MEMS switch with beam contact portion continuously extending between input and output terminal electrodes
Embodiments of the disclosure are directed to microelectromechanical system (MEMS) switches with a beam contact portion continuously extending between input and output terminal electrodes. In exemplary aspects disclosed herein, the movable beam includes a body and a contact with more conductivity and stiffness than the body. The contact continuously extends between and electrically couples the contact of the movable beam with the input and output terminal electrodes. Differing materials between the body and the contact allow for inclusion of the mechanical properties of the body (e.g., to reduce mechanical fatigue, creep, etc.) while utilizing the electrical properties of the contact (e.g., to reduce on-state electrical resistance). Accordingly, the MEMS switch provides low resistance loss during an on-state while maintaining high levels of isolation during an off-state.
1. A microelectromechanical system (MEMS) switch, comprising:
an input terminal electrode;
an output terminal electrode;
a pull-down electrode positioned between the input terminal electrode and the output terminal electrode;
a movable beam positioned proximate the input terminal electrode and the output terminal electrode, the movable beam comprising:
an upper conductive layer;
a lower conductive layer having a first conductivity;
a contact incorporated into the lower conductive layer, wherein:
the contact has a second conductivity that is more than the first conductivity; and
the contact is configured, with respect to the input terminal electrode and the output terminal electrode, to limit on-state resistance between the input terminal electrode and the output terminal electrode; and
an array of vias that join the upper conductive layer to the lower conductive layer; and
the movable beam is configured to move between:
an on-state that electrically couples the contact of the movable beam with the input terminal electrode and the output terminal electrode; and
an off-state that electrically isolates the contact of the movable beam from the input terminal electrode and the output terminal electrode.
2. The MEMS switch of claim 1 , wherein the input terminal electrode comprises an input radio frequency (RF) electrode, and the output terminal electrode comprises an output RF electrode.
3. The MEMS switch of claim 1 , wherein the movable beam is coupled to a radio frequency (RF) node.
4. The MEMS switch of claim 1 , wherein:
the upper conductive layer comprises at least one of TiAl or TiAlN; and
the lower conductive layer comprises at least one of TiAl or TiAlN.
5. The MEMS switch of claim 1 , wherein the contact comprises at least one of ruthenium, ruthenium oxide, platinum, or gold.
6. The MEMS switch of claim 1 , wherein the contact has a thickness between about 30 to 80 nm.
7. The MEMS switch of claim 1 , wherein a length of the contact is between 1% to 50% longer than a length between the input terminal electrode and the output terminal electrode.
8. The MEMS switch of claim 1 , wherein end portions of the contact are wider than a middle portion of the contact.
9. The MEMS switch of claim 1 , wherein the contact defines an aperture.
10. The MEMS switch of claim 1 , wherein:
the input terminal electrode comprises a plurality of input terminal electrodes;
the output terminal electrode comprises a plurality of output terminal electrodes; and
wherein the contact continuously extends over each of the plurality of input terminal electrodes and the plurality of output terminal electrodes.
11. The MEMS switch of claim 1 , wherein the movable beam is mechanically biased toward the off-state.
12. The MEMS switch of claim 1 , further comprising a pull-up electrode configured to electrically bias the movable beam toward the off-state.
13. The MEMS switch of claim 1 :
further comprising a substrate;
wherein the input terminal electrode, the output terminal electrode, and the pull-down electrode are mounted on the substrate; and
wherein ends of the movable beam are mounted to the substrate such that the movable beam is suspended above the input terminal electrode, the output terminal electrode, and the pull-down electrode in the off-state.
14. The MEMS switch of claim 13 :
further comprising a cover mounted to the substrate and defining a cavity between the cover and the substrate; and
wherein the movable beam is positioned within the cavity.
15. A microelectromechanical system (MEMS) device, comprising:
a plurality of MEMS switches, each switch comprising:
an input terminal electrode;
an output terminal electrode;
a pull-down electrode positioned between the input terminal electrode and the output terminal electrode;
a movable beam positioned proximate the input terminal electrode and the output terminal electrode, the movable beam comprising:
an upper conductive layer;
a lower conductive layer having a first conductivity;
an array of vias that join the upper conductive layer to the lower conductive layer; and
a contact incorporated into the lower conductive layer, the contact having a second conductivity more than the first conductivity, the contact proximate to and extending between the input terminal electrode and the output terminal electrode to limit on-state resistance therebetween; and
the movable beam configured to move between:
an on-state that electrically couples the contact of the movable beam with the input terminal electrode and the output terminal electrode; and
an off-state that electrically isolates the contact of the movable beam from the input terminal electrode and the output terminal electrode.
16. The MEMS device of claim 15 , wherein for each MEMS switch, the upper conductive layer comprises at least one of TiAl or TiAlN, the lower conductive layer comprises at least one of TiAl or TiAlN, and the contact comprises at least one of ruthenium, ruthenium oxide, platinum, or gold.
17. The MEMS device of claim 15 , wherein for each MEMS switch, the contact has a thickness between about 30 to 80 nm.
18. The MEMS device of claim 15 , wherein for each MEMS switch, a length of the contact is between 1% to 50% longer than a length between the input terminal electrode and the output terminal electrode.
19. The MEMS device of claim 15 , wherein for each MEMS switch, end portions of the contact are wider than a middle portion of the contact.
20. The MEMS device of claim 15 , wherein for each MEMS switch, the contact defines an aperture.