BAW Resonator Frame Structure Using Dielectric Layer for Mode Suppression
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Solution Overview
Problem
Existing bulk acoustic wave (BAW) devices face challenges in achieving high quality factor (Q) while effectively suppressing spurious modes, which are undesirable resonances that degrade performance.
Innovation Solution
Incorporating a dielectric layer with reduced piezoelectric properties in the frame region of BAW devices, which includes a raised frame structure and optionally a recessed frame structure, to suppress frame modes and enhance Q by reducing lateral energy leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a raised frame structure is added to suppress frame modes, then spurious mode suppression is improved, but device complexity increases
Solution Approach 1:
A dielectric layer is introduced as an intermediary element between the raised frame structure and the piezoelectric layer. This dielectric layer acts as a mediator that enhances the frame mode suppression effect while allowing for a more compact and less complex overall device structure compared to alternative approaches.
Solution Approach 2:
The device employs a composite structure combining piezoelectric material, dielectric material, and metal frame structure. This composite approach allows each material to contribute its specific properties: the piezoelectric layer for acoustic wave generation, the dielectric layer for electrical isolation and additional frame mode suppression, and the raised frame for mechanical support and spurious mode control.
2Object-generated harmful factors
If the piezoelectric layer is reduced in the frame region, then frame mode suppression is improved, but manufacturing precision requirements increase
Solution Approach 1:
The piezoelectric layer is designed with spatially varying properties: it has full thickness and standard composition in the main acoustically active region for optimal acoustic performance, while in the frame region it is reduced or removed to suppress frame modes. This local differentiation allows each region to be optimized for its specific function without compromising overall device performance.
Solution Approach 2:
The device structure is segmented into distinct functional regions: the main acoustically active region with full piezoelectric layer, and the frame region with reduced or removed piezoelectric material. This segmentation allows independent optimization of each region and simplifies manufacturing by allowing different processing steps for different areas.
3Object-generated harmful factors
If a dielectric layer is added between electrodes and piezoelectric layer, then frame mode suppression is improved, but device complexity increases
Solution Approach 1:
The dielectric layer serves multiple functions simultaneously: it provides electrical isolation between the electrodes and piezoelectric layer, acts as an acoustic barrier to suppress frame modes, and contributes to the overall mechanical stability of the device structure. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity.
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 dielectric layer effectively suppresses frame modes and increases the quality factor (Q) of BAW devices, maintaining electromechanical coupling coefficient (kt2) and improving overall performance, particularly in applications like 5G New Radio (NR).
Implementation Method 1
a piezoelectric layer positioned between a first electrode and a second electrode in the main acoustically active region and the frame region
Data Source
AI summary
A bulk acoustic wave device is disclosed. The bulk acoustic wave device can include a piezoelectric layer positioned between first and second electrodes in a main acoustically active region and a frame region, a raised frame structure positioned in the frame region, and a raised frame structure positioned in the frame region. The piezoelectric layer has a first side facing the first electrode and a second side facing the second electrode. The raised frame structure has an inner end and an outer end. The dielectric layer is positioned between the first and second sides of the piezoelectric layer. The dielectric layer has an inner edge and an outer edge. A distance between the inner end of the raised frame structure and the main acoustically active region can be equal to or greater than a distance between the inner edge of the dielectric layer and the main acoustically active region.