BAW Resonator Recess and Frame Layout for Spurious Mode Suppression
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Solution Overview
Problem
Bulk acoustic wave (BAW) devices often suffer from spurious modes that lead to undesirable energy leakage and performance degradation.
Innovation Solution
The acoustic wave device comprises a substrate with a reflector recess, a first recess surrounding the reflector recess, a frame disposed in the first recess, electrodes on the substrate and piezoelectric layer, and a sacrificial material in the reflector recess. This configuration suppresses spurious modes by reducing acoustic wave leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional BAW device structure is used, then the device can be manufactured with standard processes, but spurious modes occur causing energy leakage and performance degradation
Solution Approach 1:
The device structure is segmented by introducing a frame that divides the acoustic wave path and creates separate regions. The frame segments the acoustic field to prevent spurious mode propagation, thereby reducing energy leakage while maintaining manufacturing feasibility
Solution Approach 2:
A sacrificial material is introduced as an intermediary element during fabrication. This material is temporarily placed in the reflector recess, allows precise frame formation, and is later removed. The intermediary enables precise structural control to suppress spurious modes without complicating the overall manufacturing process
2Loss of energy
If a frame structure is added to suppress spurious modes, then acoustic wave leakage is reduced, but device complexity increases
Solution Approach 1:
The frame and electrode are merged into a single integrated structure formed in the same fabrication step. This combining reduces the number of discrete components and simplifies the overall device architecture while maintaining the spurious mode suppression function
Solution Approach 2:
The frame structure is preliminarily formed during the electrode fabrication process itself, rather than being added as a separate subsequent step. This preliminary action integrates multiple functions into existing process steps, reducing overall device complexity
3Reliability
If the first recess completely surrounds the reflector recess, then spurious mode suppression is maximized, but manufacturing precision requirements increase
Solution Approach 1:
The first recess is designed with local quality variations - it completely surrounds the reflector recess in critical regions for maximum spurious mode suppression, while having reduced or no extent in non-critical regions. This selective surrounding approach maintains suppression effectiveness while reducing manufacturing precision requirements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The described configuration effectively suppresses spurious modes, enhancing the performance and reliability of BAW devices by minimizing energy leakage and improving frequency selectivity.
Implementation Method 1
The piezoelectric layer is disposed at least on the first electrode. The second electrode is disposed at least on the piezoelectric layer.
Data Source
AI summary
An acoustic wave device and a fabricating method are provided. The acoustic wave device includes a substrate, a first frame, a first electrode, a piezoelectric layer and a second electrode. The substrate includes a first surface and a second surface opposite thereto. A reflector recess and a first recess may be depressed from the first surface. The first recess may at least partially surround the reflector recess, and may be separated from the reflector recess. The first frame is disposed in the first recess of the substrate. The first electrode is disposed on the substrate and contacts the first frame. The piezoelectric layer is disposed at least on the first electrode. The second electrode is disposed at least on the piezoelectric layer. The reflector recess of the substrate, the first electrode, the piezoelectric layer, and the second electrode at least partially overlap along a vertical direction.