MEMS variable capacitor with stabilized electrostatic drive...

Details MEMS variable capacitor with stabilized electrostatic drive... MEMS variable capacitor with stabilized electrostatic drive...

2001-10-16

2002-08-27

Flynn, Nathan J. (Department: 2826)

Active solid-state devices (e.g., transistors, solid-state diode

Responsive to non-electrical signal

C257S532000, C257S534000, C257S415000, C257S417000, C257S312000, C331S11700R, C331S17700V, C331S03600C, C331S016000, C331S034000, C438S379000, C455S260000, C361S278000, C361S281000, C361S283200, C361S283400, C505S210000

Reexamination Certificate

active

06441449

ABSTRACT:

FIELD OF THE INVENTION
This invention relates, in general, to micro electro-mechanical system (MEMS) devices and, more particularly, to a high quality (high-Q) variable capacitor fabricated using MEMS technology.
BACKGROUND OF THE INVENTION
One prior art type of variable capacitor, known as the thermal drive variable capacitor
10
, is illustrated in FIG.
1
. In this prior art version, a dielectric gap
11
between two capacitor plates
12
and
13
is controlled or altered by means of thermal expansion of lateral components. As shown in
FIG. 1
, each end of an upper plate
12
of a capacitor is connected to one end of a movable, hinged diagonal component
15
. The other end of the diagonal component is connected to a lateral component
14
. Movement of lateral component
14
, which is controlled by thermal devices, causes the hinged diagonal components
15
to translate the lateral movement to vertical movement of upper plate
12
. The vertical movement of upper plate
12
varies the capacitance of the device.
The drawbacks to thermal drive variable capacitor
10
are several. The mechanical design of the device is complicated resulting in a costly and inefficient manufacturing process. Also, the complicated design of the thermal drive negatively impacts the reliability of the device. The translation of lateral movement to vertical movement intrinsic to thermal drive devices has the negative effect of increasing the size of the device. Also, the thermal expansion and contraction operation of the device is inefficient, thus resulting in slow speed in varying the capacitance. Furthermore, thermal operation requires significantly more power consumption than electrostatically driven MEMS devices of similar capability.
Another prior art variable capacitor
20
is illustrated in FIG.
2
. MEMS variable capacitor
20
has at least one driver
21
, itself a simple variable capacitor, for determining the displacement of a dielectric membrane
22
and a variable capacitor region for employment with an external circuit (not shown). The displacement of dielectric membrane
22
is determined by the application of a voltage potential across drivers
21
.
The application of a voltage to the drivers causes an electrostatic attraction between the driver electrodes. This electrostatic attraction results in a downward movement of dielectric membrane
22
, thereby causing a downward displacement. This reduction in the gap between the upper
23
and lower
24
capacitor plates results in a corresponding variance in capacitance.
Hence, a need exists for a high-Q capacitor that is reliable, cost efficient, and has continuous dynamic response over the full displacement of the dielectric membrane.


REFERENCES:
patent: 5880921 (1999-03-01), Tham et al.
patent: 6094102 (2000-07-01), Chang et al.
patent: 6110792 (2000-08-01), Kalnitsky et al.
patent: 6160230 (2000-12-01), McMillan et al.
patent: 6242989 (2001-06-01), Barber et al.
patent: 6327463 (2001-12-01), Welland
patent: 6335665 (2002-01-01), Mendelsohn
patent: 6347237 (2002-02-01), Eden et al.

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