Transversely-excited film bulk acoustic resonators with molybdenum conductors

A filter device, comprising:

• a substrate;
• a single-crystal piezoelectric plate having 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;
• 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, the piezoelectric plate and all of the IDTs configured such that respective radio frequency signal applied to each IDT excite respective shear primary acoustic modes in the respective diaphragm, wherein
• the interleaved fingers of all of the plurality of IDTs are substantially molybdenum,
• the interleaved fingers of all of the plurality of IDTs have a common finger thickness, which is greater than or equal to 0.25 times a thickness of the piezoelectric plate and less than or equal to 2.5 times the thickness of the piezoelectric plate, and
• the diaphragms of all of the plurality of acoustic resonator are contiguous with the piezoelectric plate around at least 50% of a perimeter of the respective cavities.

An acoustic resonator device comprising:

• a substrate having a surface;
• a single-crystal piezoelectric plate having 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 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 piezoelectric plate and the IDT configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the diaphragm, wherein
• the interleaved fingers of the IDT comprise a lower layer closest to the diaphragm of a first material and an upper layer of a second material, the first material having lower acoustic loss than the second material and the second material having higher electrical and thermal conductivity than the first material, a thickness of the lower layer is different from a thickness of the upper layer.

A filter device, comprising:

• a substrate;
• a single-crystal piezoelectric plate having 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, the piezoelectric plate and all of the IDTs configured such that respective radio frequency signal applied to each IDT excite respective shear primary acoustic modes in the respective diaphragm;
• and
• a front-side dielectric layer deposited between the fingers of at least some, but not all, of the plurality of IDTs, wherein
• the interleaved fingers of all of the plurality of IDTs are substantially molybdenum, and
• the interleaved fingers of all of the plurality of IDTs have a common finger thickness, which is greater than or equal to 0.65 times a thickness of the piezoelectric plate and less than or equal to 2.5 times the thickness of the piezoelectric plate.

A filter device, comprising:

• a substrate;
• a single-crystal piezoelectric plate having 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;
• 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, the plurality of resonators including one or more shunt resonators and one or more series resonators;
• a first dielectric layer having a first thickness deposited between the fingers of the IDTs of the one or more shunt resonators;
• and
• a second dielectric layer having a second thickness less than the first thickness deposited between the fingers of the IDTs of the one or more series resonators, wherein
• the interleaved fingers of all of the plurality of IDTs are substantially molybdenum, and
• the interleaved fingers of all of the plurality of IDTs have a common thickness, which is greater than or equal to 0.65 times the thickness of the piezoelectric plate and less than or equal to 2.5 times the thickness of the piezoelectric plate.