Manufacturing process for thin film bulk acoustic resonator (FBAR) filters

• US 7,802,349 B2
• Filed: 05/15/2007
• Issued: 09/28/2010
• Est. Priority Date: 03/07/2003
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies Wireless IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Bradley, Paul D., Larson, John D., Ruby, Richard C.
• Primary Examiner(s): Banks; Derris H
• Assistant Examiner(s): NGUYEN, TAI V
• Application Number:
  US11/748,970
• Publication Number:
  US 20090146531A1
• Time in Patent Office: 1,232 Days
• Field of Search: 29/253.5, 295/94, 298/46, 298/47, 29/254.2, 310/321, 310/324, 310/348, 310/349, 310/363, 333/187, 333/189, 438/959, 427/100, 216/13, 216/38, 216/40, 216/41
• US Class Current: 29/25.35
• 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. 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, wherein the mass load lift-off process further comprises;

forming a mass-loading pattern over the second electrode, and depositing a mass-loading layer over the second electrode; and

removing said sacrificial material from said depression.

2. The method of claim 1 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.

3. The method of claim 1 further comprising:

depositing a passivation layer for protecting the second electrode.

4. The method of claim 1 wherein said sacrificial material comprises a material chosen from the group consisting of PSG, BPSG, spin-on-glass, polyvinyl, polypropylene and polystyrene.

5. The method of claim 1 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.

6. The method of claim 1 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.

7. The method of claim 1 wherein said first electrode comprises molybdenum.

8. The method of claim 1 wherein said layer of piezoelectric material comprises AlN.