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AssigneeNXP B.V.
InventorsRobert Frederick Milsom, Frederik Willem Maurits Vanhelmont, Andreas Bernardus Maria Jansman, Jaap Ruigrok, Hans-Peter Loebl
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A thin-film bulk acoustic wave (BAW) resonator, such as SBAR or FBAR, for use in RF selectivity filters operating at frequencies of the order of 1 GHz. The BAW resonator comprises a piezoelectric layer (14) having first and second surfaces on opposing sides, a first electrode (16) extending over the first surface, and a second electrode (12) extending over the second surface, the extent of the area of overlap (R1) of the first and second electrodes determining the region of excitation of the fundamental thickness extensional (TE) mode of the resonator. The insertion loss to the resonator is reduced by providing a dielectric material (18) in the same layer as the first electrode (16) and surrounding that electrode. The material constituting the dielectric material (18) has a different mass, typically between 5% and 15%, from the material comprising the first electrode (16) it surrounds. The mass of the dielectric material (18) can be lower or higher than the mass of the first electrode (16). Planarisation of the dielectric material (18) enhances the performance of the device.
A bulk acoustic wave (BAW) resonator comprising first and second layers and an intervening piezoelectric layer, the first and second layers comprising respective first and second overlapping regions of metal for use as electrodes, the first layer further comprising a region of dielectric material external to the region of the overlap and at least partially surrounding the first metal region, wherein the dielectric material has a mass different from the mass of the first metal region;
A method of reducing insertion loss in the passband of a filter comprising a plurality of bulk acoustic wave (BAW) resonators, each of the BAW resonators comprising first and second layers and an intervening piezoelectric layer, the first and second layers comprising respective first and second overlapping regions of metal for use as electrodes, the method comprising forming in the first layer a region of dielectric material external to the region of the overlap and at least partially surrounding the first metal region, wherein the dielectric material has a mass different from the mass of the first metal region;
Dependencies are inferred from the claim text.