Film bulk acoustic resonator and fabrication method thereof
View Patent ↗The present disclosure provides a film bulk acoustic resonator and a method for fabricating the film bulk acoustic resonator. The resonator includes a carrier substrate; a support layer bonded on the carrier substrate, where the support layer encloses a first cavity exposing the carrier substrate; a piezoelectric stacked structure covering the first cavity, where the piezoelectric stacked structure includes a first electrode, a piezoelectric layer, and a second electrode which are stacked sequentially from a bottom to a top; and protrusions disposed at a boundary of an effective resonance region, where the protrusions are disposed on an upper surface or a lower surface of the piezoelectric stacked structure; or a part of the protrusions is disposed on the upper surface of the piezoelectric stacked structure, and another part of the protrusions is disposed on the lower surface of the piezoelectric stacked structure.
1 . A film bulk acoustic resonator, comprising:
a carrier substrate;
a piezoelectric stacked structure, including a first electrode over the carrier substrate, a piezoelectric layer over the first electrode, and a second electrode over the piezoelectric layer;
a support layer, disposed between the carrier substrate and the first electrode of the piezoelectric stacked structure, and enclosing a first cavity there-between; and
protrusions, disposed on the first electrode of the piezoelectric stacked structure and protruding into the first cavity at a boundary of an effective resonance region of the film bulk acoustic resonator.
2 . The film bulk acoustic resonator according to claim 1 , wherein:
projections of the protrusions on the carrier substrate form a ring shape, and an inside of the ring shape is the effective resonance region; and/or
a projection of the piezoelectric layer on the carrier substrate covers the first cavity.
3 . The film bulk acoustic resonator according to claim 1 , wherein:
the protrusions are made of a material including a dielectric material; or
a material of the protrusions is same as a material of the first electrode or the second electrode.
4 . The film bulk acoustic resonator according to claim 1 , further including:
a first trench inside the first cavity, wherein the first trench passes through the first electrode, exposes a surface portion of the piezoelectric layer, and surrounds a periphery of the effective resonance region of the protrusions.
5 . The film bulk acoustic resonator according to claim 4 , further including:
a second trench, disposed opposite to the first trench, wherein the second trench passes through the second electrode, exposes a surface portion of the piezoelectric layer, and surrounds the periphery of the effective resonance region of the protrusions.
6 . The film bulk acoustic resonator according to claim 5 , wherein:
inner edges of the first trench and the second trench are coincident with an outer boundary of the protrusions.
7 . The film bulk acoustic resonator according to claim 5 , further including:
an attaching layer, disposed above the piezoelectric stacked structure, wherein the attaching layer encloses a second cavity which exposes a surface of the piezoelectric stacked structure; the second cavity is above the first cavity; and the first trench and the second trench are inside a region enclosed by the second cavity; and
a cap substrate, disposed on the attaching layer and covering the second cavity.
8 . The film bulk acoustic resonator according to claim 1 , further including:
a frequency adjustment layer, disposed on a surface of the first electrode in the effective resonance region.
9 . The film bulk acoustic resonator according to claim 1 , wherein:
the support layer is made of a material including silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride, or ethyl silicate.
10 . The film bulk acoustic resonator according to claim 8 , wherein
the frequency adjustment layer is further disposed on sidewalls of the protrusions in the effective resonance region and on top surfaces of the protrusions inside the first cavity.
11 . The film bulk acoustic resonator according to claim 1 , wherein:
the first electrode and the second electrode outside the effective resonance region have an overlapped portion along a direction perpendicular to the piezoelectric layer; and
the film bulk acoustic resonator further includes a conductive interconnection structure, connecting the first electrode and the second electrode outside the effective resonance region.