Embodiments of a Surface Acoustic Wave (SAW) device, or filter, and methods of fabrication thereof are disclosed. In some embodiments, the SAW filter comprises a piezoelectric substrate and an Interdigitated Transducer (IDT) on a surface of the piezoelectric substrate. The IDT includes multiple fingers, each comprising a metal stack. The SAW filter further includes a cap layer on a surface of the IDT opposite the piezoelectric substrate and on areas of the surface of the piezoelectric substrate exposed by the IDT. The cap layer has a thickness in a range of and including 10 to 500 Angstroms and a high electrical resistivity (and thus a low electrical conductivity). For instance, in some embodiments, the electrical resistivity of the cap layer is greater than 10 kilo-ohm meters (K.Math.m). The SAW filter further includes an oxide overcoat layer on a surface of the cap layer opposite the IDT and the piezoelectric substrate.

A piezoelectric composite substrate for SAW devices with small loss is provided. A composite substrate for a surface acoustic wave device according to one embodiment of the present invention has a piezoelectric single crystal thin film, a support substrate, and a first intervening layer between the piezoelectric single crystal thin film and the support substrate. In said composite substrate, the first intervening layer is in contact with the piezoelectric single crystal thin film, and the acoustic velocity of the transverse wave in the first intervening layer is faster than the acoustic velocity of the fast transverse wave in the piezoelectric single crystal thin film.

Aspects herein include minimizing hot spots on a filter chip by creating thermal radiators using mechano-acoustic structures and connection circuitry. A gradual increase of metal to wafer relation provides better heat dissipation and heat sinking. Shunt lines of a ladder type arrangement of SAW resonators comprise a broadened section. Resonators that are subsequent to each other in the series signal line are connected via a common busbar extending over a length of subsequent series resonators. A lateral extension of the common busbars represents a first section of a respective shunt line. A first shunt line section between a node and the parallel resonator of a shunt line comprises a section that is broader than the common busbar, the broadened section extending over the width of the parallel resonator. The first reflector of the parallel resonator that faces the laterally adjacent series resonator is formed from the broadened section.

Embodiments of a Surface Acoustic Wave (SAW) device, or filter, and methods of fabrication thereof are disclosed. In some embodiments, the SAW filter comprises a piezoelectric substrate and an Interdigitated Transducer (IDT) on a surface of the piezoelectric substrate. The IDT includes multiple fingers, each comprising a metal stack. The SAW filter further includes a cap layer on a surface of the IDT opposite the piezoelectric substrate and on areas of the surface of the piezoelectric substrate exposed by the IDT. The cap layer has a thickness in a range of and including 10 to 500 Angstroms and a high electrical resistivity (and thus a low electrical conductivity). For instance, in some embodiments, the electrical resistivity of the cap layer is greater than 10 kilo-ohm meters (K.Math.m). The SAW filter further includes an oxide overcoat layer on a surface of the cap layer opposite the IDT and the piezoelectric substrate.

An acoustic wave device includes a dielectric film covering an IDT electrode. The IDT electrode includes first and second edge regions and first and second high acoustic velocity regions. The first and second edge regions are low acoustic velocity regions. The first and second high acoustic velocity regions are on outer sides of an intersecting width region where first and second electrode fingers are adjacent to each other in an acoustic wave propagation direction. A thickness of the dielectric film on the first and second edge regions is greater than that of the dielectric film on the first and second high acoustic velocity regions.

In a method for manufacturing a piezoelectric device, a silicon oxide film is deposited by sputtering on a surface of a single-crystal piezoelectric substrate closer to an ion-implanted region, and a silicon nitride film is deposited by sputtering on a surface of the dielectric film opposite to a side thereof closer to the single-crystal piezoelectric substrate. The silicon oxide film has a composition that is deficient in oxygen relative to the stoichiometric composition. Accordingly, little oxygen is supplied from the silicon oxide film to the piezoelectric thin film during heat treatment of a piezoelectric device. This prevents oxidation of the piezoelectric thin film and therefore formation of an oxide layer with high resistivity in the piezoelectric thin film. As a result, a pyroelectric charge generated in the piezoelectric thin film can flow to the silicon oxide film.

Aspects herein include minimizing hot spots on a filter chip by creating thermal radiators using mechano-acoustic structures and connection circuitry. A gradual increase of metal to wafer relation provides better heat dissipation and heat sinking. Shunt lines of a ladder type arrangement of SAW resonators comprise a broadened section. Resonators that are subsequent to each other in the series signal line are connected via a common busbar extending over a length of subsequent series resonators. A lateral extension of the common busbars represents a first section of a respective shunt line. A first shunt line section between a node and the parallel resonator of a shunt line comprises a section that is broader than the common busbar, the broadened section extending over the width of the parallel resonator. The first reflector of the parallel resonator that faces the laterally adjacent series resonator is formed from the broadened section.

A method for blackening at least one wafer includes: (a) performing a reduction treatment on the at least one wafer; and (b) illuminating the at least one wafer with an ultraviolet light. The at least one wafer after the illumination of the UV light has a blackening uniformity value (DE value) smaller than 0.6, and a chromatic value (L value) smaller than 54. In addition, a blackened wafer made from the method is also provided.