JP2010169401A - Detection element, minute electromechanical device, and electronic equipment - Google Patents

Abstract

Even when dealing with physical quantity detection in a multi-axis direction per structure, it is possible to improve the S / N ratio of a detection result by suppressing the displacement of another axis of a detection axis from being mixed as noise. To.
A flexible first beam portion (31) arranged so as to extend along a first axial direction and a second axial direction orthogonal to the first axial direction. A second beam portion 32 having flexibility, and a weight portion 33 supported by the first beam portion 31 and the second beam portion 32 so as to be displaceable in at least two directions, In the detection element including the detection unit 21 that detects a mechanical quantity acting on the weight part 33 based on the displacement of the weight part 33, the weight part 33 is easily rotated around the first axial direction and the The first beam portion 31 and the second beam portion 32 are supported by the first beam portion 31 and the second beam portion 32 in such a manner that a difference occurs in the ease of rotation around the second axial direction.
[Selection] Figure 4

Description

  The present invention relates to a detection element, a microelectromechanical device, and an electronic apparatus.

In recent years, detection elements that detect physical quantities such as angular velocity, acceleration, pressure, and vibration frequency have been known as one of functional elements using micro electro-mechanical systems (hereinafter also referred to as “MEMS”) technology. It has been. The detection element here includes a movable part that is supported so as to be displaced by an inertial force from the outside, and a detection electrode that faces the movable part, and changes according to the magnitude of the inertial force generated between them. It is comprised so that the electrostatic capacitance value to be detected may be detected.
When the angular velocity is detected by such a detection element, it is generally necessary to excite the movable part (see, for example, Patent Documents 1 and 2). By exciting the movable part in the XY plane, the Coriolis force in the Z-axis direction is generated by rotation around the X-axis or Y-axis, and the displacement in the Z-axis direction due to the Coriolis force is detected by using the detection electrode. This is because the angular velocity around the X axis or the Y axis can be detected. Known drive sources for excitation include those using Lorentz force (for example, see Patent Document 1), those using electrostatic force (for example, see Patent Document 2), and the like. Hereinafter, the vibration caused by this excitation is also referred to as “drive vibration” or “reference vibration”.

By the way, it is desirable that the drive vibration be completely orthogonal to the detection axis of the electrostatic capacity when detecting the physical quantity (see, for example, Patent Document 3). This is because non-orthogonal components leak to the detection axis and become detection signals synchronized with the drive, and are mixed with signals that detect physical quantities to deteriorate the SN ratio of detection results.
In order to reduce this non-orthogonal component, it has been proposed to make the movable part difficult to move in the non-detection direction, for example, by changing the ratio of the horizontal and vertical directions of the movable part and changing the ratio of the spring constant. (For example, refer to Patent Document 3). In addition, the physical quantity in the detection axis direction is detected with high sensitivity by calculating two capacitances formed by two pairs of fixed electrodes and movable electrodes, and the sensitivity of other axes is suppressed by increasing the rigidity of the movable part. Has also been proposed (see, for example, Patent Document 4).

JP 2000-65581 A Japanese Patent Laid-Open No. 11-64001 Japanese Patent No. 3518067 JP 2006-250702 A

In the conventional structure described above, it is assumed that one axis is detected with one structure. That is, it corresponds to one that detects a physical quantity in one axial direction per structure.
On the other hand, in recent years, as part of efforts to improve the accuracy of camera shake correction and realize various human interfaces, for example, mobile devices represented by mobile phones, remote control devices for electronic devices and game devices, etc. Detection tends to be required. However, in a detection element that detects a physical quantity in a uniaxial direction, there is a possibility that an installation area, a volume, and the like increase when detecting a physical quantity in a multiaxial direction. This is fatal if it is assumed to be installed in mobile and wearable products, which are a large market for inertial sensors. Moreover, since it takes time and effort at the time of mounting, it causes a cost increase. Furthermore, it is known that the multi-axis sensor of a uniaxial set deteriorates the sensitivity of the other axis when the relative angle of each axis is shifted during assembly.
For this reason, recently, a detection element capable of detecting in a multi-axis direction with a single structure has attracted attention. This is because a detection element capable of detecting a physical quantity in a multi-axis direction per structure has an advantage over a single-axis assembly in terms of mass productivity such as device miniaturization and simplification of mounting, and cost.

  However, since a detection element capable of multi-axis detection generally has a multi-axis detection mode with a single structure, even if the conventional structure described above is applied, the SN ratio is not necessarily improved. Is not limited. For example, even if the aspect ratio between the horizontal direction and the vertical direction of the movable part is changed to suppress the displacement in a direction other than the mechanical quantity detection direction, the displacement in the axial direction can be suppressed for a certain detection axis, and the other axis sensitivity can be suppressed. Less effective for other axes. That is, it is difficult to ensure the SN ratio in the case of multi-axis support. In particular, an angular velocity sensor that has drive vibration (reference vibration) and detects displacement due to Coriolis force drives a vibration mode excited by continuous drive displacement generated by this electrostatic force, piezoelectricity, Lorentz force, etc. Noise is synchronized with the signal. And the noise is mixed with the signal which detected the physical quantity, and there exists a possibility of degrading the SN ratio of a detection result.

  Therefore, the present invention suppresses the mixed displacement of another detection axis as noise even when dealing with physical quantity detection in a multi-axis direction per structure, and improves the SN ratio of the detection result. An object of the present invention is to provide a detection element, a microelectromechanical device, and an electronic apparatus that can achieve the above.

  The present invention is a detection element devised to achieve the above object, and includes a first beam portion having flexibility that is arranged so as to extend along a first axial direction, and the first shaft. A second beam part having flexibility arranged to extend along a second axial direction perpendicular to the direction, and at least two directions by the first beam part and the second beam part A weight portion supported so as to be displaceable, and a detection portion that detects a mechanical quantity acting on the weight portion based on the displacement of the weight portion, the weight portion rotating about the first axial direction. The detection element is supported by the first beam portion and the second beam portion in such a manner that a difference occurs between the ease and the ease of rotation around the second axial direction.

  In the detection element having the above configuration, the ease of rotation of the weight portion around each axis is different from each other. Therefore, it is possible to make it difficult to displace the weight portion except in the direction of detecting the mechanical quantity by the detection unit. Specifically, for example, by making the spring constants of the beam portions in each axial direction different from each other or by making the inertia moments of the weight portions around each axis different from each other, compared to the mechanical quantity detection direction by the detection unit. It is conceivable to suppress the displacement of the weight portion outside the mechanical quantity detection direction.

  According to the present invention, even if it corresponds to physical quantity detection in a multi-axis direction per structure, it is possible to suppress displacement of the weight part in a direction other than the mechanical quantity detection direction by the detection unit. More specifically, for example, vibration (regardless of translation or rotation) excited by drive vibration can be suppressed. Therefore, it is possible to suppress the displacement of another axis of a certain detection axis from being mixed as noise, and the SN ratio of the detection result can be improved as compared with the case where noise mixing is not suppressed. Further, through the improvement of the SN ratio, the post-adjustment of the frequency, the center of gravity, etc. can be eliminated or reduced, and the manufacturing efficiency, the apparatus cost, etc. are good.

It is a three-plane figure which shows the structural example of MEMS which concerns on this invention. It is explanatory drawing (the 1) which shows a specific example of the manufacturing procedure of MEMS which concerns on this invention. It is explanatory drawing (the 2) which shows a specific example of the manufacturing procedure of MEMS which concerns on this invention. It is explanatory drawing which shows the schematic structural example of the detection element which concerns on this invention. It is explanatory drawing which shows the specific example of the detection procedure of angular velocity etc. by the detection element which concerns on this invention. It is explanatory drawing which shows the example of schematic structure of the detection element part in the 1st Embodiment of this invention. It is explanatory drawing which shows the example of schematic structure of the detection element part in the 2nd Embodiment of this invention. It is explanatory drawing which shows the example of schematic structure of the detection element part in the 3rd Embodiment of this invention. It is explanatory drawing which shows the example of schematic structure of the detection element part in the 4th Embodiment of this invention. It is a signal block diagram which shows the operating principle of the inertial sensor which detects an inertial force. It is the flowchart which showed an example of the inertial force detection process. It is a schematic structure perspective view which shows one specific example of SIP containing an inertial sensor. It is explanatory drawing which shows schematic structure of the HDD apparatus which is a specific example of an electronic device. It is explanatory drawing which shows schematic structure of the notebook type personal computer carrying the HDD apparatus which is a specific example of an electronic device. It is explanatory drawing which shows schematic structure of the video camera apparatus carrying the HDD apparatus which is a specific example of an electronic device. It is explanatory drawing which shows schematic structure of the game machine carrying the HDD apparatus which is a specific example of an electronic device. It is explanatory drawing which shows schematic structure of the portable terminal device with a camera which is a specific example of an electronic device. It is explanatory drawing which shows schematic structure of the video camera apparatus which is a specific example of an electronic device.

  Hereinafter, a detection element, a micro electro mechanical device, and an electronic apparatus according to the present invention will be described with reference to the drawings.

[Description of micro electromechanical device]
First, a micro electromechanical device (MEMS) according to the present invention will be described.
FIG. 1 is a three-view diagram illustrating a configuration example of a MEMS according to the present invention.

As illustrated, the MEMS described as an example here includes a first substrate 10 and a second substrate 20.
The first substrate 10 is a structure forming substrate and is made of, for example, a silicon (Si) substrate or a gallium arsenide (GaAs) substrate.
The second substrate 20 is a displacement detection substrate, and is made of, for example, a glass substrate or a Si substrate.
The first substrate 10 and the second substrate 20 are bonded by anodic bonding, Si bonding, metal bonding, or the like. Alternatively, it may be bonded by a glass frit, an adhesive or the like.

Further, the MEMS described as an example here is configured to include a drive unit 11, a support unit 12, and an elastic support 13 when viewed in plan.
The drive unit 11 is formed in a flat rectangular plate shape. Here, the “flat plate shape” refers to a shape that is sufficiently small in the thickness direction with respect to the size of the planar shape (for example, the size of a rectangular component side), and the surface is not necessarily smooth. There is no need.
The support part 12 is arranged so as to be separated from the end edge of the movable part so as to surround the outer peripheral side of the drive part 11. Here, “separation” means through a space.
The elastic support 13 supports the drive unit 11 so as to be displaceable in the in-plane direction with respect to the support unit 12. Here, the “in-plane direction” refers to a plane direction perpendicular to the thickness direction of the plate-like drive unit 11. Due to the displacement in the in-plane direction, the elastic support body 13 has one end connected to the drive unit 11 and the other end connected to the support unit 12 at each of four locations near the top of the drive unit 11. As shown in FIG.
In the MEMS having such a configuration, the driving unit 11 is displaced in the in-plane direction by utilizing the elastic deformation of the elastic support 13. The operation of the drive unit 11 in the in-plane direction is performed using Lorentz force, electrostatic force, piezo element, and the like. That is, the drive unit 11 is excited in the in-plane direction by a drive source (not shown) using a Lorentz force, an electrostatic force, a piezoelectric element, or the like.

  The drive unit 11 is provided with a detection element unit 30. The detection element unit 30 includes, for example, a weight unit as a vibrator that is displaced by Coriolis force. Details of the detection element unit 30 will be described later.

  Further, the second substrate 20 has a position perpendicular to the movable direction of the drive unit 11 (in-plane vertical direction) with respect to the transducer in the detection element unit 30 at a position facing the detection element unit 30 on the drive unit 11. The detection part 21 which detects the displacement of is formed. The detection unit 21 may be any unit that detects using a known technique, such as detecting a change in capacitance.

  2 and 3 are explanatory diagrams showing a specific example of the manufacturing procedure of the MEMS having the above-described configuration. The example shows a portion corresponding to the AA ′ cross section in FIG. 1.

Here, a case where the first substrate 10 is made of an SOI (Silicon on insulator) substrate is taken as an example.
The SOI substrate constituting the first substrate 10 is a substrate having a structure in which SiO2 (BOX layer 10b) is inserted between the support layer 10a and the active layer 10c. Since the details are publicly known, the description thereof is omitted here.

In manufacturing the MEMS having the above-described configuration, first, as shown in FIG. 2A, insulating layers 15 are formed on both surfaces of the first substrate 10 made of an SOI substrate. The insulating layer 15 may be formed of a SiO ₂ film, a silicon nitride (SiN) film, or the like.
After the formation of the insulating layer 15, subsequently, as shown in FIG. 2B, a mask pattern for forming the drive unit 11 and the elastic support 13 on the surface of the first substrate 10 on the active layer 10c side. 14 is created. It is conceivable that the mask pattern 14 is made of, for example, a photoresist film.
When the mask pattern 14 is created, as shown in FIG. 2C, an etching process is performed from the creation surface side of the mask pattern 14, and the insulating layer 15 overlapping the active layer 10c of the first substrate 10 and the active layer The layer 10c is formed with a portion to be the drive unit 11 and the elastic support body 13. This etching process may be performed by physical dry etching such as oxide film etching and D-RIE (Deep-Reactive Ion Etching).
Thereafter, the mask pattern 14 is removed. Although not shown, the first substrate 10 is provided with a contact portion, wiring, and the like with the second substrate 20 on the surface to be bonded or bonded to the second substrate 20.

After the etching process on the active layer 10c and the like, as shown in FIG. 2D, a photoresist film 16 is applied to the surface of the first substrate 10 on the active layer 10c side so as to block the etched part. To do.
Further, as shown in FIG. 2E, a mask pattern 17 for forming the drive unit 11 and the elastic support 13 is formed on the surface of the first substrate 10 on the support layer 10a side. It is conceivable that the mask pattern 17 is also made of, for example, a photoresist film, similarly to the mask pattern 14 described above. At this time, alignment with the above-described mask pattern 14, that is, the etching processing portion in the active layer 10 c of the first substrate 10 is necessary, and this may be performed using, for example, a double-side aligner.
When the mask pattern 17 is created, as shown in FIG. 2 (f), an etching process is performed from the creation surface side of the mask pattern 17, so that the insulating layer 15 that overlaps the support layer 10a of the first substrate 10 and the support. For the layer 10 a, portions to be the drive unit 11 and the elastic support 13 are formed. This etching process may be performed by oxide film etching and physical dry etching such as D-RIE.

After the etching process for the support layer 10a, the mask pattern 17 and the insulating layer 15 on the support layer 10a side are subsequently removed as shown in FIG. Then, the etching process is performed on the BOX layer 10b of the first substrate 10 to form portions that become the drive unit 11 and the elastic support 13. The etching process can be performed by wet etching with hydrofluoric acid (HF).
After the etching process for the BOX layer 10b, subsequently, as shown in FIG. 3B, the photoresist film 16 on the surface of the first substrate 10 on the active layer 10c side is removed.
As a result, the drive unit 11 and the elastic support 13 are formed on the first substrate 10 in which the support layer 10a, the BOX layer 10b, the active layer 10c, and the insulating layer 15 are stacked in the thickness direction.

On the other hand, as shown in FIG. 3C, a mask pattern 22 is formed on the surface of the second substrate 20 for forming a gap (a cross-sectional concave portion) for the detection unit 21. It is conceivable that the mask pattern 22 is made of a photoresist film, a SiO ₂ film, a thermal oxide film, or the like.
When the mask pattern 22 is created, as shown in FIG. 3D, an etching process is performed from the creation surface side of the mask pattern 22 to form a gap for the detection unit 21. The etching process is performed by wet etching, for example, and tetramethyl ammonium hydroxide (TMAH) or potassium hydroxide (KOH) aqueous solution is used as an etching solution. However, it is not limited to wet etching, and may be performed by chemical dry etching, physical dry etching, or the like.
Thereafter, the mask pattern 22 is removed, and as shown in FIG. 3E, an electrode forming film is formed in the formed gap to form the detection unit 21. For example, electron beam vapor deposition may be used for forming the electrode forming film serving as the detection unit 21. However, a sputtering method, a CVD (Chemical Vapor Deposition) method, or the like may be used. In addition, the electrode forming film includes, for example, gold, platinum, chromium three-layer metal material, gold, platinum, titanium three-layer metal material, gold, chromium, platinum, chromium or gold, titanium, platinum, titanium, etc. A double layer metal material or the like can be used. Further, a laminated material of titanium nitride and titanium may be used instead of titanium. Furthermore, copper may be used instead of chromium or titanium.
The second substrate 20 is formed with a contact portion, wiring, and the like with the second substrate 20 on the surface to be bonded or bonded to the first substrate 10.

Thereafter, as shown in FIG. 3 (f), the first substrate 10 and the second substrate 20 are bonded by anodic bonding, Si bonding, metal bonding, or the like. Alternatively, they are bonded with a glass frit, an adhesive or the like. Although not shown in the drawing, a contact portion is formed in order to establish conduction at the joint surface between the first substrate and the second substrate. This contact portion is formed with a gold support by, for example, electroless plating or electrolytic plating. Although not shown, chip separation is performed by dicing.
Through the above procedure, the MEMS having the configuration shown in FIG. 1 is manufactured.

[Description of detection element]
Next, the detection element unit 30 in the MEMS configured as described above will be described in more detail. The detection element unit 30 and the detection unit 21 correspond to the detection element according to the present invention.

<Outline of detection element>
First, a schematic configuration of the detection element unit 30 will be described. Here, the case of applying to a so-called inertial sensor will be described as an example, but it goes without saying that this does not limit the type of sensor.
FIG. 4 is an explanatory diagram showing a schematic configuration example of the detection element according to the present invention.

  As shown in FIG. 4A, the detection element unit 30 is disposed on the drive unit 11 constituting the MEMS, and is formed by processing the first substrate 10 made of an SOI substrate or the like. . More specifically, the detection element unit 30 includes a first beam unit 31, a second beam unit 32, and a weight unit 33.

Each of the first beam portion 31 and the second beam portion 32 supports the weight portion 33 so as to be displaceable with respect to the drive portion 11. Therefore, the first beam portion 31 and the second beam portion 32 are formed only by the active layer 10c of the SOI substrate, and thereby are configured to be flexible. And it arrange | positions so that the one end may be connected with the drive part 11, and the other end may be connected with the weight part 33. FIG.
However, the arrangement direction is different between the first beam portion 31 and the second beam portion 32.
The first beam portion 31 is arranged so as to extend along the first axial direction when a mechanical quantity acting on the weight portion 33 is detected. Here, the first axial direction corresponds to, for example, the x-axis direction in the in-plane direction when the drive unit 11 vibrates.
On the other hand, the 2nd beam part 32 is distribute | arranged so that it may extend along the 2nd axial direction orthogonal to a 1st axial direction. Here, the second axial direction corresponds to the y-axis direction in the in-plane direction when the drive unit 11 vibrates, for example.
Here, the case where the first axial direction is the x-axis direction and the second axial direction is the y-axis direction is taken as an example, but this correspondence is only one specific example, Of course, it is not limited.

The weight portion 33 is arranged so as to be separated from the driving portion 11 so that the outer peripheral side thereof is surrounded by the driving portion 11, and in at least two directions by the first beam portion 31 and the second beam portion 32. It is supported so that it can be displaced. That is, the first beam portion 31 and the second beam portion 32 are supported so that they can be displaced using the flexibility. Specifically, in addition to the x-axis direction and the y-axis direction, it can also be displaced in a direction perpendicular to each axial direction, that is, in the z-axis direction that is the in-plane vertical direction.
Further, the weight portion 33 is formed by stacking the support layer 10a, the BOX layer 10b, and the active layer 10c of the SOI substrate, while the first beam portion 31 and the second beam portion 32 are formed only by the active layer 10c. Formed by the body. Therefore, the weight part 33 has a bell-shaped structure as shown in FIG.
When the weight 33 supported by such a bell-shaped structure is acted on by the z-axis direction on the weight 33, the first beam 31 and the second beam 32 are bent, as shown in FIG. As shown in b), it is displaced in the translation direction.
On the other hand, when a force in the x-axis direction or the y-axis direction acts on the weight portion 33, the weight portion 33 is deformed by the first beam portion 31 and the second beam portion 32 as shown in FIG. In addition, it is displaced in the rotational direction.
In addition, as shown in FIG. 4B or FIG. 4C, at a position facing the weight portion 33, detection for detecting a mechanical quantity acting on the weight portion 33 based on the displacement of the weight portion 33. The part 21 shall be arrange | positioned.

  A specific example of the detection element unit 30 having such a configuration is one that is disposed on the drive unit 11 having a size of 1 mm square and has a detection resonance frequency of about several kHz.

Subsequently, a procedure for detecting angular velocity and the like using the detection element unit 30 having the above-described configuration will be described.
FIG. 5 is an explanatory diagram illustrating a specific example of a procedure for detecting angular velocity and the like.

In detecting the angular velocity or the like, the drive unit 11 is excited in the in-plane direction. That is, the drive in which the weight portion 33 periodically vibrates at a resonance frequency of about several kHz with respect to the entire drive portion 11 including the first beam portion 31, the second beam portion 32, and the weight portion 33. Give vibration. Specifically, for example, a drive vibration that vibrates along the y-axis direction is applied.
In this state, for example, when an angular velocity is applied around the x axis, a Coriolis force is generated in the z axis direction.
The Coriolis force is given by F _coriolis = 2 mvΩ. Here, m is the mass of the weight portion 33 which is a vibrator, v is a vibration velocity in the driving direction, and Ω is an angular velocity applied from the outside.
When the Coriolis force is generated in the z-axis direction, the Coriolis force is applied to the weight portion 33 that is a vibrator and is displaced in the z-axis direction. Since the weight portion 33 is different in height from the center of gravity position and the support position, a moment is generated by the Coriolis force and vibrates in the twisting direction.
As shown in FIG. 5, the displacement in the twisting direction is detected by a change in capacitance of the detection unit 21 including four electrodes. Of the four electrodes, the two electrodes on the side inclined and the gap widened have a reduced capacitance, and the two electrodes on the side inclined and the gap narrowed have an increased capacitance. To detect the displacement due to twisting, that is, the angular velocity efficiently by taking the sum of the capacitances on the widened sides and taking the sum of the capacitances on the narrowed sides and then taking the difference between the sums of the capacities of the respective electrodes. Can do.
Further, when an angular velocity is applied around the z axis, a Coriolis force is generated in the x axis direction. Therefore, similarly to the case described above, the angular velocity generated around the z-axis can be detected by the capacitance change of the detection unit 21 including four electrodes.
According to such a detection procedure, it is possible to detect angular velocities for two axes.
That is, when the entire drive unit 11 is translationally driven (drive vibration) in the y-axis direction, if an angular velocity is applied around the x-axis, a Coriolis force is generated in the z-axis direction. Due to the force in the z-axis direction, the weight portion 33 moves in the z translational direction. If an angular velocity is applied around the z axis, a Coriolis force is generated in the x axis direction, and the weight portion 33 rotates around the y axis.

By the way, as described above, when the Coriolis force is generated in the weight portion 33 by using the entire translational drive (drive vibration) of the drive portion 11, thereby making it possible to detect the angular velocity of two axes. The vibration mode excited by the continuous drive displacement due to the drive vibration may become noise synchronized with the drive signal. Such noise is mixed with the angular velocity detection signal and deteriorates the SN ratio, so it should be removed.
In other words, for multiple (multi-axis) detection modes, there are modes that are excited especially by driving vibration during angular velocity detection, resulting in drive noise, which is removed by synchronous detection, which is a common circuit method for angular velocity detection. Since it becomes difficult to do, it will become a factor which deteriorates SN ratio.

  Therefore, it is conceivable that the detection element unit 30 is configured as described below to suppress the displacement of the weight unit 33 in directions other than the mechanical quantity detection direction by the detection unit 21. In particular, vibration (regardless of translation and rotation) excited by the drive mode is suppressed. It is because the noise synchronized with the drive frequency can be removed by the suppression, and the S / N ratio after detection can be improved.

Specifically, the weight portion 33 is different in the ease of rotation around the first axial direction (for example, the x-axis direction) and the ease of rotation about the second axial direction (for example, the y-axis direction). In this manner, the weight portion 33 is supported by the first beam portion 31 and the second beam portion 32. That is, the ease of rotation of the weight portion 33 around each axis is made different from each other.
In particular, if the vibration excited by the drive mode is to be suppressed, the weight in such a manner that it is easier to rotate around the axial direction along the direction of the drive vibration than around the axial direction perpendicular to the direction of the drive vibration. The portion 33 is supported by the first beam portion 31 and the second beam portion 32.
In this way, it is possible to make it difficult to displace the weight part 33 in directions other than the mechanical quantity detection direction by the detection part 21.

More specifically, a configuration as described below can be considered.
For example, when the vibration excited by the drive mode is in the translation direction, the mechanical synchronization noise due to the drive vibration can be reduced by increasing the spring constant of the spring mass system. That is, the spring constants that specify the amount of deflection in the first beam portion 31 and the second beam portion 32 are made different from each other. Specifically, the actual amplitude of the mechanical synchronization component can be reduced in proportion to the spring constant, that is, in proportion to the square of the resonance frequency.
For example, when the vibration excited by the drive mode is in the rotational direction, the mechanical synchronization noise due to the drive vibration can be reduced by increasing the inertia moment of the system. If the moment of inertia is large, it is difficult to rotate, and mechanical synchronization noise is reduced.
In addition, for example, in common with translation and rotation, the mechanical coupling coefficient can be lowered by separating the driving frequency and the frequency of the unnecessary mode excited by the driving mode, so that the amplitude can be further reduced. it can.

  With such a configuration, it is possible to provide a semiconductor dynamic quantity sensor that suppresses displacements in directions other than the dynamic quantity detection direction, particularly vibrations (regardless of translation and rotation) excited by the drive mode. And the S / N ratio after a detection can be improved by removing the noise synchronized with the drive frequency. Furthermore, post-adjustment of the frequency, the center of gravity, and the like can be eliminated or reduced through the improvement of the SN ratio, and the manufacturing efficiency, the apparatus cost, and the like can be improved.

  Hereinafter, a specific configuration of the detection element unit 30 will be described in order by taking the first to fourth embodiments as examples.

<First Embodiment>
FIG. 6 is an explanatory diagram illustrating a schematic configuration example of the detection element unit according to the first embodiment.
In the illustrated detection element section 30, the first beam section 31 and the second beam section 32 have different spring constants, so that a difference in ease of rotation of the weight section 33 around each axis occurs. It has become. More specifically, the number of the first beam portions 31 and the second beam portions 32 arranged is different from each other. Specifically, as shown in the drawing, the first beam portion 31 extending along the x-axis direction has a total of four on one side, but the second beam portion extending along the y-axis direction. A total of two beam portions 32 are arranged on one side so as to pass through the center of the weight portion 33.

  In such a configuration, a total of four first beam portions 31 are located near both ends of the weight portion 33 as compared to the y-axis direction around the center of the weight portion 33 supported by the two second beam portions 32 in total. The weight portion 33 is less likely to rotate around the x-axis direction supported by. This is because the total cross-sectional area of the four first beam portions 31 is larger than the total of the two second beam portions 32, and as a result, the spring constant is also increased. Therefore, the weight portion 33 is more easily rotated around the y-axis direction along the direction of drive vibration than around the x-axis direction orthogonal to the direction of drive vibration. It is supported by the beam portion 32.

  This means that the same effect can be obtained simply by making the beam widths on the xy plane different from each other. Therefore, in order to increase the spring constant in the first beam portion 31, it is conceivable to fill the space between the two beams on one side (that is, to make the first beam portion 31 extremely thick). However, in that case, translational vibration in the z-axis direction may be hindered. The same applies to the case where the length of one beam is extremely shortened. From this, in the first embodiment, the first beam portion 31 and the second beam portion 32 are made to have the same thickness and length, but the number of arrangement is different. Thus, the spring constants are different from each other.

  Here, a case where a total of four first beam portions 31 and a total of two second beam portions 32 are disposed is described as an example, but the number of each disposed is limited to this. There may be other numbers as long as they are different from each other.

<Second Embodiment>
FIG. 7 is an explanatory diagram illustrating a schematic configuration example of the detection element unit according to the second embodiment.
Similarly to the case of the first embodiment described above, the detection element unit 30 of the illustrated example also has different spring constants for the first beam unit 31 and the second beam unit 32, so that Thus, there is a difference in the ease of rotation of the weight 33. However, unlike the case of the first embodiment, the spring constants differ from each other not by the number of the first beam portions 31 and the second beam portions 32 but by different formation thicknesses. It is supposed to be. That is, the first beam portion 31 and the second beam portion 32 have different formation thicknesses in the z-axis direction perpendicular to the x- and y-axis directions.

  Specifically, as shown in FIG. 7B, the first beam portion 31 is composed only of the active layer 10a. On the other hand, as shown in FIG.7 (c), the 2nd beam part 32 is comprised by laminating | stacking the active layer 10a and the support layer 10c. Accordingly, the first beam portion 31 and the second beam portion 32 have different formation thicknesses in the z-axis direction.

  In such a configuration, since the formation thickness of the second beam portion 32 arranged along the y-axis direction is large, the vibration is limited by the second beam portion 32, and the weight portion 33 is rotated around the x-axis direction. It becomes difficult to rotate. For example, when the active layer 10a is 10 μm thick and the support layer 10c is 400 μm thick, a resonance frequency difference of 100 times or more can be realized in the x-axis direction and the y-axis direction. Therefore, the weight portion 33 is more easily rotated around the y-axis direction along the direction of drive vibration than around the x-axis direction orthogonal to the direction of drive vibration. It is supported by the beam portion 32.

<Third Embodiment>
FIG. 8 is an explanatory diagram illustrating a schematic configuration example of the detection element unit according to the third embodiment.
FIG. 8A shows a configuration in which the number of arranged first beam portions 31 and second beam portions 32 is different from each other, as in the case of the first embodiment described above.
FIG. 8 (b) is different from the configuration shown in FIG. 8 (a) in that the support connection position of the weight portion 33 by the first beam portion 31 is changed, and thereby the weight portion 33 is easily rotated around each axis. A configuration is shown in which the easiness of rotation around the ≡ axis direction is limited in such a way that a difference in height occurs.
Specifically, in the configuration of FIG. 8A, the support point around the detection axis is outside, whereas in the configuration of FIG. 8B, the support point around the detection axis is inside. Since the support point is one of the factors that hinder the rotation, the latter with the far support point has a larger rotation angle for the same external force.
On the other hand, since the distance from the rotation center of the support point does not change in the direction orthogonal to the detection axis (corresponding to the noise component), the rotation angle with respect to the same external force is not greatly different.
Thus, while the rotation angle in the direction in which the physical quantity is detected increases, the response to the noise component does not change, so the latter becomes larger as the S / N ratio, and as a result, signal detection becomes easier.
For reference, a specific example of the distance between the support points, the frequency of the resonance mode for detecting the signal, the frequency of the resonance mode that becomes noise, and the signal / noise frequency ratio is shown in FIG. According to FIG. 8C, it can be seen that if the distance between the support points is increased, the frequency at which the signal is detected is substantially constant, but the resonance frequency of the noise is increased.

That is, when the support connection position of the weight portion 33 by the first beam portion 31 is changed with respect to the configuration shown in FIG. 8A as in the configuration of FIG. 8B, the support connection from the rotation center is changed. The moment about the position changes. Therefore, the weight part 33 is easy to rotate around the y-axis direction along the second beam part 32, and relatively difficult to rotate around the x-axis direction.
As described above, even when the support connection positions with respect to the weight portion 33 are made different from each other, the weight portion 33 is more rotated around the y-axis direction along the direction of the drive vibration than around the x-axis direction perpendicular to the direction of the drive vibration. Is supported by the first beam portion 31 and the second beam portion 32 in such a manner that it can be easily rotated.

<Fourth embodiment>
FIG. 9 is an explanatory diagram illustrating a schematic configuration example of the detection element unit according to the fourth embodiment.
FIG. 9A shows a configuration in which the number of arranged first beam portions 31 and second beam portions 32 is different from each other, as in the case of the first embodiment described above.
9B differs from the configuration shown in FIG. 9A in that the moment of inertia of the weight 33 is changed by changing the cross-sectional secondary moment of the weight 33. Thus, the structure is shown in which the ease of rotation around the ≡ axis direction is limited.

In general, a moment of inertia I of a system composed of N mass points can be expressed as I = Σm _i a _i ² using an i-th mass m _i and an i-th radius of rotation a _i .
Therefore, if the radius of rotation with respect to the noise axis is large even if the mass is the same, that is, if the moment of inertia is large, the object becomes difficult to rotate, and the noise component can be suppressed. Further, if the moment of inertia around the detection axis is reduced, the rotation angle with respect to the same torque increases, so that the signal per unit physical quantity can be increased.

Therefore, in the configuration of FIG. 9B, the sectional moment of the section around each axis is controlled by changing the sectional shape of the weight portion 33 around each axis, and the moment of inertia around each axis is thereby controlled. They are different from each other. Then, by reducing the moment of inertia around the y-axis direction, the weight portion 33 can be easily rotated around the y-axis direction, but relatively difficult to rotate around the x-axis direction. In this way, by controlling the moment of inertia of the cross section of the weight portion 33, the weight portion 33 can be moved more in the y-axis direction along the direction of the drive vibration than in the x-axis direction perpendicular to the direction of the drive vibration. It is supported by the first beam portion 31 and the second beam portion 32 in a manner that facilitates rotation.
This can also be realized by controlling the mass distribution of the weight portion 33 and thereby reducing the moment of inertia around the y-axis direction. Since the control of the mass distribution may be performed using a known technique, the description thereof is omitted here.

[Description of application example to inertial sensor]
Next, an example of application of the MEMS to the inertial sensor including the detection element unit 30 having the above-described configuration will be specifically described.

FIG. 10 is a signal block diagram illustrating the operation principle of the inertial sensor that detects the inertial force. As shown in the figure, for detecting the inertial force, an amplifier, a temperature correction circuit, and a filter for amplifying the signal obtained by each inertial sensor are provided for each one system.
FIG. 11 is a flowchart illustrating an example of the inertial force detection process. In the inertial force detection process shown in the figure, when the inertial sensor detects "inertia force (acceleration or angular velocity)", the detected inertial force is detected in the "threshold range" and the detected inertial force is preset in the inertial sensor. It is determined whether or not. In this determination unit, if the detected inertial force is within the threshold range, it is determined “yes”, and a predetermined process is executed. On the other hand, when the determination unit determines that the detected inertial force is “no” that is not in the threshold range, the inertial force is detected again by the inertial sensor.
FIG. 12 is a schematic configuration perspective view showing a specific example of a SIP (System in a Package) including an inertial sensor. The SIP shown in FIG. 1 includes an inertial sensor 100, a memory chip 81, and an ASIC (Application Specific Integrated Circuit) chip 91, to which the present invention is applied, in one package 71. Note that the SIP shown here is only a specific example, and any semiconductor chip other than the above chips can be mounted. Even if the semiconductor chip and the inertial sensor 100 are combined, the system is configured. Good.

[Description of electronic device with inertial sensor]
Next, an electronic device including an inertial sensor, which is a specific example of MEMS, will be described with a specific example. As described above, the MEMS according to the present invention can detect the inertial force of acceleration and angular velocity, and can be applied to various electronic devices.

FIG. 13 is an explanatory diagram showing a schematic configuration of a hard disk drive (hereinafter abbreviated as “HDD”), which is a specific example of an electronic apparatus.
The HDD device 110 in the example includes a base member 111 and a cover 112 that covers the base member 111. On the base substrate 113 of the base member 111, a magnetic disk 114, its drive motor 115, an actuator arm 117 that rotates about a support shaft 116, and a magnetic head formed at the tip of the head via a head suspension 118. 119 etc. are provided. Furthermore, the inertial sensor 100 is installed on the base substrate 113. The inertial sensor 100 can also be installed on the base member 111, the cover 112, and the like, and is used for drop detection means, impact detection, vibration control, and the like.

FIG. 14 is an explanatory diagram showing a schematic configuration of a notebook personal computer equipped with an HDD device which is a specific example of the electronic apparatus.
In the illustrated example, an example of a notebook personal computer equipped with an HDD device is shown. (A) shows a state in which the display unit is opened, and (b) shows a state in which the display unit is closed.
A notebook personal computer 130 in the illustrated example includes a main body 131 including a keyboard 132 that is operated when characters and the like are input, a display unit 133 that displays an image, an HDD device 134, and the like. Among these, the HDD device 134 is manufactured by using a device on which the above-described inertial sensor 100 is mounted. Further, the inertial sensor 100 may be attached to a board (not shown) of the notebook personal computer 130, a vacant area inside the casing constituting the main body 131 or the display unit 133, a drop detection means or an impact detection. Used for vibration control and the like.

FIG. 15 is an explanatory diagram showing a schematic configuration of a video camera device equipped with an HDD device which is a specific example of the electronic apparatus.
The video camera device 170 shown in the figure has a main body 171 with a subject photographing lens 172 on the side facing forward, a start / stop switch 173 at the time of photographing, a display unit 174, a viewfinder 175, and an HDD device for recording the photographed image. 176 etc. are comprised. Among these, the HDD device 176 is manufactured by using a device on which the above-described inertial sensor 100 is mounted. The inertial sensor 100 may be attached to a board (not shown) of the video camera device 170 or a vacant area on the inner side of the casing constituting the main body 171, and includes a drop detection means, impact detection, vibration control, and the like. Used for.

FIG. 16 is an explanatory diagram showing a schematic configuration of a game machine which is a specific example of the electronic device.
A game machine 150 shown in the figure includes a main body 151 including a first operation button group 152, a second operation button group 153 for operating a screen, a display unit 154 for displaying an image, an HDD device 155, and the like. . Among these, the HDD device 155 is manufactured by using a device on which the above-described inertial sensor 100 is mounted. The inertial sensor 100 may be attached to a board (not shown) of the game machine 150 or a vacant area on the inner side of the casing constituting the main body 151. The input interface, the drop detection means, the impact detection, and the operation Used for detection and the like.

FIG. 17 is an explanatory diagram illustrating a schematic configuration of a mobile terminal device which is a specific example of the electronic apparatus.
In the illustrated example, a mobile phone is shown as an example of a mobile terminal device, (a) is a front view in an open state, (b) is a side view thereof, (c) is a front view in a closed state, ( d) is a left side view, (e) is a right side view, (f) is a top view, and (g) is a bottom view.
A cellular phone 190 shown in the figure includes an upper casing 191, a lower casing 192, a connecting portion (here, a hinge portion) 193, a display 194, a sub-display 195, a picture light 196, a camera 197, an acceleration sensor 198, and the like. It is configured. Among these, the acceleration sensor 198 is manufactured by using the inertial sensor 100 described above. Further, the acceleration sensor 198 may be attached to another position inside the upper casing 191 of the mobile phone 190 or a vacant area inside the lower casing 192, and is used for input interface, operation detection, and the like. It is done.

FIG. 18 is an explanatory diagram showing a schematic configuration of a video camera device which is a specific example of the electronic apparatus.
The illustrated video camera apparatus 510 includes a main body 510 and a lens 512 for photographing a subject in front of the main body 510. In addition, a start / stop switch 513 and a display unit 514 are provided on the front (lens side) side surface of the main body 511 and a viewfinder 515 is provided on the rear side of the main body 511. In addition, the main body 511 includes a recording device (not shown) that captures or records an image, an imaging element 516 such as a solid-state imaging device, and the like. The inertial sensor 100 is attached to a substrate 517 on which the image sensor 516 is mounted, and is used for camera shake correction or the like.

In the above-described embodiments, preferred specific examples of the present invention have been described. However, the present invention is not limited to the contents, and can be appropriately changed without departing from the gist thereof. .
For example, in the above-described embodiment, an inertial sensor has been described as a specific example of the MEMS. However, for example, other devices such as an optical switch that performs switching of connections in a circuit by an optical element without depending on an electronic element may be used. However, the present invention can be applied as long as it is configured using the MEMS structure.

  DESCRIPTION OF SYMBOLS 11 ... Drive part, 12 ... Support part, 13 ... Elastic support body, 21 ... Detection part, 30 ... Detection element part, 31 ... First beam part, 32 ... Second beam part, 33 ... Weight part

Claims (10)

A first beam portion having a flexibility arranged to extend along the first axial direction;
A second beam portion having a flexibility arranged to extend along a second axial direction orthogonal to the first axial direction;
A weight portion supported so as to be displaceable in at least two directions by the first beam portion and the second beam portion; and
A detection unit that detects a mechanical quantity acting on the weight unit based on the displacement of the weight unit;
The weight portion has a mode in which a difference occurs between the ease of rotation around the first axial direction and the ease of rotation around the second axial direction, with the first beam portion and the second beam portion being different from each other. Supported sensing element. With an excitation unit that applies drive vibration to the first beam unit, the second beam unit, and the weight unit,
The weight portion is configured such that the first beam portion and the second beam are more easily rotated around the axial direction along the direction of the drive vibration than around the axial direction perpendicular to the direction of the drive vibration. The detection element according to claim 1, wherein the detection element is supported by a portion. 3. The detection element according to claim 1, wherein the first beam portion and the second beam portion have different spring constants so that a difference in ease of rotation of the weight portion around each axis occurs. . The detection element according to claim 3, wherein the number of the first beam portions and the second beam portions are different from each other. The detection element according to claim 3, wherein the first beam portion and the second beam portion have different formation thicknesses in a direction perpendicular to each axial direction. The first beam portion and the second beam portion are different from each other in support connection positions with respect to the weight portions so that a difference in ease of rotation of the weight portions around each axis occurs. 2. The detection element according to 2. The detection element according to claim 1, wherein the weight portions have different mass distributions or cross-sectional second moments around each axis so that a difference in ease of rotation of the weight portions around each axis occurs. The detection element according to claim 1, wherein the first beam portion, the second beam portion, and the weight portion are configured using an SOI substrate. A first beam portion having a flexibility arranged to extend along the first axial direction;
A second beam portion having a flexibility arranged to extend along a second axial direction orthogonal to the first axial direction;
A weight portion supported so as to be displaceable in at least two directions by the first beam portion and the second beam portion; and
A detection unit for detecting the displacement of the weight part,
The weight portion has a mode in which a difference occurs between the ease of rotation around the first axial direction and the ease of rotation around the second axial direction, with the first beam portion and the second beam portion being different from each other. Supported microelectromechanical devices. A first beam portion having a flexibility arranged to extend along the first axial direction;
A second beam portion having a flexibility arranged to extend along a second axial direction orthogonal to the first axial direction;
A weight portion supported so as to be displaceable in at least two directions by the first beam portion and the second beam portion; and
A detection unit that detects a mechanical quantity acting on the weight unit based on the displacement of the weight unit;
The weight portion has a mode in which a difference occurs between the ease of rotation around the first axial direction and the ease of rotation around the second axial direction, with the first beam portion and the second beam portion being different from each other. An electronic device configured with a supported sensing element.

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