JP2006317182A - Acceleration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To moderate movement, such as a twist and turn, of a movable electrode relative to a fixed electrode owing to thermal stress. <P>SOLUTION: A set of support parts 23<SB>1</SB>and 23<SB>2</SB>, fixed electrode parts 32a and 32b for wire connection including a fixed electrode part 24 and pads 26a and 26b for a fixed electrode, and a movable electrode part 31 for wire connection including a pad 26c for a movable electrode, are each formed and disposed into a tabular shape symmetrical about the center line of a frame body 28 in the displacement direction of an overlap part 21. The movement of the movable electrode 21a, etc. such as a twist and turn owing to thermal stress, is thereby moderated to improve temperature characteristics. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an acceleration sensor, and more particularly to a semiconductor acceleration sensor configured by microfabrication of a semiconductor substrate.

Conventionally, a movable electrode that is displaceable in a specified direction and a detection unit made up of a fixed electrode that is disposed opposite to the movable electrode are formed on a substrate, and a change in acceleration is detected between the movable electrode and the fixed electrode. There has been provided a capacitance type acceleration sensor that detects a change in capacitance (see Patent Document 1). An example of this type of acceleration sensor is shown in FIG. The acceleration sensor includes a weight portion 21 that is spaced apart from the support substrate 1 on the one surface (upper surface in FIG. 4B) side of the support substrate 1 made of a glass substrate, and the one surface side of the support substrate 1. A pair of support portions 23 ₁ , 23 that support the weight portion 21 via a spring portion 22 that is fixed and can displace the weight portion 21 in a specified direction (the left-right direction in FIG. 4A) along the one surface. ₂ and a plurality of thin plate-like fixed electrodes 24b that are fixedly attached to the one surface side of the support substrate 1 on both the upper and lower sides of the weight portion 21 in FIG. 4A and arranged so that the prescribed direction is the thickness direction. And a plurality of thin plate-like members provided on the weight portion 21 so as to enter the comb grooves 24c between the adjacent fixed electrodes 24b and 24b one by one and displace in the specified direction. Movable electrode 21a, weight 21 and support 23 1, _{23 2,} the fixed electrode portion 24, the direction in which the movable electrode 21a or the like along the surface of the supporting substrate 1 (FIG. 4 (vertical and horizontal directions in a)) supported is formed in a rectangular frame shape surrounding the substrate 1 And a second support substrate 2 made of a glass substrate covering the frame body 28 so as to face the support substrate 1 with the frame body 28 interposed therebetween.

The pair of support portions 23 ₁ and 23 ₂ is formed separately from the frame body 28 and disposed on the left and right sides of the weight portion 21 in FIG. 4A, and the back surface of the support portion 23 ₁ is placed on the substrate. A disk-shaped movable electrode pad 26c made of aluminum and electrically connected to each movable electrode 21a through a formed conductive pattern (not shown) is provided. An insertion hole 3 is formed through the support substrate 1 so that the movable electrode pad 26c faces the outside. The inner diameter of the insertion hole 3 is larger than the outer shape of the movable electrode pad 26c. Here, it will be referred to hereinafter as the support portion 23 _first support part 23 a conductive pattern formed on the ₁ and the movable electrode pad 26c as connecting movable electrode portion 31 are collectively.

The fixed electrode portion 24 is formed in a comb-like planar shape by a plurality of fixed electrodes 24b arranged in the prescribed direction and a connecting portion 24a extending in the prescribed direction and connecting the plurality of fixed electrodes 24b. , the connecting portions 24a and connecting portion 24a fixed pole portion 24d that extends laterally from one end of the extending direction of so as to sandwich the supporting portion 23 ₁ of the right from the vertical direction are a pair arranged. On the back surface of the upper fixed pole portion 24d, a disc made of aluminum that is electrically connected to each upper fixed electrode 24b of the weight portion 21 through a conductive pattern (not shown) formed on the substrate. A fixed electrode pad 26a is formed on the back surface of the lower fixed pole portion 24d, and the lower fixed electrodes 24b on the lower side of the weight portion 21 via conductive patterns (not shown) formed on the substrate. A disk-shaped fixed electrode pad 26b made of aluminum and electrically connected to each other is provided. Similarly to the movable electrode pad 26c, the insertion holes 3 for allowing the fixed electrode pads 26a and 26b to face the outside are respectively provided in the support substrate 1, and the inner diameters of these insertion holes 3 are fixed electrode pads 26a and 26a. It is formed larger than the outer shape of 26b. Here, the fixed electrode portion 24d, the conductive pattern formed on the fixed electrode portion 24d, and the fixed electrode pads 26a and 26b are collectively referred to as fixed electrode portions 32a and 32b for connection. The connection fixed electrode portion 32a corresponds to the upper fixed pole portion 24d, and the connection fixed electrode portion 32b corresponds to the lower fixed pole portion 24d.

  In an external circuit electrically connected to the fixed electrode pads 26a and 26b and the movable electrode pad 26c, static electricity between the fixed electrode 24b and the movable electrode 21a according to the displacement of the weight portion 21 in the specified direction. Acceleration can be detected as a change in capacitance value. A stopper 25 for restricting the amount of displacement of the weight portion 21 is provided on the left side of each fixed electrode portion 24.

The frame body 28 has a rectangular shape whose vertical and horizontal outer dimensions are substantially the same as those of the support substrates 1 and 2. The support substrate 1 is bonded to the back surface of the frame body 28, and the support substrate 2 is attached to the surface of the frame body 28. By joining, the weight part 21, the spring part 22, the support parts 23 ₁ and 23 ₂ , the fixed electrode part 24, the movable electrode 21 a, etc. are all sealed by the two support substrates 1 and 2 and the frame body 28. Moisture resistance can be achieved because minute dust, foreign matter, etc. do not enter the inside, and it is possible to prevent problems such as the displacement of the weight portion 21 being hindered by such foreign matter, and the inside of the frame 28 can be hermetically sealed. It is also possible to obtain effects such as improvement of the above.

Also, 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 support substrate 1 and the frame body are provided on the back surface of the base portion 28a. A disk-shaped ground electrode pad 30 made of aluminum and formed integrally with a joint for joining 28 and electrically connected to an external ground is provided. Similarly to the other electrode pads, an insertion hole 3 for allowing the ground electrode pad 30 to face the outside is provided in the support substrate 1. The inner diameter of the insertion hole 3 is larger than the outer shape of the ground electrode pad 30. Largely formed. Here, the base portion 28a and the ground electrode pad 30 are collectively referred to as a connection ground electrode portion 33 hereinafter. By connecting the joint to the external ground via the ground electrode pad 30, the fixed electrode 24b, the movable electrode 21a and the like are shielded by the joint, and noise resistance is improved.
Japanese Patent Laid-Open No. 2004-28912

  However, in the conventional example, the fixed electrode portions 32 a and 32 b for connection, the movable electrode portion 31 for connection, and the ground electrode portion 33 for connection are disposed asymmetrically with respect to the center line of the frame body 28 in the displacement direction of the weight portion 21. Is also asymmetric, and thus the movable electrode 21a and the fixed electrode portion 24 are twisted and rotated due to thermal stress caused by thermal expansion or the like, and the distance between the movable electrode 21a and the fixed electrode 24b changes due to a temperature change. Therefore, there is a problem that temperature characteristics such as detection accuracy and offset output (output when acceleration is 0 G) are deteriorated.

  The present invention has been made in view of this point, and an object thereof is to provide an acceleration sensor capable of preventing deterioration of temperature characteristics due to thermal stress.

  In order to achieve the above object, the invention according to claim 1 is fixed to the support substrate, a weight portion disposed on the 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. 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 so that the prescribed direction is the thickness direction, and fixed to one surface side of the support substrate and electrically connected to the fixed electrode portion In addition, a fixed electrode portion for connection having a fixed electrode pad to which wiring to the outside is connected, and a weight portion provided so as to be able to enter the comb groove between adjacent fixed electrodes one by one and be displaced in the prescribed direction. Multiple thin plate-like movable electrodes and support Movable electrode part for connection with a movable electrode pad fixed to one surface side of the plate and electrically connected to the movable electrode and connected to the wiring to the outside, weight part, support part, fixed A frame body formed in a frame shape surrounding the electrode portion, the fixed electrode portion for connection, the movable electrode, and the movable electrode portion for connection from the direction along the one surface of the support substrate, and fixed to the one surface side of the support substrate; The support part, the fixed connection electrode part, and the movable electrode part for connection are formed and arranged in shapes that are symmetrical with respect to the center line of the frame body in the displacement direction of the weight part.

  In order to achieve the above object, the fixed electrode part for connection and the movable electrode part for connection are arranged on one side of the weight part in the displacement direction of the weight part. A grounding electrode portion for connection having a ground electrode pad fixed to the surface side and grounded to the external ground is disposed on the opposite side across the fixed portion for connection and the movable electrode portion for connection and the weight portion, It is formed and arranged in a symmetrical shape with respect to the center line of the frame in the displacement direction of the weight portion.

  According to the present invention, the support portion, the connection fixed electrode portion, the connection movable electrode portion, or the connection ground electrode portion is formed and arranged in a symmetrical shape with respect to the center line of the frame body in the displacement direction of the weight portion. Therefore, movement of the movable electrode or the like due to thermal stress such as twisting and rotation can be mitigated, and therefore, temperature characteristics can be improved.

  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. 4, 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, support substrates 1 and 2, a weight portion 21, a spring portion 22, a set of support portions 23 ₁ and 23 ₂ , a fixed electrode portion 24, fixed electrode portions 32 a and 32 b for connection, The movable electrode 21a, the movable electrode portion 31 for connection, and the frame 28 are configured, and a pair of support portions 23 ₁ and 23 ₂ , a fixed electrode portion 24, fixed electrode portions 32a and 32b for connection, and a movable electrode portion for connection. 31 is characterized in that it is formed and arranged in a flat plate shape that is symmetrical with respect to the center line of the frame body 28 in the displacement direction of the weight portion 21 (A-A line in FIG. 1A). .

Each of the pair of support portions 23 ₁ and 23 ₂ is formed in a flat plate shape, and is disposed on both the left and right sides of the weight portion 21 in FIG. FIGS. 1 (a) right support portion 23 ₁ in the provided in the middle of vertical direction in the drawing, fixed pole portion 24d is provided with the support portion 23 ₁ so as to sandwich from the vertical direction. The fixed electrode portion 24 including the fixed pole portion 24d is formed in a comb-shaped flat plate shape, and is disposed on both the upper and lower sides of the weight portion 21 in FIG. 1A, and both have the same shape and size. .

Here the supporting portion 23 ₁ and each of the fixed electrode portion 24d connecting the movable electrode portion 31, connected fixed electrode portion 32a, corresponding to 32b, connecting the movable electrode portion 31 and the connection fixing electrode portions 32a, 32b Fig. 1 juxtaposed on the right side of the weight portion 21 in the vertical direction in (a), and the supporting portion 23 ₂ on the left side of the weight portion 21, including any and symmetrical shape and arranged with respect to the center line of the frame 28 Therefore, the movement of the movable electrode 21a and the like due to thermal stress can be mitigated, and the temperature characteristics can be improved as a result.

  Since the fixed electrode portion 24, the movable electrode 21a, the connection fixed electrode portions 32a and 32b, and the connection movable electrode portion 31 are axisymmetric with respect to the center line of the frame 28, the upper fixed electrode 24b The value of the capacitance C1 between the movable electrode 21a and the capacitance C2 between the lower fixed electrode 24b and the movable electrode 21a is substantially the same (C1≈C2), and is affected by the parasitic capacitance of the wiring. The effect of reducing can also be obtained.

The spring portion 22 is divided into four places on the left and right sides of the upper weight portion 21 and the left and right sides of the lower weight portion 21 when the weight portion 21 is vertically divided in FIG. Be placed. Each spring portion 22 has a planar shape that is formed in a folded shape, and has the same shape and dimensions. The upper right of the spring portion 22 has one end connected to a continuous integrally to the right center portion of the upper weight portion 21 and the other end connected to the continuous integral with the right side of the left upper portion of the supporting portion 23 ₁ of the weight portion 21 are, the spring portion 22 of the lower right has one end connected to a continuous integrally to the right center portion of the lower weight portion 21, the right of the left side lower end of the support portion 23 ₁ of the other end weight portions 21 The unit is connected continuously and integrally. The upper left of the spring 22 has one end connected to a continuous integrally to the left central portion of the upper weight portion 21 and the other end connected to the continuous integral with the left support portion 23 ₂ of the right side upper portion of the weight section 21 It is, the lower left of the spring 22 has one end connected to a continuous integrally to the left central portion of the lower weight portion 21 and the other end left support portion 23 ₂ of the right lower end of the weight section 21 And are continuously connected together. Since the arrangement of the spring portions 22 is vertically symmetrical with respect to the center line of the frame body 28, the arrangement of the movable electrodes 21a and the like due to thermal stress is similar to the arrangement of the fixed electrode portions 32a and 32b for connection. An effect of relaxing movement such as twisting and rotation can be obtained.

(Embodiment 2)
This embodiment will be described with reference to FIG. Since the basic configuration of the present embodiment is the same as that of the first embodiment, common components are denoted by the same reference numerals and description thereof is omitted.

The difference between the present embodiment and the first embodiment is that the left side of the weight portion 21 in FIG. 2A is a frame body in the displacement direction of the weight portion 21 with _two flat plate-like support portions 232 spaced apart by a predetermined distance. 28 arranged symmetrically with respect to the center line of these sandwiched supporting portion 23 ₂ points, the connection ground electrode 33 for connecting to an external ground is provided, this connection ground electrode 33 is a frame The body 28 is symmetrically arranged with respect to the center line.

  In the conventional example, the connection ground electrode portion 33 located at one of the four corners of the frame body 28 is arranged symmetrically with respect to the center line of the frame body 28 as described above, so that the movable electrode due to thermal stress is provided. The effect of mitigating movements such as twist and rotation of 21a and the like can be obtained.

Supporting portion 23 ₂ of the upper is connected to the continuous integral with one end of the left upper of the spring portion 22 in the right lower portion, the supporting portion 23 ₂ of the lower side end portion of the lower left of the spring portion 22 in the right upper portion And are continuously connected together. Arrangement of the support portions 23 ₂ and the spring 22, because that is symmetrical with respect to the center line of the frame 28, as in the first embodiment, such as the movable electrode 21a due to thermal stress twist, such as rotation The effect of relaxing the movement is obtained.

  Hereinafter, a method of manufacturing the acceleration sensor having the structure of FIG. 1 or 2 will be briefly described with reference to FIG.

  First, a silicon oxide film is formed on the main surface and the back surface of the n-type silicon substrate 20 by thermal oxidation or the like, and the silicon oxide film on the back surface of the silicon substrate 20 is formed by photolithography in order to form the recess 20a on the back surface of the silicon substrate 20. After patterning using a technique and an etching technique, the silicon substrate 20 is etched from the back surface to a predetermined depth using the patterned silicon oxide film as a mask, and the silicon oxide film on the main surface and the back surface of the silicon substrate 20 is removed by etching. As a result, a structure as shown in FIG. The predetermined depth is set to the distance between the support substrate 1 and the weight portion 21.

  Next, an aluminum film is formed on the back surface of the silicon substrate 20 to form pads 26a to 26c by, for example, a vapor deposition method, and the aluminum film is patterned into a rectangle or a circle by using a photolithography technique and an etching technique. Thus, by forming the pads 26a to 26c, the structure shown in FIG. 3B is obtained.

  After that, the structure shown in FIG. 3C is obtained by anodic bonding of the support substrate 1 made of a glass substrate through which the insertion hole 3 is previously penetrated and the silicon substrate 20.

  Next, an oxide film or the like is formed on the main surface of the silicon substrate 20 as a mask in the subsequent vertical etching process, and the weight portion 21, the spring portion 22, the support portion 23, the fixed electrode 24b, and the fixed portion are fixed to the silicon substrate 20. In order to form the electrode part 24, the movable electrode 21a, the frame body 28, etc., the oxide film is patterned (see FIG. 3D), and then perpendicular to the silicon substrate 20 in a direction perpendicular to the main surface. Etching is performed to obtain the structure shown in FIG. Here, by performing etching using an etching apparatus using inductively coupled plasma (ICP), vertical etching in the thickness direction of the silicon substrate 20 can be performed.

  Furthermore, the structure shown in FIG. 3F is obtained by anodically bonding the support substrate 2 made of a glass substrate to the main surface side of the silicon substrate 20. Since the steps up to here are performed in a wafer state, dicing may be performed thereafter.

Embodiment 1 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. 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. It is explanatory drawing of a manufacturing method same as the above. 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.

Explanation of symbols

1 the supporting substrate 21 weight part 21a movable electrode 22 spring portion 23 _1, 23 ₂ supports 24 fixed electrode portions 26a, 26b fixed electrode pad 26c movable electrode pad 28 frame 31 connecting the movable electrode portion 32a, the fixing 32b connected Electrode part

Claims (2)

  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. Comb-shaped fixed electrode portion having a thin plate-shaped fixed electrode, and a fixed electrode pad fixed to one surface side of the support substrate and electrically connected to the fixed electrode portion and connected to the outside wiring A plurality of thin plate-like movable electrodes provided in the weight portion so as to be displaced in the prescribed direction one by one into a comb groove between adjacent fixed electrodes, and a supporting substrate. Fixed to the surface side and electrically connected to the movable electrode In addition, a movable electrode part for connection having a movable electrode pad connected to an external wiring at the support part, a weight part, a support part, a fixed electrode part, a fixed electrode part for connection, a movable electrode, and a movable for connection A frame body that is formed in a frame shape that surrounds the electrode portion 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 support portion, the fixed electrode portion, and the fixed electrode portion for connection And the movable electrode part for connection are formed and arranged in a shape symmetrical to the center line of the frame body in the displacement direction of the weight part. The fixed electrode portion for connection and the movable electrode portion for connection are arranged on one side of the weight portion in the displacement direction of the weight portion, and are grounded electrodes fixed to the one surface side of the support substrate and grounded to an external ground A grounding electrode part for connection with a pad for connection is disposed on the opposite side of the fixed electrode part for connection and the movable electrode part for connection with the weight part, and with respect to the center line of the frame body in the displacement direction of the weight part. 2. The acceleration sensor according to claim 1, wherein the acceleration sensor is formed and arranged in a symmetrical shape.

Images