JP4600344B2 - Capacitive sensor - Google Patents

Description

  The present invention relates to a capacitance sensor that detects a predetermined physical quantity by detecting a capacitance between a fixed electrode and a movable electrode.

  Conventionally, a semiconductor substrate is processed using a known semiconductor process to form a structure in which the movable electrode is movably supported by the fixed portion via an elastic element. A capacitance type sensor is known that is capable of detecting various physical quantities such as acceleration and angular velocity by detecting changes in capacitance between these electrodes so as to be able to contact and separate from each other ( For example, Patent Document 1).

In the electrostatic capacitance sensor of Patent Document 1, the elastic element is formed as a beam (beam) extending spirally from the fixed portion, and the movable electrode that is movably supported by the fixed portion via this elastic element is mainly used. The sensor (semiconductor layer) is configured to be displaced in a direction along the surface.
JP 2000-28634 A

  However, in the structure in which the movable electrode is movably supported by the fixed portion via the beam as in Patent Document 1, the maximum displacement amount and weight of the movable electrode, the shape of the beam as the elastic element, and the maximum acting on the sensor The stress generated in the beam changes due to acceleration or the like. However, particularly when a long and narrow beam is provided in accordance with the downsizing of the sensor or the setting of the spring constant, the stress generated in the beam tends to increase, and the movable electrode In some cases, it is difficult to set specifications such as a displacement amount and a weight to desired values.

  Accordingly, an object of the present invention is to reduce beam stress in a capacitive sensor in which a movable electrode is movably supported by a fixed part via a beam.

According to the first aspect of the present invention, a fixed electrode and a movable electrode that is movably supported by a beam at a fixed portion of the semiconductor layer are provided, and the fixed electrode and the movable electrode are arranged to face each other with a gap. In the electrostatic capacitance sensor that detects a predetermined physical quantity by detecting the electrostatic capacitance according to the size of the gap, the end on the side connected to the fixed portion of the beam And at least one of the end portions on the side connected to the movable electrode is provided with a stress relaxation portion for relaxing local stress concentration, and the stress relaxation portion has a truss-shaped unit frame in a plan view. In other words, the triangular frame structure is larger than the unit frame .

Wherein the billing In the invention of claim 2, in which the pre-Symbol stress absorbing portion, provided at both ends of the front SL side connected to the end and the movable electrode on the side which is connected to the fixed portion of the beam And

In the invention of claim 3, prior Symbol beam is characterized by a torsion having a rectangular cross section is twisted in accordance with the operation of the movable electrode beam.

In the invention of claim 4, before Symbol movable electrode, said is swingably supported via a torsion beam, the front Symbol detector, the surface of the fixed electrode surface facing thereto of the movable electrode swings And detecting the electrostatic capacitance according to the size of the gap.

  According to the present invention, stress is applied to at least one of a portion where stress is likely to increase in the beam, that is, an end portion connected to the fixed portion of the beam and an end portion connected to the movable electrode. Since the stress relaxation portion for relaxing is provided, the stress generated in the beam can be reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a plan view of a semiconductor layer of the capacitive sensor according to the present embodiment, FIG. 2 is a cross-sectional view of the capacitive sensor taken along line AA in FIG. 1, and FIG. FIG. 4 is a cross-sectional view of the capacitive sensor at line -B, FIG. 4 is a cross-sectional view of the beam section (CC cross-sectional view of FIG. 2), and FIG. 5 is a schematic view showing how the movable electrode swings. (A) is a state where it is not swinging, (b) is a state where one side is close to the fixed electrode, (c) is a view showing a state where the other side is close to the fixed electrode, and FIG. It is an enlarged view which shows the electric potential extraction part as a part of semiconductor layer of a sensor, (a) is a top view, (b) is DD sectional drawing of (a), (c) is the state before an assembly. FIG. 7 and FIG. 7 are plan views showing examples of the stress relaxation part.

  As shown in FIG. 2, an electrostatic capacitance type sensor 1 (hereinafter simply referred to as sensor 1) according to the present embodiment has an insulating layer such as a glass substrate on both sides of a semiconductor layer 2 obtained by processing a semiconductor substrate. 20 and 21 are joined by anodic bonding or the like. A relatively shallow recess 22 is formed on the bonding surface between the semiconductor layer 2 and the insulating layers 20 and 21, so that insulation of each part of the semiconductor layer 2 and operability of the movable electrode 5 are ensured. In the present embodiment, the bonding surface between the semiconductor layer 2 and the insulating layer 20 is provided with the recess 22 on the semiconductor layer 2 side, while the bonding surface between the semiconductor layer 2 and the insulating layer 21 is provided on the insulating layer 21 side. A recess 22 is provided on the surface.

  A conductor layer 23 is formed on the surface 20 a of the insulating layer 20 and is used as an electrode for acquiring the potential of each part of the semiconductor layer 2. In the present embodiment, a through hole 24 is formed in the insulating layer 20 by sandblasting or the like to expose a part of the surface of the semiconductor layer 2 (the surface on the insulating layer 20 side) and penetrate from the surface of the insulating layer 20. A series of electrically connected conductor layers 23 are formed on the inner peripheral surface of the hole 24 and on the surface of the semiconductor layer 2 (the surface of the anchor portion 3 in FIG. 2). The potential of each part in the layer 2 can be detected. The surface of the insulating layer 20 is preferably covered (molded) with a resin layer (not shown).

  Then, as shown in FIGS. 1 to 3 and the like, by forming a gap 10 in the semiconductor substrate by a known semiconductor process, the anchor portion 3, the beam portion 4, the movable electrode 5, and the frame portion 7 are formed on the semiconductor layer 2. Then, the potential extraction portion 8 and the like are formed.

  As shown in FIG. 1, the semiconductor layer 2 is formed in a substantially rectangular shape as a whole in plan view, and the frame portion 7 has a frame with a substantially constant width along the four peripheral edges (four sides) of the semiconductor layer 2. It is provided in the shape.

  The gap 10 is formed by, for example, vertical etching (for example, reactive ion etching such as ICP (Inductively Coupled Plasma) processing), and wall surfaces on both sides of the gap 10 are perpendicular to the surface of the semiconductor layer 2. It is preferable that the wall surfaces face each other substantially in parallel.

  A rectangular cross section (in the present embodiment, a substantially square cross section) is located on the inner side of the frame section 7 at a position slightly shifted from the substantially central position in plan view of the semiconductor layer 2 to one long side of the frame section 7 (upper side in FIG. 1). ), And the beam portions 4 and 4 extend from the pair of side walls facing the short side of the frame portion 7 of the anchor portion 3 substantially parallel to the long side of the frame portion 7. ing. In this embodiment, as shown in FIGS. 2 and 3, the anchor portion 3 is brought into contact (bonded) only with the insulating layer 20, but is further brought into contact (bonded) with the other insulating layer 21. You may do it.

  The beam portion 4 is configured as a beam having a certain rectangular (substantially rectangular) cross section as shown in FIG. Although depending on the overall size, as an example, the height h in the thickness direction of the semiconductor layer 2 is 10 micrometers or more (500 micrometers or less), and the width w in the direction along the surface of the semiconductor layer 2 is several micrometers. It can be a meter (about 3 to 10 micrometers).

  And this beam part 4 is extended in the direction in alignment with the long side of the frame part 7 with a fixed cross section, and the edge part 4b on the opposite side with respect to the edge part 4a by the side of the anchor part 3 is connected to the movable electrode 5. ing.

  The movable electrode 5 includes a substantially rectangular outer peripheral surface 5d facing the inner peripheral surface 7a of the frame portion 7 with a gap 10, and surrounds the outside of the anchor portion 3 and the beam portions 4 and 4 with a gap 10. Is formed. That is, as shown in FIG. 1, the movable electrode 5 has a gap 10 on one long side (lower side in FIG. 1) with respect to the anchor portion 3 and the beam portions 4 and 4. On the other long side (upper side in FIG. 1) of the frame portion 7 is provided with a substantially rectangular small plate portion 5b with a gap 10 between these large rectangular plate portions 5a. The plate portion 5 a and the small plate portion 5 b are connected to each other via a pair of connection portions 5 c and 5 c along the short side of the frame portion 7. And the beam parts 4 and 4 are respectively connected to the approximate center part of the corresponding connection parts 5c and 5c. In the above configuration, the mass of the large plate portion 5a is larger than the mass of the small plate portion 5b.

  Thus, the structure in which the movable electrode 5 is movably supported by the anchor portion 3 as the fixed portion of the sensor 1 via the beam portions 4 and 4 appropriately forms the gap 10 in the semiconductor layer 2 and also insulates the semiconductor layer 2 and the insulation. It can be obtained by appropriately forming the recess 22 in at least one of the layers 20 and 21. Therefore, the anchor portion 3, the beam portions 4, 4 and the movable electrode 5 are integrally configured as a part of the semiconductor layer 2, and the potentials of the anchor portion 3, the beam portions 4, 4 and the movable electrode 5 are It can be regarded as almost equipotential.

  The beam portions 4 and 4 function as spring elements that elastically moveably support the movable electrode 5 with respect to the frame portion 7. In the present embodiment, as shown in FIG. 4, the beam portions 4 and 4 have a long cross section in the thickness direction of the sensor 1 (a cross section perpendicular to the extending axis of the beam portion 4). The movable electrode 5 is provided with a large plate portion 5a and a small plate portion 5b that are opposed to each other with the beam portions 4 and 4 interposed therebetween, and the masses on both sides of the beam portions 4 and 4 are different. Therefore, when acceleration in the thickness direction occurs in the sensor 1, the beam portions 4 and 4 are twisted by the difference in inertial force acting on the large plate portion 5a and the small plate portion 5b, and the movable electrode 5 causes the beam portions 4 and 4 to move. It will swing around the center. That is, in the present embodiment, the beam portions 4 and 4 function as a torsion beam (torsion beam).

  In this embodiment, the fixed electrodes 6A and 6B are provided on the lower surface 20b of the insulating layer 20 so as to face the large plate portion 5a and the small plate portion 5b of the movable electrode 5, respectively, and the large plate portion 5a and the fixed electrode 6A are provided. , And the capacitance between the small plate portion 5b and the fixed electrode 6B, the change in these gaps, and hence the swinging posture of the movable electrode 5 with respect to the fixed portion of the sensor 1 are detected. A change can be detected.

  FIG. 5A shows a state in which the movable electrode 5 is in a posture parallel to the lower surface 20b of the insulating layer 20 without swinging. In this state, the size of the gap 25a between the large plate portion 5a and the fixed electrode 6A is equal to the size of the gap 25b between the small plate portion 5b and the fixed electrode 6B. When the mutual facing area of the electrode 6A is equal to the mutual facing area of the small plate portion 5b and the fixed electrode 6B, the capacitance between the large plate portion 5a and the fixed electrode 6A, and the small plate portion The electrostatic capacitance between 5b and the fixed electrode 6B becomes equal.

  5B, the movable electrode 5 swings and tilts with respect to the lower surface 20b of the insulating layer 20, the large plate portion 5a is separated from the fixed electrode 6A, and the small plate portion 5b is close to the fixed electrode 6B. Shows the state. In this state, the gap 25a becomes larger and the gap 25b becomes smaller than in the state of FIG. 5A, so that the capacitance between the large plate portion 5a and the fixed electrode 6A becomes small, and the small plate The electrostatic capacitance between the part 5b and the fixed electrode 6B increases.

  5C, the movable electrode 5 swings and tilts with respect to the lower surface 20b of the insulating layer 20, the large plate portion 5a is close to the fixed electrode 6A, and the small plate portion 5b is separated from the fixed electrode 6B. Shows the state. In this state, the gap 25a becomes smaller and the gap 25b becomes larger than in the state of FIG. 5A, so that the capacitance between the large plate portion 5a and the fixed electrode 6A becomes small, and the small plate The electrostatic capacitance between the part 5b and the fixed electrode 6B increases.

  Therefore, as an example, the attitude of the movable electrode 5 is determined based on the differential output of the capacitance between the large plate portion 5a and the fixed electrode 6A and the capacitance between the small plate portion 5b and the fixed electrode 6B. Can be grasped. That is, various physical quantities such as acceleration and angular acceleration can be grasped from these capacitance values.

  The capacitance can be acquired from the potentials of the movable electrode 5 and the fixed electrodes 6A and 6B. In this embodiment, as shown in FIGS. 1 and 2, a through hole 24 is formed in the insulating layer 20 on the anchor portion 3, and the potential of the movable electrode 5 is formed on the inner surface of the through hole 24. It is taken out through the conductor layer 23.

  On the other hand, the fixed electrode 6 is formed on the lower surface 20b of the insulating layer 20 as a substantially rectangular conductor layer (for example, an aluminum alloy layer). In the step of forming the fixed electrode 6, the wiring pattern 11 and the terminal portion 9 are simultaneously formed as a continuous conductor layer with the fixed electrode 6. Therefore, the potential of the fixed electrode 6 is taken out through the wiring pattern 11 and the terminal portion 9, the potential extraction portion 8 formed in the semiconductor layer 2, and the conductor layer 23 formed in the insulating layer 20 on the potential extraction portion 8. It is supposed to be.

Here, with reference to FIG. 6, the structure of the electric potential extraction part 8 is demonstrated. The potential extraction portion 8 is insulated from other portions of the semiconductor layer 2 such as the movable electrode 5 and the frame portion 7 by the gap 10 formed in the semiconductor layer 2 and the recess 22 formed in the semiconductor layer 2 or the insulating layer 21. A pad portion 8a formed in a columnar shape and a pedestal portion 8b extending from the pad portion 8a along the short side of the frame portion 7 are provided. And the recessed part 26 provided with the flat bottom face 8c is formed so that the part corresponding to the terminal part 9 of this base part 8b may be notched. An underlayer 27 (for example, a layer of silicon dioxide (SiO ₂ )) is formed on the bottom surface 8c, and a conductor layer 28 having substantially the same height is formed at a position adjacent to the underlayer 27. At the same time, a substantially ladder-shaped contact portion 12 is formed from the upper surface of the underlying layer 27 to the upper surface of the conductor layer 28 in a plan view in which frame-shaped peaks 12a are continuously provided. At this time, the conductor layer 28 and the contact portion 12 can be formed as layers made of the same conductor material (for example, an aluminum alloy).

  Here, in the present embodiment, as shown in FIG. 6C, the crest portion 12a of the contact portion 12 is formed so as to protrude above the upper surface 2a of the semiconductor layer 2 by a height δh. Thus, by joining the semiconductor layer 2 and the insulating layer 20, the peak portion 12 a is pressed by the terminal portion 9 to be plastically deformed to increase the degree of adhesion, and between the peak portion 12 a (contact point portion 12) and the terminal portion 9. The contact and conduction are more reliable.

  As shown in FIG. 1, a stopper 13 is provided at an appropriate position on the surface of the large plate portion 5a and the small plate portion 5b so that the movable electrode 5 and the fixed electrodes 6A and 6B are in direct contact (collision). However, if the stopper 13 is formed of the same material as the underlying layer 27 in the same process, the manufacturing labor is reduced as compared with the case where these are formed separately. Manufacturing cost can be reduced.

  Next, with reference to FIG. 7, the stress relaxation parts 30, 30A, 30B provided at the longitudinal ends of the beam parts 4, 4 will be described.

  FIG. 7A is a plan view of the stress relaxation portion 30 according to the present embodiment. In this example, a rectangular frame-like structure 31 is provided at the end on the side where the beam portion 4 is connected to the connection portion 5 c of the movable electrode 5 in plan view. Specifically, an elongated frame-like structure 31 including a short side portion 32 along the extending direction of the beam portion 4 and a long side portion 33 extending in a direction orthogonal to the extending direction in plan view is connected to the connecting portion 5c. The end portion of the beam portion 4 is connected to the center portion in the longitudinal direction of the frame-like structure 31. The end of the connecting portion 5 c and the long side portion 33 are integrated, while the height of the frame-like structure 31 is the same as that of the beam portion 4. With such a structure, compared with the case where the beam portion 4 is directly connected to the connection portion 5c, the region that bends along with the operation of the movable electrode 5 can be increased, and therefore the corner portions (root portions) 4b and 5d. It is possible to reduce local stress concentration.

  Since the frame-like structure 31 is elongated in the direction perpendicular to the extending direction of the beam portion 4, when the beam portion 4 is a torsion beam that is twisted about its extending axis as in the present embodiment. Is particularly effective as long as the bending margin can be increased at the long side portion 33.

  FIG. 7B is a plan view of a stress relaxation portion 30A according to a modification of the present embodiment. In this example, frame-like structures 31 similar to those in FIG. 7A are arranged in a plurality of stages (in this example, two stages) in the extending direction of the beam portion 4, and the beam-like structures 31, 31 are arranged between the beam-like structures 31 and 31. They are connected by a connecting piece 34 provided on an extension line of the portion 4. In this example, the stress can be further relaxed as compared with the example of FIG.

  FIG. 7C is a plan view of a stress relaxation portion 30B according to another modification of the present embodiment. In this example, a meandering structure 35 is provided between the beam part 4 and the connection part 5c as a stress relaxation part 30B, in which the beam part 4 is repeatedly diffracted multiple times with a predetermined width in a direction orthogonal to the extending direction. is there. Providing such a meandering structure 35 also increases the area of bending due to the operation of the movable electrode 5 as compared with the case where the beam portion 4 is directly connected to the connection portion 5c. (Parts) Local stress concentration in 4b and 5d can be relaxed.

  In the above examples, the stress relaxation portions 30, 30A, 30B are provided on the end portion 4b of the beam portion 4 on the side connected to the movable electrode 5 (the connection portion 5c). The stress relaxation portions 30, 30 </ b> A, and 30 </ b> B can be similarly provided on the other end portion of the beam portion 4, that is, the end portion 4 a on the side connected to the anchor portion 3 of the beam portion 4. The same effect can be obtained in 4a. If the stress relaxation portions 30, 30 </ b> A, 30 </ b> B are provided at both longitudinal ends of the beam portion 4, the stress generated in the beam portion 4 can be further reduced. In addition, you may provide the stress relaxation part 30,30A, 30B which is different in both ends, and may combine these suitably.

  According to the above embodiment, stress is relieved in at least one of the end portion 4a connected to the anchor portion 3 of the beam portion 4 and the end portion 4b connected to the movable electrode 5. Since the stress relaxation portions 30, 30A and 30B are provided, the stress generated in the beam portion 4 can be reduced to improve durability, and the degree of freedom of setting specifications such as the displacement amount and weight of the movable electrode 5 is increased. can do. When the stress relaxation portions 30, 30 </ b> A, 30 </ b> B are provided on both the end portion 4 a on the side connected to the anchor portion 3 of the beam portion 4 and the end portion 4 b on the side connected to the movable electrode 5, stress is further increased. Can be reduced.

  At this time, the stress relaxation portions 30, 30 </ b> A, 30 </ b> B can be easily formed as one frame-shaped structure 31, a structure including the frame-shaped structures 31 in multiple stages, or a meandering structure 35.

  In particular, when the beam portion 4 is used as a torsion beam, the stress relaxation portions 30, 30 </ b> A, and 30 </ b> B are composed of a single frame-like structure 31, a structure containing multiple frame-like structures 31 as illustrated in the present embodiment, or meandering. When configured as the structure 35, the amount of deflection per unit length of the beam portion 4 (and the stress relaxation portions 30, 30A, 30B) can be reduced by the amount that the portion orthogonal to the axial direction can be provided relatively long. This makes it possible to reduce the stress even more effectively.

  Further, in the present embodiment, by making the cross section of the beam portion 4 a substantially rectangular cross section, the direction in which the beam portion 4 is easily bent and the direction in which the beam portion 4 is difficult to be bent are defined, and the movable electrode 5 is operated in a desired mode. Inconvenience due to operation in a mode can be suppressed.

  In particular, when the movable electrode 5 is swung and the beam portion 4 is configured as a torsion beam as in the present embodiment, the cross-sectional shape perpendicular to the extending axis of the beam portion 4 is shown in FIG. By making the length in the thickness direction (height h) longer than the length in the direction along the surface of the sensor 1 (width w), the movable electrode 5 is entirely in the thickness direction of the sensor 1 (vertical direction in FIG. 2). ) And the large plate portion 5a and the small plate portion 5b are operated so as to be close to the fixed electrodes 6A and 6B, and it is possible to suppress a decrease in detection accuracy.

  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, the case where the beam is used as the torsion beam has been illustrated. However, the present invention can be similarly applied to the case where the beam is used as a bending beam. The same can be applied to the beam.

  Also, the specifications of the frame-like structure and the meandering structure (for example, the number of steps of the frame-like structure, the number of turns of the meandering structure, the size and shape of each part, etc.) can be variously modified. For example, the frame structure may have a triangular shape (for example, a regular triangle shape or an isosceles triangle shape) in plan view as shown in FIG. 8, or the triangular unit frame may be a truss as shown in FIG. You may overlap in multiple. According to such a configuration, stress concentration can be further reduced as compared with a frame structure having a rectangular shape in plan view.

The top view of the semiconductor layer of the electrostatic capacitance type sensor concerning embodiment of this invention. Sectional drawing of the electrostatic capacitance type sensor in the AA line of FIG. Sectional drawing of the electrostatic capacitance type sensor in the BB line of FIG. Sectional drawing (CC sectional drawing of FIG. 2) of the beam part of the electrostatic capacitance type sensor concerning embodiment of this invention. It is a schematic diagram which shows a mode that the movable electrode of the capacitive sensor concerning embodiment of this invention rock | fluctuates, Comprising: (a) is the state which is not rock | fluctuating, (b) has approached the fixed electrode on one side. A state, (c) is a figure which shows the state which the other side approached the fixed electrode. It is an enlarged view which shows the electric potential extraction part as a part of semiconductor layer of the electrostatic capacitance type sensor concerning embodiment of this invention, (a) is a top view, (b) is DD cross section of (a). FIG. 3C is a diagram showing a state before assembly. The top view ((a)-(c)) which shows each Example of the stress relaxation part of the capacitance-type sensor concerning embodiment of this invention. The top view ((a) and (b)) which shows another Example of the stress relaxation part of the electrostatic capacitance type sensor concerning embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitance type sensor 2 Semiconductor layer 4 Beam part (beam)
5 Movable electrode 6A, 6B Fixed electrode 25a, 25b Gap 30, 30A, 30B Stress relaxation part 31 Frame-like structure 35 Serpentine structure

Claims (4)

A fixed electrode and a movable electrode movably supported by a fixed portion of the semiconductor layer via a beam, and the detection unit is configured by disposing the fixed electrode and the movable electrode so as to face each other with a gap. In a capacitance type sensor that detects a predetermined physical quantity by detecting a capacitance according to the size of
A stress relaxation portion for relaxing local stress concentration is provided at least one of an end portion connected to the beam fixed portion and an end portion connected to the movable electrode, and the stress relaxation portion Is a capacitive sensor characterized in that triangular unit frames in a plan view are overlapped in a truss shape to form a triangular structure larger than the unit frame .   2. The capacitance type according to claim 1, wherein the stress relieving portion is provided at both an end connected to the fixed portion of the beam and an end connected to the movable electrode. Sensor.   3. The capacitive sensor according to claim 1, wherein the beam is a torsion beam having a rectangular cross section that is twisted in accordance with the operation of the movable electrode. The movable electrode is swingably supported via the torsion beam,
The capacitance type according to claim 3, wherein the detection unit detects a capacitance according to a size of a gap between a surface of the swinging movable electrode and a surface of the fixed electrode facing the surface. Sensor.

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