WO2014061099A1 - 慣性センサ - Google Patents
慣性センサ Download PDFInfo
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- WO2014061099A1 WO2014061099A1 PCT/JP2012/076691 JP2012076691W WO2014061099A1 WO 2014061099 A1 WO2014061099 A1 WO 2014061099A1 JP 2012076691 W JP2012076691 W JP 2012076691W WO 2014061099 A1 WO2014061099 A1 WO 2014061099A1
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- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P15/125—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by capacitive pick-up
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- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
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- G01P2015/0811—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining in-plane movement of the mass, i.e. movement of the mass in the plane of the substrate for one single degree of freedom of movement of the mass
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- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
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- G01P2015/0862—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with particular means being integrated into a MEMS accelerometer structure for providing particular additional functionalities to those of a spring mass system
- G01P2015/0882—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with particular means being integrated into a MEMS accelerometer structure for providing particular additional functionalities to those of a spring mass system for providing damping of vibrations
Definitions
- the present invention relates to an inertial sensor. More specifically, the present invention relates to a technique effective when applied to an inertial sensor that detects a physical quantity having a detection axis due to an inertial force acting on an object.
- Patent Document 1 As a background art in this technical field, there is JP-T-2010-513888 (Patent Document 1).
- This Patent Document 1 has a comb-like electrode composed of a movable part (elastic wave mass body) displaced in a uniaxial direction, a movable electrode connected to the movable part, and a fixed electrode connected to the substrate.
- an acceleration sensor structure is described in which all the fixed regions are arranged in the central region of the substrate.
- a comb-like electrode composed of a movable electrode connected to the movable part and a fixed electrode connected to the substrate is arranged in parallel with respect to the displacement direction of the movable part, and overlap region In FIG. 5, the comb-shaped electrode constitutes a capacitor.
- a MEMS inertial sensor (also referred to as a sensor module) that is widely used generally includes a mechanical element including a weight (movable part) and a beam (elastically deforming part) that supports the weight.
- the weight (displacement of the weight due to the acceleration applied to the substrate) is supported by the LSI circuit on the substrate (also called MEMS element) on which the MEMS inertial sensor mechanical element is formed. What is converted into a signal is an acceleration sensor device.
- the amount of displacement of the weight can be detected as a capacitance fluctuation value of a capacitor formed by the movable electrode connected to the weight and the fixed electrode connected to the substrate.
- the facing area of the capacitor is S
- the distance between the electrodes forming the capacitor is d
- the dielectric constant of the object filling the space between the electrodes forming the capacitor is ⁇
- the displacement amount ⁇ d of the weight due to the application of acceleration is less than the distance d between the electrodes. If it is sufficiently small, the capacitance variation of the capacitor due to the application of acceleration can be expressed as ⁇ C / C ⁇ d / d. That is, the fluctuation of the capacitance value of the capacitor is proportional to the acceleration applied to the MEMS inertial sensor. The fluctuation of the capacitance value of the capacitor is converted into an electric signal by an LSI circuit and output.
- the capacitance value of the capacitor may fluctuate even if it is other than the displacement of the weight due to the application of acceleration.
- An example of such a case will be described below as ⁇ cause of offset fluctuation> and ⁇ disadvantage of offset fluctuation>.
- the substrate on which the mechanical element of the MEMS inertial sensor is formed is fixed to the package with an adhesive or the like together with the substrate of the LSI circuit.
- the package in this case is a shape whose shape is previously formed from a ceramic material.
- the inertial sensor is normally used in a temperature range of ⁇ 45 ° C. to 125 ° C. without being maintained at a constant temperature, for example, for in-vehicle use. Since the thermal expansion coefficient of the substrate on which the MEMS inertial sensor mechanical element is formed is different from that of the adhesive and the package material, the mechanical element of the MEMS inertial sensor is formed when the temperature of the environment in which the MEMS inertial sensor package is installed varies.
- Distortion occurs in the formed substrate. Due to this distortion, the relative distance between the movable electrode connected to the weight and the fixed electrode connected to the substrate varies. That is, even when no acceleration is applied, if the temperature of the environment in which the inertial sensor is installed varies, the capacitance value of the capacitor varies and the output of the inertial sensor appears. This is called a zero point offset, and an acceleration sensor having a small zero point offset due to temperature fluctuation is desirable.
- the transfer molding process is a manufacturing process as follows. First, a substrate on which a MEMS inertial sensor is formed, an LSI circuit, and a lead frame are placed in a mold, and then a warmed resin is injected under high pressure to fill the mold. The resin is cooled and solidified to form a mold resin package for fixing the substrate on which the MEMS inertial sensor is formed, the LSI circuit, and the lead frame.
- This transfer molding process has higher productivity than the conventional ceramic packaging process, and is an effective process for reducing the manufacturing cost of the inertial sensor.
- the resin as a constituent material has a feature that the volume expands due to moisture absorption and the volume shrinks due to drying.
- the humidity of the environment in which the package is installed fluctuates, distortion occurs in the substrate on which the MEMS inertial sensor installed therein is formed due to expansion and contraction of the package constituent material. Due to this distortion, the relative distance between the movable electrode connected to the weight and the fixed electrode connected to the substrate varies. That is, even when no acceleration is applied, if the humidity of the environment in which the inertial sensor is installed varies, the capacitance value of the capacitor varies, the output of the inertial sensor appears, and a zero point offset occurs.
- Patent Document 1 there is a prior art disclosed in Patent Document 1 described above for such a problem.
- the technique of this Patent Document 1 when the movable portion is displaced in one axis direction by applying acceleration, the overlap length of the capacitor formed by the comb-shaped electrodes varies, and the capacitance value of the capacitor varies. By measuring this capacitance fluctuation value, the acceleration applied to the movable part can be known.
- Patent Document 1 by arranging all the fixed regions in the central region of the substrate, high insensitivity to substrate bending and similar deformation can be obtained, that is, offset variation can be suppressed.
- the acceleration sensor structure described in Patent Document 1 described above may not be able to suppress noise output when acceleration is applied in a direction other than the acceleration detection axis that is originally desired to be measured.
- rotational acceleration having a vertical rotation axis is applied to the substrate on which the movable part of the acceleration sensor is formed, there is a possibility that noise output cannot be suppressed remarkably.
- this movable part is a mechanical element, it may be displaced even when acceleration other than measurement signals, for example, rotational acceleration having a vertical rotation axis is applied.
- rotational acceleration having a vertical rotation axis When rotational acceleration having a vertical rotation axis is input and displaced, the overlap length of the capacitors formed by all the comb-like electrodes increases or decreases all at once. That is, the capacitance values of the capacitors formed by all the comb-like electrodes increase all at once or decrease all at once.
- the sum of the capacitance values of the capacitors composed of the individual comb-like electrodes is the capacitor on the left side of the fixed area of the movable part, even if the capacitor is on the right side of the fixed area of the movable part. However, it increases all at once or decreases all at once. Such fluctuations are also converted into electric signals by the LSI circuit, and the electric signals may become noise and cause a reduction in accuracy of the inertial sensor.
- the electrical signal exceeds the range that can be handled by the LSI circuit, that is, when the LSI circuit is saturated, the electrical signal is inertial because the signal that is originally intended to be measured is buried in the saturated signal. In some cases, the sensor may stop functioning.
- the present invention has been made in view of such a problem, and a typical object thereof is to cancel a signal due to application of acceleration other than a measurement signal before input to an LSI circuit, and to detect an inertial sensor. It is to provide a technique for suppressing a function stop due to malfunction or erroneous output.
- a typical inertial sensor is a capacitance type inertial sensor and has the following characteristics.
- the inertial sensor includes a movable portion, a positive first electrode pair whose capacitance value increases with respect to a positive displacement of the detection axis of the movable portion, and a capacitance value with respect to a positive displacement of the detection shaft of the movable portion.
- a positive-direction second electrode pair that increases, a negative-direction first electrode pair whose capacitance value decreases with respect to a negative-direction displacement of the detection axis of the movable part, and a negative-direction displacement of the detection axis of the movable part A negative-direction second electrode pair whose capacitance value decreases.
- the movable part is supported at one point of a fixed part provided inside the movable part. Furthermore, the fixed part of the movable part, the fixed part of the positive first electrode pair, the fixed part of the positive second electrode pair, the fixed part of the negative first electrode pair, and the negative first
- the fixed part of the two-electrode pair is arranged on a straight line perpendicular to the detection direction of the inertial sensor. Further, the positive direction first electrode pair and the negative direction first electrode pair are provided on one side with respect to the fixed portion of the movable part, and the positive direction second electrode pair and the negative direction second electrode pair are provided on the other side. And is provided.
- FIG. 1 It is a top view which shows an example of the plane structure of the MEMS acceleration sensor in Embodiment 1 of this invention. It is a circuit diagram which shows an example of the circuit structure of the MEMS acceleration sensor in Embodiment 1 of this invention. It is explanatory drawing which shows an example of the increase / decrease in the signal in each electrode when acceleration and rotation noise are input into the MEMS acceleration sensor in Embodiment 1 of this invention.
- (A), (b) is sectional drawing which shows an example of a cross-sectional structure when the deformation
- (A), (b) is sectional drawing which shows an example of a cross-sectional structure when a deformation
- (A), (b) is sectional drawing which shows an example of a cross-sectional structure when the deformation
- (A), (b) is sectional drawing which shows an example of a cross-sectional structure when a deformation
- (A), (b) is the amount of change in the inter-electrode distance with respect to the non-linear substrate deformation that occurs in the detection axis direction in the comparison between the MEMS acceleration sensor in Embodiment 1 of the present invention and the MEMS acceleration sensor in the prior art, and It is a graph which shows an example of the analysis result of the offset fluctuation amount converted. It is sectional drawing which shows an example of the cross-sectional structure of the sensor chip of the MEMS acceleration sensor in Embodiment 1 of this invention. It is sectional drawing which shows an example of the cross-sectional structure of the package of the MEMS acceleration sensor in Embodiment 1 of this invention. It is a top view which shows an example of the plane structure of the MEMS acceleration sensor in Embodiment 2 of this invention. It is a top view which shows an example of the plane structure of the MEMS acceleration sensor in Embodiment 3 of this invention.
- the constituent elements are not necessarily indispensable unless otherwise specified and apparently indispensable in principle. Needless to say.
- the shape and positional relationship of components and the like when referring to the shape and positional relationship of components and the like, the shape is substantially the same unless otherwise specified and the case where it is not clearly apparent in principle. And the like are included. The same applies to the above numerical values and ranges.
- a typical inertial sensor of the embodiment is a capacitance type inertial sensor, and has the following characteristics.
- the inertial sensor includes a movable portion (movable portions 104, 504, 704) and a positive first electrode pair (detection movable electrodes 105a, 505a) whose capacitance value increases with a positive displacement of the detection axis of the movable portion. , 705a and P-side first electrode pair of detection fixed electrodes 106a, 506a, and 706a) and a positive-direction second electrode pair (for detection) whose capacitance value increases with respect to the positive-direction displacement of the detection axis of the movable portion.
- the capacitance value decreases with respect to the negative displacement of the electrode pair (N-side first electrode pair of detection movable electrodes 109a, 509a and 709a and detection fixed electrodes 110a, 510a and 710a) and the detection axis of the movable part.
- Negative direction A second electrode pair (the detection movable electrodes 109b, 509b, 709b and the detection fixed electrodes 110b, 510b, N second electrode pair side and 710b), the.
- the movable portion is supported at one point of a fixed portion (fixed portions 101, 501, 701) provided inside the movable portion. Furthermore, the fixed part (fixed part 101, 501, 701) of the movable part, the fixed part (fixed part 107, 507, 707) of the first positive electrode pair, and the fixed part of the second positive electrode pair. (Fixed portions 108, 508, 708), the fixed portion (fixed portions 111, 511, 711) of the negative first electrode pair, and the fixed portion (fixed portions 112, 512, 712) of the negative second electrode pair.
- the positive direction first electrode pair and the negative direction first electrode pair are provided on one side with respect to the fixed portion of the movable part, and the positive direction second electrode pair and the negative direction second electrode pair are provided on the other side. And is provided.
- a MEMS acceleration sensor will be described as an example of the inertial sensor.
- the inertial sensor in the present embodiment is not limited to this, and can be applied to an inertial sensor that detects a physical quantity having a detection axis due to an inertial force acting on an object.
- FIG. 1 is a plan view showing an example of a planar configuration of the MEMS acceleration sensor.
- FIG. 1 is a top view of the MEMS acceleration sensor. Note that the planar acceleration MEMS sensor as shown in FIG. 1 may be referred to as a MEMS acceleration sensor element. In the following description, the MEMS acceleration sensor or the MEMS acceleration sensor element may be simply referred to as an acceleration sensor or a sensor element.
- the MEMS acceleration sensor 100 is a capacitance type acceleration sensor, and includes a fixed portion 101, a rigid body 102, beams 103a and 103b, a movable portion 104, a movable detection portion as a structure formed on a substrate. Electrodes (P side) 105a, 105b, detection fixed electrodes (P side) 106a, 106b, fixed portion 107, fixed portion 108, detection movable electrodes (N side) 109a, 109b, detection fixed electrode (N side) 110a 110b, a fixed portion 111, a fixed portion 112, and the like.
- the beams 103a and 103b are also referred to as springs and elastically deformable portions.
- the movable part 104 is also called a movable part mass body.
- the movable detection electrodes 105a, 105b, 109a, and 109b are also called detection electrode movable portions, and the fixed detection electrodes 106a, 106b, 110a, and 110b are also called detection electrode fixed portions.
- the MEMS acceleration sensor 100 As shown in FIG. 1, the MEMS acceleration sensor 100 according to the present embodiment is provided with a fixed portion 101 on a substrate, and the fixed portion 101 has a rigid body extending in the detection axis direction (y direction in FIG. 1).
- the rigid body 102 is further connected to an upper beam 103a and a lower beam 103b that are deformed in the detection axis direction.
- the upper beam 103 a and the lower beam 103 b are connected to the movable portion 104 that is a weight of the MEMS acceleration sensor 100.
- the fixed portion 101 is supported by the substrate, and the fixed portion 101 and the movable portion 104 are connected by the elastically deformable beams 103a and 103b so that the movable portion 104 can be displaced in the y direction in FIG. It has become.
- the y direction in FIG. 1 is a detection direction 115 of the MEMS acceleration sensor 100.
- the detection direction 115 is also called a detection axis direction.
- the movable part 104 is formed with detection movable electrodes 105a, 105b, 109a, and 109b that are formed integrally with the movable part 104, and faces the detection movable electrodes 105a, 105b, 109a, and 109b, respectively.
- the fixed electrodes for detection 106a, 106b, 110a, 110b are formed.
- the fixed electrodes for detection 106a, 106b, 110a, 110b are supported on the substrate via the fixed portions 107, 108, 111, 112, respectively.
- the fixed portion 107 of the detection fixed electrode 106a, the fixed portion 108 of the detection fixed electrode 106b, the fixed portion 111 of the detection fixed electrode 110a, the fixed portion 112 of the detection fixed electrode 110b, and the movable portion 104 are provided at one point.
- the fixed portion 101 supported by the above is disposed on a straight line 116 perpendicular to the detection direction 115 of the MEMS acceleration sensor 100.
- the detection movable electrode 105a and the detection fixed electrode 106a, and the detection movable electrode 105b and the detection fixed electrode 106b pass through the fixed portion 101 of the movable portion 104 with respect to a straight line 116 perpendicular to the detection direction 115 of the acceleration sensor.
- the first direction the positive direction of the y direction in FIG. 1. That is, in FIG. 1, the P-side first electrode pair of the detection movable electrode 105a and the detection fixed electrode 106a is disposed at the upper right position, and the P-side second electrode pair of the detection movable electrode 105b and the detection fixed electrode 106b. Is located in the upper left position. This arrangement is line symmetric with respect to the straight line 116.
- the detection movable electrode 109a and the detection fixed electrode 110a, and the detection movable electrode 109b and the detection fixed electrode 110b pass through the fixed portion 101 of the movable portion 104, and are a straight line 116 perpendicular to the detection direction 115 of the acceleration sensor.
- it is installed in a second direction (a negative direction of the y direction in FIG. 1) different from the first direction. That is, in FIG. 1, the N-side first electrode pair of the detection movable electrode 109a and the detection fixed electrode 110a is arranged at the lower right position, and the N-side second electrode of the detection movable electrode 109b and the detection fixed electrode 110b. The pair is located in the lower left position. This arrangement is line symmetric with respect to the straight line 116.
- the detection-side fixed electrode 110a has an N-side first electrode pair
- the detection-use movable electrode 109b and the detection-use fixed electrode 110b have an N-side second electrode pair.
- Each electrode pair has an opposing parallel plate shape in which the capacitance value varies depending on the interelectrode distance between each detection movable electrode and each detection fixed electrode.
- the P side is also referred to as a positive direction, a positive direction
- the N side is also referred to as a negative direction, a negative direction, and the like.
- the detection movable electrode 105a and the detection fixed electrode 106a, or the detection movable electrode 105b and the detection fixed electrode 106b each form a capacitive element, and are movable by acceleration applied from the outside.
- the portion 104 is displaced in the positive direction of the y direction, the capacitance of each capacitive element increases.
- the detection movable electrode 109a and the detection fixed electrode 110a, or the detection movable electrode 109b and the detection fixed electrode 110b each form a capacitive element, and the movable portion 104 becomes y by the acceleration applied from the outside.
- the capacitance of each capacitive element decreases.
- the detection fixed electrode 110b function as a capacitance detection unit that detects the displacement of the movable unit 104 in the y direction as a capacitance change.
- the structure of the MEMS acceleration sensor 100 configured as described above is made of a semiconductor material such as silicon. Therefore, the beams 103 a and 103 b and the fixed portion 101 and the movable portion 104 connected via the rigid body 102 are electrically connected, and the potential applied to the movable portion 104 is connected to the fixed portion 101. It is configured to be supplied from a through electrode or a wire bonding wiring.
- the fixed portion 107 of the detection fixed electrode 106a, the fixed portion 108 of the detection fixed electrode 106b, the fixed portion 111 of the detection fixed electrode 110a, and the fixed portion 112 of the detection fixed electrode 110b are also respectively a through electrode and a wire.
- Bonding wiring is connected, and it is configured so that charges can flow into or out of the detection fixed electrodes 106a and 106b and the detection fixed electrodes 110a and 110b due to a capacitance change caused by the displacement of the movable portion 104 in the y direction. ing.
- the movable portion 104 is formed of a frame having a square outer peripheral frame and an inner peripheral frame.
- the rigid body 102 supported by the fixed portion 101 is formed in a rectangular shape that is long in the y direction of FIG.
- the beams 103a and 103b are formed from rectangular frames that are long in the x direction in FIG.
- the outer peripheral frame of the frame body of the beams 103a and 103b is connected to the inner peripheral frame of the frame body of the movable portion 104 at one point
- the outer peripheral frame of the frame body of the beams 103a and 103b is a rigid body 102 on the opposite side. Each of the short sides of the rectangle is connected at one point.
- the P-side first electrode pair of the detection movable electrode 105a and the detection fixed electrode 106a are arranged respectively.
- P-side second electrode pair of detection movable electrode 105b and detection fixed electrode 106b, N-side first electrode pair of detection movable electrode 109a and detection fixed electrode 110a, detection movable electrode 109b and detection fixed electrode 110b N-side second electrode pairs are arranged respectively.
- the detection movable electrodes 105 a, 105 b, 109 a, and 109 b are each formed in a rectangular shape that protrudes inward from the inner peripheral frame of the frame of the movable portion 104.
- the detection fixed electrodes 106a, 106b, 110a, 110b are respectively opposed to the detection movable electrodes 105a, 105b, 109a, 109b by linear or L-shaped members supported by the fixing portions 107, 108, 111, 112. As shown, it is formed in a protruding rectangle.
- FIG. 2 is a circuit diagram showing an example of a circuit configuration of the MEMS acceleration sensor.
- the MEMS acceleration sensor includes a sensor chip 170 on which mechanical elements are formed, a capacitance-voltage (CV) conversion circuit 140 as a detection circuit, a differential detection circuit 145, a carrier wave application circuit 130, and a demodulation circuit 150. , And the output terminal 160.
- CV capacitance-voltage
- a structure (movable part 104, beams 103a and 103b, rigid body 102, movable electrodes for detection 105a, 105b, 109a and 109b, fixed electrodes for detection) formed on the substrate shown in FIG. 106a, 106b, 110a, 110b, etc.).
- the P-side first electrode pair (capacitance element CP1) of the detection movable electrode 105a and the detection fixed electrode 106a
- the P-side second electrode of the detection movable electrode 105b and the detection fixed electrode 106b which form the capacitive element.
- a pair (capacitance element CP2), an N-side first electrode pair (capacitance element CN1) of detection movable electrode 109a and detection fixed electrode 110a, an N-side second electrode pair of detection movable electrode 109b and detection fixed electrode 110b ( A capacitive element CN2) is illustrated.
- the sensor chip 170 detects changes in the capacitance values of the capacitive elements CP1, CP2, CN1, and CN2. From the sensor chip 170, a detection signal 143 of capacitance value changes of the capacitive elements CP1 and CP2, and a detection signal 144 of capacitance value change of the capacitive elements CN1 and CN2 are output.
- the capacitance value change detection signals 143 and 144 from the sensor chip 170 are input to the negative input terminals ( ⁇ ) of the operational amplifiers 141 and 142 of the CV conversion circuit 140 outside the sensor chip 170, respectively.
- the positive input terminals (+) of the operational amplifiers 141 and 142 are connected to the ground.
- a capacitive element Cf is connected between the negative input terminal ( ⁇ ) and the output terminal of the operational amplifiers 141 and 142.
- the CV conversion circuit 140 converts the capacitance value change detection signals 143 and 144 from the sensor chip 170 into voltage changes, and the differential detection circuit 145 detects the voltage change amounts. Further, the potential difference signal 146 from the differential detection circuit 145 is measured by a carrier wave generated and demodulated by the carrier wave application circuit 130 and the demodulation circuit 150, converted into a displacement amount of the movable unit 104, and output from the output terminal 160. Can do.
- FIG. 3 is an explanatory diagram showing an example of signal increase / decrease in each electrode when acceleration (detection direction + acceleration application) and rotation noise (rotation ⁇ + vibration noise) are input to the MEMS acceleration sensor.
- ⁇ represents the amount of change
- + represents an increase
- ⁇ represents a decrease.
- the detection movable electrode 105a and the detection fixed electrode 106a form a capacitive element CP1, and the movable portion 104 is positively detected in the positive direction of the detection axis (detection direction 115) by the acceleration applied from the outside (the positive y direction in FIG. 1). ), The capacitance of the capacitive element CP1 increases (+ ⁇ ) as shown in FIG. Further, the detection movable electrode 105b and the detection fixed electrode 106b form a capacitive element CP2, and the movable portion 104 is positively detected by the acceleration applied from the outside (detection direction 115) (y in FIG. 1). When displaced in the positive direction), the capacitance of the capacitive element CP2 increases (+ ⁇ ) as shown in FIG.
- the capacitive element CP1 and the capacitive element CP2 are connected by electrical means such as wire bonding and through electrode wiring, and are summed before the input of the CV conversion circuit 140, which is an arithmetic circuit, to become a capacitance value CP. Therefore, when the movable part 104 is displaced in the plus direction (y positive direction in FIG. 1) of the detection axis (detection direction 115) by the rotational acceleration applied from the outside, as shown in FIG.
- the capacitance fluctuation value (+ ⁇ ) of the capacitive element CP1 and the capacitance fluctuation value (+ ⁇ ) of the capacitive element CP2 are added to double (+ 2 ⁇ ).
- the detection movable electrode 109a and the detection fixed electrode 110a form a capacitive element CN1
- the movable portion 104 is positively detected by the detection axis (detection direction 115) by the acceleration applied from the outside (y in FIG. 1).
- the capacitance of the capacitive element CN1 decreases ( ⁇ ) as shown in FIG.
- the detection movable electrode 109b and the detection fixed electrode 110b form a capacitive element CN2
- the movable portion 104 is positively detected by the acceleration applied from the outside (detection direction 115) (y in FIG. 1).
- the capacitance of the capacitive element CN2 decreases ( ⁇ ) as shown in FIG.
- the capacitive element CN1 and the capacitive element CN2 are connected by electrical means such as wire bonding and through-electrode wiring, and are summed before the input of the CV conversion circuit 140, which is an arithmetic circuit, to obtain a capacitance value CN. Therefore, when the movable part 104 is displaced in the plus direction (y positive direction in FIG. 1) of the detection axis (detection direction 115) by the rotational acceleration applied from the outside, as shown in FIG.
- the capacitance fluctuation value ( ⁇ ) of the capacitive element CN1 and the capacitance fluctuation value ( ⁇ ) of the capacitive element CN2 are added to double ( ⁇ 2 ⁇ ).
- a change in the capacitance value of each capacitor is converted into a voltage change by the CV conversion circuit 140 outside the sensor chip 170, the amount of voltage change is detected by the differential detection circuit 145, and this potential difference is detected by the carrier wave application circuit. It is measured by a carrier wave generated and demodulated by 130 and the demodulation circuit 150, converted into a displacement amount of the movable portion 104, and output from the output terminal 160.
- (+ 4 ⁇ ) is obtained by the differential calculation of (+ 2 ⁇ ) and ( ⁇ 2 ⁇ ). That is, an output signal that is four times the change amount is obtained.
- the detection movable electrode 105a and the detection fixed electrode 106a form a capacitive element CP1
- the movable portion 104 is rotated counterclockwise in the direction perpendicular to the plane of FIG.
- the capacitance of the capacitive element CP1 increases (+ ⁇ ) as shown in FIG.
- the detection movable electrode 105b and the detection fixed electrode 106b form a capacitive element CP2
- the movable portion 104 is rotated counterclockwise in the direction perpendicular to the paper surface of FIG. 1 by rotational acceleration applied from the outside (
- the capacitance of the capacitive element CP2 decreases ( ⁇ ) as shown in FIG.
- the capacitive element CP1 and the capacitive element CP2 are connected by electrical means such as wire bonding and through electrode wiring, and are summed before the input of the CV conversion circuit 140, which is an arithmetic circuit, to become a capacitance value CP. Therefore, when the movable portion 104 is displaced in the counterclockwise direction perpendicular to the paper surface of FIG. 1 (the z positive direction in FIG. 1 is the rotation axis) by the rotational acceleration applied from the outside, as shown in FIG. The capacitance value CP is canceled by the capacitance variation value (+ ⁇ ) of the capacitance element CP1 and the capacitance variation value ( ⁇ ) of the capacitance element CP2, and becomes zero (0).
- the detection movable electrode 109a and the detection fixed electrode 110a form a capacitive element CN1
- the movable portion 104 is rotated counterclockwise in the direction perpendicular to the plane of FIG.
- the capacitance of the capacitive element CN1 decreases ( ⁇ ).
- the detection movable electrode 109b and the detection fixed electrode 110b form a capacitive element CN2
- the movable portion 104 is rotated counterclockwise in the direction perpendicular to the paper surface of FIG. 1 by rotational acceleration applied from the outside (
- the capacitance of the capacitive element CN2 increases (+ ⁇ ) as shown in FIG.
- the capacitive element CN1 and the capacitive element CN2 are connected by electrical means such as wire bonding and through-electrode wiring, and are summed before the input of the CV conversion circuit 140, which is an arithmetic circuit, to obtain a capacitance value CN. Therefore, when the movable portion 104 is displaced in the counterclockwise direction perpendicular to the paper surface of FIG. 1 (the z positive direction in FIG. 1 is the rotation axis) by the rotational acceleration applied from the outside, as shown in FIG. The capacitance value CN is canceled by the capacitance variation value ( ⁇ ) of the capacitance element CN1 and the capacitance variation value (+ ⁇ ) of the capacitance element CN2, and becomes zero (0).
- electrical means such as wire bonding and through-electrode wiring
- the change in the capacitance value of each capacitor is converted into a voltage change by the CV conversion circuit 140 outside the sensor chip 170, the amount of voltage change is detected by the differential detection circuit 145, and this potential difference is detected by the carrier wave application circuit. It is measured by a carrier wave generated and demodulated by 130 and the demodulation circuit 150, converted into a displacement amount of the movable portion 104, and output from the output terminal 160.
- the output from the output terminal (Vout) when the movable portion 104 is displaced in the counterclockwise direction perpendicular to the paper surface in FIG. 1 (the z positive direction in FIG. 1 is the rotation axis) by the acceleration applied from the outside is As shown in FIG. 3, (0) is obtained by the differential operation of (0) and (0).
- a mechanical element is configured when the movable unit 104 is displaced in the counterclockwise direction perpendicular to the paper surface of FIG. 1 (the positive z direction in FIG. 1 is the rotation axis) due to the rotational acceleration applied from the outside.
- the fluctuation of the capacitance value is canceled inside the sensor chip 170, and no signal is input to the arithmetic circuit.
- the electrical signal exceeds the range that can be handled by the LSI circuit, that is, the case where the LSI circuit is saturated, the signal that is originally intended to be measured is buried in the saturated signal. Does not cause the acceleration sensor to stop functioning. That is, canceling out signals due to application of accelerations other than measurement signals before input to the LSI circuit can suppress malfunction of the acceleration sensor due to application of accelerations other than measurement signals and stoppage of functions due to erroneous output.
- FIGS. 4 and 5 are cross-sectional views showing examples of the cross-sectional configuration of the MEMS acceleration sensor.
- FIG. 4 shows a case where the substrate is not deformed
- FIG. 5 shows a case where the substrate is deformed. .
- FIG. 4 is a cross-sectional view showing an example of a cross-sectional configuration of the MEMS acceleration sensor when the substrate is not deformed. 4 is a direction along the detection axis of the MEMS acceleration sensor, (a) is a cross section taken along the line AA ′ in FIG. 1, and (b) is B— This corresponds to the cross section of the straight line indicated by B ′.
- a fixed portion 101 is provided on a substrate 113, and a rigid body 102 extending in the detection axis direction (y direction in FIG. 4) is connected to the fixed portion 101.
- 102 is connected to a beam 103a and a beam 103b which are deformed in the detection axis direction.
- the beam 103a and the beam 103b are connected with the movable part 104 used as the weight of a MEMS acceleration sensor.
- the fixed portion 101 and the substrate 113 are fixed at one point near the center of the movable portion 104 (on a straight line 116 perpendicular to the detection direction (detection axis) 115 shown in FIG. 1).
- a fixed portion 111 is provided on the substrate 113, and a fixed electrode for detection 110a is connected to the fixed portion 111.
- the fixed portion 111 and the substrate 113 are fixed at one point near the center of the movable portion 104 (on a straight line 116 perpendicular to the detection direction (detection axis) 115 shown in FIG. 1).
- FIG. 4 is provided in a direction perpendicular to the paper surface of FIG. 4, and a fixed electrode for detection 106a is connected to the fixed portion 107.
- the fixed portion 107 and the substrate 113 are fixed at one point near the center of the movable portion 104.
- the fixing portions 108 and 112 shown in FIG. 1 are provided in the direction perpendicular to the paper surface of FIG. 4, and the fixing portions 108 and 112 are provided with detection fixed electrodes 106b and 110b, respectively. It is connected.
- the fixed portions 108 and 112 and the substrate 113 are fixed at one point near the center of the movable portion 104.
- FIG. 5 is a cross-sectional view showing an example of a cross-sectional configuration of the MEMS acceleration sensor when the substrate is deformed.
- 5 is a direction along the detection axis of the MEMS acceleration sensor, as in FIG. 4 described above, and (a) is a cross section taken along the line AA ′ in FIG. ) Corresponds to the cross section taken along the line BB 'in FIG. Further, in this case, the deformation of the substrate does not draw a constant curvature along AA ′ and BB ′ but causes distortion in a non-linear manner.
- the fixing portion 101 provided on the substrate 113 is deformed along with nonlinear deformation of the substrate 113.
- the deformation in this case is connected via the rigid body 102 extending in the detection axis direction (y direction in FIG. 5), the beams 103a and 103b deformed in the detection axis direction connected to the rigid body 102, and the beams 103a and 103b.
- the deformation is such that the fixed angle between the movable portion 104 and the substrate 113 is changed.
- the fixing angle depends on the local curvature of deformation of the substrate 113 on which the fixing unit 101 is installed.
- the fixing portion 111 provided on the substrate 113 is deformed along with the non-linear deformation of the substrate 113.
- the deformation in this case is such that the fixing angle between the fixing portion 111 and the substrate 113 changes.
- the fixed angle depends on the local curvature of the deformation of the substrate 113 on which the fixed portion 111 is installed, and is the same as the local curvature of the deformation of the substrate 113 on which the fixed portion 101 of the movable unit 104 is installed. It is.
- the fixing portions 107, 108, and 112 shown in FIG. 1 provided in the direction perpendicular to the paper surface of FIG. 5 are similarly deformed along with the non-linear deformation of the substrate 113.
- the deformation in this case is such that the fixing angle between the fixing portions 107, 108, 112 and the substrate 113 changes.
- the fixing angle depends on the local curvature of the deformation of the substrate 113 on which the fixing portions 107, 108, and 112 are installed, and the local deformation of the substrate 113 on which the fixing portion 101 of the movable portion 104 described above is installed. It is the same as the curvature.
- the fixed portions 101, 111, 107, 108, 112 are installed on a straight line 116 perpendicular to the detection axis. Therefore, for example, the change in the fixing angle accompanying the deformation of the substrate 113 depends on the local curvature of the deformation of the substrate 113 on which the fixing portion 111 shown in FIG. As the substrate 113 is nonlinearly deformed, the components connected to the same deform the fixed angle equally. In other words, no matter how the substrate 113 is deformed along the detection axis direction of the MEMS acceleration sensor, the movable detection electrodes 105a, 105b, 109a, 109b provided on the movable portion 104 of the MEMS acceleration sensor are fixed.
- the detection fixed electrodes 106a, 106b, 110a, 110b, etc. connected to the part 111 and the other fixed parts 107, 108, 112 are all deformed to the same angle with respect to the substrate 113, the relative distance from each other. Will not change.
- the capacitance value formed by the electrode pairs of the detection movable electrodes 105a, 105b, 109a, 109b and the detection fixed electrodes 106a, 106b, 110a, 110b may change. Absent. As a result, the MEMS acceleration sensor according to the present embodiment does not exhibit an offset variation with the deformation of the substrate 113.
- FIG. 6 is a plan view showing an example of a planar configuration of the MEMS acceleration sensor in the prior art.
- FIG. 6 is a top view of the MEMS acceleration sensor.
- the MEMS acceleration sensor 300 is provided with two fixing portions 301a and 301b on a substrate, and the fixing portions 301a and 301b are deformed in the detection axis direction (detection direction 315, y direction in FIG. 6).
- the beams 303a and 303b to be connected are connected.
- the beam 303 a and the beam 303 b are connected to a movable part 304 that is a weight of the MEMS acceleration sensor 300.
- the movable portion 304 is formed with detection movable electrodes 305a, 305b, 309a, and 309b that are formed integrally with the movable portion 304, and so as to face the detection movable electrodes 305a, 305b, 309a, and 309b.
- Fixed detection electrodes 306a, 306b, 310a, 310b are formed.
- the detection movable electrode 305a and the detection fixed electrode 306a, or the detection movable electrode 305b and the detection fixed electrode 306b form a capacitive element, and the movable portion 304 is moved in the y direction by an acceleration applied from the outside.
- the capacitance is displaced in the plus direction, the capacitance of each capacitive element increases.
- the detection movable electrode 309a and the detection fixed electrode 310a, or the detection movable electrode 309b and the detection fixed electrode 310b each form a capacitive element, and the movable portion 304 becomes y by acceleration applied from the outside.
- the capacitance of each capacitive element decreases.
- the detection fixed electrode 310b function as a capacitance detection unit that detects the displacement of the movable unit 304 in the y direction as a capacitance change.
- the structure of the MEMS acceleration sensor 300 configured as described above is made of a semiconductor material such as silicon. Therefore, the fixed portions 301a and 301b and the movable portion 304 connected to each other through the beams 303a and 303b are electrically connected, and the potential applied to the movable portion 304 is connected to the fixed portions 301a and 301b. It is configured to be supplied from a through electrode or a wire bonding wiring.
- the fixed portion 307 of the detection fixed electrode 306a, the fixed portion 308 of the detection fixed electrode 306b, the fixed portion 311 of the detection fixed electrode 310a, and the fixed portion 312 of the detection fixed electrode 310b are also respectively a through electrode and a wire.
- Bonding wiring is connected, and it is configured such that charges can flow into or out of the detection fixed electrodes 306a and 306b and the detection fixed electrodes 310a and 310b due to a capacitance change caused by the displacement of the movable portion 304 in the y direction. ing.
- FIGS. 7 and 8 are cross-sectional views showing examples of the cross-sectional configuration of the MEMS acceleration sensor.
- FIG. 7 shows a case where the substrate is not deformed
- FIG. 8 shows a case where the substrate is deformed. .
- FIG. 7 is a cross-sectional view illustrating an example of a cross-sectional configuration of the MEMS acceleration sensor according to the related art when the substrate is not deformed. 7 is a direction along the detection axis of the MEMS acceleration sensor, (a) is a cross section taken along the line CC ′ in FIG. 6, and (b) is a cross-sectional view taken along the line D-- in FIG. This corresponds to the cross section of the straight line indicated by D ′.
- the substrate 313 is provided with two fixing portions 301a and 301b.
- the fixing portions 301a and 301b are deformed in the detection axis direction (y direction in FIG. 7). It is connected to the beam 303a and the beam 303b. And the beam 303a and the beam 303b are connected with the movable part 304 used as the weight of a MEMS acceleration sensor.
- the fixed portions 301 a and 301 b and the substrate 313 are fixed at two points at both ends of the movable portion 304.
- a fixed portion 307 is provided on the substrate 313, and a fixed electrode for detection 306a is connected to the fixed portion 307.
- the fixed portion 307 and the substrate 313 are fixed with a width in a direction along the detection axis of the MEMS acceleration sensor.
- a fixed portion 311 is provided on the substrate 313, and a fixed electrode for detection 310a is connected to the fixed portion 311.
- the fixed portion 311 and the substrate 313 are fixed with a width in a direction along the detection axis of the MEMS acceleration sensor.
- FIG. 8 is a cross-sectional view showing an example of a cross-sectional configuration of the MEMS acceleration sensor when the substrate is deformed.
- 8 is a direction along the detection axis of the MEMS acceleration sensor, as in FIG. 7 described above, and (a) is a cross section taken along a line CC ′ in FIG. ) Corresponds to the cross section taken along the line DD ′ in FIG. Further, in this case, the deformation of the substrate does not draw a constant curvature along CC ′ and DD ′, but is a non-linear distortion.
- the two fixing portions 301a and 301b provided on the substrate 313 are deformed along with nonlinear deformation of the substrate 313.
- the deformation is such that the fixing angle between the substrate 313 and the movable portion 304 connected via the beams 303a and 303b deforming in the detection axis direction (y direction in FIG. 8) is changed.
- the fixing angle depends on the local curvature of deformation of the substrate 313 on which the fixing portions 301a and 301b are installed.
- the fixing portion 311 provided on the substrate 313 is deformed along with the non-linear deformation of the substrate 313.
- the deformation in this case is such that the fixing angle between the fixing portion 311 and the substrate 313 changes.
- the fixed angle depends on the local curvature of deformation of the substrate 313 on which the fixed portion 311 is installed, and the local deformation of the substrate 313 on which the fixed portions 301a and 301b of the movable portion 304 described above are installed. It is not always the same as the curvature.
- the fixing portion 307 provided on the substrate 313 is deformed along with nonlinear deformation of the substrate 313.
- the deformation in this case is such that the fixing angle between the fixing portion 307 and the substrate 313 changes.
- the fixing angle depends on the local curvature of the deformation of the substrate 313 on which the fixing unit 307 is installed, and the local deformation of the substrate 313 on which the respective fixing units 301a and 301b of the movable unit 304 described above are installed.
- the curvature and the local curvature of the deformation of the substrate 313 on which the fixing portion 311 is installed are not necessarily the same.
- the fixing portions 301a, 301b, 311, 307, 308, and 312 for all the substrates 313 are installed with a distribution with respect to the detection axis.
- the change in the fixing angle accompanying the deformation of the substrate 313 depends on the local curvature of the deformation of the substrate 313 on which the respective fixing portions are installed. Therefore, the components connected to all the fixing portions are non-linear in the substrate 313. With such deformation, the fixed angle does not always deform equally.
- the detection movable electrodes 305a, 305b, 309a, and 309b provided on the movable portion 304 of the MEMS acceleration sensor, and the fixed portion 311
- the detection fixed electrodes 306 a, 306 b, 310 a, 310 b and the like connected to 307 and other fixed portions 308, 312 are not necessarily deformed to the same angle with respect to the substrate 313.
- FIG. 9 shows the amount of change in the interelectrode distance with respect to the nonlinear deformation of the substrate that occurs in the detection axis direction and the converted offset change in the comparison between the MEMS acceleration sensor in this embodiment and the MEMS acceleration sensor in the prior art. It is a graph which shows an example of the analysis result of quantity (capacity fluctuation amount).
- the horizontal axis indicates the end point distortion amount (relative value) of the support substrate, and the vertical axis indicates the fluctuation amount (%) of the detection direction inter-electrode distance with respect to the initial inter-electrode distance.
- the horizontal axis represents the amount of end point distortion (relative value) of the support substrate, and the vertical axis represents the amount of variation (%) of the capacity with respect to the initial capacity.
- the detection fixed electrode and the detection movable electrode are deformed when nonlinear substrate deformation occurs in the detection axis direction. Variation from the case where there is no difference occurs between the detection fixed electrode and the detection movable electrode at different values.
- the amount of distortion (relative value) of the substrate is “10”
- the amount of fluctuation is about “ ⁇ 55%” for the detection fixed electrode, and “+20” for the detection movable electrode. % ".
- the relative distance between the detection fixed electrode and the detection movable electrode varies.
- the capacitance value constituted by the electrode pair composed of the detection fixed electrode and the detection movable electrode Fluctuation occurs, and offset fluctuation appears.
- the amount of distortion (relative value) of the substrate is “10”
- the amount of change in capacitance is about “5.0%”.
- the detection fixed electrode and the detection movable electrode are non-linear deformations of the substrate that occur in the detection axis direction.
- the detection fixed electrode and the detection movable electrode have only a fluctuation amount of about “+ 3%”.
- FIG. 9B a capacitance constituted by an electrode pair composed of the detection fixed electrode and the detection movable electrode.
- the value fluctuation is small and the offset fluctuation amount is extremely small.
- the capacitance variation amount is only about “ ⁇ 0.2%”.
- FIG. 10 is a cross-sectional view showing an example of a cross-sectional configuration of a sensor chip of the MEMS acceleration sensor.
- FIG. 10 shows a cross-sectional view of a sensor chip in which a cap substrate and a through electrode are formed on a device layer.
- the sensor element of the MEMS acceleration sensor is formed on the device layer 127 fixed to the substrate 113.
- the sensor element formed in the device layer 127 includes the movable portion 104, the fixed portion 101 that supports the movable portion 104, and the detection movable electrode formed on the movable portion 104 as described above (FIG. 1 and the like). Included are fixed portions 107, 108, 111, 112, etc. that support the fixed electrodes for detection 106a, 106b, 110a, 110b that make pairs with 105a, 105b, 109a, 109b, respectively.
- the movable portion 104 of the sensor element can be moved in the cavity 120 of the device layer 127.
- the lead electrode 122 is an electrode penetrating the cap substrate 126, and is formed by embedding the insulating film 121 in the cap substrate 126 and electrically separating it.
- the cap substrate 126 is bonded to the device layer 127 on which the sensor element is formed, and the sensor element is protected by the cap substrate 126.
- the fixed portions 107, 108, 111, 112 of the detection fixed electrodes 106a, 106b, 110a, 110b to the substrate 113 and the extraction electrode 122 are electrically connected.
- the extraction electrode 122 is connected to the pad 125 through the patterned conductive film 123.
- the potentials of the detection fixed electrodes 106 a, 106 b, 110 a, and 110 b can be extracted from the pad 125 through the extraction electrode 122 and the conductive film 123.
- the surface of the conductive film 123 is protected by the protective film 124 except for the pad 125.
- FIG. 11 is a cross-sectional view showing an example of a cross-sectional configuration of the package of the MEMS acceleration sensor.
- FIG. 11 shows a cross-sectional view of a package on which the sensor chip is mounted as a mounting form of the sensor chip in FIG. 10 described above.
- a lead frame 211 is installed inside a package member 210, and a circuit chip 200 is mounted on the lead frame 211.
- the circuit chip 200 is formed with an integrated circuit (such as the CV conversion circuit 140, the differential detection circuit 145, and the demodulation circuit 150 shown in FIG. 2 described above) formed of transistors and passive elements.
- the integrated circuit formed in the circuit chip 200 has a function of processing an output signal from the acceleration sensor element, and is a circuit that finally outputs an acceleration signal.
- the pad 203 formed on the circuit chip 200 is connected to the lead frame 211 by a metal wire 204 and is electrically connected to a terminal connected to the outside of the package member 210.
- the sensor chip 170 shown in FIG. 10 described above is mounted on the circuit chip 200.
- the sensor chip 170 is formed with a structure of a MEMS acceleration sensor that constitutes an acceleration sensor element.
- the pad 125 formed on the sensor chip 170 and the pad 201 formed on the circuit chip 200 are connected by a metal wire 202.
- the package member 210 is made of resin, for example.
- a package 220 is configured by placing a circuit chip 200 and a sensor chip 170 mounted on a lead frame 211 in a mold, injecting a resin material melted at a high temperature into the mold, and cooling and curing. That is, the package 220 is formed by a transfer molding process.
- This transfer mold process has higher mass productivity than the conventional ceramic package process, and is an effective process for reducing the manufacturing cost of the acceleration sensor.
- the resin as a constituent material has a feature that the volume expands due to moisture absorption and the volume shrinks due to drying.
- the sensor chip 170 installed inside is distorted due to the expansion and contraction of the package member 210.
- the sensor chip 170 in the present embodiment is connected to the detection movable electrode that is included in the acceleration sensor element and is connected to the movable portion 104, and the substrate 113 even when the substrate 113 is distorted.
- the relative distance of the fixed electrode for detection is not easily changed. That is, when no acceleration is applied, even if the humidity of the environment where the acceleration sensor is installed fluctuates, the capacitance value of the capacitor composed of the detection movable electrode and the detection fixed electrode is unlikely to fluctuate. That is, there is a feature that the zero point offset hardly occurs even if the humidity of the environment where the acceleration sensor is installed varies.
- the movable portion 104 is supported at one point of the fixed portion 101 provided inside the movable portion 104, and further, the fixed portion 101 of the movable portion 104, the fixed portion 107 of the detection fixed electrode 106a, and the detection portion.
- the fixed portion 108 of the fixed electrode 106b, the fixed portion 111 of the detection fixed electrode 110a, and the fixed portion 112 of the detection fixed electrode 110b are detected by the MEMS acceleration sensor 100.
- the P-side first electrode pair and the N-side first electrode pair are provided on one side and the P-side second electrode is provided on the other side with respect to the fixed portion 101 of the movable portion 104.
- the movable unit 104 since the movable unit 104 is supported at one point by the fixed unit 101, the movable unit 104 is robust against distortion in the detection direction 115, and noise due to rotation is further reduced by the P-side first electrode pair ( Between the capacitive element CP1) and the P-side second electrode pair (capacitor element CP2), and between the N-side first electrode pair (capacitor element CN1) and the N-side second electrode pair (capacitor element CN2), different symbols are used. Therefore, the influence of rotational noise can be canceled mechanically in front of the LSI circuit including the CV conversion circuit 140 and the like. Thereby, it is possible to prevent the saturation of the amplifier due to the robustness and the multi-axis sensitivity mechanically.
- signals due to application of acceleration other than measurement signals can be canceled before input to the LSI circuit, and malfunction of the MEMS acceleration sensor and malfunction due to erroneous output can be suppressed. . That is, it is possible to provide a MEMS acceleration sensor that suppresses offset fluctuation when no acceleration is applied due to substrate deformation due to the temperature and humidity of the environment where the MEMS acceleration sensor is installed without increasing the manufacturing cost.
- the P-side first electrode pair and the P-side second electrode pair are arranged in one same direction with respect to a straight line 116 perpendicular to the detection direction 115 passing through the fixed portion 101 of the movable portion 104, and N
- the side first electrode pair and the N-side second electrode pair can be arranged in the same direction of the other.
- the P-side first electrode pair, the P-side second electrode pair, the N-side first electrode pair, and the N-side second electrode pair are respectively opposed types in which the capacitance value varies depending on the inter-electrode distance. It can be set as a parallel plate shape.
- the P-side first electrode pair, the P-side second electrode pair, the N-side first electrode pair, and the N-side second electrode pair are respectively included in the frame configured by the movable portion 104. It can be installed inside the peripheral frame. As these effects, various variations can be realized as a method of installing the electrode pair, which leads to easy manufacture of the acceleration sensor.
- FIG. 12 is a plan view showing an example of a planar configuration of the MEMS acceleration sensor.
- FIG. 12 is a view of the MEMS acceleration sensor as viewed from above.
- the MEMS acceleration sensor 500 in the present embodiment includes a fixed portion 501, a rigid body 502, beams 503a and 503b, a movable portion 504, detection movable electrodes (P side) 505a and 505b, and a detection body as a structure formed on a substrate.
- the description of the same configuration and effect as those of the first embodiment will be omitted, and the configuration and effect different from those of the first embodiment will be described.
- the MEMS acceleration sensor 500 in the present embodiment is provided with a fixed portion 501 on a substrate, and the fixed portion 501 has a rigid body extending in the detection axis direction (y direction in FIG. 12).
- the rigid body 502 is further connected to beams 503a and 503b that are deformed in the detection axis direction.
- the beams 503a and 503b are connected to a movable portion 504 that is a weight of the MEMS acceleration sensor 500.
- the beam 503a and the beam 503b are supported at a plurality of points (three points in the example of FIG.
- the movable portion 504 is formed with detection movable electrodes 505a, 505b, 509a, and 509b that are formed integrally with the movable portion 504, and so as to face the detection movable electrodes 505a, 505b, 509a, and 509b.
- Fixed detection electrodes 506a, 506b, 510a, 510b are formed.
- Each of the detection movable electrode 505a and the detection fixed electrode 506a, or the detection movable electrode 505b and the detection fixed electrode 506b forms a capacitive element, and the movable portion 504 is moved in the y direction by acceleration applied from the outside.
- the capacitance is displaced in the plus direction, the capacitance of each capacitive element increases.
- the detection movable electrode 509a and the detection fixed electrode 510a, or the detection movable electrode 509b and the detection fixed electrode 510b each form a capacitive element, and the movable portion 504 becomes y by acceleration applied from the outside.
- the capacitance of each capacitive element decreases.
- a hole 520 is partially formed in a linear part connecting the detection fixed electrodes 506a, 506b, 510a, 510b and the fixing portions 507, 508, 511, 512, respectively. It is open and the weight is reduced. Further, the movable portion 504 and the fixed portion 501 are connected, and a hole 520 is partially made in the rigid body 502 supported by the fixed portion 501, so that the mass is reduced. Similarly, parts that connect the movable part 504 and the fixed electrodes for diagnosis 523a, 523b, 527a, 527b and the fixed parts 524, 525, 528, 529 are also partially drilled to reduce the weight. It is also possible to do. By reducing the weight in this way, the natural frequency of the entire component can be set to the high frequency side, and the mechanical response to high frequency noise input can be reduced, providing a more reliable acceleration sensor. it can.
- the detection movable electrode 505a and the detection fixed electrode 506a, or the detection movable electrode 505b and the detection fixed electrode 506b are perpendicular to the detection direction (detection axis direction) 515 of the acceleration sensor that passes through the fixed portion 501 of the movable portion 504. It differs from the first embodiment in that the straight lines 516 are installed in opposite directions. That is, in FIG. 12, the P-side first electrode pair of the detection movable electrode 505a and the detection fixed electrode 506a is disposed at the upper right position, and the P-side second electrode pair of the detection movable electrode 505b and the detection fixed electrode 506b. Is located in the lower left position. This arrangement is point-symmetric with respect to the fixed portion 501.
- the detection movable electrode 509a and the detection fixed electrode 510a, or the detection movable electrode 509b and the detection fixed electrode 510b pass through the fixed portion 501 of the movable portion 504, and the detection direction (detection axis direction) 515 of the acceleration sensor.
- the first embodiment is different from the first embodiment in that the straight lines 516 are perpendicular to each other. That is, in FIG. 12, the N-side first electrode pair of the detection movable electrode 509a and the detection fixed electrode 510a is disposed at the lower right position, and the N-side second electrode of the detection movable electrode 509b and the detection fixed electrode 510b. The pair is located in the upper left position. This arrangement is point-symmetric with respect to the fixed portion 501.
- the detection movable electrode 505a and the P-side first electrode pair of the detection fixed electrode 506a with respect to a straight line 516 perpendicular to the detection direction 515 passing through the fixed portion 501 of the movable portion 504.
- the N-side second electrode pair of the detection movable electrode 509b and the detection fixed electrode 510b is arranged in the first direction (the positive direction in the y direction in FIG. 12), and the detection movable electrode 505b and the detection fixed electrode 506b
- the P-side second electrode pair, the detection movable electrode 509a, and the N-side first electrode pair of the detection fixed electrode 510a are arranged in a second direction (a negative direction in the y direction in FIG. 12) different from the first direction.
- the movable portion 504 includes diagnostic movable electrodes 522a, 522b, 526a, which are integrally formed with the movable portion 504. 526b is formed, and diagnostic fixed electrodes 523a, 523b, 527a, 527b are formed so as to face the movable electrodes for diagnosis 522a, 522b, 526a, 526b.
- the diagnostic N-side first electrode pair of the movable electrode 526a and the diagnostic fixed electrode 527a or the diagnostic N-side second electrode pair of the diagnostic movable electrode 526b and the diagnostic fixed electrode 527b each forms a capacitive element. is doing.
- These electrode pairs for diagnosis can be arranged line-symmetrically or point-symmetrically like the electrode pair for detection. That is, in FIG. 12, the diagnostic P-side first electrode pair and the diagnostic P-side second electrode pair are the first to the straight line 516 perpendicular to the detection direction 515 passing through the fixed portion 501 of the movable portion 504.
- the diagnostic N-side first electrode pair and the diagnostic N-side second electrode pair are arranged in a direction (a positive direction of the y direction in FIG. 12), and the second direction (y in FIG. 12) is different from the first direction. (Minus direction).
- the diagnostic P-side first electrode pair and the diagnostic N-side second electrode pair are in the first direction (
- the diagnostic P-side second electrode pair and the diagnostic N-side first electrode pair are arranged in a second direction different from the first direction (the y-direction in FIG. 12). It may be arranged in the negative direction.
- the diagnostic movable electrode 522a When a diagnostic signal is applied between the diagnostic movable electrode 522a and the diagnostic fixed electrode 523a, and the diagnostic movable electrode 522b and the diagnostic fixed electrode 523b forming the capacitive element, the diagnostic movable electrode 522a is diagnosed. Electrostatic force acts between the fixed electrode 523a for diagnosis and the movable electrode for diagnosis 522b and the fixed electrode for diagnosis 523b, and the movable electrode for diagnosis 522a and the movable electrode for diagnosis 522b are displaced in the positive direction of the y direction in FIG. To do. When the diagnostic movable electrodes 522a and 522b are displaced in the positive direction in the y direction in FIG. 12, the movable portion 504 formed integrally with the diagnostic movable electrodes 522a and 522b is also forcibly added in the positive direction in the y direction in FIG. Displace in the direction.
- the diagnostic movable electrode 526a When a diagnostic signal is applied between the diagnostic movable electrode 526a and the diagnostic fixed electrode 527a, and the diagnostic movable electrode 526b and the diagnostic fixed electrode 527b forming the capacitive element, the diagnostic movable electrode 526a Electrostatic force acts between the diagnostic fixed electrode 527a and the diagnostic movable electrode 526b and the diagnostic fixed electrode 527b, and the diagnostic movable electrode 526a and the diagnostic movable electrode 526b are in the minus direction in the y direction of FIG. Displace.
- the diagnostic movable electrodes 526a and 526b are displaced in the negative direction of the y direction in FIG. 12
- the movable portion 504 formed integrally with the diagnostic movable electrodes 526a and 526b is forcibly negative in the y direction of FIG. Displace in the direction.
- the MEMS acceleration sensor of the present embodiment has a function of forcibly displacing the movable part 504 even when no acceleration is applied to the movable part 504. That is, the acceleration sensor has a function of diagnosing a mechanical failure of the acceleration sensor using electrical means, and a highly reliable acceleration sensor can be provided. Furthermore, when the diagnostic function is not used, electrical noise can be blocked by fixing the potentials of the diagnostic fixed electrodes 523a and 523b and 527a and 527b installed around the movable portion of the acceleration sensor.
- Embodiment 3 A MEMS acceleration sensor according to Embodiment 3 will be described with reference to FIG. In the present embodiment, differences from the first embodiment will be mainly described. Further, in the present embodiment, the description will be given by attaching the reference numerals in the 700s. However, the same two digits (the 10s and the 1s) are the same, corresponding to the 100s in the first embodiment. It shall refer to the member of.
- FIG. 13 is a plan view showing an example of a planar configuration of the MEMS acceleration sensor.
- FIG. 13 is a top view of the MEMS acceleration sensor.
- the MEMS acceleration sensor 700 includes a fixed portion 701, a rigid body 702, beams 703a and 703b, a movable portion 704, detection movable electrodes (P side) 705a and 705b, and a detection body as a structure formed on a substrate.
- a MEMS acceleration sensor 700 is provided with a fixed portion 701 on a substrate.
- the fixed portion 701 has a rigid body extending in the detection axis direction (y direction in FIG. 13).
- 702 is connected, and the rigid body 702 is connected to a beam 703a and a beam 703b that are deformed in the detection axis direction.
- the beam 703a and the beam 703b are connected to a movable portion 704 serving as a weight of the MEMS acceleration sensor 700.
- the movable portion 704 is formed with detection movable electrodes 705a, 705b, 709a, and 709b that are formed integrally with the movable portion 704.
- the detection movable electrodes 705a, 705b, 709a, and 709b are opposed to each other.
- Fixed detection electrodes 706a, 706b, 710a, and 710b are formed.
- the detection movable electrode 705a and the detection fixed electrode 706a, or the detection movable electrode 705b and the detection fixed electrode 706b form a capacitive element, and the movable portion 704 is moved in the y direction by acceleration applied from the outside.
- the capacitance is displaced in the plus direction, the capacitance of each capacitive element increases.
- the detection movable electrode 709a and the detection fixed electrode 710a, or the detection movable electrode 709b and the detection fixed electrode 710b each form a capacitive element, and the movable portion 704 becomes y by acceleration applied from the outside.
- the capacitance of each capacitive element decreases.
- the N-side first electrode pair with the fixed electrode 710a and the N-side second electrode pair with the detection movable electrode 709b and the detection fixed electrode 710b are different from the first embodiment. They are respectively arranged outside the outer peripheral frame.
- holes 734 are partially formed in the linear parts connecting the fixed electrodes for detection 706a, 706b, 710a, 710b and the fixing portions 707, 708, 711, 712, respectively. It is open and the weight is reduced. Further, in addition to the rigid body 702 supported by the fixed portion 701, a hole 734 is also partially formed in the movable portion 704 and linear parts connecting the fixed electrodes 731a and 731b for the damper and the fixed portions 732 and 733, respectively. The weight is reduced. By reducing the weight in this way, the natural frequency of the entire component can be set to the high frequency side, and the mechanical response to high frequency noise input can be reduced, providing a more reliable acceleration sensor. it can.
- damper movable electrodes 730 a and 730 b formed integrally with the movable portion 704 are formed on the movable portion 704.
- the damper fixed electrodes 731a and 731b fixed to the substrate are formed so as to face the damper movable electrodes 730a and 730b.
- the damper P-side first electrode pair of the damper movable electrode 730a and the damper fixed electrode 731a and the damper N-side first electrode pair of the damper movable electrode 730b and the damper fixed electrode 731b are the damper, respectively. It constitutes a function.
- This damper function is arranged on the inner side of the inner peripheral frame of the frame body of the movable portion 704.
- the damper composed of the damper movable electrodes 730 a and 730 b and the damper fixed electrodes 731 a and 731 b has a function of inhibiting the displacement of the movable portion 704. Since the function of inhibiting the displacement has an effect proportional to the speed of the movable portion 704, the ability to inhibit is higher as the frequency of the displacement is higher.
- an acceleration sensor having a damper function has a feature that mechanically responds to acceleration in a low frequency band but does not mechanically respond to acceleration in a high frequency band. That is, it has the feature that the frequency band of the acceleration to be measured can be adjusted by the MEMS structure. That is, since the mechanical response to the input of high frequency noise can be reduced, a more reliable acceleration sensor can be provided.
- the damper fixed electrodes 731a and 731b described above may be electrically connected via the fixing portions 732 and 733, respectively, to apply a potential.
- a potential different from that of the movable portion 704 as this potential, the natural frequency of the mechanical part composed of the movable portion 704 and the beams 703a and 703b deforming in the detection axis direction is effectively reduced. "Effect" can be obtained.
- the manufacturing yield is increased as a beam structure that is not easily deformed, and when the acceleration sensor is actually used for measurement, the potential is applied to the damper fixed electrodes 731a and 731b that are electrically connected via the fixing portions 732 and 733.
- a function of adjusting to a desired natural frequency can be provided. That is, it is possible to provide a technique capable of manufacturing an acceleration sensor at a lower cost.
- the present invention made by the present inventor has been specifically described based on the embodiment.
- the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.
- the above-described first to third embodiments are described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.
- a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. .
Abstract
Description
MEMS慣性センサの機械素子が形成された基板は、LSI回路の基板とともに、接着剤などでパッケージに固定される。この場合のパッケージとは、セラミックス材料により、あらかじめ形状が成型されているものである。慣性センサは、通常、一定の温度に維持されることなく、たとえば車載用途であれば、-45℃から125℃の温度範囲で使用される。MEMS慣性センサの機械素子が形成された基板と、接着剤およびパッケージ材料の熱膨張係数は異なるため、MEMS慣性センサのパッケージが設置される環境の温度が変動すると、MEMS慣性センサの機械素子が形成された基板には歪みが発生する。この歪みにより、錘に接続されている可動電極と、基板に接続されている固定電極の相対距離が変動する。つまり、加速度が印加されない場合でも、慣性センサが設置される環境の温度が変動すると、コンデンサの容量値が変動し、慣性センサの出力が現れる。これをゼロ点オフセットと呼び、温度変動によるゼロ点オフセットが小さいものが、加速度センサとしては望ましい。
温度変動によるゼロ点オフセットの発生や、湿度変動によるゼロ点オフセットの発生は、LSI回路で補正することができる。しかし、LSI回路に温度センサや湿度センサを搭載すると、搭載面積分だけチップ面積が増大し、材料費が増大し、LSI回路の製造コストが高くなる。また、補正演算回路を追加して機能を複雑化すると、LSI回路の開発期間が長くなり、製造コストが高くなる。また、補正演算を成立させるため、慣性センサの出荷前検査時に補正調整工程を追加すると、調整費用と調整時間が増大し、慣性センサの製造コストが高くなるデメリットがある。
前述した特許文献1に記載された加速度センサ構造は、本来測定したい加速度検出軸以外の方向に加速度が印加された場合、ノイズ出力を抑制できない可能性がある。特に、加速度センサの可動部が形成された基板に対して、垂直方向の回転軸を持つような回転型の加速度が印加された場合に、顕著にノイズ出力を抑制できない可能性がある。
この可動部は、機械素子であるため、計測信号以外の加速度、たとえば、垂直方向の回転軸を持つような回転型の加速度が印加された場合であっても変位する場合がある。垂直方向の回転軸を持つような回転型の加速度が入力して変位すると、全ての櫛の歯状電極により構成されるコンデンサのオーバーラップ長は一斉に増大、もしくは一斉に減少する。つまり、全ての櫛の歯状電極により構成されるコンデンサの容量値は一斉に増大、もしくは一斉に減少する。つまり、個別の櫛の歯状電極により構成されるコンデンサの容量値の合計は、可動部の固定領域に対して右側のコンデンサであっても、可動部の固定領域に対して左側のコンデンサであっても、一斉に増大、もしくは一斉に減少する。このような変動もLSI回路によって電気信号に変換されてしまうため、当該電気信号がノイズとなって慣性センサの精度低下をもたらす場合がある。
まず、実施の形態の概要について説明する。本実施の形態の概要では、一例として、括弧内に各実施の形態の対応する構成要素および符号を付して説明する。
実施の形態1におけるMEMS加速度センサについて、図1~図11を用いて説明する。
まず、図1を用いて、本実施の形態におけるMEMS加速度センサの平面構成について説明する。図1は、このMEMS加速度センサの平面構成の一例を示す平面図である。この図1は、MEMS加速度センサを上面から見た図である。なお、図1のような平面構成のMEMS加速度センサを、MEMS加速度センサ素子と呼ぶこともある。また、以下においては、MEMS加速度センサあるいはMEMS加速度センサ素子を、単に、加速度センサ、センサ素子などと記述する場合もある。
続いて、図2を用いて、本実施の形態におけるMEMS加速度センサの回路構成について説明する。図2は、このMEMS加速度センサの回路構成の一例を示す回路図である。
検出用可動電極105aと検出用固定電極106aは、容量素子CP1を形成しており、外部から印加された加速度によって可動部104が検出軸(検出方向115)のプラス方向(図1のy正方向)に変位すると、図3に示すように、この容量素子CP1の容量が増加(+δ)するようになっている。また、検出用可動電極105bと検出用固定電極106bは、容量素子CP2を形成しており、外部から印加された加速度によって可動部104が検出軸(検出方向115)のプラス方向(図1のy正方向)に変位すると、図3に示すように、この容量素子CP2の容量が増加(+δ)するようになっている。
一方、検出用可動電極105aと検出用固定電極106aは、容量素子CP1を形成しており、外部から印加された回転型の加速度によって可動部104が図1の紙面垂直方向の反時計回り方向(図1のz正方向が回転軸)に変位すると、図3に示すように、この容量素子CP1の容量が増加(+δ)するようになっている。また、検出用可動電極105bと検出用固定電極106bは、容量素子CP2を形成しており、外部から印加された回転型の加速度によって可動部104が図1の紙面垂直方向の反時計回り方向(図1のz正方向が回転軸)に変位すると、図3に示すように、この容量素子CP2の容量が減少(-δ)するようになっている。
続いて、図4および図5を用いて、本実施の形態におけるMEMS加速度センサの断面構成について説明する。図4および図5は、このMEMS加速度センサの断面構成の一例を示す断面図であり、それぞれ、図4は基板に変形が発生していない場合、図5は基板に変形が発生した場合を示す。
図4は、MEMS加速度センサの、基板に変形が発生していない場合の断面構成の一例を示す断面図である。この図4の断面図は、MEMS加速度センサの検出軸に沿った方向であり、(a)は図1中のA-A’に示した直線における断面、(b)は図1中のB-B’に示した直線における断面に対応している。
続いて図5は、MEMS加速度センサの、基板に変形が発生した場合の断面構成の一例を示す断面図である。この図5の断面図は、前述した図4と同様に、MEMS加速度センサの検出軸に沿った方向であり、(a)は図1中のA-A’に示した直線における断面、(b)は図1中のB-B’に示した直線における断面に対応している。また、この場合の基板の変形とは、A-A’、B-B’に沿って一定の曲率を描くものではなく、非線形に歪みが発生しているものである。
以上、図1~図5を用いて説明した本実施の形態におけるMEMS加速度センサに対して、本実施の形態の特徴を分かり易くするために、図6~図8を用いて、従来技術で作成した典型的なMEMS加速度センサについて説明する。
図6は、従来技術におけるMEMS加速度センサの平面構成の一例を示す平面図である。この図6は、MEMS加速度センサを上面から見た図である。
続いて、図7および図8を用いて、従来技術におけるMEMS加速度センサの断面構成について説明する。図7および図8は、このMEMS加速度センサの断面構成の一例を示す断面図であり、それぞれ、図7は基板に変形が発生していない場合、図8は基板に変形が発生した場合を示す。
図7は、従来技術におけるMEMS加速度センサの、基板に変形が発生していない場合の断面構成の一例を示す断面図である。この図7の断面図は、MEMS加速度センサの検出軸に沿った方向であり、(a)は図6中のC-C’ に示した直線における断面、(b)は図6中のD-D’に示した直線における断面に対応している。
続いて図8は、MEMS加速度センサの、基板に変形が発生した場合の断面構成の一例を示す断面図である。この図8の断面図は、前述した図7と同様に、MEMS加速度センサの検出軸に沿った方向であり、(a)は図6中のC-C’ に示した直線における断面、(b)は図6中のD-D’に示した直線における断面に対応している。また、この場合の基板の変形とは、C-C’、D-D’に沿って一定の曲率を描くものではなく、非線形に歪みが発生しているものである。
続いて、図9を用いて、前述(図1~図5)した本実施の形態におけるMEMS加速度センサと、前述(図6~図8)した従来技術におけるMEMS加速度センサとの比較について説明する。図9は、この本実施の形態におけるMEMS加速度センサと従来技術におけるMEMS加速度センサとの比較において、検出軸方向に生じる非線形な基板の変形に対する電極間距離の変動量、および、換算されるオフセット変動量(容量の変動量)の解析結果の一例を示すグラフである。
続いて、図10を用いて、本実施の形態におけるMEMS加速度センサのセンサチップの断面構成について説明する。図10は、このMEMS加速度センサのセンサチップの断面構成の一例を示す断面図である。図10においては、デバイス層上にキャップ基板と貫通電極を形成したセンサチップの断面図を示す。
続いて、図11を用いて、本実施の形態におけるMEMS加速度センサのパッケージの断面構成について説明する。図11は、このMEMS加速度センサのパッケージの断面構成の一例を示す断面図である。図11においては、前述した図10のセンサチップの実装形態として、このセンサチップを実装したパッケージの断面図を示す。
以上説明した本実施の形態におけるMEMS加速度センサ100によれば、可動部104、検出用可動電極105aと検出用固定電極106aとのP側第1電極対、検出用可動電極105bと検出用固定電極106bとのP側第2電極対、検出用可動電極109aと検出用固定電極110aとのN側第1電極対、検出用可動電極109bと検出用固定電極110bとのN側第2電極対を有する構成において、可動部104はこの可動部104の内側に設けられた固定部101の1点で支持され、さらに、可動部104の固定部101と検出用固定電極106aの固定部107と検出用固定電極106bの固定部108と検出用固定電極110aの固定部111と検出用固定電極110bの固定部112とはMEMS加速度センサ100の検出方向115と垂直な直線116上に配置され、さらに、可動部104の固定部101に対し、一方にP側第1電極対とN側第1電極対とが設けられ、他方にP側第2電極対とN側第2電極対とが設けられていることで、以下のような効果を得ることができる。
実施の形態2におけるMEMS加速度センサについて、図12を用いて説明する。本実施の形態においては、主に前記実施の形態1と異なる点を説明する。また、本実施の形態においては、500番台の符号を付して説明するが、前記実施の形態1の100番台に対応させて、下2桁(10番台と1番台)が同一のものは同一の部材を指すものとする。
まず、図12を用いて、本実施の形態におけるMEMS加速度センサの平面構成について説明する。図12は、このMEMS加速度センサの平面構成の一例を示す平面図である。この図12は、MEMS加速度センサを上面から見た図である。
本実施の形態におけるMEMS加速度センサ500は、図12に示すように、基板に、固定部501が設けられており、この固定部501には、検出軸方向(図12のy方向)に伸びる剛体502が接続され、さらに剛体502からは検出軸方向に変形する梁503aと梁503bに接続されている。そして、梁503aと梁503bは、MEMS加速度センサ500の錘となる可動部504と接続されている。梁503aと梁503bは、それぞれ、剛体502および可動部504と接続する箇所において、複数の支持部521により複数の点(図12の例では3点)で支持されており、検出方向(検出軸方向)515以外への機械的変位が起こりにくくなっている特徴を有する。これは、梁503a,503bのz方向の剛性が強化でき、回転モーメントの抑制にも繋がる。
検出用可動電極505aと検出用固定電極506a、あるいは、検出用可動電極505bと検出用固定電極506bは、可動部504の固定部501を通る、加速度センサの検出方向(検出軸方向)515と垂直な直線516に対して、互いに逆の方向に設置されている点が、前記実施の形態1とは異なる。すなわち、図12において、検出用可動電極505aと検出用固定電極506aのP側第1電極対は右上の位置に配置され、検出用可動電極505bと検出用固定電極506bのP側第2電極対は左下の位置に配置されている。この配置は、固定部501に対して点対称となっている。
また、本実施の形態では、前記実施の形態1に対する追加構成として、図12に示すように、可動部504には、可動部504と一体に形成された診断用可動電極522a,522b,526a,526bが形成されており、この診断用可動電極522a,522b,526a,526bと対向するように、診断用固定電極523a,523b,527a,527bが形成されている。診断用可動電極522aと診断用固定電極523aとの診断用P側第1電極対、あるいは、診断用可動電極522bと診断用固定電極523bとの診断用P側第2電極対、あるいは、診断用可動電極526aと診断用固定電極527aとの診断用N側第1電極対、あるいは、診断用可動電極526bと診断用固定電極527bとの診断用N側第2電極対は、それぞれ容量素子を形成している。
実施の形態3におけるMEMS加速度センサについて、図13を用いて説明する。本実施の形態においては、主に前記実施の形態1と異なる点を説明する。また、本実施の形態においては、700番台の符号を付して説明するが、前記実施の形態1の100番台に対応させて、下2桁(10番台と1番台)が同一のものは同一の部材を指すものとする。
まず、図13を用いて、本実施の形態におけるMEMS加速度センサの平面構成について説明する。図13は、このMEMS加速度センサの平面構成の一例を示す平面図である。この図13は、MEMS加速度センサを上面から見た図である。
本実施の形態におけるMEMS加速度センサ700は、図13に示すように、基板に、固定部701が設けられており、この固定部701には、検出軸方向(図13のy方向)に伸びる剛体702が接続され、さらに剛体702からは検出軸方向に変形する梁703aと梁703bに接続されている。そして、梁703aと梁703bは、MEMS加速度センサ700の錘となる可動部704と接続されている。
また、本実施の形態では、前記実施の形態1に対する追加構成として、図13に示すように、可動部704には、可動部704と一体に形成されたダンパー用可動電極730a,730bが形成されており、このダンパー用可動電極730a,730bと対向するように、基板に固定されたダンパー用固定電極731a,731bが形成されている。ダンパー用可動電極730aとダンパー用固定電極731aとのダンパー用P側第1電極対、および、ダンパー用可動電極730bとダンパー用固定電極731bとのダンパー用N側第1電極対は、それぞれ、ダンパー機能を構成している。このダンパー機能は、可動部704の枠体の内周枠より内側に配置されている。
101 固定部
102 剛体
103a,103b 梁
104 可動部
105a,105b 検出用可動電極(P側)
106a,106b 検出用固定電極(P側)
107 固定部
108 固定部
109a,109b 検出用可動電極(N側)
110a,110b 検出用固定電極(N側)
111 固定部
112 固定部
113 基板
115 検出方向
116 検出方向と垂直な直線
120 空洞
121 絶縁膜
122 引き出し電極
123 導電膜
124 保護膜
125 パッド
126 キャップ基板
127 デバイス層
130 搬送波印加回路
140 CV変換回路
141 オペアンプ
142 オペアンプ
143 検出信号
144 検出信号
145 差動検出回路
146 電位差信号
150 復調回路
160 出力端子
170 センサチップ
200 回路チップ
201 パッド
202 金属ワイヤ
203 パッド
204 金属ワイヤ
210 パッケージ部材
211 リードフレーム
220 パッケージ
300 MEMS加速度センサ(従来技術)
301a,301b 固定部
303a,303b 梁
304 可動部
305a,305b 検出用可動電極(P側)
306a,306b 検出用固定電極(P側)
307 固定部
308 固定部
309a,309b 検出用可動電極(N側)
310a,310b 検出用可動電極(N側)
311 固定部
312 固定部
313 基板
315 検出方向
500 MEMS加速度センサ
501 固定部
502 剛体
503a,503b 梁
504 可動部
505a,505b 検出用可動電極(P側)
506a,506b 検出用固定電極(P側)
507 固定部
508 固定部
509a,509b 検出用可動電極(N側)
510a,510b 検出用固定電極(N側)
511 固定部
512 固定部
515 検出方向
516 検出方向と垂直な直線
520 穴
521 支持部
522a,522b 診断用可動電極(P側)
523a,523b 診断用固定電極(P側)
524 固定部
525 固定部
526a,526b 診断用可動電極(N側)
527a,527b 診断用固定電極(N側)
528 固定部
529 固定部
700 MEMS加速度センサ
701 固定部
702 剛体
703a,703b 梁
704 可動部
705a,705b 検出用可動電極(P側)
706a,706b 検出用固定電極(P側)
707 固定部
708 固定部
709a,709b 検出用可動電極(N側)
710a,710b 検出用固定電極(N側)
711 固定部
712 固定部
715 検出方向
716 検出方向と垂直な直線
730a,730b ダンパー用可動電極
731a,731b ダンパー用固定電極
732 固定部
733 固定部
734 穴
Claims (14)
- [規則91に基づく訂正 13.12.2012]
静電容量型の慣性センサであって、
可動部と、
前記可動部の検出軸の正方向変位に対して容量値が増加する正方向第1電極対と、
前記可動部の検出軸の正方向変位に対して容量値が増加する正方向第2電極対と、
前記可動部の検出軸の正方向変位に対して容量値が減少する負方向第1電極対と、
前記可動部の検出軸の正方向変位に対して容量値が減少する負方向第2電極対と、を有し、
前記可動部は、該可動部の内側に設けられた固定部の1点で支持され、
前記可動部の固定部と、前記正方向第1電極対の固定部と、前記正方向第2電極対の固定部と、前記負方向第1電極対の固定部と、前記負方向第2電極対の固定部とは、前記慣性センサの検出方向と垂直な直線上に配置され、
前記可動部の固定部に対し、一方に前記正方向第1電極対と前記負方向第1電極対とが設けられ、他方に前記正方向第2電極対と前記負方向第2電極対とが設けられていることを特徴とする慣性センサ。 - 請求項1に記載の慣性センサにおいて、
前記正方向第1電極対と前記正方向第2電極対とは、前記可動部の固定部を通る検出方向と垂直な直線に対して第1の方向に配置され、
前記負方向第1電極対と前記負方向第2電極対とは、前記可動部の固定部を通る検出方向と垂直な直線に対して前記第1の方向とは異なる第2の方向に配置されていることを特徴とする慣性センサ。 - 請求項1に記載の慣性センサにおいて、
前記正方向第1電極対と前記負方向第2電極対とは、前記可動部の固定部を通る検出方向と垂直な直線に対して第1の方向に配置され、
前記正方向第2電極対と前記負方向第1電極対とは、前記可動部の固定部を通る検出方向と垂直な直線に対して前記第1の方向とは異なる第2の方向に配置されていることを特徴とする慣性センサ。 - 請求項1に記載の慣性センサにおいて、
前記正方向第1電極対と前記正方向第2電極対と前記負方向第1電極対と前記負方向第2電極対とは、それぞれ、容量値が電極間距離により変動する対向型の平行平板形状であることを特徴とする慣性センサ。 - 請求項1に記載の慣性センサにおいて、
前記正方向第1電極対と前記正方向第2電極対と前記負方向第1電極対と前記負方向第2電極対とは、それぞれ、前記可動部で構成される枠体の内周枠より内側に設置されていることを特徴とする慣性センサ。 - 請求項1に記載の慣性センサにおいて、
前記正方向第1電極対と前記正方向第2電極対と前記負方向第1電極対と前記負方向第2電極対とは、それぞれ、前記可動部で構成される枠体の外周枠より外側に設置されていることを特徴とする慣性センサ。 - 請求項1に記載の慣性センサにおいて、
前記慣性センサの機械的な故障を、診断信号の印加により前記可動部を強制的に変位させて診断する複数の診断用電極対を有し、
前記複数の診断用電極対として、
前記診断信号の印加により前記可動部の検出軸の正方向に変位する診断用正方向第1電極対と、
前記診断信号の印加により前記可動部の検出軸の正方向に変位する診断用正方向第2電極対と、
前記診断信号の印加により前記可動部の検出軸の負方向に変位する診断用負方向第1電極対と、
前記診断信号の印加により前記可動部の検出軸の負方向に変位する診断用負方向第2電極対と、を有し、
前記診断用正方向第1電極対の固定部と、前記診断用正方向第2電極対の固定部と、前記診断用負方向第1電極対の固定部と、前記診断用負方向第2電極対の固定部とは、前記慣性センサの検出方向と垂直な直線上に配置され、
前記可動部の固定部に対し、一方に前記診断用正方向第1電極対と前記診断用負方向第1電極対とが設けられ、他方に前記診断用正方向第2電極対と前記診断用負方向第2電極対とが設けられていることを特徴とする慣性センサ。 - 請求項7に記載の慣性センサにおいて、
前記診断用正方向第1電極対と前記診断用正方向第2電極対とは、前記可動部の固定部を通る検出方向と垂直な直線に対して第1の方向に配置され、
前記診断用負方向第1電極対と前記診断用負方向第2電極対とは、前記可動部の固定部を通る検出方向と垂直な直線に対して前記第1の方向とは異なる第2の方向に配置されていることを特徴とする慣性センサ。 - 請求項7に記載の慣性センサにおいて、
前記診断用正方向第1電極対と前記診断用負方向第2電極対とは、前記可動部の固定部を通る検出方向と垂直な直線に対して第1の方向に配置され、
前記診断用正方向第2電極対と前記診断用負方向第1電極対とは、前記可動部の固定部を通る検出方向と垂直な直線に対して前記第1の方向とは異なる第2の方向に配置されていることを特徴とする慣性センサ。 - 請求項1に記載の慣性センサにおいて、
前記可動部の変位を阻害する複数のダンパー用電極対を有し、
前記複数のダンパー用電極対として、
前記可動部の検出軸の正方向の変位を阻害するダンパー用正方向第1電極対と、
前記可動部の検出軸の負方向の変位を阻害するダンパー用負方向第1電極対と、を有し、
前記ダンパー用正方向第1電極対の固定部と、前記ダンパー用負方向第1電極対の固定部とは、前記慣性センサの検出方向と垂直な直線上に配置され、
前記可動部の固定部に対し、一方に前記ダンパー用正方向第1電極対が設けられ、他方に前記ダンパー用負方向第1電極対が設けられていることを特徴とする慣性センサ。 - 請求項10に記載の慣性センサにおいて、
前記ダンパー用正方向第1電極対および前記ダンパー用負方向第1電極対には、第1の電位が印加され、前記可動部には前記第1の電位とは異なる第2の電位が印加されていることを特徴とする慣性センサ。 - 請求項1に記載の慣性センサにおいて、
前記正方向第1電極対と該正方向第1電極対の固定部との接続部、前記正方向第2電極対と該正方向第2電極対の固定部との接続部、前記負方向第1電極対と該負方向第1電極対の固定部との接続部、前記負方向第2電極対と該負方向第2電極対の固定部との接続部、および、前記可動部と該可動部の固定部との接続部のうちの少なくとも1つの接続部には、穴があけられていることを特徴とする慣性センサ。 - 請求項7に記載の慣性センサにおいて、
前記診断用正方向第1電極対と該診断用正方向第1電極対の固定部との接続部、前記診断用正方向第2電極対と該診断用正方向第2電極対の固定部との接続部、前記診断用負方向第1電極対と該診断用負方向第1電極対の固定部との接続部、および、前記診断用負方向第2電極対と該診断用負方向第2電極対の固定部との接続部のうちの少なくとも1つの接続部には、穴があけられていることを特徴とする慣性センサ。 - 請求項10に記載の慣性センサにおいて、
前記ダンパー用正方向第1電極対と該ダンパー用正方向第1電極対の固定部との接続部、および、前記ダンパー用負方向第1電極対と該ダンパー用負方向第1電極対の固定部との接続部のうちの少なくとも1つの接続部には、穴があけられていることを特徴とする慣性センサ。
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Also Published As
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EP2910952A1 (en) | 2015-08-26 |
JPWO2014061099A1 (ja) | 2016-09-05 |
EP2910952A4 (en) | 2016-08-03 |
US20150301075A1 (en) | 2015-10-22 |
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