Method of isolation for acoustic resonator device
View Patent ↗A method of isolating piezoelectric thin film acoustic resonator devices to prevent laterally propagating waves generated by the device from leaving the device and/or interfering with adjacent devices or systems. Specifically, this isolation technique involves the manipulation or isolation of the piezoelectric material layer between the acoustic resonator devices, in an effort to limit the amount of acoustic energy which propagates in a lateral direction away from the device. In one aspect, at least a portion of the piezoelectric material not involved in signal transmission by transduction between RF and acoustic energy is removed from the device. In another aspect, the growth a piezoelectric material is limited to certain regions during fabrication of the device. In a further aspect, the crystal orientation of the piezoelectric material is disrupted or altered during device fabrication so as to form regions having excellent piezoelectric properties and regions exhibiting poor piezoelectric characteristics.
1. A method of producing an acoustic resonator device formed by a piezoelectric material interposed between two conductors on a substrate comprising:
depositing a first metal film directly on a substrate;
patterning said first metal film to form an electrode region;
forming a layer of piezoelectric material on the patterned first metal film thereby acoustically isolating said piezoelectric material to reduce the amount of acoustic energy which propagates in a lateral direction away from the device wherein said isolating is accomplished by limiting growth of oriented piezoelectric material to the patterned electrode regions on the substrate during fabrication, thereby forming isolated islands of said piezoelectric material which are subsequently interconnected, thereby limiting the creation or propagation of energy in lateral modes wherein said step of isolating further includes disrupting crystal orientation of the piezoelectric material during growth of the piezoelectric material on the substrate by selectively altering the surface of the substrate prior to deposition of the piezoelectric material thereon, so as to form regions of piezoelectric material where transduction between acoustic and RF energy is enhanced and regions where this transduction is degraded.
2. The method of claim 1 wherein the isolated regions are formed by a masking process.
3. A method of isolating an acoustic resonator device having a piezoelectric material interposed between two conductors on a substrate, comprising:
disrupting crystal orientation of the piezoelectric material during growth of the piezoelectric material on the substrate by selectively altering the surface of the substrate prior to deposition of the piezoelectric material thereon, so as to form regions of oriented piezoelectric material where signal transmission is enhanced and regions of piezoelectric material having disrupted crystal orientation where signal transmission is degraded wherein the selective surface alteration is performed by a method selected from the group consisting of: surface roughening and deposition of a material where each of those selective surface alterations do not support oriented piezoelectric crystal growth.