JP2014238281A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration sensor with an improved temperature characteristic.SOLUTION: The acceleration sensor includes: a third movable electrode 31 that is movable according to an acceleration given from the outside; an upper clamp plate 2a which is disposed facing to one plane of the third movable electrode 31; and a lower clamp plate 2b which is disposed facing to the other plane of the third movable electrode 31. The acceleration sensor has a penetration electrode 34d pulled out from a region which does not face to the third movable electrode 31 of the upper clamp plate 2a.

Description

  The present invention relates to an acceleration sensor.

  Conventionally, a rectangular parallelepiped weight part having a movable electrode, a pair of beam parts that rotatably support the weight part, and a straight line connecting the pair of beam parts are arranged opposite to one side and the other side. An acceleration sensor including a pair of fixed electrodes is known (see, for example, Patent Document 1).

JP 2011-112391 A

  However, in the conventional acceleration sensor, when the temperature is applied, a gap difference between the upper and lower sides of the movable electrode is generated, and the temperature characteristics may be deteriorated.

  Therefore, an object of the present invention is to obtain an acceleration sensor with improved temperature characteristics.

  The present invention is an acceleration sensor, comprising a movable electrode that is movable in response to an externally applied acceleration, a one fixed plate that is disposed opposite to one surface of the movable electrode, and a second surface of the movable electrode. And the other fixed plate arranged oppositely, and the through electrode is drawn from a region of the one fixed plate that does not face the movable electrode.

  In the present invention, an electrode pad for the through electrode may be formed in a region of the one fixed plate facing the movable electrode.

  In the present invention, acceleration in the Z direction, which is the vertical direction, may be detected by translating the movable electrode in the vertical direction.

  According to the present invention, it is possible to provide an acceleration sensor with improved temperature characteristics.

FIG. 1 is an exploded perspective view of the acceleration sensor according to the embodiment. FIG. 2 is a cross-sectional view of the Z detection unit of the acceleration sensor according to the comparative example. FIG. 3 is a top view of the main part of the Z detection unit of the acceleration sensor according to the comparative example. FIG. 4 is a cross-sectional view of the Z detection unit of the acceleration sensor according to the embodiment. FIG. 5 is a top view of the main part of the Z detection unit of the acceleration sensor according to the embodiment. FIG. 6 is a graph showing the zero point maximum variation with temperature.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, below, while attaching | subjecting a common code | symbol to the same component, the overlapping description is abbreviate | omitted.

[Configuration of acceleration sensor]
FIG. 1 is an exploded perspective view of the acceleration sensor according to the embodiment. In this acceleration sensor, the weights for detecting the XYZ triaxial directions are formed as individual weights for detecting only the uniaxial acceleration, and each of these three axis weights (each sensor) is formed as one chip. It is placed inside. The acceleration in the plane direction (XY direction) is detected by performing a seesaw operation on the weight with a pair of torsion beams as axes, and the acceleration in the vertical direction (Z direction) is the vertical direction of the weight held by one or more beams. Is detected by parallel movement.

  Specifically, as shown in FIG. 1, the upper and lower surfaces of the sensor unit 1 are sandwiched between an upper fixing plate 2a and a lower fixing plate 2b. The sensor unit 1 is formed of a silicon SOI substrate or the like, and the upper fixing plate 2a and the lower fixing plate 2b are formed of an insulator such as glass.

  Hereinafter, in the sensor unit 1, the part that detects the acceleration in the X direction is “X detection part 10”, the part that detects the acceleration in the Y direction is “Y detection part 20”, and the part that detects the acceleration in the Z direction is “ This will be referred to as “Z detection unit 30”. The X direction is one of the planar directions. The Y direction is one of the planar directions and is a direction orthogonal to the X direction. The Z direction is the vertical direction.

  The X detector 10 detects the acceleration in the X direction by swinging the first movable electrode 11 around the pair of beam portions 12a and 12b. That is, the first fixed electrodes 13a and 13b are arranged so as to face one side and the other side of the surface of the first movable electrode 11 with a straight line connecting the pair of beam portions 12a and 12b as a boundary line. The first fixed electrodes 13a and 13b are formed, for example, by forming through electrodes made of silicon on the upper fixed plate 2a, and are drawn out to the upper surface (one side) of the upper fixed plate 2a using the through electrodes. Thereby, the acceleration in the X direction can be detected based on the change in capacitance between the first movable electrode 11 and the first fixed electrodes 13a and 13b.

  The Y detector 20 detects the acceleration in the Y direction by swinging the second movable electrode 21 around the pair of beam portions 22a and 22b. That is, the second fixed electrodes 23a and 23b are arranged to face one side and the other side of the surface of the second movable electrode 21 with a straight line connecting the pair of beam portions 22a and 22b as a boundary line. For the second fixed electrodes 23a and 23b, a through electrode made of, for example, silicon is formed on the upper fixed plate 2a, and the through electrode is used to draw out the upper surface of the upper fixed plate 2a. Thereby, the acceleration of a Y direction is detectable based on the change of the electrostatic capacitance between the 2nd movable electrode 21 and 2nd fixed electrode 23a, 23b.

  The Z detection unit 30 detects the acceleration in the Z direction by translating the third movable electrode 31 held by the two pairs of beam units 32a, 32b, 32c, and 32d in the vertical direction. That is, the third fixed electrodes 33a and 33b are arranged to face the front and back surfaces of the third movable electrode 31. The third fixed electrode 33a is formed, for example, by forming a through electrode made of silicon on the upper fixed plate 2a, and is drawn out to the upper surface of the upper fixed plate 2a using this through electrode. The third fixed electrode 33b is led out to the upper surface of the upper fixed plate 2a by using, for example, a columnar fixed electrode made of silicon and a through electrode. Thereby, the acceleration of a Z direction is detectable based on the change of the electrostatic capacitance between the 3rd movable electrode 31 and the 3rd fixed electrodes 33a and 33b.

[Z detector: Comparative example]
FIG. 2 is a cross-sectional view of the Z detection unit 30 of the acceleration sensor according to the comparative example, and FIG. 3 is a top view of the main part of the Z detection unit 30. Members common to the embodiment (FIG. 1) will be described using the same reference numerals.

As shown in FIGS. 2 and 3, the upper and lower surfaces of the sensor unit 1 are anodically bonded to the upper fixing plate 2a and the lower fixing plate 2b. Silicon layers 41 and 43 are formed on the upper and lower sides of an oxide film 42 such as SiO _2, and the upper and lower silicon layers 41 and 43 are connected using a conductive portion 44 such as Poly-Si. The third fixed electrode 33a is drawn out to the upper surface of the upper fixed plate 2a using the through electrode 34a, and the third fixed electrode 33b is extracted from the upper surface of the upper fixed plate 2a using the columnar fixed electrode 34c and the through electrode 34b. Has been drawn to. A plurality of convex portions 51 and an adhesion preventing film 52 are formed between the third movable electrode 31 and the upper fixed plate 2a. Thereby, even when a large acceleration exceeding the measurement range is applied, it is possible to prevent the third movable electrode 31 from colliding with the upper fixed plate 2a and being damaged. Similar convex portions 51 and adhesion preventing films 52 are also formed between the third movable electrode 31 and the lower fixed plate 2b.

  Here, in the acceleration sensor according to the comparative example, the external output wiring of the counter electrode is provided immediately above the counter electrode. Specifically, as shown in FIGS. 2 and 3, a through electrode 34a is provided immediately above the third movable electrode 31, and an electrode pad 37a is provided directly above the through electrode 34a. FIG. 3 is a diagram for explaining the arrangement of the through electrodes 34 a, and members unnecessary for the description are omitted. According to such a configuration, since the linear expansion integer is different between the silicon that is the material of the through electrode 34a and the glass that is the base material (the material of the upper fixing plate 2a), when the temperature is applied, on the upper fixing plate 2a side. A step is generated between the silicon portion and the glass portion. As a result, an opposing gap difference is generated between the upper and lower sides of the third movable electrode 31, and the temperature characteristics are deteriorated.

[Z detector: Example]
FIG. 4 is a cross-sectional view of the Z detection unit 30 of the acceleration sensor according to the embodiment, and FIG. 5 is a top view of the main part of the Z detection unit 30. Members common to the comparative example (FIGS. 2 and 3) will be described using the same reference numerals. Of course, this example corresponds to the embodiment (FIG. 1).

  As shown in FIGS. 4 and 5, in the acceleration sensor according to the embodiment, the through electrode 34 d is drawn from a region of the upper fixed plate 2 a that does not face the third movable electrode 31. Here, as shown in FIG. 5, the through electrode 34 d is arranged on the upper right side of the third movable electrode 31 in plan view, but the position of the through electrode 34 d is deviated from immediately above the third movable electrode 31. Just do it. Thereby, since there is no penetration electrode 34a immediately above the third movable electrode 31, the upper and lower sides of the third movable electrode 31 have the same structure. As a result, even if the temperature is applied, the change in the facing gap is the same above and below the third movable electrode 31, so that the temperature characteristics are improved.

  The “region not facing the third movable electrode 31” here preferably includes a region not facing the two pairs of beam portions 32a, 32b, 32c, and 32d. That is, the third movable electrode 31 may move on the two pairs of beam portions 32a, 32b, 32c, and 32d. Therefore, when the through electrode 34d is drawn from a region that does not face the third movable electrode 31 and any of the two pairs of beam portions 32a, 32b, 32c, and 32d, the temperature characteristics are further improved.

  In the acceleration sensor according to the embodiment, the electrode pad 37c for the through electrode 34d is formed in a region facing the third movable electrode 31 of the upper fixed plate 2a. Thereby, since the dead space on the upper fixing plate 2a is effectively used as the wire bonding region, it is possible to avoid an increase in the size of the acceleration sensor.

[Maximum 0 point change with temperature: comparative example and example]
FIG. 6 is a graph showing the zero point maximum variation with temperature. As shown in this figure, for example, the maximum zero point change at 125 ° C. is reduced to 60% in the example when the comparative example is 100%. That is, according to the acceleration sensor according to the example, it is understood that the temperature characteristic (offset) is improved as compared with the acceleration sensor according to the comparative example. In the embodiment, the case where the through electrode 34d is arranged on the upper right side of the third movable electrode 31 in plan view is illustrated (see FIG. 5), but the position of the through electrode 34d is deviated from immediately above the third movable electrode 31. If it is, the same effect can be acquired.

  As described above, the acceleration sensor according to the embodiment includes the movable electrode 31 that is movable according to the acceleration given from the outside, the one fixed plate 2 a that is disposed to face one surface of the movable electrode 31, and the movable sensor 31. And the other fixing plate 2b disposed to face the other surface of the electrode 31. And the penetration electrode 34d is pulled out from the area | region which does not oppose the movable electrode 31 of one fixed plate 2a. Thereby, since there is no penetration electrode 34a immediately above the movable electrode 31, the upper and lower sides of the movable electrode 31 have the same structure. As a result, even if the temperature is applied, the change in the facing gap is the same above and below the movable electrode 31, so that the temperature characteristics are improved.

  In the acceleration sensor according to the embodiment, the electrode pad 37c for the through electrode 34d may be formed in a region facing the movable electrode 31 of the one fixed plate 2a. Thereby, since the dead space on the one fixing plate 2a is effectively used as the wire bonding region, it is possible to avoid an increase in the size of the acceleration sensor.

  In the acceleration sensor according to the embodiment, the acceleration in the Z direction, which is the vertical direction, may be detected by translating the movable electrode 31 in the vertical direction. That is, this embodiment is effective when applied to an acceleration sensor having a configuration in which a difference in facing gap is generated above and below the movable electrode 31.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications can be made. For example, in the above embodiment, the acceleration sensor in which the X detection unit 10, the Y detection unit 20, and the Z detection unit 30 are arranged in one chip is illustrated, but the present invention includes only the Z detection unit 30. It can also be applied to an acceleration sensor. Of course, the shape and size of the through electrode 34d and the electrode pad 37c can be changed as appropriate.

2a Upper fixed plate (one fixed plate)
2b Lower fixed plate (other fixed plate)
31 Third movable electrode (movable electrode)
34d Through electrode 37c Electrode pad

Claims (3)

A movable electrode that can move according to acceleration given from the outside;
One fixed plate disposed opposite to one surface of the movable electrode;
The other fixed plate disposed opposite to the other surface of the movable electrode,
An acceleration sensor, wherein a through electrode is drawn from a region of the one fixed plate that does not face the movable electrode.   The acceleration sensor according to claim 1, wherein an electrode pad for the through electrode is formed in a region of the one fixed plate facing the movable electrode.   The acceleration sensor according to claim 1, wherein an acceleration in a Z direction, which is a vertical direction, is detected by translating the movable electrode in a vertical direction.

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