WO2008121845A2 - Micro-deployable devices and systems - Google Patents

Abstract

A microelectromechanical systems (MEMS) device includes a generally planar outer frame defining an inner structural portion; a plurality of first multi-angular elements (MAEs), each having a proximal portion and a distal portion, wherein the proximal portions are operably coupled to the outer frame, and wherein the plurality of first MAEs extend from the outer frame into the inner structural portion; and a plurality of second MAEs, each having a proximal portion and a distal portion, wherein the distal portions of the first and second MAEs are operably coupled to define an aperture. A microcamera includes a microautofocus system configured to focus light, and a microaperture configured to control a light passage. The microautofocus system employs a MEMS device to actuate a shape of a lends. A method of fabricating and operating the MEMS is also provided.

Description

MICRO-DEPLOYABLE DEVICES AND SYSTEMS

[0001] The present application claims priority to U.S. Provisional Application No. 60/908,884, filed March 29, 2007, and U.S. Provisional Application No. 61/004,052, filed November 21, 2007, the contents of which are incorporated herein by reference in their entirety.

BACKGROUND OF INVENTION

1. Field of the Invention

[0002] This invention relates generally to micro-deployable devices and systems incorporating same. More specifically, the invention relates to micro-deployable devices and systems realized using microelectromechanical system (MEMS) technologies.

2. Description of Related Art

[0003] Deployable antennas and deployable solar arrays have been used extensively in the space industry to allow compact space transport of devices with large surface areas by using foldable geometric configurations. Deployable devices have also been found in the consumer marketplace as lawn chairs, tents, and canopies. These deployable devices can be deployed from folded configurations to extended configurations with large changes in their apparent sizes, using a relatively small force.

BRIEF SUMMARY OF THE INVENTION

[0004] In one aspect, the invention provides a microelectromechanical systems (MEMS) device, including a generally planar outer frame defining an inner structural portion; a plurality of first multi-angular elements (MAEs), each having a proximal portion and a distal portion, wherein the proximal portions are operably coupled to the outer frame, and wherein the plurality of first MAEs extend from the outer frame into the inner structural portion; and a plurality of second MAEs, each having a proximal portion and a distal portion, wherein the distal portions of the first and second MAEs are operably coupled to define an aperture.

[0005] In one embodiment, each of the proximal portions of each of the first MAEs define a slot, wherein the outer frame comprises a plurality of pins extending upwardly therefrom in a direction substantially perpendicular to the plane of the outer frame, and wherein each of the slots is configured to engage a respective pin.

[0006] The outer frame may have a plurality of outer gear teeth on an outer surface of the outer frame, and the micro-deployable device may further include a drive gear in operable communication with at least a portion of the outer gear teeth. The drive gear may be configured to transfer a tangential force to the outer frame thereby rotating the outer frame, whereby the force is translated to the first MAEs and is configured to move the distal portions of the first MAEs in relation to the outer frame, and wherein the movement of the distal portions of the first MAEs translates into movement of the distal portions of the second MAEs, whereby the aperture changes in size. In one embodiment, the drive gear is configured to rotate the outer frame through a range of up to about 10°.

[0007] The outer frame, first MAEs, and second MAEs may comprise polysilicon. In one embodiment, the first MAEs are generally "lambda" shaped. The first and second MAEs may include elongated segments. In another embodiment, the first and second MAEs include solid plates.

[0008] The micro-deployable device may further include a retainer for retaining the outer frame to a substrate. In one embodiment, the retainer includes a retainer clip fixedly coupled to the substrate and a retainer slot on an upper surface of the outer frame for coupling to the retainer clip. The outer frame may further include a brake, wherein an interaction between the brake and the retainer clip prevents an over rotation of the outer frame.

[0009] The micro-deployable device may further include a constrainer for constraining a rotational movement of the inner structural portion. In one embodiment, the constrainer includes a constrainer clip for applying a lateral force on a pin hinge coupling the proximal portion of a first MAE and the proximal portion of the second MAE, and a vertical portion for fixedly coupling the constrainer clip to a substrate. The vertical portion may include a fused cantilever structure. In another embodiment, the constrainer includes at least one pin for restraining a rotational motion of at least one of the first MAEs.

[0010] In another aspect, the invention provides a microcamera, including a microautofocus system configured to focus light, and a microaperture configured to control a light passage. The microautofocus system may include a flexible lens and a first microelectromechanical systems (MEMS) device for actuating a shape of the lens. The first MEMS device may include a generally planar outer frame defining an inner structural portion; a plurality of first multi-angular elements (MAEs), each having a proximal portion and a distal portion, wherein the proximal portions are operably coupled to the outer frame, and wherein the plurality of first MAEs extend from the outer frame into the inner structural portion; and a plurality of second MAEs, each having a proximal portion and a distal portion, wherein the distal portions of the first and second MAEs are operably coupled to define an aperture, and wherein the lens fits substantially in the aperture.

[0011] In one embodiment, the first and second MAEs include elongated segments, wherein the first MAEs are generally "lambda" shaped. The flexible lens may be composed of polydimethylsiloxane (PDMS). The microautofocus system may include a barbell hinge to prevent lateral warping of the flexible lens, wherein the barbell hinge includes delaminated first and polysilicon layers, the first and second polysilicon layers forming a pin joint for holding the flexible lens.

[0012] In one embodiment, the microaperture includes a second MEMS device, the second MEMS device including a generally planar outer frame defining an inner structural portion; a plurality of third MAEs, each having a proximal portion and a distal portion, wherein the proximal portions are operably connected to the outer frame, and wherein the plurality of third MAEs extend from the outer frame into the inner structural portion; and a plurality of fourth MAEs each having a proximal portion and a distal portion, wherein the distal portions of the third and fourth MAEs are operably coupled to define an aperture therebetween, wherein the third and fourth MAEs comprise solid plates for blocking light. [0013] In one embodiment, each of the microautofocus system and the microaperture is disposed on a respective semiconductor die, wherein the semiconductor dies are wafer bonded.

[0014] The microcamera may further include a thermal actuator for actuating the first MEMS device.

[0015] In another aspect, the invention provides a method of fabricating and operating a microelectromechanical system (MEMS), including providing a generally planar outer frame defining an inner structural portion, providing a plurality of first multi-angular elements (MAEs) each having a proximal portion and a distal portion, wherein the proximal portions are operably coupled to the outer frame, and wherein the plurality of first MAEs extend from the outer frame into the inner structural portion, providing a plurality of second MAEs, each having a proximal portion and a distal portion, wherein the distal portions of the first and second MAEs are operably connected to define an aperture therebetween, and applying a tangential force to the outer frame while constraining a rotational motion of the inner structural portion thereby causing a relative sliding motion between the outer frame and the first MAEs, thereby changing the size of the aperture.

[0016] The method may further include providing a plurality of semiconductor dies, each having a micro-deployable device thereon, and wafer-bonding the plurality of semiconductor dies to form a system comprising a plurality of micro-deployable devices. In one embodiment, the plurality of micro-deployable devices includes a microaperature configured to control a light passage and a microautofocus system configured to focus light. Providing the plurality of semiconductor dies may include fabricating the microautofocus system on one of the dies, wherein fabricating the microautofocus system includes fabricating a barbell hinge for coupling a flexible lens to a plurality of MAEs. Fabricating the barbell hinge may include delaminating a first polysilicon layer and a second polysilicon layer to form an outer diameter of the barbell hinge, cutting the first polysilicon layer to form a cavity, and back-filling the second polysilicon into the cavity thereby forming a pin joint for locking the flexible lens. BRIEF SUMMARY OF THE DRAWINGS

[0017] FIG. 1 is a scanning electron micrograph (SEM) image of a MEMS micro- deployable system in accordance with an embodiment of the invention;

[0018] FIG. 2A is a top plan view of the micro-deployable device of the system as shown in FIG. 1;

[0019] FIG. 2B is a perspective view of the micro-deployable device of FIG. 2A;

[0020] FIG. 2C is a schematic diagram illustrating two types of multiangular elements (MAEs) included in the micro-deployable device;

[0021] FIG. 3 is a magnified micrograph of a portion of the micro-deployable device of FIG. 2B;

[0022] FIG. 4 is a schematic view of a lambda MAE used as a building block for the micro-deployable device in accordance with an embodiment of the invention;

[0023] FIG. 5A is a perspective view of a secondary, or bottom, MAE; [0024] FIG. 5B is a top plan view of a secondary, or bottom, MAE;

[0025] FIG. 6A is a top plan view of an alternative outer frame of a micro-deployable device;

[0026] FIG. 6B is a perspective view of the outer frame of FIG. 6A;

[0027] FIG. 7A is a perspective view of a constrainer of the micro-deployable device of FIG. 2A when viewed from outside the outer frame;

[0028] FIG. 7B is a perspective view of the constrainer from inside the outer frame;

[0029] FIG. 7C is a cross-sectional view of the constrainer design;

[0030] FIG. 7D is a cross-sectional micrograph image of a fabricated constrainer; [0031] FIG. 8 A is an exploded view of a portion of the micro-deployable device containing a retainer;

[0032] FIG. 8B is a further magnified SEM image showing the coupling between the restrainer clip tip portion and the retainer slot;

[0033] FIG. 8C is a cross-sectional view of the retainer design;

[0034] FIG. 8D is a cross-sectional micrograph of a fabricated retainer;

[0035] FIG. 9A is an exploded view of pin hinge used in the micro-deployable device of FIG. 2A;

[0036] FIG. 9B is an expanded view of the pin hinge including two arms coupled by the hinge;

[0037] FIG. 9C is an exploded view illustrating the coupling between the arms;

[0038] FIG. 9D is a cross-sectional view of the hinge design;

[0039] FIG. 9E is a cross-sectional micrograph image of a fabricated hinge;

[0040] FIG. 9F is a schematic diagram of the mask used to realize the hinge structures;

[0041] FIG. 1OA is an SEM image of a slot follower joint of the micro-deployable device of FIG. 2A;

[0042] FIG. 1OB is a cross-sectional view of the slot follower joint design;

[0043] FIG. 1OC is a cross-sectional micrograph image of a fabricated slot follower joint;

[0044] FIGS. 1 IA - 1 ID are time-lapse optical micrographs of the micro-deployable device of FIG. 2 A during deployment showing opening of a center aperture;

[0045] FIG. 12A is a diagram illustrating motion of an MAE and a deployable structure constructed using MAEs; [0046] FIG. 12B is a diagram illustrating a motion of an MAE in response to a tangential force;

[0047] FIG. 13A is a micrograph of a portion of the micro-deployable device of FIG. 2A showing locations where measurements of are taken to measure changes in sizes of the micro-deployable device;

[0048] FIG. 13B is a diagram illustrating the measured data;

[0049] FIG. 14A is a schematic diagram of a stacked microcamera system in accordance with an embodiment of the invention;

[0050] FIG. 14B is an isometric close-up view of the stacked microcamera system;

[0051] FIG. 14C is a perspective view of individual components of the microcamera;

[0052] FIG. 14D is a top plan view illustrating a micro-deployable solid plate aperture and a polarizing filter of the microcamera system;

[0053] FIG. 15 is an optical micrograph of a Microautofocus Lens Actuator (MAFLA) in accordance with an embodiment of the invention;

[0054] FIG. 16 is an SEM image of a portion of the MAFLA illustrating Microautofocus MAEs and radial motion constrainer pins;

[0055] FIG. 17A is an SEM image of a retainer clip slot bracket of the MAFLA in a first position;

[0056] FIG. 17B is an SEM image of the retainer clip slot bracket of the MAFLA in a second position;

[0057] FIG. 18A is an optical micrograph showing a top plan view of a Polydimethylsiloxane (PDMS) attachment point and hinge top;

[0058] FIG. 18B is a cross-sectional view of the PDMS barbell hinge design;

[0059] FIG. 19 is an optical micrograph of an unreleased microaperture device; [0060] FIGS. 2OA - 2OC are top plan views of time-lapsed diagrams illustrating deployment of the microaperture device showing a closing of the center aperture;

[0061] FIG. 21 is an SEM image of microaperture solid plate MAEs and constrainer pins of the microaperture device;

[0062] FIG. 22 is a diagraph illustrating the plano-convex thin lens approximation for radius of curvature calculation;

[0063] FIG. 23 is an SEM image of a displacement multiplier for the microaperture device;

[0064] FIG. 24 is a cross-sectional view of multiple polysilicon layers for constructing a micro-deployable device;

[0065] FIG. 25A is a cross-sectional view of multiple polysilicon layers illustrating a construction process of the micro-deployable device;

[0066] FIG. 25B is a cross-sectional micrograph of a portion of the wafer;

[0067] FIG. 26A is an SEM image showing a close-up view of MMPOLY 1 /MMPOLY2 MAE laminate; and

[0068] FIG. 26B is an exploded view of the laminate of FIG. 26A.

DETAILED DESCRIPTION

[0069] The invention may be understood more readily by reference to the following detailed description, examples, drawings, and claims, and their previous and following description. However, before the present devices, systems, and/or methods are disclosed and described, it is to be understood that this invention is not limited to the specific devices, systems, and/or methods disclosed unless otherwise specified, as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

[0070] As used in the specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to an MAE can include two or more such MAEs unless the context indicates otherwise.

[0071] Ranges may be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0072] As used herein, the terms "optional" or "optionally" mean that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0073] Reference will now be made in detail to the present preferred aspects of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like parts. [0074] Referring to the attached drawings, embodiments disclosed herein provide a micro-deployable structure, preferably fabricated on a silicon wafer substrate. In one embodiment, the micro-deployable structure comprises a closed loop and is thus referred to as a closed-loop micro-deployable (CLMD). However, open-loop structures are also within the scope of the invention. The micro-deployable structures can be employed in optical components of a microcamera, such as a microautofocus lens actuator capable of stretching a polymer lens, and a microaperture capable of accurately controlling light on a digital image sensor.

[0075] FIG. 1 illustrates a micro-deployable system 100 in accordance with an embodiment of the invention. In this exemplary system as shown, semiconductor die 102 is fabricated using Sandia National Laboratories ultra-planar multi-level MEMS technology (the SUMMiT-VTM process) which utilizes five polycrystalline silicon (polysilicon) layers, including an electrical interconnect layer and four mechanical layers. In one embodiment, three mechanical layers are used for micro-deployable system 100. Two of the mechanical layers are 2 μm thick, and the remaining layer is a laminate of two thinner sublayers of 1.5 μm and 0.3 μm thicknesses, respectively. The SUMMiT-VTM process is described in greater detail at the end of this disclosure, however, because various layers of the five polysilicon layers used in the process are referred to throughout this disclosure, a simplified layer terminology is used, wherein "PO" through "P4" will signify polycrystalline silicon (polysilicon) layers #1 through #5, respectively, and SACOX# will signify a sacrificial oxide layer.

[0076] A microengine 104 may be used to power the micro-deployable system 100 through a microtransmission 106. In this exemplary system, the microtransmission 106 is a 12:1 transmission. In the embodiment as shown, microengine 104 comprises Sandia' s electrostatic microengine having a plurality of comb drives. Microengine 104 is capable of forward and reverse motions, thereby providing bidirectionality to allow the micro- deployable aperture to open and close. Those of ordinary skill in the art will recognize that other suitable engines or actuating mechanisms may be used in the micro-deployable system of the invention. [0077] The total output force of microengine 104, when operating at its resonance frequency of 10.5 kHz, is about 12 μN, which is amplified at the output of microtransmission 106 to about 144 μN.

[0078] Microtransmission 106 is coupled to outer gear 108 of micro-deployable device 110. Micro-deployable device 110 in this case is a closed-loop micro-deployable (CLMD). A voltage is applied to microengine 104 through electrical contacts 112, 114, to power each of the orthogonal linear comb drives 105 in microengine 104.

[0079] Microengine 104 actuates (e.g. , spins) pinion gear 1 16 through linear X and Y linkages 118, 120, thereby rotating outer frame 122, which as shown is a ring, of micro- deployable device 110. As discussed in detail below, tangential force 124 is translated into radially directed motion, toward center region 126, which comprises an aperture of micro- deployable device 110. Thus, the rotational motion of the outer frame 122 as driven by tangential force 124 is translated into radial motion 128, thereby changing the size of the center region or aperture 126 of micro-deployable device 110. This is achieved, for example, using a plurality of structural members (MAEs) coupled to the outer frame 122, as described below with reference to FIGS. 2A-2C.

[0080] Manual actuation of micro-deployable device 110 can also be achieved, for example, by removing microtransmission 106 and placing microprobe tips (not shown) directly on the micro-deployable device 110.

[0081] Various components of micro-deployable device 1 10, which are described in further detail below, include a retainer 130 for retaining outer frame 122 to a substrate, thereby preventing microdeployable device 110 from floating away during an etch release process, a plurality of lambda-shaped MAEs 132 with proximal outer-ring attachment portion 134, and constrainer 136 for maintaining a lateral force that allows for deployable actuation. Retainer 130 also acts a hard-stop to prevent over rotation of outer frame 122. A scale bar 138 shows the scale of the micrograph. In this exemplary system 100, the diameter of outer frame 122 is about 1.3 millimeter. [0082] Although the term MAE is used for the building blocks 132 of micro-deployable device 110 to indicate that such MAEs are capable of rotational motion, thereby achieving various angular positions, it should be understood that at least some of the MAEs described herein are also capable of linear translational motions. In addition, the MAEs defined herein are not limited to multiangles. Rather, the term MAE should be understood as a generalized term. For example, some of the MAEs may be at a fixed, single angular position.

[0083] FIG. 2A is a top plan view of micro-deployable device 110. Retainer 130 (shown in FIG. 1) comprises a retainer clip 131 fixedly coupled to a substrate, and a retainer slot 133 on a top surface of outer frame 122. Drive gear 202 of microtransmission 106 couples to outer gear teeth 108 on an outer surface of outer frame 122. In the embodiment as shown, outer frame 122 is a substantially rigid ring and is often referred to as the outer ring. However, those of ordinary skill in the art will recognize that other shapes, such as a square, a rectangle, an ellipse, or any other geometric shapes, including nonsymmetrical shapes and open shapes, may be used as outer frame 122.

[0084] Proximal outer-ring attachment portion 134 comprises a slot-follower joint 204. Base portion 131a of retainer clip 131 serves as a stop for the outer frame 122. That is, when ring brake 206 hits base portion 131a, the motion of outer frame 122 is stopped.

[0085] Translating rotational motion of outer frame 122 into changes in the size of center region 126 of micro-deployable device 110 is realized through a plurality of MAEs 132. The MAEs may include, for example, lambda-shaped MAEs 208, and secondary MAEs 210 which are also referred to as bottom MAEs, which may be coupled via pin hinges 212 located at nodes in the structure. As can be seen in FIG. 2A, the internal structure of a micro-deployable device is determined by the obtuse angles of the MAEs and the number and locations of the internal nodes at which they are connected. In the embodiment shown in FIG. 2A, 32 internal nodes are included, and a 3-sided MAE design approach is adopted. However, the number of internal nodes may vary based on various design considerations. For example, potential for hinge stiction may render a reduction of the number of nodes desirable. [0086] FIG. 2B is a SEM image showing a perspective view of micro-deployable device 110. As shown, the substantially rigid outer ring 122 defines therein an inner structural portion 216 that is collapsible.

[0087] FIG. 2C is a schematic diagram for better visualizing the difference between lambda MAEs 208 and secondary MAEs 210. As shown, eight (8) sets of lambda MAEs 208 and secondary MAEs 210 are included in micro-deployable device 110. However, more or fewer MAEs may be used. As shown, lambda MAEs 208 are right-handed as measured from outer frame 122 toward center region 126, and secondary MAEs 210 are left-handed as measured from outer frame 122 toward center region 126. However, other configurations are possible. One advantage of using a relatively large number of MAEs is that wherever an actuation force is applied to micro-deployable device 110, the force is distributed substantially uniformly (symmetrically) among all the lambda MAEs 208. This reduces the probability of failure of a single lambda MAE.

[0088] FIG. 3 is a magnified SEM image of a portion of micro-deployable device 110 of FIG. 2B, showing more details of attachment portion 134, retainer 130, and constrainer 136. When a tangential force 124 (FIG. 1) is applied to outer frame 122, for example, in a counter-clockwise direction, inner structural portion 216 (FIG. 2B) tends to move along with outer frame 122 because of their coupling at attachment portions 134. However, as constrainer 136 constrains the rotational motion of inner structural portion 216 relative to the substrate, lambda MAEs 208 are forced to slide along their respective elongated slots at slot follower joints 204, thereby pulling secondary MAEs 210 and opening up center region 126.

[0089] FIG. 4 is a schematic view of lambda MAE 208 in accordance with an embodiment of the invention. As shown, lambda MAE 208 comprises a plurality of elongated arms or segments 402. In some other embodiments as described below, an MAE may comprise a solid plate of any geometrical shape instead of elongated arms 402. MAE 208 also comprises one or more openings 404, which as shown are substantially circular in shape and are located at vertices of the imaginary rhombi locations. Openings 404 allow for pins (not shown) to extend therethrough to form hinges. Slot 406 is part of "lambda" extension portion 408 of MAE 208 and allows for a pin (now shown) to slide therein. Angle o; between lambda extension portion 408 and one of the elongated arms is an acute angle, but may be any angle between 0° and 180°.

[0090] With respect to outer frame 122, lambda MAE 208 has a proximal portion 410 operably coupled to outer frame 122, and a distal portion 412. Lambda MAEs 208 extend from outer frame 122 into inner structural portion 216 (FIG. 2B).

[0091] FIG. 5A is a perspective view of a secondary, or bottom, MAE 210. FIG. 5B is a top plan view of same. As shown, secondary MAE 210 comprises a plurality of elongated arms 502 and a plurality of pins 504. Secondary MAE 210 also has a proximal portion 506 and a distal portion 508. As shown in FIG. 2C, distal portions of lambda MAEs 208 and secondary MAEs 210 are coupled to define center aperture 126. When coupled to lambda MAEs 208, secondary MAEs allow for the opening and closing movement of the aperture of the micro-deployable device 110.

[0092] In accordance with an embodiment of the invention, locations of pins 504 match the vertices of the lambda locations. However, geometries of elements of secondary MAEs 210 and lambda MAEs 132 may be independent of each other. That is, instead of using elongated arms 402 or 502, solid plates or any other geometrical shapes may be used for either the lambda MAEs or the secondary MAEs, or both.

[0093] FIGS. 6A and 6B are the top plan view and a perspective view, respectively, of an alternative embodiment of outer frame 600 of a micro-deployable device, in accordance with the present invention. This embodiment is different from the embodiment shown in FIGS. 2A and 2B in that the extrusions 602, which may be used as brakes or hard stops for the outer frame 600, are not aligned with slots 604. This embodiment may be used, for example, when braking using retainer clip 131 is not necessary. Instead, other mechanisms can be used for limiting the range of angular rotation of outer frame 600. In accordance with some embodiments, up to 10° of outer frame rotation is sufficient to result in a full- range internal structure displacement to fully open and close the center aperture. In a preferred embodiment, 2 - 10° of outer frame rotation is used to achieve full deployment. The system may be designed to require even a smaller outer frame rotation, for example, up to 5°.

[0094] Gear teeth can be fabricated on the outer surface of the outer frame 600. In accordance with some embodiments of the invention, the number of gear teeth may be between 50 and 350, for example. Instead of using a single microtransmission 106 shown in FIG. 1, it is also possible to couple the gear teeth to a plurality of off-die motors or engines. Such motors or engines may even be on mesoscale so long as proper transmissions are used.

[0095] FIGS. 7A and 7B are perspective views of constrainer 136. FIG. 7A shows the view from outside outer frame 122. FIG. 7B is the view from inside outer frame 122.

[0096] In accordance with an embodiment of the invention, hinges of the device 110 can move radially inward and outward as the device aperture opens and closes. Constrainer 136 applies a lateral restraining force 701 to the inner vertices when the MAEs rotate along with outer frame 122, as discussed earlier The clip is constructed using polysilicon layers P4, P3, and P1/P2 fused to the substrate via PO. Lateral force 701 is applied to the pin hinges contained within slot 704 of constrainer clip 702. During deployment, the pin hinge top 706 grinds against the inside of the constrainer clip slots 704. The slot 704 provides a force to allow the micro-deployable device 110 to open or close, while allowing the hinges to move radially.

[0097] Gap 707 between the inside edge of the clip 702 and the outer edge of the hinge top 706 represents minimum tolerance allowed by the design rules. As shown, gap 707 is about 1.5 μm.

[0098] FIG. 7C is a schematic diagram of a cross-sectional design of the constrainer 136. FIG. 7D is an optical micrograph of a fabricated constrainer. As shown, vertical portion 708 , which anchors constrainer clip 702 to substrate 710, is composed of multiple layers. However, those of ordinary skill in the art will recognize that other implementations are possible. Indeed, as discussed below with reference to FIG. 21, the whole constrainer 136, including constrainer clip 704, pin 706, and vertical portion 708, may be replaced with constrainer pins.

[0099] FIG. 8 A is an exploded view of a portion of the micro-deployable device 110 containing retainer 130. FIG. 8B is a further magnified micrograph showing the coupling between retainer clip 131 and retainer slot 133. FIG. 8C is a cross-sectional view of the retainer design, and FIG. 8D is a cross-sectional micrograph of the actual retainer fabricated.

[0100] As discussed earlier, outer frame 122 provides symmetrical force distribution to micro-deployable device 110. When coupled with retainer 130 as shown in FIGS. 8A and 8B, outer frame 122 also serves as a substrate contact during etch release/deployment, and as an over-rotation prevention system. Retainer clip 131 is secured to the substrate through a fused cantilever structure similar to vertical portion 708 of constrainer 136 as shown in FIG. 7C. The base of retainer clip 131 is fixedly coupled to the substrate with polysilicon layers PO, P1/P2 laminate and P3. P3 is extended over the P1/P2 laminated outer-ring. The base portion 131a acts as the stop for the outer-ring's brake to prevent over-rotation of the micro-deployable device.

[0101] Slot 133 and barrel 802 are employed to improve the tolerance of outer frame 122 during deployment. More specifically, in order to reduce lateral sloppiness of outer frame 122 during deployment, Pl and P2 are delaminated to produce slot 133 and barrel 802. Divot 804 is created during the etch process of P2 CUT that makes barrel 802. As microengine 104 spins microtransmission 106, outer frame 122 torques against barrel 802, and once outer frame 122 is past the interface of divot 804 and barrel 802, movement is smooth. However, once outer frame 122 reverses and counter rotates, divot 804 and barrel 802 contact each other and temporarily lock, until the outer-ring breaks free and completes its rotation.

[0102] FIG. 9A is an exploded view of a pin hinge 212 used in micro-deployable device 110 of FIG. 2A. P1/P2 laminate is fused to P3 and P4 to create Pl-to-P4 hinge 212. SACOX3 CUT mask layer allows for the connection from P3 to P1/P2, and P3 CUT produces a separation between the fused layers and the MAE that needs to rotate about the fused section. SACOX4 CUT allows for P4 to fuse to the P3 fused layer, but P4 is only patterned into its final shape.

[0103] FIG. 9B is an expanded view of the pin hinge 212 showing two arms 902, 904 of a first and a second MAE coupled by hinge 212.

[0104] FIG. 9C is an exploded view of the coupling between arms 902, 904. During processing, polysilicon is back filled to create the P1/P4 pin hinge. Pin hinge top 906 is fused to P3 barrel 908, which is fused to P1/P2 laminate 910. Dimples 912 keep the P1/P2 laminate 910 from contacting P3 and substrate 914 to reduce stiction during deployment.

[0105] FIG. 9D is a cross-sectional view of the hinge design. As shown, P1/P2 laminate 910 is used for a first MAE, which is coupled to a second MAE 916 composed of a third polysilicon material P3.

[0106] FIG. 9E is a cross-sectional micrograph image of a pin hinge following the design of FIG. 9D.

[0107] FIG. 9F is a schematic diagram of mask layers that may be used to realize the hinge structures. Each of the mask layers corresponds to some portion of hinge 212.

[0108] FIG. 1 OA is an SEM image of a slot follower joint 204 of micro-deployable device 110 of FIG. 2 A. As shown, lambda extension portion 408 of a lambda-shaped MAE (FIG. 4) is coupled to a pin 1002 on outer frame 122. Elongated slot 406 of lambda extension portion 408 allows pin 1002 to slide therein when outer frame 122 is being actuated through outer gears 108.

[0109] FIG. 1OB is a cross-sectional view of the slot follower joint design, and FIG. 1OC is a cross-sectional micrograph image of the actual slot follower joint;

[0110] FIGS. 1 IA - 1 ID are time-lapse optical micrographs of the micro-deployable device 110 of FIG. 2 A during deployment showing the opening of a center aperture 126. As shown in FIG. 1 IA, micro-deployable device 110 may start out in a first configuration with a substantially closed center region (aperture) 126. In FIG. 1 IB, outer frame 122 is rotated slightly counter-clockwise, and aperture 126 opens up slightly. In FIG. 11C, aperture 126 is further opened, and lambda extension portions 408 start to stick out of outer frame 122. In FIG. 1 ID, aperture 126 is further opened to near its fully opened configuration.

[0111] FIG. 12A is a schematic diagram illustrating the motion of an MAE and a micro- deployable device constructed using MAEs. In this exemplary configuration, 3 -sided linkages are used to form an octagonal micro-deployable device. Three-sided lambda MAE 208, represented with solid lines, is shown in panel "A" overlapping with counter-rotated secondary MAE 210 that is represented with dotted lines. Assembly 1202 comprising lambda MAE 208 and secondary MAE 210 is copied and rotated -45°, forming structure 1204 in panel "B." Structure 1204 is copied three additional times to form pattern 1206 in panel "C." Structures in pattern 1206 are coupled to produce an octagonally shaped micro- deployable 1208 in panel "D."

[0112] The ability for the CLMD to open and close lies in the physics of MAE coupled movement. During deployment, MAEs subtend angles that radiate from an imaginary centroid. FIG. 12B is a free body diagram illustrating a motion of MAE 1202 in response to a tangential force F_τ. The pair of 3 -sided MAEs as shown have two 135° obtuse angles. Each node is allowed a single degree of freedom, so that when a tangential force is applied, all of the MAE hinges move radially while the angle β remains constant. In the case of the octagonal deployable 1208, β remains about 90° throughout deployment. Each MAE node moves radially in the same direction as the applied forced until the neutral position 1203 is reached.

[0113] Functional testing of micro-deployable device 110 was conducted and the results are summarized in FIGS. 13A and l3B. FIG. 13A is a micrograph of a portion of micro- deployable device of FIG. 2 A 110 showing dimensions 1301, 1303, 1305 to be measured. The measured diameter of opening 1301 at center region 126 is represented as the horizontal axis of FIG. 13B. Measured data and fitted curves for dimensions 1303, 1305 are represented as curves 1302, 1304, respectively in FIG. 13B. The data illustrate that micro-deployable device 110 can be successfully and repeatedly deployed. [0114] The basic structures and deploying mechanisms of the micro-deployable device discussed above can be employed in many applications. In the following, an exemplary implementation of micro-deployable devices in a microcamera is descπbed

[0115] Image sensor pixel density has increased steadily in digital cameras. However, implementation of digital cameras into small portable platforms such as cell phones has been hindered by the lack of adaptive optical systems such as auto focus, image stabilization, and proper light control. A microautofocus mechanism allows for a single polymer lens to be stretched continuously depending on focal length requirements This type of mechanism has the potential of addressing challenges in digital camera manufacturing, such as camera miniaturization and digital image quality, thus opening up many new market opportunities.

[0116] As discussed above, relatively small input actuation from the outer frame of a CLMD MAE can result m large internal displacement. Similarly, a human eye, through a process known as accommodation, manipulates the focal length projection on the retina by flattening or thickening the lens which is sometimes referred to as the crystalline lens. Duπng accommodation, ciliary muscles (connected to the lens with Zonnules of Zinn) move outwardly to apply a force on the lens, causing the lens to elongate, thereby reducing its optical power.

[0117] In addition to the micro-deployable device itself, the present invention provides a "microautofocus lens actuator" (MAFLA) that incorporates the micro-deployable device. In this aspect of the invention, a microautofocus mechanism takes advantage of the radial hinge movement of the micro-deployable structures descπbed earlier to elongate a preformed, yet compliant, flexible lens The flexible lens may be composed, for example, of polymers. In one embodiment, a lens may be attached to the innermost hinge tops of the CLMD. Such a design is advantageous because the hinge tops may be formed with a relatively large width to allow for large surface area contact with the lens polymer, thereby reducing unwanted lens warping, which leads to optical aberrations The hinge tops may also provide structures into which the polymer can mold, thereby mechanically preventing the lens from detaching during actuation. Polydimethylsiloxane (PDMS) is one exemplary material that is suitable as a lens material in the microautofocus lens actuator.

[0118] Proper light control on an image plane is also important for proper image exposure and the depth of field in such applications as camera lenses. The present micro-deployable apertures are well suited for such light control applications. Thus, a microaperture in accordance with embodiments of the present invention may be utilized a to control the passage of light in a camera.

[0119] Conventional cameras usually contain an adjustable aperture for adjusting the size of pupil diameter, which adjusts the amount of light entering the image plane. To ensure proper exposure of images taken with small/portable cameras like those in mobile phones, a microaperture is preferably coupled to the microautofocus mechanism. Currently, small consumer device image sensors use a software algorithm to adjust the light on a CMOS (complimentary metal oxide semiconductor) image sensor. However, "software-only" light adjustment is inadequate during high and low lighting conditions. Hence, an improved mechanical iris diaphragm is needed.

[0120] Design modifications to the CLMD allow for the mechanism to be transformed into a pupil diameter control system resembling the iris of the human eye. When light enters the eye, brain signals tell the iris to expand/contract as needed to prevent damage to the sensitive retina. As the iris expands and contracts, ciliary muscle fibers act to adjust the lens to allow proper focus under the specific lighting conditions. The crystalline lens and the pupil work in concert to produce a properly exposed and focused image on the retina.

[0121] Thus, one aspect of the present invention provides a MEMS device with the ability to stretch a flexible lens (similar to a crystalline lens of the human eye), which has far reaching consequences in the miniaturization of current commercial optical systems. In this aspect of the invention, the micro-deployable devices in accordance with the present invention were modified to produce two key components in a microscale camera: a microautofocus mechanism and a microaperture. The microautofocus component couples a lens, preferably a flexible polymer lens, to the closed-loop micro-deployable; as it deploys open, it stretches the polymer lens radially (e.g., at eight fixed areas around the circumference of the lens). The lens deformation in turn causes a focal plane change. The ability to change the focal plane is advantageous to portable digital imaging devices such as the cell phone camera and the mini-digital camera.

[0122] In accordance with this microcamera embodiment of the invention, a microcamera system with a microaperture with a pupil diameter range of, for example, 480 - 961 μm, or f/S.d -f/2.8 may be provided. Those of ordinary skill in the art will recognize that different f-stop ranges are possible. In this embodiment, the microaperture and the MAFLA are designed to work in concert to produce a properly exposed and focused image on a digital imaging sensor. FIG. 14A is a schematic diagram of a microcamera system 1400 in accordance with this embodiment of the invention. In this embodiment, microcamera 1400 comprises a microaperture 1402, a micro-scale polarizing filter 1404, and a MAFLA 1406, all coupled to a CMOS image sensor 1408. The components are fabricated on stacked dies 1403, 1405, 1406, and may be bonded together to form microcamera 1400 using wafer bonding technologies. Stacked dies 1403, 1405, 1406 may be further coupled to CMOS digital imaging sensor 1408.

[0123] As shown in FIG. 14A, stacked- wafer microcamera 1400 may have dimensions of about 1.8 mm x 2.0 mm x 2.0 mm. FIG. 14B is a isometric close-up view of stacked microcamera system 1400. FIG. 14C is a perspective view of individual components of microcamera system 1400. FIG. 14D is a top plan view illustrating micro-deployable solid plate aperture 1402 and polarizing filter 1404 of microcamera 1400.

[0124] The microcamera functions similarly to the human eye: light enters the pupil (microaperture) and its intensity is adjusted to proper levels onto the crystalline lens (e.g., PDMS lens). Ciliary muscles (microautofocus lens actuator) connected to the crystalline lens, with Zonnules of Zinn, contract distorting the lens to bring the image into focus on the retina (CMOS image sensor). As the image plane changes, the microautofocus lens actuator (MAFLA) opens, stretches the PDMS lens, and adjusts the focal plane. Focal plane changes often require the amount of light on the image plane to be adjusted as well, so the MAFLA and the microaperture desirably work in concert to produce a high quality image. [0125] "Accommodation" within the eye enables focal length adjustments based on dynamic imaging situations. For example, a person can be reading a book and then look up to see someone walking across the room, immediately attaining focus. Fixed-focal-length cameras do not deal with moving images well nor can they handle lighting conditions outside of software-adapted ranges. The microcamera is anticipated to handle both dynamic images and the changing of lighting conditions while producing a higher quality image.

[0126] In accordance with an embodiment of the invention, individual components of a microcamera are fabricated on a plurality of semiconductor dies, and the dies are wafer- bonded together to form a microcamera system. Stacked die microcameras pose several design challenges prior to rolling out a new microcamera system. For example, technologies that need to be invented/improved include: inter-chip electrical connection techniques for stacked die-on-die assemblies, construction techniques that do not damage fragile polysilicon, glass packaging allowing for an equivalent "corneal lens" to gather light and shorten the overall stack, stacked assemblies requiring a custom CMOS image sensor or special design consideration to account for wire-bonding on the image sensor.

[0127] FIG. 15 is a micrograph of an MAFLA in accordance with the present invention. In FIG. 15, MAFLA 1500 resembles the ciliary muscle/Zonnules of Zinn complex of a human eye, and is designed for the purpose of low power actuation of a flexible lens 1502. In accordance with an embodiment of the invention, the flexible lens 1502 composed of PDMS is coupled to MAEs 1506 at a plurality of attachment points 1504. Beneath attachment points 1504 is a hinge system capable of full rotational movement independent of MAE movement. The hinge exploits the ability to delaminate Pl and P2 in the SUMMiT-VTM process to create a pin joint. This type of hinge prevents an induced lens torque in the plane of the PDMS attachment points 1504.

[0128] Instead of using microengine 104 comprising combdrives 105 shown in FIG. 1 , the embodiment shown in FIG. 15 employs a thermal actuator 1508 because of its low- voltage requirements that are compatible with portable electronics. A positive voltage is applied to thermal actuator 1508 and causes Coulomb heating as current is passed to ground 1510. Thermal actuator polysilicon expands during heating causing a force to pull on an outer- frame connector rod 1512, which causes outer frame 122 to rotate. Since the MAFLA only requires short outer-frame displacements, thermal actuator 1508 may be designed to pull, through the connecting rod 1512, on outer frame 122. Alternatively, thermal actuator 1508 may be disposed in a "pushing" position and connected to a displacement multiplier, as described below with respect to FIG. 19.

[0129] Increasing the width and/or thickness of polysilicon at the slot follower joints improves the force transfer capabilities of the lambda MAE 1506. Retainer 1514 may have a modified design with a tapered channel in which the P3 barrel may glide, thereby avoiding the sluggish motion due to the retainer clip slot divots as discussed earlier.

[0130] FIG. 16 is an SEM image of a portion of MAFLA illustrating microautofocus MAEs and radial motion constrainer pins. To ensure maximum force transfer into the interior of the MAFLA, lambda MAE polysilicon is widened around slot 1602, and is strengthened with a tapered slot side wall 1603, to reduce buckling during deployment. This modification may be desirable during the stretching of the flexible (e.g., PDMS) lens 1502, whereby the maximum force needs to be transferred to lens 1502.

[0131] Instead of using constrainer 136 that employs constrainer clip 702 discussed earlier, in accordance with an embodiment of the invention, a pair of constrainer pins 1604 are disposed adjacent slot follower joint 204. This allows for the MAFLA to rotate slightly without any deployment of the MAEs. However, once the MAEs contact constrainer pins 1604, lateral force is applied which causes the MAEs to deploy. Constrainer pins comprise fused PO, P1/P2, P3, and P4.

[0132] FIG. 17A is an SEM image of an embodiment of a retainer clip slot bracket 1702 of the MAFLA in a first position. Wide portion 1704 is the widest section of retainer slot 1706 for the MAFLA. Narrower portion 1708 has a reduced slot width.

[0133] FIG. 17B is an SEM image of the retainer clip slot bracket of the MAFLA in a second position. Divot 1710 is visible. A section 1712 of constant width is included in the slot. As shown, wide portion 1704 gradually slopes into narrower portion 1708, while divot 1710 abruptly changes to constant-width section 1712. The MAFLA was designed to operate within 50% of its fully opened and closed positions, so no hard-stops were needed to prevent over-rotation. The longer sloping section helps prevent locking.

[0134] FIG. 18A is an optical micrograph showing a top plan view of a lens attachment point 1504 and a hinge top 1800. FIG. 18B is a cross-sectional view of the barbell hinge design 1800. Here, hinge top 1800 of the micro-deployable structure is modified to create a large surface area for holding a PDMS lens 1502 (FIG. 15). Dashed line 1808 shows the location of the cross section seen in FIG. 18B.

[0135] The hinge top was designed so that PDMS could be molded into long channels on the top of the hinge. In FIG. 18A, three channels 1802, 1804, 1806 can be seen on either side of the attachment point 1504. PDMS will mold into these channels during the lens fabrication process. For example, the MAFLA die may be placed face down into a mold containing PDMS. The PDMS will flow to fill the channels and the etch release holes in the hinge top. PDMS over- flow can be controlled through mold design.

[0136] Lateral warping of the PDMS lens is prevented with the barbell hinge design, thereby allowing both the P1/P2 laminate MAE and the P3 MAE 1807 to move independently of the P4 PDMS hinge top 1805. In the cross-sectional view in FIG. 18B, P1/P2 is delaminated at location 1809 to produce the outer diameter of the hinge 1800. Pl is then cut, and P2 is allowed to back-fill into the etched cavity. This back-filling process creates the pin joint 1810. Thus, the barbell hinge 1800 takes advantage of the P 1 /P2 laminate layer to create locking feature/pin joint 1810.

[0137] FIG. 19 is an optical micrograph of an unreleased microaperture device 1900 designed to ensure proper image exposure and depth-of-field, in accordance with an embodiment of the invention. In this adaptation of the micro-deployable device, solid plates instead of arms or bar linkages are used in MAEs to form a microaperture that allows light to pass through substantially only the center region. The microaperture has a stop range of, for example, /2.8 tof/5.6. Each of these components may be integrated at the die level with a digital imaging sensor to produce a microcamera of dimensions 1.8 mm x 2.0 mm x 2.0 mm. This adaptation is particularly well-suited for use in a camera microaperture because the plates assist in blocking unwanted light from passing through the structure. As noted above, the MAEs 1902 in microaperture device 1900 employ a solid plate design and are capable of blocking light as needed. FIG. 19 also shows a displacement multiplier 1904. A thermal actuator (not shown) pushes on displacement multiplier 1904 (described in greater detail with respect to FIG. 23, below), which in turn pushes on outer ring coupling rod 1906. Solid plate hinge top 1908 is connected to solid plate MAEs 1902, which substantially block light thereby forming a pupil 1910.

[0138] FIGS. 2OA - 2OC are top plan views of time-lapsed diagrams illustrating deployment of microaperture device 1900 showing a closing of the center aperture 1910. The circular shape of aperture 1900 is substantially maintained throughout deployment.

[0139] Microaperture 1900 is designed to prevent substantial light-leaking holes to form. As solid plate MAEs are used, there is little space left inside the outer frame to place a constrainer similar to that shown in FIG. 3. Therefore, in the embodiment shown in FIG. 21, constrainer pins 2100 are disposed outside outer frame 122 and interact with a portion of MAE 1902 that extrudes out of outer frame 122 and interact with a portion of MAE 1902 that extrudes out of outer fram 122.

[0140] During deployment, solid plate MAEs 1902 may come in contact with constrainer pins 2100 as thermal actuator connecting rod 1906 actuates outer frame 122. Since the force from the thermal actuator is compressive, hold-down brackets 2102 may be included in rod 1906 to reduce the effect of vertical buckling of rode 1906 during deployment of microaperture device 1900.

[0141] To determine the range of pupil diameter, P_D, (denoted with a D in 20A) shown in FIGS. 2OA - 2OC, the flexible lens radius of curvature, R, may be estimated for a planoconvex lens (FIG. 22) as follow:

[0142] R = (h + b) Eq. (1)

where h is the thickness of the lens, and r is the radius of the lens, and b is the distance from the imaginary center of the circle to the planar side of the lens, which is ,.2 - h b =

^2I> E,. P)

[0143] By plugging Eq. (2) into Eq. (1) and solving for R with designed values of h = 25 μm and r = 250 μm in accordance with an embodiment, R = 1262.5 μm.

[0144] The focal length, fi of the lens may calculated using the Lens Maker's Formula (with R₁ = ∞ because it represents the planar side of the lens) as follows:

[0145] With R = 1262.5 and n = 1.43 (index of refraction for PDMS with white light transmission), Eq. (3) yields^? = 2.69 mm. Finally,

Po = >'

//#

Eq. (4)

where f/# is standard aperture nomenclature. Table 1 shows the results of this calculation reported to three significant figures which correspond to the number of significant figures used in AutoCAD® during the drafting of each of the components. The microaperture was designed to operate within the/2.8 tof/5.6 range. This f-stop range is chosen to be the same range as software-only cameras for effective comparison, as shown in Table 1, of the proof-of-concept to an actual cell phone camera.

[0146] Table 1 : f/# and pupil diameter for the microaperture.

[0147] Thermal actuation was chosen for the microaperture for the same reasons it was chosen for the MAFLA with one main design difference: the thermal actuator on the MAFLA pulls on the outer ring while the thermal actuator on the microaperture is reversed and pushes on the outer ring. To prevent outer ring connecting rod buckling under the compressive load, hold-down clips were added over the outer ring connecting rod for additional support.

[0148] FIG. 23 is an SEM image of a displacement multiplier 1904 for the microaperture device 1900. An actuator is attached to the input side 2302 of multiplier 1904, and the actuation subject-device is attached to output 2304 of multiplier 1904 with rod 1906. Additional displacement may be offset by a reduction in available output force. Also seen in FIG. 23 are optional hold-down clips 2306 over the compressive thermal actuator expansion bars 2308.

[0149] In the following, an overview is provided for semiconductor processing methods used for the fabrication of micro-deployable devices and systems in accordance with embodiments of the invention. Although the methods are described with reference to the SUMMiT-VTM process and the AutoCAD® macros developed by Sandia, those of ordinary skill in the art will recognize that other methods and processes can be used. [0150] MEMS Advanced Design Tools and MEMS Visualization Tools of the SUMMiT- VTM design process are used throughout the fabrication process, which employed SUMMiT-VTM masks and their associated polysilicon layers. The following description describes the nomenclature for individual design and fabrication layers, certain design features such "etch release holes" and "dimples", and other details needed for understanding the SUMMiT-VTM design process.

[0151] SUMMiT-VTM is a surface micromachining process architecture that utilizes a wafer composed of five polysilicon deposition layers, including four mechanical layers and a single electrical layer. As shown in a cross-sectional view of a wafer 2400 in FIG. 24, each polysilicon layer (referenced as MMPOLY0, MMPOLYl, MMPOLY2, MMPOLY3, and MMPOLY4, corresponding to PO, Pl, P2, P3 and P4, respectively) is separated by a thin layer of sacrificial oxide (SACOX) which is planarized. Planarization requires the wafer to be chemically or mechanically polished to prevent its topography from being transmitted to subsequently deposited polysilicon layers. Topographic transmission prevents the use of multiple layers as vertical features to "lock" against adjacent mechanical members. A metallization process, which patterns a 0.7 μm thick metal layer 2402, may be applied to several components of the microaperture and the microautofocus.

[0152] MMPOLYO layer 2408 is used as an electrical connection for bond-pads, electrical interconnects, and a ground plane, while the NITRIDE and thermal oxide layers 2410, 2412 act as an electrical insulator to the substrate. NITRIDE layer 2410 also acts as a protective layer for the thermal oxide layer 2412 during the etch release process.

[0153] FIG. 25A is a cross-sectional view of multiple polysilicon layers illustrating a construction process for making a micro-deployable device. This view shows a processed wafer prior to an etch release process which removes all sacrificial oxides. Top layers are anchored to underlying layers through the "CUT" process. For example, MMPOLY3 (also denoted P3) is cut using MMPOLY3 CUT to allow an attachment to MMPOLY2. FIG. 25B is a cross-sectional micrograph of a portion of wafer being processed.

[0154] In the SUMMiT-VTM process cross-section of FIG. 25 A, a main anchor point

2502 to the substrate for MMPOLYl and MMPOLY2 is shown. MMP0LY3 anchors to the underlying MMPOLY2 at anchor points 2504 and 2506. MMPOLY4 anchors to MMPOLY3 at anchor point 2508. Each anchor is made using the CUT nomenclature (e.g., MMPOLY3 CUT). Each MMPOLY layer creates topography, but the top layers of SACOX do not have topographic transmission because of the chemical machine polishing process.

[0155] FIG. 25A also shows an anchor to the substrate through the underlying nitride layer using NITRIDE CUT layer. This anchoring prevents the device from floating away during the etch release process. Etch release holes and polysilicon cuts are also created using the CUT layers. These layers usually define the areas to be cut. In one embodiment, for all areas of the CLMD, with the exception of the retainer clip slot bracket, Pl and P2 are considered a single layer; therefore, the two layers may be treated as a single P1/P2 laminate layer (see FIGS. 26A and 26B).

[0156] When a cut is made in one of the polysilicon layers, topography is generated on the upper fused layers. For example, a designer places dimples on P3 to reduce the interfacial area so that it does not stick to P2 during movement, so DIMP LE3 CUT is placed in the P3 layer design. The next step is to back fill polysilicon into the dimple cut. Consequently, the next polysilicon layer is deposited and fused to the dimple that has been back filled. The back filling process is a timed process so that an equal thickness of polysilicon is deposited, which leaves a small "dimple" in the top of the new polysilicon layer. FIGS. 26A and 26B provide close-up views of MMPOLYl /MMPOL Y2 MAE laminate. Dimple topography 2602, MMPOLY2 2604 and MMPOLYl 2606 are clearly visible in these SEMs. An enhanced line 2610 in FIG. 26B indicates the laminate's contact surface. A dimple 2612 can also be seen. The structures are fabricated on substrate 2614. Scale bars 2616 indicate dimensions of each micrograph.

[0157] SACOX is then deposited, which now has the dimple topography transmitted through it. Dimple topography is removed from the sacrificial oxide during SACOX chemical machine polishing. Dimple topography may come into contact with the an upper layer's dimple during movement which can hinder the proposed movement. The Design Rule Checker of the Sandia MEMS advanced design tools would give an error if the dimples were designed on top of each other, and the engineer would be prompted to redesign the location of the dimples. If dimples are going to contact each other during deployment, the engineer should recognize this and redesign the dimples to prevent contact during movement.

[0158] Sandia created the advanced MEMS design tools to assist the SUMMiT-VTM designer in keeping track of complicated design rules. Many of the tools are used throughout the design of the CLMD and the microcamera components. The tools include, for example, a library of drop-in components such as comb drives, displacement multipliers, and measurement devices, component generators such as electrical traces, gears, and words, Internet access to design rule checker, virtual 2D cross sectioning tool, and virtual 3D solid modeling generator.

[0159] A 2D cross sectioning too is used to ensure that the designer's intentions are being interpreted correctly in the individual polysilicon layers. The cross sectioning tool also helps ensure all components on the die were properly anchored to the substrate. Design rule checking ensures each mask layer is converted properly from the design to the actual mask generation file.

[0160] Sandia's "visualization" tools can be used in understanding how the SUMMiT- VTM process would be implemented and to refine the designs for better compatibility with the process. This tool package works with the 2D cross sectioning tool mentioned in the previous section by showing 2D mask layer geometry extraction and a SUMMiT VTM process simulation. For example, FIG. 9F discussed earlier shows each of the individual masks that makes up the cross-sectional view in FIG. 9D. The designer could also, in AutoCAD®, step through each of the layers (and masks) to ensure their design is being realized properly.

[0161] Those of ordinary skill in the art will recognize that other fabrication processes, including standard IC fabrication processes, can also be used. An exemplary process for fabricating the devices in accordance with embodiments of the invention uses chemical deposition, photolithographic patterning, and both dry and wet etching to create MEMS devices. In a further aspect, the device can use extensive planarization, which can allow for clean, reliable devices. [0162] While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be advised and achieved which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

Claims

WHAT IS CLAIMED IS:

1. A microelectromechanical systems (MEMS) device, comprising: a generally planar outer frame defining an inner structural portion; a plurality of first multi-angular elements (MAEs) each having a proximal portion and a distal portion, wherein the proximal portions are operably coupled to the outer frame, and wherein the plurality of first MAEs extend from the outer frame into the inner structural portion; and a plurality of second MAEs each having a proximal portion and a distal portion, wherein the distal portions of the first and second MAEs are operably coupled to define an aperture.

2. The micro-deployable device of Claim 1 , wherein each of the proximal portions of each of the first MAEs define a slot, wherein the outer frame comprises a plurality of pins extending upwardly therefrom in a direction substantially perpendicular to the plane of the outer frame, and wherein each of the slots is configured to engage a respective pin.

3. The micro-deployable device of Claim 1 , wherein the outer frame has a plurality of outer gear teeth on an outer surface of the outer frame.

4. The micro-deployable device of Claim 3, further comprising a drive gear in operable communication with at least a portion of the outer gear teeth.

5. The micro-deployable device of Claim 4, wherein the drive gear is configured to transfer a tangential force to the outer frame thereby rotating the outer frame, whereby the force is translated to the first MAEs and is configured to move the distal portions of the first MAEs in relation to the outer frame, and wherein the movement of the distal portions of the first MAEs translates into movement of the distal portions of the second MAEs, whereby the aperture changes in size.

6. The micro-deployable device of Claim 5, wherein the drive gear is configured to rotate the outer frame through a range of up to about 10°.

7. The micro-deployable device of Claim 1, wherein the outer frame, first MAEs, and second MAEs comprise polysilicon.

8. The micro-deployable device of Claim 1 , wherein the first MAEs are generally "lambda" shaped.

9. The micro-deployable device of Claim 1, wherein the first and second MAEs comprise elongated segments.

10. The micro-deployable device of Claim 1 , wherein the first and second MAEs comprise solid plates.

11. The micro-deployable device of Claim 1 , further comprising a retainer for retaining the outer frame to a substrate.

12. The micro-deployable device of Claim 11 , wherein the retainer comprises a retainer clip fixedly coupled to the substrate and retainer slot on an upper surface of the outer frame for coupling to the retainer clip.

13. The micro-deployable device of Claim 12, wherein the outer frame comprises a brake, and wherein an interaction between the brake and the retainer clip prevents an over rotation of the outer frame.

.

14. The micro-deployable device of Claim 1 , further comprising a constrainer for constraining a rotational movement of the inner structural portion.

15. The micro-deployable device of Claim 14, wherein the constrainer comprises: a constrainer clip for applying a lateral force on a pin hinge coupling the proximal portion of a first MAE and the proximal portion of the second MAE; and a vertical portion for fixedly coupling the constrainer clip to a substrate.

16. The micro-deployable device of Claim 15, wherein the vertical portion comprises a fused cantilever structure.

17. The micro-deployable device of Claim 14, wherein the constrainer comprises at least one pin for restraining a rotational motion of at least one of the first MAEs.

18. A microcamera, comprising: a microautofocus system configured to focus light; and a microaperture configured to control a light passage, wherein the microautofocus system comprises: a flexible lens; and a first microelectromechanical systems (MEMS) device for actuating a shape of the lens, the first MEMS device comprising: a generally planar outer frame defining an inner structural portion; a plurality of first multi-angular elements (MAEs) each having a proximal portion and a distal portion, wherein the proximal portions are operably coupled to the outer frame, and wherein the plurality of first MAEs extend from the outer frame into the inner structural portion; and a plurality of second MAEs each having a proximal portion and a distal portion, wherein the distal portions of the first and second MAEs are operably coupled to define an aperture, and wherein the lens fits substantially in the aperture.

19. The microcamera of claim 18, wherein the first and second MAEs comprise elongated segments, and wherein the first MAEs are generally "lambda" shaped.

20. The microcamera of claim 18, wherein the flexible lens is composed of polydimethylsiloxane (PDMS).

21. The microcamera of claim 18, wherein the microautofocus system comprises a barbell hinge to prevent lateral warping of the flexible lens, and wherein the barbell hinge comprises delaminated first and polysilicon layers, the first and second polysilicon layers forming a pin joint for holding the flexible lens.

22. The microcamera of claim 18, wherein the microaperture comprises a second MEMS device, the second MEMS device comprising: a generally planar outer frame defining an inner structural portion; a plurality of third MAEs each having a proximal portion and a distal portion, wherein the proximal portions are operably connected to the outer frame, and wherein the plurality of third MAEs extend from the outer frame into the inner structural portion; and a plurality of fourth MAEs each having a proximal portion and a distal portion, wherein the distal portions of the third and fourth MAEs are operably coupled to define an aperture therebetween, wherein the third and fourth MAEs comprise solid plates for blocking light.

23. The microcamera of claim 18, wherein each of the microautofocus system and the microaperture is disposed on a respective semiconductor die, and wherein the semiconductor dies are wafer bonded.

24. The microcamera of claim 18, further comprising a thermal actuator for actuating the first MEMS device.

25. A method of fabricating and operating a microelectromechanical system (MEMS), comprising: providing a generally planar outer frame defining an inner structural portion; providing a plurality of first multi-angular elements (MAEs) each having a proximal portion and a distal portion, wherein the proximal portions are operably coupled to the outer frame, and wherein the plurality of first MAEs extend from the outer frame into the inner structural portion; providing a plurality of second MAEs each having a proximal portion and a distal portion, wherein the distal portions of the first and second MAEs are operably connected to define an aperture therebetween; and applying a tangential force to the outer frame while constraining a rotational motion of the inner structural portion thereby causing a relative sliding motion between the outer frame and the first MAEs thereby changing a size of the aperture.

26. The method of claim 25, further comprising: providing a plurality of semiconductor dies each having a micro-deployable device thereon; and wafer-bonding the plurality of semiconductor dies to form a system comprising a plurality of micro-deployable devices.

27. The method of claim 26, wherein the plurality of micro-deployable devices include a microaperature configured to control a light passage and a microautofocus system configured to focus light.

28. The method of claim 27, wherein providing the plurality of semiconductor dies comprises fabricating the microautofocus system on one of the dies, and wherein fabricating the microautofocus system comprises fabricating a barbell hinge for coupling a flexible lens to a plurality of MAEs.

29. The method of claim 28, wherein fabricating the barbell hinge comprises: delaminating a first polysilicon layer and a second polysilicon layer to form an outer diameter of the barbell hinge; cutting the first polysilicon layer to form a cavity; back-filling the second polysilicon into the cavity thereby forming a pin joint for locking the flexible lens.