Multilayer structure for an elastic wave device

Abstract

The invention relates to a multilayer structure configured for an elastic wave device 11, in particular guided or quasi-guided with losses less than 5 mdB / λ, the elastic wave device comprising at least one transducer 19 and operating with an elastic wave having a shear wavelength λ and preferably with a frequency less than 1 GHz, in particular with a frequency between 500 MHz and 1 GHz, the multilayer structure comprising: a piezoelectric layer 3, a dielectric layer 5, and a base substrate 7, the piezoelectric layer 3 being lithium tantalate LiTaO3 (LTO), the dielectric layer 5 being silicon dioxide (SiO2), and the base substrate 7 being a silicon substrate, in particular silicon Si(100) or Si(111), characterized in that the piezoelectric layer 3 has an orientation (YXl) / θ with θ between 30° and 50°, in particular θ between 42° and 50°, even more preferably θ = 30°, θ = 36°,of θ = 42° or θ = 50° according to the IEEE 1949 std-176 standard definition, and the product f×hLTO of the frequency f and the thickness hLTO of the dielectric layer 3 is preferably between 0.7 GHz.µm and 1.5 GHz.µm, preferably between 1 GHz.µm and 1.3 GHz.µm, and hSiO2 is less than 250 nm, preferably less than 150 nm, hSiO2 being the thickness of the dielectric layer. Fig. 1,

Claims

greater than 750 nm or equal to or greater than 1 pm and / or in which hSiO2 is equal to or greater than 600 nm, in particular equal to or greater than 1 pm.

4. The multilayer structure according to any one of claims 1 to 3 wherein a trapping layer, in particular a polycrystalline silicon layer, is intercalated between the dielectric layer (5) and the base substrate (7) with in particular a thickness between 500 nm and 1 pm.

5. The multilayer structure according to any one of claims 1 to 4, wherein the resistivity of the base substrate (7) is greater than 2 kQ.cm and advantageously greater than 4 kQ.cm.

6. A method for manufacturing a substrate according to any one of claims 1 to 5 comprising the steps of: - implanting ions into a donor substrate comprising a piezoelectric layer of lithium tantalate to create a zone of embrittlement within the lithium tantalate layer, - assembling the donor substrate with the main face of the lithium tantalate layer with a base substrate via a dielectric layer, and - detaching the piezoelectric layer at the zone of embrittlement from the rest of the donor substrate.

7. A manufacturing method according to claim 6, wherein the thickness of the transferred layer is greater than or equal to 600 nm, preferably greater than or equal to 750 nm.

8. A manufacturing method according to claim 6 or 7, wherein the thickness of the transferred layer is less than or equal to 1 pm.

9. A manufacturing method according to any one of claims 6 to 8, the detachment step is followed by epitaxial growth of a piezoelectric layer on the transferred layer.

10. Surface and / or volume elastic wave device, in particular a filter or resonator, comprising a multilayer structure according to any one of claims 1 to 5.

11. Acoustic device comprising at least two elastic wave devices according to claim 10 which operate at different wavelengths, in particular elastic shear waves in a wavelength range from 4 pm to 8 pm and whose transducers of at least two elastic wave devices are made on the same multilayer structure. [Fig. 1] [Fig. 2] [Fig. 3] V* tR!C. — TCP, ^£>**88«« ~ » ■'*■■ TG^s ...... ■ - ........... TOPv .— - ~ V^ÎSSnm ïCFs tw / .-225nffl ------ [Fig. 4] ..... ^^«ygnin — ■ • '4 îg^itggnïn .----- k / .g;a,«125nm-- V - - - V W%«225nm--

Images