Common-Reflector BAW Transducers With Local Thickness Tuning
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Solution Overview
Problem
Current BAW resonators face challenges in achieving optimal performance and miniaturization due to the complexity of filtering demands in high-frequency communication applications, particularly in 3G, 4G, and emerging 5G wireless devices, where there is a need for improved frequency tuning and reduced size while maintaining low insertion loss and stability across varying temperatures.
Innovation Solution
The design incorporates a BAW device with multiple transducers over a common reflector, featuring reflector layers of varying thicknesses, where each transducer has a unique series resonance frequency and piezoelectric layer thickness, optimized to operate at specific acoustic modes, allowing for precise tuning and increased density of resonators in smaller footprints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple BAW transducers are integrated over a common reflector to increase device density, then the quantity of resonators per unit area increases, but the manufacturing precision required for varying reflector layer thicknesses increases
Solution Approach 1:
The reflector structure is designed with spatially varying local properties: different sections of the reflector have different layer thicknesses tailored to the specific resonance frequency requirements of each transducer. This allows each transducer to be optimized for its operating frequency while sharing a common reflector base, thereby increasing device density without compromising performance
Solution Approach 2:
The patent varies the physical parameters of the reflector layers (specifically thickness) across different spatial locations to achieve different resonance frequencies. By changing the thickness parameter of reflector layers in different sections, multiple transducers with distinct frequency characteristics can be integrated on a single substrate
2Measurement precision
If reflector layers are tailored to specific acoustic modes for each transducer to improve frequency accuracy, then the frequency tuning precision improves, but the device complexity increases
Solution Approach 1:
Different sections of the reflector are designed with specific layer thicknesses optimized for particular acoustic modes (longitudinal, shear, quasi-longitudinal, quasi-shear). This localized optimization enables precise frequency tuning for each transducer while maintaining a unified reflector structure that does not require completely separate reflectors for each mode
3Reliability
If BAW-based filters are designed to meet increasingly complex filtering demands for 5G devices, then the filtering performance improves, but the device size increases
Solution Approach 1:
Multiple BAW transducers with different resonance frequencies are integrated over a common reflector structure, combining multiple filtering functions into a single compact device. This merging approach allows complex filtering demands for 5G devices to be met while minimizing the overall device footprint through increased integration density
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
This approach enables more resonators with different resonance frequencies to be packed in smaller spaces, improving frequency accuracy and overall performance by tailoring the reflector layers to each transducer's specific acoustic mode, thus enhancing the efficiency and miniaturization of BAW-based filters.
Implementation Method 1
a first piezoelectric layer of a first thickness between a first top electrode and a first bottom electrode
Implementation Method 2
a first reflector... that resides over the substrate and has a plurality of reflector layers
Implementation Method 3
has a first series resonance frequency... has a second series resonance frequency that is different than the first series resonance frequency
Data Source
AI summary
A BAW device includes a substrate, a first reflector, and at least two BAW transducers. The first reflector resides over the substrate and has a plurality of reflector layers. A first BAW transducer resides over a first section of the first reflector, has a first series resonance frequency, and has a first piezoelectric layer of a first thickness between a first top electrode and a first bottom electrode. The second BAW transducer resides over a second section of the first reflector, has a second series resonance frequency that is different than the first series resonance frequency, and has a second piezoelectric layer of a second thickness, which is different than the first thickness, between a second top electrode and a second bottom electrode.