Component operating with bulk acoustic waves and a method for producing the component

• US 6,998,940 B2
• Filed: 01/15/2004
• Issued: 02/14/2006
• Est. Priority Date: 01/15/2003
• Status: Expired due to Term

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Epcos Inc (TDK Corporation)
• Inventors: Metzger, Thomas
• Primary Examiner(s): Summons, Barbara
• Application Number:
  US10/757,841
• Publication Number:
  US 20040145430A1
• Time in Patent Office: 761 Days
• Field of Search: 333186-192, 310/322, 310/335, 29/253.5
• US Class Current: 333/187
• CPC Class Codes: H03H 3/02 for the manufacture of piezoelectric or electrostrictive resonators or networks H03H3/08 takes precedence
• CPC Class Codes: H03H 9/02125 of parasitic elements
• CPC Class Codes: H03H 9/175 Acoustic mirrors
• CPC Class Codes: H03H 9/584 Coupled Resonator Filters [CFR]
• CPC Class Codes: H03H 9/589 Acoustic mirrors
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

A component operating with bulk acoustic waves has a carrier substrate, a thin-film resonator and an acoustic mirror arranged between the resonator and carrier substrate. The acoustic mirror is formed by at least one high acoustic impedance layer, which is covered by a low acoustic impedance layer and the uppermost low impedance acoustic layer is planarized to form a flat planar surface on which the thin-film resonator is formed.

Claims

1. A component operating with bulk acoustic waves, said component comprising:

a carrier substrate;

a lower electrode that faces said carrier substrate;

an upper electrode;

a piezoelectric layer between said lower electrode and said upper electrode, said piezoelectric layer comprising a multi-layer assembly; and

an acoustic mirror between said carrier substrate and said lower electrode, said acoustic mirror comprising at least one layer with a high acoustic impedance and at least one layer with low acoustic impedance arranged in a stack, said at least one layer of low acoustic impedance including an uppermost mirror layer of said stack, said at least one layer with high acoustic impedance being formed as a structured layer, said uppermost mirror layer exhibiting a varying thickness, an upper boundary surface of said uppermost mirror layer being planar to said lower electrode, and said uppermost layer enclosing a structure of said structured layer and forming a seal with a layer of said at least one layer with a low acoustic impedance or with said carrier substrate outside of an area covered by said structure.

2. A component according to claim 1, wherein said at least one layer with high acoustic impedance includes a plurality of layers which are structured.

3. A component according to claim 2, wherein said at least one layer with high acoustic impedance is formed of a material selected from a group consisting of tungsten and molybdenum, and said at least one layer with low impedance is formed of silicon oxide.

4. A component according to claim 1, wherein at least one of said upper electrode and said lower electrode is formed by a plurality of layers.

5. A component according to claim 1, wherein said at least one layer with high acoustic impedance is of a metal selected from a group consisting of tungsten and molybdenum, and said at least one layer with a low acoustic impedance is formed of silicon oxide.

6. A component operating with bulk acoustic waves, said component comprising:

a carrier substrate;

a lower electrode that faces said carrier substrate;

an upper electrode;

a piezoelectric layer between said lower electrode and said upper electrode;

an acoustic mirror between said carrier substrate and said lower electrode, said acoustic mirror comprising at least one layer with a high acoustic impedance and at least one layer with low acoustic impedance arranged in a stack, said at least one layer of low acoustic impedance including an uppermost mirror layer of said stack, said at least one layer with high acoustic impedance being formed as a structured said uppermost mirror layer exhibiting a varying thickness, an upper boundary surface of said uppermost mirror layer being planar to said lower electrode, and said uppermost layer enclosing structures of said structured layer and forming a seal with a layer of said at least one layer with a low acoustic impedance or with said carrier substrate outside of an area covered by said structure;

an additional piezoelectric layer being formed on said upper electrode and an additional electrode on said additional piezoelectric layer;

at least a partially permeable coupling layer between said upper electrode and said additional piezoelectric layer; and

a second additional electrode between said at least a partially permeable coupling layer and said additional piezoelectric layer.

7. A component according to claim 6, wherein said at least one layer with high acoustic impedance includes a plurality of layers which are structured.

8. A component according to claim 7, wherein said at least one layer with high acoustic impedance is formed of a material selected from a group consisting of tungsten and molybdenum, and said at least one layer with low impedance is formed of silicon oxide.

9. A component according to claim 6, wherein at least one of said upper electrode and said lower electrode is formed by a plurality of layers.

10. A component according to claim 6, wherein said at least one layer with high acoustic impedance is of a metal selected from a group consisting of tungsten and molybdenum, and said at least one layer with a low acoustic impedance is formed of silicon oxide.

11. A component operating with bulk acoustic waves, said component comprising:

a carrier substrate;

a lower electrode that faces said carrier substrate;

an upper electrode;

a piezoelectric layer between said lower electrode and said upper electrode; and

an acoustic mirror between said carrier substrate and said lower electrode, said acoustic mirror comprising at least one layer with a high acoustic impedance and at least one layer with low acoustic impedance arranged in a stack, said at least one layer of low acoustic impedance including an uppermost mirror layer of said stack, said at least one layer with high acoustic impedance being formed as a structured said uppermost mirror layer exhibiting a varying thickness, an upper boundary surface of said uppermost mirror layer being planar to said lower electrode, and said uppermost layer enclosing structures of said structured layer and forming a seal with a layer of said at least one layer with a low acoustic impedance or with said carrier substrate outside of an area covered by said structure

said carrier substrate including a plurality of dielectric layers with at least one metallized plane being provided between successive ones of said dielectric layers.

12. A component according to claim 11, wherein said at least one layer with high acoustic impedance includes a plurality of layers which are structured.

13. A component according to claim 12, wherein said at least one layer with high acoustic impedance is formed of a material selected from a group consisting of tungsten and molybdenum, and said at least one layer with low impedance is formed of silicon oxide.

14. A component according to claim 11, wherein at least one of said upper electrode and said lower electrode is formed by a plurality of layers.

15. A component according to claim 11, wherein said at least one layer with high acoustic impedance is of a metal selected from a group consisting of tungsten and molybdenum, and said at least one layer with a low acoustic impedance is formed of silicon oxide.

16. A method to produce a component operating with bulk acoustic waves, said method comprising the steps of:

providing a carrier substrate;

forming an acoustic mirror on the carrier substrate by depositing a layer with a high acoustic impedance on the carrier substrate;

structuring the layer of high acoustic impedance to form a structured layer;

depositing an uppermost mirror layer with a low acoustic impedance on the structured layer;

thinning and planarizing an upper surface of the uppermost mirror layer to form a planar surface;

forming a lower electrode on the planar surface;

forming a structured piezoelectric layer on the lower electrode; and

then forming an upper electrode on the structured piezoelectric layer.

17. A method according to claim 16, wherein the step of thinning the uppermost mirror layer occurs by chemical mechanical polishing.

18. A method according to claim 16, which includes, prior to depositing the uppermost mirror layer,

depositing an additional layer of low acoustic impedance on the structured layer,

depositing a second layer of high acoustic impedance on the additional layer, and

structuring the second layer to form a second structured layer so that the uppermost layer is applied on the second structured layer.

19. A method according to claim 18, wherein the step of thinning the uppermost layer occurs by chemical mechanical polishing.

20. A method according to claim 16, which includes, subsequent to depositing the upper electrode on the piezoelectric layer,

depositing a coupling layer,

then forming a lower electrode of a second resonator followed by a second piezoelectric layer and a second upper electrode on the coupling layer.