Optical: systems and elements – Mirror – Including specified control or retention of the shape of a...
Reexamination Certificate
2003-10-09
2004-10-26
Sikder, Mohammad (Department: 2872)
Optical: systems and elements
Mirror
Including specified control or retention of the shape of a...
C359S871000, C359S872000
Reexamination Certificate
active
06808275
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to microelectromechanical systems and, more particularly to an enhanced way of moving a microstructure away from a substrate to what may be characterized as a neutral position.
BACKGROUND OF THE INVENTION
There are a number of microfabrication technologies that have been utilized for making microstructures (e.g., micromechanical devices, microelectromechanical devices) by what may be characterized as micromachining, including LIGA (Lithography, Galvonoforming, Abforming), SLIGA (sacrificial LIGA), bulk micromachining, surface micromachining, micro electrodischarge machining (EDM), laser micromachining, 3-D stereolithography, and other techniques. Bulk micromachining has been utilized for making relatively simple micromechanical structures. Bulk micromachining generally entails cutting or machining a bulk substrate using an appropriate etchant (e.g., using liquid crystal-plane selective etchants; using deep reactive ion etching techniques). Another micromachining technique that allows for the formation of significantly more complex microstructures is surface micromachining. Surface micromachining generally entails depositing alternate layers of a structural material (e.g., polysilicon) and a sacrificial material (e.g., silicon dioxide) using an appropriate substrate (e.g., a silicon wafer) that functions as the foundation for the resulting microstructure(s). Various patterning operations (collectively including masking, etching, and mask removal operations) may be executed on one or more of these layers before the next layer is deposited so as to define the desired microstructure(s) from the structural material in one or more of the structural layers. After the microstructure(s) has been defined in this general manner, the various sacrificial layers are removed by exposing the microstructure(s) and the various sacrificial layers to one or more etchants. This is commonly called “releasing” the microstructure(s) from the substrate, typically to allow at least some degree of relative movement between at least some of the microstructures and the substrate.
Surface micromachining may be used to fabricate a mirror array that is defined by a plurality of mirror assemblies. Each mirror assembly may generally include a mirror and a mirror positioning assembly. Typically each mirror would be fabricated at a structural level in a surface micromachined system that is vertically spaced from a substrate that is used in the fabrication of the microelectromechanical system. It may be desirable to move each of these mirrors from their corresponding fabricated position (e.g., the position occupied by the mirrors in the microelectromechanical system prior to using an appropriate release etchant to remove the various layers of sacrificial material) to a position that is spaced further from the substrate prior to operating each of the various mirror assemblies. That is, it may be desirable to increase the spacing of each of the various mirrors from the substrate prior to tilting each of the various mirrors in a desired manner to provide the desired optical function.
SUMMARY OF THE INVENTION
The present invention is generally directed to microelectromechanical (MEM) systems, and more specifically, to an assembly for elevating and supporting a microstructure (e.g. a reflective microstructure/mirror) of a MEM system generally by engaging a positioning system of the MEM system with an elevator lifter. The assembly of the present invention desirably addresses a need to increase the vertical spacing between various microstructures and the substrate (generally after fabrication of the MEM system and prior to utilizing each of the various microstructures in operations of the MEM system) to allow for larger tilt angles and/or greater movement of the microstructures while preventing contact between the substrate and the microstructures. Another benefit of the present invention may be to avoid potential stiction-related problems between the mirror(s) and the substrate. Yet another benefit of increasing the spacing of the mirror(s) may be to reduce the potential for improper operation of the associated positioning assembly by pre-elevating it above a difficult-to-operate-in 0 degree horizontal position. While particularly desirable applications of the assembly may be in elevating and supporting reflective microstructures such as mirrors of an optical array/switch, the assembly of the present invention may be utilized in any appropriate microelectromechanical application for which elevation/lifting of a microstructure is desired/required.
A first aspect of the present invention relates to a microelectromechanical (MEM) system formed on a substrate. This MEM system generally includes a first microstructure (such as a mirror) disposed in vertically spaced relation to the substrate. In other words, this first microstructure is positioned above and preferably avoids direct contact with the substrate. In addition, the MEM system also includes an actuator assembly movably interconnected with the substrate. An elevator is generally pivotally interconnected with the substrate and further interconnected with the microstructure. This elevator is typically interconnected with the actuator assembly via a tether. In addition, this MEM system generally includes a first elevator lifter engageable with the elevator. By designing the first elevator lifter to engage the elevator (e.g., rather than the microstructure itself), this first aspect reduces the potential of subsequent operation of the microstructure being hindered due to inadvertent malpositioning of the microstructure between a portion of the elevator lifter and the substrate (i.e., reduces the potential for the microstructure to get caught under a portion of the elevator lifter).
Various refinements exist of the features noted in relation to the first aspect of the present invention. Further features may also be incorporated in this first aspect as well. These refinements and additional features may exist individually or in any combination. For example, this first aspect may utilize any appropriate number and/or type of actuator(s). In addition, any appropriate configuration of the tether and elevator may be utilized which provides for a pivotal interconnection of the elevator to the substrate as well as pivotal movement of the elevator with respect to the substrate. Herein, a “pivotal interconnection” or the like, refers to any type of interconnection that allows a microstructure to at least generally undergo a pivoting or pivotal-like motion when exposed to an appropriate force, including without limitation any interconnection that allows a microstructure or a portion thereof to move at least generally about a certain axis. Representative pivotal interconnections include the use of a flexing or elastic deformation of a microstructure or a portion thereof, as well as the use of relative motion between two or more microstructures that are typically in interfacing relation during at least a portion of the relative movement (e.g., a hinge connection; a ball and socket connection).
Some variations of this subject first aspect may also include a displacement multiplier having an input structure and an output structure. In such variations, the actuator assembly may be interconnected with the input structure and the tether may be interconnected with the output structure. Thus, movement/actuation of one or more actuator elements (such as a moveable electrostatic comb) of the actuator assembly may be magnified to provide a motive force to move/displace the tether (and generally the structure(s) attached thereto).
The first elevator lifter of the MEM system of the first aspect may be at least initially disposed in vertically spaced relation to the elevator. Thus, in some variations, the first elevator lifter may be positioned under at least a portion of the elevator. Stated another way, the first elevator lifter may be interposed between the substrate and at least a portion of the elevator. This first elevator li
Marsh & Fischmann & Breyfogle LLP
MEMX, Inc.
Sikder Mohammad
LandOfFree
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