Air-gap type FBAR, method for fabricating the same, and filter and duplexer using the same

An air-gap type FBAR (Film Bulk Acoustic Resonator) filter comprising:

• a first resonance part comprising a plurality of series-connected FBARs having a first resonance frequency;
• a second resonance part comprising a plurality of FBARs having a second resonance frequency and connected in parallel to a plurality of the FBARs of the first resonance part;
• and
• a plurality of inductors connected in series to a plurality of the FBARs constituting the second resonance part, respectively,
• wherein the FBARs constituting the first and the second resonance parts each comprises:
• a dielectric film stacked on an upper part of a first substrate, forming a first air gap on the upper part of the first substrate having a plurality of cavity parts on its upper surface;
• and a stacked resonance part comprising a lower electrode/piezoelectric layer/upper electrode formed on an upper part of the dielectric film layer,
• wherein the dielectric film comprises a liquid crystal polymer (LCP) film of predetermined thickness.

A method for fabricating an air-gap type FBAR (Film Bulk Acoustic Resonator) which comprises:

• forming a first air gap by directly forming a dielectric film directly on a first substrate having a cavity part, without using a sacrificial layer, on a predetermined region on its upper surface;
• forming a stacked resonance part on an upper surface of the dielectric film;
• and
• forming a second air gap by joining the first substrate and a second substrate having a cavity part at a predetermined region on its lower surface.

A method for fabricating an air-gap type FBAR (Film Bulk Acoustic Resonator) which comprises:

• forming a first air gap by stacking a dielectric film on a first substrate having a cavity part on a predetermined region on its upper surface;
• forming a stacked resonance part on an upper surface of the dielectric film;
• and
• forming a second air gap by joining the first substrate and a second substrate having a cavity part at a predetermined region on its lower surface,
• wherein at the step of forming the first air gap, said method comprises forming a dielectric film of predetermined thickness from a liquid crystal polymer (LCP).

A method for fabricating an air-gap type FBAR (Film Bulk Acoustic Resonator) which comprises:

• forming a first air gap by stacking a dielectric film on a first substrate having a cavity part on a predetermined region on its upper surface;
• forming a stacked resonance part on an upper surface of the dielectric film;
• and
• forming a second air gap by joining the first substrate and a second substrate having a cavity part at a predetermined region on its lower surface,
• wherein the dielectric film comprises a liquid crystal polymer (LCP) film of predetermined thickness.

An air-gap type FBAR (Film Bulk Acoustic Resonator) duplexer comprising:

• a first FBAR filter for transmitting a signal provided to a transmission terminal through an antenna;
• a second FBAR filter for receiving a signal from the antenna to be input to a reception terminal;
• and
• a phase shift part arranged between the antenna and the second filter, for preventing interference of a signal at the first and the second filters by changing a phase of a signal transmitted and received,
• wherein the first and the second filters have, respectively, first and second resonance parts having different predetermined resonance frequencies, and a plurality of FBARs formed on the first and the second resonance parts each including a dielectric film stacked on an upper part of a first substrate, thereby forming a first air gap on the upper part of the first substrate having a plurality of cavity parts on its upper surface;
• and a stacked resonance part comprising a lower electrode/piezoelectric layer/upper electrode formed on the upper part of the dielectric film, and
• wherein the dielectric film comprises a liquid crystal polymer (LCP) film of predetermined thickness.