JP2006105698A - Acceleration angular velocity composite sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce noise caused by driving vibration, while detecting acceleration and angular velocity with a simple sensor constitution, in an acceleration angular velocity composite sensor. <P>SOLUTION: This acceleration angular velocity composite sensor has a base board 1, a pair of vibrators 2 displaceably supported by the base board 1, a driving fixed electrode 3 fixed to the base board 1 and impressing voltage between the electrode and the vibrators 2, and a detecting fixed electrode 4 fixed to the base board 1 and detecting a change in capacitance between the electrode and the vibrators 2 in the detecting shaft direction. The vibrators 2 have a gimbal part 5 supported by restraining displacement in the detecting shaft direction so as to be displaceable in the driving shaft direction; a mass part 6 supported in the gimbal part 5 by restraining displacement in the driving shaft direction so as to be displaceable in the detecting shaft direction to the gimbal part 5; and a detecting movable electrode 7 for detecting a change in capacitance between the electrode and the detecting fixed electrode 4 by restraining displacement in the driving shaft direction so as to be displaceable in the detecting shaft direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an acceleration / angular velocity composite sensor capable of simultaneously detecting acceleration and angular velocity with a single sensor device.

  For example, an acceleration sensor and an angular velocity sensor (sometimes referred to as a gyro or a rate gyro) are used for an attitude control or a navigation system of an automobile. Conventionally, one acceleration sensor and one gyro are used. It was often implemented separately. Among them, a sensor (acceleration angular velocity detection) that detects acceleration and angular velocity with a sensor in which the acceleration sensor and gyro disclosed in Patent Document 1 are arranged in the same plane or one sensor device disclosed in Patent Document 2. Apparatus) is also disclosed.

In the sensor disclosed in Patent Document 1 described above, the acceleration sensor and the gyro are substantially separate, and are arranged simultaneously on the silicon wafer surface.
The acceleration angular velocity detection device disclosed in Patent Document 2 is a composite sensor having a pair of left and right vibrators. However, since the drive electrodes are arranged and the vibrator has a U-shape, the driving force In addition to displacement and / or vibration in the drive axis direction (X-axis direction) at the time of application (hereinafter referred to simply as displacement, including vibration), in FIG. The part 21a, the protruding part 36a, etc. are likely to be displaced or vibrated in the positive direction of the Y axis, and the arm part 21b, the protruding part 36b, etc. are likely to be displaced in the negative direction of the Y axis. For this reason, the detection electrode is also likely to be displaced or vibrated in the Y-axis direction during driving, and noise output tends to be generated despite no acceleration or angular velocity being applied. Further, since the detection electrode is displaced or vibrated in the X-axis direction during driving, the capacitance always changes. For this reason, it is designed to cancel the noise component by the calculation processing of the detection circuit.

JP-A-10-239347 (Claims, FIG. 1) JP 2004-28869 A (Claims, FIG. 1)

The following problems remain in the conventional technology.
In the conventional acceleration and / or angular velocity sensor, the sensor disclosed in Patent Document 1 requires a detection circuit in each of the acceleration sensor unit and the angular velocity sensor unit, and the number of vibrators. As the sensor increases, there is a problem that the sensor tends to be large. In addition, the sensor described in Patent Document 2 has a disadvantage that the detection circuit becomes complicated because the process of removing the noise component is performed, and an output with a poor S / N ratio is likely to occur.

  The present invention has been made in view of the above-described problems. An acceleration angular velocity composite sensor that can detect acceleration and angular velocity with one simple sensor configuration and can reduce noise caused by driving vibration is provided. The purpose is to provide.

  The present invention employs the following configuration in order to solve the above problems. That is, the acceleration angular velocity composite sensor of the present invention includes a substrate having an upper surface that is insulative and a pair of vibrators that are supported on the substrate so as to be displaceable with respect to the substrate and that are arranged symmetrically about the symmetry plane. A driving fixed electrode for applying a voltage between the vibrator fixed to the substrate and vibrating the vibrator in a driving axis direction orthogonal to the plane of symmetry; and a detection axis direction fixed on the substrate and orthogonal to the driving axis direction And a fixed detection electrode that detects a change in capacitance between the vibrator and the vibrator, and the vibrator is supported so that the vibrator can be displaced in the drive axis direction and the displacement in the detection axis direction is suppressed. The outer frame portion can be displaced in the detection axis direction with respect to the outer frame portion, the weight portion supported in the outer frame portion with the displacement in the drive shaft direction being suppressed, and the outer frame portion can be displaced in the detection axis direction. In addition, the displacement in the drive shaft direction is suppressed and the weight part and the base are To a detection movable electrode for detecting a change in capacitance between the support and detected fixed electrode, characterized by having the.

  In this acceleration angular velocity composite sensor, the weight part and the detection movable electrode are supported in the closed outer frame part having high rigidity, so that the generation of noise components based on the bending and deformation of the outer frame part due to drive vibration is suppressed. can do. In the present invention, “displacement” includes “vibration”.

  Further, in the acceleration angular velocity composite sensor according to the present invention, the detection movable electrode is connected to the weight part via a damper that absorbs the displacement in the drive axis direction in the weight part and transmits the displacement in the detection axis direction. Features. That is, in this acceleration angular velocity composite sensor, the weight part is displaced in the drive axis direction because the weight part and the detection movable electrode are connected by the damper which is an elastic member or a buffer member that absorbs the displacement in the drive axis direction. However, the transmission of the displacement to the detection movable electrode is suppressed, and the displacement of the weight portion in the drive axis direction is prevented from affecting the capacitance between the detection movable electrode and the detection fixed electrode.

  Furthermore, the acceleration angular velocity composite sensor according to the present invention is characterized in that the outer frame part, the weight part, the detection movable electrode, and the damper are arranged symmetrically about the center line in the detection axis direction in the weight part. To do. That is, in this acceleration angular velocity composite sensor, since the outer frame portion, the weight portion, the detection movable electrode, and the damper are arranged symmetrically, uniform displacement can be obtained on the left and right of the center line of the weight portion, with higher accuracy. Can be detected.

  In the acceleration angular velocity composite sensor according to the present invention, the detection movable electrode is a comb electrode in which comb teeth are arranged in the detection axis direction, and is supported by the substrate and the weight portion at both ends in the detection axis direction. It is characterized by. That is, in this acceleration angular velocity composite sensor, since both ends of the detection movable electrode are supported by the substrate and the weight part, the detection movable electrode is more stably biased than in a cantilever state in which only one end is supported. Less displacement is possible, and noise components can be further reduced.

  Moreover, the acceleration angular velocity composite sensor according to the present invention is characterized in that the pair of vibrators are coupled via a synchronous beam that absorbs the displacement in the drive axis direction and transmits the displacement in the detection axis direction. That is, a pair of vibrators that are not connected have a difference in driving speed and frequency due to a slight difference in dimensions, but in this acceleration angular velocity composite sensor, the pair of vibrators are connected by the synchronous beam. The driving speed and the frequency of both vibrators can be transmitted by the synchronization beam to achieve synchronization, and the detection accuracy can be improved by matching the frequency and the amplitude.

  The acceleration angular velocity composite sensor according to the present invention is characterized in that the pair of vibrators are formed by patterning a semiconductor thin plate or a semiconductor thin film by photolithography. In other words, this acceleration angular velocity composite sensor is a MEMS (Micro Electro-Mechanical Systems) device in which a pair of vibrators are microfabricated by patterning using an exposure technique, so that a very fine and high dimensional accuracy can be obtained. Therefore, high symmetry of both vibrators can be obtained.

The present invention has the following effects.
That is, according to the acceleration angular velocity composite sensor according to the present invention, the weight portion and the detection movable electrode are supported in the closed outer frame portion having high rigidity, so that the outer frame portion is bent or deformed due to drive vibration. Generation of the noise component based on this can be suppressed, and acceleration and angular velocity can be detected with high accuracy with a simple configuration. Therefore, since highly accurate detection can be performed without using a complicated detection circuit that removes noise components, it is suitable as a low-cost and high-performance gyro sensor for posture control, navigation system, and the like.

  Hereinafter, an embodiment of an acceleration angular velocity composite sensor according to the present invention will be described with reference to FIGS.

  The acceleration angular velocity composite sensor of the present embodiment is a MEMS inertial composite sensor manufactured by a silicon semiconductor process. As shown in FIG. A voltage is applied between the pair of vibrators 2 that are supported on 1 and arranged symmetrically about the mirror symmetry plane SY, and the vibrator 2 that is fixed on the substrate 1, and the vibrator 2 is A driving fixed electrode 3 that vibrates in the X-axis direction (driving axis direction) orthogonal to the mirror symmetry plane SY and a vibrator 2 in the Y-axis direction (detection axis direction) that is fixed on the substrate 1 and orthogonal to the X-axis direction. And a fixed detection electrode 4 for detecting a change in electrostatic capacity between them.

As the substrate 1, a substrate on which an insulating film such as glass is formed on the upper surface or a substrate that is entirely insulating is used.
The vibrator 2, the drive fixed electrode 3 and the detection fixed electrode 4 are simultaneously manufactured by a silicon semiconductor process which will be described later.

  FIG. 2 is a diagram showing only one of the pair of vibrators 2 in FIG. The other vibrator 2 is also symmetrically arranged with respect to the mirror plane SY and has a similar structure. The vibrator 2 is displaceable in the X-axis direction and is supported with a closed frame-like gimbal portion (outer frame portion) 5 supported by suppressing displacement in the Y-axis direction. A mass part (weight part) 6 supported in the gimbal part 5 so as to be displaceable in the Y-axis direction and suppressed in the X-axis direction, and displaceable in the Y-axis direction and in the X-axis direction Displacement is suppressed, and a movable detection electrode 7 that detects a change in capacitance between the gimbal portion 5 and the detection fixed electrode 4 supported by the mass portion 6 and the substrate 1 is provided at both ends of the gimbal portion 5 in the Y-axis direction. A pair of supported frame portions 8 and a pair of drive movable electrodes 9 supported inside the pair of frame portions 8 are provided.

The gimbal portion 5 is fixed on the substrate 1 so as to be displaceable in the X-axis direction via first drive beams 10 provided at both ends in the X-axis direction. One end of each of these first drive beams 10 is fixed to the center in the Y-axis direction of the gimbal portion 5, extends to both ends in the Y-axis direction, and the other end is fixed on the substrate 1.
The mass portion 6 is fixed to the inside of the gimbal portion 5 so as to be displaceable in the Y-axis direction via gimbal beams 11 provided at both ends in the Y-axis direction. One end of each gimbal beam 11 is fixed to the inner side of the gimbal portion 5 and the end portion in the Y-axis direction, extends to the center in the X-axis direction, and the other end is fixed to the end portion in the Y-axis direction of the mass portion 6. Yes.

The pair of detection movable electrodes 7 are coupled to the mass portion 6 via dampers 12 that absorb the displacement in the X-axis direction of the mass portion 6 and transmit the displacement in the Y-axis direction. Two dampers 12 are arranged in the Y-axis direction with respect to one detection movable electrode 7. One end of each of the dampers 12 is fixed to the mass part 6 and the end of the detection movable electrode 7 in the Y-axis direction, and a pair of Y-axis parts 12a extending from the one end to the center of the mass part 6 in the Y-axis direction. And an X-axis part 12b that connects the other end of the Y-axis part 12a. In this way, the damper 12 is formed in a U-shape that is long in the Y-axis direction and opened in the Y-axis direction by the pair of Y-axis part 12a and the X-axis part 12b, so that it is easily elastic in the X-axis direction. And is difficult to deform in the Y-axis direction.
The gimbal part 5, the mass part 6, the movable detection electrode 7, and the damper 12 are arranged symmetrically about the center line of the mass part 6 in the Y-axis direction.

The detection movable electrode 7 and the drive movable electrode 9 are comb-teeth electrodes in which a plurality of comb teeth extending in the X-axis direction are arranged in the Y-axis direction. Of the pair of drive movable electrodes 9, the drive movable electrode 9 on the gimbal portion 5 side has comb teeth arranged on both sides in the X-axis direction, and the drive movable electrode 9 on the opposite side of the gimbal portion 5 has the gimbal portion. The comb teeth are arranged only on the side portion on the 5 side.
On the substrate 1, the driving fixed electrode 3 is fixed and provided facing the comb teeth of the driving movable electrode 9 facing the gimbal portion 5 side. These drive fixed electrodes 3 are comb-shaped electrodes in which a plurality of comb teeth extending in the X-axis direction and arranged between the comb teeth of the drive movable electrode 9 are arranged in the Y-axis direction.

Further, on the substrate 1, a drive amplitude detection fixed electrode 13 is fixedly provided so as to face the comb teeth facing the gimbal portion 5 side of the drive movable electrode 9. The fixed electrode 13 for detecting drive amplitude is a comb-like electrode in which a plurality of comb teeth arranged in the Y-axis direction are arranged in the X-axis direction and arranged between the comb teeth of the drive movable electrode 9.
A detection fixed electrode 4 is fixed on the substrate 1 so as to face the detection movable electrode 7. The detection fixed electrode 4 is a comb-like electrode in which a plurality of comb teeth are arranged in the Y-axis direction, extending in the X-axis direction and arranged between the comb teeth of the detection movable electrode 7.

The detection movable electrode 7 is fixed to the substrate 1 via the detection beams 14 at both ends in the Y-axis direction so as to be displaceable in the Y-axis direction. One end of each of these detection beams 14 is fixed to the end portion in the Y-axis direction of the detection movable electrode 7, is elongated in the X-axis direction, and the other end is fixed on the substrate 1.
The frame portions 8 are fixed to the substrate 1 via the second drive beam 15 so as to be displaceable in the X-axis direction. One end of each of the second drive beams 15 is fixed inside the frame portion 8, is elongated in the Y-axis direction, and the other end is fixed on the substrate 1.

  In FIG. 1, the pair of vibrators 2 are connected via a synchronization beam 16 that absorbs displacement in the X-axis direction and transmits displacement in the Y-axis direction. One end of the synchronizing beam 16 is fixed to the frame portion 8 of one vibrator 2, extends from the one end to the center in the Y-axis direction of the drive movable electrode 9, and is folded back near the center in the Y-axis direction. The vibrator 2 is elongated to the frame portion 8 and the other end is fixed to the frame portion 8. As described above, the synchronization beam 16 is formed in a U-shape that is long in the Y-axis direction and opened in the Y-axis direction, and therefore easily deforms with elasticity in the X-axis direction.

The drive amplitude detection fixed electrode 13 and the second drive beam 15 are electrically connected to the capacitance detection circuit 20 by wiring formed on the substrate 1. The detection fixed electrode 4 and the second drive beam 15 are electrically connected to the capacitance detection circuit 23 by wiring formed on the substrate 1. The capacitance detection circuit 20 is electrically connected to the amplitude control circuit 21. In addition, the drive fixed electrode 3 is electrically connected to an AC voltage source 22 that generates an oscillation in a predetermined X-axis direction by applying an AC voltage by wiring formed on the substrate 1. The AC voltage source 22 is electrically connected to the amplitude control circuit 21.
The capacitance detection circuits 20 and 23 detect the change in capacitance between the detection movable electrode 7 and the detection fixed electrode 4 and the change in capacitance between the drive movable electrode 9 and the drive amplitude detection fixed electrode 13. It is a circuit to detect. The amplitude control circuit 21 is a circuit that adjusts the amplitude of the vibration by controlling the AC voltage source 22 based on the change in capacitance detected by the capacitance detection circuit 20.

  Next, before describing a method for detecting acceleration and angular velocity in the acceleration / angular velocity composite sensor of the present invention, the operation principle of the angular velocity sensor (gyro) will be described with reference to FIG.

For example, the position of the weight when the weight _m is vibrated with the amplitude D and the angular frequency ωx in the X-axis direction is expressed by the following equation (1).

  Here, assuming that the angular velocity Ω around the Z-axis is applied, the Coriolis force F (coriolis) is expressed by equation (2).

  When the damping coefficient in the detection (Y) axis direction is c and the spring constant in the detection axis direction is ky, the equation of motion in the Y axis direction is expressed by equation (3).

  When this equation of motion is solved, the displacement Y (t) in the Y-axis direction is obtained as shown in equation (4).

A is the detected amplitude in the Y-axis direction caused by the Coriolis force, and ψ is the phase difference between the drive vibration and the detected vibration. The detection amplitude A is the expression (5-1).

Here, ω _y is the resonance frequency in the Y-axis direction, Q _y is the Q factor in the detection axis direction, and represents the sharpness of the resonance peak of vibration.
As described above, when the angular velocity Ω acts on the vibrating body driven by ω _x , the vibrating body vibrates at the same angular frequency ω _x as that of the driving vibration but has a different amplitude and phase. Here, when ω _x ≈ω _y , equation (5-1) can be simplified as equation (5-2). In general, if the resonance frequency in the drive axis direction and the resonance frequency in the detection axis direction are completely matched, the energy of drive vibration leaks in the detection axis direction due to mechanical coupling, and no angular velocity is applied. Nevertheless, detection vibration occurs. Conversely, if ω _x / ω _y is too large or too small, the detected amplitude tends to be too small. Therefore, ω _x / ω _y is preferably 0.618 to 1.618.

When ω _x / ω _y is within this range, the detection amplitude A can be multiplied by Q _y . The detection amplitude A drive amplitude D, proportional to Q _y, omega is inversely proportional to _y, it can be seen that little to do the omega _x. From this, to obtain greater sensitivity,
(1) Increase the drive amplitude.
(2) Reducing the resonance frequency in the detection axis direction;
(3) Increase the Q factor in the detection axis direction.
Can be considered.

  Next, a method of detecting acceleration and angular velocity in the acceleration / angular velocity composite sensor of the present invention will be described with reference to FIGS.

As described above, the frame portion 8, the drive movable electrode 9, and the gimbal portion 5 are integrally formed, and the frame portion 8 and the gimbal portion 5 are supported by the first drive beam 10. By being supported by the first drive beam 10, the frame portion 8, the drive movable electrode 9, and the gimbal portion 5 are easily displaced in the X-axis direction but difficult to be displaced in the Y-axis direction.
Further, the driving fixed electrode 3 and the driving movable electrode 9 have a structure in which the comb teeth face each other. When voltages having opposite polarities are applied to the driving fixed electrode 3 and the driving movable electrode 9, respectively, The driving movable electrode 9 is displaced (vibrated) in the X-axis direction with respect to the driving fixed electrode 3 by electrostatic attraction acting between the electrodes shown in the equation (6).

Here, n is the number of gaps formed between the comb teeth of the drive fixed electrode 3 and the comb teeth of the drive movable electrode 9, ε is the dielectric constant of the atmosphere in which to operate, and t is the thickness of the drive movable electrode 9 ( Width in the Z-axis direction), V is an applied voltage, and d is a distance between the comb teeth of the drive movable electrode 9 and the comb teeth of the drive fixed electrode 3.
Therefore, the frame portion 8 and the gimbal portion 5 formed integrally with the drive movable electrode 9 are also displaced (vibrated) in the X-axis direction in synchronization with the drive movable electrode 9. At this time, the left and right frame parts 8, the gimbal part 5, and the drive movable electrode 9 arranged around the mirror symmetry plane SY in FIG. 1 are displaced (vibrated) in contrast to the mirror symmetry plane SY.

  When the drive movable electrode 9 is displaced (vibrated), the overlapping area of the comb electrodes of the drive movable electrode 9 and the drive amplitude detection fixed electrode 13 changes. When the overlapping area changes, the capacitance between the drive movable electrode 9 and the drive amplitude detection fixed electrode 13 changes. The displacement and amplitude of the drive movable electrode 9 can be calculated from this change in capacitance. The voltage applied to at least one of the drive movable electrode 9 and the drive fixed electrode 3 is appropriately adjusted so that a desired drive displacement and drive amplitude can be obtained.

Here, when a voltage is applied to at least one of the driving fixed electrode 3 and the driving movable electrode 9, the mass portion 6 connected to and supported by the gimbal portion 5 by the gimbal beam 11 has a damper 12 as shown in FIG. It is displaced (vibrated) in the X-axis direction in synchronization with the gimbal portion 5 with deformation. That is, in FIG. 4, when a voltage for displacing the mass portion 6 to the right side is applied, the pair of Y-axis portions 12a in the right damper 12 are close to the mass portion 6 and the pair in the left damper 12 is The Y-axis part 12a is deformed so as to be separated from each other, so that the mass part 6 is displaced to the right without displacing the detection movable electrode 7 connected to the damper 12 in the X-axis direction (right side).
The gimbal beam 11 is designed so that the mass portion 6 is not easily displaced in the X-axis direction with respect to the gimbal portion 5 and is easily displaced in the Y-axis direction. Therefore, when the gimbal part 5 is displaced in the X-axis direction, the mass part 6 is displaced by being stretched or pulled by the gimbal beam 11.

  If the angular velocity around the Z-axis acts on the acceleration / angular velocity composite sensor in this state, the Coriolis force expressed by the equation (7) acts on all the components vibrating in the X-axis direction.

Here, M is the mass of all the components oscillating in the X-axis direction of the vibrator, v is the velocity, and Ω is the angular velocity around the Z-axis.
Since the Coriolis force is an outer product of the velocity of the vibrating component and the applied angular velocity, plus / minus in the Y-axis direction varies depending on the vibration direction of the component and the direction of the angular velocity. Therefore, in the case of a pair of left and right vibrators 2 oscillating in a direction symmetric with respect to the mirror symmetry plane SY, the Coriolis force acting on the above-described components always has the opposite sign in the Y-axis direction.

  When the Coriolis force is applied, the component oscillating in the X-axis direction is excited by the vibration in the Y-axis direction, but the frame portion 8, the drive movable electrode 9, and the gimbal portion 5 are displaced in the Y-axis direction. Since the first drive beam 10 and the second drive beam 15 are supported on the substrate 1 so that vibration is difficult, the frame portion 8, the drive movable electrode 9, and the gimbal portion 5 cannot vibrate in the Y-axis direction. . However, since the mass portion 6 is connected and supported by the gimbal beam 11 so as to be easily displaced and vibrated in the Y-axis direction, the mass portion 6 vibrates in the Y-axis direction by Coriolis force as shown in FIG. Become. That is, when a Coriolis force that displaces the mass portion 6 upward in FIG. 5 is generated, the upper and lower gimbal beams 11 are slightly bent and deformed in a central shape fixed to the mass portion 6, and the mass portion 6 Is displaced upward with respect to the gimbal portion 5. Following the displacement of the mass portion 6, the detection movable electrode 7 connected by the damper 12 is also displaced in the Y-axis direction (upward).

  The damper 12 is designed to absorb the displacement (amplitude) when the mass portion 6 is displaced (vibrated) in the X-axis direction. Further, the detection movable electrode 7 is supported by the detection beam 14 so that it is not easily displaced (vibrated) in the X-axis direction and is easily displaced or vibrated in the Y-axis direction. Therefore, even if the mass portion 6 vibrates in the X-axis direction, the detection movable electrode 7 does not vibrate in the X-axis direction. However, when the mass portion 6 vibrates in the Y-axis direction due to the Coriolis force, the detection movable electrode 7 vibrates in the Y-axis direction following the vibration of the mass portion 6. By this vibration, the interval between the comb teeth of the detection movable electrode 7 and the detection fixed electrode 4 changes, and the capacitance changes. The capacitance is as shown in the following equation (8) in a steady state, but when the angular velocity is applied and the detection movable electrode 7 is displaced, it is as shown in the following equation (9).

  Here, n is the number of comb teeth of the detection fixed electrode 4, S is the overlapping area of the detection movable electrode 7 and the detection fixed electrode 4, ε is the dielectric constant of the operating atmosphere, and g is the detection movable electrode 7 in a steady state. An interval between the comb teeth and the detection fixed electrode 4, Δg is a change amount of an interval between the comb teeth of the detection movable electrode 7 and the detection fixed electrode 4 by application of acceleration and / or angular velocity.

  Using the acceleration angular velocity composite sensor of the present embodiment, the vibrator 2 is driven by a drive circuit (capacitance detection circuit 20, amplitude control circuit 21 and AC voltage source 22 shown in FIG. By reading the capacitance change between the electrode 7 and the detection fixed electrode 4, not only the angular velocity but also the acceleration can be measured.

  Specifically, in the sensor device using this composite sensor, when an angular velocity around the Z-axis is applied, the detection movable electrode 7 is moved in the + Y-axis direction together with the mass portion 6 on the left side of the mirror symmetry plane SY in FIG. When it vibrates, the detection movable electrode 7 in the gimbal portion 5 on the right side of the mirror symmetry plane SY in FIG. 1 vibrates in the −Y axis direction (hereinafter, “right” and “left” are described in FIG. 1). Meaning “right side” and “left side” with respect to the mirror symmetry plane SY). Accordingly, the left detection fixed electrode 4 and the right detection fixed electrode 4 appear with opposite signs of the capacitance change, for example, + C1 (F) on the left and -C1 (F) on the right. Therefore, the change in capacitance proportional to the angular velocity can be known by subtracting the change in capacitance of the left and right detection fixed electrodes 4.

  When acceleration in the Y-axis direction is applied, the left and right mass portions 6 and the detection movable electrode 7 are both displaced in the same direction. For example, if the left mass portion 6 and the detection movable electrode 7 are displaced in the + Y axis direction, the right mass portion 6 and the detection movable electrode 7 are similarly displaced in the + Y axis direction. Accordingly, the detection fixed electrodes 4 in the left and right gimbals 5 have the same sign of the change in capacitance. Therefore, it is possible to know the change in capacitance proportional to the acceleration by adding the change in capacitance of the left and right detection fixed electrodes 4. In practice, it is preferable to read a change in capacitance as a change in voltage by a C / V conversion circuit.

Thus, in this embodiment, since the mass part 6 and the detection movable electrode 7 are supported in the closed gimbal part 5 having high rigidity, the generation of noise components based on the bending or deformation of the gimbal part 5 is suppressed. be able to.
Further, since the mass portion 6 and the detection movable electrode 7 are connected by the damper 12 that absorbs the displacement in the X-axis direction, even if the mass portion 6 is displaced in the X-axis direction, the displacement is applied to the detection movable electrode 7. Transmission is suppressed, and displacement of the mass portion 6 in the X-axis direction is prevented from affecting the capacitance between the detection movable electrode 7 and the detection fixed electrode 4.

Further, since the gimbal part 5, the mass part 6, the detection movable electrode 7 and the damper 12 are arranged symmetrically about the center line of the mass part 6 in the Y-axis direction, equal displacement can be obtained on the left and right. Can be detected with higher accuracy.
Furthermore, since both end portions of the detection movable electrode 7 are supported by the substrate 1 and the mass portion 6, it is possible to perform stable displacement with less bias compared to a cantilever state in which the detection movable electrode 7 is supported only at one end portion. Thus, the noise component can be further reduced.
And since a pair of vibrator | oscillator 2 is connected with the synchronous beam 16, the drive speed and frequency of both the vibrator | oscillators 2 are transmitted with the synchronous beam 16, it synchronizes, and a detection precision is made by making a frequency and an amplitude correspond. Can be increased.

  Next, suitable dimensional conditions and the like of each component in the acceleration angular velocity composite sensor of the present embodiment will be described.

  Since the frame portion 8 and the gimbal portion 5 act as vibrators, if the width is too thin, the frame portion 8 and the gimbal portion 5 themselves are deformed and the characteristics as an inertial sensor are deteriorated. Further, when the frame portion 8 and the gimbal portion 5 are vibrated by the electrostatic attraction shown by the expression (6), if the frame portion 8 and the gimbal portion 5 are too large, it is necessary to increase the voltage for generating the electrostatic attraction. There is. For this reason, it tends to be difficult to realize low power consumption, which is an advantage of the present composite sensor, and it is difficult to reduce the size. On the other hand, if it is too small, the number n of the above-mentioned distance between the drive movable electrodes 9 formed inside the frame portion 8 becomes small, so that the driving force becomes small and the displacement and amplitude of the frame portion 8 and the gimbal portion 5 become small. It tends to be.

  Further, the detection movable electrode 7 and the detection fixed electrode 4 formed inside the gimbal portion 5 are also reduced, and the change in capacitance after application of acceleration and angular velocity is likely to be smaller than in the above formulas (8) and (9). There is a tendency. Therefore, the width of the frame portion 8 and the gimbal portion 5 is preferably 5 μm to 100 μm. The size of the frame portion 8 and the gimbal portion 5 is preferably 100 μm to 3 mm in the X-axis direction and the Y-axis direction, respectively.

If the comb teeth of the driving fixed electrode 3 and the driving movable electrode 9 are thinned, the comb teeth themselves may be deformed, and the comb teeth may come into contact with each other. If the comb teeth come into contact with each other, the potential difference becomes zero, so electrostatic attraction is not generated. On the contrary, if the comb teeth are thickened, the number of comb teeth that can be formed in the frame portion 8 is reduced, and thus the electrostatic attractive force tends to be reduced. Therefore, the width of the comb teeth is preferably 1 μm to 30 μm.
When the length of the comb teeth is increased, the comb teeth themselves are deformed and tend to come into contact with each other. Conversely, when the length of the comb teeth is shortened, the displacement and / or amplitude of the vibrator tends to be reduced. Therefore, the length of the comb teeth is preferably 1 μm to 30 μm.

  As shown in the above equation (6), the electrostatic attraction can be increased by reducing the distance d between the comb teeth of the driving fixed electrode 3 and the driving movable electrode 9. However, it is difficult to make it too small from the viewpoint of the manufacturing process, and when it is too small, the comb teeth of the drive movable electrode 9 tend to come into contact with the comb teeth of the drive fixed electrode 3. On the contrary, when the distance d between the comb teeth is increased, the electrostatic attractive force tends to be reduced, and it tends to be difficult to obtain a desired displacement and amplitude. Therefore, the comb spacing d is preferably 0.5 μm to 10 μm.

  The frame portion 8 and the gimbal portion 5 are preferably displaced (vibrated) only in the X axis direction (drive shaft direction). Therefore, the first drive beam 10 and the second drive beam 15 are designed to be short in the X axis direction and long in the Y axis direction. If the length in the X-axis direction is shortened, it tends to be difficult to manufacture, and if it is thicker, the displacement and amplitude of the frame portion 8 and the gimbal portion 5 tend to be smaller. It is necessary to lengthen the length. Increasing the length in the Y-axis direction tends to increase the size of the composite sensor. Further, when the length in the Y-axis direction is shortened, the displacement and amplitude of the frame portion 8 and the gimbal portion 5 tend to be small, and in order to obtain a desired displacement and amplitude, it is necessary to shorten the length in the X-axis direction. is there. Thus, there is a correlation between the length in the X-axis direction and the length in the Y-axis direction of the first drive beam 10 and the second drive beam 15, and it is difficult to design alone. Therefore, the length in the X-axis direction (drive beam width) is preferably 1 μm to 30 μm, and the length in the Y-axis direction (drive beam length) is preferably 50 μm to 1 mm.

  When the frame portion 8 and the gimbal portion 5 are displaced (vibrated) in the X-axis direction, the first drive beam 10 and the second drive beam 15 are displaced (vibrated) to the same extent. Therefore, in order that the first drive beam 10 and the second drive beam 15 do not contact the drive fixed electrode 3, the drive amplitude detection fixed electrode 13, and the gimbal portion 5, it is necessary to be separated from the displacement amount or the amplitude. Preferably, the distance is 0.5 μm to 10 μm. If it is smaller than 0.5 μm, the amplitude tends to be small and the sensitivity tends to be small, and if it is larger than 10 μm, the composite sensor tends to be large.

  The synchronization beam 16 connecting the left and right frame portions 8 is for the right frame portion 8 and the left frame portion 8 to vibrate at the same speed. If the length of the synchronization beam 16 in the X-axis direction is shortened, it tends to be difficult to manufacture, and if the length is increased, the displacement and amplitude tend to decrease. At this time, in order to obtain a desired displacement and amplitude, It is necessary to increase the length. If the length in the Y-axis direction is increased, downsizing, which is an advantage of the present composite sensor, becomes difficult. Further, when the length in the Y-axis direction is shortened, it is difficult to obtain a desired displacement and amplitude. Accordingly, the length in the X-axis direction (the beam width of the synchronizing beam 16) is preferably 1 μm to 30 μm, and the length in the Y-axis direction (the beam length of the synchronizing beam 16) is preferably 50 μm to 1 mm. .

If the drive fixed electrode 3, the drive amplitude detection fixed electrode 13, and the drive movable electrode 9 are made thin, they tend to be deformed themselves when a voltage is applied. Conversely, when the thickness is increased, the composite sensor tends to be larger. Therefore, the driving fixed electrode 3, the driving amplitude detecting fixed electrode 13, and the driving movable electrode 9 are preferably 5 μm to 100 μm.
The frame portion 8 and the gimbal portion 5 vibrate in the X axis direction, but cannot vibrate in the Y axis direction. Therefore, it is the mass portion 6 that causes the detection movable electrode 7 to be displaced or vibrated in the Y-axis direction (detection axis direction). As shown in the above equation (7), the Coriolis force is proportional to the mass of the vibrator 2 vibrating in the X-axis direction (drive axis direction).

  Therefore, it is necessary to enlarge the mass portion 6 in order to obtain a highly sensitive composite sensor. However, if it is made large, it tends to be difficult to reduce the size of the sensor, which is an advantage of this composite sensor. On the other hand, sensitivity tends to decrease with decreasing size. Therefore, the length of the mass portion 6 in the X-axis direction is preferably 50 μm to 1 mm, the length in the Y-axis direction depends on the size of the gimbal portion 5, and the mass portion 6 is displaced or vibrated in the Y-axis direction. It is sometimes preferable to keep the gimbal part 5 away from the gimbal part 5. Preferably, the distance is 0.5 μm to 10 μm. If it is smaller than 0.5 μm, it tends to be difficult to manufacture from the viewpoint of manufacturing error, and if it is larger than 10 μm, this composite sensor tends to be large.

  The gimbal beam 11 connects and supports the mass portion 6 with respect to the gimbal portion 5 so that it is difficult to displace and vibrate in the X-axis direction and easily displace and vibrate in the Y-axis direction. The length of the gimbal beam 11 in the X-axis direction depends on the size of the gimbal portion 5, and the length of the Y-axis direction is preferably 0 from the viewpoint of the displacement of the mass portion 6 in the Y-axis direction and the magnitude of the amplitude. The thickness is preferably 5 μm to 10 μm. If it is smaller than 0.5 μm, it tends to be difficult to manufacture from the viewpoint of manufacturing error, and if it is larger than 10 μm, the displacement and amplitude of the mass portion 6 tend to be small.

  The damper 12 is for causing the detection movable electrode 7 to be displaced or vibrated in synchronization with the displacement or vibration of the mass portion 6 in the Y-axis direction. However, the displacement and vibration of the mass portion 6 in the X-axis direction are absorbed, and the detection movable electrode 7 is connected and supported so that the displacement and vibration are difficult to occur in the X-axis direction. The Y-axis portion 12a of the damper 12 is designed to be short in the X-axis direction and long in the Y-axis direction. The length in the Y-axis direction depends on the length of the mass portion 6 in the Y-axis direction. If the length in the Y-axis direction is shortened, it tends to be difficult to absorb the displacement and vibration of the mass portion 6 in the X-axis direction, and it is necessary to shorten the length in the X-axis direction in order to almost absorb it. . Conversely, when the length in the Y-axis direction is increased, the size of the composite sensor tends to increase. Further, when the length in the X-axis direction is shortened, it tends to be difficult to manufacture. Conversely, if the length in the X-axis direction is increased, it is necessary to increase the length in the Y-axis direction in order to absorb the displacement and vibration of the mass portion 6 in the X-axis direction. Therefore, the length of the damper 12 in the X-axis direction is preferably 0.5 μm to 10 μm, and the length in the Y-axis direction is preferably 50 μm to 1.5 mm.

  The X-axis part 12b of the damper 12 tends to come into contact with the pair of Y-axis parts 12a when the length in the X-axis direction is shortened. Even if it is displaced or vibrated, it tends to be difficult to cause the movable movable electrode 7 to be displaced or vibrated in the Y-axis direction in synchronization with the mass portion 6. Therefore, the length in the X-axis direction of the X-axis portion 12b is preferably 1 μm to 30 μm, and the length in the Y-axis direction is preferably 5 μm to 100 μm.

  One end of the detection beam 14 is fixed to the substrate 1, and the other end supports the detection movable electrode 7. The detection movable electrode 7 is difficult to be displaced or vibrated in the X-axis direction, and in the Y-axis direction. Designed for easy displacement and vibration. When the length of the detection beam 14 in the X-axis direction is shortened, the displacement and vibration of the detection movable electrode 7 tend to be too small, and when the length is long, the frame portion 8 becomes large and the composite sensor tends to be large. When the length in the Y-axis direction is increased, the detection movable electrode 7 tends to be difficult to be displaced or vibrated in the Y-axis direction. Therefore, the length of the detection beam 14 in the X-axis direction is preferably 10 μm to 1 mm, and the length in the Y-axis direction is preferably 0.5 μm to 20 μm.

  Next, the manufacturing method of the acceleration angular velocity composite sensor of this embodiment is demonstrated with reference to FIG.6 and FIG.7.

First, as shown in FIG. 6A, an SOI wafer (semiconductor thin plate) 34 having a three-layer structure of Si (silicon) structure layer (semiconductor thin film) 31 / oxide film layer 32 / Si handle layer 33 is prepared. . When a thin Si structure is manufactured, a Si wafer having a desired thickness cannot be manufactured because of its low mechanical strength. However, by forming the Si handle layer 33 and the oxide film layer 32 into three layers during the manufacturing process. By removing the Si handle layer 33 and the oxide film layer 32, the Si structure having a desired thickness can be manufactured.
In order to reduce power consumption, it is preferable that the Si structure layer 31 to be used has a resistance as low as possible. However, since the SOI wafer 34 having the low-resistance Si structure layer 31 is relatively expensive, the resistivity is preferably 0.001 Ωcm to 1 Ωcm.

  The Si structure layer 31 (sometimes referred to as an SOI layer) is preferably 5 μm to 100 μm. If the Si structure layer 31 is thin, the mass of the mass portion 6 tends to be small, and the sensitivity of acceleration and angular velocity tends to be too small. Conversely, if the Si structure layer 31 is thick, the interval between the comb teeth of the drive and detection electrodes cannot be reduced from the viewpoint of the manufacturing process. For this reason, the electrostatic attraction force of driving is reduced, or the capacitance at the steady state due to the increase in the distance between the detection movable electrode 7 and the detection fixed electrode 4 is increased, and the sensitivity of acceleration and angular velocity is reduced. It tends to be too much.

  The thickness of the oxide film layer 32 (sometimes referred to as a BOX layer) is preferably 100 nm to 2 μm. If the oxide film layer 32 is thin, it tends to be difficult to release the Si structure from the Si handle layer 33. Conversely, if the oxide film layer 32 is too thick, the wafer cost tends to be too high. Next, the thickness of the Si handle layer 33 (sometimes referred to as a base wafer) is preferably 300 μm to 1 mm. When the thickness is reduced, a wafer having a large diameter cannot be used, so the yield per wafer is reduced, and the manufacturing cost of the composite sensor tends to increase. On the contrary, if the thickness of the Si handle layer 33 is increased, the wafer price is increased and the manufacturing cost of the composite sensor is increased.

First, the SOI wafer 34 is cleaned to clean the surface. Next, the SOI wafer 34 is thermally oxidized as shown in FIG. 6B to form an oxide film (SiO ₂ ) 35 on the surfaces of the Si structure layer 31 and the Si handle layer 33. Further, a photoresist is spin-coated on the surface of the Si structure layer 31 and heated, and then exposed through a desired mask. Thereafter, after developing and rinsing the photoresist, as shown in FIG. 6C, the patterned first photoresist 36 is fixed by heating.

  Using the first photoresist 36 as a mask, as shown in FIG. 6D, the oxide film 35 is selectively etched with hydrofluoric acid, and then the first photoresist 36 is removed with a solvent. The photoresist is again spin-coated and heated, and then exposed through another mask. Thereafter, after developing and rinsing the photoresist, as shown in FIG. 6E, the second photoresist 37 patterned by heating is fixed.

  Subsequently, anisotropic deep etching of Si is performed by the first ICP-RIE (inductively coupled plasma reactive ion etching) apparatus using the second photoresist 37 as a mask. The etching depth at this time is preferably 5 μm to 50 μm. The etching depth here means the distance between the substrate 1 and the vibrator 2 composed of the Si structure layer 31 in the final composite sensor. Therefore, if this etching depth is shallow, it means that the distance between the substrate 1 and the Si structure layer 31 is small, and if this distance is small, the drive amplitude tends to be small.

  The reason is that the influence of the viscous resistance of the gas in the atmosphere in which this composite sensor is used tends to increase. On the contrary, if the etching depth is to be increased, it is necessary to increase the thickness of the Si structure layer 31 of the SOI wafer 34, which is a raw material. The interval between the detection electrode comb teeth cannot be reduced. For this reason, the electrostatic attraction force of driving is reduced, or the capacitance at the steady state due to the increase in the distance between the detection movable electrode 7 and the detection fixed electrode 4 is increased, and the sensitivity of acceleration and angular velocity is reduced. It tends to be too much.

  Thereafter, as shown in FIG. 6F, the second photoresist 37 is removed with a solvent and washed. Next, as shown in FIG. 6G, Si anisotropic deep etching is performed by the second ICP-RIE apparatus using the oxide film 35 as a mask. At this time, etching is performed up to the interface between the Si structure layer 31 and the oxide film 35. Then, as shown in FIG. 6H, the oxide film 35 which is a mask for the second Si anisotropic deep etching is removed and washed. The Si structure layer 31 patterned in this manner serves as a pair of vibrators 2.

  Next, a wiring for supplying a voltage to the drive fixed electrode 3, the drive amplitude detecting fixed electrode 13 and the detection fixed electrode 4 or reading a change in capacitance is prepared.

  As shown in FIG. 7A, a metal film 41 is formed on the surface of the cleaned glass substrate 1 as shown in FIG. 7B. Specifically, a Cr film is formed by a sputtering apparatus, and then an Au film is formed to form the metal film 41. The Cr film thickness is preferably 10 nm to 100 nm. The Cr film is an adhesive layer for increasing the adhesive force of the Au film to the substrate 1 made of glass. For this reason, the thinner the Cr film, the stronger the adhesive force. However, if the Cr film is too thin, it tends to be difficult to form the Cr film on the entire surface of the substrate 1. Conversely, if the Cr film is too thick, the adhesive force tends to be weakened. The Au film only needs to have conductivity, and a thickness of 100 nm to 1 μm is suitable. If the Au film thickness is too small, the resistance tends to increase. On the contrary, if it is increased, the manufacturing cost tends to increase.

A photoresist is spin coated on the surface of the metal film 41 and heated, and then exposed through a desired mask. Then, after developing and rinsing the photoresist, as shown in FIG. 7C, the patterned third photoresist 42 is fixed by heating.
Subsequently, the Au film of the metal film 41 is selectively etched with an Au etchant (iodine 1.2 g + ammonium iodide 8 g + water 40 ml + methanol 60 ml) using the third photoresist 42 as a mask, and then washed with distilled water. The Cr film of the metal film 41 is selectively etched and cleaned with a Cr etchant (diammonium cerium (4) 20 g + perchloric acid 5.2 g + water 88 ml). Thereafter, as shown in FIG. 7D, the photoresist is removed with a solvent. The metal film 41 patterned on the substrate 1 in this way serves as a wiring for supplying a voltage to the drive amplitude detection fixed electrode 13 and the detection fixed electrode 4 and reading a change in capacitance.

  As shown in FIG. 7E, the SOI wafer 34 having the patterned Si structure layer 31 and the substrate 1 having the patterned metal film 41 are arranged so that the Si structure layer 31 faces the substrate 1 side. Anodically bonded. Finally, in order to remove the oxide film layer 32 of the SOI wafer 34 and release the Si structure layer 31 as a pair of vibrators 2 from the SOI wafer 34, as shown in FIG. Then, the oxide film layer 32 is removed, washed and dried. That is, the vibrator 2 is partially fixed on the substrate 1, and the unfixed portion is supported in a state of floating from the substrate 1. Thus, this composite sensor is produced as a MEMS device.

  As described above, the composite sensor according to the present embodiment is a MEMS device in which the pair of vibrators 2 are finely processed by patterning using an exposure technique. Therefore, a very fine and high dimensional accuracy is obtained, and the high symmetry of both vibrators 2 is obtained. Can be obtained.

  The technical scope of the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

For example, in the manufacturing method of the above embodiment, the SOI wafer 34 is used as a raw material, but it can also be manufactured using a Si wafer. Moreover, although ICP-RIE is used for anisotropic deep etching of Si, it can also be manufactured by ordinary RIE. Alternatively, anisotropic deep etching of Si can be performed by alternately performing anisotropic Si wet etching and isotropic Si wet etching. Although the metal film 41 of Au / Cr film is used for the metal wiring, other metal films 41 such as a Pt / Ti film are also possible, such as ITO (indium tin oxide) and ZnO (zinc oxide). A transparent conductive film can also be used as the metal film 41.
Moreover, in the said embodiment, although it is set as the composite sensor which detects an acceleration and an angular velocity simultaneously, it can be used also as a sensor which detects only one of an acceleration and an angular velocity.

In the acceleration angular velocity composite sensor of one embodiment concerning the present invention, it is a top view showing a structure with a wiring state. In the acceleration angular velocity composite sensor of this embodiment, it is a principal part top view which shows a vibrator | oscillator. In this embodiment, it is explanatory drawing which shows the operation | movement principle of a gyro. In this embodiment, it is an enlarged schematic diagram of the principal part which shows the displacement state of the mass part and damper by drive vibration. In this embodiment, it is an enlarged schematic diagram of the principal part which shows the displacement state of the mass part and damper by detection vibration. FIG. 2 is a cross-sectional view showing the manufacturing method of the acceleration angular velocity composite sensor of the present embodiment in the order of steps in the cross section along line A of FIG. FIG. 2 is a cross-sectional view illustrating the manufacturing method of the acceleration / angular velocity composite sensor of the present embodiment in the order of steps in the cross section along line A of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Vibrator, 3 ... Drive fixed electrode, 4 ... Detection fixed electrode, 5 ... Gimbal part (outer frame part), 6 ... Mass part (weight part), 7 ... Detection movable electrode, 8 ... Frame part , 12 ... damper, 13 ... fixed electrode for detecting drive amplitude, 16 ... synchronous beam, 31 ... Si structure layer (semiconductor thin film), 34 ... SOI wafer (semiconductor thin plate), SY ... mirror symmetry plane

Claims (6)

An insulating substrate on the top surface;
A pair of vibrators supported on the substrate so as to be displaceable with respect to the substrate and arranged symmetrically about a symmetry plane;
A driving fixed electrode which is fixed on the substrate and applies a voltage between the vibrator and vibrates the vibrator in a driving axis direction orthogonal to the symmetry plane;
A detection fixed electrode that is fixed on the substrate and detects a change in capacitance between the vibrator in a detection axis direction orthogonal to the drive axis direction, and
A closed outer frame portion supported so that the vibrator is displaceable in the drive axis direction and the displacement in the detection axis direction is suppressed;
A weight part that is displaceable in the detection axis direction with respect to the outer frame part and that is supported in the outer frame part with displacement in the drive axis direction being suppressed,
Displacement in the detection axis direction is suppressed, and displacement in the drive axis direction is suppressed, and the capacitance is changed between the weight portion and the substrate in the outer frame portion and the detection fixed electrode. An acceleration angular velocity composite sensor comprising a detection movable electrode for detection.   2. The detection movable electrode according to claim 1, wherein the detection movable electrode is coupled to the weight part via a damper that absorbs the displacement of the weight part in the drive axis direction and transmits the displacement in the detection axis direction. The described acceleration angular velocity composite sensor.   The said outer frame part, the said weight part, the said detection movable electrode, and the said damper are arrange | positioned left-right symmetrically centering | focusing on the centerline of the said detection-axis direction in the said weight part. Acceleration angular velocity composite sensor.   2. The detection movable electrode is a comb electrode in which comb teeth are arranged in the detection axis direction, and is supported by the substrate and the weight portion at both ends in the detection axis direction. Or the acceleration angular velocity composite sensor of 2.   3. The acceleration angular velocity according to claim 1, wherein the pair of vibrators are coupled via a synchronous beam that absorbs the displacement in the drive axis direction and transmits the displacement in the detection axis direction. Compound sensor.   The acceleration angular velocity composite sensor according to claim 1 or 2, wherein the pair of vibrators are formed by patterning a semiconductor thin plate or a semiconductor thin film by photolithography.

Images