JP5700652B2 - Capacitance type acceleration sensor - Google Patents

Description

  The present invention relates to an acceleration sensor, and more particularly to a capacitance-type acceleration sensor that detects acceleration using a change in capacitance.

Currently, in an acceleration sensor, a movable electrode that is displaced by the application of acceleration and a fixed electrode that is fixed to the substrate are placed opposite to each other, and an electrostatic force that detects acceleration using a change in capacitance between the two is arranged. There is a capacitive acceleration sensor.
FIG. 10 is a top view for explaining a conventional acceleration sensor. 11 is a cross-sectional view taken along the alternate long and short dash line DD shown in FIG. The illustrated acceleration sensor is a sensor for detecting acceleration applied in the Z direction shown in the drawing. A first fixed electrode 2 fixed on the silicon substrate 1 and a second fixed electrode 3 are provided.

  In the capacitance type acceleration sensor shown in FIGS. 10 and 11, the movable electrode 5 is swingably supported by the anchor portion 7. The anchor portion 7 is connected to the movable electrode 5 by a torsion beam 6, and includes an anchor upper layer portion 7 a that is connected to the torsion beam, and an anchor lower layer portion 7 b that connects the anchor upper layer portion 7 a and the substrate 1. The movable electrode 5 includes a movable electrode portion 5 a that faces the first fixed electrode 2 and a movable electrode portion 5 b that faces the second fixed electrode 3.

When acceleration in the Z direction is applied to the capacitive acceleration sensor shown in FIGS. 10 and 11, the mass body 8 is displaced downward. Since the movable electrode 5 is connected to the mass body 8 by the link beam 11 on the left side of the alternate long and short dash line CC shown in FIG. 10, the movable electrode portion 5a also moves downward as the mass body 8 is displaced downward. Displace.
Due to the displacement of the movable electrode portion 5a, a difference is generated between the electrostatic capacitance C1 generated below the movable electrode portion 5a shown in FIG. 11 and the electrostatic capacitance C2 generated below the movable electrode portion 5b. The capacitive acceleration sensor shown in FIGS. 10 and 11 detects the acceleration applied to the capacitive acceleration sensor based on the difference between the electrostatic capacitance C1 and the electrostatic capacitance C2.
Such a capacitive acceleration sensor is described in Patent Document 1, for example.

WO 03/044539 Brochure

However, in the above-described conventional capacitive acceleration sensor, when a larger acceleration than usual is applied, for example, by dropping the capacitive acceleration sensor, the coupling portion between the torsion beam 6 and the anchor upper layer portion 7a is not provided. Excessive stress is applied to the boundary between the anchor upper layer portion 7a and the anchor lower layer portion 7b. If damage such as peeling or cracking is applied to the boundary between the anchor upper layer portion 7a and the anchor lower layer portion 7b due to excessive stress, the sensitivity and offset value of the capacitive acceleration sensor fluctuate, and the reliability of the capacitive acceleration sensor It will damage the sex.
The present invention has been made in view of the above points, and even when acceleration larger than the acceleration applied during normal use is applied, damage is caused between the support portion of the movable electrode and the beam portion. An object of the present invention is to provide a highly reliable capacitive acceleration sensor.

In order to solve the above problems, a capacitive acceleration sensor according to the present invention includes a substrate (for example, the substrate 101 shown in FIG. 3) and a fixed electrode (for example, the fixed electrode shown in FIG. 3) fixed on the substrate. 123, 124), a movable electrode (for example, the movable electrode 105 shown in FIG. 3) arranged to face the upper surface of the fixed electrode, and the movable electrode can be displaced in a direction perpendicular to the upper surface of the substrate. An elastic support portion (for example, the elastic support portion 180 shown in FIG. 3) that elastically supports on the substrate, and the elastic support portion is a lower layer support portion (for example, FIG. 3) made of an insulator fixed on the substrate. Lower support portions 121 and 122), an upper support portion fixed on the lower support portion (for example, the upper support portion 117 shown in FIG. 3), and a long shape along the upper surface of the substrate, And one end is connected to the upper layer support. The other end portion of which is coupled to the movable electrode (for example, the beam portion 106 shown in FIG. 3), and the lower layer support portion is a portion of the coupling portion between the beam portion and the upper layer support portion. have a gap portion (e.g. void portion 130 shown in FIG. 3) in the portion located immediately below, the upper support portion, two long portion having a long shape along the longitudinal direction of the beam portion (e.g., Fig. 3 2) and a short portion (for example, the short portion 107 shown in FIG. 3) connecting the two long portions, and the lower layer support portion includes characterized in that it have a void portion to all parts located immediately below the short portion.

Also, the electrostatic capacitance type acceleration sensor of the present invention, in the invention described above, the lower support unit further voids shown in the gap portion (for example, FIG. 7 in a part of the portion located directly below the long portion Part 140).

  According to the above-described invention, the coupling portion with the beam portion in the upper layer support portion is not fixed to the substrate via the lower layer support portion. For this reason, there is no boundary between the upper layer support portion and the lower layer support portion at the joint portion between the upper layer support portion and the beam portion where excessive stress is generated when a large acceleration is applied. For this reason, this invention does not receive the damage of the boundary part of an upper layer support part and a lower layer support part, and can provide a capacitive acceleration sensor with high reliability.

It is a top view for demonstrating the whole capacitive acceleration sensor of Embodiment 1 of this invention. It is the perspective view of the part which cut out the capacitive acceleration sensor of Embodiment 1 of this invention in the range P shown with the broken line in FIG. It is a figure for demonstrating the capacitive acceleration sensor of Embodiment 1 of this invention. It is a figure for demonstrating the electrostatic capacitance type acceleration sensor of the reference example compared with this invention. It is a figure which shows the result obtained by simulating the stress concerning the boundary part of the upper layer support part of a capacitive acceleration sensor shown in FIG. 4, and a lower layer support part. It is a figure which shows the result obtained by simulating the stress concerning the boundary part of the upper layer support part and lower layer support part of the capacitive acceleration sensor of Embodiment 1 shown in FIG. It is a figure for demonstrating the capacitive acceleration sensor of Embodiment 2 of this invention. It is a figure which shows the result obtained by simulating the stress concerning the boundary part of the upper layer support part and lower layer support part of the capacitive acceleration sensor of Embodiment 2 shown in FIG. It is a figure for demonstrating the modification of Embodiment 1 and Embodiment 2 of this invention. It is a top view for demonstrating the conventional acceleration sensor. It is sectional drawing which follows the dashed-dotted line DD shown in FIG.

Embodiments 1 and 2 of the present invention will be described below.
(Embodiment 1)
[Overall configuration]
FIG. 1 is a top view for explaining the entire capacitive acceleration sensor according to the first embodiment. The capacitive acceleration sensor according to the first embodiment includes a movable electrode 105 and a beam portion 106 that connects the upper layer support portion 117 to the movable electrode 105. The upper layer support portion 117 is a short connecting the two long portions 155a and 155b having a long shape along the longitudinal direction (Y direction shown in the drawing) of the beam portion 106 and the two long portions 155a and 155b. It has an “H” -shaped planar shape including the portion 107. A frame 110 is provided around the movable electrode 105.
FIG. 2 is a perspective view of a portion of the capacitive acceleration sensor according to the first embodiment cut out in a range P indicated by a broken line in FIG.

[Configuration for elastic support]
Hereinafter, the capacitive acceleration sensor according to the first embodiment will be described.
FIG. 3 is a diagram for explaining the capacitive acceleration sensor 100 according to the first embodiment. 3A is a top view of the capacitive acceleration sensor 100, FIG. 3B is a cross-sectional view taken along the broken line AA shown in FIG. 3A, and FIG. 3C is FIG. It is sectional drawing which follows the line BB shown in a). In FIG. 3, the X axis, Y axis, and Z axis indicating the directions in FIG. 3 are shown, and the following description is performed using the directions indicated by the illustrated X axis, Y axis, and Z axis. The capacitive acceleration sensor 100 according to the first embodiment is a sensor that detects acceleration applied in the Z direction.

  As shown in FIGS. 3A to 3C, the capacitive acceleration sensor 100 is opposed to the substrate 101, fixed electrodes 123 and 124 fixed on the substrate 101, and the upper surfaces of the fixed electrodes 123 and 124. A movable electrode 105 arranged so as to be elastically movable, and an elastic support portion 180 that elastically supports the movable electrode 105 on the substrate 101 so as to be displaceable in a direction perpendicular to the upper surface 101a of the substrate 101 (Z direction shown in the figure), It has.

The elastic support portion 180 includes a lower layer support portion made of an insulator fixed on the substrate 101, an upper layer support portion 117 fixed on the lower layer support portion, and the substrate upper surface 101a (Y direction shown in the figure). And a beam portion 106 having a long shape, one end portion coupled to the upper layer support portion 117 and the other end portion coupled to the movable electrode 105. In the first embodiment, the lower layer support part is composed of two lower layer support parts 121 and 122.
And the lower layer support parts 121 and 122 have the space part 130 in the part located just under the coupling | bond part of the beam part 106 and the upper layer support part 117. As shown in FIG.

In the first embodiment, as shown in FIG. 3C, the lower layer support portions 121 and 122 are provided so as to have the gap portion 130 in all the portions located immediately below the short portion 107.
As shown in FIG. 1, the upper layer support portion 117 supports the movable electrode 105 at a position where the movable electrode portion 105 a is biased in the −X direction from the center of the movable electrode 105. For this reason, when acceleration in the Z direction is applied to the movable electrode 105, the movable electrode portion 105b is displaced downward, and the movable electrode portion 105a is displaced upward. At this time, a difference is generated between the capacitance between the movable electrode portion 105 a and the substrate 101 and the capacitance between the movable electrode portion 105 b and the substrate 101. The capacitive acceleration sensor according to the first embodiment detects acceleration applied in the Z direction by detecting a difference.

In Embodiment 1, the coupling | bond part with the beam part of the upper layer support part is not being fixed to the board | substrate via the lower layer support part. For this reason, there is no boundary between the upper layer support portion and the lower layer support portion at the joint portion between the upper layer support portion and the beam portion where excessive stress is generated when a large acceleration is applied.
As a result, the capacitive acceleration sensor 100 shown in FIG. 3 is not damaged at the boundary between the upper layer support portion and the lower layer support portion.

[effect]
Next, the stress relaxation effect obtained by the first embodiment will be described.
Prior to the effects obtained by the first embodiment, first, the configuration of the capacitive acceleration sensor (reference example) compared to the configuration of the first embodiment and the stress applied to the capacitive acceleration sensor of the reference example will be described. To do.
FIG. 4 is a diagram for explaining a capacitive acceleration sensor 400 of a reference example. 4A is a top view of the capacitive acceleration sensor 400, FIG. 4B is a sectional view taken along line AA in FIG. 4A, and FIG. 4C is FIG. 4A. It is sectional drawing which follows the inside line BB. In FIG. 4, the same components as those shown in FIG. 3 are denoted by the same reference numerals, and the description thereof is partially omitted.

  FIG. 5 is a diagram illustrating a result obtained by simulating the stress applied between the upper layer support portion 117 and the lower layer support portion 420 of the capacitive acceleration sensor 400 illustrated in FIG. 4. FIG. 5A shows an analysis model used for the simulation. FIG. 5A schematically shows the bottom surface of the lower layer support portion 420 shown in FIG. 4, and reference numerals 106, 117, 155 a, and 155 b denote the positions of the respective configurations on the illustrated bottom surface. Shown virtually. A range Q indicated by shading in FIG. 5A indicates a range in which the lower layer support portion 420 is in contact with the upper layer support portion 117.

FIG. 5B is a stress distribution diagram in which the stress applied between the upper layer support portion 117 and the lower layer support portion 420 is indicated by contour lines. In the simulation, the stress generated when 10000 G acceleration is applied to the capacitive acceleration sensor 400 in the X direction for 0.1 ms is obtained.
As shown in FIG. 4, the capacitive acceleration sensor 400 is a surface that is directly below the short portion 107 of the bottom surface of the upper layer support portion 117, as compared with the capacitive acceleration sensor 100 shown in FIG. 3. Is different from the capacitive acceleration sensor 100 in that all are supported by the lower layer support portion 420.

In such a capacitive acceleration sensor 400, when an excessive acceleration is received in the X direction shown in the drawing, the upper layer support portion 117 and the beam portion of the boundary portion between the upper layer support portion 117 and the lower layer support portion 420 are included. A relatively strong stress is applied at the joint with 106. In the simulation shown in FIG. 5, a maximum stress of 39.9 MPa was observed.
The boundary portion between the upper layer support portion 117 and the lower layer support portion 106 is more easily damaged by peeling or the like than other portions. For this reason, as shown in FIG. 5, the stress applied to the boundary portion may damage the boundary portion.

Next, the effect obtained by the capacitive acceleration sensor 100 of the first embodiment will be described in comparison with the capacitive acceleration sensor 400 of the reference example described above.
FIG. 6 is a diagram showing a result obtained by simulating the stress applied between the upper layer support portion 117 and the lower layer support portions 121 and 122 of the capacitive acceleration sensor 100 of the first embodiment shown in FIG. . FIG. 6A shows the analysis model used for the simulation. FIG. 6A schematically shows the bottom surface of the elastic support portion, and reference numerals 106, 117, 155 a, and 155 b virtually indicate the positions of the respective components on the illustrated bottom surface. . A range Q indicated by shading in FIG. 6A indicates a range in which the lower layer support portions 121 and 122 illustrated in FIG. 3 are in contact with the upper layer instruction portion 117.

FIG. 6B is a stress distribution diagram showing the stress applied between the upper layer support portion 117 and the lower layer support portions 121 and 122 by contour lines. In the simulation, the stress generated when 10000 G acceleration is applied to the capacitive acceleration sensor 100 in the X direction for 0.1 ms is obtained.
As shown in FIG. 6, in the capacitive acceleration sensor 100 of the first embodiment, even when excessive acceleration is applied in the X direction, the boundary between the upper layer support portion 117 and the lower layer support portions 121 and 122 is provided. The applied stress is smaller than the example shown in FIG. Specifically, in the simulation shown in FIG. 6, it was observed that the maximum stress was 8.89 Mpa. Therefore, it is clear that the embodiment 1 can reduce the stress applied to the boundary portion between the upper layer support portion 117 and the lower layer support portions 121 and 122 as compared with the reference example. According to the first embodiment, even when a device incorporating a capacitive acceleration sensor falls on the floor surface, a reduction in accuracy related to the measurement of acceleration is suppressed, and a highly reliable capacitive type. An acceleration sensor can be provided.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described. The top view and perspective view of the capacitive acceleration sensor of the second embodiment are the same as those of the first embodiment, and therefore illustration and description thereof are omitted.
[Configuration for elastic support]
FIG. 7 is a diagram for explaining the capacitive acceleration sensor 200 according to the second embodiment. 7A is a top view of the capacitive acceleration sensor 200, FIG. 7B is a sectional view taken along line AA in FIG. 7A, and FIG. 7C is FIG. 7A. It is sectional drawing which follows the inside line BB. In FIG. 7, the same components as those shown in FIG. 3 are denoted by the same reference numerals, and the description thereof is partially omitted.

  The capacitive acceleration sensor 200 is different from the capacitive acceleration sensor 100 shown in FIG. 3 in the positions of the lower layer support portions 141 and 142. That is, in the second embodiment, among the bottom surface of the upper layer support portion 117 constituting the elastic support portion 190, the entire surface immediately below the short portion 107 and a part of the bottom surface of the long portions 155a and 155b are supported by the support portions 141 and 142. The capacitive acceleration sensor 100 is different from the capacitive acceleration sensor 100 in that a gap 140 is provided between the upper surface 101a and the upper surface 101a. The gap 140 of the capacitive acceleration sensor 200 extends not only to the entire surface immediately below the short portion 107 but also to the region immediately below the long portions 155a and 155b. For this reason, the gap 140 of the capacitive acceleration sensor 200 is larger than the gap 130 of the capacitive acceleration sensor 100.

[effect]
FIG. 8 is a diagram illustrating a result obtained by simulating the stress applied between the upper layer support portion 117 and the lower layer support portions 141 and 142 of the capacitive acceleration sensor 200 illustrated in FIG. FIG. 8A shows an analysis model used in the simulation, and FIG. 8B is a stress distribution diagram showing the stress applied between the upper layer support part 117 and the lower layer support parts 141 and 142 by contour lines. In the simulation, the stress generated when 10000 G acceleration is applied to the capacitive acceleration sensor 200 in the X direction for 0.1 ms is obtained.

  As shown in FIG. 8, in the capacitive acceleration sensor 200 of the second embodiment, even when excessive acceleration is applied in the X direction, the boundary between the upper layer support portion 117 and the lower layer support portions 141 and 142 is provided. The applied stress is smaller than the example shown in FIGS. Specifically, in the simulation shown in FIG. 8, it was observed that the maximum stress was 5.44 Mpa. Therefore, it is clear that the second embodiment can reduce the stress applied to the boundary portion between the upper layer support portion 117 and the lower layer support portions 141 and 142 as compared with the reference example and the first embodiment. According to the second embodiment, even if a device incorporating a capacitive acceleration sensor falls on the floor surface, a decrease in accuracy related to the measurement of acceleration is further suppressed, and a more reliable electrostatic A capacitive acceleration sensor can be provided.

(Modification)
Furthermore, the capacitive acceleration sensor of the present invention is not limited to the first and second embodiments described above. That is, in both the first and second embodiments, the gap portions 130 and 140 are provided in contact with the entire surface immediately below the short portion 107 of the bottom surface of the upper layer support portion 117, and the bottom surfaces of the two long portions 155a and 155b are Were not connected to each other.
However, the capacitance type acceleration sensor of the present invention only needs to have a gap in a portion located immediately below the coupling portion between the beam portion 106 and the upper layer support portion 117, and the bottom surfaces of the long portions 155a and 155b are connected to each other. May be.

  FIG. 9 is a diagram for explaining a modification of the first and second embodiments described above. FIG. 9 schematically shows a capacitive acceleration sensor 300 in which the bottom surfaces of the long portions 155a and 155b among the bottom surfaces of the elastic support portions are connected to each other and fixed to the top surface 101a of the substrate 101. . A range Q indicated by shading indicates a range in which the lower layer support portion contacts the upper layer support portion. Reference numerals 105, 106, 117, 155 a, and 155 b shown in the figure virtually indicate the positions of the respective components on the illustrated bottom surface.

As shown in the figure, in the capacitive acceleration sensor 300, a part of the bottom surface of the upper layer support part directly below the short part 107 and a part of the long parts 155a and 155b are not fixed to the substrate. A gap is provided between portions of the bottom surface of the upper support portion that are not fixed to the substrate 901a and 901b and the substrate.
Such a capacitive acceleration sensor 300 also occurs at the boundary between the upper layer support portion and the lower layer support portion for the same reason as the capacitance type acceleration sensors 100 and 200 of the first and second embodiments. The stress can be made smaller than that of the capacitive acceleration sensor 400.

[Others]
In any of the capacitive acceleration sensors described above, a silicon substrate is used as the substrate 101. The lower layer support is an insulator such as SiO2, the upper layer support (long and short), the beam and the movable electrode are Si, and the fixed electrode is a conductor such as Al. Impurities are implanted into the movable electrode, and the implantation concentration is determined according to the characteristics and performance required for the capacitive acceleration sensor. The size of the gap provided between the upper layer support and the substrate is also determined according to the size, strength, and accuracy of the capacitive acceleration sensor. However, the effect of stress relaxation is higher when the size of the gap is smaller than when it is smaller, and the fixing strength of the elastic support portion with respect to the substrate is higher when it is smaller than that of the gap. For this reason, it is desirable that the size of the gap is within the allowable range of the fixed strength and is as large as possible.

  Furthermore, the capacitive acceleration sensor according to the first embodiment, the second embodiment, and the modification described above can be realized by a sacrificial oxide film etching process or a bonding process. For this reason, Embodiment 1, Embodiment 2, and a modification can be manufactured by either sacrificial oxide film etching, bonding, or a combination of both depending on the accuracy of the manufacturing process.

  The present invention can be applied to any capacitance type acceleration sensor that detects acceleration in the Z-axis direction.

101 Substrate 105 Movable electrode 105a, 105b Movable electrode part 106 Beam part 107 Short part 117 Upper layer support part 121, 122, 141, 142, 420 Lower layer support part 123, 124 Fixed electrode 130, 140 Gap part 155a, 155b Long part 100, 200, 300, 400 Capacitive acceleration sensor

Claims (2)

A substrate,
A fixed electrode fixed on the substrate;
A movable electrode arranged to face the upper surface of the fixed electrode;
An elastic support portion for elastically supporting the movable electrode on the substrate so as to be displaceable in a direction orthogonal to the upper surface of the substrate;
With
The elastic support portion is
A lower layer support made of an insulator fixed on the substrate;
An upper layer support fixed on the lower layer support;
A beam portion having a long shape along the upper surface of the substrate, one end portion coupled to the upper layer support portion, and the other end portion coupled to the movable electrode;
Have
The lower support portion have a gap portion at a portion located immediately below the binding portion between said beam portion and the upper support portion,
The upper layer support portion has a planar shape including two long portions having a long shape along the longitudinal direction of the beam portion, and a short portion connecting the two long portions,
The lower support portion, the electrostatic capacitance type acceleration sensor, characterized by have a void portion for all portions right under the short portion. 2. The capacitive acceleration sensor according to claim 1, wherein the lower layer support portion further includes a gap in a part of a portion located immediately below the long portion.

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