Abstract:
A cantilever type of electrostatic vertical combdrive actuators may generate larger actuator displacement (typically over 70 um) with a relatively small and simple structure. The actuation voltage is lower while the actuation movement is robust without any typical sideway finger snapping phenomena due to a cantilever type of structure. Because of its small form factor, it can form a high fill factor array in applications such as lower power consumption display devices, sensitive electromagnetic radiation detector/detector arrays, etc. The MEMS (Micro-Electro-Mechanical Systems) electrostatic rotational actuators may have wide applications such as in optical shutter, optical chopper, optical switches, optical attenuators, optical tunable filter, RF shunt switch, RF ohmic contact switch, RF MEMS variable capacitors, MEMS display and sensitive electromagnetic radiation detector etc.

Description:
TECHNICAL FIELD 
       [0001]    This relates to designs for a MEMS (Micro-Electro-Mechanical systems) electrostatic rotational actuator used for MEMS RF variable capacitor, MEMS RF ohmic contact switch, MEMS optical shutter/chopper, MEMS variable optical attenuator (VOA), MEMS display panel and photo diode detection array, spectrometer, atomic clock chip, printer and scanner and the like. 
       BACKGROUND 
       [0002]    The MEMS (Micro-Electro-Mechanical Systems) electrostatic rotational actuators have wide applications such as in optical shutter, optical chopper, optical switches, optical attenuators, optical tunable filter, RF shunt switch, RF ohmic contact switch, RF MEMS variable capacitors and MEMS display panel and photo diode detection array, spectrometer, printer and scanner etc. 
         [0003]    U.S. Pat. Nos. 6,275,320, 6,775,048 disclosed the MEMS variable optical attenuator/optical modulator using a thermal actuator, which consumes significant electrical power and generate over 600 degree Celsius on the silicon expansion beams; U.S. Pat. Nos. 6,751,395, 6,816,295, 6,996,306 and 7,129,617 disclosed the MEMS variable optical attenuator/switch using an electrostatic actuator, which can only generate very limited actuator displacement. 
       SUMMARY 
       [0004]    According to an aspect, there is disclosed a cantilever type of electrostatic vertical combdrive actuators to generate larger actuator displacement (typically over 70 um) with a very small and simple structure. The actuation voltage is lower while the actuation movement is very robust without any typical sideway finger snapping phenomena due to a cantilever type of structure. Because of its small form factor, it can form a high fill factor array for applications of the lower power consumption display devices, or sensitive electromagnetic radiation detector/detector arrays, spectrometer, atomic clock chip, imaging, printer and scanner. 
         [0005]    In certain aspects, the MEMS (Micro-Electro-Mechanical Systems) electrostatic rotational actuators have wide applications such as in optical shutter, optical chopper, atomic clock chip, optical switches, optical attenuators, optical tunable filter, RF shunt switch, RF ohmic contact switch, RF MEMS variable capacitors, MEMS display panel and sensitive electromagnetic radiation detector etc. Due to its small form factor, it can form a high fill factor array for applications of the lower power consumption display devices, or sensitive electromagnetic radiation detector/detector arrays, spectrometer, atomic clock chip, printer and scanner. 
         [0006]    According to an aspect, there is provided a MEMS actuator, comprising a combdrive carried by a substrate, the combdrive having a fixed comb and a movable comb, each of the fixed comb and the movable comb having comb fingers, the fixed comb being immovably carried by the substrate. A resilient body is attached between an anchor point on the substrate and the movable comb, the resilient body permitting cantilevered, pivotal movement of the movable comb parallel to a plane defined by the comb fingers of the fixed comb in response to an actuating voltage applied to the combdrive, the comb fingers of the fixed and movable combs being curved in the direction of the movement. 
         [0007]    In another aspect, the fixed comb and the movable comb are electrically isolated. 
         [0008]    In another aspect, the movable comb moves toward the fixed comb in response to the actuating voltage. 
         [0009]    In another aspect, the movable comb is attached to the resilient body by a carrier body. 
         [0010]    In another aspect, the combdrive comprises a plurality of movable combs and fixed combs. 
         [0011]    In another aspect, there are movable combs on opposed sides of a carrier body attached to the resilient body, the opposed movable combs permitting pivotal movement of the movable combs selectively in opposed directions. 
         [0012]    In another aspect, there are movable combs on the same side of a carrier body attached to the resilient body. 
         [0013]    In another aspect, the MEMS actuator further comprises at least one contact point on the substrate and the movable comb carries an electrically conductive connector, the movement of the movable comb controlling the connection of the at least one contact point and the connector. There may be more than one contact point, and the connector acting as a switch between the contact points. The connector may be mounted toward the anchor point relative to the movable comb. The connector may be electrically isolated from the movable comb and the resilient body. 
         [0014]    In another aspect, the movable comb carries a shutter, the shutter preventing transmission of some or all wavelengths in a beam of light, the movable comb controlling the position of the shutter within the beam of light. The shutter may comprise a profiled edge. The shutter may be attached at an end of the movable comb. The shutter may be mounted across at least a portion of the comb fingers of the movable comb. The substrate may comprise an aperture, the beam of light passing through the aperture. 
         [0015]    In another aspect, the resilient body comprises a beam structure. 
         [0016]    In another aspect, the resilient body comprises a double beam structure. Each beam may be electrically isolated from the other and electrically connected to separate anchor points to form a circuit through the resilient body between the anchor points. The circuit may be connected to a filament carried by the movable comb. 
         [0017]    In another aspect, the MEMS actuator further comprises a counterweight opposite the movable comb relative to the anchor point. The counterweight may comprise one or more movable combs. 
         [0018]    In another aspect, the spacing of the comb fingers of the movable comb within the comb fingers of the fixed comb is scaled to balance the applied electrostatic forces as the movable comb moves. 
         [0019]    In another aspect, the curvature of the fingers follows the trajectory of the movable comb when an electrostatic force is applied. 
         [0020]    In another aspect, the resilient body supports the movable comb in a cantilever design. 
         [0021]    In another aspect, the resilient body comprises a first part attached between a first anchor and a first side of the movable comb and a second part attached between a second anchor and a second side of the movable comb, such that the movable comb is supported by the resilient body between the first anchor and the second anchor. Each of the first and second parts of the resilient body may comprise a pair of beams, the beams being one of parallel or converging toward the movable comb from the respective anchor. The first part and the second part may be symmetrical about the movable comb. 
         [0022]    According to an aspect, there is provided a variable capacitor, comprising a combdrive carried by a substrate, the combdrive having a first electrode comprising a fixed comb and a second electrode comprising a movable comb, each of the fixed comb and the movable comb having comb fingers, the fixed comb being immovably carried by the substrate. A resilient body is attached between an anchor point on the substrate and the movable comb, the resilient body permitting cantilevered, pivotal movement of the movable comb parallel to a plane defined by the comb fingers of the fixed comb, wherein an actuating voltage moves the movable comb relative to the fixed comb, the comb fingers of the fixed and movable combs being curved in the direction of the movement the combdrive having a capacitance that increases as the overlap of the comb fingers of the fixed comb and the movable comb increases. 
         [0023]    In another aspect, in a disengaged position, the combdrive comprises a space between the comb fingers of the movable comb and the comb fingers of the fixed comb. 
         [0024]    In another aspect, the combdrive comprises a first combdrive, and further comprising a second combdrive that rotates the resilient body in a direction opposite the first combdrive. 
         [0025]    In another aspect, the combdrive comprises a first combdrive, and further comprising at least one second combdrive that rotates the resilient body in the same direction as the first combdrive. 
         [0026]    In another aspect, the variable capacitor is connected in series or in parallel with a plurality of variable capacitors mounted to a common substrate. 
         [0027]    In another aspect, the position of the movable comb and the capacitance of the combdrive is related to the actuating voltage applied to the combdrive. 
         [0028]    According to an aspect, there is provided an array of MEMS actuators mounted to a substrate, each MEMS actuator comprising a combdrive carried by a substrate, the combdrive having a fixed comb and a movable comb, each of the fixed comb and the movable comb having comb fingers, the fixed comb being immovably carried by the substrate. A resilient body is attached between an anchor point on the substrate and the movable comb, the resilient body permitting cantilevered, pivotal movement of the movable comb parallel to a plane defined by the comb fingers of the fixed comb in response to an actuating voltage, the comb fingers of the fixed and movable combs being curved in the direction of the movement. 
         [0029]    In another aspect, the substrate comprises apertures for beams of light, the movable combs carrying shutters that control passage of light through the apertures. The substrate may be a waveguide plate. The actuating voltage may comprise a periodic voltage having a frequency. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]    These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein: 
           [0031]      FIG. 1  is a perspective view of a MEMS RF variable capacitor. 
           [0032]      FIG. 2  is a perspective view of a MEMS RF variable capacitor. 
           [0033]      FIG. 3  is a perspective view of a MEMS RF variable capacitor. 
           [0034]      FIG. 4  is a perspective view of a MEMS RF variable capacitor. 
           [0035]      FIG. 5  is a perspective view of a MEMS RF variable capacitor. 
           [0036]      FIG. 6  is a perspective view of an array of MEMS RF variable capacitor. 
           [0037]      FIG. 7  is a perspective view of an array of MEMS RF variable capacitor. 
           [0038]      FIG. 8  is a perspective view of an array of MEMS RF variable capacitor. 
           [0039]      FIG. 9  is a perspective view of array of MEMS RF variable capacitor. 
           [0040]      FIG. 10  is a perspective view of multiple combdrive actuators for MEMS RF variable capacitor. 
           [0041]      FIG. 11  is a perspective view of MEMS RF ohmic contact switch. 
           [0042]      FIG. 12  is a perspective view of MEMS RF ohmic contact switch. 
           [0043]      FIG. 13  is a perspective view of MEMS RF ohmic contact switch. 
           [0044]      FIG. 14  is a perspective view of MEMS RF ohmic contact switch. 
           [0045]      FIG. 15  is a perspective view of MEMS RF ohmic contact switch with electrical isolation structure. 
           [0046]      FIG. 16  is a perspective view of MEMS RF ohmic contact switch with electrical isolation structure. 
           [0047]      FIG. 17  is a perspective view of trenching and refilling structure 
           [0048]      FIG. 18  is a perspective view of MEMS optical shutter/chopper. 
           [0049]      FIG. 19  is a perspective view of MEMS optical shutter/chopper. 
           [0050]      FIG. 20  is a perspective view of the edge profiles of shutter/chopper. 
           [0051]      FIG. 21  is a perspective view of MEMS optical shutter/chopper. 
           [0052]      FIG. 22  is a perspective view of MEMS optical shutter/chopper. 
           [0053]      FIG. 23  is a perspective view of multiple combdrive actuators for MEMS optical shutter/chopper. 
           [0054]      FIG. 24  is a perspective view of combdrive actuators with double straight beam hinges. 
           [0055]      FIG. 25  is a perspective view of combdrive actuators with double straight beam hinges with electrical isolation structure for MEMS optical IR source, shutter/chopper. 
           [0056]      FIG. 26   a - 26   e  is process flow to make a MEMS electrostatic rotational actuator. 
           [0057]      FIG. 27   a - 27   b  is a perspective view of MEMS display element. 
           [0058]      FIG. 28   a - 28   b  is a perspective view of MEMS display pixel. 
           [0059]      FIG. 29   a - 29   b  is a perspective view of MEMS display panel. 
           [0060]      FIG. 30   a  is a perspective view of comb finger gap offset. 
           [0061]      FIG. 30   b  is a perspective view of hinge design and balance weight design a MEMS electrostatic rotational actuator. 
           [0062]      FIG. 30   c  is a perspective view of shutter, hinge design and balance combdrive actuators of MEMS electrostatic rotational actuator. 
           [0063]      FIG. 30   d  is a perspective view of shutter, hinge design and balance combdrive actuators of MEMS electrostatic rotational actuator. 
           [0064]      FIG. 30   e  is a perspective view of shutter, hinge design and balance combdrive actuators of MEMS electrostatic rotational actuator.  FIG. 31  is a perspective view of a MEMS electrostatic rotational actuator with a pinhole structure. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0065]    The designs discussed herein are capable of taking different forms. However, there are shown in the drawings and will herein be described in detail preferred embodiments, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the device and is not intended to limit the broad aspects of the device or design to the embodiments illustrated. The figures are not necessarily drawn to scale and relative sizes of various elements in the structures may be different than in an actual device. 
         [0066]    MEMS RF variable capacitor is a very important component for RF networks. The capacitance of the capacitor is varied with the applied control voltage. Single capacitors or an array of such variable capacitors are used in the RF networks to tune the RF circuit performance.  FIG. 1  shows an example of a MEMS RF variable capacitor. The moveable combdrive fingers  1  and fixed combdrive fingers  4  form a variable capacitor. The movable combdrive fingers  1  are connected to the anchor  2  by a flexible hinge  3 . The hinge is shown as a straight beam shape in  FIG. 1 , but it could be any shapes such as serpentine shape, double straight beam shapes, etc. The fixed combdrive fingers  4  are anchored by a support beam  5  to form the one capacitor electrode, while the supporting beam  6  of the moveable combdrive fingers  1  forms the other capacitor electrode. The movable comb fingers  1 , anchor  2 , hinge  3 , fixed comb fingers  4 , comb finger supporting beams  5  and  6  could be made from electrical conductive silicon or other electrical conductive materials such as polysilicon, metal or metal alloy etc. 
         [0067]    In the initial state, the air gap  7  between the movable and fixed combdrive fingers is to reduce the initial electrical fringe effect between the tips of fixed and movable comb fingers  4  and  1  and to achieve as small as possible initial capacitance C i  between moveable and fixed combdrive fingers  1  and  4 . When an actuation voltage is applied between the anchor  2  and fixed part  5 , the electrostatic attraction force between fingers  1  and fingers  4  is established, which will result in the deformation of the hinge  3 . Therefore, the fixed combdrive fingers  4  and moveable combdrive fingers  1  will be engaged shown in  FIG. 2 . The engaged moveable fingers  1  and fixed combdrive fingers  4  form a capacitance C o . The larger the actuation voltage, the more engagement between fixed and movable fingers, and the larger the ratio between C o  and C i . The structure shown in  FIGS. 1 and 2  is also an electrostatic actuator. As shown, the fixed comb fingers  4  define a plane that includes the hinge  4 , and the movement of fixed comb fingers  4  is in this plane.  FIG. 3  shows another embodiment of the MEMS RF variable capacitor design. In order to further increase the gap  7 , reduce the electrical fringe effect between the tips of fixed and movable comb fingers  4  and  1  and to achieve as small as possible initial capacitance C i  between moveable comb fingers  1  and fixed combdrive fingers  4  another fixed combdrive fingers  22  connected to the supporting beam  20  is used. 
         [0068]    In the initial state ( FIG. 4 ), an actuation voltage A is applied between the anchor  2  and fixed finger supporting beam  20 , the electrostatic attraction force is established, which will result in the deformation of the hinge  3 . Therefore, the movable fingers  24  will move towards the fixed comb fingers  22 , while the movable comb fingers  1  are moving further away from the fixed comb fingers  4 . The air gap  7  between the movable comb fingers  1  and the fixed combdrive fingers  4  is further increasing while the electrical fringe effect between the tips of fixed comb fingers  4  and movable comb fingers  1  is further reduced. Therefore the initial capacitance C i  between moveable fingers  1  and fixed combdrive fingers  4  is further reduced. The higher the actuation voltage A, the smaller the initial capacitance C i . 
         [0069]    When an actuation voltage B is applied and gradually increased between the anchor  2  and fixed finger supporting beam  5  while the voltage A between the anchor  2  and fixed finger supporting beam  20  is gradually reduced to zero volt, the electrostatic attraction force is gradually increased between the fixed comb fingers  4  and movable comb fingers  1 , while the electrostatic attraction force between fixed comb fingers  22  and movable comb fingers  24  is gradually reduced. Therefore, the movable fingers  1  will move towards the fixed comb fingers  4  ( FIG. 5 ), while the movable comb fingers  24  are moving further away from the fixed comb fingers  22 . The air gap  7  between the movable comb fingers  1  and the fixed combdrive fingers  4  is further decreased while the electrical fringe effect between the tips of fixed comb fingers  4  and movable comb fingers  1  is further increased. Therefore the capacitance C o  between moveable fingers  1  and fixed combdrive fingers  4  is further increased. The higher the actuation voltage B, and the less the voltage A, the larger the capacitance C o . 
         [0070]      FIG. 6  shows an array/bank of the single variable capacitor shown in  FIG. 1 , the electrical ground line  42  is connected to supporting beams of the fixed combdrive fingers of MEMS RF variable capacitor  44 ,  45 ,  46 ,  47  and  48  via connection structure  49 . The RF signal line  40  will connect with anchors  54 ,  55 ,  56 ,  57  and  58  of the MEMS RF variable capacitor  44 ,  45 ,  46 ,  47  and  48  via an electrical structure (not shown in the  FIG. 6 ).  FIG. 6  shows the initial state of the MEMS RF variable capacitor  44 ,  45 ,  46 ,  47  and  48 .  FIG. 7  shows the not actuated MEMS RF variable capacitor  44  and actuated MEMS RF variable capacitor  45 ,  46 ,  47  and  48 . 
         [0071]      FIG. 8  shows an array/bank of the single variable capacitor shown in  FIG. 3 , the electrical ground line  60  is connected to the anchors of MEMS RF variable capacitor  61 ,  62 ,  63 ,  64  and  65 . The RF signal line  70  will connect with the supporting beams  61   a,    62   a,    63   a,    64   a  and  65 A of the MEMS RF variable capacitor  61 ,  62 ,  63 ,  64  and  65  via an electrical structure (not shown in the  FIGS. 8 and 9 ).  FIG. 8  shows the initial state of the MEMS RF variable capacitor  61 ,  62 ,  63 ,  64  and  65 .  FIG. 9  shows the not actuated MEMS RF variable capacitor  61 , and actuated MEMS RF variable capacitor  62 ,  63 ,  64  and  65 . 
         [0072]    In order to increase the capacitance of the MEMS RF variable capacitor, more capacitor structures are used.  FIG. 10  shows three single variable capacitors  71 ,  72  and  73  working together. The  71   a,    72   a  and  73   a  are the fixed combdrive fingers of variable capacitors  71 ,  72  and  73  respectively, while the  71   b,    72   b  and  73   b  are the moveable combdrive fingers of variable capacitors  71 ,  72  and  73  respectively. The  71   b,    72   b  and  73   b  with their supporting beams are connected by connection beam  70  and hinge  76  to the anchor  75 . 
         [0073]    MEMS RF ohmic contact switch is another importance component. The challenge for the successes of the MEMS RF ohmic contact switch has been the higher mechanical restoring force to overcome the stiction force, higher contact force to reduce the electrical resistance etc. 
         [0074]      FIG. 11  shows the embodiment of MEMS RF ohmic contact switch. The switch contact point  81  and contact point  82  are separated with gap  83 . The switch contact points  81  and  82  are either formed by thick metal or metal alloy film, or silicon structure coated with thick metal film such as metal gold, or other metal film or metal alloy film etc. 
         [0075]    The switch connection  85  is either formed by thick metal or metal alloy film, or silicon structure coated with thick metal film such as metal gold, other metal film or metal alloy film etc. The switch connection  85  is mechanically connected to the lower part of the supporting beam  96  of the moveable combdrive actuator  94 . The lower part is close to the combdrive anchor  90 . Such switch design will achieve the higher contact force when the switch connection  85  is turning into the on position shown in  FIG. 12 , and also the higher mechanical restoring force of hinge structure  98  when the switch connection  85  is turning into the off position shown in  FIG. 11 . When the combdrive actuator  94  is actuated, the switch connection  85  is moving with the supporting beam  96  of movable combdrive fingers and moving towards to the contact points  81  and  82  till switch connection  85  is physically contacting the switch contact points  81  and  82 , and when the combdrive actuator  94  is further actuated, and the switch connection  85  will be sliding into the gap  83  between the contacts  81  and  82 , and achieve intimate contact with the switch contacts  81  and  82 . At this time, the switch contact  81  and switch contact  82  is electrically connected via the electrically conductive switch connection  85 . When there is no electrical voltage applied to the combdrive actuator  94 , the mechanical restoring forces from the combdrive actuator hinge  98  will force the switch connection  85  away from switch contacts  81  and  82 . At this moment, the switch contact  81  is electrically isolated from the switch contact  82 . 
         [0076]    The contact surface shape of the switch contact points  81  and  82 , as well as switch connection  85  could be different shapes besides the simple flat surface shown in  FIGS. 10 ,  11  and  12 , for example, circular, arc or other special designed curve shapes. These shapes of the contact surface should provide good mechanical and electrical connection between switch connection  85  and contact point  81 , and between switch connection  85  and contact point  82 . The materials of the switch contact point  81  and  82 , as well as switch connection  85  could be metal and metal alloy, silicon coated with metal film or alloy film, polysilicon coated with metal film or alloy film etc. 
         [0077]    While  FIGS. 11 and 12  show a normally “off&#39; switch, it may also be designed as a normally “on” switch, where contact points  81  and  82  are on the opposite side of supporting beam  96 , and the comb drive pulls switch connection  85  away from contact points  81  and  82 . In addition, while two contact points are shown, there may also be only one contact point, such that the contact between connection  85  and the one contact point completes a circuit through anchor  90  and resilient beam  98 . 
         [0078]      FIG. 13  shows another embodiment of the MEMS RF ohmic contact switch, the switch connection beam  100  is either formed by thick metal or metal alloy film, or silicon/polysilicon structure coated with thick metal film such as metal gold, other metal film or metal alloy film. The beam  100  is flexible as a cantilever structure with a virtual anchor at location of  401 . 
         [0079]    The switch connection beam  100  is mechanically connected to the lower part of the supporting beam  96  of the moveable combdrive actuator. The lower part is close to the combdrive actuator anchor  90 . Such switch design will achieve the higher contact force when the switch connection beam  100  is in the on position shown in  FIG. 14 , and also higher mechanical restoring force when the switch connection  100  is turning into the off the position shown in  FIG. 13 . 
         [0080]    When the combdrive actuator  94  is actuated, the switch connection beam  100  first contacts the switch contact point  101 , and when the combdrive actuator  94  is further actuated, the connection beam will be deformed and then contact the switch contact  102 . At this time, the switch contact  101  and the contact  102  is electrically connected through the electrical conductive switch connection beam  100  which contacts both switch contacts  101  and  102  cross the gap  103 . When there is no electrical voltage applied to the combdrive actuator  94 , the mechanical restoring forces from the combdrive actuator hinge  98  and the switch connection beam  100  will force the connection beam  100  away from switch contact  102  first, and then switch contact  101 . At this moment, the switch contact  101  is electrically isolated from the switch contact  102 . 
         [0081]    The contact surface shape of the switch contact point  101  and  102 , as well as switch connection  100  could be different shapes, for example, circular, arc or other special design curve shapes. The materials of the switch contact point  101  and  102 , as well as switch connection  100  could be metal, metal alloy, silicon coated with metal film or alloy film, polysilicon coated with metal film or alloy film etc. 
         [0082]    In order to avoid the electrical interference between the RF signal circuit and combdrive actuation circuit, and switch connection  85  and switch connection beam  100  will be mechanically connected with, but electrically isolated with the support beam  96  of the moveable combdrive fingers using electrical isolation structure  120  (shown in  FIGS. 15 and 16 ). The electrical isolation structure  120  could be any format of electrical isolation structure, for example, silicon oxide structure; silicon nitride structure and trenching and dielectrical material refilling structure etc.  FIG. 17  shows the cross section of a typical trenching and dielectrical material refilling structure. The layer of the silicon is etched into silicon part A  122  and silicon part B  123  with a etched trench, the silicon oxide liners  124  are created on the sidewalls of the trench gap, depending on the trench size, the trench gap could be totally refilled with dielectrical materials such as silicon oxide and/or silicon nitride, or filled with dielectrical materials (such as silicon oxide and/or silicon nitride) and polysilicon  125 . The silicon part A  122  and silicon part B  123  are mechanically connected with, but electrically isolated by trenching and refilling dielectrical materials  124  and polysilicon  125 . 
         [0083]      FIGS. 15 and 16  show two MEMS RF ohmic contact switches with trenching and dielectrical materials refilling structure  120 . The switch connection  85  and switch connection beam  100  are mechanically connected with, but electrically isolated from the combdrive actuator  94  using the trench and dielectrical materials refilling structure  120 . 
         [0084]    The trench and dielectrical materials refilling structure  120  could be dove tail shaped, arc shaped, triangle shaped, etc. mechanical interlocking structures to increase the mechanical connection strength between two connected parts, for example, part A  122  and part B  123  in  FIG. 17 . 
         [0085]    When a thin shutter/plate  149  is placed on the tip of the support beam  147  of the combdrive actuator  140  ( FIG. 18 ), the shutter/plate will move with the supporting beam  147  of the moveable combdrive fingers to change its position, it can move into the positions which will interact with the full light beam  143  or with partial light beam  143  in order to achieve the light beam modulation such as filtering, blocking and attenuation (shown in  FIG. 19 ). The shutter  141  is preferably a thin layer of metal, dielectrical material film, etc. It could be also a layer of silicon or polysilicon etc. coated with optical film  142  such as a transmissive film which let certain light wavelengths pass or a reflective film which will block certain light wavelengths, for example, a thin layer metal film such as Al or gold film or other optical film materials coated on the surface of shutter  141 . 
         [0086]    In the combdrive structures, electrostatic actuators and their arrangement shown in  FIGS. 1 and 10 , if a thin layer of plate/shutter is placed on the tips  410  of the supporting structures of moveable fingers, then a thin plate/shutter or the thin plates/shutters will move with the moveable comb fingers under the actuation. 
         [0087]    When the shutter interacts with the partial light beam  143 , the shutter edge  148  interacting with the light beam  143  preferably has some special designed edge profiles such as the 90 deg. teeth profile in order to improve the optical performances such as reducing the PDL (Polarization Dependant Loss), The shutter edge could be straight edge such as edge or other edge profiles shown in  FIG. 20  or any other specially design profiles. Edge  161  is circular shape, edge  161  is triangle shape, edge  162  is the square shape and edge  163  is arc shape. 
         [0088]    In order to increase the displacement of the shutter  141 , two combdrive actuators  171  and  172  may be used to drive the shutter, as shown in  FIG. 21  and  FIG. 22 .  FIG. 22  shows the shutter  141  actuated by actuator  171  to allow light beam  143  to pass through without any interaction.  FIG. 21  shows the shutter  141  interacting with or fully blocking the full light beam  143 . 
         [0089]    For the applications mentioned herein such as MEMS shutter/chopper and MEMS RF ohmic contact switch etc., single combdrive actuators may not be able to supply sufficient shutter/chopper displacement, driving force and contact force. To address this, multiple combdrive actuators may be used.  FIG. 23  shows a multiple combdrive actuators used for the MEMS optical shutter/chopper or optical variable attenuator. Combdrive actuators  180 ,  181  and  182  with fixed comb fingers  180   a,    181   a  and  182   a,  movable comb fingers  180   b,    181   b  and  182   b  are working together to actuate the shutter  186 . The supporting beams of movable comb fingers are connected by the structures  191  and  193 . The shutter  186  is connected to the supporting beam of movable comb fingers  181   b.  The three combdrive actuators  180 ,  181  and  182  share the same hinge  190  and anchor  189 . The same multiple actuators arrangement could be also used for RF Ohmic contact switch or for RF variable capacitor device. 
         [0090]    The hinge of the combdrive actuators could be many different shapes, such as straight beam shape, serpentine shape etc. For example, a double straight beam hinge shown in  FIG. 24  may be used to increase the robustness of the combdrive actuator. The supporting beams  210   b  and  211   b  of the combdrive actuator  210  and  211  are connected by connection structures  204  and  205 , and connected to the anchors  202  and  203  by hinge  200  and  201  respectively. 
         [0091]    Besides providing the structure robustness, the double hinge  200  and  201  may also provide an electrical path to power the electrical components on the moveable structure of the actuators. For example,  FIG. 25  shows shutters  215   a  and  215   b,  and a thermal filament  214  actuated by the combdrive actuator  210  and  211 . The thermal filament  214  could be used as an IR light source. The supporting beams  210   b  and  211   b  are mechanically connected by the connection structures  204  and  205 , but they are electrically isolated by the trenching and dielectrical material refilling structure  208  and  209  on the connection structures  204  and  205 . If an electrical potential is applied between anchor  202  and  203 , then the filament  214  will be turned on through the electrical path from anchor  202 , hinge  200 , supporting beam  210   b,  shutter  215   a,  filament  214 , shutter  215   b,  supporting beam  211   b  and hinge  201  to the anchor  203 . 
         [0092]    There are many methods to fabricate the structures described herein. A typical microfabrication method for structures mentioned above is described below. Other fabrication techniques may be employed as will be understood by those skilled in the art, but will not be detailed herein. This process starts with a SOI (Silicon On Insulator) wafer (shown in  FIG. 26   a ). The device layer silicon  220  is thinner than the handle wafer  223 . The buried silicon oxide layer  221  is sandwiched between device layer  220  and handle wafer  223 . 
         [0093]    A lithography and DRIE (Deep Reactive Ion Etching) are used to etch the handle silicon  223  to the oxide layer  221  from backside of the wafer create a cavity  224  ( FIG. 26   b ). A subsequent oxide etching is used to remove the oxide at bottom of the cavity  224  ( FIG. 26   c ). A lithography and DRIE (Deep Reactive Ion Etching) are used to etch the device silicon layer  220  to the oxide layer  221  from front side of the wafer to create the combdrive actuator and other components  225  such as shutter, switch contacts etc. ( FIG. 26   d ). A shadow metal process is used to make the shutter metal  222 , wire bonding pads  227  as well as the contact metal or metal alloy  226  on the side wall of electrical contact structures ( FIG. 26   e ). If the special optical film is required on the shutter/plate, these special optical film coatings can be done before the wafer process to make shutter/plate, and the actuator structures etc. The electrical contact metal or metal alloy can be made by electroplating before the wafer process to make shutter/plate, and the actuator structures etc. 
         [0094]      FIG. 27   a  shows a display element using a cantilever type of MEMS electrostatic rotational actuator. The optical blocking structure or film  240  is on the top surface of the combdrive movable fingers  243 . As shown, the top surface of the combdrive fixed fingers  245  is lower than the top surface of the combdrive movable fingers  243  so that no mechanical interference between the fixed combdrive fingers  245  and the optical blocking structure or film  240 . The anchor  246  and fixed combdrive fingers  245  are attached to the waveguide plate  248 . The light is injected inside the waveguide plate from the one of its sidewall surface  250 , the light is traveling within the waveguide plate, will be reflected on the top and bottom surface of the waveguide plate. The waveguide is such designed (such as the waveguide thickness, and optical reflector attached to its bottom surface etc.) so that the light will be reflected or only seen from its top surface  255 . Or the light is injected inside the waveguide plate from the its bottom surface so the light will travel from the back surface of the transparent waveguide plate through the display element shown in  FIG. 27   a.    
         [0095]    The part of the top surface  255  of the waveguide plate is covered with optical blocking film  256  and electrical driving circuits  247  such as TFT (Thin Film Transistor) circuit which is typically used for the LCD (Liquid Crystal Display). In other words, the waveguide plate could take advantages of the design and manufacturing technology of LCD display. 
         [0096]    The bottom surface of the fixed combdrive fingers is contacted to the top surface of  255  the waveguide plate, while the bottom surfaces of the hinge  244  and movable combdrive fingers  243  are higher than the top surface  255  of the waveguide plate. A gap clearance is required to allow the free movement of the hinge  244  and moveable fingers  243 . 
         [0097]    When there is no actuation voltage between the fixed and movable comb fingers  245  and  243 , the gap  260  between the fixed and movable comb fingers will allow the pass through of light from the waveguide plate ( FIG. 27   a ). When an actuation voltage is applied between the fixed and movable fingers  245  and  243 , the moveable fingers  243  will move close to the fixed fingers  245 , the gap  260  will be smaller; therefore, less light will pass through from the gap  260 . The higher the applied voltage, the less the light will pass through. When the voltage is higher enough, the gap  260  will disappear, and no light from the waveguide plate will be totally blocked ( FIG. 27   b ). The gap  260  can be actuated in the state of on-off at different high frequency to show the different light grey scale. The light grey scale can also be achieved by size of gap  260  under different actuation voltage. 
         [0098]    The applied voltage could be DC, AC or DC plus AC. In the case of AC voltage, the frequency of the AC voltage will be close to the nature frequency of the moveable combdrive structure so that the moveable combdrive structure is working in the resonant mode. In the resonant working mode, much less electrical power consumption will be expected. 
         [0099]    One or more than one display element could be used to form the display pixel  261  of larger display panel.  FIG. 28   a  shows the two display elements to form a display pixel  261 . The maximum light passes through the finger gaps  260  when no actuation voltages are applied to the two actuators  262   a  and  262   b,  while the light path is fully closed when the two combdrive actuators  262   a  and  262   b  are fully actuated ( FIG. 28   b ). 
         [0100]    The array of such display pixel  261  shown in  FIG. 29   a  will form a high power efficiency display panel  270 . The RGB LED die array could be attached to one side wall  280  or more than one side walls of waveguide plate to inject the modulated RGB light into the waveguide plate. The right control coordination between the combdrive actuator control circuits such as TFT driving circuit and the RGB LED diode array will achieve colorful, dynamic, more power efficient color display panel. The display panel could be used for portable electronics, Smart phones and TV etc.  FIG. 29   a  shows the open states of all the combdrive actuators on the display panel  270 , in which the light from waveguide plate passes through the gap between the fixed and moveable comb fingers.  FIG. 29   b  shows the closed states of all the combdrive actuators on the display panel  270 , in which the light from waveguide plate is fully blocked from closed gap between the fixed and moveable comb fingers. The modulated RGB light can also be injected into the waveguide plate from its back surface, so the light will travel through the transparent waveguide plate, and then through the display element. 
         [0101]    There are other implementations of display panel using cantilever type of MEMS electrostatic rotational actuator. The open and close of the light path in each display element is achieved by the shutter plate shown in  FIGS. 18 ,  19 ,  21 ,  22  and  23 . The light blocking film is covered on the top surface of the waveguide plate except for the area of the light path window. The actuated combdrive will move the shutter in or out the position right above the light path window to close and open the light beam. 
         [0102]    The open and close of the light path using MEMS shutter actuated by electrostatic rotational actuators could be used for the high sensitive photo diode detection array. If the array of the electrostatic combdrive actuated shutter/chopper structures array is placed in the focal plane of, or right in front of the photo detection diode array such as IR detector array plate, then the array of the open and closed electrostatic combdrive actuated shutter/chopper structures shown in  FIGS. 18 ,  19 ,  21 ,  22 ,  23 ,  24 ,  27   a ,  27   b ,  28   a ,  28   b ,  29   a  and  29   b  will provide the function of light chopping and light modulation to each individual photo diode/pixel, which will increase the reliability and sensitive of the detection diode array. 
         [0103]    For the MEMS electrostatic rotational actuator, since the movements of the moveable fingers are moving with the bending of the hinge  312  (see  FIG. 30   a ), the rotational center is not the anchor  300 , but a virtual point  301  on the hinge  312 . For this reason, the moveable and fixed fingers shapes, and finger gaps have to be designed to make sure each movable finger has balance electrostatic forces from two adjacent fixed fingers during whole actuation phase or whole travel of the moving fingers in order to have the best actuation abilities. For example, the initial finger gap  302   d  between fingers  302   e  and  302   c  is smaller than the initial finger gap  302   b  between fingers  302   a  and  302   c,  and the initial finger gap  303   d  between fingers  303   e  and  303   c  is smaller than the initial finger gap  303   b  between fingers  303   a  and  303   c.    
         [0104]    If the more pure rotational movement of the supporting beam  328  and movable fingers of combdrive actuator  310  are required, then thin hinge  321  should be used to connect the two anchors  326   a  and  326   b.  The thicker and much stiff connection beam  322  connects to the center of hinge  321  and supporting beam  328 , while the thicker and much stiff connection beam  324  connects to the center of hinge  321  and weight balance  320  of the supporting beam  328  and movable comb fingers ( FIG. 30   b ). The finger gap  303   d  between fingers  303   e  and  303   c  is about same as the finger gap  303   b  between fingers  303   a  and  303   c  ( FIG. 30   b ). The hinge center  340  is the virtual center of the rotational movement of supporting beam  328  and movable comb fingers. The supporting beam  328  could have more moving fingers and corresponding fixed comb fingers to form the similar structure shown in  FIGS. 21 and 22 . 
         [0105]    In  FIG. 30   c , the balanced weight  320  could be replaced by an electrostatic actuator. As shown, the two actuators  253   a  and  352   b  work together to increase the actuation force, and displacement of shutter/chopper  350 . The thin plate of shutter and chopper could be also placed at the location of  355 . 
         [0106]    In  FIG. 30   d , more actuators may be added, where the actuators  352   a,    352   b,    352   c  and  352   d  are working together to establish the balanced structure and at the same time, more actuation force and larger travel displacement of shutter/chopper  350 . The thin plate of shutter and chopper could be also placed at the location of  355  as long as the balanced structure is established. 
         [0107]    In  FIG. 30   e , the balanced structure could be replaced by shutters/choppers  470  and electrostatic actuators  476   a,    476   b,    476   c  and  476   d.  As depicted, the two actuators  476   a  and  476   b  work together to increase the actuation force and to rotate the shutters/choppers anticlockwise around axis Z, while the two actuators  476   c  and  476   d  work together to rotate the shutters/choppers clockwise around axis Z. One of the shutter/chopper  470  could be replaced by a balanced weight. 
         [0108]    In the depicted embodiment, the thicker and stiffer connection beams  471  connect the shutters/choppers  470  and thin and flexible hinges  474   a,    474   b,    475   a  and  475   b,  which are anchored at anchors  472  and  473 . Hinge  474   a  and  474   b  are arranged at an angle starting from the point where hinges  474   a  and  474   b  meet the stiff connection beams  471 , the same arrangement also apply to the hinges  475   a  and  475   b.  Such angled hinge arrangement is to prevent the shutters/choppers from out of plane rotation around axis X. 
         [0109]    For electrostatic combdrive actuator, the finger gaps are designed to make sure each movable finger has balance electrostatic forces from two adjacent fixed fingers during whole actuation phase or whole travel of the moving fingers in order to have the best actuation abilities. Again the fixed comb fingers  477  and movable comb fingers  478  of actuators  476   a,    476   b,    476   c  and  476   d  are designed with curves and profiles so that there is smooth interaction during the full range of actuation and no interferences such as a pull-in effect, etc. While the fingers may have a consistent radius of curvature, this may not always be the case. For example, as the resilient beam bends, the virtual rotational center may shift, such that the curvature of the finger will also be different along the length of the fingers. In one example, the design of the fingers may be approximated by modeling the trajectory of the fixed portion of the comb under a mechanical load that approximates the electrostatic force that will be applied, and then designing the curvature of the fingers to follow this trajectory. 
         [0110]      FIG. 31  shows a thin shutter/chopper plate actuated by cantilever type of MEMS electrostatic rotational actuator with a pinhole structure. The thin shutter/chopper plate actuated by MEMS electrostatic rotational actuator is shown  FIGS. 18 ,  19 ,  21 ,  22 ,  30   a ,  30   b ,  30   c ,  30   d  and  30   e  described herein. A thin plate  423  with a pinhole  421  is separated from the shutter/chopper plate  427  by a space plate  424 . The pinhole is located right underneath the shutter/chopper plate when it is not actuated. The electrostatic actuator  426  moves the shutter/chopper  427  around its anchor  425 . When a light beam  420  passes the pinhole  421  on the plate  423 , the light beam  420  will be reshaped into light beam  422 . Typically the light beam  421  is narrower than light beam  420 . This part of light beam  420  is blocked by the plate  423  when the light beam  420  is passing pinhole  421 . 
         [0111]    The thin shutter/chopper plate actuated by cantilever type of MEMS electrostatic rotational actuator is shown  FIGS. 18 ,  19 ,  21 ,  22 ,  30   a ,  30   b ,  30   c ,  30   d  and  30   e  described herein could have the same pinhole structure shown in  FIG. 31 . 
         [0112]    In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. 
         [0113]    The following claims are to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, and what can be obviously substituted. The scope of the claims should not be limited by the preferred embodiments set forth in the examples above.