JP5724899B2 - Capacitive physical quantity detector - Google Patents

Description

  The present invention relates to a capacitive physical quantity detection device that includes a movable electrode and a fixed electrode, and that converts a capacitance between the movable electrode and the fixed electrode by a fully differential CV conversion circuit.

  Conventionally, for example, Patent Document 1 proposes an acceleration sensor as a capacitive physical quantity detection device using an SOI (Silicon on Insulator) substrate in which a support substrate, a buried insulating film, and a semiconductor layer are sequentially stacked. . Specifically, in this acceleration sensor, the semiconductor layer is disposed between the pair of fixed portions that are spaced apart from each other and have fixed electrodes, and is disposed between the pair of fixed portions, is opposed to each fixed electrode, and is accelerated. Accordingly, a movable part having a movable electrode that can be displaced in a predetermined direction is formed. And the capacity | capacitance between a movable electrode and a fixed electrode carries out voltage conversion by the fully differential type CV conversion circuit, and outputs it.

  In such a capacitive physical quantity detection device, when acceleration is applied to the movable portion (movable electrode), the capacitance between the movable electrode and the fixed electrode changes. At this time, if a pulsed carrier wave is input to the movable part (movable electrode), a voltage difference corresponding to a change in capacitance is generated in the CV conversion output before and after the carrier wave switching.

JP 2009-75097 A

  However, in the capacitive physical quantity detection device, a movable part (movable electrode) is formed in the semiconductor layer of the SOI substrate, and a coupling capacitance is generated between the movable part and the support substrate. For this reason, when a pulsed carrier wave is input to the movable part (movable electrode), there is a problem that the potential of the support substrate changes, thereby generating noise. Therefore, a signal including noise is output from the CV conversion circuit, and the detection accuracy is lowered.

  In view of the above, the present invention has a movable part having a movable electrode and a fixed part having a fixed electrode formed on an SOI substrate, and the capacitance between the movable electrode and the fixed electrode is changed to a fully differential CV conversion circuit. An object of the present invention is to provide a capacitive physical quantity detection device capable of suppressing a change in potential of a support substrate in an SOI substrate.

In order to achieve the above object, according to the first aspect of the present invention, the supporting substrate (1), the buried insulating film (2) disposed on the supporting substrate, and the opposite of the supporting substrate with the buried insulating film interposed therebetween. A semiconductor substrate (4) having a semiconductor layer (3) disposed on the side, and a pair of first fixed portions formed on the semiconductor layer and spaced apart from each other and having first fixed electrodes (21a, 21b), respectively (20a, 20b) and a pair of first fixing portions, which are opposed to the respective first fixing electrodes provided in the first fixing portion, and can be displaced in a predetermined direction according to a physical quantity. A first element part (110) including a first movable part (10) having a first movable electrode (14); and a second element part (120) formed in a region different from the first element part in the semiconductor layer. ) And a first carrier pulse (P ) And a reference signal generation circuit (230) for inputting a pulsed second carrier wave (P2) having the same frequency as the first carrier wave and having a phase difference of 180 ° to the second element section, and a first movable A fully-differential first CV conversion circuit (210) for converting the voltage between the electrode and the first fixed electrode, and the second element portions are spaced apart from each other and second fixed respectively. A pair of second fixed parts (40a, 40b) having electrodes (41a, 41b) and a pair of second fixed parts are arranged and face each second fixed electrode provided in the second fixed part. And a second movable part (30) having a second movable electrode (34) that is displaceable in a predetermined direction in accordance with a physical quantity, and the reference signal generating circuit is connected to the first movable part. When the carrier wave is input, the second carrier wave is input to the second movable part. The first CV conversion circuit is connected to the first fixed electrode via the first and second changeover switches (271 and 272) and via the third and fourth changeover switches (273 and 274). Connected to the second fixed electrode, and when the first and second changeover switches are turned on and the third and fourth switches are turned off, the gap between the first movable electrode and the first fixed electrode is Capacitance is converted into voltage, and the capacitance between the second movable electrode and the second fixed electrode is converted into voltage when the first and second changeover switches are turned off and the third and fourth changeover switches are turned on. It is characterized in that.

  According to this, when the first carrier wave is input to the first movable part, electric charges are generated on the support substrate by the coupling capacitance between the first movable part and the support substrate and the first carrier wave. In addition, when the second carrier wave is input to the second element portion, the coupling substrate between the portion of the second element portion to which the second carrier wave is input and the support substrate and the second carrier wave cause charges on the support substrate. Generated. At this time, since the first and second carrier waves have the same frequency and have a phase difference of 180 °, the potential of the support substrate can be prevented from changing.

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

It is sectional drawing of the acceleration sensor in 1st Embodiment of this invention. It is a top view of the sensor chip shown in FIG. It is a circuit diagram of the acceleration sensor shown in FIG. It is a timing chart of the acceleration sensor shown in FIG. It is a circuit diagram of the acceleration sensor in 2nd Embodiment of this invention. 6 is a timing chart of the acceleration sensor shown in FIG. It is a top view of the sensor chip in a 3rd embodiment of the present invention. It is a plane schematic diagram of the sensor chip in 4th Embodiment of this invention.

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

(First embodiment)
A first embodiment of the present invention will be described. In this embodiment, the present invention is applied to an acceleration sensor as a capacitive physical quantity detection device. For example, the present invention is applied to an automobile acceleration sensor, a gyro sensor, or the like for controlling the operation of an airbag, ABS, VSC, or the like. Is preferred.

  As shown in FIG. 1, the acceleration sensor includes a sensor chip 100 mounted on a circuit chip 200 via an adhesive 300 such as a silicone-based adhesive. First, the configuration of the sensor chip 100 will be described.

  As shown in FIGS. 1 and 2, the sensor chip 100 includes a support substrate 1, a buried insulating film 2 formed on the support substrate 1, and the opposite side of the support substrate 1 across the buried insulating film 2. And an SOI substrate 4 having a semiconductor layer 3 disposed on the substrate. The first and second element portions 110 and 120 are formed by subjecting the SOI substrate 4 to known micromachining. In the present embodiment, the first and second element parts 110 and 120 are both parts that function as a detection part that detects acceleration, and the basic configuration is the same. The sensor chip 100 in FIG. 1 corresponds to the (i)-(i) cross section in FIG. In the present embodiment, the SOI substrate 4 corresponds to the semiconductor substrate of the present invention.

  As shown in FIG. 2, the semiconductor layer 3 includes a comb-shaped beam structure including the first movable portion 10 and the first fixed portions 20 a and 20 b configured by forming the groove portion 5, and the groove portion 6. A comb-shaped beam structure made up of the second movable part 30 and the second fixed parts 40a and 40b, which are formed by forming the above, is formed. In the buried insulating film 2, openings 7 and 8 that are removed in a rectangular shape by sacrificial layer etching or the like are formed in portions corresponding to the formation regions of the beam structures 10 to 40.

  The first and second movable parts 10 and 30 are arranged so as to cross over the openings 7 and 8, respectively, and both ends of the rectangular weight parts 11 and 31 are anchor parts via the beam parts 12 and 32. It is set as the structure connected integrally to 13a, 33a and the anchor parts 13b, 33b. The anchor portions 13 a and 33 a and the anchor portions 13 b and 33 b are fixed to the opening edge portions of the opening portions 7 and 8 in the buried insulating film 2 and supported by the support substrate 1. Thereby, the weight parts 11 and 31 and the beam parts 12 and 32 are in the state which faced the opening parts 7 and 8, respectively.

  The beam portions 12 and 32 have a rectangular frame shape in which two parallel beams are connected at both ends, and have a spring function of being displaced in a direction perpendicular to the longitudinal direction of the two beams. Specifically, the beam portion 12 displaces the weight portion 11 in the x direction when receiving an acceleration including a component in the x direction in FIG. 2 and restores the original state according to the disappearance of the acceleration. It has become. Further, the beam portion 32 is configured to displace the weight portion 31 in the y direction when receiving an acceleration including a component in the y direction in FIG. 2 and to restore the original state in accordance with the disappearance of the acceleration. Yes. Therefore, the weight portions 11 and 31 connected to the support substrate 1 via the beam portions 12 and 32 are displaced in the direction of displacement of the beam portions 12 and 32 on the openings 7 and 8 in accordance with the application of acceleration. It can be displaced in the (x direction or y direction).

  Here, each direction of the x axis, the y axis, and the z axis in FIG. 2 will be described. As described above, the x-axis direction is the displacement direction of the beam portion 12 and the displacement direction of the weight portion 11. The y-axis direction is a displacement direction of the beam portion 32 and a displacement direction of the weight portion 31 and is a direction orthogonal to the x-axis in the plane of the SOI substrate 4. The z-axis direction is a direction orthogonal to the surface direction of the SOI substrate 4.

  The first and second movable parts 10 and 30 are integrated in opposite directions from both side surfaces of the weight parts 11 and 31 in directions orthogonal to the displacement direction (x direction or y direction) of the beam parts 12 and 32, respectively. A plurality of first and second movable electrodes 14, 34 projecting from each other are provided. In FIG. 2, four first movable electrodes 14 are formed so as to protrude from the left and right sides of the weight part 11, respectively, and the rectangular shape of the cross section is a beam shape and faces the opening 7. Yes. Further, four second movable electrodes 34 are formed so as to protrude from the lower side and the upper side of the weight portion 31, respectively. The rectangular shape of the second movable electrode 34 is a beam shape and faces the opening 8. . Thus, the first and second movable electrodes 14 and 34 are formed integrally with the beam portions 12 and 32 and the weight portions 11 and 31, and together with the beam portions 12 and 32 and the weight portions 11 and 31, the beam portion 12, It can be displaced in 32 displacement directions.

  The first and second movable parts 10 and 30 have the same area facing the support substrate 1. That is, the coupling capacity between the first movable part 10 and the support substrate 1 and the coupling capacity between the second movable part 30 and the support substrate 1 are made equal. In the present embodiment, the first movable portion 10 includes the weight portion 11, the beam portion 12, and the first movable electrode 14, and the second movable portion 30 includes the weight portion 31, the beam portion 32, and the second movable electrode 34. It is constituted by.

  The first and second fixing portions 20a, 20b, 40a, and 40b are anchor portions 13a and 33a and anchor portions 13b and 33b, respectively, of the opposing sides at the opening edge portions of the opening portions 7 and 8 in the buried insulating film 2. Is supported by another set of opposite sides that are not supported. In other words, the first movable part 10 is disposed between the pair of first fixed parts 20a and 20b, and the second movable part 30 is disposed between the pair of second fixed parts 40a and 40b.

  Specifically, two first fixing portions 20 a and 20 b are provided with the weight portion 11 interposed therebetween. In FIG. 2, the first fixing part 20 a is located on the left side of the weight part 11, and the first fixing part 20 b is located on the right side of the weight part 11. Further, two second fixing portions 40 a and 40 b are provided with the weight portion 31 interposed therebetween. In FIG. 2, the second fixing portion 40 a is located below the weight portion 31, and the second fixing portion 40 b is located above the weight portion 31.

  A plurality of first and second fixed portions 20a, 20b, 40a, 40b are arranged opposite to each other in parallel with the side surfaces of the first and second movable electrodes 14, 34 so as to have a predetermined detection interval (illustrated example). The first and second fixed electrodes 21 a, 21 b, 41 a, 41 b, and the wiring portions fixed to the opening edges of the openings 7, 8 in the buried insulating film 2 and supported by the support substrate 1. 22a, 22b, 42a, 42b.

  Specifically, a plurality of first fixed electrodes 21a and 21b are arranged in a comb shape so as to engage with the gaps of the comb teeth in the first movable electrode 14, and the second fixed electrodes 41a and 41b A plurality of comb teeth are arranged so as to engage with the gaps of the comb teeth in the movable electrode 34. In addition, the first and second fixed electrodes 21a, 21b, 41a, 41b have a rectangular cross section and are supported in a cantilevered manner by the wiring portions 22a, 22b, 42a, 42b. It is in a state facing parts 7 and 8.

  In addition, the outer peripheral portion of the semiconductor layer 3 through the groove portions 5 and 6 partitioning the first and second movable portions 10 and 30 and the first and second fixing portions 20a, 20b, 40a, and 40b is the peripheral fixing portion 50. It is configured as. The peripheral fixing portion 50 is fixed and supported on the support substrate 1 through the buried insulating film 2.

  First and second fixed electrode pads 23a, 23b, and 43a for wire bonding are placed at predetermined positions on the wiring portions 22a, 22b, 42a, and 42b of the first and second fixed portions 20a, 20b, 40a, and 40b, respectively. , 43b are formed. In addition, movable electrode wiring portions 15 and 35 are formed in a state of being integrally connected to one of the anchor portions 13b and 33b, and wire bonding is provided at predetermined positions on the movable electrode wiring portions 15 and 35. First and second movable electrode pads 16 and 36 are formed. Further, a peripheral fixing portion pad 51 is formed at a predetermined position of the peripheral fixing portion 50.

  Each of the electrode pads 16, 23a, 23b, 36, 43a, 43b, 51 is formed, for example, by sputtering or vapor-depositing aluminum. The electrode pads 16, 23a, 23b, 36, 43a, 43b, 51 are electrically connected to the circuit chip 200 by wires W1 to W7 formed by gold or aluminum wire bonding or the like.

  In such a configuration, as indicated by a capacitor symbol in FIG. 2, the first movable electrode 14 and the first fixed electrode 21a form a capacitor CS1, and the first movable electrode 14 and the first fixed electrode 21b A capacitor CS2 is configured. The second movable electrode 34 and the second fixed electrode 41a constitute a capacitor CS3, and the second movable electrode 34 and the second fixed electrode 41b constitute a capacitor CS4. When the acceleration is applied, the capacitances CS1 to CS4 change, and the acceleration is detected from the change in capacitance.

  The above is the configuration of the sensor chip 100 in the present embodiment. That is, the sensor chip 100 according to the present embodiment can detect acceleration in two directions.

  Next, the configuration of the circuit chip 200 will be described. As shown in FIG. 3, the circuit chip 200 includes a fully differential first CV conversion that converts capacitances CS1 and CS2 between the first movable electrode 14 and the first fixed electrodes 21a and 21b into a voltage. A fully differential second CV conversion circuit 220 that converts capacitances CS3 and CS4 between the circuit 210 and the second movable electrode 34 and the second fixed electrodes 41a and 41b into a voltage is provided.

  Specifically, the first CV conversion circuit 210 includes an operational amplifier 211, first and second capacitors 212a and 212b, and first and second switches 213a and 213b. The first capacitor 212a and the first switch 213a are connected in parallel between the non-inverting input terminal and the negative output terminal, and the second capacitor 212b is connected between the inverting input terminal and the positive output terminal. The second switch 213b is connected in parallel.

  The non-inverting input terminal of the operational amplifier 211 is connected to the first fixed electrode 21a via the first fixed electrode pad 23a, and the inverting input terminal is connected to the first fixed electrode 21b via the first fixed electrode pad 23b. Has been.

  Similarly, the second CV conversion circuit 220 includes an operational amplifier 221, third and fourth capacitors 222a and 222b, and third and fourth switches 223a and 223b. The third capacitor 222a and the third switch 223a are connected in parallel between the non-inverting input terminal and the negative output terminal, and the fourth capacitor 222b is connected between the inverting input terminal and the positive output terminal. The fourth switch 223b is connected in parallel.

  The non-inverting input terminal of the operational amplifier 221 is connected to the second fixed electrode 41a via the second fixed electrode pad 43a, and the inverting input terminal is connected to the second fixed electrode 41b via the second fixed electrode pad 43b. Has been.

  Note that the first to fourth switches 213a, 213b, 223a, and 223b are configured by transistors or the like, for example.

  The circuit chip 200 includes a reference signal generation circuit 230 that generates first and second carrier waves P1 and P2 input to the first and second movable electrodes 14 and 34, and first to fourth switches 213a and 213b, A control signal generation circuit 240 that generates a control signal SW1 for controlling on / off of 223a and 223b is provided.

  The reference signal generation circuit 230 generates, as the first carrier wave P1, for example, a pulse-like signal having an amplitude between a voltage Vdd (for example, 5V) and a voltage of 0V and a frequency of 100 kHz. Further, as the second carrier wave P2, a pulse signal having the same amplitude and frequency as the first carrier wave P1 and having a phase different by 180 ° is generated. Then, the first carrier wave P1 is input to the first movable part 10 (first movable electrode 14) via the first movable electrode pad 16, and the second carrier wave P2 is second movable via the second movable electrode pad 36. Input to the unit 30 (second movable electrode 34).

  The control signal generation circuit 240 generates a control signal SW1 that controls on / off of the first to fourth switches 213a, 213b, 223a, and 223b, and turns on the first to fourth switches 213a, 213b, 223a, and 223b. , OFF is controlled at a predetermined timing.

  The circuit chip 200 includes first and second sample and hold circuits (hereinafter referred to as S / H circuits) 250 and 260. The first and second S / H circuits 250 and 260 are connected to the output terminals of the first and second CV conversion circuits 210 and 220, respectively. And it drives based on the control signal (not shown) from the control signal generation circuit 240, samples the output of the 1st, 2nd CV conversion circuits 210 and 220, and hold | maintains for a fixed period.

  Further, although not particularly shown, the circuit chip 200 is driven based on a control signal from the control signal generation circuit 240, and a differential voltage (sampling 2) from each output voltage of the first and second S / H circuits 250 and 260. -A low-pass filter circuit (hereinafter referred to as an LPF circuit) that extracts sampling 1) and extracts only a predetermined frequency component from the differential voltage and outputs it as an acceleration signal is provided.

  The above is the basic configuration of the acceleration sensor in the present embodiment. Next, the operation of the acceleration sensor will be described with reference to FIGS.

  The acceleration sensor detects acceleration in a state where the first and second carrier waves P1 and P2 are input to the first and second movable parts (first and second movable electrodes 14 and 34) from the reference signal generation circuit 230. Is done. Specifically, the pulsed first carrier wave P1 having an amplitude between a voltage Vdd (for example, 5V) and 0V and a frequency of 100 kHz is transmitted through the first movable electrode pad 16 to the first movable portion 10 (first movable portion 10). Input to the electrode 14). Further, a second carrier wave P2 having the same amplitude and frequency as the first carrier wave P1 and having a phase difference of 180 ° is input from the reference signal generation circuit 230 to the second movable electrode 34 via the second movable electrode pad 36. .

  In the present embodiment, the second movable portion 30 corresponds to a region where the second carrier wave P2 is input in the second element portion 120 of the present invention.

  In this case, electric charges are generated on the support substrate 1 by the coupling capacitance between the first movable electrode 14 and the support substrate 1 and the first carrier wave P1. Further, electric charges are generated on the support substrate 1 by the coupling capacitance between the second movable electrode 34 and the support substrate 1 and the second carrier wave P2. At this time, since the first and second carrier waves P1 and P2 are signals having amplitude between the voltages Vdd and 0V, the same frequency, and a phase difference of 180 °, the potential of the support substrate 1 is the middle point. Of 1/2 Vdd. For this reason, it can suppress that the electric potential of the support substrate 1 changes with a carrier wave.

  In this state, when acceleration is applied in the x and y directions in FIG. 2, the first movable electrode 14 is displaced in the x direction and the second movable electrode 34 is displaced in the y direction. At this time, capacitance changes (+ ΔC, −ΔC) corresponding to the magnitude of acceleration occur in the capacitors CS1 to CS4. Then, the signals of the first and second fixed electrodes 21a, 21b, 41a and 41b corresponding to the capacitance are converted into the first and second CV conversions via the first and second fixed electrode pads 23a, 23b, 43a and 43b. ΔV1 and ΔV2 are output from the first and second CV conversion circuits 210 and 220 as potential difference signals (VOP1-VOM1, VOP2-VOM2) corresponding to the acceleration.

  When the first to fourth switches 213a, 213b, 223a, and 223b are turned on (closed) (period φ2), the first to fourth capacitors 212a, 212b, 222a, and 222b are reset, and the first to fourth switches The acceleration is detected when the four switches 213a, 213b, 223a, and 223b are turned off (opened). That is, the period other than the period φ2 in the period φ1 is a period for detecting acceleration. Therefore, after the reset, after the potentials of the first and second carriers P1 and P2 change (for example, after the potential changes from the low level to the high level in the first carrier P1), the first and second C The voltages ΔV1 and ΔV2 are output from the −V conversion circuits 210 and 220, respectively.

  The signals output from the first and second CV conversion circuits 210 and 220 are driven at predetermined intervals by the first and second S / H circuits 250 and 260 driven based on the signal from the control signal generation circuit 240. Sampled and held for a certain period. Then, the LPF circuit extracts the difference voltage (sampling 2—sampling 1) from the output voltages of the first and second S / H circuits 250 and 260, respectively, and further extracts only a predetermined frequency component from the difference voltage to obtain an acceleration signal. Is output.

  As described above, electric charges are generated on the support substrate 1 by the coupling capacitance between the first movable portion 10 and the support substrate 1 and the first carrier wave P1. In addition, a charge is generated in the support substrate 1 by the coupling capacitance between the second movable portion 30 and the support substrate 1 and the second carrier wave P2. At this time, since the first and second carrier waves P1 and P2 are signals having amplitude between the voltages Vdd and 0V, the same frequency, and a phase difference of 180 °, the potential of the support substrate 1 is the middle point. Of 1/2 Vdd. For this reason, it can suppress that the electric potential of the support substrate 1 changes with a carrier wave.

  Further, by forming a detection unit that detects acceleration in the y-axis direction in the second element unit 120, acceleration in two directions can be detected.

(Second Embodiment)
A second embodiment of the present invention will be described. The present embodiment is different from the first embodiment in that the circuit chip 200 includes only the first CV conversion circuit 210, and the other parts are the same as those in the first embodiment, and thus the description thereof is omitted here. To do.

  As shown in FIG. 5, in this embodiment, only the first CV conversion circuit 210 is provided. The operational amplifier 211 is connected to the first and second fixed electrodes 21a, 21b, 41a and 41b via the first to fourth changeover switches 271 to 274.

  Specifically, the non-inverting input terminal of the operational amplifier 211 is connected to the first fixed electrode 21a via the first changeover switch 271 and the first fixed electrode pad 23a, as well as the fourth changeover switch 274 and the second changeover switch 274. It is connected to the second fixed electrode 41b via the fixed electrode pad 43b. The inverting input terminal is connected to the first fixed electrode 21b via the second changeover switch 272 and the first fixed electrode pad 23b, and is connected to the first changeover electrode 273 via the third changeover switch 273 and the second fixed electrode pad 43a. 2 is connected to the fixed electrode 41a. That is, in the present embodiment, the capacitors CS1 to CS4 are voltage-converted by the common first CV conversion circuit 210.

  The control signal generation circuit 240 outputs a control signal SW1 for controlling on / off of the first and second switches 213a, 213b, and controls for controlling on / off of the first to fourth changeover switches 271-274. The signal SW2 is output.

  Next, the operation of the acceleration sensor will be described with reference to FIG.

  As shown in FIG. 6, in the period φ3, the first and second changeover switches 271 and 272 are turned on, and the third and fourth changeover switches 273 and 274 are turned off. For this reason, the signals of the first fixed electrodes 21a and 21b are input to the first CV conversion circuit 210 via the first fixed electrode pads 23a and 23b, and ΔV1 as a potential difference signal (VOP−VOM) corresponding to the acceleration. Is output.

  Similarly, in the period φ4, the first and second changeover switches 271 and 272 are turned off, and the third and fourth changeover switches 273 and 274 are turned on. For this reason, the signals of the second fixed electrodes 41a and 41b are input to the first C-V conversion circuit 210 via the second fixed electrode pads 43a and 43b, and ΔV2 as a potential difference signal (VOP1-VOM1) corresponding to the acceleration. Is output.

  In addition, in the period φ3 in which the third and fourth changeover switches 273 and 274 are off, the second element portion 120 cannot detect acceleration, but the second movable portion 30 (second movable electrode 34). To the second carrier wave P2. Similarly, in the period φ4 in which the first and second changeover switches 271 and 272 are off, the first element portion 110 does not detect acceleration, but the first movable portion 10 (first movable electrode 14). ) Is inputted with the first carrier wave P1. As described above, the potential of the support substrate 1 is changed by inputting the first and second carrier waves P1 and P2 to the first and second movable parts 10 and 30 (first and second movable electrodes 14 and 34). It is because it can suppress doing.

  When the first and second switches 213a and 213b are turned on (closed) (period φ2), the first and second capacitors 212a and 212b are reset, and the first and second switches 213a and 213b are turned off ( Acceleration is detected when it is open. That is, a period other than the period φ2 in the period φ3 is a period for detecting acceleration, and a period other than the period φ2 in the period φ4 is a period for detecting acceleration.

  As described above, even if the circuit chip 200 includes only the first CV conversion circuit 210 and the capacitors CS1 and CS2 and the capacitors CS3 and CS4 are sequentially voltage-converted, the first and second movable parts 10 , 30 (first and second movable electrodes 14 and 34), the same effects as in the first embodiment can be obtained by inputting the first and second carrier waves P1 and P2.

(Third embodiment)
A third embodiment of the present invention will be described. In the present embodiment, the configuration of the second element unit 120 is changed with respect to the first embodiment, and the other parts are the same as those in the first embodiment, and thus the description thereof is omitted here.

  As shown in FIG. 7, the second element portion 120 is a region partitioned from the peripheral fixed portion 50 by the groove portion 6, and no movable portion or fixed portion is formed. A pad for receiving the second carrier wave P2 is formed on the semiconductor layer 3 of the second element portion 120, although not particularly shown.

  In the second element portion 120, the coupling capacitance constituted by the semiconductor layer 3, the buried insulating film 2, and the support substrate 1 is equal to the coupling capacitance between the first movable portion 10 and the support substrate 1. It is divided by the groove 6.

  In such an acceleration sensor, as in the first embodiment, acceleration can be detected in a state where the first carrier wave P1 is input to the first movable part 10 and the second carrier wave P2 is input to the second element part 120. Done. That is, the second element unit 120 of the present embodiment is not an area that functions as a detection unit that detects acceleration, but the second carrier wave P2 is input only to suppress a change in the potential of the support substrate 1. This is a dummy area.

  As described above, the first and second movable parts 10 and 30 (the first and second movable electrodes 14 and 34) can be connected to the first and second carrier waves P1 and the second element part 120 without configuring the detection part. By inputting P2, the same effect as in the first embodiment can be obtained.

  In the present embodiment, the semiconductor layer 3 partitioned by the groove 6 corresponds to a region where the second carrier wave P2 of the present invention is input.

(Fourth embodiment)
A fourth embodiment of the present invention will be described. In the present embodiment, the configuration of the second element unit 120 is changed with respect to the first embodiment, and the other aspects are the same as those in the first embodiment, and thus the description thereof is omitted here.

  As shown in FIG. 8, the first element portion 110 is formed with an x-axis direction detection portion having the first movable portion 10 and the first fixed portions 20a and 20b. The second element portion 120 includes a y-axis direction detecting portion 120a having the second movable portion 30 and the second fixed portions 40a and 40b, and a pair of third fixed electrodes that are spaced apart from each other and have a third fixed electrode. The first and second movable parts 10 and 30 are arranged in a direction perpendicular to the displacement direction of the first and second movable parts 10 and 30 (z-axis direction). A z-axis direction detection unit 110b having a third movable part including three movable electrodes is formed.

  That is, the second element unit 120 of the present embodiment is configured by the separated y-axis direction detection unit 120a and z-axis direction detection unit 120b. The coupling capacitance between the first movable portion 10 and the support substrate 1 is the coupling capacitance between the second movable portion 30 and the support substrate 1 and the cup between the third movable portion and the support substrate 1. It is made equal to the sum of the ring capacities.

  In such an acceleration sensor, as in the first embodiment, the first carrier wave P1 is input to the first movable part 10, and the second carrier wave P2 is input to the second movable part 30 and the third movable part. The acceleration is detected at.

  As described above, even if the second element unit 120 includes a plurality of regions, the coupling capacity between the first movable unit 10 and the support substrate 1 and the second carrier wave P2 of the second element unit 120 are included. If the coupling capacitance between the input region and the support substrate 1 is equal, the first and second carrier waves P1 and P2 are input, so that the same effect as in the first embodiment can be obtained. Can be obtained.

(Other embodiments)
In the above embodiments, the first element unit 110 has been described as detecting acceleration, but the first element unit 110 may detect angular velocity. That is, in the first, second, and fourth embodiments, the sensor chip 100 may be capable of detecting both acceleration and angular velocity. In the third embodiment, the sensor chip 100 may be configured to detect only the angular velocity.

  In the first and second embodiments, the displacement directions of the first movable electrode 14 and the second movable electrode 34 are described as being orthogonal to each other. However, the displacement direction of the first movable electrode 14 and the second movable electrode 34 are described. The displacement direction of the electrode 34 may be the same direction. In this case, if the capacities of the first element unit 110 and the second element unit 120 are greatly different, it can be determined that either one has failed. Similarly, also in the said 4th Embodiment, the two detection parts of the 2nd element part 120 may detect the acceleration of the same direction, and the 1st element part 110 and the 2nd element part 120 are the same. One detection unit may detect acceleration in the same direction. Further, the first and second element units 110 and 120 may be formed with detection units that detect acceleration in the same direction.

  In the first and second embodiments, the coupling capacity between the first movable part 10 and the support substrate 1 and the coupling capacity between the second movable part 30 and the support substrate 1 are different. The first and second element portions 110 and 120 may be formed.

  Here, the charge generated in the support substrate 1 is determined by Q = CV and the potential input to the coupling capacitor and the movable portion. Therefore, the amplitudes of the first and second carrier waves P1 and P2 generated by the reference signal generation circuit 230 are different, and the coupling capacity between the first movable part 10 and the support substrate 1 and the first carrier wave P1 are different. Among the generated charge, the coupling capacity between the second movable part 30 and the support substrate 1 and the charge generated by the second carrier wave P2, the magnitude when the carrier wave is at the low level and the carrier wave at the high level. You may make it a certain size equal. Even in this case, the potential of the support substrate 1 is maintained at the midpoint potential by the charges generated by the first and second carriers P1 and P2. For this reason, it can suppress that the electric potential of the support substrate 1 changes similarly to said each embodiment.

  Similarly, also in the third and fourth embodiments, the coupling capacitance between the support substrate 1 and the portion where the first and second carrier waves P1 and P2 are input in the first and second element portions 110 and 120 is input. May be different, and the amplitude may be changed so that charges generated by the first and second carriers P1 and P2 can be eliminated.

DESCRIPTION OF SYMBOLS 1 Support substrate 2 Embedded insulating film 3 Semiconductor layer 4 SOI substrate (semiconductor substrate)
DESCRIPTION OF SYMBOLS 10 1st movable part 14 1st movable electrode 20a, 20b 1st fixed part 21a, 21b 1st fixed electrode 110 1st element part 120 2nd element part 210 1st CV conversion circuit 220 2nd CV conversion circuit

Claims (6)

A support substrate (1); a buried insulating film (2) disposed on the support substrate; and a semiconductor layer (3) disposed on the opposite side of the support substrate with the buried insulating film interposed therebetween. A semiconductor substrate (4);
A pair of first fixing portions (20a, 20b) formed on the semiconductor layer and spaced apart from each other and having first fixing electrodes (21a, 21b), respectively, and the pair of first fixing portions. A first movable part (10) having a first movable electrode (14) opposed to each of the first fixed electrodes provided in the first fixed part and capable of being displaced in a predetermined direction according to a physical quantity. A first element part (110) comprising:
A second element part (120) formed in a region different from the first element part in the semiconductor layer;
The pulsed first carrier wave (P1) is inputted to the first movable part, and the pulsed second carrier wave (P2) having the same frequency as that of the first carrier wave and having a phase different by 180 ° is used as the second element. A reference signal generation circuit (230) to be input to the unit,
A fully-differential first CV conversion circuit (210) that converts a capacitance between the first movable electrode and the first fixed electrode.
The second element portion is disposed between a pair of second fixing portions (40a, 40b) that are spaced apart from each other and have second fixing electrodes (41a, 41b), respectively, and the pair of second fixing portions. A second movable part (30) having a second movable electrode (34) opposed to each of the second fixed electrodes provided in the second fixed part and capable of being displaced in a predetermined direction according to a physical quantity. And ,
The reference signal generation circuit inputs the second carrier wave to the second movable part when inputting the first carrier wave to the first movable part,
The first CV conversion circuit is connected to the first fixed electrode via first and second changeover switches (271, 272) and via third and fourth changeover switches (273, 274). Connected to the second fixed electrode, and when the first and second changeover switches are turned on and the third and fourth switches are turned off, the first movable electrode and the first fixed electrode Capacitance conversion between the second movable electrode and the second fixed electrode is performed when the first and second changeover switches are turned off and the third and fourth changeover switches are turned on. A capacitance type physical quantity detection device characterized in that voltage conversion is performed on capacitance between electrodes .   The reference signal generation circuit is capable of generating a charge having the same magnitude as the charge determined by the coupling capacitance between the first movable part and the support substrate and the amplitude of the first carrier wave. 2. The capacitive physical quantity according to claim 1, wherein the second carrier wave is input according to a coupling capacitance between a portion of the second element part to which the second carrier wave is input and the support substrate. Detection device. In the second element portion, a coupling capacitance between the portion to which the second carrier wave is input and the support substrate is equal to a coupling capacitance between the first movable portion and the support substrate,
3. The capacitive physical quantity detection device according to claim 2, wherein the reference signal generation circuit inputs the second carrier wave having the same amplitude as the first carrier wave. Capacitive physical quantity detecting apparatus according to any one of claims 1 to 3, characterized in that it is perpendicular to the displacement direction of the displacement direction and the second movable electrode of the first movable electrode. The second element portion includes the second movable portion and the second fixed portion, a pair of third fixed portions spaced apart from each other and having a third fixed electrode, and the pair of third fixed portions. A third movable part having a third movable electrode disposed between the first movable electrode and the third fixed electrode provided in the third fixed part and facing each third fixed electrode and displaceable in a predetermined direction according to a physical quantity; , And
It said reference signal generating circuit, capacitive physical quantity detecting apparatus according to any one of claims 1 to 4, characterized in that inputting the second carrier to the second movable section and the third movable portion. 6. The capacitive physical quantity according to claim 5 , wherein a displacement direction of the first movable electrode, a displacement direction of the second movable electrode, and a displacement direction of the third movable electrode are orthogonal to each other. Detection device.

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