Solidly-mounted transversely excited film bulk acoustic resonator using rotated Y-X cut lithium niobate

A filter device comprising:

• a substrate having a surface;
• a single-crystal lithium niobate plate having front and back surfaces;
• an acoustic Bragg reflector sandwiched between the surface of the substrate and the back surface of the lithium niobate plate;
• a conductor pattern formed on the front surface of the lithium niobate plate, the conductor pattern including a plurality of interdigital transducers (IDTs) of a respective plurality of resonators including a shunt resonator and a series resonator;
• a first dielectric layer having a first thickness deposited over the IDT of the shunt resonator;
• and
• a second dielectric layer having a second thickness less than the first thickness deposited over the IDT of the series resonator,
• wherein Euler angles of the lithium niobate plate are [0°, β, 0°], where β is greater than or equal to 0° and less than or equal to 60°.

A method of fabricating an acoustic resonator device comprising:

• forming an acoustic Bragg reflector by depositing material layers on one or both of a surface of a device substrate and a first surface of a single-crystal lithium niobate plate having a second surface attached to a sacrificial substrate;
• bonding the lithium niobate plate attached to the sacrificial substrate to the device substrate such that the layers of the acoustic Bragg reflector are sandwiched between the first surface of the lithium niobate plate and the device substrate;
• removing the sacrificial substrate to expose the second surface of the lithium niobate plate;
• and
• forming an interdigital transducer (IDT) on the second surface of the lithium niobate plate, wherein
• Euler angles of the lithium niobate plate are [0°, β, 0°], where β is greater than or equal to 0° and less than or equal to 60°.

An acoustic resonator device comprising:

• a substrate having a surface;
• a single-crystal lithium niobate plate having front and back surfaces, wherein Euler angles of the lithium niobate plate are [0°, β, 0°], where β is greater than or equal to 0° and less than or equal to 60°;
• an acoustic Bragg reflector sandwiched between the surface of the substrate and the back surface of the lithium niobate plate;
• an interdigital transducer (IDT) formed on the front surface of the lithium niobate plate;
• and
• a front-side dielectric layer formed on the front surface of the lithium niobate plate between the fingers of the IDT.

A filter device comprising:

• a substrate having a surface;
• a single-crystal lithium niobate plate having front and back surfaces, wherein Euler angles of the lithium niobate plate are [0°, β, 0°], where β is greater than or equal to 0° and less than or equal to 60°;
• an acoustic Bragg reflector sandwiched between the surface of the substrate and the back surface of the lithium niobate plate, wherein the acoustic Bragg reflector comprises a plurality of dielectric layers alternating between high acoustic impedance layers and low acoustic impedance layers, and wherein the high acoustic impedance layers are one of silicon nitride and aluminum nitride and the low acoustic impedance layers are carbon-containing silicon oxide;
• and
• a conductor pattern formed on the front surface of the lithium niobate plate, the conductor pattern including a plurality of interdigital transducers (IDTs) of a respective plurality of resonators including a shunt resonator and a series resonator.