MEMS device with bi-directional element
The present invention provides a bi-directional microelectromechanical element, a microelectromechanical switch including the bi-directional element, and a method to reduce mechanical creep in the bi-directional element. In one embodiment, the bi-directional microelectromechanical element includes a cold beam having a free end and a first end connected to a cold beam anchor. The cold beam anchor is attached to a substrate. A first beam pair is coupled to the cold beam by a free end tether and is configured to elongate when heated thereby to a greater temperature than a temperature of the cold beam. A second beam pair is located on an opposing side of the cold beam from the first beam pair and is coupled to the first beam pair and the cold beam by the free end tether. The second beam pair is configured to elongate when heated thereby to the greater temperature.
1. A microelectromechanical switch comprising:
a unidirectional microelectromechanical element including:
a first cold beam having a first free end and a first end connected to a first cold beam anchor, said first cold beam anchor attached to a substrate;
a first beam pair coupled to said first cold beam by a first free end tether and configured to elongate when heated to a temperature greater than a temperature of said first cold beam; and
a first tip integral with said free end of said first cold beam, wherein said first tip includes at least two spaced apart prongs; and
a bi-directional microelectromechanical element switchably coupled to said unidirectional microelectromechanical element including:
a second cold beam having a second free end and a first end connected to a second cold beam anchor, said second cold beam anchor attached to said substrate;
a second beam pair coupled to said second cold beam by a second free end tether and configured to elongate when heated to a temperature greater than a temperature of said second cold beam;
a third beam pair located on an opposing side of said second cold beam from said second beam pair and coupled to said second beam pair and said second cold beam by said second free end tether, said third beam pair configured to elongate when heated to a temperature greater than said temperature of said second cold beam; and
a second tip integral with said free end of said second cold beam including another prong, wherein one of said at least two spaced apart prongs of said first tip and said another prong of said second tip form a conductive path when said one of said at least two spaced apart prongs of said first tip and said another prong of said second tip are in electrical contact with each other to carry an electrical signal through the microelectromechanical switch.
2. The microelectromechanical switch as recited in claim 1 , wherein said second beam pair includes a first beam member having a first end connected to a first anchor and a second beam member having a first end connected to a second anchor, said first and second anchors attached to said substrate, wherein said first beam member has a second end connected to a second end of said second beam member.
3. The microelectromechanical switch as recited in claim 2 , wherein said first beam member further comprises a strain relief at said first end.
4. The microelectromechanical switch as recited in claim 1 , further comprising at least one beam pair tether transversally disposed over said first and second beam members.
5. The microelectromechanical switch as recited in claim 1 , further comprising at least one additional tether transversally disposed over said second and third beam pairs and said second cold beam, said at least one additional tether located between said second free end and said second cold beam anchor.