Acoustic wave device with multi-layer interdigital transducer electrode having layer of more dense material over layer of less dense material
An acoustic wave device includes a piezoelectric layer and an interdigital transducer electrode disposed over the piezoelectric layer. The interdigital transducer electrode is thicker in a center region of the interdigital transducer electrode than in a gap region of the interdigital transducer electrode to thereby reduce a mass loading of the interdigital transducer electrode in the gap region. The interdigital transducer electrode has a layer of more dense material disposed of a layer of less dense material.
1 . An acoustic wave device comprising:
a piezoelectric layer; and
an interdigital transducer electrode including a first layer disposed over the piezoelectric layer and a second layer disposed over the first layer, the second layer being a top layer of the interdigital transducer electrode and of a more dense material than the first layer, a thickness of the second layer in a gap region of the interdigital transducer electrode being smaller than a thickness of the second layer in a center region of the interdigital transducer electrode to thereby reduce a mass loading of the interdigital transducer electrode in the gap region.
2 . The acoustic wave device of claim 1 wherein there is no second layer in the gap region.
3 . The acoustic wave device of claim 1 wherein the interdigital transducer electrode includes a first bus bar, first fingers extending from the first bus bar, a second bus bar, and second fingers extending from the second bus bar.
4 . The acoustic wave device of claim 3 wherein an end region of the first fingers is spaced apart from the second bus bar to define the gap region therebetween.
5 . The acoustic wave device of claim 3 wherein the first and second bus bars each include the first and second layers.
6 . The acoustic wave device of claim 1 further comprising a temperature compensation layer disposed over the interdigital transducer electrode.
7 . The acoustic wave device of claim 6 further comprising a passivation layer disposed over the temperature compensation layer.
8 . The acoustic wave device of claim 1 further comprising a pair of mass loading strips disposed over the interdigital transducer electrode, an edge of the mass loading strips aligned with end regions of the interdigital transducer electrode.
9 . The acoustic wave device of claim 1 wherein the piezoelectric layer is a part of a multilayer piezoelectric substrate, the multilayer piezoelectric substrate additionally including a support substrate underlying the piezoelectric layer.
10 . A radio frequency module comprising:
a package substrate;
an acoustic wave filter configured to filter a radiofrequency signal, the acoustic wave filter including an acoustic wave resonator that includes a piezoelectric layer and an interdigital transducer electrode including a first layer disposed over the piezoelectric layer and a second layer disposed over the first layer, the second layer being a top layer of the interdigital transducer electrode and of a more dense material than the first layer, a thickness of the second layer in a gap region of the interdigital transducer electrode being smaller than a thickness of the second layer in a center region of the interdigital transducer electrode to thereby reduce a mass loading of the interdigital transducer electrode in the gap region; and
additional circuitry, the acoustic wave filter and additional circuitry disposed on the package substrate.
11 . The radio frequency module of claim 10 wherein there is no second layer in the gap region.
12 . The radio frequency module of claim 10 further comprising a temperature compensation layer disposed over the interdigital transducer electrode.
13 . The radio frequency module of claim 12 further comprising a passivation layer disposed over the temperature compensation layer.
14 . The radio frequency module of claim 10 further comprising a pair of mass loading strips disposed over the interdigital transducer electrode, an edge of the mass loading strips aligned with end regions of interdigital transducer electrode.
15 . The radio frequency module of claim 10 wherein the piezoelectric layer is a part of a multilayer piezoelectric substrate, the multilayer piezoelectric substrate additionally including a support substrate underlying the piezoelectric layer.
16 . A wireless communication device comprising:
an antenna; and
a front end module including an acoustic wave filter configured to filter a radio frequency signal associated with the antenna, the acoustic wave filter including one or more acoustic wave devices that each include a piezoelectric layer and an interdigital transducer electrode including a first layer disposed over the piezoelectric layer and a second layer disposed over the first layer, the second layer being a top layer of the interdigital transducer electrode and of a more dense material than the first layer, a thickness of the second layer in a gap region of the interdigital transducer electrode being smaller than a thickness of the second layer in a center region of the interdigital transducer electrode to thereby reduce a mass loading of the interdigital transducer electrode in the gap region.
17 . The wireless communication device of claim 16 wherein there is no second layer in the gap region.
18 . The wireless communication device of claim 16 further comprising a temperature compensation layer disposed over the interdigital transducer electrode.
19 . The wireless communication device of claim 18 further comprising a passivation layer disposed over the temperature compensation layer.
20 . The wireless communication device of claim 16 further comprising a pair of mass loading strips disposed over the interdigital transducer electrode, an edge of the mass loading strips aligned with end regions of the interdigital transducer electrode.