JP2010249905A - Optical apparatus and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a balance between that the electrode faces of a fixed electrode and a movable electrode are made large, and that the mirror size of a movable mirror is made large, in an optical apparatus in which the electrode faces of the fixed electrode furnished on a substrate and of the movable electrode furnished on the movable mirror are perpendicular to the rocking axis of the movable mirror. <P>SOLUTION: The fixed electrode and the movable electrode are furnished under the movable mirror such that the electrode faces is be perpendicular to the rocking axis of the movable mirror. The movable electrode extends downward from the lower face of the movable mirror and the fixed electrode extends toward the movable mirror from the substrate. Since the movable electrode and the fixed electrode are provided under the movable mirror, there is no need for a region in which the movable mirror is furnished to be provided on the surface of the movable mirror. The area of the mirrors are made large, compared to the area of a material substrate, and a large aperture ratio is given. The fixed electrode and the movable electrode are used as detection devices of the rocking angle of the movable mirror and as an electrostatic driving system actuator. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical device for deflecting a light beam (referring to changing the reflection direction of the light beam) and a method for manufacturing the same.

  Patent Document 1 discloses an optical device 900 shown in FIG. In the optical device 900, a substrate 901 and a movable mirror 902 are connected by a flexible beam 903. The comb-shaped movable electrode 905 is provided at a side end near the upper surface of the movable mirror 902, and the comb-shaped fixed electrode 904 extends from the substrate 901 side to the movable electrode 905 side. The electrode surface of the fixed electrode 904 and the electrode surface of the movable electrode 905 are perpendicular to the swing axis on which the movable mirror 902 swings. A mirror 906 is installed at the center of the upper surface of the movable mirror 902. The mirror 906 is not installed on the upper surface of the portion where the movable electrode 905 is formed. By changing the angle (oscillation angle) of the movable mirror 902 with respect to the substrate 901, the light beam incident on the mirror 906 can be deflected in a predetermined direction. The opposing area of the electrode surfaces of the fixed electrode 904 and the movable electrode 905 changes according to the swing angle of the movable mirror 902. By measuring the capacitance obtained according to the facing area, the swing angle of the movable mirror 902 can be detected.

  The comb-like movable electrode and the fixed electrode are used as a device for detecting the swing angle of the movable mirror as disclosed in Patent Document 1. On the other hand, a voltage can be applied between the fixed electrode and the movable electrode, and the electrostatic force generated between them can be used as a torque for driving the movable mirror. The fixed electrode and the movable electrode can be used as a part of the electrostatic drive actuator.

JP 2006-184603 A

  In Patent Document 1, since the movable electrode is provided at the side end near the upper surface of the movable mirror, a region for providing the movable electrode on the surface of the movable mirror must be secured. If a region for providing the movable electrode is secured on the surface of the movable mirror, the area of the region for providing the mirror is reduced, and the aperture ratio (ratio of the mirror area to the substrate area) is reduced.

  Therefore, in the present invention, the substrate, the flexible beam, the movable mirror supported by the flexible beam so as to be swingable with respect to the substrate at a position away from the substrate, and a position below the movable mirror, A fixed electrode provided on the substrate so that the electrode surface is perpendicular to an oscillation axis on which the movable mirror swings, and a movable fixed to the lower surface of the movable mirror so that the oscillation axis and the electrode surface are perpendicular to each other. An optical device comprising an electrode is provided.

  Here, “oscillation” refers to rotation within a limited angular range around a predetermined axis (oscillation axis). Includes a simple tilt around the swing axis. The phrase “the movable mirror swings” includes that the movable mirror repeatedly swings around the swing axis and that the movable mirror tilts around the swing axis and stops.

  In the present invention, the movable electrode is fixed to the lower surface of the movable mirror, and the fixed electrode is provided on the substrate at a position below the movable mirror. The fixed electrode and the movable electrode face each other at a position below the movable mirror. For this reason, it is not necessary to provide the area | region which provides a movable electrode in the surface of a board | substrate. The mirror area can be made larger than the substrate area, and the aperture ratio can be increased.

  The optical device of the present invention is integrally formed from a laminate including a conductive surface layer, a conductive back surface layer, and an insulating intermediate layer provided between the surface layer and the back surface layer. May be. In this case, the movable mirror includes a surface layer, the fixed electrode includes a back surface layer, and the movable electrode includes a back surface layer. The movable electrode is fixed to the movable mirror by an intermediate layer.

  An optical device integrally formed from the above laminate includes a first step of forming a movable mirror and a flexible beam on a surface layer, a second step of forming a fixed electrode and a movable electrode on a back surface layer, It can be manufactured by a manufacturing method including a third step of removing an intermediate layer between the electrode and the movable mirror.

  In the third step, the intermediate layer between the fixed electrode and the movable mirror is removed by etching, for example, and the fixed electrode and the movable mirror are separated from each other. For this reason, in the optical device formed integrally from the above laminate, the width in the direction perpendicular to the electrode surface of the movable electrode is preferably designed to be larger than the width in the direction perpendicular to the electrode surface of the fixed electrode. . In this way, even if etching is performed under the condition that the intermediate layer between the fixed electrode and the movable mirror is removed in the third step, the intermediate layer for fixing the movable mirror and the movable electrode remains, and the movable mirror and A state where the movable electrode is fixed can be secured.

  In addition, the movable electrode includes a base portion extending in a direction perpendicular to the electrode surface of the movable electrode, and a width in a direction perpendicular to the electrode surface of the movable electrode in the base portion is set in a direction perpendicular to the electrode surface of the fixed electrode. You may design larger than a width | variety. Similarly to the above, it is possible to secure a state where the movable mirror and the movable electrode are fixed in the third step.

  In addition, a cutout portion may be provided on the fixed electrode. If the notch is provided in the upper part of the fixed electrode, it becomes difficult for the movable mirror to come into contact with the fixed electrode when swinging. The swingable angle of the movable mirror can be increased.

  The optical device of the present invention may include a combination of the first fixed electrode and the movable electrode and a combination of the second fixed electrode and the movable electrode. When the movable mirror swings at a predetermined swing angle with respect to the substrate, the area of the first counter electrode surface obtained by the combination of the first fixed electrode and the movable electrode, and the second fixed electrode and the movable mirror are movable. You may make it mutually differ from the area of the 2nd counter electrode surface obtained by a combination with an electrode.

  By doing so, it is possible to perform capacitance detection and drive torque control using the difference in the area of the opposing electrode surfaces. For example, by obtaining the difference between the capacitance obtained by the first counter electrode surface and the capacitance obtained by the second counter electrode surface, the influence of common-mode noise on the detection result of the swing angle is reduced. be able to.

  According to the present invention, since the fixed electrode and the movable electrode are provided below the movable mirror, it is not necessary to provide a region for providing the movable electrode on the surface of the substrate. The mirror area can be made larger than the substrate area, and the aperture ratio can be increased.

It is a top view of the optical apparatus of Example 1, and has shown the surface side provided with the mirror. It is a figure which shows the back surface side of the optical apparatus of FIG. FIG. 3 is a cross-sectional view of the optical device of FIG. 1 taken along line III-III. FIG. 4 is a sectional view taken along line IV-IV of the optical device of FIG. 1. It is a figure which shows typically the fixed electrode and movable electrode seen from the VV line | wire cross section of FIG. 1, and has shown the time of a stationary of a movable mirror. It is a figure which shows typically the fixed electrode and movable electrode of FIG. 5 at the time of the rocking | fluctuation of a movable mirror. 1 is a diagram illustrating a conversion device according to a first embodiment. 1 is a diagram illustrating a capacitance-voltage conversion circuit according to a first embodiment. It is a figure explaining rocking angle (theta) of the movable mirror which concerns on Example 1, and the opposing area of an electrode surface. It is a figure explaining rocking angle (theta) of the movable mirror which concerns on Example 1, and the opposing area of an electrode surface. It is a figure which shows the installation position of the fixed electrode and movable electrode of a modification. It is a figure which shows the installation position of the fixed electrode and movable electrode of a modification. It is a figure which shows the fixed electrode of a modification. 3 is a view showing a cross section of a laminate according to Example 1. FIG. 3 is a cross-sectional view of a laminate for explaining the manufacturing method of Example 1. FIG. 3 is a cross-sectional view of a laminate for explaining the manufacturing method of Example 1. FIG. It is sectional drawing of the laminated body for demonstrating the manufacturing method of a modification. 3 is a cross-sectional view of a laminate for explaining the manufacturing method of Example 1. FIG. 3 is a plan view of a laminate for explaining the manufacturing method of Example 1. FIG. FIG. 20 is a cross-sectional view of the stacked body in FIG. 19 taken along the line XX-XX. 3 is a plan view of a laminate for explaining the manufacturing method of Example 1. FIG. FIG. 22 is a cross-sectional view of the stacked body of FIG. 21 taken along line XXII-XXII. 3 is a plan view of a laminate for explaining the manufacturing method of Example 1. FIG. It is the XXIV-XXIV line sectional view of the layered product of Drawing 23. 3 is a plan view of a laminate for explaining the manufacturing method of Example 1. FIG. It is XXVI-XXVI sectional view taken on the line of FIG. 3 is a cross-sectional view of a laminate for explaining the manufacturing method of Example 1. FIG. 3 is a cross-sectional view of a laminate for explaining the manufacturing method of Example 1. FIG. 3 is a cross-sectional view of a laminate for explaining the manufacturing method of Example 1. FIG. 3 is a cross-sectional view of a laminate for explaining the manufacturing method of Example 1. FIG. It is a top view of the optical apparatus of Example 1, and has shown the surface side provided with the mirror. It is sectional drawing of the laminated body for demonstrating the manufacturing method of a modification. It is sectional drawing of the laminated body for demonstrating the manufacturing method of a modification. It is a top view of the optical apparatus of Example 2, and has shown the surface side provided with the mirror. FIG. 6 is a diagram illustrating a conversion device according to a second embodiment. It is a top view of the optical apparatus of Example 3, and has shown the surface side provided with the mirror. It is a figure explaining the rocking angle (theta) of the movable mirror which concerns on Example 3, and the opposing area of an electrode surface. It is a top view of the optical apparatus of Example 4, and has shown the surface side provided with the mirror. FIG. 10 is a diagram illustrating a drive circuit according to a fourth embodiment. It is a perspective view of the optical apparatus of a prior art example.

The main features of the embodiments described below are listed below.
(Feature 1) The fixed electrode is fixed to the side surface of the frame-shaped substrate.

  Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of the optical device 100 of the present embodiment, showing the surface side on which the mirror 106 is provided. FIG. 2 is a diagram showing the back side of FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1, and FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. The A axis and B axis shown in FIG. 1 and the like indicate coordinate axes that are orthogonal to each other.

  As shown in FIGS. 1 to 4, the optical device 100 includes a substrate 101, a pair of flexible beams 103a and 103b, a movable mirror 102 supported by the flexible beams 103a and 103b in a swingable manner, A mirror 106 provided on the surface of the movable mirror 102, fixed electrodes 104 c to 104 f fixed to the substrate 101, and a movable electrode 105 fixed to the lower surface of the movable mirror 102 are provided. A pair of flexible beams 103 a and 103 b connect the substrate 101 and the movable mirror 102.

  The movable electrode 105 is fixed to the lower surface of the movable mirror 102. The movable mirror 102 and the movable electrode 105 are substantially rigid bodies and move as a whole as a whole. The pair of flexible beams 103a and 103b is elongated and flexible, and can be twisted relatively easily. Each part of the movable mirror 102 and the movable electrode 105 and the connection point where they are connected to each other are extremely rigid with respect to the flexible beams 103a and 103b. The relative displacement angle between the movable mirror 102 and the movable electrode 105 is significantly smaller than the twist angle of the flexible beams 103a and 103b. The movable mirror 102 and the movable electrode 105 oscillate around the A axis shown in FIG. The movable electrode 105 is installed so as to be symmetric with respect to the swing axis.

  The substrate 101 is provided with fixed electrodes 104 c to 104 f and extends from the substrate 101 toward the movable electrode 105. The fixed electrodes 104c to 104f are provided in pairs at positions that are symmetric with respect to the swing axis of the movable mirror 102. A pair of fixed electrodes 104c to 104f are disposed at positions on both sides of the movable electrode 105, respectively. The distance between the fixed electrodes 104c to 104f and the movable electrode 105 (the distance in the direction perpendicular to the electrode surface (A-axis direction)) is all equal. As shown in FIGS. 2 and 3, the width of the movable electrode 105 in the direction perpendicular to the electrode surface 115 (A-axis direction) is W2. As shown in FIGS. 2 and 4, the fixed electrodes 104c to 104f have the same shape and size, and the width in the direction perpendicular to the electrode surfaces 114c to 114f of the fixed electrodes 104c to 104f (A-axis direction) is W1. As is clear from FIGS. 2 to 4, the width W2 is larger than the width W1 (W2> W1). On the upper surface of the substrate 101, there are provided a fixed electrode contact pad 121 that conducts with the fixed electrodes 104 c to 104 f and a movable electrode contact pad 122 that conducts with the movable electrode 105.

  In this embodiment, the movable mirror 102 is swung by an electromagnetically driven actuator. Inside the movable mirror 102, a drive coil is wired along the outer periphery of the movable mirror 102, and on the upper surface of the substrate 101, drive coil contact pads 123 a and 123 b that are electrically connected to the start and end of the drive coil are provided. It has been. The drive coil contact pad 123a is connected to a drive signal generator (not shown), and the drive coil contact pad 123b is grounded. The optical device 100 further includes a magnetic body (not shown) that generates a magnetic field B parallel to the B-axis direction shown in FIG. When the drive voltage Vd is applied by the drive signal generator in the magnetic field B, Lorentz force is generated by the current flowing in the drive coil in the A-axis direction and acts on the movable mirror 102. As a result, the flexible beams 103a and 103b are twisted, and the movable mirror 102 and the movable electrode 105 are united and swing about the A axis as the swing axis. In this embodiment, the drive signal output from the drive signal generation device is a voltage signal such as direct current, alternating current, triangular wave, rectangular wave, etc., but the drive signal generation device outputs direct current, alternating current, triangular wave, rectangular wave, etc. A current signal may be output.

  The movable mirror 102 and the movable electrode 105 swing around the A axis shown in FIG. 1-4, the electrode surfaces 114c to 114f of the fixed electrodes 104c to 104f and the electrode surface 115 of the movable electrode 105 are perpendicular to the longitudinal direction of the flexible beams 103a and 103b. It is vertical. That is, the electrode surfaces 114 c to 114 f of the fixed electrodes 104 c to 104 f and the electrode surface 115 of the movable electrode 105 are perpendicular to the swing axis (A axis) of the movable mirror 102. Thus, even when the movable mirror 102 and the movable electrode 105 are swung, the electrode surfaces 114c to 114f and the electrode surface 115 are opposed to each other without changing the distances in the direction perpendicular to the electrode surfaces 114c to 114f and the electrode surface 115. Only the area can be changed.

  5 and 6 are diagrams schematically showing the fixed electrode 104c and the movable electrode 105 as seen from the VV line cross section of FIG. FIG. 5 shows a state where the movable mirror 102 is not swung with respect to the substrate 101, and FIG. 6 shows a state where the movable mirror 102 is swung with respect to the substrate 101. In FIG. 6, the portion of the movable mirror 102 on the side where the fixed electrodes 104c and 104d are installed is displaced upward, and the portion of the movable mirror 102 on the side where the fixed electrodes 104e and 104f are installed is displaced downward. Yes.

  In the present embodiment, when the movable mirror 102 is not oscillated, the facing area between the electrode surface 114c of the fixed electrode 104c and the electrode surface 115 of the movable electrode 105 is zero as shown in FIG. As shown in FIG. 6, when the portion of the movable mirror 102 on the side where the fixed electrodes 104c and 104d are installed is displaced upward, the movable electrode 105 enters between the fixed electrodes 104c and 104d. As a result, the electrode surfaces 114c and 114d of the fixed electrodes 104c and 104d and the electrode surface 115 of the movable electrode 105 face each other, and a counter electrode surface 117 is obtained.

  In this embodiment, the fixed electrodes 104c to 104f are provided one by one at positions symmetrical with respect to the swing axis (A axis) of the movable mirror 102, so that the movable mirror 102 swings in the direction opposite to the above. In this case, the electrode surfaces 114e and 114f of the fixed electrodes 104e and 104f and the electrode surface 115 of the movable electrode 105 face each other, and the counter electrode surface can be obtained similarly.

  In this embodiment, the optical device 100 includes a detection device that detects a swing angle θ at which the movable mirror 102 swings with respect to the substrate 101. The fixed electrodes 104c to 104f and the movable electrode 105 are a part of them. Used as The detection device further includes a conversion device 140 shown in FIG. The conversion device 140 includes a capacitance-voltage conversion unit 141, a swing angle calculation unit 142, and a display unit 143. The capacitance-voltage conversion unit 141 outputs the capacitance of the capacitor C (θ) obtained as a result of the electrode surfaces 114c to 114f of the fixed electrodes 104c to 104f and the electrode surface 115 of the movable electrode 105 facing each other as a voltage. . The swing angle calculation unit 142 calculates the swing angle θ of the movable mirror 102 from the electrostatic capacitance C (θ) detected by the capacitance-voltage conversion unit 141, and outputs it to the display unit 143. In the display unit 143, the swing angle θ or the like is displayed on a display or the like. Note that the display unit 143 may not be included in the conversion device 140. For example, the swing angle θ or the like may be output to a display device installed separately from the conversion device 140.

In the capacitance-voltage conversion unit 141, for example, a charge amplifier type circuit as shown in FIG. 8 can be used. As a result, the capacitance of the capacitor C (θ) is converted to the output voltage _Vout . As illustrated in FIG. 8, the capacitance-voltage conversion unit 141 includes a reference signal generator (input V _r ), an output terminal (output V _out ), a capacitor C (θ) that detects capacitance, and a parasitic capacitance due to wiring. and C _p, and includes an operational amplifier, and a resistor R and a feedback capacitor C _f for discharge that is parallel-connected to the operational amplifier. Capacitor C (θ) indicates capacitor C (θ) obtained when electrode surfaces 114c to 114f of fixed electrodes 104c to 104f face electrode surface 115 of movable electrode 105. By measuring the output voltage _Vout output from the output terminal, the capacitance of the capacitor C (θ) can be detected using the following equation (1).

The swing angle calculation unit 142 derives the swing angle of the movable mirror 102 from the output voltage V _out from the capacitance-voltage conversion unit 141. As an example of the method for deriving the swing angle, a method for calculating the swing angle θ using the output voltage _Vout will be described with reference to FIGS. FIG. 9 shows the setting of the xy coordinate axes in FIG. 5, and FIG. 10 shows the setting of the xy coordinate axes in FIG. Hereinafter, the suffixes of the fixed electrodes 104c to 104f and the electrode surfaces 114c to 114f are omitted.

  In a state where the movable mirror 102 shown in FIG. 9 is stationary, the electrode surface 114 and the electrode surface 115 do not face each other. When the movable mirror 102 swings and the movable electrode 105 is displaced integrally with the movable mirror 102 and moves so that the movable electrode 105 protrudes toward the fixed electrode 104 as shown in FIG. The counter electrode surface 117 is obtained. The area S of the counter electrode surface 117 is a function of the swing angle θ of the movable mirror 102, and the capacitance detected by the movable electrode 105 and the fixed electrode 104 is proportional to the area S of the counter electrode surface 117. Accordingly, by measuring the capacitance detected by the movable electrode 105 and the fixed electrode 104, the area S of the counter electrode surface 117 can be obtained, and the swing angle θ can be obtained.

As shown in FIG. 9, the movable mirror 102 has an upper surface parallel to the x-axis when the swing angle θ = 0 °. Let R be the length from the origin O to the corner E of the fixed electrode 104 (equal to the length from the origin O to the corner C of the movable electrode 105), and let φ be the angle formed by the line OE and the y axis. That is, the angle φ is an angle determined by the position and shape of the fixed electrode 104, and the angle φ does not change and is constant even when the swing angle θ changes. In FIG. 9, t _k is the thickness of the movable mirror 102 (the length in the y-axis direction), t _b is the distance between the upper surface of the fixed electrode 104 and the lower surface of the movable mirror 102 (the length in the y-axis direction) There, the length _{t h} is the length of the y-axis direction of the electrode surface 114 of the fixed electrode 104. The upper end of the electrode surface 115 of the movable electrode 105 and the upper end of the electrode surface of the fixed electrode 104 are at the same position in the y-axis direction. Y-axis direction length of the electrode surface 115 of the movable electrode 105 is _{t h,} y-axis direction length of the electrode surface 114 of the fixed electrode 104 and equal. The movable electrode 105 is symmetric with respect to the y-axis, and b indicates a length that is half the length of the electrode surface 115 in the x-axis direction. Similarly, L indicates a length that is half the length of the movable mirror 102 in the x-axis direction.

FIG. 10 shows a state in which the movable mirror 102 is oscillated and the oscillation angle is θ (θ> 0 °). The counter electrode between the electrode surface 115 of the movable electrode 105 and the electrode surface 114 of the fixed electrode 104. The surface 117 is indicated by a square ABCD in FIG. The area S of the square ABCD can be obtained by calculating the area s _{1 of the} triangle ABC and the area s _{2 of the} triangle ACD and calculating S = s ₁ + s ₂ . The area s _{1 of the} triangle ABC can be calculated by obtaining the coordinates of the points A, B, and C and using the following equation (2). Expression (2) is an expression for calculating the area s of a triangle whose vertex coordinates are (x ₁ , y ₁ ), (x ₂ , y ₂ ), and (x ₃ , y ₃ ). The area s _{2 of the} triangle ACD can be calculated similarly.

  The side end surface of the electrode surface 115 closer to the fixed electrode 104 is indicated by a straight line 1 in FIG. 10, and the lower end surface of the electrode surface 115 is represented by a straight line 2 in FIG. The upper end surface of the electrode surface 114 is indicated by a straight line 3 in FIG. 8, and the side end surface of the electrode surface 114 closer to the movable electrode 105 is indicated by a straight line 4. The intersection of the straight line 3 and the straight line 4 is A, the intersection of the straight line 1 and the straight line 3 is B, the intersection of the straight line 1 and the straight line 2 is C, and the intersection of the straight line 2 and the straight line 4 is D. The line segment OC has a length R, and forms an angle (90 ° −θ−φ) with the x axis. According to the above, the equations showing the straight lines 1 to 4 and the coordinates of the vertices A, B, C, and D can be expressed as the following equations.

Additional vertices A, B, C, and used in formula for the area of a triangle showing the coordinates of D in formula (2), it is possible to calculate the triangle ABC of area _{s 1,} the area _{s 2} triangular ACD. If the area S of the counter electrode surface 117 is calculated by S = s ₁ + s ₂ , the capacitance C and the swing angle θ of the movable mirror θ are expressed by the capacitor capacitance equation: C = ε (S / d). Relational expressions can be derived. In the capacitance equation of the capacitor, C is the capacitance, ε is the dielectric constant, S is the facing area of the electrode surfaces, and d is the distance between the electrode surfaces (perpendicular to the electrode surfaces). Distance in the correct direction Using the relational expression between the capacitance C thus obtained and the swing angle θ of the movable mirror, the swing angle calculation unit 142 is programmed so as to calculate the swing angle θ from the output _Vout. Thus, the swing angle θ can be derived.

From equation (1), it can be seen that the larger the electrostatic capacitance C (θ) of the capacitor constituted by the fixed electrode and the movable electrode, the less the output voltage _Vout is affected by the parasitic capacitance Cp. That is, in order to improve the sensitivity of the detection device, it is better that the capacitance C (θ) is large. In this embodiment, even when the optical device is provided on a limited substrate area, the area of the electrode surface of the fixed electrode and the movable electrode can be increased, and the sensitivity of the movable mirror detection device can be improved. is there. Even if the area of the electrode surface is increased, the mirror size of the movable mirror is not reduced.

Note that the method for obtaining the swing angle θ of the movable mirror from the capacitance C is not limited to the method using the relational expression between the capacitance C and the swing angle θ as described above. For example, the relationship between the swing angle θ of the movable mirror 102 and the output voltage V _out is measured in advance by an optical method or the like, and the measured data is tabulated and stored in the swing angle calculation unit 142 in advance. May be.

  As described above, according to this embodiment, the fixed electrode and the movable electrode are provided at a position below the movable mirror, and the electrode surface of the fixed electrode and the electrode surface of the movable electrode at the position below the movable mirror. Therefore, it is not necessary to provide a region for providing the movable electrode on the surface of the substrate. The mirror area can be made larger than the substrate area, and the aperture ratio can be increased.

  In addition, as in this embodiment, when detecting the swing angle of the movable mirror with respect to the substrate using the fixed electrode and the movable electrode, the detection sensitivity increases as the electrode area of the fixed electrode and the movable electrode increases. If the fixed electrode and the movable electrode are provided on the lower surface side of the movable mirror as in this embodiment, it is necessary to reduce the area where the mirror is provided even if the electrode area of the fixed electrode and the movable electrode is sufficiently increased. Absent. It is possible to achieve both an increase in the aperture ratio and an improvement in detection sensitivity.

  In this embodiment, the movable electrode is provided so as to be symmetric with respect to the swing axis, and the fixed electrode is provided on both sides of the swing axis and extends from the substrate side to the movable electrode side. For this reason, the fixed electrode and the movable electrode can be made to face each other regardless of which direction the movable mirror swings. Regardless of the direction in which the movable mirror swings, the swing angle of the movable mirror can be detected.

  In the above embodiment, when only one movable electrode is provided at the center of the back surface of the movable mirror, and four fixed electrodes are provided two by two so as to be symmetrical with respect to a pair of flexible beams. However, the installation position, size, and shape of the fixed electrode and the movable electrode are not limited to the above embodiment. For example, as shown in FIG. 11, the fixed electrode 104 is not provided on both sides of the pair of flexible beams 103a and 103b, and may be provided only on one of them. In addition, as shown in FIG. 11, a plurality of movable electrodes 105 may be provided. Furthermore, the movable electrode 105 may have the same length as the movable mirror 102 in the B-axis direction of FIG. Even when the movable mirror 102 is stationary, the electrode surfaces of the fixed electrode 104 and the movable electrode 105 may face each other.

  Further, the fixed electrode and the movable electrode may not be entirely flat. For example, as shown in FIG. 12, a plurality of flat plates may be provided with a movable electrode formed integrally with a base portion 151. The base 151 is preferably provided in the vicinity of the swing axis of the movable mirror 102.

  In this embodiment, as shown in FIG. 13, a notch 153 may be provided at the upper end of the fixed electrode 104. When the movable mirror 102 swings in the direction indicated by the arrow in FIG. 13, a part of the movable mirror 102 is displaced downward. For this reason, when the swing angle of the movable mirror 102 is large, a part of the movable mirror 102 displaced downward may come into contact with the upper end portion of the fixed electrode 104. As shown in FIG. 13, in the fixed electrode 104 provided with the notch 153, the distance between a part of the upper surface of the fixed electrode 104 and the lower surface of the movable mirror 102 increases in a portion located below the movable mirror 102. Therefore, it becomes difficult for the movable mirror 102 to contact the fixed electrode 104. For this reason, the swingable angle of the movable mirror 102 can be increased.

  Note that the optical device of the present embodiment may further include a control device that controls the drive signal generation device based on the swing angle of the movable mirror detected by the detection device.

  Next, an example of a method for manufacturing the optical device according to the present embodiment will be described with reference to FIGS. In this embodiment, a manufacturing method for integrally forming an optical device using an SOI (Silicon On Insulator) substrate in which an insulating layer is inserted between a silicon substrate and a surface silicon layer will be described.

  In this embodiment, a plurality of optical devices are simultaneously formed on the SOI substrate. However, in FIGS. 14 to 31 used for explaining the manufacturing method according to this embodiment, a section for forming a single optical device is used. A cross section and a plane of a predetermined portion included are modeled and illustrated.

  According to the manufacturing method described below, an optical device 500 shown in FIG. 31 is obtained. The optical device 500 according to the present embodiment is different from the optical device 100 shown in FIG. 1 and the like in the installation position of the fixed electrode 504 and the width of the movable electrode 505, and other configurations are the same as the optical device 100. The description of other configurations of the optical device 500 will be omitted by replacing the reference numerals 100 to 500 in the same member.

  FIG. 14 is a diagram showing an SOI substrate. The SOI substrate used in this embodiment is a stacked body in which a conductive back surface layer 161 (handle layer), an insulating intermediate layer 162 (Box layer), and a conductive surface layer 163 (active layer) are stacked in this order. is there. The back surface layer 161 has a larger layer thickness than the intermediate layer 162 and the surface layer 163. In this embodiment, the movable mirror 502 is formed by the surface layer 163 and a layer stacked on the surface layer 163 in the manufacturing process. The fixed electrode 504 is formed by the back surface layer 161. The movable electrode 505 is formed by the back surface layer 161. The movable electrode 505 is fixed to the back surface (formed by the surface layer 163) of the movable mirror 502 by the intermediate layer 162.

In the manufacturing method of this embodiment, the first step of forming the movable mirror 502 and the flexible beams 503a and 503b on the surface layer 163, and the fixed electrode 504 and the movable electrode 505 are formed on the back surface layer 161. A second step and a third step of removing the intermediate layer 162 between the fixed electrode 504 and the movable mirror 502 are included. Hereinafter, each step will be specifically described.
<First step>

First, the SOI substrate (laminated body) shown in FIG. 14 is processed from the surface layer 163 side. First, the surface layer 163 and the intermediate layer 162 are etched to form portions to be fixed electrode contact pads 521 and the like. Etching of the surface layer 163 can be performed by forming a patterned resist on the surface of the surface layer 163, then performing dry etching such as RIE (Reactive Ion Etching) or XeF ₂ gas, and then removing the resist. . For the etching of the intermediate layer 162, after forming a patterned resist on the surface of the surface layer 163, for example, dry etching such as RIE or wet etching using a buffered hydrofluoric acid solution (buffered hydrofluoric acid) is performed. , By removing the resist. Alternatively, an oxide film may be formed in place of the resist, patterning may be performed, and then wet etching with KOH may be performed.

Next, when the insulating layer 164 is laminated on the surface layer 163 side by plasma CVD (Chemical Vapor deposition) or the like, the state shown in FIG. 15 is obtained. As the insulating layer 164, for example, an NSG film (Non-doped Silicate Glass), SiN, or the like can be used. Further, instead of plasma CVD, SiO ₂ or the like may be formed by sputtering, vapor deposition, or thermal oxidation.

  Further, a portion that becomes the fixed electrode contact pad 521 of the insulating layer 164 is etched by RIE or the like. For the etching of the insulating layer 164, after forming a patterned resist on the surface of the surface layer 163, a method such as dry etching such as RIE or wet etching using buffered hydrofluoric acid is performed, and then the resist is removed. Can be implemented. As a result, as shown in FIG. 16, a part of the back surface layer 161 is exposed to the surface layer 163 side.

  As shown in FIG. 16, in the wiring portion such as the fixed electrode contact pad 521, the intermediate layer 162, the surface layer 163, and the insulating layer 164 are etched so as to be stepped for each layer. Thus, by making it the small level | step difference shape for every layer, a big level | step difference is avoided and it suppresses that wirings, such as Al formed in the upper layer, are cut | disconnected in a level | step-difference part. Further, for example, if anisotropic etching is used in which the {100} crystal plane of the silicon crystal is used as the upper surface of each layer, and etching is performed along the {111} crystal plane of the silicon crystal in the etching step, FIG. As shown, each layer can be etched at an angle of about 55 ° with respect to the laminate plane, and the stepped portion of the wiring such as Al can be further reduced.

  Further, a wiring material such as aluminum (Al) is formed on the surface of the laminate shown in FIG. 16 by sputtering or vapor deposition to form a wiring layer. In this example, as shown in FIG. 18, an Al layer 165 was laminated as a wiring layer. In this embodiment, Al is used as the wiring material. However, for example, an Al—Si—Cu alloy, or a wiring material such as Pt, Ti, Cu, Ag, or Au can be used.

  Next, the Al layer 165 is etched, and the drive coil lower layer 172, the movable electrode wiring 174, and the like are patterned as shown in FIGS. 19 is a plan view of the laminate, and FIG. 20 is a cross-sectional view taken along the line XX-XX in FIG. In FIG. 19, the wiring pattern is shown by a solid line, and the wiring width is not shown. Etching of the Al layer 165 is performed by forming a patterned resist on the surface of the Al layer 165 and then performing a method such as dry etching such as RIE or wet etching with phosphoric acid, and then removing the resist. it can.

  Next, the insulating layer 166 is stacked, and then part of the insulating layer 166 is etched. The insulating layer 166 can be formed using a material similar to that of the insulating layer 164, and can be formed and etched by a similar method. Further, when the Al layer 168 is stacked and patterned by etching, the state shown in FIGS. 21 and 22 is obtained. 21 is a plan view of the laminate, and FIG. 22 is a sectional view taken along line XXII-XXII in FIG. FIG. 21 shows the drive coil upper layer 171 patterned on the Al layer 168. The Al layer 168 can be formed and etched by a method similar to that for the Al layer 165. Further, similarly to the Al layer 165, other wiring materials such as an Al—Si—Cu alloy can be used as appropriate.

  As shown in FIG. 22, an insulating layer 166 is provided between the drive coil upper layer 171 and the drive coil lower layer 172, and a part of the drive coil upper layer 171 penetrates the insulating layer 166 and the drive coil lower layer 172. Conducted. Accordingly, it is possible to form a drive coil starting from the drive coil contact pad 523a and wired inside the movable mirror 502 and having the drive coil contact pad 523b as an end point.

  Next, an insulating layer 169 is stacked on the surface side. The insulating layer 169 can be formed using a material similar to that of the insulating layer 164 and can be formed by a similar method. After the insulating layer 169 is deposited, the surface of the insulating layer 169 is smoothed by CMP (Chemical Mechanical Polishing) or the like. The insulating layer 169 has a sufficient stacked thickness so that the Al layer 168 is not exposed even when CMP is performed. Further, after the Al layer 170 is formed on the surface of the insulating layer 169, the Al layer 170 is etched into a mirror shape. As a result, the state shown in FIGS. 23 and 24 is obtained. FIG. 23 is a plan view of the laminate, and FIG. 24 is a cross-sectional view taken along line XXIV-XXIV in FIG. The Al layer 170 can be formed and etched by a method similar to that for the Al layer 165. Further, similarly to the Al layer 165, other wiring materials such as an Al—Si—Cu alloy can be used as appropriate.

Next, after a patterned resist is formed on the surface side, the insulating layers 164, 166, and 169 are etched by RIE or the like to remove the resist. Further, as shown in FIG. 25, the surface layer 163 is etched in accordance with the shapes of the movable mirror and the flexible beams 503a and 503b. In this case, the etching of the surface layer 163 can be performed by dry etching using DRIE (Deep-RIE), RIE, XeF ₂ , or the like.

  25 is a view as seen from the surface side of the laminate, and FIG. 26 is a cross-sectional view taken along line XXVI-XXVI in FIG. As shown in FIG. 25 and FIG. 26, in the portion above the surface layer 163, the portion that becomes the space between the substrate 501, the movable mirror 502, and the flexible beams 503 a and 503 b is removed by etching. . The movable mirror 502 includes a surface layer 163 and an insulating layer or an Al layer stacked on the upper surface of the surface layer 163.

Further, the insulating layers 166 and 169 are etched to expose the wiring layer formed by the Al layer 165 or the like on the surface side, and portions to be the fixed electrode contact pad 521 and the movable electrode contact pad 522 are formed. As the etching method, for example, RIE can be used.
<Second step>

  In the present embodiment, the second step is performed after the first step is performed. In the second step, portions that become the fixed electrode 504 and the movable electrode 505 are formed on the back surface layer 161. The surface side of the stacked body after the first step shown in FIGS. 25 and 26 is covered with a resist 175. This prevents the layer formed on the surface side of the laminate in the first step from being etched. Further, a resist 176 patterned in accordance with the installation positions of the fixed electrode 504 and the movable electrode 505 is formed on the surface on the back surface side of the back surface layer 161. In this embodiment, the back surface layer 161 is covered with a resist 176 that is patterned so that the width W1 of the fixed electrode (the length in the longitudinal direction of the flexible beam) is larger than the width W2 of the movable electrode. To do.

  The back surface layer 161 is etched by DRIE or the like, and portions to be the fixed electrode 504 and the movable electrode 505 are formed as shown in FIGS. 27 is a cross-sectional view at the same position as the cross section shown in FIG. 3, and FIG. 28 is a cross-sectional view at the same position as the cross section shown in FIG. The portions to be the fixed electrode 504 and the movable electrode 505 are joined to the movable mirror 502 and the surface layer 163 which is the lowest layer of the flexible beams 503a and 503b by the intermediate layer 162. In addition, W1 that is the width of the portion that becomes the fixed electrode 504 is smaller than W2 that is the width of the portion that becomes the movable electrode 505. That is, W1 which is the width of the intermediate layer 162 existing between the portion that becomes the fixed electrode 504 and the surface layer 163 that becomes the lowermost layer of the movable mirror 502 or the like is the lowest width of the portion that becomes the movable electrode 505 or the movable mirror 502 or the like. It is smaller than W2, which is the width of the intermediate layer 162 existing between the lower surface layer 163.

In this example, after the second step, the laminated body in the state shown in FIGS. 27 and 28 is diced to form a chip. In dicing, for example, a diamond circular rotary blade (dicing blade) is rotated at high speed while being cooled with ultrapure water, and the laminate is cut. After dicing, the process proceeds to the next third step without removing the resists 175 and 176 formed at the beginning of the second step.
<Third step>

  In the third step, the intermediate layer 162 existing between the portion that becomes the movable mirror 502 and the portion that becomes the fixed electrode 504 is removed by etching. Accordingly, as shown in FIGS. 29 and 30, the portion that becomes the movable electrode 505 and the portion that becomes the movable mirror 502 remain joined, and the portion that becomes the fixed electrode 504 and the portion that becomes the movable mirror 502 are Can be separated. The intermediate layer 162 can be etched by a method such as wet etching using a buffered hydrofluoric acid solution (buffered hydrofluoric acid). Note that wet etching may be performed using a solution obtained by adding a surfactant to a buffered hydrofluoric acid solution. Since the surface tension of the etching solution is reduced by adding the surfactant, the intermediate layer existing between the fixed electrode and the portion that becomes the fixed electrode can be removed by etching even when forming the fixed electrode with a fine pattern. .

  In this embodiment, W1 which is the width of the intermediate layer 162 existing between the portion that becomes the fixed electrode 504 and the surface layer 163 that becomes the lowermost layer of the movable mirror 502 and the like is the portion that becomes the movable electrode 505 and the movable mirror 502. It is smaller than W2 which is the width of the intermediate layer 162 existing between the surface layer 163 as the lowermost layer. Therefore, even if the etching is performed in the third step so as to remove the intermediate layer 162 existing between the portion that becomes the fixed electrode 504 and the surface layer 163 that is the lowermost layer of the movable mirror 502 and the like, the movable electrode 505 Thus, the intermediate layer 162 existing between the portion to be and the surface layer 163 that is the lowermost layer of the movable mirror 502 or the like is not completely removed. As a result, it is possible to ensure a joined state between the movable mirror 502 and the movable electrode 505. The optical device 500 shown in FIG. 31 can be obtained by removing the resists 175 and 176 formed in the second step after separating the portion to be the fixed electrode 504 and the portion to be the movable mirror 502 by etching. Furthermore, a magnetic field generator such as a magnet, a drive signal generation device, or the like may be installed.

  In this embodiment, dicing is performed between the second step and the third step. However, dicing may be performed after removing the resist in the third step. When dicing is performed after resist removal in the third step, it is preferable to use a method such as stealth dicing.

  As described above, according to the method for manufacturing an optical device of this embodiment, the optical device can be integrally formed using a laminate including a surface layer, an intermediate layer, and a back layer such as an SOI substrate. In the present embodiment, the fixed electrode and the movable electrode are formed from the back layer (handle layer) of the SOI substrate, and the movable mirror and the flexible beam are configured by the surface layer of the SOI substrate. Regardless of the shape or size of the movable mirror or flexible beam, the thickness of the back surface layer can be increased to increase the size of the fixed electrode and the movable electrode. The back surface layer of the SOI substrate is made of a silicon substrate, and is thicker than the active layer or the Box layer, and the thickness can be adjusted relatively freely. According to the present embodiment, the area of the electrode surface can be increased by increasing the thickness of the back surface layer. For example, the surface layer and the intermediate layer may be about several μm, while the back layer may be about several hundred μm. As compared with the conventional case where the movable electrode is formed using the surface layer (active layer), the movable electrode can be remarkably enlarged.

  In the method of manufacturing the optical device according to the present embodiment, a laminate other than the SOI substrate described above may be used. For example, a silicon substrate is prepared as a back surface layer, an insulating layer such as an oxide film is formed as an intermediate layer on the surface, polysilicon is formed as a surface layer on the surface, and a laminate is manufactured. You may use as a material of an optical apparatus.

  In the above embodiment, the portion that becomes the fixed electrode 504 by etching is designed so that W1 that is the width of the portion that becomes the fixed electrode 504 is smaller than W2 that is the width of the portion that becomes the movable electrode 505. The intermediate layer 162 that joins the movable mirror 502 and the movable electrode 505 is left after the portion that becomes the movable mirror 502 is separated, but for example, as shown in FIG. 12, the movable electrode 105 is movable. Also by providing the base portion 151 extending in the direction perpendicular to the electrode surface 115 of the electrode 105, it is possible to ensure a state in which the movable mirror and the movable electrode are joined as described above. . As shown in FIG. 12, if the length Wb of the base portion 151 in the B-axis direction is larger than the width W1 of the fixed electrode 104 in the A-axis direction, the portion that becomes the fixed electrode 104 and the portion that becomes the movable mirror 102 Even if etching is performed under the condition that the intermediate layer 162 is removed, the intermediate layer 162 remains between the portion that becomes the base portion 151 and the portion that becomes the movable mirror 102, and the portion that becomes the movable mirror 102 and the movable electrode 105. It is possible to secure a state in which the portion to be joined is joined.

Moreover, the notch part 153 shown in FIG. 13 can be manufactured by implementing a notch formation process between a 1st process and a 2nd process, for example. For example, in the step of etching the surface layer 163 and the intermediate layer 162 of the laminate of FIG. 14 in the first step to form a portion to be the fixed electrode contact pad 521 and the like, the movable mirror and the flexible beam The surface layer 163 and the intermediate layer 162 are etched according to the shape. Then, when the 1st process demonstrated above is performed, the laminated body shown in FIG. 32 can be obtained. In the stacked body shown in FIG. 32, the space between the portion that becomes the substrate and the portion that becomes the movable mirror reaches the upper surface of the back surface layer 161. An insulating layer 164 is formed between this space and the surface layer 163 and the intermediate layer 162. A resist 173 is formed on the surface of the laminate as shown in FIG. The resist 173 is patterned so that the back surface layer 161 can be etched from the front surface side through the space between the portion serving as the substrate and the portion serving as the movable mirror. When isotropic etching is performed on the stacked body on which the resist 173 is formed, the back surface layer 161 is etched from the portion serving as the fixed electrode to the portion serving as the movable electrode as shown in FIG. The fixed electrode 104 provided with the notch 153 can be obtained. The isotropic etching can be performed, for example, by etching with SF ₆ plasma or etching with XeF ₂ gas.

  In this way, when the back surface layer 161 is etched from the front surface side through the space between the portion to be the substrate and the portion to be the movable mirror, a notch 153 is formed between the movable mirror 102 and the substrate 101 as shown in FIG. Becomes deeper. The notch 153 can be formed in the vicinity of a region where the movable mirror 102 swings and is greatly displaced downward.

  FIG. 34 is a plan view of the optical device 200 according to the second embodiment. The optical device 200 is provided on a substrate 201, a pair of flexible beams 203a and 203b, a movable mirror 202 supported by a pair of flexible beams 203a and 203b, and a surface of the movable mirror 202. A mirror 206, two pairs of fixed electrodes 204a and 204b fixed to the substrate 201, and movable electrodes 205a and 205b fixed to the lower surface of the movable mirror 202.

  On the upper surface of the substrate 201, there are provided a fixed electrode contact pad 221 electrically connected to the fixed electrodes 204a and 204b, a movable electrode contact pad 222a electrically connected to the movable electrode 205a, and a movable electrode contact pad 222b electrically connected to the movable electrode 205b. It has been. The wiring that connects the movable electrode 205a and the movable electrode contact pad 222a and the wiring that connects the movable electrode 205b and the movable electrode contact pad 222b are provided inside the movable mirror 202 and are insulated from each other.

  Similar to the first embodiment, the movable mirror 202 is swung by the electromagnetically driven actuator. Inside the movable mirror 202, a drive coil is wired, and on the upper surface of the substrate 201, drive coil contact pads 223a and 223b that are electrically connected to the start and end of the drive coil are provided. A magnetic field in the B-axis direction shown in FIG. 34 is generated by installing a magnetic body, and a Lorentz force is generated by passing a current through the drive coil in the magnetic field B. The movable mirror 202 has the A-axis as a swing axis. And the movable electrodes 205a and 205b swing together.

  The movable electrode 205a and a pair of fixed electrodes 204a provided therefor are a first combination, and the movable electrode 205b and a pair of fixed electrodes 204b provided therefor are a second combination. And The capacitance sensor α1 is configured by the first combination. Similarly, the capacitance sensor β1 is configured by the second combination. The movable electrode 205a and the movable electrode 205b have the same shape and size, and are provided at the same position in the direction perpendicular to the swing axis of the movable mirror 202 (B-axis direction). The length of the fixed electrode 204a in the B-axis direction is longer than that of the fixed electrode 204b. When the movable mirror 202 is stationary, the facing area between the fixed electrode 204b and the movable electrode 205b is zero. On the other hand, even when the movable mirror 202 is stationary, the electrode surfaces of the fixed electrode 204a and the movable electrode 205a face each other, and the facing area is larger than zero. That is, when the movable mirror swings at the swing angle θ, the facing area of the electrode surface obtained by the first combination and the facing area of the electrode surface obtained by the second combination are different from each other. For this reason, when the movable mirror swings at the swing angle θ, the capacitance value detected by the capacitance sensor α1 and the capacitance value detected by the capacitance sensor β1 are different from each other.

  FIG. 35 shows a conversion device 240 according to this embodiment. The conversion device 240 according to the present embodiment includes a capacitance-voltage conversion unit 241a that detects the capacitance obtained by the capacitance sensor α1, and a capacitance-voltage conversion that detects the capacitance obtained by the capacitance sensor β1. A unit 241b, a subtractor 244, a swing angle calculation unit 242, and a display unit 243. Output voltages from the capacitance-voltage conversion units 241a and 241b are output to the differentiator 244. The differencer 244 derives the difference in output voltage between the capacitance-voltage conversion unit 241 a and the capacitance-voltage conversion unit 241 b and outputs the difference to the swing angle calculation unit 242. The swing angle of the movable mirror 202 obtained by the swing angle calculation unit 242 is output to the display unit 243 and displayed.

  When the movable mirror 202 swings with respect to the substrate 201 at the swing angle θ, the capacitance value detected by the capacitance sensor α1 is different from the capacitance value detected by the capacitance sensor β1. Therefore, the influence of the common-mode noise can be reduced by deriving the output voltage difference between the capacitance-voltage conversion unit 241a and the capacitance-voltage conversion unit 241b from the equation (1).

  In the present embodiment, the electrostatic capacity of the electrostatic capacitance sensor constituted by the movable electrode and the fixed electrode is changed by changing the size of the electrode surface of the fixed electrode by making the size and shape of the movable electrode the same. However, the present invention is not limited to this. The optical device includes a plurality of combinations of the fixed electrode and the movable electrode, and it is only necessary that the combination includes a combination in which the opposed areas of the electrode surfaces differ from each other with respect to the swing angle of the movable mirror. For example, the size and shape of the fixed electrode may be the same, and the size and shape of the movable electrode may be different. The electrode areas of both the fixed electrode and the movable electrode may be different.

In this embodiment, the movable mirror is swung by an electrostatic drive type actuator using the fixed electrode and the movable electrode. FIG. 36 is a diagram illustrating the optical device 300 of the present embodiment. The optical device 300 includes a substrate 301, a pair of flexible beams 303a and 303b, a movable mirror 302 supported by a pair of flexible beams 303a and 303b, a mirror 306, and a substrate 301. Two pairs of fixed electrodes 304 a and 304 b that are fixed, and a movable electrode 305 that is fixed to the lower surface of the movable mirror 302 are provided. The distance in the A-axis direction between the fixed electrode 304a and the movable electrode 305 and the distance in the A-axis direction between the fixed electrode 304b and the movable electrode 305 are both set to d _ele shown in FIG. The shapes, sizes, and installation positions of the fixed electrodes 304a and 304b and the movable electrode 305 are the same as those of the optical device according to the first embodiment shown in FIGS.

  On the upper surface of the substrate 301, there are provided a fixed electrode contact pad 321 a electrically connected to the fixed electrode 304 a, a fixed electrode contact pad 321 b electrically connected to the fixed electrode 304 b, and a movable electrode contact pad 322 electrically connected to the movable electrode 305. Yes. The fixed electrode 304a and the fixed electrode contact pad 321a are insulated from the fixed electrode 304b and the fixed electrode contact pad 321b.

  In this embodiment, the movable mirror 302 is swung by an electrostatic drive actuator. The fixed electrode contact pads 321a and 321b are connected to the drive signal generator, and the movable electrode contact pad 322 is grounded. A drive voltage V is applied to either the fixed electrode 304a or 304b by the drive signal generator. As a result, an electrostatic force (attraction) is generated between the fixed electrode 304 a or 304 b and the movable electrode 305, and acts on the movable mirror 302. When the electrostatic force acts on the movable mirror 302, the flexible beams 303a and 303b are twisted, and the movable electrode 305 and the movable mirror 302 swing together with the A axis shown in FIG. The driving torque T of the movable mirror 302 is obtained by balancing the torque Tc caused by the electrostatic force and the torque Tb caused by the elasticity of the flexible beams 303a and 303b.

As in this embodiment, the electrostatically driven actuator in which the electrode surfaces of the fixed electrode and the movable electrode are perpendicular to the swing axis of the movable mirror, the electrode surface of the fixed electrode and the movable electrode are parallel to the movable mirror. Compared with an electrostatically driven actuator (referred to as a parallel plate type), the movable mirror can be driven stably. In the parallel plate type actuator, the distance d ₀ between the fixed electrode provided on the substrate and the movable electrode provided on the movable mirror varies depending on the distance H between the movable mirror and the substrate at rest. The electrostatic force acting between the electrodes is inversely proportional to the square of the distance d ₀ between the movable electrode and the fixed electrode. When the movable mirror swings, the distance d ₀ between the electrodes decreases, and the electrostatic force for swinging the movable mirror increases. When the swing angle θ of the movable mirror becomes too large, a phenomenon (pull-in) occurs in which the movable mirror comes into contact with the substrate, and the movable mirror cannot be stably swung. For this reason, in the parallel plate type actuator, the swing angle θ of the movable mirror is such that the inter-electrode distance d ₀ is d ₀ ≧ 2H / 3 with respect to the distance H between the movable mirror and the substrate at rest. Limited.

As in this embodiment, in the electrostatic drive type actuator in which the electrode surfaces of the fixed electrode and the movable electrode are perpendicular to the swing axis of the movable mirror, the fixed electrode and the movable electrode All of the distances are d _ele and do not change. Even if the inter-electrode distance d _ele is reduced, the movable mirror can be stably swung.

  In the present embodiment, the conditions for stably swinging the movable mirror 302 will be described below. In order to stably swing the movable mirror 302, it is only necessary that the swing angle θ of the movable mirror 302 and the drive torque T satisfy dT / dθ ≦ 0. On the other hand, when the movable mirror 302 is swung under the condition of dT / dθ> 0, when the movable mirror 302 is swung and the swing angle θ is increased by Δθ, the drive torque T is increased by ΔT. Become. That is, as the swing angle θ increases, the drive torque T increases and the movable mirror 302 swings further. As a result, the swing angle θ of the movable mirror 302 becomes too large, and a phenomenon (pull-in) in which the movable mirror 302 comes into contact with the substrate may occur.

The relationship between the drive torque T and the swing angle θ will be specifically described with reference to FIG. FIG. 37 shows a state in which a drive voltage is applied to the fixed electrode 304a by the drive signal generator, and the movable mirror 302 is tilted by the swing angle θ. When the swing angle is θ, the electrode surface of the fixed electrode 304a and the electrode surface of the movable electrode 305 obtain a counter electrode surface 350. The area of the counter electrode surface 350 and _{S e.}

The torsion spring constant of the flexible beams 303a and 303b is k, the distance between the fixed electrode 304a and the movable electrode 305 is d _ele , the number of electrodes (the number of combinations of the fixed electrode 304a and the movable electrode 305) is n, and the dielectric constant is Assuming that ε is a positive torque when the movable mirror 302 is tilted with respect to the substrate 301 (a torque when the movable mirror 302 is moved in the counterclockwise direction indicated by an arrow in FIG. 37), the torque Tb due to the elasticity of the flexible beam. Is Tb = −kθ. Further, since the torque Tc due to the electrostatic force is Tc = (nεV ² / (2d _ele )) (dS / dθ), the driving torque T of the movable mirror 302 is expressed by the following equation.

When the movable mirror 302 swings and the swing angle changes by Δθ, the movable mirror 302 can be driven stably by driving the movable mirror 302 under the condition of dT / dθ ≦ 0. From equation (4), it can be seen that if d ² S / dθ ² ≦ 0, dT / dθ ≦ 0 can be satisfied regardless of the number of electrodes n or the size of the interelectrode distance d _ele .

From equation (3), it can be seen that it is effective to increase the number n of electrodes and decrease the inter-electrode distance d _ele in order to increase the driving torque of the movable mirror 302. Even in such a case, as shown in Expression (4), by adjusting the facing area S between the fixed electrode 304a and the movable electrode 305 so as to satisfy d ² S / dθ ² ≦ 0, dT / dθ ≦ 0 Can be met. The movable mirror 302 can be stably swung over a wide range of the swing angle θ. Further, in this embodiment, fixed electrodes 304 a and 304 b and a movable electrode 305 are provided below the movable mirror 302. Therefore, the design of the fixed electrodes 304a and 304b and the movable electrode 305 is not easily limited by the shape and size of the movable mirror 302, and each electrode can be easily designed to satisfy d ² S / dθ ² ≦ 0.

  As described above, in this embodiment, since the electrostatic drive actuator in which the electrode surfaces of the fixed electrode and the movable electrode are perpendicular to the swing axis of the movable mirror is used, it is fixed to obtain a large driving torque. Even if the distance between the electrodes and the movable electrode is reduced and the number of electrodes is increased, the movable mirror can be stably swung. Even if the driving torque is increased and the swing angle of the movable mirror is increased, the movable mirror can be stably swung.

  Furthermore, according to this embodiment, even when the movable mirror is swung by electrostatic force using the fixed electrode and the movable electrode having the electrode surface perpendicular to the swing axis, the fixed electrode and the movable electrode are Since it is provided below, it is not necessary to provide a region for providing the movable electrode on the surface of the substrate. The mirror area can be made larger than the substrate area, and the aperture ratio can be increased.

  An electrostatic drive type actuator is suitable for an actuator of a small optical device because it is not necessary to provide a magnet or the like. It is suitable for an integrated mirror array from the viewpoint of miniaturization of the mirror, consistency between the circuit and the mirror creation process, and power consumption. In an electrostatic drive type optical device, it is required to obtain a large swing angle of the movable mirror with a low drive voltage. In particular, when an electrostatic drive type optical device is integrated to form a mirror array such as a DMD (Digital Micromirror Device), it is necessary to swing the movable mirror at a low voltage that can be applied by the integrated drive circuit. .

  According to the present embodiment, since the movable electrode and the fixed electrode are provided below the movable mirror, the optical device can be reduced in size in the surface direction of the substrate. Also, by increasing the drive torque of the movable mirror by increasing the number of fixed electrodes and movable electrodes installed, etc., it is possible to increase both the swing angle θ of the movable mirror and stably swing the movable mirror. Therefore, a large driving torque can be obtained for the same driving voltage. Even if the optical device is downsized, the movable mirror can be swung greatly.

  Further, the optical device of this embodiment can be suitably used for a raster scan type projector that projects an image by scanning a laser beam. In such a projector or the like, for example, raster scanning is performed using an optical device that deflects in a direction parallel to the scanning direction of laser light and an optical device that deflects in a direction perpendicular to the scanning direction of laser light. Can do. In this case, the optical device that deflects the laser beam in a direction perpendicular to the scanning direction of the laser beam is preferably provided with an actuator that can accurately control the angle of the movable mirror and that performs non-resonant driving. In an optical device that deflects the laser beam in a direction perpendicular to the scanning direction, when the accurate angle control of the movable mirror is insufficient, the projected image extends in a direction perpendicular to the scanning direction.

  Examples of the non-resonant drive type actuator include an electrostatic drive type and an electromagnetic drive type. The electrostatic drive type is advantageous in downsizing compared to the electromagnetic drive type in which a magnet or the like needs to be provided in order to generate a magnetic field. However, the conventional electrostatic drive type optical device has a problem in controllability of the swing angle of the movable mirror when the swing angle is increased.

  According to the present embodiment, it is possible to provide an electrostatic drive type optical device with high controllability that can stably swing the movable mirror even if the swing angle of the movable mirror is increased. As an optical device used for a raster scan type projector or the like, an electrostatic drive type optical device that is advantageous for downsizing can be used, which can contribute to downsizing and high performance of the projector.

  As in the case of the first embodiment, the size, shape, installation position, and the like of the fixed electrode and the movable electrode according to the present embodiment are not limited to the embodiment shown in FIG. 36 described above. Similarly to FIG. 11, the fixed electrode may be provided on only one of them, or a plurality of movable electrodes may be provided. Further, similarly to FIG. 12, a plurality of movable electrodes may be integrally formed by the base portion.

  Similarly to FIG. 13, the fixed electrode may include a notch in a portion located below the movable mirror. This makes it difficult for the movable mirror to come into contact with the fixed electrode, and the angle at which the movable mirror can swing can be increased.

  In addition, the optical apparatus according to the present embodiment may further include the swing angle detection device using the fixed electrode and the movable electrode described in the first and second embodiments. In the optical apparatus according to the embodiment, the electrode area can be increased without reducing the aperture ratio by extending the movable electrode or the like below the movable mirror. Even when the fixed electrode and the movable electrode are separately provided in one optical device, the characteristics of the detection device and the electrostatic drive actuator can be ensured. Furthermore, the optical device according to the present embodiment may include a control device that controls the output of the drive voltage generation device based on the swing angle of the movable mirror detected by the detection device.

  FIG. 38 is a diagram illustrating an optical device 400 according to the present embodiment. The optical device 400 is installed on the substrate 401, a pair of flexible beams 403a and 403b, a movable mirror 402 supported by the pair of flexible beams 403a and 403b, and a movable mirror 402. A mirror 406, two pairs of fixed electrodes 404a and 404b fixed to the substrate 401, and movable electrodes 405a and 405b fixed to the lower surface of the movable mirror 402 are provided. The fixed electrode 404 a and the fixed electrode 404 b have the same shape and size, and are provided at the same position in the direction perpendicular to the swing axis of the movable mirror 402. The movable electrode 405a and the movable electrode 405b have the same shape and size, and are provided at the same position in the direction perpendicular to the swing axis of the movable mirror 402.

That is, the area S _α of the counter electrode surface of the fixed electrode 404a and the movable electrode 405a obtained when the movable mirror 402 is swung at the swing angle θ is the area S _β of the counter electrode surface of the fixed electrode 404b and the movable electrode 405b. Is the same. The distance between the fixed electrode 404a and the movable electrode 405a and the distance between the fixed electrode 404b and the movable electrode 405b are both set to _dele .

  The movable electrode 405a and a pair of fixed electrodes 404a provided for this are a first combination, and the movable electrode 405b and a pair of fixed electrodes 404b provided for this are a second combination. And The electrostatic driving mechanism α2 is configured by the first combination. Similarly, the electrostatic drive mechanism β2 is configured by the second combination.

  On the upper surface of the substrate 401, there are provided a fixed electrode contact pad 421 that is electrically connected to the fixed electrodes 404a and 404b, a movable electrode contact pad 422a that is electrically connected to the movable electrode 405a, and a movable electrode contact pad 422b that is electrically connected to the movable electrode 405b. It has been. The movable electrode 405a and the movable electrode contact pad 422a are insulated from the movable electrode 405b and the movable electrode contact pad 422b.

  As shown in FIG. 39, the movable electrode contact pads 422a and 422b are connected to the drive signal generating device 460 via switches 461 and 462, and the fixed electrode contact pad 421 is grounded. The electrostatic drive mechanism α2 (movable electrode 405a and a pair of fixed electrodes 404a) and the electrostatic drive mechanism β2 (movable electrode 405b and a pair of fixed electrodes 404b) are wired in parallel.

  In this embodiment, by switching the switches 461 and 462, the swing angle of the movable mirror can be changed stepwise. When either one of the switch 461 or the switch 462 is turned on, the drive voltage V can be applied to either the electrostatic drive mechanism α2 or the electrostatic drive mechanism β2, and a drive torque due to electrostatic force is generated. As a result, the movable mirror 402 and the movable electrodes 405a and 405b are united and oscillate with the pair of flexible beams 403a and 403b as the oscillation axes. When both the switch 461 and the switch 462 are turned on, the drive voltage V can be applied to both the electrostatic drive mechanism α2 and the electrostatic drive mechanism β2. As a result, the driving torque due to the electrostatic force becomes larger, and the swing angle of the movable mirror 402 becomes larger.

  According to the present embodiment, it is possible to provide an optical device capable of controlling the swing angle in a step shape by switching on and off of the switch. In the above-described embodiment, two sets of electrostatic drive mechanisms each including a fixed electrode and a movable electrode are provided, but three or more sets may be provided. A large number of electrostatic drive mechanisms having different areas of the fixed electrode and the counter electrode surface of the movable electrode with respect to the swing angle θ of the movable mirror may be provided. In contrast to the above embodiment, only one movable electrode contact pad may be provided and grounded, and a plurality of fixed electrode contact pads may be provided and connected to the drive signal generating device.

Further, the areas of the fixed electrodes of the two electrostatic drive mechanisms and the counter electrode surfaces of the movable electrodes may be different with respect to the swing angle θ of the movable mirror. As a result, the torque _Tc caused by the electrostatic force generated when the drive voltage V is applied to one electrostatic drive mechanism is greater than the torque _Tc caused by the electrostatic force generated when the drive voltage V is applied to the other electrostatic drive mechanism. Can also be made larger. In this case, the swing angle of the movable mirror can be changed stepwise by selecting which electrostatic drive mechanism the drive voltage is applied to.

In addition, the torque T _c due to the electrostatic force generated by the two electrostatic drive mechanisms is different by making the areas of the fixed electrodes of the two electrostatic drive mechanisms different from the counter electrode surfaces of the movable electrodes with respect to the swing angle θ of the movable mirror. The fixed electrode and the movable electrode can be designed so as to act in opposite directions. For example, if each electrode is designed so that dS / dθ <0 for the combination of the first fixed electrode and the movable electrode, the torque Tc due to the electrostatic force is Tc = (nεV ² / (2d _ele )) (dS / Dθ), the torque T _c1 obtained by the first electrostatic drive mechanism is T _c1 <0. If each electrode is designed so that dS / dθ> 0 for the combination of the second fixed electrode and the movable electrode, the torque T _c2 obtained by the second electrostatic drive mechanism becomes T _c2 > 0. If the torques T _c1 and T _c2 due to the electrostatic force generated by the first and second electrostatic drive mechanisms act in opposite directions, for example, the movable mirror is swung, and a certain swing angle with respect to the substrate is obtained. In the case where the movable mirror is stopped, the time required for the movable mirror to stop while maintaining a predetermined swing angle can be shortened.

  As in the case of the third embodiment, the optical apparatus of the present embodiment may further include the swing angle detecting device described in the first and second embodiments. Furthermore, the optical device according to the present embodiment may include a control device that controls the output of the drive voltage generator based on the swing angle of the movable mirror detected by the detection device.

  As described in the first to fourth embodiments, according to the embodiment of the present invention, since the fixed electrode and the movable electrode are provided on the lower surface side of the movable mirror, the region where the movable electrode is provided is provided on the surface of the substrate. There is no need to provide it. The mirror area can be made larger than the substrate area, and the aperture ratio can be increased. In addition, since the fixed electrode and the movable electrode are provided below the movable mirror, the fixed electrode and the movable electrode are designed in comparison with the conventional case where the movable electrode is provided on the side surface of the movable mirror. It is difficult to be limited by the shape and size of the movable mirror and the size of the substrate. Compared to the prior art, the degree of freedom in designing the fixed electrode and the movable electrode is high.

  The movable electrode and the fixed electrode according to the embodiment of the present invention can be used as a detection device that detects the swing angle of the movable mirror. In this case, the fixed electrode and the movable electrode can be designed to be larger than the size of the movable mirror in the planar direction. Further, in order to increase the area of the electrode surface of the movable electrode, it is not necessary to reduce the area of the mirror provided on the surface of the movable mirror. Thereby, it is possible to improve both the detection sensitivity of the detection device and the aperture ratio.

  The movable electrode and the fixed electrode according to the embodiment of the present invention can be used as an electrostatic drive actuator for swinging the movable mirror. In this case, it is possible to achieve both the stable swing of the movable mirror and the increase of the swing angle of the movable mirror by increasing the drive torque. Even when the size of the movable mirror is small, a large driving torque Tc can be obtained.

  As mentioned above, although the Example of this invention was described in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

  The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

100, 200, 300, 400 Optical devices 101, 201, 301, 401 Substrate 102, 202, 302, 402 Movable mirrors 103a, 103b, 203a, 203b, 303a, 303b, 403a, 403b Flexible beams 104, 104c to 104f, 204a, 204b, 304a, 304b, 404a, 404b Fixed electrode 105, 205a, 205b, 305, 405a, 405b Movable electrode 106, 206, 306, 406 Mirror 114, 114c-114f Electrode surface 115 of fixed electrode Electrode surface of movable electrode 117, 350 Counter electrode surfaces 121, 221, 321a, 321b, 421 Fixed electrode contact pads 122, 222a, 222b, 322, 422a, 422b Movable electrode contact pads 123a, 123b, 223a, 22 b Drive coil contact pads 140, 240 Converters 141, 241a, 241b Capacitance-voltage converters 142, 242 Oscillating angle calculators 143, 243 Display unit 151 Base unit 153 Notch unit 161 Back surface layer 162 Intermediate layer 163 Surface layer 164, 166, 169 Insulating layers 165, 168, 170 Al layer 171 Driving coil upper layer 172 Driving coil lower layer 173, 175, 176 Resist 174 Movable electrode wiring 244 Differencer 460 Driving signal generator 461, 462 Switch

Claims (7)

A substrate,
A flexible beam;
A movable mirror supported by the flexible beam so as to be swingable with respect to the substrate at a position away from the substrate;
A fixed electrode provided on the substrate in such a manner that the electrode surface is perpendicular to a swinging axis on which the movable mirror swings at a position below the movable mirror;
A movable electrode fixed to the lower surface of the movable mirror so that the swing axis and the electrode surface are vertical;
When the movable mirror swings with respect to the substrate, the facing area between the electrode surface of the fixed electrode and the electrode surface of the movable electrode changes. It is integrally formed from a laminate including a conductive surface layer, a conductive back layer, and an insulating intermediate layer provided between the surface layer and the back layer,
The movable mirror includes the surface layer,
The fixed electrode includes the back layer,
The optical device according to claim 1, wherein the movable electrode includes the back surface layer, and is fixed to the movable mirror by the intermediate layer.   The optical apparatus according to claim 2, wherein a width in a direction perpendicular to the electrode surface of the movable electrode is larger than a width in a direction perpendicular to the electrode surface of the fixed electrode.   The movable electrode includes a base portion extending in a direction perpendicular to the electrode surface of the movable electrode, and a width of the base portion in a direction perpendicular to the electrode surface of the movable electrode is an electrode surface of the fixed electrode. The optical device according to claim 2, wherein the optical device is larger than a width in a direction perpendicular to the optical device. Including a combination of a first fixed electrode and a movable electrode that face each other when the movable mirror swings, and a combination of a second fixed electrode and a movable electrode;
When the movable mirror swings at a predetermined swing angle with respect to the substrate,
The area of the first counter electrode surface obtained by the combination of the first fixed electrode and the movable electrode and the area of the second counter electrode surface obtained by the combination of the second fixed electrode and the movable electrode The optical device according to claim 1, wherein the optical devices are different from each other.   The optical device according to claim 1, wherein a notch is provided in an upper part of the fixed electrode. A method for manufacturing an optical device according to claim 2,
A first step of forming the movable mirror and the flexible beam on the surface layer;
A second step of forming the fixed electrode and the movable electrode on the back surface layer;
And a third step of removing an intermediate layer between the fixed electrode and the movable mirror.

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