JP7457249B2 - Piezoelectric actuator, optical scanning device - Google Patents

Description

The present invention relates to a piezoelectric actuator and an optical scanning device.

In an optical scanning device that scans light by rotating a mirror section, a piezoelectric actuator having a piezoelectric film is sometimes used as a drive source for driving the mirror section. Such a piezoelectric actuator is provided with an electrode for applying a voltage to the piezoelectric film, and the electrode and wiring are connected through a contact portion. The contact portion that connects the electrode and the wiring is, for example, circular or square, and one contact portion is usually provided at one connection point between the electrode and the wiring (see, for example, Patent Document 1).

JP 2013-78219 A

Incidentally, in recent years, studies have been made to incorporate piezoelectric actuators into small devices such as smartphones, and there is a demand for smaller piezoelectric actuators.

However, the contact area that connects the electrodes and wiring requires a certain area, which hinders the freedom of layout of the electrodes and wiring in piezoelectric actuators, and this is one of the factors that prevents the miniaturization of piezoelectric actuators. They were one.

The present invention has been made in consideration of the above points, and aims to improve the degree of freedom in the layout of electrodes, wiring, etc. in piezoelectric actuators.

This piezoelectric actuator includes a substrate (310), a piezoelectric element formed on the substrate (310), and a wiring (140) formed on the substrate (310), and the piezoelectric element includes : a first electrode (330), a first piezoelectric film (340) formed on the first electrode (330), and a second electrode (350) formed on the first piezoelectric film (340); a second piezoelectric film (360) formed on the second electrode (350); and a third electrode (370) formed on the second piezoelectric film (360), At the corner, the second electrode (350) is exposed in a notch provided in the third electrode (370), and the first electrode (330) and the third electrode (370) are connected to the piezoelectric element. The second electrode (350) is connected to the first wiring (140) via a plurality of first contact portions (140a) arranged in a straight line along the lateral direction of the It is connected to the second wiring (140) via a plurality of second contact portions (140a) arranged in a straight line along the longitudinal direction of the piezoelectric element.

The reference symbols in parentheses above are added for ease of understanding, are merely examples, and are not limited to the illustrated embodiment.

According to the disclosed technology, the degree of freedom in layout of electrodes, wiring, etc. can be improved in a piezoelectric actuator.

FIG. 1 is a plan view illustrating an optical scanning device according to a first embodiment. FIG. 3 is a partial plan view of the vicinity of a contact portion of the optical scanning device. 3 is a partial cross-sectional view taken along line AA in FIG. 2. FIG. 3 is a partial cross-sectional view taken along line BB in FIG. 2. FIG. FIG. 3 is a diagram illustrating the effects of a plurality of contact parts.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In each drawing, the same components are given the same reference numerals, and redundant explanations may be omitted.

First Embodiment
Fig. 1 is a plan view illustrating an optical scanning device according to a first embodiment, and is a view of the optical scanning device viewed from the side of a mirror reflecting surface 10. In Fig. 1, the longitudinal direction of two torsion bars 50 is defined as a vertical direction, and the direction perpendicular to the longitudinal direction of the two torsion bars 50 is defined as a horizontal direction.

Referring to FIG. 1, the optical scanning device 1 includes a mirror section 40, a torsion bar 50, a connecting section 60, a horizontal drive section 70, a movable frame 80, a vertical drive section 110, a fixed frame 120, and a terminal. 130 and a wiring 140.

The mirror section 40 has a mirror reflecting surface 10 and a stress relief region 20. The horizontal drive section 70 has a horizontal drive beam 71 and a drive source 72. The vertical drive section 110 has a vertical drive beam 90, a drive source 91, and a connecting section 100.

The mirror portion 40 is held between two vertically extending torsion bars 50 from both sides in the vertical direction. The mirror section 40 has a mirror reflective surface 10 at the center, and a stress relaxation region 20 between the mirror reflective surface 10 and the torsion bar 50. Two slits 30 are formed in each stress relaxation region 20. Further, the torsion bar 50 has a base end 50a connected to an inner corner of the horizontal drive beam 71 via a connecting portion 60. The horizontal drive beam 71 has a drive source 72 on its surface and is connected to the movable frame 80 at its outer side.

The drive source 72 uses, for example, a piezoelectric element that expands and contracts in accordance with the application of voltage. For example, a piezo element is used as the piezoelectric element.

Furthermore, a piezoelectric sensor 51 is provided at the base end 50a of the torsion bar 50. The piezoelectric sensor 51 is an oscillation angle sensor for detecting the oscillation angle in the horizontal direction of the mirror reflecting surface 10 when the mirror section 40 is oscillating in the horizontal direction. A piezoelectric element is used for the piezoelectric sensor 51, for example, a piezo element.

The movable frame 80 supports the connecting portion 60, the torsion bar 50, and the mirror portion 40 via the horizontal drive beam 71, and surrounds them. The movable frame 80 is connected to a vertical drive beam 90.

The vertical drive beams 90 are arranged on both sides of the movable frame 80 in the horizontal direction so as to sandwich the movable frame 80 therebetween. A plurality of vertical drive beams 90 are provided in parallel with the torsion bar 50. On each side of the movable frame 80, two vertical drive beams 90 are arranged adjacent to each other in the horizontal direction. Two adjacent vertical drive beams 90 are connected by a connecting part 100.

The inner vertical drive beam 90 is connected to the movable frame 80 at one end and to the outer vertical drive beam 90 at the other end. Further, the outer vertical drive beam 90 is connected at one end to the fixed frame 120 and at the other end to the inner vertical drive beam 90. Further, the vertical drive beam 90 is provided with a drive source 91 . As with the drive source 72, a piezoelectric element is used for the drive source 91, for example, a piezo element.

Furthermore, a piezoelectric sensor 92 is provided at one end of the outer vertical drive beam 90. The piezoelectric sensor 92 is an oscillation angle sensor for detecting the oscillation angle in the vertical direction of the mirror reflecting surface 10 when the mirror portion 40 is oscillating in the vertical direction. As with the piezoelectric sensor 51, a piezoelectric element is used for the piezoelectric sensor 92, for example, a piezo element.

The fixed frame 120 supports the vertical drive unit 110 via the outer vertical drive beams 90. That is, the fixed frame 120 supports the mirror unit 40 via the drive units (vertical drive unit 110 and horizontal drive unit 70). It surrounds the vertical drive unit 110 and the movable frame 80, and has a rectangular outer shape. In this embodiment, the outer shape of the fixed frame 120 is approximately square.

A plurality of terminals 130 are provided on the surface of the fixed frame 120. A wiring 140 is connected to each terminal 130. Wiring 140 is connected to drive sources 72 and 91 and piezoelectric sensors 51 and 92. Alternatively, the wiring 140 is formed with a contact portion 140a for bringing the wiring 140 into contact with each electrode of the drive sources 72, 91, etc. In addition to the terminals 130 and the wiring 140, an inspection pattern may be formed on the surface of the fixed frame 120.

Each part will be explained in more detail below.

The mirror section 40 includes a substantially circular mirror reflection surface 10 at its center. The mirror reflection surface 10 is formed of a metal film with high reflectance, such as silver, copper, or aluminum.

The stress relaxation region 20 is a spacer portion provided between the stress relaxation region 20 and the mirror reflection surface 10 in order to relieve the torsional stress of the torsion bar 50 and reduce the stress applied to the mirror reflection surface 10. The stress relaxation region 20 can disperse the stress generated by the twisting motion of the torsion bar 50 and relieve the stress applied to the mirror reflection surface 10.

The slit 30 is a hole for dispersing stress applied to the stress relaxation region 20 and is provided within the stress relaxation region 20.

The torsion bar 50 is a means for supporting the mirror section 40 from both sides and for swinging the mirror section 40 in the horizontal direction. Here, the horizontal direction is the direction in which the light reflected by the mirror reflection surface 10 scans and moves at high speed, and means the lateral direction of the projection plane. That is, this is the direction in which the mirror reflecting surface 10 swings laterally, and the torsion bar 50 is the axis. The torsion bar 50 swings the mirror section 40 in the horizontal direction by twisting alternately left and right.

The connecting portion 60 is a transmission means for transmitting the horizontal driving force generated by the horizontal drive beam 71 to the torsion bar 50.

The horizontal driving beam 71 is a driving means for horizontally swinging the mirror unit 40 and scanning the light reflected by the mirror reflecting surface 10 in the horizontal direction of the projection plane. By alternately applying voltages of different phases to the two drive sources 72, the two horizontal drive beams 71 can be alternately warped in opposite directions. Thereby, a twisting force can be applied to the torsion bar 50, and the mirror part 40 can be swung around a horizontal axis of rotation parallel to the torsion bar 50.

The horizontal drive beam 71 is driven, for example, by resonant drive. When the optical scanning device 1 of this embodiment is applied to a projector or the like, the mirror section 40 is driven by resonant drive of, for example, 30 kHz.

In addition, by applying voltages of different phases to adjacent vertical drive beams 90, the movable frame 80 can be swung vertically. Note that since the mirror section 40 is supported by the movable frame 80, it swung vertically in conjunction with the swinging of the movable frame 80.

Note that the vertical drive unit 110 swings the movable frame 80 by, for example, non-resonant drive. Vertical driving does not require high-speed driving compared to horizontal driving, and the driving frequency is, for example, about 60 Hz.

The optical scanning device 1 having the above configuration is manufactured using, for example, a silicon wafer or an SOI (Silicon On Insulator) wafer.

Figure 2 is a partial plan view of the vicinity of the contact portion of the optical scanning device. Figure 3 is a partial cross-sectional view taken along line A-A in Figure 2. Figure 4 is a partial cross-sectional view taken along line B-B in Figure 2.

Referring to FIGS. 2 and 3, the driving source 91 includes an insulating film 320, a lower electrode 330, a piezoelectric film 340, an intermediate electrode 350, a piezoelectric film 360, an upper electrode 370, and an interlayer insulating film, which are sequentially formed on a substrate 310. 380, and a piezoelectric actuator having an increased reflection film 390.

In the optical scanning device 1, for example, the intermediate electrode 350 is connected to the ground, and a drive signal for driving the drive source 91 is supplied to the lower electrode 330 and the upper electrode 370. When a drive signal is supplied to the lower electrode 330 and the upper electrode 370, the drive source 91 is displaced according to the voltage of the drive signal. Note that driving can be performed similarly even if the drive signal is supplied to the intermediate electrode 350 and the lower electrode 330 and the upper electrode 370 are connected to the ground.

The substrate 310 is, for example, a silicon substrate. An insulating film 320 such as a silicon oxide film (thermal oxide film) is formed on the upper surface of the silicon substrate. As the substrate 310, an SOI substrate having a support layer, a buried oxide (BOX) layer, and an active layer may be used.

The lower electrode 330 can be, for example, a single conductive film made of a platinum group metal such as Pt. The lower electrode 330 may be a conductive film having a three-layer structure in which a first layer, a second layer, and a third layer are sequentially stacked from the insulating film 320 side.

In the latter case, each of the first layer and the third layer is preferably a conductive oxide film containing a perovskite structure and (110) orientation. Examples of conductive oxide films containing a perovskite structure and (110) orientation include LNO (LaNiO ₃ : lanthanum nickelate) thin film, SRO (Sr ₂ RuO ₄ : strontium oxide) thin film, and BRO (BaRuO ₃ : barium ruthenate) thin film. ) thin film, etc. The thickness of each of the first layer and the third layer is, for example, 30 nm. The second layer is, for example, a Pt thin film. The second layer may be a thin film of a platinum group metal other than Pt, for example, an Ir thin film, an Os thin film, or the like. The thickness of the second layer is, for example, 150 nm.

The intermediate electrode 350, like the lower electrode 330, can be a single conductive film made of a platinum group metal such as Pt. The intermediate electrode 350, like the lower electrode 330, can also be a three-layer conductive film in which a first layer, a second layer, and a third layer are stacked in sequence from the piezoelectric film 340 side.

In the latter case, each of the first layer and the third layer is preferably a conductive oxide film containing a perovskite structure and (110) orientation. The specific materials of the first layer and the third layer are the same as those exemplified for the lower electrode 330. The thickness of each of the first layer and the third layer is, for example, 80 nm. The second layer is, for example, a Pt thin film. The second layer may be a thin film of a platinum group metal other than Pt, for example, an Ir thin film, an Os thin film, or the like. The thickness of the second layer is, for example, 150 nm.

The upper electrode 370 can be, for example, a single conductive film made of a platinum group metal such as Pt. The upper electrode 370 may be a conductive film having a two-layer structure in which a first layer and a second layer are sequentially stacked from the piezoelectric film 360 side.

In the latter case, the first layer is preferably a conductive oxide film containing a perovskite structure and (110) orientation. The specific material of the first layer is the same as that exemplified for the lower electrode 330. The thickness of the first layer is, for example, 80 nm. The second layer is, for example, a Pt thin film. The second layer may be a thin film of a platinum group metal other than Pt, for example, an Ir thin film, an Os thin film, or the like. The thickness of the second layer is, for example, 100 nm.

The first layer of the intermediate electrode 350 and the first layer of the upper electrode 370 suppress deterioration of the piezoelectric films 340 and 360 that are located in the respective lower layers.

The thicknesses of the first and third layers of the lower electrode 330, the first and third layers of the intermediate electrode 350, and the first layer of the upper electrode 370 may each be 30 nm or more. preferable. By setting the thickness of these films to 30 nm or more, a conductive oxide film such as an LNO thin film can be uniformly formed.

The average grain size of the third layer of the lower electrode 330 and the average grain size of the third layer of the intermediate electrode 350 are preferably 35 nm or less, more preferably 25 nm or less.

When the average grain size of the third layer of the lower electrode 330 is within the above range, the average grain size of the upper layer, the piezoelectric film 340, can be reduced. When the average grain size of the third layer of the intermediate electrode 350 is within the above range, the average grain size of the upper layer, the piezoelectric film 360, can be reduced. In the optical scanning device 1, the smaller the average grain size of each of the piezoelectric films 340 and 360, the more the driving voltage (hereinafter simply referred to as the driving voltage of the driving source 91) for making the mirror section driven by the driving source 91 have the same deflection angle can be reduced.

Here, the average grain size is the average value of the crystal grain size in the in-plane horizontal direction of the target film. The average grain size can be calculated by analysis using an electron beam diffraction device. The in-plane horizontal direction is the direction horizontal to the top surface of the lower layer on which the target film is formed.

The piezoelectric material constituting the piezoelectric films 340 and 360 preferably has a perovskite structure. The piezoelectric films 340 and 360 are, for example, PZT (lead zirconate titanate) having a perovskite structure. The piezoelectric film 340 can be formed on the lower electrode 330, and the piezoelectric film 360 can be formed on the intermediate electrode 350, for example, using a sol-gel method.

The piezoelectric material constituting the piezoelectric films 340 and 360 may be other than PZT as long as it has a perovskite structure; for example, PNZT (lead zirconate titanate niobate), PLZT (lead lanthanum zirconate titanate), PLT (lead zirconate titanate), etc. (lanthanum lead), PMN (lead magnesium niobate), PMNN (lead manganate niobate), BaTiO ₃ (barium titanate), and the like. By using these piezoelectric materials for the piezoelectric films 340 and 360, the driving force per unit voltage can be improved.

The average grain size of the piezoelectric film 340 and the average grain size of the piezoelectric film 360 are each preferably 1 μm or less, more preferably 600 nm or less, and even more preferably 450 nm or less. As described above, the smaller the average grain size of each of the piezoelectric films 340 and 360, the more the drive voltage of the drive source 91 can be reduced.

For example, in order to crystallize the piezoelectric films 340 and 360 formed on the respective upper layers, the lower electrode 330 and the intermediate electrode 350 are formed by heating the substrate 310 at a temperature of 500 degrees or higher and forming a perpendicular surface in the plane of the third layers 333 and 353. The film can be formed by sputtering so that the crystal orientation in the direction is preferentially oriented (110). By forming the lower electrode 330 and the intermediate electrode 350 under these conditions, it is possible to crystallize the PZT thin film and obtain good piezoelectric properties. Thereby, the drive voltage of the drive source 91 can be reduced.

The interlayer insulating film 380 is made of alumina (Al ₂ O ₃ ) or the like. The reflection enhancing film 390 is a laminated dielectric film in which dielectric films having different refractive indexes are laminated. The laminated dielectric film functions as a reflection increasing film that increases the reflectance in a low wavelength region (a region on the lower wavelength side than a wavelength of 550 nm) in the visible light region. The reflection enhancing film 390 is, for example, a laminated dielectric film in which a high refractive index film made of titanium oxide or the like is laminated on a low refractive index film made of alumina or the like. It is preferable that the difference in refractive index between the low refractive index film and the high refractive index film is large.

Note that the structure of the drive source 91 is not limited to the example shown in FIG. 3. For example, in the drive source 91, the piezoelectric film may have at least one layer. In this case, a three-layer structure is formed in which a lower electrode and an upper electrode are formed above and below the piezoelectric film, and an intermediate electrode is not necessary. Furthermore, three or more layers of piezoelectric films may be provided. In this case, the piezoelectric film and the intermediate electrode are alternately stacked on the lower electrode in the required number, and finally the piezoelectric film and the upper electrode are stacked on the uppermost layer of the intermediate electrode. are sequentially stacked.

By forming the piezoelectric film into n layers, the driving voltage of the driving source 91 can be reduced to 1/n of that in the case of one layer. Although the drive source 91 has been described above, the drive source 72 can also have the same structure as the drive source 91.

Referring to Figures 2 and 4, the lower electrode 330, the intermediate electrode 350, and the upper electrode 370 are electrically connected to the wiring 140 by a plurality of contact portions 140a. Each wiring 140 is connected to a corresponding terminal 130.

For example, in the vicinity of the contact portion 140a that connects the wiring 140 and the lower electrode 330, an interlayer insulating film 380, the wiring 140, and a reflective film 390 are stacked on the lower electrode 330. Then, three contact holes 380x that expose the lower electrode 330 are formed in a predetermined area of the interlayer insulating film 380 on the lower electrode 330, and the wiring 140 on the interlayer insulating film 380 enters into each contact hole 380x to form the lower part. It is connected to the electrode 330. The wiring 140 is made of, for example, gold (Au). Note that the contact portion 140a refers to the contact hole 380x and the wiring 140 filling the contact hole 380x.

In this manner, in this embodiment, a plurality of contact portions 140a are provided to connect the same location. As a result, the diameter of each contact hole 380x can be reduced, so the degree of freedom in layout of electrodes, wiring, etc. can be improved, and the pattern shape of the wiring can be changed.

For example, as shown on the left side of the arrow in FIG. 5, when there is one contact portion 140a connecting the same location, it is assumed that the diameter of the contact hole 380x is 40 μm. As shown on the right side of the arrow in FIG. 5 (same figure as FIG. 2), if there are a plurality of contact portions 140a (for example, three) connecting the same location, the diameter of each contact hole 380x is It can be made smaller than 40 μm. Considering workability, it is preferable that the diameter of each contact hole 380x is 3 μm or more. From the viewpoint of improving the degree of freedom in layout, the diameter of each contact hole 380x is preferably 20 μm or less, preferably 15 μm or less, and even more preferably 10 μm or less.

By shrinking the contact hole 380x in the E section and changing the layout of the wiring 140 accordingly, a vacant space is created in the F section, so that the vacant space can be used effectively. For example, the element size can be reduced.

Furthermore, in the G section, the piezoelectric film 340 and the upper electrode 370 have a notch 340x in a plan view, and a part of the intermediate electrode 350 is exposed in the notch 340x. The intermediate electrode 350 exposed within the cutout portion 340x is connected to the wiring 140 through a plurality of contact portions 140a.

With such a structure, an empty space is created above the intermediate electrode 350 by shrinking the contact hole 380x and changing the layout of the wiring 140 accordingly. Therefore, the area of the piezoelectric film 360 and the upper electrode 370 can be increased by extending the piezoelectric film 360 and the upper electrode 370 into the empty space, and as a result, the driving force of the driving source 91 can be improved.

In this manner, in a structure in which the lower electrode stacked closer to the substrate is exposed in a cutout provided in the upper electrode stacked farther from the substrate, and the lower electrode exposed in the cutout is connected to wiring at multiple contacts, the area of the piezoelectric film and upper electrode can be increased by shrinking the contact holes and changing the layout of the wiring accordingly, thereby improving the driving force of the driving source.

Note that even when the notch 340x is provided at a location other than the end (corner) of the piezoelectric film 340 and the upper electrode 370, the same process as above can be achieved by shrinking the contact hole 380x and changing the layout of the wiring 140 accordingly. be effective. Furthermore, even in the case of a structure that has an upper electrode and a lower electrode but no intermediate electrode, the same effect as above can be achieved by shrinking the contact hole and changing the wiring layout accordingly. play.

Further, the width of the wiring 140 can be reduced by shrinking the contact hole 380x in the E section and the G section, so the stress of the wiring 140 itself is reduced, and the driving force of the driving source 91 can be improved.

Note that the number of contact portions 140a connecting the same location may be any number as long as it is two or more, but it is preferable to include three or more contact portions arranged in a straight line, for example. By providing three or more contact portions 140a that connect the same location, the diameter of each contact hole 380x can be reduced, and the reliability of connection between objects to be connected can be improved.

Although the contact hole 380x can have a rectangular planar shape, it is preferably circular in consideration of resist workability and etching ease. Also, instead of arranging a plurality of circular contact holes 380x with the same diameter, it is possible to use a single elliptical contact hole, but considering resist workability and ease of etching, it is possible to use circular contact holes with the same diameter. It is preferable to arrange a plurality of contact holes 380x.

Furthermore, it is preferable that the spacing S between adjacent contact parts 140a is smaller than the diameter φ of each of the adjacent contact parts 140a. This allows the arrangement density of the multiple contact parts 140a to be increased, enabling further space saving. This is particularly effective when the optical scanning device 1 is built into a small device such as a smartphone.

However, it is not necessary to have multiple contacts for all connections between electrodes and wiring. For example, in areas where there is room in the layout, the electrode and wiring may be connected with a single contact with a relatively large diameter, as in the conventional case.

The optical scanning device 1 of the above embodiment can be applied to two-dimensional scanning type optical scanning devices such as eyewear, projectors, and smartphones, for example.

Further, in each of the above embodiments, an optical scanning device using a torsion bar is described as an example of the optical scanning device, but the present invention is also applicable to an optical scanning device that does not use a torsion bar. It is. Further, in each of the above embodiments, a two-dimensional scanning type optical scanning device is described as an example, but the device is not limited to a two-dimensional scanning type, and a one-dimensional scanning type optical scanning device in which a mirror section is oscillated in one direction is used. It may also be a scanning device.

Although the preferred embodiment has been described above, it is not limited to the embodiment described above, and various modifications and substitutions can be made to the embodiment described above without departing from the scope described in the claims. Can be done.

For example, the piezoelectric actuator according to the above embodiment may be used in devices other than optical scanning devices, such as inkjet heads.

1: optical scanning device, 10: mirror reflection surface, 20: stress relaxation region, 30: slit, 40: mirror section, 50: torsion bar, 51: piezoelectric sensor, 60, 100: connecting section, 70: horizontal drive section, 71: horizontal drive beam, 72: drive source, 80: movable frame, 90: vertical drive beam, 91: drive source, 92: piezoelectric sensor, 110: vertical drive section, 120: fixed frame, 130: terminal, 140: wiring , 140a: contact portion, 310: substrate, 320: insulating film, 330: lower electrode, 340: piezoelectric film, 350: intermediate electrode, 360: piezoelectric film, 370: upper electrode, 380: interlayer insulating film, 380x: contact hole , 390: Increased reflection film

Claims (5)

A substrate and
a piezoelectric element formed on the substrate;
and wiring formed on the substrate,
The piezoelectric element includes a first electrode, a first piezoelectric film formed on the first electrode, a second electrode formed on the first piezoelectric film, and a second electrode formed on the second electrode. 2 piezoelectric films, and a third electrode formed on the second piezoelectric film,
The second electrode is exposed in a notch provided in the third electrode at a corner of the piezoelectric element,
The first electrode and the third electrode are connected to a first wiring via a plurality of first contact portions arranged in a straight line along the width direction of the piezoelectric element,
In the piezoelectric actuator, the second electrode exposed in the notch is connected to a second wiring via a plurality of second contact parts arranged in a straight line along the longitudinal direction of the piezoelectric element. a distance between adjacent first contact portions is smaller than a diameter of the adjacent first contact portions ;
The piezoelectric actuator according to claim 1 , wherein the distance between adjacent second contact portions is smaller than a diameter of the adjacent second contact portions . The plurality of first contact parts include three or more first contact parts ,
The piezoelectric actuator according to claim 1 or 2 , wherein the plurality of second contact portions include three or more second contact portions . The piezoelectric actuator according to any one of claims 1 to 3, wherein each of the first contact portion and the second contact portion has a diameter smaller than 40 μm and 3 μm or more. An optical scanning device comprising a mirror portion driven by the piezoelectric actuator according to any one of claims 1 to 4 .

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