JP4525452B2 - Multi-axis acceleration sensor - Google Patents

Description

  The present invention relates to a multi-axis acceleration sensor that detects acceleration in a multi-axis direction, and is particularly used for posture control of a moving body such as a vehicle and a robot, and vibration measurement of a precision device.

  This type of conventional multi-axis acceleration sensor has a configuration as shown in FIG.

  FIG. 10 shows an exploded perspective view of a conventional multi-axis acceleration sensor. In FIG. 10, 1 is a movable substrate made of a semiconductor substrate such as silicon, and this movable substrate 1 is a cylinder having a predetermined thickness in the center. A mass body 4 having a shape and a movable electrode portion 3 having a thin blade-like shape that is divided into four in the X and Y directions from the periphery of the bottom surface side of the mass portion 2; It has the support part 5 located in the circumference | surroundings of the mass body 4, and the four beam parts 6 which connect this support part 5 and the said mass body 4. As shown in FIG. Reference numeral 7 denotes a fixed substrate made of a semiconductor substrate such as silicon or an insulating substrate such as a glass substrate. The fixed substrate 7 includes a fixed electrode 8 provided at a position facing the movable electrode portion 3 and an outer periphery of the fixed electrode 8. And a wiring portion 10 for outputting the output of the fixed electrode 8 to the outside. The support portion 5 of the movable substrate 1 and the frame portion 9 of the fixed substrate 7 are joined with a predetermined gap between the movable electrode portion 3 and the fixed electrode 8.

  Next, the operation of the conventional multi-axis acceleration sensor configured as described above will be described.

  When the multi-axis acceleration sensor is mounted on the XY-axis plane, the mass body 4 is displaced by a certain amount of gravity due to gravity in the Z-axis direction, and the distance in the Z-axis direction between the movable electrode portion 3 and the fixed electrode 8 is reduced. It is stationary. When acceleration in the X-axis direction is applied to the mass body 4 in this state, an inertial force consisting of the product of acceleration and mass acts on the mass body 4, and the mass body 4 is supported by the beam portion 6 at four points. In this state, it tilts at a predetermined angle forward and backward in the X axis direction together with the movable electrode portion 3. Due to this inclination, the distance in the Z-axis direction between the movable electrode portion 3 and the fixed electrode 8 that are divided into two in the X-axis direction changes, and the respective capacitances change. Here, when the capacitance is C, the dielectric constant is ε, the electrode area is S, and the distance between the electrodes is d, the capacitance can be generally calculated by C = ε × S / d. In this case, the dielectric constant and the electrode area do not change, and the acceleration is obtained by differentially processing each capacitance according to the change in the distance between the electrodes in the Z-axis direction by a processing circuit (not shown). It was detected. For acceleration in the Y-axis direction, acceleration was detected based on the same operating principle as described above.

As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.
JP 2003-152162 A

  However, in the above-described conventional configuration, the mass body 4 is supported by the beam portion 6 having a certain thin thickness in the Z-axis direction and a certain width on the XY-axis surface. Since the mass ratio of the mass body 4 in the effective space in the support portion 5 provided with the thin movable electrode portion 3 in the Z-axis direction is small and the center of gravity is low, the displacement sensitivity to the acceleration in the Z-axis direction is XY-axis. It is larger than the displacement sensitivity to the acceleration in the direction. Further, since the acceleration component of the XYZ axes is detected by a change in capacitance accompanying a change in the distance between the movable electrode part 3 and the fixed electrode 8 part in the Z axis direction, the displacement of the mass body 4 due to the acceleration in the Z axis direction is large. If it becomes too large, the distance between the electrodes will fluctuate greatly, and the acceleration detection accuracy in the XY axis direction will be based on the acceleration detection value in the state where only the acceleration in the XY axis plane is applied in the capacitance that is inversely proportional to the distance between the electrodes Has the problem of becoming non-linear and worsening.

  The present invention solves the above-mentioned conventional problems, and even if the acceleration in the Z-axis direction is applied by making the displacement sensitivity ratio of the mass part uniform with respect to the acceleration in the XY-axis direction and the Z-axis direction, An object of the present invention is to provide a multi-axis acceleration sensor in which the direction acceleration detection accuracy does not deteriorate.

  In order to achieve the above object, the present invention has the following configuration.

According to a first aspect of the present invention, there is provided a movable substrate that supports a mass part that is arranged along an XY plane in an XYZ coordinate system and that is displaced according to acceleration, to a surrounding support part via a plurality of beam parts, A fixed substrate having an upper surface provided with a fixed electrode having a predetermined distance from the mass portion of the movable substrate and bonded to the support portion of the movable substrate, and the plurality of beam portions are made of silicon having a plane orientation (100). And a first beam portion arranged in an orientation <110> extending in a direction parallel to the X-axis or the Y-axis from the support portion, and connected to the mass portion and extending obliquely in a 45 ° direction with respect to the XY axis. And a second beam portion arranged in an orientation <100>, wherein the Young's modulus of the second beam portion is smaller than the Young's modulus of the first beam portion. According to this configuration, the XYZ coordinates Placed along the XY plane in the system The plurality of beam portions that support the mass portion that is displaced according to the speed on the surrounding support portion are made of silicon having a plane orientation (100) and extend in a direction parallel to the X axis or the Y axis from the support portion <110> and a second beam part connected to the mass part and arranged in an azimuth <100> obliquely extending in the XY axis and 45 ° direction. Since the Young's modulus of the beam part 2 is smaller than the Young's modulus of the first beam part, the elasticity of the second beam part contributing to the displacement sensitivity of the mass part with respect to the acceleration in the XY axis direction is increased. Thus, since the displacement sensitivity ratio of the mass part in the XYZ-axis direction can be made uniform, even if acceleration in the Z-axis direction is applied, the acceleration detection accuracy in the XY-axis direction is not deteriorated. Yan due to silicon misorientation Since the change rate is small, and has a effect that the acceleration detection accuracy is stabilized.

As described above, the multi-axis acceleration sensor of the present invention includes a movable substrate that is arranged along the XY plane in the XYZ coordinate system and supports a mass portion that is displaced according to acceleration to a surrounding support portion via a plurality of beam portions. A fixed substrate bonded to a support portion of the movable substrate and having a fixed electrode on the upper surface having a predetermined distance from a mass portion of the movable substrate, and the plurality of beam portions are made of silicon having a plane orientation (100) And a first beam portion arranged in an orientation <110> extending in a direction parallel to the X axis or the Y axis from the support portion, and connected to the mass portion and extending obliquely in a 45 ° direction with respect to the XY axis. In which the Young's modulus of the second beam portion is smaller than the Young's modulus of the first beam portion. According to this configuration, XYZ Along the XY plane in the coordinate system A plurality of beam portions that are placed and support a mass portion that is displaced according to acceleration are supported by a surrounding support portion, are made of silicon having a plane orientation (100), and extend from the support portion in a direction parallel to the X axis or the Y axis. A first beam portion arranged in an orientation <110> and a second beam portion connected to the mass portion and arranged in an orientation <100> obliquely extending in the XY axis and 45 ° direction; Since the Young's modulus of the second beam part is smaller than the Young's modulus of the first beam part, the elasticity of the second beam part contributing to the displacement sensitivity of the mass part with respect to the acceleration in the XY axis direction is increased. Thus, since the displacement sensitivity ratio of the mass part in the XYZ-axis direction can be made uniform, even if acceleration in the Z-axis direction is applied, the accuracy of acceleration detection in the XY-axis direction is not deteriorated. In addition, the orientation angle deviation of silicon Since the change in the Young's modulus is small that is one which has the effect that also stabilize the acceleration detection accuracy.

(Embodiment 1)
Hereinafter, with reference to the first embodiment will be described the invention described in particular claim 1 of the present invention.

  1 is a perspective view of a multi-axis acceleration sensor according to Embodiment 1 of the present invention, FIG. 2 is a top view of the multi-axis acceleration sensor, FIG. 3 is a top view of a fixed substrate in the multi-axis acceleration sensor, and FIG. (B) is a cross-sectional view taken along line AA in FIG. 2, FIGS. 5 (a) and 5 (b) are cross-sectional views taken along line BB in FIG. 2, FIG. 6 is a state diagram of orientation, and FIG. FIG.

  In FIG. 1 to FIG. 5, reference numeral 11 denotes a movable substrate which is formed of an SOI substrate in which an etching stop layer such as a silicon oxide film is provided on an intermediate layer and a silicon substrate is bonded to both sides, and is disposed along the XY plane. 11 is a mass part 12 that is displaced in the center in accordance with acceleration, a support part 13 provided on the outer periphery of the mass part 12, the support part 13 and the mass part 12, and the mass part 12 It is comprised by the beam part 14 which consists of four thin silicon which can be displaced. Reference numeral 15 denotes a fixed substrate made of an insulating material such as glass. The fixed substrate 15 is provided with a fixed electrode 16 made of a conductive material such as Au, which is divided into two in the XY axis direction on the upper surface, and the mass A predetermined interval is provided between the portion 12 and the beam portion 14 and is joined to the support portion 13.

The beam portion 14 is connected to the first beam portion 17 extending in a direction parallel to the X axis or the Y axis from the support portion 13 and the mass portion 12 and extends obliquely in the 45 ° direction with respect to the XY axis. And a second moment of section perpendicular to the longitudinal direction of the second beam portion 18 is made smaller than a second moment of section perpendicular to the longitudinal direction of the first beam portion 17. Yes. With this configuration, the elasticity of the second beam portion 18 that contributes to the displacement sensitivity of the mass portion 12 with respect to the acceleration in the XY axis direction is increased, and thus the mass portion 12 in the XYZ axis direction is increased. Since the displacement sensitivity ratio can be made uniform, even if acceleration in the Z-axis direction is applied, the effect that the accuracy of acceleration detection in the XY-axis direction does not deteriorate can be obtained. Here, the second moment I, the longitudinal width of the beam portion b, if the Z-axis direction thickness of the beam portion and is h, the second moment is the equation I = b × h ^3/12 As shown in FIG. 5A, the longitudinal direction of the second beam 18 can be calculated by reducing the width in the longitudinal direction of the second beam 18 or reducing the thickness thereof. It is possible to reduce the moment of inertia of the cross section. Also, assuming that the beam deflection is Z, the inertial force at the applied acceleration is F, the beam length is L, and the Young's modulus is E, the beam deflection is an equation of Z × F × L ³ / E / I. Therefore, the deflection of the beam, that is, the displacement of the mass portion 12 can be increased by reducing the secondary moment of inertia in the inertial force due to a certain amount of acceleration.

  The beam portion 14 is made of silicon having a plane orientation (100), the first beam portion 17 is disposed in an orientation <110> extending from the support portion 13 in a direction parallel to the X axis or the Y axis, and The second beam portion 18 is connected to the mass portion 12 and arranged in the azimuth <100> obliquely extending in the 45 ° direction with respect to the XY axis. By adopting such an arrangement configuration, As shown in FIGS. 6 and 7, since the Young's modulus of the second beam portion 18 is smaller than the Young's modulus of the first beam portion 17, the displacement sensitivity of the mass portion 12 with respect to acceleration in the XY axis direction. This increases the elasticity of the second beam portion 18 that contributes to the above, and this makes it possible to equalize the displacement sensitivity ratio of the mass portion 12 in the XYZ-axis direction, so that even if acceleration in the Z-axis direction is applied, XY Axial acceleration detection accuracy is poor It never becomes further smaller even change in Young's modulus by the azimuth angle displacement of silicon, and has the effect that also stabilize the acceleration detection accuracy. Note that the Young's modulus of silicon with a plane orientation (100) is an orientation cycle every 90 °, and the orientations <100>, <010>, <-100>, and <001> have a difference in notation, but are Young. The rate is the same. In addition, the orientations <110>, <-110>, <1-10>, and <011> also have the same Young's modulus, although there are differences in notation.

  The mass portion 12 is provided with a through hole 19 from the upper surface to the lower surface. By providing the through hole 19, the mass portion 12 is displaced in a space where the distance between the electrodes is narrow. Even for squeeze film damping generated due to gas viscous resistance, pressure gradient, etc., the gas can escape through the through-hole 19 and the pressure around the mass portion 12 can be made uniform. Thus, the effect of improving the frequency responsiveness to the applied acceleration can be obtained.

  Next, the manufacturing method of the multi-axis acceleration sensor according to the first embodiment of the present invention configured as described above will be described.

  First, an SOI substrate (not shown) is prepared as the movable substrate 11, and at least one surface of the SOI substrate is subjected to photolithography and wet etching to form a groove (not shown) having a predetermined depth, and then an etching stop layer. The SOI substrate is processed into a predetermined shape by performing photolithography and wet etching or dry etching from both sides by using the substrate, and then removing the etching stop layer to provide a mass part (not shown) and a support part (not shown). ) And a beam portion (not shown).

  Next, a glass substrate (not shown) is prepared as the fixed substrate 15, and a thin film is formed on the upper surface of the glass substrate using a conductive material such as Au through an adhesion layer such as Ti by vacuum deposition or sputtering. A conductive film (not shown) is formed, and then the conductive film is processed into a predetermined shape by photolithography and wet etching to form a fixed electrode (not shown) and a common electrode (not shown).

  Next, a support substrate in the movable substrate 11 and the fixed substrate 15 are bonded together through anodic bonding or an adhesive, and a sensor substrate (not shown) in which the support portion and the common electrode are electrically connected is formed. To do.

  Finally, a plurality of multi-axis acceleration sensors (not shown) are produced by dividing the sensor substrate by dicing or laser processing.

  Next, the operation of the multi-axis acceleration sensor according to the first embodiment of the present invention manufactured as described above will be described.

  When a multi-axis acceleration sensor is mounted on the XY-axis plane, the mass portion 12 is displaced by a certain amount of gravity due to gravity in the Z-axis direction, and the distance between the mass portion 12 and the fixed electrode 16 in the Z-axis direction is reduced. Still in a state. When acceleration in the X-axis direction is applied to the mass portion 12 in this state, an inertial force that is a product of acceleration and mass acts on the mass portion 12, and the mass portion 12 is connected to the support portion 13. In a state where it is supported by the beam portion 14, it tilts at a predetermined angle in the front and rear directions in the X-axis direction as shown in FIG. Due to this inclination, the interval in the Z-axis direction between the fixed electrode 16 and the mass portion 12 that are arranged in two in the X-axis direction changes, and the respective capacitances change. Here, when the capacitance is C, the dielectric constant is ε, the electrode area is S, and the distance between the electrodes is d, the capacitance can be generally calculated from the equation C = ε × S / d. In addition, the dielectric constant and the electrode area do not change, and acceleration can be detected by differentially processing each capacitance according to the change in the distance between the electrodes in the Z-axis direction with a processing circuit (not shown). it can. Further, with respect to the acceleration in the Y-axis direction, the acceleration can be detected based on the same operation principle as described above.

  In addition, a detection electrode (not shown) is additionally arranged independently at the center of the upper surface of the fixed substrate 15 facing the center of the mass part 12 where the mass part 12 is less inclined and displaced with respect to the acceleration in the XY axis direction, or The acceleration in the Z-axis direction can be detected by processing each change in capacitance between the fixed electrode 16 and the mass unit 12 divided into two in the XY-axis direction.

(Embodiment 2)
Hereinafter, with reference to the second embodiment will be described with the present onset bright.

  FIG. 8 shows the shape of the mass part of the multi-axis acceleration sensor according to the second embodiment of the present invention. This second embodiment is the same as the multi-axis acceleration sensor according to the first embodiment of the present invention. The same reference numerals are given to the components, and only the points different from the first embodiment of the present invention will be described.

  That is, in the second embodiment of the present invention, as shown in FIG. 8, the movable substrate 21 is provided on the outer periphery of the mass portion 22 that is displaced in accordance with the acceleration provided at the center thereof. The beam portion 24 includes a support portion 23, and four beam portions 24 made of thin silicon that connect the support portion 23 and the mass portion 22 and can displace the mass portion 22. Includes a first beam portion 25 extending in a direction parallel to the X axis or the Y axis from the support portion 23, and a second beam portion 26 connected to the mass portion 22 and extending obliquely in the direction of 45 ° with respect to the XY axis. Further, a vertical groove 27 is provided from the upper surface to the lower surface in the vicinity of the portion connected to the second beam portion 26 in the mass portion 22.

  In the above-described second embodiment of the present invention, since the vertical groove 27 is provided from the upper surface to the lower surface in the vicinity of the portion of the mass portion 22 connected to the second beam portion 26, the second beam portion 26 is particularly provided. Can be increased to the center of the mass portion 22, thereby increasing the elasticity of the second beam portion 26 that contributes to the displacement sensitivity of the mass portion 22 with respect to acceleration in the XY-axis direction. The displacement sensitivity ratio of the mass portion 22 in the axial direction can be made uniform, so that even if acceleration in the Z-axis direction is applied, the accuracy of acceleration detection in the XY-axis direction is not deteriorated, and further, between the electrodes Even when squeeze film damping is generated due to gas viscous resistance, pressure gradient, etc. when the mass portion 22 is displaced in a space with a narrow gap, the gas is released through the longitudinal groove 27 and the quality is reduced. Since it is possible to equalize the pressure of the surrounding parts 22, it is possible to suppress the damping, thereby, the frequency response to applied acceleration is also what effect that improves.

(Embodiment 3)
Hereinafter, with reference to the third embodiment will be described with the present onset bright.

  FIG. 9 shows the positions of the drive electrodes of the multi-axis acceleration sensor according to the third embodiment of the present invention. This third embodiment is the same as the multi-axis acceleration sensor according to the first embodiment of the present invention. The same reference numerals are assigned to the components, and only the points different from the first embodiment of the present invention will be described.

  That is, in the third embodiment of the present invention, as shown in FIGS. 2, 3, and 9, the first beam portion 17 on the upper surface of the fixed substrate 15, in particular, the side facing the vicinity of the second beam portion 18. Two drive electrodes 31 are provided at the central diagonal of the mass portion 12.

Here, when the electrostatic attractive force is F, the dielectric constant is ε, the electrode area is S, the distance between the electrodes is d, and the applied voltage is V, the electrostatic attractive force is F = ε × S × V ² / d ² / 2 and can be generally calculated from the equation (2). When a predetermined voltage is applied between the common electrode 32 and the drive electrode 31, an electrostatic attractive force is generated. The mass portion 12 can be displaced by pulling in the axial direction.

  When a predetermined voltage is applied between the common electrode 32 and one of the two drive electrodes 31 or a different voltage is applied to the two drive electrodes 31, the mass portion 12 is moved as shown in FIG. It can be tilted at a predetermined angle in the XYZ coordinate system, and the mutual capacitance between the displacement due to the inclination of the mass portion 12 at this time and the displacement of the mass portion 12 with respect to the acceleration applied from the outside in advance is compared. As a result, it is possible to obtain the effect that self-diagnosis of the multi-axis direction can be performed at once. In addition, when the same predetermined voltage is applied to the two drive electrodes 31, the mass part 12 can be displaced only in the Z-axis direction, so that it is possible to perform fault diagnosis in the Z-axis direction alone. It is what

  It should be noted that four drive electrodes (not shown) are provided at positions symmetrical to the center of the mass part 12 and the mass part 12 is adjusted by adjusting the voltage applied between each drive electrode and the common electrode 32. Even when it is displaced, it has the same effect as the above-described third embodiment of the present invention.

  The multi-axis acceleration sensor according to the present invention has the effect of providing a multi-axis acceleration sensor with high acceleration detection accuracy, and is used for attitude control of a moving body such as a vehicle or a robot, vibration measurement of a precision instrument, or the like. This is useful as a multi-axis acceleration sensor that detects acceleration in a direction.

The perspective view of the multi-axis acceleration sensor in Embodiment 1 of this invention Top view of the multi-axis acceleration sensor Top view of fixed substrate in the multi-axis acceleration sensor (A) (b) AA line sectional view of FIG. (A) (b) BB sectional drawing of FIG. Orientation state diagram Relationship between silicon orientation and Young's modulus The top view which shows the shape of the mass part of the multi-axis acceleration sensor in Embodiment 2 of this invention Sectional drawing which shows the drive electrode position of the multi-axis acceleration sensor in Embodiment 3 of this invention Exploded perspective view of a conventional multi-axis acceleration sensor

DESCRIPTION OF SYMBOLS 11 Movable board 12 Mass part 13 Support part 14 Beam part 15 Fixed board 16 Fixed electrode 17 1st beam part 18 2nd beam part 19 Through-hole 21 Movable board 22 Mass part 23 Support part 24 Beam part 25 1st beam Part 26 Second beam part 27 Vertical groove 31 Drive electrode 32 Common electrode

Claims (1)

A movable substrate that is arranged along the XY plane in the XYZ coordinate system and that displaces according to acceleration is supported by a surrounding support portion via a plurality of beam portions, and is joined to and supported by the support portion of the movable substrate. A fixed substrate provided on the upper surface with a mass part on the substrate and a fixed electrode having a predetermined interval; and the plurality of beam portions are made of silicon having a plane orientation (100), and the X axis or Y axis extends from the support portion. A first beam portion disposed in an orientation <110> extending in a parallel direction, and a second beam portion coupled to the mass portion and disposed in an orientation <100> obliquely extending in a 45 ° direction with respect to the XY axis. And a multi-axis acceleration sensor in which the Young's modulus of the second beam portion is smaller than the Young's modulus of the first beam portion.

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