DEVICE WITH SEPARATION LIMITING STANDOFF
An MEMS device, having two substantially parallel surfaces are separated by an initial distance. At least one of the surfaces includes a raised feature that limits the gap between the surfaces to less than the initial distance when an actuating voltage is applied. In some embodiments, the raised feature limits the gap to about 66% of the initial distance.
1 . A device comprising:
a first surface separated from a second surface by an initial distance D 1 , wherein at least one of the first surface and the second surface further comprises one or more separation limiting standoffs of height D 2 , wherein the one or more separation limiting standoffs limits a gap between the surfaces to the distance D 2 , wherein D 2 <D 1 , when an actuation is applied.
2 . The device of claim 1 , wherein D 2 is about 66% of D 1 .
3 . The device of claim 1 , wherein the device is at least one of an actuator, a switch and a sensor.
4 . The device of claim 1 , wherein the actuation is at least one of electrostatic, magnetostatic, electromagnetic or piezoelectric.
5 . The device of claim 1 , wherein the device is a capacitive plate switch, which forms a closed, capacitive connection when the two plates are separated by the distance D 2 and forms an open connection when separated by the distance D 1 , for an RF signal at or above an operating frequency.
6 . The device of claim 5 , wherein the operating frequency is at least 1 MHz.
7 . The device of claim 1 , wherein the one or more separation limiting standoffs is a feature in the shape of at least one of a post, a bump, a sphere, a pyramid, a trapezoid.
8 . The device of claim 1 , wherein the one or more separation limiting standoffs is one in a plurality of raised features.
9 . The device of claim 1 , wherein the one or more separation limiting standoffs are disposed near or at the periphery of the surfaces.
10 . The device of claim 1 , wherein the one or more separation limiting standoffs comprise a dielectric substance chosen from the group consisting of silicon dioxide, silicon nitride, polysilicon, amorphous silicon, spin-on glass (SOG), or a spin coated, temperature tolerant polymer layer such as SU8, polyimide, or benzocyclobutene (BCB).
11 . The device of claim 1 , wherein the device is a MEMS electrostatic plate switch, having two substantially parallel plates.
12 . The device of claim 11 , wherein the two plates move toward one another upon application of a differential voltage between them.
13 . The device of claim 12 , wherein the two substantially parallel plates act to open and close a capacitive switch, by changing a capacitance between them as a result of their movement upon application of the differential voltage.
14 . The device of claim 13 , wherein the two plates are formed on two difference subtrates.
15 . The device of claim 14 , wherein at least one of the substrates is an SOI wafer.
16 . The device of claim 15 , wherein the movement of the plates is constrained by the separation limiting standoff to a value of closest approach equalling D 2 .
17 . The device of claim 16 , wherein the separation limiting standoff comprises an insulating pad and a mechanically competent feature.
18 . The device of claim 17 , wherein the insulating pad comprises at least one of a metal oxide, a semiconductor oxide, a photoresist, a glass or a ceramic.
19 . The device of claim 17 , wherein the mechanically competent feature comprises at least one of a metal, a metal oxide, a metal alloy, or an insulating material.
20 . The device of claim 18 , wherein the insulating pad comprises silicon dioxide.