JP2002072127A - Leaf spring structure - Google Patents

Abstract

(57) [Object] To provide a leaf spring structure in which an allowable swing angle of a movable plate is enlarged. A torsional rocking body, which is one of the leaf spring structures, includes a torsion spring, which is an elastic member having a pair of ends, and a support, to which one end of the torsion spring is connected. And a movable plate 106 to which the other end of the torsion spring 102 is connected. The movable plate 106 is swingably supported by the torsion spring 102 with respect to the support 104. Torsion oscillator 100
In, the crystal plane having excellent shear stress resistance is set substantially parallel to the cross section of the torsion spring. A crystal plane having excellent shear stress resistance is a plane having a large bond density between crystal planes. In a diamond-type crystal, a {111} plane, a {110} plane, and a {100} plane have a large bond density.
{100} plane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator used for an optical scanner, an acceleration sensor, and the like. More specifically, used for such an actuator,
The present invention relates to a leaf spring structure manufactured by a semiconductor process.

[0002]

2. Description of the Related Art Japanese Patent Laying-Open No. 7-175005 discloses an electromagnetically driven actuator including a leaf spring structure manufactured by a semiconductor process. As shown in FIGS. 31 and 32, the actuator 1 includes a flat movable plate 5, two torsion bars (elastic members) 6a and 6b for pivotally supporting the movable plate 5, and a torsion bar. 6a,
Leaf spring structure provided with a frame (support) 2 for supporting 6b
(Torsional rocking body). This leaf spring structure is integrally formed from a silicon substrate. The movable plate 5 includes a planar coil 7 provided at a peripheral portion of the upper surface thereof to generate a magnetic field when energized, and a total reflection mirror 8 provided at a central portion of the upper surface surrounded by the planar coil 7.

[0003] As shown in FIG. 32, an upper glass substrate 3 and a lower glass substrate 4 are provided on the upper and lower surfaces of the frame portion 2, respectively, and are provided at predetermined positions of the upper glass substrate 3 and the lower glass substrate 4. Are fixed with permanent magnets 10a, 11a and 10b, 11b for applying a magnetic field to the planar coil 7, respectively.

[0004] Further, as shown in FIG.
Has a pair of electrode terminals 9a, 9b provided on the upper surface thereof, and the electrode terminals 9a, 9b are respectively provided with coil wirings 12a, 1a extending on the respective upper surfaces of the torsion bars 6a, 6b.
2b, it is electrically connected to the planar coil 7. Planar coil 7, electrode terminals 9a and 9b, and coil wiring 1
2a and 12b are simultaneously formed on a silicon substrate by an electroforming method.

[0005] This electromagnetic actuator has the advantage that it can be made extremely thin compared to conventional actuators.

[0006]

Heretofore, a leaf spring structure used in the above-described actuator has been known as a silicon substrate having a thickness of several hundreds of microns or an active layer silicon substrate and a support silicon substrate having an insulating layer. Is manufactured by a semiconductor process using an SOI substrate bonded through a substrate as a start wafer. Usually, a wet etching process is used for processing silicon in consideration of production efficiency.

As the etching solution, usually, an alkaline solution such as KOH (potassium hydroxide), TMAH (tetramethylammonium hydroxide), hydrazine, EPW (ethylenediamine-pyrocatechol-water), or the like is used.
In the etching using these, the etching progresses anisotropically with the Si {111} crystal plane remaining (appearing).

In order to accurately process the elastic member of the leaf spring structure into a rectangular parallelepiped shape, the main surface of the silicon substrate as the main material of the elastic member is selected to be {100}, and the side surface of the rectangular parallelepiped of the elastic member is It is set parallel to the <110> direction of the silicon substrate. As a result, the cross section of the elastic member becomes a {110} plane, which is a second cleavage plane having a relatively weak bonding force between crystal planes.

Here, the transverse section means a virtual plane which crosses the rectangular parallelepiped in parallel with one end face of the rectangular parallelepiped.
In particular, the cross section of the elastic member refers to a virtual plane parallel to a virtual end surface of the elastic member connected to the movable plate or the support.

For this reason, in the actuator using such a leaf spring structure, the maximum swing angle (allowable swing angle) of the movable plate is the relatively weak second cleavage plane of silicon of the elastic member { It is determined by the atomic bond strength between the {110} planes. If the movable plate is forcibly swung at a large angle exceeding the allowable swing angle, the elastic portion may be broken.

The description so far has been directed to a leaf spring structure in which the movable plate is swung by the torsion of the elastic member. However, a leaf spring structure in which the movable plate is swung by the bending of the elastic member. The same can be said.

In the field of actuators using such a leaf spring structure, it is desired that the movable plate be swung at a larger angle, which also leads to an improvement in durability.

An object of the present invention is to provide a leaf spring structure in which an allowable swing angle of a movable plate is enlarged.
An object of the present invention is to provide a method for manufacturing such a leaf spring structure.

[0014]

SUMMARY OF THE INVENTION In one aspect, the present invention provides an elastic member having a pair of ends, a support to which one end of the elastic member is connected, and the other end of the elastic member. A movable plate to which the end is connected,
A movable plate is a leaf spring structure supported by an elastic member so as to be swingable with respect to a support. The elastic member is made of a single crystal material, has a rectangular parallelepiped shape, and has a cleavage plane of the single crystal material. Are not parallel to the cross section of the elastic member.

In a preferred leaf spring structure, the single crystal material has a diamond crystal structure,
The {0} plane is substantially parallel to the cross section of the elastic member. In this leaf spring structure, an SOI substrate in which a support substrate and an active layer substrate are bonded via an insulating layer is formed as a start wafer, and the elastic member mainly includes the active layer substrate. Are mainly composed of both the support substrate and the active layer substrate, and the main surfaces of the support substrate and the active layer substrate are both {100}.
The <100> orientation of the active layer substrate and the <100
110> orientation.

According to another aspect of the present invention, an elastic member having a pair of ends, a support to which one end of the elastic member is connected, and another end of the elastic member are connected. A method of manufacturing a leaf spring structure including a movable plate, comprising: a SOI substrate having a support substrate and an active layer substrate bonded together via an insulating layer; Both sides are {100} planes, a step of preparing an SOI substrate in which the <100> direction of the active layer substrate matches the <110> direction of the support substrate, and processing the active layer substrate by dry etching. And a step of processing the support substrate by wet etching.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of the embodiment, a distribution of stress generated in a torsional rocking body, which is one of the leaf spring structures, will be described. Here, a model of the torsional rocking body 100 shown in FIG. 1 is considered. As shown in FIG. 1, the torsional rocking body 100 includes a torsion spring 102 which is an elastic member having a pair of ends, and a torsion spring 10.
2 and the movable plate 10 to which the other end of the torsion spring 102 is connected.
6 is provided. The movable plate 106 includes the torsion spring 102
, Is swingably supported by the support 104, and the swing shaft passes through the torsion spring 102.

In the following discussion, the torsion spring 102
Has a substantially rectangular parallelepiped shape. That is,
The torsion spring 102 has a rectangular cross section that is uniformly rectangular in the swing axis direction except at both ends thereof, that is, except near the connection with the support 104 and near the connection with the movable plate 106. Shall be The stress generated in the torsion spring 102 due to torsional deformation is within the elastic limit of the material of the torsion spring 102, and within the elastic limit, the material of the torsion spring 102 is assumed to be an isotropic material.

In the torsion spring 102 shown in FIG. 1, the connection at both ends of the torsion spring is restricted at the center of the torsion spring 102 except for the vicinity of the connection with the support 104 and the vicinity of the connection with the movable plate 106. The effect of this is negligible, and the stress distribution can be derived from Saint-Venant's torsion theory based on elasticity.

If each stress component generated in the torsion spring 102 is defined as shown in FIG. 1 and FIG. , Τxz (= τzz), τyz (=
τzy), the stress components σx, σy, σz, and τxz become zero.

Further, FIG. 3 shows a result obtained by applying a torsion function derived from Saint-Venant's torsion theory to the shear stress τyz by applying the torsion function to a rectangular cross-sectional shape. This shear stress τyz becomes almost zero near the upper surface of FIG. On the other hand, with respect to the shear stress τyx, similarly to τyz, when the torsion function is applied to a rectangular cross-sectional shape and solved, the stress distribution becomes as shown in FIG. The stress distribution has a maximum value and is symmetric with respect to the Z axis.

FIGS. 5 to 10 show simulation results using the finite element method for the stress distribution generated by the similar torsional deformation. 5 to 7 respectively show σx generated near the upper surface of the torsion spring 102 at the time of torsional deformation,
σy and τyx are indicated by contour lines. In addition, FIG.
FIG. 10 shows σx, σy, and τyx of FIGS.
5 shows a stress component distribution along a path 1 passing through the central portion in the longitudinal direction of the torsion spring 102 in FIG.

Comparing these results with the results according to Saint-Venant's torsion theory, it is confirmed that each stress component at the center of the torsion spring 102 follows the stress distribution predicted from the torsion theory. Since the sign of the stress component is reversed by reversing the twist angle, the stress must be evaluated by its absolute value. The stress generated on the upper surface also occurs on the lower surface of the torsion spring 102 due to the reversal of the torsion angle.

On the other hand, the torsion spring 102 is
Near the connection with the movable plate 106
Since the torsional deformation of the torsion spring 102 is restricted by the connection portion, the deformation of the torsion spring 102 is not uniform in the swing axis direction, and shows a distribution different from that of the central portion of the torsion spring 102. Simulation results using the finite element method for the distribution of stress generated by torsional deformation are shown in FIGS.
Shown in 11 to 13 respectively show σ in FIGS. 5 to 7.
7 shows stress component distributions along a path 2 passing near the connection portion at x, σy, and τyx.

In the vicinity of the upper surface near the connection portion, the value of the vertical stress σy in the direction of the oscillation axis becomes the maximum value among the stress components.
However, since the sign of the vertical stress σy is reversed on both sides of the oscillating axis, that is, a tensile stress and a compressive stress are generated, there is a line element having no tensile and compressive stress in the oscillating axis direction. From FIG. 13 to FIG. 13, the stress is small near the line element and increases as the distance from the line element increases.

From the above, at the center of the torsion spring 102, τ
yx indicates the maximum value of σy at the connection portion of the torsion spring 102 in each stress component. However, in consideration of the breakage of the conductor (metal), the yield condition of the isotropic material such as a metal is further widened. It is important to identify the region where the Von Mises stress value used is high.

Vo generated near the upper surface due to torsional deformation
FIGS. 14 to 16 show simulation results of the n Mises stress distribution using the finite element method. Torsion spring 1
In the central portion of 02, as in FIGS. 5 to 10, the stress distribution has a maximum value on the Z-axis of the rectangular cross section in FIG. 2, and is symmetric with respect to the Z-axis. In the vicinity of the connection portion of the torsion spring 102,
Having a maximum near the edges on both sides of the torsion spring 102;
The stress distribution is symmetric about the Z axis.

That is, the Von Mises stress distribution has the highest value near the geometric center of the surface of the torsion spring 102. In addition, Von Mises stress distribution is as follows.
02 has a relatively high value near the geometric corner of the surface. The high value of the Von Mises stress distribution near the geometric center of the surface of the torsion spring 102 is mainly due to the shear stress. On the other hand, the high value of the Von Mises stress distribution near the geometric corner of the surface of the torsion spring 102 is
It is mainly due to tensile stress.

The above-mentioned stress distribution is obtained by assuming that the support 104 and the movable plate 106 are connected to both ends of the torsion spring 102 in FIG.
Is a result of analysis for the model of the torsional rocking body 100 shown in FIG. 1, and therefore does not depend on whether the movable plate 106 has a double-sided structure or a cantilevered structure.

As described above, the high Von Mises stress near the geometric center of the surface of the torsion spring is mainly due to shear stress. Therefore, in FIG. 17, when the movable plate 106 of the torsional rocking body 100 rocks,
That is, when the torsion spring 102 is twisted, the torsion spring 1
The largest shear stress occurs in the cross section 108 near the center of 02. This shear stress, as easily analogized,
It increases as the twist angle increases. In addition, the repeated application of the torsional motion generates a cumulative application of this shear stress,
Fatigue builds up in the cross section 108.

Next, a description will be given of the distribution of stress generated in the bending oscillator, which is another plate spring structure. Here, consider the bending oscillator shown in FIG. As shown in FIG. 18, the bending oscillator 120 includes a bending spring 122 that is an elastic member, a support 124 to which one end of the bending spring 122 is connected, and another end of the bending spring 122. And the movable plate 126 connected to the movable plate 126. The movable plate 126 is supported by the bending spring 122 so as to be able to swing up and down in the Z direction with respect to the support body 124.

In the bending oscillating body 120, a stress is generated in a direction of breaking a cross section near the center of the bending spring 122 at the time of bending deformation. This breaking stress is caused by the bending spring 12
2 is largest at a cross section 128 near the center. Also, this stress increases as the bending angle increases. Bending spring 12
If the second bend exceeds the breaking limit, the bending spring 122 breaks near the cross section 128.

Generally, when stress is applied to a dislocation-free crystal,
Crystal deformation occurs. If the displacement is small, the morphology returns to its original shape when the stress is removed. The above is a phenomenon in the range of elastic deformation, but when the externally applied stress exceeds the critical value,
Many dislocations occur and move in the crystal, the crystal undergoes plastic deformation, and the morphology cannot be restored. This is the yield phenomenon of the crystal, which is considered to be a failure when considered in a device.

In a silicon single crystal produced by a dislocation-free growth technique, the crystal has strong mechanical or electrical anisotropy due to the characteristic of SP3 hybrid covalent bond due to valence electrons of Si atoms. In a silicon single crystal having the same crystal structure as diamond, the densest plane with the highest Si atom density is the {111} plane, and conversely, the bond density connecting between the {111} atomic planes is the lowest. Is mainly cleaved on the {111} plane.
The dense surface next to the {111} plane is the {110} plane,
Since the bond density connecting the {110} atomic planes is the second lowest after the {111} plane, the {110} plane appears as the second cleavage plane when stress is applied. Incidentally, in the case of a carbon single crystal, there is an experimental result that the {100} plane has a yield stress that is 11% larger than the {110} plane.

According to the present invention, in the torsional oscillator 100 shown in FIG. 17, the crystal plane having excellent shear stress resistance is set substantially parallel to the cross section 108, and in the bending oscillator shown in FIG. The crystal plane having excellent tensile stress resistance is set substantially parallel to the cross section 128. Here, a crystal plane having excellent shear stress resistance or tensile stress resistance is a plane having a high bond density between crystal planes, and a diamond-type crystal has a {111} plane.
The {100} plane is the {100} plane between the {110} plane and the {100} plane.

The contact angle Θ (the value of Θ is a positive value of 180 degrees or less) between two types of crystal planes (the respective plane orientation vectors are a and b) can be calculated by the following equation.

A · b = | a | · | b | · cosΘ (1) In equation (1), a · b and | a | · | b |
This represents the product of the inner product and the absolute value of the vectors a and b.

In FIG. 17, the shear stress resistance is excellent.
Since the {100} plane is parallel to the cross section 108, the cosine component cos (54.7 degrees) = 0 with respect to the {111} plane included in this elastic member. .5
Only the stress multiplied by 77 is applied,
Fault tolerance due to destruction of the {111} plane is improved. Also, for the {110} plane included in this elastic member,
The cosine component cos (90) is added to the shear stress applied to the {100} plane.
Degree) = 0 or cos (45 degrees) = 0.707 multiplied only by the stress, and the fault tolerance due to the destruction of the {110} plane is improved as in the case of the {111} plane. .

Incidentally, conventionally, since the {110} plane is generally parallel to the cross section 108 shown in FIG. 17, the {111} plane included in this elastic member is applied to the {110} plane. Cosine component cos (35.3 degrees) = 0.
There is a {111} plane to which a stress multiplied by 816 is applied. The reason is that the {110} plane itself has lower shear stress resistance than the {100} plane, and the effect of the {111} plane is larger. Accordingly, the failure resistance due to destruction is lower than that of the present invention.

A single crystal material Si has been described above as an example, but a leaf spring structure using a single crystal material of carbon (C), Ge or α-Sn having a diamond-type crystal structure similar to that of Si. The present invention is also applicable to

Further, as can be easily inferred from the above description, the {100} plane is viewed crystallographically with respect to the cross section 108 shown in FIG. 17 and the cross section 128 shown in FIG. Crystal planes having a small contact angle may be set in parallel. As a similar surface, the diamond type crystal has {51
1} plane.

Compound semiconductors such as GaAs include Si and G
It has a different crystal structure from elemental semiconductors such as e.
For example, group 3-5 compound semiconductors are classified into a wurtzite structure having a hexagonal crystal structure and a zinc blende structure having a cubic crystal structure. The former includes AlN, InN, and GaN, and the latter includes GaAs, GaP, and InP.

Due to differences in the atomic radii of the constituent elements of each crystal, etc., the basic physical properties are varied from crystals having good covalent bonds to crystals having good ionic bonds. In the case of AlN or the like having a strong ionic bond, {111}
The faces are all composed of Group 3 atoms or Group 5 atoms. Since these faces are alternately stacked, the face has the strongest Coulomb force. Reflecting this situation,
The cleavage plane of AlN is the {110} plane. Therefore, when a group III-V compound semiconductor crystal having a strong ionic bond, such as AlN, is used as the elastic member material, the {111} plane may be parallel to the cross section of the elastic member.

On the other hand, in the case of GaSb or InSb having a weak ionic bond (strong covalent bond), the {111} plane and the {110} plane serve as cleavage planes like Si, and therefore, 3-Si such as GaSb has a strong covalent bond. When a Group V compound semiconductor crystal is used as the elastic member material, the {100} plane may be parallel to the cross section of the elastic member.

In addition, the conventional failure / destruction caused by shear stress is caused by the weakness of the interfacial bonding. Therefore, instead of using a single crystal material for the elastic member, a polycrystalline material, a microcrystalline material or It is also possible to improve the brittleness of the bond by using an amorphous material. For example, one example is to use polycrystalline silicon or amorphous silicon for the elastic member material instead of single crystal Si. However, in consideration of various necessary mechanical characteristics, such as Q value, which is one of the factors of power consumption, which differs for each application, in addition to the above-described fracture resistance for each application of the leaf spring structure, the overall It is necessary to select the material of the elastic member from the optimization of the mechanical properties.

Of course, in the above-described material configuration, a thin film of a metal such as nickel having a high viscosity or an insulator thin film having an amorphous structure may be additionally formed on the surface of the elastic member. The additionally formed thin film serves as a shock absorbing material, and thus improves durability and impact resistance. Further, even if the cleavage phenomenon occurs, the cleavage stops at the interface with the thin film, so that the breakdown resistance is improved.

[Embodiment] A torsional rocking body according to an embodiment of the present invention will be described. The present embodiment is a torsional rocking body applied to an electromagnetic drive type actuator.

As shown in FIGS. 19 to 21, the actuator 200 includes a torsional rocking body 210 and a pair of permanent magnets 202a and 202b. The torsional rocking body 210 includes a movable plate 212 and a pair of elastic members 214a and 214b for swingably supporting the movable plate 212.
And the support 21 holding the elastic members 214a and 214b
6 is provided. A pair of elastic members 214a, 214b
Extend symmetrically on both sides from the movable plate 212 and function as a torsion bar, that is, a torsion spring. Therefore, the movable plate 212 is swingably supported by the support 216. The pivot axis of the movable plate 212 is
4a and 214b.

The elastic members 214a and 214b have a substantially rectangular parallelepiped shape, and have a rectangular cross section perpendicular to the swing axis. More specifically, the elastic members 214a, 214a
14b has one end near the connection with the movable plate 212, the other end near the connection with the support 216, and a central part located between them. Has a rectangular parallelepiped shape. The elastic members 214a and 214b
Generally, such a shape is selected from the viewpoint of ease of design and manufacture.

The movable plate 212 has a drive coil 222 that goes around the periphery. The drive coil 222 has electrode pads 224a and 224b at both ends.
The support 216 includes a pair of electrode pads 226a and 226b for supplying external power to the drive coil 222. The torsional rocking body 210 includes an elastic member 214a.
Are provided, and the wiring 228a electrically connects the electrode pad 224a of the drive coil 222 and the electrode pad 226a on the support.

Further, the torsional rocking body 210 is
14b, a wiring 228b passing therethrough is provided.
Has one end connected to the electrode pad 226b on the support,
The other end has an electrode pad 230. Further, the torsional rocking body 210 has a jump wire 232 extending across the drive coil 222 via an insulating layer. The electrode pads 230 are electrically connected.

The movable plate 212 and the elastic members 214a and 214
b and the support 216 are monolithically formed from a single crystal silicon substrate. Therefore, the movable plate 212, the elastic members 214a and 214b, and the support 216 are all mainly made of single crystal silicon. Since single crystal silicon can be precisely processed, it is suitable for miniaturizing a torsional oscillator. In addition, single-crystal silicon has high rigidity and low internal damping of the material, so that the elastic members 214a and 2142 for resonance driving are used.
14b has excellent characteristics. Further, since single crystal silicon has high rigidity, single crystal silicon is suitable for a material of the support 216 used as an adhesive portion for fixing to outside.

The drive coil 222 and the electrode pads 224a,
224b, electrode pads 226a, 226b, and wiring 228
a, 228b and the electrode pad 230 are both formed of the same metal film, for example, an aluminum film. The movable plate 212, the elastic members 214a, 214b, and the single crystal silicon substrate which is the main material of the support 216 are, for example, a silicon oxide film. Electrically insulated by Similarly, the jump wiring is also formed of, for example, an aluminum film, and is electrically insulated from the drive coil 222 by, for example, a silicon oxide film.

The metal film including the wirings 228a, 228b and the like is generally formed near the surface for ease of fabrication. Therefore, the wirings 228a and 228b are located near the surfaces of the elastic members 214a and 214b, respectively.

The pair of permanent magnets 202a and 202b are arranged outside the vibrating ends of the movable plate 212 and substantially parallel to the swing axis. The magnetization directions of the permanent magnets 202a and 202b are opposite to each other, and are substantially perpendicular to the surface of the movable plate 212 in a stationary state. The permanent magnets 202a, 202b
A magnetic field that crosses the rocking axis at right angles is generated so that a magnetic field component in the surface direction of the movable plate 212 acts on portions of the drive coil 222 located at both ends of the movable plate 212.

Next, the operation of the actuator 200 will be described. In FIG. 19, an AC current flows through the drive coil 222 in response to the application of the AC voltage to the two electrode pads 226a and 226b on the support 216.
A current flowing through a portion of the drive coil 222 near the permanent magnets 202a and 202b receives Lorentz force due to interaction with a magnetic field generated by the permanent magnets 202a and 202b, and the movable plate 212 receives a couple in the plate thickness direction. For this reason, the movable plate 212 includes two elastic members 214a and 214
Oscillation, that is, torsional vibration, is performed with the central axis extending in the longitudinal direction of b as the oscillation axis.

The moment generating the torsional vibration is determined by the Lorentz force applied to the portion of the drive coil 222 near the permanent magnets 202a and 202b and the two elastic members 214
a, 20b from the swing shaft passing through the permanent magnets 202a, 20b.
It depends on the product of the distance to the part of the drive coil 222 near 2b. Lorentz force is determined by the permanent magnets 202a, 202
02b, the number of turns and the wiring length of the drive coil 222, the magnitude of the current, the distance from the permanent magnets 202a and 202b to the drive coil 222, and the like. Drive coil 222
Is formed so as to go around the outermost periphery of the movable plate 212 in order to increase the amount of generated force and the moment.

The movable plate 212 and the elastic members 214a, 214
By applying an AC voltage having a frequency equal to the resonance frequency uniquely determined by the shape and material of b, the movable plate 212 vibrates at the maximum amplitude of the current flowing through the drive coil 222. The actuator 200 can be used as, for example, an optical scanner that scans a reflected light beam by providing a movable mirror 212 with a reflection mirror that reflects a light beam emitted from the outside.

In this embodiment, the elastic members 214a, 214
4b is made of single-crystal silicon having a {100} plane as a main surface, and its cross section is substantially parallel to the {100} plane.

Single crystal silicon has a diamond crystal structure, and its crystal planes, {100} plane and {110} plane
Among the {111} planes, the {100} plane has excellent shear stress resistance. Since the {100} plane is parallel to the transverse section, a stress of 0.5577 times the shear stress applied to the {100} plane is applied to the {111} plane included in the elastic members 214a and 214b. And the elastic member 21
4a and 214b, {1} plane is {1}
Only a stress of 0.707 times the shear stress applied to the {00} plane is applied. Therefore, the fault tolerance due to the destruction of the {111} face and the fault tolerance due to the destruction of the {110} face are improved.

The torsional oscillator according to the present embodiment is manufactured by using a semiconductor process. Hereinafter, a method for manufacturing the torsional rocking body 210 of the present embodiment will be described with reference to FIGS. FIGS. 24 to 29 show XX′-X in FIG.
Cross section along X-ray is drawn.

Preparation step (FIG. 23): An SOI (Silicon On Insulator) substrate 300 is prepared as a start wafer. The SOI substrate 300 is a structure in which a single crystal silicon substrate 306 called an active layer substrate is bonded to a silicon substrate 302 called a support substrate with an insulating layer 304 interposed therebetween. The support substrate 302 is, for example, 200 to 500.
μm, the insulating layer 304 is, for example, 1 μm, and the active layer substrate 306
Has a thickness of, for example, 100 μm.

The main surfaces of the support substrate 302 and the active layer substrate 306 are both {100} planes, and
The <0> direction matches the <100> direction of the active layer substrate 306. Further, the <110> orientation of the support substrate 302 and the <100> orientation of the active layer substrate 306 are set in parallel with the orientation flat to facilitate fabrication of the SOI substrate 310.

As will be described later, the support substrate 302 is processed by silicon anisotropic wet etching.
The longitudinal direction of the elastic members 214a and 214b of the torsional rocking member to be formed is set parallel to the orientation flat or perpendicular to the orientation flat as shown in the figure.

Step 1 (FIG. 24): The SOI substrate 300 is cleaned, a thermal oxide film 308 is formed on the front surface, and the thermal oxide film 31 is formed on the back surface.
0 is formed.

Step 2 (FIG. 25): The thermal oxide film 308 formed on the back surface of the SOI substrate 300 is used as a mask material when separating the movable plate 212 and the support 216 from the back surface. Further, the thermal oxide film 310 formed on the surface of the SOI substrate 300 is formed by the movable plate 212 and the elastic member 2 from the front side.
It is used as a mask material when forming the support 216 and the support 216. Therefore, the thermal oxide films 308 and 3
For 10, a portion from which silicon is to be removed in a later step is removed in advance by etching.

Step 3 (FIG. 26): Thermal oxide film 310 on the front side
A drive coil 222, an electrode pad 224b, a wiring 228b, an electrode pad 226b, and the like are formed by sputtering an aluminum thin film 312 on the substrate and etching the thin film.

Step 4 (FIG. 27): Thereafter, for example, a plasma oxide film 312 to be an interlayer insulating film is formed, and the portion where the silicon oxide is exposed by etching the thermal oxide film 310 on the front surface is connected to the interlayer contact. Only the portion to be formed, the electrode pad 226b, and the other upper portion are removed by etching, and the second aluminum thin film 3 is formed on the plasma oxide film 312.
14 is formed by sputtering and is etched to form a jump wiring 232 for connecting the electrode pad 224b inside the drive coil 222 to the outside of the coil.
Further, a second plasma oxide film 314 is formed only on the upper part of the jump wiring 232 in order to protect the jump wiring 232 from being oxidized by the atmosphere.

Step 5 (FIG. 28): The movable plate 212 and the elastic members 214a and 214 are dry-etched from the front side.
The active layer substrate 306 of the SOI substrate 300 is etched into the shape of b and the support 216. At this time, ICP (Induc
RIE (Reactive Io) using tively-coupled plasma)
n Etching), the side surface of the etching is processed almost perpendicular to the substrate surface. This etching is S
When it reaches the insulating layer 304 of the OI substrate 300, it stops. Thereafter, in order to form the movable plate 212 and the support 216 from the back side, the SOI substrate 3 is formed using an alkaline solution.
Anisotropic etching is performed on the silicon substrate 302 from the back surface of the substrate 00.

Step 6 (FIG. 29): After etching the silicon substrate 302, the insulating layer 304 exposed between the back surfaces of the elastic members 214a and 214b and the movable plate 212 and the support 216 is removed by dry etching. Thus, a completed torsional rocking body 210 is obtained. This torsional rocking body 21
When 0 is used as an optical scanner, for example, it is preferable to form a reflective surface having a high reflectivity by sputtering gold or aluminum on the back surface of the movable plate 212 as necessary.

As described above, the torsional rocking body 2 of the present embodiment
Since the semiconductor device 10 is formed integrally using semiconductor manufacturing technology, subsequent assembly work is not required, the device can be mass-produced in a very small size at low cost, and the dimensional accuracy is very high. Is extremely small.

In the manufacturing method described above, the support substrate 302
Is processed by silicon anisotropic wet etching, but may be processed by another method. In this case, the orientation of the main surface of the support substrate 302 and the orientation flat may be arbitrarily selected.

Here, as a comparative example, FIG. 30 shows an SOI substrate conventionally used for manufacturing a torsional oscillator.
As shown in FIG. 30, the SOI substrate 300 '
The main surfaces of the support substrate 302 and the active layer substrate 306 are both {1
00 plane, the <110> orientation of the support substrate 302 and the <110> orientation of the active layer substrate 306 match, and this is parallel to the orientation flat.

The SOI substrate 300 'shown in FIG.
In the torsional oscillator made with the start wafer as
The {110} plane is the cross section of the elastic member (see FIG.
(Corresponding to the plane indicated by reference numeral 08). {11
The {0} plane is a crystal plane having the lowest shear stress resistance next to the {111} plane among the {100}, {110}, and {111} planes. In addition, the elastic member with the lowest shear stress resistance
The {111} plane has a shear stress of 0.8 applied to the {110} plane.
It receives 16 times the stress.

On the other hand, as in the present embodiment, FIG.
In the torsional rocking body 210 manufactured using the SOI substrate 300 as a start wafer, the {100} plane is a cross section of the elastic members 214a and 214b (see FIG.
(Corresponding to the plane indicated by reference numeral 08).

The {100} plane is a {100} plane and a {110} plane.
Among the {111} planes, this is the crystal plane having the highest shear stress resistance. The {111} plane and the {110} plane in the elastic member respectively have a shear stress of 0.5 on the {100} plane.
It receives only 77 times and 0.707 times of stress.

Therefore, the elastic member having a cross section parallel to the {100} plane has high resistance to shear stress. As a result, the durability of the elastic members 214a and 214b with respect to the twisting operation is increased, and the allowable swing angle of the movable plate 212 is improved.

Each configuration of the present embodiment is not limited to the configuration described above, and may be variously modified or changed.

For example, the drive coil 222 is formed by sputtering and forming an aluminum film in the embodiment, but may be formed by plating. In particular,
When a large deflection angle is required, the drive coil 222
It is necessary to increase the number of turns, but if only the number of turns is increased without increasing the cross-sectional area, the resistance value of the coil increases, which leads to an increase in power supply voltage and power consumption. By forming a coil having a larger thickness than the sputtering by plating and increasing the aspect ratio, it is possible to satisfy a predetermined specification.

The driving method is not limited to the reciprocating drive using an alternating current equal to the resonance frequency.
For example, static positioning may be performed by driving with a variable frequency or driving with a direct current.

Although the present embodiment described above exemplifies a torsional oscillator having one degree of freedom, the present invention may be applied to a torsional oscillator having two degrees of freedom such as a gimbal structure. .

In the above-described embodiment, the torsion rocking member in which the movable plate is rocked by the torsion of the elastic member has been described as an example of the plate spring structure. May be a bending rocker in which the movable plate is rocked, and this bending rocker can be manufactured by substantially the same manufacturing method. That is, to put it simply, a bending oscillator can be obtained only by changing the torsional oscillator 210 to a cantilever support structure.

Also in this bending oscillator, the {100} plane is parallel to the cross section of the elastic member. In bending oscillators,
The stress applied by the elastic member is not a shear stress but a tensile stress or a compressive stress. Also in this case, the {100} plane is a {100} plane, a {110} plane, and a {111} plane.
Among the surfaces, it has the highest resistance to tensile stress and compressive stress. Also, the {111} plane in the elastic member and {1}
The {10} plane receives only 0.5577 times and 0.707 times of the tensile or compressive stress applied to the {100} plane, respectively.

Accordingly, since the elastic member having a cross section parallel to the {100} plane has high resistance to tensile stress and compressive stress, durability against bending operation is enhanced, and the allowable swing angle of the movable plate is reduced. Be improved.

Finally, the selection of the conductive type of the oscillator according to the present invention will be described.

The actuator according to the present embodiment further includes a drive circuit for driving the movable plate, a circuit for detecting a signal from a detection coil or a strain detection element for monitoring a vibration state, and a resonance frequency which is changed due to an environmental change. In some cases, a control circuit for automatically following the change or controlling the deflection angle to be constant is integrally formed on the support body by a semiconductor manufacturing method.

Since such a circuit group is formed integrally by utilizing the semiconductor manufacturing technology, subsequent assembling work is unnecessary, and a very small intelligent actuator can be mass-produced at low cost, and the circuit group can be manufactured at a low cost. Is formed close to the actuator, so that an actuator with extremely small variation in characteristics can be manufactured. The other portions have basically the same configuration as the actuator shown in the above embodiment, and thus the detailed description is omitted.

The above-mentioned circuit group is formed using an MOS device (FET) or the like in an active layer substrate. Such an actuator is manufactured by mixing the semiconductor manufacturing method and the micro-machine manufacturing method.
In many cases, a large amount of positive charge is induced on the surface / interface level of an OS device. When an NMOS device is formed under such manufacturing conditions, a leakage current occurs between the devices due to the presence of the surface state, or a depletion-type N type in which a source-drain current flows even when the gate applied potential is 0V.
Various problems that only a MOS device is formed often occur.

That is, when a MOS device is formed in an active layer substrate, a PMOS device is desirable. PMO
To form an S device, it is desirable to use an n-type semiconductor as the active layer substrate, and the impurity concentration is preferably in the range of 1 × 10 ¹⁴ cm ⁻³ to 1 × 10 ¹⁷ cm ⁻³ .

Although the embodiments have been specifically described with reference to the drawings, the present invention is not limited to the above-described embodiments, and all the embodiments may be performed without departing from the gist of the invention. Including implementation.

[0091]

According to the present invention, there is provided a leaf spring structure in which the allowable swing angle of the movable plate is enlarged. This allows
An actuator capable of largely swinging the movable plate and a highly durable actuator can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a model of a torsional oscillator for analyzing a stress distribution generated in a torsional spring in a torsional oscillator, which is one of leaf spring structures.

FIG. 2 is a sectional view of the torsion spring taken along the line II-II in FIG.

FIG. 3 shows a distribution of shear stress τyz obtained by applying a torsion function derived from Saint-Bouin's torsion theory to a torsion spring having a rectangular cross section.

FIG. 4 shows a distribution of shear stress τyx solved by applying a torsion function derived from Saint-Bouin's torsion theory to a torsion spring having a rectangular cross-sectional shape.

FIG. 5 shows, by contour lines, the distribution of the normal stress σx obtained by the simulation using the finite element method for the torsional deformation under the same conditions as the analysis relating to FIGS. 3 and 4.

FIG. 6 shows, by contour lines, the distribution of normal stress σy obtained by a simulation using the finite element method for torsional deformation under the same conditions as the analysis relating to FIGS. 3 and 4.

FIG. 7 is a contour diagram showing a distribution of shear stress τyx obtained by a simulation using the finite element method for torsional deformation under the same conditions as the analysis relating to FIGS. 3 and 4.

FIG. 8 shows the distribution of the stress σx shown in FIG. 5 along a path 1 passing through the center in the longitudinal direction of the torsion spring.

FIG. 9 shows the distribution of the stress σy shown in FIG. 6 along a path 1 passing through the center in the longitudinal direction of the torsion spring.

FIG. 10 shows the distribution of the stress τyx shown in FIG. 7 along a path 1 passing through the center in the longitudinal direction of the torsion spring.

11 shows the distribution of the stress σx shown in FIG. 5 along a path 2 passing near the end of the torsion spring.

FIG. 12 shows the distribution of the stress σy shown in FIG. 6 along a path 2 passing near the end of the torsion spring.

FIG. 13 shows the distribution of the stress τyx shown in FIG. 7 along a path 2 passing near the end of the torsion spring.

FIG. 14 is a contour diagram showing the distribution of Von Mises stress generated near the upper surface of the torsion spring due to torsion deformation, obtained by simulation using the finite element method.

FIG. 15 shows a distribution of the Von Mises stress distribution shown in FIG. 14 along a path 1 passing through the center in the longitudinal direction of the torsion spring.

FIG. 16 shows a distribution of the Von Mises stress distribution shown in FIG. 14 along a path 2 passing near the end of the torsion spring.

FIG. 17 is a perspective view of a model of a torsional rocking body that is one of the leaf spring structures.

FIG. 18 is a perspective view of a model of a bending oscillator which is another one of the leaf spring structures.

FIG. 19 is a perspective view of a torsional rocking body according to an embodiment of the present invention.

20 is a sectional view of the torsional rocking body shown in FIG. 19, taken along line XX-XX.

21 is a sectional view of the torsional rocking body shown in FIG. 19, taken along line XXI-XXI.

FIG. 22 is a partial plan view of the torsional rocking body of FIG. 19, showing the movable plate and the elastic member in an enlarged manner.

FIG. 23 is a perspective view of an SOI substrate prepared in a preparation process for manufacturing a torsional oscillator according to an embodiment of the present invention.

24 shows the first step in the process of manufacturing the torsional rocking body according to the embodiment of the present invention by a cross section along line XX′-XX in FIG. 19;

FIG. 25 is a cross-sectional view of the manufacturing process of the torsional rocking body according to the embodiment of the present invention, which follows the process of FIG. 24, taken along line XX′-XX of FIG.
It is shown in a cross section along the line.

FIG. 26 is a cross-sectional view of the manufacturing process of the torsional rocking body according to the embodiment of the present invention, which is subsequent to the process of FIG. 25;
It is shown in a cross section along the line.

FIG. 27 is a cross-sectional view of the manufacturing process of the torsional rocking body according to the embodiment of the present invention, which is subsequent to the process shown in FIG. 26;
It is shown in a cross section along the line.

FIG. 28 is a cross-sectional view of the manufacturing process of the torsional oscillator according to the embodiment of the present invention, which is subsequent to the process of FIG. 27, taken along line XX′-XX of FIG. 19;
It is shown in a cross section along the line.

FIG. 29 is a diagram illustrating a final step following the step of FIG. 28 of the manufacturing process of the torsional rocking body according to the embodiment of the present invention;
It is shown in a cross section along the line X'-XX.

FIG. 30 is a perspective view of an SOI substrate conventionally used for manufacturing a torsional oscillator.

FIG. 31 is a plan view of an electromagnetically driven actuator using a conventional torsional rocking body.

FIG. 32: XXXII of the actuator shown in FIG. 31
It is sectional drawing which follows the -XXXII line.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Torsion oscillator 102 Torsion spring 104 Support 106 Movable plate 108 Cross section

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuya Matsumoto 2-43-2 Hatagaya, Shibuya-ku, Tokyo F-term in Olympus Optical Co., Ltd. (reference) 2H045 AB06 AB73 DA41

Claims (4)

[Claims] An elastic member having a pair of ends, a support to which one end of the elastic member is connected, and a movable plate to which the other end of the elastic member is connected. A leaf spring structure in which the movable plate is swingably supported by a support by an elastic member, wherein the elastic member is made of a single crystal material, has a rectangular parallelepiped shape, and is made of a single crystal material. A leaf spring structure in which a cleavage plane is non-parallel to a cross section of the elastic member. 2. The leaf spring structure according to claim 1, wherein the single crystal material has a diamond crystal structure, and a {100} plane is substantially parallel to a cross section of the elastic member. 3. The leaf spring structure according to claim 2, wherein the SOI substrate on which the support substrate and the active layer substrate are bonded via an insulating layer is formed as a start wafer, and the elastic member is mainly composed of the active layer. The movable plate and the support are both mainly composed of both the support substrate and the active layer substrate, the conductivity of the active layer substrate is n-type, and the main surfaces of the support substrate and the active layer substrate are both { A leaf spring structure having a {100} plane, in which the <100> orientation of the active layer substrate and the <110> orientation of the support substrate match. 4. An elastic member having a pair of ends, a support to which one end of the elastic member is connected, and a movable plate to which the other end of the elastic member is connected. A method for manufacturing a leaf spring structure, comprising: a SOI substrate having a support substrate bonded to an insulating layer and an active layer substrate having n-type conductivity, wherein main surfaces of the support substrate and the active layer substrate are A step of preparing an SOI substrate having both {100} planes and a <100> orientation of the active layer substrate and a <110> orientation of the support substrate, and a step of processing the active layer substrate by dry etching. And a step of processing the support substrate by wet etching.