JP4692373B2 - 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).

  Then, as this type of capacitive sensor, a part of the semiconductor layer and a predetermined position of the conductor layer as a fixed electrode formed on the insulating layer are brought into contact with each other to ensure conduction between them, A configuration in which the potential of the fixed electrode is extracted through a part of the semiconductor layer is known (for example, Patent Document 2).

In the structure of Patent Document 2, a conductor layer is sandwiched between an insulating layer and a semiconductor layer, so that a part of the semiconductor layer and the conductor layer are brought into contact with each other and conductive.
JP 2000-28634 A JP-A-8-254438

  However, in the configuration of Patent Document 2, since the conductor layer is thin and flat, it may be difficult to increase the contact pressure and to obtain a sufficient conduction state.

  Therefore, the present invention is more reliable between the fixed electrode and the potential extraction portion when the potential of the fixed electrode provided in the insulating layer in the capacitance type sensor is taken out through the potential extraction portion provided in the semiconductor layer. It aims at obtaining the structure which can ensure conduction | electrical_connection.

The invention according to claim 1 includes a fixed electrode formed on the insulating layer, and a movable electrode movably supported by a fixed portion of the semiconductor layer via a beam, and the fixed electrode and the movable electrode are provided. In a capacitive sensor that detects a predetermined physical quantity by detecting a capacitance according to the size of the gap, the detection unit is configured to be opposed to each other with a gap. Forming a potential extraction portion that is in contact with and conductive with an electrode or a conductor layer connected to the fixed electrode, and configured to take out the potential of the fixed electrode through the potential extraction portion, and the potential extraction portion includes the semiconductor Forming a recess having a recessed layer, and forming a projecting contact portion made of a conductor in a conductive state with the semiconductor layer of the potential extraction portion in the recess, and the tip portion is the semiconductor Above insulation layer Is high is formed so as to protrude from the joint surface, so that the tip portion of the contact portion is in contact over the entire width of the flat conductor layer surface which leads to the fixed electrode, the tip portion of the contact portion It is characterized by being brought into press contact with the conductor layer .

  The invention according to claim 2 is characterized in that an underlay layer having a flat upper surface is formed on the recess, and the contact portion is formed on the underlay layer.

  According to the present invention, the contact pressure is increased by pressing the fixed electrode or the conductor layer connected to the fixed electrode with the tip of the protruding contact portion formed of the conductor formed on the potential extraction portion. It is possible to ensure conduction more reliably between the voltage extraction portion and the potential extraction portion.

  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.

  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. The recess 26 is preferably formed by anisotropic etching (wet etching) to ensure depth accuracy and to obtain a flatter bottom surface 8c.

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).

In this case, if the underlying layer 27 is a layer of silicon dioxide (SiO ₂ ), the upper surface of the underlying layer 27 is formed flat (mirrored), and the peak portion 12a (contact portion 12) is provided without providing the underlying layer 27. Compared with the case of forming, the heights of the mountain portions 12a can be aligned with high accuracy. Therefore, the contact pressure between the peak portion 12a and the terminal portion 9 can be set with higher accuracy.

  Furthermore, in this embodiment, as shown in FIG. 6C, the crest portion 12a of the contact portion 12 is formed so as to protrude by a height δh above the surface 2a of the semiconductor layer 2, thereby By joining the semiconductor layer 2 and the insulating layer 20, the terminal portion 9 is pressed and plastically deformed by the terminal portion 9, and the degree of adhesion between the mountain portion 12 a (contact portion 12) and the terminal portion 9 is increased. The contact and conduction between them are made more reliable. In addition, when the thickness of the conductor layer of the terminal portion 9 can be managed with high accuracy, it is possible to set the height of the peak portion 12a in consideration of the thickness of the conductor layer (set to be lower by the thickness). .

  Further, 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. Further, in this case, if the depth of the recess 22 from the surface 2a of the semiconductor layer 2 and the depth of the recess 26 from the surface 2a of the semiconductor layer 2 are set to the same value, the recesses 22 and 26 are formed in the same process. As a result, the manufacturing cost can be further reduced.

  According to the present embodiment described above, the tip of the protruding peak portion 12a (contact point portion 12) made of a conductor formed in the potential extraction portion 8 is pressed against the terminal portion 9 as a conductor layer connected to the fixed electrodes 6A and 6B. Since the contact pressure is increased by contact, conduction between the fixed electrode 6 and the potential extraction portion 8 can be ensured more reliably.

  Further, in the present embodiment, the concave portion 26 having the flat bottom surface 8c is formed in the potential extraction portion 8 so that the thickness (height) as the mountain portion 12a (contact portion 12) can be secured. It becomes easy to adjust to a desired shape (height, tip shape, etc.), and it becomes easy to secure a desired contact pressure.

  In addition, when the conductor layer becomes too thick, minute irregularities may occur on the upper surface thereof. In this embodiment, the height of the crest portion 12a (contact portion 12) is provided by the provision of the underlay layer 27. Therefore, it is possible to suppress the occurrence of unevenness at the tip of the peak portion 12a, and as a result, it is possible to more reliably ensure conduction between the fixed electrode 6 and the potential extraction portion 8.

In particular, as in the present embodiment, if the underlying layer 27 is a silicon dioxide (SiO ₂ ) layer, the upper surface of the underlying layer 27 is formed flat (mirrored), and the ridges are formed without providing the underlying layer 27. Compared with the case where 12a (contact part 12) is formed, the heights of the crests 12a can be aligned with high accuracy, so that the contact pressure can be set with high accuracy and the contact pressure varies depending on the position and contact. Individual differences in pressure can be suppressed.

  Further, as in the present embodiment, if the crest portion 12a of the contact portion 12 protrudes above the surface 2a of the semiconductor layer 2, the terminal portion 9 causes the junction between the semiconductor layer 2 and the insulating layer 20. The crest portion 12a can be pressed and plastically deformed, and the degree of adhesion between the crest portion 12a (contact portion 12) and the terminal portion 9 is increased, and between these, by extension, between the fixed electrode 6 and the potential extracting portion 8 Thus, conduction can be ensured more reliably.

  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, the fixed electrode itself may be pressed by the contact portion, and the present invention can be implemented not only as a swing method but also as other types of sensors such as an advance / retreat method.

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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitance type sensor 2 Semiconductor layer 4 Beam part (beam)
5 Movable electrode 6A, 6B Fixed electrode 8 Potential extraction part 9 Terminal part (conductor layer)
12 Contact portion 20 Insulating layer 26 Recessed portion 27 Underlay layer

Claims (2)

A detection unit including a fixed electrode formed on the insulating layer and a movable electrode supported and supported by a fixed portion of the semiconductor layer via a beam, and the fixed electrode and the movable electrode are arranged to face each other with a gap therebetween In the capacitance type sensor that detects a predetermined physical quantity by detecting the capacitance according to the size of the gap,
The semiconductor layer is configured to form a potential extraction portion that conducts in contact with the fixed electrode or a conductor layer connected to the fixed electrode, and is configured to extract the potential of the fixed electrode through the potential extraction portion,
In the potential extraction portion, a concave portion in which the semiconductor layer is recessed is formed, and in the concave portion, a protruding contact portion made of a conductor is formed in a state of being electrically connected to the semiconductor layer of the potential extraction portion,
The contact portion is formed high so that the tip portion protrudes from the bonding surface of the semiconductor layer to the insulating layer, and the tip direction of the contact portion is connected to the fixed electrode in the width direction. A capacitance type sensor characterized in that the tip of the contact portion is pressed against the conductor layer so as to be in contact over the entire area .   The capacitive sensor according to claim 1, wherein an underlying layer having a flat upper surface is formed on the concave portion, and the contact portion is formed on the underlying layer.

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