Machine element or mechanism – Control lever and linkage systems – Multiple controlling elements for single controlled element
Reexamination Certificate
2002-05-22
2004-01-13
Bucci, David A. (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Multiple controlling elements for single controlled element
C901S029000
Reexamination Certificate
active
06675671
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to devices constructed using thin film technology, and more particularly to micro-stages having rigid legs connected to actuators through joints of varying degrees of freedom to provide varying ranges of motion.
Moveable stages are well-known in the field of robotics and manufacturing, and are frequently used to move a first object to a predetermined point relative to a fixed second object. For example, in manufacturing, an XY table may move a substrate relative to a nozzle in order that material may be deposited on the substrate in a predetermined pattern. And an XYZ table may be used to position a work piece relative to a tool in order that the tool may operate on a predetermined location on the work piece. D. Hembree, U.S. Pat. No. 6,211,960, describes a conventional multi-axis positioning machine for use in semiconductor manufacture.
It would be desirable to construct such devices using thin film technology such as microelectromechanical systems (MEMS) technology. Many materials are being studied for MEMS devices; for example, J. P. Sullivan et al,
Diamond and Amorphous Carbon MEMS, MRS Bulletin
, April 2001, pp 309-311, reports on diamond an amorphous carbon films used for MEM devices. However, the most common MEMS material at the present time is polysilicon.
Techniques for constructing MEMS devices are well known in the art. The following description by M. S. Rodgers et al.,
Advanced micromechanisms in a multi
-
level polysilicon technology
, SPIE Vol. 3224, September 1997, pp. 120-130 provides an overview of a four level process where layers of structural polysilicon (n-type) separated by sacrificial silicon oxide layers built-up on a silicon-nitride coated, <100>, n-type 6″ silicon wafer substrate. Each of the layers are patterned and etched as is commonly done in integrated circuit production, which provides the means to create complex, interconnected, micro-mechanism complete with motors and drive linkages containing spinning and translating elements with minimum features sizes of 1 &mgr;m.
The complexity of devices that can be created using surface micromachining is significantly influenced by the number of mechanical layers fabricated in the process. The four level technology available at Sandia National Laboratories, Albuquerque, NM and known as Sandia Ultra-planar Multi-level MEMS Technology (SUMMiT™) utilizes a chemical mechanical polishing technique described by R. Nasby et al., U.S. Pat. No. 5,804,084 to eliminate undesirable process artifacts generated by previous multi-level processes. Previously, the designer was constrained to defining upper level structures that were essentially isolated islands of polysilicon. Each island had to be several microns from its neighbor, which made it impractical to define close-packed electrostatic elements and intermeshing gears with reasonable geometry.
The four level process is based on a four-level polysilicon stack. Three mechanical levels of polysilicon, referred to as poly1, poly2, and poly3, are fabricated on top of a thin poly0 electrical interconnect layer. The polysilicon layers are separated by sacrificial layers of oxide that are etched away after the entire stack is fabricated. The layer thicknesses vary to allow for fabrication of different components. Poly0 is 0.3 &mgr;m, poly1 is 0.1 &mgr;m, poly2 is 1.5 &mgr;m and poly3 is 2.5 &mgr;m. The sacrificial layer between poly3 and poly 2, and layer between poly 1 and poly 0, is 2 &mgr;m, but the layer between poly2 and poly1 is 0.5 &mgr;m. In many areas, this 0.5 &mgr;m layer is removed before Poly2 is formed, so that Poly1 and Poly2 form a single 2.5 &mgr;m layer.
Subsequently, a five layer process (SUMMiT-V™) was developed at Sandia National Laboratories, as utilized in M. Rodgers et al, U.S. Pat. No. 6,082,208, the disclosure of which patent is incorporated herein by reference. For the five layer process, each of poly3 and a new poly4 are 2.25 &mgr;m, separated by a 2 &mgr;m sacrificial layer. The five layer process allows devices of additional complexity to be constructed.
Other mechanisms that pop-out of their fabrication plane are known, but they generally are controllable in one degree of freedom. Folding mirrors are one such example where two hinged planar pieces with only one end hinged to ground can be actuated to rotate out of the plane at the connecting hinge.
L. Lin et al.,
Surface
-
Micromachined Micro
-
XYZ Stages for Free
-
Space Microoptical Bench
, IEEE Photonics Technology Letters, Vol. 9, No. 3, March 1997, pp. 345-347, discloses a surface-micromachined microoptical bench that utilizes two linearly moving tilted mirrors and a linearly moving lens to accurately position an optical spot. This reference does not disclose a mechanical platform or point that can be moved to a predetermined XYZ coordinate relative to a fixed point.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a multi-legged parallel kinematic mechanism (PKM) which may be constructed in a plane using thin film technology.
It is another object of the invention to provide a stage moveable in at least three degrees of freedom and support structure which may be stowed in a plane and which rises above the plane when activated.
It is also an object of this invention to provide a fully articulated PKM constructed using thin film technology such as MEMs.
To achieve the foregoing and other objects, and in accordance with the purpose of the present invention, as embodied and broadly described herein, is a multiple degree of freedom platform formed from a plurality of thin films on a substrate, including a moveable planar platform having three connection points defining a platform triangle, the platform being capable of being moved away from the plane of the substrate. There are three fixed-length linkages capable of being moved away from the plane of the substrate. Each linkage has one end pivotally connected to one of the platform connection points through a platform joint, and each connection point is connected to only one linkage. There are also at least three linear drives, each drive including a traveling member capable of controlled movement along a linear path adjacent the substrate. Each traveling member is pivotally connected to the other end of one of the linkages through a base joint, and each linkage is connected to only one traveling member. When each of the traveling members are in a predetermined position at one end of the linear path, the linkages and platform are coplanar to and adjacent to the substrate. When any of said traveling members is in any other position along the linear path, at least the linkage connected to that member and the platform is neither coplanar to nor adjacent to the substrate.
Additional objects, advantages, and novel features of the invention will become apparent to those skilled in the art upon examination of the following description or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
REFERENCES:
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patent: 5378282 (1995-01-01), Pollard
patent: 5631514 (1997-05-01), Garcia et al.
patent: 5804084 (1998-09-01), Nasby et al.
patent: 5959376 (1999-09-01), Allen
patent: 6082208 (2000-07-01), Rodgers et al.
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patent: 6175170 (2001-01-01), Kota et al.
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NASA “Mesoscopic Steerable Mirror”; Apr. 1, 2002, pp i, 1-2.
James H. Smith et al “Microelectro-Optical Devices in a 5-Level . . .”, Sep. 1988, pp. 42-47.
“Les robots plans/Planar robots”, Mar. 19, 2002, web page at http://www-sop.inria.fr/coprin/equipe/merlet/Archi
ode1.htm.
“Les robots a mouvements Spatiaux/Spatial robots”, Mar. 19, 2002, web page at http://www-sop.inria.fr/coprin/equipe/merlet/Archi
ode1.htm.
M. S. Rodgers, et al, “Advanced Micromechanisms in a Multi-level Polysilicon
Allen James J.
Benavides Gilbert L.
Bieg Lothar F.
Jokiel, Jr. Bernhard
Bucci David A.
Libman George H.
McAnulty Timothy
Sandia Corporation
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