Micro movable element array and a communication apparatus

A micro movable element array includes a first frame; a second frame; a first movable part row including plural first movable parts and a second movable part row including plural second movable parts. The first movable parts include first movable main parts. The second movable parts include second movable main parts. The first and second frames are stacked such that the first and second movable part rows are opposed to each other. In the first movable part row, the first movable parts are located such that the first movable main parts are arranged in a first direction and the first movable main parts and gaps are disposed alternately. In the second movable part row, the second movable parts are located such that the second movable main parts are arranged in the first direction and the second movable main parts are opposed to the corresponding gaps.

FIELD

The disclosures herein generally relate to a micro movable element array and a communication apparatus.

BACKGROUND

Recently, elements including minute structures formed by MEMS (micro electro mechanical systems) technique find wide application in various technical fields. The elements include micro movable elements including minute movable parts, such as a micro-mirror element, an angular velocity sensor, an acceleration sensor, etc. The micro-mirror element is utilized as an element which serves a light reflecting function, in the field of optical communication techniques or optical disk techniques, for example. The angular velocity sensor and the acceleration sensor are utilized for applications such as image stabilizing functions for video cameras or mobile phones with cameras, car navigation systems, airbag ignition timing system, attitude controlling systems of vehicles or robots, etc. Such micro movable elements are described in the following Patent Documents 1-4, for example.

FIGS. 39-41depict an example of a related art micro movable element90.FIG. 39is a plane view of the micro movable element90.FIGS. 40 and 41depict sectional views along a line XL-XL and a line XLI-XLI inFIG. 39, respectively.

The micro movable element90includes a movable main part91; a frame92surrounding the movable main part91; a frame93surrounding the frame92; a pair of torsion bars94coupling the movable main part91and the frame92; and a pair of torsion bars95coupling the frame92and the frame93. The pair of torsion bars94defines an axis B1of rotation of the movable main part91, and the pair of torsion bars95defines an axis B2of rotation of the frame92and thus the movable main part91. The axis B1and the axis B2intersect perpendicularly. In other words, the micro movable element90is a so-called oscillating element in two axes.

If the micro movable element90is configured as a micro-mirror element, for example, a mirror surface91ais provided on the movable main part91, and a predetermined first actuator (not illustrated) for generating a driving force for the rotation of the movable main part91around the axis B1is provided. Further, a predetermined second actuator (not illustrated) for generating a driving force for the rotation of the frame92and thus the movable main part91around the axis B2is provided. The movable main part91is driven to rotate or oscillate around the respective axes B1, B2by operating the actuators as appropriate. Such driving oscillation of the movable main part91causes a reflecting direction in which an optical signal is reflected by the mirror surface91aon the movable main part91be changed.

Further, if the micro movable element90is configured as an angular velocity sensor, opposed capacitance electrodes for detection (not illustrated) are provided as a pair on the movable main part91and the frame92, respectively. The capacitance electrodes for detection have capacitances changed according to the rotation amount of the movable main part91around the axis B1, for example. Further, a predetermined actuator (not illustrated) for generating a driving force for the rotation of the frame92and thus the movable main part91around the axis B2is provided. The actuator is operated to cause the frame92and thus the movable main part91to oscillate around the axis B2at a predetermined frequency or cycle. When a predetermined angular velocity is applied to the movable main part91in such an oscillated state, the movable main part91rotates around the axis B1and thus the capacitance between the capacitance electrodes for detection changes. The rotation amount of the movable main part91is detected based on the change in the capacitance, and the angular velocity applied to the movable main part91or the micro movable element91is derived based on the detection result.

According to the related art techniques, when a micro movable element array is configured by aligning plural micro movable elements90as described above in a row and sharing the frame93among the micro movable elements90to integrate them, it may be difficult to implement a sufficiently high population of the micro movable elements91in the element arranged direction. The reason is as follows.

The respective parts of the micro movable element array or the micro movable element90are formed from a material substrate using the MEMS technique. Thus, when an air gap is formed by penetrating the material substrate with a certain thickness, there is a limit to the minimum width of the air gap in term of processing technique. In other words, it may not be possible to reduce the spaced distances between the neighboring micro movable elements90of the micro movable element array below the processing limit. Therefore, it may not be possible to reduce the spaced distances between the movable main parts91of the neighboring micro movable elements90below the processing limit.

Further, the micro movable elements90of the micro movable element array have movable parts which are driven electrically. Thus, in the micro movable element array it is preferable to ensure the spaced distance between the neighboring micro movable elements90which is required to avoid mechanical interference or electric interference.

Due to the processing limit, the preference to avoid the mechanical interference, and the preference to avoid the electrical interference, as described above, according to the related art techniques, there is a case in which it is difficult to implement a sufficiently high population of the micro movable elements91in the element arranged direction.

If the sufficiently high population of the micro movable elements91in the element arranged direction cannot be implemented, there may be a case where the functionality of the micro movable element array including plural micro movable elements cannot be sufficiently enhanced. For example, a case is assumed where the micro movable elements90are micro-mirror elements and the micro movable element array is the micro-mirror element array installed in a wavelength-selective-optical switching device. In this case, the lower the population of the micro movable elements91in the element arranged direction becomes, the more the loss of the optical signals, which are received by the micro-mirror element array as a whole and reflected by the mirror surfaces, becomes. For example, a case is assumed where the micro movable elements90are angular velocity sensors or acceleration sensors and the micro movable element array is a sensing device. In this case, the lower the population of the micro movable elements91in the element arranged direction becomes, the more sensitive to noise the detection signal becomes and thus the sensitivity of the sensor is reduced. It is predicted that the plural neighboring micro movable elements90have a noise canceling effect between the neighboring micro movable elements90for the noise generated by the micro movable elements90; however, the lower the population of the micro movable elements91in the element arranged direction becomes, the more the noise canceling effect or noise reduction effect is reduced.

SUMMARY

According to an aspect of the embodiment, a micro movable element array is provided. The micro movable element array includes a first frame; a second frame; a first movable part row including plural first movable parts and a second movable part row including plural second movable parts. The first movable parts of the first movable part row include first movable main parts and are supported by the first frame. The second movable parts of the second movable part row include second movable main parts and are supported by the second frame. The first and second frames are stacked such that the first and second movable part rows are opposed to each other. In the first movable part row, the first movable parts are located such that the first movable main parts are arranged in a first direction and the first movable main parts and gaps are disposed alternately. In the second movable part row, the second movable parts are located such that the second movable main parts are arranged in the first direction and the second movable main parts are opposed to the corresponding gaps.

DESCRIPTION OF EMBODIMENTS

FIGS. 1 and 2illustrate a micro movable element array X1according to a first embodiment.FIG. 1is an exploded partly omitted plane view of the micro movable element array X1.FIG. 2is a partly omitted cross-sectional view of the micro movable element array X1.

The micro movable element array X1is a micro-mirror element array in the embodiment and includes a first array1, a second array2, a base part3, plural spacers4and plural spacers5. The plural spacers4are provided between the first and second arrays1and2and the plural spacers5are provided between the second array2and the base part3. The base part3is a wiring board (wirings are omitted inFIGS. 1 and 2). A part of the first array1is electrically coupled to a part of the wirings of the base part3via a part of spacers4, a part of the second array2and a part of spacers5. A part of the second array2is electrically coupled to a part of the wirings of the base part3via a part of spacers5. The spacers4and5for the electrical coupling are made from an electrically conductive material. For example, the spacers4and5are single or multilayered gold bumps.

FIG. 3is a partly omitted plane view of the first array1.FIG. 4is a partly omitted plane view of the second array2. The first and second arrays1and2include plural micro movable elements Y1, respectively. It is noted that inFIGS. 3 and 4some of the micro movable elements Y1are omitted.

FIGS. 5-14illustrate the micro movable elements Y1included in the first and second arrays1and2.FIG. 5is a plane view of the micro movable element Y1.FIG. 6is a partly omitted plane view of the micro movable element Y1.FIGS. 7-14are enlarged cross-sectional views along lines VII-VII, VIII-VIII, IX-IX, X-X, XI-XI, XII-XII, XIII-XIII and XIV-XIV, respectively.

The micro movable element Y1is a micro-mirror element in the embodiment and includes an inner movable part10, a frame20as an outer movable part, a frame30as a stationary part, a pair of coupling parts40, a pair of coupling parts50A and50B, and electrode parts60,70and80. Further, the micro movable element Y1is manufactured by processing a material substrate, which is a so-called SOC (silicon on insulator) wafer using the MEMS technique. The material substrate has a multilayered structure which includes a first silicon layer, a second silicon layer and an insulating layer between the first and second first silicon layers. The silicon layers have impurities doped therein to have a predetermined electrical conductivity. The respective parts of the micro movable element Y1mainly originate from the first silicon layer and/or the second silicon layer. For the sake of clarity of drawings, inFIGS. 3-5, the parts that originate from the first silicon layer are indicated by oblique line hatchings. Further, the structure illustrated inFIG. 6is the part of the micro movable element Y1which originates from the second silicon layer.

The inner movable part10includes a land part11, an electrode part12, a beam part13and a shield part14.

The land part11is a portion originating from the first silicon layer. The surface of the land part11is provided with a mirror surface11′ which has a light reflecting function. The land part11and the mirror surface11′ are a movable main part. The movable main part or land part11includes an opposed part11awhich is opposed to the frame20and partially made thin in a thickness direction H, as illustrated inFIG. 8. The opposed part11aextends at the edge of the land part11in a direction indicated by an arrow D2inFIG. 5. Further, the length L1of the land part11illustrated inFIGS. 5 and 8is 20-300 μm, for example.

The electrode part12is a portion originating from the first silicon layer and includes a pair of arms12A and12B, plural electrode teeth12aand plural electrode teeth12b. The electrode teeth12aextend from the arm12A toward the arm12B side, as illustrated inFIGS. 5 and 10, and are spaced side by side in a direction in which the arm12A extends, as illustrated inFIG. 5. The electrode teeth12bextend from the arm12B toward the arm12A side and are spaced side by side in a direction in which the arm12A extends. In this way, the electrode part12has a comb-teeth electrode structure. Further, the electrode part12is a portion to which a predetermined reference potential (for example, ground potential) is applied at the time of driving the micro movable element Y1.

The beam part13is a portion originating from the first silicon layer. The beam part13couples the land part11and the electrode part12.

The shield part14is a portion originating from the second silicon layer, as illustrated inFIG. 6. The shield part14is coupled to the electrode part12via the insulating layer15, as illustrated inFIG. 9. The shield part14and the electrode part12are electrically coupled via electrically conductive vias16penetrating the insulating layer15.

The frame20has a multilayered structure which includes a first layer part21originating from the first silicon layer, a second layer part22originating from the second silicon layer, and an insulating layer23between the first and second layer parts21and22, as illustrated inFIGS. 7 and 11, for example. The first layer part21includes parts21a,21band21cwhich are apart from each other, as illustrated inFIG. 5. The second layer part22includes parts22aand22bwhich are apart from each other, as illustrated inFIG. 6. The part21aof the first layer part21has such a shape that it partially surrounds the inner movable part10, as illustrated inFIG. 5. The part22aof the second layer part22has such a shape that it partially surrounds the inner movable part10. The parts21aand22aare electrically coupled via electrically conductive vias24penetrating the insulating layer23, as illustrated inFIG. 11. The parts21band22bare electrically coupled via electrically conductive vias25penetrating the insulating layer23. The parts21cand22aare electrically coupled via electrically conductive vias26penetrating the insulating layer23, as illustrated inFIG. 13.

Further, a frame20includes a pair of extended parts20A which extend along the land part11of the inner movable part10or the movable main part in a direction indicated by an arrow D2inFIGS. 5 and 6.

The pair of extended parts20A is opposed to the land part11or the opposed part11aof the movable main part via a clearance in the thickness direction H, as illustrated inFIG. 8. A gap G1between the land part11and the extended part20A in the thickness direction H is greater than the thinness of the insulating layer of the material substrate and is within a range from 0.5 μm to 20 μm, for example. Further, the length L2between the outer ends of the extended parts20A as illustrated inFIG. 8is less than or equal to the length L1of the land part11or the movable main part.

The frame30has a multilayered structure which includes a first layer part31originating from the first silicon layer, a second layer part32originating from the second silicon layer, and an insulating layer33between the first and second layer parts31and32, as illustrated inFIG. 12. The first layer part31includes parts31aand31bwhich are apart from each other, as illustrated inFIGS. 5 and 12. The part31aincludes parts which are apart from each other (not illustrated). The second layer part32includes parts32a,32band32cwhich are apart from each other, as illustrated inFIGS. 6 and 12. The part32aincludes parts which are apart from each other (not illustrated). The parts31band32bare electrically coupled via electrically conductive vias34penetrating the insulating layer33, as illustrated inFIG. 12. A part of the part31aand the part32care electrically coupled via an electrically conductive via35penetrating the insulating layer33, as illustrated inFIG. 14.

The paired coupling parts40include two torsion bars41, respectively, as illustrated inFIG. 5. The coupling parts40are portions originating from the first silicon layer. The coupling parts40couple to the beam portion13of the inner movable part10and the part21aof the first layer part21of the frame20to couple the inner movable part10and the frame20. The beam part13and the part21aare electrically coupled via the coupling parts40. The spacing between two torsion bars41which form the respective coupling parts40gradually increases, when viewed from the frame20side to the inner movable part10side. Further, the torsion bars41are thinner than the inner movable part10and the first layer part21of the frame20in the thickness direction H, as illustrated inFIG. 7. The pair of the coupling parts40defines the axis A1of the rotation of the inner movable part10or the movable main part (the land part11and the mirror surface11′). The extending direction of the electrode teeth12aand12bare parallel with the extending direction of the axis A1. The coupling parts40, each of which includes two torsion bars41such that the spacing between the torsion bars41gradually increases when viewed from the frame20side to the inner movable part10side, are suited for preventing an unnecessary displacement component from generating when the inner movable part10operates.

The paired coupling parts50A,50B include two torsion bars51, respectively, as illustrated inFIG. 5. The coupling parts50A,50B are portions originating from the first silicon layer and couple the frame20and the frame30. Specifically, as illustrated inFIG. 5, the coupling part50A couples the part21bof the first layer part21of the frame20and the part31bof the first layer part31of the frame30to couple the frame20and the frame30. The parts21band31bare electrically coupled via the coupling part50A. The coupling part50B couples the part21cof the first layer part21of the frame20and a part of the part31aof the first layer part31of the frame30to couple the frame20and the frame30. The part21cand the part of the part31aare electrically coupled via the coupling part50B. The spacing between two torsion bars51which form the respective coupling parts50A and50B gradually increases, when viewed from the frame30side to the frame20side. Further, as is the case with the torsion bars41, the torsion bars51are thinner than the first layer part21of the frame20and the first layer part31of the frame30in the thickness direction H. The pair of the coupling parts50A and50B defines an axis A2of rotation of the frame20and thus the inner movable part10. In the embodiment, the axis A2and the axis A1interconnect perpendicularly. The coupling parts50A and50B, each of which includes two torsion bars51such that the spacing between the torsion bars51gradually increases when viewed from the frame30side to the frame30side, is suited for preventing an unnecessary displacement component from generating when the frame20and thus the inner movable part10operates.

The electrode part60is a portion originating from the second silicon layer and includes an arm61, plural electrode teeth62aand plural electrode teeth62b, as well-illustrated inFIG. 6. The arm61extends from the part22bof the second layer part22of the frame20. The electrode teeth62aextend from the arm61toward the arm12A side of the electrode part12, and are spaced side by side in a direction in which the arm61extends. The electrode teeth62bextend from the arm61toward the arm12B side of the electrode part12, and are spaced side by side in the direction in which the arm61extends. In this way, the electrode part60has a comb-teeth electrode structure.

The electrode part70is a portion originating from the first silicon layer and includes plural electrode teeth71, as illustrated inFIG. 5. The electrode teeth71extend from the part21cof the first layer part21of the frame20toward the electrode part80side, as illustrated inFIGS. 5 and 14, and are spaced side by side in the extending direction of the axis A2. In this way, the electrode part70has a comb-teeth electrode structure.

The electrode part80is a portion originating from the second silicon layer and includes an arm81and plural electrode teeth82, as illustrated inFIG. 6. The arm81extends in the extending direction of the axis A2. The electrode teeth82extend from the arm81toward the electrode part70side and are spaced apart side by side in a direction in which the arm81extends. In this way, the electrode part80has a comb-teeth electrode structure.

In the micro movable element Y1, the pair of the electrode part12and60may form a driving mechanism or an actuator for generating the driving force associated with the rotation of the inner movable part10around the axis A1. Further, the pair of the electrode part70and80may form a driving mechanism or an actuator for generating the driving force associated with the rotation of the frame20and thus the inner movable part10around the axis A2.

At the time of driving the micro movable element Y1, the reference potential is applied to the electrode part12of the inner movable part10and the electrode part70. The reference potential may be applied to the electrode part12via a part of the part31aof the first layer part31of the frame30, the coupling part50B (the torsion bars51), the part21cof the first layer part21of the frame20, the electrically conductive vias26(illustrated inFIG. 13), the part22aof the second layer part22of the frame20, the electrically conductive vias24(illustrated inFIG. 11), the part21aof the first layer part21of the frame20, the coupling parts40(the torsion bars41), and the beam part13of the inner movable part10. The reference potential may be applied to the electrode part70via a part of the part31aof the first layer part31of the frame30, the coupling part50B (the torsion bars51), and the part21cof the first layer part21of the frame20. A portion (a reference potential applied part) of the part31aof the first layer part31of the frame30to which the reference potential is applied is spaced apart from other portions of the part31ato be electrically isolated therefrom. The reference potential is a ground potential, for example. Preferably, the reference potential is kept constant.

The driving potential higher than the reference potential is applied to the electrode parts60and80, respectively, as necessary. The application of the driving potential to the electrode part60generates electrostatic attraction between the electrode parts12and60and thus enables the inner movable part10to rotate around the axis A1, as illustrated inFIG. 15. The application of the driving potential to the electrode part80generates electrostatic attraction between the electrode parts70and80and thus enables the frame20and thus the inner movable part10to rotate around the axis A2. The micro movable element Y1is a so-called oscillating element in two axes. The driving potential may be applied to the electrode part60via the part32bof the second layer part32of the frame30, the electrically conductive vias34(illustrated inFIG. 12), the part31bof the first layer part31of the frame30, the coupling part50A (the torsion bars51), the part21bof the first layer part21of the frame20, the electrically conductive vias25(illustrated inFIG. 11), and the part22bof the second layer part22of the frame20. Such driving in the two axes can switch the reflecting direction of the light reflected by the mirror surface11′ on the land part11of the micro movable element Y1, as appropriate.

The first array1includes plural micro movable elements Y1, as illustrated inFIGS. 1-3. In the first array1, the micro movable elements Y1are aligned in a row in the extending direction of the axis A1such that all the axes A2(not illustrated inFIGS. 1-3) are parallel with each other. In the first array1, the frame30of the respective micro movable elements Y1is an integrated frame body which surrounds the first movable parts (i.e., the inner movable parts10, the frames20, the coupling parts40and the electrode parts60) of all the micro movable elements Y1. The first movable parts of all the micro movable elements Y1in the first array1form a first movable part row. In the first movable part row, the first movable parts are aligned in a row such that the land parts11including the mirror surfaces11′ (i.e. the movable main parts) and gaps G2are located alternately and the movable main parts are aligned in a row in an arrangement direction D1of the first movable parts. In the embodiment, in the first movable part row, the length L1of the land part11or the mirror surface11′ in the arrangement direction D1is set to be the same as the gap G2. Thus, in the embodiment, the population of the land parts11or the mirror surfaces11′ in the arrangement direction D1within the frame30of the first array1is about 50 percent. The population in the first array1may be set to different values. Further, in the first array1, the reference potential applied part of the part31aof the first layer part31of the frame30is continuous over all the micro movable elements Y1. The electrode parts12and the shield parts14of the inner movable parts10, the parts21aand21cof the first layer parts21and the parts22aof the second layer parts22of the frames20, the parts32cof the second layer part32of the frame30and the electrode parts70of all the micro movable elements Y1of the first array1are electrically coupled.

The second array2includes plural micro movable elements Y1, as illustrated inFIGS. 1,2and4. In the second array2, the micro movable elements Y1are aligned in a row in the extending direction of the axis A1such that all the axes A2(not illustrated inFIG. 4) are parallel with each other. In the second array2, the frame30of the respective micro movable elements Y1is an integrated frame body which surrounds the second movable parts (i.e., the inner movable parts10, the frames20, the coupling parts40and the electrode parts60) of all the micro movable elements Y1. The second movable parts of all the micro movable elements Y1in the second array2form a second movable part row. In the second movable part row, the second movable parts are aligned in a row such that the respective land parts11including the mirror surfaces11′ (i.e. the movable main parts) are opposed to the corresponding one of the gaps G2of the first movable part row and the movable main parts are aligned via the gaps G3in a row in an arrangement direction D1. Further, in the second movable part row, the movable main parts and the gaps G3are located alternately. If in the second movable part row the length L1of the land part11or the mirror surface11′ in the arrangement direction D1is set to be the same as the gap G3, the population of the land parts11or the mirror surfaces11′ in the arrangement direction D1within the frame30of the second array2is about 50 percent. The population in the second array2may be set to different values. The length L1of the land part11(or the mirror surface11′) of the second array2may be set such that opposite ends of the respective land parts11(or the mirror surface11′) of the second array2in the arrangement direction D1overlap the land parts11(or the mirror surface11′) of the first array1. In this case, in the second array2, G3is smaller than L1and the population of the land parts11or the mirror surfaces11′ in the arrangement direction D1within the frame30of the second array2is greater than 50 percent. Further, in the second array2, the reference potential applied part of the part31aof the first layer part31of the frame30is continuous over all the micro movable elements Y1. The electrode parts12and the shield parts14of the inner movable parts10, the parts21aand21cof the first layer parts21and the parts22aof the second layer parts22of the frames20, the parts32cof the second layer part32of the frame30and the electrode parts70of all the micro movable elements Y1of the second array2are electrically coupled.

The base part3includes a reference potential wiring and plural pairs of driving wirings (first driving wirings and second driving wirings). The reference potential wiring is electrically coupled to the reference potential applied parts of the parts31aof the first layer parts31of the respective frames30of the first and second arrays1and2. The first driving wirings are electrically coupled to the electrode parts60of the micro movable elements Y1of the first and second arrays1and2. The second driving wiring is electrically coupled to the electrode parts80of the micro movable elements Y1of the first and second arrays1and2. A concrete example is as follows.

In the first array1, the reference potential applied parts of the parts31aof the first layer part31of the frame30are electrically coupled to a part (reference potential applied parts) of the parts32aof the second layer part32of the frame30via predetermined electrically conductive vias (not illustrated) penetrating the insulating layer33of the frame30. The reference potential applied parts of the parts32aare coupled to at least one of the spacers4of the electrically conductive material which in turn is coupled to the reference potential applied parts of the parts31aof the first layer part31of the frame30of the second array2. Thus, the reference potential applied parts of the parts31aof the first layer part31of the frame30of the first array1are electrically coupled to the reference potential applied parts of the parts31aof the first layer part31of the frame30of the second array2. Further, in the second array2, the reference potential applied parts of the parts31aof the first layer part31of the frame30are electrically coupled to a part (reference potential applied parts) of the parts32aof the second layer part32of the frame30via predetermined electrically conductive vias (not illustrated) penetrating the insulating layer33of the frame30. The reference potential applied parts of the parts32aare coupled to at least one of the spacers5of the electrically conductive material which in turn is coupled to a part (i.e., the reference potential wiring) of the wirings of the base part3. Thus, the reference potential applied parts of the parts31aof the first layer parts31of the respective frames30of the first and second arrays1and2are electrically coupled to the reference potential wiring of the base part3.

The parts32of the second layer part32of the frame30of the micro movable elements Y1of the first array1(which are electrically coupled to the electrode parts60of the corresponding micro movable elements Y1) are coupled to the spacers4which are made from the electrically conductive material. The spacers4are coupled to a part (first driving potential applied parts) of the parts31aof the first layer part31of the frame30of the second array2. In the second array2, the first driving potential applied parts of the parts31aof the first layer part31of the frame30are electrically coupled to a part (first driving potential applied parts) of the parts32aof the second layer part32of the frame30via predetermined electrically conductive vias (not illustrated) penetrating the insulating layer33of the frame30. The first driving potential applied parts of the parts32aare coupled to the spacers5of the electrically conductive material which in turn are coupled to one of the first driving wirings of the base part3. Thus, the parts32band thus the electrode parts60of the micro movable elements Y1of the first array1are electrically coupled to one of the first driving wirings of the base part3.

The electrode parts80of the micro movable elements Y1of the first array1are coupled to the spacers4which are made from the electrically conductive material. The spacers4are coupled to a part (second driving potential applied parts) of the parts31aof the first layer part31of the frame30of the second array2. In the second array2, the second driving potential applied parts of the parts31aof the first layer part31of the frame30are electrically coupled to a part (second driving potential applied parts) of the parts32aof the second layer part32of the frame30via predetermined electrically conductive vias (not illustrated) penetrating the insulating layer33of the frame30. The second driving potential applied parts of the parts32aare coupled to the spacers5of the electrically conductive material which in turn are coupled to one of the second driving wirings of the base part3. Thus, the electrode parts80of the micro movable elements Y1of the first array1are electrically coupled to one of the second driving wirings of the base part3.

The parts32of the second layer part32of the frame30of the micro movable elements Y1of the second array2(which are electrically coupled to the electrode parts60of the corresponding micro movable elements Y1) are coupled to the spacers5which are made from the electrically conductive material. The spacers5are coupled to one of the first driving wirings of the base part3. Thus, the parts32band thus the electrode parts60of the micro movable elements Y1of the second array2are electrically coupled to one of the first driving wirings of the base part3.

The electrode parts80of the micro movable elements Y1of the second array2are coupled to the spacers5which are made from the electrically conductive material. The spacers5are coupled to one of the second driving wirings of the base part3. Thus, the electrode parts80of the micro movable elements Y1of the second array2are electrically coupled to one of the second driving wirings of the base part3.

Specifically, the electrical coupling relationships described above are formed between the reference potential applied parts (including the electrode parts12and70) and the electrode parts60and80of the micro movable elements Y1of the micro movable element array X1and the reference potential wiring and the pairs of the driving wirings.

At the time of driving the micro movable element array X1, the driving potential is applied to the respective electrode parts60and80of the selected micro movable element Y1while the reference potential is commonly applied to the electrode parts12of the inner movable parts10and the electrode parts70of all the micro movable elements Y1. In this way, the inner movable parts10and the frames20of the respective micro movable elements Y1are separately driven to oscillate, which enables switching the reflecting directions of the light reflected by the mirror surfaces11′ on the land parts11of the inner movable parts10of the micro movable elements Y1, as appropriate.

According to the micro movable element array X1having the configuration described above, the first array1or the frame30thereof and the second array2or the frame30thereof are multilayered via the spacers4. As illustrated inFIG. 3, the first movable parts (including the inner movable parts10and the frames20) of the micro movable elements Y1are supported by the frame30of the first array1such that the first movable parts form the first movable part row as described above. In the first movable part row, as described above, the first movable parts are aligned in a row such that the land parts11including the mirror surfaces11′ (i.e. the movable main parts) and gaps G2are located alternately and the movable main parts are aligned in a row in an arrangement direction D1.

On the other hand, as illustrated inFIG. 4, the second movable parts (including the inner movable parts10and the frames20) of the micro movable elements Y1are supported by the frame30of the second array2such that the second movable parts form the second movable part row as described above. In the second movable part row, as described above, the second movable parts are aligned in a row such that the respective land parts11including the mirror surfaces11′ (i.e. the movable main parts) are opposed to the corresponding one of the gaps G2of the first movable part row and the movable main parts are aligned via the gaps G3in a row in an arrangement direction D1.

In the micro movable element array X1, one of two neighboring movable parts in the arrangement direction D1is located on the first array1and another is located on the second array2, wherein the neighboring movable parts are shifted (offset) in the multilayered direction of the first and second array1and2, as illustrated inFIG. 2. Further, two neighboring movable main parts (the first and second movable main parts) in the arrangement direction D1are also shifted in the multilayered direction of the first and second array1and2. According to the micro movable element array X1, it is possible to arrange the movable main parts (the first and second movable main parts) of the two neighboring movable parts in the arrangement direction D1such that they are close to each other in spite of the processing limit while preventing the mechanical and electrical interference between two neighboring movable parts. Therefore, the micro movable element array X1can implement high population of the movable main parts (the land parts11including the mirror surfaces11′, in the embodiment) in the arrangement direction D1of the elements or movable parts. The higher the population of the land parts11or the mirror surfaces11′ in the arrangement direction D1, the more the loss can be reduced with respect to the optical signals received by the micro movable element array X1as a whole and reflected by the mirror surfaces11′. In the micro movable element array X1, it is possible to implement greater than or equal to 99 percent, that is to say, substantially 100 percent of the population of the land parts11or the mirror surfaces11′ in the arrangement direction D1. It is assumed that the micro movable element array X1is used as a wavelength selective switch in a wavelength division multiplexing (WDM) communication system. In this case, in the micro movable element array X1, it is possible to set a great wavelength band or frequency band by setting the wavelength band or the frequency band without interruption with respect to the optical signals as reflecting target signals allocated for the respective mirror surfaces11′.

In general, the light reflected by the edge of the light reflecting surface may be scattered. In the optical switching device, the scattered light may affect the quality of the commutation signals as noise. However, most of the scattered light generated by the reflection at the edges of the respective mirror surfaces11′ of the second array2of the micro movable element array X1is blocked by the movable parts (i.e., the lend parts11and the frames20) of the first array1. Thus, if the micro movable element array X1is used as a wavelength selective switch in a WDM communication system, for example, it is possible to reduce an influence of the scattered light on the communication signals.

In the respective micro movable elements Y1of the micro movable element array X1, the electrode parts12of the inner movable part10, the shield parts14, the parts22aof the second layer parts22of the frames20, and the parts32cof the second layer part32of the frame30are electrically coupled. Thus, the reference potential (for example, ground potential) is applied to the shield parts14, the parts22aand32cas well as the electrode parts12at the time of driving the micro movable element Y1. Therefore, the electric field generated from the electrode parts60toward the land parts11side of the inner movable part10, for example, due to the driving potential higher than the reference potential at the time of driving is easily absorbed by the shield parts14. In other words, it is difficult for the electric field to go beyond the shield parts14to reach the land parts11, for example. Further, the electric field generated from the electrode parts60at the time of driving is easily absorbed by the parts22a. In other words, it is difficult for the electric field to go beyond the parts22aside of the second layer parts22of the frames20to leak out of the elements. Further, the electric field generated from the electrode parts80to the side opposite to the electrode parts70due to the driving potential higher than the reference potential at the time of driving is easily absorbed by the parts32c. In other words, it is difficult for the electric field to go beyond the parts32cto leak out of the elements. These electric field absorption effects reduce or prevent the leak of the electric field out of the elements of the micro movable elements Y1. Because of the reduction or prevention of the leak of the electric field out of the elements, it is possible to prevent the electric field leaked from the driving mechanisms (electrode parts12,60,70and80) of the respective micro movable element Y1from affecting the driving property of other adjacent micro movable element Y1. Therefore, the electric field absorption effects contribute to increased density of the micro movable elements Y1in the arrangement direction and thus improved population of the movable main parts (the land parts11and the mirror surfaces11′) in the arrangement direction.

The micro movable elements Y1of the micro movable element array X1can be sensing devices such as an angular sensor or an acceleration sensor. In the case of the micro movable elements Y1being the sensing devices, the mirror surfaces11′ are not necessarily provided on the land parts11of the inner movable parts10.

If the micro movable element Y1functions as an angular sensor, the movable parts (i.e., the inner movable part10, the frame20, the coupling parts40, and the electrode part60) are oscillated around the axis A2at a certain frequency or cycle, for example, at the time of driving the micro movable element Y1. This oscillation operation is implemented by applying the voltage between the electrode parts70and80at a certain frequency. In an embodiment, the driving potential is applied to the electrode part80at certain frequency while the electrode part70is coupled to ground.

When a predetermined angular velocity is applied to the micro movable element Y1or the inner movable part10in such an oscillated state of the movable parts, the inner movable part10rotates around the axis A1by a certain amount to change the positional relationship between the electrode parts12and60, and thus the capacitance between the electrode parts12and60changes. The amount of the rotation of the inner movable part10may be detected based on the changes in the capacitance. The angular velocity applied to the micro movable element Y1or the inner movable part10may be derived based on the detection result.

If the micro movable element Y1functions as an acceleration sensor, a predetermined direct voltage is applied to between the electrode parts12and60to make the inner movable part10stationary with respect to the frame20and the electrode part60, for example, at the time of driving the micro movable element Y1. In this state, when an acceleration in a normal direction (i.e., a direction perpendicular to a paper of a plane view ofFIG. 5) is applied to the micro movable element Y1or the inner movable part10, an inertial force parallel with the acceleration acts. Then, the torque around the axis A1defined by the pair of the coupling parts40is applied to the inner movable part10, which causes the rotation (around the axis A1) of the inner movable part10proportional to the acceleration. The inertial force may be generated if the position of the center of gravity of the inner movable part10is designed not to be on the axis A1in a plane view ofFIG. 5. The amount of the rotation may be detected electrically as a change in the capacitance between the electrode parts12and60. The acceleration applied to the micro movable element Y1or the inner movable part10may be derived based on the detection result.

FIGS. 16-18illustrate an example of a way of manufacturing the micro movable element Y1included in the micro movable element array Y1. The way is an example for manufacturing the respective micro movable elements Y1using the MEMS technique. InFIGS. 16-18, a forming process of a land part L, a beam part L, frames F1, F2and F3, coupling parts C1and C2, and a pair of electrodes E1and E2illustrated inFIG. 18(d) is illustrated by changes in a single cross-section. The single cross-section is expressed as a continuous cross-section by modeling plural cross-sections at predetermined locations included in a single micro movable element forming section in a wafer to be processed. The land part L corresponds to a part of the land part11. The beam part B corresponds to the beam part13. The frame F1corresponds to a part of the frame20. The frame F2corresponds to the extended part20A of the frame20(i.e., a part of the parts22aof the second layer part22). The frame F3corresponds to a part of the frame30. The coupling part C1corresponds to the coupling part40and illustrates a cross-section of the torsion bar41in the longitudinal direction. The coupling part C2corresponds to one of the coupling parts40,50A and50B and illustrates a transverse section of the corresponding torsion bar41. The electrode E1corresponds to a part of the electrode parts12and70and illustrates a transverse section of the pair of the electrode teeth12aand the pair of the electrode teeth71. The electrode E2corresponds to a part of the electrode parts60and80and illustrates a transverse section of the pair of the electrode teeth61and the pair of the electrode teeth82.

In order to manufacture the micro movable element Y1, at first, a silicon wafer101′ such as illustrated inFIG. 16(a) is prepared. The silicon wafer101′ includes grooves101aextending at locations where the thin opposed parts11aof the land part11are formed. In order to make such a silicon wafer101′, DRIE (deep reactive ion etching) to a predetermined depth (30 μm, for example) is performed on an unprocessed wafer with a thickness of 200 μm, for example, utilizing a resist pattern as a mask which includes openings corresponding to the grooves101a. In DRIE, a favorable anisotropic etching process can be implemented in a Bosch process in which etching with SF6gas and protecting sidewalls with C4F8gas are repeated alternately. Such a Bosch process may be adopted in the DRIE described hereinafter. Further, the silicon wafer101′ is made from silicon material which has impurities doped therein to have an electrical conductivity. The impurities may include a p-type impurity such as B or an n-type impurity such as P and Sb.

Next, as illustrated inFIG. 16(b), an insulating film101bis formed on the silicon wafer101′. The insulating film101bmay be formed by oxidizing the surface of the silicon wafer101′ using a thermal oxidation process, for example. The thickness of the insulating film101bis 500 nm, for example. After this process, plural electrically conductive parts (not illustrated), which form corresponding parts of the respective electrically conductive vias (including the electrically conductive vias16,24-26,34and35), are embedded in the insulating film101b. Specifically, opening parts are formed in the insulating film101bat predetermined locations and the opening parts are filled with electrically conductive materials. The electrically conductive materials may include tungsten or polysilicon, for example.

Next, the silicon wafer102′ having an insulating film102aon its surface, as illustrated inFIG. 16(c), is prepared. The silicon wafer102′ is made from silicon material which has impurities doped therein to have an electrical conductivity. The impurities may include a p-type impurity such as B or an n-type impurity such as P and Sb. The thickness of the silicon wafer102′ is 200 μm, for example. The thickness of the insulating film102ais 500 nm, for example. The insulating film102amay be formed by oxidizing the surface of the silicon wafer102′ using a thermal oxidation process, for example. Further, plural electrically conductive parts (not illustrated), which form corresponding parts of the respective electrically conductive vias (including the electrically conductive vias16,24-26,34and35), are embedded in the insulating film102a. The electrically conductive parts may be formed by forming opening parts in the insulating film102aat predetermined locations and filling the opening parts with the electrically conductive materials. The electrically conductive materials may include tungsten or polysilicon, for example.

Next, as illustrated inFIG. 16(d), the silicon wafers101′ and102′ are registered and then bonded to each other. In this way, the respective electrically conductive vias are formed by the electrically conductive parts embedded in the insulating film101band the electrically conductive parts embedded in the insulating film102a. In order to bond the silicon wafers101′ and102′, for example, the silicon wafers101′ and102′ are cleaned by an ammonia solution, bonded together in a clean circumstance, and then annealed in an atmosphere of nitrogen, at 1200 degree Celsius, for example.

Next, the silicon wafers101′ and102′ are polished separately to have desired thicknesses, as illustrated inFIG. 17(a). In this way, a material substrate100as a SOI wafer having a multilayered structure is obtained which includes a silicon layer101including the grooves101a, a silicon layer102, and an insulating layer103between the silicon layers101and102. The electrically conductive vias (including the electrically conductive vias16,24-26,34and35) are embedded in the insulating layer103of the material substrate100. The thickness of the silicon layer101is within a range from 20 μm to 200 μm, for example, the thickness of the silicon layer102is within a range from 20 μm to 200 μm, for example, and the thickness of the insulating layer103is within a range from 0.3 μm to 2 μm, for example.

Next, as illustrated inFIG. 17(b), the mirror surface11′ is formed on the silicon layer101. In order to form the mirror surface11′, at first, a Cr film (50 nm), for example, and then an Au film (200 nm) are formed on the silicon layer101, by a sputtering process. Next, the mirror surface11′ is pattern-formed by successively etching these metal films via masks. The etchant for Au may be a potassium iodide-iodine solution, for example. The etchant for Cr may be a di-ammonium cerium nitrate, for example.

Next, as illustrated inFIG. 17(c), an oxide film pattern110and a resist pattern111are formed on the silicon layer101and an oxide film pattern112is formed on the silicon layer102. The oxide film pattern110has a pattern shape, as illustrated inFIG. 19, which corresponds to a part of the inner movable part10(including the land part11, the electrode part12and the beam part13), the first layer part21of the frame20, the first layer part31of the frame30and the electrode part70to be formed in the silicon layer101. To form the oxide film pattern110, an oxide material is deposited on the material substrate100of the silicon layer101side, by a sputtering or CVD process, for example, and then the oxide material film is subject to patterning. The resist pattern111has a pattern shape corresponding the coupling parts40,50A and50B. In order to form the resist pattern111, the resist material is deposited on the material substrate100of the silicon layer101side, by a spin coating process, for example, and then the resist film is subject to patterning. The oxide film pattern112has a pattern shape, as illustrated inFIG. 20, which corresponds to the shield part14of the inner movable part10, the second layer part22of the frame20, the second layer part32of the frame30and the electrode parts60and80to be formed in the silicon layer102. To form the oxide film pattern112, an oxide material is deposited on the material substrate100of the silicon layer102side, by a sputtering or CVD process, and then the oxide material film is subject to patterning.

Next, as illustrated inFIG. 17(d), DRIE to a desired depth is performed on the silicon layer101utilizing the oxide film pattern110and the resist pattern111as a mask. The desired depth corresponds to the thickness of the coupling part C1and C2, and is 5 μm, for example.

Next, as illustrated inFIG. 18(a), the resist pattern111is removed. For example, the resist pattern111may removed by the action of a predetermined release agent.

Next, DRIE is performed on the silicon layer101while remaining the coupling parts C1and C2utilizing the oxide film pattern110as a mask, as illustrated inFIG. 18(b). In this process, the land part L, the beam part B, the electrode E1, a part of the frame F1(the first layer part21of the frame20), a part of the frame F3(the first layer part31of the frame30) and the coupling parts C1and C2are formed.

Next, as illustrated inFIG. 18(c), DRIE is performed on the silicon layer102utilizing the oxide film pattern112as a mask. In this process, a part of the frame F1(the second layer part22of the frame20), the frame F2(the extend parts20A which is a part of the second layer part22of the frame20), a part of the frame F3(the second layer part32of the frame30) and the electrode E2are formed.

Next, as illustrated inFIG. 18(d), exposed regions of the insulating layer103and the oxide film patterns110and112are removed by etching. The etching process may be a dry etching process or a wet etching process. In the case of the dry etching, the etching gas may be CF4or CHF3, etc., for example. In the case of the wet etching, the etchant may be Buffered Hydrofluoric acid (BHF) comprised of hydrofluoric acid and ammonium fluoride.

According to the a series of processes described above, the land part L, the micro movable element Y can be manufactured by forming or the like of the beam part B, the frames F1, F2and F3, the coupling parts C1and C2, and the pair of the electrodes E1and E2. The first and second arrays of the micro movable element array X1can be manufactured by performing these processes on a micro movable element basis.

In order to manufacture the micro movable element array X1, at first, the base part3is formed by patterning the reference potential wiring and the pairs of the driving wirings on the substrate. Next, the spacers5are formed on the base part3by wire bonding. Next, after the electrically conductive adhesive has been applied to the apexes of the head parts of the spacers5, the base part3and the second array2are registered and then bonded via the spacers5and electrically conductive adhesive. Next, the spacers4are formed on the second array2by wire bonding. Next, after the electrically conductive adhesive has been applied to the apexes of the head parts of the spacers4, the first array1and the second array2(including the base part3) are registered and then bonded via the spacers4and electrically conductive adhesive.

FIGS. 21 and 22illustrate a micro movable element array X2according to a second embodiment.FIG. 21is an exploded partly omitted plane view of the micro movable element array X2.FIG. 22is a partly omitted cross-sectional view of the micro movable element array X2.

The micro movable element array X2is a micro-mirror element array in the embodiment and includes a first array6, a second array7, the base part3, the spacers4and the spacers5. The spacers4are provided between the first and second arrays6and7and the spacers5are provided between the second array7and the base part3. The base part3is a wiring board (wirings are omitted inFIGS. 21 and 22). A part of the first array6is electrically coupled to a part of the wirings of the base part3via a part of the spacers4, a part of the second array7and a part of the spacers5. A part of the second array7is electrically coupled to a part of the wirings of the base part3via a part of the spacers5. The spacers4and5for the electrical coupling are made from an electrically conductive material. For example, the spacers4and5are single or multilayered gold bumps.

FIG. 23is a partly omitted plane view of the first array6. The first array6includes plural micro movable elements Y2. It is noted that inFIG. 23some of the micro movable elements Y2are omitted.FIG. 24is a partly omitted plane view of the second array7. The second array7includes plural micro movable elements Y3. It is noted that inFIG. 24some of the micro movable elements Y3are omitted.

FIGS. 25-34illustrate the micro movable elements Y2included in the first array6.FIG. 25is a plane view of the micro movable element Y2.FIG. 26is a partly omitted plane view of the micro movable element Y2.FIGS. 27-34are enlarged cross-sectional views along lines XXVII-XXVII, XXXVIII-XXXVIII, XXIX-XXIX, XXX-XXX, XXXI-XXXI, XXXII-XXXII, XXXIII-XXXIII and XXXIV-XXXIV, respectively.

The micro movable element Y2is a micro-mirror element in the embodiment and includes an inner movable part10, a frame20as an outer movable part, a frame30′ as a stationary part, a pair of coupling parts40, a pair of coupling parts50C and50D, and electrode parts60,70and80′. The micro movable element Y2differs from the micro movable element Y1described above in that it includes the frame30′, the pair of coupling parts50C and50D, and the electrode part80′ instead of the frame30, the pair of coupling parts50A and50B, and the electrode part80, respectively. The configuration of the micro movable element Y2is the same as the micro movable element Y1except for the frame30′, the pair of coupling parts50C and50D, and the electrode part80′. Further, the micro movable element Y2is manufactured by processing a material substrate which is the SOC wafer using the MEMS technique, as is the case with the micro movable element Y1. The material substrate has a multilayered structure which includes a first silicon layer, a second silicon layer and an insulating layer between the first and second first silicon layers. The silicon layers have impurities doped therein to have a predetermined electrical conductivity. The respective parts of the micro movable element Y2mainly originate from the first silicon layer and/or the second silicon layer. For the sake of clarity of drawings, inFIGS. 23 and 25, the parts originating from the first silicon layer are indicated by oblique line hatchings. Further, the structure illustrated inFIG. 26is the part of the micro movable element Y2which originates from the second silicon layer.

The frame30′ has a multilayered structure which includes a first layer part31originating from the first silicon layer, a second layer part32originating from the second silicon layer, and an insulating layer33between the first and second layer parts31and32, as illustrated inFIG. 32. The first layer part31includes parts31aand31bwhich are apart from each other, as illustrated inFIGS. 25 and 32. The part31aincludes parts which are apart from each other (not illustrated). The second layer part32includes parts32a,32band32cwhich are apart from each other, as illustrated inFIGS. 26 and 32. The part32aincludes parts which are apart from each other (not illustrated). The parts31band32bare electrically coupled via electrically conductive vias34penetrating the insulating layer33, as illustrated inFIG. 32.

The paired coupling parts40include two torsion bars41, respectively, as illustrated inFIG. 25. The coupling parts40are portions originating from the first silicon layer. The coupling parts40couple to the beam portion13of the inner movable part10and the part21aof the first layer part21of the frame20to couple the inner movable part10and the frame20. The beam part13and the part21aare electrically coupled via the coupling parts40. The spacing between two torsion bars41which form the respective coupling parts40gradually increases, when viewed from the frame20side to the inner movable part10side. Further, the torsion bars41are thinner than the inner movable part10and the first layer part21of the frame20in the thickness direction H, as illustrated inFIG. 27. The pair of the coupling parts40defines the axis A1of the rotation of the inner movable part10or the movable main part (the land part11and the mirror surface11′). The extending direction of the electrode teeth12aand12bare parallel with the extending direction of the axis A1. The coupling parts40, each of which includes two torsion bars41such that the spacing between the torsion bars41gradually increases when viewed from the frame20side to the inner movable part10side, are suited for preventing an unnecessary displacement component from being generated when the inner movable part10operates.

The paired coupling parts50C,50D include an elastic bar, respectively, as illustrated inFIG. 25. The coupling parts50C,50D are portions originating from the first silicon layer and couple the frame20and the frame30′. Specifically, as illustrated inFIG. 25, the coupling part50C couples the part21bof the first layer part21of the frame20and the part31bof the first layer part31of the frame30′ to couple the frame20and the frame30′. The parts21band31bare electrically coupled via the coupling part50C. The coupling part50D couples the part21cof the first layer part21of the frame20and a part of the part31aof the first layer part31of the frame30′ to couple the frame20and the frame30′. The part21cand the part of the part31aare electrically coupled via the coupling part50D. Further, as is the case with the torsion bars41, the coupling parts50C,50D are thinner than the first layer part21of the frame20and the first layer part31of the frame30′ in the thickness direction H. The paired coupling parts50C,50D are elastic portions for supporting the micro movable element Y2such that the movable parts (the inner movable part10, the frame20, the coupling parts40, and the electrode parts60and70) can perform a translational movement in the direction of the axis A1.

The electrode part80′ is a portion originating from the first silicon layer and includes an arm81and plural electrode teeth82, as illustrated inFIG. 25. The arm81extends in the extending direction of the axis A2. The electrode teeth82extend from the arm81toward the electrode part70side and are spaced apart side by side in a direction in which the arm81extends. In this way, the electrode part80′ has a comb-teeth electrode structure. Further, the arm81of the electrode part80′ is electrically coupled to the part32cof the frame30′ via the electrically conductive via35penetrating the insulating layer33, as illustrated inFIG. 34.

In the micro movable element Y2, the pair of the electrode parts12and60may form a driving mechanism or an actuator for generating the driving force associated with the rotation of the inner movable part10around the axis A1. Further, the pair of the electrode part70and80may form a driving mechanism or an actuator for generating the driving force associated with the translation of the frame20and thus the inner movable part10in the direction of the axis A1.

At the time of driving the micro movable element Y2, the reference potential is applied to the electrode part12of the inner movable part10and the electrode part70. The reference potential may be applied to the electrode part12via a part of the part31aof the first layer part31of the frame30′, the coupling part50D, the part21cof the first layer part21of the frame20, the electrically conductive vias26(illustrated inFIG. 33), the part22aof the second layer part22of the frame20, the electrically conductive vias24(illustrated inFIG. 31), the part21aof the first layer part21of the frame20, the torsion bars41of the coupling parts40, and the beam part13of the inner movable part10. The reference potential may be applied to the electrode part70via a part of the part31aof the first layer part31of the frame30′, the coupling part50D, and the part21cof the first layer part21of the frame20. A portion (a reference potential applied part) of the part31aof the first layer part31of the frame30′ to which the reference potential is applied is spaced apart from other portion of the part31ato be electrically isolated therefrom. The reference potential is ground potential, for example. Preferably, the reference potential is kept constant.

At the time of driving the micro movable element Y2, the driving potential higher than the reference potential is applied to the electrode part60, as necessary. The application of the driving potential to the electrode part60generates electrostatic attraction between the electrode parts12and60and thus enables the inner movable part10to rotate around the axis A1. The driving potential may be applied to the electrode part60via the part32bof the second layer part32of the frame30′, the electrically conductive vias34(illustrated inFIG. 32), the part31bof the first layer part31of the frame30′, the coupling part50C, the part21bof the first layer part21of the frame20, the electrically conductive vias25(illustrated inFIG. 31), and the part22bof the second layer part22of the frame20. Such driving can switch the reflecting direction of the light reflected by the mirror surface11′ on the land part11of the micro movable element Y2, as appropriate.

At the time of driving the micro movable element Y2, the driving potential higher than the reference potential is applied to the electrode part80′, as necessary. The application of the driving potential to the electrode part80′ generates electrostatic attraction between the electrode parts70and80and thus enables the frame20and thus the land part11(the mirror surface11′) of the inner movable part10to perform the translational movement in the direction of the axis A2. The driving potential may be applied to the electrode part80′ via the part32cof the second layer part32of the frame30′ and the electrically conductive via35(illustrated inFIG. 34).

FIGS. 35 and 36illustrate the micro movable elements Y3included in the second array7.FIG. 35is a plane view of the micro movable element Y3.FIG. 36is an enlarged cross-sectional view along a line XXXVI-XXXVI inFIG. 35.

The micro movable element Y3is a micro-mirror element in the embodiment and includes an inner movable part10, a frame20as an outer movable part, a frame30as a stationary part, a pair of coupling parts40, a pair of coupling parts50A and50B, electrode parts60,70and an electrode part80. The length of the land part11or the mirror surface11′ of the inner movable part10of the micro movable element Y3in the direction of the axis A1is longer than that of the micro movable element Y1. The length L3of the land part11or the mirror surface11′ of the inner movable part10of the micro movable element Y3is within a range from 50 μm to 500 μm, for example, as long as it is greater than the length L1in the micro movable element Y1. In the micro movable element Y3, the length L3of the land part11or the movable main part is greater than the length L2between the outer ends of the extended parts20A as illustrated inFIG. 36. The other configuration of the micro movable element Y3may be the same as the micro movable element Y1. Further, the micro movable element Y3is manufactured by processing a material substrate which is the SOC wafer using the MEMS technique, as is the case with the micro movable element Y1. The material substrate has a multilayered structure which includes a first silicon layer, a second silicon layer and an insulating layer between the first and second first silicon layers. The silicon layers have impurities doped therein to have a predetermined electrical conductivity. The respective parts of the micro movable element Y3mainly originate from the first silicon layer and/or the second silicon layer. For the sake of clarity of a drawing, inFIG. 35, the parts originating from the first silicon layer are indicated by oblique line hatchings.

At the time of driving the respective micro movable elements Y3, the reference potential is applied to the electrode parts12of the inner movable parts10and the electrode parts70. The electrical path for applying the reference potential to the electrode parts12and70is the same as the one described above with reference to the driving of the micro movable element Y1. The reference potential is ground potential, for example. Preferably, the reference potential is kept constant.

At the time of driving the micro movable element Y3, the driving potential higher than the reference potential is applied to the electrode parts60and80, respectively, as necessary. The application of the driving potential to the electrode part60generates electrostatic attraction between the electrode parts12and60and thus enables the inner movable part10to rotate around the axis A1. The application of the driving potential to the electrode part80generates electrostatic attraction between the electrode parts70and80and thus enables the frame20and thus the inner movable part10to rotate around the axis A2. The micro movable element Y3is a so-called oscillating element in two axes. The electrical path for applying the driving potential to the electrode parts60and80is the same as the one described above with reference to the driving of the micro movable element Y1. Such driving in the two axes can switch the reflecting direction of the light reflected by the mirror surface11′ on the land part11of the micro movable element Y3, as appropriate.

The first array6includes plural micro movable elements Y2, as illustrated inFIGS. 21-23. In the first array6, the micro movable elements Y2are aligned in a row in the extending direction of the axis A1such that all the axes A2(not illustrated inFIGS. 21-23) are parallel with each other. In the first array6, the frame30′ of the respective micro movable elements Y2is an integrated frame body which surrounds the first movable parts (i.e., the inner movable parts10, the frames20, the coupling parts40and the electrode parts60) of all the micro movable elements Y2. The first movable parts of all the micro movable elements Y2in the first array6form a first movable part row. In the first movable part row, the first movable parts are aligned in a row such that the land parts11including the mirror surfaces11′ (i.e. the movable main parts) and gaps G2are located alternately and the movable main parts are aligned in a row in an arrangement direction D1of the first movable parts. In the embodiment, in the first movable part row, the length L1of the land part11or the mirror surface11′ in the arrangement direction D1is set to be the same as the gap G2. Thus, in the embodiment, the population of the land parts11or the mirror surfaces11′ in the arrangement direction D1within the frame30′ of the first array6is about 50 percent. The population in the first array6may be set to different values. Further, in the first array6, the reference potential applied part of the part31aof the first layer part31of the frame30′ is continuous over all the micro movable elements Y2. The electrode parts12and the shield parts14of the inner movable parts10, the parts21aand21cof the first layer parts21and the parts22aof the second layer parts22of the frames20, the parts32cof the second layer part32of the frame30′ and the electrode parts70of all the micro movable elements Y2of the first array6are electrically coupled.

The second array7includes plural micro movable elements Y3, as illustrated inFIGS. 21,22and24. In the second array7, the micro movable elements Y3are aligned in a row in the extending direction of the axis A1such that all the axes A2(not illustrated inFIGS. 21,22and24) are parallel with each other. In the second array7, the frame30of the respective micro movable elements Y3is an integrated frame body which surrounds the second movable parts (i.e., the inner movable parts10, the frames20, the coupling parts40and the electrode parts60) of all the micro movable elements Y3. The second movable parts of all the micro movable elements Y3in the second array7form a second movable part row. In the second movable part row, the second movable parts are aligned in a row such that the respective land parts11including the mirror surfaces11′ (i.e. the movable main parts) are opposed to the corresponding one of the gaps G2of the first movable part row and the movable main parts are aligned via the gaps G3in a row in an arrangement direction D1. Further, in the second movable part row, the movable main parts and the gaps G3are located alternately. If in the second movable part row the length L3of the land part11or the mirror surface11′ in the arrangement direction D1is set to be the same as the gap G3, the population of the land parts11or the mirror surfaces11′ in the arrangement direction D1within the frame30of the second array7is about 50 percent. The population in the second array7may be set to different values. The length L1of the land part11(or the mirror surface11′) of the second array7may be set such that opposite ends of the respective land parts11(or the mirror surface11′) of the second array7in the arrangement direction D1overlap the land parts11(or the mirror surface11′) of the first array6. In this case, in the second array7, G3is smaller than L3and the population of the land parts11or the mirror surfaces11′ in the arrangement direction D1within the frame30of the second array7is greater than 50 percent. Further, in the second array7, the reference potential applied part of the part31aof the first layer part31of the frame30is continuous over all the micro movable elements Y3. The electrode parts12and the shield parts14of the inner movable parts10, the parts21aand21cof the first layer parts21and the parts22aof the second layer parts22of the frames20, the parts32cof the second layer part32of the frame30and the electrode parts70of all the micro movable elements Y3of the second array7are electrically coupled.

The base part3includes a reference potential wiring and plural pairs of driving wirings (first driving wirings and second driving wirings). The reference potential wiring is electrically coupled to the reference potential applied parts of the parts31aof the first layer parts31of the frames30′ and30of the first and second arrays6and7. The first driving wirings are electrically coupled to the electrode parts60of the micro movable elements Y2of the first array6and the electrode parts60of the micro movable elements Y3of the second array7. The second driving wirings are electrically coupled to the electrode parts80′ of the micro movable elements Y2of the first array6and the electrode parts80of the micro movable elements Y3of the second array7. A concrete example is as follows.

In the first array6, the reference potential applied parts of the parts31aof the first layer part31of the frame30′ are electrically coupled to a part (reference potential applied parts) of the parts32aof the second layer part32of the frame30′ via predetermined electrically conductive vias (not illustrated) penetrating the insulating layer33of the frame30′. The reference potential applied parts of the parts32aare coupled to at least one of the spacers4of the electrically conductive material which in turn is coupled to the reference potential applied parts of the parts31aof the first layer part31of the frame30of the second array7. Thus, the reference potential applied parts of the parts31aof the first layer part31of the frame30′ of the first array6are electrically coupled to the reference potential applied parts of the parts31aof the first layer part31of the frame30of the second array7. Further, in the second array7, the reference potential applied parts of the parts31aof the frame30are electrically coupled to a part (reference potential applied parts) of the parts32aof the frame30via predetermined electrically conductive vias (not illustrated) penetrating the insulating layer33of the frame30. The reference potential applied parts of the parts32aare coupled to at least one of the spacers5of the electrically conductive material which in turn is coupled to a part (i.e., the reference potential wiring) of the wirings of the base part3. Thus, the reference potential applied parts of the parts31aof the first layer parts31of the frames30′ and30of the first and second arrays6and7are electrically coupled to the reference potential wiring of the base part3.

The parts32bof the second layer part32of the frame30′ of the micro movable elements Y2of the first array6(which are electrically coupled to the electrode parts60of the corresponding micro movable elements Y2) are coupled to the spacers4which are made from the electrically conductive material. The spacers4are coupled to a part (first driving potential applied parts) of the parts31aof the first layer part31of the frame30of the second array7. In the second array7, the first driving potential applied parts of the parts31aof the first layer part31of the frame30are electrically coupled to a part (first driving potential applied parts) of the parts32aof the second layer part32of the frame30via predetermined electrically conductive vias (not illustrated) penetrating the insulating layer33of the frame30. The first driving potential applied parts of the parts32aare coupled to the spacers5of the electrically conductive material which in turn are coupled to one of the first driving wirings of the base part3. Thus, the parts32band thus the electrode parts60of the micro movable elements Y2of the first array6are electrically coupled to one of the first driving wirings of the base part3.

The parts32cof the second layer part32of the frame30′ of the micro movable elements Y2of the first array6(which are electrically coupled to the electrode parts80′ of the corresponding micro movable elements Y2) are coupled to the spacers4which are made from the electrically conductive material. The spacers4are coupled to a part (second driving potential applied parts) of the parts31aof the first layer part31of the frame30of the second array7. In the second array7, the second driving potential applied parts of the parts31aof the first layer part31of the frame30are electrically coupled to a part (second driving potential applied parts) of the parts32aof the second layer part32of the frame30via predetermined electrically conductive vias (not illustrated) penetrating the insulating layer33of the frame30. The second driving potential applied parts of the parts32aare coupled to the spacers5of the electrically conductive material which in turn are coupled to one of the second driving wirings of the base part3. Thus, the parts32cand thus the electrode parts80′ of the micro movable elements Y2of the first array6are electrically coupled to one of the second driving wirings of the base part3.

The parts32of the second layer part32of the frame30of the micro movable elements Y3of the second array7(which are electrically coupled to the electrode parts60of the corresponding micro movable elements Y3) are coupled to the spacers5which are made from the electrically conductive material. The spacers5are coupled to one of the first driving wirings of the base part3. Thus, the parts32band thus the electrode parts60of the micro movable elements Y3of the second array7are electrically coupled to one of the first driving wirings of the base part3.

The electrode parts80of the micro movable elements Y3of the second array7are coupled to the spacers5which are made from the electrically conductive material. The spacers5are coupled to one of the second driving wirings of the base part3. Thus, the electrode parts80of the micro movable elements Y3of the second array7are electrically coupled to one of the second driving wirings of the base part3.

Specifically, the electrical coupling relationships described above are formed between the reference potential applied parts (including the electrode parts12and70) and the electrode parts60,80and80′ of the micro movable elements Y2and Y3of the micro movable element array X2and the reference potential wiring and the pairs of the driving wirings.

The reference potential is commonly applied to the electrode parts12of the inner movable parts10and the electrode parts70of all the micro movable elements Y2and Y3at the time of driving the micro movable element array X2. In this state, the driving potential is applied to the respective electrode parts60and80′ of the selected micro movable element Y2, as necessary. In the micro movable element Y2, the inner movable part10can be rotated around the axis A1by the application of the driving potential to the electrode60, and the land part11(and the mirror surface11′) of the inner movable part10can be translated in the direction of the axis A1by the application of the driving potential to the electrode80′. Further, the driving potential is applied to the respective electrode parts60and80of the selected micro movable element Y3, as necessary. In this way, in the respective micro movable elements Y2, the inner movable parts10(including the land parts11with the mirror surfaces11′) are operated to oscillate, and the frames20and thus the inner movable parts10(including the land parts11with the mirror surfaces11′) are operated to oscillate. According to the micro movable elements Y2, it is possible to switch the reflecting direction of the light reflected by the mirror surfaces11′ on the land parts11of the micro movable elements Y2and Y3, as appropriate.

According to the micro movable element array X2having the configuration described above, the first array6or the frame30′ thereof and the second array7or the frame30thereof are multilayered via the spacers4. As illustrated inFIG. 23, the first movable parts (including the inner movable parts10and the frames20) of the micro movable elements Y2are supported by the frame30′ of the first array6such that the first movable parts form the first movable part row as described above.

On the other hand, as illustrated inFIG. 24, the second movable parts (including the inner movable parts10and the frames20) of the micro movable elements Y3are supported by the frame30of the second array7such that the second movable parts form the second movable part row as described above. In the second movable part row, as described above, the second movable parts are aligned in a row such that the respective land parts11including the mirror surfaces11′ (i.e. the movable main parts) are opposed to the corresponding one of the gaps G2of the first movable part row and the movable main parts are aligned via the gaps G3in a row in an arrangement direction D1.

In the micro movable element array X1, one of two neighboring movable parts in the arrangement direction D1is located on the first array6and another is located on the second array7, wherein the neighboring movable parts are shifted (offset) in the multilayered direction of the first and second array6and7, as illustrated inFIG. 22. Further, two neighboring movable main parts (the first and second movable main parts) in the arrangement direction D1are also shifted in the multilayered direction of the first and second array6and7. According to the micro movable element array X2, it is possible to arrange the movable main parts (the first and second movable main parts) of the two neighboring movable parts in the arrangement direction D1such that they are close to each other in spite of the processing limit while preventing the mechanical and electrical interference between two neighboring movable parts. Therefore, the micro movable element array X2can implement high population of the movable main parts (the land parts11including the mirror surfaces11′, in the embodiment) in the arrangement direction D1or movable part arrangement direction. The higher the population of the land parts11or the mirror surfaces11′ in the arrangement direction D1, the more the loss can be reduced with respect to the optical signals received by the micro movable element array X2as a whole and reflected by the mirror surfaces11′. In the micro movable element array X2, it is possible to implement greater than or equal to 99 percent, that is to say, substantially 100 percent of the population of the land parts11or the mirror surfaces11′ in the arrangement direction D1. It is assumed that the micro movable element array X2is used as a wavelength selective switch in the WDM communication system. In this case, in the micro movable element array X2, it is possible to set a great wavelength band or frequency band by setting the wavelength band or the frequency band without interruption with respect to the optical signals as reflecting target signals allocated for the respective mirror surfaces11′. Further, in this case, it is possible to increase the wavelength band or the frequency band of the allocated optical signal of the reflecting target with respect to the selected micro movable element Y3by driving the translation of a micro movable element adjacent to the selected micro movable element Y3as illustrated by an arrow D3inFIG. 22. In the micro movable element array X2, it is possible to increase the wavelength band or the frequency band of the allocated optical signals of the reflecting target with respect to the respective micro movable element Y3.

In the respective micro movable elements Y2of the micro movable element array X2, the electrode parts12of the inner movable part10, the shield parts14, the parts22aof the second layer parts22of the frames20, and the parts32cof the second layer part32of the frame30′ are electrically coupled. Thus, the reference potential (for example, ground potential) is applied to the shield parts14, the parts22aand32cas well as the electrode parts12at the time of driving the micro movable element Y1. Therefore, the electric field generated from the electrode parts60toward the land parts11side of the inner movable part10, for example, due to the driving potential higher than the reference potential at the time of driving is easily absorbed by the shield parts14. In other words, it is difficult for the electric field to go beyond the shield parts14to reach the land parts11, for example. Further, the electric field generated from the electrode parts60at the time of driving is easily absorbed by the parts22a. In other words, it is difficult for the electric field to go beyond the parts22aside of the second layer parts22of the frames20to leak out of the elements. Further, the electric field generated from the electrode parts80′ to the side opposite to the electrode parts70due to the driving potential higher than the reference potential at the time of driving is easily absorbed by the parts32c. In other words, it is difficult for the electric field to go beyond the parts32cto leak out of the elements. These electric field absorption effects reduce or prevent the leak of the electric field out of the elements of the micro movable elements Y2. Because of the reduction or prevention of the leak of the electric field out of the elements, it is possible to prevent the electric field leaked from the driving mechanisms (electrode parts12,60,70and80′) of the respective micro movable element Y2from affecting the driving property of other adjacent micro movable element Y2. Therefore, the electric field absorption effects contribute to increased density of the micro movable element Y2in the arrangement direction and thus improved population of the movable main parts (the land parts11and the mirror surfaces11′) in the arrangement direction.

The micro movable elements Y2of the micro movable element array X2can be sensing devices such as an angular sensor or an acceleration sensor. In the case of the micro movable elements Y2being the sensing devices, the mirror surfaces11′ are not necessarily provided on the land parts11of the inner movable parts10.

The micro movable elements Y1and Y3included in the micro movable element arrays X1and X2may be so-called oscillating elements in a single axis. If the micro movable elements Y1and Y3are oscillating elements in a single axis, a configuration is preferably adopted in which the electrode parts70and80are omitted and the frame20is secured to the frame30.

The micro movable element array X1and X2may be adopted as a micro-mirror element array for forming an optical switching apparatus included in a communication apparatus.

FIG. 37is a diagram illustrating a schematic configuration of a light switching apparatus400of a spatial light coupling type according to a third embodiment. The light switching apparatus400includes a pair of a micro-mirror element array units401and402, an input fiber array403, an output fiber array404and a plural micro lenses405and406. The input fiber array403is formed by a predetermined number of input fibers403a, and the micro-mirror element array unit401has plural micro-mirror elements401aarranged therein which are associated with the corresponding input fibers403a. The output fiber array404is formed by a predetermined number of output fibers404a, and the micro-mirror element array unit402has plural micro-mirror elements402aarranged therein which are associated with the corresponding output fibers404a. The micro-mirror elements401aand402ainclude the mirror surfaces for reflecting the light and are provided such that the orientations of the mirror surfaces can be controlled, respectively. The micro mirror array units401and402are one of the micro-mirror element arrays X1and X2. The micro lenses405are disposed such that they are opposed to the ends of the input fibers403a, respectively. Further, the micro lenses406are disposed such that they are opposed to the ends of the output fibers404a, respectively.

In the light switching apparatus400, the light beams L1emitted from the input fibers403aare made parallel with each other by passing through the corresponding micro lenses405and head to the micro-mirror element array unit401. The light beams L1are reflected by the corresponding micro-mirror elements401ato be deflected toward the micro-mirror element array unit402. At that time, the mirror surfaces of the micro-mirror elements401aare directed to predetermined directions in advance so as to make the light beams L1be input to the respective desired micro-mirror elements402a. Then, the light beams L1are reflected by the micro-mirror elements402ato be deflected to the output fiber array404. At that time, the mirror surfaces of the micro-mirror elements402aare directed to predetermined directions in advance so as to make the light beams L1be input to the respective desired output fibers404a.

In this way, according to the light switching apparatus400, the light emitted from the respective input fibers403areach the desired output fibers404aby the deflections in the micro-mirror element array units401and402. In other words, the input fibers403aare coupled to the output fibers404ain a one-to-one relationship. By changing the deflection angles in the micro-mirror element array units401and402, as appropriate, the output fibers404ato which the light beams L1reach are switched.

The properties required for the light switching apparatus for switching the transmission path of the optical signals via the optical fibers from one fiber to another are large-capacity, high-speed, high reliability, etc., in the switching operations. From this viewpoint, it is preferred that the switching elements included in the light switching apparatus are micro-mirror elements formed using the MEMS technique. This is because the micro-mirror elements are suited for obtaining the required properties described above because it is possible to perform switching processes using the optical signals as they are (i.e., without converting the optical signals into the electrical signals) between the optical transmission path on the input side and the optical transmission path on the output side in the light switching apparatus.

FIG. 38is a diagram illustrating a schematic configuration of a light switching apparatus500of a wavelength-selective type according to a fourth embodiment. The light switching apparatus500includes a micro-mirror array unit501, an input fiber502, three output fibers503, plural micro lenses504aand504b, a spectrograph505, and a condenser lens506. The micro-mirror array unit501includes plural micro-mirror elements501a. The micro-mirror elements501aare arranged in a row, for example, in the micro-mirror array unit501. The micro movable elements501ainclude the mirror surfaces for reelecting the light and are provided such that the orientations of the mirror surfaces can be controlled. The micro mirror array unit501is one of the micro movable element arrays X1and X2. The micro lens504ais disposed such that it is opposed to the end of the input fiber502. The micro lenses504bare disposed such that they are opposed to the end of the output fibers503. The spectrograph505is a reflection diffraction grating in which a diffraction angle of the reflected light varies with the wavelengths.

In the light switching apparatus500, the light L2(including plural wavelengths mixed) emitted from the input fiber502is made parallel by passing through the micro lenses504a. The light L2is reflected by the spectrograph505. At that time, light L2is reflected at the diffraction angle which varies with the wavelength. The reflected light passes through the condenser lens506. At that time, the reflected light is collected to the corresponding micro-mirror elements501ain the micro-mirror array unit501on a wavelength basis. The light with the respective wavelengths is reflected in predetermined directions by the corresponding micro-mirror elements501a. At that time, the mirror surfaces of the micro-mirror elements501aare directed to predetermined directions in advance so as to make the light with the corresponding wavelengths reach the desired output fibers503. Then, the light reflected by the micro-mirror elements501ais input to the selected predetermined output fibers503via the condenser lens506, the spectrograph505and the micro lenses504b. In this way, according to the light switching apparatus500, it is possible to select the light with the desired wavelength from the light L2.