Abstract: 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.

Abstract: A bulk acoustic resonator is provided that includes a substrate having a surface; a piezoelectric layer attached to the surface of the substrate via a bonding oxide (BOX) layer over the surface of the substrate; a conductor pattern including an interdigital transducer (IDT) that has interleaved fingers on a surface of the piezoelectric layer; at least one contact pad disposed at a selected location over the surface of the substrate and that is electrically connected to the IDT; and an electrically isolating layer between the at least one contact pad and the surface of the substrate. Moreover, at least a portion of the piezoelectric layer is absent between the at least one contact pad and the surface of the substrate.

Abstract: 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.

Abstract: 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.

Abstract: An acoustic resonator device is provided that includes a wafer having a wafer surface and a wafer conductor pattern on the wafer surface; a piezoelectric layer having front and back surfaces, a portion of the piezoelectric layer being over a cavity between the wafer and the piezoelectric layer, and the wafer conductor pattern; a device conductor pattern including a first metal layer including an interdigital transducer on the front surface of the piezoelectric layer and facing the wafer, and a second metal layer attached to a portion of the device conductor pattern to provide an electrical connection between the IDT and the wafer conductor pattern. The second metal layer is bonded to the wafer conductor pattern and the piezoelectric layer comprises openings extending therethrough.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: An acoustic resonator is provided that includes a substrate; a first piezoelectric layer having first and second surfaces that oppose each other, with the second surface coupled to the substrate directly or via one or more intermediate layers; a second piezoelectric layer having first and second opposing surfaces, with the first surface coupled to the first surface of the first piezoelectric layer and opposite to the substrate; an etch stop layer disposed between the respective first surfaces of the first and second piezoelectric layers; and first and second interdigital transducers (IDTs) on at least one of the first and second piezoelectric layers, respectively. Moreover, a portion of one of the first and second piezoelectric layers is removed between the second surface of the respective piezoelectric layer and the etch stop.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A process for fabricating a transversely-excited film bulk acoustic resonator (XBAR) and that XBAR are described. A sacrificial pillar is formed on a surface of a piezoelectric wafer and a highly conforming dielectric layer is deposited on the piezoelectric wafer to bury the sacrificial pillar. The highly conforming dielectric layer is polished to form a planar surface and to leave a thickness of the highly conforming dielectric that covers the sacrificial pillar. The planar surface of the highly conforming dielectric layer is bonded to a surface of a substrate wafer. A conductor pattern is formed on a front surface of the piezoelectric plate and holes are formed through the piezoelectric wafer to the sacrificial pillar. The sacrificial pillar is removed using an etchant introduced through the holes in the piezoelectric wafer to form a cavity under a diaphragm of the piezoelectric wafer spanning the cavity.

Abstract: Acoustic resonator devices and methods are disclosed. An acoustic resonator device includes a substrate having a front surface and a cavity. A depth of the cavity is defined by a buried oxide layer comprising etch-stop material and a perimeter of the cavity is defined by lateral fences comprising etch-stop material. A back surface of a single-crystal piezoelectric plate is attached to the front surface of the substrate except for a portion of the piezoelectric plate that forms a diaphragm that spans the cavity. An interdigital transducer (IDT) is formed on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm.

Abstract: A process for fabricating a transversely-excited film bulk acoustic resonator (XBAR) having a metal cavity, and the fabricated XBAR include forming a conductor pattern including interleaved interdigital transducer (IDT) fingers on a piezoelectric wafer. Thein forming a metal layer on a substrate, the metal layer having a cavity. Then, bonding the piezoelectric plate to the metal layer using a metal-to-metal bond such that the IDT fingers are disposed over the cavity. Then, thinning the piezoelectric wafer to form a piezoelectric plate having a portion of the piezoelectric plate forming a diaphragm that spans the cavity.

Abstract: Acoustic resonator devices and methods are disclosed. An acoustic resonator device includes a substrate having a front surface and an intervening oxide layer on the front surface and having a cavity. A thickness of the intervening oxide layer defines a depth of the cavity, and the substrate has vertical etch-stop material for etching the intervening oxide layer. Lateral fences formed in the intervening oxide layer define a perimeter of the cavity. The lateral fences has a lateral etch-stop material for etching the intervening oxide layer. A single-crystal piezoelectric plate has a back surface attached to the front surface of the intervening oxide layer except for a portion of the piezoelectric plate forming a diaphragm that spans the cavity. An interdigital transducer is formed on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm.

Abstract: 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.

Abstract: 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.