JP2006184013A - Acceleration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the influence on detection error of parasitic capacity of wires by making the length of wires for taking out signals short and substantially equal. <P>SOLUTION: At one side of a support substrate 1, end parts of fixed electrode pads 26a and 26b formed on the surface side of a fixed electrode part 24d and a movable electrode pad 26c formed on the surface side of a support part 23<SB>1</SB>are juxtaposed on one line along the vertical direction in Fig.(a). Therefore, since the length of wires with a signal processing circuit can be shortened, and three wires can be set substantially to the same length, compared with a conventional example where four pads 26<SB>1</SB>-26<SB>4</SB>are juxtaposed by twos on two sides of the support substrate 1, the parasitic capacity can be canceled among the wires while reducing the parasitic capacity of wires, and the influence on detection error of the parasitic capacity of wires can be suppressed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an acceleration sensor, and more particularly to a so-called capacitance type acceleration sensor.

  Conventionally, a structure including a vibrating body formed by integrally forming a weight, a beam, and an anchor and two fixed electrodes is made from the same semiconductor substrate, and the weight and the beam are sandwiched between the two fixed electrodes. In addition, the weight and the beam are arranged with a gap with respect to the support substrate, and the anchor and the two fixed electrodes are joined to the substrate, so that the displacement of the weight due to acceleration can be detected electrically. A type of acceleration sensor is provided (see Patent Document 1).

  The applicant has already proposed a capacitance type acceleration sensor having the structure shown in FIG. 7 (see Patent Document 2). The acceleration sensor includes a weight portion 21 disposed on the one surface (upper surface in FIG. 7B) side of the support substrate 1 made of a glass substrate and spaced from the support substrate 1, and on the one surface side of the support substrate 1. A pair of support portions 23 and 23 that support the weight portion 21 via a spring portion 22 that is fixed and displaces the weight portion 21 in a specified direction (left and right direction in FIG. 7A) along the one surface; The comb-shaped fixed electrode portion 24 having a plurality of thin plate-shaped fixed electrodes 24b fixed to the one surface side of the support substrate 1 on both sides of the weight portion 21 and arranged in such a manner that the prescribed direction is the thickness direction. And a plurality of thin plate-like movable electrodes 21a provided in the weight portion 21 so as to enter the comb grooves 24c between the adjacent fixed electrodes 24b and 24b one by one and be displaceable in the prescribed direction. That is, on both sides of the weight portion 21, the fixed electrodes 24b and the movable electrodes 21a are alternately arranged along the specified direction, and one movable is provided in the comb groove 24c between the adjacent fixed electrodes 24b and 24b in the specified direction. One fixed electrode 24b enters the comb groove 21b between the movable electrodes 21a and 21a adjacent to each other in the prescribed direction. The weight portion 21, the spring portion 22, the support portion 23, the fixed electrode 24b, the fixed electrode portion 24, and the movable electrode 21a provided on the one surface side of the support substrate 1 are obtained by etching a single crystal silicon substrate. Is formed by a part of the silicon substrate.

The weight portion 21 can be displaced in the direction of the arrow from the center O of the weight portion 21 in FIG. 7 with the left-right direction of FIG. ) On the left and right sides of the weight portion 21 in FIG. Further, pads 26 ₁ and 26 ₂ are formed on the surface side of the support portions 23 and 23. Incidentally, the upper side of the movable electrode 21a of the weight portion 21 in FIG. 7 via the diffusion layer interconnect pad 26 ₁ formed on the left side of the supporting portion 23 of the weight section 21 is not shown in FIG. 7 (a) (a) are electrically connected, the lower side of the weight portion 21 in FIGS. 7 (a) through the diffusion layer interconnect pad 26 ₂ formed on the right side of the supporting portion 23 of the weight section 21 is not shown in FIGS. 7 (a) It is electrically connected to each movable electrode 21a.

  Each spring portion 22 has a planar shape that is formed in a folded shape. One end of the right spring portion 22 in FIG. 7A is continuously connected to the upper right corner of the weight portion 21 and the other end is connected to the other end. The portion is continuously and integrally connected to the support portion 23 on the right side of the weight portion 21. Similarly, one end of the left spring portion 22 in FIG. 7A is continuously connected to the lower left corner of the weight portion 21, and the other end is continuously integrated to the left support portion 23 of the weight portion 21. It is connected.

The fixed electrode portion 24 is formed in a comb-like planar shape by a plurality of fixed electrodes 24b arranged in the specified direction and a connecting portion 24a extending in the specified direction and connecting the plurality of fixed electrodes 24b. Pads 26 ₃ and 26 ₄ made of aluminum are formed on the surface side of the connecting portion 24a and the fixed pole portion 24d extending laterally from one end in the extending direction of the connecting portion 24a. Here, FIG. 7 lower the fixed electrodes 24b and electricity of the weight portion 21 in FIG. 7 is a pad 26 ₃ formed on the right side of the fixed pole portion 24d through the diffusion layer wirings, not shown (a) in (a) are connected, and the fixed electrode 24b of the upper weight section 21 in FIGS. 7 (a) through the diffusion layer interconnect pad 26 ₄ not shown formed on the left side of the fixed electrode portion 24d in FIGS. 7 (a) Electrically connected. The fixed pole portion 24 d extends to the vicinity of the support portion 23.

Further, a support substrate 2 made of a glass substrate is disposed opposite to the support substrate 1 on the surface of the weight portion 21 and the spring portion 22 (upper surface in FIG. 7B). The support substrate 2 is bonded to the pad 26 _{1-26 4} provided on the fixed electrode portion 24d, for each pad 26 _{1-26 4} connected to an external circuit by wire bonding, one pad 26 _{1-26 4} Two insertion holes 3 are provided through each end of the longitudinal direction so as to face the part to the outside. And in the external circuit electrically connected to these pads 26 _{1 to} 26 ₄ , the capacitance value between the fixed electrode 24b and the movable electrode 21a according to the displacement of the weight portion 21 in the predetermined direction. Acceleration can be detected as a change. Note that reference numeral 25 in FIG. 7A denotes a stopper that regulates the amount of displacement of the weight portion 21.

Here, in FIG. 7A, the movable electrode 21a provided on the upper side of the weight portion 21 and the movable electrode 21a provided on the lower side are respectively arranged between the fixed electrodes 24b and 24b as shown in FIG. 8A. Are arranged in different directions from the center line M of the comb groove 24c formed in the outer periphery of the comb groove 24c. Therefore, when acceleration is applied in the prescribed direction, the movable electrode 21a is fixed between the movable electrode 21a and the fixed electrode 24b on both sides of the weight 21. Therefore, the direction of acceleration can be detected. That is, if the electrostatic capacity between the upper fixed electrode 24b and the movable electrode 21a in FIG. 8A is C1, and the electrostatic capacity between the lower fixed electrode 24b and the movable electrode 21a is C2, It is represented by an equivalent circuit shown in FIG. 8B, and in the state where no acceleration is applied, the capacitance values of the two electrostatic capacitances C1 and C2 are substantially equal, so the algebraic sum is substantially zero. As shown by the arrow in FIG. 8 (a), when a leftward acceleration is applied in the figure, the distance between the upper fixed electrode 24b and the movable electrode 21a decreases, so that the capacitance value C1 increases and the lower fixed electrode 24b. Since the distance between the electrode 21a and the movable electrode 21a increases, the capacitance value C2 decreases, and the increase ΔCg1 and the decrease ΔCg2 of the two capacitance values C1 and C2 become equal (ΔCg1 = ΔCg2). , Leftward acceleration in the figure is The algebraic sum of the two capacitance values C1 and C2 is 2 × ΔCg, and the magnitude and direction of acceleration are detected simultaneously from the absolute value ΔCg of the change in capacitance value and the sign (in this case, plus). (See FIG. 8 (c)).
Japanese Patent Laid-Open No. 8-32090 JP 2004-28912 A

By the way, the processing for detecting the magnitude and direction of acceleration based on the change in capacitance when acceleration acts as described above is performed by a signal processing circuit outside the acceleration sensor. This type of signal processing circuit is usually composed of an integrated circuit (IC), and is disposed in the vicinity of the acceleration sensor and is electrically connected to the pads 26 _{1 to} 26 _{4 of the} acceleration sensor via wires. At this time, the length of wiring for connecting the signal processing circuit and the pad 26 _{1-26 4} (wire) is equal as short as possible and between the pads 26 _{1-26 4} in order to suppress the detection error due to the parasitic capacitance of the wiring It is desirable to use a distance. However, in the above-described conventional example, two pads 26 _{1 to} 26 ₄ are disposed at both ends in the longitudinal direction, so it is difficult to make each wiring length (wire length) short and equal. .

  The present invention has been made in view of the above circumstances, and its purpose is to suppress the influence of detection errors due to parasitic capacitance of wiring by shortening and substantially equalizing the length of wiring for extracting signals to the outside. An object of the present invention is to provide an acceleration sensor that can be used.

  In order to achieve the above object, the invention according to claim 1 is fixed to the one surface side of the support substrate, the weight portion disposed away from the support substrate on one surface side of the support substrate, and the one surface side of the support substrate. At least one set of support portions that support the weight portion via a spring portion that allows the weight portion to be displaced in a specified direction along one surface, and is fixed to the one surface side of the support substrate on the side of the weight portion. A comb-shaped fixed electrode portion having a plurality of thin plate-like fixed electrodes arranged in a line so that the specified direction is the thickness direction, and can be displaced in the specified direction one by one in a comb groove between adjacent fixed electrodes A plurality of thin plate-like movable electrodes provided in the weight portion so that the acceleration changes in the capacitance value between the fixed electrode and the movable electrode according to the displacement of the weight portion in the specified direction. Acceleration sensor that detects as a fixed electrode Fixed electrode pads are provided on the surface of the fixed electrode portion to be electrically connected and connected to the external wiring, and are connected to the movable electrode and connected to the external wiring. The pad is provided on the support portion, and at least a part of the fixed electrode pad and the movable electrode pad is juxtaposed on one side of the support substrate in a plane parallel to the one surface of the support substrate. .

  According to a second aspect of the present invention, in the first aspect of the present invention, the weight portion, the support portion, the fixed electrode portion, and the movable electrode are formed in a frame shape surrounding the support substrate from the direction along the one surface. A frame body fixed to the front surface side and a second support substrate that covers the frame body so as to face the support substrate across the frame body, and the second support substrate is bonded to one surface of the frame body The connecting portion is formed over the entire circumference.

  According to a third aspect of the present invention, in the second aspect of the present invention, the joining portion is formed integrally with the fixed electrode pad.

  According to a fourth aspect of the present invention, in the second aspect of the present invention, the joining portion is formed integrally with the movable electrode pad.

  The invention of claim 5 is characterized in that, in the invention of claim 2, the frame is formed separately from the support part and the fixed electrode part.

  According to a sixth aspect of the present invention, in the first aspect of the present invention, the weight portion, the support portion, the fixed electrode portion, and the movable electrode are formed in a frame shape surrounding the support substrate from the direction along the one surface, and the one of the support substrates. A frame body fixed to the front surface side and a second support substrate that covers the frame body so as to face the support substrate across the frame body, and the insertion hole for inserting the wiring to the outside is a second The fixed electrode pad and the movable electrode pad are provided on the inner side of the inner diameter of the insertion hole.

  A seventh aspect of the invention is characterized in that, in the sixth aspect of the invention, the outer shapes of the fixed electrode pad and the movable electrode pad are substantially circular.

  The invention of claim 8 is characterized in that, in the invention of claim 5, the joint is electrically connected to an external ground.

  According to the present invention, at least a part of the fixed electrode pad and the movable electrode pad to which the wiring to the outside is connected is juxtaposed on one side of the support substrate in a plane parallel to the one surface of the support substrate. Therefore, the length of the wiring for extracting the signal to the outside can be made short and substantially equal, and as a result, the effect of the detection error due to the parasitic capacitance of the wiring can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, since each of the following embodiments has the same basic configuration as the conventional example shown in FIG. 7, the same reference numerals are given to common components, and description thereof will be omitted as appropriate.

(Embodiment 1)
In the present embodiment, as shown in FIG. 1, at least a part of the fixed electrode pads 26 a and 26 b and the movable electrode pad 26 c are juxtaposed on one side of the support substrate 1 in a plane parallel to one surface of the support substrate 1. There is a feature in that.

That is, of the pair of support portions 23 ₁ and 23 ₂ , the right support portion 23 ₁ in FIG. 1A is provided at the center in the vertical direction in the figure, and the support portion 23 ₁ is sandwiched from the vertical direction. A pair of fixed pole portions 24d are provided, and fixed electrode pads 26a and 26b formed on the surface side of the fixed pole portion 24d on one side (the right side in FIG. 1A) side of the rectangular flat support substrate 1. of the end portion, and the movable electrode pad 26c formed on the surface side of the supporting portion 23 ₁ are juxtaposed in a row along the vertical direction.

Further, on the surface side of the left support portion 23 ₂ in FIG. 1A, a joint portion 27 made of aluminum is formed in the same manner as the fixed electrode pads 26a and 26b and the movable electrode pad 26c. The support substrate 2 made of a glass substrate is joined to the joint portions 27a and 26b and the joint portion 27. In addition, an insertion hole 3 through which a part of the fixed electrode pads 26a and 26b and the movable electrode pad 26c are exposed to the outside is provided at the right end of the support substrate 2 in FIG. (Refer FIG.1 (b)). Then, the signal processing circuit for detecting the magnitude and direction of acceleration based on the change in capacitance when the acceleration is applied, the fixed electrode pads 26a and 26b, and the movable electrode pad 26c are connected to the wire through the insertion hole 3. It is electrically connected by bonding.

Thus, in the present embodiment, the fixed electrode pads 26a and 26b formed on the surface side of the fixed pole portion 24d on one side of the support substrate 1 and the surface side of the support portion 23 ₁ are formed. Since the movable electrode pads 26c are juxtaposed in a line along the vertical direction in FIG. 1A, the _four pads 26 _{1 to} 26 ₄ are juxtaposed in two on each of the two sides of the support substrate 1. Compared to the conventional example, the length of the wiring (wire) to the signal processing circuit can be shortened and the three wirings can be made substantially the same length. It is possible to cancel the parasitic capacitance between the wirings, and the influence of the detection error due to the parasitic capacitance of the wiring can be suppressed.

(Embodiment 2)
In the present embodiment, as shown in FIG. 2, the weight portion 21, the spring portion 22, the support portions 23 ₁ and 23 ₂ , the fixed electrode portion 24, the stopper 25, the movable electrode 21 a, and the like along the surface of the support substrate 1 ( A frame body 28 formed in a rectangular frame shape that surrounds from the vertical direction and the horizontal direction in FIG. 2A and fixed to the one surface side of the support substrate 1 is provided, and the surface of the frame body 28 (FIG. 2B). ) Is characterized in that the support substrate 2 is bonded to the upper surface). However, since the basic configuration is the same as that of the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

  The frame 28 has a rectangular frame shape whose vertical and horizontal outer dimensions are substantially the same as those of the support substrates 1 and 2, and the silicon substrate is simultaneously formed with the weight portion 21 and the spring portion 22 by etching a single crystal silicon substrate. Formed by a part of. Further, a lower fixed pole portion 24d in FIG. 2A is continuously and integrally formed on the frame body 28, and a joint portion 29 made of aluminum for joining the support substrate 2 is further formed on the surface of the frame body 28. It is formed integrally with the fixed electrode pad 26b of the fixed pole portion 24d.

Therefore, if the support substrate 2 is bonded to the surface of the frame body 28 at the bonding portion 29, the weight portion 21, the spring portion 22, the support portions 23 ₁ and 23 ₂ , and the fixed portion are fixed by the two support substrates 1 and 2 and the frame body 28. Since the electrode part 24, the stopper 25, the movable electrode 21a, etc. are all covered, minute dust, foreign matter, etc. do not enter the inside, and such troubles as obstruction of the displacement of the weight part 21 by such foreign matter, etc. are prevented. It is possible to improve reliability.

(Embodiment 3)
Since the basic configuration of the present embodiment is the same as that of the second embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 3, the present embodiment is different from the second embodiment in that a pair of support portions 23 are formed integrally with the frame body 28, and a joint portion 29 on the surface of the frame body 28 is formed on the surface of the support portion 23. It is in the point formed integrally with the pad 26c for movable electrodes.

  Thus, since the support portion 23 and the frame body 28 are integrally formed, and the movable electrode pad 26c and the joint portion 29 formed on the surfaces thereof are also integrally formed, the structure shown in FIG. The fixed electrode pads 26a and 26b and the movable electrode pad 26c are axisymmetric with respect to the vertical center line (A-A line), and the fixed electrode including the fixed electrode pads 26a and 26b and the movable electrode pad 26c. Since the capacitance values C1 and C2 between 24b and the movable electrode 21a are substantially the same (C1≈C2), the influence of the parasitic capacitance of the wiring can be further reduced.

(Embodiment 4)
Since the basic configuration of the present embodiment is the same as that of the second embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

This embodiment is different from the second embodiment in that the frame 28 is formed separately from the fixed pole portion 24d and the pair of support portions 23 ₁ and 23 ₂ as shown in FIG. That is, the frame body 28 is not connected to any of the fixed pole portion 24d and the support portions 23 ₁ and 23 ₂ , so that the joint portion 29 on the surface of the frame body 23 is also connected to the fixed electrode pads 26a and 26b and the movable electrode pad 26c. Both are electrically insulated. However, one of the four corners of the frame body 28 (upper right corner in FIG. 4A) is provided with a base portion 28a protruding inward, and the surface of the base portion 28a is integrated with the joint portion 29. The formed ground pad 30 is formed, and the ground pad 30 is electrically connected to the external ground through wire insertion through the insertion hole 3 provided in the support substrate 2.

Thus, since the fixed pole portion 24d and the support portions 23 ₁ and 23 ₂ and the frame body 28 are formed separately, the fixed electrode 24b, the movable electrode 21a, the fixed electrode pads 26a and 26b, and the movable electrode pad Since 26c is sealed inside the frame body 28 and is not exposed to the outside, the characteristics of the sensor against disturbances such as moisture and moisture can be stabilized. In addition, if the joint portion 29 for joining the support substrate 2 is connected to an external ground, the fixed electrode 24b, the movable electrode 21a, etc. are shielded by the joint portion 29, and there is an advantage that noise resistance is improved.

  By the way, when the frame body 28 and the support substrate 2 are joined by the joint portion 29 made of aluminum, the thermal expansion coefficient of aluminum is considerably higher than the thermal expansion coefficient of the silicon substrate constituting the frame body 28 and the glass constituting the support substrate 2. Since it is a large value, an offset due to a temperature change may occur, and the temperature characteristics of the sensor may deteriorate.

  Therefore, if the frame body 28 and the support substrate 2 are joined by anodic bonding without forming the aluminum joint portion 29 on the surface of the frame body 28 as shown in FIG. 5, the aluminum joint portion 29 is unnecessary. Thus, the temperature characteristics can be improved. At this time, the fixed electrode pads 26a and 26b and the movable electrode pad 26c are provided inside the inner diameter of the insertion hole 3 of the support substrate 2, and the fixed electrode pads 26a and 26b and the movable electrode pad 26c made of aluminum are supported. If it is not interposed between the substrate 2 and the substrate 2, the temperature characteristics can be further improved. As shown in FIG. 5A, the fixed electrode pads 26a and 26b and the movable electrode pad 26c are formed in a rectangular shape that is smaller than the inner diameter of the insertion hole 3, so that the pads are used when wire bonding is performed. There is also an advantage that recognition of 26a to 26c becomes easy. However, if the outer shape of these pads 26a to 26c is circular as shown in FIG. 6, there is a margin in the distance relationship with the through hole 3 as compared with the rectangular shape. 3 has an advantage in that the inner diameter of the three can be made small and the interval between the insertion holes 3 can be narrowed, so that the overall size can be reduced.

Embodiment 1 is shown, (a) is a plan view in which the upper support substrate is omitted, and (b) is a side view. Embodiment 2 is shown, (a) is a plan view in which the upper support substrate is omitted, and (b) is a cross-sectional view taken along line AA in (a). Embodiment 3 is shown, (a) is a plan view in which the upper support substrate is omitted, and (b) is a cross-sectional view taken along line AA in (a). Embodiment 4 is shown, (a) is a plan view in which the upper support substrate is omitted, and (b) is a cross-sectional view taken along line AA in (a). The other structure same as the above is shown, (a) is a plan view in which the upper support substrate is omitted, and (b) is a cross-sectional view taken along line AA in (a). FIG. 5A is a plan view in which the upper support substrate is omitted, and FIG. 5B is a cross-sectional view taken along the line AA in FIG. A prior art example is shown, (a) is a plan view in which the upper support substrate is omitted, and (b) is a cross-sectional view taken along line AA in (a). (A)-(c) is operation | movement explanatory drawing of a prior art example.

Explanation of symbols

1 supporting substrate 2 supporting substrate 21 weight part 21a movable electrode 22 spring portion 23 _1, 23 ₂ supports 24 fixed electrode portion 24b fixed electrode 24d fixed pole part 26a, 26b fixed electrode pad 26c movable electrode pad

Claims (8)

  A support substrate, a weight portion disposed on one surface side of the support substrate so as to be separated from the support substrate, and fixed to the one surface side of the support substrate so that the weight portion can be displaced in a specified direction along the one surface. A plurality of support portions that support the weight portion via the spring portion, and a plurality of support portions that are fixed to the one surface side of the support substrate on the side of the weight portion so that the prescribed direction is the thickness direction. A plurality of thin plate-like fixed electrode portions each having a thin plate-like fixed electrode and a plurality of thin plate-like shapes provided in the weight portion so as to be displaced one by one into a comb groove between adjacent fixed electrodes and displaced in the prescribed direction An acceleration sensor that detects an acceleration as a change in capacitance value between the fixed electrode and the movable electrode in accordance with the displacement of the weight portion in the specified direction. Connected and external wiring is connected The fixed electrode pad is provided on the surface of the fixed electrode portion, and the movable electrode pad electrically connected to the movable electrode and connected to the outside wiring is provided on the support portion, and the fixed electrode pad and An acceleration sensor characterized in that at least a part of the movable electrode pad is juxtaposed on one side of the support substrate in a plane parallel to the one surface of the support substrate.   A frame body that is formed in a frame shape that surrounds the weight portion, the support portion, the fixed electrode portion, and the movable electrode from the direction along the one surface of the support substrate and is fixed to the one surface side of the support substrate, and the frame body sandwiched between And a second support substrate that covers the frame body so as to face the support substrate, and a joint portion to which the second support substrate is bonded is formed over the entire circumference on one surface of the frame body. The acceleration sensor according to claim 1.   The acceleration sensor according to claim 2, wherein the joint is formed integrally with the fixed electrode pad.   The acceleration sensor according to claim 2, wherein the joint is formed integrally with the movable electrode pad.   The acceleration sensor according to claim 2, wherein the frame body is formed separately from the support portion and the fixed electrode portion.   A frame body that is formed in a frame shape that surrounds the weight portion, the support portion, the fixed electrode portion, and the movable electrode from the direction along the one surface of the support substrate and is fixed to the one surface side of the support substrate, and the frame body sandwiched between And a second support substrate that covers the frame so as to face the support substrate, and an insertion hole for inserting the wiring to the outside is provided in the second support substrate, and the fixed electrode pad, The acceleration sensor according to claim 1, wherein the movable electrode pad is provided inside an inner diameter of the insertion hole.   The acceleration sensor according to claim 6, wherein an outer shape of the fixed electrode pad and the movable electrode pad is substantially circular.   The acceleration sensor according to claim 5, wherein the joint is electrically connected to an external ground.

Images