JP2008190887A - Sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor which is improved in characteristics by reducing the static capacitance to be generated on the signal line. <P>SOLUTION: The sensor element is constituted of: two rectangular arms formed by crossing the first arm 2 and the second arm 4 approximately at right angle directions; and a supporting part 6 for supporting the ends of the two first arms 2, wherein first and second driving electrode parts 17a, 17b and first to fourth sensing electrodes 19a, 19b, 20a and 20b are arranged on the second arms, and the first and second driving electrodes 17a, 17b, and the first to fourth sensing electrodes 19a, 19b, 20a and 20b are formed while interposing a piezo electric layer 13 between an upper electrode 15 and a lower electrode 14, an upper signal line 15a is led out of the upper electrode 15, and a lower signal line 14a is led out of the lower electrode 14, moreover they are led out without opposing to each other. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sensor that detects inertial force used in various electronic devices such as attitude control and navigation of moving bodies such as aircraft, automobiles, robots, ships, and vehicles.

  Hereinafter, an angular velocity sensor which is one of the sensors will be described.

  Conventional angular velocity sensors, for example, vibrate detection elements of various shapes such as sound shape, H shape, T shape, etc., and electrically detect distortion of the detection elements accompanying the generation of Coriolis force to detect the angular velocity.

  For example, when a vehicle is arranged on the XY plane of the X axis and the Y axis on the X axis, the Y axis, and the Z axis substantially orthogonal to each other, the angular velocity sensor for the navigation device detects the angular velocity around the Z axis of the vehicle. ing.

  FIG. 6 is a perspective view of a conventional angular velocity sensor, and FIG. 7 is a cross-sectional view taken along the line AA of the angular velocity sensor.

  6 and 7, the detection element 51 of the conventional angular velocity sensor has a sound shape, and includes two arms 52 and a base 53 connecting the arms 52.

  The two arms 52 are provided with a drive electrode portion 54 that drives and vibrates the arm 52 and a sense electrode portion 55 that senses the distortion of the arm 52 caused by the angular velocity. For example, each of the drive electrode portions 54 and the sense electrodes The portion 55 is formed of an upper electrode 57 and a lower electrode 58 with a piezoelectric layer 56 interposed. Further, a signal line 59 is drawn from the drive electrode portion 54 and the sensing electrode portion 55, and the electrode pad 60 formed on the base portion 53 is arranged. Furthermore, the electrode pad 60 is electrically connected to a wiring pattern of a mounting substrate (not shown) on which the detection element 51 is mounted via wire bonding or the like.

  For example, the detection element is erected in the Z-axis direction with respect to the XY plane, the arm 52 is driven to vibrate in the X-axis direction, and the distortion caused by the angular velocity around the Z-axis is sensed by the arm 52. The angular velocity around the axis was detected. In such a detection element 51, the driving vibration surface (XZ plane) of the arm 52 and the distortion surface (YZ plane) of the arm 52 are substantially orthogonal to each other. The direction is opposite (if one arm 52 is distorted in the positive Y-axis direction, the other arm 52 is distorted in the negative Y-axis direction).

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
Japanese Patent Laying-Open No. 2005-201652

  In the above configuration, the drive electrode portion 54 and the sensing electrode portion 55 are formed by the upper electrode 57 and the lower electrode 58 with the piezoelectric layer 56 interposed therebetween, and the signal lines 59 are drawn from the upper electrode 57 and the lower electrode 58, respectively. It is.

  That is, the signal line 59 drawn from the upper electrode 57 and the signal line 59 drawn from the lower electrode 58 are opposed to each other vertically with the piezoelectric layer 56 interposed therebetween, and as the routing distance becomes longer, There is a problem in that an electrostatic capacity is generated between the signal lines 59 facing vertically, and this electrostatic capacity becomes a noise component and degrades the S / N ratio.

  An object of the present invention is to solve the above-mentioned problems and to provide a sensor that improves the S / N ratio by reducing the capacitance generated in a signal line.

  In order to solve the above-described problems, the present invention particularly provides a detection element, a flexible portion, a drive electrode portion that is disposed in the flexible portion and drives the flexible portion, and is disposed in the flexible portion. A sensing electrode unit that senses flexure of the flexible unit; and a signal line drawn from each of the driving electrode unit and the sensing electrode unit. The driving electrode unit and the sensing electrode unit include an upper electrode and a lower electrode, The signal line is formed by being drawn out from the upper electrode and the lower electrode, and the signal line is drawn without facing up and down.

  With the above configuration, the signal lines drawn from the upper electrode and the lower electrode are drawn without being opposed to each other, so that there is a capacitance between the signal line drawn from the upper electrode and the signal line drawn from the lower electrode. It is difficult to generate and S / N ratio deterioration due to capacitance can be suppressed. In particular, even if the signal line becomes longer, the deterioration of the S / N ratio can be suppressed and the detection accuracy can be improved.

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

  In FIG. 1, an angular velocity sensor according to an embodiment of the present invention includes a detection element 1 that detects angular velocity, and this detection element 1 is formed by connecting a first arm 2 to a second arm 4 in a substantially orthogonal direction. The two first arms 2 are supported at one end by the support portion 6 and the other ends of the two first arms 2 are fixed to a mounting board (not shown). . The second arm 4 is bent in a U shape and provided with a facing portion 16 facing the second arm 4 itself, and a weight portion 11 is connected to the tip thereof. The thickness of the 1st arm 2 is thinner than the thickness of the 2nd arm 4, and the 1st arm 2 and the 2nd arm 4 are flexible parts which have flexibility.

  In this detection element 1, the first arm 2 and the support portion 6 are arranged on substantially the same straight line, and the first arm 2 is arranged in the X-axis direction on the X-axis, Y-axis, and Z-axis orthogonal to each other. In this case, the second arm 4 is arranged in the Y-axis direction.

  Further, of the four second arms 4, one of the two second arms 4 facing each other has a first driving means 17 for driving and vibrating the weight portion 11 and a first driving means for detecting the driving vibration state of the second arm 4. The first detection means 18 is provided, and the other two second arms 4 facing each other are provided with a first detection means 19 and a second detection means 20 for detecting distortion of the second arm 4.

  The first drive means 17 has an electrode part for driving the weight part 11 of the second arm 4, and the first detection means 18 has an electrode part for detecting the drive state of the second arm 4, The second arm 4 has a first drive electrode portion 17a disposed on the inner peripheral side thereof and a second drive electrode portion 17b disposed on the outer peripheral portion side, and the other second arm 4 has an inner peripheral portion thereof. The first detection electrode part 18a is arranged on the part side and the second detection electrode part 18b is arranged on the outer peripheral part side. The first and second drive electrode portions 17a and 17b are arranged to face each other, and the first and second detection electrode portions 18a and 18b are arranged to face each other. As shown in FIG. 2, the first and second drive electrode portions 17a and 17b and the first and second detection electrode portions 18a and 18b are composed of a lower electrode 14 and an upper electrode 15 with a piezoelectric layer 13 interposed therebetween. .

  The first sensing means 19 and the second sensing means 20 are electrode portions for sensing the strain of the two second arms 4. One of the second arms 4 has a first sensing electrode on its inner peripheral side. The second sensing electrode portion 19b is disposed on the outer peripheral side while the portion 19a is disposed, and the third sensing electrode portion 20a is disposed on the inner peripheral side of the other second arm 4 and the outer peripheral side. The 4th sensing electrode part 20b is arrange | positioned. The first and second sensing electrode portions 19a and 19b are arranged to face each other, and the third and fourth sensing electrode portions 20a and 20b are arranged to face each other. As shown in FIG. 2, the first to fourth sensing electrode portions 19a, 19b, 20a, and 20b include a lower electrode 14 and an upper electrode 15 with a piezoelectric layer 13 interposed therebetween.

  Further, the lower electrode 14 and upper electrode 15 of the first and second drive electrode portions 17a and 17b, the lower electrode 14 and upper electrode 15 of the first and second detection electrode portions 18a and 18b, and the first to fourth sensing electrode portions. The lower signal line 14a and the upper signal line 15a are led out from the lower electrode 14 and the upper electrode 15 of 19a, 19b, 20a, and 20b, respectively. These signal lines 14a and 15a are led out on the substantially same plane from the vicinity of the support portion 6 toward the other end of the first arm 2 so as not to face each other up and down, and the end portions thereof are electrode pads or the like ( (Not shown).

  In particular, the lower signal line 14a of the first drive electrode unit 17a, the lower signal line 14a of the second drive electrode unit 17b, the lower signal line 14a of the first sensing electrode unit 19a, and the lower signal of the second sensing electrode unit 19b. The line 14a is the same signal line, and the upper signal line 15a of the first and second drive electrode portions 17a and 17b and the first and second sensing electrode portions 19a and 19b are sandwiched between the lower signal lines 14a. The upper signal lines 15a are led out in parallel with each other.

  Further, the lower signal line 14a of the first sensing electrode unit 18a, the lower signal line 14a of the second sensing electrode unit 18b, the lower signal line 14a of the third sensing electrode unit 20a, and the lower signal of the fourth sensing electrode unit 20b. The line 14a is the same signal line, and the upper signal line 15a of the first and second sensing electrode portions 18a and 18b and the third and fourth sensing electrode portions 20a and 20b are sandwiched between the lower signal lines 14a. The upper signal lines 15a are led out in parallel with each other.

  Next, a method for manufacturing the detection element will be described.

  First, as shown in FIGS. 3A to 3D, a first conductor layer 31 made of Pt is formed on a substrate 30 made of silicon, and a piezoelectric layer made of PZT is formed on the first conductor layer 31. 13 is formed, and a second conductor layer 32 made of Au is formed on the piezoelectric layer 13. These first conductor layer 31, piezoelectric layer 13, and second conductor layer 32 may be formed by sputtering, vapor deposition, or the like.

  Secondly, as shown in FIG. 3 (e), the first conductor layer 31 and the second conductor layer 32 with the piezoelectric layer 13 interposed therebetween are etched, and the lower electrode with the piezoelectric layer 13 having a desired shape interposed therebetween. 14 and the upper electrode 15 are formed. The lower electrode 14 and the upper electrode 15 with the piezoelectric layer 13 having a desired shape interposed therebetween are the first and second drive electrode portions 17a and 17b, the first and second detection electrode portions 18a and 18b in the detection element 1 described above. This corresponds to the first to fourth sensing electrode portions 19a, 19b, 20a, and 20b.

  Third, as shown in FIG. 4A, the second conductor layer 32 and the piezoelectric layer 13 are etched to expose a part of the lower electrode 14.

Fourth, as shown in FIGS. 4B to 4C, an insulating layer 33 such as SiO ₂ or SiN is formed on the upper electrode 15 and the lower electrode 14 by CVD, sputtering, vapor deposition, etc. Etching is performed on the layer 33 to expose a part of the upper electrode 15 and a part of the lower electrode 14 to form a lead portion 34.

  Fifth, a conductor layer is formed on the entire surface of the insulating layer 33 from which the lead-out portion 34 in FIG. 4C is exposed by sputtering or the like and etched, as shown in FIG. 4D. The upper signal line 15a and the lower signal line 14a having a predetermined shape are formed from the portion 34. The upper signal line 15a drawn out from the upper electrode 15 and the lower signal line 14a drawn out from the lower electrode 14 are formed without being vertically opposed.

  At this time, from the lower electrode 14 of the first and second drive electrode portions 17a and 17b, the position and shape of the etching shown in FIGS. 4B to 4D and the method of extracting the upper signal line 15a and the lower signal line 14a are used. The lower signal line 14a to be drawn and the upper signal line 15a to be drawn from the lower electrodes of the first and second detection electrode portions 18a and 18b are made the same signal line, or each of the first and second drive electrode portions 17a and 17b. The lower signal line 14a drawn from the lower electrode 14 is the same signal line, or the lower signal line 14a drawn from each lower electrode 14 of the first to fourth sensing electrode portions 19a, 19b, 20a, 20b is the same signal line. You can.

  As described above, the number of electrode PAD portions formed at the end portion is kept to the minimum necessary by making the signal lines the same as long as there is no problem in the characteristics of the driving / sensing signal for detecting the angular velocity. Therefore, it is possible to reduce the size of the element.

  Finally, as shown in FIG. 4E, the substrate 30 made of silicon may be etched to form the detection element 1 having the above-described shape. The first arm 2 and the second arm 4 become flexible flexible parts, and the first and second drive electrode parts 17a and 17b, the first and second detection electrode parts 18a and 18b, 1st-4th sensing electrode part 19a, 19b, 20a, 20b is arrange | positioned.

  In addition, if the position and shape which etch is controlled in the said process, not only the detection element 1 of the said shape but the detection element 1 of various shapes can be formed.

  FIG. 5 is an operation state diagram of the detection element of the angular velocity sensor according to the embodiment of the present invention.

  When the first arm 2 of the detection element 1 is arranged in the X-axis direction and the second arm 4 is arranged in the Y-axis direction on the X, Y, and Z axes orthogonal to each other, the first and second drive electrodes When an AC voltage having a resonance frequency is applied to the parts 17a and 17b, the second arm 4 is driven and oscillated from the second arm 4, and accordingly, the weight part 11 is also opposed to the second arm 4 (solid arrow and dotted line). Drive vibration in the direction indicated by the arrow). Further, all of the four second arms 4 and the four weight portions 11 are synchronously driven and vibrated in a direction opposite to the second arm 4. The driving vibration direction in the detection element 1 is the X-axis direction.

  At this time, for example, when an angular velocity is generated in the counterclockwise direction of the Z axis, a direction (solid line arrow and dotted line arrow) perpendicular to the drive vibration direction with respect to the weight part 11 is synchronized with the drive vibration of the weight part 11. Since the Coriolis force is generated in the Coriolis direction indicated by (2), distortion caused by the counterclockwise angular velocity of the Z axis can be generated in the second arm 4. The Coriolis direction of the detection element 1 is the Y-axis direction.

  When the Coriolis force is generated in the Coriolis direction indicated by the solid line arrow, the first sensing electrode unit 19a and the first sensing electrode unit 19a are connected to the first sensing electrode unit 19a in the second arm 4 provided with the first to fourth sensing electrode units 19a, 19b, 20a, and 20b. The third sensing electrode unit 20a senses the contraction of the second arm 4, and the second sensing electrode unit 19b and the fourth sensing electrode unit 20b sense the extension of the second arm 4, and coriolis in the Coriolis direction indicated by the dotted arrow. When a force is generated, it senses the expansion and contraction in the opposite direction.

  A voltage is output from the first to fourth sensing electrode portions 19a, 19b, 20a, and 20b according to the sensed expansion / contraction, and the angular velocity is detected based on the output voltage.

  On the other hand, when the angular velocity is generated clockwise around the Z axis, the opposite portion 16 of the second arm 4 is expanded and contracted in the opposite direction to the case where the angular velocity is generated counterclockwise about the Z axis. Since the fourth sensing electrode portions 19a, 19b, 20a, and 20b sense, the angular velocity is similarly detected.

  Also, when an angular velocity occurs around the Y axis, Coriolis force is generated in a direction (Z axis direction) perpendicular to the drive vibration direction with respect to the weight portion 11 in synchronization with the drive vibration of the weight portion 11. The second arm 4 is distorted due to the angular velocity around the Y axis, and the first to fourth sensing electrode portions 19a, 19b, 20a, and 20b sense the angular velocity by detecting the expansion and contraction of the second arm 4. Is done.

  The distortion that occurs when angular velocities occur around the Z-axis and Y-axis is the second arm provided with the first and second drive electrode portions 17a and 17b and the first and second detection electrode portions 18a and 18b. 4 also occurs in the same manner, the first to fourth sensing electrode portions 19a, 19b, 20a and 20b are provided with the first and second driving electrode portions 17a and 17b and the first and second sensing electrode portions 18a and 18b. It is also possible to arrange the second arm 4.

  With the above configuration, since the lower signal line 14a formed by being drawn out from the lower electrode 14 and the upper signal line 15a formed by being drawn out from the upper electrode 15 are drawn out without facing each other, the lower signal line 14a drawn out from the lower electrode 14 And the upper signal line 15a drawn from the upper electrode 15 are less likely to generate a capacitance, and can suppress the deterioration of the S / N ratio due to the capacitance. In particular, the S / N ratio does not deteriorate even when the routing distance of the lower signal line 14a and the upper signal line 15a is increased.

  Further, when the first arm 2 of the detection element 1 is arranged in the X-axis direction and the second arm 4 is arranged in the Y-axis direction on the X-axis, Y-axis, and Z-axis orthogonal to each other, the first and second When an AC voltage having a resonance frequency is applied to the drive electrode portions 17a and 17b, the second arm 4 is driven to vibrate starting from the second arm 4 on which the first and second drive electrode portions 17a and 17b are arranged. The weight portion is also driven to vibrate in the X-axis direction of the second arm 4.

  At this time, when an angular velocity is generated around the Z axis, Coriolis force is generated in the weight portion 11 in a direction orthogonal to the drive vibration direction in synchronization with the drive vibration of the weight portion 11. Distortion caused by the angular velocity around the axis can be generated, and the angular velocity can be detected by detecting this distortion. Therefore, the angular velocity around the Z axis can be detected with the detection element 1 lying down without standing in the Z axis direction, and the height can be reduced.

  The detection element 1 in the embodiment of the present invention has two orthogonal arms formed by connecting the first arm 2 to the second arm 4 in a substantially orthogonal direction, and supports one end of the two first arms 2 6 and the other end of the two first arms 2 is fixed to a mounting substrate (not shown). However, the detection element 51 of the conventional angular velocity sensor as shown in FIGS. The same effect can be obtained even in the shape of the sound, that is, the sound shape having the two arms 52 and the base 53 connecting the arms 52.

  Furthermore, although the detection element 1 in the embodiment of the present invention detects the angular velocity, it may form a portion for detecting acceleration and detect both the angular velocity and the acceleration. In this case, in FIG. 1, the arm 2 may be formed with an acceleration detection unit that detects acceleration. The acceleration detection unit may detect the acceleration by, for example, disposing a strain resistance element whose resistance value changes due to strain on the arm 2 and detecting the strain of the arm 2 caused by the acceleration by the strain resistance element. . It is desirable to make the arm 2 thinner than other portions so that the arm 2 is easily distorted. In FIG. 3, when acceleration occurs in the X-axis direction, the weight portion 11 moves in the X-axis direction, so that the arm 2 can be detected by being distorted.

  The sensor according to the present invention can be applied to various electronic devices with reduced characteristic deterioration due to capacitance between signal lines.

The top view of the detection element of the angular velocity sensor in one embodiment of this invention AA sectional view of FIG. Manufacturing process diagram of the detector Manufacturing process diagram of the detector Operation state diagram of the detector The perspective view of the detection element of the conventional angular velocity sensor AA sectional view of the same detection element

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Detection element 2 1st arm 4 2nd arm 6 Support part 11 Weight part 13 Piezoelectric layer 14 Lower electrode 14a Lower signal line 15 Upper electrode 15a Upper signal line 16 Opposing part 17a 1st drive electrode part 17b 2nd drive electrode part 18a First sensing electrode portion 18b Second sensing electrode portion 19a First sensing electrode portion 19b Second sensing electrode portion 20a Third sensing electrode portion 20b Fourth sensing electrode portion 30 Substrate 31 First conductor layer 32 Second conductor layer 33 Insulating layer 34 Drawer

Claims (5)

It has a detection element that detects inertial force,
The detection element includes a flexible portion, a drive electrode portion that is disposed in the flexible portion and drives the flexible portion, a sensing electrode portion that is disposed in the flexible portion and senses bending of the flexible portion, Each having a signal line drawn from the drive electrode part and the sensing electrode part,
The drive electrode portion and the sensing electrode portion are formed by interposing a piezoelectric layer between an upper electrode and a lower electrode, the signal line is formed by being drawn from the upper electrode and the lower electrode, and the signal The sensor is pulled out without facing up and down. 2. The sensor according to claim 1, wherein the signal line drawn from the lower electrode of the drive electrode unit and the signal line drawn from the lower electrode of the sensing electrode unit are the same signal line. The sensor according to claim 1, wherein a plurality of the drive electrode portions are provided, and signal lines led out from a plurality of lower electrodes of the drive electrode portions are the same signal lines. The sensor according to claim 1, wherein a plurality of the sensing electrode portions are provided, and signal lines led out from a plurality of lower electrodes of the sensing electrode portions are the same signal lines. The detection element includes two orthogonal arms formed by connecting the first arm to the second arm in a substantially orthogonal direction, a support portion that supports the two first arms, a support substrate that is connected to the support portion, and a mounting substrate. Two fixing arms to be fixed to the second arm, the second arm is bent to face the second arm, the drive electrode portion is disposed on the second arm, and the second arm The end portion of the second arm is driven to vibrate in the opposite direction, and the sensing electrode portion is disposed on either the first arm, the second arm, or the fixing arm, and the angular velocity is detected by detecting the distortion. The sensor according to claim 1.

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