Optical reflective element

Abstract

The optical reflective element includes: a fixed portion; and a movable part (40) supported by the fixed part so as to be rotatable about a rotation axis (R10), the movable part (40) having a reflective surface (40a) in a center portion (41) of an upper surface and a rib portion (42) in an outer peripheral region of a lower surface. A central portion (41) of the movable portion (40) has a structure in which a base layer (101) and an oxide film (102) are removed from an SOI wafer in which the base layer (101), the oxide film (102), and the active layer (103) are laminated, and the rib portion (42) has a structure in which at least a part of the active layer (103) is removed from the SOI wafer.

Description

Technical Field

[0001] The present invention relates to an optical reflection element having a movable portion formed with a reflection surface. Background Art

[0002] An optical reflection element having a movable portion formed with a reflection surface is known. In such an optical reflection element, for example, a reflection surface is disposed on a movable portion that rotates about a rotation axis, and a light beam incident on the reflection surface is scanned as the movable portion rotates.

[0003] Patent Document 1 below describes an optical scanner that includes a movable body that can swing about an axis and a drive unit that swings the movable body about the axis. The movable body includes a light reflection plate and a support frame that surrounds the light reflection plate and is thicker than the light reflection plate. Each part of the optical scanner is formed by removing unnecessary portions of an SOI (Silicon On Insulator) wafer using various etching methods such as dry etching and wet etching.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-222155 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] In the production of an SOI wafer, an oxide film is formed on the surface of a base layer by thermally oxidizing the base layer at a temperature of about 1100°C, and then an active layer is bonded to the oxide film. The coefficient of thermal expansion of the base layer is larger than that of the oxide film. When returning to room temperature, the base layer will shrink compared to the oxide film. Therefore, at this time, compressive stress is applied to the oxide film from the base layer. When such an SOI wafer is processed to remove the base layer and the oxide film from the central region of the movable portion to form ribs in the peripheral region, since the base layer in the central region is removed, a part of the above-mentioned compressive stress applied to the oxide film of the ribs is released, and the above-mentioned oxide film expands. As a result, a force is applied to the active layer in the central portion from the oxide film in the direction of the center of the central portion, causing a flexure in the active layer in the central portion.

[0009] In view of this problem, an object of the present invention is to provide an optical reflection element that can suppress flexure of a movable portion when processing an SOI wafer to form ribs in the movable portion.

[0010] Means for Solving the Problems

[0011] The optical reflection element according to the main aspect of the present invention includes a fixed portion; and a movable portion that is supported by the fixed portion so as to be rotatable about a rotation axis, has a reflection surface at the central portion of the upper surface, and has rib portions in the outer peripheral region of the lower surface. The central portion of the movable portion has a structure obtained by removing the base layer and the oxide film from a silicon-on-insulator wafer in which a base layer, an oxide film, and an active layer are laminated, and the rib portions have a structure obtained by removing at least a part of the active layer from the silicon-on-insulator wafer.

[0012] In the production of an SOI wafer, an oxide film is formed on the surface of the base layer by thermally oxidizing the base layer at a temperature of about 1100°C, and then an active layer is bonded to the oxide film. The coefficient of thermal expansion of the base layer is larger than that of the oxide film. When returning to normal temperature, the base layer will shrink compared to the oxide film. Therefore, at this time, compressive stress is applied to the oxide film from the base layer. When processing such an SOI wafer to remove the base layer and the oxide film from the central region of the movable portion to form rib portions in the outer peripheral region, since the base layer in the central region is removed, a part of the compressive stress applied to the oxide film of the rib portions is released, and the oxide film expands. As a result, a force in the central direction of the central portion is applied to the active layer of the central portion from the oxide film, and the active layer of the central portion is deflected. In contrast, according to the optical reflection element of the present aspect, since at least a part of the active layer is removed from the rib portions, the expansion of the oxide film is not easily transmitted to the active layer, and it is not easy to generate deflection in the active layer of the central portion. Therefore, when using an SOI wafer to form rib portions in the movable portion, deflection of the movable portion can be suppressed.

[0013] Effect of the Invention

[0014] As described above, according to the present invention, an optical reflection element capable of suppressing deflection of a movable portion when processing an SOI wafer to form rib portions in the movable portion can be provided.

[0015] The effect or significance of the present invention is further clarified by the description of the embodiments shown below. However, the embodiments shown below are merely examples when implementing the present invention, and the present invention is not limited by any of the contents described in the following embodiments. Brief Description of the Drawings

[0016] Figure 1 is a top view schematically showing the structure of the optical reflection element according to Embodiment 1.

[0017] Figure 2 (a) to (d) are cross-sectional views showing the production process of an SOI wafer.

[0018] Figure 3 (a) and Figure 3(b) are respectively a top view and a cross-sectional view schematically showing the structure of the movable part involved in Comparative Example 1.

[0019] Figure 4 (a) to (c) are cross-sectional views showing the formation process of the movable part involved in Embodiment 1.

[0020] Figure 5 (a) and Figure 5 (b) are respectively a top view and a cross-sectional view schematically showing the structure of the movable part involved in Embodiment 1.

[0021] Figure 6 is a graph showing the simulation results related to the amount of deflection involved in Comparative Example 1 and Embodiment 1.

[0022] Figure 7 (a) and Figure 7 (b) are respectively a top view and a cross-sectional view schematically showing the structure of the movable part involved in Modification 1 of Embodiment 1.

[0023] Figure 8 (a) and Figure 8 (b) are respectively a top view and a cross-sectional view schematically showing the structure of the movable part involved in Modification 2 of Embodiment 1.

[0024] Figure 9 is a graph showing the simulation results related to the amount of deflection involved in Embodiment 1 and Modification 2 of Embodiment 1.

[0025] Figure 10 (a) and Figure 10 (b) are respectively a top view and a cross-sectional view schematically showing the structure of the movable part involved in Modification 3 of Embodiment 1.

[0026] Figure 11 (a) and Figure 11 (b) are respectively a top view and a cross-sectional view schematically showing the structure of the movable part involved in Embodiment 2.

[0027] Figure 12 is a graph showing the simulation results related to the amount of deflection involved in Modification 2 of Embodiment 1 and Embodiment 2.

[0028] Figure 13 (a) to (c) are top views schematically showing the structure of the movable part involved in the modification of Embodiment 2.

[0029] Figure 14 (a) to (c) are top views schematically showing the structure of the movable part involved in the modification of Embodiment 2.

[0030] Figure 15 (a) - (c) of [this figure] are top views schematically showing the structure of the movable part related to the modification example of Embodiment 2.

[0031] Figure 16 (a) of [this figure] and Figure 16 (b) of [this figure] are top views schematically showing the structure of the movable part related to the modification example of Embodiment 2.

[0032] Figure 17 (a) of [this figure] and Figure 17 (b) of [this figure] are respectively top views schematically showing the structure of the movable part related to the modification example of Embodiment 2.

[0033] Figure 18 (a) of [this figure] and Figure 18 (b) of [this figure] are respectively a top view and a cross - sectional view schematically showing the structure of the movable part related to Embodiment 3.

[0034] Figure 19 (a) - (c) of [this figure] are top views schematically showing the structure of the movable part related to the modification example of Embodiment 3.

[0035] Figure 20 (a) - (c) of [this figure] are top views schematically showing the structure of the movable part related to Modification Example 1 of the movable part.

[0036] Figure 21 (a) - (c) of [this figure] are top views schematically showing the structure of the movable part related to Modification Example 1 of the movable part.

[0037] Figure 22 (a) - (c) of [this figure] are top views schematically showing the structure of the movable part related to Modification Example 2 of the movable part.

[0038] Figure 23 (a) - (c) of [this figure] are top views schematically showing the structure of the movable part related to Modification Example 2 of the movable part.

[0039] Figure 24 (a) of [this figure] is a top view schematically showing the structure of the movable part related to the simulation of Comparative Example 2. Figure 24 (b) of [this figure] shows the simulation result of the deflection amount at the center when the movable part related to Comparative Example 2 rotates.

[0040] Figure 25 (a) of [this figure] is a top view schematically showing the structure of the movable part related to the simulation of Embodiment 2. Figure 25 (b) of [this figure] shows the simulation result of the deflection amount at the center when the movable part related to Embodiment 2 rotates.

[0041] Figure 26It is a graph showing simulation results related to the amount of deflection in Comparative Example 2 and Embodiment 2.

[0042] Figure 27 For (a) of Figure 27 and (b) of

[0043] Figure 28 They are respectively a top view and a cross-sectional view schematically showing the structure of the movable part related to a modification of the reflecting surface.

[0044] Figure 29 For (a) of Figure 29 and (b) of

[0045] However, the drawings are mainly for illustration and do not limit the scope of the present invention. Detailed Embodiments

[0046] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience, the mutually orthogonal X, Y, and Z axes are marked in each drawing. The positive direction of the Z axis is the vertically upward direction.

[0047] <Embodiment 1>

[0048] Figure 1 It is a top view schematically showing the structure of the optical reflection element 1.

[0049] The optical reflection element 1 includes a fixed part 10, a pair of vibration parts 21 to 24, a pair of connection parts 31 to 34, a pair of connecting beams 35, a movable part 40, and eight driving parts 50. The optical reflection element 1 is configured to be symmetric about the center point C10. The optical reflection element 1 is formed by processing an SOI wafer 100 (refer to Figure 4 for (a)). Subsequently, refer to Figure 2 for (a) to (d) of Figure 4 and (a) to (c) of

[0050] The fixed part 10 is configured in a frame shape. A pair of vibration parts 21 to 24, a pair of connection parts 31 to 34, and a pair of connecting beams 35 are located in the opening 11 that penetrates the fixed part 10 in the Z-axis direction at the center of the fixed part 10 in a top view, and are arranged between the fixed part 10 and the movable part 40. A group composed of the vibration parts 21 to 24, the connection parts 31 to 34, and the connecting beams 35 is arranged on the positive X-axis side and the negative X-axis side of the movable part 40, respectively. The vibration parts 21 to 24 located on the positive X-axis side or the negative X-axis side of the movable part 40 are in a meandering shape in a top view.

[0051] The movable part 40 has a circular shape when viewed from above. The movable part 40 is supported by the fixed part 10 via a pair of vibrating parts 21 to 24, a pair of connecting parts 31 to 34, and a pair of connecting beams 35 so as to be rotatable about the rotation axis R10. The center of the movable part 40 coincides with the position of the center C10 of the optical reflection element 1. The movable part 40 has a central part 41 in the central region and rib parts 42 in the outer peripheral region of the lower surface. The rib parts 42 have a structure that protrudes in the negative Z-axis direction with respect to the central part 41.

[0052] The upper surface of the movable part 40 (the upper surface of the active layer 103 described later) is a reflection surface 40a that reflects light. Generally, due to the formation of the SOI wafer 100, the upper surface of the active layer 103 has a sufficient reflectivity, so the upper surface of the active layer 103 can be used as the reflection surface 40a. In addition, when the reflectivity of the upper surface of the active layer 103 is insufficient, the reflectivity of the upper surface of the active layer 103 can also be improved by polishing the upper surface of the active layer 103. Subsequently, refer to Figure 4 (a) to Figure 5 (b) of this specification to describe the structure of the movable part 40.

[0053] Drive parts 50 are respectively arranged on the upper surfaces of the pair of vibrating parts 21 to 24. The drive part 50 has a layer structure composed of a lower electrode layer, a piezoelectric layer, and an upper electrode layer. The drive part 50 is connected to the electrode on the fixed part 10 via the vibrating parts 21 to 24, the connecting parts 31 to 34, and the wiring on the fixed part 10. The electrode on the fixed part 10 is connected to a cable (external wiring) connected to an external device by wire bonding.

[0054] When drive voltages of the same phase are applied to the drive parts 50 on the vibrating parts 21 and 23, the piezoelectric layers in the drive parts 50 on the vibrating parts 21 and 23 are deformed due to the inverse piezoelectric effect, and the vibrating parts 21 and 23 perform flexural vibration. On the other hand, when drive voltages of a phase opposite to the drive voltages applied to the drive parts 50 on the vibrating parts 21 and 23 are applied to the drive parts 50 on the vibrating parts 22 and 24, the piezoelectric layers in the drive parts 50 on the vibrating parts 22 and 24 are deformed due to the inverse piezoelectric effect, and the vibrating parts 22 and 24 perform flexural deformation. Thus, due to the deformation of the vibrating parts 21 to 24, the movable part 40 rotates about the rotation axis R10.

[0055] Figure 2 (a) to (d) of this specification are cross-sectional views showing the manufacturing process of the SOI wafer 100.

[0056] As Figure 2 shown in (a) of this specification, a thermal oxidation treatment is performed on the base layer 101 made of silicon (Si) at about 1100°C. Thus, as Figure 2As shown in (b), an oxide film 102 made of silicon dioxide (SiO2) is formed on the surface of the base layer 101. In addition, in Figure 2 In (b), for convenience, only the oxide film 102 formed on the upper surface of the base layer 101 is shown.

[0057] Next, as shown in Figure 2 (c), for the structure of the base layer 101 and the oxide film 102 in Figure 2 (b), an active layer 103 made of silicon (Si) is bonded to the upper surface of the oxide film 102 at about 300 °C. Through this, the SOI wafer 100 is completed.

[0058] After that, when the SOI wafer 100 returns to room temperature, as shown in Figure 2 (d), the SOI wafer 100 shrinks in the direction parallel to the plane. At this time, the linear thermal expansion coefficient of the base layer 101 (Si) is 3.9×10 -6 , and the linear thermal expansion coefficient of the oxide film 102 (SiO2) is 0.5×10 -6 , so the base layer 101 shrinks more easily than the oxide film 102. Thus, compressive stress is applied to the oxide film 102 from the base layer 101.

[0059] In addition, when forming the movable part 40 by processing the SOI wafer 100 generated in this way, flexure occurs in the central part 41 of the movable part 40, and flexure also occurs in the reflecting surface 40a on the upper surface of the movable part 40. In this case, the light incident on the reflecting surface 40a cannot be properly reflected. Hereinafter, the case where flexure is formed on the upper surface of the movable part 40 will be described with reference to Comparative Example 1.

[0060] Figure 3 (a) and (b) of are a plan view and a cross-sectional view schematically showing the structure of the movable part 40 according to Comparative Example 1, respectively. Figure 3 (b) of is Figure 3 The cross-sectional view taken along line C1 - C2 in the plan view of (a).

[0061] In the plan view shown in Figure 3 (a), for convenience, the same materials as those in the cross-sectional view shown in Figure 3 (b) are shown with the same slashes as those in Figure 3 (b). In addition, in the following figures as well, when a plan view and a cross-sectional view are shown together, the same materials are shown with the same slashes.

[0062] As shown in Figure 3 (a) and (b), the central part 41 of the movable part 40 is composed of the active layer 103. The rib part 42 of the movable part 40 is composed of the base layer 101, the oxide film 102, and the active layer 103.

[0063] The movable part 40 of Comparative Example 1 is formed by removing Figure 2 the base layer 101 and the oxide film 102 in the central region of the lower surface of the SOI wafer 100 shown in (d). However, as described with reference to Figure 2 (d), when the ambient temperature returns to normal temperature, the oxide film 102 is forced in the shrinking direction due to the compressive stress of the base layer 101. That is, at normal temperature, the oxide film 102 is in a more shrunk state than when there is no base layer 101.

[0064] In this state, when the base layer 101 and the oxide film 102 in the central region of the lower surface of the SOI wafer 100 are removed, as Figure 3 shown in (b), the oxide film 102 of the rib 42 is released from the compressive stress and expands in the horizontal direction. As a result, the active layer 103 of the central portion 41 is lifted upward, and a flexure is generated on the reflecting surface 40a of the upper surface of the movable part 40 (the upper surface of the active layer 103).

[0065] Therefore, in Embodiment 1, for the rib 42 of the movable part 40, the active layer 103 in a specified range of the outer peripheral region is removed from the SOI wafer 100.

[0066] Figure 4 (a) to (c) are cross-sectional views showing the formation process of the movable part 40 according to Embodiment 1.

[0067] From Figure 4 the SOI wafer 100 shown in (a), as Figure 4 shown in (b), the active layer 103 in a specified range (outer peripheral region A1) of the outer peripheral region of the movable part 40 is removed by etching. The SOI wafer 100 has a cylindrical shape, and the range of the active layer 103 removed by etching is annular in a top view. Next, as Figure 4 shown in (c), the base layer 101 and the oxide film 102 in the central region are removed by etching. The base layer 101 and the oxide film 102 removed by etching have a cylindrical shape. Thus, the central portion 41 composed only of the active layer 103 is formed in the central region of the movable part 40, and the rib 42 is formed in the outer peripheral region. The movable part 40 of Embodiment 1 is completed in this way.

[0068] According to Embodiment 1, since the active layer 103 is removed from the outer peripheral region A1 of the rib 42, therefore, compared with Figure 3As compared with the comparative example shown in (b), the area of the inner peripheral region A2 where the active layer 103 extending from the central portion 41 contacts the oxide film 102 of the rib 42 is narrower. Accordingly, the expansion of the oxide film 102 is less likely to be conducted to the active layer 103, and flexure is less likely to occur in the central portion 41.

[0069] Figure 5 FIGS. (a) and (b) are a plan view and a cross-sectional view schematically showing the structure of the movable portion 40 according to Embodiment 1.

[0070] In Embodiment 1, when viewed from above, the active layer 103 is removed in an annular shape from the outer peripheral region A1 of the rib 42. In this case, the inner peripheral region A2 where the active layer 103 contacts the oxide film 102 has a narrow annular range.

[0071] In addition, the connection beam 35 connected to the movable portion 40 may have a layer structure including a base layer 101, an oxide film 102, and an active layer 103, may have a layer structure including a base layer 101 and an oxide film 102, or may be composed only of the base layer 101.

[0072] Figure 6 is a graph showing simulation results related to the amount of flexure in Comparative Example 1 and Embodiment 1.

[0073] The inventors etc. Figure 3 in the structure of Comparative Example 1 shown in FIGS. (a) and (b) and Figure 5 in the structure of Embodiment 1 shown in FIGS. (a) and (b), investigated by simulation the degree of flexure that occurs in the active layer 103 of the movable portion 40. In this simulation, the portions of a pair of connection beams 35 connected to the movable portion 40 that extend in the X-axis direction were left, and the outer ends of the pair of connection beams 35 were set as fixed ends. Further, in the simulation of the comparative example, the connection beam 35 was composed of a base layer 101, an oxide film 102, and an active layer 103, and in the simulation of Embodiment 1, the connection beam 35 was composed of a base layer 101 and an oxide film 102.

[0074] In Figure 6 the horizontal axis represents the distance from the center C10 in the horizontal direction, and the vertical axis represents the amount of flexure of the central portion 41. The amount of flexure is a value obtained by normalizing the amount of flexure of the center C100 of Comparative Example 1 to 100%.

[0075] As Figure 6 shown, in Embodiment 1, the amount of flexure near the center C10 is reduced to about 80% of that of Comparative Example 1. From this, it can be understood that, according to the structure of Embodiment 1, the flexure generated in the central portion 41 can be suppressed.

[0076] <Effects of Embodiment 1>

[0077] According to Embodiment 1, the following effects are achieved.

[0078] As Figure 5 shown in (a) and (b) thereof, the central portion 41 of the movable portion 40 has a structure obtained by removing the base layer 101 and the oxide film 102 from the SOI wafer 100 in which the base layer 101, the oxide film 102, and the active layer 103 are stacked. The rib portion 42 has a structure obtained by removing at least a part of the active layer 103 from the SOI wafer 100.

[0079] In the production of the SOI wafer 100, the oxide film 102 is formed on the surface of the base layer 101 by thermally oxidizing the base layer 101 at a temperature of about 1100°C, and then the active layer 103 is bonded to the oxide film 102. The coefficient of thermal expansion of the base layer 101 is larger than that of the oxide film 102. If the temperature returns to normal temperature, the base layer 101 will shrink more than the oxide film 102. Therefore, at this time, a compressive stress is applied to the oxide film 102 from the base layer 101. When the SOI wafer 100 is processed to remove the base layer 101 and the oxide film 102 from the central region of the movable portion 40 to form the rib portion 42 in the peripheral region, as Figure 3 shown in Comparative Example 1 of (a) and (b) thereof, since the base layer 101 in the central region is removed, a part of the above-mentioned compressive stress applied to the oxide film 102 of the rib portion 42 is released, and the oxide film 102 expands. As a result, a force in the direction of the center C10 of the central portion 41 is applied to the active layer 103 of the central portion 41 from the oxide film 102, resulting in a flexure in the active layer 103 of the central portion 41. In contrast, according to Embodiment 1, as Figure 5 shown in (a) and (b) thereof, since at least a part of the active layer 103 is removed from the rib portion 42, the expansion of the oxide film 102 is not easily transmitted to the active layer 103, and it is not easy to generate a flexure in the active layer 103 of the central portion 41. Therefore, when the SOI wafer 100 is used to form the rib portion 42 in the movable portion 40, the flexure of the movable portion 40 can be suppressed.

[0080] The rib portion 42 has a structure obtained by removing a predetermined width of the active layer 103 (the active layer 103 in the outer peripheral region A1) from the SOI wafer 100 along the circumferential direction of the movable portion 40. According to this structure, the expansion of the oxide film 102 of the rib portion 42 is not easily transmitted to the active layer 103 of the central portion 41 throughout the entire circumference, so that the flexure of the central portion 41 can be suppressed throughout the entire circumference.

[0081] <Modification Example 1 of Embodiment 1>

[0082] In Embodiment 1, all of the active layer 103 is removed from the outer peripheral region A1 of the rib 42, but a part of the active layer 103 may remain.

[0083] Figure 7 Figs. (a) and (b) respectively show a plan view and a cross-sectional view schematically showing the structure of the movable portion 40 according to this modified example.

[0084] In this modified example, compared with Figure 5 the embodiment shown in Figs. (a) and (b), an active layer 103 that is annular in a plan view remains on the outer periphery of the outer peripheral region A1 of the rib 42. A gap having a predetermined width is formed between the active layer 103 formed on the outer periphery of the rib 42 and the active layer 103 extending from the central portion 41.

[0085] Also in this modified example, since the inner peripheral region A2 where the active layer 103 extending from the central portion 41 contacts the oxide film 102 is narrow, the expansion of the oxide film 102 is not easily transmitted to the active layer 103, and flexure is not easily generated in the central portion 41.

[0086] In addition, in this modified example, since the active layer 103 remains on the outer periphery of the outer peripheral region A1 of the rib 42, the strength (hardness) of the rib 42 is higher than that in Embodiment 1. As a result, the movable portion 40 is not easily affected by the displacement of the connecting beam 35, and thus flexure of the movable portion 40 can be further suppressed.

[0087] <Modified Example 2 of Embodiment 1>

[0088] In Embodiment 1, all of the oxide film 102 remains in the outer peripheral region A1 of the rib 42, but all of the oxide film 102 may be removed.

[0089] Figure 8 Figs. (a) and (b) respectively show a plan view and a cross-sectional view schematically showing the structure of the movable portion 40 according to this modified example.

[0090] In this modified example, compared with Figure 5 the embodiment shown in Figs. (a) and (b), not only the active layer 103 but also the oxide film 102 are removed from the outer peripheral region A1 of the rib 42.

[0091] Figure 9 is a graph showing simulation results related to the amount of flexure according to Embodiment 1 and Modified Example 2 of Embodiment 1.

[0092] The inventors etc. performed simulations under the same conditions as the simulations described in Figure 6 and also in Figure 8In the structure of Modification Example 2 of Embodiment 1 shown in (a) and (b), simulation was performed to investigate the degree of flexure occurring in the active layer 103 of the movable portion 40. In the simulation of Modification Example 2 of Embodiment 1, the connecting beam 35 was formed of the base layer 101. The dashed line indicates the result of Embodiment 1, and the solid line indicates the result of Modification Example 2 of Embodiment 1. The amount of flexure is a value obtained by normalizing the amount of flexure of the center C10 of Comparative Example 1 shown in (a) and (b) of Figure 3 to 100%.

[0093] As Figure 9 shown, in this modification example, compared with Embodiment 1, the amount of flexure near the center C10 is slightly reduced. From this, it can be understood that according to the structure of this modification example, the flexure generated in the central portion 41 can be further suppressed.

[0094] According to Modification Example 2 of Embodiment 1, compared with Embodiment 1, the rib portion 42 has a structure obtained by further removing at least a part of the oxide film 102 from the SOI wafer 100. According to this structure, the volume of the oxide film 102 as a source of flexure generation becomes smaller, and thus the displacement of the oxide film 102 due to expansion becomes further smaller. Thereby, the flexure of the central portion 41 can be further suppressed.

[0095] <Modification Example 3 of Embodiment 1>

[0096] In Modification Example 2 of Embodiment 1, all of the oxide film 102 and the active layer 103 were removed from the outer peripheral region A1 of the rib portion 42, but a part of the oxide film 102 and the active layer 103 may be left.

[0097] Figure 10 (a) and (b) respectively are a plan view and a cross-sectional view schematically showing the structure of the movable portion 40 according to this modification example.

[0098] In this modification example, compared with Figure 8 (a) and (b) of Modification Example 2 of Embodiment 1 shown, an oxide film 102 and an active layer 103 in a ring shape when viewed from above remain on the outer periphery of the outer peripheral region A1 of the rib portion 42. A gap having a predetermined width is formed between the oxide film 102 and the active layer 103 formed on the outer periphery of the rib portion 42 and the active layer 103 extending from the central portion 41. The oxide film 102 and the active layer 103 formed on the outer periphery of the rib portion 42 have the same ring shape when viewed from above.

[0099] Also in this modification example, since the volume of the oxide film 102 as the source of the generation of the flexure becomes smaller, the displacement of the oxide film 102 due to the expansion becomes further smaller. As a result, the flexure of the central portion 41 can be further suppressed. In addition, since the oxide film 102 and the active layer 103 remain on the outer periphery of the outer peripheral region A1 of the rib portion 42, the strength (hardness) of the rib portion 42 becomes higher. As a result, the movable portion 40 is not easily affected by the displacement from the connecting beam 35, and thus the flexure of the movable portion 40 can be further suppressed.

[0100] <Embodiment 2>

[0101] In Embodiment 2, when viewed from above, a gap is provided between the central portion 41 and the rib portion 42, and the central portion 41 and the rib portion 42 are connected via a spring portion 43.

[0102] Figure 11 FIGS. (a) and (b) schematically show a plan view and a cross-sectional view of the structure of the movable portion 40 according to Embodiment 2.

[0103] In Embodiment 2, compared with Figure 5 Embodiment 1 shown in FIGS. (a) and (b), the diameter of the central portion 41 is smaller than the diameter of the inner periphery of the rib portion 42, and when viewed from above, the central portion 41 is positioned inside the inner periphery of the rib portion 42. The central portion 41 and the rib portion 42 are connected by four flexible spring portions 43. The spring portion 43 is formed of a shape and a material that are easily bendable.

[0104] One end of the spring portion 43 is connected to the outer peripheral portion of the central portion 41, and the other end of the spring portion 43 is connected to the active layer 103 on the oxide film 102 remaining on the rib portion 42. The oxide film 102 and the active layer 103 on the rib portion 42 have the same shape as each other when viewed from above, and are disposed only near the outer ends on the outside of the spring portion 43. The oxide film 102 and the active layer 103 for connecting the spring portion 43 to the rib portion 42 constitute a connecting portion 44. The connecting portion 44 is provided at four positions on the inner peripheral portion of the rib portion 42. Four pairs of the spring portions 43 and the connecting portions 44 are arranged at positions at equal angles (90°) in the circumferential direction along the center C10.

[0105] Typically, the spring portion 43 is made of the same material as the materials connected to both ends of the spring portion 43. That is, the spring portion 43 is made of the same silicon (Si) as the material (active layer 103) on the upper surface side of the central portion 41 (active layer 103) located inside and the connecting portion 44 located outside. In this case, the spring portion 43, the active layer 103 of the central portion 41, and the active layer 103 of the connecting portion 44 are integrally formed.

[0106] In addition, the spring portion 43 may also be made of a material other than silicon (Si) (such as metal, resin, etc.). In this case, in the manufacturing process of the movable portion 40, after forming a gap between the active layer 103 of the central portion 41 and the active layer 103 of the connecting portion 44, the spring portion 43 is formed. After that, the base layer 101 and the oxide film 102 are removed from the central region.

[0107] Figure 12 It is a graph showing the simulation results related to the amount of deflection in Modification 2 of Embodiment 1 and Embodiment 2.

[0108] The inventors etc. Figure 6 under the same conditions as the simulation described in Figure 11 also investigated by simulation how much the active layer 103 of the movable portion 40 deflects in the structure of Embodiment 2 shown in (a) and (b) of Figure 3 The amount of deflection is a value obtained by normalizing the amount of deflection of the center C10 of Comparative Example 1 shown in (a) and (b) of

[0109] As Figure 12 shown, in Embodiment 2, compared with Modification 2 of Embodiment 1, the amount of deflection near the center C10 is significantly reduced. From this, it can be seen that according to the structure of Embodiment 2, the deflection generated in the central portion 41 can be further suppressed.

[0110] <Effect of Embodiment 2>

[0111] The central portion 41 and the rib portion 42 are connected via the flexible spring portion 43. According to this structure, compared with Embodiment 1 and the modification, the expansion of the oxide film 102 of the rib portion 42 is less likely to be conducted to the active layer 103 of the central portion 41, so the deflection of the central portion 41 can be further suppressed.

[0112] The rib portion 42 has a structure obtained by removing the oxide film 102 and the active layer 103 of the region other than the connection region (connection portion 44) connected to the spring portion 43 from the SOI wafer 100. According to this structure, all of the oxide film 102 and the active layer 103 are removed from the rib portion 42 in such a way that the oxide film 102 and the active layer 103 required for connecting the spring portion 43 to the connection portion 44 remain. Thus, there is almost no oxide film 102 of the rib portion 42 as a source of deflection, so the deflection of the central portion 41 can be further suppressed.

[0113] The spring portion 43 is made of the same material as the central portion 41. According to this structure, the spring portion 43 and the central portion 41 can be formed at one time, so that the manufacturing process of the optical reflection element 1 becomes simple.

[0114] <Modification Example of Embodiment 2>

[0115] In Embodiment 2, all of the oxide film 102 and the active layer 103 are removed from the outer peripheral region located outside the connecting portion 44. However, in this outer peripheral region, if at least a part of the active layer 103 is removed in the same manner as in Embodiment 1 and Modification Examples 1 and 3 of Embodiment 1, the oxide film 102 and the active layer 103 can be left behind.

[0116] In Figure 13 the modification example shown in (a), compared with Embodiment 2, the oxide film 102 and the active layer 103 are left behind on the outer periphery of the rib portion 42 in the same manner as in Modification Example 3 of Embodiment 1 shown in (a) and (b) of Figure 10 The oxide film 102 and the active layer 103 on the outer periphery of the rib portion 42 are arranged so as to have a gap with respect to the oxide film 102 and the active layer 103 of the connecting portion 44.

[0117] In Figure 13 the modification example shown in (b), compared with Embodiment 2, all of the oxide film 102 of the rib portion 42 is left behind and a part of the active layer 103 is left behind in the same manner as in Modification Example 1 of Embodiment 1 shown in (a) and (b) of Figure 7 The active layer 103 on the outer periphery of the rib portion 42 is arranged so as to have a gap with respect to the active layer 103 of the connecting portion 44.

[0118] In Figure 13 the modification example shown in (c), compared with Embodiment 3, all of the oxide film 102 of the rib portion 42 is left behind.

[0119] In Figure 14 the modification example shown in (a), compared with Embodiment 2, the spring portion 43 is made of a material different from that of the central portion 41 (such as metal, resin, etc.) and is arranged so as to hang on the upper surface of the central portion 41 and the upper surface of the active layer 103 of the connecting portion 44. When the spring portion 43 is made of a material different from that of the central portion 41, by arranging the two ends of the spring portion 43 so as to hang on the central portion 41 and the active layer 103 of the connecting portion 44 as shown in Figure 14 (a) of, the central portion 41 and the connecting portion 44 can be firmly connected.

[0120] In Figure 14 the modification example shown in (b), compared with Figure 14 the modification example of (a), compared with Figure 13In the modification example of (a), the oxide film 102 and the active layer 103 are arranged on the outer periphery of the rib 42 with a gap relative to the connecting portion 44 in the same manner.

[0121] In Figure 14 in the modification example shown in (c), compared with Figure 14 the modification example of (b), compared with Figure 13 the modification example of (b), all of the oxide film 102 of the rib 42 remains. In addition, in Figure 14 the structure of (c), the active layer 103 on the outer periphery of the rib 42 can be further removed.

[0122] In addition, in Embodiment 2, when viewed from above, the spring portion 43 has a rectangular shape, but the shape of the spring portion 43 is not limited to this.

[0123] In Figure 15 the modification examples shown in (a) and (b), the spring portion 43 has a serpentine shape (winding shape). Thus, compared with Embodiment 2, the flexibility of the spring portion 43 is further improved, and therefore the expansion of the oxide film 102 of the rib 42 is less likely to be transmitted to the active layer 103 in the central portion 41.

[0124] In Figure 15 the modification example shown in (c), the spring portion 43 has a trapezoidal shape. By adjusting the trapezoidal shape, the flexibility or inflexibility of the spring portion 43 can be adjusted smoothly. In addition, the shape of the spring portion 43 is not limited to a trapezoid. For example, the shape of the spring portion 43 can also be a parallelogram, a hexagon, etc.

[0125] In Figure 16 the modification example shown in (a), the spring portion 43 has a Y shape. In Figure 16 the modification example shown in (b), the spring portion 43 has a T shape. In these cases, the spring portion 43 can also be smoothly adjusted to the desired flexibility.

[0126] In addition, in Embodiment 2, the end portion of the spring portion 43 on the side of the rib 42 can also be configured to be planar.

[0127] Figure 17 (a) and (b) are a top view and a cross-sectional view schematically showing the structure of the movable portion 40 according to the modification example in this case.

[0128] In a modification of this case, a face portion 43a is formed at the outer end portion of the spring portion 43. The face portion 43a has a shape that extends in the circumferential direction. When viewed from above, the outer contour of the face portion 43a is, for example, a circular shape centered on a point C11 where the direction in which the spring portion 43 extends intersects the inner circumference of the rib portion 42. A connecting portion 44 (oxide film 102 and active layer 103) is disposed at a position along the outer contour of the face portion 43a, and the outer side of the face portion 43a is connected to the active layer 103 of the connecting portion 44.

[0129] According to Figure 17 the modification examples shown in (a) and (b), even if the spring portion 43 is deflected, the stress is dispersed in the radial direction of the circle centered on the point C11, so that breakage of the connecting portion 44 between the outer end portion of the spring portion 43 and the rib portion 42 can be prevented.

[0130] <Embodiment 3>

[0131] In Embodiment 2, the outer end portion of the spring portion 43 is connected to the inner peripheral portion of the rib portion 42. In contrast, in Embodiment 3, the outer end portion of the spring portion 43 is positioned at a more outer position compared to Embodiment 2 and is connected to a cutout 42a formed in the inner circumference of the rib portion 42.

[0132] Figure 18 (a) and (b) are a top view and a cross-sectional view schematically showing the structure of the movable portion 40 according to Embodiment 3.

[0133] In Embodiment 3, compared with Figure 11 Embodiment 2 shown in (a) and (b), a cutout 42a extending outward is formed at a position on the inner circumference of the rib portion 42 where the spring portion 43 is to be disposed. On the outer side of the cutout 42a, the outer circumference of the rib portion 42 protrudes outward. The circumferential width of the cutout 42a is larger than the circumferential width of the spring portion 43, and the spring portion 43 is received in the cutout 42a. The outer end portion of the spring portion 43 is connected to the active layer 103 of the connecting portion 44 located outside the cutout 42a. Thus, the outer end portion of the spring portion 43 is connected to the rib portion 42 at a position on the rib portion 42 more outer than the inner circumference.

[0134] <Effects of Embodiment 3>

[0135] As Figure 18 shown in (b), the distance L1 from the center C10 of the central portion 41 to the inner circumference of the rib portion 42 is shorter than the distance L2 from the center C10 of the central portion 41 to the connection position between the spring portion 43 and the rib portion 42. According to this structure, the rib portion 42 can be disposed closer to the central portion 41 while keeping the radial width of the rib portion 42 constant, so that the weight of the rib portion 42 can be reduced compared to Embodiment 2. Thereby, a decrease in the driving efficiency of the movable portion 40 can be suppressed.

[0136] <Modification of Implementation Example 3>

[0137] In the third embodiment, the spring portion 43 has a rectangular shape, but the shape of the spring portion 43 is not limited thereto.

[0138] exist Figure 19 In the modification shown in (a), the spring portion 43 has a T-shape. In this case, two outer end portions of the spring portion 43 are connected to the active layer 103 of two connection portions 44 disposed around the cutout 42a to face each other.

[0139] exist Figure 19 In the modification example shown in (b), Figure 17 Similar to the modified examples shown in (a) and (b), a surface portion 43a is formed at the outer end of the spring portion 43. The outer side of the surface portion 43a is connected to the active layer 103 of the connection portion 44 arranged around the notch 42a.

[0140] exist Figure 19 In the modification example shown in (c), Figure 18 Compared with the third embodiment shown in (a) and (b), the connection position between the spring portion 43 and the rib portion 42 is closer to the center C10 of the central portion 41, and the outer periphery of the rib portion 42 is circular. In this case, since the length of the spring portion 43 is shorter than that of the third embodiment, the spring portion 43 is difficult to bend, but the rib portion 42 can be arranged close to the central portion 41 in the same manner as the third embodiment.

[0141] <Modification Example 1 of Movable Section>

[0142] As in the first to third embodiments and the modified examples, the movable portion 40 is preferably configured to be line-symmetrical with respect to a straight line R11 that passes through the center C10 of the central portion 41 and is perpendicular to the rotation axis R10. In this way, the weight balance of the movable portion 40 on both sides of the straight line R11 can be balanced, so the movable portion 40 can be appropriately driven. The following is an example of a modified example of the movable portion 40 configured to be line-symmetrical with respect to the straight line R11.

[0143] exist Figure 20 In the modification example shown in (a), Figure 11 Compared with the second embodiment shown in (a) and (b), four sets of the spring portion 43 and the connecting portion 44 outside the spring portion 43 are arranged at intervals of 60° and 120° in the circumferential direction of the center C10.

[0144] exist Figure 20 In the modification example shown in (b), Figure 18In the embodiment 3 shown in FIGS. (a) and (b), the central portion 41, the inner periphery of the rib portion 42, and the outer periphery of the rib portion 42 have a rectangular shape when viewed from above. Cuts 42a are respectively formed at the four corners of the inner periphery of the rib portion 42, and the spring portion 43 is positioned at the cuts 42a. Four sets of a group composed of the spring portion 43 and the connecting portion 44 outside the spring portion 43 are arranged at intervals of 72° and 108° in the circumferential direction of the center C10.

[0145] In Figure 20 In the modification shown in FIGS. (c), compared with Figure 11 the embodiment 2 shown in FIGS. (a) and (b), the central portion 41, the inner periphery of the rib portion 42, and the outer periphery of the rib portion 42 have an elliptical shape when viewed from above. Three sets of a group composed of the spring portion 43 and the connecting portion 44 outside the spring portion 43 are arranged at intervals of 60° and 150° in the circumferential direction of the center C10.

[0146] In Figure 21 the modification shown in FIGS. (a), compared with Figure 5 the embodiment 1 shown in FIGS. (a) and (b), four protrusions 41a protruding outward are formed on the outer periphery of the active layer 103 of the movable portion 40. An oxide film 102 and an active layer 103 having the same shape as the protrusions 41a when viewed from above are arranged below the protrusions 41a. The four protrusions 41a are arranged at intervals of 60° and 120° in the circumferential direction of the center C10.

[0147] In Figure 21 the modification shown in FIGS. (b), compared with Figure 21 the modification shown in FIGS. (a), the central portion 41, the inner periphery of the rib portion 42, and the outer periphery of the rib portion 42 have a rectangular shape when viewed from above. Protrusions 41a are respectively formed at the four corners of the active layer 103 of the movable portion 40. The four protrusions 41a are arranged at intervals of 72° and 108° in the circumferential direction of the center C10.

[0148] In Figure 21 the modification shown in FIGS. (c), compared with Figure 21 the modification shown in FIGS. (a), the central portion 41, the inner periphery of the rib portion 42, and the outer periphery of the rib portion 42 have an elliptical shape when viewed from above. Three protrusions 41a are formed on the outer periphery of the active layer 103 of the movable portion 40. The three protrusions 41a are arranged at intervals of 60° and 150° in the circumferential direction of the center C10.

[0149] In addition, in Figure 20In (a) to (c) below, if the movable part 40 is line-symmetrical with respect to the straight line R11, the plurality of sets each composed of the spring part 43 and the connecting part 44 outside the spring part 43 may also be arranged at an angle other than the above-described angle in the circumferential direction of the center C10. Further, in Figure 21 In (a) to (c) below, if the movable part 40 is line-symmetrical with respect to the straight line R11, the plurality of protruding parts 41a may also be arranged at an angle other than the above-described angle in the circumferential direction of the center C10.

[0150] In Figure 20 In any modification of (a) to Figure 21 In (c) below, the movable part 40 is configured to be line-symmetrical with respect to the straight line R11. With this configuration, the weight balance of the movable part 40 on both sides of the straight line R11 can be made uniform. Therefore, the movable part 40 can be driven appropriately.

[0151] <Modification Example 2 of Movable Part>

[0152] Similar to the above-described First to Third Embodiments and modification examples, the movable part 40 is preferably configured such that the deflection generated in the central part 41 due to the expansion of the oxide film 102 is substantially symmetrical about the central axis of the center C10 passing through the central part 41 in the vertical direction (Z-axis direction). If this is the case, the reflected light reflected by the central part 41 is distributed substantially symmetrically with respect to the optical axis, and thus the design of the subsequent optical system into which the reflected light is to be incident becomes easy. Hereinafter, a modification example of such a movable part 40 will be described by way of example.

[0153] In Figure 22 In the modification example shown in (a) below, compared with Figure 11 In the second embodiment shown in (a) and (b) below, six sets each composed of the spring part 43 and the connecting part 44 outside the spring part 43 are arranged at equal intervals of 60° in the circumferential direction with respect to the center C10.

[0154] In Figure 22 In the modification example shown in (b) below, compared with the second embodiment, three sets each composed of the spring part 43 and the connecting part 44 outside the spring part 43 are arranged at equal intervals of 120° in the circumferential direction of the center C10.

[0155] In Figure 22 In the modification example shown in (c) below, compared with the second embodiment, the central part 41, the inner circumference of the rib part 42, and the outer circumference of the rib part 42 have an elliptical shape in a plan view, and five sets each composed of the spring part 43 and the connecting part 44 outside the spring part 43 are arranged at equal intervals of 72° in the circumferential direction with respect to the center C10.

[0156] In addition, if each group is arranged in a polygonal shape at equal angles in the circumferential direction like this, the length on the outer circumference of the central portion 41 and the length on the inner circumference of the rib portion 42 between two adjacent groups are substantially equal to each other. As a result, the deformation of the central portion 41 is gradually suppressed as it approaches the center C10 of the central portion 41, and the deformation of the central portion 41 is substantially uniform with respect to the central axis passing through the center C10 in the up-down direction.

[0157] In Figure 23 in the modification example shown in (a) of Figure 5 compared with the first embodiment shown in (a) and (b) of

[0158] In Figure 23 in the modification example shown in (b) of Figure 23 compared with the modification example shown in (a) of

[0159] In Figure 23 in the modification example shown in (c) of Figure 23 compared with the modification example shown in (a) of

[0160] In addition, if the protruding portions 41a are arranged in a polygonal shape at equal angles in the circumferential direction like this, the lengths on the outer circumference of the central portion 41 between two adjacent protruding portions 41a are substantially equal to each other. As a result, the deformation of the central portion 41 is gradually suppressed as it approaches the center C10 of the central portion 41, and the deformation of the central portion 41 is substantially uniform with respect to the central axis passing through the center C10 in the up-down direction.

[0161] In Figure 22 in (a) to Figure 23In (c) thereof, the movable part 40 is configured such that the flexure generated at the central part 41 due to the expansion of the oxide film 102 is substantially symmetric about the central axis passing through the center C10 of the central part 41 in the up-down direction. According to this structure, the reflected light reflected by the movable part 40 is distributed substantially symmetrically with respect to the optical axis, so that the design of the subsequent optical system into which the reflected light is to be incident becomes easy. Specifically, when the incident light incident on the movable part 40 has a shape that is substantially symmetric with respect to the optical axis of the incident light (for example, a circular shape or an elliptical shape), the reflected light reflected by the movable part 40 also has a shape that is substantially symmetric with respect to the optical axis of the reflected light (for example, a circular shape or an elliptical shape). Thereby, the design of the subsequent optical system becomes easy.

[0162] In addition, the movable part 40 has substantially the same structure at positions at substantially equal angles in the circumferential direction with respect to the center C10 of the central part 41. According to this structure, the movable part 40 can be easily configured such that the flexure generated at the central part 41 is substantially symmetric about the central axis of the central part 41. In addition, as Figure 22 in (a) and (b) of Figure 23 and the modification examples of (a) and (b) of

[0163] when the movable part 40 has a circular shape, if the incident light incident on the movable part 40 has a circular shape, the reflected light reflected by the movable part 40 can be distributed substantially evenly with respect to the optical axis of the reflected light.

[0163] Next, verification related to the distribution of the reflected light performed by the inventors will be described. The inventors used the structures of Embodiment 2 and Comparative Example 2 and verified whether the reflected light reflected by the central part 41 is distributed substantially symmetrically with respect to the optical axis based on the flexure amount of the central part 41 obtained through simulation.

[0164] Figure 24 (a) of

[0165] Figure 24 is a plan view schematically showing the structure of the movable part 40 involved in the simulation of Comparative Example 2. In Comparative Example 2, four sets of spring parts 43 and connecting parts 44 are provided. Two sets of spring parts 43 and connecting parts 44 are arranged in a direction at 45° with respect to the rotation axis R10 and the straight line R11 and on the negative Y-axis side of the rotation axis R10. Two sets of spring parts 43 and connecting parts 44 are arranged in the direction along the straight line R11 and on the positive Y-axis side and the negative Y-axis side of the rotation axis R10. In addition, the width of one set of spring parts 43 and connecting parts 44 located on the negative Y-axis side of the center C10 is wider than the width of the other sets of spring parts 43 and connecting parts 44.

[0165] Figure 24 (b) of Figure 24As shown in (b) of Comparative Example 2, the flexure generated in the central portion 41 is not substantially symmetric about the central axis passing through the center C10 in the vertical direction.

[0166] Figure 25 Fig. (a) is a top view schematically showing the structure of the movable portion 40 involved in the simulation of Embodiment 2. In Figure 25 In the structure of Embodiment 2 shown in (a), similar to Figure 11 the structures shown in (a) and (b), the four sets of spring portions 43 and connecting portions 44 are arranged at equal angles (90°) in the circumferential direction of the center C10.

[0167] Figure 25 Fig. (b) is a simulation result showing the amount of flexure of the central portion 41 when the movable portion 40 according to Embodiment 2 rotates. It shows a case where the flexure in the dark region near the center C10 is larger than the flexure in the light region around the central portion 41. As Figure 25 shown in (b), in Embodiment 2, the flexure generated in the central portion 41 is substantially symmetric about the central axis passing through the center C10 in the vertical direction.

[0168] Figure 26 is a graph showing the simulation results representing the amount of flexure for Comparative Example 2 and Embodiment 2.

[0169] The inventors, under the same conditions as the simulation described in Figure 6 , investigated the degree of flexure of the active layer 103 of the movable portion 40 by simulation in the structure of Comparative Example 2 shown in (a) of Figure 24 and the structure of Embodiment 2 shown in (a) of Figure 25 . The horizontal axis represents the distance from the center C10 along the straight line R11, and the vertical axis represents the amount of flexure of the central portion 41. The amount of flexure is a value obtained by normalizing the maximum amount of flexure to 100% in Comparative Example 2 and Embodiment 2, respectively.

[0170] As Figure 26 shown by the dashed line, in Comparative Example 2, the amount of flexure on the left and right is not equal with respect to the center C10. If the flexure generated in the central portion 41 is uneven like this, it is considered that when the incident light incident on the central portion 41 is distributed substantially symmetrically with respect to the optical axis, the reflected light reflected by the central portion 41 will not be distributed substantially symmetrically with respect to the optical axis. In this case, the design of the subsequent optical system into which the reflected light is to be incident becomes complicated. In contrast, as Figure 26As shown by the solid line, in Embodiment 2, the amount of flexure on the left and right is substantially equal with respect to the center C10. If the flexure generated in the central portion 41 is substantially equal in this way, it is considered that when the incident light incident on the central portion 41 is distributed substantially symmetrically with respect to the optical axis, the reflected light reflected by the central portion 41 is distributed substantially symmetrically with respect to the optical axis. In this case, the design of the subsequent optical system into which the reflected light is to be incident becomes easy.

[0171] In addition, not limited to the structure of Embodiment 2, in Figure 13 the modification example 2 of Embodiment 2 shown in (a) to Figure 17 the (b) shown, Figure 18 the Embodiment 3 shown in (a) and (b), Figure 19 the modification example 3 of Embodiment 3 shown in (a) to (c), Figure 22 the (a) to Figure 23 the structure of the modification example 2 of the movable portion 40 shown in (c), the movable portion 40 is also configured such that the flexure generated in the central portion 41 due to the expansion of the oxide film 102 is substantially symmetric with respect to the central axis of the central portion 41. Therefore, even in these structures, it is possible to distribute the reflected light substantially symmetrically with respect to the optical axis, and thus the design of the subsequent optical system into which the reflected light is to be incident becomes easy.

[0172] <Modification Example of Reflective Surface>

[0173] In the above-described embodiment and modification example, the upper surface of the active layer 103 of the movable portion 40 is used as the reflective surface 40a for reflecting light. However, it is not limited thereto, and an optical reflective film 45 may be additionally disposed on the upper surface of the active layer 103, and the upper surface of the optical reflective film 45 is used as the reflective surface 40a.

[0174] Figure 27 The (a) and (b) are respectively a top view and a cross-sectional view schematically showing the structure of the movable portion 40 according to this modification example.

[0175] In this modification example, compared with Figure 5 the Embodiment 1 shown in (a) and (b), an optical reflective film 45 is formed on the upper surface of the active layer 103 forming the movable portion 40. The optical reflective film 45 is made of a material with a high reflectivity (such as metals such as gold, silver, copper, and aluminum, metal compounds, or silicon dioxide, titanium dioxide, etc.) on the upper surface of the active layer 103. The optical reflective film 45 may also be composed of a dielectric multilayer film.

[0176] In addition, in Figure 27 the (a) and (b), the optical reflective film 45 is formed inside the central portion 41 in a top view, but it may also be formed within the same range as the central portion 41, and may also be formed outside the central portion 41 as long as it is within the range of the active layer 103.

[0177] According to this modification example, an optical reflection film 45 is further provided on the upper surface of the active layer 103. With this structure, the reflectivity can be improved as compared with the case where the upper surface of the active layer 103 is used as the reflection surface 40a.

[0178] <Modification Example of the Vibration Portion>

[0179] In the above-described embodiment and modification example, the vibration portions 21 to 24 are arranged in a meandering shape, but in this modification example, the vibration portion is arranged in a tuning fork shape.

[0180] Figure 28 It is a plan view schematically showing the structure of the optical reflection element 1 according to this modification example.

[0181] The optical reflection element 1 includes a fixed portion 10, a pair of vibration portions 221, a pair of vibration portions 222, a pair of second support portions 231, a pair of first support portions 232, a movable portion 40, and four drive portions 50. The optical reflection element 1 is configured to be symmetric about the center C10 in the X-axis direction and the Y-axis direction. In addition, in Figure 28 For convenience, the same reference numerals are given to the same structures as those in the first embodiment shown in Figure 1 The following describes the structures different from those in the first embodiment.

[0182] The vibration portions 221 and 222 have an L shape in a plan view. The vibration portions 221 and 222 have a shape extending in the X-axis direction near the front end, and have a shape extending in the Y-axis direction near the connection with the second support portion 231 and the first support portion 232. The vibration portions 221 and 222 are connected to the fixed portion 10 via the second support portion 231 near the rotation axis R10, and are connected to the movable portion 40 via the first support portion 232. The vibration portion 221 is arranged on the negative Y-axis side of the rotation axis R10, and the vibration portion 222 is arranged on the positive Y-axis side of the rotation axis R10. The second support portion 231 and the first support portion 232 extend in the X-axis direction along the rotation axis R10. The vibration portions 221 and 222 located on the positive X-axis side or the negative X-axis side of the movable portion 40 have a tuning fork shape in a plan view

[0183] The drive portions 50 are arranged on the upper surfaces of the vibration portions 221 and 222. The drive portions 50 are connected to the electrodes on the fixed portion 10 via wirings on the vibration portions 221 and 222, the second support portion 231, and the fixed portion 10. The electrodes on the fixed portion 10 are connected to a cable (external wiring) connected to an external device by wire bonding.

[0184] When a driving voltage is applied to the driving unit 50 on the vibrating unit 221, the piezoelectric layer in the driving unit 50 on the vibrating unit 221 deforms due to the inverse piezoelectric effect, and the vibrating unit 221 undergoes flexural vibration. On the other hand, when a driving voltage having a phase opposite to that of the driving voltage applied to the driving unit 50 on the vibrating unit 221 is applied to the driving unit 50 on the vibrating unit 222, the piezoelectric layer in the driving unit 50 on the vibrating unit 222 deforms due to the inverse piezoelectric effect, and the vibrating unit 222 undergoes flexural vibration. Thus, due to the deformation of the vibrating units 221 and 222, the movable unit 40 rotates about the rotation axis R10 in the same manner as in the first embodiment.

[0185] In this modification example, the movable unit 40 is also configured in the same manner as in the first embodiment. That is, as shown in (a) and (b) of Figure 5 , at least a part of the active layer 103 is removed from the rib portion 42. Thus, in the same manner as in the first embodiment, the expansion of the oxide film 102 is less likely to be conducted to the active layer 103, and flexure is less likely to occur in the active layer 103 at the central portion 41.

[0186] In addition, in the above-described second and third embodiments and the modification example, the meandering vibrating units 21 to 24 of the optical reflection element 1 may be configured by tuning fork-shaped vibrating units 221 and 222 in the same manner as in this modification example.

[0187] <Other modification examples>

[0188] In the above-described first embodiment, the oxide film 102 in the outer peripheral region A1 of the rib portion 42 is disposed over the entire circumference of the outer peripheral region A1, but it may be disposed in a part of the outer peripheral region A1. Further, in modification example 1 of the above-described first embodiment, the active layer 103 in the outer peripheral region A1 is disposed over the entire circumference of the outer peripheral region A1, but it may be disposed in a part of the outer peripheral region A1. Further, in modification example 3 of the above-described first embodiment, the oxide film 102 and the active layer 103 in the outer peripheral region A1 are disposed over the entire circumference of the outer peripheral region A1, but they may be disposed in a part of the outer peripheral region A1. Further, in modification example 3 of the above-described first embodiment, at least a part of the active layer 103 in the outer peripheral region A1 may be removed.

[0189] In the above-described embodiments and modification examples, as shown in Figure 1 and Figure 28 , two driving units are disposed so as to sandwich the movable unit 40, but either one of the two driving units may be omitted. For example, in the first embodiment shown in Figure 1 , the structure on the positive X-axis side of the movable unit 40 may be omitted, and the movable unit 40 may be supported by the connecting beam 35 on the negative X-axis side. In Figure 28In the modified example of the diaphragm shown, the structure on the positive X-axis side of the movable part 40 may also be omitted, and the movable part 40 may be supported by the first support part 232 on the negative X-axis side.

[0190] In the above-described embodiment and modified example, the rib part 42 is formed over the entire circumference in the outer peripheral region of the movable part 40, but it may also be formed in a part of the outer peripheral region of the movable part 40. In this case, the part of the outer peripheral region of the movable part 40 where the rib part 42 is not formed is composed only of the active layer 103.

[0191] In the modified example of the above-described reflecting surface, an optical reflecting film 45 is additionally disposed on the upper surface of the active layer 103, and the upper surface of the optical reflecting film 45 is used as the reflecting surface 40a. However, in this structure, another optical reflecting film may also be disposed on the back surface of the central part 41 of the movable part 40.

[0192] Figure 29 (a) and (b) respectively are a plan view and a cross-sectional view schematically showing the structure of the movable part 40 according to this modified example. In Figure 29 (a), a plan view when observing the vicinity of the movable part 40 from the back side is shown.

[0193] In this modified example, compared with the modified example of the reflecting surface shown in Figure 27 (a) and (b), an optical reflecting film 46 is formed on the back surface of the central part 41 of the movable part 40. The optical reflecting film 46 is made of a material with a high reflectivity (such as metals like gold, silver, copper, aluminum, metal compounds, or silicon dioxide, titanium dioxide, etc.). The optical reflecting film 46 may also be composed of a dielectric multilayer film.

[0194] In addition, in Figure 29 (a) and (b), the optical reflecting film 46 is formed inside the central part 41 in a plan view, but it may also be formed within the same range as the central part 41, and if it is within the range of the active layer 103, it may also be formed outside the central part 41.

[0195] According to this modified example, even if stress caused by temperature changes or the like occurs in the optical reflecting film 45 formed on the upper surface of the active layer 103, this stress can be alleviated by the stress generated in the optical reflecting film 46 on the back side. Therefore, deformation occurring in the central part 41 of the movable part 40 due to stress generated in the optical reflecting film 45 caused by temperature changes or the like can be suppressed.

[0196] In order to effectively cancel out the stress generated in the optical reflecting film 45 on the upper surface side by the stress of the optical reflecting film 46 on the back side, the optical reflecting film 46 on the back side is preferably made of the same material as the optical reflecting film 45 on the upper surface side, and in addition, it is preferably disposed in a region corresponding to the optical reflecting film 45 on the upper surface side.

[0197] In addition, by irradiating light on the optical reflection film 46 on the back side and receiving the reflected light by a PSD (Position Sensitive Detector), the deflection angle of the movable part 40 can also be detected. Further, if the reflectivity of the back surface of the movable part 40 is high enough, the deflection angle of the movable part 40 can be detected by the above structure even without disposing the optical reflection film 46. However, since the reflectivity is further improved by disposing the optical reflection film 46, the deflection angle of the movable part 40 can be detected well.

[0198] In addition, the embodiments of the present invention can be appropriately modified in various ways within the scope of the technical idea shown in the claims.

[0199] (Supplementary Note)

[0200] Based on the description of the above embodiments, the following technologies are disclosed.

[0201] (Technology 1)

[0202] An optical reflection element, characterized by comprising:

[0203] A fixing part; and

[0204] A movable part, which is supported by the fixing part so as to be rotatable about a rotation axis, has a reflection surface at the central part of the upper surface, and has rib parts in the outer peripheral region of the lower surface.

[0205] Wherein, the central part of the movable part has a structure obtained by removing the base layer and the oxide film from a silicon-on-insulator wafer formed by laminating a base layer, an oxide film, and an active layer.

[0206] The rib part has a structure obtained by removing at least a part of the active layer from the silicon-on-insulator wafer.

[0207] In the production of an SOI wafer, a thermal oxidation treatment is performed on the base layer at a temperature of about 1100 °C to form an oxide film on the surface of the base layer. After that, an active layer is bonded to the oxide film. The coefficient of thermal expansion of the base layer is larger than that of the oxide film. If the temperature is restored to room temperature, the base layer will shrink compared to the oxide film. Therefore, at this time, a compressive stress is applied to the oxide film from the base layer. When processing such an SOI wafer to remove the base layer and the oxide film from the central region of the movable part to form ribs in the peripheral region, since the base layer in the central region is removed, a part of the above-mentioned compressive stress applied to the oxide film of the ribs is released, and the above-mentioned oxide film expands. As a result, a force is applied to the active layer in the central part from the oxide film in the direction of the center of the central part, and the active layer in the central part is deflected. In contrast, according to the present technology, since at least a part of the active layer is removed from the ribs, the expansion of the oxide film is not easily transmitted to the active layer, and it is not easy to generate deflection in the active layer in the central part. Therefore, it is possible to suppress the deflection of the movable part when forming ribs in the movable part using an SOI wafer.

[0208] (Technology 2)

[0209] The optical reflection element according to Technology 1, wherein

[0210] The rib has a structure obtained by further removing at least a part of the oxide film from the silicon-on-insulator wafer.

[0211] According to the present technology, since the volume of the oxide film as the source of deflection generation becomes smaller, the displacement of the oxide film caused by expansion becomes further smaller. As a result, it is possible to further suppress the deflection of the central part.

[0212] (Technology 3)

[0213] The optical reflection element according to Technology 1 or 2, wherein

[0214] The central part and the rib are connected via a flexible spring part.

[0215] According to the present technology, the expansion of the oxide film of the rib is less likely to be transmitted to the active layer in the central part, so that the deflection of the central part can be further suppressed.

[0216] (Technology 4)

[0217] The optical reflection element according to Technology 3, wherein

[0218] The rib has a structure obtained by removing the oxide film and the active layer in a region other than the connection region connected to the spring part from the silicon-on-insulator wafer.

[0219] According to the present technology, the oxide film and the active layer required in the connection region of the spring portion and the rib portion are left, and all the oxide film and the active layer are removed from the rib portion. As a result, there is almost no oxide film on the rib portion, so that the deflection of the central portion can be further suppressed.

[0220] (Technology 5)

[0221] In the optical reflection element according to Technology 3 or 4, it is characterized in that

[0222] The distance from the center of the central portion to the inner periphery of the rib portion is shorter than the distance from the center of the central portion to the connection position of the spring portion and the rib portion.

[0223] According to the present technology, the rib portion can be arranged close to the central portion, so that the weight of the rib portion can be reduced. As a result, a decrease in the driving efficiency of the movable portion can be suppressed.

[0224] (Technology 6)

[0225] In the optical reflection element according to any one of Technologies 3 to 5, it is characterized in that

[0226] The spring portion is made of the same material as the central portion.

[0227] According to the present technology, the spring portion and the central portion can be formed at once, so that the manufacturing process of the optical reflection element becomes simple.

[0228] (Technology 7)

[0229] In the optical reflection element according to any one of Technologies 1 to 6, it is characterized in that

[0230] The movable portion is configured to be line-symmetric with respect to a straight line passing through the center of the central portion and perpendicular to the rotation axis.

[0231] According to the present technology, the weight balance of the movable portion on both sides of the straight line passing through the center and perpendicular to the rotation axis can be balanced. Therefore, the movable portion can be appropriately driven.

[0232] (Technology 8)

[0233] In the optical reflection element according to any one of Technologies 1 to 7, it is characterized in that

[0234] The movable portion is configured such that the deflection generated in the central portion due to the expansion of the oxide film is substantially symmetric with respect to the central axis of the central portion.

[0235] According to the present technology, the reflected light reflected by the movable portion is distributed substantially symmetrically with respect to the optical axis, so that the design of the subsequent optical system into which the reflected light is to be incident becomes easy.

[0236] (Technology 9)

[0237] The optical reflection element according to Technique 8, wherein

[0238] the movable portions have substantially the same structure at positions at substantially equal angular intervals in the circumferential direction with respect to the center of the central portion.

[0239] According to the present technique, the movable portion can be easily configured such that the flexure generated in the central portion is substantially symmetric with respect to the central axis of the central portion.

[0240] (Technique 10)

[0241] The optical reflection element according to any one of Techniques 1 to 9, wherein

[0242] the rib portion has a structure obtained by removing a predetermined width of the active layer from the silicon-on-insulator wafer along the circumferential direction of the movable portion.

[0243] According to the present technique, the expansion of the oxide film that is the rib portion throughout the entire circumference is not easily conducted to the active layer in the central portion, and thus the flexure of the central portion can be suppressed throughout the entire circumference.

[0244] (Technique 11)

[0245] The optical reflection element according to any one of Techniques 1 to 10, wherein

[0246] an optical reflection film is further provided on the upper surface of the active layer.

[0247] According to the present technique, the reflectance can be increased as compared with the case where the upper surface of the active layer is used as the reflection surface.

[0248] (Technique 12)

[0249] The optical reflection element according to Technique 11, wherein

[0250] another optical reflection film is further provided on the back surface of the central portion of the movable portion.

[0251] According to the present technique, even if stress caused by temperature change or the like is generated in the optical reflection film formed on the upper surface of the active layer, the stress can be relieved by the stress generated in the optical reflection film on the back surface side. Therefore, deformation occurring in the central portion of the movable portion due to stress generated in the optical reflection film caused by temperature change or the like can be suppressed.

[0252] Description of Reference Numerals

[0253] 1: Optical reflection element; 10: Fixed part; 40: Movable part; 40a: Reflective surface; 41: Central part; 42: Rib part; 43: Spring part; 44: Connection part; 45: Optical reflection film; 100: SOI wafer; 101: Base layer; 102: Oxide film; 103: Active layer; C10: Center; R10: Rotation axis; R11: Straight line.

Claims

1. An optical reflection element, characterized in that, Comprising: A fixed part; and A movable part, which is supported by the fixed part so as to be rotatable about a rotation axis, has a reflective surface at the central part of the upper surface, and has rib portions in the outer peripheral region of the lower surface. Wherein, the central part of the movable part has a structure obtained by removing the base layer and the oxide film from a silicon-on-insulator wafer in which a base layer, an oxide film, and an active layer are laminated. The rib portion has a structure obtained by removing at least a part of the active layer from the silicon-on-insulator wafer.

2. The optical reflection element according to claim 1, characterized in that The rib portion has a structure obtained by further removing at least a part of the oxide film from the silicon-on-insulator wafer.

3. The optical reflection element according to claim 1, characterized in that The central part and the rib portion are connected via a flexible spring part.

4. The optical reflection element according to claim 3, characterized in that The rib portion has a structure obtained by removing the oxide film and the active layer in a region other than the connection region connected to the spring part from the silicon-on-insulator wafer.

5. The optical reflection element according to claim 3, characterized in that The distance from the center of the central part to the inner circumference of the rib portion is shorter than the distance from the center of the central part to the connection position of the spring part and the rib portion.

6. The optical reflection element according to claim 3, characterized in that The spring part is made of the same material as the central part.

7. The optical reflection element according to claim 1, characterized in that The movable part is configured to be line-symmetric with respect to a straight line passing through the center of the central part and perpendicular to the rotation axis.

8. The optical reflection element according to any one of claims 1 to 7, characterized in that The movable part is configured such that the flexure generated in the central part due to the expansion of the oxide film is substantially symmetric with respect to the central axis of the central part.

9. The optical reflection element according to claim 8, characterized in that The movable part has substantially the same structure at positions at substantially equal angles in the circumferential direction with respect to the center of the central part.

10. The optical reflection element according to claim 1, characterized in that The rib portion has a structure obtained by removing a predetermined width of the active layer from the silicon-on-insulator wafer along the circumferential direction of the movable part.

11. The optical reflection element according to claim 1, characterized in that An optical reflection film is further provided on the upper surface of the active layer.

12. The optical reflection element according to claim 11, characterized in that Another optical reflection film is further provided on the back surface of the central part of the movable part.

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