JP2009270944A - Capacitance type acceleration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably detect the acceleration by improving the temperature characteristic and reducing the influence of temperature variation. <P>SOLUTION: This capacitance type acceleration sensor comprises a silicon-made substrate 11 having spindle sections 12a-12d, a glass substrate 13 that is joined to one main surface of the silicon-made substrate 11 and has fixed electrodes 14a-14f for detecting the capacitance to the spindle sections 12a-12d, and a glass substrate 15 joined to the other main surface of the silicon-made substrate 11. A sensor section for the Z-axis direction comprises a sensing section A where the spindle section 12c is supported with a flexible beam 11c liftably with respect to the silicon-made substrate 11 by the acceleration, and a reference section B having capacity serving as a reference capacity for the capacitance of the sensing section A. In the reference section B, the spindle section 12d is supported with respect to the silicon-made substrate 11. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a capacitance type acceleration sensor that detects acceleration using capacitance.

  As a sensor for detecting acceleration, for example, there is a capacitive acceleration sensor. This capacitance type acceleration sensor is composed of a fixed electrode and a movable electrode (weight) that swings when G (acceleration) is applied, and detects a change in capacitance between the fixed electrode and the movable electrode. By doing so, the acceleration can be obtained.

As such a capacitive acceleration sensor, in particular, a capacitive acceleration sensor that detects acceleration in the Z-axis direction (vertical direction) has a structure shown in FIG. 9 (Patent Document 1). This capacitive acceleration sensor includes a sensing unit 101 in which a weight, which is a movable electrode, is supported so that it can be moved up and down by acceleration, and a reference unit 102 having a capacitance that serves as a reference capacitance with respect to the capacitance of the sensing unit 101. I have. In this capacitive acceleration sensor, a concave portion 104a on the sensing unit 101 side and a concave portion 104b on the reference portion 102 side are provided on the fixed electrode substrate 103, and the fixed electrode 105 is provided at the bottom of each of the concave portions 104a and 104b. Is formed. Further, a weight 108 supported by a beam 107 so as to be movable up and down is formed on the sensing unit 101 side of the movable electrode substrate 106 joined to the fixed electrode substrate 103.
Japanese Patent Laid-Open No. 5-203667

  In order to make it possible to surface-mount the capacitive acceleration sensor, a package incorporating the capacitive acceleration sensor has been developed. When the package is formed in this manner, since the deformation shape due to thermal stress is different between the sensing unit 101 and the reference unit 102, the capacitance difference between the sensing unit and the reference unit used for detecting the acceleration is the temperature. There is a problem that the acceleration cannot be stably detected, that is, the temperature characteristic is bad, because it is affected by the change.

  The present invention has been made in view of the above points, and provides a capacitive acceleration sensor that has good temperature characteristics, can reduce the influence of temperature change, and can stably detect acceleration. With the goal.

  The capacitive acceleration sensor of the present invention is a capacitive acceleration sensor that detects at least acceleration in the Z-axis direction from a change in capacitance between a movable electrode functioning as a weight and a fixed electrode. A first substrate having an electrode; a second substrate having a fixed electrode for detecting the capacitance with respect to the movable electrode; and being joined to one main surface of the first substrate; A third substrate bonded to the other principal surface of the one substrate, and the sensor unit for the Z-axis direction is supported so that the movable electrode can be moved up and down by a bending beam with respect to the first substrate by acceleration. And a reference unit having a capacitance that serves as a reference capacitance for the capacitance of the sensing unit, wherein the movable electrode is supported by the first substrate. It is characterized by being.

  According to this configuration, the reference unit is substantially insensitive to acceleration, and deformation due to thermal stress occurs to the same extent as the sensing unit. As a result, the deformation shape due to thermal stress does not differ, and a sufficient capacity difference for acceleration detection can be obtained between the sensing unit and the reference unit. Thereby, the influence of a temperature change can be made small and an acceleration can be detected stably.

  In the capacitive acceleration sensor according to the aspect of the invention, it is preferable that the movable electrode is supported by a diaphragm with respect to the first substrate in the reference portion.

  In the capacitive acceleration sensor according to the aspect of the invention, it is preferable that the movable electrode is supported by the bending beam with respect to the first substrate in the reference portion. In this case, it is preferable that the spring constant of the bending beam in the reference portion is five times or more than the spring constant of the bending beam in the sensing portion.

  In the capacitive acceleration sensor according to the aspect of the invention, in the sensing unit and the reference unit, the movable electrode is located at a predetermined distance from the first substrate, and in the sensing unit and the reference unit, It is preferable that the predetermined distances are substantially equal.

  In the capacitive acceleration sensor of the present invention, the capacitive acceleration sensor that detects acceleration in the Z-axis direction, the fixed electrode is a pair of detection electrodes, and the movable electrode is relative to the first substrate. It is preferable that the sensor unit for the X-axis direction and the sensor unit for the Y-axis direction that are supported so as to be swingable by the torsion beam are included in the same sensor.

  According to the capacitance type acceleration sensor of the present invention, the capacitance type acceleration sensor detects at least the acceleration in the Z-axis direction from the change in capacitance between the movable electrode functioning as a weight and the fixed electrode. A first substrate having a movable electrode and a second substrate bonded to one main surface of the first substrate and having a fixed electrode for detecting the capacitance with respect to the movable electrode; A third substrate bonded to the other main surface of the first substrate, and the sensor unit for the Z-axis direction can be moved up and down by a bending beam with respect to the first substrate due to acceleration of the movable electrode A sensing unit supported by the sensing unit, and a reference unit having a capacitance that serves as a reference capacitance with respect to the capacitance of the sensing unit. In the reference unit, the movable electrode is connected to the first substrate. Good temperature characteristics There, to reduce the influence of temperature change, it is possible to stably detect the acceleration.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1A is a plan view showing a capacitive acceleration sensor according to an embodiment of the present invention. FIG. 1B is a cross-sectional view taken along the line IB-IB in FIG.

  The capacitive acceleration sensor shown in FIG. 1 includes weight portions 12a, 12b, 12c, and 12d that are four movable electrodes for independently detecting accelerations in the X-axis direction, the Y-axis direction, and the Z-axis direction. A pair of silicon substrates 11 as a first substrate having a predetermined distance from one main surface and the respective weight portions 12a, 12b, 12c, and 12d for detecting a change in capacitance as a capacitance difference. The glass substrate 13 which is the second substrate having the detection electrode pairs (fixed electrodes) 14a, 14b, 14c and 14d and the detection electrodes (fixed electrodes) 14e and 14f is joined. Further, on the other main surface of the silicon substrate 11, a glass substrate which is a third substrate so as to constitute a region (cavity) 18 in which the weight portions 12a and 12b are swung and the weight portions 12c and 12d are moved up and down. 15 is joined.

  In the capacitive acceleration sensor shown in FIG. 1, the movable electrode sensitive to acceleration in the X-axis direction is the weight portion 12a, the movable electrode sensitive to acceleration in the Y-axis direction is the weight portion 12b, and Z The movable electrode sensitive to the acceleration in the axial direction is the weight portion 12c. The pair of detection electrode pairs for the X-axis direction weight portion 12a is the fixed electrodes 14a and 14b, and the pair of detection electrode pairs for the Y-axis direction weight portion 12b is the fixed electrodes 14c and 14d. The detection electrode for the Z-axis direction weight portion 12c is a fixed electrode 14e. The detection electrode for the Z-axis direction weight portion 12d for the reference portion B is a fixed electrode 14f.

  As shown in FIG. 1B, a conductive member (penetrating electrode) 16a is electrically connected to the fixed electrode 14e with respect to the Z-axis direction weight portion 12c for the sensing portion A, and for the reference portion B. A conductive member (through electrode) 16b is electrically connected to the fixed electrode 14f with respect to the Z-axis direction weight portion 12d. Lead electrodes 17a and 17b are formed on the other exposed surfaces of the conductive members 16a and 16b, and the conductive members 16a and 16b and the lead electrodes 17a and 17b are electrically connected to each other. Although not shown in FIG. 1B, the fixed electrodes 14a and 14b with respect to the X-axis direction weight portion 12a and the fixed electrodes 14c and 14d with respect to the Y-axis direction weight portion 12b have the same configuration and are conductive members. And an extraction electrode. An electrode 19 is formed between the glass substrate 13 and the silicon substrate 11.

  The X-axis direction weight portion 12a has a substantially rectangular shape in a plan view, and is supported by the torsion beam 11a so as to be swingable with respect to the silicon substrate 11 on opposite sides. The Y-axis direction weight portion 12b has a substantially rectangular shape in plan view, and is supported by the torsion beam 11b so as to be swingable with respect to the silicon substrate 11 on the opposite sides. Each torsion beam 11a, 11b is provided in the vicinity of the center of the opposite sides of the weight portions 12a, 12b in plan view. On the other hand, the Z-axis direction weight portion 12c of the sensing portion A has a substantially rectangular shape in plan view, and the periphery thereof is supported by the bending beam 11c so as to be movable up and down with respect to the silicon substrate 11. Further, the Z-axis direction weight portion 12d of the reference portion B has a substantially rectangular shape in plan view, and the periphery thereof is supported by the diaphragm 11d so as to be movable up and down with respect to the silicon substrate 11.

  Two pairs of detection electrodes are formed on the glass substrate 13. The fixed electrodes 14a and 14b with respect to the X-axis direction weight portion 12a have substantially the same area. As can be seen from FIG. 1, the fixed electrodes 14a and 14b are located below the X-axis direction weight portion 12a in plan view and torsion beams 11a. Is formed by dividing the central portion passing through the boundary (left and right division in FIG. 1A). The total area of the two fixed electrodes 14a and 14b is made substantially equal to the area of the weight portion 12a for the X-axis direction.

  The fixed electrodes 14c and 14d with respect to the Y-axis direction weight portion 12b have substantially the same area, and as can be seen from FIG. 1, in the plan view, below the Y-axis direction weight portion 12b and torsion beams 11b. Is formed by dividing the central portion passing through the boundary (upper and lower divisions in FIG. 1A). The total area of the two fixed electrodes 14c and 14d is made substantially equal to the area of the weight portion 12b for the Y-axis direction.

  The fixed electrodes 14e and 14f for the Z-axis direction weight portions 12c and 12d have substantially the same area as the Z-axis direction weight portions 12c and 12d, respectively, and are respectively below the Z-axis direction weight portions 12c and 12d. Is formed.

  A silicon substrate 11 is bonded on the glass substrate 13. Here, an SOI (Silicon On Insulator) substrate is used as a silicon substrate to facilitate the formation of the beam portion. A glass substrate 15 is bonded on the silicon substrate 11. Accordingly, the cavity in which the X-axis direction weight portion 12a and the corresponding fixed electrodes 14a and 14b are arranged, and the cavity in which the Y-axis direction weight portion 12b and the corresponding fixed electrodes 14c and 14d are arranged, Is formed. It should be noted that anodic bonding is performed between the glass substrate 13 and the silicon substrate 11 or between the glass substrate 15 and the silicon substrate 11 in order to enhance the airtightness of the cavity formed between the substrates. preferable. Further, in the cavity, the active layer 11f of the SOI substrate becomes the torsion beams 11a and 11b, the bending beam 11c, and the diaphragm 11d, and supports the X-axis direction weight part 12a and the Y-axis direction weight part 12b so as to be swingable. The Z-axis direction weight portions 12c and 12d are supported to be movable up and down.

  The torsion beams 11a and 11b, the bending beam 11c, and the diaphragm 11d are formed on the bottom surface side of the weight portions 12a, 12b, 12c, and 12d. That is, each of the weight portions 12a, 12b, 12c, and 12d has a pair of surfaces that face each other in the thickness direction of the silicon substrate 11, and the torsion beams 11a and 11b, the bending beam 11c, and the diaphragm 11d are respectively provided. Are formed along one surface of the weight portions 12a, 12b, 12c, and 12d.

  In the capacitive acceleration sensor of the present invention, the sensor unit for the Z-axis direction includes a sensing unit A in which the weight unit 12c is supported by the flexure beam 11c so as to be movable up and down with respect to the silicon substrate 11 by acceleration, The sensing part A includes a reference part B having a capacity that serves as a reference capacity for the electrostatic capacity of the sensing part A, and a weight part 12d supported by the diaphragm 11d with respect to the silicon substrate 11.

  The reference part B having such a configuration is substantially insensitive to acceleration, and deformation due to thermal stress occurs to the same extent as the sensing part A. As a result, the deformation shape due to thermal stress is not different, and a sufficient capacity difference for acceleration detection can be obtained between the sensing unit A and the reference unit B. Thereby, the influence of the temperature change can be reduced and the acceleration can be detected stably (that is, the temperature characteristics are good).

  In the capacitance type acceleration sensor having such a configuration, when acceleration in the X-axis direction is applied, the X-axis direction weight portion 12a swings about the torsion beam 11a. As the weight 12a swings and displaces in this way, the distance between the opposed fixed electrodes 14a and 14b changes, and a change in capacitance due to the change in the distance can be detected as a capacitance difference. The acceleration can be measured by the capacitance change. Further, when acceleration in the Y-axis direction is applied, the Y-axis direction weight portion 12b swings with the torsion beam 11b as a fulcrum. As the weight 12b swings and displaces in this way, the distance between the opposed fixed electrodes 14c and 14d changes, and a change in capacitance due to the change in the distance can be detected as a capacitance difference. The acceleration can be measured by the capacitance change. Further, when acceleration in the Z-axis direction is applied, the Z-axis direction weight portion 12c is moved up and down by the bending beam 11c, and the weight portion 12c is moved up and down and displaced. For this reason, the weight part 12c moves up and down and is displaced, and the distance between the opposed fixed electrodes 14e changes. At this time, the diaphragm 11d does not raise or lower the weight portion 12d depending on the acceleration. Therefore, a change in capacitance due to a change in the distance between the weight portion 12c and the fixed electrode 14e can be detected as a capacitance difference from the reference electrode 14f, and acceleration can be measured by the change in capacitance. .

  In the configuration shown in FIG. 1, the reference portion B shows the case where the weight portion 12 d is supported by the diaphragm 11 d with respect to the silicon substrate 11. However, the present invention is not limited to this, and the acceleration is substantially not accelerated. What is necessary is just to provide the support structure of the weight part 12d of the reference part B which does not respond and the deformation | transformation by a thermal stress occurs to the same extent as the sensing part A. For example, as shown in FIG. 2, a bending beam 21 may be used for the support structure of the weight portion 12d of the reference portion B, and as shown in FIG. 3, the bending beam 22 is used for the support structure of the weight portion 12d of the reference portion B. May be used. Further, as shown in FIG. 4, a bending beam 23 having a thickness larger than that of the bending beam 11 c of the sensing unit A may be used for the support structure of the weight portion 12 d of the reference unit B. 2 and 3, when the bending beams 21 and 22 are used for the support structure of the weight portion 12d of the reference portion B, the sensitivity of the reference portion B to the acceleration is equal to the sensitivity of the sensing portion A to the acceleration. When it is assumed that it is about 20% or less, it is preferable that the spring constant of the bending beams 21 and 22 in the reference portion B is five times or more than the spring constant of the bending beam 11c in the sensing portion A.

  In the sensing part A and the reference part B, it is preferable that the weight parts 12c and 12d are located at a predetermined distance from the silicon substrate 11, and the predetermined distances in the sensing part A and the reference part B are substantially equal. By doing in this way, when the weight parts 12c and 12d are formed from the silicon substrate 11 in the same process, the etching rate is uniform, so that a sensor exhibiting stable characteristics can be manufactured.

  Next, an example of a manufacturing method of the capacitive acceleration sensor having the above configuration will be described. Here, the case where the weight part 12d is supported with respect to the silicon substrate 11 by the diaphragm 11d in the reference part B will be described. 5 (a) to 5 (d), 6 (a), 6 (b), and 7 (a) to 7 (c) are diagrams for explaining a method of manufacturing a capacitive acceleration sensor according to the present invention. It is.

  As shown in FIG. 5 (a), protrusions to be conductive members 16a and 16b are formed on one main surface of the silicon substrate 16 by photolithography and dry etching. Next, the glass substrate 13 is placed on the protruding portion of the silicon substrate 16 and, as shown in FIG. 5B, both substrates are bonded so as to embed the protruding portion in the glass substrate 13 by pressing while heating. Then, as shown in FIG.5 (c), both the main surfaces of the obtained composite_body | complex are grind | polished, and the electroconductive members 16a and 16b are exposed by both main surfaces. FIG. 5 shows a configuration corresponding to the sensor unit for the Z-axis direction, but a configuration corresponding to the sensor unit for the X-axis direction and the sensor unit for the Y-axis direction is formed at the same time. That is, conductive members for the fixed electrodes 14a, 14b, 14c, and 14d corresponding to the X-axis direction weight portion 12a and the Y-axis direction weight portion 12b are formed in the same manner.

  Next, as shown in FIG. 5D, an electrode material is deposited on the exposed conductive members 16a and 16b by sputtering, and fixed electrodes 14e and 14f and an electrode 19 are formed by photolithography and etching, respectively.

  Next, as shown in FIG. 6A, the active layer 11f and the base layer 11e of the SOI substrate (silicon substrate 11) having the active layer 11f, the insulating layer 11g, and the base layer 11e are respectively formed into recesses 11h by photolithography and etching. , 11j. The thickness of the active layer 11f of the SOI substrate corresponds to the thickness of the beam. Next, as shown in FIG. 6B, the active layer 11f is photolithography and etched to form the deflecting beam 11c and the diaphragm 11d. FIG. 5 shows a configuration corresponding to the sensor unit for the Z-axis direction, but a configuration corresponding to the sensor unit for the X-axis direction and the sensor unit for the Y-axis direction is formed at the same time. That is, the torsion beams 11a and 11b corresponding to the X-axis direction weight portion 12a and the Y-axis direction weight portion 12b are formed in the same manner.

  Next, as shown in FIG. 7A, the silicon substrate shown in FIG. 6B is formed so that the active layer 11f of the SOI substrate covers the fixed electrode of the glass substrate 13 having the structure shown in FIG. 5D. 11 are laminated, and both substrates 11 and 13 are bonded. At this time, it is preferable to perform bonding by anodic bonding. Next, as shown in FIG. 7B, predetermined portions of the base layer and the insulating layer 11g of the SOI substrate are removed by photolithography and etching to form the Z-axis direction weight portions 12c and 12d. Next, as shown in FIG. 7C, a glass substrate 15 is bonded onto the base layer 11e of the SOI substrate. At this time, it is preferable to perform bonding by anodic bonding. Next, electrode materials are deposited on the conductive members 16a and 16b exposed on the main surface of the glass substrate 13, and lead electrodes 17a and 17b are formed by photolithography and etching, respectively.

  The capacitive acceleration sensor thus obtained can independently detect accelerations in the X-axis direction, the Y-axis direction, and the Z-axis direction. In this configuration, the reference portion B is substantially insensitive to acceleration, and deformation due to thermal stress occurs to the same extent as the sensing portion A. As a result, the deformation shape due to thermal stress is not different, and a sufficient capacity difference for acceleration detection can be obtained between the sensing unit A and the reference unit B. Thereby, the influence of a temperature change can be made small and an acceleration can be detected stably.

Next, examples performed for clarifying the effects of the present invention will be described.
In the configuration shown in FIG. 1, that is, a structure using a diaphragm to support the weight portion of the reference portion of the sensor portion for the Z-axis direction (Example), the temperature characteristics of the differential capacitance at the time of detecting the acceleration in the Z-axis direction were examined. . The result is shown in FIG. For comparison, in the structure shown in FIG. 9, that is, in the structure in which the reference part of the sensor unit for the Z-axis direction is not configured by the weight part (comparative example), the differential capacity at the time of detecting the acceleration in the Z-axis direction The temperature characteristics were investigated. The results are also shown in FIG.

  As can be seen from FIG. 8, the capacitive acceleration sensor of the example is not affected by the temperature change, and the thermal deformation between the sensing unit and the reference unit is approximately the same, and the differential capacitance sufficient for acceleration detection. However, the capacitive acceleration sensor of the comparative example is affected by temperature changes, and depending on the temperature, the thermal deformation differs between the sensing unit and the reference unit. Could not get capacity.

  The present invention is not limited to the above embodiment, and can be implemented with various modifications. Although the case where a glass substrate and a silicon substrate are used has been described in the above embodiment, in the present invention, a substrate other than a glass substrate or a silicon substrate may be used. Further, the thickness and material of the electrode and each layer in the sensor can be set as appropriate without departing from the effects of the present invention. Further, the process described in the above embodiment is not limited to this, and the process may be performed by changing the order as appropriate. For example, although the gap is formed on the side of the SOI substrate 11 that is the opposing surface, the gap may be formed by etching a glass substrate. Other modifications may be made as appropriate without departing from the scope of the object of the present invention.

(A) is a top view which shows the capacitive acceleration sensor which concerns on embodiment of this invention, (b) is sectional drawing which follows the IB-IB line | wire of FIG. It is a top view which shows the other example of the capacitive acceleration sensor which concerns on embodiment of this invention. It is a top view which shows the other example of the capacitive acceleration sensor which concerns on embodiment of this invention. It is sectional drawing which shows the other example of the capacitive acceleration sensor which concerns on embodiment of this invention. (A)-(d) is a figure for demonstrating the manufacturing method of the capacitive acceleration sensor which concerns on this invention. (A), (b) is a figure for demonstrating the manufacturing method of the electrostatic capacitance type acceleration sensor which concerns on this invention. (A)-(c) is a figure for demonstrating the manufacturing method of the capacitive acceleration sensor which concerns on this invention. It is a figure for demonstrating the characteristic of the capacitive acceleration sensor which concerns on embodiment of this invention. It is a figure which shows the conventional electrostatic capacitance type acceleration sensor.

Explanation of symbols

11 Silicon member 11a, 11b Torsion beam 11c, 21, 22, 23 Deflection beam 11d Diaphragm 11g Insulating layer 11e Base layer 11f Active layer 12a-12d Weight part 13, 15 Glass substrate 14a-14f Fixed electrode 16a, 16b Conductive member 17a 17b Lead electrode 18 Cavity 19 Electrode

Claims (6)

  A capacitance-type acceleration sensor that detects at least an acceleration in the Z-axis direction from a change in capacitance between a movable electrode that functions as a weight and a fixed electrode, the first substrate having a movable electrode, and the first Bonded to one main surface of the substrate and bonded to the second substrate and the other main surface of the first substrate when the movable electrode has a fixed electrode for detecting the capacitance. A third substrate, and the sensor unit for the Z-axis direction includes a sensing unit in which the movable electrode is supported by an acceleration to be movable up and down by a bending beam with respect to the first substrate, and the sensing unit A reference portion having a capacitance serving as a reference capacitance with respect to the capacitance, wherein the movable electrode is supported with respect to the first substrate in the reference portion. Type acceleration sensor.   2. The capacitive acceleration sensor according to claim 1, wherein the movable electrode is supported by a diaphragm with respect to the first substrate in the reference portion.   2. The capacitive acceleration sensor according to claim 1, wherein the movable electrode is supported by the bending beam with respect to the first substrate in the reference portion.   4. The capacitive acceleration sensor according to claim 3, wherein a spring constant of the bending beam in the reference portion is five times or more than a spring constant of the bending beam in the sensing portion.   In the sensing unit and the reference unit, the movable electrode is positioned at a predetermined distance from the first substrate, and the predetermined distances in the sensing unit and the reference unit are substantially equal. The capacitive acceleration sensor according to any one of claims 1 to 4.   The capacitive acceleration sensor for detecting the acceleration in the Z-axis direction, the fixed electrode is a pair of detection electrodes, and the movable electrode is supported by the torsion beam so as to be swingable with respect to the first substrate. 6. The capacitive acceleration sensor according to claim 1, wherein the sensor unit for the X-axis direction and the sensor unit for the Y-axis direction are included in the same sensor.

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