Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2000-05-24
2003-07-22
Ciric, Ljiljana (Department: 3743)
Metal working
Method of mechanical manufacture
Electrical device making
C029S874000, C438S632000, C438S646000, C072S253100, C072S273500
Reexamination Certificate
active
06594894
ABSTRACT:
STATEMENT OF GOVERNMENTAL INTEREST
The invention herein may be manufactured or used by or for the Government for governmental purposes without the payment of any royalty thereon.
BACKGROUND OF THE INVENTION
The present invention relates to the field of microelectromechanical systems (MEMS) useful in electronic/photonic integrated circuitry.
MEMS systems have been under development with regard to micrometer scale mechanics analogous to large scale mechanical systems, and their fabrication typically utilizes planar processes used in integrated circuitry (IC) fabrication. Tiny mechanical parts have been made by patterning and etching in two-dimensional structures. A new micro-extrusion process is desired employing conventional VLSI planar processing techniques to mimic three-dimensional macroscopic extrusion processes used in industry. Prior experiments have shown that aluminum extrusions can be formed by forcing the metal through dies patterned in silicon dioxide. A desired goal is to eliminate mechanical parts that would be normally used to compress a billet of material to be extruded.
Past electromigration experiments have shown that simply applying a current to a conductor builds up a large force. Such forces generated by current flow cause aluminum wiring to move slowly, opening voids that generate wiring faults. As circuit geometries continue to shrink, wires become increasingly vulnerable to this detrimental effect. Such faults produced by electro-migration are discussed in U.S. Pat. No. 5,639,345 to Haung among others.
SUMMARY OF PREFERRED EMBODIMENTS OF THE INVENTION
In accordance with the invention, we advantageously employ this normally detrimental electromigration-induced force to act as a micron sized extrusion ram. Extrusion of a heated microsized billet segment, through a die comprising a shaped hole in a planar silicon dioxide microchip encapsulation, is produced by inducing stresses within the segment by creating electromigration therein, which stresses act like a ram to force the pliable heated segment material through the shaped hole, thereby to form a tiny extruded microbeam of any desired cross section. The resulting microbeam can have multiple uses such as solderless wire connections to the conductive billet segment, and flat panel field emission display tips having novel geometries, and inherently connected to the billet segments. Scanning tunneling microscope tips may also be readily fabricated. The ability to create an array of addressable tips might lead to large scale parallel probes that could enhance throughput. Thus, the normally detrimental electromigration forces are used to good advantage in the practice of the present invention.
REFERENCES:
patent: 4728627 (1988-03-01), Mase et al.
patent: 5639345 (1997-06-01), Huang et al.
Wood et al., “Evidence for an Incubation Time in Electromigration Phenomena,” 1991, 29th Annual Proceedings, Reliability Physics Symposium, pp. 70-76.
Bernstein Gary H.
Frankovic Richard
Auton William G.
Ciric Ljiljana
The United States of America as represented by the Secretary of
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