JP4590976B2 - Mechanical quantity sensor - Google Patents

Description

  The present invention relates to a mechanical quantity sensor having a movable portion that is supported on a support substrate in a state of being separated from the support substrate and is movable in a horizontal direction with respect to the substrate surface when a mechanical quantity is applied.

  A conventional mechanical quantity sensor of this type includes a support substrate, a movable portion supported on the support substrate in a state of being arranged away from the support substrate, and a movable portion of the movable portion on the support substrate. And a peripheral fixing portion arranged around and supported by the support substrate.

  Here, the movable portion can be displaced in the horizontal direction with respect to the substrate surface of the support substrate when a mechanical quantity is applied. And in this thing, the applied mechanical quantity is detected based on the displacement state of a movable part when a mechanical quantity is applied.

As such a mechanical quantity sensor, for example, an angular velocity sensor formed by processing a semiconductor substrate has been proposed (for example, see Patent Document 1).
JP 2001-133268 A

  Specifically, in such a mechanical quantity sensor, a constant potential is applied to the movable part during operation, and an AC voltage is applied to a drive electrode provided opposite to the movable part to displace the movable part. I was letting. That is, the movable part is driven using electrostatic attraction.

  Here, conventionally, the support substrate spaced apart below the movable portion is in a GND state during operation. Therefore, during operation, a large potential difference is generated between the movable part and the support substrate, and there is a high possibility that so-called sticking occurs in which the movable part and the support substrate adhere to each other due to electrostatic attraction.

  Therefore, in view of the above problems, the present invention suppresses sticking between the movable portion and the support substrate during operation as much as possible in the mechanical quantity sensor having the movable portion supported on the support substrate in a state separated from the support substrate. With the goal.

In order to achieve the above object, according to the first aspect of the present invention, the support substrate (1a), the insulating layer (1c) provided on the support substrate (1a), and the support substrate via the insulating layer (1c) are provided. A semiconductor layer (1b) supported by (1a),
The semiconductor layer (1b) is opposed to the support substrate (1a), and is removed from the support substrate (1a) by removing the insulating layer (1c). A movable part (20, 30) that is displaceable in a horizontal direction with respect to the surface, and is arranged around the movable part (20, 30) and fixed to the support substrate (1a) via an insulating layer (1c). The supported peripheral fixed part (10) is formed by being partitioned by a groove, and the applied mechanical quantity is detected based on the displacement state of the movable part (20, 30) when the mechanical quantity is applied. In the mechanical quantity sensor designed to
In operation, the potential of the peripheral fixing part (10) is the highest potential among the parts of the sensor.

  According to this, since the potential of the peripheral fixing portion (10) is set to the highest potential among the respective portions of the sensor during operation, the large potential is applied from the peripheral fixing portion (10) to the support substrate (1a). Therefore, the potential of the support substrate (1a) can be made larger than that in the conventional GND state, and as a result, the potential difference between the movable parts (20, 30) and the support substrate (1a) can be reduced.

Therefore, according to the present invention, in the mechanical quantity sensor having the movable part (20, 30) which is opposed to the support substrate (1a) and is released from the support substrate (1a) and can be displaced , Sticking between the movable part (20, 30) and the support substrate (1a) at the time can be suppressed as much as possible.

Further, in the invention according to claim 2, in the mechanical quantity sensor according to claim 1, by a semi-conductor layer (1b) and an insulating layer (1c) is etched, the movable portion (20, 30) and around a fixed The part (10) is formed in the semiconductor layer (1b), and the pad (10a) for applying a potential to the peripheral fixing part (10) is provided on the semiconductor layer (1b). Yes.

  According to this, the pad (10a) for applying a potential to the peripheral fixing portion (10) can be easily formed, which is preferable.

  In addition, the code | symbol in the bracket | parenthesis of each said means is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a schematic plan configuration of an angular velocity sensor 100 as a mechanical quantity sensor according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view taken along a dashed line AA in FIG. .

  This angular velocity sensor 100 is formed by processing a semiconductor substrate 1 made of a silicon substrate or the like.

  Specifically, by forming a groove in the semiconductor substrate 1 using a known semiconductor manufacturing technique such as etching, as shown in FIG. 1, a frame-shaped peripheral fixing portion 10 as a fixed portion is formed. The anchor portions 11 and 12 and the detection electrode fixing portion 13 as the fixed portions located on the inner peripheral portion of the peripheral fixing portion 10 and the inner peripheral portion of the peripheral fixing portion 10 are movable. A structure including the movable parts 20 and 30 is defined and formed.

  More specifically, as shown in FIG. 2, the angular velocity sensor 100 includes, for example, an SOI (Silicon On Insulator) in which both silicon substrates 1a and 1b are bonded together with an oxide film 1c as a semiconductor substrate 1. It is formed using the substrate 1.

  Then, one of the silicon substrates 1a and 1b in the SOI substrate 1 is configured as a support substrate, and the other silicon substrate 1b as a semiconductor layer (in FIG. 2). A known micromachining technique such as trench etching or sacrificial layer etching is applied to the oxide film 1c as the insulating layer and the oxide film 1c as the insulating layer from the surface side of the other silicon substrate 1b.

  Thereby, the groove is formed in the other silicon substrate 1b, and the structures such as the parts 10 to 30 defined by the groove are formed in the other silicon substrate 1b.

  Here, FIG. 1 shows the surface side of the other silicon substrate 1b on which the structure is formed, that is, the surface side of the semiconductor layer 1b supported on the support substrate 1a. Further, as shown in FIGS. 1 and 2, the oxide film 1c is removed by sacrificial layer etching or the like in the inner peripheral portion of the peripheral fixing portion 10, the anchor portions 11, 12 and the detection electrode fixing portion 13. .

  Accordingly, the other silicon substrate 1b as the semiconductor layer on which the structure is formed is the one silicon substrate in the inner peripheral portion of the peripheral fixing portion 10, the anchor portions 11 and 12, and the detection electrode fixing portion 13. 1a, that is, separated from the support substrate 1a.

  Thus, in this example, the peripheral fixing portion 10, the anchor portions 11, 12 and the detection electrode fixing portion 13 of the other silicon substrate 1b are supported on one silicon substrate 1a via the oxide film 1c. The movable parts 20 and 30 are fixed and released from the one silicon substrate 1a.

  As shown in FIG. 1, the movable parts 20, 30 include a substantially rectangular drive vibration part 20, a rectangular frame-like detection vibration part 30 surrounding the drive vibrator part 20, and the drive vibration part 20. And a plurality (four in the illustrated example) of driving beam portions 21 that connect the detecting vibration unit 30 and a plurality (two in the illustrated example) that couple the detecting vibration unit 30 and the base 10 on the outer periphery thereof. A beam 31 for detection.

  The drive vibration unit 20 is integrated with the detection vibration unit 30 via the drive beam unit 21. More specifically, the drive vibration unit 20 includes the detection vibration unit 30 and the detection beam unit 31. Although intervening, it is connected to one silicon substrate 1a as a support substrate via the vibration part for detection 30 and the anchor parts 11 and 12.

  Each of the driving beam portions 21 has a U-shaped folded shape, and one end side thereof is connected to the driving vibration portion 20, and the other end side is connected to the inner peripheral surface of the frame in the detection vibration portion 30. Has been.

  Further, in the driving beam portion 21, a pair of parallel rod portions 22 and 23 in the U-shape are bent in a direction perpendicular to the longitudinal direction. Therefore, the driving vibration unit 20 can vibrate in the direction of the arrow X in FIG. Hereinafter, the arrow X direction is referred to as a first direction X in which the driving vibration unit 20 vibrates.

  On the other hand, each detection beam portion 31 has a rectangular frame shape in which a pair of beams 32 and 33 are spaced apart in parallel and both ends of both beams 32 and 33 are connected.

  And the intermediate part of one beam 32 is connected to the protrusion part which protruded from the inner peripheral surface in the anchor parts 11 and 12, is fixedly supported by the anchor parts 11 and 12, and the intermediate part of the other beam 33 is , Connected to the detection vibration unit 30.

  In this way, the detection vibration part 30 is connected to the anchor parts 11 and 12 and one silicon substrate 1a as a support substrate via the detection beam part 31. That is, both the vibrating parts 20 and 30 as the movable parts are connected and supported by the anchor parts 11 and 12 to the one silicon substrate 1a via the oxide film 1c.

  In the detection beam portion 31, the pair of parallel beams 32 and 33 described above are bent in a direction orthogonal to the longitudinal direction.

  Therefore, the detection vibration unit 30 can vibrate in the direction orthogonal to the first direction X that is the vibration direction of the drive vibration unit 20 in the plane of the substrate 1, that is, in the direction of the arrow Y in FIG. 1. ing. Hereinafter, this arrow Y direction is referred to as a second direction Y in which the detection vibration unit 30 vibrates.

  Further, a comb-like projection 35 is formed on the outer peripheral portion of the detection vibrating portion 30 so as to protrude toward the inner peripheral portion of the detection electrode fixing portion 13 facing the outer peripheral portion. A comb-like protrusion 15 is also formed from the inner peripheral portion of the detection electrode fixing portion 13 so as to engage with the detection electrode 35. The two projecting portions 15 and 35 constitute the detection electrode portions 15 and 35 of the sensor 100.

  As described above, in the present angular velocity sensor 100, one silicon substrate 1a as a support substrate and the one silicon substrate 1a are supported on one silicon substrate 1a in a state of being separated from the one silicon substrate 1a. A basic configuration including the movable portions 20 and 30 and the peripheral fixed portion 10 disposed around the movable portions 20 and 30 on the one silicon substrate 1a and fixed and supported by the one silicon substrate 1a; It has become.

  The movable parts 20 and 30 including the driving vibration part 20 and the detection vibration part 30 are arranged in the horizontal directions X and Y with respect to the substrate surface of one silicon substrate 1a when an angular velocity Ω which is a mechanical quantity is applied. Displaceable.

  Here, as shown in FIG. 1, one anchor portion 12 is formed with a movable portion pad 12 a for applying a potential to the movable portions 20 and 30 from an external circuit (not shown). The detection electrode fixing portion 13 is formed with a detection electrode pad 13a for taking out signals from the detection electrode portions 15 and 35 to the external circuit.

  Further, as shown in FIG. 1, a peripheral fixing portion pad 10 a for applying a potential from the external circuit to the peripheral fixing portion 10 is formed at a predetermined position of the peripheral fixing portion 10. Each of these pads 10a, 12a, and 13a is formed by depositing aluminum or the like, and is connected to the external circuit by a bonding wire or the like.

  The operation of the angular velocity sensor 100 having such a configuration will be described. First, although not shown, the drive vibration unit 20 is vibrated (drive vibration) in the first direction X in FIG. 1 by capacitive driving. In the present embodiment, a drive electrode (not shown) is provided in the vicinity of the drive vibration unit 20 so as to face the drive vibration unit 20.

  Then, a constant potential (for example, 16 V) is applied to the driving vibration unit 20 and the detection vibration unit 30, that is, the movable units 20 and 30, from the external circuit via the movable unit pad 12 a. An AC voltage (for example, 8 ± 5 V) is applied to the drive electrode. By utilizing the electrostatic attraction generated thereby, the driving vibration unit 20 vibrates in the first direction and is displaced by the action of the driving beam unit 21.

  Under this driving vibration, as shown in FIG. 1, an angular velocity Ω is applied to the angular velocity sensor 100 around an axis perpendicular to the paper surface, that is, around an axis orthogonal to the first direction X and the second direction Y. Then, a Coriolis force is generated in the second direction Y with respect to the driving vibration unit 20.

  This Coriolis force is transmitted from the drive beam portion 21 to the detection vibration portion 30, and the detection vibration portion 30 and the drive vibration portion 20 vibrate integrally in the second direction Y in FIG. 1 (detection vibration). To do. And the distance between both the said projection parts 11 and 35 changes with this detection vibration. This change in distance is detected as a change in capacitance between the protrusions 15 and 35 via a wiring part (not shown) formed on the base 10.

  Specifically, the comb-tooth portion 15 on the detection electrode fixing portion 13 side of the detection electrode portions 11 and 35 is applied to the movable portions 20 and 30 from the external circuit via the detection electrode pad 13a. A voltage smaller than the voltage (for example, 2.5 V) is applied.

  A change in differential capacitance is detected between the left detection electrode portions 15 and 35 and the right detection electrode portions 15 and 35 in FIG. 1 by the external circuit. Thus, in the present embodiment, the angular velocity Ω is detected.

  Further, in the operation for performing such angular velocity detection, in the present embodiment, a potential is applied from the external circuit to the peripheral fixing portion 10 via the peripheral fixing portion pad 10a. Among these parts, the highest potential is obtained. For example, when the potential of the movable parts 20 and 30 is 16V, the potential of the peripheral fixed part 10 is about 20V.

  As described above, according to the present embodiment, one silicon substrate 1a as a support substrate and the one silicon substrate 1a are supported on one silicon substrate 1a while being separated from the one silicon substrate 1a. When the angular velocity is applied, the movable portions 20 and 30 that are displaceable in the horizontal directions X and Y with respect to the substrate surface of one silicon substrate 1a, and the surroundings of the movable portions 20 and 30 on the one silicon substrate 1a And a peripheral fixed portion 10 fixed to and supported by one silicon substrate 1a, and the applied angular velocity is detected based on the displacement state of the movable portions 20 and 30 when the angular velocity is applied. In the angular velocity sensor 100 configured as described above, during operation, the potential of the peripheral fixed portion 10 is the highest potential among the portions of the sensor 100. Support 100 is provided.

  According to this, at the time of operation, the potential of the peripheral fixing portion 10 is set to the highest potential among the respective portions of the sensor 100, so that the large potential is applied from the peripheral fixing portion 10 to one silicon substrate 1a.

  Therefore, the potential of one silicon substrate 1a can be made larger than that in the conventional GND state, and as a result, the potential difference between the movable portions 20 and 30 and one silicon substrate 1a can be reduced.

  Specifically, in the related art, when the potential of the movable parts 20 and 30 is, for example, 16V during operation, the potential difference between the one silicon substrate 1a in the GND state and the movable parts 20 and 30 is substantially 16V. It is.

  On the other hand, in this embodiment, as in the example described above, the potential of the movable parts 20 and 30 is 16V and the potential of the peripheral fixed part 10 is 20V during operation.

  Here, in the present embodiment, the peripheral fixing portion 10 is fixed and supported on one silicon substrate 1a via an oxide film 1c that is an insulating layer. Is applied to the peripheral fixing portion 10, a leak from the peripheral fixing portion 10 to one silicon substrate 1 a through the oxide film 1 c occurs, and the potential of the one silicon substrate 1 a is higher than the potential of the peripheral fixing portion 10. Becomes a low potential, for example, about 10V.

  Therefore, in the present embodiment, the potential difference between the movable parts 20 and 30 and the one silicon substrate 1a that is the support substrate at the time of operation is, for example, about 6 V, which can be a small potential difference compared to the conventional case. As a result, the electrostatic attractive force between the movable parts 20 and 30 and the support substrate 1a during operation can be reduced.

  Therefore, according to the present embodiment, in the angular velocity sensor 100 having the movable portions 20 and 30 supported on the support substrate 1a in a state of being separated from the support substrate 1a, the movable portions 20 and 30 and the support substrate 1a in operation. Can be suppressed as much as possible.

  Incidentally, in order to suppress sticking between the movable parts 20 and 30 and the support substrate 1a as much as possible during operation, the constant voltage applied to the movable parts 20 and 30 in the angular velocity sensor 100 is simply reduced. Conceivable.

  However, in this case, the driving force itself of the movable parts 20 and 30 is also reduced, the amplitude of the driving vibration is reduced, and the sensitivity of the sensor is lowered. In this respect, in the present embodiment, such a problem can be avoided.

  In the present embodiment, the movable portions 20 and 30 are released from one silicon substrate 1a by etching the other silicon substrate 1b as a semiconductor layer supported by one silicon substrate 1a. The peripheral fixing portion pad 10a for applying a potential to the peripheral fixing portion 10 is provided on the other silicon substrate 1b.

  Accordingly, the peripheral fixing portion pad 10a for applying a potential to the peripheral fixing portion 10 can be easily formed simultaneously with the formation of the other pads 12a and 13a.

  In the example described above in the present embodiment, a constant potential (for example, 16V) is applied to the movable parts 20 and 30, and an AC voltage (for example, 8 ± 5V) is applied to the drive electrode. On the contrary, an alternating voltage may be applied to the movable parts 20 and 30 and a constant potential may be applied to the drive electrode.

  Even in this case, if the highest potential is applied to the peripheral fixing portion 10 during operation, the potential of one silicon substrate 1a becomes lower than the potential of the peripheral fixing portion 10 due to the leakage through the oxide film 1c. . Therefore, effectively, the potential difference between the movable parts 20 and 30 and the one silicon substrate 1a can be reduced as compared with the conventional case, and the effect of suppressing sticking is exhibited as described above.

(Other embodiments)
In addition, in the said embodiment, although each part on a support substrate consists of semiconductors, you may be comprised from the conductor.

  In addition to the angular velocity sensor described above, the present invention can also be applied to a mechanical quantity sensor such as an acceleration sensor that detects acceleration as a mechanical quantity.

  In short, the present invention can be displaced in the horizontal direction with respect to the support substrate and the substrate surface of the support substrate when a mechanical quantity is applied to the support substrate in a state of being arranged away from the support substrate on the support substrate. Based on the displacement state of the movable part when a mechanical quantity is applied, and a peripheral fixed part that is arranged around the movable part on the support substrate and is supported by being fixed to the support substrate. In the mechanical quantity sensor that detects the applied mechanical quantity, the main feature is that the potential of the peripheral fixed part becomes the highest potential in each part of the sensor during operation. The design of the part can be changed as appropriate.

It is a figure which shows schematic plan structure of the angular velocity sensor as a mechanical quantity sensor which concerns on embodiment of this invention. It is an AA schematic sectional drawing in FIG.

Explanation of symbols

1a: One silicon substrate as a supporting substrate,
1b ... the other silicon substrate as a semiconductor layer, 1c ... an oxide film as an insulating layer,
10 ... Peripheral fixing part, 10a ... Peripheral fixing part pad,
20 ... Driving vibration part as a movable part, 30 ... Detection vibration part as a movable part.

Claims (2)

A support substrate (1a);
An insulating layer (1c) provided on the support substrate (1a);
A semiconductor layer (1b) supported by the support substrate (1a) through the insulating layer (1c);
The semiconductor layer (1b) is opposed to the support substrate (1a) and is released from the support substrate (1a) by removing the insulating layer (1c), and a mechanical quantity is applied to the semiconductor layer (1b). and a movable portion which is displaceable to the substrate surface and the horizontal direction (20, 30) when disposed around the front Symbol movable portion (20, 30), said support through said insulating layer (1c) A peripheral fixing part (10) fixed and supported by the substrate (1a) is defined by a groove,
In the mechanical quantity sensor configured to detect the applied mechanical quantity based on the displacement state of the movable part (20, 30) when the mechanical quantity is applied,
The mechanical quantity sensor characterized in that the potential of the peripheral fixed portion (10) is the highest potential among the respective portions of the sensor during operation. By etching the semiconductor layer (1b) and the insulating layer (1c) , the movable part (20, 30) and the peripheral fixed part (10) are formed in the semiconductor layer (1b),
It said peripheral fixed part pads (10a) for applying a potential to (10), dynamic quantity sensor according to claim 1, characterized in that provided on the semiconductor layer (1b).

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