Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Physical deformation
Reexamination Certificate
1999-08-04
2001-07-31
Lee, Eddie (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Physical deformation
C257S417000
Reexamination Certificate
active
06268635
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to electromechanical systems, and more particularly to microelectromechanical systems and fabrication methods therefor.
BACKGROUND OF THE INVENTION
Microelectromechanical systems (MEMS) have been developed as alternatives to conventional electromechanical devices, such as relays, actuators, valves and sensors. MEMS devices are potentially low-cost devices, due to the use of microelectronic fabrication techniques. New functionality also may be provided, because MEMS devices can be much smaller than conventional electromechanical devices.
A major breakthrough in MEMS devices is described in U.S. Pat. 5,909,078 entitled
Thermal Arched Beam Microelectromechanical Actuators
to the present inventor et al., the disclosure of which is hereby incorporated herein by reference. Disclosed is a family of thermal arched beam microelectromechanical actuators that include an arched beam which extends between spaced apart supports on a microelectronic substrate. The arched beam expands upon application of heat thereto. Means are provided for applying beat to the arched beam to cause farther arching of the beam as a result of thermal expansion thereof, to thereby cause displacement of the arched beam.
Unexpectedly, when used as a microelectromechanical actuator, thermal expansion of the arched beam can create relatively large displacement and relatively large forces while consuming reasonable power. A coupler can be used to mechanically couple multiple arched beams. At least one compensating arched beam also can be included which is arched in a second direction opposite to the multiple arched beams and also is mechanically coupled to the coupler. The compensating arched beams can compensate for ambient temperature or other effects to allow for self-compensating actuators and sensors. Thermal arched beams can be used to provide actuators, relays, sensors, microvalves and other MEMS devices. Other thermal arched beam microelectromechanical devices and associated fabrication methods are described in U.S. Pat. No. 5,994,816 to Dhuler et al. entitled
Thermal Arched Beam Microelectromechanical Devices and Associated Fabrication Methods
, the disclosure of which is hereby incorporated herein by reference.
As MEMS devices become more sophisticated, there continues to be a need for MEMS structures that can be used in more sophisticated MEMS devices. Fabrication of these structures preferably should be accomplished using conventional MEMS fabrication process steps.
SUMMARY OF THE INVENTION
The present invention provides microelectromechanical structures that include first and second movable metallic members that extend along and are spaced apart from a microelectronic substrate and are spaced apart from one another, and a movable dielectric link or tether that mechanically links the first and second movable metallic members while electrically isolating the first and second movable metallic members from one another. The movable dielectric link preferably comprises silicon nitride. These microelectromechanical structures can be particularly useful for mechanically coupling structures that are electrically conducting, where it is desired that these structures be coupled in a manner that can reduce and preferably prevent electrical contact or crosstalk.
The movable dielectric link is attached to the first and second movable metallic members beneath the first and second movable metallic members. Alternately, the movable dielectric link can be attached to the first and second movable metallic members above the first and second movable metallic members, opposite the microelectronic substrate. When the movable dielectric link is attached to the first and second movable members beneath the first and second movable metallic members, a trench can be provided in the microelectronic substrate adjacent the movable dielectric link, to reduce and preferably prevent stiction between the movable dielectric link and the microelectronic substrate thereunder.
More than two movable metallic members can be mechanically linked to a single movable dielectric link. Moreover, a movable third conductive member can extend between the first and second movable metallic members and across the movable dielectric link. The third conductive member can be spaced apart from the first and second movable metallic members and the movable dielectric link, so that independent movement can be provided.
The movable dielectric link can be attached to the first and second movable metallic members due to the adhesion therebetween. Moreover, first and second anchors can be added to anchor the movable dielectric link to the first movable metallic member and to the second movable metallic member, respectively. The anchors can comprise an aperture in the movable metallic member, and a first mating protrusion that extends from the movable metallic member into the aperture. Alternatively, the aperture can be provided in the movable metallic member and the protrusion can be provided in the movable dielectric link. The anchor also can comprise a notch in the movable metallic member or the movable dielectric link. Other configurations of anchors can be used.
The dielectric link can link the first and second movable metallic members at respective first and second ends of the movable metallic member that are adjacent one another. Alternatively, one or more of the movable metallic members can be attached to the dielectric link at intermediate portions thereof. The movable metallic members preferably comprise electroplated members and more preferably electroplated nickel members. A plating base layer can be provided between the movable metallic members and the movable dielectric link.
Movable dielectric links according to the invention can be used with many microelectromechanical devices including microelectromechanical actuators and sensors that move at least one of the first and second movable metallic members. Movable dielectric links according to the present invention can be particularly advantageous when used with thermal arched beam microelectromechanical systems as described in the above-cited patents.
Microelectromechanical structures according to the present invention can be fabricated by forming a sacrificial layer on a microelectronic substrate and forming a dielectric link on the sacrificial layer. First and second spaced apart metallic members are electroplated on the sacrificial layer, such that the first and second spaced apart metallic members both are attached to the dielectric link. The sacrificial layer then is at least partly removed, for example by etching, to thereby release the dielectric layer and at least a portion of the first and second metallic members from the microelectronic substrate.
The dielectric link can be formed prior to electroplating the first and second spaced apart metallic members, such that the dielectric link is attached to the first and second metallic members beneath the first and second metallic members. In other embodiments, the electroplating step can precede the step of forming a dielectric link, such that the dielectric link is attached to the first and second metallic members above the first and second metallic members, opposite the microelectronic substrate.
When the electroplating is performed prior to forming the dielectric link, the dielectric link can be formed between the first and second spaced apart metallic members and extending onto the first and second spaced apart metallic members opposite the sacrificial layer. Prior to electroplating, a plating base preferably can be formed on the sacrificial layer. The first and second spaced apart metallic members are then plated on the plating base.
Alternatively, when the dielectric link is formed prior to electroplating, the first and second spaced apart metallic members can be electroplated on the sacrificial layer and extending onto the dielectric link, such that the first and second spaced apart metallic members both are attached to the dielectric link. A plating base preferably can be formed on the sacrific
JDS Uniphase Inc.
Lee Eddie
Myers Bigel & Sibley & Sajovec
Wilson Allan R.
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