JP2008052220A - Tilt mirror element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve normal production yield in a manufacturing process in which a dual shaft electrostatic type tilt mirror element is easily manufactured. <P>SOLUTION: An element 1 is composed of an SOI substrate 100 which is composed of a first silicon layer 100a and a second silicon layer 100b which are connected to each other via an oxidized layer 120. The element 1 has: a mirror part 2; a movable frame 3 which supports the mirror part 2 via a first hinge 5; a fixed frame 4 which supports the movable frame 3 via a second hinge 6; a first comb-teeth electrode 7 disposed between the mirror part 2 and the movable frame 3; and a second comb-teeth electrode 8 disposed between the movable frame 3 and the fixed frame 4. The first comb-teeth electrode 7 is formed on the second silicon layer 100b and the first hinge 5 is formed on the first silicon layer 100a. The two silicon layers 100a and 100b of the mirror part 2 are electrically interconnected via contact holes 9. The tilt mirror element is easily manufactured because a pair of comb-teeth electrodes are simultaneously formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a two-axis electrostatic tilt mirror element that rotates a mirror portion having a mirror surface around two rotation axes to deflect or scan a light beam incident from the outside in a two-dimensional manner.

  Conventionally, for example, optical devices such as a barcode reader and a projector are equipped with a tilt mirror element that swings a mirror portion provided with a mirror surface and scans a light beam incident on the mirror surface. . As such a tilt mirror element, for example, a small one formed by using micromachining technology, the mirror portion is rotated around two rotation axes by electrostatic force, and the light beam is two-dimensionally moved. A two-axis electrostatic type that deflects or scans is known (for example, see Patent Document 1).

  Such a tilt mirror element has a mirror part, a movable frame that supports the mirror part, and a fixed frame that supports the movable frame. The mirror part and the movable frame, and the movable frame and the fixed frame are connected to each other by hinges. A pair of comb-shaped electrodes that mesh with each other are formed between the mirror portion and the movable frame, and between the movable frame and the fixed frame. The comb electrodes are formed, for example, so that the electrodes are engaged with each other at intervals of about 2 μm to 5 μm, and an electrostatic force is generated when a voltage is applied between the electrodes. In such a tilt mirror element, each of the mirrors is twisted by a driving force generated by a comb-shaped electrode between the mirror portion and the movable frame and a comb-shaped electrode between the movable frame and the fixed frame. The part rotates with respect to the movable frame, and the movable frame rotates with respect to the fixed frame. As a result, the mirror unit rotates around the two rotation axes to perform a scanning operation.

Here, in order to rotate the mirror part around two rotation axes, the comb-tooth electrode provided between the mirror part and the movable frame is connected to the mirror part electrode and the movable frame side electrode to each other. It must be configured in an insulated state so that a voltage can be applied between both electrodes. Therefore, for example, in Patent Document 1, a hinge configured by an SOI (Silicon on Insulator) substrate having two silicon layers insulated from each other, a hinge connecting the mirror portion and the movable frame to one silicon layer, and the comb electrode A tilt mirror element having a configuration in which an electrode on the mirror part side is formed and an electrode on the movable frame side among the comb-tooth electrodes is formed on the other silicon layer is shown. In this tilt mirror element, the electrodes that are opposed to each other and that constitute the comb electrode are not formed on the same silicon layer, so that the mirror part and the movable frame are electrically insulated, and a voltage is applied to the comb electrode. Can be applied. Further, as a structure different from such a structure, for example, a part of the movable frame where a hinge for connecting the mirror portion and the movable frame is formed and an electrode on the movable frame side of the comb-shaped electrode is formed. There is also known a tilt mirror element in which an insulating separation structure is formed on a movable frame so as to insulate it from a portion that is present.
Japanese Patent Laid-Open No. 2004-13099

  However, in order to manufacture the tilt mirror element as described in Patent Document 1 as described above, when forming a pair of comb electrodes, electrodes on the mirror portion side are formed from the surface of each silicon layer of the SOI substrate. And the electrode on the movable frame side must be formed respectively. Therefore, when forming electrodes etc. by etching or the like, it is necessary to precisely position each other so that the electrodes mesh with each other at a narrow interval, it is difficult to manufacture the element, and it is difficult to increase the yield rate. There was a problem.

  On the other hand, in order to form an insulating separation structure in the movable frame, a step of forming a groove in a portion where the insulating separation structure in the movable frame is provided, a step of oxidizing the end surface of the groove, a step of embedding polysilicon or the like in the groove, In addition, it is necessary to perform a step of polishing the surface of the substrate on which the tilt mirror element is formed. For this reason, the manufacturing process of the tilt mirror element becomes complicated, and it is difficult to manufacture the tilt mirror element.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a biaxial electrostatic tilt mirror element that can be easily manufactured and has a high yield rate at the time of manufacture.

  In order to achieve the above object, the invention of claim 1 includes a mirror part having a mirror surface that reflects light incident from the outside, a movable frame that supports the mirror part, a fixed frame that supports the movable frame, A first hinge that serves as one axis that couples the mirror part and the movable frame; a second hinge that serves as another axis that couples the movable frame and the fixed frame; and the mirror part and the movable frame. Are arranged so as to mesh with each other, and are arranged so as to mesh with each other with the pair of first comb electrodes for giving a rotational motion to the mirror part, and the movable frame and the fixed frame, and rotate with respect to the movable frame. A biaxial electrostatic tilt mirror element having a pair of second comb electrodes for imparting motion, wherein the tilt mirror element includes two insulating layers formed of an insulating film. The SOI substrate is composed of an SOI (Silicon on Insulator) substrate bonded to each other. The first hinge is formed on one silicon layer of the SOI substrate, and the other silicon layer of the SOI substrate is formed on the other silicon layer. Is provided with a conductive structure in which the first comb-shaped electrode is formed and electrically connects the two silicon layers of the SOI substrate where the mirror portion is formed, and the conductive structure is Thus, the electrode on the mirror part side of the first comb-tooth electrode is set to the same potential as the silicon layer on which the first hinge is formed.

  According to a second aspect of the present invention, in the tilt mirror element according to the first aspect, the mirror surface is disposed on a silicon layer on which the first hinge is formed.

  According to a third aspect of the present invention, in the tilt mirror element according to the first aspect, the mirror surface is disposed on a silicon layer on which the first comb electrode is formed.

  According to invention of Claim 1, a pair of 1st comb-tooth electrode is formed in the silicon layer different from the silicon layer in which the 1st hinge is formed, and it is a mirror among 1st comb-tooth electrodes. Since the part-side electrode is configured to have the same potential as the silicon layer on which the first hinge is formed, each electrode constituting a pair of comb electrodes is formed simultaneously to produce a tilt mirror element. can do. A complicated process of forming an insulating separation structure on the movable frame is not required, and a structure in which the mirror portion and the movable frame are insulated can be easily formed, so that the tilt mirror element can be easily manufactured. Therefore, the yield rate of tilt mirror elements is increased.

  According to the invention of claim 2, since the mirror surface is disposed on the silicon layer on which the first hinge is formed, it depends on the thickness of the silicon layer on which the first comb electrode is formed. The thickness of the silicon layer on which the mirror surface is disposed can be arbitrarily selected from the two silicon layers formed with the mirror portion. Therefore, the silicon layer on which the first comb electrode is formed is thickened to increase the driving force for rotating the mirror part, and the silicon layer on which the mirror surface is disposed is thinned to reduce the weight of the mirror part. By doing so, it is possible to increase the resonance frequency and the swing angle of the mirror part and to improve the performance of the tilt mirror element.

  According to invention of Claim 3, since the mirror surface is arrange | positioned by the silicon layer in which the 1st comb-tooth electrode is formed, irrespective of the thickness of the silicon layer in which the mirror surface is arrange | positioned The thickness of the silicon layer on which the first hinge is formed can be arbitrarily selected from the two silicon layers on which the mirror part is formed, and the spring constant of the first hinge can be set within a wide range. Thus, the resonance frequency of the mirror portion can be adjusted in a wide range.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. 1 (a), (b), FIG. 2, and FIGS. 3 (a), (b), (c), and (d) are examples of tilt mirror elements (hereinafter referred to as elements) according to the present embodiment. Indicates. The element 1 is a small device mounted on an optical device such as a barcode reader, an external screen or the like, or an optical device such as an optical switch, and is incident from an external light source (not shown). It has a function of performing a scanning operation of a light beam or the like.

  First, the configuration of the element 1 will be described below. The element 1 includes a three-layer SOI (Silicon on Insulator) substrate formed by bonding a conductive first silicon layer 100a and a second silicon layer 100b via a silicon oxide film (insulating film) 120. 100. Since the oxide film 120 has an insulating property, the first silicon layer 100a and the second silicon layer 100b are insulated from each other. The element 1 is, for example, a rectangular parallelepiped element having a substantially square shape with a side of about several millimeters when viewed from above, and is disposed on a support substrate 150 such as glass and mounted on an optical device or the like. The support substrate 150 is shown in FIGS. 3C and 3D, and is not shown in FIGS. 1A, 1B, 1C, and 2D.

  The element 1 has a substantially rectangular shape in a top view and a mirror portion 2 having a mirror surface 20 formed on the upper surface, a movable frame 3 formed in a substantially rectangular annular shape so as to surround the periphery of the mirror portion 2, and movable The frame 3 is formed so as to surround the periphery of the frame 3 and has a fixed frame 4 that serves as a side peripheral portion of the element 1. The mirror part 2 and the movable frame 3 are formed as two beam-shaped first hinges formed so as to be orthogonal to each surface from two mutually facing side surfaces of the mirror part 2 so as to form one axis side by side with each other. 5 are connected. On the other hand, the movable frame 3 and the fixed frame 4 are formed by two beam-like second hinges 6 formed so as to form one axis along with each other in a direction orthogonal to the longitudinal direction of the first hinge 5. It is connected. The first hinge 5 and the second hinge 6 are formed such that their respective axes pass through the center of gravity of the mirror unit 2 when viewed from above. The mirror unit 2 is supported by the movable frame 3 so as to be rotatable with respect to the movable frame 3 about the first hinge 5 as a rotation axis. On the other hand, the movable frame 3 is supported by the fixed frame 4 so as to be rotatable with respect to the fixed frame 4 with the second hinge 6 as a rotation axis. In other words, the mirror unit 2 is configured to be two-dimensionally rotatable around two axes respectively constituted by the first hinge 5 and the second hinge 6. Hereinafter, the longitudinal direction of the first hinge 5 is referred to as an X direction, the longitudinal direction of the second hinge 6 is referred to as a Y direction, and a perpendicular direction orthogonal to the X direction and the Y direction is referred to as a Z direction.

  This element 1 rotates the mirror part 2 using an electrostatic force, and a first comb-tooth electrode is provided at a portion where the first hinge 5 between the mirror part 2 and the movable frame 3 is not formed. 7 is formed, and a second comb electrode 8 is formed at a portion where the second hinge 6 between the movable frame 3 and the fixed frame 4 is not formed. The first comb-teeth electrode 7 includes an electrode 2a formed in a comb-teeth shape on two side surfaces substantially orthogonal to the X direction of the mirror portion 2, and a comb tooth on a portion of the movable frame 3 facing the electrode 2a. A pair of electrodes 3a formed in a shape are arranged so as to mesh with each other. The second comb-teeth electrode 8 is formed on each of the movable frame 3 on the two side surfaces that are substantially orthogonal to the Y direction, respectively, and on the portion of the fixed frame 4 that faces the electrode 3b. The electrodes 4a are arranged so as to mesh with each other. In the first comb electrode 7 and the second comb electrode 8, the gap between the electrodes 2 a and 3 a and the gap between the electrodes 3 b and 4 a are configured to have a size of about 2 μm to 5 μm, for example. Yes. The first comb-teeth electrode 7 and the second comb-teeth electrode 8 are applied between the electrodes 2a and 3a, or between the electrodes 2a and 3a, or between the electrodes 2a and 3a, or between the electrodes An electrostatic force acting in the direction attracting each other is generated in 3b and 4a.

  The mirror unit 2, the movable frame 3, the fixed frame 4 and the like are each formed by processing the SOI substrate 100 using a micromachining technique as will be described later, and each of the above three layers of the SOI substrate 100. It is configured. Hereinafter, the structure of each layer of the SOI substrate 100 will be described for each part of the element 1.

  A first hinge 5 is connected to a portion of the mirror portion 2 formed by the first silicon layer 100a. In addition, an electrode 2 a constituting the first comb-tooth electrode 7 is formed in a portion of the mirror portion 2 formed by the second silicon layer 100 b. In the mirror unit 2, the mirror surface 20 is formed on the upper surface of the first silicon layer 100 a that is the upper surface of the mirror unit 2 such that the substantially Z direction is the normal direction when the mirror unit 2 is stationary. Yes. The mirror surface 20 is an aluminum film, for example, and reflects a light beam incident from the outside. The material of the mirror surface 20 is not limited to this, and various materials such as gold can be selected according to the type of light beam scanned by the element 1. On the lower surface of the second silicon layer 100b, which is the lower surface of the mirror portion 2, a hollow portion 2c is formed by leaving the side surface of the mirror portion 2 so that the oxide film 120 is exposed. Thereby, the mirror part 2 is reduced in weight compared with the case where the thinning part 2c is not formed, and the swing angle of the mirror part 2 can be increased.

  Of the movable frame 3, the part formed by the first silicon layer 100 a is oxidized downward so as to connect the part connected to the first hinge 5 and the part connected to the second hinge 6. Ribs are formed on the film 120. A portion of the movable frame 3 formed by the oxide film 120 and the second silicon layer 100 b is formed in an annular shape so as to surround the mirror portion 2. The second hinge 6 is also connected to the oxide film 120 and the second silicon layer 100b among the three layers of the SOI substrate 100 forming the movable frame 3, and the fixed frame 4 and the movable frame 3 are connected to the SOI substrate 100. The three layers of the substrate 100 are connected to each other. In the movable frame 3, the second silicon layer 100 b is formed with an electrode 3 a formed so as to face the electrode 2 a of the mirror portion 2 and an electrode 3 b constituting the second comb-tooth electrode 8. . The electrode 4 a that meshes with the electrode 3 b is formed on the second silicon layer 100 b of the fixed frame 4.

  Thus, in the element 1, the first hinge 5 is formed in the first silicon layer 100a out of the first silicon layer 100a and the second silicon layer 100b that are insulated from each other. Both the first comb-tooth electrode 7 and the second comb-tooth electrode 8 are formed on the second silicon layer 100b.

  Here, a plurality of (for example, eight) contact holes (conductive structures) 9 are formed in a portion of the upper surface of the first silicon layer 100a of the mirror portion 2 where the mirror surface 20 is not formed. This contact hole 9 penetrates through the first silicon layer 100a and the oxide film 120, and a conductive metal such as copper is formed in a through hole formed so that the second silicon layer 100b is exposed on the upper surface. Filled and configured. The first silicon layer 100a and the second silicon layer 100b constituting the mirror part 2 are electrically connected via the contact hole 9 provided in this way, and the first comb-tooth electrode 7 Of these, the electrode 2a on the mirror part 2 side is configured to have the same potential as that of the first silicon layer 100a. In addition, in the second silicon layer 100b that forms the fixed frame 4, a portion where the second hinge 6 is connected and a portion where the electrode 4a constituting the second comb-tooth electrode 8 is formed The insulating groove 4g dug so as to reach the oxide film 120 is formed between the two parts, thereby being electrically insulated. That is, in the present embodiment, a portion 4c formed by the first silicon layer 100a in the fixed frame 4 has the same potential as the electrode 2a, and the second hinge 6 formed by the second silicon layer 100b is connected. The formed portion 4d has the same potential as the electrodes 3a and 3b, and the other portion 4e formed by the second silicon layer 100b is formed to be the electrode 4a. And this element 1 changes the electric potential of the electrode pad (not shown) provided in each site | part 4c, 4d, 4e by changing the electric potential to the 1st comb-tooth electrode 7 and the 2nd comb-tooth electrode 8. Is applied so that the mirror unit 2 can be rotated.

  Next, the operation of the element 1 configured as described above will be described. The first comb-teeth electrode 7 and the second comb-teeth electrode 8 each operate as a so-called vertical electrostatic comb, and the mirror unit 2 includes the first comb-teeth electrode 7 and the second comb-teeth electrode 8 that are predetermined. It is driven by generating a driving force at a driving frequency of. The first comb-tooth electrode 7 and the second comb-tooth electrode 8 are obtained by, for example, periodically changing the potentials of the electrodes 2a and 4a while the electrodes 3a and 3b are connected to the reference potential. Driven to generate electrostatic force. In the element 1, each of the first comb-tooth electrode 7 and the second comb-tooth electrode 8 is configured to generate a driving force periodically when a rectangular wave voltage is applied, for example.

  In many cases, the mirror part 2 and the movable frame 3 formed as described above are inclined in a very slight but not horizontal state even in a stationary state due to an internal stress or the like generated at the time of molding. Therefore, for example, when the first comb-tooth electrode 7 is driven, a driving force in a direction substantially perpendicular to the mirror portion 2 is applied even when the first comb-tooth electrode 7 is in a stationary state, and the mirror portion 2 causes the first hinge 5 to rotate. The first hinge 5 is rotated while being twisted. Then, when the driving force of the first comb electrode 7 is released when the mirror portion 2 is in a posture such that the electrodes 2a and 3a are completely overlapped, the mirror portion 2 has the first force due to its inertial force. The rotation is continued while twisting the hinge 5. Then, when the inertial force in the turning direction of the mirror part 2 and the restoring force of the first hinge 5 become equal, the turning of the mirror part 2 in that direction stops. At this time, the first comb-teeth electrode 7 is driven again, and the mirror unit 2 moves in the opposite direction to the previous direction by the restoring force of the first hinge 5 and the driving force of the first comb-teeth electrode 7. Start turning. The mirror part 2 repeats the rotation by the driving force of the first comb electrode 7 and the restoring force of the first hinge 5 and swings around the first hinge 5. The movable frame 3 also repeats rotation by the driving force of the second comb-tooth electrode 8 and the restoring force of the second hinge 6 in substantially the same manner as when the mirror unit 2 rotates, and moves around the second hinge 6. Swing. At this time, since the posture of the mirror unit 2 changes according to the swing of the movable frame 3, the mirror unit 2 repeats two-dimensional swing.

  Here, the first comb-teeth electrode 7 is driven by applying a voltage having a frequency approximately twice the resonance frequency of the vibration system constituted by the mirror portion 2 and the first hinge 5. The second comb electrode 8 is driven by applying a voltage having a frequency approximately twice the resonance frequency of the vibration system constituted by the mirror unit 2, the movable frame 3, and the second hinge 6. Thereby, the mirror part 2 is driven with a resonance phenomenon, and the swing angle thereof is increased. Note that the voltage application mode and drive frequency of the first comb-tooth electrode 7 and the second comb-tooth electrode 8 are not limited to those described above, and for example, the drive voltage is configured to be applied in a sine waveform. Alternatively, the potentials of the electrodes 3a and 3b may be configured to change with the potentials of the electrodes 2a and 4a.

  Next, the manufacturing process of the element 1 will be described with reference to FIGS. 4 (a), (b), (c) and FIGS. 5 (a), (b), (c). For example, a plurality of elements 1 are simultaneously formed on an SOI substrate 100 having a size of about 4 inches, and then diced to be divided into individual elements 1 to be manufactured. In the SOI substrate 100 before processing, the second silicon layer 100b is configured to be thicker than a predetermined thickness.

  First, in the first silicon layer 100a of the SOI substrate 100, the mirror portion 2, the first hinge 5 connected to the mirror portion 2, and the portion connecting the first hinge 5 to the fixed frame 4 are formed by etching. Further, a through hole 9a is formed simultaneously with the mirror portion 2 and the like in the peripheral portion of the portion of the upper surface of the mirror portion 2 where the mirror surface 20 is formed (see FIGS. 4A, 4B, and 4C). ). Next, in order to electrically connect the first silicon layer 100a and the second silicon layer 100b in the mirror part 2, a metal such as copper is embedded in the through hole 9a to form the contact hole 9. Further, a thin film such as aluminum for improving the reflectance of the light beam is deposited on the mirror portion 2 to form the mirror surface 20 (FIGS. 5A, 5B, and 5C). After the upper portion of the element 1 is processed in this manner, the second silicon layer 100b is polished and thinned to a predetermined thickness. And in the 2nd silicon layer 100b, the part used as the lower part of the mirror part 2, the movable frame 3, the fixed frame 4, the 1st comb-tooth electrode 7, and the 2nd comb-tooth electrode 8, and these are connected. The second hinge 6 to be formed is formed by etching. The order of formation of the contact hole 9, the mirror surface 20, the comb electrodes 7 and 8, and the hinges 5 and 6 may be changed depending on the process. Thereafter, the lower surface of the fixed frame 4 is joined to the support substrate 150 to reinforce the element 1, and the element 1 as shown in FIGS. 3A, 3B, 3C, and 3D is manufactured.

  As described above, in the present embodiment, each of the electrodes 2a, 3a, 3b, and 4a constituting the pair of first comb-tooth electrode 7 and second comb-tooth electrode 8 is formed using the SOI substrate 100. The device 1 is formed by forming the silicon layer 100b at the same time. Therefore, a complicated process for forming an insulating separation structure on the movable frame 3 is not required, and a structure in which the mirror portion 2 and the movable frame 3 are insulated can be easily formed. And the yield rate of the element 1 is increased. Further, since the mirror surface 20 is formed in the first silicon layer where the first hinge 5 is formed, the mirror surface 20 of the two silicon layers 100a and 100b where the mirror part 2 is formed is the mirror surface. The thickness of the first silicon layer 100a on which the surface 20 is formed can be arbitrarily selected regardless of the thickness of the second silicon layer 100b. Therefore, the second silicon layer 100b on which the first comb-teeth electrode 7 is formed is thickened to increase the driving force for rotating the mirror part 2, and the first silicon layer 100a is thinned to make the mirror part 2 thin. By reducing the weight, the resonance frequency and deflection angle of the mirror unit 2 can be increased, and the element 1 can be improved in performance.

  Next, an element according to a second embodiment of the present invention will be described with reference to FIGS. 6 (a), (b), (c), and (d). In each of the following embodiments, the same components as those in the first embodiment described above are denoted by the same reference numerals, and only the portions different from those in the above embodiment will be described.

  The element 31 according to the second embodiment is different from the element 1 described above in that the mirror surface 30 is formed on the second silicon layer 100b on which the first comb-tooth electrode 7 is formed. . In other words, the element 31 is, unlike the element 1 described above, of the second silicon layer 100b of the SOI substrate 100 where the first comb-tooth electrode 7 and the second comb-tooth electrode 8 are formed. The surface becomes the upper surface on which the mirror surface 30 is formed, and the surface of the first silicon layer 100a on which the first hinge 5 is formed becomes the lower surface.

  In the element 31, instead of the contact hole 9 described above, a contact hole 39 formed so as to penetrate the second silicon layer 100b and the oxide film 120 from the upper surface of the element 31 is formed in the mirror portion 32. Yes. That is, the electrode 32a on the mirror part 32 side of the first comb-tooth electrode 7 is electrically connected to the part 4c of the fixed frame 4 constituted by the first silicon layer 100a through the contact hole 39. Are at the same potential. Further, on the lower surface of the first silicon layer 100a in the mirror portion 32, a hollow portion 32c is formed by leaving the side surface of the mirror portion 32 so that the oxide film 120 is exposed downward. Thereby, the mirror part 32 is reduced in weight compared with the case where the lightening part 32c is not formed, and the swing angle of the mirror part 32 can be increased.

  Next, a manufacturing process of the element 31 will be described with reference to FIGS. 7A, 7 </ b> B, and 7 </ b> C and FIGS. 8A, 8 </ b> B, and 8 </ b> C. Also when the element 31 is manufactured, the processing starts from the processing of the first silicon layer 100a in the SOI substrate 100 in substantially the same manner as in the first embodiment. First, in the first silicon layer 100a of the SOI substrate 100, the mirror portion 32, the first hinge 5 connected to the mirror portion 32, and the portion connecting the first hinge 5 to the fixed frame 4 are formed by etching. At the same time, a lightening portion 32c is formed on the lower surface of the mirror portion 32 (see FIGS. 7A, 7B, and 7C).

  Next, the second silicon layer 100b is processed. First, the second silicon layer 100b is polished and thinned to a predetermined thickness. Then, in the thinned second silicon layer 100b, a contact hole 39 is formed by embedding a metal such as copper after forming a through hole in the peripheral portion of the portion where the mirror surface 30 is formed. Further, the mirror surface 30 is formed on the upper surface of the second silicon layer 100b as in the first embodiment (FIGS. 8A, 8B, and 8C). Then, in the second silicon layer 100b, the movable frame 3 and the fixed frame 4, the first comb electrode 7 and the second comb electrode 8, and the second hinge 6 connecting them are etched. Form. Note that the order of forming the contact hole 39, the mirror surface 30, the comb-tooth electrodes 7, 8, the hinges 5, 6, etc. may be changed depending on the convenience of the process. Thereafter, the lower surface of the fixed frame 4 is joined to the support substrate 150 to reinforce the element 31, and the element 31 as shown in FIGS. 6A, 6B, 6C, and 6D is manufactured.

  Thus, in the second embodiment, since the mirror surface 30 is formed on the second silicon layer 100b on which the first comb-tooth electrode 7 is formed, the mirror portion 32 is formed. Of the two silicon layers 100a and 100b in the region, the thickness of the first silicon layer 100a on which the first hinge 5 is formed is arbitrarily selected regardless of the thickness of the second silicon layer 100b. Can do. Accordingly, the setting range of the spring constant of the first hinge 5 is widened, and the range in which the resonance frequency of the mirror part 32 can be adjusted is widened. In addition, since the element 31 can be manufactured by simultaneously forming the electrodes 2a, 3a, 3b, and 4a constituting the first comb-tooth electrode 7 and the second comb-tooth electrode 8, the element 31 can be easily formed. It can be manufactured, and the yield rate of the element 31 is increased.

  In addition, this invention is not limited to the structure of the said embodiment, A various deformation | transformation is possible suitably in the range which does not change the meaning of invention. For example, the first silicon layer and the second silicon layer in the mirror portion may be electrically connected to each other by providing another conductive structure instead of the contact hole as described above. Further, the first comb-tooth electrode and the second comb-tooth electrode may be formed in different silicon layers. That is, in the present invention, the first hinge that connects the mirror part and the movable frame and the first comb-tooth electrode between the mirror part and the movable frame are arranged in different silicon layers, and the mirror part 2 By providing a conductive structure that electrically connects two silicon layers to each other and forming a tilt mirror element using an SOI substrate, a pair of comb-tooth electrodes can be simultaneously formed to easily manufacture the tilt mirror element. it can.

(A) is a perspective view which shows the tilt mirror element based on the 1st Embodiment of this invention, (b) is a perspective view which shows the lower surface of (a). The perspective view which shows the cross section in the SS line | wire of Fig.1 (a). (A) is a plan view of the tilt mirror element, (b) is a back view of (a), (c) is a side sectional view taken along line AA of (a), and (d) is B- of (a). The sectional side view in the B line. (A) is a top view which shows the manufacturing process of the said tilt mirror element, (b) is a sectional side view in the AA line of (a), (c) is a sectional side view in the BB line of (a). 4A is a plan view showing a process subsequent to FIG. 4 in the manufacturing process of the tilt mirror element, FIG. 4B is a side sectional view taken along line AA in FIG. 4A, and FIG. The sectional side view in the B line. (A) is a top view which shows the tilt mirror element based on the 2nd Embodiment of this invention, (b) is a back view of (a), (c) is a sectional side view in the AA of (a), (D) is a sectional side view in the BB line of (a). (A) is a top view which shows the manufacturing process of the said tilt mirror element, (b) is a sectional side view in the AA line of (a), (c) is a sectional side view in the BB line of (a). (A) is a top view which shows the process after FIG. 7 of the manufacturing process of the said tilt mirror element, (b) is a sectional side view in the AA of (a), (c) is B- of (a). The sectional side view in the B line.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,31 Tilt mirror element 2,32 Mirror part 2a, 32a (Mirror part side) electrode 3 Movable frame 4 Fixed frame 5 1st hinge 6 2nd hinge 7 1st comb-tooth electrode 8 2nd comb-tooth Electrode 9,39 Contact hole (conductive structure)
20, 30 Mirror surface 100 SOI substrate 100a First silicon layer 100b Second silicon layer 120 Oxide film (insulating film)

Claims (3)

A mirror portion having a mirror surface that reflects light incident from the outside, a movable frame that supports the mirror portion, a fixed frame that supports the movable frame, and a single shaft that connects the mirror portion and the movable frame; The first hinge, the second hinge serving as another shaft for connecting the movable frame and the fixed frame, and the mirror portion and the movable frame are arranged to mesh with each other and rotate to the mirror portion. A pair of first comb-teeth electrodes for imparting motion, and a pair of second comb-teeth electrodes disposed to mesh with the movable frame and the fixed frame, and for imparting rotational motion to the movable frame; In a biaxial electrostatic tilt mirror element comprising:
The tilt mirror element is composed of an SOI (Silicon on Insulator) substrate in which two silicon layers are bonded to each other via an insulating film,
The first hinge is formed on one silicon layer of the SOI substrate,
The first comb electrode is formed on the other silicon layer of the SOI substrate,
A conductive structure that electrically connects the two silicon layers of the SOI substrate where the mirror portion is formed, and the mirror portion of the first comb-shaped electrode via the conductive structure. A tilt mirror element characterized in that a side electrode has the same potential as the silicon layer on which the first hinge is formed.   2. The tilt mirror element according to claim 1, wherein the mirror surface is disposed on a silicon layer on which the first hinge is formed. 2. The tilt mirror element according to claim 1, wherein the mirror surface is disposed on a silicon layer on which the first comb electrode is formed.

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