Film bulk acoustic wave resonators and fabrication methods thereof

A method for fabricating a film BAWR, comprising:

• forming a first insulating material layer on a first substrate;
• forming a first cavity in the first insulating material layer with an opening facing away from the first substrate;
• sequentially forming a second conductive film, a piezoelectric film, and a first conductive film on a sacrificial substrate;
• etching a portion of the first conductive film and the piezoelectric film close to an end of the sacrificial substrate to expose a portion of the second conductive film, a remaining portion of the first conductive film becoming a first electrode, a plurality of trenches formed through the first conductive film and the piezoelectric film becoming a plurality of first electrode cavities, and a portion of the piezoelectric film located between adjacent first electrode cavities becoming a plurality of second piezoelectric oscillation plates;
• bonding the first substrate and the sacrificial substrate together by bonding the first insulating material layer to the first conductive film, wherein after bonding, the plurality of first electrode cavities are located above the first cavity;
• removing the sacrificial substrate;
• and
• etching a portion of the second conductive film and a portion of the piezoelectric film close to an end of the sacrificial substrate opposite to the end where the plurality of first electrode cavities are formed to expose a portion of the first electrode, a remaining portion of the second conductive film becoming a second electrode, a remaining portion of the piezoelectric film sandwiched between the first electrode and the second electrode becoming a first piezoelectric oscillation plate, a plurality of trenches formed through the second conductive film and the piezoelectric film becoming a plurality of second electrode cavities, and a portion of the piezoelectric film located between adjacent second electrode cavities becoming a plurality of third piezoelectric oscillation plates, wherein:
• the first piezoelectric oscillation plate has a first piezoelectric-oscillation-plate boundary,
• at least a portion of the first piezoelectric-oscillation-plate boundary is an overlapping region of a portion of a boundary of the first electrode cavity and a portion of a boundary of the second electrode cavity,
• the first piezoelectric-oscillation-plate boundary has an irregular polygonal shape without having any two edges parallel to each other, and is entirely enclosed in the first cavity boundary, and
• the plurality of second piezoelectric oscillation plates and the plurality of third piezoelectric oscillation plates receive and absorb a portion of vibration energy transmitted out through vibration waves induced in the first electrode and the second electrode.

A method for fabricating a film BAWR, comprising:

• forming a first insulating material layer on a first substrate;
• forming a first cavity in the first insulating material layer with an opening facing away from the first substrate;
• forming a first sacrificial material layer in the first cavity, wherein a top surface of the first sacrificial material layer is leveled with a top surface of the first insulating material layer;
• sequentially forming a first conductive film and a piezoelectric film on the first insulating material layer and the first sacrificial material layer;
• etching a portion of the piezoelectric film and a portion of the first conductive film above the first sacrificial material layer to expose a portion of the first sacrificial material layer, a plurality of trenches formed through the piezoelectric film and the first conductive film becoming a plurality of first electrode cavities, a remaining portion of the first conductive film becoming a first electrode, and a portion of the piezoelectric film located between adjacent first electrode cavities becoming a plurality of second piezoelectric oscillation plates;
• forming a second sacrificial material layer to fill the plurality of first electrode cavities;
• forming a second conductive film on the piezoelectric film and the second sacrificial material layer;
• etching a portion of the second conductive film and a portion of the piezoelectric film formed above the first sacrificial material layer to expose a portion of the first electrode, a remaining portion of the second conductive film becoming a second electrode, a remaining portion of the piezoelectric film sandwiched between the first electrode and the second electrode becoming a first piezoelectric oscillation plate, a plurality of trenches formed through the second conductive film and the piezoelectric film becoming a plurality of second electrode cavities, and a portion of the piezoelectric film located between adjacent second electrode cavities becoming a plurality of third piezoelectric oscillation plates;
• and
• removing the first sacrificial material layer and the second sacrificial material layer, wherein:
• the first piezoelectric oscillation plate has a first piezoelectric-oscillation-plate boundary,
• at least a portion of the first piezoelectric-oscillation-plate boundary is an overlapping region of a portion of a boundary of the first electrode cavity and a portion of a boundary of the second electrode cavity,
• the first piezoelectric-oscillation-plate boundary has an irregular polygonal shape without having any two edges parallel to each other, and the first piezoelectric-oscillation-plate boundary is entirely enclosed in the first cavity boundary, and
• the plurality of second piezoelectric oscillation plates and the plurality of third piezoelectric oscillation plates receive and absorb a portion of vibration energy transmitted out through vibration waves induced in the first electrode and the second electrode.