Manufacturing method of mirror device

Abstract

To provide a mirror device manufacturing method which can suitably manufacture a mirror device having a movable part.SOLUTION: A mirror device comprises: a structure 50 having a support part 2, a first movable part 3, and a first connection part 5; and a mirror layer 7 provided on top of the first movable part 3. A mirror device manufacturing method comprises: a first formation step for forming on an SOI wafer 80 on which a plurality of portions S each corresponding to the structure 50 are formed; a second formation step for forming the mirror layer 7 on top of a portion corresponding to the first movable part 3 in each of the plurality of portions S; a heating step for heating the portion corresponding to the first movable part 3 in each of the plurality of portions S after the first and the second formation steps; and a cutting step for cutting the SOI wafer 80 after the heating step so that the plurality of portions S are separated from each other.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a mirror device having a movable part. [Background technology]

[0002] Patent Document 1 describes a method for manufacturing a mirror device having a movable part. In the manufacturing method described in Patent Document 1, a plurality of micromechanical structures having movable structures are formed on a semiconductor substrate, and then dicing is performed to separate the plurality of micromechanical structures from one another. At this point, the movable structures are curved. Next, a metal layer that functions as a mirror is formed on the movable structures, and then the entire micromechanical structure is heated. This heating process flattens the movable structures. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-168819 A Summary of the Invention [Problem to be solved by the invention]

[0004] The manufacturing method of the above-mentioned mirror device is required to manufacture the mirror device in a better manner. Therefore, an object of the present invention is to provide a manufacturing method of a mirror device that can manufacture a mirror device having a movable part in a good manner. [Means for solving the problem]

[0005] The method for manufacturing a mirror device of the present invention is a method for manufacturing a mirror device comprising a structure having a support part, a movable part, and a connecting part that connects the movable part to the support part so that the movable part can oscillate or move, and a mirror layer provided on the movable part, and includes a first formation step of forming a plurality of parts on a wafer, each of which corresponds to the structure, a second formation step of forming a mirror layer on a part of each of the plurality of parts that corresponds to the movable part, a heating step of heating the part of each of the plurality of parts that corresponds to the movable part after the first formation step and the second formation step, and a cutting step of cutting the wafer so that the plurality of parts are separated from each other after the heating step.

[0006] When the mirror layer is formed, residual stress may occur in the mirror layer, and the residual stress may cause warping in the mirror layer. If the mirror device is shipped in this state, there is a concern that the residual stress may be alleviated by the environmental temperature or self-heating during use, causing the amount of warping in the mirror layer to change. In contrast, in this manufacturing method for a mirror device, a plurality of parts each corresponding to a structure are formed on a wafer, and after a mirror layer is formed on a portion corresponding to a movable part in each of the plurality of parts, the portion corresponding to the movable part in each of the plurality of parts is heated. This allows the residual stress present in the mirror layer to be alleviated, and the amount of warping in the mirror layer to be suppressed from changing during use of the mirror device. In addition, in this manufacturing method for a mirror device, the wafer is cut after the heating. This allows the temperature of the mirror layer during heating to be uniform among the plurality of parts, as compared to a case where a heating process is performed after cutting the wafer. As a result, the variation in quality of the mirror device can be suppressed. In addition, by heating in the wafer state, many mirror devices can be placed in, for example, a thermostatic chamber used for heating. As a result, the manufacturing efficiency of the mirror device can be improved. Furthermore, when measuring the amount of warping in the mirror layer after heating, for example, the amount of warping can be measured in the wafer state. In this case, the position of the mirror layer can be easily grasped accurately, so that the measurement can be made more efficient. Furthermore, for example, when cleaning the mirror layer after heating, cleaning can be performed in the wafer state, so that the cleaning workability can be improved. Furthermore, when performing a heat treatment after cutting the wafer, chips of the wafer generated during cutting may adhere to the mirror layer. In this case, there is a concern that the chips are heated during the heat treatment, and the semiconductor material constituting the chips diffuses into the mirror layer, resulting in a decrease in the reflectance of the mirror layer. In contrast, in this method of manufacturing a mirror device, the wafer is cut after heating in the wafer state, so that such a situation can be suppressed. As a result, the quality of the mirror device can be ensured. As described above, according to this method of manufacturing a mirror device, a mirror device having a movable part can be manufactured satisfactorily.

[0007] The method for manufacturing a mirror device of the present invention may further include a measuring step for measuring the amount of warping of the mirror layer between the heating step and the cutting step. In this case, the amount of warping of the mirror layer can be measured in a wafer state, and the measurement can be made more efficient.

[0008] In the cutting step, a modified region may be formed inside the wafer by irradiating the wafer with laser light, and a crack may be propagated from the modified region in the thickness direction of the wafer to cut the wafer. In this case, the stress acting on the wafer during cutting can be reduced, and deformation of the mirror layer and the movable part due to the stress can be suppressed. In addition, the warpage of the mirror layer during cutting can be suppressed from changing.

[0009] The second forming step may be carried out after the first forming step, which can prevent the quality of the mirror layer from being deteriorated due to heat generated when forming the multiple portions.

[0010] In the heating step, the amount of warping of the mirror layer may be reduced by heating the portions of each of the plurality of parts that correspond to the movable parts. Alternatively, the amount of warping of the mirror layer may be increased by heating the portions of each of the plurality of parts that correspond to the movable parts. In either case, the residual stress present in the mirror layer can be alleviated, and the amount of warping of the mirror layer can be prevented from changing when the mirror device is used.

[0011] In the second formation step, the mirror layer may be formed by sputtering, in which case the mirror layer can be formed satisfactorily.

[0012] The mirror device may further include a coil or a piezoelectric element for applying a driving force to the movable portion. In this case, heat is likely to be generated when the mirror device is used, but according to the manufacturing method of the mirror device, even in such a case, the warping amount of the mirror layer can be suppressed from changing when the mirror device is used.

[0013] In the heating step, the portion of each of the plurality of parts corresponding to the movable part may be heated to 60° C. or more and 300° C. or less. In this case, the residual stress present in the mirror layer can be effectively alleviated.

[0014] The maximum width of the mirror layer may be 0.5 mm or more and 30 mm or less. In this case, the amount of warping of the mirror layer is likely to change when the mirror device is used. However, according to this manufacturing method for a mirror device, even in such a case, the amount of warping of the mirror layer can be prevented from changing when the mirror device is used.

[0015] The mirror layer may include an adhesion layer, a diffusion prevention layer, and a reflective layer formed in this order on the movable part. In this case, the inclusion of the adhesion layer allows the mirror layer to be stably formed on the movable part. Furthermore, the inclusion of the diffusion prevention layer can suppress metal diffusion between the reflective layer and the adhesion layer during heating.

[0016] The mirror layer includes a plurality of layers including a reflective layer, and the plurality of layers may include a layer in which compressive stress remains at the time of completion of the second formation step and a layer in which tensile stress remains at the time of completion of the second formation step. In this case, the amount of warping of the mirror layer before the heating step can be reduced. Also, the change in the amount of warping of the mirror layer during the heating step can be reduced, and as a result, the heating time can be shortened and the amount of warping of the mirror layer can be easily controlled.

[0017] In the heating step, the entire wafer may be heated, in which case the temperature of the mirror layer during heating can be made uniform among a plurality of portions.

[0018] In the heating step, the entire wafer may not be heated, but the portions of each of the plurality of portions corresponding to the movable parts may be heated. Even in this case, even if the positions and outputs of the heat sources used in the heating step vary, the temperature of the mirror layer can be uniformed among the plurality of portions by conducting heat within the wafer. Effect of the Invention

[0019] According to the present invention, it is possible to provide a method for manufacturing a mirror device that can satisfactorily manufacture a mirror device having a movable portion. [Brief description of the drawings]

[0020] [Figure 1] FIG. 2 is a plan view of the mirror device. [Diagram 2] FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. [Diagram 3] 5(a) and 5(b) are diagrams illustrating a manufacturing method of a mirror device. [Figure 4] 5(a) and 5(b) are diagrams illustrating a manufacturing method of a mirror device. [Diagram 5] 13(a) and 13(b) are diagrams illustrating a process for forming a mirror layer. [Figure 6] 10 is a graph showing an example of a change in the amount of warping of a mirror layer during a heating process. [Figure 7] FIG. 11 is a diagram for explaining a cutting process. [Figure 8] FIG. 2 is a cross-sectional view of a mirror device housed in a package. [Figure 9] 13(a) and 13(b) are diagrams illustrating a manufacturing method of a mirror device according to a modified example. [Figure 10] 13 is a graph showing an example of a change in the amount of warping of a mirror layer during a heating process in a modified example. [Figure 11] 11 is a graph showing an example of a change in the amount of warping of a mirror layer in a reliability test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding elements are designated by the same reference numerals, and duplicated description will be omitted. [Mirror device]

[0022] 1 and 2, the mirror device 1 has a support section 2 and a movable mirror section 10. The movable mirror section 10 has a first movable section 3, a second movable section 4, a pair of first connecting sections 5, a pair of second connecting sections 6, and a mirror layer 7. The support section 2, the first movable section 3, the second movable section 4, the pair of first connecting sections 5, and the pair of second connecting sections 6 configure a structure 50. In other words, the mirror device 1 includes the structure 50 and the mirror layer 7.

[0023] The structure 50 is integrally formed, for example, by an SOI (Silicon on Insulator) substrate 8. That is, the mirror device 1 is configured as a MEMS (Micro Electro Mechanical Systems) device. The SOI substrate 8 has a support layer 81, a device layer 82, and an intermediate layer 83. The support layer 81 and the device layer 82 are semiconductor layers made of, for example, silicon. The intermediate layer 83 is an insulating layer made of, for example, silicon oxide, and is disposed between the support layer 81 and the device layer 82.

[0024] The first movable part 3 is formed, for example, in a rectangular plate shape. The second movable part 4 is formed, for example, in a rectangular ring shape, and surrounds the first movable part 3 when viewed from the optical axis direction A. The support part 2 is formed, for example, in a rectangular frame shape, and surrounds the second movable part 4 when viewed from the optical axis direction A. That is, the support part 2 surrounds the first movable part 3 and the second movable part 4 when viewed from the optical axis direction A. The optical axis direction A is a direction perpendicular to a plane on which the support part 2, the first movable part 3, the second movable part 4, the pair of first connecting parts 5, and the pair of second connecting parts 6 are arranged, and is a direction intersecting with the mirror layer 7.

[0025] The first movable part 3 has a first part 31 and a second part 32. The first part 31 is formed, for example, in a circular shape when viewed from the optical axis direction A. The second part 32 is formed, for example, in a rectangular ring shape when viewed from the optical axis direction A. The second part 32 surrounds the first part 31 when viewed from the optical axis direction A, and is connected to the first part 31 via a pair of connecting parts 33. In this example, the pair of connecting parts 33 are arranged on a second axis line X2 described later so as to sandwich the first part 31. In FIG. 2, the second part 32, the connecting part 33, and the like are omitted from the illustration. The first movable part 3 does not have to have the second part 32 and the connecting part 33.

[0026] The pair of first connecting parts 5 are disposed on the first axis X1 in a gap between the second portion 32 of the first movable part 3 and the second movable part 4 so as to sandwich the first movable part 3. Each first connecting part 5 functions as a torsion bar. Each first connecting part 5 connects the first movable part 3 to the second movable part 4 so that the first movable part 3 can swing around the first axis X1. Each first connecting part 5 can also be considered as connecting the first movable part 3 to the support part 2 via the second movable part 4 and the second connecting part 6 so that the first movable part 3 can swing around the first axis X1.

[0027] A pair of second connecting parts 6 are arranged on the second axis X2 in a gap between the second movable part 4 and the support part 2 so as to sandwich the second movable part 4. Each second connecting part 6 functions as a torsion bar. Each second connecting part 6 connects the second movable part 4 to the support part 2 so that the second movable part 4 can swing around the second axis X2. When the second movable part 4 swings around the second axis X2, the first movable part 3 also swings around the second axis X2 together with the second movable part 4. In this way, the first movable part 3 can swing around each of the first axis X1 and the second axis X2. The first axis X1 and the second axis X2 are perpendicular to the optical axis direction A and intersect with each other (in this example, they are perpendicular to each other).

[0028] The support section 2, the first movable section 3 and the second movable section 4 are composed of a support layer 81, a device layer 82 and an intermediate layer 83. The first connecting section 5 and the second connecting section 6 are composed of the device layer 82. The thickness (thickness along the optical axis direction A) of the support layer 81 constituting the first movable section 3 and the second movable section 4 is thinner than the thickness of the support layer 81 constituting the support section 2. The support layer 81 constituting the first movable section 3 functions as a beam section that suppresses warping of the first movable section 3 and the mirror layer 7. The first movable section 3 and the second movable section 4 may be composed of only the device layer 82.

[0029] The mirror layer 7 is formed in a circular shape on the surface 31a of the first portion 31 of the first movable portion 3. The surface 31a is formed by the surface of the device layer 82 opposite to the intermediate layer 83, and extends so as to intersect with the optical axis direction A. The mirror layer 7 is formed in a region including the intersection of the first axis X1 and the second axis X2. The center (geometric center) of the mirror layer 7 when viewed from the optical axis direction A coincides with the intersection of the first axis X1 and the second axis X2. The outer edge of the mirror layer 7 extends at a certain interval from the outer edge of the first portion 31. The diameter of the mirror layer 7 (the maximum width when viewed from the optical axis direction A) is 0.5 mm or more and 30 mm or less. In this example, the diameter of the mirror layer 7 is about 2 mm. The mirror layer 7 may be formed in any shape, such as an ellipse, a rectangle, or a polygon. Similarly, the first portion 31 may be formed in any shape, such as an ellipse, a rectangle, or a polygon. The second portion 32 of the first movable portion 3 and the second movable portion 4 may be formed in any shape, such as a circular ring, an elliptical ring, or a polygonal ring.

[0030] The mirror layer 7 includes an adhesive layer 71, an anti-diffusion layer (intermediate layer) 72, and a reflective layer 73. The adhesive layer 71, the anti-diffusion layer 72, and the reflective layer 73 are laminated in this order on the surface 31a of the first portion 31. The adhesive layer 71 has higher adhesion to the first portion 31 (silicon) than the anti-diffusion layer 72 and the reflective layer 73. The anti-diffusion layer 72 suppresses metal diffusion between the adhesive layer 71 and the reflective layer 73 during heating. The surface of the reflective layer 73 opposite to the first portion 31 constitutes a mirror surface 73a extending to intersect with the optical axis direction A. Each of the adhesive layer 71, the anti-diffusion layer 72, and the reflective layer 73 is formed of a metal material. For example, the adhesive layer 71 is made of titanium, the anti-diffusion layer 72 is made of platinum, and the reflective layer 73 is made of gold. The thickness of each of the adhesive layer 71 and the anti-diffusion layer 72 is, for example, about 50 nm to 300 nm, and preferably about 100 nm. The thickness of the reflective layer 73 is, for example, about 50 nm to 300 nm, and preferably about 200 nm. When the thickness of the adhesive layer 71 or the diffusion prevention layer 72 is 50 nm or more, the adhesive function of the adhesive layer 71 or the diffusion prevention function of the diffusion prevention layer 72 can be effectively exhibited. When the thickness of the reflective layer 73 is 50 nm or more, the reflectance of the reflective layer 73 can be increased. When the thickness of the adhesive layer 71, the diffusion prevention layer 72, or the reflective layer 73 is 300 nm or less, the stress generated in the adhesive layer 71, the diffusion prevention layer 72, or the reflective layer 73 can be reduced, and the warpage amount of the mirror layer 7 before the heating step described later can be reduced, and the change in the warpage amount of the mirror layer 7 during the heating step can be reduced. The diffusion prevention layer 72 may be formed of tungsten. The reflective layer 73 may be formed of aluminum. When the reflective layer 73 is made of gold, the reflectance for light in the near infrared region can be increased compared to when it is made of aluminum.

[0031] In each of the adhesion layer 71, the diffusion prevention layer 72, and the reflection layer 73 constituting the mirror layer 7, compressive stress (force in a convex warping direction) or tensile stress (force in a concave warping direction) occurs as residual stress, as described later. The type (compressive or tensile) and magnitude of the stress are determined by the manufacturing conditions such as the material, thickness, area, and film formation temperature of each layer. By adjusting the material, thickness, area, film formation temperature, etc., it is possible to adjust the type and magnitude of the stress in the state before the heating step described later, and the change in the warping during the heating step. As an example, in this embodiment, the adhesion layer 71 and the diffusion prevention layer 72 are formed so that compressive stress remains in the state before the heating step (at the completion of the second formation step described later), and the reflection layer 73 is formed so that tensile stress remains in the state before the heating step (at the completion of the second formation step). By combining a layer having compressive stress and a layer having tensile stress, it is possible to reduce the amount of warping of the mirror layer 7 and the first movable part 3 before the heating step. In addition, when formed of the same material, the thicker the layer, the greater the stress generated. Therefore, from the viewpoint of minimizing the amount of warping before the heating step and the change in the amount of warping during the heating step, it is preferable that each layer is thin.

[0032] Furthermore, the mirror device 1 has a first drive coil 11, a second drive coil 12, wirings 15a, 15b, wirings 16a, 16b, electrode pads 21a, 21b, and electrode pads 22a, 22b. In Fig. 1, the first drive coil 11 and the second drive coil 12 are indicated by dashed lines, and the wirings 15a, 15b and wirings 16a, 16b are indicated by solid lines. The first drive coil 11, the second drive coil 12, and the like are actually covered by an insulating layer 42, which will be described later.

[0033] The first drive coil 11 is provided on the second portion 32 of the first movable portion 3. The first drive coil 11 is wound multiple times in a spiral shape. A magnetic field generated by a magnetic field generating unit (not shown) acts on the first drive coil 11. The magnetic field generating unit is configured to include, for example, a permanent magnet in a Halbach array.

[0034] The first drive coil 11 is disposed in a groove formed on the surface of the second portion 32. That is, the first drive coil 11 is embedded in the first movable portion 3. The first drive coil 11 is disposed in the groove via an insulating layer 41. The insulating layer 41 is, for example, a silicon nitride film. The insulating layer 41 is formed over the surfaces of the support portion 2, the first movable portion 3, the second movable portion 4, the pair of first connecting portions 5, and the pair of second connecting portions 6, but is not formed on the first portion 31 of the first movable portion 3. An insulating layer 42 made of, for example, silicon nitride is formed on the insulating layer 41.

[0035] One end of the first drive coil 11 is connected to the electrode pad 21a via the wiring 15a. The wiring 15a extends from the first movable part 3 to the support part 2 via one of the first connecting parts 5, the second movable part 4, and one of the second connecting parts 6. The wiring 15a and the electrode pad 21a are integrally formed of a metal material such as tungsten, aluminum, gold, silver, copper, or an aluminum-based alloy. The wiring 15a is provided as a surface wiring on the surfaces of one of the first connecting parts 5, the second movable part 4, and one of the second connecting parts 6. Wires 15b, 16a, and 16b, which will be described later, are provided as surface wiring like the wiring 15a.

[0036] The other end of the first drive coil 11 is connected to an electrode pad 21b via a wiring 15b. The wiring 15b extends from the first movable part 3 to the support part 2 via the other first connecting part 5, the second movable part 4 and the other second connecting part 6. The wiring 15b and the electrode pad 21b are integrally formed from the same metal material as the wiring 15a.

[0037] The second drive coil 12 is provided on the second movable part 4. The second drive coil 12 is wound multiple times in a spiral shape on the second movable part 4. A magnetic field generated by a magnetic field generating unit acts on the second drive coil 12. The second drive coil 12 is disposed in a groove 4b formed on the surface 4a of the second movable part 4. In other words, the second drive coil 12 is embedded in the second movable part 4. The second drive coil 12 is disposed in the groove via an insulating layer 41.

[0038] One end of the second actuation coil 12 is connected to an electrode pad 22a via a wiring 16a. The wiring 16a extends from the second movable part 4 to the support part 2 via one of the second connecting parts 6. The wiring 16a and the electrode pad 22a are integrally formed from the same metal material as the wiring 15a.

[0039] The other end of the second actuation coil 12 is connected to an electrode pad 22b via a wiring 16b. The wiring 16b extends from the second movable part 4 to the support part 2 via the other second connecting part 6. The wiring 16b and the electrode pad 22b are integrally formed from the same metal material as the wiring 15a.

[0040] Hereinafter, first to fifth examples will be described as examples of the operation of the movable mirror section 10 in the mirror device 1. In the first example, a high-frequency drive current is applied to the first drive coil 11. At this time, a magnetic field generated by the magnetic field generating section acts on the first drive coil 11, and a Lorentz force is generated in the first drive coil 11. This Lorentz force acts as a drive force, causing the first movable section 3 to oscillate around the first axis X1 at, for example, the resonant frequency level.

[0041] A driving current of a certain magnitude is applied to the second driving coil 12. At this time, the magnetic field generated by the magnetic field generating unit acts on the second driving coil 12, so that a Lorentz force is generated in the second driving coil 12. This Lorentz force acts as a driving force, and the second movable part 4 is rotated around the second axis X2 according to the magnitude of the driving current, for example, and stopped in that state. As a result, according to the mirror device 1, the light from the light source incident along the optical axis direction A can be reflected by the mirror surface 73a and scanned. In the first example, the first movable part 3 is oscillated at the resonant frequency, and the second movable part 4 is used statically.

[0042] In the second example, similar to the operation of the first movable part 3 in the first example, a high-frequency drive current is applied to the first drive coil 11 to cause the first movable part 3 to oscillate according to the resonant frequency, and a high-frequency drive current is applied to the second drive coil 12 to cause the second movable part 4 to oscillate according to the resonant frequency. In this way, in the second example, both the first movable part 3 and the second movable part 4 are oscillated at the resonant frequency.

[0043] In the third example, similar to the operation of the second movable part 4 in the first example, a drive current of a constant magnitude is applied to the first drive coil 11, whereby the first movable part 3 is rotated around the first axis X1 in accordance with the magnitude of the drive current and then stopped, and a drive current of a constant magnitude is applied to the second drive coil 12, whereby the second movable part 4 is rotated around the second axis X2 in accordance with the magnitude of the drive current and then stopped. Thus, in the third example, both the first movable part 3 and the second movable part 4 are used statically.

[0044] In the fourth and fifth examples, only the first movable part 3 is driven. In the fourth example, a high-frequency driving current is applied to the first driving coil 11, causing the first movable part 3 to oscillate in accordance with the resonant frequency. In the fifth example, a driving current of a constant magnitude is applied to the first driving coil 11, causing the first movable part 3 to rotate around the first axis X1 in accordance with the magnitude of the driving current and then stop. The fourth and fifth examples can be used, for example, in cases where the second movable part 4 is not provided. [Mirror device manufacturing method]

[0045] A method for manufacturing the mirror device 1 will be described with reference to FIGS. 3 to 8. First, an unprocessed SOI wafer 80 is prepared (preparation step, FIG. 3(a)). The SOI wafer 80 has a support layer 81, a device layer 82, and an intermediate layer 83. The SOI wafer 80 has a plurality of regions R. Each of the plurality of regions R will become the SOI substrate 8 of the mirror device 1 after a cutting step, which will be described later. The plurality of regions R are set to be arranged in a lattice pattern, for example, and dicing lines L are set at the boundaries between adjacent regions R. The SOI wafer 80 is cut along the dicing lines L in the cutting step.

[0046] Next, a plurality of portions S each corresponding to the structure 50 are formed on the SOI wafer 80 (first formation step, FIG. 3(b)). The "portions corresponding to the structure 50" refer to the portions that will become the structure 50 after the cutting step. In the first formation step, the structure 50 is formed in each of the plurality of regions R. As described above, the structure 50 is composed of the support portion 2, the first movable portion 3, the second movable portion 4, a pair of first connecting portions 5, and a pair of second connecting portions 6. The structure 50 (portions S) is formed using MEMS technology (patterning, etching, etc.). In addition, in the first formation step, the first drive coil 11, the second drive coil 12, etc. are formed in each of the plurality of regions R. In the first forming process, the first movable part 3 becomes swingable relative to the second movable part 4 about the first axis X1 and also becomes swingable relative to the support part 2 about the first axis X1 and the second axis X2, and the second movable part 4 becomes swingable relative to the support part 2 about the second axis X2.

[0047] In the first forming step, for example, first, the first driving coil 11, the second driving coil 12, the wirings 15a, 15b, 16a, 16b, and the electrode pads 21a, 21b, 22a, 22b are formed in each region R (wiring forming step). Then, the support portion 2, the first movable portion 3, the second movable portion 4, the pair of first connecting portions 5, and the pair of second connecting portions 6 are formed in each region R (structure forming step). The structure forming step may be performed before the wiring forming step.

[0048] Next, a mirror layer 7 is formed on a portion of each of the multiple portions S that corresponds to the first movable portion 3 (second formation step, FIG. 4(a)). More specifically, the mirror layer 7, which is composed of an adhesion layer 71, a diffusion prevention layer 72, and a reflective layer 73, is formed on the surface 31a of the first portion 31 of the first movable portion 3. In this example, the mirror layer 7 is formed by sputtering (sputtering method), but the mirror layer 7 may also be formed by vapor deposition (vapor deposition method).

[0049] 5(a) and 5(b) are diagrams for explaining the second forming step. As shown in FIG. 5(a), first, a shadow mask 91 made of silicon is placed on the multiple portions S. The shadow mask 91 has an opening 91a that exposes the region where the mirror layer 7 is to be formed. Then, as shown in FIG. 5(b), the mirror layer 7 is formed by sputtering. After the mirror layer 7 is formed, the shadow mask 91 is removed. As shown in FIG. 5(b), the mirror layer 7 formed by sputtering has a thicker center than the edge. The opening 91a of the shadow mask 91 may be larger than the mirror layer 7. In this case, the mirror layer 7 having a uniform thickness can be formed.

[0050] When the mirror layer 7 is formed by sputtering or vapor deposition in this manner, the temperature of the SOI wafer 80 rises to, for example, nearly 100° C. during processing. If the temperature of the SOI wafer 80 drops from this state, residual stress may occur in the mirror layer 7 due to the difference in thermal expansion coefficient between the mirror layer 7 and the SOI wafer 80, etc. In this case, the residual stress may cause warping of the mirror layer 7 and the first movable part 3.

[0051] More specifically, it is believed that residual stress occurs in the mirror layer 7 due to the following three reasons. (1) Difference in thermal expansion coefficient between the mirror layer 7 and the SOI wafer 80 (2) Difference in lattice constant between the mirror layer 7 and the SOI wafer 80 (3) Argon atom trapping in the SOI wafer 80 and the mirror layer 7 by sputtering

[0052] Regarding (1), the temperature of the SOI wafer 80 may be increased during the formation of the mirror layer 7. When returning to room temperature from this state, the mirror layer 7 and the SOI wafer 80 shrink. The degree of shrinkage varies depending on the thermal expansion coefficient. When the thermal expansion coefficient of the mirror layer 7 is smaller than that of the SOI wafer 80, a compressive stress is generated in the mirror layer 7 so that the mirror layer 7 warps convexly. When the thermal expansion coefficient of the mirror layer 7 is larger than that of the SOI wafer 80, a tensile stress is generated in the mirror layer 7 so that the mirror layer 7 warps concavely. Residual stress is also generated in the mirror layer 7 due to not only the difference in the thermal expansion coefficient between the mirror layer 7 and the SOI wafer 80 but also the difference in the thermal expansion coefficient between the multiple layers (the adhesion layer 71, the diffusion prevention layer 72, and the reflective layer 73) constituting the mirror layer 7.

[0053] Regarding (2), the lattice constant of the mirror layer 7 is different from that of the SOI wafer 80. In the vicinity of the interface between the mirror layer 7 and the SOI wafer 80, the lattice constant of the mirror layer 7 tends to approach that of the SOI wafer 80. On the other hand, the lattice constant of the mirror layer 7 approaches a value specific to the material as it moves away from the interface. Therefore, distortion occurs in the mirror layer 7 in the vicinity of the interface, and stress is generated accordingly. Residual stress is generated in the mirror layer 7 due to not only the difference in lattice constant between the mirror layer 7 and the SOI wafer 80, but also the difference in lattice constant between the multiple layers (adhesion layer 71, diffusion prevention layer 72, and reflective layer 73) that constitute the mirror layer 7.

[0054] Regarding (3), in sputtering, sputtered atoms emitted from the target are incident on the SOI wafer 80 to form a thin film. At the same time, a certain proportion of argon positive ions colliding with the target are neutralized and are incident with high kinetic energy on the SOI wafer 80 and the mirror layer 7 being formed. The argon atoms penetrate between the crystal lattices in the mirror layer 7 and expand the lattice spacing, generating compressive stress in the mirror layer 7 such that the mirror layer 7 warps in a convex shape.

[0055] The direction and magnitude of the warpage occurring in the mirror layer 7 and the first movable part 3 vary depending on the material, thickness, area, and forming method of the mirror layer 7. For example, in this embodiment, the mirror layer 7 is curved in a convex shape as shown in FIG. 4(a), but the mirror layer 7 may be curved in a concave shape as shown in FIG. 9(a) described later. The larger the area (diameter) of the mirror layer 7, the larger the warpage of the mirror layer 7. As described above, at the completion of the second forming step, compressive stress remains in the adhesion layer 71 and the diffusion prevention layer 72, and tensile stress remains in the reflection layer 73. These stresses may remain even after the heating step. That is, it is sufficient that at least at the completion of the second forming step, compressive stress remains in the adhesion layer 71 and the diffusion prevention layer 72, and tensile stress remains in the reflection layer 73.

[0056] Next, the SOI wafer 80 is heated (heating step, FIG. 4(b)). In this example, the entire SOI wafer 80 is heated. By heating the SOI wafer 80, the residual stress present in the mirror layer 7 is alleviated (annealing treatment). In this embodiment, the residual stress is alleviated, thereby reducing the amount of warping of the mirror layer 7 and flattening the mirror layer 7. After the heating step, a cleaning step is performed to clean the SOI wafer 80. The cleaning step may be performed if foreign matter adheres to the mirror layer 7 during the heating step, may be performed without fail, or may be omitted.

[0057] In the heating step, the residual stress is believed to be relaxed for the following reasons. First, a stress relaxation layer (alloy layer) is formed between the mirror layer 7 and the SOI wafer 80. In the heating step, some of the atoms constituting the mirror layer 7 diffuse. This atomic diffusion forms a stress relaxation layer (alloy layer) between the mirror layer 7 and the SOI wafer 80, or between the adhesion layer 71, the diffusion prevention layer 72, and the reflective layer 73 constituting the mirror layer 7, so as to reduce the difference in lattice constant, and as a result, the residual stress is believed to be relaxed. Another reason is that in the heating step, argon atoms trapped between the crystal lattices in the mirror layer 7 are released into the atmosphere as described in (3) above, and as a result, the residual stress is believed to be relaxed.

[0058] FIG. 6 is a graph showing an example of the change in the amount of warping of the mirror layer 7 during the heating process. The horizontal axis represents the time (unit: hours) elapsed from the start of heating, and the vertical axis represents the amount of warping of the mirror layer 7 (unit: nm). In this example, the SOI wafer 80 was heated at 150° C. for 30 hours. As shown in FIG. 6, the amount of warping at the start of heating was approximately 300 nm, but the mirror layer 7 became approximately flattened by the heating process, and it can be seen that the change in the amount of warping became smaller over time. The amount of warping of the mirror layer 7 was measured using the same method as in the measurement process described below.

[0059] The heating temperature for heating the SOI wafer 80 in the heating step is set to, for example, 60°C or more and 300°C or less. The higher the heating temperature, the shorter the heating time can be, but if the heating temperature is too high, defects such as cracks and metal diffusion may occur. The heating temperature of 150°C in the embodiment is a value obtained by adding 70°C assumed as the maximum environmental temperature of the mirror device 1 to 70°C assumed as the self-heating temperature and 10°C as the margin temperature. The heating time is set to a time or more until the change in the amount of warping saturates and becomes small based on the relationship between the time and the amount of warping acquired in advance. For example, in the case of FIG. 6, the change in the amount of warping reaches saturation in about 5 hours, so the heating time may be 5 hours or more. By setting the heating time to about the time until the change in the amount of warping reaches saturation, the energy required for heating can be reduced. It is preferable that the heating temperature is set to at least a value higher than the self-heating temperature of the mirror device 1 (the temperature of the mirror device 1 during operation) in order to reliably suppress the change in the amount of warping at the customer's site.

[0060] During heating, the SOI wafer 80 is placed in a thermostatic chamber (oven). As a result, the entire SOI wafer 80 is heated, and thus the portions of each of the multiple portions S corresponding to the first movable part 3 are heated simultaneously. One SOI wafer 80 may be placed in the thermostatic chamber, but multiple (e.g., two, six, or twelve) SOI wafers 80 may also be placed. The SOI wafer 80 may be placed horizontally or vertically (along the vertical direction) in the thermostatic chamber. The oven is preferably a clean oven from the viewpoint of preventing adhesion of foreign matter to the mirror layer 7.

[0061] The amount of warping of the mirror layer 7 may decrease by the heating process as in this embodiment, or may increase by the heating process. Whether the amount of warping increases or decreases depends on the material, thickness, area, and formation method of the mirror layer 7. In this embodiment, the mirror layer 7 is curved convexly before heating, and the amount of warping of the mirror layer 7 is reduced by the heating process. However, the mirror layer 7 may be curved convexly before heating, and the amount of warping of the mirror layer 7 may increase by the heating process. In addition, as in a modified example described later, the mirror layer 7 may be curved concavely before heating, and the amount of warping of the mirror layer 7 may increase by the heating process. Alternatively, the mirror layer 7 may be curved concavely before heating, and the amount of warping of the mirror layer 7 may decrease by the heating process. In addition, the mirror layer 7 that was curved convexly before heating may be curved concavely by the heating process, and the mirror layer 7 that was curved concavely before heating may be curved convexly by the heating process. Note that an increase in the amount of warping means an increase in the absolute value of the amount of warping. For example, the amount of warping may change from 200 nm to 300 nm, or from -200 nm to -300 nm. A decrease in the amount of warping means that the absolute value of the amount of warping decreases. For example, the amount of warping may change from 200 nm to 100 nm, or from -200 nm to -100 nm. A positive value for the amount of warping means that the height of the center of the mirror layer 7 is higher than the peripheral portion (convex), and a negative value for the amount of warping means that the height of the center of the mirror layer 7 is lower than the peripheral portion (concave).

[0062] Next, the amount of warping of the mirror layer 7 is measured for each of the multiple portions S (measurement step). For example, the PV value and shape data (3D data) of the mirror layer 7 are measured using a laser interferometer. As described above, the diameter of the mirror layer 7 in this embodiment is 2 mm. In this embodiment, the PV value and shape data of a region with a diameter of 1.9 mm that is concentric with the mirror layer 7 are measured. The PV value represents the difference in height between the highest point and the lowest point of the mirror layer 7 (mirror surface 73a) in the measurement range. Since the PV value is expressed as an absolute value, the shape data is also measured to determine whether the mirror layer 7 is convex or concave (whether the amount of warping is a positive value or a negative value). A predetermined mark is attached to the structure 50 in which the amount of warping of the mirror layer 7 is greater than a predetermined value (marking). The structure 50 (mirror device 1) to which the mark is attached is removed, for example, after the cutting step. The amount of warping of the mirror layer 7 may be measured by measuring the curvature of the mirror layer 7.

[0063] Next, the SOI wafer 80 is cut along the dicing lines L so that the multiple portions S are separated from one another (cutting step, FIG. 7). For example, a modified region is formed inside the SOI wafer 80 along the dicing lines L by irradiating a laser beam, and a crack is extended from the modified region in the thickness direction of the SOI wafer 80 by tape expanding or the like, thereby cutting the SOI wafer 80. In the cutting step, the SOI wafer 80 may be cut by other cutting methods such as blade dicing. By the above steps, multiple mirror devices 1 are obtained.

[0064] 8, each mirror device 1 is housed in a package 60. The package 60 has a main body 61 that houses the mirror device 1, and a transparent window member 62 arranged to cover an opening 61a of the main body 61. Light reflected by the mirror device 1 passes through the window member 62 and enters the mirror layer 7. [Action and Effects]

[0065] As described above, when the mirror layer 7 is formed, residual stress may occur in the mirror layer 7, and the residual stress may cause warping in the mirror layer 7. If the mirror device 1 is shipped in this state, there is a concern that the residual stress may be relaxed by the environmental temperature or self-heating during use, causing a change in the amount of warping in the mirror layer 7. In contrast, in the manufacturing method of the mirror device 1 according to the embodiment, a plurality of parts S each corresponding to the structure 50 are formed in the SOI wafer 80, and the mirror layer 7 is formed on a portion of each of the plurality of parts S corresponding to the first movable part 3, and then the SOI wafer 80 (the portion of each of the plurality of parts S corresponding to the first movable part 3) is heated. This makes it possible to relax (release) the residual stress present in the mirror layer 7, and to suppress a change in the amount of warping in the mirror layer 7 during use of the mirror device 1. As a result, it is possible to suppress a change in the size and focal position of the spot of the laser light reflected by the mirror layer 7 during use of the mirror device 1. In addition, in the manufacturing method of the mirror device 1 according to the embodiment, the SOI wafer 80 is cut after the heating process. As a result, the temperature of the mirror layer 7 during heating can be made uniform among the multiple portions S, compared to when the heating process is performed after the wafer is cut. That is, as described above, the heating process is performed, for example, in a thermostatic chamber, but the temperature may vary depending on the position in the thermostatic chamber due to the influence of air convection and the positions of the heat source and the object to be heated. When the heating process is performed for each chip after the wafer is cut (after chipping), there is a concern that the chip may be heated to a temperature different from the set temperature depending on the location where the chip is placed. In contrast, in the manufacturing method of the mirror device 1 according to the embodiment, the heating process is performed in the state of the SOI wafer 80, which has high thermal conductivity, and heat is easily conducted within the SOI wafer 80, so that the temperature of the mirror layer 7 can be made uniform among the multiple portions S. As a result, the variation in the quality of the mirror device 1 can be suppressed. In addition, by heating in the wafer state, many mirror devices 1 can be placed in the thermostatic chamber. As a result, the manufacturing efficiency of the mirror device 1 can be improved. Furthermore, the amount of warping of the mirror layer 7 in the wafer state can be measured in the measurement process.This makes it easier to accurately grasp the position of the mirror layer 7, and therefore the measurement can be made more efficient. Furthermore, when a cleaning step is performed to clean the mirror layer 7 after heating, cleaning can be performed in the wafer state, and cleaning workability can be improved. Furthermore, in the manufacturing method of the mirror device 1 according to the embodiment, the SOI wafer 80 is cut after the heating step, so that the semiconductor material constituting the fragments that is generated during cutting and adhered to the mirror layer 7 is prevented from diffusing into the mirror layer 7 due to heating, and the quality of the mirror device 1 can be ensured. In addition, it is not necessary to form a protective film on the mirror layer 7 to prevent the fragments from adhering to the mirror layer 7. Furthermore, when the heating step is performed after the mirror device 1 is housed in the package 60, the sealing resin used in the package 60 may deteriorate due to heating, so the upper limit of the heating temperature is limited. In contrast, in the manufacturing method of the mirror device 1 according to the embodiment, heating is performed in the wafer state, so the heating temperature can be set regardless of the deterioration start temperature of the sealing resin, and manufacturing efficiency can be improved. As described above, according to the manufacturing method of the mirror device 1 according to the embodiment, the mirror device 1 having a movable part can be manufactured satisfactorily.

[0066] Between the heating step and the cutting step, a measuring step is carried out to measure the amount of warping of the mirror layer 7. This makes it possible to measure the amount of warping of the mirror layer 7 in a wafer state, thereby improving the efficiency of the measurement.

[0067] In the cutting process, a modified region is formed inside the SOI wafer 80 by irradiating the laser light, and a crack is extended from the modified region in the thickness direction of the SOI wafer 80, thereby cutting the SOI wafer 80 (stealth dicing). This reduces the stress acting on the SOI wafer 80 during cutting, and can suppress deformation of the mirror layer 7 and the first movable part 3 due to the stress. Also, it can suppress changes in the amount of warping of the mirror layer 7 during cutting. In the above embodiment, the first movable part 3 is able to swing before the cutting process, and the mirror layer 7 is heated before the cutting process. Therefore, it is particularly effective to use stealth dicing that can suppress damage to the first movable part 3 and changes in the amount of warping.

[0068] The second forming step is carried out after the first forming step. This makes it possible to suppress the deterioration of the quality of the mirror layer 7 due to heat when forming the plurality of portions S. That is, contrary to the above embodiment, when the mirror layer 7 is formed on the portion corresponding to the first movable part 3 and then the plurality of portions S are formed on the SOI wafer 80, the heat when forming the plurality of portions S may cause metal diffusion between the adhesion layer 71 (titanium) and the reflective layer 73 (gold) constituting the mirror layer 7, and the reflectance of the mirror layer 7 may decrease. In contrast, by forming the mirror layer 7 after forming the plurality of portions S as in the above embodiment, such a situation can be suppressed and the quality of the mirror layer 7 can be ensured. Note that when the diffusion prevention layer 72 is made of tungsten, metal diffusion between the adhesion layer 71 and the reflective layer 73 can be effectively suppressed compared to when the diffusion prevention layer 72 is made of platinum. On the other hand, when the diffusion prevention layer 72 is made of platinum, the stress generated by the diffusion prevention layer 72 can be reduced compared to when the diffusion prevention layer 72 is made of tungsten, and handling can be facilitated.

[0069] In the heating step, the SOI wafer 80 is heated to reduce the amount of warping of the mirror layer 7. This can alleviate the residual stress present in the mirror layer 7, and can prevent the amount of warping of the mirror layer 7 from changing when the mirror device 1 is used. As described above, in the heating step, the SOI wafer 80 may be heated to increase the amount of warping of the mirror layer 7. In this case as well, the residual stress present in the mirror layer 7 can be alleviated, and can prevent the amount of warping of the mirror layer 7 from changing when the mirror device 1 is used.

[0070] In the second forming step, the mirror layer 7 is formed by sputtering. This allows the mirror layer 7 to be formed well. That is, when the mirror layer 7 is formed by sputtering, it is not necessary to rotate the wafer as in the case of vapor deposition, so that the structure 50 including the hollow structure is less likely to be damaged. In addition, sputtering has high directivity, so that metal is less likely to adhere to places other than the mirror layer 7. In vapor deposition with low directivity, there is a risk that the metal will pass through the slit (gap) between the support 2 and the movable mirror 10 and go around to the back side of the movable mirror 10 or adhere to the support 2. In contrast, by using sputtering with high directivity, such a situation can be suppressed. In addition, in sputtering, it is possible to use a high melting point material that is difficult to use in vapor deposition. In addition, the thickness of the mirror layer 7 can be easily controlled. On the other hand, when the mirror layer 7 is formed by vapor deposition, about 20 wafers can be processed at a time, so that the manufacturing efficiency can be improved. As described above, when sputtering is used, the amount of warping of mirror layer 7 is likely to increase due to argon atom trapping during film formation, and the amount of warping changes significantly during the heating process because the trapped argon is released into the atmosphere. According to the manufacturing method for mirror device 1 according to the embodiment, even in such cases, it is possible to effectively prevent the amount of warping of mirror layer 7 from changing when mirror device 1 is used.

[0071] The mirror device 1 includes a first drive coil 11 and a second drive coil 12 for applying a drive force to the movable mirror portion 10. In this case, heat is likely to be generated when the mirror device 1 is used, but according to the manufacturing method of the mirror device 1 according to the embodiment, even in such a case, it is possible to suppress a change in the amount of warping of the mirror layer 7 when the mirror device 1 is used.

[0072] In the heating step, the SOI wafer 80 is heated to a temperature of 60° C. or higher and 300° C. or lower, so that the residual stress present in the mirror layer 7 can be effectively alleviated.

[0073] The maximum width of the mirror layer 7 is 0.5 mm or more and 30 mm or less. In this case, the amount of warping of the mirror layer 7 is likely to change when the mirror device 1 is used, but according to the manufacturing method for the mirror device 1 according to the embodiment, even in such a case, the amount of warping of the mirror layer 7 can be prevented from changing when the mirror device 1 is used.

[0074] The mirror layer 7 includes an adhesion layer 71, a diffusion prevention layer 72, and a reflective layer 73, which are formed in this order on the first movable part 3. Thus, by including the adhesion layer 71, the mirror layer 7 can be stably formed on the first movable part 3. Furthermore, by including the diffusion prevention layer 72, it is possible to suppress metal diffusion between the reflective layer 73 and the adhesion layer 71 during heating.

[0075] The mirror layer 7 includes an adhesion layer 71 and a diffusion prevention layer 72 in which compressive stress remains at the completion of the second formation step, and a reflective layer 73 in which tensile stress remains at the completion of the second formation step. This makes it possible to reduce the amount of warping of the mirror layer 7 before the heating step. Also, it is possible to reduce the change in the amount of warping of the mirror layer 7 during the heating step, and as a result, it is possible to shorten the heating time and easily control the amount of warping of the mirror layer 7.

[0076] In the heating step, the entire SOI wafer 80 is heated. This makes it possible to uniform the temperature of the mirror layer 7 among the multiple portions S during heating. [Variations]

[0077] 9(a) and 9(b) are diagrams for explaining a manufacturing method of a mirror device 1 according to a modified example. In this modified example, as shown in FIG. 9(a), the mirror layer 7 is curved in a concave shape before the heating step. Then, as shown in FIG. 9(b), the amount of warping of the mirror layer 7 increases by heating the SOI wafer 80 in the heating step.

[0078] FIG. 10 is a graph showing an example of the change in the amount of warping of the mirror layer 7 in the heating process of the modified example. In this example, the SOI wafer 80 was heated at 150° C. for 30 hours. In FIG. 10, the change in the amount of warping for five samples is shown by different line types. As shown in FIG. 10, for all samples, the amount of warping at the start of heating was about 100 nm, but the amount of warping increased to about 250 to 350 nm by the heating process, and it can be seen that the change in the amount of warping became smaller with the passage of time. In the case of FIG. 10, the change in the amount of warping reached saturation in about 2 hours, so the heating time may be 2 hours or more. By setting the heating time to about the time until the change in the amount of warping reaches saturation, the energy required for heating can be reduced.

[0079] FIG. 11 is a graph showing an example of change in the amount of warping of the mirror layer 7 in a reliability test. In this reliability test, the mirror device 1 obtained by the manufacturing method of the mirror device 1 according to the modified example was operated, and the amount of warping of the mirror layer 7 during operation was measured. Specifically, the amount of warping of the mirror layer 7 in the initial state (0 hours) was set to 0 nm, and the change in the amount of warping of the mirror layer 7 was measured every 250 hours up to 1000 hours. The first movable part 3 was continuously operated at an optical deflection angle of 10° around the first axis X1 and an optical deflection angle of 10° around the second axis X2. As shown in FIG. 11, it can be seen that the change in the amount of warping of the mirror layer 7 during operation was suppressed to ±50 nm or less.

[0080] The present invention is not limited to the above embodiment. For example, the material and shape of each component are not limited to the above-mentioned materials and shapes, and various materials and shapes can be adopted. In the above embodiment, the mirror device 1 is configured as an electromagnetic drive type, but the mirror device 1 may be configured as a piezoelectric drive type or an electrostatic drive type. In the case of a piezoelectric drive type, for example, a piezoelectric film (piezoelectric element) may be provided instead of the first drive coil 11 and the second drive coil 12.

[0081] The first driving coil 11 may be provided on the second movable part 4. Even in this case, the first movable part 3 can be swung around the first axis X1 at the resonant frequency. Specifically, when a driving current having a frequency equal to the resonant frequency of the first movable part 3 around the first axis X1 is input to the first driving coil 11, the second movable part 4 vibrates slightly around the first axis X1 at the frequency. This vibration is transmitted to the first movable part 3 via the first connecting part 5, so that the first movable part 3 can be swung around the first axis X1 at the frequency. When the first driving coil 11 or the piezoelectric element is provided on the first movable part 3, the heat source is close to the mirror layer 7, so that heat is easily transmitted to the mirror layer 7. However, according to the manufacturing method of the mirror device 1 described above, even in such a case, it is possible to suppress the amount of warping of the mirror layer 7 from changing when the mirror device 1 is used.

[0082] The second forming step may be performed before the first forming step. For example, after the above-mentioned wiring forming step is performed, the mirror layer 7 may be formed on a portion of the SOI wafer 80 corresponding to the first movable part 3, and then the structure forming step may be performed. The measurement step may be omitted. The first connecting part 5 may connect the first movable part 3 to the support part 2 so that the first movable part 3 is movable along a predetermined direction. For example, the first movable part 3 may be movable along the optical axis direction A (a direction perpendicular to the mirror layer 7).

[0083] The mirror layer 7 may not include the adhesion layer 71. For example, when the mirror device 1 does not become hot during operation, the adhesion layer 71 may be omitted. The mirror layer 7 may not include the diffusion prevention layer 72. For example, when high reflectance is not required for the mirror layer 7 or when the appearance of the mirror layer 7 is not important, the diffusion prevention layer 72 may be omitted. By omitting at least one of the adhesion layer 71 and the diffusion prevention layer 72, the thickness of the mirror layer 7 can be reduced, and as a result, the amount of warping of the mirror layer 7 before the heating step can be reduced and the change in the amount of warping of the mirror layer 7 during the heating step can be reduced.

[0084] In the heating step of the above embodiment, the entire SOI wafer 80 is heated using a thermostatic bath, but the heating means is not limited as long as the portion corresponding to the first movable part 3 in each of the plurality of parts S is heated. For example, only the portion corresponding to the first movable part 3 in each of the plurality of parts S may be heated simultaneously by irradiating spot light such as laser light without heating the entire SOI wafer 80. Even in this case, the portion corresponding to the first movable part 3 in each of the plurality of parts S can be uniformly heated by heat conduction in the SOI wafer 80. Even if there is variation in the output of the irradiated laser light, uniform heating can be realized. In the heating step, heating is performed using a heat source located outside the mirror device 1, not self-heating generated by driving the mirror device 1. [Explanation of symbols]

[0085] 1...mirror device, 2...support portion, 3...first movable portion, 4...second movable portion, 5...first connecting portion, 6...second connecting portion, 7...mirror layer, 11...first drive coil, 12...second drive coil, 50...structure, 80...SOI wafer, S...part.

Claims

1. A method for manufacturing a mirror device comprising: a structure having a support section, a movable section, and a connecting section that connects the movable section to the support section so that the movable section can swing or move; and a mirror layer provided on only one surface of the movable section in a direction perpendicular to a plane on which the support section, the movable section, and the connecting section are arranged, the method comprising the steps of: a first forming step of forming a plurality of portions on a wafer, each portion corresponding to the structure; a second forming step of forming the mirror layer only on a surface corresponding to the one surface of a portion of each of the plurality of portions corresponding to the movable portion; a heating step of heating the portion of each of the plurality of portions corresponding to the movable portion after the first forming step and the second forming step; a cutting step of cutting the wafer after the heating step so that the plurality of portions are separated from one another.

2. The method for manufacturing a mirror device according to claim 1 , further comprising a measuring step, between the heating step and the cutting step, of measuring an amount of warping of the mirror layer.

3. 3. The method for manufacturing a mirror device as described in claim 1 or 2, wherein in the cutting process, a modified region is formed inside the wafer by irradiating laser light, and a crack is propagated from the modified region in the thickness direction of the wafer, thereby cutting the wafer.

4. The method for manufacturing a mirror device according to claim 1 , wherein the second forming step is carried out after the first forming step.

5. The method for manufacturing a mirror device described in any one of claims 1 to 4, wherein the heating step reduces the amount of warping of the mirror layer by heating the portion corresponding to the movable portion in each of the plurality of portions.

6. The method for manufacturing a mirror device described in any one of claims 1 to 4, wherein the heating step increases the amount of warping of the mirror layer by heating the portion corresponding to the movable portion in each of the plurality of portions.

7. The method for manufacturing a mirror device according to claim 1, wherein in the second formation step, the mirror layer is formed by sputtering.

8. 8. The method for manufacturing a mirror device according to claim 1, wherein the mirror device further comprises a coil or a piezoelectric element for applying a driving force to the movable portion.

9. 9. The method for manufacturing a mirror device according to claim 1, wherein in the heating step, the portion of each of the plurality of portions corresponding to the movable portion is heated to 60° C. or higher and 300° C. or lower.

10. The method for manufacturing a mirror device according to any one of claims 1 to 9, wherein the maximum width of the mirror layer is 0.5 mm or more and 30 mm or less.

11. The method for manufacturing a mirror device according to any one of claims 1 to 10, wherein the mirror layer includes an adhesion layer, an anti-diffusion layer, and a reflective layer, which are formed in this order on the movable portion.

12. The mirror layer includes a plurality of layers including a reflective layer, A method for manufacturing a mirror device described in any one of claims 1 to 11, wherein the plurality of layers includes a layer in which compressive stress remains at the completion of the second formation process and a layer in which tensile stress remains at the completion of the second formation process.

13. The method for manufacturing a mirror device according to any one of claims 1 to 12, wherein the heating step heats the entire wafer.

14. The method for manufacturing a mirror device according to claim 13 , wherein in the heating step, a plurality of the wafers are arranged vertically in a thermostatic chamber.

15. The method for manufacturing a mirror device according to any one of claims 1 to 12, wherein in the heating step, the portion corresponding to the movable portion in each of the plurality of portions is heated without heating the entire wafer.

Images