JPH0642970A - Angular-velocity sensor - Google Patents

Abstract

PURPOSE:To reduce the leakage output of the title sensor in a stationary state and to enhance the detection accuracy, the reliability and the like of an angular velocity by a method wherein a vibration force by a vibration generation part is balanced with reference to the width direction of a cantilever. CONSTITUTION:After a sensor main body 11 has been formed, a cantilever 13 is vibrated in a stationary state by a piezo-electric body 15, and the displacement amount of the cantilever 13 is inspected by a difference DELTAV (=VL-VR) in detection signals from right and left piezoresistance elements 17. On the basis of an inspection result, an upper-side electrode 15C is trimmed by a laser light source 20, and a cutout part 18 which balances the deformation force (vibration force) of the piezo-electric body 15 in the right and left direction as the width direction of the cantilever 13 is formed. Thereby, the deformation force of the piezoelectric body 15 is adjusted fine and the cantilever 13 is vibrated to the up-and-down direction without being tilted to the right and left direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity sensor suitable for detecting the rotation direction, posture, etc. of a vehicle or the like.

[0002]

2. Description of the Related Art In general, an angular velocity sensor used for detecting a rotating direction of a vehicle or the like includes a substrate, a cantilever having a base end side fixed to the substrate and a tip end free end, and the cantilever beam. And a vibration generation unit that vibrates the cantilever beam by a control signal transmitted via an electrode, and a displacement amount detection unit that detects the displacement amount of the cantilever beam. A device that uses an electrostatic force and uses a piezoresistive element for the displacement amount detecting unit is known, for example, from Japanese Patent Publication No. 3-74926.

Therefore, FIGS. 11 and 12 show a semiconductor rotation sensor disclosed in Japanese Patent Publication No. 3-74926 as an example of a conventional angular velocity sensor.

In the figure, reference numeral 1 denotes a substrate made of a silicon material. As shown in FIG. 12, the substrate 1 is a lower substrate 1A located on the lower side and an upper side formed on the lower substrate 1A. Substantially composed of a substrate 1B and the substrates 1A, 1B
A space 1C that allows vibration of the cantilever 2 to be described later is formed therebetween. Further, the oxide film 1 is formed on the upper surface side of the upper substrate 1B.
D is formed.

Reference numeral 2 denotes a cantilever which is integrally formed on the upper substrate 1B of the substrate 1 by using an etching technique or the like.
Has a base end 2A side which is a fixed end fixed to the upper substrate 1B, and a front end 2B side which is a free end which is vertically oscillating in a vertical direction with respect to the substrate 1. Further, on the base end 2A side of the cantilever 2, there is provided a rectangular slit 3 located at the center in the width direction and extending in the longitudinal direction.

Reference numeral 4 denotes an electrode as a vibration generating portion formed on the upper surface of the cantilever 2 on the side of the tip 2B, and the electrode 4 is connected to an oscillation circuit 5 which oscillates a predetermined frequency signal. When a frequency signal as a control signal is applied from the oscillation circuit 5 to the cantilever 2 via the electrode 4, the cantilever 2 vibrates upward and downward due to electrostatic force.

Reference numerals 6 and 6 denote piezoresistive elements as displacement amount detecting portions provided on the left and right sides of the slit 3 on the base end 2A side of the cantilever 2, and each of the piezoresistive elements 6 is The stress generated in the cantilever 2 when the substrate 1 is rotated is detected as a change in resistance value, and this detection signal is output to the signal processing circuit 7 described later.

Reference numeral 7 denotes a signal processing circuit connected to each piezoresistive element 6. The signal processing circuit 7 converts the detection signal from each piezoresistive element 6 into a voltage signal, and the difference between the two is detected as an angular velocity detection signal. Is output to an external control unit (not shown) or the like.

The angular velocity sensor according to the prior art has the above-mentioned structure. Next, a method for manufacturing the same will be described. First, the upper surface of the substrate 1 is oxidized to form an oxide film 1D, and then P-type impurities such as boron are diffused on the upper surface of the substrate 1 using the oxide film 1D as a mask to form each piezoresistive element 6. Next, a part of the oxide film 1D is removed by an etching technique to open a window, and a conductive material such as a gold alloy is deposited in the window by vapor deposition, sputtering or the like to form the electrode 4. Finally, the substrate 1 is electrolytically etched to form the cantilever 2.
To manufacture an angular velocity sensor.

The angular velocity sensor manufactured as described above generates an electrostatic force when a predetermined frequency signal is applied from the oscillation circuit 5 through the electrode 4, whereby the tip 2B of the cantilever 2 is, for example, its own. It vibrates vertically and vertically at the resonance frequency with respect to the substrate 1. Then, in this state, the substrate 1
When a rotational force T about the rotation axis O-O is applied to, the Coriolis force causes twisting (stress) in the cantilever 2, and the twisting due to this rotation causes compressive stress to the left and right of the slit,
It is expressed as tensile stress.

As a result, each piezoresistive element 6 outputs a signal corresponding to these compressive stress and tensile stress, the signal processing circuit 7 converts the detection signal from each piezoresistive element 6 into a voltage signal, and both Is output to an external control unit or the like as an angular velocity detection signal of the rotational force T.

[0012]

By the way, in the above-mentioned conventional angular velocity sensor, the cantilever 2, the electrode 4, each piezoresistive element is formed on the substrate 1 made of a silicon material by using a semiconductor fine processing technique such as an etching technique. Since 6 is integrally formed, it is possible to reduce the size while improving the productivity. However, since the electrode 4 is integrally formed on the substrate 1,
After the completion of the angular velocity sensor, the electrostatic force (vibration force) cannot be corrected by finely adjusting the shape and the mounting position of the electrode 4, and the electrostatic force by the electrode 4 is applied in the width direction of the cantilever 2. I can't balance it.

Therefore, according to the above-mentioned conventional technique, the stationary state (non-rotating state) in which the rotational force T is not applied
When a frequency signal is applied from the oscillation circuit 5 to the electrode 4 to oscillate the cantilever 2 in the upward and downward directions, the cantilever 2 is moved in the width direction in spite of the fact that the rotational force T is not applied. That is, there is a problem in that the left and right directions are twisted and twisted, the detection signals from the piezoresistive elements 6 do not match, and a leak output is generated in the signal processing circuit 7.

That is, according to the conventional technique, the electrostatic force generated on the cantilever 2 is different between left and right due to manufacturing errors such as the size and thickness of the electrode 4, so that the cantilever 2 is left even in a stationary state. , Twisting to the right causes kinking, which causes leakage output, which reduces the S / N ratio, and significantly decreases the angular velocity detection accuracy and reliability.

On the other hand, a method of applying an offset voltage to the signal processing circuit may be considered in order to correct the leakage output due to the above-mentioned manufacturing error. In this case, however, the entire circuit configuration corresponding to the correction circuit is required. Is complicated.

The present invention has been made in view of the above-described problems of the prior art, and effectively reduces the leakage output in a stationary state by balancing the vibration force generated by the vibration generating section in the width direction of the cantilever. Therefore, an object of the present invention is to provide an angular velocity sensor capable of improving the detection accuracy and reliability of the angular velocity.

[0017]

In order to solve the above-mentioned problems, a feature of the structure adopted by the present invention is that the electrodes of the vibration generating portion are provided with the vibration force generated by the vibration generating portion in the width direction of the cantilever. There is a notch for balancing.

[0018]

With the cutout portion, the vibration force generated by the vibration generating portion is balanced in the width direction of the cantilever. Therefore, a control signal is applied to the vibration generating portion in a stationary state, and the vibration generating portion vibrates the cantilever. Then, the cantilever vibrates without tilting in the width direction, and the displacement amount of the cantilever beam detected by the displacement amount detection unit becomes zero.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In addition, in the embodiment, the above-described FIG.
The same components as those of the conventional technique shown in FIG. 12 are designated by the same reference numerals, and the description thereof will be omitted.

In the figure, reference numeral 11 denotes a sensor body of an angular velocity sensor according to this embodiment, and the sensor body 11 constitutes an angular velocity sensor together with an oscillation circuit 16 and a signal processing circuit 19 which will be described later, as shown in FIG.

Reference numeral 12 denotes a substrate which constitutes the sensor body 11. The substrate 12 is formed of a silicon material in the same manner as the substrate 1 described in the prior art, and has a lower substrate 12A, an upper substrate 12B and the respective substrates. It is composed of a space 12C formed between 12A and 12B. However, the oxide films 12D, 1 are formed on both upper and lower surfaces of the upper substrate 12B according to this embodiment.
2D is formed.

Reference numeral 13 denotes a cantilever beam integrally formed on the upper substrate 12B of the substrate 12 by using an etching technique or the like. The cantilever beam 13 is substantially the same as the cantilever beam 2 described in the prior art.
The base end 13A side is a fixed end fixed to the upper substrate 12B, and the tip end 13B side is perpendicular to the substrate 1,
It becomes a free end that can be vibrated downward, and a rectangular slit 14 is formed at the center of the width direction on the base end 13A side and extends in the longitudinal direction. However, a piezoelectric body 15 to be described later is provided on the upper surface side of the cantilever 13 according to the present embodiment via the oxide film 12D of the substrate 12.

Reference numeral 15 denotes a piezoelectric body as a vibration generating portion provided on the upper surface side of the cantilever 13, and the piezoelectric body 15 is provided on the upper surface side of the cantilever 13 via an oxide film 12D. The side electrode 15A, the piezoelectric film 15B made of a piezoelectric material such as zinc oxide provided on the upper surface side of the lower electrode 15A, and the notch 18 described below provided on the upper surface side of the piezoelectric film 15B. It is composed of the upper electrode 15C. Further, the piezoelectric body 15 is connected to an oscillation circuit 16 which outputs a predetermined frequency signal as a control signal via the electrodes 15A and 15C. Then, the piezoelectric body 15 has an oscillation circuit 16
It deforms when a predetermined frequency signal is applied thereto, and this deforming force (vibrating force) causes the cantilever 13 to vibrate upward and downward.

Reference numerals 17 and 17 denote piezoresistive elements as displacement amount detecting portions which are provided on the left and right of the slit 14 and on the base end 13A side of the cantilever 13, and each of the piezoresistive elements 17 is The stress generated in the cantilever 13 during rotation of the substrate 12 is detected as a change in resistance value, and this detection signal is output to the signal processing circuit 19.

Reference numeral 18 denotes a cutout portion formed in the upper electrode 15C of the piezoelectric body 15, and the cutout portion 18 causes the deformation force (vibration force) of the piezoelectric body 15 in the width direction of the cantilever 13, as described later. The formation position, area, etc. are determined in order to balance in the left and right directions.

Reference numeral 19 denotes a signal processing circuit connected to each piezoresistive element 17, and the signal processing circuit 19 converts the detection signals VL and VR from the left and right piezoresistive elements 17 into voltage signals, and both Of the angular velocity detection signal ΔV (= VL
-VR) is output to the control unit 22 described later.

Reference numeral 20 denotes a laser light source as a notch forming means used for forming the notch 18, and the laser light source 2
Reference numeral 0 is configured to include an optical system for scanning a laser beam. The laser light source 20 is connected to the control unit 22 via the laser oscillation circuit 21, and outputs a laser beam to the upper electrode 15C of the piezoelectric body 15 based on the irradiation signal from the control unit 22.

Reference numeral 22 denotes a control unit which is constituted by a CPU or the like as a microcomputer and is used for forming the cutout portion 18. The control unit 22 has a signal processing circuit 19 connected to its input side and an output side thereof. The laser oscillation circuit 21 is connected. A storage area 22A is formed in the storage circuit including the ROM and RAM of the control unit 22. The storage area 22A stores the program shown in FIG. 9 and the reference value α.

Here, the reference value α is used for determining whether or not the displacement amount of the cantilever beam 13 in the stationary state becomes substantially zero.

The angular velocity sensor according to this embodiment has the above-mentioned structure, and the manufacturing method thereof will be described with reference to FIG.
The description will be made with reference to FIGS.

First, in the oxide film forming step shown in FIG. 3, an oxide film 12D is formed on both upper and lower surfaces of the upper substrate 12B of the substrate 12 made of a single crystal silicon material by using a method such as a thermal oxidation method. To do.

Next, in the piezoresistive element forming step shown in FIG. 4, a part of the oxide film 12D formed on the upper surface side of the upper substrate 12B in the oxide film forming step is removed, and the oxide film 12D is used as a mask for the upper side. A P-type impurity such as boron is injected into the substrate 12B and diffused to form each piezoresistive element 17.

Then, in the piezoelectric body forming step shown in FIG.
A resistance electrode (not shown) is formed on each piezoresistive element 17, and a lower electrode 15A of the piezoelectric body 15 is formed by a technique such as vapor deposition and sputtering. On the upper surface side of the lower electrode 15A, A piezoelectric film 15B made of a piezoelectric material such as zinc oxide;
The piezoelectric body 15 is formed by forming the upper electrode 15C located on the piezoelectric film 15B.

Next, in the groove forming step shown in FIG. 6, a resist (not shown) is applied to the surface of the upper substrate 12B, and the oxide film 12D and the upper substrate 1 are used as a mask.
By dry-etching a part of 2B to a predetermined depth, the groove 23 which will become the slit 14 in the future and the cantilever 13 are formed.
To form another groove 24.

Further, in the cantilever forming step shown in FIG.
The resist used in the groove forming step is removed, and the upper substrate 1
After protecting the upper surface side of 2B with wax or the like, the upper substrate 12
The lower surface side of B is electrolytically etched using an etching solution such as KOH to form a space 12C so that the grooves 23 and 24 are penetrated and a cantilever 13 and a slit 14 are formed.

Then, in the joining step shown in FIG. 8, the cantilever 13, the piezoelectric body 15, and the piezoresistive elements 1 are thus formed.
The lower substrate 12A formed in another process is bonded to the lower side of the upper substrate 12B on which 7 and the like are formed by using an anodic bonding technique or the like to form the sensor body 11.

Finally, the notch forming step will be described based on the notch forming process shown in FIG.

First, in step 1, the sensor main body 11 formed in the joining step is conveyed to and set on the notch forming stage, and the upper electrode 15C of the piezoelectric body 15 and the laser light source 20 are aligned.

Next, in step 2, in the stationary state in which the rotational force T is not applied to the sensor body 11, a frequency signal is applied from the oscillation circuit 16 to the piezoelectric body 15 via the electrodes 15A and 15C, so that the piezoelectric body 15 is excited. The cantilever 13 is vibrated upward and downward by the deformation force of the body 15.

Then, in step 3, the signal processing circuit 1
The difference ΔV between the detection signals from the left and right piezoresistive elements 17, 17 is read via 9 and in step 4, the detection signal ΔV from this signal processing circuit 19 and the reference value previously stored in the storage area 22A are read. Compare with α.

When it is determined in step 4 that "ΔV <α", the detection signal VL from the left piezoresistive element 17 is detected.
Since the detection signal VR from the piezoresistive element 17 on the right side is larger than that, and the cantilever 13 is vibrating while tilting to the right in the width direction, the process proceeds to step 5. Then, in step 5, the upper electrode 15C of the piezoelectric body 15 is irradiated with a laser beam from the laser light source 20, the right end portion of the upper electrode 15C is trimmed by a predetermined dimension, and the process returns to step 3.

When it is determined in step 4 that "ΔV>α", the detection signal VL from the left piezoresistive element 17 is larger than the detection signal VR from the right piezoresistive element 17, and Since the cantilever 13 is inclined and displaced leftward in the width direction, the process proceeds to step 6, and the laser beam from the laser light source 20 trims the left end portion of the upper electrode 15C by a predetermined dimension, and the process returns to step 3.

As described above, by repeating steps 3 to 6, the right end portion and the left end portion of the upper electrode 15C are trimmed by the laser beam by a predetermined dimension to form the cutout portion 18, whereby the piezoelectric body 15 is formed. The deforming force generated at the left balances in the left and right directions, and the cantilever 13 vibrates upward and downward without tilting left and right.

That is, when the notch 18 is formed in the upper electrode 15C, no frequency signal is applied to the piezoelectric film 15B corresponding to the notch 18, so that the piezoelectric film 15B corresponding to the notch 18 is not deformed. , The deformation force of the piezoelectric body 15 is adjusted.

When it is determined in step 4 that "ΔV = α", as described above, the deformation force of the piezoelectric body 15 is balanced in the left and right directions by trimming the upper electrode 15C by the laser light source 20, Since the cantilever 13 is vibrating upward and downward without tilting to the left and right, the program ends.

The angular velocity sensor according to the present embodiment is manufactured in this way, and the basic operation of detecting the angular velocity by the displacement amount of the cantilever 13 is not different from that of the prior art.

However, in this embodiment, after the sensor body 11 is formed, the piezoelectric body 15 vibrates the cantilever beam 13 in a stationary state, and the displacement amount of the cantilever beam 13 is adjusted to the left and right piezoresistive elements 17. The inspection is performed by the difference ΔV (= VL−VR) of the detection signal from the upper electrode 15C based on the inspection result.
By trimming the laser light source 20,
Since the notch portion 18 is provided to balance the deformation force (vibration force) of the piezoelectric body 15 in the left and right directions which are the width direction of the cantilever 13, the deformation force of the piezoelectric body 15 is slightly reduced after the sensor body 11 is manufactured. Adjustment can be performed, and the cantilever 13 can be vibrated in the up and down directions without tilting in the left and right directions in a stationary state where the rotational force T is not applied to the sensor body 11.

As a result, the leakage output from the signal processing circuit 19 can be effectively reduced in the stationary state,
By increasing the S / N ratio, it is possible to significantly improve the angular velocity detection accuracy and reliability.

In the present embodiment, after the sensor body 11 is manufactured, the laser light source 20 provides the notch 18 in the upper electrode 15C of the piezoelectric body 15, and the notch 18 causes the piezoelectric body 15 to deform (vibrate). Is finely adjusted, the angular velocity detection accuracy and reliability can be significantly improved without complicating the overall configuration.

Further, in the present embodiment, a part of the upper electrode 15C of the piezoelectric body 15 is trimmed to form the notch 18, so that the frequency signal to the piezoelectric film 15B corresponding to the notch 18 is cut off. Since the piezoelectric film 15B corresponding to the cutout portion 18 is prevented from being deformed and the deformation force of the piezoelectric body 15 is finely adjusted, the overall shape of the sensor body 11 and the weight of the cantilever 13 are substantially reduced. The reliability and the like can be improved without changing to

On the other hand, in this embodiment, since the piezoelectric body 15 is used for the vibration generating portion, the cantilever 13 is more accurate than the vibration generating portion (electrode 4) by electrostatic force described in the prior art. Can be vibrated upward and downward, and controllability, reliability, etc. can be greatly improved.

In the above embodiment, the piezoelectric body 15 is used as the vibration generating portion, and the notch 18 is formed in the upper electrode 15C of the piezoelectric body 15, but the present invention is not limited to this. For example, as in the modification shown in FIG. 10,
The cantilever 13 'is provided with an electrode 31 which is substantially the same as the electrode 4 as the vibration generating portion according to the conventional technique, and the notch 1
8'may be provided. Even in this case, the electrostatic force applied to the cantilever beam 13 'can be finely adjusted by the amount of the notch 18', and the electrostatic force due to the electrode 31 can be balanced in the width direction of the cantilever beam 13 '. .

In the above embodiment, the piezoelectric body 15 is made of a piezoelectric material such as zinc oxide, but other piezoelectric material such as PZT may be used.

Further, in the above-mentioned embodiment, the diffusion resistance type piezoresistive elements 17 and 17 formed by diffusing P-type impurities are used as the displacement amount detecting section, but instead of this, for example, a field effect type is used. The piezoresistive effect of the transistor may be used.

Furthermore, in the above embodiment, the piezoelectric body 15
Although the case where the rectangular single notch 18 is provided in the upper electrode 15C is illustrated, the present invention is not limited to this, and the notch may be formed into another shape such as a circle or a triangle. A plurality of small area cutouts may be provided.

[0056]

As described above in detail, according to the present invention, the electrode of the vibration generating portion is provided with the notch portion for balancing the vibration force generated by the vibration generating portion in the width direction of the cantilever. Therefore, when a control signal is applied to the vibration generator in the stationary state and the cantilever is vibrated by the vibration generator, the cantilever can be vibrated without tilting in the width direction, and the displacement amount The amount of displacement of the cantilever beam detected by the detector can be effectively zero. As a result, it is possible to effectively prevent the leakage signal from being generated in the detection signal from the displacement amount detecting section in a stationary state where the rotating force is not applied to the cantilever, and to enhance the S / N ratio to detect the angular velocity. And reliability can be improved.

[Brief description of drawings]

FIG. 1 is a plan view showing an angular velocity sensor according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a vertical sectional view showing an oxide film forming step.

FIG. 4 is a vertical cross-sectional view showing a piezoresistive element forming step following the oxide film forming step shown in FIG.

5 is a vertical cross-sectional view showing a piezoelectric body forming step following the piezoresistive element forming step shown in FIG.

FIG. 6 is a vertical cross-sectional view showing a groove forming step following the piezoelectric body forming step shown in FIG.

FIG. 7 is a vertical cross-sectional view showing a cantilever beam forming step that follows the groove forming step shown in FIG.

8 is a vertical cross-sectional view showing a joining process following the cantilever forming process shown in FIG.

FIG. 9 is a flowchart showing a notch forming process for the notch forming step.

10 is a sectional view similar to FIG. 2, showing an angular velocity sensor according to a modification of the present invention.

FIG. 11 is a plan view of an angular velocity sensor according to the related art.

FIG. 12 is a sectional view taken along line XII-XII in FIG.

[Explanation of symbols]

 12, 12 'Substrate 13, 13' Cantilever 15 Piezoelectric body (vibration generating part) 15C Upper electrode 17, 17 'Piezoresistive element (displacement amount detecting part) 18, 18' Cutout 31 Electrode (vibration generating part)

Claims (1)

[Claims] 1. A substrate, a cantilever whose base end side is fixed to the substrate and whose front end is a free end, and said cantilever beam provided on the cantilever beam by a control signal transmitted through an electrode. In an angular velocity sensor including a vibration generating unit that vibrates the cantilever and a displacement amount detecting unit that detects a displacement amount of the cantilever, an electrode of the vibration generating unit has a vibration force generated by the vibration generating unit. An angular velocity sensor characterized in that a notch portion is provided for balancing in the width direction of the angular velocity sensor.