XBAR Interposer Package for Shear-Mode RF Filtering Above 3 GHz
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Solution Overview
Problem
Current RF filters are not well-suited for higher frequency bands proposed for future communications networks, particularly those above 3 GHz, as they lack the necessary bandwidth and performance to support advanced wireless communication standards like 5G and millimeter wave communications.
Innovation Solution
The development of transversely-excited film bulk acoustic resonators (XBARs) that utilize a thin film conductor pattern on a piezoelectric plate, with a cavity structure and interdigital transducers, to achieve high piezoelectric coupling and efficient shear-mode acoustic resonances, enabling the design of RF filters with wider bandwidth and improved performance for frequencies above 3 GHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional RF filters are used, then device complexity is reduced, but bandwidth and performance at frequencies above 3 GHz are insufficient
Solution Approach 1:
The patent changes the operating parameters by using transversely-excited film bulk acoustic resonators (XBARs) that operate at frequencies above 3 GHz with enhanced bandwidth capabilities. The XBAR structure modifies the acoustic wave propagation parameters to achieve wider bandwidth while maintaining manageable device complexity through integrated design.
Solution Approach 2:
The patent employs composite material structures in the XBAR design, combining piezoelectric films with specific substrate materials and conductor patterns. This composite approach enables the resonator to achieve both high bandwidth and controlled complexity by leveraging the complementary properties of different materials.
2Adaptability or versatility
If XBARs with high piezoelectric coupling are used, then bandwidth is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by optimizing the piezoelectric coupling in specific regions of the XBAR structure. The interdigital transducer fingers and electrode patterns are locally configured to maximize piezoelectric coupling where needed, while other regions are designed for manufacturability, thus achieving high bandwidth without uniformly increasing manufacturing precision requirements across the entire device.
Solution Approach 2:
The XBAR structure is segmented into distinct functional regions including the piezoelectric film layer, interdigital transducer electrodes, and substrate regions. This segmentation allows independent optimization of each region, enabling high piezoelectric coupling in the active areas while maintaining relaxed tolerances in support structures, thereby reducing overall manufacturing precision requirements.
3Reliability
If XBARs are designed for frequencies above 3 GHz, then performance for 5G and millimeter wave communications is improved, but device complexity increases
Solution Approach 1:
The XBAR design achieves multi-functionality by enabling the same resonator structure to operate effectively across multiple frequency bands including 5G and millimeter wave communications. The universal XBAR platform can be tuned to different frequencies through parameter adjustment, reducing the need for multiple specialized devices and thereby managing overall system complexity while maintaining high performance.
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
XBARs provide enhanced bandwidth and performance for RF filters, enabling them to effectively handle higher frequency communications, such as 5G and millimeter wave frequencies, by leveraging high piezoelectric coupling and minimizing viscous losses, thus addressing the limitations of existing technologies.
Implementation Method 1
achieve high piezoelectric coupling and efficient shear-mode acoustic resonances
Implementation Method 2
efficient shear-mode acoustic resonances
Data Source
AI summary
Acoustic resonator devices and filters are disclosed. A piezoelectric plate is attached to a substrate, a portion of the piezoelectric plate forming a diaphragm spanning a chip cavity in the substrate. A first conductor pattern is formed on a surface of the piezoelectric plate. The first conductor pattern includes interleaved fingers of an interdigital transducer on the diaphragm, and first contact pads. An interposer has walls on its back surface that are attached to the chip front surface and that surround the diaphragm. An interposer cover layer spans the walls creating an enclosed interposer cavity over the diaphragm. A second conductor pattern formed on the walls and cover layer includes second contact pads on the interposer back surface. Electrical connections between the second contact pads and connection points on the chip electrically connect the first contact pads to respective ones of the second contact pads.