WO2012077494A1 - 複合センサ - Google Patents
複合センサ Download PDFInfo
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- WO2012077494A1 WO2012077494A1 PCT/JP2011/076884 JP2011076884W WO2012077494A1 WO 2012077494 A1 WO2012077494 A1 WO 2012077494A1 JP 2011076884 W JP2011076884 W JP 2011076884W WO 2012077494 A1 WO2012077494 A1 WO 2012077494A1
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- detection
- weight
- capacitance
- composite sensor
- voltage signal
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B3/00—Devices comprising flexible or deformable elements, e.g. comprising elastic tongues or membranes
- B81B3/0018—Structures acting upon the moving or flexible element for transforming energy into mechanical movement or vice versa, i.e. actuators, sensors, generators
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
- G01C19/56—Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
- G01C19/5719—Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces using planar vibrating masses driven in a translation vibration along an axis
- G01C19/5733—Structural details or topology
- G01C19/574—Structural details or topology the devices having two sensing masses in anti-phase motion
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- 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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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/18—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration in two or more dimensions
Definitions
- the present invention relates to a composite sensor, and in particular, a micro electro mechanical system (MEMS) that is formed by a semiconductor micromachining technology and detects a physical quantity related to acceleration, angular velocity (rotation), pressure, and the like as a change in capacitance.
- MEMS micro electro mechanical system
- the present invention relates to a technology that is effective when applied to a composite sensor composed of Systems).
- Patent Document 1 Japanese Patent Application Laid-Open No. 10-239347
- Patent Document 2 Japanese Patent Application Laid-Open No. 2002-005950
- These composite sensors shown in Patent Document 1 and Patent Document 2 detect movement in the plane of the device layer on which the movable part is formed, and in the same plane, the capacitance is detected by the movement of the movable part.
- the detection capacity increases and the detection capacity decreases.
- the output of the signal to be detected is obtained by differentially inputting these two capacitors to the capacitor voltage converter (CV converter). Since the angular velocity sensor and the acceleration sensor are provided on the same substrate, there are advantages that the sensor can be manufactured at low cost and can be easily downsized.
- Patent Document 3 An example of a pressure sensor is shown in JP-T-8-501156 (Patent Document 3) and JP-A-2001-235181 (Patent Document 4).
- These pressure sensors shown in Patent Literature 3 and Patent Literature 4 have a pressure-sensitive capacitive element whose capacitance changes with application of pressure, and a reference capacitance having a reference capacitance whose capacitance is invariable with respect to the pressure to be detected.
- the element is formed on one substrate, and the pressure is detected by outputting a signal corresponding to the ratio of these two capacitors.
- the composite sensor that can detect the acceleration and the angular velocity described in Patent Document 1 and Patent Document 2 can detect the displacement in the main surface of the semiconductor substrate with high sensitivity by forming a differential capacitor.
- the fixed reference capacitance to be compared.
- An element is required. This is because, when acceleration is applied in the out-of-plane direction, it is difficult to form both a detection capacitor whose capacity increases due to the movement of the movable part and a detection capacitor whose capacity decreases.
- the sensor element on which the movable part and the like are formed needs to separately form a sensor element for the reference capacitance element.
- the size of elements arranged side by side is not so different. For this reason, there is a problem that the effect of reducing the manufacturing cost due to the downsizing of the sensor element due to the combination of sensors and the increase in the number of obtained chips per semiconductor wafer becomes limited.
- An object of the present invention is to provide a composite sensor capable of realizing downsizing and cost reduction while maintaining performance by increasing the number of elements that can be shared among the sensors in the composite sensor capable of detecting a plurality of physical quantities. It is to provide.
- the composite sensor includes: (a) a first detection unit that captures application of the first physical quantity as a change in capacitance of the first detection capacitive element; and (b) second application of the second physical quantity.
- a second detection unit that captures a change in capacitance of the detection capacitive element.
- the composite sensor includes a detection signal obtained by converting a capacitance of the first detection capacitive element output from the first detection unit, and the second detection capacitive element output from the second detection unit.
- the first physical quantity is detected based on a difference from a reference signal obtained by converting the capacitance of the first physical quantity.
- the composite sensor according to the representative embodiment includes (a) a first detection unit that captures application of the first physical quantity as a change in capacitance of the first detection capacitive element, and (b) application of the second physical quantity.
- a second detection unit that captures a change in capacitance of the second detection capacitor; and (c) a reference capacitor serving as a reference for obtaining a difference.
- the composite sensor includes a first detection signal converted from the capacitance of the first detection capacitive element output from the first detection unit, and a reference signal converted from the capacitance of the reference capacitive element.
- the second physical quantity is detected based on a difference from the reference signal obtained by converting an electrostatic capacity.
- FIG. 2 is a cross-sectional view taken along line AA in FIG.
- It is a block diagram which shows the circuit structure for detecting angular velocity using an angular velocity detection part.
- It is a schematic diagram which shows the capacitive element of a parallel plate type structure.
- It is a schematic diagram which shows the capacitive element of a comb-tooth type structure.
- It is a block diagram which shows the circuit structure for detecting an acceleration using an XY direction acceleration detection part.
- It is a circuit block diagram which shows the general circuit structure which detects the acceleration of a Z direction.
- FIG. 3 is a circuit block diagram illustrating a circuit configuration for detecting an acceleration in a Z direction in the first embodiment.
- FIG. It is a graph which shows the frequency characteristic in the detection vibration system of an angular velocity detection part, and the frequency characteristic of a Z direction acceleration detection part. It is a figure which shows the bandwidth filter characteristic from a CV conversion part to a synchronous detection part.
- 5 is a cross-sectional view showing a manufacturing process of the composite sensor in the first embodiment.
- FIG. FIG. 12 is a cross-sectional view showing a manufacturing process of the composite sensor following FIG. 11.
- FIG. 13 is a cross-sectional view showing a manufacturing step of the composite sensor following FIG. 12.
- FIG. 14 is a cross-sectional view illustrating a manufacturing process of the composite sensor subsequent to FIG. 13.
- FIG. 15 is a cross-sectional view showing a manufacturing process of the composite sensor continued from FIG. 14.
- 3 is a cross-sectional view illustrating a mounting configuration of the composite sensor according to Embodiment 1.
- FIG. 6 is a plan view showing a configuration of a composite sensor in a second embodiment.
- FIG. It is sectional drawing cut
- the constituent elements are not necessarily indispensable unless otherwise specified and apparently essential in principle. Needless to say.
- FIG. 1 is a plan view showing the configuration of the composite sensor CS1 in the first embodiment.
- the composite sensor CS1 in the first embodiment has a frame FR formed on the semiconductor substrate 1S, and the angular velocity around the Y axis is set in each region partitioned by the frame FR.
- An angular velocity detection unit JA for detecting, and an acceleration detection unit AC for detecting acceleration in the X-axis direction, the Y-axis direction, and the Z-axis direction are formed.
- the acceleration detection unit AC includes an XY direction acceleration detection unit AC (XY) that detects acceleration in the X-axis direction and the Y-axis direction, and a Z-direction acceleration detection unit AC (Z) that detects acceleration in the Z-axis direction.
- XY XY direction acceleration detection unit
- Z Z-direction acceleration detection unit
- the angular velocity detection unit JA has two movable (vibrating) weights (movable parts) M1 and weights (movable parts) M2 formed on the semiconductor substrate 1S, and further includes a link beam LB. have.
- the link beam LB connects the two weights M1 and M2. Accordingly, the link beam LB forms a transmission path for vibration energy of the weight M1 and the weight M2, thereby forming a tuning fork structure (reverse phase vibration structure).
- the angular velocity detection unit JA includes a support beam SB1 that supports the weight M1 and the weight M2 and the link beam LB in a floating state with respect to the semiconductor substrate 1S.
- the support beam SB1 It is configured so that it can be deformed (elastically deformed) in both the drive direction (X direction) and the detection direction (Z direction). That is, one end of the support beam SB1 is connected to the weight M1 or the weight M2, and the other end of the support beam SB1 is connected to the fixed portion FX1 fixed to the semiconductor substrate 1S.
- the angular velocity detection unit JA includes a drive electrode DRE1 and a drive electrode DRE2 that form a capacitance with the weight M1. That is, a drive capacitor element is formed by the weight M1 and the drive electrode DRE1, and a drive capacitor element is formed by the weight M1 and the drive electrode DRE2. Similarly, a drive capacitor element is formed by the weight M2 and the drive electrode DRE1, and a drive capacitor element is formed by the weight M2 and the drive electrode DRE2. For example, a high-frequency signal (high-frequency voltage) is applied to the drive capacitive element including the drive electrode DRE1 and the weight M1, and the drive capacitive element to which the high-frequency signal (high-frequency voltage) is applied is configured.
- a high-frequency signal high-frequency voltage
- the weight M1 can be vibrated by the electrostatic attractive force.
- the drive capacitor element composed of the drive electrode DRE2 and the weight M1 the drive capacitor element composed of the drive electrode DRE1 and the weight M2, or the drive capacitor element composed of the drive electrode DRE2 and the weight M2 is similarly applied. It is configured. As a result, the weight M1 and the weight M2 are adapted to vibrate for tuning.
- the angular velocity detection unit JA has a monitor electrode ME1 and a monitor electrode ME2 for monitoring (monitoring) the drive amplitudes of the weight M1 and the weight M2 that are oscillating in the tuning fork, and further has an angular velocity around the Y-axis direction.
- it has a detection electrode DTE1 and a detection electrode DTE2 for detecting displacement in the detection direction (Z-axis direction). That is, for example, the detection capacitor element is formed by the weight M1 and the detection electrode DTE1 formed in the lower layer of the weight M1, and the displacement in the detection direction can be regarded as the capacitance change of the detection capacitor element. ing.
- the detection capacitor element is formed by the weight M2 and the detection electrode DTE2 formed in the lower layer of the weight M2, and the displacement in the detection direction can be regarded as the capacitance change of the detection capacitor element.
- a driving vibration system is formed by the weight M1, the weight M2, the link beam LB, and the support beam SB1, and the weight 1 and the support beam SB1 or the weight M2 and the support beam SB1.
- a detection vibration system is formed.
- the acceleration detection unit AC includes an XY direction acceleration detection unit AC (XY) that detects acceleration in the X axis direction and the Y axis direction, and a Z direction acceleration detection unit AC (Z) that detects acceleration in the Z axis direction.
- XY direction acceleration detection unit AC XY
- Z Z direction acceleration detection unit AC
- the support beam SB2 is detected in the detection direction (X Direction) and the detection direction (Y direction), and can be deformed (elastically deformed) in both directions. That is, one end of the support beam SB2 is connected to the weight M3, and the other end of the support beam SB2 is connected to the fixed portion FX2 fixed to the semiconductor substrate 1S.
- the XY direction acceleration detection unit AC (XY) has a detection electrode DTE3 for detecting displacement in the detection direction (X axis direction) when acceleration is applied in the X direction. That is, for example, the detection capacitor element is formed by the weight M3 and the detection electrode DTE3, and the displacement in the detection direction (X-axis direction) can be regarded as the capacitance change of the detection capacitor element.
- the XY direction acceleration detection unit AC (XY) has a detection electrode DTE4 for detecting displacement in the detection direction (Y-axis direction) when acceleration is applied in the Y direction. That is, for example, the detection capacitor element is formed by the weight M3 and the detection electrode DTE4, and the displacement in the detection direction (Y-axis direction) can be regarded as the capacitance change of the detection capacitor element.
- the Z-direction acceleration detector AC (Z) has one movable weight M4 formed on the semiconductor substrate 1S.
- the Z-direction acceleration detection unit AC (Z) includes a support beam SB3 that supports the weight M4 in a floating state with a certain distance from the semiconductor substrate 1S, and the support beam SB3 has a detection direction (Z It can be deformed (elastically deformed) in the direction). That is, one end of the support beam SB3 is connected to the weight M4, and the other end of the support beam SB3 is connected to the fixed portion FX3 fixed to the semiconductor substrate 1S.
- the Z-direction acceleration detection unit AC (Z) has a detection electrode DTE5 for detecting displacement in the detection direction (Z-axis direction) when acceleration is applied in the Z direction. That is, for example, the detection capacitor element is formed by the weight M4 and the detection electrode DTE5 formed in the lower layer of the weight M4, and the displacement in the detection direction (X-axis direction) is regarded as the capacitance change of the detection capacitor element. It is configured to be able to.
- the weights M1 and M2, the link beam LB, the support beam SB1, and the fixed portion FX1 that constitute the angular velocity detection unit JA are made of a conductive member such as a polysilicon film, and the fixed portion FX1 is, for example, It is electrically connected to the pad PD1. Therefore, an electrical signal can be applied from the fixed portion FX1 to the weight M1 via the support beam SB1 via the pad PD1 that is an external connection terminal.
- the drive electrode DRE1, the drive electrode DRE2, the monitor electrode ME1, the monitor electrode ME2, the detection electrode DTE1, and the detection electrode DTE2 that constitute the angular velocity detection unit JA are also made of a conductive member, and are pads that are external connection terminals. It is electrically connected to PD1. Therefore, an electric signal can be applied to these components.
- the weight M3, the support beam SB2, and the fixed portion FX2 constituting the XY direction acceleration detection unit AC (XY) are formed of a conductive member such as a polysilicon film, and the fixed portion FX2 is formed of, for example, a pad. It is electrically connected to PD1. Accordingly, an electric signal can be applied from the fixed portion FX2 to the weight M3 via the support beam SB2 via the pad PD1 that is an external connection terminal.
- the detection electrode DTE3, the detection electrode DTE4, and the like constituting the XY direction acceleration detection unit AC (XY) are also made of a conductive member, and are electrically connected to the pad PD1 that is an external connection terminal. Therefore, an electric signal can be applied to these components.
- the weight M4, the support beam SB3, and the fixed portion FX3 that constitute the Z-direction acceleration detection unit AC (Z) are formed of a conductive member such as a polysilicon film, and the fixed portion FX3 is, for example, It is electrically connected to the pad PD1. Accordingly, an electric signal can be applied from the fixed portion FX3 to the weight M4 via the support beam SB3 via the pad PD1 which is an external connection terminal.
- the detection electrode DTE5 and the like constituting the Z-direction acceleration detection unit AC (Z) are also made of a conductive member, and are electrically connected to the pad PD1 that is an external connection terminal. Therefore, an electric signal can be applied to these components.
- FIG. 2 is a view showing a cross-sectional structure of the composite sensor CS1 according to the first embodiment, and is a cross-sectional view taken along the line AA in FIG.
- the composite sensor CS1 in the first embodiment includes a semiconductor substrate 1S made of, for example, silicon, and an insulating film OX1 made of, for example, a silicon oxide film is formed on the semiconductor substrate 1S. Is formed.
- a detection electrode DTE1 and a detection electrode DTE5 formed by patterning a conductive film such as a polysilicon film are formed.
- an insulating film OX2 made of a silicon oxide film is formed so as to fill a gap formed between the detection electrodes DTE1 and DTE5.
- the surfaces of the detection electrode DTE1 and the detection electrode DTE5 and the surface of the insulating film OX2 are aligned, and an insulating film SN1 made of, for example, a silicon nitride film is formed on the aligned surfaces.
- the frame body FR is formed on the insulating film SN1 via an insulating film OX3 made of, for example, a silicon oxide film.
- the frame FR is made of, for example, a conductor film such as a polysilicon film, and is provided to partition the formation region of the angular velocity detection unit JA and the formation region of the acceleration detection unit AC shown in FIG. .
- a cavity CAV1 is formed in one region partitioned by the frame body FR, and a weight M1 that is a component of the angular velocity detection unit JA is formed in the cavity CAV1.
- a cavity CAV2 is formed in another area partitioned by the frame body FR, and the weight M4 and the support beam, which are components of the Z-direction acceleration detector AC (Z), are formed in the cavity CAV2.
- SB3 is formed.
- the two areas partitioned by the frame body FR are sealed with a cover COV.
- a plug PLG1 connected to the detection electrode DTE1 is formed so as to penetrate the insulating film SN1 and the insulating film OX3.
- a polysilicon film is formed on the plug PLG1.
- a pedestal PED1 is formed.
- a pad PD1 is formed on the pedestal PED1.
- the detection electrode DTE1 is electrically connected to the pad PD1 via the plug PLG1 and the pedestal part PED1.
- a plug PLG2 connected to the detection electrode DTE5 is formed so as to penetrate the insulating film SN1 and the insulating film OX3.
- polysilicon A pedestal PED2 made of a film is formed on the plug PLG2. Therefore, it can be seen that the detection electrode DTE5 is electrically connected to the pad PD1 via the plug PLG2 and the pedestal part PED2.
- FIG. 3 is a block diagram showing a circuit configuration for detecting the angular velocity using the angular velocity detector.
- the drive electrode DRE1 is disposed outside the weight M1 and the weight M2, and the drive electrode DRE2 is disposed inside the weight M1 and the weight M2.
- the drive electrode DRE1 and the weight M1, the drive electrode DRE1 and the weight M2, the drive electrode DRE2 and the weight M1, and the drive electrode DRE2 and the weight M2 form a drive capacitance element, respectively.
- Vcom + Vb + Vd is applied as a drive signal to the drive electrode DRE1
- Vcom + Vb ⁇ Vd is applied as a drive signal to the drive electrode DRE2.
- Vcom and Vca are applied to the weight M1 and the weight M2.
- Vcom indicates a common voltage
- Vb indicates a bias voltage.
- Vcom common voltage
- Vb bias voltage
- + Vd and -Vd indicate drive voltages
- Vca indicates a carrier voltage.
- the monitor electrode ME1 is disposed outside the weight M1 and the weight M2, and the monitor electrode ME2 is disposed inside the weight M1 and the weight M2.
- the monitor electrode ME1 and the weight M1, the monitor electrode ME1 and the weight M2, the monitor electrode ME2 and the weight M1, and the monitor electrode ME2 and the weight M2 form a monitor capacitive element, respectively.
- the monitor electrode ME1 connected to the weight M1 and the monitor electrode ME1 connected to the weight M2 are connected to each other and connected to the CV conversion unit CVU1.
- the monitor electrode ME2 connected to the weight M1 and the monitor electrode ME2 connected to the weight M2 are connected to each other and connected to the CV conversion unit CVU1.
- the CV converter CVU1 is connected to the monitor electrode ME1, and the capacitance of the monitor capacitor element composed of the monitor electrode ME1 and the weight M1 and the monitor capacitor element composed of the monitor electrode ME1 and the weight M2 is converted into the first monitor analog voltage. It is configured to convert to a signal.
- the CV conversion unit CVU1 is connected to the monitor electrode ME2, and the second monitor monitors the capacitance of the monitor capacitive element including the monitor electrode ME2 and the weight M1, and the monitor capacitive element including the monitor electrode ME2 and the weight M2. It is comprised so that it may convert into an analog voltage signal.
- the AD conversion unit ADU1 receives the first monitor analog voltage signal output from the CV conversion unit CVU1, converts the first monitor analog voltage signal into the first monitor digital voltage signal,
- the second monitor analog voltage signal output from the conversion unit CVU1 is input, and the second monitor analog voltage signal is converted into a second monitor digital voltage signal.
- the differential detection unit DMU1 is configured to take the difference between the first monitor digital voltage signal and the second monitor digital voltage signal output from the AD conversion unit ADU1 and output the monitor differential voltage signal Has been.
- the synchronous detection unit WDU1 is configured to demodulate (down-convert) the monitor differential voltage signal and output the monitor demodulated voltage signal.
- the AGC unit AGC is configured to control the amplitude of the drive voltage (+ Vd or ⁇ Vd) to be constant based on the monitor demodulated voltage signal demodulated by the synchronous detector WDU1.
- the AFC unit AFC is configured to cause the frequency of the drive voltage (drive frequency) to follow the change in the natural frequency of the drive vibration system based on the demodulated voltage signal for monitoring demodulated by the synchronous detection unit WDU1.
- the DA converter DAU1 is configured to convert the analog signal generated by the AGC unit AGC and the analog signal generated by the AFC unit AFC into a digital signal.
- the detection electrode DTE1 is disposed below the weight M1, and the detection electrode DTE2 is disposed below the weight M2.
- the detection electrode DTE1 and the weight M1, and the detection electrode DTE2 and the weight M2 form a detection capacitive element, respectively.
- the detection electrode DTE1 and the detection electrode DTE2 are electrically connected to the CV conversion unit CVU2.
- the CV converter CVU2 is connected to the detection electrode DTE1, and is configured to convert the capacitance of the detection capacitor element including the detection electrode DTE1 and the weight M1 into a first detection analog voltage signal.
- the CV conversion unit CVU2 is connected to the detection electrode DTE2, and is configured to convert the capacitance of the detection capacitive element including the detection electrode DTE2 and the weight M2 into a second detection analog voltage signal. .
- the AD conversion unit ADU2 receives the first detection analog voltage signal output from the CV conversion unit CVU2, converts the first detection analog voltage signal into a first detection digital voltage signal,
- the second detection analog voltage signal output from the conversion unit CVU2 is input, and the second detection analog voltage signal is converted into a second detection digital voltage signal.
- the differential detection unit DMU2 is configured to take the difference between the first detection digital voltage signal and the second detection digital voltage signal output from the AD conversion unit ADU2 and output the detection differential voltage signal Has been.
- the synchronous detection unit WDU2 is configured to demodulate the detection differential voltage signal and output the detection demodulated voltage signal.
- the low-pass filter LPF1 is configured to pass a signal having a frequency lower than the specific frequency without being attenuated, and to attenuate and block a signal having a frequency higher than the specific frequency.
- the circuit that detects the angular velocity using the angular velocity detector is configured as described above, and the principle of detecting the angular velocity using the circuit configured in this way and The operation will be described with reference to FIG.
- the weight M1 and the weight M2 are constituted by a drive electrode DRE1 disposed outside the respective weight M1 and weight M2, and a drive electrode DRE2 disposed inside the respective weight M1 and weight M2.
- Vcom + Vb + Vd is applied as a drive signal to the drive electrode DRE1
- Vcom + Vb ⁇ Vd is applied as a drive signal to the drive electrode DRE2.
- Vcom + Vca is applied to the weight M1 and the weight M2. Therefore, for example, the potential difference between the weight M1 and the drive electrode DRE1 is Vb + Vd, and the potential difference between the weight M1 and the drive electrode DRE2 is Vb ⁇ Vd.
- the potential difference between the weight M2 and the drive electrode DRE1 is Vb + Vd
- the potential difference between the weight M2 and the drive electrode DRE2 is Vb ⁇ Vd.
- a drive capacitor element is formed by the drive electrode DRE1 and the weight M1, the drive electrode DRE1 and the weight M2, the drive electrode DRE2 and the weight M1, and the drive electrode DRE2 and the weight M2, respectively. Occurs.
- an electrostatic force is generated in each drive capacitor element, and the weight M1 and the weight M2 vibrate in reverse phase based on the electrostatic force. That is, the weight M1 and the weight M2 are driven to vibrate.
- the carrier voltage (Vca) is also applied to the weight M1 and the weight M2, but the frequency of the carrier voltage (Vca) is several hundred kHz.
- the carrier voltage (Vca) does not act as a driving force for vibrating the weight M1 and the weight M2 because the driving vibration system of M2 is sufficiently high to be unable to follow.
- Expression (1) is an expression showing the relationship between the amplitude of the driving vibration in the X direction (driving amplitude AX) and the Coriolis force Fc
- Expression (2) is the detected amplitude z in the Z direction and the Coriolis force Fc. It is a formula which shows the relationship.
- Fc 2 ⁇ m ⁇ ⁇ ⁇ AX ⁇ ⁇ x ⁇ cos ( ⁇ x ⁇ t) (1)
- Fc is the Coriolis force
- m is the mass of the weight
- ⁇ is the applied angular velocity
- AX is the drive amplitude
- ⁇ x / 2 ⁇ is the drive frequency
- t is the time.
- z Fc ⁇ Qz / kz (2)
- Fc is the Coriolis force
- z is the detection amplitude
- Qz is the mechanical quality factor in the detection direction (Z direction)
- kz is the spring constant in the z direction of the support beam.
- the mass m of the weight M1 and the weight M2 and the drive angular frequency ⁇ x (divided by 2 ⁇ is the frequency, so the drive angular frequency and the drive frequency are mixed.
- the Coriolis force Fc converted as the output of the angular velocity sensor and the detected amplitude z are functions of only the drive amplitude AX. Therefore, in order to maintain the sensitivity of the angular velocity sensor at a constant level and ensure reliability even when there are fluctuations in the ambient pressure or vibration disturbance, the drive amplitude AX may be controlled to be constant. From this point of view, in the first embodiment, the drive amplitude AX is constantly monitored, and feedback control is performed so that the monitored drive amplitude AX is constant, thereby maintaining the sensitivity of the angular velocity sensor constant and reliability. Is secured.
- the drive amplitude AX using the monitor electrode ME1 disposed outside the weight M1 and the weight M2 and the monitor electrode ME2 disposed inside the weight M1 and the weight M2.
- Monitoring Specifically, a change in electrostatic capacitance of a monitor capacitive element including the weight M1 and the monitor electrode ME1, the weight M2 and the monitor electrode ME1, the weight M1 and the monitor electrode ME2, and the weight M2 and the monitor electrode ME2 is detected.
- the drive amplitude AX is monitored. The principle of monitoring the drive amplitude AX will be described with reference to FIG.
- a carrier voltage (Vca) of several hundred kHz is applied to the weight M1 and the weight M2, and this carrier voltage (Vca) is applied to the monitor electrode ME1 and the monitor electrode ME2 according to the capacitance of the monitor capacitor element. Generates charge transfer. Due to the movement of charges at the monitor electrode ME1, the CV converter CVU1 generates a first monitor analog voltage signal. Similarly, the second monitor analog voltage signal is generated in the CV conversion unit CVU1 by the movement of the electric charge at the monitor electrode ME2. Then, the first monitor analog voltage signal and the second monitor analog voltage signal generated by the CV converter CVU1 are respectively converted into the first monitor digital voltage signal and the second monitor digital voltage by the AD converter ADU1. Converted to a signal.
- the first monitor digital voltage signal and the second monitor digital voltage signal output from the AD conversion unit ADU1 are input to the differential detection unit DMU1 for calculation.
- the differential detection unit DMU1 takes the difference between the first monitor digital voltage signal and the second monitor digital voltage signal and outputs the monitor differential voltage signal.
- the weight M1 and the weight M2 are not driven to vibrate, that is, when the drive amplitude AX is 0, only the carrier voltage (Vca) is applied to the weight M1 and the weight M2. Since the carrier voltage (Vca) is a high-frequency voltage of several hundred kHz and the weight M1 and the weight M2 cannot follow, the weight M1 and the weight M2 are in a stationary state. In this case, since the electrostatic capacitance of the monitor capacitive element by the monitor electrode ME1 and the electrostatic capacitance of the monitor capacitive element by the monitor electrode ME2 are equal, the first monitor analog voltage signal generated by the CV converter CVU1 and the second The analog voltage signals for monitoring are equal.
- the first monitor digital voltage signal obtained by converting the first monitor analog voltage signal by the AD converter ADU1 and the second monitor digital voltage signal obtained by converting the second monitor analog voltage signal by the AD converter ADU1 are also equal. Become. Therefore, when the weight M1 and the weight M2 are not driven to vibrate, that is, when the drive amplitude AX is 0, the monitoring differential voltage signal generated by the differential detection unit DMU1 is 0.
- the weight M1 and the weight M2 are in driving vibration (reverse phase vibration), that is, when the driving amplitude AX is not 0, the carrier voltage (Vca) and the driving voltage (+ Vd and ⁇ Vd) will be applied. Therefore, when the weight M1 and the weight M2 are in reverse phase vibration, for example, the capacitance of the monitor capacitive element having the monitor electrode ME1 as a component increases in proportion to the drive amplitude AX of the weight M1 and the weight M2.
- the first monitor analog voltage signal and the second monitor analog voltage signal generated by the CV converter CVU1 are different.
- the first monitor digital voltage signal converted from the first monitor analog voltage signal by the AD converter ADU1 is different from the second monitor digital voltage signal converted from the second monitor analog voltage signal by the AD converter ADU1. It will be. Therefore, when the weight M1 and the weight M2 are driven to vibrate (reverse phase vibration), a differential voltage signal for monitoring proportional to the drive amplitude AX is output from the differential detection unit DMU1.
- the differential voltage signal for monitoring output from the differential detection unit DMU1 is converted (demodulated) from a carrier frequency signal to a drive frequency (for example, several tens of kHz) and a signal by the synchronous detection unit WDU1, and further driven.
- the frequency signal is converted (demodulated) into a low frequency (DC to several hundred Hz) signal.
- the drive amplitude AX converted into a low-frequency signal in this way is input to the AGC unit AGC and compared with a preset target value. Based on the comparison result, the magnitude of the drive voltage Vd ( ⁇ Vd) is adjusted via the DA converter DAU1. In this way, feedback control can be performed so that the drive amplitude AX becomes a preset target value.
- the frequency is also controlled to be constant.
- the drive frequency of the drive voltage (Vd or ⁇ Vd) is set to a value of the drive vibration system including the weight M1, the weight M2, the link beam LB, and the support beam SB1. It is effective to resonate according to the natural frequency.
- the natural frequency of the drive vibration system is not necessarily constant and varies depending on the surrounding environment (temperature and pressure).
- feedback control using PLL Phase Locked Loop
- AFC Automatic Frequency Control
- the capacitances of the monitor capacitive elements having the monitor electrodes ME1 that are electrically connected to each other as constituent elements are both in the same direction (increase direction, Or, the direction of decrease).
- the capacitances of the monitor capacitive elements having the monitor electrodes ME2 that are electrically connected to each other as constituent elements are both in the same direction (decreasing direction, Or the direction of increase).
- each of the two monitor electrodes ME2 electrically connected to each other is a component.
- the capacitance of the monitor capacitor element decreases.
- each of the two monitor electrodes ME2 electrically connected to each other is a component.
- the capacitance of the monitor capacitor element increases. Therefore, when the weight M1 and the weight M2 vibrate in reverse phase, the differential voltage signal for monitoring proportional to the vibration amplitude AX can be obtained by the differential detection unit DMU1.
- the capacitance of one of the monitor capacitive elements each including the two monitor electrodes ME1 electrically connected to each other increases.
- the other capacitance decreases. Therefore, when the two monitor electrodes ME1 are electrically connected to each other, an increase in capacitance and a decrease in capacitance are combined.
- the weight M1 and the weight M2 vibrate in phase they are electrically connected to each other.
- the total capacitance obtained by combining the monitor capacitive elements each having the connected two monitor electrodes ME1 as a component does not change.
- the monitor capacitive element including each of the two monitor electrodes ME2 that are electrically connected to each other has one of the capacitances increased.
- the other capacitance decreases. Therefore, when the two monitor electrodes ME2 are electrically connected to each other, an increase in capacitance and a decrease in capacitance are combined.
- the weight M1 and the weight M2 vibrate in phase they are electrically connected to each other.
- the total capacitance obtained by combining the monitor capacitive elements having the two connected monitor electrodes ME2 as constituent elements does not change.
- the monitoring differential voltage signal output from the differential detection unit DMU1 becomes 0, while the weight M1 and the weight M2 ,
- the differential detection unit DMU1 can obtain a monitoring differential voltage signal proportional to the vibration amplitude AX. That is, there is an advantage that the monitor capacitive element that does not react to the common-mode vibration and has sensitivity only to the reverse-phase vibration can be hardly affected by the common-mode noise from the outside.
- the monitor capacitor element including the monitor electrode ME1 and the monitor electrode ME2 as a constituent element is shown as a parallel plate type structure. It is good also as a tooth type structure. In this way, by adopting a comb-shaped structure for the monitor capacitor element, it is possible to suppress non-linear behavior (capacitance change and drive amplitude ratio) behavior that occurs in the parallel plate structure.
- FIG. 4 is a schematic view showing a capacitive element having a parallel plate structure.
- the distance between the electrode EL1 and the electrode EL2 is d (x)
- the area of the electrode EL1 and the electrode EL2 is S.
- ⁇ is a dielectric constant.
- FIG. 5 is a schematic diagram showing a comb-shaped capacitive element.
- the distance between the electrode EL1 and the electrode EL2 is d (fixed), and the area where the electrodes EL1 and EL2 overlap in plan view is S (x).
- the capacitance S changes when the area S (x) where the electrodes EL1 and EL2 overlap in plan view changes.
- ⁇ is a dielectric constant.
- variable S (x) is present in the molecule, it can be seen that the change in capacitance is less likely to exhibit non-linearity. From this, it can be seen that the non-linear behavior generated in the parallel plate structure can be suppressed by making the monitor capacitor element have a comb-tooth structure.
- the capacitance of the detection capacitor element including the weight M1 and the detection electrode DTE1 changes.
- the capacitance of the detection capacitive element including the weight M2 and the detection electrode DTE2 also changes.
- the capacitance of the detection capacitive element including the weight M1 and the detection electrode DTE1 increases.
- the capacitance of the detection capacitive element including the weight M2 and the detection electrode DTE2 changes in a decreasing direction.
- the capacitance of the detection capacitance element including the weight M2 and the detection electrode DTE2 changes in an increasing direction.
- the detection electrode DTE1 and the detection electrode DTE2 cause charge movement. Due to the movement of charges at the detection electrode DTE1, a first detection analog voltage signal is generated at the CV converter CVU2. Similarly, the second analog voltage signal for detection is generated in the CV conversion unit CVU2 by the movement of the charge in the detection electrode DTE2.
- the change in the capacitance of the detection capacitor element including the weight M1 and the detection electrode DTE1 and the change in the capacitance of the detection capacitor element including the weight M2 and the detection electrode DTE2 are different as described above.
- the detection analog voltage signal and the second detection analog voltage signal are different signals.
- the first detection analog voltage signal and the second detection analog voltage signal generated by the CV conversion unit CVU2 are respectively converted into a first detection digital voltage signal and a second detection digital voltage by the AD conversion unit ADU2. Converted to a signal. Thereafter, the first detection digital voltage signal and the second detection digital voltage signal output from the AD conversion unit ADU2 are input to the differential detection unit DMU2 and calculated. Specifically, the differential detection unit DMU2 takes the difference between the first detection digital voltage signal and the second detection digital voltage signal, and outputs the detection differential voltage signal.
- the differential voltage signal for detection output from the differential detection unit DMU2 is converted (demodulated) from a carrier frequency signal to a drive frequency (for example, several tens of kHz) and a signal by the synchronous detection unit WDU2, and further driven.
- the frequency signal is converted (demodulated) into a low frequency (DC to several hundred Hz) signal (detection demodulated voltage signal).
- the low-frequency signal thus converted is subjected to removal of high-frequency components by the low-pass filter LPF1, and a signal corresponding to the angular velocity ⁇ is output. In this way, the angular velocity ⁇ around the Y axis can be detected.
- the natural frequency of the drive vibration system including the weight M1, the weight M2, the link beam LB, and the support beam SB1 is designed to be more than 10 kHz, and the frequency of the drive vibration (drive) The frequency) is matched to the natural frequency of this drive vibration system.
- the natural frequency of the detection vibration system is designed in the vicinity of the natural frequency of the drive vibration system.
- ⁇ z ⁇ (kz / m) (4)
- ⁇ z is the natural frequency of the detection vibration system. Since ⁇ x (the natural frequency of the drive vibration system) and ⁇ z (the natural frequency of the detection vibration system) are substantially the same and the mass m of the weight is the same, kx ⁇ kz holds.
- the sensitivity S is a function of only the mass m of the weight, the drive amplitude AX, and the damping coefficient Cz in the Z direction, and the natural frequency ⁇ x of the drive vibration system and the natural vibration of the detection vibration system It turns out that it is unrelated to the number ⁇ z. Therefore, it can be seen that the natural frequency ⁇ x of the drive vibration system and the natural frequency ⁇ z of the detection vibration system can be selected without affecting the sensitivity S.
- FIG. 6 is a block diagram illustrating a circuit configuration for detecting acceleration using the XY direction acceleration detection unit.
- the detection electrodes DTE3 are formed on the left and right sides of the weight M3, and one detection capacitance element is formed by the detection electrode DTE3 and the weight M3 arranged on the left side of the weight M3. Similarly, another detection capacitor element is formed by the detection electrode DTE3 and the weight M3 arranged on the right side of the weight M3.
- Vcom and Vca are applied to the weight M3.
- Vcom indicates a common voltage. This common voltage (Vcom) is a DC voltage.
- Vca indicates a carrier voltage. This carrier voltage is an alternating voltage.
- the CV conversion unit CVU3 is connected to the two detection electrodes DTE3, and is configured to convert the capacitance of the detection capacitor element including the one detection electrode DTE3 and the weight M3 into the first X-direction detection analog voltage signal. ing. Similarly, the CV conversion unit CVU3 is configured to convert the capacitance of the detection capacitive element including the other detection electrode DTE3 and the weight M3 into a second X-direction detection analog voltage signal.
- the AD conversion unit ADU3 inputs the first X direction detection analog voltage signal output from the CV conversion unit CVU3, and converts the first X direction detection analog voltage signal into a first X direction detection digital voltage signal.
- the second X-direction detection analog voltage signal output from the CV conversion unit CVU3 is input, and the second X-direction detection analog voltage signal is converted into a second X-direction detection digital voltage signal.
- the differential detection unit DMU3 takes the difference between the first X direction detection digital voltage signal and the second X direction detection digital voltage signal output from the AD conversion unit ADU3, and outputs an X direction detection differential voltage signal Is configured to do.
- the synchronous detection unit WDU3 is configured to demodulate (down-convert) the X direction detection differential voltage signal and output the X direction detection demodulated voltage signal.
- the low-pass filter LPF2 is configured to pass a signal having a frequency lower than the specific frequency without being attenuated and to attenuate and block a signal having a frequency higher than the specific frequency.
- the detection electrodes DTE4 are formed on both upper and lower sides of the weight M3, and one detection capacitance element is formed by the detection electrode DTE4 and the weight M3 arranged on the upper side of the weight M3. Similarly, another detection capacitor element is formed by the detection electrode DTE4 and the weight M3 disposed below the weight M3.
- Vcom and Vca are applied to the weight M3.
- Vcom indicates a common voltage. This common voltage (Vcom) is a DC voltage.
- Vca indicates a carrier voltage. This carrier voltage is an alternating voltage.
- the CV conversion unit CVU4 is connected to the two detection electrodes DTE4, and is configured to convert the capacitance of the detection capacitive element including the one detection electrode DTE4 and the weight M3 into the first Y-direction detection analog voltage signal. ing. Similarly, the CV conversion unit CVU4 is configured to convert the capacitance of the detection capacitive element including the other detection electrode DTE4 and the weight M3 into a second Y-direction detection analog voltage signal.
- the AD conversion unit ADU4 receives the first Y-direction detection analog voltage signal output from the CV conversion unit CVU4, and converts the first Y-direction detection analog voltage signal into a first Y-direction detection digital voltage signal.
- the second Y-direction detection analog voltage signal output from the CV conversion unit CVU4 is input, and the second Y-direction detection analog voltage signal is converted into a second Y-direction detection digital voltage signal.
- the differential detection unit DMU4 takes the difference between the first Y-direction detection digital voltage signal and the second Y-direction detection digital voltage signal output from the AD conversion unit ADU4, and outputs the Y-direction detection differential voltage signal. Is configured to do.
- the synchronous detection unit WDU4 is configured to demodulate (down-convert) the Y-direction detection differential voltage signal and output a Y-direction detection demodulated voltage signal.
- the low-pass filter LPF3 is configured to pass a signal having a frequency lower than the specific frequency without being attenuated, and to attenuate and block a signal having a frequency higher than the specific frequency.
- the circuit for detecting the acceleration in the XY direction using the XY direction acceleration detection unit is configured as described above, and hereinafter, the circuit configured in this way is used for XY.
- the operation for detecting the acceleration in the direction will be described with reference to FIG.
- a carrier voltage (Vca) of several hundred kHz is applied to the weight M3, and this carrier voltage (Vca) is charged by the two detection electrodes DTE3 according to the capacitance of the detection capacitor element.
- Vca carrier voltage
- the CV conversion unit CVU3 Due to the movement of the charge at one detection electrode DTE3, the CV conversion unit CVU3 generates a first X-direction detection analog voltage signal.
- a second X-direction detection analog voltage signal is generated by the CV conversion unit CVU3 due to the movement of electric charge at the other detection electrode DTE3.
- the first X direction detection analog voltage signal and the second X direction detection analog voltage signal generated by the CV conversion unit CVU3 are respectively converted into the first X direction detection digital voltage signal and the second X direction by the AD conversion unit ADU3. It is converted into a digital voltage signal for detection. Thereafter, the first X-direction detection digital voltage signal and the second X-direction detection digital voltage signal output from the AD conversion unit ADU3 are input to the differential detection unit DMU3 and calculated. Specifically, the differential detection unit DMU3 takes the difference between the first X-direction detection digital voltage signal and the second X-direction detection digital voltage signal and outputs an X-direction detection differential voltage signal.
- the weight M3 is in a stationary state.
- the capacitance of the detection capacitive element by one detection electrode DTE3 is equal to the capacitance of the detection capacitive element by the other detection electrode DTE3, and therefore the first X direction detection for the first X direction generated by the CV conversion unit CVU3.
- the analog voltage signal and the second X-direction detection analog voltage signal are equal.
- the voltage signals are also equal.
- the X direction detection differential voltage signal generated by the differential detection unit DMU3 is zero.
- the differential voltage signal for X direction detection output from the differential detection unit DMU3 is converted (demodulated) from a carrier frequency signal to a drive frequency (for example, several tens of kHz) and a signal by the synchronous detection unit WDU3.
- the drive frequency signal is converted (demodulated) into a low frequency (DC to several hundred Hz) signal (a demodulated voltage signal for X direction detection).
- the low-frequency signal thus converted is subjected to removal of high-frequency components by the low-pass filter LPF2, and a signal corresponding to the acceleration in the X direction is output. In this way, the acceleration in the X direction can be detected.
- a carrier voltage (Vca) of several hundred kHz is applied to the weight M3, and this carrier voltage (Vca) is charged by the two detection electrodes DTE4 according to the capacitance of the detection capacitor element.
- Vca carrier voltage
- the CV converter CVU4 Due to the movement of the charge at one detection electrode DTE4, the CV converter CVU4 generates a first Y-direction detection analog voltage signal.
- a second Y-direction detection analog voltage signal is generated by the CV conversion unit CVU4 due to the movement of electric charge at the other detection electrode DTE4.
- the first Y-direction detection analog voltage signal and the second Y-direction detection analog voltage signal generated by the CV conversion unit CVU4 are respectively converted into the first Y-direction detection digital voltage signal and the second Y-direction in the AD conversion unit ADU4. It is converted into a digital voltage signal for detection. Thereafter, the first Y-direction detection digital voltage signal and the second Y-direction detection digital voltage signal output from the AD conversion unit ADU4 are input to the differential detection unit DMU4 and calculated. Specifically, the differential detection unit DMU4 calculates a difference between the first Y-direction detection digital voltage signal and the second Y-direction detection digital voltage signal and outputs a Y-direction detection differential voltage signal.
- the weight M3 is in a stationary state.
- the capacitance of the detection capacitive element by one detection electrode DTE4 and the capacitance of the detection capacitive element by the other detection electrode DTE4 are equal, the first Y-direction detection for the Y direction generated by the CV conversion unit CVU4 The analog voltage signal and the second Y-direction detection analog voltage signal are equal.
- the voltage signals are also equal. Therefore, when no acceleration is applied in the Y direction, the Y direction detection differential voltage signal generated by the differential detection unit DMU4 is zero.
- the first Y-direction detection analog voltage signal and the second Y-direction detection analog voltage signal generated by the CV conversion unit CVU4 are different. Then, the first Y direction detection digital voltage signal converted from the first Y direction detection analog voltage signal by the AD conversion unit ADU4, and the second Y direction detection digital signal converted from the second Y direction detection analog voltage signal by the AD conversion unit ADU4.
- the voltage signal will also be different. Therefore, for example, when acceleration is applied in the + Y direction, a differential voltage signal for Y direction detection that is proportional to the magnitude of acceleration is output from the differential detection unit DMU4.
- the differential voltage signal for Y direction detection output from the differential detection unit DMU4 is converted (demodulated) from a carrier frequency signal to a drive frequency (for example, several tens of kHz) and a signal by the synchronous detection unit WDU4, and
- the drive frequency signal is converted (demodulated) into a low frequency (DC to several hundred Hz) signal (a demodulated voltage signal for X direction detection).
- the low-frequency signal thus converted is subjected to removal of high-frequency components by the low-pass filter LPF3, and a signal corresponding to the acceleration in the Y direction is output. In this way, the acceleration in the Y direction can be detected.
- the circuit configuration for detecting the acceleration in the Z direction will be described.
- the technical idea of the first embodiment is characterized by a circuit configuration that detects acceleration in the Z direction.
- a general circuit configuration for detecting acceleration in the Z direction will be described, then problems of this general technique will be described, and then this embodiment in which a device for solving this problem has been devised will be described. 1 will be described.
- FIG. 7 is a circuit block diagram showing a general circuit configuration for detecting the acceleration in the Z direction.
- a detection electrode DTE5 is formed on the lower side of the weight M4 in the Z direction, and one detection capacitance element is formed by the detection electrode DTE5 and the weight M4.
- Vcom and Vca are applied to the weight M4.
- Vcom indicates a common voltage.
- This common voltage (Vcom) is a DC voltage.
- Vca indicates a carrier voltage.
- This carrier voltage is an alternating voltage.
- the CV conversion unit CVU5 is connected to the detection electrode DTE5, and is configured to convert the capacitance of the detection capacitive element including the detection electrode DTE5 and the weight M4 into a first Z-direction detection analog voltage signal.
- the AD conversion unit ADU5 receives the first Z-direction detection analog voltage signal output from the CV conversion unit CVU5, and converts the first Z-direction detection analog voltage signal into a first Z-direction detection digital voltage signal. It is configured as follows.
- the synchronous detection unit WDU5 is configured to demodulate (down-convert) the first Z-direction detection digital voltage signal and output an X-direction detection demodulated voltage signal. Furthermore, the low-pass filter LPF4 is configured to pass a signal having a frequency lower than the specific frequency without being attenuated, and to attenuate and block a signal having a frequency higher than the specific frequency.
- a general circuit for detecting the acceleration in the Z direction is configured as described above, and the operation for detecting the acceleration in the Z direction using the circuit configured in this way is described below with reference to FIG. While explaining.
- a carrier voltage (Vca) of several hundred kHz is applied to the weight M4, and this carrier voltage (Vca) is charged at the detection electrode DTE5 according to the capacitance of the detection capacitor element.
- Vca carrier voltage
- the CV conversion unit CVU5 Due to the movement of charges at the detection electrode DTE5, the CV conversion unit CVU5 generates a first Z-direction detection analog voltage signal.
- the first Z-direction detection analog voltage signal generated by the CV conversion unit CVU5 is converted into a first Z-direction detection digital voltage signal by the AD conversion unit ADU5.
- the first Z-direction detection digital voltage signal output from the AD conversion unit ADU5 is the synchronous detection unit WDU5, and the low-frequency (DC to several hundred Hz) signal (demodulation voltage for Z-direction detection) from the carrier frequency signal. Signal).
- the low-frequency signal thus converted is subjected to removal of high-frequency components by the low-pass filter LPF4, and a signal corresponding to the acceleration in the Z direction is output.
- a signal corresponding to the initial capacity C 0 of the constructed detection capacitor elements in the detection electrode DTE5 a weight M4 which is stationary is output.
- the weight M4 is displaced in the + Z direction.
- the capacitance of the detection capacitive element including the weight M4 and the detection electrode DTE5 is C 0 - ⁇ C.
- a signal corresponding to the electric capacity (C 0 - ⁇ C) is output.
- the acceleration applied in the + Z direction can be detected.
- the general circuit configuration is configured to form both a detection capacitor element whose capacitance increases when the weight M4 is displaced and a detection capacitor element whose capacitance decreases in the Z direction. Absent. This is because the Z direction is the stacking direction (thickness direction) of the semiconductor substrate, and when an acceleration is applied in the out-of-plane direction (Z direction), the electrostatic capacitance increases with the capacitance of the detection capacitive element. This is because it is difficult in the manufacturing process to form both of the detection capacitor elements whose capacitance is reduced. Therefore, as shown in FIG. 7, in the general circuit configuration for detecting the acceleration in the Z direction, only the detection capacitive element including the weight M4 and the detection electrode DTE5 is formed.
- the acceleration sensor detects the acceleration in the Z direction. Is 1 fF.
- the dynamic range of the acceleration sensor that detects the acceleration in the Z direction is defined as the ratio of the resolution of the acceleration sensor and the maximum signal amount input to the synchronous detection unit WDU5
- the dynamic range of the acceleration sensor is 1 fF / 1000 fF (1 pF). ), which is 0.1%.
- the initial capacitance (C 0 ) is canceled by performing differential detection using a reference capacitive element having the same capacity as the initial capacitance of the detection capacitive element composed of the detection electrode DTE5 and the weight M4. ing.
- the dynamic range is 1 fF / 10 fF, which is 10%. Therefore, it is possible to obtain a dynamic range that is 100 times that in the case where no reference capacitor is used. Therefore, by performing differential detection that cancels the initial capacitance using the reference capacitance element, the dynamic range can be greatly increased, and as a result, the detection sensitivity of the acceleration sensor that detects acceleration in the Z direction. It can be seen that can be improved.
- the acceleration sensor that detects the acceleration in the Z direction, it is desirable to perform differential detection using a reference capacitor element in order to achieve high sensitivity.
- a reference capacitor element fixed capacitor element
- the sensor can be downsized or the acquisition chip per semiconductor wafer can be obtained.
- the effect of reducing the manufacturing cost due to the increase in the number is limited. That is, from the viewpoint of improving the sensitivity of the acceleration sensor that detects acceleration in the Z direction, it is desirable to form the reference capacitor element on the semiconductor chip, but simply form the reference capacitor element that is a fixed capacitor on the semiconductor chip. This technique is not desirable from the viewpoint of miniaturization and cost reduction of the sensor.
- FIG. 8 is a circuit block diagram showing a circuit configuration for detecting the acceleration in the Z direction in the first embodiment.
- a detection electrode DTE5 is formed below the weight M4 in the Z direction, and one detection capacitor element is formed by the detection electrode DTE5 and the weight M4.
- Vcom and Vca are applied to the weight M4.
- Vcom indicates a common voltage.
- This common voltage (Vcom) is a DC voltage.
- Vca indicates a carrier voltage.
- This carrier voltage is an alternating voltage.
- the common voltage (Vcom) and the carrier voltage (Vca) described above are also applied to the weight M2.
- a detection electrode DTE2 is disposed on the lower side of the weight M2 in the Z direction, and one reference capacitance element is formed by the detection electrode DTE2 and the weight M2. That is, the first embodiment is characterized in that the weight M2 and the detection electrode DTE2 used in the angular velocity detection unit are also used as a reference capacitance element of the Z direction acceleration detection unit that detects acceleration in the Z direction. . That is, the Z-direction acceleration detection unit according to the first embodiment is characterized in that a detection capacitor composed of the weight M2 and the detection electrode DTE2 constituting the angular velocity detection unit is used as a reference capacitor element for the detection capacitor element composed of the detection electrode DTE5 and the weight M4. The element is in use.
- the reference capacitance is provided without other functions. Therefore, the reference capacitive element (fixed capacitive element) formed only for the purpose is not necessary, and the composite sensor including the angular velocity detection unit and the Z-direction acceleration detection unit can be downsized.
- the CV conversion unit CVU5 is connected to the detection electrode DTE2 and the detection electrode DTE5, and converts the capacitance of the detection capacitive element including the detection electrode DTE5 and the weight M4 into the first Z-direction detection analog voltage signal. It is configured. Similarly, the CV conversion unit CVU5 is configured to convert the capacitance of the reference capacitive element including the detection electrode DTE2 and the weight M2 into a second Z-direction reference analog voltage signal.
- the gain adjustment unit GAU1 is configured to adjust the magnitude (gain) of the second Z-direction reference analog voltage signal output from the CV conversion unit CVU5.
- the AD conversion unit ADU5 receives the first Z direction detection analog voltage signal output from the CV conversion unit CVU5 and converts the first Z direction detection analog voltage signal into a first Z direction detection digital voltage signal.
- the second Z-direction reference analog voltage signal output from the gain adjustment unit GAU1 is input, and the second Z-direction reference analog voltage signal is converted into a second Z-direction reference digital voltage signal.
- the differential detection unit DMU5 takes the difference between the first Z-direction detection digital voltage signal and the second Z-direction reference digital voltage signal output from the AD conversion unit ADU5, and outputs a Z-direction detection differential voltage signal Is configured to do.
- the synchronous detection unit WDU5 is configured to demodulate (down-convert) the Z direction detection differential voltage signal and output a Z direction detection demodulated voltage signal.
- the low-pass filter LPF4 is configured to pass a signal having a frequency lower than the specific frequency without being attenuated, and to attenuate and block a signal having a frequency higher than the specific frequency.
- the reason why the gain adjustment unit GAU1 is provided to adjust the magnitude of the second Z-direction reference analog voltage signal will be described.
- a detection capacitive element including the weight M4 and the detection electrode DTE5 is used, and the weight M2 and the detection electrode DTE2 constituting the angular velocity detection unit are used as the reference capacitive element.
- the reference capacitive element made up of the weight M2 and the detection electrode DTE2 and the detection capacitive element made up of the weight M4 and the detection electrode DTE5 are constituent elements originally belonging to different detection units (Z-direction acceleration detection unit and angular velocity detection unit).
- the detection capacitor element and the reference capacitor element described above usually have different shapes (area and distance between elements). This means that the initial capacitance of the detection capacitive element constituted by the weight M4 and the detection electrode DTE5 is different from the reference capacitance of the reference capacitive element constituted by the weight M2 and the detection electrode DTE2.
- the first Z direction detection analog voltage signal obtained by converting the initial capacitance of the detection capacitive element by the CV conversion unit CVU5 and the reference capacitive element by the CV conversion unit CVU5 The second Z-direction reference analog voltage signal obtained by converting the reference capacitance is different, and the Z-direction detection differential voltage signal output from the differential detection unit DMU5 does not become zero.
- an acceleration sensor when no acceleration is applied in the Z direction, it is desirable that the Z direction detection differential voltage signal output from the differential detection unit DMU5 is zero.
- the gain adjustment unit GAU1 that adjusts the magnitude (gain) of the second analog voltage signal for reference in the Z direction
- differential detection is performed when no acceleration is applied in the Z direction.
- the differential voltage signal for Z direction detection output from the unit DMU5 is set to zero. That is, in the first embodiment, the zero point resulting from the difference between the initial capacitance of the detection capacitive element constituted by the weight M4 and the detection electrode DTE5 and the reference capacitance of the reference capacitive element constituted by the weight M2 and the detection electrode DTE2
- a gain adjustment unit GAU1 is provided.
- the gain adjustment unit GAU1 is configured to adjust the magnitude of the second Z-direction reference analog voltage signal.
- the gain adjustment unit GAU1 may be provided so as to adjust the magnitude of the detection analog voltage signal.
- the Z-direction acceleration detection unit according to the first embodiment is characterized by the weight M2 and the detection electrode DTE2 constituting the angular velocity detection unit as the reference capacitance element for the detection capacitance element including the detection electrode DTE5 and the weight M4.
- the detection capacitor element is used.
- the technical idea of the first embodiment is that (a) a first detection unit that captures the application of the first physical quantity (acceleration) as a change in capacitance of the first detection capacitive element; A second detection unit that captures application of two physical quantities (angular velocity) as a change in capacitance of the second detection capacitor element.
- the composite sensor includes a detection signal obtained by converting a capacitance of the first detection capacitive element output from the first detection unit, and the second detection capacitive element output from the second detection unit.
- the first physical quantity is detected based on a difference from a reference signal obtained by converting the capacitance of the first physical quantity.
- the circuit for detecting the acceleration in the Z direction using the Z direction acceleration detection unit is configured as described above.
- the circuit configured as described above is used to perform Z The operation for detecting the acceleration in the direction will be described with reference to FIG.
- a carrier voltage (Vca) of several hundred kHz is applied to the weight M4 and the weight M2, and this carrier voltage (Vca) is determined by the electrostatic capacitance of the detection capacitive element and the static capacitance of the reference capacitive element.
- the detection electrode DTE2 and the detection electrode DTE5 cause charge movement. Due to the movement of the charge at the detection electrode DTE5, the first Z-direction detection analog voltage signal is generated at the CV conversion unit CVU5. Similarly, the second Z-direction reference analog voltage signal is generated by the CV conversion unit CVU5 due to the movement of the charge at the detection electrode DTE2.
- the second Z-direction reference analog voltage signal output from the CV conversion unit CVU5 is input to the gain adjustment unit GAU1, and the magnitude of the second Z-direction reference analog voltage signal is adjusted.
- the first Z-direction detection analog voltage signal generated by the CV conversion unit CVU5 and the second Z-direction reference analog voltage signal whose magnitude is adjusted by the gain adjustment unit GAU1 are respectively converted by the AD conversion unit ADU5. It is converted into a 1Z direction detection digital voltage signal and a second Z direction reference digital voltage signal.
- the first Z-direction detection digital voltage signal and the second Z-direction reference digital voltage signal output from the AD conversion unit ADU5 are input to the differential detection unit DMU5 and calculated.
- the differential detection unit DMU5 takes the difference between the first Z-direction detection digital voltage signal and the second Z-direction reference digital voltage signal and outputs a Z-direction detection differential voltage signal.
- the first Z-direction detection analog voltage signal generated by the CV conversion unit CVU5 is equal to the second Z-direction reference analog voltage signal whose magnitude is adjusted by the gain adjustment unit GAU1. Therefore, the first Z direction detection digital voltage signal obtained by converting the first Z direction detection analog voltage signal by the AD conversion unit ADU5 and the second Z direction reference digital signal obtained by converting the second Z direction reference analog voltage signal by the AD conversion unit ADU5. The voltage signals are also equal. Therefore, when no acceleration is applied in the Z direction, the Z direction detection differential voltage signal generated by the differential detection unit DMU5 is zero.
- the direction detection analog voltage signal and the second Z-direction reference analog voltage signal output from the gain adjustment unit GAU1 are different. Then, the first Z direction detection digital voltage signal converted from the first Z direction detection analog voltage signal by the AD conversion unit ADU5 and the second Z direction reference digital signal converted from the second Z direction reference analog voltage signal by the AD conversion unit ADU5. The voltage signal will also be different. Therefore, for example, when acceleration is applied in the + Z direction, the differential detection unit DMU5 outputs a Z-direction detection differential voltage signal proportional to the magnitude of the acceleration.
- the differential voltage signal for Z-direction detection output from the differential detection unit DMU5 is converted into a low-frequency (DC to several hundred Hz) signal (demodulation voltage signal for Z-direction detection) from a carrier frequency signal by the synchronous detection unit WDU5. ) Is converted (demodulated).
- the low-frequency signal thus converted is subjected to removal of high-frequency components by the low-pass filter LPF4, and a signal corresponding to the acceleration in the Z direction is output. In this way, the acceleration in the Z direction can be detected.
- the detection capacitive element including the weight M2 and the detection electrode DTE2 constituting the angular velocity detection unit is used as a reference capacitive element for the detection capacitive element including the detection electrode DTE5 and the weight M4. Used together.
- the reference capacitive element including the weight M2 and the detection electrode DTE2 constituting the angular velocity detection unit is provided without other functions. Therefore, the reference capacitive element (fixed capacitive element) formed only for the purpose is not necessary, and the composite sensor including the angular velocity detection unit and the Z-direction acceleration detection unit can be downsized. That is, in the first embodiment, by using differential detection using a reference capacitive element for detection of acceleration in the Z direction, high-sensitivity sensing can be realized, and angular velocity detection can be performed as a reference capacitive element.
- the detection capacitor element composed of the weight M2 and the detection electrode DTE2 constituting the unit is used, there is no other function, and a reference capacitor element (fixed capacitor element) formed only for providing a reference capacitor is provided. Since a space to be formed is not necessary, a remarkable effect that the composite sensor including the angular velocity detection unit and the Z-direction acceleration detection unit can be reduced in size can be obtained.
- FIG. 9 is a graph showing frequency characteristics in the detection vibration system of the angular velocity detection unit and frequency characteristics of the Z-direction acceleration detection unit.
- the horizontal axis indicates the frequency (Hz), and the vertical axis indicates the displacement.
- the frequency characteristic of the detection vibration system of the angular velocity detector has a frequency characteristic that has a resonance peak at several tens of kHz.
- the frequency characteristic of the Z-direction acceleration detector has a frequency characteristic that does not have a resonance peak and is sensitive to several hundred Hz.
- the angular velocity detection unit obtains a large drive amplitude AX for the purpose of high sensitivity. It is designed to be.
- the Z-direction acceleration detection unit is designed so as to reduce the natural frequency as much as possible, strengthen the damping, and have no resonance peak because there are many demands for measuring low-frequency vibrations such as gravity and inclination. Further, in the Z direction acceleration sensor, unnecessary high frequency signals are processed so as not to be output using a low pass filter.
- the Z-direction acceleration detection unit is configured such that the weight M4 is displaced in the Z direction by the input acceleration.
- the relationship between the displacement (z 0 ) and the input acceleration (a) is as shown in equation (6).
- Equation (7) a ⁇ (1 / ⁇ 0 2 ⁇ 1 / ⁇ 1 2 ) (7)
- the natural frequency of the detection vibration system in the angular velocity detection unit is set to several tens of kHz (for example, 10 to 30 kHz), while the detection vibration system has a natural frequency in the Z-direction acceleration detection unit.
- the frequency is designed to be, for example, 1 to 3 kHz.
- the detection vibration system in the Z-direction acceleration detection unit ⁇ which is the ratio of the natural frequency ( ⁇ 0 ) to the natural frequency ( ⁇ 1 ) of the reference capacitive element, is a value of 10 or more, and the differential displacement ⁇ z is a value of 99% or more of the displacement z 0 .
- the natural frequency ( ⁇ 1 ) of the detection vibration system in the angular velocity detection unit is made larger than the natural frequency ( ⁇ 0 ) of the detection vibration system in the Z-direction acceleration detection unit, Even when the detection vibration system in the angular velocity detection unit is used as a reference capacitance element of the Z-direction acceleration detection unit, a differential displacement ⁇ z that is substantially equivalent to that when a fixed capacitance element with a fixed capacitance is used as the reference capacitance element is obtained. Can do. This is because the fixed vibration element is not used by using the detection vibration system as a reference capacitor element in the angular velocity detector that can be regarded as being relatively stationary as seen from the movement of the Z direction acceleration detector. However, this means that a high-performance and small composite sensor can be obtained. From the above, it can be seen that the detection capacitive element of the angular velocity detection unit can be used as the reference capacitive element of the Z-direction acceleration detection unit.
- the natural frequency of the angular velocity detection unit does not correlate with the sensitivity of the angular velocity detection unit, as described in Expression (5), so the sensitivity of the angular velocity detection unit is lowered.
- the natural frequency of the angular velocity detector can be arbitrarily selected.
- the detection vibration system in the angular velocity detection unit is used as the reference capacitive element of the Z direction acceleration detection unit, the detection in the angular velocity detection unit has a natural frequency larger than the natural frequency of the detection vibration system in the Z direction acceleration detection unit.
- the natural frequency of the vibration system can be set.
- the angular velocity detection unit becomes insensitive to low-frequency vibration disturbances.
- An angular velocity detector can be realized.
- the detection capacitor element of the angular velocity detector that can be regarded as a relatively fixed capacitor can be used as the reference capacitor element.
- the Z direction acceleration detection unit hardly reacts and remains stationary, but the angular velocity detection unit has a resonance peak. Therefore, a capacitance change occurs in the detection capacitive element of the angular velocity detection unit used as the reference capacitive element. This capacitance change is input to the CV conversion unit CVU5 shown in FIG. 8, and then cut by the low-pass filter LPF4 through the synchronous detection unit WDU5.
- this capacitance change is cut by the low-pass filter LPF4, it does not appear as the output of the Z-direction acceleration detector, but depending on the magnitude of the input high frequency vibration of tens of kHz, the low-pass filter LPF4 There is a risk of causing saturation or a zero point shift of the AD conversion unit disposed before, and the function of the Z-direction acceleration detection unit may be lost.
- the frequency of the voltage signal input to the synchronous detection unit WDU5 illustrated in FIG. (Frequency of (Vca)) ⁇ (the natural frequency of the detected vibration system in the angular velocity detector). Therefore, the signal pass band (frequency characteristic) from the CV conversion unit CVU5 to the synchronous detection unit WDU5 is obtained by subtracting the natural frequency of the detection vibration system in the angular velocity detection unit from the frequency of the carrier wave (frequency of the carrier voltage (Vca)).
- FIG. 10 is a diagram illustrating bandwidth filter characteristics from the CV conversion unit CVU5 to the synchronous detection unit WDU5.
- the horizontal axis indicates the frequency (Hz), and the vertical axis indicates the magnitude (gain) of the signal passing therethrough.
- the bandwidth filter characteristic from the CV conversion unit CVU5 to the synchronous detection unit WDU5 is more than the value obtained by subtracting the natural frequency (frg) of the detection vibration system in the angular velocity detection unit from the carrier frequency (fca). It can be seen that the value is larger and smaller than the sum of the carrier frequency (fca) and the natural frequency (frg) of the detected vibration system in the angular velocity detection unit.
- the signal passing band includes the signal that passes through the signal passing through the original signal size (0 dB) to the half size ( ⁇ 3 dB).
- the detection capacitive element of the angular velocity detection unit is used as the reference capacitive element of the Z direction acceleration detection unit.
- the present invention is not limited thereto, and the weight M3 of the XY direction acceleration detection unit Even when a capacitor formed between the semiconductor substrates is used as a reference capacitor, the same effect as in the first embodiment can be obtained.
- the weight M3 of the XY direction acceleration detection unit is difficult to be displaced in the Z direction
- this reference capacitance has the advantage of being a complete fixed capacitance element.
- the composite sensor according to the first embodiment the composite sensor that can detect the angular velocity of one axis (Y direction) and the acceleration of three axes (XYZ direction) is taken as an example. However, only the acceleration of three axes can be detected.
- the technical idea of the first embodiment can also be applied to the composite sensor.
- the composite sensor according to the first embodiment is configured as described above, and the manufacturing method thereof will be described below with reference to the drawings. Specifically, in the first embodiment, a method for manufacturing a composite sensor will be described using a cross-sectional view taken along line AA in FIG.
- a semiconductor substrate 1S on which an insulating film OX1 made of a silicon oxide film having a thickness of about 1 ⁇ m is formed is prepared.
- the thickness of the semiconductor substrate 1S is, for example, about several hundred ⁇ m.
- a polysilicon film (polycrystalline silicon film) having a thickness of, for example, about 1 ⁇ m is formed on the insulating film OX1, and this polysilicon film is patterned, for example, to detect the detection electrode DTE1.
- a wiring layer such as a detection electrode DTE5.
- the wiring layers such as the detection electrode DTE1 and the detection electrode DTE5 are formed of a polysilicon film.
- the present invention is not limited to this.
- aluminum (Al), titanium tungsten (TiW), tungsten silicide ( A metallic conductive film such as WSi) can also be used.
- an insulating film OX2 made of a silicon oxide film (TEOS (Tetra Ethyl Ortho Silicate) film) is formed so as to cover the detection electrode DTE1 and the detection electrode DTE5.
- the insulating film OX2 can be formed by, for example, a CVD (Chemical Vapor Deposition) method. Thereafter, the insulating film OX2 is polished by CMP (Chemical-Mechanical-Polishing) method until the detection electrode DTE1 and the detection electrode DTE5 are exposed. Subsequently, an insulating film SN1 made of a silicon nitride film is formed on the insulating film OX2 including the exposed detection electrodes DTE1 and DTE5.
- CMP Chemical-Mechanical-Polishing
- an insulating film OX3 made of, for example, a silicon oxide film having a thickness of about 1 ⁇ m to 4 ⁇ m is formed on the insulating film SN1.
- This insulating film OX3 can be formed by using, for example, a CVD method.
- a contact hole CNT1 that penetrates the insulating film OX3 and the insulating film SN1 and reaches the detection electrode DTE1 is formed by using a photolithography technique and an etching technique.
- a contact hole CNT2 that penetrates the insulating film OX3 and the insulating film SN1 and reaches the detection electrode DTE5 is formed by using a photolithography technique and an etching technique.
- a polysilicon film is formed on the insulating film OX3 in which the contact holes CNT1 and CNT2 are formed.
- This polysilicon film is formed so as to fill the insides of the contact hole CNT1 and the contact hole CNT2.
- the unnecessary polysilicon film formed on the insulating film OX3 is removed by using, for example, a CMP method so that the polysilicon film is embedded only in the contact hole CNT1 and the contact hole CNT2, and the plug PLG1 And the plug PLG2 is formed.
- a device layer DL made of, for example, silicon is pasted on the insulating film OX3 on which the plugs PLG1 and PLG2 are formed.
- the device layer DL is made of, for example, silicon having a thickness of several tens of ⁇ m. Actually, it is difficult to directly attach silicon having a thickness of several tens of ⁇ m to the insulating film OX3. Therefore, after silicon having a thickness of several hundred ⁇ m is attached to the insulating film OX3, A method of polishing to a thickness of several tens of ⁇ m is employed. Thereafter, the pad PD1 is formed on the device layer DL.
- the device layer DL is processed by using a photolithography technique and an etching technique. Specifically, by processing the device layer DL, for example, a pedestal part PED1, a frame body FR, a weight M1, a support beam SB3, a weight M4, a pedestal part PED2, and the like are formed. At this time, although not shown in FIG. 15, the elements having a relatively large area such as the weight M1 and the weight M4 are etched from the viewpoint of reducing the time required for etching the insulating film OX3 serving as the sacrifice layer. A hole is formed.
- the insulating film OX3 serving as a sacrificial layer is removed using, for example, hydrofluoric acid from the etching hole and the gap formed by processing the device layer DL.
- the insulating film SN1 formed under the insulating film OX3 functions as an etching stopper.
- the insulating film OX3 formed in the lower layer such as the weight M1, the support beam SB3, and the weight M4 is removed, and a gap is formed between these elements and the insulating film SN1.
- the weight M1, the support beam SB3, and the weight M4 are movable.
- the insulating film OX3 formed in the lower layer remains on the pedestal part PED1, the frame body FR, and the pedestal part PED2, and the pedestal part PED1, the frame body FR, and the pedestal part PED2 are formed by the insulating film OX3 formed in the lower layer. It will be in the state fixed to semiconductor substrate 1S.
- a cover COV is disposed on the frame body FR, and the cavity CAV1 in which the weight M1 is formed and the cavity CAV2 in which the support beam SB3 and the weight M4 are formed are sealed.
- glass or silicon can be used for the cover COV, and the cavity CAV1 and the cavity CAV2 can be hermetically sealed by a method such as anodic bonding or surface activation bonding.
- the cover COV can be sealed using, for example, a glass frit or an adhesive, and the cover COV can be made of metal or the like.
- a gas absorbing material (getter) or a gas generating material (reverse getter) may be formed on the cover COV for the purpose of controlling the pressure of the cavity portion CAV1 and the cavity portion CAV2.
- a gas absorbing material (getter) or a gas generating material (reverse getter) may be formed on the cover COV for the purpose of controlling the pressure of the cavity portion CAV1 and the cavity portion CAV2.
- FIG. 16 is a cross-sectional view showing a mounting configuration of the composite sensor according to the first embodiment.
- the composite sensor CS1 semiconductor chip CHP1
- the composite sensor CS1 is mounted on a ceramic package PAC together with a signal processing semiconductor chip CHP2.
- a signal processing semiconductor chip CHP2 is mounted on the bottom surface of the ceramic package PAC via an adhesive ADH1
- the composite sensor CS1 is mounted on the semiconductor chip CHP2 via an adhesive ADH2.
- the potential of the semiconductor chip CHP1 can be fixed by configuring the adhesive ADH2 from a conductive adhesive.
- the pad PD1 formed on the composite sensor CS1 and the pad PD2 formed on the semiconductor chip CHP2 are electrically connected by a wire W1.
- the pad PD2 formed on the semiconductor chip CHP2 is electrically connected to the pad PD3 formed inside the ceramic package PAC by a wire W2.
- the pad PD3 formed inside the ceramic package PAC is electrically connected to a terminal TE1 formed outside the ceramic package PAC via the wiring WL1.
- the internal space of the ceramic package PAC in which the composite sensor CS1 and the signal processing semiconductor chip CHP2 are arranged is sealed with a cap CAP.
- the composite sensor CS1 according to the first embodiment is mounted and configured.
- a plastic package or the like may be used in addition to the ceramic package PAC as a package into which the composite sensor CS1 and the signal processing semiconductor chip CHP2 are placed.
- the package is not particularly limited as long as it can protect the composite sensor CS1, the signal processing semiconductor chip CHP2, the wire W1, the wire W2, and the like and can exchange signals with the outside. May be.
- the first reference capacitive element used in the angular velocity detection unit and the second reference capacitive element used in the Z-direction acceleration detection unit are one shared reference capacitive element shared with each other. An example will be described.
- FIG. 17 is a plan view showing the configuration of the composite sensor CS2 in the second embodiment.
- the composite sensor CS2 according to the second embodiment includes an angular velocity detection unit JA and a Z-direction acceleration detection unit AC (Z).
- the angular velocity detection unit JA has a weight (movable part) M1 formed on the semiconductor substrate 1S and capable of moving (vibrating).
- the angular velocity detection unit JA includes a support beam SB1 that supports the weight M1 in a floating state with respect to the semiconductor substrate 1S, and the support beam SB1 includes a drive direction (X direction) and a detection direction. It is configured to be deformable (elastically deformed) in both directions (Z direction). That is, one end of the support beam SB1 is connected to the weight M1, and the other end of the support beam SB1 is connected to the fixed portion FX1 fixed to the semiconductor substrate 1S.
- the angular velocity detection unit JA includes a drive electrode DRE1 and a drive electrode DRE2 that form a capacitance with the weight M1. That is, one drive capacitor element is formed by the weight M1 and the drive electrode DRE1, and another drive capacitor element is formed by the weight M1 and the drive electrode DRE2.
- a high-frequency signal high-frequency voltage
- the drive capacitive element to which the high-frequency signal (high-frequency voltage) is applied is configured.
- An electrostatic attractive force is generated, and the weight M1 can be vibrated by the electrostatic attractive force.
- the drive capacitor element composed of the drive electrode DRE2 and the weight M1 is similarly configured. As a result, the weight M1 is driven to vibrate.
- the angular velocity detection unit JA has a monitor electrode ME1 and a monitor electrode ME2 for monitoring the drive amplitude of the weight M1 that is driving and vibrating, and an angular velocity around the Y-axis direction is applied.
- a detection electrode DTE1 for detecting displacement in the detection direction (Z-axis direction) is provided. That is, for example, the detection capacitor element is formed by the weight M1 and the detection electrode DTE1 formed in the lower layer of the weight M1, and the displacement in the detection direction can be regarded as the capacitance change of the detection capacitor element. ing.
- the angular velocity detection unit JA of the first embodiment is configured as a tuning fork structure having two weights, when the angular velocity around the Y axis is applied, a detection capacitive element whose capacitance increases; There are detection capacitive elements whose capacitance is reduced. For this reason, in the angular velocity detection unit JA of the first embodiment, differential detection can be performed between the detection capacitive element whose capacitance increases and the detection capacitive element whose capacitance decreases. Sensitive sensing can be realized without using a capacitive element.
- the angular velocity detection unit JA of the second embodiment has only one weight and does not constitute a tuning fork structure.
- a reference capacitive element is required to detect displacement in the Z direction (detection direction) due to application of angular velocity around the Y axis with high sensitivity.
- the Z-direction acceleration detection unit AC (Z) has one movable weight M4 formed on the semiconductor substrate 1S.
- the Z-direction acceleration detection unit AC (Z) includes a support beam SB3 that supports the weight M4 in a floating state with a certain distance from the semiconductor substrate 1S, and the support beam SB3 has a detection direction (Z It can be deformed (elastically deformed) in the direction). That is, one end of the support beam SB3 is connected to the weight M4, and the other end of the support beam SB3 is connected to the fixed portion FX3 fixed to the semiconductor substrate 1S.
- the Z-direction acceleration detection unit AC (Z) has a detection electrode DTE5 for detecting displacement in the detection direction (Z-axis direction) when acceleration is applied in the Z direction. That is, for example, the detection capacitor element is formed by the weight M4 and the detection electrode DTE5 formed in the lower layer of the weight M4, and the displacement in the detection direction (X-axis direction) is regarded as the capacitance change of the detection capacitor element. It is configured to be able to.
- the Z-direction acceleration detector AC (Z) in the second embodiment has the same configuration as the Z-direction acceleration detector AC (Z) in the first embodiment. Therefore, also in the second embodiment, when the acceleration in the Z direction is applied, in order to detect the displacement of the weight M4 in the Z direction with high sensitivity, the reference capacitive element is required together with the detection electrode DTE5.
- one reference capacitive element RC is provided on the semiconductor substrate 1S, and the reference capacitive element RC is mutually connected by the angular velocity detection unit JA and the Z-direction acceleration detection unit AC (Z). Sharing. That is, in the second embodiment, since both the angular velocity detection unit JA and the Z-direction acceleration detection unit AC (Z) require the reference capacitive element, one reference capacitive element RC that can be shared with each other is provided on the semiconductor substrate 1S. Forming. As described above, in the second embodiment, since the single reference capacitive element RC is shared by both the angular velocity detection unit JA and the Z-direction acceleration detection unit AC (Z), it is possible to reduce the size of the composite sensor CS2. it can.
- the composite sensor CS2 can be reduced in size. Can be achieved.
- such a reference capacitive element RC has an upper electrode RE1 and a lower electrode RE2.
- FIG. 18 is a diagram showing a cross-sectional structure of the reference capacitor element RC, and is a cross-sectional view taken along line AA of FIG.
- a silicon oxide film OX1 is formed on a semiconductor substrate 1S, and a wiring WL2 and a lower electrode RE2 are formed on the silicon oxide film OX1.
- a silicon oxide film OX2 is buried in a gap between the wiring WL2 and the lower electrode RE2.
- a silicon nitride film SN1 is formed over the wiring WL2 and the lower electrode RE2, and a silicon oxide film OX3 is formed over the silicon nitride film SN1.
- An upper electrode RE1 is formed on the silicon oxide film OX3.
- a frame FR, a pedestal part PED1, and a pedestal part PED2 are formed in the same layer as the upper electrode RE1.
- a plurality of etching holes are formed in the upper electrode RE1, and a part of the silicon oxide film OX3 is removed through the etching holes.
- a cover COV is disposed on the frame FR, and the cavity CAV in which the upper electrode RE1 is formed is sealed.
- the reference capacitive element RC configured as described above has an upper electrode RE1 and a lower electrode RE2, and the upper electrode RE1 is electrically connected to the pad PD4 via the wiring WL2 and the pedestal part PED1. .
- the lower electrode RE2 is electrically connected to the pad PD5 via the pedestal part PED2.
- the capacitive insulating film of the reference capacitive element RC is formed of a silicon nitride film and a silicon oxide film OX3 formed between the upper electrode RE1 and the lower electrode RE2.
- FIG. 19 is a circuit block showing a circuit configuration of the composite sensor according to the second embodiment.
- the weight M1 is excited in the X direction by the drive electrode DRE1 disposed on the left side of the weight M1 and the drive electrode DRE2 disposed on the right side of the weight M1.
- Vcom + Vb + Vd is applied as a drive signal to the drive electrode DRE1
- Vcom + Vb ⁇ Vd is applied as a drive signal to the drive electrode DRE2.
- Vcom + Vca is applied to the weight M1. Therefore, for example, the potential difference between the weight M1 and the drive electrode DRE1 is Vb + Vd, and the potential difference between the weight M1 and the drive electrode DRE2 is Vb ⁇ Vd.
- the drive electrodes DRE1 and the weight M1 and the drive electrodes DRE2 and the weight M1 form drive capacitance elements, respectively, and the above-described potential difference is generated in these drive capacitance elements.
- an electrostatic force is generated in each drive capacitive element, and the weight M1 is driven to vibrate based on the electrostatic force.
- the drive amplitude AX is monitored by using the monitor electrode ME1 disposed on the left side of the weight M1 and the monitor electrode ME2 disposed on the right side of the weight M1. Specifically, the drive amplitude AX is monitored by detecting changes in the capacitance of the monitor capacitive element composed of the weight M1 and the monitor electrode ME1, and the weight M1 and the monitor electrode ME2.
- a carrier voltage (Vca) of several hundreds kHz is applied to the weight M1, and this carrier voltage (Vca) depends on the capacitance of the monitor capacitive element and the monitor electrode ME1 and the monitor electrode.
- Electric charge movement is generated in ME2. Due to the movement of charges at the monitor electrode ME1, the CV converter CVU6 generates a first monitor analog voltage signal.
- the second monitor analog voltage signal is generated by the CV converter CVU6 due to the movement of the electric charge at the monitor electrode ME2. Then, the first monitor analog voltage signal and the second monitor analog voltage signal generated by the CV converter CVU6 are respectively converted into the first monitor digital voltage signal and the second monitor digital voltage by the AD converter ADU6. Converted to a signal.
- the first monitor digital voltage signal and the second monitor digital voltage signal output from the AD conversion unit ADU6 are input to the differential detection unit DMU6 and operated.
- the differential detection unit DMU6 takes the difference between the first monitor digital voltage signal and the second monitor digital voltage signal and outputs the monitor differential voltage signal.
- the carrier voltage (Vca) and the driving voltage (+ Vd or ⁇ Vd) are applied to the spindle M1. Accordingly, when the weight M1 is driven to vibrate, for example, the capacitance of the monitor capacitive element including the monitor electrode ME1 as a component increases in proportion to the drive amplitude AX of the weight M1, and the monitor electrode ME2 is configured as a component.
- the change in the capacitance of the monitor capacitance element to decrease, or the capacitance of the monitor capacitance element having the monitor electrode ME1 as a constituent element decreases, and the capacitance of the monitor capacitance element having the monitor electrode ME2 as a constituent element. Changes that increase.
- the first monitor analog voltage signal and the second monitor analog voltage signal generated by the CV converter CVU6 are different.
- the first monitor digital voltage signal obtained by converting the first monitor analog voltage signal by the AD converter ADU6 is different from the second monitor digital voltage signal obtained by converting the second monitor analog voltage signal by the AD converter ADU6. It will be. Therefore, when the weight M1 is driven to vibrate, the differential detection unit DMU6 outputs a monitoring differential voltage signal proportional to the drive amplitude AX.
- the differential voltage signal for monitoring output from the differential detection unit DMU6 is converted (demodulated) from a carrier frequency signal to a drive frequency (for example, several tens of kHz) and a signal by the synchronous detection unit WDU6, and further driven.
- the frequency signal is converted (demodulated) into a low frequency (DC to several hundred Hz) signal.
- the drive amplitude AX converted into a low-frequency signal in this way is input to the AGC unit AGC and compared with a preset target value. Based on the comparison result, the magnitude of the drive voltage Vd ( ⁇ Vd) is adjusted via the DA converter DAU2. In this way, feedback control can be performed so that the drive amplitude AX becomes a preset target value.
- the frequency (drive frequency) of the drive voltage (Vd or ⁇ Vd) for driving and vibrating the weight M1 is also set. It is controlled to be constant.
- feedback control using PLL (Phase Locked Loop) is performed in order to make the drive frequency follow the change in the natural frequency of the drive vibration system caused by the change in the surrounding environment.
- AFC Auto Frequency Control
- the carrier voltage (Vca) is also applied to the reference capacitive element composed of the upper electrode RE1 and the lower electrode RE2, and CV conversion is performed by the movement of charges proportional to the capacitance between the upper electrode RE1 and the lower electrode RE2.
- the second reference analog voltage signal is generated by the unit CVU7.
- the first detection analog voltage signal output from the CV conversion unit CVU7 is input to the gain adjustment unit GAU2, and the magnitude of the first detection analog voltage signal is adjusted. Thereafter, the first detection analog voltage signal and the second reference analog voltage signal are converted into a first detection digital voltage signal and a second reference digital voltage signal, respectively, in the AD converter ADU7. Thereafter, the first detection digital voltage signal and the second reference digital voltage signal output from the AD conversion unit ADU7 are input to the differential detection unit DMU7 and operated. Specifically, the differential detection unit DMU 7 takes the difference between the first detection digital voltage signal and the second reference digital voltage signal, and outputs the detection differential voltage signal.
- the differential voltage signal for detection output from the differential detection unit DMU7 is converted (demodulated) from a carrier frequency signal to a drive frequency (for example, several tens of kHz) and a signal by the synchronous detection unit WDU7, and further driven.
- the frequency signal is converted (demodulated) into a low frequency (DC to several hundred Hz) signal (detection demodulated voltage signal).
- the low-frequency signal thus converted is subjected to removal of high-frequency components by the low-pass filter LPF5, and a signal corresponding to the angular velocity is output. In this way, the angular velocity around the Y axis can be detected.
- a carrier voltage (Vca) of several hundred kHz is applied to the weight M4 and the reference capacitive element, and this carrier voltage (Vca) is determined by the capacitance of the detection capacitive element and the reference capacitive element.
- the lower electrode RE2 and the detection electrode DTE5 cause charge movement. Due to the movement of the charges at the detection electrode DTE5, the CV conversion unit CVU8 generates a first Z-direction detection analog voltage signal. Similarly, the second reference analog voltage signal is generated in the CV conversion unit CVU8 due to the movement of the electric charge in the lower electrode RE2 of the reference capacitance element.
- the first Z-direction detection analog voltage signal output from the CV conversion unit CVU8 is input to the gain adjustment unit GAU3, and the magnitude of the first Z-direction detection analog voltage signal is adjusted. Thereafter, the second reference analog voltage signal generated by the CV conversion unit CVU8 and the first Z-direction detection analog voltage signal whose magnitude is adjusted by the gain adjustment unit GAU3 are respectively converted by the AD conversion unit ADU8. It is converted into a digital voltage signal for direction detection and a digital voltage signal for second reference. Thereafter, the first Z-direction detection digital voltage signal and the second reference digital voltage signal output from the AD conversion unit ADU8 are input to the differential detection unit DMU8 and operated. Specifically, the differential detection unit DMU8 takes the difference between the first Z-direction detection digital voltage signal and the second reference digital voltage signal and outputs a Z-direction detection differential voltage signal.
- the analog voltage signal for reference 2 is different from the analog voltage signal for detection in the first Z direction output from the gain adjustment unit GAU3. Then, the first Z direction detection digital voltage signal converted from the first Z direction detection analog voltage signal by the AD conversion unit ADU8, and the second reference digital voltage signal converted from the second reference analog voltage signal by the AD conversion unit ADU8. Will also be different. Therefore, for example, when acceleration is applied in the + Z direction, a differential voltage signal for Z direction detection that is proportional to the magnitude of acceleration is output from the differential detection unit DMU8.
- the differential voltage signal for Z-direction detection output from the differential detection unit DMU8 is a synchronous detection unit WDU8, and a low-frequency (DC to several hundred Hz) signal (demodulation voltage signal for Z-direction detection) from a carrier frequency signal. ) Is converted (demodulated).
- the low-frequency signal thus converted is subjected to removal of high-frequency components by the low-pass filter LPF6, and a signal corresponding to the acceleration in the Z direction is output. In this way, the acceleration in the Z direction can be detected.
- the angular velocity detection unit and the Z-direction acceleration detection unit refer to different reference capacitive elements, respectively. Compared to the case, the size of the composite sensor can be reduced. Furthermore, in the second embodiment, gain adjustment units are provided in the signal processing unit of the angular velocity detection unit and the signal processing unit of the Z direction acceleration detection unit, respectively. Thereby, the imbalance between the initial capacitance of the detection capacitive element and the reference capacitance of the reference capacitive element in the angular velocity detection unit can be adjusted. Similarly, the imbalance between the initial capacitance of the detection capacitive element and the reference capacitance of the reference capacitive element in the Z-direction acceleration detection unit can be adjusted. Therefore, it is possible to individually adjust the initial zero offset of the composite sensor.
- a reference capacitance element can be shared by the acceleration detection unit and the pressure detection unit.
- the detection capacitive element of the angular velocity detection unit can be used as the reference capacitive element of the pressure detection unit.
- each other can be used as a reference capacitive element.
- the present invention can be widely used in fields such as attitude detection of automobiles and robots, camera shake correction of digital cameras, attitude detection and direction detection of navigation systems, and attitude detection sensors for game machines.
- it can be expected to exert its power when used in a moving object or when there are vibration sources such as motors, valves, speakers, etc. in the vicinity.
Abstract
Description
<本実施の形態1における複合センサの構成>
本実施の形態1における複合センサCS1の構成について図面を参照しながら説明する。図1は、本実施の形態1における複合センサCS1の構成を示す平面図である。図1において、本実施の形態1における複合センサCS1は、半導体基板1S上に形成された枠体FRを有し、この枠体FRで区画されたそれぞれの領域内に、Y軸周りの角速度を検知する角速度検知部JAと、X軸方向、Y軸方向、Z軸方向の加速度を検知する加速度検知部ACが形成されている。そして、加速度検知部ACは、X軸方向およびY軸方向の加速度を検知するXY方向加速度検知部AC(XY)と、Z軸方向の加速度を検知するZ方向加速度検知部AC(Z)から構成されている。
次に、角速度検知部を使用して角速度を検出する回路構成について、図面を参照しながら説明する。図3は、角速度検知部を使用して角速度を検出するための回路構成を示すブロック図である。図3に示すように、錘M1および錘M2の外側には、駆動電極DRE1が配置され、錘M1および錘M2の内側には、駆動電極DRE2が配置されている。そして、駆動電極DRE1と錘M1、駆動電極DRE1と錘M2、駆動電極DRE2と錘M1、駆動電極DRE2と錘M2によって、それぞれ、駆動容量素子が形成されていることになる。このとき、駆動電極DRE1には、駆動信号として、Vcom+Vb+Vdが印加されるようになっており、駆動電極DRE2には、駆動信号として、Vcom+Vb-Vdが印加されるようになっている。また、錘M1および錘M2には、VcomとVcaが印加される。ここで、Vcomはコモン電圧を示し、Vbはバイアス電圧を示している。これらのコモン電圧(Vcom)およびバイアス電圧(Vb)は直流電圧となっている。一方、+Vdや-Vdは駆動電圧を示しており、Vcaはキャリア電圧を示している。これらの駆動電圧やキャリア電圧は交流電圧となっている。
本実施の形態1において、角速度検知部を使用して角速度を検出する回路は上記のように構成されており、以下に、このように構成されている回路を使用して角速度を検出する原理および動作について、図3を参照しながら説明する。
ここで、Fcはコリオリ力、mは錘の質量、Ωは印加される角速度、AXは駆動振幅、ωx/2πは駆動周波数、tは時間を示している。
ここで、Fcはコリオリ力、zは検出振幅、Qzは検出方向(Z方向)の機械品質係数、kzは支持梁のz方向のバネ定数を示している。
ここで、CzはZ方向のダンピング係数を示している。
ここで、ωzは検出振動系の固有振動数である。ωx(駆動振動系の固有振動数)とωz(検出振動系の固有振動数)は、ほぼ同じであり、錘の質量mが同じであるため、kx≒kzが成立する。
上述した式(5)から、感度Sは錘の質量mと、駆動振幅AX、および、Z方向のダンピング係数Czのみの関数であり、駆動振動系の固有振動数ωxや検出振動系の固有振動数ωzには無関係であることがわかる。したがって、感度Sに影響を与えることなく、駆動振動系の固有振動数ωxや検出振動系の固有振動数ωzを選択することができることがわかる。
続いて、XY方向加速度検知部を使用してX方向の加速度とY方向の加速度を検出する回路構成について、図面を参照しながら説明する。図6は、XY方向加速度検知部を使用して加速度を検出するための回路構成を示すブロック図である。
本実施の形態1において、XY方向加速度検知部を使用してXY方向の加速度を検出する回路は上記のように構成されており、以下に、このように構成されている回路を使用してXY方向の加速度を検出する動作について、図6を参照しながら説明する。
図7は、Z方向の加速度を検出する一般的な回路構成を示す回路ブロック図である。図7において、錘M4のZ方向下側に検出電極DTE5が形成されており、この検出電極DTE5と錘M4によって1つの検出容量素子が形成されている。このとき、錘M4には、VcomとVcaが印加される。ここで、Vcomはコモン電圧を示している。このコモン電圧(Vcom)は直流電圧となっている。一方、Vcaはキャリア電圧を示している。このキャリア電圧は交流電圧となっている。
しかし、上述したZ方向の加速度を検出する一般的な回路構成には、錘M4と検出電極DTE5から構成される検出容量素子しか形成されていない。このことから、錘M4が+Z方向に変位した場合、錘M4と検出電極DTE5から構成される検出容量素子の静電容量は減少するが、上述した回路には、錘M4が+Z方向に変位した場合に静電容量が増加する検出容量素子に対応する検出電極が存在しない。つまり、一般的な回路構成では、Z方向において、錘M4が変位した場合に静電容量が増加する検出容量素子と、静電容量が減少する検出容量素子と両方を形成するように構成されていない。これは、Z方向が半導体基板の積層方向(厚さ方向)であり、面外方向(Z方向)において加速度が印加された場合、錘M4の動きによって静電容量が増える検出容量素子と静電容量が減る検出容量素子の両方を形成することが製造プロセス上で困難となるからである。したがって、図7に示すように、Z方向の加速度を検出する一般的な回路構成では、錘M4と検出電極DTE5から構成される検出容量素子しか形成されていないのである。このとき、図7に示すように、同期検波部WDU5には、C0(初期容量)±ΔC(変位によって発生した容量変化)からなる容量に対応した大きな第1Z方向検出用デジタル信号がそのまま入力することになる。この場合、Z方向の加速度を検出する感度が低下する問題点が発生する。
図8は、本実施の形態1におけるZ方向の加速度を検出する回路構成を示す回路ブロック図である。図8において、錘M4のZ方向下側に検出電極DTE5が形成されており、この検出電極DTE5と錘M4によって1つの検出容量素子が形成されている。このとき、錘M4には、VcomとVcaが印加される。ここで、Vcomはコモン電圧を示している。このコモン電圧(Vcom)は直流電圧となっている。一方、Vcaはキャリア電圧を示している。このキャリア電圧は交流電圧となっている。また、上述したコモン電圧(Vcom)およびキャリア電圧(Vca)は錘M2にも印加されるように構成されている。そして、錘M2のZ方向下側には検出電極DTE2が配置されており、この検出電極DTE2と錘M2によって1つの参照容量素子が形成されている。つまり、本実施の形態1では、角速度検知部に使用されている錘M2と検出電極DTE2を、Z方向の加速度を検出するZ方向加速度検知部の参照容量素子としても使用する点に特徴がある。すなわち、本実施の形態1のZ方向加速度検知部の特徴は、検出電極DTE5と錘M4からなる検出容量素子に対する参照容量素子として、角速度検知部を構成する錘M2と検出電極DTE2からなる検出容量素子を使用していることにある。このように、角速度検知部を構成する錘M2と検出電極DTE2からなる検出容量素子を、Z方向加速度検知部の参照容量素子として使用することにより、他の機能は持たず、参照容量を提供するだけのために形成される参照容量素子(固定容量素子)が不要となるため、角速度検知部とZ方向加速度検知部を備える複合センサの小型化を図ることができる。
本実施の形態1において、Z方向加速度検知部を使用してZ方向の加速度を検出する回路は上記のように構成されており、以下に、このように構成されている回路を使用してZ方向の加速度を検出する動作について、図8を参照しながら説明する。
続いて、角速度検知部の検出容量素子をZ方向加速度検知部の参照容量素子として使用できる理由について説明する。図9は、角速度検知部の検出振動系における周波数特性と、Z方向加速度検知部の周波数特性を示すグラフである。図9において、横軸は周波数(Hz)を示しており、縦軸は変位を示している。図9に示すように、角速度検知部の検出振動系の周波数特性は、十数kHzに共振ピークを有するような周波数特性をしていることがわかる。一方、Z方向加速度検知部の周波数特性は、共振ピークを持たず、数百Hzに感度を有するような周波数特性をしていることがわかる。
ω0=√(k/m)
式(6)から、変位z0は、錘M4の質量mと支持梁SB3のばね定数kによって決まる検出振動系の固有振動数ω0の関数であることがわかる。したがって、参照容量素子の固有振動数をω1とする場合、差分変位Δzは、式(7)のように定義することができる。
このとき、参照容量素子の固有振動数ω1をα×ω0とおくと、式(7)は式(8)のようになる。
式(8)において、参照容量素子として固定容量素子を使用する場合、αは無限大となり、Δz=z0となる。一方、α=1の場合、すなわち、Z方向加速度検知部の検出振動系と同じ固有振動数を持つ参照容量素子を使用する場合、Δz=0となり、Z方向加速度センサの出力が得られなくなってしまうことがわかる。つまり、参照容量素子として充分な機能を果たすためには、Z方向加速度検知部の検出振動系の固有振動数ω0よりも充分大きな固有振動数を有する参照容量素子を使用する必要があることがわかる。
本実施の形態1では、Z方向加速度検知部の参照容量素子として、角速度検知部の検出容量素子を使用する例について説明しているが、これに限らず、XY方向加速度検知部の錘M3と半導体基板間に形成される容量素子を参照容量素子として使用する場合も、本実施の形態1と同様の効果を得ることができる。特に、XY方向加速度検知部の錘M3はZ方向には変位しにくいため、XY方向加速度検知部の錘M3と半導体基板間に形成される容量素子を参照容量素子として使用した場合、この参照容量素子は、完全な固定容量素子となる利点が得られる。なお、本実施の形態1における複合センサでは、1軸(Y方向)の角速度と3軸(XYZ方向)の加速度を検出できる複合センサを例に挙げているが、3軸の加速度だけを検出できる複合センサにおいても、本実施の形態1の技術的思想を適用することができる。
本実施の形態1における複合センサは、上記のように構成されており、以下に、その製造方法について、図面を参照しながら説明する。具体的に、本実施の形態1では、図1のA-A線で切断した断面図を使用して、複合センサの製造方法について説明する。
次に、本実施の形態1における複合センサの実装構成について説明する。図16は、本実施の形態1における複合センサの実装構成を示す断面図である。図16に示すように、本実施の形態1における複合センサCS1(半導体チップCHP1)は、信号処理用の半導体チップCHP2とともにセラミックパッケージPACに実装される。具体的には、セラミックパッケージPACの底面に接着材ADH1を介して信号処理用の半導体チップCHP2が搭載されており、この半導体チップCHP2上に接着材ADH2を介して複合センサCS1が搭載されている。このとき、接着材ADH2を導電性接着材から構成することにより、半導体チップCHP1の電位を固定することができる。そして、複合センサCS1に形成されているパッドPD1と、半導体チップCHP2に形成されているパッドPD2が、ワイヤW1で電気的に接続されている。また、半導体チップCHP2に形成されているパッドPD2は、セラミックパッケージPACの内部に形成されているパッドPD3とワイヤW2で電気的に接続されている。さらに、セラミックパッケージPACの内部に形成されているパッドPD3は、配線WL1を介してセラミックパッケージPACの外部に形成されている端子TE1と電気的に接続されている。最後に、複合センサCS1や信号処理用の半導体チップCHP2が配置されているセラミックパッケージPACの内部空間は、キャップCAPによって封止されている。以上のようにして、本実施の形態1における複合センサCS1は実装構成されている。
本実施の形態2では、角速度検知部で使用する第1参照容量素子と、Z方向加速度検知部で使用する第2参照容量素子が、互いに共有される1つの共有参照容量素子であることを特徴とする例について説明する。
図17は、本実施の形態2における複合センサCS2の構成を示す平面図である。図17において、本実施の形態2における複合センサCS2は、角速度検知部JAと、Z方向加速度検知部AC(Z)とを備えている。
本実施の形態2における複合センサCS2は上記のように構成されており、以下に、このように構成されている複合センサCS2を使用して角速度を検出する動作について、図19を参照しながら説明する。図19は、本実施の形態2における複合センサの回路構成を示す回路ブロックである。
AC 加速度検知部
AC(XY) XY方向加速度検知部
AC(Z) Z方向加速度検知部
ADH1 接着材
ADH2 接着材
ADU1 AD変換部
ADU2 AD変換部
ADU3 AD変換部
ADU4 AD変換部
ADU5 AD変換部
ADU6 AD変換部
ADU7 AD変換部
ADU8 AD変換部
AFC部 AFC
AGC部 AGC
CAP キャップ
CAV 空洞部
CAV1 空洞部
CAV2 空洞部
CHP1 半導体チップ
CHP2 半導体チップ
CNT1 コンタクトホール
CNT2 コンタクトホール
COV カバー
CS1 複合センサ
CS2 複合センサ
CVU1 CV変換部
CVU2 CV変換部
CVU3 CV変換部
CVU4 CV変換部
CVU5 CV変換部
CVU6 CV変換部
CVU7 CV変換部
CVU8 CV変換部
DAU1 DA変換部
DAU2 DA変換部
DL デバイス層
DMU1 差動検出部
DMU2 差動検出部
DMU3 差動検出部
DMU4 差動検出部
DMU5 差動検出部
DMU6 差動検出部
DMU7 差動検出部
DMU8 差動検出部
DRE1 駆動電極
DRE2 駆動電極
DTE1 検出電極
DTE2 検出電極
DTE3 検出電極
DTE4 検出電極
DTE5 検出電極
EL1 電極
EL2 電極
FR 枠体
FX1 固定部
FX2 固定部
FX3 固定部
GAU1 ゲイン調整部
GAU2 ゲイン調整部
GAU3 ゲイン調整部
JA 角速度検知部
LB リンク梁
LPF1 ローパスフィルタ
LPF2 ローパスフィルタ
LPF3 ローパスフィルタ
LPF4 ローパスフィルタ
M1 錘
M2 錘
M3 錘
M4 錘
ME1 モニタ電極
ME2 モニタ電極
OX1 絶縁膜
OX2 絶縁膜
OX3 絶縁膜
PAC セラミックパッケージ
PD1 パッド
PD2 パッド
PD3 パッド
PD4 パッド
PD5 パッド
PED1 台座部
PED2 台座部
PLG1 プラグ
PLG2 プラグ
RC 参照容量素子
RE1 上部電極
RE2 下部電極
SB1 支持梁
SB2 支持梁
SB3 支持梁
SN1 絶縁膜
TE1 端子
W1 ワイヤ
W2 ワイヤ
WDU1 同期検波部
WDU2 同期検波部
WDU3 同期検波部
WDU4 同期検波部
WDU5 同期検波部
WDU6 同期検波部
WDU7 同期検波部
WDU8 同期検波部
WL1 配線
WL2 配線
Claims (14)
- (a)第1物理量の印加を第1検出容量素子の静電容量の変化として捉える第1検知部と、
(b)第2物理量の印加を第2検出容量素子の静電容量の変化として捉える第2検知部とを備え、
前記第1検知部から出力される前記第1検出容量素子の静電容量を変換した検出用信号と、前記第2検知部から出力される前記第2検出容量素子の静電容量を変換した参照用信号との差分に基づいて、前記第1物理量を検知することを特徴とする複合センサ。 - 請求項1記載の複合センサであって、
前記第1検知部は、
(a1)半導体基板に固定された第1固定部と、
(a2)前記第1固定部と接続された第1弾性変形部と、
(a3)前記第1弾性変形部と接続された第1可動部と、
(a4)前記半導体基板に形成された第1検出電極とを有し
前記第1検出容量素子は、前記第1可動部と前記第1検出電極により形成され、
前記第2検知部は、
(b1)前記半導体基板に固定された第2固定部と、
(b2)前記第2固定部と接続された第2弾性変形部と、
(b3)前記第2弾性変形部と接続された第2可動部と、
(b4)前記半導体基板に形成された第2検出電極とを有し、
前記第2検出容量素子は、前記第2可動部と前記第2検出電極により形成されていることを特徴とする複合センサ。 - 請求項2記載の複合センサであって、
前記第1検知部における検出振動系の固有振動数は、前記第2検知部における検出振動系の固有振動数よりも小さいことを特徴とする複合センサ。 - 請求項1記載の複合センサであって、
前記複合センサは、さらに、前記第1物理量が印加されていない場合に、前記検出用信号と前記参照用信号の差分が0となるように調整するゲイン調整部を備えることを特徴とする複合センサ。 - 請求項1記載の複合センサであって、
前記第1物理量は、加速度であり、
前記第2物理量は、角速度であることを特徴とする複合センサ。 - 請求項1記載の複合センサであって、
前記第1検知部の前記第1検出容量素子は、半導体基板の主面に垂直な方向の変位に基づく静電容量変化を検出し、
前記第2検知部の前記第2検出容量素子は、半導体基板の主面に垂直な方向の変位に基づく静電容量変化を検出することを特徴とする複合センサ。 - 請求項1記載の複合センサであって、
前記複合センサは、さらに、前記第1検知部から出力される前記第1検出容量素子の静電容量を第1電圧信号に変換し、
前記第2検出部から出力される前記第2検出容量素子の静電容量を第2電圧信号に変換する容量電圧変換部を備えることを特徴とする複合センサ。 - 請求項7記載の複合センサであって、
前記第1検知部および前記第2検知部には搬送波が印加されており、
前記容量電圧変換部の信号通過帯域は、前記搬送波の周波数から前記第2検知部の固有振動数を引いた値よりも大きく、
前記搬送波の周波数と前記第2検知部の固有振動数を足した値よりも小さいことを特徴とする複合センサ。 - 請求項1記載の複合センサであって、
前記第1物理量は、第1方向の加速度であり、
前記第2物理量は、前記第1方向とは異なる第2方向の加速度であることを特徴とする複合センサ。 - 請求項9記載の複合センサであって、
前記第1方向は、半導体基板の主面の面内方向であり、
前記第2方向は、半導体基板の主面に対して垂直な方向である面外方向であることを特徴とする複合センサ。 - (a)第1物理量の印加を第1検出容量素子の静電容量の変化として捉える第1検知部と、
(b)第2物理量の印加を第2検出容量素子の静電容量の変化として捉える第2検知部と、
(c)差分をとる基準となる参照容量素子とを備え、
前記第1検知部から出力される前記第1検出容量素子の静電容量を変換した第1検出用信号と、前記参照容量素子の静電容量を変換した参照用信号との差分に基づいて、前記第1物理量を検知し、
前記第2検知部から出力される前記第2検出容量素子の静電容量を変換した第2検出用信号と、前記参照容量素子の静電容量を変換した前記参照用信号との差分に基づいて、前記第2物理量を検知することを特徴とする複合センサ。 - 請求項11記載の複合センサであって、
前記第1検知部は、
(a1)半導体基板に固定された第1固定部と、
(a2)前記第1固定部と接続された第1弾性変形部と、
(a3)前記第1弾性変形部と接続された第1可動部と、
(a4)前記半導体基板に形成された第1検出電極とを有し、
前記第1検出容量素子は、前記第1可動部と前記第1検出電極により形成され、
前記第2検知部は、
(b1)前記半導体基板に固定された第2固定部と、
(b2)前記第2固定部と接続された第2弾性変形部と、
(b3)前記第2弾性変形部と接続された第2可動部と、
(b4)前記半導体基板に形成された第2検出電極とを有し、
前記第2検出容量素子は、前記第2可動部と前記第2検出電極により形成されていることを特徴とする複合センサ。 - 請求項11記載の複合センサであって、
前記複合センサは、さらに、前記第1物理量が印加されていない場合に、前記第1検出用信号と前記参照用信号との差分が0となるように調整する第1ゲイン調整部と、
前記第2物理量が印加されていない場合に、前記第2検出用信号と前記参照用信号との差分が0となるように調整する第2ゲイン調整部とを備えることを特徴とする複合センサ。 - 請求項11記載の複合センサであって、
前記第1物理量は、加速度であり、
前記第2物理量は、角速度であることを特徴とする複合センサ。
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