Surface acoustic wave device having a small acoustic velocity distribution and method of producing the same
AssigneeMurata Manufacturing Co., Ltd.
InventorsTakeshi Nakao, Michio Kadota
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Abstract
A surface acoustic wave device includes a piezoelectric substrate, and at least one interdigital transducer disposed thereon which is made of a metal or an alloy that is heavier than Al. The acoustic velocity distribution of surface acoustic waves in the extending direction of electrode fingers of the at least one interdigital transducer is not greater than about 276 ppm, thereby effectively suppressing considerable ripples, which are noticeably found in the group delay time characteristic in particular, within the bandpass area.
Claims20
A surface acoustic wave device comprising:
- a piezoelectric substrate;
- and
- at least one interdigital transducer having a plurality of electrode fingers extending substantially parallel to each other, said at least one interdigital transducer being disposed on said piezoelectric substrate and made of a metal heavier than Al or an alloy heavier than Al;
- wherein the acoustic velocity distribution of surface acoustic waves in the extending direction of the electrode fingers of said at least one interdigital transducer is not greater than about 276 ppm.
A method of manufacturing a surface acoustic wave device, said surface acoustic wave device including a piezoelectric substrate, and at least one interdigital transducer having a plurality of electrode fingers extending substantially parallel to each other, the interdigital transducer being formed on the piezoelectric substrate and made of a metal heavier than Al or an alloy heavier than Al, wherein the acoustic velocity distribution of surface acoustic waves in the extending direction of the electrode fingers of the interdigital transducer is not greater than about 276 ppm, said method comprising the steps of:
- preparing a wafer having a plurality of surface acoustic wave devices formed thereon;
- measuring the acoustic velocity distribution of the surface acoustic waves in the extending direction of the electrode fingers in each of the surface acoustic wave devices formed on the wafer;
- and
- cutting out of the wafer a surface acoustic wave device in which the acoustic velocity distribution of the surface waves is not greater than about 276 ppm.
A method of producing a surface acoustic wave device, said surface acoustic wave device including a piezoelectric substrate, and at least one interdigital transducer having a plurality of electrode fingers extending substantially parallel to each other, the interdigital transducer being formed on the piezoelectric substrate and made of a metal heavier than Al or an alloy heavier than Al, wherein the acoustic velocity distribution of surface acoustic waves in the extending direction of the electrode fingers of the interdigital transducer is not greater than about 276 ppm, said method comprising the steps of:
- depositing a metal film on the piezoelectric substrate to form the interdigital transducer;
- and
- patterning the metal film via photolithography,
- wherein the depositing step and the patterning step are performed such that the effect of the film thickness profile in the extending direction of the electrode fingers on the acoustic velocity distribution is cancelled out by the effect of the film width profile in the extending direction of the electrode fingers on the acoustic velocity distribution.
Dependencies are inferred from the claim text.