Piezoresonator

• US 6,534,900 B2
• Filed: 02/20/2001
• Issued: 03/18/2003
• Est. Priority Date: 02/18/2000
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Infineon Technologies AG
• Inventors: Aigner, Robert, Marksteiner, Stephan
• Primary Examiner(s): Dougherty, Thomas M.
• Application Number:
  US09/789,342
• Publication Number:
  US 20010017504A1
• Time in Patent Office: 756 Days
• Field of Search: 310/326, 310/327, 310/331, 310/366
• US Class Current: 310/326
• CPC Class Codes: H03H 2009/02196 operating on the FBAR element, e.g. by direct application of a tuning DC voltage
• CPC Class Codes: H03H 2009/02204 operating on an additional circuit element, e.g. applying a tuning DC voltage to a passive circuit element connected to the resonator
• CPC Class Codes: H03H 9/175 Acoustic mirrors

Abstract

A thin film piezoresonator, which can be tuned over a wide range of RF frequencies, includes a piezo layer between a first electrode layer and a second electrode layer. An electroactive layer of an electrostrictive material, which experiences a mechanical deformation when an electrical voltage is applied, is disposed between a third electrode layer and the second electrode layer.

Claims

1. A thin film piezoresonator, comprising:

a first electrode layer;

a second electrode layer;

a third electrode layer;

a piezo layer disposed between said first and second electrode layers;

an electroactive layer disposed between said second and third electrode layers;

said second and third electrode layers and said electroactive layer defining a layer stack, a layer plane, and a vertical direction along a line substantially perpendicular to said layer plane;

said electroactive layer being formed of a material contracting said electroactive layer in said vertical direction when a D.C. voltage is applied between said second electrode layer and said third electrode layer to change a resonance frequency of said layer stack for tuning the piezoresonator; and

a series of layers formed alternately of a material of low acoustic impedance and a material of high acoustic impedance, said piezo layer and said electroactive layer disposed on said series of layers.

2. The piezoresonator according to claim 1, wherein said piezo layer is a material selected from the group consisting of AlN, ZnO and a PZT ceramic (PbZrTi).

3. The piezoresonator according to claim 1, wherein said electroactive layer is a further layer of low acoustic impedance, and said third electrode layer is a further layer of high acoustic impedance.

4. The piezoresonator according to claim 1, wherein said piezo layer is a material selected from the group consisting of AlN, ZnO and a PZT ceramic (PbZrTi).

5. The piezoresonator according to claim 1, wherein said electroactive layer is a polymer.

6. A thin film piezoresonator, comprising:

a first electrode layer;

a second electrode layer;

a third electrode layer;

a piezo layer disposed between said first and second electrode layers;

an at least predominantly electrostrictive electro-active material layer disposed between said second and third electrode layers;

said second and third electrode layers and said at least predominantly electrostrictive electro-active material layer defining a layer stack, a layer plane, and a vertical direction along a line substantially perpendicular to said layer plane; and

said at least predominantly electrostrictive electro-active material layer being formed of a material contracting said at least predominantly electrostrictive electro-active material layer in said vertical direction when a D.C. voltage is applied between said second electrode layer and said third electrode layer to change a resonance frequency of said layer stack for tuning the piezoresonator.

7. The piezoresonator according to claim 6, wherein said piezo layer is a material selected from the group consisting of AlN, ZnO and a PZT ceramic (PbZrTi).

8. The piezoresonator according to claim 6, including a series of layers formed alternately of a material of low acoustic impedance and a material of high acoustic impedance, said piezo layer and said at least predominantly electrostrictive electro-active material layer disposed on said series of layers.

9. The piezoresonator according to claim 8, wherein said electrostrictive layer is a further layer of low acoustic impedance, and said third electrode layer is a further layer of high acoustic impedance.

10. The piezoresonator according to claim 6, wherein said at least predominantly electrostrictive electro-active material layer is lead magnesium niobate.

11. The piezoresonator according to claim 6, wherein said at least predominantly electrostrictive electro-active material layer is a polymer.

12. A thin film piezoresonator, comprising:

a first electrode layer;

a second electrode layer;

a third electrode layer;

a piezo layer disposed between said first and second electrode layers;

an electroactive layer being formed of lead magnesium niobate disposed between said second and third electrode layers;

said second and third electrode layers and said electroactive layer defining a layer stack, a layer plane, and a vertical direction along a line substantially perpendicular to said layer plane; and

said electroactive layer being formed of a material contracting said electroactive layer in said vertical direction when a D.C. voltage is applied between said second electrode layer and said third electrode layer to change a resonance frequency of said layer stack for tuning the piezoresonator.

13. The piezoresonator according to claim 12, including a series of layers formed alternately of a material of low acoustic impedance and a material of high acoustic impedance, said piezo layer and said electroactive layer disposed on said series of layers.

14. The piezoresonator according to claim 13, wherein said electroactive layer is a further layer of low acoustic impedance, and said third electrode layer is a further layer of high acoustic impedance.