JP2012115981A - Micro-oscillation element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a micro-oscillation element which is suitable for adjusting a natural frequency related to the oscillation of an oscillation part.SOLUTION: The micro-oscillation element X2 includes an oscillation part 210, a frame 220, and a connection part 230 that connects the oscillation part to the frame and prescribes an oscillation axis A2. The connection part includes a plurality of torsion bars 231, 232, 233 that juxtapose to each other. Two torsion bars selected from the plurality of the torsion bars can relatively come close to each other and move away from each other. The oscillation part includes an oscillating main part 211 and first movable parts 212A, 212B that are mounted on the oscillating main part 211 and can be shifted in a direction that crosses the oscillation axis. The frame includes a frame main part and second movable parts 223A, 223B that are mounted on the frame main part can be shifted in the same direction as the first movable parts 212A, 212B. One of the torsion bars 232, 233 included in the connection part connects the first and second movable parts.

Description

  The present invention relates to a micro oscillating device having a micro oscillating portion, such as a micromirror device, an acceleration sensor, and an angular velocity sensor.

  In recent years, in various technical fields, devices having a micro structure formed by a micromachining technique have been applied. Such an element includes a micro oscillating element having a minute movable part or oscillating part, such as a micromirror element, an acceleration sensor, and an angular velocity sensor. The micromirror element is used as an element having a light reflection function in the fields of optical disc technology and optical communication technology, for example. The acceleration sensor and the angular velocity sensor are used for applications such as robot posture control and camera shake prevention, for example.

  The micromirror element includes a mirror surface for reflecting light, and the light reflection direction can be changed by swinging the mirror surface. Many devices employ electrostatically driven micromirror elements that use electrostatic force to swing the mirror surface. The electrostatic drive type micromirror element can be roughly classified into two types: a micromirror element manufactured by a so-called surface micromachining technique and a micromirror element manufactured by a so-called bulk micromachining technique.

  In surface micromachining technology, a material thin film corresponding to each component part is processed into a desired pattern on a substrate, and such a pattern is sequentially laminated to configure elements such as a support, a mirror surface, and an electrode part. Each part to be formed and a sacrificial layer to be removed later are formed. On the other hand, in the bulk micromachining technique, the material substrate itself is etched to form a support, a mirror portion, and the like into a desired shape, and a mirror surface and electrodes are formed as a thin film as necessary. The bulk micromachining technology is described in, for example, the following Patent Documents 1 to 3.

Japanese Patent Laid-Open No. 10-190007 Japanese Patent Laid-Open No. 10-270714 Japanese Patent Laid-Open No. 2000-31502

  One of the technical matters required for the micromirror element is that the flatness of the mirror surface responsible for light reflection is high. However, according to the surface micromachining technology, since the mirror surface finally formed is thin, the mirror surface is easily curved, and thus it is difficult to achieve high flatness in a large-area mirror surface. On the other hand, according to the bulk micromachining technology, a relatively thick material substrate itself is cut by etching technology to form a mirror portion and a mirror surface is provided on the mirror portion. Also, its rigidity can be ensured. As a result, it is possible to form a mirror surface having sufficiently high optical flatness.

  26 and 27 show a conventional electrostatically driven micromirror element X4 manufactured by a bulk micromachining technique. FIG. 26 is an exploded perspective view of the micromirror element X4, and FIG. 27 is a cross-sectional view taken along line XXVII-XXVII in FIG. 26 in the assembled micromirror element X4.

  The micromirror element X4 has a structure in which a mirror substrate 40 and a base substrate 46 are stacked. The mirror substrate 40 includes a mirror portion 41, a frame 42, and a pair of torsion bars 43 that connect them. The outer shape of the mirror portion 41, the frame 42, and the pair of torsion bars 43 in the mirror substrate 40 is formed by etching a predetermined material substrate such as a conductive silicon substrate from one side thereof. Can do. A mirror surface 44 is provided on the surface of the mirror portion 41. A pair of electrodes 45 a and 45 b are provided on the back surface of the mirror portion 41. The pair of torsion bars 43 defines an axis A <b> 4 in the later-described rotational operation of the mirror unit 41. The base substrate 46 is provided with an electrode 47a facing the electrode 45a of the mirror part 41 and an electrode 47b facing the electrode 45b.

  In the micromirror element X4, when a potential is applied to the frame 42 of the mirror substrate 40, the electrodes 45a and 45a are connected via a pair of torsion bars 43 and a mirror part 41 that are integrally formed of the same conductive material as the frame 42. A potential is transmitted to the electrode 45b. Therefore, by applying a predetermined potential to the frame 42, the electrodes 45a and 45b can be positively charged, for example. In this state, when the electrode 47a of the base substrate 46 is negatively charged, an electrostatic attractive force is generated between the electrode 45a and the electrode 47a, and the mirror unit 41 twists the pair of torsion bars 43 as shown in FIG. Rotate in the direction of arrow M4. The mirror part 41 can swing to an angle at which the electrostatic attractive force between the electrodes and the sum of the torsional resistance forces of the torsion bars 43 are balanced. Instead, when the electrode 47b is negatively charged while the electrodes 45a and 45b of the mirror part 41 are positively charged, an electrostatic attractive force is generated between the electrode 45b and the electrode 47b. It rotates in the direction opposite to the arrow M4. The reflection direction of the light reflected by the mirror surface 44 can be switched by the swing drive of the mirror part 41 as described above.

  For a micro oscillating device having an oscillating portion, the natural frequency or resonance frequency related to the oscillating operation of the oscillating portion is decisive for the operating speed and the operation amplitude (maximum value of the oscillating angle) of the oscillating portion. It is an important characteristic that has a significant impact. In the conventional micro oscillating device, in order to adjust the natural frequency of the oscillating unit after the device is once completed, the oscillating unit is subjected to trimming using a laser or a focused ion beam. The rocking part is cut to reduce the mass of the rocking part, and hence the inertia, or by trimming the connecting part that connects the rocking part and the frame (fixed part), It is necessary to reduce the torsion spring constant of the connecting portion by cutting (the natural frequency tends to increase as the inertia of the swinging portion decreases, and the natural frequency tends to decrease as the torsion spring constant of the connecting portion decreases. It is in). For example, in order to adjust the natural frequency of the mirror part 41 (swing part) in the micromirror element X4, trimming is applied to the mirror part 41 to reduce the inertia of the mirror part 41, or the mirror part 41 It is necessary to reduce the torsion spring constant of the torsion bar 43 by trimming the torsion bar 43 connecting the frame 42 (fixed part). The necessity of adjusting the natural frequency of the oscillating portion after the device is once completed is particularly high when mass-producing the same micro oscillating device in design by batch processing on a wafer. This is because in the case of mass production, variations in the natural frequency occur between elements due to errors in processing dimensions at the oscillating part and the connecting part.

  However, the adjustment of the natural frequency by the ex-post mechanical processing (trimming processing) as described above is not preferable because it increases the manufacturing process of the micro oscillating device and increases the manufacturing cost. In addition, according to the ex-post mechanical processing as described above, it can only be adjusted so that the inertia of the swinging part and the torsion spring constant of the connecting part are reduced, and in adjusting the natural frequency of the swinging part. The degree of freedom is low.

  The present invention has been conceived under such circumstances, and provides a micro oscillating device suitable for adjusting the natural frequency (resonance frequency) related to the oscillating operation of the oscillating portion. The purpose is to do.

  The micro oscillating device provided by the present invention is formed on a material substrate having a first layer having conductivity, a second layer having conductivity, and an insulating layer of the first layer and the second layer. A connecting portion that is obtained by processing and connects the swinging portion, the frame, the swinging portion, and the frame, and defines a swing axis in swinging motion of the swinging portion with respect to the frame And the connecting part includes a plurality of torsion bars arranged in parallel, and two torsion bars selected from the plurality of torsion bars are relatively close to and away from each other, The swing part includes a swing main part, and a first movable part attached to the swing main part and capable of changing in a direction intersecting the swing axis, and the frame includes a frame main part. And attached to the main part of the frame, The first movable part and a second movable part that can be shifted in the same direction, and one torsion bar included in the connecting part connects the first and second movable parts, and The main part is derived from the first layer, the first movable part is derived from the second layer, the second movable part is derived from the second layer and the frame main part. The one torsion bar is derived from the second layer.

  A micro-oscillation comprising an oscillating portion, a frame, and a connecting portion (twisted connecting portion) that connects the oscillating portion and the frame to define an oscillation axis of the oscillating operation of the oscillating portion relative to the frame. In the element, the natural frequency (resonance frequency) f related to the swinging motion of the swinging part is expressed by the following formula (1). In Equation (1), k represents the torsion spring constant of the connecting portion, and I represents the inertia of the swinging portion.

  In the micro oscillating device of the present invention, the connecting portion has two torsion bars that can relatively move toward and away from each other, and the two torsion bars relatively move toward and away from each other to move the connecting portion. The torsion spring constant k changes. The shorter the distance between the torsion bar pair is, the smaller the torsion spring constant k of the connecting portion including the torsion bar pair is. The longer the distance between the torsion bar pair, the greater the torsion spring constant k of the connecting portion. As can be understood from the above equation (1), the smaller the torsion spring constant k of the connecting portion, the smaller the natural frequency (resonance frequency) f related to the swinging motion of the swinging portion, and the greater the torsion spring constant k. The natural frequency f is large.

  Therefore, in the present micro oscillating device, the torsion spring constant k of the connecting portion is controlled by the relative approach and separation of the two torsion bars, and the natural frequency f related to the oscillating operation of the oscillating portion is set. It is possible to adjust. According to such natural frequency adjustment, the natural frequency f related to the swinging operation of the swinging portion is finely adjusted in an analog manner, compared to the above-described conventional natural frequency adjustment using mechanical processing. Can be adjusted with high accuracy.

  In the micro oscillating device, in order to adjust the natural frequency f, it is not necessary to mechanically process the oscillating portion after the device is once completed. In addition, in the present micro oscillating device, the torsion spring constant k of the connecting portion can be decreased or increased, and therefore the degree of freedom in adjusting the natural frequency f is high.

  As described above, the micro oscillating device of the present invention is suitable for adjusting the natural frequency (resonance frequency) related to the oscillating operation of the oscillating portion.

  Preferably, the swing part has a first comb electrode fixed to the swing main part, and the frame is a second comb for generating electrostatic attraction in cooperation with the first comb electrode. It has a tooth electrode. Alternatively, the frame has a third comb electrode fixed to the main part of the frame, and the second movable part is a fourth comb for generating electrostatic attraction in cooperation with the third comb electrode. You may have a tooth electrode. These configurations are preferable for realizing good approaching / separating motion of the torsion bar pair.

1 is a plan view of a micromirror element according to a first embodiment of the present invention. FIG. 6 is another plan view of the micromirror element according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 1. FIG. 5 is a cross-sectional view taken along line VV in FIG. 2. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 2. FIG. 3 is a cross-sectional view taken along line VII-VII in FIG. 2. The aspect of the position control of a weight part is represented. It is a top view of the micromirror element which concerns on the 2nd Embodiment of this invention. It is another top view of the micromirror element concerning the 2nd Embodiment of this invention. FIG. 10 is a cross-sectional view taken along line XI-XI in FIG. 9. It is sectional drawing along line XII-XII of FIG. It is sectional drawing along line XIII-XIII of FIG. It is sectional drawing along line XIV-XIV of FIG. The aspect of the width control of a connection part is represented. It is a top view of the micromirror element which concerns on the 3rd Embodiment of this invention. It is another top view of the micromirror element concerning the 3rd Embodiment of this invention. It is sectional drawing along line XVIII-XVIII of FIG. It is sectional drawing along line XIX-XIX of FIG. It is sectional drawing along line XX-XX of FIG. An example of the drive mode of the micromirror element of FIG. 16 is represented. The other voltage application aspect with respect to a comb-tooth electrode is represented. The other voltage application aspect with respect to a comb-tooth electrode is represented. The other voltage application aspect with respect to a comb-tooth electrode is represented. The other voltage application aspect with respect to a comb-tooth electrode is represented. It is a disassembled perspective view of the conventional micromirror element. FIG. 27 is a cross-sectional view taken along line XXVII-XXVII of the micromirror element of FIG. 26 in an assembled state.

  1 to 7 show a micromirror element X1 according to the first embodiment of the present invention. FIG. 1 is a plan view of the micromirror element X1, and FIG. 2 is another plan view of the micromirror element X1. 3 and 4 are sectional views taken along lines III-III and IV-IV in FIG. 1, respectively. 5 to 7 are sectional views taken along lines VV, VI-VI, and VII-VII in FIG. 2, respectively.

  The micromirror element X1 includes a swinging part 110, a frame 120, a pair of connecting parts 130, and comb electrodes 140, 150, 160, and 170. The micromirror element X1 is manufactured by processing a material substrate which is a so-called SOI (silicon on insulator) substrate by a bulk micromachining technology such as a MEMS technology. The material substrate has, for example, a laminated structure including first and second silicon layers and an insulating layer between the silicon layers, and each silicon layer is given predetermined conductivity by doping with impurities. FIG. 1 is a plan view mainly showing a structure derived from the first silicon layer, and FIG. 2 is a plan view mainly showing a structure derived from the second silicon layer. From the viewpoint of clarifying the figure, in FIG. 1, a portion (excluding a mirror surface 111a described later) that is derived from the first silicon layer and protrudes from the insulating layer toward the front side of the drawing is indicated by hatching. In 2, a portion derived from the second silicon layer and protruding from the insulating layer toward the front side of the drawing is indicated by hatching.

  The swing part 110 includes a swing main part 111, a pair of weight parts 112, support base parts 113A and 113B, support beams 114A and 114B, a pair of comb electrodes 115, and wiring parts 116 and 117. In addition, it can swing with respect to the frame 120.

  The swinging main part 111 is a part formed in the first silicon layer, and has a mirror surface 111a having a light reflecting function on its surface, for example, as shown in FIG. The mirror surface 111a has a laminated structure including a Cr layer formed on the first silicon layer and an Au layer thereon.

  As shown in FIG. 5, each weight 112 includes support bases 113A and 113B fixed to the swing main part 111 via an insulating layer 118, a support beam 114A connecting the support base 113A and the weight 112, and It is attached to the swinging main part 111 via a support beam 114B that connects the support base part 113B and the weight part 112, and can be changed as indicated by an arrow D1 in FIG. Each weight portion 112 has a comb-tooth electrode 112a composed of a plurality of parallel electrode teeth 112a '. The comb electrode 112a of the weight portion 112, which is a movable body, constitutes a movable electrode in the weight portion changing mechanism. Each support base 113A is connected to the wiring part 116 as shown in FIG. As shown in FIG. 6, the wiring part 116 is fixed to the swinging main part 111 via an insulating layer 118. The weight portion 112, the support base portions 113A and 113B, the support beams 114A and 114B, and the wiring portion 116 are portions formed in the second silicon layer.

  Each comb-tooth electrode 115 is for generating electrostatic attraction in cooperation with the comb-tooth electrode 112a of the weight portion 112, and is fixed to the wiring portion 117 as shown in FIG. It consists of a plurality of electrode teeth 115a. As shown in FIGS. 6 and 7, the wiring part 117 is partially fixed to the swinging main part 111 via the insulating layer 118. Each comb-tooth electrode 115 fixed with respect to the wiring part 117 fixed to the rocking | swiveling main part 111 comprises the fixed electrode in a weight part transition mechanism. The comb electrode 115 and the wiring part 117 are parts formed in the second silicon layer.

  The frame 120 has a first layer portion 121 and a second layer portion 122 and has a shape surrounding the swinging portion 110. The first layer part 121 is a part molded in the first silicon layer, and the second layer part 122 is a part molded in the second silicon layer. The first layer part 121 and the second layer part 122 are joined via an insulating layer 123.

  As shown in FIGS. 1, 2, and 4, the pair of connecting portions 130 includes three torsion bars 131, 132, and 133, and connects the swinging portion 110 and the frame 120. The torsion bars 131 and 132 are portions formed in the first silicon layer, and connect the swinging main part 111 of the swinging part 110 and the first layer part 121 of the frame 120 as shown in FIG. The distance between the torsion bars 131 and 132 in each connecting portion 130 gradually increases from the frame 120 side to the swinging portion 110 side. Each torsion bar 133 is a part formed in the second silicon layer. As shown in FIGS. 2 and 6, one torsion bar 133 connects the wiring part 116 of the swing part 110 and the second layer part 122 of the frame 120, and the other torsion bar 133 is connected to the swing part 110. The wiring portion 117 and the second layer portion 122 of the frame 120 are connected. In each connecting portion 130, the torsion bars 131 and 132 and the torsion bar 133 are electrically separated. Further, the portion where one torsion bar 133 is joined in the second layer portion 122 and the portion where the other torsion bar 133 is joined in the second layer portion 122 are electrically separated. 133 is electrically isolated.

  Such a pair of connecting portions 130 defines a swing axis A <b> 1 of the rotational motion of the swing portion 110 relative to the frame 120. Each connecting portion 130 including two torsion bars 131 and 132 whose intervals gradually increase from the frame 120 side to the swinging portion 110 side is suitable for preventing an unnecessary displacement component in the rotation operation of the swinging portion 110. It is.

  The comb-teeth electrode 140 includes a plurality of electrode teeth 141 formed in the first silicon layer, and each of these electrode teeth 141 extends from a swing main portion 111 of the swing portion 110 as shown in FIG. Are parallel to each other.

  The comb electrode 150 is composed of a plurality of electrode teeth 151 formed in the first silicon layer, and these electrode teeth 151 are arranged on the side opposite to the electrode teeth 141 of the comb electrode 140 as shown in FIG. Each extends from the swinging main part 111 and is parallel to each other.

  The comb-tooth electrode 160 is a part for generating electrostatic attractive force in cooperation with the comb-tooth electrode 140, and includes a plurality of electrode teeth 161 derived from the second silicon layer. As shown in FIG. 2, these electrode teeth 161 extend from the second layer portion 122 of the frame 120, are parallel to each other, and are also parallel to the electrode teeth 141 of the comb-tooth electrode 140. For example, as shown in FIG. 3, the comb-tooth electrodes 140 and 160 are arranged in such a manner that the electrode teeth 141 and 161 are displaced. The pair of comb electrodes 140 and 160 constitutes one actuator in the micromirror element X1.

  The comb-teeth electrode 170 is a part for generating an electrostatic attractive force in cooperation with the comb-teeth electrode 150, and includes a plurality of electrode teeth 171 derived from the second silicon layer. As shown in FIG. 2, these electrode teeth 171 extend from the second layer portion 122 of the frame 120, are parallel to each other, and are also parallel to the electrode teeth 151 of the comb-tooth electrode 150. The comb-tooth electrodes 150 and 170 are arranged in such a manner that the electrode teeth 151 and 171 are displaced. The pair of comb electrodes 150 and 170 constitute one actuator in the micromirror element X1. Further, the portion where the comb electrode 160 is joined in the second layer portion 122 and the portion where the comb electrode 170 is joined in the second layer portion 122 are electrically separated. , 170 are electrically isolated.

  As described above, the micromirror element X1 is manufactured by processing a material substrate having a multilayer structure by a bulk micromachining technique such as a MEMS technique. Further, as described above, the material substrate has a laminated structure including the first and second silicon layers and the insulating layer between them in the present embodiment.

In the manufacture of the micromirror element X1, for example, an etching mask covering portions corresponding to the swinging main portion 111, the first layer portion 121, and the torsion bars 131, 132, the weight portion 112, the support base portions 113A, 113B, the support Etching processing using the etching masks covering the portions corresponding to the beams 114A and 114B, the comb-tooth electrode 115, the wiring portions 116 and 117, the second layer portion 122, and the torsion bar 133 on the material substrate at a predetermined timing. Each silicon layer is processed by applying. As an etching method, Deep RIE
Dry etching by (Reactive Ion Etching) method or wet etching such as KOH can be used. Unnecessary portions in the insulating layer are removed by etching as appropriate. In this way, each part of the micromirror element X1 is formed in the material substrate having the first and second silicon layers and the insulating layer.

  In the micromirror element X1, the swinging portion 110 swings around the swing axis A1 by applying a predetermined potential to each of the comb electrodes 140, 150, 160, 170 as necessary. Or it can be rotationally displaced. The potential application to the comb electrodes 140 and 150 can be realized through the first layer portion 121 of the frame 120, the torsion bars 131 and 132 of each connecting portion 130, and the swing main portion 111 of the swing portion 110. it can. The comb electrodes 140 and 150 are grounded, for example. On the other hand, the potential application to the comb electrode 160 can be realized through a part of the second layer portion 122 of the frame 120, and the potential application to the comb electrode 170 is another part of the second layer portion 122. It can be realized through. Since the comb electrode 160 and the comb electrode 170 are electrically separated as described above, potential application to the comb electrodes 160 and 170 can be performed independently.

  When a desired electrostatic attraction is generated between the comb-tooth electrodes 140 and 160 by applying a predetermined potential to each of the comb-tooth electrodes 140 and 160, the comb-tooth electrode 140 is drawn into the comb-tooth electrode 160. Therefore, the oscillating portion 110 oscillates around the oscillating axis A1, and the electrostatic attraction force and the total of the torsional resistance forces of the coupling portions 130 that are torsionally deformed are rotationally displaced to an angle that balances. The amount of rotational displacement in such a swinging operation can be adjusted by adjusting the potential applied to the comb-tooth electrodes 140 and 160. Further, when the electrostatic attractive force between the comb-tooth electrodes 140 and 160 is extinguished, each connecting portion 130 (torsion bar 131, 132, 133) releases its torsional stress and returns to a natural state.

  Further, when a desired electrostatic attraction is generated between the comb-shaped electrodes 150 and 170 by applying a predetermined potential to each of the comb-shaped electrodes 150 and 170, the comb-shaped electrode 150 is drawn into the comb-shaped electrode 170. Therefore, the oscillating portion 110 oscillates around the oscillating axis A1 in the direction opposite to the aforementioned oscillating operation, and the electrostatic attraction force and the sum of the torsional resistance forces of the respective connecting portions 130 are Rotate to a balanced angle. The amount of rotational displacement in such a swinging operation can be adjusted by adjusting the potential applied to the comb electrodes 150 and 170. Further, when the electrostatic attractive force between the comb electrodes 150 and 170 is extinguished, each connecting portion 130 (torsion bars 131, 132, 133) releases its torsional stress and returns to a natural state.

  In the micromirror element X1, the reflection direction of the light reflected by the mirror surface 111a provided on the swing main part 111 can be appropriately switched by the swing drive of the swing part 110 as described above.

  On the other hand, in the micromirror element X1, by applying a predetermined potential to the comb-tooth electrode 112a and each comb-tooth electrode 115 of each weight portion 112 in the oscillating portion 110 as required, each weight portion 112 is It can be shifted in a direction intersecting the swing axis A1 (a direction orthogonal in the present embodiment). The potential application to the comb-shaped electrode 112a is performed through a part of the second layer portion 122 of the frame 120, the torsion bar 133 of one connecting portion 130, the wiring portion 116 of the swinging portion 110, the support base portion 113A, and the support beam 114A. Can be realized. The comb electrode 112a is grounded, for example. On the other hand, the potential application to the comb electrode 115 is realized through another part of the second layer portion 122 of the frame 120, the torsion bar 133 of the other connecting portion 130, and the wiring portion 117 of the swinging portion 110. Can do. Since both the torsion bars 133 are electrically separated as described above, potential application to the comb electrodes 112a and 115 can be performed independently.

  When a desired electrostatic attraction is generated between the comb-tooth electrodes 112a and 115 by applying a predetermined potential to each of the comb-tooth electrodes 112a and 115, each comb-tooth electrode 112a is applied to the comb-tooth electrode 115 opposed thereto. Be drawn. For example, as shown in FIG. 8, each weight portion 112 stops at a position where the sum of the restoring forces of the elastically deformed support beams 114 </ b> A and 114 </ b> B and the electrostatic attraction force balance. By adjusting the potential applied to the comb electrodes 112a and 115, the electrostatic attractive force generated between the comb electrodes 112a and 115 can be adjusted. Therefore, the stationary position of each weight part 112 or each weight part The distance of 112 from the swing axis A1 can be controlled.

  In the micromirror element X1, the oscillating portion 110 has the weight portion 112 that can be displaced as described above in a direction intersecting with the oscillating axis A1 (orthogonal in the present embodiment), and the weight portion 112 changes. As a result, the inertia I of the oscillating portion 110 changes (the inertia I includes the inertia component of each portion constituting the oscillating portion 110). The closer the weight portion 112 is to the swing axis A1, that is, the smaller the rotation radius of the weight portion 112, the smaller the inertia component of the weight portion 112 and the smaller the inertia I of the swing portion 110. The farther the weight 112 is from the swing axis A1, that is, the greater the rotation radius of the weight 112, the greater the inertia component of the weight 112 and the greater the inertia I of the swing. As can be understood from the above equation (1), the smaller the inertia I of the oscillating unit 110 is, the larger the natural frequency (resonance frequency) f related to the oscillating operation of the oscillating unit 110 is. The frequency f is small.

  Therefore, in the micromirror element X1, the inertia frequency I of the oscillating portion 110 is controlled by adjusting the weight 112 of the oscillating portion 110 to adjust the natural frequency f related to the oscillating operation of the oscillating portion 110. It is possible. According to such natural frequency adjustment, the natural frequency f related to the swinging operation of the swinging portion is finely adjusted in an analog manner, compared to the above-described conventional natural frequency adjustment using mechanical processing. Can be adjusted with high accuracy.

  Further, in the micromirror element X1, in order to adjust the natural frequency f, it is not necessary to mechanically process the oscillating portion 110 after the element is once completed. In addition, in the micromirror element X1, the inertia I of the oscillating portion 110 can be increased or decreased, and therefore, the degree of freedom in adjusting the natural frequency f is high.

  9 to 14 show a micromirror element X2 according to the second embodiment of the present invention. FIG. 9 is a plan view of the micromirror element X2, and FIG. 10 is another plan view of the micromirror element X2. 11 and 12 are cross-sectional views taken along lines XI-XI and XII-XII in FIG. 9, respectively. 13 and 14 are cross-sectional views taken along lines XIII-XIII and XIV-XIV in FIG. 10, respectively.

  The micromirror element X2 includes a swinging part 210, a frame 220, a pair of connecting parts 230, and comb-tooth electrodes 240, 250, 260, and 270. The micromirror element X2 is manufactured by processing a material substrate which is a so-called SOI substrate by a bulk micromachining technology such as a MEMS technology. The material substrate has, for example, a laminated structure including first and second silicon layers and an insulating layer between the silicon layers, and each silicon layer is given predetermined conductivity by doping with impurities. FIG. 9 is a plan view mainly showing a structure derived from the first silicon layer, and FIG. 10 is a plan view mainly showing a structure derived from the second silicon layer. From the viewpoint of clarifying the figure, in FIG. 9, a portion (excluding a mirror surface 211a described later) derived from the first silicon layer and protruding from the insulating layer toward the front side of the drawing is indicated by hatching. In FIG. 10, a portion derived from the second silicon layer and projecting in front of the paper surface from the insulating layer is indicated by hatching.

  The swinging part 210 has a swinging main part 211, a pair of movable parts 212 </ b> A and 212 </ b> B, four support bases 213, and four spring parts 214, and can swing with respect to the frame 220. .

  The swinging main part 211 is a part formed in the first silicon layer, and has a mirror surface 211a having a light reflecting function on its surface, for example, as shown in FIG. The mirror surface 211a has a laminated structure including a Cr layer formed on the first silicon layer and an Au layer thereon.

  Each of the movable portions 212A and 212B can be understood by referring to FIG. 10 and FIG. 13 in combination, the support base 213 fixed to the swinging main portion 211 via the insulating layer 215, the support base 213 and the support base 213. It is attached to the swinging main portion 211 via a spring portion 214 that couples the movable portion, and can be changed as indicated by an arrow D2 in FIG. The movable parts 212A and 212B, the support base part 213, and the spring part 214 are parts formed in the second silicon layer.

  The frame 220 includes a first layer part 221, a second layer part 222, two movable parts 223A, two movable parts 223B, four support bases 224, four spring parts 225, and four combs. It has a tooth electrode 226 and two wiring parts 227 and has a shape surrounding the swinging part 210. The first layer part 221 is a part formed in the first silicon layer. The second layer part 222 is a part formed in the second silicon layer. These first and second layer portions 221 and 222 are joined via an insulating layer 228. In addition, the movable parts 223A and 223B, the support base part 224, the spring part 225, the comb-tooth electrode 226, and the wiring part 227 are parts formed in the second silicon layer.

  Each of the movable parts 223A and 223B includes a support base 224 fixed to the first layer part 221 via an insulating layer 228 and a support, as can be understood by referring to FIG. 10, FIG. 13, and FIG. It is attached to the 1st layer part 221 via the spring part 225 which connects the base part 224 and the said movable part, and it can change as represented by arrow D3 in FIG. Each movable part 223A, 223B has a comb-tooth electrode 223a composed of a plurality of parallel electrode teeth 223a '. Each comb electrode 223a of the movable portions 223A and 223B constitutes a movable electrode in the movable portion transition mechanism.

  Each comb-tooth electrode 226 is for generating electrostatic attraction in cooperation with the comb-tooth electrode 223a of the movable portions 223A and 223B, and is fixed to the wiring portion 227 as shown in FIG. It consists of a plurality of parallel electrode teeth 226a. As shown in FIG. 14, the wiring part 227 is fixed to the first layer part 221 through an insulating layer 228. Each comb electrode 226 fixed to the wiring part 227 fixed to the first layer part 221 constitutes a fixed electrode in the movable part shifting mechanism.

  As shown in FIGS. 9, 10, and 12, the pair of connecting portions 230 includes three torsion bars 231, 232, and 233, and connects the swinging portion 210 and the frame 220. Each torsion bar 231 is a portion formed in the first silicon layer, and connects the swinging main part 211 of the swinging part 210 and the first layer part 221 of the frame 220 as shown in FIG. On the other hand, the torsion bars 232 and 233 are portions formed in the second silicon layer. As shown in FIG. 10, one end of the torsion bar 232 is connected to the movable part 212 </ b> A of the swinging part 210, and the other end of the torsion bar 232 is connected to the movable part 223 </ b> A of the frame 220. One end of the torsion bar 233 is connected to the movable part 212B of the swinging part 210, and the other end of the torsion bar 233 is connected to the movable part 223B of the frame 220. The torsion bars 231, 232, 233 in each connecting portion 230 are parallel to each other, and the torsion bar 231 and the torsion bars 232, 233 are electrically separated. Such a pair of connecting portions 230 defines a swing axis A <b> 2 of the rotational motion of the swing portion 210 relative to the frame 220.

  The comb-tooth electrode 240 is composed of a plurality of electrode teeth 241 formed in the first silicon layer, and each of these electrode teeth 241 extends from the swing main portion 211 of the swing portion 210 as shown in FIG. Are parallel to each other.

  The comb electrode 250 includes a plurality of electrode teeth 251 formed in the first silicon layer, and these electrode teeth 251 are provided on the side opposite to the electrode teeth 241 of the comb electrode 240 as shown in FIG. Each extends from the swinging main part 211 and is parallel to each other.

  The comb-tooth electrode 260 is a part for generating electrostatic attractive force in cooperation with the comb-tooth electrode 240, and includes a plurality of electrode teeth 261 derived from the second silicon layer. As shown in FIG. 10, these electrode teeth 261 extend from the second layer portion 222 of the frame 220, are parallel to each other, and are also parallel to the electrode teeth 241 of the comb-tooth electrode 240. For example, as shown in FIG. 11, the comb-tooth electrodes 240 and 260 are arranged in such a manner that the electrode teeth 241 and 261 are displaced. The pair of comb electrodes 240 and 260 constitute one actuator in the micromirror element X2.

  The comb-tooth electrode 270 is a part for generating electrostatic attraction in cooperation with the comb-tooth electrode 250, and includes a plurality of electrode teeth 271 derived from the second silicon layer. As shown in FIG. 10, these electrode teeth 271 extend from the second layer portion 222 of the frame 220, are parallel to each other, and are also parallel to the electrode teeth 251 of the comb electrode 250. The pair of comb electrodes 250 and 270 constitute one actuator in the micromirror element X2. The comb-tooth electrodes 250 and 270 are arranged in such a manner that the electrode teeth 251 and 271 are displaced. Further, the portion where the comb electrode 260 is joined in the second layer portion 222 and the portion where the comb electrode 270 is joined in the second layer portion 222 are electrically separated. , 270 are electrically isolated.

  As described above, the micromirror element X2 is manufactured by processing a material substrate having a multilayer structure by a bulk micromachining technique such as a MEMS technique. Further, as described above, the material substrate has a laminated structure including the first and second silicon layers and the insulating layer between them in the present embodiment.

In the manufacture of the micromirror element X2, for example, an etching mask that covers portions corresponding to the swing main portion 211, the first layer portion 221, and the torsion bar 231, the movable portions 212A and 212B, the support base portion 213, and the spring portion 214. The second layer part 222, the movable parts 223A and 223B, the support base part 224, the spring part 225, the comb-tooth electrode 226, the wiring part 227, and the etching mask that covers the portions corresponding to the torsion bars 232 and 233, etc. Each silicon layer is processed by performing an etching process on the material substrate at a predetermined timing. As an etching method, dry etching by Deep RIE method, wet etching such as KOH, or the like can be used. Unnecessary portions in the insulating layer are removed by etching as appropriate. In this way, each part of the micromirror element X2 is formed in the material substrate having the first and second silicon layers and the insulating layer.

  In the micromirror element X2, the swinging part 210 is swung around the swing axis A2 by applying a predetermined potential to each of the comb electrodes 240, 250, 260, 270 as necessary. Or it can be rotationally displaced. The potential application to the comb electrodes 240 and 250 can be realized through the first layer portion 221 of the frame 220, the torsion bar 231 of each connecting portion 230, and the swing main portion 211 of the swing portion 210. The comb electrodes 240 and 250 are grounded, for example. On the other hand, the potential application to the comb electrode 260 can be realized via a part of the second layer portion 222 of the frame 220, and the potential application to the comb electrode 270 is performed to the other part of the second layer portion 222. It can be realized through. Since the comb electrode 260 and the comb electrode 270 are electrically separated as described above, potential application to the comb electrodes 260 and 270 can be performed independently.

  When a desired electrostatic attraction is generated between the comb-tooth electrodes 240 and 260 by applying a predetermined potential to each of the comb-tooth electrodes 240 and 260, the comb-tooth electrode 240 is drawn into the comb-tooth electrode 260. Therefore, the oscillating part 210 oscillates around the oscillating axis A2, and the electrostatic attractive force and the total sum of the torsional resistance forces of the connecting parts 230 that are torsionally deformed are rotationally displaced to an angle that balances. The amount of rotational displacement in such a swing operation can be adjusted by adjusting the potential applied to the comb electrodes 240 and 260. Further, when the electrostatic attractive force between the comb-tooth electrodes 240 and 260 is extinguished, each connecting portion 230 (torsion bars 231, 232, 233) releases its torsional stress and returns to a natural state.

  Further, when a desired electrostatic attraction is generated between the comb electrodes 250 and 270 by applying a predetermined potential to each of the comb electrodes 250 and 270, the comb electrode 250 is drawn into the comb electrodes 270. Therefore, the swinging part 210 swings around the swinging axis A2 in the direction opposite to the swinging action described above, and the angle at which the electrostatic attraction force and the total of the torsional resistance force of each connecting part 230 are balanced. Rotating displacement up to The amount of rotational displacement in such a swing operation can be adjusted by adjusting the potential applied to the comb electrodes 250 and 270. Further, when the electrostatic attractive force between the comb-tooth electrodes 250 and 270 is extinguished, each connecting portion 230 (torsion bars 231, 232, 233) releases its torsional stress and returns to a natural state.

  In the micromirror element X2, the reflection direction of the light reflected by the mirror surface 211a provided on the swing main part 211 can be appropriately switched by the swing drive of the swing part 210 as described above.

  On the other hand, in the micromirror element X2, a total of four comb-tooth electrodes 223a of the movable portions 223A and 223B in the frame 220 are connected to the ground, and the comb-tooth electrode 226 facing them is given a predetermined number as necessary. By applying a potential, the distance between the torsion bars 232 and 233 in each connecting portion 230 can be changed. As for the ground connection of the comb electrode 223a, for example, a conductive plug that penetrates the insulating layer 228 and electrically connects the support base 224 and the first layer part 221 is provided, and the first layer part 221 is grounded. Can be realized. The potential application to the comb electrode 226 can be realized through the wiring portion 227.

  When a desired electrostatic attraction is generated between the comb-shaped electrodes 223a and 226 facing each other by applying a predetermined potential to the comb-shaped electrode 226, each comb-shaped electrode 223a is drawn into the comb-shaped electrode 226 facing the comb-shaped electrode 226a. It is. In conjunction with this, the torsion bar 232 and the movable part 212A are displaced together with the movable part 223A, and the torsion bar 233 and the movable part 212B are displaced together with the movable part 223B. As shown in FIG. 15, for example, the movable unit composed of the movable portions 212A and 223A and the torsion bar 232 is connected to the movable unit and elastically deformed and elastically deformed spring portions 214 and 225, and the two of the movable units. It stops at a position where the electrostatic attractive force acting on the location balances. At the same time, the movable unit composed of the movable portions 212B and 223B and the torsion bar 233 is connected to the movable unit, for example, as shown in FIG. The electrostatic attraction acting on the two parts of the unit stops at a balance position. By adjusting the potential applied to the comb electrode 226, the electrostatic attractive force generated between the comb electrodes 223a and 226 facing each other can be adjusted. Accordingly, the torsion bars 232 and 233 of each connecting portion 230 can be adjusted. The rest position or the distance between the torsion bars 232 and 233 can be controlled.

  In the micromirror element X2, each connecting portion 230 has two torsion bars 232 and 233 that can relatively move toward and away from each other. The torsion spring constant k of the portion 230 changes. The shorter the distance between the torsion bars 232 and 233, the smaller the torsion spring constant k of the connecting portion 230 including the torsion bars 232 and 233 is. The longer the distance between the torsion bars 232 and 233, the greater the torsion spring constant k of the connecting portion 230. As can be understood from the above equation (1), the smaller the torsion spring constant k of the connecting portion 230 is, the smaller the natural frequency (resonance frequency) f related to the swinging motion of the swinging portion 210 is, and the torsion spring constant k is smaller. The larger the frequency, the larger the natural frequency f.

  Therefore, in the micromirror element X2, the torsion spring constant k of the connecting portion 230 is controlled by the relative approach and separation of the torsion bars 232 and 233, and the natural frequency f related to the swinging motion of the swinging portion 210 is controlled. Can be adjusted. According to such natural frequency adjustment, the natural frequency f related to the swinging operation of the swinging portion is finely adjusted in an analog manner, compared to the above-described conventional natural frequency adjustment using mechanical processing. Can be adjusted with high accuracy.

  Further, in the micromirror element X2, in order to adjust the natural frequency f, it is not necessary to mechanically process the oscillating portion 210 after the element is once completed. In addition, in the micromirror element X2, it is possible to increase or decrease the torsion spring constant k of the connecting portion 230, and therefore, the degree of freedom in adjusting the natural frequency f is high.

  In the present embodiment, the drive mechanism for moving the movable unit is provided on the frame 220 side. However, in the present invention, instead of such a configuration, the drive mechanism for moving the movable unit is replaced with the swinging portion. It may be provided on the 210 side. In that case, the above-described oscillating portion 210 in the micromirror element X2 has two first comb electrodes fixed to the oscillating main portion 211, and the above-mentioned movable portion 212A includes one first comb electrode. A second comb electrode for generating an electrostatic attractive force in cooperation with the first movable electrode 212B. The movable portion 212B described above cooperates with the other first comb electrode to generate an electrostatic attractive force. It has 2 comb electrodes.

  16 to 20 show a micromirror element X3 according to a third embodiment of the present invention. FIG. 16 is a plan view of the micromirror element X3. FIG. 17 is another plan view of the micromirror element X3. 18 to 20 are sectional views taken along line XVIII-XVIII, line XIX-XIX, and line XX-XX in FIG. 16, respectively.

  The micromirror element X3 includes a swinging part 310, a frame 320, a pair of connecting parts 330, and comb-tooth electrodes 340, 350, 360, 370, 380, and 390. The micromirror element X3 is manufactured by processing a material substrate which is a so-called SOI substrate by a bulk micromachining technology such as a MEMS technology. The material substrate has, for example, a laminated structure including first and second silicon layers and an insulating layer between the silicon layers, and each silicon layer is given predetermined conductivity by doping with impurities. FIG. 16 is a plan view mainly showing a structure derived from the first silicon layer, and FIG. 17 is a plan view mainly showing a structure derived from the second silicon layer. From the viewpoint of clarifying the figure, in FIG. 16, a portion (excluding a mirror surface 311 described later) that is derived from the first silicon layer and protrudes from the insulating layer toward the front side of the drawing is indicated by hatching. In FIG. 17, a portion derived from the second silicon layer and protruding from the insulating layer toward the front side of the drawing is indicated by hatching.

  The oscillating portion 310 is a portion molded in the first silicon layer, and has a mirror surface 311 having a light reflecting function on its surface as shown in FIG. The mirror surface 311 has a laminated structure including a Cr layer formed on the first silicon layer and an Au layer thereon.

  The frame 320 has a first layer portion 321 and a second layer portion 322 and has a shape surrounding the swinging portion 310. The first layer part 321 is a part molded in the first silicon layer, and the second layer part 322 is a part molded in the second silicon layer. These first and second layer portions 321 and 322 are joined via an insulating layer 323 as shown in FIGS. 18 and 19.

  As shown in FIGS. 16, 17, and 20, the pair of connecting portions 330 includes two torsion bars 331, and connects the swinging portion 310 and the frame 320. The torsion bar 331 is a part formed in the first silicon layer, and connects the swinging part 310 and the first layer part 321 of the frame 320. The interval between the two torsion bars 331 in each connecting portion 330 gradually increases from the frame 320 side to the swinging portion 310 side. Such a pair of connecting portions 330 defines a swing axis A <b> 3 of the rotational motion of the swing portion 310 relative to the frame 320. Each connecting portion 330 including two torsion bars 331 whose interval gradually increases from the frame 320 side to the swinging portion 310 side is suitable for preventing unnecessary displacement components in the rotational operation of the swinging portion 310. .

  The comb-teeth electrode 340 includes a plurality of electrode teeth 341 formed in the first silicon layer. These electrode teeth 341 extend from the swinging portion 310 and are parallel to each other, for example, as shown in FIG. is there.

  The comb electrode 350 is composed of a plurality of electrode teeth 351 formed in the first silicon layer, and these electrode teeth 351 are arranged on the side opposite to the electrode teeth 341 of the comb electrode 340, for example, as shown in FIG. Each extends from the swinging portion 310 and is parallel to each other.

  The comb-tooth electrode 360 is a part for generating electrostatic attraction in cooperation with the comb-tooth electrode 340. The comb-tooth electrode 360 is placed on the frame 320 at a position facing the comb-tooth electrode 340 during non-oscillation driving of the element. It consists of a plurality of electrode teeth 361 fixed and derived from the first silicon layer. As shown in FIG. 16, these electrode teeth 361 extend from the first layer portion 321, are parallel to each other, and are also parallel to the electrode teeth 341 of the comb electrode 340.

  The comb electrode 370 is a part for generating electrostatic attraction in cooperation with the comb electrode 340, and is fixed to the frame 320 at a position not facing the comb electrode 340 when not driven. It consists of a plurality of electrode teeth 371 derived from the silicon layer. As shown in FIG. 17, these electrode teeth 371 each extend from the second layer portion 322, are parallel to each other, and are also parallel to the electrode teeth 341, 361 of the comb electrodes 340, 360. An insulating part is preferably interposed between the electrode teeth 371 of the comb-teeth electrode 370 and the electrode teeth 361 of the comb-teeth electrode 360.

  The comb-teeth electrode 380 is a part for generating electrostatic attraction in cooperation with the comb-teeth electrode 350, and is fixed to the frame 320 at a position facing the comb-teeth electrode 350 when not driven. It consists of a plurality of electrode teeth 381 derived from the silicon layer. As shown in FIG. 16, these electrode teeth 381 extend from the first layer portion 321, are parallel to each other, and are also parallel to the electrode teeth 351 of the comb electrode 350.

  The comb-tooth electrode 390 is a portion for generating electrostatic attraction in cooperation with the comb-tooth electrode 350, and is fixed to the frame 320 at a position not facing the comb-tooth electrode 350 when not driven. It consists of a plurality of electrode teeth 391 derived from the silicon layer. As shown in FIG. 17, these electrode teeth 391 each extend from the second layer portion 322, are parallel to each other, and are also parallel to the electrode teeth 351, 381 of the comb electrodes 350, 380. An insulating part is preferably interposed between the electrode teeth 391 of the comb-tooth electrode 390 and the electrode teeth 381 of the comb-tooth electrode 380.

  The comb-tooth electrodes 340 and 350 and the comb-tooth electrodes 360 to 390 are electrically separated. The comb electrodes 360 to 390 are electrically separated from each other.

  In the above comb electrodes 340 to 390, a set of comb electrodes 340 and 360, a set of comb electrodes 340 and 370, a set of comb electrodes 350 and 380, and a set of comb electrodes 350 , 390 each constitute one drive mechanism in the present invention. For example, each of the comb electrodes 360 to 390 is electrically connected to a voltage generating mechanism capable of controlling the magnitude of the applied potential and the potential applying period. Thereby, in the drive mechanism composed of the comb-tooth electrodes 340 and 360, the magnitude of the electrostatic attraction generated between the comb-tooth electrodes 340 and 360 and the electrostatic attraction generation period can be controlled. Similarly, in the drive mechanism including the comb electrodes 340 and 370, the magnitude of the electrostatic attraction generated between the comb teeth electrodes 340 and 370 and the electrostatic attraction generation period can be controlled. In the driving mechanism, the magnitude of electrostatic attraction generated between the comb-tooth electrodes 350 and 380 and the period of generation of electrostatic attraction can be controlled. In the driving mechanism including the comb-tooth electrodes 350 and 390, the comb-tooth electrode 350 is controlled. , 390 and the electrostatic attractive force generation period can be controlled.

  As described above, the micromirror element X3 is manufactured by processing a material substrate having a multilayer structure by a bulk micromachining technique such as a MEMS technique. Further, as described above, the material substrate has a laminated structure including the first and second silicon layers and the insulating layer between them in the present embodiment.

  In the manufacture of the micromirror element X3, for example, an etching mask that covers portions corresponding to the oscillating portion 310, the first layer portion 321, the torsion bar 331, and the comb electrodes 340, 350, 360, and 380, or the second layer Each silicon layer is processed by subjecting the material substrate to an appropriate etching process using an etching mask or the like that covers portions corresponding to the portion 322 and the comb-tooth electrodes 370 and 390 at appropriate timing. As an etching method, dry etching by Deep RIE method, wet etching such as KOH, or the like can be used. Unnecessary portions in the insulating layer are removed by etching as appropriate. In this way, each part of the micromirror element X3 is formed in the material substrate having the first and second silicon layers and the insulating layer.

  In the micromirror element X3, by applying a predetermined potential to each of the comb electrodes 340 to 390 as necessary, the swinging portion 310 can be rotated around the rotation axis A3. The reflection direction of the light reflected by the mirror surface 311 provided on the moving part 310 can be appropriately switched.

  FIG. 21 illustrates an example of a driving mode of the micromirror element X3. This drive mode is a normal drive example. FIG. 21A shows the change over time of the voltage applied to the comb electrode 370. FIG. 21B shows the change over time of the voltage applied to the comb electrode 390. FIG. 21 (c) represents a change with time of the voltage applied to the comb electrodes 360 and 380. In this driving mode, the comb electrodes 340 and 350 are grounded. In each of the graphs of FIGS. 21A to 21C, the horizontal axis represents time (t), and the vertical axis represents applied voltage (v). FIG. 21D shows the change over time of the swing angle of the swinging part 310 in this driving mode. In the graph of FIG. 21D, the horizontal axis represents time (t), and the vertical axis represents the swing angle (θ).

In this drive mode, first, the swinging portion at time T _{1 is} compared with the comb electrode 370 of the micromirror element X3 in the initial state (the swinging angle of the swinging portion 310 is 0 °) at time T ₀ . A predetermined voltage V ₁ is applied between time T ₀ and time T ₁ so that the rotational displacement of 310 reaches the maximum swing angle θ ₁ as shown in FIG. From time T ₀ to time T _1, an electrostatic attractive force is generated between the comb-tooth electrode 370 and the comb-tooth electrode 340, and the swing angle of the swing portion 310 continues to increase in the first swing direction. At time T ₁ , the pair of comb electrodes 340 and 370 have the orientation shown in FIG. 18B, for example, and the swing angle reaches θ ₁ as shown in FIG. At this time, a predetermined torsional stress is generated in each connecting portion 330.

Next, between time T ₁ and time T ₂ , a predetermined voltage V ₂ is applied to the comb electrodes 360 and 380 as shown in FIG. During this time, in addition to the torsional stress of each connecting portion 330 acting as a restoring force, an electrostatic attractive force is generated between the comb-tooth electrodes 340 and 360 and between the comb-tooth electrodes 350 and 380, and the swing angle of the swing portion 310 Keeps decreasing. At time T ₂ , the pair of comb electrodes 340 and 360 have the orientation shown in FIG. 18A, and the pair of comb electrodes 350 and 380 have the orientation shown in FIG. The angle reaches 0 ° as shown in FIG.

Then, as the rotational displacement of the oscillating member 310 reaches the maximum oscillation angle theta ₂ at time T _3, between time T ₂ of the time T _3, in FIG. 21 (b) with respect to the comb-tooth electrode 390 As shown, a predetermined voltage V ₃ is applied. From time T ₂ to time T _3, an electrostatic attractive force is generated between the comb electrode 390 and the comb electrode 350, and the swing angle of the swing portion 310 is opposite to the first swing direction described above. It continues to increase in the second swing direction. At time T ₃ , the pair of comb electrodes 350 and 390 have the orientation shown in FIG. 19B, for example, and the swing angle reaches θ ₂ as shown in FIG. At this time, a predetermined torsional stress is generated in each connecting portion 330.

Next, during a time T ₃ to a time T ₄ , a predetermined voltage V ₄ is applied to the comb electrodes 360 and 380 as shown in FIG. During this time, in addition to the torsional stress of each connecting portion 330 acting as a restoring force, an electrostatic attractive force is generated between the comb-tooth electrodes 340 and 360 and between the comb-tooth electrodes 350 and 380, and the swing angle of the swing portion 310 Keeps decreasing. At time T ₄ , the pair of comb electrodes 340 and 360 have the orientation shown in FIG. 18A, and the pair of comb electrodes 350 and 380 have the orientation shown in FIG. The angle reaches 0 ° as shown in FIG. A series of voltage application as described above from time T ₀ to time T ₄ and the operation of the oscillating unit 310 accompanying it are repeated as necessary.

In the normal driving of the micromirror element X3, the voltage V ₁ and the voltage V ₃ are set to be the same so that the same rotational torque always acts on the swinging part 310 during the swinging operation, and the voltage V ₂ and The voltage V ₄ is set to be the same, the voltages V ₂ and V ₄ are set to be smaller than the voltages V ₁ and V ₃ by a predetermined amount, and from the time T ₀ to the time T ₁ , the time T ₁ to the time T ₂ , Between time T ₂ and time T ₃ , and between time T ₃ and time T ₄ , are set to the same length, and each has a quarter period of the swinging motion of the swinging portion 310. Is done. The absolute value of the swing angle θ _{1 is the same as} the absolute value of the swing angle θ ₂ . By normal driving as described above in which the same rotational torque always acts on the swinging portion 310 during the swinging operation, a periodic swinging operation can be achieved for the swinging portion 310 of the micromirror element X3. .

  On the other hand, in the micromirror element X3, in the adjustment of the natural frequency f related to the swinging operation of the swinging part 310, a state equivalent to an increase or decrease in the torsion spring constant k of the connecting part 310 can be electrically created. it can. Specifically, with respect to the operation mode of each comb-tooth electrode in the above-described normal drive in which each comb-tooth electrode is operated so that the same rotational torque always acts on the swinging portion 310 during the swing operation. By changing the operation mode of the predetermined comb-teeth electrode, a state equivalent to an increase or decrease in the torsion spring constant of the connecting portion 330 is obtained in a part of the swing angle range in the swing operation of the swing portion 310. Thus, a state equivalent to an increase or decrease in the average torsion spring constant k of the connecting portion 330 during the swinging operation of the swinging portion 310 can be created.

For example, when the voltage V ₁ applied to the comb electrode 370 between time T ₀ and time T ₁ in the normal driving described above is replaced with V ₁₁ (> V ₁ ) as shown in FIG. The rotational torque that acts on the swinging portion 310 between time T ₀ and time T ₁ becomes larger than that during normal driving. Due to such an increase in the rotational torque, the torsion spring constant of the connecting portion 330 decreases during the time T ₀ to the time T ₁ (that is, while the swing angle of the swing portion 310 increases from 0 ° to θ ₁ ). You can create an equivalent state of doing.

If the voltage V ₁ applied to the comb electrode 370 between time T ₀ and time T _{1 in} the above-described normal driving is replaced with V ₁₂ (<V ₁ ) as shown in FIG. _The rotational torque acting on the swinging part 310 between ₀ and time T ₁ is smaller than that during normal driving. Due to such a decrease in rotational torque, the torsion spring constant of the connecting portion 330 increases during the time T ₀ to the time T ₁ (that is, while the swing angle of the swing portion 310 increases from 0 ° to θ ₁ ). You can create an equivalent state of doing.

When the voltage V ₂ applied to the comb electrodes 360 and 380 between time T ₁ and time T _{2 in} the above-described normal driving is replaced with V ₂₁ (> V ₂ ) as shown in FIG. the rotational torque applied from the time T ₁ to the swinging portion 310 during the time T ₂ are larger than that in the normal driving. Due to such an increase in rotational torque, the torsion spring constant of the connecting portion 330 increases during the time T ₁ to the time T ₂ (that is, while the swing angle of the swing portion 310 decreases from θ ₁ to 0 °). You can create an equivalent state of doing.

When the voltage V ₂ applied to the comb electrodes 360 and 380 between time T ₁ and time T _{2 in} the above-described normal driving is replaced with V ₂₂ (<V ₂ ) as shown in FIG. the rotational torque applied from the time T ₁ to the swinging portion 310 during the time T ₂ are smaller than that in the normal driving. Due to such a decrease in the rotational torque, the torsion spring constant of the connecting portion 330 decreases during the time T ₁ to the time T ₂ (that is, while the swing angle of the swing portion 310 decreases from θ ₁ to 0 °). You can create an equivalent state of doing.

When the voltage V ₃ applied to the comb electrode 390 between time T ₂ and time T ₃ in the normal driving described above is replaced with V ₃₁ (> V ₃ ) as shown in FIG. _The rotational torque that acts on the swinging part 310 between ₂ and time T ₃ is larger than that during normal driving. Due to such an increase in rotational torque, the torsion spring constant of the connecting portion 330 decreases during the time T ₂ to the time T ₃ (that is, while the swing angle of the swing portion 310 increases from 0 ° to θ ₂ ). You can create an equivalent state of doing.

When the voltage V ₃ applied to the comb electrode 390 between time T ₂ and time T ₃ in the normal driving described above is replaced with V ₃₂ (<V ₃ ) as shown in FIG. _The rotational torque acting on the swinging portion 310 between ₂ and time T ₃ is smaller than that during normal driving. Due to such a decrease in rotational torque, the torsion spring constant of the connecting portion 330 increases during the time T ₂ to the time T ₃ (that is, while the swing angle of the swing portion 310 increases from 0 ° to θ ₂ ). You can create an equivalent state of doing.

When the voltage V ₄ applied to the comb electrodes 360 and 380 between time T ₃ and time T _{4 in} the above-described normal driving is replaced with V ₄₁ (> V ₄ ) as shown in FIG. the rotational torque applied from time T ₃ to the swinging portion 310 during the time T ₄ is greater than that in the normal driving. Due to such an increase in the rotational torque, the torsion spring constant of the connecting portion 330 increases during the time T ₃ to the time T ₄ (that is, while the swing angle of the swing portion 310 decreases from θ ₂ to 0 °). You can create an equivalent state of doing.

When the voltage V ₄ applied to the comb electrodes 360 and 380 between time T ₃ and time T _{4 in} the above-described normal driving is replaced with V ₄₂ (<V ₄ ) as shown in FIG. the rotational torque applied from time T ₃ to the swinging portion 310 during the time T ₄ is smaller than that in the normal driving. Due to such a decrease in the rotational torque, the torsion spring constant of the connecting portion 330 decreases during the time T ₃ to the time T ₄ (that is, while the swing angle of the swing portion 310 decreases from θ ₂ to 0 °). You can create an equivalent state of doing.

  In the micromirror element X3, for example, any one of the above driving mode changes (changes from the above-described normal driving) is adopted, or an appropriate combination of the above driving mode changes is used, for example. By doing so, it is possible to create a state equivalent to an increase or decrease in the torsion spring constant of the connecting portion 310 within a part of the swing angle range in the swing operation of the swing portion 310. A state equivalent to the change of the average torsion spring constant k of the connecting portion 330 during the swinging motion of the portion 310 can be created.

  As can be understood from the above equation (1), the smaller the torsion spring constant k of the connecting portion 330 is, the smaller the natural frequency (resonance frequency) f related to the swinging motion of the swinging portion 310 is, and the torsion spring constant k is smaller. The larger the frequency, the larger the natural frequency f. Therefore, in the micromirror element X3, for example, by adopting any one of the above drive mode changes, or by adopting an appropriate combination of the above drive mode changes, for example, the connecting portion 310 It is possible to adjust the natural frequency f related to the swinging motion of the swinging portion 310 by electrically controlling the torsion spring constant k. According to such natural frequency adjustment, the natural frequency f related to the swinging operation of the swinging portion is finely adjusted in an analog manner, compared to the above-described conventional natural frequency adjustment using mechanical processing. Can be adjusted with high accuracy.

  Further, in the micromirror element X3, in order to adjust the natural frequency f, it is not necessary to mechanically process the swinging portion 330 after the element is once completed. In addition, in the micromirror element X3, the torsion spring constant k of the connecting portion 330 can be decreased or increased electrically, and thus the degree of freedom in adjusting the natural frequency f is high.

  Each of the above-described micromirror elements X1, X2, and X3 has a swing axis, a frame, and a swing axis in the swing operation of the swing section relative to the frame by connecting the swing section and the frame. And a connecting portion that defines the micro oscillating device. The micromirror element X1 has a configuration (first configuration) for changing the inertia of the oscillating portion in the micro oscillating device. The micromirror element X2 has a configuration (second configuration) for changing the torsion spring constant of the connecting portion by changing the shape of the connecting portion in the micro oscillating device. The micromirror element X3 includes a configuration (third configuration) for electrically creating a state equivalent to a change in the torsion spring constant of the connecting portion in the micro oscillating device. In the present invention, the first configuration and the second configuration may be combined, the second configuration and the third configuration may be combined, or the third configuration and the first configuration may be combined. Alternatively, all of the first to third configurations may be combined.

  As a summary of the above, the configurations of the present invention and variations thereof are listed below as supplementary notes.

(Appendix 1) a swinging part;
Frame,
A coupling part that couples the rocking part and the frame and defines a pivot axis in a rocking motion of the rocking part with respect to the frame;
The oscillating part includes a oscillating main part and a weight part attached to the oscillating main part and capable of changing in a direction intersecting the oscillating axis.
(Supplementary note 2) The micro oscillating device according to supplementary note 1, wherein the oscillating portion includes a support base fixed to the oscillating main portion, and a support beam connecting the support base and the weight portion.
(Additional remark 3) The said rocking | swiveling part has the 1st comb-tooth electrode fixed to the said rocking | fluctuation main part, and the said weight part cooperates with the said 1st comb-tooth electrode, and generates an electrostatic attraction. 3. The micro oscillating device according to appendix 1 or 2, which has a second comb electrode for the purpose.
(Supplementary Note 4) From the supplementary note 1, the connecting portion includes a plurality of torsion bars arranged in parallel, and two torsion bars selected from the plurality of torsion bars are relatively close to and away from each other. 4. The micro oscillating device according to any one of 3 above.
(Supplementary Note 5) A first drive mechanism capable of generating rotational torque in the first swing direction and controlling the magnitude and / or generation period of the rotational torque for the swing portion, and the swing A second drive mechanism capable of generating a rotational torque in a second swinging direction opposite to the first swinging direction and controlling a magnitude and / or generation period of the rotational torque. The micro oscillating device according to any one of appendices 1 to 4, further comprising:
(Appendix 6) a swinging part;
Frame,
A coupling part that couples the rocking part and the frame and defines a pivot axis in a rocking motion of the rocking part with respect to the frame;
The connecting portion includes a plurality of torsion bars arranged in parallel, and two torsion bars selected from the plurality of torsion bars are provided so as to be relatively close to and away from each other.
(Additional remark 7) The said rocking | swiveling part has a rocking | fluctuation main part and the 1st movable part which can be moved to the direction which is attached to the said rocking | fluctuation main part, and cross | intersects the said rocking | fluctuation axis, The said frame is The main frame part and a second movable part attached to the main frame part and displaceable in the same direction as the first movable part, and one torsion bar included in the connecting part is the first torsion bar The micro oscillating device according to appendix 4 or 6, which connects the second movable portion.
(Additional remark 8) The said rocking | swiveling part has the 1st comb-tooth electrode fixed to the said rocking | fluctuation main part, and the said 1st movable part cooperates with the said 1st comb-tooth electrode, and electrostatic attraction is carried out. The micro oscillating device according to appendix 7, which has a second comb electrode for generation.
(Supplementary Note 9) The frame includes a first comb electrode fixed to the frame main portion, and the second movable portion generates electrostatic attraction in cooperation with the first comb electrode. 9. The micro oscillating device according to appendix 7 or 8, having the second comb electrode.
(Supplementary Note 10) A first drive mechanism capable of generating a rotational torque in the first swing direction and controlling a magnitude and / or generation period of the rotational torque for the swing portion, and the swing A second drive mechanism capable of generating a rotational torque in a second swinging direction opposite to the first swinging direction and controlling a magnitude and / or generation period of the rotational torque. The micro oscillating device according to any one of appendices 6 to 9, further comprising:
(Supplementary note 11) a swing part;
Frame,
A connecting portion that connects the swinging portion and the frame, and that defines a swing axis in swinging motion of the swinging portion relative to the frame;
A first drive mechanism capable of generating a rotational torque in the first swing direction with respect to the swinging portion and controlling a magnitude and / or generation period of the rotational torque;
A second drive capable of generating rotational torque in a second swinging direction opposite to the first swinging direction and controlling a magnitude and / or generation period of the rotational torque with respect to the swinging unit; A micro oscillating device comprising a mechanism.
(Additional remark 12) The first driving mechanism and the second driving mechanism include a first comb electrode, a second comb electrode for generating electrostatic attraction in cooperation with the first comb electrode, and A third comb electrode for generating electrostatic attraction in cooperation with the first comb electrode; the first comb electrode is fixed to the swinging portion; and the second comb electrode is The third comb electrode is fixed to the frame at a position not facing the first comb electrode when not driven, and the third comb electrode is fixed to the frame at a position facing the first comb electrode when not driven. The micro oscillating device according to any one of appendices 5, 10, and 11, wherein the second and third comb electrodes are arranged in parallel.

X1, X2, X3, X4 Micromirror element 110 Oscillating part 111 Oscillating main part 112 Weight part 112a, 115, 140, 150, 160, 170 Comb electrode 113A, 113B Support base part 114A, 114B Support beam 116, 117 Wiring Part 120 Frame 121 First layer part 122 Second layer part 130 Connecting part 131, 132, 133 Torsion bar 210 Oscillating part 211 Oscillating main part 212A, 212B, 223A, 223B Movable part 213, 224 Support base part 214, 225 Spring Part 220 Frame 221 First layer part 222 Second layer part 223a, 226, 240, 250, 260, 270 Comb electrode 227 Wiring part 230 Connecting part 231, 232, 233 Torsion bar 310 Oscillating part 320 Frame 321 First layer Part 322 second layer part 330 connection 331 torsion bar 340,350,360,370,380,390 comb electrodes

Claims (3)

A swinging portion obtained by processing a material substrate having a conductive first layer, a conductive second layer, and an insulating layer between the first layer and the second layer. A frame, and a connecting portion that connects the swinging portion and the frame, and that defines a swing axis in a swinging operation of the swinging portion with respect to the frame, and the connecting portions are arranged in parallel A micro oscillating device including a plurality of torsion bars, and two torsion bars selected from the plurality of torsion bars are relatively close to and away from each other,
The swing part includes a swing main part, and a first movable part attached to the swing main part and capable of changing in a direction intersecting the swing axis, and the frame includes a frame main part. And a second movable part that is attached to the main frame part and can be displaced in the same direction as the first movable part, and one torsion bar included in the connecting part has the first and second movable parts Are connected,
The swinging main part is derived from the first layer, the first movable part is derived from the second layer, and the second movable part is derived from the second layer and the A micro oscillating device attached to a portion derived from the first layer in the main frame portion, wherein the one torsion bar is derived from the second layer.   The swing part has a first comb electrode fixed to the swing main part, and the frame is a second comb for generating electrostatic attraction in cooperation with the first comb electrode. The micro oscillating device according to claim 1, comprising a tooth electrode.   The frame includes a third comb electrode fixed to the frame main portion, and the second movable portion is a fourth comb for generating electrostatic attraction in cooperation with the third comb electrode. The micro oscillating device according to claim 2, comprising a tooth electrode.

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