Elastic wave device, high-frequency front-end circuit, and communication device
AssigneeMurata Manufacturing Co., Ltd.
InventorHideki IWAMOTO
Life of this patent
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Abstract
An elastic wave device includes a support substrate made of silicon, a piezoelectric film disposed directly or indirectly on the support substrate, and an interdigital transducer electrode disposed on one surface of the piezoelectric film. A higher-order mode acoustic velocity of propagation through the piezoelectric film is equal or substantially equal to an acoustic velocity Vsi=(V1)1/2 of propagation through silicon or higher than the acoustic velocity Vsi, where Vsi is specified by V1 among solutions V1, V2, and V3 with respect to x derived from Ax3+Bx2+Cx+D=0.
Claims20
An elastic wave device comprising:
- a support substrate made of silicon;
- a piezoelectric film disposed directly or indirectly on the support substrate;
- a dielectric film disposed between the support substrate and the piezoelectric film;
- and
- an interdigital transducer electrode disposed on one surface of the piezoelectric film;
- wherein
- the dielectric film is made of silicon oxide,
- a film thickness of the dielectric film is about 0.4λ or less, where a wavelength of an elastic wave, which is determined in accordance with an electrode finger pitch of the interdigital transducer electrode, is denoted as λ,
- a higher-order mode acoustic velocity of propagation through the piezoelectric film is equal or substantially equal to an acoustic velocity Vsi denoted by formula (1) or higher than the acoustic velocity Vsi,
- Vsi=(V1)1/2 (m/sec) formula (1),
- in the formula (1), V1 is a solution to formula (2), wherein
- Ax3+Bx2+Cx+D=0 formula (2),
- in the formula (2), A, B, C, and D are values denoted by formulae (2A) to (2D), respectively, wherein
- A=−ρ3 formula (2A),
- B=ρ2(L11+L22+L33) formula (2B),
- C=ρ(L212+L232+L312−L11·L33−L22·L33−L11·L22) formula (2C),
- D=2·L21·L23·L31+L11·L22·L33−L312·L22−L11·L232−L212·L33 formula (2D),
- in each of the formula (2A), the formula (2B), the formula (2C), and the formula (2D), p represents a density (g/cm3) of silicon and L11, L22, L33, L21, L31, and L23 are values denoted by formulae (3A) to (3F), respectively, wherein
- L11=c11·a12+c44·a22+c44·a32 formula (3A)
- L22=c44·a12+c11·a22+c44·a32 formula (3B)
- L33=c44·a12+c44·a22+c11·a32 formula (3C)
- L21=(c12+c44)·a2·a1 formula (3D)
- L31=(c12+c44)·a1·a3 formula (3E)
- L23=(c44+c12)·a3·a2 formula (3F)
- in the formulae (3A) to (3F), each of c11, c12, and c44 is an elastic constant (N/m2) of silicon, and
- a1, a2, and a3 are values denoted by formulae (4A) to (4C), respectively, wherein
- a1=cos(Φ)·cos(ψ)−sin(Φ)·cos(θ)·sin(ψ) formula (4A),
- a2=sin(Φ)·cos(ψ)+cos(Φ)·cos(θ)·sin(ψ) formula (4B),
- a3=sin(θ)·sin(ψ) formula (4C),
- in the formulae (4A) to (4C), Φ, θ, and ψ represent Φ, θ, and ψ in a crystal orientation (Φ,θ,ψ) of silicon.
An elastic wave device comprising:
- a support substrate made of silicon;
- a piezoelectric film disposed on the support substrate;
- a dielectric film disposed between the support substrate and the piezoelectric film;
- and
- an interdigital transducer electrode disposed on one surface of the piezoelectric film;
- wherein
- the piezoelectric film is made of LiTaO3,
- a film thickness of the piezoelectric film is within a range of about 0.05λ or more and about 3.5λ or less, where a wavelength of an elastic wave, which is determined in accordance with an electrode finger pitch of the interdigital transducer electrode, is denoted as λ,
- the dielectric film is made of silicon oxide, and
- a film thickness of the dielectric film is within a range of 0.6λ or more and about 1.2λ or less.
Dependencies are inferred from the claim text.