MEMS plate switch and method of manufacture
View Patent ↗Systems and methods for forming an electrostatic MEMS plate switch include forming a deformable plate on a first substrate, forming the electrical contacts on a second substrate, and coupling the two substrates using a hermetic seal. The deformable plate may have a flexible shunt bar which has one end coupled to the deformable plate, and the other end coupled to a contact on the second substrate. Upon activating the switch, the deformable plate urges the shunt bar against a second contact formed in the second substrate, thereby closing the switch. The hermetic seal may be a gold/indium alloy, formed by heating a layer of indium plated over a layer of gold. Electrical access to the electrostatic MEMS switch may be made by forming vias through the thickness of the second substrate.
1. A method for manufacturing a switch, comprising:
forming a first plate suspended adjacent to a first substrate by at least one spring beam;
coupling at least one conductive bar to the first plate at a location on the at least one conductive bar;
coupling the at least one conductive bar to a first contact, wherein the first contact can protrude into without touching the first plate, at another location on the at least one conductive bar; and
configuring the first plate to activate the switch by pressing the at least one conductive bar against a second contact.
2. The method of claim 1 , wherein the first contact is formed on a second substrate.
3. The method of claim 2 , further comprising:
forming an electrostatic second plate and the second contact on the second substrate;
aligning the first substrate to the second substrate; and
coupling the first substrate to the second substrate with a seal.
4. The method of claim 1 , wherein the conductive bar is electrically isolated from the first plate by a dielectric layer.
5. The method of claim 3 , further comprising:
forming at least one electrical via through a thickness of the second substrate, and electrically coupling the at least one electrical via to the second contact.
6. The method of claim 5 , wherein forming the at least one electrical via comprises:
forming at least one blind hole with a dead end wall on a front side of the second substrate;
forming a seed layer in the at least one blind hole;
depositing a conductive material onto the seed layer; and
removing material from a rear side of the second substrate to remove the dead-end wall of the at least one blind hole.
7. The method of claim 1 , wherein forming the at least one conductive bar further comprises:
forming a cavity in the first substrate;
filling the cavity with a sacrificial material;
depositing conductive material of the conductive bar over the cavity filled with the sacrificial material; and
removing at least a portion of the sacrificial material beneath the conductive material of the conductive bar.
8. The method of claim 7 , wherein forming the at least one conductive bar further comprises:
forming a first void in the first plate that extends laterally from the first contact toward the second contact.
9. The method of claim 8 , further comprising;
forming a second void in the first plate near the second contact, wherein the first void is separated from the second void by a narrow isthmus of material.
10. The method of claim 9 , wherein the isthmus is configured to have at least one of lateral and rotational movement as the switch is activated.
11. The method of claim 3 , wherein coupling the first substrate to the second substrate with a seal comprises:
depositing a first metal between the first substrate and the second substrate; and
depositing a second metal between the first substrate and the second substrate; and
coupling the first substrate to the second substrate by heating the first metal and the second metal to at least a melting point of at least one of the first metal and the second metal, to form a substantially hermetic alloy seal around the switch.
12. The method of claim 1 , wherein the first substrate comprises a silicon-on-insulator substrate, and the second substrate comprises at least one of a silicon wafer and a silicon-on-insulator substrate.
13. The method of claim 8 , wherein forming the first plate suspended over the first substrate comprises:
etching a plurality of holes into a device layer of the silicon-on-insulator substrate;
etching a dielectric layer beneath the device layer of the silicon-on-insulator substrate through the plurality of holes; and
etching an outline of the first plate in the device layer of the silicon-on-insulator substrate.
14. A switch, comprising:
a first plate suspended adjacent to a first substrate and coupled to the first substrate by at least one spring beam;
at least one conductive bar coupled to the first plate at a location on the at least one conductive bar, and coupled to a first contact at another location on the at least one conductive bar, wherein the first contact can protrude into without touching the first plate, wherein the first plate is configured to activate the switch by pressing the at least one conductive bar against a second contact.
15. The switch of claim 14 , wherein the second contact is coupled to a second substrate and wherein a hermetic seal couples the first substrate to the second substrate, to enclose the switch.
16. The switch of claim 14 , wherein the at least one spring beam comprises at least two spring beams, at least one of the two spring beams disposed on one side of the first plate, and at least one other of the at least two spring beams disposed on an opposite side of the first plate, wherein each spring beam has a segment extending from the first plate which is coupled to an adjoining segment by a bend.
17. The switch of claim 14 , wherein the first plate and spring beams are substantially symmetric about at least one of a longitudinal and latitudinal axis of the first plate.
18. The switch of claim 14 , wherein the at least one spring beam disposed on one side of the first plate is substantially anti-symmetric with respect to the at least one other spring beam disposed on an opposite side of the first plate.
19. The switch of claim 15 , wherein the first substrate is a silicon-on-insulator substrate comprising a device layer, a handle layer and a dielectric layer between the device layer and the handle layer, and the second substrate is at least one of a silicon substrate and a silicon-on-insulator substrate.
20. The switch of claim 15 , further comprising:
electrical vias formed through a thickness of the second substrate; and
an electrostatic second plate formed on the second substrate.
21. The switch of claim 14 , further comprising:
a first void formed around the first contact.
22. The switch of claim 21 , further comprising:
a second void formed near the second contact, wherein the first void is separated from the second void by an isthmus of material.
23. The switch of claim 22 , wherein the isthmus of material is configured to have at least one of lateral and rotational movement upon activation of the switch.
24. The switch of claim 15 , wherein the hermetic seal comprises:
a gold/indium alloy which bonds the first substrate to the second substrate with a substantially hermetic seal around the switch.
25. An apparatus for manufacturing a switch, comprising:
means for forming a first plate suspended adjacent to a first substrate by at least one spring beam;
means for coupling at least one conductive bar to the first plate at one location on the at least one conductive bar;
means for coupling the at least one conductive bar to a first contact which can protrude into without touching the first plate, at another location on the at least one conductive bar; and
means for configuring the first plate to activate the switch by pressing the at least one conductive bar coupled to the first plate against a second contact.