Etching a substrate: processes – Etching of semiconductor material to produce an article...
Reexamination Certificate
2002-09-27
2004-09-21
Olsen, Allan (Department: 1763)
Etching a substrate: processes
Etching of semiconductor material to produce an article...
C216S036000, C216S051000, C438S055000, C438S690000
Reexamination Certificate
active
06793830
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a method for forming microstructures from a substrate and more specifically to a method for forming microstructures from a substrate using ion implantation.
BACKGROUND OF THE INVENTION
Semiconductor devices continue to shrink in size while growing exponentially in function. One class of small-scale semiconductor devices is microelectromechanical systems (MEMS), which are gaining ever-growing popularity in the microelectronics industry. MEMS are semiconductor device systems that include one or more microstructures, that is, structures of the size on the order of sub-&mgr;m to millimeters. MEMS devices include, without limitation, microhinges, microgears, micro-accelerometers, microbeams, microvalves, proof masses, switching cells, and microsensors. Such devices have found applications in optical systems, inkjet printers, telecommunications systems, medical devices, computer disk drives, and fluid measurement devices, to name just a few technologies.
MEMS systems typically are fabricated using surface micromachining technology that includes a number of intricate, and often costly, processing and fabrication steps that are conducted on a very small, microscopic scale. Surface micromachining technology often involves the formation of microstructures overlying materials with crystal structures different from those of the microstructures. Such processing may result in microstructures that are inherently stressed and that are undesirably bent or flexed in the MEMS devices. In addition, typical surface micromachining technology often requires the use of lateral etching for long processing times, which may result in slower throughput and higher production costs. Such etching also requires the need for selective etchants and often requires exposure to dangerous chemicals, such as hydrofluoric acid. Further, surface micromachining technology may result in microstructures formed of materials susceptible to stiction, a phenomenon induced by trapped liquids that causes a microstructure to attach to a substrate during final rinsing and drying steps.
Accordingly, a need exists for a method for forming microstructures from a substrate. In addition, a need exists for forming microstructures from a substrate using ion implantation.
SUMMARY OF THE INVENTION
This summary of the invention section is intended to introduce the reader to aspects of the invention and may not be a complete description of the invention. Particular aspects of the invention are pointed out in other sections herein below, and the invention is set forth in the appended claims which alone demarcate its scope.
In accordance with an exemplary embodiment of the present invention, a method for forming a microstructure from a substrate is provided. The method includes providing a monocrystalline substrate having a (100) orientation and subjecting a first portion of the substrate to ion bombardment to effect ion implantation to a desired penetration depth. A second portion of the substrate is etched to a depth at least as great as the desired penetration depth. The substrate is thermally treated to form a microstructure at a surface of the substrate and to effect at least partial separation between the microstructure and the substrate.
In another exemplary embodiment of the present invention, a method for micromachining a monocrystalline structure from the surface of a substrate is provided. The method includes providing a monocrystalline substrate having a (100) orientation and forming a first patterned hard mask on the substrate to expose a first portion of the substrate. The first portion of the substrate is subjected to ion bombardment to effect ion implantation to a desired penetration depth and the first patterned hard mask is removed. A second patterned hard mask is formed on the substrate to expose a second portion of the substrate. The second portion of the substrate is etched to a depth at least as great as the desired penetration depth. The substrate is thermally treated to form a microstructure at a surface of the substrate and to effect at least partial separation between the microstructure and the substrate.
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Excerpts from a book entitled “Fundamentals Of Microfabrication”, Marc Madou, 1997, p231-239, 243-244, 249-250.
“A ‘Smarter-Cut’ Approach to Low Temperature Silicon Layer Transfer,”Appl. Phys. Lett.vol. 72, No. 1, p49, Tong et al (Jan. 1998).
“A Lower Bound On Implant Density To Induce Wafer Splitting In Forming Compliant Substrate Structures,”Appl. Phys. Lett., vol. 70, No. 26, p. 3519, L. B. Fruend (Jun. 1997).
“The History, Physics, and Applications of the Smart-Cut Process,” MRS Bulletin, M. Bruel, p. 35 (Dec. 1998).
Danzl Ralph B.
Mattes Michael F.
Medtronic Inc.
Olsen Allan
Soldner Michael C.
Wolde-Michael Girma
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