JP2013127388A - Capacitance type sensor - Google Patents

Abstract

A capacitive sensor capable of suppressing breakage of a stopper is obtained.
[Solution]
An acceleration sensor (capacitance sensor) in which protruding stoppers 51 and 61 are provided between the movable electrodes 5a and 6a and the fixed electrodes 21a and 21b and 22a and 22b arranged to face each other via a gap (gap) G1. ) 1, the hollow portion 30 is formed in the stoppers 51 and 61 to form a hollow structure. As a result, when the movable electrodes 5a and 6a are operated and the stoppers 51 and 61 collide, the leading ends of the stoppers 51 and 61 can be bent to absorb the impact. Damage can be suppressed.
[Selection] Figure 10

Description

  The present invention relates to a capacitive sensor.

  As a conventional capacitive sensor, there is known an acceleration sensor in which a protruding stopper is provided between a movable electrode and a fixed electrode that are arranged to face each other with a gap (see, for example, Patent Document 1). .

  According to such a sensor configuration, for example, even when an excessive physical quantity (acceleration) exceeding the measurement range is input to the weight portion having the movable electrode, the movable electrode Direct contact with the fixed electrode can be prevented.

JP 2010-127648 A

  However, although the conventional electrostatic capacitance sensor can prevent the electrodes from being damaged due to a direct collision between the movable electrode and the fixed electrode by the stopper, the stopper cannot be prevented from being damaged. As described above, when the stopper is broken, foreign matter is generated inside the sensor, and the foreign matter may cause malfunction.

  Therefore, an object of the present invention is to obtain a capacitance type sensor that can suppress breakage of a stopper.

  In order to achieve the above object, a first feature of the present invention is that in the capacitive sensor in which a protruding stopper is provided between the movable electrode and the fixed electrode that are arranged to face each other with a gap therebetween, A hollow portion is formed in the stopper to form a hollow structure.

  According to a second aspect of the present invention, the stopper is provided on one of the opposing surfaces of the movable electrode and the fixed electrode.

  According to a third aspect of the present invention, the stopper is provided on both of the opposed surfaces of the movable electrode and the fixed electrode, and the pair of stoppers are arranged to face each other.

  According to a fourth aspect of the present invention, the stopper is formed so that the thickness of the hollow portion is equal to the thickness of the outer portion of the stopper.

  According to a fifth feature of the present invention, the stopper is made of an insulating material such as silicon dioxide or silicon nitride.

  The sixth feature of the present invention is that the stopper is formed by using graphite as a sacrificial layer.

  The seventh feature of the present invention is that the stopper is formed by using a photoresist as a sacrificial layer.

  According to the present invention, since the hollow portion is formed in the stopper to form a hollow structure, when the stopper collides, the tip side of the stopper can be bent to absorb the impact. Thereby, it becomes possible to suppress breakage of the stopper, and the risk of malfunctioning can be further reduced.

It is an exploded perspective view of the acceleration sensor concerning one embodiment of the present invention. It is the top view which showed the silicon substrate of FIG. It is the reverse view which showed the silicon substrate of FIG. It is sectional drawing of the acceleration sensor corresponding to the AA line of FIG. It is operation | movement explanatory drawing of an acceleration sensor. It is a system block diagram of an acceleration sensor. It is explanatory drawing which shows typically the detection principle of the acceleration applied to the X direction. It is explanatory drawing which shows typically the detection principle of the acceleration applied to the Z direction. It is explanatory drawing which shows the output calculation type | formula of an acceleration sensor in a tabular form. It is an enlarged view of the B section of FIG. It is an enlarged view of the C section of FIG. It is explanatory drawing which showed the formation method of the stopper shown in FIG. 10 in order of (a), (b), (c). It is the figure which showed the 1st modification of the acceleration sensor concerning one Embodiment of this invention, Comprising: It is an enlarged view of the same position as the B section in FIG. It is the figure which showed the 2nd modification of the acceleration sensor concerning one Embodiment of this invention, Comprising: It is an enlarged view of the same position as the B section in FIG. It is the figure which showed the 3rd modification of the acceleration sensor concerning one Embodiment of this invention, Comprising: It is explanatory drawing which followed the formation method of the stopper in order of (a), (b), (c).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, an acceleration sensor will be exemplified as the capacitance type sensor. Further, the side of the weight portion on which the movable electrode is formed is defined as the surface side of the silicon substrate. In the following description, the short direction of the silicon substrate is the X direction, the long direction of the silicon substrate is the Y direction, and the thickness direction of the silicon substrate is the Z direction.

  As shown in FIG. 1, the acceleration sensor (capacitance type sensor) 1 of this embodiment is a pair of silicon substrate 4 on which a semiconductor element device is formed, and a pair bonded to the front surface 4a and the back surface 4b of the silicon substrate 4, respectively. Glass substrates 2 and 3. In this embodiment, the silicon substrate 4 is bonded to the first glass substrate 2 and the second glass substrate 3 by anodic bonding.

  On the lower surface of the first glass substrate 2, fixed electrodes 21a, 21b and 22a, 22b corresponding to the installation areas of the weight portions 5, 6 of the silicon substrate 4 are provided, respectively.

  On the other hand, adhesion preventing films 31 and 32 are formed on the surface of the second glass substrate 3 in areas corresponding to the installation areas of the weight parts 5 and 6, respectively. The adhesion preventing films 31 and 32 can be formed of the same material as the fixed electrodes 21a and 21b and 22a and 22b, for example.

  The silicon substrate 4 has a gap 43 with respect to the frame portion 40 in which two frame portions 40a and 40b are arranged in parallel in the Y direction (longitudinal direction of the silicon substrate 4) and the inner peripheral surface of the frame portions 40a and 40b. The weight parts 5 and 6 arrange | positioned inside frame part 40a, 40b in the state are provided. In addition, the silicon substrate 4 has a pair of beam portions 7a, 7b and 8a, 8b that rotatably support the weight portions 5, 6 with respect to the frame portion 40, and on the surface (one surface) of the weight portions 5, 6. Movable electrodes 5a and 6a to be formed.

In this embodiment, the silicon substrate 4 is a rectangular SOI in which a buried insulating layer 112 made of SiO ₂ is interposed between a silicon active layer 111 made of Si (see FIG. 4) and a support substrate 113 made of Si. A substrate is used. The longitudinal side of the silicon substrate 4 is about 2 to 4 mm, the thickness is about 0.4 to 0.6 mm, the thickness of the silicon active layer 111 is about 10 to 20 μm, and the thickness of the buried insulating layer 112 The thickness is about 0.5 μm.

  In the present embodiment, the frame portion 40 extends in the X direction (the short direction of the silicon substrate 4) and the Y direction of the outer frame portion 41 (the longitudinal direction of the silicon substrate 4). And a central frame portion 42 for connecting the substantially central portions.

  As shown in FIGS. 3 and 4, the weight portions 5, 6 are integrally formed with recesses 55, 65 opening on the back surface and solid portions 53, 63 excluding the recesses 55, 65. That is, by forming concave portions 55 and 65 opened on one surface (rear surface) on the weight portions 5 and 6, the thick portions 53 and 63 and the thin thin portions 54 and 64 are formed on the weight portions 5 and 6. Forming.

  As shown in FIG. 3, the solid portions 53 and 63 are formed in a rectangular shape as viewed from the back side, and diagonal grooves 63 and 66 are formed in the movable portions 5 and 66 in the solid portions 53 and 63, respectively. , 6a.

  Further, the recesses 55 and 65 are formed in a rectangle having side walls on four sides, and reinforcing walls 57 and 67 are provided in the interior perpendicular to the movable electrodes 5a and 6a.

  In the present embodiment, the recess 55 is formed on one side in the X direction (the back side in FIG. 1) with respect to the rotation axis A1 described later, and the recess 65 is on the other side in the X direction with respect to the rotation axis A2 described later. It is formed on the front side of FIG.

  The beam portions 7a, 7b and 8a, 8b are formed in the silicon active layer 111 of the SOI substrate (silicon substrate 4), deep etching is performed using the embedded insulating layer 112 of the SOI substrate as an etching stop, and further the embedded insulating layer It is formed by selectively removing 112.

  The beam portions 7a and 7b are respectively positioned on two opposite sides of the surface of the weight portion 5 (movable electrode 5a). When the beam portions 7a and 7b are twisted, the movable electrode 5a causes the beam portions 7a and 7b to be mutually connected. The connecting straight line swings as a rotation axis (axis) A1. Similarly, the beam portions 8a and 8b are respectively located on two opposite sides of the surface of the weight portion 6 (movable electrode 6a), and the movable electrode 6a has a rotation axis (axis) connecting the beam portions 8a and 8b to each other. ) Swings as A2.

  The beam portions 7a, 7b and 8a, 8b are located at the midpoints of the two sides of the surfaces of the weight portions 5, 6, respectively.

  Further, in the present embodiment, the weight portion 5 and the weight portion 6, the beam portion 7a and the beam portion 8a, and the beam portion 7b and the beam portion 8b are respectively connected to one point of the silicon substrate 4 (a line connecting the beam portion 7b and the beam portion 8b). It is arranged so as to be point symmetric with respect to the midpoint of the minute).

  Specifically, in this embodiment, as shown in FIG. 4, a recess 55 is formed on one side of the rotation axis (axis) A1 on the back side of the weight part 5, and the center of gravity of the weight part 5 is on the other side. I try to divide it. Similarly, a recess 65 is formed on the other side (the other side of the rotation axis (axis) A2) opposite to the one side where the recess 55 is provided on one weight 5 on the back side of the weight 6, The center of gravity of the weight portion 6 is shifted to one side. When acceleration is applied in the X direction or the Z direction, the operation is performed as shown in FIG. 5 so that the acceleration a applied in the X direction and the Z direction can be detected (see FIGS. 7 and 8). .

  At this time, for example, if one of the weight parts 5 is described with reference to FIG. 4, for example, the weight parts 5 and 6 are perpendicular to the surface from the center of gravity G on the side where the recess 55 is not formed, the center of gravity G and the rotation axis. The angle θ formed by the straight line connecting (axis) A1 is set to be approximately 45 degrees. The same applies to the other weight portion 6, but in this case, as described above, the position of the center of gravity exists on the opposite side of the center of gravity G of the weight portion 5 across the rotation axis (axis) A 2. Become. If the center of gravity G is arranged in this way, the detection sensitivities in the X direction and the Z direction are equivalent, so that the detection sensitivities in the respective directions can be made substantially the same.

  In addition, relatively shallow gaps G1 and G2 are formed on the bonding surfaces of the silicon substrate 4 and the first glass substrate 2 and the second glass substrate 3, respectively. The operability of the movable electrodes 5a, 6a) 5, 6 is ensured.

  The gap G2 on the back side of the silicon substrate 4 can be formed by etching away a part of the silicon substrate 4 by silicon anisotropic etching using an alkaline wet anisotropic etching solution. At this time, it is preferable to form the concave portions 55 and 65 described above at the same time. As the alkaline wet anisotropic etching solution, for example, KOH (potassium hydroxide aqueous solution), TMAH (tetramethyl ammonium hydroxide aqueous solution) or the like is preferably used.

  In addition, the gap 43 and the gap 44 are formed by performing a vertical etching process by reactive ion etching (RIE) or the like. As reactive ion etching, for example, ICP processing by an etching apparatus provided with inductively coupled plasma (ICP) can be used.

  Further, in the present embodiment, the outer frame portion 41 is formed with a wide X-direction one end (the lower side in FIG. 2), and the weight portions 5, 6 are disposed on the X-direction one end of the outer frame portion 41. Clearances 44, 44 are formed so as to be continuous with the clearances 43, 43 where the In addition, two electrode bases 9 are arranged with two gaps 44 therebetween.

  Detection electrodes 10a, 10b, 11a, and 11b made of metal films are provided on the surface of the electrode table 9, respectively.

  The electrode table 9 is disposed separately from the frame part 40 and the weight parts 5 and 6, and the upper and lower surfaces thereof are fixed by the first glass substrate 2 and the second glass substrate 3. Further, a common electrode 12 wired outside the acceleration sensor 1 is provided at the center in the Y direction on the surface of the outer frame portion 41, and the frame portion 40 takes a common potential by the common electrode 12.

  As described above, the fixed electrodes 21a, 21b and 22a, 22b corresponding to the installation areas of the weight parts 5, 6 are provided on the lower surface of the first glass substrate 2, respectively. These fixed electrodes 21a, 21b and 22a, 22b are formed to have substantially the same shape and the same area.

  The fixed electrodes 21a and 21b are spaced apart from each other with a straight line (rotation axis A1) connecting the beam portions 7a and 7b as a boundary line. Similarly, the fixed electrodes 22a and 22b are spaced apart from each other with a straight line (rotation axis A2) connecting the beam portions 8a and 8b as a boundary line. In this embodiment, each fixed electrode 21a, 21b and 22a, 22b is formed by vapor-depositing aluminum (Al) on the first glass substrate 2 by a sputtering method, a CVD method, or the like.

  The fixed electrodes 21a and 21b are electrically connected to the detection electrodes 10a and 10b, respectively, and the fixed electrodes 22a and 22b are electrically connected to the detection electrodes 11a and 11b, respectively.

  Specifically, the fixed electrodes 21a, 21b and 22a, 22b are led out toward the fixed electrode base 9 on which the detection electrodes 10a, 10b and 11a, 11b are respectively connected (see FIG. 4). Are provided.

  Each fixed electrode base 9 is formed with an aluminum conductive layer 13 with which the lead wire 25 contacts. In the present embodiment, a step 9a is provided on the other end side in the X direction of each fixed electrode base 9 (upper side in FIG. 2: weight side), and the lower surface of the step 9a, that is, the detection electrodes 10a, 10b and 11a. , 11b is formed at a position lower than the surface on which 11b is formed.

  The lead wire 25 and the conductive layer 13 are crushed and brought into contact with each other when the silicon substrate 4 and the first glass substrate 2 are anodic bonded. Thus, the fixed electrodes 21a, 21b and 22a, 22b are electrically connected to the detection electrodes 10a, 10b and 11a, 11b.

  The detection electrodes 10a, 10b and 11a, 11b are separated from each other, and are separated from the frame portion 40 and the weight portions 5, 6, respectively. Therefore, the detection electrodes 10a to 11b are insulated from each other, the parasitic capacitance of the detection electrodes 10a to 11b and the crosstalk between the detection electrodes 10a to 11b can be reduced, and highly accurate capacitance detection can be performed.

  In addition, through holes 23 are respectively formed by sandblasting or the like at portions corresponding to the electrode table 9 of the first glass substrate 2, and at portions corresponding to the common electrode 12 of the first glass substrate 2, A through hole 24 is formed by sandblasting or the like. The detection electrodes 10a, 10b, 11a, and 11b are exposed and wired to the outside through the through holes 23, respectively, and the common electrode 12 is exposed and wired to the outside through the through holes 24. Thus, the potentials of the fixed electrodes 21a, 21b, 22a, 22b and the movable electrodes 5a, 6a can be taken out to the outside.

  In the acceleration sensor 1 configured as described above, when the acceleration indicated by the arrow a in FIG. 5 is applied, both the weight portions 5 and 6 swing, and both ends of the weight portions 5 and 6 and the fixed electrode are moved. The gap d between 21a, 21b and 22a, 22b changes, and the capacitances C1, C2, C3, C4 between these gaps d change. In addition, in FIG. 5, one weight part 5 is illustrated.

  The capacitance C at this time is known to be C = ε × S / d (ε: dielectric constant, S: electrode area, d: gap), and the electrostatic capacity increases as the gap d increases from this equation. The capacitance C decreases, and the capacitance C increases as the gap d decreases.

  Then, as shown in the system configuration of FIG. 6, the acceleration sensor 1 sends the detected electrostatic capacitances C1, C2, C3, and C4 to an arithmetic circuit 100 configured by, for example, an ASIC, and accelerates in the X direction. And the acceleration of a Z direction is calculated | required and the data which show the acceleration are output. At this time, an arithmetic expression executed by the arithmetic circuit 100 is shown in FIG. 9, and C1 obtained by applying the acceleration a in the X direction shown in FIG. 7 and applying the acceleration a in the Z direction shown in FIG. , C2, C3, and C4 determine the direction of acceleration a. Note that a parameter C0 in the following expression indicates the capacitance between the weights 5 and 6 and the fixed electrodes 21a and 21b and 22a and 22b in a state where the acceleration a is not applied.

  When acceleration a is applied in the + X direction (see FIG. 7), both the weight portions 5 and 6 swing in the same direction, so C1 = C0 + ΔC, C2 = C0−ΔC, C3 = C0 + ΔC, C4 = C0−ΔC. When the acceleration a is applied in the −X direction, the swinging directions of the weight portions 5 and 6 are opposite to the + direction, so that C1 = C0−ΔC, C2 = C0 + ΔC, and C3 = C0−. ΔC, C4 = C0 + ΔC.

  On the other hand, when acceleration a is applied in the + Z direction (see FIG. 8), both weight portions 5 and 6 swing in opposite directions, so that C1 = C0−ΔC, C2 = C0 + ΔC, C3 = C0 + ΔC, C4 = C0−ΔC. When the acceleration a is applied in the −Z direction, the swinging directions of the weights 5 and 6 are opposite to the + direction, so C1 = C0 + ΔC, C2 = C0−ΔC, and C3 = C0−. ΔC, C4 = C0 + ΔC.

  Therefore, the capacitance difference CA (= C1-C2) between the one weight portion 5 and the fixed electrodes 21a and 21b is + 2ΔC in the + X direction, −2ΔC in the −X direction, −2ΔC in the + Z direction, − + 2ΔC in the Z direction. Further, the difference in capacitance CB (= C3−C4) between the other weight 6 and the fixed electrodes 22a and 22b is + 2ΔC in the + X direction, −2ΔC in the −X direction, + 2ΔC in the + Z direction, and −Z. -2ΔC in the direction.

  Here, the output in the X direction can be obtained as the sum of both differences CA and CB, and the output in the Z direction can be obtained as the difference between both differences CA and CB. As a result, the output in the X direction becomes + 4ΔC when the acceleration a in the + X direction is applied, and becomes −4ΔC when the acceleration a in the −X direction is applied. The output in the Z direction is −4ΔC when the acceleration a in the + Z direction is applied, and is + 4ΔC when the acceleration a in the −Z direction is applied.

  As described above, in the acceleration sensor 1 of the present embodiment, the first acceleration sensor single unit including one weight part 5 and the second acceleration sensor single unit including the other weight part 6 are the same chip. In the plane, each sensor unit is disposed in a state of being relatively rotated by 180 degrees. Thus, the gravity center positions of one weight part 5 in the first acceleration sensor unit and the other weight part 6 in the second acceleration sensor unit are located on the opposite sides with respect to the rotation axes A1 and A2. By arranging in this way, the acceleration a in the X direction and the Z direction can be detected.

By the way, in the acceleration sensor 1 of the present embodiment, a protruding stopper 51, between the movable electrodes 5a, 6a and the fixed electrodes 21a, 21b and 22a, 22b arranged to face each other via a gap (gap) G1. 61 is provided. The stoppers 51 and 61 are for preventing the movable electrodes 5a and 6a and the fixed electrodes 21a and 21b and 22a and 22b from coming into direct contact, such as silicon dioxide (SiO ₂ ) or silicon nitride (SiN). The insulating material is preferably used.

  In the present embodiment, stoppers 51 and 61 project from the surfaces (movable electrodes 5a and 6a) of the respective weight portions 5 and 6 serving as one of the opposed surfaces toward the fixed electrodes 21a and 21b and 22a and 22b, respectively. Has been. In addition, the stoppers 51 and 61 of the present embodiment include four corners of the weight parts 5 and 6 and four positions inside the four corners and surrounding the approximate center of the weight parts 5 and 6 in a rectangular shape. A total of eight are provided.

  According to such a sensor configuration, for example, when an excessive physical quantity (acceleration) exceeding the measurement range is input to the weight portions 5 and 6, the movable electrodes 5a and 6a and the fixed electrodes 21a and 21b and 22a and 22b These electrodes can be prevented from being damaged by preventing them from directly colliding with each other. At this time, by forming the stoppers 51 and 61 with the insulating material as described above, it is possible to prevent the movable electrodes 5a and 6a and the fixed electrodes 21a and 21b and 22a and 22b from being electrically short-circuited. it can. However, simply providing the stoppers 51 and 61 can prevent the electrodes from being damaged, but cannot prevent the stoppers 51 and 61 from being damaged.

  Therefore, in this embodiment, the hollow portion 30 is formed in the stoppers 51 and 61, and the stoppers 51 and 61 have a hollow structure. Specifically, as shown in FIGS. 1 and 10, in the present embodiment, the outer portions 31 of the stoppers 51 and 61 are formed so as to protrude in a rectangular shape from the surfaces of the weight portions 5 and 6 (movable electrodes 5a and 6a). A hollow portion 30 is formed as a rectangular space inside the outer shell portion 31.

  As shown in FIG. 11, the outer shell portion 31 has a substantially U-shape that is open toward the surface (movable electrodes 5 a, 6 a) side of the weight portions 5, 6 in a cross-sectional view. At this time, the impact absorbability of the stoppers 51 and 61 is determined by the relative thickness d2 of the cavity 30 and the outer shell 31. Here, if the thickness d2 of the hollow portion 30 is too thin, the shock absorption of the outer portion 31 is reduced. Conversely, if the thickness d2 is too thick, the outer portion 31 may be damaged. Therefore, in this embodiment, the stoppers 51 and 61 are formed so that the thickness d2 of the cavity 30 and the thickness d2 of the outer shell 31 are equal. In this way, it is possible to form the stoppers 51 and 61 with optimum dimensions capable of suppressing breakage while improving the shock absorption of the outer shell portion 31.

  The thickness d2 of the cavity 30 and the outer shell 31 is, for example, a distance d1 between the surfaces of the weights 5 and 6 (movable electrodes 5a and 6a) and the fixed electrodes 21a and 21b and 22a and 22b (see FIG. 10). It is preferable to design so as to be about 1/4 of that. Therefore, in this embodiment, the stoppers 51 and 61 (outer part 31) are protruded from the surfaces of the weight parts 5 and 6 (movable electrodes 5a and 6a) so as to be about half of the distance d1 between the electrodes. become.

  By the way, in FIG. 10 and FIG. 11, only a part of the stoppers 51 in one weight part 5 is illustrated, but all the stoppers 51 provided in all the weight parts 5 and all the weight parts 6 are provided. The stopper 61 has a similar structure.

  Further, as shown in FIGS. 3 and 4, in this embodiment, the weight portions 5 and 6 are attached to the four glass corners 3 on the back surfaces of the weight portions 5 and 6. , 32 is provided with protrusion-like stoppers 52 and 62 for preventing direct collision with the. It is preferable that the stoppers 52 and 62 have the same structure as the stoppers 51 and 61 (that is, the stoppers 52 and 62 in which the cavity 30 is formed).

  The stoppers 51 and 61 (52 and 62) are formed by using graphite as the sacrificial layer 33 in this embodiment, as shown in FIG.

That is, as shown in FIG. 12A, first, a rectangular sacrificial layer 33 that forms the cavity 30 is formed on the front surfaces (movable electrodes 5a, 6a) and back surfaces of the weight portions 5, 6. Next, as shown in FIG. 12B, an insulating layer 34 such as silicon dioxide (SiO ₂ ) or silicon nitride (SiN) is formed so as to cover the sacrificial layer 33. A hole 35 communicating with the sacrificial layer 33 is formed in at least a part of the surface side of the insulating layer 34. Finally, as shown in FIG. 12C, a process of burning the sacrificial layer 33 is performed by, for example, an oxygen plasma process.

  Thus, in this embodiment, since the formation method by the combustion of graphite is used, the sacrificial layer 33 is easily ashed by oxygen plasma treatment or the like, and the stoppers 51 and 61 having the cavity 30 are relatively inexpensive. And 52, 62 can be formed. That is, the cavity 30 is formed by removing the gas formed by reacting carbon and oxygen in the sacrificial layer 33 from the hole 35.

  As described above, according to the present embodiment, the protruding stoppers 51 provided between the surfaces of the weight parts 5 and 6 (movable electrodes 5a and 6a) and the fixed electrodes 21a and 21b and 22a and 22b, A hollow portion 30 is formed in 61 to form a hollow structure. Therefore, when the weights 5 and 6 are operated and the stoppers 51 and 61 collide, the leading ends of the stoppers 51 and 61 can be bent to absorb the impact. Thereby, the breakage of the stoppers 51 and 61 can be suppressed, and the risk of malfunctioning in the acceleration sensor 1 can be further reduced.

  Further, according to the present embodiment, the stoppers 51 and 61 are arranged so that the movable electrodes 5a and 6a and the fixed electrodes 21a and 21b and the opposing surfaces of the 22a and 22b are either one (the movable electrodes 5a and 6a in the present embodiment). Provided. Therefore, it is possible to manufacture the acceleration sensor 1 at a lower cost as compared with the configuration in which the stoppers 51 and 61 can be prevented from being damaged and the stoppers are provided on both opposing surfaces.

  Further, according to the present embodiment, the stoppers 51 and 61 are formed so that the thickness d2 of the cavity 30 and the thickness d2 of the outer shell 31 are equal. Therefore, it is possible to form the stoppers 51 and 61 with optimal dimensions that can prevent the stoppers 51 and 61 (outer part 31) from being damaged while improving the shock absorption of the stoppers 51 and 61 (outer part 31).

  Furthermore, according to the present embodiment, the stoppers 51 and 61 are made of an insulating material such as silicon dioxide or silicon nitride. Therefore, when an excessive physical quantity (acceleration) exceeding the measurement range is input to the weight portions 5 and 6, damage to the movable electrodes 5a and 6a and the fixed electrodes 21a and 21b and 22a and 22b can be prevented. These electrodes can be prevented from being electrically short-circuited.

  According to the present embodiment, the stoppers 51 and 61 are formed by using graphite as the sacrificial layer 33. Therefore, graphite can be easily ashed by, for example, oxygen plasma treatment, so that the stoppers 51 and 61 having the cavity 30 can be formed relatively easily.

  Next, a modified example of the acceleration sensor (capacitance sensor) 1 according to the present embodiment will be described with reference to FIGS.

  FIG. 13 is a view showing a first modification of the acceleration sensor 1, and is an enlarged view at the same position as the portion B in FIG.

  In this modification, the stoppers 51A, 61A are provided on the fixed electrodes 21a, 21b and 22a, 22b side as one of the opposing surfaces of the movable electrodes 5a, 6a and the fixed electrodes 21a, 21b and 22a, 22b. The point is mainly different from the above embodiment.

  Specifically, in this modification, the stoppers 51A, 61A are provided on the fixed electrodes 21a, 21b and 22a, 22b at all positions opposed to the stoppers 51, 61 provided in total of eight shown in FIG. Is provided.

  Also according to the above modification, the same operations and effects as those of the above embodiment can be obtained.

  FIG. 14 is a view showing a second modification of the acceleration sensor 1, and is an enlarged view at the same position as the portion B in FIG.

  In this modification, stoppers 51, 61 and 51A and 61A are provided on both of the opposed surfaces of the movable electrodes 5a and 6a and the fixed electrodes 21a, 21b and 22a, 22b, and the pair of stoppers 51, 61 and 51A, 61A. Is different from the above embodiment mainly in that they are arranged opposite to each other.

  That is, in this modification, a total of eight stoppers 51 and 61 shown in FIG. 1 of the above-described embodiment, and fixed electrodes 21a and 21b and 22a and 22b at all positions facing it in the first modification are shown. Are provided with stoppers 51A and 61A.

  Also according to the above modification, the same operations and effects as those of the above embodiment can be obtained.

  Further, according to this modification, the stoppers 51, 61 and 51A, 61A are provided on both of the movable electrodes 5a, 6a and the fixed electrodes 21a, 21b and 22a, 22b, and the pair of stoppers 51, 61 are provided. And 51A and 61A are arranged to face each other. Therefore, compared to a configuration in which the impact is received by only one stopper (for example, 51) on one side, the impact when the stopper collides can be distributed and received in each of the pair of stoppers 51, 51A (61, 61A). become. Therefore, damage to the stoppers 51 and 51A (61 and 61A) can be further suppressed.

  FIG. 15 is a diagram illustrating a third modification of the acceleration sensor 1 and is an explanatory diagram illustrating the formation method of the stoppers 51 and 61 in the order of (a), (b), and (c).

  This modification mainly differs from the above embodiment in that the stoppers 51 and 61 (62 and 62) are formed by using a photoresist as the sacrificial layer 37.

That is, in this modified example, as shown in FIG. 15A, a sacrificial layer 37 made of a rectangular photoresist that becomes the hollow portion 30 is formed on the front surfaces (movable electrodes 5a, 6a) and back surfaces of the weight portions 5, 6. Form. Next, as shown in FIG. 15B, an insulating layer 34 such as silicon dioxide (SiO ₂ ) or silicon nitride (SiN) is formed so as to cover the sacrificial layer 37. Finally, as shown in FIG. 15C, a process of ashing the sacrificial layer 37 is performed by, for example, an oxygen plasma process.

  As described above, in the present modification, the formation method by ashing the photoresist is used. Therefore, the sacrificial layer 37 can be easily ashed by oxygen plasma treatment or the like, and the stopper 51 having the cavity 30 at a relatively low cost. 61 and 52, 62 can be formed. That is, by placing the photoresist in oxygen plasma, the photoresist and oxygen radicals are combined to change into carbon dioxide and water, and these are evaporated and removed, whereby the cavity 30 is formed. Become.

  Also according to the above modification, the same operations and effects as those of the above embodiment can be obtained.

  Further, according to this modification, the stoppers 51 and 61 are formed by using a photoresist as the sacrificial layer 37. Therefore, since the photoresist can be easily ashed by, for example, oxygen plasma treatment, the stoppers 51 and 61 having the cavity 30 can be formed relatively easily.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications can be made.

  For example, in the above-described embodiment, an acceleration sensor that detects acceleration in two directions of the X direction and the Z direction has been exemplified. However, one of the weight portions is arranged by being rotated 90 degrees in the XY plane, and the Y direction is added. An acceleration sensor that detects acceleration in three directions may be used.

  Moreover, although the acceleration sensor was illustrated as an electrostatic capacitance type sensor in the said embodiment, this invention is applicable even if it is not only this but another electrostatic capacitance type sensor.

  Further, the specifications (shape, size, layout, etc.) of the weight portion, fixed electrode, and other details can be changed as appropriate.

1 Acceleration sensor (capacitance sensor)
5a, 6a Movable electrode 21a, 21b Fixed electrode 22a, 22b Fixed electrode 30 Cavity 31 Outer part 51, 61 Stopper G1 Gap (gap)

Claims (7)

In the capacitive sensor in which a protruding stopper is provided between the movable electrode and the fixed electrode arranged to face each other via a gap,
A capacitance type sensor characterized in that a hollow portion is formed in the stopper to form a hollow structure.   The capacitive sensor according to claim 1, wherein the stopper is provided on any one of opposing surfaces of the movable electrode and the fixed electrode.   2. The capacitive sensor according to claim 1, wherein the stopper is provided on both of the opposing surfaces of the movable electrode and the fixed electrode, and the pair of stoppers are arranged to face each other.   The capacitance type sensor according to any one of claims 1 to 3, wherein the stopper is formed so that a thickness of the hollow portion is equal to a thickness of an outer portion of the stopper. .   The capacitive sensor according to claim 1, wherein the stopper is made of an insulating material such as silicon dioxide or silicon nitride.   The capacitive sensor according to claim 1, wherein the stopper is formed by using graphite as a sacrificial layer.   The capacitive sensor according to any one of claims 1 to 5, wherein the stopper is formed by using a photoresist as a sacrificial layer.

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