JP5441027B2 - Inspection method and inspection apparatus for capacitive acceleration sensor - Google Patents

Description

  The present invention relates to an inspection method and an inspection apparatus for a capacitance-type acceleration sensor, and more specifically, a capacitance between a displaceable weight body and a detection electrode disposed opposite to the weight body. The present invention relates to an inspection method and an inspection apparatus for a capacitive acceleration sensor that accurately adjusts an offset to adjust an offset and calibrate a sensitivity.

  In general, a device for detecting a physical quantity using a change in the distance between electrodes and an operation test method thereof are well known. For example, a detection device having a simple structure in which two substrates are arranged to face each other and electrodes are formed on the respective substrates is known. In this detection device, one substrate is displaced based on a physical quantity such as acceleration, the distance between the electrodes formed on both substrates is changed by this displacement, and this is detected as a change in capacitance between both electrodes. ing. In addition, this detection device can be used as an acceleration detection device that detects the applied acceleration if a weight body is bonded to one substrate and the substrate is displaced based on the acceleration applied to the weight body. Is.

  Usually, when a detection device of some physical quantity is commercialized, it is necessary to perform an operation test as to whether or not this detection device outputs a correct detection signal. Conventionally, in such an operation test, a method has been adopted in which a physical quantity to be detected is actually applied to the detection device and a detection signal at that time is examined. For example, in the case of an acceleration detection device, whether or not an acceleration of a predetermined magnitude is actually applied to the detection device from a predetermined direction, and the detection signal at that time is correct according to the applied acceleration. Determine. However, in order to perform such an operation test, a dedicated test facility is required, and the test work is complicated and time-consuming. In particular, the quantity that can be tested with a dedicated test facility is limited, leading to a decrease in productivity. Therefore, such a conventional test method has a problem that it is not suitable as an operation test for a mass-produced apparatus.

  Thus, for example, an acceleration sensor inspection device and an operation test method thereof have been proposed as disclosed in Patent Document 1. In this patent document 1, a displacement electrode supported so as to be able to be displaced by the action of an external force, a fixed electrode fixed to an apparatus housing at a position facing the displacement electrode, and a distance between these two electrodes An acceleration detecting device operation test method for detecting an acceleration corresponding to an external force as an electrical signal, wherein a predetermined voltage is applied between both electrodes, and the applied voltage In the state where the displacement electrode is displaced by the Coulomb force generated based on the electric signal, an electric signal having a temporal variation component having a predetermined magnitude is given to one electrode of both electrodes, and transmitted to the other electrode at this time By comparing the magnitude of the fluctuation component to be applied with the applied voltage, the operation of this detection device is tested, and the acceleration detection device that detects the acceleration using the change in the distance between the electrodes is used. It is a work test method.

  In addition, a device for detecting a physical quantity using other changes in the distance between electrodes and its operation test method, that is, applying a voltage to the test electrode and displacing it by Coulomb force, the magnitude of the applied voltage and the amount of displacement (capacity change) For example, Patent Documents 2 and 3 have been proposed for performing an operation test by comparing (1) and (2).

  Further, for example, Patent Document 4 discloses a capacitance type sensor having a structure in which four beam members are provided orthogonally to a weight body constituting an intermediate substrate.

  Further, as a detection device for a capacitance type acceleration sensor, a device using a switched capacitor method disclosed in Patent Document 5 has been proposed.

JP 2002-221463 A International Publication WO1992 / 17759 JP 2000-146729 A JP 2007-46927 A JP-A-10-170544

  However, the above-described inspection apparatus and its operation test method have a problem that basically only a rough operation test such as failure detection can be performed. When calibration is performed with respect to variations in sensitivity and offset with the acceleration sensor, the reference Coulomb force itself varies and cannot be accurately calibrated. In other words, the acceleration sensor detects a force proportional to mass and acceleration, whereas the Coulomb force correlates with the capacitance value in addition to the applied voltage, so if the process varies, the exact Coulomb force Cannot be estimated. For this reason, it has been difficult to estimate the sensitivity of the sensor (F / G: change in capacity per gram of gravitational acceleration) by inspection using Coulomb force.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a capacitance between a displaceable weight body and a detection electrode disposed opposite to the weight body. It is an object of the present invention to provide an inspection method and an inspection apparatus for a capacitive acceleration sensor that are accurately detected to adjust offset and calibrate sensitivity.

  The present invention has been made to achieve such an object, and the invention according to claim 1 is directed to one detection electrode and the other detection electrode provided to face the one detection electrode. And a displacement-type weight body provided so as to be sandwiched between the detection electrodes. First, the weight body of the capacitance-type acceleration sensor, Detecting a capacitance between each of the detection electrodes and calculating an offset from the capacitance value of the capacitance; and next, generating a potential difference between the weight body and the one detection electrode. And then applying a different applied voltage to the one detection electrode due to the potential difference between the other detection electrode and the weight body in the Coulomb force acting on the weight body. Detecting the capacitance and Next, comparing the amount of change in capacitance between the other detection electrode and the weight body before and after applying a potential difference between the one detection electrode and the weight body; Next, the capacitance between the weight body and the one detection electrode, the applied voltage, and the other detection electrode and the weight body in the Coulomb force acting on the weight body And a step of calibrating the sensitivity by obtaining a correction value of the sensitivity from the amount of change in capacitance between.

  According to a second aspect of the present invention, in the first aspect of the invention, the step of detecting the capacitance is equal to the one detection electrode, the other detection electrode, and the weight body. In a state where an applied voltage is applied, detecting a capacitance between the other detection electrode and the weight body; the one detection electrode; the other detection electrode; and the weight body; And detecting a capacitance between the other detection electrode and the weight body in a Coulomb force acting on the weight body in a state where different applied voltages are applied.

  According to a third aspect of the present invention, one detection electrode, the other detection electrode provided to face the one detection electrode, and a displaceable provided to be sandwiched between the detection electrodes A capacitance type acceleration sensor inspection device having a weight body, wherein the capacitance between the weight body of the capacitance type acceleration sensor and each detection electrode is detected, and A first and second capacitance calculating means for calculating an offset from a capacitance value of the capacity; a voltage applying means for providing a potential difference between the weight body and the one detection electrode; and the voltage applying means. Capacitance between the one detection electrode and the weight body in the Coulomb force acting on the weight body and the other in a state where a different applied voltage is applied to the one detection electrode by applying a potential difference Between the detection electrode and the weight body Third capacitance calculating means for detecting electrostatic capacity, and static electricity between the other detection electrode and the weight body before and after applying a potential difference between the one detection electrode and the weight body. A comparison means for comparing the amount of change in capacitance, the capacitance between the weight body and the one detection electrode, the applied voltage, and the other in the Coulomb force acting on the weight body. Sensitivity adjusting means for obtaining a correction value of sensitivity from the amount of change in capacitance between the detection electrode and the weight body and calibrating the sensitivity is provided.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the capacitance detecting means is applied to the one detection electrode, the other detection electrode, and the weight body. A first and second capacitance calculating means for detecting a capacitance between the other detection electrode and the weight body in a state where a voltage is applied; and the one detection electrode and the other detection electrode. And, in a state in which an applied voltage different from that of the weight body is applied, a capacitance between the other detection electrode and the weight body in a Coulomb force acting on the weight body is detected. And a capacity calculating means.

  According to a fifth aspect of the present invention, in the invention according to the third or fourth aspect, the capacitance detection means includes a high-frequency voltage application device that modulates the voltage of the weight body to a high-frequency voltage, and a first detection electrode. And a demodulating circuit for demodulating the high frequency into a DC component.

  The invention according to claim 6 is the invention according to claim 5, wherein the capacitive acceleration sensor includes a first substrate having one detection electrode and the one detection electrode of the first substrate. A second substrate having the other detection electrode provided to face the first electrode, a holding member provided so as to be sandwiched between the first substrate and the second substrate, and the detection electrode in an internal space of the holding member Displaceable weight body provided so as to be sandwiched between the plurality of beam members, a plurality of beam members supporting the weight body, and a plurality of column members supporting the beam members, the beam member and the column members Is not in contact with the holding member.

  The invention described in claim 7 is characterized in that, in the invention described in claim 6, a gap is provided between the beam member, the column member, and the holding member.

  The invention according to claim 8 is the invention according to claim 6 or 7, wherein the holding member is grounded.

  According to the present invention, a first substrate having one detection electrode, a second substrate having the other detection electrode provided to face the one detection electrode of the first substrate, a first substrate, A holding member provided to be sandwiched between the second substrates, a displaceable weight body provided to be sandwiched between the detection electrodes in an internal space of the holding member, and a plurality of beams supporting the weight body Member and a plurality of support members that support the beam member, and the beam member and the support member are not in contact with the holding member. The effect of removing the influence of the parasitic capacitance between each detection electrode and the ability to detect only the capacitance value between each detection electrode and the weight body acting on the Coulomb force is achieved.

  Further, in addition to the failure detection, the sensitivity of the acceleration sensor and the offset variation can be corrected, and it is possible to easily inspect with an existing semiconductor tester using the voltage applying unit and the voltage detecting unit.

It is a block diagram for demonstrating the capacitance-type acceleration sensor as a comparative example which concerns on this invention, (a) is a top view, (b) is AA sectional drawing and board | substrate sectional drawing of (a). It is a figure for demonstrating the test | inspection method of the capacitive acceleration sensor shown in FIG. It is a circuit diagram for demonstrating the CV conversion system by the CV conversion circuit in the conventional electrostatic capacitance type acceleration detection apparatus. It is a circuit diagram for demonstrating the CV conversion system by the CV conversion circuit in the conventional electrostatic capacitance type acceleration detection apparatus. FIG. 5 is a circuit diagram for explaining a CV conversion method by a CV conversion circuit in the capacitive acceleration detection device shown in FIG. 4. BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram for demonstrating one Example of the capacitive acceleration sensor which concerns on this invention, (a) is a top view, (b) is BB sectional drawing and board | substrate sectional drawing of (a). It is a block diagram for demonstrating the detection apparatus using the capacitive acceleration sensor shown in FIG.6 (b). It is a circuit diagram for demonstrating the CV conversion system by the CV conversion circuit in the electrostatic capacitance type acceleration detection apparatus shown in FIG. (A) thru | or (c) are process drawings for demonstrating the inspection method (offset and sensitivity calculation method) of the capacitive acceleration sensor of this invention. It is a figure which shows the flowchart for demonstrating the calculation method of the offset and sensitivity of the capacitive acceleration sensor of this invention. (A), (b) is a figure for demonstrating the calculation method (X-axis) of an offset and a sensitivity in the inspection method of the capacitive acceleration sensor which concerns on this invention. (A), (b) is a figure for demonstrating the calculation method (Y-axis) of an offset and a sensitivity in the test | inspection method of the capacitive acceleration sensor which concerns on this invention. (A), (b) is a figure for demonstrating the calculation method (Z-axis) of an offset and a sensitivity in the inspection method of the capacitive acceleration sensor which concerns on this invention. It is a block diagram for demonstrating the inspection apparatus of the capacitive acceleration sensor which concerns on this invention. It is a block diagram (top view) for demonstrating the other Example of the capacitive acceleration sensor which concerns on this invention.

First, a comparative example according to the present invention will be described with reference to the drawings.
FIGS. 1A and 1B are configuration diagrams for explaining a capacitance type acceleration sensor as a comparative example according to the present invention. FIG. 1A is a top view and FIG. It is AA sectional drawing and board | substrate sectional drawing of 1 (a). This capacitive sensor is mounted on the first substrate 11 so as to oppose the weight bodies 22a to 22e and a frame body (holding member) 21 that holds the displaceable weight bodies 22 (22a to 22e). The detection electrodes 11a to 11d (11b and 11d are not shown) provided are configured to detect a change in electrostatic capacitance between the weight bodies 22a to 22d and the detection electrodes 11a to 11d. Yes.

  The weight bodies 22a to 22e are held by the frame body 21 via beam members 23a, 23b, 23c, and 23d. The detection electrodes 12a to 12d provided on the first substrate 11 include X-axis detection electrodes 11a and 11c and Y-axis detection electrodes 11b and 11d arranged to face the weights 22a to 22d. ing.

  The beam member 23a is sandwiched between the weight body 22d and the weight body 22a, the beam member 23b is sandwiched between the weight body 22a and the weight body 22b, and the beam member 23c is sandwiched between the weight body 22b and the weight body 22b. The beam member 23d is a beam member sandwiched between the weight body 22c and the weight body 22d.

  The weight bodies 22a to 22e have a center portion 22e disposed at the intersections of the beam members 23a to 23d, and are disposed in a clover shape from the center portion 22e along the frame body 21 and the beam members 23a to 23d. Peripheral portions 22a to 22d are provided.

  Further, the beam members 23 a to 23 d are arranged so as to be sandwiched between adjacent peripheral portions 22 a to 22 d of the weight body along the diagonal line of the frame body 21 from the center portion 22 e of the weight body 22. The shape of the detection electrodes 11a to 11d is a triangle similar to the peripheral portions 22a to 22d of the weight body arranged in a crowbar shape extending in four directions from the center.

  Similarly, detection electrodes 31a to 31d (31b and 31d are not shown) provided on the second substrate 31 are provided, and electrostatic capacitances between the weight bodies 22a to 22d and the detection electrodes 31a to 31d are provided. It is configured to detect a change in capacity.

FIG. 2 is a diagram for explaining an inspection method of the capacitive acceleration sensor shown in FIG. The weight body 22 is held on the frame body 21 by a beam member 23. Detection electrodes 11 a and 11 c are arranged on the first substrate 11 corresponding to the weight body 22, and detection electrodes 31 a and 31 c are arranged on the second substrate 31 corresponding to the weight body 22. When the distance between the beam member 23 holding the weight body 22 and the detection electrodes 11a and 11c provided on the first substrate 11 is d ₀ and the area of the detection electrodes 11a and 11c is S, the inertial force due to acceleration is In Ma, the Coulomb force is expressed as follows.

Since M and S are on the order of mm, they are constant regardless of variations. The most affected by the process variation is d ₀ (several μm). If this d ₀ varies, the Coulomb force also varies, making it difficult to correct the sensitivity. Therefore, it is necessary to estimate this d ₀ by combining with the measurement of the capacitance value between the detection electrode and the weight body, to calculate the correct Coulomb force, and to deal with the inertial force.

  The inspection apparatus in this case requires a CV conversion circuit and a sensor structure that can accurately detect the capacitance between the weight body and the detection electrode without being affected by the parasitic capacitance.

  3 and 4 are circuit diagrams for explaining a CV conversion method using a CV conversion circuit in a conventional capacitive acceleration detection device. Cs is a capacitance between the weight body of the sensor unit 42 and the detection electrode, Cp is a parasitic capacitance between the sensor unit 42 and the CV conversion circuit 43 between the wiring and the electrode pad, and Cp ′ is each detection electrode and the frame. It shows the parasitic capacitance between the body. In the conventional CV conversion method using a switched capacitor, the output is determined according to the ratio between the equivalent resistance value of the switched capacitor and the resistance value of the resistor circuit, and the output of the operational amplifier is as follows.

FIG. 5 is an explanatory diagram for explaining the CV conversion method by the CV conversion circuit of the present invention. In the CV conversion circuit 43, a non-inverting input terminal is connected to the detection electrode of the capacitive element Cs of the sensor unit. The operational amplifier 43a includes a resistor R and a capacitive element _CFB connected in parallel between the non-inverting input terminal and the output terminal. Further, Vcom is applied to the inverting input terminal of the operational amplifier 43a. In addition, a high-frequency voltage application circuit 41 that modulates the potential of the weight body of the sensor unit 42 into a high-frequency voltage is provided.

  When the voltage of the weight body is modulated at a high frequency with respect to the output of the sensor unit 42, the output of the operational amplifier 43a is as follows.

  In this case, the parasitic capacitance Cp between the wiring between the sensor unit 42 and the CV conversion circuit 43 and the ground (or other fixed potential) on the electrode pad does not appear as an output. Further, since the high frequency is modulated, the capacitance value can be detected regardless of the offset of the operational amplifier.

  6A and 6B are configuration diagrams for explaining an embodiment of the capacitive acceleration sensor according to the present invention. FIG. 6A is a top view and FIG. 6B is a diagram. FIG. 1A is a cross-sectional view taken along line BB and a cross-sectional view of a substrate. The capacitance type sensor of the present invention includes a frame body (holding member) 121 that holds a displaceable weight body 122 (122a to 122e) and a first substrate 111 so as to face the weight bodies 122a to 122e. It includes detection electrodes 111a to 111d (111b and 111d not shown) provided on the top, and is configured to detect a change in electrostatic capacitance between the weight bodies 122a to 122d and the detection electrodes 111a to 111d. Has been.

  The weight bodies 122a to 122e are held by beam members 123a, 123b, 123c, and 123d, and the distal ends of the beam members 123a to 123d are held by column members (pillars) 124a, 124b, 124c, and 124d. Yes. The beam members 123 a to 123 d and the pillars 124 a to 124 d are not in contact with the frame body 121 in the internal space of the frame body 121.

  The detection electrodes 112a to 112d provided on the first substrate 111 include X-axis detection electrodes 111a and 111c and Y-axis detection electrodes 111b and 111d arranged to face the weight bodies 122a to 122d, respectively. It has.

  The beam member 123a is sandwiched between the weight body 122d and the weight body 122a, the beam member 123b is sandwiched between the weight body 122a and the weight body 122b, and the beam member 123c is sandwiched between the weight body 122b and the weight body 122b. The beam member 123d is sandwiched between the body 122c and the beam member 122c and the weight body 122d.

  The weight bodies 122a to 122e have a center portion 122e disposed at the intersections of the beam members 123a to 123d, and are disposed in a clover shape from the center portion 122e along the frame body 121 and the beam members 123a to 123d. Peripheral portions 122a to 122d are provided.

  Further, the beam members 123a to 123d are arranged so as to be sandwiched between adjacent peripheral portions 122a to 122d of the weight body along the diagonal line of the frame body 121 from the center portion 122e of the weight body 122. The detection electrodes 111a to 111d are triangular in shape similar to the peripheral portions 122a to 122d of the weight body arranged in a crowbar shape extending in four directions from the center.

  Similarly, detection electrodes 131a to 131d (131b and 131d are not shown) provided on the second substrate 131 are provided, and electrostatic capacitances between the weight bodies 122a to 122d and the detection electrodes 131a to 131d are provided. It is configured to detect a change in capacity.

  That is, the first substrate 111 having one detection electrode 111a to 111d and the second substrate having the other detection electrode 131a to 131d provided to face the one detection electrode 111a to 111d of the first substrate 111. 131, a frame body 121 provided so as to be sandwiched between the first substrate 111 and the second substrate 131, and a displaceable weight body 122 provided so as to be sandwiched between detection electrodes in the internal space of the frame body 121. (122a to 122d), a plurality of beam members 123 (123a to 123d) provided in the internal space of the frame body 121 and supporting the weight body 122, and provided in the internal space of the frame body 121. A plurality of pillars 124 (124a to 124d) to be supported, so that the beam member 121 and the pillar 124 are not in contact with the frame body 121. It has been made. Therefore, a gap 125 is provided between the beam member 123 and the pillar 124 and the frame body 121.

  FIG. 7 is a configuration diagram for explaining a detection device using the capacitive acceleration sensor shown in FIG. The capacitance Cs between the weight body of the sensor unit and each detection electrode and the parasitic capacitance Cp ′ between each detection electrode and the frame are taken into consideration. A high frequency voltage is applied to the weight body 122 and the frame body 121 by the high frequency voltage application circuit 141, and the frame body 121 is grounded, and a parasitic capacitance Cp ′ between each detection electrode and the frame body is removed. It is supposed to be. In this embodiment, the frame body 121 and the beam member have a non-contact structure. However, as long as the frame body 121 and the beam member are electrically separated, an insulating material may be inserted therebetween.

  FIG. 8 is a circuit configuration diagram for explaining a CV conversion method using a CV conversion circuit in the capacitive acceleration detecting device shown in FIG. When the voltage of the weight body is modulated at a high frequency with respect to the output of the sensor unit 142, the output of the operational amplifier 143a is as follows.

  In the capacitive acceleration sensor of the present invention, the parasitic capacitance Cp ′ between the frame body 121 and each detection electrode is removed by separating the potentials of the frame body 121 and the weight body 122, and the Coulomb force is involved. Only the capacitance value Cs between each detection electrode and the weight body 122 can be detected.

  FIGS. 9A to 9C are process diagrams for explaining the inspection method (offset and sensitivity) of the capacitive acceleration sensor of the present invention, and FIG. 10 is a capacitive acceleration sensor of the present invention. It is a figure which shows the flowchart for demonstrating the calculation method of an offset and sensitivity.

First, the capacitances Cs1, Cs2 (（Va, Vb) between the weight body 122 and the detection electrodes 111, 131 in the capacitance type acceleration sensor according to the present invention are changed to the first CV conversion circuit 143a and the first CV conversion circuit 143a. 2 is detected by the CV conversion circuit 143b, and an offset is calculated from the capacitance value (step S1, FIGS. 9A and 9B). At this time, the potentials of the weight body 122 and all the detection electrodes are Vcom, there is no potential difference, and no Coulomb force is applied (Fco = 0). Next, a potential difference VDD is applied between the weight body 122 and one detection electrode 111 (step S2). Next, in a state where the applied voltage VDD is applied to one detection electrode 111, the magnitude of the Coulomb force acting on the weight body 122 is obtained from the magnitude of the applied voltage and the capacitance value, and the other detection is performed. The capacitance Cs2 ′ (∝Vc) between the electrode 131 and the weight body 122 is detected by the third CV conversion circuit 143c (step S3, FIG. 9C). Next, the value of this Coulomb force Fco = Cs1 (VDD−Vcom) ² / d ₀ ∝Cs1 ² · (VDD−Vcom) ² and the capacitance between the other detection electrode 131 and the weight body 122 The amount of change (∝Vb−Vc) is compared (step S4). Next, a sensitivity correction value is obtained from Va, Vb-Vc, and the applied voltage (VDD-Vcom) to calibrate the sensitivity (step S5).

  Next, a method for calculating sensitivity and offset will be described more specifically based on FIGS. 11 (a) and 11 (b) to FIG.

  FIGS. 11A and 11B are diagrams for explaining an offset and sensitivity calculation method (X axis) in the inspection method of the capacitive acceleration sensor according to the present invention. The capacitance value between the detection electrode 111c and the weight body 122 is Cx1, the capacitance value between the detection electrode 111a and the weight body 122 is Cx2, and the capacitance value between the detection electrode 131c and the weight body 122. Is Cx3, and the capacitance value between the detection electrode 131a and the weight body 122 is Cx4. A CV conversion circuit 143 is connected to each of the detection electrodes 111a, 111c, 131a, and 131c.

First, as shown in FIG. 11A, the capacitance values of Cx1 to Cx4 are detected using the above-described CV conversion circuit and electrostatic capacitance type acceleration sensor. Next, (Cx1 + Cx4) − (Cx2 + Cx3) is calculated to calculate an offset. Next, as shown in FIG. 11 (b), Cx2 and CX3 are set to VDD and a Coulomb force is applied to detect capacitance changes (ΔCx1, ΔCx4) of Cx1 and Cx4. Next, the sensitivity Sx (F / G) is calculated from the capacitance change (ΔCx1, ΔCx4) and the Coulomb force (∝Cx2 ² , Cx3 ² ).

  FIGS. 12A and 12B are diagrams for explaining a calculation method (Y axis) of offset and sensitivity in the inspection method of the capacitive acceleration sensor according to the present invention. The capacitance value between the detection electrode 111d and the weight body 122 is Cy1, the capacitance value between the detection electrode 111b and the weight body 122 is Cy2, and the capacitance value between the detection electrode 131d and the weight body 122. Is Cy3, and the capacitance value between the detection electrode 131b and the weight body 122 is Cy4. A CV conversion circuit 143 is connected to each of the detection electrodes 111b, 111d, 131b, and 131d.

First, as shown in FIG. 12A, the capacitance values of Cy1 to Cy4 are detected by using the CV conversion circuit and the capacitive acceleration sensor described above. Next, (Cy1 + Cy4) − (Cy2 + Cy3) is calculated to calculate an offset. Next, as shown in FIG. 12 (b), Cy2 and Cy3 are set to VDD and a Coulomb force is applied to detect capacitance changes (ΔCy1, ΔCy4) of Cy1 and Cy4. Next, the sensitivity Sy (F / G) is calculated from the ratio between the capacitance change (ΔCy1, ΔCy4) and the Coulomb force (∝Cy2 ² , Cy3 ² ).

  FIG. 13 is a diagram for explaining a calculation method (Z axis) of offset and sensitivity in the inspection method for the capacitive acceleration sensor according to the present invention. The capacitance value between the detection electrode 111c and the weight body 122 is Cx1, Cy1, the capacitance value between the detection electrode 111a and the weight body 122 is Cx2, Cy2, and the detection electrode 131c and the weight body 122 are The capacitance value between them is Cx3, Cy3, and the capacitance value between the detection electrode 131a and the weight body 122 is Cx4, Cy4. A CV conversion circuit 143 is connected to each of the detection electrodes 111a, 111c, 131a, and 131c.

First, the capacitance value of (Cx1 + Cx2 + Cy1 + Cy2) − (Cx3 + Cx4 + Cy3 + Cy4) is detected using the above-described CV conversion circuit and capacitive acceleration sensor. Next, Cx1, Cx4, Cy3, and Cy4 are set to VDD, and the capacitance change (ΔCx1, ΔCy1, ΔCx2, ΔCy2) of Cx1, Cx2, Cy1, and Cy2 is calculated. Next, the sensitivity Sz (F / G) is calculated from the ratio between the capacitance change (ΔCx1, ΔCy1, ΔCx2, ΔCy2) and the Coulomb force (∝Cx3 ² , Cx4 ² , Cy3 ² , Cy4 ² ). Next, the Z-axis offset is corrected by 1G (because 1G is originally applied by gravitational acceleration). That is, (Cx1 + Cx2 + Cy1 + Cy2) − (Cx3 + Cx4 + Cy3 + Cy4) + Sz · G.

  FIG. 14 is a block diagram for explaining an inspection apparatus for a capacitive acceleration sensor according to the present invention, in which 51 is a capacitive acceleration sensor, 52 is a CV conversion circuit, 53 is an E2PROM (EEPROM; Electrically Erasable). and Programmable ROM), 54 is an XYZ sensitivity adjustment circuit (PGA; programmable gain amplifier), 55 is a demodulation circuit, 56 is a high frequency voltage application circuit, and 57 is an XYZ offset adjustment circuit.

  The high frequency voltage application circuit 56 applies a high frequency voltage to the weight body 122 and the frame body 121 of the capacitive acceleration sensor 51, as shown in FIGS. The capacitive acceleration sensor 51 has a configuration as shown in FIG. The CV conversion circuit 52 converts a capacitance change into a detection voltage based on an output signal from the capacitive acceleration sensor 51, and outputs an acceleration signal. A specific CV conversion method and circuit diagram in the CV conversion circuit 52 are as shown in FIG.

  The XYZ sensitivity adjustment circuit 54 adjusts the sensitivity of the X, Y, and Z axes based on the acceleration signal from the CV conversion circuit 52. The demodulating circuit 55 demodulates an acceleration signal modulated into a high frequency into a DC component based on the X, Y, and Z axis sensitivity signals from the XYZ sensitivity adjusting circuit 54. The XYZ offset adjustment circuit 57 adjusts the X, Y, and Z axis offsets based on the output from the demodulation circuit 55, and outputs acceleration components Ax, Ay, and Az, respectively. The E2PROM 53 is a memory for writing sensitivity and offset correction values.

  That is, the inspection apparatus for the capacitive acceleration sensor according to the present invention includes the electrostatic capacitances Cs1, Cs2 (（Va, Vb) between the weight body 122 and the detection electrodes 111, 131 in the capacitive acceleration sensor. Is detected (FIGS. 9A and 9B), and the first CV conversion circuit (first capacitance calculation means) 143a and the second CV conversion circuit ( Second potential calculation means) 143b, a weight difference VDD is provided between the weight body 122 and one of the detection electrodes 111, and the weight body 122 works on the basis of the magnitude of the applied voltage and the offset value of the capacitance. A third CV conversion circuit (the first CV conversion circuit) for detecting the magnitude of the Coulomb force and detecting the capacitance Cs2 ′ (∝Vc) between the other detection electrode 131 and the weight body 122 (FIG. 9C). 3 capacity calculation means) 143c and the other detection A comparator that compares the capacitance change (Vb−Vc) between the pole 131 and the weight body 122, and a sensitivity correction value is obtained from Va, Vb−Vc, and the applied voltage (VDD−Vcom). And an XYZ sensitivity adjustment circuit 54 for performing the calibration.

  With such a configuration, in addition to detecting a failure, it is possible to correct for variations in sensitivity of the acceleration sensor, and it is possible to easily inspect with an existing semiconductor tester using the voltage applying means and the voltage detecting means.

  In addition, this invention is not limited to the Example mentioned above, A various Example can be taken. For example, in the configuration of the CV conversion circuit, other methods can be applied as long as the parasitic capacitance attached to the wiring and the electrode pad is not offset.

  In addition, regarding the sensor structure, the gap portion 125 is provided between the frame body 121 and the weight body 122 in the above-described embodiment. However, if the frame body 121 and the weight body 122 are electrically separated, the sensor structure may be different. It is also possible to apply this configuration. Further, the frame and the beam member as shown in FIG.

  FIG. 15 is a configuration diagram (top view) for explaining another embodiment of the capacitive acceleration sensor according to the present invention. The capacitive sensor according to another embodiment of the present invention is configured to oppose the weight bodies 222a to 222e and the frame body (holding member) 221 that holds the displaceable weight bodies 222 (222a to 222e). And a detection electrode provided on the first substrate, and configured to detect a change in capacitance between the weights 222a to 222d and the detection electrode.

  The weight bodies 222a to 222e are held by beam members 223a, 223b, 223c, and 223d, and the tip portions of the beam members 223a to 223d are held by column members (pillars) 224a, 224b, 224c, and 224d. Yes. The beam members 223 a to 223 d and the pillars 224 a to 224 d are not in contact with the frame body 221 in the internal space of the frame body 221. In this embodiment, the frame body 221 and the beam member have a non-contact structure. However, as long as the frame body 221 and the beam member are electrically separated from each other, a structure in which an insulator is inserted may be used.

  The detection electrode provided on the first substrate includes an X-axis detection electrode and a Y-axis detection electrode arranged to face the weight bodies 222a to 222d.

  The beam member 223a is sandwiched between the weight body 222a and the weight body 222b, the beam member 223b is sandwiched between the weight body 222b and the weight body 222c, and the beam member 223c is sandwiched between the weight body 222c and the weight body 222c. The beam member 223d is a beam member sandwiched between the weight body 222d and the weight body 222a.

  In addition, the weight bodies 222a to 222e have a center portion 222e disposed at the intersections of the beam members 223a to 223d, and the periphery disposed in a square shape from the center portion 222e along the frame body 221 and the beam members 223a to 223d. It has parts 222a to 222d.

  Further, the beam members 223a to 223d are arranged so as to be sandwiched between adjacent peripheral portions 222a to 222d of the weight body along each side of the frame body 221 from the center portion 222e of the weight body 222. Moreover, the shape of the detection electrode is preferably a rice field-like arrangement similar to the peripheral parts 222a to 222d of the weight body arranged in a rice field.

  Similarly, it includes a detection electrode provided on the second substrate, and is configured to detect a change in capacitance between the weights 222a to 222d and the detection electrode.

  In addition, the applied voltage when applying the Coulomb force is exemplified by VDD in the embodiment, but may be another predetermined potential such as GND or an AC voltage.

  In the embodiment, the influence of the parasitic capacitance between the detection electrode and the frame is described. However, when the substrate is conductive, the weight 122 is similarly applied to the capacitance between the substrate and the detection electrode. The influence can be removed by electrically separating the substrate.

  In the embodiment, the detection electrode in the Z direction is shared with the detection electrode in the X and Y directions, but the Z detection electrode may be prepared separately.

  Moreover, although the detection apparatus in an Example has mentioned the thing using E2PROM and PGA as an example, it is not limited to it, What is necessary is just a structure which can calibrate a sensitivity and an offset.

11, 111 1st board | substrate 11a thru | or 11d, 111a thru | or 111d Detection electrode 21, 121 Frame (holding member)
22 (22a to 22e), 122 (122a to 122e), 222 (222a to 222e) Weights 23a to 23d, 123a to 123d, 223a to 223d Beam members 31, 131 Second substrates 31a to 31d, 131a to 131d Detection Electrodes 41, 141 High-frequency voltage application circuits 42, 142 Sensor units 43, 143 (143a to 143c) CV conversion circuit (capacity calculation means)
43a, 143a Operational amplifier 51 Capacitive acceleration sensor 52 CV conversion circuit 53 E2PROM
54 XYZ sensitivity adjustment circuit 55 Demodulation circuit 56 High frequency voltage application circuit 57 XYZ offset voltage adjustment circuits 124a to 124d, 224a to 224d Post members (pillars)

Claims (8)

A capacitive acceleration having one detection electrode, the other detection electrode provided to face the one detection electrode, and a displaceable weight body provided to be sandwiched between the detection electrodes A sensor inspection method,
First, detecting a capacitance between the weight body of the capacitive acceleration sensor and each detection electrode, and calculating an offset from a capacitance value of the capacitance;
Next, providing a potential difference between the weight body and the one detection electrode;
Next, in a state where different applied voltages are applied to the one detection electrode due to the potential difference, a capacitance between the other detection electrode and the weight body in the Coulomb force acting on the weight body is determined. Detecting step;
Next, comparing the amount of change in capacitance between the other detection electrode and the weight body before and after applying a potential difference between the one detection electrode and the weight body;
Next, the capacitance between the weight body and the one detection electrode, the applied voltage, and the other detection electrode and the weight body in the Coulomb force acting on the weight body A method for inspecting a capacitance type acceleration sensor, comprising: obtaining a correction value of sensitivity from an amount of change in capacitance between the two and performing calibration of sensitivity. Detecting the capacitance comprises:
Detecting a capacitance between the other detection electrode and the weight body in a state where an applied voltage equal to the weight body is applied to the one detection electrode, the other detection electrode, and the weight body; ,
The other detection electrode and the weight body in the Coulomb force acting on the weight body in a state where an applied voltage different from that of the other weight detection body and the weight body is applied to the one detection electrode. The method for detecting a capacitance type acceleration sensor according to claim 1, further comprising: detecting a capacitance between the two. A capacitive acceleration having one detection electrode, the other detection electrode provided to face the one detection electrode, and a displaceable weight body provided to be sandwiched between the detection electrodes A sensor inspection device,
First and second capacitances for detecting an electrostatic capacitance between the weight body of the capacitive acceleration sensor and each of the detection electrodes and calculating an offset from the capacitance value of the electrostatic capacitance. A calculation means;
Voltage application means for providing a potential difference between the weight body and the one detection electrode;
In a state in which a different potential is applied to the one detection electrode by applying a potential difference by the voltage application means, a static force between the one detection electrode and the weight body in the Coulomb force acting on the weight body. A third capacitance calculating means for detecting a capacitance and a capacitance between the other detection electrode and the weight body;
Comparison means for comparing the amount of change in capacitance between the other detection electrode and the weight body before and after applying a potential difference between the one detection electrode and the weight body;
The electrostatic capacitance between the weight body and the one detection electrode, the applied voltage, and the static electricity between the other detection electrode and the weight body at the Coulomb force acting on the weight body. An inspection apparatus for a capacitive acceleration sensor, comprising: a sensitivity adjustment unit that obtains a sensitivity correction value from the amount of change in capacitance and calibrates the sensitivity. The capacitance detection means is
First, a capacitance between the other detection electrode and the weight body is detected in a state where an equal applied voltage is applied to the one detection electrode, the other detection electrode, and the weight body. First and second capacity calculating means;
The other detection electrode and the weight body in the Coulomb force acting on the weight body in a state where an applied voltage different from that of the other weight detection body and the weight body is applied to the one detection electrode. The capacitance type acceleration sensor inspection apparatus according to claim 3, further comprising: a third capacitance calculation unit that detects a capacitance between the first and second capacitance calculation units. The capacity detection means;
4. A high-frequency voltage applying device for modulating the voltage of the weight body to a high-frequency voltage, an operational amplifier connected to the detection electrode in the previous period, and a demodulating circuit for demodulating the high-frequency into a DC component. Or the inspection apparatus for a capacitive acceleration sensor according to 4; The capacitive acceleration sensor is
A first substrate having one detection electrode;
A second substrate having the other detection electrode provided to face the one detection electrode of the first substrate;
A holding member provided to be sandwiched between the first substrate and the second substrate;
A displaceable weight body provided so as to be sandwiched between the detection electrodes in the internal space of the holding member;
A plurality of beam members for supporting the weight body;
A plurality of support members that support the beam member;
The inspection apparatus for a capacitive acceleration sensor according to claim 5, wherein the beam member and the support member are not in contact with the holding member.   The inspection apparatus for a capacitive acceleration sensor according to claim 6, wherein a gap is provided between the beam member and the support member and the holding member.   8. The capacitive acceleration sensor inspection apparatus according to claim 6, wherein the holding member is grounded.

Images