Bulk acoustic wave resonator and filter including the same
A bulk acoustic wave resonator includes a substrate, a first electrode and a second electrode formed on the substrate, and a piezoelectric layer provided between the first electrode and the second electrode. Either one or both of the first electrode and the second electrode include a molybdenum-tungsten alloy having a weight ratio of molybdenum to tungsten in a range of 3:1 to 1:3.
1. A bulk acoustic wave resonator comprising:
a substrate;
a first electrode and a second electrode formed on the substrate;
a seed layer formed between the substrate and at least one of the first and second electrodes, wherein the seed layer has a hexagonal close packing (HCP) structure, and comprises an alloy containing Ti; and
a piezoelectric layer disposed between the first electrode and the second electrode,
wherein either one or both of the first electrode and the second electrode comprise a molybdenum-tungsten alloy, and the seed layer is disposed in an active region of the bulk acoustic wave resonator,
wherein the weight ratio between the molybdenum and the tungsten in the molybdenum-tungsten alloy is about 3:1.
2. The bulk acoustic wave resonator of claim 1 , wherein the seed layer comprises TiW.
3. The bulk acoustic wave resonator of claim 1 , wherein the molybdenum-tungsten alloy has a 110 crystal face orientation.
4. The bulk acoustic wave resonator of claim 1 , wherein the piezoelectric layer is formed of aluminum nitride.
5. The bulk acoustic wave resonator of claim 1 , wherein the piezoelectric layer includes a rare earth metal or transition metal.
6. The bulk acoustic wave resonator of claim 1 , wherein the seed layer is formed between the substrate and the first electrode.
7. The bulk acoustic wave resonator of claim 1 , wherein the first electrode is bent to conform to an air cavity.