Guided Acoustic Wave Resonant Device and Method for Producing the Device

• US 20100327995A1
• Filed: 06/30/2010
• Published: 12/30/2010
• Est. Priority Date: 06/30/2009
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission), Stmicroelectronics France (STMicroelectronics NV)
• Original Assignee: Centre National De La Recherche Scientifique, Energies Alternatives Commissariat A L'Energie Atomique et AUX, STMicroelectronics SA (STMicroelectronics NV)
• Inventors: Kone, Issiaka, Reinhardt, Alexandre
• Granted Patent: US 8,692,630 B2
• Time in Patent Office: Days
• US Class Current: 333/195
• CPC Class Codes: H03H 3/04 for obtaining desired frequency or temperature coefficient
• CPC Class Codes: H03H 9/02228 Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer
• CPC Class Codes: H03H 9/589 Acoustic mirrors

Abstract

A guided acoustic wave resonant device is provided. The device comprises at least two filters (F₁, . . . , F_i, . . . , F_N), each filter comprising at least two acoustic wave resonators (R₁₁- R₁₂, . . . , R_i1-R_i2, . . . , R_N1-R_N2), each filter having a useful frequency band (BF₁, . . . , BF_i, . . . , BF_N) centred on a central frequency (f₁, . . . , f_i, . . . , f_N), each resonator comprising at least one suite of inter-digitated upper electrodes exhibiting a periodic structure of period (Λ_ij) and a layer of piezoelectric material, each resonator having a coupling coefficient (k²₁, k²₂, . . . , k²_n) and a resonant frequency (fr₁, . . . , f_r2, . . . , f_N), wherein at least one of the resonators comprises a differentiation layer (CDf_i) making it possible in combination with the period of the inter-digitated electrodes to modify the coupling coefficient of the said resonator, the useful band and the central frequency being determined by the resonant frequencies and the coupling coefficients of the resonators which are adapted so as to have a determined useful bandwidth.

Claims

1. A guided acoustic wave resonant device, comprising:

at least two filters (F₁, . . . , F_i, . . . , F_N), each filter comprising at least two acoustic wave resonators (R₁₁-R₁₂, . . . , R_i1-R_i2, . . . , R_N1-R_N2), each filter having a useful frequency band (BF₁, . . . , BF_i, . . . , BF_N) centred on a central frequency (f₁, . . . , f_i, . . . , f_N), each resonator comprising at least one suite of inter-digitated upper electrodes exhibiting a periodic structure of period (Λ

_ij) and a layer of piezoelectric material, each resonator having a coupling coefficient (k²₁, k²₂, k²_n) and a resonant frequency (fr₁, . . . , f_r2, . . . , f_N),

wherein at least one of the resonators comprises a differentiation layer (CDf_i) making it possible in combination with the period of the inter-digitated electrodes to modify the coupling coefficient of the said resonator, the useful band and the central frequency being determined by the resonant frequencies and the coupling coefficients of the resonators which are adapted so as to have a determined useful bandwidth.

2. The device according to claim 1, wherein the differentiation layer (CDf_i) of the resonator furthermore makes it possible in combination with the period of the inter-digitated electrodes to modify the resonant frequency.

3. The device according to claim 1, wherein the differentiation layer is positioned on the surface of the resonator.

4. The device according to claim 1, wherein the differentiation layer is positioned between the resonator and a substrate.

5. The device according to claim 4, wherein the resonators are produced on the surface of a common stack of layers ensuring a Bragg mirror function, the said Bragg mirror being on the surface of a substrate.

6. The device according to claim 5, wherein the differentiation layers belong to one of the constituent layers of the stack of the Bragg mirror.

7. The device according to claim 1, wherein the differentiation layers comprise porous elements making it possible to modify the acoustic characteristics thereof.

8. The device according to claim 1, wherein the differentiation layers comprise structures exhibiting sub-micronic patterns making it possible to modify the acoustic characteristics thereof.

9. The device according to claim 1, wherein at least one part of the resonators comprises several differentiation layers.

10. The device according to claim 1, wherein the resonators furthermore comprise a so-called lower electrode.

11. The device according to claim 10, wherein the so-called lower electrode is a continuous electrode.

12. The device according to claim 10, wherein the lower electrode is a comb of inter-digitated electrodes.

13. The device according to claim 1, wherein the device comprises a membrane structure coupled to the resonators making it possible to create a gap capable of confining the acoustic waves in the piezoelectric material.