JP2010210422A - Acceleration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acceleration sensor capable of reducing an influence of a stray capacitance, while enhancing sealability. <P>SOLUTION: Through-holes 80a, 80b, 90a, 90b of through-hole wiring parts 8a, 8b, 9a, 9b are blocked by electrode parts 81a, 81b, 91a, 91b made of silicon substrates. Hereby, sealability of a sensor chip 1 can be enhanced. Each dimension (longitudinal/lateral dimension) of the electrode parts 81a, 81b, 91a, 91b is set to be smaller than an opening diameter ϕ1 on each one surface side (each under surface side) of the through-holes 80a, 80b, 90a, 90b, and set to be larger than an opening diameter ϕ2 on each other surface side (each upper surface side) thereof, to thereby reduce an influence of a stray capacitance generated between the electrode parts 81a, 81b, 91a, 91b and the sensor chip 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a capacitance type acceleration sensor.

  Conventionally, as shown in FIG. 3, a rectangular parallelepiped weight portion 100 having a movable electrode, a pair of beam portions 101 that rotatably supports the weight portion 100 at a substantially center in the longitudinal direction of the weight portion 100, and a pair of beams First and second fixed electrodes 102 and 103 arranged to face each other on the one side and the other side of the weight part 100 with a straight line (beam axis) connecting the parts 101 as a boundary line. An acceleration sensor provided is known. This acceleration sensor includes a movable electrode (a portion facing the fixed electrodes 102 and 103 of the weight portion 100) and the first and second fixed electrodes 102 and 103 that accompany the rotation of the weight portion 100 about the beam axis. The acceleration applied to the weight part 100 is detected by differentially detecting the change in capacitance between the two. In such an acceleration sensor, when the acceleration is applied, a moment with the beam axis as the rotation axis is generated in the weight portion 100, so that the beam axis on the back surface of the weight portion 100 is used as one boundary (see FIG. 3 is formed on the one side (right side) and the other side (left side) of the weight part 100 with the beam axis as a boundary line (for example, Patent Document 1). reference).

  By the way, in the acceleration sensor as described above, it is difficult to be affected by the atmosphere during use, and foreign matter is prevented from entering the capacitance gap portion (the gap between the fixed electrodes 102 and 103 and the movable electrode). Further, a sensor chip made of a semiconductor substrate having a weight portion is sandwiched in a thickness direction by a plate material made of an insulating material (for example, a glass plate), and is inserted in the glass plate for wiring to a fixed electrode or a movable electrode. The through-hole is closed with a semiconductor substrate, and the capacitance gap is sealed with the wiring connected from the semiconductor substrate to the fixed electrode and the movable electrode through the through-hole wiring (through-hole plating) (for example, patents) References 2-4).

Special table 2008-544243 gazette JP 2000-275272 A JP-A-10-177034 JP-A-6-273442

  However, in the conventional examples described in the cited documents 2 to 4, the size of the semiconductor substrate that closes the through hole of the glass plate is larger than the diameter of the through hole, and the semiconductor substrate is opposed to the glass plate. There is a possibility that a stray capacitance is generated between the sensor chip and the sensor chip, and the capacitance between the fixed electrode and the movable electrode is changed by the stray capacitance.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an acceleration sensor capable of reducing the influence of stray capacitance while improving hermeticity.

  In order to achieve the above object, the invention according to claim 1 is characterized in that a weight part provided with a movable electrode on one surface and a beam part for rotatably supporting the weight part around a rotation axis are formed on a semiconductor substrate. The formed sensor chip, an insulating cover that is formed on one surface and is bonded to one surface side of the sensor chip in a direction facing the fixed electrode to the movable electrode, a through-hole that penetrates the cover, and the fixed electrode A through-hole wiring portion that is electrically connected to the through-hole and drawn to the other surface of the cover, and an electrode portion that is made of a semiconductor substrate and closes the through-hole on the other surface side of the cover and is electrically connected to the through-hole wiring portion. The through hole has a smaller opening diameter on the other surface side than the opening diameter on the one surface side, and the electrode portion has a size smaller than the opening diameter on the one surface side of the through hole and larger than the opening diameter on the other surface side. It is characterized by having .

  According to the first aspect of the present invention, sealing can be improved by closing the through hole wiring portion with the electrode portion made of a semiconductor substrate, and the size of the electrode portion can be made larger than the opening diameter on the one surface side of the through hole. In addition, the influence of stray capacitance generated between the electrode portion and the sensor chip can be reduced by setting the size to be smaller and larger than the opening diameter on the other surface side.

  According to the first aspect of the present invention, the effect of stray capacitance can be reduced while improving the sealing performance.

The embodiment of the present invention is shown, (a) is a top view and (b) is a sectional view. (A)-(e) is sectional drawing for demonstrating the manufacturing method same as the above. A prior art example is shown, (a) is a sectional view and (b) is a plan view.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, in the following description, the x-axis direction in FIG. 1 is defined as the vertical direction, the y-axis direction is defined as the horizontal direction, and the z-axis direction is defined as the vertical direction.

  In the present embodiment, as shown in FIG. 1, the sensor chip 1 whose outer shape is a rectangular flat plate, the upper cover 2 a fixed to the upper surface side of the sensor chip 1, and the lower cover fixed to the lower surface side of the sensor chip 1 2b. The sensor chip 1 has a gap with respect to the frame part 3 in which two rectangular frame parts 3a and 3b viewed in the vertical direction are arranged in the longitudinal direction (lateral direction) and the inner peripheral surface of the frame parts 3a and 3b. The rectangular parallelepiped weight parts 4 and 5 arranged in the frame parts 3a and 3b in the opened state, the inner peripheral surface of the frame parts 3a and 3b and the side surfaces of the weight parts 4 and 5 are connected to the frame part 3 And a pair of beam portions 6a, 6b and 7a, 7b that support the weight portions 4, 5 so as to be rotatable about a rotation axis, and movable electrodes 4a, 5a formed on the upper surfaces of the weight portions 4, 5. It has.

  One end of the pair of beam portions 6a and 6b is connected to the central portion in the vertical direction on the inner peripheral surface of the frame portion 3a facing in the horizontal direction, and the other is near the boundary between the concave portion 11 and the solid portion 12 on the side surface of the weight portion 4. The ends are connected. Similarly, one pair of beam portions 7a and 7b is connected at one end to the longitudinal center portion of the inner peripheral surface of the frame portion 3b facing in the lateral direction, and near the boundary between the concave portion 13 and the solid portion 14 on the side surface of the weight portion 5. The other end is connected. That is, a straight line connecting the pair of beam portions 6a and 6b and 7a and 7b serves as a rotation shaft, and the weight portions 4 and 5 rotate around the rotation shaft.

  As shown in FIG. 1B, the weight portions 4 and 5 are arranged on one side (the lower surface) on one side (the right side in FIG. 1 for the weight portion 4 and the left side in FIG. 1 for the weight portion 5) with the rotation axis as a boundary. On the other side (the weight portion 4 on the left side in FIG. 1 and the weight portion 5 on the right side in FIG. 1), the solid portions 12 and 14 are formed. In addition, the recessed parts 11 and 13 are formed in the planar view square shape seeing from the normal line direction (up-down direction) of the opening surface. The sensor chip 1 is formed by processing a silicon substrate (silicon SOI substrate) by a semiconductor microfabrication technique as will be described later, and the portions including the upper surfaces of the weight portions 4 and 5 are movable electrodes 4a, 5a. Further, at the four corners on the upper surface and the lower surface of the weight portions 4 and 5, a plurality of protrusions 15 are provided so as to prevent the weight portions 4 and 5 from directly colliding with the upper cover 2a and the lower cover 2b. .

  The lower cover 2 b is formed in a rectangular flat plate shape whose vertical and horizontal dimensions are substantially the same as the vertical and horizontal dimensions of the frame portion 3 by an insulating material such as quartz glass, and is joined to the lower surface of the frame portion 3.

  The upper cover 2a is made of an insulating material such as quartz glass, and has a first fixed electrode 20a on the lower surface thereof at a position facing the weight portion 4 (movable electrode 4a) of the sensor chip 1 along the vertical direction. The second fixed electrode 20b is juxtaposed in the vertical direction, and the first fixed electrode 21a and the second fixed electrode are disposed at positions facing the weight portion 5 (movable electrode 5a) of the sensor chip 1 along the vertical direction. 21b is juxtaposed in the vertical direction. The upper cover 2a has through holes 80a, 80b, 90a, 90b penetratingly provided at positions facing the gaps (gap) between the frame portions 3a, 3b and the weight portions 4, 5 in the vertical direction. The through holes 80a, 80b, 90a, 90b are plated through holes and electrically connected to the fixed electrodes 20a, 20b, 21a, 21b, so that a total of four through hole wiring portions 8a, 8b, 9a, 9b is formed. Further, the through holes 80a, 80b, 90a, 90b opened on the upper surface of the upper cover 2a are closed by electrode portions 81a, 81b, 91a, 91b formed in a rectangular flat plate shape by a semiconductor substrate (silicon substrate). At this time, the electrode portions 81a, 81b, 91a, 91b are electrically connected to the corresponding through-hole wiring portions 8a, 8b, 9a, 9b, respectively.

  Here, in the through holes 80a, 80b, 90a, 90b penetrating the upper cover 2a, the opening diameter φ2 on the upper surface side is smaller than the opening diameter φ1 on the lower surface side, and the electrode portions 81a, 81b, 91a, 91b is formed in dimensions (vertical and horizontal dimensions) smaller than the opening diameter φ1 on the lower surface side and larger than the opening diameter φ2 on the upper surface side of the through holes 80a, 80b, 90a, 90b (see FIG. 1). The upper cover 2a has substantially the same horizontal dimension as the sensor chip 1, but the vertical dimension is slightly shorter than that of the sensor chip 1, and one side surface along the horizontal direction (the left side in FIG. 1). To the upper surface of the frame portion 3. The end portion (the right end portion in FIG. 1) that is not covered with the upper cover 2a on the upper surface of the sensor chip 1 becomes the ground electrode portion 10 that is electrically connected to the movable electrodes 4a and 5a.

  Here, in this embodiment, the frame portion 3a, the weight portion 4, the beam portions 6a and 6b, the movable electrode 4a, the first and second fixed electrodes 20a and 20b, the through-hole wiring portions 8a and 8b, the electrode portion 81a, 81b, frame portion 3b, weight portion 5, beam portions 7a and 7b, movable electrode 5a, first and second fixed electrodes 21a and 21b, through-hole wiring portions 9a and 9b, and electrode portions 91a and 91b are accelerated. A sensor is formed, and two acceleration sensors are integrally formed with the directions of the weight portions 4 and 5 (the arrangement of the concave portions 11 and 13 and the solid portions 12 and 14) reversed by 180 degrees (FIG. 1A )reference).

  Next, the detection operation of this embodiment will be described.

First, consider a case where an acceleration in the x-axis direction is applied to one weight portion 4. When acceleration is applied in the x-axis direction, the weight portion 4 rotates around the rotation axis, and the distance between the movable electrode 4a and the first fixed electrode 20a and the second fixed electrode 20b changes. As a result, the capacitances C1 and C2 between the movable electrode 4a and the fixed electrodes 20a and 20b also change. Here, the capacitance between the movable electrode 4a and the fixed electrodes 20a and 20b when no acceleration in the x-axis direction is applied is C0, and the change in capacitance caused by the application of acceleration is ΔC. Then, the capacitances C1 and C2 when the acceleration in the x-axis direction is applied are
C1 = C0−ΔC (1)
C2 = C0 + ΔC (2)
It can be expressed as.

Similarly, when acceleration in the x-axis direction is applied to the other weight portion 5, the capacitances C3 and C4 between the movable electrode 5a and the fixed electrodes 21a and 21b are:
C3 = C0−ΔC (3)
C4 = C0 + ΔC (4)
It can be expressed as.

  Here, the values of the electrostatic capacitances C1 to C4 can be detected by calculating voltage signals taken out from the electrode portions 80a and 80b and 81a and 81b. Then, the difference value CA (= C1-C2) between the capacitances C1, C2 obtained from one acceleration sensor and the difference value CB (= C3-C4) between the capacitances C3, C4 obtained from the other acceleration sensor. Is calculated (± 4ΔC), the direction and magnitude of the acceleration applied in the x-axis direction can be calculated based on the sum of the difference values CA and CB.

Next, consider a case where acceleration in the z-axis direction is applied to one weight portion 4. When acceleration is applied in the z-axis direction, the weight portion 4 rotates about the rotation axis, and the distance between the movable electrode 4a and the first fixed electrode 20a and the second fixed electrode 20b changes. As a result, the capacitances C1 and C2 between the movable electrode 4a and the fixed electrodes 20a and 20b also change. Here, the capacitance between the movable electrode 4a and the fixed electrodes 20a and 20b when no acceleration in the z-axis direction is applied is C0, and the change in capacitance caused by the application of acceleration is ΔC. Then, the capacitances C1 and C2 when the acceleration in the z-axis direction is applied are:
C1 = C0 + ΔC (5)
C2 = C0−ΔC (6)
It can be expressed as.

Similarly, when acceleration in the z-axis direction is applied to the other weight portion 5, the capacitances C3 and C4 between the movable electrode 5a and the fixed electrodes 21a and 21b are:
C3 = C0−ΔC (7)
C4 = C0 + ΔC (8)
It can be expressed as.

  Then, the difference value CA (= C1-C2) between the capacitances C1, C2 obtained from one acceleration sensor and the difference value CB (= C3-C4) between the capacitances C3, C4 obtained from the other acceleration sensor. Is calculated (± 4ΔC), the direction and magnitude of the acceleration applied in the z-axis direction can be calculated based on the difference between the difference values CA and CB. Since the calculation processing for obtaining the direction and magnitude of acceleration in the x-axis direction and the z-axis direction based on the sum and difference of the difference values CA and CB is well known in the art, detailed description thereof will be omitted.

  Next, the manufacturing method of this embodiment will be described with reference to FIG.

  In this embodiment, the sensor chip 1 is formed by processing a silicon SOI substrate composed of a support substrate, an intermediate oxide film, and an active layer using a semiconductor microfabrication technique. First, a mask material such as a silicon oxide film or a photoresist film is formed on both surfaces of a silicon SOI substrate, and after removing the mask material at a position corresponding to the weights 4 and 5, TMAH (tetramethyl ammonium hydroxide solution) or Space for displacing the weight portions 4 and 5 on the upper and lower surfaces of the silicon SOI substrate by performing wet etching using KOH (potassium hydroxide solution) or dry etching such as reactive ion etching (RIE). (Recess) is formed. And the projection part 15 which consists of a silicon oxide film or a carbon nanotube is formed in the predetermined position of a recess bottom face. Subsequently, the weight portions 4 and 5 (recess portions 11 and 13 and the solid portions 12 and 14) are formed by etching the lower surface of the silicon SOI substrate in the order of the support substrate and the intermediate oxide film.

  On the other hand, through holes 80a, 80b, 90a, and 90b are formed through the upper cover 2a made of a glass substrate by a processing method such as sandblasting (see FIG. 2A), and the silicon substrate 100 is joined to the upper surface of the upper cover 2a. (See FIG. 2 (b)). Next, the silicon substrate 100 other than the electrode portions 81a, 81b, 91a, 91b is removed by etching (see FIG. 2C), and the fixed electrodes 20a, 20b, 21a, 21b are penetrated into the lower surface of the upper cover 2a by sputtering. The hole wiring portions 8a, 8b, 9a, and 9b are formed at the same time (see FIG. 2D).

  And the manufacturing process of this embodiment is completed by anodically bonding the lower cover 2b and the upper cover 2a to the lower surface and the upper surface of the sensor chip 1, respectively (see FIG. 2E).

  Thus, in this embodiment, the through-hole wiring portions 8a, 8b, 9a, 9b (through-holes 80a, 80b, 90a, 90b) are blocked by the electrode portions 81a, 81b, 91a, 91b made of a semiconductor substrate (silicon substrate). By doing so, the sealing property can be enhanced, and the dimensions (vertical and horizontal dimensions) of the electrode portions 81a, 81b, 91a, 91b are set to the opening diameter φ1 on one surface side (lower surface side) of the through holes 80a, 80b, 90a, 90b. By making the size smaller than the opening diameter φ2 on the other side (upper side), the influence of stray capacitance generated between the electrode portions 81a, 81b, 91a, 91b and the sensor chip 1 can be reduced. it can.

1 Sensor chip 2a Upper cover (cover)
4,5 Weight part 4a, 5a Movable electrode 6a, 6b Beam part 7a, 7b Beam part 8a, 8b Through-hole wiring part 9a, 9b Through-hole wiring part 20a, 21a First fixed electrode 20b, 21b Second fixed electrode 80a, 80b Through hole 90a, 90b Through hole 81a, 81b Electrode part 91a, 91b Electrode part

Claims (1)

A sensor chip formed by processing a semiconductor substrate with a weight portion provided with a movable electrode on one surface and a beam portion that supports the weight portion so as to be rotatable about a rotation axis, and a fixed electrode is formed on one surface. An insulating cover joined to one surface side of the sensor chip with the fixed electrode facing the movable electrode, a through hole penetrating the cover, and the other surface of the cover electrically connected to the fixed electrode and through the through hole A through-hole wiring portion that is drawn out to an electrode, and an electrode portion that is made of a semiconductor substrate and closes the through-hole on the other surface side of the cover and is electrically connected to the through-hole wiring portion,
The through hole has a smaller opening diameter on the other surface side than the opening diameter on the one surface side, and the electrode portion has a size smaller than the opening diameter on the one surface side of the through hole and larger than the opening diameter on the other surface side. Acceleration sensor featuring.

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