Bulk-acoustic wave resonator

Abstract

A bulk-acoustic wave resonator comprises a substrate, a resonant portion comprising a first electrode, a piezoelectric layer, and a second electrode sequentially stacked on the substrate, and further comprising a center portion and an extension portion that is disposed along a periphery of the center portion, and an insertion layer that is disposed in the extension portion between the first electrode and the piezoelectric layer, and the insertion layer is formed of an aluminum alloy containing scandium (Sc).

What is claimed is: 
     
         1 . A bulk-acoustic wave resonator, comprising:
 a substrate;   a resonant portion, comprising a first electrode, a piezoelectric layer, and a second electrode sequentially stacked on the substrate, and further comprising a center portion, and an extension portion that is disposed along a periphery of the center portion;   an insertion layer that is disposed in the extension portion between the first electrode and the piezoelectric layer; and   a seed layer formed of a metal material, and disposed between the first electrode and the insertion layer.   
     
     
         2 . The bulk-acoustic wave resonator of  claim 1 , wherein the seed layer is formed of a metal having a hexagonal close packed (HCP) crystal structure. 
     
     
         3 . The bulk-acoustic wave resonator of  claim 2 , wherein the seed layer is formed of one of a titanium (Ti) element and a ruthenium (Ru) material. 
     
     
         4 . The bulk-acoustic wave resonator of  claim 2 , wherein the insertion layer has a face-centered cubic (FCC) crystal structure. 
     
     
         5 . The bulk-acoustic wave resonator of  claim 1 , wherein the piezoelectric layer is formed of one of aluminum nitride (AlN) and doped aluminum nitride that contains a rare earth metal. 
     
     
         6 . The bulk-acoustic wave resonator of  claim 5 , wherein the rare earth metal is formed of a metal containing one of scandium, erbium, yttrium, and lanthanum, or combinations thereof. 
     
     
         7 . The bulk-acoustic wave resonator of  claim 1 , wherein the insertion layer contains scandium (Sc), and
 the content of the scandium (Sc) is 0.1 at % to 5 at %.   
     
     
         8 . The bulk-acoustic wave resonator of  claim 1 , wherein the insertion layer has a thickness of 100 Å or more, and has a thickness less than a thickness of the piezoelectric layer. 
     
     
         9 . The bulk-acoustic wave resonator of  claim 1 , wherein the insertion layer has an inclined surface that has a thickness that increases as a distance of the inclined surface increases from the center portion, and
 the piezoelectric layer comprises an inclined portion that is disposed on the inclined surface.   
     
     
         10 . The bulk-acoustic wave resonator of  claim 9 , wherein the second electrode is provided with at least a portion thereof disposed on the inclined surface of the inclined portion of the piezoelectric layer. 
     
     
         11 . The bulk-acoustic wave resonator of  claim 1 , further comprising:
 a protective layer stacked on the second electrode.   
     
     
         12 . The bulk-acoustic wave resonator of  claim 1 , wherein the piezoelectric layer comprises a piezoelectric portion disposed in the center portion, and a bent portion disposed in the extension portion, and extended from the piezoelectric portion to be inclined along a shape of the insertion layer. 
     
     
         13 . The bulk-acoustic wave resonator of  claim 1 , further comprising:
 a second metal layer connected to the second electrode and separated from the first electrode; and   a first metal layer connected to the insertion layer and separated from the second electrode,   wherein a portion of the insertion layer is disposed between a lower surface of the first metal layer and an upper surface of the seed layer.   
     
     
         14 . The bulk-acoustic wave resonator of  claim 13 , wherein the insertion layer is configured to be formed with an aluminum alloy containing scandium in a range of 0.1 at % to 5 at %, and
 the seed layer is formed of one of a titanium (Ti) element and a ruthenium (Ru) material.   
     
     
         15 . The bulk-acoustic wave resonator of  claim 14 , wherein the seed layer is formed of a metal having a hexagonal close packed (HCP) crystal structure, and
 the insertion layer has a face-centered cubic (FCC) crystal structure.   
     
     
         16 . The bulk-acoustic wave resonator of  claim 15 , wherein the insertion layer has an inclined surface that has a thickness that increases as a distance of the inclined surface increases from the center portion,
 the piezoelectric layer comprises an inclined portion that is disposed on the inclined surface, and   the second electrode is provided with at least a portion thereof disposed on the inclined surface of the inclined portion of the piezoelectric layer.   
     
     
         17 . The bulk-acoustic wave resonator of  claim 1 , further comprising:
 a second metal layer connected to the second electrode and separated from the first electrode; and   a first metal layer connected to the first electrode and separated from the second electrode,   wherein the insertion layer is separated from the first and second metal layers.   
     
     
         18 . The bulk-acoustic wave resonator of  claim 17 , wherein the insertion layer is configured to be formed with an aluminum alloy containing scandium in a range of 0.1 at % to 5 at %, and
 the seed layer is formed of one of a titanium (Ti) element and a ruthenium (Ru) material.   
     
     
         19 . The bulk-acoustic wave resonator of  claim 18 , wherein the seed layer is formed of a metal having a hexagonal close packed (HCP) crystal structure, and
 the insertion layer has a face-centered cubic (FCC) crystal structure.   
     
     
         20 . The bulk-acoustic wave resonator of  claim 19 , wherein the insertion layer has an inclined surface that has a thickness that increases as a distance of the inclined surface increases from the center portion,
 the piezoelectric layer comprises an inclined portion that is disposed on the inclined surface, and   the second electrode is provided with at least a portion thereof disposed on the inclined surface of the inclined portion of the piezoelectric layer.