Manufacturing Process For Thin Film Bulk Acoustic Resonator (FBAR) Filters

• US 20090146531A1
• Filed: 05/15/2007
• Published: 06/11/2009
• Est. Priority Date: 03/07/2003
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: John D. Larson, Paul D. Bradley, Richard C. Ruby
• Inventors: Ruby, Richard C., Bradley, Paul D., Larson, John D.
• Granted Patent: US 7,802,349 B2
• Time in Patent Office: Days
• US Class Current: 310/324
• CPC Class Codes: H03H 2003/0471 of a plurality of resonators at different frequencies
• CPC Class Codes: H03H 3/02 for the manufacture of piezoelectric or electrostrictive resonators or networks H03H3/08 takes precedence
• CPC Class Codes: H03H 3/04 for obtaining desired frequency or temperature coefficient
• CPC Class Codes: H03H 9/02149 of ageing changes of characteristics, e.g. electro-acousto-migration
• CPC Class Codes: Y10T 29/42 Piezoelectric device making
• CPC Class Codes: Y10T 29/49002 Electrical device making
• CPC Class Codes: Y10T 29/49005 Acoustic transducer
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base
• CPC Class Codes: Y10T 29/49156 with selective destruction of conductive paths

Abstract

Method for fabricating an acoustical resonator on a substrate having a top surface. First, a depression in said top surface is generated. Next, the depression is filled with a sacrificial material. The filled depression has an upper surface level with said top surface of said substrate. Next, a first electrode is deposited on said upper surface. Then, a layer of piezoelectric material is deposited on said first electrode. A second electrode is deposited on the layer of piezoelectric material using a mass load lift-off process.

Claims

1-8. -8. (canceled)

9. A method for fabricating an acoustical resonator on a substrate having a top surface, said method comprising steps of:

generating a depression in said top surface;

filling said depression with a sacrificial material, said filled depression having an upper surface level with said top surface of said substrate;

depositing a first electrode on said upper surface;

depositing a layer of piezoelectric material on said first electrode;

depositing a second electrode on said layer of piezoelectric material by employing a mass load lift-off process; and

removing said sacrificial material from said depression.

10. The method of claim 9 wherein the step of depositing a first electrode on said upper surface comprises the steps of:

depositing a seed layer;

depositing a conductive material;

applying a patterned mask;

etching the conductive material and seed layer in accordance with the patterned mask to form a bottom electrode.

11. The method of claim 9 further comprising:

depositing a passivation layer for protecting the second electrode.

12. The method of claim 9 wherein said sacrificial material comprises a material chosen from the group consisting of PSG, BPSG, spin-on-glass, polyvinyl, polypropylene and polystyrene.

13. The method of claim 9 wherein said step of filling said depression comprises the steps of:

depositing a layer of said sacrificial material over said depression;

planarizing said deposited layer; and

polishing said planarized layer.

14. The method of claim 11 further comprising the step of providing a layer of an electrically insulating material on the surface of said substrate and depression prior to depositing said layer of sacrificial material, said electrically insulating material preventing a diffusion of elements in said sacrificial material from diffusing into said substrate.

15. The method of claim 9 wherein said first electrode comprises molybdenum.

16. The method of claim 9 wherein said layer of piezoelectric material comprises AIN.

17-20. -20. (canceled)