| Project: |
Alternative MEMS switch configurations |
| Investigators: |
Yu Liu, Andrea Borgioli, and Bob
York |
| Collaborators: |
TOYON Corporation |
| Funded
by: |
TOYON Corporation, DARPA Program |
| Description: |
One
important issue in the design and fabrication of MEMS capacitive
switches is the value of the DOWN capacitance actually achieved by the
switch. The larger the DOWN capacitance, the more isolation can be
achieved in the DOWN state. The designed value of the capacitance of
the switch in the DOWN state is computed by means of the simple laws
of electrostatics.
Our
novel design is intended to cope with this issue. As illustrated in
right figure, unlike the traditional MEMS switch structure, a metal
cap and a metal notch have been added right above the dielectric layer
by means of two separate metal evaporations. In this fashion, it is
possible to create a perfect, reproducible contact with the upper
surface of the coating dielectric. When the actuation voltage induces
the suspended metal bridge to snap down, an electrical path is created
between the upper bridge and the metal cap by means of the notch. The
function of the notch is to prevent possible stiction due to a full
metal-to-metal contact between the upper membrane and the metal cap.
RF
MEMS with separated bias lines is another approach to improve DOWN
capacitance. Since DC bias is applied from separate pad, no dielectric
isolation is needed between suspended membrane and CPW central
conductor, as shown in right plot.
|
| Plot
descriptions: |
Top: MEMS switch with metal cap
Bottom: MEMS switch with separate bias line, and S-parameter
measurements for fabricated sample. |
|
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