Semiconductor device manufacturing: process – Making device or circuit responsive to nonelectrical signal – Responsive to electromagnetic radiation
Reexamination Certificate
1998-06-30
2001-01-09
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Making device or circuit responsive to nonelectrical signal
Responsive to electromagnetic radiation
C438S003000, C438S098000, C438S054000, C438S055000, C438S064000
Reexamination Certificate
active
06171886
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to fabrication of integrated hybrid silicon-based micro electromechanical devices. This invention specifically utilizes the conventional silicon planar technology to build integrated three-dimensional arrays of hybrid silicon-based micro-actuators.
BACKGROUND OF THE INVENTION
Micro-Electromechanical Systems (MEMS) is a rapidly growing field that is impacting many applications today. Three dimensional micro-engineered devices and systems involving silicon planar technology can be mass produced with features from one to a few hundred microns having tolerances in micron or sub-micron level. Most of the current micro-engineering technologies are evolved from the adaptation of thin films, photolithographic and etching technologies generally applied to silicon wafers on which silicon monoxide, silicon dioxide, silicon nitride and the like thin films are deposited and etched thereafter yielding planar configuration.
Although the planar silicon technology is capable of building a three dimensional array, the process steps involved in building those structures are many and very often exceed 20 to 30 steps thus making the process less attractive for many applications. Furthermore, there are many complicated structures that are not possible to be incorporated in the silicon planar technology because of certain limitations of the thin film technology.
Moreover, experience indicates that the current planar technologies using silicon substrates are inadequate for the fabrication of an integrated and self-contained three-dimensional arrays of micro-devices which can be used as solenoids, actuators, transformers and the like.
The limitation of the planar silicon technologies stems from the fact that the multi-step thin film technology along with etching processes which are usually used to build three dimensional structures on a silicon wafer can not produce complex structures. As for example, one of the greatest drawbacks of the silicon technology is that it is not possible to build a buried helical coil or a uniform vertical cylindrical column having higher length to radius aspect ratio, and similar complex configurations. Furthermore, building three-dimensional multi-layered structures using thin film technology involves multiple process steps, generally twenty or more, and therefore makes this process not economically feasible.
Therefore, there persists a need for a method to fabricate integrated hybrid silicon-based micro electromechanical devices, such as solenoids, actuators, and transformers, that requires substantially fewer steps thereby reducing production cycle time and increasing cost efficiency.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a method of making integrated hybrid silicon-based micro-actuator devices which is cost effective and requires minimal production steps.
It is another object of the invention to provide a method of making integrated hybrid micro-actuator devices that uses silicon wafer technology in conjunction with micro-molding technology consisting of ceramic, magnetic and polymeric materials.
It is a feature of the invention that a method of fabricating integrated hybrid silicon-based micro-actuator devices comprises the step of arranging an actuator assemblage having a displaceable ferromagnetic member into a cavity of a silicon wafer, the ferromagnetic member being reciprocatingly axially displaced in an actuating chamber in response to an applied current to conductive pads on the silicon wafer.
Accordingly, for accomplishing these and other objects, features and advantages of the invention, there is provided, in one aspect of the invention, a method of fabricating hybrid micro-actuator comprising the step of providing a generally planar silicon wafer having at least one generally cylindrical, etched cavity therein and at least two electrical contacts arranged about the at least one cavity. A micro-molded ferromagnetic member is provided having a first and second ends and a non-magnetic actuator arm extending from any one of the first and second ends. Also provided is an electrically insulated actuating chamber for receiving the ferromagnetic member and for enabling reciprocating displacements of the ferromagnetic member therein. The actuating chamber has a first electrical coil wound partially lengthwise about a first half portion of the chamber and a second electrical coil wound lengthwise about a second half portion of the chamber. Each of the first and second coils having a pair of free end portions for electrically connecting to the electrical contacts of the silicon wafers. The ferromagnetic member is arranged for axial reciprocating displacement inside the actuating chamber with the actuator arm protruding outwardly from the actuating chamber. This arrangement forms an electromagnetic actuator assemblage. A closure member having an opening is securely applied to the open end of the actuating chamber containing the ferromagnetic member such that the actuator arm protrudes through the opening in the closure member. The electromagnetic actuator assemblage is then arranged securely into one cavity in the silicon wafer such that the pair of free end portions of the first and second coils surrounding the actuating chamber provides an electrically conductive path to corresponding electrical contacts arranged about the at least one cavity in the silicon wafer. Thus, current flow through the electrically conductive path causes reciprocating axial displacements of the ferromagnetic member inside the actuating chamber in response to the current flow thereby defining a micro-actuator.
It is, therefore, an advantage of the present invention that the disclosed method of fabrication surmounts the several problems associated with the planar silicon technology in that the buried coil structure, monolithic ceramic columnar structure and other complex three dimensional features can be integrated as a hybrid device. Moreover, the present invention offers a unique solution to the conventional silicon technology by integrating the micro-molded three-dimensional monolithic components within a silicon wafer. Further advantages of this invention include its cost-effectiveness associated with the manufacturing of three-dimensional arrays of micro-devices. Also, the method of the invention overcomes many of the disadvantages of planar silicon-based thin film technology. The method of the invention further enables the manufacture of micro-devices utilizing automated silicon technology for integrated electronics. Finally, the method of the invention enables the utilization of the cost-effective criteria of silicon technology in conjunction with micro-molding technologies.
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“Advances in Actuators”, edited by A. P. Dorey, Lancaster University, UK and J. H. Moore, Lucas Bryce, Gloucester, UK, “Institute of Physics Publishing Bristorl and Philadelphia”, “Silicon Microactuators”, by Mehran Mehregany, pp. 135-178.*
Chatterjee Dilip K.
Furlani Edward P.
Ghosh Syamal K.
Bailey, Sr. Clyde E.
Eastman Kodak Company
Shaw Stephen H.
Smith Matthew
Yevsikov Victor
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