Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2001-08-14
2003-05-13
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S208100, C359S291000
Reexamination Certificate
active
06563106
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to the field of micro-electro-mechanical-system (MEMS) devices. More particularly, the present invention relates to a MEMS mirror devices and methods for fabricating the same.
BACKGROUND OF THE INVENTION
A MEMS device is a micro-sized mechanical structure having electrical circuitry fabricated using conventional integrated circuit (IC) fabrication methods. A well-known MEMS device is a microscopic gimbaled mirror mounted on a substrate. A gimbaled mirror is a device that may pivot on a hinge about an axis. By pivoting about an axis, a gimbaled mirror can redirect light beams to varying positions. Typically, MEMS gimbaled mirrors are arranged in an array on single silicon wafer substrate.
A prior process for fabricating MEMS gimbaled mirrors on a substrate is a surface micro-machining process. A surface micro-machining process-utilizes thin layers to mount the MEMS mirrors off the substrate. A disadvantage with using the micro-machining process is that the gimbaled mirrors are mounted by only a few &mgr;m (“micro-meters”) off the substrate. At such a small height, the gimbaled mirror is inhibited from pivoting at large angles with respect to an axis thereby limiting the number of positions for redirecting light.
One kind of micro-machining process to make gimbaled mirrors is the stress curling method. The stress curling method applies a stress gradient on a thin cantilever layer. The stress gradient causes the end of the cantilever layer to curl that is used to lift a gimbaled mirror off the substrate. A disadvantage with using the stress curling method is that it is process dependent and it is difficult to control the stress gradient. Another disadvantage with the stress curling method is that cantilever layer requires a large area on the substrate that reduces the number of gimbaled mirrors that can be arranged on the substrate.
Another kind of micro-machining process to make gimbaled mirrors utilizes hinges and scratch motors. A scratch motor uses electrostatic force to move a mass that raises a gimbaled mirror off the substrate by rotating the mass around a hinge. A disadvantage with using scratch motors and hinges is that it requires a large area of space on the substrate to make the scratch motors and hinges thereby limiting the number of gimbaled mirrors to be arranged on the substrate. Furthermore, scratch motors are difficult to make at a microscopic level.
SUMMARY OF THE INVENTION
A micro-electro-mechanical-system (MEMS) mirror device is disclosed. The MEMS mirror device includes a substrate. Electrodes are formed supported by the substrate. A support structure is formed adjacent to the electrodes. A hinge pattern and a mirror pattern having a center mirror component are formed such that support structure supports the hinge pattern and mirror pattern. The support structure also supports the hinge pattern and mirror pattern such that a bottom surface of the center mirror component in a stationary non-rotating position is capable of exceeding a height of 50 &mgr;m above the electrodes.
A MEMS mirror device fabrication method is disclosed. A substrate is exposed selectively to form exposed regions and unexposed regions in the substrate. Electrodes are formed supported by the substrate. A mirror pattern having a center mirror component and a hinge pattern are formed supported by the substrate. Portions of the substrate are removed in the exposed regions to form a support structure from the unexposed regions such that the support structure supports the mirror pattern and hinge pattern.
Another method for fabricating a MEMS mirror device is disclosed. A release layer is formed on a first substrate. A mirror pattern having a center mirror component and a hinge pattern are formed supported by the release layer. Electrodes are formed supported by a second substrate. A support structure is formed. The first substrate is attached with the second substrate using the support structure. The first substrate and the release layer are removed such that the support structure supports the mirror pattern and hinge pattern.
Another method for fabricating a MEMS mirror device is disclosed. A release layer is formed on a first substrate. A mirror pattern having a center mirror component and a hinge pattern are formed supported by the release layer. Electrodes are formed supported by a second substrate. A support structure is formed using a third substrate. The first substrate is attached with the second substrate using the support structure. The first substrate and release layer are removed.
Another method for fabricating a MEM gimbaled mirror device is disclosed. Electrodes are formed supported by a first substrate. Portions of a second substrate on a bottom side are removed selectively. Portions of the second substrate on a topside are removed selectively to form a mirror, frame pattern, and hinge pattern. The first substrate is attached with the second substrate.
Other features and advantages of the present invention will be apparent from the accompanying drawings, and from the detailed description, which follows below.
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Bowers John Edward
Corbalis Charles
Helkey Roger Jonathan
Lee Seung Bok
MacDonald Noel
Calient Networks, Inc.
Le Que T.
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