JP2012163507A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration sensor that can be manufactured and assembled without high accuracy compared to a prior art one.SOLUTION: An acceleration sensor includes: a substrate 1; displacement members 3, 7 displaceably supported by the substrate and having a movable electrode 12; and a first fixed electrode 11 generating electrostatic force between the first fixed electrode and the movable electrode, where the first fixed electrode is supported by the substrate opposing the movable electrode in a direction perpendicular to a thickness direction of the substrate and changes its area opposing the movable electrode due to effects of acceleration.

Description

  The present invention relates to an acceleration sensor, and more particularly to a capacitance type acceleration sensor.

  2. Description of the Related Art Conventionally, there is known an acceleration sensor that obtains an applied acceleration by detecting a change in capacitance between electrodes in the sensor when the acceleration is applied. In this capacitance-type acceleration sensor, an acceleration sensor using a so-called servo system has been proposed in which acceleration is detected by a physical quantity such as voltage or current that is controlled so that the distance between electrodes is constant during acceleration action. In such a servo system, the physical quantity is controlled so that the displacement of the electrode is constant, so that the change in the mechanical shape in the sensor is small during the detection operation, and generally the influence of the signal change accompanying the displacement is small. Easy to keep small. As a result, for example, the output linearity can be improved and the dynamic range of the signal (the ratio of the maximum detectable acceleration that can be detected to the minimum resolution of the detectable acceleration that can be detected) can be increased. In addition, since the change in the mechanical shape is small as described above, there is an effect that it is hard to break and the reliability can be improved.

  For example, Japanese Patent Laid-Open No. 5-26902 (Patent Document 1) proposes an acceleration sensor using a servo system that detects acceleration in a direction perpendicular to a substrate. In Patent Document 1, a movable electrode that is displaced in response to acceleration is disposed between two fixed electrodes that are disposed to face each other. Then, an electrostatic attraction is generated by applying a voltage in a pulsed manner between the fixed electrode and the movable electrode so that the displacement of the movable electrode becomes zero at the time of acceleration action, and the displacement of the movable electrode is caused by this electrostatic attraction. Control is constant.

Japanese Patent Laid-Open No. 5-26902

  In the acceleration sensor of Patent Document 1, the movable electrode supported by the silicon beam is disposed between two fixed electrodes respectively formed on two opposing glass substrates. The capacitance depends on the gap between the movable electrode and the fixed electrode.

  Thus, in the conventional acceleration sensor, the movable electrode and the fixed electrode are configured by different members. Furthermore, in the state where the applied acceleration (acting acceleration) is zero, in order to make the capacitances formed in the two gaps between the movable electrode and the fixed electrodes equal, the gap distance between the two is the same. Thus, there is a problem that it is necessary to manufacture and assemble the movable electrode and the two fixed electrodes with high accuracy.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an acceleration sensor that does not require production and assembly with higher accuracy than in the past.

In order to achieve the above object, the present invention is configured as follows.
In other words, the acceleration sensor according to one embodiment of the present invention generates an electrostatic force between the movable electrode, the displacement member having the movable electrode supported by the substrate and displaceable in the thickness direction of the substrate, and the movable electrode. An acceleration sensor comprising: a first fixed electrode that controls the displacement of the displacement member, wherein the first fixed electrode is supported by the substrate so as to face the movable electrode in a direction orthogonal to the thickness direction of the substrate; The area facing the movable electrode is changed by the action of acceleration.

  According to the acceleration sensor of one aspect of the present invention, the first fixed electrode is disposed opposite to the movable electrode supported by the substrate so as to be displaceable in the thickness direction of the substrate in a direction orthogonal to the thickness direction of the substrate. Thus, the process of mechanically bonding members such as electrodes on the upper and lower sides with the movable electrode sandwiched therebetween is not necessary. Therefore, the acceleration sensor can be easily and integrally manufactured by so-called semiconductor fine processing technology, that is, MEMS technology. In other words, it is possible to manufacture with a precision on the order of submicrons by a so-called semiconductor microfabrication process such as film formation, patterning and etching in one direction only from the substrate surface side. Thus, compared with the conventional technology, high accuracy is not required for production and assembly, and it is possible to reduce the size and weight compared to the conventional technology.

  In addition, by providing the first fixed electrode, in order to generate an electrostatic force having a direction and magnitude that returns the displacement to a predetermined displacement with respect to the displacement of the displacement member due to the application of acceleration in the thickness direction of the substrate. It is possible to apply a servo control method for controlling the voltage applied to the. By this servo control, the displacement of the mechanically shaped portion can be reduced, and in general, the influence of a signal change accompanying the displacement can be reduced. Therefore, for example, the output linearity can be improved and the dynamic range of the signal can be increased.

  Further, since the displacement of the mechanically shaped portion is small, it is difficult to break and the reliability can be improved.

1 is a schematic plan view of an acceleration sensor according to Embodiment 1 of the present invention. FIG. 2 is a schematic sectional view taken along line AA shown in FIG. 1. FIG. 2 is a schematic cross-sectional view along the line BB shown in FIG. 1. FIG. 4 is a schematic cross-sectional view taken along the line CC shown in FIG. 3. It is sectional drawing for demonstrating the manufacturing process of the acceleration sensor shown in FIG. 1, and is schematic sectional drawing in the part in alignment with the AA of FIG. It is sectional drawing for demonstrating the manufacturing process of the acceleration sensor shown in FIG. 1, and is schematic sectional drawing in the part in alignment with the AA of FIG. It is sectional drawing for demonstrating the manufacturing process of the acceleration sensor shown in FIG. 1, and is schematic sectional drawing in the part in alignment with the AA of FIG. It is sectional drawing for demonstrating the manufacturing process of the acceleration sensor shown in FIG. 1, and is schematic sectional drawing in the part in alignment with the AA of FIG. It is sectional drawing for demonstrating the manufacturing process of the acceleration sensor shown in FIG. 1, and is schematic sectional drawing in the part in alignment with the AA of FIG. It is sectional drawing for demonstrating the manufacturing process of the acceleration sensor shown in FIG. 1, and is schematic sectional drawing in the part in alignment with the AA of FIG. It is sectional drawing for demonstrating the manufacturing process of the acceleration sensor shown in FIG. 1, and is schematic sectional drawing in the part in alignment with the AA of FIG. It is sectional drawing for demonstrating the manufacturing process of the acceleration sensor shown in FIG. 1, and is schematic sectional drawing in the part in alignment with the AA of FIG. It is sectional drawing for demonstrating the manufacturing process of the acceleration sensor shown in FIG. 1, and is schematic sectional drawing in the part in alignment with the AA of FIG. It is sectional drawing for demonstrating the manufacturing process of the acceleration sensor shown in FIG. 1, and is schematic sectional drawing in the part in alignment with the AA of FIG. In the acceleration sensor shown in FIG. 1, it is the schematic sectional drawing which displayed the part which has the same electric potential in the cross section of the part in alignment with the AA of FIG. In the acceleration sensor shown in FIG. 1, it is a figure explaining the electrostatic capacitance between a detection electrode and a detection frame. In the acceleration sensor shown in FIG. 1, it is the figure which showed the displacement of the inertial mass body in the state which applied the offset voltage to the 2nd fixed electrode. In the acceleration sensor shown in FIG. 1, it is the figure which showed the displacement of an inertial mass body when an offset voltage is applied to a 2nd fixed electrode and a drive voltage is applied to a 1st fixed electrode. It is sectional drawing which shows the modification of the acceleration sensor shown in FIG. It is sectional drawing which shows the other modification of the acceleration sensor shown in FIG. It is general | schematic sectional drawing which follows the DD line | wire shown in FIG. It is general | schematic sectional drawing which follows the EE line shown in FIG. It is sectional drawing which shows another modification of the acceleration sensor shown in FIG. FIG. 24 is a schematic sectional view taken along line FF shown in FIG. 23. FIG. 5 is a schematic plan view corresponding to FIG. 4 in the acceleration sensor according to the second embodiment of the present invention. FIG. 5 is a schematic plan view corresponding to FIG. 4 in the acceleration sensor according to the third embodiment of the present invention. FIG. 27 is a schematic cross-sectional view along the line GG shown in FIG. 26. In the acceleration sensor of Embodiment 4 of this invention, it is a schematic sectional drawing in the part corresponded to the AA line shown in FIG. In the acceleration sensor of Embodiment 4 of this invention, it is a schematic sectional drawing in the part corresponded to the BB line | wire shown in FIG. FIG. 30 is a cross-sectional view of a variation of the acceleration sensor shown in FIGS. 28 and 29, and is a schematic cross-sectional view taken along the line AA shown in FIG. 1. FIG. 30 is a cross-sectional view of a variation of the acceleration sensor shown in FIGS. 28 and 29, and is a schematic cross-sectional view taken along a line BB shown in FIG. 1. It is a block diagram which shows the structure of the acceleration detection apparatus provided with the acceleration sensor of Embodiment 1-4 of this invention. In the acceleration sensor of Embodiment 1, it is a figure for demonstrating the relationship between the electrostatic force Fm produced between a 1st fixed electrode and a movable electrode, and the voltage applied to a 1st fixed electrode. In the acceleration sensor of Embodiment 1, it is a figure for demonstrating the relationship between the electrostatic force Fm produced between a 1st fixed electrode and a movable electrode, and the voltage applied to a 1st fixed electrode. In the acceleration sensor of Embodiment 1, it is a figure for demonstrating the relationship between the electrostatic force Fm produced between a 1st fixed electrode and a movable electrode, and the voltage applied to a 1st fixed electrode.

  An acceleration sensor according to an embodiment of the present invention will be described below with reference to the drawings. In each figure, the same or similar components are denoted by the same reference numerals.

Embodiment 1 FIG.
1 to 4 show the configuration of the acceleration sensor 101 according to the first embodiment. In FIGS. 1 and 4, the direction perpendicular to the paper surface is the acceleration detection axis direction 1 a of the acceleration sensor 101.

  First, the main configuration of the acceleration sensor 101 according to the first embodiment will be described. The acceleration sensor 101 includes a substrate 1, a displacement member, and a first fixed electrode 11 as basic components, and further includes optional second components such as a second fixed electrode 13 and detection electrodes 81 and 82 (summarized). In some cases, the detection electrode 8 may be described. As is apparent from the manufacturing method described later, the acceleration sensor 101 can be formed by a so-called MEMS (Micro Electro Mechanical Systems) technique. Hereinafter, each component of the acceleration sensor 101 will be described.

  In this embodiment, the substrate 1 is a semiconductor substrate, for example, a silicon substrate. In addition, the board | substrate 1 is not limited to a silicon substrate, For example, a glass substrate, an organic material board | substrate, etc. can also be used. For such a substrate 1, the displacement member, the first fixed electrode 11, the second fixed electrode 13, and the detection electrodes 81 and 82 can be made of a conductive polysilicon film. It is desirable that this polysilicon film has low stress and has no stress distribution particularly in the thickness direction.

  The thickness direction of the substrate 1 corresponds to the acceleration detection axis direction 1a as shown in FIG. For convenience of explanation, as shown in FIG. 1, two axes along the plane of the substrate 1 and orthogonal to each other are taken as an X axis and a Y axis.

In the acceleration sensor 101, the displacement member includes an inertial mass body 3, a link beam 4, an anchor 5, a torsion beam 6, and a detection frame 7.
The anchor 5 is a columnar member formed by being erected on the substrate 1 via an insulator 9 along the detection axis direction 1a. The insulator 9 can be a silicon nitride film or a silicon oxide film. Two torsion beams 6 are strip-shaped beam members extending in the same length in opposite directions around the anchor 5 in the Y-axis direction, and one end of each is connected to and supported by the anchor 5. Each other end is connected to the detection frame 7. These two torsion beams 6 are located on a torsion axis 6a along the Y-axis direction, and can be twisted around the axis with the torsion axis 6a as a center.

  As shown in FIG. 1, the detection frame 7 is a plate-like frame-like member, has conductivity, and is rotatable about the torsion shaft 6 a so that the substrate is interposed via the torsion beam 6 and the anchor 5. 1 is supported. The torsion beam 6 is located at the center of the detection frame 7 in the X-axis direction. Therefore, the detection frame 7 has a line-symmetric shape around the torsion axis 6a.

  There are two link beams 4 which are strip-shaped and extend along the Y-axis direction. Each link beam 4 has one end connected to the detection frame 7 and the other end connected to the inertial mass body 3. These two link beams 4 are located on the axis 4a along the Y-axis direction. The torsion axis 6a of the torsion beam 6 and the axis 4a of the link beam 4 are located in parallel as shown in the figure, but are arranged at different positions in the X-axis direction.

  The inertia mass body 3 is a plate-like frame-shaped member as shown in FIG. 1, has conductivity, and can be displaced in the thickness direction of the substrate 1 (acceleration detection axis direction 1a) via the shaft 4a. Yes, it has a movable electrode 12. The inertia mass body 3 has a line-symmetric shape about the torsion axis 6a.

  The movable electrode 12 is a plate-like and conductive member in the present embodiment, and protrudes from the two side surfaces 3a parallel to the Y-axis direction of the inertial mass body 3 in the X-axis direction. A plurality of sheets are arranged in a comb-teeth shape at regular intervals along the regular interval in this embodiment. These movable electrodes 12 move together with the inertial mass body 3 according to the displacement of the inertial mass body 3. All the movable electrodes 12 have the same shape and the same size.

  The first fixed electrode 11 is a plate-like and conductive member in the present embodiment, and is not contacted with the movable electrode 12 between the movable electrodes 12 arranged at regular intervals as described above. In the embodiment, a plurality of sheets are arranged at equal intervals, and are arranged at equal intervals with the movable electrode 12. Each first fixed electrode 11 has the same shape and the same size, and in the present embodiment, the first electrode 11 also has the same shape and the same size as the movable electrode 12. Each such first fixed electrode 11 is connected to a fixed portion 2 erected on the substrate 1 via an insulator 9. Therefore, the first fixed electrode 11 is fixed and faces the movable electrode 12 in the direction orthogonal to the thickness direction of the substrate 1, that is, in the X-axis and Y-axis directions, in this embodiment, the Y-axis direction. In addition, since the movable electrode 12 moves according to the displacement of the inertial mass body 3, the area where the first fixed electrode 11 faces the movable electrode 12 changes according to the displacement of the inertial mass body 3.

  As shown in FIG. 32 and described later, the acceleration sensor 101 is electrically connected to the servo control and acceleration detection circuit 110, and a voltage can be applied to the first fixed electrode 11 and the movable electrode 12. Therefore, when a voltage is applied to the first fixed electrode 11, the first fixed electrode 11 generates an electrostatic force between the movable electrode 12 and the inertial mass body 3 via the movable electrode 12 due to the electrostatic force. Drive. Therefore, in the following description, the first fixed electrode 11 may be referred to as the drive electrode 11.

  The second fixed electrode 13 is opposed to the inertia mass body 3 in the thickness direction of the substrate 1 and is formed on the substrate 1 with the same shape on the plane as the inertia mass body 3 via the insulator 9 as shown in FIG. Electrode. Such a second fixed electrode 13 is an electrode that generates an electrostatic force with the inertial mass body 3 by applying a voltage and controls the displacement of the inertial mass body 3. Therefore, in the following description, the second fixed electrode 13 may be referred to as an offset electrode 13.

  As shown in FIG. 4, the detection electrodes 81 and 82 are formed on the substrate 1 via the insulator 9 at two locations on the X axis along the Y axis direction so as to face the detection frame 7 in the thickness direction of the substrate 1. Electrode. In the present embodiment, as shown in FIG. 4, the detection electrodes 81 and 82 provided at two locations have the same shape and the same size. Such detection electrodes 81 and 82 are electrodes for detecting the capacitance formed between the detection frames 7.

Next, an example of a method for manufacturing the acceleration sensor 101 according to the first embodiment will be described with reference to FIGS.
The above-described configuration of the acceleration sensor 101 can be manufactured by, for example, a so-called semiconductor microfabrication technology or MEMS technology in which processes such as film formation, patterning, and etching are repeatedly performed on the silicon substrate 1. 5 to 14 are views in the manufacturing process corresponding to the cross-sectional position shown in FIG.

  Referring to FIG. 5, an insulator 9 made of a silicon nitride film or a silicon oxide film is formed on substrate 1 by LPCVD (Low Pressure Chemical Vapor Deposition) method. Next, as shown in FIG. 6, a conductive polysilicon film 91 is formed on the insulator 9, and the conductive polysilicon film 91 is patterned and etched as shown in FIG. The electrode 13 and the detection electrodes 81 and 82 are formed. Next, as shown in FIG. 8, a PSG (Phosphosilicate Glass) film 92 is formed, the PSG film 92 is planarized and polished as shown in FIG. 9, and the PSG film 92 is patterned and etched as shown in FIG. I do. Next, as shown in FIG. 11, the fixed portion 2, the inertia mass body 3, the link beam 4, the anchor 5, the torsion beam 6, the detection frame 7, the fixed electrode 11, and the movable electrode 12 are formed on the PSG film 92. A conductive polysilicon film 93 is formed, the conductive polysilicon film 93 is planarized and polished as shown in FIG. 12, and the conductive polysilicon film 93 is patterned and etched as shown in FIG. Finally, the PSG film 92 is removed by etching, and the acceleration sensor 101 according to the first embodiment shown in FIG. 14 is manufactured.

With reference to FIG. 15, the electrical connection between the components of the acceleration sensor 101 of the first embodiment will be described. FIG. 15 is a cross-sectional view of the acceleration sensor 101 in which components that are electrically connected so as to be equipotential to each other are indicated by the same hatching.
The fixed part 2 and the first fixed electrode 11 (drive electrode 11) are connected so as to be equipotential.
The anchor 5, the torsion beam 6, the detection frame 7, the link beam 4, the inertia mass body 3, and the movable electrode 12 are connected so as to be equipotential.
The substrate 1, the second fixed electrode 13 (offset electrode 13), and the detection electrodes 81 and 82 are not electrically connected to any of the above-described components via the insulator 9.

  Further, as shown in FIG. 16, capacitances C <b> 1 and C <b> 2 are formed between the two detection electrodes 81 and 82 and the detection frame 7, respectively. Here, a capacitance difference ΔC = C1−C2 is defined.

  Further, as shown in FIG. 32, the acceleration sensor 101 configured as described above is electrically connected to the servo control and acceleration detection circuit 110, and by the acceleration sensor 101 and the servo control and acceleration detection circuit 110, The acceleration detection device 150 is configured.

Fixed part 2, that is, first fixed electrode 11 (drive electrode 11),
The anchor 5 portion, that is, the torsion beam 6, the detection frame 7, the link beam 4, the inertia mass 3 and the movable electrode 12, and
In order to apply a voltage to the second fixed electrode 13 (offset electrode 13),
Further, each component is electrically connected to the servo control and acceleration detection circuit 110 in order to convert the capacitance value formed between the detection frame 7 and the detection electrodes 81 and 82 into a voltage or the like. Is done.

  Hereinafter, the operation of the acceleration sensor 101 according to the first embodiment will be described with reference to FIGS. 17 and 18. In the following description of the operation, the “anchor 5 portion” includes the anchor 5, the torsion beam 6, the detection frame 7, the link beam 4, the inertia mass body 3, and the movable electrode 12 that are at the same potential as described above. Refers to the component.

  As shown in FIG. 17, in the acceleration sensor 101 according to the first embodiment, when a constant voltage Vf is applied to the second fixed electrode (offset electrode) 13 with respect to the anchor 5 portion, inertia with the second fixed electrode 13 is achieved. An electrostatic force Ff is generated between the mass body 3 and a potential difference between them. The electrostatic force Ff is proportional to the square of the voltage Vf and is proportional to the gap between the second fixed electrode 13 and the inertial mass body 3. The inertial mass body 3 is displaced toward the substrate 1 so that such an electrostatic force Ff and a restoring force Fb due to deformation of the torsion beam 6 and the link beam 4 are balanced.

  As the inertia mass body 3 is displaced, the detection frame 7 connected to the inertia mass body 3 and the anchor 5 by the link beam 4 and the torsion beam 6 is deformed by the link beam 4 and the torsion beam 6 so that the torsion shaft 6a. Rotating displacement around Therefore, the gap intervals between the detection electrodes 81 and 82 and the detection frame 7 change, the capacitance c1 increases, and the capacitance c2 decreases. Since the capacitances C1 and C2 are monotone functions with respect to the displacement of the inertial mass 3, the displacement of the inertial mass 3 is measured by measuring the capacitance difference ΔC by the servo control and acceleration detection circuit 110. I can know. In general, the capacitance can be converted into a voltage by connection with a switched capacitor circuit or the like to know the capacitance value.

  Further, when the voltage Vm is applied to the anchor 2 to the anchor 2, the anchor 5 and the inertial mass body 3 are at the same potential, and the anchor 2 and the first anchor electrode (drive electrode) 11 are at the same potential. Therefore, a potential difference is generated between the first fixed electrode 11 and the inertial mass body 3. On the other hand, as described above, the first fixed electrode 11 and the movable electrode 12 form a so-called comb electrode structure so as to be combined in a comb shape. The capacitance formed therebetween decreases due to the displacement of the inertial mass body 3. Therefore, the electrostatic force Fm is generated between the first fixed electrode 11 and the movable electrode 12 in the direction in which the capacitance increases, that is, in the direction in which the inertia mass 3 is separated from the substrate 1. Here, the electrostatic force Fm is proportional to the differential value of the opposing area of the first fixed electrode 11 and the movable electrode 12 in the substrate thickness direction, and is proportional to the square of the voltage Vm. As shown in FIG. It occurs in the direction of pulling up the mass body 3. Therefore, at this time, the electrostatic mass Ff, the electrostatic force Fm, and the restoring force Fb due to the deformation of the torsion beam 6 and the link beam 4 act on the inertial mass body 3, and the inertial mass body 3 moves to a position where they are balanced. Displace. The displacement of the inertial mass body 3 in the substrate thickness direction when balanced in this way is Zo, and the capacitance difference ΔC is (ΔC) o.

  In this state, when the acceleration A in the detection axis direction 1a is applied, the inertial mass body 3 receives the force Fa by the acceleration A and is displaced to a position where the force Fa, the restoring force Fb, the electrostatic force Ff, and the electrostatic force Fm are balanced. . The inertial mass body 3 is downward (toward the substrate 1) with respect to the positive acceleration (upward in the figure), and the inertial mass body 3 is upward (reverse to the negative direction acceleration (downward in the figure)). Displacement to the substrate 1 side). Here, by adjusting the voltage Vm so that the capacitance difference ΔC becomes (ΔC) o, the electrostatic force Fm can be changed, and the displacement of the inertial mass body 3 can be controlled to Zo.

Here, the force Fa is proportional to the acceleration A. The capacitance C1, capacitance C2, and restoring force Fb are proportional to the displacement of the inertial mass 3, and the electrostatic force Ff is a monotonic function with respect to the displacement of the inertial mass 3 when the voltage Vf is constant. .
As shown in FIG. 33, the height of the movable electrode 12 and the first fixed electrode 11 is h, the displacement position of the movable electrode 12 with respect to the first fixed electrode 11 in the thickness direction of the substrate 1 is Z, and both are completely When the displacement position Z when facing each other is 0, the movable electrode 12 is “on the opposite side” (Z> 0) away from the first fixed electrode 11, that is, away from the substrate 1 (Z> 0), or lower, ie, toward the substrate 1. When moving closer to the “substrate side” (Z <0) (Z ≠ 0), the opposing area S of both becomes smaller in proportion to the displacement position Z. Therefore, as shown in FIG. 34, the opposing area S with respect to the displacement Z decreases with a constant slope in the range of Z> 0 and Z <0 (until there is no overlap between the electrodes) with Z = 0 as the peak. To do. Therefore, as shown in FIG. 35, when the inertial mass body 3 is displaced, the value obtained by differentiating the facing area S between the first fixed electrode 11 and the movable electrode 12 by the displacement Z is movable with respect to the first fixed electrode 11. When the electrode 12 is positioned on the “non-substrate side” (h>Z> 0) or the “substrate side” (0 <Z <−h), it is constant (∂S / ∂Z, the sign is opposite in the case of “non-substrate side” and “substrate side”). Therefore, when the voltage Vm is constant, the electrostatic force Fm is constant regardless of the displacement of the inertial mass body 3, and the electrostatic force Fm is a monotonic function with respect to the change of the voltage Vm.

  Therefore, the acceleration A can be uniquely known from the value of the voltage Vm, and a servo system in which the target value is (ΔC) o and the voltage Vm is the control amount can be applied.

  By applying such a servo system, the displacement of the mechanically shaped portion is small, so the influence of the signal change accompanying the displacement can be reduced. For example, the output linearity is improved, the signal dynamic range (detectable) It is possible to obtain good acceleration detection characteristics such as an increase in the ratio of the maximum detectable acceleration to the minimum resolution of the applied acceleration.

  Further, since the displacement of the mechanically shaped part is small and the possibility that the movable part comes into contact with other parts can be kept low, it is possible to obtain an acceleration sensor that is hard to break and has high reliability.

  Further, since it can be produced by repeatedly performing processes such as film formation, patterning, and etching on the substrate 1, there is an advantage that it is not necessary to assemble members with high accuracy. In addition, since the first fixed electrode 11 is arranged so as to face the movable electrode 12 in a direction orthogonal to the thickness direction of the substrate 1, the acceleration sensor is integrally manufactured by the MEMS technique as described above. can do. Therefore, it is not necessary to manufacture and assemble with higher accuracy than in the past, and the sensor can be reduced in size and weight.

  In the acceleration sensor 101 of the first embodiment, the inertial mass body 3 can be forcibly displaced by applying a voltage to the second fixed electrode (offset electrode) 13 even when no acceleration is applied. it can. Therefore, the acceleration sensor 101 also has a function of self-diagnosis whether or not the acceleration sensor 101 is destroyed.

  Further, in the acceleration sensor 101 of the first embodiment, as described above, the servo system is applied in which the voltage Vf is constant and the voltage Vm is a control amount. On the other hand, as described above, the inertial mass is obtained when the movable electrode 12 is positioned either on the upper side (on the side opposite to the substrate) or on the lower side (on the substrate side) with respect to the first fixed electrode (drive electrode) 11. The differential value of the opposed area of the first fixed electrode 11 and the movable electrode 12 with respect to the displacement of the body 3 is constant regardless of the displacement of the inertial mass body. Therefore, since the generated electrostatic force does not depend on the displacement of the inertial mass body 3 when the voltage Vm is constant, there is an advantage that servo control can be easily performed.

  Further, in the acceleration sensor 101 of the first embodiment, two detection electrodes 8 are provided, and the capacitance difference between them is used as a target value when performing servo control. By setting the capacitance difference between the two detection electrodes 81 and 82 as the target of servo control, the absolute value of the target value can be reduced, so that servo control can be easily performed and the load on the electric circuit is reduced. Can be reduced. In addition, it is possible to suppress target value variations caused by process variations and the like.

  Further, in the acceleration sensor 101 of the first embodiment, the displacement of the inertial mass body 3 due to the acting acceleration is converted into the rotational displacement of the detection frame 7 and detected. Therefore, an air damping effect, which is an effect that the air layer between the detection frame 7 and the substrate 1 acts as a cushioning material to reduce the impact, is generated for acceleration in either positive or negative direction, and the element structure is hardly broken. Can do.

  In the acceleration sensor 101 according to the first embodiment, the servo method is applied in which the voltage Vf is constant and the voltage Vm is the controlled variable. However, the servo method is also used in which the voltage Vm is constant and the voltage Vf is the controlled variable. The applied acceleration sensor can be realized.

  Further, in the acceleration sensor 101 of the first embodiment, the first fixed electrode 11 and the movable electrode 12 are configured in a comb-like shape, but as shown in FIG. The fixed portion 2 and the inertial mass body 3 may be configured to face each other. By applying the voltage Vm between the fixed portion 2 and the inertial mass body 3, an electrostatic force in the substrate thickness direction can be obtained by the displacement of the inertial mass body 3, and an acceleration sensor to which a servo system is applied can be realized.

  In the acceleration sensor 101 of the first embodiment, the first fixed electrode 11 is arranged symmetrically with respect to the torsion axis 6a so as to face the movable part such as the inertial mass body 3 or the like. The first fixed electrode 11 may be disposed so as to surround the outer periphery of the inertial mass body 3 or may be disposed to face a part of the inertial mass body 3. Even in this configuration, by applying the voltage Vm, an electrostatic force in the substrate thickness direction can be obtained by the displacement of the inertial mass body 3, and an acceleration sensor to which a servo system is applied can be realized.

  Further, in the acceleration sensor 101 of the first embodiment, two detection electrodes 8 are provided and the capacitance difference is set as a target value for servo control. However, the number of detection electrodes 8 may be one. In this configuration, servo control can be performed using the electrostatic capacitance when the voltage Vf is applied as a target value.

  Further, in the acceleration sensor 101 of the first embodiment, the displacement of the inertial mass body 3 due to the acceleration is detected by converting it into the rotational displacement of the detection frame 7, but as shown in FIGS. 20 to 22, the torsion beam 6, the detection frame 7 and the link beam 4 may be omitted, and the inertial mass 3 having the movable electrode 12 that can be displaced in the substrate thickness direction by the beam member 61 may be used. Even in such a configuration, by applying the voltage Vm, an electrostatic force in the substrate thickness direction can be obtained by the displacement of the inertial mass body 3, and an acceleration sensor to which a servo system is applied can be realized.

  Further, in the acceleration sensor 101 of the first embodiment, the capacitance C1 is increased and the capacitance C2 is decreased by the application of the voltage Vf, but the capacitance C1 is decreased and the capacitance C2 is increased. Also good. Further, although the controlled capacitance difference ΔC is (C1-C2), it may be (C2-C1).

  In the acceleration sensor 101 according to the first embodiment, the inertia mass body 3 surrounds one detection frame 7, but may be configured to surround a plurality of detection frames 7. That is, as shown in FIGS. 23 and 24, the inertial mass body 3 surrounds two detection frames 7, for example. When the relative positional relationship between the torsion beam 6 and the link beam 4 is reversed in the two detection frames 7, when the inertial mass body 3 is displaced in the thickness direction of the substrate 1, the two detection frames 7 are respectively When the rotational mass is reversed and the inertial mass 3 is tilted or displaced in a direction parallel to or substantially parallel to the substrate 1 (in-plane direction), the two detection frames 7 are rotationally displaced in the same direction. . For this reason, the detection electrode 81 and the detection electrode 84 are connected to each other and the detection electrode 82 and the detection electrode 83 are connected to each other so that the sensitivity is increased only when the respective detection frames 7 are rotationally displaced in opposite directions. By setting the capacitances C1 and C2, the sensitivity to accelerations other than the detection axis direction 1a can be suppressed, and the influence of angular velocity and angular acceleration can be reduced.

Embodiment 2. FIG.
Next, the acceleration sensor 102 according to Embodiment 2 of the present invention will be described with reference to FIG. In FIG. 25, the same reference numerals as those used in the drawings referred to in the first embodiment are assigned to components that perform the same or similar functions, and only differences will be described below.

  In the acceleration sensor 101 according to the first embodiment described above, the detection electrodes 81 and 82 have the same shape and the same area as shown in FIG. On the other hand, in the acceleration sensor 101 according to the second embodiment, as shown in FIG. 25, when a constant voltage Vf is applied to the second fixed electrode (offset electrode) 13 with respect to the anchor 5 portion, The areas of the two detection electrodes 8 are made different so that the capacitance C1 and the capacitance C2 are equal, in other words, the initial capacitance when the acceleration sensor 102 is not operating is C1 <C2. Yes. That is, in the acceleration sensor 102 according to the second embodiment, the detection electrode in the acceleration sensor 102 corresponding to the detection electrode 81 of the acceleration sensor 101 is numbered as 81-1, and the detection electrode 81 is compared with the area of the detection electrode 82. The area of −1 was reduced.

With this configuration, the target value of ΔC when performing servo control can be set to “0”, servo control can be easily performed, and the burden on the electric circuit can be reduced.
Of course, the acceleration sensor 102 according to the second embodiment can also achieve the effects achieved by the acceleration sensor 101 according to the first embodiment described above, and each modification described above can also be applied to the acceleration sensor 102. it can.

Embodiment 3 FIG.
Next, the acceleration sensor 103 according to the third embodiment of the present invention will be described with reference to FIGS. In the drawings, the same or similar components having the same functions are denoted by the same reference numerals as those in the drawings referred to in the first embodiment, and only differences will be described below.

As a method for setting the target value of ΔC at the time of servo control to “0”, the configuration of the above-described second embodiment has been described, but the third embodiment discloses still another method.
That is, as described above, when the constant voltage Vf is applied to the second fixed electrode (offset electrode) 13 with respect to the anchor 5 portion, a difference is generated between the capacitance C1 and the capacitance C2. In the third embodiment, the fixed capacitor 21 having the capacitance C3 having a value equal to this difference is placed on the insulator 9 of the substrate 1 except where the detection unit such as the fixed unit 2 and the inertia mass body 3 is formed. It is formed in the part of. That is, the capacitance difference ΔC = (C1) − (C2 + C3) is obtained by connecting the capacitance C2 and the capacitance C3 in parallel to the insulator 9 with a wiring pattern. By setting the capacitance C3 of the fixed capacitor 21 so that C2 + C3 is equal to C1, the target value of ΔC when performing servo control can be set to “0”. Thereby, servo control can be easily performed and the burden on the electric circuit can be reduced.

  Here, since the fixed capacitor 21 can be manufactured by the same manufacturing process as the second fixed electrode 13 and the anchor 5 portion related to the capacitances C1 and C2, the process variation and the like are caused by the capacitances C1, C2, and C3. Acts in the same way. Therefore, it is possible to reduce the variation in capacitance caused by process variation and the like.

  In the third embodiment, the method of forming the fixed capacitor 21 on the substrate 1 is used as a method of adding the capacitance C3. However, the input of the capacitance to the voltage conversion circuit installed outside the acceleration sensor 103 is adopted. Before, a capacitor having a capacitance value equal to the difference between C1 and C2 may be connected in parallel with C2.

  Of course, the acceleration sensor 103 according to the third embodiment can also achieve the effects exhibited by the acceleration sensor 101 according to the first embodiment described above, and each modification described above can also be applied to the acceleration sensor 103. it can.

Embodiment 4 FIG.
Next, the acceleration sensor 104 according to the fourth embodiment of the present invention will be described with reference to FIGS. In the drawings, the same or similar components having the same functions are denoted by the same reference numerals as those in the drawings referred to in the first embodiment, and only differences will be described below.

  The acceleration sensor 104 according to the fourth embodiment employs a configuration in which the second fixed electrode (offset electrode) 13 is not provided. That is, the acceleration sensor 104 according to the fourth embodiment is manufactured so that the first fixed electrode (drive electrode) 11 is located on the side opposite to the substrate (upper side) than the movable electrode 12 as shown in FIGS. In addition, the second fixed electrode 13 is not provided. With such a configuration, the same effect is obtained as when the inertial mass body 3 is displaced by applying the voltage Vf without applying the offset voltage Vf to the second fixed electrode 13. In the acceleration detection area, the displacement range of the displacement member such as the inertia mass body 3 and the detection frame 7 can be limited to the lower side (substrate side) of the first fixed electrode (drive electrode) 11, and the applied acceleration and the first fixed The voltage Vm applied to the electrode 11 can be uniquely associated. In addition, since the detected capacitance difference ΔC can be zero when the applied acceleration is zero and the voltage application to the first fixed electrode 11 is zero, the target value of ΔC when performing servo control can be zero. Servo control can be easily performed, and the burden on the electric circuit can be reduced.

  On the other hand, as shown in FIGS. 30 and 31, on the other hand, the first fixed electrode 11 is fabricated so as to be positioned on the substrate side (lower side) of the movable electrode 12, and the second fixed electrode (offset electrode) is formed. ) 13 may be omitted. Even in such a configuration, the displacement range of the displacement member such as the inertial mass body 3 and the detection frame 7 can be set to the first fixed electrode (without applying the voltage Vf to the second fixed electrode 13 in the acceleration detection range. The driving electrode 11 can be limited to the upper side (on the side opposite to the substrate), and the applied acceleration can be uniquely associated with the applied voltage Vm to the first fixed electrode 11. In addition, since the detected capacitance difference ΔC can be zero when the applied acceleration is zero and the voltage application to the first fixed electrode 11 is zero, the target value of ΔC when performing servo control can be zero. Servo control can be easily performed, and the burden on the electric circuit can be reduced.

  Of course, also in the acceleration sensor 104 of the fourth embodiment, the effects exhibited by the acceleration sensor 101 of the first embodiment described above can be achieved, and the above-described modifications can also be applied to the acceleration sensor 104. it can.

1 substrate, 3 inertia mass body, 4 link beam, 5 anchor, 6 torsion beam,
7 detection frame, 8 detection electrode, 11 first fixed electrode, 12 movable electrode,
13 second fixed electrode, 21 fixed capacity,
81, 82 detection electrodes,
101-104 acceleration sensor, 110 servo control and acceleration detection circuit,
150 Acceleration detector.

Claims (10)

A substrate,
A displacement member supported by the substrate so as to be displaceable in the thickness direction of the substrate and having a movable electrode;
A first fixed electrode that generates an electrostatic force between the movable electrode and controls the displacement of the displacement member;
An acceleration sensor equipped with
The first fixed electrode is supported on the substrate facing the movable electrode in a direction orthogonal to the thickness direction of the substrate, and an area facing the movable electrode changes due to an action of acceleration.
An acceleration sensor characterized by that.   2. The apparatus according to claim 1, further comprising a second fixed electrode that is disposed on the substrate so as to face the displacement member in a thickness direction of the substrate, and that controls the displacement of the displacement member by generating an electrostatic force between the displacement member and the displacement member. Acceleration sensor.   The acceleration sensor according to claim 1, wherein the first fixed electrode is disposed on a side opposite to the movable electrode with respect to the movable electrode in a thickness direction of the substrate.   The acceleration sensor according to claim 1, wherein the first fixed electrode is disposed on a substrate side with respect to the movable electrode in a thickness direction of the substrate.   The acceleration sensor according to any one of claims 1 to 4, wherein the displacement member has a support structure that supports the displacement member on the substrate so as to be displaceable. The displacement member is
A torsion beam extending along the orthogonal direction, twisted about a torsion axis, and supported by the substrate;
A detection frame that is rotatable about the torsion axis and supported by the torsion beam;
A link beam extending along the orthogonal direction and supported by the detection frame at a position different from the twist axis;
The acceleration sensor according to claim 1, further comprising: an inertial mass body supported by the link beam and capable of being displaced in a thickness direction of the substrate by an action of acceleration.   The detection electrode according to claim 1, further comprising a detection electrode disposed on the substrate facing the displacement member in a thickness direction of the substrate, and detecting a displacement of the displacement member by forming a capacitance between the displacement member and the displacement member. The acceleration sensor according to any one of the above.   The acceleration sensor according to claim 7, wherein the detection electrode has a first detection electrode whose capacitance increases and a second detection electrode whose capacitance decreases with respect to acceleration in the same direction. A second fixed electrode disposed on the substrate opposite to the displacement member in the thickness direction of the substrate and generating an electrostatic force between the displacement member and controlling the displacement of the displacement member;
The acceleration sensor according to claim 8, wherein the first detection electrode and the second detection electrode have different electrostatic capacities in a state where no acceleration acts and no voltage is applied to the second fixed electrode. A second fixed electrode disposed on the substrate facing the displacement member in the thickness direction of the substrate and generating an electrostatic force between the second fixed electrode and the displacement member to control the displacement of the displacement member;
The acceleration according to claim 8, further comprising: a fixed capacitor having a capacity corresponding to a difference between the capacitances of the first detection electrode and the second detection electrode in a state where a constant voltage is applied to the second fixed electrode. Sensor.

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