nd movable part 20 and 30 side from the support substrate 11 is applied, and the case where the acceleration which goes to the support substrate 11 side from the 1st, 2nd movable part 20 and 30 is applied The detection range can be made equal, and as a result, the responsiveness can be made equal.

(Other embodiments)
The present invention is not limited to the embodiment described above, and can be appropriately changed within the scope described in the claims.

  In each of the above embodiments, as shown in FIG. 10, the circuit unit 100 includes a fully differential circuit including an operational amplifier 101, first and second capacitors 102a and 102b, and first and second switches 103a and 103b. A type CV conversion circuit 110 may be provided. In this case, the first capacitor 102a and the first switch 103a are arranged in parallel between the inverting input terminal and the + side output terminal of the operational amplifier 101, and the second capacitor 102b and the second switch 103b are composed of the operational amplifier. 101 is arranged in parallel between the non-inverting input terminal 101 and the negative output terminal. The operational amplifier 101 has an inverting input terminal electrically connected to the first and third lower electrodes 71 and 73 via the pads 82 and 84, and a non-inverting input terminal connected to the second and second via the pads 83 and 85, respectively. The fourth lower electrodes 72 and 74 are electrically connected.

  In addition, a pulse-like carrier wave P having an amplitude between the voltage Vcc and 0 V and having a predetermined frequency is input from the circuit unit 100 to the first and second movable units 20 and 30 via the pad 81. It has become.

As described above, the sensor signals V _out (V1−V2) may be output by calculating the capacitors C _{s1 to} C _s4 using the fully differential CV conversion circuit 110.

  In each of the above embodiments, the first and second movable parts 20 and 30 include the rectangular frame-shaped frame parts 22 and 32, but the frame parts 22 and 32 may not be rectangular frame-shaped.

  In the fourth embodiment, a plurality of through holes 22c and 32c may be formed in the second portions 22b and 32b. In this case, it is preferable that the through holes 22c and 32c are arranged symmetrically with respect to an extension line passing through the center of gravity of the second portions 22b and 32b and extending in the x-axis direction. Further, for example, instead of forming the through holes 22c and 32c in the second parts 22b and 32b, by forming a notch at the end of the second parts 22b and 32b, the mass of the second parts 22b and 32b can be reduced. You may make it smaller than the mass of 1st site | part 22a, 32a.

DESCRIPTION OF SYMBOLS 11 Support substrate 19 Reference point 60 Connection beam 20, 30 1st, 2nd movable part 71-74 1st-4th lower electrode

Claims (5)

A support substrate (11);
First and second movable parts (disposed from the support substrate in a direction normal to the surface direction of the support substrate and capable of rotating in accordance with the acceleration when acceleration is applied in the normal direction. 20, 30),
A lower electrode (71 to 74) disposed on the support substrate in a state of facing the first and second movable parts,
The first and second movable parts each have a torsion beam (23, 33) which serves as a rotation axis when rotating and is supported on the support substrate via anchor parts (24, 34). The plane shapes are the same and are arranged rotationally symmetrically so that the virtual lines (L) extending along the torsion beam about the predetermined reference point (19) of the support substrate coincide with each other. An acceleration sensor, which is integrated through a connecting beam (60) located on a line.   2. The acceleration sensor according to claim 1, wherein the torsion spring constant [k] of the connecting beam is larger than the torsion spring constant [km] of the torsion beam in the first and second movable parts.   The torsion spring constant [km] of the connecting beam is set to be 1.5 times or more larger than the torsion spring constant [k] of the torsion beam in the first and second movable parts. 2. The acceleration sensor according to 2.   The acceleration sensor according to any one of claims 1 to 3, wherein the support substrate includes a cap portion (200) that covers the movable portion. The first and second movable parts have the torsion when one part divided by the virtual line is a first part (22a, 32a) and the other part is a second part (22b, 32b). The length (L1) from the beam to the end of the first part farthest from the torsion beam, and the length from the torsion beam to the end of the second part farthest from the torsion beam (L2) is made equal,
The acceleration according to any one of claims 1 to 4, wherein the second portion has a smaller mass than the first portion by forming a notch (22c, 32c). Sensor.

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