JP6180074B2 - Planar type electromagnetic actuator - Google Patents

Description

  The present invention relates to a planar electromagnetic actuator manufactured using a semiconductor manufacturing technique, and more particularly to a planar electromagnetic actuator that reduces warpage of a movable part due to residual stress of a drive coil formed on the movable part.

  Conventionally, as this type of planar electromagnetic actuator, as described in Patent Document 1, for example, a semiconductor substrate is anisotropically etched to provide a frame-shaped fixed portion, a movable portion, and a movable portion on the fixed portion. A static magnetic field generating means that integrally forms a torsion bar that is pivotally supported, has a drive coil on the movable portion, and applies a static magnetic field to the drive coil portions at both ends of the movable portion parallel to the axial direction of the torsion bar (For example, a permanent magnet) is provided, and the drive force (Lorentz force) generated by the interaction between the magnetic field generated in the drive coil and the static magnetic field of the permanent magnet can be moved by supplying current to the drive coil from an external drive circuit. There is a configuration in which the movable portion is driven around the axis of the torsion bar by acting on the portion.

Japanese Patent No. 2722314

  By the way, this type of planar electromagnetic actuator is generally formed by forming a metal layer for forming a drive coil on an insulating film on a semiconductor substrate using a film formation technique such as vapor deposition or sputtering. A resist pattern of electric wiring including a driving coil is formed on the layer, and the metal layer is etched using the resist pattern as a mask, thereby forming electric wiring including the driving coil. However, there is a residual stress in the formed drive coil, and the extremely thin movable part is warped due to the residual stress. For this reason, for example, when the present invention is applied to an optical scanning device that deflects and scans a light beam by providing a reflecting mirror on a movable part, the reflection mirror surface may be warped, which may hinder the optical scanning function of the optical scanning device.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a planar type electromagnetic actuator capable of reducing the warp of the movable part due to the residual stress of the drive coil.

For this reason, the present invention integrally forms a fixed part, a movable part having a substantially rectangular plane, and a torsion bar that pivotally supports the movable part on the fixed part so as to be swingable. In a planar type electromagnetic actuator that is provided by winding a drive coil along the peripheral edge of a part and drives the movable part by electromagnetic force generated by supplying current to the drive coil, each angle of the drive coil By fixing the portion to the surface of the movable portion and floating the drive coil portion other than each corner portion from the surface of the movable portion, the floating portion of the drive coil is orthogonal to the axial direction of the torsion bar, set to be substantially symmetrical for a straight line passing through the center, characterized in that.

According to the planar type electromagnetic actuator of the present invention, each corner of the drive coil is fixed to the surface of the movable part and the other parts are floated, so the influence of the residual stress of the drive coil that is directly transmitted from the drive coil to the movable part. Can be suppressed as compared with the conventional case, and the warp of the movable part can be reduced. Furthermore, the residual stress of the drive coil with respect to the movable part is provided by providing the floating part of the drive coil so as to be orthogonal to the axial direction of the torsion bar and substantially symmetric with respect to a straight line passing through the center of the movable part. Can be made to act substantially evenly. For this reason, when applied to an optical scanning device that deflects and scans a light beam by providing a reflecting mirror in the movable part, the reflection mirror surface can be reduced in warpage and the flatness of the reflecting mirror can be increased, and the distortion of the scanning light can be reduced. Fewer optical scanning devices can be realized.

The top view which shows 1st Embodiment of the planar type electromagnetic actuator which concerns on this invention. AA arrow sectional drawing of FIG. Explanatory drawing of the manufacturing process of the planar type electromagnetic actuator of 1st Embodiment same as the above. Explanatory drawing of the manufacturing process following FIG. Explanatory drawing of the manufacturing process following FIG. The top view of the principal part of 2nd Embodiment of the planar type | mold electromagnetic actuator which concerns on this invention. The top view of the principal part of 3rd Embodiment of the planar type electromagnetic actuator which concerns on this invention. The top view which shows 4th Embodiment of the planar type electromagnetic actuator which concerns on this invention. BB arrow sectional drawing of FIG. Explanatory drawing of the manufacturing process of the planar type electromagnetic actuator of 4th Embodiment same as the above. Explanatory drawing of the manufacturing process following FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a plan view of a first embodiment of a planar electromagnetic actuator according to the present invention. FIG. 2 is a cross-sectional view taken along the line AA of FIG.
The planar electromagnetic actuator 1 of this embodiment includes a movable part 4 pivotally supported by a frame-like fixed part 2 via a pair of torsion bars 3 and 3, and a drive coil 5 that generates a magnetic field when energized. And, for example, permanent magnets 6 and 6 as static magnetic field generating means for applying a static magnetic field to the drive coil 5, and the torsion is caused by the interaction between the magnetic field generated in the drive coil 5 by energization and the static magnetic field of the permanent magnets 6 and 6 A driving force (Lorentz force) is applied to both end edges of the movable portion 4 parallel to the axial direction of the bars 3 and 3 to rotate the movable portion 4.

  The fixed portion 2, the torsion bars 3, 3 and the movable portion 4 are integrally formed as a semiconductor substrate, for example, using an SOI substrate.

As shown in FIG. 1, the drive coil 5 is wound around the peripheral portion of the movable portion 4 formed in a substantially planar rectangular shape. The drive coil 5 is electrically connected to a pair of external connection terminals 8 and 8 formed on the fixed portion 2 side by a lead wiring portion 7 formed from the torsion bars 3 and 3 to the fixed portion 2 portion. A part of the drive coil 5 is provided in a state of floating from the surface of the movable part 4. Specifically, as shown in FIGS. 1 and 2, the floating portion of the drive coil 5 is substantially symmetric with respect to the central axis of the movable portion 4 (in the present embodiment, the central axes orthogonal to each other). Each corner (the portion shown in black in FIG. 1) of the drive coil 5 is fixed to the surface of the movable portion 4, and the coil portion other than each corner (the portion shown in white in FIG. 1) from the surface of the movable portion 4. It ’s floating. In the present embodiment, the torsion bars 3 and 3 wiring portions of the lead wiring portion 7 that connects the drive coil 5 on the movable portion 4 and the pair of external connection terminals 8 and 8 are also shown in FIGS. It is formed floating from the surface of the torsion bars 3 and 3. For the sake of convenience, the drive coil 5 and the lead-out wiring portion 7 are distinguished from the portions that are floating with respect to the surfaces of the movable portion 4, the torsion bars 3, 3, and the fixed portion 2 for the sake of convenience. In FIG. 2, the floating portion is shown in white, and the fixed portion is shown in black. And the fixed part (black part in a figure) of the drive coil 5 and the lead-out wiring part 7 is the wiring layer 9 etched away as a sacrificial layer in a floating part (white part in a figure) as shown in FIG. It is fixed on the SiO ₂ insulating layer 10 on the surface of the movable part 4 and the fixed part 2 through the intermediate part.

  As shown in FIG. 1, the permanent magnets 6 and 6 are provided on the outer side of the fixed portion 2 so that opposite magnetic poles face each other with the movable portion 4 interposed therebetween. An electromagnet can also be used as the static magnetic field generating means.

On the back side of the movable portion 4, a reflection mirror 11 for optical scanning is provided as shown in FIG. Needless to say, it is not necessary to provide the reflecting mirror 11 in the case of an electromagnetic actuator applied to an application that does not require optical scanning.
In FIG. 2, reference numeral 12 denotes an insulating layer for removing the wiring layer 9 in the floating portion (white portion in the drawing) of the drive coil 5 and the lead-out wiring portion 7 by sacrificial etching, This is a protective layer that covers the surfaces of the drive coil 5, the lead-out wiring portion 7, and the external electrode terminals 8 and 8.

The operation of the planar type electromagnetic actuator of this embodiment will be described.
The driving principle of the movable part 4 is the same as the conventional one. When a current is supplied from an external drive circuit (not shown) to the drive coil 5 on the movable part 4 via the external connection terminals 8 and 8 and the lead-out wiring part 7, a magnetic field is generated. Occur. Due to the interaction between this magnetic field and the static magnetic field generated by the permanent magnets 6 and 6, a driving force (Lorentz force) in opposite directions is generated at both end edges of the movable part 4 parallel to the axial direction of the torsion bars 3 and 3. The movable part 4 rotates around the torsion bars 3 and 3 as the axis center. With this turning operation, the torsion bars 3 and 3 are twisted to generate a spring force in the torsion bars 3 and 3, and the movable portion 4 is rotated to a position where the spring force and the generated driving force are balanced. If an alternating current such as a sine wave is supplied to the drive coil 5A, the movable part 4 can be swung. If the reflecting mirror 11 is provided on the movable part 4 as shown in FIG. 2, the light beam can be deflected and scanned. It becomes. If the frequency of the alternating current supplied to the drive coil 5 is set to the resonance frequency of the oscillating motion of the movable portion 4, an optical scanning device capable of continuous scanning at a constant period can be realized.

  According to the electromagnetic actuator of the present embodiment, as shown in FIGS. 1 and 2, the coil portions other than the corners of the drive coil 5 are floated from the surface of the movable portion 4, so that the drive coil 5 moves to the movable portion 4. The influence of the residual stress of the drive coil 5 that is transmitted can be reduced. For this reason, since the curvature of the movable part 4 can be reduced, when the reflection mirror 11 is provided, the curvature of the reflection mirror 11 is reduced, and the distortion of the scanning light by the optical scanning device can be reduced. Further, the floating portion (white portion in the figure) of the drive coil 5 is provided so as to be substantially symmetric with respect to the central axis of the movable portion 4 (in the present embodiment, the respective central axes orthogonal to each other). 4, the residual stress of the drive coil 5 can be applied substantially evenly.

  In the present embodiment, the torsion bars 3 and 3 of the lead-out wiring part 7 are also lifted from the surface of the torsion bars 3 and 3, so that the torsional stress of the lead-out wiring part 7 in the torsion bars 3 and 3 is applied to the torsion bars 3 and 3. It does not act directly, and the movement of the torsion bars 3 and 3 is not constrained by the stress of the lead wiring part 7. For this reason, the movable part 4 can be rotated with a large deflection angle even with the same supply current as compared with the conventional structure. In other words, when the movable part 4 is driven with the same deflection angle as in the prior art, a small amount of current is required, so that the drive efficiency of the electromagnetic actuator 1 is improved and power consumption can be reduced.

Next, a manufacturing process of the electromagnetic actuator according to the first embodiment shown in FIG. 1 having a structure in which a part of the drive coil 5 is floated will be described with reference to FIGS.
In this embodiment, a case where an SOI (Silicon On Insulator) substrate 100 having a box layer 100C between silicon layers 100A and 100B on the front side and the back side of the substrate is used as the semiconductor substrate will be described.

In step (a), the surface of the silicon layer 100A on the surface side of the SOI substrate 100 is thermally oxidized to form the SiO ₂ insulating layer 101 (which becomes the SiO ₂ insulating layer 10 in FIG. 2).
In step (b), a wiring layer of, for example, Al (aluminum) is formed on the entire surface of the SiO ₂ insulating layer 101 by a known film forming technique such as sputtering or vapor deposition, a resist is applied thereon, and the drive coil 5 Then, a resist pattern is formed while leaving portions of the resist corresponding to the lead wiring portion 7 and the external electrode terminals 8 and 8. Using this as a mask, the wiring layer is etched, and the wiring layer 102 is formed as a sacrificial layer, part of which is removed by etching.

In step (c), an insulating layer of polyimide, for example, is formed on the entire surface of the SOI substrate 100, and the insulating layer 103 is formed by removing the portions where the drive coil 5 and the lead-out wiring portion 7 are lifted by etching. To do.
In step (d), an Al (aluminum) wiring layer is formed on the entire substrate 100 by sputtering, for example, a resist is applied on the wiring layer, and the drive coil 5, lead-out wiring portion 7, external electrode terminal portion 8, A resist pattern is formed leaving the resist of the wiring portion 8, and the wiring layer is etched using the resist pattern as a mask to form the drive coil 5, the lead-out wiring portion 7, and the external connection terminals 8 and 8.

In step (e), a protective film 13 that covers the drive coil 5, the lead-out wiring portion 7, and the external connection terminals 8 and 8 is formed.
In step (f), the protective film 13 and the insulating layer 103 are used as a mask to remove the wiring layer 102 portion that becomes a sacrificial layer below the insulating layer 103 in the drive coil 5 portion and the lead-out wiring portion 7 portion by etching. As a result, the corners shown in black in FIG. 1 are fixed, and the drive coil 5 in a state where the portions other than the corners (the white portions in FIG. 1) float from the surface of the movable portion 4, and FIG. 2. Thus, the lead-out wiring part 7 is formed in a state where the lower part of the insulating layer 12 of the torsion bars 3 and 3 is floating from the surface of the torsion bars 3 and 3.

In step (g), the insulating layer 101 is etched by covering the portions corresponding to the fixed portion 2, the torsion bars 3, 3, and the movable portion 4 with a resist mask and etching the silicon layer 100 </ b> A. Pattern the part.
In step (h), the silicon layer 100A on the surface side of the SOI substrate 100 is etched using the insulating layer portion as a mask.

In step (i), a portion corresponding to the fixed portion 2 of the silicon layer 100B on the back side of the SOI substrate 100 is covered with a resist mask, and the silicon layer 100B is etched.
In step (j), the box layer 100C of the SOI substrate 100 is etched. In this step, the fixed portion 2, the torsion bars 3 and 3, and the movable portion 4 of the electromagnetic actuator 1 are formed, and the planar shape as shown in FIG. 1 is obtained.
In the step (k), the reflection mirror 11 when used as an optical scanning actuator is formed on the back surface side of the movable portion 4 by, for example, aluminum vapor deposition using a mask such as a stencil mask. As a result, the planar electromagnetic actuator 1 having the cross-sectional shape shown in FIG. 2 is formed.

In the first embodiment described above, only the corners of the drive coil 5 are fixed locations (black portions in the figure) and the other coil portions are raised portions (white portions in the drawings). The configuration is not limited to this. For example, like the electromagnetic actuator 20 of the second embodiment shown in FIG. 6, a coil portion that does not contribute much to the driving of the movable portion 4 along the opposite side portion of the movable portion 4 orthogonal to the axial direction of the torsion bars 3 and 3. As in the first embodiment, a coil portion that contributes to driving of the movable portion 4 along the opposite side portion of the movable portion 4 parallel to the axial direction of the torsion bars 3 and 3 is defined as a floating portion (white portion in the figure). It is good also as a structure which provides a fixed location (a black part in a figure) over the full length, and the movable part 4 parallel to the axial direction of the torsion bars 3 and 3 like the electromagnetic actuator 30 of 3rd Embodiment shown in FIG. It is good also as a structure which provides a some fixed location (a black part in a figure) in the intermediate part of the coil part in alignment with the opposite side part substantially equally. In the second and third embodiments, the same elements as those in the first embodiment are denoted by the same reference numerals.
It should be noted that with regard to the lead-out wiring section 7, the torsion bars 3 and 3 wiring portions do not necessarily have to be floated and may be fixed.

Next, FIGS. 8 and 9 show a fourth embodiment of the planar electromagnetic actuator of the present invention.
In the electromagnetic actuators 1, 20, and 30 of the first to third embodiments described above, a part of the drive coil 5 is lifted from the surface of the movable part 4, thereby causing the warp of the movable part 4 due to the residual stress of the drive coil 5. In the electromagnetic actuator 40 of the fourth embodiment, a stress relaxation layer that relaxes the action of the residual stress of the drive coil 5 on the movable part 4 is interposed between the drive coil 5 and the movable part 4. Thus, the warp of the movable part 4 is reduced.

  FIG. 8 is a plan view of the electromagnetic actuator 40 of the fourth embodiment, and FIG. 9 is a cross-sectional view taken along the line BB in FIG. In addition, the same code | symbol is attached | subjected to the same part as 1st Embodiment.

  As shown in FIG. 9, the planar electromagnetic actuator 40 of the fourth embodiment has a rigidity that relaxes the action of the residual stress in the drive coil 5 on the movable part 4 between the drive coil 5 and the movable part 4 surface. The drive coil 5 is fixed to the surface of the movable portion 4 with a stress relaxation layer 41 made of a low material such as polyimide interposed.

  According to such a configuration, the warp of the movable part 4 can be reduced by absorbing the action of the residual stress transmitted from the drive coil 5 to the movable part 4 by the stress relaxation layer 41.

  Next, a manufacturing process of the planar electromagnetic actuator 40 of the fourth embodiment will be described with reference to FIGS. A case where an SOI substrate is used as the semiconductor substrate as in the first embodiment will be described.

In step (a), the surface of the silicon layer 200A on the surface side of the SOI substrate 200 is thermally oxidized to form the SiO ₂ insulating layer 201 (which becomes the SiO ₂ insulating layer 10 in FIG. 9).
In step (b), a polyimide layer is formed on the entire surface of the SiO ₂ insulating layer 201, and a resist is applied thereon, and portions corresponding to the drive coil 5, lead-out wiring portion 7, and external electrode terminals 8, 8 are formed. A resist pattern is formed leaving the resist. Using this as a mask, the polyimide layer is etched to form the stress relaxation layer 41.

  In step (c), a wiring layer of Al (aluminum) is formed on the entire surface of the SOI substrate 200 by sputtering, for example, a resist is applied on the wiring layer, and the drive coil 5, the lead wiring portion 7 and the external electrode terminal portion 8 are coated. , 8 leaving a resist of the wiring portion, forming a resist pattern, and using this as a mask, the wiring layer is etched to form the drive coil 5, lead-out wiring portion 7 and external connection terminals 8, 8 on the stress relaxation layer 41. To do.

  In step (d), a protective film 13 that covers the drive coil 5, the lead-out wiring portion 7, and the external connection terminals 8 and 8 is formed.

  The subsequent steps (e) to (i) are the same as in the first embodiment. That is, in the step (e), the portions corresponding to the fixed portion 2, the torsion bars 3 and 3 and the movable portion 4 of the insulating layer 201 are covered with a resist mask, and etching is performed, so that the silicon layer 100A is etched. The insulating layer portion is patterned.

In step (f), the silicon layer 200A on the surface side of the SOI substrate 200 is etched using the insulating layer portion as a mask.
In step (g), a portion corresponding to the fixed portion 2 of the silicon layer 200B on the back side of the SOI substrate 200 is covered with a resist mask, and the silicon layer 200B is etched.

In step (h), the box layer 200C of the SOI substrate 200 is etched. In this step, the fixed portion 2, the torsion bars 3 and 3, and the movable portion 4 of the electromagnetic actuator 40 are formed.
In step (i), the reflection mirror 11 when used as an optical scanning actuator is formed on the back surface side of the movable portion 4. As a result, the planar electromagnetic actuator 40 having the cross-sectional shape shown in FIG. 9 is formed.

  In each of the above-described embodiments, an SOI substrate is used as the semiconductor substrate. However, for example, the fixed portion 2, the torsion bars 3, 3, and the movable portion are formed by using anisotropic etching by time control of a semiconductor substrate such as a silicon substrate. 4 may be integrally formed.

  In addition, each of the above-described embodiments has shown an example of a planar electromagnetic actuator of a one-dimensional drive type. However, a planar electromagnetic actuator of a two-dimensional drive type that includes two pairs of torsion bars whose torsion bar axes are orthogonal to each other. Needless to say, the present invention can be applied.

1, 20, 30, 40 Electromagnetic actuator 2 Fixed portion 3 Torsion bar 4 Movable portion 5 Driving coil 6 Permanent magnet 7 Lead-out wiring portions 8 and 8 External connection terminal 11 Reflecting mirror 12 Insulating layer 41 Stress relaxation layer

Claims (2)

A fixed portion, a movable portion having a substantially rectangular shape on a plane, and a torsion bar that pivotally supports the movable portion on the fixed portion so as to be swingable are integrally formed with a semiconductor substrate, and along the peripheral portion of the movable portion. In a planar type electromagnetic actuator provided by winding a drive coil and driving the movable part by electromagnetic force generated by supplying current to the drive coil,
Each corner portion of the drive coil is fixed to the surface of the movable portion, and the drive coil portion other than each corner portion is floated from the surface of the movable portion, so that the floating portion of the drive coil is orthogonal to the axial direction of the torsion bar It was set to be substantially symmetrical for a straight line passing through the center of the movable portion, a planar type electromagnetic actuator, characterized in that.   The planar electromagnetic actuator according to claim 1, wherein the torsion bar portion of the lead-out wiring portion is configured to float from the surface of the torsion bar.