US 5,185,589 AGranted

Microwave film bulk acoustic resonator and manifolded filter bank

AssigneeWestinghouse Electric Corp.

InventorsS. Visvanathan Krishnaswamy, Stuart S. Horwitz, Robert A. Moore

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Abstract

A film bulk acoustic resonator (FBAR) configured as a coplanar transmission line structure. A film resonator formed over an opening in a substrate is connected to associated circuitry by one or more transmission lines formed on the substrate. The coplanar ground plane of this structure provides a simple mechanism for providing a true ground connection to the resonator without the need for vias passing through the substrate. The transmission line connection eliminates the need for wirebonds, thus simplifying fabrication, allowing the device to be more easily modified for computer simulation, and facilitating the operation of the device at microwave frequencies. Embodiments for standard, stacked, and 3-port FBAR's as well as a filter bank consisting of a plurality of coplanar 3-port FBAR's, are described.

Claims12

Dependent claims

A device comprising:

a semiconductor substrate having an opening formed therein;
a bottom piezoelectric layer disposed on said substrate and spanning said opening;
a first transmission line disposed on said substrate and having a section thereof extending under said bottom piezoelectric layer opposed said opening;
a second transmission line disposed on said substrate and having a section thereof extending over said bottom piezoelectric layer opposed said opening;
a first conductive layer disposed on said substrate, said first conducting layer comprising a ground plane coplanar with sections of said first transmission line and said second transmission line disposed on said substrate;
an insulating membrane disposed over said substrate, said first transmission line, said second transmission line, said first piezoelectric layer, and said first conductive layer;
a second conductive layer disposed on said insulating membrane;
a second piezoelectric layer disposed on said second conductive layer opposed said opening;
and
a third transmission line disposed on said insulating membrane and having a section thereof extending over said second piezoelectric layer comprises a ground plane coplanar with that portion of said third transmission line disposed on said insulating membrane.

7 more elements

A filter bank comprising:

a substrate having a plurality of openings formed therein;
and
a plurality of resonators respectively disposed over corresponding ones of said openings, each resonator comprising;
a bottom piezoelectric layer disposed on said substrate and spanning a corresponding one of said openings;
a first transmission line disposed on said substrate and having a section thereof extending under said bottom piezoelectric layer and opposed said corresponding opening;
a second transmission line disposed on said substrate and having a section thereof extending over said bottom piezoelectric layer opposed said corresponding opening;
a first conductive layer disposed on said substrate, said first conducting layer comprising a ground plane coplanar with sections of said first transmission line and said second transmission line disposed on said substrate;
an insulating membrane disposed over said substrate, said first transmission line, said second transmission line, said first piezoelectric layer, and said first conductive layer;
a second conductive layer disposed on said insulating membrane;
a second piezoelectric layer disposed on said second conductive layer opposed said corresponding opening;
and
a third transmission line disposed on said insulating membrane and having a section thereof extending over said second piezoelectric layer opposed said corresponding opening, wherein, said second conductive layer comprises a ground plane coplanar with that portion of said third transmission line disposed on said insulating membrane;
wherein said first and second transmission lines of said resonators are operatively connected to realize a series manifold filter circuit.

10 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/702,647Filed 17 May 1991
Granted: 9 Feb 1993
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

H03H 9/174
Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume: membranes
H03H 9/584
Comprising a plurality of piezoelectric layers acoustically coupled: coupled Resonator Filters [CFR]
H03H 9/585
Comprising a plurality of piezoelectric layers acoustically coupled: stacked Crystal Filters [SCF]
H03H 9/588
Means for mounting to a substrate, i.e. means constituting the material interface confining the waves to a volume: membranes