JP2015059830A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure capable of suppressing the movement of a movable electrode in a surface direction parallel to the surface of a substrate in a seesaw type capacitance type acceleration sensor.SOLUTION: A first spring part 70 includes: a first linear beam part 71 inclined to a perpendicular direction perpendicular to the longitudinal direction of a pair of connection parts 53 in a plane direction parallel to a surface 23 of a substrate 20; and a second linear beam part 72 inclined to the direction opposite to the first beam 71 for the perpendicular direction. The first beam part 71 and the second beam part 72 are arranged in such a manner that a spacing between the sides of both fixing parts 60 becomes narrower than the spacing between the sides of the pair of connection parts 53, thereby being arranged in a V-shape. In the same way, a second spring part 80 has a third beam part 81 and a fourth beam part 82, and a third beam part 81 and a fourth beam part 82 are also arranged in the V-shape.

Description

  The present invention relates to a seesaw type capacitive acceleration sensor.

  Conventionally, a seesaw-type capacitive acceleration sensor has been proposed in, for example, Patent Document 1. Specifically, the acceleration sensor includes a substrate, a first fixed electrode and a second fixed electrode, an anchor portion, and a movable electrode. Each fixed electrode is spaced apart on the substrate, and the anchor portion is disposed between each fixed electrode.

  In addition, the movable electrode is connected to a portion disposed opposite to the first fixed electrode and a portion disposed opposite to the second fixed electrode, and is supported by the anchor portion via a linear torsion beam. . Further, the movable electrode is disposed around the movable electrode and has a mass body connected to the movable electrode. The mass body plays a role of moving the movable electrode by receiving an acceleration applied in a direction perpendicular to the surface of the substrate.

  The movable electrode rotates to the first fixed electrode side or the second fixed electrode side with the torsion beam as the central axis. That is, the movable electrode rotates like a seesaw with the torsion beam as a rotation axis. Therefore, when the mass body receives acceleration, the distance between each fixed electrode and the movable electrode changes. Thereby, acceleration is detected based on the change in capacitance between each fixed electrode and the movable electrode.

International Publication No. 03/044539

  However, in the above conventional technique, since the movable electrode is fixed to the anchor portion by a linear torsion beam, when the mass body receives acceleration in a plane direction parallel to the surface of the substrate, the movable electrode is moved in the plane direction. Will be moved to. For this reason, since the opposing area of each fixed electrode and the movable electrode changes, there is a problem that the measurement accuracy of the change in capacitance is lowered.

  An object of the present invention is to provide a structure capable of suppressing the movement of a movable electrode in a plane direction parallel to the surface of a substrate in a seesaw-type capacitive acceleration sensor.

  In order to achieve the above object, in the invention according to claim 1, the substrate (20) having the surface (23), the first fixed electrode (30) disposed on the surface (23) of the substrate (20), And a second fixed electrode (40) disposed on the surface (23) of the substrate (20) and spaced apart from the first fixed electrode (30).

  A first facing portion (51) disposed opposite to the first fixed electrode (30), a second facing portion (52) disposed facing the second fixed electrode (40), a first facing portion (51), The movable electrode (50) which has a pair of linear connection part (53, 54) which connects a 2nd opposing part (52) is provided.

  Moreover, it arrange | positions in the area | region enclosed by the part corresponding to a 1st opposing part (51), a 2nd opposing part (52), and a pair of connection part (53,54) among the surfaces (23) of a board | substrate (20). The fixed portion (60), the first spring portion (70) connecting one of the pair of connecting portions (53, 54) and the fixing portion (60), and the pair of connecting portions (53, 54). A second spring part (80) for connecting the other of the first part and the fixing part (60).

  When the movable electrode (50) receives an acceleration, the first opposing portion (51) rotates toward the first fixed electrode (30) due to the torsion of the first spring portion (70) and the second spring portion (80). Alternatively, when the second facing portion (52) rotates toward the second fixed electrode (40), the static electricity between the first fixed electrode (30) and the second fixed electrode (40) and the movable electrode (50) is obtained. An acceleration is detected based on a change in capacitance.

  Further, the first spring portion (70) and the second spring portion (80) are perpendicular to the longitudinal direction of the pair of connecting portions (53, 54) in the plane direction parallel to the surface (23) of the substrate (20). Linear first beam portion (71, 81) inclined with respect to the direction and linear second beam portion inclined to the opposite side of the first beam portion (71, 81) with respect to the vertical direction (72, 82), respectively.

  According to this, even if the movable electrode (50) receives acceleration in a plane direction parallel to the surface (23) of the substrate (20), the first spring portion (70) and the second spring portion (80) are movable electrodes. The force applied to (50) is no longer received. That is, since the force applied to the movable electrode (50) is distributed to the first beam portion (71, 81) and the second beam portion (72, 82), the movable electrode (50) is moved to the first beam portion (71, 81). 81) and the second beam portions (72, 82) make it difficult to move in the surface direction. Therefore, the movement of the movable electrode (50) in the surface direction can be suppressed.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

1 is a plan view of an acceleration sensor according to a first embodiment of the present invention. It is II-II sectional drawing of FIG. It is the figure which showed a mode that the force concerning a connection part was disperse | distributed to a beam part. It is a top view of the acceleration sensor which concerns on 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The acceleration sensor according to the present embodiment is a seesaw type capacitive sensor that detects acceleration based on the capacitance of a capacitor formed by a movable electrode and a fixed electrode by moving the movable electrode like a seesaw. .

  As shown in FIGS. 1 and 2, the acceleration sensor 10 includes a substrate 20, a first fixed electrode 30, a second fixed electrode 40, a movable electrode 50, a fixed portion 60, a first spring portion 70, and a second spring portion. 80.

As shown in FIG. 2, the substrate 20 includes a semiconductor substrate 21 such as a Si substrate and an insulating film 22 such as SiO ₂ formed on the semiconductor substrate 21. The surface of the insulating film 22 opposite to the silicon substrate 20 is the surface 23 of the substrate 20. The semiconductor substrate 21 is formed with a control circuit unit having a function of calculating and amplifying a signal corresponding to the capacitance of the capacitor composed of the fixed electrodes 30 and 40 and the movable electrode 50 and outputting the signal to the outside. ing.

  The first fixed electrode 30 and the second fixed electrode 40 are electrode portions arranged on the surface 23 of the substrate 20, and are laid out in a rectangular shape, for example. The first fixed electrode 30 and the second fixed electrode 40 are spaced apart from each other. Each of the fixed electrodes 30 and 40 is formed by patterning a conductive layer such as a silicon layer into a predetermined shape. The fixed electrodes 30 and 40 are electrically connected to the control circuit unit via wiring (not shown).

  The movable electrode 50 includes a first facing portion 51, a second facing portion 52, and a pair of connecting portions 53 and 54. The first facing portion 51 is an electrode portion disposed to face the first fixed electrode 30, and the second facing portion 52 is an electrode portion disposed to face the second fixed electrode 40. The opposing portions 51 and 52 are laid out in a rectangular shape like the fixed electrodes 30 and 40. The pair of connecting portions 53 and 54 are linear connecting portions that connect the first facing portion 51 and the second facing portion 52.

  The fixing part 60 plays a role of fixing the movable electrode 50 to the substrate 20 via the first spring part 70 and the second spring part 80. As shown in FIG. 1, the fixing portion 60 is in a region surrounded by a portion corresponding to the first facing portion 51, the second facing portion 52, and the pair of connecting portions 53 and 54 on the surface 23 of the substrate 20. Has been placed.

  Further, as shown in FIG. 2, the fixing portion 60 is disposed on the insulating film 22. The fixing unit 60 is configured by, for example, a stacked structure of a first support layer 61, an insulating film 62, and a second support layer 63. The second support layer 63 of the fixed portion 60 is electrically connected to the movable electrode 50. Further, the second support layer 63 is electrically connected to the control circuit unit through a through electrode formed in the fixed unit 60, for example.

  The first spring portion 70 is a connecting portion that connects one connecting portion 53 of the pair of connecting portions 53 and 54 and the fixing portion 60. The first spring part 70 has a first beam part 71 and a second beam part 72.

  As shown in FIG. 1, the first beam portion 71 has a vertical direction (in the plane direction parallel to the surface 23 of the substrate 20, that is, the XY plane, perpendicular to the longitudinal direction (X direction) of one connecting portion 53. It is a linear beam portion inclined with respect to (Y direction). The second beam portion 72 is a linear beam portion that is inclined to the opposite side of the first beam portion 71 with respect to the vertical direction (Y direction). The first beam portion 71 is located on the first facing portion 51 side, and the second beam portion 72 is located on the second facing portion 52 side. In the present embodiment, the first beam portion 71 and the second beam portion 72 are laid out in line symmetry with respect to an axis of symmetry parallel to the vertical direction (Y direction).

  The second spring portion 80 is a connecting portion that connects the other connecting portion 54 of the pair of connecting portions 53 and 54 and the fixing portion 60. The second spring part 80 includes a third beam part 81 and a fourth beam part 82.

  Similar to the first beam portion 71, the third beam portion 81 is a linear beam portion that is inclined with respect to a vertical direction (Y direction) perpendicular to the longitudinal direction (X direction) of the other connecting portion 54. . Similar to the second beam portion 72, the fourth beam portion 82 is a linear beam portion inclined to the opposite side of the third beam portion 81 with respect to the vertical direction (Y direction). The third beam portion 81 is located on the first facing portion 51 side, and the fourth beam portion 82 is located on the second facing portion 52 side. The third beam portion 81 and the fourth beam portion 82 are laid out in line symmetry with respect to an axis of symmetry parallel to the vertical direction (Y direction).

  In this embodiment, the 1st beam part 71 and the 2nd beam part 72 were arrange | positioned so that the mutual space | interval by the side of the fixing | fixed part 60 might become narrower than the mutual space | interval by the side of a pair of connection parts 53 and 54. It is laid out in a V shape. The third beam portion 81 and the fourth beam portion 82 are similarly laid out in a V shape. In other words, it can be said that the first spring portion 70 and the second spring portion 80 are laid out in an X shape. Thus, since each spring part 70 and 80 is comprised by V shape, it can arrange | position so that the rigidity of the surface direction parallel to the surface 23 of the board | substrate 20 of each spring part 70 and 80 may be made high.

  Furthermore, the fixed portion 60 side of the first beam portion 71 and the fixed portion 60 side of the second beam portion 72 are fixed to the fixed portion 60 at one point. Similarly, the fixed portion 60 side of the third beam portion 81 and the fixed portion 60 side of the fourth beam portion 82 are fixed to the fixed portion 60 at one point. Thus, since the two beams are fixed at one point, it is possible to prevent the springs 70 and 80 from being twisted. That is, the rotation of the movable electrode 50 can be prevented from being hindered.

  The fixed electrodes 30, 40, the movable electrode 50, the fixed portion 60, and the spring portions 70, 80 are laid out in a predetermined pattern by etching each layer of the SOI substrate, for example. For this reason, the fixing portion 60 has a three-layer structure.

  The above is the overall configuration of the acceleration sensor 10 according to the present embodiment. In the above configuration, when the movable electrode 50 receives acceleration in a direction perpendicular to the surface 23 of the substrate 20, that is, in the Z direction, the first spring portion 70 and the second spring portion 80 are twisted. Accordingly, the first facing portion 51 rotates to the first fixed electrode 30 side or the second facing portion 52 rotates to the second fixed electrode 40 side. Thereby, the distance between the 1st fixed electrode 30 and the 1st opposing part 51 and the distance between the 2nd fixed electrode 40 and the 2nd opposing part 52 change. Therefore, the control circuit unit provided on the substrate 20 acquires a capacitance corresponding to the change in the distance, and acquires an acceleration corresponding to the capacitance.

  Then, the effect that each spring part 70 and 80 is comprised in V shape as mentioned above is demonstrated. For example, it is assumed that the movable electrode 50 receives acceleration in the X direction (from the first facing portion 51 side to the second facing portion 52 side) parallel to the surface 23 of the substrate 20. In this case, as shown in FIG. 3, the acceleration applied in the X direction is distributed to the one connection portion 53 and the first beam portion 71 at the connection portion between the one connection portion 53 and the first beam portion 71. . Although not shown, also in the connecting portion between the other connecting portion 54 and the third beam portion 81, the acceleration applied in the X direction is distributed to the other connecting portion 54 and the third beam portion 81.

  Thus, since the first spring part 70 and the second spring part 80 do not receive the X-direction acceleration applied to the movable electrode 50 as they are, the movable electrode 50 becomes difficult to move in the X direction. This is the same when the movable electrode 50 receives acceleration in the Y direction. Therefore, the movement of the movable electrode 50 can be suppressed in the XY plane. That is, since the change in the facing area between the facing portions 51 and 52 of the movable electrode 50 and the fixed electrodes 30 and 40 can be reduced, it is possible to suppress a decrease in measurement accuracy of the change in capacitance.

  As for the correspondence between the description of the present embodiment and the description of the claims, the third beam portion 81 corresponds to the “first beam portion” in the claims, and the fourth beam portion 82 claims. This corresponds to the “second beam portion” in the range.

(Second Embodiment)
In the present embodiment, parts different from the first embodiment will be described. As shown in FIG. 4, the first beam portion 71 and the second beam portion 72 of the first spring portion 70 are spaced apart from each other on the paired connecting portions 53 and 54 side than on the fixed portion 60 side. Is also arranged so as to be narrow, so that it is laid out in a V shape. The third beam portion 81 and the fourth beam portion 82 are similarly laid out in a V shape. In other words, it can be said that the first spring part 70 and the second spring part 80 are laid out in a ◇ shape.

  Further, one connecting portion 53 side of the first beam portion 71 and one connecting portion 53 side of the second beam portion 72 are fixed to the fixing portion 60 at one point. Similarly, the other connecting portion 54 side of the third beam portion 81 and the other connecting portion 54 side of the fourth beam portion 82 are fixed to the fixing portion 60 at one point.

  As described above, even if the first spring portion 70 and the second spring portion 80 are laid out in a square shape, the acceleration applied to the XY plane can be dispersed similarly to the first embodiment.

(Other embodiments)
The configuration of the acceleration sensor 10 shown in each of the above embodiments is an example, and is not limited to the configuration shown above, and may be another configuration that can realize the present invention. For example, the acceleration sensor 10 is configured based on an SOI substrate or the like, but this is an example of the configuration, and may be configured using another substrate.

  In each of the above embodiments, the beam portions 71 and 72 of the first spring portion 70 are laid out in line symmetry, so that the lengths in the longitudinal direction are the same, but this is an example of a layout. Therefore, the beam portions 71 and 72 do not have to have different lengths, that is, be laid out in line symmetry. The same applies to the beam portions 81 and 82 of the second spring portion 80.

  In each of the embodiments described above, the first and second beam portions 71 and 72 are laid out in a V shape, but other layouts may be used instead of the V shape. In addition, the first and second beam portions 71 and 72 are fixed at one point to the one connection portion 53 or the fixed portion 60, but the first and second beam portions 71 and 72 are separated from each other. It may be fixed to the connecting portion 53 or the fixing portion 60. The same applies to the third and fourth beam portions 81 and 82.

20 Substrate 23 Surface 30, 40 Fixed electrode 50 Movable electrode 51, 52 Opposing part 53, 54 Connection part 60 Fixed part 70, 80 Spring part 71, 72, 81, 82 Beam part

Claims (5)

A substrate (20) having a surface (23);
A first fixed electrode (30) disposed on a surface (23) of the substrate (20);
A second fixed electrode (40) disposed on the surface (23) of the substrate (20) and spaced apart from the first fixed electrode (30);
A first opposing portion (51) disposed opposite to the first fixed electrode (30); a second opposing portion (52) disposed opposite to the second fixed electrode (40); and the first opposing portion ( 51) and a pair of linear connecting portions (53, 54) that connect the second facing portion (52), and a movable electrode (50) having
A region surrounded by a portion of the surface (23) of the substrate (20) corresponding to the first facing portion (51), the second facing portion (52), and the pair of connecting portions (53, 54). A fixing part (60) arranged in
A first spring part (70) for connecting one of the pair of coupling parts (53, 54) and the fixing part (60);
A second spring part (80) for connecting the other of the pair of connecting parts (53, 54) and the fixing part (60);
With
When the movable electrode (50) receives an acceleration, the first opposing portion (51) is turned into the first fixed electrode (30) by the torsion of the first spring portion (70) and the second spring portion (80). The first fixed electrode (30), the second fixed electrode (40), and the movable electrode (52) are rotated to the side or the second facing portion (52) is rotated to the second fixed electrode (40) side. 50) and a seesaw-type capacitive acceleration sensor that detects the acceleration based on a change in capacitance between
The first spring part (70) and the second spring part (80) are arranged in a longitudinal direction of the pair of connection parts (53, 54) in a plane direction parallel to the surface (23) of the substrate (20). A linear first beam portion (71, 81) inclined with respect to a vertical direction perpendicular to the vertical direction and a linear shape inclined to the opposite side of the first beam portion (71, 81) with respect to the vertical direction. Each of the second beam portions (72, 82).   The first beam portion (71, 81) and the second beam portion (72, 82) are spaced apart from each other on the fixed portion (60) side. The acceleration sensor according to claim 1, wherein the acceleration sensor is laid out in a V shape by being arranged so as to be narrower than the interval.   The fixed portion (60) side of the first beam portion (71, 81) and the fixed portion (60) side of the second beam portion (72, 82) are the fixed portion (60). The acceleration sensor according to claim 2, wherein the acceleration sensor is fixed at one point.   The first beam portion (71, 81) and the second beam portion (72, 82) are spaced apart from each other on the fixed portion (60) side. The acceleration sensor according to claim 1, wherein the acceleration sensor is laid out in a V shape by being arranged so as to be narrower than the interval.   The pair of connecting portions (53, 54) side of the first beam portions (71, 81) and the pair of connecting portions (53, 54) side of the second beam portions (72, 82). The acceleration sensor according to claim 4, wherein the acceleration sensor is fixed at one point with respect to the pair of connecting portions (53, 54).

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