Filter using piezoelectric film bonded to high resistivity silicon substrate with trap-rich layer

An acoustic resonator device comprising:

• a substrate having a trap-rich region adjacent to a surface;
• a single-crystal piezoelectric plate having parallel front and back surfaces, the back surface attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity formed in the substrate;
• and
• an interdigital transducer (IDT) formed on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm, the single-crystal piezoelectric plate and the IDT configured such that a radio frequency signal applied to the IDT excites a shear primary acoustic mode within the diaphragm, wherein the substrate comprises a single-crystal silicon plate, and wherein the trap-rich region is a portion of the silicon plate containing deep trap impurities.

A filter device, comprising:

• a substrate having a trap-rich region adjacent to a surface;
• a single-crystal piezoelectric plate having parallel front and back surfaces, the back surface attached to the surface of the substrate, portions of the single-crystal piezoelectric plate forming one or more diaphragms spanning respective cavities in the substrate;
• and
• a conductor pattern formed on the front surface, the conductor pattern including a plurality of interdigital transducers (IDTs) of a respective plurality of acoustic resonators, interleaved fingers of each of the plurality of IDTs disposed on one of the one or more diaphragms, wherein
• the single-crystal piezoelectric plate and all of the IDTs are configured such that a respective radio frequency signal applied to each IDT excites a respective shear primary acoustic mode within the respective diaphragm, wherein the substrate comprises a single-crystal silicon plate, and wherein the trap-rich region is a portion of the silicon plate that has been irradiated to create defects in the crystalline structure.

A filter device, comprising:

• a substrate having a trap-rich region adjacent to a surface;
• a single-crystal piezoelectric plate having parallel front and back surfaces, the back surface attached to the surface of the substrate, portions of the single-crystal piezoelectric plate forming one or more diaphragms spanning respective cavities in the substrate;
• and
• a conductor pattern formed on the front surface, the conductor pattern including a plurality of interdigital transducers (IDTs) of a respective plurality of acoustic resonators, interleaved fingers of each of the plurality of IDTs disposed on one of the one or more diaphragms, wherein
• the single-crystal piezoelectric plate and all of the IDTs are configured such that a respective radio frequency signal applied to each IDT excites a respective shear primary acoustic mode within the respective diaphragm, wherein the substrate comprises a single-crystal silicon plate, and wherein the trap-rich region is a portion of the silicon plate containing deep trap impurities.

A method of fabricating an acoustic resonator device on a substrate having a trap-rich region adjacent to a surface, the method comprising:

• attaching a back surface of a single crystal piezoelectric plate to the surface of the substrate;
• forming a cavity in the substrate such that a portion of the single-crystal piezoelectric plate forms a diaphragm spanning the cavity;
• and
• forming an interdigital transducer (IDT) on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm, the single-crystal piezoelectric plate and the IDT configured such that a radio frequency signal applied to the IDT excites a shear primary acoustic mode within the diaphragm, wherein the cavity is formed prior to attaching the single crystal piezoelectric plate to the surface of the substrate.

A method of fabricating an acoustic resonator device on a substrate having a trap-rich region adjacent to a surface, the method comprising:

• attaching a back surface of a single crystal piezoelectric plate to the surface of the substrate;
• forming a cavity in the substrate such that a portion of the single-crystal piezoelectric plate forms a diaphragm spanning the cavity;
• and
• forming an interdigital transducer (IDT) on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm, the single-crystal piezoelectric plate and the IDT configured such that a radio frequency signal applied to the IDT excites a shear primary acoustic mode within the diaphragm, wherein the cavity is formed after attaching the single crystal piezoelectric plate to the surface of the substrate.