JP5654916B2 - 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 from a change in capacitance.

Some current mobile devices include an acceleration sensor and detect the operation of a user carrying the mobile device. In such an acceleration sensor, electrodes are arranged at positions facing each other, and acceleration is obtained by utilizing the fact that the capacitance changes as the distance between the electrodes changes when acceleration is applied to the electrodes. There is a capacitive acceleration sensor to detect.
6A and 6B are diagrams illustrating a conventional capacitive acceleration sensor. 6A shows a plan view shape of the capacitive acceleration sensor 900 when the capacitive acceleration sensor 900 is viewed from the Z-axis direction shown in the figure, and FIG. 6B is a plan view of FIG. It is sectional drawing which follows the broken line DD shown in the inside. The capacitive acceleration sensor 900 is an acceleration sensor that detects acceleration applied in the X-axis direction shown in the drawing.

  As shown in FIGS. 6A and 6B, the capacitive acceleration sensor 900 is connected to the support substrate 909, the displaceable mass unit 901 provided on the support substrate 909, and the mass unit 901. And a beam portion 902 having a spring property. A movable electrode 903 extends from the mass portion 901, and fixed electrodes 904 and 905 are arranged so as to face the movable electrode 903. The mass portion 901, the beam portion 902, and the fixed electrodes 904 and 905 are supported on the support substrate 909 by the fixed anchor 906. In FIG. 6A, the fixed anchor 906 is indicated by a broken line. The broken line indicating the fixed anchor 906 is a virtual line that indicates the position of the fixed anchor 906 that is actually provided on the back surface of the beam portion 902.

  In addition, the mass portion 901 is connected to the beam portion 902 at two positions, and when acceleration is applied to the capacitive acceleration sensor 900, the mass portion 901 is relatively displaced with respect to the support substrate 909 by an inertial force. At this time, the capacitance between the movable electrode 903 and the fixed electrode 904 and the capacitance between the movable electrode 903 and the fixed electrode 905 change. The capacitive acceleration sensor 900 is configured to detect the acceleration applied to the capacitive acceleration sensor 900 based on the change in capacitance.

  When a mobile device or the like with a built-in capacitive acceleration sensor 900 is dropped or the like, the capacitive acceleration sensor 900 has an acceleration greater than the detected acceleration assumed in normal use in the Z-axis direction in the figure. . At this time, even if the mass part 901 and the movable electrode 903 come into contact with the support substrate 909, after the disappearance of the acceleration, the mass part 901 and the movable electrode 903 are brought into contact with the support substrate 909 by the restoring force of the movable electrode 903 itself and the beam part 902. Designed to return to its original state.

  Incidentally, in such a capacitive acceleration sensor 900, a phenomenon called stiction has been reported for a long time. Stiction is a phenomenon in which the mass portion 901 and the movable electrode 903 are not separated from the support substrate 909 even after the acceleration disappears after strong acceleration in the Z-axis direction is applied to the capacitive acceleration sensor 900. This phenomenon is thought to be caused by capillary action, electrostatic force, van der Waals force and the like. Note that stiction is also described in Patent Document 2.

When stiction occurs, the capacitive acceleration sensor loses its function. In consideration of stiction, the capacitive acceleration sensor 900 shown in FIG.
1 and a projecting portion 910 is provided at a position where the movable electrode 903 and the support substrate 909 are in contact with each other. In the case where the protruding portion 910 is provided, even if the mass portion 901 and the movable electrode 903 are in contact with the support substrate 909, the contact area is reduced. If the contact area is reduced, the electrostatic force or van der Waals force acting between the mass portion 901 and the movable electrode 903 and the support substrate 909 is reduced, and the occurrence of stiction can be suppressed.

JP-A-11-230986 JP 2001-121499 A

However, as described in Patent Document 1 described above, the configuration that suppresses the occurrence of stiction using the protrusion 910 adds a process of forming the protrusion 910 to the manufacturing process of the capacitive acceleration sensor 900. It becomes necessary to do. In general, in a semiconductor device, it is needless to say that adding a process leads to a complicated manufacturing process, a decrease in yield, and an increase in cost.
The present invention has been made in view of the above points, and provides a capacitive acceleration sensor in which stiction is unlikely to occur without adding a new process to the manufacturing process of the capacitive acceleration sensor. For the purpose.

In order to solve the above problems, a capacitive acceleration sensor according to the present invention is a capacitive sensor that detects acceleration using a change in electrostatic capacitance that occurs between a movable electrode and a fixed electrode facing each other. Type acceleration sensor, which has a substrate (for example, the support substrate 109 shown in FIG. 1B), the fixed electrode on the substrate, and a spring property, and has a first anchor portion on the substrate. A first beam portion to be fixed (for example, the beam portion 102 shown in FIG. 1A) and a second beam portion to be fixed through a second anchor portion (for example, shown in FIG. 1A). A beam portion 102), and a mass portion (for example, a mass portion 111 shown in FIG. 1A) between the first beam portion and the second beam portion and having the movable electrode, A straight line obtained by translating a virtual straight line connecting the first anchor part and the second anchor part to the mass part. For example, the mass unit is divided into a first mass unit (for example, the first mass unit 110 illustrated in FIG. 1A) and a second mass unit (for example, FIG. 1A by the straight line r) illustrated in FIG. ) when divided into the second mass 120) and shown, the a first mass of the mass, the mass of the second mass Ri is Do different, both ends of the movable electrode is the mass The mass of the entire convex part formed in the first mass part is supported by a part, and the mass part has a convex part (for example, the convex part 730 shown in FIG. 5) extending in the horizontal direction with respect to the substrate. Is larger than the mass of the entire convex portion formed in the second mass portion.

Further, in the capacitive acceleration sensor of the present invention, in the above-described invention, the first anchor portion is located at a position where the mass of the first mass portion is larger than the mass of the second mass portion, Preferably, the second anchor portion is provided.
Further, in the capacitance type acceleration sensor of the present invention, in the above-described invention, the total mass of the movable electrode (for example, the movable electrodes 303a and 303b shown in FIG. 2) in the first mass portion is It is desirable that the total mass of the movable electrode (for example, 303b shown in FIG. 2) of the second mass is larger.

Further, the capacitance type acceleration sensor of the present invention is the above-described invention, wherein the mass portion has a cutout portion cut out in a horizontal or vertical direction with respect to the substrate, and the first mass portion includes The mass lost from the first mass part by the formed notch is lost from the second mass by the notch (for example, the hole 530 shown in FIG. 4) formed in the second mass. It is desirable that the mass be larger than the mass .

  According to the present invention described above, when a strong acceleration is applied to the capacitive acceleration sensor in the vertical direction, the mass part and the movable electrode are inclined and approach the substrate, and the mass part and the movable electrode are in contact with the substrate. In this case, the mass part and the edge part of the movable electrode are in line contact with the substrate. For this reason, it is possible to provide a capacitive acceleration sensor in which stiction hardly occurs. Further, since such a configuration can be realized only by changing the patterning pattern of the mass part and the movable electrode, it is not necessary to add a new process to the manufacturing process of the capacitive acceleration sensor.

It is a figure for demonstrating the capacitive acceleration sensor of Embodiment 1 of this invention. It is the figure which showed the planar view shape of the capacitive acceleration sensor of Embodiment 2 of this invention. It is the figure which showed the planar view shape of the capacitive acceleration sensor of Embodiment 3 of this invention. It is a figure for demonstrating the electrostatic capacitance type acceleration sensor of Embodiment 4 of this invention. It is a figure for demonstrating the electrostatic capacitance type acceleration sensor of Embodiment 5 of this invention. It is the figure which illustrated the conventional capacitance type acceleration sensor

Embodiments 1 to 5 of the capacitive acceleration sensor of the present invention will be described below.
[Embodiment 1]
FIGS. 1A, 1B, and 1C are diagrams for explaining a capacitive acceleration sensor according to Embodiment 1 of the present invention. FIG. It is the figure which showed the planar view shape which looked at the capacitive acceleration sensor 100 from the Z-axis direction shown in the figure. Moreover, FIG.1 (b) is sectional drawing which follows the broken line AA shown in FIG. FIG. 1C is a cross-sectional view taken along the broken line DD ′, and shows a cross section of the region F surrounded by the broken line shown in the drawing.
In the first embodiment, five sets of the movable electrode and the fixed electrode are shown in the plan view shape of the capacitive acceleration sensor 100. However, the actual capacitive acceleration sensor includes the movable electrode and the fixed electrode. 20 to 30 sets are included.

  The capacitive acceleration sensor shown in FIGS. 1A and 1B detects acceleration using a change in electrostatic capacitance generated between a movable electrode and a fixed electrode facing each other. . As shown in FIGS. 1A and 1B, the capacitive acceleration sensor 100 has a support substrate 109, fixed electrodes 104 and 105 fixed to the support substrate 109, and has a spring property. Two beam portions 102 fixed to the substrate 109 via a fixed anchor 106 and a mass portion 111 having a movable electrode 103 between the two beam portions 102 are provided. A portion of the mass portion 111 excluding the movable electrode 103 is referred to as a mass portion main body 101. The mass part 111 is a member in which the mass part main body 101 and the movable electrode 103 are combined.

The two end portions 102a of the beam portion 102 are fixed to the substrate by fixed anchors 106, respectively. The fixed anchor 106 is indicated by a broken line in FIG. The fixed anchor 106 is actually provided on the back surface of the end portion 102a. In the first embodiment, a straight line obtained by translating a virtual straight line connecting two fixed anchors 106 onto the support substrate 109 is shown as a straight line r in FIG. Moreover, the location of the upper surface of the end portion 102a immediately above the connection location where the fixed anchor 106 and the back surface of the end portion 102a are connected is shown in FIGS. 1A and 1B as the connection location p and the connection location q.

The capacitive acceleration sensor 100 detects acceleration applied in parallel to the support substrate 109 and in the arrangement direction of the beam portions 102. In this specification, the arrangement direction of the beam portions 102 parallel to the support substrate 109 is the X-axis direction shown in the drawing.
When acceleration is applied to the capacitive acceleration sensor 100 in the X-axis direction, the mass portion main body 101 is displaced relative to the support substrate 109 by the inertial force, and the movable electrode 103 and the fixed electrode 104 are displaced. The capacitance between the movable electrode 103 and the fixed electrode 105 changes. The capacitive acceleration sensor 100 is configured to detect acceleration from a change in capacitance at this time.

  A mass part body 101 of the capacitive acceleration sensor 100 shown in FIG. 1 has a rectangular planar shape with a uniform thickness, and extends from the mass part body 101 in the + Y direction or the −Y direction. The movable electrode 103 is assumed to have the same length, width and mass. The center of mass of the mass unit 111 that combines the mass unit main body 101 and the plurality of movable electrodes 103 has a straight line t that bisects the side of the mass unit main body 101 along the Y-axis direction, and the X of the mass unit main body 101. It is at the intersection (indicated by point o in FIG. 1) with a straight line s that bisects the side along the axial direction.

On the other hand, the connection points p and q of the beam portion 102 are shifted in the −Y direction from the point o as shown in FIG. That is, the two beam portions 102 are fixed to the support substrate 109 via the fixed anchors 106 at positions deviating from the straight line passing through the center of gravity of the mass portion 111.
Here, in the plan view shape of the mass part 111, when the mass part 111 is distinguished into the first mass part 110 and the second mass part 120 with the straight line r as a boundary, in the first embodiment, it is clear from FIG. As described above, the length of the first mass unit 110 in the Y-axis direction is longer than the length of the second mass unit 120 in the Y-axis direction. That is, it can be said that the connection points p and q of the mass unit 111 are provided at positions where the mass of the first mass unit 110 is larger than the mass of the second mass unit 120.

In the capacitive acceleration sensor 100 configured as described above, when excessive acceleration is applied to the support substrate 109 in the Z-axis direction, the mass portion 111 and the movable electrode 103 are rotated about the straight line r. Power is generated.
The mass portion 111 and the movable electrode 103 approach the support substrate 109 while being inclined with respect to the support substrate 109 by the rotational force. At this time, when the first mass unit 110 having a larger mass is inclined downward and the first mass unit 110 and the movable electrode 103 come into contact with the support substrate 109, the first mass unit 110 or the movable electrode 103 Only the edge portion makes line contact with the support substrate 109.

The above state is shown in FIG. In FIG. 1C, the movable electrode 103 when the mass unit main body 101 is supported horizontally with respect to the support substrate 109 is indicated by a broken line, and the acceleration in the Z-axis direction in the first embodiment is a capacitive acceleration sensor. The movable electrode 103 when added to is indicated by a solid line.
As described above, in the capacitive acceleration sensor 100 of the first embodiment, the contact area between the mass unit 111 and the movable electrode 103 and the support substrate 109 is reduced, and stiction is less likely to occur. Further, providing the connection points p and q by shifting them from the center of gravity can be realized by changing a mask pattern when forming the mass portion main body 101 and the beam portion 102. For this reason, the capacitive acceleration sensor 100 shown in FIG. 1 can be realized without adding a new process to the manufacturing process of a general capacitive acceleration sensor.

In the first embodiment, the mass unit main body 101 is inclined to contact the support substrate 109 by making the mass of the first mass unit 110 larger than the mass of the second mass unit 120. However, the embodiment of the present invention is not limited to such a configuration, and the mass of the mass portion 111 is distinguished on the boundary of the straight line r, and the masses of the two distinguished members are different. May be.
In the capacitive acceleration sensor 100 of the first embodiment described above, a silicon substrate is used as the support substrate 109. Further, the beam portion 102, the movable electrode 103, deposited silicon film is used if example embodiment the fixed electrode 104 and 105.

[Embodiment 2]
Next, the capacitive acceleration sensor according to the second embodiment will be described. FIG. 2 is a diagram illustrating a plan view shape of the capacitive acceleration sensor 300 according to the second embodiment when viewed from the Z-axis direction illustrated in the drawing. Note that, among the configurations and symbols shown in FIG. 2, the same configurations and symbols as those shown in FIG.

  The capacitive acceleration sensor 300 according to the second embodiment includes a beam unit 102 whose one end is fixed to a support substrate (not shown), a mass unit 311 elastically supported between the two beam units 102, and a mass unit body in the mass unit 311. A movable electrode 103 extending from 301 to the + Y direction or the −Y direction in the figure, and fixed electrodes 104 and 105 fixed to the support substrate 109 so as to oppose the movable electrode 103 along the X-axis direction are provided.

The beam portion 102 is connected to the mass portion 311 at connection points p and q on a straight line (corresponding to the straight line r shown in the drawing) that bisects the side along the Y-axis direction of the mass portion main body 301. . In the second embodiment, in the plan view shape of the mass part 311, the mass part 311 is distinguished into a first mass part 310 and a second mass part 320 with a straight line r as a boundary.
The plurality of movable electrodes are provided with a movable electrode 303b having a predetermined length (for example, the same length as the movable electrode 103 of Embodiment 1) and a movable electrode 303a longer than the movable electrode 303b. Of the six movable electrodes extending from the mass part main body 301 on the first mass part 310 side, two are movable electrodes 303a, and the other four are movable electrodes 303b. On the other hand, all of the six movable electrodes extending from the mass part main body 301 on the second mass part 320 side are movable electrodes 303b.

  According to such a configuration, the masses of the plurality of movable electrodes 303a and 303b on the first mass unit 310 side are larger than the masses of the plurality of movable electrodes 303b on the second mass unit 320 side. At this time, as a matter of course, the center of gravity (indicated by a point o in FIG. 2) of the mass unit 311 including the mass unit main body 301 and the movable electrodes 303a and 303b is closer to the first mass unit 310 having a larger mass. Is biased. On the other hand, since the connection points p and q are provided on a straight line that bisects the side along the Y-axis direction of the mass unit main body 301, in the second embodiment, the straight line r passing through the connection points p and q is a dotted line. It is provided at a position not passing through o.

From the above, when a large acceleration is applied to the capacitive acceleration sensor 300 in the Z-axis direction, the mass portion 311 is inclined with respect to the straight line r. At this time, when the movable electrodes 303 a and 303 b of the first mass portion 310 having a larger mass are inclined downward and come into contact with the support substrate 109, only the edge portions thereof are in line contact with the support substrate 109. For this reason, in Embodiment 2, even when the mass part 311 and the support substrate 109 are in contact with each other, the contact area is reduced, and the possibility that stiction occurs between the two can be reduced.
Moreover, the structure demonstrated above is realizable by changing the mask which patterns the mass part 311. FIG. For this reason, the second embodiment can be realized without increasing the number of steps of a general capacitive acceleration sensor, as in the first embodiment.

[Embodiment 3]
Next, the capacitive acceleration sensor of the third embodiment will be described. FIG. 3 is a diagram showing a plan view shape of the capacitive acceleration sensor 400 according to the third embodiment when viewed from the Z-axis direction shown in the figure. Note that, among the configurations and symbols shown in FIG. 3, the same configurations and symbols as those shown in FIGS. 1 and 2 are denoted by the same reference numerals, and a part of the description is omitted.
The capacitive acceleration sensor 400 according to the third embodiment includes a beam unit 102 having one end fixed to a support substrate (not shown), a mass unit 311 elastically supported between the two beam units 102, and a mass unit body of the mass unit 311. A fixed electrode 104 and 105 fixed on the support substrate so as to oppose the movable electrode 403 along the X-axis direction 403 and the 403 extending in the + Y direction or the −Y direction in FIG.

The beam portion 102 is connected to the support substrate 109 at connection points p and q on a straight line (corresponding to the straight line r shown in the drawing) that bisects the side of the mass portion main body 301 along the Y-axis direction. . In the third embodiment, in the plan view shape of the mass part 311, the mass part 311 is distinguished from the first mass part 310 and the second mass part 320 with the straight line r as a boundary.
In the third embodiment, five movable electrodes 403 extend from the mass part main body 301 on the first mass part 310 side. On the other hand, six movable electrodes 403 extend from the mass part main body 301 on the second mass part 320 side. The movable electrodes 403 all have the same length and the same width, and their masses are all the same.

According to such a configuration, the mass of the plurality of movable electrodes of the second mass unit 320 is larger than the mass of the plurality of movable electrodes of the first mass unit 310. At this time, as a matter of course, the center of gravity (indicated by a point o in FIG. 3) of the mass unit 311 including the mass unit main body 301 and the movable electrode 403 is biased toward the second mass unit 320 having a larger mass. ing. On the other hand, since the connection points p and q are on a straight line that bisects the side along the Y-axis direction of the mass part main body 301, in the third embodiment, the straight line r passing through the connection points p and q passes through the point o. Will be in no position.

From the above, when a large acceleration is applied to the capacitive acceleration sensor 400 in the Z-axis direction, the mass portion 311 is inclined with respect to the straight line r. At this time, even when the movable electrode 403 of the second mass unit 320 is inclined downward and comes into contact with the support substrate, only the edge portion of the mass unit main body 301 on the second mass unit 320 side or the movable electrode 403 is the support substrate. Line contact with For this reason, in Embodiment 3, the contact area of the mass part 311 and the support substrate is reduced, and the possibility that stiction occurs between the two is reduced.
Moreover, the structure demonstrated above is realizable by changing the mask which patterns the mass part 311. FIG. For this reason, the third embodiment can be realized without increasing the number of man-hours of a general capacitive acceleration sensor, similarly to the first and second embodiments.

[Embodiment 4]
Next, the capacitive acceleration sensor of the fourth embodiment will be described. FIG. 4A is a diagram showing a plan view shape of the capacitive acceleration sensor 500 according to the fourth embodiment viewed from the Z-axis direction shown in the figure, and FIG. 4B is a diagram of FIG. It is sectional drawing which follows the broken line BB shown in the inside. Among the configurations and symbols shown in FIGS. 4A and 4B, the same configurations and symbols as those shown in FIGS. Shall.
The capacitive acceleration sensor 500 according to the fourth embodiment includes a beam portion 102 having one end fixed to the support substrate 109 shown in FIG. 4B and a mass portion 511 elastically supported between the two beam portions 102. The movable electrode 103 extending from the mass portion main body 501 of the portion 511 in the + Y direction or the −Y direction in the drawing, and the fixed electrode 104 fixed on the support substrate 109 so as to oppose the movable electrode 103 along the X direction. , 105.

The beam portion 102 is connected to the support substrate 109 by connection points p and q provided on a straight line (corresponding to a straight line r shown in the drawing) that bisects the side of the mass portion main body 501 along the Y-axis direction. Connected. In the fourth embodiment, in the plan view shape of the mass part 511, the mass part 511 is distinguished into a first mass part 510 and a second mass part 520 with the straight line r as a boundary. First mass part 5
10 and a plurality of movable electrodes 103 having the same length and the same width all extend from the mass part main body 501 on either side of the second mass part 520.

The mass portion main body 501 of the capacitive acceleration sensor 500 has a plurality of through holes (hereinafter referred to as “hole portions”) 530 cut out in the vertical direction with respect to the support substrate 109. In the mass body 501, three holes 530 are formed in the mass body 501 on the first mass 510 side, and two holes 530 are formed in the mass body 501 on the second mass 520 side. Is formed.
The plurality of hole portions 530 all have a rectangular shape in plan view, and the length and depth of the vertical and horizontal sides are all the same. Moreover, the thickness of the mass part 511 is uniform as a whole. Therefore, in the fourth embodiment, the mass lost from the first mass unit 510 by the hole 530 formed in the mass unit main body 501 on the first mass unit 510 side is the mass unit main body on the second mass unit 520 side. It becomes larger than the mass lost from the 2nd mass part 520 by the hole part 530 formed in 501.

  According to such a configuration, the mass of the second mass unit 520 is larger than the mass of the first mass unit 510, and naturally, the center of gravity of the mass unit 511 (indicated by a point o in FIG. 4) is The mass is biased toward the second mass portion 520 having a larger mass. On the other hand, since the connection points p and q are on a straight line that bisects the side of the mass body 501 along the Y-axis direction, in the fourth embodiment, the straight line r passing through the connection points p and q passes through the point o. There will be no position.

  From the above, when a large acceleration is applied to the capacitive acceleration sensor 500 in the Z-axis direction, the mass portion 511 is inclined with respect to the straight line r. At this time, when the second mass unit 520 and the movable electrode 103 of the second mass unit 520 are inclined downward and come into contact with the support substrate 109, only the edge portions thereof are in line contact with the support substrate 109. For this reason, in Embodiment 4, the contact area of the mass part 511 and the support substrate 109 becomes small, and possibility that stiction will generate | occur | produce between both will be reduced.

The hole 530 can be formed simultaneously with the patterning of the mass portion 511. For this reason, the fourth embodiment can be realized by changing a mask for patterning the mass portion 511. Therefore, as in the first to third embodiments, the fourth embodiment can be realized without increasing the number of steps of a general capacitive acceleration sensor. be able to.
In the fourth embodiment described above, the holes 530 are provided in the mass unit main body 501, and the masses of the first mass unit 510 and the second mass unit 520 are made different. However, the fourth embodiment is not limited to such a configuration. For example, a concave portion that does not penetrate the mass portion main body 501 by cutting out the mass portion main body 501 in the horizontal direction as well as in the vertical direction instead of the hole portion 530. May be provided.

[Embodiment 5]
Next, the capacitive acceleration sensor of Embodiment 5 will be described. FIG. 5A is a diagram showing a planar view shape of the capacitive acceleration sensor 700 of the fifth embodiment, and FIG. 5B is along the broken line CC shown in FIG. It is sectional drawing. The capacitive acceleration sensor 700 is a so-called “cantilever” type in which the capacitive acceleration sensor according to the first to fourth embodiments is supported by the mass portion only at one end of the movable electrode. It is configured as a so-called “both-end” type in which both end portions of the movable electrode are supported by the mass portion. Of the configurations and symbols shown in FIGS. 5A and 5B, the same configurations and symbols as those shown in FIGS. 1 to 4 are denoted by the same reference numerals, and a part of the description is omitted. Shall.

The capacitive acceleration sensor 700 according to the fifth embodiment includes a beam portion 702 having one end fixed to the support substrate 109 shown in FIG. 5B and a mass portion 701 elastically supported between the two beam portions 702 and a mass. The part 701 includes a movable electrode 703 extending in the Y-axis direction in the figure, and a fixed electrode 704 and 705 fixed on the support substrate 109 so as to oppose the movable electrode 703 along the X-axis direction. In the fifth embodiment, the mass unit 701 includes the movable electrode 703.

  The mass part 701 is connected to the beam part 702 at the connection points p and q. The beam portion 702 is connected to the mass portion 701 at connection points p and q on a straight line that bisects the side of the mass portion 701 along the Y-axis direction. In Embodiment 5, in the planar shape of the mass part 701, the mass part 701 is distinguished into a first mass part 710 and a second mass part 720 with a straight line r connecting the connection point p and the connection point q as a boundary. To do.

In the fifth embodiment, the movable electrode on the first mass part 710 side is 703a, and the movable electrode on the second mass part 720 side is 703b. The plurality of movable electrodes 703a and movable electrodes 703b are movable electrodes having the same length and the same width and the same mass.
The mass portion 701 of the capacitive acceleration sensor 700 has a convex portion 730 extending in the horizontal direction with respect to the support substrate 109 at the outer edge thereof. Four convex portions 730 are formed on the outer edge portion of the first mass portion 710, and three convex portions 730 are formed on the outer edge portion of the second mass portion 720. In the fifth embodiment, it is assumed that the plurality of convex portions 730 all have the same length of the vertical and horizontal sides.

Further, all the convex portions 730 are made of the same material as the mass portion 701 and have the same mass. Therefore, in Embodiment 5, the mass of the first mass portions 710 of the four formed protrusion 730 is larger than the mass of the second mass portions 3 formed in 720 protrusion 730.
At this time, as a matter of course, the center of gravity of the mass part 701 (indicated by a point o in FIG. 5) is biased toward the first mass part 710 having a larger mass. On the other hand, since the connection points p and q are provided on a straight line that bisects the side of the mass portion 701 along the Y-axis direction, in the fifth embodiment, the straight line r passing through the connection points p and q is a point o. It is provided at a position that does not pass.

  From the above, when a large acceleration is applied to the capacitive acceleration sensor 700 in the Z-axis direction, the mass portion 701 is inclined with respect to the straight line r. At this time, the first mass part 710 and the convex part 730 are inclined downward. When the first mass portion 710 and the convex portion 730 are in contact with the support substrate 109, only the edge portion of the first mass portion 710 is in line contact with the support substrate 109. For this reason, in Embodiment 5, the contact area of the mass part 701 or the convex part 730 and the support substrate 109 becomes small, and possibility that stiction will generate | occur | produce between both will be reduced.

Moreover, in the structure demonstrated above, the convex part 730 can be formed simultaneously with the patterning of the mass part 701. FIG. For this reason, the fifth embodiment can be realized by changing a mask for patterning the mass portion 701. Therefore, as in the first to fourth embodiments, the fifth embodiment can be realized without increasing the number of steps of a general capacitive acceleration sensor. be able to.
In the fifth embodiment described above, the capacitive acceleration sensor is configured as a double-sided capacitive acceleration sensor. However, the fifth embodiment is not limited to such a configuration, and can be configured as a cantilever type. Furthermore, the capacitive acceleration sensor of Embodiments 1 to 4 can be configured as a double-sided capacitive acceleration sensor.

  The present invention is an electrostatic capacitance type acceleration sensor that detects the acceleration in the X-axis direction and the Y-axis direction due to a change in capacitance, and can generate stiction when acceleration in the Z-axis direction is applied. The present invention can be applied to any capacitance type acceleration sensor.

100, 300, 400, 500, 700 Capacitive acceleration sensor 101, 301, 501 Mass body 102 Beam 103, 303a, 303b, 403, 703a, 703b Movable electrode 104, 105 Fixed electrode 106 Fixed anchor 109 Support substrate 110, 310, 510, 710 First mass part
111, 311, 511, 701 Mass part 120, 320, 520, 720 Second mass part 530 Hole part 730 Convex part

Claims (4)

A capacitance type acceleration sensor that detects acceleration using a change in capacitance generated between an electrode between a movable electrode and a fixed electrode facing each other,
A substrate,
The fixed electrode on the substrate;
A first beam portion having a spring property and fixed to the substrate via a first anchor portion;
A second beam portion fixed via a second anchor portion;
A mass part between the first beam part and the second beam part and having the movable electrode,
The mass part is divided into a first mass part and a second mass part by a straight line obtained by translating a virtual straight line connecting the first anchor part and the second anchor part onto the mass part. and if the mass of the first mass, Ri said second parts by mass and the Do different of,
Both ends of the movable electrode are supported by the mass part,
The mass portion has a convex portion extending in a horizontal direction with respect to the substrate at an outer edge portion thereof,
The capacitance type acceleration sensor characterized in that the mass of the entire convex portion formed in the first mass portion is larger than the mass of the entire convex portion formed in the second mass portion .   The first anchor part and the second anchor part are provided at a position where the mass of the first mass part is larger than the mass of the second mass part. The capacitive acceleration sensor described in 1.   2. The electrostatic capacitance according to claim 1, wherein an entire mass of the movable electrode in the first mass portion is larger than an entire mass of the movable electrode in the second mass. Type acceleration sensor. The mass portion has a notch cut out in a horizontal or vertical direction with respect to the substrate,
The mass lost from the first mass part by the notch formed in the first mass part is larger than the mass lost from the second mass part by the notch formed in the second mass part. The capacitance type acceleration sensor according to claim 1, wherein the capacitance type acceleration sensor is large.

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