Acoustic wave guide device and method for minimizing trimming effects and piston mode instabilities
First Claim
1. An acoustic wave device comprising:
- a piezoelectric substrate having a surface for supporting an acoustic wave;
an interdigital transducer carried on the surface of the piezoelectric substrate,wherein each of a plurality of electrodes of the transducer has a first end electrically connected to at least one of first and second busbars and an opposing second end having an edge spaced from the opposing busbar so as to form a gap between the edge of each electrode and the opposing busbar, the gaps forming a gap region extending longitudinally along the transducer,wherein each electrode is further defined by a first transversely extending portion proximate the busbar and generally contained within the gap region, a second transversely extending portion proximate the edge and defining an edge region extending longitudinally along the transducer, and a third transversely extending portion of the electrode therebetween, the third transversely extending portion defining a transducer center region, anda first dielectric layer covering the transducer for a burying thereof;
a second dielectric layer covering the plurality of electrodes at least within the center and edge regions, the second dielectric layer sufficient for providing a frequency modification to the acoustic wave within the center region; and
a third layer extending within only one of the center region and both edge regions, the third layer sufficient for modifying a velocity of the acoustic wave within at least one of the center region and the edge regions, wherein the velocity in the edge regions is less than the velocity in the center region.
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Accused Products
Abstract
An acoustic wave device operable as a piston mode wave guide includes electrodes forming an interdigital transducer on a surface of the piezoelectric substrate, wherein each of the plurality of electrodes is defined as having a transversely extending center region and transversely opposing edge regions for guiding an acoustic wave longitudinally through the transducer. A Silicon Oxide overcoat covers the transducer and a Silicon Nitride layer covers the Silicon Oxide overcoat within only the center and edge regions. The thickness of the Silicon Nitride layer is sufficient for providing a frequency modification to the acoustic wave within the center region and is optimized with a positioning of a Titanium strip within each of the opposing edge regions. The Titanium strip reduces the acoustic wave velocity within the edge regions with the velocity in the edge regions being less than the wave velocity within the transducer center region.
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Citations
26 Claims
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1. An acoustic wave device comprising:
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a piezoelectric substrate having a surface for supporting an acoustic wave; an interdigital transducer carried on the surface of the piezoelectric substrate, wherein each of a plurality of electrodes of the transducer has a first end electrically connected to at least one of first and second busbars and an opposing second end having an edge spaced from the opposing busbar so as to form a gap between the edge of each electrode and the opposing busbar, the gaps forming a gap region extending longitudinally along the transducer, wherein each electrode is further defined by a first transversely extending portion proximate the busbar and generally contained within the gap region, a second transversely extending portion proximate the edge and defining an edge region extending longitudinally along the transducer, and a third transversely extending portion of the electrode therebetween, the third transversely extending portion defining a transducer center region, and a first dielectric layer covering the transducer for a burying thereof; a second dielectric layer covering the plurality of electrodes at least within the center and edge regions, the second dielectric layer sufficient for providing a frequency modification to the acoustic wave within the center region; and a third layer extending within only one of the center region and both edge regions, the third layer sufficient for modifying a velocity of the acoustic wave within at least one of the center region and the edge regions, wherein the velocity in the edge regions is less than the velocity in the center region. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An acoustic wave device comprising:
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a piezoelectric substrate; a plurality of electrodes forming an interdigital transducer on a surface of the piezoelectric substrate, wherein each of the plurality of electrodes includes a transversely extending center region and transversely opposing edge regions for guiding an acoustic wave longitudinally through the transducer; a first dielectric layer covering the interdigital transducer; a second dielectric layer covering the first dielectric layer at least within the center and edge regions of the electrodes, the second dielectric layer sufficient for providing a frequency modification to the acoustic wave within the center region; and a metal layer extending only within each of the opposing edge regions, the metal layer sufficient for reducing a velocity of the acoustic wave within the edge regions, wherein the velocity in the edge regions is less than the wave velocity within the transducer center region. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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21. A method of manufacturing a surface acoustic wave device for operating as a piston mode wave guide, the method comprising:
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forming a plurality of electrodes into an interdigital transducer on a surface of a piezoelectric substrate, wherein each of the plurality of electrodes includes a transversely extending center region and transversely opposing edge regions for guiding an acoustic wave longitudinally through the interdigital transducer; covering the interdigital transducer with a first dielectric layer to form an overcoat; positioning a third layer within only each of the opposing edge regions, the third layer sufficient for reducing a velocity of the acoustic wave within the edge regions, wherein the velocity in the edge regions is less than the wave velocity within the transducer center region; and covering the first dielectric layer with a second dielectric layer at least over the center and edge regions of the electrodes, the second dielectric layer sufficient for providing a frequency modification to the acoustic wave within the center region. - View Dependent Claims (22, 23, 24, 25, 26)
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Specification