JP2005055377A - Speed detection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a speed detection device capable of miniaturizing the occupancy area of the speed detection device for detecting two axial angular velocity. <P>SOLUTION: A 1st vibration electrode 3 and a 2nd vibration electrode 4 arranged along the normal line of the device substrate (Z axis) are vibrated mutually in reverse phase in a direction of Z axis, while being supported on the device substrate displaceably in X axis and Y axis directions. At the same height in Z axis of the 1st vibration electrode 3 and in a positive X axis direction, a 1st X axis electrode 5 is arranged, and in a positive Y direction, a 1st Y axis electrode 7 is arranged. At the same height in Z axis of the 2nd vibration electrode 4 and in the negative X axis direction, a 2nd X axis electrode 6 is arranged, and in the negative Y direction, a 2nd Y axis electrode 8 is arranged. The force acting in the X axis direction is detected from the capacitance between the 1st vibration electrode 3 to the 1st X axis electrode 5, and the capacitance between the 2nd vibration electrode 4 to the 2nd X axis electrode 6. The force acting in Y axis direction is detected from the capacitance between the 1st vibration electrode 3 to the 1st Y axis electrode 7, and the capacitance between the 2nd vibration electrode 4 to the 2nd Y axis electrode 8. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a speed detection device, and more particularly to a speed detection device using a vibration gyro.

  A speed detection device that detects acceleration and angular velocity is used for controlling the posture of a vehicle in a car navigation system, calculating a traveling direction, and preventing camera shake in a handy camera. This speed detection device is desired to stably detect and detect only the angular velocity component or the acceleration component without being affected by environmental disturbances such as internal noise and irregular acceleration.

  There are various types of such speed detection devices, and a vibrating gyroscope is used for an ultra-compact speed detection device to which micromachine technology is applied. A speed detection device using a vibrating gyroscope includes a vibrating body, a drive electrode unit that electrically vibrates the vibrating body, and a pair of detection electrode units that electrostatically detect displacement of the vibrating body. These detection electrode portions are arranged with the vibrating body sandwiched from a predetermined direction with respect to the vibration direction of the vibrating body, and the detection electrode portion outputs two signals that are 180 ° out of phase with each other. Yes.

  In the speed detection device having such a configuration, by applying a driving signal having a constant frequency and a constant amplitude from the driving circuit to the driving electrode unit, a driving force Fe is applied to the vibrating body to cause mechanical vibration at a specific vibration frequency. Let me. In this state, when acceleration or angular velocity is applied to the vibrating body, the vibrating body is displaced, and a change in capacitance appears in the detection electrode portion. At this time, when acceleration is given, the vibrating body is displaced in the direction of the acceleration force Fk, and therefore vibrates with a vibration vector obtained by combining the driving force Fe and the acceleration force Fk. On the other hand, when the angular velocity is given, the vibrating body is displaced in the direction in which the Coriolis force Fc is generated, and thus vibrates with a vibration vector obtained by combining the driving force Fe and the Coriolis force Fc. When acceleration and angular velocity occur simultaneously, these combined vector vibrations are obtained.

  For this reason, the detection electrode unit is provided with an acceleration signal component removal circuit that removes a signal component generated by the acceleration acting on the vibrating body, so that only the signal component due to the angular velocity is detected. , See Patent Document 1 below).

Japanese Patent Laid-Open No. 2001-183137 (see FIGS. 1 and 6, pages 2 to 4)

  However, in the velocity detection device having the above-described configuration, only the angular velocity component in the direction corresponding to the axial direction in which the detection electrode unit is disposed is detected. Therefore, in order to detect the biaxial angular velocity, the detection electrode unit Two velocity output devices with different arrangement directions must be arranged on the same device substrate. Therefore, the area occupied by the speed detection device is increased, and further miniaturization of a portable device such as a handy camera provided with the speed detection device is prevented. Also, the provision of a separation circuit for separating the angular velocity and the acceleration is a factor that increases the area occupied by the velocity detection device.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a speed detection device capable of reducing the area occupied by a speed detection device that detects a biaxial angular velocity.

  In order to achieve such an object, the speed detection device of the present invention includes a first vibration electrode, a second vibration electrode, a first detection electrode, and a second detection electrode. Among these, the first vibration electrode and the second vibration electrode are disposed above the device substrate along a first axis that is a normal line of the device substrate. The first vibration electrode and the second vibration electrode vibrate in the first axial direction in opposite phases and are displaceable in the second axial direction orthogonal to the first axis. It is supported by. The first detection electrode has the same height as the first vibration electrode and the first axis, and a predetermined distance between the first detection electrode and the first vibration electrode. Is arranged. On the other hand, the second detection electrode has the same height on the first axis as that of the second vibration electrode and a predetermined interval between the second vibration electrode and the negative direction of the second axis. Is arranged. In such an arrangement state, the force applied in the second axial direction is detected by the capacitance between the first vibration electrode and the first detection electrode and the capacitance between the second vibration electrode and the second detection electrode. It is the composition to do.

  In the speed detection device having such a configuration, a force in the second axial direction orthogonal to the first axial direction is applied to the first vibrating electrode and the second vibrating electrode that vibrate in the first axial direction in opposite phases to each other. If the force is acceleration, the first vibrating electrode and the second vibrating electrode are displaced with the same magnitude in the same direction of the second axis. Therefore, the combined capacitance obtained by combining the capacitance between the first vibrating electrode and the first detection electrode and the capacitance between the second vibrating electrode and the second detection electrode in series does not change.

  On the other hand, if the force applied in the second axial direction orthogonal to the first axial direction is the Coriolis force due to the angular velocity, the first vibrating electrode and the second vibrating electrode are the same in the opposite direction of the second axis. Displace with the size of. Therefore, the combined capacitance obtained by combining the capacitance between the first vibration electrode and the first detection electrode and the capacitance between the second vibration electrode and the second detection electrode in series is the first vibration electrode and the second detection electrode. It changes according to the displacement of the vibrating electrode.

  Therefore, only the Coriolis force generated by the angular velocity can be obtained separately from the acceleration. A two-axis Coriolis force can be obtained by arranging two sets of the first detection electrode and the second detection electrode along two second axes orthogonal to each other.

  In addition, since the first vibration electrode and the second vibration electrode are disposed along the first axis that is the normal line of the device substrate, the first vibration electrode and the second vibration electrode are located above the device substrate. Thus, the area occupied by the two-axis speed detection device is almost the same as that of the one-axis speed detection device.

  As described above, according to the speed detection device of the present invention, the biaxial angular velocity can be detected without providing a separation circuit for separating the acceleration, and the two vibration electrodes are connected to the normal line of the device substrate. The area occupied by the speed detection device for detecting the biaxial angular velocity can be reduced, and the portable device such as a handy camera using the speed detection device can be downsized. Can be achieved.

  Embodiments of the speed detection device of the present invention will be described below in detail with reference to the drawings.

<Configuration of speed detection device>
FIG. 1 is a schematic diagram illustrating a configuration of a speed detection device according to the embodiment, and FIG. 2 is a cross-sectional view in the X-axis direction (Y-axis direction) of FIG. In FIG. 2, reference numerals of members in the cross section in the Y-axis direction are shown with parentheses.

  The speed detection apparatus shown in these drawings is a speed detection apparatus using a vibrating gyroscope, and is used, for example, to detect an angular velocity. This speed detection device is formed on a device substrate 1 made of, for example, single crystal silicon (shown only in FIG. 2), and is arranged along a first axis (Z axis) that is a normal line of the device substrate 1. The first detection electrode 5 and the second detection electrode 6 (hereinafter referred to as the first X-axis electrode 5 and the second X-axis) arranged in the X-axis direction of each of the vibration electrodes 3 and 4. In addition, a first detection electrode 7 and a second detection electrode 8 (hereinafter referred to as a first Y-axis electrode 7 and a second Y-axis electrode 8) arranged in the Y-axis direction of each vibration electrode 3, 4. I have.

  Among these, the first vibration electrode 3 and the second vibration electrode 4 are arranged in the order of the first vibration electrode 3 and the second vibration electrode 4 from the device substrate 1 side. The first vibrating electrode 3 and the second vibrating electrode 4 include a substantially square plate-like vibrating portion 3a, 4a and wirings 3b, 4b extending in four directions from the four corners of the vibrating portions 3a, 4a. And is composed of. The vibrating portions 3a and 4a are supported on the device substrate 1 via the wirings 3b and 4b so that the vibrating portions 3a and 4a are arranged in the same direction at intervals along the Z axis that is the normal line of the device substrate 1. .

  In the state supported by the wirings 3b and 4b, the vibrating portions 3a and 4a can vibrate in the opposite phase in the Z-axis direction and in the X-axis and Y-axis (that is, second axis) directions perpendicular to the Z-axis. Displaceable. Each of the vibrating portions 3a and 4a is configured to vibrate in the Z-axis direction in opposite phases with the alternating drive voltage supplied from the wirings 3b and 4b. The wirings 3b and 4b are kept in an insulated state. Suppose that you are leaning.

  In addition, the first X-axis electrode 5 has the same height on the Z-axis as the first vibrating electrode 3 and a predetermined distance dx (see FIG. 2) between the first vibrating electrode 3 and the first X-axis electrode 5. It is arranged in the positive direction of the X axis with respect to the vibrating electrode 3. The first X-axis electrode 5 is supported on, for example, a support column 5a erected on the device substrate 1, and one end side in the X-axis direction is arranged at a predetermined interval dx on the side end of the first vibration electrode 3a. As a result, the capacitive element 1 x is configured together with the first vibrating electrode 3. The first vibrating electrode 3 vibrates in the Z-axis direction so that the capacitance C1x of the capacitive element 1x is kept constant regardless of the vibration of the first vibrating electrode 3 in the normal state in the Z-axis direction. It is assumed that the film thickness of the first X-axis electrode 5 is set so that the film thickness range of the first X-axis electrode 5 is within the film thickness range of the first vibrating electrode 3.

  On the other hand, the second X-axis electrode 6 has the same height on the Z-axis as the second vibration electrode 4 and a predetermined distance dx (see FIG. 2) between the second vibration electrode 4 and the second X-axis electrode 6. It is arranged in the negative direction of the X axis with respect to the vibrating electrode 4. Similarly to the first X-axis electrode 5, the second X-axis electrode 6 is also supported, for example, on a column 6a erected on the apparatus substrate 1, and constitutes a capacitive element 2x together with the second vibration electrode 4. The capacitive element 2x has a configuration similar to that of the capacitive element 1x described above and is connected in series with the capacitive element 1x so that the combined capacitance is detected.

  Note that the capacitive element 1x and the capacitive element 2x have the same capacitance in a normal state where the first vibrating electrode 3 and the second vibrating electrode 4 are not displaced in the X-axis direction. Further, when the distances dx ± δ between the opposing electrodes in the capacitive elements 1x and 2x are the same, the amount of change in the capacitance of the capacitance C1x of the capacitive element 1x and the capacitance C2x of the capacitive element 2x is configured to be the same. I will do it. Accordingly, the predetermined distance dx between the first vibrating electrode 3 and the first X-axis electrode 5 and the predetermined distance dx between the second vibrating electrode 4 and the second X-axis electrode 6 in the normal state are the same. And Further, the capacitive element 1x and the capacitive element 2x are configured to have the same dielectric constant ε between the electrodes and the same facing area S between the electrodes, and each capacitance in a normal state is C1x = C2x = εS / dx. To do.

  The first Y-axis electrode 7 and the second Y-axis electrode 8 are arranged in the Y-axis direction of the first vibrating electrode 3 and the second vibrating electrode 4, respectively. The configuration is the same as that of the shaft electrode 6, and X is replaced with Y in the description of the first X-axis electrode 5 and the second X-axis electrode 6. The capacitive element 1y between the first Y-axis electrode 7 and the first vibrating electrode 3 and the capacitive element 2y between the second Y-axis electrode 8 and the second vibrating electrode 4 are also the capacitive element 1x and the capacitive element. The configuration is the same as 2x, and the respective capacities in the normal state are C1y = C2y = εS / dy.

<Operation of speed detection device>
Next, the operation of the speed detecting device configured as described above will be described with reference to a schematic cross-sectional view of FIG. Here, the operation of the speed detection device in the X-axis direction will be described, but the operation in the Y-axis direction is the same.

  First, as shown in FIG. 3A, in the normal state, the speed detecting device is in a state where the first vibrating electrode 3 and the second vibrating electrode 4 vibrate in the Z-axis direction in opposite phases. Yes. In this normal state, the capacitances of the capacitive elements 1x and 2x are C1x = C2x = εS / dx, and the combined capacitance Cx connected in series is 1 / Cx = 1 / C1x + 1 / C2x = dx / εS + dx / εS = 2dx / εS.

  In such a state, when a force in the X-axis direction is applied to the speed detection device, if this force is an acceleration force Fa due to acceleration, the first vibrating electrode 3 and the second vibration electrode 3 as shown in FIG. The oscillating electrode 4 is applied with an acceleration force Fa having the same magnitude in the same direction of the X axis (for example, in the negative direction). For this reason, the first vibrating electrode 3 and the second vibrating electrode 4 are displaced by the same magnitude δ in the negative direction of the X axis.

  In this case, the combined capacitance Cx of the capacitive element 1x and the capacitive element 2x connected in series is 1 / Cx = 1 / C1x + 1 / C2x = (dx + δ) / εS + (dx−δ) / εS = 2dx / εS. . For this reason, when the acceleration force Fa in the x direction is applied to the speed detection device in the normal state, a change in the combined capacity due to the acceleration force Fa is not detected.

  On the other hand, as shown in FIG. 3 (3), if the force in the X-axis direction applied to the speed detection device is the Coriolis force Fc due to the angular velocity Ω, the state oscillates in the Z-axis direction in opposite phases. The first vibration electrode 3 and the second vibration electrode 4 are applied with a Coriolis force Fc having the same magnitude in the direction opposite to the X axis. For this reason, the first vibrating electrode 3 and the second vibrating electrode 4 are displaced by the same magnitude δ in the reverse direction of the X axis.

  In this case, the combined capacitance Cx of the capacitive element 1x and the capacitive element 2x connected in series is 1 / Cx = 1 / C1x + 1 / C2x = (dx−δ) / εS + (dx−δ) / εS = 2 (dx −δ) / εS. For this reason, when the Coriolis force Fc in the X-axis direction is applied to the speed detection device in the normal state by the angular velocity, a change in the combined capacity due to the Coriolis force Fc is detected. 3 (3), when the first vibrating electrode 3 and the second vibrating electrode 4 are displaced in the opposite direction of the Z-axis due to vibration, the first vibrating electrode 3 and the second vibrating electrode 3 caused by the Coriolis force Fc are used. The displacement in the X-axis direction of the vibrating electrode 4 is reversed. Therefore, the combined capacitance Cx of the capacitive element 1x and the capacitive element 2x is 1 / Cx = 1 / C1x + 1 / C2x = (dx + δ) / εS + (dx + δ) / εS = 2 (dx + δ) / εS. A change in the composite capacity due to this Coriolis force Fc is detected.

  For this reason, when the acceleration force Fa and the Coriolis force Fc in the X-axis direction are applied to the speed detection device, only the capacity change due to the Coriolis force Fc is detected. From this value, the angular velocity of rotation around the Y axis is determined as the acceleration. It can be obtained in a separated state.

  Since the same detection is performed when the acceleration force Fa and the Coriolis force Fc are applied in the Y-axis direction of the speed detection device, the angular velocity of rotation about the X-axis is obtained in a state separated from the disturbance acceleration. be able to.

  As described above, the velocity detection device of the present embodiment can detect the biaxial angular velocity without providing a separation circuit for separating acceleration. Further, by arranging the first vibrating electrode 3 and the second vibrating electrode 4 along the Z-axis that is the normal line of the apparatus substrate, it is possible to detect the speed of two axes with one element. It is possible to reduce the area occupied by the speed detection device for detecting the angular speed. As a result, it is possible to reduce the size of a portable device such as a handy camera in which this speed detection device is used.

<Method for Manufacturing Speed Detection Device>
Next, a method of manufacturing such a speed detection device will be described based on the sectional process diagrams of FIGS. 5 and 6 with reference to the schematic plan view of FIG. 4 is a schematic plan view of FIG. 1 as viewed from above. Each of FIGS. 5 and 6 corresponds to the AA ′ cross section and the BB ′ cross section in FIG. 4.

  First, as shown in FIG. 5A, a silicon nitride film 101 and a silicon oxide film 102 are formed in this order on the device substrate 1 made of single crystal silicon.

  Next, as shown in FIG. 5 (2), two holes 102x (refer to the AA ′ cross section) in which pillars supporting the first X-axis electrode 5 and the second X-axis electrode 6 are formed, and the first vibrating electrode 4 holes 102a in which pillars supporting 3 are formed, and two holes 102y in which pillars supporting the first Y-axis electrode 7 and the second Y-axis electrode 8 are formed (see the BB ′ cross section) are oxidized. Formed on the silicon film 102.

  Among these, the four holes 102a are arranged at the apexes of a substantially square having sides along the X-axis and Y-axis directions, and the hole 102y is arranged between the two holes 102a arranged along the X-axis direction, A hole 102x is arranged between two holes 102a arranged along the Y-axis direction.

  After that, in particular, the upper opening of one of the two holes 102x is expanded toward the center side in the X-axis direction (C portion of the A-A ′ cross section). Similarly, although not shown here, the upper part of one of the two holes 102y is expanded toward the center in the Y-axis direction.

  Next, as shown in FIG. 5 (3), the pillars 103a, 103x, 103y in which the polysilicon film is embedded in the holes 102a, 102x, 102y are formed by forming the polysilicon film and CMP polishing, The first X-axis electrode 5 and the first Y-axis electrode (7) supported by the pillars 103x and 103y are formed in the portion C where the openings of the holes 102x and 102y are widened. The first Y-axis electrode (7) is not shown. Moreover, the support | pillar 103x is corresponded to the support | pillar 5a demonstrated previously using FIG. Similarly, the column 103y on the side supporting the first Y-axis electrode (7) corresponds to the column (7a) described above with reference to FIG.

  Next, as shown in FIG. 5D, after the whole is covered with the silicon oxide film 104, a recess 104a having a predetermined depth is formed in the silicon oxide films 102 and 104 in correspondence with the formation position of the first vibration electrode. To do. The concave portion 104a has a central portion sandwiched between the four support pillars 103a for supporting the first vibration electrode, and a wiring groove reaching the upper part of the four support pillars 103a from the four corners of the rectangular shape. It will be formed. The recess 104a is formed with only the upper surfaces of the four columns 103a exposed, and the columns 103x and 103y, the first X-axis electrode 5 and the first Y-axis electrode (7) are exposed from the silicon oxides 102 and 104. It will be formed so that it will not occur. The recess 104a is deeper than the first X-axis electrode 5 and the first Y-axis electrode (7).

  Next, as shown in FIG. 6 (5), the polysilicon film is embedded in the recess 104a by the polysilicon film formation and CMP polishing, and the first vibrating electrode 3 (vibration) supported by the four columns 103a. Part 3a and wiring 3b) are formed.

  Thereafter, as shown in FIG. 6 (6), the silicon oxide films (102, 104) on the device substrate 1 are removed by etching. Thereby, the space part a is formed in the lower part of the 1st vibration electrode 3 supported by the four support | pillars 103a. Further, a capacitive element C1x composed of the vibrating portion 3a of the first vibrating electrode 3 and the first X-axis electrode 5 is formed, and similarly, a capacitance formed of the vibrating portion 3a of the first vibrating electrode 3 and the first Y-axis electrode (7). An element (C1y) is formed.

  On the other hand, another identical set 106 formed by the above series of steps is prepared, and this is set as the second vibrating electrode side.

  Then, as shown in FIG. 6 (7), these two sets 106 and 106 are arranged with the first vibrating electrode 3 and the second drive electrode 4 facing each other, and are made of an insulating material such as glass. These two sets 106 and 106 are bonded via a ring-shaped spacer 107. In addition, when the height adjustment is difficult, the two sets 106 and 106 may be bonded by an insulating adhesive in which spacer particles are dispersed. As a result, the second X-axis electrode 6 on the second drive electrode 4 side is supported on the device substrate 1 by the support column 103 x and the spacer 107. For this reason, the support | pillar 103x and the spacer 107 are equivalent to the support | pillar 6a demonstrated previously using FIG. Similarly, the second Y-axis electrode (8) not shown in the cross-sectional view is supported on the device substrate 1 by the support column 103y and the spacer 107. For this reason, these support | pillar 103y and the spacer 107 correspond to the support | pillar (8a) demonstrated previously using FIG.

  As described above, the speed detection device having the configuration described with reference to FIGS. 1 and 2 can be obtained.

  In addition, the manufacturing method demonstrated above is an example to the last, and the speed detection apparatus of this invention is not limited by such a manufacturing method.

  Moreover, in the above embodiment, the structure of the speed detection apparatus of the structure which isolate | separates and detects an angular velocity with respect to acceleration was demonstrated. However, the present invention can also be applied to a speed detection device configured to separate acceleration from angular velocity by connecting a capacitive element and connecting a separation circuit to the capacitive element. Even in this case, since the vibration electrodes for detecting the biaxial acceleration are disposed so as to overlap along the normal line of the device substrate, it is possible to reduce the area occupied by the device.

It is a block diagram of the speed detection apparatus of embodiment. FIG. 2 is a cross-sectional view in the X direction (Y direction) of FIG. 1. It is a cross-sectional schematic diagram explaining the action | operation of a speed detection apparatus. It is a plane schematic diagram explaining the manufacturing method of a speed detection apparatus. It is sectional process drawing (the 1) which shows the manufacturing method of a speed detection apparatus. It is sectional process drawing (the 2) which shows the manufacturing method of a speed detection apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Device substrate, 3 ... 1st vibration electrode, 4 ... 2nd vibration electrode, 5 ... 1st X-axis electrode (1st detection electrode of X-axis direction), 6 ... 2nd X-axis electrode (2nd detection of X-axis direction) Electrode), 7 ... first Y-axis electrode (first detection electrode in the Y-axis direction), 8 ... second Y-axis electrode (second detection electrode in the Y-axis direction), 1x, 2x, 1y, 2y ... capacitance element, dx, dy ... predetermined interval, Fc ... Coriolis force

Claims (3)

A second axis that is arranged above the apparatus substrate along a first axis that is a normal line of the apparatus substrate, vibrates in the first axis direction in opposite phases, and is orthogonal to the first axis A first vibration electrode and a second vibration electrode supported on the device substrate in a state displaceable in a direction;
A first detection electrode disposed in the positive direction of the second axis at the same height on the first axis and the first vibration electrode with a predetermined distance between the first vibration electrode and the first vibration electrode When,
A second detection electrode disposed in the negative direction of the second axis at the same height on the first axis with a predetermined distance between the second vibration electrode and the second vibration electrode And
Detecting a force applied in the second axial direction by a capacitance between the first vibration electrode and the first detection electrode and a capacitance between the second vibration electrode and the second detection electrode. A speed detection device characterized by the above. The speed detection device according to claim 1,
A capacitive element composed of the first vibration electrode and the first detection electrode and a capacitive element composed of the second vibration electrode and the second detection electrode are connected in series, and the two capacitive elements A speed detection apparatus that detects a Coriolis force applied in the second axial direction due to a change in the combined capacity of the first and second axes. The speed detection device according to claim 1,
Two sets of the first detection electrode and the second detection electrode are arranged along two second axes that are orthogonal to each other.

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