JP2008261773A - Acceleration sensor - Google Patents

Abstract

An object of the present invention is to provide a sensor manufacturing method in which the capacitance generated in a signal line is reduced and the characteristics are improved.
A detection element 1 having an acceleration detection unit is provided. The detection element 1 includes a fixed part 4 connected to a weight part 2 via a flexible part, a counter substrate 6 opposed to the weight part 2, and The first counter electrode to the fourth counter electrodes 14, 16, 18, 20 disposed on the facing surfaces of the weight part 2 and the counter substrate 6 and signal lines 21 drawn from these electrodes, The acceleration is detected by detecting the capacitance change of the first counter electrode to the fourth counter electrodes 14, 16, 18, and 20 disposed on the opposing surfaces of the weight portion 2 and the counter substrate 6, respectively. 6 and the first counter electrode to the fourth counter electrode 14, 16, 18, 20 or the signal line 21.
[Selection] Figure 1

Description

  The present invention relates to an acceleration sensor used in various electronic devices such as attitude control and navigation of a moving body such as an aircraft, an automobile, a robot, a ship, and a vehicle.

  Hereinafter, a conventional acceleration sensor will be described.

  In FIG. 9, a conventional acceleration sensor is provided with a detection element 50 for detecting acceleration, a processing circuit for calculating an acceleration by processing a detection signal detected by the detection element 50, and this processing circuit. 50 is mounted. The detection element 50 includes a base substrate 53, a diaphragm 54 disposed so as to face the base substrate 53, and a weight portion 55 connected to the lower side of the diaphragm 54. A counter electrode 56 is disposed on the opposing surfaces of the base substrate 53 and the diaphragm 54 facing each other. Further, an adhesive 57 is applied to a desired portion between the base substrate 53 and the diaphragm 54, and the base substrate 53 and the diaphragm 54 are bonded and fixed by the adhesive 57.

  Next, detection of acceleration will be described.

  When acceleration occurs, the weight portion 55 tends to move in the axial direction in which the acceleration occurs, so that the diaphragm 54 on which the weight portion 55 is disposed bends. Then, since the gap between the base substrate 53 and the diaphragm 54 changes, the acceleration is detected based on the change in capacitance between the counter electrodes 56 due to the change in the gap.

  Such an acceleration sensor is used in a posture control device, a navigation device, or the like of a moving body such as a vehicle corresponding to a detection axis to be detected.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
Japanese Patent Laid-Open No. 11-344506

  In the above configuration, acceleration is detected based on the change in capacitance between the counter electrodes 56, but a signal line 59 is drawn from the counter electrode 56 disposed on the base substrate 53 and the counter electrode 56 disposed on the diaphragm 54. Yes. The end portions of these signal lines 59 are connected to electrode pads 60 and 61, and are electrically connected to the wiring pattern 62 disposed on the mounting substrate 52 by wire bonding 63 via the electrode pads 60 and 61. The

  In the above configuration, for example, when the base substrate 53 and the diaphragm 54 are formed using a material containing silicon as a main component, a silicon oxide layer is formed on the silicon layer. Therefore, a minute electrostatic capacity is formed between the counter electrode 56 and the signal line 59 disposed on the base substrate 53 and the diaphragm 54 and the silicon layer, and this electrostatic capacity becomes a noise component, and the S / N ratio. It had the problem of deteriorating.

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

  In order to solve the above problems, in particular, the present invention is configured such that the detection element is placed on a fixed portion in which a weight portion is connected via a flexible portion, and a protrusion formed on the fixed portion, and is interposed via a gap. A counter substrate disposed opposite to the weight portion; a counter electrode disposed on each of the counter surfaces of the weight portion and the counter substrate; and a signal line drawn from the counter electrode. Acceleration is detected by detecting a change in capacitance between the counter electrodes arranged on the opposing surfaces of the weight portion and the counter substrate, and is generated between the counter substrate and the counter electrode or the signal line. It is the structure which provided the suppression means which suppresses electrostatic capacitance.

  With the above configuration, since the suppression means for suppressing the capacitance generated between the counter substrate and the counter electrode or the signal line is provided, the capacitance is generated between the counter substrate and the counter electrode or the signal line. Hard to do. That is, it is difficult for noise components to be generated, deterioration of the S / N ratio can be suppressed, and detection accuracy can be improved.

  1 is an exploded perspective view of a detection element of a composite sensor according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1 before arrangement of the counter substrate, and FIG. 4 is a cross-sectional view taken along the line BB in FIG. 1, and FIG. 5 is a cross-sectional view taken along the line CC in FIG.

  In FIG. 1, a composite sensor according to an embodiment of the present invention includes a detection element 1 having an acceleration detection unit and an angular velocity detection unit, and the detection element 1 is fixed by connecting a weight part 2 via a flexible part. Part 4, counter substrate 6 opposed to weight part 2, first electrode disposed on each of the opposing surfaces of weight part 2 and counter substrate 6, and second electrode disposed on the flexible part.

  Specifically, the detection element 1 includes two orthogonal arms formed by connecting the first arm 8 to the second arm 10 in a substantially orthogonal direction, and a support portion 12 that supports one end of the two first arms 8. And a frame-shaped fixing portion 4 in which the other ends of the two first arms 8 are connected. The thickness of the first arm 8 is much thinner than the thickness of the second arm 10, and the second arm 10 is bent until it faces the second arm 10 itself, and the tip of the bent second arm 10 is bent. The weight part 2 is connected to the part. The first arm 8 and the support portion 12 are arranged on substantially the same straight line, and the first arm 8 and the second arm 10 are arranged symmetrically with respect to the center of the detection element 1. Here, the flexible portion refers to a portion connecting the fixed portion 4 and the weight portion 2, and the first arm 8 and the second arm 10 correspond to at least the flexible portion.

  Further, the counter substrate 6 is disposed so as to face the weight portion 2, and the counter substrate 6 is opposed to the weight portion 2 by a protrusion 13 through a certain gap. At this time, if the adhesive is applied to a desired position, the fixing portion 4 and the counter substrate 6 can be easily fixed. First counter electrode to fourth counter electrode 14, 16, 18, 20 are arranged as first electrodes on the opposing surfaces of the weight portion 2 and the counter substrate 6, and one of the two second arms 10 facing each other. Includes a drive electrode 22 and a detection electrode 24 that drive and vibrate the weight portion 2, and the other two second arms 10 that face each other have a first sensing that senses distortion of the second arm 10 as a second electrode. An electrode 26 and a second sensing electrode 28 are disposed.

  Further, the signal line 21 led out from the first to fourth counter electrodes 14, 16, 18, 20 arranged on the opposing surface of the weight part 2 is connected to the fixing part 4 via the second arm 10 and the first arm 8. The electrode pads 23 are provided up to the electrodes. The signal lines 21 drawn from the first to fourth counter electrodes 14, 16, 18, and 20 disposed on the counter surface of the counter substrate 6 are also connected to the electrode pads 23 provided on the fixing portion 4 through the conductive resin 15. Pull out. The electrode pad 23 which is the end of the signal line 21 is electrically connected to the wiring pattern of the mounting board using wire bonding or the like.

  In addition, the first to fourth counter electrodes 14, 16, 18, 20, the drive electrode 22, the detection electrode 24, the first detection electrode 26, and the second detection electrode 28 arranged in the weight portion 2 are shown in FIGS. 3 includes an upper electrode 32 and a lower electrode 34 with a piezoelectric layer 30 interposed therebetween, and the signal line 21 has the same configuration.

  Further, the weight part 2, the fixed part 4, the counter substrate 6, the first arm 8 and the second arm 10 are formed by processing a silicon substrate into a desired shape, and include a drive electrode 22, a detection electrode 24, a first electrode. For the first sensing electrode 26 and the second sensing electrode 28, for example, a lower electrode 34 made of Pt is formed on the silicon substrate by sputtering, and a piezoelectric layer 30 made of PZT is formed on the lower electrode 34 by sputtering. Then, the upper electrode 32 made of Au may be formed by sputtering on the piezoelectric layer 30 made of PZT and processed into a desired shape.

  In particular, in the above configuration, the suppression means for suppressing the capacitance generated between the first counter electrode to the fourth counter electrodes 14, 16, 18, 20 and the signal line 21 disposed on the counter substrate 6 and the weight portion 2. Is provided. As this suppression means, the counter substrate 6 is an insulating substrate made of glass or the like, and a signal is transmitted from the first counter electrode to the fourth counter electrodes 14, 16, 18, 20 arranged on the counter surface of the counter substrate 6 to the fixed portion 4. In addition to drawing the line 21, the drawing distance of the signal line 21 on the facing surface of the counter substrate 6 is made longer than the drawing distance of the signal line 21 on the fixed portion 4.

  Next, the angular velocity detection unit and the acceleration detection unit will be described.

  First, the angular velocity detection unit will be described.

  As shown in FIG. 6, when the first arm 8 of the detection element 1 is arranged in the X-axis direction and the second arm 10 is arranged in the Y-axis direction on the X axis, Y axis, and Z axis orthogonal to each other, When an AC voltage having a resonance frequency is applied to the drive electrode 22, the second arm 10 is driven to vibrate starting from the second arm 10 on which the drive electrode 22 is disposed, and accordingly, the weight portion 2 is also opposed to the second arm 10. Drive vibration occurs in the drive vibration direction indicated by the solid arrow and the dotted arrow. In addition, all of the four second arms 10 and the four weight portions 2 are synchronously driven and vibrated in the opposite direction of the second arm 10. 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 2 is synchronized with the drive vibration of the weight part 2. Since the Coriolis force is generated in the Coriolis direction (Y-axis direction) described above, distortion caused by the counterclockwise angular velocity of the Z-axis can be generated in the second arm 10. That is, a voltage is output from the first and second sensing electrodes 26 and 28 due to a change in the state of the second arm 10 that is bent due to the Coriolis force (a strain generated in the second arm 10). Based on this, the angular velocity is detected.

  Next, the acceleration detection unit will be described.

  As shown in FIG. 7, when the counter substrate 6 is arranged on the XY plane in the X axis, the Y axis, and the Z axis orthogonal to each other, if no acceleration is generated, the surface of the counter substrate 6 facing the weight portion 2 is not affected. The gap (H1) of the first counter electrode 14 is equal to the gap (H2) of the second counter electrode 16 on the facing surface of the counter substrate 6 and the weight portion 2. Although not shown, the facing distance of the third counter electrode 18 and the gap of the fourth counter electrode 20 are also equal.

  At this time, for example, when acceleration occurs in the X-axis direction, the weight portion 2 tends to rotate around the Y-axis around the support portion 12 as shown in FIG. As a result, the gap (H1) between the counter substrate 6 and the first counter electrode 14 on the counter surface of the weight part 2 is reduced, and the gap (H2) between the counter electrode 6 and the counter electrode 6 on the counter surface of the weight part 2 is reduced. Becomes larger. The same applies to the facing distance of the third counter electrode 18 and the gap between the fourth counter electrode 20.

  On the other hand, when acceleration occurs in the Y-axis direction, the weight portion 2 tries to rotate around the X-axis around the support portion 12, so that, for example, the gap between the third and fourth counter electrodes 18 and 20 is, for example, Increases, and the gap between the first and second counter electrodes 14, 16 decreases. That is, since the capacitance between the electrodes changes, acceleration in the X-axis direction or Y-axis direction is detected based on the change in capacitance.

  With the above configuration, the acceleration detection unit detects the capacitances of the first to fourth counter electrodes 14, 16, 18, and 20 disposed on the opposing surfaces of the weight unit 2 and the counter substrate 6, and thereby accelerates the acceleration. The change in the state of the flexible part that is bent due to the Coriolis force can be detected by the first sensing electrode 26 and the second sensing electrode 28, and the acceleration and angular velocity can be detected by the single detection element 1. Therefore, the mounting area can be reduced and the size can be reduced.

  Moreover, since the suppression means which suppresses the electrostatic capacitance which generate | occur | produces between the opposing board | substrate 6 and the 1st opposing electrode-the 4th opposing electrodes 14, 16, 18, 20 or the signal wire | line 21 is provided, an electrostatic capacitance generate | occur | produces. Hard to do. That is, it is difficult for noise components to be generated, deterioration of the S / N ratio can be suppressed, and detection accuracy can be improved.

  In particular, since the fixed portion 4 is made of a silicon substrate and a silicon oxide layer is formed on the silicon layer, the signal line 21 on the fixed portion 4 generates a capacitance with the silicon layer. As a suppression means for suppressing capacitance, the counter substrate 6 is an insulating substrate, and the lead-out distance of the signal line 21 on the counter surface of the counter substrate 6 is longer than the lead-out distance of the signal line 21 on the fixed portion 4. The generation of capacitance between the signal line 21 and the counter substrate 6 can be suppressed.

  As the suppression means, the signal line 21 may be drawn from the end of the first counter electrode to the fourth counter electrode 14, 16, 18, 20 disposed on the counter substrate 6 to the counter surface of the weight part 2, At that time, the signal line 21 may be pulled out through the conductive resin 15. In this case, since the routing of the signal line 21 on the fixed portion 4 can be shortened, the generation of noise components can be further suppressed and the detection accuracy can be improved.

  The acceleration sensor according to the present invention can be applied to various electronic devices by reducing the capacitance generated in the counter electrode and the signal line and improving the S / N ratio.

The disassembled perspective view of the detection element of the composite sensor in one embodiment of this invention AA sectional view before arrangement of the counter substrate in FIG. BB sectional view before arrangement of the counter substrate in FIG. BB sectional view at the time of arrangement of the counter substrate in FIG. 1. CC sectional drawing at the time of opposing board | substrate arrangement | positioning in FIG. Explanatory drawing which shows the operation state of the detection element at the time of angular velocity generation Cross section of the detector Explanatory drawing which shows the operation state of the detection element at the time of acceleration generation Cross-sectional view of a conventional acceleration sensor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Detection element 2 Weight part 4 Fixed part 6 Opposite substrate 8 1st arm 10 2nd arm 12 Support part 13 Projection part 14 1st counter electrode 15 Conductive resin 16 2nd counter electrode 18 3rd counter electrode 20 4th counter electrode 21 signal line 22 drive electrode 23 electrode pad 24 sensing electrode 26 first sensing electrode 28 second sensing electrode 30 piezoelectric layer 32 upper electrode 34 lower electrode

Claims (3)

A detection element having an acceleration detection unit;
The detection element is mounted on a fixed portion having a weight portion connected through a flexible portion, a protruding substrate formed on the fixed portion, and opposed to the weight portion through a gap, and the weight And the counter electrode disposed on each counter surface of the counter substrate and a signal line drawn from the counter electrode, and the acceleration detection unit is disposed on each counter surface of the weight portion and the counter substrate. An acceleration sensor that detects acceleration by detecting a change in capacitance between the counter electrodes, and includes suppression means for suppressing capacitance generated between the counter substrate and the counter electrodes or the signal lines. . The suppression means uses the counter substrate as an insulating substrate, pulls out a signal line from a counter electrode arranged on the counter surface of the counter substrate to the fixed portion, and extracts the signal line on the counter surface of the counter substrate. The acceleration sensor according to claim 1, wherein the length of the signal line is longer than a drawing distance of the signal line on the fixed portion. The acceleration sensor according to claim 2, wherein the signal line is drawn from a counter electrode disposed on a counter surface of the counter substrate to the fixing portion via a conductive resin.

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