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Bulk acoustic resonator comprising non-piezoelectric layer and bridge

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Bulk acoustic resonator comprising non-piezoelectric layer and bridge


A bulk acoustic wave (BAW) resonator, comprises: a first electrode formed on a substrate; a piezoelectric layer formed on the first electrode; a second electrode formed on the first piezoelectric layer; a non-piezoelectric layer formed on the first electrode and adjacent to the piezoelectric layer; and a bridge formed between the non-piezoelectric layer and the first or second electrode.

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Inventors: Alexandre SHIRAKAWA, Dariusz BURAK, Phil NIKKEL
USPTO Applicaton #: #20120319534 - Class: 310365 (USPTO) - 12/20/12 - Class 310 


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The Patent Description & Claims data below is from USPTO Patent Application 20120319534, Bulk acoustic resonator comprising non-piezoelectric layer and bridge.

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CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of commonly owned U.S. patent application Ser. No. 13/161,946 entitled “Bulk Acoustic Resonator Comprising Non-Piezoelectric Layer” filed on Jun. 16, 2011 to Dariusz Burak, et al. The present application claims priority under 35 U.S.C. §120 to U.S. patent application Ser. No. 13/161,946, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND

Transducers generally convert electrical signals to mechanical signals or vibrations, and/or mechanical signals or vibrations to electrical signals. Acoustic transducers, in particular, convert electrical signals to acoustic waves and acoustic waves to electrical signals using inverse and direct piezoelectric effects. Acoustic transducers generally include acoustic resonators, such as thin film bulk acoustic resonators (FBARs), surface acoustic wave (SAW) resonators or bulk acoustic wave (BAW) resonators, and may be used in a wide variety of electronic applications, such as cellular telephones, personal digital assistants (PDAs), electronic gaming devices, laptop computers and other portable communications devices. For example, FBARs may be used for electrical filters and voltage transformers.

An acoustic resonator can be formed by a layer of piezoelectric material between two conductive plates (electrodes), which can be formed on a thin membrane. Such a resonator can generate acoustic waves that propagate in lateral directions when stimulated by an applied time-varying electric field, as well as higher order harmonic mixing products. The laterally propagating modes and the higher order harmonic mixing products may have a deleterious impact on functionality.

What is needed, therefore, is a structure useful in mitigating acoustic losses at the boundaries of the BAW resonator to improve mode confinement in the region of overlap of the top electrode, the piezoelectric layer, and the bottom electrode of a BAW resonator (commonly referred to as the active region).

SUMMARY

In accordance with a representative embodiment, a bulk acoustic wave (BAW) resonator, comprises: a first electrode formed on a substrate; a piezoelectric layer formed on the first electrode; a second electrode formed on the first piezoelectric layer; a non-piezoelectric layer formed on the first electrode and adjacent to the piezoelectric layer; and a bridge formed between the non-piezoelectric layer and the first or second electrode.

In accordance with another representative embodiment, a method of forming a bulk acoustic wave (BAW) resonator is disclosed. The method comprises: forming an acoustic reflector in a substrate; forming a first electrode on the substrate over the acoustic reflector; forming a piezoelectric layer and an non-piezoelectric layer adjacent to each other on the first electrode; forming a second electrode over the piezoelectric layer and the non-piezoelectric layer; and forming a layer between the non-piezoelectric layer and the first or second electrode to define a region for a bridge.

BRIEF DESCRIPTION OF THE DRAWINGS

The illustrative embodiments are best understood from the following detailed description when read with the accompanying drawing figures. It is emphasized that the various features are not necessarily drawn to scale. In fact, the dimensions may be arbitrarily increased or decreased for clarity of discussion. Wherever applicable and practical, like reference numerals refer to like elements.

FIG. 1 is a top-view of an FBAR in accordance with a representative embodiment.

FIG. 2 is a cross-sectional view of the FBAR of FIG. 1, taken along a line A-B.

FIGS. 3A and 3B are cross-sectional views illustrating the use of a non-piezoelectric material to prevent loss of acoustic energy in the FBAR of FIG. 2.

FIGS. 4A and 4B are cross-sectional views illustrating the use of an air-bridge to prevent loss of acoustic energy in the FBAR of FIG. 2.

FIG. 5 is a cross-sectional view of the FBAR of FIG. 2, with illustrations of contained acoustic energy.

FIGS. 6A through 6C are cross-sectional views of different variations of the FBAR of FIG. 2 in accordance with representative embodiments.

FIG. 7 is a flowchart illustrating a method of fabricating an FBAR in accordance with a representative embodiment.

FIG. 8 is a flowchart illustrating a method of forming a piezoelectric layer and a non-piezoelectric layer on an electrode in accordance with a representative embodiment.

FIG. 9 is a flowchart illustrating another method of forming a piezoelectric layer and a non-piezoelectric layer on an electrode in accordance with a representative embodiment.

FIG. 10 is a graph illustrating the quality (Q) factor of an FBAR as a function of frequency in accordance with a representative embodiment.



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Previous Patent Application:
Piezoelectric thin film, piezoelectric element, and manufacturing method thereof
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Methods for forming piezoelectric ultrasonic transducers, and associated apparatuses
Industry Class:
Electrical generator or motor structure
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stats Patent Info
Application #
US 20120319534 A1
Publish Date
12/20/2012
Document #
13168101
File Date
06/24/2011
USPTO Class
310365
Other USPTO Classes
International Class
01L41/02
Drawings
11



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