Movable device

Abstract

Provided is a movable device that can mitigate deterioration of a portion of wiring formed on a torsion bar.　A movable device according to the present disclosure comprises: a silicon structure including a torsion bar (26B) formed by processing a silicon substrate (30); and wiring (94) formed on the silicon structure, wherein a portion (94B) of the wiring that is formed on the torsion bar contains an amorphous alloy.

Description

Mobile

[0001] The technology of this disclosure relates to mobile devices.

[0002] Micromirror devices (also called microscanners) are known as one type of microelectromechanical systems (MEMS) device fabricated using silicon (Si) microfabrication technology. Because these micromirror devices are small and consume little power, they are expected to be widely used in laser displays, laser projectors, optical coherence tomography, and other applications.

[0003] Generally, a micromirror device includes a mirror portion, a torsion bar that supports the mirror portion so that the mirror portion can oscillate, and an actuator that oscillates the mirror portion.

[0004] Micromirror devices are formed by processing a silicon substrate. The torsion bars formed by processing the silicon substrate are vulnerable to stresses such as torsional stress, so it is known that the torsion bars are formed from an amorphous alloy, which has excellent mechanical properties (see, for example, JP 2017-032627 A).

[0005] However, in micromirror devices, wiring is sometimes formed on the torsion bars. This means that the wiring on the torsion bars, which are subject to high stress, is prone to deterioration such as cracking and peeling. Similar problems can occur in moving devices other than micromirror devices.

[0006] The technique of the present disclosure aims to provide a movable device that can suppress deterioration of the portion of the wiring formed on the torsion bar.

[0007] In order to achieve the above object, the movable device of the present disclosure is a movable device comprising a silicon structure including a torsion bar formed by processing a silicon substrate, and wiring formed on the silicon structure, wherein the portion of the wiring formed on the torsion bar contains an amorphous alloy.

[0008] When X-ray diffraction measurement is performed on the torsion bar, the peak value of the diffracted X-ray intensity corresponding to the amorphous alloy is preferably 0.2 times or less the peak value of the diffracted X-ray intensity corresponding to the silicon structure.

[0009] The amorphous alloy preferably contains Al and Ti.

[0010] When the portion of the wiring that does not contain an amorphous alloy is designated as the first wiring and the portion that contains an amorphous alloy is designated as the second wiring, it is preferable that the second wiring is formed in a state where a portion of it overlaps the first wiring.

[0011] The first wiring is preferably an Au wiring.

[0012] It is preferable that the device includes a mirror portion, a drive portion that applies a rotational torque to the mirror portion to cause it to oscillate, and a fixed frame that surrounds the mirror portion and the drive portion, and that the torsion bar be connected between the fixed frame and the drive portion.

[0013] The wiring preferably transmits a drive signal applied to the drive unit.

[0014] The silicon substrate is preferably an SOI substrate.

[0015] According to the technology of the present disclosure, it is possible to provide a movable device that can suppress deterioration of the portion of the wiring formed on the torsion bar.

[0016] 1 is a schematic diagram of an optical scanning device. FIG. 2 is a perspective view of the appearance of a micromirror device. FIG. 3 is a cross-sectional view of the micromirror device cut along a second axis. FIG. 4 is a cross-sectional view showing a state in which the mirror section has rotated around the first axis. FIG. 5 is a plan view showing an example of the layout of electrode pads and wiring provided on the micromirror device. FIG. 6 is a diagram showing an example of the configuration of wiring that transmits a first drive signal. FIG. 7 is a diagram showing an example of the process of forming wiring. FIG. 8 is a diagram showing a cross-section of a second wiring when the annealing temperature is below a certain temperature. FIG. 9 is a diagram showing an electron diffraction image of the second wiring when the annealing temperature is below a certain temperature. FIG. 10 is a diagram showing a cross-section of the second wiring when the annealing temperature is equal to or higher than a certain temperature. FIG. 11 is a diagram showing an electron diffraction image of the second wiring when the annealing temperature is equal to or higher than a certain temperature. FIG. 12 is a diagram showing a diffraction spectrum measured by an X-ray diffraction device. FIG. 13 is a diagram explaining the definition of the peak value of diffracted X-ray intensity.

[0017] An example of an embodiment of the technology of the present disclosure will be described with reference to the accompanying drawings.

[0018] 1 is a schematic diagram of an optical scanning device 10 according to one embodiment. The optical scanning device 10 includes a micro mirror device (MMD) 2, a light source 3, and a drive controller 4. The optical scanning device 10 optically scans a scanned surface 5 by reflecting a light beam LB emitted from the light source 3 by the MMD 2 under the control of the drive controller 4. The scanned surface 5 may be a screen, a human retina, or the like. The MMD 2 is an example of a "movable device" according to the technology of the present disclosure.

[0019] MMD2 is the first axis a １ and the first axis a １ The second axis a intersecting ２ The micromirror device is a piezoelectric two-axis drive type that can oscillate the mirror portion 20 (see FIG. 2) around the first axis a. １ The direction parallel to this is the X direction, and the second axis a ２ The direction parallel to the axis a is the Y direction. １ and the second axis a ２ The direction perpendicular to the X direction is called the Z direction. In this embodiment, the X direction and the Y direction are perpendicular to each other.

[0020] The light source 3 is a laser device that emits, for example, laser light as the light beam LB. It is preferable that the light source 3 irradiates the light beam LB perpendicularly to a reflecting surface 20A (see FIG. 2) of the mirror portion 20 when the mirror portion 20 of the MMD 2 is stationary.

[0021] The drive control unit 4 outputs drive signals to the light source 3 and the MMD 2 based on the optical scanning information. The light source 3 generates a light beam LB based on the input drive signal and irradiates the MMD 2 with the light beam LB. The MMD 2 rotates the mirror unit 20 along the first axis a based on the input drive signal. １ and the second axis a ２ Rock it around.

[0022] The drive control unit 4 rotates the mirror unit 20 along the first axis a １ and the second axis a ２ , and the light beam LB reflected by the mirror portion 20 is scanned so as to trace a Lissajous waveform on the surface to be scanned 5. This optical scanning method is called a Lissajous scanning method.

[0023] The optical scanning device 10 is applicable to, for example, a Lissajous scanning laser display. Specifically, the optical scanning device 10 is applicable to a laser scanning display such as an augmented reality (AR) glass or a virtual reality (VR) glass.

[0024] Next, the configuration of the MMD 2 will be described with reference to Figures 2 and 3. Figure 2 is a perspective view of the appearance of the MMD 2. Figure 3 shows the MMD 2 mounted on the second axis a ２ FIG.

[0025] 2, the MMD 2 has a mirror section 20, a pair of first support sections 21, a pair of movable frames 22, a pair of second support sections 23, a first actuator 24, a second actuator 25, a pair of first connection sections 26A, a pair of second connection sections 26B, and a fixed frame 27. The MMD 2 is a so-called MEMS scanner.

[0026] The mirror section 20 has a reflecting surface 20A that reflects incident light. The reflecting surface 20A is formed of a thin metal film such as gold (Au) or aluminum (Al) provided on one surface of the mirror section 20. The shape of the reflecting surface 20A is, for example, a first axis a １ and the second axis a ２ It is a circle with the intersection point of

[0027] 1st axis a １ and the second axis a ２ For example, when the mirror unit 20 is stationary, the first axis a is present in a plane including the reflecting surface 20A. １ and is symmetrical about the second axis a ２ It is symmetrical about the center.

[0028] The pair of first support portions 21 are ２ and the second axis a ２ Each of the first support portions 21 has a shape that is line-symmetrical about the first axis a. １ Each of the first support portions 21 has a shape that is line-symmetrical about the first axis a １ The mirror section 20 is connected to the first axis a １ It is supported so that it can swing around.

[0029] The pair of movable frames 22 are arranged along a first axis a １ and are arranged at positions facing each other across the first axis a １ Each of the movable frames 22 has a shape that is line-symmetrical about the second axis a ２ The movable frames 22 are shaped to be line-symmetrical about the center. Each movable frame 22 is curved along the outer periphery of the mirror section 20. Both ends of each movable frame 22 are connected to a pair of first support sections 21.

[0030] The pair of first support parts 21 and the pair of movable frames 22 are connected to each other to surround the mirror part 20. The mirror part 20, the pair of first support parts 21, and the pair of movable frames 22 constitute the movable part 60.

[0031] The pair of second support portions 23 are １and are arranged at positions facing each other across the first axis a １ Each of the second support portions 23 has a shape that is line-symmetrical about the second axis a ２ Each of the second support portions 23 has a shape that is line-symmetrical about the second axis a ２ The movable portion 60 having the mirror portion 20 is connected to the movable frame 22 on the second axis a. ２ Both ends of each of the second support portions 23 are connected to a first actuator 24.

[0032] The first actuator 24 is ２ The piezoelectric actuator is configured by a pair of piezoelectric actuators facing each other with the second axis a ２ Each of the first actuators 24 has a shape that is symmetrical about the first axis a. １ The first actuator 24 is disposed along the outer periphery of the pair of movable frames 22 and the pair of first support portions 21.

[0033] In FIG. 2, the piezoelectric actuator constituting the first actuator 24 is １ It appears to be separated by the first axis a １ The two piezoelectric actuators facing each other with the piezoelectric element sandwiched therebetween are electrically connected by wiring (not shown).

[0034] The pair of second support portions 23 and the first actuator 24 are connected to each other, thereby surrounding the movable portion 60 .

[0035] The second actuator 25 is １ The piezoelectric actuator is configured by a pair of piezoelectric actuators facing each other with a first axis a １ The second actuator 25 has a shape that is symmetrical about the second axis a. ２ The second actuator 25 is disposed along the outer periphery of the first actuator 24 and the pair of second support portions 23.

[0036] In FIG. 2, the piezoelectric actuator constituting the second actuator 25 is ２Although it appears to be separated near the second axis a ２ The two piezoelectric actuators facing each other with the piezoelectric element sandwiched therebetween are electrically connected by wiring (not shown).

[0037] The pair of first connecting portions 26A are connected to the second axis a ２ and the second axis a ２ Each of the first connection portions 26A has a shape that is line-symmetrical about the first axis a. １ Each of the first connection portions 26A has a shape that is line-symmetrical about the first axis a. １ and arranged along a first axis a １ The first connecting portion 26A connects the first actuator 24 and the second actuator 25. Each of the first connecting portions 26A is an example of a "torsion bar" according to the technology of the present disclosure.

[0038] The pair of second connection portions 26B are connected to the first axis a １ and are arranged at positions facing each other across the first axis a １ Each of the second connection portions 26B extends in the Y direction and is symmetrical about the second axis a ２ Each of the second connection portions 26B has a shape that is line-symmetrical about the second axis a ２ and arranged along a second axis a ２ The second connecting portion 26B connects the second actuator 25 and the fixed frame 27. Each of the second connecting portions 26B is an example of a "torsion bar" according to the technology of the present disclosure.

[0039] The second actuator 25 and the pair of second connection portions 26B are connected to each other, thereby surrounding the pair of movable portions 60 and the first actuator 24. The first actuator 24 and the second actuator 25 constitute a drive unit arranged to surround the pair of movable frames 22. That is, the drive unit is １ or the second axis a ２ The piezoelectric actuators are arranged opposite each other with the piezoelectric element therebetween.

[0040] The fixed frame 27 is a frame-shaped member having a rectangular outer shape, and has a first axis a １ and the second axis a ２The fixed frame 27 surrounds the outer periphery of the second actuator 25 and the pair of second connection portions 26B. In other words, the fixed frame 27 is disposed surrounding the drive unit. The pair of second connection portions 26B are connected between the fixed frame 27 and the drive unit.

[0041] The first actuator 24 is connected to the mirror unit 20 and the pair of movable frames 22 by a second axis a ２ By applying a rotational torque around the second axis a, the movable part 60 is rotated ２ The second actuator 25 rotates the mirror unit 20, the pair of movable frames 22, and the first actuator 24 around the first axis a. １ By applying a rotation torque around the first axis a １ Swing it around.

[0042] Four piezoelectric sensors 51 to 54 are provided near the pair of second connection portions 26B as angle sensors for detecting the angle of the mirror portion 20. The piezoelectric sensors 51 to 54 are formed of piezoelectric elements, similar to the first actuator 24 and the second actuator 25. The piezoelectric sensors 51 to 54 are arranged along the first axis a １ and the second axis a ２ Specifically, the piezoelectric sensors 51 and 52 are arranged near one of the pair of second connection portions 26B, and the positions and shapes of the piezoelectric sensors 51 and 52 are aligned with each other about the second axis a ２ The piezoelectric sensors 53 and 54 are arranged near the other of the pair of second connection portions 26B, and are positioned and shaped such that they are symmetrical about the second axis a ２ They are in a line-symmetric relationship with respect to each other.

[0043] 2 does not show wiring and electrode pads for transmitting drive signals to the first actuator 24 and the second actuator 25. Also, wiring and electrode pads for acquiring voltage signals output from the piezoelectric sensors 51 to 54 are not shown. A plurality of electrode pads are provided on the fixed frame 27.

[0044] 3, the MMD 2 is formed, for example, by etching an SOI (Silicon On Insulator) substrate 30. The SOI substrate 30 is a substrate in which a silicon oxide layer 32 is provided on a silicon support layer 31 made of single crystal silicon, and a silicon active layer 33 made of single crystal silicon is provided on the silicon oxide layer 32. The SOI substrate 30 is an example of a "silicon substrate" according to the technology of the present disclosure.

[0045] The mirror section 20, the pair of first support sections 21, the pair of movable frames 22, the pair of second support sections 23, the first actuator 24, the second actuator 25, the pair of first connecting sections 26A, and the pair of second connecting sections 26B are formed from a silicon active layer 33 that remains when the silicon support layer 31 and the silicon oxide layer 32 are removed from the SOI substrate 30 by etching. The silicon active layer 33 functions as an elastic section having elasticity. The silicon active layer 33 is an example of a "silicon structure including torsion bars formed by processing a silicon substrate" according to the technology of the present disclosure.

[0046] The fixed frame 27 is formed of three layers: a silicon support layer 31, a silicon oxide layer 32, and a silicon active layer 33. That is, the mirror section 20, the pair of first support sections 21, the pair of movable frames 22, the pair of second support sections 23, the first actuator 24, the second actuator 25, the pair of first connecting sections 26A, and the pair of second connecting sections 26B are each thinner than the fixed frame 27.

[0047] The piezoelectric actuator constituting the first actuator 24 is composed of a piezoelectric element formed on a silicon active layer 33. The piezoelectric element has a layered structure in which a lower electrode, a piezoelectric film, and an upper electrode are layered in this order on the silicon active layer 33. The second actuator 25 has the same configuration as the first actuator 24.

[0048] The lower electrode and the upper electrode are made of a metal such as gold (Au) or platinum (Pt). The piezoelectric film is made of a piezoelectric material such as PZT (lead zirconate titanate). The lower electrode and the upper electrode are electrically connected to the drive control unit 4 via wiring and electrode pads.

[0049] The lower electrode is connected to the drive control unit 4 via wiring and an electrode pad, and is supplied with a ground potential. A drive voltage is applied from the drive control unit 4 to the upper electrode.

[0050] When a positive or negative voltage is applied to the piezoelectric film in the polarization direction, the piezoelectric film undergoes deformation (e.g., expansion and contraction) proportional to the applied voltage. In other words, the piezoelectric film exhibits the so-called inverse piezoelectric effect. When a drive voltage is applied to the upper electrode from the drive control unit 4, the piezoelectric film exhibits the inverse piezoelectric effect, displacing the first actuator 24 and the second actuator 25.

[0051] FIG. 4 shows a state in which one of a pair of piezoelectric actuators constituting the second actuator 25 is expanded and the other is contracted, whereby the second actuator 25 is caused to move along the first axis a １ In this way, one of the pair of piezoelectric actuators is displaced in the opposite directions, so that the mirror section 20 rotates around the first axis a １ Similarly, when one of the pair of piezoelectric actuators constituting the first actuator 24 is displaced in the opposite directions, the mirror section 20 rotates around the second axis a ２ When the mirror section 20 rotates in this manner, high stress is applied to the pair of first connecting sections 26A, the pair of second connecting sections 26B, and the like.

[0052] Fig. 5 shows an example of the layout of electrode pads and wiring provided on the MMD 2. Fig. 5 is a partial enlarged view of a region including one second connection portion 26B.

[0053] A plurality of electrode pads 80 to 84 are formed on the fixed frame 27. The electrode pad 80 is an electrode pad for applying a ground potential, and is connected to a wiring 90. The wiring 90 is connected to the lower electrodes of the piezoelectric actuators that make up the first actuator 24 and the second actuator 25, and the lower electrodes of the piezoelectric sensors 51 to 54.

[0054] The electrode pad 81 is an electrode pad for acquiring a voltage signal from the piezoelectric sensor 51, and is connected to the above-mentioned wiring 91. Similarly, the electrode pad 82 is an electrode pad for acquiring a voltage signal from the piezoelectric sensor 52, and is connected to the wiring 92.

[0055] The electrode pad 83 is an electrode pad for applying a second drive signal to the first actuator 24, and is connected to a wiring 93. The wiring 93 is connected to the upper electrode of the piezoelectric actuator that constitutes the first actuator 24. In addition, on the fixed frame 27, a second axis a ２ A pair of electrode pads 83 are provided at positions facing each other with the electrode 83 sandwiched therebetween, and are electrically connected to each other via wiring 93 .

[0056] The electrode pad 84 is an electrode pad for applying a first drive signal to the second actuator 25, and is connected to a wiring 94. The wiring 94 is connected to the upper electrode of the piezoelectric actuator that constitutes the second actuator 25.

[0057] The wiring 90, 93, and 94 are routed from above the fixing frame 27, passing over the second connection portion 26B, to the formation region of the second actuator 25. Furthermore, although not shown in Fig. 5, the wiring 90 and 93 are further routed from the second actuator 25, passing over the first connection portion 26A, to the formation region of the first actuator 24. In other words, the wiring 90, 93, and 94 are an example of "wiring formed on a silicon structure" according to the technology of the present disclosure.

[0058] Furthermore, wirings 95 and 93D are formed on the MMD 2. The wirings 95 are included in each of the first actuators 24 and are connected to the second axis a ２ The wiring 93D connects the upper electrodes of the two piezoelectric actuators that face each other across the second axis a. ２ The dummy wiring is formed at a position that is line-symmetrical to the wiring 93 with respect to the center, and is electrically isolated.

[0059] 6 is a schematic diagram showing an example of the structure of the wiring 94 for transmitting the first drive signal. The wiring 94 is formed on the silicon active layer 33. Specifically, the surface of the silicon active layer 33 is covered with silicon dioxide (SiO ２ ) and wiring 94 is formed on the thermal oxide film 33A.

[0060] The wiring 94 is configured to include a first wiring 94A and a second wiring 94B. One end of the first wiring 94A is connected to the electrode pad 84, and the other end is connected to the second wiring 94B. The first wiring 94A is mainly provided in an area (such as the fixed frame 27) where stress applied when the mirror section 20 oscillates is small. The second wiring 94B is mainly provided in an area (such as the surfaces of the first connection section 26A and the second connection section 26B) where stress applied when the mirror section 20 oscillates is large.

[0061] For example, the first wiring 94A is an Au wiring formed from gold (Au). The second wiring 94B is formed from an amorphous alloy. That is, the wiring 94 contains an amorphous alloy in the portion formed on the first connection portion 26A (i.e., the torsion bar). The portion of the wiring 94 that does not contain an amorphous alloy is the first wiring 94A, and the portion that contains an amorphous alloy is the second wiring 94B.

[0062] An amorphous alloy is an alloy that does not have a regular arrangement of atoms over a range of several atoms or more in size and does not have a crystalline structure. In this embodiment, the second interconnect 94B is an amorphous alloy containing aluminum (Al) and titanium (Ti). The composition ratio of Al to Ti contained in the amorphous alloy is, for example, 75%:25% in atomic ratio. Note that a barrier metal layer made of titanium (Ti) or the like is integrally formed on the bottom of each of the first interconnect 94A and the second interconnect 94B.

[0063] The first wiring 94A has better conductivity than the second wiring 94B. On the other hand, the second wiring 94B has better mechanical properties than the second wiring 94B. For this reason, in this embodiment, the portion of the wiring 94 above the torsion bar, which is subjected to high stress, is made into the second wiring 94B, and the other portion is made into the first wiring 94A. This prevents deterioration of the portion above the torsion bar due to stress (for example, the occurrence of cracks, peeling, etc.), and provides the wiring 94 with excellent conductivity.

[0064] Like the wiring 94, the wirings 90 and 93 are configured by connecting a first wiring such as an Au wiring to a second wiring formed of an amorphous alloy. Furthermore, the wirings 90 and 93 have the second wiring formed on the torsion bar where high stress is applied. This prevents deterioration of the wirings 90 and 93 on the torsion bar due to stress (e.g., cracks, peeling, etc.), and provides excellent conductivity.

[0065] 7A and 7B schematically show the steps of forming the wiring 94. First, an Au film is evaporated onto the surface of the silicon active layer 33 of the SOI substrate 30, and the evaporated Au film is patterned to form the first wiring 94A. The Au film is evaporated after a barrier metal is evaporated.

[0066] After the first wiring 94A is formed, an amorphous alloy film is evaporated and the evaporated amorphous alloy film is patterned to form the second wiring 94B. The amorphous alloy film is evaporated after a barrier metal is evaporated.

[0067] The first and second wirings constituting the wirings 90 and 93 are formed simultaneously with the first and second wirings 94A and 94B constituting the wiring 94.

[0068] After all structures such as wiring, electrode pads, piezoelectric actuators, and piezoelectric sensors are formed on the silicon active layer 33, the SOI substrate 30 is subjected to an etching process.

[0069] In this way, the second wiring 94B is formed after the first wiring 94A is formed, so that the second wiring 94B is formed in a state where a part of it overlaps the first wiring 94A.

[0070] The second wiring 94B, which is made of an amorphous alloy, has a high resistance due to surface oxidation over time, but the surface of the first wiring 94A, which is an Au wiring, does not oxidize and maintains a low resistance. As described above, by making the second wiring 94B partially overlap the first wiring 94A, the contact resistance between the first wiring 94A and the second wiring 94B is reduced, improving the conductivity of the wiring 94. The same effect can be obtained with the wirings 90 and 93, which are formed simultaneously with the wiring 94.

[0071] The MMD 2 is used in a hermetically sealed state in a package (not shown). The package has an opening, and a cover glass is attached to the opening to allow the light beam LB to pass through. Annealing is performed in a post-processing step after sealing the MMD 2 in the package. Although amorphous alloys have excellent mechanical properties, high temperatures during the annealing process can cause crystallization, which can degrade the mechanical properties. The present applicant has discovered that even if the wiring 90, 93, and 94 are formed as described above, high temperatures during the annealing process in a post-processing step (hereinafter referred to as the annealing temperature) can cause deterioration (e.g., cracking, peeling, etc.) of the second wiring formed from the amorphous alloy. Therefore, by setting the annealing temperature below a certain temperature, the second wiring can be maintained in an amorphous state, thereby suppressing deterioration of the second wiring.

[0072] Fig. 8 shows a cross section of the second wiring when the annealing temperature is below a certain temperature. Fig. 9 shows an electron diffraction image of the second wiring when the annealing temperature is below a certain temperature. When the annealing temperature is below a certain temperature, the second wiring remains in an amorphous state. Fig. 9 shows that there are no diffraction points in the electron diffraction image, indicating that crystallization has not occurred.

[0073] Fig. 10 shows a cross section of the second wiring when the annealing temperature is equal to or higher than a certain temperature. Fig. 11 shows an electron diffraction image of the second wiring when the annealing temperature is equal to or higher than a certain temperature. When the annealing temperature is equal to or higher than a certain temperature, crystallization occurs in the second wiring. Fig. 11 shows that diffraction points exist in the electron diffraction image, indicating that crystallization has occurred.

[0074] FIG. 12 shows the diffraction spectrum obtained by performing X-ray diffraction measurement on the torsion bar. In FIG. 12, the vertical axis represents the diffracted X-ray intensity, and the horizontal axis represents the diffraction angle. The applicant prepared multiple samples of MMD2, annealed each sample at different annealing temperatures Ta, and then measured the diffraction spectrum. FIG. 12(A) shows the diffraction spectrum when Ta = 200°C. FIG. 12(B) shows the diffraction spectrum when Ta = 250°C. FIG. 12(C) shows the diffraction spectrum when Ta = 275°C. FIG. 12(D) shows the diffraction spectrum when Ta = 300°C. The annealing time was 10 minutes in all cases.

[0075] 12A to 12D, P1 represents the peak of diffracted X-ray intensity corresponding to the silicon structure (in the above embodiment, the silicon active layer 33) present below the second wiring. P2 represents the peak of diffracted X-ray intensity corresponding to the amorphous alloy contained in the second wiring (in the above embodiment, for example, the second wiring 94B). Specifically, peak P1 represents the intensity of X-rays diffracted by the silicon crystals that make up the silicon structure. Peak P2 represents the intensity of X-rays diffracted by the crystallization of the amorphous alloy contained in the second wiring.

[0076] As shown in Figures 12(A) to 12(D), as the annealing temperature Ta increases, peak P2 appears in the diffraction spectrum. This is because the amorphous alloy is partially crystallized by the annealing process. When the second wiring crystallizes, deterioration (e.g., cracks, peeling, etc.) occurs due to stress. The applicant has confirmed that by setting the annealing temperature Ta to less than 260°C in a post-process, crystallization of the amorphous alloy is suppressed, and deterioration due to stress is suppressed. In other words, when Ta is less than 260°C, peak P2 hardly appears in the diffraction spectrum.

[0077] 13, the peak value of the diffracted X-ray intensity corresponding to the silicon structure is I1, and the peak value of the diffracted X-ray intensity corresponding to the amorphous alloy contained in the second wiring is I2. In order to suppress deterioration of the second wiring due to stress, it is preferable that the peak value I2 be 0.2 times or less the peak value I1 (i.e., I2≦0.2×I1) after the annealing treatment.

[0078] The configuration of the MMD 2 according to the above embodiment is an example, and various modifications are possible. Furthermore, the technology of the present disclosure is not limited to MMDs, and can be applied to other movable devices formed by MEMS technology.

[0079] The above description allows the understanding of the following technologies. [Supplementary Item 1] A movable device comprising: a silicon structure including torsion bars formed by processing a silicon substrate; and wiring formed on the silicon structure, wherein a portion of the wiring formed on the torsion bars contains an amorphous alloy. [Supplementary Item 2] The movable device according to Supplementary Item 1, wherein, when X-ray diffraction measurement is performed on the torsion bars, the peak value of the diffracted X-ray intensity corresponding to the amorphous alloy is 0.2 times or less the peak value of the diffracted X-ray intensity corresponding to the silicon structure. [Supplementary Item 3] The movable device according to Supplementary Item 1 or Supplementary Item 2, wherein the amorphous alloy contains Al and Ti. [Supplementary Item 4] The movable device according to any one of Supplementary Items 1 to 3, wherein, when a portion of the wiring not containing the amorphous alloy is defined as a first wiring and a portion containing the amorphous alloy is defined as a second wiring, the second wiring is formed so as to partially overlap the first wiring. [Supplementary Item 5] The movable device according to Supplementary Item 4, wherein the first wiring is an Au wiring. [Supplementary Item 6] The movable device according to any one of Supplementary Items 1 to 5, including: a mirror section; a driver section that applies rotational torque to the mirror section to cause it to oscillate; and a fixed frame that surrounds the mirror section and the driver section, wherein the torsion bar is connected between the fixed frame and the driver section. [Supplementary Item 7] The movable device according to Supplementary Item 6, wherein the wiring transmits a drive signal applied to the driver section. [Supplementary Item 8] The movable device according to any one of Supplementary Items 1 to 7, wherein the silicon substrate is an SOI substrate.

Claims

1. A movable device comprising: a silicon structure including a torsion bar formed by processing a silicon substrate; and wiring formed on the silicon structure, wherein the portion of the wiring formed on the torsion bar contains an amorphous alloy.

2. The movable device according to claim 1, wherein, when X-ray diffraction measurement is performed on the torsion bar, the peak value of the diffracted X-ray intensity corresponding to the amorphous alloy is 0.2 times or less the peak value of the diffracted X-ray intensity corresponding to the silicon structure.

3. The movable device according to claim 1, wherein the amorphous alloy contains Al and Ti.

4. A movable device as described in claim 1, wherein, when a portion of the wiring that does not contain the amorphous alloy is defined as a first wiring and a portion that contains the amorphous alloy is defined as a second wiring, the second wiring is formed in a state where a portion of the second wiring overlaps the first wiring.

5. The movable device according to claim 4, wherein the first wiring is an Au wiring.

6. A movable device as described in claim 1, comprising: a mirror section; a drive section which applies a rotational torque to the mirror section to cause it to oscillate; and a fixed frame which surrounds the mirror section and the drive section, wherein the torsion bar is connected between the fixed frame and the drive section.

7. The movable device according to claim 6, wherein the wiring transmits a drive signal applied to the drive section.

8. The movable device according to claim 1, wherein the silicon substrate is an SOI substrate.

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