Murata Manufacturing Co., Ltd.

Chris O'Brien

Albert Cardona

Greg Dyer

Neal O Fenzi

Andrew Kay

James R Costa

Patrick J Turner

Ventsislav Yantchev

Robert B Hammond

Douglas Jachowski

Acoustic resonators, filters and methods of making resonators are disclosed. An acoustic resonator includes a substrate, a piezoelectric plate, and an acoustic Bragg reflector between a surface of the substrate and a back surface of the piezoelectric plate. An interdigital transducer (IDT) on a front surface of the piezoelectric plate includes first and second busbars and a plurality of interleaved fingers extending alternately from the first and second busbars. At least a portion of the first busbar contacts the substrate through an opening in the piezoelectric plate and acoustic Bragg reflector.

Solidly-mounted transversely-excited film bulk acoustic resonators with low thermal impedance

Methods of fabricating filter devices are disclosed. A back surface of a piezoelectric plate having a first thickness is attached to a substrate. The front surface of the piezoelectric plate is selectively etched to thin a portion of the piezoelectric plate from the first thickness to a second thickness less than the first thickness. Cavities are formed in the substrate such that portions of the piezoelectric plate form a plurality of diaphragms spanning respective cavities. A conductor pattern is formed on the front surface. The conductor pattern includes a first interdigital transducer (IDT) with interleaved fingers on a first diaphragm having the first thickness and a second IDT with interleaved fingers on a second diaphragm having the second thickness.

Transversely-excited film bulk acoustic resonator with multiple diaphragm thicknesses and fabrication method

An acoustic resonator device is formed using a wafer-to-wafer bonding process by etching recesses into a first surface of a piezoelectric substrate, a depth of the recesses greater than a target piezoelectric membrane thickness; then wafer-to-wafer bonding the first surface of the piezoelectric substrate to a handle wafer using a releasable bonding method. The piezoelectric substrate is then thinned to the target piezoelectric membrane thickness to form a piezoelectric plate and at least one conductor pattern is formed on the thinned piezoelectric plate. The side of the thinned piezoelectric plate having the conductor pattern is bonded to a carrier wafer using a metal-to-metal wafer bonding process and the handle wafer is removed.

Transversely-excited film bulk acoustic resonator fabrication using wafer-to-wafer bonding

An acoustic resonator device with low thermal impedance has a substrate and a single-crystal piezoelectric plate having a back surface attached to a top surface of the substrate via a bonding oxide (BOX) layer. An interdigital transducer (IDT) formed on the front surface of the plate has interleaved fingers disposed on the diaphragm, the overlapping distance of the interleaved fingers defining an aperture of the resonator device. Contact pads are formed at selected locations over the surface of the substrate to provide electrical connections between the IDT and contact bumps to be attached to the contact pads. The piezoelectric plate is removed from at least a portion of the surface area of the device beneath each of the contact pads to provide lower thermal resistance between the contact bumps and the substrate.

Transversely-excited film bulk acoustic resonator with reduced substrate to contact bump thermal resistance

Transversely-excited film bulk acoustic resonator

An acoustic resonator device is formed using a sacrificial layer and a front side etched cavity by forming a recess in a silicon substrate with a trap-rich top layer and filling the recess with sacrificial silicon nitride. A bonding oxide (BOX) layer is formed over the trap-rich layer and the sacrificial silicon nitride filled recess and a piezoelectric plate is bonded to the BOX layer. The sacrificial silicon nitride is then removed to form a cavity by using an etchant introduced through holes in the piezoelectric plate and BOX layer without removing the BOX layer from over the cavity.

Substrate processing and membrane release of transversely-excited film bulk acoustic resonator using a sacrificial tub

An acoustic resonator device is formed using sacrificial polysilicon pillar by forming a polysilicon pillar on a substrate and depositing a dielectric layer to bury the polysilicon pillar and planarizing the surface of the dielectric layer. A piezoelectric plate is bonded to the planarized surface of the dielectric layer and thinned to a target piezoelectric membrane thickness. At least one conductor pattern is formed on the thinned piezoelectric plate and the polysilicon pillar is then removed using an etchant introduced through holes in the piezoelectric plate to form an air cavity where the pillar was removed.

Transversely-excited film bulk acoustic resonator fabrication using polysilicon pillars

An acoustic resonator device with low thermal impedance has a substrate and a single-crystal piezoelectric plate having a back surface attached to a top surface of the substrate via a bonding oxide (BOX) layer. An interdigital transducer (IDT) formed on the front surface of the plate has interleaved fingers disposed on a diaphragm of the plate that is formed over a cavity in the substrate. The piezoelectric plate and the BOX layer are removed from a least a portion of the surface area of the substrate to provide lower thermal resistance between the IDT and the substrate.

Transversely-excited film bulk acoustic resonator with low thermal impedance

An acoustic resonator device with low thermal impedance has a substrate and a single-crystal piezoelectric plate having a back surface attached to a top surface of the substrate via a bonding oxide (BOX) layer. An interdigital transducer (IDT) formed on the front surface of the plate has interleaved fingers disposed on the diaphragm. The piezoelectric plate and the BOX layer are removed from a least a portion of the surface area of the device to provide lower thermal resistance between the conductor pattern and the substrate.

An acoustic resonator device with low thermal impedance has a substrate and a single-crystal piezoelectric plate having a back surface attached to a top surface of the substrate via a bonding oxide (BOX) layer. An interdigital transducer (IDT) formed on the front surface of the plate has interleaved fingers disposed on the diaphragm. The piezoelectric plate and the BOX layer are removed from a least a portion of the surface area of the device to provide lower thermal resistance between the IDT and the substrate.

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San Diego, CA, United States of America

Chris O'Brien