JP4775165B2 - Actuator - Google Patents

Description

  The present invention relates to an actuator.

For example, an optical scanner for performing drawing by optical scanning with a laser printer, a display, or the like is known that uses an actuator composed of a torsional vibrator (see, for example, Patent Document 1).
Patent Document 1 discloses an actuator including a torsional vibrator having a one-degree-of-freedom vibration system. Such an actuator has a structure in which a mass portion is supported by a torsion spring as a torsional vibrator of a one-degree-of-freedom vibration system. A light reflecting portion having light reflectivity is provided on the mass portion, and the mass portion is rotationally driven while torsionally deforming the torsion spring, and the light reflecting portion reflects and scans the light. Thereby, drawing can be performed by optical scanning.

In the actuator according to Patent Document 1, a p-type diffusion resistor having a longitudinal shape is formed on a linear torsion spring. Then, the mass portion is rotated while torsionally deforming the torsion spring, and the rotation angle of the mass portion is detected based on the amount of change in the specific resistance value of the diffusion resistance. By rotating the mass unit based on such a detection result, the behavior of the mass unit can be made desired. Here, the change in the specific resistance value of the diffusion resistance is due to a tensile stress or a compressive stress generated in the diffusion resistance due to the bending deformation of the diffusion resistance accompanying the torsional deformation of the torsion spring.
However, since the stress generated on the torsion spring is dominated by the shear stress rather than the tensile stress and the compressive stress, in the structure for detecting the tensile stress and the compressive stress on the torsion spring as in the actuator according to Patent Document 1, There was a problem that the change in the specific resistance value of the diffused resistor was small and the detection accuracy was low.

JP 2002-116403 A (see paragraph 0014 and the like)

  An object of the present invention is to provide an actuator capable of detecting the behavior of the mass part with high accuracy and making the behavior of the mass part desired.

Such an object is achieved by the present invention described below.
The actuator of the present invention includes a pair of first mass parts that form a plate shape,
Provided between the first mass of the pair, and the second mass to form a plate shape,
A support part;
A pair of elastically deformable first pairs that connect the support portion and the pair of first mass portions such that the pair of first mass portions are rotatable with respect to the support portion. The elastic part of
Elastically deformable to connect the pair of first mass parts and the second mass part so that the second mass parts can rotate with respect to the pair of first mass parts. A pair of second elastic portions;
Behavior detecting means for detecting the behavior of the second mass part ;
Based on the detection result of the behavior detecting means, the first mass portions are rotated while twisting and deforming the first elastic portions, and accordingly, the second elastic portions are twisted and deformed. An actuator having a driving means for rotating the second mass part ,
The pair of first mass parts, the second mass part, the support part, the pair of first elastic parts, and the pair of second elastic parts are (001) plane p-type. The silicon single crystal substrate is integrally formed by processing, and the first elastic portions and the second elastic portions extend along the <110> direction of the p-type silicon single crystal substrate. Exist,
The behavior detecting means, have a piezoresistive element comprising an n-type resistance region provided at an end portion of at least one of the second longitudinal direction on the elastic portion of the second elastic portion of said pair And it is comprised so that the behavior of the said 2nd mass part may be detected based on the change of the specific resistance value of this piezoresistive element.
Thereby, the relationship between the crystal orientation of the resistance region and the extending direction of the second elastic portion ( the rotation center axis direction of the second mass portion) is optimized, and with the rotation of the second mass portion. The specific resistance value of the resistance region changes greatly due to the shear stress generated on the second elastic portion. Therefore, the behavior of the second mass part can be detected with high accuracy based on the specific resistance value of the resistance region, and the behavior of the second mass part can be made as desired.

The actuator of the present invention includes a pair of first mass parts that form a plate shape,
Provided between the first mass of the pair, and the second mass to form a plate shape,
A support part;
A pair of elastically deformable first pairs that connect the support portion and the pair of first mass portions such that the pair of first mass portions are rotatable with respect to the support portion. The elastic part of
Elastically deformable to connect the pair of first mass parts and the second mass part so that the second mass parts can rotate with respect to the pair of first mass parts. A pair of second elastic portions;
Behavior detecting means for detecting the behavior of the second mass part ;
Based on the detection result of the behavior detecting means, the first mass portions are rotated while twisting and deforming the first elastic portions, and accordingly, the second elastic portions are twisted and deformed. An actuator having a driving means for rotating the second mass part ,
The pair of first mass portions, the second mass portion, the support portion, the pair of first elastic portions, and the pair of second elastic portions are (001) plane n-type. The silicon single crystal substrate is integrally formed by processing, and each of the first elastic portion and each of the second elastic portions is in the <100> direction or <010> of the n-type silicon single crystal substrate. Extending along the direction,
The behavior detecting means, have the piezoresistive element comprises a p-type resistance region provided at an end portion of at least one of the second longitudinal direction on the elastic portion of the second elastic portion of said pair And it is comprised so that the behavior of the said 2nd mass part may be detected based on the change of the specific resistance value of this piezoresistive element.
Thereby, the relationship between the crystal orientation of the resistance region and the extending direction of the second elastic portion ( the rotation center axis direction of the second mass portion) is optimized, and with the rotation of the second mass portion. The specific resistance value of the resistance region changes greatly due to the shear stress generated on the second elastic portion. Therefore, the behavior of the second mass part can be detected with high accuracy based on the specific resistance value of the resistance region, and the behavior of the second mass part can be made as desired.
In the actuator according to the aspect of the invention, the driving unit rotates the first mass portion while twisting and deforming the first elastic portion, and accordingly, the first elastic portion is twisted and deformed while the second elastic portion is twisted. Since the second mass portion is rotated, the deflection angle of the mass portion can be increased while reducing the driving voltage.
In the actuator of the present invention, since the piezoresistive element is provided on the second elastic portion, the amount of change in the specific resistance value of the piezoresistive element accompanying the rotation of the mass portion is increased, and the mass The behavior of the part can be detected with high accuracy. In general, the deflection angle of the second mass part is larger than the deflection angle of the first mass part, and the torsional deformation amount of the second elastic part is larger than the torsional deformation amount of the first elastic part. Because.
Further, in the actuator according to the present invention, the piezoresistive element is provided at an end portion in the longitudinal direction of the second elastic portion, and a shear stress generated on the second elastic portion due to torsional deformation of the second elastic portion is The second elastic portion increases from the central portion toward the end in the longitudinal direction. Therefore, the change amount of the specific resistance value of the piezoresistive element with respect to the rotation angle of the mass part can be increased to improve the detection accuracy of the mass part.

In the actuator of the present invention, it is preferable that the resistance region is formed by doping impurities on the surface of the second elastic portion.
Thereby, the crystal orientation of the resistance region can be set to a desired one relatively easily.
In the actuator of the present invention, the piezoresistive element includes a pair of input electrodes juxtaposed on the resistance region in a direction perpendicular to the rotation center axis of the second mass unit, and the resistance region. A pair of output electrodes juxtaposed in the direction of the central axis of rotation, while applying an electric field to the resistance region via the pair of input electrodes, and via the pair of output electrodes It is preferable to be configured to detect the specific resistance value of the resistance region.
As a result, the specific resistance value change in the resistance region with respect to the rotation amount of the mass part is detected as a voltage value change between the pair of output electrodes, and the voltage value change is caused only by the shear stress on the elastic part. it can. Therefore, the behavior of the mass portion can be detected with higher accuracy, and the behavior of the mass portion can be made more surely desired.

In the actuator according to the aspect of the invention, it is preferable that the output electrode is connected to a differential amplifier circuit.
Thereby, a change in specific resistance value (voltage value change) of the piezoresistive element can be detected with high accuracy (with high sensitivity). As a result, the behavior of the mass part can be detected with higher accuracy.
In the actuator according to the aspect of the invention, the piezoresistive element is provided on each second elastic part on one surface side of the second mass part, and one of the pair of piezoresistive elements. The direction of the electric field in the piezoresistive element is preferably the same as the direction of the electric field in the other piezoresistive element.
Thereby, the change in the specific resistance value of the piezoresistive element can be detected with higher accuracy (with high sensitivity) as the voltage value change. As a result, the behavior of the mass part can be detected with higher accuracy.

In the actuator according to the aspect of the invention, it is preferable that the pair of piezoresistive elements is provided symmetrically with respect to the second mass portion.
Thereby, a change in the specific resistance value of the piezoresistive element can be detected as a voltage value change with higher accuracy (with high sensitivity). As a result, the behavior of the mass portion can be detected with extremely high accuracy.

In the actuator according to the aspect of the invention, it is preferable that the second mass portion is provided with a light reflecting portion.
Thereby, the actuator can be applied to an optical device such as an optical scanner, an optical attenuator, or an optical switch.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of an actuator of the invention will be described with reference to the accompanying drawings.
<First Reference Example >
First, a first reference example of the actuator of the present invention will be described.
1 is a plan view showing a first reference example of the actuator of the present invention, FIG. 2 is a sectional view taken along line AA in FIG. 1, FIG. 3 is a sectional view taken along line BB in FIG. FIG. 5 is a partially enlarged perspective view showing a second mass part and a second elastic part of the actuator shown in FIG. 1, and FIGS. 5 and 6 illustrate a piezoresistive element provided in the actuator shown in FIG. 1, respectively. FIG. 7 is a diagram showing the relationship between the crystal orientation and the piezoresistance coefficient in the (001) plane silicon substrate, FIG. 8 is a diagram showing a schematic configuration of the actuator control system shown in FIG. 1, and FIG. FIG. 10 is a diagram showing an example of the voltage waveform of the drive voltage of the actuator shown in FIG. 1. FIG. 10 shows the frequency of the AC voltage when the AC voltage is used as the drive voltage of the actuator shown in FIG. Relationship with amplitude of each second mass part It is a graph showing. In the following, for convenience of explanation, the front side of the page in FIG. 1 is referred to as “up”, the back side of the page is referred to as “down”, the right side is referred to as “right”, and the left side is referred to as “left”. The upper side is called “upper”, the lower side is called “lower”, the right side is called “right”, and the left side is called “left”.

The actuator 1 has a base 2 having a two-degree-of-freedom vibration system as shown in FIGS. 1 to 3 and a support substrate 3 that supports the base 2.
The base body 2 includes a pair of first mass units (drive units) 21 and 22, a pair of support units 23 and 24, a second mass unit (movable unit) 25, and a pair of first elastic members. Parts 26 and 27, a pair of second elastic parts 28 and 29, and a pair of electrodes 32 and 33. Here, the first mass parts 21, 22, the first elastic parts 26, 27 and the second elastic parts 28, 29 are different from the second mass part 25, which is a mass part, with respect to the support parts 23, 24. It is a pair of elastic parts that connect the second mass part 25 and the support parts 23 and 24 so as to be rotatable.

  In such an actuator 1, by applying a voltage to the pair of electrodes 32 and 33, the pair of first elastic portions 26 and 27 is twisted and deformed, and the pair of first mass portions 21 is formed. , 22 is rotated, and the second mass portion 25 is rotated while twisting and deforming the pair of second elastic portions 28, 29. At this time, the pair of first mass parts 21 and 22 and the second mass part 25 rotate about the rotation center axis X shown in FIG.

The pair of first mass portions 21 and 22 each have a plate shape, and have substantially the same dimensions and the same shape.
Further, combs having a comb-tooth shape are formed at both ends (both ends on the distal side from the rotation center axis X) in a direction perpendicular to the rotation center axis X in a plan view of the first mass unit 21. Toothed electrode portions 211 and 212 are provided. Similarly, both ends in the direction perpendicular to the rotation center axis X in the plan view of the first mass portion 22 (both ends on the distal side from the rotation center axis X) are comb-like. Comb-like electrode portions 221 and 222 are provided.

Moreover, the 2nd mass part 25 is provided between the pair of mass parts 21 and 22, and the pair of mass parts 21 and 22 is the second mass part in a plan view in FIG. 25 is provided so as to be substantially symmetrical with respect to 25.
The second mass unit 25 has a plate shape, and a light reflection unit 251 is provided on the plate surface. Thereby, the actuator 1 can be applied to optical devices such as an optical scanner, an optical attenuator, and an optical switch.
In such first mass parts 21, 22 and second mass part 25, the first mass parts 21, 22 are connected to the support parts 23, 24 via the first elastic parts 26, 27. The second mass portion 25 is connected to the first mass portions 21 and 22 via the second elastic portions 28 and 29.

The first elastic portion 26 connects the first mass portion 21 and the support portion 23 so that the first mass portion 21 can be rotated with respect to the support portion 23. Similarly, the first elastic portion 27 connects the first mass portion 22 and the support portion 24 so that the first mass portion 22 can be rotated with respect to the support portion 24. .
The second elastic portion 28 connects the second mass portion 25 and the first mass portion 21 so that the second mass portion 25 can be rotated with respect to the first mass portion 21. Yes. Similarly, the second elastic portion 29 is configured so that the second mass portion 25 and the first mass portion 22 are configured so that the second mass portion 25 can be rotated with respect to the first mass portion 22. Are linked.

The first elastic portions 26 and 27 and the second elastic portions 28 and 29 are provided coaxially. The first mass portions 21 and 22 are set with the rotation central axis (rotation axis) X as the first elastic portions 26 and 27 and the second elastic portions 28 and 29. The second mass portion 25 is rotatable with respect to the support portions 23 and 24 and the second mass portion 25 is rotatable with respect to the first mass portions 21 and 22.
As described above, the base 2 includes the first vibration system including the first mass parts 21 and 22 and the first elastic parts 26 and 27, the second mass part 25, and the second elastic part 28. , 29 and a second vibration system. That is, the base body 2 has a two-degree-of-freedom vibration system including a first vibration system and a second vibration system.

  Such a two-degree-of-freedom vibration system is formed thinner than the entire thickness of the base 2 and is located above the base 2 in the vertical direction in FIGS. 2 and 3. In other words, the base 2 is formed with a portion thinner than the entire thickness of the base 2, and the odd-shaped holes are formed in the thin portion, whereby the first mass parts 21, 22 and the second mass are formed. The mass portion 25, the first elastic portions 26 and 27, and the second elastic portions 28 and 29 are formed.

In the present reference example , the upper surface of the thin portion is positioned on the same plane as the upper surfaces of the support portions 23 and 24, so that the mass portions 21, 22, and 25 are rotated below the thin portion. A space (concave portion) 30 is formed.
Such a substrate 2 is formed by processing a (001) plane p-type silicon single crystal substrate or an n-type silicon single crystal substrate, as will be described later. That is, the first mass parts 21 and 22, the second mass part 25, the support parts 23 and 24, the first elastic parts 26 and 27, and the second elastic parts 28 and 29 are (001 ) Surface p-type silicon single crystal substrate or n-type silicon single crystal substrate is integrally formed.

  When the base 2 is formed by processing a (001) plane p-type silicon single crystal substrate, the first elastic portions 26 and 27 and the second elastic portions 28 and 29 are respectively It extends along the <110> direction of the (001) plane p-type silicon single crystal substrate. On the other hand, when the base 2 is formed by processing a (001) -plane n-type silicon single crystal substrate, the first elastic portions 26 and 27 and the second elastic portions 28 and 29 are (001 ) Plane extending along the <100> direction or the <010> direction of the n-type silicon single crystal substrate.

  The base 2 is made of a substrate having a laminated structure, such as an SOI substrate, from the first mass parts 21, 22, the second mass part 25, the support parts 23, 24, and the first elastic parts 26, 27. Alternatively, the second elastic portions 28 and 29 and the electrodes 32 and 33 may be formed. In that case, the 1st mass parts 21 and 22, the 2nd mass part 25, a part of support parts 23 and 24, the 1st elastic parts 26 and 27, and the 2nd elastic parts 28 and 29, Are preferably formed of one layer of a substrate having a laminated structure.

As shown in FIGS. 1 and 4, a piezoresistive element 41 is provided on the upper surface of the second elastic portion 28 described above along the longitudinal direction thereof. Similarly, as shown in FIGS. 1 and 4, a piezoresistive element 42 is provided on the upper surface of the second elastic portion 29 along the longitudinal direction thereof.
More specifically, the piezoresistive element 41 is provided in the central portion of the second elastic portion 28 in the rotation central axis X direction in the plan view of the second mass portion 25.

  As shown in FIGS. 5 and 6, the piezoresistive element 41 includes a resistance region 411 formed by diffusion or ion implantation of an n-type or p-type impurity provided on the second elastic portion 28, and a resistance. A pair of input electrodes 412 and 413 juxtaposed in a direction perpendicular to the rotation center axis X on the region 411 and a pair of output electrodes juxtaposed in the direction of the rotation center axis X on the resistance region 411 414, 415.

  The resistance region 411 is formed by doping impurities on the surface of the second elastic portion 28. More specifically, when the base 2 is formed by processing a (001) plane p-type silicon single crystal substrate, the surface of the second elastic portion 28 is doped with an impurity such as phosphorus. It is the formed n-type silicon single crystal (n-type resistance region). On the other hand, when the base 2 is formed by processing a (001) plane n-type silicon single crystal substrate, p formed by doping impurities such as boron on the surface of the second elastic portion 28. Type silicon single crystal (p-type resistance region).

When the base 2 is formed by processing a (001) -plane p-type silicon single crystal substrate, along the <110> direction of the resistance region 411 (that is, the rotation center axis X direction). The second elastic portion 28 extends. On the other hand, when the base 2 is formed by processing an (001) -plane n-type silicon single crystal substrate, the <100> direction or <010> direction (that is, the rotation center axis X of the resistance region 411). The second elastic portion 28 extends along (direction).
When the second elastic portion 28 extends along such a crystal orientation, when a shear stress is generated in the resistance region 411 due to torsional deformation of the second elastic portion 28, the specific resistance value of the resistance region 411 is obtained. The rate of change can be maximized.

Here, the relationship between the crystal orientation in the resistance region 411 and the change rate of the specific resistance value will be described.
When the second elastic portion 28 is torsionally deformed, shear stress is predominantly generated on the upper surface of the second elastic portion 28 rather than tensile stress or compressive stress. Thereby, a shear stress is generated in the resistance region 411.
On the other hand, when the shear stress τ _xy is generated in the silicon single crystal (cubic crystal), the specific resistance change rate Δρ _xy / ρ ₀ in the silicon single crystal is expressed by the following equation (1).

Δρ _xy / ρ ₀ = π _s τ _xy (1)
Here, π _s is a piezoresistance coefficient.
As apparent from the equation (1), under a constant shear stress τ _xy , the specific resistance change rate Δρ _xy / ρ ₀ in the silicon single crystal increases as the piezoresistance coefficient π _s increases. That is, as the piezoresistance coefficient π _s increases, the specific resistance value of the silicon single crystal greatly changes with respect to the shear stress τ _xy generated in the silicon single crystal.
The piezoresistance coefficient has anisotropy due to the crystal structure of the silicon single crystal. When the silicon single crystal is p-type, the piezoresistance coefficient π _s is < It becomes maximum at 010> orientation or <100> orientation. On the other hand, when the silicon single crystal is n-type, the piezoresistance coefficient π _s is maximum in the <110> orientation, as shown in FIG.

  In the actuator 1, as described above, when the base 2 is formed by processing a (001) plane p-type silicon single crystal substrate, the resistance region 411 is an n-type silicon single crystal, and The second elastic portion 28 extends along the <110> direction of the resistance region 411 (that is, the rotation center axis X direction). On the other hand, when the base 2 is formed by processing a (001) -plane n-type silicon single crystal substrate, the resistance region 411 is a p-type silicon single crystal, and the resistance region 411 < The second elastic portion 28 extends along the 100> direction or the <010> direction (that is, the rotation center axis X direction).

Therefore, the specific resistance value of the resistance region 411 changes greatly with respect to the shear stress generated in the resistance region 411.
An input electrode 412 is provided at one end (upper end in FIGS. 5 and 6) of the both ends in the direction perpendicular to the rotation center axis X on the resistance region 411 and the other end. An input electrode 413 is provided on the portion (the lower end in FIGS. 5 and 6). The input electrode 412 is connected to the terminal 416 provided on the support portion 23 described above, and the input electrode 413 is connected to the terminal 417 provided on the support portion 23 described above (see FIG. 1). A voltage can be applied between the pair of input electrodes 412 and 413 through such terminals 416 and 417.

  In addition, an output electrode 414 is provided at one end (the left end in FIGS. 5 and 6) of the both ends in the rotation center axis X direction on the resistance region 411, and the other end (see FIGS. 5 and 6). An output electrode 415 is provided at the right end in FIG. The output electrode 414 is connected to the terminal 418 provided on the support part 23 described above, and the output electrode 415 is connected to the terminal 419 provided on the support part 23 described above (see FIG. 1). The voltage value and specific resistance value between the pair of output electrodes 414 and 415 can be detected via such terminals 418 and 419.

In the piezoresistive element 41 configured as described above, an electric field is applied to the resistance region 411 via the pair of input electrodes 412 and 413, and the resistance region 411 is set via the pair of output electrodes 414 and 415. The voltage value (specific resistance value) is detected.
More specifically, an electric field is generated on the resistance region 411 by applying a voltage between the pair of input electrodes 412 and 413. When a shear stress is generated in the resistance region 411 under such an electric field, a potential difference is generated between the pair of output electrodes 414 and 415. This potential difference depends on the specific resistance value of the resistance region 411, the torsional deformation amount of the second elastic portion 28, and the rotation angle of the second mass portion 25. Therefore, the behavior of the second mass unit 25 can be detected based on this potential difference.

  When the piezoresistive element 41 is configured as described above, a change in the specific resistance value of the resistance region 411 with respect to the rotation amount of the second mass unit 25 is detected as a voltage value change, and the voltage value change is detected by the second elasticity. It can be due only to the shear stress on the portion 28. Therefore, the behavior of the second mass unit 25 can be detected with higher accuracy, and the behavior of the second mass unit 25 can be made more surely desired.

  Similarly to the piezoresistive element 41 described above, the piezoresistive element 42 also includes an n-type or p-type resistance region 421 provided on the second elastic portion 29, as shown in FIGS. A pair of input electrodes 422 and 423 juxtaposed in a direction perpendicular to the rotation center axis X on the resistance region 421 and a pair of outputs juxtaposed in the direction of the rotation center axis X on the resistance region 421 And electrodes 424 and 425.

  The resistance region 421 is formed by doping impurities on the surface of the second elastic portion 29. Here, when the base 2 is formed by processing a (001) plane p-type silicon single crystal substrate, it follows the <110> direction of the resistance region 421 (that is, the rotation center axis X direction). Thus, the second elastic portion 29 extends. On the other hand, when the base 2 is formed by processing an (001) -plane n-type silicon single crystal substrate, the <100> direction or <010> direction of the resistance region 421 (that is, the rotation center axis X The second elastic portion 29 extends along (direction).

When the second elastic portion 29 extends along such a crystal orientation, when a shear stress is generated in the resistance region 421 due to the torsional deformation of the second elastic portion 29, the same as the resistance region 411 described above. In addition, the rate of change of the specific resistance value of the resistance region 421 can be maximized.
The input electrode 422 is provided at one end (upper end in FIG. 6) of the both ends in the direction perpendicular to the rotation center axis X on the resistance region 421, and the other end (see FIG. 6 is provided with an input electrode 423 at the lower end). The input electrode 422 is connected to the terminal 426 provided on the support 24 described above, and the input electrode 423 is connected to the terminal 427 provided on the support 24 described above (see FIG. 1). A voltage can be applied between the pair of input electrodes 422 and 423 through such terminals 426 and 427.

  In addition, an output electrode 424 is provided at one end (the left end in FIG. 6) of both ends in the rotation center axis X direction on the resistance region 421, and the other end (the right side in FIG. 6). An output electrode 425 is provided at the end). The output electrode 424 is connected to the terminal 428 provided on the support 24 described above, and the output electrode 425 is connected to the terminal 429 provided on the support 24 described above (see FIG. 1). The voltage value and specific resistance value between the pair of output electrodes 424 and 425 can be detected through such terminals 428 and 429.

In the piezoresistive element 42 configured as described above, an electric field is applied to the resistance region 421 via the pair of input electrodes 422 and 423, and the resistance region 421 is set via the pair of output electrodes 424 and 425. The voltage value (specific resistance value) is detected.
More specifically, an electric field is generated on the resistance region 421 by applying a voltage between the pair of input electrodes 422 and 423. When a shear stress is generated in the resistance region 421 under such an electric field, a potential difference is generated between the pair of output electrodes 414 and 415 depending on the degree of the shear stress. This potential difference depends on the specific resistance value of the resistance region 421, the torsional deformation amount of the second elastic portion 29, and the rotation angle of the second mass portion 25. Therefore, the behavior of the second mass unit 25 can be detected based on this potential difference.

  When the piezoresistive element 42 is configured as described above, a change in the specific resistance value of the resistance region 421 with respect to the rotation amount of the second mass unit 25 is detected as a voltage value change, and the voltage value change is detected by the second elasticity. It can be due only to the shear stress on the part 29. Therefore, the behavior of the second mass unit 25 can be detected with higher accuracy, and the behavior of the second mass unit 25 can be made more surely desired.

  In particular, the relationship between the crystal orientation of the resistance regions 411 and 421 and the extending direction of the second elastic portions 28 and 29 (the rotation center axis X direction of the second mass portion 25) is optimized, and the second mass The specific resistance values of the resistance regions 411 and 421 greatly change due to the shear stress generated on the second elastic portions 28 and 29 as the portion 25 rotates. Therefore, based on the specific resistance values of the resistance regions 411 and 421, the behavior of the second mass unit 25 can be detected with high accuracy, and the behavior of the second mass unit 25 can be set as desired.

In such piezoresistive elements 41 and 42, the impurity concentrations in the resistance regions 411 and 421 are not particularly limited, but are, for example, 1.0 × 10 ^{18 to} 1.0 × 10 ²⁰ cm ⁻³ . Is preferred. In this reference example , although not shown in the drawing, an insulating layer such as a silicon oxide film is formed on the upper surface of the substrate 2 other than the piezoresistive elements 41 and 42 in FIG. 2, and a terminal is formed on the insulating layer. 416 to 419, 426 to 429 and wirings are formed.

  The electrodes 32 and 33 are connected to the first mass parts 21 and 22, the second mass part 25, the support parts 23 and 24, the first elastic parts 26 and 27, and the second elastic parts 28 and 29. , Separated. Thus, the electrodes 32 and 33 are connected to the first mass parts 21 and 22, the second mass part 25, the support parts 23 and 24, the first elastic parts 26 and 27, and the second elastic parts 28 and 29. It is electrically insulated.

The electrode 32 includes a comb-like electrode portion 321 provided so as to mesh with the comb-like electrode portion 211 of the first mass portion 21 described above with a space therebetween, and a comb-teeth of the first mass portion 22. A comb-like electrode portion 322 is formed so as to mesh with the electrode portion 221 with a space therebetween.
Similarly to this, the electrode 33 includes a comb-like electrode portion 331 provided so as to be engaged with the comb-like electrode portion 212 of the first mass portion 21 with a space therebetween, and the first mass portion 22. The comb-tooth-shaped electrode portion 332 is formed so as to mesh with the comb-tooth-shaped electrode portion 222 while being spaced apart from each other.

  Here, it is preferable that the comb-shaped electrode portion 211 is initially displaced in the vertical direction with respect to the comb-shaped electrode portion 321. In the same manner, the comb-like electrode part 212 is for the comb-like electrode part 331, the comb-like electrode part 221 is for the comb-like electrode part 322, and the comb-like electrode part 222 is for the comb-like electrode part 332. On the other hand, it is preferable that the initial displacement is in the vertical direction. Thereby, the start of the rotational drive of the 1st mass parts 21 and 22 can be simplified.

The electrodes 32 and 33 are connected to a power supply circuit 12 to be described later, and are configured so that an AC voltage (drive voltage) can be applied to the electrodes 32 and 33.
The support substrate 3 bonded to the base 2 as described above is made of, for example, glass or silicon as a main material.
As shown in FIGS. 2 and 3, an opening 31 is formed in the upper surface of the support substrate 3 at a portion corresponding to the second mass portion 25.

The opening 31 constitutes an escape portion that prevents contact with the support substrate 3 when the second mass portion 25 rotates (vibrates). By providing the opening (escape portion) 31, the deflection angle (amplitude) of the second mass portion 25 can be set larger while preventing the actuator 1 from being enlarged.
Note that the relief portion as described above is not necessarily opened (opened) on the lower surface (the surface opposite to the second mass portion 25) of the support substrate 3 as long as the above-described effect can be sufficiently exerted. May be. In other words, the escape portion can also be configured by a recess formed on the upper surface of the support substrate 3. Further, when the depth of the space 30 is larger than the deflection angle (amplitude) of the second mass portion 25, the escape portion need not be provided.

Here, the control system of the actuator 1 will be described.
As shown in FIG. 8, the actuator 1 according to this reference example includes a detection circuit 11 connected to the piezoresistive elements 41 and 42, a power supply circuit 12 that applies a voltage to the electrodes 32 and 33, and a detection circuit 11. And a control circuit 13 (control means) for controlling driving of the power supply circuit 12 in accordance with the output signal.

  The detection circuit 11 includes a differential amplifier circuit 112 (differential amplifier) that amplifies a voltage according to a change in specific resistance value of the piezoresistive elements 41 and 42. The detection circuit 11 configured in this way outputs a signal corresponding to the distortion amount (deformation amount) of the piezoresistive elements 41 and 42. That is, the detection circuit 11 detects the behavior of the second mass unit 25 based on the change in the specific resistance value of the piezoresistive elements 41 and 42 provided on the second elastic portions 28 and 29 described above. It is configured. That is, the detection circuit 11 and the piezoresistive elements 41 and 42 constitute a behavior detection unit that detects the behavior of the mass unit 25.

The power supply circuit 12 is configured to apply an AC voltage as a drive voltage to the electrodes 32 and 33. Here, the electrodes 32 and 33 and the power supply circuit 12 constitute driving means for driving the first mass parts 21 and 22 to rotate.
The control circuit 13 is configured to control driving of the power supply circuit 12 based on the output signal of the detection circuit 11.

The actuator 1 having the above configuration is driven as follows.
That is, for example, a sine wave (AC voltage) or the like is applied to the electrodes 32 and 33. Specifically, for example, the first mass parts 21 and 22 are grounded, a voltage having a waveform as shown in FIG. 9A is applied to the electrode 32, and the electrode 33 is applied to FIG. 9B. A voltage having a waveform as shown in FIG. That is, a voltage is applied alternately to the electrode 32 and the electrode 33. Then, between the electrode 32 and the first mass parts 21 and 22 (more specifically, between the comb-like electrode part 321 and the comb-like electrode part 211 and between the comb-like electrode part 322 and the comb. (Between the tooth-like electrode part 221), between the electrode 33 and the first mass parts 21 and 22 (more specifically, between the comb-like electrode part 331 and the comb-like electrode part 212, and The electrostatic attractive force is alternately generated between the comb-shaped electrode portion 332 and the comb-shaped electrode portion 222).

This electrostatic force causes the first elastic portions 26 and 27 to vibrate (rotate around the rotation center axis X) so as to be inclined with respect to the plate surface of the support substrate 3 (the paper surface in FIG. 1). Move).
The second mass part 25 connected via the second elastic parts 28 and 29 in accordance with the vibration (drive) of the first mass parts 21 and 22 is also connected to the second elastic part 28, With the axis 29 as an axis (that is, around the rotation center axis X), it vibrates (rotates) so as to be inclined with respect to the plate surface of the support substrate 3 (the paper surface in FIG. 1).

At this time, shear stress is mainly generated on the second elastic portions 28 and 29 that are torsionally deformed. Thereby, the piezoresistive elements 41 and 42 are each subjected to shear stress.
More specifically, for example, when the second elastic portion 28 is torsionally deformed when the second mass portion 25 is rotated, the resistance region 411 of the piezoresistive element 41 has a direction as indicated by an arrow in FIG. Shear stress is generated.

Similarly, when the second elastic portion 29 is torsionally deformed when the second mass portion 25 is rotated, a shear stress is applied to the resistance region 421 of the piezoresistive element 42 in the direction indicated by the arrow in FIG. Occurs.
As shown in FIG. 6, the resistance regions 411 and 421 that receive such shear stress have the same electric field direction. Therefore, as the second mass unit 25 rotates, one of the specific resistance value of the piezoresistive element 41 and the specific resistance value of the piezoresistive element 42 increases and the other decreases.

Such changes in the specific resistance values of the piezoresistive elements 41 and 42 correspond to the amount of torsional deformation of the second elastic portion 28 (the amount of rotation of the second mass portion 25), respectively.
When the specific resistance values of the piezoresistive elements 41 and 42 change with the rotation of the second mass unit 25 in this way, the output signal (voltage value) of the detection circuit 11 shown in FIG. 5 according to the change amount. Also changes.

That is, the output signal from the detection circuit 11 corresponds to the behavior of the second mass unit 25 (for example, the rotation angle, amplitude, frequency, etc.).
Therefore, the control circuit 13 can control the drive of the power supply circuit 12 based on the output signal from the detection circuit 11 to make the behavior of the second mass unit 25 desired.
In particular, since the actuator 1 is configured to amplify a voltage corresponding to a change in the specific resistance value of the piezoresistive elements 41 and 42 by the differential amplifier circuit 112, a change in the specific resistance value of the piezoresistive elements 41 and 42 is achieved. (Voltage change) can be detected with high accuracy (with high sensitivity). As a result, the behavior of the second mass unit 25 can be detected with higher accuracy.

Here, since the direction of the electric field in the piezoresistive element 41 and the direction of the electric field in the piezoresistive element 42 are the same, the voltage corresponding to the change in the specific resistance value can be amplified by the differential amplifier circuit 112. It is possible to detect a change in the specific resistance value of the piezoresistive elements 41 and 42 with higher accuracy (with high sensitivity). As a result, the behavior of the second mass unit 25 can be detected with higher accuracy.
Further, since the pair of piezoresistive elements 41 and 42 are provided symmetrically with respect to the second mass part 25 in plan view, the specific resistance value change of the piezoresistive elements 41 and 42 is regarded as a voltage value change. Further, it can be detected with high accuracy (with high sensitivity). As a result, the behavior of the second mass unit 25 can be detected with extremely high accuracy.

As described above, as described above, the actuator 1 of this reference example has the crystal orientation of the resistance regions 411 and 421 and the extending direction of the second elastic portions 28 and 29 (rotation central axis X direction). Since the relationship is optimized, the specific resistance values of the resistance regions 411 and 421 greatly change due to the shear stress generated on the second elastic portions 28 and 29 as the second mass portion 25 rotates. Therefore, based on the specific resistance values of the resistance regions 411 and 421, the behavior of the second mass unit 25 can be detected with high accuracy, and the behavior of the second mass unit 25 can be set as desired.

Since the resistance regions 411 and 412 as described above are formed by doping impurities on the surfaces of the second elastic portions 28 and 29, the crystal orientation of the resistance regions 411 and 421 can be set to a desired direction relatively easily. That is, the crystal orientation of the resistance regions 411 and 421 can be made exactly parallel to the rotation center axis X direction.
In this reference example , the piezoresistive element 41 is provided at the center of the second elastic portion 28 in the longitudinal direction, and the piezoresistive element 42 is provided at the center of the second elastic portion 29 in the longitudinal direction. ing. The shear stress generated on the second elastic portions 28 and 29 due to the torsional deformation of the second elastic portions 28 and 29 is the central portion in the longitudinal direction of the second elastic portions 28 and 29 and extends in the longitudinal direction. Almost constant. Therefore, when the resistance regions 411 and 412 are formed at the time of manufacturing the actuator 1, it is possible to reduce variations in the quality of the actuator 1 for each product even if the formation position does not require high accuracy. As a result, the cost of the actuator 1 can be reduced.

  The piezoresistive element 41 may be provided at an end portion in the longitudinal direction of the second elastic portion 28, and the piezoresistive element 42 is provided at an end portion in the longitudinal direction of the second elastic portion 29. It may be done. The shear stress generated on the second elastic portions 28 and 29 due to the torsional deformation of the second elastic portions 28 and 29 increases from the center portion to the end portion in the longitudinal direction of the second elastic portions 28 and 29. Yes. Therefore, when the piezoresistive elements 41 and 42 are arranged as described above, the amount of change in the specific resistance value of the piezoresistive elements 41 and 42 with respect to the rotation angle of the second mass part 25 is increased, and the second mass part. 25 detection accuracy can be improved.

The length of the first substantially vertical direction from the rotational center axis X to the mass portion 21 (longitudinal direction) (the maximum length) and L _1, the rotational axis X of the first mass portion 22 the length in the direction substantially perpendicular thereto from the length in the (longitudinal) (maximum length) of the L _2, substantially perpendicular to the rotational axis X of the second mass portion 25 (the longitudinal direction) When the length (maximum length) is L ₃ , in the present reference example , the first mass parts 21 and 22 are provided independently of each other, and therefore the size (length L) of the second mass part 25 is provided. Regardless of ₃ ), the first mass parts 21 and 22 and the second mass part 25 do not interfere with each other, and L ₁ and L ₂ can be reduced. Thereby, the rotation angle (swing angle) of the first mass parts 21 and 22 can be increased, and as a result, the rotation angle of the second mass part 25 can be increased.

Further, the dimensions of the first mass portions 21 and 22 and the second mass portion 25, _{respectively,} preferably set to satisfy L 1 _{<L 3} and _L 2 _{<L 3} becomes relevant.
By satisfying the above relationship, L ₁ and L ₂ can be made smaller, the rotation angle of the first mass parts 21 and 22 can be made larger, and the rotation angle of the second mass part 25 can be further increased. Can be bigger.

In this case, it is preferable that the maximum rotation angle of the second mass unit 25 is configured to be 20 ° or more.
By these, the low voltage drive of the 1st mass parts 21 and 22 and the vibration (rotation) in the large rotation angle of the 2nd mass part 25 are realizable.
For this reason, when such an actuator 1 is applied to, for example, an optical scanner used in an apparatus such as a laser printer or a scanning confocal laser microscope, the apparatus can be more easily downsized.

As described above, in this reference example , L ₁ and L ₂ are set to be approximately equal, but it goes without saying that L ₁ and L ₂ may be different.
By the way, in such a vibration system (two-degree-of-freedom vibration system) of the mass parts 21, 22, 25, the amplitude (deflection angle) of the first mass parts 21, 22 and the second mass part 25 and the AC applied A frequency characteristic as shown in FIG. 9 exists between the frequency of the voltage.

That is, the vibration system has two resonance frequencies fm ₁ [kHz] and fm ₃ [kHz] (however, fm) in which the amplitude of the first mass parts 21 and 22 and the amplitude of the second mass part 25 are increased. ₁ <fm ₃ ) and one anti-resonance frequency fm ₂ [kHz] at which the amplitude of the first mass parts 21 and 22 is substantially zero.
In this vibration system, it is preferable that the frequency F of the alternating voltage applied to the electrodes 32 and 33 is set so as to be approximately equal to the lower of the two resonance frequencies, that is, fm ₁ . Thereby, the deflection angle (rotation angle) of the 2nd mass part 25 can be enlarged, suppressing the amplitude of the 1st mass parts 21 and 22. FIG.

In this specification, F [kHz] and fm ₁ [kHz] being substantially equal means that the condition of (fm ₁ −1) ≦ F ≦ (fm ₁ +1) is satisfied.
The average thicknesses of the first mass parts 21 and 22 are each preferably 1 to 1500 μm, and more preferably 10 to 300 μm.
The average thickness of the second mass part 25 is preferably 1 to 1500 μm, and more preferably 10 to 300 μm.
The spring constant k ₁ of the first elastic portions 26 and 27 is preferably 1 × 10 ⁻⁴ to 1 × 10 ⁴ Nm / rad, and preferably 1 × 10 ⁻² to 1 × 10 ³ Nm / rad. Is more preferably 1 × 10 ⁻¹ to 1 × 10 ² Nm / rad. Thereby, the rotation angle (swing angle) of the second mass unit 25 can be further increased.

On the other hand, the spring constant k ₂ of the second elastic portions 28 and 29 is preferably 1 × 10 ⁻⁴ to 1 × 10 ⁴ Nm / rad, and 1 × 10 ⁻² to 1 × 10 ³ Nm / rad. More preferably, it is 1 × 10 ⁻¹ to 1 × 10 ² Nm / rad. Thereby, the deflection angle of the second mass unit 25 can be further increased while suppressing the deflection angle of the first mass units 21 and 22.

Further, the spring constant _{k 1} of the first resilient portion 26, 27 and _{k 2} the spring constant of the second elastic portion 28, _29, preferably satisfies the k 1> _{k 2} the relationship. Thereby, the rotation angle (swing angle) of the second mass unit 25 can be further increased while suppressing the deflection angle of the first mass units 21 and 22.
Furthermore, the moment of inertia of the first mass portions 21 and 22 and _{J 1,} when the moment of inertia of the second mass 25 has a _{J 2,} and _{J 1} and _{J 2,} the _{J 1} ≦ _{J 2} the relationship It is preferable to satisfy, and it is more preferable to satisfy the relationship of J ₁ <J ₂ . Thereby, the rotation angle (swing angle) of the second mass unit 25 can be further increased while suppressing the deflection angle of the first mass units 21 and 22.

By the way, the natural frequency ω ₁ of the first vibration system including the first mass parts 21 and 22 and the first elastic parts 26 and 27 is the inertia moment J _{1 of} the first mass parts 21 and 22, and According to the spring constant k _{1 of} the first elastic part 26, 27, it is given by ω ₁ = (k ₁ / J ₁ ) ^1/2 . On the other hand, the natural frequency ω ₂ of the second vibration system including the second mass part 25 and the second elastic parts 28 and 29 is the inertia moment J _{2 of} the second mass part 25 and the second elasticity. With the spring constant k ₂ of the parts 28, 29, it is given by ω ₂ = (k ₂ / J ₂ ) ^1/2

It is preferable that the natural frequency ω ₁ of the first vibration system and the natural frequency ω ₂ of the second vibration system obtained in this way satisfy the relationship ω ₁ > ω ₂ . Thereby, the rotation angle (swing angle) of the second mass unit 25 can be further increased while suppressing the deflection angle of the first mass units 21 and 22.
As described above, the actuator 1 having the two-degree-of-freedom vibration system can increase the deflection angle of the second mass unit 25 while reducing the drive voltage. In particular, the actuator 1 of this reference example is configured to rotate the first mass portions 21 and 22 using the comb-like electrode portions 211, 212, 221, 222, 321, 322, 331, and 332 as described above. Therefore, the rotation angle of the first mass portions 21 and 22 is made larger than that in which the first mass portions 21 and 22 are rotated using parallel plate type electrodes. Accordingly, the rotation angle of the second mass unit 25 can be increased.

  In addition, as described above, in the actuator 1 having a two-degree-of-freedom vibration system, generally, the deflection angle of the second mass unit 25 is larger than the deflection angle of the first mass units 21 and 22, Since the amount of torsional deformation of the elastic portions 28 and 29 is larger than the amount of torsional deformation of the first elastic portions 26 and 27, if the piezoresistive elements 41 and 42 are provided on the second elastic portion, the second It is possible to detect the behavior of the second mass unit 25 with high accuracy by increasing the amount of change in the specific resistance value of the piezoresistive elements 41 and 42 accompanying the rotation of the mass unit 25.

Such an actuator 1 can be manufactured as follows, for example.
11 and 12 are views (longitudinal sectional views) for explaining a method of manufacturing the actuator of the first reference example . In the following, for convenience of explanation, the upper side in FIGS. 11 and 12 is referred to as “upper” and the lower side is referred to as “lower”.
[A1] First, as shown in FIG. 11A, for example, a silicon substrate 5 (n-type single crystal silicon substrate) is prepared.

  Next, on one surface of the silicon substrate 5, as shown in FIG. 11 (b), support portions 23, 24, mass portions 21, 22, 25, elastic portions 26, 27, 28, 29, and electrodes 32 are provided. , 33, the metal mask 6 is formed of aluminum or the like, for example. At this time, although not shown, the metal mask 6 has a shape in which a portion corresponding to the support portions 23 and 24 and a portion corresponding to the electrodes 32 and 33 are connected to each other.

Then, as shown in FIG. 11 (c), a photoresist is applied to the other surface of the silicon substrate 5, and exposure and development are performed, so that a resist having an opening that has the same shape as the plan view of the space 30 is formed. A mask 7 is formed. The resist mask 7 may be formed before the metal mask 6 is formed.
Next, after etching the other surface of the silicon substrate 5 through the resist mask 7, the resist mask 7 is removed. As a result, as shown in FIG. 11 (d), a recess 51 is formed in a region corresponding to the plan view of the space 30.

  As an etching method, for example, one or more of physical etching methods such as plasma etching, reactive ion etching, beam etching, and light-assisted etching, and chemical etching methods such as wet etching are used in combination. be able to. Note that the same method can be used for etching in the following steps.

Next, the one surface side of the silicon substrate 5 is etched through the metal mask 6 until a portion corresponding to the recess 51 penetrates.
Then, when the metal mask 6 is removed, a metal film is formed on the second mass portion 25 to form the light reflecting portion 251.
Here, after etching the silicon substrate 5, the metal mask 6 may be removed or may be left without being removed. When the metal mask 6 is not removed, the metal mask 6 remaining on the second mass portion 25 can be used as the light reflecting portion 251.

Examples of the method for forming a metal film include vacuum plating, sputtering (low temperature sputtering), dry plating methods such as ion plating, wet plating methods such as electrolytic plating and electroless plating, thermal spraying methods, and joining metal foils. . Note that the same method can also be used for forming a metal film in the following steps.
Further, the regions corresponding to the support portions 23 and 24 and the second elastic portions 28 and 29 are doped with impurities to form resistance regions 411 and 421. At this time, prior to the formation of the resistance regions 411 and 421, an insulating film such as an oxide film is formed in a portion other than the formation regions of the resistance regions 411 and 421. Further, after the resistance regions 411 and 421 are formed, terminals 416 to 419 and 426 to 429 and wirings are formed on the insulating film by a known film formation method.
Through the above steps, as shown in FIG. 11E, the support portions 23, 24, the mass portions 21, 22, 25, the elastic portions 26, 27, 28, 29 and the electrodes 32, 33 are integrally formed. The obtained structure is obtained. In addition, the part between the support parts 23 and 24 and the electrodes 32 and 33 is removed in the process mentioned later.

[A2] Next, as shown in FIG. 12A, for example, a silicon substrate 9 is prepared as a substrate for forming the support substrate 3.
Then, a metal mask is formed on one surface of the silicon substrate 9 with, for example, aluminum so as to correspond to a portion excluding the region where the opening 31 is formed.
Next, after etching one surface side of the silicon substrate 9 through this metal mask, the metal mask is removed, and an opening 31 is formed as shown in FIG. That is, the support substrate 3 is obtained.

[A3] Next, as shown in FIG. 12C, after the structure obtained in the step [A1] and the support substrate 3 obtained in the step [A2] are bonded by direct bonding, The actuator 1 is obtained by removing portions between the support portions 23 and 24 and the electrodes 32 and 33 of the structure. Note that a glass such as borosilicate glass containing mobile ions may be interposed between the base 2 and the support substrate 3, and these may be joined by anodic bonding. Further, it is possible to join the base 2 and the support substrate 3 by anodic bonding using a glass substrate instead of the silicon substrate 9.
As described above, the actuator 1 of the first reference example is manufactured.

<Second Reference Example >
Next, a second reference example of the actuator of the present invention will be described.
FIG. 13 is a plan view showing a second reference example of the actuator of the present invention. In the following, for convenience of explanation, the front side with respect to the paper surface in FIG. 13 is referred to as “up”, the back side with respect to the paper surface is referred to as “down”, the right side is referred to as “right”, and the left side is referred to as “left”.

Hereinafter, the actuator of the second reference example will be described focusing on the differences from the actuator of the first reference example described above, and the description of the same matters will be omitted.
As shown in FIG. 13, the actuator 1A of the second reference example is substantially the same as the actuator 1 of the first reference example except that the arrangement of the piezoresistive elements 41 and 42 is different.
In the actuator 1A of the second reference example , as shown in FIG. 13, the piezoresistive element 41 is provided on the first elastic part 26, and the piezoresistive element 42 is provided on the first elastic part 27. Yes. Accordingly, the wiring for the piezoresistive elements 41 and 42 is not provided on the first mass portions 21 and 22 or the second elastic portions 28 and 29, and the configuration of the actuator 1A is simplified. The behavior of the mass part 25 can be detected.

In particular, in this reference example , the piezoresistive element 41 is provided at the end of the first elastic part 26 in the longitudinal direction, and the piezoresistive element 42 is provided at the end of the first elastic part 27 in the longitudinal direction. Is provided.
The shear stress generated on the first elastic portions 26 and 27 due to the torsional deformation of the first elastic portions 26 and 27 increases from the central portion to the end in the longitudinal direction of the first elastic portions 26 and 27. Yes. Therefore, the change amount of the specific resistance value of the piezoresistive elements 41 and 42 with respect to the rotation angle of the second mass unit 25 can be increased, and the detection accuracy of the second mass unit 25 can be improved.

Such an arrangement of the piezoresistive elements 41 and 42 is particularly effective when detecting a shear stress on the first elastic parts 26 and 27 having a smaller amount of torsional deformation than the second elastic parts 28 and 29. .
Note that the piezoresistive element 41 may be provided in the central portion of the first elastic portion 26 in the longitudinal direction, and the piezoresistive element 42 may be provided in the central portion of the first elastic portion 27 in the longitudinal direction. In this case, similarly to the first reference example described above, when the resistance regions 411 and 421 are formed at the time of manufacturing the actuator 1A, the quality of each actuator 1A varies depending on the product even if the formation positions do not require high accuracy. Can be reduced. As a result, the cost of the actuator 1A can be reduced.

Even with the actuator 1A of the second reference example as described above, the same effects as those of the actuator 1 of the first reference example described above can be obtained.
The actuators 1 and 1A as described above can be applied to various electronic devices, and the obtained electronic devices are highly reliable.
The actuators 1 and 1A as described above can be suitably applied to, for example, a laser printer, a barcode reader, an optical scanner such as a scanning confocal laser microscope, an imaging display, and the like.

The actuator of the present invention has been described based on the illustrated embodiment, but the present invention is not limited to this. For example, in the actuator of the present invention, the configuration of each part can be replaced with an arbitrary configuration that exhibits the same function, and an arbitrary configuration can be added.
For example, in the above-described embodiment, an actuator having a pair of piezoresistive elements has been described. However, the number of piezoresistive elements may be one or three or more. Further, the installation position of the piezoresistive element is not limited to that of the above-described embodiment, and may be on the first mass parts 21 and 22. Moreover, when it has a some piezoresistive element, the some piezoresistive element may be arrange | positioned asymmetrically with respect to the mass part (2nd mass part 25) by planar view.

Further, in the above-described embodiment, the actuator of the two free motion vibration system (that is, having the first mass parts 21 and 22 and the second mass part 25 as the mass part and the first elastic part 26 as the elastic part, 27 and the second elastic portions 28 and 29), the present invention can be applied to a vibration system actuator having one degree of freedom or three degrees of freedom or more.
In the above-described embodiment, the configuration in which the light reflecting portion is provided on the upper surface of the second mass portion (the surface opposite to the support substrate) has been described. For example, the light reflecting portion is provided on the opposite surface. The structure which is provided may be sufficient and the structure provided in both surfaces may be sufficient.

  Moreover, although what was driven by the electrostatic drive system was demonstrated in embodiment mentioned above, it is not limited to this. For example, as a driving method of an actuator having a two-degree-of-freedom vibration system, the first mass unit is rotated, and the second mass unit is rotated while twisting and deforming the second elastic unit accordingly. As long as it can be used, the present invention is not limited to the above-described one. For example, a driving method using a piezoelectric element or a driving method using a magnetic force may be used.

It is a top view which shows the 1st reference example of the actuator of this invention. It is the sectional view on the AA line in FIG. It is the BB sectional view taken on the line in FIG. FIG. 3 is a partially enlarged perspective view showing a second mass part and a second elastic part of the actuator shown in FIG. 1. It is a figure for demonstrating the piezoresistive element with which the actuator shown in FIG. 1 was equipped. It is a figure for demonstrating the piezoresistive element with which the actuator shown in FIG. 1 was equipped. It is a figure which shows the relationship between the crystal orientation in a (001) plane silicon substrate, and a piezoresistance coefficient. It is a figure which shows schematic structure of the control system of the actuator shown in FIG. It is a figure which shows an example of the voltage waveform of the drive voltage of the actuator shown in FIG. 2 is a graph showing the relationship between the frequency of an AC voltage and the amplitude of each of a first mass part and a second mass part when an AC voltage is used as the drive voltage for the actuator shown in FIG. 1. It is a figure for demonstrating the manufacturing method of the actuator shown in FIG. It is a figure for demonstrating the manufacturing method of the actuator shown in FIG. It is a top view which shows the 2nd reference example of the actuator of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 1A ... Actuator 11 ... Detection circuit 112 ... Differential amplifier circuit 12 ... Power supply circuit 13 ... Control circuit 2 ... Base | substrate 21, 22 ... 1st mass part 211, 212, 221, 222 ... ... comb-teeth electrode parts 23, 24 ... support part 25 ... second mass part 251 ... light reflecting part 26, 27 ... first elastic part 28, 29 ... second elastic part 3 ... Support substrate 30 ... Space 31 ... Opening 32, 33 ... Electrodes 321, 322, 331, 332 ... Comb-shaped electrode parts 41, 42 ... Piezoresistive elements 411, 421 ... Resistance regions 412, 413, 422, 423 ... Input electrode 414, 415, 424, 425 ... Output electrode 416-419, 426-429 ... Terminal 5 ... Silicon substrate 51 ... Recess 6 ... Metal mask 7 ... Resist mask 9: Silicon substrate

Claims (8)

A pair of first mass parts in the form of a plate;
Provided between the first mass of the pair, and the second mass to form a plate shape,
A support part;
A pair of elastically deformable first pairs that connect the support portion and the pair of first mass portions such that the pair of first mass portions are rotatable with respect to the support portion. The elastic part of
Elastically deformable to connect the pair of first mass parts and the second mass part so that the second mass parts can rotate with respect to the pair of first mass parts. A pair of second elastic portions;
Behavior detecting means for detecting the behavior of the second mass part ;
Based on the detection result of the behavior detecting means, the first mass portions are rotated while twisting and deforming the first elastic portions, and accordingly, the second elastic portions are twisted and deformed. An actuator having a driving means for rotating the second mass part ,
The pair of first mass parts, the second mass part, the support part, the pair of first elastic parts, and the pair of second elastic parts are (001) plane p-type. The silicon single crystal substrate is integrally formed by processing, and the first elastic portions and the second elastic portions extend along the <110> direction of the p-type silicon single crystal substrate. Exist,
The behavior detecting means, have a piezoresistive element comprising an n-type resistance region provided at an end portion of at least one of the second longitudinal direction on the elastic portion of the second elastic portion of said pair And an actuator configured to detect the behavior of the second mass portion based on a change in a specific resistance value of the piezoresistive element. A pair of first mass parts in the form of a plate;
Provided between the first mass of the pair, and the second mass to form a plate shape,
A support part;
A pair of elastically deformable first pairs that connect the support portion and the pair of first mass portions such that the pair of first mass portions are rotatable with respect to the support portion. The elastic part of
Elastically deformable to connect the pair of first mass parts and the second mass part so that the second mass parts can rotate with respect to the pair of first mass parts. A pair of second elastic portions;
Behavior detecting means for detecting the behavior of the second mass part ;
Based on the detection result of the behavior detecting means, the first mass portions are rotated while twisting and deforming the first elastic portions, and accordingly, the second elastic portions are twisted and deformed. An actuator having a driving means for rotating the second mass part ,
The pair of first mass portions, the second mass portion, the support portion, the pair of first elastic portions, and the pair of second elastic portions are (001) plane n-type. The silicon single crystal substrate is integrally formed by processing, and each of the first elastic portion and each of the second elastic portions is in the <100> direction or <010> of the n-type silicon single crystal substrate. Extending along the direction,
The behavior detecting means, have the piezoresistive element comprises a p-type resistance region provided at an end portion of at least one of the second longitudinal direction on the elastic portion of the second elastic portion of said pair And an actuator configured to detect the behavior of the second mass portion based on a change in a specific resistance value of the piezoresistive element. 3. The actuator according to claim 1, wherein the resistance region is formed by doping impurities on a surface of the second elastic portion. The piezoresistive element includes a pair of input electrodes juxtaposed on the resistance region in a direction perpendicular to the rotation center axis of the second mass portion, and the rotation center axis direction on the resistance region. A pair of output electrodes juxtaposed to each other, and applying an electric field to the resistance region via the pair of input electrodes, and a specific resistance value of the resistance region via the pair of output electrodes The actuator according to any one of claims 1 to 3, wherein the actuator is configured to detect.   The actuator according to claim 4, wherein the output electrode is connected to a differential amplifier circuit. The piezoresistive element is provided on each second elastic part on one surface side of the second mass part, and an electric field in one piezoresistive element of the pair of piezoresistive elements. The actuator according to claim 5, wherein the direction of and the direction of the electric field in the other piezoresistive element are the same. The actuator according to claim 6, wherein the pair of piezoresistive elements are provided symmetrically with respect to the second mass portion. The second mass portion, an actuator according to any one of claims 1 light reflecting portion is provided 7.

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