Etching a substrate: processes – Etching of semiconductor material to produce an article...
Reexamination Certificate
2002-02-13
2004-07-06
Alanko, Anita (Department: 1765)
Etching a substrate: processes
Etching of semiconductor material to produce an article...
C216S024000, C216S033000, C216S036000, C216S067000
Reexamination Certificate
active
06758983
ABSTRACT:
BRIEF DESCRIPTION OF THE INVENTION
This invention relates generally to Micro-Electro Mechanical Systems (MEMS). More particularly, this invention relates to a staggered torsional electrostatic combdrive that may be used to control a micromirror or paddle structure for mounted electronic components.
BACKGROUND OF THE INVENTION
Micro-Electro Mechanical Systems (MEMS), which are sometimes called micromechanical devices or micromachines, are three-dimensional objects having one or more dimensions ranging from microns to millimeters in size. The devices are generally fabricated utilizing semiconductor processing techniques, such as lithographic technologies.
There are on going efforts to develop MEMS with scanning mirrors, referred to as scanning micromirrors. It is a goal to use scanning micromirrors in the place of scanning macro-scale mirrors, which are used in a variety of applications. For example, macro-scale mirrors are used in: barcode readers, laser printers, confocal microscopes, and fiber-optic network components. There are significant limitations to the performance of macro-scale scanners; in particular, their scanning speed, power consumption, cost, and size often preclude their use in portable systems. Scanning micromirrors could overcome these problems. In addition, higher-frequency optical scanning could enable new applications that are not practical with conventional scanning mirrors, such as raster-scanning projection video displays, and would significantly improve the performance of scanning mirrors in existing applications, such as laser printers. MEMS optical scanners promise to enable these new applications, and dramatically reduce the cost of optical systems.
Unfortunately, previously demonstrated MEMS mirrors have not been able to simultaneously meet the requirements of high scan speed and high resolution. A plethora of micromirror designs have been presented, but not one has been able to satisfy the potential of MEMS: a high-speed, high-performance scanning mirror.
In view of the foregoing, it would be highly desirable to provide a high-speed, high-performance scanning micromirror system. Such a system should include improved system components, such as an improved combdrive for implementing scanning operations.
SUMMARY OF THE INVENTION
A staggered torsional electrostatic combdrive includes a stationary combteeth assembly and a moving combteeth assembly with a mirror and a torsional hinge. The moving combteeth assembly is positioned entirely above the stationary combteeth assembly by a predetermined vertical displacement during a combdrive resting state. A method of fabricating the staggered torsional electrostatic combdrive includes the step of deep trench etching a stationary combteeth assembly in a first wafer. A second wafer is bonded to the first wafer to form a sandwich including the first wafer, an oxide layer, and the second wafer. A moving combteeth assembly is formed in the second wafer. The moving combteeth assembly includes a mirror and a torsional hinge. The moving combteeth assembly is separated from the first wafer by the oxide layer. The oxide layer is subsequently removed to release the staggered torsional electrostatic combdrive.
The micromirror of the invention fulfills the potential of micromachined mirrors over conventional scanning mirrors—high scan speed, small size, and low cost with diffraction-limited optical performance. The scan speed of the micromirror is difficult to achieve with large-scale optical scanners, and exceeds the performance of previously demonstrated micromachined scanning mirrors.
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Conant Robert A.
Lau Kam-Yin
Muller Richard S.
Nee Jocelyn T.
Alanko Anita
Fish & Richardson P.C.
The Regents of the University of California
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