Bulk acoustic resonator
A bulk acoustic resonator includes a first electrode disposed on an upper side of a substrate, a piezoelectric layer disposed on an upper surface of the first electrode, and a second electrode disposed on an upper surface of the piezoelectric layer, wherein an upper surface of at least one of the first electrode and the second electrode has a recess region, wherein a depth of the recess region is D, a width of the recess region is W, and a resonance frequency is F, and ln is a natural logarithm, and wherein [{ln(D*W)}/(−0.59*F)] is [[ln{0.008 (μm) 2 }]/{−0.59*(3.5 GHz)}] or more and [[ln{0.022 (μm) 2 }]/{−0.59*(3.5 GHz)}] or less.
1. A bulk acoustic resonator, comprising:
a first electrode disposed on an upper side of a substrate;
a piezoelectric layer disposed on an upper surface of the first electrode; and
a second electrode disposed on an upper surface of the piezoelectric layer,
wherein an upper surface of at least one of the first electrode and the second electrode has a recess region,
wherein a depth of the recess region is D, a width of the recess region is W, and a resonance frequency is F, and ln is a natural logarithm, and
wherein [{ln(D*W)}/(−0.59*F)] is within a range of [[ln{0.008 (μm) 2 }]/{−0.59*(3.5 GHZ)}] to [[ln{0.022 (μm) 2 }]/{−0.59*(3.5 GHZ)}].
2. The bulk acoustic resonator of claim 1 , wherein D*W is 0.008 (μm) 2 or more and 0.022 (μm) 2 or less.
3. The bulk acoustic resonator of claim 2 , wherein D*W is 0.010 (μm) 2 or more and 0.016 (μm) 2 or less.
4. The bulk acoustic resonator of claim 1 , wherein D is 5 nm or more.
5. The bulk acoustic resonator of claim 1 , wherein D is 1% or more of a thickness of the piezoelectric layer.
6. The bulk acoustic resonator of claim 1 , wherein the recess region is located on an upper surface of the second electrode, and
wherein D is 5/174 times a thickness of the second electrode or more and less than a thickness of the second electrode.
7. The bulk acoustic resonator of claim 1 , wherein each of the first electrode and the second electrode comprises molybdenum (Mo).
8. The bulk acoustic resonator of claim 1 , wherein the upper surface of the piezoelectric layer has a recess region, and
wherein a product of depth and width of the recess region of at least one of the first electrode and the second electrode is less than a product of depth and width of the recess region of the piezoelectric layer.
9. The bulk acoustic resonator of claim 8 , further comprising a protective layer disposed on the upper surface of the second electrode,
wherein an upper surface of the protective layer has a recess region, and
wherein the product of depth and width of the recess region of the piezoelectric layer is less than a product of depth and width of the recess region of the protective layer.
10. The bulk acoustic resonator of claim 9 , further comprising a seed layer disposed on the lower surface of the first electrode,
wherein an upper surface of the seed layer has a recess region, and
wherein the product of a depth and a width of a recess region of the protective layer is less than a product of a depth and a width of the recess region of the seed layer.
11. The bulk acoustic resonator of claim 10 , wherein the seed layer comprises AlN, and
wherein the protective layer comprises SiO 2 .
12. A bulk acoustic resonator, comprising:
a first electrode disposed on an upper side of a substrate;
a piezoelectric layer disposed on an upper surface of the first electrode; and
a second electrode disposed on an upper surface of the piezoelectric layer,
wherein the upper surface of the piezoelectric layer has a recess region,
wherein a depth of the recess region is D, a width of the recess region is W, a resonance frequency is F, and ln is a natural logarithm,
wherein D is 1% or more and less than 100% of a thickness of the piezoelectric layer, and
wherein [{ln(D*W)}/(−0.412*F)] is within a range of [[ln{0.015 (μm) 2 }]/{−0.412*(3.5 GHZ)}] to [[ln{0.03 (μm) 2 }]/{−0.412*(3.5 GHZ)}].
13. The bulk acoustic resonator of claim 12 , wherein D*W is 0.015 (μm) 2 or more and 0.03 (μm) 2 or less.
14. The bulk acoustic resonator of claim 12 , further comprising a protective layer disposed on the upper surface of the second electrode,
wherein an upper surface of the protective layer has a recess region, and
wherein a product of depth and width of the recess region of the piezoelectric layer is less than a product of depth and width of the recess region of the protective layer.
15. The bulk acoustic resonator of claim 12 , further comprising a seed layer disposed on the lower surface of the first electrode,
wherein an upper surface of the seed layer has a recess region, and
wherein a product of depth and width of the recess region of the piezoelectric layer is less than a product of depth and width of the recess region of the seed layer.
16. A bulk acoustic resonator, comprising:
a seed layer;
a first electrode disposed on an upper surface of the seed layer;
a piezoelectric layer disposed on an upper surface of the first electrode;
a second electrode disposed on an upper surface of the piezoelectric layer; and
a protective layer disposed on an upper surface of the second electrode,
wherein upper surfaces of at least two of the seed layer, the first electrode, the piezoelectric layer, the second electrode, and the protective layer have first and second recess regions having different products of depth and width, respectively.
17. The bulk acoustic resonator of claim 16 , wherein the first recess region is located on an upper surface of at least one of the first electrode and the second electrode,
wherein the second recess region is located on an upper surface of at least one of the seed layer, the piezoelectric layer, and the protective layer, and
wherein a product of depth and width of the first recess region is less than a product of depth and width of the second recess region.
18. The bulk acoustic resonator of claim 17 , wherein each of the first electrode and the second electrode comprises molybdenum (Mo), and
wherein at least one of the seed layer, the piezoelectric layer, and the protective layer comprises at least one of AlN, ScAlN, and SiO 2 .
19. The bulk acoustic resonator of claim 16 , wherein the first recess region is located on an upper surface of at least one of the first electrode, the piezoelectric layer, and the second electrode,
wherein the second recess region is located on an upper surface of at least one of the seed layer and the protective layer, and
wherein a product of depth and width of the first recess region is less than a product of depth and width of the second recess region.
20. The bulk acoustic resonator of claim 16 , wherein the first recess region is located on an upper surface of at least one of the first electrode, the piezoelectric layer, the second electrode, and the protective layer,
wherein the second recess region is located on the upper surface of the seed layer, and
wherein a product of depth and width of the first recess region is less than a product of depth and width of the second recess region.
21. The bulk acoustic resonator of claim 20 , wherein the seed layer comprises AlN, and
wherein the protective layer comprises SiO 2 .
22. The bulk acoustic resonator of claim 16 , wherein the first and second recess regions have different depths.