XBAR Electrode Geometry for Spurious Mode and Heat Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing RF filters are not well-suited for higher frequencies and bandwidths required by future communications networks, particularly in 5G NR and WiFi bands, and face challenges in heat dissipation and spurious acoustic modes in XBAR devices.
Innovation Solution
The use of transversely-excited film bulk acoustic resonators (XBARs) with irregular hexagon cross-sectional shapes for IDT fingers, featuring dual-layer metal structures and optimized geometries to reduce spurious modes and improve heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional RF filters are used for higher frequencies, then existing technology can be maintained, but performance is not suitable for future communications networks requiring higher frequencies and bandwidths
Solution Approach 1:
The patent modifies the operating parameters of the XBAR device by changing the electrode geometry to irregular hexagon cross-sections and optimizing the piezoelectric material composition to achieve higher frequency operation (e.g., 5G NR bands at 3.3-4.2 GHz and 4.4-5.0 GHz) and wider bandwidths while maintaining reliability
2Speed
If XBAR devices are used for high-frequency operation, then higher frequencies and bandwidths are achieved, but spurious acoustic modes are generated
Solution Approach 1:
The patent employs asymmetric irregular hexagon cross-sectional shapes for the IDT electrodes instead of conventional symmetric rectangular or circular shapes. This asymmetric geometry creates specific acoustic radiation patterns that suppress spurious modes while enabling higher frequency operation in the 5G NR bands
Solution Approach 2:
The patent optimizes specific local geometric parameters of the irregular hexagon electrodes (such as side lengths and internal angles) to create localized acoustic field distributions that minimize spurious mode generation at high frequencies while maintaining the desired fundamental mode operation
3Power
If XBAR devices operate at high power levels, then sufficient power handling is achieved, but heat dissipation becomes problematic
Solution Approach 1:
The patent utilizes thin film piezoelectric layers (e.g., aluminum nitride or gallium nitride films) with optimized thicknesses to create a structure that provides sufficient power handling capability while enabling efficient heat dissipation through the thin film architecture and underlying substrate
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
Enhances performance by reducing spurious modes and improving heat dissipation, enabling efficient operation in high-frequency bands with reduced insertion loss and increased Q-factor.
Implementation Method 1
transversely-excited film bulk acoustic resonators (XBARs) with irregular hexagon cross-sectional shapes for IDT fingers
Implementation Method 2
LATERALLY-EXCITED BULK WAVE RESONATOR (XBAR)
Implementation Method 3
dual-layer metal structures and optimized geometries to reduce spurious modes and improve heat dissipation
Implementation Method 4
transversely-excited film bulk acoustic resonators (XBARs)
Data Source
AI summary
Acoustic resonators and filter devices, and method of making acoustic resonators and filter devices. An acoustic resonator is provided that includes a piezoelectric layer; and an interdigital transducer (IDT) having interleaved fingers on a surface of the piezoelectric layer. At least one finger of the interleaved fingers has an irregular hexagon cross-sectional shape. Moreover, sides of the irregular hexagon cross-sectional shape are not all a same length.