Manufacturing method for mirror devices

Abstract

To provide a method for manufacturing a mirror device, by which the mirror device having a movable portion can be favorably manufactured.SOLUTION: A method for manufacturing a mirror device includes: a first forming step of forming, on a SOI wafer 80, a plurality of parts S, each corresponding to a structural body 50, such that a part of each of the plurality of parts S corresponding to a first movable portion 3 is swingable or movable to a part of each of the plurality of parts S corresponding to a support portion 2; a second forming step of forming a mirror layer 7 on the part corresponding to the first movable portion 3; a heating step of heating the part corresponding to the first movable portion 3, in a state where the part corresponding to the first movable portion 3 is swingable or movable to the part corresponding to the support portion 2, after the first forming step and the second forming step; and a cutting step of cutting the SOI wafer 80 so as to separate the plurality of parts S from one another, in a state where the part corresponding to the first movable portion 3 is swingable or movable to the part corresponding to the support portion 2, after the heating step.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 Art

[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, after forming a plurality of micro-mechanical structures having a movable structure on a semiconductor substrate, dicing is performed to separate the plurality of micro-mechanical structures from each other. At this point, the movable structure is curved. Subsequently, after forming a metal layer that functions as a mirror on the movable structure, the entire micro-mechanical structure is heated. By this heat treatment, the movable structure is flattened.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the method for manufacturing a mirror device as described above, it is required to manufacture the mirror device better. Therefore, an object of the present invention is to provide a method for manufacturing a mirror device that can manufacture a mirror device having a movable part well.

Means for Solving the Problems

[0005] The present invention provides a method for manufacturing a mirror device comprising: a structure having a support portion, a movable portion, and a connecting portion that connects the movable portion to the support portion so that the movable portion can swing or move; and a mirror layer provided on the movable portion, the method comprising: a first forming step of forming a plurality of portions on a wafer, each corresponding to the structure; a second forming step of forming a mirror layer on the portion corresponding to the movable portion in each of the plurality of portions; a heating step of heating the portion corresponding to the movable portion in each of the plurality of portions after the first forming step and the second forming step; and a cutting step of cutting the wafer after the heating step so that the plurality of portions are separated from each other.

[0006] During the formation of the mirror layer, residual stress may occur, which can cause warping of the mirror layer. If the mirror device is shipped in this state, there is a concern that the amount of warping of the mirror layer may change during use as the residual stress is relieved by ambient temperature and self-heating. In contrast, in this manufacturing method for the mirror device, multiple parts corresponding to the structure are formed on the wafer, and after the mirror layer is formed on the part corresponding to the movable part of each of the multiple parts, the part corresponding to the movable part of each of the multiple parts is heated. This relieves the residual stress present in the mirror layer and suppresses changes in the amount of warping of the mirror layer during use of the mirror device. Furthermore, in this manufacturing method for the mirror device, the wafer is cut after heating. This allows for uniform heating of the mirror layer across multiple parts compared to heating after cutting the wafer. As a result, variations in the quality of the mirror device can be suppressed. Also, by heating in the wafer state, many mirror devices can be placed in a constant temperature bath used for heating, for example. As a result, the manufacturing efficiency of the mirror device can be improved. Moreover, when measuring the amount of warping of 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 accurately determined, thus improving the efficiency of measurement. Furthermore, for example, when cleaning the mirror layer after heating, cleaning can be done in the wafer state, improving the workability of cleaning. Moreover, when heat treatment is performed after cutting the wafer, wafer fragments generated during cutting may adhere to the mirror layer. In this case, there is a concern that the semiconductor material constituting the fragments will diffuse into the mirror layer as the fragments are heated during the heat treatment, reducing the reflectivity of the mirror layer. In contrast, this method of manufacturing a mirror device involves heating the wafer in the wafer state before cutting, thus suppressing such a situation. As a result, the quality of the mirror device can be ensured. As described above, this method of manufacturing a mirror device makes it possible to manufacture a mirror device with movable parts in good condition.

[0007] The method for manufacturing the mirror device of the present invention may further include a measurement step between the heating step and the cutting step to measure the amount of warpage of the mirror layer. In this case, the amount of warpage of the mirror layer can be measured in wafer form, and the efficiency of the measurement can be improved.

[0008] In the cutting process, a modified region may be formed inside the wafer by irradiation with laser light, and the wafer may be cut by extending a crack from the modified region in the thickness direction of the wafer. In this case, the stress acting on the wafer during cutting can be reduced, and deformation of the mirror layer and movable parts due to this stress can be suppressed. In addition, changes in the amount of warping of the mirror layer during cutting can be suppressed.

[0009] A second forming step may be performed after the first forming step. In this case, it is possible to suppress the deterioration of the mirror layer quality due to the heat generated when forming multiple parts.

[0010] In the heating process, the amount of warping of the mirror layer may be reduced by heating the portion corresponding to the movable part in each of the multiple parts. Alternatively, the amount of warping of the mirror layer may be increased by heating the portion corresponding to the movable part in each of the multiple parts. In either case, residual stress present in the mirror layer can be relieved, and changes in the amount of warping of the mirror layer during use of the mirror device can be suppressed.

[0011] In the second forming step, the mirror layer may be formed by sputtering. In this case, the mirror layer can be formed well.

[0012] The mirror device may further include a coil or piezoelectric element for applying driving force to the movable part. In this case, heat tends to be generated when the mirror device is in use, but according to this method of manufacturing the mirror device, even in such cases, it is possible to suppress changes in the amount of warping of the mirror layer when the mirror device is in use.

[0013] In the heating process, the portion of each of the multiple parts corresponding to the movable part may be heated to a temperature between 60°C and 300°C. In this case, residual stress present in the mirror layer can be effectively relieved.

[0014] The maximum width of the mirror layer may be between 0.5 mm and 30 mm. In this case, the amount of warping of the mirror layer tends to change when the mirror device is used, but according to this method of manufacturing the mirror device, even in such cases, it is possible to suppress the change in the amount of warping of the mirror layer 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, including the adhesion layer allows for stable formation of the mirror layer on the movable part. Furthermore, including the diffusion prevention layer suppresses metal diffusion between the reflective layer and the adhesion layer during heating.

[0016] The mirror layer includes multiple layers, including a reflective layer, and these multiple layers may include a layer in which compressive stress remains at the completion of the second forming process and a layer in which tensile stress remains at the completion of the second forming process. In this case, the amount of warping of the mirror layer before the heating process can be reduced. Furthermore, the change in the amount of warping of the mirror layer during the heating process can be reduced, resulting in a shorter heating time and easier control of the amount of warping of the mirror layer.

[0017] In the heating process, the entire wafer may be heated. In this case, the temperature of the mirror layer during heating can be made uniform across multiple parts.

[0018] In the heating process, instead of heating the entire wafer, the portion corresponding to the movable part in each of the multiple sections may be heated. Even in this case, even if there are variations in the position and output of the heat source used in the heating process, the temperature of the mirror layer can be made uniform among the multiple sections by conducting heat through the wafer. [Effects of the Invention]

[0019] According to the present invention, it becomes possible to provide a method for manufacturing a mirror device capable of favorably manufacturing a mirror device having a movable part.

Brief Description of the Drawings

[0020] [Figure 1] It is a plan view of the mirror device. [Figure 2] It is a schematic cross-sectional view taken along line II-II of FIG. 1. [Figure 3] (a) and (b) are diagrams for explaining a method for manufacturing the mirror device. [Figure 4] (a) and (b) are diagrams for explaining a method for manufacturing the mirror device. [Figure 5] (a) and (b) are diagrams for explaining a step of forming a mirror layer. [Figure 6] It is a graph showing an example of a change in the amount of warpage of the mirror layer in the heating step. [Figure 7] It is a diagram for explaining a cutting step. [Figure 8] It is a cross-sectional view of the mirror device housed in a package. [Figure 9] (a) and (b) are diagrams for explaining a method for manufacturing a mirror device according to a modification. [Figure 10] It is a graph showing an example of a change in the amount of warpage of the mirror layer in the heating step of the modification. [Figure 11] It is a graph showing an example of a change in the amount of warpage of the mirror layer in a reliability test.

Mode for Carrying Out the Invention

[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 denoted by the same reference numerals, and redundant descriptions are omitted. [Mirror Device]

[0022] As shown in Figures 1 and 2, the mirror device 1 has a support portion 2 and a movable mirror portion 10. The movable mirror portion 10 has a first movable portion 3, a second movable portion 4, a pair of first connecting portions 5, a pair of second connecting portions 6, and a mirror layer 7. 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 constitute a structure 50. In other words, the mirror device 1 comprises a structure 50 and a mirror layer 7.

[0023] The structure 50 is integrally formed by, for example, 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 placed between the support layer 81 and the device layer 82.

[0024] The first movable part 3 is formed, for example, in the shape of a rectangular plate. The second movable part 4 is formed, for example, in the shape of a rectangular ring and surrounds the first movable part 3 when viewed from the optical axis direction A. The support part 2 is formed, for example, in the shape of a rectangular frame 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 the plane in 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 that intersects with the mirror layer 7.

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

[0026] The pair of first connecting parts 5 are positioned on the first axis X1 so as to sandwich the first movable part 3 in the gap between the second part 32 and the second movable part 4 of 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. It can also be considered that each first connecting part 5 connects 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 positioned on the second axis X2 so as to sandwich the second movable part 4 in the gap between the second movable part 4 and the support part 2. 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 is able to swing around the first axis X1 and the second axis X2, respectively. The first axis X1 and the second axis X2 are perpendicular to the optical axis A and intersect each other (in this example, they are orthogonal to each other).

[0028] The support portion 2, the first movable portion 3, and the second movable portion 4 are composed of a support layer 81, a device layer 82, and an intermediate layer 83. The first connecting portion 5 and the second connecting portion 6 are composed of the device layer 82. The thickness of the support layer 81 constituting the first movable portion 3 and the second movable portion 4 (thickness along the optical axis direction A) is thinner than the thickness of the support layer 81 constituting the support portion 2. The support layer 81 constituting the first movable portion 3 functions as a beam that suppresses warping of the first movable portion 3 and the mirror layer 7. The first movable portion 3 and the second movable portion 4 may also 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 part 3. The surface 31a is composed of 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 that includes 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 from the outer edge of the first portion 31 at a constant distance. The diameter of the mirror layer 7 (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, rectangle or polygon. Similarly, the first portion 31 may be formed in any shape such as an ellipse, rectangle or polygon. The second portion 32 of the first movable portion 3 and the second movable portion 4 may be formed into any shape, such as an annular, elliptical annular, or polygonal annular shape.

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

[0031] As described later, each layer constituting the mirror layer 7—the adhesion layer 71, the diffusion prevention layer 72, and the reflective layer 73—experiencing residual stresses of compressive stress (a force causing a convex curve) or tensile stress (a force causing a concave curve). The type (compressive or tensile) and magnitude of the stress are determined by the manufacturing conditions of each layer, such as the material, thickness, area, and deposition temperature. By adjusting the material, thickness, area, deposition temperature, etc., the type and magnitude of stress in the state before the heating process (described later), as well as the amount of change in curvature during the heating process, can be adjusted. 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 process (at the completion of the second forming process described later), and the reflective layer 73 is formed so that tensile stress remains in the state before the heating process (at the completion of the second forming process). By combining a layer with compressive stress and a layer with tensile stress, the amount of curvature of the mirror layer 7 and the first movable part 3 before the heating process can be reduced. Also, when formed from the same material, greater stress is generated as the layer thickness increases. Therefore, from the viewpoint of minimizing the amount of warping before the heating process and the change in the amount of warping during the heating process, it is preferable that each layer be thin.

[0032] Furthermore, the mirror device 1 includes a first drive coil 11, a second drive coil 12, wiring 15a, 15b, wiring 16a, 16b, electrode pads 21a, 21b, and electrode pads 22a, 22b. In Figure 1, the first drive coil 11 and the second drive coil 12 are shown by dashed lines, and the wiring 15a, 15b and wiring 16a, 16b are shown by solid lines. The first drive coil 11 and the second drive coil 12, etc., 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 part 3. The first drive coil 11 is wound multiple times in a spiral (vortex) 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 composed of, for example, permanent magnets arranged in a Halbach configuration.

[0034] The first drive coil 11 is positioned 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 positioned 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 not 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 wiring 15a. Wiring 15a extends from the first movable part 3 to the support part 2 via one first connecting part 5, the second movable part 4, and one second connecting part 6. Wiring 15a and the electrode pad 21a are integrally formed from a metallic material such as tungsten, aluminum, gold, silver, copper, or an aluminum alloy. Wiring 15a is provided as surface wiring on the surface of one first connecting part 5, the second movable part 4, and one second connecting part 6. Wirings 15b, 16a, and 16b, described later, are provided as surface wiring in the same way as wiring 15a.

[0036] The other end of the first drive coil 11 is connected to the electrode pad 21b via 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 in the second movable part 4. The second drive coil 12 is wound spirally (vortex-shaped) multiple times in the second movable part 4. A magnetic field generated by the magnetic field generating unit acts on the second drive coil 12. The second drive coil 12 is positioned in a groove 4b formed in 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 positioned in the groove via an insulating layer 41.

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

[0039] The other end of the second drive coil 12 is connected to the electrode pad 22b via 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] The following describes five examples of the operation of the movable mirror portion 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 generator acts on the first drive coil 11, so a Lorentz force is generated on the first drive coil 11. This Lorentz force acts as a driving force, causing the first movable portion 3 to oscillate around the first axis X1, for example, at the resonant frequency level.

[0041] Furthermore, a drive current of a certain magnitude is applied to the second drive coil 12. At this time, a magnetic field generated by the magnetic field generator acts on the second drive coil 12, so a Lorentz force is generated in the second drive coil 12. This Lorentz force acts as a driving force, causing the second movable part 4 to rotate around the second axis X2, for example, according to the magnitude of the drive current, and then to stop in that state. As a result, the mirror device 1 can scan light from a light source incident along the optical axis A by reflecting it off the mirror surface 73a. In the first example, the first movable part 3 is oscillated at the resonant frequency, while 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, the first movable part 3 is oscillated according to the resonant frequency by applying a high-frequency drive current to the first drive coil 11, and the second movable part 4 is oscillated according to the resonant frequency by applying a high-frequency drive current to the second drive coil 12. Thus, 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 fixed drive current is applied to the first drive coil 11, causing the first movable part 3 to rotate around the first axis X1 in proportion to the magnitude of the drive current and then be stopped. Similarly, a fixed drive current is applied to the second drive coil 12, causing the second movable part 4 to rotate around the second axis X2 in proportion to the magnitude of the drive current and then be 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 drive current is applied to the first drive coil 11, causing the first movable part 3 to oscillate according to the resonant frequency. In the fifth example, a drive current of a constant magnitude is applied to the first drive coil 11, causing the first movable part 3 to rotate around the first axis X1 according to the magnitude of the drive current and then be stopped. The fourth and fifth examples can be used, for example, when the second movable part 4 is not provided. [Manufacturing method for mirror devices]

[0045] The manufacturing method of the mirror device 1 will be explained with reference to Figures 3 to 8. First, an SOI wafer 80 is prepared before processing (preparation step, Figure 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 multiple regions R. Each of the multiple regions R becomes the SOI substrate 8 of the mirror device 1 after the cutting step described later. The multiple regions R are arranged, for example, in a grid pattern, and dicing lines L are set at the boundaries of adjacent regions R. The SOI wafer 80 is cut along the dicing lines L in the cutting step.

[0046] Next, multiple parts S, each corresponding to a structure 50, are formed on the SOI wafer 80 (first formation step, Figure 3(b)). "Parts corresponding to a structure 50" means parts that will become a structure 50 after the cutting step. In the first formation step, a structure 50 is formed in each of the multiple regions R. As described above, the structure 50 consists of a support part 2, a first movable part 3, a second movable part 4, a pair of first connecting parts 5, and a pair of second connecting parts 6. The structure 50 (part S) is formed using MEMS technology (patterning, etching, etc.). Also in the first formation step, a first drive coil 11 and a second drive coil 12, etc., are formed in each of the multiple regions R. In the first forming step, the first movable part 3 becomes pivotable around the first axis X1 relative to the second movable part 4 and also pivotable around the first axis X1 and the second axis X2 relative to the support part 2, and the second movable part 4 becomes pivotable around the second axis X2 relative to the support part 2.

[0047] In the first forming step, for example, first, the first drive coil 11, the second drive coil 12, wiring 15a, 15b, 16a, 16b, and electrode pads 21a, 21b, 22a, 22b are formed in each region R (wiring forming step). Subsequently, the support part 2, the first movable part 3, the second movable part 4, a pair of first connecting parts 5, and a pair of second connecting parts 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 the portion corresponding to the first movable part 3 in each of the multiple parts S (second forming step, Figure 4(a)). More specifically, a mirror layer 7 consisting 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 part 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] Figures 5(a) and 5(b) illustrate the second formation process. As shown in Figure 5(a), first, a shadow mask 91 made of silicon is placed on a plurality of portions S. The shadow mask 91 has an opening 91a that exposes the area where the mirror layer 7 is to be formed. Next, as shown in Figure 5(b), the mirror layer 7 is formed by sputtering. After the formation of the mirror layer 7, the shadow mask 91 is removed. As shown in Figure 5(b), in the mirror layer 7 formed by sputtering, the central part is thicker than the edges. Note that the opening 91a of the shadow mask 91 may be larger than the mirror layer 7. In this case, a mirror layer 7 with 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. When the temperature of the SOI wafer 80 decreases from this state, residual stress may be generated in the mirror layer 7 due to differences in thermal expansion coefficients between the mirror layer 7 and the SOI wafer 80. In this case, warping may occur in the mirror layer 7 and the first movable part 3 due to this residual stress.

[0051] More specifically, residual stress is thought to occur in the mirror layer 7 for the following three reasons. (1) Difference in thermal expansion coefficient between mirror layer 7 and SOI wafer 80 (2) Difference in lattice constant between mirror layer 7 and SOI wafer 80 (3) Argon atom trapping in SOI wafer 80 and 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 the temperature returns to room temperature from this state, the mirror layer 7 and the SOI wafer 80 contract. The degree of contraction varies depending on the thermal expansion coefficient. If the thermal expansion coefficient of the mirror layer 7 is smaller than that of the SOI wafer 80, compressive stress is generated in the mirror layer 7 so that it bends convexly. If the thermal expansion coefficient of the mirror layer 7 is larger than that of the SOI wafer 80, tensile stress is generated in the mirror layer 7 so that it bends concavely. In addition, residual stress is generated in the mirror layer 7 not only due to the difference in thermal expansion coefficients between the mirror layer 7 and the SOI wafer 80, but also due to the difference in thermal expansion coefficients between the multiple layers that make up the mirror layer 7 (adhesion layer 71, diffusion prevention layer 72, and reflection layer 73).

[0053] Regarding (2), the lattice constant of the mirror layer 7 is different from that of the SOI wafer 80. Near 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, as you move away from the interface, the lattice constant of the mirror layer 7 approaches a material-specific value. As a result, strain occurs in the mirror layer 7 near the interface, and stress is generated as a result. Furthermore, residual stress is generated in the mirror layer 7 not only due to the difference in lattice constants between the mirror layer 7 and the SOI wafer 80, but also due to the difference in lattice constants between the multiple layers that make up the mirror layer 7 (adhesion layer 71, diffusion prevention layer 72, and reflection layer 73).

[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 cations that collide with the target are neutralized and incident on the SOI wafer 80 and the mirror layer 7 being formed with high kinetic energy. The argon atoms penetrate between the crystal lattice within the mirror layer 7 and widen the lattice spacing, generating compressive stress in the mirror layer 7 so that it bends into a convex shape.

[0055] The direction and magnitude of the warping that occurs in the mirror layer 7 and the first movable part 3 vary depending on the material, thickness, area, and formation method of the mirror layer 7. For example, in this embodiment, the mirror layer 7 curves in a convex shape as shown in Figure 4(a), but it may also curve in a concave shape as shown in Figure 9(a), which will be described later. The larger the area (diameter) of the mirror layer 7, the greater the amount of warping of the mirror layer 7. As described above, at the completion of the second forming process, compressive stress remains in the adhesion layer 71 and the diffusion prevention layer 72, and tensile stress remains in the reflective layer 73. These stresses may remain even after the heating process. That is, it is sufficient that compressive stress remains in the adhesion layer 71 and the diffusion prevention layer 72 and tensile stress remains in the reflective layer 73 at least at the completion of the second forming process.

[0056] Next, the SOI wafer 80 is heated (heating step, Figure 4(b)). In this example, the entire SOI wafer 80 is heated. Heating the SOI wafer 80 relieves residual stress present in the mirror layer 7 (annealing). In this embodiment, the amount of warping of the mirror layer 7 is reduced and the mirror layer 7 is flattened by the relief of residual stress. 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, it may be required, or it may be omitted.

[0057] During the heating process, residual stress is thought to be relieved for the following reasons. First, a stress-relieving layer (alloy layer) is formed between the mirror layer 7 and the SOI wafer 80. During the heating process, some of the atoms constituting the mirror layer 7 diffuse. Due to this diffusion of atoms, a stress-relieving layer (alloy layer) is formed between the mirror layer 7 and the SOI wafer 80, or between the adhesion layer 71, diffusion prevention layer 72, and reflection layer 73 constituting the mirror layer 7, in order to reduce the difference in lattice constants, and as a result, residual stress is thought to be relieved. Another reason is that during the heating process, as described in (3) above, argon atoms that were trapped between the crystal lattices in the mirror layer 7 are released into the atmosphere, and as a result, residual stress is thought to be relieved.

[0058] Figure 6 is a graph showing an example of the change in the amount of warpage of the mirror layer 7 during the heating process. The horizontal axis represents the elapsed time from the start of heating (in hours), and the vertical axis represents the amount of warpage of the mirror layer 7 (in nm). In this example, the SOI wafer 80 was heated at 150°C for 30 hours. As shown in Figure 6, the amount of warpage at the start of heating was approximately 300 nm, but the mirror layer 7 became almost flat during the heating process, and the change in the amount of warpage decreased over time. The amount of warpage of the mirror layer 7 was measured using the same method as the measurement process described later.

[0059] In the heating process, the heating temperature for heating the SOI wafer 80 is set to, for example, 60°C to 300°C. A higher heating temperature allows for a shorter heating time, but if the heating temperature is too high, defects such as cracks and metal diffusion may occur. In this embodiment, the heating temperature of 150°C is the sum of 70°C, which is assumed to be the maximum ambient temperature of the mirror device 1, 70°C, which is assumed to be the self-heating temperature, and 10°C, which is the margin temperature. The heating time is set to be longer than the time it takes for the change in warpage to saturate and become small, based on the relationship between time and warpage obtained in advance. For example, in the case of Figure 6, the change in warpage reaches saturation in about 5 hours, so the heating time should be 5 hours or longer. By setting the heating time to be about the time it takes for the change in warpage to reach saturation, the energy required for heating can be reduced. In order to reliably suppress changes in warpage at the customer's site, it is preferable to set the heating temperature to be at least higher than the self-heating temperature of the mirror device 1 (the temperature of the mirror device 1 during operation).

[0060] During heating, the SOI wafer 80 is placed in a constant temperature chamber (oven). This heats the entire SOI wafer 80, and consequently, the parts of each of the multiple parts S corresponding to the first movable part 3 are heated simultaneously. One SOI wafer 80 may be placed in the constant temperature chamber, or multiple (for example, two, six, or twelve) SOI wafers 80 may be placed. The SOI wafer 80 may be placed horizontally or vertically (along the vertical direction) in the constant temperature chamber. From the viewpoint of preventing foreign matter from adhering to the mirror layer 7, a clean oven is preferable.

[0061] The amount of warping of the mirror layer 7 may decrease or increase due to the heating process, as in this embodiment. 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 was curved convexly before heating, and the amount of warping of the mirror layer 7 decreased due to the heating process. However, there are also cases where the mirror layer 7 was curved convexly before heating, and the amount of warping of the mirror layer 7 increased due to the heating process. Furthermore, as shown in the modified example described later, there are also cases where the mirror layer 7 was curved concavely before heating, and the amount of warping of the mirror layer 7 increased due to the heating process. Alternatively, there are cases where the mirror layer 7 was curved concavely before heating, and the amount of warping of the mirror layer 7 decreased due to the heating process. In addition, there are cases where the mirror layer 7 that was curved convexly before heating curves concavely after heating, and conversely, there are cases where the mirror layer 7 that was curved concavely before heating curves convexly after heating. Note that an increase in the amount of warping means an increase in the absolute value of the amount of warping. For example, this could be a change in the amount of curvature from 200 nm to 300 nm, or from -200 nm to -300 nm. A decrease in the amount of curvature means a decrease in the absolute value of the amount of curvature. For example, this could be a change in the amount of curvature from 200 nm to 100 nm, or from -200 nm to -100 nm. Furthermore, a positive value for the amount of curvature means that the height of the central part of the mirror layer 7 is higher than the peripheral part (convex), and a negative value for the amount of curvature means that the height of the central part of the mirror layer 7 is lower than the peripheral part (concave).

[0062] Next, the amount of warpage of the mirror layer 7 is measured for each of the multiple parts 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 are measured for a region with a diameter of 1.9 mm concentric with the mirror layer 7. The PV value represents the difference in height between the highest and lowest points of the mirror layer 7 (mirror surface 73a) within the measurement range. Since the PV value is expressed as an absolute value, shape data is also measured to determine whether the mirror layer 7 is convex or concave (whether the amount of warpage is a positive or negative value). Structures 50 with a mirror layer 7 warpage greater than a predetermined value are marked (marking). The marked structures 50 (mirror device 1) are removed, for example, after the cutting step. The amount of warpage of the mirror layer 7 may also be measured by measuring the curvature of the mirror layer 7.

[0063] Next, the SOI wafer 80 is cut along the dicing line L so that multiple portions S are separated from each other (cutting step, Figure 7). For example, a modified region is formed inside the SOI wafer 80 along the dicing line L by irradiation with laser light, and the SOI wafer 80 is cut by extending a crack in the thickness direction of the SOI wafer 80 from the modified region using tape expansion or the like. In the cutting step, the SOI wafer 80 may be cut by other cutting methods such as blade dicing. Multiple mirror devices 1 are obtained by the above steps.

[0064] Subsequently, as shown in Figure 8, each mirror device 1 is housed in a package 60. The package 60 has a main body 61 that houses the mirror devices 1 and a transparent window member 62 positioned to close the opening 61a of the main body 61. Light reflected by the mirror devices 1 passes through the window member 62 and enters the mirror layer 7. [Mechanism of Action and Effects]

[0065] As described above, residual stress may occur in the mirror layer 7 during its formation, and this residual stress may cause warping of the mirror layer 7. If the mirror device 1 is shipped in this state, there is a concern that the amount of warping of the mirror layer 7 may change during use as the residual stress is relieved by ambient temperature and self-heating. 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 on the SOI wafer 80, and after the mirror layer 7 is formed on the part corresponding to the first movable part 3 in each of the plurality of parts S, the SOI wafer 80 (the part corresponding to the first movable part 3 in each of the plurality of parts S) is heated. This relieves (releases) the residual stress present in the mirror layer 7, and suppresses changes in the amount of warping of the mirror layer 7 during use of the mirror device 1. As a result, it is possible to suppress changes in the size of the spot and the focal position of the laser light reflected by the mirror layer 7 during use of the mirror device 1. Furthermore, in the manufacturing method of the mirror device 1 according to the embodiment, the SOI wafer 80 is cut after the heating process. This makes it possible to equalize the temperature of the mirror layer 7 during heating across multiple sections S, compared to when heat treatment is performed after cutting the wafer. That is, as described above, the heat treatment is performed, for example, in a constant temperature bath, but due to the influence of air convection, the position of the heat source and the object being heated, there may be temperature variations depending on the location within the constant temperature bath. When heat treatment is performed on each chip after cutting the wafer (after chipping), there is a concern that the chip may be heated to a temperature different from the set temperature depending on where the chip is placed. In contrast, in the manufacturing method of the mirror device 1 according to the embodiment, the heat treatment is performed in the state of the SOI wafer 80, which has high thermal conductivity, and since heat is easily conducted within the SOI wafer 80, the temperature of the mirror layer 7 can be equalized across multiple sections S. As a result, variations 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 constant temperature bath. As a result, the manufacturing efficiency of the mirror device 1 can be improved. Furthermore, the amount of warpage of the mirror layer 7 can be measured in the wafer state during the measurement process.This makes it easier to accurately determine the position of the mirror layer 7, thereby improving the efficiency of measurement. Furthermore, when a cleaning process is performed to clean the mirror layer 7 after heating, cleaning can be done in the wafer state, improving the workability of the cleaning process. Moreover, in the manufacturing method of the mirror device 1 according to the embodiment, since the SOI wafer 80 is cut after the heating process, it is possible to suppress the diffusion of semiconductor material constituting the fragments of the SOI wafer 80 that are generated during cutting and adhere to the mirror layer 7 into the mirror layer 7 due to heating, thereby ensuring the quality of the mirror device 1. In addition, there is no need 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 process is performed after the mirror device 1 is housed in the package 60, the upper limit of the heating temperature is limited because the sealing resin used in the package 60 may deteriorate due to heating. In contrast, in the manufacturing method of the mirror device 1 according to the embodiment, since heating is performed in the wafer state, the heating temperature can be set regardless of the deterioration start temperature of the sealing resin, thereby improving manufacturing efficiency. As described above, according to the manufacturing method of the mirror device 1 according to the embodiment, a mirror device 1 having a movable part can be manufactured well.

[0066] Between the heating and cutting processes, a measurement process is performed to measure the amount of warpage of the mirror layer 7. This allows for the measurement of the amount of warpage of the mirror layer 7 in wafer form, thereby improving the efficiency of the measurement.

[0067] In the cutting process, a modified region is formed inside the SOI wafer 80 by irradiation with laser light, and the SOI wafer 80 is cut by extending a crack in the thickness direction of the SOI wafer 80 from the modified region (stealth dicing). This reduces the stress acting on the SOI wafer 80 during cutting, and suppresses deformation of the mirror layer 7 and the first movable part 3 due to this stress. It also suppresses changes in the amount of warping of the mirror layer 7 during cutting. Furthermore, in the above embodiment, since the first movable part 3 is oscillating before the cutting process, and the mirror layer 7 is heated before the cutting process, using stealth dicing, which can suppress damage to the first movable part 3 and changes in the amount of warping, is particularly effective.

[0068] A second forming step is performed after the first forming step. This makes it possible to suppress the deterioration of the quality of the mirror layer 7 due to the heat generated when forming the multiple parts S. In other words, contrary to the above embodiment, if the multiple parts S are formed on the SOI wafer 80 after the mirror layer 7 is formed on the part corresponding to the first movable part 3, metal diffusion may occur between the adhesion layer 71 (titanium) and the reflective layer 73 (gold) that constitute the mirror layer 7 due to the heat generated when forming the multiple parts S, which may reduce the reflectivity of the mirror layer 7. In contrast, by forming the mirror layer 7 after forming the multiple parts S as in the above embodiment, such a situation can be suppressed, and the quality of the mirror layer 7 can be ensured. Furthermore, if the diffusion prevention layer 72 is formed of tungsten, metal diffusion between the adhesion layer 71 and the reflective layer 73 can be effectively suppressed compared to the case where the diffusion prevention layer 72 is formed of platinum. On the other hand, if the diffusion prevention layer 72 is formed of platinum, the stress generated by the diffusion prevention layer 72 can be reduced compared to the case where the diffusion prevention layer 72 is formed of tungsten, making it easier to handle.

[0069] In the heating process, heating the SOI wafer 80 reduces the amount of warping of the mirror layer 7. This relieves residual stress present in the mirror layer 7, thereby suppressing changes in the amount of warping of the mirror layer 7 when the mirror device 1 is used. Alternatively, as described above, heating the SOI wafer 80 in the heating process may increase the amount of warping of the mirror layer 7. In this case as well, residual stress present in the mirror layer 7 can be relieved, and changes in the amount of warping of the mirror layer 7 when the mirror device 1 is used can be suppressed.

[0070] In the second forming step, the mirror layer 7 is formed by sputtering. This allows for the formation of a good mirror layer 7. Specifically, when forming the mirror layer 7 by sputtering, there is no need to rotate the wafer as in the case of vapor deposition, so damage to the structure 50, including the hollow structure, is less likely to occur. In addition, sputtering has high directionality, making it difficult for metal to adhere to areas other than the mirror layer 7. In vapor deposition, which has low directionality, there is a risk that metal will pass through the slit (gap) between the support part 2 and the movable mirror part 10 and wrap around to the back side of the movable mirror part 10 or adhere to the support part 2. In contrast, by using highly directional sputtering, such situations can be suppressed. Furthermore, sputtering allows the use of high-melting-point materials that are difficult to use in vapor deposition. Also, the thickness of the mirror layer 7 can be easily controlled. On the other hand, when forming the mirror layer 7 by vapor deposition, about 20 wafers can be processed at once, thus improving manufacturing efficiency. As described above, when using sputtering, the amount of warping of the mirror layer 7 tends to increase due to argon atom trapping during film formation, and the amount of warping changes significantly when the trapped argon is released into the atmosphere during the heating process. According to the manufacturing method of the mirror device 1 of the embodiment, even in such cases, it is possible to effectively suppress changes in the amount of warping of the mirror layer 7 when the mirror device 1 is used.

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

[0072] During the heating process, the SOI wafer 80 is heated to a temperature between 60°C and 300°C. This effectively relieves residual stress present within the mirror layer 7.

[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 tends to change 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 cases, it is possible to suppress the change in the amount of warping of the mirror layer 7 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. The inclusion of the adhesion layer 71 allows for the stable formation of the mirror layer 7 on the first movable part 3. Furthermore, the inclusion of the diffusion prevention layer 72 suppresses 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 forming process, and a reflective layer 73 in which tensile stress remains at the completion of the second forming process. This makes it possible to reduce the amount of warping of the mirror layer 7 before the heating process. Furthermore, it is possible to reduce the change in the amount of warping of the mirror layer 7 during the heating process, which in turn shortens the heating time and allows for easy control of the amount of warping of the mirror layer 7.

[0076] During the heating process, the entire SOI wafer 80 is heated. This allows the temperature of the mirror layer 7 to be made uniform across multiple sections S during heating. [Differentiation]

[0077] Figures 9(a) and 9(b) illustrate a modified method for manufacturing the mirror device 1. In this modified method, as shown in Figure 9(a), the mirror layer 7 is curved in a concave shape before the heating process. Then, as shown in Figure 9(b), the amount of warping of the mirror layer 7 increases by heating the SOI wafer 80 during the heating process.

[0078] Figure 10 is a graph showing an example of the change in the amount of warpage of the mirror layer 7 during the heating process of a modified example. In this example, the SOI wafer 80 was heated at 150°C for 30 hours. Figure 10 shows the change in the amount of warpage for five samples using different line types. As shown in Figure 10, for all samples, the amount of warpage at the start of heating was about 100 nm, but it increased to about 250-350 nm during the heating process, and it can be seen that the change in the amount of warpage became smaller over time. In the case of Figure 10, the change in the amount of warpage reached saturation in about 2 hours, so the heating time should be 2 hours or longer. By setting the heating time to the time it takes for the change in the amount of warpage to reach saturation, the energy required for heating can be reduced.

[0079] Figure 11 is a graph showing an example of the change in the amount of warpage of the mirror layer 7 during a reliability test. In this reliability test, the mirror device 1 obtained by the manufacturing method of the modified mirror device 1 was operated, and the amount of warpage of the mirror layer 7 during operation was measured. Specifically, the amount of warpage of the mirror layer 7 in the initial state (0 hours) was set to 0 nm, and the change in the amount of warpage of the mirror layer 7 was measured every 250 hours up to 1000 hours. The first movable part 3 was operated continuously with 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 Figure 11, it can be seen that the change in the amount of warpage of the mirror layer 7 during operation was suppressed to ±50 nm or less.

[0080] The present invention is not limited to the embodiments described above. For example, the materials and shapes of each component are not limited to those described above, but can be made from a variety of materials and shapes. In the embodiments described above, the mirror device 1 was configured to be electromagnetically driven, but the mirror device 1 may be configured to be piezoelectrically driven or electrostatically driven. In the case of piezoelectric drive, for example, a piezoelectric film (piezoelectric element) may be provided instead of the first driving coil 11 and the second driving coil 12.

[0081] The first drive coil 11 may be provided on the second movable part 4. Even in this case, the first movable part 3 can be oscillated around the first axis X1 at the resonant frequency. Specifically, when a drive current with a frequency equal to the resonant frequency of the first movable part 3 around the first axis X1 is input to the first drive coil 11, the second movable part 4 vibrates slightly around the first axis X1 at that frequency. This vibration is transmitted to the first movable part 3 via the first connecting part 5, thereby allowing the first movable part 3 to oscillate around the first axis X1 at that frequency. When the first drive coil 11 or piezoelectric element is provided on the first movable part 3, the heat source is close to the mirror layer 7, making it easy for heat to be transferred to the mirror layer 7. However, according to the manufacturing method of the mirror device 1 described above, even in such cases, it is possible to suppress changes in the amount of warping of the mirror layer 7 when the mirror device 1 is in use.

[0082] The second forming step may be performed before the first forming step. For example, after the wiring forming step described above is performed, the mirror layer 7 may be formed on the 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 can move 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 does not necessarily have to include the adhesion layer 71. For example, if the mirror device 1 does not become hot during operation, the adhesion layer 71 may be omitted. The mirror layer 7 does not necessarily have to include the diffusion prevention layer 72. For example, if a high reflectivity is not required for the mirror layer 7, or if the appearance of the mirror layer 7 is not a concern, 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 process can be reduced, as well as the change in the amount of warping of the mirror layer 7 during the heating process can be reduced.

[0084] In the heating step of the above embodiment, the entire SOI wafer 80 was heated using a constant temperature bath, but the heating means is not limited, as it is sufficient for the portion corresponding to the first movable part 3 in each of the multiple parts S to be heated. For example, instead of heating the entire SOI wafer 80, only the portion corresponding to the first movable part 3 in each of the multiple parts S may be heated simultaneously by irradiating it with spot light such as laser light. Even in this case, the portion corresponding to the first movable part 3 in each of the multiple parts S can be heated uniformly by heat conduction within the SOI wafer 80. Furthermore, even if there is variation in the output of the irradiated laser light, uniform heating can be achieved. In the heating step, heating is performed using a heat source located outside the mirror device 1, rather than self-heating generated by the driving of the mirror device 1. [Explanation of Symbols]

[0085] 1...Mirror device, 2...Support part, 3...First movable part, 4...Second movable part, 5...First connecting part, 6...Second connecting part, 7...Mirror layer, 11...First driving coil, 12...Second driving coil, 50...Structure, 80...SOI wafer, S...Part.

Claims

1. A method for manufacturing a mirror device comprising: a structure having a support portion, a movable portion, and a connecting portion that connects the movable portion to the support portion so that the movable portion can swing or move; and a mirror layer provided on the movable portion, A first forming step of forming a plurality of parts on a wafer, each corresponding to the structure, such that the part of each of the plurality of parts corresponding to the movable part is swingable or movable relative to the part of each of the plurality of parts corresponding to the support part, A second forming step is performed after the first forming step, in which the mirror layer is formed on the portion corresponding to the movable part in each of the plurality of parts, A heating step is performed after the first forming step and the second forming step, in which the portion of each of the plurality of parts corresponding to the movable part is heated so that the portion of each of the plurality of parts corresponding to the movable part is swingable or movable relative to the portion of each of the plurality of parts corresponding to the support part, thereby relieving residual stress present in the mirror layer. A method for manufacturing a mirror device, comprising: a cutting step, after the heating step, cutting the wafer such that the plurality of parts are separated from each other, with each of the plurality of parts having a portion corresponding to the movable part that can swing or move relative to the portion corresponding to the support part that can move relative to each of the plurality of parts.

2. A method for manufacturing a mirror device comprising: a structure having a support portion, a movable portion, and a connecting portion for connecting the movable portion to the support portion so that the movable portion can swing or move; and a mirror layer provided on the movable portion, A first forming step of forming a plurality of parts on a wafer, each corresponding to the structure, such that the part of each of the plurality of parts corresponding to the movable part is swingable or movable relative to the part of each of the plurality of parts corresponding to the support part, A second forming step of forming the mirror layer on the portion corresponding to the movable part in each of the plurality of parts, A heating step is performed after the first forming step and the second forming step, in which the portion of each of the plurality of parts corresponding to the movable part is heated so that the portion of each of the plurality of parts corresponding to the movable part is swingable or movable relative to the portion of each of the plurality of parts corresponding to the support part, The process includes, after the heating step, cutting the wafer such that the plurality of parts are separated from each other, with each of the plurality of parts having a portion corresponding to the movable part that can swing or move relative to the portion corresponding to the support part that can move relative to each of the plurality of parts, The structure is formed from a semiconductor substrate including a support layer, a device layer, and an intermediate layer disposed between the support layer and the device layer. The support portion and the movable portion are composed of the support layer, the device layer, and the intermediate layer, A method for manufacturing a mirror device, wherein the thickness of the support layer constituting the movable part is thinner than the thickness of the support layer constituting the support part.

3. A method for manufacturing a mirror device comprising: a structure having a support portion, a movable portion, and a connecting portion that connects the movable portion to the support portion so that the movable portion can swing or move; and a mirror layer provided on the movable portion, A first forming step of forming a plurality of parts on a wafer, each corresponding to the structure, such that the part of each of the plurality of parts corresponding to the movable part is swingable or movable relative to the part of each of the plurality of parts corresponding to the support part, A second forming step of forming the mirror layer on the portion corresponding to the movable part in each of the plurality of parts, A heating step is performed after the first forming step and the second forming step, in which the portion of each of the plurality of parts corresponding to the movable part is heated so that the portion of each of the plurality of parts corresponding to the movable part is swingable or movable relative to the portion of each of the plurality of parts corresponding to the support part, The process includes, after the heating step, cutting the wafer such that the plurality of parts are separated from each other, with each of the plurality of parts having a portion corresponding to the movable part that can swing or move relative to the portion corresponding to the support part that can move relative to each of the plurality of parts, The process further includes a measurement step between the heating step and the cutting step for measuring the amount of warping of the mirror layer, A method for manufacturing a mirror device, comprising removing the structure in which the amount of warping of the mirror layer is determined to be greater than a predetermined value in the measurement step after the cutting step.

4. The method for manufacturing a mirror device according to any one of claims 1 to 3, wherein the heating step involves simultaneously heating the portion of each of the plurality of parts corresponding to the movable part.

5. The movable part comprises a first portion on which the mirror layer is provided, and a second portion that surrounds the first portion when viewed from a direction perpendicular to the plane in which the support portion, the movable part, and the connecting portion are arranged, is connected to the first portion via a connecting portion, and is connected to the support portion by the connecting portion. A method for manufacturing a mirror device according to any one of claims 1 to 4.

6. A method for manufacturing a mirror device according to any one of claims 1 to 5, wherein the thickness of the central part of the mirror layer is greater than the thickness of the edge of the mirror layer.

7. A method for manufacturing a mirror device according to any one of claims 1 to 6, wherein the lattice constant of the mirror layer is different from the lattice constant of the wafer.

8. A method for manufacturing a mirror device according to any one of claims 1 to 7, wherein at the end of the heating step, the mirror layer is curved in a convex shape.

9. A method for manufacturing a mirror device according to any one of claims 1 to 7, wherein at the end of the heating step, the mirror layer is curved in a concave shape.

10. In the second formation step described above, the mirror layer is formed by sputtering, and argon atoms penetrate into the mirror layer. A method for manufacturing a mirror device according to any one of claims 1 to 9, wherein in the heating step, argon atoms trapped in the mirror layer are released into the atmosphere.

11. The method for manufacturing a mirror device according to any one of claims 1 to 10, wherein the wafer has a plurality of regions, each corresponding to the structure and arranged in a grid pattern.

12. Each of the wafers has a plurality of regions corresponding to the structure, A method for manufacturing a mirror device according to any one of claims 1 to 11, wherein a dicing line is set at the boundary between adjacent regions, extending from one end of the wafer to the other end.

13. A method for manufacturing a mirror device according to any one of claims 1 to 12, wherein in the heating step, the portion of each of the plurality of parts corresponding to the movable part is heated while no protective film is formed on the mirror layer.

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